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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/mm.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,
20 do_invalidatepage */
21 #include "internal.h"
22
23
24 /**
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
28 *
29 * do_invalidatepage() is called when all or part of the page has become
30 * invalidated by a truncate operation.
31 *
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
36 * blocks on-disk.
37 */
38 void do_invalidatepage(struct page *page, unsigned long offset)
39 {
40 void (*invalidatepage)(struct page *, unsigned long);
41 invalidatepage = page->mapping->a_ops->invalidatepage;
42 #ifdef CONFIG_BLOCK
43 if (!invalidatepage)
44 invalidatepage = block_invalidatepage;
45 #endif
46 if (invalidatepage)
47 (*invalidatepage)(page, offset);
48 }
49
50 static inline void truncate_partial_page(struct page *page, unsigned partial)
51 {
52 zero_user_segment(page, partial, PAGE_CACHE_SIZE);
53 if (page_has_private(page))
54 do_invalidatepage(page, partial);
55 }
56
57 /*
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
63 * the VM.
64 *
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.
70 */
71 void cancel_dirty_page(struct page *page, unsigned int account_size)
72 {
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,
78 BDI_RECLAIMABLE);
79 if (account_size)
80 task_io_account_cancelled_write(account_size);
81 }
82 }
83 }
84 EXPORT_SYMBOL(cancel_dirty_page);
85
86 /*
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().
90 *
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.
95 */
96 static void
97 truncate_complete_page(struct address_space *mapping, struct page *page)
98 {
99 if (page->mapping != mapping)
100 return;
101
102 if (page_has_private(page))
103 do_invalidatepage(page, 0);
104
105 cancel_dirty_page(page, PAGE_CACHE_SIZE);
106
107 clear_page_mlock(page);
108 remove_from_page_cache(page);
109 ClearPageMappedToDisk(page);
110 page_cache_release(page); /* pagecache ref */
111 }
112
113 /*
114 * This is for invalidate_mapping_pages(). That function can be called at
115 * any time, and is not supposed to throw away dirty pages. But pages can
116 * be marked dirty at any time too, so use remove_mapping which safely
117 * discards clean, unused pages.
118 *
119 * Returns non-zero if the page was successfully invalidated.
120 */
121 static int
122 invalidate_complete_page(struct address_space *mapping, struct page *page)
123 {
124 int ret;
125
126 if (page->mapping != mapping)
127 return 0;
128
129 if (page_has_private(page) && !try_to_release_page(page, 0))
130 return 0;
131
132 clear_page_mlock(page);
133 ret = remove_mapping(mapping, page);
134
135 return ret;
136 }
137
138 /**
139 * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
140 * @mapping: mapping to truncate
141 * @lstart: offset from which to truncate
142 * @lend: offset to which to truncate
143 *
144 * Truncate the page cache, removing the pages that are between
145 * specified offsets (and zeroing out partial page
146 * (if lstart is not page aligned)).
147 *
148 * Truncate takes two passes - the first pass is nonblocking. It will not
149 * block on page locks and it will not block on writeback. The second pass
150 * will wait. This is to prevent as much IO as possible in the affected region.
151 * The first pass will remove most pages, so the search cost of the second pass
152 * is low.
153 *
154 * When looking at page->index outside the page lock we need to be careful to
155 * copy it into a local to avoid races (it could change at any time).
156 *
157 * We pass down the cache-hot hint to the page freeing code. Even if the
158 * mapping is large, it is probably the case that the final pages are the most
159 * recently touched, and freeing happens in ascending file offset order.
160 */
161 void truncate_inode_pages_range(struct address_space *mapping,
162 loff_t lstart, loff_t lend)
163 {
164 const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
165 pgoff_t end;
166 const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
167 struct pagevec pvec;
168 pgoff_t next;
169 int i;
170
171 if (mapping->nrpages == 0)
172 return;
173
174 BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
175 end = (lend >> PAGE_CACHE_SHIFT);
176
177 pagevec_init(&pvec, 0);
178 next = start;
179 while (next <= end &&
180 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
181 for (i = 0; i < pagevec_count(&pvec); i++) {
182 struct page *page = pvec.pages[i];
183 pgoff_t page_index = page->index;
184
185 if (page_index > end) {
186 next = page_index;
187 break;
188 }
189
190 if (page_index > next)
191 next = page_index;
192 next++;
193 if (!trylock_page(page))
194 continue;
195 if (PageWriteback(page)) {
196 unlock_page(page);
197 continue;
198 }
199 if (page_mapped(page)) {
200 unmap_mapping_range(mapping,
201 (loff_t)page_index<<PAGE_CACHE_SHIFT,
202 PAGE_CACHE_SIZE, 0);
203 }
204 truncate_complete_page(mapping, page);
205 unlock_page(page);
206 }
207 pagevec_release(&pvec);
208 cond_resched();
209 }
210
211 if (partial) {
212 struct page *page = find_lock_page(mapping, start - 1);
213 if (page) {
214 wait_on_page_writeback(page);
215 truncate_partial_page(page, partial);
216 unlock_page(page);
217 page_cache_release(page);
218 }
219 }
220
221 next = start;
222 for ( ; ; ) {
223 cond_resched();
224 if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
225 if (next == start)
226 break;
227 next = start;
228 continue;
229 }
230 if (pvec.pages[0]->index > end) {
231 pagevec_release(&pvec);
232 break;
233 }
234 for (i = 0; i < pagevec_count(&pvec); i++) {
235 struct page *page = pvec.pages[i];
236
237 if (page->index > end)
238 break;
239 lock_page(page);
240 wait_on_page_writeback(page);
241 if (page_mapped(page)) {
242 unmap_mapping_range(mapping,
243 (loff_t)page->index<<PAGE_CACHE_SHIFT,
244 PAGE_CACHE_SIZE, 0);
245 }
246 if (page->index > next)
247 next = page->index;
248 next++;
249 truncate_complete_page(mapping, page);
250 unlock_page(page);
251 }
252 pagevec_release(&pvec);
253 }
254 }
255 EXPORT_SYMBOL(truncate_inode_pages_range);
256
257 /**
258 * truncate_inode_pages - truncate *all* the pages from an offset
259 * @mapping: mapping to truncate
260 * @lstart: offset from which to truncate
261 *
262 * Called under (and serialised by) inode->i_mutex.
263 */
264 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
265 {
266 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
267 }
268 EXPORT_SYMBOL(truncate_inode_pages);
269
270 /**
271 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
272 * @mapping: the address_space which holds the pages to invalidate
273 * @start: the offset 'from' which to invalidate
274 * @end: the offset 'to' which to invalidate (inclusive)
275 *
276 * This function only removes the unlocked pages, if you want to
277 * remove all the pages of one inode, you must call truncate_inode_pages.
278 *
279 * invalidate_mapping_pages() will not block on IO activity. It will not
280 * invalidate pages which are dirty, locked, under writeback or mapped into
281 * pagetables.
282 */
283 unsigned long invalidate_mapping_pages(struct address_space *mapping,
284 pgoff_t start, pgoff_t end)
285 {
286 struct pagevec pvec;
287 pgoff_t next = start;
288 unsigned long ret = 0;
289 int i;
290
291 pagevec_init(&pvec, 0);
292 while (next <= end &&
293 pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
294 for (i = 0; i < pagevec_count(&pvec); i++) {
295 struct page *page = pvec.pages[i];
296 pgoff_t index;
297 int lock_failed;
298
299 lock_failed = !trylock_page(page);
300
301 /*
302 * We really shouldn't be looking at the ->index of an
303 * unlocked page. But we're not allowed to lock these
304 * pages. So we rely upon nobody altering the ->index
305 * of this (pinned-by-us) page.
306 */
307 index = page->index;
308 if (index > next)
309 next = index;
310 next++;
311 if (lock_failed)
312 continue;
313
314 if (PageDirty(page) || PageWriteback(page))
315 goto unlock;
316 if (page_mapped(page))
317 goto unlock;
318 ret += invalidate_complete_page(mapping, page);
319 unlock:
320 unlock_page(page);
321 if (next > end)
322 break;
323 }
324 pagevec_release(&pvec);
325 cond_resched();
326 }
327 return ret;
328 }
329 EXPORT_SYMBOL(invalidate_mapping_pages);
330
331 /*
332 * This is like invalidate_complete_page(), except it ignores the page's
333 * refcount. We do this because invalidate_inode_pages2() needs stronger
334 * invalidation guarantees, and cannot afford to leave pages behind because
335 * shrink_page_list() has a temp ref on them, or because they're transiently
336 * sitting in the lru_cache_add() pagevecs.
337 */
338 static int
339 invalidate_complete_page2(struct address_space *mapping, struct page *page)
340 {
341 if (page->mapping != mapping)
342 return 0;
343
344 if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
345 return 0;
346
347 spin_lock_irq(&mapping->tree_lock);
348 if (PageDirty(page))
349 goto failed;
350
351 clear_page_mlock(page);
352 BUG_ON(page_has_private(page));
353 __remove_from_page_cache(page);
354 spin_unlock_irq(&mapping->tree_lock);
355 mem_cgroup_uncharge_cache_page(page);
356 page_cache_release(page); /* pagecache ref */
357 return 1;
358 failed:
359 spin_unlock_irq(&mapping->tree_lock);
360 return 0;
361 }
362
363 static int do_launder_page(struct address_space *mapping, struct page *page)
364 {
365 if (!PageDirty(page))
366 return 0;
367 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
368 return 0;
369 return mapping->a_ops->launder_page(page);
370 }
371
372 /**
373 * invalidate_inode_pages2_range - remove range of pages from an address_space
374 * @mapping: the address_space
375 * @start: the page offset 'from' which to invalidate
376 * @end: the page offset 'to' which to invalidate (inclusive)
377 *
378 * Any pages which are found to be mapped into pagetables are unmapped prior to
379 * invalidation.
380 *
381 * Returns -EBUSY if any pages could not be invalidated.
382 */
383 int invalidate_inode_pages2_range(struct address_space *mapping,
384 pgoff_t start, pgoff_t end)
385 {
386 struct pagevec pvec;
387 pgoff_t next;
388 int i;
389 int ret = 0;
390 int ret2 = 0;
391 int did_range_unmap = 0;
392 int wrapped = 0;
393
394 pagevec_init(&pvec, 0);
395 next = start;
396 while (next <= end && !wrapped &&
397 pagevec_lookup(&pvec, mapping, next,
398 min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
399 for (i = 0; i < pagevec_count(&pvec); i++) {
400 struct page *page = pvec.pages[i];
401 pgoff_t page_index;
402
403 lock_page(page);
404 if (page->mapping != mapping) {
405 unlock_page(page);
406 continue;
407 }
408 page_index = page->index;
409 next = page_index + 1;
410 if (next == 0)
411 wrapped = 1;
412 if (page_index > end) {
413 unlock_page(page);
414 break;
415 }
416 wait_on_page_writeback(page);
417 if (page_mapped(page)) {
418 if (!did_range_unmap) {
419 /*
420 * Zap the rest of the file in one hit.
421 */
422 unmap_mapping_range(mapping,
423 (loff_t)page_index<<PAGE_CACHE_SHIFT,
424 (loff_t)(end - page_index + 1)
425 << PAGE_CACHE_SHIFT,
426 0);
427 did_range_unmap = 1;
428 } else {
429 /*
430 * Just zap this page
431 */
432 unmap_mapping_range(mapping,
433 (loff_t)page_index<<PAGE_CACHE_SHIFT,
434 PAGE_CACHE_SIZE, 0);
435 }
436 }
437 BUG_ON(page_mapped(page));
438 ret2 = do_launder_page(mapping, page);
439 if (ret2 == 0) {
440 if (!invalidate_complete_page2(mapping, page))
441 ret2 = -EBUSY;
442 }
443 if (ret2 < 0)
444 ret = ret2;
445 unlock_page(page);
446 }
447 pagevec_release(&pvec);
448 cond_resched();
449 }
450 return ret;
451 }
452 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
453
454 /**
455 * invalidate_inode_pages2 - remove all pages from an address_space
456 * @mapping: the address_space
457 *
458 * Any pages which are found to be mapped into pagetables are unmapped prior to
459 * invalidation.
460 *
461 * Returns -EIO if any pages could not be invalidated.
462 */
463 int invalidate_inode_pages2(struct address_space *mapping)
464 {
465 return invalidate_inode_pages2_range(mapping, 0, -1);
466 }
467 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);