NFS: Kill fscache warnings when mounting without -ofsc

The fscache code will currently bleat a "non-unique superblock keys"
warning even if the user is mounting without the 'fsc' option.

There should be no reason to even initialise the superblock cache cookie
unless we're planning on using fscache for something, so ensure that we
check for the NFS_OPTION_FSCACHE flag before calling into the fscache
code.
Reported-by: NPaweł Sikora <pawel.sikora@agmk.net>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>
Cc: David Howells <dhowells@redhat.com>
Acked-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/nfs/super.c

@@ -2375,19 +2375,30 @@ static void nfs_get_cache_cookie(struct super_block *sb,
 				 struct nfs_parsed_mount_data *parsed,
 				 struct nfs_clone_mount *cloned)
 {
+	struct nfs_server *nfss = NFS_SB(sb);
 	char *uniq = NULL;
 	int ulen = 0;
 
-	if (parsed && parsed->fscache_uniq) {
-		uniq = parsed->fscache_uniq;
-		ulen = strlen(parsed->fscache_uniq);
+	nfss->fscache_key = NULL;
+	nfss->fscache = NULL;
+
+	if (parsed) {
+		if (!(parsed->options & NFS_OPTION_FSCACHE))
+			return;
+		if (parsed->fscache_uniq) {
+			uniq = parsed->fscache_uniq;
+			ulen = strlen(parsed->fscache_uniq);
+		}
 	} else if (cloned) {
 		struct nfs_server *mnt_s = NFS_SB(cloned->sb);
+		if (!(mnt_s->options & NFS_OPTION_FSCACHE))
+			return;
 		if (mnt_s->fscache_key) {
 			uniq = mnt_s->fscache_key->key.uniquifier;
 			ulen = mnt_s->fscache_key->key.uniq_len;
 		};
-	}
+	} else
+		return;
 
 	nfs_fscache_get_super_cookie(sb, uniq, ulen);
 }