From patchwork Thu Mar 11 18:32:31 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever III X-Patchwork-Id: 12132465 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00CEAC433DB for ; Thu, 11 Mar 2021 18:33:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B804564FBA for ; Thu, 11 Mar 2021 18:33:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229944AbhCKScm (ORCPT ); Thu, 11 Mar 2021 13:32:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:33200 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230162AbhCKScj (ORCPT ); Thu, 11 Mar 2021 13:32:39 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6BED564FEF; Thu, 11 Mar 2021 18:32:32 +0000 (UTC) Subject: [PATCH] svcrdma: Revert "svcrdma: Reduce Receive doorbell rate" From: Chuck Lever To: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Date: Thu, 11 Mar 2021 13:32:31 -0500 Message-ID: <161548755089.1565.6879184359338461328.stgit@klimt.1015granger.net> User-Agent: StGit/1.0-5-g755c MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org I tested commit 43042b90cae1 ("svcrdma: Reduce Receive doorbell rate") with mlx4 (IB) and software iWARP and didn't find any issues. However, I recently got my hardware iWARP setup back on line (FastLinQ) and it's crashing hard on this commit (confirmed via bisect). The failure mode is complex. - After a connection is established, the first Receive completes normally. - But the second and third Receives have garbage in their Receive buffers. The server responds with ERR_VERS as a result. - When the client tears down the connection to retry, a couple of posted Receives flush twice, and that corrupts the recv_ctxt free list. - __svc_rdma_free then faults or loops infinitely while destroying the xprt's recv_ctxts. Since 43042b90cae1 ("svcrdma: Reduce Receive doorbell rate") does not fix a bug but is a scalability enhancement, it's safe and appropriate to revert it while working on a replacement. Fixes: 43042b90cae1 ("svcrdma: Reduce Receive doorbell rate") Signed-off-by: Chuck Lever --- include/linux/sunrpc/svc_rdma.h | 1 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 82 +++++++++++++++---------------- 2 files changed, 39 insertions(+), 44 deletions(-) diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h index 7c693b31965e..1e76ed688044 100644 --- a/include/linux/sunrpc/svc_rdma.h +++ b/include/linux/sunrpc/svc_rdma.h @@ -104,7 +104,6 @@ struct svcxprt_rdma { wait_queue_head_t sc_send_wait; /* SQ exhaustion waitlist */ unsigned long sc_flags; - u32 sc_pending_recvs; struct list_head sc_read_complete_q; struct work_struct sc_work; diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index 6d28f23ceb35..7d34290e2ff8 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -266,46 +266,33 @@ void svc_rdma_release_rqst(struct svc_rqst *rqstp) svc_rdma_recv_ctxt_put(rdma, ctxt); } -static bool svc_rdma_refresh_recvs(struct svcxprt_rdma *rdma, - unsigned int wanted, bool temp) +static int __svc_rdma_post_recv(struct svcxprt_rdma *rdma, + struct svc_rdma_recv_ctxt *ctxt) { - const struct ib_recv_wr *bad_wr = NULL; - struct svc_rdma_recv_ctxt *ctxt; - struct ib_recv_wr *recv_chain; int ret; - recv_chain = NULL; - while (wanted--) { - ctxt = svc_rdma_recv_ctxt_get(rdma); - if (!ctxt) - break; - - trace_svcrdma_post_recv(ctxt); - ctxt->rc_temp = temp; - ctxt->rc_recv_wr.next = recv_chain; - recv_chain = &ctxt->rc_recv_wr; - rdma->sc_pending_recvs++; - } - if (!recv_chain) - return false; - - ret = ib_post_recv(rdma->sc_qp, recv_chain, &bad_wr); + trace_svcrdma_post_recv(ctxt); + ret = ib_post_recv(rdma->sc_qp, &ctxt->rc_recv_wr, NULL); if (ret) goto err_post; - return true; + return 0; err_post: - while (bad_wr) { - ctxt = container_of(bad_wr, struct svc_rdma_recv_ctxt, - rc_recv_wr); - bad_wr = bad_wr->next; - svc_rdma_recv_ctxt_put(rdma, ctxt); - } - trace_svcrdma_rq_post_err(rdma, ret); - /* Since we're destroying the xprt, no need to reset - * sc_pending_recvs. */ - return false; + svc_rdma_recv_ctxt_put(rdma, ctxt); + return ret; +} + +static int svc_rdma_post_recv(struct svcxprt_rdma *rdma) +{ + struct svc_rdma_recv_ctxt *ctxt; + + if (test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags)) + return 0; + ctxt = svc_rdma_recv_ctxt_get(rdma); + if (!ctxt) + return -ENOMEM; + return __svc_rdma_post_recv(rdma, ctxt); } /** @@ -316,7 +303,20 @@ static bool svc_rdma_refresh_recvs(struct svcxprt_rdma *rdma, */ bool svc_rdma_post_recvs(struct svcxprt_rdma *rdma) { - return svc_rdma_refresh_recvs(rdma, rdma->sc_max_requests, true); + struct svc_rdma_recv_ctxt *ctxt; + unsigned int i; + int ret; + + for (i = 0; i < rdma->sc_max_requests; i++) { + ctxt = svc_rdma_recv_ctxt_get(rdma); + if (!ctxt) + return false; + ctxt->rc_temp = true; + ret = __svc_rdma_post_recv(rdma, ctxt); + if (ret) + return false; + } + return true; } /** @@ -324,6 +324,8 @@ bool svc_rdma_post_recvs(struct svcxprt_rdma *rdma) * @cq: Completion Queue context * @wc: Work Completion object * + * NB: The svc_xprt/svcxprt_rdma is pinned whenever it's possible that + * the Receive completion handler could be running. */ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc) { @@ -331,8 +333,6 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc) struct ib_cqe *cqe = wc->wr_cqe; struct svc_rdma_recv_ctxt *ctxt; - rdma->sc_pending_recvs--; - /* WARNING: Only wc->wr_cqe and wc->status are reliable */ ctxt = container_of(cqe, struct svc_rdma_recv_ctxt, rc_cqe); @@ -340,6 +340,9 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc) if (wc->status != IB_WC_SUCCESS) goto flushed; + if (svc_rdma_post_recv(rdma)) + goto post_err; + /* All wc fields are now known to be valid */ ctxt->rc_byte_len = wc->byte_len; @@ -350,18 +353,11 @@ static void svc_rdma_wc_receive(struct ib_cq *cq, struct ib_wc *wc) spin_unlock(&rdma->sc_rq_dto_lock); if (!test_bit(RDMAXPRT_CONN_PENDING, &rdma->sc_flags)) svc_xprt_enqueue(&rdma->sc_xprt); - - if (!test_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags) && - rdma->sc_pending_recvs < rdma->sc_max_requests) - if (!svc_rdma_refresh_recvs(rdma, RPCRDMA_MAX_RECV_BATCH, - false)) - goto post_err; - return; flushed: - svc_rdma_recv_ctxt_put(rdma, ctxt); post_err: + svc_rdma_recv_ctxt_put(rdma, ctxt); set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags); svc_xprt_enqueue(&rdma->sc_xprt); }