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Subject: Re: bdi: register sysfs bdi device only once per queue
From: Peter Zijlstra <peterz@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, kay.sievers@vrfy.org,
       folkert@vanheusden.com, jacmet@sunsite.dk, linux-kernel@vger.kernel.org
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Date: Wed, 05 Nov 2008 23:21:25 +0100
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On Wed, 2008-11-05 at 23:10 +0100, David Woodhouse wrote:
> On Wed, 2008-11-05 at 12:10 -0800, Andrew Morton wrote:
> > > > Devices which share the same queue, like floppies and mtd devices,
> > > > get registered multiple times in the bdi interface, but bdi accounts
> > > > only the last registered device of the devices sharing one queue.
> > > 
> > > David, is there any reason the mtd devices do this?
> > 
> > [tap tap - is this thing turned on?]
> 
> No particular reason. It's been done that way since the dawn of time,
> when it was perfectly normal. Nobody's yet bothered to change that, when
> changing the rules.

I don't think it ever made sense, or was intended that way, but yeah it
didn't really matter in any substantial way.

I can remember touching some mtd stuff back when I did the
per-bdi-writeback stuff, but I can't seem to recall all the details.

Might be time to stare at the mtd code a bit...