NFSv4: Cache the NFSv4/v4.1 client owner_id in the struct nfs_client

Ensure that we cache the NFSv4/v4.1 client owner_id so that we can
verify it when we're doing trunking detection.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index e7f8d5f..1fab516 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -4917,11 +4917,14 @@
 }
 
 static unsigned int
-nfs4_init_nonuniform_client_string(const struct nfs_client *clp,
+nfs4_init_nonuniform_client_string(struct nfs_client *clp,
 				   char *buf, size_t len)
 {
 	unsigned int result;
 
+	if (clp->cl_owner_id != NULL)
+		return strlcpy(buf, clp->cl_owner_id, len);
+
 	rcu_read_lock();
 	result = scnprintf(buf, len, "Linux NFSv4.0 %s/%s %s",
 				clp->cl_ipaddr,
@@ -4930,24 +4933,32 @@
 				rpc_peeraddr2str(clp->cl_rpcclient,
 							RPC_DISPLAY_PROTO));
 	rcu_read_unlock();
+	clp->cl_owner_id = kstrdup(buf, GFP_KERNEL);
 	return result;
 }
 
 static unsigned int
-nfs4_init_uniform_client_string(const struct nfs_client *clp,
+nfs4_init_uniform_client_string(struct nfs_client *clp,
 				char *buf, size_t len)
 {
 	const char *nodename = clp->cl_rpcclient->cl_nodename;
+	unsigned int result;
+
+	if (clp->cl_owner_id != NULL)
+		return strlcpy(buf, clp->cl_owner_id, len);
 
 	if (nfs4_client_id_uniquifier[0] != '\0')
-		return scnprintf(buf, len, "Linux NFSv%u.%u %s/%s",
+		result = scnprintf(buf, len, "Linux NFSv%u.%u %s/%s",
 				clp->rpc_ops->version,
 				clp->cl_minorversion,
 				nfs4_client_id_uniquifier,
 				nodename);
-	return scnprintf(buf, len, "Linux NFSv%u.%u %s",
+	else
+		result = scnprintf(buf, len, "Linux NFSv%u.%u %s",
 				clp->rpc_ops->version, clp->cl_minorversion,
 				nodename);
+	clp->cl_owner_id = kstrdup(buf, GFP_KERNEL);
+	return result;
 }
 
 /*