Re: [PATCH 2/2] block: use DAX for partition table reads

[Jens Axboe]

On 01/29/2016 08:18 AM, Dan Williams wrote:
> +unsigned char *read_dev_sector(struct block_device *bdev, sector_t n, Sector *p)
> +{
>   	struct page *page;
>
> -	page = read_mapping_page(mapping, (pgoff_t)(n >> (PAGE_CACHE_SHIFT-9)),
> -				 NULL);
> +	/* don't populate page cache for dax capable devices */
> +	if (IS_DAX(bdev->bd_inode))
> +		page = read_dax_sector(bdev, n);
> +	else
> +		page = read_pagecache_sector(bdev, n);
> +

Fall back to non-dax, if dax fails?

> +struct page *read_dax_sector(struct block_device *bdev, sector_t n)
> +{
> +	struct page *page = __page_cache_alloc(GFP_KERNEL | __GFP_COLD);

Why isn't that just alloc_pages()?

--
Jens Axboe