From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760671Ab2CTPvZ (ORCPT ); Tue, 20 Mar 2012 11:51:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51914 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755679Ab2CTPvY (ORCPT ); Tue, 20 Mar 2012 11:51:24 -0400 Date: Tue, 20 Mar 2012 11:51:18 -0400 From: Vivek Goyal To: Tejun Heo Cc: axboe@kernel.dk, linux-kernel@vger.kernel.org, ctalbott@google.com, rni@google.com Subject: Re: [PATCHSET] block: remove ioc_*_changed() Message-ID: <20120320155118.GC17071@redhat.com> References: <1332195059-2750-1-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1332195059-2750-1-git-send-email-tj@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 19, 2012 at 03:10:55PM -0700, Tejun Heo wrote: > Hello, guys. > > The changed notification used by cfq is rather odd. cfq caches the > associated cfqqs per cic and uses the changed notification to expire > those lookup caches. > > The explicit notification mechanism might make sense if determining > whether the current cache is up-to-date is difficult or expensive; > however, that isn't the case here. Determining whether ioprio or > cgroup has changed is straight-forward and inexpensive. > > This patchset updates cfq to so that it remembers the current ioprio > and blkcg in the cic and determines whether cfqq's need to be reset > without using the changed notification and drops the changed > notification code. Hi Tejun, So this patch still breaks cic->cfqq association in asynchronous manner, when new request comes in. So it will still not solve the problem I reported where after doing IO a task changes cgroup and tries to delete the old cgroup and hangs forever as cic->cfqq is still holding a reference to cgroup? Thanks Vivek