linux-kernel - Re: Mount ext3 with barrier=1 doesn't send real barrier bio?

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Message-ID: <20080821052604.GM20055@kernel.dk>
Date:	Thu, 21 Aug 2008 07:26:05 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Eric Sandeen <sandeen@...deen.net>
Cc:	Milan Broz <mbroz@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Ric Wheeler <rwheeler@...hat.com>,
	"MASON,CHRISTOPHER" <CHRIS.MASON@...cle.com>
Subject: Re: Mount ext3 with barrier=1 doesn't send real barrier bio?

On Wed, Aug 20 2008, Eric Sandeen wrote:
> Milan Broz wrote:
> > Hi,
> > 
> > I run some barrier tests over device-mapper (which currently doesn't
> > support barrier bio at all) and even if I set barrier=1 in ext3 mount,
> > there is never any bio with barrier flag... (in 2.6.27-rc)
> > 
> > How is the barrier=1 flag supposed to work in ext3 (JBD) now?
> 
> Milan, you're right.  Ric saw this same strange behavior when doing some
> benchmarking with and without barriers; Chris noticed the change in
> submit_bh; I was about to write up a similar patch to what you've sent
> already.  Jens, does Milan's fix look good to you?

Yep looks good, thanks a lot Milan! I'll send in the patch, unless I'm
badly mistaken we need it for 2.6.26-stable as well.

-- 
Jens Axboe

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