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>
36 #include <linux/rmap.h>
39 #define CREATE_TRACE_POINTS
40 #include <trace/events/filemap.h>
43 * FIXME: remove all knowledge of the buffer layer from the core VM
45 #include <linux/buffer_head.h> /* for try_to_free_buffers */
50 * Shared mappings implemented 30.11.1994. It's not fully working yet,
53 * Shared mappings now work. 15.8.1995 Bruno.
55 * finished 'unifying' the page and buffer cache and SMP-threaded the
56 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
64 * ->i_mmap_mutex (truncate_pagecache)
65 * ->private_lock (__free_pte->__set_page_dirty_buffers)
66 * ->swap_lock (exclusive_swap_page, others)
67 * ->mapping->tree_lock
70 * ->i_mmap_mutex (truncate->unmap_mapping_range)
74 * ->page_table_lock or pte_lock (various, mainly in memory.c)
75 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
78 * ->lock_page (access_process_vm)
80 * ->i_mutex (generic_perform_write)
81 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
84 * sb_lock (fs/fs-writeback.c)
85 * ->mapping->tree_lock (__sync_single_inode)
88 * ->anon_vma.lock (vma_adjust)
91 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 * ->page_table_lock or pte_lock
94 * ->swap_lock (try_to_unmap_one)
95 * ->private_lock (try_to_unmap_one)
96 * ->tree_lock (try_to_unmap_one)
97 * ->zone.lru_lock (follow_page->mark_page_accessed)
98 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
99 * ->private_lock (page_remove_rmap->set_page_dirty)
100 * ->tree_lock (page_remove_rmap->set_page_dirty)
101 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
102 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
103 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
104 * ->inode->i_lock (zap_pte_range->set_page_dirty)
105 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
108 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 static void page_cache_tree_delete(struct address_space
*mapping
,
112 struct page
*page
, void *shadow
)
114 struct radix_tree_node
*node
;
120 VM_BUG_ON(!PageLocked(page
));
122 __radix_tree_lookup(&mapping
->page_tree
, page
->index
, &node
, &slot
);
125 mapping
->nrshadows
++;
127 * Make sure the nrshadows update is committed before
128 * the nrpages update so that final truncate racing
129 * with reclaim does not see both counters 0 at the
130 * same time and miss a shadow entry.
137 /* Clear direct pointer tags in root node */
138 mapping
->page_tree
.gfp_mask
&= __GFP_BITS_MASK
;
139 radix_tree_replace_slot(slot
, shadow
);
143 /* Clear tree tags for the removed page */
145 offset
= index
& RADIX_TREE_MAP_MASK
;
146 for (tag
= 0; tag
< RADIX_TREE_MAX_TAGS
; tag
++) {
147 if (test_bit(offset
, node
->tags
[tag
]))
148 radix_tree_tag_clear(&mapping
->page_tree
, index
, tag
);
151 /* Delete page, swap shadow entry */
152 radix_tree_replace_slot(slot
, shadow
);
153 workingset_node_pages_dec(node
);
155 workingset_node_shadows_inc(node
);
157 if (__radix_tree_delete_node(&mapping
->page_tree
, node
))
161 * Track node that only contains shadow entries.
163 * Avoid acquiring the list_lru lock if already tracked. The
164 * list_empty() test is safe as node->private_list is
165 * protected by mapping->tree_lock.
167 if (!workingset_node_pages(node
) &&
168 list_empty(&node
->private_list
)) {
169 node
->private_data
= mapping
;
170 list_lru_add(&workingset_shadow_nodes
, &node
->private_list
);
175 * Delete a page from the page cache and free it. Caller has to make
176 * sure the page is locked and that nobody else uses it - or that usage
177 * is safe. The caller must hold the mapping's tree_lock.
179 void __delete_from_page_cache(struct page
*page
, void *shadow
)
181 struct address_space
*mapping
= page
->mapping
;
183 trace_mm_filemap_delete_from_page_cache(page
);
185 * if we're uptodate, flush out into the cleancache, otherwise
186 * invalidate any existing cleancache entries. We can't leave
187 * stale data around in the cleancache once our page is gone
189 if (PageUptodate(page
) && PageMappedToDisk(page
))
190 cleancache_put_page(page
);
192 cleancache_invalidate_page(mapping
, page
);
194 page_cache_tree_delete(mapping
, page
, shadow
);
196 page
->mapping
= NULL
;
197 /* Leave page->index set: truncation lookup relies upon it */
199 __dec_zone_page_state(page
, NR_FILE_PAGES
);
200 if (PageSwapBacked(page
))
201 __dec_zone_page_state(page
, NR_SHMEM
);
202 BUG_ON(page_mapped(page
));
205 * Some filesystems seem to re-dirty the page even after
206 * the VM has canceled the dirty bit (eg ext3 journaling).
208 * Fix it up by doing a final dirty accounting check after
209 * having removed the page entirely.
211 if (PageDirty(page
) && mapping_cap_account_dirty(mapping
)) {
212 dec_zone_page_state(page
, NR_FILE_DIRTY
);
213 dec_bdi_stat(mapping
->backing_dev_info
, BDI_RECLAIMABLE
);
218 * delete_from_page_cache - delete page from page cache
219 * @page: the page which the kernel is trying to remove from page cache
221 * This must be called only on pages that have been verified to be in the page
222 * cache and locked. It will never put the page into the free list, the caller
223 * has a reference on the page.
225 void delete_from_page_cache(struct page
*page
)
227 struct address_space
*mapping
= page
->mapping
;
228 void (*freepage
)(struct page
*);
230 BUG_ON(!PageLocked(page
));
232 freepage
= mapping
->a_ops
->freepage
;
233 spin_lock_irq(&mapping
->tree_lock
);
234 __delete_from_page_cache(page
, NULL
);
235 spin_unlock_irq(&mapping
->tree_lock
);
236 mem_cgroup_uncharge_cache_page(page
);
240 page_cache_release(page
);
242 EXPORT_SYMBOL(delete_from_page_cache
);
244 static int filemap_check_errors(struct address_space
*mapping
)
247 /* Check for outstanding write errors */
248 if (test_bit(AS_ENOSPC
, &mapping
->flags
) &&
249 test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
251 if (test_bit(AS_EIO
, &mapping
->flags
) &&
252 test_and_clear_bit(AS_EIO
, &mapping
->flags
))
258 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
259 * @mapping: address space structure to write
260 * @start: offset in bytes where the range starts
261 * @end: offset in bytes where the range ends (inclusive)
262 * @sync_mode: enable synchronous operation
264 * Start writeback against all of a mapping's dirty pages that lie
265 * within the byte offsets <start, end> inclusive.
267 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
268 * opposed to a regular memory cleansing writeback. The difference between
269 * these two operations is that if a dirty page/buffer is encountered, it must
270 * be waited upon, and not just skipped over.
272 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
273 loff_t end
, int sync_mode
)
276 struct writeback_control wbc
= {
277 .sync_mode
= sync_mode
,
278 .nr_to_write
= LONG_MAX
,
279 .range_start
= start
,
283 if (!mapping_cap_writeback_dirty(mapping
))
286 ret
= do_writepages(mapping
, &wbc
);
290 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
293 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
296 int filemap_fdatawrite(struct address_space
*mapping
)
298 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
300 EXPORT_SYMBOL(filemap_fdatawrite
);
302 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
305 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
307 EXPORT_SYMBOL(filemap_fdatawrite_range
);
310 * filemap_flush - mostly a non-blocking flush
311 * @mapping: target address_space
313 * This is a mostly non-blocking flush. Not suitable for data-integrity
314 * purposes - I/O may not be started against all dirty pages.
316 int filemap_flush(struct address_space
*mapping
)
318 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
320 EXPORT_SYMBOL(filemap_flush
);
323 * filemap_fdatawait_range - wait for writeback to complete
324 * @mapping: address space structure to wait for
325 * @start_byte: offset in bytes where the range starts
326 * @end_byte: offset in bytes where the range ends (inclusive)
328 * Walk the list of under-writeback pages of the given address space
329 * in the given range and wait for all of them.
331 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
334 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
335 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
340 if (end_byte
< start_byte
)
343 pagevec_init(&pvec
, 0);
344 while ((index
<= end
) &&
345 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
346 PAGECACHE_TAG_WRITEBACK
,
347 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
350 for (i
= 0; i
< nr_pages
; i
++) {
351 struct page
*page
= pvec
.pages
[i
];
353 /* until radix tree lookup accepts end_index */
354 if (page
->index
> end
)
357 wait_on_page_writeback(page
);
358 if (TestClearPageError(page
))
361 pagevec_release(&pvec
);
365 ret2
= filemap_check_errors(mapping
);
371 EXPORT_SYMBOL(filemap_fdatawait_range
);
374 * filemap_fdatawait - wait for all under-writeback pages to complete
375 * @mapping: address space structure to wait for
377 * Walk the list of under-writeback pages of the given address space
378 * and wait for all of them.
380 int filemap_fdatawait(struct address_space
*mapping
)
382 loff_t i_size
= i_size_read(mapping
->host
);
387 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
389 EXPORT_SYMBOL(filemap_fdatawait
);
391 int filemap_write_and_wait(struct address_space
*mapping
)
395 if (mapping
->nrpages
) {
396 err
= filemap_fdatawrite(mapping
);
398 * Even if the above returned error, the pages may be
399 * written partially (e.g. -ENOSPC), so we wait for it.
400 * But the -EIO is special case, it may indicate the worst
401 * thing (e.g. bug) happened, so we avoid waiting for it.
404 int err2
= filemap_fdatawait(mapping
);
409 err
= filemap_check_errors(mapping
);
413 EXPORT_SYMBOL(filemap_write_and_wait
);
416 * filemap_write_and_wait_range - write out & wait on a file range
417 * @mapping: the address_space for the pages
418 * @lstart: offset in bytes where the range starts
419 * @lend: offset in bytes where the range ends (inclusive)
421 * Write out and wait upon file offsets lstart->lend, inclusive.
423 * Note that `lend' is inclusive (describes the last byte to be written) so
424 * that this function can be used to write to the very end-of-file (end = -1).
426 int filemap_write_and_wait_range(struct address_space
*mapping
,
427 loff_t lstart
, loff_t lend
)
431 if (mapping
->nrpages
) {
432 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
434 /* See comment of filemap_write_and_wait() */
436 int err2
= filemap_fdatawait_range(mapping
,
442 err
= filemap_check_errors(mapping
);
446 EXPORT_SYMBOL(filemap_write_and_wait_range
);
449 * replace_page_cache_page - replace a pagecache page with a new one
450 * @old: page to be replaced
451 * @new: page to replace with
452 * @gfp_mask: allocation mode
454 * This function replaces a page in the pagecache with a new one. On
455 * success it acquires the pagecache reference for the new page and
456 * drops it for the old page. Both the old and new pages must be
457 * locked. This function does not add the new page to the LRU, the
458 * caller must do that.
460 * The remove + add is atomic. The only way this function can fail is
461 * memory allocation failure.
463 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
467 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
468 VM_BUG_ON_PAGE(!PageLocked(new), new);
469 VM_BUG_ON_PAGE(new->mapping
, new);
471 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
473 struct address_space
*mapping
= old
->mapping
;
474 void (*freepage
)(struct page
*);
476 pgoff_t offset
= old
->index
;
477 freepage
= mapping
->a_ops
->freepage
;
480 new->mapping
= mapping
;
483 spin_lock_irq(&mapping
->tree_lock
);
484 __delete_from_page_cache(old
, NULL
);
485 error
= radix_tree_insert(&mapping
->page_tree
, offset
, new);
488 __inc_zone_page_state(new, NR_FILE_PAGES
);
489 if (PageSwapBacked(new))
490 __inc_zone_page_state(new, NR_SHMEM
);
491 spin_unlock_irq(&mapping
->tree_lock
);
492 /* mem_cgroup codes must not be called under tree_lock */
493 mem_cgroup_replace_page_cache(old
, new);
494 radix_tree_preload_end();
497 page_cache_release(old
);
502 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
504 static int page_cache_tree_insert(struct address_space
*mapping
,
505 struct page
*page
, void **shadowp
)
507 struct radix_tree_node
*node
;
511 error
= __radix_tree_create(&mapping
->page_tree
, page
->index
,
518 p
= radix_tree_deref_slot_protected(slot
, &mapping
->tree_lock
);
519 if (!radix_tree_exceptional_entry(p
))
523 mapping
->nrshadows
--;
525 workingset_node_shadows_dec(node
);
527 radix_tree_replace_slot(slot
, page
);
530 workingset_node_pages_inc(node
);
532 * Don't track node that contains actual pages.
534 * Avoid acquiring the list_lru lock if already
535 * untracked. The list_empty() test is safe as
536 * node->private_list is protected by
537 * mapping->tree_lock.
539 if (!list_empty(&node
->private_list
))
540 list_lru_del(&workingset_shadow_nodes
,
541 &node
->private_list
);
546 static int __add_to_page_cache_locked(struct page
*page
,
547 struct address_space
*mapping
,
548 pgoff_t offset
, gfp_t gfp_mask
,
553 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
554 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
556 error
= mem_cgroup_charge_file(page
, current
->mm
,
557 gfp_mask
& GFP_RECLAIM_MASK
);
561 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
563 mem_cgroup_uncharge_cache_page(page
);
567 page_cache_get(page
);
568 page
->mapping
= mapping
;
569 page
->index
= offset
;
571 spin_lock_irq(&mapping
->tree_lock
);
572 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
573 radix_tree_preload_end();
576 __inc_zone_page_state(page
, NR_FILE_PAGES
);
577 spin_unlock_irq(&mapping
->tree_lock
);
578 trace_mm_filemap_add_to_page_cache(page
);
581 page
->mapping
= NULL
;
582 /* Leave page->index set: truncation relies upon it */
583 spin_unlock_irq(&mapping
->tree_lock
);
584 mem_cgroup_uncharge_cache_page(page
);
585 page_cache_release(page
);
590 * add_to_page_cache_locked - add a locked page to the pagecache
592 * @mapping: the page's address_space
593 * @offset: page index
594 * @gfp_mask: page allocation mode
596 * This function is used to add a page to the pagecache. It must be locked.
597 * This function does not add the page to the LRU. The caller must do that.
599 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
600 pgoff_t offset
, gfp_t gfp_mask
)
602 return __add_to_page_cache_locked(page
, mapping
, offset
,
605 EXPORT_SYMBOL(add_to_page_cache_locked
);
607 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
608 pgoff_t offset
, gfp_t gfp_mask
)
613 __set_page_locked(page
);
614 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
617 __clear_page_locked(page
);
620 * The page might have been evicted from cache only
621 * recently, in which case it should be activated like
622 * any other repeatedly accessed page.
624 if (shadow
&& workingset_refault(shadow
)) {
626 workingset_activation(page
);
628 ClearPageActive(page
);
633 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
636 struct page
*__page_cache_alloc(gfp_t gfp
)
641 if (cpuset_do_page_mem_spread()) {
642 unsigned int cpuset_mems_cookie
;
644 cpuset_mems_cookie
= read_mems_allowed_begin();
645 n
= cpuset_mem_spread_node();
646 page
= alloc_pages_exact_node(n
, gfp
, 0);
647 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
651 return alloc_pages(gfp
, 0);
653 EXPORT_SYMBOL(__page_cache_alloc
);
657 * In order to wait for pages to become available there must be
658 * waitqueues associated with pages. By using a hash table of
659 * waitqueues where the bucket discipline is to maintain all
660 * waiters on the same queue and wake all when any of the pages
661 * become available, and for the woken contexts to check to be
662 * sure the appropriate page became available, this saves space
663 * at a cost of "thundering herd" phenomena during rare hash
666 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
668 const struct zone
*zone
= page_zone(page
);
670 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
673 static inline void wake_up_page(struct page
*page
, int bit
)
675 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
678 void wait_on_page_bit(struct page
*page
, int bit_nr
)
680 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
682 if (test_bit(bit_nr
, &page
->flags
))
683 __wait_on_bit(page_waitqueue(page
), &wait
, bit_wait_io
,
684 TASK_UNINTERRUPTIBLE
);
686 EXPORT_SYMBOL(wait_on_page_bit
);
688 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
690 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
692 if (!test_bit(bit_nr
, &page
->flags
))
695 return __wait_on_bit(page_waitqueue(page
), &wait
,
696 bit_wait_io
, TASK_KILLABLE
);
700 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
701 * @page: Page defining the wait queue of interest
702 * @waiter: Waiter to add to the queue
704 * Add an arbitrary @waiter to the wait queue for the nominated @page.
706 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
708 wait_queue_head_t
*q
= page_waitqueue(page
);
711 spin_lock_irqsave(&q
->lock
, flags
);
712 __add_wait_queue(q
, waiter
);
713 spin_unlock_irqrestore(&q
->lock
, flags
);
715 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
718 * unlock_page - unlock a locked page
721 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
722 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
723 * mechananism between PageLocked pages and PageWriteback pages is shared.
724 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
726 * The mb is necessary to enforce ordering between the clear_bit and the read
727 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
729 void unlock_page(struct page
*page
)
731 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
732 clear_bit_unlock(PG_locked
, &page
->flags
);
733 smp_mb__after_atomic();
734 wake_up_page(page
, PG_locked
);
736 EXPORT_SYMBOL(unlock_page
);
739 * end_page_writeback - end writeback against a page
742 void end_page_writeback(struct page
*page
)
745 * TestClearPageReclaim could be used here but it is an atomic
746 * operation and overkill in this particular case. Failing to
747 * shuffle a page marked for immediate reclaim is too mild to
748 * justify taking an atomic operation penalty at the end of
749 * ever page writeback.
751 if (PageReclaim(page
)) {
752 ClearPageReclaim(page
);
753 rotate_reclaimable_page(page
);
756 if (!test_clear_page_writeback(page
))
759 smp_mb__after_atomic();
760 wake_up_page(page
, PG_writeback
);
762 EXPORT_SYMBOL(end_page_writeback
);
765 * After completing I/O on a page, call this routine to update the page
766 * flags appropriately
768 void page_endio(struct page
*page
, int rw
, int err
)
772 SetPageUptodate(page
);
774 ClearPageUptodate(page
);
778 } else { /* rw == WRITE */
782 mapping_set_error(page
->mapping
, err
);
784 end_page_writeback(page
);
787 EXPORT_SYMBOL_GPL(page_endio
);
790 * __lock_page - get a lock on the page, assuming we need to sleep to get it
791 * @page: the page to lock
793 void __lock_page(struct page
*page
)
795 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
797 __wait_on_bit_lock(page_waitqueue(page
), &wait
, bit_wait_io
,
798 TASK_UNINTERRUPTIBLE
);
800 EXPORT_SYMBOL(__lock_page
);
802 int __lock_page_killable(struct page
*page
)
804 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
806 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
807 bit_wait_io
, TASK_KILLABLE
);
809 EXPORT_SYMBOL_GPL(__lock_page_killable
);
813 * 1 - page is locked; mmap_sem is still held.
814 * 0 - page is not locked.
815 * mmap_sem has been released (up_read()), unless flags had both
816 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
817 * which case mmap_sem is still held.
819 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
820 * with the page locked and the mmap_sem unperturbed.
822 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
825 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
827 * CAUTION! In this case, mmap_sem is not released
828 * even though return 0.
830 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
833 up_read(&mm
->mmap_sem
);
834 if (flags
& FAULT_FLAG_KILLABLE
)
835 wait_on_page_locked_killable(page
);
837 wait_on_page_locked(page
);
840 if (flags
& FAULT_FLAG_KILLABLE
) {
843 ret
= __lock_page_killable(page
);
845 up_read(&mm
->mmap_sem
);
855 * page_cache_next_hole - find the next hole (not-present entry)
858 * @max_scan: maximum range to search
860 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
861 * lowest indexed hole.
863 * Returns: the index of the hole if found, otherwise returns an index
864 * outside of the set specified (in which case 'return - index >=
865 * max_scan' will be true). In rare cases of index wrap-around, 0 will
868 * page_cache_next_hole may be called under rcu_read_lock. However,
869 * like radix_tree_gang_lookup, this will not atomically search a
870 * snapshot of the tree at a single point in time. For example, if a
871 * hole is created at index 5, then subsequently a hole is created at
872 * index 10, page_cache_next_hole covering both indexes may return 10
873 * if called under rcu_read_lock.
875 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
876 pgoff_t index
, unsigned long max_scan
)
880 for (i
= 0; i
< max_scan
; i
++) {
883 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
884 if (!page
|| radix_tree_exceptional_entry(page
))
893 EXPORT_SYMBOL(page_cache_next_hole
);
896 * page_cache_prev_hole - find the prev hole (not-present entry)
899 * @max_scan: maximum range to search
901 * Search backwards in the range [max(index-max_scan+1, 0), index] for
904 * Returns: the index of the hole if found, otherwise returns an index
905 * outside of the set specified (in which case 'index - return >=
906 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
909 * page_cache_prev_hole may be called under rcu_read_lock. However,
910 * like radix_tree_gang_lookup, this will not atomically search a
911 * snapshot of the tree at a single point in time. For example, if a
912 * hole is created at index 10, then subsequently a hole is created at
913 * index 5, page_cache_prev_hole covering both indexes may return 5 if
914 * called under rcu_read_lock.
916 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
917 pgoff_t index
, unsigned long max_scan
)
921 for (i
= 0; i
< max_scan
; i
++) {
924 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
925 if (!page
|| radix_tree_exceptional_entry(page
))
928 if (index
== ULONG_MAX
)
934 EXPORT_SYMBOL(page_cache_prev_hole
);
937 * find_get_entry - find and get a page cache entry
938 * @mapping: the address_space to search
939 * @offset: the page cache index
941 * Looks up the page cache slot at @mapping & @offset. If there is a
942 * page cache page, it is returned with an increased refcount.
944 * If the slot holds a shadow entry of a previously evicted page, or a
945 * swap entry from shmem/tmpfs, it is returned.
947 * Otherwise, %NULL is returned.
949 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
957 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
959 page
= radix_tree_deref_slot(pagep
);
962 if (radix_tree_exception(page
)) {
963 if (radix_tree_deref_retry(page
))
966 * A shadow entry of a recently evicted page,
967 * or a swap entry from shmem/tmpfs. Return
968 * it without attempting to raise page count.
972 if (!page_cache_get_speculative(page
))
976 * Has the page moved?
977 * This is part of the lockless pagecache protocol. See
978 * include/linux/pagemap.h for details.
980 if (unlikely(page
!= *pagep
)) {
981 page_cache_release(page
);
990 EXPORT_SYMBOL(find_get_entry
);
993 * find_lock_entry - locate, pin and lock a page cache entry
994 * @mapping: the address_space to search
995 * @offset: the page cache index
997 * Looks up the page cache slot at @mapping & @offset. If there is a
998 * page cache page, it is returned locked and with an increased
1001 * If the slot holds a shadow entry of a previously evicted page, or a
1002 * swap entry from shmem/tmpfs, it is returned.
1004 * Otherwise, %NULL is returned.
1006 * find_lock_entry() may sleep.
1008 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1013 page
= find_get_entry(mapping
, offset
);
1014 if (page
&& !radix_tree_exception(page
)) {
1016 /* Has the page been truncated? */
1017 if (unlikely(page
->mapping
!= mapping
)) {
1019 page_cache_release(page
);
1022 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1026 EXPORT_SYMBOL(find_lock_entry
);
1029 * pagecache_get_page - find and get a page reference
1030 * @mapping: the address_space to search
1031 * @offset: the page index
1032 * @fgp_flags: PCG flags
1033 * @cache_gfp_mask: gfp mask to use for the page cache data page allocation
1034 * @radix_gfp_mask: gfp mask to use for radix tree node allocation
1036 * Looks up the page cache slot at @mapping & @offset.
1038 * PCG flags modify how the page is returned.
1040 * FGP_ACCESSED: the page will be marked accessed
1041 * FGP_LOCK: Page is return locked
1042 * FGP_CREAT: If page is not present then a new page is allocated using
1043 * @cache_gfp_mask and added to the page cache and the VM's LRU
1044 * list. If radix tree nodes are allocated during page cache
1045 * insertion then @radix_gfp_mask is used. The page is returned
1046 * locked and with an increased refcount. Otherwise, %NULL is
1049 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1050 * if the GFP flags specified for FGP_CREAT are atomic.
1052 * If there is a page cache page, it is returned with an increased refcount.
1054 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1055 int fgp_flags
, gfp_t cache_gfp_mask
, gfp_t radix_gfp_mask
)
1060 page
= find_get_entry(mapping
, offset
);
1061 if (radix_tree_exceptional_entry(page
))
1066 if (fgp_flags
& FGP_LOCK
) {
1067 if (fgp_flags
& FGP_NOWAIT
) {
1068 if (!trylock_page(page
)) {
1069 page_cache_release(page
);
1076 /* Has the page been truncated? */
1077 if (unlikely(page
->mapping
!= mapping
)) {
1079 page_cache_release(page
);
1082 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1085 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1086 mark_page_accessed(page
);
1089 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1091 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1092 cache_gfp_mask
|= __GFP_WRITE
;
1093 if (fgp_flags
& FGP_NOFS
) {
1094 cache_gfp_mask
&= ~__GFP_FS
;
1095 radix_gfp_mask
&= ~__GFP_FS
;
1098 page
= __page_cache_alloc(cache_gfp_mask
);
1102 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1103 fgp_flags
|= FGP_LOCK
;
1105 /* Init accessed so avoid atomic mark_page_accessed later */
1106 if (fgp_flags
& FGP_ACCESSED
)
1107 __SetPageReferenced(page
);
1109 err
= add_to_page_cache_lru(page
, mapping
, offset
, radix_gfp_mask
);
1110 if (unlikely(err
)) {
1111 page_cache_release(page
);
1120 EXPORT_SYMBOL(pagecache_get_page
);
1123 * find_get_entries - gang pagecache lookup
1124 * @mapping: The address_space to search
1125 * @start: The starting page cache index
1126 * @nr_entries: The maximum number of entries
1127 * @entries: Where the resulting entries are placed
1128 * @indices: The cache indices corresponding to the entries in @entries
1130 * find_get_entries() will search for and return a group of up to
1131 * @nr_entries entries in the mapping. The entries are placed at
1132 * @entries. find_get_entries() takes a reference against any actual
1135 * The search returns a group of mapping-contiguous page cache entries
1136 * with ascending indexes. There may be holes in the indices due to
1137 * not-present pages.
1139 * Any shadow entries of evicted pages, or swap entries from
1140 * shmem/tmpfs, are included in the returned array.
1142 * find_get_entries() returns the number of pages and shadow entries
1145 unsigned find_get_entries(struct address_space
*mapping
,
1146 pgoff_t start
, unsigned int nr_entries
,
1147 struct page
**entries
, pgoff_t
*indices
)
1150 unsigned int ret
= 0;
1151 struct radix_tree_iter iter
;
1158 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1161 page
= radix_tree_deref_slot(slot
);
1162 if (unlikely(!page
))
1164 if (radix_tree_exception(page
)) {
1165 if (radix_tree_deref_retry(page
))
1168 * A shadow entry of a recently evicted page,
1169 * or a swap entry from shmem/tmpfs. Return
1170 * it without attempting to raise page count.
1174 if (!page_cache_get_speculative(page
))
1177 /* Has the page moved? */
1178 if (unlikely(page
!= *slot
)) {
1179 page_cache_release(page
);
1183 indices
[ret
] = iter
.index
;
1184 entries
[ret
] = page
;
1185 if (++ret
== nr_entries
)
1193 * find_get_pages - gang pagecache lookup
1194 * @mapping: The address_space to search
1195 * @start: The starting page index
1196 * @nr_pages: The maximum number of pages
1197 * @pages: Where the resulting pages are placed
1199 * find_get_pages() will search for and return a group of up to
1200 * @nr_pages pages in the mapping. The pages are placed at @pages.
1201 * find_get_pages() takes a reference against the returned pages.
1203 * The search returns a group of mapping-contiguous pages with ascending
1204 * indexes. There may be holes in the indices due to not-present pages.
1206 * find_get_pages() returns the number of pages which were found.
1208 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
1209 unsigned int nr_pages
, struct page
**pages
)
1211 struct radix_tree_iter iter
;
1215 if (unlikely(!nr_pages
))
1220 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1223 page
= radix_tree_deref_slot(slot
);
1224 if (unlikely(!page
))
1227 if (radix_tree_exception(page
)) {
1228 if (radix_tree_deref_retry(page
)) {
1230 * Transient condition which can only trigger
1231 * when entry at index 0 moves out of or back
1232 * to root: none yet gotten, safe to restart.
1234 WARN_ON(iter
.index
);
1238 * A shadow entry of a recently evicted page,
1239 * or a swap entry from shmem/tmpfs. Skip
1245 if (!page_cache_get_speculative(page
))
1248 /* Has the page moved? */
1249 if (unlikely(page
!= *slot
)) {
1250 page_cache_release(page
);
1255 if (++ret
== nr_pages
)
1264 * find_get_pages_contig - gang contiguous pagecache lookup
1265 * @mapping: The address_space to search
1266 * @index: The starting page index
1267 * @nr_pages: The maximum number of pages
1268 * @pages: Where the resulting pages are placed
1270 * find_get_pages_contig() works exactly like find_get_pages(), except
1271 * that the returned number of pages are guaranteed to be contiguous.
1273 * find_get_pages_contig() returns the number of pages which were found.
1275 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1276 unsigned int nr_pages
, struct page
**pages
)
1278 struct radix_tree_iter iter
;
1280 unsigned int ret
= 0;
1282 if (unlikely(!nr_pages
))
1287 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1290 page
= radix_tree_deref_slot(slot
);
1291 /* The hole, there no reason to continue */
1292 if (unlikely(!page
))
1295 if (radix_tree_exception(page
)) {
1296 if (radix_tree_deref_retry(page
)) {
1298 * Transient condition which can only trigger
1299 * when entry at index 0 moves out of or back
1300 * to root: none yet gotten, safe to restart.
1305 * A shadow entry of a recently evicted page,
1306 * or a swap entry from shmem/tmpfs. Stop
1307 * looking for contiguous pages.
1312 if (!page_cache_get_speculative(page
))
1315 /* Has the page moved? */
1316 if (unlikely(page
!= *slot
)) {
1317 page_cache_release(page
);
1322 * must check mapping and index after taking the ref.
1323 * otherwise we can get both false positives and false
1324 * negatives, which is just confusing to the caller.
1326 if (page
->mapping
== NULL
|| page
->index
!= iter
.index
) {
1327 page_cache_release(page
);
1332 if (++ret
== nr_pages
)
1338 EXPORT_SYMBOL(find_get_pages_contig
);
1341 * find_get_pages_tag - find and return pages that match @tag
1342 * @mapping: the address_space to search
1343 * @index: the starting page index
1344 * @tag: the tag index
1345 * @nr_pages: the maximum number of pages
1346 * @pages: where the resulting pages are placed
1348 * Like find_get_pages, except we only return pages which are tagged with
1349 * @tag. We update @index to index the next page for the traversal.
1351 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1352 int tag
, unsigned int nr_pages
, struct page
**pages
)
1354 struct radix_tree_iter iter
;
1358 if (unlikely(!nr_pages
))
1363 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1364 &iter
, *index
, tag
) {
1367 page
= radix_tree_deref_slot(slot
);
1368 if (unlikely(!page
))
1371 if (radix_tree_exception(page
)) {
1372 if (radix_tree_deref_retry(page
)) {
1374 * Transient condition which can only trigger
1375 * when entry at index 0 moves out of or back
1376 * to root: none yet gotten, safe to restart.
1381 * A shadow entry of a recently evicted page.
1383 * Those entries should never be tagged, but
1384 * this tree walk is lockless and the tags are
1385 * looked up in bulk, one radix tree node at a
1386 * time, so there is a sizable window for page
1387 * reclaim to evict a page we saw tagged.
1394 if (!page_cache_get_speculative(page
))
1397 /* Has the page moved? */
1398 if (unlikely(page
!= *slot
)) {
1399 page_cache_release(page
);
1404 if (++ret
== nr_pages
)
1411 *index
= pages
[ret
- 1]->index
+ 1;
1415 EXPORT_SYMBOL(find_get_pages_tag
);
1418 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1419 * a _large_ part of the i/o request. Imagine the worst scenario:
1421 * ---R__________________________________________B__________
1422 * ^ reading here ^ bad block(assume 4k)
1424 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1425 * => failing the whole request => read(R) => read(R+1) =>
1426 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1427 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1428 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1430 * It is going insane. Fix it by quickly scaling down the readahead size.
1432 static void shrink_readahead_size_eio(struct file
*filp
,
1433 struct file_ra_state
*ra
)
1439 * do_generic_file_read - generic file read routine
1440 * @filp: the file to read
1441 * @ppos: current file position
1442 * @iter: data destination
1443 * @written: already copied
1445 * This is a generic file read routine, and uses the
1446 * mapping->a_ops->readpage() function for the actual low-level stuff.
1448 * This is really ugly. But the goto's actually try to clarify some
1449 * of the logic when it comes to error handling etc.
1451 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1452 struct iov_iter
*iter
, ssize_t written
)
1454 struct address_space
*mapping
= filp
->f_mapping
;
1455 struct inode
*inode
= mapping
->host
;
1456 struct file_ra_state
*ra
= &filp
->f_ra
;
1460 unsigned long offset
; /* offset into pagecache page */
1461 unsigned int prev_offset
;
1464 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1465 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1466 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1467 last_index
= (*ppos
+ iter
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1468 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1474 unsigned long nr
, ret
;
1478 page
= find_get_page(mapping
, index
);
1480 page_cache_sync_readahead(mapping
,
1482 index
, last_index
- index
);
1483 page
= find_get_page(mapping
, index
);
1484 if (unlikely(page
== NULL
))
1485 goto no_cached_page
;
1487 if (PageReadahead(page
)) {
1488 page_cache_async_readahead(mapping
,
1490 index
, last_index
- index
);
1492 if (!PageUptodate(page
)) {
1493 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1494 !mapping
->a_ops
->is_partially_uptodate
)
1495 goto page_not_up_to_date
;
1496 if (!trylock_page(page
))
1497 goto page_not_up_to_date
;
1498 /* Did it get truncated before we got the lock? */
1500 goto page_not_up_to_date_locked
;
1501 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1502 offset
, iter
->count
))
1503 goto page_not_up_to_date_locked
;
1508 * i_size must be checked after we know the page is Uptodate.
1510 * Checking i_size after the check allows us to calculate
1511 * the correct value for "nr", which means the zero-filled
1512 * part of the page is not copied back to userspace (unless
1513 * another truncate extends the file - this is desired though).
1516 isize
= i_size_read(inode
);
1517 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1518 if (unlikely(!isize
|| index
> end_index
)) {
1519 page_cache_release(page
);
1523 /* nr is the maximum number of bytes to copy from this page */
1524 nr
= PAGE_CACHE_SIZE
;
1525 if (index
== end_index
) {
1526 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1528 page_cache_release(page
);
1534 /* If users can be writing to this page using arbitrary
1535 * virtual addresses, take care about potential aliasing
1536 * before reading the page on the kernel side.
1538 if (mapping_writably_mapped(mapping
))
1539 flush_dcache_page(page
);
1542 * When a sequential read accesses a page several times,
1543 * only mark it as accessed the first time.
1545 if (prev_index
!= index
|| offset
!= prev_offset
)
1546 mark_page_accessed(page
);
1550 * Ok, we have the page, and it's up-to-date, so
1551 * now we can copy it to user space...
1554 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
1556 index
+= offset
>> PAGE_CACHE_SHIFT
;
1557 offset
&= ~PAGE_CACHE_MASK
;
1558 prev_offset
= offset
;
1560 page_cache_release(page
);
1562 if (!iov_iter_count(iter
))
1570 page_not_up_to_date
:
1571 /* Get exclusive access to the page ... */
1572 error
= lock_page_killable(page
);
1573 if (unlikely(error
))
1574 goto readpage_error
;
1576 page_not_up_to_date_locked
:
1577 /* Did it get truncated before we got the lock? */
1578 if (!page
->mapping
) {
1580 page_cache_release(page
);
1584 /* Did somebody else fill it already? */
1585 if (PageUptodate(page
)) {
1592 * A previous I/O error may have been due to temporary
1593 * failures, eg. multipath errors.
1594 * PG_error will be set again if readpage fails.
1596 ClearPageError(page
);
1597 /* Start the actual read. The read will unlock the page. */
1598 error
= mapping
->a_ops
->readpage(filp
, page
);
1600 if (unlikely(error
)) {
1601 if (error
== AOP_TRUNCATED_PAGE
) {
1602 page_cache_release(page
);
1606 goto readpage_error
;
1609 if (!PageUptodate(page
)) {
1610 error
= lock_page_killable(page
);
1611 if (unlikely(error
))
1612 goto readpage_error
;
1613 if (!PageUptodate(page
)) {
1614 if (page
->mapping
== NULL
) {
1616 * invalidate_mapping_pages got it
1619 page_cache_release(page
);
1623 shrink_readahead_size_eio(filp
, ra
);
1625 goto readpage_error
;
1633 /* UHHUH! A synchronous read error occurred. Report it */
1634 page_cache_release(page
);
1639 * Ok, it wasn't cached, so we need to create a new
1642 page
= page_cache_alloc_cold(mapping
);
1647 error
= add_to_page_cache_lru(page
, mapping
,
1650 page_cache_release(page
);
1651 if (error
== -EEXIST
) {
1661 ra
->prev_pos
= prev_index
;
1662 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1663 ra
->prev_pos
|= prev_offset
;
1665 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1666 file_accessed(filp
);
1667 return written
? written
: error
;
1671 * generic_file_read_iter - generic filesystem read routine
1672 * @iocb: kernel I/O control block
1673 * @iter: destination for the data read
1675 * This is the "read_iter()" routine for all filesystems
1676 * that can use the page cache directly.
1679 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
1681 struct file
*file
= iocb
->ki_filp
;
1683 loff_t
*ppos
= &iocb
->ki_pos
;
1686 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1687 if (file
->f_flags
& O_DIRECT
) {
1688 struct address_space
*mapping
= file
->f_mapping
;
1689 struct inode
*inode
= mapping
->host
;
1690 size_t count
= iov_iter_count(iter
);
1694 goto out
; /* skip atime */
1695 size
= i_size_read(inode
);
1696 retval
= filemap_write_and_wait_range(mapping
, pos
,
1699 struct iov_iter data
= *iter
;
1700 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
, &data
, pos
);
1704 *ppos
= pos
+ retval
;
1705 iov_iter_advance(iter
, retval
);
1709 * Btrfs can have a short DIO read if we encounter
1710 * compressed extents, so if there was an error, or if
1711 * we've already read everything we wanted to, or if
1712 * there was a short read because we hit EOF, go ahead
1713 * and return. Otherwise fallthrough to buffered io for
1714 * the rest of the read.
1716 if (retval
< 0 || !iov_iter_count(iter
) || *ppos
>= size
) {
1717 file_accessed(file
);
1722 retval
= do_generic_file_read(file
, ppos
, iter
, retval
);
1726 EXPORT_SYMBOL(generic_file_read_iter
);
1730 * page_cache_read - adds requested page to the page cache if not already there
1731 * @file: file to read
1732 * @offset: page index
1734 * This adds the requested page to the page cache if it isn't already there,
1735 * and schedules an I/O to read in its contents from disk.
1737 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1739 struct address_space
*mapping
= file
->f_mapping
;
1744 page
= page_cache_alloc_cold(mapping
);
1748 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1750 ret
= mapping
->a_ops
->readpage(file
, page
);
1751 else if (ret
== -EEXIST
)
1752 ret
= 0; /* losing race to add is OK */
1754 page_cache_release(page
);
1756 } while (ret
== AOP_TRUNCATED_PAGE
);
1761 #define MMAP_LOTSAMISS (100)
1764 * Synchronous readahead happens when we don't even find
1765 * a page in the page cache at all.
1767 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1768 struct file_ra_state
*ra
,
1772 unsigned long ra_pages
;
1773 struct address_space
*mapping
= file
->f_mapping
;
1775 /* If we don't want any read-ahead, don't bother */
1776 if (vma
->vm_flags
& VM_RAND_READ
)
1781 if (vma
->vm_flags
& VM_SEQ_READ
) {
1782 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1787 /* Avoid banging the cache line if not needed */
1788 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
1792 * Do we miss much more than hit in this file? If so,
1793 * stop bothering with read-ahead. It will only hurt.
1795 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1801 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1802 ra
->start
= max_t(long, 0, offset
- ra_pages
/ 2);
1803 ra
->size
= ra_pages
;
1804 ra
->async_size
= ra_pages
/ 4;
1805 ra_submit(ra
, mapping
, file
);
1809 * Asynchronous readahead happens when we find the page and PG_readahead,
1810 * so we want to possibly extend the readahead further..
1812 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1813 struct file_ra_state
*ra
,
1818 struct address_space
*mapping
= file
->f_mapping
;
1820 /* If we don't want any read-ahead, don't bother */
1821 if (vma
->vm_flags
& VM_RAND_READ
)
1823 if (ra
->mmap_miss
> 0)
1825 if (PageReadahead(page
))
1826 page_cache_async_readahead(mapping
, ra
, file
,
1827 page
, offset
, ra
->ra_pages
);
1831 * filemap_fault - read in file data for page fault handling
1832 * @vma: vma in which the fault was taken
1833 * @vmf: struct vm_fault containing details of the fault
1835 * filemap_fault() is invoked via the vma operations vector for a
1836 * mapped memory region to read in file data during a page fault.
1838 * The goto's are kind of ugly, but this streamlines the normal case of having
1839 * it in the page cache, and handles the special cases reasonably without
1840 * having a lot of duplicated code.
1842 * vma->vm_mm->mmap_sem must be held on entry.
1844 * If our return value has VM_FAULT_RETRY set, it's because
1845 * lock_page_or_retry() returned 0.
1846 * The mmap_sem has usually been released in this case.
1847 * See __lock_page_or_retry() for the exception.
1849 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
1850 * has not been released.
1852 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
1854 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1857 struct file
*file
= vma
->vm_file
;
1858 struct address_space
*mapping
= file
->f_mapping
;
1859 struct file_ra_state
*ra
= &file
->f_ra
;
1860 struct inode
*inode
= mapping
->host
;
1861 pgoff_t offset
= vmf
->pgoff
;
1866 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1867 if (offset
>= size
>> PAGE_CACHE_SHIFT
)
1868 return VM_FAULT_SIGBUS
;
1871 * Do we have something in the page cache already?
1873 page
= find_get_page(mapping
, offset
);
1874 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
1876 * We found the page, so try async readahead before
1877 * waiting for the lock.
1879 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1881 /* No page in the page cache at all */
1882 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1883 count_vm_event(PGMAJFAULT
);
1884 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
1885 ret
= VM_FAULT_MAJOR
;
1887 page
= find_get_page(mapping
, offset
);
1889 goto no_cached_page
;
1892 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
1893 page_cache_release(page
);
1894 return ret
| VM_FAULT_RETRY
;
1897 /* Did it get truncated? */
1898 if (unlikely(page
->mapping
!= mapping
)) {
1903 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1906 * We have a locked page in the page cache, now we need to check
1907 * that it's up-to-date. If not, it is going to be due to an error.
1909 if (unlikely(!PageUptodate(page
)))
1910 goto page_not_uptodate
;
1913 * Found the page and have a reference on it.
1914 * We must recheck i_size under page lock.
1916 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1917 if (unlikely(offset
>= size
>> PAGE_CACHE_SHIFT
)) {
1919 page_cache_release(page
);
1920 return VM_FAULT_SIGBUS
;
1924 return ret
| VM_FAULT_LOCKED
;
1928 * We're only likely to ever get here if MADV_RANDOM is in
1931 error
= page_cache_read(file
, offset
);
1934 * The page we want has now been added to the page cache.
1935 * In the unlikely event that someone removed it in the
1936 * meantime, we'll just come back here and read it again.
1942 * An error return from page_cache_read can result if the
1943 * system is low on memory, or a problem occurs while trying
1946 if (error
== -ENOMEM
)
1947 return VM_FAULT_OOM
;
1948 return VM_FAULT_SIGBUS
;
1952 * Umm, take care of errors if the page isn't up-to-date.
1953 * Try to re-read it _once_. We do this synchronously,
1954 * because there really aren't any performance issues here
1955 * and we need to check for errors.
1957 ClearPageError(page
);
1958 error
= mapping
->a_ops
->readpage(file
, page
);
1960 wait_on_page_locked(page
);
1961 if (!PageUptodate(page
))
1964 page_cache_release(page
);
1966 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
1969 /* Things didn't work out. Return zero to tell the mm layer so. */
1970 shrink_readahead_size_eio(file
, ra
);
1971 return VM_FAULT_SIGBUS
;
1973 EXPORT_SYMBOL(filemap_fault
);
1975 void filemap_map_pages(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1977 struct radix_tree_iter iter
;
1979 struct file
*file
= vma
->vm_file
;
1980 struct address_space
*mapping
= file
->f_mapping
;
1983 unsigned long address
= (unsigned long) vmf
->virtual_address
;
1988 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, vmf
->pgoff
) {
1989 if (iter
.index
> vmf
->max_pgoff
)
1992 page
= radix_tree_deref_slot(slot
);
1993 if (unlikely(!page
))
1995 if (radix_tree_exception(page
)) {
1996 if (radix_tree_deref_retry(page
))
2002 if (!page_cache_get_speculative(page
))
2005 /* Has the page moved? */
2006 if (unlikely(page
!= *slot
)) {
2007 page_cache_release(page
);
2011 if (!PageUptodate(page
) ||
2012 PageReadahead(page
) ||
2015 if (!trylock_page(page
))
2018 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2021 size
= round_up(i_size_read(mapping
->host
), PAGE_CACHE_SIZE
);
2022 if (page
->index
>= size
>> PAGE_CACHE_SHIFT
)
2025 pte
= vmf
->pte
+ page
->index
- vmf
->pgoff
;
2026 if (!pte_none(*pte
))
2029 if (file
->f_ra
.mmap_miss
> 0)
2030 file
->f_ra
.mmap_miss
--;
2031 addr
= address
+ (page
->index
- vmf
->pgoff
) * PAGE_SIZE
;
2032 do_set_pte(vma
, addr
, page
, pte
, false, false);
2038 page_cache_release(page
);
2040 if (iter
.index
== vmf
->max_pgoff
)
2045 EXPORT_SYMBOL(filemap_map_pages
);
2047 int filemap_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2049 struct page
*page
= vmf
->page
;
2050 struct inode
*inode
= file_inode(vma
->vm_file
);
2051 int ret
= VM_FAULT_LOCKED
;
2053 sb_start_pagefault(inode
->i_sb
);
2054 file_update_time(vma
->vm_file
);
2056 if (page
->mapping
!= inode
->i_mapping
) {
2058 ret
= VM_FAULT_NOPAGE
;
2062 * We mark the page dirty already here so that when freeze is in
2063 * progress, we are guaranteed that writeback during freezing will
2064 * see the dirty page and writeprotect it again.
2066 set_page_dirty(page
);
2067 wait_for_stable_page(page
);
2069 sb_end_pagefault(inode
->i_sb
);
2072 EXPORT_SYMBOL(filemap_page_mkwrite
);
2074 const struct vm_operations_struct generic_file_vm_ops
= {
2075 .fault
= filemap_fault
,
2076 .map_pages
= filemap_map_pages
,
2077 .page_mkwrite
= filemap_page_mkwrite
,
2078 .remap_pages
= generic_file_remap_pages
,
2081 /* This is used for a general mmap of a disk file */
2083 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2085 struct address_space
*mapping
= file
->f_mapping
;
2087 if (!mapping
->a_ops
->readpage
)
2089 file_accessed(file
);
2090 vma
->vm_ops
= &generic_file_vm_ops
;
2095 * This is for filesystems which do not implement ->writepage.
2097 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2099 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2101 return generic_file_mmap(file
, vma
);
2104 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2108 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2112 #endif /* CONFIG_MMU */
2114 EXPORT_SYMBOL(generic_file_mmap
);
2115 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2117 static struct page
*wait_on_page_read(struct page
*page
)
2119 if (!IS_ERR(page
)) {
2120 wait_on_page_locked(page
);
2121 if (!PageUptodate(page
)) {
2122 page_cache_release(page
);
2123 page
= ERR_PTR(-EIO
);
2129 static struct page
*__read_cache_page(struct address_space
*mapping
,
2131 int (*filler
)(void *, struct page
*),
2138 page
= find_get_page(mapping
, index
);
2140 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2142 return ERR_PTR(-ENOMEM
);
2143 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2144 if (unlikely(err
)) {
2145 page_cache_release(page
);
2148 /* Presumably ENOMEM for radix tree node */
2149 return ERR_PTR(err
);
2151 err
= filler(data
, page
);
2153 page_cache_release(page
);
2154 page
= ERR_PTR(err
);
2156 page
= wait_on_page_read(page
);
2162 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2164 int (*filler
)(void *, struct page
*),
2173 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
2176 if (PageUptodate(page
))
2180 if (!page
->mapping
) {
2182 page_cache_release(page
);
2185 if (PageUptodate(page
)) {
2189 err
= filler(data
, page
);
2191 page_cache_release(page
);
2192 return ERR_PTR(err
);
2194 page
= wait_on_page_read(page
);
2199 mark_page_accessed(page
);
2204 * read_cache_page - read into page cache, fill it if needed
2205 * @mapping: the page's address_space
2206 * @index: the page index
2207 * @filler: function to perform the read
2208 * @data: first arg to filler(data, page) function, often left as NULL
2210 * Read into the page cache. If a page already exists, and PageUptodate() is
2211 * not set, try to fill the page and wait for it to become unlocked.
2213 * If the page does not get brought uptodate, return -EIO.
2215 struct page
*read_cache_page(struct address_space
*mapping
,
2217 int (*filler
)(void *, struct page
*),
2220 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2222 EXPORT_SYMBOL(read_cache_page
);
2225 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2226 * @mapping: the page's address_space
2227 * @index: the page index
2228 * @gfp: the page allocator flags to use if allocating
2230 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2231 * any new page allocations done using the specified allocation flags.
2233 * If the page does not get brought uptodate, return -EIO.
2235 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2239 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2241 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2243 EXPORT_SYMBOL(read_cache_page_gfp
);
2246 * Performs necessary checks before doing a write
2248 * Can adjust writing position or amount of bytes to write.
2249 * Returns appropriate error code that caller should return or
2250 * zero in case that write should be allowed.
2252 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
2254 struct inode
*inode
= file
->f_mapping
->host
;
2255 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2257 if (unlikely(*pos
< 0))
2261 /* FIXME: this is for backwards compatibility with 2.4 */
2262 if (file
->f_flags
& O_APPEND
)
2263 *pos
= i_size_read(inode
);
2265 if (limit
!= RLIM_INFINITY
) {
2266 if (*pos
>= limit
) {
2267 send_sig(SIGXFSZ
, current
, 0);
2270 if (*count
> limit
- (typeof(limit
))*pos
) {
2271 *count
= limit
- (typeof(limit
))*pos
;
2279 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2280 !(file
->f_flags
& O_LARGEFILE
))) {
2281 if (*pos
>= MAX_NON_LFS
) {
2284 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2285 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2290 * Are we about to exceed the fs block limit ?
2292 * If we have written data it becomes a short write. If we have
2293 * exceeded without writing data we send a signal and return EFBIG.
2294 * Linus frestrict idea will clean these up nicely..
2296 if (likely(!isblk
)) {
2297 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2298 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2301 /* zero-length writes at ->s_maxbytes are OK */
2304 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2305 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2309 if (bdev_read_only(I_BDEV(inode
)))
2311 isize
= i_size_read(inode
);
2312 if (*pos
>= isize
) {
2313 if (*count
|| *pos
> isize
)
2317 if (*pos
+ *count
> isize
)
2318 *count
= isize
- *pos
;
2325 EXPORT_SYMBOL(generic_write_checks
);
2327 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2328 loff_t pos
, unsigned len
, unsigned flags
,
2329 struct page
**pagep
, void **fsdata
)
2331 const struct address_space_operations
*aops
= mapping
->a_ops
;
2333 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2336 EXPORT_SYMBOL(pagecache_write_begin
);
2338 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2339 loff_t pos
, unsigned len
, unsigned copied
,
2340 struct page
*page
, void *fsdata
)
2342 const struct address_space_operations
*aops
= mapping
->a_ops
;
2344 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2346 EXPORT_SYMBOL(pagecache_write_end
);
2349 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
, loff_t pos
)
2351 struct file
*file
= iocb
->ki_filp
;
2352 struct address_space
*mapping
= file
->f_mapping
;
2353 struct inode
*inode
= mapping
->host
;
2357 struct iov_iter data
;
2359 write_len
= iov_iter_count(from
);
2360 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2362 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2367 * After a write we want buffered reads to be sure to go to disk to get
2368 * the new data. We invalidate clean cached page from the region we're
2369 * about to write. We do this *before* the write so that we can return
2370 * without clobbering -EIOCBQUEUED from ->direct_IO().
2372 if (mapping
->nrpages
) {
2373 written
= invalidate_inode_pages2_range(mapping
,
2374 pos
>> PAGE_CACHE_SHIFT
, end
);
2376 * If a page can not be invalidated, return 0 to fall back
2377 * to buffered write.
2380 if (written
== -EBUSY
)
2387 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, &data
, pos
);
2390 * Finally, try again to invalidate clean pages which might have been
2391 * cached by non-direct readahead, or faulted in by get_user_pages()
2392 * if the source of the write was an mmap'ed region of the file
2393 * we're writing. Either one is a pretty crazy thing to do,
2394 * so we don't support it 100%. If this invalidation
2395 * fails, tough, the write still worked...
2397 if (mapping
->nrpages
) {
2398 invalidate_inode_pages2_range(mapping
,
2399 pos
>> PAGE_CACHE_SHIFT
, end
);
2404 iov_iter_advance(from
, written
);
2405 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2406 i_size_write(inode
, pos
);
2407 mark_inode_dirty(inode
);
2414 EXPORT_SYMBOL(generic_file_direct_write
);
2417 * Find or create a page at the given pagecache position. Return the locked
2418 * page. This function is specifically for buffered writes.
2420 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2421 pgoff_t index
, unsigned flags
)
2424 int fgp_flags
= FGP_LOCK
|FGP_ACCESSED
|FGP_WRITE
|FGP_CREAT
;
2426 if (flags
& AOP_FLAG_NOFS
)
2427 fgp_flags
|= FGP_NOFS
;
2429 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2430 mapping_gfp_mask(mapping
),
2433 wait_for_stable_page(page
);
2437 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2439 ssize_t
generic_perform_write(struct file
*file
,
2440 struct iov_iter
*i
, loff_t pos
)
2442 struct address_space
*mapping
= file
->f_mapping
;
2443 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2445 ssize_t written
= 0;
2446 unsigned int flags
= 0;
2449 * Copies from kernel address space cannot fail (NFSD is a big user).
2451 if (segment_eq(get_fs(), KERNEL_DS
))
2452 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2456 unsigned long offset
; /* Offset into pagecache page */
2457 unsigned long bytes
; /* Bytes to write to page */
2458 size_t copied
; /* Bytes copied from user */
2461 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2462 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2467 * Bring in the user page that we will copy from _first_.
2468 * Otherwise there's a nasty deadlock on copying from the
2469 * same page as we're writing to, without it being marked
2472 * Not only is this an optimisation, but it is also required
2473 * to check that the address is actually valid, when atomic
2474 * usercopies are used, below.
2476 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2481 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2483 if (unlikely(status
< 0))
2486 if (mapping_writably_mapped(mapping
))
2487 flush_dcache_page(page
);
2489 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2490 flush_dcache_page(page
);
2492 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2494 if (unlikely(status
< 0))
2500 iov_iter_advance(i
, copied
);
2501 if (unlikely(copied
== 0)) {
2503 * If we were unable to copy any data at all, we must
2504 * fall back to a single segment length write.
2506 * If we didn't fallback here, we could livelock
2507 * because not all segments in the iov can be copied at
2508 * once without a pagefault.
2510 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2511 iov_iter_single_seg_count(i
));
2517 balance_dirty_pages_ratelimited(mapping
);
2518 if (fatal_signal_pending(current
)) {
2522 } while (iov_iter_count(i
));
2524 return written
? written
: status
;
2526 EXPORT_SYMBOL(generic_perform_write
);
2529 * __generic_file_write_iter - write data to a file
2530 * @iocb: IO state structure (file, offset, etc.)
2531 * @from: iov_iter with data to write
2533 * This function does all the work needed for actually writing data to a
2534 * file. It does all basic checks, removes SUID from the file, updates
2535 * modification times and calls proper subroutines depending on whether we
2536 * do direct IO or a standard buffered write.
2538 * It expects i_mutex to be grabbed unless we work on a block device or similar
2539 * object which does not need locking at all.
2541 * This function does *not* take care of syncing data in case of O_SYNC write.
2542 * A caller has to handle it. This is mainly due to the fact that we want to
2543 * avoid syncing under i_mutex.
2545 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2547 struct file
*file
= iocb
->ki_filp
;
2548 struct address_space
* mapping
= file
->f_mapping
;
2549 struct inode
*inode
= mapping
->host
;
2550 loff_t pos
= iocb
->ki_pos
;
2551 ssize_t written
= 0;
2554 size_t count
= iov_iter_count(from
);
2556 /* We can write back this queue in page reclaim */
2557 current
->backing_dev_info
= mapping
->backing_dev_info
;
2558 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2565 iov_iter_truncate(from
, count
);
2567 err
= file_remove_suid(file
);
2571 err
= file_update_time(file
);
2575 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2576 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2579 written
= generic_file_direct_write(iocb
, from
, pos
);
2580 if (written
< 0 || written
== count
)
2584 * direct-io write to a hole: fall through to buffered I/O
2585 * for completing the rest of the request.
2590 status
= generic_perform_write(file
, from
, pos
);
2592 * If generic_perform_write() returned a synchronous error
2593 * then we want to return the number of bytes which were
2594 * direct-written, or the error code if that was zero. Note
2595 * that this differs from normal direct-io semantics, which
2596 * will return -EFOO even if some bytes were written.
2598 if (unlikely(status
< 0) && !written
) {
2602 iocb
->ki_pos
= pos
+ status
;
2604 * We need to ensure that the page cache pages are written to
2605 * disk and invalidated to preserve the expected O_DIRECT
2608 endbyte
= pos
+ status
- 1;
2609 err
= filemap_write_and_wait_range(file
->f_mapping
, pos
, endbyte
);
2612 invalidate_mapping_pages(mapping
,
2613 pos
>> PAGE_CACHE_SHIFT
,
2614 endbyte
>> PAGE_CACHE_SHIFT
);
2617 * We don't know how much we wrote, so just return
2618 * the number of bytes which were direct-written
2622 written
= generic_perform_write(file
, from
, pos
);
2623 if (likely(written
>= 0))
2624 iocb
->ki_pos
= pos
+ written
;
2627 current
->backing_dev_info
= NULL
;
2628 return written
? written
: err
;
2630 EXPORT_SYMBOL(__generic_file_write_iter
);
2633 * generic_file_write_iter - write data to a file
2634 * @iocb: IO state structure
2635 * @from: iov_iter with data to write
2637 * This is a wrapper around __generic_file_write_iter() to be used by most
2638 * filesystems. It takes care of syncing the file in case of O_SYNC file
2639 * and acquires i_mutex as needed.
2641 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2643 struct file
*file
= iocb
->ki_filp
;
2644 struct inode
*inode
= file
->f_mapping
->host
;
2647 mutex_lock(&inode
->i_mutex
);
2648 ret
= __generic_file_write_iter(iocb
, from
);
2649 mutex_unlock(&inode
->i_mutex
);
2654 err
= generic_write_sync(file
, iocb
->ki_pos
- ret
, ret
);
2660 EXPORT_SYMBOL(generic_file_write_iter
);
2663 * try_to_release_page() - release old fs-specific metadata on a page
2665 * @page: the page which the kernel is trying to free
2666 * @gfp_mask: memory allocation flags (and I/O mode)
2668 * The address_space is to try to release any data against the page
2669 * (presumably at page->private). If the release was successful, return `1'.
2670 * Otherwise return zero.
2672 * This may also be called if PG_fscache is set on a page, indicating that the
2673 * page is known to the local caching routines.
2675 * The @gfp_mask argument specifies whether I/O may be performed to release
2676 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2679 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2681 struct address_space
* const mapping
= page
->mapping
;
2683 BUG_ON(!PageLocked(page
));
2684 if (PageWriteback(page
))
2687 if (mapping
&& mapping
->a_ops
->releasepage
)
2688 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2689 return try_to_free_buffers(page
);
2692 EXPORT_SYMBOL(try_to_release_page
);