blk-iocost: do not WARN if iocg was already offlined

mainline inclusion
from mainline-v6.9-rc5
commit 01bc4fda9ea0a6b52f12326486f07a4910666cf6
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9UABH
CVE: CVE-2024-36908

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=01bc4fda9ea0a6b52f12326486f07a4910666cf6



--------------------------------

In iocg_pay_debt(), warn is triggered if 'active_list' is empty, which
is intended to confirm iocg is active when it has debt. However, warn
can be triggered during a blkcg or disk removal, if iocg_waitq_timer_fn()
is run at that time:

  WARNING: CPU: 0 PID: 2344971 at block/blk-iocost.c:1402 iocg_pay_debt+0x14c/0x190
  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 ensures
iocg is freed after iocg_waitq_timer_fn() returns.

Therefore, add the check if iocg was already offlined to avoid warn
when removing a blkcg or disk.

Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20240419093257.3004211-1-linan666@huaweicloud.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Conflict:
	block/blk-iocost.c
	Mainline checks 'pd.online', but there is no member online of
	pd in 5.10. Check 'iocg->online' instead.
Signed-off-by: Li Nan <linan122@huawei.com>