Fix a leak in failure exit in 9p ->get_sb()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/9p/vfs_super.c

@@ -156,6 +156,7 @@ static int v9fs_get_sb(struct file_system_type *fs_type, int flags,
 
 	root = d_alloc_root(inode);
 	if (!root) {
+		iput(inode);
 		retval = -ENOMEM;
 		goto release_sb;
 	}