From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: v3.15 dm-mpath regression: cable pull test causes I/O hang Date: Thu, 03 Jul 2014 15:56:48 +0200 Message-ID: <53B56120.8040802@acm.org> References: <53AD6B62.2020407@acm.org> <20140627133345.GA6150@redhat.com> <20140702220223.GA23894@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140702220223.GA23894@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mike Snitzer Cc: Jun'ichi Nomura , device-mapper development List-Id: dm-devel.ids On 07/03/14 00:02, Mike Snitzer wrote: > On Fri, Jun 27 2014 at 9:33am -0400, > Mike Snitzer wrote: > >> On Fri, Jun 27 2014 at 9:02am -0400, >> Bart Van Assche wrote: >> >>> Hello, >>> >>> While running a cable pull simulation test with dm_multipath on top of >>> the SRP initiator driver I noticed that after a few iterations I/O locks >>> up instead of dm_multipath processing the path failure properly (see also >>> below for a call trace). At least kernel versions 3.15 and 3.16-rc2 are >>> vulnerable. This issue does not occur with kernel 3.14. I have tried to >>> bisect this but gave up when I noticed that I/O locked up completely with >>> a kernel built from git commit ID e809917735ebf1b9a56c24e877ce0d320baee2ec >>> (dm mpath: push back requests instead of queueing). But with the bisect I >>> have been able to narrow down this issue to one of the patches in "Merge >>> tag 'dm-3.15-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/ >>> device-mapper/linux-dm". Does anyone have a suggestion how to analyze this >>> further or how to fix this ? > > I still don't have a _known_ fix for your issue but I reviewed commit > e809917735ebf1b9a56c24e877ce0d320baee2ec closer and identified what > looks to be a regression in logic for multipath_busy, it now calls > !pg_ready() instead of directly checking pg_init_in_progress. I think > this is needed (Hannes, what do you think?): > > diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c > index 3f6fd9d..561ead6 100644 > --- a/drivers/md/dm-mpath.c > +++ b/drivers/md/dm-mpath.c > @@ -373,7 +373,7 @@ static int __must_push_back(struct multipath *m) > dm_noflush_suspending(m->ti))); > } > > -#define pg_ready(m) (!(m)->queue_io && !(m)->pg_init_required) > +#define pg_ready(m) (!(m)->queue_io && !(m)->pg_init_required && !(m)->pg_init_in_progress) > > /* > * Map cloned requests Hello Mike, Sorry but even with this patch applied and additionally with commit IDs 86d56134f1b6 ("kobject: Make support for uevent_helper optional") and bcccff93af35 ("kobject: don't block for each kobject_uevent") reverted my multipath test still hangs after a few iterations. I also reran the same test with kernel 3.14.3 and it is still running after 30 iterations. Bart.