Messages in this thread | | | Date | Thu, 13 Apr 2023 11:23:21 +0800 | Subject | Re: [PATCH 1/2] blk-stat: fix QUEUE_FLAG_STATS clear | From | Chengming Zhou <> |
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On 2023/4/13 01:12, Tejun Heo wrote: > On Thu, Apr 13, 2023 at 12:07:53AM +0800, chengming.zhou@linux.dev wrote: >> From: Chengming Zhou <zhouchengming@bytedance.com> >> >> We need to set QUEUE_FLAG_STATS for two cases: >> 1. blk_stat_enable_accounting() >> 2. blk_stat_add_callback() >> >> So we should clear it only when ((q->stats->accounting == 0) && >> list_empty(&q->stats->callbacks)). >> >> blk_stat_disable_accounting() only check if q->stats->accounting >> is 0 before clear the flag, this patch fix it. >> >> Also add list_empty(&q->stats->callbacks)) check when enable, or >> the flag is already set. >> >> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> > > Acked-by: Tejun Heo <tj@kernel.org> > > It'd be useful to explicitly illustrate the buggy behavior in the > description (e.g. if you do X, Y and then Z, then X incorrectly loses
Yes, I will add below buggy behavior in the next version:
This bug can be reproduced as below on kernel without BLK_DEV_THROTTLING (since it will unconditionally enable accounting, see the second patch).
# cat /sys/block/sr0/queue/scheduler none mq-deadline [bfq]
# cat /sys/kernel/debug/block/sr0/state SAME_COMP|IO_STAT|INIT_DONE|STATS|REGISTERED|NOWAIT|30
# echo none > /sys/block/sr0/queue/scheduler
# cat /sys/kernel/debug/block/sr0/state SAME_COMP|IO_STAT|INIT_DONE|REGISTERED|NOWAIT
# cat /sys/block/sr0/queue/wbt_lat_usec 75000
We can see that after changing elevator from "bfq" to "none", "STATS" flag is lost even though WBT callback still need it.
> accounting). Can you also please add the appropriate stable cc?
Ok, will do.
Thanks.
> > Thanks. >
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