On Fri, Feb 12, 2016 at 11:52 AM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
> RPC-over-RDMA Version One transports have a limit on how large
> a backward direction RPC (backchannel) message can be. Ensure
> that the NFSv4.x CREATE_SESSION operation advertises the
> correct value to servers.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
>
> This patch makes the client advertise the maximum size of a
> backchannel RPC message, which is 996 bytes with the current RDMA
> transport implementation.
>
> I wanted to propose this patch for v4.6, but it breaks
> Linux-to-Linux NFSv4.1 over RDMA. When attempting a mount, the Linux
> client reports this in its log:
>
> NFS: state manager: lease expired failed on NFSv4 server klimt-ib with error 525
> NFS: nfs4_discover_server_trunking unhandled error -512. Exiting with error EIO
>
> Then the mount command hangs (interruptibly).
Agreed: We should have nfs4_handle_reclaim_lease_error() call
nfs_mark_client_ready() on all fatal errors during session
initialisation (i.e. as long as we're still in
NFS_CS_SESSION_INITING).
> On the Linux server, CREATE_SESSION calls check_backchannel_attrs()
> which checks the maxreq_sz and maxresp_sz on the backchannel and
> returns NFS4ERR_TOOSMALL because it wants maxreq_sz to be larger
> than 1044 bytes.
>
> [ The client could do a better job of recovering, perhaps. Should it
> fall back to NFSv4.0 if vers= was not specified, and otherwise
> have mount exit with an error code? ]
>
> We have:
>
> #define NFSD_CB_MAX_REQ_SZ ((NFS4_enc_cb_recall_sz + \
> RPC_MAX_HEADER_WITH_AUTH) * sizeof(__be32))
>
> NFS4_enc_cb_recall_sz is 51 and RPC_MAX_HEADER_WITH_AUTH is 210.
>
> The comment in check_backchannel_attrs() says:
>
> /*
> * These RPC_MAX_HEADER macros are overkill, especially since we
> * don't even do gss on the backchannel yet. But this is still
> * less than 1k. Tighten up this estimate in the unlikely event
> * it turns out to be a problem for some client:
> */
>
> It seems that "still less than 1k" is not strictly true.
>
> To address this, a new minimum could be chosen that assumes that
> RPC_AUTH_GSS is not going to be used for now.
>
> Thoughts?
Why make this a transport variable? It seems more appropriate to just
have it be a per-transport function.
>
>
> fs/nfs/nfs4proc.c | 10 ++++++----
> include/linux/sunrpc/clnt.h | 1 +
> include/linux/sunrpc/xprt.h | 1 +
> net/sunrpc/clnt.c | 15 +++++++++++++++
> net/sunrpc/xprtrdma/transport.c | 1 +
> net/sunrpc/xprtsock.c | 4 ++++
> 6 files changed, 28 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 4bfc33a..a0e2cda 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -7295,9 +7295,11 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
> * always set csa_cachethis to FALSE because the current implementation
> * of the back channel DRC only supports caching the CB_SEQUENCE operation.
> */
> -static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args)
> +static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args,
> + struct rpc_clnt *clnt)
> {
> unsigned int max_rqst_sz, max_resp_sz;
> + unsigned int max_bc_payload = rpc_max_bc_payload(clnt);
>
> max_rqst_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxwrite_overhead;
> max_resp_sz = NFS_MAX_FILE_IO_SIZE + nfs41_maxread_overhead;
> @@ -7315,8 +7317,8 @@ static void nfs4_init_channel_attrs(struct nfs41_create_session_args *args)
> args->fc_attrs.max_ops, args->fc_attrs.max_reqs);
>
> /* Back channel attributes */
> - args->bc_attrs.max_rqst_sz = PAGE_SIZE;
> - args->bc_attrs.max_resp_sz = PAGE_SIZE;
> + args->bc_attrs.max_rqst_sz = max_bc_payload;
> + args->bc_attrs.max_resp_sz = max_bc_payload;
> args->bc_attrs.max_resp_sz_cached = 0;
> args->bc_attrs.max_ops = NFS4_MAX_BACK_CHANNEL_OPS;
> args->bc_attrs.max_reqs = 1;
> @@ -7420,7 +7422,7 @@ static int _nfs4_proc_create_session(struct nfs_client *clp,
> };
> int status;
>
> - nfs4_init_channel_attrs(&args);
> + nfs4_init_channel_attrs(&args, clp->cl_rpcclient);
> args.flags = (SESSION4_PERSIST | SESSION4_BACK_CHAN);
>
> status = rpc_call_sync(session->clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
> diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h
> index 131032f..1cad92e 100644
> --- a/include/linux/sunrpc/clnt.h
> +++ b/include/linux/sunrpc/clnt.h
> @@ -175,6 +175,7 @@ void rpc_setbufsize(struct rpc_clnt *, unsigned int, unsigned int);
> int rpc_protocol(struct rpc_clnt *);
> struct net * rpc_net_ns(struct rpc_clnt *);
> size_t rpc_max_payload(struct rpc_clnt *);
> +size_t rpc_max_bc_payload(struct rpc_clnt *);
> unsigned long rpc_get_timeout(struct rpc_clnt *clnt);
> void rpc_force_rebind(struct rpc_clnt *);
> size_t rpc_peeraddr(struct rpc_clnt *, struct sockaddr *, size_t);
> diff --git a/include/linux/sunrpc/xprt.h b/include/linux/sunrpc/xprt.h
> index 69ef5b3..d32c319 100644
> --- a/include/linux/sunrpc/xprt.h
> +++ b/include/linux/sunrpc/xprt.h
> @@ -179,6 +179,7 @@ struct rpc_xprt {
>
> size_t max_payload; /* largest RPC payload size,
> in bytes */
> + size_t max_bc_payload; /* max bytes per bc payload */
> unsigned int tsh_size; /* size of transport specific
> header */
>
> diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
> index b7f2104..ac3dbde 100644
> --- a/net/sunrpc/clnt.c
> +++ b/net/sunrpc/clnt.c
> @@ -1335,6 +1335,21 @@ size_t rpc_max_payload(struct rpc_clnt *clnt)
> EXPORT_SYMBOL_GPL(rpc_max_payload);
>
> /**
> + * rpc_max_bc_payload - Get maximum backchannel payload size, in bytes
> + * @clnt: RPC client to query
> + */
> +size_t rpc_max_bc_payload(struct rpc_clnt *clnt)
> +{
> + size_t ret;
> +
> + rcu_read_lock();
> + ret = rcu_dereference(clnt->cl_xprt)->max_bc_payload;
> + rcu_read_unlock();
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(rpc_max_bc_payload);
> +
> +/**
> * rpc_get_timeout - Get timeout for transport in units of HZ
> * @clnt: RPC client to query
> */
> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
> index b1b009f..06fe152 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -402,6 +402,7 @@ xprt_setup_rdma(struct xprt_create *args)
> xprt->max_payload <<= PAGE_SHIFT;
> dprintk("RPC: %s: transport data payload maximum: %zu bytes\n",
> __func__, xprt->max_payload);
> + xprt->max_bc_payload = cdata.inline_rsize - RPCRDMA_HDRLEN_MIN;
>
> if (!try_module_get(THIS_MODULE))
> goto out4;
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index fde2138..910e192 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -2781,6 +2781,7 @@ static struct rpc_xprt *xs_setup_local(struct xprt_create *args)
> xprt->prot = 0;
> xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
> xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
> + xprt->max_bc_payload = PAGE_SIZE;
>
> xprt->bind_timeout = XS_BIND_TO;
> xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
> @@ -2852,6 +2853,7 @@ static struct rpc_xprt *xs_setup_udp(struct xprt_create *args)
> xprt->tsh_size = 0;
> /* XXX: header size can vary due to auth type, IPv6, etc. */
> xprt->max_payload = (1U << 16) - (MAX_HEADER << 3);
> + xprt->max_bc_payload = PAGE_SIZE;
>
> xprt->bind_timeout = XS_BIND_TO;
> xprt->reestablish_timeout = XS_UDP_REEST_TO;
> @@ -2931,6 +2933,7 @@ static struct rpc_xprt *xs_setup_tcp(struct xprt_create *args)
> xprt->prot = IPPROTO_TCP;
> xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
> xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
> + xprt->max_bc_payload = PAGE_SIZE;
>
> xprt->bind_timeout = XS_BIND_TO;
> xprt->reestablish_timeout = XS_TCP_INIT_REEST_TO;
> @@ -3000,6 +3003,7 @@ static struct rpc_xprt *xs_setup_bc_tcp(struct xprt_create *args)
> xprt->prot = IPPROTO_TCP;
> xprt->tsh_size = sizeof(rpc_fraghdr) / sizeof(u32);
> xprt->max_payload = RPC_MAX_FRAGMENT_SIZE;
> + xprt->max_bc_payload = PAGE_SIZE;
> xprt->timeout = &xs_tcp_default_timeout;
>
> /* backchannel */
>
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