[PATCH v2] block: Move a misplaced comment in queue_wb_lat_store()

[PATCH v2] block: Move a misplaced comment in queue_wb_lat_store()

[Bart Van Assche]

blk_mq_quiesce_queue() does not wait for pending I/O to finish. Freezing
a queue waits for pending I/O to finish. Hence move the comment that
refers to waiting for pending I/O above the call that freezes the
request queue. This patch moves this comment back to the position where
it was when this comment was introduced. See also commit c125311d96b1
("blk-wbt: don't maintain inflight counts if disabled").

Cc: Christoph Hellwig <hch@lst.de>
Cc: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---

Changes compared to v1: rebased on top of Jen's for-next branch.

 block/blk-sysfs.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 4a7f1a349998..c94b8b6ab024 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -620,6 +620,11 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
 	if (val < -1)
 		return -EINVAL;
 
+	/*
+	 * Ensure that the queue is idled, in case the latency update
+	 * ends up either enabling or disabling wbt completely. We can't
+	 * have IO inflight if that happens.
+	 */
 	memflags = blk_mq_freeze_queue(q);
 
 	rqos = wbt_rq_qos(q);
@@ -638,11 +643,6 @@ static ssize_t queue_wb_lat_store(struct gendisk *disk, const char *page,
 	if (wbt_get_min_lat(q) == val)
 		goto out;
 
-	/*
-	 * Ensure that the queue is idled, in case the latency update
-	 * ends up either enabling or disabling wbt completely. We can't
-	 * have IO inflight if that happens.
-	 */
 	blk_mq_quiesce_queue(q);
 
 	mutex_lock(&disk->rqos_state_mutex);

Re: [PATCH v2] block: Move a misplaced comment in queue_wb_lat_store()

[Martin K. Petersen]

Bart,

> blk_mq_quiesce_queue() does not wait for pending I/O to finish. Freezing
> a queue waits for pending I/O to finish. Hence move the comment that
> refers to waiting for pending I/O above the call that freezes the
> request queue. This patch moves this comment back to the position where
> it was when this comment was introduced. See also commit c125311d96b1
> ("blk-wbt: don't maintain inflight counts if disabled").

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen

Re: [PATCH v2] block: Move a misplaced comment in queue_wb_lat_store()

[Jens Axboe]

On Mon, 25 Aug 2025 08:14:24 -0700, Bart Van Assche wrote:
> blk_mq_quiesce_queue() does not wait for pending I/O to finish. Freezing
> a queue waits for pending I/O to finish. Hence move the comment that
> refers to waiting for pending I/O above the call that freezes the
> request queue. This patch moves this comment back to the position where
> it was when this comment was introduced. See also commit c125311d96b1
> ("blk-wbt: don't maintain inflight counts if disabled").
> 
> [...]

Applied, thanks!

[1/1] block: Move a misplaced comment in queue_wb_lat_store()
      commit: f5d10e6915d80f7f4c4ed445a8b8ba4a5ee79318

Best regards,
-- 
Jens Axboe