// SPDX-License-Identifier: GPL-2.0-only /* * mm/truncate.c - code for taking down pages from address_spaces * * Copyright (C) 2002, Linus Torvalds * * 10Sep2002 Andrew Morton * Initial version. */ #include #include #include #include #include #include #include #include #include #include #include #include /* grr. try_to_release_page */ #include #include #include "internal.h" /* * Regular page slots are stabilized by the page lock even without the tree * itself locked. These unlocked entries need verification under the tree * lock. */ static inline void __clear_shadow_entry(struct address_space *mapping, pgoff_t index, void *entry) { XA_STATE(xas, &mapping->i_pages, index); xas_set_update(&xas, workingset_update_node); if (xas_load(&xas) != entry) return; xas_store(&xas, NULL); } static void clear_shadow_entry(struct address_space *mapping, pgoff_t index, void *entry) { spin_lock(&mapping->host->i_lock); xa_lock_irq(&mapping->i_pages); __clear_shadow_entry(mapping, index, entry); xa_unlock_irq(&mapping->i_pages); if (mapping_shrinkable(mapping)) inode_add_lru(mapping->host); spin_unlock(&mapping->host->i_lock); } /* * Unconditionally remove exceptional entries. Usually called from truncate * path. Note that the folio_batch may be altered by this function by removing * exceptional entries similar to what folio_batch_remove_exceptionals() does. */ static void truncate_folio_batch_exceptionals(struct address_space *mapping, struct folio_batch *fbatch, pgoff_t *indices) { int i, j; bool dax; /* Handled by shmem itself */ if (shmem_mapping(mapping)) return; for (j = 0; j < folio_batch_count(fbatch); j++) if (xa_is_value(fbatch->folios[j])) break; if (j == folio_batch_count(fbatch)) return; dax = dax_mapping(mapping); if (!dax) { spin_lock(&mapping->host->i_lock); xa_lock_irq(&mapping->i_pages); } for (i = j; i < folio_batch_count(fbatch); i++) { struct folio *folio = fbatch->folios[i]; pgoff_t index = indices[i]; if (!xa_is_value(folio)) { fbatch->folios[j++] = folio; continue; } if (unlikely(dax)) { dax_delete_mapping_entry(mapping, index); continue; } __clear_shadow_entry(mapping, index, folio); } if (!dax) { xa_unlock_irq(&mapping->i_pages); if (mapping_shrinkable(mapping)) inode_add_lru(mapping->host); spin_unlock(&mapping->host->i_lock); } fbatch->nr = j; } /* * Invalidate exceptional entry if easily possible. This handles exceptional * entries for invalidate_inode_pages(). */ static int invalidate_exceptional_entry(struct address_space *mapping, pgoff_t index, void *entry) { /* Handled by shmem itself, or for DAX we do nothing. */ if (shmem_mapping(mapping) || dax_mapping(mapping)) return 1; clear_shadow_entry(mapping, index, entry); return 1; } /* * Invalidate exceptional entry if clean. This handles exceptional entries for * invalidate_inode_pages2() so for DAX it evicts only clean entries. */ static int invalidate_exceptional_entry2(struct address_space *mapping, pgoff_t index, void *entry) { /* Handled by shmem itself */ if (shmem_mapping(mapping)) return 1; if (dax_mapping(mapping)) return dax_invalidate_mapping_entry_sync(mapping, index); clear_shadow_entry(mapping, index, entry); return 1; } /** * folio_invalidate - Invalidate part or all of a folio. * @folio: The folio which is affected. * @offset: start of the range to invalidate * @length: length of the range to invalidate * * folio_invalidate() is called when all or part of the folio has become * invalidated by a truncate operation. * * folio_invalidate() does not have to release all buffers, but it must * ensure that no dirty buffer is left outside @offset and that no I/O * is underway against any of the blocks which are outside the truncation * point. Because the caller is about to free (and possibly reuse) those * blocks on-disk. */ void folio_invalidate(struct folio *folio, size_t offset, size_t length) { const struct address_space_operations *aops = folio->mapping->a_ops; if (aops->invalidate_folio) aops->invalidate_folio(folio, offset, length); } EXPORT_SYMBOL_GPL(folio_invalidate); /* * If truncate cannot remove the fs-private metadata from the page, the page * becomes orphaned. It will be left on the LRU and may even be mapped into * user pagetables if we're racing with filemap_fault(). * * We need to bail out if page->mapping is no longer equal to the original * mapping. This happens a) when the VM reclaimed the page while we waited on * its lock, b) when a concurrent invalidate_mapping_pages got there first and * c) when tmpfs swizzles a page between a tmpfs inode and swapper_space. */ static void truncate_cleanup_folio(struct folio *folio) { if (folio_mapped(folio)) unmap_mapping_folio(folio); if (folio_has_private(folio)) folio_invalidate(folio, 0, folio_size(folio)); /* * Some filesystems seem to re-dirty the page even after * the VM has canceled the dirty bit (eg ext3 journaling). * Hence dirty accounting check is placed after invalidation. */ folio_cancel_dirty(folio); folio_clear_mappedtodisk(folio); } int truncate_inode_folio(struct address_space *mapping, struct folio *folio) { if (folio->mapping != mapping) return -EIO; truncate_cleanup_folio(folio); filemap_remove_folio(folio); return 0; } /* * Handle partial folios. The folio may be entirely within the * range if a split has raced with us. If not, we zero the part of the * folio that's within the [start, end] range, and then split the folio if * it's large. split_page_range() will discard pages which now lie beyond * i_size, and we rely on the caller to discard pages which lie within a * newly created hole. * * Returns false if splitting failed so the caller can avoid * discarding the entire folio which is stubbornly unsplit. */ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end) { loff_t pos = folio_pos(folio); unsigned int offset, length; if (pos < start) offset = start - pos; else offset = 0; length = folio_size(folio); if (pos + length <= (u64)end) length = length - offset; else length = end + 1 - pos - offset; folio_wait_writeback(folio); if (length == folio_size(folio)) { truncate_inode_folio(folio->mapping, folio); return true; } /* * We may be zeroing pages we're about to discard, but it avoids * doing a complex calculation here, and then doing the zeroing * anyway if the page split fails. */ folio_zero_range(folio, offset, length); if (folio_has_private(folio)) folio_invalidate(folio, offset, length); if (!folio_test_large(folio)) return true; if (split_huge_page(&folio->page) == 0) return true; if (folio_test_dirty(folio)) return false; truncate_inode_folio(folio->mapping, folio); return true; } /* * Used to get rid of pages on hardware memory corruption. */ int generic_error_remove_page(struct address_space *mapping, struct page *page) { VM_BUG_ON_PAGE(PageTail(page), page); if (!mapping) return -EINVAL; /* * Only punch for normal data pages for now. * Handling other types like directories would need more auditing. */ if (!S_ISREG(mapping->host->i_mode)) return -EIO; return truncate_inode_folio(mapping, page_folio(page)); } EXPORT_SYMBOL(generic_error_remove_page); static long mapping_evict_folio(struct address_space *mapping, struct folio *folio) { if (folio_test_dirty(folio) || folio_test_writeback(folio)) return 0; /* The refcount will be elevated if any page in the folio is mapped */ if (folio_ref_count(folio) > folio_nr_pages(folio) + folio_has_private(folio) + 1) return 0; if (folio_has_private(folio) && !filemap_release_folio(folio, 0)) return 0; return remove_mapping(mapping, folio); } /** * invalidate_inode_page() - Remove an unused page from the pagecache. * @page: The page to remove. * * Safely invalidate one page from its pagecache mapping. * It only drops clean, unused pages. * * Context: Page must be locked. * Return: The number of pages successfully removed. */ long invalidate_inode_page(struct page *page) { struct folio *folio = page_folio(page); struct address_space *mapping = folio_mapping(folio); /* The page may have been truncated before it was locked */ if (!mapping) return 0; return mapping_evict_folio(mapping, folio); } /** * truncate_inode_pages_range - truncate range of pages specified by start & end byte offsets * @mapping: mapping to truncate * @lstart: offset from which to truncate * @lend: offset to which to truncate (inclusive) * * Truncate the page cache, removing the pages that are between * specified offsets (and zeroing out partial pages * if lstart or lend + 1 is not page aligned). * * Truncate takes two passes - the first pass is nonblocking. It will not * block on page locks and it will not block on writeback. The second pass * will wait. This is to prevent as much IO as possible in the affected region. * The first pass will remove most pages, so the search cost of the second pass * is low. * * We pass down the cache-hot hint to the page freeing code. Even if the * mapping is large, it is probably the case that the final pages are the most * recently touched, and freeing happens in ascending file offset order. * * Note that since ->invalidate_folio() accepts range to invalidate * truncate_inode_pages_range is able to handle cases where lend + 1 is not * page aligned properly. */ void truncate_inode_pages_range(struct address_space *mapping, loff_t lstart, loff_t lend) { pgoff_t start; /* inclusive */ pgoff_t end; /* exclusive */ struct folio_batch fbatch; pgoff_t indices[PAGEVEC_SIZE]; pgoff_t index; int i; struct folio *folio; bool same_folio; if (mapping_empty(mapping)) return; /* * 'start' and 'end' always covers the range of pages to be fully * truncated. Partial pages are covered with 'partial_start' at the * start of the range and 'partial_end' at the end of the range. * Note that 'end' is exclusive while 'lend' is inclusive. */ start = (lstart + PAGE_SIZE - 1) >> PAGE_SHIFT; if (lend == -1) /* * lend == -1 indicates end-of-file so we have to set 'end' * to the highest possible pgoff_t and since the type is * unsigned we're using -1. */ end = -1; else end = (lend + 1) >> PAGE_SHIFT; folio_batch_init(&fbatch); index = start; while (index < end && find_lock_entries(mapping, index, end - 1, &fbatch, indices)) { index = indices[folio_batch_count(&fbatch) - 1] + 1; truncate_folio_batch_exceptionals(mapping, &fbatch, indices); for (i = 0; i < folio_batch_count(&fbatch); i++) truncate_cleanup_folio(fbatch.folios[i]); delete_from_page_cache_batch(mapping, &fbatch); for (i = 0; i < folio_batch_count(&fbatch); i++) folio_unlock(fbatch.folios[i]); folio_batch_release(&fbatch); cond_resched(); } same_folio = (lstart >> PAGE_SHIFT) == (lend >> PAGE_SHIFT); folio = __filemap_get_folio(mapping, lstart >> PAGE_SHIFT, FGP_LOCK, 0); if (folio) { same_folio = lend < folio_pos(folio) + folio_size(folio); if (!truncate_inode_partial_folio(folio, lstart, lend)) { start = folio->index + folio_nr_pages(folio); if (same_folio) end = folio->index; } folio_unlock(folio); folio_put(folio); folio = NULL; } if (!same_folio) folio = __filemap_get_folio(mapping, lend >> PAGE_SHIFT, FGP_LOCK, 0); if (folio) { if (!truncate_inode_partial_folio(folio, lstart, lend)) end = folio->index; folio_unlock(folio); folio_put(folio); } index = start; while (index < end) { cond_resched(); if (!find_get_entries(mapping, index, end - 1, &fbatch, indices)) { /* If all gone from start onwards, we're done */ if (index == start) break; /* Otherwise restart to make sure all gone */ index = start; continue; } for (i = 0; i < folio_batch_count(&fbatch); i++) { struct folio *folio = fbatch.folios[i]; /* We rely upon deletion not changing page->index */ index = indices[i]; if (xa_is_value(folio)) continue; folio_lock(folio); VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); folio_wait_writeback(folio); truncate_inode_folio(mapping, folio); folio_unlock(folio); index = folio_index(folio) + folio_nr_pages(folio) - 1; } truncate_folio_batch_exceptionals(mapping, &fbatch, indices); folio_batch_release(&fbatch); index++; } } EXPORT_SYMBOL(truncate_inode_pages_range); /** * truncate_inode_pages - truncate *all* the pages from an offset * @mapping: mapping to truncate * @lstart: offset from which to truncate * * Called under (and serialised by) inode->i_rwsem and * mapping->invalidate_lock. * * Note: When this function returns, there can be a page in the process of * deletion (inside __delete_from_page_cache()) in the specified range. Thus * mapping->nrpages can be non-zero when this function returns even after * truncation of the whole mapping. */ void truncate_inode_pages(struct address_space *mapping, loff_t lstart) { truncate_inode_pages_range(mapping, lstart, (loff_t)-1); } EXPORT_SYMBOL(truncate_inode_pages); /** * truncate_inode_pages_final - truncate *all* pages before inode dies * @mapping: mapping to truncate * * Called under (and serialized by) inode->i_rwsem. * * Filesystems have to use this in the .evict_inode path to inform the * VM that this is the final truncate and the inode is going away. */ void truncate_inode_pages_final(struct address_space *mapping) { /* * Page reclaim can not participate in regular inode lifetime * management (can't call iput()) and thus can race with the * inode teardown. Tell it when the address space is exiting, * so that it does not install eviction information after the * final truncate has begun. */ mapping_set_exiting(mapping); if (!mapping_empty(mapping)) { /* * As truncation uses a lockless tree lookup, cycle * the tree lock to make sure any ongoing tree * modification that does not see AS_EXITING is * completed before starting the final truncate. */ xa_lock_irq(&mapping->i_pages); xa_unlock_irq(&mapping->i_pages); } truncate_inode_pages(mapping, 0); } EXPORT_SYMBOL(truncate_inode_pages_final); /** * invalidate_mapping_pagevec - Invalidate all the unlocked pages of one inode * @mapping: the address_space which holds the pages to invalidate * @start: the offset 'from' which to invalidate * @end: the offset 'to' which to invalidate (inclusive) * @nr_pagevec: invalidate failed page number for caller * * This helper is similar to invalidate_mapping_pages(), except that it accounts * for pages that are likely on a pagevec and counts them in @nr_pagevec, which * will be used by the caller. */ unsigned long invalidate_mapping_pagevec(struct address_space *mapping, pgoff_t start, pgoff_t end, unsigned long *nr_pagevec) { pgoff_t indices[PAGEVEC_SIZE]; struct folio_batch fbatch; pgoff_t index = start; unsigned long ret; unsigned long count = 0; int i; folio_batch_init(&fbatch); while (find_lock_entries(mapping, index, end, &fbatch, indices)) { for (i = 0; i < folio_batch_count(&fbatch); i++) { struct folio *folio = fbatch.folios[i]; /* We rely upon deletion not changing folio->index */ index = indices[i]; if (xa_is_value(folio)) { count += invalidate_exceptional_entry(mapping, index, folio); continue; } index += folio_nr_pages(folio) - 1; ret = mapping_evict_folio(mapping, folio); folio_unlock(folio); /* * Invalidation is a hint that the folio is no longer * of interest and try to speed up its reclaim. */ if (!ret) { deactivate_file_folio(folio); /* It is likely on the pagevec of a remote CPU */ if (nr_pagevec) (*nr_pagevec)++; } count += ret; } folio_batch_remove_exceptionals(&fbatch); folio_batch_release(&fbatch); cond_resched(); index++; } return count; } /** * invalidate_mapping_pages - Invalidate all clean, unlocked cache of one inode * @mapping: the address_space which holds the cache to invalidate * @start: the offset 'from' which to invalidate * @end: the offset 'to' which to invalidate (inclusive) * * This function removes pages that are clean, unmapped and unlocked, * as well as shadow entries. It will not block on IO activity. * * If you want to remove all the pages of one inode, regardless of * their use and writeback state, use truncate_inode_pages(). * * Return: the number of the cache entries that were invalidated */ unsigned long invalidate_mapping_pages(struct address_space *mapping, pgoff_t start, pgoff_t end) { return invalidate_mapping_pagevec(mapping, start, end, NULL); } EXPORT_SYMBOL(invalidate_mapping_pages); /* * This is like invalidate_inode_page(), except it ignores the page's * refcount. We do this because invalidate_inode_pages2() needs stronger * invalidation guarantees, and cannot afford to leave pages behind because * shrink_page_list() has a temp ref on them, or because they're transiently * sitting in the lru_cache_add() pagevecs. */ static int invalidate_complete_folio2(struct address_space *mapping, struct folio *folio) { if (folio->mapping != mapping) return 0; if (folio_has_private(folio) && !filemap_release_folio(folio, GFP_KERNEL)) return 0; spin_lock(&mapping->host->i_lock); xa_lock_irq(&mapping->i_pages); if (folio_test_dirty(folio)) goto failed; BUG_ON(folio_has_private(folio)); __filemap_remove_folio(folio, NULL); xa_unlock_irq(&mapping->i_pages); if (mapping_shrinkable(mapping)) inode_add_lru(mapping->host); spin_unlock(&mapping->host->i_lock); filemap_free_folio(mapping, folio); return 1; failed: xa_unlock_irq(&mapping->i_pages); spin_unlock(&mapping->host->i_lock); return 0; } static int folio_launder(struct address_space *mapping, struct folio *folio) { if (!folio_test_dirty(folio)) return 0; if (folio->mapping != mapping || mapping->a_ops->launder_folio == NULL) return 0; return mapping->a_ops->launder_folio(folio); } /** * invalidate_inode_pages2_range - remove range of pages from an address_space * @mapping: the address_space * @start: the page offset 'from' which to invalidate * @end: the page offset 'to' which to invalidate (inclusive) * * Any pages which are found to be mapped into pagetables are unmapped prior to * invalidation. * * Return: -EBUSY if any pages could not be invalidated. */ int invalidate_inode_pages2_range(struct address_space *mapping, pgoff_t start, pgoff_t end) { pgoff_t indices[PAGEVEC_SIZE]; struct folio_batch fbatch; pgoff_t index; int i; int ret = 0; int ret2 = 0; int did_range_unmap = 0; if (mapping_empty(mapping)) return 0; folio_batch_init(&fbatch); index = start; while (find_get_entries(mapping, index, end, &fbatch, indices)) { for (i = 0; i < folio_batch_count(&fbatch); i++) { struct folio *folio = fbatch.folios[i]; /* We rely upon deletion not changing folio->index */ index = indices[i]; if (xa_is_value(folio)) { if (!invalidate_exceptional_entry2(mapping, index, folio)) ret = -EBUSY; continue; } if (!did_range_unmap && folio_mapped(folio)) { /* * If folio is mapped, before taking its lock, * zap the rest of the file in one hit. */ unmap_mapping_pages(mapping, index, (1 + end - index), false); did_range_unmap = 1; } folio_lock(folio); VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio); if (folio->mapping != mapping) { folio_unlock(folio); continue; } folio_wait_writeback(folio); if (folio_mapped(folio)) unmap_mapping_folio(folio); BUG_ON(folio_mapped(folio)); ret2 = folio_launder(mapping, folio); if (ret2 == 0) { if (!invalidate_complete_folio2(mapping, folio)) ret2 = -EBUSY; } if (ret2 < 0) ret = ret2; folio_unlock(folio); } folio_batch_remove_exceptionals(&fbatch); folio_batch_release(&fbatch); cond_resched(); index++; } /* * For DAX we invalidate page tables after invalidating page cache. We * could invalidate page tables while invalidating each entry however * that would be expensive. And doing range unmapping before doesn't * work as we have no cheap way to find whether page cache entry didn't * get remapped later. */ if (dax_mapping(mapping)) { unmap_mapping_pages(mapping, start, end - start + 1, false); } return ret; } EXPORT_SYMBOL_GPL(invalidate_inode_pages2_range); /** * invalidate_inode_pages2 - remove all pages from an address_space * @mapping: the address_space * * Any pages which are found to be mapped into pagetables are unmapped prior to * invalidation. * * Return: -EBUSY if any pages could not be invalidated. */ int invalidate_inode_pages2(struct address_space *mapping) { return invalidate_inode_pages2_range(mapping, 0, -1); } EXPORT_SYMBOL_GPL(invalidate_inode_pages2); /** * truncate_pagecache - unmap and remove pagecache that has been truncated * @inode: inode * @newsize: new file size * * inode's new i_size must already be written before truncate_pagecache * is called. * * This function should typically be called before the filesystem * releases resources associated with the freed range (eg. deallocates * blocks). This way, pagecache will always stay logically coherent * with on-disk format, and the filesystem would not have to deal with * situations such as writepage being called for a page that has already * had its underlying blocks deallocated. */ void truncate_pagecache(struct inode *inode, loff_t newsize) { struct address_space *mapping = inode->i_mapping; loff_t holebegin = round_up(newsize, PAGE_SIZE); /* * unmap_mapping_range is called twice, first simply for * efficiency so that truncate_inode_pages does fewer * single-page unmaps. However after this first call, and * before truncate_inode_pages finishes, it is possible for * private pages to be COWed, which remain after * truncate_inode_pages finishes, hence the second * unmap_mapping_range call must be made for correctness. */ unmap_mapping_range(mapping, holebegin, 0, 1); truncate_inode_pages(mapping, newsize); unmap_mapping_range(mapping, holebegin, 0, 1); } EXPORT_SYMBOL(truncate_pagecache); /** * truncate_setsize - update inode and pagecache for a new file size * @inode: inode * @newsize: new file size * * truncate_setsize updates i_size and performs pagecache truncation (if * necessary) to @newsize. It will be typically be called from the filesystem's * setattr function when ATTR_SIZE is passed in. * * Must be called with a lock serializing truncates and writes (generally * i_rwsem but e.g. xfs uses a different lock) and before all filesystem * specific block truncation has been performed. */ void truncate_setsize(struct inode *inode, loff_t newsize) { loff_t oldsize = inode->i_size; i_size_write(inode, newsize); if (newsize > oldsize) pagecache_isize_extended(inode, oldsize, newsize); truncate_pagecache(inode, newsize); } EXPORT_SYMBOL(truncate_setsize); /** * pagecache_isize_extended - update pagecache after extension of i_size * @inode: inode for which i_size was extended * @from: original inode size * @to: new inode size * * Handle extension of inode size either caused by extending truncate or by * write starting after current i_size. We mark the page straddling current * i_size RO so that page_mkwrite() is called on the nearest write access to * the page. This way filesystem can be sure that page_mkwrite() is called on * the page before user writes to the page via mmap after the i_size has been * changed. * * The function must be called after i_size is updated so that page fault * coming after we unlock the page will already see the new i_size. * The function must be called while we still hold i_rwsem - this not only * makes sure i_size is stable but also that userspace cannot observe new * i_size value before we are prepared to store mmap writes at new inode size. */ void pagecache_isize_extended(struct inode *inode, loff_t from, loff_t to) { int bsize = i_blocksize(inode); loff_t rounded_from; struct page *page; pgoff_t index; WARN_ON(to > inode->i_size); if (from >= to || bsize == PAGE_SIZE) return; /* Page straddling @from will not have any hole block created? */ rounded_from = round_up(from, bsize); if (to <= rounded_from || !(rounded_from & (PAGE_SIZE - 1))) return; index = from >> PAGE_SHIFT; page = find_lock_page(inode->i_mapping, index); /* Page not cached? Nothing to do */ if (!page) return; /* * See clear_page_dirty_for_io() for details why set_page_dirty() * is needed. */ if (page_mkclean(page)) set_page_dirty(page); unlock_page(page); put_page(page); } EXPORT_SYMBOL(pagecache_isize_extended); /** * truncate_pagecache_range - unmap and remove pagecache that is hole-punched * @inode: inode * @lstart: offset of beginning of hole * @lend: offset of last byte of hole * * This function should typically be called before the filesystem * releases resources associated with the freed range (eg. deallocates * blocks). This way, pagecache will always stay logically coherent * with on-disk format, and the filesystem would not have to deal with * situations such as writepage being called for a page that has already * had its underlying blocks deallocated. */ void truncate_pagecache_range(struct inode *inode, loff_t lstart, loff_t lend) { struct address_space *mapping = inode->i_mapping; loff_t unmap_start = round_up(lstart, PAGE_SIZE); loff_t unmap_end = round_down(1 + lend, PAGE_SIZE) - 1; /* * This rounding is currently just for example: unmap_mapping_range * expands its hole outwards, whereas we want it to contract the hole * inwards. However, existing callers of truncate_pagecache_range are * doing their own page rounding first. Note that unmap_mapping_range * allows holelen 0 for all, and we allow lend -1 for end of file. */ /* * Unlike in truncate_pagecache, unmap_mapping_range is called only * once (before truncating pagecache), and without "even_cows" flag: * hole-punching should not remove private COWed pages from the hole. */ if ((u64)unmap_end > (u64)unmap_start) unmap_mapping_range(mapping, unmap_start, 1 + unmap_end - unmap_start, 0); truncate_inode_pages_range(mapping, lstart, lend); } EXPORT_SYMBOL(truncate_pagecache_range);