Re: [PATCH] blk-iocost: do not WARNING if iocg has already offlined

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在 2024/04/18 15:23, linan666@xxxxxxxxxxxxxxx 写道:
From: Li Nan <linan122@xxxxxxxxxx>

In iocg_pay_debt(), warn is triggered if 'active_list' is empty, which
is intended to confirm iocg is avitve when it has debt. However, warn
can be triggered during removing cgroup controller, as
iocg_waitq_timer_fn() is awakened at that time.

   WARNING: CPU: 0 PID: 2344971 at block/blk-iocost.c:1402 iocg_pay_debt+0x14c/0x190

This line doesn't match the code from mainline, please mention that
which kernel release you're testing.

Other than that, ioc_pd_free() indeed clear 'active_list' before
canceling the timer, this patch looks good to me.

Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
   Call trace:
   iocg_pay_debt+0x14c/0x190
   iocg_kick_waitq+0x438/0x4c0
   iocg_waitq_timer_fn+0xd8/0x130
   __run_hrtimer+0x144/0x45c
   __hrtimer_run_queues+0x16c/0x244
   hrtimer_interrupt+0x2cc/0x7b0

The warn in this situation is meaningless. Since this iocg is being
removed, the state of the 'active_list' is irrelevant, and 'waitq_timer'
is canceled after removing 'active_list' in ioc_pd_free(), which ensure
iocg is freed after iocg_waitq_timer_fn() returns.

Therefore, add the check if iocg has already offlined to avoid warn
when removing cgroup controller.

Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
---
  block/blk-iocost.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index baa20c85799d..2e109c016a39 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -1440,7 +1440,7 @@ static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
  	lockdep_assert_held(&iocg->waitq.lock);
/* make sure that nobody messed with @iocg */
-	WARN_ON_ONCE(list_empty(&iocg->active_list));
+	WARN_ON_ONCE(list_empty(&iocg->active_list) && iocg->pd.online);
  	WARN_ON_ONCE(iocg->inuse > 1);
iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);






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