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>
13 #include <linux/swap.h>
14 #include <linux/module.h>
15 #include <linux/pagemap.h>
16 #include <linux/highmem.h>
17 #include <linux/pagevec.h>
18 #include <linux/task_io_accounting_ops.h>
19 #include <linux/buffer_head.h> /* grr. try_to_release_page,
25 * do_invalidatepage - invalidate part or all of a page
26 * @page: the page which is affected
27 * @offset: the index of the truncation point
29 * do_invalidatepage() is called when all or part of the page has become
30 * invalidated by a truncate operation.
32 * do_invalidatepage() does not have to release all buffers, but it must
33 * ensure that no dirty buffer is left outside @offset and that no I/O
34 * is underway against any of the blocks which are outside the truncation
35 * point. Because the caller is about to free (and possibly reuse) those
38 void do_invalidatepage(struct page *page, unsigned long offset)
40 void (*invalidatepage)(struct page *, unsigned long);
41 invalidatepage = page->mapping->a_ops->invalidatepage;
44 invalidatepage = block_invalidatepage;
47 (*invalidatepage)(page, offset);
50 static inline void truncate_partial_page(struct page *page, unsigned partial)
52 zero_user_segment(page, partial, PAGE_CACHE_SIZE);
53 if (page_has_private(page))
54 do_invalidatepage(page, partial);
58 * This cancels just the dirty bit on the kernel page itself, it
59 * does NOT actually remove dirty bits on any mmap's that may be
60 * around. It also leaves the page tagged dirty, so any sync
61 * activity will still find it on the dirty lists, and in particular,
62 * clear_page_dirty_for_io() will still look at the dirty bits in
65 * Doing this should *normally* only ever be done when a page
66 * is truncated, and is not actually mapped anywhere at all. However,
67 * fs/buffer.c does this when it notices that somebody has cleaned
68 * out all the buffers on a page without actually doing it through
69 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
71 void cancel_dirty_page(struct page *page, unsigned int account_size)
73 if (TestClearPageDirty(page)) {
74 struct address_space *mapping = page->mapping;
75 if (mapping && mapping_cap_account_dirty(mapping)) {
76 dec_zone_page_state(page, NR_FILE_DIRTY);
77 dec_bdi_stat(mapping->backing_dev_info,
80 task_io_account_cancelled_write(account_size);
84 EXPORT_SYMBOL(cancel_dirty_page);
87 * If truncate cannot remove the fs-private metadata from the page, the page
88 * becomes orphaned. It will be left on the LRU and may even be mapped into
89 * user pagetables if we're racing with filemap_fault().
91 * We need to bale out if page->mapping is no longer equal to the original
92 * mapping. This happens a) when the VM reclaimed the page while we waited on
93 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
94 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
97 truncate_complete_page(struct address_space *mapping, struct page *page)
99 if (page->mapping != mapping)
102 if (page_has_private(page))
103 do_invalidatepage(page, 0);
105 cancel_dirty_page(page, PAGE_CACHE_SIZE);
107 clear_page_mlock(page);
108 remove_from_page_cache(page);
109 ClearPageMappedToDisk(page);
110 page_cache_release(page); /* pagecache ref */
115 * This is for invalidate_mapping_pages(). That function can be called at
116 * any time, and is not supposed to throw away dirty pages. But pages can
117 * be marked dirty at any time too, so use remove_mapping which safely
118 * discards clean, unused pages.
120 * Returns non-zero if the page was successfully invalidated.
123 invalidate_complete_page(struct address_space *mapping, struct page *page)
127 if (page->mapping != mapping)
130 if (page_has_private(page) && !try_to_release_page(page, 0))
133 clear_page_mlock(page);
134 ret = remove_mapping(mapping, page);
139 int truncate_inode_page(struct address_space *mapping, struct page *page)
141 if (page_mapped(page)) {
142 unmap_mapping_range(mapping,
143 (loff_t)page->index << PAGE_CACHE_SHIFT,
146 return truncate_complete_page(mapping, page);
150 * Safely invalidate one page from its pagecache mapping.
151 * It only drops clean, unused pages. The page must be locked.
153 * Returns 1 if the page is successfully invalidated, otherwise 0.
155 int invalidate_inode_page(struct page *page)
157 struct address_space *mapping = page_mapping(page);
160 if (PageDirty(page) || PageWriteback(page))
162 if (page_mapped(page))
164 return invalidate_complete_page(mapping, page);
168 * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
169 * @mapping: mapping to truncate
170 * @lstart: offset from which to truncate
171 * @lend: offset to which to truncate
173 * Truncate the page cache, removing the pages that are between
174 * specified offsets (and zeroing out partial page
175 * (if lstart is not page aligned)).
177 * Truncate takes two passes - the first pass is nonblocking. It will not
178 * block on page locks and it will not block on writeback. The second pass
179 * will wait. This is to prevent as much IO as possible in the affected region.
180 * The first pass will remove most pages, so the search cost of the second pass
183 * When looking at page->index outside the page lock we need to be careful to
184 * copy it into a local to avoid races (it could change at any time).
186 * We pass down the cache-hot hint to the page freeing code. Even if the
187 * mapping is large, it is probably the case that the final pages are the most
188 * recently touched, and freeing happens in ascending file offset order.
190 void truncate_inode_pages_range(struct address_space *mapping,
191 loff_t lstart, loff_t lend)
193 const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
195 const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
200 if (mapping->nrpages == 0)
203 BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
204 end = (lend >> PAGE_CACHE_SHIFT);
206 pagevec_init(&pvec, 0);
208 while (next <= end &&
209 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
210 for (i = 0; i < pagevec_count(&pvec); i++) {
211 struct page *page = pvec.pages[i];
212 pgoff_t page_index = page->index;
214 if (page_index > end) {
219 if (page_index > next)
222 if (!trylock_page(page))
224 if (PageWriteback(page)) {
228 truncate_inode_page(mapping, page);
231 pagevec_release(&pvec);
236 struct page *page = find_lock_page(mapping, start - 1);
238 wait_on_page_writeback(page);
239 truncate_partial_page(page, partial);
241 page_cache_release(page);
248 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
254 if (pvec.pages[0]->index > end) {
255 pagevec_release(&pvec);
258 for (i = 0; i < pagevec_count(&pvec); i++) {
259 struct page *page = pvec.pages[i];
261 if (page->index > end)
264 wait_on_page_writeback(page);
265 truncate_inode_page(mapping, page);
266 if (page->index > next)
271 pagevec_release(&pvec);
274 EXPORT_SYMBOL(truncate_inode_pages_range);
277 * truncate_inode_pages - truncate *all* the pages from an offset
278 * @mapping: mapping to truncate
279 * @lstart: offset from which to truncate
281 * Called under (and serialised by) inode->i_mutex.
283 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
285 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
287 EXPORT_SYMBOL(truncate_inode_pages);
290 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
291 * @mapping: the address_space which holds the pages to invalidate
292 * @start: the offset 'from' which to invalidate
293 * @end: the offset 'to' which to invalidate (inclusive)
295 * This function only removes the unlocked pages, if you want to
296 * remove all the pages of one inode, you must call truncate_inode_pages.
298 * invalidate_mapping_pages() will not block on IO activity. It will not
299 * invalidate pages which are dirty, locked, under writeback or mapped into
302 unsigned long invalidate_mapping_pages(struct address_space *mapping,
303 pgoff_t start, pgoff_t end)
306 pgoff_t next = start;
307 unsigned long ret = 0;
310 pagevec_init(&pvec, 0);
311 while (next <= end &&
312 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
313 for (i = 0; i < pagevec_count(&pvec); i++) {
314 struct page *page = pvec.pages[i];
318 lock_failed = !trylock_page(page);
321 * We really shouldn't be looking at the ->index of an
322 * unlocked page. But we're not allowed to lock these
323 * pages. So we rely upon nobody altering the ->index
324 * of this (pinned-by-us) page.
333 ret += invalidate_inode_page(page);
339 pagevec_release(&pvec);
344 EXPORT_SYMBOL(invalidate_mapping_pages);
347 * This is like invalidate_complete_page(), except it ignores the page's
348 * refcount. We do this because invalidate_inode_pages2() needs stronger
349 * invalidation guarantees, and cannot afford to leave pages behind because
350 * shrink_page_list() has a temp ref on them, or because they're transiently
351 * sitting in the lru_cache_add() pagevecs.
354 invalidate_complete_page2(struct address_space *mapping, struct page *page)
356 if (page->mapping != mapping)
359 if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
362 spin_lock_irq(&mapping->tree_lock);
366 clear_page_mlock(page);
367 BUG_ON(page_has_private(page));
368 __remove_from_page_cache(page);
369 spin_unlock_irq(&mapping->tree_lock);
370 mem_cgroup_uncharge_cache_page(page);
371 page_cache_release(page); /* pagecache ref */
374 spin_unlock_irq(&mapping->tree_lock);
378 static int do_launder_page(struct address_space *mapping, struct page *page)
380 if (!PageDirty(page))
382 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
384 return mapping->a_ops->launder_page(page);
388 * invalidate_inode_pages2_range - remove range of pages from an address_space
389 * @mapping: the address_space
390 * @start: the page offset 'from' which to invalidate
391 * @end: the page offset 'to' which to invalidate (inclusive)
393 * Any pages which are found to be mapped into pagetables are unmapped prior to
396 * Returns -EBUSY if any pages could not be invalidated.
398 int invalidate_inode_pages2_range(struct address_space *mapping,
399 pgoff_t start, pgoff_t end)
406 int did_range_unmap = 0;
409 pagevec_init(&pvec, 0);
411 while (next <= end && !wrapped &&
412 pagevec_lookup(&pvec, mapping, next,
413 min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
414 for (i = 0; i < pagevec_count(&pvec); i++) {
415 struct page *page = pvec.pages[i];
419 if (page->mapping != mapping) {
423 page_index = page->index;
424 next = page_index + 1;
427 if (page_index > end) {
431 wait_on_page_writeback(page);
432 if (page_mapped(page)) {
433 if (!did_range_unmap) {
435 * Zap the rest of the file in one hit.
437 unmap_mapping_range(mapping,
438 (loff_t)page_index<<PAGE_CACHE_SHIFT,
439 (loff_t)(end - page_index + 1)
447 unmap_mapping_range(mapping,
448 (loff_t)page_index<<PAGE_CACHE_SHIFT,
452 BUG_ON(page_mapped(page));
453 ret2 = do_launder_page(mapping, page);
455 if (!invalidate_complete_page2(mapping, page))
462 pagevec_release(&pvec);
467 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
470 * invalidate_inode_pages2 - remove all pages from an address_space
471 * @mapping: the address_space
473 * Any pages which are found to be mapped into pagetables are unmapped prior to
476 * Returns -EIO if any pages could not be invalidated.
478 int invalidate_inode_pages2(struct address_space *mapping)
480 return invalidate_inode_pages2_range(mapping, 0, -1);
482 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);