From: Christoph Hellwig <hch@infradead.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: linux-block@vger.kernel.org, dm-devel@redhat.com,
linux-nvme@lists.infradead.org
Subject: Re: data corruption with 'splt' workload to XFS on DM cache with its 3 underlying devices being on same NVMe device
Date: Tue, 24 Jul 2018 10:42:41 -0700 [thread overview]
Message-ID: <20180724174241.GA828@infradead.org> (raw)
In-Reply-To: <20180724130703.GA30804@redhat.com>
On Tue, Jul 24, 2018 at 09:07:03AM -0400, Mike Snitzer wrote:
> True. We only ever support mapping the partitions ontop of
> request-based multipath (via dm-linear volumes created by kpartx).
>
> > So, have you tested that request-based multipathing works on a
> > partition _at all_? I'm not sure if partition mapping is done
> > correctly here; we never remap the start of the request (nor bio,
> > come to speak of it), so it looks as if we would be doing the wrong
> > things here.
> >
> > Have you checked that partition remapping is done correctly?
>
> It clearly doesn't work. Not quite following why but...
blk_insert_cloned_request seems to be missing a call to
blk_partition_remap. Given that no one but dm-multipath uses this
request clone insert helper, and people generally run multipath on
the whole device this is a code path that is almost never exercised.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
dm-devel@redhat.com
Subject: Re: data corruption with 'splt' workload to XFS on DM cache with its 3 underlying devices being on same NVMe device
Date: Tue, 24 Jul 2018 10:42:41 -0700 [thread overview]
Message-ID: <20180724174241.GA828@infradead.org> (raw)
In-Reply-To: <20180724130703.GA30804@redhat.com>
On Tue, Jul 24, 2018 at 09:07:03AM -0400, Mike Snitzer wrote:
> True. We only ever support mapping the partitions ontop of
> request-based multipath (via dm-linear volumes created by kpartx).
>
> > So, have you tested that request-based multipathing works on a
> > partition _at all_? I'm not sure if partition mapping is done
> > correctly here; we never remap the start of the request (nor bio,
> > come to speak of it), so it looks as if we would be doing the wrong
> > things here.
> >
> > Have you checked that partition remapping is done correctly?
>
> It clearly doesn't work. Not quite following why but...
blk_insert_cloned_request seems to be missing a call to
blk_partition_remap. Given that no one but dm-multipath uses this
request clone insert helper, and people generally run multipath on
the whole device this is a code path that is almost never exercised.
WARNING: multiple messages have this Message-ID (diff)
From: hch@infradead.org (Christoph Hellwig)
Subject: data corruption with 'splt' workload to XFS on DM cache with its 3 underlying devices being on same NVMe device
Date: Tue, 24 Jul 2018 10:42:41 -0700 [thread overview]
Message-ID: <20180724174241.GA828@infradead.org> (raw)
In-Reply-To: <20180724130703.GA30804@redhat.com>
On Tue, Jul 24, 2018@09:07:03AM -0400, Mike Snitzer wrote:
> True. We only ever support mapping the partitions ontop of
> request-based multipath (via dm-linear volumes created by kpartx).
>
> > So, have you tested that request-based multipathing works on a
> > partition _at all_? I'm not sure if partition mapping is done
> > correctly here; we never remap the start of the request (nor bio,
> > come to speak of it), so it looks as if we would be doing the wrong
> > things here.
> >
> > Have you checked that partition remapping is done correctly?
>
> It clearly doesn't work. Not quite following why but...
blk_insert_cloned_request seems to be missing a call to
blk_partition_remap. Given that no one but dm-multipath uses this
request clone insert helper, and people generally run multipath on
the whole device this is a code path that is almost never exercised.
next prev parent reply other threads:[~2018-07-24 17:42 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-23 16:33 data corruption with 'splt' workload to XFS on DM cache with its 3 underlying devices being on same NVMe device Mike Snitzer
2018-07-23 16:33 ` Mike Snitzer
2018-07-23 16:33 ` Mike Snitzer
2018-07-24 6:00 ` Hannes Reinecke
2018-07-24 6:00 ` Hannes Reinecke
2018-07-24 13:07 ` Mike Snitzer
2018-07-24 13:07 ` Mike Snitzer
2018-07-24 13:07 ` Mike Snitzer
2018-07-24 13:22 ` Laurence Oberman
2018-07-24 13:22 ` Laurence Oberman
2018-07-24 13:22 ` Laurence Oberman
2018-07-24 13:51 ` Hannes Reinecke
2018-07-24 13:51 ` Hannes Reinecke
2018-07-24 13:51 ` Hannes Reinecke
2018-07-24 13:57 ` Laurence Oberman
2018-07-24 13:57 ` Laurence Oberman
2018-07-24 13:57 ` Laurence Oberman
2018-07-24 15:18 ` Mike Snitzer
2018-07-24 15:18 ` Mike Snitzer
2018-07-24 15:18 ` Mike Snitzer
2018-07-24 15:31 ` Laurence Oberman
2018-07-24 15:31 ` Laurence Oberman
2018-07-24 15:31 ` Laurence Oberman
2018-07-24 17:42 ` Christoph Hellwig [this message]
2018-07-24 17:42 ` Christoph Hellwig
2018-07-24 17:42 ` Christoph Hellwig
2018-07-24 14:25 ` Bart Van Assche
2018-07-24 14:25 ` Bart Van Assche
2018-07-24 14:25 ` Bart Van Assche
2018-07-24 15:07 ` Mike Snitzer
2018-07-24 15:07 ` Mike Snitzer
2018-07-24 15:07 ` Mike Snitzer
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