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/sched/signal.h>
17 #include <linux/uaccess.h>
18 #include <linux/capability.h>
19 #include <linux/kernel_stat.h>
20 #include <linux/gfp.h>
22 #include <linux/swap.h>
23 #include <linux/mman.h>
24 #include <linux/pagemap.h>
25 #include <linux/file.h>
26 #include <linux/uio.h>
27 #include <linux/hash.h>
28 #include <linux/writeback.h>
29 #include <linux/backing-dev.h>
30 #include <linux/pagevec.h>
31 #include <linux/blkdev.h>
32 #include <linux/security.h>
33 #include <linux/cpuset.h>
34 #include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
35 #include <linux/hugetlb.h>
36 #include <linux/memcontrol.h>
37 #include <linux/cleancache.h>
38 #include <linux/rmap.h>
41 #define CREATE_TRACE_POINTS
42 #include <trace/events/filemap.h>
45 * FIXME: remove all knowledge of the buffer layer from the core VM
47 #include <linux/buffer_head.h> /* for try_to_free_buffers */
52 * Shared mappings implemented 30.11.1994. It's not fully working yet,
55 * Shared mappings now work. 15.8.1995 Bruno.
57 * finished 'unifying' the page and buffer cache and SMP-threaded the
58 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
60 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
66 * ->i_mmap_rwsem (truncate_pagecache)
67 * ->private_lock (__free_pte->__set_page_dirty_buffers)
68 * ->swap_lock (exclusive_swap_page, others)
69 * ->mapping->tree_lock
72 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
76 * ->page_table_lock or pte_lock (various, mainly in memory.c)
77 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
80 * ->lock_page (access_process_vm)
82 * ->i_mutex (generic_perform_write)
83 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
86 * sb_lock (fs/fs-writeback.c)
87 * ->mapping->tree_lock (__sync_single_inode)
90 * ->anon_vma.lock (vma_adjust)
93 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
95 * ->page_table_lock or pte_lock
96 * ->swap_lock (try_to_unmap_one)
97 * ->private_lock (try_to_unmap_one)
98 * ->tree_lock (try_to_unmap_one)
99 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
100 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
101 * ->private_lock (page_remove_rmap->set_page_dirty)
102 * ->tree_lock (page_remove_rmap->set_page_dirty)
103 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
104 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
105 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
106 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
107 * ->inode->i_lock (zap_pte_range->set_page_dirty)
108 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
111 * ->tasklist_lock (memory_failure, collect_procs_ao)
114 static int page_cache_tree_insert(struct address_space
*mapping
,
115 struct page
*page
, void **shadowp
)
117 struct radix_tree_node
*node
;
121 error
= __radix_tree_create(&mapping
->page_tree
, page
->index
, 0,
128 p
= radix_tree_deref_slot_protected(slot
, &mapping
->tree_lock
);
129 if (!radix_tree_exceptional_entry(p
))
132 mapping
->nrexceptional
--;
136 __radix_tree_replace(&mapping
->page_tree
, node
, slot
, page
,
137 workingset_update_node
, mapping
);
142 static void page_cache_tree_delete(struct address_space
*mapping
,
143 struct page
*page
, void *shadow
)
147 /* hugetlb pages are represented by one entry in the radix tree */
148 nr
= PageHuge(page
) ? 1 : hpage_nr_pages(page
);
150 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
151 VM_BUG_ON_PAGE(PageTail(page
), page
);
152 VM_BUG_ON_PAGE(nr
!= 1 && shadow
, page
);
154 for (i
= 0; i
< nr
; i
++) {
155 struct radix_tree_node
*node
;
158 __radix_tree_lookup(&mapping
->page_tree
, page
->index
+ i
,
161 VM_BUG_ON_PAGE(!node
&& nr
!= 1, page
);
163 radix_tree_clear_tags(&mapping
->page_tree
, node
, slot
);
164 __radix_tree_replace(&mapping
->page_tree
, node
, slot
, shadow
,
165 workingset_update_node
, mapping
);
169 mapping
->nrexceptional
+= nr
;
171 * Make sure the nrexceptional update is committed before
172 * the nrpages update so that final truncate racing
173 * with reclaim does not see both counters 0 at the
174 * same time and miss a shadow entry.
178 mapping
->nrpages
-= nr
;
182 * Delete a page from the page cache and free it. Caller has to make
183 * sure the page is locked and that nobody else uses it - or that usage
184 * is safe. The caller must hold the mapping's tree_lock.
186 void __delete_from_page_cache(struct page
*page
, void *shadow
)
188 struct address_space
*mapping
= page
->mapping
;
189 int nr
= hpage_nr_pages(page
);
191 trace_mm_filemap_delete_from_page_cache(page
);
193 * if we're uptodate, flush out into the cleancache, otherwise
194 * invalidate any existing cleancache entries. We can't leave
195 * stale data around in the cleancache once our page is gone
197 if (PageUptodate(page
) && PageMappedToDisk(page
))
198 cleancache_put_page(page
);
200 cleancache_invalidate_page(mapping
, page
);
202 VM_BUG_ON_PAGE(PageTail(page
), page
);
203 VM_BUG_ON_PAGE(page_mapped(page
), page
);
204 if (!IS_ENABLED(CONFIG_DEBUG_VM
) && unlikely(page_mapped(page
))) {
207 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
208 current
->comm
, page_to_pfn(page
));
209 dump_page(page
, "still mapped when deleted");
211 add_taint(TAINT_BAD_PAGE
, LOCKDEP_NOW_UNRELIABLE
);
213 mapcount
= page_mapcount(page
);
214 if (mapping_exiting(mapping
) &&
215 page_count(page
) >= mapcount
+ 2) {
217 * All vmas have already been torn down, so it's
218 * a good bet that actually the page is unmapped,
219 * and we'd prefer not to leak it: if we're wrong,
220 * some other bad page check should catch it later.
222 page_mapcount_reset(page
);
223 page_ref_sub(page
, mapcount
);
227 page_cache_tree_delete(mapping
, page
, shadow
);
229 page
->mapping
= NULL
;
230 /* Leave page->index set: truncation lookup relies upon it */
232 /* hugetlb pages do not participate in page cache accounting. */
236 __mod_node_page_state(page_pgdat(page
), NR_FILE_PAGES
, -nr
);
237 if (PageSwapBacked(page
)) {
238 __mod_node_page_state(page_pgdat(page
), NR_SHMEM
, -nr
);
239 if (PageTransHuge(page
))
240 __dec_node_page_state(page
, NR_SHMEM_THPS
);
242 VM_BUG_ON_PAGE(PageTransHuge(page
), page
);
246 * At this point page must be either written or cleaned by truncate.
247 * Dirty page here signals a bug and loss of unwritten data.
249 * This fixes dirty accounting after removing the page entirely but
250 * leaves PageDirty set: it has no effect for truncated page and
251 * anyway will be cleared before returning page into buddy allocator.
253 if (WARN_ON_ONCE(PageDirty(page
)))
254 account_page_cleaned(page
, mapping
, inode_to_wb(mapping
->host
));
258 * delete_from_page_cache - delete page from page cache
259 * @page: the page which the kernel is trying to remove from page cache
261 * This must be called only on pages that have been verified to be in the page
262 * cache and locked. It will never put the page into the free list, the caller
263 * has a reference on the page.
265 void delete_from_page_cache(struct page
*page
)
267 struct address_space
*mapping
= page_mapping(page
);
269 void (*freepage
)(struct page
*);
271 BUG_ON(!PageLocked(page
));
273 freepage
= mapping
->a_ops
->freepage
;
275 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
276 __delete_from_page_cache(page
, NULL
);
277 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
282 if (PageTransHuge(page
) && !PageHuge(page
)) {
283 page_ref_sub(page
, HPAGE_PMD_NR
);
284 VM_BUG_ON_PAGE(page_count(page
) <= 0, page
);
289 EXPORT_SYMBOL(delete_from_page_cache
);
291 int filemap_check_errors(struct address_space
*mapping
)
294 /* Check for outstanding write errors */
295 if (test_bit(AS_ENOSPC
, &mapping
->flags
) &&
296 test_and_clear_bit(AS_ENOSPC
, &mapping
->flags
))
298 if (test_bit(AS_EIO
, &mapping
->flags
) &&
299 test_and_clear_bit(AS_EIO
, &mapping
->flags
))
303 EXPORT_SYMBOL(filemap_check_errors
);
305 static int filemap_check_and_keep_errors(struct address_space
*mapping
)
307 /* Check for outstanding write errors */
308 if (test_bit(AS_EIO
, &mapping
->flags
))
310 if (test_bit(AS_ENOSPC
, &mapping
->flags
))
316 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
317 * @mapping: address space structure to write
318 * @start: offset in bytes where the range starts
319 * @end: offset in bytes where the range ends (inclusive)
320 * @sync_mode: enable synchronous operation
322 * Start writeback against all of a mapping's dirty pages that lie
323 * within the byte offsets <start, end> inclusive.
325 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
326 * opposed to a regular memory cleansing writeback. The difference between
327 * these two operations is that if a dirty page/buffer is encountered, it must
328 * be waited upon, and not just skipped over.
330 int __filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
331 loff_t end
, int sync_mode
)
334 struct writeback_control wbc
= {
335 .sync_mode
= sync_mode
,
336 .nr_to_write
= LONG_MAX
,
337 .range_start
= start
,
341 if (!mapping_cap_writeback_dirty(mapping
))
344 wbc_attach_fdatawrite_inode(&wbc
, mapping
->host
);
345 ret
= do_writepages(mapping
, &wbc
);
346 wbc_detach_inode(&wbc
);
350 static inline int __filemap_fdatawrite(struct address_space
*mapping
,
353 return __filemap_fdatawrite_range(mapping
, 0, LLONG_MAX
, sync_mode
);
356 int filemap_fdatawrite(struct address_space
*mapping
)
358 return __filemap_fdatawrite(mapping
, WB_SYNC_ALL
);
360 EXPORT_SYMBOL(filemap_fdatawrite
);
362 int filemap_fdatawrite_range(struct address_space
*mapping
, loff_t start
,
365 return __filemap_fdatawrite_range(mapping
, start
, end
, WB_SYNC_ALL
);
367 EXPORT_SYMBOL(filemap_fdatawrite_range
);
370 * filemap_flush - mostly a non-blocking flush
371 * @mapping: target address_space
373 * This is a mostly non-blocking flush. Not suitable for data-integrity
374 * purposes - I/O may not be started against all dirty pages.
376 int filemap_flush(struct address_space
*mapping
)
378 return __filemap_fdatawrite(mapping
, WB_SYNC_NONE
);
380 EXPORT_SYMBOL(filemap_flush
);
383 * filemap_range_has_page - check if a page exists in range.
384 * @mapping: address space within which to check
385 * @start_byte: offset in bytes where the range starts
386 * @end_byte: offset in bytes where the range ends (inclusive)
388 * Find at least one page in the range supplied, usually used to check if
389 * direct writing in this range will trigger a writeback.
391 bool filemap_range_has_page(struct address_space
*mapping
,
392 loff_t start_byte
, loff_t end_byte
)
394 pgoff_t index
= start_byte
>> PAGE_SHIFT
;
395 pgoff_t end
= end_byte
>> PAGE_SHIFT
;
399 if (end_byte
< start_byte
)
402 if (mapping
->nrpages
== 0)
405 pagevec_init(&pvec
, 0);
406 if (!pagevec_lookup(&pvec
, mapping
, index
, 1))
408 ret
= (pvec
.pages
[0]->index
<= end
);
409 pagevec_release(&pvec
);
412 EXPORT_SYMBOL(filemap_range_has_page
);
414 static void __filemap_fdatawait_range(struct address_space
*mapping
,
415 loff_t start_byte
, loff_t end_byte
)
417 pgoff_t index
= start_byte
>> PAGE_SHIFT
;
418 pgoff_t end
= end_byte
>> PAGE_SHIFT
;
422 if (end_byte
< start_byte
)
425 pagevec_init(&pvec
, 0);
426 while ((index
<= end
) &&
427 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
428 PAGECACHE_TAG_WRITEBACK
,
429 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
432 for (i
= 0; i
< nr_pages
; i
++) {
433 struct page
*page
= pvec
.pages
[i
];
435 /* until radix tree lookup accepts end_index */
436 if (page
->index
> end
)
439 wait_on_page_writeback(page
);
440 ClearPageError(page
);
442 pagevec_release(&pvec
);
448 * filemap_fdatawait_range - wait for writeback to complete
449 * @mapping: address space structure to wait for
450 * @start_byte: offset in bytes where the range starts
451 * @end_byte: offset in bytes where the range ends (inclusive)
453 * Walk the list of under-writeback pages of the given address space
454 * in the given range and wait for all of them. Check error status of
455 * the address space and return it.
457 * Since the error status of the address space is cleared by this function,
458 * callers are responsible for checking the return value and handling and/or
459 * reporting the error.
461 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
464 __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
465 return filemap_check_errors(mapping
);
467 EXPORT_SYMBOL(filemap_fdatawait_range
);
470 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
471 * @mapping: address space structure to wait for
473 * Walk the list of under-writeback pages of the given address space
474 * and wait for all of them. Unlike filemap_fdatawait(), this function
475 * does not clear error status of the address space.
477 * Use this function if callers don't handle errors themselves. Expected
478 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
481 int filemap_fdatawait_keep_errors(struct address_space
*mapping
)
483 loff_t i_size
= i_size_read(mapping
->host
);
488 __filemap_fdatawait_range(mapping
, 0, i_size
- 1);
489 return filemap_check_and_keep_errors(mapping
);
491 EXPORT_SYMBOL(filemap_fdatawait_keep_errors
);
494 * filemap_fdatawait - wait for all under-writeback pages to complete
495 * @mapping: address space structure to wait for
497 * Walk the list of under-writeback pages of the given address space
498 * and wait for all of them. Check error status of the address space
501 * Since the error status of the address space is cleared by this function,
502 * callers are responsible for checking the return value and handling and/or
503 * reporting the error.
505 int filemap_fdatawait(struct address_space
*mapping
)
507 loff_t i_size
= i_size_read(mapping
->host
);
512 return filemap_fdatawait_range(mapping
, 0, i_size
- 1);
514 EXPORT_SYMBOL(filemap_fdatawait
);
516 int filemap_write_and_wait(struct address_space
*mapping
)
520 if ((!dax_mapping(mapping
) && mapping
->nrpages
) ||
521 (dax_mapping(mapping
) && mapping
->nrexceptional
)) {
522 err
= filemap_fdatawrite(mapping
);
524 * Even if the above returned error, the pages may be
525 * written partially (e.g. -ENOSPC), so we wait for it.
526 * But the -EIO is special case, it may indicate the worst
527 * thing (e.g. bug) happened, so we avoid waiting for it.
530 int err2
= filemap_fdatawait(mapping
);
534 /* Clear any previously stored errors */
535 filemap_check_errors(mapping
);
538 err
= filemap_check_errors(mapping
);
542 EXPORT_SYMBOL(filemap_write_and_wait
);
545 * filemap_write_and_wait_range - write out & wait on a file range
546 * @mapping: the address_space for the pages
547 * @lstart: offset in bytes where the range starts
548 * @lend: offset in bytes where the range ends (inclusive)
550 * Write out and wait upon file offsets lstart->lend, inclusive.
552 * Note that @lend is inclusive (describes the last byte to be written) so
553 * that this function can be used to write to the very end-of-file (end = -1).
555 int filemap_write_and_wait_range(struct address_space
*mapping
,
556 loff_t lstart
, loff_t lend
)
560 if ((!dax_mapping(mapping
) && mapping
->nrpages
) ||
561 (dax_mapping(mapping
) && mapping
->nrexceptional
)) {
562 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
564 /* See comment of filemap_write_and_wait() */
566 int err2
= filemap_fdatawait_range(mapping
,
571 /* Clear any previously stored errors */
572 filemap_check_errors(mapping
);
575 err
= filemap_check_errors(mapping
);
579 EXPORT_SYMBOL(filemap_write_and_wait_range
);
581 void __filemap_set_wb_err(struct address_space
*mapping
, int err
)
583 errseq_t eseq
= __errseq_set(&mapping
->wb_err
, err
);
585 trace_filemap_set_wb_err(mapping
, eseq
);
587 EXPORT_SYMBOL(__filemap_set_wb_err
);
590 * file_check_and_advance_wb_err - report wb error (if any) that was previously
591 * and advance wb_err to current one
592 * @file: struct file on which the error is being reported
594 * When userland calls fsync (or something like nfsd does the equivalent), we
595 * want to report any writeback errors that occurred since the last fsync (or
596 * since the file was opened if there haven't been any).
598 * Grab the wb_err from the mapping. If it matches what we have in the file,
599 * then just quickly return 0. The file is all caught up.
601 * If it doesn't match, then take the mapping value, set the "seen" flag in
602 * it and try to swap it into place. If it works, or another task beat us
603 * to it with the new value, then update the f_wb_err and return the error
604 * portion. The error at this point must be reported via proper channels
605 * (a'la fsync, or NFS COMMIT operation, etc.).
607 * While we handle mapping->wb_err with atomic operations, the f_wb_err
608 * value is protected by the f_lock since we must ensure that it reflects
609 * the latest value swapped in for this file descriptor.
611 int file_check_and_advance_wb_err(struct file
*file
)
614 errseq_t old
= READ_ONCE(file
->f_wb_err
);
615 struct address_space
*mapping
= file
->f_mapping
;
617 /* Locklessly handle the common case where nothing has changed */
618 if (errseq_check(&mapping
->wb_err
, old
)) {
619 /* Something changed, must use slow path */
620 spin_lock(&file
->f_lock
);
621 old
= file
->f_wb_err
;
622 err
= errseq_check_and_advance(&mapping
->wb_err
,
624 trace_file_check_and_advance_wb_err(file
, old
);
625 spin_unlock(&file
->f_lock
);
629 EXPORT_SYMBOL(file_check_and_advance_wb_err
);
632 * file_write_and_wait_range - write out & wait on a file range
633 * @file: file pointing to address_space with pages
634 * @lstart: offset in bytes where the range starts
635 * @lend: offset in bytes where the range ends (inclusive)
637 * Write out and wait upon file offsets lstart->lend, inclusive.
639 * Note that @lend is inclusive (describes the last byte to be written) so
640 * that this function can be used to write to the very end-of-file (end = -1).
642 * After writing out and waiting on the data, we check and advance the
643 * f_wb_err cursor to the latest value, and return any errors detected there.
645 int file_write_and_wait_range(struct file
*file
, loff_t lstart
, loff_t lend
)
648 struct address_space
*mapping
= file
->f_mapping
;
650 if ((!dax_mapping(mapping
) && mapping
->nrpages
) ||
651 (dax_mapping(mapping
) && mapping
->nrexceptional
)) {
652 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
654 /* See comment of filemap_write_and_wait() */
656 __filemap_fdatawait_range(mapping
, lstart
, lend
);
658 err2
= file_check_and_advance_wb_err(file
);
663 EXPORT_SYMBOL(file_write_and_wait_range
);
666 * replace_page_cache_page - replace a pagecache page with a new one
667 * @old: page to be replaced
668 * @new: page to replace with
669 * @gfp_mask: allocation mode
671 * This function replaces a page in the pagecache with a new one. On
672 * success it acquires the pagecache reference for the new page and
673 * drops it for the old page. Both the old and new pages must be
674 * locked. This function does not add the new page to the LRU, the
675 * caller must do that.
677 * The remove + add is atomic. The only way this function can fail is
678 * memory allocation failure.
680 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
684 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
685 VM_BUG_ON_PAGE(!PageLocked(new), new);
686 VM_BUG_ON_PAGE(new->mapping
, new);
688 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
690 struct address_space
*mapping
= old
->mapping
;
691 void (*freepage
)(struct page
*);
694 pgoff_t offset
= old
->index
;
695 freepage
= mapping
->a_ops
->freepage
;
698 new->mapping
= mapping
;
701 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
702 __delete_from_page_cache(old
, NULL
);
703 error
= page_cache_tree_insert(mapping
, new, NULL
);
707 * hugetlb pages do not participate in page cache accounting.
710 __inc_node_page_state(new, NR_FILE_PAGES
);
711 if (PageSwapBacked(new))
712 __inc_node_page_state(new, NR_SHMEM
);
713 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
714 mem_cgroup_migrate(old
, new);
715 radix_tree_preload_end();
723 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
725 static int __add_to_page_cache_locked(struct page
*page
,
726 struct address_space
*mapping
,
727 pgoff_t offset
, gfp_t gfp_mask
,
730 int huge
= PageHuge(page
);
731 struct mem_cgroup
*memcg
;
734 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
735 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
738 error
= mem_cgroup_try_charge(page
, current
->mm
,
739 gfp_mask
, &memcg
, false);
744 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
747 mem_cgroup_cancel_charge(page
, memcg
, false);
752 page
->mapping
= mapping
;
753 page
->index
= offset
;
755 spin_lock_irq(&mapping
->tree_lock
);
756 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
757 radix_tree_preload_end();
761 /* hugetlb pages do not participate in page cache accounting. */
763 __inc_node_page_state(page
, NR_FILE_PAGES
);
764 spin_unlock_irq(&mapping
->tree_lock
);
766 mem_cgroup_commit_charge(page
, memcg
, false, false);
767 trace_mm_filemap_add_to_page_cache(page
);
770 page
->mapping
= NULL
;
771 /* Leave page->index set: truncation relies upon it */
772 spin_unlock_irq(&mapping
->tree_lock
);
774 mem_cgroup_cancel_charge(page
, memcg
, false);
780 * add_to_page_cache_locked - add a locked page to the pagecache
782 * @mapping: the page's address_space
783 * @offset: page index
784 * @gfp_mask: page allocation mode
786 * This function is used to add a page to the pagecache. It must be locked.
787 * This function does not add the page to the LRU. The caller must do that.
789 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
790 pgoff_t offset
, gfp_t gfp_mask
)
792 return __add_to_page_cache_locked(page
, mapping
, offset
,
795 EXPORT_SYMBOL(add_to_page_cache_locked
);
797 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
798 pgoff_t offset
, gfp_t gfp_mask
)
803 __SetPageLocked(page
);
804 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
807 __ClearPageLocked(page
);
810 * The page might have been evicted from cache only
811 * recently, in which case it should be activated like
812 * any other repeatedly accessed page.
813 * The exception is pages getting rewritten; evicting other
814 * data from the working set, only to cache data that will
815 * get overwritten with something else, is a waste of memory.
817 if (!(gfp_mask
& __GFP_WRITE
) &&
818 shadow
&& workingset_refault(shadow
)) {
820 workingset_activation(page
);
822 ClearPageActive(page
);
827 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
830 struct page
*__page_cache_alloc(gfp_t gfp
)
835 if (cpuset_do_page_mem_spread()) {
836 unsigned int cpuset_mems_cookie
;
838 cpuset_mems_cookie
= read_mems_allowed_begin();
839 n
= cpuset_mem_spread_node();
840 page
= __alloc_pages_node(n
, gfp
, 0);
841 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
845 return alloc_pages(gfp
, 0);
847 EXPORT_SYMBOL(__page_cache_alloc
);
851 * In order to wait for pages to become available there must be
852 * waitqueues associated with pages. By using a hash table of
853 * waitqueues where the bucket discipline is to maintain all
854 * waiters on the same queue and wake all when any of the pages
855 * become available, and for the woken contexts to check to be
856 * sure the appropriate page became available, this saves space
857 * at a cost of "thundering herd" phenomena during rare hash
860 #define PAGE_WAIT_TABLE_BITS 8
861 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
862 static wait_queue_head_t page_wait_table
[PAGE_WAIT_TABLE_SIZE
] __cacheline_aligned
;
864 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
866 return &page_wait_table
[hash_ptr(page
, PAGE_WAIT_TABLE_BITS
)];
869 void __init
pagecache_init(void)
873 for (i
= 0; i
< PAGE_WAIT_TABLE_SIZE
; i
++)
874 init_waitqueue_head(&page_wait_table
[i
]);
876 page_writeback_init();
879 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
880 struct wait_page_key
{
886 struct wait_page_queue
{
889 wait_queue_entry_t wait
;
892 static int wake_page_function(wait_queue_entry_t
*wait
, unsigned mode
, int sync
, void *arg
)
894 struct wait_page_key
*key
= arg
;
895 struct wait_page_queue
*wait_page
896 = container_of(wait
, struct wait_page_queue
, wait
);
898 if (wait_page
->page
!= key
->page
)
902 if (wait_page
->bit_nr
!= key
->bit_nr
)
905 /* Stop walking if it's locked */
906 if (test_bit(key
->bit_nr
, &key
->page
->flags
))
909 return autoremove_wake_function(wait
, mode
, sync
, key
);
912 static void wake_up_page_bit(struct page
*page
, int bit_nr
)
914 wait_queue_head_t
*q
= page_waitqueue(page
);
915 struct wait_page_key key
;
922 spin_lock_irqsave(&q
->lock
, flags
);
923 __wake_up_locked_key(q
, TASK_NORMAL
, &key
);
925 * It is possible for other pages to have collided on the waitqueue
926 * hash, so in that case check for a page match. That prevents a long-
929 * It is still possible to miss a case here, when we woke page waiters
930 * and removed them from the waitqueue, but there are still other
933 if (!waitqueue_active(q
) || !key
.page_match
) {
934 ClearPageWaiters(page
);
936 * It's possible to miss clearing Waiters here, when we woke
937 * our page waiters, but the hashed waitqueue has waiters for
940 * That's okay, it's a rare case. The next waker will clear it.
943 spin_unlock_irqrestore(&q
->lock
, flags
);
946 static void wake_up_page(struct page
*page
, int bit
)
948 if (!PageWaiters(page
))
950 wake_up_page_bit(page
, bit
);
953 static inline int wait_on_page_bit_common(wait_queue_head_t
*q
,
954 struct page
*page
, int bit_nr
, int state
, bool lock
)
956 struct wait_page_queue wait_page
;
957 wait_queue_entry_t
*wait
= &wait_page
.wait
;
961 wait
->flags
= lock
? WQ_FLAG_EXCLUSIVE
: 0;
962 wait
->func
= wake_page_function
;
963 wait_page
.page
= page
;
964 wait_page
.bit_nr
= bit_nr
;
967 spin_lock_irq(&q
->lock
);
969 if (likely(list_empty(&wait
->entry
))) {
970 __add_wait_queue_entry_tail(q
, wait
);
971 SetPageWaiters(page
);
974 set_current_state(state
);
976 spin_unlock_irq(&q
->lock
);
978 if (likely(test_bit(bit_nr
, &page
->flags
))) {
983 if (!test_and_set_bit_lock(bit_nr
, &page
->flags
))
986 if (!test_bit(bit_nr
, &page
->flags
))
990 if (unlikely(signal_pending_state(state
, current
))) {
996 finish_wait(q
, wait
);
999 * A signal could leave PageWaiters set. Clearing it here if
1000 * !waitqueue_active would be possible (by open-coding finish_wait),
1001 * but still fail to catch it in the case of wait hash collision. We
1002 * already can fail to clear wait hash collision cases, so don't
1003 * bother with signals either.
1009 void wait_on_page_bit(struct page
*page
, int bit_nr
)
1011 wait_queue_head_t
*q
= page_waitqueue(page
);
1012 wait_on_page_bit_common(q
, page
, bit_nr
, TASK_UNINTERRUPTIBLE
, false);
1014 EXPORT_SYMBOL(wait_on_page_bit
);
1016 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
1018 wait_queue_head_t
*q
= page_waitqueue(page
);
1019 return wait_on_page_bit_common(q
, page
, bit_nr
, TASK_KILLABLE
, false);
1023 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1024 * @page: Page defining the wait queue of interest
1025 * @waiter: Waiter to add to the queue
1027 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1029 void add_page_wait_queue(struct page
*page
, wait_queue_entry_t
*waiter
)
1031 wait_queue_head_t
*q
= page_waitqueue(page
);
1032 unsigned long flags
;
1034 spin_lock_irqsave(&q
->lock
, flags
);
1035 __add_wait_queue_entry_tail(q
, waiter
);
1036 SetPageWaiters(page
);
1037 spin_unlock_irqrestore(&q
->lock
, flags
);
1039 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
1041 #ifndef clear_bit_unlock_is_negative_byte
1044 * PG_waiters is the high bit in the same byte as PG_lock.
1046 * On x86 (and on many other architectures), we can clear PG_lock and
1047 * test the sign bit at the same time. But if the architecture does
1048 * not support that special operation, we just do this all by hand
1051 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1052 * being cleared, but a memory barrier should be unneccssary since it is
1053 * in the same byte as PG_locked.
1055 static inline bool clear_bit_unlock_is_negative_byte(long nr
, volatile void *mem
)
1057 clear_bit_unlock(nr
, mem
);
1058 /* smp_mb__after_atomic(); */
1059 return test_bit(PG_waiters
, mem
);
1065 * unlock_page - unlock a locked page
1068 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1069 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1070 * mechanism between PageLocked pages and PageWriteback pages is shared.
1071 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1073 * Note that this depends on PG_waiters being the sign bit in the byte
1074 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1075 * clear the PG_locked bit and test PG_waiters at the same time fairly
1076 * portably (architectures that do LL/SC can test any bit, while x86 can
1077 * test the sign bit).
1079 void unlock_page(struct page
*page
)
1081 BUILD_BUG_ON(PG_waiters
!= 7);
1082 page
= compound_head(page
);
1083 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1084 if (clear_bit_unlock_is_negative_byte(PG_locked
, &page
->flags
))
1085 wake_up_page_bit(page
, PG_locked
);
1087 EXPORT_SYMBOL(unlock_page
);
1090 * end_page_writeback - end writeback against a page
1093 void end_page_writeback(struct page
*page
)
1096 * TestClearPageReclaim could be used here but it is an atomic
1097 * operation and overkill in this particular case. Failing to
1098 * shuffle a page marked for immediate reclaim is too mild to
1099 * justify taking an atomic operation penalty at the end of
1100 * ever page writeback.
1102 if (PageReclaim(page
)) {
1103 ClearPageReclaim(page
);
1104 rotate_reclaimable_page(page
);
1107 if (!test_clear_page_writeback(page
))
1110 smp_mb__after_atomic();
1111 wake_up_page(page
, PG_writeback
);
1113 EXPORT_SYMBOL(end_page_writeback
);
1116 * After completing I/O on a page, call this routine to update the page
1117 * flags appropriately
1119 void page_endio(struct page
*page
, bool is_write
, int err
)
1123 SetPageUptodate(page
);
1125 ClearPageUptodate(page
);
1131 struct address_space
*mapping
;
1134 mapping
= page_mapping(page
);
1136 mapping_set_error(mapping
, err
);
1138 end_page_writeback(page
);
1141 EXPORT_SYMBOL_GPL(page_endio
);
1144 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1145 * @__page: the page to lock
1147 void __lock_page(struct page
*__page
)
1149 struct page
*page
= compound_head(__page
);
1150 wait_queue_head_t
*q
= page_waitqueue(page
);
1151 wait_on_page_bit_common(q
, page
, PG_locked
, TASK_UNINTERRUPTIBLE
, true);
1153 EXPORT_SYMBOL(__lock_page
);
1155 int __lock_page_killable(struct page
*__page
)
1157 struct page
*page
= compound_head(__page
);
1158 wait_queue_head_t
*q
= page_waitqueue(page
);
1159 return wait_on_page_bit_common(q
, page
, PG_locked
, TASK_KILLABLE
, true);
1161 EXPORT_SYMBOL_GPL(__lock_page_killable
);
1165 * 1 - page is locked; mmap_sem is still held.
1166 * 0 - page is not locked.
1167 * mmap_sem has been released (up_read()), unless flags had both
1168 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1169 * which case mmap_sem is still held.
1171 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1172 * with the page locked and the mmap_sem unperturbed.
1174 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
1177 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1179 * CAUTION! In this case, mmap_sem is not released
1180 * even though return 0.
1182 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
1185 up_read(&mm
->mmap_sem
);
1186 if (flags
& FAULT_FLAG_KILLABLE
)
1187 wait_on_page_locked_killable(page
);
1189 wait_on_page_locked(page
);
1192 if (flags
& FAULT_FLAG_KILLABLE
) {
1195 ret
= __lock_page_killable(page
);
1197 up_read(&mm
->mmap_sem
);
1207 * page_cache_next_hole - find the next hole (not-present entry)
1210 * @max_scan: maximum range to search
1212 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1213 * lowest indexed hole.
1215 * Returns: the index of the hole if found, otherwise returns an index
1216 * outside of the set specified (in which case 'return - index >=
1217 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1220 * page_cache_next_hole may be called under rcu_read_lock. However,
1221 * like radix_tree_gang_lookup, this will not atomically search a
1222 * snapshot of the tree at a single point in time. For example, if a
1223 * hole is created at index 5, then subsequently a hole is created at
1224 * index 10, page_cache_next_hole covering both indexes may return 10
1225 * if called under rcu_read_lock.
1227 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
1228 pgoff_t index
, unsigned long max_scan
)
1232 for (i
= 0; i
< max_scan
; i
++) {
1235 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1236 if (!page
|| radix_tree_exceptional_entry(page
))
1245 EXPORT_SYMBOL(page_cache_next_hole
);
1248 * page_cache_prev_hole - find the prev hole (not-present entry)
1251 * @max_scan: maximum range to search
1253 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1256 * Returns: the index of the hole if found, otherwise returns an index
1257 * outside of the set specified (in which case 'index - return >=
1258 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1261 * page_cache_prev_hole may be called under rcu_read_lock. However,
1262 * like radix_tree_gang_lookup, this will not atomically search a
1263 * snapshot of the tree at a single point in time. For example, if a
1264 * hole is created at index 10, then subsequently a hole is created at
1265 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1266 * called under rcu_read_lock.
1268 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
1269 pgoff_t index
, unsigned long max_scan
)
1273 for (i
= 0; i
< max_scan
; i
++) {
1276 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1277 if (!page
|| radix_tree_exceptional_entry(page
))
1280 if (index
== ULONG_MAX
)
1286 EXPORT_SYMBOL(page_cache_prev_hole
);
1289 * find_get_entry - find and get a page cache entry
1290 * @mapping: the address_space to search
1291 * @offset: the page cache index
1293 * Looks up the page cache slot at @mapping & @offset. If there is a
1294 * page cache page, it is returned with an increased refcount.
1296 * If the slot holds a shadow entry of a previously evicted page, or a
1297 * swap entry from shmem/tmpfs, it is returned.
1299 * Otherwise, %NULL is returned.
1301 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
1304 struct page
*head
, *page
;
1309 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
1311 page
= radix_tree_deref_slot(pagep
);
1312 if (unlikely(!page
))
1314 if (radix_tree_exception(page
)) {
1315 if (radix_tree_deref_retry(page
))
1318 * A shadow entry of a recently evicted page,
1319 * or a swap entry from shmem/tmpfs. Return
1320 * it without attempting to raise page count.
1325 head
= compound_head(page
);
1326 if (!page_cache_get_speculative(head
))
1329 /* The page was split under us? */
1330 if (compound_head(page
) != head
) {
1336 * Has the page moved?
1337 * This is part of the lockless pagecache protocol. See
1338 * include/linux/pagemap.h for details.
1340 if (unlikely(page
!= *pagep
)) {
1350 EXPORT_SYMBOL(find_get_entry
);
1353 * find_lock_entry - locate, pin and lock a page cache entry
1354 * @mapping: the address_space to search
1355 * @offset: the page cache index
1357 * Looks up the page cache slot at @mapping & @offset. If there is a
1358 * page cache page, it is returned locked and with an increased
1361 * If the slot holds a shadow entry of a previously evicted page, or a
1362 * swap entry from shmem/tmpfs, it is returned.
1364 * Otherwise, %NULL is returned.
1366 * find_lock_entry() may sleep.
1368 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1373 page
= find_get_entry(mapping
, offset
);
1374 if (page
&& !radix_tree_exception(page
)) {
1376 /* Has the page been truncated? */
1377 if (unlikely(page_mapping(page
) != mapping
)) {
1382 VM_BUG_ON_PAGE(page_to_pgoff(page
) != offset
, page
);
1386 EXPORT_SYMBOL(find_lock_entry
);
1389 * pagecache_get_page - find and get a page reference
1390 * @mapping: the address_space to search
1391 * @offset: the page index
1392 * @fgp_flags: PCG flags
1393 * @gfp_mask: gfp mask to use for the page cache data page allocation
1395 * Looks up the page cache slot at @mapping & @offset.
1397 * PCG flags modify how the page is returned.
1399 * @fgp_flags can be:
1401 * - FGP_ACCESSED: the page will be marked accessed
1402 * - FGP_LOCK: Page is return locked
1403 * - FGP_CREAT: If page is not present then a new page is allocated using
1404 * @gfp_mask and added to the page cache and the VM's LRU
1405 * list. The page is returned locked and with an increased
1406 * refcount. Otherwise, NULL is returned.
1408 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1409 * if the GFP flags specified for FGP_CREAT are atomic.
1411 * If there is a page cache page, it is returned with an increased refcount.
1413 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1414 int fgp_flags
, gfp_t gfp_mask
)
1419 page
= find_get_entry(mapping
, offset
);
1420 if (radix_tree_exceptional_entry(page
))
1425 if (fgp_flags
& FGP_LOCK
) {
1426 if (fgp_flags
& FGP_NOWAIT
) {
1427 if (!trylock_page(page
)) {
1435 /* Has the page been truncated? */
1436 if (unlikely(page
->mapping
!= mapping
)) {
1441 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1444 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1445 mark_page_accessed(page
);
1448 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1450 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1451 gfp_mask
|= __GFP_WRITE
;
1452 if (fgp_flags
& FGP_NOFS
)
1453 gfp_mask
&= ~__GFP_FS
;
1455 page
= __page_cache_alloc(gfp_mask
);
1459 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1460 fgp_flags
|= FGP_LOCK
;
1462 /* Init accessed so avoid atomic mark_page_accessed later */
1463 if (fgp_flags
& FGP_ACCESSED
)
1464 __SetPageReferenced(page
);
1466 err
= add_to_page_cache_lru(page
, mapping
, offset
,
1467 gfp_mask
& GFP_RECLAIM_MASK
);
1468 if (unlikely(err
)) {
1478 EXPORT_SYMBOL(pagecache_get_page
);
1481 * find_get_entries - gang pagecache lookup
1482 * @mapping: The address_space to search
1483 * @start: The starting page cache index
1484 * @nr_entries: The maximum number of entries
1485 * @entries: Where the resulting entries are placed
1486 * @indices: The cache indices corresponding to the entries in @entries
1488 * find_get_entries() will search for and return a group of up to
1489 * @nr_entries entries in the mapping. The entries are placed at
1490 * @entries. find_get_entries() takes a reference against any actual
1493 * The search returns a group of mapping-contiguous page cache entries
1494 * with ascending indexes. There may be holes in the indices due to
1495 * not-present pages.
1497 * Any shadow entries of evicted pages, or swap entries from
1498 * shmem/tmpfs, are included in the returned array.
1500 * find_get_entries() returns the number of pages and shadow entries
1503 unsigned find_get_entries(struct address_space
*mapping
,
1504 pgoff_t start
, unsigned int nr_entries
,
1505 struct page
**entries
, pgoff_t
*indices
)
1508 unsigned int ret
= 0;
1509 struct radix_tree_iter iter
;
1515 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1516 struct page
*head
, *page
;
1518 page
= radix_tree_deref_slot(slot
);
1519 if (unlikely(!page
))
1521 if (radix_tree_exception(page
)) {
1522 if (radix_tree_deref_retry(page
)) {
1523 slot
= radix_tree_iter_retry(&iter
);
1527 * A shadow entry of a recently evicted page, a swap
1528 * entry from shmem/tmpfs or a DAX entry. Return it
1529 * without attempting to raise page count.
1534 head
= compound_head(page
);
1535 if (!page_cache_get_speculative(head
))
1538 /* The page was split under us? */
1539 if (compound_head(page
) != head
) {
1544 /* Has the page moved? */
1545 if (unlikely(page
!= *slot
)) {
1550 indices
[ret
] = iter
.index
;
1551 entries
[ret
] = page
;
1552 if (++ret
== nr_entries
)
1560 * find_get_pages - gang pagecache lookup
1561 * @mapping: The address_space to search
1562 * @start: The starting page index
1563 * @nr_pages: The maximum number of pages
1564 * @pages: Where the resulting pages are placed
1566 * find_get_pages() will search for and return a group of up to
1567 * @nr_pages pages in the mapping. The pages are placed at @pages.
1568 * find_get_pages() takes a reference against the returned pages.
1570 * The search returns a group of mapping-contiguous pages with ascending
1571 * indexes. There may be holes in the indices due to not-present pages.
1573 * find_get_pages() returns the number of pages which were found.
1575 unsigned find_get_pages(struct address_space
*mapping
, pgoff_t start
,
1576 unsigned int nr_pages
, struct page
**pages
)
1578 struct radix_tree_iter iter
;
1582 if (unlikely(!nr_pages
))
1586 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1587 struct page
*head
, *page
;
1589 page
= radix_tree_deref_slot(slot
);
1590 if (unlikely(!page
))
1593 if (radix_tree_exception(page
)) {
1594 if (radix_tree_deref_retry(page
)) {
1595 slot
= radix_tree_iter_retry(&iter
);
1599 * A shadow entry of a recently evicted page,
1600 * or a swap entry from shmem/tmpfs. Skip
1606 head
= compound_head(page
);
1607 if (!page_cache_get_speculative(head
))
1610 /* The page was split under us? */
1611 if (compound_head(page
) != head
) {
1616 /* Has the page moved? */
1617 if (unlikely(page
!= *slot
)) {
1623 if (++ret
== nr_pages
)
1632 * find_get_pages_contig - gang contiguous pagecache lookup
1633 * @mapping: The address_space to search
1634 * @index: The starting page index
1635 * @nr_pages: The maximum number of pages
1636 * @pages: Where the resulting pages are placed
1638 * find_get_pages_contig() works exactly like find_get_pages(), except
1639 * that the returned number of pages are guaranteed to be contiguous.
1641 * find_get_pages_contig() returns the number of pages which were found.
1643 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1644 unsigned int nr_pages
, struct page
**pages
)
1646 struct radix_tree_iter iter
;
1648 unsigned int ret
= 0;
1650 if (unlikely(!nr_pages
))
1654 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1655 struct page
*head
, *page
;
1657 page
= radix_tree_deref_slot(slot
);
1658 /* The hole, there no reason to continue */
1659 if (unlikely(!page
))
1662 if (radix_tree_exception(page
)) {
1663 if (radix_tree_deref_retry(page
)) {
1664 slot
= radix_tree_iter_retry(&iter
);
1668 * A shadow entry of a recently evicted page,
1669 * or a swap entry from shmem/tmpfs. Stop
1670 * looking for contiguous pages.
1675 head
= compound_head(page
);
1676 if (!page_cache_get_speculative(head
))
1679 /* The page was split under us? */
1680 if (compound_head(page
) != head
) {
1685 /* Has the page moved? */
1686 if (unlikely(page
!= *slot
)) {
1692 * must check mapping and index after taking the ref.
1693 * otherwise we can get both false positives and false
1694 * negatives, which is just confusing to the caller.
1696 if (page
->mapping
== NULL
|| page_to_pgoff(page
) != iter
.index
) {
1702 if (++ret
== nr_pages
)
1708 EXPORT_SYMBOL(find_get_pages_contig
);
1711 * find_get_pages_tag - find and return pages that match @tag
1712 * @mapping: the address_space to search
1713 * @index: the starting page index
1714 * @tag: the tag index
1715 * @nr_pages: the maximum number of pages
1716 * @pages: where the resulting pages are placed
1718 * Like find_get_pages, except we only return pages which are tagged with
1719 * @tag. We update @index to index the next page for the traversal.
1721 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1722 int tag
, unsigned int nr_pages
, struct page
**pages
)
1724 struct radix_tree_iter iter
;
1728 if (unlikely(!nr_pages
))
1732 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1733 &iter
, *index
, tag
) {
1734 struct page
*head
, *page
;
1736 page
= radix_tree_deref_slot(slot
);
1737 if (unlikely(!page
))
1740 if (radix_tree_exception(page
)) {
1741 if (radix_tree_deref_retry(page
)) {
1742 slot
= radix_tree_iter_retry(&iter
);
1746 * A shadow entry of a recently evicted page.
1748 * Those entries should never be tagged, but
1749 * this tree walk is lockless and the tags are
1750 * looked up in bulk, one radix tree node at a
1751 * time, so there is a sizable window for page
1752 * reclaim to evict a page we saw tagged.
1759 head
= compound_head(page
);
1760 if (!page_cache_get_speculative(head
))
1763 /* The page was split under us? */
1764 if (compound_head(page
) != head
) {
1769 /* Has the page moved? */
1770 if (unlikely(page
!= *slot
)) {
1776 if (++ret
== nr_pages
)
1783 *index
= pages
[ret
- 1]->index
+ 1;
1787 EXPORT_SYMBOL(find_get_pages_tag
);
1790 * find_get_entries_tag - find and return entries that match @tag
1791 * @mapping: the address_space to search
1792 * @start: the starting page cache index
1793 * @tag: the tag index
1794 * @nr_entries: the maximum number of entries
1795 * @entries: where the resulting entries are placed
1796 * @indices: the cache indices corresponding to the entries in @entries
1798 * Like find_get_entries, except we only return entries which are tagged with
1801 unsigned find_get_entries_tag(struct address_space
*mapping
, pgoff_t start
,
1802 int tag
, unsigned int nr_entries
,
1803 struct page
**entries
, pgoff_t
*indices
)
1806 unsigned int ret
= 0;
1807 struct radix_tree_iter iter
;
1813 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1814 &iter
, start
, tag
) {
1815 struct page
*head
, *page
;
1817 page
= radix_tree_deref_slot(slot
);
1818 if (unlikely(!page
))
1820 if (radix_tree_exception(page
)) {
1821 if (radix_tree_deref_retry(page
)) {
1822 slot
= radix_tree_iter_retry(&iter
);
1827 * A shadow entry of a recently evicted page, a swap
1828 * entry from shmem/tmpfs or a DAX entry. Return it
1829 * without attempting to raise page count.
1834 head
= compound_head(page
);
1835 if (!page_cache_get_speculative(head
))
1838 /* The page was split under us? */
1839 if (compound_head(page
) != head
) {
1844 /* Has the page moved? */
1845 if (unlikely(page
!= *slot
)) {
1850 indices
[ret
] = iter
.index
;
1851 entries
[ret
] = page
;
1852 if (++ret
== nr_entries
)
1858 EXPORT_SYMBOL(find_get_entries_tag
);
1861 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1862 * a _large_ part of the i/o request. Imagine the worst scenario:
1864 * ---R__________________________________________B__________
1865 * ^ reading here ^ bad block(assume 4k)
1867 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1868 * => failing the whole request => read(R) => read(R+1) =>
1869 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1870 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1871 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1873 * It is going insane. Fix it by quickly scaling down the readahead size.
1875 static void shrink_readahead_size_eio(struct file
*filp
,
1876 struct file_ra_state
*ra
)
1882 * do_generic_file_read - generic file read routine
1883 * @filp: the file to read
1884 * @ppos: current file position
1885 * @iter: data destination
1886 * @written: already copied
1888 * This is a generic file read routine, and uses the
1889 * mapping->a_ops->readpage() function for the actual low-level stuff.
1891 * This is really ugly. But the goto's actually try to clarify some
1892 * of the logic when it comes to error handling etc.
1894 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1895 struct iov_iter
*iter
, ssize_t written
)
1897 struct address_space
*mapping
= filp
->f_mapping
;
1898 struct inode
*inode
= mapping
->host
;
1899 struct file_ra_state
*ra
= &filp
->f_ra
;
1903 unsigned long offset
; /* offset into pagecache page */
1904 unsigned int prev_offset
;
1907 if (unlikely(*ppos
>= inode
->i_sb
->s_maxbytes
))
1909 iov_iter_truncate(iter
, inode
->i_sb
->s_maxbytes
);
1911 index
= *ppos
>> PAGE_SHIFT
;
1912 prev_index
= ra
->prev_pos
>> PAGE_SHIFT
;
1913 prev_offset
= ra
->prev_pos
& (PAGE_SIZE
-1);
1914 last_index
= (*ppos
+ iter
->count
+ PAGE_SIZE
-1) >> PAGE_SHIFT
;
1915 offset
= *ppos
& ~PAGE_MASK
;
1921 unsigned long nr
, ret
;
1925 if (fatal_signal_pending(current
)) {
1930 page
= find_get_page(mapping
, index
);
1932 page_cache_sync_readahead(mapping
,
1934 index
, last_index
- index
);
1935 page
= find_get_page(mapping
, index
);
1936 if (unlikely(page
== NULL
))
1937 goto no_cached_page
;
1939 if (PageReadahead(page
)) {
1940 page_cache_async_readahead(mapping
,
1942 index
, last_index
- index
);
1944 if (!PageUptodate(page
)) {
1946 * See comment in do_read_cache_page on why
1947 * wait_on_page_locked is used to avoid unnecessarily
1948 * serialisations and why it's safe.
1950 error
= wait_on_page_locked_killable(page
);
1951 if (unlikely(error
))
1952 goto readpage_error
;
1953 if (PageUptodate(page
))
1956 if (inode
->i_blkbits
== PAGE_SHIFT
||
1957 !mapping
->a_ops
->is_partially_uptodate
)
1958 goto page_not_up_to_date
;
1959 /* pipes can't handle partially uptodate pages */
1960 if (unlikely(iter
->type
& ITER_PIPE
))
1961 goto page_not_up_to_date
;
1962 if (!trylock_page(page
))
1963 goto page_not_up_to_date
;
1964 /* Did it get truncated before we got the lock? */
1966 goto page_not_up_to_date_locked
;
1967 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1968 offset
, iter
->count
))
1969 goto page_not_up_to_date_locked
;
1974 * i_size must be checked after we know the page is Uptodate.
1976 * Checking i_size after the check allows us to calculate
1977 * the correct value for "nr", which means the zero-filled
1978 * part of the page is not copied back to userspace (unless
1979 * another truncate extends the file - this is desired though).
1982 isize
= i_size_read(inode
);
1983 end_index
= (isize
- 1) >> PAGE_SHIFT
;
1984 if (unlikely(!isize
|| index
> end_index
)) {
1989 /* nr is the maximum number of bytes to copy from this page */
1991 if (index
== end_index
) {
1992 nr
= ((isize
- 1) & ~PAGE_MASK
) + 1;
2000 /* If users can be writing to this page using arbitrary
2001 * virtual addresses, take care about potential aliasing
2002 * before reading the page on the kernel side.
2004 if (mapping_writably_mapped(mapping
))
2005 flush_dcache_page(page
);
2008 * When a sequential read accesses a page several times,
2009 * only mark it as accessed the first time.
2011 if (prev_index
!= index
|| offset
!= prev_offset
)
2012 mark_page_accessed(page
);
2016 * Ok, we have the page, and it's up-to-date, so
2017 * now we can copy it to user space...
2020 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
2022 index
+= offset
>> PAGE_SHIFT
;
2023 offset
&= ~PAGE_MASK
;
2024 prev_offset
= offset
;
2028 if (!iov_iter_count(iter
))
2036 page_not_up_to_date
:
2037 /* Get exclusive access to the page ... */
2038 error
= lock_page_killable(page
);
2039 if (unlikely(error
))
2040 goto readpage_error
;
2042 page_not_up_to_date_locked
:
2043 /* Did it get truncated before we got the lock? */
2044 if (!page
->mapping
) {
2050 /* Did somebody else fill it already? */
2051 if (PageUptodate(page
)) {
2058 * A previous I/O error may have been due to temporary
2059 * failures, eg. multipath errors.
2060 * PG_error will be set again if readpage fails.
2062 ClearPageError(page
);
2063 /* Start the actual read. The read will unlock the page. */
2064 error
= mapping
->a_ops
->readpage(filp
, page
);
2066 if (unlikely(error
)) {
2067 if (error
== AOP_TRUNCATED_PAGE
) {
2072 goto readpage_error
;
2075 if (!PageUptodate(page
)) {
2076 error
= lock_page_killable(page
);
2077 if (unlikely(error
))
2078 goto readpage_error
;
2079 if (!PageUptodate(page
)) {
2080 if (page
->mapping
== NULL
) {
2082 * invalidate_mapping_pages got it
2089 shrink_readahead_size_eio(filp
, ra
);
2091 goto readpage_error
;
2099 /* UHHUH! A synchronous read error occurred. Report it */
2105 * Ok, it wasn't cached, so we need to create a new
2108 page
= page_cache_alloc_cold(mapping
);
2113 error
= add_to_page_cache_lru(page
, mapping
, index
,
2114 mapping_gfp_constraint(mapping
, GFP_KERNEL
));
2117 if (error
== -EEXIST
) {
2127 ra
->prev_pos
= prev_index
;
2128 ra
->prev_pos
<<= PAGE_SHIFT
;
2129 ra
->prev_pos
|= prev_offset
;
2131 *ppos
= ((loff_t
)index
<< PAGE_SHIFT
) + offset
;
2132 file_accessed(filp
);
2133 return written
? written
: error
;
2137 * generic_file_read_iter - generic filesystem read routine
2138 * @iocb: kernel I/O control block
2139 * @iter: destination for the data read
2141 * This is the "read_iter()" routine for all filesystems
2142 * that can use the page cache directly.
2145 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
2147 struct file
*file
= iocb
->ki_filp
;
2149 size_t count
= iov_iter_count(iter
);
2152 goto out
; /* skip atime */
2154 if (iocb
->ki_flags
& IOCB_DIRECT
) {
2155 struct address_space
*mapping
= file
->f_mapping
;
2156 struct inode
*inode
= mapping
->host
;
2159 size
= i_size_read(inode
);
2160 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2161 if (filemap_range_has_page(mapping
, iocb
->ki_pos
,
2162 iocb
->ki_pos
+ count
- 1))
2165 retval
= filemap_write_and_wait_range(mapping
,
2167 iocb
->ki_pos
+ count
- 1);
2172 file_accessed(file
);
2174 retval
= mapping
->a_ops
->direct_IO(iocb
, iter
);
2176 iocb
->ki_pos
+= retval
;
2179 iov_iter_revert(iter
, count
- iov_iter_count(iter
));
2182 * Btrfs can have a short DIO read if we encounter
2183 * compressed extents, so if there was an error, or if
2184 * we've already read everything we wanted to, or if
2185 * there was a short read because we hit EOF, go ahead
2186 * and return. Otherwise fallthrough to buffered io for
2187 * the rest of the read. Buffered reads will not work for
2188 * DAX files, so don't bother trying.
2190 if (retval
< 0 || !count
|| iocb
->ki_pos
>= size
||
2195 retval
= do_generic_file_read(file
, &iocb
->ki_pos
, iter
, retval
);
2199 EXPORT_SYMBOL(generic_file_read_iter
);
2203 * page_cache_read - adds requested page to the page cache if not already there
2204 * @file: file to read
2205 * @offset: page index
2206 * @gfp_mask: memory allocation flags
2208 * This adds the requested page to the page cache if it isn't already there,
2209 * and schedules an I/O to read in its contents from disk.
2211 static int page_cache_read(struct file
*file
, pgoff_t offset
, gfp_t gfp_mask
)
2213 struct address_space
*mapping
= file
->f_mapping
;
2218 page
= __page_cache_alloc(gfp_mask
|__GFP_COLD
);
2222 ret
= add_to_page_cache_lru(page
, mapping
, offset
, gfp_mask
& GFP_KERNEL
);
2224 ret
= mapping
->a_ops
->readpage(file
, page
);
2225 else if (ret
== -EEXIST
)
2226 ret
= 0; /* losing race to add is OK */
2230 } while (ret
== AOP_TRUNCATED_PAGE
);
2235 #define MMAP_LOTSAMISS (100)
2238 * Synchronous readahead happens when we don't even find
2239 * a page in the page cache at all.
2241 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
2242 struct file_ra_state
*ra
,
2246 struct address_space
*mapping
= file
->f_mapping
;
2248 /* If we don't want any read-ahead, don't bother */
2249 if (vma
->vm_flags
& VM_RAND_READ
)
2254 if (vma
->vm_flags
& VM_SEQ_READ
) {
2255 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
2260 /* Avoid banging the cache line if not needed */
2261 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
2265 * Do we miss much more than hit in this file? If so,
2266 * stop bothering with read-ahead. It will only hurt.
2268 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
2274 ra
->start
= max_t(long, 0, offset
- ra
->ra_pages
/ 2);
2275 ra
->size
= ra
->ra_pages
;
2276 ra
->async_size
= ra
->ra_pages
/ 4;
2277 ra_submit(ra
, mapping
, file
);
2281 * Asynchronous readahead happens when we find the page and PG_readahead,
2282 * so we want to possibly extend the readahead further..
2284 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
2285 struct file_ra_state
*ra
,
2290 struct address_space
*mapping
= file
->f_mapping
;
2292 /* If we don't want any read-ahead, don't bother */
2293 if (vma
->vm_flags
& VM_RAND_READ
)
2295 if (ra
->mmap_miss
> 0)
2297 if (PageReadahead(page
))
2298 page_cache_async_readahead(mapping
, ra
, file
,
2299 page
, offset
, ra
->ra_pages
);
2303 * filemap_fault - read in file data for page fault handling
2304 * @vmf: struct vm_fault containing details of the fault
2306 * filemap_fault() is invoked via the vma operations vector for a
2307 * mapped memory region to read in file data during a page fault.
2309 * The goto's are kind of ugly, but this streamlines the normal case of having
2310 * it in the page cache, and handles the special cases reasonably without
2311 * having a lot of duplicated code.
2313 * vma->vm_mm->mmap_sem must be held on entry.
2315 * If our return value has VM_FAULT_RETRY set, it's because
2316 * lock_page_or_retry() returned 0.
2317 * The mmap_sem has usually been released in this case.
2318 * See __lock_page_or_retry() for the exception.
2320 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2321 * has not been released.
2323 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2325 int filemap_fault(struct vm_fault
*vmf
)
2328 struct file
*file
= vmf
->vma
->vm_file
;
2329 struct address_space
*mapping
= file
->f_mapping
;
2330 struct file_ra_state
*ra
= &file
->f_ra
;
2331 struct inode
*inode
= mapping
->host
;
2332 pgoff_t offset
= vmf
->pgoff
;
2337 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2338 if (unlikely(offset
>= max_off
))
2339 return VM_FAULT_SIGBUS
;
2342 * Do we have something in the page cache already?
2344 page
= find_get_page(mapping
, offset
);
2345 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
2347 * We found the page, so try async readahead before
2348 * waiting for the lock.
2350 do_async_mmap_readahead(vmf
->vma
, ra
, file
, page
, offset
);
2352 /* No page in the page cache at all */
2353 do_sync_mmap_readahead(vmf
->vma
, ra
, file
, offset
);
2354 count_vm_event(PGMAJFAULT
);
2355 count_memcg_event_mm(vmf
->vma
->vm_mm
, PGMAJFAULT
);
2356 ret
= VM_FAULT_MAJOR
;
2358 page
= find_get_page(mapping
, offset
);
2360 goto no_cached_page
;
2363 if (!lock_page_or_retry(page
, vmf
->vma
->vm_mm
, vmf
->flags
)) {
2365 return ret
| VM_FAULT_RETRY
;
2368 /* Did it get truncated? */
2369 if (unlikely(page
->mapping
!= mapping
)) {
2374 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
2377 * We have a locked page in the page cache, now we need to check
2378 * that it's up-to-date. If not, it is going to be due to an error.
2380 if (unlikely(!PageUptodate(page
)))
2381 goto page_not_uptodate
;
2384 * Found the page and have a reference on it.
2385 * We must recheck i_size under page lock.
2387 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2388 if (unlikely(offset
>= max_off
)) {
2391 return VM_FAULT_SIGBUS
;
2395 return ret
| VM_FAULT_LOCKED
;
2399 * We're only likely to ever get here if MADV_RANDOM is in
2402 error
= page_cache_read(file
, offset
, vmf
->gfp_mask
);
2405 * The page we want has now been added to the page cache.
2406 * In the unlikely event that someone removed it in the
2407 * meantime, we'll just come back here and read it again.
2413 * An error return from page_cache_read can result if the
2414 * system is low on memory, or a problem occurs while trying
2417 if (error
== -ENOMEM
)
2418 return VM_FAULT_OOM
;
2419 return VM_FAULT_SIGBUS
;
2423 * Umm, take care of errors if the page isn't up-to-date.
2424 * Try to re-read it _once_. We do this synchronously,
2425 * because there really aren't any performance issues here
2426 * and we need to check for errors.
2428 ClearPageError(page
);
2429 error
= mapping
->a_ops
->readpage(file
, page
);
2431 wait_on_page_locked(page
);
2432 if (!PageUptodate(page
))
2437 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2440 /* Things didn't work out. Return zero to tell the mm layer so. */
2441 shrink_readahead_size_eio(file
, ra
);
2442 return VM_FAULT_SIGBUS
;
2444 EXPORT_SYMBOL(filemap_fault
);
2446 void filemap_map_pages(struct vm_fault
*vmf
,
2447 pgoff_t start_pgoff
, pgoff_t end_pgoff
)
2449 struct radix_tree_iter iter
;
2451 struct file
*file
= vmf
->vma
->vm_file
;
2452 struct address_space
*mapping
= file
->f_mapping
;
2453 pgoff_t last_pgoff
= start_pgoff
;
2454 unsigned long max_idx
;
2455 struct page
*head
, *page
;
2458 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
,
2460 if (iter
.index
> end_pgoff
)
2463 page
= radix_tree_deref_slot(slot
);
2464 if (unlikely(!page
))
2466 if (radix_tree_exception(page
)) {
2467 if (radix_tree_deref_retry(page
)) {
2468 slot
= radix_tree_iter_retry(&iter
);
2474 head
= compound_head(page
);
2475 if (!page_cache_get_speculative(head
))
2478 /* The page was split under us? */
2479 if (compound_head(page
) != head
) {
2484 /* Has the page moved? */
2485 if (unlikely(page
!= *slot
)) {
2490 if (!PageUptodate(page
) ||
2491 PageReadahead(page
) ||
2494 if (!trylock_page(page
))
2497 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2500 max_idx
= DIV_ROUND_UP(i_size_read(mapping
->host
), PAGE_SIZE
);
2501 if (page
->index
>= max_idx
)
2504 if (file
->f_ra
.mmap_miss
> 0)
2505 file
->f_ra
.mmap_miss
--;
2507 vmf
->address
+= (iter
.index
- last_pgoff
) << PAGE_SHIFT
;
2509 vmf
->pte
+= iter
.index
- last_pgoff
;
2510 last_pgoff
= iter
.index
;
2511 if (alloc_set_pte(vmf
, NULL
, page
))
2520 /* Huge page is mapped? No need to proceed. */
2521 if (pmd_trans_huge(*vmf
->pmd
))
2523 if (iter
.index
== end_pgoff
)
2528 EXPORT_SYMBOL(filemap_map_pages
);
2530 int filemap_page_mkwrite(struct vm_fault
*vmf
)
2532 struct page
*page
= vmf
->page
;
2533 struct inode
*inode
= file_inode(vmf
->vma
->vm_file
);
2534 int ret
= VM_FAULT_LOCKED
;
2536 sb_start_pagefault(inode
->i_sb
);
2537 vma_file_update_time(vmf
->vma
);
2539 if (page
->mapping
!= inode
->i_mapping
) {
2541 ret
= VM_FAULT_NOPAGE
;
2545 * We mark the page dirty already here so that when freeze is in
2546 * progress, we are guaranteed that writeback during freezing will
2547 * see the dirty page and writeprotect it again.
2549 set_page_dirty(page
);
2550 wait_for_stable_page(page
);
2552 sb_end_pagefault(inode
->i_sb
);
2555 EXPORT_SYMBOL(filemap_page_mkwrite
);
2557 const struct vm_operations_struct generic_file_vm_ops
= {
2558 .fault
= filemap_fault
,
2559 .map_pages
= filemap_map_pages
,
2560 .page_mkwrite
= filemap_page_mkwrite
,
2563 /* This is used for a general mmap of a disk file */
2565 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2567 struct address_space
*mapping
= file
->f_mapping
;
2569 if (!mapping
->a_ops
->readpage
)
2571 file_accessed(file
);
2572 vma
->vm_ops
= &generic_file_vm_ops
;
2577 * This is for filesystems which do not implement ->writepage.
2579 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2581 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2583 return generic_file_mmap(file
, vma
);
2586 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2590 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2594 #endif /* CONFIG_MMU */
2596 EXPORT_SYMBOL(generic_file_mmap
);
2597 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2599 static struct page
*wait_on_page_read(struct page
*page
)
2601 if (!IS_ERR(page
)) {
2602 wait_on_page_locked(page
);
2603 if (!PageUptodate(page
)) {
2605 page
= ERR_PTR(-EIO
);
2611 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2613 int (*filler
)(void *, struct page
*),
2620 page
= find_get_page(mapping
, index
);
2622 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2624 return ERR_PTR(-ENOMEM
);
2625 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2626 if (unlikely(err
)) {
2630 /* Presumably ENOMEM for radix tree node */
2631 return ERR_PTR(err
);
2635 err
= filler(data
, page
);
2638 return ERR_PTR(err
);
2641 page
= wait_on_page_read(page
);
2646 if (PageUptodate(page
))
2650 * Page is not up to date and may be locked due one of the following
2651 * case a: Page is being filled and the page lock is held
2652 * case b: Read/write error clearing the page uptodate status
2653 * case c: Truncation in progress (page locked)
2654 * case d: Reclaim in progress
2656 * Case a, the page will be up to date when the page is unlocked.
2657 * There is no need to serialise on the page lock here as the page
2658 * is pinned so the lock gives no additional protection. Even if the
2659 * the page is truncated, the data is still valid if PageUptodate as
2660 * it's a race vs truncate race.
2661 * Case b, the page will not be up to date
2662 * Case c, the page may be truncated but in itself, the data may still
2663 * be valid after IO completes as it's a read vs truncate race. The
2664 * operation must restart if the page is not uptodate on unlock but
2665 * otherwise serialising on page lock to stabilise the mapping gives
2666 * no additional guarantees to the caller as the page lock is
2667 * released before return.
2668 * Case d, similar to truncation. If reclaim holds the page lock, it
2669 * will be a race with remove_mapping that determines if the mapping
2670 * is valid on unlock but otherwise the data is valid and there is
2671 * no need to serialise with page lock.
2673 * As the page lock gives no additional guarantee, we optimistically
2674 * wait on the page to be unlocked and check if it's up to date and
2675 * use the page if it is. Otherwise, the page lock is required to
2676 * distinguish between the different cases. The motivation is that we
2677 * avoid spurious serialisations and wakeups when multiple processes
2678 * wait on the same page for IO to complete.
2680 wait_on_page_locked(page
);
2681 if (PageUptodate(page
))
2684 /* Distinguish between all the cases under the safety of the lock */
2687 /* Case c or d, restart the operation */
2688 if (!page
->mapping
) {
2694 /* Someone else locked and filled the page in a very small window */
2695 if (PageUptodate(page
)) {
2702 mark_page_accessed(page
);
2707 * read_cache_page - read into page cache, fill it if needed
2708 * @mapping: the page's address_space
2709 * @index: the page index
2710 * @filler: function to perform the read
2711 * @data: first arg to filler(data, page) function, often left as NULL
2713 * Read into the page cache. If a page already exists, and PageUptodate() is
2714 * not set, try to fill the page and wait for it to become unlocked.
2716 * If the page does not get brought uptodate, return -EIO.
2718 struct page
*read_cache_page(struct address_space
*mapping
,
2720 int (*filler
)(void *, struct page
*),
2723 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2725 EXPORT_SYMBOL(read_cache_page
);
2728 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2729 * @mapping: the page's address_space
2730 * @index: the page index
2731 * @gfp: the page allocator flags to use if allocating
2733 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2734 * any new page allocations done using the specified allocation flags.
2736 * If the page does not get brought uptodate, return -EIO.
2738 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2742 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2744 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2746 EXPORT_SYMBOL(read_cache_page_gfp
);
2749 * Performs necessary checks before doing a write
2751 * Can adjust writing position or amount of bytes to write.
2752 * Returns appropriate error code that caller should return or
2753 * zero in case that write should be allowed.
2755 inline ssize_t
generic_write_checks(struct kiocb
*iocb
, struct iov_iter
*from
)
2757 struct file
*file
= iocb
->ki_filp
;
2758 struct inode
*inode
= file
->f_mapping
->host
;
2759 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2762 if (!iov_iter_count(from
))
2765 /* FIXME: this is for backwards compatibility with 2.4 */
2766 if (iocb
->ki_flags
& IOCB_APPEND
)
2767 iocb
->ki_pos
= i_size_read(inode
);
2771 if ((iocb
->ki_flags
& IOCB_NOWAIT
) && !(iocb
->ki_flags
& IOCB_DIRECT
))
2774 if (limit
!= RLIM_INFINITY
) {
2775 if (iocb
->ki_pos
>= limit
) {
2776 send_sig(SIGXFSZ
, current
, 0);
2779 iov_iter_truncate(from
, limit
- (unsigned long)pos
);
2785 if (unlikely(pos
+ iov_iter_count(from
) > MAX_NON_LFS
&&
2786 !(file
->f_flags
& O_LARGEFILE
))) {
2787 if (pos
>= MAX_NON_LFS
)
2789 iov_iter_truncate(from
, MAX_NON_LFS
- (unsigned long)pos
);
2793 * Are we about to exceed the fs block limit ?
2795 * If we have written data it becomes a short write. If we have
2796 * exceeded without writing data we send a signal and return EFBIG.
2797 * Linus frestrict idea will clean these up nicely..
2799 if (unlikely(pos
>= inode
->i_sb
->s_maxbytes
))
2802 iov_iter_truncate(from
, inode
->i_sb
->s_maxbytes
- pos
);
2803 return iov_iter_count(from
);
2805 EXPORT_SYMBOL(generic_write_checks
);
2807 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2808 loff_t pos
, unsigned len
, unsigned flags
,
2809 struct page
**pagep
, void **fsdata
)
2811 const struct address_space_operations
*aops
= mapping
->a_ops
;
2813 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2816 EXPORT_SYMBOL(pagecache_write_begin
);
2818 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2819 loff_t pos
, unsigned len
, unsigned copied
,
2820 struct page
*page
, void *fsdata
)
2822 const struct address_space_operations
*aops
= mapping
->a_ops
;
2824 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2826 EXPORT_SYMBOL(pagecache_write_end
);
2829 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
)
2831 struct file
*file
= iocb
->ki_filp
;
2832 struct address_space
*mapping
= file
->f_mapping
;
2833 struct inode
*inode
= mapping
->host
;
2834 loff_t pos
= iocb
->ki_pos
;
2839 write_len
= iov_iter_count(from
);
2840 end
= (pos
+ write_len
- 1) >> PAGE_SHIFT
;
2842 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2843 /* If there are pages to writeback, return */
2844 if (filemap_range_has_page(inode
->i_mapping
, pos
,
2845 pos
+ iov_iter_count(from
)))
2848 written
= filemap_write_and_wait_range(mapping
, pos
,
2849 pos
+ write_len
- 1);
2855 * After a write we want buffered reads to be sure to go to disk to get
2856 * the new data. We invalidate clean cached page from the region we're
2857 * about to write. We do this *before* the write so that we can return
2858 * without clobbering -EIOCBQUEUED from ->direct_IO().
2860 written
= invalidate_inode_pages2_range(mapping
,
2861 pos
>> PAGE_SHIFT
, end
);
2863 * If a page can not be invalidated, return 0 to fall back
2864 * to buffered write.
2867 if (written
== -EBUSY
)
2872 written
= mapping
->a_ops
->direct_IO(iocb
, from
);
2875 * Finally, try again to invalidate clean pages which might have been
2876 * cached by non-direct readahead, or faulted in by get_user_pages()
2877 * if the source of the write was an mmap'ed region of the file
2878 * we're writing. Either one is a pretty crazy thing to do,
2879 * so we don't support it 100%. If this invalidation
2880 * fails, tough, the write still worked...
2882 invalidate_inode_pages2_range(mapping
,
2883 pos
>> PAGE_SHIFT
, end
);
2887 write_len
-= written
;
2888 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2889 i_size_write(inode
, pos
);
2890 mark_inode_dirty(inode
);
2894 iov_iter_revert(from
, write_len
- iov_iter_count(from
));
2898 EXPORT_SYMBOL(generic_file_direct_write
);
2901 * Find or create a page at the given pagecache position. Return the locked
2902 * page. This function is specifically for buffered writes.
2904 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2905 pgoff_t index
, unsigned flags
)
2908 int fgp_flags
= FGP_LOCK
|FGP_WRITE
|FGP_CREAT
;
2910 if (flags
& AOP_FLAG_NOFS
)
2911 fgp_flags
|= FGP_NOFS
;
2913 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2914 mapping_gfp_mask(mapping
));
2916 wait_for_stable_page(page
);
2920 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2922 ssize_t
generic_perform_write(struct file
*file
,
2923 struct iov_iter
*i
, loff_t pos
)
2925 struct address_space
*mapping
= file
->f_mapping
;
2926 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2928 ssize_t written
= 0;
2929 unsigned int flags
= 0;
2933 unsigned long offset
; /* Offset into pagecache page */
2934 unsigned long bytes
; /* Bytes to write to page */
2935 size_t copied
; /* Bytes copied from user */
2938 offset
= (pos
& (PAGE_SIZE
- 1));
2939 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
2944 * Bring in the user page that we will copy from _first_.
2945 * Otherwise there's a nasty deadlock on copying from the
2946 * same page as we're writing to, without it being marked
2949 * Not only is this an optimisation, but it is also required
2950 * to check that the address is actually valid, when atomic
2951 * usercopies are used, below.
2953 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2958 if (fatal_signal_pending(current
)) {
2963 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2965 if (unlikely(status
< 0))
2968 if (mapping_writably_mapped(mapping
))
2969 flush_dcache_page(page
);
2971 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2972 flush_dcache_page(page
);
2974 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2976 if (unlikely(status
< 0))
2982 iov_iter_advance(i
, copied
);
2983 if (unlikely(copied
== 0)) {
2985 * If we were unable to copy any data at all, we must
2986 * fall back to a single segment length write.
2988 * If we didn't fallback here, we could livelock
2989 * because not all segments in the iov can be copied at
2990 * once without a pagefault.
2992 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
2993 iov_iter_single_seg_count(i
));
2999 balance_dirty_pages_ratelimited(mapping
);
3000 } while (iov_iter_count(i
));
3002 return written
? written
: status
;
3004 EXPORT_SYMBOL(generic_perform_write
);
3007 * __generic_file_write_iter - write data to a file
3008 * @iocb: IO state structure (file, offset, etc.)
3009 * @from: iov_iter with data to write
3011 * This function does all the work needed for actually writing data to a
3012 * file. It does all basic checks, removes SUID from the file, updates
3013 * modification times and calls proper subroutines depending on whether we
3014 * do direct IO or a standard buffered write.
3016 * It expects i_mutex to be grabbed unless we work on a block device or similar
3017 * object which does not need locking at all.
3019 * This function does *not* take care of syncing data in case of O_SYNC write.
3020 * A caller has to handle it. This is mainly due to the fact that we want to
3021 * avoid syncing under i_mutex.
3023 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3025 struct file
*file
= iocb
->ki_filp
;
3026 struct address_space
* mapping
= file
->f_mapping
;
3027 struct inode
*inode
= mapping
->host
;
3028 ssize_t written
= 0;
3032 /* We can write back this queue in page reclaim */
3033 current
->backing_dev_info
= inode_to_bdi(inode
);
3034 err
= file_remove_privs(file
);
3038 err
= file_update_time(file
);
3042 if (iocb
->ki_flags
& IOCB_DIRECT
) {
3043 loff_t pos
, endbyte
;
3045 written
= generic_file_direct_write(iocb
, from
);
3047 * If the write stopped short of completing, fall back to
3048 * buffered writes. Some filesystems do this for writes to
3049 * holes, for example. For DAX files, a buffered write will
3050 * not succeed (even if it did, DAX does not handle dirty
3051 * page-cache pages correctly).
3053 if (written
< 0 || !iov_iter_count(from
) || IS_DAX(inode
))
3056 status
= generic_perform_write(file
, from
, pos
= iocb
->ki_pos
);
3058 * If generic_perform_write() returned a synchronous error
3059 * then we want to return the number of bytes which were
3060 * direct-written, or the error code if that was zero. Note
3061 * that this differs from normal direct-io semantics, which
3062 * will return -EFOO even if some bytes were written.
3064 if (unlikely(status
< 0)) {
3069 * We need to ensure that the page cache pages are written to
3070 * disk and invalidated to preserve the expected O_DIRECT
3073 endbyte
= pos
+ status
- 1;
3074 err
= filemap_write_and_wait_range(mapping
, pos
, endbyte
);
3076 iocb
->ki_pos
= endbyte
+ 1;
3078 invalidate_mapping_pages(mapping
,
3080 endbyte
>> PAGE_SHIFT
);
3083 * We don't know how much we wrote, so just return
3084 * the number of bytes which were direct-written
3088 written
= generic_perform_write(file
, from
, iocb
->ki_pos
);
3089 if (likely(written
> 0))
3090 iocb
->ki_pos
+= written
;
3093 current
->backing_dev_info
= NULL
;
3094 return written
? written
: err
;
3096 EXPORT_SYMBOL(__generic_file_write_iter
);
3099 * generic_file_write_iter - write data to a file
3100 * @iocb: IO state structure
3101 * @from: iov_iter with data to write
3103 * This is a wrapper around __generic_file_write_iter() to be used by most
3104 * filesystems. It takes care of syncing the file in case of O_SYNC file
3105 * and acquires i_mutex as needed.
3107 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3109 struct file
*file
= iocb
->ki_filp
;
3110 struct inode
*inode
= file
->f_mapping
->host
;
3114 ret
= generic_write_checks(iocb
, from
);
3116 ret
= __generic_file_write_iter(iocb
, from
);
3117 inode_unlock(inode
);
3120 ret
= generic_write_sync(iocb
, ret
);
3123 EXPORT_SYMBOL(generic_file_write_iter
);
3126 * try_to_release_page() - release old fs-specific metadata on a page
3128 * @page: the page which the kernel is trying to free
3129 * @gfp_mask: memory allocation flags (and I/O mode)
3131 * The address_space is to try to release any data against the page
3132 * (presumably at page->private). If the release was successful, return '1'.
3133 * Otherwise return zero.
3135 * This may also be called if PG_fscache is set on a page, indicating that the
3136 * page is known to the local caching routines.
3138 * The @gfp_mask argument specifies whether I/O may be performed to release
3139 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3142 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
3144 struct address_space
* const mapping
= page
->mapping
;
3146 BUG_ON(!PageLocked(page
));
3147 if (PageWriteback(page
))
3150 if (mapping
&& mapping
->a_ops
->releasepage
)
3151 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
3152 return try_to_free_buffers(page
);
3155 EXPORT_SYMBOL(try_to_release_page
);