Return-Path: linux-nfs-owner@vger.kernel.org Received: from linode.aoot.com ([69.164.194.13]:53515 "EHLO linode.aoot.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754731AbaIVTAj (ORCPT ); Mon, 22 Sep 2014 15:00:39 -0400 Message-ID: <54206D7F.6070603@opengridcomputing.com> Date: Mon, 22 Sep 2014 13:42:07 -0500 From: Steve Wise MIME-Version: 1.0 To: "J. Bruce Fields" CC: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH] svcrdma: Advertise the correct max payload References: <20140922183653.19376.14276.stgit@build.ogc.int> <20140922183922.GB26763@fieldses.org> In-Reply-To: <20140922183922.GB26763@fieldses.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 9/22/2014 1:39 PM, J. Bruce Fields wrote: > On Mon, Sep 22, 2014 at 01:36:53PM -0500, Steve Wise wrote: >> Svcrdma currently advertises 1MB, which is too large. The correct value >> is the max scatter-gather allowed in an NFSRDMA IO chunk * the host page >> size. This bug is usually benign because the Linux X64 NFSRDMA client >> correctly limits the payload size to the correct value (64*4096 = 256KB). >> But if the Linux client is PPC64 with a 64KB page size, then the client >> will indeed use a payload size that will overflow the server. >> >> Signed-off-by: Steve Wise >> --- >> >> net/sunrpc/xprtrdma/svc_rdma_transport.c | 2 +- >> net/sunrpc/xprtrdma/xprt_rdma.h | 2 ++ >> 2 files changed, 3 insertions(+), 1 deletions(-) >> >> diff --git a/net/sunrpc/xprtrdma/svc_rdma_transport.c b/net/sunrpc/xprtrdma/svc_rdma_transport.c >> index 374feb4..4e61880 100644 >> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c >> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c >> @@ -91,7 +91,7 @@ struct svc_xprt_class svc_rdma_class = { >> .xcl_name = "rdma", >> .xcl_owner = THIS_MODULE, >> .xcl_ops = &svc_rdma_ops, >> - .xcl_max_payload = RPCSVC_MAXPAYLOAD_TCP, >> + .xcl_max_payload = RPCSVC_MAXPAYLOAD_RDMA, >> .xcl_ident = XPRT_TRANSPORT_RDMA, >> }; >> >> diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h >> index c419498..467a77c 100644 >> --- a/net/sunrpc/xprtrdma/xprt_rdma.h >> +++ b/net/sunrpc/xprtrdma/xprt_rdma.h >> @@ -392,4 +392,6 @@ extern struct kmem_cache *svc_rdma_ctxt_cachep; >> /* Workqueue created in svc_rdma.c */ >> extern struct workqueue_struct *svc_rdma_wq; >> >> +#define RPCSVC_MAXPAYLOAD_RDMA (RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT) > Do you want to define this as the minimum of this and > RPCSVC_MAXPAYLOAD_TCP, in case RPCRDMA_MAX_DATA_SEGS gets increased some > day? Why would it need to be limited by MAXPAYLOAD_TCP?