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
) &&
424 (nr_pages
= pagevec_lookup_tag(&pvec
, mapping
, &index
,
425 PAGECACHE_TAG_WRITEBACK
,
426 min(end
- index
, (pgoff_t
)PAGEVEC_SIZE
-1) + 1)) != 0) {
429 for (i
= 0; i
< nr_pages
; i
++) {
430 struct page
*page
= pvec
.pages
[i
];
432 /* until radix tree lookup accepts end_index */
433 if (page
->index
> end
)
436 wait_on_page_writeback(page
);
437 ClearPageError(page
);
439 pagevec_release(&pvec
);
445 * filemap_fdatawait_range - wait for writeback to complete
446 * @mapping: address space structure to wait for
447 * @start_byte: offset in bytes where the range starts
448 * @end_byte: offset in bytes where the range ends (inclusive)
450 * Walk the list of under-writeback pages of the given address space
451 * in the given range and wait for all of them. Check error status of
452 * the address space and return it.
454 * Since the error status of the address space is cleared by this function,
455 * callers are responsible for checking the return value and handling and/or
456 * reporting the error.
458 int filemap_fdatawait_range(struct address_space
*mapping
, loff_t start_byte
,
461 __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
462 return filemap_check_errors(mapping
);
464 EXPORT_SYMBOL(filemap_fdatawait_range
);
467 * file_fdatawait_range - wait for writeback to complete
468 * @file: file pointing to address space structure to wait for
469 * @start_byte: offset in bytes where the range starts
470 * @end_byte: offset in bytes where the range ends (inclusive)
472 * Walk the list of under-writeback pages of the address space that file
473 * refers to, in the given range and wait for all of them. Check error
474 * status of the address space vs. the file->f_wb_err cursor and return it.
476 * Since the error status of the file is advanced by this function,
477 * callers are responsible for checking the return value and handling and/or
478 * reporting the error.
480 int file_fdatawait_range(struct file
*file
, loff_t start_byte
, loff_t end_byte
)
482 struct address_space
*mapping
= file
->f_mapping
;
484 __filemap_fdatawait_range(mapping
, start_byte
, end_byte
);
485 return file_check_and_advance_wb_err(file
);
487 EXPORT_SYMBOL(file_fdatawait_range
);
490 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
491 * @mapping: address space structure to wait for
493 * Walk the list of under-writeback pages of the given address space
494 * and wait for all of them. Unlike filemap_fdatawait(), this function
495 * does not clear error status of the address space.
497 * Use this function if callers don't handle errors themselves. Expected
498 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
501 int filemap_fdatawait_keep_errors(struct address_space
*mapping
)
503 __filemap_fdatawait_range(mapping
, 0, LLONG_MAX
);
504 return filemap_check_and_keep_errors(mapping
);
506 EXPORT_SYMBOL(filemap_fdatawait_keep_errors
);
508 static bool mapping_needs_writeback(struct address_space
*mapping
)
510 return (!dax_mapping(mapping
) && mapping
->nrpages
) ||
511 (dax_mapping(mapping
) && mapping
->nrexceptional
);
514 int filemap_write_and_wait(struct address_space
*mapping
)
518 if (mapping_needs_writeback(mapping
)) {
519 err
= filemap_fdatawrite(mapping
);
521 * Even if the above returned error, the pages may be
522 * written partially (e.g. -ENOSPC), so we wait for it.
523 * But the -EIO is special case, it may indicate the worst
524 * thing (e.g. bug) happened, so we avoid waiting for it.
527 int err2
= filemap_fdatawait(mapping
);
531 /* Clear any previously stored errors */
532 filemap_check_errors(mapping
);
535 err
= filemap_check_errors(mapping
);
539 EXPORT_SYMBOL(filemap_write_and_wait
);
542 * filemap_write_and_wait_range - write out & wait on a file range
543 * @mapping: the address_space for the pages
544 * @lstart: offset in bytes where the range starts
545 * @lend: offset in bytes where the range ends (inclusive)
547 * Write out and wait upon file offsets lstart->lend, inclusive.
549 * Note that @lend is inclusive (describes the last byte to be written) so
550 * that this function can be used to write to the very end-of-file (end = -1).
552 int filemap_write_and_wait_range(struct address_space
*mapping
,
553 loff_t lstart
, loff_t lend
)
557 if (mapping_needs_writeback(mapping
)) {
558 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
560 /* See comment of filemap_write_and_wait() */
562 int err2
= filemap_fdatawait_range(mapping
,
567 /* Clear any previously stored errors */
568 filemap_check_errors(mapping
);
571 err
= filemap_check_errors(mapping
);
575 EXPORT_SYMBOL(filemap_write_and_wait_range
);
577 void __filemap_set_wb_err(struct address_space
*mapping
, int err
)
579 errseq_t eseq
= errseq_set(&mapping
->wb_err
, err
);
581 trace_filemap_set_wb_err(mapping
, eseq
);
583 EXPORT_SYMBOL(__filemap_set_wb_err
);
586 * file_check_and_advance_wb_err - report wb error (if any) that was previously
587 * and advance wb_err to current one
588 * @file: struct file on which the error is being reported
590 * When userland calls fsync (or something like nfsd does the equivalent), we
591 * want to report any writeback errors that occurred since the last fsync (or
592 * since the file was opened if there haven't been any).
594 * Grab the wb_err from the mapping. If it matches what we have in the file,
595 * then just quickly return 0. The file is all caught up.
597 * If it doesn't match, then take the mapping value, set the "seen" flag in
598 * it and try to swap it into place. If it works, or another task beat us
599 * to it with the new value, then update the f_wb_err and return the error
600 * portion. The error at this point must be reported via proper channels
601 * (a'la fsync, or NFS COMMIT operation, etc.).
603 * While we handle mapping->wb_err with atomic operations, the f_wb_err
604 * value is protected by the f_lock since we must ensure that it reflects
605 * the latest value swapped in for this file descriptor.
607 int file_check_and_advance_wb_err(struct file
*file
)
610 errseq_t old
= READ_ONCE(file
->f_wb_err
);
611 struct address_space
*mapping
= file
->f_mapping
;
613 /* Locklessly handle the common case where nothing has changed */
614 if (errseq_check(&mapping
->wb_err
, old
)) {
615 /* Something changed, must use slow path */
616 spin_lock(&file
->f_lock
);
617 old
= file
->f_wb_err
;
618 err
= errseq_check_and_advance(&mapping
->wb_err
,
620 trace_file_check_and_advance_wb_err(file
, old
);
621 spin_unlock(&file
->f_lock
);
625 EXPORT_SYMBOL(file_check_and_advance_wb_err
);
628 * file_write_and_wait_range - write out & wait on a file range
629 * @file: file pointing to address_space with pages
630 * @lstart: offset in bytes where the range starts
631 * @lend: offset in bytes where the range ends (inclusive)
633 * Write out and wait upon file offsets lstart->lend, inclusive.
635 * Note that @lend is inclusive (describes the last byte to be written) so
636 * that this function can be used to write to the very end-of-file (end = -1).
638 * After writing out and waiting on the data, we check and advance the
639 * f_wb_err cursor to the latest value, and return any errors detected there.
641 int file_write_and_wait_range(struct file
*file
, loff_t lstart
, loff_t lend
)
644 struct address_space
*mapping
= file
->f_mapping
;
646 if (mapping_needs_writeback(mapping
)) {
647 err
= __filemap_fdatawrite_range(mapping
, lstart
, lend
,
649 /* See comment of filemap_write_and_wait() */
651 __filemap_fdatawait_range(mapping
, lstart
, lend
);
653 err2
= file_check_and_advance_wb_err(file
);
658 EXPORT_SYMBOL(file_write_and_wait_range
);
661 * replace_page_cache_page - replace a pagecache page with a new one
662 * @old: page to be replaced
663 * @new: page to replace with
664 * @gfp_mask: allocation mode
666 * This function replaces a page in the pagecache with a new one. On
667 * success it acquires the pagecache reference for the new page and
668 * drops it for the old page. Both the old and new pages must be
669 * locked. This function does not add the new page to the LRU, the
670 * caller must do that.
672 * The remove + add is atomic. The only way this function can fail is
673 * memory allocation failure.
675 int replace_page_cache_page(struct page
*old
, struct page
*new, gfp_t gfp_mask
)
679 VM_BUG_ON_PAGE(!PageLocked(old
), old
);
680 VM_BUG_ON_PAGE(!PageLocked(new), new);
681 VM_BUG_ON_PAGE(new->mapping
, new);
683 error
= radix_tree_preload(gfp_mask
& ~__GFP_HIGHMEM
);
685 struct address_space
*mapping
= old
->mapping
;
686 void (*freepage
)(struct page
*);
689 pgoff_t offset
= old
->index
;
690 freepage
= mapping
->a_ops
->freepage
;
693 new->mapping
= mapping
;
696 spin_lock_irqsave(&mapping
->tree_lock
, flags
);
697 __delete_from_page_cache(old
, NULL
);
698 error
= page_cache_tree_insert(mapping
, new, NULL
);
702 * hugetlb pages do not participate in page cache accounting.
705 __inc_node_page_state(new, NR_FILE_PAGES
);
706 if (PageSwapBacked(new))
707 __inc_node_page_state(new, NR_SHMEM
);
708 spin_unlock_irqrestore(&mapping
->tree_lock
, flags
);
709 mem_cgroup_migrate(old
, new);
710 radix_tree_preload_end();
718 EXPORT_SYMBOL_GPL(replace_page_cache_page
);
720 static int __add_to_page_cache_locked(struct page
*page
,
721 struct address_space
*mapping
,
722 pgoff_t offset
, gfp_t gfp_mask
,
725 int huge
= PageHuge(page
);
726 struct mem_cgroup
*memcg
;
729 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
730 VM_BUG_ON_PAGE(PageSwapBacked(page
), page
);
733 error
= mem_cgroup_try_charge(page
, current
->mm
,
734 gfp_mask
, &memcg
, false);
739 error
= radix_tree_maybe_preload(gfp_mask
& ~__GFP_HIGHMEM
);
742 mem_cgroup_cancel_charge(page
, memcg
, false);
747 page
->mapping
= mapping
;
748 page
->index
= offset
;
750 spin_lock_irq(&mapping
->tree_lock
);
751 error
= page_cache_tree_insert(mapping
, page
, shadowp
);
752 radix_tree_preload_end();
756 /* hugetlb pages do not participate in page cache accounting. */
758 __inc_node_page_state(page
, NR_FILE_PAGES
);
759 spin_unlock_irq(&mapping
->tree_lock
);
761 mem_cgroup_commit_charge(page
, memcg
, false, false);
762 trace_mm_filemap_add_to_page_cache(page
);
765 page
->mapping
= NULL
;
766 /* Leave page->index set: truncation relies upon it */
767 spin_unlock_irq(&mapping
->tree_lock
);
769 mem_cgroup_cancel_charge(page
, memcg
, false);
775 * add_to_page_cache_locked - add a locked page to the pagecache
777 * @mapping: the page's address_space
778 * @offset: page index
779 * @gfp_mask: page allocation mode
781 * This function is used to add a page to the pagecache. It must be locked.
782 * This function does not add the page to the LRU. The caller must do that.
784 int add_to_page_cache_locked(struct page
*page
, struct address_space
*mapping
,
785 pgoff_t offset
, gfp_t gfp_mask
)
787 return __add_to_page_cache_locked(page
, mapping
, offset
,
790 EXPORT_SYMBOL(add_to_page_cache_locked
);
792 int add_to_page_cache_lru(struct page
*page
, struct address_space
*mapping
,
793 pgoff_t offset
, gfp_t gfp_mask
)
798 __SetPageLocked(page
);
799 ret
= __add_to_page_cache_locked(page
, mapping
, offset
,
802 __ClearPageLocked(page
);
805 * The page might have been evicted from cache only
806 * recently, in which case it should be activated like
807 * any other repeatedly accessed page.
808 * The exception is pages getting rewritten; evicting other
809 * data from the working set, only to cache data that will
810 * get overwritten with something else, is a waste of memory.
812 if (!(gfp_mask
& __GFP_WRITE
) &&
813 shadow
&& workingset_refault(shadow
)) {
815 workingset_activation(page
);
817 ClearPageActive(page
);
822 EXPORT_SYMBOL_GPL(add_to_page_cache_lru
);
825 struct page
*__page_cache_alloc(gfp_t gfp
)
830 if (cpuset_do_page_mem_spread()) {
831 unsigned int cpuset_mems_cookie
;
833 cpuset_mems_cookie
= read_mems_allowed_begin();
834 n
= cpuset_mem_spread_node();
835 page
= __alloc_pages_node(n
, gfp
, 0);
836 } while (!page
&& read_mems_allowed_retry(cpuset_mems_cookie
));
840 return alloc_pages(gfp
, 0);
842 EXPORT_SYMBOL(__page_cache_alloc
);
846 * In order to wait for pages to become available there must be
847 * waitqueues associated with pages. By using a hash table of
848 * waitqueues where the bucket discipline is to maintain all
849 * waiters on the same queue and wake all when any of the pages
850 * become available, and for the woken contexts to check to be
851 * sure the appropriate page became available, this saves space
852 * at a cost of "thundering herd" phenomena during rare hash
855 #define PAGE_WAIT_TABLE_BITS 8
856 #define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
857 static wait_queue_head_t page_wait_table
[PAGE_WAIT_TABLE_SIZE
] __cacheline_aligned
;
859 static wait_queue_head_t
*page_waitqueue(struct page
*page
)
861 return &page_wait_table
[hash_ptr(page
, PAGE_WAIT_TABLE_BITS
)];
864 void __init
pagecache_init(void)
868 for (i
= 0; i
< PAGE_WAIT_TABLE_SIZE
; i
++)
869 init_waitqueue_head(&page_wait_table
[i
]);
871 page_writeback_init();
874 /* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
875 struct wait_page_key
{
881 struct wait_page_queue
{
884 wait_queue_entry_t wait
;
887 static int wake_page_function(wait_queue_entry_t
*wait
, unsigned mode
, int sync
, void *arg
)
889 struct wait_page_key
*key
= arg
;
890 struct wait_page_queue
*wait_page
891 = container_of(wait
, struct wait_page_queue
, wait
);
893 if (wait_page
->page
!= key
->page
)
897 if (wait_page
->bit_nr
!= key
->bit_nr
)
900 /* Stop walking if it's locked */
901 if (test_bit(key
->bit_nr
, &key
->page
->flags
))
904 return autoremove_wake_function(wait
, mode
, sync
, key
);
907 static void wake_up_page_bit(struct page
*page
, int bit_nr
)
909 wait_queue_head_t
*q
= page_waitqueue(page
);
910 struct wait_page_key key
;
917 spin_lock_irqsave(&q
->lock
, flags
);
918 __wake_up_locked_key(q
, TASK_NORMAL
, &key
);
920 * It is possible for other pages to have collided on the waitqueue
921 * hash, so in that case check for a page match. That prevents a long-
924 * It is still possible to miss a case here, when we woke page waiters
925 * and removed them from the waitqueue, but there are still other
928 if (!waitqueue_active(q
) || !key
.page_match
) {
929 ClearPageWaiters(page
);
931 * It's possible to miss clearing Waiters here, when we woke
932 * our page waiters, but the hashed waitqueue has waiters for
935 * That's okay, it's a rare case. The next waker will clear it.
938 spin_unlock_irqrestore(&q
->lock
, flags
);
941 static void wake_up_page(struct page
*page
, int bit
)
943 if (!PageWaiters(page
))
945 wake_up_page_bit(page
, bit
);
948 static inline int wait_on_page_bit_common(wait_queue_head_t
*q
,
949 struct page
*page
, int bit_nr
, int state
, bool lock
)
951 struct wait_page_queue wait_page
;
952 wait_queue_entry_t
*wait
= &wait_page
.wait
;
956 wait
->flags
= lock
? WQ_FLAG_EXCLUSIVE
: 0;
957 wait
->func
= wake_page_function
;
958 wait_page
.page
= page
;
959 wait_page
.bit_nr
= bit_nr
;
962 spin_lock_irq(&q
->lock
);
964 if (likely(list_empty(&wait
->entry
))) {
965 __add_wait_queue_entry_tail(q
, wait
);
966 SetPageWaiters(page
);
969 set_current_state(state
);
971 spin_unlock_irq(&q
->lock
);
973 if (likely(test_bit(bit_nr
, &page
->flags
))) {
978 if (!test_and_set_bit_lock(bit_nr
, &page
->flags
))
981 if (!test_bit(bit_nr
, &page
->flags
))
985 if (unlikely(signal_pending_state(state
, current
))) {
991 finish_wait(q
, wait
);
994 * A signal could leave PageWaiters set. Clearing it here if
995 * !waitqueue_active would be possible (by open-coding finish_wait),
996 * but still fail to catch it in the case of wait hash collision. We
997 * already can fail to clear wait hash collision cases, so don't
998 * bother with signals either.
1004 void wait_on_page_bit(struct page
*page
, int bit_nr
)
1006 wait_queue_head_t
*q
= page_waitqueue(page
);
1007 wait_on_page_bit_common(q
, page
, bit_nr
, TASK_UNINTERRUPTIBLE
, false);
1009 EXPORT_SYMBOL(wait_on_page_bit
);
1011 int wait_on_page_bit_killable(struct page
*page
, int bit_nr
)
1013 wait_queue_head_t
*q
= page_waitqueue(page
);
1014 return wait_on_page_bit_common(q
, page
, bit_nr
, TASK_KILLABLE
, false);
1018 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1019 * @page: Page defining the wait queue of interest
1020 * @waiter: Waiter to add to the queue
1022 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1024 void add_page_wait_queue(struct page
*page
, wait_queue_entry_t
*waiter
)
1026 wait_queue_head_t
*q
= page_waitqueue(page
);
1027 unsigned long flags
;
1029 spin_lock_irqsave(&q
->lock
, flags
);
1030 __add_wait_queue_entry_tail(q
, waiter
);
1031 SetPageWaiters(page
);
1032 spin_unlock_irqrestore(&q
->lock
, flags
);
1034 EXPORT_SYMBOL_GPL(add_page_wait_queue
);
1036 #ifndef clear_bit_unlock_is_negative_byte
1039 * PG_waiters is the high bit in the same byte as PG_lock.
1041 * On x86 (and on many other architectures), we can clear PG_lock and
1042 * test the sign bit at the same time. But if the architecture does
1043 * not support that special operation, we just do this all by hand
1046 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1047 * being cleared, but a memory barrier should be unneccssary since it is
1048 * in the same byte as PG_locked.
1050 static inline bool clear_bit_unlock_is_negative_byte(long nr
, volatile void *mem
)
1052 clear_bit_unlock(nr
, mem
);
1053 /* smp_mb__after_atomic(); */
1054 return test_bit(PG_waiters
, mem
);
1060 * unlock_page - unlock a locked page
1063 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1064 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1065 * mechanism between PageLocked pages and PageWriteback pages is shared.
1066 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1068 * Note that this depends on PG_waiters being the sign bit in the byte
1069 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1070 * clear the PG_locked bit and test PG_waiters at the same time fairly
1071 * portably (architectures that do LL/SC can test any bit, while x86 can
1072 * test the sign bit).
1074 void unlock_page(struct page
*page
)
1076 BUILD_BUG_ON(PG_waiters
!= 7);
1077 page
= compound_head(page
);
1078 VM_BUG_ON_PAGE(!PageLocked(page
), page
);
1079 if (clear_bit_unlock_is_negative_byte(PG_locked
, &page
->flags
))
1080 wake_up_page_bit(page
, PG_locked
);
1082 EXPORT_SYMBOL(unlock_page
);
1085 * end_page_writeback - end writeback against a page
1088 void end_page_writeback(struct page
*page
)
1091 * TestClearPageReclaim could be used here but it is an atomic
1092 * operation and overkill in this particular case. Failing to
1093 * shuffle a page marked for immediate reclaim is too mild to
1094 * justify taking an atomic operation penalty at the end of
1095 * ever page writeback.
1097 if (PageReclaim(page
)) {
1098 ClearPageReclaim(page
);
1099 rotate_reclaimable_page(page
);
1102 if (!test_clear_page_writeback(page
))
1105 smp_mb__after_atomic();
1106 wake_up_page(page
, PG_writeback
);
1108 EXPORT_SYMBOL(end_page_writeback
);
1111 * After completing I/O on a page, call this routine to update the page
1112 * flags appropriately
1114 void page_endio(struct page
*page
, bool is_write
, int err
)
1118 SetPageUptodate(page
);
1120 ClearPageUptodate(page
);
1126 struct address_space
*mapping
;
1129 mapping
= page_mapping(page
);
1131 mapping_set_error(mapping
, err
);
1133 end_page_writeback(page
);
1136 EXPORT_SYMBOL_GPL(page_endio
);
1139 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1140 * @__page: the page to lock
1142 void __lock_page(struct page
*__page
)
1144 struct page
*page
= compound_head(__page
);
1145 wait_queue_head_t
*q
= page_waitqueue(page
);
1146 wait_on_page_bit_common(q
, page
, PG_locked
, TASK_UNINTERRUPTIBLE
, true);
1148 EXPORT_SYMBOL(__lock_page
);
1150 int __lock_page_killable(struct page
*__page
)
1152 struct page
*page
= compound_head(__page
);
1153 wait_queue_head_t
*q
= page_waitqueue(page
);
1154 return wait_on_page_bit_common(q
, page
, PG_locked
, TASK_KILLABLE
, true);
1156 EXPORT_SYMBOL_GPL(__lock_page_killable
);
1160 * 1 - page is locked; mmap_sem is still held.
1161 * 0 - page is not locked.
1162 * mmap_sem has been released (up_read()), unless flags had both
1163 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1164 * which case mmap_sem is still held.
1166 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1167 * with the page locked and the mmap_sem unperturbed.
1169 int __lock_page_or_retry(struct page
*page
, struct mm_struct
*mm
,
1172 if (flags
& FAULT_FLAG_ALLOW_RETRY
) {
1174 * CAUTION! In this case, mmap_sem is not released
1175 * even though return 0.
1177 if (flags
& FAULT_FLAG_RETRY_NOWAIT
)
1180 up_read(&mm
->mmap_sem
);
1181 if (flags
& FAULT_FLAG_KILLABLE
)
1182 wait_on_page_locked_killable(page
);
1184 wait_on_page_locked(page
);
1187 if (flags
& FAULT_FLAG_KILLABLE
) {
1190 ret
= __lock_page_killable(page
);
1192 up_read(&mm
->mmap_sem
);
1202 * page_cache_next_hole - find the next hole (not-present entry)
1205 * @max_scan: maximum range to search
1207 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1208 * lowest indexed hole.
1210 * Returns: the index of the hole if found, otherwise returns an index
1211 * outside of the set specified (in which case 'return - index >=
1212 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1215 * page_cache_next_hole may be called under rcu_read_lock. However,
1216 * like radix_tree_gang_lookup, this will not atomically search a
1217 * snapshot of the tree at a single point in time. For example, if a
1218 * hole is created at index 5, then subsequently a hole is created at
1219 * index 10, page_cache_next_hole covering both indexes may return 10
1220 * if called under rcu_read_lock.
1222 pgoff_t
page_cache_next_hole(struct address_space
*mapping
,
1223 pgoff_t index
, unsigned long max_scan
)
1227 for (i
= 0; i
< max_scan
; i
++) {
1230 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1231 if (!page
|| radix_tree_exceptional_entry(page
))
1240 EXPORT_SYMBOL(page_cache_next_hole
);
1243 * page_cache_prev_hole - find the prev hole (not-present entry)
1246 * @max_scan: maximum range to search
1248 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1251 * Returns: the index of the hole if found, otherwise returns an index
1252 * outside of the set specified (in which case 'index - return >=
1253 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1256 * page_cache_prev_hole may be called under rcu_read_lock. However,
1257 * like radix_tree_gang_lookup, this will not atomically search a
1258 * snapshot of the tree at a single point in time. For example, if a
1259 * hole is created at index 10, then subsequently a hole is created at
1260 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1261 * called under rcu_read_lock.
1263 pgoff_t
page_cache_prev_hole(struct address_space
*mapping
,
1264 pgoff_t index
, unsigned long max_scan
)
1268 for (i
= 0; i
< max_scan
; i
++) {
1271 page
= radix_tree_lookup(&mapping
->page_tree
, index
);
1272 if (!page
|| radix_tree_exceptional_entry(page
))
1275 if (index
== ULONG_MAX
)
1281 EXPORT_SYMBOL(page_cache_prev_hole
);
1284 * find_get_entry - find and get a page cache entry
1285 * @mapping: the address_space to search
1286 * @offset: the page cache index
1288 * Looks up the page cache slot at @mapping & @offset. If there is a
1289 * page cache page, it is returned with an increased refcount.
1291 * If the slot holds a shadow entry of a previously evicted page, or a
1292 * swap entry from shmem/tmpfs, it is returned.
1294 * Otherwise, %NULL is returned.
1296 struct page
*find_get_entry(struct address_space
*mapping
, pgoff_t offset
)
1299 struct page
*head
, *page
;
1304 pagep
= radix_tree_lookup_slot(&mapping
->page_tree
, offset
);
1306 page
= radix_tree_deref_slot(pagep
);
1307 if (unlikely(!page
))
1309 if (radix_tree_exception(page
)) {
1310 if (radix_tree_deref_retry(page
))
1313 * A shadow entry of a recently evicted page,
1314 * or a swap entry from shmem/tmpfs. Return
1315 * it without attempting to raise page count.
1320 head
= compound_head(page
);
1321 if (!page_cache_get_speculative(head
))
1324 /* The page was split under us? */
1325 if (compound_head(page
) != head
) {
1331 * Has the page moved?
1332 * This is part of the lockless pagecache protocol. See
1333 * include/linux/pagemap.h for details.
1335 if (unlikely(page
!= *pagep
)) {
1345 EXPORT_SYMBOL(find_get_entry
);
1348 * find_lock_entry - locate, pin and lock a page cache entry
1349 * @mapping: the address_space to search
1350 * @offset: the page cache index
1352 * Looks up the page cache slot at @mapping & @offset. If there is a
1353 * page cache page, it is returned locked and with an increased
1356 * If the slot holds a shadow entry of a previously evicted page, or a
1357 * swap entry from shmem/tmpfs, it is returned.
1359 * Otherwise, %NULL is returned.
1361 * find_lock_entry() may sleep.
1363 struct page
*find_lock_entry(struct address_space
*mapping
, pgoff_t offset
)
1368 page
= find_get_entry(mapping
, offset
);
1369 if (page
&& !radix_tree_exception(page
)) {
1371 /* Has the page been truncated? */
1372 if (unlikely(page_mapping(page
) != mapping
)) {
1377 VM_BUG_ON_PAGE(page_to_pgoff(page
) != offset
, page
);
1381 EXPORT_SYMBOL(find_lock_entry
);
1384 * pagecache_get_page - find and get a page reference
1385 * @mapping: the address_space to search
1386 * @offset: the page index
1387 * @fgp_flags: PCG flags
1388 * @gfp_mask: gfp mask to use for the page cache data page allocation
1390 * Looks up the page cache slot at @mapping & @offset.
1392 * PCG flags modify how the page is returned.
1394 * @fgp_flags can be:
1396 * - FGP_ACCESSED: the page will be marked accessed
1397 * - FGP_LOCK: Page is return locked
1398 * - FGP_CREAT: If page is not present then a new page is allocated using
1399 * @gfp_mask and added to the page cache and the VM's LRU
1400 * list. The page is returned locked and with an increased
1401 * refcount. Otherwise, NULL is returned.
1403 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1404 * if the GFP flags specified for FGP_CREAT are atomic.
1406 * If there is a page cache page, it is returned with an increased refcount.
1408 struct page
*pagecache_get_page(struct address_space
*mapping
, pgoff_t offset
,
1409 int fgp_flags
, gfp_t gfp_mask
)
1414 page
= find_get_entry(mapping
, offset
);
1415 if (radix_tree_exceptional_entry(page
))
1420 if (fgp_flags
& FGP_LOCK
) {
1421 if (fgp_flags
& FGP_NOWAIT
) {
1422 if (!trylock_page(page
)) {
1430 /* Has the page been truncated? */
1431 if (unlikely(page
->mapping
!= mapping
)) {
1436 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
1439 if (page
&& (fgp_flags
& FGP_ACCESSED
))
1440 mark_page_accessed(page
);
1443 if (!page
&& (fgp_flags
& FGP_CREAT
)) {
1445 if ((fgp_flags
& FGP_WRITE
) && mapping_cap_account_dirty(mapping
))
1446 gfp_mask
|= __GFP_WRITE
;
1447 if (fgp_flags
& FGP_NOFS
)
1448 gfp_mask
&= ~__GFP_FS
;
1450 page
= __page_cache_alloc(gfp_mask
);
1454 if (WARN_ON_ONCE(!(fgp_flags
& FGP_LOCK
)))
1455 fgp_flags
|= FGP_LOCK
;
1457 /* Init accessed so avoid atomic mark_page_accessed later */
1458 if (fgp_flags
& FGP_ACCESSED
)
1459 __SetPageReferenced(page
);
1461 err
= add_to_page_cache_lru(page
, mapping
, offset
,
1462 gfp_mask
& GFP_RECLAIM_MASK
);
1463 if (unlikely(err
)) {
1473 EXPORT_SYMBOL(pagecache_get_page
);
1476 * find_get_entries - gang pagecache lookup
1477 * @mapping: The address_space to search
1478 * @start: The starting page cache index
1479 * @nr_entries: The maximum number of entries
1480 * @entries: Where the resulting entries are placed
1481 * @indices: The cache indices corresponding to the entries in @entries
1483 * find_get_entries() will search for and return a group of up to
1484 * @nr_entries entries in the mapping. The entries are placed at
1485 * @entries. find_get_entries() takes a reference against any actual
1488 * The search returns a group of mapping-contiguous page cache entries
1489 * with ascending indexes. There may be holes in the indices due to
1490 * not-present pages.
1492 * Any shadow entries of evicted pages, or swap entries from
1493 * shmem/tmpfs, are included in the returned array.
1495 * find_get_entries() returns the number of pages and shadow entries
1498 unsigned find_get_entries(struct address_space
*mapping
,
1499 pgoff_t start
, unsigned int nr_entries
,
1500 struct page
**entries
, pgoff_t
*indices
)
1503 unsigned int ret
= 0;
1504 struct radix_tree_iter iter
;
1510 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, start
) {
1511 struct page
*head
, *page
;
1513 page
= radix_tree_deref_slot(slot
);
1514 if (unlikely(!page
))
1516 if (radix_tree_exception(page
)) {
1517 if (radix_tree_deref_retry(page
)) {
1518 slot
= radix_tree_iter_retry(&iter
);
1522 * A shadow entry of a recently evicted page, a swap
1523 * entry from shmem/tmpfs or a DAX entry. Return it
1524 * without attempting to raise page count.
1529 head
= compound_head(page
);
1530 if (!page_cache_get_speculative(head
))
1533 /* The page was split under us? */
1534 if (compound_head(page
) != head
) {
1539 /* Has the page moved? */
1540 if (unlikely(page
!= *slot
)) {
1545 indices
[ret
] = iter
.index
;
1546 entries
[ret
] = page
;
1547 if (++ret
== nr_entries
)
1555 * find_get_pages_range - gang pagecache lookup
1556 * @mapping: The address_space to search
1557 * @start: The starting page index
1558 * @end: The final page index (inclusive)
1559 * @nr_pages: The maximum number of pages
1560 * @pages: Where the resulting pages are placed
1562 * find_get_pages_range() will search for and return a group of up to @nr_pages
1563 * pages in the mapping starting at index @start and up to index @end
1564 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1565 * a reference against the returned pages.
1567 * The search returns a group of mapping-contiguous pages with ascending
1568 * indexes. There may be holes in the indices due to not-present pages.
1569 * We also update @start to index the next page for the traversal.
1571 * find_get_pages_range() returns the number of pages which were found. If this
1572 * number is smaller than @nr_pages, the end of specified range has been
1575 unsigned find_get_pages_range(struct address_space
*mapping
, pgoff_t
*start
,
1576 pgoff_t end
, unsigned int nr_pages
,
1577 struct page
**pages
)
1579 struct radix_tree_iter iter
;
1583 if (unlikely(!nr_pages
))
1587 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
, *start
) {
1588 struct page
*head
, *page
;
1590 if (iter
.index
> end
)
1593 page
= radix_tree_deref_slot(slot
);
1594 if (unlikely(!page
))
1597 if (radix_tree_exception(page
)) {
1598 if (radix_tree_deref_retry(page
)) {
1599 slot
= radix_tree_iter_retry(&iter
);
1603 * A shadow entry of a recently evicted page,
1604 * or a swap entry from shmem/tmpfs. Skip
1610 head
= compound_head(page
);
1611 if (!page_cache_get_speculative(head
))
1614 /* The page was split under us? */
1615 if (compound_head(page
) != head
) {
1620 /* Has the page moved? */
1621 if (unlikely(page
!= *slot
)) {
1627 if (++ret
== nr_pages
) {
1628 *start
= pages
[ret
- 1]->index
+ 1;
1634 * We come here when there is no page beyond @end. We take care to not
1635 * overflow the index @start as it confuses some of the callers. This
1636 * breaks the iteration when there is page at index -1 but that is
1637 * already broken anyway.
1639 if (end
== (pgoff_t
)-1)
1640 *start
= (pgoff_t
)-1;
1650 * find_get_pages_contig - gang contiguous pagecache lookup
1651 * @mapping: The address_space to search
1652 * @index: The starting page index
1653 * @nr_pages: The maximum number of pages
1654 * @pages: Where the resulting pages are placed
1656 * find_get_pages_contig() works exactly like find_get_pages(), except
1657 * that the returned number of pages are guaranteed to be contiguous.
1659 * find_get_pages_contig() returns the number of pages which were found.
1661 unsigned find_get_pages_contig(struct address_space
*mapping
, pgoff_t index
,
1662 unsigned int nr_pages
, struct page
**pages
)
1664 struct radix_tree_iter iter
;
1666 unsigned int ret
= 0;
1668 if (unlikely(!nr_pages
))
1672 radix_tree_for_each_contig(slot
, &mapping
->page_tree
, &iter
, index
) {
1673 struct page
*head
, *page
;
1675 page
= radix_tree_deref_slot(slot
);
1676 /* The hole, there no reason to continue */
1677 if (unlikely(!page
))
1680 if (radix_tree_exception(page
)) {
1681 if (radix_tree_deref_retry(page
)) {
1682 slot
= radix_tree_iter_retry(&iter
);
1686 * A shadow entry of a recently evicted page,
1687 * or a swap entry from shmem/tmpfs. Stop
1688 * looking for contiguous pages.
1693 head
= compound_head(page
);
1694 if (!page_cache_get_speculative(head
))
1697 /* The page was split under us? */
1698 if (compound_head(page
) != head
) {
1703 /* Has the page moved? */
1704 if (unlikely(page
!= *slot
)) {
1710 * must check mapping and index after taking the ref.
1711 * otherwise we can get both false positives and false
1712 * negatives, which is just confusing to the caller.
1714 if (page
->mapping
== NULL
|| page_to_pgoff(page
) != iter
.index
) {
1720 if (++ret
== nr_pages
)
1726 EXPORT_SYMBOL(find_get_pages_contig
);
1729 * find_get_pages_tag - find and return pages that match @tag
1730 * @mapping: the address_space to search
1731 * @index: the starting page index
1732 * @tag: the tag index
1733 * @nr_pages: the maximum number of pages
1734 * @pages: where the resulting pages are placed
1736 * Like find_get_pages, except we only return pages which are tagged with
1737 * @tag. We update @index to index the next page for the traversal.
1739 unsigned find_get_pages_tag(struct address_space
*mapping
, pgoff_t
*index
,
1740 int tag
, unsigned int nr_pages
, struct page
**pages
)
1742 struct radix_tree_iter iter
;
1746 if (unlikely(!nr_pages
))
1750 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1751 &iter
, *index
, tag
) {
1752 struct page
*head
, *page
;
1754 page
= radix_tree_deref_slot(slot
);
1755 if (unlikely(!page
))
1758 if (radix_tree_exception(page
)) {
1759 if (radix_tree_deref_retry(page
)) {
1760 slot
= radix_tree_iter_retry(&iter
);
1764 * A shadow entry of a recently evicted page.
1766 * Those entries should never be tagged, but
1767 * this tree walk is lockless and the tags are
1768 * looked up in bulk, one radix tree node at a
1769 * time, so there is a sizable window for page
1770 * reclaim to evict a page we saw tagged.
1777 head
= compound_head(page
);
1778 if (!page_cache_get_speculative(head
))
1781 /* The page was split under us? */
1782 if (compound_head(page
) != head
) {
1787 /* Has the page moved? */
1788 if (unlikely(page
!= *slot
)) {
1794 if (++ret
== nr_pages
)
1801 *index
= pages
[ret
- 1]->index
+ 1;
1805 EXPORT_SYMBOL(find_get_pages_tag
);
1808 * find_get_entries_tag - find and return entries that match @tag
1809 * @mapping: the address_space to search
1810 * @start: the starting page cache index
1811 * @tag: the tag index
1812 * @nr_entries: the maximum number of entries
1813 * @entries: where the resulting entries are placed
1814 * @indices: the cache indices corresponding to the entries in @entries
1816 * Like find_get_entries, except we only return entries which are tagged with
1819 unsigned find_get_entries_tag(struct address_space
*mapping
, pgoff_t start
,
1820 int tag
, unsigned int nr_entries
,
1821 struct page
**entries
, pgoff_t
*indices
)
1824 unsigned int ret
= 0;
1825 struct radix_tree_iter iter
;
1831 radix_tree_for_each_tagged(slot
, &mapping
->page_tree
,
1832 &iter
, start
, tag
) {
1833 struct page
*head
, *page
;
1835 page
= radix_tree_deref_slot(slot
);
1836 if (unlikely(!page
))
1838 if (radix_tree_exception(page
)) {
1839 if (radix_tree_deref_retry(page
)) {
1840 slot
= radix_tree_iter_retry(&iter
);
1845 * A shadow entry of a recently evicted page, a swap
1846 * entry from shmem/tmpfs or a DAX entry. Return it
1847 * without attempting to raise page count.
1852 head
= compound_head(page
);
1853 if (!page_cache_get_speculative(head
))
1856 /* The page was split under us? */
1857 if (compound_head(page
) != head
) {
1862 /* Has the page moved? */
1863 if (unlikely(page
!= *slot
)) {
1868 indices
[ret
] = iter
.index
;
1869 entries
[ret
] = page
;
1870 if (++ret
== nr_entries
)
1876 EXPORT_SYMBOL(find_get_entries_tag
);
1879 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1880 * a _large_ part of the i/o request. Imagine the worst scenario:
1882 * ---R__________________________________________B__________
1883 * ^ reading here ^ bad block(assume 4k)
1885 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1886 * => failing the whole request => read(R) => read(R+1) =>
1887 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1888 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1889 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1891 * It is going insane. Fix it by quickly scaling down the readahead size.
1893 static void shrink_readahead_size_eio(struct file
*filp
,
1894 struct file_ra_state
*ra
)
1900 * do_generic_file_read - generic file read routine
1901 * @filp: the file to read
1902 * @ppos: current file position
1903 * @iter: data destination
1904 * @written: already copied
1906 * This is a generic file read routine, and uses the
1907 * mapping->a_ops->readpage() function for the actual low-level stuff.
1909 * This is really ugly. But the goto's actually try to clarify some
1910 * of the logic when it comes to error handling etc.
1912 static ssize_t
do_generic_file_read(struct file
*filp
, loff_t
*ppos
,
1913 struct iov_iter
*iter
, ssize_t written
)
1915 struct address_space
*mapping
= filp
->f_mapping
;
1916 struct inode
*inode
= mapping
->host
;
1917 struct file_ra_state
*ra
= &filp
->f_ra
;
1921 unsigned long offset
; /* offset into pagecache page */
1922 unsigned int prev_offset
;
1925 if (unlikely(*ppos
>= inode
->i_sb
->s_maxbytes
))
1927 iov_iter_truncate(iter
, inode
->i_sb
->s_maxbytes
);
1929 index
= *ppos
>> PAGE_SHIFT
;
1930 prev_index
= ra
->prev_pos
>> PAGE_SHIFT
;
1931 prev_offset
= ra
->prev_pos
& (PAGE_SIZE
-1);
1932 last_index
= (*ppos
+ iter
->count
+ PAGE_SIZE
-1) >> PAGE_SHIFT
;
1933 offset
= *ppos
& ~PAGE_MASK
;
1939 unsigned long nr
, ret
;
1943 if (fatal_signal_pending(current
)) {
1948 page
= find_get_page(mapping
, index
);
1950 page_cache_sync_readahead(mapping
,
1952 index
, last_index
- index
);
1953 page
= find_get_page(mapping
, index
);
1954 if (unlikely(page
== NULL
))
1955 goto no_cached_page
;
1957 if (PageReadahead(page
)) {
1958 page_cache_async_readahead(mapping
,
1960 index
, last_index
- index
);
1962 if (!PageUptodate(page
)) {
1964 * See comment in do_read_cache_page on why
1965 * wait_on_page_locked is used to avoid unnecessarily
1966 * serialisations and why it's safe.
1968 error
= wait_on_page_locked_killable(page
);
1969 if (unlikely(error
))
1970 goto readpage_error
;
1971 if (PageUptodate(page
))
1974 if (inode
->i_blkbits
== PAGE_SHIFT
||
1975 !mapping
->a_ops
->is_partially_uptodate
)
1976 goto page_not_up_to_date
;
1977 /* pipes can't handle partially uptodate pages */
1978 if (unlikely(iter
->type
& ITER_PIPE
))
1979 goto page_not_up_to_date
;
1980 if (!trylock_page(page
))
1981 goto page_not_up_to_date
;
1982 /* Did it get truncated before we got the lock? */
1984 goto page_not_up_to_date_locked
;
1985 if (!mapping
->a_ops
->is_partially_uptodate(page
,
1986 offset
, iter
->count
))
1987 goto page_not_up_to_date_locked
;
1992 * i_size must be checked after we know the page is Uptodate.
1994 * Checking i_size after the check allows us to calculate
1995 * the correct value for "nr", which means the zero-filled
1996 * part of the page is not copied back to userspace (unless
1997 * another truncate extends the file - this is desired though).
2000 isize
= i_size_read(inode
);
2001 end_index
= (isize
- 1) >> PAGE_SHIFT
;
2002 if (unlikely(!isize
|| index
> end_index
)) {
2007 /* nr is the maximum number of bytes to copy from this page */
2009 if (index
== end_index
) {
2010 nr
= ((isize
- 1) & ~PAGE_MASK
) + 1;
2018 /* If users can be writing to this page using arbitrary
2019 * virtual addresses, take care about potential aliasing
2020 * before reading the page on the kernel side.
2022 if (mapping_writably_mapped(mapping
))
2023 flush_dcache_page(page
);
2026 * When a sequential read accesses a page several times,
2027 * only mark it as accessed the first time.
2029 if (prev_index
!= index
|| offset
!= prev_offset
)
2030 mark_page_accessed(page
);
2034 * Ok, we have the page, and it's up-to-date, so
2035 * now we can copy it to user space...
2038 ret
= copy_page_to_iter(page
, offset
, nr
, iter
);
2040 index
+= offset
>> PAGE_SHIFT
;
2041 offset
&= ~PAGE_MASK
;
2042 prev_offset
= offset
;
2046 if (!iov_iter_count(iter
))
2054 page_not_up_to_date
:
2055 /* Get exclusive access to the page ... */
2056 error
= lock_page_killable(page
);
2057 if (unlikely(error
))
2058 goto readpage_error
;
2060 page_not_up_to_date_locked
:
2061 /* Did it get truncated before we got the lock? */
2062 if (!page
->mapping
) {
2068 /* Did somebody else fill it already? */
2069 if (PageUptodate(page
)) {
2076 * A previous I/O error may have been due to temporary
2077 * failures, eg. multipath errors.
2078 * PG_error will be set again if readpage fails.
2080 ClearPageError(page
);
2081 /* Start the actual read. The read will unlock the page. */
2082 error
= mapping
->a_ops
->readpage(filp
, page
);
2084 if (unlikely(error
)) {
2085 if (error
== AOP_TRUNCATED_PAGE
) {
2090 goto readpage_error
;
2093 if (!PageUptodate(page
)) {
2094 error
= lock_page_killable(page
);
2095 if (unlikely(error
))
2096 goto readpage_error
;
2097 if (!PageUptodate(page
)) {
2098 if (page
->mapping
== NULL
) {
2100 * invalidate_mapping_pages got it
2107 shrink_readahead_size_eio(filp
, ra
);
2109 goto readpage_error
;
2117 /* UHHUH! A synchronous read error occurred. Report it */
2123 * Ok, it wasn't cached, so we need to create a new
2126 page
= page_cache_alloc_cold(mapping
);
2131 error
= add_to_page_cache_lru(page
, mapping
, index
,
2132 mapping_gfp_constraint(mapping
, GFP_KERNEL
));
2135 if (error
== -EEXIST
) {
2145 ra
->prev_pos
= prev_index
;
2146 ra
->prev_pos
<<= PAGE_SHIFT
;
2147 ra
->prev_pos
|= prev_offset
;
2149 *ppos
= ((loff_t
)index
<< PAGE_SHIFT
) + offset
;
2150 file_accessed(filp
);
2151 return written
? written
: error
;
2155 * generic_file_read_iter - generic filesystem read routine
2156 * @iocb: kernel I/O control block
2157 * @iter: destination for the data read
2159 * This is the "read_iter()" routine for all filesystems
2160 * that can use the page cache directly.
2163 generic_file_read_iter(struct kiocb
*iocb
, struct iov_iter
*iter
)
2165 struct file
*file
= iocb
->ki_filp
;
2167 size_t count
= iov_iter_count(iter
);
2170 goto out
; /* skip atime */
2172 if (iocb
->ki_flags
& IOCB_DIRECT
) {
2173 struct address_space
*mapping
= file
->f_mapping
;
2174 struct inode
*inode
= mapping
->host
;
2177 size
= i_size_read(inode
);
2178 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2179 if (filemap_range_has_page(mapping
, iocb
->ki_pos
,
2180 iocb
->ki_pos
+ count
- 1))
2183 retval
= filemap_write_and_wait_range(mapping
,
2185 iocb
->ki_pos
+ count
- 1);
2190 file_accessed(file
);
2192 retval
= mapping
->a_ops
->direct_IO(iocb
, iter
);
2194 iocb
->ki_pos
+= retval
;
2197 iov_iter_revert(iter
, count
- iov_iter_count(iter
));
2200 * Btrfs can have a short DIO read if we encounter
2201 * compressed extents, so if there was an error, or if
2202 * we've already read everything we wanted to, or if
2203 * there was a short read because we hit EOF, go ahead
2204 * and return. Otherwise fallthrough to buffered io for
2205 * the rest of the read. Buffered reads will not work for
2206 * DAX files, so don't bother trying.
2208 if (retval
< 0 || !count
|| iocb
->ki_pos
>= size
||
2213 retval
= do_generic_file_read(file
, &iocb
->ki_pos
, iter
, retval
);
2217 EXPORT_SYMBOL(generic_file_read_iter
);
2221 * page_cache_read - adds requested page to the page cache if not already there
2222 * @file: file to read
2223 * @offset: page index
2224 * @gfp_mask: memory allocation flags
2226 * This adds the requested page to the page cache if it isn't already there,
2227 * and schedules an I/O to read in its contents from disk.
2229 static int page_cache_read(struct file
*file
, pgoff_t offset
, gfp_t gfp_mask
)
2231 struct address_space
*mapping
= file
->f_mapping
;
2236 page
= __page_cache_alloc(gfp_mask
|__GFP_COLD
);
2240 ret
= add_to_page_cache_lru(page
, mapping
, offset
, gfp_mask
& GFP_KERNEL
);
2242 ret
= mapping
->a_ops
->readpage(file
, page
);
2243 else if (ret
== -EEXIST
)
2244 ret
= 0; /* losing race to add is OK */
2248 } while (ret
== AOP_TRUNCATED_PAGE
);
2253 #define MMAP_LOTSAMISS (100)
2256 * Synchronous readahead happens when we don't even find
2257 * a page in the page cache at all.
2259 static void do_sync_mmap_readahead(struct vm_area_struct
*vma
,
2260 struct file_ra_state
*ra
,
2264 struct address_space
*mapping
= file
->f_mapping
;
2266 /* If we don't want any read-ahead, don't bother */
2267 if (vma
->vm_flags
& VM_RAND_READ
)
2272 if (vma
->vm_flags
& VM_SEQ_READ
) {
2273 page_cache_sync_readahead(mapping
, ra
, file
, offset
,
2278 /* Avoid banging the cache line if not needed */
2279 if (ra
->mmap_miss
< MMAP_LOTSAMISS
* 10)
2283 * Do we miss much more than hit in this file? If so,
2284 * stop bothering with read-ahead. It will only hurt.
2286 if (ra
->mmap_miss
> MMAP_LOTSAMISS
)
2292 ra
->start
= max_t(long, 0, offset
- ra
->ra_pages
/ 2);
2293 ra
->size
= ra
->ra_pages
;
2294 ra
->async_size
= ra
->ra_pages
/ 4;
2295 ra_submit(ra
, mapping
, file
);
2299 * Asynchronous readahead happens when we find the page and PG_readahead,
2300 * so we want to possibly extend the readahead further..
2302 static void do_async_mmap_readahead(struct vm_area_struct
*vma
,
2303 struct file_ra_state
*ra
,
2308 struct address_space
*mapping
= file
->f_mapping
;
2310 /* If we don't want any read-ahead, don't bother */
2311 if (vma
->vm_flags
& VM_RAND_READ
)
2313 if (ra
->mmap_miss
> 0)
2315 if (PageReadahead(page
))
2316 page_cache_async_readahead(mapping
, ra
, file
,
2317 page
, offset
, ra
->ra_pages
);
2321 * filemap_fault - read in file data for page fault handling
2322 * @vmf: struct vm_fault containing details of the fault
2324 * filemap_fault() is invoked via the vma operations vector for a
2325 * mapped memory region to read in file data during a page fault.
2327 * The goto's are kind of ugly, but this streamlines the normal case of having
2328 * it in the page cache, and handles the special cases reasonably without
2329 * having a lot of duplicated code.
2331 * vma->vm_mm->mmap_sem must be held on entry.
2333 * If our return value has VM_FAULT_RETRY set, it's because
2334 * lock_page_or_retry() returned 0.
2335 * The mmap_sem has usually been released in this case.
2336 * See __lock_page_or_retry() for the exception.
2338 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2339 * has not been released.
2341 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2343 int filemap_fault(struct vm_fault
*vmf
)
2346 struct file
*file
= vmf
->vma
->vm_file
;
2347 struct address_space
*mapping
= file
->f_mapping
;
2348 struct file_ra_state
*ra
= &file
->f_ra
;
2349 struct inode
*inode
= mapping
->host
;
2350 pgoff_t offset
= vmf
->pgoff
;
2355 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2356 if (unlikely(offset
>= max_off
))
2357 return VM_FAULT_SIGBUS
;
2360 * Do we have something in the page cache already?
2362 page
= find_get_page(mapping
, offset
);
2363 if (likely(page
) && !(vmf
->flags
& FAULT_FLAG_TRIED
)) {
2365 * We found the page, so try async readahead before
2366 * waiting for the lock.
2368 do_async_mmap_readahead(vmf
->vma
, ra
, file
, page
, offset
);
2370 /* No page in the page cache at all */
2371 do_sync_mmap_readahead(vmf
->vma
, ra
, file
, offset
);
2372 count_vm_event(PGMAJFAULT
);
2373 count_memcg_event_mm(vmf
->vma
->vm_mm
, PGMAJFAULT
);
2374 ret
= VM_FAULT_MAJOR
;
2376 page
= find_get_page(mapping
, offset
);
2378 goto no_cached_page
;
2381 if (!lock_page_or_retry(page
, vmf
->vma
->vm_mm
, vmf
->flags
)) {
2383 return ret
| VM_FAULT_RETRY
;
2386 /* Did it get truncated? */
2387 if (unlikely(page
->mapping
!= mapping
)) {
2392 VM_BUG_ON_PAGE(page
->index
!= offset
, page
);
2395 * We have a locked page in the page cache, now we need to check
2396 * that it's up-to-date. If not, it is going to be due to an error.
2398 if (unlikely(!PageUptodate(page
)))
2399 goto page_not_uptodate
;
2402 * Found the page and have a reference on it.
2403 * We must recheck i_size under page lock.
2405 max_off
= DIV_ROUND_UP(i_size_read(inode
), PAGE_SIZE
);
2406 if (unlikely(offset
>= max_off
)) {
2409 return VM_FAULT_SIGBUS
;
2413 return ret
| VM_FAULT_LOCKED
;
2417 * We're only likely to ever get here if MADV_RANDOM is in
2420 error
= page_cache_read(file
, offset
, vmf
->gfp_mask
);
2423 * The page we want has now been added to the page cache.
2424 * In the unlikely event that someone removed it in the
2425 * meantime, we'll just come back here and read it again.
2431 * An error return from page_cache_read can result if the
2432 * system is low on memory, or a problem occurs while trying
2435 if (error
== -ENOMEM
)
2436 return VM_FAULT_OOM
;
2437 return VM_FAULT_SIGBUS
;
2441 * Umm, take care of errors if the page isn't up-to-date.
2442 * Try to re-read it _once_. We do this synchronously,
2443 * because there really aren't any performance issues here
2444 * and we need to check for errors.
2446 ClearPageError(page
);
2447 error
= mapping
->a_ops
->readpage(file
, page
);
2449 wait_on_page_locked(page
);
2450 if (!PageUptodate(page
))
2455 if (!error
|| error
== AOP_TRUNCATED_PAGE
)
2458 /* Things didn't work out. Return zero to tell the mm layer so. */
2459 shrink_readahead_size_eio(file
, ra
);
2460 return VM_FAULT_SIGBUS
;
2462 EXPORT_SYMBOL(filemap_fault
);
2464 void filemap_map_pages(struct vm_fault
*vmf
,
2465 pgoff_t start_pgoff
, pgoff_t end_pgoff
)
2467 struct radix_tree_iter iter
;
2469 struct file
*file
= vmf
->vma
->vm_file
;
2470 struct address_space
*mapping
= file
->f_mapping
;
2471 pgoff_t last_pgoff
= start_pgoff
;
2472 unsigned long max_idx
;
2473 struct page
*head
, *page
;
2476 radix_tree_for_each_slot(slot
, &mapping
->page_tree
, &iter
,
2478 if (iter
.index
> end_pgoff
)
2481 page
= radix_tree_deref_slot(slot
);
2482 if (unlikely(!page
))
2484 if (radix_tree_exception(page
)) {
2485 if (radix_tree_deref_retry(page
)) {
2486 slot
= radix_tree_iter_retry(&iter
);
2492 head
= compound_head(page
);
2493 if (!page_cache_get_speculative(head
))
2496 /* The page was split under us? */
2497 if (compound_head(page
) != head
) {
2502 /* Has the page moved? */
2503 if (unlikely(page
!= *slot
)) {
2508 if (!PageUptodate(page
) ||
2509 PageReadahead(page
) ||
2512 if (!trylock_page(page
))
2515 if (page
->mapping
!= mapping
|| !PageUptodate(page
))
2518 max_idx
= DIV_ROUND_UP(i_size_read(mapping
->host
), PAGE_SIZE
);
2519 if (page
->index
>= max_idx
)
2522 if (file
->f_ra
.mmap_miss
> 0)
2523 file
->f_ra
.mmap_miss
--;
2525 vmf
->address
+= (iter
.index
- last_pgoff
) << PAGE_SHIFT
;
2527 vmf
->pte
+= iter
.index
- last_pgoff
;
2528 last_pgoff
= iter
.index
;
2529 if (alloc_set_pte(vmf
, NULL
, page
))
2538 /* Huge page is mapped? No need to proceed. */
2539 if (pmd_trans_huge(*vmf
->pmd
))
2541 if (iter
.index
== end_pgoff
)
2546 EXPORT_SYMBOL(filemap_map_pages
);
2548 int filemap_page_mkwrite(struct vm_fault
*vmf
)
2550 struct page
*page
= vmf
->page
;
2551 struct inode
*inode
= file_inode(vmf
->vma
->vm_file
);
2552 int ret
= VM_FAULT_LOCKED
;
2554 sb_start_pagefault(inode
->i_sb
);
2555 file_update_time(vmf
->vma
->vm_file
);
2557 if (page
->mapping
!= inode
->i_mapping
) {
2559 ret
= VM_FAULT_NOPAGE
;
2563 * We mark the page dirty already here so that when freeze is in
2564 * progress, we are guaranteed that writeback during freezing will
2565 * see the dirty page and writeprotect it again.
2567 set_page_dirty(page
);
2568 wait_for_stable_page(page
);
2570 sb_end_pagefault(inode
->i_sb
);
2573 EXPORT_SYMBOL(filemap_page_mkwrite
);
2575 const struct vm_operations_struct generic_file_vm_ops
= {
2576 .fault
= filemap_fault
,
2577 .map_pages
= filemap_map_pages
,
2578 .page_mkwrite
= filemap_page_mkwrite
,
2581 /* This is used for a general mmap of a disk file */
2583 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2585 struct address_space
*mapping
= file
->f_mapping
;
2587 if (!mapping
->a_ops
->readpage
)
2589 file_accessed(file
);
2590 vma
->vm_ops
= &generic_file_vm_ops
;
2595 * This is for filesystems which do not implement ->writepage.
2597 int generic_file_readonly_mmap(struct file
*file
, struct vm_area_struct
*vma
)
2599 if ((vma
->vm_flags
& VM_SHARED
) && (vma
->vm_flags
& VM_MAYWRITE
))
2601 return generic_file_mmap(file
, vma
);
2604 int generic_file_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2608 int generic_file_readonly_mmap(struct file
* file
, struct vm_area_struct
* vma
)
2612 #endif /* CONFIG_MMU */
2614 EXPORT_SYMBOL(generic_file_mmap
);
2615 EXPORT_SYMBOL(generic_file_readonly_mmap
);
2617 static struct page
*wait_on_page_read(struct page
*page
)
2619 if (!IS_ERR(page
)) {
2620 wait_on_page_locked(page
);
2621 if (!PageUptodate(page
)) {
2623 page
= ERR_PTR(-EIO
);
2629 static struct page
*do_read_cache_page(struct address_space
*mapping
,
2631 int (*filler
)(void *, struct page
*),
2638 page
= find_get_page(mapping
, index
);
2640 page
= __page_cache_alloc(gfp
| __GFP_COLD
);
2642 return ERR_PTR(-ENOMEM
);
2643 err
= add_to_page_cache_lru(page
, mapping
, index
, gfp
);
2644 if (unlikely(err
)) {
2648 /* Presumably ENOMEM for radix tree node */
2649 return ERR_PTR(err
);
2653 err
= filler(data
, page
);
2656 return ERR_PTR(err
);
2659 page
= wait_on_page_read(page
);
2664 if (PageUptodate(page
))
2668 * Page is not up to date and may be locked due one of the following
2669 * case a: Page is being filled and the page lock is held
2670 * case b: Read/write error clearing the page uptodate status
2671 * case c: Truncation in progress (page locked)
2672 * case d: Reclaim in progress
2674 * Case a, the page will be up to date when the page is unlocked.
2675 * There is no need to serialise on the page lock here as the page
2676 * is pinned so the lock gives no additional protection. Even if the
2677 * the page is truncated, the data is still valid if PageUptodate as
2678 * it's a race vs truncate race.
2679 * Case b, the page will not be up to date
2680 * Case c, the page may be truncated but in itself, the data may still
2681 * be valid after IO completes as it's a read vs truncate race. The
2682 * operation must restart if the page is not uptodate on unlock but
2683 * otherwise serialising on page lock to stabilise the mapping gives
2684 * no additional guarantees to the caller as the page lock is
2685 * released before return.
2686 * Case d, similar to truncation. If reclaim holds the page lock, it
2687 * will be a race with remove_mapping that determines if the mapping
2688 * is valid on unlock but otherwise the data is valid and there is
2689 * no need to serialise with page lock.
2691 * As the page lock gives no additional guarantee, we optimistically
2692 * wait on the page to be unlocked and check if it's up to date and
2693 * use the page if it is. Otherwise, the page lock is required to
2694 * distinguish between the different cases. The motivation is that we
2695 * avoid spurious serialisations and wakeups when multiple processes
2696 * wait on the same page for IO to complete.
2698 wait_on_page_locked(page
);
2699 if (PageUptodate(page
))
2702 /* Distinguish between all the cases under the safety of the lock */
2705 /* Case c or d, restart the operation */
2706 if (!page
->mapping
) {
2712 /* Someone else locked and filled the page in a very small window */
2713 if (PageUptodate(page
)) {
2720 mark_page_accessed(page
);
2725 * read_cache_page - read into page cache, fill it if needed
2726 * @mapping: the page's address_space
2727 * @index: the page index
2728 * @filler: function to perform the read
2729 * @data: first arg to filler(data, page) function, often left as NULL
2731 * Read into the page cache. If a page already exists, and PageUptodate() is
2732 * not set, try to fill the page and wait for it to become unlocked.
2734 * If the page does not get brought uptodate, return -EIO.
2736 struct page
*read_cache_page(struct address_space
*mapping
,
2738 int (*filler
)(void *, struct page
*),
2741 return do_read_cache_page(mapping
, index
, filler
, data
, mapping_gfp_mask(mapping
));
2743 EXPORT_SYMBOL(read_cache_page
);
2746 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2747 * @mapping: the page's address_space
2748 * @index: the page index
2749 * @gfp: the page allocator flags to use if allocating
2751 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2752 * any new page allocations done using the specified allocation flags.
2754 * If the page does not get brought uptodate, return -EIO.
2756 struct page
*read_cache_page_gfp(struct address_space
*mapping
,
2760 filler_t
*filler
= (filler_t
*)mapping
->a_ops
->readpage
;
2762 return do_read_cache_page(mapping
, index
, filler
, NULL
, gfp
);
2764 EXPORT_SYMBOL(read_cache_page_gfp
);
2767 * Performs necessary checks before doing a write
2769 * Can adjust writing position or amount of bytes to write.
2770 * Returns appropriate error code that caller should return or
2771 * zero in case that write should be allowed.
2773 inline ssize_t
generic_write_checks(struct kiocb
*iocb
, struct iov_iter
*from
)
2775 struct file
*file
= iocb
->ki_filp
;
2776 struct inode
*inode
= file
->f_mapping
->host
;
2777 unsigned long limit
= rlimit(RLIMIT_FSIZE
);
2780 if (!iov_iter_count(from
))
2783 /* FIXME: this is for backwards compatibility with 2.4 */
2784 if (iocb
->ki_flags
& IOCB_APPEND
)
2785 iocb
->ki_pos
= i_size_read(inode
);
2789 if ((iocb
->ki_flags
& IOCB_NOWAIT
) && !(iocb
->ki_flags
& IOCB_DIRECT
))
2792 if (limit
!= RLIM_INFINITY
) {
2793 if (iocb
->ki_pos
>= limit
) {
2794 send_sig(SIGXFSZ
, current
, 0);
2797 iov_iter_truncate(from
, limit
- (unsigned long)pos
);
2803 if (unlikely(pos
+ iov_iter_count(from
) > MAX_NON_LFS
&&
2804 !(file
->f_flags
& O_LARGEFILE
))) {
2805 if (pos
>= MAX_NON_LFS
)
2807 iov_iter_truncate(from
, MAX_NON_LFS
- (unsigned long)pos
);
2811 * Are we about to exceed the fs block limit ?
2813 * If we have written data it becomes a short write. If we have
2814 * exceeded without writing data we send a signal and return EFBIG.
2815 * Linus frestrict idea will clean these up nicely..
2817 if (unlikely(pos
>= inode
->i_sb
->s_maxbytes
))
2820 iov_iter_truncate(from
, inode
->i_sb
->s_maxbytes
- pos
);
2821 return iov_iter_count(from
);
2823 EXPORT_SYMBOL(generic_write_checks
);
2825 int pagecache_write_begin(struct file
*file
, struct address_space
*mapping
,
2826 loff_t pos
, unsigned len
, unsigned flags
,
2827 struct page
**pagep
, void **fsdata
)
2829 const struct address_space_operations
*aops
= mapping
->a_ops
;
2831 return aops
->write_begin(file
, mapping
, pos
, len
, flags
,
2834 EXPORT_SYMBOL(pagecache_write_begin
);
2836 int pagecache_write_end(struct file
*file
, struct address_space
*mapping
,
2837 loff_t pos
, unsigned len
, unsigned copied
,
2838 struct page
*page
, void *fsdata
)
2840 const struct address_space_operations
*aops
= mapping
->a_ops
;
2842 return aops
->write_end(file
, mapping
, pos
, len
, copied
, page
, fsdata
);
2844 EXPORT_SYMBOL(pagecache_write_end
);
2847 generic_file_direct_write(struct kiocb
*iocb
, struct iov_iter
*from
)
2849 struct file
*file
= iocb
->ki_filp
;
2850 struct address_space
*mapping
= file
->f_mapping
;
2851 struct inode
*inode
= mapping
->host
;
2852 loff_t pos
= iocb
->ki_pos
;
2857 write_len
= iov_iter_count(from
);
2858 end
= (pos
+ write_len
- 1) >> PAGE_SHIFT
;
2860 if (iocb
->ki_flags
& IOCB_NOWAIT
) {
2861 /* If there are pages to writeback, return */
2862 if (filemap_range_has_page(inode
->i_mapping
, pos
,
2863 pos
+ iov_iter_count(from
)))
2866 written
= filemap_write_and_wait_range(mapping
, pos
,
2867 pos
+ write_len
- 1);
2873 * After a write we want buffered reads to be sure to go to disk to get
2874 * the new data. We invalidate clean cached page from the region we're
2875 * about to write. We do this *before* the write so that we can return
2876 * without clobbering -EIOCBQUEUED from ->direct_IO().
2878 written
= invalidate_inode_pages2_range(mapping
,
2879 pos
>> PAGE_SHIFT
, end
);
2881 * If a page can not be invalidated, return 0 to fall back
2882 * to buffered write.
2885 if (written
== -EBUSY
)
2890 written
= mapping
->a_ops
->direct_IO(iocb
, from
);
2893 * Finally, try again to invalidate clean pages which might have been
2894 * cached by non-direct readahead, or faulted in by get_user_pages()
2895 * if the source of the write was an mmap'ed region of the file
2896 * we're writing. Either one is a pretty crazy thing to do,
2897 * so we don't support it 100%. If this invalidation
2898 * fails, tough, the write still worked...
2900 invalidate_inode_pages2_range(mapping
,
2901 pos
>> PAGE_SHIFT
, end
);
2905 write_len
-= written
;
2906 if (pos
> i_size_read(inode
) && !S_ISBLK(inode
->i_mode
)) {
2907 i_size_write(inode
, pos
);
2908 mark_inode_dirty(inode
);
2912 iov_iter_revert(from
, write_len
- iov_iter_count(from
));
2916 EXPORT_SYMBOL(generic_file_direct_write
);
2919 * Find or create a page at the given pagecache position. Return the locked
2920 * page. This function is specifically for buffered writes.
2922 struct page
*grab_cache_page_write_begin(struct address_space
*mapping
,
2923 pgoff_t index
, unsigned flags
)
2926 int fgp_flags
= FGP_LOCK
|FGP_WRITE
|FGP_CREAT
;
2928 if (flags
& AOP_FLAG_NOFS
)
2929 fgp_flags
|= FGP_NOFS
;
2931 page
= pagecache_get_page(mapping
, index
, fgp_flags
,
2932 mapping_gfp_mask(mapping
));
2934 wait_for_stable_page(page
);
2938 EXPORT_SYMBOL(grab_cache_page_write_begin
);
2940 ssize_t
generic_perform_write(struct file
*file
,
2941 struct iov_iter
*i
, loff_t pos
)
2943 struct address_space
*mapping
= file
->f_mapping
;
2944 const struct address_space_operations
*a_ops
= mapping
->a_ops
;
2946 ssize_t written
= 0;
2947 unsigned int flags
= 0;
2951 unsigned long offset
; /* Offset into pagecache page */
2952 unsigned long bytes
; /* Bytes to write to page */
2953 size_t copied
; /* Bytes copied from user */
2956 offset
= (pos
& (PAGE_SIZE
- 1));
2957 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
2962 * Bring in the user page that we will copy from _first_.
2963 * Otherwise there's a nasty deadlock on copying from the
2964 * same page as we're writing to, without it being marked
2967 * Not only is this an optimisation, but it is also required
2968 * to check that the address is actually valid, when atomic
2969 * usercopies are used, below.
2971 if (unlikely(iov_iter_fault_in_readable(i
, bytes
))) {
2976 if (fatal_signal_pending(current
)) {
2981 status
= a_ops
->write_begin(file
, mapping
, pos
, bytes
, flags
,
2983 if (unlikely(status
< 0))
2986 if (mapping_writably_mapped(mapping
))
2987 flush_dcache_page(page
);
2989 copied
= iov_iter_copy_from_user_atomic(page
, i
, offset
, bytes
);
2990 flush_dcache_page(page
);
2992 status
= a_ops
->write_end(file
, mapping
, pos
, bytes
, copied
,
2994 if (unlikely(status
< 0))
3000 iov_iter_advance(i
, copied
);
3001 if (unlikely(copied
== 0)) {
3003 * If we were unable to copy any data at all, we must
3004 * fall back to a single segment length write.
3006 * If we didn't fallback here, we could livelock
3007 * because not all segments in the iov can be copied at
3008 * once without a pagefault.
3010 bytes
= min_t(unsigned long, PAGE_SIZE
- offset
,
3011 iov_iter_single_seg_count(i
));
3017 balance_dirty_pages_ratelimited(mapping
);
3018 } while (iov_iter_count(i
));
3020 return written
? written
: status
;
3022 EXPORT_SYMBOL(generic_perform_write
);
3025 * __generic_file_write_iter - write data to a file
3026 * @iocb: IO state structure (file, offset, etc.)
3027 * @from: iov_iter with data to write
3029 * This function does all the work needed for actually writing data to a
3030 * file. It does all basic checks, removes SUID from the file, updates
3031 * modification times and calls proper subroutines depending on whether we
3032 * do direct IO or a standard buffered write.
3034 * It expects i_mutex to be grabbed unless we work on a block device or similar
3035 * object which does not need locking at all.
3037 * This function does *not* take care of syncing data in case of O_SYNC write.
3038 * A caller has to handle it. This is mainly due to the fact that we want to
3039 * avoid syncing under i_mutex.
3041 ssize_t
__generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3043 struct file
*file
= iocb
->ki_filp
;
3044 struct address_space
* mapping
= file
->f_mapping
;
3045 struct inode
*inode
= mapping
->host
;
3046 ssize_t written
= 0;
3050 /* We can write back this queue in page reclaim */
3051 current
->backing_dev_info
= inode_to_bdi(inode
);
3052 err
= file_remove_privs(file
);
3056 err
= file_update_time(file
);
3060 if (iocb
->ki_flags
& IOCB_DIRECT
) {
3061 loff_t pos
, endbyte
;
3063 written
= generic_file_direct_write(iocb
, from
);
3065 * If the write stopped short of completing, fall back to
3066 * buffered writes. Some filesystems do this for writes to
3067 * holes, for example. For DAX files, a buffered write will
3068 * not succeed (even if it did, DAX does not handle dirty
3069 * page-cache pages correctly).
3071 if (written
< 0 || !iov_iter_count(from
) || IS_DAX(inode
))
3074 status
= generic_perform_write(file
, from
, pos
= iocb
->ki_pos
);
3076 * If generic_perform_write() returned a synchronous error
3077 * then we want to return the number of bytes which were
3078 * direct-written, or the error code if that was zero. Note
3079 * that this differs from normal direct-io semantics, which
3080 * will return -EFOO even if some bytes were written.
3082 if (unlikely(status
< 0)) {
3087 * We need to ensure that the page cache pages are written to
3088 * disk and invalidated to preserve the expected O_DIRECT
3091 endbyte
= pos
+ status
- 1;
3092 err
= filemap_write_and_wait_range(mapping
, pos
, endbyte
);
3094 iocb
->ki_pos
= endbyte
+ 1;
3096 invalidate_mapping_pages(mapping
,
3098 endbyte
>> PAGE_SHIFT
);
3101 * We don't know how much we wrote, so just return
3102 * the number of bytes which were direct-written
3106 written
= generic_perform_write(file
, from
, iocb
->ki_pos
);
3107 if (likely(written
> 0))
3108 iocb
->ki_pos
+= written
;
3111 current
->backing_dev_info
= NULL
;
3112 return written
? written
: err
;
3114 EXPORT_SYMBOL(__generic_file_write_iter
);
3117 * generic_file_write_iter - write data to a file
3118 * @iocb: IO state structure
3119 * @from: iov_iter with data to write
3121 * This is a wrapper around __generic_file_write_iter() to be used by most
3122 * filesystems. It takes care of syncing the file in case of O_SYNC file
3123 * and acquires i_mutex as needed.
3125 ssize_t
generic_file_write_iter(struct kiocb
*iocb
, struct iov_iter
*from
)
3127 struct file
*file
= iocb
->ki_filp
;
3128 struct inode
*inode
= file
->f_mapping
->host
;
3132 ret
= generic_write_checks(iocb
, from
);
3134 ret
= __generic_file_write_iter(iocb
, from
);
3135 inode_unlock(inode
);
3138 ret
= generic_write_sync(iocb
, ret
);
3141 EXPORT_SYMBOL(generic_file_write_iter
);
3144 * try_to_release_page() - release old fs-specific metadata on a page
3146 * @page: the page which the kernel is trying to free
3147 * @gfp_mask: memory allocation flags (and I/O mode)
3149 * The address_space is to try to release any data against the page
3150 * (presumably at page->private). If the release was successful, return '1'.
3151 * Otherwise return zero.
3153 * This may also be called if PG_fscache is set on a page, indicating that the
3154 * page is known to the local caching routines.
3156 * The @gfp_mask argument specifies whether I/O may be performed to release
3157 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3160 int try_to_release_page(struct page
*page
, gfp_t gfp_mask
)
3162 struct address_space
* const mapping
= page
->mapping
;
3164 BUG_ON(!PageLocked(page
));
3165 if (PageWriteback(page
))
3168 if (mapping
&& mapping
->a_ops
->releasepage
)
3169 return mapping
->a_ops
->releasepage(page
, gfp_mask
);
3170 return try_to_free_buffers(page
);
3173 EXPORT_SYMBOL(try_to_release_page
);