From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shaohua Li Subject: Re: [PATCH 1/7] blkcg: relocate __blkg_release_rcu() Date: Tue, 14 Nov 2017 15:12:26 -0800 Message-ID: <20171114231226.bnqrb2xadiw7ba2q@kernel.org> References: <20171112222613.3613362-1-tj@kernel.org> <20171112222613.3613362-2-tj@kernel.org> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20171112222613.3613362-2-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, guro-b10kYP2dOMg@public.gmane.org On Sun, Nov 12, 2017 at 02:26:07PM -0800, Tejun Heo wrote: > Move __blkg_release_rcu() above blkg_alloc(). This is a pure code > reorganization to prepare for the switch to percpu_ref. > > Signed-off-by: Tejun Heo Reviewed-by: Shaohua Li > --- > block/blk-cgroup.c | 46 +++++++++++++++++++++++----------------------- > 1 file changed, 23 insertions(+), 23 deletions(-) > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > index d3f56ba..6482be5 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -81,6 +81,29 @@ static void blkg_free(struct blkcg_gq *blkg) > kfree(blkg); > } > > +/* > + * A group is RCU protected, but having an rcu lock does not mean that one > + * can access all the fields of blkg and assume these are valid. For > + * example, don't try to follow throtl_data and request queue links. > + * > + * Having a reference to blkg under an rcu allows accesses to only values > + * local to groups like group stats and group rate limits. > + */ > +void __blkg_release_rcu(struct rcu_head *rcu_head) > +{ > + struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head); > + > + /* release the blkcg and parent blkg refs this blkg has been holding */ > + css_put(&blkg->blkcg->css); > + if (blkg->parent) > + blkg_put(blkg->parent); > + > + wb_congested_put(blkg->wb_congested); > + > + blkg_free(blkg); > +} > +EXPORT_SYMBOL_GPL(__blkg_release_rcu); > + > /** > * blkg_alloc - allocate a blkg > * @blkcg: block cgroup the new blkg is associated with > @@ -378,29 +401,6 @@ static void blkg_destroy_all(struct request_queue *q) > } > > /* > - * A group is RCU protected, but having an rcu lock does not mean that one > - * can access all the fields of blkg and assume these are valid. For > - * example, don't try to follow throtl_data and request queue links. > - * > - * Having a reference to blkg under an rcu allows accesses to only values > - * local to groups like group stats and group rate limits. > - */ > -void __blkg_release_rcu(struct rcu_head *rcu_head) > -{ > - struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head); > - > - /* release the blkcg and parent blkg refs this blkg has been holding */ > - css_put(&blkg->blkcg->css); > - if (blkg->parent) > - blkg_put(blkg->parent); > - > - wb_congested_put(blkg->wb_congested); > - > - blkg_free(blkg); > -} > -EXPORT_SYMBOL_GPL(__blkg_release_rcu); > - > -/* > * The next function used by blk_queue_for_each_rl(). It's a bit tricky > * because the root blkg uses @q->root_rl instead of its own rl. > */ > -- > 2.9.5 >