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bh=TnGFtpo/Gv6B9vWS/Wf+h/ZzAKUAJ0Ui+Kiqz4jbn+8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NWAKTsGuzWZbpFnlq/Ya+YL1ixTLq31LqywtwQUjkK1tyhWceH4KXHLwdQoa1ss6F JR766RqxBcp3uYEOZjSRggwmyJUciPFnsK7DeH9uCOD2H7y8Pp5a5rGI1f7/9sRwTj btehXRDmlEJZWxCf82CkB1n1OSY0GHxC0an+2zobCA4R81RK97DMM2TrTSBYpqgxry c6eLSdg69Y46jZaoEgP78R44IofwHRJU9CNPIPvR6knuUlAessUYZ9L8zHOByJETQa 2Yins9gTJyEfS+Ml7zQJbCxTI5ism0KQBlPrEaKcTFwZlx8p4OS7sGXYwpIUQ7WAiz g2RxbaBH+etyw== From: SeongJae Park To: Matthew Wilcox Cc: Kefeng Wang , Andrew Morton , David Hildenbrand , Oscar Salvador , SeongJae Park , linux-mm@kvack.org, linux-kernel@vger.kernel.org, damon@lists.linux.dev, vishal.moola@gmail.com Subject: Re: [PATCH -next 4/8] mm: damon: add temporary damon_get_folio() Date: Tue, 13 Dec 2022 19:18:51 +0000 Message-Id: <20221213191851.138660-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7794E20002 X-Stat-Signature: miqbgmus8znk6o9ijrw3z78mx4beyapd X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1670959136-978447 X-HE-Meta: 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 QyAL4e5J EeCm49uU6GYT+AmvXmv5OQjs+Yfqo/04++5aSrq0lEa8AtkyPlZtQ3Oygg3mMhwFfBcBmqyQtJOG6L/8h5cRz9MbZlMxEJIRSDBJ6Z29cncqRuBCFgc6zOQMZbaIzSglk0dOMMj1F76bBt9NN070LMbXVqqk6zoNhQJxd6JY+grEN+hkvk8aqAyz2ndO+zlEYwhFU 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, 13 Dec 2022 14:40:41 +0000 Matthew Wilcox wrote: > On Tue, Dec 13, 2022 at 05:27:31PM +0800, Kefeng Wang wrote: > > -struct page *damon_get_page(unsigned long pfn) > > +struct folio *damon_get_folio(unsigned long pfn) > > { > > - struct page *page = pfn_to_online_page(pfn); > > + struct folio *folio = pfn_to_online_folio(pfn); > > > > - if (!page || !PageLRU(page) || !get_page_unless_zero(page)) > > + if (!folio || !folio_test_lru(folio) || !folio_try_get(folio)) > > return NULL; > > Well, this is awkward. I asked Vishal to think about exactly this problem > and we were going to talk about it after we're both back from vacation > in January. But I guess we're going to do this in public instead ... > > Specifically, what should the semantics be for a putative > damon_get_folio() when it encounters a tail page? Should it return > the containing folio, or should it return NULL? And if the semantics > change here to return the containing folio, what adjustments need to > be made to the callers? I'd prefer to simply keep the original behavior, returning NULL, for now unless someone complaints. Thanks, SJ