On 2023/1/6 11:06, Andrew Morton wrote:
On Tue, 3 Jan 2023 09:58:36 +0800 Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:
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?
Nobody would think to look at a private function in gup.c.
Sorry，I mean that comment is to explain why adding a new recheck.
I suggest this folio_try_get() rule be documented at the
folio_try_get() implementation site.
Most callers do perform this check, but not the ones in vmscan.c ?
Hope Matthew could give some advise, thanks
