Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:42501 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751476AbbEGNi6 convert rfc822-to-8bit (ORCPT ); Thu, 7 May 2015 09:38:58 -0400 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Subject: Re: [PATCH v1 04/14] xprtrdma: Use ib_device pointer safely From: Chuck Lever In-Reply-To: <554B37CF.2070206@dev.mellanox.co.il> Date: Thu, 7 May 2015 09:39:24 -0400 Cc: linux-rdma@vger.kernel.org, Linux NFS Mailing List Message-Id: References: <20150504174626.3483.97639.stgit@manet.1015granger.net> <20150504175720.3483.80356.stgit@manet.1015granger.net> <554B37CF.2070206@dev.mellanox.co.il> To: Sagi Grimberg Sender: linux-nfs-owner@vger.kernel.org List-ID: On May 7, 2015, at 6:00 AM, Sagi Grimberg wrote: > On 5/4/2015 8:57 PM, Chuck Lever wrote: >> The connect worker can replace ri_id, but prevents ri_id->device >> from changing during the lifetime of a transport instance. >> >> Cache a copy of ri_id->device in rpcrdma_ia and in rpcrdma_rep. >> The cached copy can be used safely in code that does not serialize >> with the connect worker. >> >> Other code can use it to save an extra address generation (one >> pointer dereference instead of two). >> >> Signed-off-by: Chuck Lever >> --- >> net/sunrpc/xprtrdma/fmr_ops.c | 8 +---- >> net/sunrpc/xprtrdma/frwr_ops.c | 12 +++---- >> net/sunrpc/xprtrdma/physical_ops.c | 8 +---- >> net/sunrpc/xprtrdma/verbs.c | 61 +++++++++++++++++++----------------- >> net/sunrpc/xprtrdma/xprt_rdma.h | 2 + >> 5 files changed, 43 insertions(+), 48 deletions(-) >> >> diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c >> index 302d4eb..0a96155 100644 >> --- a/net/sunrpc/xprtrdma/fmr_ops.c >> +++ b/net/sunrpc/xprtrdma/fmr_ops.c >> @@ -85,7 +85,7 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg, >> int nsegs, bool writing) >> { >> struct rpcrdma_ia *ia = &r_xprt->rx_ia; >> - struct ib_device *device = ia->ri_id->device; >> + struct ib_device *device = ia->ri_device; >> enum dma_data_direction direction = rpcrdma_data_dir(writing); >> struct rpcrdma_mr_seg *seg1 = seg; >> struct rpcrdma_mw *mw = seg1->rl_mw; >> @@ -137,17 +137,13 @@ fmr_op_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg) >> { >> struct rpcrdma_ia *ia = &r_xprt->rx_ia; >> struct rpcrdma_mr_seg *seg1 = seg; >> - struct ib_device *device; >> int rc, nsegs = seg->mr_nsegs; >> LIST_HEAD(l); >> >> list_add(&seg1->rl_mw->r.fmr->list, &l); >> rc = ib_unmap_fmr(&l); >> - read_lock(&ia->ri_qplock); >> - device = ia->ri_id->device; >> while (seg1->mr_nsegs--) >> - rpcrdma_unmap_one(device, seg++); >> - read_unlock(&ia->ri_qplock); >> + rpcrdma_unmap_one(ia->ri_device, seg++); > > Umm, I'm wandering if this is guaranteed to be the same device as > ri_id->device? > > Imagine you are working on a bond device where each slave belongs to > a different adapter. When the active port toggles, you will see a > ADDR_CHANGED event (that the current code does not handle...), what > you'd want to do is just reconnect and rdma_cm will resolve the new > address for you (via the backup slave). I suspect that in case this > flow is concurrent with the reconnects you may end up with a stale > device handle. I?m not sure what you mean by ?stale? : freed memory? I?m looking at this code in rpcrdma_ep_connect() : 916 if (ia->ri_id->device != id->device) { 917 printk("RPC: %s: can't reconnect on " 918 "different device!\n", __func__); 919 rdma_destroy_id(id); 920 rc = -ENETUNREACH; 921 goto out; 922 } After reconnecting, if the ri_id has changed, the connect fails. Today, xprtrdma does not support the device changing out from under it. Note also that our receive completion upcall uses ri_id->device for DMA map syncing. Would that also be a problem during a bond failover? -- Chuck Lever chuck[dot]lever[at]oracle[dot]com