Re: [PATCH 4/4] lightnvm: Precalculate max/min sectors per req.

["Matias Bjørling" <mb@lightnvm.io>]

On 05/04/2016 05:31 PM, Javier González wrote:
> Add two precalculated values to nvm_rq: (i) maximum number of sectors
> per general request; and (ii) minimum number of sectors per write
> request.
>
> Signed-off-by: Javier González <javier@cnexlabs.com>
> ---
>   drivers/lightnvm/core.c  | 3 +++
>   include/linux/lightnvm.h | 4 +++-
>   2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index 4cd9803..85682d91 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -573,6 +573,9 @@ static int nvm_core_init(struct nvm_dev *dev)
>
>   	dev->plane_mode = NVM_PLANE_SINGLE;
>   	dev->max_rq_size = dev->ops->max_phys_sect * dev->sec_size;
> +	dev->max_sec_rq = dev->ops->max_phys_sect;
> +	/* assume max_phys_sect % dev->min_write_pgs == 0 */
> +	dev->min_sec_w_rq = dev->sec_per_pl * (dev->sec_size / PAGE_SIZE);
>
>   	if (grp->mpos & 0x020202)
>   		dev->plane_mode = NVM_PLANE_DOUBLE;
> diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
> index 67e72f5..c2dfd0c 100644
> --- a/include/linux/lightnvm.h
> +++ b/include/linux/lightnvm.h
> @@ -351,7 +351,9 @@ struct nvm_dev {
>   	/* Calculated/Cached values. These do not reflect the actual usable
>   	 * blocks at run-time.
>   	 */
> -	int max_rq_size;
> +	int max_rq_size; /* maximum size of a single request */
> +	int max_sec_rq; /* maximum amount of sectors that fit in one req. */
> +	int min_sec_w_rq; /* minimum amount of sectors required on write req. */
>   	int plane_mode; /* drive device in single, double or quad mode */
>
>   	int sec_per_pl; /* all sectors across planes */
>

I think this is best kept within pblk for now. The min_sec_w_rq is not 
enough to describe the pages to be written. It must also follow a 
specific order, which is not communicated only with minimum page writes.