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[68.61.232.219]) by smtp.gmail.com with ESMTPSA id e26sm11973844qka.85.2020.05.12.14.22.10 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 May 2020 14:22:11 -0700 (PDT) Received: from klimt.1015granger.net (klimt.1015granger.net [192.168.1.55]) by gateway.1015granger.net (8.14.7/8.14.7) with ESMTP id 04CLMAVg009875; Tue, 12 May 2020 21:22:10 GMT Subject: [PATCH v2 01/29] SUNRPC: Move xpt_mutex into socket xpo_sendto methods From: Chuck Lever To: bfields@fieldses.org Cc: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Date: Tue, 12 May 2020 17:22:10 -0400 Message-ID: <20200512212210.5826.49628.stgit@klimt.1015granger.net> In-Reply-To: <20200512211640.5826.77139.stgit@klimt.1015granger.net> References: <20200512211640.5826.77139.stgit@klimt.1015granger.net> User-Agent: StGit/0.22-31-g4b47 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org It appears that the RPC/RDMA transport does not need serialization of calls to its xpo_sendto method. Move the mutex into the socket methods that still need that serialization. Tail latencies are unambiguously better with this patch applied. fio randrw 8KB 70/30 on NFSv3, smaller numbers are better: clat percentiles (usec): With xpt_mutex: r | 99.99th=[ 8848] w | 99.99th=[ 9634] Without xpt_mutex: r | 99.99th=[ 8586] w | 99.99th=[ 8979] Serializing the construction of RPC/RDMA transport headers is not really necessary at this point, because the Linux NFS server implementation never changes its credit grant on a connection. If that should change, then svc_rdma_sendto will need to serialize access to the transport's credit grant fields. Reported-by: kbuild test robot [ cel: fix uninitialized variable warning ] Signed-off-by: Chuck Lever --- include/linux/sunrpc/svc_xprt.h | 6 +++++ net/sunrpc/svc_xprt.c | 12 ++-------- net/sunrpc/svcsock.c | 25 ++++++++++++++++++++ net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 35 +++++++++++++--------------- net/sunrpc/xprtrdma/svc_rdma_sendto.c | 10 +++----- net/sunrpc/xprtsock.c | 12 ++++++++-- 6 files changed, 64 insertions(+), 36 deletions(-) diff --git a/include/linux/sunrpc/svc_xprt.h b/include/linux/sunrpc/svc_xprt.h index 9e1e046de176..aca35ab5cff2 100644 --- a/include/linux/sunrpc/svc_xprt.h +++ b/include/linux/sunrpc/svc_xprt.h @@ -117,6 +117,12 @@ static inline int register_xpt_user(struct svc_xprt *xpt, struct svc_xpt_user *u return 0; } +static inline bool svc_xprt_is_dead(const struct svc_xprt *xprt) +{ + return (test_bit(XPT_DEAD, &xprt->xpt_flags) != 0) || + (test_bit(XPT_CLOSE, &xprt->xpt_flags) != 0); +} + int svc_reg_xprt_class(struct svc_xprt_class *); void svc_unreg_xprt_class(struct svc_xprt_class *); void svc_xprt_init(struct net *, struct svc_xprt_class *, struct svc_xprt *, diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 2284ff038dad..07cdbf7d5764 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -914,16 +914,10 @@ int svc_send(struct svc_rqst *rqstp) xb->page_len + xb->tail[0].iov_len; trace_svc_sendto(xb); - - /* Grab mutex to serialize outgoing data. */ - mutex_lock(&xprt->xpt_mutex); trace_svc_stats_latency(rqstp); - if (test_bit(XPT_DEAD, &xprt->xpt_flags) - || test_bit(XPT_CLOSE, &xprt->xpt_flags)) - len = -ENOTCONN; - else - len = xprt->xpt_ops->xpo_sendto(rqstp); - mutex_unlock(&xprt->xpt_mutex); + + len = xprt->xpt_ops->xpo_sendto(rqstp); + trace_svc_send(rqstp, len); svc_xprt_release(rqstp); diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c index 023514e392b3..3e7b6445e317 100644 --- a/net/sunrpc/svcsock.c +++ b/net/sunrpc/svcsock.c @@ -506,6 +506,9 @@ static int svc_udp_recvfrom(struct svc_rqst *rqstp) * svc_udp_sendto - Send out a reply on a UDP socket * @rqstp: completed svc_rqst * + * xpt_mutex ensures @rqstp's whole message is written to the socket + * without interruption. + * * Returns the number of bytes sent, or a negative errno. */ static int svc_udp_sendto(struct svc_rqst *rqstp) @@ -531,6 +534,11 @@ static int svc_udp_sendto(struct svc_rqst *rqstp) svc_set_cmsg_data(rqstp, cmh); + mutex_lock(&xprt->xpt_mutex); + + if (svc_xprt_is_dead(xprt)) + goto out_notconn; + err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, 0, &sent); xdr_free_bvec(xdr); if (err == -ECONNREFUSED) { @@ -538,9 +546,15 @@ static int svc_udp_sendto(struct svc_rqst *rqstp) err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, 0, &sent); xdr_free_bvec(xdr); } + + mutex_unlock(&xprt->xpt_mutex); if (err < 0) return err; return sent; + +out_notconn: + mutex_unlock(&xprt->xpt_mutex); + return -ENOTCONN; } static int svc_udp_has_wspace(struct svc_xprt *xprt) @@ -1063,6 +1077,9 @@ static int svc_tcp_recvfrom(struct svc_rqst *rqstp) * svc_tcp_sendto - Send out a reply on a TCP socket * @rqstp: completed svc_rqst * + * xpt_mutex ensures @rqstp's whole message is written to the socket + * without interruption. + * * Returns the number of bytes sent, or a negative errno. */ static int svc_tcp_sendto(struct svc_rqst *rqstp) @@ -1080,12 +1097,19 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp) svc_release_skb(rqstp); + mutex_lock(&xprt->xpt_mutex); + if (svc_xprt_is_dead(xprt)) + goto out_notconn; err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, marker, &sent); xdr_free_bvec(xdr); if (err < 0 || sent != (xdr->len + sizeof(marker))) goto out_close; + mutex_unlock(&xprt->xpt_mutex); return sent; +out_notconn: + mutex_unlock(&xprt->xpt_mutex); + return -ENOTCONN; out_close: pr_notice("rpc-srv/tcp: %s: %s %d when sending %d bytes - shutting down socket\n", xprt->xpt_server->sv_name, @@ -1093,6 +1117,7 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp) (err < 0) ? err : sent, xdr->len); set_bit(XPT_CLOSE, &xprt->xpt_flags); svc_xprt_enqueue(xprt); + mutex_unlock(&xprt->xpt_mutex); return -EAGAIN; } diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c index af7eb8d202ae..d9aab4504f2c 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c +++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c @@ -210,34 +210,31 @@ rpcrdma_bc_send_request(struct svcxprt_rdma *rdma, struct rpc_rqst *rqst) return -ENOTCONN; } -/* Send an RPC call on the passive end of a transport - * connection. +/** + * xprt_rdma_bc_send_request - Send a reverse-direction Call + * @rqst: rpc_rqst containing Call message to be sent + * + * Return values: + * %0 if the message was sent successfully + * %ENOTCONN if the message was not sent */ -static int -xprt_rdma_bc_send_request(struct rpc_rqst *rqst) +static int xprt_rdma_bc_send_request(struct rpc_rqst *rqst) { struct svc_xprt *sxprt = rqst->rq_xprt->bc_xprt; - struct svcxprt_rdma *rdma; + struct svcxprt_rdma *rdma = + container_of(sxprt, struct svcxprt_rdma, sc_xprt); int ret; dprintk("svcrdma: sending bc call with xid: %08x\n", be32_to_cpu(rqst->rq_xid)); - mutex_lock(&sxprt->xpt_mutex); - - ret = -ENOTCONN; - rdma = container_of(sxprt, struct svcxprt_rdma, sc_xprt); - if (!test_bit(XPT_DEAD, &sxprt->xpt_flags)) { - ret = rpcrdma_bc_send_request(rdma, rqst); - if (ret == -ENOTCONN) - svc_close_xprt(sxprt); - } + if (test_bit(XPT_DEAD, &sxprt->xpt_flags)) + return -ENOTCONN; - mutex_unlock(&sxprt->xpt_mutex); - - if (ret < 0) - return ret; - return 0; + ret = rpcrdma_bc_send_request(rdma, rqst); + if (ret == -ENOTCONN) + svc_close_xprt(sxprt); + return ret; } static void diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c index b6c8643867f2..38e7c3c8c4a9 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c @@ -868,12 +868,10 @@ int svc_rdma_sendto(struct svc_rqst *rqstp) __be32 *p; int ret; - /* Create the RDMA response header. xprt->xpt_mutex, - * acquired in svc_send(), serializes RPC replies. The - * code path below that inserts the credit grant value - * into each transport header runs only inside this - * critical section. - */ + ret = -ENOTCONN; + if (svc_xprt_is_dead(xprt)) + goto err0; + ret = -ENOMEM; sctxt = svc_rdma_send_ctxt_get(rdma); if (!sctxt) diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 845d0be805ec..839c49330785 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2548,8 +2548,16 @@ static int bc_sendto(struct rpc_rqst *req) return sent; } -/* - * The send routine. Borrows from svc_send +/** + * bc_send_request - Send a backchannel Call on a TCP socket + * @req: rpc_rqst containing Call message to be sent + * + * xpt_mutex ensures @rqstp's whole message is written to the socket + * without interruption. + * + * Return values: + * %0 if the message was sent successfully + * %ENOTCONN if the message was not sent */ static int bc_send_request(struct rpc_rqst *req) {