[PATCH -next] block, bfq: cleanup 'bfqg->online'

[PATCH -next] block, bfq: cleanup 'bfqg->online'

[Yu Kuai]

From: Yu Kuai <yukuai3@huawei.com>

After commit dfd6200a0954 ("blk-cgroup: support to track if policy is
online"), there is no need to do this again in bfq.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
 block/bfq-cgroup.c  | 4 +---
 block/bfq-iosched.h | 2 --
 2 files changed, 1 insertion(+), 5 deletions(-)

diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index b42956ab5550..a35136dae713 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -551,7 +551,6 @@ static void bfq_pd_init(struct blkg_policy_data *pd)
 	bfqg->bfqd = bfqd;
 	bfqg->active_entities = 0;
 	bfqg->num_queues_with_pending_reqs = 0;
-	bfqg->online = true;
 	bfqg->rq_pos_tree = RB_ROOT;
 }
 
@@ -614,7 +613,7 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
 			continue;
 		}
 		bfqg = blkg_to_bfqg(blkg);
-		if (bfqg->online) {
+		if (bfqg->pd.online) {
 			bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
 			return bfqg;
 		}
@@ -985,7 +984,6 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
 
 put_async_queues:
 	bfq_put_async_queues(bfqd, bfqg);
-	bfqg->online = false;
 
 	spin_unlock_irqrestore(&bfqd->lock, flags);
 	/*
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 75cc6a324267..69aaee52285a 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1009,8 +1009,6 @@ struct bfq_group {
 
 	/* reference counter (see comments in bfq_bic_update_cgroup) */
 	refcount_t ref;
-	/* Is bfq_group still online? */
-	bool online;
 
 	struct bfq_entity entity;
 	struct bfq_sched_data sched_data;
-- 
2.31.1

Re: [PATCH -next] block, bfq: cleanup 'bfqg->online'

[Jan Kara]

On Wed 01-02-23 20:06:09, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> After commit dfd6200a0954 ("blk-cgroup: support to track if policy is
> online"), there is no need to do this again in bfq.
> 
> Signed-off-by: Yu Kuai <yukuai3@huawei.com>

So I agree this is nice to do but it isn't so simple. BFQ relies on the
fact that 'online' is cleared under bfqd->lock so we cannot associate bio
in bfq_bio_bfqg() with a bfqg that has already its bfq_pd_offline()
function run.

Maybe if you set 'online' to false before calling ->pd_offline() things
would work fine for BFQ.

								Honza
> ---
>  block/bfq-cgroup.c  | 4 +---
>  block/bfq-iosched.h | 2 --
>  2 files changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
> index b42956ab5550..a35136dae713 100644
> --- a/block/bfq-cgroup.c
> +++ b/block/bfq-cgroup.c
> @@ -551,7 +551,6 @@ static void bfq_pd_init(struct blkg_policy_data *pd)
>  	bfqg->bfqd = bfqd;
>  	bfqg->active_entities = 0;
>  	bfqg->num_queues_with_pending_reqs = 0;
> -	bfqg->online = true;
>  	bfqg->rq_pos_tree = RB_ROOT;
>  }
>  
> @@ -614,7 +613,7 @@ struct bfq_group *bfq_bio_bfqg(struct bfq_data *bfqd, struct bio *bio)
>  			continue;
>  		}
>  		bfqg = blkg_to_bfqg(blkg);
> -		if (bfqg->online) {
> +		if (bfqg->pd.online) {
>  			bio_associate_blkg_from_css(bio, &blkg->blkcg->css);
>  			return bfqg;
>  		}
> @@ -985,7 +984,6 @@ static void bfq_pd_offline(struct blkg_policy_data *pd)
>  
>  put_async_queues:
>  	bfq_put_async_queues(bfqd, bfqg);
> -	bfqg->online = false;
>  
>  	spin_unlock_irqrestore(&bfqd->lock, flags);
>  	/*
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 75cc6a324267..69aaee52285a 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -1009,8 +1009,6 @@ struct bfq_group {
>  
>  	/* reference counter (see comments in bfq_bic_update_cgroup) */
>  	refcount_t ref;
> -	/* Is bfq_group still online? */
> -	bool online;
>  
>  	struct bfq_entity entity;
>  	struct bfq_sched_data sched_data;
> -- 
> 2.31.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

Re: [PATCH -next] block, bfq: cleanup 'bfqg->online'

[Yu Kuai]

Hi, Jan!

在 2023/02/01 21:10, Jan Kara 写道:
> On Wed 01-02-23 20:06:09, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> After commit dfd6200a0954 ("blk-cgroup: support to track if policy is
>> online"), there is no need to do this again in bfq.
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> 
> So I agree this is nice to do but it isn't so simple. BFQ relies on the
> fact that 'online' is cleared under bfqd->lock so we cannot associate bio
> in bfq_bio_bfqg() with a bfqg that has already its bfq_pd_offline()
> function run.
> 
> Maybe if you set 'online' to false before calling ->pd_offline() things
> would work fine for BFQ.

Yes, you're right. Thanks for the explanation.

Kuai

Re: [PATCH -next] block, bfq: cleanup 'bfqg->online'

[Yu Kuai]

Hi, Jan!

ÔÚ 2023/02/01 21:10, Jan Kara дµÀ:
> On Wed 01-02-23 20:06:09, Yu Kuai wrote:
>> From: Yu Kuai <yukuai3@huawei.com>
>>
>> After commit dfd6200a0954 ("blk-cgroup: support to track if policy is
>> online"), there is no need to do this again in bfq.
>>
>> Signed-off-by: Yu Kuai <yukuai3@huawei.com>
> 
> So I agree this is nice to do but it isn't so simple. BFQ relies on the
> fact that 'online' is cleared under bfqd->lock so we cannot associate bio
> in bfq_bio_bfqg() with a bfqg that has already its bfq_pd_offline()
> function run.
> 
> Maybe if you set 'online' to false before calling ->pd_offline() things
> would work fine for BFQ.

Yes, you're right. Thanks for the explanation.

Kuai