Re: [PATCH 1/4] mm: factor zone-device page init helpers out of __init_zone_device_page

[Mike Rapoport <rppt@kernel.org>]

Hi,

On Fri, May 15, 2026 at 04:20:42PM +0800, Li Zhe wrote:
> __init_zone_device_page() currently mixes three different jobs: deciding
> the initial page refcount, initializing the generic ZONE_DEVICE state, and
> setting up pageblock metadata.
> 
> Split the refcount policy into zone_device_page_init_refcount() and move
> the generic page initialization into generic_init_zone_device_page(). This
> keeps the slow path behavior unchanged, but makes the individual pieces
> reusable by later fast-path patches.
> 
> No functional change intended.
> 
> Signed-off-by: Li Zhe <lizhe.67@bytedance.com>
> ---
>  mm/mm_init.c | 62 ++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 38 insertions(+), 24 deletions(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index f9f8e1af921c..5244acb96dbb 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -987,11 +987,36 @@ static void __init memmap_init(void)
>  }
>  
>  #ifdef CONFIG_ZONE_DEVICE
> -static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
> -					  unsigned long zone_idx, int nid,
> -					  struct dev_pagemap *pgmap)

Since you are already changing __init_zone_device_page(), I'd suggest
renaming it to zone_device_page_init().

> +static inline int zone_device_page_init_refcount(
> +		const struct dev_pagemap *pgmap)
>  {
> +	/*
> +	 * ZONE_DEVICE pages other than MEMORY_TYPE_GENERIC are released
> +	 * directly to the driver page allocator which will set the page count
> +	 * to 1 when allocating the page.
> +	 *
> +	 * MEMORY_TYPE_GENERIC and MEMORY_TYPE_FS_DAX pages automatically have
> +	 * their refcount reset to one whenever they are freed (ie. after
> +	 * their refcount drops to 0).
> +	 */
> +	switch (pgmap->type) {
> +	case MEMORY_DEVICE_FS_DAX:
> +	case MEMORY_DEVICE_PRIVATE:
> +	case MEMORY_DEVICE_COHERENT:
> +	case MEMORY_DEVICE_PCI_P2PDMA:
> +		return 0;
> +	case MEMORY_DEVICE_GENERIC:
> +		return 1;
> +	default:
> +		WARN_ONCE(1, "Unknown memory type!");
> +		return 1;
> +	}
> +}
>  
> +static void __ref generic_init_zone_device_page(struct page *page,
> +		unsigned long pfn, unsigned long zone_idx, int nid,
> +		struct dev_pagemap *pgmap)
> +{

Here also would be better to use zone_device_page_ prefix. 
And I don't think "generic" adds clarity about what this function is doing.

Seeing that later patches rename it again to _slow variant, I'd suggest to
call it __zone_device_page_init() at keep this name going forward.

>  	__init_single_page(page, pfn, zone_idx, nid);
>  
>  	/*

-- 
Sincerely yours,
Mike.