Btrfs: skip readonly root for snapshot-aware defragment

Btrfs send is assuming readonly root won't change, let's skip readonly root.

Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5b8925003090..b88f6221b48b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2240,6 +2240,11 @@ static noinline int relink_extent_backref(struct btrfs_path *path,
                 return PTR_ERR(root);
         }
 
+        if (btrfs_root_readonly(root)) {
+                srcu_read_unlock(&fs_info->subvol_srcu, index);
+                return 0;
+        }
+
         /* step 2: get inode */
         key.objectid = backref->inum;
         key.type = BTRFS_INODE_ITEM_KEY;