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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/uaccess.h>
17#include <linux/capability.h>
18#include <linux/kernel_stat.h>
19#include <linux/gfp.h>
20#include <linux/mm.h>
21#include <linux/swap.h>
22#include <linux/mman.h>
23#include <linux/pagemap.h>
24#include <linux/file.h>
25#include <linux/uio.h>
26#include <linux/hash.h>
27#include <linux/writeback.h>
28#include <linux/backing-dev.h>
29#include <linux/pagevec.h>
30#include <linux/blkdev.h>
31#include <linux/security.h>
32#include <linux/cpuset.h>
33#include <linux/hardirq.h> /* for BUG_ON(!in_atomic()) only */
34#include <linux/hugetlb.h>
35#include <linux/memcontrol.h>
36#include <linux/cleancache.h>
37#include <linux/rmap.h>
38#include "internal.h"
39
40#define CREATE_TRACE_POINTS
41#include <trace/events/filemap.h>
42
43/*
44 * FIXME: remove all knowledge of the buffer layer from the core VM
45 */
46#include <linux/buffer_head.h> /* for try_to_free_buffers */
47
48#include <asm/mman.h>
49
50/*
51 * Shared mappings implemented 30.11.1994. It's not fully working yet,
52 * though.
53 *
54 * Shared mappings now work. 15.8.1995 Bruno.
55 *
56 * finished 'unifying' the page and buffer cache and SMP-threaded the
57 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
58 *
59 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
60 */
61
62/*
63 * Lock ordering:
64 *
65 * ->i_mmap_rwsem (truncate_pagecache)
66 * ->private_lock (__free_pte->__set_page_dirty_buffers)
67 * ->swap_lock (exclusive_swap_page, others)
68 * ->mapping->tree_lock
69 *
70 * ->i_mutex
71 * ->i_mmap_rwsem (truncate->unmap_mapping_range)
72 *
73 * ->mmap_sem
74 * ->i_mmap_rwsem
75 * ->page_table_lock or pte_lock (various, mainly in memory.c)
76 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
77 *
78 * ->mmap_sem
79 * ->lock_page (access_process_vm)
80 *
81 * ->i_mutex (generic_perform_write)
82 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
83 *
84 * bdi->wb.list_lock
85 * sb_lock (fs/fs-writeback.c)
86 * ->mapping->tree_lock (__sync_single_inode)
87 *
88 * ->i_mmap_rwsem
89 * ->anon_vma.lock (vma_adjust)
90 *
91 * ->anon_vma.lock
92 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
93 *
94 * ->page_table_lock or pte_lock
95 * ->swap_lock (try_to_unmap_one)
96 * ->private_lock (try_to_unmap_one)
97 * ->tree_lock (try_to_unmap_one)
98 * ->zone.lru_lock (follow_page->mark_page_accessed)
99 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
100 * ->private_lock (page_remove_rmap->set_page_dirty)
101 * ->tree_lock (page_remove_rmap->set_page_dirty)
102 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
103 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
104 * ->memcg->move_lock (page_remove_rmap->lock_page_memcg)
105 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
106 * ->inode->i_lock (zap_pte_range->set_page_dirty)
107 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
108 *
109 * ->i_mmap_rwsem
110 * ->tasklist_lock (memory_failure, collect_procs_ao)
111 */
112
113static void page_cache_tree_delete(struct address_space *mapping,
114 struct page *page, void *shadow)
115{
116 struct radix_tree_node *node;
117 unsigned long index;
118 unsigned int offset;
119 unsigned int tag;
120 void **slot;
121
122 VM_BUG_ON(!PageLocked(page));
123
124 __radix_tree_lookup(&mapping->page_tree, page->index, &node, &slot);
125
126 if (shadow) {
127 mapping->nrexceptional++;
128 /*
129 * Make sure the nrexceptional update is committed before
130 * the nrpages update so that final truncate racing
131 * with reclaim does not see both counters 0 at the
132 * same time and miss a shadow entry.
133 */
134 smp_wmb();
135 }
136 mapping->nrpages--;
137
138 if (!node) {
139 /* Clear direct pointer tags in root node */
140 mapping->page_tree.gfp_mask &= __GFP_BITS_MASK;
141 radix_tree_replace_slot(slot, shadow);
142 return;
143 }
144
145 /* Clear tree tags for the removed page */
146 index = page->index;
147 offset = index & RADIX_TREE_MAP_MASK;
148 for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
149 if (test_bit(offset, node->tags[tag]))
150 radix_tree_tag_clear(&mapping->page_tree, index, tag);
151 }
152
153 /* Delete page, swap shadow entry */
154 radix_tree_replace_slot(slot, shadow);
155 workingset_node_pages_dec(node);
156 if (shadow)
157 workingset_node_shadows_inc(node);
158 else
159 if (__radix_tree_delete_node(&mapping->page_tree, node))
160 return;
161
162 /*
163 * Track node that only contains shadow entries.
164 *
165 * Avoid acquiring the list_lru lock if already tracked. The
166 * list_empty() test is safe as node->private_list is
167 * protected by mapping->tree_lock.
168 */
169 if (!workingset_node_pages(node) &&
170 list_empty(&node->private_list)) {
171 node->private_data = mapping;
172 list_lru_add(&workingset_shadow_nodes, &node->private_list);
173 }
174}
175
176/*
177 * Delete a page from the page cache and free it. Caller has to make
178 * sure the page is locked and that nobody else uses it - or that usage
179 * is safe. The caller must hold the mapping's tree_lock.
180 */
181void __delete_from_page_cache(struct page *page, void *shadow)
182{
183 struct address_space *mapping = page->mapping;
184
185 trace_mm_filemap_delete_from_page_cache(page);
186 /*
187 * if we're uptodate, flush out into the cleancache, otherwise
188 * invalidate any existing cleancache entries. We can't leave
189 * stale data around in the cleancache once our page is gone
190 */
191 if (PageUptodate(page) && PageMappedToDisk(page))
192 cleancache_put_page(page);
193 else
194 cleancache_invalidate_page(mapping, page);
195
196 VM_BUG_ON_PAGE(page_mapped(page), page);
197 if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(page_mapped(page))) {
198 int mapcount;
199
200 pr_alert("BUG: Bad page cache in process %s pfn:%05lx\n",
201 current->comm, page_to_pfn(page));
202 dump_page(page, "still mapped when deleted");
203 dump_stack();
204 add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
205
206 mapcount = page_mapcount(page);
207 if (mapping_exiting(mapping) &&
208 page_count(page) >= mapcount + 2) {
209 /*
210 * All vmas have already been torn down, so it's
211 * a good bet that actually the page is unmapped,
212 * and we'd prefer not to leak it: if we're wrong,
213 * some other bad page check should catch it later.
214 */
215 page_mapcount_reset(page);
216 atomic_sub(mapcount, &page->_count);
217 }
218 }
219
220 page_cache_tree_delete(mapping, page, shadow);
221
222 page->mapping = NULL;
223 /* Leave page->index set: truncation lookup relies upon it */
224
225 /* hugetlb pages do not participate in page cache accounting. */
226 if (!PageHuge(page))
227 __dec_zone_page_state(page, NR_FILE_PAGES);
228 if (PageSwapBacked(page))
229 __dec_zone_page_state(page, NR_SHMEM);
230
231 /*
232 * At this point page must be either written or cleaned by truncate.
233 * Dirty page here signals a bug and loss of unwritten data.
234 *
235 * This fixes dirty accounting after removing the page entirely but
236 * leaves PageDirty set: it has no effect for truncated page and
237 * anyway will be cleared before returning page into buddy allocator.
238 */
239 if (WARN_ON_ONCE(PageDirty(page)))
240 account_page_cleaned(page, mapping, inode_to_wb(mapping->host));
241}
242
243/**
244 * delete_from_page_cache - delete page from page cache
245 * @page: the page which the kernel is trying to remove from page cache
246 *
247 * This must be called only on pages that have been verified to be in the page
248 * cache and locked. It will never put the page into the free list, the caller
249 * has a reference on the page.
250 */
251void delete_from_page_cache(struct page *page)
252{
253 struct address_space *mapping = page->mapping;
254 unsigned long flags;
255
256 void (*freepage)(struct page *);
257
258 BUG_ON(!PageLocked(page));
259
260 freepage = mapping->a_ops->freepage;
261
262 spin_lock_irqsave(&mapping->tree_lock, flags);
263 __delete_from_page_cache(page, NULL);
264 spin_unlock_irqrestore(&mapping->tree_lock, flags);
265
266 if (freepage)
267 freepage(page);
268 put_page(page);
269}
270EXPORT_SYMBOL(delete_from_page_cache);
271
272static int filemap_check_errors(struct address_space *mapping)
273{
274 int ret = 0;
275 /* Check for outstanding write errors */
276 if (test_bit(AS_ENOSPC, &mapping->flags) &&
277 test_and_clear_bit(AS_ENOSPC, &mapping->flags))
278 ret = -ENOSPC;
279 if (test_bit(AS_EIO, &mapping->flags) &&
280 test_and_clear_bit(AS_EIO, &mapping->flags))
281 ret = -EIO;
282 return ret;
283}
284
285/**
286 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
287 * @mapping: address space structure to write
288 * @start: offset in bytes where the range starts
289 * @end: offset in bytes where the range ends (inclusive)
290 * @sync_mode: enable synchronous operation
291 *
292 * Start writeback against all of a mapping's dirty pages that lie
293 * within the byte offsets <start, end> inclusive.
294 *
295 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
296 * opposed to a regular memory cleansing writeback. The difference between
297 * these two operations is that if a dirty page/buffer is encountered, it must
298 * be waited upon, and not just skipped over.
299 */
300int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
301 loff_t end, int sync_mode)
302{
303 int ret;
304 struct writeback_control wbc = {
305 .sync_mode = sync_mode,
306 .nr_to_write = LONG_MAX,
307 .range_start = start,
308 .range_end = end,
309 };
310
311 if (!mapping_cap_writeback_dirty(mapping))
312 return 0;
313
314 wbc_attach_fdatawrite_inode(&wbc, mapping->host);
315 ret = do_writepages(mapping, &wbc);
316 wbc_detach_inode(&wbc);
317 return ret;
318}
319
320static inline int __filemap_fdatawrite(struct address_space *mapping,
321 int sync_mode)
322{
323 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
324}
325
326int filemap_fdatawrite(struct address_space *mapping)
327{
328 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
329}
330EXPORT_SYMBOL(filemap_fdatawrite);
331
332int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
333 loff_t end)
334{
335 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
336}
337EXPORT_SYMBOL(filemap_fdatawrite_range);
338
339/**
340 * filemap_flush - mostly a non-blocking flush
341 * @mapping: target address_space
342 *
343 * This is a mostly non-blocking flush. Not suitable for data-integrity
344 * purposes - I/O may not be started against all dirty pages.
345 */
346int filemap_flush(struct address_space *mapping)
347{
348 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
349}
350EXPORT_SYMBOL(filemap_flush);
351
352static int __filemap_fdatawait_range(struct address_space *mapping,
353 loff_t start_byte, loff_t end_byte)
354{
355 pgoff_t index = start_byte >> PAGE_SHIFT;
356 pgoff_t end = end_byte >> PAGE_SHIFT;
357 struct pagevec pvec;
358 int nr_pages;
359 int ret = 0;
360
361 if (end_byte < start_byte)
362 goto out;
363
364 pagevec_init(&pvec, 0);
365 while ((index <= end) &&
366 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
367 PAGECACHE_TAG_WRITEBACK,
368 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
369 unsigned i;
370
371 for (i = 0; i < nr_pages; i++) {
372 struct page *page = pvec.pages[i];
373
374 /* until radix tree lookup accepts end_index */
375 if (page->index > end)
376 continue;
377
378 wait_on_page_writeback(page);
379 if (TestClearPageError(page))
380 ret = -EIO;
381 }
382 pagevec_release(&pvec);
383 cond_resched();
384 }
385out:
386 return ret;
387}
388
389/**
390 * filemap_fdatawait_range - wait for writeback to complete
391 * @mapping: address space structure to wait for
392 * @start_byte: offset in bytes where the range starts
393 * @end_byte: offset in bytes where the range ends (inclusive)
394 *
395 * Walk the list of under-writeback pages of the given address space
396 * in the given range and wait for all of them. Check error status of
397 * the address space and return it.
398 *
399 * Since the error status of the address space is cleared by this function,
400 * callers are responsible for checking the return value and handling and/or
401 * reporting the error.
402 */
403int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
404 loff_t end_byte)
405{
406 int ret, ret2;
407
408 ret = __filemap_fdatawait_range(mapping, start_byte, end_byte);
409 ret2 = filemap_check_errors(mapping);
410 if (!ret)
411 ret = ret2;
412
413 return ret;
414}
415EXPORT_SYMBOL(filemap_fdatawait_range);
416
417/**
418 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
419 * @mapping: address space structure to wait for
420 *
421 * Walk the list of under-writeback pages of the given address space
422 * and wait for all of them. Unlike filemap_fdatawait(), this function
423 * does not clear error status of the address space.
424 *
425 * Use this function if callers don't handle errors themselves. Expected
426 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
427 * fsfreeze(8)
428 */
429void filemap_fdatawait_keep_errors(struct address_space *mapping)
430{
431 loff_t i_size = i_size_read(mapping->host);
432
433 if (i_size == 0)
434 return;
435
436 __filemap_fdatawait_range(mapping, 0, i_size - 1);
437}
438
439/**
440 * filemap_fdatawait - wait for all under-writeback pages to complete
441 * @mapping: address space structure to wait for
442 *
443 * Walk the list of under-writeback pages of the given address space
444 * and wait for all of them. Check error status of the address space
445 * and return it.
446 *
447 * Since the error status of the address space is cleared by this function,
448 * callers are responsible for checking the return value and handling and/or
449 * reporting the error.
450 */
451int filemap_fdatawait(struct address_space *mapping)
452{
453 loff_t i_size = i_size_read(mapping->host);
454
455 if (i_size == 0)
456 return 0;
457
458 return filemap_fdatawait_range(mapping, 0, i_size - 1);
459}
460EXPORT_SYMBOL(filemap_fdatawait);
461
462int filemap_write_and_wait(struct address_space *mapping)
463{
464 int err = 0;
465
466 if ((!dax_mapping(mapping) && mapping->nrpages) ||
467 (dax_mapping(mapping) && mapping->nrexceptional)) {
468 err = filemap_fdatawrite(mapping);
469 /*
470 * Even if the above returned error, the pages may be
471 * written partially (e.g. -ENOSPC), so we wait for it.
472 * But the -EIO is special case, it may indicate the worst
473 * thing (e.g. bug) happened, so we avoid waiting for it.
474 */
475 if (err != -EIO) {
476 int err2 = filemap_fdatawait(mapping);
477 if (!err)
478 err = err2;
479 }
480 } else {
481 err = filemap_check_errors(mapping);
482 }
483 return err;
484}
485EXPORT_SYMBOL(filemap_write_and_wait);
486
487/**
488 * filemap_write_and_wait_range - write out & wait on a file range
489 * @mapping: the address_space for the pages
490 * @lstart: offset in bytes where the range starts
491 * @lend: offset in bytes where the range ends (inclusive)
492 *
493 * Write out and wait upon file offsets lstart->lend, inclusive.
494 *
495 * Note that `lend' is inclusive (describes the last byte to be written) so
496 * that this function can be used to write to the very end-of-file (end = -1).
497 */
498int filemap_write_and_wait_range(struct address_space *mapping,
499 loff_t lstart, loff_t lend)
500{
501 int err = 0;
502
503 if ((!dax_mapping(mapping) && mapping->nrpages) ||
504 (dax_mapping(mapping) && mapping->nrexceptional)) {
505 err = __filemap_fdatawrite_range(mapping, lstart, lend,
506 WB_SYNC_ALL);
507 /* See comment of filemap_write_and_wait() */
508 if (err != -EIO) {
509 int err2 = filemap_fdatawait_range(mapping,
510 lstart, lend);
511 if (!err)
512 err = err2;
513 }
514 } else {
515 err = filemap_check_errors(mapping);
516 }
517 return err;
518}
519EXPORT_SYMBOL(filemap_write_and_wait_range);
520
521/**
522 * replace_page_cache_page - replace a pagecache page with a new one
523 * @old: page to be replaced
524 * @new: page to replace with
525 * @gfp_mask: allocation mode
526 *
527 * This function replaces a page in the pagecache with a new one. On
528 * success it acquires the pagecache reference for the new page and
529 * drops it for the old page. Both the old and new pages must be
530 * locked. This function does not add the new page to the LRU, the
531 * caller must do that.
532 *
533 * The remove + add is atomic. The only way this function can fail is
534 * memory allocation failure.
535 */
536int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
537{
538 int error;
539
540 VM_BUG_ON_PAGE(!PageLocked(old), old);
541 VM_BUG_ON_PAGE(!PageLocked(new), new);
542 VM_BUG_ON_PAGE(new->mapping, new);
543
544 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
545 if (!error) {
546 struct address_space *mapping = old->mapping;
547 void (*freepage)(struct page *);
548 unsigned long flags;
549
550 pgoff_t offset = old->index;
551 freepage = mapping->a_ops->freepage;
552
553 get_page(new);
554 new->mapping = mapping;
555 new->index = offset;
556
557 spin_lock_irqsave(&mapping->tree_lock, flags);
558 __delete_from_page_cache(old, NULL);
559 error = radix_tree_insert(&mapping->page_tree, offset, new);
560 BUG_ON(error);
561 mapping->nrpages++;
562
563 /*
564 * hugetlb pages do not participate in page cache accounting.
565 */
566 if (!PageHuge(new))
567 __inc_zone_page_state(new, NR_FILE_PAGES);
568 if (PageSwapBacked(new))
569 __inc_zone_page_state(new, NR_SHMEM);
570 spin_unlock_irqrestore(&mapping->tree_lock, flags);
571 mem_cgroup_migrate(old, new);
572 radix_tree_preload_end();
573 if (freepage)
574 freepage(old);
575 put_page(old);
576 }
577
578 return error;
579}
580EXPORT_SYMBOL_GPL(replace_page_cache_page);
581
582static int page_cache_tree_insert(struct address_space *mapping,
583 struct page *page, void **shadowp)
584{
585 struct radix_tree_node *node;
586 void **slot;
587 int error;
588
589 error = __radix_tree_create(&mapping->page_tree, page->index, 0,
590 &node, &slot);
591 if (error)
592 return error;
593 if (*slot) {
594 void *p;
595
596 p = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
597 if (!radix_tree_exceptional_entry(p))
598 return -EEXIST;
599
600 if (WARN_ON(dax_mapping(mapping)))
601 return -EINVAL;
602
603 if (shadowp)
604 *shadowp = p;
605 mapping->nrexceptional--;
606 if (node)
607 workingset_node_shadows_dec(node);
608 }
609 radix_tree_replace_slot(slot, page);
610 mapping->nrpages++;
611 if (node) {
612 workingset_node_pages_inc(node);
613 /*
614 * Don't track node that contains actual pages.
615 *
616 * Avoid acquiring the list_lru lock if already
617 * untracked. The list_empty() test is safe as
618 * node->private_list is protected by
619 * mapping->tree_lock.
620 */
621 if (!list_empty(&node->private_list))
622 list_lru_del(&workingset_shadow_nodes,
623 &node->private_list);
624 }
625 return 0;
626}
627
628static int __add_to_page_cache_locked(struct page *page,
629 struct address_space *mapping,
630 pgoff_t offset, gfp_t gfp_mask,
631 void **shadowp)
632{
633 int huge = PageHuge(page);
634 struct mem_cgroup *memcg;
635 int error;
636
637 VM_BUG_ON_PAGE(!PageLocked(page), page);
638 VM_BUG_ON_PAGE(PageSwapBacked(page), page);
639
640 if (!huge) {
641 error = mem_cgroup_try_charge(page, current->mm,
642 gfp_mask, &memcg, false);
643 if (error)
644 return error;
645 }
646
647 error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
648 if (error) {
649 if (!huge)
650 mem_cgroup_cancel_charge(page, memcg, false);
651 return error;
652 }
653
654 get_page(page);
655 page->mapping = mapping;
656 page->index = offset;
657
658 spin_lock_irq(&mapping->tree_lock);
659 error = page_cache_tree_insert(mapping, page, shadowp);
660 radix_tree_preload_end();
661 if (unlikely(error))
662 goto err_insert;
663
664 /* hugetlb pages do not participate in page cache accounting. */
665 if (!huge)
666 __inc_zone_page_state(page, NR_FILE_PAGES);
667 spin_unlock_irq(&mapping->tree_lock);
668 if (!huge)
669 mem_cgroup_commit_charge(page, memcg, false, false);
670 trace_mm_filemap_add_to_page_cache(page);
671 return 0;
672err_insert:
673 page->mapping = NULL;
674 /* Leave page->index set: truncation relies upon it */
675 spin_unlock_irq(&mapping->tree_lock);
676 if (!huge)
677 mem_cgroup_cancel_charge(page, memcg, false);
678 put_page(page);
679 return error;
680}
681
682/**
683 * add_to_page_cache_locked - add a locked page to the pagecache
684 * @page: page to add
685 * @mapping: the page's address_space
686 * @offset: page index
687 * @gfp_mask: page allocation mode
688 *
689 * This function is used to add a page to the pagecache. It must be locked.
690 * This function does not add the page to the LRU. The caller must do that.
691 */
692int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
693 pgoff_t offset, gfp_t gfp_mask)
694{
695 return __add_to_page_cache_locked(page, mapping, offset,
696 gfp_mask, NULL);
697}
698EXPORT_SYMBOL(add_to_page_cache_locked);
699
700int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
701 pgoff_t offset, gfp_t gfp_mask)
702{
703 void *shadow = NULL;
704 int ret;
705
706 __SetPageLocked(page);
707 ret = __add_to_page_cache_locked(page, mapping, offset,
708 gfp_mask, &shadow);
709 if (unlikely(ret))
710 __ClearPageLocked(page);
711 else {
712 /*
713 * The page might have been evicted from cache only
714 * recently, in which case it should be activated like
715 * any other repeatedly accessed page.
716 */
717 if (shadow && workingset_refault(shadow)) {
718 SetPageActive(page);
719 workingset_activation(page);
720 } else
721 ClearPageActive(page);
722 lru_cache_add(page);
723 }
724 return ret;
725}
726EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
727
728#ifdef CONFIG_NUMA
729struct page *__page_cache_alloc(gfp_t gfp)
730{
731 int n;
732 struct page *page;
733
734 if (cpuset_do_page_mem_spread()) {
735 unsigned int cpuset_mems_cookie;
736 do {
737 cpuset_mems_cookie = read_mems_allowed_begin();
738 n = cpuset_mem_spread_node();
739 page = __alloc_pages_node(n, gfp, 0);
740 } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
741
742 return page;
743 }
744 return alloc_pages(gfp, 0);
745}
746EXPORT_SYMBOL(__page_cache_alloc);
747#endif
748
749/*
750 * In order to wait for pages to become available there must be
751 * waitqueues associated with pages. By using a hash table of
752 * waitqueues where the bucket discipline is to maintain all
753 * waiters on the same queue and wake all when any of the pages
754 * become available, and for the woken contexts to check to be
755 * sure the appropriate page became available, this saves space
756 * at a cost of "thundering herd" phenomena during rare hash
757 * collisions.
758 */
759wait_queue_head_t *page_waitqueue(struct page *page)
760{
761 const struct zone *zone = page_zone(page);
762
763 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
764}
765EXPORT_SYMBOL(page_waitqueue);
766
767void wait_on_page_bit(struct page *page, int bit_nr)
768{
769 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
770
771 if (test_bit(bit_nr, &page->flags))
772 __wait_on_bit(page_waitqueue(page), &wait, bit_wait_io,
773 TASK_UNINTERRUPTIBLE);
774}
775EXPORT_SYMBOL(wait_on_page_bit);
776
777int wait_on_page_bit_killable(struct page *page, int bit_nr)
778{
779 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
780
781 if (!test_bit(bit_nr, &page->flags))
782 return 0;
783
784 return __wait_on_bit(page_waitqueue(page), &wait,
785 bit_wait_io, TASK_KILLABLE);
786}
787
788int wait_on_page_bit_killable_timeout(struct page *page,
789 int bit_nr, unsigned long timeout)
790{
791 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
792
793 wait.key.timeout = jiffies + timeout;
794 if (!test_bit(bit_nr, &page->flags))
795 return 0;
796 return __wait_on_bit(page_waitqueue(page), &wait,
797 bit_wait_io_timeout, TASK_KILLABLE);
798}
799EXPORT_SYMBOL_GPL(wait_on_page_bit_killable_timeout);
800
801/**
802 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
803 * @page: Page defining the wait queue of interest
804 * @waiter: Waiter to add to the queue
805 *
806 * Add an arbitrary @waiter to the wait queue for the nominated @page.
807 */
808void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
809{
810 wait_queue_head_t *q = page_waitqueue(page);
811 unsigned long flags;
812
813 spin_lock_irqsave(&q->lock, flags);
814 __add_wait_queue(q, waiter);
815 spin_unlock_irqrestore(&q->lock, flags);
816}
817EXPORT_SYMBOL_GPL(add_page_wait_queue);
818
819/**
820 * unlock_page - unlock a locked page
821 * @page: the page
822 *
823 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
824 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
825 * mechanism between PageLocked pages and PageWriteback pages is shared.
826 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
827 *
828 * The mb is necessary to enforce ordering between the clear_bit and the read
829 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
830 */
831void unlock_page(struct page *page)
832{
833 page = compound_head(page);
834 VM_BUG_ON_PAGE(!PageLocked(page), page);
835 clear_bit_unlock(PG_locked, &page->flags);
836 smp_mb__after_atomic();
837 wake_up_page(page, PG_locked);
838}
839EXPORT_SYMBOL(unlock_page);
840
841/**
842 * end_page_writeback - end writeback against a page
843 * @page: the page
844 */
845void end_page_writeback(struct page *page)
846{
847 /*
848 * TestClearPageReclaim could be used here but it is an atomic
849 * operation and overkill in this particular case. Failing to
850 * shuffle a page marked for immediate reclaim is too mild to
851 * justify taking an atomic operation penalty at the end of
852 * ever page writeback.
853 */
854 if (PageReclaim(page)) {
855 ClearPageReclaim(page);
856 rotate_reclaimable_page(page);
857 }
858
859 if (!test_clear_page_writeback(page))
860 BUG();
861
862 smp_mb__after_atomic();
863 wake_up_page(page, PG_writeback);
864}
865EXPORT_SYMBOL(end_page_writeback);
866
867/*
868 * After completing I/O on a page, call this routine to update the page
869 * flags appropriately
870 */
871void page_endio(struct page *page, int rw, int err)
872{
873 if (rw == READ) {
874 if (!err) {
875 SetPageUptodate(page);
876 } else {
877 ClearPageUptodate(page);
878 SetPageError(page);
879 }
880 unlock_page(page);
881 } else { /* rw == WRITE */
882 if (err) {
883 SetPageError(page);
884 if (page->mapping)
885 mapping_set_error(page->mapping, err);
886 }
887 end_page_writeback(page);
888 }
889}
890EXPORT_SYMBOL_GPL(page_endio);
891
892/**
893 * __lock_page - get a lock on the page, assuming we need to sleep to get it
894 * @page: the page to lock
895 */
896void __lock_page(struct page *page)
897{
898 struct page *page_head = compound_head(page);
899 DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);
900
901 __wait_on_bit_lock(page_waitqueue(page_head), &wait, bit_wait_io,
902 TASK_UNINTERRUPTIBLE);
903}
904EXPORT_SYMBOL(__lock_page);
905
906int __lock_page_killable(struct page *page)
907{
908 struct page *page_head = compound_head(page);
909 DEFINE_WAIT_BIT(wait, &page_head->flags, PG_locked);
910
911 return __wait_on_bit_lock(page_waitqueue(page_head), &wait,
912 bit_wait_io, TASK_KILLABLE);
913}
914EXPORT_SYMBOL_GPL(__lock_page_killable);
915
916/*
917 * Return values:
918 * 1 - page is locked; mmap_sem is still held.
919 * 0 - page is not locked.
920 * mmap_sem has been released (up_read()), unless flags had both
921 * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in
922 * which case mmap_sem is still held.
923 *
924 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 1
925 * with the page locked and the mmap_sem unperturbed.
926 */
927int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
928 unsigned int flags)
929{
930 if (flags & FAULT_FLAG_ALLOW_RETRY) {
931 /*
932 * CAUTION! In this case, mmap_sem is not released
933 * even though return 0.
934 */
935 if (flags & FAULT_FLAG_RETRY_NOWAIT)
936 return 0;
937
938 up_read(&mm->mmap_sem);
939 if (flags & FAULT_FLAG_KILLABLE)
940 wait_on_page_locked_killable(page);
941 else
942 wait_on_page_locked(page);
943 return 0;
944 } else {
945 if (flags & FAULT_FLAG_KILLABLE) {
946 int ret;
947
948 ret = __lock_page_killable(page);
949 if (ret) {
950 up_read(&mm->mmap_sem);
951 return 0;
952 }
953 } else
954 __lock_page(page);
955 return 1;
956 }
957}
958
959/**
960 * page_cache_next_hole - find the next hole (not-present entry)
961 * @mapping: mapping
962 * @index: index
963 * @max_scan: maximum range to search
964 *
965 * Search the set [index, min(index+max_scan-1, MAX_INDEX)] for the
966 * lowest indexed hole.
967 *
968 * Returns: the index of the hole if found, otherwise returns an index
969 * outside of the set specified (in which case 'return - index >=
970 * max_scan' will be true). In rare cases of index wrap-around, 0 will
971 * be returned.
972 *
973 * page_cache_next_hole may be called under rcu_read_lock. However,
974 * like radix_tree_gang_lookup, this will not atomically search a
975 * snapshot of the tree at a single point in time. For example, if a
976 * hole is created at index 5, then subsequently a hole is created at
977 * index 10, page_cache_next_hole covering both indexes may return 10
978 * if called under rcu_read_lock.
979 */
980pgoff_t page_cache_next_hole(struct address_space *mapping,
981 pgoff_t index, unsigned long max_scan)
982{
983 unsigned long i;
984
985 for (i = 0; i < max_scan; i++) {
986 struct page *page;
987
988 page = radix_tree_lookup(&mapping->page_tree, index);
989 if (!page || radix_tree_exceptional_entry(page))
990 break;
991 index++;
992 if (index == 0)
993 break;
994 }
995
996 return index;
997}
998EXPORT_SYMBOL(page_cache_next_hole);
999
1000/**
1001 * page_cache_prev_hole - find the prev hole (not-present entry)
1002 * @mapping: mapping
1003 * @index: index
1004 * @max_scan: maximum range to search
1005 *
1006 * Search backwards in the range [max(index-max_scan+1, 0), index] for
1007 * the first hole.
1008 *
1009 * Returns: the index of the hole if found, otherwise returns an index
1010 * outside of the set specified (in which case 'index - return >=
1011 * max_scan' will be true). In rare cases of wrap-around, ULONG_MAX
1012 * will be returned.
1013 *
1014 * page_cache_prev_hole may be called under rcu_read_lock. However,
1015 * like radix_tree_gang_lookup, this will not atomically search a
1016 * snapshot of the tree at a single point in time. For example, if a
1017 * hole is created at index 10, then subsequently a hole is created at
1018 * index 5, page_cache_prev_hole covering both indexes may return 5 if
1019 * called under rcu_read_lock.
1020 */
1021pgoff_t page_cache_prev_hole(struct address_space *mapping,
1022 pgoff_t index, unsigned long max_scan)
1023{
1024 unsigned long i;
1025
1026 for (i = 0; i < max_scan; i++) {
1027 struct page *page;
1028
1029 page = radix_tree_lookup(&mapping->page_tree, index);
1030 if (!page || radix_tree_exceptional_entry(page))
1031 break;
1032 index--;
1033 if (index == ULONG_MAX)
1034 break;
1035 }
1036
1037 return index;
1038}
1039EXPORT_SYMBOL(page_cache_prev_hole);
1040
1041/**
1042 * find_get_entry - find and get a page cache entry
1043 * @mapping: the address_space to search
1044 * @offset: the page cache index
1045 *
1046 * Looks up the page cache slot at @mapping & @offset. If there is a
1047 * page cache page, it is returned with an increased refcount.
1048 *
1049 * If the slot holds a shadow entry of a previously evicted page, or a
1050 * swap entry from shmem/tmpfs, it is returned.
1051 *
1052 * Otherwise, %NULL is returned.
1053 */
1054struct page *find_get_entry(struct address_space *mapping, pgoff_t offset)
1055{
1056 void **pagep;
1057 struct page *page;
1058
1059 rcu_read_lock();
1060repeat:
1061 page = NULL;
1062 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
1063 if (pagep) {
1064 page = radix_tree_deref_slot(pagep);
1065 if (unlikely(!page))
1066 goto out;
1067 if (radix_tree_exception(page)) {
1068 if (radix_tree_deref_retry(page))
1069 goto repeat;
1070 /*
1071 * A shadow entry of a recently evicted page,
1072 * or a swap entry from shmem/tmpfs. Return
1073 * it without attempting to raise page count.
1074 */
1075 goto out;
1076 }
1077 if (!page_cache_get_speculative(page))
1078 goto repeat;
1079
1080 /*
1081 * Has the page moved?
1082 * This is part of the lockless pagecache protocol. See
1083 * include/linux/pagemap.h for details.
1084 */
1085 if (unlikely(page != *pagep)) {
1086 put_page(page);
1087 goto repeat;
1088 }
1089 }
1090out:
1091 rcu_read_unlock();
1092
1093 return page;
1094}
1095EXPORT_SYMBOL(find_get_entry);
1096
1097/**
1098 * find_lock_entry - locate, pin and lock a page cache entry
1099 * @mapping: the address_space to search
1100 * @offset: the page cache index
1101 *
1102 * Looks up the page cache slot at @mapping & @offset. If there is a
1103 * page cache page, it is returned locked and with an increased
1104 * refcount.
1105 *
1106 * If the slot holds a shadow entry of a previously evicted page, or a
1107 * swap entry from shmem/tmpfs, it is returned.
1108 *
1109 * Otherwise, %NULL is returned.
1110 *
1111 * find_lock_entry() may sleep.
1112 */
1113struct page *find_lock_entry(struct address_space *mapping, pgoff_t offset)
1114{
1115 struct page *page;
1116
1117repeat:
1118 page = find_get_entry(mapping, offset);
1119 if (page && !radix_tree_exception(page)) {
1120 lock_page(page);
1121 /* Has the page been truncated? */
1122 if (unlikely(page->mapping != mapping)) {
1123 unlock_page(page);
1124 put_page(page);
1125 goto repeat;
1126 }
1127 VM_BUG_ON_PAGE(page->index != offset, page);
1128 }
1129 return page;
1130}
1131EXPORT_SYMBOL(find_lock_entry);
1132
1133/**
1134 * pagecache_get_page - find and get a page reference
1135 * @mapping: the address_space to search
1136 * @offset: the page index
1137 * @fgp_flags: PCG flags
1138 * @gfp_mask: gfp mask to use for the page cache data page allocation
1139 *
1140 * Looks up the page cache slot at @mapping & @offset.
1141 *
1142 * PCG flags modify how the page is returned.
1143 *
1144 * FGP_ACCESSED: the page will be marked accessed
1145 * FGP_LOCK: Page is return locked
1146 * FGP_CREAT: If page is not present then a new page is allocated using
1147 * @gfp_mask and added to the page cache and the VM's LRU
1148 * list. The page is returned locked and with an increased
1149 * refcount. Otherwise, %NULL is returned.
1150 *
1151 * If FGP_LOCK or FGP_CREAT are specified then the function may sleep even
1152 * if the GFP flags specified for FGP_CREAT are atomic.
1153 *
1154 * If there is a page cache page, it is returned with an increased refcount.
1155 */
1156struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
1157 int fgp_flags, gfp_t gfp_mask)
1158{
1159 struct page *page;
1160
1161repeat:
1162 page = find_get_entry(mapping, offset);
1163 if (radix_tree_exceptional_entry(page))
1164 page = NULL;
1165 if (!page)
1166 goto no_page;
1167
1168 if (fgp_flags & FGP_LOCK) {
1169 if (fgp_flags & FGP_NOWAIT) {
1170 if (!trylock_page(page)) {
1171 put_page(page);
1172 return NULL;
1173 }
1174 } else {
1175 lock_page(page);
1176 }
1177
1178 /* Has the page been truncated? */
1179 if (unlikely(page->mapping != mapping)) {
1180 unlock_page(page);
1181 put_page(page);
1182 goto repeat;
1183 }
1184 VM_BUG_ON_PAGE(page->index != offset, page);
1185 }
1186
1187 if (page && (fgp_flags & FGP_ACCESSED))
1188 mark_page_accessed(page);
1189
1190no_page:
1191 if (!page && (fgp_flags & FGP_CREAT)) {
1192 int err;
1193 if ((fgp_flags & FGP_WRITE) && mapping_cap_account_dirty(mapping))
1194 gfp_mask |= __GFP_WRITE;
1195 if (fgp_flags & FGP_NOFS)
1196 gfp_mask &= ~__GFP_FS;
1197
1198 page = __page_cache_alloc(gfp_mask);
1199 if (!page)
1200 return NULL;
1201
1202 if (WARN_ON_ONCE(!(fgp_flags & FGP_LOCK)))
1203 fgp_flags |= FGP_LOCK;
1204
1205 /* Init accessed so avoid atomic mark_page_accessed later */
1206 if (fgp_flags & FGP_ACCESSED)
1207 __SetPageReferenced(page);
1208
1209 err = add_to_page_cache_lru(page, mapping, offset,
1210 gfp_mask & GFP_RECLAIM_MASK);
1211 if (unlikely(err)) {
1212 put_page(page);
1213 page = NULL;
1214 if (err == -EEXIST)
1215 goto repeat;
1216 }
1217 }
1218
1219 return page;
1220}
1221EXPORT_SYMBOL(pagecache_get_page);
1222
1223/**
1224 * find_get_entries - gang pagecache lookup
1225 * @mapping: The address_space to search
1226 * @start: The starting page cache index
1227 * @nr_entries: The maximum number of entries
1228 * @entries: Where the resulting entries are placed
1229 * @indices: The cache indices corresponding to the entries in @entries
1230 *
1231 * find_get_entries() will search for and return a group of up to
1232 * @nr_entries entries in the mapping. The entries are placed at
1233 * @entries. find_get_entries() takes a reference against any actual
1234 * pages it returns.
1235 *
1236 * The search returns a group of mapping-contiguous page cache entries
1237 * with ascending indexes. There may be holes in the indices due to
1238 * not-present pages.
1239 *
1240 * Any shadow entries of evicted pages, or swap entries from
1241 * shmem/tmpfs, are included in the returned array.
1242 *
1243 * find_get_entries() returns the number of pages and shadow entries
1244 * which were found.
1245 */
1246unsigned find_get_entries(struct address_space *mapping,
1247 pgoff_t start, unsigned int nr_entries,
1248 struct page **entries, pgoff_t *indices)
1249{
1250 void **slot;
1251 unsigned int ret = 0;
1252 struct radix_tree_iter iter;
1253
1254 if (!nr_entries)
1255 return 0;
1256
1257 rcu_read_lock();
1258 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1259 struct page *page;
1260repeat:
1261 page = radix_tree_deref_slot(slot);
1262 if (unlikely(!page))
1263 continue;
1264 if (radix_tree_exception(page)) {
1265 if (radix_tree_deref_retry(page)) {
1266 slot = radix_tree_iter_retry(&iter);
1267 continue;
1268 }
1269 /*
1270 * A shadow entry of a recently evicted page, a swap
1271 * entry from shmem/tmpfs or a DAX entry. Return it
1272 * without attempting to raise page count.
1273 */
1274 goto export;
1275 }
1276 if (!page_cache_get_speculative(page))
1277 goto repeat;
1278
1279 /* Has the page moved? */
1280 if (unlikely(page != *slot)) {
1281 put_page(page);
1282 goto repeat;
1283 }
1284export:
1285 indices[ret] = iter.index;
1286 entries[ret] = page;
1287 if (++ret == nr_entries)
1288 break;
1289 }
1290 rcu_read_unlock();
1291 return ret;
1292}
1293
1294/**
1295 * find_get_pages - gang pagecache lookup
1296 * @mapping: The address_space to search
1297 * @start: The starting page index
1298 * @nr_pages: The maximum number of pages
1299 * @pages: Where the resulting pages are placed
1300 *
1301 * find_get_pages() will search for and return a group of up to
1302 * @nr_pages pages in the mapping. The pages are placed at @pages.
1303 * find_get_pages() takes a reference against the returned pages.
1304 *
1305 * The search returns a group of mapping-contiguous pages with ascending
1306 * indexes. There may be holes in the indices due to not-present pages.
1307 *
1308 * find_get_pages() returns the number of pages which were found.
1309 */
1310unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
1311 unsigned int nr_pages, struct page **pages)
1312{
1313 struct radix_tree_iter iter;
1314 void **slot;
1315 unsigned ret = 0;
1316
1317 if (unlikely(!nr_pages))
1318 return 0;
1319
1320 rcu_read_lock();
1321 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
1322 struct page *page;
1323repeat:
1324 page = radix_tree_deref_slot(slot);
1325 if (unlikely(!page))
1326 continue;
1327
1328 if (radix_tree_exception(page)) {
1329 if (radix_tree_deref_retry(page)) {
1330 slot = radix_tree_iter_retry(&iter);
1331 continue;
1332 }
1333 /*
1334 * A shadow entry of a recently evicted page,
1335 * or a swap entry from shmem/tmpfs. Skip
1336 * over it.
1337 */
1338 continue;
1339 }
1340
1341 if (!page_cache_get_speculative(page))
1342 goto repeat;
1343
1344 /* Has the page moved? */
1345 if (unlikely(page != *slot)) {
1346 put_page(page);
1347 goto repeat;
1348 }
1349
1350 pages[ret] = page;
1351 if (++ret == nr_pages)
1352 break;
1353 }
1354
1355 rcu_read_unlock();
1356 return ret;
1357}
1358
1359/**
1360 * find_get_pages_contig - gang contiguous pagecache lookup
1361 * @mapping: The address_space to search
1362 * @index: The starting page index
1363 * @nr_pages: The maximum number of pages
1364 * @pages: Where the resulting pages are placed
1365 *
1366 * find_get_pages_contig() works exactly like find_get_pages(), except
1367 * that the returned number of pages are guaranteed to be contiguous.
1368 *
1369 * find_get_pages_contig() returns the number of pages which were found.
1370 */
1371unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
1372 unsigned int nr_pages, struct page **pages)
1373{
1374 struct radix_tree_iter iter;
1375 void **slot;
1376 unsigned int ret = 0;
1377
1378 if (unlikely(!nr_pages))
1379 return 0;
1380
1381 rcu_read_lock();
1382 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
1383 struct page *page;
1384repeat:
1385 page = radix_tree_deref_slot(slot);
1386 /* The hole, there no reason to continue */
1387 if (unlikely(!page))
1388 break;
1389
1390 if (radix_tree_exception(page)) {
1391 if (radix_tree_deref_retry(page)) {
1392 slot = radix_tree_iter_retry(&iter);
1393 continue;
1394 }
1395 /*
1396 * A shadow entry of a recently evicted page,
1397 * or a swap entry from shmem/tmpfs. Stop
1398 * looking for contiguous pages.
1399 */
1400 break;
1401 }
1402
1403 if (!page_cache_get_speculative(page))
1404 goto repeat;
1405
1406 /* Has the page moved? */
1407 if (unlikely(page != *slot)) {
1408 put_page(page);
1409 goto repeat;
1410 }
1411
1412 /*
1413 * must check mapping and index after taking the ref.
1414 * otherwise we can get both false positives and false
1415 * negatives, which is just confusing to the caller.
1416 */
1417 if (page->mapping == NULL || page->index != iter.index) {
1418 put_page(page);
1419 break;
1420 }
1421
1422 pages[ret] = page;
1423 if (++ret == nr_pages)
1424 break;
1425 }
1426 rcu_read_unlock();
1427 return ret;
1428}
1429EXPORT_SYMBOL(find_get_pages_contig);
1430
1431/**
1432 * find_get_pages_tag - find and return pages that match @tag
1433 * @mapping: the address_space to search
1434 * @index: the starting page index
1435 * @tag: the tag index
1436 * @nr_pages: the maximum number of pages
1437 * @pages: where the resulting pages are placed
1438 *
1439 * Like find_get_pages, except we only return pages which are tagged with
1440 * @tag. We update @index to index the next page for the traversal.
1441 */
1442unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
1443 int tag, unsigned int nr_pages, struct page **pages)
1444{
1445 struct radix_tree_iter iter;
1446 void **slot;
1447 unsigned ret = 0;
1448
1449 if (unlikely(!nr_pages))
1450 return 0;
1451
1452 rcu_read_lock();
1453 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1454 &iter, *index, tag) {
1455 struct page *page;
1456repeat:
1457 page = radix_tree_deref_slot(slot);
1458 if (unlikely(!page))
1459 continue;
1460
1461 if (radix_tree_exception(page)) {
1462 if (radix_tree_deref_retry(page)) {
1463 slot = radix_tree_iter_retry(&iter);
1464 continue;
1465 }
1466 /*
1467 * A shadow entry of a recently evicted page.
1468 *
1469 * Those entries should never be tagged, but
1470 * this tree walk is lockless and the tags are
1471 * looked up in bulk, one radix tree node at a
1472 * time, so there is a sizable window for page
1473 * reclaim to evict a page we saw tagged.
1474 *
1475 * Skip over it.
1476 */
1477 continue;
1478 }
1479
1480 if (!page_cache_get_speculative(page))
1481 goto repeat;
1482
1483 /* Has the page moved? */
1484 if (unlikely(page != *slot)) {
1485 put_page(page);
1486 goto repeat;
1487 }
1488
1489 pages[ret] = page;
1490 if (++ret == nr_pages)
1491 break;
1492 }
1493
1494 rcu_read_unlock();
1495
1496 if (ret)
1497 *index = pages[ret - 1]->index + 1;
1498
1499 return ret;
1500}
1501EXPORT_SYMBOL(find_get_pages_tag);
1502
1503/**
1504 * find_get_entries_tag - find and return entries that match @tag
1505 * @mapping: the address_space to search
1506 * @start: the starting page cache index
1507 * @tag: the tag index
1508 * @nr_entries: the maximum number of entries
1509 * @entries: where the resulting entries are placed
1510 * @indices: the cache indices corresponding to the entries in @entries
1511 *
1512 * Like find_get_entries, except we only return entries which are tagged with
1513 * @tag.
1514 */
1515unsigned find_get_entries_tag(struct address_space *mapping, pgoff_t start,
1516 int tag, unsigned int nr_entries,
1517 struct page **entries, pgoff_t *indices)
1518{
1519 void **slot;
1520 unsigned int ret = 0;
1521 struct radix_tree_iter iter;
1522
1523 if (!nr_entries)
1524 return 0;
1525
1526 rcu_read_lock();
1527 radix_tree_for_each_tagged(slot, &mapping->page_tree,
1528 &iter, start, tag) {
1529 struct page *page;
1530repeat:
1531 page = radix_tree_deref_slot(slot);
1532 if (unlikely(!page))
1533 continue;
1534 if (radix_tree_exception(page)) {
1535 if (radix_tree_deref_retry(page)) {
1536 slot = radix_tree_iter_retry(&iter);
1537 continue;
1538 }
1539
1540 /*
1541 * A shadow entry of a recently evicted page, a swap
1542 * entry from shmem/tmpfs or a DAX entry. Return it
1543 * without attempting to raise page count.
1544 */
1545 goto export;
1546 }
1547 if (!page_cache_get_speculative(page))
1548 goto repeat;
1549
1550 /* Has the page moved? */
1551 if (unlikely(page != *slot)) {
1552 put_page(page);
1553 goto repeat;
1554 }
1555export:
1556 indices[ret] = iter.index;
1557 entries[ret] = page;
1558 if (++ret == nr_entries)
1559 break;
1560 }
1561 rcu_read_unlock();
1562 return ret;
1563}
1564EXPORT_SYMBOL(find_get_entries_tag);
1565
1566/*
1567 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1568 * a _large_ part of the i/o request. Imagine the worst scenario:
1569 *
1570 * ---R__________________________________________B__________
1571 * ^ reading here ^ bad block(assume 4k)
1572 *
1573 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1574 * => failing the whole request => read(R) => read(R+1) =>
1575 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1576 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1577 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1578 *
1579 * It is going insane. Fix it by quickly scaling down the readahead size.
1580 */
1581static void shrink_readahead_size_eio(struct file *filp,
1582 struct file_ra_state *ra)
1583{
1584 ra->ra_pages /= 4;
1585}
1586
1587/**
1588 * do_generic_file_read - generic file read routine
1589 * @filp: the file to read
1590 * @ppos: current file position
1591 * @iter: data destination
1592 * @written: already copied
1593 *
1594 * This is a generic file read routine, and uses the
1595 * mapping->a_ops->readpage() function for the actual low-level stuff.
1596 *
1597 * This is really ugly. But the goto's actually try to clarify some
1598 * of the logic when it comes to error handling etc.
1599 */
1600static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
1601 struct iov_iter *iter, ssize_t written)
1602{
1603 struct address_space *mapping = filp->f_mapping;
1604 struct inode *inode = mapping->host;
1605 struct file_ra_state *ra = &filp->f_ra;
1606 pgoff_t index;
1607 pgoff_t last_index;
1608 pgoff_t prev_index;
1609 unsigned long offset; /* offset into pagecache page */
1610 unsigned int prev_offset;
1611 int error = 0;
1612
1613 index = *ppos >> PAGE_SHIFT;
1614 prev_index = ra->prev_pos >> PAGE_SHIFT;
1615 prev_offset = ra->prev_pos & (PAGE_SIZE-1);
1616 last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
1617 offset = *ppos & ~PAGE_MASK;
1618
1619 for (;;) {
1620 struct page *page;
1621 pgoff_t end_index;
1622 loff_t isize;
1623 unsigned long nr, ret;
1624
1625 cond_resched();
1626find_page:
1627 page = find_get_page(mapping, index);
1628 if (!page) {
1629 page_cache_sync_readahead(mapping,
1630 ra, filp,
1631 index, last_index - index);
1632 page = find_get_page(mapping, index);
1633 if (unlikely(page == NULL))
1634 goto no_cached_page;
1635 }
1636 if (PageReadahead(page)) {
1637 page_cache_async_readahead(mapping,
1638 ra, filp, page,
1639 index, last_index - index);
1640 }
1641 if (!PageUptodate(page)) {
1642 /*
1643 * See comment in do_read_cache_page on why
1644 * wait_on_page_locked is used to avoid unnecessarily
1645 * serialisations and why it's safe.
1646 */
1647 wait_on_page_locked_killable(page);
1648 if (PageUptodate(page))
1649 goto page_ok;
1650
1651 if (inode->i_blkbits == PAGE_SHIFT ||
1652 !mapping->a_ops->is_partially_uptodate)
1653 goto page_not_up_to_date;
1654 if (!trylock_page(page))
1655 goto page_not_up_to_date;
1656 /* Did it get truncated before we got the lock? */
1657 if (!page->mapping)
1658 goto page_not_up_to_date_locked;
1659 if (!mapping->a_ops->is_partially_uptodate(page,
1660 offset, iter->count))
1661 goto page_not_up_to_date_locked;
1662 unlock_page(page);
1663 }
1664page_ok:
1665 /*
1666 * i_size must be checked after we know the page is Uptodate.
1667 *
1668 * Checking i_size after the check allows us to calculate
1669 * the correct value for "nr", which means the zero-filled
1670 * part of the page is not copied back to userspace (unless
1671 * another truncate extends the file - this is desired though).
1672 */
1673
1674 isize = i_size_read(inode);
1675 end_index = (isize - 1) >> PAGE_SHIFT;
1676 if (unlikely(!isize || index > end_index)) {
1677 put_page(page);
1678 goto out;
1679 }
1680
1681 /* nr is the maximum number of bytes to copy from this page */
1682 nr = PAGE_SIZE;
1683 if (index == end_index) {
1684 nr = ((isize - 1) & ~PAGE_MASK) + 1;
1685 if (nr <= offset) {
1686 put_page(page);
1687 goto out;
1688 }
1689 }
1690 nr = nr - offset;
1691
1692 /* If users can be writing to this page using arbitrary
1693 * virtual addresses, take care about potential aliasing
1694 * before reading the page on the kernel side.
1695 */
1696 if (mapping_writably_mapped(mapping))
1697 flush_dcache_page(page);
1698
1699 /*
1700 * When a sequential read accesses a page several times,
1701 * only mark it as accessed the first time.
1702 */
1703 if (prev_index != index || offset != prev_offset)
1704 mark_page_accessed(page);
1705 prev_index = index;
1706
1707 /*
1708 * Ok, we have the page, and it's up-to-date, so
1709 * now we can copy it to user space...
1710 */
1711
1712 ret = copy_page_to_iter(page, offset, nr, iter);
1713 offset += ret;
1714 index += offset >> PAGE_SHIFT;
1715 offset &= ~PAGE_MASK;
1716 prev_offset = offset;
1717
1718 put_page(page);
1719 written += ret;
1720 if (!iov_iter_count(iter))
1721 goto out;
1722 if (ret < nr) {
1723 error = -EFAULT;
1724 goto out;
1725 }
1726 continue;
1727
1728page_not_up_to_date:
1729 /* Get exclusive access to the page ... */
1730 error = lock_page_killable(page);
1731 if (unlikely(error))
1732 goto readpage_error;
1733
1734page_not_up_to_date_locked:
1735 /* Did it get truncated before we got the lock? */
1736 if (!page->mapping) {
1737 unlock_page(page);
1738 put_page(page);
1739 continue;
1740 }
1741
1742 /* Did somebody else fill it already? */
1743 if (PageUptodate(page)) {
1744 unlock_page(page);
1745 goto page_ok;
1746 }
1747
1748readpage:
1749 /*
1750 * A previous I/O error may have been due to temporary
1751 * failures, eg. multipath errors.
1752 * PG_error will be set again if readpage fails.
1753 */
1754 ClearPageError(page);
1755 /* Start the actual read. The read will unlock the page. */
1756 error = mapping->a_ops->readpage(filp, page);
1757
1758 if (unlikely(error)) {
1759 if (error == AOP_TRUNCATED_PAGE) {
1760 put_page(page);
1761 error = 0;
1762 goto find_page;
1763 }
1764 goto readpage_error;
1765 }
1766
1767 if (!PageUptodate(page)) {
1768 error = lock_page_killable(page);
1769 if (unlikely(error))
1770 goto readpage_error;
1771 if (!PageUptodate(page)) {
1772 if (page->mapping == NULL) {
1773 /*
1774 * invalidate_mapping_pages got it
1775 */
1776 unlock_page(page);
1777 put_page(page);
1778 goto find_page;
1779 }
1780 unlock_page(page);
1781 shrink_readahead_size_eio(filp, ra);
1782 error = -EIO;
1783 goto readpage_error;
1784 }
1785 unlock_page(page);
1786 }
1787
1788 goto page_ok;
1789
1790readpage_error:
1791 /* UHHUH! A synchronous read error occurred. Report it */
1792 put_page(page);
1793 goto out;
1794
1795no_cached_page:
1796 /*
1797 * Ok, it wasn't cached, so we need to create a new
1798 * page..
1799 */
1800 page = page_cache_alloc_cold(mapping);
1801 if (!page) {
1802 error = -ENOMEM;
1803 goto out;
1804 }
1805 error = add_to_page_cache_lru(page, mapping, index,
1806 mapping_gfp_constraint(mapping, GFP_KERNEL));
1807 if (error) {
1808 put_page(page);
1809 if (error == -EEXIST) {
1810 error = 0;
1811 goto find_page;
1812 }
1813 goto out;
1814 }
1815 goto readpage;
1816 }
1817
1818out:
1819 ra->prev_pos = prev_index;
1820 ra->prev_pos <<= PAGE_SHIFT;
1821 ra->prev_pos |= prev_offset;
1822
1823 *ppos = ((loff_t)index << PAGE_SHIFT) + offset;
1824 file_accessed(filp);
1825 return written ? written : error;
1826}
1827
1828/**
1829 * generic_file_read_iter - generic filesystem read routine
1830 * @iocb: kernel I/O control block
1831 * @iter: destination for the data read
1832 *
1833 * This is the "read_iter()" routine for all filesystems
1834 * that can use the page cache directly.
1835 */
1836ssize_t
1837generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
1838{
1839 struct file *file = iocb->ki_filp;
1840 ssize_t retval = 0;
1841 loff_t *ppos = &iocb->ki_pos;
1842 loff_t pos = *ppos;
1843 size_t count = iov_iter_count(iter);
1844
1845 if (!count)
1846 goto out; /* skip atime */
1847
1848 if (iocb->ki_flags & IOCB_DIRECT) {
1849 struct address_space *mapping = file->f_mapping;
1850 struct inode *inode = mapping->host;
1851 loff_t size;
1852
1853 size = i_size_read(inode);
1854 retval = filemap_write_and_wait_range(mapping, pos,
1855 pos + count - 1);
1856 if (!retval) {
1857 struct iov_iter data = *iter;
1858 retval = mapping->a_ops->direct_IO(iocb, &data, pos);
1859 }
1860
1861 if (retval > 0) {
1862 *ppos = pos + retval;
1863 iov_iter_advance(iter, retval);
1864 }
1865
1866 /*
1867 * Btrfs can have a short DIO read if we encounter
1868 * compressed extents, so if there was an error, or if
1869 * we've already read everything we wanted to, or if
1870 * there was a short read because we hit EOF, go ahead
1871 * and return. Otherwise fallthrough to buffered io for
1872 * the rest of the read. Buffered reads will not work for
1873 * DAX files, so don't bother trying.
1874 */
1875 if (retval < 0 || !iov_iter_count(iter) || *ppos >= size ||
1876 IS_DAX(inode)) {
1877 file_accessed(file);
1878 goto out;
1879 }
1880 }
1881
1882 retval = do_generic_file_read(file, ppos, iter, retval);
1883out:
1884 return retval;
1885}
1886EXPORT_SYMBOL(generic_file_read_iter);
1887
1888#ifdef CONFIG_MMU
1889/**
1890 * page_cache_read - adds requested page to the page cache if not already there
1891 * @file: file to read
1892 * @offset: page index
1893 * @gfp_mask: memory allocation flags
1894 *
1895 * This adds the requested page to the page cache if it isn't already there,
1896 * and schedules an I/O to read in its contents from disk.
1897 */
1898static int page_cache_read(struct file *file, pgoff_t offset, gfp_t gfp_mask)
1899{
1900 struct address_space *mapping = file->f_mapping;
1901 struct page *page;
1902 int ret;
1903
1904 do {
1905 page = __page_cache_alloc(gfp_mask|__GFP_COLD);
1906 if (!page)
1907 return -ENOMEM;
1908
1909 ret = add_to_page_cache_lru(page, mapping, offset, gfp_mask & GFP_KERNEL);
1910 if (ret == 0)
1911 ret = mapping->a_ops->readpage(file, page);
1912 else if (ret == -EEXIST)
1913 ret = 0; /* losing race to add is OK */
1914
1915 put_page(page);
1916
1917 } while (ret == AOP_TRUNCATED_PAGE);
1918
1919 return ret;
1920}
1921
1922#define MMAP_LOTSAMISS (100)
1923
1924/*
1925 * Synchronous readahead happens when we don't even find
1926 * a page in the page cache at all.
1927 */
1928static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1929 struct file_ra_state *ra,
1930 struct file *file,
1931 pgoff_t offset)
1932{
1933 struct address_space *mapping = file->f_mapping;
1934
1935 /* If we don't want any read-ahead, don't bother */
1936 if (vma->vm_flags & VM_RAND_READ)
1937 return;
1938 if (!ra->ra_pages)
1939 return;
1940
1941 if (vma->vm_flags & VM_SEQ_READ) {
1942 page_cache_sync_readahead(mapping, ra, file, offset,
1943 ra->ra_pages);
1944 return;
1945 }
1946
1947 /* Avoid banging the cache line if not needed */
1948 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1949 ra->mmap_miss++;
1950
1951 /*
1952 * Do we miss much more than hit in this file? If so,
1953 * stop bothering with read-ahead. It will only hurt.
1954 */
1955 if (ra->mmap_miss > MMAP_LOTSAMISS)
1956 return;
1957
1958 /*
1959 * mmap read-around
1960 */
1961 ra->start = max_t(long, 0, offset - ra->ra_pages / 2);
1962 ra->size = ra->ra_pages;
1963 ra->async_size = ra->ra_pages / 4;
1964 ra_submit(ra, mapping, file);
1965}
1966
1967/*
1968 * Asynchronous readahead happens when we find the page and PG_readahead,
1969 * so we want to possibly extend the readahead further..
1970 */
1971static void do_async_mmap_readahead(struct vm_area_struct *vma,
1972 struct file_ra_state *ra,
1973 struct file *file,
1974 struct page *page,
1975 pgoff_t offset)
1976{
1977 struct address_space *mapping = file->f_mapping;
1978
1979 /* If we don't want any read-ahead, don't bother */
1980 if (vma->vm_flags & VM_RAND_READ)
1981 return;
1982 if (ra->mmap_miss > 0)
1983 ra->mmap_miss--;
1984 if (PageReadahead(page))
1985 page_cache_async_readahead(mapping, ra, file,
1986 page, offset, ra->ra_pages);
1987}
1988
1989/**
1990 * filemap_fault - read in file data for page fault handling
1991 * @vma: vma in which the fault was taken
1992 * @vmf: struct vm_fault containing details of the fault
1993 *
1994 * filemap_fault() is invoked via the vma operations vector for a
1995 * mapped memory region to read in file data during a page fault.
1996 *
1997 * The goto's are kind of ugly, but this streamlines the normal case of having
1998 * it in the page cache, and handles the special cases reasonably without
1999 * having a lot of duplicated code.
2000 *
2001 * vma->vm_mm->mmap_sem must be held on entry.
2002 *
2003 * If our return value has VM_FAULT_RETRY set, it's because
2004 * lock_page_or_retry() returned 0.
2005 * The mmap_sem has usually been released in this case.
2006 * See __lock_page_or_retry() for the exception.
2007 *
2008 * If our return value does not have VM_FAULT_RETRY set, the mmap_sem
2009 * has not been released.
2010 *
2011 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
2012 */
2013int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
2014{
2015 int error;
2016 struct file *file = vma->vm_file;
2017 struct address_space *mapping = file->f_mapping;
2018 struct file_ra_state *ra = &file->f_ra;
2019 struct inode *inode = mapping->host;
2020 pgoff_t offset = vmf->pgoff;
2021 struct page *page;
2022 loff_t size;
2023 int ret = 0;
2024
2025 size = round_up(i_size_read(inode), PAGE_SIZE);
2026 if (offset >= size >> PAGE_SHIFT)
2027 return VM_FAULT_SIGBUS;
2028
2029 /*
2030 * Do we have something in the page cache already?
2031 */
2032 page = find_get_page(mapping, offset);
2033 if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
2034 /*
2035 * We found the page, so try async readahead before
2036 * waiting for the lock.
2037 */
2038 do_async_mmap_readahead(vma, ra, file, page, offset);
2039 } else if (!page) {
2040 /* No page in the page cache at all */
2041 do_sync_mmap_readahead(vma, ra, file, offset);
2042 count_vm_event(PGMAJFAULT);
2043 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
2044 ret = VM_FAULT_MAJOR;
2045retry_find:
2046 page = find_get_page(mapping, offset);
2047 if (!page)
2048 goto no_cached_page;
2049 }
2050
2051 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
2052 put_page(page);
2053 return ret | VM_FAULT_RETRY;
2054 }
2055
2056 /* Did it get truncated? */
2057 if (unlikely(page->mapping != mapping)) {
2058 unlock_page(page);
2059 put_page(page);
2060 goto retry_find;
2061 }
2062 VM_BUG_ON_PAGE(page->index != offset, page);
2063
2064 /*
2065 * We have a locked page in the page cache, now we need to check
2066 * that it's up-to-date. If not, it is going to be due to an error.
2067 */
2068 if (unlikely(!PageUptodate(page)))
2069 goto page_not_uptodate;
2070
2071 /*
2072 * Found the page and have a reference on it.
2073 * We must recheck i_size under page lock.
2074 */
2075 size = round_up(i_size_read(inode), PAGE_SIZE);
2076 if (unlikely(offset >= size >> PAGE_SHIFT)) {
2077 unlock_page(page);
2078 put_page(page);
2079 return VM_FAULT_SIGBUS;
2080 }
2081
2082 vmf->page = page;
2083 return ret | VM_FAULT_LOCKED;
2084
2085no_cached_page:
2086 /*
2087 * We're only likely to ever get here if MADV_RANDOM is in
2088 * effect.
2089 */
2090 error = page_cache_read(file, offset, vmf->gfp_mask);
2091
2092 /*
2093 * The page we want has now been added to the page cache.
2094 * In the unlikely event that someone removed it in the
2095 * meantime, we'll just come back here and read it again.
2096 */
2097 if (error >= 0)
2098 goto retry_find;
2099
2100 /*
2101 * An error return from page_cache_read can result if the
2102 * system is low on memory, or a problem occurs while trying
2103 * to schedule I/O.
2104 */
2105 if (error == -ENOMEM)
2106 return VM_FAULT_OOM;
2107 return VM_FAULT_SIGBUS;
2108
2109page_not_uptodate:
2110 /*
2111 * Umm, take care of errors if the page isn't up-to-date.
2112 * Try to re-read it _once_. We do this synchronously,
2113 * because there really aren't any performance issues here
2114 * and we need to check for errors.
2115 */
2116 ClearPageError(page);
2117 error = mapping->a_ops->readpage(file, page);
2118 if (!error) {
2119 wait_on_page_locked(page);
2120 if (!PageUptodate(page))
2121 error = -EIO;
2122 }
2123 put_page(page);
2124
2125 if (!error || error == AOP_TRUNCATED_PAGE)
2126 goto retry_find;
2127
2128 /* Things didn't work out. Return zero to tell the mm layer so. */
2129 shrink_readahead_size_eio(file, ra);
2130 return VM_FAULT_SIGBUS;
2131}
2132EXPORT_SYMBOL(filemap_fault);
2133
2134void filemap_map_pages(struct vm_area_struct *vma, struct vm_fault *vmf)
2135{
2136 struct radix_tree_iter iter;
2137 void **slot;
2138 struct file *file = vma->vm_file;
2139 struct address_space *mapping = file->f_mapping;
2140 loff_t size;
2141 struct page *page;
2142 unsigned long address = (unsigned long) vmf->virtual_address;
2143 unsigned long addr;
2144 pte_t *pte;
2145
2146 rcu_read_lock();
2147 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, vmf->pgoff) {
2148 if (iter.index > vmf->max_pgoff)
2149 break;
2150repeat:
2151 page = radix_tree_deref_slot(slot);
2152 if (unlikely(!page))
2153 goto next;
2154 if (radix_tree_exception(page)) {
2155 if (radix_tree_deref_retry(page)) {
2156 slot = radix_tree_iter_retry(&iter);
2157 continue;
2158 }
2159 goto next;
2160 }
2161
2162 if (!page_cache_get_speculative(page))
2163 goto repeat;
2164
2165 /* Has the page moved? */
2166 if (unlikely(page != *slot)) {
2167 put_page(page);
2168 goto repeat;
2169 }
2170
2171 if (!PageUptodate(page) ||
2172 PageReadahead(page) ||
2173 PageHWPoison(page))
2174 goto skip;
2175 if (!trylock_page(page))
2176 goto skip;
2177
2178 if (page->mapping != mapping || !PageUptodate(page))
2179 goto unlock;
2180
2181 size = round_up(i_size_read(mapping->host), PAGE_SIZE);
2182 if (page->index >= size >> PAGE_SHIFT)
2183 goto unlock;
2184
2185 pte = vmf->pte + page->index - vmf->pgoff;
2186 if (!pte_none(*pte))
2187 goto unlock;
2188
2189 if (file->f_ra.mmap_miss > 0)
2190 file->f_ra.mmap_miss--;
2191 addr = address + (page->index - vmf->pgoff) * PAGE_SIZE;
2192 do_set_pte(vma, addr, page, pte, false, false);
2193 unlock_page(page);
2194 goto next;
2195unlock:
2196 unlock_page(page);
2197skip:
2198 put_page(page);
2199next:
2200 if (iter.index == vmf->max_pgoff)
2201 break;
2202 }
2203 rcu_read_unlock();
2204}
2205EXPORT_SYMBOL(filemap_map_pages);
2206
2207int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
2208{
2209 struct page *page = vmf->page;
2210 struct inode *inode = file_inode(vma->vm_file);
2211 int ret = VM_FAULT_LOCKED;
2212
2213 sb_start_pagefault(inode->i_sb);
2214 file_update_time(vma->vm_file);
2215 lock_page(page);
2216 if (page->mapping != inode->i_mapping) {
2217 unlock_page(page);
2218 ret = VM_FAULT_NOPAGE;
2219 goto out;
2220 }
2221 /*
2222 * We mark the page dirty already here so that when freeze is in
2223 * progress, we are guaranteed that writeback during freezing will
2224 * see the dirty page and writeprotect it again.
2225 */
2226 set_page_dirty(page);
2227 wait_for_stable_page(page);
2228out:
2229 sb_end_pagefault(inode->i_sb);
2230 return ret;
2231}
2232EXPORT_SYMBOL(filemap_page_mkwrite);
2233
2234const struct vm_operations_struct generic_file_vm_ops = {
2235 .fault = filemap_fault,
2236 .map_pages = filemap_map_pages,
2237 .page_mkwrite = filemap_page_mkwrite,
2238};
2239
2240/* This is used for a general mmap of a disk file */
2241
2242int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2243{
2244 struct address_space *mapping = file->f_mapping;
2245
2246 if (!mapping->a_ops->readpage)
2247 return -ENOEXEC;
2248 file_accessed(file);
2249 vma->vm_ops = &generic_file_vm_ops;
2250 return 0;
2251}
2252
2253/*
2254 * This is for filesystems which do not implement ->writepage.
2255 */
2256int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
2257{
2258 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
2259 return -EINVAL;
2260 return generic_file_mmap(file, vma);
2261}
2262#else
2263int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
2264{
2265 return -ENOSYS;
2266}
2267int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
2268{
2269 return -ENOSYS;
2270}
2271#endif /* CONFIG_MMU */
2272
2273EXPORT_SYMBOL(generic_file_mmap);
2274EXPORT_SYMBOL(generic_file_readonly_mmap);
2275
2276static struct page *wait_on_page_read(struct page *page)
2277{
2278 if (!IS_ERR(page)) {
2279 wait_on_page_locked(page);
2280 if (!PageUptodate(page)) {
2281 put_page(page);
2282 page = ERR_PTR(-EIO);
2283 }
2284 }
2285 return page;
2286}
2287
2288static struct page *do_read_cache_page(struct address_space *mapping,
2289 pgoff_t index,
2290 int (*filler)(void *, struct page *),
2291 void *data,
2292 gfp_t gfp)
2293{
2294 struct page *page;
2295 int err;
2296repeat:
2297 page = find_get_page(mapping, index);
2298 if (!page) {
2299 page = __page_cache_alloc(gfp | __GFP_COLD);
2300 if (!page)
2301 return ERR_PTR(-ENOMEM);
2302 err = add_to_page_cache_lru(page, mapping, index, gfp);
2303 if (unlikely(err)) {
2304 put_page(page);
2305 if (err == -EEXIST)
2306 goto repeat;
2307 /* Presumably ENOMEM for radix tree node */
2308 return ERR_PTR(err);
2309 }
2310
2311filler:
2312 err = filler(data, page);
2313 if (err < 0) {
2314 put_page(page);
2315 return ERR_PTR(err);
2316 }
2317
2318 page = wait_on_page_read(page);
2319 if (IS_ERR(page))
2320 return page;
2321 goto out;
2322 }
2323 if (PageUptodate(page))
2324 goto out;
2325
2326 /*
2327 * Page is not up to date and may be locked due one of the following
2328 * case a: Page is being filled and the page lock is held
2329 * case b: Read/write error clearing the page uptodate status
2330 * case c: Truncation in progress (page locked)
2331 * case d: Reclaim in progress
2332 *
2333 * Case a, the page will be up to date when the page is unlocked.
2334 * There is no need to serialise on the page lock here as the page
2335 * is pinned so the lock gives no additional protection. Even if the
2336 * the page is truncated, the data is still valid if PageUptodate as
2337 * it's a race vs truncate race.
2338 * Case b, the page will not be up to date
2339 * Case c, the page may be truncated but in itself, the data may still
2340 * be valid after IO completes as it's a read vs truncate race. The
2341 * operation must restart if the page is not uptodate on unlock but
2342 * otherwise serialising on page lock to stabilise the mapping gives
2343 * no additional guarantees to the caller as the page lock is
2344 * released before return.
2345 * Case d, similar to truncation. If reclaim holds the page lock, it
2346 * will be a race with remove_mapping that determines if the mapping
2347 * is valid on unlock but otherwise the data is valid and there is
2348 * no need to serialise with page lock.
2349 *
2350 * As the page lock gives no additional guarantee, we optimistically
2351 * wait on the page to be unlocked and check if it's up to date and
2352 * use the page if it is. Otherwise, the page lock is required to
2353 * distinguish between the different cases. The motivation is that we
2354 * avoid spurious serialisations and wakeups when multiple processes
2355 * wait on the same page for IO to complete.
2356 */
2357 wait_on_page_locked(page);
2358 if (PageUptodate(page))
2359 goto out;
2360
2361 /* Distinguish between all the cases under the safety of the lock */
2362 lock_page(page);
2363
2364 /* Case c or d, restart the operation */
2365 if (!page->mapping) {
2366 unlock_page(page);
2367 put_page(page);
2368 goto repeat;
2369 }
2370
2371 /* Someone else locked and filled the page in a very small window */
2372 if (PageUptodate(page)) {
2373 unlock_page(page);
2374 goto out;
2375 }
2376 goto filler;
2377
2378out:
2379 mark_page_accessed(page);
2380 return page;
2381}
2382
2383/**
2384 * read_cache_page - read into page cache, fill it if needed
2385 * @mapping: the page's address_space
2386 * @index: the page index
2387 * @filler: function to perform the read
2388 * @data: first arg to filler(data, page) function, often left as NULL
2389 *
2390 * Read into the page cache. If a page already exists, and PageUptodate() is
2391 * not set, try to fill the page and wait for it to become unlocked.
2392 *
2393 * If the page does not get brought uptodate, return -EIO.
2394 */
2395struct page *read_cache_page(struct address_space *mapping,
2396 pgoff_t index,
2397 int (*filler)(void *, struct page *),
2398 void *data)
2399{
2400 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
2401}
2402EXPORT_SYMBOL(read_cache_page);
2403
2404/**
2405 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
2406 * @mapping: the page's address_space
2407 * @index: the page index
2408 * @gfp: the page allocator flags to use if allocating
2409 *
2410 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
2411 * any new page allocations done using the specified allocation flags.
2412 *
2413 * If the page does not get brought uptodate, return -EIO.
2414 */
2415struct page *read_cache_page_gfp(struct address_space *mapping,
2416 pgoff_t index,
2417 gfp_t gfp)
2418{
2419 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
2420
2421 return do_read_cache_page(mapping, index, filler, NULL, gfp);
2422}
2423EXPORT_SYMBOL(read_cache_page_gfp);
2424
2425/*
2426 * Performs necessary checks before doing a write
2427 *
2428 * Can adjust writing position or amount of bytes to write.
2429 * Returns appropriate error code that caller should return or
2430 * zero in case that write should be allowed.
2431 */
2432inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
2433{
2434 struct file *file = iocb->ki_filp;
2435 struct inode *inode = file->f_mapping->host;
2436 unsigned long limit = rlimit(RLIMIT_FSIZE);
2437 loff_t pos;
2438
2439 if (!iov_iter_count(from))
2440 return 0;
2441
2442 /* FIXME: this is for backwards compatibility with 2.4 */
2443 if (iocb->ki_flags & IOCB_APPEND)
2444 iocb->ki_pos = i_size_read(inode);
2445
2446 pos = iocb->ki_pos;
2447
2448 if (limit != RLIM_INFINITY) {
2449 if (iocb->ki_pos >= limit) {
2450 send_sig(SIGXFSZ, current, 0);
2451 return -EFBIG;
2452 }
2453 iov_iter_truncate(from, limit - (unsigned long)pos);
2454 }
2455
2456 /*
2457 * LFS rule
2458 */
2459 if (unlikely(pos + iov_iter_count(from) > MAX_NON_LFS &&
2460 !(file->f_flags & O_LARGEFILE))) {
2461 if (pos >= MAX_NON_LFS)
2462 return -EFBIG;
2463 iov_iter_truncate(from, MAX_NON_LFS - (unsigned long)pos);
2464 }
2465
2466 /*
2467 * Are we about to exceed the fs block limit ?
2468 *
2469 * If we have written data it becomes a short write. If we have
2470 * exceeded without writing data we send a signal and return EFBIG.
2471 * Linus frestrict idea will clean these up nicely..
2472 */
2473 if (unlikely(pos >= inode->i_sb->s_maxbytes))
2474 return -EFBIG;
2475
2476 iov_iter_truncate(from, inode->i_sb->s_maxbytes - pos);
2477 return iov_iter_count(from);
2478}
2479EXPORT_SYMBOL(generic_write_checks);
2480
2481int pagecache_write_begin(struct file *file, struct address_space *mapping,
2482 loff_t pos, unsigned len, unsigned flags,
2483 struct page **pagep, void **fsdata)
2484{
2485 const struct address_space_operations *aops = mapping->a_ops;
2486
2487 return aops->write_begin(file, mapping, pos, len, flags,
2488 pagep, fsdata);
2489}
2490EXPORT_SYMBOL(pagecache_write_begin);
2491
2492int pagecache_write_end(struct file *file, struct address_space *mapping,
2493 loff_t pos, unsigned len, unsigned copied,
2494 struct page *page, void *fsdata)
2495{
2496 const struct address_space_operations *aops = mapping->a_ops;
2497
2498 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2499}
2500EXPORT_SYMBOL(pagecache_write_end);
2501
2502ssize_t
2503generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos)
2504{
2505 struct file *file = iocb->ki_filp;
2506 struct address_space *mapping = file->f_mapping;
2507 struct inode *inode = mapping->host;
2508 ssize_t written;
2509 size_t write_len;
2510 pgoff_t end;
2511 struct iov_iter data;
2512
2513 write_len = iov_iter_count(from);
2514 end = (pos + write_len - 1) >> PAGE_SHIFT;
2515
2516 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2517 if (written)
2518 goto out;
2519
2520 /*
2521 * After a write we want buffered reads to be sure to go to disk to get
2522 * the new data. We invalidate clean cached page from the region we're
2523 * about to write. We do this *before* the write so that we can return
2524 * without clobbering -EIOCBQUEUED from ->direct_IO().
2525 */
2526 if (mapping->nrpages) {
2527 written = invalidate_inode_pages2_range(mapping,
2528 pos >> PAGE_SHIFT, end);
2529 /*
2530 * If a page can not be invalidated, return 0 to fall back
2531 * to buffered write.
2532 */
2533 if (written) {
2534 if (written == -EBUSY)
2535 return 0;
2536 goto out;
2537 }
2538 }
2539
2540 data = *from;
2541 written = mapping->a_ops->direct_IO(iocb, &data, pos);
2542
2543 /*
2544 * Finally, try again to invalidate clean pages which might have been
2545 * cached by non-direct readahead, or faulted in by get_user_pages()
2546 * if the source of the write was an mmap'ed region of the file
2547 * we're writing. Either one is a pretty crazy thing to do,
2548 * so we don't support it 100%. If this invalidation
2549 * fails, tough, the write still worked...
2550 */
2551 if (mapping->nrpages) {
2552 invalidate_inode_pages2_range(mapping,
2553 pos >> PAGE_SHIFT, end);
2554 }
2555
2556 if (written > 0) {
2557 pos += written;
2558 iov_iter_advance(from, written);
2559 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2560 i_size_write(inode, pos);
2561 mark_inode_dirty(inode);
2562 }
2563 iocb->ki_pos = pos;
2564 }
2565out:
2566 return written;
2567}
2568EXPORT_SYMBOL(generic_file_direct_write);
2569
2570/*
2571 * Find or create a page at the given pagecache position. Return the locked
2572 * page. This function is specifically for buffered writes.
2573 */
2574struct page *grab_cache_page_write_begin(struct address_space *mapping,
2575 pgoff_t index, unsigned flags)
2576{
2577 struct page *page;
2578 int fgp_flags = FGP_LOCK|FGP_ACCESSED|FGP_WRITE|FGP_CREAT;
2579
2580 if (flags & AOP_FLAG_NOFS)
2581 fgp_flags |= FGP_NOFS;
2582
2583 page = pagecache_get_page(mapping, index, fgp_flags,
2584 mapping_gfp_mask(mapping));
2585 if (page)
2586 wait_for_stable_page(page);
2587
2588 return page;
2589}
2590EXPORT_SYMBOL(grab_cache_page_write_begin);
2591
2592ssize_t generic_perform_write(struct file *file,
2593 struct iov_iter *i, loff_t pos)
2594{
2595 struct address_space *mapping = file->f_mapping;
2596 const struct address_space_operations *a_ops = mapping->a_ops;
2597 long status = 0;
2598 ssize_t written = 0;
2599 unsigned int flags = 0;
2600
2601 /*
2602 * Copies from kernel address space cannot fail (NFSD is a big user).
2603 */
2604 if (!iter_is_iovec(i))
2605 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2606
2607 do {
2608 struct page *page;
2609 unsigned long offset; /* Offset into pagecache page */
2610 unsigned long bytes; /* Bytes to write to page */
2611 size_t copied; /* Bytes copied from user */
2612 void *fsdata;
2613
2614 offset = (pos & (PAGE_SIZE - 1));
2615 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2616 iov_iter_count(i));
2617
2618again:
2619 /*
2620 * Bring in the user page that we will copy from _first_.
2621 * Otherwise there's a nasty deadlock on copying from the
2622 * same page as we're writing to, without it being marked
2623 * up-to-date.
2624 *
2625 * Not only is this an optimisation, but it is also required
2626 * to check that the address is actually valid, when atomic
2627 * usercopies are used, below.
2628 */
2629 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2630 status = -EFAULT;
2631 break;
2632 }
2633
2634 if (fatal_signal_pending(current)) {
2635 status = -EINTR;
2636 break;
2637 }
2638
2639 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2640 &page, &fsdata);
2641 if (unlikely(status < 0))
2642 break;
2643
2644 if (mapping_writably_mapped(mapping))
2645 flush_dcache_page(page);
2646
2647 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2648 flush_dcache_page(page);
2649
2650 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2651 page, fsdata);
2652 if (unlikely(status < 0))
2653 break;
2654 copied = status;
2655
2656 cond_resched();
2657
2658 iov_iter_advance(i, copied);
2659 if (unlikely(copied == 0)) {
2660 /*
2661 * If we were unable to copy any data at all, we must
2662 * fall back to a single segment length write.
2663 *
2664 * If we didn't fallback here, we could livelock
2665 * because not all segments in the iov can be copied at
2666 * once without a pagefault.
2667 */
2668 bytes = min_t(unsigned long, PAGE_SIZE - offset,
2669 iov_iter_single_seg_count(i));
2670 goto again;
2671 }
2672 pos += copied;
2673 written += copied;
2674
2675 balance_dirty_pages_ratelimited(mapping);
2676 } while (iov_iter_count(i));
2677
2678 return written ? written : status;
2679}
2680EXPORT_SYMBOL(generic_perform_write);
2681
2682/**
2683 * __generic_file_write_iter - write data to a file
2684 * @iocb: IO state structure (file, offset, etc.)
2685 * @from: iov_iter with data to write
2686 *
2687 * This function does all the work needed for actually writing data to a
2688 * file. It does all basic checks, removes SUID from the file, updates
2689 * modification times and calls proper subroutines depending on whether we
2690 * do direct IO or a standard buffered write.
2691 *
2692 * It expects i_mutex to be grabbed unless we work on a block device or similar
2693 * object which does not need locking at all.
2694 *
2695 * This function does *not* take care of syncing data in case of O_SYNC write.
2696 * A caller has to handle it. This is mainly due to the fact that we want to
2697 * avoid syncing under i_mutex.
2698 */
2699ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2700{
2701 struct file *file = iocb->ki_filp;
2702 struct address_space * mapping = file->f_mapping;
2703 struct inode *inode = mapping->host;
2704 ssize_t written = 0;
2705 ssize_t err;
2706 ssize_t status;
2707
2708 /* We can write back this queue in page reclaim */
2709 current->backing_dev_info = inode_to_bdi(inode);
2710 err = file_remove_privs(file);
2711 if (err)
2712 goto out;
2713
2714 err = file_update_time(file);
2715 if (err)
2716 goto out;
2717
2718 if (iocb->ki_flags & IOCB_DIRECT) {
2719 loff_t pos, endbyte;
2720
2721 written = generic_file_direct_write(iocb, from, iocb->ki_pos);
2722 /*
2723 * If the write stopped short of completing, fall back to
2724 * buffered writes. Some filesystems do this for writes to
2725 * holes, for example. For DAX files, a buffered write will
2726 * not succeed (even if it did, DAX does not handle dirty
2727 * page-cache pages correctly).
2728 */
2729 if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
2730 goto out;
2731
2732 status = generic_perform_write(file, from, pos = iocb->ki_pos);
2733 /*
2734 * If generic_perform_write() returned a synchronous error
2735 * then we want to return the number of bytes which were
2736 * direct-written, or the error code if that was zero. Note
2737 * that this differs from normal direct-io semantics, which
2738 * will return -EFOO even if some bytes were written.
2739 */
2740 if (unlikely(status < 0)) {
2741 err = status;
2742 goto out;
2743 }
2744 /*
2745 * We need to ensure that the page cache pages are written to
2746 * disk and invalidated to preserve the expected O_DIRECT
2747 * semantics.
2748 */
2749 endbyte = pos + status - 1;
2750 err = filemap_write_and_wait_range(mapping, pos, endbyte);
2751 if (err == 0) {
2752 iocb->ki_pos = endbyte + 1;
2753 written += status;
2754 invalidate_mapping_pages(mapping,
2755 pos >> PAGE_SHIFT,
2756 endbyte >> PAGE_SHIFT);
2757 } else {
2758 /*
2759 * We don't know how much we wrote, so just return
2760 * the number of bytes which were direct-written
2761 */
2762 }
2763 } else {
2764 written = generic_perform_write(file, from, iocb->ki_pos);
2765 if (likely(written > 0))
2766 iocb->ki_pos += written;
2767 }
2768out:
2769 current->backing_dev_info = NULL;
2770 return written ? written : err;
2771}
2772EXPORT_SYMBOL(__generic_file_write_iter);
2773
2774/**
2775 * generic_file_write_iter - write data to a file
2776 * @iocb: IO state structure
2777 * @from: iov_iter with data to write
2778 *
2779 * This is a wrapper around __generic_file_write_iter() to be used by most
2780 * filesystems. It takes care of syncing the file in case of O_SYNC file
2781 * and acquires i_mutex as needed.
2782 */
2783ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
2784{
2785 struct file *file = iocb->ki_filp;
2786 struct inode *inode = file->f_mapping->host;
2787 ssize_t ret;
2788
2789 inode_lock(inode);
2790 ret = generic_write_checks(iocb, from);
2791 if (ret > 0)
2792 ret = __generic_file_write_iter(iocb, from);
2793 inode_unlock(inode);
2794
2795 if (ret > 0) {
2796 ssize_t err;
2797
2798 err = generic_write_sync(file, iocb->ki_pos - ret, ret);
2799 if (err < 0)
2800 ret = err;
2801 }
2802 return ret;
2803}
2804EXPORT_SYMBOL(generic_file_write_iter);
2805
2806/**
2807 * try_to_release_page() - release old fs-specific metadata on a page
2808 *
2809 * @page: the page which the kernel is trying to free
2810 * @gfp_mask: memory allocation flags (and I/O mode)
2811 *
2812 * The address_space is to try to release any data against the page
2813 * (presumably at page->private). If the release was successful, return `1'.
2814 * Otherwise return zero.
2815 *
2816 * This may also be called if PG_fscache is set on a page, indicating that the
2817 * page is known to the local caching routines.
2818 *
2819 * The @gfp_mask argument specifies whether I/O may be performed to release
2820 * this page (__GFP_IO), and whether the call may block (__GFP_RECLAIM & __GFP_FS).
2821 *
2822 */
2823int try_to_release_page(struct page *page, gfp_t gfp_mask)
2824{
2825 struct address_space * const mapping = page->mapping;
2826
2827 BUG_ON(!PageLocked(page));
2828 if (PageWriteback(page))
2829 return 0;
2830
2831 if (mapping && mapping->a_ops->releasepage)
2832 return mapping->a_ops->releasepage(page, gfp_mask);
2833 return try_to_free_buffers(page);
2834}
2835
2836EXPORT_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 "internal.h"
37
38/*
39 * FIXME: remove all knowledge of the buffer layer from the core VM
40 */
41#include <linux/buffer_head.h> /* for try_to_free_buffers */
42
43#include <asm/mman.h>
44
45/*
46 * Shared mappings implemented 30.11.1994. It's not fully working yet,
47 * though.
48 *
49 * Shared mappings now work. 15.8.1995 Bruno.
50 *
51 * finished 'unifying' the page and buffer cache and SMP-threaded the
52 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
53 *
54 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
55 */
56
57/*
58 * Lock ordering:
59 *
60 * ->i_mmap_mutex (truncate_pagecache)
61 * ->private_lock (__free_pte->__set_page_dirty_buffers)
62 * ->swap_lock (exclusive_swap_page, others)
63 * ->mapping->tree_lock
64 *
65 * ->i_mutex
66 * ->i_mmap_mutex (truncate->unmap_mapping_range)
67 *
68 * ->mmap_sem
69 * ->i_mmap_mutex
70 * ->page_table_lock or pte_lock (various, mainly in memory.c)
71 * ->mapping->tree_lock (arch-dependent flush_dcache_mmap_lock)
72 *
73 * ->mmap_sem
74 * ->lock_page (access_process_vm)
75 *
76 * ->i_mutex (generic_file_buffered_write)
77 * ->mmap_sem (fault_in_pages_readable->do_page_fault)
78 *
79 * bdi->wb.list_lock
80 * sb_lock (fs/fs-writeback.c)
81 * ->mapping->tree_lock (__sync_single_inode)
82 *
83 * ->i_mmap_mutex
84 * ->anon_vma.lock (vma_adjust)
85 *
86 * ->anon_vma.lock
87 * ->page_table_lock or pte_lock (anon_vma_prepare and various)
88 *
89 * ->page_table_lock or pte_lock
90 * ->swap_lock (try_to_unmap_one)
91 * ->private_lock (try_to_unmap_one)
92 * ->tree_lock (try_to_unmap_one)
93 * ->zone.lru_lock (follow_page->mark_page_accessed)
94 * ->zone.lru_lock (check_pte_range->isolate_lru_page)
95 * ->private_lock (page_remove_rmap->set_page_dirty)
96 * ->tree_lock (page_remove_rmap->set_page_dirty)
97 * bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
98 * ->inode->i_lock (page_remove_rmap->set_page_dirty)
99 * bdi.wb->list_lock (zap_pte_range->set_page_dirty)
100 * ->inode->i_lock (zap_pte_range->set_page_dirty)
101 * ->private_lock (zap_pte_range->__set_page_dirty_buffers)
102 *
103 * ->i_mmap_mutex
104 * ->tasklist_lock (memory_failure, collect_procs_ao)
105 */
106
107/*
108 * Delete a page from the page cache and free it. Caller has to make
109 * sure the page is locked and that nobody else uses it - or that usage
110 * is safe. The caller must hold the mapping's tree_lock.
111 */
112void __delete_from_page_cache(struct page *page)
113{
114 struct address_space *mapping = page->mapping;
115
116 /*
117 * if we're uptodate, flush out into the cleancache, otherwise
118 * invalidate any existing cleancache entries. We can't leave
119 * stale data around in the cleancache once our page is gone
120 */
121 if (PageUptodate(page) && PageMappedToDisk(page))
122 cleancache_put_page(page);
123 else
124 cleancache_invalidate_page(mapping, page);
125
126 radix_tree_delete(&mapping->page_tree, page->index);
127 page->mapping = NULL;
128 /* Leave page->index set: truncation lookup relies upon it */
129 mapping->nrpages--;
130 __dec_zone_page_state(page, NR_FILE_PAGES);
131 if (PageSwapBacked(page))
132 __dec_zone_page_state(page, NR_SHMEM);
133 BUG_ON(page_mapped(page));
134
135 /*
136 * Some filesystems seem to re-dirty the page even after
137 * the VM has canceled the dirty bit (eg ext3 journaling).
138 *
139 * Fix it up by doing a final dirty accounting check after
140 * having removed the page entirely.
141 */
142 if (PageDirty(page) && mapping_cap_account_dirty(mapping)) {
143 dec_zone_page_state(page, NR_FILE_DIRTY);
144 dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE);
145 }
146}
147
148/**
149 * delete_from_page_cache - delete page from page cache
150 * @page: the page which the kernel is trying to remove from page cache
151 *
152 * This must be called only on pages that have been verified to be in the page
153 * cache and locked. It will never put the page into the free list, the caller
154 * has a reference on the page.
155 */
156void delete_from_page_cache(struct page *page)
157{
158 struct address_space *mapping = page->mapping;
159 void (*freepage)(struct page *);
160
161 BUG_ON(!PageLocked(page));
162
163 freepage = mapping->a_ops->freepage;
164 spin_lock_irq(&mapping->tree_lock);
165 __delete_from_page_cache(page);
166 spin_unlock_irq(&mapping->tree_lock);
167 mem_cgroup_uncharge_cache_page(page);
168
169 if (freepage)
170 freepage(page);
171 page_cache_release(page);
172}
173EXPORT_SYMBOL(delete_from_page_cache);
174
175static int sleep_on_page(void *word)
176{
177 io_schedule();
178 return 0;
179}
180
181static int sleep_on_page_killable(void *word)
182{
183 sleep_on_page(word);
184 return fatal_signal_pending(current) ? -EINTR : 0;
185}
186
187/**
188 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
189 * @mapping: address space structure to write
190 * @start: offset in bytes where the range starts
191 * @end: offset in bytes where the range ends (inclusive)
192 * @sync_mode: enable synchronous operation
193 *
194 * Start writeback against all of a mapping's dirty pages that lie
195 * within the byte offsets <start, end> inclusive.
196 *
197 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
198 * opposed to a regular memory cleansing writeback. The difference between
199 * these two operations is that if a dirty page/buffer is encountered, it must
200 * be waited upon, and not just skipped over.
201 */
202int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
203 loff_t end, int sync_mode)
204{
205 int ret;
206 struct writeback_control wbc = {
207 .sync_mode = sync_mode,
208 .nr_to_write = LONG_MAX,
209 .range_start = start,
210 .range_end = end,
211 };
212
213 if (!mapping_cap_writeback_dirty(mapping))
214 return 0;
215
216 ret = do_writepages(mapping, &wbc);
217 return ret;
218}
219
220static inline int __filemap_fdatawrite(struct address_space *mapping,
221 int sync_mode)
222{
223 return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
224}
225
226int filemap_fdatawrite(struct address_space *mapping)
227{
228 return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
229}
230EXPORT_SYMBOL(filemap_fdatawrite);
231
232int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
233 loff_t end)
234{
235 return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
236}
237EXPORT_SYMBOL(filemap_fdatawrite_range);
238
239/**
240 * filemap_flush - mostly a non-blocking flush
241 * @mapping: target address_space
242 *
243 * This is a mostly non-blocking flush. Not suitable for data-integrity
244 * purposes - I/O may not be started against all dirty pages.
245 */
246int filemap_flush(struct address_space *mapping)
247{
248 return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
249}
250EXPORT_SYMBOL(filemap_flush);
251
252/**
253 * filemap_fdatawait_range - wait for writeback to complete
254 * @mapping: address space structure to wait for
255 * @start_byte: offset in bytes where the range starts
256 * @end_byte: offset in bytes where the range ends (inclusive)
257 *
258 * Walk the list of under-writeback pages of the given address space
259 * in the given range and wait for all of them.
260 */
261int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
262 loff_t end_byte)
263{
264 pgoff_t index = start_byte >> PAGE_CACHE_SHIFT;
265 pgoff_t end = end_byte >> PAGE_CACHE_SHIFT;
266 struct pagevec pvec;
267 int nr_pages;
268 int ret = 0;
269
270 if (end_byte < start_byte)
271 return 0;
272
273 pagevec_init(&pvec, 0);
274 while ((index <= end) &&
275 (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
276 PAGECACHE_TAG_WRITEBACK,
277 min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
278 unsigned i;
279
280 for (i = 0; i < nr_pages; i++) {
281 struct page *page = pvec.pages[i];
282
283 /* until radix tree lookup accepts end_index */
284 if (page->index > end)
285 continue;
286
287 wait_on_page_writeback(page);
288 if (TestClearPageError(page))
289 ret = -EIO;
290 }
291 pagevec_release(&pvec);
292 cond_resched();
293 }
294
295 /* Check for outstanding write errors */
296 if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
297 ret = -ENOSPC;
298 if (test_and_clear_bit(AS_EIO, &mapping->flags))
299 ret = -EIO;
300
301 return ret;
302}
303EXPORT_SYMBOL(filemap_fdatawait_range);
304
305/**
306 * filemap_fdatawait - wait for all under-writeback pages to complete
307 * @mapping: address space structure to wait for
308 *
309 * Walk the list of under-writeback pages of the given address space
310 * and wait for all of them.
311 */
312int filemap_fdatawait(struct address_space *mapping)
313{
314 loff_t i_size = i_size_read(mapping->host);
315
316 if (i_size == 0)
317 return 0;
318
319 return filemap_fdatawait_range(mapping, 0, i_size - 1);
320}
321EXPORT_SYMBOL(filemap_fdatawait);
322
323int filemap_write_and_wait(struct address_space *mapping)
324{
325 int err = 0;
326
327 if (mapping->nrpages) {
328 err = filemap_fdatawrite(mapping);
329 /*
330 * Even if the above returned error, the pages may be
331 * written partially (e.g. -ENOSPC), so we wait for it.
332 * But the -EIO is special case, it may indicate the worst
333 * thing (e.g. bug) happened, so we avoid waiting for it.
334 */
335 if (err != -EIO) {
336 int err2 = filemap_fdatawait(mapping);
337 if (!err)
338 err = err2;
339 }
340 }
341 return err;
342}
343EXPORT_SYMBOL(filemap_write_and_wait);
344
345/**
346 * filemap_write_and_wait_range - write out & wait on a file range
347 * @mapping: the address_space for the pages
348 * @lstart: offset in bytes where the range starts
349 * @lend: offset in bytes where the range ends (inclusive)
350 *
351 * Write out and wait upon file offsets lstart->lend, inclusive.
352 *
353 * Note that `lend' is inclusive (describes the last byte to be written) so
354 * that this function can be used to write to the very end-of-file (end = -1).
355 */
356int filemap_write_and_wait_range(struct address_space *mapping,
357 loff_t lstart, loff_t lend)
358{
359 int err = 0;
360
361 if (mapping->nrpages) {
362 err = __filemap_fdatawrite_range(mapping, lstart, lend,
363 WB_SYNC_ALL);
364 /* See comment of filemap_write_and_wait() */
365 if (err != -EIO) {
366 int err2 = filemap_fdatawait_range(mapping,
367 lstart, lend);
368 if (!err)
369 err = err2;
370 }
371 }
372 return err;
373}
374EXPORT_SYMBOL(filemap_write_and_wait_range);
375
376/**
377 * replace_page_cache_page - replace a pagecache page with a new one
378 * @old: page to be replaced
379 * @new: page to replace with
380 * @gfp_mask: allocation mode
381 *
382 * This function replaces a page in the pagecache with a new one. On
383 * success it acquires the pagecache reference for the new page and
384 * drops it for the old page. Both the old and new pages must be
385 * locked. This function does not add the new page to the LRU, the
386 * caller must do that.
387 *
388 * The remove + add is atomic. The only way this function can fail is
389 * memory allocation failure.
390 */
391int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask)
392{
393 int error;
394
395 VM_BUG_ON(!PageLocked(old));
396 VM_BUG_ON(!PageLocked(new));
397 VM_BUG_ON(new->mapping);
398
399 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
400 if (!error) {
401 struct address_space *mapping = old->mapping;
402 void (*freepage)(struct page *);
403
404 pgoff_t offset = old->index;
405 freepage = mapping->a_ops->freepage;
406
407 page_cache_get(new);
408 new->mapping = mapping;
409 new->index = offset;
410
411 spin_lock_irq(&mapping->tree_lock);
412 __delete_from_page_cache(old);
413 error = radix_tree_insert(&mapping->page_tree, offset, new);
414 BUG_ON(error);
415 mapping->nrpages++;
416 __inc_zone_page_state(new, NR_FILE_PAGES);
417 if (PageSwapBacked(new))
418 __inc_zone_page_state(new, NR_SHMEM);
419 spin_unlock_irq(&mapping->tree_lock);
420 /* mem_cgroup codes must not be called under tree_lock */
421 mem_cgroup_replace_page_cache(old, new);
422 radix_tree_preload_end();
423 if (freepage)
424 freepage(old);
425 page_cache_release(old);
426 }
427
428 return error;
429}
430EXPORT_SYMBOL_GPL(replace_page_cache_page);
431
432/**
433 * add_to_page_cache_locked - add a locked page to the pagecache
434 * @page: page to add
435 * @mapping: the page's address_space
436 * @offset: page index
437 * @gfp_mask: page allocation mode
438 *
439 * This function is used to add a page to the pagecache. It must be locked.
440 * This function does not add the page to the LRU. The caller must do that.
441 */
442int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
443 pgoff_t offset, gfp_t gfp_mask)
444{
445 int error;
446
447 VM_BUG_ON(!PageLocked(page));
448 VM_BUG_ON(PageSwapBacked(page));
449
450 error = mem_cgroup_cache_charge(page, current->mm,
451 gfp_mask & GFP_RECLAIM_MASK);
452 if (error)
453 goto out;
454
455 error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM);
456 if (error == 0) {
457 page_cache_get(page);
458 page->mapping = mapping;
459 page->index = offset;
460
461 spin_lock_irq(&mapping->tree_lock);
462 error = radix_tree_insert(&mapping->page_tree, offset, page);
463 if (likely(!error)) {
464 mapping->nrpages++;
465 __inc_zone_page_state(page, NR_FILE_PAGES);
466 spin_unlock_irq(&mapping->tree_lock);
467 } else {
468 page->mapping = NULL;
469 /* Leave page->index set: truncation relies upon it */
470 spin_unlock_irq(&mapping->tree_lock);
471 mem_cgroup_uncharge_cache_page(page);
472 page_cache_release(page);
473 }
474 radix_tree_preload_end();
475 } else
476 mem_cgroup_uncharge_cache_page(page);
477out:
478 return error;
479}
480EXPORT_SYMBOL(add_to_page_cache_locked);
481
482int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
483 pgoff_t offset, gfp_t gfp_mask)
484{
485 int ret;
486
487 ret = add_to_page_cache(page, mapping, offset, gfp_mask);
488 if (ret == 0)
489 lru_cache_add_file(page);
490 return ret;
491}
492EXPORT_SYMBOL_GPL(add_to_page_cache_lru);
493
494#ifdef CONFIG_NUMA
495struct page *__page_cache_alloc(gfp_t gfp)
496{
497 int n;
498 struct page *page;
499
500 if (cpuset_do_page_mem_spread()) {
501 unsigned int cpuset_mems_cookie;
502 do {
503 cpuset_mems_cookie = get_mems_allowed();
504 n = cpuset_mem_spread_node();
505 page = alloc_pages_exact_node(n, gfp, 0);
506 } while (!put_mems_allowed(cpuset_mems_cookie) && !page);
507
508 return page;
509 }
510 return alloc_pages(gfp, 0);
511}
512EXPORT_SYMBOL(__page_cache_alloc);
513#endif
514
515/*
516 * In order to wait for pages to become available there must be
517 * waitqueues associated with pages. By using a hash table of
518 * waitqueues where the bucket discipline is to maintain all
519 * waiters on the same queue and wake all when any of the pages
520 * become available, and for the woken contexts to check to be
521 * sure the appropriate page became available, this saves space
522 * at a cost of "thundering herd" phenomena during rare hash
523 * collisions.
524 */
525static wait_queue_head_t *page_waitqueue(struct page *page)
526{
527 const struct zone *zone = page_zone(page);
528
529 return &zone->wait_table[hash_ptr(page, zone->wait_table_bits)];
530}
531
532static inline void wake_up_page(struct page *page, int bit)
533{
534 __wake_up_bit(page_waitqueue(page), &page->flags, bit);
535}
536
537void wait_on_page_bit(struct page *page, int bit_nr)
538{
539 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
540
541 if (test_bit(bit_nr, &page->flags))
542 __wait_on_bit(page_waitqueue(page), &wait, sleep_on_page,
543 TASK_UNINTERRUPTIBLE);
544}
545EXPORT_SYMBOL(wait_on_page_bit);
546
547int wait_on_page_bit_killable(struct page *page, int bit_nr)
548{
549 DEFINE_WAIT_BIT(wait, &page->flags, bit_nr);
550
551 if (!test_bit(bit_nr, &page->flags))
552 return 0;
553
554 return __wait_on_bit(page_waitqueue(page), &wait,
555 sleep_on_page_killable, TASK_KILLABLE);
556}
557
558/**
559 * add_page_wait_queue - Add an arbitrary waiter to a page's wait queue
560 * @page: Page defining the wait queue of interest
561 * @waiter: Waiter to add to the queue
562 *
563 * Add an arbitrary @waiter to the wait queue for the nominated @page.
564 */
565void add_page_wait_queue(struct page *page, wait_queue_t *waiter)
566{
567 wait_queue_head_t *q = page_waitqueue(page);
568 unsigned long flags;
569
570 spin_lock_irqsave(&q->lock, flags);
571 __add_wait_queue(q, waiter);
572 spin_unlock_irqrestore(&q->lock, flags);
573}
574EXPORT_SYMBOL_GPL(add_page_wait_queue);
575
576/**
577 * unlock_page - unlock a locked page
578 * @page: the page
579 *
580 * Unlocks the page and wakes up sleepers in ___wait_on_page_locked().
581 * Also wakes sleepers in wait_on_page_writeback() because the wakeup
582 * mechananism between PageLocked pages and PageWriteback pages is shared.
583 * But that's OK - sleepers in wait_on_page_writeback() just go back to sleep.
584 *
585 * The mb is necessary to enforce ordering between the clear_bit and the read
586 * of the waitqueue (to avoid SMP races with a parallel wait_on_page_locked()).
587 */
588void unlock_page(struct page *page)
589{
590 VM_BUG_ON(!PageLocked(page));
591 clear_bit_unlock(PG_locked, &page->flags);
592 smp_mb__after_clear_bit();
593 wake_up_page(page, PG_locked);
594}
595EXPORT_SYMBOL(unlock_page);
596
597/**
598 * end_page_writeback - end writeback against a page
599 * @page: the page
600 */
601void end_page_writeback(struct page *page)
602{
603 if (TestClearPageReclaim(page))
604 rotate_reclaimable_page(page);
605
606 if (!test_clear_page_writeback(page))
607 BUG();
608
609 smp_mb__after_clear_bit();
610 wake_up_page(page, PG_writeback);
611}
612EXPORT_SYMBOL(end_page_writeback);
613
614/**
615 * __lock_page - get a lock on the page, assuming we need to sleep to get it
616 * @page: the page to lock
617 */
618void __lock_page(struct page *page)
619{
620 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
621
622 __wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
623 TASK_UNINTERRUPTIBLE);
624}
625EXPORT_SYMBOL(__lock_page);
626
627int __lock_page_killable(struct page *page)
628{
629 DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
630
631 return __wait_on_bit_lock(page_waitqueue(page), &wait,
632 sleep_on_page_killable, TASK_KILLABLE);
633}
634EXPORT_SYMBOL_GPL(__lock_page_killable);
635
636int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
637 unsigned int flags)
638{
639 if (flags & FAULT_FLAG_ALLOW_RETRY) {
640 /*
641 * CAUTION! In this case, mmap_sem is not released
642 * even though return 0.
643 */
644 if (flags & FAULT_FLAG_RETRY_NOWAIT)
645 return 0;
646
647 up_read(&mm->mmap_sem);
648 if (flags & FAULT_FLAG_KILLABLE)
649 wait_on_page_locked_killable(page);
650 else
651 wait_on_page_locked(page);
652 return 0;
653 } else {
654 if (flags & FAULT_FLAG_KILLABLE) {
655 int ret;
656
657 ret = __lock_page_killable(page);
658 if (ret) {
659 up_read(&mm->mmap_sem);
660 return 0;
661 }
662 } else
663 __lock_page(page);
664 return 1;
665 }
666}
667
668/**
669 * find_get_page - find and get a page reference
670 * @mapping: the address_space to search
671 * @offset: the page index
672 *
673 * Is there a pagecache struct page at the given (mapping, offset) tuple?
674 * If yes, increment its refcount and return it; if no, return NULL.
675 */
676struct page *find_get_page(struct address_space *mapping, pgoff_t offset)
677{
678 void **pagep;
679 struct page *page;
680
681 rcu_read_lock();
682repeat:
683 page = NULL;
684 pagep = radix_tree_lookup_slot(&mapping->page_tree, offset);
685 if (pagep) {
686 page = radix_tree_deref_slot(pagep);
687 if (unlikely(!page))
688 goto out;
689 if (radix_tree_exception(page)) {
690 if (radix_tree_deref_retry(page))
691 goto repeat;
692 /*
693 * Otherwise, shmem/tmpfs must be storing a swap entry
694 * here as an exceptional entry: so return it without
695 * attempting to raise page count.
696 */
697 goto out;
698 }
699 if (!page_cache_get_speculative(page))
700 goto repeat;
701
702 /*
703 * Has the page moved?
704 * This is part of the lockless pagecache protocol. See
705 * include/linux/pagemap.h for details.
706 */
707 if (unlikely(page != *pagep)) {
708 page_cache_release(page);
709 goto repeat;
710 }
711 }
712out:
713 rcu_read_unlock();
714
715 return page;
716}
717EXPORT_SYMBOL(find_get_page);
718
719/**
720 * find_lock_page - locate, pin and lock a pagecache page
721 * @mapping: the address_space to search
722 * @offset: the page index
723 *
724 * Locates the desired pagecache page, locks it, increments its reference
725 * count and returns its address.
726 *
727 * Returns zero if the page was not present. find_lock_page() may sleep.
728 */
729struct page *find_lock_page(struct address_space *mapping, pgoff_t offset)
730{
731 struct page *page;
732
733repeat:
734 page = find_get_page(mapping, offset);
735 if (page && !radix_tree_exception(page)) {
736 lock_page(page);
737 /* Has the page been truncated? */
738 if (unlikely(page->mapping != mapping)) {
739 unlock_page(page);
740 page_cache_release(page);
741 goto repeat;
742 }
743 VM_BUG_ON(page->index != offset);
744 }
745 return page;
746}
747EXPORT_SYMBOL(find_lock_page);
748
749/**
750 * find_or_create_page - locate or add a pagecache page
751 * @mapping: the page's address_space
752 * @index: the page's index into the mapping
753 * @gfp_mask: page allocation mode
754 *
755 * Locates a page in the pagecache. If the page is not present, a new page
756 * is allocated using @gfp_mask and is added to the pagecache and to the VM's
757 * LRU list. The returned page is locked and has its reference count
758 * incremented.
759 *
760 * find_or_create_page() may sleep, even if @gfp_flags specifies an atomic
761 * allocation!
762 *
763 * find_or_create_page() returns the desired page's address, or zero on
764 * memory exhaustion.
765 */
766struct page *find_or_create_page(struct address_space *mapping,
767 pgoff_t index, gfp_t gfp_mask)
768{
769 struct page *page;
770 int err;
771repeat:
772 page = find_lock_page(mapping, index);
773 if (!page) {
774 page = __page_cache_alloc(gfp_mask);
775 if (!page)
776 return NULL;
777 /*
778 * We want a regular kernel memory (not highmem or DMA etc)
779 * allocation for the radix tree nodes, but we need to honour
780 * the context-specific requirements the caller has asked for.
781 * GFP_RECLAIM_MASK collects those requirements.
782 */
783 err = add_to_page_cache_lru(page, mapping, index,
784 (gfp_mask & GFP_RECLAIM_MASK));
785 if (unlikely(err)) {
786 page_cache_release(page);
787 page = NULL;
788 if (err == -EEXIST)
789 goto repeat;
790 }
791 }
792 return page;
793}
794EXPORT_SYMBOL(find_or_create_page);
795
796/**
797 * find_get_pages - gang pagecache lookup
798 * @mapping: The address_space to search
799 * @start: The starting page index
800 * @nr_pages: The maximum number of pages
801 * @pages: Where the resulting pages are placed
802 *
803 * find_get_pages() will search for and return a group of up to
804 * @nr_pages pages in the mapping. The pages are placed at @pages.
805 * find_get_pages() takes a reference against the returned pages.
806 *
807 * The search returns a group of mapping-contiguous pages with ascending
808 * indexes. There may be holes in the indices due to not-present pages.
809 *
810 * find_get_pages() returns the number of pages which were found.
811 */
812unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
813 unsigned int nr_pages, struct page **pages)
814{
815 struct radix_tree_iter iter;
816 void **slot;
817 unsigned ret = 0;
818
819 if (unlikely(!nr_pages))
820 return 0;
821
822 rcu_read_lock();
823restart:
824 radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
825 struct page *page;
826repeat:
827 page = radix_tree_deref_slot(slot);
828 if (unlikely(!page))
829 continue;
830
831 if (radix_tree_exception(page)) {
832 if (radix_tree_deref_retry(page)) {
833 /*
834 * Transient condition which can only trigger
835 * when entry at index 0 moves out of or back
836 * to root: none yet gotten, safe to restart.
837 */
838 WARN_ON(iter.index);
839 goto restart;
840 }
841 /*
842 * Otherwise, shmem/tmpfs must be storing a swap entry
843 * here as an exceptional entry: so skip over it -
844 * we only reach this from invalidate_mapping_pages().
845 */
846 continue;
847 }
848
849 if (!page_cache_get_speculative(page))
850 goto repeat;
851
852 /* Has the page moved? */
853 if (unlikely(page != *slot)) {
854 page_cache_release(page);
855 goto repeat;
856 }
857
858 pages[ret] = page;
859 if (++ret == nr_pages)
860 break;
861 }
862
863 rcu_read_unlock();
864 return ret;
865}
866
867/**
868 * find_get_pages_contig - gang contiguous pagecache lookup
869 * @mapping: The address_space to search
870 * @index: The starting page index
871 * @nr_pages: The maximum number of pages
872 * @pages: Where the resulting pages are placed
873 *
874 * find_get_pages_contig() works exactly like find_get_pages(), except
875 * that the returned number of pages are guaranteed to be contiguous.
876 *
877 * find_get_pages_contig() returns the number of pages which were found.
878 */
879unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index,
880 unsigned int nr_pages, struct page **pages)
881{
882 struct radix_tree_iter iter;
883 void **slot;
884 unsigned int ret = 0;
885
886 if (unlikely(!nr_pages))
887 return 0;
888
889 rcu_read_lock();
890restart:
891 radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) {
892 struct page *page;
893repeat:
894 page = radix_tree_deref_slot(slot);
895 /* The hole, there no reason to continue */
896 if (unlikely(!page))
897 break;
898
899 if (radix_tree_exception(page)) {
900 if (radix_tree_deref_retry(page)) {
901 /*
902 * Transient condition which can only trigger
903 * when entry at index 0 moves out of or back
904 * to root: none yet gotten, safe to restart.
905 */
906 goto restart;
907 }
908 /*
909 * Otherwise, shmem/tmpfs must be storing a swap entry
910 * here as an exceptional entry: so stop looking for
911 * contiguous pages.
912 */
913 break;
914 }
915
916 if (!page_cache_get_speculative(page))
917 goto repeat;
918
919 /* Has the page moved? */
920 if (unlikely(page != *slot)) {
921 page_cache_release(page);
922 goto repeat;
923 }
924
925 /*
926 * must check mapping and index after taking the ref.
927 * otherwise we can get both false positives and false
928 * negatives, which is just confusing to the caller.
929 */
930 if (page->mapping == NULL || page->index != iter.index) {
931 page_cache_release(page);
932 break;
933 }
934
935 pages[ret] = page;
936 if (++ret == nr_pages)
937 break;
938 }
939 rcu_read_unlock();
940 return ret;
941}
942EXPORT_SYMBOL(find_get_pages_contig);
943
944/**
945 * find_get_pages_tag - find and return pages that match @tag
946 * @mapping: the address_space to search
947 * @index: the starting page index
948 * @tag: the tag index
949 * @nr_pages: the maximum number of pages
950 * @pages: where the resulting pages are placed
951 *
952 * Like find_get_pages, except we only return pages which are tagged with
953 * @tag. We update @index to index the next page for the traversal.
954 */
955unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
956 int tag, unsigned int nr_pages, struct page **pages)
957{
958 struct radix_tree_iter iter;
959 void **slot;
960 unsigned ret = 0;
961
962 if (unlikely(!nr_pages))
963 return 0;
964
965 rcu_read_lock();
966restart:
967 radix_tree_for_each_tagged(slot, &mapping->page_tree,
968 &iter, *index, tag) {
969 struct page *page;
970repeat:
971 page = radix_tree_deref_slot(slot);
972 if (unlikely(!page))
973 continue;
974
975 if (radix_tree_exception(page)) {
976 if (radix_tree_deref_retry(page)) {
977 /*
978 * Transient condition which can only trigger
979 * when entry at index 0 moves out of or back
980 * to root: none yet gotten, safe to restart.
981 */
982 goto restart;
983 }
984 /*
985 * This function is never used on a shmem/tmpfs
986 * mapping, so a swap entry won't be found here.
987 */
988 BUG();
989 }
990
991 if (!page_cache_get_speculative(page))
992 goto repeat;
993
994 /* Has the page moved? */
995 if (unlikely(page != *slot)) {
996 page_cache_release(page);
997 goto repeat;
998 }
999
1000 pages[ret] = page;
1001 if (++ret == nr_pages)
1002 break;
1003 }
1004
1005 rcu_read_unlock();
1006
1007 if (ret)
1008 *index = pages[ret - 1]->index + 1;
1009
1010 return ret;
1011}
1012EXPORT_SYMBOL(find_get_pages_tag);
1013
1014/**
1015 * grab_cache_page_nowait - returns locked page at given index in given cache
1016 * @mapping: target address_space
1017 * @index: the page index
1018 *
1019 * Same as grab_cache_page(), but do not wait if the page is unavailable.
1020 * This is intended for speculative data generators, where the data can
1021 * be regenerated if the page couldn't be grabbed. This routine should
1022 * be safe to call while holding the lock for another page.
1023 *
1024 * Clear __GFP_FS when allocating the page to avoid recursion into the fs
1025 * and deadlock against the caller's locked page.
1026 */
1027struct page *
1028grab_cache_page_nowait(struct address_space *mapping, pgoff_t index)
1029{
1030 struct page *page = find_get_page(mapping, index);
1031
1032 if (page) {
1033 if (trylock_page(page))
1034 return page;
1035 page_cache_release(page);
1036 return NULL;
1037 }
1038 page = __page_cache_alloc(mapping_gfp_mask(mapping) & ~__GFP_FS);
1039 if (page && add_to_page_cache_lru(page, mapping, index, GFP_NOFS)) {
1040 page_cache_release(page);
1041 page = NULL;
1042 }
1043 return page;
1044}
1045EXPORT_SYMBOL(grab_cache_page_nowait);
1046
1047/*
1048 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
1049 * a _large_ part of the i/o request. Imagine the worst scenario:
1050 *
1051 * ---R__________________________________________B__________
1052 * ^ reading here ^ bad block(assume 4k)
1053 *
1054 * read(R) => miss => readahead(R...B) => media error => frustrating retries
1055 * => failing the whole request => read(R) => read(R+1) =>
1056 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
1057 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
1058 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
1059 *
1060 * It is going insane. Fix it by quickly scaling down the readahead size.
1061 */
1062static void shrink_readahead_size_eio(struct file *filp,
1063 struct file_ra_state *ra)
1064{
1065 ra->ra_pages /= 4;
1066}
1067
1068/**
1069 * do_generic_file_read - generic file read routine
1070 * @filp: the file to read
1071 * @ppos: current file position
1072 * @desc: read_descriptor
1073 * @actor: read method
1074 *
1075 * This is a generic file read routine, and uses the
1076 * mapping->a_ops->readpage() function for the actual low-level stuff.
1077 *
1078 * This is really ugly. But the goto's actually try to clarify some
1079 * of the logic when it comes to error handling etc.
1080 */
1081static void do_generic_file_read(struct file *filp, loff_t *ppos,
1082 read_descriptor_t *desc, read_actor_t actor)
1083{
1084 struct address_space *mapping = filp->f_mapping;
1085 struct inode *inode = mapping->host;
1086 struct file_ra_state *ra = &filp->f_ra;
1087 pgoff_t index;
1088 pgoff_t last_index;
1089 pgoff_t prev_index;
1090 unsigned long offset; /* offset into pagecache page */
1091 unsigned int prev_offset;
1092 int error;
1093
1094 index = *ppos >> PAGE_CACHE_SHIFT;
1095 prev_index = ra->prev_pos >> PAGE_CACHE_SHIFT;
1096 prev_offset = ra->prev_pos & (PAGE_CACHE_SIZE-1);
1097 last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
1098 offset = *ppos & ~PAGE_CACHE_MASK;
1099
1100 for (;;) {
1101 struct page *page;
1102 pgoff_t end_index;
1103 loff_t isize;
1104 unsigned long nr, ret;
1105
1106 cond_resched();
1107find_page:
1108 page = find_get_page(mapping, index);
1109 if (!page) {
1110 page_cache_sync_readahead(mapping,
1111 ra, filp,
1112 index, last_index - index);
1113 page = find_get_page(mapping, index);
1114 if (unlikely(page == NULL))
1115 goto no_cached_page;
1116 }
1117 if (PageReadahead(page)) {
1118 page_cache_async_readahead(mapping,
1119 ra, filp, page,
1120 index, last_index - index);
1121 }
1122 if (!PageUptodate(page)) {
1123 if (inode->i_blkbits == PAGE_CACHE_SHIFT ||
1124 !mapping->a_ops->is_partially_uptodate)
1125 goto page_not_up_to_date;
1126 if (!trylock_page(page))
1127 goto page_not_up_to_date;
1128 /* Did it get truncated before we got the lock? */
1129 if (!page->mapping)
1130 goto page_not_up_to_date_locked;
1131 if (!mapping->a_ops->is_partially_uptodate(page,
1132 desc, offset))
1133 goto page_not_up_to_date_locked;
1134 unlock_page(page);
1135 }
1136page_ok:
1137 /*
1138 * i_size must be checked after we know the page is Uptodate.
1139 *
1140 * Checking i_size after the check allows us to calculate
1141 * the correct value for "nr", which means the zero-filled
1142 * part of the page is not copied back to userspace (unless
1143 * another truncate extends the file - this is desired though).
1144 */
1145
1146 isize = i_size_read(inode);
1147 end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
1148 if (unlikely(!isize || index > end_index)) {
1149 page_cache_release(page);
1150 goto out;
1151 }
1152
1153 /* nr is the maximum number of bytes to copy from this page */
1154 nr = PAGE_CACHE_SIZE;
1155 if (index == end_index) {
1156 nr = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
1157 if (nr <= offset) {
1158 page_cache_release(page);
1159 goto out;
1160 }
1161 }
1162 nr = nr - offset;
1163
1164 /* If users can be writing to this page using arbitrary
1165 * virtual addresses, take care about potential aliasing
1166 * before reading the page on the kernel side.
1167 */
1168 if (mapping_writably_mapped(mapping))
1169 flush_dcache_page(page);
1170
1171 /*
1172 * When a sequential read accesses a page several times,
1173 * only mark it as accessed the first time.
1174 */
1175 if (prev_index != index || offset != prev_offset)
1176 mark_page_accessed(page);
1177 prev_index = index;
1178
1179 /*
1180 * Ok, we have the page, and it's up-to-date, so
1181 * now we can copy it to user space...
1182 *
1183 * The actor routine returns how many bytes were actually used..
1184 * NOTE! This may not be the same as how much of a user buffer
1185 * we filled up (we may be padding etc), so we can only update
1186 * "pos" here (the actor routine has to update the user buffer
1187 * pointers and the remaining count).
1188 */
1189 ret = actor(desc, page, offset, nr);
1190 offset += ret;
1191 index += offset >> PAGE_CACHE_SHIFT;
1192 offset &= ~PAGE_CACHE_MASK;
1193 prev_offset = offset;
1194
1195 page_cache_release(page);
1196 if (ret == nr && desc->count)
1197 continue;
1198 goto out;
1199
1200page_not_up_to_date:
1201 /* Get exclusive access to the page ... */
1202 error = lock_page_killable(page);
1203 if (unlikely(error))
1204 goto readpage_error;
1205
1206page_not_up_to_date_locked:
1207 /* Did it get truncated before we got the lock? */
1208 if (!page->mapping) {
1209 unlock_page(page);
1210 page_cache_release(page);
1211 continue;
1212 }
1213
1214 /* Did somebody else fill it already? */
1215 if (PageUptodate(page)) {
1216 unlock_page(page);
1217 goto page_ok;
1218 }
1219
1220readpage:
1221 /*
1222 * A previous I/O error may have been due to temporary
1223 * failures, eg. multipath errors.
1224 * PG_error will be set again if readpage fails.
1225 */
1226 ClearPageError(page);
1227 /* Start the actual read. The read will unlock the page. */
1228 error = mapping->a_ops->readpage(filp, page);
1229
1230 if (unlikely(error)) {
1231 if (error == AOP_TRUNCATED_PAGE) {
1232 page_cache_release(page);
1233 goto find_page;
1234 }
1235 goto readpage_error;
1236 }
1237
1238 if (!PageUptodate(page)) {
1239 error = lock_page_killable(page);
1240 if (unlikely(error))
1241 goto readpage_error;
1242 if (!PageUptodate(page)) {
1243 if (page->mapping == NULL) {
1244 /*
1245 * invalidate_mapping_pages got it
1246 */
1247 unlock_page(page);
1248 page_cache_release(page);
1249 goto find_page;
1250 }
1251 unlock_page(page);
1252 shrink_readahead_size_eio(filp, ra);
1253 error = -EIO;
1254 goto readpage_error;
1255 }
1256 unlock_page(page);
1257 }
1258
1259 goto page_ok;
1260
1261readpage_error:
1262 /* UHHUH! A synchronous read error occurred. Report it */
1263 desc->error = error;
1264 page_cache_release(page);
1265 goto out;
1266
1267no_cached_page:
1268 /*
1269 * Ok, it wasn't cached, so we need to create a new
1270 * page..
1271 */
1272 page = page_cache_alloc_cold(mapping);
1273 if (!page) {
1274 desc->error = -ENOMEM;
1275 goto out;
1276 }
1277 error = add_to_page_cache_lru(page, mapping,
1278 index, GFP_KERNEL);
1279 if (error) {
1280 page_cache_release(page);
1281 if (error == -EEXIST)
1282 goto find_page;
1283 desc->error = error;
1284 goto out;
1285 }
1286 goto readpage;
1287 }
1288
1289out:
1290 ra->prev_pos = prev_index;
1291 ra->prev_pos <<= PAGE_CACHE_SHIFT;
1292 ra->prev_pos |= prev_offset;
1293
1294 *ppos = ((loff_t)index << PAGE_CACHE_SHIFT) + offset;
1295 file_accessed(filp);
1296}
1297
1298int file_read_actor(read_descriptor_t *desc, struct page *page,
1299 unsigned long offset, unsigned long size)
1300{
1301 char *kaddr;
1302 unsigned long left, count = desc->count;
1303
1304 if (size > count)
1305 size = count;
1306
1307 /*
1308 * Faults on the destination of a read are common, so do it before
1309 * taking the kmap.
1310 */
1311 if (!fault_in_pages_writeable(desc->arg.buf, size)) {
1312 kaddr = kmap_atomic(page);
1313 left = __copy_to_user_inatomic(desc->arg.buf,
1314 kaddr + offset, size);
1315 kunmap_atomic(kaddr);
1316 if (left == 0)
1317 goto success;
1318 }
1319
1320 /* Do it the slow way */
1321 kaddr = kmap(page);
1322 left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
1323 kunmap(page);
1324
1325 if (left) {
1326 size -= left;
1327 desc->error = -EFAULT;
1328 }
1329success:
1330 desc->count = count - size;
1331 desc->written += size;
1332 desc->arg.buf += size;
1333 return size;
1334}
1335
1336/*
1337 * Performs necessary checks before doing a write
1338 * @iov: io vector request
1339 * @nr_segs: number of segments in the iovec
1340 * @count: number of bytes to write
1341 * @access_flags: type of access: %VERIFY_READ or %VERIFY_WRITE
1342 *
1343 * Adjust number of segments and amount of bytes to write (nr_segs should be
1344 * properly initialized first). Returns appropriate error code that caller
1345 * should return or zero in case that write should be allowed.
1346 */
1347int generic_segment_checks(const struct iovec *iov,
1348 unsigned long *nr_segs, size_t *count, int access_flags)
1349{
1350 unsigned long seg;
1351 size_t cnt = 0;
1352 for (seg = 0; seg < *nr_segs; seg++) {
1353 const struct iovec *iv = &iov[seg];
1354
1355 /*
1356 * If any segment has a negative length, or the cumulative
1357 * length ever wraps negative then return -EINVAL.
1358 */
1359 cnt += iv->iov_len;
1360 if (unlikely((ssize_t)(cnt|iv->iov_len) < 0))
1361 return -EINVAL;
1362 if (access_ok(access_flags, iv->iov_base, iv->iov_len))
1363 continue;
1364 if (seg == 0)
1365 return -EFAULT;
1366 *nr_segs = seg;
1367 cnt -= iv->iov_len; /* This segment is no good */
1368 break;
1369 }
1370 *count = cnt;
1371 return 0;
1372}
1373EXPORT_SYMBOL(generic_segment_checks);
1374
1375/**
1376 * generic_file_aio_read - generic filesystem read routine
1377 * @iocb: kernel I/O control block
1378 * @iov: io vector request
1379 * @nr_segs: number of segments in the iovec
1380 * @pos: current file position
1381 *
1382 * This is the "read()" routine for all filesystems
1383 * that can use the page cache directly.
1384 */
1385ssize_t
1386generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
1387 unsigned long nr_segs, loff_t pos)
1388{
1389 struct file *filp = iocb->ki_filp;
1390 ssize_t retval;
1391 unsigned long seg = 0;
1392 size_t count;
1393 loff_t *ppos = &iocb->ki_pos;
1394
1395 count = 0;
1396 retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
1397 if (retval)
1398 return retval;
1399
1400 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
1401 if (filp->f_flags & O_DIRECT) {
1402 loff_t size;
1403 struct address_space *mapping;
1404 struct inode *inode;
1405
1406 mapping = filp->f_mapping;
1407 inode = mapping->host;
1408 if (!count)
1409 goto out; /* skip atime */
1410 size = i_size_read(inode);
1411 if (pos < size) {
1412 retval = filemap_write_and_wait_range(mapping, pos,
1413 pos + iov_length(iov, nr_segs) - 1);
1414 if (!retval) {
1415 struct blk_plug plug;
1416
1417 blk_start_plug(&plug);
1418 retval = mapping->a_ops->direct_IO(READ, iocb,
1419 iov, pos, nr_segs);
1420 blk_finish_plug(&plug);
1421 }
1422 if (retval > 0) {
1423 *ppos = pos + retval;
1424 count -= retval;
1425 }
1426
1427 /*
1428 * Btrfs can have a short DIO read if we encounter
1429 * compressed extents, so if there was an error, or if
1430 * we've already read everything we wanted to, or if
1431 * there was a short read because we hit EOF, go ahead
1432 * and return. Otherwise fallthrough to buffered io for
1433 * the rest of the read.
1434 */
1435 if (retval < 0 || !count || *ppos >= size) {
1436 file_accessed(filp);
1437 goto out;
1438 }
1439 }
1440 }
1441
1442 count = retval;
1443 for (seg = 0; seg < nr_segs; seg++) {
1444 read_descriptor_t desc;
1445 loff_t offset = 0;
1446
1447 /*
1448 * If we did a short DIO read we need to skip the section of the
1449 * iov that we've already read data into.
1450 */
1451 if (count) {
1452 if (count > iov[seg].iov_len) {
1453 count -= iov[seg].iov_len;
1454 continue;
1455 }
1456 offset = count;
1457 count = 0;
1458 }
1459
1460 desc.written = 0;
1461 desc.arg.buf = iov[seg].iov_base + offset;
1462 desc.count = iov[seg].iov_len - offset;
1463 if (desc.count == 0)
1464 continue;
1465 desc.error = 0;
1466 do_generic_file_read(filp, ppos, &desc, file_read_actor);
1467 retval += desc.written;
1468 if (desc.error) {
1469 retval = retval ?: desc.error;
1470 break;
1471 }
1472 if (desc.count > 0)
1473 break;
1474 }
1475out:
1476 return retval;
1477}
1478EXPORT_SYMBOL(generic_file_aio_read);
1479
1480#ifdef CONFIG_MMU
1481/**
1482 * page_cache_read - adds requested page to the page cache if not already there
1483 * @file: file to read
1484 * @offset: page index
1485 *
1486 * This adds the requested page to the page cache if it isn't already there,
1487 * and schedules an I/O to read in its contents from disk.
1488 */
1489static int page_cache_read(struct file *file, pgoff_t offset)
1490{
1491 struct address_space *mapping = file->f_mapping;
1492 struct page *page;
1493 int ret;
1494
1495 do {
1496 page = page_cache_alloc_cold(mapping);
1497 if (!page)
1498 return -ENOMEM;
1499
1500 ret = add_to_page_cache_lru(page, mapping, offset, GFP_KERNEL);
1501 if (ret == 0)
1502 ret = mapping->a_ops->readpage(file, page);
1503 else if (ret == -EEXIST)
1504 ret = 0; /* losing race to add is OK */
1505
1506 page_cache_release(page);
1507
1508 } while (ret == AOP_TRUNCATED_PAGE);
1509
1510 return ret;
1511}
1512
1513#define MMAP_LOTSAMISS (100)
1514
1515/*
1516 * Synchronous readahead happens when we don't even find
1517 * a page in the page cache at all.
1518 */
1519static void do_sync_mmap_readahead(struct vm_area_struct *vma,
1520 struct file_ra_state *ra,
1521 struct file *file,
1522 pgoff_t offset)
1523{
1524 unsigned long ra_pages;
1525 struct address_space *mapping = file->f_mapping;
1526
1527 /* If we don't want any read-ahead, don't bother */
1528 if (VM_RandomReadHint(vma))
1529 return;
1530 if (!ra->ra_pages)
1531 return;
1532
1533 if (VM_SequentialReadHint(vma)) {
1534 page_cache_sync_readahead(mapping, ra, file, offset,
1535 ra->ra_pages);
1536 return;
1537 }
1538
1539 /* Avoid banging the cache line if not needed */
1540 if (ra->mmap_miss < MMAP_LOTSAMISS * 10)
1541 ra->mmap_miss++;
1542
1543 /*
1544 * Do we miss much more than hit in this file? If so,
1545 * stop bothering with read-ahead. It will only hurt.
1546 */
1547 if (ra->mmap_miss > MMAP_LOTSAMISS)
1548 return;
1549
1550 /*
1551 * mmap read-around
1552 */
1553 ra_pages = max_sane_readahead(ra->ra_pages);
1554 ra->start = max_t(long, 0, offset - ra_pages / 2);
1555 ra->size = ra_pages;
1556 ra->async_size = ra_pages / 4;
1557 ra_submit(ra, mapping, file);
1558}
1559
1560/*
1561 * Asynchronous readahead happens when we find the page and PG_readahead,
1562 * so we want to possibly extend the readahead further..
1563 */
1564static void do_async_mmap_readahead(struct vm_area_struct *vma,
1565 struct file_ra_state *ra,
1566 struct file *file,
1567 struct page *page,
1568 pgoff_t offset)
1569{
1570 struct address_space *mapping = file->f_mapping;
1571
1572 /* If we don't want any read-ahead, don't bother */
1573 if (VM_RandomReadHint(vma))
1574 return;
1575 if (ra->mmap_miss > 0)
1576 ra->mmap_miss--;
1577 if (PageReadahead(page))
1578 page_cache_async_readahead(mapping, ra, file,
1579 page, offset, ra->ra_pages);
1580}
1581
1582/**
1583 * filemap_fault - read in file data for page fault handling
1584 * @vma: vma in which the fault was taken
1585 * @vmf: struct vm_fault containing details of the fault
1586 *
1587 * filemap_fault() is invoked via the vma operations vector for a
1588 * mapped memory region to read in file data during a page fault.
1589 *
1590 * The goto's are kind of ugly, but this streamlines the normal case of having
1591 * it in the page cache, and handles the special cases reasonably without
1592 * having a lot of duplicated code.
1593 */
1594int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
1595{
1596 int error;
1597 struct file *file = vma->vm_file;
1598 struct address_space *mapping = file->f_mapping;
1599 struct file_ra_state *ra = &file->f_ra;
1600 struct inode *inode = mapping->host;
1601 pgoff_t offset = vmf->pgoff;
1602 struct page *page;
1603 pgoff_t size;
1604 int ret = 0;
1605
1606 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1607 if (offset >= size)
1608 return VM_FAULT_SIGBUS;
1609
1610 /*
1611 * Do we have something in the page cache already?
1612 */
1613 page = find_get_page(mapping, offset);
1614 if (likely(page)) {
1615 /*
1616 * We found the page, so try async readahead before
1617 * waiting for the lock.
1618 */
1619 do_async_mmap_readahead(vma, ra, file, page, offset);
1620 } else {
1621 /* No page in the page cache at all */
1622 do_sync_mmap_readahead(vma, ra, file, offset);
1623 count_vm_event(PGMAJFAULT);
1624 mem_cgroup_count_vm_event(vma->vm_mm, PGMAJFAULT);
1625 ret = VM_FAULT_MAJOR;
1626retry_find:
1627 page = find_get_page(mapping, offset);
1628 if (!page)
1629 goto no_cached_page;
1630 }
1631
1632 if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
1633 page_cache_release(page);
1634 return ret | VM_FAULT_RETRY;
1635 }
1636
1637 /* Did it get truncated? */
1638 if (unlikely(page->mapping != mapping)) {
1639 unlock_page(page);
1640 put_page(page);
1641 goto retry_find;
1642 }
1643 VM_BUG_ON(page->index != offset);
1644
1645 /*
1646 * We have a locked page in the page cache, now we need to check
1647 * that it's up-to-date. If not, it is going to be due to an error.
1648 */
1649 if (unlikely(!PageUptodate(page)))
1650 goto page_not_uptodate;
1651
1652 /*
1653 * Found the page and have a reference on it.
1654 * We must recheck i_size under page lock.
1655 */
1656 size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1657 if (unlikely(offset >= size)) {
1658 unlock_page(page);
1659 page_cache_release(page);
1660 return VM_FAULT_SIGBUS;
1661 }
1662
1663 vmf->page = page;
1664 return ret | VM_FAULT_LOCKED;
1665
1666no_cached_page:
1667 /*
1668 * We're only likely to ever get here if MADV_RANDOM is in
1669 * effect.
1670 */
1671 error = page_cache_read(file, offset);
1672
1673 /*
1674 * The page we want has now been added to the page cache.
1675 * In the unlikely event that someone removed it in the
1676 * meantime, we'll just come back here and read it again.
1677 */
1678 if (error >= 0)
1679 goto retry_find;
1680
1681 /*
1682 * An error return from page_cache_read can result if the
1683 * system is low on memory, or a problem occurs while trying
1684 * to schedule I/O.
1685 */
1686 if (error == -ENOMEM)
1687 return VM_FAULT_OOM;
1688 return VM_FAULT_SIGBUS;
1689
1690page_not_uptodate:
1691 /*
1692 * Umm, take care of errors if the page isn't up-to-date.
1693 * Try to re-read it _once_. We do this synchronously,
1694 * because there really aren't any performance issues here
1695 * and we need to check for errors.
1696 */
1697 ClearPageError(page);
1698 error = mapping->a_ops->readpage(file, page);
1699 if (!error) {
1700 wait_on_page_locked(page);
1701 if (!PageUptodate(page))
1702 error = -EIO;
1703 }
1704 page_cache_release(page);
1705
1706 if (!error || error == AOP_TRUNCATED_PAGE)
1707 goto retry_find;
1708
1709 /* Things didn't work out. Return zero to tell the mm layer so. */
1710 shrink_readahead_size_eio(file, ra);
1711 return VM_FAULT_SIGBUS;
1712}
1713EXPORT_SYMBOL(filemap_fault);
1714
1715const struct vm_operations_struct generic_file_vm_ops = {
1716 .fault = filemap_fault,
1717};
1718
1719/* This is used for a general mmap of a disk file */
1720
1721int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1722{
1723 struct address_space *mapping = file->f_mapping;
1724
1725 if (!mapping->a_ops->readpage)
1726 return -ENOEXEC;
1727 file_accessed(file);
1728 vma->vm_ops = &generic_file_vm_ops;
1729 vma->vm_flags |= VM_CAN_NONLINEAR;
1730 return 0;
1731}
1732
1733/*
1734 * This is for filesystems which do not implement ->writepage.
1735 */
1736int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
1737{
1738 if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
1739 return -EINVAL;
1740 return generic_file_mmap(file, vma);
1741}
1742#else
1743int generic_file_mmap(struct file * file, struct vm_area_struct * vma)
1744{
1745 return -ENOSYS;
1746}
1747int generic_file_readonly_mmap(struct file * file, struct vm_area_struct * vma)
1748{
1749 return -ENOSYS;
1750}
1751#endif /* CONFIG_MMU */
1752
1753EXPORT_SYMBOL(generic_file_mmap);
1754EXPORT_SYMBOL(generic_file_readonly_mmap);
1755
1756static struct page *__read_cache_page(struct address_space *mapping,
1757 pgoff_t index,
1758 int (*filler)(void *, struct page *),
1759 void *data,
1760 gfp_t gfp)
1761{
1762 struct page *page;
1763 int err;
1764repeat:
1765 page = find_get_page(mapping, index);
1766 if (!page) {
1767 page = __page_cache_alloc(gfp | __GFP_COLD);
1768 if (!page)
1769 return ERR_PTR(-ENOMEM);
1770 err = add_to_page_cache_lru(page, mapping, index, gfp);
1771 if (unlikely(err)) {
1772 page_cache_release(page);
1773 if (err == -EEXIST)
1774 goto repeat;
1775 /* Presumably ENOMEM for radix tree node */
1776 return ERR_PTR(err);
1777 }
1778 err = filler(data, page);
1779 if (err < 0) {
1780 page_cache_release(page);
1781 page = ERR_PTR(err);
1782 }
1783 }
1784 return page;
1785}
1786
1787static struct page *do_read_cache_page(struct address_space *mapping,
1788 pgoff_t index,
1789 int (*filler)(void *, struct page *),
1790 void *data,
1791 gfp_t gfp)
1792
1793{
1794 struct page *page;
1795 int err;
1796
1797retry:
1798 page = __read_cache_page(mapping, index, filler, data, gfp);
1799 if (IS_ERR(page))
1800 return page;
1801 if (PageUptodate(page))
1802 goto out;
1803
1804 lock_page(page);
1805 if (!page->mapping) {
1806 unlock_page(page);
1807 page_cache_release(page);
1808 goto retry;
1809 }
1810 if (PageUptodate(page)) {
1811 unlock_page(page);
1812 goto out;
1813 }
1814 err = filler(data, page);
1815 if (err < 0) {
1816 page_cache_release(page);
1817 return ERR_PTR(err);
1818 }
1819out:
1820 mark_page_accessed(page);
1821 return page;
1822}
1823
1824/**
1825 * read_cache_page_async - read into page cache, fill it if needed
1826 * @mapping: the page's address_space
1827 * @index: the page index
1828 * @filler: function to perform the read
1829 * @data: first arg to filler(data, page) function, often left as NULL
1830 *
1831 * Same as read_cache_page, but don't wait for page to become unlocked
1832 * after submitting it to the filler.
1833 *
1834 * Read into the page cache. If a page already exists, and PageUptodate() is
1835 * not set, try to fill the page but don't wait for it to become unlocked.
1836 *
1837 * If the page does not get brought uptodate, return -EIO.
1838 */
1839struct page *read_cache_page_async(struct address_space *mapping,
1840 pgoff_t index,
1841 int (*filler)(void *, struct page *),
1842 void *data)
1843{
1844 return do_read_cache_page(mapping, index, filler, data, mapping_gfp_mask(mapping));
1845}
1846EXPORT_SYMBOL(read_cache_page_async);
1847
1848static struct page *wait_on_page_read(struct page *page)
1849{
1850 if (!IS_ERR(page)) {
1851 wait_on_page_locked(page);
1852 if (!PageUptodate(page)) {
1853 page_cache_release(page);
1854 page = ERR_PTR(-EIO);
1855 }
1856 }
1857 return page;
1858}
1859
1860/**
1861 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
1862 * @mapping: the page's address_space
1863 * @index: the page index
1864 * @gfp: the page allocator flags to use if allocating
1865 *
1866 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
1867 * any new page allocations done using the specified allocation flags.
1868 *
1869 * If the page does not get brought uptodate, return -EIO.
1870 */
1871struct page *read_cache_page_gfp(struct address_space *mapping,
1872 pgoff_t index,
1873 gfp_t gfp)
1874{
1875 filler_t *filler = (filler_t *)mapping->a_ops->readpage;
1876
1877 return wait_on_page_read(do_read_cache_page(mapping, index, filler, NULL, gfp));
1878}
1879EXPORT_SYMBOL(read_cache_page_gfp);
1880
1881/**
1882 * read_cache_page - read into page cache, fill it if needed
1883 * @mapping: the page's address_space
1884 * @index: the page index
1885 * @filler: function to perform the read
1886 * @data: first arg to filler(data, page) function, often left as NULL
1887 *
1888 * Read into the page cache. If a page already exists, and PageUptodate() is
1889 * not set, try to fill the page then wait for it to become unlocked.
1890 *
1891 * If the page does not get brought uptodate, return -EIO.
1892 */
1893struct page *read_cache_page(struct address_space *mapping,
1894 pgoff_t index,
1895 int (*filler)(void *, struct page *),
1896 void *data)
1897{
1898 return wait_on_page_read(read_cache_page_async(mapping, index, filler, data));
1899}
1900EXPORT_SYMBOL(read_cache_page);
1901
1902static size_t __iovec_copy_from_user_inatomic(char *vaddr,
1903 const struct iovec *iov, size_t base, size_t bytes)
1904{
1905 size_t copied = 0, left = 0;
1906
1907 while (bytes) {
1908 char __user *buf = iov->iov_base + base;
1909 int copy = min(bytes, iov->iov_len - base);
1910
1911 base = 0;
1912 left = __copy_from_user_inatomic(vaddr, buf, copy);
1913 copied += copy;
1914 bytes -= copy;
1915 vaddr += copy;
1916 iov++;
1917
1918 if (unlikely(left))
1919 break;
1920 }
1921 return copied - left;
1922}
1923
1924/*
1925 * Copy as much as we can into the page and return the number of bytes which
1926 * were successfully copied. If a fault is encountered then return the number of
1927 * bytes which were copied.
1928 */
1929size_t iov_iter_copy_from_user_atomic(struct page *page,
1930 struct iov_iter *i, unsigned long offset, size_t bytes)
1931{
1932 char *kaddr;
1933 size_t copied;
1934
1935 BUG_ON(!in_atomic());
1936 kaddr = kmap_atomic(page);
1937 if (likely(i->nr_segs == 1)) {
1938 int left;
1939 char __user *buf = i->iov->iov_base + i->iov_offset;
1940 left = __copy_from_user_inatomic(kaddr + offset, buf, bytes);
1941 copied = bytes - left;
1942 } else {
1943 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1944 i->iov, i->iov_offset, bytes);
1945 }
1946 kunmap_atomic(kaddr);
1947
1948 return copied;
1949}
1950EXPORT_SYMBOL(iov_iter_copy_from_user_atomic);
1951
1952/*
1953 * This has the same sideeffects and return value as
1954 * iov_iter_copy_from_user_atomic().
1955 * The difference is that it attempts to resolve faults.
1956 * Page must not be locked.
1957 */
1958size_t iov_iter_copy_from_user(struct page *page,
1959 struct iov_iter *i, unsigned long offset, size_t bytes)
1960{
1961 char *kaddr;
1962 size_t copied;
1963
1964 kaddr = kmap(page);
1965 if (likely(i->nr_segs == 1)) {
1966 int left;
1967 char __user *buf = i->iov->iov_base + i->iov_offset;
1968 left = __copy_from_user(kaddr + offset, buf, bytes);
1969 copied = bytes - left;
1970 } else {
1971 copied = __iovec_copy_from_user_inatomic(kaddr + offset,
1972 i->iov, i->iov_offset, bytes);
1973 }
1974 kunmap(page);
1975 return copied;
1976}
1977EXPORT_SYMBOL(iov_iter_copy_from_user);
1978
1979void iov_iter_advance(struct iov_iter *i, size_t bytes)
1980{
1981 BUG_ON(i->count < bytes);
1982
1983 if (likely(i->nr_segs == 1)) {
1984 i->iov_offset += bytes;
1985 i->count -= bytes;
1986 } else {
1987 const struct iovec *iov = i->iov;
1988 size_t base = i->iov_offset;
1989 unsigned long nr_segs = i->nr_segs;
1990
1991 /*
1992 * The !iov->iov_len check ensures we skip over unlikely
1993 * zero-length segments (without overruning the iovec).
1994 */
1995 while (bytes || unlikely(i->count && !iov->iov_len)) {
1996 int copy;
1997
1998 copy = min(bytes, iov->iov_len - base);
1999 BUG_ON(!i->count || i->count < copy);
2000 i->count -= copy;
2001 bytes -= copy;
2002 base += copy;
2003 if (iov->iov_len == base) {
2004 iov++;
2005 nr_segs--;
2006 base = 0;
2007 }
2008 }
2009 i->iov = iov;
2010 i->iov_offset = base;
2011 i->nr_segs = nr_segs;
2012 }
2013}
2014EXPORT_SYMBOL(iov_iter_advance);
2015
2016/*
2017 * Fault in the first iovec of the given iov_iter, to a maximum length
2018 * of bytes. Returns 0 on success, or non-zero if the memory could not be
2019 * accessed (ie. because it is an invalid address).
2020 *
2021 * writev-intensive code may want this to prefault several iovecs -- that
2022 * would be possible (callers must not rely on the fact that _only_ the
2023 * first iovec will be faulted with the current implementation).
2024 */
2025int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes)
2026{
2027 char __user *buf = i->iov->iov_base + i->iov_offset;
2028 bytes = min(bytes, i->iov->iov_len - i->iov_offset);
2029 return fault_in_pages_readable(buf, bytes);
2030}
2031EXPORT_SYMBOL(iov_iter_fault_in_readable);
2032
2033/*
2034 * Return the count of just the current iov_iter segment.
2035 */
2036size_t iov_iter_single_seg_count(struct iov_iter *i)
2037{
2038 const struct iovec *iov = i->iov;
2039 if (i->nr_segs == 1)
2040 return i->count;
2041 else
2042 return min(i->count, iov->iov_len - i->iov_offset);
2043}
2044EXPORT_SYMBOL(iov_iter_single_seg_count);
2045
2046/*
2047 * Performs necessary checks before doing a write
2048 *
2049 * Can adjust writing position or amount of bytes to write.
2050 * Returns appropriate error code that caller should return or
2051 * zero in case that write should be allowed.
2052 */
2053inline int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk)
2054{
2055 struct inode *inode = file->f_mapping->host;
2056 unsigned long limit = rlimit(RLIMIT_FSIZE);
2057
2058 if (unlikely(*pos < 0))
2059 return -EINVAL;
2060
2061 if (!isblk) {
2062 /* FIXME: this is for backwards compatibility with 2.4 */
2063 if (file->f_flags & O_APPEND)
2064 *pos = i_size_read(inode);
2065
2066 if (limit != RLIM_INFINITY) {
2067 if (*pos >= limit) {
2068 send_sig(SIGXFSZ, current, 0);
2069 return -EFBIG;
2070 }
2071 if (*count > limit - (typeof(limit))*pos) {
2072 *count = limit - (typeof(limit))*pos;
2073 }
2074 }
2075 }
2076
2077 /*
2078 * LFS rule
2079 */
2080 if (unlikely(*pos + *count > MAX_NON_LFS &&
2081 !(file->f_flags & O_LARGEFILE))) {
2082 if (*pos >= MAX_NON_LFS) {
2083 return -EFBIG;
2084 }
2085 if (*count > MAX_NON_LFS - (unsigned long)*pos) {
2086 *count = MAX_NON_LFS - (unsigned long)*pos;
2087 }
2088 }
2089
2090 /*
2091 * Are we about to exceed the fs block limit ?
2092 *
2093 * If we have written data it becomes a short write. If we have
2094 * exceeded without writing data we send a signal and return EFBIG.
2095 * Linus frestrict idea will clean these up nicely..
2096 */
2097 if (likely(!isblk)) {
2098 if (unlikely(*pos >= inode->i_sb->s_maxbytes)) {
2099 if (*count || *pos > inode->i_sb->s_maxbytes) {
2100 return -EFBIG;
2101 }
2102 /* zero-length writes at ->s_maxbytes are OK */
2103 }
2104
2105 if (unlikely(*pos + *count > inode->i_sb->s_maxbytes))
2106 *count = inode->i_sb->s_maxbytes - *pos;
2107 } else {
2108#ifdef CONFIG_BLOCK
2109 loff_t isize;
2110 if (bdev_read_only(I_BDEV(inode)))
2111 return -EPERM;
2112 isize = i_size_read(inode);
2113 if (*pos >= isize) {
2114 if (*count || *pos > isize)
2115 return -ENOSPC;
2116 }
2117
2118 if (*pos + *count > isize)
2119 *count = isize - *pos;
2120#else
2121 return -EPERM;
2122#endif
2123 }
2124 return 0;
2125}
2126EXPORT_SYMBOL(generic_write_checks);
2127
2128int pagecache_write_begin(struct file *file, struct address_space *mapping,
2129 loff_t pos, unsigned len, unsigned flags,
2130 struct page **pagep, void **fsdata)
2131{
2132 const struct address_space_operations *aops = mapping->a_ops;
2133
2134 return aops->write_begin(file, mapping, pos, len, flags,
2135 pagep, fsdata);
2136}
2137EXPORT_SYMBOL(pagecache_write_begin);
2138
2139int pagecache_write_end(struct file *file, struct address_space *mapping,
2140 loff_t pos, unsigned len, unsigned copied,
2141 struct page *page, void *fsdata)
2142{
2143 const struct address_space_operations *aops = mapping->a_ops;
2144
2145 mark_page_accessed(page);
2146 return aops->write_end(file, mapping, pos, len, copied, page, fsdata);
2147}
2148EXPORT_SYMBOL(pagecache_write_end);
2149
2150ssize_t
2151generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov,
2152 unsigned long *nr_segs, loff_t pos, loff_t *ppos,
2153 size_t count, size_t ocount)
2154{
2155 struct file *file = iocb->ki_filp;
2156 struct address_space *mapping = file->f_mapping;
2157 struct inode *inode = mapping->host;
2158 ssize_t written;
2159 size_t write_len;
2160 pgoff_t end;
2161
2162 if (count != ocount)
2163 *nr_segs = iov_shorten((struct iovec *)iov, *nr_segs, count);
2164
2165 write_len = iov_length(iov, *nr_segs);
2166 end = (pos + write_len - 1) >> PAGE_CACHE_SHIFT;
2167
2168 written = filemap_write_and_wait_range(mapping, pos, pos + write_len - 1);
2169 if (written)
2170 goto out;
2171
2172 /*
2173 * After a write we want buffered reads to be sure to go to disk to get
2174 * the new data. We invalidate clean cached page from the region we're
2175 * about to write. We do this *before* the write so that we can return
2176 * without clobbering -EIOCBQUEUED from ->direct_IO().
2177 */
2178 if (mapping->nrpages) {
2179 written = invalidate_inode_pages2_range(mapping,
2180 pos >> PAGE_CACHE_SHIFT, end);
2181 /*
2182 * If a page can not be invalidated, return 0 to fall back
2183 * to buffered write.
2184 */
2185 if (written) {
2186 if (written == -EBUSY)
2187 return 0;
2188 goto out;
2189 }
2190 }
2191
2192 written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
2193
2194 /*
2195 * Finally, try again to invalidate clean pages which might have been
2196 * cached by non-direct readahead, or faulted in by get_user_pages()
2197 * if the source of the write was an mmap'ed region of the file
2198 * we're writing. Either one is a pretty crazy thing to do,
2199 * so we don't support it 100%. If this invalidation
2200 * fails, tough, the write still worked...
2201 */
2202 if (mapping->nrpages) {
2203 invalidate_inode_pages2_range(mapping,
2204 pos >> PAGE_CACHE_SHIFT, end);
2205 }
2206
2207 if (written > 0) {
2208 pos += written;
2209 if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
2210 i_size_write(inode, pos);
2211 mark_inode_dirty(inode);
2212 }
2213 *ppos = pos;
2214 }
2215out:
2216 return written;
2217}
2218EXPORT_SYMBOL(generic_file_direct_write);
2219
2220/*
2221 * Find or create a page at the given pagecache position. Return the locked
2222 * page. This function is specifically for buffered writes.
2223 */
2224struct page *grab_cache_page_write_begin(struct address_space *mapping,
2225 pgoff_t index, unsigned flags)
2226{
2227 int status;
2228 gfp_t gfp_mask;
2229 struct page *page;
2230 gfp_t gfp_notmask = 0;
2231
2232 gfp_mask = mapping_gfp_mask(mapping);
2233 if (mapping_cap_account_dirty(mapping))
2234 gfp_mask |= __GFP_WRITE;
2235 if (flags & AOP_FLAG_NOFS)
2236 gfp_notmask = __GFP_FS;
2237repeat:
2238 page = find_lock_page(mapping, index);
2239 if (page)
2240 goto found;
2241
2242 page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
2243 if (!page)
2244 return NULL;
2245 status = add_to_page_cache_lru(page, mapping, index,
2246 GFP_KERNEL & ~gfp_notmask);
2247 if (unlikely(status)) {
2248 page_cache_release(page);
2249 if (status == -EEXIST)
2250 goto repeat;
2251 return NULL;
2252 }
2253found:
2254 wait_on_page_writeback(page);
2255 return page;
2256}
2257EXPORT_SYMBOL(grab_cache_page_write_begin);
2258
2259static ssize_t generic_perform_write(struct file *file,
2260 struct iov_iter *i, loff_t pos)
2261{
2262 struct address_space *mapping = file->f_mapping;
2263 const struct address_space_operations *a_ops = mapping->a_ops;
2264 long status = 0;
2265 ssize_t written = 0;
2266 unsigned int flags = 0;
2267
2268 /*
2269 * Copies from kernel address space cannot fail (NFSD is a big user).
2270 */
2271 if (segment_eq(get_fs(), KERNEL_DS))
2272 flags |= AOP_FLAG_UNINTERRUPTIBLE;
2273
2274 do {
2275 struct page *page;
2276 unsigned long offset; /* Offset into pagecache page */
2277 unsigned long bytes; /* Bytes to write to page */
2278 size_t copied; /* Bytes copied from user */
2279 void *fsdata;
2280
2281 offset = (pos & (PAGE_CACHE_SIZE - 1));
2282 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2283 iov_iter_count(i));
2284
2285again:
2286 /*
2287 * Bring in the user page that we will copy from _first_.
2288 * Otherwise there's a nasty deadlock on copying from the
2289 * same page as we're writing to, without it being marked
2290 * up-to-date.
2291 *
2292 * Not only is this an optimisation, but it is also required
2293 * to check that the address is actually valid, when atomic
2294 * usercopies are used, below.
2295 */
2296 if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
2297 status = -EFAULT;
2298 break;
2299 }
2300
2301 status = a_ops->write_begin(file, mapping, pos, bytes, flags,
2302 &page, &fsdata);
2303 if (unlikely(status))
2304 break;
2305
2306 if (mapping_writably_mapped(mapping))
2307 flush_dcache_page(page);
2308
2309 pagefault_disable();
2310 copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
2311 pagefault_enable();
2312 flush_dcache_page(page);
2313
2314 mark_page_accessed(page);
2315 status = a_ops->write_end(file, mapping, pos, bytes, copied,
2316 page, fsdata);
2317 if (unlikely(status < 0))
2318 break;
2319 copied = status;
2320
2321 cond_resched();
2322
2323 iov_iter_advance(i, copied);
2324 if (unlikely(copied == 0)) {
2325 /*
2326 * If we were unable to copy any data at all, we must
2327 * fall back to a single segment length write.
2328 *
2329 * If we didn't fallback here, we could livelock
2330 * because not all segments in the iov can be copied at
2331 * once without a pagefault.
2332 */
2333 bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
2334 iov_iter_single_seg_count(i));
2335 goto again;
2336 }
2337 pos += copied;
2338 written += copied;
2339
2340 balance_dirty_pages_ratelimited(mapping);
2341 if (fatal_signal_pending(current)) {
2342 status = -EINTR;
2343 break;
2344 }
2345 } while (iov_iter_count(i));
2346
2347 return written ? written : status;
2348}
2349
2350ssize_t
2351generic_file_buffered_write(struct kiocb *iocb, const struct iovec *iov,
2352 unsigned long nr_segs, loff_t pos, loff_t *ppos,
2353 size_t count, ssize_t written)
2354{
2355 struct file *file = iocb->ki_filp;
2356 ssize_t status;
2357 struct iov_iter i;
2358
2359 iov_iter_init(&i, iov, nr_segs, count, written);
2360 status = generic_perform_write(file, &i, pos);
2361
2362 if (likely(status >= 0)) {
2363 written += status;
2364 *ppos = pos + status;
2365 }
2366
2367 return written ? written : status;
2368}
2369EXPORT_SYMBOL(generic_file_buffered_write);
2370
2371/**
2372 * __generic_file_aio_write - write data to a file
2373 * @iocb: IO state structure (file, offset, etc.)
2374 * @iov: vector with data to write
2375 * @nr_segs: number of segments in the vector
2376 * @ppos: position where to write
2377 *
2378 * This function does all the work needed for actually writing data to a
2379 * file. It does all basic checks, removes SUID from the file, updates
2380 * modification times and calls proper subroutines depending on whether we
2381 * do direct IO or a standard buffered write.
2382 *
2383 * It expects i_mutex to be grabbed unless we work on a block device or similar
2384 * object which does not need locking at all.
2385 *
2386 * This function does *not* take care of syncing data in case of O_SYNC write.
2387 * A caller has to handle it. This is mainly due to the fact that we want to
2388 * avoid syncing under i_mutex.
2389 */
2390ssize_t __generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2391 unsigned long nr_segs, loff_t *ppos)
2392{
2393 struct file *file = iocb->ki_filp;
2394 struct address_space * mapping = file->f_mapping;
2395 size_t ocount; /* original count */
2396 size_t count; /* after file limit checks */
2397 struct inode *inode = mapping->host;
2398 loff_t pos;
2399 ssize_t written;
2400 ssize_t err;
2401
2402 ocount = 0;
2403 err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
2404 if (err)
2405 return err;
2406
2407 count = ocount;
2408 pos = *ppos;
2409
2410 vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2411
2412 /* We can write back this queue in page reclaim */
2413 current->backing_dev_info = mapping->backing_dev_info;
2414 written = 0;
2415
2416 err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2417 if (err)
2418 goto out;
2419
2420 if (count == 0)
2421 goto out;
2422
2423 err = file_remove_suid(file);
2424 if (err)
2425 goto out;
2426
2427 err = file_update_time(file);
2428 if (err)
2429 goto out;
2430
2431 /* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
2432 if (unlikely(file->f_flags & O_DIRECT)) {
2433 loff_t endbyte;
2434 ssize_t written_buffered;
2435
2436 written = generic_file_direct_write(iocb, iov, &nr_segs, pos,
2437 ppos, count, ocount);
2438 if (written < 0 || written == count)
2439 goto out;
2440 /*
2441 * direct-io write to a hole: fall through to buffered I/O
2442 * for completing the rest of the request.
2443 */
2444 pos += written;
2445 count -= written;
2446 written_buffered = generic_file_buffered_write(iocb, iov,
2447 nr_segs, pos, ppos, count,
2448 written);
2449 /*
2450 * If generic_file_buffered_write() retuned a synchronous error
2451 * then we want to return the number of bytes which were
2452 * direct-written, or the error code if that was zero. Note
2453 * that this differs from normal direct-io semantics, which
2454 * will return -EFOO even if some bytes were written.
2455 */
2456 if (written_buffered < 0) {
2457 err = written_buffered;
2458 goto out;
2459 }
2460
2461 /*
2462 * We need to ensure that the page cache pages are written to
2463 * disk and invalidated to preserve the expected O_DIRECT
2464 * semantics.
2465 */
2466 endbyte = pos + written_buffered - written - 1;
2467 err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
2468 if (err == 0) {
2469 written = written_buffered;
2470 invalidate_mapping_pages(mapping,
2471 pos >> PAGE_CACHE_SHIFT,
2472 endbyte >> PAGE_CACHE_SHIFT);
2473 } else {
2474 /*
2475 * We don't know how much we wrote, so just return
2476 * the number of bytes which were direct-written
2477 */
2478 }
2479 } else {
2480 written = generic_file_buffered_write(iocb, iov, nr_segs,
2481 pos, ppos, count, written);
2482 }
2483out:
2484 current->backing_dev_info = NULL;
2485 return written ? written : err;
2486}
2487EXPORT_SYMBOL(__generic_file_aio_write);
2488
2489/**
2490 * generic_file_aio_write - write data to a file
2491 * @iocb: IO state structure
2492 * @iov: vector with data to write
2493 * @nr_segs: number of segments in the vector
2494 * @pos: position in file where to write
2495 *
2496 * This is a wrapper around __generic_file_aio_write() to be used by most
2497 * filesystems. It takes care of syncing the file in case of O_SYNC file
2498 * and acquires i_mutex as needed.
2499 */
2500ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2501 unsigned long nr_segs, loff_t pos)
2502{
2503 struct file *file = iocb->ki_filp;
2504 struct inode *inode = file->f_mapping->host;
2505 struct blk_plug plug;
2506 ssize_t ret;
2507
2508 BUG_ON(iocb->ki_pos != pos);
2509
2510 mutex_lock(&inode->i_mutex);
2511 blk_start_plug(&plug);
2512 ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
2513 mutex_unlock(&inode->i_mutex);
2514
2515 if (ret > 0 || ret == -EIOCBQUEUED) {
2516 ssize_t err;
2517
2518 err = generic_write_sync(file, pos, ret);
2519 if (err < 0 && ret > 0)
2520 ret = err;
2521 }
2522 blk_finish_plug(&plug);
2523 return ret;
2524}
2525EXPORT_SYMBOL(generic_file_aio_write);
2526
2527/**
2528 * try_to_release_page() - release old fs-specific metadata on a page
2529 *
2530 * @page: the page which the kernel is trying to free
2531 * @gfp_mask: memory allocation flags (and I/O mode)
2532 *
2533 * The address_space is to try to release any data against the page
2534 * (presumably at page->private). If the release was successful, return `1'.
2535 * Otherwise return zero.
2536 *
2537 * This may also be called if PG_fscache is set on a page, indicating that the
2538 * page is known to the local caching routines.
2539 *
2540 * The @gfp_mask argument specifies whether I/O may be performed to release
2541 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT & __GFP_FS).
2542 *
2543 */
2544int try_to_release_page(struct page *page, gfp_t gfp_mask)
2545{
2546 struct address_space * const mapping = page->mapping;
2547
2548 BUG_ON(!PageLocked(page));
2549 if (PageWriteback(page))
2550 return 0;
2551
2552 if (mapping && mapping->a_ops->releasepage)
2553 return mapping->a_ops->releasepage(page, gfp_mask);
2554 return try_to_free_buffers(page);
2555}
2556
2557EXPORT_SYMBOL(try_to_release_page);