Return-Path: Received: from fieldses.org ([173.255.197.46]:43994 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753995AbbJGRBx (ORCPT ); Wed, 7 Oct 2015 13:01:53 -0400 Date: Wed, 7 Oct 2015 13:01:51 -0400 From: "J. Bruce Fields" To: Doug Ledford Cc: Steve Wise , linux-nfs@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH RESEND] svcrdma: handle rdma read with a non-zero initial page offset Message-ID: <20151007170151.GB26514@fieldses.org> References: <20150928214605.17900.50257.stgit@build2.ogc.int> <56140879.3040000@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <56140879.3040000@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, Oct 06, 2015 at 01:44:25PM -0400, Doug Ledford wrote: > On 09/28/2015 05:46 PM, Steve Wise wrote: > > The server rdma_read_chunk_lcl() and rdma_read_chunk_frmr() functions > > were not taking into account the initial page_offset when determining > > the rdma read length. This resulted in a read who's starting address > > and length exceeded the base/bounds of the frmr. > > > > Most work loads don't tickle this bug apparently, but one test hit it > > every time: building the linux kernel on a 16 core node with 'make -j > > 16 O=/mnt/0' where /mnt/0 is a ramdisk mounted via NFSRDMA. > > > > This bug seems to only be tripped with devices having small fastreg page > > list depths. I didn't see it with mlx4, for instance. > > Bruce, what's you're take on this? Do you want to push this through or > would you care if I push it through my tree? Whoops, sorry, I meant to send a pull request for that last week. Uh, I think I'll go ahead and do that now if it's OK with you. --b. > > > Fixes: 0bf4828983df ('svcrdma: refactor marshalling logic') > > Signed-off-by: Steve Wise > > Tested-by: Chuck Lever > > --- > > > > net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 6 ++++-- > > 1 files changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > > index cb51742..5f6ca47 100644 > > --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > > +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c > > @@ -136,7 +136,8 @@ int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt, > > ctxt->direction = DMA_FROM_DEVICE; > > ctxt->read_hdr = head; > > pages_needed = min_t(int, pages_needed, xprt->sc_max_sge_rd); > > - read = min_t(int, pages_needed << PAGE_SHIFT, rs_length); > > + read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset, > > + rs_length); > > > > for (pno = 0; pno < pages_needed; pno++) { > > int len = min_t(int, rs_length, PAGE_SIZE - pg_off); > > @@ -235,7 +236,8 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt, > > ctxt->direction = DMA_FROM_DEVICE; > > ctxt->frmr = frmr; > > pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len); > > - read = min_t(int, pages_needed << PAGE_SHIFT, rs_length); > > + read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset, > > + rs_length); > > > > frmr->kva = page_address(rqstp->rq_arg.pages[pg_no]); > > frmr->direction = DMA_FROM_DEVICE; > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > -- > Doug Ledford > GPG KeyID: 0E572FDD > >