Re: [PATCH v2] mm: huge_memory: convert split_huge_pages_all() to use a folio

From: Kefeng Wang
Date: Mon Jan 02 2023 - 20:58:55 EST




On 2022/12/31 5:45, Andrew Morton wrote:
On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:

Straightforwardly convert split_huge_pages_all() to use a folio.

...

--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2932,6 +2932,7 @@ static void split_huge_pages_all(void)
{
struct zone *zone;
struct page *page;
+ struct folio *folio;
unsigned long pfn, max_zone_pfn;
unsigned long total = 0, split = 0;
@@ -2944,24 +2945,32 @@ static void split_huge_pages_all(void)
int nr_pages;
page = pfn_to_online_page(pfn);
- if (!page || !get_page_unless_zero(page))
+ if (!page || PageTail(page))
+ continue;
+ folio = page_folio(page);
+ if (!folio_try_get(folio))
continue;
- if (zone != page_zone(page))
+ if (unlikely(page_folio(page) != folio))
+ goto next;
+
+ if (zone != folio_zone(folio))
goto next;

I'm still not understanding the above hunk. Why is the
"page_folio(page) != folio" check added? Should it be commented?

There is a comment in try_get_folio(), is it enough?