Merge 4.4.88 into android-4.4
[GitHub/exynos8895/android_kernel_samsung_universal8895.git] / mm / truncate.c
1 /*
2 * mm/truncate.c - code for taking down pages from address_spaces
3 *
4 * Copyright (C) 2002, Linus Torvalds
5 *
6 * 10Sep2002 Andrew Morton
7 * Initial version.
8 */
9
10 #include <linux/kernel.h>
11 #include <linux/backing-dev.h>
12 #include <linux/gfp.h>
13 #include <linux/mm.h>
14 #include <linux/swap.h>
15 #include <linux/export.h>
16 #include <linux/pagemap.h>
17 #include <linux/highmem.h>
18 #include <linux/pagevec.h>
19 #include <linux/task_io_accounting_ops.h>
20 #include <linux/buffer_head.h> /* grr. try_to_release_page,
21 do_invalidatepage */
22 #include <linux/cleancache.h>
23 #include <linux/rmap.h>
24 #include "internal.h"
25
26 static void clear_exceptional_entry(struct address_space *mapping,
27 pgoff_t index, void *entry)
28 {
29 struct radix_tree_node *node;
30 void **slot;
31
32 /* Handled by shmem itself */
33 if (shmem_mapping(mapping))
34 return;
35
36 spin_lock_irq(&mapping->tree_lock);
37 /*
38 * Regular page slots are stabilized by the page lock even
39 * without the tree itself locked. These unlocked entries
40 * need verification under the tree lock.
41 */
42 if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot))
43 goto unlock;
44 if (*slot != entry)
45 goto unlock;
46 radix_tree_replace_slot(slot, NULL);
47 mapping->nrshadows--;
48 if (!node)
49 goto unlock;
50 workingset_node_shadows_dec(node);
51 /*
52 * Don't track node without shadow entries.
53 *
54 * Avoid acquiring the list_lru lock if already untracked.
55 * The list_empty() test is safe as node->private_list is
56 * protected by mapping->tree_lock.
57 */
58 if (!workingset_node_shadows(node) &&
59 !list_empty(&node->private_list))
60 list_lru_del(&workingset_shadow_nodes, &node->private_list);
61 __radix_tree_delete_node(&mapping->page_tree, node);
62 unlock:
63 spin_unlock_irq(&mapping->tree_lock);
64 }
65
66 /**
67 * do_invalidatepage - invalidate part or all of a page
68 * @page: the page which is affected
69 * @offset: start of the range to invalidate
70 * @length: length of the range to invalidate
71 *
72 * do_invalidatepage() is called when all or part of the page has become
73 * invalidated by a truncate operation.
74 *
75 * do_invalidatepage() does not have to release all buffers, but it must
76 * ensure that no dirty buffer is left outside @offset and that no I/O
77 * is underway against any of the blocks which are outside the truncation
78 * point. Because the caller is about to free (and possibly reuse) those
79 * blocks on-disk.
80 */
81 void do_invalidatepage(struct page *page, unsigned int offset,
82 unsigned int length)
83 {
84 void (*invalidatepage)(struct page *, unsigned int, unsigned int);
85
86 invalidatepage = page->mapping->a_ops->invalidatepage;
87 #ifdef CONFIG_BLOCK
88 if (!invalidatepage)
89 invalidatepage = block_invalidatepage;
90 #endif
91 if (invalidatepage)
92 (*invalidatepage)(page, offset, length);
93 }
94
95 /*
96 * If truncate cannot remove the fs-private metadata from the page, the page
97 * becomes orphaned. It will be left on the LRU and may even be mapped into
98 * user pagetables if we're racing with filemap_fault().
99 *
100 * We need to bale out if page->mapping is no longer equal to the original
101 * mapping. This happens a) when the VM reclaimed the page while we waited on
102 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
103 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
104 */
105 static int
106 truncate_complete_page(struct address_space *mapping, struct page *page)
107 {
108 if (page->mapping != mapping)
109 return -EIO;
110
111 if (page_has_private(page))
112 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
113
114 /*
115 * Some filesystems seem to re-dirty the page even after
116 * the VM has canceled the dirty bit (eg ext3 journaling).
117 * Hence dirty accounting check is placed after invalidation.
118 */
119 cancel_dirty_page(page);
120 ClearPageMappedToDisk(page);
121 delete_from_page_cache(page);
122 return 0;
123 }
124
125 /*
126 * This is for invalidate_mapping_pages(). That function can be called at
127 * any time, and is not supposed to throw away dirty pages. But pages can
128 * be marked dirty at any time too, so use remove_mapping which safely
129 * discards clean, unused pages.
130 *
131 * Returns non-zero if the page was successfully invalidated.
132 */
133 static int
134 invalidate_complete_page(struct address_space *mapping, struct page *page)
135 {
136 int ret;
137
138 if (page->mapping != mapping)
139 return 0;
140
141 if (page_has_private(page) && !try_to_release_page(page, 0))
142 return 0;
143
144 ret = remove_mapping(mapping, page);
145
146 return ret;
147 }
148
149 int truncate_inode_page(struct address_space *mapping, struct page *page)
150 {
151 if (page_mapped(page)) {
152 unmap_mapping_range(mapping,
153 (loff_t)page->index << PAGE_CACHE_SHIFT,
154 PAGE_CACHE_SIZE, 0);
155 }
156 return truncate_complete_page(mapping, page);
157 }
158
159 /*
160 * Used to get rid of pages on hardware memory corruption.
161 */
162 int generic_error_remove_page(struct address_space *mapping, struct page *page)
163 {
164 if (!mapping)
165 return -EINVAL;
166 /*
167 * Only punch for normal data pages for now.
168 * Handling other types like directories would need more auditing.
169 */
170 if (!S_ISREG(mapping->host->i_mode))
171 return -EIO;
172 return truncate_inode_page(mapping, page);
173 }
174 EXPORT_SYMBOL(generic_error_remove_page);
175
176 /*
177 * Safely invalidate one page from its pagecache mapping.
178 * It only drops clean, unused pages. The page must be locked.
179 *
180 * Returns 1 if the page is successfully invalidated, otherwise 0.
181 */
182 int invalidate_inode_page(struct page *page)
183 {
184 struct address_space *mapping = page_mapping(page);
185 if (!mapping)
186 return 0;
187 if (PageDirty(page) || PageWriteback(page))
188 return 0;
189 if (page_mapped(page))
190 return 0;
191 return invalidate_complete_page(mapping, page);
192 }
193
194 /**
195 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
196 * @mapping: mapping to truncate
197 * @lstart: offset from which to truncate
198 * @lend: offset to which to truncate (inclusive)
199 *
200 * Truncate the page cache, removing the pages that are between
201 * specified offsets (and zeroing out partial pages
202 * if lstart or lend + 1 is not page aligned).
203 *
204 * Truncate takes two passes - the first pass is nonblocking. It will not
205 * block on page locks and it will not block on writeback. The second pass
206 * will wait. This is to prevent as much IO as possible in the affected region.
207 * The first pass will remove most pages, so the search cost of the second pass
208 * is low.
209 *
210 * We pass down the cache-hot hint to the page freeing code. Even if the
211 * mapping is large, it is probably the case that the final pages are the most
212 * recently touched, and freeing happens in ascending file offset order.
213 *
214 * Note that since ->invalidatepage() accepts range to invalidate
215 * truncate_inode_pages_range is able to handle cases where lend + 1 is not
216 * page aligned properly.
217 */
218 void truncate_inode_pages_range(struct address_space *mapping,
219 loff_t lstart, loff_t lend)
220 {
221 pgoff_t start; /* inclusive */
222 pgoff_t end; /* exclusive */
223 unsigned int partial_start; /* inclusive */
224 unsigned int partial_end; /* exclusive */
225 struct pagevec pvec;
226 pgoff_t indices[PAGEVEC_SIZE];
227 pgoff_t index;
228 int i;
229
230 cleancache_invalidate_inode(mapping);
231 if (mapping->nrpages == 0 && mapping->nrshadows == 0)
232 return;
233
234 /* Offsets within partial pages */
235 partial_start = lstart & (PAGE_CACHE_SIZE - 1);
236 partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
237
238 /*
239 * 'start' and 'end' always covers the range of pages to be fully
240 * truncated. Partial pages are covered with 'partial_start' at the
241 * start of the range and 'partial_end' at the end of the range.
242 * Note that 'end' is exclusive while 'lend' is inclusive.
243 */
244 start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
245 if (lend == -1)
246 /*
247 * lend == -1 indicates end-of-file so we have to set 'end'
248 * to the highest possible pgoff_t and since the type is
249 * unsigned we're using -1.
250 */
251 end = -1;
252 else
253 end = (lend + 1) >> PAGE_CACHE_SHIFT;
254
255 pagevec_init(&pvec, 0);
256 index = start;
257 while (index < end && pagevec_lookup_entries(&pvec, mapping, index,
258 min(end - index, (pgoff_t)PAGEVEC_SIZE),
259 indices)) {
260 for (i = 0; i < pagevec_count(&pvec); i++) {
261 struct page *page = pvec.pages[i];
262
263 /* We rely upon deletion not changing page->index */
264 index = indices[i];
265 if (index >= end)
266 break;
267
268 if (radix_tree_exceptional_entry(page)) {
269 clear_exceptional_entry(mapping, index, page);
270 continue;
271 }
272
273 if (!trylock_page(page))
274 continue;
275 WARN_ON(page->index != index);
276 if (PageWriteback(page)) {
277 unlock_page(page);
278 continue;
279 }
280 truncate_inode_page(mapping, page);
281 unlock_page(page);
282 }
283 pagevec_remove_exceptionals(&pvec);
284 pagevec_release(&pvec);
285 cond_resched();
286 index++;
287 }
288
289 if (partial_start) {
290 struct page *page = find_lock_page(mapping, start - 1);
291 if (page) {
292 unsigned int top = PAGE_CACHE_SIZE;
293 if (start > end) {
294 /* Truncation within a single page */
295 top = partial_end;
296 partial_end = 0;
297 }
298 wait_on_page_writeback(page);
299 zero_user_segment(page, partial_start, top);
300 cleancache_invalidate_page(mapping, page);
301 if (page_has_private(page))
302 do_invalidatepage(page, partial_start,
303 top - partial_start);
304 unlock_page(page);
305 page_cache_release(page);
306 }
307 }
308 if (partial_end) {
309 struct page *page = find_lock_page(mapping, end);
310 if (page) {
311 wait_on_page_writeback(page);
312 zero_user_segment(page, 0, partial_end);
313 cleancache_invalidate_page(mapping, page);
314 if (page_has_private(page))
315 do_invalidatepage(page, 0,
316 partial_end);
317 unlock_page(page);
318 page_cache_release(page);
319 }
320 }
321 /*
322 * If the truncation happened within a single page no pages
323 * will be released, just zeroed, so we can bail out now.
324 */
325 if (start >= end)
326 return;
327
328 index = start;
329 for ( ; ; ) {
330 cond_resched();
331 if (!pagevec_lookup_entries(&pvec, mapping, index,
332 min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) {
333 /* If all gone from start onwards, we're done */
334 if (index == start)
335 break;
336 /* Otherwise restart to make sure all gone */
337 index = start;
338 continue;
339 }
340 if (index == start && indices[0] >= end) {
341 /* All gone out of hole to be punched, we're done */
342 pagevec_remove_exceptionals(&pvec);
343 pagevec_release(&pvec);
344 break;
345 }
346 for (i = 0; i < pagevec_count(&pvec); i++) {
347 struct page *page = pvec.pages[i];
348
349 /* We rely upon deletion not changing page->index */
350 index = indices[i];
351 if (index >= end) {
352 /* Restart punch to make sure all gone */
353 index = start - 1;
354 break;
355 }
356
357 if (radix_tree_exceptional_entry(page)) {
358 clear_exceptional_entry(mapping, index, page);
359 continue;
360 }
361
362 lock_page(page);
363 WARN_ON(page->index != index);
364 wait_on_page_writeback(page);
365 truncate_inode_page(mapping, page);
366 unlock_page(page);
367 }
368 pagevec_remove_exceptionals(&pvec);
369 pagevec_release(&pvec);
370 index++;
371 }
372 cleancache_invalidate_inode(mapping);
373 }
374 EXPORT_SYMBOL(truncate_inode_pages_range);
375
376 /**
377 * truncate_inode_pages - truncate *all* the pages from an offset
378 * @mapping: mapping to truncate
379 * @lstart: offset from which to truncate
380 *
381 * Called under (and serialised by) inode->i_mutex.
382 *
383 * Note: When this function returns, there can be a page in the process of
384 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
385 * mapping->nrpages can be non-zero when this function returns even after
386 * truncation of the whole mapping.
387 */
388 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
389 {
390 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
391 }
392 EXPORT_SYMBOL(truncate_inode_pages);
393
394 /**
395 * truncate_inode_pages_final - truncate *all* pages before inode dies
396 * @mapping: mapping to truncate
397 *
398 * Called under (and serialized by) inode->i_mutex.
399 *
400 * Filesystems have to use this in the .evict_inode path to inform the
401 * VM that this is the final truncate and the inode is going away.
402 */
403 void truncate_inode_pages_final(struct address_space *mapping)
404 {
405 unsigned long nrshadows;
406 unsigned long nrpages;
407
408 /*
409 * Page reclaim can not participate in regular inode lifetime
410 * management (can't call iput()) and thus can race with the
411 * inode teardown. Tell it when the address space is exiting,
412 * so that it does not install eviction information after the
413 * final truncate has begun.
414 */
415 mapping_set_exiting(mapping);
416
417 /*
418 * When reclaim installs eviction entries, it increases
419 * nrshadows first, then decreases nrpages. Make sure we see
420 * this in the right order or we might miss an entry.
421 */
422 nrpages = mapping->nrpages;
423 smp_rmb();
424 nrshadows = mapping->nrshadows;
425
426 if (nrpages || nrshadows) {
427 /*
428 * As truncation uses a lockless tree lookup, cycle
429 * the tree lock to make sure any ongoing tree
430 * modification that does not see AS_EXITING is
431 * completed before starting the final truncate.
432 */
433 spin_lock_irq(&mapping->tree_lock);
434 spin_unlock_irq(&mapping->tree_lock);
435
436 truncate_inode_pages(mapping, 0);
437 }
438 }
439 EXPORT_SYMBOL(truncate_inode_pages_final);
440
441 /**
442 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
443 * @mapping: the address_space which holds the pages to invalidate
444 * @start: the offset 'from' which to invalidate
445 * @end: the offset 'to' which to invalidate (inclusive)
446 *
447 * This function only removes the unlocked pages, if you want to
448 * remove all the pages of one inode, you must call truncate_inode_pages.
449 *
450 * invalidate_mapping_pages() will not block on IO activity. It will not
451 * invalidate pages which are dirty, locked, under writeback or mapped into
452 * pagetables.
453 */
454 unsigned long invalidate_mapping_pages(struct address_space *mapping,
455 pgoff_t start, pgoff_t end)
456 {
457 pgoff_t indices[PAGEVEC_SIZE];
458 struct pagevec pvec;
459 pgoff_t index = start;
460 unsigned long ret;
461 unsigned long count = 0;
462 int i;
463
464 pagevec_init(&pvec, 0);
465 while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
466 min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
467 indices)) {
468 for (i = 0; i < pagevec_count(&pvec); i++) {
469 struct page *page = pvec.pages[i];
470
471 /* We rely upon deletion not changing page->index */
472 index = indices[i];
473 if (index > end)
474 break;
475
476 if (radix_tree_exceptional_entry(page)) {
477 clear_exceptional_entry(mapping, index, page);
478 continue;
479 }
480
481 if (!trylock_page(page))
482 continue;
483 WARN_ON(page->index != index);
484 ret = invalidate_inode_page(page);
485 unlock_page(page);
486 /*
487 * Invalidation is a hint that the page is no longer
488 * of interest and try to speed up its reclaim.
489 */
490 if (!ret)
491 deactivate_file_page(page);
492 count += ret;
493 }
494 pagevec_remove_exceptionals(&pvec);
495 pagevec_release(&pvec);
496 cond_resched();
497 index++;
498 }
499 return count;
500 }
501 EXPORT_SYMBOL(invalidate_mapping_pages);
502
503 /*
504 * This is like invalidate_complete_page(), except it ignores the page's
505 * refcount. We do this because invalidate_inode_pages2() needs stronger
506 * invalidation guarantees, and cannot afford to leave pages behind because
507 * shrink_page_list() has a temp ref on them, or because they're transiently
508 * sitting in the lru_cache_add() pagevecs.
509 */
510 static int
511 invalidate_complete_page2(struct address_space *mapping, struct page *page)
512 {
513 struct mem_cgroup *memcg;
514 unsigned long flags;
515
516 if (page->mapping != mapping)
517 return 0;
518
519 if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
520 return 0;
521
522 memcg = mem_cgroup_begin_page_stat(page);
523 spin_lock_irqsave(&mapping->tree_lock, flags);
524 if (PageDirty(page))
525 goto failed;
526
527 BUG_ON(page_has_private(page));
528 __delete_from_page_cache(page, NULL, memcg);
529 spin_unlock_irqrestore(&mapping->tree_lock, flags);
530 mem_cgroup_end_page_stat(memcg);
531
532 if (mapping->a_ops->freepage)
533 mapping->a_ops->freepage(page);
534
535 page_cache_release(page); /* pagecache ref */
536 return 1;
537 failed:
538 spin_unlock_irqrestore(&mapping->tree_lock, flags);
539 mem_cgroup_end_page_stat(memcg);
540 return 0;
541 }
542
543 static int do_launder_page(struct address_space *mapping, struct page *page)
544 {
545 if (!PageDirty(page))
546 return 0;
547 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
548 return 0;
549 return mapping->a_ops->launder_page(page);
550 }
551
552 /**
553 * invalidate_inode_pages2_range - remove range of pages from an address_space
554 * @mapping: the address_space
555 * @start: the page offset 'from' which to invalidate
556 * @end: the page offset 'to' which to invalidate (inclusive)
557 *
558 * Any pages which are found to be mapped into pagetables are unmapped prior to
559 * invalidation.
560 *
561 * Returns -EBUSY if any pages could not be invalidated.
562 */
563 int invalidate_inode_pages2_range(struct address_space *mapping,
564 pgoff_t start, pgoff_t end)
565 {
566 pgoff_t indices[PAGEVEC_SIZE];
567 struct pagevec pvec;
568 pgoff_t index;
569 int i;
570 int ret = 0;
571 int ret2 = 0;
572 int did_range_unmap = 0;
573
574 cleancache_invalidate_inode(mapping);
575 pagevec_init(&pvec, 0);
576 index = start;
577 while (index <= end && pagevec_lookup_entries(&pvec, mapping, index,
578 min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
579 indices)) {
580 for (i = 0; i < pagevec_count(&pvec); i++) {
581 struct page *page = pvec.pages[i];
582
583 /* We rely upon deletion not changing page->index */
584 index = indices[i];
585 if (index > end)
586 break;
587
588 if (radix_tree_exceptional_entry(page)) {
589 clear_exceptional_entry(mapping, index, page);
590 continue;
591 }
592
593 lock_page(page);
594 WARN_ON(page->index != index);
595 if (page->mapping != mapping) {
596 unlock_page(page);
597 continue;
598 }
599 wait_on_page_writeback(page);
600 if (page_mapped(page)) {
601 if (!did_range_unmap) {
602 /*
603 * Zap the rest of the file in one hit.
604 */
605 unmap_mapping_range(mapping,
606 (loff_t)index << PAGE_CACHE_SHIFT,
607 (loff_t)(1 + end - index)
608 << PAGE_CACHE_SHIFT,
609 0);
610 did_range_unmap = 1;
611 } else {
612 /*
613 * Just zap this page
614 */
615 unmap_mapping_range(mapping,
616 (loff_t)index << PAGE_CACHE_SHIFT,
617 PAGE_CACHE_SIZE, 0);
618 }
619 }
620 BUG_ON(page_mapped(page));
621 ret2 = do_launder_page(mapping, page);
622 if (ret2 == 0) {
623 if (!invalidate_complete_page2(mapping, page))
624 ret2 = -EBUSY;
625 }
626 if (ret2 < 0)
627 ret = ret2;
628 unlock_page(page);
629 }
630 pagevec_remove_exceptionals(&pvec);
631 pagevec_release(&pvec);
632 cond_resched();
633 index++;
634 }
635 cleancache_invalidate_inode(mapping);
636 return ret;
637 }
638 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
639
640 /**
641 * invalidate_inode_pages2 - remove all pages from an address_space
642 * @mapping: the address_space
643 *
644 * Any pages which are found to be mapped into pagetables are unmapped prior to
645 * invalidation.
646 *
647 * Returns -EBUSY if any pages could not be invalidated.
648 */
649 int invalidate_inode_pages2(struct address_space *mapping)
650 {
651 return invalidate_inode_pages2_range(mapping, 0, -1);
652 }
653 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
654
655 /**
656 * truncate_pagecache - unmap and remove pagecache that has been truncated
657 * @inode: inode
658 * @newsize: new file size
659 *
660 * inode's new i_size must already be written before truncate_pagecache
661 * is called.
662 *
663 * This function should typically be called before the filesystem
664 * releases resources associated with the freed range (eg. deallocates
665 * blocks). This way, pagecache will always stay logically coherent
666 * with on-disk format, and the filesystem would not have to deal with
667 * situations such as writepage being called for a page that has already
668 * had its underlying blocks deallocated.
669 */
670 void truncate_pagecache(struct inode *inode, loff_t newsize)
671 {
672 struct address_space *mapping = inode->i_mapping;
673 loff_t holebegin = round_up(newsize, PAGE_SIZE);
674
675 /*
676 * unmap_mapping_range is called twice, first simply for
677 * efficiency so that truncate_inode_pages does fewer
678 * single-page unmaps. However after this first call, and
679 * before truncate_inode_pages finishes, it is possible for
680 * private pages to be COWed, which remain after
681 * truncate_inode_pages finishes, hence the second
682 * unmap_mapping_range call must be made for correctness.
683 */
684 unmap_mapping_range(mapping, holebegin, 0, 1);
685 truncate_inode_pages(mapping, newsize);
686 unmap_mapping_range(mapping, holebegin, 0, 1);
687 }
688 EXPORT_SYMBOL(truncate_pagecache);
689
690 /**
691 * truncate_setsize - update inode and pagecache for a new file size
692 * @inode: inode
693 * @newsize: new file size
694 *
695 * truncate_setsize updates i_size and performs pagecache truncation (if
696 * necessary) to @newsize. It will be typically be called from the filesystem's
697 * setattr function when ATTR_SIZE is passed in.
698 *
699 * Must be called with a lock serializing truncates and writes (generally
700 * i_mutex but e.g. xfs uses a different lock) and before all filesystem
701 * specific block truncation has been performed.
702 */
703 void truncate_setsize(struct inode *inode, loff_t newsize)
704 {
705 loff_t oldsize = inode->i_size;
706
707 i_size_write(inode, newsize);
708 if (newsize > oldsize)
709 pagecache_isize_extended(inode, oldsize, newsize);
710 truncate_pagecache(inode, newsize);
711 }
712 EXPORT_SYMBOL(truncate_setsize);
713
714 /**
715 * pagecache_isize_extended - update pagecache after extension of i_size
716 * @inode: inode for which i_size was extended
717 * @from: original inode size
718 * @to: new inode size
719 *
720 * Handle extension of inode size either caused by extending truncate or by
721 * write starting after current i_size. We mark the page straddling current
722 * i_size RO so that page_mkwrite() is called on the nearest write access to
723 * the page. This way filesystem can be sure that page_mkwrite() is called on
724 * the page before user writes to the page via mmap after the i_size has been
725 * changed.
726 *
727 * The function must be called after i_size is updated so that page fault
728 * coming after we unlock the page will already see the new i_size.
729 * The function must be called while we still hold i_mutex - this not only
730 * makes sure i_size is stable but also that userspace cannot observe new
731 * i_size value before we are prepared to store mmap writes at new inode size.
732 */
733 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
734 {
735 int bsize = i_blocksize(inode);
736 loff_t rounded_from;
737 struct page *page;
738 pgoff_t index;
739
740 WARN_ON(to > inode->i_size);
741
742 if (from >= to || bsize == PAGE_CACHE_SIZE)
743 return;
744 /* Page straddling @from will not have any hole block created? */
745 rounded_from = round_up(from, bsize);
746 if (to <= rounded_from || !(rounded_from & (PAGE_CACHE_SIZE - 1)))
747 return;
748
749 index = from >> PAGE_CACHE_SHIFT;
750 page = find_lock_page(inode->i_mapping, index);
751 /* Page not cached? Nothing to do */
752 if (!page)
753 return;
754 /*
755 * See clear_page_dirty_for_io() for details why set_page_dirty()
756 * is needed.
757 */
758 if (page_mkclean(page))
759 set_page_dirty(page);
760 unlock_page(page);
761 page_cache_release(page);
762 }
763 EXPORT_SYMBOL(pagecache_isize_extended);
764
765 /**
766 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
767 * @inode: inode
768 * @lstart: offset of beginning of hole
769 * @lend: offset of last byte of hole
770 *
771 * This function should typically be called before the filesystem
772 * releases resources associated with the freed range (eg. deallocates
773 * blocks). This way, pagecache will always stay logically coherent
774 * with on-disk format, and the filesystem would not have to deal with
775 * situations such as writepage being called for a page that has already
776 * had its underlying blocks deallocated.
777 */
778 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
779 {
780 struct address_space *mapping = inode->i_mapping;
781 loff_t unmap_start = round_up(lstart, PAGE_SIZE);
782 loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
783 /*
784 * This rounding is currently just for example: unmap_mapping_range
785 * expands its hole outwards, whereas we want it to contract the hole
786 * inwards. However, existing callers of truncate_pagecache_range are
787 * doing their own page rounding first. Note that unmap_mapping_range
788 * allows holelen 0 for all, and we allow lend -1 for end of file.
789 */
790
791 /*
792 * Unlike in truncate_pagecache, unmap_mapping_range is called only
793 * once (before truncating pagecache), and without "even_cows" flag:
794 * hole-punching should not remove private COWed pages from the hole.
795 */
796 if ((u64)unmap_end > (u64)unmap_start)
797 unmap_mapping_range(mapping, unmap_start,
798 1 + unmap_end - unmap_start, 0);
799 truncate_inode_pages_range(mapping, lstart, lend);
800 }
801 EXPORT_SYMBOL(truncate_pagecache_range);