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H A Dblk-stat.c20de765f Thu Apr 13 01:28:04 CDT 2023 Chengming Zhou <zhouchengming@bytedance.com> 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>
68497092 Tue Dec 14 18:23:05 CST 2021 Jens Axboe <axboe@kernel.dk> block: make queue stat accounting a reference

kyber turns on IO statistics when it is loaded on a queue, which means
that even if kyber is then later unloaded, we're still stuck with stats
enabled on the queue.

Change the account enabled from a bool to an int, and pair the enable call
with the equivalent disable call. This ensures that stats gets turned off
again appropriately.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
H A Dblk-stat.h68497092 Tue Dec 14 18:23:05 CST 2021 Jens Axboe <axboe@kernel.dk> block: make queue stat accounting a reference

kyber turns on IO statistics when it is loaded on a queue, which means
that even if kyber is then later unloaded, we're still stuck with stats
enabled on the queue.

Change the account enabled from a bool to an int, and pair the enable call
with the equivalent disable call. This ensures that stats gets turned off
again appropriately.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
H A Dkyber-iosched.c68497092 Tue Dec 14 18:23:05 CST 2021 Jens Axboe <axboe@kernel.dk> block: make queue stat accounting a reference

kyber turns on IO statistics when it is loaded on a queue, which means
that even if kyber is then later unloaded, we're still stuck with stats
enabled on the queue.

Change the account enabled from a bool to an int, and pair the enable call
with the equivalent disable call. This ensures that stats gets turned off
again appropriately.

Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
H A Dblk-sysfs.c37e11c36 Mon Dec 20 22:04:36 CST 2021 Ming Lei <ming.lei@redhat.com> block: call blk_exit_queue() before freeing q->stats

blk_stat_disable_accounting() is added in commit 68497092bde9
("block: make queue stat accounting a reference"), and called in
kyber_exit_sched().

So we have to free q->stats after elevator is unloaded from
blk_exit_queue() in blk_release_queue(). Otherwise kernel panic
is caused.

Fixes: 68497092bde9 ("block: make queue stat accounting a reference")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211221040436.1333880-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
37e11c36 Mon Dec 20 22:04:36 CST 2021 Ming Lei <ming.lei@redhat.com> block: call blk_exit_queue() before freeing q->stats

blk_stat_disable_accounting() is added in commit 68497092bde9
("block: make queue stat accounting a reference"), and called in
kyber_exit_sched().

So we have to free q->stats after elevator is unloaded from
blk_exit_queue() in blk_release_queue(). Otherwise kernel panic
is caused.

Fixes: 68497092bde9 ("block: make queue stat accounting a reference")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20211221040436.1333880-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>