nfsd4: cross mountpoints when looking up parents

3c394ddaa7ea4205f933fd9b481166b2669368a9 "nfsd4: nfsv4 clients should
cross mountpoints" forgot to handle lookups of parents directories.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

fs/nfsd/vfs.c

@@ -169,7 +169,7 @@ nfsd_lookup_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp,
 			dentry = dget(dparent);
 		else if (dparent != exp->ex_path.dentry)
 			dentry = dget_parent(dparent);
-		else if (!EX_NOHIDE(exp))
+		else if (!EX_NOHIDE(exp) && !nfsd_v4client(rqstp))
 			dentry = dget(dparent); /* .. == . just like at / */
 		else {
 			/* checking mountpoint crossing is very different when stepping up */