Re: [PATCH v3 4/6] mm/thp: add THP allocation helper

[Christoph Hellwig]

> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +extern struct page *alloc_transhugepage(struct vm_area_struct *vma,
> +					unsigned long addr);

No need for the extern.  And also here: do we actually need the stub,
or can the caller make sure (using IS_ENABLED and similar) that the
compiler knows the code is dead?

> +struct page *alloc_transhugepage(struct vm_area_struct *vma,
> +				 unsigned long haddr)
> +{
> +	gfp_t gfp;
> +	struct page *page;
> +
> +	gfp = alloc_hugepage_direct_gfpmask(vma);
> +	page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
> +	if (page)
> +		prep_transhuge_page(page);
> +	return page;

I think do_huge_pmd_anonymous_page should be switched to use this
helper as well.