2 * mm/truncate.c - code for taking down pages from address_spaces
4 * Copyright (C) 2002, Linus Torvalds
6 * 10Sep2002 Andrew Morton
10 #include <linux/kernel.h>
11 #include <linux/backing-dev.h>
12 #include <linux/gfp.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,
22 #include <linux/cleancache.h>
27 * do_invalidatepage - invalidate part or all of a page
28 * @page: the page which is affected
29 * @offset: start of the range to invalidate
30 * @length: length of the range to invalidate
32 * do_invalidatepage() is called when all or part of the page has become
33 * invalidated by a truncate operation.
35 * do_invalidatepage() does not have to release all buffers, but it must
36 * ensure that no dirty buffer is left outside @offset and that no I/O
37 * is underway against any of the blocks which are outside the truncation
38 * point. Because the caller is about to free (and possibly reuse) those
41 void do_invalidatepage(struct page *page, unsigned int offset,
44 void (*invalidatepage)(struct page *, unsigned int, unsigned int);
46 invalidatepage = page->mapping->a_ops->invalidatepage;
49 invalidatepage = block_invalidatepage;
52 (*invalidatepage)(page, offset, length);
56 * This cancels just the dirty bit on the kernel page itself, it
57 * does NOT actually remove dirty bits on any mmap's that may be
58 * around. It also leaves the page tagged dirty, so any sync
59 * activity will still find it on the dirty lists, and in particular,
60 * clear_page_dirty_for_io() will still look at the dirty bits in
63 * Doing this should *normally* only ever be done when a page
64 * is truncated, and is not actually mapped anywhere at all. However,
65 * fs/buffer.c does this when it notices that somebody has cleaned
66 * out all the buffers on a page without actually doing it through
67 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
69 void cancel_dirty_page(struct page *page, unsigned int account_size)
71 if (TestClearPageDirty(page)) {
72 struct address_space *mapping = page->mapping;
73 if (mapping && mapping_cap_account_dirty(mapping)) {
74 dec_zone_page_state(page, NR_FILE_DIRTY);
75 dec_bdi_stat(mapping->backing_dev_info,
78 task_io_account_cancelled_write(account_size);
82 EXPORT_SYMBOL(cancel_dirty_page);
85 * If truncate cannot remove the fs-private metadata from the page, the page
86 * becomes orphaned. It will be left on the LRU and may even be mapped into
87 * user pagetables if we're racing with filemap_fault().
89 * We need to bale out if page->mapping is no longer equal to the original
90 * mapping. This happens a) when the VM reclaimed the page while we waited on
91 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
92 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
95 truncate_complete_page(struct address_space *mapping, struct page *page)
97 if (page->mapping != mapping)
100 if (page_has_private(page))
101 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
103 cancel_dirty_page(page, PAGE_CACHE_SIZE);
105 ClearPageMappedToDisk(page);
106 delete_from_page_cache(page);
111 * This is for invalidate_mapping_pages(). That function can be called at
112 * any time, and is not supposed to throw away dirty pages. But pages can
113 * be marked dirty at any time too, so use remove_mapping which safely
114 * discards clean, unused pages.
116 * Returns non-zero if the page was successfully invalidated.
119 invalidate_complete_page(struct address_space *mapping, struct page *page)
123 if (page->mapping != mapping)
126 if (page_has_private(page) && !try_to_release_page(page, 0))
129 ret = remove_mapping(mapping, page);
134 int truncate_inode_page(struct address_space *mapping, struct page *page)
136 if (page_mapped(page)) {
137 unmap_mapping_range(mapping,
138 (loff_t)page->index << PAGE_CACHE_SHIFT,
141 return truncate_complete_page(mapping, page);
145 * Used to get rid of pages on hardware memory corruption.
147 int generic_error_remove_page(struct address_space *mapping, struct page *page)
152 * Only punch for normal data pages for now.
153 * Handling other types like directories would need more auditing.
155 if (!S_ISREG(mapping->host->i_mode))
157 return truncate_inode_page(mapping, page);
159 EXPORT_SYMBOL(generic_error_remove_page);
162 * Safely invalidate one page from its pagecache mapping.
163 * It only drops clean, unused pages. The page must be locked.
165 * Returns 1 if the page is successfully invalidated, otherwise 0.
167 int invalidate_inode_page(struct page *page)
169 struct address_space *mapping = page_mapping(page);
172 if (PageDirty(page) || PageWriteback(page))
174 if (page_mapped(page))
176 return invalidate_complete_page(mapping, page);
180 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
181 * @mapping: mapping to truncate
182 * @lstart: offset from which to truncate
183 * @lend: offset to which to truncate (inclusive)
185 * Truncate the page cache, removing the pages that are between
186 * specified offsets (and zeroing out partial pages
187 * if lstart or lend + 1 is not page aligned).
189 * Truncate takes two passes - the first pass is nonblocking. It will not
190 * block on page locks and it will not block on writeback. The second pass
191 * will wait. This is to prevent as much IO as possible in the affected region.
192 * The first pass will remove most pages, so the search cost of the second pass
195 * We pass down the cache-hot hint to the page freeing code. Even if the
196 * mapping is large, it is probably the case that the final pages are the most
197 * recently touched, and freeing happens in ascending file offset order.
199 * Note that since ->invalidatepage() accepts range to invalidate
200 * truncate_inode_pages_range is able to handle cases where lend + 1 is not
201 * page aligned properly.
203 void truncate_inode_pages_range(struct address_space *mapping,
204 loff_t lstart, loff_t lend)
206 pgoff_t start; /* inclusive */
207 pgoff_t end; /* exclusive */
208 unsigned int partial_start; /* inclusive */
209 unsigned int partial_end; /* exclusive */
214 cleancache_invalidate_inode(mapping);
215 if (mapping->nrpages == 0)
218 /* Offsets within partial pages */
219 partial_start = lstart & (PAGE_CACHE_SIZE - 1);
220 partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1);
223 * 'start' and 'end' always covers the range of pages to be fully
224 * truncated. Partial pages are covered with 'partial_start' at the
225 * start of the range and 'partial_end' at the end of the range.
226 * Note that 'end' is exclusive while 'lend' is inclusive.
228 start = (lstart + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
231 * lend == -1 indicates end-of-file so we have to set 'end'
232 * to the highest possible pgoff_t and since the type is
233 * unsigned we're using -1.
237 end = (lend + 1) >> PAGE_CACHE_SHIFT;
239 pagevec_init(&pvec, 0);
241 while (index < end && pagevec_lookup(&pvec, mapping, index,
242 min(end - index, (pgoff_t)PAGEVEC_SIZE))) {
243 mem_cgroup_uncharge_start();
244 for (i = 0; i < pagevec_count(&pvec); i++) {
245 struct page *page = pvec.pages[i];
247 /* We rely upon deletion not changing page->index */
252 if (!trylock_page(page))
254 WARN_ON(page->index != index);
255 if (PageWriteback(page)) {
259 truncate_inode_page(mapping, page);
262 pagevec_release(&pvec);
263 mem_cgroup_uncharge_end();
269 struct page *page = find_lock_page(mapping, start - 1);
271 unsigned int top = PAGE_CACHE_SIZE;
273 /* Truncation within a single page */
277 wait_on_page_writeback(page);
278 zero_user_segment(page, partial_start, top);
279 cleancache_invalidate_page(mapping, page);
280 if (page_has_private(page))
281 do_invalidatepage(page, partial_start,
282 top - partial_start);
284 page_cache_release(page);
288 struct page *page = find_lock_page(mapping, end);
290 wait_on_page_writeback(page);
291 zero_user_segment(page, 0, partial_end);
292 cleancache_invalidate_page(mapping, page);
293 if (page_has_private(page))
294 do_invalidatepage(page, 0,
297 page_cache_release(page);
301 * If the truncation happened within a single page no pages
302 * will be released, just zeroed, so we can bail out now.
310 if (!pagevec_lookup(&pvec, mapping, index,
311 min(end - index, (pgoff_t)PAGEVEC_SIZE))) {
317 if (index == start && pvec.pages[0]->index >= end) {
318 pagevec_release(&pvec);
321 mem_cgroup_uncharge_start();
322 for (i = 0; i < pagevec_count(&pvec); i++) {
323 struct page *page = pvec.pages[i];
325 /* We rely upon deletion not changing page->index */
331 WARN_ON(page->index != index);
332 wait_on_page_writeback(page);
333 truncate_inode_page(mapping, page);
336 pagevec_release(&pvec);
337 mem_cgroup_uncharge_end();
340 cleancache_invalidate_inode(mapping);
342 EXPORT_SYMBOL(truncate_inode_pages_range);
345 * truncate_inode_pages - truncate *all* the pages from an offset
346 * @mapping: mapping to truncate
347 * @lstart: offset from which to truncate
349 * Called under (and serialised by) inode->i_mutex.
351 * Note: When this function returns, there can be a page in the process of
352 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
353 * mapping->nrpages can be non-zero when this function returns even after
354 * truncation of the whole mapping.
356 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
358 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
360 EXPORT_SYMBOL(truncate_inode_pages);
363 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
364 * @mapping: the address_space which holds the pages to invalidate
365 * @start: the offset 'from' which to invalidate
366 * @end: the offset 'to' which to invalidate (inclusive)
368 * This function only removes the unlocked pages, if you want to
369 * remove all the pages of one inode, you must call truncate_inode_pages.
371 * invalidate_mapping_pages() will not block on IO activity. It will not
372 * invalidate pages which are dirty, locked, under writeback or mapped into
375 unsigned long invalidate_mapping_pages(struct address_space *mapping,
376 pgoff_t start, pgoff_t end)
379 pgoff_t index = start;
381 unsigned long count = 0;
385 * Note: this function may get called on a shmem/tmpfs mapping:
386 * pagevec_lookup() might then return 0 prematurely (because it
387 * got a gangful of swap entries); but it's hardly worth worrying
388 * about - it can rarely have anything to free from such a mapping
389 * (most pages are dirty), and already skips over any difficulties.
392 pagevec_init(&pvec, 0);
393 while (index <= end && pagevec_lookup(&pvec, mapping, index,
394 min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
395 mem_cgroup_uncharge_start();
396 for (i = 0; i < pagevec_count(&pvec); i++) {
397 struct page *page = pvec.pages[i];
399 /* We rely upon deletion not changing page->index */
404 if (!trylock_page(page))
406 WARN_ON(page->index != index);
407 ret = invalidate_inode_page(page);
410 * Invalidation is a hint that the page is no longer
411 * of interest and try to speed up its reclaim.
414 deactivate_page(page);
417 pagevec_release(&pvec);
418 mem_cgroup_uncharge_end();
424 EXPORT_SYMBOL(invalidate_mapping_pages);
427 * This is like invalidate_complete_page(), except it ignores the page's
428 * refcount. We do this because invalidate_inode_pages2() needs stronger
429 * invalidation guarantees, and cannot afford to leave pages behind because
430 * shrink_page_list() has a temp ref on them, or because they're transiently
431 * sitting in the lru_cache_add() pagevecs.
434 invalidate_complete_page2(struct address_space *mapping, struct page *page)
436 if (page->mapping != mapping)
439 if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
442 spin_lock_irq(&mapping->tree_lock);
446 BUG_ON(page_has_private(page));
447 __delete_from_page_cache(page);
448 spin_unlock_irq(&mapping->tree_lock);
449 mem_cgroup_uncharge_cache_page(page);
451 if (mapping->a_ops->freepage)
452 mapping->a_ops->freepage(page);
454 page_cache_release(page); /* pagecache ref */
457 spin_unlock_irq(&mapping->tree_lock);
461 static int do_launder_page(struct address_space *mapping, struct page *page)
463 if (!PageDirty(page))
465 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
467 return mapping->a_ops->launder_page(page);
471 * invalidate_inode_pages2_range - remove range of pages from an address_space
472 * @mapping: the address_space
473 * @start: the page offset 'from' which to invalidate
474 * @end: the page offset 'to' which to invalidate (inclusive)
476 * Any pages which are found to be mapped into pagetables are unmapped prior to
479 * Returns -EBUSY if any pages could not be invalidated.
481 int invalidate_inode_pages2_range(struct address_space *mapping,
482 pgoff_t start, pgoff_t end)
489 int did_range_unmap = 0;
491 cleancache_invalidate_inode(mapping);
492 pagevec_init(&pvec, 0);
494 while (index <= end && pagevec_lookup(&pvec, mapping, index,
495 min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
496 mem_cgroup_uncharge_start();
497 for (i = 0; i < pagevec_count(&pvec); i++) {
498 struct page *page = pvec.pages[i];
500 /* We rely upon deletion not changing page->index */
506 WARN_ON(page->index != index);
507 if (page->mapping != mapping) {
511 wait_on_page_writeback(page);
512 if (page_mapped(page)) {
513 if (!did_range_unmap) {
515 * Zap the rest of the file in one hit.
517 unmap_mapping_range(mapping,
518 (loff_t)index << PAGE_CACHE_SHIFT,
519 (loff_t)(1 + end - index)
527 unmap_mapping_range(mapping,
528 (loff_t)index << PAGE_CACHE_SHIFT,
532 BUG_ON(page_mapped(page));
533 ret2 = do_launder_page(mapping, page);
535 if (!invalidate_complete_page2(mapping, page))
542 pagevec_release(&pvec);
543 mem_cgroup_uncharge_end();
547 cleancache_invalidate_inode(mapping);
550 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
553 * invalidate_inode_pages2 - remove all pages from an address_space
554 * @mapping: the address_space
556 * Any pages which are found to be mapped into pagetables are unmapped prior to
559 * Returns -EBUSY if any pages could not be invalidated.
561 int invalidate_inode_pages2(struct address_space *mapping)
563 return invalidate_inode_pages2_range(mapping, 0, -1);
565 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
568 * truncate_pagecache - unmap and remove pagecache that has been truncated
570 * @newsize: new file size
572 * inode's new i_size must already be written before truncate_pagecache
575 * This function should typically be called before the filesystem
576 * releases resources associated with the freed range (eg. deallocates
577 * blocks). This way, pagecache will always stay logically coherent
578 * with on-disk format, and the filesystem would not have to deal with
579 * situations such as writepage being called for a page that has already
580 * had its underlying blocks deallocated.
582 void truncate_pagecache(struct inode *inode, loff_t newsize)
584 struct address_space *mapping = inode->i_mapping;
585 loff_t holebegin = round_up(newsize, PAGE_SIZE);
588 * unmap_mapping_range is called twice, first simply for
589 * efficiency so that truncate_inode_pages does fewer
590 * single-page unmaps. However after this first call, and
591 * before truncate_inode_pages finishes, it is possible for
592 * private pages to be COWed, which remain after
593 * truncate_inode_pages finishes, hence the second
594 * unmap_mapping_range call must be made for correctness.
596 unmap_mapping_range(mapping, holebegin, 0, 1);
597 truncate_inode_pages(mapping, newsize);
598 unmap_mapping_range(mapping, holebegin, 0, 1);
600 EXPORT_SYMBOL(truncate_pagecache);
603 * truncate_setsize - update inode and pagecache for a new file size
605 * @newsize: new file size
607 * truncate_setsize updates i_size and performs pagecache truncation (if
608 * necessary) to @newsize. It will be typically be called from the filesystem's
609 * setattr function when ATTR_SIZE is passed in.
611 * Must be called with inode_mutex held and before all filesystem specific
612 * block truncation has been performed.
614 void truncate_setsize(struct inode *inode, loff_t newsize)
616 i_size_write(inode, newsize);
617 truncate_pagecache(inode, newsize);
619 EXPORT_SYMBOL(truncate_setsize);
622 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
624 * @lstart: offset of beginning of hole
625 * @lend: offset of last byte of hole
627 * This function should typically be called before the filesystem
628 * releases resources associated with the freed range (eg. deallocates
629 * blocks). This way, pagecache will always stay logically coherent
630 * with on-disk format, and the filesystem would not have to deal with
631 * situations such as writepage being called for a page that has already
632 * had its underlying blocks deallocated.
634 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
636 struct address_space *mapping = inode->i_mapping;
637 loff_t unmap_start = round_up(lstart, PAGE_SIZE);
638 loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
640 * This rounding is currently just for example: unmap_mapping_range
641 * expands its hole outwards, whereas we want it to contract the hole
642 * inwards. However, existing callers of truncate_pagecache_range are
643 * doing their own page rounding first. Note that unmap_mapping_range
644 * allows holelen 0 for all, and we allow lend -1 for end of file.
648 * Unlike in truncate_pagecache, unmap_mapping_range is called only
649 * once (before truncating pagecache), and without "even_cows" flag:
650 * hole-punching should not remove private COWed pages from the hole.
652 if ((u64)unmap_end > (u64)unmap_start)
653 unmap_mapping_range(mapping, unmap_start,
654 1 + unmap_end - unmap_start, 0);
655 truncate_inode_pages_range(mapping, lstart, lend);
657 EXPORT_SYMBOL(truncate_pagecache_range);