linux-kernel - Re: [PATCH] dm: dm-cache fails to write the cache device in writethrough mode

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Message-ID: <1363983716.3728.42.camel@deadeye.wl.decadent.org.uk>
Date:	Fri, 22 Mar 2013 20:21:56 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	"Darrick J. Wong" <darrick.wong@...cle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	dm-devel@...hat.com, linux-kernel@...r.kernel.org,
	Heinz Mauelshagen <heinzm@...hat.com>,
	Joe Thornber <ejt@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Paul Taysom <taysom@...omium.org>,
	Randy Dunlap <rdunlap@...radead.org>, stable@...r.kernel.org
Subject: Re: [PATCH] dm: dm-cache fails to write the cache device in
 writethrough mode

On Fri, 2013-03-22 at 13:11 -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.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
[...]

This is not the correct way to submit a change to stable.  See
Documentation/stable_kernel_rules.txt

Ben.

-- 
Ben Hutchings
Make three consecutive correct guesses and you will be considered an expert.

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