diff options
Diffstat (limited to 'mm/truncate.c')
| -rw-r--r-- | mm/truncate.c | 473 |
1 files changed, 473 insertions, 0 deletions
diff --git a/mm/truncate.c b/mm/truncate.c new file mode 100644 index 0000000..1229211 --- /dev/null +++ b/mm/truncate.c @@ -0,0 +1,473 @@ +/* + * 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 (PagePrivate(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 void +truncate_complete_page(struct address_space *mapping, struct page *page) +{ + if (page->mapping != mapping) + return; + + if (PagePrivate(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 */ +} + +/* + * 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 (PagePrivate(page) && !try_to_release_page(page, 0)) + return 0; + + clear_page_mlock(page); + ret = remove_mapping(mapping, page); + + return ret; +} + +/** + * 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; + } + if (page_mapped(page)) { + unmap_mapping_range(mapping, + (loff_t)page_index<<PAGE_CACHE_SHIFT, + PAGE_CACHE_SIZE, 0); + } + truncate_complete_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); + if (page_mapped(page)) { + unmap_mapping_range(mapping, + (loff_t)page->index<<PAGE_CACHE_SHIFT, + PAGE_CACHE_SIZE, 0); + } + if (page->index > next) + next = page->index; + next++; + truncate_complete_page(mapping, page); + 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); + +unsigned long __invalidate_mapping_pages(struct address_space *mapping, + pgoff_t start, pgoff_t end, bool be_atomic) +{ + 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; + + if (PageDirty(page) || PageWriteback(page)) + goto unlock; + if (page_mapped(page)) + goto unlock; + ret += invalidate_complete_page(mapping, page); +unlock: + unlock_page(page); + if (next > end) + break; + } + pagevec_release(&pvec); + if (likely(!be_atomic)) + cond_resched(); + } + return ret; +} + +/** + * 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) +{ + return __invalidate_mapping_pages(mapping, start, end, false); +} +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 (PagePrivate(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(PagePrivate(page)); + __remove_from_page_cache(page); + spin_unlock_irq(&mapping->tree_lock); + 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); |
