nfsd: Reorder nfsd_cache_match to check more powerful discriminators first

We would normally expect the xid and the checksum to be the best
discriminators. Check them before looking at the procedure number,
etc.
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: NJ. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfscache.c

@@ -338,20 +338,24 @@ nfsd_cache_csum(struct svc_rqst *rqstp)
 static bool
 nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
 {
-	/* Check RPC header info first */
-	if (rqstp->rq_xid != rp->c_xid || rqstp->rq_proc != rp->c_proc ||
-	    rqstp->rq_prot != rp->c_prot || rqstp->rq_vers != rp->c_vers ||
-	    rqstp->rq_arg.len != rp->c_len ||
-	    !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
-	    rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
+	/* Check RPC XID first */
+	if (rqstp->rq_xid != rp->c_xid)
 		return false;
-
 	/* compare checksum of NFS data */
 	if (csum != rp->c_csum) {
 		++payload_misses;
 		return false;
 	}
 
+	/* Other discriminators */
+	if (rqstp->rq_proc != rp->c_proc ||
+	    rqstp->rq_prot != rp->c_prot ||
+	    rqstp->rq_vers != rp->c_vers ||
+	    rqstp->rq_arg.len != rp->c_len ||
+	    !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) ||
+	    rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr))
+		return false;
+
 	return true;
 }