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Message-ID: <20120203215349.GF9683@redhat.com> Date: Fri, 3 Feb 2012 16:53:49 -0500 From: Vivek Goyal <vgoyal@...hat.com> To: Tejun Heo <tj@...nel.org> Cc: axboe@...nel.dk, ctalbott@...gle.com, rni@...gle.com, linux-kernel@...r.kernel.org Subject: Re: [PATCH UPDATED 11/11] blkcg: unify blkg's for blkcg policies On Fri, Feb 03, 2012 at 01:47:19PM -0800, Tejun Heo wrote: > On Fri, Feb 03, 2012 at 04:44:35PM -0500, Vivek Goyal wrote: > > Ok, looks like now it is needed because blkcg lock will just gurantee that > > blkg is around but blkg->pd[plid] can disappear if you are not holding > > blkio_list lock (update_root_blkgs). > > > > I am wondering if we should take blkcg->lock if blkg is on blkcg list and > > is being modified in place. That way, once we are switching elevator, > > we should be able to shoot down the policy data without taking blkio_list > > lock. > > I think it gotta become something per-queue, not global, and if we > make it per-queue, it should be able to live inside queue_lock. Hmm... then blkiocg_reset_stats() will run into lock ordering issue. Can't hold queue lock inside blkcg lock. I guess you will do some kind of locking trick again as you did for io context logic. Thanks Vivek -- 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/
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