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 <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_flush_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 - 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 * When looking at page->index outside the page lock we need to be careful to
203 * copy it into a local to avoid races (it could change at any time).
204 *
205 * We pass down the cache-hot hint to the page freeing code. Even if the
206 * mapping is large, it is probably the case that the final pages are the most
207 * recently touched, and freeing happens in ascending file offset order.
208 */
209void truncate_inode_pages_range(struct address_space *mapping,
210                loff_t lstart, loff_t lend)
211{
212    const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
213    pgoff_t end;
214    const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
215    struct pagevec pvec;
216    pgoff_t next;
217    int i;
218
219    cleancache_flush_inode(mapping);
220    if (mapping->nrpages == 0)
221        return;
222
223    BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
224    end = (lend >> PAGE_CACHE_SHIFT);
225
226    pagevec_init(&pvec, 0);
227    next = start;
228    while (next <= end &&
229           pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
230        mem_cgroup_uncharge_start();
231        for (i = 0; i < pagevec_count(&pvec); i++) {
232            struct page *page = pvec.pages[i];
233            pgoff_t page_index = page->index;
234
235            if (page_index > end) {
236                next = page_index;
237                break;
238            }
239
240            if (page_index > next)
241                next = page_index;
242            next++;
243            if (!trylock_page(page))
244                continue;
245            if (PageWriteback(page)) {
246                unlock_page(page);
247                continue;
248            }
249            truncate_inode_page(mapping, page);
250            unlock_page(page);
251        }
252        pagevec_release(&pvec);
253        mem_cgroup_uncharge_end();
254        cond_resched();
255    }
256
257    if (partial) {
258        struct page *page = find_lock_page(mapping, start - 1);
259        if (page) {
260            wait_on_page_writeback(page);
261            truncate_partial_page(page, partial);
262            unlock_page(page);
263            page_cache_release(page);
264        }
265    }
266
267    next = start;
268    for ( ; ; ) {
269        cond_resched();
270        if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
271            if (next == start)
272                break;
273            next = start;
274            continue;
275        }
276        if (pvec.pages[0]->index > end) {
277            pagevec_release(&pvec);
278            break;
279        }
280        mem_cgroup_uncharge_start();
281        for (i = 0; i < pagevec_count(&pvec); i++) {
282            struct page *page = pvec.pages[i];
283
284            if (page->index > end)
285                break;
286            lock_page(page);
287            wait_on_page_writeback(page);
288            truncate_inode_page(mapping, page);
289            if (page->index > next)
290                next = page->index;
291            next++;
292            unlock_page(page);
293        }
294        pagevec_release(&pvec);
295        mem_cgroup_uncharge_end();
296    }
297    cleancache_flush_inode(mapping);
298}
299EXPORT_SYMBOL(truncate_inode_pages_range);
300
301/**
302 * truncate_inode_pages - truncate *all* the pages from an offset
303 * @mapping: mapping to truncate
304 * @lstart: offset from which to truncate
305 *
306 * Called under (and serialised by) inode->i_mutex.
307 *
308 * Note: When this function returns, there can be a page in the process of
309 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
310 * mapping->nrpages can be non-zero when this function returns even after
311 * truncation of the whole mapping.
312 */
313void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
314{
315    truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
316}
317EXPORT_SYMBOL(truncate_inode_pages);
318
319/**
320 * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
321 * @mapping: the address_space which holds the pages to invalidate
322 * @start: the offset 'from' which to invalidate
323 * @end: the offset 'to' which to invalidate (inclusive)
324 *
325 * This function only removes the unlocked pages, if you want to
326 * remove all the pages of one inode, you must call truncate_inode_pages.
327 *
328 * invalidate_mapping_pages() will not block on IO activity. It will not
329 * invalidate pages which are dirty, locked, under writeback or mapped into
330 * pagetables.
331 */
332unsigned long invalidate_mapping_pages(struct address_space *mapping,
333        pgoff_t start, pgoff_t end)
334{
335    struct pagevec pvec;
336    pgoff_t next = start;
337    unsigned long ret;
338    unsigned long count = 0;
339    int i;
340
341    pagevec_init(&pvec, 0);
342    while (next <= end &&
343            pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
344        mem_cgroup_uncharge_start();
345        for (i = 0; i < pagevec_count(&pvec); i++) {
346            struct page *page = pvec.pages[i];
347            pgoff_t index;
348            int lock_failed;
349
350            lock_failed = !trylock_page(page);
351
352            /*
353             * We really shouldn't be looking at the ->index of an
354             * unlocked page. But we're not allowed to lock these
355             * pages. So we rely upon nobody altering the ->index
356             * of this (pinned-by-us) page.
357             */
358            index = page->index;
359            if (index > next)
360                next = index;
361            next++;
362            if (lock_failed)
363                continue;
364
365            ret = invalidate_inode_page(page);
366            unlock_page(page);
367            /*
368             * Invalidation is a hint that the page is no longer
369             * of interest and try to speed up its reclaim.
370             */
371            if (!ret)
372                deactivate_page(page);
373            count += ret;
374            if (next > end)
375                break;
376        }
377        pagevec_release(&pvec);
378        mem_cgroup_uncharge_end();
379        cond_resched();
380    }
381    return count;
382}
383EXPORT_SYMBOL(invalidate_mapping_pages);
384
385/*
386 * This is like invalidate_complete_page(), except it ignores the page's
387 * refcount. We do this because invalidate_inode_pages2() needs stronger
388 * invalidation guarantees, and cannot afford to leave pages behind because
389 * shrink_page_list() has a temp ref on them, or because they're transiently
390 * sitting in the lru_cache_add() pagevecs.
391 */
392static int
393invalidate_complete_page2(struct address_space *mapping, struct page *page)
394{
395    if (page->mapping != mapping)
396        return 0;
397
398    if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL))
399        return 0;
400
401    spin_lock_irq(&mapping->tree_lock);
402    if (PageDirty(page))
403        goto failed;
404
405    clear_page_mlock(page);
406    BUG_ON(page_has_private(page));
407    __delete_from_page_cache(page);
408    spin_unlock_irq(&mapping->tree_lock);
409    mem_cgroup_uncharge_cache_page(page);
410
411    if (mapping->a_ops->freepage)
412        mapping->a_ops->freepage(page);
413
414    page_cache_release(page); /* pagecache ref */
415    return 1;
416failed:
417    spin_unlock_irq(&mapping->tree_lock);
418    return 0;
419}
420
421static int do_launder_page(struct address_space *mapping, struct page *page)
422{
423    if (!PageDirty(page))
424        return 0;
425    if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
426        return 0;
427    return mapping->a_ops->launder_page(page);
428}
429
430/**
431 * invalidate_inode_pages2_range - remove range of pages from an address_space
432 * @mapping: the address_space
433 * @start: the page offset 'from' which to invalidate
434 * @end: the page offset 'to' which to invalidate (inclusive)
435 *
436 * Any pages which are found to be mapped into pagetables are unmapped prior to
437 * invalidation.
438 *
439 * Returns -EBUSY if any pages could not be invalidated.
440 */
441int invalidate_inode_pages2_range(struct address_space *mapping,
442                  pgoff_t start, pgoff_t end)
443{
444    struct pagevec pvec;
445    pgoff_t next;
446    int i;
447    int ret = 0;
448    int ret2 = 0;
449    int did_range_unmap = 0;
450    int wrapped = 0;
451
452    cleancache_flush_inode(mapping);
453    pagevec_init(&pvec, 0);
454    next = start;
455    while (next <= end && !wrapped &&
456        pagevec_lookup(&pvec, mapping, next,
457            min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
458        mem_cgroup_uncharge_start();
459        for (i = 0; i < pagevec_count(&pvec); i++) {
460            struct page *page = pvec.pages[i];
461            pgoff_t page_index;
462
463            lock_page(page);
464            if (page->mapping != mapping) {
465                unlock_page(page);
466                continue;
467            }
468            page_index = page->index;
469            next = page_index + 1;
470            if (next == 0)
471                wrapped = 1;
472            if (page_index > end) {
473                unlock_page(page);
474                break;
475            }
476            wait_on_page_writeback(page);
477            if (page_mapped(page)) {
478                if (!did_range_unmap) {
479                    /*
480                     * Zap the rest of the file in one hit.
481                     */
482                    unmap_mapping_range(mapping,
483                       (loff_t)page_index<<PAGE_CACHE_SHIFT,
484                       (loff_t)(end - page_index + 1)
485                            << PAGE_CACHE_SHIFT,
486                        0);
487                    did_range_unmap = 1;
488                } else {
489                    /*
490                     * Just zap this page
491                     */
492                    unmap_mapping_range(mapping,
493                      (loff_t)page_index<<PAGE_CACHE_SHIFT,
494                      PAGE_CACHE_SIZE, 0);
495                }
496            }
497            BUG_ON(page_mapped(page));
498            ret2 = do_launder_page(mapping, page);
499            if (ret2 == 0) {
500                if (!invalidate_complete_page2(mapping, page))
501                    ret2 = -EBUSY;
502            }
503            if (ret2 < 0)
504                ret = ret2;
505            unlock_page(page);
506        }
507        pagevec_release(&pvec);
508        mem_cgroup_uncharge_end();
509        cond_resched();
510    }
511    cleancache_flush_inode(mapping);
512    return ret;
513}
514EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
515
516/**
517 * invalidate_inode_pages2 - remove all pages from an address_space
518 * @mapping: the address_space
519 *
520 * Any pages which are found to be mapped into pagetables are unmapped prior to
521 * invalidation.
522 *
523 * Returns -EBUSY if any pages could not be invalidated.
524 */
525int invalidate_inode_pages2(struct address_space *mapping)
526{
527    return invalidate_inode_pages2_range(mapping, 0, -1);
528}
529EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
530
531/**
532 * truncate_pagecache - unmap and remove pagecache that has been truncated
533 * @inode: inode
534 * @old: old file offset
535 * @new: new file offset
536 *
537 * inode's new i_size must already be written before truncate_pagecache
538 * is called.
539 *
540 * This function should typically be called before the filesystem
541 * releases resources associated with the freed range (eg. deallocates
542 * blocks). This way, pagecache will always stay logically coherent
543 * with on-disk format, and the filesystem would not have to deal with
544 * situations such as writepage being called for a page that has already
545 * had its underlying blocks deallocated.
546 */
547void truncate_pagecache(struct inode *inode, loff_t old, loff_t new)
548{
549    struct address_space *mapping = inode->i_mapping;
550
551    /*
552     * unmap_mapping_range is called twice, first simply for
553     * efficiency so that truncate_inode_pages does fewer
554     * single-page unmaps. However after this first call, and
555     * before truncate_inode_pages finishes, it is possible for
556     * private pages to be COWed, which remain after
557     * truncate_inode_pages finishes, hence the second
558     * unmap_mapping_range call must be made for correctness.
559     */
560    unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
561    truncate_inode_pages(mapping, new);
562    unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1);
563}
564EXPORT_SYMBOL(truncate_pagecache);
565
566/**
567 * truncate_setsize - update inode and pagecache for a new file size
568 * @inode: inode
569 * @newsize: new file size
570 *
571 * truncate_setsize updates i_size and performs pagecache truncation (if
572 * necessary) to @newsize. It will be typically be called from the filesystem's
573 * setattr function when ATTR_SIZE is passed in.
574 *
575 * Must be called with inode_mutex held and before all filesystem specific
576 * block truncation has been performed.
577 */
578void truncate_setsize(struct inode *inode, loff_t newsize)
579{
580    loff_t oldsize;
581
582    oldsize = inode->i_size;
583    i_size_write(inode, newsize);
584
585    truncate_pagecache(inode, oldsize, newsize);
586}
587EXPORT_SYMBOL(truncate_setsize);
588
589/**
590 * vmtruncate - unmap mappings "freed" by truncate() syscall
591 * @inode: inode of the file used
592 * @offset: file offset to start truncating
593 *
594 * This function is deprecated and truncate_setsize or truncate_pagecache
595 * should be used instead, together with filesystem specific block truncation.
596 */
597int vmtruncate(struct inode *inode, loff_t offset)
598{
599    int error;
600
601    error = inode_newsize_ok(inode, offset);
602    if (error)
603        return error;
604
605    truncate_setsize(inode, offset);
606    if (inode->i_op->truncate)
607        inode->i_op->truncate(inode);
608    return 0;
609}
610EXPORT_SYMBOL(vmtruncate);
611
612int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end)
613{
614    struct address_space *mapping = inode->i_mapping;
615
616    /*
617     * If the underlying filesystem is not going to provide
618     * a way to truncate a range of blocks (punch a hole) -
619     * we should return failure right now.
620     */
621    if (!inode->i_op->truncate_range)
622        return -ENOSYS;
623
624    mutex_lock(&inode->i_mutex);
625    down_write(&inode->i_alloc_sem);
626    unmap_mapping_range(mapping, offset, (end - offset), 1);
627    inode->i_op->truncate_range(inode, offset, end);
628    /* unmap again to remove racily COWed private pages */
629    unmap_mapping_range(mapping, offset, (end - offset), 1);
630    up_write(&inode->i_alloc_sem);
631    mutex_unlock(&inode->i_mutex);
632
633    return 0;
634}
635

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