sunrpc: Hash uids by first computing their value in the initial userns

In svcauth_unix introduce a helper unix_gid_hash as otherwise the
expresion to generate the hash value is just too long.

Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/net/sunrpc/svcauth_unix.c b/net/sunrpc/svcauth_unix.c
index 92166b5..faf1719 100644
--- a/net/sunrpc/svcauth_unix.c
+++ b/net/sunrpc/svcauth_unix.c
@@ -419,6 +419,11 @@
 	struct group_info	*gi;
 };
 
+static int unix_gid_hash(kuid_t uid)
+{
+	return hash_long(from_kuid(&init_user_ns, uid), GID_HASHBITS);
+}
+
 static void unix_gid_put(struct kref *kref)
 {
 	struct cache_head *item = container_of(kref, struct cache_head, ref);
@@ -530,7 +535,7 @@
 		ug.h.expiry_time = expiry;
 		ch = sunrpc_cache_update(cd,
 					 &ug.h, &ugp->h,
-					 hash_long(uid, GID_HASHBITS));
+					 unix_gid_hash(uid));
 		if (!ch)
 			err = -ENOMEM;
 		else {
@@ -621,7 +626,7 @@
 	struct cache_head *ch;
 
 	ug.uid = uid;
-	ch = sunrpc_cache_lookup(cd, &ug.h, hash_long(uid, GID_HASHBITS));
+	ch = sunrpc_cache_lookup(cd, &ug.h, unix_gid_hash(uid));
 	if (ch)
 		return container_of(ch, struct unix_gid, h);
 	else