4 * Copyright (C) 1994-1999 Linus Torvalds
8 * This file handles the generic file mmap semantics used by
9 * most "normal" filesystems (but you don't /have/ to use this:
10 * the NFS filesystem used to do this differently, for example)
12 #include <linux/export.h>
13 #include <linux/compiler.h>
15 #include <linux/uaccess.h>
16 #include <linux/aio.h>
17 #include <linux/capability.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/gfp.h>
21 #include <linux/swap.h>
22 #include <linux/mman.h>
23 #include <linux/pagemap.h>
24 #include <linux/file.h>
25 #include <linux/uio.h>
26 #include <linux/hash.h>
27 #include <linux/writeback.h>
28 #include <linux/backing-dev.h>
29 #include <linux/pagevec.h>
30 #include <linux/blkdev.h>
31 #include <linux/security.h>
32 #include <linux/cpuset.h>
33 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34 #include <linux/memcontrol.h>
35 #include <linux/cleancache.h>
38 #define CREATE_TRACE_POINTS
39 #include <trace/events/filemap.h>
42 * FIXME: remove all knowledge of the buffer layer from the core VM
44 #include <linux/buffer_head.h> /* for try_to_free_buffers */
49 * Shared mappings implemented 30.11.1994. It's not fully working yet,
52 * Shared mappings now work. 15.8.1995 Bruno.
54 * finished 'unifying' the page and buffer cache and SMP-threaded the
55 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
57 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
63 * ->i_mmap_mutex (truncate_pagecache)
64 * ->private_lock (__free_pte->__set_page_dirty_buffers)
65 * ->swap_lock (exclusive_swap_page, others)
66 * ->mapping->tree_lock
69 * ->i_mmap_mutex (truncate->unmap_mapping_range)
73 * ->page_table_lock or pte_lock (various, mainly in memory.c)
74 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
77 * ->lock_page (access_process_vm)
79 * ->i_mutex (generic_file_buffered_write)
80 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
83 * sb_lock (fs/fs-writeback.c)
84 * ->mapping->tree_lock (__sync_single_inode)
87 * ->anon_vma.lock (vma_adjust)
90 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
92 * ->page_table_lock or pte_lock
93 * ->swap_lock (try_to_unmap_one)
94 * ->private_lock (try_to_unmap_one)
95 * ->tree_lock (try_to_unmap_one)
96 * ->zone.lru_lock (follow_page->mark_page_accessed)
97 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
98 * ->private_lock (page_remove_rmap->set_page_dirty)
99 * ->tree_lock (page_remove_rmap->set_page_dirty)
100 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
101 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
103 * ->inode->i_lock (zap_pte_range->set_page_dirty)
104 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
107 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 * Delete a page from the page cache and free it. Caller has to make
112 * sure the page is locked and that nobody else uses it - or that usage
113 * is safe. The caller must hold the mapping's tree_lock.
115 void __delete_from_page_cache(struct page
*page
)
117 struct address_space
*mapping
= page
->mapping
;
119 trace_mm_filemap_delete_from_page_cache(page
);
121 * if we're uptodate, flush out into the cleancache, otherwise
122 * invalidate any existing cleancache entries. We can't leave
123 * stale data around in the cleancache once our page is gone
125 if (PageUptodate(page
) && PageMappedToDisk(page
))
126 cleancache_put_page(page
);
128 cleancache_invalidate_page(mapping
, page
);
130 radix_tree_delete(&mapping
->page_tree
, page
->index
);
131 page
->mapping
= NULL
;
132 /* Leave page->index set: truncation lookup relies upon it */
134 __dec_zone_page_state(page
, NR_FILE_PAGES
);
135 if (PageSwapBacked(page
))
136 __dec_zone_page_state(page
, NR_SHMEM
);
137 BUG_ON(page_mapped(page
));
140 * Some filesystems seem to re-dirty the page even after
141 * the VM has canceled the dirty bit (eg ext3 journaling).
143 * Fix it up by doing a final dirty accounting check after
144 * having removed the page entirely.
146 if (PageDirty(page
) && mapping_cap_account_dirty(mapping
)) {
147 dec_zone_page_state(page
, NR_FILE_DIRTY
);
148 dec_bdi_stat(mapping
->backing_dev_info
, BDI_RECLAIMABLE
);
153 * delete_from_page_cache - delete page from page cache
154 * @page: the page which the kernel is trying to remove from page cache
156 * This must be called only on pages that have been verified to be in the page
157 * cache and locked. It will never put the page into the free list, the caller
158 * has a reference on the page.
160 void delete_from_page_cache(struct page
*page
)
162 struct address_space
*mapping
= page
->mapping
;
163 void (*freepage
)(struct page
*);
165 BUG_ON(!PageLocked(page
));
167 freepage
= mapping
->a_ops
->freepage
;
168 spin_lock_irq(&mapping
->tree_lock
);
169 __delete_from_page_cache(page
);
170 spin_unlock_irq(&mapping
->tree_lock
);
171 mem_cgroup_uncharge_cache_page(page
);
175 page_cache_release(page
);
177 EXPORT_SYMBOL(delete_from_page_cache
);
179 static int sleep_on_page(void *word
)
185 static int sleep_on_page_killable(void *word
)
188 return fatal_signal_pending(current
) ? -EINTR
: 0;
191 static int filemap_check_errors(struct address_space
*mapping
)
194 /* Check for outstanding write errors */
195 if (test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
197 if (test_and_clear_bit(AS_EIO
, &mapping
->flags
))
203 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
204 * @mapping: address space structure to write
205 * @start: offset in bytes where the range starts
206 * @end: offset in bytes where the range ends (inclusive)
207 * @sync_mode: enable synchronous operation
209 * Start writeback against all of a mapping's dirty pages that lie
210 * within the byte offsets <start, end> inclusive.
212 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
213 * opposed to a regular memory cleansing writeback. The difference between
214 * these two operations is that if a dirty page/buffer is encountered, it must
215 * be waited upon, and not just skipped over.
217 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
218 loff_t end
, int sync_mode
)
221 struct writeback_control wbc
= {
222 .sync_mode
= sync_mode
,
223 .nr_to_write
= LONG_MAX
,
224 .range_start
= start
,
228 if (!mapping_cap_writeback_dirty(mapping
))
231 ret
= do_writepages(mapping
, &wbc
);
235 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
238 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
241 int filemap_fdatawrite(struct address_space
*mapping
)
243 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
245 EXPORT_SYMBOL(filemap_fdatawrite
);
247 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
250 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
252 EXPORT_SYMBOL(filemap_fdatawrite_range
);
255 * filemap_flush - mostly a non-blocking flush
256 * @mapping: target address_space
258 * This is a mostly non-blocking flush. Not suitable for data-integrity
259 * purposes - I/O may not be started against all dirty pages.
261 int filemap_flush(struct address_space
*mapping
)
263 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
265 EXPORT_SYMBOL(filemap_flush
);
268 * filemap_fdatawait_range - wait for writeback to complete
269 * @mapping: address space structure to wait for
270 * @start_byte: offset in bytes where the range starts
271 * @end_byte: offset in bytes where the range ends (inclusive)
273 * Walk the list of under-writeback pages of the given address space
274 * in the given range and wait for all of them.
276 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
279 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
280 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
285 if (end_byte
< start_byte
)
288 pagevec_init(&pvec
, 0);
289 while ((index
<= end
) &&
290 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
291 PAGECACHE_TAG_WRITEBACK
,
292 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
295 for (i
= 0; i
< nr_pages
; i
++) {
296 struct page
*page
= pvec
.pages
[i
];
298 /* until radix tree lookup accepts end_index */
299 if (page
->index
> end
)
302 wait_on_page_writeback(page
);
303 if (TestClearPageError(page
))
306 pagevec_release(&pvec
);
310 ret2
= filemap_check_errors(mapping
);
316 EXPORT_SYMBOL(filemap_fdatawait_range
);
319 * filemap_fdatawait - wait for all under-writeback pages to complete
320 * @mapping: address space structure to wait for
322 * Walk the list of under-writeback pages of the given address space
323 * and wait for all of them.
325 int filemap_fdatawait(struct address_space
*mapping
)
327 loff_t i_size
= i_size_read(mapping
->host
);
332 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
334 EXPORT_SYMBOL(filemap_fdatawait
);
336 int filemap_write_and_wait(struct address_space
*mapping
)
340 if (mapping
->nrpages
) {
341 err
= filemap_fdatawrite(mapping
);
343 * Even if the above returned error, the pages may be
344 * written partially (e.g. -ENOSPC), so we wait for it.
345 * But the -EIO is special case, it may indicate the worst
346 * thing (e.g. bug) happened, so we avoid waiting for it.
349 int err2
= filemap_fdatawait(mapping
);
354 err
= filemap_check_errors(mapping
);
358 EXPORT_SYMBOL(filemap_write_and_wait
);
361 * filemap_write_and_wait_range - write out & wait on a file range
362 * @mapping: the address_space for the pages
363 * @lstart: offset in bytes where the range starts
364 * @lend: offset in bytes where the range ends (inclusive)
366 * Write out and wait upon file offsets lstart->lend, inclusive.
368 * Note that `lend' is inclusive (describes the last byte to be written) so
369 * that this function can be used to write to the very end-of-file (end = -1).
371 int filemap_write_and_wait_range(struct address_space
*mapping
,
372 loff_t lstart
, loff_t lend
)
376 if (mapping
->nrpages
) {
377 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
379 /* See comment of filemap_write_and_wait() */
381 int err2
= filemap_fdatawait_range(mapping
,
387 err
= filemap_check_errors(mapping
);
391 EXPORT_SYMBOL(filemap_write_and_wait_range
);
394 * replace_page_cache_page - replace a pagecache page with a new one
395 * @old: page to be replaced
396 * @new: page to replace with
397 * @gfp_mask: allocation mode
399 * This function replaces a page in the pagecache with a new one. On
400 * success it acquires the pagecache reference for the new page and
401 * drops it for the old page. Both the old and new pages must be
402 * locked. This function does not add the new page to the LRU, the
403 * caller must do that.
405 * The remove + add is atomic. The only way this function can fail is
406 * memory allocation failure.
408 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
412 VM_BUG_ON(!PageLocked(old
));
413 VM_BUG_ON(!PageLocked(new));
414 VM_BUG_ON(new->mapping
);
416 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
418 struct address_space
*mapping
= old
->mapping
;
419 void (*freepage
)(struct page
*);
421 pgoff_t offset
= old
->index
;
422 freepage
= mapping
->a_ops
->freepage
;
425 new->mapping
= mapping
;
428 spin_lock_irq(&mapping
->tree_lock
);
429 __delete_from_page_cache(old
);
430 error
= radix_tree_insert(&mapping
->page_tree
, offset
, new);
433 __inc_zone_page_state(new, NR_FILE_PAGES
);
434 if (PageSwapBacked(new))
435 __inc_zone_page_state(new, NR_SHMEM
);
436 spin_unlock_irq(&mapping
->tree_lock
);
437 /* mem_cgroup codes must not be called under tree_lock */
438 mem_cgroup_replace_page_cache(old
, new);
439 radix_tree_preload_end();
442 page_cache_release(old
);
447 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
450 * add_to_page_cache_locked - add a locked page to the pagecache
452 * @mapping: the page's address_space
453 * @offset: page index
454 * @gfp_mask: page allocation mode
456 * This function is used to add a page to the pagecache. It must be locked.
457 * This function does not add the page to the LRU. The caller must do that.
459 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
460 pgoff_t offset
, gfp_t gfp_mask
)
464 VM_BUG_ON(!PageLocked(page
));
465 VM_BUG_ON(PageSwapBacked(page
));
467 error
= mem_cgroup_cache_charge(page
, current
->mm
,
468 gfp_mask
& GFP_RECLAIM_MASK
);
472 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
474 page_cache_get(page
);
475 page
->mapping
= mapping
;
476 page
->index
= offset
;
478 spin_lock_irq(&mapping
->tree_lock
);
479 error
= radix_tree_insert(&mapping
->page_tree
, offset
, page
);
480 if (likely(!error
)) {
482 __inc_zone_page_state(page
, NR_FILE_PAGES
);
483 spin_unlock_irq(&mapping
->tree_lock
);
484 trace_mm_filemap_add_to_page_cache(page
);
486 page
->mapping
= NULL
;
487 /* Leave page->index set: truncation relies upon it */
488 spin_unlock_irq(&mapping
->tree_lock
);
489 mem_cgroup_uncharge_cache_page(page
);
490 page_cache_release(page
);
492 radix_tree_preload_end();
494 mem_cgroup_uncharge_cache_page(page
);
498 EXPORT_SYMBOL(add_to_page_cache_locked
);
500 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
501 pgoff_t offset
, gfp_t gfp_mask
)
505 ret
= add_to_page_cache(page
, mapping
, offset
, gfp_mask
);
507 lru_cache_add_file(page
);
510 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
513 struct page
*__page_cache_alloc(gfp_t gfp
)
518 if (cpuset_do_page_mem_spread()) {
519 unsigned int cpuset_mems_cookie
;
521 cpuset_mems_cookie
= get_mems_allowed();
522 n
= cpuset_mem_spread_node();
523 page
= alloc_pages_exact_node(n
, gfp
, 0);
524 } while (!put_mems_allowed(cpuset_mems_cookie
) && !page
);
528 return alloc_pages(gfp
, 0);
530 EXPORT_SYMBOL(__page_cache_alloc
);
534 * In order to wait for pages to become available there must be
535 * waitqueues associated with pages. By using a hash table of
536 * waitqueues where the bucket discipline is to maintain all
537 * waiters on the same queue and wake all when any of the pages
538 * become available, and for the woken contexts to check to be
539 * sure the appropriate page became available, this saves space
540 * at a cost of "thundering herd" phenomena during rare hash
543 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
545 const struct zone
*zone
= page_zone(page
);
547 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
550 static inline void wake_up_page(struct page
*page
, int bit
)
552 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
555 void wait_on_page_bit(struct page
*page
, int bit_nr
)
557 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
559 if (test_bit(bit_nr
, &page
->flags
))
560 __wait_on_bit(page_waitqueue(page
), &wait
, sleep_on_page
,
561 TASK_UNINTERRUPTIBLE
);
563 EXPORT_SYMBOL(wait_on_page_bit
);
565 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
567 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
569 if (!test_bit(bit_nr
, &page
->flags
))
572 return __wait_on_bit(page_waitqueue(page
), &wait
,
573 sleep_on_page_killable
, TASK_KILLABLE
);
577 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
578 * @page: Page defining the wait queue of interest
579 * @waiter: Waiter to add to the queue
581 * Add an arbitrary @waiter to the wait queue for the nominated @page.
583 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
585 wait_queue_head_t
*q
= page_waitqueue(page
);
588 spin_lock_irqsave(&q
->lock
, flags
);
589 __add_wait_queue(q
, waiter
);
590 spin_unlock_irqrestore(&q
->lock
, flags
);
592 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
595 * unlock_page - unlock a locked page
598 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
599 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
600 * mechananism between PageLocked pages and PageWriteback pages is shared.
601 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
603 * The mb is necessary to enforce ordering between the clear_bit and the read
604 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
606 void unlock_page(struct page
*page
)
608 VM_BUG_ON(!PageLocked(page
));
609 clear_bit_unlock(PG_locked
, &page
->flags
);
610 smp_mb__after_clear_bit();
611 wake_up_page(page
, PG_locked
);
613 EXPORT_SYMBOL(unlock_page
);
616 * end_page_writeback - end writeback against a page
619 void end_page_writeback(struct page
*page
)
621 if (TestClearPageReclaim(page
))
622 rotate_reclaimable_page(page
);
624 if (!test_clear_page_writeback(page
))
627 smp_mb__after_clear_bit();
628 wake_up_page(page
, PG_writeback
);
630 EXPORT_SYMBOL(end_page_writeback
);
633 * __lock_page - get a lock on the page, assuming we need to sleep to get it
634 * @page: the page to lock
636 void __lock_page(struct page
*page
)
638 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
640 __wait_on_bit_lock(page_waitqueue(page
), &wait
, sleep_on_page
,
641 TASK_UNINTERRUPTIBLE
);
643 EXPORT_SYMBOL(__lock_page
);
645 int __lock_page_killable(struct page
*page
)
647 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
649 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
650 sleep_on_page_killable
, TASK_KILLABLE
);
652 EXPORT_SYMBOL_GPL(__lock_page_killable
);
654 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
657 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
659 * CAUTION! In this case, mmap_sem is not released
660 * even though return 0.
662 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
665 up_read(&mm
->mmap_sem
);
666 if (flags
& FAULT_FLAG_KILLABLE
)
667 wait_on_page_locked_killable(page
);
669 wait_on_page_locked(page
);
672 if (flags
& FAULT_FLAG_KILLABLE
) {
675 ret
= __lock_page_killable(page
);
677 up_read(&mm
->mmap_sem
);
687 * find_get_page - find and get a page reference
688 * @mapping: the address_space to search
689 * @offset: the page index
691 * Is there a pagecache struct page at the given (mapping, offset) tuple?
692 * If yes, increment its refcount and return it; if no, return NULL.
694 struct page
*find_get_page(struct address_space
*mapping
, pgoff_t offset
)
702 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
704 page
= radix_tree_deref_slot(pagep
);
707 if (radix_tree_exception(page
)) {
708 if (radix_tree_deref_retry(page
))
711 * Otherwise, shmem/tmpfs must be storing a swap entry
712 * here as an exceptional entry: so return it without
713 * attempting to raise page count.
717 if (!page_cache_get_speculative(page
))
721 * Has the page moved?
722 * This is part of the lockless pagecache protocol. See
723 * include/linux/pagemap.h for details.
725 if (unlikely(page
!= *pagep
)) {
726 page_cache_release(page
);
735 EXPORT_SYMBOL(find_get_page
);
738 * find_lock_page - locate, pin and lock a pagecache page
739 * @mapping: the address_space to search
740 * @offset: the page index
742 * Locates the desired pagecache page, locks it, increments its reference
743 * count and returns its address.
745 * Returns zero if the page was not present. find_lock_page() may sleep.
747 struct page
*find_lock_page(struct address_space
*mapping
, pgoff_t offset
)
752 page
= find_get_page(mapping
, offset
);
753 if (page
&& !radix_tree_exception(page
)) {
755 /* Has the page been truncated? */
756 if (unlikely(page
->mapping
!= mapping
)) {
758 page_cache_release(page
);
761 VM_BUG_ON(page
->index
!= offset
);
765 EXPORT_SYMBOL(find_lock_page
);
768 * find_or_create_page - locate or add a pagecache page
769 * @mapping: the page's address_space
770 * @index: the page's index into the mapping
771 * @gfp_mask: page allocation mode
773 * Locates a page in the pagecache. If the page is not present, a new page
774 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
775 * LRU list. The returned page is locked and has its reference count
778 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
781 * find_or_create_page() returns the desired page's address, or zero on
784 struct page
*find_or_create_page(struct address_space
*mapping
,
785 pgoff_t index
, gfp_t gfp_mask
)
790 page
= find_lock_page(mapping
, index
);
792 page
= __page_cache_alloc(gfp_mask
);
796 * We want a regular kernel memory (not highmem or DMA etc)
797 * allocation for the radix tree nodes, but we need to honour
798 * the context-specific requirements the caller has asked for.
799 * GFP_RECLAIM_MASK collects those requirements.
801 err
= add_to_page_cache_lru(page
, mapping
, index
,
802 (gfp_mask
& GFP_RECLAIM_MASK
));
804 page_cache_release(page
);
812 EXPORT_SYMBOL(find_or_create_page
);
815 * find_get_pages - gang pagecache lookup
816 * @mapping: The address_space to search
817 * @start: The starting page index
818 * @nr_pages: The maximum number of pages
819 * @pages: Where the resulting pages are placed
821 * find_get_pages() will search for and return a group of up to
822 * @nr_pages pages in the mapping. The pages are placed at @pages.
823 * find_get_pages() takes a reference against the returned pages.
825 * The search returns a group of mapping-contiguous pages with ascending
826 * indexes. There may be holes in the indices due to not-present pages.
828 * find_get_pages() returns the number of pages which were found.
830 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
831 unsigned int nr_pages
, struct page
**pages
)
833 struct radix_tree_iter iter
;
837 if (unlikely(!nr_pages
))
842 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
845 page
= radix_tree_deref_slot(slot
);
849 if (radix_tree_exception(page
)) {
850 if (radix_tree_deref_retry(page
)) {
852 * Transient condition which can only trigger
853 * when entry at index 0 moves out of or back
854 * to root: none yet gotten, safe to restart.
860 * Otherwise, shmem/tmpfs must be storing a swap entry
861 * here as an exceptional entry: so skip over it -
862 * we only reach this from invalidate_mapping_pages().
867 if (!page_cache_get_speculative(page
))
870 /* Has the page moved? */
871 if (unlikely(page
!= *slot
)) {
872 page_cache_release(page
);
877 if (++ret
== nr_pages
)
886 * find_get_pages_contig - gang contiguous pagecache lookup
887 * @mapping: The address_space to search
888 * @index: The starting page index
889 * @nr_pages: The maximum number of pages
890 * @pages: Where the resulting pages are placed
892 * find_get_pages_contig() works exactly like find_get_pages(), except
893 * that the returned number of pages are guaranteed to be contiguous.
895 * find_get_pages_contig() returns the number of pages which were found.
897 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
898 unsigned int nr_pages
, struct page
**pages
)
900 struct radix_tree_iter iter
;
902 unsigned int ret
= 0;
904 if (unlikely(!nr_pages
))
909 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
912 page
= radix_tree_deref_slot(slot
);
913 /* The hole, there no reason to continue */
917 if (radix_tree_exception(page
)) {
918 if (radix_tree_deref_retry(page
)) {
920 * Transient condition which can only trigger
921 * when entry at index 0 moves out of or back
922 * to root: none yet gotten, safe to restart.
927 * Otherwise, shmem/tmpfs must be storing a swap entry
928 * here as an exceptional entry: so stop looking for
934 if (!page_cache_get_speculative(page
))
937 /* Has the page moved? */
938 if (unlikely(page
!= *slot
)) {
939 page_cache_release(page
);
944 * must check mapping and index after taking the ref.
945 * otherwise we can get both false positives and false
946 * negatives, which is just confusing to the caller.
948 if (page
->mapping
== NULL
|| page
->index
!= iter
.index
) {
949 page_cache_release(page
);
954 if (++ret
== nr_pages
)
960 EXPORT_SYMBOL(find_get_pages_contig
);
963 * find_get_pages_tag - find and return pages that match @tag
964 * @mapping: the address_space to search
965 * @index: the starting page index
966 * @tag: the tag index
967 * @nr_pages: the maximum number of pages
968 * @pages: where the resulting pages are placed
970 * Like find_get_pages, except we only return pages which are tagged with
971 * @tag. We update @index to index the next page for the traversal.
973 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
974 int tag
, unsigned int nr_pages
, struct page
**pages
)
976 struct radix_tree_iter iter
;
980 if (unlikely(!nr_pages
))
985 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
986 &iter
, *index
, tag
) {
989 page
= radix_tree_deref_slot(slot
);
993 if (radix_tree_exception(page
)) {
994 if (radix_tree_deref_retry(page
)) {
996 * Transient condition which can only trigger
997 * when entry at index 0 moves out of or back
998 * to root: none yet gotten, safe to restart.
1003 * This function is never used on a shmem/tmpfs
1004 * mapping, so a swap entry won't be found here.
1009 if (!page_cache_get_speculative(page
))
1012 /* Has the page moved? */
1013 if (unlikely(page
!= *slot
)) {
1014 page_cache_release(page
);
1019 if (++ret
== nr_pages
)
1026 *index
= pages
[ret
- 1]->index
+ 1;
1030 EXPORT_SYMBOL(find_get_pages_tag
);
1033 * grab_cache_page_nowait - returns locked page at given index in given cache
1034 * @mapping: target address_space
1035 * @index: the page index
1037 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1038 * This is intended for speculative data generators, where the data can
1039 * be regenerated if the page couldn't be grabbed. This routine should
1040 * be safe to call while holding the lock for another page.
1042 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1043 * and deadlock against the caller's locked page.
1046 grab_cache_page_nowait(struct address_space
*mapping
, pgoff_t index
)
1048 struct page
*page
= find_get_page(mapping
, index
);
1051 if (trylock_page(page
))
1053 page_cache_release(page
);
1056 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~__GFP_FS
);
1057 if (page
&& add_to_page_cache_lru(page
, mapping
, index
, GFP_NOFS
)) {
1058 page_cache_release(page
);
1063 EXPORT_SYMBOL(grab_cache_page_nowait
);
1066 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1067 * a _large_ part of the i/o request. Imagine the worst scenario:
1069 * ---R__________________________________________B__________
1070 * ^ reading here ^ bad block(assume 4k)
1072 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1073 * => failing the whole request => read(R) => read(R+1) =>
1074 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1075 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1076 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1078 * It is going insane. Fix it by quickly scaling down the readahead size.
1080 static void shrink_readahead_size_eio(struct file
*filp
,
1081 struct file_ra_state
*ra
)
1087 * do_generic_file_read - generic file read routine
1088 * @filp: the file to read
1089 * @ppos: current file position
1090 * @desc: read_descriptor
1091 * @actor: read method
1093 * This is a generic file read routine, and uses the
1094 * mapping->a_ops->readpage() function for the actual low-level stuff.
1096 * This is really ugly. But the goto's actually try to clarify some
1097 * of the logic when it comes to error handling etc.
1099 static void do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1100 read_descriptor_t
*desc
, read_actor_t actor
)
1102 struct address_space
*mapping
= filp
->f_mapping
;
1103 struct inode
*inode
= mapping
->host
;
1104 struct file_ra_state
*ra
= &filp
->f_ra
;
1108 unsigned long offset
; /* offset into pagecache page */
1109 unsigned int prev_offset
;
1112 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1113 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1114 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1115 last_index
= (*ppos
+ desc
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1116 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1122 unsigned long nr
, ret
;
1126 if (fatal_signal_pending(current
)) {
1131 page
= find_get_page(mapping
, index
);
1133 page_cache_sync_readahead(mapping
,
1135 index
, last_index
- index
);
1136 page
= find_get_page(mapping
, index
);
1137 if (unlikely(page
== NULL
))
1138 goto no_cached_page
;
1140 if (PageReadahead(page
)) {
1141 page_cache_async_readahead(mapping
,
1143 index
, last_index
- index
);
1145 if (!PageUptodate(page
)) {
1146 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1147 !mapping
->a_ops
->is_partially_uptodate
)
1148 goto page_not_up_to_date
;
1149 if (!trylock_page(page
))
1150 goto page_not_up_to_date
;
1151 /* Did it get truncated before we got the lock? */
1153 goto page_not_up_to_date_locked
;
1154 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1156 goto page_not_up_to_date_locked
;
1161 * i_size must be checked after we know the page is Uptodate.
1163 * Checking i_size after the check allows us to calculate
1164 * the correct value for "nr", which means the zero-filled
1165 * part of the page is not copied back to userspace (unless
1166 * another truncate extends the file - this is desired though).
1169 isize
= i_size_read(inode
);
1170 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1171 if (unlikely(!isize
|| index
> end_index
)) {
1172 page_cache_release(page
);
1176 /* nr is the maximum number of bytes to copy from this page */
1177 nr
= PAGE_CACHE_SIZE
;
1178 if (index
== end_index
) {
1179 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1181 page_cache_release(page
);
1187 /* If users can be writing to this page using arbitrary
1188 * virtual addresses, take care about potential aliasing
1189 * before reading the page on the kernel side.
1191 if (mapping_writably_mapped(mapping
))
1192 flush_dcache_page(page
);
1195 * When a sequential read accesses a page several times,
1196 * only mark it as accessed the first time.
1198 if (prev_index
!= index
|| offset
!= prev_offset
)
1199 mark_page_accessed(page
);
1203 * Ok, we have the page, and it's up-to-date, so
1204 * now we can copy it to user space...
1206 * The actor routine returns how many bytes were actually used..
1207 * NOTE! This may not be the same as how much of a user buffer
1208 * we filled up (we may be padding etc), so we can only update
1209 * "pos" here (the actor routine has to update the user buffer
1210 * pointers and the remaining count).
1212 ret
= actor(desc
, page
, offset
, nr
);
1214 index
+= offset
>> PAGE_CACHE_SHIFT
;
1215 offset
&= ~PAGE_CACHE_MASK
;
1216 prev_offset
= offset
;
1218 page_cache_release(page
);
1219 if (ret
== nr
&& desc
->count
)
1223 page_not_up_to_date
:
1224 /* Get exclusive access to the page ... */
1225 error
= lock_page_killable(page
);
1226 if (unlikely(error
))
1227 goto readpage_error
;
1229 page_not_up_to_date_locked
:
1230 /* Did it get truncated before we got the lock? */
1231 if (!page
->mapping
) {
1233 page_cache_release(page
);
1237 /* Did somebody else fill it already? */
1238 if (PageUptodate(page
)) {
1245 * A previous I/O error may have been due to temporary
1246 * failures, eg. multipath errors.
1247 * PG_error will be set again if readpage fails.
1249 ClearPageError(page
);
1250 /* Start the actual read. The read will unlock the page. */
1251 error
= mapping
->a_ops
->readpage(filp
, page
);
1253 if (unlikely(error
)) {
1254 if (error
== AOP_TRUNCATED_PAGE
) {
1255 page_cache_release(page
);
1258 goto readpage_error
;
1261 if (!PageUptodate(page
)) {
1262 error
= lock_page_killable(page
);
1263 if (unlikely(error
))
1264 goto readpage_error
;
1265 if (!PageUptodate(page
)) {
1266 if (page
->mapping
== NULL
) {
1268 * invalidate_mapping_pages got it
1271 page_cache_release(page
);
1275 shrink_readahead_size_eio(filp
, ra
);
1277 goto readpage_error
;
1285 /* UHHUH! A synchronous read error occurred. Report it */
1286 desc
->error
= error
;
1287 page_cache_release(page
);
1292 * Ok, it wasn't cached, so we need to create a new
1295 page
= page_cache_alloc_cold(mapping
);
1297 desc
->error
= -ENOMEM
;
1300 error
= add_to_page_cache_lru(page
, mapping
,
1303 page_cache_release(page
);
1304 if (error
== -EEXIST
)
1306 desc
->error
= error
;
1313 ra
->prev_pos
= prev_index
;
1314 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1315 ra
->prev_pos
|= prev_offset
;
1317 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1318 file_accessed(filp
);
1321 int file_read_actor(read_descriptor_t
*desc
, struct page
*page
,
1322 unsigned long offset
, unsigned long size
)
1325 unsigned long left
, count
= desc
->count
;
1331 * Faults on the destination of a read are common, so do it before
1334 if (!fault_in_pages_writeable(desc
->arg
.buf
, size
)) {
1335 kaddr
= kmap_atomic(page
);
1336 left
= __copy_to_user_inatomic(desc
->arg
.buf
,
1337 kaddr
+ offset
, size
);
1338 kunmap_atomic(kaddr
);
1343 /* Do it the slow way */
1345 left
= __copy_to_user(desc
->arg
.buf
, kaddr
+ offset
, size
);
1350 desc
->error
= -EFAULT
;
1353 desc
->count
= count
- size
;
1354 desc
->written
+= size
;
1355 desc
->arg
.buf
+= size
;
1360 * Performs necessary checks before doing a write
1361 * @iov: io vector request
1362 * @nr_segs: number of segments in the iovec
1363 * @count: number of bytes to write
1364 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1366 * Adjust number of segments and amount of bytes to write (nr_segs should be
1367 * properly initialized first). Returns appropriate error code that caller
1368 * should return or zero in case that write should be allowed.
1370 int generic_segment_checks(const struct iovec
*iov
,
1371 unsigned long *nr_segs
, size_t *count
, int access_flags
)
1375 for (seg
= 0; seg
< *nr_segs
; seg
++) {
1376 const struct iovec
*iv
= &iov
[seg
];
1379 * If any segment has a negative length, or the cumulative
1380 * length ever wraps negative then return -EINVAL.
1383 if (unlikely((ssize_t
)(cnt
|iv
->iov_len
) < 0))
1385 if (access_ok(access_flags
, iv
->iov_base
, iv
->iov_len
))
1390 cnt
-= iv
->iov_len
; /* This segment is no good */
1396 EXPORT_SYMBOL(generic_segment_checks
);
1399 * generic_file_aio_read - generic filesystem read routine
1400 * @iocb: kernel I/O control block
1401 * @iov: io vector request
1402 * @nr_segs: number of segments in the iovec
1403 * @pos: current file position
1405 * This is the "read()" routine for all filesystems
1406 * that can use the page cache directly.
1409 generic_file_aio_read(struct kiocb
*iocb
, const struct iovec
*iov
,
1410 unsigned long nr_segs
, loff_t pos
)
1412 struct file
*filp
= iocb
->ki_filp
;
1414 unsigned long seg
= 0;
1416 loff_t
*ppos
= &iocb
->ki_pos
;
1419 retval
= generic_segment_checks(iov
, &nr_segs
, &count
, VERIFY_WRITE
);
1423 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1424 if (filp
->f_flags
& O_DIRECT
) {
1426 struct address_space
*mapping
;
1427 struct inode
*inode
;
1429 mapping
= filp
->f_mapping
;
1430 inode
= mapping
->host
;
1432 goto out
; /* skip atime */
1433 size
= i_size_read(inode
);
1435 retval
= filemap_write_and_wait_range(mapping
, pos
,
1436 pos
+ iov_length(iov
, nr_segs
) - 1);
1438 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
,
1442 *ppos
= pos
+ retval
;
1447 * Btrfs can have a short DIO read if we encounter
1448 * compressed extents, so if there was an error, or if
1449 * we've already read everything we wanted to, or if
1450 * there was a short read because we hit EOF, go ahead
1451 * and return. Otherwise fallthrough to buffered io for
1452 * the rest of the read.
1454 if (retval
< 0 || !count
|| *ppos
>= size
) {
1455 file_accessed(filp
);
1462 for (seg
= 0; seg
< nr_segs
; seg
++) {
1463 read_descriptor_t desc
;
1467 * If we did a short DIO read we need to skip the section of the
1468 * iov that we've already read data into.
1471 if (count
> iov
[seg
].iov_len
) {
1472 count
-= iov
[seg
].iov_len
;
1480 desc
.arg
.buf
= iov
[seg
].iov_base
+ offset
;
1481 desc
.count
= iov
[seg
].iov_len
- offset
;
1482 if (desc
.count
== 0)
1485 do_generic_file_read(filp
, ppos
, &desc
, file_read_actor
);
1486 retval
+= desc
.written
;
1488 retval
= retval
?: desc
.error
;
1497 EXPORT_SYMBOL(generic_file_aio_read
);
1501 * page_cache_read - adds requested page to the page cache if not already there
1502 * @file: file to read
1503 * @offset: page index
1505 * This adds the requested page to the page cache if it isn't already there,
1506 * and schedules an I/O to read in its contents from disk.
1508 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1510 struct address_space
*mapping
= file
->f_mapping
;
1515 page
= page_cache_alloc_cold(mapping
);
1519 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1521 ret
= mapping
->a_ops
->readpage(file
, page
);
1522 else if (ret
== -EEXIST
)
1523 ret
= 0; /* losing race to add is OK */
1525 page_cache_release(page
);
1527 } while (ret
== AOP_TRUNCATED_PAGE
);
1532 #define MMAP_LOTSAMISS (100)
1535 * Synchronous readahead happens when we don't even find
1536 * a page in the page cache at all.
1538 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1539 struct file_ra_state
*ra
,
1543 unsigned long ra_pages
;
1544 struct address_space
*mapping
= file
->f_mapping
;
1546 /* If we don't want any read-ahead, don't bother */
1547 if (VM_RandomReadHint(vma
))
1552 if (VM_SequentialReadHint(vma
)) {
1553 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1558 /* Avoid banging the cache line if not needed */
1559 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
1563 * Do we miss much more than hit in this file? If so,
1564 * stop bothering with read-ahead. It will only hurt.
1566 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1572 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1573 ra
->start
= max_t(long, 0, offset
- ra_pages
/ 2);
1574 ra
->size
= ra_pages
;
1575 ra
->async_size
= ra_pages
/ 4;
1576 ra_submit(ra
, mapping
, file
);
1580 * Asynchronous readahead happens when we find the page and PG_readahead,
1581 * so we want to possibly extend the readahead further..
1583 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1584 struct file_ra_state
*ra
,
1589 struct address_space
*mapping
= file
->f_mapping
;
1591 /* If we don't want any read-ahead, don't bother */
1592 if (VM_RandomReadHint(vma
))
1594 if (ra
->mmap_miss
> 0)
1596 if (PageReadahead(page
))
1597 page_cache_async_readahead(mapping
, ra
, file
,
1598 page
, offset
, ra
->ra_pages
);
1602 * filemap_fault - read in file data for page fault handling
1603 * @vma: vma in which the fault was taken
1604 * @vmf: struct vm_fault containing details of the fault
1606 * filemap_fault() is invoked via the vma operations vector for a
1607 * mapped memory region to read in file data during a page fault.
1609 * The goto's are kind of ugly, but this streamlines the normal case of having
1610 * it in the page cache, and handles the special cases reasonably without
1611 * having a lot of duplicated code.
1613 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1616 struct file
*file
= vma
->vm_file
;
1617 struct address_space
*mapping
= file
->f_mapping
;
1618 struct file_ra_state
*ra
= &file
->f_ra
;
1619 struct inode
*inode
= mapping
->host
;
1620 pgoff_t offset
= vmf
->pgoff
;
1625 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1627 return VM_FAULT_SIGBUS
;
1630 * Do we have something in the page cache already?
1632 page
= find_get_page(mapping
, offset
);
1633 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
1635 * We found the page, so try async readahead before
1636 * waiting for the lock.
1638 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1640 /* No page in the page cache at all */
1641 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1645 count_vm_event(PGFMFAULT
);
1646 count_vm_event(PGMAJFAULT
);
1647 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
1648 ret
= VM_FAULT_MAJOR
;
1650 page
= find_get_page(mapping
, offset
);
1652 goto no_cached_page
;
1655 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
1656 page_cache_release(page
);
1657 return ret
| VM_FAULT_RETRY
;
1660 /* Did it get truncated? */
1661 if (unlikely(page
->mapping
!= mapping
)) {
1666 VM_BUG_ON(page
->index
!= offset
);
1669 * We have a locked page in the page cache, now we need to check
1670 * that it's up-to-date. If not, it is going to be due to an error.
1672 if (unlikely(!PageUptodate(page
)))
1673 goto page_not_uptodate
;
1676 * Found the page and have a reference on it.
1677 * We must recheck i_size under page lock.
1679 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1680 if (unlikely(offset
>= size
)) {
1682 page_cache_release(page
);
1683 return VM_FAULT_SIGBUS
;
1687 return ret
| VM_FAULT_LOCKED
;
1691 * We're only likely to ever get here if MADV_RANDOM is in
1694 error
= page_cache_read(file
, offset
);
1697 * The page we want has now been added to the page cache.
1698 * In the unlikely event that someone removed it in the
1699 * meantime, we'll just come back here and read it again.
1705 * An error return from page_cache_read can result if the
1706 * system is low on memory, or a problem occurs while trying
1709 if (error
== -ENOMEM
)
1710 return VM_FAULT_OOM
;
1711 return VM_FAULT_SIGBUS
;
1715 * Umm, take care of errors if the page isn't up-to-date.
1716 * Try to re-read it _once_. We do this synchronously,
1717 * because there really aren't any performance issues here
1718 * and we need to check for errors.
1720 ClearPageError(page
);
1721 error
= mapping
->a_ops
->readpage(file
, page
);
1723 wait_on_page_locked(page
);
1724 if (!PageUptodate(page
))
1727 page_cache_release(page
);
1729 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
1732 /* Things didn't work out. Return zero to tell the mm layer so. */
1733 shrink_readahead_size_eio(file
, ra
);
1734 return VM_FAULT_SIGBUS
;
1736 EXPORT_SYMBOL(filemap_fault
);
1738 int filemap_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1740 struct page
*page
= vmf
->page
;
1741 struct inode
*inode
= file_inode(vma
->vm_file
);
1742 int ret
= VM_FAULT_LOCKED
;
1744 sb_start_pagefault(inode
->i_sb
);
1745 file_update_time(vma
->vm_file
);
1747 if (page
->mapping
!= inode
->i_mapping
) {
1749 ret
= VM_FAULT_NOPAGE
;
1753 * We mark the page dirty already here so that when freeze is in
1754 * progress, we are guaranteed that writeback during freezing will
1755 * see the dirty page and writeprotect it again.
1757 set_page_dirty(page
);
1758 wait_for_stable_page(page
);
1760 sb_end_pagefault(inode
->i_sb
);
1763 EXPORT_SYMBOL(filemap_page_mkwrite
);
1765 const struct vm_operations_struct generic_file_vm_ops
= {
1766 .fault
= filemap_fault
,
1767 .page_mkwrite
= filemap_page_mkwrite
,
1768 .remap_pages
= generic_file_remap_pages
,
1771 /* This is used for a general mmap of a disk file */
1773 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1775 struct address_space
*mapping
= file
->f_mapping
;
1777 if (!mapping
->a_ops
->readpage
)
1779 file_accessed(file
);
1780 vma
->vm_ops
= &generic_file_vm_ops
;
1785 * This is for filesystems which do not implement ->writepage.
1787 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
1789 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
1791 return generic_file_mmap(file
, vma
);
1794 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1798 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1802 #endif /* CONFIG_MMU */
1804 EXPORT_SYMBOL(generic_file_mmap
);
1805 EXPORT_SYMBOL(generic_file_readonly_mmap
);
1807 static struct page
*__read_cache_page(struct address_space
*mapping
,
1809 int (*filler
)(void *, struct page
*),
1816 page
= find_get_page(mapping
, index
);
1818 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
1820 return ERR_PTR(-ENOMEM
);
1821 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
1822 if (unlikely(err
)) {
1823 page_cache_release(page
);
1826 /* Presumably ENOMEM for radix tree node */
1827 return ERR_PTR(err
);
1829 err
= filler(data
, page
);
1831 page_cache_release(page
);
1832 page
= ERR_PTR(err
);
1838 static struct page
*do_read_cache_page(struct address_space
*mapping
,
1840 int (*filler
)(void *, struct page
*),
1849 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
1852 if (PageUptodate(page
))
1856 if (!page
->mapping
) {
1858 page_cache_release(page
);
1861 if (PageUptodate(page
)) {
1865 err
= filler(data
, page
);
1867 page_cache_release(page
);
1868 return ERR_PTR(err
);
1871 mark_page_accessed(page
);
1876 * read_cache_page_async - read into page cache, fill it if needed
1877 * @mapping: the page's address_space
1878 * @index: the page index
1879 * @filler: function to perform the read
1880 * @data: first arg to filler(data, page) function, often left as NULL
1882 * Same as read_cache_page, but don't wait for page to become unlocked
1883 * after submitting it to the filler.
1885 * Read into the page cache. If a page already exists, and PageUptodate() is
1886 * not set, try to fill the page but don't wait for it to become unlocked.
1888 * If the page does not get brought uptodate, return -EIO.
1890 struct page
*read_cache_page_async(struct address_space
*mapping
,
1892 int (*filler
)(void *, struct page
*),
1895 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
1897 EXPORT_SYMBOL(read_cache_page_async
);
1899 static struct page
*wait_on_page_read(struct page
*page
)
1901 if (!IS_ERR(page
)) {
1902 wait_on_page_locked(page
);
1903 if (!PageUptodate(page
)) {
1904 page_cache_release(page
);
1905 page
= ERR_PTR(-EIO
);
1912 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1913 * @mapping: the page's address_space
1914 * @index: the page index
1915 * @gfp: the page allocator flags to use if allocating
1917 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1918 * any new page allocations done using the specified allocation flags.
1920 * If the page does not get brought uptodate, return -EIO.
1922 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
1926 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
1928 return wait_on_page_read(do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
));
1930 EXPORT_SYMBOL(read_cache_page_gfp
);
1933 * read_cache_page - read into page cache, fill it if needed
1934 * @mapping: the page's address_space
1935 * @index: the page index
1936 * @filler: function to perform the read
1937 * @data: first arg to filler(data, page) function, often left as NULL
1939 * Read into the page cache. If a page already exists, and PageUptodate() is
1940 * not set, try to fill the page then wait for it to become unlocked.
1942 * If the page does not get brought uptodate, return -EIO.
1944 struct page
*read_cache_page(struct address_space
*mapping
,
1946 int (*filler
)(void *, struct page
*),
1949 return wait_on_page_read(read_cache_page_async(mapping
, index
, filler
, data
));
1951 EXPORT_SYMBOL(read_cache_page
);
1953 static size_t __iovec_copy_from_user_inatomic(char *vaddr
,
1954 const struct iovec
*iov
, size_t base
, size_t bytes
)
1956 size_t copied
= 0, left
= 0;
1959 char __user
*buf
= iov
->iov_base
+ base
;
1960 int copy
= min(bytes
, iov
->iov_len
- base
);
1963 left
= __copy_from_user_inatomic(vaddr
, buf
, copy
);
1972 return copied
- left
;
1976 * Copy as much as we can into the page and return the number of bytes which
1977 * were successfully copied. If a fault is encountered then return the number of
1978 * bytes which were copied.
1980 size_t iov_iter_copy_from_user_atomic(struct page
*page
,
1981 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1986 BUG_ON(!in_atomic());
1987 kaddr
= kmap_atomic(page
);
1988 if (likely(i
->nr_segs
== 1)) {
1990 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1991 left
= __copy_from_user_inatomic(kaddr
+ offset
, buf
, bytes
);
1992 copied
= bytes
- left
;
1994 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1995 i
->iov
, i
->iov_offset
, bytes
);
1997 kunmap_atomic(kaddr
);
2001 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic
);
2004 * This has the same sideeffects and return value as
2005 * iov_iter_copy_from_user_atomic().
2006 * The difference is that it attempts to resolve faults.
2007 * Page must not be locked.
2009 size_t iov_iter_copy_from_user(struct page
*page
,
2010 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
2016 if (likely(i
->nr_segs
== 1)) {
2018 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
2019 left
= __copy_from_user(kaddr
+ offset
, buf
, bytes
);
2020 copied
= bytes
- left
;
2022 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
2023 i
->iov
, i
->iov_offset
, bytes
);
2028 EXPORT_SYMBOL(iov_iter_copy_from_user
);
2030 void iov_iter_advance(struct iov_iter
*i
, size_t bytes
)
2032 BUG_ON(i
->count
< bytes
);
2034 if (likely(i
->nr_segs
== 1)) {
2035 i
->iov_offset
+= bytes
;
2038 const struct iovec
*iov
= i
->iov
;
2039 size_t base
= i
->iov_offset
;
2040 unsigned long nr_segs
= i
->nr_segs
;
2043 * The !iov->iov_len check ensures we skip over unlikely
2044 * zero-length segments (without overruning the iovec).
2046 while (bytes
|| unlikely(i
->count
&& !iov
->iov_len
)) {
2049 copy
= min(bytes
, iov
->iov_len
- base
);
2050 BUG_ON(!i
->count
|| i
->count
< copy
);
2054 if (iov
->iov_len
== base
) {
2061 i
->iov_offset
= base
;
2062 i
->nr_segs
= nr_segs
;
2065 EXPORT_SYMBOL(iov_iter_advance
);
2068 * Fault in the first iovec of the given iov_iter, to a maximum length
2069 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2070 * accessed (ie. because it is an invalid address).
2072 * writev-intensive code may want this to prefault several iovecs -- that
2073 * would be possible (callers must not rely on the fact that _only_ the
2074 * first iovec will be faulted with the current implementation).
2076 int iov_iter_fault_in_readable(struct iov_iter
*i
, size_t bytes
)
2078 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
2079 bytes
= min(bytes
, i
->iov
->iov_len
- i
->iov_offset
);
2080 return fault_in_pages_readable(buf
, bytes
);
2082 EXPORT_SYMBOL(iov_iter_fault_in_readable
);
2085 * Return the count of just the current iov_iter segment.
2087 size_t iov_iter_single_seg_count(const struct iov_iter
*i
)
2089 const struct iovec
*iov
= i
->iov
;
2090 if (i
->nr_segs
== 1)
2093 return min(i
->count
, iov
->iov_len
- i
->iov_offset
);
2095 EXPORT_SYMBOL(iov_iter_single_seg_count
);
2098 * Performs necessary checks before doing a write
2100 * Can adjust writing position or amount of bytes to write.
2101 * Returns appropriate error code that caller should return or
2102 * zero in case that write should be allowed.
2104 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
2106 struct inode
*inode
= file
->f_mapping
->host
;
2107 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2109 if (unlikely(*pos
< 0))
2113 /* FIXME: this is for backwards compatibility with 2.4 */
2114 if (file
->f_flags
& O_APPEND
)
2115 *pos
= i_size_read(inode
);
2117 if (limit
!= RLIM_INFINITY
) {
2118 if (*pos
>= limit
) {
2119 send_sig(SIGXFSZ
, current
, 0);
2122 if (*count
> limit
- (typeof(limit
))*pos
) {
2123 *count
= limit
- (typeof(limit
))*pos
;
2131 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2132 !(file
->f_flags
& O_LARGEFILE
))) {
2133 if (*pos
>= MAX_NON_LFS
) {
2136 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2137 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2142 * Are we about to exceed the fs block limit ?
2144 * If we have written data it becomes a short write. If we have
2145 * exceeded without writing data we send a signal and return EFBIG.
2146 * Linus frestrict idea will clean these up nicely..
2148 if (likely(!isblk
)) {
2149 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2150 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2153 /* zero-length writes at ->s_maxbytes are OK */
2156 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2157 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2161 if (bdev_read_only(I_BDEV(inode
)))
2163 isize
= i_size_read(inode
);
2164 if (*pos
>= isize
) {
2165 if (*count
|| *pos
> isize
)
2169 if (*pos
+ *count
> isize
)
2170 *count
= isize
- *pos
;
2177 EXPORT_SYMBOL(generic_write_checks
);
2179 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2180 loff_t pos
, unsigned len
, unsigned flags
,
2181 struct page
**pagep
, void **fsdata
)
2183 const struct address_space_operations
*aops
= mapping
->a_ops
;
2185 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2188 EXPORT_SYMBOL(pagecache_write_begin
);
2190 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2191 loff_t pos
, unsigned len
, unsigned copied
,
2192 struct page
*page
, void *fsdata
)
2194 const struct address_space_operations
*aops
= mapping
->a_ops
;
2196 mark_page_accessed(page
);
2197 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2199 EXPORT_SYMBOL(pagecache_write_end
);
2202 generic_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2203 unsigned long *nr_segs
, loff_t pos
, loff_t
*ppos
,
2204 size_t count
, size_t ocount
)
2206 struct file
*file
= iocb
->ki_filp
;
2207 struct address_space
*mapping
= file
->f_mapping
;
2208 struct inode
*inode
= mapping
->host
;
2213 if (count
!= ocount
)
2214 *nr_segs
= iov_shorten((struct iovec
*)iov
, *nr_segs
, count
);
2216 write_len
= iov_length(iov
, *nr_segs
);
2217 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2219 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2224 * After a write we want buffered reads to be sure to go to disk to get
2225 * the new data. We invalidate clean cached page from the region we're
2226 * about to write. We do this *before* the write so that we can return
2227 * without clobbering -EIOCBQUEUED from ->direct_IO().
2229 if (mapping
->nrpages
) {
2230 written
= invalidate_inode_pages2_range(mapping
,
2231 pos
>> PAGE_CACHE_SHIFT
, end
);
2233 * If a page can not be invalidated, return 0 to fall back
2234 * to buffered write.
2237 if (written
== -EBUSY
)
2243 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, iov
, pos
, *nr_segs
);
2246 * Finally, try again to invalidate clean pages which might have been
2247 * cached by non-direct readahead, or faulted in by get_user_pages()
2248 * if the source of the write was an mmap'ed region of the file
2249 * we're writing. Either one is a pretty crazy thing to do,
2250 * so we don't support it 100%. If this invalidation
2251 * fails, tough, the write still worked...
2253 if (mapping
->nrpages
) {
2254 invalidate_inode_pages2_range(mapping
,
2255 pos
>> PAGE_CACHE_SHIFT
, end
);
2260 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2261 i_size_write(inode
, pos
);
2262 mark_inode_dirty(inode
);
2269 EXPORT_SYMBOL(generic_file_direct_write
);
2272 * Find or create a page at the given pagecache position. Return the locked
2273 * page. This function is specifically for buffered writes.
2275 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2276 pgoff_t index
, unsigned flags
)
2281 gfp_t gfp_notmask
= 0;
2283 gfp_mask
= mapping_gfp_mask(mapping
);
2284 if (mapping_cap_account_dirty(mapping
))
2285 gfp_mask
|= __GFP_WRITE
;
2286 if (flags
& AOP_FLAG_NOFS
)
2287 gfp_notmask
= __GFP_FS
;
2289 page
= find_lock_page(mapping
, index
);
2293 page
= __page_cache_alloc(gfp_mask
& ~gfp_notmask
);
2296 status
= add_to_page_cache_lru(page
, mapping
, index
,
2297 GFP_KERNEL
& ~gfp_notmask
);
2298 if (unlikely(status
)) {
2299 page_cache_release(page
);
2300 if (status
== -EEXIST
)
2305 wait_for_stable_page(page
);
2308 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2310 static ssize_t
generic_perform_write(struct file
*file
,
2311 struct iov_iter
*i
, loff_t pos
)
2313 struct address_space
*mapping
= file
->f_mapping
;
2314 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2316 ssize_t written
= 0;
2317 unsigned int flags
= 0;
2320 * Copies from kernel address space cannot fail (NFSD is a big user).
2322 if (segment_eq(get_fs(), KERNEL_DS
))
2323 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2327 unsigned long offset
; /* Offset into pagecache page */
2328 unsigned long bytes
; /* Bytes to write to page */
2329 size_t copied
; /* Bytes copied from user */
2332 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2333 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2338 * Bring in the user page that we will copy from _first_.
2339 * Otherwise there's a nasty deadlock on copying from the
2340 * same page as we're writing to, without it being marked
2343 * Not only is this an optimisation, but it is also required
2344 * to check that the address is actually valid, when atomic
2345 * usercopies are used, below.
2347 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2352 if (fatal_signal_pending(current
)) {
2357 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2359 if (unlikely(status
))
2362 if (mapping_writably_mapped(mapping
))
2363 flush_dcache_page(page
);
2365 pagefault_disable();
2366 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2368 flush_dcache_page(page
);
2370 mark_page_accessed(page
);
2371 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2373 if (unlikely(status
< 0))
2379 iov_iter_advance(i
, copied
);
2380 if (unlikely(copied
== 0)) {
2382 * If we were unable to copy any data at all, we must
2383 * fall back to a single segment length write.
2385 * If we didn't fallback here, we could livelock
2386 * because not all segments in the iov can be copied at
2387 * once without a pagefault.
2389 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2390 iov_iter_single_seg_count(i
));
2396 balance_dirty_pages_ratelimited(mapping
);
2397 } while (iov_iter_count(i
));
2399 return written
? written
: status
;
2403 generic_file_buffered_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2404 unsigned long nr_segs
, loff_t pos
, loff_t
*ppos
,
2405 size_t count
, ssize_t written
)
2407 struct file
*file
= iocb
->ki_filp
;
2411 iov_iter_init(&i
, iov
, nr_segs
, count
, written
);
2412 status
= generic_perform_write(file
, &i
, pos
);
2414 if (likely(status
>= 0)) {
2416 *ppos
= pos
+ status
;
2419 return written
? written
: status
;
2421 EXPORT_SYMBOL(generic_file_buffered_write
);
2424 * __generic_file_aio_write - write data to a file
2425 * @iocb: IO state structure (file, offset, etc.)
2426 * @iov: vector with data to write
2427 * @nr_segs: number of segments in the vector
2428 * @ppos: position where to write
2430 * This function does all the work needed for actually writing data to a
2431 * file. It does all basic checks, removes SUID from the file, updates
2432 * modification times and calls proper subroutines depending on whether we
2433 * do direct IO or a standard buffered write.
2435 * It expects i_mutex to be grabbed unless we work on a block device or similar
2436 * object which does not need locking at all.
2438 * This function does *not* take care of syncing data in case of O_SYNC write.
2439 * A caller has to handle it. This is mainly due to the fact that we want to
2440 * avoid syncing under i_mutex.
2442 ssize_t
__generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2443 unsigned long nr_segs
, loff_t
*ppos
)
2445 struct file
*file
= iocb
->ki_filp
;
2446 struct address_space
* mapping
= file
->f_mapping
;
2447 size_t ocount
; /* original count */
2448 size_t count
; /* after file limit checks */
2449 struct inode
*inode
= mapping
->host
;
2455 err
= generic_segment_checks(iov
, &nr_segs
, &ocount
, VERIFY_READ
);
2462 /* We can write back this queue in page reclaim */
2463 current
->backing_dev_info
= mapping
->backing_dev_info
;
2466 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2473 err
= file_remove_suid(file
);
2477 err
= file_update_time(file
);
2481 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2482 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2484 ssize_t written_buffered
;
2486 written
= generic_file_direct_write(iocb
, iov
, &nr_segs
, pos
,
2487 ppos
, count
, ocount
);
2488 if (written
< 0 || written
== count
)
2491 * direct-io write to a hole: fall through to buffered I/O
2492 * for completing the rest of the request.
2496 written_buffered
= generic_file_buffered_write(iocb
, iov
,
2497 nr_segs
, pos
, ppos
, count
,
2500 * If generic_file_buffered_write() retuned a synchronous error
2501 * then we want to return the number of bytes which were
2502 * direct-written, or the error code if that was zero. Note
2503 * that this differs from normal direct-io semantics, which
2504 * will return -EFOO even if some bytes were written.
2506 if (written_buffered
< 0) {
2507 err
= written_buffered
;
2512 * We need to ensure that the page cache pages are written to
2513 * disk and invalidated to preserve the expected O_DIRECT
2516 endbyte
= pos
+ written_buffered
- written
- 1;
2517 err
= filemap_write_and_wait_range(file
->f_mapping
, pos
, endbyte
);
2519 written
= written_buffered
;
2520 invalidate_mapping_pages(mapping
,
2521 pos
>> PAGE_CACHE_SHIFT
,
2522 endbyte
>> PAGE_CACHE_SHIFT
);
2525 * We don't know how much we wrote, so just return
2526 * the number of bytes which were direct-written
2530 written
= generic_file_buffered_write(iocb
, iov
, nr_segs
,
2531 pos
, ppos
, count
, written
);
2534 current
->backing_dev_info
= NULL
;
2535 return written
? written
: err
;
2537 EXPORT_SYMBOL(__generic_file_aio_write
);
2540 * generic_file_aio_write - write data to a file
2541 * @iocb: IO state structure
2542 * @iov: vector with data to write
2543 * @nr_segs: number of segments in the vector
2544 * @pos: position in file where to write
2546 * This is a wrapper around __generic_file_aio_write() to be used by most
2547 * filesystems. It takes care of syncing the file in case of O_SYNC file
2548 * and acquires i_mutex as needed.
2550 ssize_t
generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2551 unsigned long nr_segs
, loff_t pos
)
2553 struct file
*file
= iocb
->ki_filp
;
2554 struct inode
*inode
= file
->f_mapping
->host
;
2557 BUG_ON(iocb
->ki_pos
!= pos
);
2559 mutex_lock(&inode
->i_mutex
);
2560 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
, &iocb
->ki_pos
);
2561 mutex_unlock(&inode
->i_mutex
);
2563 if (ret
> 0 || ret
== -EIOCBQUEUED
) {
2566 err
= generic_write_sync(file
, pos
, ret
);
2567 if (err
< 0 && ret
> 0)
2572 EXPORT_SYMBOL(generic_file_aio_write
);
2575 * try_to_release_page() - release old fs-specific metadata on a page
2577 * @page: the page which the kernel is trying to free
2578 * @gfp_mask: memory allocation flags (and I/O mode)
2580 * The address_space is to try to release any data against the page
2581 * (presumably at page->private). If the release was successful, return `1'.
2582 * Otherwise return zero.
2584 * This may also be called if PG_fscache is set on a page, indicating that the
2585 * page is known to the local caching routines.
2587 * The @gfp_mask argument specifies whether I/O may be performed to release
2588 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2591 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2593 struct address_space
* const mapping
= page
->mapping
;
2595 BUG_ON(!PageLocked(page
));
2596 if (PageWriteback(page
))
2599 if (mapping
&& mapping
->a_ops
->releasepage
)
2600 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2601 return try_to_free_buffers(page
);
2604 EXPORT_SYMBOL(try_to_release_page
);