6.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Julian Sun sunjunchao2870@gmail.com
commit 8f5845e0743bf3512b71b3cb8afe06c192d6acc4 upstream.
The commit 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock") protected wbt_enable_default() with q->elevator_lock; however, it also placed wbt_enable_default() before blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);, resulting in wbt failing to be enabled.
Moreover, the protection of wbt_enable_default() by q->elevator_lock was removed in commit 78c271344b6f ("block: move wbt_enable_default() out of queue freezing from sched ->exit()"), so we can directly fix this issue by placing wbt_enable_default() after blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);.
Additionally, this issue also causes the inability to read the wbt_lat_usec file, and the scenario is as follows:
root@q:/sys/block/sda/queue# cat wbt_lat_usec cat: wbt_lat_usec: Invalid argument
root@q:/data00/sjc/linux# ls /sys/kernel/debug/block/sda/rqos cannot access '/sys/kernel/debug/block/sda/rqos': No such file or directory
root@q:/data00/sjc/linux# find /sys -name wbt /sys/kernel/debug/tracing/events/wbt
After testing with this patch, wbt can be enabled normally.
Signed-off-by: Julian Sun sunjunchao@bytedance.com Cc: stable@vger.kernel.org Fixes: 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock") Reviewed-by: Nilay Shroff nilay@linux.ibm.com Reviewed-by: Yu Kuai yukuai3@huawei.com Reviewed-by: Ming Lei ming.lei@redhat.com Link: https://lore.kernel.org/r/20250812154257.57540-1-sunjunchao@bytedance.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-sysfs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -876,9 +876,9 @@ int blk_register_queue(struct gendisk *d
if (queue_is_mq(q)) elevator_set_default(q); - wbt_enable_default(disk);
blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q); + wbt_enable_default(disk);
/* Now everything is ready and send out KOBJ_ADD uevent */ kobject_uevent(&disk->queue_kobj, KOBJ_ADD);