Re: [PATCH v2 14/22] mm: encode freetype flags in pageblock flags

["Vlastimil Babka (SUSE)" <vbabka@kernel.org>]

On 3/20/26 19:23, Brendan Jackman wrote:
> In preparation for implementing allocation from FREETYPE_UNMAPPED lists.
> 
> Since it works nicely with the existing allocator logic, and also offers
> a simple way to amortize TLB flushing costs, __GFP_UNMAPPED will be
> implemented by changing mappings at pageblock granularity. Therefore,
> encode the mapping state in the pageblock flags.
> 
> Also add the necessary logic to record this from a freetype, and
> reconstruct a freetype from the pageblock flags.
> 
> Signed-off-by: Brendan Jackman <jackmanb@google.com>

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>

nit:

> @@ -434,9 +431,20 @@ __always_inline freetype_t
>  __get_pfnblock_freetype(const struct page *page, unsigned long pfn,
>  			bool ignore_iso)
>  {
> -	int mt = get_pfnblock_migratetype(page, pfn);
> +	unsigned long mask = PAGEBLOCK_FREETYPE_MASK;
> +	enum migratetype migratetype;
> +	unsigned int ft_flags;
> +	unsigned long flags;
>  
> -	return migrate_to_freetype(mt, 0);
> +	flags = __get_pfnblock_flags_mask(page, pfn, mask);
> +	ft_flags = (flags & PAGEBLOCK_FREETYPE_FLAGS_MASK) >> PB_freetype_flags;
> +
> +	migratetype = flags & PAGEBLOCK_MIGRATETYPE_MASK;
> +#ifdef CONFIG_MEMORY_ISOLATION
> +	if (!ignore_iso && flags & BIT(PB_migrate_isolate))

			  (flags & BIT(PB_migrate_isolate)) ?

> +		migratetype = MIGRATE_ISOLATE;
> +#endif
> +	return migrate_to_freetype(migratetype, ft_flags);
>  }
>  
>  /**
> @@ -570,6 +578,15 @@ static void set_pageblock_migratetype(struct page *page,
>  				  PAGEBLOCK_MIGRATETYPE_MASK | PAGEBLOCK_ISO_MASK);
>  }
>  
> +static inline void set_pageblock_freetype_flags(struct page *page,
> +						unsigned int ft_flags)
> +{
> +	unsigned int flags = ft_flags << PB_freetype_flags;
> +
> +	__set_pfnblock_flags_mask(page, page_to_pfn(page), flags,
> +				  PAGEBLOCK_FREETYPE_FLAGS_MASK);
> +}
> +
>  void __meminit init_pageblock_migratetype(struct page *page,
>  					  enum migratetype migratetype,
>  					  bool isolate)
> @@ -593,7 +610,7 @@ void __meminit init_pageblock_migratetype(struct page *page,
>  		flags |= BIT(PB_migrate_isolate);
>  #endif
>  	__set_pfnblock_flags_mask(page, page_to_pfn(page), flags,
> -				  PAGEBLOCK_MIGRATETYPE_MASK | PAGEBLOCK_ISO_MASK);
> +				  PAGEBLOCK_FREETYPE_MASK);
>  }
>  
>  #ifdef CONFIG_DEBUG_VM
>