Return-Path: linux-nfs-owner@vger.kernel.org Received: from fieldses.org ([174.143.236.118]:35680 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754119AbaIVSjX (ORCPT ); Mon, 22 Sep 2014 14:39:23 -0400 Date: Mon, 22 Sep 2014 14:39:22 -0400 From: "J. Bruce Fields" To: Steve Wise Cc: linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH] svcrdma: Advertise the correct max payload Message-ID: <20140922183922.GB26763@fieldses.org> References: <20140922183653.19376.14276.stgit@build.ogc.int> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20140922183653.19376.14276.stgit@build.ogc.int> Sender: linux-nfs-owner@vger.kernel.org List-ID: 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? --b. > + > #endif /* _LINUX_SUNRPC_XPRT_RDMA_H */ >