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

[David Hildenbrand <david@redhat.com>]

On 26.08.25 11:31, 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)
>   
>   #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


Hm, I wonder if we can get rid of PB_migratetype_bits

diff --git a/include/linux/pageblock-flags.h 
b/include/linux/pageblock-flags.h
index 6a44be0f39f45..70c988dbdddc8 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -13,12 +13,11 @@

  #include <linux/types.h>

-#define PB_migratetype_bits 3
  /* Bit indices that affect a whole block of pages */
  enum pageblock_bits {
-       PB_migrate,
-       PB_migrate_end = PB_migrate + PB_migratetype_bits - 1,
-                       /* 3 bits required for migrate types */
+       PB_migrate_0,
+       PB_migrate_1,
+       PB_migrate_2,
         PB_compact_skip,/* If set the block is skipped by compaction */

  #ifdef CONFIG_MEMORY_ISOLATION

And then just work with the bits. No magical computations.

-- 
Cheers

David / dhildenb