[PATCH 05/15] block: add a max_user_discard_sectors queue limit

[Keith Busch]

On Mon, Jan 22, 2024 at 06:36:35PM +0100, Christoph Hellwig wrote:
> @@ -174,23 +174,23 @@ static ssize_t queue_discard_max_show(struct request_queue *q, char *page)
>  static ssize_t queue_discard_max_store(struct request_queue *q,
>  				       const char *page, size_t count)
>  {
> -	unsigned long max_discard;
> -	ssize_t ret = queue_var_store(&max_discard, page, count);
> +	unsigned long max_discard_bytes;
> +	ssize_t ret;
>  
> +	ret = queue_var_store(&max_discard_bytes, page, count);
>  	if (ret < 0)
>  		return ret;
>  
> -	if (max_discard & (q->limits.discard_granularity - 1))
> +	if (max_discard_bytes & (q->limits.discard_granularity - 1))
>  		return -EINVAL;
>  
> -	max_discard >>= 9;
> -	if (max_discard > UINT_MAX)
> +	if ((max_discard_bytes >> SECTOR_SHIFT) > UINT_MAX)
>  		return -EINVAL;
>  
> -	if (max_discard > q->limits.max_hw_discard_sectors)
> -		max_discard = q->limits.max_hw_discard_sectors;
> -
> -	q->limits.max_discard_sectors = max_discard;
> +	q->limits.max_user_discard_sectors = max_discard_bytes >> SECTOR_SHIFT;
> +	q->limits.max_discard_sectors =
> +		min_not_zero(q->limits.max_hw_discard_sectors,
> +			     q->limits.max_user_discard_sectors);

Shouldn't writing 0 disable discards?