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| author | Chengming Zhou <zhouchengming@bytedance.com> | 2023-04-13 14:28:04 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-04-13 06:48:11 -0600 |
| commit | 20de765f6d9da0c47b756429c60b41063b990a10 (patch) | |
| tree | aa9322e26ba50c53a9f784b083c9fda4cae5bed6 /block/blk-stat.c | |
| parent | a13696b83da4f1e53e192ec3e239afd3a96ff747 (diff) | |
| download | lwn-20de765f6d9da0c47b756429c60b41063b990a10.tar.gz lwn-20de765f6d9da0c47b756429c60b41063b990a10.zip | |
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: 68497092bde9 ("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.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-stat.c')
| -rw-r--r-- | block/blk-stat.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-stat.c b/block/blk-stat.c index 74a1a8c32d86..bc7e0ed81642 100644 --- a/block/blk-stat.c +++ b/block/blk-stat.c @@ -190,7 +190,7 @@ void blk_stat_disable_accounting(struct request_queue *q) unsigned long flags; spin_lock_irqsave(&q->stats->lock, flags); - if (!--q->stats->accounting) + if (!--q->stats->accounting && list_empty(&q->stats->callbacks)) blk_queue_flag_clear(QUEUE_FLAG_STATS, q); spin_unlock_irqrestore(&q->stats->lock, flags); } @@ -201,7 +201,7 @@ void blk_stat_enable_accounting(struct request_queue *q) unsigned long flags; spin_lock_irqsave(&q->stats->lock, flags); - if (!q->stats->accounting++) + if (!q->stats->accounting++ && list_empty(&q->stats->callbacks)) blk_queue_flag_set(QUEUE_FLAG_STATS, q); spin_unlock_irqrestore(&q->stats->lock, flags); } |