Re: [PATCH v15 03/11] mm/hmm: preparations for HMM to participate in migration

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] mm: migrate: missing MIGRATE_VMA_SELECT_NONE under CONFIG_MIGRATION
--

commit b1bec522cfd1d7118c74e979fcadbaa2b246dc13
Author: Mika Penttilä <mpenttil@redhat.com>

mm/hmm: preparations for HMM to participate in migration

This commit prepares HMM for migration by retrieving the VMA during page
walks and ensuring the mmap_lock is held. It also renames some hmm_vma_walk
fields to prevent namespace collisions.

> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 78424b3824c29..01c5f62a56e99 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
[ ... ]
> @@ -150,7 +175,7 @@ static inline unsigned long migrate_pfn(unsigned long pfn)
>  	return (pfn << MIGRATE_PFN_SHIFT) | MIGRATE_PFN_VALID;
>  }
>  
> -enum migrate_vma_direction {
> +enum migrate_vma_info {
>  	MIGRATE_VMA_SELECT_SYSTEM = 1 << 0,
>  	MIGRATE_VMA_SELECT_DEVICE_PRIVATE = 1 << 1,
>  	MIGRATE_VMA_SELECT_DEVICE_COHERENT = 1 << 2,

[Severity: Low]
This is not a bug, but could we add MIGRATE_VMA_SELECT_NONE to this enum
under CONFIG_MIGRATION?

It looks like it is missing here, even though it is defined in the fallback
block when CONFIG_MIGRATION is disabled. This is strictly a compile-time naming
and style issue and has no runtime effect. Note that I initially thought
MIGRATE_VMA_SELECT_COMPOUND was also missing, but I see it is correctly
defined in the tree.

[ ... ]
> @@ -192,6 +217,29 @@ struct migrate_vma {
>  	struct page		*fault_page;
>  };
>  
> +// TODO: enable migration
> +static inline enum migrate_vma_info hmm_select_migrate(struct hmm_range *range)
> +{
> +	return 0;

[Severity: Low]
Does the missing MIGRATE_VMA_SELECT_NONE in the enum definition force this
code to use a literal 0 as a workaround instead of a named enum value?

Could we define MIGRATE_VMA_SELECT_NONE and use it here for better
consistency?

> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260924065313.899730-1-mpenttil@redhat.com?part=3