From 1f12bd063285b059cb63315d1424dae1ddd87a64 Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Thu, 29 Mar 2012 09:57:44 -0400 Subject: [PATCH] Btrfs: fix the mismatch of page->mapping commit 600a45e1d5e376f679ff9ecc4ce9452710a6d27c (Btrfs: fix deadlock on page lock when doing auto-defragment) fixes the deadlock on page, but it also introduces another bug. A page may have been truncated after unlock & lock. So we need to find it again to get the right one. And since we've held i_mutex lock, inode size remains unchanged and we can drop isize overflow checks. Signed-off-by: Liu Bo Signed-off-by: Miao Xie Signed-off-by: Chris Mason --- fs/btrfs/ioctl.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 45910d4b8f65..de46fa218590 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -871,6 +871,7 @@ static int cluster_pages_for_defrag(struct inode *inode, u64 isize = i_size_read(inode); u64 page_start; u64 page_end; + u64 page_cnt; int ret; int i; int i_done; @@ -879,19 +880,21 @@ static int cluster_pages_for_defrag(struct inode *inode, struct extent_io_tree *tree; gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping); - if (isize == 0) - return 0; file_end = (isize - 1) >> PAGE_CACHE_SHIFT; + if (!isize || start_index > file_end) + return 0; + + page_cnt = min_t(u64, (u64)num_pages, (u64)file_end - start_index + 1); ret = btrfs_delalloc_reserve_space(inode, - num_pages << PAGE_CACHE_SHIFT); + page_cnt << PAGE_CACHE_SHIFT); if (ret) return ret; i_done = 0; tree = &BTRFS_I(inode)->io_tree; /* step one, lock all the pages */ - for (i = 0; i < num_pages; i++) { + for (i = 0; i < page_cnt; i++) { struct page *page; again: page = find_or_create_page(inode->i_mapping, @@ -913,6 +916,15 @@ again: btrfs_start_ordered_extent(inode, ordered, 1); btrfs_put_ordered_extent(ordered); lock_page(page); + /* + * we unlocked the page above, so we need check if + * it was released or not. + */ + if (page->mapping != inode->i_mapping) { + unlock_page(page); + page_cache_release(page); + goto again; + } } if (!PageUptodate(page)) { @@ -926,15 +938,6 @@ again: } } - isize = i_size_read(inode); - file_end = (isize - 1) >> PAGE_CACHE_SHIFT; - if (!isize || page->index > file_end) { - /* whoops, we blew past eof, skip this page */ - unlock_page(page); - page_cache_release(page); - break; - } - if (page->mapping != inode->i_mapping) { unlock_page(page); page_cache_release(page); @@ -967,12 +970,12 @@ again: EXTENT_DO_ACCOUNTING, 0, 0, &cached_state, GFP_NOFS); - if (i_done != num_pages) { + if (i_done != page_cnt) { spin_lock(&BTRFS_I(inode)->lock); BTRFS_I(inode)->outstanding_extents++; spin_unlock(&BTRFS_I(inode)->lock); btrfs_delalloc_release_space(inode, - (num_pages - i_done) << PAGE_CACHE_SHIFT); + (page_cnt - i_done) << PAGE_CACHE_SHIFT); } @@ -997,7 +1000,7 @@ out: unlock_page(pages[i]); page_cache_release(pages[i]); } - btrfs_delalloc_release_space(inode, num_pages << PAGE_CACHE_SHIFT); + btrfs_delalloc_release_space(inode, page_cnt << PAGE_CACHE_SHIFT); return ret; } -- 2.20.1