blk-stat: fix QUEUE_FLAG_STATS clear
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. The bug can be reproduced on kernel without BLK_DEV_THROTTLING (since it unconditionally enable accounting, see the next 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. Fixes: 68497092 ("block: make queue stat accounting a reference") Cc: <stable@vger.kernel.org> # v5.17+ Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com> Acked-by: Tejun Heo <tj@kernel.org> Link: https://lore.kernel.org/r/20230413062805.2081970-1-chengming.zhou@linux.devSigned-off-by: Jens Axboe <axboe@kernel.dk>
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