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[2003:cb:c702:6e00:8b72:420e:df27:90c2]) by smtp.gmail.com with ESMTPSA id k18-20020a05600c1c9200b003d22528decesm8899801wms.43.2022.12.13.03.40.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Dec 2022 03:40:27 -0800 (PST) Message-ID: Date: Tue, 13 Dec 2022 12:40:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH -next 1/8] mm: memory_hotplug: add pfn_to_online_folio() To: Kefeng Wang , Andrew Morton , Oscar Salvador , SeongJae Park Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, damon@lists.linux.dev, vishal.moola@gmail.com, willy@infradead.org References: <20221213092735.187924-1-wangkefeng.wang@huawei.com> <20221213092735.187924-2-wangkefeng.wang@huawei.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20221213092735.187924-2-wangkefeng.wang@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2E11C40005 X-Stat-Signature: gwdcjibicfedryny14jrqdc6k3bgri1u X-Rspam-User: X-HE-Tag: 1670931632-138015 X-HE-Meta: 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 vIshyeUR +/0ORJiRN3IMNgGL5FxUwXr37kp/FImgLpLB5gT6a/zVZZ2mjKIzfCP702AoDeCpHfVTlRuBZKI9xyZlNdgMGXKruwyX9+HCgOhSypzNak4rgE4BYC/308iXL+BVjMbam66mYqC6RrXMbvfXuZi6v5U2FizxCG7NzDb8rA9eduBkyXEctu+y+nLHG+9rPXQ6vcGbmWGBOs8HTZOejilzNmiFFgLF2XWiLA6qhMaUxmuk7Rx/EsCd86QgfuWQ0YwS2fCBlwfFQD8f/bfw= 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 13.12.22 10:27, Kefeng Wang wrote: > Introduce a wrapper function pfn_to_online_folio(), which calls > pfn_to_online_page() and returns the folio of the page found, > or null if no page. > > Signed-off-by: Kefeng Wang > --- > include/linux/memory_hotplug.h | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h > index 9fcbf5706595..e841e4fb52a7 100644 > --- a/include/linux/memory_hotplug.h > +++ b/include/linux/memory_hotplug.h > @@ -265,6 +265,13 @@ static inline void pgdat_kswapd_unlock(pg_data_t *pgdat) {} > static inline void pgdat_kswapd_lock_init(pg_data_t *pgdat) {} > #endif /* ! CONFIG_MEMORY_HOTPLUG */ > > +static inline struct folio *pfn_to_online_folio(unsigned long pfn) > +{ > + struct page *page = pfn_to_online_page(pfn); > + > + return page ? page_folio(page) : NULL; > +} Who guarantees that page_folio() is safe and stable at that point? IIRC, that's very tricky. We could have the page concurrently getting freed and the folio dissolved. -- Thanks, David / dhildenb