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在 2024/8/17 15:11, Li Lingfeng 写道:
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);
