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/module.h>
13 #include <linux/slab.h>
14 #include <linux/compiler.h>
16 #include <linux/uaccess.h>
17 #include <linux/aio.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.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/syscalls.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/memcontrol.h>
36 #include <linux/mm_inline.h> /* for page_is_file_cache() */
40 * FIXME: remove all knowledge of the buffer layer from the core VM
42 #include <linux/buffer_head.h> /* for generic_osync_inode */
48 * Shared mappings implemented 30.11.1994. It's not fully working yet,
51 * Shared mappings now work. 15.8.1995 Bruno.
53 * finished 'unifying' the page and buffer cache and SMP-threaded the
54 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
56 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
62 * ->i_mmap_lock (vmtruncate)
63 * ->private_lock (__free_pte->__set_page_dirty_buffers)
64 * ->swap_lock (exclusive_swap_page, others)
65 * ->mapping->tree_lock
68 * ->i_mmap_lock (truncate->unmap_mapping_range)
72 * ->page_table_lock or pte_lock (various, mainly in memory.c)
73 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
76 * ->lock_page (access_process_vm)
78 * ->i_mutex (generic_file_buffered_write)
79 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
82 * ->i_alloc_sem (various)
85 * ->sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
89 * ->anon_vma.lock (vma_adjust)
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone.lru_lock (follow_page->mark_page_accessed)
99 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * ->inode_lock (page_remove_rmap->set_page_dirty)
103 * ->inode_lock (zap_pte_range->set_page_dirty)
104 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
107 * ->dcache_lock (proc_pid_lookup)
111 * Remove 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 __remove_from_page_cache(struct page
*page
)
117 struct address_space
*mapping
= page
->mapping
;
119 radix_tree_delete(&mapping
->page_tree
, page
->index
);
120 page
->mapping
= NULL
;
122 __dec_zone_page_state(page
, NR_FILE_PAGES
);
123 BUG_ON(page_mapped(page
));
126 * Some filesystems seem to re-dirty the page even after
127 * the VM has canceled the dirty bit (eg ext3 journaling).
129 * Fix it up by doing a final dirty accounting check after
130 * having removed the page entirely.
132 if (PageDirty(page
) && mapping_cap_account_dirty(mapping
)) {
133 dec_zone_page_state(page
, NR_FILE_DIRTY
);
134 dec_bdi_stat(mapping
->backing_dev_info
, BDI_RECLAIMABLE
);
138 void remove_from_page_cache(struct page
*page
)
140 struct address_space
*mapping
= page
->mapping
;
142 BUG_ON(!PageLocked(page
));
144 spin_lock_irq(&mapping
->tree_lock
);
145 __remove_from_page_cache(page
);
146 spin_unlock_irq(&mapping
->tree_lock
);
147 mem_cgroup_uncharge_cache_page(page
);
150 static int sync_page(void *word
)
152 struct address_space
*mapping
;
155 page
= container_of((unsigned long *)word
, struct page
, flags
);
158 * page_mapping() is being called without PG_locked held.
159 * Some knowledge of the state and use of the page is used to
160 * reduce the requirements down to a memory barrier.
161 * The danger here is of a stale page_mapping() return value
162 * indicating a struct address_space different from the one it's
163 * associated with when it is associated with one.
164 * After smp_mb(), it's either the correct page_mapping() for
165 * the page, or an old page_mapping() and the page's own
166 * page_mapping() has gone NULL.
167 * The ->sync_page() address_space operation must tolerate
168 * page_mapping() going NULL. By an amazing coincidence,
169 * this comes about because none of the users of the page
170 * in the ->sync_page() methods make essential use of the
171 * page_mapping(), merely passing the page down to the backing
172 * device's unplug functions when it's non-NULL, which in turn
173 * ignore it for all cases but swap, where only page_private(page) is
174 * of interest. When page_mapping() does go NULL, the entire
175 * call stack gracefully ignores the page and returns.
179 mapping
= page_mapping(page
);
180 if (mapping
&& mapping
->a_ops
&& mapping
->a_ops
->sync_page
)
181 mapping
->a_ops
->sync_page(page
);
186 static int sync_page_killable(void *word
)
189 return fatal_signal_pending(current
) ? -EINTR
: 0;
193 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
194 * @mapping: address space structure to write
195 * @start: offset in bytes where the range starts
196 * @end: offset in bytes where the range ends (inclusive)
197 * @sync_mode: enable synchronous operation
199 * Start writeback against all of a mapping's dirty pages that lie
200 * within the byte offsets <start, end> inclusive.
202 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
203 * opposed to a regular memory cleansing writeback. The difference between
204 * these two operations is that if a dirty page/buffer is encountered, it must
205 * be waited upon, and not just skipped over.
207 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
208 loff_t end
, int sync_mode
)
211 struct writeback_control wbc
= {
212 .sync_mode
= sync_mode
,
213 .nr_to_write
= LONG_MAX
,
214 .range_start
= start
,
218 if (!mapping_cap_writeback_dirty(mapping
))
221 ret
= do_writepages(mapping
, &wbc
);
225 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
228 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
231 int filemap_fdatawrite(struct address_space
*mapping
)
233 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
235 EXPORT_SYMBOL(filemap_fdatawrite
);
237 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
240 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
242 EXPORT_SYMBOL(filemap_fdatawrite_range
);
245 * filemap_flush - mostly a non-blocking flush
246 * @mapping: target address_space
248 * This is a mostly non-blocking flush. Not suitable for data-integrity
249 * purposes - I/O may not be started against all dirty pages.
251 int filemap_flush(struct address_space
*mapping
)
253 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
255 EXPORT_SYMBOL(filemap_flush
);
258 * wait_on_page_writeback_range - wait for writeback to complete
259 * @mapping: target address_space
260 * @start: beginning page index
261 * @end: ending page index
263 * Wait for writeback to complete against pages indexed by start->end
266 int wait_on_page_writeback_range(struct address_space
*mapping
,
267 pgoff_t start
, pgoff_t end
)
277 pagevec_init(&pvec
, 0);
279 while ((index
<= end
) &&
280 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
281 PAGECACHE_TAG_WRITEBACK
,
282 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
285 for (i
= 0; i
< nr_pages
; i
++) {
286 struct page
*page
= pvec
.pages
[i
];
288 /* until radix tree lookup accepts end_index */
289 if (page
->index
> end
)
292 wait_on_page_writeback(page
);
296 pagevec_release(&pvec
);
300 /* Check for outstanding write errors */
301 if (test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
303 if (test_and_clear_bit(AS_EIO
, &mapping
->flags
))
310 * filemap_fdatawait_range - wait for all under-writeback pages to complete in a given range
311 * @mapping: address space structure to wait for
312 * @start: offset in bytes where the range starts
313 * @end: offset in bytes where the range ends (inclusive)
315 * Walk the list of under-writeback pages of the given address space
316 * in the given range and wait for all of them.
318 * This is just a simple wrapper so that callers don't have to convert offsets
319 * to page indexes themselves
321 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start
,
324 return wait_on_page_writeback_range(mapping
, start
>> PAGE_CACHE_SHIFT
,
325 end
>> PAGE_CACHE_SHIFT
);
327 EXPORT_SYMBOL(filemap_fdatawait_range
);
330 * sync_page_range - write and wait on all pages in the passed range
331 * @inode: target inode
332 * @mapping: target address_space
333 * @pos: beginning offset in pages to write
334 * @count: number of bytes to write
336 * Write and wait upon all the pages in the passed range. This is a "data
337 * integrity" operation. It waits upon in-flight writeout before starting and
338 * waiting upon new writeout. If there was an IO error, return it.
340 * We need to re-take i_mutex during the generic_osync_inode list walk because
341 * it is otherwise livelockable.
343 int sync_page_range(struct inode
*inode
, struct address_space
*mapping
,
344 loff_t pos
, loff_t count
)
346 pgoff_t start
= pos
>> PAGE_CACHE_SHIFT
;
347 pgoff_t end
= (pos
+ count
- 1) >> PAGE_CACHE_SHIFT
;
350 if (!mapping_cap_writeback_dirty(mapping
) || !count
)
352 ret
= filemap_fdatawrite_range(mapping
, pos
, pos
+ count
- 1);
354 mutex_lock(&inode
->i_mutex
);
355 ret
= generic_osync_inode(inode
, mapping
, OSYNC_METADATA
);
356 mutex_unlock(&inode
->i_mutex
);
359 ret
= wait_on_page_writeback_range(mapping
, start
, end
);
362 EXPORT_SYMBOL(sync_page_range
);
365 * sync_page_range_nolock - write & wait on all pages in the passed range without locking
366 * @inode: target inode
367 * @mapping: target address_space
368 * @pos: beginning offset in pages to write
369 * @count: number of bytes to write
371 * Note: Holding i_mutex across sync_page_range_nolock() is not a good idea
372 * as it forces O_SYNC writers to different parts of the same file
373 * to be serialised right until io completion.
375 int sync_page_range_nolock(struct inode
*inode
, struct address_space
*mapping
,
376 loff_t pos
, loff_t count
)
378 pgoff_t start
= pos
>> PAGE_CACHE_SHIFT
;
379 pgoff_t end
= (pos
+ count
- 1) >> PAGE_CACHE_SHIFT
;
382 if (!mapping_cap_writeback_dirty(mapping
) || !count
)
384 ret
= filemap_fdatawrite_range(mapping
, pos
, pos
+ count
- 1);
386 ret
= generic_osync_inode(inode
, mapping
, OSYNC_METADATA
);
388 ret
= wait_on_page_writeback_range(mapping
, start
, end
);
391 EXPORT_SYMBOL(sync_page_range_nolock
);
394 * filemap_fdatawait - wait for all under-writeback pages to complete
395 * @mapping: address space structure to wait for
397 * Walk the list of under-writeback pages of the given address space
398 * and wait for all of them.
400 int filemap_fdatawait(struct address_space
*mapping
)
402 loff_t i_size
= i_size_read(mapping
->host
);
407 return wait_on_page_writeback_range(mapping
, 0,
408 (i_size
- 1) >> PAGE_CACHE_SHIFT
);
410 EXPORT_SYMBOL(filemap_fdatawait
);
412 int filemap_write_and_wait(struct address_space
*mapping
)
416 if (mapping
->nrpages
) {
417 err
= filemap_fdatawrite(mapping
);
419 * Even if the above returned error, the pages may be
420 * written partially (e.g. -ENOSPC), so we wait for it.
421 * But the -EIO is special case, it may indicate the worst
422 * thing (e.g. bug) happened, so we avoid waiting for it.
425 int err2
= filemap_fdatawait(mapping
);
432 EXPORT_SYMBOL(filemap_write_and_wait
);
435 * filemap_write_and_wait_range - write out & wait on a file range
436 * @mapping: the address_space for the pages
437 * @lstart: offset in bytes where the range starts
438 * @lend: offset in bytes where the range ends (inclusive)
440 * Write out and wait upon file offsets lstart->lend, inclusive.
442 * Note that `lend' is inclusive (describes the last byte to be written) so
443 * that this function can be used to write to the very end-of-file (end = -1).
445 int filemap_write_and_wait_range(struct address_space
*mapping
,
446 loff_t lstart
, loff_t lend
)
450 if (mapping
->nrpages
) {
451 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
453 /* See comment of filemap_write_and_wait() */
455 int err2
= wait_on_page_writeback_range(mapping
,
456 lstart
>> PAGE_CACHE_SHIFT
,
457 lend
>> PAGE_CACHE_SHIFT
);
464 EXPORT_SYMBOL(filemap_write_and_wait_range
);
467 * add_to_page_cache_locked - add a locked page to the pagecache
469 * @mapping: the page's address_space
470 * @offset: page index
471 * @gfp_mask: page allocation mode
473 * This function is used to add a page to the pagecache. It must be locked.
474 * This function does not add the page to the LRU. The caller must do that.
476 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
477 pgoff_t offset
, gfp_t gfp_mask
)
481 VM_BUG_ON(!PageLocked(page
));
483 error
= mem_cgroup_cache_charge(page
, current
->mm
,
484 gfp_mask
& GFP_RECLAIM_MASK
);
488 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
490 page_cache_get(page
);
491 page
->mapping
= mapping
;
492 page
->index
= offset
;
494 spin_lock_irq(&mapping
->tree_lock
);
495 error
= radix_tree_insert(&mapping
->page_tree
, offset
, page
);
496 if (likely(!error
)) {
498 __inc_zone_page_state(page
, NR_FILE_PAGES
);
499 spin_unlock_irq(&mapping
->tree_lock
);
501 page
->mapping
= NULL
;
502 spin_unlock_irq(&mapping
->tree_lock
);
503 mem_cgroup_uncharge_cache_page(page
);
504 page_cache_release(page
);
506 radix_tree_preload_end();
508 mem_cgroup_uncharge_cache_page(page
);
512 EXPORT_SYMBOL(add_to_page_cache_locked
);
514 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
515 pgoff_t offset
, gfp_t gfp_mask
)
520 * Splice_read and readahead add shmem/tmpfs pages into the page cache
521 * before shmem_readpage has a chance to mark them as SwapBacked: they
522 * need to go on the active_anon lru below, and mem_cgroup_cache_charge
523 * (called in add_to_page_cache) needs to know where they're going too.
525 if (mapping_cap_swap_backed(mapping
))
526 SetPageSwapBacked(page
);
528 ret
= add_to_page_cache(page
, mapping
, offset
, gfp_mask
);
530 if (page_is_file_cache(page
))
531 lru_cache_add_file(page
);
533 lru_cache_add_active_anon(page
);
537 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
540 struct page
*__page_cache_alloc(gfp_t gfp
)
542 if (cpuset_do_page_mem_spread()) {
543 int n
= cpuset_mem_spread_node();
544 return alloc_pages_exact_node(n
, gfp
, 0);
546 return alloc_pages(gfp
, 0);
548 EXPORT_SYMBOL(__page_cache_alloc
);
551 static int __sleep_on_page_lock(void *word
)
558 * In order to wait for pages to become available there must be
559 * waitqueues associated with pages. By using a hash table of
560 * waitqueues where the bucket discipline is to maintain all
561 * waiters on the same queue and wake all when any of the pages
562 * become available, and for the woken contexts to check to be
563 * sure the appropriate page became available, this saves space
564 * at a cost of "thundering herd" phenomena during rare hash
567 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
569 const struct zone
*zone
= page_zone(page
);
571 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
574 static inline void wake_up_page(struct page
*page
, int bit
)
576 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
579 void wait_on_page_bit(struct page
*page
, int bit_nr
)
581 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
583 if (test_bit(bit_nr
, &page
->flags
))
584 __wait_on_bit(page_waitqueue(page
), &wait
, sync_page
,
585 TASK_UNINTERRUPTIBLE
);
587 EXPORT_SYMBOL(wait_on_page_bit
);
590 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
591 * @page: Page defining the wait queue of interest
592 * @waiter: Waiter to add to the queue
594 * Add an arbitrary @waiter to the wait queue for the nominated @page.
596 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
598 wait_queue_head_t
*q
= page_waitqueue(page
);
601 spin_lock_irqsave(&q
->lock
, flags
);
602 __add_wait_queue(q
, waiter
);
603 spin_unlock_irqrestore(&q
->lock
, flags
);
605 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
608 * unlock_page - unlock a locked page
611 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
612 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
613 * mechananism between PageLocked pages and PageWriteback pages is shared.
614 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
616 * The mb is necessary to enforce ordering between the clear_bit and the read
617 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
619 void unlock_page(struct page
*page
)
621 VM_BUG_ON(!PageLocked(page
));
622 clear_bit_unlock(PG_locked
, &page
->flags
);
623 smp_mb__after_clear_bit();
624 wake_up_page(page
, PG_locked
);
626 EXPORT_SYMBOL(unlock_page
);
629 * end_page_writeback - end writeback against a page
632 void end_page_writeback(struct page
*page
)
634 if (TestClearPageReclaim(page
))
635 rotate_reclaimable_page(page
);
637 if (!test_clear_page_writeback(page
))
640 smp_mb__after_clear_bit();
641 wake_up_page(page
, PG_writeback
);
643 EXPORT_SYMBOL(end_page_writeback
);
646 * __lock_page - get a lock on the page, assuming we need to sleep to get it
647 * @page: the page to lock
649 * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some
650 * random driver's requestfn sets TASK_RUNNING, we could busywait. However
651 * chances are that on the second loop, the block layer's plug list is empty,
652 * so sync_page() will then return in state TASK_UNINTERRUPTIBLE.
654 void __lock_page(struct page
*page
)
656 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
658 __wait_on_bit_lock(page_waitqueue(page
), &wait
, sync_page
,
659 TASK_UNINTERRUPTIBLE
);
661 EXPORT_SYMBOL(__lock_page
);
663 int __lock_page_killable(struct page
*page
)
665 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
667 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
668 sync_page_killable
, TASK_KILLABLE
);
670 EXPORT_SYMBOL_GPL(__lock_page_killable
);
673 * __lock_page_nosync - get a lock on the page, without calling sync_page()
674 * @page: the page to lock
676 * Variant of lock_page that does not require the caller to hold a reference
677 * on the page's mapping.
679 void __lock_page_nosync(struct page
*page
)
681 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
682 __wait_on_bit_lock(page_waitqueue(page
), &wait
, __sleep_on_page_lock
,
683 TASK_UNINTERRUPTIBLE
);
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
);
705 if (unlikely(!page
|| page
== RADIX_TREE_RETRY
))
708 if (!page_cache_get_speculative(page
))
712 * Has the page moved?
713 * This is part of the lockless pagecache protocol. See
714 * include/linux/pagemap.h for details.
716 if (unlikely(page
!= *pagep
)) {
717 page_cache_release(page
);
725 EXPORT_SYMBOL(find_get_page
);
728 * find_lock_page - locate, pin and lock a pagecache page
729 * @mapping: the address_space to search
730 * @offset: the page index
732 * Locates the desired pagecache page, locks it, increments its reference
733 * count and returns its address.
735 * Returns zero if the page was not present. find_lock_page() may sleep.
737 struct page
*find_lock_page(struct address_space
*mapping
, pgoff_t offset
)
742 page
= find_get_page(mapping
, offset
);
745 /* Has the page been truncated? */
746 if (unlikely(page
->mapping
!= mapping
)) {
748 page_cache_release(page
);
751 VM_BUG_ON(page
->index
!= offset
);
755 EXPORT_SYMBOL(find_lock_page
);
758 * find_or_create_page - locate or add a pagecache page
759 * @mapping: the page's address_space
760 * @index: the page's index into the mapping
761 * @gfp_mask: page allocation mode
763 * Locates a page in the pagecache. If the page is not present, a new page
764 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
765 * LRU list. The returned page is locked and has its reference count
768 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
771 * find_or_create_page() returns the desired page's address, or zero on
774 struct page
*find_or_create_page(struct address_space
*mapping
,
775 pgoff_t index
, gfp_t gfp_mask
)
780 page
= find_lock_page(mapping
, index
);
782 page
= __page_cache_alloc(gfp_mask
);
786 * We want a regular kernel memory (not highmem or DMA etc)
787 * allocation for the radix tree nodes, but we need to honour
788 * the context-specific requirements the caller has asked for.
789 * GFP_RECLAIM_MASK collects those requirements.
791 err
= add_to_page_cache_lru(page
, mapping
, index
,
792 (gfp_mask
& GFP_RECLAIM_MASK
));
794 page_cache_release(page
);
802 EXPORT_SYMBOL(find_or_create_page
);
805 * find_get_pages - gang pagecache lookup
806 * @mapping: The address_space to search
807 * @start: The starting page index
808 * @nr_pages: The maximum number of pages
809 * @pages: Where the resulting pages are placed
811 * find_get_pages() will search for and return a group of up to
812 * @nr_pages pages in the mapping. The pages are placed at @pages.
813 * find_get_pages() takes a reference against the returned pages.
815 * The search returns a group of mapping-contiguous pages with ascending
816 * indexes. There may be holes in the indices due to not-present pages.
818 * find_get_pages() returns the number of pages which were found.
820 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
821 unsigned int nr_pages
, struct page
**pages
)
825 unsigned int nr_found
;
829 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
830 (void ***)pages
, start
, nr_pages
);
832 for (i
= 0; i
< nr_found
; i
++) {
835 page
= radix_tree_deref_slot((void **)pages
[i
]);
839 * this can only trigger if nr_found == 1, making livelock
842 if (unlikely(page
== RADIX_TREE_RETRY
))
845 if (!page_cache_get_speculative(page
))
848 /* Has the page moved? */
849 if (unlikely(page
!= *((void **)pages
[i
]))) {
850 page_cache_release(page
);
862 * find_get_pages_contig - gang contiguous pagecache lookup
863 * @mapping: The address_space to search
864 * @index: The starting page index
865 * @nr_pages: The maximum number of pages
866 * @pages: Where the resulting pages are placed
868 * find_get_pages_contig() works exactly like find_get_pages(), except
869 * that the returned number of pages are guaranteed to be contiguous.
871 * find_get_pages_contig() returns the number of pages which were found.
873 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
874 unsigned int nr_pages
, struct page
**pages
)
878 unsigned int nr_found
;
882 nr_found
= radix_tree_gang_lookup_slot(&mapping
->page_tree
,
883 (void ***)pages
, index
, nr_pages
);
885 for (i
= 0; i
< nr_found
; i
++) {
888 page
= radix_tree_deref_slot((void **)pages
[i
]);
892 * this can only trigger if nr_found == 1, making livelock
895 if (unlikely(page
== RADIX_TREE_RETRY
))
898 if (page
->mapping
== NULL
|| page
->index
!= index
)
901 if (!page_cache_get_speculative(page
))
904 /* Has the page moved? */
905 if (unlikely(page
!= *((void **)pages
[i
]))) {
906 page_cache_release(page
);
917 EXPORT_SYMBOL(find_get_pages_contig
);
920 * find_get_pages_tag - find and return pages that match @tag
921 * @mapping: the address_space to search
922 * @index: the starting page index
923 * @tag: the tag index
924 * @nr_pages: the maximum number of pages
925 * @pages: where the resulting pages are placed
927 * Like find_get_pages, except we only return pages which are tagged with
928 * @tag. We update @index to index the next page for the traversal.
930 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
931 int tag
, unsigned int nr_pages
, struct page
**pages
)
935 unsigned int nr_found
;
939 nr_found
= radix_tree_gang_lookup_tag_slot(&mapping
->page_tree
,
940 (void ***)pages
, *index
, nr_pages
, tag
);
942 for (i
= 0; i
< nr_found
; i
++) {
945 page
= radix_tree_deref_slot((void **)pages
[i
]);
949 * this can only trigger if nr_found == 1, making livelock
952 if (unlikely(page
== RADIX_TREE_RETRY
))
955 if (!page_cache_get_speculative(page
))
958 /* Has the page moved? */
959 if (unlikely(page
!= *((void **)pages
[i
]))) {
960 page_cache_release(page
);
970 *index
= pages
[ret
- 1]->index
+ 1;
974 EXPORT_SYMBOL(find_get_pages_tag
);
977 * grab_cache_page_nowait - returns locked page at given index in given cache
978 * @mapping: target address_space
979 * @index: the page index
981 * Same as grab_cache_page(), but do not wait if the page is unavailable.
982 * This is intended for speculative data generators, where the data can
983 * be regenerated if the page couldn't be grabbed. This routine should
984 * be safe to call while holding the lock for another page.
986 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
987 * and deadlock against the caller's locked page.
990 grab_cache_page_nowait(struct address_space
*mapping
, pgoff_t index
)
992 struct page
*page
= find_get_page(mapping
, index
);
995 if (trylock_page(page
))
997 page_cache_release(page
);
1000 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~__GFP_FS
);
1001 if (page
&& add_to_page_cache_lru(page
, mapping
, index
, GFP_NOFS
)) {
1002 page_cache_release(page
);
1007 EXPORT_SYMBOL(grab_cache_page_nowait
);
1010 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1011 * a _large_ part of the i/o request. Imagine the worst scenario:
1013 * ---R__________________________________________B__________
1014 * ^ reading here ^ bad block(assume 4k)
1016 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1017 * => failing the whole request => read(R) => read(R+1) =>
1018 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1019 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1020 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1022 * It is going insane. Fix it by quickly scaling down the readahead size.
1024 static void shrink_readahead_size_eio(struct file
*filp
,
1025 struct file_ra_state
*ra
)
1031 * do_generic_file_read - generic file read routine
1032 * @filp: the file to read
1033 * @ppos: current file position
1034 * @desc: read_descriptor
1035 * @actor: read method
1037 * This is a generic file read routine, and uses the
1038 * mapping->a_ops->readpage() function for the actual low-level stuff.
1040 * This is really ugly. But the goto's actually try to clarify some
1041 * of the logic when it comes to error handling etc.
1043 static void do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1044 read_descriptor_t
*desc
, read_actor_t actor
)
1046 struct address_space
*mapping
= filp
->f_mapping
;
1047 struct inode
*inode
= mapping
->host
;
1048 struct file_ra_state
*ra
= &filp
->f_ra
;
1052 unsigned long offset
; /* offset into pagecache page */
1053 unsigned int prev_offset
;
1056 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1057 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1058 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1059 last_index
= (*ppos
+ desc
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1060 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1066 unsigned long nr
, ret
;
1070 page
= find_get_page(mapping
, index
);
1072 page_cache_sync_readahead(mapping
,
1074 index
, last_index
- index
);
1075 page
= find_get_page(mapping
, index
);
1076 if (unlikely(page
== NULL
))
1077 goto no_cached_page
;
1079 if (PageReadahead(page
)) {
1080 page_cache_async_readahead(mapping
,
1082 index
, last_index
- index
);
1084 if (!PageUptodate(page
)) {
1085 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1086 !mapping
->a_ops
->is_partially_uptodate
)
1087 goto page_not_up_to_date
;
1088 if (!trylock_page(page
))
1089 goto page_not_up_to_date
;
1090 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1092 goto page_not_up_to_date_locked
;
1097 * i_size must be checked after we know the page is Uptodate.
1099 * Checking i_size after the check allows us to calculate
1100 * the correct value for "nr", which means the zero-filled
1101 * part of the page is not copied back to userspace (unless
1102 * another truncate extends the file - this is desired though).
1105 isize
= i_size_read(inode
);
1106 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1107 if (unlikely(!isize
|| index
> end_index
)) {
1108 page_cache_release(page
);
1112 /* nr is the maximum number of bytes to copy from this page */
1113 nr
= PAGE_CACHE_SIZE
;
1114 if (index
== end_index
) {
1115 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1117 page_cache_release(page
);
1123 /* If users can be writing to this page using arbitrary
1124 * virtual addresses, take care about potential aliasing
1125 * before reading the page on the kernel side.
1127 if (mapping_writably_mapped(mapping
))
1128 flush_dcache_page(page
);
1131 * When a sequential read accesses a page several times,
1132 * only mark it as accessed the first time.
1134 if (prev_index
!= index
|| offset
!= prev_offset
)
1135 mark_page_accessed(page
);
1139 * Ok, we have the page, and it's up-to-date, so
1140 * now we can copy it to user space...
1142 * The actor routine returns how many bytes were actually used..
1143 * NOTE! This may not be the same as how much of a user buffer
1144 * we filled up (we may be padding etc), so we can only update
1145 * "pos" here (the actor routine has to update the user buffer
1146 * pointers and the remaining count).
1148 ret
= actor(desc
, page
, offset
, nr
);
1150 index
+= offset
>> PAGE_CACHE_SHIFT
;
1151 offset
&= ~PAGE_CACHE_MASK
;
1152 prev_offset
= offset
;
1154 page_cache_release(page
);
1155 if (ret
== nr
&& desc
->count
)
1159 page_not_up_to_date
:
1160 /* Get exclusive access to the page ... */
1161 error
= lock_page_killable(page
);
1162 if (unlikely(error
))
1163 goto readpage_error
;
1165 page_not_up_to_date_locked
:
1166 /* Did it get truncated before we got the lock? */
1167 if (!page
->mapping
) {
1169 page_cache_release(page
);
1173 /* Did somebody else fill it already? */
1174 if (PageUptodate(page
)) {
1180 /* Start the actual read. The read will unlock the page. */
1181 error
= mapping
->a_ops
->readpage(filp
, page
);
1183 if (unlikely(error
)) {
1184 if (error
== AOP_TRUNCATED_PAGE
) {
1185 page_cache_release(page
);
1188 goto readpage_error
;
1191 if (!PageUptodate(page
)) {
1192 error
= lock_page_killable(page
);
1193 if (unlikely(error
))
1194 goto readpage_error
;
1195 if (!PageUptodate(page
)) {
1196 if (page
->mapping
== NULL
) {
1198 * invalidate_inode_pages got it
1201 page_cache_release(page
);
1205 shrink_readahead_size_eio(filp
, ra
);
1207 goto readpage_error
;
1215 /* UHHUH! A synchronous read error occurred. Report it */
1216 desc
->error
= error
;
1217 page_cache_release(page
);
1222 * Ok, it wasn't cached, so we need to create a new
1225 page
= page_cache_alloc_cold(mapping
);
1227 desc
->error
= -ENOMEM
;
1230 error
= add_to_page_cache_lru(page
, mapping
,
1233 page_cache_release(page
);
1234 if (error
== -EEXIST
)
1236 desc
->error
= error
;
1243 ra
->prev_pos
= prev_index
;
1244 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1245 ra
->prev_pos
|= prev_offset
;
1247 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1248 file_accessed(filp
);
1251 int file_read_actor(read_descriptor_t
*desc
, struct page
*page
,
1252 unsigned long offset
, unsigned long size
)
1255 unsigned long left
, count
= desc
->count
;
1261 * Faults on the destination of a read are common, so do it before
1264 if (!fault_in_pages_writeable(desc
->arg
.buf
, size
)) {
1265 kaddr
= kmap_atomic(page
, KM_USER0
);
1266 left
= __copy_to_user_inatomic(desc
->arg
.buf
,
1267 kaddr
+ offset
, size
);
1268 kunmap_atomic(kaddr
, KM_USER0
);
1273 /* Do it the slow way */
1275 left
= __copy_to_user(desc
->arg
.buf
, kaddr
+ offset
, size
);
1280 desc
->error
= -EFAULT
;
1283 desc
->count
= count
- size
;
1284 desc
->written
+= size
;
1285 desc
->arg
.buf
+= size
;
1290 * Performs necessary checks before doing a write
1291 * @iov: io vector request
1292 * @nr_segs: number of segments in the iovec
1293 * @count: number of bytes to write
1294 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1296 * Adjust number of segments and amount of bytes to write (nr_segs should be
1297 * properly initialized first). Returns appropriate error code that caller
1298 * should return or zero in case that write should be allowed.
1300 int generic_segment_checks(const struct iovec
*iov
,
1301 unsigned long *nr_segs
, size_t *count
, int access_flags
)
1305 for (seg
= 0; seg
< *nr_segs
; seg
++) {
1306 const struct iovec
*iv
= &iov
[seg
];
1309 * If any segment has a negative length, or the cumulative
1310 * length ever wraps negative then return -EINVAL.
1313 if (unlikely((ssize_t
)(cnt
|iv
->iov_len
) < 0))
1315 if (access_ok(access_flags
, iv
->iov_base
, iv
->iov_len
))
1320 cnt
-= iv
->iov_len
; /* This segment is no good */
1326 EXPORT_SYMBOL(generic_segment_checks
);
1329 * generic_file_aio_read - generic filesystem read routine
1330 * @iocb: kernel I/O control block
1331 * @iov: io vector request
1332 * @nr_segs: number of segments in the iovec
1333 * @pos: current file position
1335 * This is the "read()" routine for all filesystems
1336 * that can use the page cache directly.
1339 generic_file_aio_read(struct kiocb
*iocb
, const struct iovec
*iov
,
1340 unsigned long nr_segs
, loff_t pos
)
1342 struct file
*filp
= iocb
->ki_filp
;
1346 loff_t
*ppos
= &iocb
->ki_pos
;
1349 retval
= generic_segment_checks(iov
, &nr_segs
, &count
, VERIFY_WRITE
);
1353 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1354 if (filp
->f_flags
& O_DIRECT
) {
1356 struct address_space
*mapping
;
1357 struct inode
*inode
;
1359 mapping
= filp
->f_mapping
;
1360 inode
= mapping
->host
;
1362 goto out
; /* skip atime */
1363 size
= i_size_read(inode
);
1365 retval
= filemap_write_and_wait_range(mapping
, pos
,
1366 pos
+ iov_length(iov
, nr_segs
) - 1);
1368 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
,
1372 *ppos
= pos
+ retval
;
1374 file_accessed(filp
);
1380 for (seg
= 0; seg
< nr_segs
; seg
++) {
1381 read_descriptor_t desc
;
1384 desc
.arg
.buf
= iov
[seg
].iov_base
;
1385 desc
.count
= iov
[seg
].iov_len
;
1386 if (desc
.count
== 0)
1389 do_generic_file_read(filp
, ppos
, &desc
, file_read_actor
);
1390 retval
+= desc
.written
;
1392 retval
= retval
?: desc
.error
;
1401 EXPORT_SYMBOL(generic_file_aio_read
);
1404 do_readahead(struct address_space
*mapping
, struct file
*filp
,
1405 pgoff_t index
, unsigned long nr
)
1407 if (!mapping
|| !mapping
->a_ops
|| !mapping
->a_ops
->readpage
)
1410 force_page_cache_readahead(mapping
, filp
, index
, nr
);
1414 SYSCALL_DEFINE(readahead
)(int fd
, loff_t offset
, size_t count
)
1422 if (file
->f_mode
& FMODE_READ
) {
1423 struct address_space
*mapping
= file
->f_mapping
;
1424 pgoff_t start
= offset
>> PAGE_CACHE_SHIFT
;
1425 pgoff_t end
= (offset
+ count
- 1) >> PAGE_CACHE_SHIFT
;
1426 unsigned long len
= end
- start
+ 1;
1427 ret
= do_readahead(mapping
, file
, start
, len
);
1433 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1434 asmlinkage
long SyS_readahead(long fd
, loff_t offset
, long count
)
1436 return SYSC_readahead((int) fd
, offset
, (size_t) count
);
1438 SYSCALL_ALIAS(sys_readahead
, SyS_readahead
);
1443 * page_cache_read - adds requested page to the page cache if not already there
1444 * @file: file to read
1445 * @offset: page index
1447 * This adds the requested page to the page cache if it isn't already there,
1448 * and schedules an I/O to read in its contents from disk.
1450 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1452 struct address_space
*mapping
= file
->f_mapping
;
1457 page
= page_cache_alloc_cold(mapping
);
1461 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1463 ret
= mapping
->a_ops
->readpage(file
, page
);
1464 else if (ret
== -EEXIST
)
1465 ret
= 0; /* losing race to add is OK */
1467 page_cache_release(page
);
1469 } while (ret
== AOP_TRUNCATED_PAGE
);
1474 #define MMAP_LOTSAMISS (100)
1477 * Synchronous readahead happens when we don't even find
1478 * a page in the page cache at all.
1480 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1481 struct file_ra_state
*ra
,
1485 unsigned long ra_pages
;
1486 struct address_space
*mapping
= file
->f_mapping
;
1488 /* If we don't want any read-ahead, don't bother */
1489 if (VM_RandomReadHint(vma
))
1492 if (VM_SequentialReadHint(vma
) ||
1493 offset
- 1 == (ra
->prev_pos
>> PAGE_CACHE_SHIFT
)) {
1494 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1499 if (ra
->mmap_miss
< INT_MAX
)
1503 * Do we miss much more than hit in this file? If so,
1504 * stop bothering with read-ahead. It will only hurt.
1506 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1512 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1514 ra
->start
= max_t(long, 0, offset
- ra_pages
/2);
1515 ra
->size
= ra_pages
;
1517 ra_submit(ra
, mapping
, file
);
1522 * Asynchronous readahead happens when we find the page and PG_readahead,
1523 * so we want to possibly extend the readahead further..
1525 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1526 struct file_ra_state
*ra
,
1531 struct address_space
*mapping
= file
->f_mapping
;
1533 /* If we don't want any read-ahead, don't bother */
1534 if (VM_RandomReadHint(vma
))
1536 if (ra
->mmap_miss
> 0)
1538 if (PageReadahead(page
))
1539 page_cache_async_readahead(mapping
, ra
, file
,
1540 page
, offset
, ra
->ra_pages
);
1544 * filemap_fault - read in file data for page fault handling
1545 * @vma: vma in which the fault was taken
1546 * @vmf: struct vm_fault containing details of the fault
1548 * filemap_fault() is invoked via the vma operations vector for a
1549 * mapped memory region to read in file data during a page fault.
1551 * The goto's are kind of ugly, but this streamlines the normal case of having
1552 * it in the page cache, and handles the special cases reasonably without
1553 * having a lot of duplicated code.
1555 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1558 struct file
*file
= vma
->vm_file
;
1559 struct address_space
*mapping
= file
->f_mapping
;
1560 struct file_ra_state
*ra
= &file
->f_ra
;
1561 struct inode
*inode
= mapping
->host
;
1562 pgoff_t offset
= vmf
->pgoff
;
1567 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1569 return VM_FAULT_SIGBUS
;
1572 * Do we have something in the page cache already?
1574 page
= find_get_page(mapping
, offset
);
1577 * We found the page, so try async readahead before
1578 * waiting for the lock.
1580 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1583 /* Did it get truncated? */
1584 if (unlikely(page
->mapping
!= mapping
)) {
1587 goto no_cached_page
;
1590 /* No page in the page cache at all */
1591 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1592 count_vm_event(PGMAJFAULT
);
1593 ret
= VM_FAULT_MAJOR
;
1595 page
= find_lock_page(mapping
, offset
);
1597 goto no_cached_page
;
1601 * We have a locked page in the page cache, now we need to check
1602 * that it's up-to-date. If not, it is going to be due to an error.
1604 if (unlikely(!PageUptodate(page
)))
1605 goto page_not_uptodate
;
1608 * Found the page and have a reference on it.
1609 * We must recheck i_size under page lock.
1611 size
= (i_size_read(inode
) + PAGE_CACHE_SIZE
- 1) >> PAGE_CACHE_SHIFT
;
1612 if (unlikely(offset
>= size
)) {
1614 page_cache_release(page
);
1615 return VM_FAULT_SIGBUS
;
1618 ra
->prev_pos
= (loff_t
)offset
<< PAGE_CACHE_SHIFT
;
1620 return ret
| VM_FAULT_LOCKED
;
1624 * We're only likely to ever get here if MADV_RANDOM is in
1627 error
= page_cache_read(file
, offset
);
1630 * The page we want has now been added to the page cache.
1631 * In the unlikely event that someone removed it in the
1632 * meantime, we'll just come back here and read it again.
1638 * An error return from page_cache_read can result if the
1639 * system is low on memory, or a problem occurs while trying
1642 if (error
== -ENOMEM
)
1643 return VM_FAULT_OOM
;
1644 return VM_FAULT_SIGBUS
;
1648 * Umm, take care of errors if the page isn't up-to-date.
1649 * Try to re-read it _once_. We do this synchronously,
1650 * because there really aren't any performance issues here
1651 * and we need to check for errors.
1653 ClearPageError(page
);
1654 error
= mapping
->a_ops
->readpage(file
, page
);
1656 wait_on_page_locked(page
);
1657 if (!PageUptodate(page
))
1660 page_cache_release(page
);
1662 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
1665 /* Things didn't work out. Return zero to tell the mm layer so. */
1666 shrink_readahead_size_eio(file
, ra
);
1667 return VM_FAULT_SIGBUS
;
1669 EXPORT_SYMBOL(filemap_fault
);
1671 struct vm_operations_struct generic_file_vm_ops
= {
1672 .fault
= filemap_fault
,
1675 /* This is used for a general mmap of a disk file */
1677 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1679 struct address_space
*mapping
= file
->f_mapping
;
1681 if (!mapping
->a_ops
->readpage
)
1683 file_accessed(file
);
1684 vma
->vm_ops
= &generic_file_vm_ops
;
1685 vma
->vm_flags
|= VM_CAN_NONLINEAR
;
1690 * This is for filesystems which do not implement ->writepage.
1692 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
1694 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
1696 return generic_file_mmap(file
, vma
);
1699 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1703 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
1707 #endif /* CONFIG_MMU */
1709 EXPORT_SYMBOL(generic_file_mmap
);
1710 EXPORT_SYMBOL(generic_file_readonly_mmap
);
1712 static struct page
*__read_cache_page(struct address_space
*mapping
,
1714 int (*filler
)(void *,struct page
*),
1720 page
= find_get_page(mapping
, index
);
1722 page
= page_cache_alloc_cold(mapping
);
1724 return ERR_PTR(-ENOMEM
);
1725 err
= add_to_page_cache_lru(page
, mapping
, index
, GFP_KERNEL
);
1726 if (unlikely(err
)) {
1727 page_cache_release(page
);
1730 /* Presumably ENOMEM for radix tree node */
1731 return ERR_PTR(err
);
1733 err
= filler(data
, page
);
1735 page_cache_release(page
);
1736 page
= ERR_PTR(err
);
1743 * read_cache_page_async - read into page cache, fill it if needed
1744 * @mapping: the page's address_space
1745 * @index: the page index
1746 * @filler: function to perform the read
1747 * @data: destination for read data
1749 * Same as read_cache_page, but don't wait for page to become unlocked
1750 * after submitting it to the filler.
1752 * Read into the page cache. If a page already exists, and PageUptodate() is
1753 * not set, try to fill the page but don't wait for it to become unlocked.
1755 * If the page does not get brought uptodate, return -EIO.
1757 struct page
*read_cache_page_async(struct address_space
*mapping
,
1759 int (*filler
)(void *,struct page
*),
1766 page
= __read_cache_page(mapping
, index
, filler
, data
);
1769 if (PageUptodate(page
))
1773 if (!page
->mapping
) {
1775 page_cache_release(page
);
1778 if (PageUptodate(page
)) {
1782 err
= filler(data
, page
);
1784 page_cache_release(page
);
1785 return ERR_PTR(err
);
1788 mark_page_accessed(page
);
1791 EXPORT_SYMBOL(read_cache_page_async
);
1794 * read_cache_page - read into page cache, fill it if needed
1795 * @mapping: the page's address_space
1796 * @index: the page index
1797 * @filler: function to perform the read
1798 * @data: destination for read data
1800 * Read into the page cache. If a page already exists, and PageUptodate() is
1801 * not set, try to fill the page then wait for it to become unlocked.
1803 * If the page does not get brought uptodate, return -EIO.
1805 struct page
*read_cache_page(struct address_space
*mapping
,
1807 int (*filler
)(void *,struct page
*),
1812 page
= read_cache_page_async(mapping
, index
, filler
, data
);
1815 wait_on_page_locked(page
);
1816 if (!PageUptodate(page
)) {
1817 page_cache_release(page
);
1818 page
= ERR_PTR(-EIO
);
1823 EXPORT_SYMBOL(read_cache_page
);
1826 * The logic we want is
1828 * if suid or (sgid and xgrp)
1831 int should_remove_suid(struct dentry
*dentry
)
1833 mode_t mode
= dentry
->d_inode
->i_mode
;
1836 /* suid always must be killed */
1837 if (unlikely(mode
& S_ISUID
))
1838 kill
= ATTR_KILL_SUID
;
1841 * sgid without any exec bits is just a mandatory locking mark; leave
1842 * it alone. If some exec bits are set, it's a real sgid; kill it.
1844 if (unlikely((mode
& S_ISGID
) && (mode
& S_IXGRP
)))
1845 kill
|= ATTR_KILL_SGID
;
1847 if (unlikely(kill
&& !capable(CAP_FSETID
) && S_ISREG(mode
)))
1852 EXPORT_SYMBOL(should_remove_suid
);
1854 static int __remove_suid(struct dentry
*dentry
, int kill
)
1856 struct iattr newattrs
;
1858 newattrs
.ia_valid
= ATTR_FORCE
| kill
;
1859 return notify_change(dentry
, &newattrs
);
1862 int file_remove_suid(struct file
*file
)
1864 struct dentry
*dentry
= file
->f_path
.dentry
;
1865 int killsuid
= should_remove_suid(dentry
);
1866 int killpriv
= security_inode_need_killpriv(dentry
);
1872 error
= security_inode_killpriv(dentry
);
1873 if (!error
&& killsuid
)
1874 error
= __remove_suid(dentry
, killsuid
);
1878 EXPORT_SYMBOL(file_remove_suid
);
1880 static size_t __iovec_copy_from_user_inatomic(char *vaddr
,
1881 const struct iovec
*iov
, size_t base
, size_t bytes
)
1883 size_t copied
= 0, left
= 0;
1886 char __user
*buf
= iov
->iov_base
+ base
;
1887 int copy
= min(bytes
, iov
->iov_len
- base
);
1890 left
= __copy_from_user_inatomic(vaddr
, buf
, copy
);
1899 return copied
- left
;
1903 * Copy as much as we can into the page and return the number of bytes which
1904 * were sucessfully copied. If a fault is encountered then return the number of
1905 * bytes which were copied.
1907 size_t iov_iter_copy_from_user_atomic(struct page
*page
,
1908 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1913 BUG_ON(!in_atomic());
1914 kaddr
= kmap_atomic(page
, KM_USER0
);
1915 if (likely(i
->nr_segs
== 1)) {
1917 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1918 left
= __copy_from_user_inatomic(kaddr
+ offset
, buf
, bytes
);
1919 copied
= bytes
- left
;
1921 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1922 i
->iov
, i
->iov_offset
, bytes
);
1924 kunmap_atomic(kaddr
, KM_USER0
);
1928 EXPORT_SYMBOL(iov_iter_copy_from_user_atomic
);
1931 * This has the same sideeffects and return value as
1932 * iov_iter_copy_from_user_atomic().
1933 * The difference is that it attempts to resolve faults.
1934 * Page must not be locked.
1936 size_t iov_iter_copy_from_user(struct page
*page
,
1937 struct iov_iter
*i
, unsigned long offset
, size_t bytes
)
1943 if (likely(i
->nr_segs
== 1)) {
1945 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
1946 left
= __copy_from_user(kaddr
+ offset
, buf
, bytes
);
1947 copied
= bytes
- left
;
1949 copied
= __iovec_copy_from_user_inatomic(kaddr
+ offset
,
1950 i
->iov
, i
->iov_offset
, bytes
);
1955 EXPORT_SYMBOL(iov_iter_copy_from_user
);
1957 void iov_iter_advance(struct iov_iter
*i
, size_t bytes
)
1959 BUG_ON(i
->count
< bytes
);
1961 if (likely(i
->nr_segs
== 1)) {
1962 i
->iov_offset
+= bytes
;
1965 const struct iovec
*iov
= i
->iov
;
1966 size_t base
= i
->iov_offset
;
1969 * The !iov->iov_len check ensures we skip over unlikely
1970 * zero-length segments (without overruning the iovec).
1972 while (bytes
|| unlikely(i
->count
&& !iov
->iov_len
)) {
1975 copy
= min(bytes
, iov
->iov_len
- base
);
1976 BUG_ON(!i
->count
|| i
->count
< copy
);
1980 if (iov
->iov_len
== base
) {
1986 i
->iov_offset
= base
;
1989 EXPORT_SYMBOL(iov_iter_advance
);
1992 * Fault in the first iovec of the given iov_iter, to a maximum length
1993 * of bytes. Returns 0 on success, or non-zero if the memory could not be
1994 * accessed (ie. because it is an invalid address).
1996 * writev-intensive code may want this to prefault several iovecs -- that
1997 * would be possible (callers must not rely on the fact that _only_ the
1998 * first iovec will be faulted with the current implementation).
2000 int iov_iter_fault_in_readable(struct iov_iter
*i
, size_t bytes
)
2002 char __user
*buf
= i
->iov
->iov_base
+ i
->iov_offset
;
2003 bytes
= min(bytes
, i
->iov
->iov_len
- i
->iov_offset
);
2004 return fault_in_pages_readable(buf
, bytes
);
2006 EXPORT_SYMBOL(iov_iter_fault_in_readable
);
2009 * Return the count of just the current iov_iter segment.
2011 size_t iov_iter_single_seg_count(struct iov_iter
*i
)
2013 const struct iovec
*iov
= i
->iov
;
2014 if (i
->nr_segs
== 1)
2017 return min(i
->count
, iov
->iov_len
- i
->iov_offset
);
2019 EXPORT_SYMBOL(iov_iter_single_seg_count
);
2022 * Performs necessary checks before doing a write
2024 * Can adjust writing position or amount of bytes to write.
2025 * Returns appropriate error code that caller should return or
2026 * zero in case that write should be allowed.
2028 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
2030 struct inode
*inode
= file
->f_mapping
->host
;
2031 unsigned long limit
= current
->signal
->rlim
[RLIMIT_FSIZE
].rlim_cur
;
2033 if (unlikely(*pos
< 0))
2037 /* FIXME: this is for backwards compatibility with 2.4 */
2038 if (file
->f_flags
& O_APPEND
)
2039 *pos
= i_size_read(inode
);
2041 if (limit
!= RLIM_INFINITY
) {
2042 if (*pos
>= limit
) {
2043 send_sig(SIGXFSZ
, current
, 0);
2046 if (*count
> limit
- (typeof(limit
))*pos
) {
2047 *count
= limit
- (typeof(limit
))*pos
;
2055 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2056 !(file
->f_flags
& O_LARGEFILE
))) {
2057 if (*pos
>= MAX_NON_LFS
) {
2060 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2061 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2066 * Are we about to exceed the fs block limit ?
2068 * If we have written data it becomes a short write. If we have
2069 * exceeded without writing data we send a signal and return EFBIG.
2070 * Linus frestrict idea will clean these up nicely..
2072 if (likely(!isblk
)) {
2073 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2074 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2077 /* zero-length writes at ->s_maxbytes are OK */
2080 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2081 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2085 if (bdev_read_only(I_BDEV(inode
)))
2087 isize
= i_size_read(inode
);
2088 if (*pos
>= isize
) {
2089 if (*count
|| *pos
> isize
)
2093 if (*pos
+ *count
> isize
)
2094 *count
= isize
- *pos
;
2101 EXPORT_SYMBOL(generic_write_checks
);
2103 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2104 loff_t pos
, unsigned len
, unsigned flags
,
2105 struct page
**pagep
, void **fsdata
)
2107 const struct address_space_operations
*aops
= mapping
->a_ops
;
2109 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2112 EXPORT_SYMBOL(pagecache_write_begin
);
2114 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2115 loff_t pos
, unsigned len
, unsigned copied
,
2116 struct page
*page
, void *fsdata
)
2118 const struct address_space_operations
*aops
= mapping
->a_ops
;
2120 mark_page_accessed(page
);
2121 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2123 EXPORT_SYMBOL(pagecache_write_end
);
2126 generic_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2127 unsigned long *nr_segs
, loff_t pos
, loff_t
*ppos
,
2128 size_t count
, size_t ocount
)
2130 struct file
*file
= iocb
->ki_filp
;
2131 struct address_space
*mapping
= file
->f_mapping
;
2132 struct inode
*inode
= mapping
->host
;
2137 if (count
!= ocount
)
2138 *nr_segs
= iov_shorten((struct iovec
*)iov
, *nr_segs
, count
);
2140 write_len
= iov_length(iov
, *nr_segs
);
2141 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2143 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2148 * After a write we want buffered reads to be sure to go to disk to get
2149 * the new data. We invalidate clean cached page from the region we're
2150 * about to write. We do this *before* the write so that we can return
2151 * without clobbering -EIOCBQUEUED from ->direct_IO().
2153 if (mapping
->nrpages
) {
2154 written
= invalidate_inode_pages2_range(mapping
,
2155 pos
>> PAGE_CACHE_SHIFT
, end
);
2157 * If a page can not be invalidated, return 0 to fall back
2158 * to buffered write.
2161 if (written
== -EBUSY
)
2167 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, iov
, pos
, *nr_segs
);
2170 * Finally, try again to invalidate clean pages which might have been
2171 * cached by non-direct readahead, or faulted in by get_user_pages()
2172 * if the source of the write was an mmap'ed region of the file
2173 * we're writing. Either one is a pretty crazy thing to do,
2174 * so we don't support it 100%. If this invalidation
2175 * fails, tough, the write still worked...
2177 if (mapping
->nrpages
) {
2178 invalidate_inode_pages2_range(mapping
,
2179 pos
>> PAGE_CACHE_SHIFT
, end
);
2183 loff_t end
= pos
+ written
;
2184 if (end
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2185 i_size_write(inode
, end
);
2186 mark_inode_dirty(inode
);
2193 EXPORT_SYMBOL(generic_file_direct_write
);
2196 * Find or create a page at the given pagecache position. Return the locked
2197 * page. This function is specifically for buffered writes.
2199 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2200 pgoff_t index
, unsigned flags
)
2204 gfp_t gfp_notmask
= 0;
2205 if (flags
& AOP_FLAG_NOFS
)
2206 gfp_notmask
= __GFP_FS
;
2208 page
= find_lock_page(mapping
, index
);
2212 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~gfp_notmask
);
2215 status
= add_to_page_cache_lru(page
, mapping
, index
,
2216 GFP_KERNEL
& ~gfp_notmask
);
2217 if (unlikely(status
)) {
2218 page_cache_release(page
);
2219 if (status
== -EEXIST
)
2225 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2227 static ssize_t
generic_perform_write(struct file
*file
,
2228 struct iov_iter
*i
, loff_t pos
)
2230 struct address_space
*mapping
= file
->f_mapping
;
2231 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2233 ssize_t written
= 0;
2234 unsigned int flags
= 0;
2237 * Copies from kernel address space cannot fail (NFSD is a big user).
2239 if (segment_eq(get_fs(), KERNEL_DS
))
2240 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2244 pgoff_t index
; /* Pagecache index for current page */
2245 unsigned long offset
; /* Offset into pagecache page */
2246 unsigned long bytes
; /* Bytes to write to page */
2247 size_t copied
; /* Bytes copied from user */
2250 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2251 index
= pos
>> PAGE_CACHE_SHIFT
;
2252 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2258 * Bring in the user page that we will copy from _first_.
2259 * Otherwise there's a nasty deadlock on copying from the
2260 * same page as we're writing to, without it being marked
2263 * Not only is this an optimisation, but it is also required
2264 * to check that the address is actually valid, when atomic
2265 * usercopies are used, below.
2267 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2272 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2274 if (unlikely(status
))
2277 pagefault_disable();
2278 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2280 flush_dcache_page(page
);
2282 mark_page_accessed(page
);
2283 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2285 if (unlikely(status
< 0))
2291 iov_iter_advance(i
, copied
);
2292 if (unlikely(copied
== 0)) {
2294 * If we were unable to copy any data at all, we must
2295 * fall back to a single segment length write.
2297 * If we didn't fallback here, we could livelock
2298 * because not all segments in the iov can be copied at
2299 * once without a pagefault.
2301 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2302 iov_iter_single_seg_count(i
));
2308 balance_dirty_pages_ratelimited(mapping
);
2310 } while (iov_iter_count(i
));
2312 return written
? written
: status
;
2316 generic_file_buffered_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2317 unsigned long nr_segs
, loff_t pos
, loff_t
*ppos
,
2318 size_t count
, ssize_t written
)
2320 struct file
*file
= iocb
->ki_filp
;
2321 struct address_space
*mapping
= file
->f_mapping
;
2325 iov_iter_init(&i
, iov
, nr_segs
, count
, written
);
2326 status
= generic_perform_write(file
, &i
, pos
);
2328 if (likely(status
>= 0)) {
2330 *ppos
= pos
+ status
;
2334 * If we get here for O_DIRECT writes then we must have fallen through
2335 * to buffered writes (block instantiation inside i_size). So we sync
2336 * the file data here, to try to honour O_DIRECT expectations.
2338 if (unlikely(file
->f_flags
& O_DIRECT
) && written
)
2339 status
= filemap_write_and_wait_range(mapping
,
2340 pos
, pos
+ written
- 1);
2342 return written
? written
: status
;
2344 EXPORT_SYMBOL(generic_file_buffered_write
);
2347 * __generic_file_aio_write - write data to a file
2348 * @iocb: IO state structure (file, offset, etc.)
2349 * @iov: vector with data to write
2350 * @nr_segs: number of segments in the vector
2351 * @ppos: position where to write
2353 * This function does all the work needed for actually writing data to a
2354 * file. It does all basic checks, removes SUID from the file, updates
2355 * modification times and calls proper subroutines depending on whether we
2356 * do direct IO or a standard buffered write.
2358 * It expects i_mutex to be grabbed unless we work on a block device or similar
2359 * object which does not need locking at all.
2361 * This function does *not* take care of syncing data in case of O_SYNC write.
2362 * A caller has to handle it. This is mainly due to the fact that we want to
2363 * avoid syncing under i_mutex.
2365 ssize_t
__generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2366 unsigned long nr_segs
, loff_t
*ppos
)
2368 struct file
*file
= iocb
->ki_filp
;
2369 struct address_space
* mapping
= file
->f_mapping
;
2370 size_t ocount
; /* original count */
2371 size_t count
; /* after file limit checks */
2372 struct inode
*inode
= mapping
->host
;
2378 err
= generic_segment_checks(iov
, &nr_segs
, &ocount
, VERIFY_READ
);
2385 vfs_check_frozen(inode
->i_sb
, SB_FREEZE_WRITE
);
2387 /* We can write back this queue in page reclaim */
2388 current
->backing_dev_info
= mapping
->backing_dev_info
;
2391 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2398 err
= file_remove_suid(file
);
2402 file_update_time(file
);
2404 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2405 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2407 ssize_t written_buffered
;
2409 written
= generic_file_direct_write(iocb
, iov
, &nr_segs
, pos
,
2410 ppos
, count
, ocount
);
2411 if (written
< 0 || written
== count
)
2414 * direct-io write to a hole: fall through to buffered I/O
2415 * for completing the rest of the request.
2419 written_buffered
= generic_file_buffered_write(iocb
, iov
,
2420 nr_segs
, pos
, ppos
, count
,
2423 * If generic_file_buffered_write() retuned a synchronous error
2424 * then we want to return the number of bytes which were
2425 * direct-written, or the error code if that was zero. Note
2426 * that this differs from normal direct-io semantics, which
2427 * will return -EFOO even if some bytes were written.
2429 if (written_buffered
< 0) {
2430 err
= written_buffered
;
2435 * We need to ensure that the page cache pages are written to
2436 * disk and invalidated to preserve the expected O_DIRECT
2439 endbyte
= pos
+ written_buffered
- written
- 1;
2440 err
= do_sync_mapping_range(file
->f_mapping
, pos
, endbyte
,
2441 SYNC_FILE_RANGE_WAIT_BEFORE
|
2442 SYNC_FILE_RANGE_WRITE
|
2443 SYNC_FILE_RANGE_WAIT_AFTER
);
2445 written
= written_buffered
;
2446 invalidate_mapping_pages(mapping
,
2447 pos
>> PAGE_CACHE_SHIFT
,
2448 endbyte
>> PAGE_CACHE_SHIFT
);
2451 * We don't know how much we wrote, so just return
2452 * the number of bytes which were direct-written
2456 written
= generic_file_buffered_write(iocb
, iov
, nr_segs
,
2457 pos
, ppos
, count
, written
);
2460 current
->backing_dev_info
= NULL
;
2461 return written
? written
: err
;
2463 EXPORT_SYMBOL(__generic_file_aio_write
);
2467 * generic_file_aio_write_nolock - write data, usually to a device
2468 * @iocb: IO state structure
2469 * @iov: vector with data to write
2470 * @nr_segs: number of segments in the vector
2471 * @pos: position in file where to write
2473 * This is a wrapper around __generic_file_aio_write() which takes care of
2474 * syncing the file in case of O_SYNC file. It does not take i_mutex for the
2475 * write itself but may do so during syncing. It is meant for users like block
2476 * devices which do not need i_mutex during write. If your filesystem needs to
2477 * do a write but already holds i_mutex, use __generic_file_aio_write()
2478 * directly and then sync the file like generic_file_aio_write().
2480 ssize_t
generic_file_aio_write_nolock(struct kiocb
*iocb
,
2481 const struct iovec
*iov
, unsigned long nr_segs
, loff_t pos
)
2483 struct file
*file
= iocb
->ki_filp
;
2484 struct address_space
*mapping
= file
->f_mapping
;
2485 struct inode
*inode
= mapping
->host
;
2488 BUG_ON(iocb
->ki_pos
!= pos
);
2490 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
, &iocb
->ki_pos
);
2492 if ((ret
> 0 || ret
== -EIOCBQUEUED
) &&
2493 ((file
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
2496 err
= sync_page_range_nolock(inode
, mapping
, pos
, ret
);
2497 if (err
< 0 && ret
> 0)
2502 EXPORT_SYMBOL(generic_file_aio_write_nolock
);
2505 * generic_file_aio_write - write data to a file
2506 * @iocb: IO state structure
2507 * @iov: vector with data to write
2508 * @nr_segs: number of segments in the vector
2509 * @pos: position in file where to write
2511 * This is a wrapper around __generic_file_aio_write() to be used by most
2512 * filesystems. It takes care of syncing the file in case of O_SYNC file
2513 * and acquires i_mutex as needed.
2515 ssize_t
generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2516 unsigned long nr_segs
, loff_t pos
)
2518 struct file
*file
= iocb
->ki_filp
;
2519 struct address_space
*mapping
= file
->f_mapping
;
2520 struct inode
*inode
= mapping
->host
;
2523 BUG_ON(iocb
->ki_pos
!= pos
);
2525 mutex_lock(&inode
->i_mutex
);
2526 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
, &iocb
->ki_pos
);
2527 mutex_unlock(&inode
->i_mutex
);
2529 if ((ret
> 0 || ret
== -EIOCBQUEUED
) &&
2530 ((file
->f_flags
& O_SYNC
) || IS_SYNC(inode
))) {
2533 err
= sync_page_range(inode
, mapping
, pos
, ret
);
2534 if (err
< 0 && ret
> 0)
2539 EXPORT_SYMBOL(generic_file_aio_write
);
2542 * try_to_release_page() - release old fs-specific metadata on a page
2544 * @page: the page which the kernel is trying to free
2545 * @gfp_mask: memory allocation flags (and I/O mode)
2547 * The address_space is to try to release any data against the page
2548 * (presumably at page->private). If the release was successful, return `1'.
2549 * Otherwise return zero.
2551 * This may also be called if PG_fscache is set on a page, indicating that the
2552 * page is known to the local caching routines.
2554 * The @gfp_mask argument specifies whether I/O may be performed to release
2555 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2558 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2560 struct address_space
* const mapping
= page
->mapping
;
2562 BUG_ON(!PageLocked(page
));
2563 if (PageWriteback(page
))
2566 if (mapping
&& mapping
->a_ops
->releasepage
)
2567 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2568 return try_to_free_buffers(page
);
2571 EXPORT_SYMBOL(try_to_release_page
);