From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757978Ab2BCVr0 (ORCPT ); Fri, 3 Feb 2012 16:47:26 -0500 Received: from mail-tul01m020-f174.google.com ([209.85.214.174]:58211 "EHLO mail-tul01m020-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755695Ab2BCVrY (ORCPT ); Fri, 3 Feb 2012 16:47:24 -0500 Date: Fri, 3 Feb 2012 13:47:19 -0800 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH UPDATED 11/11] blkcg: unify blkg's for blkcg policies Message-ID: <20120203214719.GE14209@google.com> References: <1328131156-13290-1-git-send-email-tj@kernel.org> <1328131156-13290-12-git-send-email-tj@kernel.org> <20120202003730.GC19837@google.com> <20120203194105.GA12616@redhat.com> <20120203205910.GB14209@google.com> <20120203214435.GC12616@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120203214435.GC12616@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks. -- tejun