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[209.132.180.67]) by mx.google.com with ESMTP id l2-v6si7488434pgb.417.2018.09.07.00.01.18; Fri, 07 Sep 2018 00:01:50 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Ks0lJN1C; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727212AbeIGK5T (ORCPT + 99 others); Fri, 7 Sep 2018 06:57:19 -0400 Received: from mail-it0-f67.google.com ([209.85.214.67]:52230 "EHLO mail-it0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725843AbeIGK5T (ORCPT ); Fri, 7 Sep 2018 06:57:19 -0400 Received: by mail-it0-f67.google.com with SMTP id h3-v6so19245627ita.2; Thu, 06 Sep 2018 23:17:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=i2ul3SyBZE3L/f+n/d50KIsjUWKjrby2SXdJL+3XjX0=; b=Ks0lJN1Cq+YE7586k6j2Z98QuuE20c7i8S03Jn59EmCgzkFnbUsZGxqSIHav8dbdsj 77D+OYAW0oXrCYZuqcgCOBG82KFHc2//0oLHX2MOo4uEaNgOH62mVzqpAPVjr1Qm58ar 9d9UebUcyhqGzqdGEa6fagxsx3WkTvEWOK3j0pcfO8/ca44NhavytoJ1c317Zb6oxkDi brGpBvv72DW+vW8XZ5F1QlBHjHNhK7G1Z6jhKGlm1O/B7/34qDZDfObdYx/4zA10QkXT DIMlBRuuB8cGjT9a/OG9xAdsDQjCmFiqnNOsda4JLAcA1MiUuqqZNZyDh9fF4PtF6Cfn yyHA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=i2ul3SyBZE3L/f+n/d50KIsjUWKjrby2SXdJL+3XjX0=; b=LLHNnGMGXodeFbRW6OUEFjnWi2YahBTptvKGlTDh5Ra9IuQmoDso9EsrrxkzN3UtV6 fhaiOUe1n1IXPBUqxXOG1kDrq1m0jRlLdGMU9ngtcFrou13ZcAoobpxtrvDYZfNmeRY4 jBMq8ciL28FMuUZdQpG/DHdriE+Gk4Wi4XSboxc/UTpCOvVne6loABHpNayGNj/52alF VtoltlZGJxhq0cuj2YLZ5IjiYQVrV24+RlOv1VmeqW2JeuG31dRyrI1W2KG4TuiTyQg+ Rg30VPDaW0HGN+4YN586mlVqHShFanVDkGEi7gqDgilORPqk0nLRARhmHgHR90MdbOzL 4i7A== X-Gm-Message-State: APzg51DGPIOI4xdJYt6ncskkoob0vyZ4wQ6X/co/gqw9dyjZHJ0hrBwO UtkQqigYecw3POYzk5P2Hyxiw/RlFQvwnRgVZdE= X-Received: by 2002:a24:c2c5:: with SMTP id i188-v6mr5851443itg.23.1536301077075; Thu, 06 Sep 2018 23:17:57 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a02:4ad4:0:0:0:0:0 with HTTP; Thu, 6 Sep 2018 23:17:56 -0700 (PDT) In-Reply-To: <20180906211045.29055-3-dennisszhou@gmail.com> References: <20180906211045.29055-1-dennisszhou@gmail.com> <20180906211045.29055-3-dennisszhou@gmail.com> From: Liu Bo Date: Thu, 6 Sep 2018 23:17:56 -0700 Message-ID: Subject: Re: [PATCH 02/12] blkcg: update blkg_lookup_create to do locking To: Dennis Zhou Cc: Jens Axboe , Tejun Heo , Johannes Weiner , Josef Bacik , kernel-team@fb.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 6, 2018 at 2:10 PM, Dennis Zhou wrote: > From: "Dennis Zhou (Facebook)" > > To know when to create a blkg, the general pattern is to do a > blkg_lookup and if that fails, lock and then do a lookup again and if > that fails finally create. It doesn't make much sense for everyone who > wants to do creation to write this themselves. > > This changes blkg_lookup_create to do locking and implement this > pattern. The old blkg_lookup_create is renamed to __blkg_lookup_create. > If a call site wants to do its own error handling or already owns the > queue lock, they can use __blkg_lookup_create. This will be used in > upcoming patches. > Reviewed-by: Liu Bo thanks, liubo > Signed-off-by: Dennis Zhou > Reviewed-by: Josef Bacik > Acked-by: Tejun Heo > --- > block/blk-cgroup.c | 31 ++++++++++++++++++++++++++++--- > block/blk-iolatency.c | 2 +- > include/linux/blk-cgroup.h | 4 +++- > 3 files changed, 32 insertions(+), 5 deletions(-) > > diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c > index c19f9078da1e..cd0d97bed83d 100644 > --- a/block/blk-cgroup.c > +++ b/block/blk-cgroup.c > @@ -259,7 +259,7 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, > } > > /** > - * blkg_lookup_create - lookup blkg, try to create one if not there > + * __blkg_lookup_create - lookup blkg, try to create one if not there > * @blkcg: blkcg of interest > * @q: request_queue of interest > * > @@ -272,8 +272,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg, > * value on error. If @q is dead, returns ERR_PTR(-EINVAL). If @q is not > * dead and bypassing, returns ERR_PTR(-EBUSY). > */ > -struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, > - struct request_queue *q) > +struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, > + struct request_queue *q) > { > struct blkcg_gq *blkg; > > @@ -310,6 +310,31 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, > } > } > > +/** > + * blkg_lookup_create - find or create a blkg > + * @blkcg: target block cgroup > + * @q: target request_queue > + * > + * This looks up or creates the blkg representing the unique pair > + * of the blkcg and the request_queue. > + */ > +struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, > + struct request_queue *q) > +{ > + struct blkcg_gq *blkg = blkg_lookup(blkcg, q); > + unsigned long flags; > + > + if (unlikely(!blkg)) { > + spin_lock_irqsave(q->queue_lock, flags); > + > + blkg = __blkg_lookup_create(blkcg, q); > + > + spin_unlock_irqrestore(q->queue_lock, flags); > + } > + > + return blkg; > +} > + > static void blkg_destroy(struct blkcg_gq *blkg) > { > struct blkcg *blkcg = blkg->blkcg; > diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c > index 62fdd9002c29..22b2ff0440cc 100644 > --- a/block/blk-iolatency.c > +++ b/block/blk-iolatency.c > @@ -410,7 +410,7 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio, > if (unlikely(!blkg)) { > if (!lock) > spin_lock_irq(q->queue_lock); > - blkg = blkg_lookup_create(blkcg, q); > + blkg = __blkg_lookup_create(blkcg, q); > if (IS_ERR(blkg)) > blkg = NULL; > if (!lock) > diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h > index 24067a1f8b36..cc0f238530f6 100644 > --- a/include/linux/blk-cgroup.h > +++ b/include/linux/blk-cgroup.h > @@ -184,6 +184,8 @@ extern struct cgroup_subsys_state * const blkcg_root_css; > > struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg, > struct request_queue *q, bool update_hint); > +struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg, > + struct request_queue *q); > struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg, > struct request_queue *q); > int blkcg_init_queue(struct request_queue *q); > @@ -897,7 +899,7 @@ static inline bool blkcg_bio_issue_check(struct request_queue *q, > blkg = blkg_lookup(blkcg, q); > if (unlikely(!blkg)) { > spin_lock_irq(q->queue_lock); > - blkg = blkg_lookup_create(blkcg, q); > + blkg = __blkg_lookup_create(blkcg, q); > if (IS_ERR(blkg)) > blkg = NULL; > spin_unlock_irq(q->queue_lock); > -- > 2.17.1 >