Subject: Re: [PATCH 1/1 v3] drivers/nvme: default to 4k device page size

From: Christoph Hellwig <[email-masked]>
Date: Tue, 3 Nov 2015 05:18:24 -0800

On Fri, Oct 30, 2015 at 02:35:11PM -0700, Nishanth Aravamudan wrote:
> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index ccc0c1f93daa..a9a5285bdb39 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -1717,7 +1717,12 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
>  	u32 aqa;
>  	u64 cap = readq(&dev->bar->cap);
>  	struct nvme_queue *nvmeq;
> -	unsigned page_shift = PAGE_SHIFT;
> +	/*
> +	 * default to a 4K page size, with the intention to update this
> +	 * path in the future to accomodate architectures with differing
> +	 * kernel and IO page sizes.
> +	 */
> +	unsigned page_shift = 12;
>  	unsigned dev_page_min = NVME_CAP_MPSMIN(cap) + 12;
>  	unsigned dev_page_max = NVME_CAP_MPSMAX(cap) + 12;

Looks good as a start.  Note that all the MPSMIN/MAX checking could
be removed as NVMe devices must support 4k pages.