[PATCH 1/2] block: add a helper to cancel atomic queue limit updates

[Kanchan Joshi]

On 3/27/2024 10:51 PM, Christoph Hellwig wrote:
> Drivers might have to perform complex actions to determine queue limits,
> and those might fail.  Add a helper to cancel a queue limit update
> that can be called in those cases.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>   include/linux/blkdev.h | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index f9b87c39cab047..39fedc8ef9c41f 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -892,6 +892,19 @@ int queue_limits_commit_update(struct request_queue *q,
>   		struct queue_limits *lim);
>   int queue_limits_set(struct request_queue *q, struct queue_limits *lim);
>   
> +/**
> + * queue_limits_cancel_update - cancel an atomic update of queue limits
> + * @q:		queue to update
> + *
> + * This functions cancels an atomic update of the queue limits started by
> + * queue_limits_start_update() and should be used when an error occurs after
> + * starting update.
> + */
> +static inline void queue_limits_cancel_update(struct request_queue *q)
> +{
> +	mutex_lock(&q->limits_lock);

mutex_unlock is needed here.