From: Li Lingfeng <lilingfeng3@xxxxxxxxxx> 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@xxxxxxxxxx [2] https://lore.kernel.org/all/da861d63-58c6-3ca0-2535-9089993e9e28@xxxxxxxxxxxxxxx/ Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx> --- 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); -- 2.39.2
