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/capability.h>
17 #include <linux/kernel_stat.h>
18 #include <linux/gfp.h>
20 #include <linux/swap.h>
21 #include <linux/mman.h>
22 #include <linux/pagemap.h>
23 #include <linux/file.h>
24 #include <linux/uio.h>
25 #include <linux/hash.h>
26 #include <linux/writeback.h>
27 #include <linux/backing-dev.h>
28 #include <linux/pagevec.h>
29 #include <linux/blkdev.h>
30 #include <linux/security.h>
31 #include <linux/cpuset.h>
32 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
33 #include <linux/hugetlb.h>
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_rwsem (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_rwsem (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 * ->memcg->move_lock (page_remove_rmap->mem_cgroup_begin_page_stat)
104 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
105 * ->inode->i_lock (zap_pte_range->set_page_dirty)
106 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
109 * ->tasklist_lock (memory_failure, collect_procs_ao)
112 static void page_cache_tree_delete(struct address_space
*mapping
,
113 struct page
*page
, void *shadow
)
115 struct radix_tree_node
*node
;
121 VM_BUG_ON(!PageLocked(page
));
123 __radix_tree_lookup(&mapping
->page_tree
, page
->index
, &node
, &slot
);
126 mapping
->nrshadows
++;
128 * Make sure the nrshadows update is committed before
129 * the nrpages update so that final truncate racing
130 * with reclaim does not see both counters 0 at the
131 * same time and miss a shadow entry.
138 /* Clear direct pointer tags in root node */
139 mapping
->page_tree
.gfp_mask
&= __GFP_BITS_MASK
;
140 radix_tree_replace_slot(slot
, shadow
);
144 /* Clear tree tags for the removed page */
146 offset
= index
& RADIX_TREE_MAP_MASK
;
147 for (tag
= 0; tag
< RADIX_TREE_MAX_TAGS
; tag
++) {
148 if (test_bit(offset
, node
->tags
[tag
]))
149 radix_tree_tag_clear(&mapping
->page_tree
, index
, tag
);
152 /* Delete page, swap shadow entry */
153 radix_tree_replace_slot(slot
, shadow
);
154 workingset_node_pages_dec(node
);
156 workingset_node_shadows_inc(node
);
158 if (__radix_tree_delete_node(&mapping
->page_tree
, node
))
162 * Track node that only contains shadow entries.
164 * Avoid acquiring the list_lru lock if already tracked. The
165 * list_empty() test is safe as node->private_list is
166 * protected by mapping->tree_lock.
168 if (!workingset_node_pages(node
) &&
169 list_empty(&node
->private_list
)) {
170 node
->private_data
= mapping
;
171 list_lru_add(&workingset_shadow_nodes
, &node
->private_list
);
176 * Delete a page from the page cache and free it. Caller has to make
177 * sure the page is locked and that nobody else uses it - or that usage
178 * is safe. The caller must hold the mapping's tree_lock and
179 * mem_cgroup_begin_page_stat().
181 void __delete_from_page_cache(struct page
*page
, void *shadow
,
182 struct mem_cgroup
*memcg
)
184 struct address_space
*mapping
= page
->mapping
;
186 trace_mm_filemap_delete_from_page_cache(page
);
188 * if we're uptodate, flush out into the cleancache, otherwise
189 * invalidate any existing cleancache entries. We can't leave
190 * stale data around in the cleancache once our page is gone
192 if (PageUptodate(page
) && PageMappedToDisk(page
))
193 cleancache_put_page(page
);
195 cleancache_invalidate_page(mapping
, page
);
197 page_cache_tree_delete(mapping
, page
, shadow
);
199 page
->mapping
= NULL
;
200 /* Leave page->index set: truncation lookup relies upon it */
202 /* hugetlb pages do not participate in page cache accounting. */
204 __dec_zone_page_state(page
, NR_FILE_PAGES
);
205 if (PageSwapBacked(page
))
206 __dec_zone_page_state(page
, NR_SHMEM
);
207 BUG_ON(page_mapped(page
));
210 * At this point page must be either written or cleaned by truncate.
211 * Dirty page here signals a bug and loss of unwritten data.
213 * This fixes dirty accounting after removing the page entirely but
214 * leaves PageDirty set: it has no effect for truncated page and
215 * anyway will be cleared before returning page into buddy allocator.
217 if (WARN_ON_ONCE(PageDirty(page
)))
218 account_page_cleaned(page
, mapping
, memcg
,
219 inode_to_wb(mapping
->host
));
223 * delete_from_page_cache - delete page from page cache
224 * @page: the page which the kernel is trying to remove from page cache
226 * This must be called only on pages that have been verified to be in the page
227 * cache and locked. It will never put the page into the free list, the caller
228 * has a reference on the page.
230 void delete_from_page_cache(struct page
*page
)
232 struct address_space
*mapping
= page
->mapping
;
233 struct mem_cgroup
*memcg
;
236 void (*freepage
)(struct page
*);
238 BUG_ON(!PageLocked(page
));
240 freepage
= mapping
->a_ops
->freepage
;
242 memcg
= mem_cgroup_begin_page_stat(page
);
243 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
244 __delete_from_page_cache(page
, NULL
, memcg
);
245 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
246 mem_cgroup_end_page_stat(memcg
);
250 page_cache_release(page
);
252 EXPORT_SYMBOL(delete_from_page_cache
);
254 static int filemap_check_errors(struct address_space
*mapping
)
257 /* Check for outstanding write errors */
258 if (test_bit(AS_ENOSPC
, &mapping
->flags
) &&
259 test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
261 if (test_bit(AS_EIO
, &mapping
->flags
) &&
262 test_and_clear_bit(AS_EIO
, &mapping
->flags
))
268 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
269 * @mapping: address space structure to write
270 * @start: offset in bytes where the range starts
271 * @end: offset in bytes where the range ends (inclusive)
272 * @sync_mode: enable synchronous operation
274 * Start writeback against all of a mapping's dirty pages that lie
275 * within the byte offsets <start, end> inclusive.
277 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
278 * opposed to a regular memory cleansing writeback. The difference between
279 * these two operations is that if a dirty page/buffer is encountered, it must
280 * be waited upon, and not just skipped over.
282 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
283 loff_t end
, int sync_mode
)
286 struct writeback_control wbc
= {
287 .sync_mode
= sync_mode
,
288 .nr_to_write
= LONG_MAX
,
289 .range_start
= start
,
293 if (!mapping_cap_writeback_dirty(mapping
))
296 wbc_attach_fdatawrite_inode(&wbc
, mapping
->host
);
297 ret
= do_writepages(mapping
, &wbc
);
298 wbc_detach_inode(&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
*);
487 struct mem_cgroup
*memcg
;
490 pgoff_t offset
= old
->index
;
491 freepage
= mapping
->a_ops
->freepage
;
494 new->mapping
= mapping
;
497 memcg
= mem_cgroup_begin_page_stat(old
);
498 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
499 __delete_from_page_cache(old
, NULL
, memcg
);
500 error
= radix_tree_insert(&mapping
->page_tree
, offset
, new);
505 * hugetlb pages do not participate in page cache accounting.
508 __inc_zone_page_state(new, NR_FILE_PAGES
);
509 if (PageSwapBacked(new))
510 __inc_zone_page_state(new, NR_SHMEM
);
511 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
512 mem_cgroup_end_page_stat(memcg
);
513 mem_cgroup_migrate(old
, new, true);
514 radix_tree_preload_end();
517 page_cache_release(old
);
522 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
524 static int page_cache_tree_insert(struct address_space
*mapping
,
525 struct page
*page
, void **shadowp
)
527 struct radix_tree_node
*node
;
531 error
= __radix_tree_create(&mapping
->page_tree
, page
->index
,
538 p
= radix_tree_deref_slot_protected(slot
, &mapping
->tree_lock
);
539 if (!radix_tree_exceptional_entry(p
))
543 mapping
->nrshadows
--;
545 workingset_node_shadows_dec(node
);
547 radix_tree_replace_slot(slot
, page
);
550 workingset_node_pages_inc(node
);
552 * Don't track node that contains actual pages.
554 * Avoid acquiring the list_lru lock if already
555 * untracked. The list_empty() test is safe as
556 * node->private_list is protected by
557 * mapping->tree_lock.
559 if (!list_empty(&node
->private_list
))
560 list_lru_del(&workingset_shadow_nodes
,
561 &node
->private_list
);
566 static int __add_to_page_cache_locked(struct page
*page
,
567 struct address_space
*mapping
,
568 pgoff_t offset
, gfp_t gfp_mask
,
571 int huge
= PageHuge(page
);
572 struct mem_cgroup
*memcg
;
575 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
576 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
579 error
= mem_cgroup_try_charge(page
, current
->mm
,
585 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
588 mem_cgroup_cancel_charge(page
, memcg
);
592 page_cache_get(page
);
593 page
->mapping
= mapping
;
594 page
->index
= offset
;
596 spin_lock_irq(&mapping
->tree_lock
);
597 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
598 radix_tree_preload_end();
602 /* hugetlb pages do not participate in page cache accounting. */
604 __inc_zone_page_state(page
, NR_FILE_PAGES
);
605 spin_unlock_irq(&mapping
->tree_lock
);
607 mem_cgroup_commit_charge(page
, memcg
, false);
608 trace_mm_filemap_add_to_page_cache(page
);
611 page
->mapping
= NULL
;
612 /* Leave page->index set: truncation relies upon it */
613 spin_unlock_irq(&mapping
->tree_lock
);
615 mem_cgroup_cancel_charge(page
, memcg
);
616 page_cache_release(page
);
621 * add_to_page_cache_locked - add a locked page to the pagecache
623 * @mapping: the page's address_space
624 * @offset: page index
625 * @gfp_mask: page allocation mode
627 * This function is used to add a page to the pagecache. It must be locked.
628 * This function does not add the page to the LRU. The caller must do that.
630 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
631 pgoff_t offset
, gfp_t gfp_mask
)
633 return __add_to_page_cache_locked(page
, mapping
, offset
,
636 EXPORT_SYMBOL(add_to_page_cache_locked
);
638 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
639 pgoff_t offset
, gfp_t gfp_mask
)
644 __set_page_locked(page
);
645 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
648 __clear_page_locked(page
);
651 * The page might have been evicted from cache only
652 * recently, in which case it should be activated like
653 * any other repeatedly accessed page.
655 if (shadow
&& workingset_refault(shadow
)) {
657 workingset_activation(page
);
659 ClearPageActive(page
);
664 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
667 struct page
*__page_cache_alloc(gfp_t gfp
)
672 if (cpuset_do_page_mem_spread()) {
673 unsigned int cpuset_mems_cookie
;
675 cpuset_mems_cookie
= read_mems_allowed_begin();
676 n
= cpuset_mem_spread_node();
677 page
= __alloc_pages_node(n
, gfp
, 0);
678 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
682 return alloc_pages(gfp
, 0);
684 EXPORT_SYMBOL(__page_cache_alloc
);
688 * In order to wait for pages to become available there must be
689 * waitqueues associated with pages. By using a hash table of
690 * waitqueues where the bucket discipline is to maintain all
691 * waiters on the same queue and wake all when any of the pages
692 * become available, and for the woken contexts to check to be
693 * sure the appropriate page became available, this saves space
694 * at a cost of "thundering herd" phenomena during rare hash
697 wait_queue_head_t
*page_waitqueue(struct page
*page
)
699 const struct zone
*zone
= page_zone(page
);
701 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
703 EXPORT_SYMBOL(page_waitqueue
);
705 void wait_on_page_bit(struct page
*page
, int bit_nr
)
707 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
709 if (test_bit(bit_nr
, &page
->flags
))
710 __wait_on_bit(page_waitqueue(page
), &wait
, bit_wait_io
,
711 TASK_UNINTERRUPTIBLE
);
713 EXPORT_SYMBOL(wait_on_page_bit
);
715 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
717 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
719 if (!test_bit(bit_nr
, &page
->flags
))
722 return __wait_on_bit(page_waitqueue(page
), &wait
,
723 bit_wait_io
, TASK_KILLABLE
);
726 int wait_on_page_bit_killable_timeout(struct page
*page
,
727 int bit_nr
, unsigned long timeout
)
729 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
731 wait
.key
.timeout
= jiffies
+ timeout
;
732 if (!test_bit(bit_nr
, &page
->flags
))
734 return __wait_on_bit(page_waitqueue(page
), &wait
,
735 bit_wait_io_timeout
, TASK_KILLABLE
);
737 EXPORT_SYMBOL_GPL(wait_on_page_bit_killable_timeout
);
740 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
741 * @page: Page defining the wait queue of interest
742 * @waiter: Waiter to add to the queue
744 * Add an arbitrary @waiter to the wait queue for the nominated @page.
746 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
748 wait_queue_head_t
*q
= page_waitqueue(page
);
751 spin_lock_irqsave(&q
->lock
, flags
);
752 __add_wait_queue(q
, waiter
);
753 spin_unlock_irqrestore(&q
->lock
, flags
);
755 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
758 * unlock_page - unlock a locked page
761 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
762 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
763 * mechanism between PageLocked pages and PageWriteback pages is shared.
764 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
766 * The mb is necessary to enforce ordering between the clear_bit and the read
767 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
769 void unlock_page(struct page
*page
)
771 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
772 clear_bit_unlock(PG_locked
, &page
->flags
);
773 smp_mb__after_atomic();
774 wake_up_page(page
, PG_locked
);
776 EXPORT_SYMBOL(unlock_page
);
779 * end_page_writeback - end writeback against a page
782 void end_page_writeback(struct page
*page
)
785 * TestClearPageReclaim could be used here but it is an atomic
786 * operation and overkill in this particular case. Failing to
787 * shuffle a page marked for immediate reclaim is too mild to
788 * justify taking an atomic operation penalty at the end of
789 * ever page writeback.
791 if (PageReclaim(page
)) {
792 ClearPageReclaim(page
);
793 rotate_reclaimable_page(page
);
796 if (!test_clear_page_writeback(page
))
799 smp_mb__after_atomic();
800 wake_up_page(page
, PG_writeback
);
802 EXPORT_SYMBOL(end_page_writeback
);
805 * After completing I/O on a page, call this routine to update the page
806 * flags appropriately
808 void page_endio(struct page
*page
, int rw
, int err
)
812 SetPageUptodate(page
);
814 ClearPageUptodate(page
);
818 } else { /* rw == WRITE */
822 mapping_set_error(page
->mapping
, err
);
824 end_page_writeback(page
);
827 EXPORT_SYMBOL_GPL(page_endio
);
830 * __lock_page - get a lock on the page, assuming we need to sleep to get it
831 * @page: the page to lock
833 void __lock_page(struct page
*page
)
835 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
837 __wait_on_bit_lock(page_waitqueue(page
), &wait
, bit_wait_io
,
838 TASK_UNINTERRUPTIBLE
);
840 EXPORT_SYMBOL(__lock_page
);
842 int __lock_page_killable(struct page
*page
)
844 DEFINE_WAIT_BIT(wait
, &page
->flags
, PG_locked
);
846 return __wait_on_bit_lock(page_waitqueue(page
), &wait
,
847 bit_wait_io
, TASK_KILLABLE
);
849 EXPORT_SYMBOL_GPL(__lock_page_killable
);
853 * 1 - page is locked; mmap_sem is still held.
854 * 0 - page is not locked.
855 * mmap_sem has been released (up_read()), unless flags had both
856 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
857 * which case mmap_sem is still held.
859 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
860 * with the page locked and the mmap_sem unperturbed.
862 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
865 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
867 * CAUTION! In this case, mmap_sem is not released
868 * even though return 0.
870 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
873 up_read(&mm
->mmap_sem
);
874 if (flags
& FAULT_FLAG_KILLABLE
)
875 wait_on_page_locked_killable(page
);
877 wait_on_page_locked(page
);
880 if (flags
& FAULT_FLAG_KILLABLE
) {
883 ret
= __lock_page_killable(page
);
885 up_read(&mm
->mmap_sem
);
895 * page_cache_next_hole - find the next hole (not-present entry)
898 * @max_scan: maximum range to search
900 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
901 * lowest indexed hole.
903 * Returns: the index of the hole if found, otherwise returns an index
904 * outside of the set specified (in which case 'return - index >=
905 * max_scan' will be true). In rare cases of index wrap-around, 0 will
908 * page_cache_next_hole may be called under rcu_read_lock. However,
909 * like radix_tree_gang_lookup, this will not atomically search a
910 * snapshot of the tree at a single point in time. For example, if a
911 * hole is created at index 5, then subsequently a hole is created at
912 * index 10, page_cache_next_hole covering both indexes may return 10
913 * if called under rcu_read_lock.
915 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
916 pgoff_t index
, unsigned long max_scan
)
920 for (i
= 0; i
< max_scan
; i
++) {
923 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
924 if (!page
|| radix_tree_exceptional_entry(page
))
933 EXPORT_SYMBOL(page_cache_next_hole
);
936 * page_cache_prev_hole - find the prev hole (not-present entry)
939 * @max_scan: maximum range to search
941 * Search backwards in the range [max(index-max_scan+1, 0), index] for
944 * Returns: the index of the hole if found, otherwise returns an index
945 * outside of the set specified (in which case 'index - return >=
946 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
949 * page_cache_prev_hole may be called under rcu_read_lock. However,
950 * like radix_tree_gang_lookup, this will not atomically search a
951 * snapshot of the tree at a single point in time. For example, if a
952 * hole is created at index 10, then subsequently a hole is created at
953 * index 5, page_cache_prev_hole covering both indexes may return 5 if
954 * called under rcu_read_lock.
956 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
957 pgoff_t index
, unsigned long max_scan
)
961 for (i
= 0; i
< max_scan
; i
++) {
964 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
965 if (!page
|| radix_tree_exceptional_entry(page
))
968 if (index
== ULONG_MAX
)
974 EXPORT_SYMBOL(page_cache_prev_hole
);
977 * find_get_entry - find and get a page cache entry
978 * @mapping: the address_space to search
979 * @offset: the page cache index
981 * Looks up the page cache slot at @mapping & @offset. If there is a
982 * page cache page, it is returned with an increased refcount.
984 * If the slot holds a shadow entry of a previously evicted page, or a
985 * swap entry from shmem/tmpfs, it is returned.
987 * Otherwise, %NULL is returned.
989 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
997 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
999 page
= radix_tree_deref_slot(pagep
);
1000 if (unlikely(!page
))
1002 if (radix_tree_exception(page
)) {
1003 if (radix_tree_deref_retry(page
))
1006 * A shadow entry of a recently evicted page,
1007 * or a swap entry from shmem/tmpfs. Return
1008 * it without attempting to raise page count.
1012 if (!page_cache_get_speculative(page
))
1016 * Has the page moved?
1017 * This is part of the lockless pagecache protocol. See
1018 * include/linux/pagemap.h for details.
1020 if (unlikely(page
!= *pagep
)) {
1021 page_cache_release(page
);
1030 EXPORT_SYMBOL(find_get_entry
);
1033 * find_lock_entry - locate, pin and lock a page cache entry
1034 * @mapping: the address_space to search
1035 * @offset: the page cache index
1037 * Looks up the page cache slot at @mapping & @offset. If there is a
1038 * page cache page, it is returned locked and with an increased
1041 * If the slot holds a shadow entry of a previously evicted page, or a
1042 * swap entry from shmem/tmpfs, it is returned.
1044 * Otherwise, %NULL is returned.
1046 * find_lock_entry() may sleep.
1048 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1053 page
= find_get_entry(mapping
, offset
);
1054 if (page
&& !radix_tree_exception(page
)) {
1056 /* Has the page been truncated? */
1057 if (unlikely(page
->mapping
!= mapping
)) {
1059 page_cache_release(page
);
1062 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1066 EXPORT_SYMBOL(find_lock_entry
);
1069 * pagecache_get_page - find and get a page reference
1070 * @mapping: the address_space to search
1071 * @offset: the page index
1072 * @fgp_flags: PCG flags
1073 * @gfp_mask: gfp mask to use for the page cache data page allocation
1075 * Looks up the page cache slot at @mapping & @offset.
1077 * PCG flags modify how the page is returned.
1079 * FGP_ACCESSED: the page will be marked accessed
1080 * FGP_LOCK: Page is return locked
1081 * FGP_CREAT: If page is not present then a new page is allocated using
1082 * @gfp_mask and added to the page cache and the VM's LRU
1083 * list. The page is returned locked and with an increased
1084 * refcount. Otherwise, %NULL is returned.
1086 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1087 * if the GFP flags specified for FGP_CREAT are atomic.
1089 * If there is a page cache page, it is returned with an increased refcount.
1091 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1092 int fgp_flags
, gfp_t gfp_mask
)
1097 page
= find_get_entry(mapping
, offset
);
1098 if (radix_tree_exceptional_entry(page
))
1103 if (fgp_flags
& FGP_LOCK
) {
1104 if (fgp_flags
& FGP_NOWAIT
) {
1105 if (!trylock_page(page
)) {
1106 page_cache_release(page
);
1113 /* Has the page been truncated? */
1114 if (unlikely(page
->mapping
!= mapping
)) {
1116 page_cache_release(page
);
1119 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1122 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1123 mark_page_accessed(page
);
1126 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1128 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1129 gfp_mask
|= __GFP_WRITE
;
1130 if (fgp_flags
& FGP_NOFS
)
1131 gfp_mask
&= ~__GFP_FS
;
1133 page
= __page_cache_alloc(gfp_mask
);
1137 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1138 fgp_flags
|= FGP_LOCK
;
1140 /* Init accessed so avoid atomic mark_page_accessed later */
1141 if (fgp_flags
& FGP_ACCESSED
)
1142 __SetPageReferenced(page
);
1144 err
= add_to_page_cache_lru(page
, mapping
, offset
,
1145 gfp_mask
& GFP_RECLAIM_MASK
);
1146 if (unlikely(err
)) {
1147 page_cache_release(page
);
1156 EXPORT_SYMBOL(pagecache_get_page
);
1159 * find_get_entries - gang pagecache lookup
1160 * @mapping: The address_space to search
1161 * @start: The starting page cache index
1162 * @nr_entries: The maximum number of entries
1163 * @entries: Where the resulting entries are placed
1164 * @indices: The cache indices corresponding to the entries in @entries
1166 * find_get_entries() will search for and return a group of up to
1167 * @nr_entries entries in the mapping. The entries are placed at
1168 * @entries. find_get_entries() takes a reference against any actual
1171 * The search returns a group of mapping-contiguous page cache entries
1172 * with ascending indexes. There may be holes in the indices due to
1173 * not-present pages.
1175 * Any shadow entries of evicted pages, or swap entries from
1176 * shmem/tmpfs, are included in the returned array.
1178 * find_get_entries() returns the number of pages and shadow entries
1181 unsigned find_get_entries(struct address_space
*mapping
,
1182 pgoff_t start
, unsigned int nr_entries
,
1183 struct page
**entries
, pgoff_t
*indices
)
1186 unsigned int ret
= 0;
1187 struct radix_tree_iter iter
;
1194 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1197 page
= radix_tree_deref_slot(slot
);
1198 if (unlikely(!page
))
1200 if (radix_tree_exception(page
)) {
1201 if (radix_tree_deref_retry(page
))
1204 * A shadow entry of a recently evicted page,
1205 * or a swap entry from shmem/tmpfs. Return
1206 * it without attempting to raise page count.
1210 if (!page_cache_get_speculative(page
))
1213 /* Has the page moved? */
1214 if (unlikely(page
!= *slot
)) {
1215 page_cache_release(page
);
1219 indices
[ret
] = iter
.index
;
1220 entries
[ret
] = page
;
1221 if (++ret
== nr_entries
)
1229 * find_get_pages - gang pagecache lookup
1230 * @mapping: The address_space to search
1231 * @start: The starting page index
1232 * @nr_pages: The maximum number of pages
1233 * @pages: Where the resulting pages are placed
1235 * find_get_pages() will search for and return a group of up to
1236 * @nr_pages pages in the mapping. The pages are placed at @pages.
1237 * find_get_pages() takes a reference against the returned pages.
1239 * The search returns a group of mapping-contiguous pages with ascending
1240 * indexes. There may be holes in the indices due to not-present pages.
1242 * find_get_pages() returns the number of pages which were found.
1244 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
1245 unsigned int nr_pages
, struct page
**pages
)
1247 struct radix_tree_iter iter
;
1251 if (unlikely(!nr_pages
))
1256 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1259 page
= radix_tree_deref_slot(slot
);
1260 if (unlikely(!page
))
1263 if (radix_tree_exception(page
)) {
1264 if (radix_tree_deref_retry(page
)) {
1266 * Transient condition which can only trigger
1267 * when entry at index 0 moves out of or back
1268 * to root: none yet gotten, safe to restart.
1270 WARN_ON(iter
.index
);
1274 * A shadow entry of a recently evicted page,
1275 * or a swap entry from shmem/tmpfs. Skip
1281 if (!page_cache_get_speculative(page
))
1284 /* Has the page moved? */
1285 if (unlikely(page
!= *slot
)) {
1286 page_cache_release(page
);
1291 if (++ret
== nr_pages
)
1300 * find_get_pages_contig - gang contiguous pagecache lookup
1301 * @mapping: The address_space to search
1302 * @index: The starting page index
1303 * @nr_pages: The maximum number of pages
1304 * @pages: Where the resulting pages are placed
1306 * find_get_pages_contig() works exactly like find_get_pages(), except
1307 * that the returned number of pages are guaranteed to be contiguous.
1309 * find_get_pages_contig() returns the number of pages which were found.
1311 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1312 unsigned int nr_pages
, struct page
**pages
)
1314 struct radix_tree_iter iter
;
1316 unsigned int ret
= 0;
1318 if (unlikely(!nr_pages
))
1323 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1326 page
= radix_tree_deref_slot(slot
);
1327 /* The hole, there no reason to continue */
1328 if (unlikely(!page
))
1331 if (radix_tree_exception(page
)) {
1332 if (radix_tree_deref_retry(page
)) {
1334 * Transient condition which can only trigger
1335 * when entry at index 0 moves out of or back
1336 * to root: none yet gotten, safe to restart.
1341 * A shadow entry of a recently evicted page,
1342 * or a swap entry from shmem/tmpfs. Stop
1343 * looking for contiguous pages.
1348 if (!page_cache_get_speculative(page
))
1351 /* Has the page moved? */
1352 if (unlikely(page
!= *slot
)) {
1353 page_cache_release(page
);
1358 * must check mapping and index after taking the ref.
1359 * otherwise we can get both false positives and false
1360 * negatives, which is just confusing to the caller.
1362 if (page
->mapping
== NULL
|| page
->index
!= iter
.index
) {
1363 page_cache_release(page
);
1368 if (++ret
== nr_pages
)
1374 EXPORT_SYMBOL(find_get_pages_contig
);
1377 * find_get_pages_tag - find and return pages that match @tag
1378 * @mapping: the address_space to search
1379 * @index: the starting page index
1380 * @tag: the tag index
1381 * @nr_pages: the maximum number of pages
1382 * @pages: where the resulting pages are placed
1384 * Like find_get_pages, except we only return pages which are tagged with
1385 * @tag. We update @index to index the next page for the traversal.
1387 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1388 int tag
, unsigned int nr_pages
, struct page
**pages
)
1390 struct radix_tree_iter iter
;
1394 if (unlikely(!nr_pages
))
1399 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1400 &iter
, *index
, tag
) {
1403 page
= radix_tree_deref_slot(slot
);
1404 if (unlikely(!page
))
1407 if (radix_tree_exception(page
)) {
1408 if (radix_tree_deref_retry(page
)) {
1410 * Transient condition which can only trigger
1411 * when entry at index 0 moves out of or back
1412 * to root: none yet gotten, safe to restart.
1417 * A shadow entry of a recently evicted page.
1419 * Those entries should never be tagged, but
1420 * this tree walk is lockless and the tags are
1421 * looked up in bulk, one radix tree node at a
1422 * time, so there is a sizable window for page
1423 * reclaim to evict a page we saw tagged.
1430 if (!page_cache_get_speculative(page
))
1433 /* Has the page moved? */
1434 if (unlikely(page
!= *slot
)) {
1435 page_cache_release(page
);
1440 if (++ret
== nr_pages
)
1447 *index
= pages
[ret
- 1]->index
+ 1;
1451 EXPORT_SYMBOL(find_get_pages_tag
);
1454 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1455 * a _large_ part of the i/o request. Imagine the worst scenario:
1457 * ---R__________________________________________B__________
1458 * ^ reading here ^ bad block(assume 4k)
1460 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1461 * => failing the whole request => read(R) => read(R+1) =>
1462 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1463 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1464 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1466 * It is going insane. Fix it by quickly scaling down the readahead size.
1468 static void shrink_readahead_size_eio(struct file
*filp
,
1469 struct file_ra_state
*ra
)
1475 * do_generic_file_read - generic file read routine
1476 * @filp: the file to read
1477 * @ppos: current file position
1478 * @iter: data destination
1479 * @written: already copied
1481 * This is a generic file read routine, and uses the
1482 * mapping->a_ops->readpage() function for the actual low-level stuff.
1484 * This is really ugly. But the goto's actually try to clarify some
1485 * of the logic when it comes to error handling etc.
1487 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1488 struct iov_iter
*iter
, ssize_t written
)
1490 struct address_space
*mapping
= filp
->f_mapping
;
1491 struct inode
*inode
= mapping
->host
;
1492 struct file_ra_state
*ra
= &filp
->f_ra
;
1496 unsigned long offset
; /* offset into pagecache page */
1497 unsigned int prev_offset
;
1500 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1501 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1502 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1503 last_index
= (*ppos
+ iter
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1504 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1510 unsigned long nr
, ret
;
1514 page
= find_get_page(mapping
, index
);
1516 page_cache_sync_readahead(mapping
,
1518 index
, last_index
- index
);
1519 page
= find_get_page(mapping
, index
);
1520 if (unlikely(page
== NULL
))
1521 goto no_cached_page
;
1523 if (PageReadahead(page
)) {
1524 page_cache_async_readahead(mapping
,
1526 index
, last_index
- index
);
1528 if (!PageUptodate(page
)) {
1529 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1530 !mapping
->a_ops
->is_partially_uptodate
)
1531 goto page_not_up_to_date
;
1532 if (!trylock_page(page
))
1533 goto page_not_up_to_date
;
1534 /* Did it get truncated before we got the lock? */
1536 goto page_not_up_to_date_locked
;
1537 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1538 offset
, iter
->count
))
1539 goto page_not_up_to_date_locked
;
1544 * i_size must be checked after we know the page is Uptodate.
1546 * Checking i_size after the check allows us to calculate
1547 * the correct value for "nr", which means the zero-filled
1548 * part of the page is not copied back to userspace (unless
1549 * another truncate extends the file - this is desired though).
1552 isize
= i_size_read(inode
);
1553 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1554 if (unlikely(!isize
|| index
> end_index
)) {
1555 page_cache_release(page
);
1559 /* nr is the maximum number of bytes to copy from this page */
1560 nr
= PAGE_CACHE_SIZE
;
1561 if (index
== end_index
) {
1562 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1564 page_cache_release(page
);
1570 /* If users can be writing to this page using arbitrary
1571 * virtual addresses, take care about potential aliasing
1572 * before reading the page on the kernel side.
1574 if (mapping_writably_mapped(mapping
))
1575 flush_dcache_page(page
);
1578 * When a sequential read accesses a page several times,
1579 * only mark it as accessed the first time.
1581 if (prev_index
!= index
|| offset
!= prev_offset
)
1582 mark_page_accessed(page
);
1586 * Ok, we have the page, and it's up-to-date, so
1587 * now we can copy it to user space...
1590 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
1592 index
+= offset
>> PAGE_CACHE_SHIFT
;
1593 offset
&= ~PAGE_CACHE_MASK
;
1594 prev_offset
= offset
;
1596 page_cache_release(page
);
1598 if (!iov_iter_count(iter
))
1606 page_not_up_to_date
:
1607 /* Get exclusive access to the page ... */
1608 error
= lock_page_killable(page
);
1609 if (unlikely(error
))
1610 goto readpage_error
;
1612 page_not_up_to_date_locked
:
1613 /* Did it get truncated before we got the lock? */
1614 if (!page
->mapping
) {
1616 page_cache_release(page
);
1620 /* Did somebody else fill it already? */
1621 if (PageUptodate(page
)) {
1628 * A previous I/O error may have been due to temporary
1629 * failures, eg. multipath errors.
1630 * PG_error will be set again if readpage fails.
1632 ClearPageError(page
);
1633 /* Start the actual read. The read will unlock the page. */
1634 error
= mapping
->a_ops
->readpage(filp
, page
);
1636 if (unlikely(error
)) {
1637 if (error
== AOP_TRUNCATED_PAGE
) {
1638 page_cache_release(page
);
1642 goto readpage_error
;
1645 if (!PageUptodate(page
)) {
1646 error
= lock_page_killable(page
);
1647 if (unlikely(error
))
1648 goto readpage_error
;
1649 if (!PageUptodate(page
)) {
1650 if (page
->mapping
== NULL
) {
1652 * invalidate_mapping_pages got it
1655 page_cache_release(page
);
1659 shrink_readahead_size_eio(filp
, ra
);
1661 goto readpage_error
;
1669 /* UHHUH! A synchronous read error occurred. Report it */
1670 page_cache_release(page
);
1675 * Ok, it wasn't cached, so we need to create a new
1678 page
= page_cache_alloc_cold(mapping
);
1683 error
= add_to_page_cache_lru(page
, mapping
, index
,
1684 GFP_KERNEL
& mapping_gfp_mask(mapping
));
1686 page_cache_release(page
);
1687 if (error
== -EEXIST
) {
1697 ra
->prev_pos
= prev_index
;
1698 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1699 ra
->prev_pos
|= prev_offset
;
1701 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1702 file_accessed(filp
);
1703 return written
? written
: error
;
1707 * generic_file_read_iter - generic filesystem read routine
1708 * @iocb: kernel I/O control block
1709 * @iter: destination for the data read
1711 * This is the "read_iter()" routine for all filesystems
1712 * that can use the page cache directly.
1715 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
1717 struct file
*file
= iocb
->ki_filp
;
1719 loff_t
*ppos
= &iocb
->ki_pos
;
1722 if (iocb
->ki_flags
& IOCB_DIRECT
) {
1723 struct address_space
*mapping
= file
->f_mapping
;
1724 struct inode
*inode
= mapping
->host
;
1725 size_t count
= iov_iter_count(iter
);
1729 goto out
; /* skip atime */
1730 size
= i_size_read(inode
);
1731 retval
= filemap_write_and_wait_range(mapping
, pos
,
1734 struct iov_iter data
= *iter
;
1735 retval
= mapping
->a_ops
->direct_IO(iocb
, &data
, pos
);
1739 *ppos
= pos
+ retval
;
1740 iov_iter_advance(iter
, retval
);
1744 * Btrfs can have a short DIO read if we encounter
1745 * compressed extents, so if there was an error, or if
1746 * we've already read everything we wanted to, or if
1747 * there was a short read because we hit EOF, go ahead
1748 * and return. Otherwise fallthrough to buffered io for
1749 * the rest of the read. Buffered reads will not work for
1750 * DAX files, so don't bother trying.
1752 if (retval
< 0 || !iov_iter_count(iter
) || *ppos
>= size
||
1754 file_accessed(file
);
1759 retval
= do_generic_file_read(file
, ppos
, iter
, retval
);
1763 EXPORT_SYMBOL(generic_file_read_iter
);
1767 * page_cache_read - adds requested page to the page cache if not already there
1768 * @file: file to read
1769 * @offset: page index
1771 * This adds the requested page to the page cache if it isn't already there,
1772 * and schedules an I/O to read in its contents from disk.
1774 static int page_cache_read(struct file
*file
, pgoff_t offset
)
1776 struct address_space
*mapping
= file
->f_mapping
;
1781 page
= page_cache_alloc_cold(mapping
);
1785 ret
= add_to_page_cache_lru(page
, mapping
, offset
,
1786 GFP_KERNEL
& mapping_gfp_mask(mapping
));
1788 ret
= mapping
->a_ops
->readpage(file
, page
);
1789 else if (ret
== -EEXIST
)
1790 ret
= 0; /* losing race to add is OK */
1792 page_cache_release(page
);
1794 } while (ret
== AOP_TRUNCATED_PAGE
);
1799 #define MMAP_LOTSAMISS (100)
1802 * Synchronous readahead happens when we don't even find
1803 * a page in the page cache at all.
1805 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1806 struct file_ra_state
*ra
,
1810 struct address_space
*mapping
= file
->f_mapping
;
1812 /* If we don't want any read-ahead, don't bother */
1813 if (vma
->vm_flags
& VM_RAND_READ
)
1818 if (vma
->vm_flags
& VM_SEQ_READ
) {
1819 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1824 /* Avoid banging the cache line if not needed */
1825 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
1829 * Do we miss much more than hit in this file? If so,
1830 * stop bothering with read-ahead. It will only hurt.
1832 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1838 ra
->start
= max_t(long, 0, offset
- ra
->ra_pages
/ 2);
1839 ra
->size
= ra
->ra_pages
;
1840 ra
->async_size
= ra
->ra_pages
/ 4;
1841 ra_submit(ra
, mapping
, file
);
1845 * Asynchronous readahead happens when we find the page and PG_readahead,
1846 * so we want to possibly extend the readahead further..
1848 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1849 struct file_ra_state
*ra
,
1854 struct address_space
*mapping
= file
->f_mapping
;
1856 /* If we don't want any read-ahead, don't bother */
1857 if (vma
->vm_flags
& VM_RAND_READ
)
1859 if (ra
->mmap_miss
> 0)
1861 if (PageReadahead(page
))
1862 page_cache_async_readahead(mapping
, ra
, file
,
1863 page
, offset
, ra
->ra_pages
);
1867 * filemap_fault - read in file data for page fault handling
1868 * @vma: vma in which the fault was taken
1869 * @vmf: struct vm_fault containing details of the fault
1871 * filemap_fault() is invoked via the vma operations vector for a
1872 * mapped memory region to read in file data during a page fault.
1874 * The goto's are kind of ugly, but this streamlines the normal case of having
1875 * it in the page cache, and handles the special cases reasonably without
1876 * having a lot of duplicated code.
1878 * vma->vm_mm->mmap_sem must be held on entry.
1880 * If our return value has VM_FAULT_RETRY set, it's because
1881 * lock_page_or_retry() returned 0.
1882 * The mmap_sem has usually been released in this case.
1883 * See __lock_page_or_retry() for the exception.
1885 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
1886 * has not been released.
1888 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
1890 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
1893 struct file
*file
= vma
->vm_file
;
1894 struct address_space
*mapping
= file
->f_mapping
;
1895 struct file_ra_state
*ra
= &file
->f_ra
;
1896 struct inode
*inode
= mapping
->host
;
1897 pgoff_t offset
= vmf
->pgoff
;
1902 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1903 if (offset
>= size
>> PAGE_CACHE_SHIFT
)
1904 return VM_FAULT_SIGBUS
;
1907 * Do we have something in the page cache already?
1909 page
= find_get_page(mapping
, offset
);
1910 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
1912 * We found the page, so try async readahead before
1913 * waiting for the lock.
1915 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
1917 /* No page in the page cache at all */
1918 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
1919 count_vm_event(PGMAJFAULT
);
1920 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
1921 ret
= VM_FAULT_MAJOR
;
1923 page
= find_get_page(mapping
, offset
);
1925 goto no_cached_page
;
1928 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
1929 page_cache_release(page
);
1930 return ret
| VM_FAULT_RETRY
;
1933 /* Did it get truncated? */
1934 if (unlikely(page
->mapping
!= mapping
)) {
1939 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1942 * We have a locked page in the page cache, now we need to check
1943 * that it's up-to-date. If not, it is going to be due to an error.
1945 if (unlikely(!PageUptodate(page
)))
1946 goto page_not_uptodate
;
1949 * Found the page and have a reference on it.
1950 * We must recheck i_size under page lock.
1952 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
1953 if (unlikely(offset
>= size
>> PAGE_CACHE_SHIFT
)) {
1955 page_cache_release(page
);
1956 return VM_FAULT_SIGBUS
;
1960 return ret
| VM_FAULT_LOCKED
;
1964 * We're only likely to ever get here if MADV_RANDOM is in
1967 error
= page_cache_read(file
, offset
);
1970 * The page we want has now been added to the page cache.
1971 * In the unlikely event that someone removed it in the
1972 * meantime, we'll just come back here and read it again.
1978 * An error return from page_cache_read can result if the
1979 * system is low on memory, or a problem occurs while trying
1982 if (error
== -ENOMEM
)
1983 return VM_FAULT_OOM
;
1984 return VM_FAULT_SIGBUS
;
1988 * Umm, take care of errors if the page isn't up-to-date.
1989 * Try to re-read it _once_. We do this synchronously,
1990 * because there really aren't any performance issues here
1991 * and we need to check for errors.
1993 ClearPageError(page
);
1994 error
= mapping
->a_ops
->readpage(file
, page
);
1996 wait_on_page_locked(page
);
1997 if (!PageUptodate(page
))
2000 page_cache_release(page
);
2002 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2005 /* Things didn't work out. Return zero to tell the mm layer so. */
2006 shrink_readahead_size_eio(file
, ra
);
2007 return VM_FAULT_SIGBUS
;
2009 EXPORT_SYMBOL(filemap_fault
);
2011 void filemap_map_pages(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2013 struct radix_tree_iter iter
;
2015 struct file
*file
= vma
->vm_file
;
2016 struct address_space
*mapping
= file
->f_mapping
;
2019 unsigned long address
= (unsigned long) vmf
->virtual_address
;
2024 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, vmf
->pgoff
) {
2025 if (iter
.index
> vmf
->max_pgoff
)
2028 page
= radix_tree_deref_slot(slot
);
2029 if (unlikely(!page
))
2031 if (radix_tree_exception(page
)) {
2032 if (radix_tree_deref_retry(page
))
2038 if (!page_cache_get_speculative(page
))
2041 /* Has the page moved? */
2042 if (unlikely(page
!= *slot
)) {
2043 page_cache_release(page
);
2047 if (!PageUptodate(page
) ||
2048 PageReadahead(page
) ||
2051 if (!trylock_page(page
))
2054 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2057 size
= round_up(i_size_read(mapping
->host
), PAGE_CACHE_SIZE
);
2058 if (page
->index
>= size
>> PAGE_CACHE_SHIFT
)
2061 pte
= vmf
->pte
+ page
->index
- vmf
->pgoff
;
2062 if (!pte_none(*pte
))
2065 if (file
->f_ra
.mmap_miss
> 0)
2066 file
->f_ra
.mmap_miss
--;
2067 addr
= address
+ (page
->index
- vmf
->pgoff
) * PAGE_SIZE
;
2068 do_set_pte(vma
, addr
, page
, pte
, false, false);
2074 page_cache_release(page
);
2076 if (iter
.index
== vmf
->max_pgoff
)
2081 EXPORT_SYMBOL(filemap_map_pages
);
2083 int filemap_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2085 struct page
*page
= vmf
->page
;
2086 struct inode
*inode
= file_inode(vma
->vm_file
);
2087 int ret
= VM_FAULT_LOCKED
;
2089 sb_start_pagefault(inode
->i_sb
);
2090 file_update_time(vma
->vm_file
);
2092 if (page
->mapping
!= inode
->i_mapping
) {
2094 ret
= VM_FAULT_NOPAGE
;
2098 * We mark the page dirty already here so that when freeze is in
2099 * progress, we are guaranteed that writeback during freezing will
2100 * see the dirty page and writeprotect it again.
2102 set_page_dirty(page
);
2103 wait_for_stable_page(page
);
2105 sb_end_pagefault(inode
->i_sb
);
2108 EXPORT_SYMBOL(filemap_page_mkwrite
);
2110 const struct vm_operations_struct generic_file_vm_ops
= {
2111 .fault
= filemap_fault
,
2112 .map_pages
= filemap_map_pages
,
2113 .page_mkwrite
= filemap_page_mkwrite
,
2116 /* This is used for a general mmap of a disk file */
2118 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2120 struct address_space
*mapping
= file
->f_mapping
;
2122 if (!mapping
->a_ops
->readpage
)
2124 file_accessed(file
);
2125 vma
->vm_ops
= &generic_file_vm_ops
;
2130 * This is for filesystems which do not implement ->writepage.
2132 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2134 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2136 return generic_file_mmap(file
, vma
);
2139 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2143 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2147 #endif /* CONFIG_MMU */
2149 EXPORT_SYMBOL(generic_file_mmap
);
2150 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2152 static struct page
*wait_on_page_read(struct page
*page
)
2154 if (!IS_ERR(page
)) {
2155 wait_on_page_locked(page
);
2156 if (!PageUptodate(page
)) {
2157 page_cache_release(page
);
2158 page
= ERR_PTR(-EIO
);
2164 static struct page
*__read_cache_page(struct address_space
*mapping
,
2166 int (*filler
)(void *, struct page
*),
2173 page
= find_get_page(mapping
, index
);
2175 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2177 return ERR_PTR(-ENOMEM
);
2178 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2179 if (unlikely(err
)) {
2180 page_cache_release(page
);
2183 /* Presumably ENOMEM for radix tree node */
2184 return ERR_PTR(err
);
2186 err
= filler(data
, page
);
2188 page_cache_release(page
);
2189 page
= ERR_PTR(err
);
2191 page
= wait_on_page_read(page
);
2197 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2199 int (*filler
)(void *, struct page
*),
2208 page
= __read_cache_page(mapping
, index
, filler
, data
, gfp
);
2211 if (PageUptodate(page
))
2215 if (!page
->mapping
) {
2217 page_cache_release(page
);
2220 if (PageUptodate(page
)) {
2224 err
= filler(data
, page
);
2226 page_cache_release(page
);
2227 return ERR_PTR(err
);
2229 page
= wait_on_page_read(page
);
2234 mark_page_accessed(page
);
2239 * read_cache_page - read into page cache, fill it if needed
2240 * @mapping: the page's address_space
2241 * @index: the page index
2242 * @filler: function to perform the read
2243 * @data: first arg to filler(data, page) function, often left as NULL
2245 * Read into the page cache. If a page already exists, and PageUptodate() is
2246 * not set, try to fill the page and wait for it to become unlocked.
2248 * If the page does not get brought uptodate, return -EIO.
2250 struct page
*read_cache_page(struct address_space
*mapping
,
2252 int (*filler
)(void *, struct page
*),
2255 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2257 EXPORT_SYMBOL(read_cache_page
);
2260 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2261 * @mapping: the page's address_space
2262 * @index: the page index
2263 * @gfp: the page allocator flags to use if allocating
2265 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2266 * any new page allocations done using the specified allocation flags.
2268 * If the page does not get brought uptodate, return -EIO.
2270 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2274 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2276 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2278 EXPORT_SYMBOL(read_cache_page_gfp
);
2281 * Performs necessary checks before doing a write
2283 * Can adjust writing position or amount of bytes to write.
2284 * Returns appropriate error code that caller should return or
2285 * zero in case that write should be allowed.
2287 inline ssize_t
generic_write_checks(struct kiocb
*iocb
, struct iov_iter
*from
)
2289 struct file
*file
= iocb
->ki_filp
;
2290 struct inode
*inode
= file
->f_mapping
->host
;
2291 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2294 if (!iov_iter_count(from
))
2297 /* FIXME: this is for backwards compatibility with 2.4 */
2298 if (iocb
->ki_flags
& IOCB_APPEND
)
2299 iocb
->ki_pos
= i_size_read(inode
);
2303 if (limit
!= RLIM_INFINITY
) {
2304 if (iocb
->ki_pos
>= limit
) {
2305 send_sig(SIGXFSZ
, current
, 0);
2308 iov_iter_truncate(from
, limit
- (unsigned long)pos
);
2314 if (unlikely(pos
+ iov_iter_count(from
) > MAX_NON_LFS
&&
2315 !(file
->f_flags
& O_LARGEFILE
))) {
2316 if (pos
>= MAX_NON_LFS
)
2318 iov_iter_truncate(from
, MAX_NON_LFS
- (unsigned long)pos
);
2322 * Are we about to exceed the fs block limit ?
2324 * If we have written data it becomes a short write. If we have
2325 * exceeded without writing data we send a signal and return EFBIG.
2326 * Linus frestrict idea will clean these up nicely..
2328 if (unlikely(pos
>= inode
->i_sb
->s_maxbytes
))
2331 iov_iter_truncate(from
, inode
->i_sb
->s_maxbytes
- pos
);
2332 return iov_iter_count(from
);
2334 EXPORT_SYMBOL(generic_write_checks
);
2336 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2337 loff_t pos
, unsigned len
, unsigned flags
,
2338 struct page
**pagep
, void **fsdata
)
2340 const struct address_space_operations
*aops
= mapping
->a_ops
;
2342 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2345 EXPORT_SYMBOL(pagecache_write_begin
);
2347 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2348 loff_t pos
, unsigned len
, unsigned copied
,
2349 struct page
*page
, void *fsdata
)
2351 const struct address_space_operations
*aops
= mapping
->a_ops
;
2353 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2355 EXPORT_SYMBOL(pagecache_write_end
);
2358 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
, loff_t pos
)
2360 struct file
*file
= iocb
->ki_filp
;
2361 struct address_space
*mapping
= file
->f_mapping
;
2362 struct inode
*inode
= mapping
->host
;
2366 struct iov_iter data
;
2368 write_len
= iov_iter_count(from
);
2369 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2371 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2376 * After a write we want buffered reads to be sure to go to disk to get
2377 * the new data. We invalidate clean cached page from the region we're
2378 * about to write. We do this *before* the write so that we can return
2379 * without clobbering -EIOCBQUEUED from ->direct_IO().
2381 if (mapping
->nrpages
) {
2382 written
= invalidate_inode_pages2_range(mapping
,
2383 pos
>> PAGE_CACHE_SHIFT
, end
);
2385 * If a page can not be invalidated, return 0 to fall back
2386 * to buffered write.
2389 if (written
== -EBUSY
)
2396 written
= mapping
->a_ops
->direct_IO(iocb
, &data
, pos
);
2399 * Finally, try again to invalidate clean pages which might have been
2400 * cached by non-direct readahead, or faulted in by get_user_pages()
2401 * if the source of the write was an mmap'ed region of the file
2402 * we're writing. Either one is a pretty crazy thing to do,
2403 * so we don't support it 100%. If this invalidation
2404 * fails, tough, the write still worked...
2406 if (mapping
->nrpages
) {
2407 invalidate_inode_pages2_range(mapping
,
2408 pos
>> PAGE_CACHE_SHIFT
, end
);
2413 iov_iter_advance(from
, written
);
2414 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2415 i_size_write(inode
, pos
);
2416 mark_inode_dirty(inode
);
2423 EXPORT_SYMBOL(generic_file_direct_write
);
2426 * Find or create a page at the given pagecache position. Return the locked
2427 * page. This function is specifically for buffered writes.
2429 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2430 pgoff_t index
, unsigned flags
)
2433 int fgp_flags
= FGP_LOCK
|FGP_ACCESSED
|FGP_WRITE
|FGP_CREAT
;
2435 if (flags
& AOP_FLAG_NOFS
)
2436 fgp_flags
|= FGP_NOFS
;
2438 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2439 mapping_gfp_mask(mapping
));
2441 wait_for_stable_page(page
);
2445 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2447 ssize_t
generic_perform_write(struct file
*file
,
2448 struct iov_iter
*i
, loff_t pos
)
2450 struct address_space
*mapping
= file
->f_mapping
;
2451 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2453 ssize_t written
= 0;
2454 unsigned int flags
= 0;
2457 * Copies from kernel address space cannot fail (NFSD is a big user).
2459 if (!iter_is_iovec(i
))
2460 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2464 unsigned long offset
; /* Offset into pagecache page */
2465 unsigned long bytes
; /* Bytes to write to page */
2466 size_t copied
; /* Bytes copied from user */
2469 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2470 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2475 * Bring in the user page that we will copy from _first_.
2476 * Otherwise there's a nasty deadlock on copying from the
2477 * same page as we're writing to, without it being marked
2480 * Not only is this an optimisation, but it is also required
2481 * to check that the address is actually valid, when atomic
2482 * usercopies are used, below.
2484 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2489 if (fatal_signal_pending(current
)) {
2494 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2496 if (unlikely(status
< 0))
2499 if (mapping_writably_mapped(mapping
))
2500 flush_dcache_page(page
);
2502 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2503 flush_dcache_page(page
);
2505 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2507 if (unlikely(status
< 0))
2513 iov_iter_advance(i
, copied
);
2514 if (unlikely(copied
== 0)) {
2516 * If we were unable to copy any data at all, we must
2517 * fall back to a single segment length write.
2519 * If we didn't fallback here, we could livelock
2520 * because not all segments in the iov can be copied at
2521 * once without a pagefault.
2523 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2524 iov_iter_single_seg_count(i
));
2530 balance_dirty_pages_ratelimited(mapping
);
2531 } while (iov_iter_count(i
));
2533 return written
? written
: status
;
2535 EXPORT_SYMBOL(generic_perform_write
);
2538 * __generic_file_write_iter - write data to a file
2539 * @iocb: IO state structure (file, offset, etc.)
2540 * @from: iov_iter with data to write
2542 * This function does all the work needed for actually writing data to a
2543 * file. It does all basic checks, removes SUID from the file, updates
2544 * modification times and calls proper subroutines depending on whether we
2545 * do direct IO or a standard buffered write.
2547 * It expects i_mutex to be grabbed unless we work on a block device or similar
2548 * object which does not need locking at all.
2550 * This function does *not* take care of syncing data in case of O_SYNC write.
2551 * A caller has to handle it. This is mainly due to the fact that we want to
2552 * avoid syncing under i_mutex.
2554 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2556 struct file
*file
= iocb
->ki_filp
;
2557 struct address_space
* mapping
= file
->f_mapping
;
2558 struct inode
*inode
= mapping
->host
;
2559 ssize_t written
= 0;
2563 /* We can write back this queue in page reclaim */
2564 current
->backing_dev_info
= inode_to_bdi(inode
);
2565 err
= file_remove_privs(file
);
2569 err
= file_update_time(file
);
2573 if (iocb
->ki_flags
& IOCB_DIRECT
) {
2574 loff_t pos
, endbyte
;
2576 written
= generic_file_direct_write(iocb
, from
, iocb
->ki_pos
);
2578 * If the write stopped short of completing, fall back to
2579 * buffered writes. Some filesystems do this for writes to
2580 * holes, for example. For DAX files, a buffered write will
2581 * not succeed (even if it did, DAX does not handle dirty
2582 * page-cache pages correctly).
2584 if (written
< 0 || !iov_iter_count(from
) || IS_DAX(inode
))
2587 status
= generic_perform_write(file
, from
, pos
= iocb
->ki_pos
);
2589 * If generic_perform_write() returned a synchronous error
2590 * then we want to return the number of bytes which were
2591 * direct-written, or the error code if that was zero. Note
2592 * that this differs from normal direct-io semantics, which
2593 * will return -EFOO even if some bytes were written.
2595 if (unlikely(status
< 0)) {
2600 * We need to ensure that the page cache pages are written to
2601 * disk and invalidated to preserve the expected O_DIRECT
2604 endbyte
= pos
+ status
- 1;
2605 err
= filemap_write_and_wait_range(mapping
, pos
, endbyte
);
2607 iocb
->ki_pos
= endbyte
+ 1;
2609 invalidate_mapping_pages(mapping
,
2610 pos
>> PAGE_CACHE_SHIFT
,
2611 endbyte
>> PAGE_CACHE_SHIFT
);
2614 * We don't know how much we wrote, so just return
2615 * the number of bytes which were direct-written
2619 written
= generic_perform_write(file
, from
, iocb
->ki_pos
);
2620 if (likely(written
> 0))
2621 iocb
->ki_pos
+= written
;
2624 current
->backing_dev_info
= NULL
;
2625 return written
? written
: err
;
2627 EXPORT_SYMBOL(__generic_file_write_iter
);
2630 * generic_file_write_iter - write data to a file
2631 * @iocb: IO state structure
2632 * @from: iov_iter with data to write
2634 * This is a wrapper around __generic_file_write_iter() to be used by most
2635 * filesystems. It takes care of syncing the file in case of O_SYNC file
2636 * and acquires i_mutex as needed.
2638 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2640 struct file
*file
= iocb
->ki_filp
;
2641 struct inode
*inode
= file
->f_mapping
->host
;
2644 mutex_lock(&inode
->i_mutex
);
2645 ret
= generic_write_checks(iocb
, from
);
2647 ret
= __generic_file_write_iter(iocb
, from
);
2648 mutex_unlock(&inode
->i_mutex
);
2653 err
= generic_write_sync(file
, iocb
->ki_pos
- ret
, ret
);
2659 EXPORT_SYMBOL(generic_file_write_iter
);
2662 * try_to_release_page() - release old fs-specific metadata on a page
2664 * @page: the page which the kernel is trying to free
2665 * @gfp_mask: memory allocation flags (and I/O mode)
2667 * The address_space is to try to release any data against the page
2668 * (presumably at page->private). If the release was successful, return `1'.
2669 * Otherwise return zero.
2671 * This may also be called if PG_fscache is set on a page, indicating that the
2672 * page is known to the local caching routines.
2674 * The @gfp_mask argument specifies whether I/O may be performed to release
2675 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2678 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2680 struct address_space
* const mapping
= page
->mapping
;
2682 BUG_ON(!PageLocked(page
));
2683 if (PageWriteback(page
))
2686 if (mapping
&& mapping
->a_ops
->releasepage
)
2687 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2688 return try_to_free_buffers(page
);
2691 EXPORT_SYMBOL(try_to_release_page
);