Date: Fri, 15 Aug 2003 14:27:07 -0700
From: Mike Fedyk <mfedyk@matchmail.com>
To: Neil Brown <neilb@cse.unsw.edu.au>
Cc: Andrew Morton <akpm@osdl.org>, Tupshin Harper <tupshin@tupshin.com>,
       linux-kernel@vger.kernel.org, Jens Axboe <axboe@suse.de>
Subject: Re: data corruption using raid0+lvm2+jfs with 2.6.0-test3
Message-ID: <20030815212707.GR1027@matchmail.com>
Mail-Followup-To: Neil Brown <neilb@cse.unsw.edu.au>,
	Andrew Morton <akpm@osdl.org>, Tupshin Harper <tupshin@tupshin.com>,
	linux-kernel@vger.kernel.org, Jens Axboe <axboe@suse.de>
References: <3F3951F1.9040605@tupshin.com> <20030812142846.46eacc48.akpm@osdl.org> <16185.29398.80225.875488@gargle.gargle.HOWL>
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On Wed, Aug 13, 2003 at 09:05:58AM +1000, Neil Brown wrote:
> On Tuesday August 12, akpm@osdl.org wrote:
> > Tupshin Harper <tupshin@tupshin.com> wrote:
> > >
> > > raid0_make_request bug: can't convert block across chunks or bigger than 
> > > 8k 12436792 8
> > 
> > There is a fix for this at
> > 
> > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.0-test3/2.6.0-test3-mm1/broken-out/bio-too-big-fix.patch
> > 
> > Results of testing are always appreciated...
> 
> I don't think this will help.  It is a different problem.
> 
> As far as I can tell, the problem is that dm doesn't honour the
> merge_bvec_fn of the underlying device (neither does md for that
> matter).
> I think it does honour the max_sectors restriction, so it will only
> allow a request as big as one chunk, but it will allow such a requests
> to span a chunk boundary.
> 
> Probably the simplest solution to this is to put in calls to
> bio_split, which will need to be strengthed to handle multi-page bios.
> 
> The policy would be:
>   "a client of a block device *should* honour the various bio size 
>    restrictions, and may suffer performance loss if it doesn't;
>    a block device driver *must* handle any bio it is passed, and may
>    call bio_split to help out".
> 

Any progress on this?
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