/* * 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/mm.h> #include <linux/swap.h> #include <linux/module.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 "internal.h" /** * do_invalidatepage - invalidate part or all of a page * @page: the page which is affected * @offset: the index of the truncation point * * 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 long offset) { void (*invalidatepage)(struct page *, unsigned long); invalidatepage = page->mapping->a_ops->invalidatepage; #ifdef CONFIG_BLOCK if (!invalidatepage) invalidatepage = block_invalidatepage; #endif if (invalidatepage) (*invalidatepage)(page, offset); } static inline void truncate_partial_page(struct page *page, unsigned partial) { zero_user_segment(page, partial, PAGE_CACHE_SIZE); if (page_has_private(page)) do_invalidatepage(page, partial); } /* * 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); cancel_dirty_page(page, PAGE_CACHE_SIZE); clear_page_mlock(page); remove_from_page_cache(page); ClearPageMappedToDisk(page); page_cache_release(page); /* pagecache ref */ 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; clear_page_mlock(page); 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 - 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 * * Truncate the page cache, removing the pages that are between * specified offsets (and zeroing out partial page * (if lstart 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. * * When looking at page->index outside the page lock we need to be careful to * copy it into a local to avoid races (it could change at any time). * * 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. */ void truncate_inode_pages_range(struct address_space *mapping, loff_t lstart, loff_t lend) { const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT; pgoff_t end; const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1); struct pagevec pvec; pgoff_t next; int i; if (mapping->nrpages == 0) return; BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1)); end = (lend >> PAGE_CACHE_SHIFT); pagevec_init(&pvec, 0); next = start; while (next <= end && pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; pgoff_t page_index = page->index; if (page_index > end) { next = page_index; break; } if (page_index > next) next = page_index; next++; if (!trylock_page(page)) continue; if (PageWriteback(page)) { unlock_page(page); continue; } truncate_inode_page(mapping, page); unlock_page(page); } pagevec_release(&pvec); cond_resched(); } if (partial) { struct page *page = find_lock_page(mapping, start - 1); if (page) { wait_on_page_writeback(page); truncate_partial_page(page, partial); unlock_page(page); page_cache_release(page); } } next = start; for ( ; ; ) { cond_resched(); if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { if (next == start) break; next = start; continue; } if (pvec.pages[0]->index > end) { pagevec_release(&pvec); break; } for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; if (page->index > end) break; lock_page(page); wait_on_page_writeback(page); truncate_inode_page(mapping, page); if (page->index > next) next = page->index; next++; unlock_page(page); } pagevec_release(&pvec); } } 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. */ 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); /** * 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) { struct pagevec pvec; pgoff_t next = start; unsigned long ret = 0; int i; pagevec_init(&pvec, 0); while (next <= end && pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; pgoff_t index; int lock_failed; lock_failed = !trylock_page(page); /* * We really shouldn't be looking at the ->index of an * unlocked page. But we're not allowed to lock these * pages. So we rely upon nobody altering the ->index * of this (pinned-by-us) page. */ index = page->index; if (index > next) next = index; next++; if (lock_failed) continue; ret += invalidate_inode_page(page); unlock_page(page); if (next > end) break; } pagevec_release(&pvec); cond_resched(); } return ret; } 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; clear_page_mlock(page); BUG_ON(page_has_private(page)); __remove_from_page_cache(page); spin_unlock_irq(&mapping->tree_lock); mem_cgroup_uncharge_cache_page(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) { struct pagevec pvec; pgoff_t next; int i; int ret = 0; int ret2 = 0; int did_range_unmap = 0; int wrapped = 0; pagevec_init(&pvec, 0); next = start; while (next <= end && !wrapped && pagevec_lookup(&pvec, mapping, next, min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) { for (i = 0; i < pagevec_count(&pvec); i++) { struct page *page = pvec.pages[i]; pgoff_t page_index; lock_page(page); if (page->mapping != mapping) { unlock_page(page); continue; } page_index = page->index; next = page_index + 1; if (next == 0) wrapped = 1; if (page_index > end) { unlock_page(page); break; } 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)page_index<<PAGE_CACHE_SHIFT, (loff_t)(end - page_index + 1) << PAGE_CACHE_SHIFT, 0); did_range_unmap = 1; } else { /* * Just zap this page */ unmap_mapping_range(mapping, (loff_t)page_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_release(&pvec); cond_resched(); } 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 -EIO 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 * @old: old file offset * @new: new file offset * * 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 old, loff_t new) { if (new < old) { struct address_space *mapping = inode->i_mapping; /* * 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, new + PAGE_SIZE - 1, 0, 1); truncate_inode_pages(mapping, new); unmap_mapping_range(mapping, new + PAGE_SIZE - 1, 0, 1); } } EXPORT_SYMBOL(truncate_pagecache); /** * vmtruncate - unmap mappings "freed" by truncate() syscall * @inode: inode of the file used * @offset: file offset to start truncating * * NOTE! We have to be ready to update the memory sharing * between the file and the memory map for a potential last * incomplete page. Ugly, but necessary. */ int vmtruncate(struct inode *inode, loff_t offset) { loff_t oldsize; int error; error = inode_newsize_ok(inode, offset); if (error) return error; oldsize = inode->i_size; i_size_write(inode, offset); truncate_pagecache(inode, oldsize, offset); if (inode->i_op->truncate) inode->i_op->truncate(inode); return error; } EXPORT_SYMBOL(vmtruncate);