Root/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/module.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 "internal.h"
23
24
25/**
26 * do_invalidatepage - invalidate part or all of a page
27 * @page: the page which is affected
28 * @offset: the index of the truncation point
29 *
30 * do_invalidatepage() is called when all or part of the page has become
31 * invalidated by a truncate operation.
32 *
33 * do_invalidatepage() does not have to release all buffers, but it must
34 * ensure that no dirty buffer is left outside @offset and that no I/O
35 * is underway against any of the blocks which are outside the truncation
36 * point. Because the caller is about to free (and possibly reuse) those
37 * blocks on-disk.
38 */
39void do_invalidatepage(struct page *page, unsigned long offset)
40{
41    void (*invalidatepage)(struct page *, unsigned long);
42    invalidatepage = page->mapping->a_ops->invalidatepage;
43#ifdef CONFIG_BLOCK
44    if (!invalidatepage)
45        invalidatepage = block_invalidatepage;
46#endif
47    if (invalidatepage)
48        (*invalidatepage)(page, offset);
49}
50
51static inline void truncate_partial_page(struct page *page, unsigned partial)
52{
53    zero_user_segment(page, partial, PAGE_CACHE_SIZE);
54    if (page_has_private(page))
55        do_invalidatepage(page, partial);
56}
57
58/*
59 * This cancels just the dirty bit on the kernel page itself, it
60 * does NOT actually remove dirty bits on any mmap's that may be
61 * around. It also leaves the page tagged dirty, so any sync
62 * activity will still find it on the dirty lists, and in particular,
63 * clear_page_dirty_for_io() will still look at the dirty bits in
64 * the VM.
65 *
66 * Doing this should *normally* only ever be done when a page
67 * is truncated, and is not actually mapped anywhere at all. However,
68 * fs/buffer.c does this when it notices that somebody has cleaned
69 * out all the buffers on a page without actually doing it through
70 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
71 */
72void cancel_dirty_page(struct page *page, unsigned int account_size)
73{
74    if (TestClearPageDirty(page)) {
75        struct address_space *mapping = page->mapping;
76        if (mapping && mapping_cap_account_dirty(mapping)) {
77            dec_zone_page_state(page, NR_FILE_DIRTY);
78            dec_bdi_stat(mapping->backing_dev_info,
79                    BDI_RECLAIMABLE);
80            if (account_size)
81                task_io_account_cancelled_write(account_size);
82        }
83    }
84}
85EXPORT_SYMBOL(cancel_dirty_page);
86
87/*
88 * If truncate cannot remove the fs-private metadata from the page, the page
89 * becomes orphaned. It will be left on the LRU and may even be mapped into
90 * user pagetables if we're racing with filemap_fault().
91 *
92 * We need to bale out if page->mapping is no longer equal to the original
93 * mapping. This happens a) when the VM reclaimed the page while we waited on
94 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
95 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
96 */
97static int
98truncate_complete_page(struct address_space *mapping, struct page *page)
99{
100    if (page->mapping != mapping)
101        return -EIO;
102
103    if (page_has_private(page))
104        do_invalidatepage(page, 0);
105
106    cancel_dirty_page(page, PAGE_CACHE_SIZE);
107
108    clear_page_mlock(page);
109    remove_from_page_cache(page);
110    ClearPageMappedToDisk(page);
111    page_cache_release(page); /* pagecache ref */
112    return 0;
113}
114
115/*
116 * This is for invalidate_mapping_pages(). That function can be called at
117 * any time, and is not supposed to throw away dirty pages. But pages can
118 * be marked dirty at any time too, so use remove_mapping which safely
119 * discards clean, unused pages.
120 *
121 * Returns non-zero if the page was successfully invalidated.
122 */
123static int
124invalidate_complete_page(struct address_space *mapping, struct page *page)
125{
126    int ret;
127
128    if (page->mapping != mapping)
129        return 0;
130
131    if (page_has_private(page) && !try_to_release_page(page, 0))
132        return 0;
133
134    clear_page_mlock(page);
135    ret = remove_mapping(mapping, page);
136
137    return ret;
138}
139
140int truncate_inode_page(struct address_space *mapping, struct page *page)
141{
142    if (page_mapped(page)) {
143        unmap_mapping_range(mapping,
144                   (loff_t)page->index << PAGE_CACHE_SHIFT,
145                   PAGE_CACHE_SIZE, 0);
146    }
147    return truncate_complete_page(mapping, page);
148}
149
150/*
151 * Used to get rid of pages on hardware memory corruption.
152 */
153int generic_error_remove_page(struct address_space *mapping, struct page *page)
154{
155    if (!mapping)
156        return -EINVAL;
157    /*
158     * Only punch for normal data pages for now.
159     * Handling other types like directories would need more auditing.
160     */
161    if (!S_ISREG(mapping->host->i_mode))
162        return -EIO;
163    return truncate_inode_page(mapping, page);
164}
165EXPORT_SYMBOL(generic_error_remove_page);
166
167/*
168 * Safely invalidate one page from its pagecache mapping.
169 * It only drops clean, unused pages. The page must be locked.
170 *
171 * Returns 1 if the page is successfully invalidated, otherwise 0.
172 */
173int invalidate_inode_page(struct page *page)
174{
175    struct address_space *mapping = page_mapping(page);
176    if (!mapping)
177        return 0;
178    if (PageDirty(page) || PageWriteback(page))
179        return 0;
180    if (page_mapped(page))
181        return 0;
182    return invalidate_complete_page(mapping, page);
183}
184
185/**
186 * truncate_inode_pages - truncate range of pages specified by start & end byte offsets
187 * @mapping: mapping to truncate
188 * @lstart: offset from which to truncate
189 * @lend: offset to which to truncate
190 *
191 * Truncate the page cache, removing the pages that are between
192 * specified offsets (and zeroing out partial page
193 * (if lstart is not page aligned)).
194 *
195 * Truncate takes two passes - the first pass is nonblocking. It will not
196 * block on page locks and it will not block on writeback. The second pass
197 * will wait. This is to prevent as much IO as possible in the affected region.
198 * The first pass will remove most pages, so the search cost of the second pass
199 * is low.
200 *
201 * When looking at page->index outside the page lock we need to be careful to
202 * copy it into a local to avoid races (it could change at any time).
203 *
204 * We pass down the cache-hot hint to the page freeing code. Even if the
205 * mapping is large, it is probably the case that the final pages are the most
206 * recently touched, and freeing happens in ascending file offset order.
207 */
208void truncate_inode_pages_range(struct address_space *mapping,
209                loff_t lstart, loff_t lend)
210{
211    const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
212    pgoff_t end;
213    const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
214    struct pagevec pvec;
215    pgoff_t next;
216    int i;
217
218    if (mapping->nrpages == 0)
219        return;
220
221    BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
222    end = (lend >> PAGE_CACHE_SHIFT);
223
224    pagevec_init(&pvec, 0);
225    next = start;
226    while (next <= end &&
227           pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
228        for (i = 0; i < pagevec_count(&pvec); i++) {
229            struct page *page = pvec.pages[i];
230            pgoff_t page_index = page->index;
231
232            if (page_index > end) {
233                next = page_index;
234                break;
235            }
236
237            if (page_index > next)
238                next = page_index;
239            next++;
240            if (!trylock_page(page))
241                continue;
242            if (PageWriteback(page)) {
243                unlock_page(page);
244                continue;
245            }
246            truncate_inode_page(mapping, page);
247            unlock_page(page);
248        }
249        pagevec_release(&pvec);
250        cond_resched();
251    }
252
253    if (partial) {
254        struct page *page = find_lock_page(mapping, start - 1);
255        if (page) {
256            wait_on_page_writeback(page);
257            truncate_partial_page(page, partial);
258            unlock_page(page);
259            page_cache_release(page);
260        }
261    }
262
263    next = start;
264    for ( ; ; ) {
265        cond_resched();
266        if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
267            if (next == start)
268                break;
269            next = start;
270            continue;
271        }
272        if (pvec.pages[0]->index > end) {
273            pagevec_release(&pvec);
274            break;
275        }
276        mem_cgroup_uncharge_start();
277        for (i = 0; i < pagevec_count(&pvec); i++) {
278            struct page *page = pvec.pages[i];
279
280            if (page->index > end)
281                break;
282            lock_page(page);
283            wait_on_page_writeback(page);
284            truncate_inode_page(mapping, page);
285            if (page->index > next)
286                next = page->index;
287            next++;
288            unlock_page(page);
289        }
290        pagevec_release(&pvec);
291        mem_cgroup_uncharge_end();
292    }
293}
294EXPORT_SYMBOL(truncate_inode_pages_range);
295
296/**
297 * truncate_inode_pages - truncate *all* the pages from an offset
298 * @mapping: mapping to truncate
299 * @lstart: offset from which to truncate
300 *
301 * Called under (and serialised by) inode->i_mutex.
302 */
303void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
304{
305    truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
306}
307EXPORT_SYMBOL(truncate_inode_pages);
308
309/**
310 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
311 * @mapping: the address_space which holds the pages to invalidate
312 * @start: the offset 'from' which to invalidate
313 * @end: the offset 'to' which to invalidate (inclusive)
314 *
315 * This function only removes the unlocked pages, if you want to
316 * remove all the pages of one inode, you must call truncate_inode_pages.
317 *
318 * invalidate_mapping_pages() will not block on IO activity. It will not
319 * invalidate pages which are dirty, locked, under writeback or mapped into
320 * pagetables.
321 */
322unsigned long invalidate_mapping_pages(struct address_space *mapping,
323                       pgoff_t start, pgoff_t end)
324{
325    struct pagevec pvec;
326    pgoff_t next = start;
327    unsigned long ret = 0;
328    int i;
329
330    pagevec_init(&pvec, 0);
331    while (next <= end &&
332            pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
333        mem_cgroup_uncharge_start();
334        for (i = 0; i < pagevec_count(&pvec); i++) {
335            struct page *page = pvec.pages[i];
336            pgoff_t index;
337            int lock_failed;
338
339            lock_failed = !trylock_page(page);
340
341            /*
342             * We really shouldn't be looking at the ->index of an
343             * unlocked page. But we're not allowed to lock these
344             * pages. So we rely upon nobody altering the ->index
345             * of this (pinned-by-us) page.
346             */
347            index = page->index;
348            if (index > next)
349                next = index;
350            next++;
351            if (lock_failed)
352                continue;
353
354            ret += invalidate_inode_page(page);
355
356            unlock_page(page);
357            if (next > end)
358                break;
359        }
360        pagevec_release(&pvec);
361        mem_cgroup_uncharge_end();
362        cond_resched();
363    }
364    return ret;
365}
366EXPORT_SYMBOL(invalidate_mapping_pages);
367
368/*
369 * This is like invalidate_complete_page(), except it ignores the page's
370 * refcount. We do this because invalidate_inode_pages2() needs stronger
371 * invalidation guarantees, and cannot afford to leave pages behind because
372 * shrink_page_list() has a temp ref on them, or because they're transiently
373 * sitting in the lru_cache_add() pagevecs.
374 */
375static int
376invalidate_complete_page2(struct address_space *mapping, struct page *page)
377{
378    if (page->mapping != mapping)
379        return 0;
380
381    if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
382        return 0;
383
384    spin_lock_irq(&mapping->tree_lock);
385    if (PageDirty(page))
386        goto failed;
387
388    clear_page_mlock(page);
389    BUG_ON(page_has_private(page));
390    __remove_from_page_cache(page);
391    spin_unlock_irq(&mapping->tree_lock);
392    mem_cgroup_uncharge_cache_page(page);
393    page_cache_release(page); /* pagecache ref */
394    return 1;
395failed:
396    spin_unlock_irq(&mapping->tree_lock);
397    return 0;
398}
399
400static int do_launder_page(struct address_space *mapping, struct page *page)
401{
402    if (!PageDirty(page))
403        return 0;
404    if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
405        return 0;
406    return mapping->a_ops->launder_page(page);
407}
408
409/**
410 * invalidate_inode_pages2_range - remove range of pages from an address_space
411 * @mapping: the address_space
412 * @start: the page offset 'from' which to invalidate
413 * @end: the page offset 'to' which to invalidate (inclusive)
414 *
415 * Any pages which are found to be mapped into pagetables are unmapped prior to
416 * invalidation.
417 *
418 * Returns -EBUSY if any pages could not be invalidated.
419 */
420int invalidate_inode_pages2_range(struct address_space *mapping,
421                  pgoff_t start, pgoff_t end)
422{
423    struct pagevec pvec;
424    pgoff_t next;
425    int i;
426    int ret = 0;
427    int ret2 = 0;
428    int did_range_unmap = 0;
429    int wrapped = 0;
430
431    pagevec_init(&pvec, 0);
432    next = start;
433    while (next <= end && !wrapped &&
434        pagevec_lookup(&pvec, mapping, next,
435            min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
436        mem_cgroup_uncharge_start();
437        for (i = 0; i < pagevec_count(&pvec); i++) {
438            struct page *page = pvec.pages[i];
439            pgoff_t page_index;
440
441            lock_page(page);
442            if (page->mapping != mapping) {
443                unlock_page(page);
444                continue;
445            }
446            page_index = page->index;
447            next = page_index + 1;
448            if (next == 0)
449                wrapped = 1;
450            if (page_index > end) {
451                unlock_page(page);
452                break;
453            }
454            wait_on_page_writeback(page);
455            if (page_mapped(page)) {
456                if (!did_range_unmap) {
457                    /*
458                     * Zap the rest of the file in one hit.
459                     */
460                    unmap_mapping_range(mapping,
461                       (loff_t)page_index<<PAGE_CACHE_SHIFT,
462                       (loff_t)(end - page_index + 1)
463                            << PAGE_CACHE_SHIFT,
464                        0);
465                    did_range_unmap = 1;
466                } else {
467                    /*
468                     * Just zap this page
469                     */
470                    unmap_mapping_range(mapping,
471                      (loff_t)page_index<<PAGE_CACHE_SHIFT,
472                      PAGE_CACHE_SIZE, 0);
473                }
474            }
475            BUG_ON(page_mapped(page));
476            ret2 = do_launder_page(mapping, page);
477            if (ret2 == 0) {
478                if (!invalidate_complete_page2(mapping, page))
479                    ret2 = -EBUSY;
480            }
481            if (ret2 < 0)
482                ret = ret2;
483            unlock_page(page);
484        }
485        pagevec_release(&pvec);
486        mem_cgroup_uncharge_end();
487        cond_resched();
488    }
489    return ret;
490}
491EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
492
493/**
494 * invalidate_inode_pages2 - remove all pages from an address_space
495 * @mapping: the address_space
496 *
497 * Any pages which are found to be mapped into pagetables are unmapped prior to
498 * invalidation.
499 *
500 * Returns -EBUSY if any pages could not be invalidated.
501 */
502int invalidate_inode_pages2(struct address_space *mapping)
503{
504    return invalidate_inode_pages2_range(mapping, 0, -1);
505}
506EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
507
508/**
509 * truncate_pagecache - unmap and remove pagecache that has been truncated
510 * @inode: inode
511 * @old: old file offset
512 * @new: new file offset
513 *
514 * inode's new i_size must already be written before truncate_pagecache
515 * is called.
516 *
517 * This function should typically be called before the filesystem
518 * releases resources associated with the freed range (eg. deallocates
519 * blocks). This way, pagecache will always stay logically coherent
520 * with on-disk format, and the filesystem would not have to deal with
521 * situations such as writepage being called for a page that has already
522 * had its underlying blocks deallocated.
523 */
524void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
525{
526    struct address_space *mapping = inode->i_mapping;
527
528    /*
529     * unmap_mapping_range is called twice, first simply for
530     * efficiency so that truncate_inode_pages does fewer
531     * single-page unmaps. However after this first call, and
532     * before truncate_inode_pages finishes, it is possible for
533     * private pages to be COWed, which remain after
534     * truncate_inode_pages finishes, hence the second
535     * unmap_mapping_range call must be made for correctness.
536     */
537    unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
538    truncate_inode_pages(mapping, new);
539    unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
540}
541EXPORT_SYMBOL(truncate_pagecache);
542
543/**
544 * truncate_setsize - update inode and pagecache for a new file size
545 * @inode: inode
546 * @newsize: new file size
547 *
548 * truncate_setsize updastes i_size update and performs pagecache
549 * truncation (if necessary) for a file size updates. It will be
550 * typically be called from the filesystem's setattr function when
551 * ATTR_SIZE is passed in.
552 *
553 * Must be called with inode_mutex held and after all filesystem
554 * specific block truncation has been performed.
555 */
556void truncate_setsize(struct inode *inode, loff_t newsize)
557{
558    loff_t oldsize;
559
560    oldsize = inode->i_size;
561    i_size_write(inode, newsize);
562
563    truncate_pagecache(inode, oldsize, newsize);
564}
565EXPORT_SYMBOL(truncate_setsize);
566
567/**
568 * vmtruncate - unmap mappings "freed" by truncate() syscall
569 * @inode: inode of the file used
570 * @offset: file offset to start truncating
571 *
572 * This function is deprecated and truncate_setsize or truncate_pagecache
573 * should be used instead, together with filesystem specific block truncation.
574 */
575int vmtruncate(struct inode *inode, loff_t offset)
576{
577    int error;
578
579    error = inode_newsize_ok(inode, offset);
580    if (error)
581        return error;
582
583    truncate_setsize(inode, offset);
584    if (inode->i_op->truncate)
585        inode->i_op->truncate(inode);
586    return 0;
587}
588EXPORT_SYMBOL(vmtruncate);
589

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