From patchwork Mon Apr 4 18:09:04 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 12800721 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CE73C4707E for ; Mon, 4 Apr 2022 21:18:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377843AbiDDVUX (ORCPT ); Mon, 4 Apr 2022 17:20:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379818AbiDDSLF (ORCPT ); Mon, 4 Apr 2022 14:11:05 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2E8C1ADAA for ; Mon, 4 Apr 2022 11:09:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A6677B818D4 for ; Mon, 4 Apr 2022 18:09:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 58BDDC2BBE4 for ; Mon, 4 Apr 2022 18:09:05 +0000 (UTC) Subject: [PATCH v1 1/6] SUNRPC: Fix NFSD's request deferral on RDMA transports From: Chuck Lever To: linux-nfs@vger.kernel.org Date: Mon, 04 Apr 2022 14:09:04 -0400 Message-ID: <164909574412.3716.7890208148717978731.stgit@manet.1015granger.net> In-Reply-To: <164909503892.3716.8666091898179474248.stgit@manet.1015granger.net> References: <164909503892.3716.8666091898179474248.stgit@manet.1015granger.net> User-Agent: StGit/1.5 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org Trond Myklebust reports an NFSD crash in svc_rdma_sendto(). Further investigation shows that the crash occurred while NFSD was handling a deferred request. This patch addresses two inter-related issues that prevent request deferral from working correctly: 1. Prevent the crash by ensuring that the svc_rqst::rq_xprt_ctxt value is available once the request is revisited. Otherwise svc_rdma_sendto() does not have a proper Receive context available with which to construct its reply. 2. Possibly since before commit 71641d99ce03 ("svcrdma: Properly compute .len and .buflen for received RPC Calls"), svc_rdma_recvfrom() did not include the transport header in the returned xdr_buf. There should have been no need for svc_defer() and friends to save and restore that header as of that commit. This issue is addressed in a backport-friendly way by simply having svc_rdma_recvfrom() set rq_xprt_hlen to zero unconditionally, as svc_tcp_recvfrom() does. This enables svc_deferred_recv() to correctly reconstruct an RPC received via RPC/RDMA. Reported-by: Trond Myklebust Link: https://lore.kernel.org/linux-nfs/82662b7190f26fb304eb0ab1bb04279072439d4e.camel@hammerspace.com/ Signed-off-by: Chuck Lever Cc: --- include/linux/sunrpc/svc.h | 1 + net/sunrpc/svc_xprt.c | 3 +++ net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 2 +- 3 files changed, 5 insertions(+), 1 deletion(-) diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index a5dda4987e8b..217711fc9cac 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -395,6 +395,7 @@ struct svc_deferred_req { size_t addrlen; struct sockaddr_storage daddr; /* where reply must come from */ size_t daddrlen; + void *xprt_ctxt; struct cache_deferred_req handle; size_t xprt_hlen; int argslen; diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 297c49855038..5b59e2103526 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -1231,6 +1231,8 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req) dr->daddr = rqstp->rq_daddr; dr->argslen = rqstp->rq_arg.len >> 2; dr->xprt_hlen = rqstp->rq_xprt_hlen; + dr->xprt_ctxt = rqstp->rq_xprt_ctxt; + rqstp->rq_xprt_ctxt = NULL; /* back up head to the start of the buffer and copy */ skip = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len; @@ -1269,6 +1271,7 @@ static noinline int svc_deferred_recv(struct svc_rqst *rqstp) rqstp->rq_xprt_hlen = dr->xprt_hlen; rqstp->rq_daddr = dr->daddr; rqstp->rq_respages = rqstp->rq_pages; + rqstp->rq_xprt_ctxt = dr->xprt_ctxt; svc_xprt_received(rqstp->rq_xprt); return (dr->argslen<<2) - dr->xprt_hlen; } diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index cf76a6ad127b..864131a9fc6e 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -831,7 +831,7 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp) goto out_err; if (ret == 0) goto out_drop; - rqstp->rq_xprt_hlen = ret; + rqstp->rq_xprt_hlen = 0; if (svc_rdma_is_reverse_direction_reply(xprt, ctxt)) goto out_backchannel;