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1/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
7/*
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)
11 */
12#include <linux/export.h>
13#include <linux/compiler.h>
14#include <linux/dax.h>
15#include <linux/fs.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>
21#include <linux/mm.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/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/shmem_fs.h>
38#include <linux/rmap.h>
39#include "internal.h"
40
41#define CREATE_TRACE_POINTS
42#include <trace/events/filemap.h>
43
44/*
45 * FIXME: remove all knowledge of the buffer layer from the core VM
46 */
47#include <linux/buffer_head.h> /* for try_to_free_buffers */
48
49#include <asm/mman.h>
50
51/*
52 * Shared mappings implemented 30.11.1994. It's not fully working yet,
53 * though.
54 *
55 * Shared mappings now work. 15.8.1995 Bruno.
56 *
57 * finished 'unifying' the page and buffer cache and SMP-threaded the
58 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
59 *
60 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
61 */
62
63/*
64 * Lock ordering:
65 *
66 * ->i_mmap_rwsem (truncate_pagecache)
67 * ->private_lock (__free_pte->__set_page_dirty_buffers)
68 * ->swap_lock (exclusive_swap_page, others)
69 * ->i_pages lock
70 *
71 * ->i_mutex
72 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
73 *
74 * ->mmap_sem
75 * ->i_mmap_rwsem
76 * ->page_table_lock or pte_lock (various, mainly in memory.c)
77 * ->i_pages lock (arch-dependent flush_dcache_mmap_lock)
78 *
79 * ->mmap_sem
80 * ->lock_page (access_process_vm)
81 *
82 * ->i_mutex (generic_perform_write)
83 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
84 *
85 * bdi->wb.list_lock
86 * sb_lock (fs/fs-writeback.c)
87 * ->i_pages lock (__sync_single_inode)
88 *
89 * ->i_mmap_rwsem
90 * ->anon_vma.lock (vma_adjust)
91 *
92 * ->anon_vma.lock
93 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
94 *
95 * ->page_table_lock or pte_lock
96 * ->swap_lock (try_to_unmap_one)
97 * ->private_lock (try_to_unmap_one)
98 * ->i_pages 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 * ->i_pages 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)
109 *
110 * ->i_mmap_rwsem
111 * ->tasklist_lock (memory_failure, collect_procs_ao)
112 */
113
114static int page_cache_tree_insert(struct address_space *mapping,
115 struct page *page, void **shadowp)
116{
117 struct radix_tree_node *node;
118 void **slot;
119 int error;
120
121 error = __radix_tree_create(&mapping->i_pages, page->index, 0,
122 &node, &slot);
123 if (error)
124 return error;
125 if (*slot) {
126 void *p;
127
128 p = radix_tree_deref_slot_protected(slot,
129 &mapping->i_pages.xa_lock);
130 if (!radix_tree_exceptional_entry(p))
131 return -EEXIST;
132
133 mapping->nrexceptional--;
134 if (shadowp)
135 *shadowp = p;
136 }
137 __radix_tree_replace(&mapping->i_pages, node, slot, page,
138 workingset_lookup_update(mapping));
139 mapping->nrpages++;
140 return 0;
141}
142
143static void page_cache_tree_delete(struct address_space *mapping,
144 struct page *page, void *shadow)
145{
146 int i, nr;
147
148 /* hugetlb pages are represented by one entry in the radix tree */
149 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
150
151 VM_BUG_ON_PAGE(!PageLocked(page), page);
152 VM_BUG_ON_PAGE(PageTail(page), page);
153 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
154
155 for (i = 0; i < nr; i++) {
156 struct radix_tree_node *node;
157 void **slot;
158
159 __radix_tree_lookup(&mapping->i_pages, page->index + i,
160 &node, &slot);
161
162 VM_BUG_ON_PAGE(!node && nr != 1, page);
163
164 radix_tree_clear_tags(&mapping->i_pages, node, slot);
165 __radix_tree_replace(&mapping->i_pages, node, slot, shadow,
166 workingset_lookup_update(mapping));
167 }
168
169 page->mapping = NULL;
170 /* Leave page->index set: truncation lookup relies upon it */
171
172 if (shadow) {
173 mapping->nrexceptional += nr;
174 /*
175 * Make sure the nrexceptional update is committed before
176 * the nrpages update so that final truncate racing
177 * with reclaim does not see both counters 0 at the
178 * same time and miss a shadow entry.
179 */
180 smp_wmb();
181 }
182 mapping->nrpages -= nr;
183}
184
185static void unaccount_page_cache_page(struct address_space *mapping,
186 struct page *page)
187{
188 int nr;
189
190 /*
191 * if we're uptodate, flush out into the cleancache, otherwise
192 * invalidate any existing cleancache entries. We can't leave
193 * stale data around in the cleancache once our page is gone
194 */
195 if (PageUptodate(page) && PageMappedToDisk(page))
196 cleancache_put_page(page);
197 else
198 cleancache_invalidate_page(mapping, page);
199
200 VM_BUG_ON_PAGE(PageTail(page), page);
201 VM_BUG_ON_PAGE(page_mapped(page), page);
202 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
203 int mapcount;
204
205 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
206 current->comm, page_to_pfn(page));
207 dump_page(page, "still mapped when deleted");
208 dump_stack();
209 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
210
211 mapcount = page_mapcount(page);
212 if (mapping_exiting(mapping) &&
213 page_count(page) >= mapcount + 2) {
214 /*
215 * All vmas have already been torn down, so it's
216 * a good bet that actually the page is unmapped,
217 * and we'd prefer not to leak it: if we're wrong,
218 * some other bad page check should catch it later.
219 */
220 page_mapcount_reset(page);
221 page_ref_sub(page, mapcount);
222 }
223 }
224
225 /* hugetlb pages do not participate in page cache accounting. */
226 if (PageHuge(page))
227 return;
228
229 nr = hpage_nr_pages(page);
230
231 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
232 if (PageSwapBacked(page)) {
233 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
234 if (PageTransHuge(page))
235 __dec_node_page_state(page, NR_SHMEM_THPS);
236 } else {
237 VM_BUG_ON_PAGE(PageTransHuge(page), page);
238 }
239
240 /*
241 * At this point page must be either written or cleaned by
242 * truncate. Dirty page here signals a bug and loss of
243 * unwritten data.
244 *
245 * This fixes dirty accounting after removing the page entirely
246 * but leaves PageDirty set: it has no effect for truncated
247 * page and anyway will be cleared before returning page into
248 * buddy allocator.
249 */
250 if (WARN_ON_ONCE(PageDirty(page)))
251 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
252}
253
254/*
255 * Delete a page from the page cache and free it. Caller has to make
256 * sure the page is locked and that nobody else uses it - or that usage
257 * is safe. The caller must hold the i_pages lock.
258 */
259void __delete_from_page_cache(struct page *page, void *shadow)
260{
261 struct address_space *mapping = page->mapping;
262
263 trace_mm_filemap_delete_from_page_cache(page);
264
265 unaccount_page_cache_page(mapping, page);
266 page_cache_tree_delete(mapping, page, shadow);
267}
268
269static void page_cache_free_page(struct address_space *mapping,
270 struct page *page)
271{
272 void (*freepage)(struct page *);
273
274 freepage = mapping->a_ops->freepage;
275 if (freepage)
276 freepage(page);
277
278 if (PageTransHuge(page) && !PageHuge(page)) {
279 page_ref_sub(page, HPAGE_PMD_NR);
280 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
281 } else {
282 put_page(page);
283 }
284}
285
286/**
287 * delete_from_page_cache - delete page from page cache
288 * @page: the page which the kernel is trying to remove from page cache
289 *
290 * This must be called only on pages that have been verified to be in the page
291 * cache and locked. It will never put the page into the free list, the caller
292 * has a reference on the page.
293 */
294void delete_from_page_cache(struct page *page)
295{
296 struct address_space *mapping = page_mapping(page);
297 unsigned long flags;
298
299 BUG_ON(!PageLocked(page));
300 xa_lock_irqsave(&mapping->i_pages, flags);
301 __delete_from_page_cache(page, NULL);
302 xa_unlock_irqrestore(&mapping->i_pages, flags);
303
304 page_cache_free_page(mapping, page);
305}
306EXPORT_SYMBOL(delete_from_page_cache);
307
308/*
309 * page_cache_tree_delete_batch - delete several pages from page cache
310 * @mapping: the mapping to which pages belong
311 * @pvec: pagevec with pages to delete
312 *
313 * The function walks over mapping->i_pages and removes pages passed in @pvec
314 * from the mapping. The function expects @pvec to be sorted by page index.
315 * It tolerates holes in @pvec (mapping entries at those indices are not
316 * modified). The function expects only THP head pages to be present in the
317 * @pvec and takes care to delete all corresponding tail pages from the
318 * mapping as well.
319 *
320 * The function expects the i_pages lock to be held.
321 */
322static void
323page_cache_tree_delete_batch(struct address_space *mapping,
324 struct pagevec *pvec)
325{
326 struct radix_tree_iter iter;
327 void **slot;
328 int total_pages = 0;
329 int i = 0, tail_pages = 0;
330 struct page *page;
331 pgoff_t start;
332
333 start = pvec->pages[0]->index;
334 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
335 if (i >= pagevec_count(pvec) && !tail_pages)
336 break;
337 page = radix_tree_deref_slot_protected(slot,
338 &mapping->i_pages.xa_lock);
339 if (radix_tree_exceptional_entry(page))
340 continue;
341 if (!tail_pages) {
342 /*
343 * Some page got inserted in our range? Skip it. We
344 * have our pages locked so they are protected from
345 * being removed.
346 */
347 if (page != pvec->pages[i])
348 continue;
349 WARN_ON_ONCE(!PageLocked(page));
350 if (PageTransHuge(page) && !PageHuge(page))
351 tail_pages = HPAGE_PMD_NR - 1;
352 page->mapping = NULL;
353 /*
354 * Leave page->index set: truncation lookup relies
355 * upon it
356 */
357 i++;
358 } else {
359 tail_pages--;
360 }
361 radix_tree_clear_tags(&mapping->i_pages, iter.node, slot);
362 __radix_tree_replace(&mapping->i_pages, iter.node, slot, NULL,
363 workingset_lookup_update(mapping));
364 total_pages++;
365 }
366 mapping->nrpages -= total_pages;
367}
368
369void delete_from_page_cache_batch(struct address_space *mapping,
370 struct pagevec *pvec)
371{
372 int i;
373 unsigned long flags;
374
375 if (!pagevec_count(pvec))
376 return;
377
378 xa_lock_irqsave(&mapping->i_pages, flags);
379 for (i = 0; i < pagevec_count(pvec); i++) {
380 trace_mm_filemap_delete_from_page_cache(pvec->pages[i]);
381
382 unaccount_page_cache_page(mapping, pvec->pages[i]);
383 }
384 page_cache_tree_delete_batch(mapping, pvec);
385 xa_unlock_irqrestore(&mapping->i_pages, flags);
386
387 for (i = 0; i < pagevec_count(pvec); i++)
388 page_cache_free_page(mapping, pvec->pages[i]);
389}
390
391int filemap_check_errors(struct address_space *mapping)
392{
393 int ret = 0;
394 /* Check for outstanding write errors */
395 if (test_bit(AS_ENOSPC, &mapping->flags) &&
396 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
397 ret = -ENOSPC;
398 if (test_bit(AS_EIO, &mapping->flags) &&
399 test_and_clear_bit(AS_EIO, &mapping->flags))
400 ret = -EIO;
401 return ret;
402}
403EXPORT_SYMBOL(filemap_check_errors);
404
405static int filemap_check_and_keep_errors(struct address_space *mapping)
406{
407 /* Check for outstanding write errors */
408 if (test_bit(AS_EIO, &mapping->flags))
409 return -EIO;
410 if (test_bit(AS_ENOSPC, &mapping->flags))
411 return -ENOSPC;
412 return 0;
413}
414
415/**
416 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
417 * @mapping: address space structure to write
418 * @start: offset in bytes where the range starts
419 * @end: offset in bytes where the range ends (inclusive)
420 * @sync_mode: enable synchronous operation
421 *
422 * Start writeback against all of a mapping's dirty pages that lie
423 * within the byte offsets <start, end> inclusive.
424 *
425 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
426 * opposed to a regular memory cleansing writeback. The difference between
427 * these two operations is that if a dirty page/buffer is encountered, it must
428 * be waited upon, and not just skipped over.
429 */
430int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
431 loff_t end, int sync_mode)
432{
433 int ret;
434 struct writeback_control wbc = {
435 .sync_mode = sync_mode,
436 .nr_to_write = LONG_MAX,
437 .range_start = start,
438 .range_end = end,
439 };
440
441 if (!mapping_cap_writeback_dirty(mapping))
442 return 0;
443
444 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
445 ret = do_writepages(mapping, &wbc);
446 wbc_detach_inode(&wbc);
447 return ret;
448}
449
450static inline int __filemap_fdatawrite(struct address_space *mapping,
451 int sync_mode)
452{
453 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
454}
455
456int filemap_fdatawrite(struct address_space *mapping)
457{
458 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
459}
460EXPORT_SYMBOL(filemap_fdatawrite);
461
462int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
463 loff_t end)
464{
465 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
466}
467EXPORT_SYMBOL(filemap_fdatawrite_range);
468
469/**
470 * filemap_flush - mostly a non-blocking flush
471 * @mapping: target address_space
472 *
473 * This is a mostly non-blocking flush. Not suitable for data-integrity
474 * purposes - I/O may not be started against all dirty pages.
475 */
476int filemap_flush(struct address_space *mapping)
477{
478 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
479}
480EXPORT_SYMBOL(filemap_flush);
481
482/**
483 * filemap_range_has_page - check if a page exists in range.
484 * @mapping: address space within which to check
485 * @start_byte: offset in bytes where the range starts
486 * @end_byte: offset in bytes where the range ends (inclusive)
487 *
488 * Find at least one page in the range supplied, usually used to check if
489 * direct writing in this range will trigger a writeback.
490 */
491bool filemap_range_has_page(struct address_space *mapping,
492 loff_t start_byte, loff_t end_byte)
493{
494 pgoff_t index = start_byte >> PAGE_SHIFT;
495 pgoff_t end = end_byte >> PAGE_SHIFT;
496 struct page *page;
497
498 if (end_byte < start_byte)
499 return false;
500
501 if (mapping->nrpages == 0)
502 return false;
503
504 if (!find_get_pages_range(mapping, &index, end, 1, &page))
505 return false;
506 put_page(page);
507 return true;
508}
509EXPORT_SYMBOL(filemap_range_has_page);
510
511static void __filemap_fdatawait_range(struct address_space *mapping,
512 loff_t start_byte, loff_t end_byte)
513{
514 pgoff_t index = start_byte >> PAGE_SHIFT;
515 pgoff_t end = end_byte >> PAGE_SHIFT;
516 struct pagevec pvec;
517 int nr_pages;
518
519 if (end_byte < start_byte)
520 return;
521
522 pagevec_init(&pvec);
523 while (index <= end) {
524 unsigned i;
525
526 nr_pages = pagevec_lookup_range_tag(&pvec, mapping, &index,
527 end, PAGECACHE_TAG_WRITEBACK);
528 if (!nr_pages)
529 break;
530
531 for (i = 0; i < nr_pages; i++) {
532 struct page *page = pvec.pages[i];
533
534 wait_on_page_writeback(page);
535 ClearPageError(page);
536 }
537 pagevec_release(&pvec);
538 cond_resched();
539 }
540}
541
542/**
543 * filemap_fdatawait_range - wait for writeback to complete
544 * @mapping: address space structure to wait for
545 * @start_byte: offset in bytes where the range starts
546 * @end_byte: offset in bytes where the range ends (inclusive)
547 *
548 * Walk the list of under-writeback pages of the given address space
549 * in the given range and wait for all of them. Check error status of
550 * the address space and return it.
551 *
552 * Since the error status of the address space is cleared by this function,
553 * callers are responsible for checking the return value and handling and/or
554 * reporting the error.
555 */
556int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
557 loff_t end_byte)
558{
559 __filemap_fdatawait_range(mapping, start_byte, end_byte);
560 return filemap_check_errors(mapping);
561}
562EXPORT_SYMBOL(filemap_fdatawait_range);
563
564/**
565 * file_fdatawait_range - wait for writeback to complete
566 * @file: file pointing to address space structure to wait for
567 * @start_byte: offset in bytes where the range starts
568 * @end_byte: offset in bytes where the range ends (inclusive)
569 *
570 * Walk the list of under-writeback pages of the address space that file
571 * refers to, in the given range and wait for all of them. Check error
572 * status of the address space vs. the file->f_wb_err cursor and return it.
573 *
574 * Since the error status of the file is advanced by this function,
575 * callers are responsible for checking the return value and handling and/or
576 * reporting the error.
577 */
578int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
579{
580 struct address_space *mapping = file->f_mapping;
581
582 __filemap_fdatawait_range(mapping, start_byte, end_byte);
583 return file_check_and_advance_wb_err(file);
584}
585EXPORT_SYMBOL(file_fdatawait_range);
586
587/**
588 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
589 * @mapping: address space structure to wait for
590 *
591 * Walk the list of under-writeback pages of the given address space
592 * and wait for all of them. Unlike filemap_fdatawait(), this function
593 * does not clear error status of the address space.
594 *
595 * Use this function if callers don't handle errors themselves. Expected
596 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
597 * fsfreeze(8)
598 */
599int filemap_fdatawait_keep_errors(struct address_space *mapping)
600{
601 __filemap_fdatawait_range(mapping, 0, LLONG_MAX);
602 return filemap_check_and_keep_errors(mapping);
603}
604EXPORT_SYMBOL(filemap_fdatawait_keep_errors);
605
606static bool mapping_needs_writeback(struct address_space *mapping)
607{
608 return (!dax_mapping(mapping) && mapping->nrpages) ||
609 (dax_mapping(mapping) && mapping->nrexceptional);
610}
611
612int filemap_write_and_wait(struct address_space *mapping)
613{
614 int err = 0;
615
616 if (mapping_needs_writeback(mapping)) {
617 err = filemap_fdatawrite(mapping);
618 /*
619 * Even if the above returned error, the pages may be
620 * written partially (e.g. -ENOSPC), so we wait for it.
621 * But the -EIO is special case, it may indicate the worst
622 * thing (e.g. bug) happened, so we avoid waiting for it.
623 */
624 if (err != -EIO) {
625 int err2 = filemap_fdatawait(mapping);
626 if (!err)
627 err = err2;
628 } else {
629 /* Clear any previously stored errors */
630 filemap_check_errors(mapping);
631 }
632 } else {
633 err = filemap_check_errors(mapping);
634 }
635 return err;
636}
637EXPORT_SYMBOL(filemap_write_and_wait);
638
639/**
640 * filemap_write_and_wait_range - write out & wait on a file range
641 * @mapping: the address_space for the pages
642 * @lstart: offset in bytes where the range starts
643 * @lend: offset in bytes where the range ends (inclusive)
644 *
645 * Write out and wait upon file offsets lstart->lend, inclusive.
646 *
647 * Note that @lend is inclusive (describes the last byte to be written) so
648 * that this function can be used to write to the very end-of-file (end = -1).
649 */
650int filemap_write_and_wait_range(struct address_space *mapping,
651 loff_t lstart, loff_t lend)
652{
653 int err = 0;
654
655 if (mapping_needs_writeback(mapping)) {
656 err = __filemap_fdatawrite_range(mapping, lstart, lend,
657 WB_SYNC_ALL);
658 /* See comment of filemap_write_and_wait() */
659 if (err != -EIO) {
660 int err2 = filemap_fdatawait_range(mapping,
661 lstart, lend);
662 if (!err)
663 err = err2;
664 } else {
665 /* Clear any previously stored errors */
666 filemap_check_errors(mapping);
667 }
668 } else {
669 err = filemap_check_errors(mapping);
670 }
671 return err;
672}
673EXPORT_SYMBOL(filemap_write_and_wait_range);
674
675void __filemap_set_wb_err(struct address_space *mapping, int err)
676{
677 errseq_t eseq = errseq_set(&mapping->wb_err, err);
678
679 trace_filemap_set_wb_err(mapping, eseq);
680}
681EXPORT_SYMBOL(__filemap_set_wb_err);
682
683/**
684 * file_check_and_advance_wb_err - report wb error (if any) that was previously
685 * and advance wb_err to current one
686 * @file: struct file on which the error is being reported
687 *
688 * When userland calls fsync (or something like nfsd does the equivalent), we
689 * want to report any writeback errors that occurred since the last fsync (or
690 * since the file was opened if there haven't been any).
691 *
692 * Grab the wb_err from the mapping. If it matches what we have in the file,
693 * then just quickly return 0. The file is all caught up.
694 *
695 * If it doesn't match, then take the mapping value, set the "seen" flag in
696 * it and try to swap it into place. If it works, or another task beat us
697 * to it with the new value, then update the f_wb_err and return the error
698 * portion. The error at this point must be reported via proper channels
699 * (a'la fsync, or NFS COMMIT operation, etc.).
700 *
701 * While we handle mapping->wb_err with atomic operations, the f_wb_err
702 * value is protected by the f_lock since we must ensure that it reflects
703 * the latest value swapped in for this file descriptor.
704 */
705int file_check_and_advance_wb_err(struct file *file)
706{
707 int err = 0;
708 errseq_t old = READ_ONCE(file->f_wb_err);
709 struct address_space *mapping = file->f_mapping;
710
711 /* Locklessly handle the common case where nothing has changed */
712 if (errseq_check(&mapping->wb_err, old)) {
713 /* Something changed, must use slow path */
714 spin_lock(&file->f_lock);
715 old = file->f_wb_err;
716 err = errseq_check_and_advance(&mapping->wb_err,
717 &file->f_wb_err);
718 trace_file_check_and_advance_wb_err(file, old);
719 spin_unlock(&file->f_lock);
720 }
721
722 /*
723 * We're mostly using this function as a drop in replacement for
724 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
725 * that the legacy code would have had on these flags.
726 */
727 clear_bit(AS_EIO, &mapping->flags);
728 clear_bit(AS_ENOSPC, &mapping->flags);
729 return err;
730}
731EXPORT_SYMBOL(file_check_and_advance_wb_err);
732
733/**
734 * file_write_and_wait_range - write out & wait on a file range
735 * @file: file pointing to address_space with pages
736 * @lstart: offset in bytes where the range starts
737 * @lend: offset in bytes where the range ends (inclusive)
738 *
739 * Write out and wait upon file offsets lstart->lend, inclusive.
740 *
741 * Note that @lend is inclusive (describes the last byte to be written) so
742 * that this function can be used to write to the very end-of-file (end = -1).
743 *
744 * After writing out and waiting on the data, we check and advance the
745 * f_wb_err cursor to the latest value, and return any errors detected there.
746 */
747int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
748{
749 int err = 0, err2;
750 struct address_space *mapping = file->f_mapping;
751
752 if (mapping_needs_writeback(mapping)) {
753 err = __filemap_fdatawrite_range(mapping, lstart, lend,
754 WB_SYNC_ALL);
755 /* See comment of filemap_write_and_wait() */
756 if (err != -EIO)
757 __filemap_fdatawait_range(mapping, lstart, lend);
758 }
759 err2 = file_check_and_advance_wb_err(file);
760 if (!err)
761 err = err2;
762 return err;
763}
764EXPORT_SYMBOL(file_write_and_wait_range);
765
766/**
767 * replace_page_cache_page - replace a pagecache page with a new one
768 * @old: page to be replaced
769 * @new: page to replace with
770 * @gfp_mask: allocation mode
771 *
772 * This function replaces a page in the pagecache with a new one. On
773 * success it acquires the pagecache reference for the new page and
774 * drops it for the old page. Both the old and new pages must be
775 * locked. This function does not add the new page to the LRU, the
776 * caller must do that.
777 *
778 * The remove + add is atomic. The only way this function can fail is
779 * memory allocation failure.
780 */
781int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
782{
783 int error;
784
785 VM_BUG_ON_PAGE(!PageLocked(old), old);
786 VM_BUG_ON_PAGE(!PageLocked(new), new);
787 VM_BUG_ON_PAGE(new->mapping, new);
788
789 error = radix_tree_preload(gfp_mask & GFP_RECLAIM_MASK);
790 if (!error) {
791 struct address_space *mapping = old->mapping;
792 void (*freepage)(struct page *);
793 unsigned long flags;
794
795 pgoff_t offset = old->index;
796 freepage = mapping->a_ops->freepage;
797
798 get_page(new);
799 new->mapping = mapping;
800 new->index = offset;
801
802 xa_lock_irqsave(&mapping->i_pages, flags);
803 __delete_from_page_cache(old, NULL);
804 error = page_cache_tree_insert(mapping, new, NULL);
805 BUG_ON(error);
806
807 /*
808 * hugetlb pages do not participate in page cache accounting.
809 */
810 if (!PageHuge(new))
811 __inc_node_page_state(new, NR_FILE_PAGES);
812 if (PageSwapBacked(new))
813 __inc_node_page_state(new, NR_SHMEM);
814 xa_unlock_irqrestore(&mapping->i_pages, flags);
815 mem_cgroup_migrate(old, new);
816 radix_tree_preload_end();
817 if (freepage)
818 freepage(old);
819 put_page(old);
820 }
821
822 return error;
823}
824EXPORT_SYMBOL_GPL(replace_page_cache_page);
825
826static int __add_to_page_cache_locked(struct page *page,
827 struct address_space *mapping,
828 pgoff_t offset, gfp_t gfp_mask,
829 void **shadowp)
830{
831 int huge = PageHuge(page);
832 struct mem_cgroup *memcg;
833 int error;
834
835 VM_BUG_ON_PAGE(!PageLocked(page), page);
836 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
837
838 if (!huge) {
839 error = mem_cgroup_try_charge(page, current->mm,
840 gfp_mask, &memcg, false);
841 if (error)
842 return error;
843 }
844
845 error = radix_tree_maybe_preload(gfp_mask & GFP_RECLAIM_MASK);
846 if (error) {
847 if (!huge)
848 mem_cgroup_cancel_charge(page, memcg, false);
849 return error;
850 }
851
852 get_page(page);
853 page->mapping = mapping;
854 page->index = offset;
855
856 xa_lock_irq(&mapping->i_pages);
857 error = page_cache_tree_insert(mapping, page, shadowp);
858 radix_tree_preload_end();
859 if (unlikely(error))
860 goto err_insert;
861
862 /* hugetlb pages do not participate in page cache accounting. */
863 if (!huge)
864 __inc_node_page_state(page, NR_FILE_PAGES);
865 xa_unlock_irq(&mapping->i_pages);
866 if (!huge)
867 mem_cgroup_commit_charge(page, memcg, false, false);
868 trace_mm_filemap_add_to_page_cache(page);
869 return 0;
870err_insert:
871 page->mapping = NULL;
872 /* Leave page->index set: truncation relies upon it */
873 xa_unlock_irq(&mapping->i_pages);
874 if (!huge)
875 mem_cgroup_cancel_charge(page, memcg, false);
876 put_page(page);
877 return error;
878}
879
880/**
881 * add_to_page_cache_locked - add a locked page to the pagecache
882 * @page: page to add
883 * @mapping: the page's address_space
884 * @offset: page index
885 * @gfp_mask: page allocation mode
886 *
887 * This function is used to add a page to the pagecache. It must be locked.
888 * This function does not add the page to the LRU. The caller must do that.
889 */
890int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
891 pgoff_t offset, gfp_t gfp_mask)
892{
893 return __add_to_page_cache_locked(page, mapping, offset,
894 gfp_mask, NULL);
895}
896EXPORT_SYMBOL(add_to_page_cache_locked);
897
898int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
899 pgoff_t offset, gfp_t gfp_mask)
900{
901 void *shadow = NULL;
902 int ret;
903
904 __SetPageLocked(page);
905 ret = __add_to_page_cache_locked(page, mapping, offset,
906 gfp_mask, &shadow);
907 if (unlikely(ret))
908 __ClearPageLocked(page);
909 else {
910 /*
911 * The page might have been evicted from cache only
912 * recently, in which case it should be activated like
913 * any other repeatedly accessed page.
914 * The exception is pages getting rewritten; evicting other
915 * data from the working set, only to cache data that will
916 * get overwritten with something else, is a waste of memory.
917 */
918 if (!(gfp_mask & __GFP_WRITE) &&
919 shadow && workingset_refault(shadow)) {
920 SetPageActive(page);
921 workingset_activation(page);
922 } else
923 ClearPageActive(page);
924 lru_cache_add(page);
925 }
926 return ret;
927}
928EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
929
930#ifdef CONFIG_NUMA
931struct page *__page_cache_alloc(gfp_t gfp)
932{
933 int n;
934 struct page *page;
935
936 if (cpuset_do_page_mem_spread()) {
937 unsigned int cpuset_mems_cookie;
938 do {
939 cpuset_mems_cookie = read_mems_allowed_begin();
940 n = cpuset_mem_spread_node();
941 page = __alloc_pages_node(n, gfp, 0);
942 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
943
944 return page;
945 }
946 return alloc_pages(gfp, 0);
947}
948EXPORT_SYMBOL(__page_cache_alloc);
949#endif
950
951/*
952 * In order to wait for pages to become available there must be
953 * waitqueues associated with pages. By using a hash table of
954 * waitqueues where the bucket discipline is to maintain all
955 * waiters on the same queue and wake all when any of the pages
956 * become available, and for the woken contexts to check to be
957 * sure the appropriate page became available, this saves space
958 * at a cost of "thundering herd" phenomena during rare hash
959 * collisions.
960 */
961#define PAGE_WAIT_TABLE_BITS 8
962#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
963static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
964
965static wait_queue_head_t *page_waitqueue(struct page *page)
966{
967 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
968}
969
970void __init pagecache_init(void)
971{
972 int i;
973
974 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
975 init_waitqueue_head(&page_wait_table[i]);
976
977 page_writeback_init();
978}
979
980/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
981struct wait_page_key {
982 struct page *page;
983 int bit_nr;
984 int page_match;
985};
986
987struct wait_page_queue {
988 struct page *page;
989 int bit_nr;
990 wait_queue_entry_t wait;
991};
992
993static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
994{
995 struct wait_page_key *key = arg;
996 struct wait_page_queue *wait_page
997 = container_of(wait, struct wait_page_queue, wait);
998
999 if (wait_page->page != key->page)
1000 return 0;
1001 key->page_match = 1;
1002
1003 if (wait_page->bit_nr != key->bit_nr)
1004 return 0;
1005
1006 /* Stop walking if it's locked */
1007 if (test_bit(key->bit_nr, &key->page->flags))
1008 return -1;
1009
1010 return autoremove_wake_function(wait, mode, sync, key);
1011}
1012
1013static void wake_up_page_bit(struct page *page, int bit_nr)
1014{
1015 wait_queue_head_t *q = page_waitqueue(page);
1016 struct wait_page_key key;
1017 unsigned long flags;
1018 wait_queue_entry_t bookmark;
1019
1020 key.page = page;
1021 key.bit_nr = bit_nr;
1022 key.page_match = 0;
1023
1024 bookmark.flags = 0;
1025 bookmark.private = NULL;
1026 bookmark.func = NULL;
1027 INIT_LIST_HEAD(&bookmark.entry);
1028
1029 spin_lock_irqsave(&q->lock, flags);
1030 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1031
1032 while (bookmark.flags & WQ_FLAG_BOOKMARK) {
1033 /*
1034 * Take a breather from holding the lock,
1035 * allow pages that finish wake up asynchronously
1036 * to acquire the lock and remove themselves
1037 * from wait queue
1038 */
1039 spin_unlock_irqrestore(&q->lock, flags);
1040 cpu_relax();
1041 spin_lock_irqsave(&q->lock, flags);
1042 __wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
1043 }
1044
1045 /*
1046 * It is possible for other pages to have collided on the waitqueue
1047 * hash, so in that case check for a page match. That prevents a long-
1048 * term waiter
1049 *
1050 * It is still possible to miss a case here, when we woke page waiters
1051 * and removed them from the waitqueue, but there are still other
1052 * page waiters.
1053 */
1054 if (!waitqueue_active(q) || !key.page_match) {
1055 ClearPageWaiters(page);
1056 /*
1057 * It's possible to miss clearing Waiters here, when we woke
1058 * our page waiters, but the hashed waitqueue has waiters for
1059 * other pages on it.
1060 *
1061 * That's okay, it's a rare case. The next waker will clear it.
1062 */
1063 }
1064 spin_unlock_irqrestore(&q->lock, flags);
1065}
1066
1067static void wake_up_page(struct page *page, int bit)
1068{
1069 if (!PageWaiters(page))
1070 return;
1071 wake_up_page_bit(page, bit);
1072}
1073
1074static inline int wait_on_page_bit_common(wait_queue_head_t *q,
1075 struct page *page, int bit_nr, int state, bool lock)
1076{
1077 struct wait_page_queue wait_page;
1078 wait_queue_entry_t *wait = &wait_page.wait;
1079 int ret = 0;
1080
1081 init_wait(wait);
1082 wait->flags = lock ? WQ_FLAG_EXCLUSIVE : 0;
1083 wait->func = wake_page_function;
1084 wait_page.page = page;
1085 wait_page.bit_nr = bit_nr;
1086
1087 for (;;) {
1088 spin_lock_irq(&q->lock);
1089
1090 if (likely(list_empty(&wait->entry))) {
1091 __add_wait_queue_entry_tail(q, wait);
1092 SetPageWaiters(page);
1093 }
1094
1095 set_current_state(state);
1096
1097 spin_unlock_irq(&q->lock);
1098
1099 if (likely(test_bit(bit_nr, &page->flags))) {
1100 io_schedule();
1101 }
1102
1103 if (lock) {
1104 if (!test_and_set_bit_lock(bit_nr, &page->flags))
1105 break;
1106 } else {
1107 if (!test_bit(bit_nr, &page->flags))
1108 break;
1109 }
1110
1111 if (unlikely(signal_pending_state(state, current))) {
1112 ret = -EINTR;
1113 break;
1114 }
1115 }
1116
1117 finish_wait(q, wait);
1118
1119 /*
1120 * A signal could leave PageWaiters set. Clearing it here if
1121 * !waitqueue_active would be possible (by open-coding finish_wait),
1122 * but still fail to catch it in the case of wait hash collision. We
1123 * already can fail to clear wait hash collision cases, so don't
1124 * bother with signals either.
1125 */
1126
1127 return ret;
1128}
1129
1130void wait_on_page_bit(struct page *page, int bit_nr)
1131{
1132 wait_queue_head_t *q = page_waitqueue(page);
1133 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
1134}
1135EXPORT_SYMBOL(wait_on_page_bit);
1136
1137int wait_on_page_bit_killable(struct page *page, int bit_nr)
1138{
1139 wait_queue_head_t *q = page_waitqueue(page);
1140 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
1141}
1142EXPORT_SYMBOL(wait_on_page_bit_killable);
1143
1144/**
1145 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
1146 * @page: Page defining the wait queue of interest
1147 * @waiter: Waiter to add to the queue
1148 *
1149 * Add an arbitrary @waiter to the wait queue for the nominated @page.
1150 */
1151void add_page_wait_queue(struct page *page, wait_queue_entry_t *waiter)
1152{
1153 wait_queue_head_t *q = page_waitqueue(page);
1154 unsigned long flags;
1155
1156 spin_lock_irqsave(&q->lock, flags);
1157 __add_wait_queue_entry_tail(q, waiter);
1158 SetPageWaiters(page);
1159 spin_unlock_irqrestore(&q->lock, flags);
1160}
1161EXPORT_SYMBOL_GPL(add_page_wait_queue);
1162
1163#ifndef clear_bit_unlock_is_negative_byte
1164
1165/*
1166 * PG_waiters is the high bit in the same byte as PG_lock.
1167 *
1168 * On x86 (and on many other architectures), we can clear PG_lock and
1169 * test the sign bit at the same time. But if the architecture does
1170 * not support that special operation, we just do this all by hand
1171 * instead.
1172 *
1173 * The read of PG_waiters has to be after (or concurrently with) PG_locked
1174 * being cleared, but a memory barrier should be unneccssary since it is
1175 * in the same byte as PG_locked.
1176 */
1177static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
1178{
1179 clear_bit_unlock(nr, mem);
1180 /* smp_mb__after_atomic(); */
1181 return test_bit(PG_waiters, mem);
1182}
1183
1184#endif
1185
1186/**
1187 * unlock_page - unlock a locked page
1188 * @page: the page
1189 *
1190 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
1191 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
1192 * mechanism between PageLocked pages and PageWriteback pages is shared.
1193 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
1194 *
1195 * Note that this depends on PG_waiters being the sign bit in the byte
1196 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
1197 * clear the PG_locked bit and test PG_waiters at the same time fairly
1198 * portably (architectures that do LL/SC can test any bit, while x86 can
1199 * test the sign bit).
1200 */
1201void unlock_page(struct page *page)
1202{
1203 BUILD_BUG_ON(PG_waiters != 7);
1204 page = compound_head(page);
1205 VM_BUG_ON_PAGE(!PageLocked(page), page);
1206 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
1207 wake_up_page_bit(page, PG_locked);
1208}
1209EXPORT_SYMBOL(unlock_page);
1210
1211/**
1212 * end_page_writeback - end writeback against a page
1213 * @page: the page
1214 */
1215void end_page_writeback(struct page *page)
1216{
1217 /*
1218 * TestClearPageReclaim could be used here but it is an atomic
1219 * operation and overkill in this particular case. Failing to
1220 * shuffle a page marked for immediate reclaim is too mild to
1221 * justify taking an atomic operation penalty at the end of
1222 * ever page writeback.
1223 */
1224 if (PageReclaim(page)) {
1225 ClearPageReclaim(page);
1226 rotate_reclaimable_page(page);
1227 }
1228
1229 if (!test_clear_page_writeback(page))
1230 BUG();
1231
1232 smp_mb__after_atomic();
1233 wake_up_page(page, PG_writeback);
1234}
1235EXPORT_SYMBOL(end_page_writeback);
1236
1237/*
1238 * After completing I/O on a page, call this routine to update the page
1239 * flags appropriately
1240 */
1241void page_endio(struct page *page, bool is_write, int err)
1242{
1243 if (!is_write) {
1244 if (!err) {
1245 SetPageUptodate(page);
1246 } else {
1247 ClearPageUptodate(page);
1248 SetPageError(page);
1249 }
1250 unlock_page(page);
1251 } else {
1252 if (err) {
1253 struct address_space *mapping;
1254
1255 SetPageError(page);
1256 mapping = page_mapping(page);
1257 if (mapping)
1258 mapping_set_error(mapping, err);
1259 }
1260 end_page_writeback(page);
1261 }
1262}
1263EXPORT_SYMBOL_GPL(page_endio);
1264
1265/**
1266 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1267 * @__page: the page to lock
1268 */
1269void __lock_page(struct page *__page)
1270{
1271 struct page *page = compound_head(__page);
1272 wait_queue_head_t *q = page_waitqueue(page);
1273 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1274}
1275EXPORT_SYMBOL(__lock_page);
1276
1277int __lock_page_killable(struct page *__page)
1278{
1279 struct page *page = compound_head(__page);
1280 wait_queue_head_t *q = page_waitqueue(page);
1281 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1282}
1283EXPORT_SYMBOL_GPL(__lock_page_killable);
1284
1285/*
1286 * Return values:
1287 * 1 - page is locked; mmap_sem is still held.
1288 * 0 - page is not locked.
1289 * mmap_sem has been released (up_read()), unless flags had both
1290 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1291 * which case mmap_sem is still held.
1292 *
1293 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1294 * with the page locked and the mmap_sem unperturbed.
1295 */
1296int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1297 unsigned int flags)
1298{
1299 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1300 /*
1301 * CAUTION! In this case, mmap_sem is not released
1302 * even though return 0.
1303 */
1304 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1305 return 0;
1306
1307 up_read(&mm->mmap_sem);
1308 if (flags & FAULT_FLAG_KILLABLE)
1309 wait_on_page_locked_killable(page);
1310 else
1311 wait_on_page_locked(page);
1312 return 0;
1313 } else {
1314 if (flags & FAULT_FLAG_KILLABLE) {
1315 int ret;
1316
1317 ret = __lock_page_killable(page);
1318 if (ret) {
1319 up_read(&mm->mmap_sem);
1320 return 0;
1321 }
1322 } else
1323 __lock_page(page);
1324 return 1;
1325 }
1326}
1327
1328/**
1329 * page_cache_next_hole - find the next hole (not-present entry)
1330 * @mapping: mapping
1331 * @index: index
1332 * @max_scan: maximum range to search
1333 *
1334 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1335 * lowest indexed hole.
1336 *
1337 * Returns: the index of the hole if found, otherwise returns an index
1338 * outside of the set specified (in which case 'return - index >=
1339 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1340 * be returned.
1341 *
1342 * page_cache_next_hole may be called under rcu_read_lock. However,
1343 * like radix_tree_gang_lookup, this will not atomically search a
1344 * snapshot of the tree at a single point in time. For example, if a
1345 * hole is created at index 5, then subsequently a hole is created at
1346 * index 10, page_cache_next_hole covering both indexes may return 10
1347 * if called under rcu_read_lock.
1348 */
1349pgoff_t page_cache_next_hole(struct address_space *mapping,
1350 pgoff_t index, unsigned long max_scan)
1351{
1352 unsigned long i;
1353
1354 for (i = 0; i < max_scan; i++) {
1355 struct page *page;
1356
1357 page = radix_tree_lookup(&mapping->i_pages, index);
1358 if (!page || radix_tree_exceptional_entry(page))
1359 break;
1360 index++;
1361 if (index == 0)
1362 break;
1363 }
1364
1365 return index;
1366}
1367EXPORT_SYMBOL(page_cache_next_hole);
1368
1369/**
1370 * page_cache_prev_hole - find the prev hole (not-present entry)
1371 * @mapping: mapping
1372 * @index: index
1373 * @max_scan: maximum range to search
1374 *
1375 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1376 * the first hole.
1377 *
1378 * Returns: the index of the hole if found, otherwise returns an index
1379 * outside of the set specified (in which case 'index - return >=
1380 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1381 * will be returned.
1382 *
1383 * page_cache_prev_hole may be called under rcu_read_lock. However,
1384 * like radix_tree_gang_lookup, this will not atomically search a
1385 * snapshot of the tree at a single point in time. For example, if a
1386 * hole is created at index 10, then subsequently a hole is created at
1387 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1388 * called under rcu_read_lock.
1389 */
1390pgoff_t page_cache_prev_hole(struct address_space *mapping,
1391 pgoff_t index, unsigned long max_scan)
1392{
1393 unsigned long i;
1394
1395 for (i = 0; i < max_scan; i++) {
1396 struct page *page;
1397
1398 page = radix_tree_lookup(&mapping->i_pages, index);
1399 if (!page || radix_tree_exceptional_entry(page))
1400 break;
1401 index--;
1402 if (index == ULONG_MAX)
1403 break;
1404 }
1405
1406 return index;
1407}
1408EXPORT_SYMBOL(page_cache_prev_hole);
1409
1410/**
1411 * find_get_entry - find and get a page cache entry
1412 * @mapping: the address_space to search
1413 * @offset: the page cache index
1414 *
1415 * Looks up the page cache slot at @mapping & @offset. If there is a
1416 * page cache page, it is returned with an increased refcount.
1417 *
1418 * If the slot holds a shadow entry of a previously evicted page, or a
1419 * swap entry from shmem/tmpfs, it is returned.
1420 *
1421 * Otherwise, %NULL is returned.
1422 */
1423struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1424{
1425 void **pagep;
1426 struct page *head, *page;
1427
1428 rcu_read_lock();
1429repeat:
1430 page = NULL;
1431 pagep = radix_tree_lookup_slot(&mapping->i_pages, offset);
1432 if (pagep) {
1433 page = radix_tree_deref_slot(pagep);
1434 if (unlikely(!page))
1435 goto out;
1436 if (radix_tree_exception(page)) {
1437 if (radix_tree_deref_retry(page))
1438 goto repeat;
1439 /*
1440 * A shadow entry of a recently evicted page,
1441 * or a swap entry from shmem/tmpfs. Return
1442 * it without attempting to raise page count.
1443 */
1444 goto out;
1445 }
1446
1447 head = compound_head(page);
1448 if (!page_cache_get_speculative(head))
1449 goto repeat;
1450
1451 /* The page was split under us? */
1452 if (compound_head(page) != head) {
1453 put_page(head);
1454 goto repeat;
1455 }
1456
1457 /*
1458 * Has the page moved?
1459 * This is part of the lockless pagecache protocol. See
1460 * include/linux/pagemap.h for details.
1461 */
1462 if (unlikely(page != *pagep)) {
1463 put_page(head);
1464 goto repeat;
1465 }
1466 }
1467out:
1468 rcu_read_unlock();
1469
1470 return page;
1471}
1472EXPORT_SYMBOL(find_get_entry);
1473
1474/**
1475 * find_lock_entry - locate, pin and lock a page cache entry
1476 * @mapping: the address_space to search
1477 * @offset: the page cache index
1478 *
1479 * Looks up the page cache slot at @mapping & @offset. If there is a
1480 * page cache page, it is returned locked and with an increased
1481 * refcount.
1482 *
1483 * If the slot holds a shadow entry of a previously evicted page, or a
1484 * swap entry from shmem/tmpfs, it is returned.
1485 *
1486 * Otherwise, %NULL is returned.
1487 *
1488 * find_lock_entry() may sleep.
1489 */
1490struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1491{
1492 struct page *page;
1493
1494repeat:
1495 page = find_get_entry(mapping, offset);
1496 if (page && !radix_tree_exception(page)) {
1497 lock_page(page);
1498 /* Has the page been truncated? */
1499 if (unlikely(page_mapping(page) != mapping)) {
1500 unlock_page(page);
1501 put_page(page);
1502 goto repeat;
1503 }
1504 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1505 }
1506 return page;
1507}
1508EXPORT_SYMBOL(find_lock_entry);
1509
1510/**
1511 * pagecache_get_page - find and get a page reference
1512 * @mapping: the address_space to search
1513 * @offset: the page index
1514 * @fgp_flags: PCG flags
1515 * @gfp_mask: gfp mask to use for the page cache data page allocation
1516 *
1517 * Looks up the page cache slot at @mapping & @offset.
1518 *
1519 * PCG flags modify how the page is returned.
1520 *
1521 * @fgp_flags can be:
1522 *
1523 * - FGP_ACCESSED: the page will be marked accessed
1524 * - FGP_LOCK: Page is return locked
1525 * - FGP_CREAT: If page is not present then a new page is allocated using
1526 * @gfp_mask and added to the page cache and the VM's LRU
1527 * list. The page is returned locked and with an increased
1528 * refcount. Otherwise, NULL is returned.
1529 *
1530 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1531 * if the GFP flags specified for FGP_CREAT are atomic.
1532 *
1533 * If there is a page cache page, it is returned with an increased refcount.
1534 */
1535struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1536 int fgp_flags, gfp_t gfp_mask)
1537{
1538 struct page *page;
1539
1540repeat:
1541 page = find_get_entry(mapping, offset);
1542 if (radix_tree_exceptional_entry(page))
1543 page = NULL;
1544 if (!page)
1545 goto no_page;
1546
1547 if (fgp_flags & FGP_LOCK) {
1548 if (fgp_flags & FGP_NOWAIT) {
1549 if (!trylock_page(page)) {
1550 put_page(page);
1551 return NULL;
1552 }
1553 } else {
1554 lock_page(page);
1555 }
1556
1557 /* Has the page been truncated? */
1558 if (unlikely(page->mapping != mapping)) {
1559 unlock_page(page);
1560 put_page(page);
1561 goto repeat;
1562 }
1563 VM_BUG_ON_PAGE(page->index != offset, page);
1564 }
1565
1566 if (page && (fgp_flags & FGP_ACCESSED))
1567 mark_page_accessed(page);
1568
1569no_page:
1570 if (!page && (fgp_flags & FGP_CREAT)) {
1571 int err;
1572 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1573 gfp_mask |= __GFP_WRITE;
1574 if (fgp_flags & FGP_NOFS)
1575 gfp_mask &= ~__GFP_FS;
1576
1577 page = __page_cache_alloc(gfp_mask);
1578 if (!page)
1579 return NULL;
1580
1581 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1582 fgp_flags |= FGP_LOCK;
1583
1584 /* Init accessed so avoid atomic mark_page_accessed later */
1585 if (fgp_flags & FGP_ACCESSED)
1586 __SetPageReferenced(page);
1587
1588 err = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
1589 if (unlikely(err)) {
1590 put_page(page);
1591 page = NULL;
1592 if (err == -EEXIST)
1593 goto repeat;
1594 }
1595 }
1596
1597 return page;
1598}
1599EXPORT_SYMBOL(pagecache_get_page);
1600
1601/**
1602 * find_get_entries - gang pagecache lookup
1603 * @mapping: The address_space to search
1604 * @start: The starting page cache index
1605 * @nr_entries: The maximum number of entries
1606 * @entries: Where the resulting entries are placed
1607 * @indices: The cache indices corresponding to the entries in @entries
1608 *
1609 * find_get_entries() will search for and return a group of up to
1610 * @nr_entries entries in the mapping. The entries are placed at
1611 * @entries. find_get_entries() takes a reference against any actual
1612 * pages it returns.
1613 *
1614 * The search returns a group of mapping-contiguous page cache entries
1615 * with ascending indexes. There may be holes in the indices due to
1616 * not-present pages.
1617 *
1618 * Any shadow entries of evicted pages, or swap entries from
1619 * shmem/tmpfs, are included in the returned array.
1620 *
1621 * find_get_entries() returns the number of pages and shadow entries
1622 * which were found.
1623 */
1624unsigned find_get_entries(struct address_space *mapping,
1625 pgoff_t start, unsigned int nr_entries,
1626 struct page **entries, pgoff_t *indices)
1627{
1628 void **slot;
1629 unsigned int ret = 0;
1630 struct radix_tree_iter iter;
1631
1632 if (!nr_entries)
1633 return 0;
1634
1635 rcu_read_lock();
1636 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start) {
1637 struct page *head, *page;
1638repeat:
1639 page = radix_tree_deref_slot(slot);
1640 if (unlikely(!page))
1641 continue;
1642 if (radix_tree_exception(page)) {
1643 if (radix_tree_deref_retry(page)) {
1644 slot = radix_tree_iter_retry(&iter);
1645 continue;
1646 }
1647 /*
1648 * A shadow entry of a recently evicted page, a swap
1649 * entry from shmem/tmpfs or a DAX entry. Return it
1650 * without attempting to raise page count.
1651 */
1652 goto export;
1653 }
1654
1655 head = compound_head(page);
1656 if (!page_cache_get_speculative(head))
1657 goto repeat;
1658
1659 /* The page was split under us? */
1660 if (compound_head(page) != head) {
1661 put_page(head);
1662 goto repeat;
1663 }
1664
1665 /* Has the page moved? */
1666 if (unlikely(page != *slot)) {
1667 put_page(head);
1668 goto repeat;
1669 }
1670export:
1671 indices[ret] = iter.index;
1672 entries[ret] = page;
1673 if (++ret == nr_entries)
1674 break;
1675 }
1676 rcu_read_unlock();
1677 return ret;
1678}
1679
1680/**
1681 * find_get_pages_range - gang pagecache lookup
1682 * @mapping: The address_space to search
1683 * @start: The starting page index
1684 * @end: The final page index (inclusive)
1685 * @nr_pages: The maximum number of pages
1686 * @pages: Where the resulting pages are placed
1687 *
1688 * find_get_pages_range() will search for and return a group of up to @nr_pages
1689 * pages in the mapping starting at index @start and up to index @end
1690 * (inclusive). The pages are placed at @pages. find_get_pages_range() takes
1691 * a reference against the returned pages.
1692 *
1693 * The search returns a group of mapping-contiguous pages with ascending
1694 * indexes. There may be holes in the indices due to not-present pages.
1695 * We also update @start to index the next page for the traversal.
1696 *
1697 * find_get_pages_range() returns the number of pages which were found. If this
1698 * number is smaller than @nr_pages, the end of specified range has been
1699 * reached.
1700 */
1701unsigned find_get_pages_range(struct address_space *mapping, pgoff_t *start,
1702 pgoff_t end, unsigned int nr_pages,
1703 struct page **pages)
1704{
1705 struct radix_tree_iter iter;
1706 void **slot;
1707 unsigned ret = 0;
1708
1709 if (unlikely(!nr_pages))
1710 return 0;
1711
1712 rcu_read_lock();
1713 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, *start) {
1714 struct page *head, *page;
1715
1716 if (iter.index > end)
1717 break;
1718repeat:
1719 page = radix_tree_deref_slot(slot);
1720 if (unlikely(!page))
1721 continue;
1722
1723 if (radix_tree_exception(page)) {
1724 if (radix_tree_deref_retry(page)) {
1725 slot = radix_tree_iter_retry(&iter);
1726 continue;
1727 }
1728 /*
1729 * A shadow entry of a recently evicted page,
1730 * or a swap entry from shmem/tmpfs. Skip
1731 * over it.
1732 */
1733 continue;
1734 }
1735
1736 head = compound_head(page);
1737 if (!page_cache_get_speculative(head))
1738 goto repeat;
1739
1740 /* The page was split under us? */
1741 if (compound_head(page) != head) {
1742 put_page(head);
1743 goto repeat;
1744 }
1745
1746 /* Has the page moved? */
1747 if (unlikely(page != *slot)) {
1748 put_page(head);
1749 goto repeat;
1750 }
1751
1752 pages[ret] = page;
1753 if (++ret == nr_pages) {
1754 *start = pages[ret - 1]->index + 1;
1755 goto out;
1756 }
1757 }
1758
1759 /*
1760 * We come here when there is no page beyond @end. We take care to not
1761 * overflow the index @start as it confuses some of the callers. This
1762 * breaks the iteration when there is page at index -1 but that is
1763 * already broken anyway.
1764 */
1765 if (end == (pgoff_t)-1)
1766 *start = (pgoff_t)-1;
1767 else
1768 *start = end + 1;
1769out:
1770 rcu_read_unlock();
1771
1772 return ret;
1773}
1774
1775/**
1776 * find_get_pages_contig - gang contiguous pagecache lookup
1777 * @mapping: The address_space to search
1778 * @index: The starting page index
1779 * @nr_pages: The maximum number of pages
1780 * @pages: Where the resulting pages are placed
1781 *
1782 * find_get_pages_contig() works exactly like find_get_pages(), except
1783 * that the returned number of pages are guaranteed to be contiguous.
1784 *
1785 * find_get_pages_contig() returns the number of pages which were found.
1786 */
1787unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1788 unsigned int nr_pages, struct page **pages)
1789{
1790 struct radix_tree_iter iter;
1791 void **slot;
1792 unsigned int ret = 0;
1793
1794 if (unlikely(!nr_pages))
1795 return 0;
1796
1797 rcu_read_lock();
1798 radix_tree_for_each_contig(slot, &mapping->i_pages, &iter, index) {
1799 struct page *head, *page;
1800repeat:
1801 page = radix_tree_deref_slot(slot);
1802 /* The hole, there no reason to continue */
1803 if (unlikely(!page))
1804 break;
1805
1806 if (radix_tree_exception(page)) {
1807 if (radix_tree_deref_retry(page)) {
1808 slot = radix_tree_iter_retry(&iter);
1809 continue;
1810 }
1811 /*
1812 * A shadow entry of a recently evicted page,
1813 * or a swap entry from shmem/tmpfs. Stop
1814 * looking for contiguous pages.
1815 */
1816 break;
1817 }
1818
1819 head = compound_head(page);
1820 if (!page_cache_get_speculative(head))
1821 goto repeat;
1822
1823 /* The page was split under us? */
1824 if (compound_head(page) != head) {
1825 put_page(head);
1826 goto repeat;
1827 }
1828
1829 /* Has the page moved? */
1830 if (unlikely(page != *slot)) {
1831 put_page(head);
1832 goto repeat;
1833 }
1834
1835 /*
1836 * must check mapping and index after taking the ref.
1837 * otherwise we can get both false positives and false
1838 * negatives, which is just confusing to the caller.
1839 */
1840 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1841 put_page(page);
1842 break;
1843 }
1844
1845 pages[ret] = page;
1846 if (++ret == nr_pages)
1847 break;
1848 }
1849 rcu_read_unlock();
1850 return ret;
1851}
1852EXPORT_SYMBOL(find_get_pages_contig);
1853
1854/**
1855 * find_get_pages_range_tag - find and return pages in given range matching @tag
1856 * @mapping: the address_space to search
1857 * @index: the starting page index
1858 * @end: The final page index (inclusive)
1859 * @tag: the tag index
1860 * @nr_pages: the maximum number of pages
1861 * @pages: where the resulting pages are placed
1862 *
1863 * Like find_get_pages, except we only return pages which are tagged with
1864 * @tag. We update @index to index the next page for the traversal.
1865 */
1866unsigned find_get_pages_range_tag(struct address_space *mapping, pgoff_t *index,
1867 pgoff_t end, int tag, unsigned int nr_pages,
1868 struct page **pages)
1869{
1870 struct radix_tree_iter iter;
1871 void **slot;
1872 unsigned ret = 0;
1873
1874 if (unlikely(!nr_pages))
1875 return 0;
1876
1877 rcu_read_lock();
1878 radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, *index, tag) {
1879 struct page *head, *page;
1880
1881 if (iter.index > end)
1882 break;
1883repeat:
1884 page = radix_tree_deref_slot(slot);
1885 if (unlikely(!page))
1886 continue;
1887
1888 if (radix_tree_exception(page)) {
1889 if (radix_tree_deref_retry(page)) {
1890 slot = radix_tree_iter_retry(&iter);
1891 continue;
1892 }
1893 /*
1894 * A shadow entry of a recently evicted page.
1895 *
1896 * Those entries should never be tagged, but
1897 * this tree walk is lockless and the tags are
1898 * looked up in bulk, one radix tree node at a
1899 * time, so there is a sizable window for page
1900 * reclaim to evict a page we saw tagged.
1901 *
1902 * Skip over it.
1903 */
1904 continue;
1905 }
1906
1907 head = compound_head(page);
1908 if (!page_cache_get_speculative(head))
1909 goto repeat;
1910
1911 /* The page was split under us? */
1912 if (compound_head(page) != head) {
1913 put_page(head);
1914 goto repeat;
1915 }
1916
1917 /* Has the page moved? */
1918 if (unlikely(page != *slot)) {
1919 put_page(head);
1920 goto repeat;
1921 }
1922
1923 pages[ret] = page;
1924 if (++ret == nr_pages) {
1925 *index = pages[ret - 1]->index + 1;
1926 goto out;
1927 }
1928 }
1929
1930 /*
1931 * We come here when we got at @end. We take care to not overflow the
1932 * index @index as it confuses some of the callers. This breaks the
1933 * iteration when there is page at index -1 but that is already broken
1934 * anyway.
1935 */
1936 if (end == (pgoff_t)-1)
1937 *index = (pgoff_t)-1;
1938 else
1939 *index = end + 1;
1940out:
1941 rcu_read_unlock();
1942
1943 return ret;
1944}
1945EXPORT_SYMBOL(find_get_pages_range_tag);
1946
1947/**
1948 * find_get_entries_tag - find and return entries that match @tag
1949 * @mapping: the address_space to search
1950 * @start: the starting page cache index
1951 * @tag: the tag index
1952 * @nr_entries: the maximum number of entries
1953 * @entries: where the resulting entries are placed
1954 * @indices: the cache indices corresponding to the entries in @entries
1955 *
1956 * Like find_get_entries, except we only return entries which are tagged with
1957 * @tag.
1958 */
1959unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1960 int tag, unsigned int nr_entries,
1961 struct page **entries, pgoff_t *indices)
1962{
1963 void **slot;
1964 unsigned int ret = 0;
1965 struct radix_tree_iter iter;
1966
1967 if (!nr_entries)
1968 return 0;
1969
1970 rcu_read_lock();
1971 radix_tree_for_each_tagged(slot, &mapping->i_pages, &iter, start, tag) {
1972 struct page *head, *page;
1973repeat:
1974 page = radix_tree_deref_slot(slot);
1975 if (unlikely(!page))
1976 continue;
1977 if (radix_tree_exception(page)) {
1978 if (radix_tree_deref_retry(page)) {
1979 slot = radix_tree_iter_retry(&iter);
1980 continue;
1981 }
1982
1983 /*
1984 * A shadow entry of a recently evicted page, a swap
1985 * entry from shmem/tmpfs or a DAX entry. Return it
1986 * without attempting to raise page count.
1987 */
1988 goto export;
1989 }
1990
1991 head = compound_head(page);
1992 if (!page_cache_get_speculative(head))
1993 goto repeat;
1994
1995 /* The page was split under us? */
1996 if (compound_head(page) != head) {
1997 put_page(head);
1998 goto repeat;
1999 }
2000
2001 /* Has the page moved? */
2002 if (unlikely(page != *slot)) {
2003 put_page(head);
2004 goto repeat;
2005 }
2006export:
2007 indices[ret] = iter.index;
2008 entries[ret] = page;
2009 if (++ret == nr_entries)
2010 break;
2011 }
2012 rcu_read_unlock();
2013 return ret;
2014}
2015EXPORT_SYMBOL(find_get_entries_tag);
2016
2017/*
2018 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
2019 * a _large_ part of the i/o request. Imagine the worst scenario:
2020 *
2021 * ---R__________________________________________B__________
2022 * ^ reading here ^ bad block(assume 4k)
2023 *
2024 * read(R) => miss => readahead(R...B) => media error => frustrating retries
2025 * => failing the whole request => read(R) => read(R+1) =>
2026 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
2027 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
2028 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
2029 *
2030 * It is going insane. Fix it by quickly scaling down the readahead size.
2031 */
2032static void shrink_readahead_size_eio(struct file *filp,
2033 struct file_ra_state *ra)
2034{
2035 ra->ra_pages /= 4;
2036}
2037
2038/**
2039 * generic_file_buffered_read - generic file read routine
2040 * @iocb: the iocb to read
2041 * @iter: data destination
2042 * @written: already copied
2043 *
2044 * This is a generic file read routine, and uses the
2045 * mapping->a_ops->readpage() function for the actual low-level stuff.
2046 *
2047 * This is really ugly. But the goto's actually try to clarify some
2048 * of the logic when it comes to error handling etc.
2049 */
2050static ssize_t generic_file_buffered_read(struct kiocb *iocb,
2051 struct iov_iter *iter, ssize_t written)
2052{
2053 struct file *filp = iocb->ki_filp;
2054 struct address_space *mapping = filp->f_mapping;
2055 struct inode *inode = mapping->host;
2056 struct file_ra_state *ra = &filp->f_ra;
2057 loff_t *ppos = &iocb->ki_pos;
2058 pgoff_t index;
2059 pgoff_t last_index;
2060 pgoff_t prev_index;
2061 unsigned long offset; /* offset into pagecache page */
2062 unsigned int prev_offset;
2063 int error = 0;
2064
2065 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
2066 return 0;
2067 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
2068
2069 index = *ppos >> PAGE_SHIFT;
2070 prev_index = ra->prev_pos >> PAGE_SHIFT;
2071 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
2072 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
2073 offset = *ppos & ~PAGE_MASK;
2074
2075 for (;;) {
2076 struct page *page;
2077 pgoff_t end_index;
2078 loff_t isize;
2079 unsigned long nr, ret;
2080
2081 cond_resched();
2082find_page:
2083 if (fatal_signal_pending(current)) {
2084 error = -EINTR;
2085 goto out;
2086 }
2087
2088 page = find_get_page(mapping, index);
2089 if (!page) {
2090 if (iocb->ki_flags & IOCB_NOWAIT)
2091 goto would_block;
2092 page_cache_sync_readahead(mapping,
2093 ra, filp,
2094 index, last_index - index);
2095 page = find_get_page(mapping, index);
2096 if (unlikely(page == NULL))
2097 goto no_cached_page;
2098 }
2099 if (PageReadahead(page)) {
2100 page_cache_async_readahead(mapping,
2101 ra, filp, page,
2102 index, last_index - index);
2103 }
2104 if (!PageUptodate(page)) {
2105 if (iocb->ki_flags & IOCB_NOWAIT) {
2106 put_page(page);
2107 goto would_block;
2108 }
2109
2110 /*
2111 * See comment in do_read_cache_page on why
2112 * wait_on_page_locked is used to avoid unnecessarily
2113 * serialisations and why it's safe.
2114 */
2115 error = wait_on_page_locked_killable(page);
2116 if (unlikely(error))
2117 goto readpage_error;
2118 if (PageUptodate(page))
2119 goto page_ok;
2120
2121 if (inode->i_blkbits == PAGE_SHIFT ||
2122 !mapping->a_ops->is_partially_uptodate)
2123 goto page_not_up_to_date;
2124 /* pipes can't handle partially uptodate pages */
2125 if (unlikely(iter->type & ITER_PIPE))
2126 goto page_not_up_to_date;
2127 if (!trylock_page(page))
2128 goto page_not_up_to_date;
2129 /* Did it get truncated before we got the lock? */
2130 if (!page->mapping)
2131 goto page_not_up_to_date_locked;
2132 if (!mapping->a_ops->is_partially_uptodate(page,
2133 offset, iter->count))
2134 goto page_not_up_to_date_locked;
2135 unlock_page(page);
2136 }
2137page_ok:
2138 /*
2139 * i_size must be checked after we know the page is Uptodate.
2140 *
2141 * Checking i_size after the check allows us to calculate
2142 * the correct value for "nr", which means the zero-filled
2143 * part of the page is not copied back to userspace (unless
2144 * another truncate extends the file - this is desired though).
2145 */
2146
2147 isize = i_size_read(inode);
2148 end_index = (isize - 1) >> PAGE_SHIFT;
2149 if (unlikely(!isize || index > end_index)) {
2150 put_page(page);
2151 goto out;
2152 }
2153
2154 /* nr is the maximum number of bytes to copy from this page */
2155 nr = PAGE_SIZE;
2156 if (index == end_index) {
2157 nr = ((isize - 1) & ~PAGE_MASK) + 1;
2158 if (nr <= offset) {
2159 put_page(page);
2160 goto out;
2161 }
2162 }
2163 nr = nr - offset;
2164
2165 /* If users can be writing to this page using arbitrary
2166 * virtual addresses, take care about potential aliasing
2167 * before reading the page on the kernel side.
2168 */
2169 if (mapping_writably_mapped(mapping))
2170 flush_dcache_page(page);
2171
2172 /*
2173 * When a sequential read accesses a page several times,
2174 * only mark it as accessed the first time.
2175 */
2176 if (prev_index != index || offset != prev_offset)
2177 mark_page_accessed(page);
2178 prev_index = index;
2179
2180 /*
2181 * Ok, we have the page, and it's up-to-date, so
2182 * now we can copy it to user space...
2183 */
2184
2185 ret = copy_page_to_iter(page, offset, nr, iter);
2186 offset += ret;
2187 index += offset >> PAGE_SHIFT;
2188 offset &= ~PAGE_MASK;
2189 prev_offset = offset;
2190
2191 put_page(page);
2192 written += ret;
2193 if (!iov_iter_count(iter))
2194 goto out;
2195 if (ret < nr) {
2196 error = -EFAULT;
2197 goto out;
2198 }
2199 continue;
2200
2201page_not_up_to_date:
2202 /* Get exclusive access to the page ... */
2203 error = lock_page_killable(page);
2204 if (unlikely(error))
2205 goto readpage_error;
2206
2207page_not_up_to_date_locked:
2208 /* Did it get truncated before we got the lock? */
2209 if (!page->mapping) {
2210 unlock_page(page);
2211 put_page(page);
2212 continue;
2213 }
2214
2215 /* Did somebody else fill it already? */
2216 if (PageUptodate(page)) {
2217 unlock_page(page);
2218 goto page_ok;
2219 }
2220
2221readpage:
2222 /*
2223 * A previous I/O error may have been due to temporary
2224 * failures, eg. multipath errors.
2225 * PG_error will be set again if readpage fails.
2226 */
2227 ClearPageError(page);
2228 /* Start the actual read. The read will unlock the page. */
2229 error = mapping->a_ops->readpage(filp, page);
2230
2231 if (unlikely(error)) {
2232 if (error == AOP_TRUNCATED_PAGE) {
2233 put_page(page);
2234 error = 0;
2235 goto find_page;
2236 }
2237 goto readpage_error;
2238 }
2239
2240 if (!PageUptodate(page)) {
2241 error = lock_page_killable(page);
2242 if (unlikely(error))
2243 goto readpage_error;
2244 if (!PageUptodate(page)) {
2245 if (page->mapping == NULL) {
2246 /*
2247 * invalidate_mapping_pages got it
2248 */
2249 unlock_page(page);
2250 put_page(page);
2251 goto find_page;
2252 }
2253 unlock_page(page);
2254 shrink_readahead_size_eio(filp, ra);
2255 error = -EIO;
2256 goto readpage_error;
2257 }
2258 unlock_page(page);
2259 }
2260
2261 goto page_ok;
2262
2263readpage_error:
2264 /* UHHUH! A synchronous read error occurred. Report it */
2265 put_page(page);
2266 goto out;
2267
2268no_cached_page:
2269 /*
2270 * Ok, it wasn't cached, so we need to create a new
2271 * page..
2272 */
2273 page = page_cache_alloc(mapping);
2274 if (!page) {
2275 error = -ENOMEM;
2276 goto out;
2277 }
2278 error = add_to_page_cache_lru(page, mapping, index,
2279 mapping_gfp_constraint(mapping, GFP_KERNEL));
2280 if (error) {
2281 put_page(page);
2282 if (error == -EEXIST) {
2283 error = 0;
2284 goto find_page;
2285 }
2286 goto out;
2287 }
2288 goto readpage;
2289 }
2290
2291would_block:
2292 error = -EAGAIN;
2293out:
2294 ra->prev_pos = prev_index;
2295 ra->prev_pos <<= PAGE_SHIFT;
2296 ra->prev_pos |= prev_offset;
2297
2298 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2299 file_accessed(filp);
2300 return written ? written : error;
2301}
2302
2303/**
2304 * generic_file_read_iter - generic filesystem read routine
2305 * @iocb: kernel I/O control block
2306 * @iter: destination for the data read
2307 *
2308 * This is the "read_iter()" routine for all filesystems
2309 * that can use the page cache directly.
2310 */
2311ssize_t
2312generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2313{
2314 size_t count = iov_iter_count(iter);
2315 ssize_t retval = 0;
2316
2317 if (!count)
2318 goto out; /* skip atime */
2319
2320 if (iocb->ki_flags & IOCB_DIRECT) {
2321 struct file *file = iocb->ki_filp;
2322 struct address_space *mapping = file->f_mapping;
2323 struct inode *inode = mapping->host;
2324 loff_t size;
2325
2326 size = i_size_read(inode);
2327 if (iocb->ki_flags & IOCB_NOWAIT) {
2328 if (filemap_range_has_page(mapping, iocb->ki_pos,
2329 iocb->ki_pos + count - 1))
2330 return -EAGAIN;
2331 } else {
2332 retval = filemap_write_and_wait_range(mapping,
2333 iocb->ki_pos,
2334 iocb->ki_pos + count - 1);
2335 if (retval < 0)
2336 goto out;
2337 }
2338
2339 file_accessed(file);
2340
2341 retval = mapping->a_ops->direct_IO(iocb, iter);
2342 if (retval >= 0) {
2343 iocb->ki_pos += retval;
2344 count -= retval;
2345 }
2346 iov_iter_revert(iter, count - iov_iter_count(iter));
2347
2348 /*
2349 * Btrfs can have a short DIO read if we encounter
2350 * compressed extents, so if there was an error, or if
2351 * we've already read everything we wanted to, or if
2352 * there was a short read because we hit EOF, go ahead
2353 * and return. Otherwise fallthrough to buffered io for
2354 * the rest of the read. Buffered reads will not work for
2355 * DAX files, so don't bother trying.
2356 */
2357 if (retval < 0 || !count || iocb->ki_pos >= size ||
2358 IS_DAX(inode))
2359 goto out;
2360 }
2361
2362 retval = generic_file_buffered_read(iocb, iter, retval);
2363out:
2364 return retval;
2365}
2366EXPORT_SYMBOL(generic_file_read_iter);
2367
2368#ifdef CONFIG_MMU
2369/**
2370 * page_cache_read - adds requested page to the page cache if not already there
2371 * @file: file to read
2372 * @offset: page index
2373 * @gfp_mask: memory allocation flags
2374 *
2375 * This adds the requested page to the page cache if it isn't already there,
2376 * and schedules an I/O to read in its contents from disk.
2377 */
2378static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2379{
2380 struct address_space *mapping = file->f_mapping;
2381 struct page *page;
2382 int ret;
2383
2384 do {
2385 page = __page_cache_alloc(gfp_mask);
2386 if (!page)
2387 return -ENOMEM;
2388
2389 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask);
2390 if (ret == 0)
2391 ret = mapping->a_ops->readpage(file, page);
2392 else if (ret == -EEXIST)
2393 ret = 0; /* losing race to add is OK */
2394
2395 put_page(page);
2396
2397 } while (ret == AOP_TRUNCATED_PAGE);
2398
2399 return ret;
2400}
2401
2402#define MMAP_LOTSAMISS (100)
2403
2404/*
2405 * Synchronous readahead happens when we don't even find
2406 * a page in the page cache at all.
2407 */
2408static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2409 struct file_ra_state *ra,
2410 struct file *file,
2411 pgoff_t offset)
2412{
2413 struct address_space *mapping = file->f_mapping;
2414
2415 /* If we don't want any read-ahead, don't bother */
2416 if (vma->vm_flags & VM_RAND_READ)
2417 return;
2418 if (!ra->ra_pages)
2419 return;
2420
2421 if (vma->vm_flags & VM_SEQ_READ) {
2422 page_cache_sync_readahead(mapping, ra, file, offset,
2423 ra->ra_pages);
2424 return;
2425 }
2426
2427 /* Avoid banging the cache line if not needed */
2428 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2429 ra->mmap_miss++;
2430
2431 /*
2432 * Do we miss much more than hit in this file? If so,
2433 * stop bothering with read-ahead. It will only hurt.
2434 */
2435 if (ra->mmap_miss > MMAP_LOTSAMISS)
2436 return;
2437
2438 /*
2439 * mmap read-around
2440 */
2441 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2442 ra->size = ra->ra_pages;
2443 ra->async_size = ra->ra_pages / 4;
2444 ra_submit(ra, mapping, file);
2445}
2446
2447/*
2448 * Asynchronous readahead happens when we find the page and PG_readahead,
2449 * so we want to possibly extend the readahead further..
2450 */
2451static void do_async_mmap_readahead(struct vm_area_struct *vma,
2452 struct file_ra_state *ra,
2453 struct file *file,
2454 struct page *page,
2455 pgoff_t offset)
2456{
2457 struct address_space *mapping = file->f_mapping;
2458
2459 /* If we don't want any read-ahead, don't bother */
2460 if (vma->vm_flags & VM_RAND_READ)
2461 return;
2462 if (ra->mmap_miss > 0)
2463 ra->mmap_miss--;
2464 if (PageReadahead(page))
2465 page_cache_async_readahead(mapping, ra, file,
2466 page, offset, ra->ra_pages);
2467}
2468
2469/**
2470 * filemap_fault - read in file data for page fault handling
2471 * @vmf: struct vm_fault containing details of the fault
2472 *
2473 * filemap_fault() is invoked via the vma operations vector for a
2474 * mapped memory region to read in file data during a page fault.
2475 *
2476 * The goto's are kind of ugly, but this streamlines the normal case of having
2477 * it in the page cache, and handles the special cases reasonably without
2478 * having a lot of duplicated code.
2479 *
2480 * vma->vm_mm->mmap_sem must be held on entry.
2481 *
2482 * If our return value has VM_FAULT_RETRY set, it's because
2483 * lock_page_or_retry() returned 0.
2484 * The mmap_sem has usually been released in this case.
2485 * See __lock_page_or_retry() for the exception.
2486 *
2487 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2488 * has not been released.
2489 *
2490 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2491 */
2492int filemap_fault(struct vm_fault *vmf)
2493{
2494 int error;
2495 struct file *file = vmf->vma->vm_file;
2496 struct address_space *mapping = file->f_mapping;
2497 struct file_ra_state *ra = &file->f_ra;
2498 struct inode *inode = mapping->host;
2499 pgoff_t offset = vmf->pgoff;
2500 pgoff_t max_off;
2501 struct page *page;
2502 int ret = 0;
2503
2504 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2505 if (unlikely(offset >= max_off))
2506 return VM_FAULT_SIGBUS;
2507
2508 /*
2509 * Do we have something in the page cache already?
2510 */
2511 page = find_get_page(mapping, offset);
2512 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2513 /*
2514 * We found the page, so try async readahead before
2515 * waiting for the lock.
2516 */
2517 do_async_mmap_readahead(vmf->vma, ra, file, page, offset);
2518 } else if (!page) {
2519 /* No page in the page cache at all */
2520 do_sync_mmap_readahead(vmf->vma, ra, file, offset);
2521 count_vm_event(PGMAJFAULT);
2522 count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
2523 ret = VM_FAULT_MAJOR;
2524retry_find:
2525 page = find_get_page(mapping, offset);
2526 if (!page)
2527 goto no_cached_page;
2528 }
2529
2530 if (!lock_page_or_retry(page, vmf->vma->vm_mm, vmf->flags)) {
2531 put_page(page);
2532 return ret | VM_FAULT_RETRY;
2533 }
2534
2535 /* Did it get truncated? */
2536 if (unlikely(page->mapping != mapping)) {
2537 unlock_page(page);
2538 put_page(page);
2539 goto retry_find;
2540 }
2541 VM_BUG_ON_PAGE(page->index != offset, page);
2542
2543 /*
2544 * We have a locked page in the page cache, now we need to check
2545 * that it's up-to-date. If not, it is going to be due to an error.
2546 */
2547 if (unlikely(!PageUptodate(page)))
2548 goto page_not_uptodate;
2549
2550 /*
2551 * Found the page and have a reference on it.
2552 * We must recheck i_size under page lock.
2553 */
2554 max_off = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
2555 if (unlikely(offset >= max_off)) {
2556 unlock_page(page);
2557 put_page(page);
2558 return VM_FAULT_SIGBUS;
2559 }
2560
2561 vmf->page = page;
2562 return ret | VM_FAULT_LOCKED;
2563
2564no_cached_page:
2565 /*
2566 * We're only likely to ever get here if MADV_RANDOM is in
2567 * effect.
2568 */
2569 error = page_cache_read(file, offset, vmf->gfp_mask);
2570
2571 /*
2572 * The page we want has now been added to the page cache.
2573 * In the unlikely event that someone removed it in the
2574 * meantime, we'll just come back here and read it again.
2575 */
2576 if (error >= 0)
2577 goto retry_find;
2578
2579 /*
2580 * An error return from page_cache_read can result if the
2581 * system is low on memory, or a problem occurs while trying
2582 * to schedule I/O.
2583 */
2584 if (error == -ENOMEM)
2585 return VM_FAULT_OOM;
2586 return VM_FAULT_SIGBUS;
2587
2588page_not_uptodate:
2589 /*
2590 * Umm, take care of errors if the page isn't up-to-date.
2591 * Try to re-read it _once_. We do this synchronously,
2592 * because there really aren't any performance issues here
2593 * and we need to check for errors.
2594 */
2595 ClearPageError(page);
2596 error = mapping->a_ops->readpage(file, page);
2597 if (!error) {
2598 wait_on_page_locked(page);
2599 if (!PageUptodate(page))
2600 error = -EIO;
2601 }
2602 put_page(page);
2603
2604 if (!error || error == AOP_TRUNCATED_PAGE)
2605 goto retry_find;
2606
2607 /* Things didn't work out. Return zero to tell the mm layer so. */
2608 shrink_readahead_size_eio(file, ra);
2609 return VM_FAULT_SIGBUS;
2610}
2611EXPORT_SYMBOL(filemap_fault);
2612
2613void filemap_map_pages(struct vm_fault *vmf,
2614 pgoff_t start_pgoff, pgoff_t end_pgoff)
2615{
2616 struct radix_tree_iter iter;
2617 void **slot;
2618 struct file *file = vmf->vma->vm_file;
2619 struct address_space *mapping = file->f_mapping;
2620 pgoff_t last_pgoff = start_pgoff;
2621 unsigned long max_idx;
2622 struct page *head, *page;
2623
2624 rcu_read_lock();
2625 radix_tree_for_each_slot(slot, &mapping->i_pages, &iter, start_pgoff) {
2626 if (iter.index > end_pgoff)
2627 break;
2628repeat:
2629 page = radix_tree_deref_slot(slot);
2630 if (unlikely(!page))
2631 goto next;
2632 if (radix_tree_exception(page)) {
2633 if (radix_tree_deref_retry(page)) {
2634 slot = radix_tree_iter_retry(&iter);
2635 continue;
2636 }
2637 goto next;
2638 }
2639
2640 head = compound_head(page);
2641 if (!page_cache_get_speculative(head))
2642 goto repeat;
2643
2644 /* The page was split under us? */
2645 if (compound_head(page) != head) {
2646 put_page(head);
2647 goto repeat;
2648 }
2649
2650 /* Has the page moved? */
2651 if (unlikely(page != *slot)) {
2652 put_page(head);
2653 goto repeat;
2654 }
2655
2656 if (!PageUptodate(page) ||
2657 PageReadahead(page) ||
2658 PageHWPoison(page))
2659 goto skip;
2660 if (!trylock_page(page))
2661 goto skip;
2662
2663 if (page->mapping != mapping || !PageUptodate(page))
2664 goto unlock;
2665
2666 max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
2667 if (page->index >= max_idx)
2668 goto unlock;
2669
2670 if (file->f_ra.mmap_miss > 0)
2671 file->f_ra.mmap_miss--;
2672
2673 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2674 if (vmf->pte)
2675 vmf->pte += iter.index - last_pgoff;
2676 last_pgoff = iter.index;
2677 if (alloc_set_pte(vmf, NULL, page))
2678 goto unlock;
2679 unlock_page(page);
2680 goto next;
2681unlock:
2682 unlock_page(page);
2683skip:
2684 put_page(page);
2685next:
2686 /* Huge page is mapped? No need to proceed. */
2687 if (pmd_trans_huge(*vmf->pmd))
2688 break;
2689 if (iter.index == end_pgoff)
2690 break;
2691 }
2692 rcu_read_unlock();
2693}
2694EXPORT_SYMBOL(filemap_map_pages);
2695
2696int filemap_page_mkwrite(struct vm_fault *vmf)
2697{
2698 struct page *page = vmf->page;
2699 struct inode *inode = file_inode(vmf->vma->vm_file);
2700 int ret = VM_FAULT_LOCKED;
2701
2702 sb_start_pagefault(inode->i_sb);
2703 file_update_time(vmf->vma->vm_file);
2704 lock_page(page);
2705 if (page->mapping != inode->i_mapping) {
2706 unlock_page(page);
2707 ret = VM_FAULT_NOPAGE;
2708 goto out;
2709 }
2710 /*
2711 * We mark the page dirty already here so that when freeze is in
2712 * progress, we are guaranteed that writeback during freezing will
2713 * see the dirty page and writeprotect it again.
2714 */
2715 set_page_dirty(page);
2716 wait_for_stable_page(page);
2717out:
2718 sb_end_pagefault(inode->i_sb);
2719 return ret;
2720}
2721
2722const struct vm_operations_struct generic_file_vm_ops = {
2723 .fault = filemap_fault,
2724 .map_pages = filemap_map_pages,
2725 .page_mkwrite = filemap_page_mkwrite,
2726};
2727
2728/* This is used for a general mmap of a disk file */
2729
2730int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2731{
2732 struct address_space *mapping = file->f_mapping;
2733
2734 if (!mapping->a_ops->readpage)
2735 return -ENOEXEC;
2736 file_accessed(file);
2737 vma->vm_ops = &generic_file_vm_ops;
2738 return 0;
2739}
2740
2741/*
2742 * This is for filesystems which do not implement ->writepage.
2743 */
2744int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2745{
2746 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2747 return -EINVAL;
2748 return generic_file_mmap(file, vma);
2749}
2750#else
2751int filemap_page_mkwrite(struct vm_fault *vmf)
2752{
2753 return -ENOSYS;
2754}
2755int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2756{
2757 return -ENOSYS;
2758}
2759int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2760{
2761 return -ENOSYS;
2762}
2763#endif /* CONFIG_MMU */
2764
2765EXPORT_SYMBOL(filemap_page_mkwrite);
2766EXPORT_SYMBOL(generic_file_mmap);
2767EXPORT_SYMBOL(generic_file_readonly_mmap);
2768
2769static struct page *wait_on_page_read(struct page *page)
2770{
2771 if (!IS_ERR(page)) {
2772 wait_on_page_locked(page);
2773 if (!PageUptodate(page)) {
2774 put_page(page);
2775 page = ERR_PTR(-EIO);
2776 }
2777 }
2778 return page;
2779}
2780
2781static struct page *do_read_cache_page(struct address_space *mapping,
2782 pgoff_t index,
2783 int (*filler)(void *, struct page *),
2784 void *data,
2785 gfp_t gfp)
2786{
2787 struct page *page;
2788 int err;
2789repeat:
2790 page = find_get_page(mapping, index);
2791 if (!page) {
2792 page = __page_cache_alloc(gfp);
2793 if (!page)
2794 return ERR_PTR(-ENOMEM);
2795 err = add_to_page_cache_lru(page, mapping, index, gfp);
2796 if (unlikely(err)) {
2797 put_page(page);
2798 if (err == -EEXIST)
2799 goto repeat;
2800 /* Presumably ENOMEM for radix tree node */
2801 return ERR_PTR(err);
2802 }
2803
2804filler:
2805 err = filler(data, page);
2806 if (err < 0) {
2807 put_page(page);
2808 return ERR_PTR(err);
2809 }
2810
2811 page = wait_on_page_read(page);
2812 if (IS_ERR(page))
2813 return page;
2814 goto out;
2815 }
2816 if (PageUptodate(page))
2817 goto out;
2818
2819 /*
2820 * Page is not up to date and may be locked due one of the following
2821 * case a: Page is being filled and the page lock is held
2822 * case b: Read/write error clearing the page uptodate status
2823 * case c: Truncation in progress (page locked)
2824 * case d: Reclaim in progress
2825 *
2826 * Case a, the page will be up to date when the page is unlocked.
2827 * There is no need to serialise on the page lock here as the page
2828 * is pinned so the lock gives no additional protection. Even if the
2829 * the page is truncated, the data is still valid if PageUptodate as
2830 * it's a race vs truncate race.
2831 * Case b, the page will not be up to date
2832 * Case c, the page may be truncated but in itself, the data may still
2833 * be valid after IO completes as it's a read vs truncate race. The
2834 * operation must restart if the page is not uptodate on unlock but
2835 * otherwise serialising on page lock to stabilise the mapping gives
2836 * no additional guarantees to the caller as the page lock is
2837 * released before return.
2838 * Case d, similar to truncation. If reclaim holds the page lock, it
2839 * will be a race with remove_mapping that determines if the mapping
2840 * is valid on unlock but otherwise the data is valid and there is
2841 * no need to serialise with page lock.
2842 *
2843 * As the page lock gives no additional guarantee, we optimistically
2844 * wait on the page to be unlocked and check if it's up to date and
2845 * use the page if it is. Otherwise, the page lock is required to
2846 * distinguish between the different cases. The motivation is that we
2847 * avoid spurious serialisations and wakeups when multiple processes
2848 * wait on the same page for IO to complete.
2849 */
2850 wait_on_page_locked(page);
2851 if (PageUptodate(page))
2852 goto out;
2853
2854 /* Distinguish between all the cases under the safety of the lock */
2855 lock_page(page);
2856
2857 /* Case c or d, restart the operation */
2858 if (!page->mapping) {
2859 unlock_page(page);
2860 put_page(page);
2861 goto repeat;
2862 }
2863
2864 /* Someone else locked and filled the page in a very small window */
2865 if (PageUptodate(page)) {
2866 unlock_page(page);
2867 goto out;
2868 }
2869 goto filler;
2870
2871out:
2872 mark_page_accessed(page);
2873 return page;
2874}
2875
2876/**
2877 * read_cache_page - read into page cache, fill it if needed
2878 * @mapping: the page's address_space
2879 * @index: the page index
2880 * @filler: function to perform the read
2881 * @data: first arg to filler(data, page) function, often left as NULL
2882 *
2883 * Read into the page cache. If a page already exists, and PageUptodate() is
2884 * not set, try to fill the page and wait for it to become unlocked.
2885 *
2886 * If the page does not get brought uptodate, return -EIO.
2887 */
2888struct page *read_cache_page(struct address_space *mapping,
2889 pgoff_t index,
2890 int (*filler)(void *, struct page *),
2891 void *data)
2892{
2893 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2894}
2895EXPORT_SYMBOL(read_cache_page);
2896
2897/**
2898 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2899 * @mapping: the page's address_space
2900 * @index: the page index
2901 * @gfp: the page allocator flags to use if allocating
2902 *
2903 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2904 * any new page allocations done using the specified allocation flags.
2905 *
2906 * If the page does not get brought uptodate, return -EIO.
2907 */
2908struct page *read_cache_page_gfp(struct address_space *mapping,
2909 pgoff_t index,
2910 gfp_t gfp)
2911{
2912 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2913
2914 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2915}
2916EXPORT_SYMBOL(read_cache_page_gfp);
2917
2918/*
2919 * Performs necessary checks before doing a write
2920 *
2921 * Can adjust writing position or amount of bytes to write.
2922 * Returns appropriate error code that caller should return or
2923 * zero in case that write should be allowed.
2924 */
2925inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2926{
2927 struct file *file = iocb->ki_filp;
2928 struct inode *inode = file->f_mapping->host;
2929 unsigned long limit = rlimit(RLIMIT_FSIZE);
2930 loff_t pos;
2931
2932 if (!iov_iter_count(from))
2933 return 0;
2934
2935 /* FIXME: this is for backwards compatibility with 2.4 */
2936 if (iocb->ki_flags & IOCB_APPEND)
2937 iocb->ki_pos = i_size_read(inode);
2938
2939 pos = iocb->ki_pos;
2940
2941 if ((iocb->ki_flags & IOCB_NOWAIT) && !(iocb->ki_flags & IOCB_DIRECT))
2942 return -EINVAL;
2943
2944 if (limit != RLIM_INFINITY) {
2945 if (iocb->ki_pos >= limit) {
2946 send_sig(SIGXFSZ, current, 0);
2947 return -EFBIG;
2948 }
2949 iov_iter_truncate(from, limit - (unsigned long)pos);
2950 }
2951
2952 /*
2953 * LFS rule
2954 */
2955 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2956 !(file->f_flags & O_LARGEFILE))) {
2957 if (pos >= MAX_NON_LFS)
2958 return -EFBIG;
2959 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2960 }
2961
2962 /*
2963 * Are we about to exceed the fs block limit ?
2964 *
2965 * If we have written data it becomes a short write. If we have
2966 * exceeded without writing data we send a signal and return EFBIG.
2967 * Linus frestrict idea will clean these up nicely..
2968 */
2969 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2970 return -EFBIG;
2971
2972 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2973 return iov_iter_count(from);
2974}
2975EXPORT_SYMBOL(generic_write_checks);
2976
2977int pagecache_write_begin(struct file *file, struct address_space *mapping,
2978 loff_t pos, unsigned len, unsigned flags,
2979 struct page **pagep, void **fsdata)
2980{
2981 const struct address_space_operations *aops = mapping->a_ops;
2982
2983 return aops->write_begin(file, mapping, pos, len, flags,
2984 pagep, fsdata);
2985}
2986EXPORT_SYMBOL(pagecache_write_begin);
2987
2988int pagecache_write_end(struct file *file, struct address_space *mapping,
2989 loff_t pos, unsigned len, unsigned copied,
2990 struct page *page, void *fsdata)
2991{
2992 const struct address_space_operations *aops = mapping->a_ops;
2993
2994 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2995}
2996EXPORT_SYMBOL(pagecache_write_end);
2997
2998ssize_t
2999generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
3000{
3001 struct file *file = iocb->ki_filp;
3002 struct address_space *mapping = file->f_mapping;
3003 struct inode *inode = mapping->host;
3004 loff_t pos = iocb->ki_pos;
3005 ssize_t written;
3006 size_t write_len;
3007 pgoff_t end;
3008
3009 write_len = iov_iter_count(from);
3010 end = (pos + write_len - 1) >> PAGE_SHIFT;
3011
3012 if (iocb->ki_flags & IOCB_NOWAIT) {
3013 /* If there are pages to writeback, return */
3014 if (filemap_range_has_page(inode->i_mapping, pos,
3015 pos + iov_iter_count(from)))
3016 return -EAGAIN;
3017 } else {
3018 written = filemap_write_and_wait_range(mapping, pos,
3019 pos + write_len - 1);
3020 if (written)
3021 goto out;
3022 }
3023
3024 /*
3025 * After a write we want buffered reads to be sure to go to disk to get
3026 * the new data. We invalidate clean cached page from the region we're
3027 * about to write. We do this *before* the write so that we can return
3028 * without clobbering -EIOCBQUEUED from ->direct_IO().
3029 */
3030 written = invalidate_inode_pages2_range(mapping,
3031 pos >> PAGE_SHIFT, end);
3032 /*
3033 * If a page can not be invalidated, return 0 to fall back
3034 * to buffered write.
3035 */
3036 if (written) {
3037 if (written == -EBUSY)
3038 return 0;
3039 goto out;
3040 }
3041
3042 written = mapping->a_ops->direct_IO(iocb, from);
3043
3044 /*
3045 * Finally, try again to invalidate clean pages which might have been
3046 * cached by non-direct readahead, or faulted in by get_user_pages()
3047 * if the source of the write was an mmap'ed region of the file
3048 * we're writing. Either one is a pretty crazy thing to do,
3049 * so we don't support it 100%. If this invalidation
3050 * fails, tough, the write still worked...
3051 *
3052 * Most of the time we do not need this since dio_complete() will do
3053 * the invalidation for us. However there are some file systems that
3054 * do not end up with dio_complete() being called, so let's not break
3055 * them by removing it completely
3056 */
3057 if (mapping->nrpages)
3058 invalidate_inode_pages2_range(mapping,
3059 pos >> PAGE_SHIFT, end);
3060
3061 if (written > 0) {
3062 pos += written;
3063 write_len -= written;
3064 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
3065 i_size_write(inode, pos);
3066 mark_inode_dirty(inode);
3067 }
3068 iocb->ki_pos = pos;
3069 }
3070 iov_iter_revert(from, write_len - iov_iter_count(from));
3071out:
3072 return written;
3073}
3074EXPORT_SYMBOL(generic_file_direct_write);
3075
3076/*
3077 * Find or create a page at the given pagecache position. Return the locked
3078 * page. This function is specifically for buffered writes.
3079 */
3080struct page *grab_cache_page_write_begin(struct address_space *mapping,
3081 pgoff_t index, unsigned flags)
3082{
3083 struct page *page;
3084 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
3085
3086 if (flags & AOP_FLAG_NOFS)
3087 fgp_flags |= FGP_NOFS;
3088
3089 page = pagecache_get_page(mapping, index, fgp_flags,
3090 mapping_gfp_mask(mapping));
3091 if (page)
3092 wait_for_stable_page(page);
3093
3094 return page;
3095}
3096EXPORT_SYMBOL(grab_cache_page_write_begin);
3097
3098ssize_t generic_perform_write(struct file *file,
3099 struct iov_iter *i, loff_t pos)
3100{
3101 struct address_space *mapping = file->f_mapping;
3102 const struct address_space_operations *a_ops = mapping->a_ops;
3103 long status = 0;
3104 ssize_t written = 0;
3105 unsigned int flags = 0;
3106
3107 do {
3108 struct page *page;
3109 unsigned long offset; /* Offset into pagecache page */
3110 unsigned long bytes; /* Bytes to write to page */
3111 size_t copied; /* Bytes copied from user */
3112 void *fsdata;
3113
3114 offset = (pos & (PAGE_SIZE - 1));
3115 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3116 iov_iter_count(i));
3117
3118again:
3119 /*
3120 * Bring in the user page that we will copy from _first_.
3121 * Otherwise there's a nasty deadlock on copying from the
3122 * same page as we're writing to, without it being marked
3123 * up-to-date.
3124 *
3125 * Not only is this an optimisation, but it is also required
3126 * to check that the address is actually valid, when atomic
3127 * usercopies are used, below.
3128 */
3129 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
3130 status = -EFAULT;
3131 break;
3132 }
3133
3134 if (fatal_signal_pending(current)) {
3135 status = -EINTR;
3136 break;
3137 }
3138
3139 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
3140 &page, &fsdata);
3141 if (unlikely(status < 0))
3142 break;
3143
3144 if (mapping_writably_mapped(mapping))
3145 flush_dcache_page(page);
3146
3147 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
3148 flush_dcache_page(page);
3149
3150 status = a_ops->write_end(file, mapping, pos, bytes, copied,
3151 page, fsdata);
3152 if (unlikely(status < 0))
3153 break;
3154 copied = status;
3155
3156 cond_resched();
3157
3158 iov_iter_advance(i, copied);
3159 if (unlikely(copied == 0)) {
3160 /*
3161 * If we were unable to copy any data at all, we must
3162 * fall back to a single segment length write.
3163 *
3164 * If we didn't fallback here, we could livelock
3165 * because not all segments in the iov can be copied at
3166 * once without a pagefault.
3167 */
3168 bytes = min_t(unsigned long, PAGE_SIZE - offset,
3169 iov_iter_single_seg_count(i));
3170 goto again;
3171 }
3172 pos += copied;
3173 written += copied;
3174
3175 balance_dirty_pages_ratelimited(mapping);
3176 } while (iov_iter_count(i));
3177
3178 return written ? written : status;
3179}
3180EXPORT_SYMBOL(generic_perform_write);
3181
3182/**
3183 * __generic_file_write_iter - write data to a file
3184 * @iocb: IO state structure (file, offset, etc.)
3185 * @from: iov_iter with data to write
3186 *
3187 * This function does all the work needed for actually writing data to a
3188 * file. It does all basic checks, removes SUID from the file, updates
3189 * modification times and calls proper subroutines depending on whether we
3190 * do direct IO or a standard buffered write.
3191 *
3192 * It expects i_mutex to be grabbed unless we work on a block device or similar
3193 * object which does not need locking at all.
3194 *
3195 * This function does *not* take care of syncing data in case of O_SYNC write.
3196 * A caller has to handle it. This is mainly due to the fact that we want to
3197 * avoid syncing under i_mutex.
3198 */
3199ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3200{
3201 struct file *file = iocb->ki_filp;
3202 struct address_space * mapping = file->f_mapping;
3203 struct inode *inode = mapping->host;
3204 ssize_t written = 0;
3205 ssize_t err;
3206 ssize_t status;
3207
3208 /* We can write back this queue in page reclaim */
3209 current->backing_dev_info = inode_to_bdi(inode);
3210 err = file_remove_privs(file);
3211 if (err)
3212 goto out;
3213
3214 err = file_update_time(file);
3215 if (err)
3216 goto out;
3217
3218 if (iocb->ki_flags & IOCB_DIRECT) {
3219 loff_t pos, endbyte;
3220
3221 written = generic_file_direct_write(iocb, from);
3222 /*
3223 * If the write stopped short of completing, fall back to
3224 * buffered writes. Some filesystems do this for writes to
3225 * holes, for example. For DAX files, a buffered write will
3226 * not succeed (even if it did, DAX does not handle dirty
3227 * page-cache pages correctly).
3228 */
3229 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
3230 goto out;
3231
3232 status = generic_perform_write(file, from, pos = iocb->ki_pos);
3233 /*
3234 * If generic_perform_write() returned a synchronous error
3235 * then we want to return the number of bytes which were
3236 * direct-written, or the error code if that was zero. Note
3237 * that this differs from normal direct-io semantics, which
3238 * will return -EFOO even if some bytes were written.
3239 */
3240 if (unlikely(status < 0)) {
3241 err = status;
3242 goto out;
3243 }
3244 /*
3245 * We need to ensure that the page cache pages are written to
3246 * disk and invalidated to preserve the expected O_DIRECT
3247 * semantics.
3248 */
3249 endbyte = pos + status - 1;
3250 err = filemap_write_and_wait_range(mapping, pos, endbyte);
3251 if (err == 0) {
3252 iocb->ki_pos = endbyte + 1;
3253 written += status;
3254 invalidate_mapping_pages(mapping,
3255 pos >> PAGE_SHIFT,
3256 endbyte >> PAGE_SHIFT);
3257 } else {
3258 /*
3259 * We don't know how much we wrote, so just return
3260 * the number of bytes which were direct-written
3261 */
3262 }
3263 } else {
3264 written = generic_perform_write(file, from, iocb->ki_pos);
3265 if (likely(written > 0))
3266 iocb->ki_pos += written;
3267 }
3268out:
3269 current->backing_dev_info = NULL;
3270 return written ? written : err;
3271}
3272EXPORT_SYMBOL(__generic_file_write_iter);
3273
3274/**
3275 * generic_file_write_iter - write data to a file
3276 * @iocb: IO state structure
3277 * @from: iov_iter with data to write
3278 *
3279 * This is a wrapper around __generic_file_write_iter() to be used by most
3280 * filesystems. It takes care of syncing the file in case of O_SYNC file
3281 * and acquires i_mutex as needed.
3282 */
3283ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
3284{
3285 struct file *file = iocb->ki_filp;
3286 struct inode *inode = file->f_mapping->host;
3287 ssize_t ret;
3288
3289 inode_lock(inode);
3290 ret = generic_write_checks(iocb, from);
3291 if (ret > 0)
3292 ret = __generic_file_write_iter(iocb, from);
3293 inode_unlock(inode);
3294
3295 if (ret > 0)
3296 ret = generic_write_sync(iocb, ret);
3297 return ret;
3298}
3299EXPORT_SYMBOL(generic_file_write_iter);
3300
3301/**
3302 * try_to_release_page() - release old fs-specific metadata on a page
3303 *
3304 * @page: the page which the kernel is trying to free
3305 * @gfp_mask: memory allocation flags (and I/O mode)
3306 *
3307 * The address_space is to try to release any data against the page
3308 * (presumably at page->private). If the release was successful, return '1'.
3309 * Otherwise return zero.
3310 *
3311 * This may also be called if PG_fscache is set on a page, indicating that the
3312 * page is known to the local caching routines.
3313 *
3314 * The @gfp_mask argument specifies whether I/O may be performed to release
3315 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3316 *
3317 */
3318int try_to_release_page(struct page *page, gfp_t gfp_mask)
3319{
3320 struct address_space * const mapping = page->mapping;
3321
3322 BUG_ON(!PageLocked(page));
3323 if (PageWriteback(page))
3324 return 0;
3325
3326 if (mapping && mapping->a_ops->releasepage)
3327 return mapping->a_ops->releasepage(page, gfp_mask);
3328 return try_to_free_buffers(page);
3329}
3330
3331EXPORT_SYMBOL(try_to_release_page);
1/*
2 * linux/mm/filemap.c
3 *
4 * Copyright (C) 1994-1999 Linus Torvalds
5 */
6
7/*
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)
11 */
12#include <linux/export.h>
13#include <linux/compiler.h>
14#include <linux/dax.h>
15#include <linux/fs.h>
16#include <linux/uaccess.h>
17#include <linux/capability.h>
18#include <linux/kernel_stat.h>
19#include <linux/gfp.h>
20#include <linux/mm.h>
21#include <linux/swap.h>
22#include <linux/mman.h>
23#include <linux/pagemap.h>
24#include <linux/file.h>
25#include <linux/uio.h>
26#include <linux/hash.h>
27#include <linux/writeback.h>
28#include <linux/backing-dev.h>
29#include <linux/pagevec.h>
30#include <linux/blkdev.h>
31#include <linux/security.h>
32#include <linux/cpuset.h>
33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34#include <linux/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/rmap.h>
38#include "internal.h"
39
40#define CREATE_TRACE_POINTS
41#include <trace/events/filemap.h>
42
43/*
44 * FIXME: remove all knowledge of the buffer layer from the core VM
45 */
46#include <linux/buffer_head.h> /* for try_to_free_buffers */
47
48#include <asm/mman.h>
49
50/*
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
52 * though.
53 *
54 * Shared mappings now work. 15.8.1995 Bruno.
55 *
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 *
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
60 */
61
62/*
63 * Lock ordering:
64 *
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
69 *
70 * ->i_mutex
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
72 *
73 * ->mmap_sem
74 * ->i_mmap_rwsem
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
77 *
78 * ->mmap_sem
79 * ->lock_page (access_process_vm)
80 *
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
83 *
84 * bdi->wb.list_lock
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
87 *
88 * ->i_mmap_rwsem
89 * ->anon_vma.lock (vma_adjust)
90 *
91 * ->anon_vma.lock
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 *
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone_lru_lock(zone) (follow_page->mark_page_accessed)
99 * ->zone_lru_lock(zone) (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
108 *
109 * ->i_mmap_rwsem
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 */
112
113static int page_cache_tree_insert(struct address_space *mapping,
114 struct page *page, void **shadowp)
115{
116 struct radix_tree_node *node;
117 void **slot;
118 int error;
119
120 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
121 &node, &slot);
122 if (error)
123 return error;
124 if (*slot) {
125 void *p;
126
127 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
128 if (!radix_tree_exceptional_entry(p))
129 return -EEXIST;
130
131 mapping->nrexceptional--;
132 if (!dax_mapping(mapping)) {
133 if (shadowp)
134 *shadowp = p;
135 } else {
136 /* DAX can replace empty locked entry with a hole */
137 WARN_ON_ONCE(p !=
138 dax_radix_locked_entry(0, RADIX_DAX_EMPTY));
139 /* Wakeup waiters for exceptional entry lock */
140 dax_wake_mapping_entry_waiter(mapping, page->index, p,
141 true);
142 }
143 }
144 __radix_tree_replace(&mapping->page_tree, node, slot, page,
145 workingset_update_node, mapping);
146 mapping->nrpages++;
147 return 0;
148}
149
150static void page_cache_tree_delete(struct address_space *mapping,
151 struct page *page, void *shadow)
152{
153 int i, nr;
154
155 /* hugetlb pages are represented by one entry in the radix tree */
156 nr = PageHuge(page) ? 1 : hpage_nr_pages(page);
157
158 VM_BUG_ON_PAGE(!PageLocked(page), page);
159 VM_BUG_ON_PAGE(PageTail(page), page);
160 VM_BUG_ON_PAGE(nr != 1 && shadow, page);
161
162 for (i = 0; i < nr; i++) {
163 struct radix_tree_node *node;
164 void **slot;
165
166 __radix_tree_lookup(&mapping->page_tree, page->index + i,
167 &node, &slot);
168
169 VM_BUG_ON_PAGE(!node && nr != 1, page);
170
171 radix_tree_clear_tags(&mapping->page_tree, node, slot);
172 __radix_tree_replace(&mapping->page_tree, node, slot, shadow,
173 workingset_update_node, mapping);
174 }
175
176 if (shadow) {
177 mapping->nrexceptional += nr;
178 /*
179 * Make sure the nrexceptional update is committed before
180 * the nrpages update so that final truncate racing
181 * with reclaim does not see both counters 0 at the
182 * same time and miss a shadow entry.
183 */
184 smp_wmb();
185 }
186 mapping->nrpages -= nr;
187}
188
189/*
190 * Delete a page from the page cache and free it. Caller has to make
191 * sure the page is locked and that nobody else uses it - or that usage
192 * is safe. The caller must hold the mapping's tree_lock.
193 */
194void __delete_from_page_cache(struct page *page, void *shadow)
195{
196 struct address_space *mapping = page->mapping;
197 int nr = hpage_nr_pages(page);
198
199 trace_mm_filemap_delete_from_page_cache(page);
200 /*
201 * if we're uptodate, flush out into the cleancache, otherwise
202 * invalidate any existing cleancache entries. We can't leave
203 * stale data around in the cleancache once our page is gone
204 */
205 if (PageUptodate(page) && PageMappedToDisk(page))
206 cleancache_put_page(page);
207 else
208 cleancache_invalidate_page(mapping, page);
209
210 VM_BUG_ON_PAGE(PageTail(page), page);
211 VM_BUG_ON_PAGE(page_mapped(page), page);
212 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
213 int mapcount;
214
215 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
216 current->comm, page_to_pfn(page));
217 dump_page(page, "still mapped when deleted");
218 dump_stack();
219 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
220
221 mapcount = page_mapcount(page);
222 if (mapping_exiting(mapping) &&
223 page_count(page) >= mapcount + 2) {
224 /*
225 * All vmas have already been torn down, so it's
226 * a good bet that actually the page is unmapped,
227 * and we'd prefer not to leak it: if we're wrong,
228 * some other bad page check should catch it later.
229 */
230 page_mapcount_reset(page);
231 page_ref_sub(page, mapcount);
232 }
233 }
234
235 page_cache_tree_delete(mapping, page, shadow);
236
237 page->mapping = NULL;
238 /* Leave page->index set: truncation lookup relies upon it */
239
240 /* hugetlb pages do not participate in page cache accounting. */
241 if (!PageHuge(page))
242 __mod_node_page_state(page_pgdat(page), NR_FILE_PAGES, -nr);
243 if (PageSwapBacked(page)) {
244 __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr);
245 if (PageTransHuge(page))
246 __dec_node_page_state(page, NR_SHMEM_THPS);
247 } else {
248 VM_BUG_ON_PAGE(PageTransHuge(page) && !PageHuge(page), page);
249 }
250
251 /*
252 * At this point page must be either written or cleaned by truncate.
253 * Dirty page here signals a bug and loss of unwritten data.
254 *
255 * This fixes dirty accounting after removing the page entirely but
256 * leaves PageDirty set: it has no effect for truncated page and
257 * anyway will be cleared before returning page into buddy allocator.
258 */
259 if (WARN_ON_ONCE(PageDirty(page)))
260 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
261}
262
263/**
264 * delete_from_page_cache - delete page from page cache
265 * @page: the page which the kernel is trying to remove from page cache
266 *
267 * This must be called only on pages that have been verified to be in the page
268 * cache and locked. It will never put the page into the free list, the caller
269 * has a reference on the page.
270 */
271void delete_from_page_cache(struct page *page)
272{
273 struct address_space *mapping = page_mapping(page);
274 unsigned long flags;
275 void (*freepage)(struct page *);
276
277 BUG_ON(!PageLocked(page));
278
279 freepage = mapping->a_ops->freepage;
280
281 spin_lock_irqsave(&mapping->tree_lock, flags);
282 __delete_from_page_cache(page, NULL);
283 spin_unlock_irqrestore(&mapping->tree_lock, flags);
284
285 if (freepage)
286 freepage(page);
287
288 if (PageTransHuge(page) && !PageHuge(page)) {
289 page_ref_sub(page, HPAGE_PMD_NR);
290 VM_BUG_ON_PAGE(page_count(page) <= 0, page);
291 } else {
292 put_page(page);
293 }
294}
295EXPORT_SYMBOL(delete_from_page_cache);
296
297int filemap_check_errors(struct address_space *mapping)
298{
299 int ret = 0;
300 /* Check for outstanding write errors */
301 if (test_bit(AS_ENOSPC, &mapping->flags) &&
302 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
303 ret = -ENOSPC;
304 if (test_bit(AS_EIO, &mapping->flags) &&
305 test_and_clear_bit(AS_EIO, &mapping->flags))
306 ret = -EIO;
307 return ret;
308}
309EXPORT_SYMBOL(filemap_check_errors);
310
311/**
312 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
313 * @mapping: address space structure to write
314 * @start: offset in bytes where the range starts
315 * @end: offset in bytes where the range ends (inclusive)
316 * @sync_mode: enable synchronous operation
317 *
318 * Start writeback against all of a mapping's dirty pages that lie
319 * within the byte offsets <start, end> inclusive.
320 *
321 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
322 * opposed to a regular memory cleansing writeback. The difference between
323 * these two operations is that if a dirty page/buffer is encountered, it must
324 * be waited upon, and not just skipped over.
325 */
326int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
327 loff_t end, int sync_mode)
328{
329 int ret;
330 struct writeback_control wbc = {
331 .sync_mode = sync_mode,
332 .nr_to_write = LONG_MAX,
333 .range_start = start,
334 .range_end = end,
335 };
336
337 if (!mapping_cap_writeback_dirty(mapping))
338 return 0;
339
340 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
341 ret = do_writepages(mapping, &wbc);
342 wbc_detach_inode(&wbc);
343 return ret;
344}
345
346static inline int __filemap_fdatawrite(struct address_space *mapping,
347 int sync_mode)
348{
349 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
350}
351
352int filemap_fdatawrite(struct address_space *mapping)
353{
354 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
355}
356EXPORT_SYMBOL(filemap_fdatawrite);
357
358int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
359 loff_t end)
360{
361 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
362}
363EXPORT_SYMBOL(filemap_fdatawrite_range);
364
365/**
366 * filemap_flush - mostly a non-blocking flush
367 * @mapping: target address_space
368 *
369 * This is a mostly non-blocking flush. Not suitable for data-integrity
370 * purposes - I/O may not be started against all dirty pages.
371 */
372int filemap_flush(struct address_space *mapping)
373{
374 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
375}
376EXPORT_SYMBOL(filemap_flush);
377
378static int __filemap_fdatawait_range(struct address_space *mapping,
379 loff_t start_byte, loff_t end_byte)
380{
381 pgoff_t index = start_byte >> PAGE_SHIFT;
382 pgoff_t end = end_byte >> PAGE_SHIFT;
383 struct pagevec pvec;
384 int nr_pages;
385 int ret = 0;
386
387 if (end_byte < start_byte)
388 goto out;
389
390 pagevec_init(&pvec, 0);
391 while ((index <= end) &&
392 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
393 PAGECACHE_TAG_WRITEBACK,
394 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
395 unsigned i;
396
397 for (i = 0; i < nr_pages; i++) {
398 struct page *page = pvec.pages[i];
399
400 /* until radix tree lookup accepts end_index */
401 if (page->index > end)
402 continue;
403
404 wait_on_page_writeback(page);
405 if (TestClearPageError(page))
406 ret = -EIO;
407 }
408 pagevec_release(&pvec);
409 cond_resched();
410 }
411out:
412 return ret;
413}
414
415/**
416 * filemap_fdatawait_range - wait for writeback to complete
417 * @mapping: address space structure to wait for
418 * @start_byte: offset in bytes where the range starts
419 * @end_byte: offset in bytes where the range ends (inclusive)
420 *
421 * Walk the list of under-writeback pages of the given address space
422 * in the given range and wait for all of them. Check error status of
423 * the address space and return it.
424 *
425 * Since the error status of the address space is cleared by this function,
426 * callers are responsible for checking the return value and handling and/or
427 * reporting the error.
428 */
429int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
430 loff_t end_byte)
431{
432 int ret, ret2;
433
434 ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
435 ret2 = filemap_check_errors(mapping);
436 if (!ret)
437 ret = ret2;
438
439 return ret;
440}
441EXPORT_SYMBOL(filemap_fdatawait_range);
442
443/**
444 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
445 * @mapping: address space structure to wait for
446 *
447 * Walk the list of under-writeback pages of the given address space
448 * and wait for all of them. Unlike filemap_fdatawait(), this function
449 * does not clear error status of the address space.
450 *
451 * Use this function if callers don't handle errors themselves. Expected
452 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
453 * fsfreeze(8)
454 */
455void filemap_fdatawait_keep_errors(struct address_space *mapping)
456{
457 loff_t i_size = i_size_read(mapping->host);
458
459 if (i_size == 0)
460 return;
461
462 __filemap_fdatawait_range(mapping, 0, i_size - 1);
463}
464
465/**
466 * filemap_fdatawait - wait for all under-writeback pages to complete
467 * @mapping: address space structure to wait for
468 *
469 * Walk the list of under-writeback pages of the given address space
470 * and wait for all of them. Check error status of the address space
471 * and return it.
472 *
473 * Since the error status of the address space is cleared by this function,
474 * callers are responsible for checking the return value and handling and/or
475 * reporting the error.
476 */
477int filemap_fdatawait(struct address_space *mapping)
478{
479 loff_t i_size = i_size_read(mapping->host);
480
481 if (i_size == 0)
482 return 0;
483
484 return filemap_fdatawait_range(mapping, 0, i_size - 1);
485}
486EXPORT_SYMBOL(filemap_fdatawait);
487
488int filemap_write_and_wait(struct address_space *mapping)
489{
490 int err = 0;
491
492 if ((!dax_mapping(mapping) && mapping->nrpages) ||
493 (dax_mapping(mapping) && mapping->nrexceptional)) {
494 err = filemap_fdatawrite(mapping);
495 /*
496 * Even if the above returned error, the pages may be
497 * written partially (e.g. -ENOSPC), so we wait for it.
498 * But the -EIO is special case, it may indicate the worst
499 * thing (e.g. bug) happened, so we avoid waiting for it.
500 */
501 if (err != -EIO) {
502 int err2 = filemap_fdatawait(mapping);
503 if (!err)
504 err = err2;
505 }
506 } else {
507 err = filemap_check_errors(mapping);
508 }
509 return err;
510}
511EXPORT_SYMBOL(filemap_write_and_wait);
512
513/**
514 * filemap_write_and_wait_range - write out & wait on a file range
515 * @mapping: the address_space for the pages
516 * @lstart: offset in bytes where the range starts
517 * @lend: offset in bytes where the range ends (inclusive)
518 *
519 * Write out and wait upon file offsets lstart->lend, inclusive.
520 *
521 * Note that `lend' is inclusive (describes the last byte to be written) so
522 * that this function can be used to write to the very end-of-file (end = -1).
523 */
524int filemap_write_and_wait_range(struct address_space *mapping,
525 loff_t lstart, loff_t lend)
526{
527 int err = 0;
528
529 if ((!dax_mapping(mapping) && mapping->nrpages) ||
530 (dax_mapping(mapping) && mapping->nrexceptional)) {
531 err = __filemap_fdatawrite_range(mapping, lstart, lend,
532 WB_SYNC_ALL);
533 /* See comment of filemap_write_and_wait() */
534 if (err != -EIO) {
535 int err2 = filemap_fdatawait_range(mapping,
536 lstart, lend);
537 if (!err)
538 err = err2;
539 }
540 } else {
541 err = filemap_check_errors(mapping);
542 }
543 return err;
544}
545EXPORT_SYMBOL(filemap_write_and_wait_range);
546
547/**
548 * replace_page_cache_page - replace a pagecache page with a new one
549 * @old: page to be replaced
550 * @new: page to replace with
551 * @gfp_mask: allocation mode
552 *
553 * This function replaces a page in the pagecache with a new one. On
554 * success it acquires the pagecache reference for the new page and
555 * drops it for the old page. Both the old and new pages must be
556 * locked. This function does not add the new page to the LRU, the
557 * caller must do that.
558 *
559 * The remove + add is atomic. The only way this function can fail is
560 * memory allocation failure.
561 */
562int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
563{
564 int error;
565
566 VM_BUG_ON_PAGE(!PageLocked(old), old);
567 VM_BUG_ON_PAGE(!PageLocked(new), new);
568 VM_BUG_ON_PAGE(new->mapping, new);
569
570 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
571 if (!error) {
572 struct address_space *mapping = old->mapping;
573 void (*freepage)(struct page *);
574 unsigned long flags;
575
576 pgoff_t offset = old->index;
577 freepage = mapping->a_ops->freepage;
578
579 get_page(new);
580 new->mapping = mapping;
581 new->index = offset;
582
583 spin_lock_irqsave(&mapping->tree_lock, flags);
584 __delete_from_page_cache(old, NULL);
585 error = page_cache_tree_insert(mapping, new, NULL);
586 BUG_ON(error);
587
588 /*
589 * hugetlb pages do not participate in page cache accounting.
590 */
591 if (!PageHuge(new))
592 __inc_node_page_state(new, NR_FILE_PAGES);
593 if (PageSwapBacked(new))
594 __inc_node_page_state(new, NR_SHMEM);
595 spin_unlock_irqrestore(&mapping->tree_lock, flags);
596 mem_cgroup_migrate(old, new);
597 radix_tree_preload_end();
598 if (freepage)
599 freepage(old);
600 put_page(old);
601 }
602
603 return error;
604}
605EXPORT_SYMBOL_GPL(replace_page_cache_page);
606
607static int __add_to_page_cache_locked(struct page *page,
608 struct address_space *mapping,
609 pgoff_t offset, gfp_t gfp_mask,
610 void **shadowp)
611{
612 int huge = PageHuge(page);
613 struct mem_cgroup *memcg;
614 int error;
615
616 VM_BUG_ON_PAGE(!PageLocked(page), page);
617 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
618
619 if (!huge) {
620 error = mem_cgroup_try_charge(page, current->mm,
621 gfp_mask, &memcg, false);
622 if (error)
623 return error;
624 }
625
626 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
627 if (error) {
628 if (!huge)
629 mem_cgroup_cancel_charge(page, memcg, false);
630 return error;
631 }
632
633 get_page(page);
634 page->mapping = mapping;
635 page->index = offset;
636
637 spin_lock_irq(&mapping->tree_lock);
638 error = page_cache_tree_insert(mapping, page, shadowp);
639 radix_tree_preload_end();
640 if (unlikely(error))
641 goto err_insert;
642
643 /* hugetlb pages do not participate in page cache accounting. */
644 if (!huge)
645 __inc_node_page_state(page, NR_FILE_PAGES);
646 spin_unlock_irq(&mapping->tree_lock);
647 if (!huge)
648 mem_cgroup_commit_charge(page, memcg, false, false);
649 trace_mm_filemap_add_to_page_cache(page);
650 return 0;
651err_insert:
652 page->mapping = NULL;
653 /* Leave page->index set: truncation relies upon it */
654 spin_unlock_irq(&mapping->tree_lock);
655 if (!huge)
656 mem_cgroup_cancel_charge(page, memcg, false);
657 put_page(page);
658 return error;
659}
660
661/**
662 * add_to_page_cache_locked - add a locked page to the pagecache
663 * @page: page to add
664 * @mapping: the page's address_space
665 * @offset: page index
666 * @gfp_mask: page allocation mode
667 *
668 * This function is used to add a page to the pagecache. It must be locked.
669 * This function does not add the page to the LRU. The caller must do that.
670 */
671int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
672 pgoff_t offset, gfp_t gfp_mask)
673{
674 return __add_to_page_cache_locked(page, mapping, offset,
675 gfp_mask, NULL);
676}
677EXPORT_SYMBOL(add_to_page_cache_locked);
678
679int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
680 pgoff_t offset, gfp_t gfp_mask)
681{
682 void *shadow = NULL;
683 int ret;
684
685 __SetPageLocked(page);
686 ret = __add_to_page_cache_locked(page, mapping, offset,
687 gfp_mask, &shadow);
688 if (unlikely(ret))
689 __ClearPageLocked(page);
690 else {
691 /*
692 * The page might have been evicted from cache only
693 * recently, in which case it should be activated like
694 * any other repeatedly accessed page.
695 * The exception is pages getting rewritten; evicting other
696 * data from the working set, only to cache data that will
697 * get overwritten with something else, is a waste of memory.
698 */
699 if (!(gfp_mask & __GFP_WRITE) &&
700 shadow && workingset_refault(shadow)) {
701 SetPageActive(page);
702 workingset_activation(page);
703 } else
704 ClearPageActive(page);
705 lru_cache_add(page);
706 }
707 return ret;
708}
709EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
710
711#ifdef CONFIG_NUMA
712struct page *__page_cache_alloc(gfp_t gfp)
713{
714 int n;
715 struct page *page;
716
717 if (cpuset_do_page_mem_spread()) {
718 unsigned int cpuset_mems_cookie;
719 do {
720 cpuset_mems_cookie = read_mems_allowed_begin();
721 n = cpuset_mem_spread_node();
722 page = __alloc_pages_node(n, gfp, 0);
723 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
724
725 return page;
726 }
727 return alloc_pages(gfp, 0);
728}
729EXPORT_SYMBOL(__page_cache_alloc);
730#endif
731
732/*
733 * In order to wait for pages to become available there must be
734 * waitqueues associated with pages. By using a hash table of
735 * waitqueues where the bucket discipline is to maintain all
736 * waiters on the same queue and wake all when any of the pages
737 * become available, and for the woken contexts to check to be
738 * sure the appropriate page became available, this saves space
739 * at a cost of "thundering herd" phenomena during rare hash
740 * collisions.
741 */
742#define PAGE_WAIT_TABLE_BITS 8
743#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
744static wait_queue_head_t page_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;
745
746static wait_queue_head_t *page_waitqueue(struct page *page)
747{
748 return &page_wait_table[hash_ptr(page, PAGE_WAIT_TABLE_BITS)];
749}
750
751void __init pagecache_init(void)
752{
753 int i;
754
755 for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
756 init_waitqueue_head(&page_wait_table[i]);
757
758 page_writeback_init();
759}
760
761struct wait_page_key {
762 struct page *page;
763 int bit_nr;
764 int page_match;
765};
766
767struct wait_page_queue {
768 struct page *page;
769 int bit_nr;
770 wait_queue_t wait;
771};
772
773static int wake_page_function(wait_queue_t *wait, unsigned mode, int sync, void *arg)
774{
775 struct wait_page_key *key = arg;
776 struct wait_page_queue *wait_page
777 = container_of(wait, struct wait_page_queue, wait);
778
779 if (wait_page->page != key->page)
780 return 0;
781 key->page_match = 1;
782
783 if (wait_page->bit_nr != key->bit_nr)
784 return 0;
785 if (test_bit(key->bit_nr, &key->page->flags))
786 return 0;
787
788 return autoremove_wake_function(wait, mode, sync, key);
789}
790
791void wake_up_page_bit(struct page *page, int bit_nr)
792{
793 wait_queue_head_t *q = page_waitqueue(page);
794 struct wait_page_key key;
795 unsigned long flags;
796
797 key.page = page;
798 key.bit_nr = bit_nr;
799 key.page_match = 0;
800
801 spin_lock_irqsave(&q->lock, flags);
802 __wake_up_locked_key(q, TASK_NORMAL, &key);
803 /*
804 * It is possible for other pages to have collided on the waitqueue
805 * hash, so in that case check for a page match. That prevents a long-
806 * term waiter
807 *
808 * It is still possible to miss a case here, when we woke page waiters
809 * and removed them from the waitqueue, but there are still other
810 * page waiters.
811 */
812 if (!waitqueue_active(q) || !key.page_match) {
813 ClearPageWaiters(page);
814 /*
815 * It's possible to miss clearing Waiters here, when we woke
816 * our page waiters, but the hashed waitqueue has waiters for
817 * other pages on it.
818 *
819 * That's okay, it's a rare case. The next waker will clear it.
820 */
821 }
822 spin_unlock_irqrestore(&q->lock, flags);
823}
824EXPORT_SYMBOL(wake_up_page_bit);
825
826static inline int wait_on_page_bit_common(wait_queue_head_t *q,
827 struct page *page, int bit_nr, int state, bool lock)
828{
829 struct wait_page_queue wait_page;
830 wait_queue_t *wait = &wait_page.wait;
831 int ret = 0;
832
833 init_wait(wait);
834 wait->func = wake_page_function;
835 wait_page.page = page;
836 wait_page.bit_nr = bit_nr;
837
838 for (;;) {
839 spin_lock_irq(&q->lock);
840
841 if (likely(list_empty(&wait->task_list))) {
842 if (lock)
843 __add_wait_queue_tail_exclusive(q, wait);
844 else
845 __add_wait_queue(q, wait);
846 SetPageWaiters(page);
847 }
848
849 set_current_state(state);
850
851 spin_unlock_irq(&q->lock);
852
853 if (likely(test_bit(bit_nr, &page->flags))) {
854 io_schedule();
855 if (unlikely(signal_pending_state(state, current))) {
856 ret = -EINTR;
857 break;
858 }
859 }
860
861 if (lock) {
862 if (!test_and_set_bit_lock(bit_nr, &page->flags))
863 break;
864 } else {
865 if (!test_bit(bit_nr, &page->flags))
866 break;
867 }
868 }
869
870 finish_wait(q, wait);
871
872 /*
873 * A signal could leave PageWaiters set. Clearing it here if
874 * !waitqueue_active would be possible (by open-coding finish_wait),
875 * but still fail to catch it in the case of wait hash collision. We
876 * already can fail to clear wait hash collision cases, so don't
877 * bother with signals either.
878 */
879
880 return ret;
881}
882
883void wait_on_page_bit(struct page *page, int bit_nr)
884{
885 wait_queue_head_t *q = page_waitqueue(page);
886 wait_on_page_bit_common(q, page, bit_nr, TASK_UNINTERRUPTIBLE, false);
887}
888EXPORT_SYMBOL(wait_on_page_bit);
889
890int wait_on_page_bit_killable(struct page *page, int bit_nr)
891{
892 wait_queue_head_t *q = page_waitqueue(page);
893 return wait_on_page_bit_common(q, page, bit_nr, TASK_KILLABLE, false);
894}
895
896/**
897 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
898 * @page: Page defining the wait queue of interest
899 * @waiter: Waiter to add to the queue
900 *
901 * Add an arbitrary @waiter to the wait queue for the nominated @page.
902 */
903void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
904{
905 wait_queue_head_t *q = page_waitqueue(page);
906 unsigned long flags;
907
908 spin_lock_irqsave(&q->lock, flags);
909 __add_wait_queue(q, waiter);
910 SetPageWaiters(page);
911 spin_unlock_irqrestore(&q->lock, flags);
912}
913EXPORT_SYMBOL_GPL(add_page_wait_queue);
914
915#ifndef clear_bit_unlock_is_negative_byte
916
917/*
918 * PG_waiters is the high bit in the same byte as PG_lock.
919 *
920 * On x86 (and on many other architectures), we can clear PG_lock and
921 * test the sign bit at the same time. But if the architecture does
922 * not support that special operation, we just do this all by hand
923 * instead.
924 *
925 * The read of PG_waiters has to be after (or concurrently with) PG_locked
926 * being cleared, but a memory barrier should be unneccssary since it is
927 * in the same byte as PG_locked.
928 */
929static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
930{
931 clear_bit_unlock(nr, mem);
932 /* smp_mb__after_atomic(); */
933 return test_bit(PG_waiters, mem);
934}
935
936#endif
937
938/**
939 * unlock_page - unlock a locked page
940 * @page: the page
941 *
942 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
943 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
944 * mechanism between PageLocked pages and PageWriteback pages is shared.
945 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
946 *
947 * Note that this depends on PG_waiters being the sign bit in the byte
948 * that contains PG_locked - thus the BUILD_BUG_ON(). That allows us to
949 * clear the PG_locked bit and test PG_waiters at the same time fairly
950 * portably (architectures that do LL/SC can test any bit, while x86 can
951 * test the sign bit).
952 */
953void unlock_page(struct page *page)
954{
955 BUILD_BUG_ON(PG_waiters != 7);
956 page = compound_head(page);
957 VM_BUG_ON_PAGE(!PageLocked(page), page);
958 if (clear_bit_unlock_is_negative_byte(PG_locked, &page->flags))
959 wake_up_page_bit(page, PG_locked);
960}
961EXPORT_SYMBOL(unlock_page);
962
963/**
964 * end_page_writeback - end writeback against a page
965 * @page: the page
966 */
967void end_page_writeback(struct page *page)
968{
969 /*
970 * TestClearPageReclaim could be used here but it is an atomic
971 * operation and overkill in this particular case. Failing to
972 * shuffle a page marked for immediate reclaim is too mild to
973 * justify taking an atomic operation penalty at the end of
974 * ever page writeback.
975 */
976 if (PageReclaim(page)) {
977 ClearPageReclaim(page);
978 rotate_reclaimable_page(page);
979 }
980
981 if (!test_clear_page_writeback(page))
982 BUG();
983
984 smp_mb__after_atomic();
985 wake_up_page(page, PG_writeback);
986}
987EXPORT_SYMBOL(end_page_writeback);
988
989/*
990 * After completing I/O on a page, call this routine to update the page
991 * flags appropriately
992 */
993void page_endio(struct page *page, bool is_write, int err)
994{
995 if (!is_write) {
996 if (!err) {
997 SetPageUptodate(page);
998 } else {
999 ClearPageUptodate(page);
1000 SetPageError(page);
1001 }
1002 unlock_page(page);
1003 } else {
1004 if (err) {
1005 struct address_space *mapping;
1006
1007 SetPageError(page);
1008 mapping = page_mapping(page);
1009 if (mapping)
1010 mapping_set_error(mapping, err);
1011 }
1012 end_page_writeback(page);
1013 }
1014}
1015EXPORT_SYMBOL_GPL(page_endio);
1016
1017/**
1018 * __lock_page - get a lock on the page, assuming we need to sleep to get it
1019 * @page: the page to lock
1020 */
1021void __lock_page(struct page *__page)
1022{
1023 struct page *page = compound_head(__page);
1024 wait_queue_head_t *q = page_waitqueue(page);
1025 wait_on_page_bit_common(q, page, PG_locked, TASK_UNINTERRUPTIBLE, true);
1026}
1027EXPORT_SYMBOL(__lock_page);
1028
1029int __lock_page_killable(struct page *__page)
1030{
1031 struct page *page = compound_head(__page);
1032 wait_queue_head_t *q = page_waitqueue(page);
1033 return wait_on_page_bit_common(q, page, PG_locked, TASK_KILLABLE, true);
1034}
1035EXPORT_SYMBOL_GPL(__lock_page_killable);
1036
1037/*
1038 * Return values:
1039 * 1 - page is locked; mmap_sem is still held.
1040 * 0 - page is not locked.
1041 * mmap_sem has been released (up_read()), unless flags had both
1042 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
1043 * which case mmap_sem is still held.
1044 *
1045 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
1046 * with the page locked and the mmap_sem unperturbed.
1047 */
1048int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
1049 unsigned int flags)
1050{
1051 if (flags & FAULT_FLAG_ALLOW_RETRY) {
1052 /*
1053 * CAUTION! In this case, mmap_sem is not released
1054 * even though return 0.
1055 */
1056 if (flags & FAULT_FLAG_RETRY_NOWAIT)
1057 return 0;
1058
1059 up_read(&mm->mmap_sem);
1060 if (flags & FAULT_FLAG_KILLABLE)
1061 wait_on_page_locked_killable(page);
1062 else
1063 wait_on_page_locked(page);
1064 return 0;
1065 } else {
1066 if (flags & FAULT_FLAG_KILLABLE) {
1067 int ret;
1068
1069 ret = __lock_page_killable(page);
1070 if (ret) {
1071 up_read(&mm->mmap_sem);
1072 return 0;
1073 }
1074 } else
1075 __lock_page(page);
1076 return 1;
1077 }
1078}
1079
1080/**
1081 * page_cache_next_hole - find the next hole (not-present entry)
1082 * @mapping: mapping
1083 * @index: index
1084 * @max_scan: maximum range to search
1085 *
1086 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
1087 * lowest indexed hole.
1088 *
1089 * Returns: the index of the hole if found, otherwise returns an index
1090 * outside of the set specified (in which case 'return - index >=
1091 * max_scan' will be true). In rare cases of index wrap-around, 0 will
1092 * be returned.
1093 *
1094 * page_cache_next_hole may be called under rcu_read_lock. However,
1095 * like radix_tree_gang_lookup, this will not atomically search a
1096 * snapshot of the tree at a single point in time. For example, if a
1097 * hole is created at index 5, then subsequently a hole is created at
1098 * index 10, page_cache_next_hole covering both indexes may return 10
1099 * if called under rcu_read_lock.
1100 */
1101pgoff_t page_cache_next_hole(struct address_space *mapping,
1102 pgoff_t index, unsigned long max_scan)
1103{
1104 unsigned long i;
1105
1106 for (i = 0; i < max_scan; i++) {
1107 struct page *page;
1108
1109 page = radix_tree_lookup(&mapping->page_tree, index);
1110 if (!page || radix_tree_exceptional_entry(page))
1111 break;
1112 index++;
1113 if (index == 0)
1114 break;
1115 }
1116
1117 return index;
1118}
1119EXPORT_SYMBOL(page_cache_next_hole);
1120
1121/**
1122 * page_cache_prev_hole - find the prev hole (not-present entry)
1123 * @mapping: mapping
1124 * @index: index
1125 * @max_scan: maximum range to search
1126 *
1127 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1128 * the first hole.
1129 *
1130 * Returns: the index of the hole if found, otherwise returns an index
1131 * outside of the set specified (in which case 'index - return >=
1132 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1133 * will be returned.
1134 *
1135 * page_cache_prev_hole may be called under rcu_read_lock. However,
1136 * like radix_tree_gang_lookup, this will not atomically search a
1137 * snapshot of the tree at a single point in time. For example, if a
1138 * hole is created at index 10, then subsequently a hole is created at
1139 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1140 * called under rcu_read_lock.
1141 */
1142pgoff_t page_cache_prev_hole(struct address_space *mapping,
1143 pgoff_t index, unsigned long max_scan)
1144{
1145 unsigned long i;
1146
1147 for (i = 0; i < max_scan; i++) {
1148 struct page *page;
1149
1150 page = radix_tree_lookup(&mapping->page_tree, index);
1151 if (!page || radix_tree_exceptional_entry(page))
1152 break;
1153 index--;
1154 if (index == ULONG_MAX)
1155 break;
1156 }
1157
1158 return index;
1159}
1160EXPORT_SYMBOL(page_cache_prev_hole);
1161
1162/**
1163 * find_get_entry - find and get a page cache entry
1164 * @mapping: the address_space to search
1165 * @offset: the page cache index
1166 *
1167 * Looks up the page cache slot at @mapping & @offset. If there is a
1168 * page cache page, it is returned with an increased refcount.
1169 *
1170 * If the slot holds a shadow entry of a previously evicted page, or a
1171 * swap entry from shmem/tmpfs, it is returned.
1172 *
1173 * Otherwise, %NULL is returned.
1174 */
1175struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1176{
1177 void **pagep;
1178 struct page *head, *page;
1179
1180 rcu_read_lock();
1181repeat:
1182 page = NULL;
1183 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1184 if (pagep) {
1185 page = radix_tree_deref_slot(pagep);
1186 if (unlikely(!page))
1187 goto out;
1188 if (radix_tree_exception(page)) {
1189 if (radix_tree_deref_retry(page))
1190 goto repeat;
1191 /*
1192 * A shadow entry of a recently evicted page,
1193 * or a swap entry from shmem/tmpfs. Return
1194 * it without attempting to raise page count.
1195 */
1196 goto out;
1197 }
1198
1199 head = compound_head(page);
1200 if (!page_cache_get_speculative(head))
1201 goto repeat;
1202
1203 /* The page was split under us? */
1204 if (compound_head(page) != head) {
1205 put_page(head);
1206 goto repeat;
1207 }
1208
1209 /*
1210 * Has the page moved?
1211 * This is part of the lockless pagecache protocol. See
1212 * include/linux/pagemap.h for details.
1213 */
1214 if (unlikely(page != *pagep)) {
1215 put_page(head);
1216 goto repeat;
1217 }
1218 }
1219out:
1220 rcu_read_unlock();
1221
1222 return page;
1223}
1224EXPORT_SYMBOL(find_get_entry);
1225
1226/**
1227 * find_lock_entry - locate, pin and lock a page cache entry
1228 * @mapping: the address_space to search
1229 * @offset: the page cache index
1230 *
1231 * Looks up the page cache slot at @mapping & @offset. If there is a
1232 * page cache page, it is returned locked and with an increased
1233 * refcount.
1234 *
1235 * If the slot holds a shadow entry of a previously evicted page, or a
1236 * swap entry from shmem/tmpfs, it is returned.
1237 *
1238 * Otherwise, %NULL is returned.
1239 *
1240 * find_lock_entry() may sleep.
1241 */
1242struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1243{
1244 struct page *page;
1245
1246repeat:
1247 page = find_get_entry(mapping, offset);
1248 if (page && !radix_tree_exception(page)) {
1249 lock_page(page);
1250 /* Has the page been truncated? */
1251 if (unlikely(page_mapping(page) != mapping)) {
1252 unlock_page(page);
1253 put_page(page);
1254 goto repeat;
1255 }
1256 VM_BUG_ON_PAGE(page_to_pgoff(page) != offset, page);
1257 }
1258 return page;
1259}
1260EXPORT_SYMBOL(find_lock_entry);
1261
1262/**
1263 * pagecache_get_page - find and get a page reference
1264 * @mapping: the address_space to search
1265 * @offset: the page index
1266 * @fgp_flags: PCG flags
1267 * @gfp_mask: gfp mask to use for the page cache data page allocation
1268 *
1269 * Looks up the page cache slot at @mapping & @offset.
1270 *
1271 * PCG flags modify how the page is returned.
1272 *
1273 * FGP_ACCESSED: the page will be marked accessed
1274 * FGP_LOCK: Page is return locked
1275 * FGP_CREAT: If page is not present then a new page is allocated using
1276 * @gfp_mask and added to the page cache and the VM's LRU
1277 * list. The page is returned locked and with an increased
1278 * refcount. Otherwise, %NULL is returned.
1279 *
1280 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1281 * if the GFP flags specified for FGP_CREAT are atomic.
1282 *
1283 * If there is a page cache page, it is returned with an increased refcount.
1284 */
1285struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1286 int fgp_flags, gfp_t gfp_mask)
1287{
1288 struct page *page;
1289
1290repeat:
1291 page = find_get_entry(mapping, offset);
1292 if (radix_tree_exceptional_entry(page))
1293 page = NULL;
1294 if (!page)
1295 goto no_page;
1296
1297 if (fgp_flags & FGP_LOCK) {
1298 if (fgp_flags & FGP_NOWAIT) {
1299 if (!trylock_page(page)) {
1300 put_page(page);
1301 return NULL;
1302 }
1303 } else {
1304 lock_page(page);
1305 }
1306
1307 /* Has the page been truncated? */
1308 if (unlikely(page->mapping != mapping)) {
1309 unlock_page(page);
1310 put_page(page);
1311 goto repeat;
1312 }
1313 VM_BUG_ON_PAGE(page->index != offset, page);
1314 }
1315
1316 if (page && (fgp_flags & FGP_ACCESSED))
1317 mark_page_accessed(page);
1318
1319no_page:
1320 if (!page && (fgp_flags & FGP_CREAT)) {
1321 int err;
1322 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1323 gfp_mask |= __GFP_WRITE;
1324 if (fgp_flags & FGP_NOFS)
1325 gfp_mask &= ~__GFP_FS;
1326
1327 page = __page_cache_alloc(gfp_mask);
1328 if (!page)
1329 return NULL;
1330
1331 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1332 fgp_flags |= FGP_LOCK;
1333
1334 /* Init accessed so avoid atomic mark_page_accessed later */
1335 if (fgp_flags & FGP_ACCESSED)
1336 __SetPageReferenced(page);
1337
1338 err = add_to_page_cache_lru(page, mapping, offset,
1339 gfp_mask & GFP_RECLAIM_MASK);
1340 if (unlikely(err)) {
1341 put_page(page);
1342 page = NULL;
1343 if (err == -EEXIST)
1344 goto repeat;
1345 }
1346 }
1347
1348 return page;
1349}
1350EXPORT_SYMBOL(pagecache_get_page);
1351
1352/**
1353 * find_get_entries - gang pagecache lookup
1354 * @mapping: The address_space to search
1355 * @start: The starting page cache index
1356 * @nr_entries: The maximum number of entries
1357 * @entries: Where the resulting entries are placed
1358 * @indices: The cache indices corresponding to the entries in @entries
1359 *
1360 * find_get_entries() will search for and return a group of up to
1361 * @nr_entries entries in the mapping. The entries are placed at
1362 * @entries. find_get_entries() takes a reference against any actual
1363 * pages it returns.
1364 *
1365 * The search returns a group of mapping-contiguous page cache entries
1366 * with ascending indexes. There may be holes in the indices due to
1367 * not-present pages.
1368 *
1369 * Any shadow entries of evicted pages, or swap entries from
1370 * shmem/tmpfs, are included in the returned array.
1371 *
1372 * find_get_entries() returns the number of pages and shadow entries
1373 * which were found.
1374 */
1375unsigned find_get_entries(struct address_space *mapping,
1376 pgoff_t start, unsigned int nr_entries,
1377 struct page **entries, pgoff_t *indices)
1378{
1379 void **slot;
1380 unsigned int ret = 0;
1381 struct radix_tree_iter iter;
1382
1383 if (!nr_entries)
1384 return 0;
1385
1386 rcu_read_lock();
1387 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1388 struct page *head, *page;
1389repeat:
1390 page = radix_tree_deref_slot(slot);
1391 if (unlikely(!page))
1392 continue;
1393 if (radix_tree_exception(page)) {
1394 if (radix_tree_deref_retry(page)) {
1395 slot = radix_tree_iter_retry(&iter);
1396 continue;
1397 }
1398 /*
1399 * A shadow entry of a recently evicted page, a swap
1400 * entry from shmem/tmpfs or a DAX entry. Return it
1401 * without attempting to raise page count.
1402 */
1403 goto export;
1404 }
1405
1406 head = compound_head(page);
1407 if (!page_cache_get_speculative(head))
1408 goto repeat;
1409
1410 /* The page was split under us? */
1411 if (compound_head(page) != head) {
1412 put_page(head);
1413 goto repeat;
1414 }
1415
1416 /* Has the page moved? */
1417 if (unlikely(page != *slot)) {
1418 put_page(head);
1419 goto repeat;
1420 }
1421export:
1422 indices[ret] = iter.index;
1423 entries[ret] = page;
1424 if (++ret == nr_entries)
1425 break;
1426 }
1427 rcu_read_unlock();
1428 return ret;
1429}
1430
1431/**
1432 * find_get_pages - gang pagecache lookup
1433 * @mapping: The address_space to search
1434 * @start: The starting page index
1435 * @nr_pages: The maximum number of pages
1436 * @pages: Where the resulting pages are placed
1437 *
1438 * find_get_pages() will search for and return a group of up to
1439 * @nr_pages pages in the mapping. The pages are placed at @pages.
1440 * find_get_pages() takes a reference against the returned pages.
1441 *
1442 * The search returns a group of mapping-contiguous pages with ascending
1443 * indexes. There may be holes in the indices due to not-present pages.
1444 *
1445 * find_get_pages() returns the number of pages which were found.
1446 */
1447unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1448 unsigned int nr_pages, struct page **pages)
1449{
1450 struct radix_tree_iter iter;
1451 void **slot;
1452 unsigned ret = 0;
1453
1454 if (unlikely(!nr_pages))
1455 return 0;
1456
1457 rcu_read_lock();
1458 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1459 struct page *head, *page;
1460repeat:
1461 page = radix_tree_deref_slot(slot);
1462 if (unlikely(!page))
1463 continue;
1464
1465 if (radix_tree_exception(page)) {
1466 if (radix_tree_deref_retry(page)) {
1467 slot = radix_tree_iter_retry(&iter);
1468 continue;
1469 }
1470 /*
1471 * A shadow entry of a recently evicted page,
1472 * or a swap entry from shmem/tmpfs. Skip
1473 * over it.
1474 */
1475 continue;
1476 }
1477
1478 head = compound_head(page);
1479 if (!page_cache_get_speculative(head))
1480 goto repeat;
1481
1482 /* The page was split under us? */
1483 if (compound_head(page) != head) {
1484 put_page(head);
1485 goto repeat;
1486 }
1487
1488 /* Has the page moved? */
1489 if (unlikely(page != *slot)) {
1490 put_page(head);
1491 goto repeat;
1492 }
1493
1494 pages[ret] = page;
1495 if (++ret == nr_pages)
1496 break;
1497 }
1498
1499 rcu_read_unlock();
1500 return ret;
1501}
1502
1503/**
1504 * find_get_pages_contig - gang contiguous pagecache lookup
1505 * @mapping: The address_space to search
1506 * @index: The starting page index
1507 * @nr_pages: The maximum number of pages
1508 * @pages: Where the resulting pages are placed
1509 *
1510 * find_get_pages_contig() works exactly like find_get_pages(), except
1511 * that the returned number of pages are guaranteed to be contiguous.
1512 *
1513 * find_get_pages_contig() returns the number of pages which were found.
1514 */
1515unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1516 unsigned int nr_pages, struct page **pages)
1517{
1518 struct radix_tree_iter iter;
1519 void **slot;
1520 unsigned int ret = 0;
1521
1522 if (unlikely(!nr_pages))
1523 return 0;
1524
1525 rcu_read_lock();
1526 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1527 struct page *head, *page;
1528repeat:
1529 page = radix_tree_deref_slot(slot);
1530 /* The hole, there no reason to continue */
1531 if (unlikely(!page))
1532 break;
1533
1534 if (radix_tree_exception(page)) {
1535 if (radix_tree_deref_retry(page)) {
1536 slot = radix_tree_iter_retry(&iter);
1537 continue;
1538 }
1539 /*
1540 * A shadow entry of a recently evicted page,
1541 * or a swap entry from shmem/tmpfs. Stop
1542 * looking for contiguous pages.
1543 */
1544 break;
1545 }
1546
1547 head = compound_head(page);
1548 if (!page_cache_get_speculative(head))
1549 goto repeat;
1550
1551 /* The page was split under us? */
1552 if (compound_head(page) != head) {
1553 put_page(head);
1554 goto repeat;
1555 }
1556
1557 /* Has the page moved? */
1558 if (unlikely(page != *slot)) {
1559 put_page(head);
1560 goto repeat;
1561 }
1562
1563 /*
1564 * must check mapping and index after taking the ref.
1565 * otherwise we can get both false positives and false
1566 * negatives, which is just confusing to the caller.
1567 */
1568 if (page->mapping == NULL || page_to_pgoff(page) != iter.index) {
1569 put_page(page);
1570 break;
1571 }
1572
1573 pages[ret] = page;
1574 if (++ret == nr_pages)
1575 break;
1576 }
1577 rcu_read_unlock();
1578 return ret;
1579}
1580EXPORT_SYMBOL(find_get_pages_contig);
1581
1582/**
1583 * find_get_pages_tag - find and return pages that match @tag
1584 * @mapping: the address_space to search
1585 * @index: the starting page index
1586 * @tag: the tag index
1587 * @nr_pages: the maximum number of pages
1588 * @pages: where the resulting pages are placed
1589 *
1590 * Like find_get_pages, except we only return pages which are tagged with
1591 * @tag. We update @index to index the next page for the traversal.
1592 */
1593unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1594 int tag, unsigned int nr_pages, struct page **pages)
1595{
1596 struct radix_tree_iter iter;
1597 void **slot;
1598 unsigned ret = 0;
1599
1600 if (unlikely(!nr_pages))
1601 return 0;
1602
1603 rcu_read_lock();
1604 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1605 &iter, *index, tag) {
1606 struct page *head, *page;
1607repeat:
1608 page = radix_tree_deref_slot(slot);
1609 if (unlikely(!page))
1610 continue;
1611
1612 if (radix_tree_exception(page)) {
1613 if (radix_tree_deref_retry(page)) {
1614 slot = radix_tree_iter_retry(&iter);
1615 continue;
1616 }
1617 /*
1618 * A shadow entry of a recently evicted page.
1619 *
1620 * Those entries should never be tagged, but
1621 * this tree walk is lockless and the tags are
1622 * looked up in bulk, one radix tree node at a
1623 * time, so there is a sizable window for page
1624 * reclaim to evict a page we saw tagged.
1625 *
1626 * Skip over it.
1627 */
1628 continue;
1629 }
1630
1631 head = compound_head(page);
1632 if (!page_cache_get_speculative(head))
1633 goto repeat;
1634
1635 /* The page was split under us? */
1636 if (compound_head(page) != head) {
1637 put_page(head);
1638 goto repeat;
1639 }
1640
1641 /* Has the page moved? */
1642 if (unlikely(page != *slot)) {
1643 put_page(head);
1644 goto repeat;
1645 }
1646
1647 pages[ret] = page;
1648 if (++ret == nr_pages)
1649 break;
1650 }
1651
1652 rcu_read_unlock();
1653
1654 if (ret)
1655 *index = pages[ret - 1]->index + 1;
1656
1657 return ret;
1658}
1659EXPORT_SYMBOL(find_get_pages_tag);
1660
1661/**
1662 * find_get_entries_tag - find and return entries that match @tag
1663 * @mapping: the address_space to search
1664 * @start: the starting page cache index
1665 * @tag: the tag index
1666 * @nr_entries: the maximum number of entries
1667 * @entries: where the resulting entries are placed
1668 * @indices: the cache indices corresponding to the entries in @entries
1669 *
1670 * Like find_get_entries, except we only return entries which are tagged with
1671 * @tag.
1672 */
1673unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1674 int tag, unsigned int nr_entries,
1675 struct page **entries, pgoff_t *indices)
1676{
1677 void **slot;
1678 unsigned int ret = 0;
1679 struct radix_tree_iter iter;
1680
1681 if (!nr_entries)
1682 return 0;
1683
1684 rcu_read_lock();
1685 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1686 &iter, start, tag) {
1687 struct page *head, *page;
1688repeat:
1689 page = radix_tree_deref_slot(slot);
1690 if (unlikely(!page))
1691 continue;
1692 if (radix_tree_exception(page)) {
1693 if (radix_tree_deref_retry(page)) {
1694 slot = radix_tree_iter_retry(&iter);
1695 continue;
1696 }
1697
1698 /*
1699 * A shadow entry of a recently evicted page, a swap
1700 * entry from shmem/tmpfs or a DAX entry. Return it
1701 * without attempting to raise page count.
1702 */
1703 goto export;
1704 }
1705
1706 head = compound_head(page);
1707 if (!page_cache_get_speculative(head))
1708 goto repeat;
1709
1710 /* The page was split under us? */
1711 if (compound_head(page) != head) {
1712 put_page(head);
1713 goto repeat;
1714 }
1715
1716 /* Has the page moved? */
1717 if (unlikely(page != *slot)) {
1718 put_page(head);
1719 goto repeat;
1720 }
1721export:
1722 indices[ret] = iter.index;
1723 entries[ret] = page;
1724 if (++ret == nr_entries)
1725 break;
1726 }
1727 rcu_read_unlock();
1728 return ret;
1729}
1730EXPORT_SYMBOL(find_get_entries_tag);
1731
1732/*
1733 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1734 * a _large_ part of the i/o request. Imagine the worst scenario:
1735 *
1736 * ---R__________________________________________B__________
1737 * ^ reading here ^ bad block(assume 4k)
1738 *
1739 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1740 * => failing the whole request => read(R) => read(R+1) =>
1741 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1742 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1743 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1744 *
1745 * It is going insane. Fix it by quickly scaling down the readahead size.
1746 */
1747static void shrink_readahead_size_eio(struct file *filp,
1748 struct file_ra_state *ra)
1749{
1750 ra->ra_pages /= 4;
1751}
1752
1753/**
1754 * do_generic_file_read - generic file read routine
1755 * @filp: the file to read
1756 * @ppos: current file position
1757 * @iter: data destination
1758 * @written: already copied
1759 *
1760 * This is a generic file read routine, and uses the
1761 * mapping->a_ops->readpage() function for the actual low-level stuff.
1762 *
1763 * This is really ugly. But the goto's actually try to clarify some
1764 * of the logic when it comes to error handling etc.
1765 */
1766static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1767 struct iov_iter *iter, ssize_t written)
1768{
1769 struct address_space *mapping = filp->f_mapping;
1770 struct inode *inode = mapping->host;
1771 struct file_ra_state *ra = &filp->f_ra;
1772 pgoff_t index;
1773 pgoff_t last_index;
1774 pgoff_t prev_index;
1775 unsigned long offset; /* offset into pagecache page */
1776 unsigned int prev_offset;
1777 int error = 0;
1778
1779 if (unlikely(*ppos >= inode->i_sb->s_maxbytes))
1780 return 0;
1781 iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
1782
1783 index = *ppos >> PAGE_SHIFT;
1784 prev_index = ra->prev_pos >> PAGE_SHIFT;
1785 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1786 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1787 offset = *ppos & ~PAGE_MASK;
1788
1789 for (;;) {
1790 struct page *page;
1791 pgoff_t end_index;
1792 loff_t isize;
1793 unsigned long nr, ret;
1794
1795 cond_resched();
1796find_page:
1797 if (fatal_signal_pending(current)) {
1798 error = -EINTR;
1799 goto out;
1800 }
1801
1802 page = find_get_page(mapping, index);
1803 if (!page) {
1804 page_cache_sync_readahead(mapping,
1805 ra, filp,
1806 index, last_index - index);
1807 page = find_get_page(mapping, index);
1808 if (unlikely(page == NULL))
1809 goto no_cached_page;
1810 }
1811 if (PageReadahead(page)) {
1812 page_cache_async_readahead(mapping,
1813 ra, filp, page,
1814 index, last_index - index);
1815 }
1816 if (!PageUptodate(page)) {
1817 /*
1818 * See comment in do_read_cache_page on why
1819 * wait_on_page_locked is used to avoid unnecessarily
1820 * serialisations and why it's safe.
1821 */
1822 error = wait_on_page_locked_killable(page);
1823 if (unlikely(error))
1824 goto readpage_error;
1825 if (PageUptodate(page))
1826 goto page_ok;
1827
1828 if (inode->i_blkbits == PAGE_SHIFT ||
1829 !mapping->a_ops->is_partially_uptodate)
1830 goto page_not_up_to_date;
1831 /* pipes can't handle partially uptodate pages */
1832 if (unlikely(iter->type & ITER_PIPE))
1833 goto page_not_up_to_date;
1834 if (!trylock_page(page))
1835 goto page_not_up_to_date;
1836 /* Did it get truncated before we got the lock? */
1837 if (!page->mapping)
1838 goto page_not_up_to_date_locked;
1839 if (!mapping->a_ops->is_partially_uptodate(page,
1840 offset, iter->count))
1841 goto page_not_up_to_date_locked;
1842 unlock_page(page);
1843 }
1844page_ok:
1845 /*
1846 * i_size must be checked after we know the page is Uptodate.
1847 *
1848 * Checking i_size after the check allows us to calculate
1849 * the correct value for "nr", which means the zero-filled
1850 * part of the page is not copied back to userspace (unless
1851 * another truncate extends the file - this is desired though).
1852 */
1853
1854 isize = i_size_read(inode);
1855 end_index = (isize - 1) >> PAGE_SHIFT;
1856 if (unlikely(!isize || index > end_index)) {
1857 put_page(page);
1858 goto out;
1859 }
1860
1861 /* nr is the maximum number of bytes to copy from this page */
1862 nr = PAGE_SIZE;
1863 if (index == end_index) {
1864 nr = ((isize - 1) & ~PAGE_MASK) + 1;
1865 if (nr <= offset) {
1866 put_page(page);
1867 goto out;
1868 }
1869 }
1870 nr = nr - offset;
1871
1872 /* If users can be writing to this page using arbitrary
1873 * virtual addresses, take care about potential aliasing
1874 * before reading the page on the kernel side.
1875 */
1876 if (mapping_writably_mapped(mapping))
1877 flush_dcache_page(page);
1878
1879 /*
1880 * When a sequential read accesses a page several times,
1881 * only mark it as accessed the first time.
1882 */
1883 if (prev_index != index || offset != prev_offset)
1884 mark_page_accessed(page);
1885 prev_index = index;
1886
1887 /*
1888 * Ok, we have the page, and it's up-to-date, so
1889 * now we can copy it to user space...
1890 */
1891
1892 ret = copy_page_to_iter(page, offset, nr, iter);
1893 offset += ret;
1894 index += offset >> PAGE_SHIFT;
1895 offset &= ~PAGE_MASK;
1896 prev_offset = offset;
1897
1898 put_page(page);
1899 written += ret;
1900 if (!iov_iter_count(iter))
1901 goto out;
1902 if (ret < nr) {
1903 error = -EFAULT;
1904 goto out;
1905 }
1906 continue;
1907
1908page_not_up_to_date:
1909 /* Get exclusive access to the page ... */
1910 error = lock_page_killable(page);
1911 if (unlikely(error))
1912 goto readpage_error;
1913
1914page_not_up_to_date_locked:
1915 /* Did it get truncated before we got the lock? */
1916 if (!page->mapping) {
1917 unlock_page(page);
1918 put_page(page);
1919 continue;
1920 }
1921
1922 /* Did somebody else fill it already? */
1923 if (PageUptodate(page)) {
1924 unlock_page(page);
1925 goto page_ok;
1926 }
1927
1928readpage:
1929 /*
1930 * A previous I/O error may have been due to temporary
1931 * failures, eg. multipath errors.
1932 * PG_error will be set again if readpage fails.
1933 */
1934 ClearPageError(page);
1935 /* Start the actual read. The read will unlock the page. */
1936 error = mapping->a_ops->readpage(filp, page);
1937
1938 if (unlikely(error)) {
1939 if (error == AOP_TRUNCATED_PAGE) {
1940 put_page(page);
1941 error = 0;
1942 goto find_page;
1943 }
1944 goto readpage_error;
1945 }
1946
1947 if (!PageUptodate(page)) {
1948 error = lock_page_killable(page);
1949 if (unlikely(error))
1950 goto readpage_error;
1951 if (!PageUptodate(page)) {
1952 if (page->mapping == NULL) {
1953 /*
1954 * invalidate_mapping_pages got it
1955 */
1956 unlock_page(page);
1957 put_page(page);
1958 goto find_page;
1959 }
1960 unlock_page(page);
1961 shrink_readahead_size_eio(filp, ra);
1962 error = -EIO;
1963 goto readpage_error;
1964 }
1965 unlock_page(page);
1966 }
1967
1968 goto page_ok;
1969
1970readpage_error:
1971 /* UHHUH! A synchronous read error occurred. Report it */
1972 put_page(page);
1973 goto out;
1974
1975no_cached_page:
1976 /*
1977 * Ok, it wasn't cached, so we need to create a new
1978 * page..
1979 */
1980 page = page_cache_alloc_cold(mapping);
1981 if (!page) {
1982 error = -ENOMEM;
1983 goto out;
1984 }
1985 error = add_to_page_cache_lru(page, mapping, index,
1986 mapping_gfp_constraint(mapping, GFP_KERNEL));
1987 if (error) {
1988 put_page(page);
1989 if (error == -EEXIST) {
1990 error = 0;
1991 goto find_page;
1992 }
1993 goto out;
1994 }
1995 goto readpage;
1996 }
1997
1998out:
1999 ra->prev_pos = prev_index;
2000 ra->prev_pos <<= PAGE_SHIFT;
2001 ra->prev_pos |= prev_offset;
2002
2003 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
2004 file_accessed(filp);
2005 return written ? written : error;
2006}
2007
2008/**
2009 * generic_file_read_iter - generic filesystem read routine
2010 * @iocb: kernel I/O control block
2011 * @iter: destination for the data read
2012 *
2013 * This is the "read_iter()" routine for all filesystems
2014 * that can use the page cache directly.
2015 */
2016ssize_t
2017generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
2018{
2019 struct file *file = iocb->ki_filp;
2020 ssize_t retval = 0;
2021 size_t count = iov_iter_count(iter);
2022
2023 if (!count)
2024 goto out; /* skip atime */
2025
2026 if (iocb->ki_flags & IOCB_DIRECT) {
2027 struct address_space *mapping = file->f_mapping;
2028 struct inode *inode = mapping->host;
2029 struct iov_iter data = *iter;
2030 loff_t size;
2031
2032 size = i_size_read(inode);
2033 retval = filemap_write_and_wait_range(mapping, iocb->ki_pos,
2034 iocb->ki_pos + count - 1);
2035 if (retval < 0)
2036 goto out;
2037
2038 file_accessed(file);
2039
2040 retval = mapping->a_ops->direct_IO(iocb, &data);
2041 if (retval >= 0) {
2042 iocb->ki_pos += retval;
2043 iov_iter_advance(iter, retval);
2044 }
2045
2046 /*
2047 * Btrfs can have a short DIO read if we encounter
2048 * compressed extents, so if there was an error, or if
2049 * we've already read everything we wanted to, or if
2050 * there was a short read because we hit EOF, go ahead
2051 * and return. Otherwise fallthrough to buffered io for
2052 * the rest of the read. Buffered reads will not work for
2053 * DAX files, so don't bother trying.
2054 */
2055 if (retval < 0 || !iov_iter_count(iter) || iocb->ki_pos >= size ||
2056 IS_DAX(inode))
2057 goto out;
2058 }
2059
2060 retval = do_generic_file_read(file, &iocb->ki_pos, iter, retval);
2061out:
2062 return retval;
2063}
2064EXPORT_SYMBOL(generic_file_read_iter);
2065
2066#ifdef CONFIG_MMU
2067/**
2068 * page_cache_read - adds requested page to the page cache if not already there
2069 * @file: file to read
2070 * @offset: page index
2071 * @gfp_mask: memory allocation flags
2072 *
2073 * This adds the requested page to the page cache if it isn't already there,
2074 * and schedules an I/O to read in its contents from disk.
2075 */
2076static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
2077{
2078 struct address_space *mapping = file->f_mapping;
2079 struct page *page;
2080 int ret;
2081
2082 do {
2083 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
2084 if (!page)
2085 return -ENOMEM;
2086
2087 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
2088 if (ret == 0)
2089 ret = mapping->a_ops->readpage(file, page);
2090 else if (ret == -EEXIST)
2091 ret = 0; /* losing race to add is OK */
2092
2093 put_page(page);
2094
2095 } while (ret == AOP_TRUNCATED_PAGE);
2096
2097 return ret;
2098}
2099
2100#define MMAP_LOTSAMISS (100)
2101
2102/*
2103 * Synchronous readahead happens when we don't even find
2104 * a page in the page cache at all.
2105 */
2106static void do_sync_mmap_readahead(struct vm_area_struct *vma,
2107 struct file_ra_state *ra,
2108 struct file *file,
2109 pgoff_t offset)
2110{
2111 struct address_space *mapping = file->f_mapping;
2112
2113 /* If we don't want any read-ahead, don't bother */
2114 if (vma->vm_flags & VM_RAND_READ)
2115 return;
2116 if (!ra->ra_pages)
2117 return;
2118
2119 if (vma->vm_flags & VM_SEQ_READ) {
2120 page_cache_sync_readahead(mapping, ra, file, offset,
2121 ra->ra_pages);
2122 return;
2123 }
2124
2125 /* Avoid banging the cache line if not needed */
2126 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
2127 ra->mmap_miss++;
2128
2129 /*
2130 * Do we miss much more than hit in this file? If so,
2131 * stop bothering with read-ahead. It will only hurt.
2132 */
2133 if (ra->mmap_miss > MMAP_LOTSAMISS)
2134 return;
2135
2136 /*
2137 * mmap read-around
2138 */
2139 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
2140 ra->size = ra->ra_pages;
2141 ra->async_size = ra->ra_pages / 4;
2142 ra_submit(ra, mapping, file);
2143}
2144
2145/*
2146 * Asynchronous readahead happens when we find the page and PG_readahead,
2147 * so we want to possibly extend the readahead further..
2148 */
2149static void do_async_mmap_readahead(struct vm_area_struct *vma,
2150 struct file_ra_state *ra,
2151 struct file *file,
2152 struct page *page,
2153 pgoff_t offset)
2154{
2155 struct address_space *mapping = file->f_mapping;
2156
2157 /* If we don't want any read-ahead, don't bother */
2158 if (vma->vm_flags & VM_RAND_READ)
2159 return;
2160 if (ra->mmap_miss > 0)
2161 ra->mmap_miss--;
2162 if (PageReadahead(page))
2163 page_cache_async_readahead(mapping, ra, file,
2164 page, offset, ra->ra_pages);
2165}
2166
2167/**
2168 * filemap_fault - read in file data for page fault handling
2169 * @vma: vma in which the fault was taken
2170 * @vmf: struct vm_fault containing details of the fault
2171 *
2172 * filemap_fault() is invoked via the vma operations vector for a
2173 * mapped memory region to read in file data during a page fault.
2174 *
2175 * The goto's are kind of ugly, but this streamlines the normal case of having
2176 * it in the page cache, and handles the special cases reasonably without
2177 * having a lot of duplicated code.
2178 *
2179 * vma->vm_mm->mmap_sem must be held on entry.
2180 *
2181 * If our return value has VM_FAULT_RETRY set, it's because
2182 * lock_page_or_retry() returned 0.
2183 * The mmap_sem has usually been released in this case.
2184 * See __lock_page_or_retry() for the exception.
2185 *
2186 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2187 * has not been released.
2188 *
2189 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2190 */
2191int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
2192{
2193 int error;
2194 struct file *file = vma->vm_file;
2195 struct address_space *mapping = file->f_mapping;
2196 struct file_ra_state *ra = &file->f_ra;
2197 struct inode *inode = mapping->host;
2198 pgoff_t offset = vmf->pgoff;
2199 struct page *page;
2200 loff_t size;
2201 int ret = 0;
2202
2203 size = round_up(i_size_read(inode), PAGE_SIZE);
2204 if (offset >= size >> PAGE_SHIFT)
2205 return VM_FAULT_SIGBUS;
2206
2207 /*
2208 * Do we have something in the page cache already?
2209 */
2210 page = find_get_page(mapping, offset);
2211 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2212 /*
2213 * We found the page, so try async readahead before
2214 * waiting for the lock.
2215 */
2216 do_async_mmap_readahead(vma, ra, file, page, offset);
2217 } else if (!page) {
2218 /* No page in the page cache at all */
2219 do_sync_mmap_readahead(vma, ra, file, offset);
2220 count_vm_event(PGMAJFAULT);
2221 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
2222 ret = VM_FAULT_MAJOR;
2223retry_find:
2224 page = find_get_page(mapping, offset);
2225 if (!page)
2226 goto no_cached_page;
2227 }
2228
2229 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
2230 put_page(page);
2231 return ret | VM_FAULT_RETRY;
2232 }
2233
2234 /* Did it get truncated? */
2235 if (unlikely(page->mapping != mapping)) {
2236 unlock_page(page);
2237 put_page(page);
2238 goto retry_find;
2239 }
2240 VM_BUG_ON_PAGE(page->index != offset, page);
2241
2242 /*
2243 * We have a locked page in the page cache, now we need to check
2244 * that it's up-to-date. If not, it is going to be due to an error.
2245 */
2246 if (unlikely(!PageUptodate(page)))
2247 goto page_not_uptodate;
2248
2249 /*
2250 * Found the page and have a reference on it.
2251 * We must recheck i_size under page lock.
2252 */
2253 size = round_up(i_size_read(inode), PAGE_SIZE);
2254 if (unlikely(offset >= size >> PAGE_SHIFT)) {
2255 unlock_page(page);
2256 put_page(page);
2257 return VM_FAULT_SIGBUS;
2258 }
2259
2260 vmf->page = page;
2261 return ret | VM_FAULT_LOCKED;
2262
2263no_cached_page:
2264 /*
2265 * We're only likely to ever get here if MADV_RANDOM is in
2266 * effect.
2267 */
2268 error = page_cache_read(file, offset, vmf->gfp_mask);
2269
2270 /*
2271 * The page we want has now been added to the page cache.
2272 * In the unlikely event that someone removed it in the
2273 * meantime, we'll just come back here and read it again.
2274 */
2275 if (error >= 0)
2276 goto retry_find;
2277
2278 /*
2279 * An error return from page_cache_read can result if the
2280 * system is low on memory, or a problem occurs while trying
2281 * to schedule I/O.
2282 */
2283 if (error == -ENOMEM)
2284 return VM_FAULT_OOM;
2285 return VM_FAULT_SIGBUS;
2286
2287page_not_uptodate:
2288 /*
2289 * Umm, take care of errors if the page isn't up-to-date.
2290 * Try to re-read it _once_. We do this synchronously,
2291 * because there really aren't any performance issues here
2292 * and we need to check for errors.
2293 */
2294 ClearPageError(page);
2295 error = mapping->a_ops->readpage(file, page);
2296 if (!error) {
2297 wait_on_page_locked(page);
2298 if (!PageUptodate(page))
2299 error = -EIO;
2300 }
2301 put_page(page);
2302
2303 if (!error || error == AOP_TRUNCATED_PAGE)
2304 goto retry_find;
2305
2306 /* Things didn't work out. Return zero to tell the mm layer so. */
2307 shrink_readahead_size_eio(file, ra);
2308 return VM_FAULT_SIGBUS;
2309}
2310EXPORT_SYMBOL(filemap_fault);
2311
2312void filemap_map_pages(struct vm_fault *vmf,
2313 pgoff_t start_pgoff, pgoff_t end_pgoff)
2314{
2315 struct radix_tree_iter iter;
2316 void **slot;
2317 struct file *file = vmf->vma->vm_file;
2318 struct address_space *mapping = file->f_mapping;
2319 pgoff_t last_pgoff = start_pgoff;
2320 loff_t size;
2321 struct page *head, *page;
2322
2323 rcu_read_lock();
2324 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
2325 start_pgoff) {
2326 if (iter.index > end_pgoff)
2327 break;
2328repeat:
2329 page = radix_tree_deref_slot(slot);
2330 if (unlikely(!page))
2331 goto next;
2332 if (radix_tree_exception(page)) {
2333 if (radix_tree_deref_retry(page)) {
2334 slot = radix_tree_iter_retry(&iter);
2335 continue;
2336 }
2337 goto next;
2338 }
2339
2340 head = compound_head(page);
2341 if (!page_cache_get_speculative(head))
2342 goto repeat;
2343
2344 /* The page was split under us? */
2345 if (compound_head(page) != head) {
2346 put_page(head);
2347 goto repeat;
2348 }
2349
2350 /* Has the page moved? */
2351 if (unlikely(page != *slot)) {
2352 put_page(head);
2353 goto repeat;
2354 }
2355
2356 if (!PageUptodate(page) ||
2357 PageReadahead(page) ||
2358 PageHWPoison(page))
2359 goto skip;
2360 if (!trylock_page(page))
2361 goto skip;
2362
2363 if (page->mapping != mapping || !PageUptodate(page))
2364 goto unlock;
2365
2366 size = round_up(i_size_read(mapping->host), PAGE_SIZE);
2367 if (page->index >= size >> PAGE_SHIFT)
2368 goto unlock;
2369
2370 if (file->f_ra.mmap_miss > 0)
2371 file->f_ra.mmap_miss--;
2372
2373 vmf->address += (iter.index - last_pgoff) << PAGE_SHIFT;
2374 if (vmf->pte)
2375 vmf->pte += iter.index - last_pgoff;
2376 last_pgoff = iter.index;
2377 if (alloc_set_pte(vmf, NULL, page))
2378 goto unlock;
2379 unlock_page(page);
2380 goto next;
2381unlock:
2382 unlock_page(page);
2383skip:
2384 put_page(page);
2385next:
2386 /* Huge page is mapped? No need to proceed. */
2387 if (pmd_trans_huge(*vmf->pmd))
2388 break;
2389 if (iter.index == end_pgoff)
2390 break;
2391 }
2392 rcu_read_unlock();
2393}
2394EXPORT_SYMBOL(filemap_map_pages);
2395
2396int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
2397{
2398 struct page *page = vmf->page;
2399 struct inode *inode = file_inode(vma->vm_file);
2400 int ret = VM_FAULT_LOCKED;
2401
2402 sb_start_pagefault(inode->i_sb);
2403 file_update_time(vma->vm_file);
2404 lock_page(page);
2405 if (page->mapping != inode->i_mapping) {
2406 unlock_page(page);
2407 ret = VM_FAULT_NOPAGE;
2408 goto out;
2409 }
2410 /*
2411 * We mark the page dirty already here so that when freeze is in
2412 * progress, we are guaranteed that writeback during freezing will
2413 * see the dirty page and writeprotect it again.
2414 */
2415 set_page_dirty(page);
2416 wait_for_stable_page(page);
2417out:
2418 sb_end_pagefault(inode->i_sb);
2419 return ret;
2420}
2421EXPORT_SYMBOL(filemap_page_mkwrite);
2422
2423const struct vm_operations_struct generic_file_vm_ops = {
2424 .fault = filemap_fault,
2425 .map_pages = filemap_map_pages,
2426 .page_mkwrite = filemap_page_mkwrite,
2427};
2428
2429/* This is used for a general mmap of a disk file */
2430
2431int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2432{
2433 struct address_space *mapping = file->f_mapping;
2434
2435 if (!mapping->a_ops->readpage)
2436 return -ENOEXEC;
2437 file_accessed(file);
2438 vma->vm_ops = &generic_file_vm_ops;
2439 return 0;
2440}
2441
2442/*
2443 * This is for filesystems which do not implement ->writepage.
2444 */
2445int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2446{
2447 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2448 return -EINVAL;
2449 return generic_file_mmap(file, vma);
2450}
2451#else
2452int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2453{
2454 return -ENOSYS;
2455}
2456int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2457{
2458 return -ENOSYS;
2459}
2460#endif /* CONFIG_MMU */
2461
2462EXPORT_SYMBOL(generic_file_mmap);
2463EXPORT_SYMBOL(generic_file_readonly_mmap);
2464
2465static struct page *wait_on_page_read(struct page *page)
2466{
2467 if (!IS_ERR(page)) {
2468 wait_on_page_locked(page);
2469 if (!PageUptodate(page)) {
2470 put_page(page);
2471 page = ERR_PTR(-EIO);
2472 }
2473 }
2474 return page;
2475}
2476
2477static struct page *do_read_cache_page(struct address_space *mapping,
2478 pgoff_t index,
2479 int (*filler)(void *, struct page *),
2480 void *data,
2481 gfp_t gfp)
2482{
2483 struct page *page;
2484 int err;
2485repeat:
2486 page = find_get_page(mapping, index);
2487 if (!page) {
2488 page = __page_cache_alloc(gfp | __GFP_COLD);
2489 if (!page)
2490 return ERR_PTR(-ENOMEM);
2491 err = add_to_page_cache_lru(page, mapping, index, gfp);
2492 if (unlikely(err)) {
2493 put_page(page);
2494 if (err == -EEXIST)
2495 goto repeat;
2496 /* Presumably ENOMEM for radix tree node */
2497 return ERR_PTR(err);
2498 }
2499
2500filler:
2501 err = filler(data, page);
2502 if (err < 0) {
2503 put_page(page);
2504 return ERR_PTR(err);
2505 }
2506
2507 page = wait_on_page_read(page);
2508 if (IS_ERR(page))
2509 return page;
2510 goto out;
2511 }
2512 if (PageUptodate(page))
2513 goto out;
2514
2515 /*
2516 * Page is not up to date and may be locked due one of the following
2517 * case a: Page is being filled and the page lock is held
2518 * case b: Read/write error clearing the page uptodate status
2519 * case c: Truncation in progress (page locked)
2520 * case d: Reclaim in progress
2521 *
2522 * Case a, the page will be up to date when the page is unlocked.
2523 * There is no need to serialise on the page lock here as the page
2524 * is pinned so the lock gives no additional protection. Even if the
2525 * the page is truncated, the data is still valid if PageUptodate as
2526 * it's a race vs truncate race.
2527 * Case b, the page will not be up to date
2528 * Case c, the page may be truncated but in itself, the data may still
2529 * be valid after IO completes as it's a read vs truncate race. The
2530 * operation must restart if the page is not uptodate on unlock but
2531 * otherwise serialising on page lock to stabilise the mapping gives
2532 * no additional guarantees to the caller as the page lock is
2533 * released before return.
2534 * Case d, similar to truncation. If reclaim holds the page lock, it
2535 * will be a race with remove_mapping that determines if the mapping
2536 * is valid on unlock but otherwise the data is valid and there is
2537 * no need to serialise with page lock.
2538 *
2539 * As the page lock gives no additional guarantee, we optimistically
2540 * wait on the page to be unlocked and check if it's up to date and
2541 * use the page if it is. Otherwise, the page lock is required to
2542 * distinguish between the different cases. The motivation is that we
2543 * avoid spurious serialisations and wakeups when multiple processes
2544 * wait on the same page for IO to complete.
2545 */
2546 wait_on_page_locked(page);
2547 if (PageUptodate(page))
2548 goto out;
2549
2550 /* Distinguish between all the cases under the safety of the lock */
2551 lock_page(page);
2552
2553 /* Case c or d, restart the operation */
2554 if (!page->mapping) {
2555 unlock_page(page);
2556 put_page(page);
2557 goto repeat;
2558 }
2559
2560 /* Someone else locked and filled the page in a very small window */
2561 if (PageUptodate(page)) {
2562 unlock_page(page);
2563 goto out;
2564 }
2565 goto filler;
2566
2567out:
2568 mark_page_accessed(page);
2569 return page;
2570}
2571
2572/**
2573 * read_cache_page - read into page cache, fill it if needed
2574 * @mapping: the page's address_space
2575 * @index: the page index
2576 * @filler: function to perform the read
2577 * @data: first arg to filler(data, page) function, often left as NULL
2578 *
2579 * Read into the page cache. If a page already exists, and PageUptodate() is
2580 * not set, try to fill the page and wait for it to become unlocked.
2581 *
2582 * If the page does not get brought uptodate, return -EIO.
2583 */
2584struct page *read_cache_page(struct address_space *mapping,
2585 pgoff_t index,
2586 int (*filler)(void *, struct page *),
2587 void *data)
2588{
2589 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2590}
2591EXPORT_SYMBOL(read_cache_page);
2592
2593/**
2594 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2595 * @mapping: the page's address_space
2596 * @index: the page index
2597 * @gfp: the page allocator flags to use if allocating
2598 *
2599 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2600 * any new page allocations done using the specified allocation flags.
2601 *
2602 * If the page does not get brought uptodate, return -EIO.
2603 */
2604struct page *read_cache_page_gfp(struct address_space *mapping,
2605 pgoff_t index,
2606 gfp_t gfp)
2607{
2608 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2609
2610 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2611}
2612EXPORT_SYMBOL(read_cache_page_gfp);
2613
2614/*
2615 * Performs necessary checks before doing a write
2616 *
2617 * Can adjust writing position or amount of bytes to write.
2618 * Returns appropriate error code that caller should return or
2619 * zero in case that write should be allowed.
2620 */
2621inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2622{
2623 struct file *file = iocb->ki_filp;
2624 struct inode *inode = file->f_mapping->host;
2625 unsigned long limit = rlimit(RLIMIT_FSIZE);
2626 loff_t pos;
2627
2628 if (!iov_iter_count(from))
2629 return 0;
2630
2631 /* FIXME: this is for backwards compatibility with 2.4 */
2632 if (iocb->ki_flags & IOCB_APPEND)
2633 iocb->ki_pos = i_size_read(inode);
2634
2635 pos = iocb->ki_pos;
2636
2637 if (limit != RLIM_INFINITY) {
2638 if (iocb->ki_pos >= limit) {
2639 send_sig(SIGXFSZ, current, 0);
2640 return -EFBIG;
2641 }
2642 iov_iter_truncate(from, limit - (unsigned long)pos);
2643 }
2644
2645 /*
2646 * LFS rule
2647 */
2648 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2649 !(file->f_flags & O_LARGEFILE))) {
2650 if (pos >= MAX_NON_LFS)
2651 return -EFBIG;
2652 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2653 }
2654
2655 /*
2656 * Are we about to exceed the fs block limit ?
2657 *
2658 * If we have written data it becomes a short write. If we have
2659 * exceeded without writing data we send a signal and return EFBIG.
2660 * Linus frestrict idea will clean these up nicely..
2661 */
2662 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2663 return -EFBIG;
2664
2665 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2666 return iov_iter_count(from);
2667}
2668EXPORT_SYMBOL(generic_write_checks);
2669
2670int pagecache_write_begin(struct file *file, struct address_space *mapping,
2671 loff_t pos, unsigned len, unsigned flags,
2672 struct page **pagep, void **fsdata)
2673{
2674 const struct address_space_operations *aops = mapping->a_ops;
2675
2676 return aops->write_begin(file, mapping, pos, len, flags,
2677 pagep, fsdata);
2678}
2679EXPORT_SYMBOL(pagecache_write_begin);
2680
2681int pagecache_write_end(struct file *file, struct address_space *mapping,
2682 loff_t pos, unsigned len, unsigned copied,
2683 struct page *page, void *fsdata)
2684{
2685 const struct address_space_operations *aops = mapping->a_ops;
2686
2687 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2688}
2689EXPORT_SYMBOL(pagecache_write_end);
2690
2691ssize_t
2692generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
2693{
2694 struct file *file = iocb->ki_filp;
2695 struct address_space *mapping = file->f_mapping;
2696 struct inode *inode = mapping->host;
2697 loff_t pos = iocb->ki_pos;
2698 ssize_t written;
2699 size_t write_len;
2700 pgoff_t end;
2701 struct iov_iter data;
2702
2703 write_len = iov_iter_count(from);
2704 end = (pos + write_len - 1) >> PAGE_SHIFT;
2705
2706 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2707 if (written)
2708 goto out;
2709
2710 /*
2711 * After a write we want buffered reads to be sure to go to disk to get
2712 * the new data. We invalidate clean cached page from the region we're
2713 * about to write. We do this *before* the write so that we can return
2714 * without clobbering -EIOCBQUEUED from ->direct_IO().
2715 */
2716 if (mapping->nrpages) {
2717 written = invalidate_inode_pages2_range(mapping,
2718 pos >> PAGE_SHIFT, end);
2719 /*
2720 * If a page can not be invalidated, return 0 to fall back
2721 * to buffered write.
2722 */
2723 if (written) {
2724 if (written == -EBUSY)
2725 return 0;
2726 goto out;
2727 }
2728 }
2729
2730 data = *from;
2731 written = mapping->a_ops->direct_IO(iocb, &data);
2732
2733 /*
2734 * Finally, try again to invalidate clean pages which might have been
2735 * cached by non-direct readahead, or faulted in by get_user_pages()
2736 * if the source of the write was an mmap'ed region of the file
2737 * we're writing. Either one is a pretty crazy thing to do,
2738 * so we don't support it 100%. If this invalidation
2739 * fails, tough, the write still worked...
2740 */
2741 if (mapping->nrpages) {
2742 invalidate_inode_pages2_range(mapping,
2743 pos >> PAGE_SHIFT, end);
2744 }
2745
2746 if (written > 0) {
2747 pos += written;
2748 iov_iter_advance(from, written);
2749 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2750 i_size_write(inode, pos);
2751 mark_inode_dirty(inode);
2752 }
2753 iocb->ki_pos = pos;
2754 }
2755out:
2756 return written;
2757}
2758EXPORT_SYMBOL(generic_file_direct_write);
2759
2760/*
2761 * Find or create a page at the given pagecache position. Return the locked
2762 * page. This function is specifically for buffered writes.
2763 */
2764struct page *grab_cache_page_write_begin(struct address_space *mapping,
2765 pgoff_t index, unsigned flags)
2766{
2767 struct page *page;
2768 int fgp_flags = FGP_LOCK|FGP_WRITE|FGP_CREAT;
2769
2770 if (flags & AOP_FLAG_NOFS)
2771 fgp_flags |= FGP_NOFS;
2772
2773 page = pagecache_get_page(mapping, index, fgp_flags,
2774 mapping_gfp_mask(mapping));
2775 if (page)
2776 wait_for_stable_page(page);
2777
2778 return page;
2779}
2780EXPORT_SYMBOL(grab_cache_page_write_begin);
2781
2782ssize_t generic_perform_write(struct file *file,
2783 struct iov_iter *i, loff_t pos)
2784{
2785 struct address_space *mapping = file->f_mapping;
2786 const struct address_space_operations *a_ops = mapping->a_ops;
2787 long status = 0;
2788 ssize_t written = 0;
2789 unsigned int flags = 0;
2790
2791 /*
2792 * Copies from kernel address space cannot fail (NFSD is a big user).
2793 */
2794 if (!iter_is_iovec(i))
2795 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2796
2797 do {
2798 struct page *page;
2799 unsigned long offset; /* Offset into pagecache page */
2800 unsigned long bytes; /* Bytes to write to page */
2801 size_t copied; /* Bytes copied from user */
2802 void *fsdata;
2803
2804 offset = (pos & (PAGE_SIZE - 1));
2805 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2806 iov_iter_count(i));
2807
2808again:
2809 /*
2810 * Bring in the user page that we will copy from _first_.
2811 * Otherwise there's a nasty deadlock on copying from the
2812 * same page as we're writing to, without it being marked
2813 * up-to-date.
2814 *
2815 * Not only is this an optimisation, but it is also required
2816 * to check that the address is actually valid, when atomic
2817 * usercopies are used, below.
2818 */
2819 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2820 status = -EFAULT;
2821 break;
2822 }
2823
2824 if (fatal_signal_pending(current)) {
2825 status = -EINTR;
2826 break;
2827 }
2828
2829 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2830 &page, &fsdata);
2831 if (unlikely(status < 0))
2832 break;
2833
2834 if (mapping_writably_mapped(mapping))
2835 flush_dcache_page(page);
2836
2837 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2838 flush_dcache_page(page);
2839
2840 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2841 page, fsdata);
2842 if (unlikely(status < 0))
2843 break;
2844 copied = status;
2845
2846 cond_resched();
2847
2848 iov_iter_advance(i, copied);
2849 if (unlikely(copied == 0)) {
2850 /*
2851 * If we were unable to copy any data at all, we must
2852 * fall back to a single segment length write.
2853 *
2854 * If we didn't fallback here, we could livelock
2855 * because not all segments in the iov can be copied at
2856 * once without a pagefault.
2857 */
2858 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2859 iov_iter_single_seg_count(i));
2860 goto again;
2861 }
2862 pos += copied;
2863 written += copied;
2864
2865 balance_dirty_pages_ratelimited(mapping);
2866 } while (iov_iter_count(i));
2867
2868 return written ? written : status;
2869}
2870EXPORT_SYMBOL(generic_perform_write);
2871
2872/**
2873 * __generic_file_write_iter - write data to a file
2874 * @iocb: IO state structure (file, offset, etc.)
2875 * @from: iov_iter with data to write
2876 *
2877 * This function does all the work needed for actually writing data to a
2878 * file. It does all basic checks, removes SUID from the file, updates
2879 * modification times and calls proper subroutines depending on whether we
2880 * do direct IO or a standard buffered write.
2881 *
2882 * It expects i_mutex to be grabbed unless we work on a block device or similar
2883 * object which does not need locking at all.
2884 *
2885 * This function does *not* take care of syncing data in case of O_SYNC write.
2886 * A caller has to handle it. This is mainly due to the fact that we want to
2887 * avoid syncing under i_mutex.
2888 */
2889ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2890{
2891 struct file *file = iocb->ki_filp;
2892 struct address_space * mapping = file->f_mapping;
2893 struct inode *inode = mapping->host;
2894 ssize_t written = 0;
2895 ssize_t err;
2896 ssize_t status;
2897
2898 /* We can write back this queue in page reclaim */
2899 current->backing_dev_info = inode_to_bdi(inode);
2900 err = file_remove_privs(file);
2901 if (err)
2902 goto out;
2903
2904 err = file_update_time(file);
2905 if (err)
2906 goto out;
2907
2908 if (iocb->ki_flags & IOCB_DIRECT) {
2909 loff_t pos, endbyte;
2910
2911 written = generic_file_direct_write(iocb, from);
2912 /*
2913 * If the write stopped short of completing, fall back to
2914 * buffered writes. Some filesystems do this for writes to
2915 * holes, for example. For DAX files, a buffered write will
2916 * not succeed (even if it did, DAX does not handle dirty
2917 * page-cache pages correctly).
2918 */
2919 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
2920 goto out;
2921
2922 status = generic_perform_write(file, from, pos = iocb->ki_pos);
2923 /*
2924 * If generic_perform_write() returned a synchronous error
2925 * then we want to return the number of bytes which were
2926 * direct-written, or the error code if that was zero. Note
2927 * that this differs from normal direct-io semantics, which
2928 * will return -EFOO even if some bytes were written.
2929 */
2930 if (unlikely(status < 0)) {
2931 err = status;
2932 goto out;
2933 }
2934 /*
2935 * We need to ensure that the page cache pages are written to
2936 * disk and invalidated to preserve the expected O_DIRECT
2937 * semantics.
2938 */
2939 endbyte = pos + status - 1;
2940 err = filemap_write_and_wait_range(mapping, pos, endbyte);
2941 if (err == 0) {
2942 iocb->ki_pos = endbyte + 1;
2943 written += status;
2944 invalidate_mapping_pages(mapping,
2945 pos >> PAGE_SHIFT,
2946 endbyte >> PAGE_SHIFT);
2947 } else {
2948 /*
2949 * We don't know how much we wrote, so just return
2950 * the number of bytes which were direct-written
2951 */
2952 }
2953 } else {
2954 written = generic_perform_write(file, from, iocb->ki_pos);
2955 if (likely(written > 0))
2956 iocb->ki_pos += written;
2957 }
2958out:
2959 current->backing_dev_info = NULL;
2960 return written ? written : err;
2961}
2962EXPORT_SYMBOL(__generic_file_write_iter);
2963
2964/**
2965 * generic_file_write_iter - write data to a file
2966 * @iocb: IO state structure
2967 * @from: iov_iter with data to write
2968 *
2969 * This is a wrapper around __generic_file_write_iter() to be used by most
2970 * filesystems. It takes care of syncing the file in case of O_SYNC file
2971 * and acquires i_mutex as needed.
2972 */
2973ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2974{
2975 struct file *file = iocb->ki_filp;
2976 struct inode *inode = file->f_mapping->host;
2977 ssize_t ret;
2978
2979 inode_lock(inode);
2980 ret = generic_write_checks(iocb, from);
2981 if (ret > 0)
2982 ret = __generic_file_write_iter(iocb, from);
2983 inode_unlock(inode);
2984
2985 if (ret > 0)
2986 ret = generic_write_sync(iocb, ret);
2987 return ret;
2988}
2989EXPORT_SYMBOL(generic_file_write_iter);
2990
2991/**
2992 * try_to_release_page() - release old fs-specific metadata on a page
2993 *
2994 * @page: the page which the kernel is trying to free
2995 * @gfp_mask: memory allocation flags (and I/O mode)
2996 *
2997 * The address_space is to try to release any data against the page
2998 * (presumably at page->private). If the release was successful, return `1'.
2999 * Otherwise return zero.
3000 *
3001 * This may also be called if PG_fscache is set on a page, indicating that the
3002 * page is known to the local caching routines.
3003 *
3004 * The @gfp_mask argument specifies whether I/O may be performed to release
3005 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
3006 *
3007 */
3008int try_to_release_page(struct page *page, gfp_t gfp_mask)
3009{
3010 struct address_space * const mapping = page->mapping;
3011
3012 BUG_ON(!PageLocked(page));
3013 if (PageWriteback(page))
3014 return 0;
3015
3016 if (mapping && mapping->a_ops->releasepage)
3017 return mapping->a_ops->releasepage(page, gfp_mask);
3018 return try_to_free_buffers(page);
3019}
3020
3021EXPORT_SYMBOL(try_to_release_page);