linux-kernel - [PATCH 5/7] blk-mq: remove unnecessary "set->queue_depth == 0" check in blk_mq_alloc_set_map_and

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Message-Id: <20230209201116.579809-6-shikemeng@huaweicloud.com>
Date:   Fri, 10 Feb 2023 04:11:14 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     axboe@...nel.dk, hch@....de, jack@...e.cz
Cc:     andriy.shevchenko@...ux.intel.com, qiulaibin@...wei.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 5/7] blk-mq: remove unnecessary "set->queue_depth == 0" check in blk_mq_alloc_set_map_and_rqs

We will break the loop and set err to -ENOMEM if "set->queue_depth" is
less than "set->reserved_tags + BLK_MQ_TAG_MIN". set->reserved_tags is
unsigned int and should not be less than 0 logically. BLK_MQ_TAG_MIN is
1 and should be greater than 0 logically. So "set->reserved_tags +
BLK_MQ_TAG_MIN" should be greater than 0. For case set->queue_depth is
halved to zero, "set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN"
check is always met first, then this branch will set err to -ENOMEM and
break the loop. Then the loop break condition "while(set->queue_depth)"
is never met and set->queue_depth check in "if (!set->queue_depth ||
err)" is redundant. Just remove these checks.

Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
---
 block/blk-mq.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6014d9b5e296..4d2ab01549cd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -4324,9 +4324,9 @@ static int blk_mq_alloc_set_map_and_rqs(struct blk_mq_tag_set *set)
 			err = -ENOMEM;
 			break;
 		}
-	} while (set->queue_depth);
+	} while (true);

-	if (!set->queue_depth || err) {
+	if (err) {
 		pr_err("blk-mq: failed to allocate request map\n");
 		return -ENOMEM;
 	}
-- 
2.30.0