1 // SPDX-License-Identifier: GPL-2.0-only
3 * mm/truncate.c - code for taking down pages from address_spaces
5 * Copyright (C) 2002, Linus Torvalds
7 * 10Sep2002 Andrew Morton
11 #include <linux/kernel.h>
12 #include <linux/backing-dev.h>
13 #include <linux/dax.h>
14 #include <linux/gfp.h>
16 #include <linux/swap.h>
17 #include <linux/export.h>
18 #include <linux/pagemap.h>
19 #include <linux/highmem.h>
20 #include <linux/pagevec.h>
21 #include <linux/task_io_accounting_ops.h>
22 #include <linux/buffer_head.h> /* grr. try_to_release_page,
24 #include <linux/shmem_fs.h>
25 #include <linux/cleancache.h>
26 #include <linux/rmap.h>
30 * Regular page slots are stabilized by the page lock even without the tree
31 * itself locked. These unlocked entries need verification under the tree
34 static inline void __clear_shadow_entry(struct address_space *mapping,
35 pgoff_t index, void *entry)
37 XA_STATE(xas, &mapping->i_pages, index);
39 xas_set_update(&xas, workingset_update_node);
40 if (xas_load(&xas) != entry)
42 xas_store(&xas, NULL);
45 static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
48 spin_lock(&mapping->host->i_lock);
49 xa_lock_irq(&mapping->i_pages);
50 __clear_shadow_entry(mapping, index, entry);
51 xa_unlock_irq(&mapping->i_pages);
52 if (mapping_shrinkable(mapping))
53 inode_add_lru(mapping->host);
54 spin_unlock(&mapping->host->i_lock);
58 * Unconditionally remove exceptional entries. Usually called from truncate
59 * path. Note that the folio_batch may be altered by this function by removing
60 * exceptional entries similar to what folio_batch_remove_exceptionals() does.
62 static void truncate_folio_batch_exceptionals(struct address_space *mapping,
63 struct folio_batch *fbatch, pgoff_t *indices)
68 /* Handled by shmem itself */
69 if (shmem_mapping(mapping))
72 for (j = 0; j < folio_batch_count(fbatch); j++)
73 if (xa_is_value(fbatch->folios[j]))
76 if (j == folio_batch_count(fbatch))
79 dax = dax_mapping(mapping);
81 spin_lock(&mapping->host->i_lock);
82 xa_lock_irq(&mapping->i_pages);
85 for (i = j; i < folio_batch_count(fbatch); i++) {
86 struct folio *folio = fbatch->folios[i];
87 pgoff_t index = indices[i];
89 if (!xa_is_value(folio)) {
90 fbatch->folios[j++] = folio;
95 dax_delete_mapping_entry(mapping, index);
99 __clear_shadow_entry(mapping, index, folio);
103 xa_unlock_irq(&mapping->i_pages);
104 if (mapping_shrinkable(mapping))
105 inode_add_lru(mapping->host);
106 spin_unlock(&mapping->host->i_lock);
112 * Invalidate exceptional entry if easily possible. This handles exceptional
113 * entries for invalidate_inode_pages().
115 static int invalidate_exceptional_entry(struct address_space *mapping,
116 pgoff_t index, void *entry)
118 /* Handled by shmem itself, or for DAX we do nothing. */
119 if (shmem_mapping(mapping) || dax_mapping(mapping))
121 clear_shadow_entry(mapping, index, entry);
126 * Invalidate exceptional entry if clean. This handles exceptional entries for
127 * invalidate_inode_pages2() so for DAX it evicts only clean entries.
129 static int invalidate_exceptional_entry2(struct address_space *mapping,
130 pgoff_t index, void *entry)
132 /* Handled by shmem itself */
133 if (shmem_mapping(mapping))
135 if (dax_mapping(mapping))
136 return dax_invalidate_mapping_entry_sync(mapping, index);
137 clear_shadow_entry(mapping, index, entry);
142 * do_invalidatepage - invalidate part or all of a page
143 * @page: the page which is affected
144 * @offset: start of the range to invalidate
145 * @length: length of the range to invalidate
147 * do_invalidatepage() is called when all or part of the page has become
148 * invalidated by a truncate operation.
150 * do_invalidatepage() does not have to release all buffers, but it must
151 * ensure that no dirty buffer is left outside @offset and that no I/O
152 * is underway against any of the blocks which are outside the truncation
153 * point. Because the caller is about to free (and possibly reuse) those
156 void do_invalidatepage(struct page *page, unsigned int offset,
159 void (*invalidatepage)(struct page *, unsigned int, unsigned int);
161 invalidatepage = page->mapping->a_ops->invalidatepage;
164 invalidatepage = block_invalidatepage;
167 (*invalidatepage)(page, offset, length);
171 * If truncate cannot remove the fs-private metadata from the page, the page
172 * becomes orphaned. It will be left on the LRU and may even be mapped into
173 * user pagetables if we're racing with filemap_fault().
175 * We need to bail out if page->mapping is no longer equal to the original
176 * mapping. This happens a) when the VM reclaimed the page while we waited on
177 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
178 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
180 static void truncate_cleanup_folio(struct folio *folio)
182 if (folio_mapped(folio))
183 unmap_mapping_folio(folio);
185 if (folio_has_private(folio))
186 do_invalidatepage(&folio->page, 0, folio_size(folio));
189 * Some filesystems seem to re-dirty the page even after
190 * the VM has canceled the dirty bit (eg ext3 journaling).
191 * Hence dirty accounting check is placed after invalidation.
193 folio_cancel_dirty(folio);
194 folio_clear_mappedtodisk(folio);
198 * This is for invalidate_mapping_pages(). That function can be called at
199 * any time, and is not supposed to throw away dirty pages. But pages can
200 * be marked dirty at any time too, so use remove_mapping which safely
201 * discards clean, unused pages.
203 * Returns non-zero if the page was successfully invalidated.
206 invalidate_complete_page(struct address_space *mapping, struct page *page)
210 if (page->mapping != mapping)
213 if (page_has_private(page) && !try_to_release_page(page, 0))
216 ret = remove_mapping(mapping, page);
221 int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
223 if (folio->mapping != mapping)
226 truncate_cleanup_folio(folio);
227 filemap_remove_folio(folio);
232 * Used to get rid of pages on hardware memory corruption.
234 int generic_error_remove_page(struct address_space *mapping, struct page *page)
236 VM_BUG_ON_PAGE(PageTail(page), page);
241 * Only punch for normal data pages for now.
242 * Handling other types like directories would need more auditing.
244 if (!S_ISREG(mapping->host->i_mode))
246 return truncate_inode_folio(mapping, page_folio(page));
248 EXPORT_SYMBOL(generic_error_remove_page);
251 * Safely invalidate one page from its pagecache mapping.
252 * It only drops clean, unused pages. The page must be locked.
254 * Returns 1 if the page is successfully invalidated, otherwise 0.
256 int invalidate_inode_page(struct page *page)
258 struct address_space *mapping = page_mapping(page);
261 if (PageDirty(page) || PageWriteback(page))
263 if (page_mapped(page))
265 return invalidate_complete_page(mapping, page);
269 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
270 * @mapping: mapping to truncate
271 * @lstart: offset from which to truncate
272 * @lend: offset to which to truncate (inclusive)
274 * Truncate the page cache, removing the pages that are between
275 * specified offsets (and zeroing out partial pages
276 * if lstart or lend + 1 is not page aligned).
278 * Truncate takes two passes - the first pass is nonblocking. It will not
279 * block on page locks and it will not block on writeback. The second pass
280 * will wait. This is to prevent as much IO as possible in the affected region.
281 * The first pass will remove most pages, so the search cost of the second pass
284 * We pass down the cache-hot hint to the page freeing code. Even if the
285 * mapping is large, it is probably the case that the final pages are the most
286 * recently touched, and freeing happens in ascending file offset order.
288 * Note that since ->invalidatepage() accepts range to invalidate
289 * truncate_inode_pages_range is able to handle cases where lend + 1 is not
290 * page aligned properly.
292 void truncate_inode_pages_range(struct address_space *mapping,
293 loff_t lstart, loff_t lend)
295 pgoff_t start; /* inclusive */
296 pgoff_t end; /* exclusive */
297 unsigned int partial_start; /* inclusive */
298 unsigned int partial_end; /* exclusive */
299 struct folio_batch fbatch;
300 pgoff_t indices[PAGEVEC_SIZE];
304 if (mapping_empty(mapping))
307 /* Offsets within partial pages */
308 partial_start = lstart & (PAGE_SIZE - 1);
309 partial_end = (lend + 1) & (PAGE_SIZE - 1);
312 * 'start' and 'end' always covers the range of pages to be fully
313 * truncated. Partial pages are covered with 'partial_start' at the
314 * start of the range and 'partial_end' at the end of the range.
315 * Note that 'end' is exclusive while 'lend' is inclusive.
317 start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
320 * lend == -1 indicates end-of-file so we have to set 'end'
321 * to the highest possible pgoff_t and since the type is
322 * unsigned we're using -1.
326 end = (lend + 1) >> PAGE_SHIFT;
328 folio_batch_init(&fbatch);
330 while (index < end && find_lock_entries(mapping, index, end - 1,
332 index = indices[folio_batch_count(&fbatch) - 1] + 1;
333 truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
334 for (i = 0; i < folio_batch_count(&fbatch); i++)
335 truncate_cleanup_folio(fbatch.folios[i]);
336 delete_from_page_cache_batch(mapping, &fbatch);
337 for (i = 0; i < folio_batch_count(&fbatch); i++)
338 folio_unlock(fbatch.folios[i]);
339 folio_batch_release(&fbatch);
344 struct page *page = find_lock_page(mapping, start - 1);
346 unsigned int top = PAGE_SIZE;
348 /* Truncation within a single page */
352 wait_on_page_writeback(page);
353 zero_user_segment(page, partial_start, top);
354 cleancache_invalidate_page(mapping, page);
355 if (page_has_private(page))
356 do_invalidatepage(page, partial_start,
357 top - partial_start);
363 struct page *page = find_lock_page(mapping, end);
365 wait_on_page_writeback(page);
366 zero_user_segment(page, 0, partial_end);
367 cleancache_invalidate_page(mapping, page);
368 if (page_has_private(page))
369 do_invalidatepage(page, 0,
376 * If the truncation happened within a single page no pages
377 * will be released, just zeroed, so we can bail out now.
385 if (!find_get_entries(mapping, index, end - 1, &fbatch,
387 /* If all gone from start onwards, we're done */
390 /* Otherwise restart to make sure all gone */
395 for (i = 0; i < folio_batch_count(&fbatch); i++) {
396 struct folio *folio = fbatch.folios[i];
398 /* We rely upon deletion not changing page->index */
401 if (xa_is_value(folio))
405 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
406 folio_wait_writeback(folio);
407 truncate_inode_folio(mapping, folio);
409 index = folio_index(folio) + folio_nr_pages(folio) - 1;
411 truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
412 folio_batch_release(&fbatch);
417 cleancache_invalidate_inode(mapping);
419 EXPORT_SYMBOL(truncate_inode_pages_range);
422 * truncate_inode_pages - truncate *all* the pages from an offset
423 * @mapping: mapping to truncate
424 * @lstart: offset from which to truncate
426 * Called under (and serialised by) inode->i_rwsem and
427 * mapping->invalidate_lock.
429 * Note: When this function returns, there can be a page in the process of
430 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
431 * mapping->nrpages can be non-zero when this function returns even after
432 * truncation of the whole mapping.
434 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
436 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
438 EXPORT_SYMBOL(truncate_inode_pages);
441 * truncate_inode_pages_final - truncate *all* pages before inode dies
442 * @mapping: mapping to truncate
444 * Called under (and serialized by) inode->i_rwsem.
446 * Filesystems have to use this in the .evict_inode path to inform the
447 * VM that this is the final truncate and the inode is going away.
449 void truncate_inode_pages_final(struct address_space *mapping)
452 * Page reclaim can not participate in regular inode lifetime
453 * management (can't call iput()) and thus can race with the
454 * inode teardown. Tell it when the address space is exiting,
455 * so that it does not install eviction information after the
456 * final truncate has begun.
458 mapping_set_exiting(mapping);
460 if (!mapping_empty(mapping)) {
462 * As truncation uses a lockless tree lookup, cycle
463 * the tree lock to make sure any ongoing tree
464 * modification that does not see AS_EXITING is
465 * completed before starting the final truncate.
467 xa_lock_irq(&mapping->i_pages);
468 xa_unlock_irq(&mapping->i_pages);
472 * Cleancache needs notification even if there are no pages or shadow
475 truncate_inode_pages(mapping, 0);
477 EXPORT_SYMBOL(truncate_inode_pages_final);
479 static unsigned long __invalidate_mapping_pages(struct address_space *mapping,
480 pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
482 pgoff_t indices[PAGEVEC_SIZE];
483 struct folio_batch fbatch;
484 pgoff_t index = start;
486 unsigned long count = 0;
489 folio_batch_init(&fbatch);
490 while (find_lock_entries(mapping, index, end, &fbatch, indices)) {
491 for (i = 0; i < folio_batch_count(&fbatch); i++) {
492 struct page *page = &fbatch.folios[i]->page;
494 /* We rely upon deletion not changing page->index */
497 if (xa_is_value(page)) {
498 count += invalidate_exceptional_entry(mapping,
503 index += thp_nr_pages(page) - 1;
505 ret = invalidate_inode_page(page);
508 * Invalidation is a hint that the page is no longer
509 * of interest and try to speed up its reclaim.
512 deactivate_file_page(page);
513 /* It is likely on the pagevec of a remote CPU */
519 folio_batch_remove_exceptionals(&fbatch);
520 folio_batch_release(&fbatch);
528 * invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode
529 * @mapping: the address_space which holds the cache to invalidate
530 * @start: the offset 'from' which to invalidate
531 * @end: the offset 'to' which to invalidate (inclusive)
533 * This function removes pages that are clean, unmapped and unlocked,
534 * as well as shadow entries. It will not block on IO activity.
536 * If you want to remove all the pages of one inode, regardless of
537 * their use and writeback state, use truncate_inode_pages().
539 * Return: the number of the cache entries that were invalidated
541 unsigned long invalidate_mapping_pages(struct address_space *mapping,
542 pgoff_t start, pgoff_t end)
544 return __invalidate_mapping_pages(mapping, start, end, NULL);
546 EXPORT_SYMBOL(invalidate_mapping_pages);
549 * invalidate_mapping_pagevec - Invalidate all the unlocked pages of one inode
550 * @mapping: the address_space which holds the pages to invalidate
551 * @start: the offset 'from' which to invalidate
552 * @end: the offset 'to' which to invalidate (inclusive)
553 * @nr_pagevec: invalidate failed page number for caller
555 * This helper is similar to invalidate_mapping_pages(), except that it accounts
556 * for pages that are likely on a pagevec and counts them in @nr_pagevec, which
557 * will be used by the caller.
559 void invalidate_mapping_pagevec(struct address_space *mapping,
560 pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
562 __invalidate_mapping_pages(mapping, start, end, nr_pagevec);
566 * This is like invalidate_complete_page(), except it ignores the page's
567 * refcount. We do this because invalidate_inode_pages2() needs stronger
568 * invalidation guarantees, and cannot afford to leave pages behind because
569 * shrink_page_list() has a temp ref on them, or because they're transiently
570 * sitting in the lru_cache_add() pagevecs.
572 static int invalidate_complete_folio2(struct address_space *mapping,
575 if (folio->mapping != mapping)
578 if (folio_has_private(folio) &&
579 !filemap_release_folio(folio, GFP_KERNEL))
582 spin_lock(&mapping->host->i_lock);
583 xa_lock_irq(&mapping->i_pages);
584 if (folio_test_dirty(folio))
587 BUG_ON(folio_has_private(folio));
588 __filemap_remove_folio(folio, NULL);
589 xa_unlock_irq(&mapping->i_pages);
590 if (mapping_shrinkable(mapping))
591 inode_add_lru(mapping->host);
592 spin_unlock(&mapping->host->i_lock);
594 filemap_free_folio(mapping, folio);
597 xa_unlock_irq(&mapping->i_pages);
598 spin_unlock(&mapping->host->i_lock);
602 static int do_launder_page(struct address_space *mapping, struct page *page)
604 if (!PageDirty(page))
606 if (page->mapping != mapping || mapping->a_ops->launder_page == NULL)
608 return mapping->a_ops->launder_page(page);
612 * invalidate_inode_pages2_range - remove range of pages from an address_space
613 * @mapping: the address_space
614 * @start: the page offset 'from' which to invalidate
615 * @end: the page offset 'to' which to invalidate (inclusive)
617 * Any pages which are found to be mapped into pagetables are unmapped prior to
620 * Return: -EBUSY if any pages could not be invalidated.
622 int invalidate_inode_pages2_range(struct address_space *mapping,
623 pgoff_t start, pgoff_t end)
625 pgoff_t indices[PAGEVEC_SIZE];
626 struct folio_batch fbatch;
631 int did_range_unmap = 0;
633 if (mapping_empty(mapping))
636 folio_batch_init(&fbatch);
638 while (find_get_entries(mapping, index, end, &fbatch, indices)) {
639 for (i = 0; i < folio_batch_count(&fbatch); i++) {
640 struct folio *folio = fbatch.folios[i];
642 /* We rely upon deletion not changing folio->index */
645 if (xa_is_value(folio)) {
646 if (!invalidate_exceptional_entry2(mapping,
652 if (!did_range_unmap && folio_mapped(folio)) {
654 * If folio is mapped, before taking its lock,
655 * zap the rest of the file in one hit.
657 unmap_mapping_pages(mapping, index,
658 (1 + end - index), false);
663 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
664 if (folio->mapping != mapping) {
668 folio_wait_writeback(folio);
670 if (folio_mapped(folio))
671 unmap_mapping_folio(folio);
672 BUG_ON(folio_mapped(folio));
674 ret2 = do_launder_page(mapping, &folio->page);
676 if (!invalidate_complete_folio2(mapping, folio))
683 folio_batch_remove_exceptionals(&fbatch);
684 folio_batch_release(&fbatch);
689 * For DAX we invalidate page tables after invalidating page cache. We
690 * could invalidate page tables while invalidating each entry however
691 * that would be expensive. And doing range unmapping before doesn't
692 * work as we have no cheap way to find whether page cache entry didn't
693 * get remapped later.
695 if (dax_mapping(mapping)) {
696 unmap_mapping_pages(mapping, start, end - start + 1, false);
699 cleancache_invalidate_inode(mapping);
702 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
705 * invalidate_inode_pages2 - remove all pages from an address_space
706 * @mapping: the address_space
708 * Any pages which are found to be mapped into pagetables are unmapped prior to
711 * Return: -EBUSY if any pages could not be invalidated.
713 int invalidate_inode_pages2(struct address_space *mapping)
715 return invalidate_inode_pages2_range(mapping, 0, -1);
717 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
720 * truncate_pagecache - unmap and remove pagecache that has been truncated
722 * @newsize: new file size
724 * inode's new i_size must already be written before truncate_pagecache
727 * This function should typically be called before the filesystem
728 * releases resources associated with the freed range (eg. deallocates
729 * blocks). This way, pagecache will always stay logically coherent
730 * with on-disk format, and the filesystem would not have to deal with
731 * situations such as writepage being called for a page that has already
732 * had its underlying blocks deallocated.
734 void truncate_pagecache(struct inode *inode, loff_t newsize)
736 struct address_space *mapping = inode->i_mapping;
737 loff_t holebegin = round_up(newsize, PAGE_SIZE);
740 * unmap_mapping_range is called twice, first simply for
741 * efficiency so that truncate_inode_pages does fewer
742 * single-page unmaps. However after this first call, and
743 * before truncate_inode_pages finishes, it is possible for
744 * private pages to be COWed, which remain after
745 * truncate_inode_pages finishes, hence the second
746 * unmap_mapping_range call must be made for correctness.
748 unmap_mapping_range(mapping, holebegin, 0, 1);
749 truncate_inode_pages(mapping, newsize);
750 unmap_mapping_range(mapping, holebegin, 0, 1);
752 EXPORT_SYMBOL(truncate_pagecache);
755 * truncate_setsize - update inode and pagecache for a new file size
757 * @newsize: new file size
759 * truncate_setsize updates i_size and performs pagecache truncation (if
760 * necessary) to @newsize. It will be typically be called from the filesystem's
761 * setattr function when ATTR_SIZE is passed in.
763 * Must be called with a lock serializing truncates and writes (generally
764 * i_rwsem but e.g. xfs uses a different lock) and before all filesystem
765 * specific block truncation has been performed.
767 void truncate_setsize(struct inode *inode, loff_t newsize)
769 loff_t oldsize = inode->i_size;
771 i_size_write(inode, newsize);
772 if (newsize > oldsize)
773 pagecache_isize_extended(inode, oldsize, newsize);
774 truncate_pagecache(inode, newsize);
776 EXPORT_SYMBOL(truncate_setsize);
779 * pagecache_isize_extended - update pagecache after extension of i_size
780 * @inode: inode for which i_size was extended
781 * @from: original inode size
782 * @to: new inode size
784 * Handle extension of inode size either caused by extending truncate or by
785 * write starting after current i_size. We mark the page straddling current
786 * i_size RO so that page_mkwrite() is called on the nearest write access to
787 * the page. This way filesystem can be sure that page_mkwrite() is called on
788 * the page before user writes to the page via mmap after the i_size has been
791 * The function must be called after i_size is updated so that page fault
792 * coming after we unlock the page will already see the new i_size.
793 * The function must be called while we still hold i_rwsem - this not only
794 * makes sure i_size is stable but also that userspace cannot observe new
795 * i_size value before we are prepared to store mmap writes at new inode size.
797 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
799 int bsize = i_blocksize(inode);
804 WARN_ON(to > inode->i_size);
806 if (from >= to || bsize == PAGE_SIZE)
808 /* Page straddling @from will not have any hole block created? */
809 rounded_from = round_up(from, bsize);
810 if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
813 index = from >> PAGE_SHIFT;
814 page = find_lock_page(inode->i_mapping, index);
815 /* Page not cached? Nothing to do */
819 * See clear_page_dirty_for_io() for details why set_page_dirty()
822 if (page_mkclean(page))
823 set_page_dirty(page);
827 EXPORT_SYMBOL(pagecache_isize_extended);
830 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
832 * @lstart: offset of beginning of hole
833 * @lend: offset of last byte of hole
835 * This function should typically be called before the filesystem
836 * releases resources associated with the freed range (eg. deallocates
837 * blocks). This way, pagecache will always stay logically coherent
838 * with on-disk format, and the filesystem would not have to deal with
839 * situations such as writepage being called for a page that has already
840 * had its underlying blocks deallocated.
842 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
844 struct address_space *mapping = inode->i_mapping;
845 loff_t unmap_start = round_up(lstart, PAGE_SIZE);
846 loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
848 * This rounding is currently just for example: unmap_mapping_range
849 * expands its hole outwards, whereas we want it to contract the hole
850 * inwards. However, existing callers of truncate_pagecache_range are
851 * doing their own page rounding first. Note that unmap_mapping_range
852 * allows holelen 0 for all, and we allow lend -1 for end of file.
856 * Unlike in truncate_pagecache, unmap_mapping_range is called only
857 * once (before truncating pagecache), and without "even_cows" flag:
858 * hole-punching should not remove private COWed pages from the hole.
860 if ((u64)unmap_end > (u64)unmap_start)
861 unmap_mapping_range(mapping, unmap_start,
862 1 + unmap_end - unmap_start, 0);
863 truncate_inode_pages_range(mapping, lstart, lend);
865 EXPORT_SYMBOL(truncate_pagecache_range);