linux-kernel - [PATCH] block: use dedicated list iterator variable

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Date:   Sun, 27 Mar 2022 23:47:04 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH] block: use dedicated list iterator variable

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/
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 block/blk-mq.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8e659dc5fcf3..455fdd488f3c 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4466,12 +4466,14 @@ static bool blk_mq_elv_switch_none(struct list_head *head,
 static void blk_mq_elv_switch_back(struct list_head *head,
 		struct request_queue *q)
 {
-	struct blk_mq_qe_pair *qe;
+	struct blk_mq_qe_pair *qe = NULL;
+	struct blk_mq_qe_pair *iter;
 	struct elevator_type *t = NULL;
 
-	list_for_each_entry(qe, head, node)
-		if (qe->q == q) {
-			t = qe->type;
+	list_for_each_entry(iter, head, node)
+		if (iter->q == q) {
+			t = iter->type;
+			qe = iter;
 			break;
 		}
 

base-commit: b47d5a4f6b8d42f8a8fbe891b36215e4fddc53be
-- 
2.25.1