Re: [PATCH v2] s390/mm: Allow hugepage migration for s390

[Heiko Carstens <hca@linux.ibm.com>]

On Thu, Nov 12, 2026 at 08:54:51AM +0100, Alexander Gordeev wrote:
> On Wed, Nov 11, 2026 at 07:29:44PM +0100, Gerald Schaefer wrote:
> 
> > +#if IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION)
> > +bool arch_hugetlb_migration_supported(struct hstate *h)
> > +{
> 
> Oh, would you agree to such one? ;)
> 
> 	return IS_ENABLED(CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION) &&
> 	       __hugetlb_valid_size(huge_page_size(h));
> 
> > +	return __hugetlb_valid_size(huge_page_size(h));
> > +}
> > +#endif

Out of curiosity: why?

All other architectures do ifdef, instead if IS_ENABLED to make sure the
function exists only if the config option is enabled (IS_ENABLED would also
make sense if "m" would be a possible option, but that is not the case
here).

Then if this is only inline within the function, like suggested above, the
prototype in the header does not exist (rightfully), leading to compile time
warnings. The arch_hugetlb_migration_supported define also indicates the
availability of the feature.

So I'm wondering what the point of this exercise is and what the
deviation compared to other architectures would buy us.