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/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 "internal.h"
24
25
26/**
27 * do_invalidatepage - invalidate part or all of a page
28 * @page: the page which is affected
29 * @offset: the index of the truncation point
30 *
31 * do_invalidatepage() is called when all or part of the page has become
32 * invalidated by a truncate operation.
33 *
34 * do_invalidatepage() does not have to release all buffers, but it must
35 * ensure that no dirty buffer is left outside @offset and that no I/O
36 * is underway against any of the blocks which are outside the truncation
37 * point. Because the caller is about to free (and possibly reuse) those
38 * blocks on-disk.
39 */
40void do_invalidatepage(struct page *page, unsigned long offset)
41{
42    void (*invalidatepage)(struct page *, unsigned long);
43    invalidatepage = page->mapping->a_ops->invalidatepage;
44#ifdef CONFIG_BLOCK
45    if (!invalidatepage)
46        invalidatepage = block_invalidatepage;
47#endif
48    if (invalidatepage)
49        (*invalidatepage)(page, offset);
50}
51
52static inline void truncate_partial_page(struct page *page, unsigned partial)
53{
54    zero_user_segment(page, partial, PAGE_CACHE_SIZE);
55    cleancache_invalidate_page(page->mapping, page);
56    if (page_has_private(page))
57        do_invalidatepage(page, partial);
58}
59
60/*
61 * This cancels just the dirty bit on the kernel page itself, it
62 * does NOT actually remove dirty bits on any mmap's that may be
63 * around. It also leaves the page tagged dirty, so any sync
64 * activity will still find it on the dirty lists, and in particular,
65 * clear_page_dirty_for_io() will still look at the dirty bits in
66 * the VM.
67 *
68 * Doing this should *normally* only ever be done when a page
69 * is truncated, and is not actually mapped anywhere at all. However,
70 * fs/buffer.c does this when it notices that somebody has cleaned
71 * out all the buffers on a page without actually doing it through
72 * the VM. Can you say "ext3 is horribly ugly"? Tought you could.
73 */
74void cancel_dirty_page(struct page *page, unsigned int account_size)
75{
76    if (TestClearPageDirty(page)) {
77        struct address_space *mapping = page->mapping;
78        if (mapping && mapping_cap_account_dirty(mapping)) {
79            dec_zone_page_state(page, NR_FILE_DIRTY);
80            dec_bdi_stat(mapping->backing_dev_info,
81                    BDI_RECLAIMABLE);
82            if (account_size)
83                task_io_account_cancelled_write(account_size);
84        }
85    }
86}
87EXPORT_SYMBOL(cancel_dirty_page);
88
89/*
90 * If truncate cannot remove the fs-private metadata from the page, the page
91 * becomes orphaned. It will be left on the LRU and may even be mapped into
92 * user pagetables if we're racing with filemap_fault().
93 *
94 * We need to bale out if page->mapping is no longer equal to the original
95 * mapping. This happens a) when the VM reclaimed the page while we waited on
96 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
97 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
98 */
99static int
100truncate_complete_page(struct address_space *mapping, struct page *page)
101{
102    if (page->mapping != mapping)
103        return -EIO;
104
105    if (page_has_private(page))
106        do_invalidatepage(page, 0);
107
108    cancel_dirty_page(page, PAGE_CACHE_SIZE);
109
110    clear_page_mlock(page);
111    ClearPageMappedToDisk(page);
112    delete_from_page_cache(page);
113    return 0;
114}
115
116/*
117 * This is for invalidate_mapping_pages(). That function can be called at
118 * any time, and is not supposed to throw away dirty pages. But pages can
119 * be marked dirty at any time too, so use remove_mapping which safely
120 * discards clean, unused pages.
121 *
122 * Returns non-zero if the page was successfully invalidated.
123 */
124static int
125invalidate_complete_page(struct address_space *mapping, struct page *page)
126{
127    int ret;
128
129    if (page->mapping != mapping)
130        return 0;
131
132    if (page_has_private(page) && !try_to_release_page(page, 0))
133        return 0;
134
135    clear_page_mlock(page);
136    ret = remove_mapping(mapping, page);
137
138    return ret;
139}
140
141int truncate_inode_page(struct address_space *mapping, struct page *page)
142{
143    if (page_mapped(page)) {
144        unmap_mapping_range(mapping,
145                   (loff_t)page->index << PAGE_CACHE_SHIFT,
146                   PAGE_CACHE_SIZE, 0);
147    }
148    return truncate_complete_page(mapping, page);
149}
150
151/*
152 * Used to get rid of pages on hardware memory corruption.
153 */
154int generic_error_remove_page(struct address_space *mapping, struct page *page)
155{
156    if (!mapping)
157        return -EINVAL;
158    /*
159     * Only punch for normal data pages for now.
160     * Handling other types like directories would need more auditing.
161     */
162    if (!S_ISREG(mapping->host->i_mode))
163        return -EIO;
164    return truncate_inode_page(mapping, page);
165}
166EXPORT_SYMBOL(generic_error_remove_page);
167
168/*
169 * Safely invalidate one page from its pagecache mapping.
170 * It only drops clean, unused pages. The page must be locked.
171 *
172 * Returns 1 if the page is successfully invalidated, otherwise 0.
173 */
174int invalidate_inode_page(struct page *page)
175{
176    struct address_space *mapping = page_mapping(page);
177    if (!mapping)
178        return 0;
179    if (PageDirty(page) || PageWriteback(page))
180        return 0;
181    if (page_mapped(page))
182        return 0;
183    return invalidate_complete_page(mapping, page);
184}
185
186/**
187 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
188 * @mapping: mapping to truncate
189 * @lstart: offset from which to truncate
190 * @lend: offset to which to truncate
191 *
192 * Truncate the page cache, removing the pages that are between
193 * specified offsets (and zeroing out partial page
194 * (if lstart is not page aligned)).
195 *
196 * Truncate takes two passes - the first pass is nonblocking. It will not
197 * block on page locks and it will not block on writeback. The second pass
198 * will wait. This is to prevent as much IO as possible in the affected region.
199 * The first pass will remove most pages, so the search cost of the second pass
200 * is low.
201 *
202 * We pass down the cache-hot hint to the page freeing code. Even if the
203 * mapping is large, it is probably the case that the final pages are the most
204 * recently touched, and freeing happens in ascending file offset order.
205 */
206void truncate_inode_pages_range(struct address_space *mapping,
207                loff_t lstart, loff_t lend)
208{
209    const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
210    const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
211    struct pagevec pvec;
212    pgoff_t index;
213    pgoff_t end;
214    int i;
215
216    cleancache_invalidate_inode(mapping);
217    if (mapping->nrpages == 0)
218        return;
219
220    BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
221    end = (lend >> PAGE_CACHE_SHIFT);
222
223    pagevec_init(&pvec, 0);
224    index = start;
225    while (index <= end && pagevec_lookup(&pvec, mapping, index,
226            min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
227        mem_cgroup_uncharge_start();
228        for (i = 0; i < pagevec_count(&pvec); i++) {
229            struct page *page = pvec.pages[i];
230
231            /* We rely upon deletion not changing page->index */
232            index = page->index;
233            if (index > end)
234                break;
235
236            if (!trylock_page(page))
237                continue;
238            WARN_ON(page->index != index);
239            if (PageWriteback(page)) {
240                unlock_page(page);
241                continue;
242            }
243            truncate_inode_page(mapping, page);
244            unlock_page(page);
245        }
246        pagevec_release(&pvec);
247        mem_cgroup_uncharge_end();
248        cond_resched();
249        index++;
250    }
251
252    if (partial) {
253        struct page *page = find_lock_page(mapping, start - 1);
254        if (page) {
255            wait_on_page_writeback(page);
256            truncate_partial_page(page, partial);
257            unlock_page(page);
258            page_cache_release(page);
259        }
260    }
261
262    index = start;
263    for ( ; ; ) {
264        cond_resched();
265        if (!pagevec_lookup(&pvec, mapping, index,
266            min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
267            if (index == start)
268                break;
269            index = start;
270            continue;
271        }
272        if (index == start && 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            /* We rely upon deletion not changing page->index */
281            index = page->index;
282            if (index > end)
283                break;
284
285            lock_page(page);
286            WARN_ON(page->index != index);
287            wait_on_page_writeback(page);
288            truncate_inode_page(mapping, page);
289            unlock_page(page);
290        }
291        pagevec_release(&pvec);
292        mem_cgroup_uncharge_end();
293        index++;
294    }
295    cleancache_invalidate_inode(mapping);
296}
297EXPORT_SYMBOL(truncate_inode_pages_range);
298
299/**
300 * truncate_inode_pages - truncate *all* the pages from an offset
301 * @mapping: mapping to truncate
302 * @lstart: offset from which to truncate
303 *
304 * Called under (and serialised by) inode->i_mutex.
305 *
306 * Note: When this function returns, there can be a page in the process of
307 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
308 * mapping->nrpages can be non-zero when this function returns even after
309 * truncation of the whole mapping.
310 */
311void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
312{
313    truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
314}
315EXPORT_SYMBOL(truncate_inode_pages);
316
317/**
318 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
319 * @mapping: the address_space which holds the pages to invalidate
320 * @start: the offset 'from' which to invalidate
321 * @end: the offset 'to' which to invalidate (inclusive)
322 *
323 * This function only removes the unlocked pages, if you want to
324 * remove all the pages of one inode, you must call truncate_inode_pages.
325 *
326 * invalidate_mapping_pages() will not block on IO activity. It will not
327 * invalidate pages which are dirty, locked, under writeback or mapped into
328 * pagetables.
329 */
330unsigned long invalidate_mapping_pages(struct address_space *mapping,
331        pgoff_t start, pgoff_t end)
332{
333    struct pagevec pvec;
334    pgoff_t index = start;
335    unsigned long ret;
336    unsigned long count = 0;
337    int i;
338
339    /*
340     * Note: this function may get called on a shmem/tmpfs mapping:
341     * pagevec_lookup() might then return 0 prematurely (because it
342     * got a gangful of swap entries); but it's hardly worth worrying
343     * about - it can rarely have anything to free from such a mapping
344     * (most pages are dirty), and already skips over any difficulties.
345     */
346
347    pagevec_init(&pvec, 0);
348    while (index <= end && pagevec_lookup(&pvec, mapping, index,
349            min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
350        mem_cgroup_uncharge_start();
351        for (i = 0; i < pagevec_count(&pvec); i++) {
352            struct page *page = pvec.pages[i];
353
354            /* We rely upon deletion not changing page->index */
355            index = page->index;
356            if (index > end)
357                break;
358
359            if (!trylock_page(page))
360                continue;
361            WARN_ON(page->index != index);
362            ret = invalidate_inode_page(page);
363            unlock_page(page);
364            /*
365             * Invalidation is a hint that the page is no longer
366             * of interest and try to speed up its reclaim.
367             */
368            if (!ret)
369                deactivate_page(page);
370            count += ret;
371        }
372        pagevec_release(&pvec);
373        mem_cgroup_uncharge_end();
374        cond_resched();
375        index++;
376    }
377    return count;
378}
379EXPORT_SYMBOL(invalidate_mapping_pages);
380
381/*
382 * This is like invalidate_complete_page(), except it ignores the page's
383 * refcount. We do this because invalidate_inode_pages2() needs stronger
384 * invalidation guarantees, and cannot afford to leave pages behind because
385 * shrink_page_list() has a temp ref on them, or because they're transiently
386 * sitting in the lru_cache_add() pagevecs.
387 */
388static int
389invalidate_complete_page2(struct address_space *mapping, struct page *page)
390{
391    if (page->mapping != mapping)
392        return 0;
393
394    if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
395        return 0;
396
397    spin_lock_irq(&mapping->tree_lock);
398    if (PageDirty(page))
399        goto failed;
400
401    clear_page_mlock(page);
402    BUG_ON(page_has_private(page));
403    __delete_from_page_cache(page);
404    spin_unlock_irq(&mapping->tree_lock);
405    mem_cgroup_uncharge_cache_page(page);
406
407    if (mapping->a_ops->freepage)
408        mapping->a_ops->freepage(page);
409
410    page_cache_release(page); /* pagecache ref */
411    return 1;
412failed:
413    spin_unlock_irq(&mapping->tree_lock);
414    return 0;
415}
416
417static int do_launder_page(struct address_space *mapping, struct page *page)
418{
419    if (!PageDirty(page))
420        return 0;
421    if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
422        return 0;
423    return mapping->a_ops->launder_page(page);
424}
425
426/**
427 * invalidate_inode_pages2_range - remove range of pages from an address_space
428 * @mapping: the address_space
429 * @start: the page offset 'from' which to invalidate
430 * @end: the page offset 'to' which to invalidate (inclusive)
431 *
432 * Any pages which are found to be mapped into pagetables are unmapped prior to
433 * invalidation.
434 *
435 * Returns -EBUSY if any pages could not be invalidated.
436 */
437int invalidate_inode_pages2_range(struct address_space *mapping,
438                  pgoff_t start, pgoff_t end)
439{
440    struct pagevec pvec;
441    pgoff_t index;
442    int i;
443    int ret = 0;
444    int ret2 = 0;
445    int did_range_unmap = 0;
446
447    cleancache_invalidate_inode(mapping);
448    pagevec_init(&pvec, 0);
449    index = start;
450    while (index <= end && pagevec_lookup(&pvec, mapping, index,
451            min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
452        mem_cgroup_uncharge_start();
453        for (i = 0; i < pagevec_count(&pvec); i++) {
454            struct page *page = pvec.pages[i];
455
456            /* We rely upon deletion not changing page->index */
457            index = page->index;
458            if (index > end)
459                break;
460
461            lock_page(page);
462            WARN_ON(page->index != index);
463            if (page->mapping != mapping) {
464                unlock_page(page);
465                continue;
466            }
467            wait_on_page_writeback(page);
468            if (page_mapped(page)) {
469                if (!did_range_unmap) {
470                    /*
471                     * Zap the rest of the file in one hit.
472                     */
473                    unmap_mapping_range(mapping,
474                       (loff_t)index << PAGE_CACHE_SHIFT,
475                       (loff_t)(1 + end - index)
476                             << PAGE_CACHE_SHIFT,
477                        0);
478                    did_range_unmap = 1;
479                } else {
480                    /*
481                     * Just zap this page
482                     */
483                    unmap_mapping_range(mapping,
484                       (loff_t)index << PAGE_CACHE_SHIFT,
485                       PAGE_CACHE_SIZE, 0);
486                }
487            }
488            BUG_ON(page_mapped(page));
489            ret2 = do_launder_page(mapping, page);
490            if (ret2 == 0) {
491                if (!invalidate_complete_page2(mapping, page))
492                    ret2 = -EBUSY;
493            }
494            if (ret2 < 0)
495                ret = ret2;
496            unlock_page(page);
497        }
498        pagevec_release(&pvec);
499        mem_cgroup_uncharge_end();
500        cond_resched();
501        index++;
502    }
503    cleancache_invalidate_inode(mapping);
504    return ret;
505}
506EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
507
508/**
509 * invalidate_inode_pages2 - remove all pages from an address_space
510 * @mapping: the address_space
511 *
512 * Any pages which are found to be mapped into pagetables are unmapped prior to
513 * invalidation.
514 *
515 * Returns -EBUSY if any pages could not be invalidated.
516 */
517int invalidate_inode_pages2(struct address_space *mapping)
518{
519    return invalidate_inode_pages2_range(mapping, 0, -1);
520}
521EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
522
523/**
524 * truncate_pagecache - unmap and remove pagecache that has been truncated
525 * @inode: inode
526 * @oldsize: old file size
527 * @newsize: new file size
528 *
529 * inode's new i_size must already be written before truncate_pagecache
530 * is called.
531 *
532 * This function should typically be called before the filesystem
533 * releases resources associated with the freed range (eg. deallocates
534 * blocks). This way, pagecache will always stay logically coherent
535 * with on-disk format, and the filesystem would not have to deal with
536 * situations such as writepage being called for a page that has already
537 * had its underlying blocks deallocated.
538 */
539void truncate_pagecache(struct inode *inode, loff_t oldsize, loff_t newsize)
540{
541    struct address_space *mapping = inode->i_mapping;
542    loff_t holebegin = round_up(newsize, PAGE_SIZE);
543
544    /*
545     * unmap_mapping_range is called twice, first simply for
546     * efficiency so that truncate_inode_pages does fewer
547     * single-page unmaps. However after this first call, and
548     * before truncate_inode_pages finishes, it is possible for
549     * private pages to be COWed, which remain after
550     * truncate_inode_pages finishes, hence the second
551     * unmap_mapping_range call must be made for correctness.
552     */
553    unmap_mapping_range(mapping, holebegin, 0, 1);
554    truncate_inode_pages(mapping, newsize);
555    unmap_mapping_range(mapping, holebegin, 0, 1);
556}
557EXPORT_SYMBOL(truncate_pagecache);
558
559/**
560 * truncate_setsize - update inode and pagecache for a new file size
561 * @inode: inode
562 * @newsize: new file size
563 *
564 * truncate_setsize updates i_size and performs pagecache truncation (if
565 * necessary) to @newsize. It will be typically be called from the filesystem's
566 * setattr function when ATTR_SIZE is passed in.
567 *
568 * Must be called with inode_mutex held and before all filesystem specific
569 * block truncation has been performed.
570 */
571void truncate_setsize(struct inode *inode, loff_t newsize)
572{
573    loff_t oldsize;
574
575    oldsize = inode->i_size;
576    i_size_write(inode, newsize);
577
578    truncate_pagecache(inode, oldsize, newsize);
579}
580EXPORT_SYMBOL(truncate_setsize);
581
582/**
583 * vmtruncate - unmap mappings "freed" by truncate() syscall
584 * @inode: inode of the file used
585 * @newsize: file offset to start truncating
586 *
587 * This function is deprecated and truncate_setsize or truncate_pagecache
588 * should be used instead, together with filesystem specific block truncation.
589 */
590int vmtruncate(struct inode *inode, loff_t newsize)
591{
592    int error;
593
594    error = inode_newsize_ok(inode, newsize);
595    if (error)
596        return error;
597
598    truncate_setsize(inode, newsize);
599    if (inode->i_op->truncate)
600        inode->i_op->truncate(inode);
601    return 0;
602}
603EXPORT_SYMBOL(vmtruncate);
604
605/**
606 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
607 * @inode: inode
608 * @lstart: offset of beginning of hole
609 * @lend: offset of last byte of hole
610 *
611 * This function should typically be called before the filesystem
612 * releases resources associated with the freed range (eg. deallocates
613 * blocks). This way, pagecache will always stay logically coherent
614 * with on-disk format, and the filesystem would not have to deal with
615 * situations such as writepage being called for a page that has already
616 * had its underlying blocks deallocated.
617 */
618void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
619{
620    struct address_space *mapping = inode->i_mapping;
621    loff_t unmap_start = round_up(lstart, PAGE_SIZE);
622    loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
623    /*
624     * This rounding is currently just for example: unmap_mapping_range
625     * expands its hole outwards, whereas we want it to contract the hole
626     * inwards. However, existing callers of truncate_pagecache_range are
627     * doing their own page rounding first; and truncate_inode_pages_range
628     * currently BUGs if lend is not pagealigned-1 (it handles partial
629     * page at start of hole, but not partial page at end of hole). Note
630     * unmap_mapping_range allows holelen 0 for all, and we allow lend -1.
631     */
632
633    /*
634     * Unlike in truncate_pagecache, unmap_mapping_range is called only
635     * once (before truncating pagecache), and without "even_cows" flag:
636     * hole-punching should not remove private COWed pages from the hole.
637     */
638    if ((u64)unmap_end > (u64)unmap_start)
639        unmap_mapping_range(mapping, unmap_start,
640                    1 + unmap_end - unmap_start, 0);
641    truncate_inode_pages_range(mapping, lstart, lend);
642}
643EXPORT_SYMBOL(truncate_pagecache_range);
644

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