cifs_get_root shouldn't use path with tree name

When a server returns the optional flag SMB_SHARE_IS_IN_DFS in response
to a tree connect, cifs_build_path_to_root() will return a pathname
which includes the hostname. This causes problems with cifs_get_root()
which separates each component and does a lookup for each component of
the path which in this case will incorrectly include looking up the
hostname component as a path component.

We encountered a problem with dfs shares hosted by a Netapp. When
connecting to nodes pointed to by the DFS share. The tree connect for
these nodes return SMB_SHARE_IS_IN_DFS resulting failures in lookup
in cifs_get_root().

RH bz: 1373153
The patch was tested against a Netapp simulator and by a user using an
actual Netapp server.

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reported-by: Pierguido Lambri <plambri@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 15261ba..f135f08 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -615,7 +615,7 @@
 		return dget(sb->s_root);
 
 	full_path = cifs_build_path_to_root(vol, cifs_sb,
-					    cifs_sb_master_tcon(cifs_sb));
+				cifs_sb_master_tcon(cifs_sb), 0);
 	if (full_path == NULL)
 		return ERR_PTR(-ENOMEM);