Re: [PATCH 04/15] block: prevent elevator switch during updating nr_hw_queues

[Nilay Shroff <nilay@xxxxxxxxxxxxx>]

On 4/10/25 7:00 PM, Ming Lei wrote:
> @@ -5081,7 +5087,18 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
>  void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
>  {
>  	mutex_lock(&set->tag_list_lock);
> +	/*
> +	 * Mark us in updating nr_hw_queues for preventing switching
> +	 * elevator
> +	 *
> +	 * Elevator switch code can _not_ acquire ->tag_list_lock
> +	 */
> +	set->flags |= BLK_MQ_F_UPDATE_HW_QUEUES;
> +	synchronize_srcu(&set->update_nr_hwq_srcu);
> +
>  	__blk_mq_update_nr_hw_queues(set, nr_hw_queues);
> +
> +	set->flags &= BLK_MQ_F_UPDATE_HW_QUEUES;

I think here we want to clear BLK_MQ_F_UPDATE_HW_QUEUES, so we need to
have set->flags updated as below:

set->flags &= ~BLK_MQ_F_UPDATE_HW_QUEUES;

Thanks,
--Nilay