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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/fs.h>
15#include <linux/uaccess.h>
16#include <linux/aio.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/memcontrol.h>
35#include <linux/cleancache.h>
36#include <linux/rmap.h>
37#include "internal.h"
38
39#define CREATE_TRACE_POINTS
40#include <trace/events/filemap.h>
41
42/*
43 * FIXME: remove all knowledge of the buffer layer from the core VM
44 */
45#include <linux/buffer_head.h> /* for try_to_free_buffers */
46
47#include <asm/mman.h>
48
49/*
50 * Shared mappings implemented 30.11.1994. It's not fully working yet,
51 * though.
52 *
53 * Shared mappings now work. 15.8.1995 Bruno.
54 *
55 * finished 'unifying' the page and buffer cache and SMP-threaded the
56 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
57 *
58 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
59 */
60
61/*
62 * Lock ordering:
63 *
64 * ->i_mmap_mutex (truncate_pagecache)
65 * ->private_lock (__free_pte->__set_page_dirty_buffers)
66 * ->swap_lock (exclusive_swap_page, others)
67 * ->mapping->tree_lock
68 *
69 * ->i_mutex
70 * ->i_mmap_mutex (truncate->unmap_mapping_range)
71 *
72 * ->mmap_sem
73 * ->i_mmap_mutex
74 * ->page_table_lock or pte_lock (various, mainly in memory.c)
75 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
76 *
77 * ->mmap_sem
78 * ->lock_page (access_process_vm)
79 *
80 * ->i_mutex (generic_perform_write)
81 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
82 *
83 * bdi->wb.list_lock
84 * sb_lock (fs/fs-writeback.c)
85 * ->mapping->tree_lock (__sync_single_inode)
86 *
87 * ->i_mmap_mutex
88 * ->anon_vma.lock (vma_adjust)
89 *
90 * ->anon_vma.lock
91 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
92 *
93 * ->page_table_lock or pte_lock
94 * ->swap_lock (try_to_unmap_one)
95 * ->private_lock (try_to_unmap_one)
96 * ->tree_lock (try_to_unmap_one)
97 * ->zone.lru_lock (follow_page->mark_page_accessed)
98 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
99 * ->private_lock (page_remove_rmap->set_page_dirty)
100 * ->tree_lock (page_remove_rmap->set_page_dirty)
101 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
102 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
103 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
104 * ->inode->i_lock (zap_pte_range->set_page_dirty)
105 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
106 *
107 * ->i_mmap_mutex
108 * ->tasklist_lock (memory_failure, collect_procs_ao)
109 */
110
111static void page_cache_tree_delete(struct address_space *mapping,
112 struct page *page, void *shadow)
113{
114 struct radix_tree_node *node;
115 unsigned long index;
116 unsigned int offset;
117 unsigned int tag;
118 void **slot;
119
120 VM_BUG_ON(!PageLocked(page));
121
122 __radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
123
124 if (shadow) {
125 mapping->nrshadows++;
126 /*
127 * Make sure the nrshadows update is committed before
128 * the nrpages update so that final truncate racing
129 * with reclaim does not see both counters 0 at the
130 * same time and miss a shadow entry.
131 */
132 smp_wmb();
133 }
134 mapping->nrpages--;
135
136 if (!node) {
137 /* Clear direct pointer tags in root node */
138 mapping->page_tree.gfp_mask &= __GFP_BITS_MASK;
139 radix_tree_replace_slot(slot, shadow);
140 return;
141 }
142
143 /* Clear tree tags for the removed page */
144 index = page->index;
145 offset = index & RADIX_TREE_MAP_MASK;
146 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
147 if (test_bit(offset, node->tags[tag]))
148 radix_tree_tag_clear(&mapping->page_tree, index, tag);
149 }
150
151 /* Delete page, swap shadow entry */
152 radix_tree_replace_slot(slot, shadow);
153 workingset_node_pages_dec(node);
154 if (shadow)
155 workingset_node_shadows_inc(node);
156 else
157 if (__radix_tree_delete_node(&mapping->page_tree, node))
158 return;
159
160 /*
161 * Track node that only contains shadow entries.
162 *
163 * Avoid acquiring the list_lru lock if already tracked. The
164 * list_empty() test is safe as node->private_list is
165 * protected by mapping->tree_lock.
166 */
167 if (!workingset_node_pages(node) &&
168 list_empty(&node->private_list)) {
169 node->private_data = mapping;
170 list_lru_add(&workingset_shadow_nodes, &node->private_list);
171 }
172}
173
174/*
175 * Delete a page from the page cache and free it. Caller has to make
176 * sure the page is locked and that nobody else uses it - or that usage
177 * is safe. The caller must hold the mapping's tree_lock.
178 */
179void __delete_from_page_cache(struct page *page, void *shadow)
180{
181 struct address_space *mapping = page->mapping;
182
183 trace_mm_filemap_delete_from_page_cache(page);
184 /*
185 * if we're uptodate, flush out into the cleancache, otherwise
186 * invalidate any existing cleancache entries. We can't leave
187 * stale data around in the cleancache once our page is gone
188 */
189 if (PageUptodate(page) && PageMappedToDisk(page))
190 cleancache_put_page(page);
191 else
192 cleancache_invalidate_page(mapping, page);
193
194 page_cache_tree_delete(mapping, page, shadow);
195
196 page->mapping = NULL;
197 /* Leave page->index set: truncation lookup relies upon it */
198
199 __dec_zone_page_state(page, NR_FILE_PAGES);
200 if (PageSwapBacked(page))
201 __dec_zone_page_state(page, NR_SHMEM);
202 BUG_ON(page_mapped(page));
203
204 /*
205 * Some filesystems seem to re-dirty the page even after
206 * the VM has canceled the dirty bit (eg ext3 journaling).
207 *
208 * Fix it up by doing a final dirty accounting check after
209 * having removed the page entirely.
210 */
211 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
212 dec_zone_page_state(page, NR_FILE_DIRTY);
213 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
214 }
215}
216
217/**
218 * delete_from_page_cache - delete page from page cache
219 * @page: the page which the kernel is trying to remove from page cache
220 *
221 * This must be called only on pages that have been verified to be in the page
222 * cache and locked. It will never put the page into the free list, the caller
223 * has a reference on the page.
224 */
225void delete_from_page_cache(struct page *page)
226{
227 struct address_space *mapping = page->mapping;
228 void (*freepage)(struct page *);
229
230 BUG_ON(!PageLocked(page));
231
232 freepage = mapping->a_ops->freepage;
233 spin_lock_irq(&mapping->tree_lock);
234 __delete_from_page_cache(page, NULL);
235 spin_unlock_irq(&mapping->tree_lock);
236 mem_cgroup_uncharge_cache_page(page);
237
238 if (freepage)
239 freepage(page);
240 page_cache_release(page);
241}
242EXPORT_SYMBOL(delete_from_page_cache);
243
244static int sleep_on_page(void *word)
245{
246 io_schedule();
247 return 0;
248}
249
250static int sleep_on_page_killable(void *word)
251{
252 sleep_on_page(word);
253 return fatal_signal_pending(current) ? -EINTR : 0;
254}
255
256static int filemap_check_errors(struct address_space *mapping)
257{
258 int ret = 0;
259 /* Check for outstanding write errors */
260 if (test_bit(AS_ENOSPC, &mapping->flags) &&
261 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
262 ret = -ENOSPC;
263 if (test_bit(AS_EIO, &mapping->flags) &&
264 test_and_clear_bit(AS_EIO, &mapping->flags))
265 ret = -EIO;
266 return ret;
267}
268
269/**
270 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
271 * @mapping: address space structure to write
272 * @start: offset in bytes where the range starts
273 * @end: offset in bytes where the range ends (inclusive)
274 * @sync_mode: enable synchronous operation
275 *
276 * Start writeback against all of a mapping's dirty pages that lie
277 * within the byte offsets <start, end> inclusive.
278 *
279 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
280 * opposed to a regular memory cleansing writeback. The difference between
281 * these two operations is that if a dirty page/buffer is encountered, it must
282 * be waited upon, and not just skipped over.
283 */
284int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
285 loff_t end, int sync_mode)
286{
287 int ret;
288 struct writeback_control wbc = {
289 .sync_mode = sync_mode,
290 .nr_to_write = LONG_MAX,
291 .range_start = start,
292 .range_end = end,
293 };
294
295 if (!mapping_cap_writeback_dirty(mapping))
296 return 0;
297
298 ret = do_writepages(mapping, &wbc);
299 return ret;
300}
301
302static inline int __filemap_fdatawrite(struct address_space *mapping,
303 int sync_mode)
304{
305 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
306}
307
308int filemap_fdatawrite(struct address_space *mapping)
309{
310 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
311}
312EXPORT_SYMBOL(filemap_fdatawrite);
313
314int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
315 loff_t end)
316{
317 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
318}
319EXPORT_SYMBOL(filemap_fdatawrite_range);
320
321/**
322 * filemap_flush - mostly a non-blocking flush
323 * @mapping: target address_space
324 *
325 * This is a mostly non-blocking flush. Not suitable for data-integrity
326 * purposes - I/O may not be started against all dirty pages.
327 */
328int filemap_flush(struct address_space *mapping)
329{
330 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
331}
332EXPORT_SYMBOL(filemap_flush);
333
334/**
335 * filemap_fdatawait_range - wait for writeback to complete
336 * @mapping: address space structure to wait for
337 * @start_byte: offset in bytes where the range starts
338 * @end_byte: offset in bytes where the range ends (inclusive)
339 *
340 * Walk the list of under-writeback pages of the given address space
341 * in the given range and wait for all of them.
342 */
343int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
344 loff_t end_byte)
345{
346 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
347 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
348 struct pagevec pvec;
349 int nr_pages;
350 int ret2, ret = 0;
351
352 if (end_byte < start_byte)
353 goto out;
354
355 pagevec_init(&pvec, 0);
356 while ((index <= end) &&
357 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
358 PAGECACHE_TAG_WRITEBACK,
359 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
360 unsigned i;
361
362 for (i = 0; i < nr_pages; i++) {
363 struct page *page = pvec.pages[i];
364
365 /* until radix tree lookup accepts end_index */
366 if (page->index > end)
367 continue;
368
369 wait_on_page_writeback(page);
370 if (TestClearPageError(page))
371 ret = -EIO;
372 }
373 pagevec_release(&pvec);
374 cond_resched();
375 }
376out:
377 ret2 = filemap_check_errors(mapping);
378 if (!ret)
379 ret = ret2;
380
381 return ret;
382}
383EXPORT_SYMBOL(filemap_fdatawait_range);
384
385/**
386 * filemap_fdatawait - wait for all under-writeback pages to complete
387 * @mapping: address space structure to wait for
388 *
389 * Walk the list of under-writeback pages of the given address space
390 * and wait for all of them.
391 */
392int filemap_fdatawait(struct address_space *mapping)
393{
394 loff_t i_size = i_size_read(mapping->host);
395
396 if (i_size == 0)
397 return 0;
398
399 return filemap_fdatawait_range(mapping, 0, i_size - 1);
400}
401EXPORT_SYMBOL(filemap_fdatawait);
402
403int filemap_write_and_wait(struct address_space *mapping)
404{
405 int err = 0;
406
407 if (mapping->nrpages) {
408 err = filemap_fdatawrite(mapping);
409 /*
410 * Even if the above returned error, the pages may be
411 * written partially (e.g. -ENOSPC), so we wait for it.
412 * But the -EIO is special case, it may indicate the worst
413 * thing (e.g. bug) happened, so we avoid waiting for it.
414 */
415 if (err != -EIO) {
416 int err2 = filemap_fdatawait(mapping);
417 if (!err)
418 err = err2;
419 }
420 } else {
421 err = filemap_check_errors(mapping);
422 }
423 return err;
424}
425EXPORT_SYMBOL(filemap_write_and_wait);
426
427/**
428 * filemap_write_and_wait_range - write out & wait on a file range
429 * @mapping: the address_space for the pages
430 * @lstart: offset in bytes where the range starts
431 * @lend: offset in bytes where the range ends (inclusive)
432 *
433 * Write out and wait upon file offsets lstart->lend, inclusive.
434 *
435 * Note that `lend' is inclusive (describes the last byte to be written) so
436 * that this function can be used to write to the very end-of-file (end = -1).
437 */
438int filemap_write_and_wait_range(struct address_space *mapping,
439 loff_t lstart, loff_t lend)
440{
441 int err = 0;
442
443 if (mapping->nrpages) {
444 err = __filemap_fdatawrite_range(mapping, lstart, lend,
445 WB_SYNC_ALL);
446 /* See comment of filemap_write_and_wait() */
447 if (err != -EIO) {
448 int err2 = filemap_fdatawait_range(mapping,
449 lstart, lend);
450 if (!err)
451 err = err2;
452 }
453 } else {
454 err = filemap_check_errors(mapping);
455 }
456 return err;
457}
458EXPORT_SYMBOL(filemap_write_and_wait_range);
459
460/**
461 * replace_page_cache_page - replace a pagecache page with a new one
462 * @old: page to be replaced
463 * @new: page to replace with
464 * @gfp_mask: allocation mode
465 *
466 * This function replaces a page in the pagecache with a new one. On
467 * success it acquires the pagecache reference for the new page and
468 * drops it for the old page. Both the old and new pages must be
469 * locked. This function does not add the new page to the LRU, the
470 * caller must do that.
471 *
472 * The remove + add is atomic. The only way this function can fail is
473 * memory allocation failure.
474 */
475int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
476{
477 int error;
478
479 VM_BUG_ON_PAGE(!PageLocked(old), old);
480 VM_BUG_ON_PAGE(!PageLocked(new), new);
481 VM_BUG_ON_PAGE(new->mapping, new);
482
483 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
484 if (!error) {
485 struct address_space *mapping = old->mapping;
486 void (*freepage)(struct page *);
487
488 pgoff_t offset = old->index;
489 freepage = mapping->a_ops->freepage;
490
491 page_cache_get(new);
492 new->mapping = mapping;
493 new->index = offset;
494
495 spin_lock_irq(&mapping->tree_lock);
496 __delete_from_page_cache(old, NULL);
497 error = radix_tree_insert(&mapping->page_tree, offset, new);
498 BUG_ON(error);
499 mapping->nrpages++;
500 __inc_zone_page_state(new, NR_FILE_PAGES);
501 if (PageSwapBacked(new))
502 __inc_zone_page_state(new, NR_SHMEM);
503 spin_unlock_irq(&mapping->tree_lock);
504 /* mem_cgroup codes must not be called under tree_lock */
505 mem_cgroup_replace_page_cache(old, new);
506 radix_tree_preload_end();
507 if (freepage)
508 freepage(old);
509 page_cache_release(old);
510 }
511
512 return error;
513}
514EXPORT_SYMBOL_GPL(replace_page_cache_page);
515
516static int page_cache_tree_insert(struct address_space *mapping,
517 struct page *page, void **shadowp)
518{
519 struct radix_tree_node *node;
520 void **slot;
521 int error;
522
523 error = __radix_tree_create(&mapping->page_tree, page->index,
524 &node, &slot);
525 if (error)
526 return error;
527 if (*slot) {
528 void *p;
529
530 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
531 if (!radix_tree_exceptional_entry(p))
532 return -EEXIST;
533 if (shadowp)
534 *shadowp = p;
535 mapping->nrshadows--;
536 if (node)
537 workingset_node_shadows_dec(node);
538 }
539 radix_tree_replace_slot(slot, page);
540 mapping->nrpages++;
541 if (node) {
542 workingset_node_pages_inc(node);
543 /*
544 * Don't track node that contains actual pages.
545 *
546 * Avoid acquiring the list_lru lock if already
547 * untracked. The list_empty() test is safe as
548 * node->private_list is protected by
549 * mapping->tree_lock.
550 */
551 if (!list_empty(&node->private_list))
552 list_lru_del(&workingset_shadow_nodes,
553 &node->private_list);
554 }
555 return 0;
556}
557
558static int __add_to_page_cache_locked(struct page *page,
559 struct address_space *mapping,
560 pgoff_t offset, gfp_t gfp_mask,
561 void **shadowp)
562{
563 int error;
564
565 VM_BUG_ON_PAGE(!PageLocked(page), page);
566 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
567
568 error = mem_cgroup_charge_file(page, current->mm,
569 gfp_mask & GFP_RECLAIM_MASK);
570 if (error)
571 return error;
572
573 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
574 if (error) {
575 mem_cgroup_uncharge_cache_page(page);
576 return error;
577 }
578
579 page_cache_get(page);
580 page->mapping = mapping;
581 page->index = offset;
582
583 spin_lock_irq(&mapping->tree_lock);
584 error = page_cache_tree_insert(mapping, page, shadowp);
585 radix_tree_preload_end();
586 if (unlikely(error))
587 goto err_insert;
588 __inc_zone_page_state(page, NR_FILE_PAGES);
589 spin_unlock_irq(&mapping->tree_lock);
590 trace_mm_filemap_add_to_page_cache(page);
591 return 0;
592err_insert:
593 page->mapping = NULL;
594 /* Leave page->index set: truncation relies upon it */
595 spin_unlock_irq(&mapping->tree_lock);
596 mem_cgroup_uncharge_cache_page(page);
597 page_cache_release(page);
598 return error;
599}
600
601/**
602 * add_to_page_cache_locked - add a locked page to the pagecache
603 * @page: page to add
604 * @mapping: the page's address_space
605 * @offset: page index
606 * @gfp_mask: page allocation mode
607 *
608 * This function is used to add a page to the pagecache. It must be locked.
609 * This function does not add the page to the LRU. The caller must do that.
610 */
611int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
612 pgoff_t offset, gfp_t gfp_mask)
613{
614 return __add_to_page_cache_locked(page, mapping, offset,
615 gfp_mask, NULL);
616}
617EXPORT_SYMBOL(add_to_page_cache_locked);
618
619int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
620 pgoff_t offset, gfp_t gfp_mask)
621{
622 void *shadow = NULL;
623 int ret;
624
625 __set_page_locked(page);
626 ret = __add_to_page_cache_locked(page, mapping, offset,
627 gfp_mask, &shadow);
628 if (unlikely(ret))
629 __clear_page_locked(page);
630 else {
631 /*
632 * The page might have been evicted from cache only
633 * recently, in which case it should be activated like
634 * any other repeatedly accessed page.
635 */
636 if (shadow && workingset_refault(shadow)) {
637 SetPageActive(page);
638 workingset_activation(page);
639 } else
640 ClearPageActive(page);
641 lru_cache_add(page);
642 }
643 return ret;
644}
645EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
646
647#ifdef CONFIG_NUMA
648struct page *__page_cache_alloc(gfp_t gfp)
649{
650 int n;
651 struct page *page;
652
653 if (cpuset_do_page_mem_spread()) {
654 unsigned int cpuset_mems_cookie;
655 do {
656 cpuset_mems_cookie = read_mems_allowed_begin();
657 n = cpuset_mem_spread_node();
658 page = alloc_pages_exact_node(n, gfp, 0);
659 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
660
661 return page;
662 }
663 return alloc_pages(gfp, 0);
664}
665EXPORT_SYMBOL(__page_cache_alloc);
666#endif
667
668/*
669 * In order to wait for pages to become available there must be
670 * waitqueues associated with pages. By using a hash table of
671 * waitqueues where the bucket discipline is to maintain all
672 * waiters on the same queue and wake all when any of the pages
673 * become available, and for the woken contexts to check to be
674 * sure the appropriate page became available, this saves space
675 * at a cost of "thundering herd" phenomena during rare hash
676 * collisions.
677 */
678static wait_queue_head_t *page_waitqueue(struct page *page)
679{
680 const struct zone *zone = page_zone(page);
681
682 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
683}
684
685static inline void wake_up_page(struct page *page, int bit)
686{
687 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
688}
689
690void wait_on_page_bit(struct page *page, int bit_nr)
691{
692 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
693
694 if (test_bit(bit_nr, &page->flags))
695 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
696 TASK_UNINTERRUPTIBLE);
697}
698EXPORT_SYMBOL(wait_on_page_bit);
699
700int wait_on_page_bit_killable(struct page *page, int bit_nr)
701{
702 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
703
704 if (!test_bit(bit_nr, &page->flags))
705 return 0;
706
707 return __wait_on_bit(page_waitqueue(page), &wait,
708 sleep_on_page_killable, TASK_KILLABLE);
709}
710
711/**
712 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
713 * @page: Page defining the wait queue of interest
714 * @waiter: Waiter to add to the queue
715 *
716 * Add an arbitrary @waiter to the wait queue for the nominated @page.
717 */
718void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
719{
720 wait_queue_head_t *q = page_waitqueue(page);
721 unsigned long flags;
722
723 spin_lock_irqsave(&q->lock, flags);
724 __add_wait_queue(q, waiter);
725 spin_unlock_irqrestore(&q->lock, flags);
726}
727EXPORT_SYMBOL_GPL(add_page_wait_queue);
728
729/**
730 * unlock_page - unlock a locked page
731 * @page: the page
732 *
733 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
734 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
735 * mechananism between PageLocked pages and PageWriteback pages is shared.
736 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
737 *
738 * The mb is necessary to enforce ordering between the clear_bit and the read
739 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
740 */
741void unlock_page(struct page *page)
742{
743 VM_BUG_ON_PAGE(!PageLocked(page), page);
744 clear_bit_unlock(PG_locked, &page->flags);
745 smp_mb__after_clear_bit();
746 wake_up_page(page, PG_locked);
747}
748EXPORT_SYMBOL(unlock_page);
749
750/**
751 * end_page_writeback - end writeback against a page
752 * @page: the page
753 */
754void end_page_writeback(struct page *page)
755{
756 if (TestClearPageReclaim(page))
757 rotate_reclaimable_page(page);
758
759 if (!test_clear_page_writeback(page))
760 BUG();
761
762 smp_mb__after_clear_bit();
763 wake_up_page(page, PG_writeback);
764}
765EXPORT_SYMBOL(end_page_writeback);
766
767/**
768 * __lock_page - get a lock on the page, assuming we need to sleep to get it
769 * @page: the page to lock
770 */
771void __lock_page(struct page *page)
772{
773 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
774
775 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
776 TASK_UNINTERRUPTIBLE);
777}
778EXPORT_SYMBOL(__lock_page);
779
780int __lock_page_killable(struct page *page)
781{
782 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
783
784 return __wait_on_bit_lock(page_waitqueue(page), &wait,
785 sleep_on_page_killable, TASK_KILLABLE);
786}
787EXPORT_SYMBOL_GPL(__lock_page_killable);
788
789int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
790 unsigned int flags)
791{
792 if (flags & FAULT_FLAG_ALLOW_RETRY) {
793 /*
794 * CAUTION! In this case, mmap_sem is not released
795 * even though return 0.
796 */
797 if (flags & FAULT_FLAG_RETRY_NOWAIT)
798 return 0;
799
800 up_read(&mm->mmap_sem);
801 if (flags & FAULT_FLAG_KILLABLE)
802 wait_on_page_locked_killable(page);
803 else
804 wait_on_page_locked(page);
805 return 0;
806 } else {
807 if (flags & FAULT_FLAG_KILLABLE) {
808 int ret;
809
810 ret = __lock_page_killable(page);
811 if (ret) {
812 up_read(&mm->mmap_sem);
813 return 0;
814 }
815 } else
816 __lock_page(page);
817 return 1;
818 }
819}
820
821/**
822 * page_cache_next_hole - find the next hole (not-present entry)
823 * @mapping: mapping
824 * @index: index
825 * @max_scan: maximum range to search
826 *
827 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
828 * lowest indexed hole.
829 *
830 * Returns: the index of the hole if found, otherwise returns an index
831 * outside of the set specified (in which case 'return - index >=
832 * max_scan' will be true). In rare cases of index wrap-around, 0 will
833 * be returned.
834 *
835 * page_cache_next_hole may be called under rcu_read_lock. However,
836 * like radix_tree_gang_lookup, this will not atomically search a
837 * snapshot of the tree at a single point in time. For example, if a
838 * hole is created at index 5, then subsequently a hole is created at
839 * index 10, page_cache_next_hole covering both indexes may return 10
840 * if called under rcu_read_lock.
841 */
842pgoff_t page_cache_next_hole(struct address_space *mapping,
843 pgoff_t index, unsigned long max_scan)
844{
845 unsigned long i;
846
847 for (i = 0; i < max_scan; i++) {
848 struct page *page;
849
850 page = radix_tree_lookup(&mapping->page_tree, index);
851 if (!page || radix_tree_exceptional_entry(page))
852 break;
853 index++;
854 if (index == 0)
855 break;
856 }
857
858 return index;
859}
860EXPORT_SYMBOL(page_cache_next_hole);
861
862/**
863 * page_cache_prev_hole - find the prev hole (not-present entry)
864 * @mapping: mapping
865 * @index: index
866 * @max_scan: maximum range to search
867 *
868 * Search backwards in the range [max(index-max_scan+1, 0), index] for
869 * the first hole.
870 *
871 * Returns: the index of the hole if found, otherwise returns an index
872 * outside of the set specified (in which case 'index - return >=
873 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
874 * will be returned.
875 *
876 * page_cache_prev_hole may be called under rcu_read_lock. However,
877 * like radix_tree_gang_lookup, this will not atomically search a
878 * snapshot of the tree at a single point in time. For example, if a
879 * hole is created at index 10, then subsequently a hole is created at
880 * index 5, page_cache_prev_hole covering both indexes may return 5 if
881 * called under rcu_read_lock.
882 */
883pgoff_t page_cache_prev_hole(struct address_space *mapping,
884 pgoff_t index, unsigned long max_scan)
885{
886 unsigned long i;
887
888 for (i = 0; i < max_scan; i++) {
889 struct page *page;
890
891 page = radix_tree_lookup(&mapping->page_tree, index);
892 if (!page || radix_tree_exceptional_entry(page))
893 break;
894 index--;
895 if (index == ULONG_MAX)
896 break;
897 }
898
899 return index;
900}
901EXPORT_SYMBOL(page_cache_prev_hole);
902
903/**
904 * find_get_entry - find and get a page cache entry
905 * @mapping: the address_space to search
906 * @offset: the page cache index
907 *
908 * Looks up the page cache slot at @mapping & @offset. If there is a
909 * page cache page, it is returned with an increased refcount.
910 *
911 * If the slot holds a shadow entry of a previously evicted page, or a
912 * swap entry from shmem/tmpfs, it is returned.
913 *
914 * Otherwise, %NULL is returned.
915 */
916struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
917{
918 void **pagep;
919 struct page *page;
920
921 rcu_read_lock();
922repeat:
923 page = NULL;
924 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
925 if (pagep) {
926 page = radix_tree_deref_slot(pagep);
927 if (unlikely(!page))
928 goto out;
929 if (radix_tree_exception(page)) {
930 if (radix_tree_deref_retry(page))
931 goto repeat;
932 /*
933 * A shadow entry of a recently evicted page,
934 * or a swap entry from shmem/tmpfs. Return
935 * it without attempting to raise page count.
936 */
937 goto out;
938 }
939 if (!page_cache_get_speculative(page))
940 goto repeat;
941
942 /*
943 * Has the page moved?
944 * This is part of the lockless pagecache protocol. See
945 * include/linux/pagemap.h for details.
946 */
947 if (unlikely(page != *pagep)) {
948 page_cache_release(page);
949 goto repeat;
950 }
951 }
952out:
953 rcu_read_unlock();
954
955 return page;
956}
957EXPORT_SYMBOL(find_get_entry);
958
959/**
960 * find_get_page - find and get a page reference
961 * @mapping: the address_space to search
962 * @offset: the page index
963 *
964 * Looks up the page cache slot at @mapping & @offset. If there is a
965 * page cache page, it is returned with an increased refcount.
966 *
967 * Otherwise, %NULL is returned.
968 */
969struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
970{
971 struct page *page = find_get_entry(mapping, offset);
972
973 if (radix_tree_exceptional_entry(page))
974 page = NULL;
975 return page;
976}
977EXPORT_SYMBOL(find_get_page);
978
979/**
980 * find_lock_entry - locate, pin and lock a page cache entry
981 * @mapping: the address_space to search
982 * @offset: the page cache index
983 *
984 * Looks up the page cache slot at @mapping & @offset. If there is a
985 * page cache page, it is returned locked and with an increased
986 * refcount.
987 *
988 * If the slot holds a shadow entry of a previously evicted page, or a
989 * swap entry from shmem/tmpfs, it is returned.
990 *
991 * Otherwise, %NULL is returned.
992 *
993 * find_lock_entry() may sleep.
994 */
995struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
996{
997 struct page *page;
998
999repeat:
1000 page = find_get_entry(mapping, offset);
1001 if (page && !radix_tree_exception(page)) {
1002 lock_page(page);
1003 /* Has the page been truncated? */
1004 if (unlikely(page->mapping != mapping)) {
1005 unlock_page(page);
1006 page_cache_release(page);
1007 goto repeat;
1008 }
1009 VM_BUG_ON_PAGE(page->index != offset, page);
1010 }
1011 return page;
1012}
1013EXPORT_SYMBOL(find_lock_entry);
1014
1015/**
1016 * find_lock_page - locate, pin and lock a pagecache page
1017 * @mapping: the address_space to search
1018 * @offset: the page index
1019 *
1020 * Looks up the page cache slot at @mapping & @offset. If there is a
1021 * page cache page, it is returned locked and with an increased
1022 * refcount.
1023 *
1024 * Otherwise, %NULL is returned.
1025 *
1026 * find_lock_page() may sleep.
1027 */
1028struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
1029{
1030 struct page *page = find_lock_entry(mapping, offset);
1031
1032 if (radix_tree_exceptional_entry(page))
1033 page = NULL;
1034 return page;
1035}
1036EXPORT_SYMBOL(find_lock_page);
1037
1038/**
1039 * find_or_create_page - locate or add a pagecache page
1040 * @mapping: the page's address_space
1041 * @index: the page's index into the mapping
1042 * @gfp_mask: page allocation mode
1043 *
1044 * Looks up the page cache slot at @mapping & @offset. If there is a
1045 * page cache page, it is returned locked and with an increased
1046 * refcount.
1047 *
1048 * If the page is not present, a new page is allocated using @gfp_mask
1049 * and added to the page cache and the VM's LRU list. The page is
1050 * returned locked and with an increased refcount.
1051 *
1052 * On memory exhaustion, %NULL is returned.
1053 *
1054 * find_or_create_page() may sleep, even if @gfp_flags specifies an
1055 * atomic allocation!
1056 */
1057struct page *find_or_create_page(struct address_space *mapping,
1058 pgoff_t index, gfp_t gfp_mask)
1059{
1060 struct page *page;
1061 int err;
1062repeat:
1063 page = find_lock_page(mapping, index);
1064 if (!page) {
1065 page = __page_cache_alloc(gfp_mask);
1066 if (!page)
1067 return NULL;
1068 /*
1069 * We want a regular kernel memory (not highmem or DMA etc)
1070 * allocation for the radix tree nodes, but we need to honour
1071 * the context-specific requirements the caller has asked for.
1072 * GFP_RECLAIM_MASK collects those requirements.
1073 */
1074 err = add_to_page_cache_lru(page, mapping, index,
1075 (gfp_mask & GFP_RECLAIM_MASK));
1076 if (unlikely(err)) {
1077 page_cache_release(page);
1078 page = NULL;
1079 if (err == -EEXIST)
1080 goto repeat;
1081 }
1082 }
1083 return page;
1084}
1085EXPORT_SYMBOL(find_or_create_page);
1086
1087/**
1088 * find_get_entries - gang pagecache lookup
1089 * @mapping: The address_space to search
1090 * @start: The starting page cache index
1091 * @nr_entries: The maximum number of entries
1092 * @entries: Where the resulting entries are placed
1093 * @indices: The cache indices corresponding to the entries in @entries
1094 *
1095 * find_get_entries() will search for and return a group of up to
1096 * @nr_entries entries in the mapping. The entries are placed at
1097 * @entries. find_get_entries() takes a reference against any actual
1098 * pages it returns.
1099 *
1100 * The search returns a group of mapping-contiguous page cache entries
1101 * with ascending indexes. There may be holes in the indices due to
1102 * not-present pages.
1103 *
1104 * Any shadow entries of evicted pages, or swap entries from
1105 * shmem/tmpfs, are included in the returned array.
1106 *
1107 * find_get_entries() returns the number of pages and shadow entries
1108 * which were found.
1109 */
1110unsigned find_get_entries(struct address_space *mapping,
1111 pgoff_t start, unsigned int nr_entries,
1112 struct page **entries, pgoff_t *indices)
1113{
1114 void **slot;
1115 unsigned int ret = 0;
1116 struct radix_tree_iter iter;
1117
1118 if (!nr_entries)
1119 return 0;
1120
1121 rcu_read_lock();
1122restart:
1123 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1124 struct page *page;
1125repeat:
1126 page = radix_tree_deref_slot(slot);
1127 if (unlikely(!page))
1128 continue;
1129 if (radix_tree_exception(page)) {
1130 if (radix_tree_deref_retry(page))
1131 goto restart;
1132 /*
1133 * A shadow entry of a recently evicted page,
1134 * or a swap entry from shmem/tmpfs. Return
1135 * it without attempting to raise page count.
1136 */
1137 goto export;
1138 }
1139 if (!page_cache_get_speculative(page))
1140 goto repeat;
1141
1142 /* Has the page moved? */
1143 if (unlikely(page != *slot)) {
1144 page_cache_release(page);
1145 goto repeat;
1146 }
1147export:
1148 indices[ret] = iter.index;
1149 entries[ret] = page;
1150 if (++ret == nr_entries)
1151 break;
1152 }
1153 rcu_read_unlock();
1154 return ret;
1155}
1156
1157/**
1158 * find_get_pages - gang pagecache lookup
1159 * @mapping: The address_space to search
1160 * @start: The starting page index
1161 * @nr_pages: The maximum number of pages
1162 * @pages: Where the resulting pages are placed
1163 *
1164 * find_get_pages() will search for and return a group of up to
1165 * @nr_pages pages in the mapping. The pages are placed at @pages.
1166 * find_get_pages() takes a reference against the returned pages.
1167 *
1168 * The search returns a group of mapping-contiguous pages with ascending
1169 * indexes. There may be holes in the indices due to not-present pages.
1170 *
1171 * find_get_pages() returns the number of pages which were found.
1172 */
1173unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1174 unsigned int nr_pages, struct page **pages)
1175{
1176 struct radix_tree_iter iter;
1177 void **slot;
1178 unsigned ret = 0;
1179
1180 if (unlikely(!nr_pages))
1181 return 0;
1182
1183 rcu_read_lock();
1184restart:
1185 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1186 struct page *page;
1187repeat:
1188 page = radix_tree_deref_slot(slot);
1189 if (unlikely(!page))
1190 continue;
1191
1192 if (radix_tree_exception(page)) {
1193 if (radix_tree_deref_retry(page)) {
1194 /*
1195 * Transient condition which can only trigger
1196 * when entry at index 0 moves out of or back
1197 * to root: none yet gotten, safe to restart.
1198 */
1199 WARN_ON(iter.index);
1200 goto restart;
1201 }
1202 /*
1203 * A shadow entry of a recently evicted page,
1204 * or a swap entry from shmem/tmpfs. Skip
1205 * over it.
1206 */
1207 continue;
1208 }
1209
1210 if (!page_cache_get_speculative(page))
1211 goto repeat;
1212
1213 /* Has the page moved? */
1214 if (unlikely(page != *slot)) {
1215 page_cache_release(page);
1216 goto repeat;
1217 }
1218
1219 pages[ret] = page;
1220 if (++ret == nr_pages)
1221 break;
1222 }
1223
1224 rcu_read_unlock();
1225 return ret;
1226}
1227
1228/**
1229 * find_get_pages_contig - gang contiguous pagecache lookup
1230 * @mapping: The address_space to search
1231 * @index: The starting page index
1232 * @nr_pages: The maximum number of pages
1233 * @pages: Where the resulting pages are placed
1234 *
1235 * find_get_pages_contig() works exactly like find_get_pages(), except
1236 * that the returned number of pages are guaranteed to be contiguous.
1237 *
1238 * find_get_pages_contig() returns the number of pages which were found.
1239 */
1240unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1241 unsigned int nr_pages, struct page **pages)
1242{
1243 struct radix_tree_iter iter;
1244 void **slot;
1245 unsigned int ret = 0;
1246
1247 if (unlikely(!nr_pages))
1248 return 0;
1249
1250 rcu_read_lock();
1251restart:
1252 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1253 struct page *page;
1254repeat:
1255 page = radix_tree_deref_slot(slot);
1256 /* The hole, there no reason to continue */
1257 if (unlikely(!page))
1258 break;
1259
1260 if (radix_tree_exception(page)) {
1261 if (radix_tree_deref_retry(page)) {
1262 /*
1263 * Transient condition which can only trigger
1264 * when entry at index 0 moves out of or back
1265 * to root: none yet gotten, safe to restart.
1266 */
1267 goto restart;
1268 }
1269 /*
1270 * A shadow entry of a recently evicted page,
1271 * or a swap entry from shmem/tmpfs. Stop
1272 * looking for contiguous pages.
1273 */
1274 break;
1275 }
1276
1277 if (!page_cache_get_speculative(page))
1278 goto repeat;
1279
1280 /* Has the page moved? */
1281 if (unlikely(page != *slot)) {
1282 page_cache_release(page);
1283 goto repeat;
1284 }
1285
1286 /*
1287 * must check mapping and index after taking the ref.
1288 * otherwise we can get both false positives and false
1289 * negatives, which is just confusing to the caller.
1290 */
1291 if (page->mapping == NULL || page->index != iter.index) {
1292 page_cache_release(page);
1293 break;
1294 }
1295
1296 pages[ret] = page;
1297 if (++ret == nr_pages)
1298 break;
1299 }
1300 rcu_read_unlock();
1301 return ret;
1302}
1303EXPORT_SYMBOL(find_get_pages_contig);
1304
1305/**
1306 * find_get_pages_tag - find and return pages that match @tag
1307 * @mapping: the address_space to search
1308 * @index: the starting page index
1309 * @tag: the tag index
1310 * @nr_pages: the maximum number of pages
1311 * @pages: where the resulting pages are placed
1312 *
1313 * Like find_get_pages, except we only return pages which are tagged with
1314 * @tag. We update @index to index the next page for the traversal.
1315 */
1316unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1317 int tag, unsigned int nr_pages, struct page **pages)
1318{
1319 struct radix_tree_iter iter;
1320 void **slot;
1321 unsigned ret = 0;
1322
1323 if (unlikely(!nr_pages))
1324 return 0;
1325
1326 rcu_read_lock();
1327restart:
1328 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1329 &iter, *index, tag) {
1330 struct page *page;
1331repeat:
1332 page = radix_tree_deref_slot(slot);
1333 if (unlikely(!page))
1334 continue;
1335
1336 if (radix_tree_exception(page)) {
1337 if (radix_tree_deref_retry(page)) {
1338 /*
1339 * Transient condition which can only trigger
1340 * when entry at index 0 moves out of or back
1341 * to root: none yet gotten, safe to restart.
1342 */
1343 goto restart;
1344 }
1345 /*
1346 * A shadow entry of a recently evicted page.
1347 *
1348 * Those entries should never be tagged, but
1349 * this tree walk is lockless and the tags are
1350 * looked up in bulk, one radix tree node at a
1351 * time, so there is a sizable window for page
1352 * reclaim to evict a page we saw tagged.
1353 *
1354 * Skip over it.
1355 */
1356 continue;
1357 }
1358
1359 if (!page_cache_get_speculative(page))
1360 goto repeat;
1361
1362 /* Has the page moved? */
1363 if (unlikely(page != *slot)) {
1364 page_cache_release(page);
1365 goto repeat;
1366 }
1367
1368 pages[ret] = page;
1369 if (++ret == nr_pages)
1370 break;
1371 }
1372
1373 rcu_read_unlock();
1374
1375 if (ret)
1376 *index = pages[ret - 1]->index + 1;
1377
1378 return ret;
1379}
1380EXPORT_SYMBOL(find_get_pages_tag);
1381
1382/**
1383 * grab_cache_page_nowait - returns locked page at given index in given cache
1384 * @mapping: target address_space
1385 * @index: the page index
1386 *
1387 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1388 * This is intended for speculative data generators, where the data can
1389 * be regenerated if the page couldn't be grabbed. This routine should
1390 * be safe to call while holding the lock for another page.
1391 *
1392 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1393 * and deadlock against the caller's locked page.
1394 */
1395struct page *
1396grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1397{
1398 struct page *page = find_get_page(mapping, index);
1399
1400 if (page) {
1401 if (trylock_page(page))
1402 return page;
1403 page_cache_release(page);
1404 return NULL;
1405 }
1406 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1407 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1408 page_cache_release(page);
1409 page = NULL;
1410 }
1411 return page;
1412}
1413EXPORT_SYMBOL(grab_cache_page_nowait);
1414
1415/*
1416 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1417 * a _large_ part of the i/o request. Imagine the worst scenario:
1418 *
1419 * ---R__________________________________________B__________
1420 * ^ reading here ^ bad block(assume 4k)
1421 *
1422 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1423 * => failing the whole request => read(R) => read(R+1) =>
1424 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1425 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1426 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1427 *
1428 * It is going insane. Fix it by quickly scaling down the readahead size.
1429 */
1430static void shrink_readahead_size_eio(struct file *filp,
1431 struct file_ra_state *ra)
1432{
1433 ra->ra_pages /= 4;
1434}
1435
1436/**
1437 * do_generic_file_read - generic file read routine
1438 * @filp: the file to read
1439 * @ppos: current file position
1440 * @iter: data destination
1441 * @written: already copied
1442 *
1443 * This is a generic file read routine, and uses the
1444 * mapping->a_ops->readpage() function for the actual low-level stuff.
1445 *
1446 * This is really ugly. But the goto's actually try to clarify some
1447 * of the logic when it comes to error handling etc.
1448 */
1449static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1450 struct iov_iter *iter, ssize_t written)
1451{
1452 struct address_space *mapping = filp->f_mapping;
1453 struct inode *inode = mapping->host;
1454 struct file_ra_state *ra = &filp->f_ra;
1455 pgoff_t index;
1456 pgoff_t last_index;
1457 pgoff_t prev_index;
1458 unsigned long offset; /* offset into pagecache page */
1459 unsigned int prev_offset;
1460 int error = 0;
1461
1462 index = *ppos >> PAGE_CACHE_SHIFT;
1463 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1464 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1465 last_index = (*ppos + iter->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1466 offset = *ppos & ~PAGE_CACHE_MASK;
1467
1468 for (;;) {
1469 struct page *page;
1470 pgoff_t end_index;
1471 loff_t isize;
1472 unsigned long nr, ret;
1473
1474 cond_resched();
1475find_page:
1476 page = find_get_page(mapping, index);
1477 if (!page) {
1478 page_cache_sync_readahead(mapping,
1479 ra, filp,
1480 index, last_index - index);
1481 page = find_get_page(mapping, index);
1482 if (unlikely(page == NULL))
1483 goto no_cached_page;
1484 }
1485 if (PageReadahead(page)) {
1486 page_cache_async_readahead(mapping,
1487 ra, filp, page,
1488 index, last_index - index);
1489 }
1490 if (!PageUptodate(page)) {
1491 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1492 !mapping->a_ops->is_partially_uptodate)
1493 goto page_not_up_to_date;
1494 if (!trylock_page(page))
1495 goto page_not_up_to_date;
1496 /* Did it get truncated before we got the lock? */
1497 if (!page->mapping)
1498 goto page_not_up_to_date_locked;
1499 if (!mapping->a_ops->is_partially_uptodate(page,
1500 offset, iter->count))
1501 goto page_not_up_to_date_locked;
1502 unlock_page(page);
1503 }
1504page_ok:
1505 /*
1506 * i_size must be checked after we know the page is Uptodate.
1507 *
1508 * Checking i_size after the check allows us to calculate
1509 * the correct value for "nr", which means the zero-filled
1510 * part of the page is not copied back to userspace (unless
1511 * another truncate extends the file - this is desired though).
1512 */
1513
1514 isize = i_size_read(inode);
1515 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1516 if (unlikely(!isize || index > end_index)) {
1517 page_cache_release(page);
1518 goto out;
1519 }
1520
1521 /* nr is the maximum number of bytes to copy from this page */
1522 nr = PAGE_CACHE_SIZE;
1523 if (index == end_index) {
1524 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1525 if (nr <= offset) {
1526 page_cache_release(page);
1527 goto out;
1528 }
1529 }
1530 nr = nr - offset;
1531
1532 /* If users can be writing to this page using arbitrary
1533 * virtual addresses, take care about potential aliasing
1534 * before reading the page on the kernel side.
1535 */
1536 if (mapping_writably_mapped(mapping))
1537 flush_dcache_page(page);
1538
1539 /*
1540 * When a sequential read accesses a page several times,
1541 * only mark it as accessed the first time.
1542 */
1543 if (prev_index != index || offset != prev_offset)
1544 mark_page_accessed(page);
1545 prev_index = index;
1546
1547 /*
1548 * Ok, we have the page, and it's up-to-date, so
1549 * now we can copy it to user space...
1550 */
1551
1552 ret = copy_page_to_iter(page, offset, nr, iter);
1553 offset += ret;
1554 index += offset >> PAGE_CACHE_SHIFT;
1555 offset &= ~PAGE_CACHE_MASK;
1556 prev_offset = offset;
1557
1558 page_cache_release(page);
1559 written += ret;
1560 if (!iov_iter_count(iter))
1561 goto out;
1562 if (ret < nr) {
1563 error = -EFAULT;
1564 goto out;
1565 }
1566 continue;
1567
1568page_not_up_to_date:
1569 /* Get exclusive access to the page ... */
1570 error = lock_page_killable(page);
1571 if (unlikely(error))
1572 goto readpage_error;
1573
1574page_not_up_to_date_locked:
1575 /* Did it get truncated before we got the lock? */
1576 if (!page->mapping) {
1577 unlock_page(page);
1578 page_cache_release(page);
1579 continue;
1580 }
1581
1582 /* Did somebody else fill it already? */
1583 if (PageUptodate(page)) {
1584 unlock_page(page);
1585 goto page_ok;
1586 }
1587
1588readpage:
1589 /*
1590 * A previous I/O error may have been due to temporary
1591 * failures, eg. multipath errors.
1592 * PG_error will be set again if readpage fails.
1593 */
1594 ClearPageError(page);
1595 /* Start the actual read. The read will unlock the page. */
1596 error = mapping->a_ops->readpage(filp, page);
1597
1598 if (unlikely(error)) {
1599 if (error == AOP_TRUNCATED_PAGE) {
1600 page_cache_release(page);
1601 error = 0;
1602 goto find_page;
1603 }
1604 goto readpage_error;
1605 }
1606
1607 if (!PageUptodate(page)) {
1608 error = lock_page_killable(page);
1609 if (unlikely(error))
1610 goto readpage_error;
1611 if (!PageUptodate(page)) {
1612 if (page->mapping == NULL) {
1613 /*
1614 * invalidate_mapping_pages got it
1615 */
1616 unlock_page(page);
1617 page_cache_release(page);
1618 goto find_page;
1619 }
1620 unlock_page(page);
1621 shrink_readahead_size_eio(filp, ra);
1622 error = -EIO;
1623 goto readpage_error;
1624 }
1625 unlock_page(page);
1626 }
1627
1628 goto page_ok;
1629
1630readpage_error:
1631 /* UHHUH! A synchronous read error occurred. Report it */
1632 page_cache_release(page);
1633 goto out;
1634
1635no_cached_page:
1636 /*
1637 * Ok, it wasn't cached, so we need to create a new
1638 * page..
1639 */
1640 page = page_cache_alloc_cold(mapping);
1641 if (!page) {
1642 error = -ENOMEM;
1643 goto out;
1644 }
1645 error = add_to_page_cache_lru(page, mapping,
1646 index, GFP_KERNEL);
1647 if (error) {
1648 page_cache_release(page);
1649 if (error == -EEXIST) {
1650 error = 0;
1651 goto find_page;
1652 }
1653 goto out;
1654 }
1655 goto readpage;
1656 }
1657
1658out:
1659 ra->prev_pos = prev_index;
1660 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1661 ra->prev_pos |= prev_offset;
1662
1663 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1664 file_accessed(filp);
1665 return written ? written : error;
1666}
1667
1668/*
1669 * Performs necessary checks before doing a write
1670 * @iov: io vector request
1671 * @nr_segs: number of segments in the iovec
1672 * @count: number of bytes to write
1673 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1674 *
1675 * Adjust number of segments and amount of bytes to write (nr_segs should be
1676 * properly initialized first). Returns appropriate error code that caller
1677 * should return or zero in case that write should be allowed.
1678 */
1679int generic_segment_checks(const struct iovec *iov,
1680 unsigned long *nr_segs, size_t *count, int access_flags)
1681{
1682 unsigned long seg;
1683 size_t cnt = 0;
1684 for (seg = 0; seg < *nr_segs; seg++) {
1685 const struct iovec *iv = &iov[seg];
1686
1687 /*
1688 * If any segment has a negative length, or the cumulative
1689 * length ever wraps negative then return -EINVAL.
1690 */
1691 cnt += iv->iov_len;
1692 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1693 return -EINVAL;
1694 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1695 continue;
1696 if (seg == 0)
1697 return -EFAULT;
1698 *nr_segs = seg;
1699 cnt -= iv->iov_len; /* This segment is no good */
1700 break;
1701 }
1702 *count = cnt;
1703 return 0;
1704}
1705EXPORT_SYMBOL(generic_segment_checks);
1706
1707/**
1708 * generic_file_aio_read - generic filesystem read routine
1709 * @iocb: kernel I/O control block
1710 * @iov: io vector request
1711 * @nr_segs: number of segments in the iovec
1712 * @pos: current file position
1713 *
1714 * This is the "read()" routine for all filesystems
1715 * that can use the page cache directly.
1716 */
1717ssize_t
1718generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1719 unsigned long nr_segs, loff_t pos)
1720{
1721 struct file *filp = iocb->ki_filp;
1722 ssize_t retval;
1723 size_t count;
1724 loff_t *ppos = &iocb->ki_pos;
1725 struct iov_iter i;
1726
1727 count = 0;
1728 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1729 if (retval)
1730 return retval;
1731 iov_iter_init(&i, iov, nr_segs, count, 0);
1732
1733 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1734 if (filp->f_flags & O_DIRECT) {
1735 loff_t size;
1736 struct address_space *mapping;
1737 struct inode *inode;
1738
1739 mapping = filp->f_mapping;
1740 inode = mapping->host;
1741 if (!count)
1742 goto out; /* skip atime */
1743 size = i_size_read(inode);
1744 retval = filemap_write_and_wait_range(mapping, pos,
1745 pos + iov_length(iov, nr_segs) - 1);
1746 if (!retval) {
1747 retval = mapping->a_ops->direct_IO(READ, iocb,
1748 iov, pos, nr_segs);
1749 }
1750 if (retval > 0) {
1751 *ppos = pos + retval;
1752 count -= retval;
1753 /*
1754 * If we did a short DIO read we need to skip the
1755 * section of the iov that we've already read data into.
1756 */
1757 iov_iter_advance(&i, retval);
1758 }
1759
1760 /*
1761 * Btrfs can have a short DIO read if we encounter
1762 * compressed extents, so if there was an error, or if
1763 * we've already read everything we wanted to, or if
1764 * there was a short read because we hit EOF, go ahead
1765 * and return. Otherwise fallthrough to buffered io for
1766 * the rest of the read.
1767 */
1768 if (retval < 0 || !count || *ppos >= size) {
1769 file_accessed(filp);
1770 goto out;
1771 }
1772 }
1773
1774 retval = do_generic_file_read(filp, ppos, &i, retval);
1775out:
1776 return retval;
1777}
1778EXPORT_SYMBOL(generic_file_aio_read);
1779
1780#ifdef CONFIG_MMU
1781/**
1782 * page_cache_read - adds requested page to the page cache if not already there
1783 * @file: file to read
1784 * @offset: page index
1785 *
1786 * This adds the requested page to the page cache if it isn't already there,
1787 * and schedules an I/O to read in its contents from disk.
1788 */
1789static int page_cache_read(struct file *file, pgoff_t offset)
1790{
1791 struct address_space *mapping = file->f_mapping;
1792 struct page *page;
1793 int ret;
1794
1795 do {
1796 page = page_cache_alloc_cold(mapping);
1797 if (!page)
1798 return -ENOMEM;
1799
1800 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1801 if (ret == 0)
1802 ret = mapping->a_ops->readpage(file, page);
1803 else if (ret == -EEXIST)
1804 ret = 0; /* losing race to add is OK */
1805
1806 page_cache_release(page);
1807
1808 } while (ret == AOP_TRUNCATED_PAGE);
1809
1810 return ret;
1811}
1812
1813#define MMAP_LOTSAMISS (100)
1814
1815/*
1816 * Synchronous readahead happens when we don't even find
1817 * a page in the page cache at all.
1818 */
1819static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1820 struct file_ra_state *ra,
1821 struct file *file,
1822 pgoff_t offset)
1823{
1824 unsigned long ra_pages;
1825 struct address_space *mapping = file->f_mapping;
1826
1827 /* If we don't want any read-ahead, don't bother */
1828 if (vma->vm_flags & VM_RAND_READ)
1829 return;
1830 if (!ra->ra_pages)
1831 return;
1832
1833 if (vma->vm_flags & VM_SEQ_READ) {
1834 page_cache_sync_readahead(mapping, ra, file, offset,
1835 ra->ra_pages);
1836 return;
1837 }
1838
1839 /* Avoid banging the cache line if not needed */
1840 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1841 ra->mmap_miss++;
1842
1843 /*
1844 * Do we miss much more than hit in this file? If so,
1845 * stop bothering with read-ahead. It will only hurt.
1846 */
1847 if (ra->mmap_miss > MMAP_LOTSAMISS)
1848 return;
1849
1850 /*
1851 * mmap read-around
1852 */
1853 ra_pages = max_sane_readahead(ra->ra_pages);
1854 ra->start = max_t(long, 0, offset - ra_pages / 2);
1855 ra->size = ra_pages;
1856 ra->async_size = ra_pages / 4;
1857 ra_submit(ra, mapping, file);
1858}
1859
1860/*
1861 * Asynchronous readahead happens when we find the page and PG_readahead,
1862 * so we want to possibly extend the readahead further..
1863 */
1864static void do_async_mmap_readahead(struct vm_area_struct *vma,
1865 struct file_ra_state *ra,
1866 struct file *file,
1867 struct page *page,
1868 pgoff_t offset)
1869{
1870 struct address_space *mapping = file->f_mapping;
1871
1872 /* If we don't want any read-ahead, don't bother */
1873 if (vma->vm_flags & VM_RAND_READ)
1874 return;
1875 if (ra->mmap_miss > 0)
1876 ra->mmap_miss--;
1877 if (PageReadahead(page))
1878 page_cache_async_readahead(mapping, ra, file,
1879 page, offset, ra->ra_pages);
1880}
1881
1882/**
1883 * filemap_fault - read in file data for page fault handling
1884 * @vma: vma in which the fault was taken
1885 * @vmf: struct vm_fault containing details of the fault
1886 *
1887 * filemap_fault() is invoked via the vma operations vector for a
1888 * mapped memory region to read in file data during a page fault.
1889 *
1890 * The goto's are kind of ugly, but this streamlines the normal case of having
1891 * it in the page cache, and handles the special cases reasonably without
1892 * having a lot of duplicated code.
1893 */
1894int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1895{
1896 int error;
1897 struct file *file = vma->vm_file;
1898 struct address_space *mapping = file->f_mapping;
1899 struct file_ra_state *ra = &file->f_ra;
1900 struct inode *inode = mapping->host;
1901 pgoff_t offset = vmf->pgoff;
1902 struct page *page;
1903 loff_t size;
1904 int ret = 0;
1905
1906 size = round_up(i_size_read(inode), PAGE_CACHE_SIZE);
1907 if (offset >= size >> PAGE_CACHE_SHIFT)
1908 return VM_FAULT_SIGBUS;
1909
1910 /*
1911 * Do we have something in the page cache already?
1912 */
1913 page = find_get_page(mapping, offset);
1914 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
1915 /*
1916 * We found the page, so try async readahead before
1917 * waiting for the lock.
1918 */
1919 do_async_mmap_readahead(vma, ra, file, page, offset);
1920 } else if (!page) {
1921 /* No page in the page cache at all */
1922 do_sync_mmap_readahead(vma, ra, file, offset);
1923 count_vm_event(PGMAJFAULT);
1924 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1925 ret = VM_FAULT_MAJOR;
1926retry_find:
1927 page = find_get_page(mapping, offset);
1928 if (!page)
1929 goto no_cached_page;
1930 }
1931
1932 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1933 page_cache_release(page);
1934 return ret | VM_FAULT_RETRY;
1935 }
1936
1937 /* Did it get truncated? */
1938 if (unlikely(page->mapping != mapping)) {
1939 unlock_page(page);
1940 put_page(page);
1941 goto retry_find;
1942 }
1943 VM_BUG_ON_PAGE(page->index != offset, page);
1944
1945 /*
1946 * We have a locked page in the page cache, now we need to check
1947 * that it's up-to-date. If not, it is going to be due to an error.
1948 */
1949 if (unlikely(!PageUptodate(page)))
1950 goto page_not_uptodate;
1951
1952 /*
1953 * Found the page and have a reference on it.
1954 * We must recheck i_size under page lock.
1955 */
1956 size = round_up(i_size_read(inode), PAGE_CACHE_SIZE);
1957 if (unlikely(offset >= size >> PAGE_CACHE_SHIFT)) {
1958 unlock_page(page);
1959 page_cache_release(page);
1960 return VM_FAULT_SIGBUS;
1961 }
1962
1963 vmf->page = page;
1964 return ret | VM_FAULT_LOCKED;
1965
1966no_cached_page:
1967 /*
1968 * We're only likely to ever get here if MADV_RANDOM is in
1969 * effect.
1970 */
1971 error = page_cache_read(file, offset);
1972
1973 /*
1974 * The page we want has now been added to the page cache.
1975 * In the unlikely event that someone removed it in the
1976 * meantime, we'll just come back here and read it again.
1977 */
1978 if (error >= 0)
1979 goto retry_find;
1980
1981 /*
1982 * An error return from page_cache_read can result if the
1983 * system is low on memory, or a problem occurs while trying
1984 * to schedule I/O.
1985 */
1986 if (error == -ENOMEM)
1987 return VM_FAULT_OOM;
1988 return VM_FAULT_SIGBUS;
1989
1990page_not_uptodate:
1991 /*
1992 * Umm, take care of errors if the page isn't up-to-date.
1993 * Try to re-read it _once_. We do this synchronously,
1994 * because there really aren't any performance issues here
1995 * and we need to check for errors.
1996 */
1997 ClearPageError(page);
1998 error = mapping->a_ops->readpage(file, page);
1999 if (!error) {
2000 wait_on_page_locked(page);
2001 if (!PageUptodate(page))
2002 error = -EIO;
2003 }
2004 page_cache_release(page);
2005
2006 if (!error || error == AOP_TRUNCATED_PAGE)
2007 goto retry_find;
2008
2009 /* Things didn't work out. Return zero to tell the mm layer so. */
2010 shrink_readahead_size_eio(file, ra);
2011 return VM_FAULT_SIGBUS;
2012}
2013EXPORT_SYMBOL(filemap_fault);
2014
2015void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
2016{
2017 struct radix_tree_iter iter;
2018 void **slot;
2019 struct file *file = vma->vm_file;
2020 struct address_space *mapping = file->f_mapping;
2021 loff_t size;
2022 struct page *page;
2023 unsigned long address = (unsigned long) vmf->virtual_address;
2024 unsigned long addr;
2025 pte_t *pte;
2026
2027 rcu_read_lock();
2028 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, vmf->pgoff) {
2029 if (iter.index > vmf->max_pgoff)
2030 break;
2031repeat:
2032 page = radix_tree_deref_slot(slot);
2033 if (unlikely(!page))
2034 goto next;
2035 if (radix_tree_exception(page)) {
2036 if (radix_tree_deref_retry(page))
2037 break;
2038 else
2039 goto next;
2040 }
2041
2042 if (!page_cache_get_speculative(page))
2043 goto repeat;
2044
2045 /* Has the page moved? */
2046 if (unlikely(page != *slot)) {
2047 page_cache_release(page);
2048 goto repeat;
2049 }
2050
2051 if (!PageUptodate(page) ||
2052 PageReadahead(page) ||
2053 PageHWPoison(page))
2054 goto skip;
2055 if (!trylock_page(page))
2056 goto skip;
2057
2058 if (page->mapping != mapping || !PageUptodate(page))
2059 goto unlock;
2060
2061 size = round_up(i_size_read(mapping->host), PAGE_CACHE_SIZE);
2062 if (page->index >= size >> PAGE_CACHE_SHIFT)
2063 goto unlock;
2064
2065 pte = vmf->pte + page->index - vmf->pgoff;
2066 if (!pte_none(*pte))
2067 goto unlock;
2068
2069 if (file->f_ra.mmap_miss > 0)
2070 file->f_ra.mmap_miss--;
2071 addr = address + (page->index - vmf->pgoff) * PAGE_SIZE;
2072 do_set_pte(vma, addr, page, pte, false, false);
2073 unlock_page(page);
2074 goto next;
2075unlock:
2076 unlock_page(page);
2077skip:
2078 page_cache_release(page);
2079next:
2080 if (iter.index == vmf->max_pgoff)
2081 break;
2082 }
2083 rcu_read_unlock();
2084}
2085EXPORT_SYMBOL(filemap_map_pages);
2086
2087int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
2088{
2089 struct page *page = vmf->page;
2090 struct inode *inode = file_inode(vma->vm_file);
2091 int ret = VM_FAULT_LOCKED;
2092
2093 sb_start_pagefault(inode->i_sb);
2094 file_update_time(vma->vm_file);
2095 lock_page(page);
2096 if (page->mapping != inode->i_mapping) {
2097 unlock_page(page);
2098 ret = VM_FAULT_NOPAGE;
2099 goto out;
2100 }
2101 /*
2102 * We mark the page dirty already here so that when freeze is in
2103 * progress, we are guaranteed that writeback during freezing will
2104 * see the dirty page and writeprotect it again.
2105 */
2106 set_page_dirty(page);
2107 wait_for_stable_page(page);
2108out:
2109 sb_end_pagefault(inode->i_sb);
2110 return ret;
2111}
2112EXPORT_SYMBOL(filemap_page_mkwrite);
2113
2114const struct vm_operations_struct generic_file_vm_ops = {
2115 .fault = filemap_fault,
2116 .map_pages = filemap_map_pages,
2117 .page_mkwrite = filemap_page_mkwrite,
2118 .remap_pages = generic_file_remap_pages,
2119};
2120
2121/* This is used for a general mmap of a disk file */
2122
2123int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2124{
2125 struct address_space *mapping = file->f_mapping;
2126
2127 if (!mapping->a_ops->readpage)
2128 return -ENOEXEC;
2129 file_accessed(file);
2130 vma->vm_ops = &generic_file_vm_ops;
2131 return 0;
2132}
2133
2134/*
2135 * This is for filesystems which do not implement ->writepage.
2136 */
2137int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2138{
2139 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2140 return -EINVAL;
2141 return generic_file_mmap(file, vma);
2142}
2143#else
2144int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2145{
2146 return -ENOSYS;
2147}
2148int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2149{
2150 return -ENOSYS;
2151}
2152#endif /* CONFIG_MMU */
2153
2154EXPORT_SYMBOL(generic_file_mmap);
2155EXPORT_SYMBOL(generic_file_readonly_mmap);
2156
2157static struct page *wait_on_page_read(struct page *page)
2158{
2159 if (!IS_ERR(page)) {
2160 wait_on_page_locked(page);
2161 if (!PageUptodate(page)) {
2162 page_cache_release(page);
2163 page = ERR_PTR(-EIO);
2164 }
2165 }
2166 return page;
2167}
2168
2169static struct page *__read_cache_page(struct address_space *mapping,
2170 pgoff_t index,
2171 int (*filler)(void *, struct page *),
2172 void *data,
2173 gfp_t gfp)
2174{
2175 struct page *page;
2176 int err;
2177repeat:
2178 page = find_get_page(mapping, index);
2179 if (!page) {
2180 page = __page_cache_alloc(gfp | __GFP_COLD);
2181 if (!page)
2182 return ERR_PTR(-ENOMEM);
2183 err = add_to_page_cache_lru(page, mapping, index, gfp);
2184 if (unlikely(err)) {
2185 page_cache_release(page);
2186 if (err == -EEXIST)
2187 goto repeat;
2188 /* Presumably ENOMEM for radix tree node */
2189 return ERR_PTR(err);
2190 }
2191 err = filler(data, page);
2192 if (err < 0) {
2193 page_cache_release(page);
2194 page = ERR_PTR(err);
2195 } else {
2196 page = wait_on_page_read(page);
2197 }
2198 }
2199 return page;
2200}
2201
2202static struct page *do_read_cache_page(struct address_space *mapping,
2203 pgoff_t index,
2204 int (*filler)(void *, struct page *),
2205 void *data,
2206 gfp_t gfp)
2207
2208{
2209 struct page *page;
2210 int err;
2211
2212retry:
2213 page = __read_cache_page(mapping, index, filler, data, gfp);
2214 if (IS_ERR(page))
2215 return page;
2216 if (PageUptodate(page))
2217 goto out;
2218
2219 lock_page(page);
2220 if (!page->mapping) {
2221 unlock_page(page);
2222 page_cache_release(page);
2223 goto retry;
2224 }
2225 if (PageUptodate(page)) {
2226 unlock_page(page);
2227 goto out;
2228 }
2229 err = filler(data, page);
2230 if (err < 0) {
2231 page_cache_release(page);
2232 return ERR_PTR(err);
2233 } else {
2234 page = wait_on_page_read(page);
2235 if (IS_ERR(page))
2236 return page;
2237 }
2238out:
2239 mark_page_accessed(page);
2240 return page;
2241}
2242
2243/**
2244 * read_cache_page - read into page cache, fill it if needed
2245 * @mapping: the page's address_space
2246 * @index: the page index
2247 * @filler: function to perform the read
2248 * @data: first arg to filler(data, page) function, often left as NULL
2249 *
2250 * Read into the page cache. If a page already exists, and PageUptodate() is
2251 * not set, try to fill the page and wait for it to become unlocked.
2252 *
2253 * If the page does not get brought uptodate, return -EIO.
2254 */
2255struct page *read_cache_page(struct address_space *mapping,
2256 pgoff_t index,
2257 int (*filler)(void *, struct page *),
2258 void *data)
2259{
2260 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2261}
2262EXPORT_SYMBOL(read_cache_page);
2263
2264/**
2265 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2266 * @mapping: the page's address_space
2267 * @index: the page index
2268 * @gfp: the page allocator flags to use if allocating
2269 *
2270 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2271 * any new page allocations done using the specified allocation flags.
2272 *
2273 * If the page does not get brought uptodate, return -EIO.
2274 */
2275struct page *read_cache_page_gfp(struct address_space *mapping,
2276 pgoff_t index,
2277 gfp_t gfp)
2278{
2279 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2280
2281 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2282}
2283EXPORT_SYMBOL(read_cache_page_gfp);
2284
2285/*
2286 * Performs necessary checks before doing a write
2287 *
2288 * Can adjust writing position or amount of bytes to write.
2289 * Returns appropriate error code that caller should return or
2290 * zero in case that write should be allowed.
2291 */
2292inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2293{
2294 struct inode *inode = file->f_mapping->host;
2295 unsigned long limit = rlimit(RLIMIT_FSIZE);
2296
2297 if (unlikely(*pos < 0))
2298 return -EINVAL;
2299
2300 if (!isblk) {
2301 /* FIXME: this is for backwards compatibility with 2.4 */
2302 if (file->f_flags & O_APPEND)
2303 *pos = i_size_read(inode);
2304
2305 if (limit != RLIM_INFINITY) {
2306 if (*pos >= limit) {
2307 send_sig(SIGXFSZ, current, 0);
2308 return -EFBIG;
2309 }
2310 if (*count > limit - (typeof(limit))*pos) {
2311 *count = limit - (typeof(limit))*pos;
2312 }
2313 }
2314 }
2315
2316 /*
2317 * LFS rule
2318 */
2319 if (unlikely(*pos + *count > MAX_NON_LFS &&
2320 !(file->f_flags & O_LARGEFILE))) {
2321 if (*pos >= MAX_NON_LFS) {
2322 return -EFBIG;
2323 }
2324 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2325 *count = MAX_NON_LFS - (unsigned long)*pos;
2326 }
2327 }
2328
2329 /*
2330 * Are we about to exceed the fs block limit ?
2331 *
2332 * If we have written data it becomes a short write. If we have
2333 * exceeded without writing data we send a signal and return EFBIG.
2334 * Linus frestrict idea will clean these up nicely..
2335 */
2336 if (likely(!isblk)) {
2337 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2338 if (*count || *pos > inode->i_sb->s_maxbytes) {
2339 return -EFBIG;
2340 }
2341 /* zero-length writes at ->s_maxbytes are OK */
2342 }
2343
2344 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2345 *count = inode->i_sb->s_maxbytes - *pos;
2346 } else {
2347#ifdef CONFIG_BLOCK
2348 loff_t isize;
2349 if (bdev_read_only(I_BDEV(inode)))
2350 return -EPERM;
2351 isize = i_size_read(inode);
2352 if (*pos >= isize) {
2353 if (*count || *pos > isize)
2354 return -ENOSPC;
2355 }
2356
2357 if (*pos + *count > isize)
2358 *count = isize - *pos;
2359#else
2360 return -EPERM;
2361#endif
2362 }
2363 return 0;
2364}
2365EXPORT_SYMBOL(generic_write_checks);
2366
2367int pagecache_write_begin(struct file *file, struct address_space *mapping,
2368 loff_t pos, unsigned len, unsigned flags,
2369 struct page **pagep, void **fsdata)
2370{
2371 const struct address_space_operations *aops = mapping->a_ops;
2372
2373 return aops->write_begin(file, mapping, pos, len, flags,
2374 pagep, fsdata);
2375}
2376EXPORT_SYMBOL(pagecache_write_begin);
2377
2378int pagecache_write_end(struct file *file, struct address_space *mapping,
2379 loff_t pos, unsigned len, unsigned copied,
2380 struct page *page, void *fsdata)
2381{
2382 const struct address_space_operations *aops = mapping->a_ops;
2383
2384 mark_page_accessed(page);
2385 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2386}
2387EXPORT_SYMBOL(pagecache_write_end);
2388
2389ssize_t
2390generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2391 unsigned long *nr_segs, loff_t pos,
2392 size_t count, size_t ocount)
2393{
2394 struct file *file = iocb->ki_filp;
2395 struct address_space *mapping = file->f_mapping;
2396 struct inode *inode = mapping->host;
2397 ssize_t written;
2398 size_t write_len;
2399 pgoff_t end;
2400
2401 if (count != ocount)
2402 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2403
2404 write_len = iov_length(iov, *nr_segs);
2405 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2406
2407 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2408 if (written)
2409 goto out;
2410
2411 /*
2412 * After a write we want buffered reads to be sure to go to disk to get
2413 * the new data. We invalidate clean cached page from the region we're
2414 * about to write. We do this *before* the write so that we can return
2415 * without clobbering -EIOCBQUEUED from ->direct_IO().
2416 */
2417 if (mapping->nrpages) {
2418 written = invalidate_inode_pages2_range(mapping,
2419 pos >> PAGE_CACHE_SHIFT, end);
2420 /*
2421 * If a page can not be invalidated, return 0 to fall back
2422 * to buffered write.
2423 */
2424 if (written) {
2425 if (written == -EBUSY)
2426 return 0;
2427 goto out;
2428 }
2429 }
2430
2431 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2432
2433 /*
2434 * Finally, try again to invalidate clean pages which might have been
2435 * cached by non-direct readahead, or faulted in by get_user_pages()
2436 * if the source of the write was an mmap'ed region of the file
2437 * we're writing. Either one is a pretty crazy thing to do,
2438 * so we don't support it 100%. If this invalidation
2439 * fails, tough, the write still worked...
2440 */
2441 if (mapping->nrpages) {
2442 invalidate_inode_pages2_range(mapping,
2443 pos >> PAGE_CACHE_SHIFT, end);
2444 }
2445
2446 if (written > 0) {
2447 pos += written;
2448 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2449 i_size_write(inode, pos);
2450 mark_inode_dirty(inode);
2451 }
2452 iocb->ki_pos = pos;
2453 }
2454out:
2455 return written;
2456}
2457EXPORT_SYMBOL(generic_file_direct_write);
2458
2459/*
2460 * Find or create a page at the given pagecache position. Return the locked
2461 * page. This function is specifically for buffered writes.
2462 */
2463struct page *grab_cache_page_write_begin(struct address_space *mapping,
2464 pgoff_t index, unsigned flags)
2465{
2466 int status;
2467 gfp_t gfp_mask;
2468 struct page *page;
2469 gfp_t gfp_notmask = 0;
2470
2471 gfp_mask = mapping_gfp_mask(mapping);
2472 if (mapping_cap_account_dirty(mapping))
2473 gfp_mask |= __GFP_WRITE;
2474 if (flags & AOP_FLAG_NOFS)
2475 gfp_notmask = __GFP_FS;
2476repeat:
2477 page = find_lock_page(mapping, index);
2478 if (page)
2479 goto found;
2480
2481 page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2482 if (!page)
2483 return NULL;
2484 status = add_to_page_cache_lru(page, mapping, index,
2485 GFP_KERNEL & ~gfp_notmask);
2486 if (unlikely(status)) {
2487 page_cache_release(page);
2488 if (status == -EEXIST)
2489 goto repeat;
2490 return NULL;
2491 }
2492found:
2493 wait_for_stable_page(page);
2494 return page;
2495}
2496EXPORT_SYMBOL(grab_cache_page_write_begin);
2497
2498ssize_t generic_perform_write(struct file *file,
2499 struct iov_iter *i, loff_t pos)
2500{
2501 struct address_space *mapping = file->f_mapping;
2502 const struct address_space_operations *a_ops = mapping->a_ops;
2503 long status = 0;
2504 ssize_t written = 0;
2505 unsigned int flags = 0;
2506
2507 /*
2508 * Copies from kernel address space cannot fail (NFSD is a big user).
2509 */
2510 if (segment_eq(get_fs(), KERNEL_DS))
2511 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2512
2513 do {
2514 struct page *page;
2515 unsigned long offset; /* Offset into pagecache page */
2516 unsigned long bytes; /* Bytes to write to page */
2517 size_t copied; /* Bytes copied from user */
2518 void *fsdata;
2519
2520 offset = (pos & (PAGE_CACHE_SIZE - 1));
2521 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2522 iov_iter_count(i));
2523
2524again:
2525 /*
2526 * Bring in the user page that we will copy from _first_.
2527 * Otherwise there's a nasty deadlock on copying from the
2528 * same page as we're writing to, without it being marked
2529 * up-to-date.
2530 *
2531 * Not only is this an optimisation, but it is also required
2532 * to check that the address is actually valid, when atomic
2533 * usercopies are used, below.
2534 */
2535 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2536 status = -EFAULT;
2537 break;
2538 }
2539
2540 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2541 &page, &fsdata);
2542 if (unlikely(status))
2543 break;
2544
2545 if (mapping_writably_mapped(mapping))
2546 flush_dcache_page(page);
2547
2548 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2549 flush_dcache_page(page);
2550
2551 mark_page_accessed(page);
2552 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2553 page, fsdata);
2554 if (unlikely(status < 0))
2555 break;
2556 copied = status;
2557
2558 cond_resched();
2559
2560 iov_iter_advance(i, copied);
2561 if (unlikely(copied == 0)) {
2562 /*
2563 * If we were unable to copy any data at all, we must
2564 * fall back to a single segment length write.
2565 *
2566 * If we didn't fallback here, we could livelock
2567 * because not all segments in the iov can be copied at
2568 * once without a pagefault.
2569 */
2570 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2571 iov_iter_single_seg_count(i));
2572 goto again;
2573 }
2574 pos += copied;
2575 written += copied;
2576
2577 balance_dirty_pages_ratelimited(mapping);
2578 if (fatal_signal_pending(current)) {
2579 status = -EINTR;
2580 break;
2581 }
2582 } while (iov_iter_count(i));
2583
2584 return written ? written : status;
2585}
2586EXPORT_SYMBOL(generic_perform_write);
2587
2588/**
2589 * __generic_file_aio_write - write data to a file
2590 * @iocb: IO state structure (file, offset, etc.)
2591 * @iov: vector with data to write
2592 * @nr_segs: number of segments in the vector
2593 *
2594 * This function does all the work needed for actually writing data to a
2595 * file. It does all basic checks, removes SUID from the file, updates
2596 * modification times and calls proper subroutines depending on whether we
2597 * do direct IO or a standard buffered write.
2598 *
2599 * It expects i_mutex to be grabbed unless we work on a block device or similar
2600 * object which does not need locking at all.
2601 *
2602 * This function does *not* take care of syncing data in case of O_SYNC write.
2603 * A caller has to handle it. This is mainly due to the fact that we want to
2604 * avoid syncing under i_mutex.
2605 */
2606ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2607 unsigned long nr_segs)
2608{
2609 struct file *file = iocb->ki_filp;
2610 struct address_space * mapping = file->f_mapping;
2611 size_t ocount; /* original count */
2612 size_t count; /* after file limit checks */
2613 struct inode *inode = mapping->host;
2614 loff_t pos = iocb->ki_pos;
2615 ssize_t written = 0;
2616 ssize_t err;
2617 ssize_t status;
2618 struct iov_iter from;
2619
2620 ocount = 0;
2621 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2622 if (err)
2623 return err;
2624
2625 count = ocount;
2626
2627 /* We can write back this queue in page reclaim */
2628 current->backing_dev_info = mapping->backing_dev_info;
2629 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2630 if (err)
2631 goto out;
2632
2633 if (count == 0)
2634 goto out;
2635
2636 err = file_remove_suid(file);
2637 if (err)
2638 goto out;
2639
2640 err = file_update_time(file);
2641 if (err)
2642 goto out;
2643
2644 iov_iter_init(&from, iov, nr_segs, count, 0);
2645
2646 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2647 if (unlikely(file->f_flags & O_DIRECT)) {
2648 loff_t endbyte;
2649
2650 written = generic_file_direct_write(iocb, iov, &from.nr_segs, pos,
2651 count, ocount);
2652 if (written < 0 || written == count)
2653 goto out;
2654 iov_iter_advance(&from, written);
2655
2656 /*
2657 * direct-io write to a hole: fall through to buffered I/O
2658 * for completing the rest of the request.
2659 */
2660 pos += written;
2661 count -= written;
2662
2663 status = generic_perform_write(file, &from, pos);
2664 /*
2665 * If generic_perform_write() returned a synchronous error
2666 * then we want to return the number of bytes which were
2667 * direct-written, or the error code if that was zero. Note
2668 * that this differs from normal direct-io semantics, which
2669 * will return -EFOO even if some bytes were written.
2670 */
2671 if (unlikely(status < 0) && !written) {
2672 err = status;
2673 goto out;
2674 }
2675 iocb->ki_pos = pos + status;
2676 /*
2677 * We need to ensure that the page cache pages are written to
2678 * disk and invalidated to preserve the expected O_DIRECT
2679 * semantics.
2680 */
2681 endbyte = pos + status - 1;
2682 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2683 if (err == 0) {
2684 written += status;
2685 invalidate_mapping_pages(mapping,
2686 pos >> PAGE_CACHE_SHIFT,
2687 endbyte >> PAGE_CACHE_SHIFT);
2688 } else {
2689 /*
2690 * We don't know how much we wrote, so just return
2691 * the number of bytes which were direct-written
2692 */
2693 }
2694 } else {
2695 written = generic_perform_write(file, &from, pos);
2696 if (likely(written >= 0))
2697 iocb->ki_pos = pos + written;
2698 }
2699out:
2700 current->backing_dev_info = NULL;
2701 return written ? written : err;
2702}
2703EXPORT_SYMBOL(__generic_file_aio_write);
2704
2705/**
2706 * generic_file_aio_write - write data to a file
2707 * @iocb: IO state structure
2708 * @iov: vector with data to write
2709 * @nr_segs: number of segments in the vector
2710 * @pos: position in file where to write
2711 *
2712 * This is a wrapper around __generic_file_aio_write() to be used by most
2713 * filesystems. It takes care of syncing the file in case of O_SYNC file
2714 * and acquires i_mutex as needed.
2715 */
2716ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2717 unsigned long nr_segs, loff_t pos)
2718{
2719 struct file *file = iocb->ki_filp;
2720 struct inode *inode = file->f_mapping->host;
2721 ssize_t ret;
2722
2723 BUG_ON(iocb->ki_pos != pos);
2724
2725 mutex_lock(&inode->i_mutex);
2726 ret = __generic_file_aio_write(iocb, iov, nr_segs);
2727 mutex_unlock(&inode->i_mutex);
2728
2729 if (ret > 0) {
2730 ssize_t err;
2731
2732 err = generic_write_sync(file, iocb->ki_pos - ret, ret);
2733 if (err < 0)
2734 ret = err;
2735 }
2736 return ret;
2737}
2738EXPORT_SYMBOL(generic_file_aio_write);
2739
2740/**
2741 * try_to_release_page() - release old fs-specific metadata on a page
2742 *
2743 * @page: the page which the kernel is trying to free
2744 * @gfp_mask: memory allocation flags (and I/O mode)
2745 *
2746 * The address_space is to try to release any data against the page
2747 * (presumably at page->private). If the release was successful, return `1'.
2748 * Otherwise return zero.
2749 *
2750 * This may also be called if PG_fscache is set on a page, indicating that the
2751 * page is known to the local caching routines.
2752 *
2753 * The @gfp_mask argument specifies whether I/O may be performed to release
2754 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2755 *
2756 */
2757int try_to_release_page(struct page *page, gfp_t gfp_mask)
2758{
2759 struct address_space * const mapping = page->mapping;
2760
2761 BUG_ON(!PageLocked(page));
2762 if (PageWriteback(page))
2763 return 0;
2764
2765 if (mapping && mapping->a_ops->releasepage)
2766 return mapping->a_ops->releasepage(page, gfp_mask);
2767 return try_to_free_buffers(page);
2768}
2769
2770EXPORT_SYMBOL(try_to_release_page);