cifs: allow calling cifs_build_path_to_root on incomplete cifs_sb

It's possible that cifs_mount will call cifs_build_path_to_root on a
newly instantiated cifs_sb. In that case, it's likely that the
master_tlink pointer has not yet been instantiated.

Fix this by having cifs_build_path_to_root take a cifsTconInfo pointer
as well, and have the caller pass that in.

Reported-and-Tested-by: Robbert Kouprie <robbert@exx.nl>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 5523047..e6d1481 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -54,7 +54,8 @@
 	     __func__, curr_xid, (int)rc);			\
 } while (0)
 extern char *build_path_from_dentry(struct dentry *);
-extern char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb);
+extern char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb,
+					struct cifsTconInfo *tcon);
 extern char *build_wildcard_path_from_dentry(struct dentry *direntry);
 extern char *cifs_compose_mount_options(const char *sb_mountdata,
 		const char *fullpath, const struct dfs_info3_param *ref,