On 10/16/14 15:40, Chuck Lever wrote:
> So far, TCP is the only transport that supports bi-directional RPC.
>
> When mounting with NFSv4.1 using a transport that does not support
> bi-directional RPC, establish a TCP sidecar connection to handle
> backchannel traffic for a session. The sidecar transport does not
> use its forward channel except for sending BIND_CONN_TO_SESSION
> operations.
>
> This commit adds logic to create and destroy the sidecar transport.
> Subsequent commits add logic to use the transport.
I thought NFS v4.0 also uses a separate connection for the backchannel? Can any of that code be reused here, rather than creating new sidecar structures?
Anna
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfs/client.c | 1 +
> fs/nfs/nfs4client.c | 54 +++++++++++++++++++++++++++++++++++++++++++++
> include/linux/nfs_fs_sb.h | 2 ++
> 3 files changed, 57 insertions(+)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 6a4f366..19f49bf 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -78,6 +78,7 @@ const struct rpc_program nfs_program = {
> .stats = &nfs_rpcstat,
> .pipe_dir_name = NFS_PIPE_DIRNAME,
> };
> +EXPORT_SYMBOL_GPL(nfs_program);
>
> struct rpc_stat nfs_rpcstat = {
> .program = &nfs_program
> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
> index 5f4b818..b1cc35e 100644
> --- a/fs/nfs/nfs4client.c
> +++ b/fs/nfs/nfs4client.c
> @@ -213,6 +213,8 @@ static void nfs4_destroy_callback(struct nfs_client *clp)
> {
> if (__test_and_clear_bit(NFS_CS_CALLBACK, &clp->cl_res_state))
> nfs_callback_down(clp->cl_mvops->minor_version, clp->cl_net);
> + if (clp->cl_bc_rpcclient)
> + rpc_shutdown_client(clp->cl_bc_rpcclient);
> }
>
> static void nfs4_shutdown_client(struct nfs_client *clp)
> @@ -291,6 +293,53 @@ int nfs40_init_client(struct nfs_client *clp)
>
> #if defined(CONFIG_NFS_V4_1)
>
> +/*
> + * Create a separate rpc_clnt using TCP that can provide a
> + * backchannel service.
> + */
> +static int nfs41_create_sidecar_rpc_client(struct nfs_client *clp)
> +{
> + struct sockaddr_storage address;
> + struct sockaddr *sap = (struct sockaddr *)&address;
> + struct rpc_create_args args = {
> + .net = clp->cl_net,
> + .protocol = XPRT_TRANSPORT_TCP,
> + .address = sap,
> + .addrsize = clp->cl_addrlen,
> + .servername = clp->cl_hostname,
> + .program = &nfs_program,
> + .version = clp->rpc_ops->version,
> + .flags = (RPC_CLNT_CREATE_DISCRTRY |
> + RPC_CLNT_CREATE_NOPING),
> + };
> + struct rpc_clnt *clnt;
> + struct rpc_cred *cred;
> +
> + if (rpc_xprt_is_bidirectional(clp->cl_rpcclient))
> + return 0;
> +
> + if (test_bit(NFS_CS_NORESVPORT, &clp->cl_flags))
> + args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
> + memcpy(sap, &clp->cl_addr, clp->cl_addrlen);
> + rpc_set_port(sap, NFS_PORT);
> + cred = nfs4_get_clid_cred(clp);
> + if (cred) {
> + args.authflavor = cred->cr_auth->au_flavor;
> + put_rpccred(cred);
> + } else
> + args.authflavor = RPC_AUTH_UNIX;
> +
> + clnt = rpc_create(&args);
> + if (IS_ERR(clnt)) {
> + dprintk("%s: cannot create side-car RPC client. Error = %ld\n",
> + __func__, PTR_ERR(clnt));
> + return PTR_ERR(clnt);
> + }
> +
> + clp->cl_bc_rpcclient = clnt;
> + return 0;
> +}
> +
> /**
> * nfs41_init_client - nfs_client initialization tasks for NFSv4.1+
> * @clp - nfs_client to initialize
> @@ -300,6 +349,11 @@ int nfs40_init_client(struct nfs_client *clp)
> int nfs41_init_client(struct nfs_client *clp)
> {
> struct nfs4_session *session = NULL;
> + int ret;
> +
> + ret = nfs41_create_sidecar_rpc_client(clp);
> + if (ret)
> + return ret;
>
> /*
> * Create the session and mark it expired.
> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> index 922be2e..159d703 100644
> --- a/include/linux/nfs_fs_sb.h
> +++ b/include/linux/nfs_fs_sb.h
> @@ -87,6 +87,8 @@ struct nfs_client {
>
> /* The sequence id to use for the next CREATE_SESSION */
> u32 cl_seqid;
> + /* The optional sidecar backchannel transport */
> + struct rpc_clnt *cl_bc_rpcclient;
> /* The flags used for obtaining the clientid during EXCHANGE_ID */
> u32 cl_exchange_flags;
> struct nfs4_session *cl_session; /* shared session */
>
> --
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