Btrfs: fix unprotected extent map operation when logging file extents

We forget to protect the modified_extents list, fix it.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index bcf0e48b1932..d1947af67bcd 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3526,8 +3526,10 @@ next_slot:
                 struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
                 struct extent_map *em, *n;
 
+                write_lock(&tree->lock);
                 list_for_each_entry_safe(em, n, &tree->modified_extents, list)
                         list_del_init(&em->list);
+                write_unlock(&tree->lock);
         }
 
         if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {