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/rmap.h>
29 * Regular page slots are stabilized by the page lock even without the tree
30 * itself locked. These unlocked entries need verification under the tree
33 static inline void __clear_shadow_entry(struct address_space *mapping,
34 pgoff_t index, void *entry)
36 XA_STATE(xas, &mapping->i_pages, index);
38 xas_set_update(&xas, workingset_update_node);
39 if (xas_load(&xas) != entry)
41 xas_store(&xas, NULL);
44 static void clear_shadow_entry(struct address_space *mapping, pgoff_t index,
47 spin_lock(&mapping->host->i_lock);
48 xa_lock_irq(&mapping->i_pages);
49 __clear_shadow_entry(mapping, index, entry);
50 xa_unlock_irq(&mapping->i_pages);
51 if (mapping_shrinkable(mapping))
52 inode_add_lru(mapping->host);
53 spin_unlock(&mapping->host->i_lock);
57 * Unconditionally remove exceptional entries. Usually called from truncate
58 * path. Note that the folio_batch may be altered by this function by removing
59 * exceptional entries similar to what folio_batch_remove_exceptionals() does.
61 static void truncate_folio_batch_exceptionals(struct address_space *mapping,
62 struct folio_batch *fbatch, pgoff_t *indices)
67 /* Handled by shmem itself */
68 if (shmem_mapping(mapping))
71 for (j = 0; j < folio_batch_count(fbatch); j++)
72 if (xa_is_value(fbatch->folios[j]))
75 if (j == folio_batch_count(fbatch))
78 dax = dax_mapping(mapping);
80 spin_lock(&mapping->host->i_lock);
81 xa_lock_irq(&mapping->i_pages);
84 for (i = j; i < folio_batch_count(fbatch); i++) {
85 struct folio *folio = fbatch->folios[i];
86 pgoff_t index = indices[i];
88 if (!xa_is_value(folio)) {
89 fbatch->folios[j++] = folio;
94 dax_delete_mapping_entry(mapping, index);
98 __clear_shadow_entry(mapping, index, folio);
102 xa_unlock_irq(&mapping->i_pages);
103 if (mapping_shrinkable(mapping))
104 inode_add_lru(mapping->host);
105 spin_unlock(&mapping->host->i_lock);
111 * Invalidate exceptional entry if easily possible. This handles exceptional
112 * entries for invalidate_inode_pages().
114 static int invalidate_exceptional_entry(struct address_space *mapping,
115 pgoff_t index, void *entry)
117 /* Handled by shmem itself, or for DAX we do nothing. */
118 if (shmem_mapping(mapping) || dax_mapping(mapping))
120 clear_shadow_entry(mapping, index, entry);
125 * Invalidate exceptional entry if clean. This handles exceptional entries for
126 * invalidate_inode_pages2() so for DAX it evicts only clean entries.
128 static int invalidate_exceptional_entry2(struct address_space *mapping,
129 pgoff_t index, void *entry)
131 /* Handled by shmem itself */
132 if (shmem_mapping(mapping))
134 if (dax_mapping(mapping))
135 return dax_invalidate_mapping_entry_sync(mapping, index);
136 clear_shadow_entry(mapping, index, entry);
141 * do_invalidatepage - invalidate part or all of a page
142 * @page: the page which is affected
143 * @offset: start of the range to invalidate
144 * @length: length of the range to invalidate
146 * do_invalidatepage() is called when all or part of the page has become
147 * invalidated by a truncate operation.
149 * do_invalidatepage() does not have to release all buffers, but it must
150 * ensure that no dirty buffer is left outside @offset and that no I/O
151 * is underway against any of the blocks which are outside the truncation
152 * point. Because the caller is about to free (and possibly reuse) those
155 void do_invalidatepage(struct page *page, unsigned int offset,
158 void (*invalidatepage)(struct page *, unsigned int, unsigned int);
160 invalidatepage = page->mapping->a_ops->invalidatepage;
163 invalidatepage = block_invalidatepage;
166 (*invalidatepage)(page, offset, length);
170 * If truncate cannot remove the fs-private metadata from the page, the page
171 * becomes orphaned. It will be left on the LRU and may even be mapped into
172 * user pagetables if we're racing with filemap_fault().
174 * We need to bail out if page->mapping is no longer equal to the original
175 * mapping. This happens a) when the VM reclaimed the page while we waited on
176 * its lock, b) when a concurrent invalidate_mapping_pages got there first and
177 * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space.
179 static void truncate_cleanup_folio(struct folio *folio)
181 if (folio_mapped(folio))
182 unmap_mapping_folio(folio);
184 if (folio_has_private(folio))
185 do_invalidatepage(&folio->page, 0, folio_size(folio));
188 * Some filesystems seem to re-dirty the page even after
189 * the VM has canceled the dirty bit (eg ext3 journaling).
190 * Hence dirty accounting check is placed after invalidation.
192 folio_cancel_dirty(folio);
193 folio_clear_mappedtodisk(folio);
196 int truncate_inode_folio(struct address_space *mapping, struct folio *folio)
198 if (folio->mapping != mapping)
201 truncate_cleanup_folio(folio);
202 filemap_remove_folio(folio);
207 * Handle partial folios. The folio may be entirely within the
208 * range if a split has raced with us. If not, we zero the part of the
209 * folio that's within the [start, end] range, and then split the folio if
210 * it's large. split_page_range() will discard pages which now lie beyond
211 * i_size, and we rely on the caller to discard pages which lie within a
212 * newly created hole.
214 * Returns false if splitting failed so the caller can avoid
215 * discarding the entire folio which is stubbornly unsplit.
217 bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
219 loff_t pos = folio_pos(folio);
220 unsigned int offset, length;
223 offset = start - pos;
226 length = folio_size(folio);
227 if (pos + length <= (u64)end)
228 length = length - offset;
230 length = end + 1 - pos - offset;
232 folio_wait_writeback(folio);
233 if (length == folio_size(folio)) {
234 truncate_inode_folio(folio->mapping, folio);
239 * We may be zeroing pages we're about to discard, but it avoids
240 * doing a complex calculation here, and then doing the zeroing
241 * anyway if the page split fails.
243 folio_zero_range(folio, offset, length);
245 if (folio_has_private(folio))
246 do_invalidatepage(&folio->page, offset, length);
247 if (!folio_test_large(folio))
249 if (split_huge_page(&folio->page) == 0)
251 if (folio_test_dirty(folio))
253 truncate_inode_folio(folio->mapping, folio);
258 * Used to get rid of pages on hardware memory corruption.
260 int generic_error_remove_page(struct address_space *mapping, struct page *page)
262 VM_BUG_ON_PAGE(PageTail(page), page);
267 * Only punch for normal data pages for now.
268 * Handling other types like directories would need more auditing.
270 if (!S_ISREG(mapping->host->i_mode))
272 return truncate_inode_folio(mapping, page_folio(page));
274 EXPORT_SYMBOL(generic_error_remove_page);
277 * Safely invalidate one page from its pagecache mapping.
278 * It only drops clean, unused pages. The page must be locked.
280 * Returns 1 if the page is successfully invalidated, otherwise 0.
282 int invalidate_inode_page(struct page *page)
284 struct folio *folio = page_folio(page);
285 struct address_space *mapping = folio_mapping(folio);
288 if (folio_test_dirty(folio) || folio_test_writeback(folio))
290 if (page_mapped(page))
292 if (folio_has_private(folio) && !filemap_release_folio(folio, 0))
295 return remove_mapping(mapping, page);
299 * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets
300 * @mapping: mapping to truncate
301 * @lstart: offset from which to truncate
302 * @lend: offset to which to truncate (inclusive)
304 * Truncate the page cache, removing the pages that are between
305 * specified offsets (and zeroing out partial pages
306 * if lstart or lend + 1 is not page aligned).
308 * Truncate takes two passes - the first pass is nonblocking. It will not
309 * block on page locks and it will not block on writeback. The second pass
310 * will wait. This is to prevent as much IO as possible in the affected region.
311 * The first pass will remove most pages, so the search cost of the second pass
314 * We pass down the cache-hot hint to the page freeing code. Even if the
315 * mapping is large, it is probably the case that the final pages are the most
316 * recently touched, and freeing happens in ascending file offset order.
318 * Note that since ->invalidatepage() accepts range to invalidate
319 * truncate_inode_pages_range is able to handle cases where lend + 1 is not
320 * page aligned properly.
322 void truncate_inode_pages_range(struct address_space *mapping,
323 loff_t lstart, loff_t lend)
325 pgoff_t start; /* inclusive */
326 pgoff_t end; /* exclusive */
327 struct folio_batch fbatch;
328 pgoff_t indices[PAGEVEC_SIZE];
334 if (mapping_empty(mapping))
338 * 'start' and 'end' always covers the range of pages to be fully
339 * truncated. Partial pages are covered with 'partial_start' at the
340 * start of the range and 'partial_end' at the end of the range.
341 * Note that 'end' is exclusive while 'lend' is inclusive.
343 start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT;
346 * lend == -1 indicates end-of-file so we have to set 'end'
347 * to the highest possible pgoff_t and since the type is
348 * unsigned we're using -1.
352 end = (lend + 1) >> PAGE_SHIFT;
354 folio_batch_init(&fbatch);
356 while (index < end && find_lock_entries(mapping, index, end - 1,
358 index = indices[folio_batch_count(&fbatch) - 1] + 1;
359 truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
360 for (i = 0; i < folio_batch_count(&fbatch); i++)
361 truncate_cleanup_folio(fbatch.folios[i]);
362 delete_from_page_cache_batch(mapping, &fbatch);
363 for (i = 0; i < folio_batch_count(&fbatch); i++)
364 folio_unlock(fbatch.folios[i]);
365 folio_batch_release(&fbatch);
369 same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT);
370 folio = __filemap_get_folio(mapping, lstart >> PAGE_SHIFT, FGP_LOCK, 0);
372 same_folio = lend < folio_pos(folio) + folio_size(folio);
373 if (!truncate_inode_partial_folio(folio, lstart, lend)) {
374 start = folio->index + folio_nr_pages(folio);
384 folio = __filemap_get_folio(mapping, lend >> PAGE_SHIFT,
387 if (!truncate_inode_partial_folio(folio, lstart, lend))
394 while (index < end) {
396 if (!find_get_entries(mapping, index, end - 1, &fbatch,
398 /* If all gone from start onwards, we're done */
401 /* Otherwise restart to make sure all gone */
406 for (i = 0; i < folio_batch_count(&fbatch); i++) {
407 struct folio *folio = fbatch.folios[i];
409 /* We rely upon deletion not changing page->index */
412 if (xa_is_value(folio))
416 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
417 folio_wait_writeback(folio);
418 truncate_inode_folio(mapping, folio);
420 index = folio_index(folio) + folio_nr_pages(folio) - 1;
422 truncate_folio_batch_exceptionals(mapping, &fbatch, indices);
423 folio_batch_release(&fbatch);
427 EXPORT_SYMBOL(truncate_inode_pages_range);
430 * truncate_inode_pages - truncate *all* the pages from an offset
431 * @mapping: mapping to truncate
432 * @lstart: offset from which to truncate
434 * Called under (and serialised by) inode->i_rwsem and
435 * mapping->invalidate_lock.
437 * Note: When this function returns, there can be a page in the process of
438 * deletion (inside __delete_from_page_cache()) in the specified range. Thus
439 * mapping->nrpages can be non-zero when this function returns even after
440 * truncation of the whole mapping.
442 void truncate_inode_pages(struct address_space *mapping, loff_t lstart)
444 truncate_inode_pages_range(mapping, lstart, (loff_t)-1);
446 EXPORT_SYMBOL(truncate_inode_pages);
449 * truncate_inode_pages_final - truncate *all* pages before inode dies
450 * @mapping: mapping to truncate
452 * Called under (and serialized by) inode->i_rwsem.
454 * Filesystems have to use this in the .evict_inode path to inform the
455 * VM that this is the final truncate and the inode is going away.
457 void truncate_inode_pages_final(struct address_space *mapping)
460 * Page reclaim can not participate in regular inode lifetime
461 * management (can't call iput()) and thus can race with the
462 * inode teardown. Tell it when the address space is exiting,
463 * so that it does not install eviction information after the
464 * final truncate has begun.
466 mapping_set_exiting(mapping);
468 if (!mapping_empty(mapping)) {
470 * As truncation uses a lockless tree lookup, cycle
471 * the tree lock to make sure any ongoing tree
472 * modification that does not see AS_EXITING is
473 * completed before starting the final truncate.
475 xa_lock_irq(&mapping->i_pages);
476 xa_unlock_irq(&mapping->i_pages);
479 truncate_inode_pages(mapping, 0);
481 EXPORT_SYMBOL(truncate_inode_pages_final);
483 static unsigned long __invalidate_mapping_pages(struct address_space *mapping,
484 pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
486 pgoff_t indices[PAGEVEC_SIZE];
487 struct folio_batch fbatch;
488 pgoff_t index = start;
490 unsigned long count = 0;
493 folio_batch_init(&fbatch);
494 while (find_lock_entries(mapping, index, end, &fbatch, indices)) {
495 for (i = 0; i < folio_batch_count(&fbatch); i++) {
496 struct page *page = &fbatch.folios[i]->page;
498 /* We rely upon deletion not changing page->index */
501 if (xa_is_value(page)) {
502 count += invalidate_exceptional_entry(mapping,
507 index += thp_nr_pages(page) - 1;
509 ret = invalidate_inode_page(page);
512 * Invalidation is a hint that the page is no longer
513 * of interest and try to speed up its reclaim.
516 deactivate_file_page(page);
517 /* It is likely on the pagevec of a remote CPU */
523 folio_batch_remove_exceptionals(&fbatch);
524 folio_batch_release(&fbatch);
532 * invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode
533 * @mapping: the address_space which holds the cache to invalidate
534 * @start: the offset 'from' which to invalidate
535 * @end: the offset 'to' which to invalidate (inclusive)
537 * This function removes pages that are clean, unmapped and unlocked,
538 * as well as shadow entries. It will not block on IO activity.
540 * If you want to remove all the pages of one inode, regardless of
541 * their use and writeback state, use truncate_inode_pages().
543 * Return: the number of the cache entries that were invalidated
545 unsigned long invalidate_mapping_pages(struct address_space *mapping,
546 pgoff_t start, pgoff_t end)
548 return __invalidate_mapping_pages(mapping, start, end, NULL);
550 EXPORT_SYMBOL(invalidate_mapping_pages);
553 * invalidate_mapping_pagevec - Invalidate all the unlocked pages of one inode
554 * @mapping: the address_space which holds the pages to invalidate
555 * @start: the offset 'from' which to invalidate
556 * @end: the offset 'to' which to invalidate (inclusive)
557 * @nr_pagevec: invalidate failed page number for caller
559 * This helper is similar to invalidate_mapping_pages(), except that it accounts
560 * for pages that are likely on a pagevec and counts them in @nr_pagevec, which
561 * will be used by the caller.
563 void invalidate_mapping_pagevec(struct address_space *mapping,
564 pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
566 __invalidate_mapping_pages(mapping, start, end, nr_pagevec);
570 * This is like invalidate_inode_page(), except it ignores the page's
571 * refcount. We do this because invalidate_inode_pages2() needs stronger
572 * invalidation guarantees, and cannot afford to leave pages behind because
573 * shrink_page_list() has a temp ref on them, or because they're transiently
574 * sitting in the lru_cache_add() pagevecs.
576 static int invalidate_complete_folio2(struct address_space *mapping,
579 if (folio->mapping != mapping)
582 if (folio_has_private(folio) &&
583 !filemap_release_folio(folio, GFP_KERNEL))
586 spin_lock(&mapping->host->i_lock);
587 xa_lock_irq(&mapping->i_pages);
588 if (folio_test_dirty(folio))
591 BUG_ON(folio_has_private(folio));
592 __filemap_remove_folio(folio, NULL);
593 xa_unlock_irq(&mapping->i_pages);
594 if (mapping_shrinkable(mapping))
595 inode_add_lru(mapping->host);
596 spin_unlock(&mapping->host->i_lock);
598 filemap_free_folio(mapping, folio);
601 xa_unlock_irq(&mapping->i_pages);
602 spin_unlock(&mapping->host->i_lock);
606 static int do_launder_folio(struct address_space *mapping, struct folio *folio)
608 if (!folio_test_dirty(folio))
610 if (folio->mapping != mapping || mapping->a_ops->launder_page == NULL)
612 return mapping->a_ops->launder_page(&folio->page);
616 * invalidate_inode_pages2_range - remove range of pages from an address_space
617 * @mapping: the address_space
618 * @start: the page offset 'from' which to invalidate
619 * @end: the page offset 'to' which to invalidate (inclusive)
621 * Any pages which are found to be mapped into pagetables are unmapped prior to
624 * Return: -EBUSY if any pages could not be invalidated.
626 int invalidate_inode_pages2_range(struct address_space *mapping,
627 pgoff_t start, pgoff_t end)
629 pgoff_t indices[PAGEVEC_SIZE];
630 struct folio_batch fbatch;
635 int did_range_unmap = 0;
637 if (mapping_empty(mapping))
640 folio_batch_init(&fbatch);
642 while (find_get_entries(mapping, index, end, &fbatch, indices)) {
643 for (i = 0; i < folio_batch_count(&fbatch); i++) {
644 struct folio *folio = fbatch.folios[i];
646 /* We rely upon deletion not changing folio->index */
649 if (xa_is_value(folio)) {
650 if (!invalidate_exceptional_entry2(mapping,
656 if (!did_range_unmap && folio_mapped(folio)) {
658 * If folio is mapped, before taking its lock,
659 * zap the rest of the file in one hit.
661 unmap_mapping_pages(mapping, index,
662 (1 + end - index), false);
667 VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
668 if (folio->mapping != mapping) {
672 folio_wait_writeback(folio);
674 if (folio_mapped(folio))
675 unmap_mapping_folio(folio);
676 BUG_ON(folio_mapped(folio));
678 ret2 = do_launder_folio(mapping, folio);
680 if (!invalidate_complete_folio2(mapping, folio))
687 folio_batch_remove_exceptionals(&fbatch);
688 folio_batch_release(&fbatch);
693 * For DAX we invalidate page tables after invalidating page cache. We
694 * could invalidate page tables while invalidating each entry however
695 * that would be expensive. And doing range unmapping before doesn't
696 * work as we have no cheap way to find whether page cache entry didn't
697 * get remapped later.
699 if (dax_mapping(mapping)) {
700 unmap_mapping_pages(mapping, start, end - start + 1, false);
704 EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range);
707 * invalidate_inode_pages2 - remove all pages from an address_space
708 * @mapping: the address_space
710 * Any pages which are found to be mapped into pagetables are unmapped prior to
713 * Return: -EBUSY if any pages could not be invalidated.
715 int invalidate_inode_pages2(struct address_space *mapping)
717 return invalidate_inode_pages2_range(mapping, 0, -1);
719 EXPORT_SYMBOL_GPL(invalidate_inode_pages2);
722 * truncate_pagecache - unmap and remove pagecache that has been truncated
724 * @newsize: new file size
726 * inode's new i_size must already be written before truncate_pagecache
729 * This function should typically be called before the filesystem
730 * releases resources associated with the freed range (eg. deallocates
731 * blocks). This way, pagecache will always stay logically coherent
732 * with on-disk format, and the filesystem would not have to deal with
733 * situations such as writepage being called for a page that has already
734 * had its underlying blocks deallocated.
736 void truncate_pagecache(struct inode *inode, loff_t newsize)
738 struct address_space *mapping = inode->i_mapping;
739 loff_t holebegin = round_up(newsize, PAGE_SIZE);
742 * unmap_mapping_range is called twice, first simply for
743 * efficiency so that truncate_inode_pages does fewer
744 * single-page unmaps. However after this first call, and
745 * before truncate_inode_pages finishes, it is possible for
746 * private pages to be COWed, which remain after
747 * truncate_inode_pages finishes, hence the second
748 * unmap_mapping_range call must be made for correctness.
750 unmap_mapping_range(mapping, holebegin, 0, 1);
751 truncate_inode_pages(mapping, newsize);
752 unmap_mapping_range(mapping, holebegin, 0, 1);
754 EXPORT_SYMBOL(truncate_pagecache);
757 * truncate_setsize - update inode and pagecache for a new file size
759 * @newsize: new file size
761 * truncate_setsize updates i_size and performs pagecache truncation (if
762 * necessary) to @newsize. It will be typically be called from the filesystem's
763 * setattr function when ATTR_SIZE is passed in.
765 * Must be called with a lock serializing truncates and writes (generally
766 * i_rwsem but e.g. xfs uses a different lock) and before all filesystem
767 * specific block truncation has been performed.
769 void truncate_setsize(struct inode *inode, loff_t newsize)
771 loff_t oldsize = inode->i_size;
773 i_size_write(inode, newsize);
774 if (newsize > oldsize)
775 pagecache_isize_extended(inode, oldsize, newsize);
776 truncate_pagecache(inode, newsize);
778 EXPORT_SYMBOL(truncate_setsize);
781 * pagecache_isize_extended - update pagecache after extension of i_size
782 * @inode: inode for which i_size was extended
783 * @from: original inode size
784 * @to: new inode size
786 * Handle extension of inode size either caused by extending truncate or by
787 * write starting after current i_size. We mark the page straddling current
788 * i_size RO so that page_mkwrite() is called on the nearest write access to
789 * the page. This way filesystem can be sure that page_mkwrite() is called on
790 * the page before user writes to the page via mmap after the i_size has been
793 * The function must be called after i_size is updated so that page fault
794 * coming after we unlock the page will already see the new i_size.
795 * The function must be called while we still hold i_rwsem - this not only
796 * makes sure i_size is stable but also that userspace cannot observe new
797 * i_size value before we are prepared to store mmap writes at new inode size.
799 void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to)
801 int bsize = i_blocksize(inode);
806 WARN_ON(to > inode->i_size);
808 if (from >= to || bsize == PAGE_SIZE)
810 /* Page straddling @from will not have any hole block created? */
811 rounded_from = round_up(from, bsize);
812 if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1)))
815 index = from >> PAGE_SHIFT;
816 page = find_lock_page(inode->i_mapping, index);
817 /* Page not cached? Nothing to do */
821 * See clear_page_dirty_for_io() for details why set_page_dirty()
824 if (page_mkclean(page))
825 set_page_dirty(page);
829 EXPORT_SYMBOL(pagecache_isize_extended);
832 * truncate_pagecache_range - unmap and remove pagecache that is hole-punched
834 * @lstart: offset of beginning of hole
835 * @lend: offset of last byte of hole
837 * This function should typically be called before the filesystem
838 * releases resources associated with the freed range (eg. deallocates
839 * blocks). This way, pagecache will always stay logically coherent
840 * with on-disk format, and the filesystem would not have to deal with
841 * situations such as writepage being called for a page that has already
842 * had its underlying blocks deallocated.
844 void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend)
846 struct address_space *mapping = inode->i_mapping;
847 loff_t unmap_start = round_up(lstart, PAGE_SIZE);
848 loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1;
850 * This rounding is currently just for example: unmap_mapping_range
851 * expands its hole outwards, whereas we want it to contract the hole
852 * inwards. However, existing callers of truncate_pagecache_range are
853 * doing their own page rounding first. Note that unmap_mapping_range
854 * allows holelen 0 for all, and we allow lend -1 for end of file.
858 * Unlike in truncate_pagecache, unmap_mapping_range is called only
859 * once (before truncating pagecache), and without "even_cows" flag:
860 * hole-punching should not remove private COWed pages from the hole.
862 if ((u64)unmap_end > (u64)unmap_start)
863 unmap_mapping_range(mapping, unmap_start,
864 1 + unmap_end - unmap_start, 0);
865 truncate_inode_pages_range(mapping, lstart, lend);
867 EXPORT_SYMBOL(truncate_pagecache_range);