From: Jakob Koschel <jakobkoschel@gmail.com>
Date: Thu, 31 Mar 2022 11:12:18 +0200
Subject: [PATCH] block: use dedicated list iterator variable
Git-commit: 4a3b666e0ea977dd40adb56c37a91370f76fa19e
Patch-mainline: v5.18-rc1
References: jsc#PED-1183

To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.

To *never* use the list iterator variable after the loop it was
concluded to use a separate iterator variable instead of a
found boolean [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220331091218.641532-1-jakobkoschel@gmail.com
[axboe: move lookup to where return value is checked]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 213bb5979bed..176b031510ff 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4448,21 +4448,28 @@ static bool blk_mq_elv_switch_none(struct list_head *head,
 	return true;
 }
 
-static void blk_mq_elv_switch_back(struct list_head *head,
-		struct request_queue *q)
+static struct blk_mq_qe_pair *blk_lookup_qe_pair(struct list_head *head,
+						struct request_queue *q)
 {
 	struct blk_mq_qe_pair *qe;
-	struct elevator_type *t = NULL;
 
 	list_for_each_entry(qe, head, node)
-		if (qe->q == q) {
-			t = qe->type;
-			break;
-		}
+		if (qe->q == q)
+			return qe;
 
-	if (!t)
-		return;
+	return NULL;
+}
 
+static void blk_mq_elv_switch_back(struct list_head *head,
+				  struct request_queue *q)
+{
+	struct blk_mq_qe_pair *qe;
+	struct elevator_type *t;
+
+	qe = blk_lookup_qe_pair(head, q);
+	if (!qe)
+		return;
+	t = qe->type;
 	list_del(&qe->node);
 	kfree(qe);
 
-- 
2.35.3