Commit 919b5139 authored by Li Lingfeng's avatar Li Lingfeng Committed by Jens Axboe
Browse files

block: flush all throttled bios when deleting the cgroup 

When a process migrates to another cgroup and the original cgroup is deleted,
the restrictions of throttled bios cannot be removed. If the restrictions
are set too low, it will take a long time to complete these bios.

Refer to the process of deleting a disk to remove the restrictions and
issue bios when deleting the cgroup.

This makes difference on the behavior of throttled bios:
Before: the limit of the throttled bios can't be changed and the bios will
complete under this limit;
Now: the limit will be canceled and the throttled bios will be flushed
immediately.

References:
[1] https://lore.kernel.org/r/20220318130144.1066064-4-ming.lei@redhat.com
[2] https://lore.kernel.org/all/da861d63-58c6-3ca0-2535-9089993e9e28@huaweicloud.com/



Signed-off-by: default avatarLi Lingfeng <lilingfeng3@huawei.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240817071108.1919729-1-lilingfeng@huaweicloud.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 96a9fe64

block/blk-throttle.c

+44 −24
Original line number Diff line number Diff line
@@ -1526,6 +1526,42 @@ static void throtl_shutdown_wq(struct request_queue *q) 
	cancel_work_sync(&td->dispatch_work);

}



static void tg_flush_bios(struct throtl_grp *tg)

{

	struct throtl_service_queue *sq = &tg->service_queue;



	if (tg->flags & THROTL_TG_CANCELING)

		return;

	/*

	 * Set the flag to make sure throtl_pending_timer_fn() won't

	 * stop until all throttled bios are dispatched.

	 */

	tg->flags |= THROTL_TG_CANCELING;



	/*

	 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup

	 * will be inserted to service queue without THROTL_TG_PENDING

	 * set in tg_update_disptime below. Then IO dispatched from

	 * child in tg_dispatch_one_bio will trigger double insertion

	 * and corrupt the tree.

	 */

	if (!(tg->flags & THROTL_TG_PENDING))

		return;



	/*

	 * Update disptime after setting the above flag to make sure

	 * throtl_select_dispatch() won't exit without dispatching.

	 */

	tg_update_disptime(tg);



	throtl_schedule_pending_timer(sq, jiffies + 1);

}



static void throtl_pd_offline(struct blkg_policy_data *pd)

{

	tg_flush_bios(pd_to_tg(pd));

}



struct blkcg_policy blkcg_policy_throtl = {

	.dfl_cftypes		= throtl_files,

	.legacy_cftypes		= throtl_legacy_files,
@@ -1533,6 +1569,7 @@ struct blkcg_policy blkcg_policy_throtl = { 
	.pd_alloc_fn		= throtl_pd_alloc,

	.pd_init_fn		= throtl_pd_init,

	.pd_online_fn		= throtl_pd_online,

	.pd_offline_fn		= throtl_pd_offline,

	.pd_free_fn		= throtl_pd_free,

};
@@ -1553,32 +1590,15 @@ void blk_throtl_cancel_bios(struct gendisk *disk) 
	 */

	rcu_read_lock();

	blkg_for_each_descendant_post(blkg, pos_css, q->root_blkg) {

		struct throtl_grp *tg = blkg_to_tg(blkg);

		struct throtl_service_queue *sq = &tg->service_queue;



		/*

		 * Set the flag to make sure throtl_pending_timer_fn() won't

		 * stop until all throttled bios are dispatched.

		 */

		tg->flags |= THROTL_TG_CANCELING;



		/*

		 * Do not dispatch cgroup without THROTL_TG_PENDING or cgroup

		 * will be inserted to service queue without THROTL_TG_PENDING

		 * set in tg_update_disptime below. Then IO dispatched from

		 * child in tg_dispatch_one_bio will trigger double insertion

		 * and corrupt the tree.

		 */

		if (!(tg->flags & THROTL_TG_PENDING))

			continue;



		/*

		 * Update disptime after setting the above flag to make sure

		 * throtl_select_dispatch() won't exit without dispatching.

		 * disk_release will call pd_offline_fn to cancel bios.

		 * However, disk_release can't be called if someone get

		 * the refcount of device and issued bios which are

		 * inflight after del_gendisk.

		 * Cancel bios here to ensure no bios are inflight after

		 * del_gendisk.

		 */

		tg_update_disptime(tg);



		throtl_schedule_pending_timer(sq, jiffies + 1);

		tg_flush_bios(blkg_to_tg(blkg));

	}

	rcu_read_unlock();

	spin_unlock_irq(&q->queue_lock);