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>

1 files changed, 2 insertions, 0 deletions

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 *,