On 2023/4/13 01:12, Tejun Heo wrote: > On Thu, Apr 13, 2023 at 12:07:53AM +0800, chengming.zhou@xxxxxxxxx wrote: >> From: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx> >> >> 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@xxxxxxxxxxxxx> > > Acked-by: Tejun Heo <tj@xxxxxxxxxx> > > 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. >
