linux-kernel - Re: [PATCH 1/8] blkcg: kill blkio_list and replace blkio_list

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Message-ID: <20120413165519.GA12233@google.com>
Date:	Fri, 13 Apr 2012 09:55:19 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	axboe@...nel.dk, ctalbott@...gle.com, rni@...gle.com,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	containers@...ts.linux-foundation.org
Subject: Re: [PATCH 1/8] blkcg: kill blkio_list and replace blkio_list_lock
 with a mutex

On Fri, Apr 13, 2012 at 09:32:26AM -0400, Vivek Goyal wrote:
> On Thu, Apr 12, 2012 at 04:29:33PM -0700, Tejun Heo wrote:
> 
> Hi Tejun,
> 
> > @@ -732,20 +732,21 @@ void blkio_policy_register(struct blkio_policy_type *blkiop)
> >  {
> >  	struct request_queue *q;
> >  
> > +	mutex_lock(&blkcg_pol_mutex);
> > +
> >  	blkcg_bypass_start();
> > -	spin_lock(&blkio_list_lock);
> >  
> >  	BUG_ON(blkio_policy[blkiop->plid]);
> 
> A minor nit. It might be a good idea to check that blkiop->plid is not
> greater than BLKIO_NR_POLICIES for both registration and unresitration
> functions to avoid touching memory beyond blkio_policy[] array.

I'm making ->plid to be dynamically allocated on registration anyway,
so I don't think it really matters.  The updated unregistration
function does BUG_ON(blkio_policy[pol->plid] != pol) which should
catch stray plid.

Thanks.

-- 
tejun
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