block, bfq: cleanup 'bfqg->online'

After commit dfd6200a ("blk-cgroup: support to track if policy is
online"), there is no need to do this again in bfq.

However, 'pd->online' is not protected by 'bfqd->lock', in order to make
sure bfq won't see that 'pd->online' is still set after bfq_pd_offline(),
clear it before bfq_pd_offline() is called. This is fine because other
polices doesn't use 'pd->online' and bfq_pd_offline() will move active
bfqq to root cgroup anyway.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230202134913.2364549-1-yukuai1@huaweicloud.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

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);
 	/*

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;

block/blk-cgroup.c

@@ -479,9 +479,9 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 		struct blkcg_policy *pol = blkcg_policy[i];
 
 		if (blkg->pd[i] && blkg->pd[i]->online) {
+			blkg->pd[i]->online = false;
 			if (pol->pd_offline_fn)
 				pol->pd_offline_fn(blkg->pd[i]);
-			blkg->pd[i]->online = false;
 		}
 	}