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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672177115; bh=acdQy0Fz5MV+4Q92/bTs266NGfZ7aBnK5NRffLaTJ3A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JEARoZa3KHVgNO3Rfiv1ejsZi0dzhu6j6oNXslOM261dXGjVVIWn0Fh7WRcn90rsE rghHVYdBp6rnpsBoeSx7X9qRr7OesSQ37ZJRuwouQaHtmYw6owwBQkpD/QJDf+Ghma JlqTNCcIcM+9yU5FSwvMOL85ITCwS7t9bU7sefXWN+pP3vZl2iEcAR3CWgjVn+5YVs S21p5KSs/q1ofVl7IJmpOQWw3ZNA0+NdE/9u3zZiylLVY60qnsghBsla/ML6LpUkjx 2pEiwKhpX85Tj8FyvEfdp+XCL8nQU0yKomz5lyPxuZ46sfvf5GjvcTcEYPxDs/yEr/ YcEiOQchqD+MQ== From: SeongJae Park To: Matthew Wilcox Cc: SeongJae Park , Kefeng Wang , Andrew Morton , damon@lists.linux.dev, linux-mm@kvack.org, vishal.moola@gmail.com, david@redhat.com Subject: Re: [PATCH -next v2 2/7] mm: damon: introduce damon_get_folio() Date: Tue, 27 Dec 2022 21:38:33 +0000 Message-Id: <20221227213833.3261-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C5832140006 X-Stat-Signature: xokndpg871czeqg3e961cbwf1wy7txew X-HE-Tag: 1672177118-850619 X-HE-Meta: U2FsdGVkX19nsfXEeo9eiH+u0lu5/OAegzNDCvrcXdOHlGqcnsW8kFCOl1YcG9mCNwiTXdGOry8TpB28xP4448GzH9Wcs/fwxiYV5/c+cjOKhwT+S0Q9fz5HnZT6+gIdaiWrVsI0xm1AGjqPWv3SrYgkd5kXQySrWVT2Au1NZ9fpUVVaK6M7PBEoVOdqW14GyLqBTFO+o9vkS0Gf4leyM0sqFF/PwaHdOm8d/R2ZIpszH7KZsaW8ja762snCBIaqbvnq6voZ29rhcgScGopO6EOafPcW1o2r326nba4pBgG39yZrgdeccq3Iag63cMC24DqCxRcIrrw4lmAkRxzhrEC2HI9AK4TuNeDjAzgy0tO4u1U5Vg47rp1gFPThwoJlOhmPpvTIP9YwIbjtiKjPb886kJ8O4jFdkDTnhSSCfviiiRwqn1jmIrZbS15rJdIZ5NVwQ17hG5ZBjfdH5q540fPQzLuH+pMw+mxJYnnDTJ8g4U9z/Ne90QLNotYj2rCuE9+w2/Llafwlab7IzqWGvKEnWZTmv+DNEHbRXHx9GpTJKriuxMOduthp+UaZiORjsRJ20T3oHsYjrBzC74/0jH3VLyIELMlsgI/vZlQa7Xb2U8DAxLlCcHWm1RxCARNLvnXp+GlPoUcoDCY5wndJ7iEmvSFsG8O3OuAwAnLuShlBhPyBedcpTSSIXj8tQf5dShxNMjkfeXgpzdzBj6cOeazc3uphP2qblMB85VascWw/rnvd8ktFlb8zu2eaCgmzmJZQRNUnloISS/8Qib1UYyiKprdGjlbP/+DMWDN5nuz/XXesLlyI9XKu01oY+L+x063GD7O3UKMYp2GXII2JmcQCSmovzz+XTMVQ85Vakv/5fnX9a3NU5+uuZwm+kkaKcaRHgSvDpIgTqITZQkzQWxGVIJfkNOsWfx3p6V/YvAnAj9UzHlcsnwHFJowN0Tfqse1pILazAYcI1G/f8Y5 PpUiBHth T4t8ho9GSL5Hmx4UsXjZhAJeVkxe3h8C2UFNHHeg7bDLsmg1GWt0znYe0ANqmf45NbmrR9BDQVs4xP8zJgb4xVUQzXbJgODueWZv72KdF87migmPuxUTPK7KUYYnDv3XWmv8sW97LtPuklnft5PzzIJ2UBRr+GhXn2GW1g/tkWUSUo2Z2EwvjEzMmBqcBSli4EyUO 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, 27 Dec 2022 19:49:56 +0000 Matthew Wilcox wrote: > On Tue, Dec 27, 2022 at 07:42:57PM +0000, SeongJae Park wrote: > > > +static inline struct page *damon_get_page(unsigned long pfn) > > > +{ > > > + struct folio *folio = damon_get_folio(pfn); > > > + > > > + return &folio->page; > > > > I think we should check if folio is NULL before dereferencing it? > > &folio->page does not dereeference folio. Ah, ok. And this is safe because ->page is at the beginning of folio, right? Kefeng, could we add a comment explaining it, for people having bad eyes like me? Thanks, SJ