Revert "mm: simplify code of swap.c"

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / btrfs / inode.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/bit_spinlock.h>
#include <linux/xattr.h>
#include <linux/posix_acl.h>
#include <linux/falloc.h>
#include <linux/slab.h>
#include "compat.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "ioctl.h"
#include "print-tree.h"
#include "volumes.h"
#include "ordered-data.h"
#include "xattr.h"
#include "tree-log.h"
#include "compression.h"
#include "locking.h"

struct btrfs_iget_args {
        u64 ino;
        struct btrfs_root *root;
};

static const struct inode_operations btrfs_dir_inode_operations;
static const struct inode_operations btrfs_symlink_inode_operations;
static const struct inode_operations btrfs_dir_ro_inode_operations;
static const struct inode_operations btrfs_special_inode_operations;
static const struct inode_operations btrfs_file_inode_operations;
static const struct address_space_operations btrfs_aops;
static const struct address_space_operations btrfs_symlink_aops;
static const struct file_operations btrfs_dir_file_operations;
static struct extent_io_ops btrfs_extent_io_ops;

static struct kmem_cache *btrfs_inode_cachep;
struct kmem_cache *btrfs_trans_handle_cachep;
struct kmem_cache *btrfs_transaction_cachep;
struct kmem_cache *btrfs_path_cachep;

#define S_SHIFT 12
static unsigned char btrfs_type_by_mode[S_IFMT >> S_SHIFT] = {
        [S_IFREG >> S_SHIFT]    = BTRFS_FT_REG_FILE,
        [S_IFDIR >> S_SHIFT]    = BTRFS_FT_DIR,
        [S_IFCHR >> S_SHIFT]    = BTRFS_FT_CHRDEV,
        [S_IFBLK >> S_SHIFT]    = BTRFS_FT_BLKDEV,
        [S_IFIFO >> S_SHIFT]    = BTRFS_FT_FIFO,
        [S_IFSOCK >> S_SHIFT]   = BTRFS_FT_SOCK,
        [S_IFLNK >> S_SHIFT]    = BTRFS_FT_SYMLINK,
};

static void btrfs_truncate(struct inode *inode);
static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end);
static noinline int cow_file_range(struct inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written, int unlock);

static int btrfs_init_inode_security(struct btrfs_trans_handle *trans,
                                     struct inode *inode,  struct inode *dir)
{
        int err;

        err = btrfs_init_acl(trans, inode, dir);
        if (!err)
                err = btrfs_xattr_security_init(trans, inode, dir);
        return err;
}

/*
 * this does all the hard work for inserting an inline extent into
 * the btree.  The caller should have done a btrfs_drop_extents so that
 * no overlapping inline items exist in the btree
 */
static noinline int insert_inline_extent(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode,
                                u64 start, size_t size, size_t compressed_size,
                                struct page **compressed_pages)
{
        struct btrfs_key key;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct page *page = NULL;
        char *kaddr;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        int err = 0;
        int ret;
        size_t cur_size = size;
        size_t datasize;
        unsigned long offset;
        int use_compress = 0;

        if (compressed_size && compressed_pages) {
                use_compress = 1;
                cur_size = compressed_size;
        }

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        path->leave_spinning = 1;
        btrfs_set_trans_block_group(trans, inode);

        key.objectid = inode->i_ino;
        key.offset = start;
        btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
        datasize = btrfs_file_extent_calc_inline_size(cur_size);

        inode_add_bytes(inode, size);
        ret = btrfs_insert_empty_item(trans, root, path, &key,
                                      datasize);
        BUG_ON(ret);
        if (ret) {
                err = ret;
                goto fail;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei, BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, size);
        ptr = btrfs_file_extent_inline_start(ei);

        if (use_compress) {
                struct page *cpage;
                int i = 0;
                while (compressed_size > 0) {
                        cpage = compressed_pages[i];
                        cur_size = min_t(unsigned long, compressed_size,
                                       PAGE_CACHE_SIZE);

                        kaddr = kmap_atomic(cpage, KM_USER0);
                        write_extent_buffer(leaf, kaddr, ptr, cur_size);
                        kunmap_atomic(kaddr, KM_USER0);

                        i++;
                        ptr += cur_size;
                        compressed_size -= cur_size;
                }
                btrfs_set_file_extent_compression(leaf, ei,
                                                  BTRFS_COMPRESS_ZLIB);
        } else {
                page = find_get_page(inode->i_mapping,
                                     start >> PAGE_CACHE_SHIFT);
                btrfs_set_file_extent_compression(leaf, ei, 0);
                kaddr = kmap_atomic(page, KM_USER0);
                offset = start & (PAGE_CACHE_SIZE - 1);
                write_extent_buffer(leaf, kaddr + offset, ptr, size);
                kunmap_atomic(kaddr, KM_USER0);
                page_cache_release(page);
        }
        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        /*
         * we're an inline extent, so nobody can
         * extend the file past i_size without locking
         * a page we already have locked.
         *
         * We must do any isize and inode updates
         * before we unlock the pages.  Otherwise we
         * could end up racing with unlink.
         */
        BTRFS_I(inode)->disk_i_size = inode->i_size;
        btrfs_update_inode(trans, root, inode);

        return 0;
fail:
        btrfs_free_path(path);
        return err;
}


/*
 * conditionally insert an inline extent into the file.  This
 * does the checks required to make sure the data is small enough
 * to fit as an inline extent.
 */
static noinline int cow_file_range_inline(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct inode *inode, u64 start, u64 end,
                                 size_t compressed_size,
                                 struct page **compressed_pages)
{
        u64 isize = i_size_read(inode);
        u64 actual_end = min(end + 1, isize);
        u64 inline_len = actual_end - start;
        u64 aligned_end = (end + root->sectorsize - 1) &
                        ~((u64)root->sectorsize - 1);
        u64 hint_byte;
        u64 data_len = inline_len;
        int ret;

        if (compressed_size)
                data_len = compressed_size;

        if (start > 0 ||
            actual_end >= PAGE_CACHE_SIZE ||
            data_len >= BTRFS_MAX_INLINE_DATA_SIZE(root) ||
            (!compressed_size &&
            (actual_end & (root->sectorsize - 1)) == 0) ||
            end + 1 < isize ||
            data_len > root->fs_info->max_inline) {
                return 1;
        }

        ret = btrfs_drop_extents(trans, inode, start, aligned_end,
                                 &hint_byte, 1);
        BUG_ON(ret);

        if (isize > actual_end)
                inline_len = min_t(u64, isize, actual_end);
        ret = insert_inline_extent(trans, root, inode, start,
                                   inline_len, compressed_size,
                                   compressed_pages);
        BUG_ON(ret);
        btrfs_delalloc_release_metadata(inode, end + 1 - start);
        btrfs_drop_extent_cache(inode, start, aligned_end - 1, 0);
        return 0;
}

struct async_extent {
        u64 start;
        u64 ram_size;
        u64 compressed_size;
        struct page **pages;
        unsigned long nr_pages;
        struct list_head list;
};

struct async_cow {
        struct inode *inode;
        struct btrfs_root *root;
        struct page *locked_page;
        u64 start;
        u64 end;
        struct list_head extents;
        struct btrfs_work work;
};

static noinline int add_async_extent(struct async_cow *cow,
                                     u64 start, u64 ram_size,
                                     u64 compressed_size,
                                     struct page **pages,
                                     unsigned long nr_pages)
{
        struct async_extent *async_extent;

        async_extent = kmalloc(sizeof(*async_extent), GFP_NOFS);
        async_extent->start = start;
        async_extent->ram_size = ram_size;
        async_extent->compressed_size = compressed_size;
        async_extent->pages = pages;
        async_extent->nr_pages = nr_pages;
        list_add_tail(&async_extent->list, &cow->extents);
        return 0;
}

/*
 * we create compressed extents in two phases.  The first
 * phase compresses a range of pages that have already been
 * locked (both pages and state bits are locked).
 *
 * This is done inside an ordered work queue, and the compression
 * is spread across many cpus.  The actual IO submission is step
 * two, and the ordered work queue takes care of making sure that
 * happens in the same order things were put onto the queue by
 * writepages and friends.
 *
 * If this code finds it can't get good compression, it puts an
 * entry onto the work queue to write the uncompressed bytes.  This
 * makes sure that both compressed inodes and uncompressed inodes
 * are written in the same order that pdflush sent them down.
 */
static noinline int compress_file_range(struct inode *inode,
                                        struct page *locked_page,
                                        u64 start, u64 end,
                                        struct async_cow *async_cow,
                                        int *num_added)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        u64 num_bytes;
        u64 blocksize = root->sectorsize;
        u64 actual_end;
        u64 isize = i_size_read(inode);
        int ret = 0;
        struct page **pages = NULL;
        unsigned long nr_pages;
        unsigned long nr_pages_ret = 0;
        unsigned long total_compressed = 0;
        unsigned long total_in = 0;
        unsigned long max_compressed = 128 * 1024;
        unsigned long max_uncompressed = 128 * 1024;
        int i;
        int will_compress;

        actual_end = min_t(u64, isize, end + 1);
again:
        will_compress = 0;
        nr_pages = (end >> PAGE_CACHE_SHIFT) - (start >> PAGE_CACHE_SHIFT) + 1;
        nr_pages = min(nr_pages, (128 * 1024UL) / PAGE_CACHE_SIZE);

        /*
         * we don't want to send crud past the end of i_size through
         * compression, that's just a waste of CPU time.  So, if the
         * end of the file is before the start of our current
         * requested range of bytes, we bail out to the uncompressed
         * cleanup code that can deal with all of this.
         *
         * It isn't really the fastest way to fix things, but this is a
         * very uncommon corner.
         */
        if (actual_end <= start)
                goto cleanup_and_bail_uncompressed;

        total_compressed = actual_end - start;

        /* we want to make sure that amount of ram required to uncompress
         * an extent is reasonable, so we limit the total size in ram
         * of a compressed extent to 128k.  This is a crucial number
         * because it also controls how easily we can spread reads across
         * cpus for decompression.
         *
         * We also want to make sure the amount of IO required to do
         * a random read is reasonably small, so we limit the size of
         * a compressed extent to 128k.
         */
        total_compressed = min(total_compressed, max_uncompressed);
        num_bytes = (end - start + blocksize) & ~(blocksize - 1);
        num_bytes = max(blocksize,  num_bytes);
        total_in = 0;
        ret = 0;

        /*
         * we do compression for mount -o compress and when the
         * inode has not been flagged as nocompress.  This flag can
         * change at any time if we discover bad compression ratios.
         */
        if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS) &&
            (btrfs_test_opt(root, COMPRESS) ||
             (BTRFS_I(inode)->force_compress))) {
                WARN_ON(pages);
                pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);

                ret = btrfs_zlib_compress_pages(inode->i_mapping, start,
                                                total_compressed, pages,
                                                nr_pages, &nr_pages_ret,
                                                &total_in,
                                                &total_compressed,
                                                max_compressed);

                if (!ret) {
                        unsigned long offset = total_compressed &
                                (PAGE_CACHE_SIZE - 1);
                        struct page *page = pages[nr_pages_ret - 1];
                        char *kaddr;

                        /* zero the tail end of the last page, we might be
                         * sending it down to disk
                         */
                        if (offset) {
                                kaddr = kmap_atomic(page, KM_USER0);
                                memset(kaddr + offset, 0,
                                       PAGE_CACHE_SIZE - offset);
                                kunmap_atomic(kaddr, KM_USER0);
                        }
                        will_compress = 1;
                }
        }
        if (start == 0) {
                trans = btrfs_join_transaction(root, 1);
                BUG_ON(!trans);
                btrfs_set_trans_block_group(trans, inode);
                trans->block_rsv = &root->fs_info->delalloc_block_rsv;

                /* lets try to make an inline extent */
                if (ret || total_in < (actual_end - start)) {
                        /* we didn't compress the entire range, try
                         * to make an uncompressed inline extent.
                         */
                        ret = cow_file_range_inline(trans, root, inode,
                                                    start, end, 0, NULL);
                } else {
                        /* try making a compressed inline extent */
                        ret = cow_file_range_inline(trans, root, inode,
                                                    start, end,
                                                    total_compressed, pages);
                }
                if (ret == 0) {
                        /*
                         * inline extent creation worked, we don't need
                         * to create any more async work items.  Unlock
                         * and free up our temp pages.
                         */
                        extent_clear_unlock_delalloc(inode,
                             &BTRFS_I(inode)->io_tree,
                             start, end, NULL,
                             EXTENT_CLEAR_UNLOCK_PAGE | EXTENT_CLEAR_DIRTY |
                             EXTENT_CLEAR_DELALLOC |
                             EXTENT_SET_WRITEBACK | EXTENT_END_WRITEBACK);

                        btrfs_end_transaction(trans, root);
                        goto free_pages_out;
                }
                btrfs_end_transaction(trans, root);
        }

        if (will_compress) {
                /*
                 * we aren't doing an inline extent round the compressed size
                 * up to a block size boundary so the allocator does sane
                 * things
                 */
                total_compressed = (total_compressed + blocksize - 1) &
                        ~(blocksize - 1);

                /*
                 * one last check to make sure the compression is really a
                 * win, compare the page count read with the blocks on disk
                 */
                total_in = (total_in + PAGE_CACHE_SIZE - 1) &
                        ~(PAGE_CACHE_SIZE - 1);
                if (total_compressed >= total_in) {
                        will_compress = 0;
                } else {
                        num_bytes = total_in;
                }
        }
        if (!will_compress && pages) {
                /*
                 * the compression code ran but failed to make things smaller,
                 * free any pages it allocated and our page pointer array
                 */
                for (i = 0; i < nr_pages_ret; i++) {
                        WARN_ON(pages[i]->mapping);
                        page_cache_release(pages[i]);
                }
                kfree(pages);
                pages = NULL;
                total_compressed = 0;
                nr_pages_ret = 0;

                /* flag the file so we don't compress in the future */
                if (!btrfs_test_opt(root, FORCE_COMPRESS) &&
                    !(BTRFS_I(inode)->force_compress)) {
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NOCOMPRESS;
                }
        }
        if (will_compress) {
                *num_added += 1;

                /* the async work queues will take care of doing actual
                 * allocation on disk for these compressed pages,
                 * and will submit them to the elevator.
                 */
                add_async_extent(async_cow, start, num_bytes,
                                 total_compressed, pages, nr_pages_ret);

                if (start + num_bytes < end) {
                        start += num_bytes;
                        pages = NULL;
                        cond_resched();
                        goto again;
                }
        } else {
cleanup_and_bail_uncompressed:
                /*
                 * No compression, but we still need to write the pages in
                 * the file we've been given so far.  redirty the locked
                 * page if it corresponds to our extent and set things up
                 * for the async work queue to run cow_file_range to do
                 * the normal delalloc dance
                 */
                if (page_offset(locked_page) >= start &&
                    page_offset(locked_page) <= end) {
                        __set_page_dirty_nobuffers(locked_page);
                        /* unlocked later on in the async handlers */
                }
                add_async_extent(async_cow, start, end - start + 1, 0, NULL, 0);
                *num_added += 1;
        }

out:
        return 0;

free_pages_out:
        for (i = 0; i < nr_pages_ret; i++) {
                WARN_ON(pages[i]->mapping);
                page_cache_release(pages[i]);
        }
        kfree(pages);

        goto out;
}

/*
 * phase two of compressed writeback.  This is the ordered portion
 * of the code, which only gets called in the order the work was
 * queued.  We walk all the async extents created by compress_file_range
 * and send them down to the disk.
 */
static noinline int submit_compressed_extents(struct inode *inode,
                                              struct async_cow *async_cow)
{
        struct async_extent *async_extent;
        u64 alloc_hint = 0;
        struct btrfs_trans_handle *trans;
        struct btrfs_key ins;
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_io_tree *io_tree;
        int ret = 0;

        if (list_empty(&async_cow->extents))
                return 0;


        while (!list_empty(&async_cow->extents)) {
                async_extent = list_entry(async_cow->extents.next,
                                          struct async_extent, list);
                list_del(&async_extent->list);

                io_tree = &BTRFS_I(inode)->io_tree;

retry:
                /* did the compression code fall back to uncompressed IO? */
                if (!async_extent->pages) {
                        int page_started = 0;
                        unsigned long nr_written = 0;

                        lock_extent(io_tree, async_extent->start,
                                         async_extent->start +
                                         async_extent->ram_size - 1, GFP_NOFS);

                        /* allocate blocks */
                        ret = cow_file_range(inode, async_cow->locked_page,
                                             async_extent->start,
                                             async_extent->start +
                                             async_extent->ram_size - 1,
                                             &page_started, &nr_written, 0);

                        /*
                         * if page_started, cow_file_range inserted an
                         * inline extent and took care of all the unlocking
                         * and IO for us.  Otherwise, we need to submit
                         * all those pages down to the drive.
                         */
                        if (!page_started && !ret)
                                extent_write_locked_range(io_tree,
                                                  inode, async_extent->start,
                                                  async_extent->start +
                                                  async_extent->ram_size - 1,
                                                  btrfs_get_extent,
                                                  WB_SYNC_ALL);
                        kfree(async_extent);
                        cond_resched();
                        continue;
                }

                lock_extent(io_tree, async_extent->start,
                            async_extent->start + async_extent->ram_size - 1,
                            GFP_NOFS);

                trans = btrfs_join_transaction(root, 1);
                ret = btrfs_reserve_extent(trans, root,
                                           async_extent->compressed_size,
                                           async_extent->compressed_size,
                                           0, alloc_hint,
                                           (u64)-1, &ins, 1);
                btrfs_end_transaction(trans, root);

                if (ret) {
                        int i;
                        for (i = 0; i < async_extent->nr_pages; i++) {
                                WARN_ON(async_extent->pages[i]->mapping);
                                page_cache_release(async_extent->pages[i]);
                        }
                        kfree(async_extent->pages);
                        async_extent->nr_pages = 0;
                        async_extent->pages = NULL;
                        unlock_extent(io_tree, async_extent->start,
                                      async_extent->start +
                                      async_extent->ram_size - 1, GFP_NOFS);
                        goto retry;
                }

                /*
                 * here we're doing allocation and writeback of the
                 * compressed pages
                 */
                btrfs_drop_extent_cache(inode, async_extent->start,
                                        async_extent->start +
                                        async_extent->ram_size - 1, 0);

                em = alloc_extent_map(GFP_NOFS);
                em->start = async_extent->start;
                em->len = async_extent->ram_size;
                em->orig_start = em->start;

                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                set_bit(EXTENT_FLAG_PINNED, &em->flags);
                set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST) {
                                free_extent_map(em);
                                break;
                        }
                        btrfs_drop_extent_cache(inode, async_extent->start,
                                                async_extent->start +
                                                async_extent->ram_size - 1, 0);
                }

                ret = btrfs_add_ordered_extent(inode, async_extent->start,
                                               ins.objectid,
                                               async_extent->ram_size,
                                               ins.offset,
                                               BTRFS_ORDERED_COMPRESSED);
                BUG_ON(ret);

                /*
                 * clear dirty, set writeback and unlock the pages.
                 */
                extent_clear_unlock_delalloc(inode,
                                &BTRFS_I(inode)->io_tree,
                                async_extent->start,
                                async_extent->start +
                                async_extent->ram_size - 1,
                                NULL, EXTENT_CLEAR_UNLOCK_PAGE |
                                EXTENT_CLEAR_UNLOCK |
                                EXTENT_CLEAR_DELALLOC |
                                EXTENT_CLEAR_DIRTY | EXTENT_SET_WRITEBACK);

                ret = btrfs_submit_compressed_write(inode,
                                    async_extent->start,
                                    async_extent->ram_size,
                                    ins.objectid,
                                    ins.offset, async_extent->pages,
                                    async_extent->nr_pages);

                BUG_ON(ret);
                alloc_hint = ins.objectid + ins.offset;
                kfree(async_extent);
                cond_resched();
        }

        return 0;
}

static u64 get_extent_allocation_hint(struct inode *inode, u64 start,
                                      u64 num_bytes)
{
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_map *em;
        u64 alloc_hint = 0;

        read_lock(&em_tree->lock);
        em = search_extent_mapping(em_tree, start, num_bytes);
        if (em) {
                /*
                 * if block start isn't an actual block number then find the
                 * first block in this inode and use that as a hint.  If that
                 * block is also bogus then just don't worry about it.
                 */
                if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
                        free_extent_map(em);
                        em = search_extent_mapping(em_tree, 0, 0);
                        if (em && em->block_start < EXTENT_MAP_LAST_BYTE)
                                alloc_hint = em->block_start;
                        if (em)
                                free_extent_map(em);
                } else {
                        alloc_hint = em->block_start;
                        free_extent_map(em);
                }
        }
        read_unlock(&em_tree->lock);

        return alloc_hint;
}

/*
 * when extent_io.c finds a delayed allocation range in the file,
 * the call backs end up in this code.  The basic idea is to
 * allocate extents on disk for the range, and create ordered data structs
 * in ram to track those extents.
 *
 * locked_page is the page that writepage had locked already.  We use
 * it to make sure we don't do extra locks or unlocks.
 *
 * *page_started is set to one if we unlock locked_page and do everything
 * required to start IO on it.  It may be clean and already done with
 * IO when we return.
 */
static noinline int cow_file_range(struct inode *inode,
                                   struct page *locked_page,
                                   u64 start, u64 end, int *page_started,
                                   unsigned long *nr_written,
                                   int unlock)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        u64 alloc_hint = 0;
        u64 num_bytes;
        unsigned long ram_size;
        u64 disk_num_bytes;
        u64 cur_alloc_size;
        u64 blocksize = root->sectorsize;
        struct btrfs_key ins;
        struct extent_map *em;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        int ret = 0;

        BUG_ON(root == root->fs_info->tree_root);
        trans = btrfs_join_transaction(root, 1);
        BUG_ON(!trans);
        btrfs_set_trans_block_group(trans, inode);
        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        num_bytes = (end - start + blocksize) & ~(blocksize - 1);
        num_bytes = max(blocksize,  num_bytes);
        disk_num_bytes = num_bytes;
        ret = 0;

        if (start == 0) {
                /* lets try to make an inline extent */
                ret = cow_file_range_inline(trans, root, inode,
                                            start, end, 0, NULL);
                if (ret == 0) {
                        extent_clear_unlock_delalloc(inode,
                                     &BTRFS_I(inode)->io_tree,
                                     start, end, NULL,
                                     EXTENT_CLEAR_UNLOCK_PAGE |
                                     EXTENT_CLEAR_UNLOCK |
                                     EXTENT_CLEAR_DELALLOC |
                                     EXTENT_CLEAR_DIRTY |
                                     EXTENT_SET_WRITEBACK |
                                     EXTENT_END_WRITEBACK);

                        *nr_written = *nr_written +
                             (end - start + PAGE_CACHE_SIZE) / PAGE_CACHE_SIZE;
                        *page_started = 1;
                        ret = 0;
                        goto out;
                }
        }

        BUG_ON(disk_num_bytes >
               btrfs_super_total_bytes(&root->fs_info->super_copy));

        alloc_hint = get_extent_allocation_hint(inode, start, num_bytes);
        btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);

        while (disk_num_bytes > 0) {
                unsigned long op;

                cur_alloc_size = disk_num_bytes;
                ret = btrfs_reserve_extent(trans, root, cur_alloc_size,
                                           root->sectorsize, 0, alloc_hint,
                                           (u64)-1, &ins, 1);
                BUG_ON(ret);

                em = alloc_extent_map(GFP_NOFS);
                em->start = start;
                em->orig_start = em->start;
                ram_size = ins.offset;
                em->len = ins.offset;

                em->block_start = ins.objectid;
                em->block_len = ins.offset;
                em->bdev = root->fs_info->fs_devices->latest_bdev;
                set_bit(EXTENT_FLAG_PINNED, &em->flags);

                while (1) {
                        write_lock(&em_tree->lock);
                        ret = add_extent_mapping(em_tree, em);
                        write_unlock(&em_tree->lock);
                        if (ret != -EEXIST) {
                                free_extent_map(em);
                                break;
                        }
                        btrfs_drop_extent_cache(inode, start,
                                                start + ram_size - 1, 0);
                }

                cur_alloc_size = ins.offset;
                ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
                                               ram_size, cur_alloc_size, 0);
                BUG_ON(ret);

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
                        ret = btrfs_reloc_clone_csums(inode, start,
                                                      cur_alloc_size);
                        BUG_ON(ret);
                }

                if (disk_num_bytes < cur_alloc_size)
                        break;

                /* we're not doing compressed IO, don't unlock the first
                 * page (which the caller expects to stay locked), don't
                 * clear any dirty bits and don't set any writeback bits
                 *
                 * Do set the Private2 bit so we know this page was properly
                 * setup for writepage
                 */
                op = unlock ? EXTENT_CLEAR_UNLOCK_PAGE : 0;
                op |= EXTENT_CLEAR_UNLOCK | EXTENT_CLEAR_DELALLOC |
                        EXTENT_SET_PRIVATE2;

                extent_clear_unlock_delalloc(inode, &BTRFS_I(inode)->io_tree,
                                             start, start + ram_size - 1,
                                             locked_page, op);
                disk_num_bytes -= cur_alloc_size;
                num_bytes -= cur_alloc_size;
                alloc_hint = ins.objectid + ins.offset;
                start += cur_alloc_size;
        }
out:
        ret = 0;
        btrfs_end_transaction(trans, root);

        return ret;
}

/*
 * work queue call back to started compression on a file and pages
 */
static noinline void async_cow_start(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        int num_added = 0;
        async_cow = container_of(work, struct async_cow, work);

        compress_file_range(async_cow->inode, async_cow->locked_page,
                            async_cow->start, async_cow->end, async_cow,
                            &num_added);
        if (num_added == 0)
                async_cow->inode = NULL;
}

/*
 * work queue call back to submit previously compressed pages
 */
static noinline void async_cow_submit(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        struct btrfs_root *root;
        unsigned long nr_pages;

        async_cow = container_of(work, struct async_cow, work);

        root = async_cow->root;
        nr_pages = (async_cow->end - async_cow->start + PAGE_CACHE_SIZE) >>
                PAGE_CACHE_SHIFT;

        atomic_sub(nr_pages, &root->fs_info->async_delalloc_pages);

        if (atomic_read(&root->fs_info->async_delalloc_pages) <
            5 * 1042 * 1024 &&
            waitqueue_active(&root->fs_info->async_submit_wait))
                wake_up(&root->fs_info->async_submit_wait);

        if (async_cow->inode)
                submit_compressed_extents(async_cow->inode, async_cow);
}

static noinline void async_cow_free(struct btrfs_work *work)
{
        struct async_cow *async_cow;
        async_cow = container_of(work, struct async_cow, work);
        kfree(async_cow);
}

static int cow_file_range_async(struct inode *inode, struct page *locked_page,
                                u64 start, u64 end, int *page_started,
                                unsigned long *nr_written)
{
        struct async_cow *async_cow;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        unsigned long nr_pages;
        u64 cur_end;
        int limit = 10 * 1024 * 1042;

        clear_extent_bit(&BTRFS_I(inode)->io_tree, start, end, EXTENT_LOCKED,
                         1, 0, NULL, GFP_NOFS);
        while (start < end) {
                async_cow = kmalloc(sizeof(*async_cow), GFP_NOFS);
                async_cow->inode = inode;
                async_cow->root = root;
                async_cow->locked_page = locked_page;
                async_cow->start = start;

                if (BTRFS_I(inode)->flags & BTRFS_INODE_NOCOMPRESS)
                        cur_end = end;
                else
                        cur_end = min(end, start + 512 * 1024 - 1);

                async_cow->end = cur_end;
                INIT_LIST_HEAD(&async_cow->extents);

                async_cow->work.func = async_cow_start;
                async_cow->work.ordered_func = async_cow_submit;
                async_cow->work.ordered_free = async_cow_free;
                async_cow->work.flags = 0;

                nr_pages = (cur_end - start + PAGE_CACHE_SIZE) >>
                        PAGE_CACHE_SHIFT;
                atomic_add(nr_pages, &root->fs_info->async_delalloc_pages);

                btrfs_queue_worker(&root->fs_info->delalloc_workers,
                                   &async_cow->work);

                if (atomic_read(&root->fs_info->async_delalloc_pages) > limit) {
                        wait_event(root->fs_info->async_submit_wait,
                           (atomic_read(&root->fs_info->async_delalloc_pages) <
                            limit));
                }

                while (atomic_read(&root->fs_info->async_submit_draining) &&
                      atomic_read(&root->fs_info->async_delalloc_pages)) {
                        wait_event(root->fs_info->async_submit_wait,
                          (atomic_read(&root->fs_info->async_delalloc_pages) ==
                           0));
                }

                *nr_written += nr_pages;
                start = cur_end + 1;
        }
        *page_started = 1;
        return 0;
}

static noinline int csum_exist_in_range(struct btrfs_root *root,
                                        u64 bytenr, u64 num_bytes)
{
        int ret;
        struct btrfs_ordered_sum *sums;
        LIST_HEAD(list);

        ret = btrfs_lookup_csums_range(root->fs_info->csum_root, bytenr,
                                       bytenr + num_bytes - 1, &list);
        if (ret == 0 && list_empty(&list))
                return 0;

        while (!list_empty(&list)) {
                sums = list_entry(list.next, struct btrfs_ordered_sum, list);
                list_del(&sums->list);
                kfree(sums);
        }
        return 1;
}

/*
 * when nowcow writeback call back.  This checks for snapshots or COW copies
 * of the extents that exist in the file, and COWs the file as required.
 *
 * If no cow copies or snapshots exist, we write directly to the existing
 * blocks on disk
 */
static noinline int run_delalloc_nocow(struct inode *inode,
                                       struct page *locked_page,
                              u64 start, u64 end, int *page_started, int force,
                              unsigned long *nr_written)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key found_key;
        u64 cow_start;
        u64 cur_offset;
        u64 extent_end;
        u64 extent_offset;
        u64 disk_bytenr;
        u64 num_bytes;
        int extent_type;
        int ret;
        int type;
        int nocow;
        int check_prev = 1;
        bool nolock = false;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        if (root == root->fs_info->tree_root) {
                nolock = true;
                trans = btrfs_join_transaction_nolock(root, 1);
        } else {
                trans = btrfs_join_transaction(root, 1);
        }
        BUG_ON(!trans);

        cow_start = (u64)-1;
        cur_offset = start;
        while (1) {
                ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
                                               cur_offset, 0);
                BUG_ON(ret < 0);
                if (ret > 0 && path->slots[0] > 0 && check_prev) {
                        leaf = path->nodes[0];
                        btrfs_item_key_to_cpu(leaf, &found_key,
                                              path->slots[0] - 1);
                        if (found_key.objectid == inode->i_ino &&
                            found_key.type == BTRFS_EXTENT_DATA_KEY)
                                path->slots[0]--;
                }
                check_prev = 0;
next_slot:
                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                BUG_ON(1);
                        if (ret > 0)
                                break;
                        leaf = path->nodes[0];
                }

                nocow = 0;
                disk_bytenr = 0;
                num_bytes = 0;
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                if (found_key.objectid > inode->i_ino ||
                    found_key.type > BTRFS_EXTENT_DATA_KEY ||
                    found_key.offset > end)
                        break;

                if (found_key.offset > cur_offset) {
                        extent_end = found_key.offset;
                        extent_type = 0;
                        goto out_check;
                }

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_type = btrfs_file_extent_type(leaf, fi);

                if (extent_type == BTRFS_FILE_EXTENT_REG ||
                    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                        extent_offset = btrfs_file_extent_offset(leaf, fi);
                        extent_end = found_key.offset +
                                btrfs_file_extent_num_bytes(leaf, fi);
                        if (extent_end <= start) {
                                path->slots[0]++;
                                goto next_slot;
                        }
                        if (disk_bytenr == 0)
                                goto out_check;
                        if (btrfs_file_extent_compression(leaf, fi) ||
                            btrfs_file_extent_encryption(leaf, fi) ||
                            btrfs_file_extent_other_encoding(leaf, fi))
                                goto out_check;
                        if (extent_type == BTRFS_FILE_EXTENT_REG && !force)
                                goto out_check;
                        if (btrfs_extent_readonly(root, disk_bytenr))
                                goto out_check;
                        if (btrfs_cross_ref_exist(trans, root, inode->i_ino,
                                                  found_key.offset -
                                                  extent_offset, disk_bytenr))
                                goto out_check;
                        disk_bytenr += extent_offset;
                        disk_bytenr += cur_offset - found_key.offset;
                        num_bytes = min(end + 1, extent_end) - cur_offset;
                        /*
                         * force cow if csum exists in the range.
                         * this ensure that csum for a given extent are
                         * either valid or do not exist.
                         */
                        if (csum_exist_in_range(root, disk_bytenr, num_bytes))
                                goto out_check;
                        nocow = 1;
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        extent_end = found_key.offset +
                                btrfs_file_extent_inline_len(leaf, fi);
                        extent_end = ALIGN(extent_end, root->sectorsize);
                } else {
                        BUG_ON(1);
                }
out_check:
                if (extent_end <= start) {
                        path->slots[0]++;
                        goto next_slot;
                }
                if (!nocow) {
                        if (cow_start == (u64)-1)
                                cow_start = cur_offset;
                        cur_offset = extent_end;
                        if (cur_offset > end)
                                break;
                        path->slots[0]++;
                        goto next_slot;
                }

                btrfs_release_path(root, path);
                if (cow_start != (u64)-1) {
                        ret = cow_file_range(inode, locked_page, cow_start,
                                        found_key.offset - 1, page_started,
                                        nr_written, 1);
                        BUG_ON(ret);
                        cow_start = (u64)-1;
                }

                if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        struct extent_map *em;
                        struct extent_map_tree *em_tree;
                        em_tree = &BTRFS_I(inode)->extent_tree;
                        em = alloc_extent_map(GFP_NOFS);
                        em->start = cur_offset;
                        em->orig_start = em->start;
                        em->len = num_bytes;
                        em->block_len = num_bytes;
                        em->block_start = disk_bytenr;
                        em->bdev = root->fs_info->fs_devices->latest_bdev;
                        set_bit(EXTENT_FLAG_PINNED, &em->flags);
                        while (1) {
                                write_lock(&em_tree->lock);
                                ret = add_extent_mapping(em_tree, em);
                                write_unlock(&em_tree->lock);
                                if (ret != -EEXIST) {
                                        free_extent_map(em);
                                        break;
                                }
                                btrfs_drop_extent_cache(inode, em->start,
                                                em->start + em->len - 1, 0);
                        }
                        type = BTRFS_ORDERED_PREALLOC;
                } else {
                        type = BTRFS_ORDERED_NOCOW;
                }

                ret = btrfs_add_ordered_extent(inode, cur_offset, disk_bytenr,
                                               num_bytes, num_bytes, type);
                BUG_ON(ret);

                if (root->root_key.objectid ==
                    BTRFS_DATA_RELOC_TREE_OBJECTID) {
                        ret = btrfs_reloc_clone_csums(inode, cur_offset,
                                                      num_bytes);
                        BUG_ON(ret);
                }

                extent_clear_unlock_delalloc(inode, &BTRFS_I(inode)->io_tree,
                                cur_offset, cur_offset + num_bytes - 1,
                                locked_page, EXTENT_CLEAR_UNLOCK_PAGE |
                                EXTENT_CLEAR_UNLOCK | EXTENT_CLEAR_DELALLOC |
                                EXTENT_SET_PRIVATE2);
                cur_offset = extent_end;
                if (cur_offset > end)
                        break;
        }
        btrfs_release_path(root, path);

        if (cur_offset <= end && cow_start == (u64)-1)
                cow_start = cur_offset;
        if (cow_start != (u64)-1) {
                ret = cow_file_range(inode, locked_page, cow_start, end,
                                     page_started, nr_written, 1);
                BUG_ON(ret);
        }

        if (nolock) {
                ret = btrfs_end_transaction_nolock(trans, root);
                BUG_ON(ret);
        } else {
                ret = btrfs_end_transaction(trans, root);
                BUG_ON(ret);
        }
        btrfs_free_path(path);
        return 0;
}

/*
 * extent_io.c call back to do delayed allocation processing
 */
static int run_delalloc_range(struct inode *inode, struct page *locked_page,
                              u64 start, u64 end, int *page_started,
                              unsigned long *nr_written)
{
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW)
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 1, nr_written);
        else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC)
                ret = run_delalloc_nocow(inode, locked_page, start, end,
                                         page_started, 0, nr_written);
        else if (!btrfs_test_opt(root, COMPRESS) &&
                 !(BTRFS_I(inode)->force_compress))
                ret = cow_file_range(inode, locked_page, start, end,
                                      page_started, nr_written, 1);
        else
                ret = cow_file_range_async(inode, locked_page, start, end,
                                           page_started, nr_written);
        return ret;
}

static int btrfs_split_extent_hook(struct inode *inode,
                                   struct extent_state *orig, u64 split)
{
        /* not delalloc, ignore it */
        if (!(orig->state & EXTENT_DELALLOC))
                return 0;

        atomic_inc(&BTRFS_I(inode)->outstanding_extents);
        return 0;
}

/*
 * extent_io.c merge_extent_hook, used to track merged delayed allocation
 * extents so we can keep track of new extents that are just merged onto old
 * extents, such as when we are doing sequential writes, so we can properly
 * account for the metadata space we'll need.
 */
static int btrfs_merge_extent_hook(struct inode *inode,
                                   struct extent_state *new,
                                   struct extent_state *other)
{
        /* not delalloc, ignore it */
        if (!(other->state & EXTENT_DELALLOC))
                return 0;

        atomic_dec(&BTRFS_I(inode)->outstanding_extents);
        return 0;
}

/*
 * extent_io.c set_bit_hook, used to track delayed allocation
 * bytes in this file, and to maintain the list of inodes that
 * have pending delalloc work to be done.
 */
static int btrfs_set_bit_hook(struct inode *inode,
                              struct extent_state *state, int *bits)
{

        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testeing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if (!(state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                u64 len = state->end + 1 - state->start;
                int do_list = (root->root_key.objectid !=
                               BTRFS_ROOT_TREE_OBJECTID);

                if (*bits & EXTENT_FIRST_DELALLOC)
                        *bits &= ~EXTENT_FIRST_DELALLOC;
                else
                        atomic_inc(&BTRFS_I(inode)->outstanding_extents);

                spin_lock(&root->fs_info->delalloc_lock);
                BTRFS_I(inode)->delalloc_bytes += len;
                root->fs_info->delalloc_bytes += len;
                if (do_list && list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
                        list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
                                      &root->fs_info->delalloc_inodes);
                }
                spin_unlock(&root->fs_info->delalloc_lock);
        }
        return 0;
}

/*
 * extent_io.c clear_bit_hook, see set_bit_hook for why
 */
static int btrfs_clear_bit_hook(struct inode *inode,
                                struct extent_state *state, int *bits)
{
        /*
         * set_bit and clear bit hooks normally require _irqsave/restore
         * but in this case, we are only testeing for the DELALLOC
         * bit, which is only set or cleared with irqs on
         */
        if ((state->state & EXTENT_DELALLOC) && (*bits & EXTENT_DELALLOC)) {
                struct btrfs_root *root = BTRFS_I(inode)->root;
                u64 len = state->end + 1 - state->start;
                int do_list = (root->root_key.objectid !=
                               BTRFS_ROOT_TREE_OBJECTID);

                if (*bits & EXTENT_FIRST_DELALLOC)
                        *bits &= ~EXTENT_FIRST_DELALLOC;
                else if (!(*bits & EXTENT_DO_ACCOUNTING))
                        atomic_dec(&BTRFS_I(inode)->outstanding_extents);

                if (*bits & EXTENT_DO_ACCOUNTING)
                        btrfs_delalloc_release_metadata(inode, len);

                if (root->root_key.objectid != BTRFS_DATA_RELOC_TREE_OBJECTID
                    && do_list)
                        btrfs_free_reserved_data_space(inode, len);

                spin_lock(&root->fs_info->delalloc_lock);
                root->fs_info->delalloc_bytes -= len;
                BTRFS_I(inode)->delalloc_bytes -= len;

                if (do_list && BTRFS_I(inode)->delalloc_bytes == 0 &&
                    !list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
                        list_del_init(&BTRFS_I(inode)->delalloc_inodes);
                }
                spin_unlock(&root->fs_info->delalloc_lock);
        }
        return 0;
}

/*
 * extent_io.c merge_bio_hook, this must check the chunk tree to make sure
 * we don't create bios that span stripes or chunks
 */
int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
                         size_t size, struct bio *bio,
                         unsigned long bio_flags)
{
        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
        struct btrfs_mapping_tree *map_tree;
        u64 logical = (u64)bio->bi_sector << 9;
        u64 length = 0;
        u64 map_length;
        int ret;

        if (bio_flags & EXTENT_BIO_COMPRESSED)
                return 0;

        length = bio->bi_size;
        map_tree = &root->fs_info->mapping_tree;
        map_length = length;
        ret = btrfs_map_block(map_tree, READ, logical,
                              &map_length, NULL, 0);

        if (map_length < length + size)
                return 1;
        return ret;
}

/*
 * in order to insert checksums into the metadata in large chunks,
 * we wait until bio submission time.   All the pages in the bio are
 * checksummed and sums are attached onto the ordered extent record.
 *
 * At IO completion time the cums attached on the ordered extent record
 * are inserted into the btree
 */
static int __btrfs_submit_bio_start(struct inode *inode, int rw,
                                    struct bio *bio, int mirror_num,
                                    unsigned long bio_flags,
                                    u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;

        ret = btrfs_csum_one_bio(root, inode, bio, 0, 0);
        BUG_ON(ret);
        return 0;
}

/*
 * in order to insert checksums into the metadata in large chunks,
 * we wait until bio submission time.   All the pages in the bio are
 * checksummed and sums are attached onto the ordered extent record.
 *
 * At IO completion time the cums attached on the ordered extent record
 * are inserted into the btree
 */
static int __btrfs_submit_bio_done(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num, unsigned long bio_flags,
                          u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        return btrfs_map_bio(root, rw, bio, mirror_num, 1);
}

/*
 * extent_io.c submission hook. This does the right thing for csum calculation
 * on write, or reading the csums from the tree before a read
 */
static int btrfs_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
                          int mirror_num, unsigned long bio_flags,
                          u64 bio_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;
        int skip_sum;

        skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        if (root == root->fs_info->tree_root)
                ret = btrfs_bio_wq_end_io(root->fs_info, bio, 2);
        else
                ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
        BUG_ON(ret);

        if (!(rw & REQ_WRITE)) {
                if (bio_flags & EXTENT_BIO_COMPRESSED) {
                        return btrfs_submit_compressed_read(inode, bio,
                                                    mirror_num, bio_flags);
                } else if (!skip_sum)
                        btrfs_lookup_bio_sums(root, inode, bio, NULL);
                goto mapit;
        } else if (!skip_sum) {
                /* csum items have already been cloned */
                if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID)
                        goto mapit;
                /* we're doing a write, do the async checksumming */
                return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
                                   inode, rw, bio, mirror_num,
                                   bio_flags, bio_offset,
                                   __btrfs_submit_bio_start,
                                   __btrfs_submit_bio_done);
        }

mapit:
        return btrfs_map_bio(root, rw, bio, mirror_num, 0);
}

/*
 * given a list of ordered sums record them in the inode.  This happens
 * at IO completion time based on sums calculated at bio submission time.
 */
static noinline int add_pending_csums(struct btrfs_trans_handle *trans,
                             struct inode *inode, u64 file_offset,
                             struct list_head *list)
{
        struct btrfs_ordered_sum *sum;

        btrfs_set_trans_block_group(trans, inode);

        list_for_each_entry(sum, list, list) {
                btrfs_csum_file_blocks(trans,
                       BTRFS_I(inode)->root->fs_info->csum_root, sum);
        }
        return 0;
}

int btrfs_set_extent_delalloc(struct inode *inode, u64 start, u64 end,
                              struct extent_state **cached_state)
{
        if ((end & (PAGE_CACHE_SIZE - 1)) == 0)
                WARN_ON(1);
        return set_extent_delalloc(&BTRFS_I(inode)->io_tree, start, end,
                                   cached_state, GFP_NOFS);
}

/* see btrfs_writepage_start_hook for details on why this is required */
struct btrfs_writepage_fixup {
        struct page *page;
        struct btrfs_work work;
};

static void btrfs_writepage_fixup_worker(struct btrfs_work *work)
{
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        struct page *page;
        struct inode *inode;
        u64 page_start;
        u64 page_end;

        fixup = container_of(work, struct btrfs_writepage_fixup, work);
        page = fixup->page;
again:
        lock_page(page);
        if (!page->mapping || !PageDirty(page) || !PageChecked(page)) {
                ClearPageChecked(page);
                goto out_page;
        }

        inode = page->mapping->host;
        page_start = page_offset(page);
        page_end = page_offset(page) + PAGE_CACHE_SIZE - 1;

        lock_extent_bits(&BTRFS_I(inode)->io_tree, page_start, page_end, 0,
                         &cached_state, GFP_NOFS);

        /* already ordered? We're done */
        if (PagePrivate2(page))
                goto out;

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start,
                                     page_end, &cached_state, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                goto again;
        }

        BUG();
        btrfs_set_extent_delalloc(inode, page_start, page_end, &cached_state);
        ClearPageChecked(page);
out:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, page_start, page_end,
                             &cached_state, GFP_NOFS);
out_page:
        unlock_page(page);
        page_cache_release(page);
}

/*
 * There are a few paths in the higher layers of the kernel that directly
 * set the page dirty bit without asking the filesystem if it is a
 * good idea.  This causes problems because we want to make sure COW
 * properly happens and the data=ordered rules are followed.
 *
 * In our case any range that doesn't have the ORDERED bit set
 * hasn't been properly setup for IO.  We kick off an async process
 * to fix it up.  The async helper will wait for ordered extents, set
 * the delalloc bit and make it safe to write the page.
 */
static int btrfs_writepage_start_hook(struct page *page, u64 start, u64 end)
{
        struct inode *inode = page->mapping->host;
        struct btrfs_writepage_fixup *fixup;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        /* this page is properly in the ordered list */
        if (TestClearPagePrivate2(page))
                return 0;

        if (PageChecked(page))
                return -EAGAIN;

        fixup = kzalloc(sizeof(*fixup), GFP_NOFS);
        if (!fixup)
                return -EAGAIN;

        SetPageChecked(page);
        page_cache_get(page);
        fixup->work.func = btrfs_writepage_fixup_worker;
        fixup->page = page;
        btrfs_queue_worker(&root->fs_info->fixup_workers, &fixup->work);
        return -EAGAIN;
}

static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
                                       struct inode *inode, u64 file_pos,
                                       u64 disk_bytenr, u64 disk_num_bytes,
                                       u64 num_bytes, u64 ram_bytes,
                                       u8 compression, u8 encryption,
                                       u16 other_encoding, int extent_type)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *fi;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key ins;
        u64 hint;
        int ret;

        path = btrfs_alloc_path();
        BUG_ON(!path);

        path->leave_spinning = 1;

        /*
         * we may be replacing one extent in the tree with another.
         * The new extent is pinned in the extent map, and we don't want
         * to drop it from the cache until it is completely in the btree.
         *
         * So, tell btrfs_drop_extents to leave this extent in the cache.
         * the caller is expected to unpin it and allow it to be merged
         * with the others.
         */
        ret = btrfs_drop_extents(trans, inode, file_pos, file_pos + num_bytes,
                                 &hint, 0);
        BUG_ON(ret);

        ins.objectid = inode->i_ino;
        ins.offset = file_pos;
        ins.type = BTRFS_EXTENT_DATA_KEY;
        ret = btrfs_insert_empty_item(trans, root, path, &ins, sizeof(*fi));
        BUG_ON(ret);
        leaf = path->nodes[0];
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, fi, trans->transid);
        btrfs_set_file_extent_type(leaf, fi, extent_type);
        btrfs_set_file_extent_disk_bytenr(leaf, fi, disk_bytenr);
        btrfs_set_file_extent_disk_num_bytes(leaf, fi, disk_num_bytes);
        btrfs_set_file_extent_offset(leaf, fi, 0);
        btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
        btrfs_set_file_extent_ram_bytes(leaf, fi, ram_bytes);
        btrfs_set_file_extent_compression(leaf, fi, compression);
        btrfs_set_file_extent_encryption(leaf, fi, encryption);
        btrfs_set_file_extent_other_encoding(leaf, fi, other_encoding);

        btrfs_unlock_up_safe(path, 1);
        btrfs_set_lock_blocking(leaf);

        btrfs_mark_buffer_dirty(leaf);

        inode_add_bytes(inode, num_bytes);

        ins.objectid = disk_bytenr;
        ins.offset = disk_num_bytes;
        ins.type = BTRFS_EXTENT_ITEM_KEY;
        ret = btrfs_alloc_reserved_file_extent(trans, root,
                                        root->root_key.objectid,
                                        inode->i_ino, file_pos, &ins);
        BUG_ON(ret);
        btrfs_free_path(path);

        return 0;
}

/*
 * helper function for btrfs_finish_ordered_io, this
 * just reads in some of the csum leaves to prime them into ram
 * before we start the transaction.  It limits the amount of btree
 * reads required while inside the transaction.
 */
/* as ordered data IO finishes, this gets called so we can finish
 * an ordered extent if the range of bytes in the file it covers are
 * fully written.
 */
static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans = NULL;
        struct btrfs_ordered_extent *ordered_extent = NULL;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_state *cached_state = NULL;
        int compressed = 0;
        int ret;
        bool nolock = false;

        ret = btrfs_dec_test_ordered_pending(inode, &ordered_extent, start,
                                             end - start + 1);
        if (!ret)
                return 0;
        BUG_ON(!ordered_extent);

        nolock = (root == root->fs_info->tree_root);

        if (test_bit(BTRFS_ORDERED_NOCOW, &ordered_extent->flags)) {
                BUG_ON(!list_empty(&ordered_extent->list));
                ret = btrfs_ordered_update_i_size(inode, 0, ordered_extent);
                if (!ret) {
                        if (nolock)
                                trans = btrfs_join_transaction_nolock(root, 1);
                        else
                                trans = btrfs_join_transaction(root, 1);
                        BUG_ON(!trans);
                        btrfs_set_trans_block_group(trans, inode);
                        trans->block_rsv = &root->fs_info->delalloc_block_rsv;
                        ret = btrfs_update_inode(trans, root, inode);
                        BUG_ON(ret);
                }
                goto out;
        }

        lock_extent_bits(io_tree, ordered_extent->file_offset,
                         ordered_extent->file_offset + ordered_extent->len - 1,
                         0, &cached_state, GFP_NOFS);

        if (nolock)
                trans = btrfs_join_transaction_nolock(root, 1);
        else
                trans = btrfs_join_transaction(root, 1);
        btrfs_set_trans_block_group(trans, inode);
        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        if (test_bit(BTRFS_ORDERED_COMPRESSED, &ordered_extent->flags))
                compressed = 1;
        if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
                BUG_ON(compressed);
                ret = btrfs_mark_extent_written(trans, inode,
                                                ordered_extent->file_offset,
                                                ordered_extent->file_offset +
                                                ordered_extent->len);
                BUG_ON(ret);
        } else {
                BUG_ON(root == root->fs_info->tree_root);
                ret = insert_reserved_file_extent(trans, inode,
                                                ordered_extent->file_offset,
                                                ordered_extent->start,
                                                ordered_extent->disk_len,
                                                ordered_extent->len,
                                                ordered_extent->len,
                                                compressed, 0, 0,
                                                BTRFS_FILE_EXTENT_REG);
                unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
                                   ordered_extent->file_offset,
                                   ordered_extent->len);
                BUG_ON(ret);
        }
        unlock_extent_cached(io_tree, ordered_extent->file_offset,
                             ordered_extent->file_offset +
                             ordered_extent->len - 1, &cached_state, GFP_NOFS);

        add_pending_csums(trans, inode, ordered_extent->file_offset,
                          &ordered_extent->list);

        btrfs_ordered_update_i_size(inode, 0, ordered_extent);
        ret = btrfs_update_inode(trans, root, inode);
        BUG_ON(ret);
out:
        if (nolock) {
                if (trans)
                        btrfs_end_transaction_nolock(trans, root);
        } else {
                btrfs_delalloc_release_metadata(inode, ordered_extent->len);
                if (trans)
                        btrfs_end_transaction(trans, root);
        }

        /* once for us */
        btrfs_put_ordered_extent(ordered_extent);
        /* once for the tree */
        btrfs_put_ordered_extent(ordered_extent);

        return 0;
}

static int btrfs_writepage_end_io_hook(struct page *page, u64 start, u64 end,
                                struct extent_state *state, int uptodate)
{
        ClearPagePrivate2(page);
        return btrfs_finish_ordered_io(page->mapping->host, start, end);
}

/*
 * When IO fails, either with EIO or csum verification fails, we
 * try other mirrors that might have a good copy of the data.  This
 * io_failure_record is used to record state as we go through all the
 * mirrors.  If another mirror has good data, the page is set up to date
 * and things continue.  If a good mirror can't be found, the original
 * bio end_io callback is called to indicate things have failed.
 */
struct io_failure_record {
        struct page *page;
        u64 start;
        u64 len;
        u64 logical;
        unsigned long bio_flags;
        int last_mirror;
};

static int btrfs_io_failed_hook(struct bio *failed_bio,
                         struct page *page, u64 start, u64 end,
                         struct extent_state *state)
{
        struct io_failure_record *failrec = NULL;
        u64 private;
        struct extent_map *em;
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *failure_tree = &BTRFS_I(inode)->io_failure_tree;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct bio *bio;
        int num_copies;
        int ret;
        int rw;
        u64 logical;

        ret = get_state_private(failure_tree, start, &private);
        if (ret) {
                failrec = kmalloc(sizeof(*failrec), GFP_NOFS);
                if (!failrec)
                        return -ENOMEM;
                failrec->start = start;
                failrec->len = end - start + 1;
                failrec->last_mirror = 0;
                failrec->bio_flags = 0;

                read_lock(&em_tree->lock);
                em = lookup_extent_mapping(em_tree, start, failrec->len);
                if (em->start > start || em->start + em->len < start) {
                        free_extent_map(em);
                        em = NULL;
                }
                read_unlock(&em_tree->lock);

                if (!em || IS_ERR(em)) {
                        kfree(failrec);
                        return -EIO;
                }
                logical = start - em->start;
                logical = em->block_start + logical;
                if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
                        logical = em->block_start;
                        failrec->bio_flags = EXTENT_BIO_COMPRESSED;
                }
                failrec->logical = logical;
                free_extent_map(em);
                set_extent_bits(failure_tree, start, end, EXTENT_LOCKED |
                                EXTENT_DIRTY, GFP_NOFS);
                set_state_private(failure_tree, start,
                                 (u64)(unsigned long)failrec);
        } else {
                failrec = (struct io_failure_record *)(unsigned long)private;
        }
        num_copies = btrfs_num_copies(
                              &BTRFS_I(inode)->root->fs_info->mapping_tree,
                              failrec->logical, failrec->len);
        failrec->last_mirror++;
        if (!state) {
                spin_lock(&BTRFS_I(inode)->io_tree.lock);
                state = find_first_extent_bit_state(&BTRFS_I(inode)->io_tree,
                                                    failrec->start,
                                                    EXTENT_LOCKED);
                if (state && state->start != failrec->start)
                        state = NULL;
                spin_unlock(&BTRFS_I(inode)->io_tree.lock);
        }
        if (!state || failrec->last_mirror > num_copies) {
                set_state_private(failure_tree, failrec->start, 0);
                clear_extent_bits(failure_tree, failrec->start,
                                  failrec->start + failrec->len - 1,
                                  EXTENT_LOCKED | EXTENT_DIRTY, GFP_NOFS);
                kfree(failrec);
                return -EIO;
        }
        bio = bio_alloc(GFP_NOFS, 1);
        bio->bi_private = state;
        bio->bi_end_io = failed_bio->bi_end_io;
        bio->bi_sector = failrec->logical >> 9;
        bio->bi_bdev = failed_bio->bi_bdev;
        bio->bi_size = 0;

        bio_add_page(bio, page, failrec->len, start - page_offset(page));
        if (failed_bio->bi_rw & REQ_WRITE)
                rw = WRITE;
        else
                rw = READ;

        BTRFS_I(inode)->io_tree.ops->submit_bio_hook(inode, rw, bio,
                                                      failrec->last_mirror,
                                                      failrec->bio_flags, 0);
        return 0;
}

/*
 * each time an IO finishes, we do a fast check in the IO failure tree
 * to see if we need to process or clean up an io_failure_record
 */
static int btrfs_clean_io_failures(struct inode *inode, u64 start)
{
        u64 private;
        u64 private_failure;
        struct io_failure_record *failure;
        int ret;

        private = 0;
        if (count_range_bits(&BTRFS_I(inode)->io_failure_tree, &private,
                             (u64)-1, 1, EXTENT_DIRTY)) {
                ret = get_state_private(&BTRFS_I(inode)->io_failure_tree,
                                        start, &private_failure);
                if (ret == 0) {
                        failure = (struct io_failure_record *)(unsigned long)
                                   private_failure;
                        set_state_private(&BTRFS_I(inode)->io_failure_tree,
                                          failure->start, 0);
                        clear_extent_bits(&BTRFS_I(inode)->io_failure_tree,
                                          failure->start,
                                          failure->start + failure->len - 1,
                                          EXTENT_DIRTY | EXTENT_LOCKED,
                                          GFP_NOFS);
                        kfree(failure);
                }
        }
        return 0;
}

/*
 * when reads are done, we need to check csums to verify the data is correct
 * if there's a match, we allow the bio to finish.  If not, we go through
 * the io_failure_record routines to find good copies
 */
static int btrfs_readpage_end_io_hook(struct page *page, u64 start, u64 end,
                               struct extent_state *state)
{
        size_t offset = start - ((u64)page->index << PAGE_CACHE_SHIFT);
        struct inode *inode = page->mapping->host;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        char *kaddr;
        u64 private = ~(u32)0;
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u32 csum = ~(u32)0;

        if (PageChecked(page)) {
                ClearPageChecked(page);
                goto good;
        }

        if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
                return 0;

        if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID &&
            test_range_bit(io_tree, start, end, EXTENT_NODATASUM, 1, NULL)) {
                clear_extent_bits(io_tree, start, end, EXTENT_NODATASUM,
                                  GFP_NOFS);
                return 0;
        }

        if (state && state->start == start) {
                private = state->private;
                ret = 0;
        } else {
                ret = get_state_private(io_tree, start, &private);
        }
        kaddr = kmap_atomic(page, KM_USER0);
        if (ret)
                goto zeroit;

        csum = btrfs_csum_data(root, kaddr + offset, csum,  end - start + 1);
        btrfs_csum_final(csum, (char *)&csum);
        if (csum != private)
                goto zeroit;

        kunmap_atomic(kaddr, KM_USER0);
good:
        /* if the io failure tree for this inode is non-empty,
         * check to see if we've recovered from a failed IO
         */
        btrfs_clean_io_failures(inode, start);
        return 0;

zeroit:
        if (printk_ratelimit()) {
                printk(KERN_INFO "btrfs csum failed ino %lu off %llu csum %u "
                       "private %llu\n", page->mapping->host->i_ino,
                       (unsigned long long)start, csum,
                       (unsigned long long)private);
        }
        memset(kaddr + offset, 1, end - start + 1);
        flush_dcache_page(page);
        kunmap_atomic(kaddr, KM_USER0);
        if (private == 0)
                return 0;
        return -EIO;
}

struct delayed_iput {
        struct list_head list;
        struct inode *inode;
};

void btrfs_add_delayed_iput(struct inode *inode)
{
        struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
        struct delayed_iput *delayed;

        if (atomic_add_unless(&inode->i_count, -1, 1))
                return;

        delayed = kmalloc(sizeof(*delayed), GFP_NOFS | __GFP_NOFAIL);
        delayed->inode = inode;

        spin_lock(&fs_info->delayed_iput_lock);
        list_add_tail(&delayed->list, &fs_info->delayed_iputs);
        spin_unlock(&fs_info->delayed_iput_lock);
}

void btrfs_run_delayed_iputs(struct btrfs_root *root)
{
        LIST_HEAD(list);
        struct btrfs_fs_info *fs_info = root->fs_info;
        struct delayed_iput *delayed;
        int empty;

        spin_lock(&fs_info->delayed_iput_lock);
        empty = list_empty(&fs_info->delayed_iputs);
        spin_unlock(&fs_info->delayed_iput_lock);
        if (empty)
                return;

        down_read(&root->fs_info->cleanup_work_sem);
        spin_lock(&fs_info->delayed_iput_lock);
        list_splice_init(&fs_info->delayed_iputs, &list);
        spin_unlock(&fs_info->delayed_iput_lock);

        while (!list_empty(&list)) {
                delayed = list_entry(list.next, struct delayed_iput, list);
                list_del(&delayed->list);
                iput(delayed->inode);
                kfree(delayed);
        }
        up_read(&root->fs_info->cleanup_work_sem);
}

/*
 * calculate extra metadata reservation when snapshotting a subvolume
 * contains orphan files.
 */
void btrfs_orphan_pre_snapshot(struct btrfs_trans_handle *trans,
                                struct btrfs_pending_snapshot *pending,
                                u64 *bytes_to_reserve)
{
        struct btrfs_root *root;
        struct btrfs_block_rsv *block_rsv;
        u64 num_bytes;
        int index;

        root = pending->root;
        if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
                return;

        block_rsv = root->orphan_block_rsv;

        /* orphan block reservation for the snapshot */
        num_bytes = block_rsv->size;

        /*
         * after the snapshot is created, COWing tree blocks may use more
         * space than it frees. So we should make sure there is enough
         * reserved space.
         */
        index = trans->transid & 0x1;
        if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
                num_bytes += block_rsv->size -
                             (block_rsv->reserved + block_rsv->freed[index]);
        }

        *bytes_to_reserve += num_bytes;
}

void btrfs_orphan_post_snapshot(struct btrfs_trans_handle *trans,
                                struct btrfs_pending_snapshot *pending)
{
        struct btrfs_root *root = pending->root;
        struct btrfs_root *snap = pending->snap;
        struct btrfs_block_rsv *block_rsv;
        u64 num_bytes;
        int index;
        int ret;

        if (!root->orphan_block_rsv || list_empty(&root->orphan_list))
                return;

        /* refill source subvolume's orphan block reservation */
        block_rsv = root->orphan_block_rsv;
        index = trans->transid & 0x1;
        if (block_rsv->reserved + block_rsv->freed[index] < block_rsv->size) {
                num_bytes = block_rsv->size -
                            (block_rsv->reserved + block_rsv->freed[index]);
                ret = btrfs_block_rsv_migrate(&pending->block_rsv,
                                              root->orphan_block_rsv,
                                              num_bytes);
                BUG_ON(ret);
        }

        /* setup orphan block reservation for the snapshot */
        block_rsv = btrfs_alloc_block_rsv(snap);
        BUG_ON(!block_rsv);

        btrfs_add_durable_block_rsv(root->fs_info, block_rsv);
        snap->orphan_block_rsv = block_rsv;

        num_bytes = root->orphan_block_rsv->size;
        ret = btrfs_block_rsv_migrate(&pending->block_rsv,
                                      block_rsv, num_bytes);
        BUG_ON(ret);

#if 0
        /* insert orphan item for the snapshot */
        WARN_ON(!root->orphan_item_inserted);
        ret = btrfs_insert_orphan_item(trans, root->fs_info->tree_root,
                                       snap->root_key.objectid);
        BUG_ON(ret);
        snap->orphan_item_inserted = 1;
#endif
}

enum btrfs_orphan_cleanup_state {
        ORPHAN_CLEANUP_STARTED  = 1,
        ORPHAN_CLEANUP_DONE     = 2,
};

/*
 * This is called in transaction commmit time. If there are no orphan
 * files in the subvolume, it removes orphan item and frees block_rsv
 * structure.
 */
void btrfs_orphan_commit_root(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root)
{
        int ret;

        if (!list_empty(&root->orphan_list) ||
            root->orphan_cleanup_state != ORPHAN_CLEANUP_DONE)
                return;

        if (root->orphan_item_inserted &&
            btrfs_root_refs(&root->root_item) > 0) {
                ret = btrfs_del_orphan_item(trans, root->fs_info->tree_root,
                                            root->root_key.objectid);
                BUG_ON(ret);
                root->orphan_item_inserted = 0;
        }

        if (root->orphan_block_rsv) {
                WARN_ON(root->orphan_block_rsv->size > 0);
                btrfs_free_block_rsv(root, root->orphan_block_rsv);
                root->orphan_block_rsv = NULL;
        }
}

/*
 * This creates an orphan entry for the given inode in case something goes
 * wrong in the middle of an unlink/truncate.
 *
 * NOTE: caller of this function should reserve 5 units of metadata for
 *       this function.
 */
int btrfs_orphan_add(struct btrfs_trans_handle *trans, struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_block_rsv *block_rsv = NULL;
        int reserve = 0;
        int insert = 0;
        int ret;

        if (!root->orphan_block_rsv) {
                block_rsv = btrfs_alloc_block_rsv(root);
                BUG_ON(!block_rsv);
        }

        spin_lock(&root->orphan_lock);
        if (!root->orphan_block_rsv) {
                root->orphan_block_rsv = block_rsv;
        } else if (block_rsv) {
                btrfs_free_block_rsv(root, block_rsv);
                block_rsv = NULL;
        }

        if (list_empty(&BTRFS_I(inode)->i_orphan)) {
                list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);
#if 0
                /*
                 * For proper ENOSPC handling, we should do orphan
                 * cleanup when mounting. But this introduces backward
                 * compatibility issue.
                 */
                if (!xchg(&root->orphan_item_inserted, 1))
                        insert = 2;
                else
                        insert = 1;
#endif
                insert = 1;
        } else {
                WARN_ON(!BTRFS_I(inode)->orphan_meta_reserved);
        }

        if (!BTRFS_I(inode)->orphan_meta_reserved) {
                BTRFS_I(inode)->orphan_meta_reserved = 1;
                reserve = 1;
        }
        spin_unlock(&root->orphan_lock);

        if (block_rsv)
                btrfs_add_durable_block_rsv(root->fs_info, block_rsv);

        /* grab metadata reservation from transaction handle */
        if (reserve) {
                ret = btrfs_orphan_reserve_metadata(trans, inode);
                BUG_ON(ret);
        }

        /* insert an orphan item to track this unlinked/truncated file */
        if (insert >= 1) {
                ret = btrfs_insert_orphan_item(trans, root, inode->i_ino);
                BUG_ON(ret);
        }

        /* insert an orphan item to track subvolume contains orphan files */
        if (insert >= 2) {
                ret = btrfs_insert_orphan_item(trans, root->fs_info->tree_root,
                                               root->root_key.objectid);
                BUG_ON(ret);
        }
        return 0;
}

/*
 * We have done the truncate/delete so we can go ahead and remove the orphan
 * item for this particular inode.
 */
int btrfs_orphan_del(struct btrfs_trans_handle *trans, struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int delete_item = 0;
        int release_rsv = 0;
        int ret = 0;

        spin_lock(&root->orphan_lock);
        if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                list_del_init(&BTRFS_I(inode)->i_orphan);
                delete_item = 1;
        }

        if (BTRFS_I(inode)->orphan_meta_reserved) {
                BTRFS_I(inode)->orphan_meta_reserved = 0;
                release_rsv = 1;
        }
        spin_unlock(&root->orphan_lock);

        if (trans && delete_item) {
                ret = btrfs_del_orphan_item(trans, root, inode->i_ino);
                BUG_ON(ret);
        }

        if (release_rsv)
                btrfs_orphan_release_metadata(inode);

        return 0;
}

/*
 * this cleans up any orphans that may be left on the list from the last use
 * of this root.
 */
void btrfs_orphan_cleanup(struct btrfs_root *root)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_key key, found_key;
        struct btrfs_trans_handle *trans;
        struct inode *inode;
        int ret = 0, nr_unlink = 0, nr_truncate = 0;

        if (cmpxchg(&root->orphan_cleanup_state, 0, ORPHAN_CLEANUP_STARTED))
                return;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        path->reada = -1;

        key.objectid = BTRFS_ORPHAN_OBJECTID;
        btrfs_set_key_type(&key, BTRFS_ORPHAN_ITEM_KEY);
        key.offset = (u64)-1;

        while (1) {
                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
                if (ret < 0) {
                        printk(KERN_ERR "Error searching slot for orphan: %d"
                               "\n", ret);
                        break;
                }

                /*
                 * if ret == 0 means we found what we were searching for, which
                 * is weird, but possible, so only screw with path if we didnt
                 * find the key and see if we have stuff that matches
                 */
                if (ret > 0) {
                        if (path->slots[0] == 0)
                                break;
                        path->slots[0]--;
                }

                /* pull out the item */
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

                /* make sure the item matches what we want */
                if (found_key.objectid != BTRFS_ORPHAN_OBJECTID)
                        break;
                if (btrfs_key_type(&found_key) != BTRFS_ORPHAN_ITEM_KEY)
                        break;

                /* release the path since we're done with it */
                btrfs_release_path(root, path);

                /*
                 * this is where we are basically btrfs_lookup, without the
                 * crossing root thing.  we store the inode number in the
                 * offset of the orphan item.
                 */
                found_key.objectid = found_key.offset;
                found_key.type = BTRFS_INODE_ITEM_KEY;
                found_key.offset = 0;
                inode = btrfs_iget(root->fs_info->sb, &found_key, root, NULL);
                BUG_ON(IS_ERR(inode));

                /*
                 * add this inode to the orphan list so btrfs_orphan_del does
                 * the proper thing when we hit it
                 */
                spin_lock(&root->orphan_lock);
                list_add(&BTRFS_I(inode)->i_orphan, &root->orphan_list);
                spin_unlock(&root->orphan_lock);

                /*
                 * if this is a bad inode, means we actually succeeded in
                 * removing the inode, but not the orphan record, which means
                 * we need to manually delete the orphan since iput will just
                 * do a destroy_inode
                 */
                if (is_bad_inode(inode)) {
                        trans = btrfs_start_transaction(root, 0);
                        btrfs_orphan_del(trans, inode);
                        btrfs_end_transaction(trans, root);
                        iput(inode);
                        continue;
                }

                /* if we have links, this was a truncate, lets do that */
                if (inode->i_nlink) {
                        nr_truncate++;
                        btrfs_truncate(inode);
                } else {
                        nr_unlink++;
                }

                /* this will do delete_inode and everything for us */
                iput(inode);
        }
        btrfs_free_path(path);

        root->orphan_cleanup_state = ORPHAN_CLEANUP_DONE;

        if (root->orphan_block_rsv)
                btrfs_block_rsv_release(root, root->orphan_block_rsv,
                                        (u64)-1);

        if (root->orphan_block_rsv || root->orphan_item_inserted) {
                trans = btrfs_join_transaction(root, 1);
                btrfs_end_transaction(trans, root);
        }

        if (nr_unlink)
                printk(KERN_INFO "btrfs: unlinked %d orphans\n", nr_unlink);
        if (nr_truncate)
                printk(KERN_INFO "btrfs: truncated %d orphans\n", nr_truncate);
}

/*
 * very simple check to peek ahead in the leaf looking for xattrs.  If we
 * don't find any xattrs, we know there can't be any acls.
 *
 * slot is the slot the inode is in, objectid is the objectid of the inode
 */
static noinline int acls_after_inode_item(struct extent_buffer *leaf,
                                          int slot, u64 objectid)
{
        u32 nritems = btrfs_header_nritems(leaf);
        struct btrfs_key found_key;
        int scanned = 0;

        slot++;
        while (slot < nritems) {
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                /* we found a different objectid, there must not be acls */
                if (found_key.objectid != objectid)
                        return 0;

                /* we found an xattr, assume we've got an acl */
                if (found_key.type == BTRFS_XATTR_ITEM_KEY)
                        return 1;

                /*
                 * we found a key greater than an xattr key, there can't
                 * be any acls later on
                 */
                if (found_key.type > BTRFS_XATTR_ITEM_KEY)
                        return 0;

                slot++;
                scanned++;

                /*
                 * it goes inode, inode backrefs, xattrs, extents,
                 * so if there are a ton of hard links to an inode there can
                 * be a lot of backrefs.  Don't waste time searching too hard,
                 * this is just an optimization
                 */
                if (scanned >= 8)
                        break;
        }
        /* we hit the end of the leaf before we found an xattr or
         * something larger than an xattr.  We have to assume the inode
         * has acls
         */
        return 1;
}

/*
 * read an inode from the btree into the in-memory inode
 */
static void btrfs_read_locked_inode(struct inode *inode)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_inode_item *inode_item;
        struct btrfs_timespec *tspec;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key location;
        int maybe_acls;
        u64 alloc_group_block;
        u32 rdev;
        int ret;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        memcpy(&location, &BTRFS_I(inode)->location, sizeof(location));

        ret = btrfs_lookup_inode(NULL, root, path, &location, 0);
        if (ret)
                goto make_bad;

        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_inode_item);

        inode->i_mode = btrfs_inode_mode(leaf, inode_item);
        inode->i_nlink = btrfs_inode_nlink(leaf, inode_item);
        inode->i_uid = btrfs_inode_uid(leaf, inode_item);
        inode->i_gid = btrfs_inode_gid(leaf, inode_item);
        btrfs_i_size_write(inode, btrfs_inode_size(leaf, inode_item));

        tspec = btrfs_inode_atime(inode_item);
        inode->i_atime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_atime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        tspec = btrfs_inode_mtime(inode_item);
        inode->i_mtime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_mtime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        tspec = btrfs_inode_ctime(inode_item);
        inode->i_ctime.tv_sec = btrfs_timespec_sec(leaf, tspec);
        inode->i_ctime.tv_nsec = btrfs_timespec_nsec(leaf, tspec);

        inode_set_bytes(inode, btrfs_inode_nbytes(leaf, inode_item));
        BTRFS_I(inode)->generation = btrfs_inode_generation(leaf, inode_item);
        BTRFS_I(inode)->sequence = btrfs_inode_sequence(leaf, inode_item);
        inode->i_generation = BTRFS_I(inode)->generation;
        inode->i_rdev = 0;
        rdev = btrfs_inode_rdev(leaf, inode_item);

        BTRFS_I(inode)->index_cnt = (u64)-1;
        BTRFS_I(inode)->flags = btrfs_inode_flags(leaf, inode_item);

        alloc_group_block = btrfs_inode_block_group(leaf, inode_item);

        /*
         * try to precache a NULL acl entry for files that don't have
         * any xattrs or acls
         */
        maybe_acls = acls_after_inode_item(leaf, path->slots[0], inode->i_ino);
        if (!maybe_acls)
                cache_no_acl(inode);

        BTRFS_I(inode)->block_group = btrfs_find_block_group(root, 0,
                                                alloc_group_block, 0);
        btrfs_free_path(path);
        inode_item = NULL;

        switch (inode->i_mode & S_IFMT) {
        case S_IFREG:
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                break;
        case S_IFDIR:
                inode->i_fop = &btrfs_dir_file_operations;
                if (root == root->fs_info->tree_root)
                        inode->i_op = &btrfs_dir_ro_inode_operations;
                else
                        inode->i_op = &btrfs_dir_inode_operations;
                break;
        case S_IFLNK:
                inode->i_op = &btrfs_symlink_inode_operations;
                inode->i_mapping->a_ops = &btrfs_symlink_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                break;
        default:
                inode->i_op = &btrfs_special_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                break;
        }

        btrfs_update_iflags(inode);
        return;

make_bad:
        btrfs_free_path(path);
        make_bad_inode(inode);
}

/*
 * given a leaf and an inode, copy the inode fields into the leaf
 */
static void fill_inode_item(struct btrfs_trans_handle *trans,
                            struct extent_buffer *leaf,
                            struct btrfs_inode_item *item,
                            struct inode *inode)
{
        btrfs_set_inode_uid(leaf, item, inode->i_uid);
        btrfs_set_inode_gid(leaf, item, inode->i_gid);
        btrfs_set_inode_size(leaf, item, BTRFS_I(inode)->disk_i_size);
        btrfs_set_inode_mode(leaf, item, inode->i_mode);
        btrfs_set_inode_nlink(leaf, item, inode->i_nlink);

        btrfs_set_timespec_sec(leaf, btrfs_inode_atime(item),
                               inode->i_atime.tv_sec);
        btrfs_set_timespec_nsec(leaf, btrfs_inode_atime(item),
                                inode->i_atime.tv_nsec);

        btrfs_set_timespec_sec(leaf, btrfs_inode_mtime(item),
                               inode->i_mtime.tv_sec);
        btrfs_set_timespec_nsec(leaf, btrfs_inode_mtime(item),
                                inode->i_mtime.tv_nsec);

        btrfs_set_timespec_sec(leaf, btrfs_inode_ctime(item),
                               inode->i_ctime.tv_sec);
        btrfs_set_timespec_nsec(leaf, btrfs_inode_ctime(item),
                                inode->i_ctime.tv_nsec);

        btrfs_set_inode_nbytes(leaf, item, inode_get_bytes(inode));
        btrfs_set_inode_generation(leaf, item, BTRFS_I(inode)->generation);
        btrfs_set_inode_sequence(leaf, item, BTRFS_I(inode)->sequence);
        btrfs_set_inode_transid(leaf, item, trans->transid);
        btrfs_set_inode_rdev(leaf, item, inode->i_rdev);
        btrfs_set_inode_flags(leaf, item, BTRFS_I(inode)->flags);
        btrfs_set_inode_block_group(leaf, item, BTRFS_I(inode)->block_group);
}

/*
 * copy everything in the in-memory inode into the btree.
 */
noinline int btrfs_update_inode(struct btrfs_trans_handle *trans,
                                struct btrfs_root *root, struct inode *inode)
{
        struct btrfs_inode_item *inode_item;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        path->leave_spinning = 1;
        ret = btrfs_lookup_inode(trans, root, path,
                                 &BTRFS_I(inode)->location, 1);
        if (ret) {
                if (ret > 0)
                        ret = -ENOENT;
                goto failed;
        }

        btrfs_unlock_up_safe(path, 1);
        leaf = path->nodes[0];
        inode_item = btrfs_item_ptr(leaf, path->slots[0],
                                  struct btrfs_inode_item);

        fill_inode_item(trans, leaf, inode_item, inode);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_set_inode_last_trans(trans, inode);
        ret = 0;
failed:
        btrfs_free_path(path);
        return ret;
}


/*
 * unlink helper that gets used here in inode.c and in the tree logging
 * recovery code.  It remove a link in a directory with a given name, and
 * also drops the back refs in the inode to the directory
 */
int btrfs_unlink_inode(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root,
                       struct inode *dir, struct inode *inode,
                       const char *name, int name_len)
{
        struct btrfs_path *path;
        int ret = 0;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 index;

        path = btrfs_alloc_path();
        if (!path) {
                ret = -ENOMEM;
                goto err;
        }

        path->leave_spinning = 1;
        di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
                                    name, name_len, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto err;
        }
        if (!di) {
                ret = -ENOENT;
                goto err;
        }
        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        if (ret)
                goto err;
        btrfs_release_path(root, path);

        ret = btrfs_del_inode_ref(trans, root, name, name_len,
                                  inode->i_ino,
                                  dir->i_ino, &index);
        if (ret) {
                printk(KERN_INFO "btrfs failed to delete reference to %.*s, "
                       "inode %lu parent %lu\n", name_len, name,
                       inode->i_ino, dir->i_ino);
                goto err;
        }

        di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino,
                                         index, name, name_len, -1);
        if (IS_ERR(di)) {
                ret = PTR_ERR(di);
                goto err;
        }
        if (!di) {
                ret = -ENOENT;
                goto err;
        }
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        btrfs_release_path(root, path);

        ret = btrfs_del_inode_ref_in_log(trans, root, name, name_len,
                                         inode, dir->i_ino);
        BUG_ON(ret != 0 && ret != -ENOENT);

        ret = btrfs_del_dir_entries_in_log(trans, root, name, name_len,
                                           dir, index);
        if (ret == -ENOENT)
                ret = 0;
err:
        btrfs_free_path(path);
        if (ret)
                goto out;

        btrfs_i_size_write(dir, dir->i_size - name_len * 2);
        inode->i_ctime = dir->i_mtime = dir->i_ctime = CURRENT_TIME;
        btrfs_update_inode(trans, root, dir);
        btrfs_drop_nlink(inode);
        ret = btrfs_update_inode(trans, root, inode);
out:
        return ret;
}

/* helper to check if there is any shared block in the path */
static int check_path_shared(struct btrfs_root *root,
                             struct btrfs_path *path)
{
        struct extent_buffer *eb;
        int level;
        u64 refs = 1;
        int uninitialized_var(ret);

        for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
                if (!path->nodes[level])
                        break;
                eb = path->nodes[level];
                if (!btrfs_block_can_be_shared(root, eb))
                        continue;
                ret = btrfs_lookup_extent_info(NULL, root, eb->start, eb->len,
                                               &refs, NULL);
                if (refs > 1)
                        return 1;
        }
        return ret; /* XXX callers? */
}

/*
 * helper to start transaction for unlink and rmdir.
 *
 * unlink and rmdir are special in btrfs, they do not always free space.
 * so in enospc case, we should make sure they will free space before
 * allowing them to use the global metadata reservation.
 */
static struct btrfs_trans_handle *__unlink_start_trans(struct inode *dir,
                                                       struct dentry *dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_path *path;
        struct btrfs_inode_ref *ref;
        struct btrfs_dir_item *di;
        struct inode *inode = dentry->d_inode;
        u64 index;
        int check_link = 1;
        int err = -ENOSPC;
        int ret;

        trans = btrfs_start_transaction(root, 10);
        if (!IS_ERR(trans) || PTR_ERR(trans) != -ENOSPC)
                return trans;

        if (inode->i_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                return ERR_PTR(-ENOSPC);

        /* check if there is someone else holds reference */
        if (S_ISDIR(inode->i_mode) && atomic_read(&inode->i_count) > 1)
                return ERR_PTR(-ENOSPC);

        if (atomic_read(&inode->i_count) > 2)
                return ERR_PTR(-ENOSPC);

        if (xchg(&root->fs_info->enospc_unlink, 1))
                return ERR_PTR(-ENOSPC);

        path = btrfs_alloc_path();
        if (!path) {
                root->fs_info->enospc_unlink = 0;
                return ERR_PTR(-ENOMEM);
        }

        trans = btrfs_start_transaction(root, 0);
        if (IS_ERR(trans)) {
                btrfs_free_path(path);
                root->fs_info->enospc_unlink = 0;
                return trans;
        }

        path->skip_locking = 1;
        path->search_commit_root = 1;

        ret = btrfs_lookup_inode(trans, root, path,
                                &BTRFS_I(dir)->location, 0);
        if (ret < 0) {
                err = ret;
                goto out;
        }
        if (ret == 0) {
                if (check_path_shared(root, path))
                        goto out;
        } else {
                check_link = 0;
        }
        btrfs_release_path(root, path);

        ret = btrfs_lookup_inode(trans, root, path,
                                &BTRFS_I(inode)->location, 0);
        if (ret < 0) {
                err = ret;
                goto out;
        }
        if (ret == 0) {
                if (check_path_shared(root, path))
                        goto out;
        } else {
                check_link = 0;
        }
        btrfs_release_path(root, path);

        if (ret == 0 && S_ISREG(inode->i_mode)) {
                ret = btrfs_lookup_file_extent(trans, root, path,
                                               inode->i_ino, (u64)-1, 0);
                if (ret < 0) {
                        err = ret;
                        goto out;
                }
                BUG_ON(ret == 0);
                if (check_path_shared(root, path))
                        goto out;
                btrfs_release_path(root, path);
        }

        if (!check_link) {
                err = 0;
                goto out;
        }

        di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
                                dentry->d_name.name, dentry->d_name.len, 0);
        if (IS_ERR(di)) {
                err = PTR_ERR(di);
                goto out;
        }
        if (di) {
                if (check_path_shared(root, path))
                        goto out;
        } else {
                err = 0;
                goto out;
        }
        btrfs_release_path(root, path);

        ref = btrfs_lookup_inode_ref(trans, root, path,
                                dentry->d_name.name, dentry->d_name.len,
                                inode->i_ino, dir->i_ino, 0);
        if (IS_ERR(ref)) {
                err = PTR_ERR(ref);
                goto out;
        }
        BUG_ON(!ref);
        if (check_path_shared(root, path))
                goto out;
        index = btrfs_inode_ref_index(path->nodes[0], ref);
        btrfs_release_path(root, path);

        di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino, index,
                                dentry->d_name.name, dentry->d_name.len, 0);
        if (IS_ERR(di)) {
                err = PTR_ERR(di);
                goto out;
        }
        BUG_ON(ret == -ENOENT);
        if (check_path_shared(root, path))
                goto out;

        err = 0;
out:
        btrfs_free_path(path);
        if (err) {
                btrfs_end_transaction(trans, root);
                root->fs_info->enospc_unlink = 0;
                return ERR_PTR(err);
        }

        trans->block_rsv = &root->fs_info->global_block_rsv;
        return trans;
}

static void __unlink_end_trans(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root)
{
        if (trans->block_rsv == &root->fs_info->global_block_rsv) {
                BUG_ON(!root->fs_info->enospc_unlink);
                root->fs_info->enospc_unlink = 0;
        }
        btrfs_end_transaction_throttle(trans, root);
}

static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        struct inode *inode = dentry->d_inode;
        int ret;
        unsigned long nr = 0;

        trans = __unlink_start_trans(dir, dentry);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, dir);

        btrfs_record_unlink_dir(trans, dir, dentry->d_inode, 0);

        ret = btrfs_unlink_inode(trans, root, dir, dentry->d_inode,
                                 dentry->d_name.name, dentry->d_name.len);
        BUG_ON(ret);

        if (inode->i_nlink == 0) {
                ret = btrfs_orphan_add(trans, inode);
                BUG_ON(ret);
        }

        nr = trans->blocks_used;
        __unlink_end_trans(trans, root);
        btrfs_btree_balance_dirty(root, nr);
        return ret;
}

int btrfs_unlink_subvol(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root,
                        struct inode *dir, u64 objectid,
                        const char *name, int name_len)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        u64 index;
        int ret;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
                                   name, name_len, -1);
        BUG_ON(!di || IS_ERR(di));

        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        WARN_ON(key.type != BTRFS_ROOT_ITEM_KEY || key.objectid != objectid);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        BUG_ON(ret);
        btrfs_release_path(root, path);

        ret = btrfs_del_root_ref(trans, root->fs_info->tree_root,
                                 objectid, root->root_key.objectid,
                                 dir->i_ino, &index, name, name_len);
        if (ret < 0) {
                BUG_ON(ret != -ENOENT);
                di = btrfs_search_dir_index_item(root, path, dir->i_ino,
                                                 name, name_len);
                BUG_ON(!di || IS_ERR(di));

                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                btrfs_release_path(root, path);
                index = key.offset;
        }

        di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino,
                                         index, name, name_len, -1);
        BUG_ON(!di || IS_ERR(di));

        leaf = path->nodes[0];
        btrfs_dir_item_key_to_cpu(leaf, di, &key);
        WARN_ON(key.type != BTRFS_ROOT_ITEM_KEY || key.objectid != objectid);
        ret = btrfs_delete_one_dir_name(trans, root, path, di);
        BUG_ON(ret);
        btrfs_release_path(root, path);

        btrfs_i_size_write(dir, dir->i_size - name_len * 2);
        dir->i_mtime = dir->i_ctime = CURRENT_TIME;
        ret = btrfs_update_inode(trans, root, dir);
        BUG_ON(ret);

        btrfs_free_path(path);
        return 0;
}

static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;
        int err = 0;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_trans_handle *trans;
        unsigned long nr = 0;

        if (inode->i_size > BTRFS_EMPTY_DIR_SIZE ||
            inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                return -ENOTEMPTY;

        trans = __unlink_start_trans(dir, dentry);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, dir);

        if (unlikely(inode->i_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                err = btrfs_unlink_subvol(trans, root, dir,
                                          BTRFS_I(inode)->location.objectid,
                                          dentry->d_name.name,
                                          dentry->d_name.len);
                goto out;
        }

        err = btrfs_orphan_add(trans, inode);
        if (err)
                goto out;

        /* now the directory is empty */
        err = btrfs_unlink_inode(trans, root, dir, dentry->d_inode,
                                 dentry->d_name.name, dentry->d_name.len);
        if (!err)
                btrfs_i_size_write(inode, 0);
out:
        nr = trans->blocks_used;
        __unlink_end_trans(trans, root);
        btrfs_btree_balance_dirty(root, nr);

        return err;
}

#if 0
/*
 * when truncating bytes in a file, it is possible to avoid reading
 * the leaves that contain only checksum items.  This can be the
 * majority of the IO required to delete a large file, but it must
 * be done carefully.
 *
 * The keys in the level just above the leaves are checked to make sure
 * the lowest key in a given leaf is a csum key, and starts at an offset
 * after the new  size.
 *
 * Then the key for the next leaf is checked to make sure it also has
 * a checksum item for the same file.  If it does, we know our target leaf
 * contains only checksum items, and it can be safely freed without reading
 * it.
 *
 * This is just an optimization targeted at large files.  It may do
 * nothing.  It will return 0 unless things went badly.
 */
static noinline int drop_csum_leaves(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct btrfs_path *path,
                                     struct inode *inode, u64 new_size)
{
        struct btrfs_key key;
        int ret;
        int nritems;
        struct btrfs_key found_key;
        struct btrfs_key other_key;
        struct btrfs_leaf_ref *ref;
        u64 leaf_gen;
        u64 leaf_start;

        path->lowest_level = 1;
        key.objectid = inode->i_ino;
        key.type = BTRFS_CSUM_ITEM_KEY;
        key.offset = new_size;
again:
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0)
                goto out;

        if (path->nodes[1] == NULL) {
                ret = 0;
                goto out;
        }
        ret = 0;
        btrfs_node_key_to_cpu(path->nodes[1], &found_key, path->slots[1]);
        nritems = btrfs_header_nritems(path->nodes[1]);

        if (!nritems)
                goto out;

        if (path->slots[1] >= nritems)
                goto next_node;

        /* did we find a key greater than anything we want to delete? */
        if (found_key.objectid > inode->i_ino ||
           (found_key.objectid == inode->i_ino && found_key.type > key.type))
                goto out;

        /* we check the next key in the node to make sure the leave contains
         * only checksum items.  This comparison doesn't work if our
         * leaf is the last one in the node
         */
        if (path->slots[1] + 1 >= nritems) {
next_node:
                /* search forward from the last key in the node, this
                 * will bring us into the next node in the tree
                 */
                btrfs_node_key_to_cpu(path->nodes[1], &found_key, nritems - 1);

                /* unlikely, but we inc below, so check to be safe */
                if (found_key.offset == (u64)-1)
                        goto out;

                /* search_forward needs a path with locks held, do the
                 * search again for the original key.  It is possible
                 * this will race with a balance and return a path that
                 * we could modify, but this drop is just an optimization
                 * and is allowed to miss some leaves.
                 */
                btrfs_release_path(root, path);
                found_key.offset++;

                /* setup a max key for search_forward */
                other_key.offset = (u64)-1;
                other_key.type = key.type;
                other_key.objectid = key.objectid;

                path->keep_locks = 1;
                ret = btrfs_search_forward(root, &found_key, &other_key,
                                           path, 0, 0);
                path->keep_locks = 0;
                if (ret || found_key.objectid != key.objectid ||
                    found_key.type != key.type) {
                        ret = 0;
                        goto out;
                }

                key.offset = found_key.offset;
                btrfs_release_path(root, path);
                cond_resched();
                goto again;
        }

        /* we know there's one more slot after us in the tree,
         * read that key so we can verify it is also a checksum item
         */
        btrfs_node_key_to_cpu(path->nodes[1], &other_key, path->slots[1] + 1);

        if (found_key.objectid < inode->i_ino)
                goto next_key;

        if (found_key.type != key.type || found_key.offset < new_size)
                goto next_key;

        /*
         * if the key for the next leaf isn't a csum key from this objectid,
         * we can't be sure there aren't good items inside this leaf.
         * Bail out
         */
        if (other_key.objectid != inode->i_ino || other_key.type != key.type)
                goto out;

        leaf_start = btrfs_node_blockptr(path->nodes[1], path->slots[1]);
        leaf_gen = btrfs_node_ptr_generation(path->nodes[1], path->slots[1]);
        /*
         * it is safe to delete this leaf, it contains only
         * csum items from this inode at an offset >= new_size
         */
        ret = btrfs_del_leaf(trans, root, path, leaf_start);
        BUG_ON(ret);

        if (root->ref_cows && leaf_gen < trans->transid) {
                ref = btrfs_alloc_leaf_ref(root, 0);
                if (ref) {
                        ref->root_gen = root->root_key.offset;
                        ref->bytenr = leaf_start;
                        ref->owner = 0;
                        ref->generation = leaf_gen;
                        ref->nritems = 0;

                        btrfs_sort_leaf_ref(ref);

                        ret = btrfs_add_leaf_ref(root, ref, 0);
                        WARN_ON(ret);
                        btrfs_free_leaf_ref(root, ref);
                } else {
                        WARN_ON(1);
                }
        }
next_key:
        btrfs_release_path(root, path);

        if (other_key.objectid == inode->i_ino &&
            other_key.type == key.type && other_key.offset > key.offset) {
                key.offset = other_key.offset;
                cond_resched();
                goto again;
        }
        ret = 0;
out:
        /* fixup any changes we've made to the path */
        path->lowest_level = 0;
        path->keep_locks = 0;
        btrfs_release_path(root, path);
        return ret;
}

#endif

/*
 * this can truncate away extent items, csum items and directory items.
 * It starts at a high offset and removes keys until it can't find
 * any higher than new_size
 *
 * csum items that cross the new i_size are truncated to the new size
 * as well.
 *
 * min_type is the minimum key type to truncate down to.  If set to 0, this
 * will kill all the items on this inode, including the INODE_ITEM_KEY.
 */
int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               struct inode *inode,
                               u64 new_size, u32 min_type)
{
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        struct btrfs_key found_key;
        u64 extent_start = 0;
        u64 extent_num_bytes = 0;
        u64 extent_offset = 0;
        u64 item_end = 0;
        u64 mask = root->sectorsize - 1;
        u32 found_type = (u8)-1;
        int found_extent;
        int del_item;
        int pending_del_nr = 0;
        int pending_del_slot = 0;
        int extent_type = -1;
        int encoding;
        int ret;
        int err = 0;

        BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);

        if (root->ref_cows || root == root->fs_info->tree_root)
                btrfs_drop_extent_cache(inode, new_size & (~mask), (u64)-1, 0);

        path = btrfs_alloc_path();
        BUG_ON(!path);
        path->reada = -1;

        key.objectid = inode->i_ino;
        key.offset = (u64)-1;
        key.type = (u8)-1;

search_again:
        path->leave_spinning = 1;
        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0) {
                err = ret;
                goto out;
        }

        if (ret > 0) {
                /* there are no items in the tree for us to truncate, we're
                 * done
                 */
                if (path->slots[0] == 0)
                        goto out;
                path->slots[0]--;
        }

        while (1) {
                fi = NULL;
                leaf = path->nodes[0];
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                found_type = btrfs_key_type(&found_key);
                encoding = 0;

                if (found_key.objectid != inode->i_ino)
                        break;

                if (found_type < min_type)
                        break;

                item_end = found_key.offset;
                if (found_type == BTRFS_EXTENT_DATA_KEY) {
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        extent_type = btrfs_file_extent_type(leaf, fi);
                        encoding = btrfs_file_extent_compression(leaf, fi);
                        encoding |= btrfs_file_extent_encryption(leaf, fi);
                        encoding |= btrfs_file_extent_other_encoding(leaf, fi);

                        if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                                item_end +=
                                    btrfs_file_extent_num_bytes(leaf, fi);
                        } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                                item_end += btrfs_file_extent_inline_len(leaf,
                                                                         fi);
                        }
                        item_end--;
                }
                if (found_type > min_type) {
                        del_item = 1;
                } else {
                        if (item_end < new_size)
                                break;
                        if (found_key.offset >= new_size)
                                del_item = 1;
                        else
                                del_item = 0;
                }
                found_extent = 0;
                /* FIXME, shrink the extent if the ref count is only 1 */
                if (found_type != BTRFS_EXTENT_DATA_KEY)
                        goto delete;

                if (extent_type != BTRFS_FILE_EXTENT_INLINE) {
                        u64 num_dec;
                        extent_start = btrfs_file_extent_disk_bytenr(leaf, fi);
                        if (!del_item && !encoding) {
                                u64 orig_num_bytes =
                                        btrfs_file_extent_num_bytes(leaf, fi);
                                extent_num_bytes = new_size -
                                        found_key.offset + root->sectorsize - 1;
                                extent_num_bytes = extent_num_bytes &
                                        ~((u64)root->sectorsize - 1);
                                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                         extent_num_bytes);
                                num_dec = (orig_num_bytes -
                                           extent_num_bytes);
                                if (root->ref_cows && extent_start != 0)
                                        inode_sub_bytes(inode, num_dec);
                                btrfs_mark_buffer_dirty(leaf);
                        } else {
                                extent_num_bytes =
                                        btrfs_file_extent_disk_num_bytes(leaf,
                                                                         fi);
                                extent_offset = found_key.offset -
                                        btrfs_file_extent_offset(leaf, fi);

                                /* FIXME blocksize != 4096 */
                                num_dec = btrfs_file_extent_num_bytes(leaf, fi);
                                if (extent_start != 0) {
                                        found_extent = 1;
                                        if (root->ref_cows)
                                                inode_sub_bytes(inode, num_dec);
                                }
                        }
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        /*
                         * we can't truncate inline items that have had
                         * special encodings
                         */
                        if (!del_item &&
                            btrfs_file_extent_compression(leaf, fi) == 0 &&
                            btrfs_file_extent_encryption(leaf, fi) == 0 &&
                            btrfs_file_extent_other_encoding(leaf, fi) == 0) {
                                u32 size = new_size - found_key.offset;

                                if (root->ref_cows) {
                                        inode_sub_bytes(inode, item_end + 1 -
                                                        new_size);
                                }
                                size =
                                    btrfs_file_extent_calc_inline_size(size);
                                ret = btrfs_truncate_item(trans, root, path,
                                                          size, 1);
                                BUG_ON(ret);
                        } else if (root->ref_cows) {
                                inode_sub_bytes(inode, item_end + 1 -
                                                found_key.offset);
                        }
                }
delete:
                if (del_item) {
                        if (!pending_del_nr) {
                                /* no pending yet, add ourselves */
                                pending_del_slot = path->slots[0];
                                pending_del_nr = 1;
                        } else if (pending_del_nr &&
                                   path->slots[0] + 1 == pending_del_slot) {
                                /* hop on the pending chunk */
                                pending_del_nr++;
                                pending_del_slot = path->slots[0];
                        } else {
                                BUG();
                        }
                } else {
                        break;
                }
                if (found_extent && (root->ref_cows ||
                                     root == root->fs_info->tree_root)) {
                        btrfs_set_path_blocking(path);
                        ret = btrfs_free_extent(trans, root, extent_start,
                                                extent_num_bytes, 0,
                                                btrfs_header_owner(leaf),
                                                inode->i_ino, extent_offset);
                        BUG_ON(ret);
                }

                if (found_type == BTRFS_INODE_ITEM_KEY)
                        break;

                if (path->slots[0] == 0 ||
                    path->slots[0] != pending_del_slot) {
                        if (root->ref_cows) {
                                err = -EAGAIN;
                                goto out;
                        }
                        if (pending_del_nr) {
                                ret = btrfs_del_items(trans, root, path,
                                                pending_del_slot,
                                                pending_del_nr);
                                BUG_ON(ret);
                                pending_del_nr = 0;
                        }
                        btrfs_release_path(root, path);
                        goto search_again;
                } else {
                        path->slots[0]--;
                }
        }
out:
        if (pending_del_nr) {
                ret = btrfs_del_items(trans, root, path, pending_del_slot,
                                      pending_del_nr);
                BUG_ON(ret);
        }
        btrfs_free_path(path);
        return err;
}

/*
 * taken from block_truncate_page, but does cow as it zeros out
 * any bytes left in the last page in the file.
 */
static int btrfs_truncate_page(struct address_space *mapping, loff_t from)
{
        struct inode *inode = mapping->host;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        char *kaddr;
        u32 blocksize = root->sectorsize;
        pgoff_t index = from >> PAGE_CACHE_SHIFT;
        unsigned offset = from & (PAGE_CACHE_SIZE-1);
        struct page *page;
        int ret = 0;
        u64 page_start;
        u64 page_end;

        if ((offset & (blocksize - 1)) == 0)
                goto out;
        ret = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
        if (ret)
                goto out;

        ret = -ENOMEM;
again:
        page = grab_cache_page(mapping, index);
        if (!page) {
                btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
                goto out;
        }

        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if (!PageUptodate(page)) {
                ret = btrfs_readpage(NULL, page);
                lock_page(page);
                if (page->mapping != mapping) {
                        unlock_page(page);
                        page_cache_release(page);
                        goto again;
                }
                if (!PageUptodate(page)) {
                        ret = -EIO;
                        goto out_unlock;
                }
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, page_start, page_end, 0, &cached_state,
                         GFP_NOFS);
        set_page_extent_mapped(page);

        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                unlock_page(page);
                page_cache_release(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
                          EXTENT_DIRTY | EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING,
                          0, 0, &cached_state, GFP_NOFS);

        ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
                                        &cached_state);
        if (ret) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                goto out_unlock;
        }

        ret = 0;
        if (offset != PAGE_CACHE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        unlock_extent_cached(io_tree, page_start, page_end, &cached_state,
                             GFP_NOFS);

out_unlock:
        if (ret)
                btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
        unlock_page(page);
        page_cache_release(page);
out:
        return ret;
}

int btrfs_cont_expand(struct inode *inode, loff_t size)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct extent_map *em = NULL;
        struct extent_state *cached_state = NULL;
        u64 mask = root->sectorsize - 1;
        u64 hole_start = (inode->i_size + mask) & ~mask;
        u64 block_end = (size + mask) & ~mask;
        u64 last_byte;
        u64 cur_offset;
        u64 hole_size;
        int err = 0;

        if (size <= hole_start)
                return 0;

        while (1) {
                struct btrfs_ordered_extent *ordered;
                btrfs_wait_ordered_range(inode, hole_start,
                                         block_end - hole_start);
                lock_extent_bits(io_tree, hole_start, block_end - 1, 0,
                                 &cached_state, GFP_NOFS);
                ordered = btrfs_lookup_ordered_extent(inode, hole_start);
                if (!ordered)
                        break;
                unlock_extent_cached(io_tree, hole_start, block_end - 1,
                                     &cached_state, GFP_NOFS);
                btrfs_put_ordered_extent(ordered);
        }

        cur_offset = hole_start;
        while (1) {
                em = btrfs_get_extent(inode, NULL, 0, cur_offset,
                                block_end - cur_offset, 0);
                BUG_ON(IS_ERR(em) || !em);
                last_byte = min(extent_map_end(em), block_end);
                last_byte = (last_byte + mask) & ~mask;
                if (!test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
                        u64 hint_byte = 0;
                        hole_size = last_byte - cur_offset;

                        trans = btrfs_start_transaction(root, 2);
                        if (IS_ERR(trans)) {
                                err = PTR_ERR(trans);
                                break;
                        }
                        btrfs_set_trans_block_group(trans, inode);

                        err = btrfs_drop_extents(trans, inode, cur_offset,
                                                 cur_offset + hole_size,
                                                 &hint_byte, 1);
                        BUG_ON(err);

                        err = btrfs_insert_file_extent(trans, root,
                                        inode->i_ino, cur_offset, 0,
                                        0, hole_size, 0, hole_size,
                                        0, 0, 0);
                        BUG_ON(err);

                        btrfs_drop_extent_cache(inode, hole_start,
                                        last_byte - 1, 0);

                        btrfs_end_transaction(trans, root);
                }
                free_extent_map(em);
                em = NULL;
                cur_offset = last_byte;
                if (cur_offset >= block_end)
                        break;
        }

        free_extent_map(em);
        unlock_extent_cached(io_tree, hole_start, block_end - 1, &cached_state,
                             GFP_NOFS);
        return err;
}

static int btrfs_setattr_size(struct inode *inode, struct iattr *attr)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        unsigned long nr;
        int ret;

        if (attr->ia_size == inode->i_size)
                return 0;

        if (attr->ia_size > inode->i_size) {
                unsigned long limit;
                limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
                if (attr->ia_size > inode->i_sb->s_maxbytes)
                        return -EFBIG;
                if (limit != RLIM_INFINITY && attr->ia_size > limit) {
                        send_sig(SIGXFSZ, current, 0);
                        return -EFBIG;
                }
        }

        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, inode);

        ret = btrfs_orphan_add(trans, inode);
        BUG_ON(ret);

        nr = trans->blocks_used;
        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root, nr);

        if (attr->ia_size > inode->i_size) {
                ret = btrfs_cont_expand(inode, attr->ia_size);
                if (ret) {
                        btrfs_truncate(inode);
                        return ret;
                }

                i_size_write(inode, attr->ia_size);
                btrfs_ordered_update_i_size(inode, inode->i_size, NULL);

                trans = btrfs_start_transaction(root, 0);
                BUG_ON(IS_ERR(trans));
                btrfs_set_trans_block_group(trans, inode);
                trans->block_rsv = root->orphan_block_rsv;
                BUG_ON(!trans->block_rsv);

                ret = btrfs_update_inode(trans, root, inode);
                BUG_ON(ret);
                if (inode->i_nlink > 0) {
                        ret = btrfs_orphan_del(trans, inode);
                        BUG_ON(ret);
                }
                nr = trans->blocks_used;
                btrfs_end_transaction(trans, root);
                btrfs_btree_balance_dirty(root, nr);
                return 0;
        }

        /*
         * We're truncating a file that used to have good data down to
         * zero. Make sure it gets into the ordered flush list so that
         * any new writes get down to disk quickly.
         */
        if (attr->ia_size == 0)
                BTRFS_I(inode)->ordered_data_close = 1;

        /* we don't support swapfiles, so vmtruncate shouldn't fail */
        ret = vmtruncate(inode, attr->ia_size);
        BUG_ON(ret);

        return 0;
}

static int btrfs_setattr(struct dentry *dentry, struct iattr *attr)
{
        struct inode *inode = dentry->d_inode;
        int err;

        err = inode_change_ok(inode, attr);
        if (err)
                return err;

        if (S_ISREG(inode->i_mode) && (attr->ia_valid & ATTR_SIZE)) {
                err = btrfs_setattr_size(inode, attr);
                if (err)
                        return err;
        }

        if (attr->ia_valid) {
                setattr_copy(inode, attr);
                mark_inode_dirty(inode);

                if (attr->ia_valid & ATTR_MODE)
                        err = btrfs_acl_chmod(inode);
        }

        return err;
}

void btrfs_evict_inode(struct inode *inode)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        unsigned long nr;
        int ret;

        truncate_inode_pages(&inode->i_data, 0);
        if (inode->i_nlink && (btrfs_root_refs(&root->root_item) != 0 ||
                               root == root->fs_info->tree_root))
                goto no_delete;

        if (is_bad_inode(inode)) {
                btrfs_orphan_del(NULL, inode);
                goto no_delete;
        }
        /* do we really want it for ->i_nlink > 0 and zero btrfs_root_refs? */
        btrfs_wait_ordered_range(inode, 0, (u64)-1);

        if (root->fs_info->log_root_recovering) {
                BUG_ON(!list_empty(&BTRFS_I(inode)->i_orphan));
                goto no_delete;
        }

        if (inode->i_nlink > 0) {
                BUG_ON(btrfs_root_refs(&root->root_item) != 0);
                goto no_delete;
        }

        btrfs_i_size_write(inode, 0);

        while (1) {
                trans = btrfs_start_transaction(root, 0);
                BUG_ON(IS_ERR(trans));
                btrfs_set_trans_block_group(trans, inode);
                trans->block_rsv = root->orphan_block_rsv;

                ret = btrfs_block_rsv_check(trans, root,
                                            root->orphan_block_rsv, 0, 5);
                if (ret) {
                        BUG_ON(ret != -EAGAIN);
                        ret = btrfs_commit_transaction(trans, root);
                        BUG_ON(ret);
                        continue;
                }

                ret = btrfs_truncate_inode_items(trans, root, inode, 0, 0);
                if (ret != -EAGAIN)
                        break;

                nr = trans->blocks_used;
                btrfs_end_transaction(trans, root);
                trans = NULL;
                btrfs_btree_balance_dirty(root, nr);

        }

        if (ret == 0) {
                ret = btrfs_orphan_del(trans, inode);
                BUG_ON(ret);
        }

        nr = trans->blocks_used;
        btrfs_end_transaction(trans, root);
        btrfs_btree_balance_dirty(root, nr);
no_delete:
        end_writeback(inode);
        return;
}

/*
 * this returns the key found in the dir entry in the location pointer.
 * If no dir entries were found, location->objectid is 0.
 */
static int btrfs_inode_by_name(struct inode *dir, struct dentry *dentry,
                               struct btrfs_key *location)
{
        const char *name = dentry->d_name.name;
        int namelen = dentry->d_name.len;
        struct btrfs_dir_item *di;
        struct btrfs_path *path;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int ret = 0;

        path = btrfs_alloc_path();
        BUG_ON(!path);

        di = btrfs_lookup_dir_item(NULL, root, path, dir->i_ino, name,
                                    namelen, 0);
        if (IS_ERR(di))
                ret = PTR_ERR(di);

        if (!di || IS_ERR(di))
                goto out_err;

        btrfs_dir_item_key_to_cpu(path->nodes[0], di, location);
out:
        btrfs_free_path(path);
        return ret;
out_err:
        location->objectid = 0;
        goto out;
}

/*
 * when we hit a tree root in a directory, the btrfs part of the inode
 * needs to be changed to reflect the root directory of the tree root.  This
 * is kind of like crossing a mount point.
 */
static int fixup_tree_root_location(struct btrfs_root *root,
                                    struct inode *dir,
                                    struct dentry *dentry,
                                    struct btrfs_key *location,
                                    struct btrfs_root **sub_root)
{
        struct btrfs_path *path;
        struct btrfs_root *new_root;
        struct btrfs_root_ref *ref;
        struct extent_buffer *leaf;
        int ret;
        int err = 0;

        path = btrfs_alloc_path();
        if (!path) {
                err = -ENOMEM;
                goto out;
        }

        err = -ENOENT;
        ret = btrfs_find_root_ref(root->fs_info->tree_root, path,
                                  BTRFS_I(dir)->root->root_key.objectid,
                                  location->objectid);
        if (ret) {
                if (ret < 0)
                        err = ret;
                goto out;
        }

        leaf = path->nodes[0];
        ref = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_root_ref);
        if (btrfs_root_ref_dirid(leaf, ref) != dir->i_ino ||
            btrfs_root_ref_name_len(leaf, ref) != dentry->d_name.len)
                goto out;

        ret = memcmp_extent_buffer(leaf, dentry->d_name.name,
                                   (unsigned long)(ref + 1),
                                   dentry->d_name.len);
        if (ret)
                goto out;

        btrfs_release_path(root->fs_info->tree_root, path);

        new_root = btrfs_read_fs_root_no_name(root->fs_info, location);
        if (IS_ERR(new_root)) {
                err = PTR_ERR(new_root);
                goto out;
        }

        if (btrfs_root_refs(&new_root->root_item) == 0) {
                err = -ENOENT;
                goto out;
        }

        *sub_root = new_root;
        location->objectid = btrfs_root_dirid(&new_root->root_item);
        location->type = BTRFS_INODE_ITEM_KEY;
        location->offset = 0;
        err = 0;
out:
        btrfs_free_path(path);
        return err;
}

static void inode_tree_add(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_inode *entry;
        struct rb_node **p;
        struct rb_node *parent;
again:
        p = &root->inode_tree.rb_node;
        parent = NULL;

        if (inode_unhashed(inode))
                return;

        spin_lock(&root->inode_lock);
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct btrfs_inode, rb_node);

                if (inode->i_ino < entry->vfs_inode.i_ino)
                        p = &parent->rb_left;
                else if (inode->i_ino > entry->vfs_inode.i_ino)
                        p = &parent->rb_right;
                else {
                        WARN_ON(!(entry->vfs_inode.i_state &
                                  (I_WILL_FREE | I_FREEING)));
                        rb_erase(parent, &root->inode_tree);
                        RB_CLEAR_NODE(parent);
                        spin_unlock(&root->inode_lock);
                        goto again;
                }
        }
        rb_link_node(&BTRFS_I(inode)->rb_node, parent, p);
        rb_insert_color(&BTRFS_I(inode)->rb_node, &root->inode_tree);
        spin_unlock(&root->inode_lock);
}

static void inode_tree_del(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int empty = 0;

        spin_lock(&root->inode_lock);
        if (!RB_EMPTY_NODE(&BTRFS_I(inode)->rb_node)) {
                rb_erase(&BTRFS_I(inode)->rb_node, &root->inode_tree);
                RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
        }
        spin_unlock(&root->inode_lock);

        /*
         * Free space cache has inodes in the tree root, but the tree root has a
         * root_refs of 0, so this could end up dropping the tree root as a
         * snapshot, so we need the extra !root->fs_info->tree_root check to
         * make sure we don't drop it.
         */
        if (empty && btrfs_root_refs(&root->root_item) == 0 &&
            root != root->fs_info->tree_root) {
                synchronize_srcu(&root->fs_info->subvol_srcu);
                spin_lock(&root->inode_lock);
                empty = RB_EMPTY_ROOT(&root->inode_tree);
                spin_unlock(&root->inode_lock);
                if (empty)
                        btrfs_add_dead_root(root);
        }
}

int btrfs_invalidate_inodes(struct btrfs_root *root)
{
        struct rb_node *node;
        struct rb_node *prev;
        struct btrfs_inode *entry;
        struct inode *inode;
        u64 objectid = 0;

        WARN_ON(btrfs_root_refs(&root->root_item) != 0);

        spin_lock(&root->inode_lock);
again:
        node = root->inode_tree.rb_node;
        prev = NULL;
        while (node) {
                prev = node;
                entry = rb_entry(node, struct btrfs_inode, rb_node);

                if (objectid < entry->vfs_inode.i_ino)
                        node = node->rb_left;
                else if (objectid > entry->vfs_inode.i_ino)
                        node = node->rb_right;
                else
                        break;
        }
        if (!node) {
                while (prev) {
                        entry = rb_entry(prev, struct btrfs_inode, rb_node);
                        if (objectid <= entry->vfs_inode.i_ino) {
                                node = prev;
                                break;
                        }
                        prev = rb_next(prev);
                }
        }
        while (node) {
                entry = rb_entry(node, struct btrfs_inode, rb_node);
                objectid = entry->vfs_inode.i_ino + 1;
                inode = igrab(&entry->vfs_inode);
                if (inode) {
                        spin_unlock(&root->inode_lock);
                        if (atomic_read(&inode->i_count) > 1)
                                d_prune_aliases(inode);
                        /*
                         * btrfs_drop_inode will have it removed from
                         * the inode cache when its usage count
                         * hits zero.
                         */
                        iput(inode);
                        cond_resched();
                        spin_lock(&root->inode_lock);
                        goto again;
                }

                if (cond_resched_lock(&root->inode_lock))
                        goto again;

                node = rb_next(node);
        }
        spin_unlock(&root->inode_lock);
        return 0;
}

static int btrfs_init_locked_inode(struct inode *inode, void *p)
{
        struct btrfs_iget_args *args = p;
        inode->i_ino = args->ino;
        BTRFS_I(inode)->root = args->root;
        btrfs_set_inode_space_info(args->root, inode);
        return 0;
}

static int btrfs_find_actor(struct inode *inode, void *opaque)
{
        struct btrfs_iget_args *args = opaque;
        return args->ino == inode->i_ino &&
                args->root == BTRFS_I(inode)->root;
}

static struct inode *btrfs_iget_locked(struct super_block *s,
                                       u64 objectid,
                                       struct btrfs_root *root)
{
        struct inode *inode;
        struct btrfs_iget_args args;
        args.ino = objectid;
        args.root = root;

        inode = iget5_locked(s, objectid, btrfs_find_actor,
                             btrfs_init_locked_inode,
                             (void *)&args);
        return inode;
}

/* Get an inode object given its location and corresponding root.
 * Returns in *is_new if the inode was read from disk
 */
struct inode *btrfs_iget(struct super_block *s, struct btrfs_key *location,
                         struct btrfs_root *root, int *new)
{
        struct inode *inode;

        inode = btrfs_iget_locked(s, location->objectid, root);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        if (inode->i_state & I_NEW) {
                BTRFS_I(inode)->root = root;
                memcpy(&BTRFS_I(inode)->location, location, sizeof(*location));
                btrfs_read_locked_inode(inode);

                inode_tree_add(inode);
                unlock_new_inode(inode);
                if (new)
                        *new = 1;
        }

        return inode;
}

static struct inode *new_simple_dir(struct super_block *s,
                                    struct btrfs_key *key,
                                    struct btrfs_root *root)
{
        struct inode *inode = new_inode(s);

        if (!inode)
                return ERR_PTR(-ENOMEM);

        BTRFS_I(inode)->root = root;
        memcpy(&BTRFS_I(inode)->location, key, sizeof(*key));
        BTRFS_I(inode)->dummy_inode = 1;

        inode->i_ino = BTRFS_EMPTY_SUBVOL_DIR_OBJECTID;
        inode->i_op = &simple_dir_inode_operations;
        inode->i_fop = &simple_dir_operations;
        inode->i_mode = S_IFDIR | S_IRUGO | S_IWUSR | S_IXUGO;
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

        return inode;
}

struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_root *sub_root = root;
        struct btrfs_key location;
        int index;
        int ret;

        if (dentry->d_name.len > BTRFS_NAME_LEN)
                return ERR_PTR(-ENAMETOOLONG);

        ret = btrfs_inode_by_name(dir, dentry, &location);

        if (ret < 0)
                return ERR_PTR(ret);

        if (location.objectid == 0)
                return NULL;

        if (location.type == BTRFS_INODE_ITEM_KEY) {
                inode = btrfs_iget(dir->i_sb, &location, root, NULL);
                return inode;
        }

        BUG_ON(location.type != BTRFS_ROOT_ITEM_KEY);

        index = srcu_read_lock(&root->fs_info->subvol_srcu);
        ret = fixup_tree_root_location(root, dir, dentry,
                                       &location, &sub_root);
        if (ret < 0) {
                if (ret != -ENOENT)
                        inode = ERR_PTR(ret);
                else
                        inode = new_simple_dir(dir->i_sb, &location, sub_root);
        } else {
                inode = btrfs_iget(dir->i_sb, &location, sub_root, NULL);
        }
        srcu_read_unlock(&root->fs_info->subvol_srcu, index);

        if (root != sub_root) {
                down_read(&root->fs_info->cleanup_work_sem);
                if (!(inode->i_sb->s_flags & MS_RDONLY))
                        btrfs_orphan_cleanup(sub_root);
                up_read(&root->fs_info->cleanup_work_sem);
        }

        return inode;
}

static int btrfs_dentry_delete(const struct dentry *dentry)
{
        struct btrfs_root *root;

        if (!dentry->d_inode && !IS_ROOT(dentry))
                dentry = dentry->d_parent;

        if (dentry->d_inode) {
                root = BTRFS_I(dentry->d_inode)->root;
                if (btrfs_root_refs(&root->root_item) == 0)
                        return 1;
        }
        return 0;
}

static struct dentry *btrfs_lookup(struct inode *dir, struct dentry *dentry,
                                   struct nameidata *nd)
{
        struct inode *inode;

        inode = btrfs_lookup_dentry(dir, dentry);
        if (IS_ERR(inode))
                return ERR_CAST(inode);

        return d_splice_alias(inode, dentry);
}

static unsigned char btrfs_filetype_table[] = {
        DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK, DT_FIFO, DT_SOCK, DT_LNK
};

static int btrfs_real_readdir(struct file *filp, void *dirent,
                              filldir_t filldir)
{
        struct inode *inode = filp->f_dentry->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_item *item;
        struct btrfs_dir_item *di;
        struct btrfs_key key;
        struct btrfs_key found_key;
        struct btrfs_path *path;
        int ret;
        u32 nritems;
        struct extent_buffer *leaf;
        int slot;
        int advance;
        unsigned char d_type;
        int over = 0;
        u32 di_cur;
        u32 di_total;
        u32 di_len;
        int key_type = BTRFS_DIR_INDEX_KEY;
        char tmp_name[32];
        char *name_ptr;
        int name_len;

        /* FIXME, use a real flag for deciding about the key type */
        if (root->fs_info->tree_root == root)
                key_type = BTRFS_DIR_ITEM_KEY;

        /* special case for "." */
        if (filp->f_pos == 0) {
                over = filldir(dirent, ".", 1,
                               1, inode->i_ino,
                               DT_DIR);
                if (over)
                        return 0;
                filp->f_pos = 1;
        }
        /* special case for .., just use the back ref */
        if (filp->f_pos == 1) {
                u64 pino = parent_ino(filp->f_path.dentry);
                over = filldir(dirent, "..", 2,
                               2, pino, DT_DIR);
                if (over)
                        return 0;
                filp->f_pos = 2;
        }
        path = btrfs_alloc_path();
        path->reada = 2;

        btrfs_set_key_type(&key, key_type);
        key.offset = filp->f_pos;
        key.objectid = inode->i_ino;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto err;
        advance = 0;

        while (1) {
                leaf = path->nodes[0];
                nritems = btrfs_header_nritems(leaf);
                slot = path->slots[0];
                if (advance || slot >= nritems) {
                        if (slot >= nritems - 1) {
                                ret = btrfs_next_leaf(root, path);
                                if (ret)
                                        break;
                                leaf = path->nodes[0];
                                nritems = btrfs_header_nritems(leaf);
                                slot = path->slots[0];
                        } else {
                                slot++;
                                path->slots[0]++;
                        }
                }

                advance = 1;
                item = btrfs_item_nr(leaf, slot);
                btrfs_item_key_to_cpu(leaf, &found_key, slot);

                if (found_key.objectid != key.objectid)
                        break;
                if (btrfs_key_type(&found_key) != key_type)
                        break;
                if (found_key.offset < filp->f_pos)
                        continue;

                filp->f_pos = found_key.offset;

                di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
                di_cur = 0;
                di_total = btrfs_item_size(leaf, item);

                while (di_cur < di_total) {
                        struct btrfs_key location;

                        name_len = btrfs_dir_name_len(leaf, di);
                        if (name_len <= sizeof(tmp_name)) {
                                name_ptr = tmp_name;
                        } else {
                                name_ptr = kmalloc(name_len, GFP_NOFS);
                                if (!name_ptr) {
                                        ret = -ENOMEM;
                                        goto err;
                                }
                        }
                        read_extent_buffer(leaf, name_ptr,
                                           (unsigned long)(di + 1), name_len);

                        d_type = btrfs_filetype_table[btrfs_dir_type(leaf, di)];
                        btrfs_dir_item_key_to_cpu(leaf, di, &location);

                        /* is this a reference to our own snapshot? If so
                         * skip it
                         */
                        if (location.type == BTRFS_ROOT_ITEM_KEY &&
                            location.objectid == root->root_key.objectid) {
                                over = 0;
                                goto skip;
                        }
                        over = filldir(dirent, name_ptr, name_len,
                                       found_key.offset, location.objectid,
                                       d_type);

skip:
                        if (name_ptr != tmp_name)
                                kfree(name_ptr);

                        if (over)
                                goto nopos;
                        di_len = btrfs_dir_name_len(leaf, di) +
                                 btrfs_dir_data_len(leaf, di) + sizeof(*di);
                        di_cur += di_len;
                        di = (struct btrfs_dir_item *)((char *)di + di_len);
                }
        }

        /* Reached end of directory/root. Bump pos past the last item. */
        if (key_type == BTRFS_DIR_INDEX_KEY)
                /*
                 * 32-bit glibc will use getdents64, but then strtol -
                 * so the last number we can serve is this.
                 */
                filp->f_pos = 0x7fffffff;
        else
                filp->f_pos++;
nopos:
        ret = 0;
err:
        btrfs_free_path(path);
        return ret;
}

int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret = 0;
        bool nolock = false;

        if (BTRFS_I(inode)->dummy_inode)
                return 0;

        smp_mb();
        nolock = (root->fs_info->closing && root == root->fs_info->tree_root);

        if (wbc->sync_mode == WB_SYNC_ALL) {
                if (nolock)
                        trans = btrfs_join_transaction_nolock(root, 1);
                else
                        trans = btrfs_join_transaction(root, 1);
                btrfs_set_trans_block_group(trans, inode);
                if (nolock)
                        ret = btrfs_end_transaction_nolock(trans, root);
                else
                        ret = btrfs_commit_transaction(trans, root);
        }
        return ret;
}

/*
 * This is somewhat expensive, updating the tree every time the
 * inode changes.  But, it is most likely to find the inode in cache.
 * FIXME, needs more benchmarking...there are no reasons other than performance
 * to keep or drop this code.
 */
void btrfs_dirty_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        int ret;

        if (BTRFS_I(inode)->dummy_inode)
                return;

        trans = btrfs_join_transaction(root, 1);
        btrfs_set_trans_block_group(trans, inode);

        ret = btrfs_update_inode(trans, root, inode);
        if (ret && ret == -ENOSPC) {
                /* whoops, lets try again with the full transaction */
                btrfs_end_transaction(trans, root);
                trans = btrfs_start_transaction(root, 1);
                if (IS_ERR(trans)) {
                        if (printk_ratelimit()) {
                                printk(KERN_ERR "btrfs: fail to "
                                       "dirty  inode %lu error %ld\n",
                                       inode->i_ino, PTR_ERR(trans));
                        }
                        return;
                }
                btrfs_set_trans_block_group(trans, inode);

                ret = btrfs_update_inode(trans, root, inode);
                if (ret) {
                        if (printk_ratelimit()) {
                                printk(KERN_ERR "btrfs: fail to "
                                       "dirty  inode %lu error %d\n",
                                       inode->i_ino, ret);
                        }
                }
        }
        btrfs_end_transaction(trans, root);
}

/*
 * find the highest existing sequence number in a directory
 * and then set the in-memory index_cnt variable to reflect
 * free sequence numbers
 */
static int btrfs_set_inode_index_count(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key key, found_key;
        struct btrfs_path *path;
        struct extent_buffer *leaf;
        int ret;

        key.objectid = inode->i_ino;
        btrfs_set_key_type(&key, BTRFS_DIR_INDEX_KEY);
        key.offset = (u64)-1;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
        if (ret < 0)
                goto out;
        /* FIXME: we should be able to handle this */
        if (ret == 0)
                goto out;
        ret = 0;

        /*
         * MAGIC NUMBER EXPLANATION:
         * since we search a directory based on f_pos we have to start at 2
         * since '.' and '..' have f_pos of 0 and 1 respectively, so everybody
         * else has to start at 2
         */
        if (path->slots[0] == 0) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        path->slots[0]--;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

        if (found_key.objectid != inode->i_ino ||
            btrfs_key_type(&found_key) != BTRFS_DIR_INDEX_KEY) {
                BTRFS_I(inode)->index_cnt = 2;
                goto out;
        }

        BTRFS_I(inode)->index_cnt = found_key.offset + 1;
out:
        btrfs_free_path(path);
        return ret;
}

/*
 * helper to find a free sequence number in a given directory.  This current
 * code is very simple, later versions will do smarter things in the btree
 */
int btrfs_set_inode_index(struct inode *dir, u64 *index)
{
        int ret = 0;

        if (BTRFS_I(dir)->index_cnt == (u64)-1) {
                ret = btrfs_set_inode_index_count(dir);
                if (ret)
                        return ret;
        }

        *index = BTRFS_I(dir)->index_cnt;
        BTRFS_I(dir)->index_cnt++;

        return ret;
}

static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
                                     struct btrfs_root *root,
                                     struct inode *dir,
                                     const char *name, int name_len,
                                     u64 ref_objectid, u64 objectid,
                                     u64 alloc_hint, int mode, u64 *index)
{
        struct inode *inode;
        struct btrfs_inode_item *inode_item;
        struct btrfs_key *location;
        struct btrfs_path *path;
        struct btrfs_inode_ref *ref;
        struct btrfs_key key[2];
        u32 sizes[2];
        unsigned long ptr;
        int ret;
        int owner;

        path = btrfs_alloc_path();
        BUG_ON(!path);

        inode = new_inode(root->fs_info->sb);
        if (!inode)
                return ERR_PTR(-ENOMEM);

        if (dir) {
                ret = btrfs_set_inode_index(dir, index);
                if (ret) {
                        iput(inode);
                        return ERR_PTR(ret);
                }
        }
        /*
         * index_cnt is ignored for everything but a dir,
         * btrfs_get_inode_index_count has an explanation for the magic
         * number
         */
        BTRFS_I(inode)->index_cnt = 2;
        BTRFS_I(inode)->root = root;
        BTRFS_I(inode)->generation = trans->transid;
        inode->i_generation = BTRFS_I(inode)->generation;
        btrfs_set_inode_space_info(root, inode);

        if (mode & S_IFDIR)
                owner = 0;
        else
                owner = 1;
        BTRFS_I(inode)->block_group =
                        btrfs_find_block_group(root, 0, alloc_hint, owner);

        key[0].objectid = objectid;
        btrfs_set_key_type(&key[0], BTRFS_INODE_ITEM_KEY);
        key[0].offset = 0;

        key[1].objectid = objectid;
        btrfs_set_key_type(&key[1], BTRFS_INODE_REF_KEY);
        key[1].offset = ref_objectid;

        sizes[0] = sizeof(struct btrfs_inode_item);
        sizes[1] = name_len + sizeof(*ref);

        path->leave_spinning = 1;
        ret = btrfs_insert_empty_items(trans, root, path, key, sizes, 2);
        if (ret != 0)
                goto fail;

        inode_init_owner(inode, dir, mode);
        inode->i_ino = objectid;
        inode_set_bytes(inode, 0);
        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
        inode_item = btrfs_item_ptr(path->nodes[0], path->slots[0],
                                  struct btrfs_inode_item);
        fill_inode_item(trans, path->nodes[0], inode_item, inode);

        ref = btrfs_item_ptr(path->nodes[0], path->slots[0] + 1,
                             struct btrfs_inode_ref);
        btrfs_set_inode_ref_name_len(path->nodes[0], ref, name_len);
        btrfs_set_inode_ref_index(path->nodes[0], ref, *index);
        ptr = (unsigned long)(ref + 1);
        write_extent_buffer(path->nodes[0], name, ptr, name_len);

        btrfs_mark_buffer_dirty(path->nodes[0]);
        btrfs_free_path(path);

        location = &BTRFS_I(inode)->location;
        location->objectid = objectid;
        location->offset = 0;
        btrfs_set_key_type(location, BTRFS_INODE_ITEM_KEY);

        btrfs_inherit_iflags(inode, dir);

        if ((mode & S_IFREG)) {
                if (btrfs_test_opt(root, NODATASUM))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
                if (btrfs_test_opt(root, NODATACOW))
                        BTRFS_I(inode)->flags |= BTRFS_INODE_NODATACOW;
        }

        insert_inode_hash(inode);
        inode_tree_add(inode);
        return inode;
fail:
        if (dir)
                BTRFS_I(dir)->index_cnt--;
        btrfs_free_path(path);
        iput(inode);
        return ERR_PTR(ret);
}

static inline u8 btrfs_inode_type(struct inode *inode)
{
        return btrfs_type_by_mode[(inode->i_mode & S_IFMT) >> S_SHIFT];
}

/*
 * utility function to add 'inode' into 'parent_inode' with
 * a give name and a given sequence number.
 * if 'add_backref' is true, also insert a backref from the
 * inode to the parent directory.
 */
int btrfs_add_link(struct btrfs_trans_handle *trans,
                   struct inode *parent_inode, struct inode *inode,
                   const char *name, int name_len, int add_backref, u64 index)
{
        int ret = 0;
        struct btrfs_key key;
        struct btrfs_root *root = BTRFS_I(parent_inode)->root;

        if (unlikely(inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                memcpy(&key, &BTRFS_I(inode)->root->root_key, sizeof(key));
        } else {
                key.objectid = inode->i_ino;
                btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
                key.offset = 0;
        }

        if (unlikely(inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                ret = btrfs_add_root_ref(trans, root->fs_info->tree_root,
                                         key.objectid, root->root_key.objectid,
                                         parent_inode->i_ino,
                                         index, name, name_len);
        } else if (add_backref) {
                ret = btrfs_insert_inode_ref(trans, root,
                                             name, name_len, inode->i_ino,
                                             parent_inode->i_ino, index);
        }

        if (ret == 0) {
                ret = btrfs_insert_dir_item(trans, root, name, name_len,
                                            parent_inode->i_ino, &key,
                                            btrfs_inode_type(inode), index);
                BUG_ON(ret);

                btrfs_i_size_write(parent_inode, parent_inode->i_size +
                                   name_len * 2);
                parent_inode->i_mtime = parent_inode->i_ctime = CURRENT_TIME;
                ret = btrfs_update_inode(trans, root, parent_inode);
        }
        return ret;
}

static int btrfs_add_nondir(struct btrfs_trans_handle *trans,
                            struct inode *dir, struct dentry *dentry,
                            struct inode *inode, int backref, u64 index)
{
        int err = btrfs_add_link(trans, dir, inode,
                                 dentry->d_name.name, dentry->d_name.len,
                                 backref, index);
        if (!err) {
                d_instantiate(dentry, inode);
                return 0;
        }
        if (err > 0)
                err = -EEXIST;
        return err;
}

static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
                        int mode, dev_t rdev)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        unsigned long nr = 0;
        u64 index = 0;

        if (!new_valid_dev(rdev))
                return -EINVAL;

        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
        if (err)
                return err;

        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, dir);

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, dir->i_ino, objectid,
                                BTRFS_I(dir)->block_group, mode, &index);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_inode_security(trans, inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err)
                drop_inode = 1;
        else {
                inode->i_op = &btrfs_special_inode_operations;
                init_special_inode(inode, inode->i_mode, rdev);
                btrfs_update_inode(trans, root, inode);
        }
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
        btrfs_btree_balance_dirty(root, nr);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        return err;
}

static int btrfs_create(struct inode *dir, struct dentry *dentry,
                        int mode, struct nameidata *nd)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = NULL;
        int drop_inode = 0;
        int err;
        unsigned long nr = 0;
        u64 objectid;
        u64 index = 0;

        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
        if (err)
                return err;
        /*
         * 2 for inode item and ref
         * 2 for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, dir);

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, dir->i_ino, objectid,
                                BTRFS_I(dir)->block_group, mode, &index);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_inode_security(trans, inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err)
                drop_inode = 1;
        else {
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
        }
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
                      struct dentry *dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct inode *inode = old_dentry->d_inode;
        u64 index;
        unsigned long nr = 0;
        int err;
        int drop_inode = 0;

        if (inode->i_nlink == 0)
                return -ENOENT;

        /* do not allow sys_link's with other subvols of the same device */
        if (root->objectid != BTRFS_I(inode)->root->objectid)
                return -EPERM;

        btrfs_inc_nlink(inode);
        inode->i_ctime = CURRENT_TIME;

        err = btrfs_set_inode_index(dir, &index);
        if (err)
                goto fail;

        /*
         * 1 item for inode ref
         * 2 items for dir items
         */
        trans = btrfs_start_transaction(root, 3);
        if (IS_ERR(trans)) {
                err = PTR_ERR(trans);
                goto fail;
        }

        btrfs_set_trans_block_group(trans, dir);
        ihold(inode);

        err = btrfs_add_nondir(trans, dir, dentry, inode, 1, index);

        if (err) {
                drop_inode = 1;
        } else {
                struct dentry *parent = dget_parent(dentry);
                btrfs_update_inode_block_group(trans, dir);
                err = btrfs_update_inode(trans, root, inode);
                BUG_ON(err);
                btrfs_log_new_name(trans, inode, NULL, parent);
                dput(parent);
        }

        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
fail:
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
        struct inode *inode = NULL;
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        int err = 0;
        int drop_on_err = 0;
        u64 objectid = 0;
        u64 index = 0;
        unsigned long nr = 1;

        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
        if (err)
                return err;

        /*
         * 2 items for inode and ref
         * 2 items for dir items
         * 1 for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);
        btrfs_set_trans_block_group(trans, dir);

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, dir->i_ino, objectid,
                                BTRFS_I(dir)->block_group, S_IFDIR | mode,
                                &index);
        if (IS_ERR(inode)) {
                err = PTR_ERR(inode);
                goto out_fail;
        }

        drop_on_err = 1;

        err = btrfs_init_inode_security(trans, inode, dir);
        if (err)
                goto out_fail;

        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;
        btrfs_set_trans_block_group(trans, inode);

        btrfs_i_size_write(inode, 0);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                goto out_fail;

        err = btrfs_add_link(trans, dir, inode, dentry->d_name.name,
                             dentry->d_name.len, 0, index);
        if (err)
                goto out_fail;

        d_instantiate(dentry, inode);
        drop_on_err = 0;
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);

out_fail:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
        if (drop_on_err)
                iput(inode);
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

/* helper for btfs_get_extent.  Given an existing extent in the tree,
 * and an extent that you want to insert, deal with overlap and insert
 * the new extent into the tree.
 */
static int merge_extent_mapping(struct extent_map_tree *em_tree,
                                struct extent_map *existing,
                                struct extent_map *em,
                                u64 map_start, u64 map_len)
{
        u64 start_diff;

        BUG_ON(map_start < em->start || map_start >= extent_map_end(em));
        start_diff = map_start - em->start;
        em->start = map_start;
        em->len = map_len;
        if (em->block_start < EXTENT_MAP_LAST_BYTE &&
            !test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) {
                em->block_start += start_diff;
                em->block_len -= start_diff;
        }
        return add_extent_mapping(em_tree, em);
}

static noinline int uncompress_inline(struct btrfs_path *path,
                                      struct inode *inode, struct page *page,
                                      size_t pg_offset, u64 extent_offset,
                                      struct btrfs_file_extent_item *item)
{
        int ret;
        struct extent_buffer *leaf = path->nodes[0];
        char *tmp;
        size_t max_size;
        unsigned long inline_size;
        unsigned long ptr;

        WARN_ON(pg_offset != 0);
        max_size = btrfs_file_extent_ram_bytes(leaf, item);
        inline_size = btrfs_file_extent_inline_item_len(leaf,
                                        btrfs_item_nr(leaf, path->slots[0]));
        tmp = kmalloc(inline_size, GFP_NOFS);
        ptr = btrfs_file_extent_inline_start(item);

        read_extent_buffer(leaf, tmp, ptr, inline_size);

        max_size = min_t(unsigned long, PAGE_CACHE_SIZE, max_size);
        ret = btrfs_zlib_decompress(tmp, page, extent_offset,
                                    inline_size, max_size);
        if (ret) {
                char *kaddr = kmap_atomic(page, KM_USER0);
                unsigned long copy_size = min_t(u64,
                                  PAGE_CACHE_SIZE - pg_offset,
                                  max_size - extent_offset);
                memset(kaddr + pg_offset, 0, copy_size);
                kunmap_atomic(kaddr, KM_USER0);
        }
        kfree(tmp);
        return 0;
}

/*
 * a bit scary, this does extent mapping from logical file offset to the disk.
 * the ugly parts come from merging extents from the disk with the in-ram
 * representation.  This gets more complex because of the data=ordered code,
 * where the in-ram extents might be locked pending data=ordered completion.
 *
 * This also copies inline extents directly into the page.
 */

struct extent_map *btrfs_get_extent(struct inode *inode, struct page *page,
                                    size_t pg_offset, u64 start, u64 len,
                                    int create)
{
        int ret;
        int err = 0;
        u64 bytenr;
        u64 extent_start = 0;
        u64 extent_end = 0;
        u64 objectid = inode->i_ino;
        u32 found_type;
        struct btrfs_path *path = NULL;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *item;
        struct extent_buffer *leaf;
        struct btrfs_key found_key;
        struct extent_map *em = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_trans_handle *trans = NULL;
        int compressed;

again:
        read_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        if (em)
                em->bdev = root->fs_info->fs_devices->latest_bdev;
        read_unlock(&em_tree->lock);

        if (em) {
                if (em->start > start || em->start + em->len <= start)
                        free_extent_map(em);
                else if (em->block_start == EXTENT_MAP_INLINE && page)
                        free_extent_map(em);
                else
                        goto out;
        }
        em = alloc_extent_map(GFP_NOFS);
        if (!em) {
                err = -ENOMEM;
                goto out;
        }
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        em->start = EXTENT_MAP_HOLE;
        em->orig_start = EXTENT_MAP_HOLE;
        em->len = (u64)-1;
        em->block_len = (u64)-1;

        if (!path) {
                path = btrfs_alloc_path();
                BUG_ON(!path);
        }

        ret = btrfs_lookup_file_extent(trans, root, path,
                                       objectid, start, trans != NULL);
        if (ret < 0) {
                err = ret;
                goto out;
        }

        if (ret != 0) {
                if (path->slots[0] == 0)
                        goto not_found;
                path->slots[0]--;
        }

        leaf = path->nodes[0];
        item = btrfs_item_ptr(leaf, path->slots[0],
                              struct btrfs_file_extent_item);
        /* are we inside the extent that was found? */
        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
        found_type = btrfs_key_type(&found_key);
        if (found_key.objectid != objectid ||
            found_type != BTRFS_EXTENT_DATA_KEY) {
                goto not_found;
        }

        found_type = btrfs_file_extent_type(leaf, item);
        extent_start = found_key.offset;
        compressed = btrfs_file_extent_compression(leaf, item);
        if (found_type == BTRFS_FILE_EXTENT_REG ||
            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                extent_end = extent_start +
                       btrfs_file_extent_num_bytes(leaf, item);
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                size_t size;
                size = btrfs_file_extent_inline_len(leaf, item);
                extent_end = (extent_start + size + root->sectorsize - 1) &
                        ~((u64)root->sectorsize - 1);
        }

        if (start >= extent_end) {
                path->slots[0]++;
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0) {
                                err = ret;
                                goto out;
                        }
                        if (ret > 0)
                                goto not_found;
                        leaf = path->nodes[0];
                }
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
                if (found_key.objectid != objectid ||
                    found_key.type != BTRFS_EXTENT_DATA_KEY)
                        goto not_found;
                if (start + len <= found_key.offset)
                        goto not_found;
                em->start = start;
                em->len = found_key.offset - start;
                goto not_found_em;
        }

        if (found_type == BTRFS_FILE_EXTENT_REG ||
            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                em->start = extent_start;
                em->len = extent_end - extent_start;
                em->orig_start = extent_start -
                                 btrfs_file_extent_offset(leaf, item);
                bytenr = btrfs_file_extent_disk_bytenr(leaf, item);
                if (bytenr == 0) {
                        em->block_start = EXTENT_MAP_HOLE;
                        goto insert;
                }
                if (compressed) {
                        set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
                        em->block_start = bytenr;
                        em->block_len = btrfs_file_extent_disk_num_bytes(leaf,
                                                                         item);
                } else {
                        bytenr += btrfs_file_extent_offset(leaf, item);
                        em->block_start = bytenr;
                        em->block_len = em->len;
                        if (found_type == BTRFS_FILE_EXTENT_PREALLOC)
                                set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
                }
                goto insert;
        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                unsigned long ptr;
                char *map;
                size_t size;
                size_t extent_offset;
                size_t copy_size;

                em->block_start = EXTENT_MAP_INLINE;
                if (!page || create) {
                        em->start = extent_start;
                        em->len = extent_end - extent_start;
                        goto out;
                }

                size = btrfs_file_extent_inline_len(leaf, item);
                extent_offset = page_offset(page) + pg_offset - extent_start;
                copy_size = min_t(u64, PAGE_CACHE_SIZE - pg_offset,
                                size - extent_offset);
                em->start = extent_start + extent_offset;
                em->len = (copy_size + root->sectorsize - 1) &
                        ~((u64)root->sectorsize - 1);
                em->orig_start = EXTENT_MAP_INLINE;
                if (compressed)
                        set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
                ptr = btrfs_file_extent_inline_start(item) + extent_offset;
                if (create == 0 && !PageUptodate(page)) {
                        if (btrfs_file_extent_compression(leaf, item) ==
                            BTRFS_COMPRESS_ZLIB) {
                                ret = uncompress_inline(path, inode, page,
                                                        pg_offset,
                                                        extent_offset, item);
                                BUG_ON(ret);
                        } else {
                                map = kmap(page);
                                read_extent_buffer(leaf, map + pg_offset, ptr,
                                                   copy_size);
                                if (pg_offset + copy_size < PAGE_CACHE_SIZE) {
                                        memset(map + pg_offset + copy_size, 0,
                                               PAGE_CACHE_SIZE - pg_offset -
                                               copy_size);
                                }
                                kunmap(page);
                        }
                        flush_dcache_page(page);
                } else if (create && PageUptodate(page)) {
                        WARN_ON(1);
                        if (!trans) {
                                kunmap(page);
                                free_extent_map(em);
                                em = NULL;
                                btrfs_release_path(root, path);
                                trans = btrfs_join_transaction(root, 1);
                                goto again;
                        }
                        map = kmap(page);
                        write_extent_buffer(leaf, map + pg_offset, ptr,
                                            copy_size);
                        kunmap(page);
                        btrfs_mark_buffer_dirty(leaf);
                }
                set_extent_uptodate(io_tree, em->start,
                                    extent_map_end(em) - 1, GFP_NOFS);
                goto insert;
        } else {
                printk(KERN_ERR "btrfs unknown found_type %d\n", found_type);
                WARN_ON(1);
        }
not_found:
        em->start = start;
        em->len = len;
not_found_em:
        em->block_start = EXTENT_MAP_HOLE;
        set_bit(EXTENT_FLAG_VACANCY, &em->flags);
insert:
        btrfs_release_path(root, path);
        if (em->start > start || extent_map_end(em) <= start) {
                printk(KERN_ERR "Btrfs: bad extent! em: [%llu %llu] passed "
                       "[%llu %llu]\n", (unsigned long long)em->start,
                       (unsigned long long)em->len,
                       (unsigned long long)start,
                       (unsigned long long)len);
                err = -EIO;
                goto out;
        }

        err = 0;
        write_lock(&em_tree->lock);
        ret = add_extent_mapping(em_tree, em);
        /* it is possible that someone inserted the extent into the tree
         * while we had the lock dropped.  It is also possible that
         * an overlapping map exists in the tree
         */
        if (ret == -EEXIST) {
                struct extent_map *existing;

                ret = 0;

                existing = lookup_extent_mapping(em_tree, start, len);
                if (existing && (existing->start > start ||
                    existing->start + existing->len <= start)) {
                        free_extent_map(existing);
                        existing = NULL;
                }
                if (!existing) {
                        existing = lookup_extent_mapping(em_tree, em->start,
                                                         em->len);
                        if (existing) {
                                err = merge_extent_mapping(em_tree, existing,
                                                           em, start,
                                                           root->sectorsize);
                                free_extent_map(existing);
                                if (err) {
                                        free_extent_map(em);
                                        em = NULL;
                                }
                        } else {
                                err = -EIO;
                                free_extent_map(em);
                                em = NULL;
                        }
                } else {
                        free_extent_map(em);
                        em = existing;
                        err = 0;
                }
        }
        write_unlock(&em_tree->lock);
out:
        if (path)
                btrfs_free_path(path);
        if (trans) {
                ret = btrfs_end_transaction(trans, root);
                if (!err)
                        err = ret;
        }
        if (err) {
                free_extent_map(em);
                return ERR_PTR(err);
        }
        return em;
}

static struct extent_map *btrfs_new_extent_direct(struct inode *inode,
                                                  u64 start, u64 len)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct extent_map *em;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        struct btrfs_key ins;
        u64 alloc_hint;
        int ret;

        btrfs_drop_extent_cache(inode, start, start + len - 1, 0);

        trans = btrfs_join_transaction(root, 0);
        if (!trans)
                return ERR_PTR(-ENOMEM);

        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        alloc_hint = get_extent_allocation_hint(inode, start, len);
        ret = btrfs_reserve_extent(trans, root, len, root->sectorsize, 0,
                                   alloc_hint, (u64)-1, &ins, 1);
        if (ret) {
                em = ERR_PTR(ret);
                goto out;
        }

        em = alloc_extent_map(GFP_NOFS);
        if (!em) {
                em = ERR_PTR(-ENOMEM);
                goto out;
        }

        em->start = start;
        em->orig_start = em->start;
        em->len = ins.offset;

        em->block_start = ins.objectid;
        em->block_len = ins.offset;
        em->bdev = root->fs_info->fs_devices->latest_bdev;
        set_bit(EXTENT_FLAG_PINNED, &em->flags);

        while (1) {
                write_lock(&em_tree->lock);
                ret = add_extent_mapping(em_tree, em);
                write_unlock(&em_tree->lock);
                if (ret != -EEXIST)
                        break;
                btrfs_drop_extent_cache(inode, start, start + em->len - 1, 0);
        }

        ret = btrfs_add_ordered_extent_dio(inode, start, ins.objectid,
                                           ins.offset, ins.offset, 0);
        if (ret) {
                btrfs_free_reserved_extent(root, ins.objectid, ins.offset);
                em = ERR_PTR(ret);
        }
out:
        btrfs_end_transaction(trans, root);
        return em;
}

/*
 * returns 1 when the nocow is safe, < 1 on error, 0 if the
 * block must be cow'd
 */
static noinline int can_nocow_odirect(struct btrfs_trans_handle *trans,
                                      struct inode *inode, u64 offset, u64 len)
{
        struct btrfs_path *path;
        int ret;
        struct extent_buffer *leaf;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 disk_bytenr;
        u64 backref_offset;
        u64 extent_end;
        u64 num_bytes;
        int slot;
        int found_type;

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
                                       offset, 0);
        if (ret < 0)
                goto out;

        slot = path->slots[0];
        if (ret == 1) {
                if (slot == 0) {
                        /* can't find the item, must cow */
                        ret = 0;
                        goto out;
                }
                slot--;
        }
        ret = 0;
        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, slot);
        if (key.objectid != inode->i_ino ||
            key.type != BTRFS_EXTENT_DATA_KEY) {
                /* not our file or wrong item type, must cow */
                goto out;
        }

        if (key.offset > offset) {
                /* Wrong offset, must cow */
                goto out;
        }

        fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
        found_type = btrfs_file_extent_type(leaf, fi);
        if (found_type != BTRFS_FILE_EXTENT_REG &&
            found_type != BTRFS_FILE_EXTENT_PREALLOC) {
                /* not a regular extent, must cow */
                goto out;
        }
        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
        backref_offset = btrfs_file_extent_offset(leaf, fi);

        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
        if (extent_end < offset + len) {
                /* extent doesn't include our full range, must cow */
                goto out;
        }

        if (btrfs_extent_readonly(root, disk_bytenr))
                goto out;

        /*
         * look for other files referencing this extent, if we
         * find any we must cow
         */
        if (btrfs_cross_ref_exist(trans, root, inode->i_ino,
                                  key.offset - backref_offset, disk_bytenr))
                goto out;

        /*
         * adjust disk_bytenr and num_bytes to cover just the bytes
         * in this extent we are about to write.  If there
         * are any csums in that range we have to cow in order
         * to keep the csums correct
         */
        disk_bytenr += backref_offset;
        disk_bytenr += offset - key.offset;
        num_bytes = min(offset + len, extent_end) - offset;
        if (csum_exist_in_range(root, disk_bytenr, num_bytes))
                                goto out;
        /*
         * all of the above have passed, it is safe to overwrite this extent
         * without cow
         */
        ret = 1;
out:
        btrfs_free_path(path);
        return ret;
}

static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock,
                                   struct buffer_head *bh_result, int create)
{
        struct extent_map *em;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 start = iblock << inode->i_blkbits;
        u64 len = bh_result->b_size;
        struct btrfs_trans_handle *trans;

        em = btrfs_get_extent(inode, NULL, 0, start, len, 0);
        if (IS_ERR(em))
                return PTR_ERR(em);

        /*
         * Ok for INLINE and COMPRESSED extents we need to fallback on buffered
         * io.  INLINE is special, and we could probably kludge it in here, but
         * it's still buffered so for safety lets just fall back to the generic
         * buffered path.
         *
         * For COMPRESSED we _have_ to read the entire extent in so we can
         * decompress it, so there will be buffering required no matter what we
         * do, so go ahead and fallback to buffered.
         *
         * We return -ENOTBLK because thats what makes DIO go ahead and go back
         * to buffered IO.  Don't blame me, this is the price we pay for using
         * the generic code.
         */
        if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags) ||
            em->block_start == EXTENT_MAP_INLINE) {
                free_extent_map(em);
                return -ENOTBLK;
        }

        /* Just a good old fashioned hole, return */
        if (!create && (em->block_start == EXTENT_MAP_HOLE ||
                        test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
                free_extent_map(em);
                /* DIO will do one hole at a time, so just unlock a sector */
                unlock_extent(&BTRFS_I(inode)->io_tree, start,
                              start + root->sectorsize - 1, GFP_NOFS);
                return 0;
        }

        /*
         * We don't allocate a new extent in the following cases
         *
         * 1) The inode is marked as NODATACOW.  In this case we'll just use the
         * existing extent.
         * 2) The extent is marked as PREALLOC.  We're good to go here and can
         * just use the extent.
         *
         */
        if (!create) {
                len = em->len - (start - em->start);
                goto map;
        }

        if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) ||
            ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) &&
             em->block_start != EXTENT_MAP_HOLE)) {
                int type;
                int ret;
                u64 block_start;

                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                        type = BTRFS_ORDERED_PREALLOC;
                else
                        type = BTRFS_ORDERED_NOCOW;
                len = min(len, em->len - (start - em->start));
                block_start = em->block_start + (start - em->start);

                /*
                 * we're not going to log anything, but we do need
                 * to make sure the current transaction stays open
                 * while we look for nocow cross refs
                 */
                trans = btrfs_join_transaction(root, 0);
                if (!trans)
                        goto must_cow;

                if (can_nocow_odirect(trans, inode, start, len) == 1) {
                        ret = btrfs_add_ordered_extent_dio(inode, start,
                                           block_start, len, len, type);
                        btrfs_end_transaction(trans, root);
                        if (ret) {
                                free_extent_map(em);
                                return ret;
                        }
                        goto unlock;
                }
                btrfs_end_transaction(trans, root);
        }
must_cow:
        /*
         * this will cow the extent, reset the len in case we changed
         * it above
         */
        len = bh_result->b_size;
        free_extent_map(em);
        em = btrfs_new_extent_direct(inode, start, len);
        if (IS_ERR(em))
                return PTR_ERR(em);
        len = min(len, em->len - (start - em->start));
unlock:
        clear_extent_bit(&BTRFS_I(inode)->io_tree, start, start + len - 1,
                          EXTENT_LOCKED | EXTENT_DELALLOC | EXTENT_DIRTY, 1,
                          0, NULL, GFP_NOFS);
map:
        bh_result->b_blocknr = (em->block_start + (start - em->start)) >>
                inode->i_blkbits;
        bh_result->b_size = len;
        bh_result->b_bdev = em->bdev;
        set_buffer_mapped(bh_result);
        if (create && !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
                set_buffer_new(bh_result);

        free_extent_map(em);

        return 0;
}

struct btrfs_dio_private {
        struct inode *inode;
        u64 logical_offset;
        u64 disk_bytenr;
        u64 bytes;
        u32 *csums;
        void *private;

        /* number of bios pending for this dio */
        atomic_t pending_bios;

        /* IO errors */
        int errors;

        struct bio *orig_bio;
};

static void btrfs_endio_direct_read(struct bio *bio, int err)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        struct bio_vec *bvec_end = bio->bi_io_vec + bio->bi_vcnt - 1;
        struct bio_vec *bvec = bio->bi_io_vec;
        struct inode *inode = dip->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        u64 start;
        u32 *private = dip->csums;

        start = dip->logical_offset;
        do {
                if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
                        struct page *page = bvec->bv_page;
                        char *kaddr;
                        u32 csum = ~(u32)0;
                        unsigned long flags;

                        local_irq_save(flags);
                        kaddr = kmap_atomic(page, KM_IRQ0);
                        csum = btrfs_csum_data(root, kaddr + bvec->bv_offset,
                                               csum, bvec->bv_len);
                        btrfs_csum_final(csum, (char *)&csum);
                        kunmap_atomic(kaddr, KM_IRQ0);
                        local_irq_restore(flags);

                        flush_dcache_page(bvec->bv_page);
                        if (csum != *private) {
                                printk(KERN_ERR "btrfs csum failed ino %lu off"
                                      " %llu csum %u private %u\n",
                                      inode->i_ino, (unsigned long long)start,
                                      csum, *private);
                                err = -EIO;
                        }
                }

                start += bvec->bv_len;
                private++;
                bvec++;
        } while (bvec <= bvec_end);

        unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,
                      dip->logical_offset + dip->bytes - 1, GFP_NOFS);
        bio->bi_private = dip->private;

        kfree(dip->csums);
        kfree(dip);
        dio_end_io(bio, err);
}

static void btrfs_endio_direct_write(struct bio *bio, int err)
{
        struct btrfs_dio_private *dip = bio->bi_private;
        struct inode *inode = dip->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_trans_handle *trans;
        struct btrfs_ordered_extent *ordered = NULL;
        struct extent_state *cached_state = NULL;
        u64 ordered_offset = dip->logical_offset;
        u64 ordered_bytes = dip->bytes;
        int ret;

        if (err)
                goto out_done;
again:
        ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
                                                   &ordered_offset,
                                                   ordered_bytes);
        if (!ret)
                goto out_test;

        BUG_ON(!ordered);

        trans = btrfs_join_transaction(root, 1);
        if (!trans) {
                err = -ENOMEM;
                goto out;
        }
        trans->block_rsv = &root->fs_info->delalloc_block_rsv;

        if (test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags)) {
                ret = btrfs_ordered_update_i_size(inode, 0, ordered);
                if (!ret)
                        ret = btrfs_update_inode(trans, root, inode);
                err = ret;
                goto out;
        }

        lock_extent_bits(&BTRFS_I(inode)->io_tree, ordered->file_offset,
                         ordered->file_offset + ordered->len - 1, 0,
                         &cached_state, GFP_NOFS);

        if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags)) {
                ret = btrfs_mark_extent_written(trans, inode,
                                                ordered->file_offset,
                                                ordered->file_offset +
                                                ordered->len);
                if (ret) {
                        err = ret;
                        goto out_unlock;
                }
        } else {
                ret = insert_reserved_file_extent(trans, inode,
                                                  ordered->file_offset,
                                                  ordered->start,
                                                  ordered->disk_len,
                                                  ordered->len,
                                                  ordered->len,
                                                  0, 0, 0,
                                                  BTRFS_FILE_EXTENT_REG);
                unpin_extent_cache(&BTRFS_I(inode)->extent_tree,
                                   ordered->file_offset, ordered->len);
                if (ret) {
                        err = ret;
                        WARN_ON(1);
                        goto out_unlock;
                }
        }

        add_pending_csums(trans, inode, ordered->file_offset, &ordered->list);
        btrfs_ordered_update_i_size(inode, 0, ordered);
        btrfs_update_inode(trans, root, inode);
out_unlock:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, ordered->file_offset,
                             ordered->file_offset + ordered->len - 1,
                             &cached_state, GFP_NOFS);
out:
        btrfs_delalloc_release_metadata(inode, ordered->len);
        btrfs_end_transaction(trans, root);
        ordered_offset = ordered->file_offset + ordered->len;
        btrfs_put_ordered_extent(ordered);
        btrfs_put_ordered_extent(ordered);

out_test:
        /*
         * our bio might span multiple ordered extents.  If we haven't
         * completed the accounting for the whole dio, go back and try again
         */
        if (ordered_offset < dip->logical_offset + dip->bytes) {
                ordered_bytes = dip->logical_offset + dip->bytes -
                        ordered_offset;
                goto again;
        }
out_done:
        bio->bi_private = dip->private;

        kfree(dip->csums);
        kfree(dip);
        dio_end_io(bio, err);
}

static int __btrfs_submit_bio_start_direct_io(struct inode *inode, int rw,
                                    struct bio *bio, int mirror_num,
                                    unsigned long bio_flags, u64 offset)
{
        int ret;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        ret = btrfs_csum_one_bio(root, inode, bio, offset, 1);
        BUG_ON(ret);
        return 0;
}

static void btrfs_end_dio_bio(struct bio *bio, int err)
{
        struct btrfs_dio_private *dip = bio->bi_private;

        if (err) {
                printk(KERN_ERR "btrfs direct IO failed ino %lu rw %lu "
                      "sector %#Lx len %u err no %d\n",
                      dip->inode->i_ino, bio->bi_rw,
                      (unsigned long long)bio->bi_sector, bio->bi_size, err);
                dip->errors = 1;

                /*
                 * before atomic variable goto zero, we must make sure
                 * dip->errors is perceived to be set.
                 */
                smp_mb__before_atomic_dec();
        }

        /* if there are more bios still pending for this dio, just exit */
        if (!atomic_dec_and_test(&dip->pending_bios))
                goto out;

        if (dip->errors)
                bio_io_error(dip->orig_bio);
        else {
                set_bit(BIO_UPTODATE, &dip->orig_bio->bi_flags);
                bio_endio(dip->orig_bio, 0);
        }
out:
        bio_put(bio);
}

static struct bio *btrfs_dio_bio_alloc(struct block_device *bdev,
                                       u64 first_sector, gfp_t gfp_flags)
{
        int nr_vecs = bio_get_nr_vecs(bdev);
        return btrfs_bio_alloc(bdev, first_sector, nr_vecs, gfp_flags);
}

static inline int __btrfs_submit_dio_bio(struct bio *bio, struct inode *inode,
                                         int rw, u64 file_offset, int skip_sum,
                                         u32 *csums)
{
        int write = rw & REQ_WRITE;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;

        bio_get(bio);
        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
        if (ret)
                goto err;

        if (write && !skip_sum) {
                ret = btrfs_wq_submit_bio(root->fs_info,
                                   inode, rw, bio, 0, 0,
                                   file_offset,
                                   __btrfs_submit_bio_start_direct_io,
                                   __btrfs_submit_bio_done);
                goto err;
        } else if (!skip_sum)
                btrfs_lookup_bio_sums_dio(root, inode, bio,
                                          file_offset, csums);

        ret = btrfs_map_bio(root, rw, bio, 0, 1);
err:
        bio_put(bio);
        return ret;
}

static int btrfs_submit_direct_hook(int rw, struct btrfs_dio_private *dip,
                                    int skip_sum)
{
        struct inode *inode = dip->inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
        struct bio *bio;
        struct bio *orig_bio = dip->orig_bio;
        struct bio_vec *bvec = orig_bio->bi_io_vec;
        u64 start_sector = orig_bio->bi_sector;
        u64 file_offset = dip->logical_offset;
        u64 submit_len = 0;
        u64 map_length;
        int nr_pages = 0;
        u32 *csums = dip->csums;
        int ret = 0;

        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev, start_sector, GFP_NOFS);
        if (!bio)
                return -ENOMEM;
        bio->bi_private = dip;
        bio->bi_end_io = btrfs_end_dio_bio;
        atomic_inc(&dip->pending_bios);

        map_length = orig_bio->bi_size;
        ret = btrfs_map_block(map_tree, READ, start_sector << 9,
                              &map_length, NULL, 0);
        if (ret) {
                bio_put(bio);
                return -EIO;
        }

        while (bvec <= (orig_bio->bi_io_vec + orig_bio->bi_vcnt - 1)) {
                if (unlikely(map_length < submit_len + bvec->bv_len ||
                    bio_add_page(bio, bvec->bv_page, bvec->bv_len,
                                 bvec->bv_offset) < bvec->bv_len)) {
                        /*
                         * inc the count before we submit the bio so
                         * we know the end IO handler won't happen before
                         * we inc the count. Otherwise, the dip might get freed
                         * before we're done setting it up
                         */
                        atomic_inc(&dip->pending_bios);
                        ret = __btrfs_submit_dio_bio(bio, inode, rw,
                                                     file_offset, skip_sum,
                                                     csums);
                        if (ret) {
                                bio_put(bio);
                                atomic_dec(&dip->pending_bios);
                                goto out_err;
                        }

                        if (!skip_sum)
                                csums = csums + nr_pages;
                        start_sector += submit_len >> 9;
                        file_offset += submit_len;

                        submit_len = 0;
                        nr_pages = 0;

                        bio = btrfs_dio_bio_alloc(orig_bio->bi_bdev,
                                                  start_sector, GFP_NOFS);
                        if (!bio)
                                goto out_err;
                        bio->bi_private = dip;
                        bio->bi_end_io = btrfs_end_dio_bio;

                        map_length = orig_bio->bi_size;
                        ret = btrfs_map_block(map_tree, READ, start_sector << 9,
                                              &map_length, NULL, 0);
                        if (ret) {
                                bio_put(bio);
                                goto out_err;
                        }
                } else {
                        submit_len += bvec->bv_len;
                        nr_pages ++;
                        bvec++;
                }
        }

        ret = __btrfs_submit_dio_bio(bio, inode, rw, file_offset, skip_sum,
                                     csums);
        if (!ret)
                return 0;

        bio_put(bio);
out_err:
        dip->errors = 1;
        /*
         * before atomic variable goto zero, we must
         * make sure dip->errors is perceived to be set.
         */
        smp_mb__before_atomic_dec();
        if (atomic_dec_and_test(&dip->pending_bios))
                bio_io_error(dip->orig_bio);

        /* bio_end_io() will handle error, so we needn't return it */
        return 0;
}

static void btrfs_submit_direct(int rw, struct bio *bio, struct inode *inode,
                                loff_t file_offset)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_dio_private *dip;
        struct bio_vec *bvec = bio->bi_io_vec;
        int skip_sum;
        int write = rw & REQ_WRITE;
        int ret = 0;

        skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;

        dip = kmalloc(sizeof(*dip), GFP_NOFS);
        if (!dip) {
                ret = -ENOMEM;
                goto free_ordered;
        }
        dip->csums = NULL;

        if (!skip_sum) {
                dip->csums = kmalloc(sizeof(u32) * bio->bi_vcnt, GFP_NOFS);
                if (!dip->csums) {
                        ret = -ENOMEM;
                        goto free_ordered;
                }
        }

        dip->private = bio->bi_private;
        dip->inode = inode;
        dip->logical_offset = file_offset;

        dip->bytes = 0;
        do {
                dip->bytes += bvec->bv_len;
                bvec++;
        } while (bvec <= (bio->bi_io_vec + bio->bi_vcnt - 1));

        dip->disk_bytenr = (u64)bio->bi_sector << 9;
        bio->bi_private = dip;
        dip->errors = 0;
        dip->orig_bio = bio;
        atomic_set(&dip->pending_bios, 0);

        if (write)
                bio->bi_end_io = btrfs_endio_direct_write;
        else
                bio->bi_end_io = btrfs_endio_direct_read;

        ret = btrfs_submit_direct_hook(rw, dip, skip_sum);
        if (!ret)
                return;
free_ordered:
        /*
         * If this is a write, we need to clean up the reserved space and kill
         * the ordered extent.
         */
        if (write) {
                struct btrfs_ordered_extent *ordered;
                ordered = btrfs_lookup_ordered_extent(inode, file_offset);
                if (!test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags) &&
                    !test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags))
                        btrfs_free_reserved_extent(root, ordered->start,
                                                   ordered->disk_len);
                btrfs_put_ordered_extent(ordered);
                btrfs_put_ordered_extent(ordered);
        }
        bio_endio(bio, ret);
}

static ssize_t check_direct_IO(struct btrfs_root *root, int rw, struct kiocb *iocb,
                        const struct iovec *iov, loff_t offset,
                        unsigned long nr_segs)
{
        int seg;
        size_t size;
        unsigned long addr;
        unsigned blocksize_mask = root->sectorsize - 1;
        ssize_t retval = -EINVAL;
        loff_t end = offset;

        if (offset & blocksize_mask)
                goto out;

        /* Check the memory alignment.  Blocks cannot straddle pages */
        for (seg = 0; seg < nr_segs; seg++) {
                addr = (unsigned long)iov[seg].iov_base;
                size = iov[seg].iov_len;
                end += size;
                if ((addr & blocksize_mask) || (size & blocksize_mask)) 
                        goto out;
        }
        retval = 0;
out:
        return retval;
}
static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
                        const struct iovec *iov, loff_t offset,
                        unsigned long nr_segs)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        u64 lockstart, lockend;
        ssize_t ret;
        int writing = rw & WRITE;
        int write_bits = 0;
        size_t count = iov_length(iov, nr_segs);

        if (check_direct_IO(BTRFS_I(inode)->root, rw, iocb, iov,
                            offset, nr_segs)) {
                return 0;
        }

        lockstart = offset;
        lockend = offset + count - 1;

        if (writing) {
                ret = btrfs_delalloc_reserve_space(inode, count);
                if (ret)
                        goto out;
        }

        while (1) {
                lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                 0, &cached_state, GFP_NOFS);
                /*
                 * We're concerned with the entire range that we're going to be
                 * doing DIO to, so we need to make sure theres no ordered
                 * extents in this range.
                 */
                ordered = btrfs_lookup_ordered_range(inode, lockstart,
                                                     lockend - lockstart + 1);
                if (!ordered)
                        break;
                unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                     &cached_state, GFP_NOFS);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                cond_resched();
        }

        /*
         * we don't use btrfs_set_extent_delalloc because we don't want
         * the dirty or uptodate bits
         */
        if (writing) {
                write_bits = EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING;
                ret = set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                                     EXTENT_DELALLOC, 0, NULL, &cached_state,
                                     GFP_NOFS);
                if (ret) {
                        clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
                                         lockend, EXTENT_LOCKED | write_bits,
                                         1, 0, &cached_state, GFP_NOFS);
                        goto out;
                }
        }

        free_extent_state(cached_state);
        cached_state = NULL;

        ret = __blockdev_direct_IO(rw, iocb, inode,
                   BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev,
                   iov, offset, nr_segs, btrfs_get_blocks_direct, NULL,
                   btrfs_submit_direct, 0);

        if (ret < 0 && ret != -EIOCBQUEUED) {
                clear_extent_bit(&BTRFS_I(inode)->io_tree, offset,
                              offset + iov_length(iov, nr_segs) - 1,
                              EXTENT_LOCKED | write_bits, 1, 0,
                              &cached_state, GFP_NOFS);
        } else if (ret >= 0 && ret < iov_length(iov, nr_segs)) {
                /*
                 * We're falling back to buffered, unlock the section we didn't
                 * do IO on.
                 */
                clear_extent_bit(&BTRFS_I(inode)->io_tree, offset + ret,
                              offset + iov_length(iov, nr_segs) - 1,
                              EXTENT_LOCKED | write_bits, 1, 0,
                              &cached_state, GFP_NOFS);
        }
out:
        free_extent_state(cached_state);
        return ret;
}

static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
                __u64 start, __u64 len)
{
        return extent_fiemap(inode, fieinfo, start, len, btrfs_get_extent);
}

int btrfs_readpage(struct file *file, struct page *page)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_read_full_page(tree, page, btrfs_get_extent);
}

static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
{
        struct extent_io_tree *tree;


        if (current->flags & PF_MEMALLOC) {
                redirty_page_for_writepage(wbc, page);
                unlock_page(page);
                return 0;
        }
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
}

int btrfs_writepages(struct address_space *mapping,
                     struct writeback_control *wbc)
{
        struct extent_io_tree *tree;

        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_writepages(tree, mapping, btrfs_get_extent, wbc);
}

static int
btrfs_readpages(struct file *file, struct address_space *mapping,
                struct list_head *pages, unsigned nr_pages)
{
        struct extent_io_tree *tree;
        tree = &BTRFS_I(mapping->host)->io_tree;
        return extent_readpages(tree, mapping, pages, nr_pages,
                                btrfs_get_extent);
}
static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct extent_io_tree *tree;
        struct extent_map_tree *map;
        int ret;

        tree = &BTRFS_I(page->mapping->host)->io_tree;
        map = &BTRFS_I(page->mapping->host)->extent_tree;
        ret = try_release_extent_mapping(map, tree, page, gfp_flags);
        if (ret == 1) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
        return ret;
}

static int btrfs_releasepage(struct page *page, gfp_t gfp_flags)
{
        if (PageWriteback(page) || PageDirty(page))
                return 0;
        return __btrfs_releasepage(page, gfp_flags & GFP_NOFS);
}

static void btrfs_invalidatepage(struct page *page, unsigned long offset)
{
        struct extent_io_tree *tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        u64 page_start = page_offset(page);
        u64 page_end = page_start + PAGE_CACHE_SIZE - 1;


        /*
         * we have the page locked, so new writeback can't start,
         * and the dirty bit won't be cleared while we are here.
         *
         * Wait for IO on this page so that we can safely clear
         * the PagePrivate2 bit and do ordered accounting
         */
        wait_on_page_writeback(page);

        tree = &BTRFS_I(page->mapping->host)->io_tree;
        if (offset) {
                btrfs_releasepage(page, GFP_NOFS);
                return;
        }
        lock_extent_bits(tree, page_start, page_end, 0, &cached_state,
                         GFP_NOFS);
        ordered = btrfs_lookup_ordered_extent(page->mapping->host,
                                           page_offset(page));
        if (ordered) {
                /*
                 * IO on this page will never be started, so we need
                 * to account for any ordered extents now
                 */
                clear_extent_bit(tree, page_start, page_end,
                                 EXTENT_DIRTY | EXTENT_DELALLOC |
                                 EXTENT_LOCKED | EXTENT_DO_ACCOUNTING, 1, 0,
                                 &cached_state, GFP_NOFS);
                /*
                 * whoever cleared the private bit is responsible
                 * for the finish_ordered_io
                 */
                if (TestClearPagePrivate2(page)) {
                        btrfs_finish_ordered_io(page->mapping->host,
                                                page_start, page_end);
                }
                btrfs_put_ordered_extent(ordered);
                cached_state = NULL;
                lock_extent_bits(tree, page_start, page_end, 0, &cached_state,
                                 GFP_NOFS);
        }
        clear_extent_bit(tree, page_start, page_end,
                 EXTENT_LOCKED | EXTENT_DIRTY | EXTENT_DELALLOC |
                 EXTENT_DO_ACCOUNTING, 1, 1, &cached_state, GFP_NOFS);
        __btrfs_releasepage(page, GFP_NOFS);

        ClearPageChecked(page);
        if (PagePrivate(page)) {
                ClearPagePrivate(page);
                set_page_private(page, 0);
                page_cache_release(page);
        }
}

/*
 * btrfs_page_mkwrite() is not allowed to change the file size as it gets
 * called from a page fault handler when a page is first dirtied. Hence we must
 * be careful to check for EOF conditions here. We set the page up correctly
 * for a written page which means we get ENOSPC checking when writing into
 * holes and correct delalloc and unwritten extent mapping on filesystems that
 * support these features.
 *
 * We are not allowed to take the i_mutex here so we have to play games to
 * protect against truncate races as the page could now be beyond EOF.  Because
 * vmtruncate() writes the inode size before removing pages, once we have the
 * page lock we can determine safely if the page is beyond EOF. If it is not
 * beyond EOF, then the page is guaranteed safe against truncation until we
 * unlock the page.
 */
int btrfs_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct inode *inode = fdentry(vma->vm_file)->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
        struct btrfs_ordered_extent *ordered;
        struct extent_state *cached_state = NULL;
        char *kaddr;
        unsigned long zero_start;
        loff_t size;
        int ret;
        u64 page_start;
        u64 page_end;

        ret  = btrfs_delalloc_reserve_space(inode, PAGE_CACHE_SIZE);
        if (ret) {
                if (ret == -ENOMEM)
                        ret = VM_FAULT_OOM;
                else /* -ENOSPC, -EIO, etc */
                        ret = VM_FAULT_SIGBUS;
                goto out;
        }

        ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
again:
        lock_page(page);
        size = i_size_read(inode);
        page_start = page_offset(page);
        page_end = page_start + PAGE_CACHE_SIZE - 1;

        if ((page->mapping != inode->i_mapping) ||
            (page_start >= size)) {
                /* page got truncated out from underneath us */
                goto out_unlock;
        }
        wait_on_page_writeback(page);

        lock_extent_bits(io_tree, page_start, page_end, 0, &cached_state,
                         GFP_NOFS);
        set_page_extent_mapped(page);

        /*
         * we can't set the delalloc bits if there are pending ordered
         * extents.  Drop our locks and wait for them to finish
         */
        ordered = btrfs_lookup_ordered_extent(inode, page_start);
        if (ordered) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                unlock_page(page);
                btrfs_start_ordered_extent(inode, ordered, 1);
                btrfs_put_ordered_extent(ordered);
                goto again;
        }

        /*
         * XXX - page_mkwrite gets called every time the page is dirtied, even
         * if it was already dirty, so for space accounting reasons we need to
         * clear any delalloc bits for the range we are fixing to save.  There
         * is probably a better way to do this, but for now keep consistent with
         * prepare_pages in the normal write path.
         */
        clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start, page_end,
                          EXTENT_DIRTY | EXTENT_DELALLOC | EXTENT_DO_ACCOUNTING,
                          0, 0, &cached_state, GFP_NOFS);

        ret = btrfs_set_extent_delalloc(inode, page_start, page_end,
                                        &cached_state);
        if (ret) {
                unlock_extent_cached(io_tree, page_start, page_end,
                                     &cached_state, GFP_NOFS);
                ret = VM_FAULT_SIGBUS;
                goto out_unlock;
        }
        ret = 0;

        /* page is wholly or partially inside EOF */
        if (page_start + PAGE_CACHE_SIZE > size)
                zero_start = size & ~PAGE_CACHE_MASK;
        else
                zero_start = PAGE_CACHE_SIZE;

        if (zero_start != PAGE_CACHE_SIZE) {
                kaddr = kmap(page);
                memset(kaddr + zero_start, 0, PAGE_CACHE_SIZE - zero_start);
                flush_dcache_page(page);
                kunmap(page);
        }
        ClearPageChecked(page);
        set_page_dirty(page);
        SetPageUptodate(page);

        BTRFS_I(inode)->last_trans = root->fs_info->generation;
        BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;

        unlock_extent_cached(io_tree, page_start, page_end, &cached_state, GFP_NOFS);

out_unlock:
        if (!ret)
                return VM_FAULT_LOCKED;
        unlock_page(page);
        btrfs_delalloc_release_space(inode, PAGE_CACHE_SIZE);
out:
        return ret;
}

static void btrfs_truncate(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret;
        struct btrfs_trans_handle *trans;
        unsigned long nr;
        u64 mask = root->sectorsize - 1;

        if (!S_ISREG(inode->i_mode)) {
                WARN_ON(1);
                return;
        }

        ret = btrfs_truncate_page(inode->i_mapping, inode->i_size);
        if (ret)
                return;

        btrfs_wait_ordered_range(inode, inode->i_size & (~mask), (u64)-1);
        btrfs_ordered_update_i_size(inode, inode->i_size, NULL);

        trans = btrfs_start_transaction(root, 0);
        BUG_ON(IS_ERR(trans));
        btrfs_set_trans_block_group(trans, inode);
        trans->block_rsv = root->orphan_block_rsv;

        /*
         * setattr is responsible for setting the ordered_data_close flag,
         * but that is only tested during the last file release.  That
         * could happen well after the next commit, leaving a great big
         * window where new writes may get lost if someone chooses to write
         * to this file after truncating to zero
         *
         * The inode doesn't have any dirty data here, and so if we commit
         * this is a noop.  If someone immediately starts writing to the inode
         * it is very likely we'll catch some of their writes in this
         * transaction, and the commit will find this file on the ordered
         * data list with good things to send down.
         *
         * This is a best effort solution, there is still a window where
         * using truncate to replace the contents of the file will
         * end up with a zero length file after a crash.
         */
        if (inode->i_size == 0 && BTRFS_I(inode)->ordered_data_close)
                btrfs_add_ordered_operation(trans, root, inode);

        while (1) {
                if (!trans) {
                        trans = btrfs_start_transaction(root, 0);
                        BUG_ON(IS_ERR(trans));
                        btrfs_set_trans_block_group(trans, inode);
                        trans->block_rsv = root->orphan_block_rsv;
                }

                ret = btrfs_block_rsv_check(trans, root,
                                            root->orphan_block_rsv, 0, 5);
                if (ret) {
                        BUG_ON(ret != -EAGAIN);
                        ret = btrfs_commit_transaction(trans, root);
                        BUG_ON(ret);
                        trans = NULL;
                        continue;
                }

                ret = btrfs_truncate_inode_items(trans, root, inode,
                                                 inode->i_size,
                                                 BTRFS_EXTENT_DATA_KEY);
                if (ret != -EAGAIN)
                        break;

                ret = btrfs_update_inode(trans, root, inode);
                BUG_ON(ret);

                nr = trans->blocks_used;
                btrfs_end_transaction(trans, root);
                trans = NULL;
                btrfs_btree_balance_dirty(root, nr);
        }

        if (ret == 0 && inode->i_nlink > 0) {
                ret = btrfs_orphan_del(trans, inode);
                BUG_ON(ret);
        }

        ret = btrfs_update_inode(trans, root, inode);
        BUG_ON(ret);

        nr = trans->blocks_used;
        ret = btrfs_end_transaction_throttle(trans, root);
        BUG_ON(ret);
        btrfs_btree_balance_dirty(root, nr);
}

/*
 * create a new subvolume directory/inode (helper for the ioctl).
 */
int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
                             struct btrfs_root *new_root,
                             u64 new_dirid, u64 alloc_hint)
{
        struct inode *inode;
        int err;
        u64 index = 0;

        inode = btrfs_new_inode(trans, new_root, NULL, "..", 2, new_dirid,
                                new_dirid, alloc_hint, S_IFDIR | 0700, &index);
        if (IS_ERR(inode))
                return PTR_ERR(inode);
        inode->i_op = &btrfs_dir_inode_operations;
        inode->i_fop = &btrfs_dir_file_operations;

        inode->i_nlink = 1;
        btrfs_i_size_write(inode, 0);

        err = btrfs_update_inode(trans, new_root, inode);
        BUG_ON(err);

        iput(inode);
        return 0;
}

/* helper function for file defrag and space balancing.  This
 * forces readahead on a given range of bytes in an inode
 */
unsigned long btrfs_force_ra(struct address_space *mapping,
                              struct file_ra_state *ra, struct file *file,
                              pgoff_t offset, pgoff_t last_index)
{
        pgoff_t req_size = last_index - offset + 1;

        page_cache_sync_readahead(mapping, ra, file, offset, req_size);
        return offset + req_size;
}

struct inode *btrfs_alloc_inode(struct super_block *sb)
{
        struct btrfs_inode *ei;
        struct inode *inode;

        ei = kmem_cache_alloc(btrfs_inode_cachep, GFP_NOFS);
        if (!ei)
                return NULL;

        ei->root = NULL;
        ei->space_info = NULL;
        ei->generation = 0;
        ei->sequence = 0;
        ei->last_trans = 0;
        ei->last_sub_trans = 0;
        ei->logged_trans = 0;
        ei->delalloc_bytes = 0;
        ei->reserved_bytes = 0;
        ei->disk_i_size = 0;
        ei->flags = 0;
        ei->index_cnt = (u64)-1;
        ei->last_unlink_trans = 0;

        spin_lock_init(&ei->accounting_lock);
        atomic_set(&ei->outstanding_extents, 0);
        ei->reserved_extents = 0;

        ei->ordered_data_close = 0;
        ei->orphan_meta_reserved = 0;
        ei->dummy_inode = 0;
        ei->force_compress = 0;

        inode = &ei->vfs_inode;
        extent_map_tree_init(&ei->extent_tree, GFP_NOFS);
        extent_io_tree_init(&ei->io_tree, &inode->i_data, GFP_NOFS);
        extent_io_tree_init(&ei->io_failure_tree, &inode->i_data, GFP_NOFS);
        mutex_init(&ei->log_mutex);
        btrfs_ordered_inode_tree_init(&ei->ordered_tree);
        INIT_LIST_HEAD(&ei->i_orphan);
        INIT_LIST_HEAD(&ei->delalloc_inodes);
        INIT_LIST_HEAD(&ei->ordered_operations);
        RB_CLEAR_NODE(&ei->rb_node);

        return inode;
}

static void btrfs_i_callback(struct rcu_head *head)
{
        struct inode *inode = container_of(head, struct inode, i_rcu);
        INIT_LIST_HEAD(&inode->i_dentry);
        kmem_cache_free(btrfs_inode_cachep, BTRFS_I(inode));
}

void btrfs_destroy_inode(struct inode *inode)
{
        struct btrfs_ordered_extent *ordered;
        struct btrfs_root *root = BTRFS_I(inode)->root;

        WARN_ON(!list_empty(&inode->i_dentry));
        WARN_ON(inode->i_data.nrpages);
        WARN_ON(atomic_read(&BTRFS_I(inode)->outstanding_extents));
        WARN_ON(BTRFS_I(inode)->reserved_extents);

        /*
         * This can happen where we create an inode, but somebody else also
         * created the same inode and we need to destroy the one we already
         * created.
         */
        if (!root)
                goto free;

        /*
         * Make sure we're properly removed from the ordered operation
         * lists.
         */
        smp_mb();
        if (!list_empty(&BTRFS_I(inode)->ordered_operations)) {
                spin_lock(&root->fs_info->ordered_extent_lock);
                list_del_init(&BTRFS_I(inode)->ordered_operations);
                spin_unlock(&root->fs_info->ordered_extent_lock);
        }

        if (root == root->fs_info->tree_root) {
                struct btrfs_block_group_cache *block_group;

                block_group = btrfs_lookup_block_group(root->fs_info,
                                                BTRFS_I(inode)->block_group);
                if (block_group && block_group->inode == inode) {
                        spin_lock(&block_group->lock);
                        block_group->inode = NULL;
                        spin_unlock(&block_group->lock);
                        btrfs_put_block_group(block_group);
                } else if (block_group) {
                        btrfs_put_block_group(block_group);
                }
        }

        spin_lock(&root->orphan_lock);
        if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                printk(KERN_INFO "BTRFS: inode %lu still on the orphan list\n",
                       inode->i_ino);
                list_del_init(&BTRFS_I(inode)->i_orphan);
        }
        spin_unlock(&root->orphan_lock);

        while (1) {
                ordered = btrfs_lookup_first_ordered_extent(inode, (u64)-1);
                if (!ordered)
                        break;
                else {
                        printk(KERN_ERR "btrfs found ordered "
                               "extent %llu %llu on inode cleanup\n",
                               (unsigned long long)ordered->file_offset,
                               (unsigned long long)ordered->len);
                        btrfs_remove_ordered_extent(inode, ordered);
                        btrfs_put_ordered_extent(ordered);
                        btrfs_put_ordered_extent(ordered);
                }
        }
        inode_tree_del(inode);
        btrfs_drop_extent_cache(inode, 0, (u64)-1, 0);
free:
        call_rcu(&inode->i_rcu, btrfs_i_callback);
}

int btrfs_drop_inode(struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;

        if (btrfs_root_refs(&root->root_item) == 0 &&
            root != root->fs_info->tree_root)
                return 1;
        else
                return generic_drop_inode(inode);
}

static void init_once(void *foo)
{
        struct btrfs_inode *ei = (struct btrfs_inode *) foo;

        inode_init_once(&ei->vfs_inode);
}

void btrfs_destroy_cachep(void)
{
        if (btrfs_inode_cachep)
                kmem_cache_destroy(btrfs_inode_cachep);
        if (btrfs_trans_handle_cachep)
                kmem_cache_destroy(btrfs_trans_handle_cachep);
        if (btrfs_transaction_cachep)
                kmem_cache_destroy(btrfs_transaction_cachep);
        if (btrfs_path_cachep)
                kmem_cache_destroy(btrfs_path_cachep);
}

int btrfs_init_cachep(void)
{
        btrfs_inode_cachep = kmem_cache_create("btrfs_inode_cache",
                        sizeof(struct btrfs_inode), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, init_once);
        if (!btrfs_inode_cachep)
                goto fail;

        btrfs_trans_handle_cachep = kmem_cache_create("btrfs_trans_handle_cache",
                        sizeof(struct btrfs_trans_handle), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_trans_handle_cachep)
                goto fail;

        btrfs_transaction_cachep = kmem_cache_create("btrfs_transaction_cache",
                        sizeof(struct btrfs_transaction), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_transaction_cachep)
                goto fail;

        btrfs_path_cachep = kmem_cache_create("btrfs_path_cache",
                        sizeof(struct btrfs_path), 0,
                        SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD, NULL);
        if (!btrfs_path_cachep)
                goto fail;

        return 0;
fail:
        btrfs_destroy_cachep();
        return -ENOMEM;
}

static int btrfs_getattr(struct vfsmount *mnt,
                         struct dentry *dentry, struct kstat *stat)
{
        struct inode *inode = dentry->d_inode;
        generic_fillattr(inode, stat);
        stat->dev = BTRFS_I(inode)->root->anon_super.s_dev;
        stat->blksize = PAGE_CACHE_SIZE;
        stat->blocks = (inode_get_bytes(inode) +
                        BTRFS_I(inode)->delalloc_bytes) >> 9;
        return 0;
}

static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
                           struct inode *new_dir, struct dentry *new_dentry)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(old_dir)->root;
        struct btrfs_root *dest = BTRFS_I(new_dir)->root;
        struct inode *new_inode = new_dentry->d_inode;
        struct inode *old_inode = old_dentry->d_inode;
        struct timespec ctime = CURRENT_TIME;
        u64 index = 0;
        u64 root_objectid;
        int ret;

        if (new_dir->i_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
                return -EPERM;

        /* we only allow rename subvolume link between subvolumes */
        if (old_inode->i_ino != BTRFS_FIRST_FREE_OBJECTID && root != dest)
                return -EXDEV;

        if (old_inode->i_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID ||
            (new_inode && new_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID))
                return -ENOTEMPTY;

        if (S_ISDIR(old_inode->i_mode) && new_inode &&
            new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                return -ENOTEMPTY;
        /*
         * we're using rename to replace one file with another.
         * and the replacement file is large.  Start IO on it now so
         * we don't add too much work to the end of the transaction
         */
        if (new_inode && S_ISREG(old_inode->i_mode) && new_inode->i_size &&
            old_inode->i_size > BTRFS_ORDERED_OPERATIONS_FLUSH_LIMIT)
                filemap_flush(old_inode->i_mapping);

        /* close the racy window with snapshot create/destroy ioctl */
        if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                down_read(&root->fs_info->subvol_sem);
        /*
         * We want to reserve the absolute worst case amount of items.  So if
         * both inodes are subvols and we need to unlink them then that would
         * require 4 item modifications, but if they are both normal inodes it
         * would require 5 item modifications, so we'll assume their normal
         * inodes.  So 5 * 2 is 10, plus 1 for the new link, so 11 total items
         * should cover the worst case number of items we'll modify.
         */
        trans = btrfs_start_transaction(root, 20);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, new_dir);

        if (dest != root)
                btrfs_record_root_in_trans(trans, dest);

        ret = btrfs_set_inode_index(new_dir, &index);
        if (ret)
                goto out_fail;

        if (unlikely(old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                /* force full log commit if subvolume involved. */
                root->fs_info->last_trans_log_full_commit = trans->transid;
        } else {
                ret = btrfs_insert_inode_ref(trans, dest,
                                             new_dentry->d_name.name,
                                             new_dentry->d_name.len,
                                             old_inode->i_ino,
                                             new_dir->i_ino, index);
                if (ret)
                        goto out_fail;
                /*
                 * this is an ugly little race, but the rename is required
                 * to make sure that if we crash, the inode is either at the
                 * old name or the new one.  pinning the log transaction lets
                 * us make sure we don't allow a log commit to come in after
                 * we unlink the name but before we add the new name back in.
                 */
                btrfs_pin_log_trans(root);
        }
        /*
         * make sure the inode gets flushed if it is replacing
         * something.
         */
        if (new_inode && new_inode->i_size &&
            old_inode && S_ISREG(old_inode->i_mode)) {
                btrfs_add_ordered_operation(trans, root, old_inode);
        }

        old_dir->i_ctime = old_dir->i_mtime = ctime;
        new_dir->i_ctime = new_dir->i_mtime = ctime;
        old_inode->i_ctime = ctime;

        if (old_dentry->d_parent != new_dentry->d_parent)
                btrfs_record_unlink_dir(trans, old_dir, old_inode, 1);

        if (unlikely(old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)) {
                root_objectid = BTRFS_I(old_inode)->root->root_key.objectid;
                ret = btrfs_unlink_subvol(trans, root, old_dir, root_objectid,
                                        old_dentry->d_name.name,
                                        old_dentry->d_name.len);
        } else {
                btrfs_inc_nlink(old_dentry->d_inode);
                ret = btrfs_unlink_inode(trans, root, old_dir,
                                         old_dentry->d_inode,
                                         old_dentry->d_name.name,
                                         old_dentry->d_name.len);
        }
        BUG_ON(ret);

        if (new_inode) {
                new_inode->i_ctime = CURRENT_TIME;
                if (unlikely(new_inode->i_ino ==
                             BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)) {
                        root_objectid = BTRFS_I(new_inode)->location.objectid;
                        ret = btrfs_unlink_subvol(trans, dest, new_dir,
                                                root_objectid,
                                                new_dentry->d_name.name,
                                                new_dentry->d_name.len);
                        BUG_ON(new_inode->i_nlink == 0);
                } else {
                        ret = btrfs_unlink_inode(trans, dest, new_dir,
                                                 new_dentry->d_inode,
                                                 new_dentry->d_name.name,
                                                 new_dentry->d_name.len);
                }
                BUG_ON(ret);
                if (new_inode->i_nlink == 0) {
                        ret = btrfs_orphan_add(trans, new_dentry->d_inode);
                        BUG_ON(ret);
                }
        }

        ret = btrfs_add_link(trans, new_dir, old_inode,
                             new_dentry->d_name.name,
                             new_dentry->d_name.len, 0, index);
        BUG_ON(ret);

        if (old_inode->i_ino != BTRFS_FIRST_FREE_OBJECTID) {
                struct dentry *parent = dget_parent(new_dentry);
                btrfs_log_new_name(trans, old_inode, old_dir, parent);
                dput(parent);
                btrfs_end_log_trans(root);
        }
out_fail:
        btrfs_end_transaction_throttle(trans, root);

        if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                up_read(&root->fs_info->subvol_sem);

        return ret;
}

/*
 * some fairly slow code that needs optimization. This walks the list
 * of all the inodes with pending delalloc and forces them to disk.
 */
int btrfs_start_delalloc_inodes(struct btrfs_root *root, int delay_iput)
{
        struct list_head *head = &root->fs_info->delalloc_inodes;
        struct btrfs_inode *binode;
        struct inode *inode;

        if (root->fs_info->sb->s_flags & MS_RDONLY)
                return -EROFS;

        spin_lock(&root->fs_info->delalloc_lock);
        while (!list_empty(head)) {
                binode = list_entry(head->next, struct btrfs_inode,
                                    delalloc_inodes);
                inode = igrab(&binode->vfs_inode);
                if (!inode)
                        list_del_init(&binode->delalloc_inodes);
                spin_unlock(&root->fs_info->delalloc_lock);
                if (inode) {
                        filemap_flush(inode->i_mapping);
                        if (delay_iput)
                                btrfs_add_delayed_iput(inode);
                        else
                                iput(inode);
                }
                cond_resched();
                spin_lock(&root->fs_info->delalloc_lock);
        }
        spin_unlock(&root->fs_info->delalloc_lock);

        /* the filemap_flush will queue IO into the worker threads, but
         * we have to make sure the IO is actually started and that
         * ordered extents get created before we return
         */
        atomic_inc(&root->fs_info->async_submit_draining);
        while (atomic_read(&root->fs_info->nr_async_submits) ||
              atomic_read(&root->fs_info->async_delalloc_pages)) {
                wait_event(root->fs_info->async_submit_wait,
                   (atomic_read(&root->fs_info->nr_async_submits) == 0 &&
                    atomic_read(&root->fs_info->async_delalloc_pages) == 0));
        }
        atomic_dec(&root->fs_info->async_submit_draining);
        return 0;
}

int btrfs_start_one_delalloc_inode(struct btrfs_root *root, int delay_iput,
                                   int sync)
{
        struct btrfs_inode *binode;
        struct inode *inode = NULL;

        spin_lock(&root->fs_info->delalloc_lock);
        while (!list_empty(&root->fs_info->delalloc_inodes)) {
                binode = list_entry(root->fs_info->delalloc_inodes.next,
                                    struct btrfs_inode, delalloc_inodes);
                inode = igrab(&binode->vfs_inode);
                if (inode) {
                        list_move_tail(&binode->delalloc_inodes,
                                       &root->fs_info->delalloc_inodes);
                        break;
                }

                list_del_init(&binode->delalloc_inodes);
                cond_resched_lock(&root->fs_info->delalloc_lock);
        }
        spin_unlock(&root->fs_info->delalloc_lock);

        if (inode) {
                if (sync) {
                        filemap_write_and_wait(inode->i_mapping);
                        /*
                         * We have to do this because compression doesn't
                         * actually set PG_writeback until it submits the pages
                         * for IO, which happens in an async thread, so we could
                         * race and not actually wait for any writeback pages
                         * because they've not been submitted yet.  Technically
                         * this could still be the case for the ordered stuff
                         * since the async thread may not have started to do its
                         * work yet.  If this becomes the case then we need to
                         * figure out a way to make sure that in writepage we
                         * wait for any async pages to be submitted before
                         * returning so that fdatawait does what its supposed to
                         * do.
                         */
                        btrfs_wait_ordered_range(inode, 0, (u64)-1);
                } else {
                        filemap_flush(inode->i_mapping);
                }
                if (delay_iput)
                        btrfs_add_delayed_iput(inode);
                else
                        iput(inode);
                return 1;
        }
        return 0;
}

static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
                         const char *symname)
{
        struct btrfs_trans_handle *trans;
        struct btrfs_root *root = BTRFS_I(dir)->root;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct inode *inode = NULL;
        int err;
        int drop_inode = 0;
        u64 objectid;
        u64 index = 0 ;
        int name_len;
        int datasize;
        unsigned long ptr;
        struct btrfs_file_extent_item *ei;
        struct extent_buffer *leaf;
        unsigned long nr = 0;

        name_len = strlen(symname) + 1;
        if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                return -ENAMETOOLONG;

        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
        if (err)
                return err;
        /*
         * 2 items for inode item and ref
         * 2 items for dir items
         * 1 item for xattr if selinux is on
         */
        trans = btrfs_start_transaction(root, 5);
        if (IS_ERR(trans))
                return PTR_ERR(trans);

        btrfs_set_trans_block_group(trans, dir);

        inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                dentry->d_name.len, dir->i_ino, objectid,
                                BTRFS_I(dir)->block_group, S_IFLNK|S_IRWXUGO,
                                &index);
        err = PTR_ERR(inode);
        if (IS_ERR(inode))
                goto out_unlock;

        err = btrfs_init_inode_security(trans, inode, dir);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }

        btrfs_set_trans_block_group(trans, inode);
        err = btrfs_add_nondir(trans, dir, dentry, inode, 0, index);
        if (err)
                drop_inode = 1;
        else {
                inode->i_mapping->a_ops = &btrfs_aops;
                inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
                inode->i_fop = &btrfs_file_operations;
                inode->i_op = &btrfs_file_inode_operations;
                BTRFS_I(inode)->io_tree.ops = &btrfs_extent_io_ops;
        }
        btrfs_update_inode_block_group(trans, inode);
        btrfs_update_inode_block_group(trans, dir);
        if (drop_inode)
                goto out_unlock;

        path = btrfs_alloc_path();
        BUG_ON(!path);
        key.objectid = inode->i_ino;
        key.offset = 0;
        btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
        datasize = btrfs_file_extent_calc_inline_size(name_len);
        err = btrfs_insert_empty_item(trans, root, path, &key,
                                      datasize);
        if (err) {
                drop_inode = 1;
                goto out_unlock;
        }
        leaf = path->nodes[0];
        ei = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, ei, trans->transid);
        btrfs_set_file_extent_type(leaf, ei,
                                   BTRFS_FILE_EXTENT_INLINE);
        btrfs_set_file_extent_encryption(leaf, ei, 0);
        btrfs_set_file_extent_compression(leaf, ei, 0);
        btrfs_set_file_extent_other_encoding(leaf, ei, 0);
        btrfs_set_file_extent_ram_bytes(leaf, ei, name_len);

        ptr = btrfs_file_extent_inline_start(ei);
        write_extent_buffer(leaf, symname, ptr, name_len);
        btrfs_mark_buffer_dirty(leaf);
        btrfs_free_path(path);

        inode->i_op = &btrfs_symlink_inode_operations;
        inode->i_mapping->a_ops = &btrfs_symlink_aops;
        inode->i_mapping->backing_dev_info = &root->fs_info->bdi;
        inode_set_bytes(inode, name_len);
        btrfs_i_size_write(inode, name_len - 1);
        err = btrfs_update_inode(trans, root, inode);
        if (err)
                drop_inode = 1;

out_unlock:
        nr = trans->blocks_used;
        btrfs_end_transaction_throttle(trans, root);
        if (drop_inode) {
                inode_dec_link_count(inode);
                iput(inode);
        }
        btrfs_btree_balance_dirty(root, nr);
        return err;
}

static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
                                       u64 start, u64 num_bytes, u64 min_size,
                                       loff_t actual_len, u64 *alloc_hint,
                                       struct btrfs_trans_handle *trans)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct btrfs_key ins;
        u64 cur_offset = start;
        u64 i_size;
        int ret = 0;
        bool own_trans = true;

        if (trans)
                own_trans = false;
        while (num_bytes > 0) {
                if (own_trans) {
                        trans = btrfs_start_transaction(root, 3);
                        if (IS_ERR(trans)) {
                                ret = PTR_ERR(trans);
                                break;
                        }
                }

                ret = btrfs_reserve_extent(trans, root, num_bytes, min_size,
                                           0, *alloc_hint, (u64)-1, &ins, 1);
                if (ret) {
                        if (own_trans)
                                btrfs_end_transaction(trans, root);
                        break;
                }

                ret = insert_reserved_file_extent(trans, inode,
                                                  cur_offset, ins.objectid,
                                                  ins.offset, ins.offset,
                                                  ins.offset, 0, 0, 0,
                                                  BTRFS_FILE_EXTENT_PREALLOC);
                BUG_ON(ret);
                btrfs_drop_extent_cache(inode, cur_offset,
                                        cur_offset + ins.offset -1, 0);

                num_bytes -= ins.offset;
                cur_offset += ins.offset;
                *alloc_hint = ins.objectid + ins.offset;

                inode->i_ctime = CURRENT_TIME;
                BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
                if (!(mode & FALLOC_FL_KEEP_SIZE) &&
                    (actual_len > inode->i_size) &&
                    (cur_offset > inode->i_size)) {
                        if (cur_offset > actual_len)
                                i_size = actual_len;
                        else
                                i_size = cur_offset;
                        i_size_write(inode, i_size);
                        btrfs_ordered_update_i_size(inode, i_size, NULL);
                }

                ret = btrfs_update_inode(trans, root, inode);
                BUG_ON(ret);

                if (own_trans)
                        btrfs_end_transaction(trans, root);
        }
        return ret;
}

int btrfs_prealloc_file_range(struct inode *inode, int mode,
                              u64 start, u64 num_bytes, u64 min_size,
                              loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint,
                                           NULL);
}

int btrfs_prealloc_file_range_trans(struct inode *inode,
                                    struct btrfs_trans_handle *trans, int mode,
                                    u64 start, u64 num_bytes, u64 min_size,
                                    loff_t actual_len, u64 *alloc_hint)
{
        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
                                           min_size, actual_len, alloc_hint, trans);
}

static int btrfs_set_page_dirty(struct page *page)
{
        return __set_page_dirty_nobuffers(page);
}

static int btrfs_permission(struct inode *inode, int mask, unsigned int flags)
{
        if ((BTRFS_I(inode)->flags & BTRFS_INODE_READONLY) && (mask & MAY_WRITE))
                return -EACCES;
        return generic_permission(inode, mask, flags, btrfs_check_acl);
}

static const struct inode_operations btrfs_dir_inode_operations = {
        .getattr        = btrfs_getattr,
        .lookup         = btrfs_lookup,
        .create         = btrfs_create,
        .unlink         = btrfs_unlink,
        .link           = btrfs_link,
        .mkdir          = btrfs_mkdir,
        .rmdir          = btrfs_rmdir,
        .rename         = btrfs_rename,
        .symlink        = btrfs_symlink,
        .setattr        = btrfs_setattr,
        .mknod          = btrfs_mknod,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .permission     = btrfs_permission,
};
static const struct inode_operations btrfs_dir_ro_inode_operations = {
        .lookup         = btrfs_lookup,
        .permission     = btrfs_permission,
};

static const struct file_operations btrfs_dir_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = generic_read_dir,
        .readdir        = btrfs_real_readdir,
        .unlocked_ioctl = btrfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = btrfs_ioctl,
#endif
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
};

static struct extent_io_ops btrfs_extent_io_ops = {
        .fill_delalloc = run_delalloc_range,
        .submit_bio_hook = btrfs_submit_bio_hook,
        .merge_bio_hook = btrfs_merge_bio_hook,
        .readpage_end_io_hook = btrfs_readpage_end_io_hook,
        .writepage_end_io_hook = btrfs_writepage_end_io_hook,
        .writepage_start_hook = btrfs_writepage_start_hook,
        .readpage_io_failed_hook = btrfs_io_failed_hook,
        .set_bit_hook = btrfs_set_bit_hook,
        .clear_bit_hook = btrfs_clear_bit_hook,
        .merge_extent_hook = btrfs_merge_extent_hook,
        .split_extent_hook = btrfs_split_extent_hook,
};

/*
 * btrfs doesn't support the bmap operation because swapfiles
 * use bmap to make a mapping of extents in the file.  They assume
 * these extents won't change over the life of the file and they
 * use the bmap result to do IO directly to the drive.
 *
 * the btrfs bmap call would return logical addresses that aren't
 * suitable for IO and they also will change frequently as COW
 * operations happen.  So, swapfile + btrfs == corruption.
 *
 * For now we're avoiding this by dropping bmap.
 */
static const struct address_space_operations btrfs_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .writepages     = btrfs_writepages,
        .readpages      = btrfs_readpages,
        .sync_page      = block_sync_page,
        .direct_IO      = btrfs_direct_IO,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
        .set_page_dirty = btrfs_set_page_dirty,
        .error_remove_page = generic_error_remove_page,
};

static const struct address_space_operations btrfs_symlink_aops = {
        .readpage       = btrfs_readpage,
        .writepage      = btrfs_writepage,
        .invalidatepage = btrfs_invalidatepage,
        .releasepage    = btrfs_releasepage,
};

static const struct inode_operations btrfs_file_inode_operations = {
        .truncate       = btrfs_truncate,
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
        .permission     = btrfs_permission,
        .fiemap         = btrfs_fiemap,
};
static const struct inode_operations btrfs_special_inode_operations = {
        .getattr        = btrfs_getattr,
        .setattr        = btrfs_setattr,
        .permission     = btrfs_permission,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
};
static const struct inode_operations btrfs_symlink_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = page_follow_link_light,
        .put_link       = page_put_link,
        .getattr        = btrfs_getattr,
        .permission     = btrfs_permission,
        .setxattr       = btrfs_setxattr,
        .getxattr       = btrfs_getxattr,
        .listxattr      = btrfs_listxattr,
        .removexattr    = btrfs_removexattr,
};

const struct dentry_operations btrfs_dentry_operations = {
        .d_delete       = btrfs_dentry_delete,
};