Btrfs: Fix an off by one in the extent_map prepare write code

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index a9f5d6d417f0..5f5b7b89b144 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1956,7 +1956,7 @@ static int btrfs_prepare_write(struct file *file, struct page *page,
 
         mutex_lock(&root->fs_info->fs_mutex);
         err = btrfs_check_free_space(root, PAGE_CACHE_SIZE, 0);
-        mutex_lock(&root->fs_info->fs_mutex);
+        mutex_unlock(&root->fs_info->fs_mutex);
         if (err)
                 return -ENOSPC;