linux-kernel - Re: blk_throtl_exit taking q->queue

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Date:	Mon, 21 Feb 2011 18:24:19 +1100
From:	NeilBrown <neilb@...e.de>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	Mike Snitzer <snitzer@...hat.com>,
	Jens Axboe <jaxboe@...ionio.com>, linux-kernel@...r.kernel.org
Subject: Re: blk_throtl_exit taking q->queue_lock is problematic

On Fri, 18 Feb 2011 10:04:29 -0500 Vivek Goyal <vgoyal@...hat.com> wrote:

> On Fri, Feb 18, 2011 at 02:33:25PM +1100, NeilBrown wrote:
> > On Thu, 17 Feb 2011 22:19:52 -0500 Mike Snitzer <snitzer@...hat.com> wrote:

> > > Noticed an inconsistency, raid10.c's additional locking also protects
> > > the bio_list_add() whereas raid1.c's doesn't.  Seems the additional
> > > protection in raid10 isn't needed?
> > 
> > Correct - not needed at all.
> > I put it there because it felt a little cleaner keeping the two 'lock's
> > together like the two 'unlock's.  Probably confusing though...
> 
> I guess you could use blk_plug_device_unlocked() to get rid of ugliness
> and this routine will take care of taking queue lock.
> 

Yep, that gets rid of some ugliness.
I've made that change and will submit it in due course.
So blk_throtl doesn't need any change to avoid the problem with md - that
changes are made in md instead.

Thanks,
NeilBrown

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