Return-Path: Received: from mail-ob0-f177.google.com ([209.85.214.177]:33855 "EHLO mail-ob0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751242AbcBLR1Q (ORCPT ); Fri, 12 Feb 2016 12:27:16 -0500 Received: by mail-ob0-f177.google.com with SMTP id wb13so131545539obb.1 for ; Fri, 12 Feb 2016 09:27:16 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20160212161758.32662.73404.stgit@manet.1015granger.net> References: <20160212161758.32662.73404.stgit@manet.1015granger.net> Date: Fri, 12 Feb 2016 12:27:16 -0500 Message-ID: Subject: Re: [PATCH RFC] sunrpc: Advertise maximum backchannel payload size From: Trond Myklebust To: Chuck Lever Cc: Linux NFS Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Feb 12, 2016 at 11:52 AM, Chuck Lever 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 > --- > > 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 */ > > -- > To unsubscribe from this list: send the line "unsubscribe linux-nfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html