From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754375Ab2AXPxR (ORCPT ); Tue, 24 Jan 2012 10:53:17 -0500 Received: from mail-iy0-f174.google.com ([209.85.210.174]:37028 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752166Ab2AXPxP (ORCPT ); Tue, 24 Jan 2012 10:53:15 -0500 Date: Tue, 24 Jan 2012 07:53:09 -0800 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org, Kay Sievers Subject: Re: [PATCH 14/16] blkcg: don't allow or retain configuration of missing devices Message-ID: <20120124155309.GA12906@google.com> References: <1327360193-24679-1-git-send-email-tj@kernel.org> <1327360193-24679-15-git-send-email-tj@kernel.org> <20120124154224.GA17291@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120124154224.GA17291@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 Tue, Jan 24, 2012 at 10:42:24AM -0500, Vivek Goyal wrote: > On Mon, Jan 23, 2012 at 03:09:51PM -0800, Tejun Heo wrote: > > + disk = get_gendisk(dev, &part); > > + > > + if ((!disk || part) && temp) { > > + ret = -ENODEV; > > + goto out; > > + } > > + > > + rcu_read_lock(); > > + > > + if (disk && !part) { > > + spin_lock_irq(disk->queue->queue_lock); > > + blkg = blkg_lookup_create(blkcg, disk->queue, plid); > > + spin_unlock_irq(disk->queue->queue_lock); > > If queue is in bypass mode, is group creation and linking allowed when > somebody is trying to set per device rules. (/me is thinking if there are > any potential races between elevator switch and rule setting in cgroup). Yeap, there is. Nice catch. blkg_lookup_create() should be testing blk_queue_bypass() instead of blk_queue_dead() and parse_and_set should probably retry after a bit. Will update. Thanks. -- tejun