[PATCH 6.1 52/71] blk-wbt: don't enable throttling if default elevator is bfq

Sasha Levin
2024-03-13T16:41:01Z

From: Yu Kuai <yukuai3@huawei.com>

[ Upstream commit 671fae5e51297fc76b3758ca2edd514858734a6a ]

Commit b5dc5d4d1f4f ("block,bfq: Disable writeback throttling") tries to
disable wbt for bfq, it's done by calling wbt_disable_default() in
bfq_init_queue(). However, wbt is still enabled if default elevator is
bfq:

device_add_disk
elevator_init_mq
bfq_init_queue
wbt_disable_default -> done nothing

blk_register_queue
wbt_enable_default -> wbt is enabled

Fix the problem by adding a new flag ELEVATOR_FLAG_DISBALE_WBT, bfq
will set the flag in bfq_init_queue, and following wbt_enable_default()
won't enable wbt while the flag is set.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221019121518.3865235-7-yukuai1@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Stable-dep-of: f814bdda774c ("blk-wbt: Fix detection of dirty-throttled tasks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/bfq-iosched.c | 2 ++
block/blk-wbt.c | 11 ++++++++---
block/elevator.h | 3 ++-
3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 52eb79d60a3f3..e4699291aee23 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -7059,6 +7059,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
#endif

blk_stat_disable_accounting(bfqd->queue);
+ clear_bit(ELEVATOR_FLAG_DISABLE_WBT, &e->flags);
wbt_enable_default(bfqd->queue);

kfree(bfqd);
@@ -7204,6 +7205,7 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
/* We dispatch from request queue wide instead of hw queue */
blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q);

+ set_bit(ELEVATOR_FLAG_DISABLE_WBT, &eq->flags);
wbt_disable_default(q);
blk_stat_enable_accounting(q);

diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index c5a8c10028a08..afb1782b4255e 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -27,6 +27,7 @@

#include "blk-wbt.h"
#include "blk-rq-qos.h"
+#include "elevator.h"

#define CREATE_TRACE_POINTS
#include <trace/events/wbt.h>
@@ -638,11 +639,15 @@ void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
*/
void wbt_enable_default(struct request_queue *q)
{
- struct rq_qos *rqos = wbt_rq_qos(q);
+ struct rq_qos *rqos;
+ bool disable_flag = q->elevator &&
+ test_bit(ELEVATOR_FLAG_DISABLE_WBT, &q->elevator->flags);

/* Throttling already enabled? */
+ rqos = wbt_rq_qos(q);
if (rqos) {
- if (RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
+ if (!disable_flag &&
+ RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
return;
}
@@ -651,7 +656,7 @@ void wbt_enable_default(struct request_queue *q)
if (!blk_queue_registered(q))
return;

- if (queue_is_mq(q))
+ if (queue_is_mq(q) && !disable_flag)
wbt_init(q);
}
EXPORT_SYMBOL_GPL(wbt_enable_default);
diff --git a/block/elevator.h b/block/elevator.h
index ed574bf3e629e..75382471222d1 100644
--- a/block/elevator.h
+++ b/block/elevator.h
@@ -104,7 +104,8 @@ struct elevator_queue
DECLARE_HASHTABLE(hash, ELV_HASH_BITS);
};

-#define ELEVATOR_FLAG_REGISTERED 0
+#define ELEVATOR_FLAG_REGISTERED 0
+#define ELEVATOR_FLAG_DISABLE_WBT 1

/*
* block elevator interface
--
2.43.0