NFS: disconnect before retrying NFSv4 requests over TCP

RFC3530 section 3.1.1 states an NFSv4 client MUST NOT send a request
twice on the same connection unless it is the NULL procedure.  Section
3.1.1 suggests that the client should disconnect and reconnect if it
wants to retry a request.

Implement this by adding an rpc_clnt flag that an ULP can use to
specify that the underlying transport should be disconnected on a
major timeout.  The NFSv4 client asserts this new flag, and requests
no retries after a minor retransmit timeout.

Note that disconnecting on a retransmit is in general not safe to do
if the RPC client does not reuse the TCP port number when reconnecting.

See http://bugzilla.linux-nfs.org/show_bug.cgi?id=6

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

4 files changed, 20 insertions, 3 deletions

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index a3191f023490..c46e94fed9eb 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -394,7 +394,8 @@ static void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
 static int nfs_create_rpc_client(struct nfs_client *clp, int proto,
                                                 unsigned int timeo,
                                                 unsigned int retrans,
-                                                rpc_authflavor_t flavor)
+                                                rpc_authflavor_t flavor,
+                                                int flags)
 {
         struct rpc_timeout      timeparms;
         struct rpc_clnt         *clnt = NULL;
@@ -407,6 +408,7 @@ static int nfs_create_rpc_client(struct nfs_client *clp, int proto,
                 .program        = &nfs_program,
                 .version        = clp->rpc_ops->version,
                 .authflavor     = flavor,
+                .flags          = flags,
         };
 
         if (!IS_ERR(clp->cl_rpcclient))
@@ -548,7 +550,7 @@ static int nfs_init_client(struct nfs_client *clp, const struct nfs_mount_data *
          * - RFC 2623, sec 2.3.2
          */
         error = nfs_create_rpc_client(clp, proto, data->timeo, data->retrans,
-                        RPC_AUTH_UNIX);
+                                        RPC_AUTH_UNIX, 0);
         if (error < 0)
                 goto error;
         nfs_mark_client_ready(clp, NFS_CS_READY);
@@ -868,7 +870,8 @@ static int nfs4_init_client(struct nfs_client *clp,
         /* Check NFS protocol revision and initialize RPC op vector */
         clp->rpc_ops = &nfs_v4_clientops;
 
-        error = nfs_create_rpc_client(clp, proto, timeo, retrans, authflavour);
+        error = nfs_create_rpc_client(clp, proto, timeo, retrans, authflavour,
+                                        RPC_CLNT_CREATE_DISCRTRY);
         if (error < 0)
                 goto error;
         memcpy(clp->cl_ipaddr, ip_addr, sizeof(clp->cl_ipaddr));
diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
index a1be89deb3af..c7a78eef2b4f 100644
--- a/include/linux/sunrpc/clnt.h
+++ b/include/linux/sunrpc/clnt.h
@@ -40,6 +40,7 @@ struct rpc_clnt {
 
         unsigned int            cl_softrtry : 1,/* soft timeouts */
                                 cl_intr     : 1,/* interruptible */
+                                cl_discrtry : 1,/* disconnect before retry */
                                 cl_autobind : 1,/* use getport() */
                                 cl_oneshot  : 1,/* dispose after use */
                                 cl_dead     : 1;/* abandoned */
@@ -111,6 +112,7 @@ struct rpc_create_args {
 #define RPC_CLNT_CREATE_ONESHOT         (1UL << 3)
 #define RPC_CLNT_CREATE_NONPRIVPORT     (1UL << 4)
 #define RPC_CLNT_CREATE_NOPING          (1UL << 5)
+#define RPC_CLNT_CREATE_DISCRTRY        (1UL << 6)
 
 struct rpc_clnt *rpc_create(struct rpc_create_args *args);
 struct rpc_clnt *rpc_bind_new_program(struct rpc_clnt *,
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 393e70aee181..c21aa0a7f770 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -249,6 +249,8 @@ struct rpc_clnt *rpc_create(struct rpc_create_args *args)
                 clnt->cl_autobind = 1;
         if (args->flags & RPC_CLNT_CREATE_ONESHOT)
                 clnt->cl_oneshot = 1;
+        if (args->flags & RPC_CLNT_CREATE_DISCRTRY)
+                clnt->cl_discrtry = 1;
 
         return clnt;
 }
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index cf59f7d315d0..1975139b26e7 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -735,6 +735,16 @@ void xprt_transmit(struct rpc_task *task)
                         xprt_reset_majortimeo(req);
                         /* Turn off autodisconnect */
                         del_singleshot_timer_sync(&xprt->timer);
+                } else {
+                        /* If all request bytes have been sent,
+                         * then we must be retransmitting this one */
+                        if (!req->rq_bytes_sent) {
+                                if (task->tk_client->cl_discrtry) {
+                                        xprt_disconnect(xprt);
+                                        task->tk_status = -ENOTCONN;
+                                        return;
+                                }
+                        }
                 }
         } else if (!req->rq_bytes_sent)
                 return;