On Thu, Aug 14, 2025 at 01:54:58PM +0530, Nilay Shroff wrote:
> rq_qos_add() increments the block_rq_qos static key when a QoS
> policy is attached. When a QoS policy is removed via rq_qos_del(),
> we must symmetrically decrement the static key. If this removal drops
> the last QoS policy from the queue (q->rq_qos becomes NULL), the
> static branch can be disabled and the jump label patched to a NOP,
> avoiding overhead on the hot path.
>
> This change ensures rq_qos_add()/rq_qos_del() keep the
> block_rq_qos static key balanced and prevents leaving the branch
> permanently enabled after the last policy is removed.
>
> Fixes: 033b667a823e ("block: blk-rq-qos: guard rq-qos helpers by static key")
> Signed-off-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
Thanks,
Ming
