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
;
398 if (end_byte
< start_byte
)
401 if (mapping
->nrpages
== 0)
404 if (!find_get_pages_range(mapping
, &index
, end
, 1, &page
))
409 EXPORT_SYMBOL(filemap_range_has_page
);
411 static void __filemap_fdatawait_range(struct address_space
*mapping
,
412 loff_t start_byte
, loff_t end_byte
)
414 pgoff_t index
= start_byte
>> PAGE_SHIFT
;
415 pgoff_t end
= end_byte
>> PAGE_SHIFT
;
419 if (end_byte
< start_byte
)
422 pagevec_init(&pvec
, 0);
423 while (index
<= end
) {
426 nr_pages
= pagevec_lookup_range_tag(&pvec
, mapping
, &index
,
427 end
, PAGECACHE_TAG_WRITEBACK
, PAGEVEC_SIZE
);
431 for (i
= 0; i
< nr_pages
; i
++) {
432 struct page
*page
= pvec
.pages
[i
];
434 wait_on_page_writeback(page
);
435 ClearPageError(page
);
437 pagevec_release(&pvec
);
443 * filemap_fdatawait_range - wait for writeback to complete
444 * @mapping: address space structure to wait for
445 * @start_byte: offset in bytes where the range starts
446 * @end_byte: offset in bytes where the range ends (inclusive)
448 * Walk the list of under-writeback pages of the given address space
449 * in the given range and wait for all of them. Check error status of
450 * the address space and return it.
452 * Since the error status of the address space is cleared by this function,
453 * callers are responsible for checking the return value and handling and/or
454 * reporting the error.
456 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
459 __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
460 return filemap_check_errors(mapping
);
462 EXPORT_SYMBOL(filemap_fdatawait_range
);
465 * file_fdatawait_range - wait for writeback to complete
466 * @file: file pointing to address space structure to wait for
467 * @start_byte: offset in bytes where the range starts
468 * @end_byte: offset in bytes where the range ends (inclusive)
470 * Walk the list of under-writeback pages of the address space that file
471 * refers to, in the given range and wait for all of them. Check error
472 * status of the address space vs. the file->f_wb_err cursor and return it.
474 * Since the error status of the file is advanced by this function,
475 * callers are responsible for checking the return value and handling and/or
476 * reporting the error.
478 int file_fdatawait_range(struct file
*file
, loff_t start_byte
, loff_t end_byte
)
480 struct address_space
*mapping
= file
->f_mapping
;
482 __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
483 return file_check_and_advance_wb_err(file
);
485 EXPORT_SYMBOL(file_fdatawait_range
);
488 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
489 * @mapping: address space structure to wait for
491 * Walk the list of under-writeback pages of the given address space
492 * and wait for all of them. Unlike filemap_fdatawait(), this function
493 * does not clear error status of the address space.
495 * Use this function if callers don't handle errors themselves. Expected
496 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
499 int filemap_fdatawait_keep_errors(struct address_space
*mapping
)
501 __filemap_fdatawait_range(mapping
, 0, LLONG_MAX
);
502 return filemap_check_and_keep_errors(mapping
);
504 EXPORT_SYMBOL(filemap_fdatawait_keep_errors
);
506 static bool mapping_needs_writeback(struct address_space
*mapping
)
508 return (!dax_mapping(mapping
) && mapping
->nrpages
) ||
509 (dax_mapping(mapping
) && mapping
->nrexceptional
);
512 int filemap_write_and_wait(struct address_space
*mapping
)
516 if (mapping_needs_writeback(mapping
)) {
517 err
= filemap_fdatawrite(mapping
);
519 * Even if the above returned error, the pages may be
520 * written partially (e.g. -ENOSPC), so we wait for it.
521 * But the -EIO is special case, it may indicate the worst
522 * thing (e.g. bug) happened, so we avoid waiting for it.
525 int err2
= filemap_fdatawait(mapping
);
529 /* Clear any previously stored errors */
530 filemap_check_errors(mapping
);
533 err
= filemap_check_errors(mapping
);
537 EXPORT_SYMBOL(filemap_write_and_wait
);
540 * filemap_write_and_wait_range - write out & wait on a file range
541 * @mapping: the address_space for the pages
542 * @lstart: offset in bytes where the range starts
543 * @lend: offset in bytes where the range ends (inclusive)
545 * Write out and wait upon file offsets lstart->lend, inclusive.
547 * Note that @lend is inclusive (describes the last byte to be written) so
548 * that this function can be used to write to the very end-of-file (end = -1).
550 int filemap_write_and_wait_range(struct address_space
*mapping
,
551 loff_t lstart
, loff_t lend
)
555 if (mapping_needs_writeback(mapping
)) {
556 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
558 /* See comment of filemap_write_and_wait() */
560 int err2
= filemap_fdatawait_range(mapping
,
565 /* Clear any previously stored errors */
566 filemap_check_errors(mapping
);
569 err
= filemap_check_errors(mapping
);
573 EXPORT_SYMBOL(filemap_write_and_wait_range
);
575 void __filemap_set_wb_err(struct address_space
*mapping
, int err
)
577 errseq_t eseq
= errseq_set(&mapping
->wb_err
, err
);
579 trace_filemap_set_wb_err(mapping
, eseq
);
581 EXPORT_SYMBOL(__filemap_set_wb_err
);
584 * file_check_and_advance_wb_err - report wb error (if any) that was previously
585 * and advance wb_err to current one
586 * @file: struct file on which the error is being reported
588 * When userland calls fsync (or something like nfsd does the equivalent), we
589 * want to report any writeback errors that occurred since the last fsync (or
590 * since the file was opened if there haven't been any).
592 * Grab the wb_err from the mapping. If it matches what we have in the file,
593 * then just quickly return 0. The file is all caught up.
595 * If it doesn't match, then take the mapping value, set the "seen" flag in
596 * it and try to swap it into place. If it works, or another task beat us
597 * to it with the new value, then update the f_wb_err and return the error
598 * portion. The error at this point must be reported via proper channels
599 * (a'la fsync, or NFS COMMIT operation, etc.).
601 * While we handle mapping->wb_err with atomic operations, the f_wb_err
602 * value is protected by the f_lock since we must ensure that it reflects
603 * the latest value swapped in for this file descriptor.
605 int file_check_and_advance_wb_err(struct file
*file
)
608 errseq_t old
= READ_ONCE(file
->f_wb_err
);
609 struct address_space
*mapping
= file
->f_mapping
;
611 /* Locklessly handle the common case where nothing has changed */
612 if (errseq_check(&mapping
->wb_err
, old
)) {
613 /* Something changed, must use slow path */
614 spin_lock(&file
->f_lock
);
615 old
= file
->f_wb_err
;
616 err
= errseq_check_and_advance(&mapping
->wb_err
,
618 trace_file_check_and_advance_wb_err(file
, old
);
619 spin_unlock(&file
->f_lock
);
623 * We're mostly using this function as a drop in replacement for
624 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
625 * that the legacy code would have had on these flags.
627 clear_bit(AS_EIO
, &mapping
->flags
);
628 clear_bit(AS_ENOSPC
, &mapping
->flags
);
631 EXPORT_SYMBOL(file_check_and_advance_wb_err
);
634 * file_write_and_wait_range - write out & wait on a file range
635 * @file: file pointing to address_space with pages
636 * @lstart: offset in bytes where the range starts
637 * @lend: offset in bytes where the range ends (inclusive)
639 * Write out and wait upon file offsets lstart->lend, inclusive.
641 * Note that @lend is inclusive (describes the last byte to be written) so
642 * that this function can be used to write to the very end-of-file (end = -1).
644 * After writing out and waiting on the data, we check and advance the
645 * f_wb_err cursor to the latest value, and return any errors detected there.
647 int file_write_and_wait_range(struct file
*file
, loff_t lstart
, loff_t lend
)
650 struct address_space
*mapping
= file
->f_mapping
;
652 if (mapping_needs_writeback(mapping
)) {
653 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
655 /* See comment of filemap_write_and_wait() */
657 __filemap_fdatawait_range(mapping
, lstart
, lend
);
659 err2
= file_check_and_advance_wb_err(file
);
664 EXPORT_SYMBOL(file_write_and_wait_range
);
667 * replace_page_cache_page - replace a pagecache page with a new one
668 * @old: page to be replaced
669 * @new: page to replace with
670 * @gfp_mask: allocation mode
672 * This function replaces a page in the pagecache with a new one. On
673 * success it acquires the pagecache reference for the new page and
674 * drops it for the old page. Both the old and new pages must be
675 * locked. This function does not add the new page to the LRU, the
676 * caller must do that.
678 * The remove + add is atomic. The only way this function can fail is
679 * memory allocation failure.
681 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
685 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
686 VM_BUG_ON_PAGE(!PageLocked(new), new);
687 VM_BUG_ON_PAGE(new->mapping
, new);
689 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
691 struct address_space
*mapping
= old
->mapping
;
692 void (*freepage
)(struct page
*);
695 pgoff_t offset
= old
->index
;
696 freepage
= mapping
->a_ops
->freepage
;
699 new->mapping
= mapping
;
702 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
703 __delete_from_page_cache(old
, NULL
);
704 error
= page_cache_tree_insert(mapping
, new, NULL
);
708 * hugetlb pages do not participate in page cache accounting.
711 __inc_node_page_state(new, NR_FILE_PAGES
);
712 if (PageSwapBacked(new))
713 __inc_node_page_state(new, NR_SHMEM
);
714 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
715 mem_cgroup_migrate(old
, new);
716 radix_tree_preload_end();
724 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
726 static int __add_to_page_cache_locked(struct page
*page
,
727 struct address_space
*mapping
,
728 pgoff_t offset
, gfp_t gfp_mask
,
731 int huge
= PageHuge(page
);
732 struct mem_cgroup
*memcg
;
735 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
736 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
739 error
= mem_cgroup_try_charge(page
, current
->mm
,
740 gfp_mask
, &memcg
, false);
745 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
748 mem_cgroup_cancel_charge(page
, memcg
, false);
753 page
->mapping
= mapping
;
754 page
->index
= offset
;
756 spin_lock_irq(&mapping
->tree_lock
);
757 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
758 radix_tree_preload_end();
762 /* hugetlb pages do not participate in page cache accounting. */
764 __inc_node_page_state(page
, NR_FILE_PAGES
);
765 spin_unlock_irq(&mapping
->tree_lock
);
767 mem_cgroup_commit_charge(page
, memcg
, false, false);
768 trace_mm_filemap_add_to_page_cache(page
);
771 page
->mapping
= NULL
;
772 /* Leave page->index set: truncation relies upon it */
773 spin_unlock_irq(&mapping
->tree_lock
);
775 mem_cgroup_cancel_charge(page
, memcg
, false);
781 * add_to_page_cache_locked - add a locked page to the pagecache
783 * @mapping: the page's address_space
784 * @offset: page index
785 * @gfp_mask: page allocation mode
787 * This function is used to add a page to the pagecache. It must be locked.
788 * This function does not add the page to the LRU. The caller must do that.
790 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
791 pgoff_t offset
, gfp_t gfp_mask
)
793 return __add_to_page_cache_locked(page
, mapping
, offset
,
796 EXPORT_SYMBOL(add_to_page_cache_locked
);
798 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
799 pgoff_t offset
, gfp_t gfp_mask
)
804 __SetPageLocked(page
);
805 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
808 __ClearPageLocked(page
);
811 * The page might have been evicted from cache only
812 * recently, in which case it should be activated like
813 * any other repeatedly accessed page.
814 * The exception is pages getting rewritten; evicting other
815 * data from the working set, only to cache data that will
816 * get overwritten with something else, is a waste of memory.
818 if (!(gfp_mask
& __GFP_WRITE
) &&
819 shadow
&& workingset_refault(shadow
)) {
821 workingset_activation(page
);
823 ClearPageActive(page
);
828 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
831 struct page
*__page_cache_alloc(gfp_t gfp
)
836 if (cpuset_do_page_mem_spread()) {
837 unsigned int cpuset_mems_cookie
;
839 cpuset_mems_cookie
= read_mems_allowed_begin();
840 n
= cpuset_mem_spread_node();
841 page
= __alloc_pages_node(n
, gfp
, 0);
842 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
846 return alloc_pages(gfp
, 0);
848 EXPORT_SYMBOL(__page_cache_alloc
);
852 * In order to wait for pages to become available there must be
853 * waitqueues associated with pages. By using a hash table of
854 * waitqueues where the bucket discipline is to maintain all
855 * waiters on the same queue and wake all when any of the pages
856 * become available, and for the woken contexts to check to be
857 * sure the appropriate page became available, this saves space
858 * at a cost of "thundering herd" phenomena during rare hash
861 #define PAGE_WAIT_TABLE_BITS 8
862 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
863 static wait_queue_head_t page_wait_table
[PAGE_WAIT_TABLE_SIZE
] __cacheline_aligned
;
865 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
867 return &page_wait_table
[hash_ptr(page
, PAGE_WAIT_TABLE_BITS
)];
870 void __init
pagecache_init(void)
874 for (i
= 0; i
< PAGE_WAIT_TABLE_SIZE
; i
++)
875 init_waitqueue_head(&page_wait_table
[i
]);
877 page_writeback_init();
880 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
881 struct wait_page_key
{
887 struct wait_page_queue
{
890 wait_queue_entry_t wait
;
893 static int wake_page_function(wait_queue_entry_t
*wait
, unsigned mode
, int sync
, void *arg
)
895 struct wait_page_key
*key
= arg
;
896 struct wait_page_queue
*wait_page
897 = container_of(wait
, struct wait_page_queue
, wait
);
899 if (wait_page
->page
!= key
->page
)
903 if (wait_page
->bit_nr
!= key
->bit_nr
)
906 /* Stop walking if it's locked */
907 if (test_bit(key
->bit_nr
, &key
->page
->flags
))
910 return autoremove_wake_function(wait
, mode
, sync
, key
);
913 static void wake_up_page_bit(struct page
*page
, int bit_nr
)
915 wait_queue_head_t
*q
= page_waitqueue(page
);
916 struct wait_page_key key
;
918 wait_queue_entry_t bookmark
;
925 bookmark
.private = NULL
;
926 bookmark
.func
= NULL
;
927 INIT_LIST_HEAD(&bookmark
.entry
);
929 spin_lock_irqsave(&q
->lock
, flags
);
930 __wake_up_locked_key_bookmark(q
, TASK_NORMAL
, &key
, &bookmark
);
932 while (bookmark
.flags
& WQ_FLAG_BOOKMARK
) {
934 * Take a breather from holding the lock,
935 * allow pages that finish wake up asynchronously
936 * to acquire the lock and remove themselves
939 spin_unlock_irqrestore(&q
->lock
, flags
);
941 spin_lock_irqsave(&q
->lock
, flags
);
942 __wake_up_locked_key_bookmark(q
, TASK_NORMAL
, &key
, &bookmark
);
946 * It is possible for other pages to have collided on the waitqueue
947 * hash, so in that case check for a page match. That prevents a long-
950 * It is still possible to miss a case here, when we woke page waiters
951 * and removed them from the waitqueue, but there are still other
954 if (!waitqueue_active(q
) || !key
.page_match
) {
955 ClearPageWaiters(page
);
957 * It's possible to miss clearing Waiters here, when we woke
958 * our page waiters, but the hashed waitqueue has waiters for
961 * That's okay, it's a rare case. The next waker will clear it.
964 spin_unlock_irqrestore(&q
->lock
, flags
);
967 static void wake_up_page(struct page
*page
, int bit
)
969 if (!PageWaiters(page
))
971 wake_up_page_bit(page
, bit
);
974 static inline int wait_on_page_bit_common(wait_queue_head_t
*q
,
975 struct page
*page
, int bit_nr
, int state
, bool lock
)
977 struct wait_page_queue wait_page
;
978 wait_queue_entry_t
*wait
= &wait_page
.wait
;
982 wait
->flags
= lock
? WQ_FLAG_EXCLUSIVE
: 0;
983 wait
->func
= wake_page_function
;
984 wait_page
.page
= page
;
985 wait_page
.bit_nr
= bit_nr
;
988 spin_lock_irq(&q
->lock
);
990 if (likely(list_empty(&wait
->entry
))) {
991 __add_wait_queue_entry_tail(q
, wait
);
992 SetPageWaiters(page
);
995 set_current_state(state
);
997 spin_unlock_irq(&q
->lock
);
999 if (likely(test_bit(bit_nr
, &page
->flags
))) {
1004 if (!test_and_set_bit_lock(bit_nr
, &page
->flags
))
1007 if (!test_bit(bit_nr
, &page
->flags
))
1011 if (unlikely(signal_pending_state(state
, current
))) {
1017 finish_wait(q
, wait
);
1020 * A signal could leave PageWaiters set. Clearing it here if
1021 * !waitqueue_active would be possible (by open-coding finish_wait),
1022 * but still fail to catch it in the case of wait hash collision. We
1023 * already can fail to clear wait hash collision cases, so don't
1024 * bother with signals either.
1030 void wait_on_page_bit(struct page
*page
, int bit_nr
)
1032 wait_queue_head_t
*q
= page_waitqueue(page
);
1033 wait_on_page_bit_common(q
, page
, bit_nr
, TASK_UNINTERRUPTIBLE
, false);
1035 EXPORT_SYMBOL(wait_on_page_bit
);
1037 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
1039 wait_queue_head_t
*q
= page_waitqueue(page
);
1040 return wait_on_page_bit_common(q
, page
, bit_nr
, TASK_KILLABLE
, false);
1044 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1045 * @page: Page defining the wait queue of interest
1046 * @waiter: Waiter to add to the queue
1048 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1050 void add_page_wait_queue(struct page
*page
, wait_queue_entry_t
*waiter
)
1052 wait_queue_head_t
*q
= page_waitqueue(page
);
1053 unsigned long flags
;
1055 spin_lock_irqsave(&q
->lock
, flags
);
1056 __add_wait_queue_entry_tail(q
, waiter
);
1057 SetPageWaiters(page
);
1058 spin_unlock_irqrestore(&q
->lock
, flags
);
1060 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
1062 #ifndef clear_bit_unlock_is_negative_byte
1065 * PG_waiters is the high bit in the same byte as PG_lock.
1067 * On x86 (and on many other architectures), we can clear PG_lock and
1068 * test the sign bit at the same time. But if the architecture does
1069 * not support that special operation, we just do this all by hand
1072 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1073 * being cleared, but a memory barrier should be unneccssary since it is
1074 * in the same byte as PG_locked.
1076 static inline bool clear_bit_unlock_is_negative_byte(long nr
, volatile void *mem
)
1078 clear_bit_unlock(nr
, mem
);
1079 /* smp_mb__after_atomic(); */
1080 return test_bit(PG_waiters
, mem
);
1086 * unlock_page - unlock a locked page
1089 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1090 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1091 * mechanism between PageLocked pages and PageWriteback pages is shared.
1092 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1094 * Note that this depends on PG_waiters being the sign bit in the byte
1095 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1096 * clear the PG_locked bit and test PG_waiters at the same time fairly
1097 * portably (architectures that do LL/SC can test any bit, while x86 can
1098 * test the sign bit).
1100 void unlock_page(struct page
*page
)
1102 BUILD_BUG_ON(PG_waiters
!= 7);
1103 page
= compound_head(page
);
1104 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1105 if (clear_bit_unlock_is_negative_byte(PG_locked
, &page
->flags
))
1106 wake_up_page_bit(page
, PG_locked
);
1108 EXPORT_SYMBOL(unlock_page
);
1111 * end_page_writeback - end writeback against a page
1114 void end_page_writeback(struct page
*page
)
1117 * TestClearPageReclaim could be used here but it is an atomic
1118 * operation and overkill in this particular case. Failing to
1119 * shuffle a page marked for immediate reclaim is too mild to
1120 * justify taking an atomic operation penalty at the end of
1121 * ever page writeback.
1123 if (PageReclaim(page
)) {
1124 ClearPageReclaim(page
);
1125 rotate_reclaimable_page(page
);
1128 if (!test_clear_page_writeback(page
))
1131 smp_mb__after_atomic();
1132 wake_up_page(page
, PG_writeback
);
1134 EXPORT_SYMBOL(end_page_writeback
);
1137 * After completing I/O on a page, call this routine to update the page
1138 * flags appropriately
1140 void page_endio(struct page
*page
, bool is_write
, int err
)
1144 SetPageUptodate(page
);
1146 ClearPageUptodate(page
);
1152 struct address_space
*mapping
;
1155 mapping
= page_mapping(page
);
1157 mapping_set_error(mapping
, err
);
1159 end_page_writeback(page
);
1162 EXPORT_SYMBOL_GPL(page_endio
);
1165 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1166 * @__page: the page to lock
1168 void __lock_page(struct page
*__page
)
1170 struct page
*page
= compound_head(__page
);
1171 wait_queue_head_t
*q
= page_waitqueue(page
);
1172 wait_on_page_bit_common(q
, page
, PG_locked
, TASK_UNINTERRUPTIBLE
, true);
1174 EXPORT_SYMBOL(__lock_page
);
1176 int __lock_page_killable(struct page
*__page
)
1178 struct page
*page
= compound_head(__page
);
1179 wait_queue_head_t
*q
= page_waitqueue(page
);
1180 return wait_on_page_bit_common(q
, page
, PG_locked
, TASK_KILLABLE
, true);
1182 EXPORT_SYMBOL_GPL(__lock_page_killable
);
1186 * 1 - page is locked; mmap_sem is still held.
1187 * 0 - page is not locked.
1188 * mmap_sem has been released (up_read()), unless flags had both
1189 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1190 * which case mmap_sem is still held.
1192 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1193 * with the page locked and the mmap_sem unperturbed.
1195 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
1198 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1200 * CAUTION! In this case, mmap_sem is not released
1201 * even though return 0.
1203 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
1206 up_read(&mm
->mmap_sem
);
1207 if (flags
& FAULT_FLAG_KILLABLE
)
1208 wait_on_page_locked_killable(page
);
1210 wait_on_page_locked(page
);
1213 if (flags
& FAULT_FLAG_KILLABLE
) {
1216 ret
= __lock_page_killable(page
);
1218 up_read(&mm
->mmap_sem
);
1228 * page_cache_next_hole - find the next hole (not-present entry)
1231 * @max_scan: maximum range to search
1233 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1234 * lowest indexed hole.
1236 * Returns: the index of the hole if found, otherwise returns an index
1237 * outside of the set specified (in which case 'return - index >=
1238 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1241 * page_cache_next_hole may be called under rcu_read_lock. However,
1242 * like radix_tree_gang_lookup, this will not atomically search a
1243 * snapshot of the tree at a single point in time. For example, if a
1244 * hole is created at index 5, then subsequently a hole is created at
1245 * index 10, page_cache_next_hole covering both indexes may return 10
1246 * if called under rcu_read_lock.
1248 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
1249 pgoff_t index
, unsigned long max_scan
)
1253 for (i
= 0; i
< max_scan
; i
++) {
1256 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1257 if (!page
|| radix_tree_exceptional_entry(page
))
1266 EXPORT_SYMBOL(page_cache_next_hole
);
1269 * page_cache_prev_hole - find the prev hole (not-present entry)
1272 * @max_scan: maximum range to search
1274 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1277 * Returns: the index of the hole if found, otherwise returns an index
1278 * outside of the set specified (in which case 'index - return >=
1279 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1282 * page_cache_prev_hole may be called under rcu_read_lock. However,
1283 * like radix_tree_gang_lookup, this will not atomically search a
1284 * snapshot of the tree at a single point in time. For example, if a
1285 * hole is created at index 10, then subsequently a hole is created at
1286 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1287 * called under rcu_read_lock.
1289 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
1290 pgoff_t index
, unsigned long max_scan
)
1294 for (i
= 0; i
< max_scan
; i
++) {
1297 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1298 if (!page
|| radix_tree_exceptional_entry(page
))
1301 if (index
== ULONG_MAX
)
1307 EXPORT_SYMBOL(page_cache_prev_hole
);
1310 * find_get_entry - find and get a page cache entry
1311 * @mapping: the address_space to search
1312 * @offset: the page cache index
1314 * Looks up the page cache slot at @mapping & @offset. If there is a
1315 * page cache page, it is returned with an increased refcount.
1317 * If the slot holds a shadow entry of a previously evicted page, or a
1318 * swap entry from shmem/tmpfs, it is returned.
1320 * Otherwise, %NULL is returned.
1322 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
1325 struct page
*head
, *page
;
1330 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
1332 page
= radix_tree_deref_slot(pagep
);
1333 if (unlikely(!page
))
1335 if (radix_tree_exception(page
)) {
1336 if (radix_tree_deref_retry(page
))
1339 * A shadow entry of a recently evicted page,
1340 * or a swap entry from shmem/tmpfs. Return
1341 * it without attempting to raise page count.
1346 head
= compound_head(page
);
1347 if (!page_cache_get_speculative(head
))
1350 /* The page was split under us? */
1351 if (compound_head(page
) != head
) {
1357 * Has the page moved?
1358 * This is part of the lockless pagecache protocol. See
1359 * include/linux/pagemap.h for details.
1361 if (unlikely(page
!= *pagep
)) {
1371 EXPORT_SYMBOL(find_get_entry
);
1374 * find_lock_entry - locate, pin and lock a page cache entry
1375 * @mapping: the address_space to search
1376 * @offset: the page cache index
1378 * Looks up the page cache slot at @mapping & @offset. If there is a
1379 * page cache page, it is returned locked and with an increased
1382 * If the slot holds a shadow entry of a previously evicted page, or a
1383 * swap entry from shmem/tmpfs, it is returned.
1385 * Otherwise, %NULL is returned.
1387 * find_lock_entry() may sleep.
1389 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1394 page
= find_get_entry(mapping
, offset
);
1395 if (page
&& !radix_tree_exception(page
)) {
1397 /* Has the page been truncated? */
1398 if (unlikely(page_mapping(page
) != mapping
)) {
1403 VM_BUG_ON_PAGE(page_to_pgoff(page
) != offset
, page
);
1407 EXPORT_SYMBOL(find_lock_entry
);
1410 * pagecache_get_page - find and get a page reference
1411 * @mapping: the address_space to search
1412 * @offset: the page index
1413 * @fgp_flags: PCG flags
1414 * @gfp_mask: gfp mask to use for the page cache data page allocation
1416 * Looks up the page cache slot at @mapping & @offset.
1418 * PCG flags modify how the page is returned.
1420 * @fgp_flags can be:
1422 * - FGP_ACCESSED: the page will be marked accessed
1423 * - FGP_LOCK: Page is return locked
1424 * - FGP_CREAT: If page is not present then a new page is allocated using
1425 * @gfp_mask and added to the page cache and the VM's LRU
1426 * list. The page is returned locked and with an increased
1427 * refcount. Otherwise, NULL is returned.
1429 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1430 * if the GFP flags specified for FGP_CREAT are atomic.
1432 * If there is a page cache page, it is returned with an increased refcount.
1434 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1435 int fgp_flags
, gfp_t gfp_mask
)
1440 page
= find_get_entry(mapping
, offset
);
1441 if (radix_tree_exceptional_entry(page
))
1446 if (fgp_flags
& FGP_LOCK
) {
1447 if (fgp_flags
& FGP_NOWAIT
) {
1448 if (!trylock_page(page
)) {
1456 /* Has the page been truncated? */
1457 if (unlikely(page
->mapping
!= mapping
)) {
1462 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1465 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1466 mark_page_accessed(page
);
1469 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1471 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1472 gfp_mask
|= __GFP_WRITE
;
1473 if (fgp_flags
& FGP_NOFS
)
1474 gfp_mask
&= ~__GFP_FS
;
1476 page
= __page_cache_alloc(gfp_mask
);
1480 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1481 fgp_flags
|= FGP_LOCK
;
1483 /* Init accessed so avoid atomic mark_page_accessed later */
1484 if (fgp_flags
& FGP_ACCESSED
)
1485 __SetPageReferenced(page
);
1487 err
= add_to_page_cache_lru(page
, mapping
, offset
,
1488 gfp_mask
& GFP_RECLAIM_MASK
);
1489 if (unlikely(err
)) {
1499 EXPORT_SYMBOL(pagecache_get_page
);
1502 * find_get_entries - gang pagecache lookup
1503 * @mapping: The address_space to search
1504 * @start: The starting page cache index
1505 * @nr_entries: The maximum number of entries
1506 * @entries: Where the resulting entries are placed
1507 * @indices: The cache indices corresponding to the entries in @entries
1509 * find_get_entries() will search for and return a group of up to
1510 * @nr_entries entries in the mapping. The entries are placed at
1511 * @entries. find_get_entries() takes a reference against any actual
1514 * The search returns a group of mapping-contiguous page cache entries
1515 * with ascending indexes. There may be holes in the indices due to
1516 * not-present pages.
1518 * Any shadow entries of evicted pages, or swap entries from
1519 * shmem/tmpfs, are included in the returned array.
1521 * find_get_entries() returns the number of pages and shadow entries
1524 unsigned find_get_entries(struct address_space
*mapping
,
1525 pgoff_t start
, unsigned int nr_entries
,
1526 struct page
**entries
, pgoff_t
*indices
)
1529 unsigned int ret
= 0;
1530 struct radix_tree_iter iter
;
1536 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1537 struct page
*head
, *page
;
1539 page
= radix_tree_deref_slot(slot
);
1540 if (unlikely(!page
))
1542 if (radix_tree_exception(page
)) {
1543 if (radix_tree_deref_retry(page
)) {
1544 slot
= radix_tree_iter_retry(&iter
);
1548 * A shadow entry of a recently evicted page, a swap
1549 * entry from shmem/tmpfs or a DAX entry. Return it
1550 * without attempting to raise page count.
1555 head
= compound_head(page
);
1556 if (!page_cache_get_speculative(head
))
1559 /* The page was split under us? */
1560 if (compound_head(page
) != head
) {
1565 /* Has the page moved? */
1566 if (unlikely(page
!= *slot
)) {
1571 indices
[ret
] = iter
.index
;
1572 entries
[ret
] = page
;
1573 if (++ret
== nr_entries
)
1581 * find_get_pages_range - gang pagecache lookup
1582 * @mapping: The address_space to search
1583 * @start: The starting page index
1584 * @end: The final page index (inclusive)
1585 * @nr_pages: The maximum number of pages
1586 * @pages: Where the resulting pages are placed
1588 * find_get_pages_range() will search for and return a group of up to @nr_pages
1589 * pages in the mapping starting at index @start and up to index @end
1590 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1591 * a reference against the returned pages.
1593 * The search returns a group of mapping-contiguous pages with ascending
1594 * indexes. There may be holes in the indices due to not-present pages.
1595 * We also update @start to index the next page for the traversal.
1597 * find_get_pages_range() returns the number of pages which were found. If this
1598 * number is smaller than @nr_pages, the end of specified range has been
1601 unsigned find_get_pages_range(struct address_space
*mapping
, pgoff_t
*start
,
1602 pgoff_t end
, unsigned int nr_pages
,
1603 struct page
**pages
)
1605 struct radix_tree_iter iter
;
1609 if (unlikely(!nr_pages
))
1613 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, *start
) {
1614 struct page
*head
, *page
;
1616 if (iter
.index
> end
)
1619 page
= radix_tree_deref_slot(slot
);
1620 if (unlikely(!page
))
1623 if (radix_tree_exception(page
)) {
1624 if (radix_tree_deref_retry(page
)) {
1625 slot
= radix_tree_iter_retry(&iter
);
1629 * A shadow entry of a recently evicted page,
1630 * or a swap entry from shmem/tmpfs. Skip
1636 head
= compound_head(page
);
1637 if (!page_cache_get_speculative(head
))
1640 /* The page was split under us? */
1641 if (compound_head(page
) != head
) {
1646 /* Has the page moved? */
1647 if (unlikely(page
!= *slot
)) {
1653 if (++ret
== nr_pages
) {
1654 *start
= pages
[ret
- 1]->index
+ 1;
1660 * We come here when there is no page beyond @end. We take care to not
1661 * overflow the index @start as it confuses some of the callers. This
1662 * breaks the iteration when there is page at index -1 but that is
1663 * already broken anyway.
1665 if (end
== (pgoff_t
)-1)
1666 *start
= (pgoff_t
)-1;
1676 * find_get_pages_contig - gang contiguous pagecache lookup
1677 * @mapping: The address_space to search
1678 * @index: The starting page index
1679 * @nr_pages: The maximum number of pages
1680 * @pages: Where the resulting pages are placed
1682 * find_get_pages_contig() works exactly like find_get_pages(), except
1683 * that the returned number of pages are guaranteed to be contiguous.
1685 * find_get_pages_contig() returns the number of pages which were found.
1687 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1688 unsigned int nr_pages
, struct page
**pages
)
1690 struct radix_tree_iter iter
;
1692 unsigned int ret
= 0;
1694 if (unlikely(!nr_pages
))
1698 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1699 struct page
*head
, *page
;
1701 page
= radix_tree_deref_slot(slot
);
1702 /* The hole, there no reason to continue */
1703 if (unlikely(!page
))
1706 if (radix_tree_exception(page
)) {
1707 if (radix_tree_deref_retry(page
)) {
1708 slot
= radix_tree_iter_retry(&iter
);
1712 * A shadow entry of a recently evicted page,
1713 * or a swap entry from shmem/tmpfs. Stop
1714 * looking for contiguous pages.
1719 head
= compound_head(page
);
1720 if (!page_cache_get_speculative(head
))
1723 /* The page was split under us? */
1724 if (compound_head(page
) != head
) {
1729 /* Has the page moved? */
1730 if (unlikely(page
!= *slot
)) {
1736 * must check mapping and index after taking the ref.
1737 * otherwise we can get both false positives and false
1738 * negatives, which is just confusing to the caller.
1740 if (page
->mapping
== NULL
|| page_to_pgoff(page
) != iter
.index
) {
1746 if (++ret
== nr_pages
)
1752 EXPORT_SYMBOL(find_get_pages_contig
);
1755 * find_get_pages_range_tag - find and return pages in given range matching @tag
1756 * @mapping: the address_space to search
1757 * @index: the starting page index
1758 * @end: The final page index (inclusive)
1759 * @tag: the tag index
1760 * @nr_pages: the maximum number of pages
1761 * @pages: where the resulting pages are placed
1763 * Like find_get_pages, except we only return pages which are tagged with
1764 * @tag. We update @index to index the next page for the traversal.
1766 unsigned find_get_pages_range_tag(struct address_space
*mapping
, pgoff_t
*index
,
1767 pgoff_t end
, int tag
, unsigned int nr_pages
,
1768 struct page
**pages
)
1770 struct radix_tree_iter iter
;
1774 if (unlikely(!nr_pages
))
1778 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1779 &iter
, *index
, tag
) {
1780 struct page
*head
, *page
;
1782 if (iter
.index
> end
)
1785 page
= radix_tree_deref_slot(slot
);
1786 if (unlikely(!page
))
1789 if (radix_tree_exception(page
)) {
1790 if (radix_tree_deref_retry(page
)) {
1791 slot
= radix_tree_iter_retry(&iter
);
1795 * A shadow entry of a recently evicted page.
1797 * Those entries should never be tagged, but
1798 * this tree walk is lockless and the tags are
1799 * looked up in bulk, one radix tree node at a
1800 * time, so there is a sizable window for page
1801 * reclaim to evict a page we saw tagged.
1808 head
= compound_head(page
);
1809 if (!page_cache_get_speculative(head
))
1812 /* The page was split under us? */
1813 if (compound_head(page
) != head
) {
1818 /* Has the page moved? */
1819 if (unlikely(page
!= *slot
)) {
1825 if (++ret
== nr_pages
) {
1826 *index
= pages
[ret
- 1]->index
+ 1;
1832 * We come here when we got at @end. We take care to not overflow the
1833 * index @index as it confuses some of the callers. This breaks the
1834 * iteration when there is page at index -1 but that is already broken
1837 if (end
== (pgoff_t
)-1)
1838 *index
= (pgoff_t
)-1;
1846 EXPORT_SYMBOL(find_get_pages_range_tag
);
1849 * find_get_entries_tag - find and return entries that match @tag
1850 * @mapping: the address_space to search
1851 * @start: the starting page cache index
1852 * @tag: the tag index
1853 * @nr_entries: the maximum number of entries
1854 * @entries: where the resulting entries are placed
1855 * @indices: the cache indices corresponding to the entries in @entries
1857 * Like find_get_entries, except we only return entries which are tagged with
1860 unsigned find_get_entries_tag(struct address_space
*mapping
, pgoff_t start
,
1861 int tag
, unsigned int nr_entries
,
1862 struct page
**entries
, pgoff_t
*indices
)
1865 unsigned int ret
= 0;
1866 struct radix_tree_iter iter
;
1872 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1873 &iter
, start
, tag
) {
1874 struct page
*head
, *page
;
1876 page
= radix_tree_deref_slot(slot
);
1877 if (unlikely(!page
))
1879 if (radix_tree_exception(page
)) {
1880 if (radix_tree_deref_retry(page
)) {
1881 slot
= radix_tree_iter_retry(&iter
);
1886 * A shadow entry of a recently evicted page, a swap
1887 * entry from shmem/tmpfs or a DAX entry. Return it
1888 * without attempting to raise page count.
1893 head
= compound_head(page
);
1894 if (!page_cache_get_speculative(head
))
1897 /* The page was split under us? */
1898 if (compound_head(page
) != head
) {
1903 /* Has the page moved? */
1904 if (unlikely(page
!= *slot
)) {
1909 indices
[ret
] = iter
.index
;
1910 entries
[ret
] = page
;
1911 if (++ret
== nr_entries
)
1917 EXPORT_SYMBOL(find_get_entries_tag
);
1920 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1921 * a _large_ part of the i/o request. Imagine the worst scenario:
1923 * ---R__________________________________________B__________
1924 * ^ reading here ^ bad block(assume 4k)
1926 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1927 * => failing the whole request => read(R) => read(R+1) =>
1928 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1929 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1930 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1932 * It is going insane. Fix it by quickly scaling down the readahead size.
1934 static void shrink_readahead_size_eio(struct file
*filp
,
1935 struct file_ra_state
*ra
)
1941 * generic_file_buffered_read - generic file read routine
1942 * @iocb: the iocb to read
1943 * @iter: data destination
1944 * @written: already copied
1946 * This is a generic file read routine, and uses the
1947 * mapping->a_ops->readpage() function for the actual low-level stuff.
1949 * This is really ugly. But the goto's actually try to clarify some
1950 * of the logic when it comes to error handling etc.
1952 static ssize_t
generic_file_buffered_read(struct kiocb
*iocb
,
1953 struct iov_iter
*iter
, ssize_t written
)
1955 struct file
*filp
= iocb
->ki_filp
;
1956 struct address_space
*mapping
= filp
->f_mapping
;
1957 struct inode
*inode
= mapping
->host
;
1958 struct file_ra_state
*ra
= &filp
->f_ra
;
1959 loff_t
*ppos
= &iocb
->ki_pos
;
1963 unsigned long offset
; /* offset into pagecache page */
1964 unsigned int prev_offset
;
1967 if (unlikely(*ppos
>= inode
->i_sb
->s_maxbytes
))
1969 iov_iter_truncate(iter
, inode
->i_sb
->s_maxbytes
);
1971 index
= *ppos
>> PAGE_SHIFT
;
1972 prev_index
= ra
->prev_pos
>> PAGE_SHIFT
;
1973 prev_offset
= ra
->prev_pos
& (PAGE_SIZE
-1);
1974 last_index
= (*ppos
+ iter
->count
+ PAGE_SIZE
-1) >> PAGE_SHIFT
;
1975 offset
= *ppos
& ~PAGE_MASK
;
1981 unsigned long nr
, ret
;
1985 if (fatal_signal_pending(current
)) {
1990 page
= find_get_page(mapping
, index
);
1992 if (iocb
->ki_flags
& IOCB_NOWAIT
)
1994 page_cache_sync_readahead(mapping
,
1996 index
, last_index
- index
);
1997 page
= find_get_page(mapping
, index
);
1998 if (unlikely(page
== NULL
))
1999 goto no_cached_page
;
2001 if (PageReadahead(page
)) {
2002 page_cache_async_readahead(mapping
,
2004 index
, last_index
- index
);
2006 if (!PageUptodate(page
)) {
2007 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2013 * See comment in do_read_cache_page on why
2014 * wait_on_page_locked is used to avoid unnecessarily
2015 * serialisations and why it's safe.
2017 error
= wait_on_page_locked_killable(page
);
2018 if (unlikely(error
))
2019 goto readpage_error
;
2020 if (PageUptodate(page
))
2023 if (inode
->i_blkbits
== PAGE_SHIFT
||
2024 !mapping
->a_ops
->is_partially_uptodate
)
2025 goto page_not_up_to_date
;
2026 /* pipes can't handle partially uptodate pages */
2027 if (unlikely(iter
->type
& ITER_PIPE
))
2028 goto page_not_up_to_date
;
2029 if (!trylock_page(page
))
2030 goto page_not_up_to_date
;
2031 /* Did it get truncated before we got the lock? */
2033 goto page_not_up_to_date_locked
;
2034 if (!mapping
->a_ops
->is_partially_uptodate(page
,
2035 offset
, iter
->count
))
2036 goto page_not_up_to_date_locked
;
2041 * i_size must be checked after we know the page is Uptodate.
2043 * Checking i_size after the check allows us to calculate
2044 * the correct value for "nr", which means the zero-filled
2045 * part of the page is not copied back to userspace (unless
2046 * another truncate extends the file - this is desired though).
2049 isize
= i_size_read(inode
);
2050 end_index
= (isize
- 1) >> PAGE_SHIFT
;
2051 if (unlikely(!isize
|| index
> end_index
)) {
2056 /* nr is the maximum number of bytes to copy from this page */
2058 if (index
== end_index
) {
2059 nr
= ((isize
- 1) & ~PAGE_MASK
) + 1;
2067 /* If users can be writing to this page using arbitrary
2068 * virtual addresses, take care about potential aliasing
2069 * before reading the page on the kernel side.
2071 if (mapping_writably_mapped(mapping
))
2072 flush_dcache_page(page
);
2075 * When a sequential read accesses a page several times,
2076 * only mark it as accessed the first time.
2078 if (prev_index
!= index
|| offset
!= prev_offset
)
2079 mark_page_accessed(page
);
2083 * Ok, we have the page, and it's up-to-date, so
2084 * now we can copy it to user space...
2087 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
2089 index
+= offset
>> PAGE_SHIFT
;
2090 offset
&= ~PAGE_MASK
;
2091 prev_offset
= offset
;
2095 if (!iov_iter_count(iter
))
2103 page_not_up_to_date
:
2104 /* Get exclusive access to the page ... */
2105 error
= lock_page_killable(page
);
2106 if (unlikely(error
))
2107 goto readpage_error
;
2109 page_not_up_to_date_locked
:
2110 /* Did it get truncated before we got the lock? */
2111 if (!page
->mapping
) {
2117 /* Did somebody else fill it already? */
2118 if (PageUptodate(page
)) {
2125 * A previous I/O error may have been due to temporary
2126 * failures, eg. multipath errors.
2127 * PG_error will be set again if readpage fails.
2129 ClearPageError(page
);
2130 /* Start the actual read. The read will unlock the page. */
2131 error
= mapping
->a_ops
->readpage(filp
, page
);
2133 if (unlikely(error
)) {
2134 if (error
== AOP_TRUNCATED_PAGE
) {
2139 goto readpage_error
;
2142 if (!PageUptodate(page
)) {
2143 error
= lock_page_killable(page
);
2144 if (unlikely(error
))
2145 goto readpage_error
;
2146 if (!PageUptodate(page
)) {
2147 if (page
->mapping
== NULL
) {
2149 * invalidate_mapping_pages got it
2156 shrink_readahead_size_eio(filp
, ra
);
2158 goto readpage_error
;
2166 /* UHHUH! A synchronous read error occurred. Report it */
2172 * Ok, it wasn't cached, so we need to create a new
2175 page
= page_cache_alloc_cold(mapping
);
2180 error
= add_to_page_cache_lru(page
, mapping
, index
,
2181 mapping_gfp_constraint(mapping
, GFP_KERNEL
));
2184 if (error
== -EEXIST
) {
2196 ra
->prev_pos
= prev_index
;
2197 ra
->prev_pos
<<= PAGE_SHIFT
;
2198 ra
->prev_pos
|= prev_offset
;
2200 *ppos
= ((loff_t
)index
<< PAGE_SHIFT
) + offset
;
2201 file_accessed(filp
);
2202 return written
? written
: error
;
2206 * generic_file_read_iter - generic filesystem read routine
2207 * @iocb: kernel I/O control block
2208 * @iter: destination for the data read
2210 * This is the "read_iter()" routine for all filesystems
2211 * that can use the page cache directly.
2214 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
2216 size_t count
= iov_iter_count(iter
);
2220 goto out
; /* skip atime */
2222 if (iocb
->ki_flags
& IOCB_DIRECT
) {
2223 struct file
*file
= iocb
->ki_filp
;
2224 struct address_space
*mapping
= file
->f_mapping
;
2225 struct inode
*inode
= mapping
->host
;
2228 size
= i_size_read(inode
);
2229 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2230 if (filemap_range_has_page(mapping
, iocb
->ki_pos
,
2231 iocb
->ki_pos
+ count
- 1))
2234 retval
= filemap_write_and_wait_range(mapping
,
2236 iocb
->ki_pos
+ count
- 1);
2241 file_accessed(file
);
2243 retval
= mapping
->a_ops
->direct_IO(iocb
, iter
);
2245 iocb
->ki_pos
+= retval
;
2248 iov_iter_revert(iter
, count
- iov_iter_count(iter
));
2251 * Btrfs can have a short DIO read if we encounter
2252 * compressed extents, so if there was an error, or if
2253 * we've already read everything we wanted to, or if
2254 * there was a short read because we hit EOF, go ahead
2255 * and return. Otherwise fallthrough to buffered io for
2256 * the rest of the read. Buffered reads will not work for
2257 * DAX files, so don't bother trying.
2259 if (retval
< 0 || !count
|| iocb
->ki_pos
>= size
||
2264 retval
= generic_file_buffered_read(iocb
, iter
, retval
);
2268 EXPORT_SYMBOL(generic_file_read_iter
);
2272 * page_cache_read - adds requested page to the page cache if not already there
2273 * @file: file to read
2274 * @offset: page index
2275 * @gfp_mask: memory allocation flags
2277 * This adds the requested page to the page cache if it isn't already there,
2278 * and schedules an I/O to read in its contents from disk.
2280 static int page_cache_read(struct file
*file
, pgoff_t offset
, gfp_t gfp_mask
)
2282 struct address_space
*mapping
= file
->f_mapping
;
2287 page
= __page_cache_alloc(gfp_mask
|__GFP_COLD
);
2291 ret
= add_to_page_cache_lru(page
, mapping
, offset
, gfp_mask
& GFP_KERNEL
);
2293 ret
= mapping
->a_ops
->readpage(file
, page
);
2294 else if (ret
== -EEXIST
)
2295 ret
= 0; /* losing race to add is OK */
2299 } while (ret
== AOP_TRUNCATED_PAGE
);
2304 #define MMAP_LOTSAMISS (100)
2307 * Synchronous readahead happens when we don't even find
2308 * a page in the page cache at all.
2310 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
2311 struct file_ra_state
*ra
,
2315 struct address_space
*mapping
= file
->f_mapping
;
2317 /* If we don't want any read-ahead, don't bother */
2318 if (vma
->vm_flags
& VM_RAND_READ
)
2323 if (vma
->vm_flags
& VM_SEQ_READ
) {
2324 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
2329 /* Avoid banging the cache line if not needed */
2330 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
2334 * Do we miss much more than hit in this file? If so,
2335 * stop bothering with read-ahead. It will only hurt.
2337 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
2343 ra
->start
= max_t(long, 0, offset
- ra
->ra_pages
/ 2);
2344 ra
->size
= ra
->ra_pages
;
2345 ra
->async_size
= ra
->ra_pages
/ 4;
2346 ra_submit(ra
, mapping
, file
);
2350 * Asynchronous readahead happens when we find the page and PG_readahead,
2351 * so we want to possibly extend the readahead further..
2353 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
2354 struct file_ra_state
*ra
,
2359 struct address_space
*mapping
= file
->f_mapping
;
2361 /* If we don't want any read-ahead, don't bother */
2362 if (vma
->vm_flags
& VM_RAND_READ
)
2364 if (ra
->mmap_miss
> 0)
2366 if (PageReadahead(page
))
2367 page_cache_async_readahead(mapping
, ra
, file
,
2368 page
, offset
, ra
->ra_pages
);
2372 * filemap_fault - read in file data for page fault handling
2373 * @vmf: struct vm_fault containing details of the fault
2375 * filemap_fault() is invoked via the vma operations vector for a
2376 * mapped memory region to read in file data during a page fault.
2378 * The goto's are kind of ugly, but this streamlines the normal case of having
2379 * it in the page cache, and handles the special cases reasonably without
2380 * having a lot of duplicated code.
2382 * vma->vm_mm->mmap_sem must be held on entry.
2384 * If our return value has VM_FAULT_RETRY set, it's because
2385 * lock_page_or_retry() returned 0.
2386 * The mmap_sem has usually been released in this case.
2387 * See __lock_page_or_retry() for the exception.
2389 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2390 * has not been released.
2392 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2394 int filemap_fault(struct vm_fault
*vmf
)
2397 struct file
*file
= vmf
->vma
->vm_file
;
2398 struct address_space
*mapping
= file
->f_mapping
;
2399 struct file_ra_state
*ra
= &file
->f_ra
;
2400 struct inode
*inode
= mapping
->host
;
2401 pgoff_t offset
= vmf
->pgoff
;
2406 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2407 if (unlikely(offset
>= max_off
))
2408 return VM_FAULT_SIGBUS
;
2411 * Do we have something in the page cache already?
2413 page
= find_get_page(mapping
, offset
);
2414 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
2416 * We found the page, so try async readahead before
2417 * waiting for the lock.
2419 do_async_mmap_readahead(vmf
->vma
, ra
, file
, page
, offset
);
2421 /* No page in the page cache at all */
2422 do_sync_mmap_readahead(vmf
->vma
, ra
, file
, offset
);
2423 count_vm_event(PGMAJFAULT
);
2424 count_memcg_event_mm(vmf
->vma
->vm_mm
, PGMAJFAULT
);
2425 ret
= VM_FAULT_MAJOR
;
2427 page
= find_get_page(mapping
, offset
);
2429 goto no_cached_page
;
2432 if (!lock_page_or_retry(page
, vmf
->vma
->vm_mm
, vmf
->flags
)) {
2434 return ret
| VM_FAULT_RETRY
;
2437 /* Did it get truncated? */
2438 if (unlikely(page
->mapping
!= mapping
)) {
2443 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
2446 * We have a locked page in the page cache, now we need to check
2447 * that it's up-to-date. If not, it is going to be due to an error.
2449 if (unlikely(!PageUptodate(page
)))
2450 goto page_not_uptodate
;
2453 * Found the page and have a reference on it.
2454 * We must recheck i_size under page lock.
2456 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2457 if (unlikely(offset
>= max_off
)) {
2460 return VM_FAULT_SIGBUS
;
2464 return ret
| VM_FAULT_LOCKED
;
2468 * We're only likely to ever get here if MADV_RANDOM is in
2471 error
= page_cache_read(file
, offset
, vmf
->gfp_mask
);
2474 * The page we want has now been added to the page cache.
2475 * In the unlikely event that someone removed it in the
2476 * meantime, we'll just come back here and read it again.
2482 * An error return from page_cache_read can result if the
2483 * system is low on memory, or a problem occurs while trying
2486 if (error
== -ENOMEM
)
2487 return VM_FAULT_OOM
;
2488 return VM_FAULT_SIGBUS
;
2492 * Umm, take care of errors if the page isn't up-to-date.
2493 * Try to re-read it _once_. We do this synchronously,
2494 * because there really aren't any performance issues here
2495 * and we need to check for errors.
2497 ClearPageError(page
);
2498 error
= mapping
->a_ops
->readpage(file
, page
);
2500 wait_on_page_locked(page
);
2501 if (!PageUptodate(page
))
2506 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2509 /* Things didn't work out. Return zero to tell the mm layer so. */
2510 shrink_readahead_size_eio(file
, ra
);
2511 return VM_FAULT_SIGBUS
;
2513 EXPORT_SYMBOL(filemap_fault
);
2515 void filemap_map_pages(struct vm_fault
*vmf
,
2516 pgoff_t start_pgoff
, pgoff_t end_pgoff
)
2518 struct radix_tree_iter iter
;
2520 struct file
*file
= vmf
->vma
->vm_file
;
2521 struct address_space
*mapping
= file
->f_mapping
;
2522 pgoff_t last_pgoff
= start_pgoff
;
2523 unsigned long max_idx
;
2524 struct page
*head
, *page
;
2527 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
,
2529 if (iter
.index
> end_pgoff
)
2532 page
= radix_tree_deref_slot(slot
);
2533 if (unlikely(!page
))
2535 if (radix_tree_exception(page
)) {
2536 if (radix_tree_deref_retry(page
)) {
2537 slot
= radix_tree_iter_retry(&iter
);
2543 head
= compound_head(page
);
2544 if (!page_cache_get_speculative(head
))
2547 /* The page was split under us? */
2548 if (compound_head(page
) != head
) {
2553 /* Has the page moved? */
2554 if (unlikely(page
!= *slot
)) {
2559 if (!PageUptodate(page
) ||
2560 PageReadahead(page
) ||
2563 if (!trylock_page(page
))
2566 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2569 max_idx
= DIV_ROUND_UP(i_size_read(mapping
->host
), PAGE_SIZE
);
2570 if (page
->index
>= max_idx
)
2573 if (file
->f_ra
.mmap_miss
> 0)
2574 file
->f_ra
.mmap_miss
--;
2576 vmf
->address
+= (iter
.index
- last_pgoff
) << PAGE_SHIFT
;
2578 vmf
->pte
+= iter
.index
- last_pgoff
;
2579 last_pgoff
= iter
.index
;
2580 if (alloc_set_pte(vmf
, NULL
, page
))
2589 /* Huge page is mapped? No need to proceed. */
2590 if (pmd_trans_huge(*vmf
->pmd
))
2592 if (iter
.index
== end_pgoff
)
2597 EXPORT_SYMBOL(filemap_map_pages
);
2599 int filemap_page_mkwrite(struct vm_fault
*vmf
)
2601 struct page
*page
= vmf
->page
;
2602 struct inode
*inode
= file_inode(vmf
->vma
->vm_file
);
2603 int ret
= VM_FAULT_LOCKED
;
2605 sb_start_pagefault(inode
->i_sb
);
2606 file_update_time(vmf
->vma
->vm_file
);
2608 if (page
->mapping
!= inode
->i_mapping
) {
2610 ret
= VM_FAULT_NOPAGE
;
2614 * We mark the page dirty already here so that when freeze is in
2615 * progress, we are guaranteed that writeback during freezing will
2616 * see the dirty page and writeprotect it again.
2618 set_page_dirty(page
);
2619 wait_for_stable_page(page
);
2621 sb_end_pagefault(inode
->i_sb
);
2624 EXPORT_SYMBOL(filemap_page_mkwrite
);
2626 const struct vm_operations_struct generic_file_vm_ops
= {
2627 .fault
= filemap_fault
,
2628 .map_pages
= filemap_map_pages
,
2629 .page_mkwrite
= filemap_page_mkwrite
,
2632 /* This is used for a general mmap of a disk file */
2634 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2636 struct address_space
*mapping
= file
->f_mapping
;
2638 if (!mapping
->a_ops
->readpage
)
2640 file_accessed(file
);
2641 vma
->vm_ops
= &generic_file_vm_ops
;
2646 * This is for filesystems which do not implement ->writepage.
2648 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2650 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2652 return generic_file_mmap(file
, vma
);
2655 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2659 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2663 #endif /* CONFIG_MMU */
2665 EXPORT_SYMBOL(generic_file_mmap
);
2666 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2668 static struct page
*wait_on_page_read(struct page
*page
)
2670 if (!IS_ERR(page
)) {
2671 wait_on_page_locked(page
);
2672 if (!PageUptodate(page
)) {
2674 page
= ERR_PTR(-EIO
);
2680 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2682 int (*filler
)(void *, struct page
*),
2689 page
= find_get_page(mapping
, index
);
2691 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2693 return ERR_PTR(-ENOMEM
);
2694 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2695 if (unlikely(err
)) {
2699 /* Presumably ENOMEM for radix tree node */
2700 return ERR_PTR(err
);
2704 err
= filler(data
, page
);
2707 return ERR_PTR(err
);
2710 page
= wait_on_page_read(page
);
2715 if (PageUptodate(page
))
2719 * Page is not up to date and may be locked due one of the following
2720 * case a: Page is being filled and the page lock is held
2721 * case b: Read/write error clearing the page uptodate status
2722 * case c: Truncation in progress (page locked)
2723 * case d: Reclaim in progress
2725 * Case a, the page will be up to date when the page is unlocked.
2726 * There is no need to serialise on the page lock here as the page
2727 * is pinned so the lock gives no additional protection. Even if the
2728 * the page is truncated, the data is still valid if PageUptodate as
2729 * it's a race vs truncate race.
2730 * Case b, the page will not be up to date
2731 * Case c, the page may be truncated but in itself, the data may still
2732 * be valid after IO completes as it's a read vs truncate race. The
2733 * operation must restart if the page is not uptodate on unlock but
2734 * otherwise serialising on page lock to stabilise the mapping gives
2735 * no additional guarantees to the caller as the page lock is
2736 * released before return.
2737 * Case d, similar to truncation. If reclaim holds the page lock, it
2738 * will be a race with remove_mapping that determines if the mapping
2739 * is valid on unlock but otherwise the data is valid and there is
2740 * no need to serialise with page lock.
2742 * As the page lock gives no additional guarantee, we optimistically
2743 * wait on the page to be unlocked and check if it's up to date and
2744 * use the page if it is. Otherwise, the page lock is required to
2745 * distinguish between the different cases. The motivation is that we
2746 * avoid spurious serialisations and wakeups when multiple processes
2747 * wait on the same page for IO to complete.
2749 wait_on_page_locked(page
);
2750 if (PageUptodate(page
))
2753 /* Distinguish between all the cases under the safety of the lock */
2756 /* Case c or d, restart the operation */
2757 if (!page
->mapping
) {
2763 /* Someone else locked and filled the page in a very small window */
2764 if (PageUptodate(page
)) {
2771 mark_page_accessed(page
);
2776 * read_cache_page - read into page cache, fill it if needed
2777 * @mapping: the page's address_space
2778 * @index: the page index
2779 * @filler: function to perform the read
2780 * @data: first arg to filler(data, page) function, often left as NULL
2782 * Read into the page cache. If a page already exists, and PageUptodate() is
2783 * not set, try to fill the page and wait for it to become unlocked.
2785 * If the page does not get brought uptodate, return -EIO.
2787 struct page
*read_cache_page(struct address_space
*mapping
,
2789 int (*filler
)(void *, struct page
*),
2792 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2794 EXPORT_SYMBOL(read_cache_page
);
2797 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2798 * @mapping: the page's address_space
2799 * @index: the page index
2800 * @gfp: the page allocator flags to use if allocating
2802 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2803 * any new page allocations done using the specified allocation flags.
2805 * If the page does not get brought uptodate, return -EIO.
2807 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2811 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2813 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2815 EXPORT_SYMBOL(read_cache_page_gfp
);
2818 * Performs necessary checks before doing a write
2820 * Can adjust writing position or amount of bytes to write.
2821 * Returns appropriate error code that caller should return or
2822 * zero in case that write should be allowed.
2824 inline ssize_t
generic_write_checks(struct kiocb
*iocb
, struct iov_iter
*from
)
2826 struct file
*file
= iocb
->ki_filp
;
2827 struct inode
*inode
= file
->f_mapping
->host
;
2828 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2831 if (!iov_iter_count(from
))
2834 /* FIXME: this is for backwards compatibility with 2.4 */
2835 if (iocb
->ki_flags
& IOCB_APPEND
)
2836 iocb
->ki_pos
= i_size_read(inode
);
2840 if ((iocb
->ki_flags
& IOCB_NOWAIT
) && !(iocb
->ki_flags
& IOCB_DIRECT
))
2843 if (limit
!= RLIM_INFINITY
) {
2844 if (iocb
->ki_pos
>= limit
) {
2845 send_sig(SIGXFSZ
, current
, 0);
2848 iov_iter_truncate(from
, limit
- (unsigned long)pos
);
2854 if (unlikely(pos
+ iov_iter_count(from
) > MAX_NON_LFS
&&
2855 !(file
->f_flags
& O_LARGEFILE
))) {
2856 if (pos
>= MAX_NON_LFS
)
2858 iov_iter_truncate(from
, MAX_NON_LFS
- (unsigned long)pos
);
2862 * Are we about to exceed the fs block limit ?
2864 * If we have written data it becomes a short write. If we have
2865 * exceeded without writing data we send a signal and return EFBIG.
2866 * Linus frestrict idea will clean these up nicely..
2868 if (unlikely(pos
>= inode
->i_sb
->s_maxbytes
))
2871 iov_iter_truncate(from
, inode
->i_sb
->s_maxbytes
- pos
);
2872 return iov_iter_count(from
);
2874 EXPORT_SYMBOL(generic_write_checks
);
2876 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2877 loff_t pos
, unsigned len
, unsigned flags
,
2878 struct page
**pagep
, void **fsdata
)
2880 const struct address_space_operations
*aops
= mapping
->a_ops
;
2882 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2885 EXPORT_SYMBOL(pagecache_write_begin
);
2887 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2888 loff_t pos
, unsigned len
, unsigned copied
,
2889 struct page
*page
, void *fsdata
)
2891 const struct address_space_operations
*aops
= mapping
->a_ops
;
2893 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2895 EXPORT_SYMBOL(pagecache_write_end
);
2898 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
)
2900 struct file
*file
= iocb
->ki_filp
;
2901 struct address_space
*mapping
= file
->f_mapping
;
2902 struct inode
*inode
= mapping
->host
;
2903 loff_t pos
= iocb
->ki_pos
;
2908 write_len
= iov_iter_count(from
);
2909 end
= (pos
+ write_len
- 1) >> PAGE_SHIFT
;
2911 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2912 /* If there are pages to writeback, return */
2913 if (filemap_range_has_page(inode
->i_mapping
, pos
,
2914 pos
+ iov_iter_count(from
)))
2917 written
= filemap_write_and_wait_range(mapping
, pos
,
2918 pos
+ write_len
- 1);
2924 * After a write we want buffered reads to be sure to go to disk to get
2925 * the new data. We invalidate clean cached page from the region we're
2926 * about to write. We do this *before* the write so that we can return
2927 * without clobbering -EIOCBQUEUED from ->direct_IO().
2929 written
= invalidate_inode_pages2_range(mapping
,
2930 pos
>> PAGE_SHIFT
, end
);
2932 * If a page can not be invalidated, return 0 to fall back
2933 * to buffered write.
2936 if (written
== -EBUSY
)
2941 written
= mapping
->a_ops
->direct_IO(iocb
, from
);
2944 * Finally, try again to invalidate clean pages which might have been
2945 * cached by non-direct readahead, or faulted in by get_user_pages()
2946 * if the source of the write was an mmap'ed region of the file
2947 * we're writing. Either one is a pretty crazy thing to do,
2948 * so we don't support it 100%. If this invalidation
2949 * fails, tough, the write still worked...
2951 * Most of the time we do not need this since dio_complete() will do
2952 * the invalidation for us. However there are some file systems that
2953 * do not end up with dio_complete() being called, so let's not break
2954 * them by removing it completely
2956 if (mapping
->nrpages
)
2957 invalidate_inode_pages2_range(mapping
,
2958 pos
>> PAGE_SHIFT
, end
);
2962 write_len
-= written
;
2963 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2964 i_size_write(inode
, pos
);
2965 mark_inode_dirty(inode
);
2969 iov_iter_revert(from
, write_len
- iov_iter_count(from
));
2973 EXPORT_SYMBOL(generic_file_direct_write
);
2976 * Find or create a page at the given pagecache position. Return the locked
2977 * page. This function is specifically for buffered writes.
2979 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2980 pgoff_t index
, unsigned flags
)
2983 int fgp_flags
= FGP_LOCK
|FGP_WRITE
|FGP_CREAT
;
2985 if (flags
& AOP_FLAG_NOFS
)
2986 fgp_flags
|= FGP_NOFS
;
2988 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2989 mapping_gfp_mask(mapping
));
2991 wait_for_stable_page(page
);
2995 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2997 ssize_t
generic_perform_write(struct file
*file
,
2998 struct iov_iter
*i
, loff_t pos
)
3000 struct address_space
*mapping
= file
->f_mapping
;
3001 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
3003 ssize_t written
= 0;
3004 unsigned int flags
= 0;
3008 unsigned long offset
; /* Offset into pagecache page */
3009 unsigned long bytes
; /* Bytes to write to page */
3010 size_t copied
; /* Bytes copied from user */
3013 offset
= (pos
& (PAGE_SIZE
- 1));
3014 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
3019 * Bring in the user page that we will copy from _first_.
3020 * Otherwise there's a nasty deadlock on copying from the
3021 * same page as we're writing to, without it being marked
3024 * Not only is this an optimisation, but it is also required
3025 * to check that the address is actually valid, when atomic
3026 * usercopies are used, below.
3028 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
3033 if (fatal_signal_pending(current
)) {
3038 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
3040 if (unlikely(status
< 0))
3043 if (mapping_writably_mapped(mapping
))
3044 flush_dcache_page(page
);
3046 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
3047 flush_dcache_page(page
);
3049 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
3051 if (unlikely(status
< 0))
3057 iov_iter_advance(i
, copied
);
3058 if (unlikely(copied
== 0)) {
3060 * If we were unable to copy any data at all, we must
3061 * fall back to a single segment length write.
3063 * If we didn't fallback here, we could livelock
3064 * because not all segments in the iov can be copied at
3065 * once without a pagefault.
3067 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
3068 iov_iter_single_seg_count(i
));
3074 balance_dirty_pages_ratelimited(mapping
);
3075 } while (iov_iter_count(i
));
3077 return written
? written
: status
;
3079 EXPORT_SYMBOL(generic_perform_write
);
3082 * __generic_file_write_iter - write data to a file
3083 * @iocb: IO state structure (file, offset, etc.)
3084 * @from: iov_iter with data to write
3086 * This function does all the work needed for actually writing data to a
3087 * file. It does all basic checks, removes SUID from the file, updates
3088 * modification times and calls proper subroutines depending on whether we
3089 * do direct IO or a standard buffered write.
3091 * It expects i_mutex to be grabbed unless we work on a block device or similar
3092 * object which does not need locking at all.
3094 * This function does *not* take care of syncing data in case of O_SYNC write.
3095 * A caller has to handle it. This is mainly due to the fact that we want to
3096 * avoid syncing under i_mutex.
3098 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3100 struct file
*file
= iocb
->ki_filp
;
3101 struct address_space
* mapping
= file
->f_mapping
;
3102 struct inode
*inode
= mapping
->host
;
3103 ssize_t written
= 0;
3107 /* We can write back this queue in page reclaim */
3108 current
->backing_dev_info
= inode_to_bdi(inode
);
3109 err
= file_remove_privs(file
);
3113 err
= file_update_time(file
);
3117 if (iocb
->ki_flags
& IOCB_DIRECT
) {
3118 loff_t pos
, endbyte
;
3120 written
= generic_file_direct_write(iocb
, from
);
3122 * If the write stopped short of completing, fall back to
3123 * buffered writes. Some filesystems do this for writes to
3124 * holes, for example. For DAX files, a buffered write will
3125 * not succeed (even if it did, DAX does not handle dirty
3126 * page-cache pages correctly).
3128 if (written
< 0 || !iov_iter_count(from
) || IS_DAX(inode
))
3131 status
= generic_perform_write(file
, from
, pos
= iocb
->ki_pos
);
3133 * If generic_perform_write() returned a synchronous error
3134 * then we want to return the number of bytes which were
3135 * direct-written, or the error code if that was zero. Note
3136 * that this differs from normal direct-io semantics, which
3137 * will return -EFOO even if some bytes were written.
3139 if (unlikely(status
< 0)) {
3144 * We need to ensure that the page cache pages are written to
3145 * disk and invalidated to preserve the expected O_DIRECT
3148 endbyte
= pos
+ status
- 1;
3149 err
= filemap_write_and_wait_range(mapping
, pos
, endbyte
);
3151 iocb
->ki_pos
= endbyte
+ 1;
3153 invalidate_mapping_pages(mapping
,
3155 endbyte
>> PAGE_SHIFT
);
3158 * We don't know how much we wrote, so just return
3159 * the number of bytes which were direct-written
3163 written
= generic_perform_write(file
, from
, iocb
->ki_pos
);
3164 if (likely(written
> 0))
3165 iocb
->ki_pos
+= written
;
3168 current
->backing_dev_info
= NULL
;
3169 return written
? written
: err
;
3171 EXPORT_SYMBOL(__generic_file_write_iter
);
3174 * generic_file_write_iter - write data to a file
3175 * @iocb: IO state structure
3176 * @from: iov_iter with data to write
3178 * This is a wrapper around __generic_file_write_iter() to be used by most
3179 * filesystems. It takes care of syncing the file in case of O_SYNC file
3180 * and acquires i_mutex as needed.
3182 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3184 struct file
*file
= iocb
->ki_filp
;
3185 struct inode
*inode
= file
->f_mapping
->host
;
3189 ret
= generic_write_checks(iocb
, from
);
3191 ret
= __generic_file_write_iter(iocb
, from
);
3192 inode_unlock(inode
);
3195 ret
= generic_write_sync(iocb
, ret
);
3198 EXPORT_SYMBOL(generic_file_write_iter
);
3201 * try_to_release_page() - release old fs-specific metadata on a page
3203 * @page: the page which the kernel is trying to free
3204 * @gfp_mask: memory allocation flags (and I/O mode)
3206 * The address_space is to try to release any data against the page
3207 * (presumably at page->private). If the release was successful, return '1'.
3208 * Otherwise return zero.
3210 * This may also be called if PG_fscache is set on a page, indicating that the
3211 * page is known to the local caching routines.
3213 * The @gfp_mask argument specifies whether I/O may be performed to release
3214 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3217 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
3219 struct address_space
* const mapping
= page
->mapping
;
3221 BUG_ON(!PageLocked(page
));
3222 if (PageWriteback(page
))
3225 if (mapping
&& mapping
->a_ops
->releasepage
)
3226 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
3227 return try_to_free_buffers(page
);
3230 EXPORT_SYMBOL(try_to_release_page
);