Date: Mon, 10 Dec 2007 13:32:44 +0100
From: Jens Axboe <jens.axboe@oracle.com>
To: Daniel Phillips <phillips@phunq.net>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>,
       Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC] [PATCH] A clean aEvgeniy pproach to writeout throttling
Message-ID: <20071210123244.GG5008@kernel.dk>
References: <200712051603.02183.phillips@phunq.net> <200712100413.38077.phillips@phunq.net> <20071210121627.GF5008@kernel.dk> <200712100427.58288.phillips@phunq.net>
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On Mon, Dec 10 2007, Daniel Phillips wrote:
> On Monday 10 December 2007 04:16, Jens Axboe wrote:
> > OK, let me get the neon out then. This has nothing to do with
> > throttling, I thought I made it clear that I get why you store the
> > origin queue in ->bi_queue. I'm concerned with the workings of
> > redirecting a bio. Previously we looked up the queue associated with
> > bio->bi_bdev inside the loop in __generic_make_request(), as is
> > REQUIRED to correctly locate a DIFFERENT queue if bio->bi_bdev has
> > been changed to point somewhere else.
> 
> Rhetoric aside, again.
> 
> We are only interested in throttling against the bio->bi_bdev that was 
> stored in the bio at the time of the call to generic_make_request, why 
> should we care about the redirected value?

Let me repeat - this has nothing to do with throttling! You are breaking
the bio redirection by killing that bdev_get_queue() in the
__generic_make_request().

I honestly don't know how to make this any clearer than I already did
above. Sleep on it.

-- 
Jens Axboe

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