From f1de968376340c97ac2d7acd25fa3107c398e0e5 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Thu, 9 Jan 2014 10:06:10 +0800 Subject: [PATCH] Btrfs: fix the race between write back and nocow buffered write When we ran the 274th case of xfstests with nodatacow mount option, We met the following warning message: WARNING: CPU: 1 PID: 14185 at fs/btrfs/extent-tree.c:3734 btrfs_free_reserved_data_space+0xa6/0xd0 It is caused by the race between the write back and nocow buffered write: Task1 Task2 __btrfs_buffered_write() skip data reservation reserve the metadata space copy the data dirty the pages unlock the pages write back the pages release the data space becasue there is no noreserve flag set the noreserve flag This patch fixes this problem by unlocking the pages after the noreserve flag is set. Reported-by: Tsutomu Itoh Signed-off-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/file.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 72df63b0c799..3dfd8db0e243 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1591,9 +1591,10 @@ again: unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend, &cached_state, GFP_NOFS); - btrfs_drop_pages(pages, num_pages); - if (ret) + if (ret) { + btrfs_drop_pages(pages, num_pages); break; + } release_bytes = 0; if (only_release_metadata && copied > 0) { @@ -1607,6 +1608,8 @@ again: only_release_metadata = false; } + btrfs_drop_pages(pages, num_pages); + cond_resched(); balance_dirty_pages_ratelimited(inode->i_mapping);