[PATCH] SGI 921857: find broken with nohide on NFSv3

This patch makes "find" work when traversing nohide exports on NFSv3.  The
READDIRPLUS reply needs to not return a file handle for the ".." entry when
the directory is a server side mountpoint, which would be the directory
itself, otherwise the client remembers the wrong file handle and gets
confused.
Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nfsd/nfs3xdr.c

@@ -801,6 +801,11 @@ compose_entry_fh(struct nfsd3_readdirres *cd, struct svc_fh *fhp,
 	if (isdotent(name, namlen)) {
 		if (namlen == 2) {
 			dchild = dget_parent(dparent);
+			if (dchild == dparent) {
+				/* filesystem root - cannot return filehandle for ".." */
+				dput(dchild);
+				return 1;
+			}
 		} else
 			dchild = dget(dparent);
 	} else