Messages in this thread | | | Date | Fri, 6 Jan 2023 14:23:25 +0800 | Subject | Re: [PATCH v2] mm: huge_memory: convert split_huge_pages_all() to use a folio | From | Kefeng Wang <> |
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On 2023/1/6 11:06, Andrew Morton wrote: > On Tue, 3 Jan 2023 09:58:36 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote: > >> >> >> On 2022/12/31 5:45, Andrew Morton wrote: >>> On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> 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
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