linux-kernel - Re: [PATCH 05/12] blkcg: update blkg get functions take blkio

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 19 Jan 2012 07:45:15 -0800
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
Subject: Re: [PATCH 05/12] blkcg: update blkg get functions take
 blkio_cgroup as parameter

On Thu, Jan 19, 2012 at 06:21:02AM -0500, Vivek Goyal wrote:
> On Wed, Jan 18, 2012 at 05:11:23PM -0800, Tejun Heo wrote:
> 
> [..]
> > -static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
> > +static struct throtl_grp *throtl_get_tg(struct throtl_data *td,
> > +					struct blkio_cgroup *blkcg)
> >  {
> >  	struct throtl_grp *tg = NULL, *__tg = NULL;
> > -	struct blkio_cgroup *blkcg;
> >  	struct request_queue *q = td->queue;
> >  
> >  	/* no throttling for dead queue */
> >  	if (unlikely(blk_queue_dead(q)))
> >  		return NULL;
> >  
> > -	blkcg = task_blkio_cgroup(current);
> >  	tg = throtl_find_tg(td, blkcg);
> >  	if (tg)
> >  		return tg;
> >  
> > +	if (!css_tryget(&blkcg->css))
> > +		return NULL;
> > +
> 
> This reference is to make sure that blkcg does not go away while we drop
> the rcu lock and do the group allocation?

Yeah, for now but later patch will make blkg's hold onto the
associated blkcg and this reference will be dropped on blkg
destruction.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/