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>
14 #include <linux/dax.h>
16 #include <linux/uaccess.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/hugetlb.h>
35 #include <linux/memcontrol.h>
36 #include <linux/cleancache.h>
37 #include <linux/rmap.h>
40 #define CREATE_TRACE_POINTS
41 #include <trace/events/filemap.h>
44 * FIXME: remove all knowledge of the buffer layer from the core VM
46 #include <linux/buffer_head.h> /* for try_to_free_buffers */
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
54 * Shared mappings now work. 15.8.1995 Bruno.
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
79 * ->lock_page (access_process_vm)
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
89 * ->anon_vma.lock (vma_adjust)
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone.lru_lock (follow_page->mark_page_accessed)
99 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
113 static void page_cache_tree_delete(struct address_space
*mapping
,
114 struct page
*page
, void *shadow
)
116 struct radix_tree_node
*node
;
122 VM_BUG_ON(!PageLocked(page
));
124 __radix_tree_lookup(&mapping
->page_tree
, page
->index
, &node
, &slot
);
127 mapping
->nrexceptional
++;
129 * Make sure the nrexceptional update is committed before
130 * the nrpages update so that final truncate racing
131 * with reclaim does not see both counters 0 at the
132 * same time and miss a shadow entry.
139 /* Clear direct pointer tags in root node */
140 mapping
->page_tree
.gfp_mask
&= __GFP_BITS_MASK
;
141 radix_tree_replace_slot(slot
, shadow
);
145 /* Clear tree tags for the removed page */
147 offset
= index
& RADIX_TREE_MAP_MASK
;
148 for (tag
= 0; tag
< RADIX_TREE_MAX_TAGS
; tag
++) {
149 if (test_bit(offset
, node
->tags
[tag
]))
150 radix_tree_tag_clear(&mapping
->page_tree
, index
, tag
);
153 /* Delete page, swap shadow entry */
154 radix_tree_replace_slot(slot
, shadow
);
155 workingset_node_pages_dec(node
);
157 workingset_node_shadows_inc(node
);
159 if (__radix_tree_delete_node(&mapping
->page_tree
, node
))
163 * Track node that only contains shadow entries.
165 * Avoid acquiring the list_lru lock if already tracked. The
166 * list_empty() test is safe as node->private_list is
167 * protected by mapping->tree_lock.
169 if (!workingset_node_pages(node
) &&
170 list_empty(&node
->private_list
)) {
171 node
->private_data
= mapping
;
172 list_lru_add(&workingset_shadow_nodes
, &node
->private_list
);
177 * Delete a page from the page cache and free it. Caller has to make
178 * sure the page is locked and that nobody else uses it - or that usage
179 * is safe. The caller must hold the mapping's tree_lock and
182 void __delete_from_page_cache(struct page
*page
, void *shadow
)
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 VM_BUG_ON_PAGE(page_mapped(page
), page
);
198 if (!IS_ENABLED(CONFIG_DEBUG_VM
) && unlikely(page_mapped(page
))) {
201 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
202 current
->comm
, page_to_pfn(page
));
203 dump_page(page
, "still mapped when deleted");
205 add_taint(TAINT_BAD_PAGE
, LOCKDEP_NOW_UNRELIABLE
);
207 mapcount
= page_mapcount(page
);
208 if (mapping_exiting(mapping
) &&
209 page_count(page
) >= mapcount
+ 2) {
211 * All vmas have already been torn down, so it's
212 * a good bet that actually the page is unmapped,
213 * and we'd prefer not to leak it: if we're wrong,
214 * some other bad page check should catch it later.
216 page_mapcount_reset(page
);
217 atomic_sub(mapcount
, &page
->_count
);
221 page_cache_tree_delete(mapping
, page
, shadow
);
223 page
->mapping
= NULL
;
224 /* Leave page->index set: truncation lookup relies upon it */
226 /* hugetlb pages do not participate in page cache accounting. */
228 __dec_zone_page_state(page
, NR_FILE_PAGES
);
229 if (PageSwapBacked(page
))
230 __dec_zone_page_state(page
, NR_SHMEM
);
233 * At this point page must be either written or cleaned by truncate.
234 * Dirty page here signals a bug and loss of unwritten data.
236 * This fixes dirty accounting after removing the page entirely but
237 * leaves PageDirty set: it has no effect for truncated page and
238 * anyway will be cleared before returning page into buddy allocator.
240 if (WARN_ON_ONCE(PageDirty(page
)))
241 account_page_cleaned(page
, mapping
, inode_to_wb(mapping
->host
));
245 * delete_from_page_cache - delete page from page cache
246 * @page: the page which the kernel is trying to remove from page cache
248 * This must be called only on pages that have been verified to be in the page
249 * cache and locked. It will never put the page into the free list, the caller
250 * has a reference on the page.
252 void delete_from_page_cache(struct page
*page
)
254 struct address_space
*mapping
= page
->mapping
;
257 void (*freepage
)(struct page
*);
259 BUG_ON(!PageLocked(page
));
261 freepage
= mapping
->a_ops
->freepage
;
263 lock_page_memcg(page
);
264 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
265 __delete_from_page_cache(page
, NULL
);
266 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
267 unlock_page_memcg(page
);
271 page_cache_release(page
);
273 EXPORT_SYMBOL(delete_from_page_cache
);
275 static int filemap_check_errors(struct address_space
*mapping
)
278 /* Check for outstanding write errors */
279 if (test_bit(AS_ENOSPC
, &mapping
->flags
) &&
280 test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
282 if (test_bit(AS_EIO
, &mapping
->flags
) &&
283 test_and_clear_bit(AS_EIO
, &mapping
->flags
))
289 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
290 * @mapping: address space structure to write
291 * @start: offset in bytes where the range starts
292 * @end: offset in bytes where the range ends (inclusive)
293 * @sync_mode: enable synchronous operation
295 * Start writeback against all of a mapping's dirty pages that lie
296 * within the byte offsets <start, end> inclusive.
298 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
299 * opposed to a regular memory cleansing writeback. The difference between
300 * these two operations is that if a dirty page/buffer is encountered, it must
301 * be waited upon, and not just skipped over.
303 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
304 loff_t end
, int sync_mode
)
307 struct writeback_control wbc
= {
308 .sync_mode
= sync_mode
,
309 .nr_to_write
= LONG_MAX
,
310 .range_start
= start
,
314 if (!mapping_cap_writeback_dirty(mapping
))
317 wbc_attach_fdatawrite_inode(&wbc
, mapping
->host
);
318 ret
= do_writepages(mapping
, &wbc
);
319 wbc_detach_inode(&wbc
);
323 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
326 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
329 int filemap_fdatawrite(struct address_space
*mapping
)
331 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
333 EXPORT_SYMBOL(filemap_fdatawrite
);
335 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
338 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
340 EXPORT_SYMBOL(filemap_fdatawrite_range
);
343 * filemap_flush - mostly a non-blocking flush
344 * @mapping: target address_space
346 * This is a mostly non-blocking flush. Not suitable for data-integrity
347 * purposes - I/O may not be started against all dirty pages.
349 int filemap_flush(struct address_space
*mapping
)
351 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
353 EXPORT_SYMBOL(filemap_flush
);
355 static int __filemap_fdatawait_range(struct address_space
*mapping
,
356 loff_t start_byte
, loff_t end_byte
)
358 pgoff_t index
= start_byte
>> PAGE_CACHE_SHIFT
;
359 pgoff_t end
= end_byte
>> PAGE_CACHE_SHIFT
;
364 if (end_byte
< start_byte
)
367 pagevec_init(&pvec
, 0);
368 while ((index
<= end
) &&
369 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
370 PAGECACHE_TAG_WRITEBACK
,
371 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
374 for (i
= 0; i
< nr_pages
; i
++) {
375 struct page
*page
= pvec
.pages
[i
];
377 /* until radix tree lookup accepts end_index */
378 if (page
->index
> end
)
381 wait_on_page_writeback(page
);
382 if (TestClearPageError(page
))
385 pagevec_release(&pvec
);
393 * filemap_fdatawait_range - wait for writeback to complete
394 * @mapping: address space structure to wait for
395 * @start_byte: offset in bytes where the range starts
396 * @end_byte: offset in bytes where the range ends (inclusive)
398 * Walk the list of under-writeback pages of the given address space
399 * in the given range and wait for all of them. Check error status of
400 * the address space and return it.
402 * Since the error status of the address space is cleared by this function,
403 * callers are responsible for checking the return value and handling and/or
404 * reporting the error.
406 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
411 ret
= __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
412 ret2
= filemap_check_errors(mapping
);
418 EXPORT_SYMBOL(filemap_fdatawait_range
);
421 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
422 * @mapping: address space structure to wait for
424 * Walk the list of under-writeback pages of the given address space
425 * and wait for all of them. Unlike filemap_fdatawait(), this function
426 * does not clear error status of the address space.
428 * Use this function if callers don't handle errors themselves. Expected
429 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
432 void filemap_fdatawait_keep_errors(struct address_space
*mapping
)
434 loff_t i_size
= i_size_read(mapping
->host
);
439 __filemap_fdatawait_range(mapping
, 0, i_size
- 1);
443 * filemap_fdatawait - wait for all under-writeback pages to complete
444 * @mapping: address space structure to wait for
446 * Walk the list of under-writeback pages of the given address space
447 * and wait for all of them. Check error status of the address space
450 * Since the error status of the address space is cleared by this function,
451 * callers are responsible for checking the return value and handling and/or
452 * reporting the error.
454 int filemap_fdatawait(struct address_space
*mapping
)
456 loff_t i_size
= i_size_read(mapping
->host
);
461 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
463 EXPORT_SYMBOL(filemap_fdatawait
);
465 int filemap_write_and_wait(struct address_space
*mapping
)
469 if ((!dax_mapping(mapping
) && mapping
->nrpages
) ||
470 (dax_mapping(mapping
) && mapping
->nrexceptional
)) {
471 err
= filemap_fdatawrite(mapping
);
473 * Even if the above returned error, the pages may be
474 * written partially (e.g. -ENOSPC), so we wait for it.
475 * But the -EIO is special case, it may indicate the worst
476 * thing (e.g. bug) happened, so we avoid waiting for it.
479 int err2
= filemap_fdatawait(mapping
);
484 err
= filemap_check_errors(mapping
);
488 EXPORT_SYMBOL(filemap_write_and_wait
);
491 * filemap_write_and_wait_range - write out & wait on a file range
492 * @mapping: the address_space for the pages
493 * @lstart: offset in bytes where the range starts
494 * @lend: offset in bytes where the range ends (inclusive)
496 * Write out and wait upon file offsets lstart->lend, inclusive.
498 * Note that `lend' is inclusive (describes the last byte to be written) so
499 * that this function can be used to write to the very end-of-file (end = -1).
501 int filemap_write_and_wait_range(struct address_space
*mapping
,
502 loff_t lstart
, loff_t lend
)
506 if ((!dax_mapping(mapping
) && mapping
->nrpages
) ||
507 (dax_mapping(mapping
) && mapping
->nrexceptional
)) {
508 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
510 /* See comment of filemap_write_and_wait() */
512 int err2
= filemap_fdatawait_range(mapping
,
518 err
= filemap_check_errors(mapping
);
522 EXPORT_SYMBOL(filemap_write_and_wait_range
);
525 * replace_page_cache_page - replace a pagecache page with a new one
526 * @old: page to be replaced
527 * @new: page to replace with
528 * @gfp_mask: allocation mode
530 * This function replaces a page in the pagecache with a new one. On
531 * success it acquires the pagecache reference for the new page and
532 * drops it for the old page. Both the old and new pages must be
533 * locked. This function does not add the new page to the LRU, the
534 * caller must do that.
536 * The remove + add is atomic. The only way this function can fail is
537 * memory allocation failure.
539 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
543 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
544 VM_BUG_ON_PAGE(!PageLocked(new), new);
545 VM_BUG_ON_PAGE(new->mapping
, new);
547 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
549 struct address_space
*mapping
= old
->mapping
;
550 void (*freepage
)(struct page
*);
553 pgoff_t offset
= old
->index
;
554 freepage
= mapping
->a_ops
->freepage
;
557 new->mapping
= mapping
;
560 lock_page_memcg(old
);
561 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
562 __delete_from_page_cache(old
, NULL
);
563 error
= radix_tree_insert(&mapping
->page_tree
, offset
, new);
568 * hugetlb pages do not participate in page cache accounting.
571 __inc_zone_page_state(new, NR_FILE_PAGES
);
572 if (PageSwapBacked(new))
573 __inc_zone_page_state(new, NR_SHMEM
);
574 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
575 unlock_page_memcg(old
);
576 mem_cgroup_migrate(old
, new);
577 radix_tree_preload_end();
580 page_cache_release(old
);
585 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
587 static int page_cache_tree_insert(struct address_space
*mapping
,
588 struct page
*page
, void **shadowp
)
590 struct radix_tree_node
*node
;
594 error
= __radix_tree_create(&mapping
->page_tree
, page
->index
,
601 p
= radix_tree_deref_slot_protected(slot
, &mapping
->tree_lock
);
602 if (!radix_tree_exceptional_entry(p
))
605 if (WARN_ON(dax_mapping(mapping
)))
610 mapping
->nrexceptional
--;
612 workingset_node_shadows_dec(node
);
614 radix_tree_replace_slot(slot
, page
);
617 workingset_node_pages_inc(node
);
619 * Don't track node that contains actual pages.
621 * Avoid acquiring the list_lru lock if already
622 * untracked. The list_empty() test is safe as
623 * node->private_list is protected by
624 * mapping->tree_lock.
626 if (!list_empty(&node
->private_list
))
627 list_lru_del(&workingset_shadow_nodes
,
628 &node
->private_list
);
633 static int __add_to_page_cache_locked(struct page
*page
,
634 struct address_space
*mapping
,
635 pgoff_t offset
, gfp_t gfp_mask
,
638 int huge
= PageHuge(page
);
639 struct mem_cgroup
*memcg
;
642 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
643 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
646 error
= mem_cgroup_try_charge(page
, current
->mm
,
647 gfp_mask
, &memcg
, false);
652 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
655 mem_cgroup_cancel_charge(page
, memcg
, false);
659 page_cache_get(page
);
660 page
->mapping
= mapping
;
661 page
->index
= offset
;
663 spin_lock_irq(&mapping
->tree_lock
);
664 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
665 radix_tree_preload_end();
669 /* hugetlb pages do not participate in page cache accounting. */
671 __inc_zone_page_state(page
, NR_FILE_PAGES
);
672 spin_unlock_irq(&mapping
->tree_lock
);
674 mem_cgroup_commit_charge(page
, memcg
, false, false);
675 trace_mm_filemap_add_to_page_cache(page
);
678 page
->mapping
= NULL
;
679 /* Leave page->index set: truncation relies upon it */
680 spin_unlock_irq(&mapping
->tree_lock
);
682 mem_cgroup_cancel_charge(page
, memcg
, false);
683 page_cache_release(page
);
688 * add_to_page_cache_locked - add a locked page to the pagecache
690 * @mapping: the page's address_space
691 * @offset: page index
692 * @gfp_mask: page allocation mode
694 * This function is used to add a page to the pagecache. It must be locked.
695 * This function does not add the page to the LRU. The caller must do that.
697 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
698 pgoff_t offset
, gfp_t gfp_mask
)
700 return __add_to_page_cache_locked(page
, mapping
, offset
,
703 EXPORT_SYMBOL(add_to_page_cache_locked
);
705 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
706 pgoff_t offset
, gfp_t gfp_mask
)
711 __SetPageLocked(page
);
712 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
715 __ClearPageLocked(page
);
718 * The page might have been evicted from cache only
719 * recently, in which case it should be activated like
720 * any other repeatedly accessed page.
722 if (shadow
&& workingset_refault(shadow
)) {
724 workingset_activation(page
);
726 ClearPageActive(page
);
731 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
734 struct page
*__page_cache_alloc(gfp_t gfp
)
739 if (cpuset_do_page_mem_spread()) {
740 unsigned int cpuset_mems_cookie
;
742 cpuset_mems_cookie
= read_mems_allowed_begin();
743 n
= cpuset_mem_spread_node();
744 page
= __alloc_pages_node(n
, gfp
, 0);
745 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
749 return alloc_pages(gfp
, 0);
751 EXPORT_SYMBOL(__page_cache_alloc
);
755 * In order to wait for pages to become available there must be
756 * waitqueues associated with pages. By using a hash table of
757 * waitqueues where the bucket discipline is to maintain all
758 * waiters on the same queue and wake all when any of the pages
759 * become available, and for the woken contexts to check to be
760 * sure the appropriate page became available, this saves space
761 * at a cost of "thundering herd" phenomena during rare hash
764 wait_queue_head_t
*page_waitqueue(struct page
*page
)
766 const struct zone
*zone
= page_zone(page
);
768 return &zone
->wait_table
[hash_ptr(page
, zone
->wait_table_bits
)];
770 EXPORT_SYMBOL(page_waitqueue
);
772 void wait_on_page_bit(struct page
*page
, int bit_nr
)
774 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
776 if (test_bit(bit_nr
, &page
->flags
))
777 __wait_on_bit(page_waitqueue(page
), &wait
, bit_wait_io
,
778 TASK_UNINTERRUPTIBLE
);
780 EXPORT_SYMBOL(wait_on_page_bit
);
782 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
784 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
786 if (!test_bit(bit_nr
, &page
->flags
))
789 return __wait_on_bit(page_waitqueue(page
), &wait
,
790 bit_wait_io
, TASK_KILLABLE
);
793 int wait_on_page_bit_killable_timeout(struct page
*page
,
794 int bit_nr
, unsigned long timeout
)
796 DEFINE_WAIT_BIT(wait
, &page
->flags
, bit_nr
);
798 wait
.key
.timeout
= jiffies
+ timeout
;
799 if (!test_bit(bit_nr
, &page
->flags
))
801 return __wait_on_bit(page_waitqueue(page
), &wait
,
802 bit_wait_io_timeout
, TASK_KILLABLE
);
804 EXPORT_SYMBOL_GPL(wait_on_page_bit_killable_timeout
);
807 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
808 * @page: Page defining the wait queue of interest
809 * @waiter: Waiter to add to the queue
811 * Add an arbitrary @waiter to the wait queue for the nominated @page.
813 void add_page_wait_queue(struct page
*page
, wait_queue_t
*waiter
)
815 wait_queue_head_t
*q
= page_waitqueue(page
);
818 spin_lock_irqsave(&q
->lock
, flags
);
819 __add_wait_queue(q
, waiter
);
820 spin_unlock_irqrestore(&q
->lock
, flags
);
822 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
825 * unlock_page - unlock a locked page
828 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
829 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
830 * mechanism between PageLocked pages and PageWriteback pages is shared.
831 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
833 * The mb is necessary to enforce ordering between the clear_bit and the read
834 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
836 void unlock_page(struct page
*page
)
838 page
= compound_head(page
);
839 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
840 clear_bit_unlock(PG_locked
, &page
->flags
);
841 smp_mb__after_atomic();
842 wake_up_page(page
, PG_locked
);
844 EXPORT_SYMBOL(unlock_page
);
847 * end_page_writeback - end writeback against a page
850 void end_page_writeback(struct page
*page
)
853 * TestClearPageReclaim could be used here but it is an atomic
854 * operation and overkill in this particular case. Failing to
855 * shuffle a page marked for immediate reclaim is too mild to
856 * justify taking an atomic operation penalty at the end of
857 * ever page writeback.
859 if (PageReclaim(page
)) {
860 ClearPageReclaim(page
);
861 rotate_reclaimable_page(page
);
864 if (!test_clear_page_writeback(page
))
867 smp_mb__after_atomic();
868 wake_up_page(page
, PG_writeback
);
870 EXPORT_SYMBOL(end_page_writeback
);
873 * After completing I/O on a page, call this routine to update the page
874 * flags appropriately
876 void page_endio(struct page
*page
, int rw
, int err
)
880 SetPageUptodate(page
);
882 ClearPageUptodate(page
);
886 } else { /* rw == WRITE */
890 mapping_set_error(page
->mapping
, err
);
892 end_page_writeback(page
);
895 EXPORT_SYMBOL_GPL(page_endio
);
898 * __lock_page - get a lock on the page, assuming we need to sleep to get it
899 * @page: the page to lock
901 void __lock_page(struct page
*page
)
903 struct page
*page_head
= compound_head(page
);
904 DEFINE_WAIT_BIT(wait
, &page_head
->flags
, PG_locked
);
906 __wait_on_bit_lock(page_waitqueue(page_head
), &wait
, bit_wait_io
,
907 TASK_UNINTERRUPTIBLE
);
909 EXPORT_SYMBOL(__lock_page
);
911 int __lock_page_killable(struct page
*page
)
913 struct page
*page_head
= compound_head(page
);
914 DEFINE_WAIT_BIT(wait
, &page_head
->flags
, PG_locked
);
916 return __wait_on_bit_lock(page_waitqueue(page_head
), &wait
,
917 bit_wait_io
, TASK_KILLABLE
);
919 EXPORT_SYMBOL_GPL(__lock_page_killable
);
923 * 1 - page is locked; mmap_sem is still held.
924 * 0 - page is not locked.
925 * mmap_sem has been released (up_read()), unless flags had both
926 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
927 * which case mmap_sem is still held.
929 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
930 * with the page locked and the mmap_sem unperturbed.
932 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
935 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
937 * CAUTION! In this case, mmap_sem is not released
938 * even though return 0.
940 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
943 up_read(&mm
->mmap_sem
);
944 if (flags
& FAULT_FLAG_KILLABLE
)
945 wait_on_page_locked_killable(page
);
947 wait_on_page_locked(page
);
950 if (flags
& FAULT_FLAG_KILLABLE
) {
953 ret
= __lock_page_killable(page
);
955 up_read(&mm
->mmap_sem
);
965 * page_cache_next_hole - find the next hole (not-present entry)
968 * @max_scan: maximum range to search
970 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
971 * lowest indexed hole.
973 * Returns: the index of the hole if found, otherwise returns an index
974 * outside of the set specified (in which case 'return - index >=
975 * max_scan' will be true). In rare cases of index wrap-around, 0 will
978 * page_cache_next_hole may be called under rcu_read_lock. However,
979 * like radix_tree_gang_lookup, this will not atomically search a
980 * snapshot of the tree at a single point in time. For example, if a
981 * hole is created at index 5, then subsequently a hole is created at
982 * index 10, page_cache_next_hole covering both indexes may return 10
983 * if called under rcu_read_lock.
985 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
986 pgoff_t index
, unsigned long max_scan
)
990 for (i
= 0; i
< max_scan
; i
++) {
993 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
994 if (!page
|| radix_tree_exceptional_entry(page
))
1003 EXPORT_SYMBOL(page_cache_next_hole
);
1006 * page_cache_prev_hole - find the prev hole (not-present entry)
1009 * @max_scan: maximum range to search
1011 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1014 * Returns: the index of the hole if found, otherwise returns an index
1015 * outside of the set specified (in which case 'index - return >=
1016 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1019 * page_cache_prev_hole may be called under rcu_read_lock. However,
1020 * like radix_tree_gang_lookup, this will not atomically search a
1021 * snapshot of the tree at a single point in time. For example, if a
1022 * hole is created at index 10, then subsequently a hole is created at
1023 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1024 * called under rcu_read_lock.
1026 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
1027 pgoff_t index
, unsigned long max_scan
)
1031 for (i
= 0; i
< max_scan
; i
++) {
1034 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1035 if (!page
|| radix_tree_exceptional_entry(page
))
1038 if (index
== ULONG_MAX
)
1044 EXPORT_SYMBOL(page_cache_prev_hole
);
1047 * find_get_entry - find and get a page cache entry
1048 * @mapping: the address_space to search
1049 * @offset: the page cache index
1051 * Looks up the page cache slot at @mapping & @offset. If there is a
1052 * page cache page, it is returned with an increased refcount.
1054 * If the slot holds a shadow entry of a previously evicted page, or a
1055 * swap entry from shmem/tmpfs, it is returned.
1057 * Otherwise, %NULL is returned.
1059 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
1067 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
1069 page
= radix_tree_deref_slot(pagep
);
1070 if (unlikely(!page
))
1072 if (radix_tree_exception(page
)) {
1073 if (radix_tree_deref_retry(page
))
1076 * A shadow entry of a recently evicted page,
1077 * or a swap entry from shmem/tmpfs. Return
1078 * it without attempting to raise page count.
1082 if (!page_cache_get_speculative(page
))
1086 * Has the page moved?
1087 * This is part of the lockless pagecache protocol. See
1088 * include/linux/pagemap.h for details.
1090 if (unlikely(page
!= *pagep
)) {
1091 page_cache_release(page
);
1100 EXPORT_SYMBOL(find_get_entry
);
1103 * find_lock_entry - locate, pin and lock a page cache entry
1104 * @mapping: the address_space to search
1105 * @offset: the page cache index
1107 * Looks up the page cache slot at @mapping & @offset. If there is a
1108 * page cache page, it is returned locked and with an increased
1111 * If the slot holds a shadow entry of a previously evicted page, or a
1112 * swap entry from shmem/tmpfs, it is returned.
1114 * Otherwise, %NULL is returned.
1116 * find_lock_entry() may sleep.
1118 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1123 page
= find_get_entry(mapping
, offset
);
1124 if (page
&& !radix_tree_exception(page
)) {
1126 /* Has the page been truncated? */
1127 if (unlikely(page
->mapping
!= mapping
)) {
1129 page_cache_release(page
);
1132 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1136 EXPORT_SYMBOL(find_lock_entry
);
1139 * pagecache_get_page - find and get a page reference
1140 * @mapping: the address_space to search
1141 * @offset: the page index
1142 * @fgp_flags: PCG flags
1143 * @gfp_mask: gfp mask to use for the page cache data page allocation
1145 * Looks up the page cache slot at @mapping & @offset.
1147 * PCG flags modify how the page is returned.
1149 * FGP_ACCESSED: the page will be marked accessed
1150 * FGP_LOCK: Page is return locked
1151 * FGP_CREAT: If page is not present then a new page is allocated using
1152 * @gfp_mask and added to the page cache and the VM's LRU
1153 * list. The page is returned locked and with an increased
1154 * refcount. Otherwise, %NULL is returned.
1156 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1157 * if the GFP flags specified for FGP_CREAT are atomic.
1159 * If there is a page cache page, it is returned with an increased refcount.
1161 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1162 int fgp_flags
, gfp_t gfp_mask
)
1167 page
= find_get_entry(mapping
, offset
);
1168 if (radix_tree_exceptional_entry(page
))
1173 if (fgp_flags
& FGP_LOCK
) {
1174 if (fgp_flags
& FGP_NOWAIT
) {
1175 if (!trylock_page(page
)) {
1176 page_cache_release(page
);
1183 /* Has the page been truncated? */
1184 if (unlikely(page
->mapping
!= mapping
)) {
1186 page_cache_release(page
);
1189 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1192 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1193 mark_page_accessed(page
);
1196 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1198 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1199 gfp_mask
|= __GFP_WRITE
;
1200 if (fgp_flags
& FGP_NOFS
)
1201 gfp_mask
&= ~__GFP_FS
;
1203 page
= __page_cache_alloc(gfp_mask
);
1207 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1208 fgp_flags
|= FGP_LOCK
;
1210 /* Init accessed so avoid atomic mark_page_accessed later */
1211 if (fgp_flags
& FGP_ACCESSED
)
1212 __SetPageReferenced(page
);
1214 err
= add_to_page_cache_lru(page
, mapping
, offset
,
1215 gfp_mask
& GFP_RECLAIM_MASK
);
1216 if (unlikely(err
)) {
1217 page_cache_release(page
);
1226 EXPORT_SYMBOL(pagecache_get_page
);
1229 * find_get_entries - gang pagecache lookup
1230 * @mapping: The address_space to search
1231 * @start: The starting page cache index
1232 * @nr_entries: The maximum number of entries
1233 * @entries: Where the resulting entries are placed
1234 * @indices: The cache indices corresponding to the entries in @entries
1236 * find_get_entries() will search for and return a group of up to
1237 * @nr_entries entries in the mapping. The entries are placed at
1238 * @entries. find_get_entries() takes a reference against any actual
1241 * The search returns a group of mapping-contiguous page cache entries
1242 * with ascending indexes. There may be holes in the indices due to
1243 * not-present pages.
1245 * Any shadow entries of evicted pages, or swap entries from
1246 * shmem/tmpfs, are included in the returned array.
1248 * find_get_entries() returns the number of pages and shadow entries
1251 unsigned find_get_entries(struct address_space
*mapping
,
1252 pgoff_t start
, unsigned int nr_entries
,
1253 struct page
**entries
, pgoff_t
*indices
)
1256 unsigned int ret
= 0;
1257 struct radix_tree_iter iter
;
1264 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1267 page
= radix_tree_deref_slot(slot
);
1268 if (unlikely(!page
))
1270 if (radix_tree_exception(page
)) {
1271 if (radix_tree_deref_retry(page
))
1274 * A shadow entry of a recently evicted page, a swap
1275 * entry from shmem/tmpfs or a DAX entry. Return it
1276 * without attempting to raise page count.
1280 if (!page_cache_get_speculative(page
))
1283 /* Has the page moved? */
1284 if (unlikely(page
!= *slot
)) {
1285 page_cache_release(page
);
1289 indices
[ret
] = iter
.index
;
1290 entries
[ret
] = page
;
1291 if (++ret
== nr_entries
)
1299 * find_get_pages - gang pagecache lookup
1300 * @mapping: The address_space to search
1301 * @start: The starting page index
1302 * @nr_pages: The maximum number of pages
1303 * @pages: Where the resulting pages are placed
1305 * find_get_pages() will search for and return a group of up to
1306 * @nr_pages pages in the mapping. The pages are placed at @pages.
1307 * find_get_pages() takes a reference against the returned pages.
1309 * The search returns a group of mapping-contiguous pages with ascending
1310 * indexes. There may be holes in the indices due to not-present pages.
1312 * find_get_pages() returns the number of pages which were found.
1314 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
1315 unsigned int nr_pages
, struct page
**pages
)
1317 struct radix_tree_iter iter
;
1321 if (unlikely(!nr_pages
))
1326 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1329 page
= radix_tree_deref_slot(slot
);
1330 if (unlikely(!page
))
1333 if (radix_tree_exception(page
)) {
1334 if (radix_tree_deref_retry(page
)) {
1336 * Transient condition which can only trigger
1337 * when entry at index 0 moves out of or back
1338 * to root: none yet gotten, safe to restart.
1340 WARN_ON(iter
.index
);
1344 * A shadow entry of a recently evicted page,
1345 * or a swap entry from shmem/tmpfs. Skip
1351 if (!page_cache_get_speculative(page
))
1354 /* Has the page moved? */
1355 if (unlikely(page
!= *slot
)) {
1356 page_cache_release(page
);
1361 if (++ret
== nr_pages
)
1370 * find_get_pages_contig - gang contiguous pagecache lookup
1371 * @mapping: The address_space to search
1372 * @index: The starting page index
1373 * @nr_pages: The maximum number of pages
1374 * @pages: Where the resulting pages are placed
1376 * find_get_pages_contig() works exactly like find_get_pages(), except
1377 * that the returned number of pages are guaranteed to be contiguous.
1379 * find_get_pages_contig() returns the number of pages which were found.
1381 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1382 unsigned int nr_pages
, struct page
**pages
)
1384 struct radix_tree_iter iter
;
1386 unsigned int ret
= 0;
1388 if (unlikely(!nr_pages
))
1393 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1396 page
= radix_tree_deref_slot(slot
);
1397 /* The hole, there no reason to continue */
1398 if (unlikely(!page
))
1401 if (radix_tree_exception(page
)) {
1402 if (radix_tree_deref_retry(page
)) {
1404 * Transient condition which can only trigger
1405 * when entry at index 0 moves out of or back
1406 * to root: none yet gotten, safe to restart.
1411 * A shadow entry of a recently evicted page,
1412 * or a swap entry from shmem/tmpfs. Stop
1413 * looking for contiguous pages.
1418 if (!page_cache_get_speculative(page
))
1421 /* Has the page moved? */
1422 if (unlikely(page
!= *slot
)) {
1423 page_cache_release(page
);
1428 * must check mapping and index after taking the ref.
1429 * otherwise we can get both false positives and false
1430 * negatives, which is just confusing to the caller.
1432 if (page
->mapping
== NULL
|| page
->index
!= iter
.index
) {
1433 page_cache_release(page
);
1438 if (++ret
== nr_pages
)
1444 EXPORT_SYMBOL(find_get_pages_contig
);
1447 * find_get_pages_tag - find and return pages that match @tag
1448 * @mapping: the address_space to search
1449 * @index: the starting page index
1450 * @tag: the tag index
1451 * @nr_pages: the maximum number of pages
1452 * @pages: where the resulting pages are placed
1454 * Like find_get_pages, except we only return pages which are tagged with
1455 * @tag. We update @index to index the next page for the traversal.
1457 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1458 int tag
, unsigned int nr_pages
, struct page
**pages
)
1460 struct radix_tree_iter iter
;
1464 if (unlikely(!nr_pages
))
1469 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1470 &iter
, *index
, tag
) {
1473 page
= radix_tree_deref_slot(slot
);
1474 if (unlikely(!page
))
1477 if (radix_tree_exception(page
)) {
1478 if (radix_tree_deref_retry(page
)) {
1480 * Transient condition which can only trigger
1481 * when entry at index 0 moves out of or back
1482 * to root: none yet gotten, safe to restart.
1487 * A shadow entry of a recently evicted page.
1489 * Those entries should never be tagged, but
1490 * this tree walk is lockless and the tags are
1491 * looked up in bulk, one radix tree node at a
1492 * time, so there is a sizable window for page
1493 * reclaim to evict a page we saw tagged.
1500 if (!page_cache_get_speculative(page
))
1503 /* Has the page moved? */
1504 if (unlikely(page
!= *slot
)) {
1505 page_cache_release(page
);
1510 if (++ret
== nr_pages
)
1517 *index
= pages
[ret
- 1]->index
+ 1;
1521 EXPORT_SYMBOL(find_get_pages_tag
);
1524 * find_get_entries_tag - find and return entries that match @tag
1525 * @mapping: the address_space to search
1526 * @start: the starting page cache index
1527 * @tag: the tag index
1528 * @nr_entries: the maximum number of entries
1529 * @entries: where the resulting entries are placed
1530 * @indices: the cache indices corresponding to the entries in @entries
1532 * Like find_get_entries, except we only return entries which are tagged with
1535 unsigned find_get_entries_tag(struct address_space
*mapping
, pgoff_t start
,
1536 int tag
, unsigned int nr_entries
,
1537 struct page
**entries
, pgoff_t
*indices
)
1540 unsigned int ret
= 0;
1541 struct radix_tree_iter iter
;
1548 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1549 &iter
, start
, tag
) {
1552 page
= radix_tree_deref_slot(slot
);
1553 if (unlikely(!page
))
1555 if (radix_tree_exception(page
)) {
1556 if (radix_tree_deref_retry(page
)) {
1558 * Transient condition which can only trigger
1559 * when entry at index 0 moves out of or back
1560 * to root: none yet gotten, safe to restart.
1566 * A shadow entry of a recently evicted page, a swap
1567 * entry from shmem/tmpfs or a DAX entry. Return it
1568 * without attempting to raise page count.
1572 if (!page_cache_get_speculative(page
))
1575 /* Has the page moved? */
1576 if (unlikely(page
!= *slot
)) {
1577 page_cache_release(page
);
1581 indices
[ret
] = iter
.index
;
1582 entries
[ret
] = page
;
1583 if (++ret
== nr_entries
)
1589 EXPORT_SYMBOL(find_get_entries_tag
);
1592 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1593 * a _large_ part of the i/o request. Imagine the worst scenario:
1595 * ---R__________________________________________B__________
1596 * ^ reading here ^ bad block(assume 4k)
1598 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1599 * => failing the whole request => read(R) => read(R+1) =>
1600 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1601 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1602 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1604 * It is going insane. Fix it by quickly scaling down the readahead size.
1606 static void shrink_readahead_size_eio(struct file
*filp
,
1607 struct file_ra_state
*ra
)
1613 * do_generic_file_read - generic file read routine
1614 * @filp: the file to read
1615 * @ppos: current file position
1616 * @iter: data destination
1617 * @written: already copied
1619 * This is a generic file read routine, and uses the
1620 * mapping->a_ops->readpage() function for the actual low-level stuff.
1622 * This is really ugly. But the goto's actually try to clarify some
1623 * of the logic when it comes to error handling etc.
1625 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1626 struct iov_iter
*iter
, ssize_t written
)
1628 struct address_space
*mapping
= filp
->f_mapping
;
1629 struct inode
*inode
= mapping
->host
;
1630 struct file_ra_state
*ra
= &filp
->f_ra
;
1634 unsigned long offset
; /* offset into pagecache page */
1635 unsigned int prev_offset
;
1638 index
= *ppos
>> PAGE_CACHE_SHIFT
;
1639 prev_index
= ra
->prev_pos
>> PAGE_CACHE_SHIFT
;
1640 prev_offset
= ra
->prev_pos
& (PAGE_CACHE_SIZE
-1);
1641 last_index
= (*ppos
+ iter
->count
+ PAGE_CACHE_SIZE
-1) >> PAGE_CACHE_SHIFT
;
1642 offset
= *ppos
& ~PAGE_CACHE_MASK
;
1648 unsigned long nr
, ret
;
1652 page
= find_get_page(mapping
, index
);
1654 page_cache_sync_readahead(mapping
,
1656 index
, last_index
- index
);
1657 page
= find_get_page(mapping
, index
);
1658 if (unlikely(page
== NULL
))
1659 goto no_cached_page
;
1661 if (PageReadahead(page
)) {
1662 page_cache_async_readahead(mapping
,
1664 index
, last_index
- index
);
1666 if (!PageUptodate(page
)) {
1668 * See comment in do_read_cache_page on why
1669 * wait_on_page_locked is used to avoid unnecessarily
1670 * serialisations and why it's safe.
1672 wait_on_page_locked_killable(page
);
1673 if (PageUptodate(page
))
1676 if (inode
->i_blkbits
== PAGE_CACHE_SHIFT
||
1677 !mapping
->a_ops
->is_partially_uptodate
)
1678 goto page_not_up_to_date
;
1679 if (!trylock_page(page
))
1680 goto page_not_up_to_date
;
1681 /* Did it get truncated before we got the lock? */
1683 goto page_not_up_to_date_locked
;
1684 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1685 offset
, iter
->count
))
1686 goto page_not_up_to_date_locked
;
1691 * i_size must be checked after we know the page is Uptodate.
1693 * Checking i_size after the check allows us to calculate
1694 * the correct value for "nr", which means the zero-filled
1695 * part of the page is not copied back to userspace (unless
1696 * another truncate extends the file - this is desired though).
1699 isize
= i_size_read(inode
);
1700 end_index
= (isize
- 1) >> PAGE_CACHE_SHIFT
;
1701 if (unlikely(!isize
|| index
> end_index
)) {
1702 page_cache_release(page
);
1706 /* nr is the maximum number of bytes to copy from this page */
1707 nr
= PAGE_CACHE_SIZE
;
1708 if (index
== end_index
) {
1709 nr
= ((isize
- 1) & ~PAGE_CACHE_MASK
) + 1;
1711 page_cache_release(page
);
1717 /* If users can be writing to this page using arbitrary
1718 * virtual addresses, take care about potential aliasing
1719 * before reading the page on the kernel side.
1721 if (mapping_writably_mapped(mapping
))
1722 flush_dcache_page(page
);
1725 * When a sequential read accesses a page several times,
1726 * only mark it as accessed the first time.
1728 if (prev_index
!= index
|| offset
!= prev_offset
)
1729 mark_page_accessed(page
);
1733 * Ok, we have the page, and it's up-to-date, so
1734 * now we can copy it to user space...
1737 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
1739 index
+= offset
>> PAGE_CACHE_SHIFT
;
1740 offset
&= ~PAGE_CACHE_MASK
;
1741 prev_offset
= offset
;
1743 page_cache_release(page
);
1745 if (!iov_iter_count(iter
))
1753 page_not_up_to_date
:
1754 /* Get exclusive access to the page ... */
1755 error
= lock_page_killable(page
);
1756 if (unlikely(error
))
1757 goto readpage_error
;
1759 page_not_up_to_date_locked
:
1760 /* Did it get truncated before we got the lock? */
1761 if (!page
->mapping
) {
1763 page_cache_release(page
);
1767 /* Did somebody else fill it already? */
1768 if (PageUptodate(page
)) {
1775 * A previous I/O error may have been due to temporary
1776 * failures, eg. multipath errors.
1777 * PG_error will be set again if readpage fails.
1779 ClearPageError(page
);
1780 /* Start the actual read. The read will unlock the page. */
1781 error
= mapping
->a_ops
->readpage(filp
, page
);
1783 if (unlikely(error
)) {
1784 if (error
== AOP_TRUNCATED_PAGE
) {
1785 page_cache_release(page
);
1789 goto readpage_error
;
1792 if (!PageUptodate(page
)) {
1793 error
= lock_page_killable(page
);
1794 if (unlikely(error
))
1795 goto readpage_error
;
1796 if (!PageUptodate(page
)) {
1797 if (page
->mapping
== NULL
) {
1799 * invalidate_mapping_pages got it
1802 page_cache_release(page
);
1806 shrink_readahead_size_eio(filp
, ra
);
1808 goto readpage_error
;
1816 /* UHHUH! A synchronous read error occurred. Report it */
1817 page_cache_release(page
);
1822 * Ok, it wasn't cached, so we need to create a new
1825 page
= page_cache_alloc_cold(mapping
);
1830 error
= add_to_page_cache_lru(page
, mapping
, index
,
1831 mapping_gfp_constraint(mapping
, GFP_KERNEL
));
1833 page_cache_release(page
);
1834 if (error
== -EEXIST
) {
1844 ra
->prev_pos
= prev_index
;
1845 ra
->prev_pos
<<= PAGE_CACHE_SHIFT
;
1846 ra
->prev_pos
|= prev_offset
;
1848 *ppos
= ((loff_t
)index
<< PAGE_CACHE_SHIFT
) + offset
;
1849 file_accessed(filp
);
1850 return written
? written
: error
;
1854 * generic_file_read_iter - generic filesystem read routine
1855 * @iocb: kernel I/O control block
1856 * @iter: destination for the data read
1858 * This is the "read_iter()" routine for all filesystems
1859 * that can use the page cache directly.
1862 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
1864 struct file
*file
= iocb
->ki_filp
;
1866 loff_t
*ppos
= &iocb
->ki_pos
;
1869 if (iocb
->ki_flags
& IOCB_DIRECT
) {
1870 struct address_space
*mapping
= file
->f_mapping
;
1871 struct inode
*inode
= mapping
->host
;
1872 size_t count
= iov_iter_count(iter
);
1876 goto out
; /* skip atime */
1877 size
= i_size_read(inode
);
1878 retval
= filemap_write_and_wait_range(mapping
, pos
,
1881 struct iov_iter data
= *iter
;
1882 retval
= mapping
->a_ops
->direct_IO(iocb
, &data
, pos
);
1886 *ppos
= pos
+ retval
;
1887 iov_iter_advance(iter
, retval
);
1891 * Btrfs can have a short DIO read if we encounter
1892 * compressed extents, so if there was an error, or if
1893 * we've already read everything we wanted to, or if
1894 * there was a short read because we hit EOF, go ahead
1895 * and return. Otherwise fallthrough to buffered io for
1896 * the rest of the read. Buffered reads will not work for
1897 * DAX files, so don't bother trying.
1899 if (retval
< 0 || !iov_iter_count(iter
) || *ppos
>= size
||
1901 file_accessed(file
);
1906 retval
= do_generic_file_read(file
, ppos
, iter
, retval
);
1910 EXPORT_SYMBOL(generic_file_read_iter
);
1914 * page_cache_read - adds requested page to the page cache if not already there
1915 * @file: file to read
1916 * @offset: page index
1917 * @gfp_mask: memory allocation flags
1919 * This adds the requested page to the page cache if it isn't already there,
1920 * and schedules an I/O to read in its contents from disk.
1922 static int page_cache_read(struct file
*file
, pgoff_t offset
, gfp_t gfp_mask
)
1924 struct address_space
*mapping
= file
->f_mapping
;
1929 page
= __page_cache_alloc(gfp_mask
|__GFP_COLD
);
1933 ret
= add_to_page_cache_lru(page
, mapping
, offset
, gfp_mask
& GFP_KERNEL
);
1935 ret
= mapping
->a_ops
->readpage(file
, page
);
1936 else if (ret
== -EEXIST
)
1937 ret
= 0; /* losing race to add is OK */
1939 page_cache_release(page
);
1941 } while (ret
== AOP_TRUNCATED_PAGE
);
1946 #define MMAP_LOTSAMISS (100)
1949 * Synchronous readahead happens when we don't even find
1950 * a page in the page cache at all.
1952 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
1953 struct file_ra_state
*ra
,
1957 struct address_space
*mapping
= file
->f_mapping
;
1959 /* If we don't want any read-ahead, don't bother */
1960 if (vma
->vm_flags
& VM_RAND_READ
)
1965 if (vma
->vm_flags
& VM_SEQ_READ
) {
1966 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
1971 /* Avoid banging the cache line if not needed */
1972 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
1976 * Do we miss much more than hit in this file? If so,
1977 * stop bothering with read-ahead. It will only hurt.
1979 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
1985 ra
->start
= max_t(long, 0, offset
- ra
->ra_pages
/ 2);
1986 ra
->size
= ra
->ra_pages
;
1987 ra
->async_size
= ra
->ra_pages
/ 4;
1988 ra_submit(ra
, mapping
, file
);
1992 * Asynchronous readahead happens when we find the page and PG_readahead,
1993 * so we want to possibly extend the readahead further..
1995 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
1996 struct file_ra_state
*ra
,
2001 struct address_space
*mapping
= file
->f_mapping
;
2003 /* If we don't want any read-ahead, don't bother */
2004 if (vma
->vm_flags
& VM_RAND_READ
)
2006 if (ra
->mmap_miss
> 0)
2008 if (PageReadahead(page
))
2009 page_cache_async_readahead(mapping
, ra
, file
,
2010 page
, offset
, ra
->ra_pages
);
2014 * filemap_fault - read in file data for page fault handling
2015 * @vma: vma in which the fault was taken
2016 * @vmf: struct vm_fault containing details of the fault
2018 * filemap_fault() is invoked via the vma operations vector for a
2019 * mapped memory region to read in file data during a page fault.
2021 * The goto's are kind of ugly, but this streamlines the normal case of having
2022 * it in the page cache, and handles the special cases reasonably without
2023 * having a lot of duplicated code.
2025 * vma->vm_mm->mmap_sem must be held on entry.
2027 * If our return value has VM_FAULT_RETRY set, it's because
2028 * lock_page_or_retry() returned 0.
2029 * The mmap_sem has usually been released in this case.
2030 * See __lock_page_or_retry() for the exception.
2032 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2033 * has not been released.
2035 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2037 int filemap_fault(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2040 struct file
*file
= vma
->vm_file
;
2041 struct address_space
*mapping
= file
->f_mapping
;
2042 struct file_ra_state
*ra
= &file
->f_ra
;
2043 struct inode
*inode
= mapping
->host
;
2044 pgoff_t offset
= vmf
->pgoff
;
2049 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
2050 if (offset
>= size
>> PAGE_CACHE_SHIFT
)
2051 return VM_FAULT_SIGBUS
;
2054 * Do we have something in the page cache already?
2056 page
= find_get_page(mapping
, offset
);
2057 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
2059 * We found the page, so try async readahead before
2060 * waiting for the lock.
2062 do_async_mmap_readahead(vma
, ra
, file
, page
, offset
);
2064 /* No page in the page cache at all */
2065 do_sync_mmap_readahead(vma
, ra
, file
, offset
);
2066 count_vm_event(PGMAJFAULT
);
2067 mem_cgroup_count_vm_event(vma
->vm_mm
, PGMAJFAULT
);
2068 ret
= VM_FAULT_MAJOR
;
2070 page
= find_get_page(mapping
, offset
);
2072 goto no_cached_page
;
2075 if (!lock_page_or_retry(page
, vma
->vm_mm
, vmf
->flags
)) {
2076 page_cache_release(page
);
2077 return ret
| VM_FAULT_RETRY
;
2080 /* Did it get truncated? */
2081 if (unlikely(page
->mapping
!= mapping
)) {
2086 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
2089 * We have a locked page in the page cache, now we need to check
2090 * that it's up-to-date. If not, it is going to be due to an error.
2092 if (unlikely(!PageUptodate(page
)))
2093 goto page_not_uptodate
;
2096 * Found the page and have a reference on it.
2097 * We must recheck i_size under page lock.
2099 size
= round_up(i_size_read(inode
), PAGE_CACHE_SIZE
);
2100 if (unlikely(offset
>= size
>> PAGE_CACHE_SHIFT
)) {
2102 page_cache_release(page
);
2103 return VM_FAULT_SIGBUS
;
2107 return ret
| VM_FAULT_LOCKED
;
2111 * We're only likely to ever get here if MADV_RANDOM is in
2114 error
= page_cache_read(file
, offset
, vmf
->gfp_mask
);
2117 * The page we want has now been added to the page cache.
2118 * In the unlikely event that someone removed it in the
2119 * meantime, we'll just come back here and read it again.
2125 * An error return from page_cache_read can result if the
2126 * system is low on memory, or a problem occurs while trying
2129 if (error
== -ENOMEM
)
2130 return VM_FAULT_OOM
;
2131 return VM_FAULT_SIGBUS
;
2135 * Umm, take care of errors if the page isn't up-to-date.
2136 * Try to re-read it _once_. We do this synchronously,
2137 * because there really aren't any performance issues here
2138 * and we need to check for errors.
2140 ClearPageError(page
);
2141 error
= mapping
->a_ops
->readpage(file
, page
);
2143 wait_on_page_locked(page
);
2144 if (!PageUptodate(page
))
2147 page_cache_release(page
);
2149 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2152 /* Things didn't work out. Return zero to tell the mm layer so. */
2153 shrink_readahead_size_eio(file
, ra
);
2154 return VM_FAULT_SIGBUS
;
2156 EXPORT_SYMBOL(filemap_fault
);
2158 void filemap_map_pages(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2160 struct radix_tree_iter iter
;
2162 struct file
*file
= vma
->vm_file
;
2163 struct address_space
*mapping
= file
->f_mapping
;
2166 unsigned long address
= (unsigned long) vmf
->virtual_address
;
2171 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, vmf
->pgoff
) {
2172 if (iter
.index
> vmf
->max_pgoff
)
2175 page
= radix_tree_deref_slot(slot
);
2176 if (unlikely(!page
))
2178 if (radix_tree_exception(page
)) {
2179 if (radix_tree_deref_retry(page
))
2185 if (!page_cache_get_speculative(page
))
2188 /* Has the page moved? */
2189 if (unlikely(page
!= *slot
)) {
2190 page_cache_release(page
);
2194 if (!PageUptodate(page
) ||
2195 PageReadahead(page
) ||
2198 if (!trylock_page(page
))
2201 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2204 size
= round_up(i_size_read(mapping
->host
), PAGE_CACHE_SIZE
);
2205 if (page
->index
>= size
>> PAGE_CACHE_SHIFT
)
2208 pte
= vmf
->pte
+ page
->index
- vmf
->pgoff
;
2209 if (!pte_none(*pte
))
2212 if (file
->f_ra
.mmap_miss
> 0)
2213 file
->f_ra
.mmap_miss
--;
2214 addr
= address
+ (page
->index
- vmf
->pgoff
) * PAGE_SIZE
;
2215 do_set_pte(vma
, addr
, page
, pte
, false, false);
2221 page_cache_release(page
);
2223 if (iter
.index
== vmf
->max_pgoff
)
2228 EXPORT_SYMBOL(filemap_map_pages
);
2230 int filemap_page_mkwrite(struct vm_area_struct
*vma
, struct vm_fault
*vmf
)
2232 struct page
*page
= vmf
->page
;
2233 struct inode
*inode
= file_inode(vma
->vm_file
);
2234 int ret
= VM_FAULT_LOCKED
;
2236 sb_start_pagefault(inode
->i_sb
);
2237 file_update_time(vma
->vm_file
);
2239 if (page
->mapping
!= inode
->i_mapping
) {
2241 ret
= VM_FAULT_NOPAGE
;
2245 * We mark the page dirty already here so that when freeze is in
2246 * progress, we are guaranteed that writeback during freezing will
2247 * see the dirty page and writeprotect it again.
2249 set_page_dirty(page
);
2250 wait_for_stable_page(page
);
2252 sb_end_pagefault(inode
->i_sb
);
2255 EXPORT_SYMBOL(filemap_page_mkwrite
);
2257 const struct vm_operations_struct generic_file_vm_ops
= {
2258 .fault
= filemap_fault
,
2259 .map_pages
= filemap_map_pages
,
2260 .page_mkwrite
= filemap_page_mkwrite
,
2263 /* This is used for a general mmap of a disk file */
2265 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2267 struct address_space
*mapping
= file
->f_mapping
;
2269 if (!mapping
->a_ops
->readpage
)
2271 file_accessed(file
);
2272 vma
->vm_ops
= &generic_file_vm_ops
;
2277 * This is for filesystems which do not implement ->writepage.
2279 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2281 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2283 return generic_file_mmap(file
, vma
);
2286 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2290 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2294 #endif /* CONFIG_MMU */
2296 EXPORT_SYMBOL(generic_file_mmap
);
2297 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2299 static struct page
*wait_on_page_read(struct page
*page
)
2301 if (!IS_ERR(page
)) {
2302 wait_on_page_locked(page
);
2303 if (!PageUptodate(page
)) {
2304 page_cache_release(page
);
2305 page
= ERR_PTR(-EIO
);
2311 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2313 int (*filler
)(void *, struct page
*),
2320 page
= find_get_page(mapping
, index
);
2322 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2324 return ERR_PTR(-ENOMEM
);
2325 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2326 if (unlikely(err
)) {
2327 page_cache_release(page
);
2330 /* Presumably ENOMEM for radix tree node */
2331 return ERR_PTR(err
);
2335 err
= filler(data
, page
);
2337 page_cache_release(page
);
2338 return ERR_PTR(err
);
2341 page
= wait_on_page_read(page
);
2346 if (PageUptodate(page
))
2350 * Page is not up to date and may be locked due one of the following
2351 * case a: Page is being filled and the page lock is held
2352 * case b: Read/write error clearing the page uptodate status
2353 * case c: Truncation in progress (page locked)
2354 * case d: Reclaim in progress
2356 * Case a, the page will be up to date when the page is unlocked.
2357 * There is no need to serialise on the page lock here as the page
2358 * is pinned so the lock gives no additional protection. Even if the
2359 * the page is truncated, the data is still valid if PageUptodate as
2360 * it's a race vs truncate race.
2361 * Case b, the page will not be up to date
2362 * Case c, the page may be truncated but in itself, the data may still
2363 * be valid after IO completes as it's a read vs truncate race. The
2364 * operation must restart if the page is not uptodate on unlock but
2365 * otherwise serialising on page lock to stabilise the mapping gives
2366 * no additional guarantees to the caller as the page lock is
2367 * released before return.
2368 * Case d, similar to truncation. If reclaim holds the page lock, it
2369 * will be a race with remove_mapping that determines if the mapping
2370 * is valid on unlock but otherwise the data is valid and there is
2371 * no need to serialise with page lock.
2373 * As the page lock gives no additional guarantee, we optimistically
2374 * wait on the page to be unlocked and check if it's up to date and
2375 * use the page if it is. Otherwise, the page lock is required to
2376 * distinguish between the different cases. The motivation is that we
2377 * avoid spurious serialisations and wakeups when multiple processes
2378 * wait on the same page for IO to complete.
2380 wait_on_page_locked(page
);
2381 if (PageUptodate(page
))
2384 /* Distinguish between all the cases under the safety of the lock */
2387 /* Case c or d, restart the operation */
2388 if (!page
->mapping
) {
2390 page_cache_release(page
);
2394 /* Someone else locked and filled the page in a very small window */
2395 if (PageUptodate(page
)) {
2402 mark_page_accessed(page
);
2407 * read_cache_page - read into page cache, fill it if needed
2408 * @mapping: the page's address_space
2409 * @index: the page index
2410 * @filler: function to perform the read
2411 * @data: first arg to filler(data, page) function, often left as NULL
2413 * Read into the page cache. If a page already exists, and PageUptodate() is
2414 * not set, try to fill the page and wait for it to become unlocked.
2416 * If the page does not get brought uptodate, return -EIO.
2418 struct page
*read_cache_page(struct address_space
*mapping
,
2420 int (*filler
)(void *, struct page
*),
2423 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2425 EXPORT_SYMBOL(read_cache_page
);
2428 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2429 * @mapping: the page's address_space
2430 * @index: the page index
2431 * @gfp: the page allocator flags to use if allocating
2433 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2434 * any new page allocations done using the specified allocation flags.
2436 * If the page does not get brought uptodate, return -EIO.
2438 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2442 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2444 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2446 EXPORT_SYMBOL(read_cache_page_gfp
);
2449 * Performs necessary checks before doing a write
2451 * Can adjust writing position or amount of bytes to write.
2452 * Returns appropriate error code that caller should return or
2453 * zero in case that write should be allowed.
2455 inline ssize_t
generic_write_checks(struct kiocb
*iocb
, struct iov_iter
*from
)
2457 struct file
*file
= iocb
->ki_filp
;
2458 struct inode
*inode
= file
->f_mapping
->host
;
2459 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2462 if (!iov_iter_count(from
))
2465 /* FIXME: this is for backwards compatibility with 2.4 */
2466 if (iocb
->ki_flags
& IOCB_APPEND
)
2467 iocb
->ki_pos
= i_size_read(inode
);
2471 if (limit
!= RLIM_INFINITY
) {
2472 if (iocb
->ki_pos
>= limit
) {
2473 send_sig(SIGXFSZ
, current
, 0);
2476 iov_iter_truncate(from
, limit
- (unsigned long)pos
);
2482 if (unlikely(pos
+ iov_iter_count(from
) > MAX_NON_LFS
&&
2483 !(file
->f_flags
& O_LARGEFILE
))) {
2484 if (pos
>= MAX_NON_LFS
)
2486 iov_iter_truncate(from
, MAX_NON_LFS
- (unsigned long)pos
);
2490 * Are we about to exceed the fs block limit ?
2492 * If we have written data it becomes a short write. If we have
2493 * exceeded without writing data we send a signal and return EFBIG.
2494 * Linus frestrict idea will clean these up nicely..
2496 if (unlikely(pos
>= inode
->i_sb
->s_maxbytes
))
2499 iov_iter_truncate(from
, inode
->i_sb
->s_maxbytes
- pos
);
2500 return iov_iter_count(from
);
2502 EXPORT_SYMBOL(generic_write_checks
);
2504 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2505 loff_t pos
, unsigned len
, unsigned flags
,
2506 struct page
**pagep
, void **fsdata
)
2508 const struct address_space_operations
*aops
= mapping
->a_ops
;
2510 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2513 EXPORT_SYMBOL(pagecache_write_begin
);
2515 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2516 loff_t pos
, unsigned len
, unsigned copied
,
2517 struct page
*page
, void *fsdata
)
2519 const struct address_space_operations
*aops
= mapping
->a_ops
;
2521 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2523 EXPORT_SYMBOL(pagecache_write_end
);
2526 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
, loff_t pos
)
2528 struct file
*file
= iocb
->ki_filp
;
2529 struct address_space
*mapping
= file
->f_mapping
;
2530 struct inode
*inode
= mapping
->host
;
2534 struct iov_iter data
;
2536 write_len
= iov_iter_count(from
);
2537 end
= (pos
+ write_len
- 1) >> PAGE_CACHE_SHIFT
;
2539 written
= filemap_write_and_wait_range(mapping
, pos
, pos
+ write_len
- 1);
2544 * After a write we want buffered reads to be sure to go to disk to get
2545 * the new data. We invalidate clean cached page from the region we're
2546 * about to write. We do this *before* the write so that we can return
2547 * without clobbering -EIOCBQUEUED from ->direct_IO().
2549 if (mapping
->nrpages
) {
2550 written
= invalidate_inode_pages2_range(mapping
,
2551 pos
>> PAGE_CACHE_SHIFT
, end
);
2553 * If a page can not be invalidated, return 0 to fall back
2554 * to buffered write.
2557 if (written
== -EBUSY
)
2564 written
= mapping
->a_ops
->direct_IO(iocb
, &data
, pos
);
2567 * Finally, try again to invalidate clean pages which might have been
2568 * cached by non-direct readahead, or faulted in by get_user_pages()
2569 * if the source of the write was an mmap'ed region of the file
2570 * we're writing. Either one is a pretty crazy thing to do,
2571 * so we don't support it 100%. If this invalidation
2572 * fails, tough, the write still worked...
2574 if (mapping
->nrpages
) {
2575 invalidate_inode_pages2_range(mapping
,
2576 pos
>> PAGE_CACHE_SHIFT
, end
);
2581 iov_iter_advance(from
, written
);
2582 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2583 i_size_write(inode
, pos
);
2584 mark_inode_dirty(inode
);
2591 EXPORT_SYMBOL(generic_file_direct_write
);
2594 * Find or create a page at the given pagecache position. Return the locked
2595 * page. This function is specifically for buffered writes.
2597 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2598 pgoff_t index
, unsigned flags
)
2601 int fgp_flags
= FGP_LOCK
|FGP_ACCESSED
|FGP_WRITE
|FGP_CREAT
;
2603 if (flags
& AOP_FLAG_NOFS
)
2604 fgp_flags
|= FGP_NOFS
;
2606 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2607 mapping_gfp_mask(mapping
));
2609 wait_for_stable_page(page
);
2613 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2615 ssize_t
generic_perform_write(struct file
*file
,
2616 struct iov_iter
*i
, loff_t pos
)
2618 struct address_space
*mapping
= file
->f_mapping
;
2619 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2621 ssize_t written
= 0;
2622 unsigned int flags
= 0;
2625 * Copies from kernel address space cannot fail (NFSD is a big user).
2627 if (!iter_is_iovec(i
))
2628 flags
|= AOP_FLAG_UNINTERRUPTIBLE
;
2632 unsigned long offset
; /* Offset into pagecache page */
2633 unsigned long bytes
; /* Bytes to write to page */
2634 size_t copied
; /* Bytes copied from user */
2637 offset
= (pos
& (PAGE_CACHE_SIZE
- 1));
2638 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2643 * Bring in the user page that we will copy from _first_.
2644 * Otherwise there's a nasty deadlock on copying from the
2645 * same page as we're writing to, without it being marked
2648 * Not only is this an optimisation, but it is also required
2649 * to check that the address is actually valid, when atomic
2650 * usercopies are used, below.
2652 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2657 if (fatal_signal_pending(current
)) {
2662 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2664 if (unlikely(status
< 0))
2667 if (mapping_writably_mapped(mapping
))
2668 flush_dcache_page(page
);
2670 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2671 flush_dcache_page(page
);
2673 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2675 if (unlikely(status
< 0))
2681 iov_iter_advance(i
, copied
);
2682 if (unlikely(copied
== 0)) {
2684 * If we were unable to copy any data at all, we must
2685 * fall back to a single segment length write.
2687 * If we didn't fallback here, we could livelock
2688 * because not all segments in the iov can be copied at
2689 * once without a pagefault.
2691 bytes
= min_t(unsigned long, PAGE_CACHE_SIZE
- offset
,
2692 iov_iter_single_seg_count(i
));
2698 balance_dirty_pages_ratelimited(mapping
);
2699 } while (iov_iter_count(i
));
2701 return written
? written
: status
;
2703 EXPORT_SYMBOL(generic_perform_write
);
2706 * __generic_file_write_iter - write data to a file
2707 * @iocb: IO state structure (file, offset, etc.)
2708 * @from: iov_iter with data to write
2710 * This function does all the work needed for actually writing data to a
2711 * file. It does all basic checks, removes SUID from the file, updates
2712 * modification times and calls proper subroutines depending on whether we
2713 * do direct IO or a standard buffered write.
2715 * It expects i_mutex to be grabbed unless we work on a block device or similar
2716 * object which does not need locking at all.
2718 * This function does *not* take care of syncing data in case of O_SYNC write.
2719 * A caller has to handle it. This is mainly due to the fact that we want to
2720 * avoid syncing under i_mutex.
2722 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2724 struct file
*file
= iocb
->ki_filp
;
2725 struct address_space
* mapping
= file
->f_mapping
;
2726 struct inode
*inode
= mapping
->host
;
2727 ssize_t written
= 0;
2731 /* We can write back this queue in page reclaim */
2732 current
->backing_dev_info
= inode_to_bdi(inode
);
2733 err
= file_remove_privs(file
);
2737 err
= file_update_time(file
);
2741 if (iocb
->ki_flags
& IOCB_DIRECT
) {
2742 loff_t pos
, endbyte
;
2744 written
= generic_file_direct_write(iocb
, from
, iocb
->ki_pos
);
2746 * If the write stopped short of completing, fall back to
2747 * buffered writes. Some filesystems do this for writes to
2748 * holes, for example. For DAX files, a buffered write will
2749 * not succeed (even if it did, DAX does not handle dirty
2750 * page-cache pages correctly).
2752 if (written
< 0 || !iov_iter_count(from
) || IS_DAX(inode
))
2755 status
= generic_perform_write(file
, from
, pos
= iocb
->ki_pos
);
2757 * If generic_perform_write() returned a synchronous error
2758 * then we want to return the number of bytes which were
2759 * direct-written, or the error code if that was zero. Note
2760 * that this differs from normal direct-io semantics, which
2761 * will return -EFOO even if some bytes were written.
2763 if (unlikely(status
< 0)) {
2768 * We need to ensure that the page cache pages are written to
2769 * disk and invalidated to preserve the expected O_DIRECT
2772 endbyte
= pos
+ status
- 1;
2773 err
= filemap_write_and_wait_range(mapping
, pos
, endbyte
);
2775 iocb
->ki_pos
= endbyte
+ 1;
2777 invalidate_mapping_pages(mapping
,
2778 pos
>> PAGE_CACHE_SHIFT
,
2779 endbyte
>> PAGE_CACHE_SHIFT
);
2782 * We don't know how much we wrote, so just return
2783 * the number of bytes which were direct-written
2787 written
= generic_perform_write(file
, from
, iocb
->ki_pos
);
2788 if (likely(written
> 0))
2789 iocb
->ki_pos
+= written
;
2792 current
->backing_dev_info
= NULL
;
2793 return written
? written
: err
;
2795 EXPORT_SYMBOL(__generic_file_write_iter
);
2798 * generic_file_write_iter - write data to a file
2799 * @iocb: IO state structure
2800 * @from: iov_iter with data to write
2802 * This is a wrapper around __generic_file_write_iter() to be used by most
2803 * filesystems. It takes care of syncing the file in case of O_SYNC file
2804 * and acquires i_mutex as needed.
2806 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
2808 struct file
*file
= iocb
->ki_filp
;
2809 struct inode
*inode
= file
->f_mapping
->host
;
2813 ret
= generic_write_checks(iocb
, from
);
2815 ret
= __generic_file_write_iter(iocb
, from
);
2816 inode_unlock(inode
);
2821 err
= generic_write_sync(file
, iocb
->ki_pos
- ret
, ret
);
2827 EXPORT_SYMBOL(generic_file_write_iter
);
2830 * try_to_release_page() - release old fs-specific metadata on a page
2832 * @page: the page which the kernel is trying to free
2833 * @gfp_mask: memory allocation flags (and I/O mode)
2835 * The address_space is to try to release any data against the page
2836 * (presumably at page->private). If the release was successful, return `1'.
2837 * Otherwise return zero.
2839 * This may also be called if PG_fscache is set on a page, indicating that the
2840 * page is known to the local caching routines.
2842 * The @gfp_mask argument specifies whether I/O may be performed to release
2843 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
2846 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
2848 struct address_space
* const mapping
= page
->mapping
;
2850 BUG_ON(!PageLocked(page
));
2851 if (PageWriteback(page
))
2854 if (mapping
&& mapping
->a_ops
->releasepage
)
2855 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
2856 return try_to_free_buffers(page
);
2859 EXPORT_SYMBOL(try_to_release_page
);