btrfs: Drop inode if inode root is NULL

There is a path where btrfs_drop_inode() is called with its inode's root
is NULL: In btrfs_new_inode(), when btrfs_set_inode_index() fails,
iput() is called. We should handle this case before taking look at the
root->root_item.

Signed-off-by: Naohiro Aota <naota@elisp.net>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 23c596cd1b98..c931a4dbd031 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8011,6 +8011,9 @@ int btrfs_drop_inode(struct inode *inode)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
 
+        if (root == NULL)
+                return 1;
+
         /* the snap/subvol tree is on deleting */
         if (btrfs_root_refs(&root->root_item) == 0 &&
             root != root->fs_info->tree_root)