From: Daniel Phillips <phillips@phunq.net>
To: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] [PATCH] A clean approach to writeout throttling
Date: Thu, 6 Dec 2007 23:13:42 -0800
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References: <200712051603.02183.phillips@phunq.net> <200712061604.41490.phillips@phunq.net> <20071206162915.a3917d1c.akpm@linux-foundation.org>
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On Thursday 06 December 2007 16:29, Andrew Morton wrote:
> On Thu, 6 Dec 2007 16:04:41 -0800
>
> Daniel Phillips <phillips@phunq.net> wrote:
> > The runner up key idea is that we will gain a notion of "block
> > device stack" (or block stack for short, so that we may implement
> > block stackers) which for the time being will simply be Device
> > Mapper's notion of device stack, however many warts that may have. 
> > It's there now and we use it for ddsnap.
>
> Perhaps all we need to track is the outermost point?
>
> submit_bio(...)
> {
> 	bool remove_the_rq = false;
>
> 	...
> 	if (current->the_rq == NULL) {
> 		current->the_rq = rq;
> 		remove_the_rq = true;
> 	}
> 	...
> 	if (remove_the_rq)
> 		current->the_rq = NULL;
> }
>
> ?

The parent patch already has that crucial property in a simple say, see

       if (q && q->metric && !bio->bi_queue) {
               bio->bi_queue = q;

Regards,

Daniel
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