Return-Path: Received: from mail-lb0-f174.google.com ([209.85.217.174]:36053 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753025AbbEGKAk (ORCPT ); Thu, 7 May 2015 06:00:40 -0400 Received: by lbbqq2 with SMTP id qq2so27067919lbb.3 for ; Thu, 07 May 2015 03:00:38 -0700 (PDT) Message-ID: <554B37CF.2070206@dev.mellanox.co.il> Date: Thu, 07 May 2015 13:00:47 +0300 From: Sagi Grimberg MIME-Version: 1.0 To: Chuck Lever , linux-rdma@vger.kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH v1 04/14] xprtrdma: Use ib_device pointer safely References: <20150504174626.3483.97639.stgit@manet.1015granger.net> <20150504175720.3483.80356.stgit@manet.1015granger.net> In-Reply-To: <20150504175720.3483.80356.stgit@manet.1015granger.net> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: 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.