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From: Dennis Zhou <dennis@kernel.org>
To: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Josef Bacik <josef@toxicpanda.com>
Cc: kernel-team@fb.com, linux-block@vger.kernel.org,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	Dennis Zhou <dennis@kernel.org>
Subject: [PATCH 02/14] blkcg: update blkg_lookup_create() to do locking
Date: Wed,  5 Dec 2018 12:10:27 -0500	[thread overview]
Message-ID: <20181205171039.73066-3-dennis@kernel.org> (raw)
In-Reply-To: <20181205171039.73066-1-dennis@kernel.org>

To know when to create a blkg, the general pattern is to do a
blkg_lookup() and if that fails, lock and do the 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.

Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
---
 block/blk-cgroup.c         | 28 +++++++++++++++++++++++++---
 block/blk-iolatency.c      |  2 +-
 include/linux/blk-cgroup.h |  4 +++-
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 63d226a084cd..b421a9457e05 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -249,7 +249,7 @@ 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
  *
@@ -262,8 +262,8 @@ 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;
 
@@ -293,6 +293,28 @@ 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);
+
+	if (unlikely(!blkg)) {
+		spin_lock_irq(&q->queue_lock);
+		blkg = __blkg_lookup_create(blkcg, q);
+		spin_unlock_irq(&q->queue_lock);
+	}
+
+	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 fe0c4ca312ff..e6f68f15dee9 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -486,7 +486,7 @@ static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
 	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);
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index f619307171a6..b3b1a8187d23 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -181,6 +181,8 @@ 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);
@@ -799,7 +801,7 @@ 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


  parent reply	other threads:[~2018-12-05 17:12 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-05 17:10 [PATCH v6 00/14] block: always associate blkg and refcount cleanup Dennis Zhou
2018-12-05 17:10 ` [PATCH 01/14] blkcg: fix ref count issue with bio_blkcg() using task_css Dennis Zhou
2018-12-05 17:10 ` Dennis Zhou [this message]
2018-12-05 17:10 ` [PATCH 03/14] blkcg: convert blkg_lookup_create() to find closest blkg Dennis Zhou
2018-12-05 17:10 ` [PATCH 04/14] blkcg: introduce common blkg association logic Dennis Zhou
2018-12-05 17:10 ` [PATCH 05/14] dm: set the static flush bio device on demand Dennis Zhou
2018-12-05 17:10 ` [PATCH 06/14] blkcg: associate blkg when associating a device Dennis Zhou
2018-12-05 17:10 ` [PATCH 07/14] blkcg: consolidate bio_issue_init() to be a part of core Dennis Zhou
2018-12-05 17:10 ` [PATCH 08/14] blkcg: associate a blkg for pages being evicted by swap Dennis Zhou
2018-12-05 17:10 ` [PATCH 09/14] blkcg: associate writeback bios with a blkg Dennis Zhou
2018-12-05 17:10 ` [PATCH 10/14] blkcg: remove bio->bi_css and instead use bio->bi_blkg Dennis Zhou
2018-12-05 17:10 ` [PATCH 11/14] blkcg: remove additional reference to the css Dennis Zhou
2018-12-05 17:10 ` [PATCH 12/14] blkcg: remove bio_disassociate_task() Dennis Zhou
2018-12-05 17:10 ` [PATCH 13/14] blkcg: change blkg reference counting to use percpu_ref Dennis Zhou
2018-12-05 17:10 ` [PATCH 14/14] blkcg: rename blkg_try_get() to blkg_tryget() Dennis Zhou
2018-12-05 17:26 ` [PATCH v6 00/14] block: always associate blkg and refcount cleanup Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2018-12-04 18:35 [PATCH v5 " Dennis Zhou
2018-12-04 18:35 ` [PATCH 02/14] blkcg: update blkg_lookup_create() to do locking Dennis Zhou

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