NFSv4.1: Don't clobber the seqid if exchange_id returns a confirmed clientid

If the EXCHGID4_FLAG_CONFIRMED_R flag is set, the client is in theory
supposed to already know the correct value of the seqid, in which case
RFC5661 states that it should ignore the value returned.

Also ensure that if the sanity check in nfs4_check_cl_exchange_flags
fails, then we must not change the nfs_client fields.

Finally, clean up the code: we don't need to retest the value of
'status' unless it can change.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4proc.c

@@ -5171,7 +5171,7 @@ int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
 		.flags = EXCHGID4_FLAG_SUPP_MOVED_REFER,
 	};
 	struct nfs41_exchange_id_res res = {
-		.client = clp,
+		0
 	};
 	int status;
 	struct rpc_message msg = {
@@ -5214,22 +5214,22 @@ int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
 
 	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
 	if (status == 0)
-		status = nfs4_check_cl_exchange_flags(clp->cl_exchange_flags);
+		status = nfs4_check_cl_exchange_flags(res.flags);
 
 	if (status == 0) {
+		clp->cl_clientid = res.clientid;
+		clp->cl_exchange_flags = (res.flags & ~EXCHGID4_FLAG_CONFIRMED_R);
+		if (!(res.flags & EXCHGID4_FLAG_CONFIRMED_R))
+			clp->cl_seqid = res.seqid;
+
 		kfree(clp->cl_serverowner);
 		clp->cl_serverowner = res.server_owner;
 		res.server_owner = NULL;
-	}
 
-	if (status == 0) {
 		/* use the most recent implementation id */
 		kfree(clp->cl_implid);
 		clp->cl_implid = res.impl_id;
-	} else
-		kfree(res.impl_id);
 
-	if (status == 0) {
 		if (clp->cl_serverscope != NULL &&
 		    !nfs41_same_server_scope(clp->cl_serverscope,
 					     res.server_scope)) {
@@ -5244,7 +5244,8 @@ int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
 			clp->cl_serverscope = res.server_scope;
 			goto out;
 		}
-	}
+	} else
+		kfree(res.impl_id);
 
 out_server_owner:
 	kfree(res.server_owner);

fs/nfs/nfs4xdr.c

@@ -5319,7 +5319,6 @@ static int decode_exchange_id(struct xdr_stream *xdr,
 	uint32_t dummy;
 	char *dummy_str;
 	int status;
-	struct nfs_client *clp = res->client;
 	uint32_t impl_id_count;
 
 	status = decode_op_hdr(xdr, OP_EXCHANGE_ID);
@@ -5329,12 +5328,12 @@ static int decode_exchange_id(struct xdr_stream *xdr,
 	p = xdr_inline_decode(xdr, 8);
 	if (unlikely(!p))
 		goto out_overflow;
-	xdr_decode_hyper(p, &clp->cl_clientid);
+	xdr_decode_hyper(p, &res->clientid);
 	p = xdr_inline_decode(xdr, 12);
 	if (unlikely(!p))
 		goto out_overflow;
-	clp->cl_seqid = be32_to_cpup(p++);
-	clp->cl_exchange_flags = be32_to_cpup(p++);
+	res->seqid = be32_to_cpup(p++);
+	res->flags = be32_to_cpup(p++);
 
 	/* We ask for SP4_NONE */
 	dummy = be32_to_cpup(p);

include/linux/nfs_xdr.h

@@ -1132,7 +1132,8 @@ struct nfs41_bind_conn_to_session_res {
 };
 
 struct nfs41_exchange_id_res {
-	struct nfs_client		*client;
+	u64				clientid;
+	u32				seqid;
 	u32				flags;
 	struct nfs41_server_owner	*server_owner;
 	struct nfs41_server_scope	*server_scope;