From 2dcba4781fa3842e28f47ab23056d58cd283fca6 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 7 Dec 2015 15:04:57 -0500 Subject: [PATCH] ext4: get rid of EXT4_GET_BLOCKS_NO_LOCK flag When dioread_nolock mode is enabled, we grab i_data_sem in ext4_ext_direct_IO() and therefore we need to instruct _ext4_get_block() not to grab i_data_sem again using EXT4_GET_BLOCKS_NO_LOCK. However holding i_data_sem over overwrite direct IO isn't needed these days. We have exclusion against truncate / hole punching because we increase i_dio_count under i_mutex in ext4_ext_direct_IO() so once ext4_file_write_iter() verifies blocks are allocated & written, they are guaranteed to stay so during the whole direct IO even after we drop i_mutex. So we can just remove this locking abuse and the no longer necessary EXT4_GET_BLOCKS_NO_LOCK flag. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o --- fs/ext4/ext4.h | 4 +--- fs/ext4/inode.c | 43 +++++++++++++++++-------------------- include/trace/events/ext4.h | 3 +-- 3 files changed, 22 insertions(+), 28 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 80f76f092079..1008caf3136d 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -555,10 +555,8 @@ enum { #define EXT4_GET_BLOCKS_NO_NORMALIZE 0x0040 /* Request will not result in inode size update (user for fallocate) */ #define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080 - /* Do not take i_data_sem locking in ext4_map_blocks */ -#define EXT4_GET_BLOCKS_NO_LOCK 0x0100 /* Convert written extents to unwritten */ -#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0200 +#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0100 /* * The bit position of these flags must not overlap with any of the diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 472e608da13d..f100c1780e03 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -403,8 +403,7 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, * out taking i_data_sem. So at the time the unwritten extent * could be converted. */ - if (!(flags & EXT4_GET_BLOCKS_NO_LOCK)) - down_read(&EXT4_I(inode)->i_data_sem); + down_read(&EXT4_I(inode)->i_data_sem); if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) { retval = ext4_ext_map_blocks(handle, inode, map, flags & EXT4_GET_BLOCKS_KEEP_SIZE); @@ -412,8 +411,7 @@ static void ext4_map_blocks_es_recheck(handle_t *handle, retval = ext4_ind_map_blocks(handle, inode, map, flags & EXT4_GET_BLOCKS_KEEP_SIZE); } - if (!(flags & EXT4_GET_BLOCKS_NO_LOCK)) - up_read((&EXT4_I(inode)->i_data_sem)); + up_read((&EXT4_I(inode)->i_data_sem)); /* * We don't check m_len because extent will be collpased in status @@ -509,8 +507,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, * Try to see if we can get the block without requesting a new * file system block. */ - if (!(flags & EXT4_GET_BLOCKS_NO_LOCK)) - down_read(&EXT4_I(inode)->i_data_sem); + down_read(&EXT4_I(inode)->i_data_sem); if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) { retval = ext4_ext_map_blocks(handle, inode, map, flags & EXT4_GET_BLOCKS_KEEP_SIZE); @@ -541,8 +538,7 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, if (ret < 0) retval = ret; } - if (!(flags & EXT4_GET_BLOCKS_NO_LOCK)) - up_read((&EXT4_I(inode)->i_data_sem)); + up_read((&EXT4_I(inode)->i_data_sem)); found: if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) { @@ -674,7 +670,7 @@ static int _ext4_get_block(struct inode *inode, sector_t iblock, map.m_lblk = iblock; map.m_len = bh->b_size >> inode->i_blkbits; - if (flags && !(flags & EXT4_GET_BLOCKS_NO_LOCK) && !handle) { + if (flags && !handle) { /* Direct IO write... */ if (map.m_len > DIO_MAX_BLOCKS) map.m_len = DIO_MAX_BLOCKS; @@ -879,9 +875,6 @@ int do_journal_get_write_access(handle_t *handle, return ret; } -static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock, - struct buffer_head *bh_result, int create); - #ifdef CONFIG_EXT4_FS_ENCRYPTION static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len, get_block_t *get_block) @@ -3054,13 +3047,21 @@ int ext4_get_block_write(struct inode *inode, sector_t iblock, EXT4_GET_BLOCKS_IO_CREATE_EXT); } -static int ext4_get_block_write_nolock(struct inode *inode, sector_t iblock, +static int ext4_get_block_overwrite(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) { - ext4_debug("ext4_get_block_write_nolock: inode %lu, create flag %d\n", + int ret; + + ext4_debug("ext4_get_block_overwrite: inode %lu, create flag %d\n", inode->i_ino, create); - return _ext4_get_block(inode, iblock, bh_result, - EXT4_GET_BLOCKS_NO_LOCK); + ret = _ext4_get_block(inode, iblock, bh_result, 0); + /* + * Blocks should have been preallocated! ext4_file_write_iter() checks + * that. + */ + WARN_ON_ONCE(!buffer_mapped(bh_result)); + + return ret; } int ext4_get_block_dax(struct inode *inode, sector_t iblock, @@ -3143,10 +3144,8 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, /* If we do a overwrite dio, i_mutex locking can be released */ overwrite = *((int *)iocb->private); - if (overwrite) { - down_read(&EXT4_I(inode)->i_data_sem); + if (overwrite) mutex_unlock(&inode->i_mutex); - } /* * We could direct write to holes and fallocate. @@ -3189,7 +3188,7 @@ static ssize_t ext4_ext_direct_IO(struct kiocb *iocb, struct iov_iter *iter, } if (overwrite) { - get_block_func = ext4_get_block_write_nolock; + get_block_func = ext4_get_block_overwrite; } else { get_block_func = ext4_get_block_write; dio_flags = DIO_LOCKING; @@ -3245,10 +3244,8 @@ retake_lock: if (iov_iter_rw(iter) == WRITE) inode_dio_end(inode); /* take i_mutex locking again if we do a ovewrite dio */ - if (overwrite) { - up_read(&EXT4_I(inode)->i_data_sem); + if (overwrite) mutex_lock(&inode->i_mutex); - } return ret; } diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h index 594b4b29a224..5f2ace56efc5 100644 --- a/include/trace/events/ext4.h +++ b/include/trace/events/ext4.h @@ -42,8 +42,7 @@ struct extent_status; { EXT4_GET_BLOCKS_CONVERT, "CONVERT" }, \ { EXT4_GET_BLOCKS_METADATA_NOFAIL, "METADATA_NOFAIL" }, \ { EXT4_GET_BLOCKS_NO_NORMALIZE, "NO_NORMALIZE" }, \ - { EXT4_GET_BLOCKS_KEEP_SIZE, "KEEP_SIZE" }, \ - { EXT4_GET_BLOCKS_NO_LOCK, "NO_LOCK" }) + { EXT4_GET_BLOCKS_KEEP_SIZE, "KEEP_SIZE" }) #define show_mflags(flags) __print_flags(flags, "", \ { EXT4_MAP_NEW, "N" }, \ -- 2.20.1