From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752654Ab3ABSsZ (ORCPT ); Wed, 2 Jan 2013 13:48:25 -0500 Received: from mx1.redhat.com ([209.132.183.28]:49043 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887Ab3ABSsX (ORCPT ); Wed, 2 Jan 2013 13:48:23 -0500 Date: Wed, 2 Jan 2013 13:48:15 -0500 From: Vivek Goyal To: Tejun Heo Cc: lizefan@huawei.com, axboe@kernel.dk, containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, ctalbott@google.com, rni@google.com Subject: Re: [PATCH 20/24] block: RCU free request_queue Message-ID: <20130102184814.GD4306@redhat.com> References: <1356726946-26037-1-git-send-email-tj@kernel.org> <1356726946-26037-21-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1356726946-26037-21-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 Fri, Dec 28, 2012 at 12:35:42PM -0800, Tejun Heo wrote: > RCU free request_queue so that blkcg_gq->q can be dereferenced under > RCU lock. This will be used to implement hierarchical stats. Can we just take a blkg reference on ->q in blkg_alloc() and drop that reference in blkg_free(), instead of RCU freeing up queue. Thanks Vivek > > Signed-off-by: Tejun Heo > --- > block/blk-sysfs.c | 9 ++++++++- > include/linux/blkdev.h | 2 ++ > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c > index 7881477..6206a93 100644 > --- a/block/blk-sysfs.c > +++ b/block/blk-sysfs.c > @@ -497,6 +497,13 @@ queue_attr_store(struct kobject *kobj, struct attribute *attr, > return res; > } > > +static void blk_free_queue_rcu(struct rcu_head *rcu_head) > +{ > + struct request_queue *q = container_of(rcu_head, struct request_queue, > + rcu_head); > + kmem_cache_free(blk_requestq_cachep, q); > +} > + > /** > * blk_release_queue: - release a &struct request_queue when it is no longer needed > * @kobj: the kobj belonging to the request queue to be released > @@ -538,7 +545,7 @@ static void blk_release_queue(struct kobject *kobj) > bdi_destroy(&q->backing_dev_info); > > ida_simple_remove(&blk_queue_ida, q->id); > - kmem_cache_free(blk_requestq_cachep, q); > + call_rcu(&q->rcu_head, blk_free_queue_rcu); > } > > static const struct sysfs_ops queue_sysfs_ops = { > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index f94bc83..406343c 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > > #include > > @@ -437,6 +438,7 @@ struct request_queue { > /* Throttle data */ > struct throtl_data *td; > #endif > + struct rcu_head rcu_head; > }; > > #define QUEUE_FLAG_QUEUED 1 /* uses generic tag queueing */ > -- > 1.8.0.2