Re: [PATCH v2 04/12] mm: hugetlb_vmemmap: generalize vmemmap page allocation

[Mike Rapoport]

Hi Muchun,

> Vmemmap page allocation is currently tied to restoring a virtual range
> and assumes an empty destination list.  These constraints prevent it from
> being reused when pages are requested independently of a vmemmap range or
> appended to an existing list.
> 
> Generalize the allocator and give it an all-or-nothing list contract so
> the restore and optimization paths can share the same allocation policy.
> This also allows HVO head-page allocation to fail gracefully under memory
> pressure without triggering the OOM killer.
> 
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Reviewed-by: Lance Yang <lance.yang@xxxxxxxxx>
> Reviewed-by: Qi Zheng <qi.zheng@xxxxxxxxx>
> ---
> v2:
> - Collect Reviewed-by from Lance Yang and Qi Zheng
> ---
>  mm/hugetlb_vmemmap.c | 39 ++++++++++++++++++---------------------
>  1 file changed, 18 insertions(+), 21 deletions(-)
>
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 0e5b2b182d1bf..4b20a8efc0678 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -334,28 +334,26 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
>  	return ret;
>  }
>  
> -static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
> -				   struct list_head *list)
> +static int alloc_vmemmap_page_list(struct list_head *head, unsigned int nr_pages,
> +				   int nid)

Please indent with two tabs, like David likes :)
Applies throughout the series.

>  {
> -	gfp_t gfp_mask = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
> -	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
> -	int nid = page_to_nid((struct page *)start);
> -	struct page *page, *next;
> -	int i;
> +	LIST_HEAD(local);

Can we use a better name here please? E.g new_pages?

>  
> -	for (i = 0; i < nr_pages; i++) {
> -		page = alloc_pages_node(nid, gfp_mask, 0);
> -		if (!page)
> -			goto out;
> -		list_add(&page->lru, list);
> +	for (unsigned int i = 0; i < nr_pages; i++) {
> +		struct page *page;
> +
> +		page = alloc_pages_node(nid, GFP_KERNEL | __GFP_RETRY_MAYFAIL, 0);
> +		if (!page) {

I think goto err_do_cleanup is cleaner than ad-hok cleanups

> +			memmap_pages_add(i);

This is confusing. Updating counters only to use
free_vmemmap_page_list() seems worse choice than walking the list and
__free_page().

-- 
Sincerely yours,
Mike.