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Message-ID: <b49ccd16-d31c-af03-7833-d8caaa71d7f6@huaweicloud.com>
Date: Tue, 22 Oct 2024 10:43:23 +0800
From: Li Lingfeng <lilingfeng@...weicloud.com>
To: tj@...nel.org, josef@...icpanda.com, hch@....de, mkoutny@...e.com,
axboe@...nel.dk
Cc: cgroups@...r.kernel.org, linux-block@...r.kernel.org,
linux-kernel@...r.kernel.org, yukuai1@...weicloud.com, houtao1@...wei.com,
yi.zhang@...wei.com, yangerkun@...wei.com, yukuai3@...wei.com,
lilingfeng3@...wei.com
Subject: Re: [PATCH v3] block: flush all throttled bios when deleting the
cgroup
Friendly ping ...
Thanks
在 2024/8/17 15:11, Li Lingfeng 写道:
> From: Li Lingfeng <lilingfeng3@...wei.com>
>
> 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: Li Lingfeng <lilingfeng3@...wei.com>
> ---
> v2->v3:
> Change "tg_cancel_bios" to "tg_flush_bios";
> Add reference of v2 to describe the background.
> block/blk-throttle.c | 68 ++++++++++++++++++++++++++++----------------
> 1 file changed, 44 insertions(+), 24 deletions(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 6943ec720f39..cf7f4912c57a 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -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.
> + * 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.
> */
> - 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.
> - */
> - 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);
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