Re: [PATCH v6 04/10] mm/memremap: add ZONE_DEVICE support for compound pages

[Christoph Hellwig <hch@lst.de>]

On Wed, Nov 24, 2021 at 07:09:59PM +0000, Joao Martins wrote:
> Add a new @vmemmap_shift property for struct dev_pagemap which specifies that a
> devmap is composed of a set of compound pages of order @vmemmap_shift, instead of
> base pages. When a compound page devmap is requested, all but the first
> page are initialised as tail pages instead of order-0 pages.

Please wrap commit log lines after 73 characters.

>  #define for_each_device_pfn(pfn, map, i) \
> -	for (pfn = pfn_first(map, i); pfn < pfn_end(map, i); pfn = pfn_next(pfn))
> +	for (pfn = pfn_first(map, i); pfn < pfn_end(map, i); pfn = pfn_next(map, pfn))

It would be nice to fix up this long line while you're at it.

>  static void dev_pagemap_kill(struct dev_pagemap *pgmap)
>  {
> @@ -315,8 +315,8 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
>  	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
>  				PHYS_PFN(range->start),
>  				PHYS_PFN(range_len(range)), pgmap);
> -	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap, range_id)
> -			- pfn_first(pgmap, range_id));
> +	percpu_ref_get_many(pgmap->ref, (pfn_end(pgmap, range_id)
> +			- pfn_first(pgmap, range_id)) >> pgmap->vmemmap_shift);

In the Linux coding style the - goes ointo the first line.

But it would be really nice to clean this up with a helper ala pfn_len
anyway:

	percpu_ref_get_many(pgmap->ref,
			    pfn_len(pgmap, range_id) >> pgmap->vmemmap_shift);