[PATCH 08/20] drbd: add DAX/PMEM support for metadata access

[Christoph Hellwig]

Adding the dax maintainers and they really need to review this.

> +	long want = (drbd_md_last_sector(bdev) + 1 - first_sector) >> (PAGE_SHIFT - SECTOR_SHIFT);
> +	pgoff_t pgoff = first_sector >> (PAGE_SHIFT - SECTOR_SHIFT);
> +	long md_offset_byte = (bdev->md.md_offset - first_sector) << SECTOR_SHIFT;
> +	long al_offset_byte = (al_sector - first_sector) << SECTOR_SHIFT;

You really want helpers to make all these unit conversions maintainable.