Just testing the i_sb isn't really enough, at least the vfsmnt must be the
same.  Thanks Al.
Cc: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
        tdir = tdentry->d_inode;
 
        err = (rqstp->rq_vers == 2) ? nfserr_acces : nfserr_xdev;
-       if (fdir->i_sb != tdir->i_sb)
+       if (ffhp->fh_export != tfhp->fh_export)
                goto out;
 
        err = nfserr_perm;