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 sleep_on_page(void *word
)
250 static int sleep_on_page_killable(void *word
)
253 return fatal_signal_pending(current
) ? -EINTR
: 0;
256 static int filemap_check_errors(struct address_space
*mapping
)
259 /* Check for outstanding write errors */
260 if (test_bit(AS_ENOSPC
, &mapping
->flags
) &&
261 test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
263 if (test_bit(AS_EIO
, &mapping
->flags
) &&
264 test_and_clear_bit(AS_EIO
, &mapping
->flags
))
270 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
271 * @mapping: address space structure to write
272 * @start: offset in bytes where the range starts
273 * @end: offset in bytes where the range ends (inclusive)
274 * @sync_mode: enable synchronous operation
276 * Start writeback against all of a mapping's dirty pages that lie
277 * within the byte offsets <start, end> inclusive.
279 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
280 * opposed to a regular memory cleansing writeback. The difference between
281 * these two operations is that if a dirty page/buffer is encountered, it must
282 * be waited upon, and not just skipped over.
284 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
285 loff_t end
, int sync_mode
)
288 struct writeback_control wbc
= {
289 .sync_mode
= sync_mode
,
290 .nr_to_write
= LONG_MAX
,
291 .range_start
= start
,
295 if (!mapping_cap_writeback_dirty(mapping
))
298 ret
= do_writepages(mapping
, &wbc
);
302 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
305 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
308 int filemap_fdatawrite(struct address_space
*mapping
)
310 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
312 EXPORT_SYMBOL(filemap_fdatawrite
);
314 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
317 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
319 EXPORT_SYMBOL(filemap_fdatawrite_range
);
322 * filemap_flush - mostly a non-blocking flush
323 * @mapping: target address_space
325 * This is a mostly non-blocking flush. Not suitable for data-integrity
326 * purposes - I/O may not be started against all dirty pages.
328 int filemap_flush(struct address_space
*mapping
)
330 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
332 EXPORT_SYMBOL(filemap_flush
);
335 * filemap_fdatawait_range - wait for writeback to complete
336 * @mapping: address space structure to wait for
337 * @start_byte: offset in bytes where the range starts
338 * @end_byte: offset in bytes where the range ends (inclusive)
340 * Walk the list of under-writeback pages of the given address space
341 * in the given range and wait for all of them.
343 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
346 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
347 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
352 if (end_byte
< start_byte
)
355 pagevec_init(&pvec
, 0);
356 while ((index
<= end
) &&
357 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
358 PAGECACHE_TAG_WRITEBACK
,
359 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
362 for (i
= 0; i
< nr_pages
; i
++) {
363 struct page
*page
= pvec
.pages
[i
];
365 /* until radix tree lookup accepts end_index */
366 if (page
->index
> end
)
369 wait_on_page_writeback(page
);
370 if (TestClearPageError(page
))
373 pagevec_release(&pvec
);
377 ret2
= filemap_check_errors(mapping
);
383 EXPORT_SYMBOL(filemap_fdatawait_range
);
386 * filemap_fdatawait - wait for all under-writeback pages to complete
387 * @mapping: address space structure to wait for
389 * Walk the list of under-writeback pages of the given address space
390 * and wait for all of them.
392 int filemap_fdatawait(struct address_space
*mapping
)
394 loff_t i_size
= i_size_read(mapping
->host
);
399 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
401 EXPORT_SYMBOL(filemap_fdatawait
);
403 int filemap_write_and_wait(struct address_space
*mapping
)
407 if (mapping
->nrpages
) {
408 err
= filemap_fdatawrite(mapping
);
410 * Even if the above returned error, the pages may be
411 * written partially (e.g. -ENOSPC), so we wait for it.
412 * But the -EIO is special case, it may indicate the worst
413 * thing (e.g. bug) happened, so we avoid waiting for it.
416 int err2
= filemap_fdatawait(mapping
);
421 err
= filemap_check_errors(mapping
);
425 EXPORT_SYMBOL(filemap_write_and_wait
);
428 * filemap_write_and_wait_range - write out & wait on a file range
429 * @mapping: the address_space for the pages
430 * @lstart: offset in bytes where the range starts
431 * @lend: offset in bytes where the range ends (inclusive)
433 * Write out and wait upon file offsets lstart->lend, inclusive.
435 * Note that `lend' is inclusive (describes the last byte to be written) so
436 * that this function can be used to write to the very end-of-file (end = -1).
438 int filemap_write_and_wait_range(struct address_space
*mapping
,
439 loff_t lstart
, loff_t lend
)
443 if (mapping
->nrpages
) {
444 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
446 /* See comment of filemap_write_and_wait() */
448 int err2
= filemap_fdatawait_range(mapping
,
454 err
= filemap_check_errors(mapping
);
458 EXPORT_SYMBOL(filemap_write_and_wait_range
);
461 * replace_page_cache_page - replace a pagecache page with a new one
462 * @old: page to be replaced
463 * @new: page to replace with
464 * @gfp_mask: allocation mode
466 * This function replaces a page in the pagecache with a new one. On
467 * success it acquires the pagecache reference for the new page and
468 * drops it for the old page. Both the old and new pages must be
469 * locked. This function does not add the new page to the LRU, the
470 * caller must do that.
472 * The remove + add is atomic. The only way this function can fail is
473 * memory allocation failure.
475 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
479 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
480 VM_BUG_ON_PAGE(!PageLocked(new), new);
481 VM_BUG_ON_PAGE(new->mapping
, new);
483 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
485 struct address_space
*mapping
= old
->mapping
;
486 void (*freepage
)(struct page
*);
488 pgoff_t offset
= old
->index
;
489 freepage
= mapping
->a_ops
->freepage
;
492 new->mapping
= mapping
;
495 spin_lock_irq(&mapping
->tree_lock
);
496 __delete_from_page_cache(old
, NULL
);
497 error
= radix_tree_insert(&mapping
->page_tree
, offset
, new);
500 __inc_zone_page_state(new, NR_FILE_PAGES
);
501 if (PageSwapBacked(new))
502 __inc_zone_page_state(new, NR_SHMEM
);
503 spin_unlock_irq(&mapping
->tree_lock
);
504 /* mem_cgroup codes must not be called under tree_lock */
505 mem_cgroup_replace_page_cache(old
, new);
506 radix_tree_preload_end();
509 page_cache_release(old
);
514 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
516 static int page_cache_tree_insert(struct address_space
*mapping
,
517 struct page
*page
, void **shadowp
)
519 struct radix_tree_node
*node
;
523 error
= __radix_tree_create(&mapping
->page_tree
, page
->index
,
530 p
= radix_tree_deref_slot_protected(slot
, &mapping
->tree_lock
);
531 if (!radix_tree_exceptional_entry(p
))
535 mapping
->nrshadows
--;
537 workingset_node_shadows_dec(node
);
539 radix_tree_replace_slot(slot
, page
);
542 workingset_node_pages_inc(node
);
544 * Don't track node that contains actual pages.
546 * Avoid acquiring the list_lru lock if already
547 * untracked. The list_empty() test is safe as
548 * node->private_list is protected by
549 * mapping->tree_lock.
551 if (!list_empty(&node
->private_list
))
552 list_lru_del(&workingset_shadow_nodes
,
553 &node
->private_list
);
558 static int __add_to_page_cache_locked(struct page
*page
,
559 struct address_space
*mapping
,
560 pgoff_t offset
, gfp_t gfp_mask
,
565 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
566 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
568 error
= mem_cgroup_charge_file(page
, current
->mm
,
569 gfp_mask
& GFP_RECLAIM_MASK
);
573 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
575 mem_cgroup_uncharge_cache_page(page
);
579 page_cache_get(page
);
580 page
->mapping
= mapping
;
581 page
->index
= offset
;
583 spin_lock_irq(&mapping
->tree_lock
);
584 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
585 radix_tree_preload_end();
588 __inc_zone_page_state(page
, NR_FILE_PAGES
);
589 spin_unlock_irq(&mapping
->tree_lock
);
590 trace_mm_filemap_add_to_page_cache(page
);
593 page
->mapping
= NULL
;
594 /* Leave page->index set: truncation relies upon it */
595 spin_unlock_irq(&mapping
->tree_lock
);
596 mem_cgroup_uncharge_cache_page(page
);
597 page_cache_release(page
);
602 * add_to_page_cache_locked - add a locked page to the pagecache
604 * @mapping: the page's address_space
605 * @offset: page index
606 * @gfp_mask: page allocation mode
608 * This function is used to add a page to the pagecache. It must be locked.
609 * This function does not add the page to the LRU. The caller must do that.
611 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
612 pgoff_t offset
, gfp_t gfp_mask
)
614 return __add_to_page_cache_locked(page
, mapping
, offset
,
617 EXPORT_SYMBOL(add_to_page_cache_locked
);
619 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
620 pgoff_t offset
, gfp_t gfp_mask
)
625 __set_page_locked(page
);
626 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
629 __clear_page_locked(page
);
632 * The page might have been evicted from cache only
633 * recently, in which case it should be activated like
634 * any other repeatedly accessed page.
636 if (shadow
&& workingset_refault(shadow
)) {
638 workingset_activation(page
);
640 ClearPageActive(page
);
645 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
648 struct page
*__page_cache_alloc(gfp_t gfp
)
653 if (cpuset_do_page_mem_spread()) {
654 unsigned int cpuset_mems_cookie
;
656 cpuset_mems_cookie
= read_mems_allowed_begin();
657 n
= cpuset_mem_spread_node();
658 page
= alloc_pages_exact_node(n
, gfp
, 0);
659 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
663 return alloc_pages(gfp
, 0);
665 EXPORT_SYMBOL(__page_cache_alloc
);
669 * In order to wait for pages to become available there must be
670 * waitqueues associated with pages. By using a hash table of
671 * waitqueues where the bucket discipline is to maintain all
672 * waiters on the same queue and wake all when any of the pages
673 * become available, and for the woken contexts to check to be
674 * sure the appropriate page became available, this saves space
675 * at a cost of "thundering herd" phenomena during rare hash
678 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
680 const struct zone
*zone
= page_zone(page
);
682 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
685 static inline void wake_up_page(struct page
*page
, int bit
)
687 __wake_up_bit(page_waitqueue(page
), &page
->flags
, bit
);
690 void wait_on_page_bit(struct page
*page
, int bit_nr
)
692 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
694 if (test_bit(bit_nr
, &page
->flags
))
695 __wait_on_bit(page_waitqueue(page
), &wait
, sleep_on_page
,
696 TASK_UNINTERRUPTIBLE
);
698 EXPORT_SYMBOL(wait_on_page_bit
);
700 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
702 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
704 if (!test_bit(bit_nr
, &page
->flags
))
707 return __wait_on_bit(page_waitqueue(page
), &wait
,
708 sleep_on_page_killable
, TASK_KILLABLE
);
712 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
713 * @page: Page defining the wait queue of interest
714 * @waiter: Waiter to add to the queue
716 * Add an arbitrary @waiter to the wait queue for the nominated @page.
718 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
720 wait_queue_head_t
*q
= page_waitqueue(page
);
723 spin_lock_irqsave(&q
->lock
, flags
);
724 __add_wait_queue(q
, waiter
);
725 spin_unlock_irqrestore(&q
->lock
, flags
);
727 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
730 * unlock_page - unlock a locked page
733 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
734 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
735 * mechananism between PageLocked pages and PageWriteback pages is shared.
736 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
738 * The mb is necessary to enforce ordering between the clear_bit and the read
739 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
741 void unlock_page(struct page
*page
)
743 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
744 clear_bit_unlock(PG_locked
, &page
->flags
);
745 smp_mb__after_clear_bit();
746 wake_up_page(page
, PG_locked
);
748 EXPORT_SYMBOL(unlock_page
);
751 * end_page_writeback - end writeback against a page
754 void end_page_writeback(struct page
*page
)
756 if (TestClearPageReclaim(page
))
757 rotate_reclaimable_page(page
);
759 if (!test_clear_page_writeback(page
))
762 smp_mb__after_clear_bit();
763 wake_up_page(page
, PG_writeback
);
765 EXPORT_SYMBOL(end_page_writeback
);
768 * __lock_page - get a lock on the page, assuming we need to sleep to get it
769 * @page: the page to lock
771 void __lock_page(struct page
*page
)
773 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
775 __wait_on_bit_lock(page_waitqueue(page
), &wait
, sleep_on_page
,
776 TASK_UNINTERRUPTIBLE
);
778 EXPORT_SYMBOL(__lock_page
);
780 int __lock_page_killable(struct page
*page
)
782 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
784 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
785 sleep_on_page_killable
, TASK_KILLABLE
);
787 EXPORT_SYMBOL_GPL(__lock_page_killable
);
789 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
792 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
794 * CAUTION! In this case, mmap_sem is not released
795 * even though return 0.
797 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
800 up_read(&mm
->mmap_sem
);
801 if (flags
& FAULT_FLAG_KILLABLE
)
802 wait_on_page_locked_killable(page
);
804 wait_on_page_locked(page
);
807 if (flags
& FAULT_FLAG_KILLABLE
) {
810 ret
= __lock_page_killable(page
);
812 up_read(&mm
->mmap_sem
);
822 * page_cache_next_hole - find the next hole (not-present entry)
825 * @max_scan: maximum range to search
827 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
828 * lowest indexed hole.
830 * Returns: the index of the hole if found, otherwise returns an index
831 * outside of the set specified (in which case 'return - index >=
832 * max_scan' will be true). In rare cases of index wrap-around, 0 will
835 * page_cache_next_hole may be called under rcu_read_lock. However,
836 * like radix_tree_gang_lookup, this will not atomically search a
837 * snapshot of the tree at a single point in time. For example, if a
838 * hole is created at index 5, then subsequently a hole is created at
839 * index 10, page_cache_next_hole covering both indexes may return 10
840 * if called under rcu_read_lock.
842 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
843 pgoff_t index
, unsigned long max_scan
)
847 for (i
= 0; i
< max_scan
; i
++) {
850 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
851 if (!page
|| radix_tree_exceptional_entry(page
))
860 EXPORT_SYMBOL(page_cache_next_hole
);
863 * page_cache_prev_hole - find the prev hole (not-present entry)
866 * @max_scan: maximum range to search
868 * Search backwards in the range [max(index-max_scan+1, 0), index] for
871 * Returns: the index of the hole if found, otherwise returns an index
872 * outside of the set specified (in which case 'index - return >=
873 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
876 * page_cache_prev_hole may be called under rcu_read_lock. However,
877 * like radix_tree_gang_lookup, this will not atomically search a
878 * snapshot of the tree at a single point in time. For example, if a
879 * hole is created at index 10, then subsequently a hole is created at
880 * index 5, page_cache_prev_hole covering both indexes may return 5 if
881 * called under rcu_read_lock.
883 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
884 pgoff_t index
, unsigned long max_scan
)
888 for (i
= 0; i
< max_scan
; i
++) {
891 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
892 if (!page
|| radix_tree_exceptional_entry(page
))
895 if (index
== ULONG_MAX
)
901 EXPORT_SYMBOL(page_cache_prev_hole
);
904 * find_get_entry - find and get a page cache entry
905 * @mapping: the address_space to search
906 * @offset: the page cache index
908 * Looks up the page cache slot at @mapping & @offset. If there is a
909 * page cache page, it is returned with an increased refcount.
911 * If the slot holds a shadow entry of a previously evicted page, or a
912 * swap entry from shmem/tmpfs, it is returned.
914 * Otherwise, %NULL is returned.
916 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
924 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
926 page
= radix_tree_deref_slot(pagep
);
929 if (radix_tree_exception(page
)) {
930 if (radix_tree_deref_retry(page
))
933 * A shadow entry of a recently evicted page,
934 * or a swap entry from shmem/tmpfs. Return
935 * it without attempting to raise page count.
939 if (!page_cache_get_speculative(page
))
943 * Has the page moved?
944 * This is part of the lockless pagecache protocol. See
945 * include/linux/pagemap.h for details.
947 if (unlikely(page
!= *pagep
)) {
948 page_cache_release(page
);
957 EXPORT_SYMBOL(find_get_entry
);
960 * find_get_page - find and get a page reference
961 * @mapping: the address_space to search
962 * @offset: the page index
964 * Looks up the page cache slot at @mapping & @offset. If there is a
965 * page cache page, it is returned with an increased refcount.
967 * Otherwise, %NULL is returned.
969 struct page
*find_get_page(struct address_space
*mapping
, pgoff_t offset
)
971 struct page
*page
= find_get_entry(mapping
, offset
);
973 if (radix_tree_exceptional_entry(page
))
977 EXPORT_SYMBOL(find_get_page
);
980 * find_lock_entry - locate, pin and lock a page cache entry
981 * @mapping: the address_space to search
982 * @offset: the page cache index
984 * Looks up the page cache slot at @mapping & @offset. If there is a
985 * page cache page, it is returned locked and with an increased
988 * If the slot holds a shadow entry of a previously evicted page, or a
989 * swap entry from shmem/tmpfs, it is returned.
991 * Otherwise, %NULL is returned.
993 * find_lock_entry() may sleep.
995 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1000 page
= find_get_entry(mapping
, offset
);
1001 if (page
&& !radix_tree_exception(page
)) {
1003 /* Has the page been truncated? */
1004 if (unlikely(page
->mapping
!= mapping
)) {
1006 page_cache_release(page
);
1009 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1013 EXPORT_SYMBOL(find_lock_entry
);
1016 * find_lock_page - locate, pin and lock a pagecache page
1017 * @mapping: the address_space to search
1018 * @offset: the page index
1020 * Looks up the page cache slot at @mapping & @offset. If there is a
1021 * page cache page, it is returned locked and with an increased
1024 * Otherwise, %NULL is returned.
1026 * find_lock_page() may sleep.
1028 struct page
*find_lock_page(struct address_space
*mapping
, pgoff_t offset
)
1030 struct page
*page
= find_lock_entry(mapping
, offset
);
1032 if (radix_tree_exceptional_entry(page
))
1036 EXPORT_SYMBOL(find_lock_page
);
1039 * find_or_create_page - locate or add a pagecache page
1040 * @mapping: the page's address_space
1041 * @index: the page's index into the mapping
1042 * @gfp_mask: page allocation mode
1044 * Looks up the page cache slot at @mapping & @offset. If there is a
1045 * page cache page, it is returned locked and with an increased
1048 * If the page is not present, a new page is allocated using @gfp_mask
1049 * and added to the page cache and the VM's LRU list. The page is
1050 * returned locked and with an increased refcount.
1052 * On memory exhaustion, %NULL is returned.
1054 * find_or_create_page() may sleep, even if @gfp_flags specifies an
1055 * atomic allocation!
1057 struct page
*find_or_create_page(struct address_space
*mapping
,
1058 pgoff_t index
, gfp_t gfp_mask
)
1063 page
= find_lock_page(mapping
, index
);
1065 page
= __page_cache_alloc(gfp_mask
);
1069 * We want a regular kernel memory (not highmem or DMA etc)
1070 * allocation for the radix tree nodes, but we need to honour
1071 * the context-specific requirements the caller has asked for.
1072 * GFP_RECLAIM_MASK collects those requirements.
1074 err
= add_to_page_cache_lru(page
, mapping
, index
,
1075 (gfp_mask
& GFP_RECLAIM_MASK
));
1076 if (unlikely(err
)) {
1077 page_cache_release(page
);
1085 EXPORT_SYMBOL(find_or_create_page
);
1088 * find_get_entries - gang pagecache lookup
1089 * @mapping: The address_space to search
1090 * @start: The starting page cache index
1091 * @nr_entries: The maximum number of entries
1092 * @entries: Where the resulting entries are placed
1093 * @indices: The cache indices corresponding to the entries in @entries
1095 * find_get_entries() will search for and return a group of up to
1096 * @nr_entries entries in the mapping. The entries are placed at
1097 * @entries. find_get_entries() takes a reference against any actual
1100 * The search returns a group of mapping-contiguous page cache entries
1101 * with ascending indexes. There may be holes in the indices due to
1102 * not-present pages.
1104 * Any shadow entries of evicted pages, or swap entries from
1105 * shmem/tmpfs, are included in the returned array.
1107 * find_get_entries() returns the number of pages and shadow entries
1110 unsigned find_get_entries(struct address_space
*mapping
,
1111 pgoff_t start
, unsigned int nr_entries
,
1112 struct page
**entries
, pgoff_t
*indices
)
1115 unsigned int ret
= 0;
1116 struct radix_tree_iter iter
;
1123 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1126 page
= radix_tree_deref_slot(slot
);
1127 if (unlikely(!page
))
1129 if (radix_tree_exception(page
)) {
1130 if (radix_tree_deref_retry(page
))
1133 * A shadow entry of a recently evicted page,
1134 * or a swap entry from shmem/tmpfs. Return
1135 * it without attempting to raise page count.
1139 if (!page_cache_get_speculative(page
))
1142 /* Has the page moved? */
1143 if (unlikely(page
!= *slot
)) {
1144 page_cache_release(page
);
1148 indices
[ret
] = iter
.index
;
1149 entries
[ret
] = page
;
1150 if (++ret
== nr_entries
)
1158 * find_get_pages - gang pagecache lookup
1159 * @mapping: The address_space to search
1160 * @start: The starting page index
1161 * @nr_pages: The maximum number of pages
1162 * @pages: Where the resulting pages are placed
1164 * find_get_pages() will search for and return a group of up to
1165 * @nr_pages pages in the mapping. The pages are placed at @pages.
1166 * find_get_pages() takes a reference against the returned pages.
1168 * The search returns a group of mapping-contiguous pages with ascending
1169 * indexes. There may be holes in the indices due to not-present pages.
1171 * find_get_pages() returns the number of pages which were found.
1173 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
1174 unsigned int nr_pages
, struct page
**pages
)
1176 struct radix_tree_iter iter
;
1180 if (unlikely(!nr_pages
))
1185 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1188 page
= radix_tree_deref_slot(slot
);
1189 if (unlikely(!page
))
1192 if (radix_tree_exception(page
)) {
1193 if (radix_tree_deref_retry(page
)) {
1195 * Transient condition which can only trigger
1196 * when entry at index 0 moves out of or back
1197 * to root: none yet gotten, safe to restart.
1199 WARN_ON(iter
.index
);
1203 * A shadow entry of a recently evicted page,
1204 * or a swap entry from shmem/tmpfs. Skip
1210 if (!page_cache_get_speculative(page
))
1213 /* Has the page moved? */
1214 if (unlikely(page
!= *slot
)) {
1215 page_cache_release(page
);
1220 if (++ret
== nr_pages
)
1229 * find_get_pages_contig - gang contiguous pagecache lookup
1230 * @mapping: The address_space to search
1231 * @index: The starting page index
1232 * @nr_pages: The maximum number of pages
1233 * @pages: Where the resulting pages are placed
1235 * find_get_pages_contig() works exactly like find_get_pages(), except
1236 * that the returned number of pages are guaranteed to be contiguous.
1238 * find_get_pages_contig() returns the number of pages which were found.
1240 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1241 unsigned int nr_pages
, struct page
**pages
)
1243 struct radix_tree_iter iter
;
1245 unsigned int ret
= 0;
1247 if (unlikely(!nr_pages
))
1252 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1255 page
= radix_tree_deref_slot(slot
);
1256 /* The hole, there no reason to continue */
1257 if (unlikely(!page
))
1260 if (radix_tree_exception(page
)) {
1261 if (radix_tree_deref_retry(page
)) {
1263 * Transient condition which can only trigger
1264 * when entry at index 0 moves out of or back
1265 * to root: none yet gotten, safe to restart.
1270 * A shadow entry of a recently evicted page,
1271 * or a swap entry from shmem/tmpfs. Stop
1272 * looking for contiguous pages.
1277 if (!page_cache_get_speculative(page
))
1280 /* Has the page moved? */
1281 if (unlikely(page
!= *slot
)) {
1282 page_cache_release(page
);
1287 * must check mapping and index after taking the ref.
1288 * otherwise we can get both false positives and false
1289 * negatives, which is just confusing to the caller.
1291 if (page
->mapping
== NULL
|| page
->index
!= iter
.index
) {
1292 page_cache_release(page
);
1297 if (++ret
== nr_pages
)
1303 EXPORT_SYMBOL(find_get_pages_contig
);
1306 * find_get_pages_tag - find and return pages that match @tag
1307 * @mapping: the address_space to search
1308 * @index: the starting page index
1309 * @tag: the tag index
1310 * @nr_pages: the maximum number of pages
1311 * @pages: where the resulting pages are placed
1313 * Like find_get_pages, except we only return pages which are tagged with
1314 * @tag. We update @index to index the next page for the traversal.
1316 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1317 int tag
, unsigned int nr_pages
, struct page
**pages
)
1319 struct radix_tree_iter iter
;
1323 if (unlikely(!nr_pages
))
1328 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1329 &iter
, *index
, tag
) {
1332 page
= radix_tree_deref_slot(slot
);
1333 if (unlikely(!page
))
1336 if (radix_tree_exception(page
)) {
1337 if (radix_tree_deref_retry(page
)) {
1339 * Transient condition which can only trigger
1340 * when entry at index 0 moves out of or back
1341 * to root: none yet gotten, safe to restart.
1346 * A shadow entry of a recently evicted page.
1348 * Those entries should never be tagged, but
1349 * this tree walk is lockless and the tags are
1350 * looked up in bulk, one radix tree node at a
1351 * time, so there is a sizable window for page
1352 * reclaim to evict a page we saw tagged.
1359 if (!page_cache_get_speculative(page
))
1362 /* Has the page moved? */
1363 if (unlikely(page
!= *slot
)) {
1364 page_cache_release(page
);
1369 if (++ret
== nr_pages
)
1376 *index
= pages
[ret
- 1]->index
+ 1;
1380 EXPORT_SYMBOL(find_get_pages_tag
);
1383 * grab_cache_page_nowait - returns locked page at given index in given cache
1384 * @mapping: target address_space
1385 * @index: the page index
1387 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1388 * This is intended for speculative data generators, where the data can
1389 * be regenerated if the page couldn't be grabbed. This routine should
1390 * be safe to call while holding the lock for another page.
1392 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1393 * and deadlock against the caller's locked page.
1396 grab_cache_page_nowait(struct address_space
*mapping
, pgoff_t index
)
1398 struct page
*page
= find_get_page(mapping
, index
);
1401 if (trylock_page(page
))
1403 page_cache_release(page
);
1406 page
= __page_cache_alloc(mapping_gfp_mask(mapping
) & ~__GFP_FS
);
1407 if (page
&& add_to_page_cache_lru(page
, mapping
, index
, GFP_NOFS
)) {
1408 page_cache_release(page
);
1413 EXPORT_SYMBOL(grab_cache_page_nowait
);
1416 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1417 * a _large_ part of the i/o request. Imagine the worst scenario:
1419 * ---R__________________________________________B__________
1420 * ^ reading here ^ bad block(assume 4k)
1422 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1423 * => failing the whole request => read(R) => read(R+1) =>
1424 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1425 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1426 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1428 * It is going insane. Fix it by quickly scaling down the readahead size.
1430 static void shrink_readahead_size_eio(struct file
*filp
,
1431 struct file_ra_state
*ra
)
1437 * do_generic_file_read - generic file read routine
1438 * @filp: the file to read
1439 * @ppos: current file position
1440 * @iter: data destination
1441 * @written: already copied
1443 * This is a generic file read routine, and uses the
1444 * mapping->a_ops->readpage() function for the actual low-level stuff.
1446 * This is really ugly. But the goto's actually try to clarify some
1447 * of the logic when it comes to error handling etc.
1449 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1450 struct iov_iter
*iter
, ssize_t written
)
1452 struct address_space
*mapping
= filp
->f_mapping
;
1453 struct inode
*inode
= mapping
->host
;
1454 struct file_ra_state
*ra
= &filp
->f_ra
;
1458 unsigned long offset
; /* offset into pagecache page */
1459 unsigned int prev_offset
;
1462 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1463 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1464 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1465 last_index
= (*ppos
+ iter
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1466 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1472 unsigned long nr
, ret
;
1476 page
= find_get_page(mapping
, index
);
1478 page_cache_sync_readahead(mapping
,
1480 index
, last_index
- index
);
1481 page
= find_get_page(mapping
, index
);
1482 if (unlikely(page
== NULL
))
1483 goto no_cached_page
;
1485 if (PageReadahead(page
)) {
1486 page_cache_async_readahead(mapping
,
1488 index
, last_index
- index
);
1490 if (!PageUptodate(page
)) {
1491 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1492 !mapping
->a_ops
->is_partially_uptodate
)
1493 goto page_not_up_to_date
;
1494 if (!trylock_page(page
))
1495 goto page_not_up_to_date
;
1496 /* Did it get truncated before we got the lock? */
1498 goto page_not_up_to_date_locked
;
1499 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1500 offset
, iter
->count
))
1501 goto page_not_up_to_date_locked
;
1506 * i_size must be checked after we know the page is Uptodate.
1508 * Checking i_size after the check allows us to calculate
1509 * the correct value for "nr", which means the zero-filled
1510 * part of the page is not copied back to userspace (unless
1511 * another truncate extends the file - this is desired though).
1514 isize
= i_size_read(inode
);
1515 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1516 if (unlikely(!isize
|| index
> end_index
)) {
1517 page_cache_release(page
);
1521 /* nr is the maximum number of bytes to copy from this page */
1522 nr
= PAGE_CACHE_SIZE
;
1523 if (index
== end_index
) {
1524 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1526 page_cache_release(page
);
1532 /* If users can be writing to this page using arbitrary
1533 * virtual addresses, take care about potential aliasing
1534 * before reading the page on the kernel side.
1536 if (mapping_writably_mapped(mapping
))
1537 flush_dcache_page(page
);
1540 * When a sequential read accesses a page several times,
1541 * only mark it as accessed the first time.
1543 if (prev_index
!= index
|| offset
!= prev_offset
)
1544 mark_page_accessed(page
);
1548 * Ok, we have the page, and it's up-to-date, so
1549 * now we can copy it to user space...
1552 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
1554 index
+= offset
>> PAGE_CACHE_SHIFT
;
1555 offset
&= ~PAGE_CACHE_MASK
;
1556 prev_offset
= offset
;
1558 page_cache_release(page
);
1560 if (!iov_iter_count(iter
))
1568 page_not_up_to_date
:
1569 /* Get exclusive access to the page ... */
1570 error
= lock_page_killable(page
);
1571 if (unlikely(error
))
1572 goto readpage_error
;
1574 page_not_up_to_date_locked
:
1575 /* Did it get truncated before we got the lock? */
1576 if (!page
->mapping
) {
1578 page_cache_release(page
);
1582 /* Did somebody else fill it already? */
1583 if (PageUptodate(page
)) {
1590 * A previous I/O error may have been due to temporary
1591 * failures, eg. multipath errors.
1592 * PG_error will be set again if readpage fails.
1594 ClearPageError(page
);
1595 /* Start the actual read. The read will unlock the page. */
1596 error
= mapping
->a_ops
->readpage(filp
, page
);
1598 if (unlikely(error
)) {
1599 if (error
== AOP_TRUNCATED_PAGE
) {
1600 page_cache_release(page
);
1604 goto readpage_error
;
1607 if (!PageUptodate(page
)) {
1608 error
= lock_page_killable(page
);
1609 if (unlikely(error
))
1610 goto readpage_error
;
1611 if (!PageUptodate(page
)) {
1612 if (page
->mapping
== NULL
) {
1614 * invalidate_mapping_pages got it
1617 page_cache_release(page
);
1621 shrink_readahead_size_eio(filp
, ra
);
1623 goto readpage_error
;
1631 /* UHHUH! A synchronous read error occurred. Report it */
1632 page_cache_release(page
);
1637 * Ok, it wasn't cached, so we need to create a new
1640 page
= page_cache_alloc_cold(mapping
);
1645 error
= add_to_page_cache_lru(page
, mapping
,
1648 page_cache_release(page
);
1649 if (error
== -EEXIST
) {
1659 ra
->prev_pos
= prev_index
;
1660 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1661 ra
->prev_pos
|= prev_offset
;
1663 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1664 file_accessed(filp
);
1665 return written
? written
: error
;
1669 * Performs necessary checks before doing a write
1670 * @iov: io vector request
1671 * @nr_segs: number of segments in the iovec
1672 * @count: number of bytes to write
1673 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1675 * Adjust number of segments and amount of bytes to write (nr_segs should be
1676 * properly initialized first). Returns appropriate error code that caller
1677 * should return or zero in case that write should be allowed.
1679 int generic_segment_checks(const struct iovec
*iov
,
1680 unsigned long *nr_segs
, size_t *count
, int access_flags
)
1684 for (seg
= 0; seg
< *nr_segs
; seg
++) {
1685 const struct iovec
*iv
= &iov
[seg
];
1688 * If any segment has a negative length, or the cumulative
1689 * length ever wraps negative then return -EINVAL.
1692 if (unlikely((ssize_t
)(cnt
|iv
->iov_len
) < 0))
1694 if (access_ok(access_flags
, iv
->iov_base
, iv
->iov_len
))
1699 cnt
-= iv
->iov_len
; /* This segment is no good */
1705 EXPORT_SYMBOL(generic_segment_checks
);
1708 * generic_file_aio_read - generic filesystem read routine
1709 * @iocb: kernel I/O control block
1710 * @iov: io vector request
1711 * @nr_segs: number of segments in the iovec
1712 * @pos: current file position
1714 * This is the "read()" routine for all filesystems
1715 * that can use the page cache directly.
1718 generic_file_aio_read(struct kiocb
*iocb
, const struct iovec
*iov
,
1719 unsigned long nr_segs
, loff_t pos
)
1721 struct file
*filp
= iocb
->ki_filp
;
1724 loff_t
*ppos
= &iocb
->ki_pos
;
1728 retval
= generic_segment_checks(iov
, &nr_segs
, &count
, VERIFY_WRITE
);
1731 iov_iter_init(&i
, iov
, nr_segs
, count
, 0);
1733 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1734 if (filp
->f_flags
& O_DIRECT
) {
1736 struct address_space
*mapping
;
1737 struct inode
*inode
;
1739 mapping
= filp
->f_mapping
;
1740 inode
= mapping
->host
;
1742 goto out
; /* skip atime */
1743 size
= i_size_read(inode
);
1744 retval
= filemap_write_and_wait_range(mapping
, pos
,
1745 pos
+ iov_length(iov
, nr_segs
) - 1);
1747 retval
= mapping
->a_ops
->direct_IO(READ
, iocb
,
1751 *ppos
= pos
+ retval
;
1754 * If we did a short DIO read we need to skip the
1755 * section of the iov that we've already read data into.
1757 iov_iter_advance(&i
, retval
);
1761 * Btrfs can have a short DIO read if we encounter
1762 * compressed extents, so if there was an error, or if
1763 * we've already read everything we wanted to, or if
1764 * there was a short read because we hit EOF, go ahead
1765 * and return. Otherwise fallthrough to buffered io for
1766 * the rest of the read.
1768 if (retval
< 0 || !count
|| *ppos
>= size
) {
1769 file_accessed(filp
);
1774 retval
= do_generic_file_read(filp
, ppos
, &i
, retval
);
1778 EXPORT_SYMBOL(generic_file_aio_read
);
1782 * page_cache_read - adds requested page to the page cache if not already there
1783 * @file: file to read
1784 * @offset: page index
1786 * This adds the requested page to the page cache if it isn't already there,
1787 * and schedules an I/O to read in its contents from disk.
1789 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1791 struct address_space
*mapping
= file
->f_mapping
;
1796 page
= page_cache_alloc_cold(mapping
);
1800 ret
= add_to_page_cache_lru(page
, mapping
, offset
, GFP_KERNEL
);
1802 ret
= mapping
->a_ops
->readpage(file
, page
);
1803 else if (ret
== -EEXIST
)
1804 ret
= 0; /* losing race to add is OK */
1806 page_cache_release(page
);
1808 } while (ret
== AOP_TRUNCATED_PAGE
);
1813 #define MMAP_LOTSAMISS (100)
1816 * Synchronous readahead happens when we don't even find
1817 * a page in the page cache at all.
1819 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1820 struct file_ra_state
*ra
,
1824 unsigned long ra_pages
;
1825 struct address_space
*mapping
= file
->f_mapping
;
1827 /* If we don't want any read-ahead, don't bother */
1828 if (vma
->vm_flags
& VM_RAND_READ
)
1833 if (vma
->vm_flags
& VM_SEQ_READ
) {
1834 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1839 /* Avoid banging the cache line if not needed */
1840 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
1844 * Do we miss much more than hit in this file? If so,
1845 * stop bothering with read-ahead. It will only hurt.
1847 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1853 ra_pages
= max_sane_readahead(ra
->ra_pages
);
1854 ra
->start
= max_t(long, 0, offset
- ra_pages
/ 2);
1855 ra
->size
= ra_pages
;
1856 ra
->async_size
= ra_pages
/ 4;
1857 ra_submit(ra
, mapping
, file
);
1861 * Asynchronous readahead happens when we find the page and PG_readahead,
1862 * so we want to possibly extend the readahead further..
1864 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1865 struct file_ra_state
*ra
,
1870 struct address_space
*mapping
= file
->f_mapping
;
1872 /* If we don't want any read-ahead, don't bother */
1873 if (vma
->vm_flags
& VM_RAND_READ
)
1875 if (ra
->mmap_miss
> 0)
1877 if (PageReadahead(page
))
1878 page_cache_async_readahead(mapping
, ra
, file
,
1879 page
, offset
, ra
->ra_pages
);
1883 * filemap_fault - read in file data for page fault handling
1884 * @vma: vma in which the fault was taken
1885 * @vmf: struct vm_fault containing details of the fault
1887 * filemap_fault() is invoked via the vma operations vector for a
1888 * mapped memory region to read in file data during a page fault.
1890 * The goto's are kind of ugly, but this streamlines the normal case of having
1891 * it in the page cache, and handles the special cases reasonably without
1892 * having a lot of duplicated code.
1894 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1897 struct file
*file
= vma
->vm_file
;
1898 struct address_space
*mapping
= file
->f_mapping
;
1899 struct file_ra_state
*ra
= &file
->f_ra
;
1900 struct inode
*inode
= mapping
->host
;
1901 pgoff_t offset
= vmf
->pgoff
;
1906 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1907 if (offset
>= size
>> PAGE_CACHE_SHIFT
)
1908 return VM_FAULT_SIGBUS
;
1911 * Do we have something in the page cache already?
1913 page
= find_get_page(mapping
, offset
);
1914 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
1916 * We found the page, so try async readahead before
1917 * waiting for the lock.
1919 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1921 /* No page in the page cache at all */
1922 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1923 count_vm_event(PGMAJFAULT
);
1924 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
1925 ret
= VM_FAULT_MAJOR
;
1927 page
= find_get_page(mapping
, offset
);
1929 goto no_cached_page
;
1932 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
1933 page_cache_release(page
);
1934 return ret
| VM_FAULT_RETRY
;
1937 /* Did it get truncated? */
1938 if (unlikely(page
->mapping
!= mapping
)) {
1943 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1946 * We have a locked page in the page cache, now we need to check
1947 * that it's up-to-date. If not, it is going to be due to an error.
1949 if (unlikely(!PageUptodate(page
)))
1950 goto page_not_uptodate
;
1953 * Found the page and have a reference on it.
1954 * We must recheck i_size under page lock.
1956 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1957 if (unlikely(offset
>= size
>> PAGE_CACHE_SHIFT
)) {
1959 page_cache_release(page
);
1960 return VM_FAULT_SIGBUS
;
1964 return ret
| VM_FAULT_LOCKED
;
1968 * We're only likely to ever get here if MADV_RANDOM is in
1971 error
= page_cache_read(file
, offset
);
1974 * The page we want has now been added to the page cache.
1975 * In the unlikely event that someone removed it in the
1976 * meantime, we'll just come back here and read it again.
1982 * An error return from page_cache_read can result if the
1983 * system is low on memory, or a problem occurs while trying
1986 if (error
== -ENOMEM
)
1987 return VM_FAULT_OOM
;
1988 return VM_FAULT_SIGBUS
;
1992 * Umm, take care of errors if the page isn't up-to-date.
1993 * Try to re-read it _once_. We do this synchronously,
1994 * because there really aren't any performance issues here
1995 * and we need to check for errors.
1997 ClearPageError(page
);
1998 error
= mapping
->a_ops
->readpage(file
, page
);
2000 wait_on_page_locked(page
);
2001 if (!PageUptodate(page
))
2004 page_cache_release(page
);
2006 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2009 /* Things didn't work out. Return zero to tell the mm layer so. */
2010 shrink_readahead_size_eio(file
, ra
);
2011 return VM_FAULT_SIGBUS
;
2013 EXPORT_SYMBOL(filemap_fault
);
2015 void filemap_map_pages(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2017 struct radix_tree_iter iter
;
2019 struct file
*file
= vma
->vm_file
;
2020 struct address_space
*mapping
= file
->f_mapping
;
2023 unsigned long address
= (unsigned long) vmf
->virtual_address
;
2028 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, vmf
->pgoff
) {
2029 if (iter
.index
> vmf
->max_pgoff
)
2032 page
= radix_tree_deref_slot(slot
);
2033 if (unlikely(!page
))
2035 if (radix_tree_exception(page
)) {
2036 if (radix_tree_deref_retry(page
))
2042 if (!page_cache_get_speculative(page
))
2045 /* Has the page moved? */
2046 if (unlikely(page
!= *slot
)) {
2047 page_cache_release(page
);
2051 if (!PageUptodate(page
) ||
2052 PageReadahead(page
) ||
2055 if (!trylock_page(page
))
2058 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2061 size
= round_up(i_size_read(mapping
->host
), PAGE_CACHE_SIZE
);
2062 if (page
->index
>= size
>> PAGE_CACHE_SHIFT
)
2065 pte
= vmf
->pte
+ page
->index
- vmf
->pgoff
;
2066 if (!pte_none(*pte
))
2069 if (file
->f_ra
.mmap_miss
> 0)
2070 file
->f_ra
.mmap_miss
--;
2071 addr
= address
+ (page
->index
- vmf
->pgoff
) * PAGE_SIZE
;
2072 do_set_pte(vma
, addr
, page
, pte
, false, false);
2078 page_cache_release(page
);
2080 if (iter
.index
== vmf
->max_pgoff
)
2085 EXPORT_SYMBOL(filemap_map_pages
);
2087 int filemap_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2089 struct page
*page
= vmf
->page
;
2090 struct inode
*inode
= file_inode(vma
->vm_file
);
2091 int ret
= VM_FAULT_LOCKED
;
2093 sb_start_pagefault(inode
->i_sb
);
2094 file_update_time(vma
->vm_file
);
2096 if (page
->mapping
!= inode
->i_mapping
) {
2098 ret
= VM_FAULT_NOPAGE
;
2102 * We mark the page dirty already here so that when freeze is in
2103 * progress, we are guaranteed that writeback during freezing will
2104 * see the dirty page and writeprotect it again.
2106 set_page_dirty(page
);
2107 wait_for_stable_page(page
);
2109 sb_end_pagefault(inode
->i_sb
);
2112 EXPORT_SYMBOL(filemap_page_mkwrite
);
2114 const struct vm_operations_struct generic_file_vm_ops
= {
2115 .fault
= filemap_fault
,
2116 .map_pages
= filemap_map_pages
,
2117 .page_mkwrite
= filemap_page_mkwrite
,
2118 .remap_pages
= generic_file_remap_pages
,
2121 /* This is used for a general mmap of a disk file */
2123 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2125 struct address_space
*mapping
= file
->f_mapping
;
2127 if (!mapping
->a_ops
->readpage
)
2129 file_accessed(file
);
2130 vma
->vm_ops
= &generic_file_vm_ops
;
2135 * This is for filesystems which do not implement ->writepage.
2137 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2139 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2141 return generic_file_mmap(file
, vma
);
2144 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2148 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2152 #endif /* CONFIG_MMU */
2154 EXPORT_SYMBOL(generic_file_mmap
);
2155 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2157 static struct page
*wait_on_page_read(struct page
*page
)
2159 if (!IS_ERR(page
)) {
2160 wait_on_page_locked(page
);
2161 if (!PageUptodate(page
)) {
2162 page_cache_release(page
);
2163 page
= ERR_PTR(-EIO
);
2169 static struct page
*__read_cache_page(struct address_space
*mapping
,
2171 int (*filler
)(void *, struct page
*),
2178 page
= find_get_page(mapping
, index
);
2180 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2182 return ERR_PTR(-ENOMEM
);
2183 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2184 if (unlikely(err
)) {
2185 page_cache_release(page
);
2188 /* Presumably ENOMEM for radix tree node */
2189 return ERR_PTR(err
);
2191 err
= filler(data
, page
);
2193 page_cache_release(page
);
2194 page
= ERR_PTR(err
);
2196 page
= wait_on_page_read(page
);
2202 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2204 int (*filler
)(void *, struct page
*),
2213 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
2216 if (PageUptodate(page
))
2220 if (!page
->mapping
) {
2222 page_cache_release(page
);
2225 if (PageUptodate(page
)) {
2229 err
= filler(data
, page
);
2231 page_cache_release(page
);
2232 return ERR_PTR(err
);
2234 page
= wait_on_page_read(page
);
2239 mark_page_accessed(page
);
2244 * read_cache_page - read into page cache, fill it if needed
2245 * @mapping: the page's address_space
2246 * @index: the page index
2247 * @filler: function to perform the read
2248 * @data: first arg to filler(data, page) function, often left as NULL
2250 * Read into the page cache. If a page already exists, and PageUptodate() is
2251 * not set, try to fill the page and wait for it to become unlocked.
2253 * If the page does not get brought uptodate, return -EIO.
2255 struct page
*read_cache_page(struct address_space
*mapping
,
2257 int (*filler
)(void *, struct page
*),
2260 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2262 EXPORT_SYMBOL(read_cache_page
);
2265 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2266 * @mapping: the page's address_space
2267 * @index: the page index
2268 * @gfp: the page allocator flags to use if allocating
2270 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2271 * any new page allocations done using the specified allocation flags.
2273 * If the page does not get brought uptodate, return -EIO.
2275 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2279 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2281 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2283 EXPORT_SYMBOL(read_cache_page_gfp
);
2286 * Performs necessary checks before doing a write
2288 * Can adjust writing position or amount of bytes to write.
2289 * Returns appropriate error code that caller should return or
2290 * zero in case that write should be allowed.
2292 inline int generic_write_checks(struct file
*file
, loff_t
*pos
, size_t *count
, int isblk
)
2294 struct inode
*inode
= file
->f_mapping
->host
;
2295 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2297 if (unlikely(*pos
< 0))
2301 /* FIXME: this is for backwards compatibility with 2.4 */
2302 if (file
->f_flags
& O_APPEND
)
2303 *pos
= i_size_read(inode
);
2305 if (limit
!= RLIM_INFINITY
) {
2306 if (*pos
>= limit
) {
2307 send_sig(SIGXFSZ
, current
, 0);
2310 if (*count
> limit
- (typeof(limit
))*pos
) {
2311 *count
= limit
- (typeof(limit
))*pos
;
2319 if (unlikely(*pos
+ *count
> MAX_NON_LFS
&&
2320 !(file
->f_flags
& O_LARGEFILE
))) {
2321 if (*pos
>= MAX_NON_LFS
) {
2324 if (*count
> MAX_NON_LFS
- (unsigned long)*pos
) {
2325 *count
= MAX_NON_LFS
- (unsigned long)*pos
;
2330 * Are we about to exceed the fs block limit ?
2332 * If we have written data it becomes a short write. If we have
2333 * exceeded without writing data we send a signal and return EFBIG.
2334 * Linus frestrict idea will clean these up nicely..
2336 if (likely(!isblk
)) {
2337 if (unlikely(*pos
>= inode
->i_sb
->s_maxbytes
)) {
2338 if (*count
|| *pos
> inode
->i_sb
->s_maxbytes
) {
2341 /* zero-length writes at ->s_maxbytes are OK */
2344 if (unlikely(*pos
+ *count
> inode
->i_sb
->s_maxbytes
))
2345 *count
= inode
->i_sb
->s_maxbytes
- *pos
;
2349 if (bdev_read_only(I_BDEV(inode
)))
2351 isize
= i_size_read(inode
);
2352 if (*pos
>= isize
) {
2353 if (*count
|| *pos
> isize
)
2357 if (*pos
+ *count
> isize
)
2358 *count
= isize
- *pos
;
2365 EXPORT_SYMBOL(generic_write_checks
);
2367 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2368 loff_t pos
, unsigned len
, unsigned flags
,
2369 struct page
**pagep
, void **fsdata
)
2371 const struct address_space_operations
*aops
= mapping
->a_ops
;
2373 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2376 EXPORT_SYMBOL(pagecache_write_begin
);
2378 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2379 loff_t pos
, unsigned len
, unsigned copied
,
2380 struct page
*page
, void *fsdata
)
2382 const struct address_space_operations
*aops
= mapping
->a_ops
;
2384 mark_page_accessed(page
);
2385 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2387 EXPORT_SYMBOL(pagecache_write_end
);
2390 generic_file_direct_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2391 unsigned long *nr_segs
, loff_t pos
,
2392 size_t count
, size_t ocount
)
2394 struct file
*file
= iocb
->ki_filp
;
2395 struct address_space
*mapping
= file
->f_mapping
;
2396 struct inode
*inode
= mapping
->host
;
2401 if (count
!= ocount
)
2402 *nr_segs
= iov_shorten((struct iovec
*)iov
, *nr_segs
, count
);
2404 write_len
= iov_length(iov
, *nr_segs
);
2405 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2407 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2412 * After a write we want buffered reads to be sure to go to disk to get
2413 * the new data. We invalidate clean cached page from the region we're
2414 * about to write. We do this *before* the write so that we can return
2415 * without clobbering -EIOCBQUEUED from ->direct_IO().
2417 if (mapping
->nrpages
) {
2418 written
= invalidate_inode_pages2_range(mapping
,
2419 pos
>> PAGE_CACHE_SHIFT
, end
);
2421 * If a page can not be invalidated, return 0 to fall back
2422 * to buffered write.
2425 if (written
== -EBUSY
)
2431 written
= mapping
->a_ops
->direct_IO(WRITE
, iocb
, iov
, pos
, *nr_segs
);
2434 * Finally, try again to invalidate clean pages which might have been
2435 * cached by non-direct readahead, or faulted in by get_user_pages()
2436 * if the source of the write was an mmap'ed region of the file
2437 * we're writing. Either one is a pretty crazy thing to do,
2438 * so we don't support it 100%. If this invalidation
2439 * fails, tough, the write still worked...
2441 if (mapping
->nrpages
) {
2442 invalidate_inode_pages2_range(mapping
,
2443 pos
>> PAGE_CACHE_SHIFT
, end
);
2448 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2449 i_size_write(inode
, pos
);
2450 mark_inode_dirty(inode
);
2457 EXPORT_SYMBOL(generic_file_direct_write
);
2460 * Find or create a page at the given pagecache position. Return the locked
2461 * page. This function is specifically for buffered writes.
2463 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2464 pgoff_t index
, unsigned flags
)
2469 gfp_t gfp_notmask
= 0;
2471 gfp_mask
= mapping_gfp_mask(mapping
);
2472 if (mapping_cap_account_dirty(mapping
))
2473 gfp_mask
|= __GFP_WRITE
;
2474 if (flags
& AOP_FLAG_NOFS
)
2475 gfp_notmask
= __GFP_FS
;
2477 page
= find_lock_page(mapping
, index
);
2481 page
= __page_cache_alloc(gfp_mask
& ~gfp_notmask
);
2484 status
= add_to_page_cache_lru(page
, mapping
, index
,
2485 GFP_KERNEL
& ~gfp_notmask
);
2486 if (unlikely(status
)) {
2487 page_cache_release(page
);
2488 if (status
== -EEXIST
)
2493 wait_for_stable_page(page
);
2496 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2498 ssize_t
generic_perform_write(struct file
*file
,
2499 struct iov_iter
*i
, loff_t pos
)
2501 struct address_space
*mapping
= file
->f_mapping
;
2502 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2504 ssize_t written
= 0;
2505 unsigned int flags
= 0;
2508 * Copies from kernel address space cannot fail (NFSD is a big user).
2510 if (segment_eq(get_fs(), KERNEL_DS
))
2511 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2515 unsigned long offset
; /* Offset into pagecache page */
2516 unsigned long bytes
; /* Bytes to write to page */
2517 size_t copied
; /* Bytes copied from user */
2520 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2521 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2526 * Bring in the user page that we will copy from _first_.
2527 * Otherwise there's a nasty deadlock on copying from the
2528 * same page as we're writing to, without it being marked
2531 * Not only is this an optimisation, but it is also required
2532 * to check that the address is actually valid, when atomic
2533 * usercopies are used, below.
2535 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2540 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2542 if (unlikely(status
))
2545 if (mapping_writably_mapped(mapping
))
2546 flush_dcache_page(page
);
2548 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2549 flush_dcache_page(page
);
2551 mark_page_accessed(page
);
2552 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2554 if (unlikely(status
< 0))
2560 iov_iter_advance(i
, copied
);
2561 if (unlikely(copied
== 0)) {
2563 * If we were unable to copy any data at all, we must
2564 * fall back to a single segment length write.
2566 * If we didn't fallback here, we could livelock
2567 * because not all segments in the iov can be copied at
2568 * once without a pagefault.
2570 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2571 iov_iter_single_seg_count(i
));
2577 balance_dirty_pages_ratelimited(mapping
);
2578 if (fatal_signal_pending(current
)) {
2582 } while (iov_iter_count(i
));
2584 return written
? written
: status
;
2586 EXPORT_SYMBOL(generic_perform_write
);
2589 * __generic_file_aio_write - write data to a file
2590 * @iocb: IO state structure (file, offset, etc.)
2591 * @iov: vector with data to write
2592 * @nr_segs: number of segments in the vector
2594 * This function does all the work needed for actually writing data to a
2595 * file. It does all basic checks, removes SUID from the file, updates
2596 * modification times and calls proper subroutines depending on whether we
2597 * do direct IO or a standard buffered write.
2599 * It expects i_mutex to be grabbed unless we work on a block device or similar
2600 * object which does not need locking at all.
2602 * This function does *not* take care of syncing data in case of O_SYNC write.
2603 * A caller has to handle it. This is mainly due to the fact that we want to
2604 * avoid syncing under i_mutex.
2606 ssize_t
__generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2607 unsigned long nr_segs
)
2609 struct file
*file
= iocb
->ki_filp
;
2610 struct address_space
* mapping
= file
->f_mapping
;
2611 size_t ocount
; /* original count */
2612 size_t count
; /* after file limit checks */
2613 struct inode
*inode
= mapping
->host
;
2614 loff_t pos
= iocb
->ki_pos
;
2615 ssize_t written
= 0;
2618 struct iov_iter from
;
2621 err
= generic_segment_checks(iov
, &nr_segs
, &ocount
, VERIFY_READ
);
2627 /* We can write back this queue in page reclaim */
2628 current
->backing_dev_info
= mapping
->backing_dev_info
;
2629 err
= generic_write_checks(file
, &pos
, &count
, S_ISBLK(inode
->i_mode
));
2636 err
= file_remove_suid(file
);
2640 err
= file_update_time(file
);
2644 iov_iter_init(&from
, iov
, nr_segs
, count
, 0);
2646 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2647 if (unlikely(file
->f_flags
& O_DIRECT
)) {
2650 written
= generic_file_direct_write(iocb
, iov
, &from
.nr_segs
, pos
,
2652 if (written
< 0 || written
== count
)
2654 iov_iter_advance(&from
, written
);
2657 * direct-io write to a hole: fall through to buffered I/O
2658 * for completing the rest of the request.
2663 status
= generic_perform_write(file
, &from
, pos
);
2665 * If generic_perform_write() returned a synchronous error
2666 * then we want to return the number of bytes which were
2667 * direct-written, or the error code if that was zero. Note
2668 * that this differs from normal direct-io semantics, which
2669 * will return -EFOO even if some bytes were written.
2671 if (unlikely(status
< 0) && !written
) {
2675 iocb
->ki_pos
= pos
+ status
;
2677 * We need to ensure that the page cache pages are written to
2678 * disk and invalidated to preserve the expected O_DIRECT
2681 endbyte
= pos
+ status
- 1;
2682 err
= filemap_write_and_wait_range(file
->f_mapping
, pos
, endbyte
);
2685 invalidate_mapping_pages(mapping
,
2686 pos
>> PAGE_CACHE_SHIFT
,
2687 endbyte
>> PAGE_CACHE_SHIFT
);
2690 * We don't know how much we wrote, so just return
2691 * the number of bytes which were direct-written
2695 written
= generic_perform_write(file
, &from
, pos
);
2696 if (likely(written
>= 0))
2697 iocb
->ki_pos
= pos
+ written
;
2700 current
->backing_dev_info
= NULL
;
2701 return written
? written
: err
;
2703 EXPORT_SYMBOL(__generic_file_aio_write
);
2706 * generic_file_aio_write - write data to a file
2707 * @iocb: IO state structure
2708 * @iov: vector with data to write
2709 * @nr_segs: number of segments in the vector
2710 * @pos: position in file where to write
2712 * This is a wrapper around __generic_file_aio_write() to be used by most
2713 * filesystems. It takes care of syncing the file in case of O_SYNC file
2714 * and acquires i_mutex as needed.
2716 ssize_t
generic_file_aio_write(struct kiocb
*iocb
, const struct iovec
*iov
,
2717 unsigned long nr_segs
, loff_t pos
)
2719 struct file
*file
= iocb
->ki_filp
;
2720 struct inode
*inode
= file
->f_mapping
->host
;
2723 BUG_ON(iocb
->ki_pos
!= pos
);
2725 mutex_lock(&inode
->i_mutex
);
2726 ret
= __generic_file_aio_write(iocb
, iov
, nr_segs
);
2727 mutex_unlock(&inode
->i_mutex
);
2732 err
= generic_write_sync(file
, iocb
->ki_pos
- ret
, ret
);
2738 EXPORT_SYMBOL(generic_file_aio_write
);
2741 * try_to_release_page() - release old fs-specific metadata on a page
2743 * @page: the page which the kernel is trying to free
2744 * @gfp_mask: memory allocation flags (and I/O mode)
2746 * The address_space is to try to release any data against the page
2747 * (presumably at page->private). If the release was successful, return `1'.
2748 * Otherwise return zero.
2750 * This may also be called if PG_fscache is set on a page, indicating that the
2751 * page is known to the local caching routines.
2753 * The @gfp_mask argument specifies whether I/O may be performed to release
2754 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2757 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2759 struct address_space
* const mapping
= page
->mapping
;
2761 BUG_ON(!PageLocked(page
));
2762 if (PageWriteback(page
))
2765 if (mapping
&& mapping
->a_ops
->releasepage
)
2766 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2767 return try_to_free_buffers(page
);
2770 EXPORT_SYMBOL(try_to_release_page
);