Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755497AbYCQIIy (ORCPT ); Mon, 17 Mar 2008 04:08:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752781AbYCQIIo (ORCPT ); Mon, 17 Mar 2008 04:08:44 -0400 Received: from brick.kernel.dk ([87.55.233.238]:13374 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752718AbYCQIIn (ORCPT ); Mon, 17 Mar 2008 04:08:43 -0400 Date: Mon, 17 Mar 2008 09:08:37 +0100 From: Jens Axboe To: Christof Schmitt Cc: David Wilder , linux-btrace@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, wilder@us.ibm.com Subject: Re: blktrace/relay/s390: Oops in subbuf_splice_actor Message-ID: <20080317080836.GZ17940@kernel.dk> References: <20080314084337.GA9436@schmichrtp.de.ibm.com> <20080314115802.GK17940@kernel.dk> <20080314130552.GA9352@schmichrtp.de.ibm.com> <20080314131007.GQ17940@kernel.dk> <20080314132238.GA9815@schmichrtp.de.ibm.com> <47DA97DF.6010008@us.ibm.com> <20080314162807.GA4488@schmichrtp.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080314162807.GA4488@schmichrtp.de.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3635 Lines: 78 On Fri, Mar 14 2008, Christof Schmitt wrote: > On Fri, Mar 14, 2008 at 08:21:03AM -0700, David Wilder wrote: > > Christof Schmitt wrote: > > >On Fri, Mar 14, 2008 at 02:10:07PM +0100, Jens Axboe wrote: > > >>On Fri, Mar 14 2008, Christof Schmitt wrote: > > >>>On Fri, Mar 14, 2008 at 12:58:03PM +0100, Jens Axboe wrote: > > >>>>That is indeed a bug, does this work for you? > > >>>> > > >>>>diff --git a/kernel/relay.c b/kernel/relay.c > > >>>>index d080b9d..39d1fa8 100644 > > >>>>--- a/kernel/relay.c > > >>>>+++ b/kernel/relay.c > > >>>>@@ -1066,7 +1066,7 @@ static int subbuf_splice_actor(struct file *in, > > >>>> unsigned int flags, > > >>>> int *nonpad_ret) > > >>>> { > > >>>>- unsigned int pidx, poff, total_len, subbuf_pages, ret; > > >>>>+ unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret; > > >>>> struct rchan_buf *rbuf = in->private_data; > > >>>> unsigned int subbuf_size = rbuf->chan->subbuf_size; > > >>>> uint64_t pos = (uint64_t) *ppos; > > >>>>@@ -1098,7 +1098,9 @@ static int subbuf_splice_actor(struct file *in, > > >>>> pidx = (read_start / PAGE_SIZE) % subbuf_pages; > > >>>> poff = read_start & ~PAGE_MASK; > > >>>> > > >>>>- for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) { > > >>>>+ nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS); > > >>>>+ > > >>>>+ for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) { > > >>>> unsigned int this_len, this_end, private; > > >>>> unsigned int cur_pos = read_start + total_len; > > >>>With the patch, i can run dd and 'blktrace -h traceserver' without the > > >>>oops. But the output from blktrace only contains only zeros and no > > >>>usable data for blkparse. Using blktrace to write the data directly to > > >>>disk, without using the blktrace server works. Is there anything i > > >>>should look for to help debugging the problem? > > >>We should probably get Tom in the loop, as he is the relay expert. I'll > > >>make sure the above patch gets into 2.6.25, as it is definitely a bug > > >>that needs fixing. > > > > > >http://relayfs.sourceforge.net/contact.html mentions Tom Zanussi, but > > >his email address seems to be no longer valid. I copy Dave Wilder > > >here, since he is mentioned as relay maintainer on the web page. > > > > > >Dave, can you have a look at this? I can easily reproduce the problem > > >on s390 Linux for testing and getting more debug information. > > > > > >Christof > > >-- > > >To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > >the body of a message to majordomo@vger.kernel.org > > >More majordomo info at http://vger.kernel.org/majordomo-info.html > > >Please read the FAQ at http://www.tux.org/lkml/ > > > > > > > I will take a look at the problem. > > Any thing special about the test you are running I need to know? > > The test is about using the blktrace network feature on a 64 bit s390 > guest on z/VM. I don't know if 64 bit and z/VM are related to the > problem scenario, it is the only setup i tested. To reproduce, start > somewhere 'blktrace -l' as a server and issue > blktrace -h tracehostname > dd if=/dev/sda of=/dev/null > to start blktrace and some I/O load. If the problem is in the splice part of relay, then the problem will likely go away if you add the -s parameter to blktrace. Might be handy to know if you are experimenting. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/