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From: Joe Thornber <thornber@redhat.com>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: dm-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dm: dm-cache fails to write the cache device in writethrough mode
Date: Mon, 25 Mar 2013 10:28:38 +0000	[thread overview]
Message-ID: <20130325102837.GB6340@debian> (raw)
In-Reply-To: <20130322201151.GB5357@blackbox.djwong.org>

Hi Darrick,

On Fri, Mar 22, 2013 at 01:11:51PM -0700, Darrick J. Wong wrote:
> The new writethrough strategy for dm-cache issues a bio to the origin device,
> remaps the bio to the cache device, and issues the bio to the cache device.
> However, the block layer modifies bi_sector and bi_size, so we need to preserve
> these or else nothing gets written to the cache (bi_size == 0).  This fixes the
> problem where someone writes a block through the cache, but a subsequent reread
> (from the cache) returns old contents.

Thanks for diagnosing this, as you may have gathered none of the
hardware we're testing on does this.  I've pushed a patch to dm-devel
that hopefully will make it's way upstream very quickly.  I used
dm_bio_record/restore, since there are many more fields that
underlying drivers make tweak in the bio.

- Joe

      parent reply	other threads:[~2013-03-25 10:28 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-03-22 20:11 [PATCH] dm: dm-cache fails to write the cache device in writethrough mode Darrick J. Wong
2013-03-22 20:21 ` Ben Hutchings
2013-03-22 20:50   ` Darrick J. Wong
2013-03-22 21:35     ` Mike Snitzer
2013-03-22 22:34 ` Mike Snitzer
2013-03-22 23:16   ` [dm-devel] " Darrick J. Wong
2013-03-23  3:27     ` Mike Snitzer
2013-03-23  3:48       ` [dm-devel] " Alasdair G Kergon
2013-03-23  5:15       ` Darrick J. Wong
2013-03-23 21:08         ` Mike Snitzer
2013-03-23 22:56           ` Mike Snitzer
2013-03-25 23:59             ` [PATCH v2] dm cache: fix writes to " Mike Snitzer
2013-03-23 21:13         ` [dm-devel] dm: dm-cache fails to write the " Alasdair G Kergon
2013-03-23  3:00 ` [dm-devel] [PATCH] " Alasdair G Kergon
2013-03-25 10:28 ` Joe Thornber [this message]

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