This is a note to let you know that I've just added the patch titled
Revert "block/mq-deadline: use correct way to throttling write requests"
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-block-mq-deadline-use-correct-way-to-throttli.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 75d7f318700e43e4c2d8b57522d545b2ffb533c9
Author: Bart Van Assche <bvanassche@xxxxxxx>
Date: Wed Mar 13 14:42:18 2024 -0700
Revert "block/mq-deadline: use correct way to throttling write requests"
[ Upstream commit 256aab46e31683d76d45ccbedc287b4d3f3e322b ]
The code "max(1U, 3 * (1U << shift) / 4)" comes from the Kyber I/O
scheduler. The Kyber I/O scheduler maintains one internal queue per hwq
and hence derives its async_depth from the number of hwq tags. Using
this approach for the mq-deadline scheduler is wrong since the
mq-deadline scheduler maintains one internal queue for all hwqs
combined. Hence this revert.
Cc: stable@xxxxxxxxxxxxxxx
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx>
Cc: Zhiguo Niu <Zhiguo.Niu@xxxxxxxxxx>
Fixes: d47f9717e5cf ("block/mq-deadline: use correct way to throttling write requests")
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Link: https://lore.kernel.org/r/20240313214218.1736147-1-bvanassche@xxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index f958e79277b8b..02a916ba62ee7 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -646,9 +646,8 @@ static void dd_depth_updated(struct blk_mq_hw_ctx *hctx)
struct request_queue *q = hctx->queue;
struct deadline_data *dd = q->elevator->elevator_data;
struct blk_mq_tags *tags = hctx->sched_tags;
- unsigned int shift = tags->bitmap_tags.sb.shift;
- dd->async_depth = max(1U, 3 * (1U << shift) / 4);
+ dd->async_depth = max(1UL, 3 * q->nr_requests / 4);
sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, dd->async_depth);
}
