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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH v2] mm: huge_memory: convert split_huge_pages_all() to use a folio Content-Language: en-US To: Andrew Morton CC: , , References: <20221230093020.9664-1-wangkefeng.wang@huawei.com> <20221230134535.240f49e0ad8bf6d82f8cc393@linux-foundation.org> <20230105190658.f5d9a4bc9619ad6bec91a973@linux-foundation.org> From: Kefeng Wang In-Reply-To: <20230105190658.f5d9a4bc9619ad6bec91a973@linux-foundation.org> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 3E0E5140010 X-Stat-Signature: 3s5e4uihjey6bbkiwhb18gzhkrj7pyt7 X-HE-Tag: 1672986212-913805 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2023/1/6 11:06, Andrew Morton wrote: > On Tue, 3 Jan 2023 09:58:36 +0800 Kefeng Wang wrote: > >> >> >> On 2022/12/31 5:45, Andrew Morton wrote: >>> On Fri, 30 Dec 2022 17:30:20 +0800 Kefeng Wang 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