Re: [PATCH 2/2] mm/pageblock-flags: simplify MIGRATETYPE_MASK definition

[Zi Yan <ziy@nvidia.com>]

On 26 Aug 2025, at 5:31, Wei Yang wrote:

> MIGRATETYPE_MASK is defined to be the mask of possible migratetype.
>
> Define it with PB_migratetype_bits directly would be more clear.
>
> Also, MIGRATETYPE_AND_ISO_MASK is MIGRATETYPE_MASK add isolation bit.
> Use MIGRATETYPE_MASK in the definition of MIGRATETYPE_AND_ISO_MASK looks
> cleaner.
>
> No functional change intended.
>
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Cc: Zi Yan <ziy@nvidia.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: David Hildenbrand <david@redhat.com>
> ---
>  include/linux/pageblock-flags.h | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
> index 6a44be0f39f4..1489c062a5a7 100644
> --- a/include/linux/pageblock-flags.h
> +++ b/include/linux/pageblock-flags.h
> @@ -37,11 +37,10 @@ enum pageblock_bits {
>
>  #define NR_PAGEBLOCK_BITS (roundup_pow_of_two(__NR_PAGEBLOCK_BITS))
>
> -#define MIGRATETYPE_MASK ((1UL << (PB_migrate_end + 1)) - 1)
> +#define MIGRATETYPE_MASK (BIT(PB_migratetype_bits) - 1)

I am not sure about this one, even if PB_migrate_end + 1 == PB_migratetype_bits.
PB_migrate_end represents a bit index, where PB_migratetype_bits means
the number of the bits.

David's suggestion in another email might be better.

>
>  #ifdef CONFIG_MEMORY_ISOLATION
> -#define MIGRATETYPE_AND_ISO_MASK \
> -	(((1UL << (PB_migrate_end + 1)) - 1) | BIT(PB_migrate_isolate))
> +#define MIGRATETYPE_AND_ISO_MASK (MIGRATETYPE_MASK | BIT(PB_migrate_isolate))
>  #else
>  #define MIGRATETYPE_AND_ISO_MASK MIGRATETYPE_MASK
>  #endif

This one looks good to me.

--
Best Regards,
Yan, Zi