[PATCH 6.6 151/396] Revert "block/mq-deadline: use correct way to throttling write requests"

Greg Kroah-Hartman
2024-04-01T16:44:36Z

From: Bart Van Assche <bvanassche@acm.org>

[ 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@vger.kernel.org
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Cc: Zhiguo Niu <Zhiguo.Niu@unisoc.com>
Fixes: d47f9717e5cf ("block/mq-deadline: use correct way to throttling write requests")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20240313214218.1736147-1-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/mq-deadline.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

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);
}
--
2.43.0