From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dennis Zhou Subject: [PATCH 05/15] blkcg: update blkg_lookup_create to do locking Date: Thu, 30 Aug 2018 21:53:46 -0400 Message-ID: <20180831015356.69796-6-dennisszhou@gmail.com> References: <20180831015356.69796-1-dennisszhou@gmail.com> Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=V/nPLJiLoMbwxwUN+SeDjrPjMrJFtIi3YKNpVCr/rfI=; b=cHIUDDO7zpJyjduUj1AwohQqhchaeZcF5rHzrvC830EPVE0vyg+4cTpVyh4a4QtOpU +G9wWJT7qq6cToApALaQAi5T6bf1NbGO24PCuieqXgOz2/YsonS49UPFUl1UdubPctmx F7rY9id1fp/KHKAJ8Tz8JTc+66obEHPfA0q+C6PiT0/7FlWtnXEtToIU4PCwJSkb4CLT JUd+dM0bMrpjsOxGVs3MmiX9hfP6yeltlF/Vs+//MI2Onv+Ly3QKp2V5Fy5v8ul5qVPM q4L4s3/h27gsLS0zx4y2ev2/+80AIbpNemaARAo3pBIWbTfe7+ABErERcJYDvMngGfrv ALOw== In-Reply-To: <20180831015356.69796-1-dennisszhou@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jens Axboe , Tejun Heo , Johannes Weiner , Josef Bacik Cc: kernel-team@fb.com, linux-block@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, "Dennis Zhou (Facebook)" 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. Signed-off-by: Dennis Zhou --- 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 d7114308a480..f678cd555814 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 d3cafb1eda48..ea2dd6e6baf2 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); @@ -835,7 +837,7 @@ 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