Re: [PATCH v5 03/13] mm/khugepaged: dedup and simplify hugepage alloc and charging

[David Rientjes <rientjes@google.com>]

On Wed, 4 May 2022, Zach O'Keefe wrote:

> @@ -1069,10 +1067,34 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
>  	return true;
>  }
>  
> -static void collapse_huge_page(struct mm_struct *mm,
> -				   unsigned long address,
> -				   struct page **hpage,
> -				   int node, int referenced, int unmapped)
> +static int alloc_charge_hpage(struct page **hpage, struct mm_struct *mm,
> +			      struct collapse_control *cc)
> +{
> +#ifdef CONFIG_NUMA
> +	const struct cpumask *cpumask;
> +#endif
> +	gfp_t gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
> +	int node = khugepaged_find_target_node(cc);
> +
> +#ifdef CONFIG_NUMA
> +	/* sched to specified node before huge page memory copy */
> +	if (task_node(current) != node) {
> +		cpumask = cpumask_of_node(node);
> +		if (!cpumask_empty(cpumask))
> +			set_cpus_allowed_ptr(current, cpumask);
> +	}
> +#endif
> +	if (!khugepaged_alloc_page(hpage, gfp, node))
> +		return SCAN_ALLOC_HUGE_PAGE_FAIL;
> +	if (unlikely(mem_cgroup_charge(page_folio(*hpage), mm, gfp)))
> +		return SCAN_CGROUP_CHARGE_FAIL;
> +	count_memcg_page_event(*hpage, THP_COLLAPSE_ALLOC);
> +	return SCAN_SUCCEED;
> +}

Lots of ifdefs here, I wonder if we can define a helper function that is a 
no-op when CONFIG_NUMA is disabled that we can call into here instead.

Otherwise this looks like a nice unification.  After this is cleaned up 
feel free to add

	Acked-by: David Rientjes <rientjes@google.com>