Btrfs: fix unprotected root node of the subvolume's inode rb-tree

The root node of the rb-tree may be changed, so we should get it under
the lock. Fix it.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 790eceb48fb0..19eef3e852b0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4843,14 +4843,13 @@ static void inode_tree_add(struct inode *inode)
         struct rb_node **p;
         struct rb_node *parent;
         u64 ino = btrfs_ino(inode);
-again:
-        p = &root->inode_tree.rb_node;
-        parent = NULL;
 
         if (inode_unhashed(inode))
                 return;
-
+again:
+        parent = NULL;
         spin_lock(&root->inode_lock);
+        p = &root->inode_tree.rb_node;
         while (*p) {
                 parent = *p;
                 entry = rb_entry(parent, struct btrfs_inode, rb_node);