/* * mm/truncate.c - code for taking down pages from address_spaces * * Copyright (C) 2002, Linus Torvalds * * 10Sep2002 Andrew Morton * Initial version. */ #include <linux/kernel.h> #include <linux/backing-dev.h> #include <linux/gfp.h> #include <linux/mm.h> #include <linux/swap.h> #include <linux/export.h> #include <linux/pagemap.h> #include <linux/highmem.h> #include <linux/pagevec.h> #include <linux/task_io_accounting_ops.h> #include <linux/buffer_head.h> /* grr. try_to_release_page, do_invalidatepage */ #include <linux/cleancache.h> #include "internal.h" static void clear_exceptional_entry(struct address_space *mapping, pgoff_t index, void *entry) { struct radix_tree_node *node; void **slot; /* Handled by shmem itself */ if (shmem_mapping(mapping)) return; spin_lock_irq(&mapping->tree_lock); /* * Regular page slots are stabilized by the page lock even * without the tree itself locked. These unlocked entries * need verification under the tree lock. */ if (!__radix_tree_lookup(&mapping->page_tree, index, &node, &slot)) goto unlock; if (*slot != entry) goto unlock; radix_tree_replace_slot(slot, NULL); mapping->nrshadows--; if (!node) goto unlock; workingset_node_shadows_dec(node); /* * Don't track node without shadow entries. * * Avoid acquiring the list_lru lock if already untracked. * The list_empty() test is safe as node->private_list is * protected by mapping->tree_lock. */ if (!workingset_node_shadows(node) && !list_empty(&node->private_list)) list_lru_del(&workingset_shadow_nodes, &node->private_list); __radix_tree_delete_node(&mapping->page_tree, node); unlock: spin_unlock_irq(&mapping->tree_lock); } /** * do_invalidatepage - invalidate part or all of a page * @page: the page which is affected * @offset: start of the range to invalidate * @length: length of the range to invalidate * * do_invalidatepage() is called when all or part of the page has become * invalidated by a truncate operation. * * do_invalidatepage() 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 do_invalidatepage(struct page *page, unsigned int offset, unsigned int length) { void (*invalidatepage)(struct page *, unsigned int, unsigned int); invalidatepage = page->mapping->a_ops->invalidatepage; #ifdef CONFIG_BLOCK if (!invalidatepage) invalidatepage = block_invalidatepage; #endif if (invalidatepage) (*invalidatepage)(page, offset, length); } /* * This cancels just the dirty bit on the kernel page itself, it * does NOT actually remove dirty bits on any mmap's that may be * around. It also leaves the page tagged dirty, so any sync * activity will still find it on the dirty lists, and in particular, * clear_page_dirty_for_io() will still look at the dirty bits in * the VM. * * Doing this should *normally* only ever be done when a page * is truncated, and is not actually mapped anywhere at all. However, * fs/buffer.c does this when it notices that somebody has cleaned * out all the buffers on a page without actually doing it through * the VM. Can you say "ext3 is horribly ugly"? Tought you could. */ void cancel_dirty_page(struct page *page, unsigned int account_size) { if (TestClearPageDirty(page)) { struct address_space *mapping = page->mapping; if (mapping && mapping_cap_account_dirty(mapping)) { dec_zone_page_state(page, NR_FILE_DIRTY); dec_bdi_stat(mapping->backing_dev_info, BDI_RECLAIMABLE); if (account_size) task_io_account_cancelled_write(account_size); } } } EXPORT_SYMBOL(cancel_dirty_page); /* * 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 bale 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 int truncate_complete_page(struct address_space *mapping, struct page *page) { if (page->mapping != mapping) return -EIO; if (page_has_private(page)) do_invalidatepage(page, 0, PAGE_CACHE_SIZE); cancel_dirty_page(page, PAGE_CACHE_SIZE); ClearPageMappedToDisk(page); delete_from_page_cache(page); return 0; } /* * This is for invalidate_mapping_pages(). That function can be called at * any time, and is not supposed to throw away dirty pages. But pages can * be marked dirty at any time too, so use remove_mapping which safely * discards clean, unused pages. * * Returns non-zero if the page was successfully invalidated. */ static int invalidate_complete_page(struct address_space *mapping, struct page *page) { int ret; if (page->mapping != mapping) return 0; if (page_has_private(page) && !try_to_release_page(page, 0)) return 0; ret = remove_mapping(mapping, page); return ret; } int truncate_inode_page(struct address_space *mapping, struct page *page) { if (page_mapped(page)) { unmap_mapping_range(mapping, (loff_t)page->index << PAGE_CACHE_SHIFT, PAGE_CACHE_SIZE, 0); } return truncate_complete_page(mapping, page); } /* * Used to get rid of pages on hardware memory corruption. */ int generic_error_remove_page(struct address_space *mapping, struct 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_page(mapping, page); } EXPORT_SYMBOL(generic_error_remove_page); /* * Safely invalidate one page from its pagecache mapping. * It only drops clean, unused pages. The page must be locked. * * Returns 1 if the page is successfully invalidated, otherwise 0. */ int invalidate_inode_page(struct page *page) { struct address_space *mapping = page_mapping(page); if (!mapping) return 0; if (PageDirty(page) || PageWriteback(page)) return 0; if (page_mapped(page)) return 0; return invalidate_complete_page(mapping, page); } /** * 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 ->invalidatepage() 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 */ unsigned int partial_start; /* inclusive */ unsigned int partial_end; /* exclusive */ struct pagevec pvec; pgoff_t indices[PAGEVEC_SIZE]; pgoff_t index; int i; cleancache_invalidate_inode(mapping); if (mapping->nrpages == 0 && mapping->nrshadows == 0) return; /* Offsets within partial pages */ partial_start = lstart & (PAGE_CACHE_SIZE - 1); partial_end = (lend + 1) & (PAGE_CACHE_SIZE - 1); /* * '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_CACHE_SIZE - 1) >> PAGE_CACHE_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_CACHE_SHIFT; pagevec_init(&pvec, 0); index = start; while (index < end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; /* We rely upon deletion not changing page->index */ index = indices[i]; if (index >= end) break; if (radix_tree_exceptional_entry(page)) { clear_exceptional_entry(mapping, index, page); continue; } if (!trylock_page(page)) continue; WARN_ON(page->index != index); if (PageWriteback(page)) { unlock_page(page); continue; } truncate_inode_page(mapping, page); unlock_page(page); } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); cond_resched(); index++; } if (partial_start) { struct page *page = find_lock_page(mapping, start - 1); if (page) { unsigned int top = PAGE_CACHE_SIZE; if (start > end) { /* Truncation within a single page */ top = partial_end; partial_end = 0; } wait_on_page_writeback(page); zero_user_segment(page, partial_start, top); cleancache_invalidate_page(mapping, page); if (page_has_private(page)) do_invalidatepage(page, partial_start, top - partial_start); unlock_page(page); page_cache_release(page); } } if (partial_end) { struct page *page = find_lock_page(mapping, end); if (page) { wait_on_page_writeback(page); zero_user_segment(page, 0, partial_end); cleancache_invalidate_page(mapping, page); if (page_has_private(page)) do_invalidatepage(page, 0, partial_end); unlock_page(page); page_cache_release(page); } } /* * If the truncation happened within a single page no pages * will be released, just zeroed, so we can bail out now. */ if (start >= end) return; index = start; for ( ; ; ) { cond_resched(); if (!pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { /* If all gone from start onwards, we're done */ if (index == start) break; /* Otherwise restart to make sure all gone */ index = start; continue; } if (index == start && indices[0] >= end) { /* All gone out of hole to be punched, we're done */ pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); break; } for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; /* We rely upon deletion not changing page->index */ index = indices[i]; if (index >= end) { /* Restart punch to make sure all gone */ index = start - 1; break; } if (radix_tree_exceptional_entry(page)) { clear_exceptional_entry(mapping, index, page); continue; } lock_page(page); WARN_ON(page->index != index); wait_on_page_writeback(page); truncate_inode_page(mapping, page); unlock_page(page); } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); index++; } cleancache_invalidate_inode(mapping); } 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_mutex. * * 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_mutex. * * 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) { unsigned long nrshadows; unsigned long nrpages; /* * 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); /* * When reclaim installs eviction entries, it increases * nrshadows first, then decreases nrpages. Make sure we see * this in the right order or we might miss an entry. */ nrpages = mapping->nrpages; smp_rmb(); nrshadows = mapping->nrshadows; if (nrpages || nrshadows) { /* * 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. */ spin_lock_irq(&mapping->tree_lock); spin_unlock_irq(&mapping->tree_lock); truncate_inode_pages(mapping, 0); } } EXPORT_SYMBOL(truncate_inode_pages_final); /** * invalidate_mapping_pages - 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) * * This function only removes the unlocked pages, if you want to * remove all the pages of one inode, you must call truncate_inode_pages. * * invalidate_mapping_pages() will not block on IO activity. It will not * invalidate pages which are dirty, locked, under writeback or mapped into * pagetables. */ unsigned long invalidate_mapping_pages(struct address_space *mapping, pgoff_t start, pgoff_t end) { pgoff_t indices[PAGEVEC_SIZE]; struct pagevec pvec; pgoff_t index = start; unsigned long ret; unsigned long count = 0; int i; pagevec_init(&pvec, 0); while (index <= end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1, indices)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; /* We rely upon deletion not changing page->index */ index = indices[i]; if (index > end) break; if (radix_tree_exceptional_entry(page)) { clear_exceptional_entry(mapping, index, page); continue; } if (!trylock_page(page)) continue; WARN_ON(page->index != index); ret = invalidate_inode_page(page); unlock_page(page); /* * Invalidation is a hint that the page is no longer * of interest and try to speed up its reclaim. */ if (!ret) deactivate_page(page); count += ret; } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); cond_resched(); index++; } return count; } EXPORT_SYMBOL(invalidate_mapping_pages); /* * This is like invalidate_complete_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_page2(struct address_space *mapping, struct page *page) { if (page->mapping != mapping) return 0; if (page_has_private(page) && !try_to_release_page(page, GFP_KERNEL)) return 0; spin_lock_irq(&mapping->tree_lock); if (PageDirty(page)) goto failed; BUG_ON(page_has_private(page)); __delete_from_page_cache(page, NULL); spin_unlock_irq(&mapping->tree_lock); if (mapping->a_ops->freepage) mapping->a_ops->freepage(page); page_cache_release(page); /* pagecache ref */ return 1; failed: spin_unlock_irq(&mapping->tree_lock); return 0; } static int do_launder_page(struct address_space *mapping, struct page *page) { if (!PageDirty(page)) return 0; if (page->mapping != mapping || mapping->a_ops->launder_page == NULL) return 0; return mapping->a_ops->launder_page(page); } /** * 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. * * Returns -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 pagevec pvec; pgoff_t index; int i; int ret = 0; int ret2 = 0; int did_range_unmap = 0; cleancache_invalidate_inode(mapping); pagevec_init(&pvec, 0); index = start; while (index <= end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1, indices)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; /* We rely upon deletion not changing page->index */ index = indices[i]; if (index > end) break; if (radix_tree_exceptional_entry(page)) { clear_exceptional_entry(mapping, index, page); continue; } lock_page(page); WARN_ON(page->index != index); if (page->mapping != mapping) { unlock_page(page); continue; } wait_on_page_writeback(page); if (page_mapped(page)) { if (!did_range_unmap) { /* * Zap the rest of the file in one hit. */ unmap_mapping_range(mapping, (loff_t)index << PAGE_CACHE_SHIFT, (loff_t)(1 + end - index) << PAGE_CACHE_SHIFT, 0); did_range_unmap = 1; } else { /* * Just zap this page */ unmap_mapping_range(mapping, (loff_t)index << PAGE_CACHE_SHIFT, PAGE_CACHE_SIZE, 0); } } BUG_ON(page_mapped(page)); ret2 = do_launder_page(mapping, page); if (ret2 == 0) { if (!invalidate_complete_page2(mapping, page)) ret2 = -EBUSY; } if (ret2 < 0) ret = ret2; unlock_page(page); } pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); cond_resched(); index++; } cleancache_invalidate_inode(mapping); 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. * * Returns -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 inode_mutex held and before all filesystem specific * block truncation has been performed. */ void truncate_setsize(struct inode *inode, loff_t newsize) { i_size_write(inode, newsize); truncate_pagecache(inode, newsize); } EXPORT_SYMBOL(truncate_setsize); /** * 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);