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bh=T+DIgbx0TN06FPH+vlHy8WVMyBolsDeruztbB4dJxSE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=cXeVw7iowabcjhBfgLE1p17wdUYlLu1BgeVeQQ8UijZw7aI95QojB3rMCKd0tjW7Y WS3j63R9NOLu1FknBmCFXsF/VkCZEPzx0EcXBFtP3y3dhfWN+R/ebd8DqZaMkF3uO5 eBRXwFJreXb5DVfS3fu2FD2CBr7qnyP0PJ/Y2LgI= Date: Thu, 5 Jan 2023 19:06:58 -0800 From: Andrew Morton To: Kefeng Wang Cc: , , Subject: Re: [PATCH v2] mm: huge_memory: convert split_huge_pages_all() to use a folio Message-Id: <20230105190658.f5d9a4bc9619ad6bec91a973@linux-foundation.org> In-Reply-To: References: <20221230093020.9664-1-wangkefeng.wang@huawei.com> <20221230134535.240f49e0ad8bf6d82f8cc393@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: p3865xaw9no7ac1oyj9pcnj3rjg8yss4 X-Rspam-User: X-Rspamd-Queue-Id: 9D7211C0009 X-Rspamd-Server: rspam06 X-HE-Tag: 1672974425-868517 X-HE-Meta: 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 3ix4Kt3E kd47ln07xjufQUJwHjhBW2d80oengu5Y+HaoTtsg9H4sxU6gXiXKjkBuYM9uib0PN62Gv0Uho1D4UtLy0i92dmcK/3LsXlFTaAzT0cv7m5Ul/6poWQnAGqy8UYA== 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 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. 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?