linux-kernel - [PATCH 07/14] block: merge blkg_lookup_create and __blkg_lookup

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Message-Id: <20200627073159.2447325-8-hch@lst.de>
Date:   Sat, 27 Jun 2020 09:31:52 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>
Cc:     Dennis Zhou <dennis@...nel.org>, Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, dm-devel@...hat.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 07/14] block: merge blkg_lookup_create and __blkg_lookup_create

No good reason to keep these two functions split.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 block/blk-cgroup.c | 49 +++++++++++++++++-----------------------------
 1 file changed, 18 insertions(+), 31 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bb0607bfd771cd..6aedb73ffbf473 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -316,30 +316,35 @@ 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
  *
  * Lookup blkg for the @blkcg - @q pair.  If it doesn't exist, try to
  * create one.  blkg creation is performed recursively from blkcg_root such
  * that all non-root blkg's have access to the parent blkg.  This function
- * should be called under RCU read lock and @q->queue_lock.
+ * should be called under RCU read lock and takes @q->queue_lock.
  *
  * Returns the blkg or the closest blkg if blkg_create() fails as it walks
  * down from root.
  */
-static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
-				      struct request_queue *q)
+static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+		struct request_queue *q)
 {
 	struct blkcg_gq *blkg;
+	unsigned long flags;
 
 	WARN_ON_ONCE(!rcu_read_lock_held());
-	lockdep_assert_held(&q->queue_lock);
 
-	blkg = __blkg_lookup(blkcg, q, true);
+	blkg = blkg_lookup(blkcg, q);
 	if (blkg)
 		return blkg;
 
+	spin_lock_irqsave(&q->queue_lock, flags);
+	blkg = __blkg_lookup(blkcg, q, true);
+	if (blkg)
+		goto found;
+
 	/*
 	 * Create blkgs walking down from blkcg_root to @blkcg, so that all
 	 * non-root blkgs have access to their parents.  Returns the closest
@@ -362,34 +367,16 @@ static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
 		}
 
 		blkg = blkg_create(pos, q, NULL);
-		if (IS_ERR(blkg))
-			return ret_blkg;
+		if (IS_ERR(blkg)) {
+			blkg = ret_blkg;
+			break;
+		}
 		if (pos == blkcg)
-			return blkg;
-	}
-}
-
-/**
- * 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.
- */
-static struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
-				    struct request_queue *q)
-{
-	struct blkcg_gq *blkg = blkg_lookup(blkcg, q);
-
-	if (unlikely(!blkg)) {
-		unsigned long flags;
-
-		spin_lock_irqsave(&q->queue_lock, flags);
-		blkg = __blkg_lookup_create(blkcg, q);
-		spin_unlock_irqrestore(&q->queue_lock, flags);
+			break;
 	}
 
+found:
+	spin_unlock_irqrestore(&q->queue_lock, flags);
 	return blkg;
 }
 
-- 
2.26.2