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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pDsHc-00HR2F-Dc; Fri, 06 Jan 2023 19:21:40 +0000 Date: Fri, 6 Jan 2023 19:21:40 +0000 From: Matthew Wilcox To: SeongJae Park Cc: Andrew Morton , Xiubo Li , Ilya Dryomov , Jeff Layton , linux-mm@kvack.org, ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] add folio_headpage() macro Message-ID: References: <20230106174028.151384-1-sj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230106174028.151384-1-sj@kernel.org> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 27A291C0015 X-Stat-Signature: 4asdj7z77i4qsszeu99ukdt4f3oijuyh X-HE-Tag: 1673032896-312210 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 Fri, Jan 06, 2023 at 05:40:25PM +0000, SeongJae Park wrote: > The standard idiom for getting head page of a given folio is > '&folio->page'. It is efficient and safe even if the folio is NULL, > because the offset of page field in folio is zero. However, it makes > the code not that easy to understand at the first glance, especially the > NULL safety. Also, sometimes people forget the idiom and use > 'folio_page(folio, 0)' instead. To make it easier to read and remember, > add a new macro function called 'folio_headpage()' with the NULL case > explanation. Then, replace the 'folio_page(folio, 0)' calls with > 'folio_headpage(folio)'. No. Everywhere that uses &folio->page is a place that needs to be fixed. It shouldn't have a nice convenience macro. It should make you mildly uncomfortable.