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Shutemov" To: John Hubbard Cc: Matthew Wilcox , linux-mm@kvack.org, "Kirill A . Shutemov" Subject: Re: [PATCH] mm: Improve dump_page() for compound pages Message-ID: <20200210215449.ao7q5x4no5y2j6pc@box> References: <20200208044415.30012-1-willy@infradead.org> <20200210124225.56cjwblfa7njgp5o@box> <92d69132-6664-3fc3-4743-11109df0b079@nvidia.com> <20200210212125.f24n5javxkfv6uvi@box> <85d46612-b5b1-f566-7026-e4fec9166c3b@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <85d46612-b5b1-f566-7026-e4fec9166c3b@nvidia.com> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000042, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Feb 10, 2020 at 01:33:22PM -0800, John Hubbard wrote: > > PageSlab() can be called for the head page. > > > It's not clear to me whether it's safer to use the...user-provided page, or the > head page, for checking PageSlab()--it's probably set on both head and non-head > pages, right? PageSlab() will call compound_head() inside. > I guess you're saying it should be like this: > > mapcount = PageSlab(head) ? 0 : page_mapcount(page); > > ...yes? Yes. -- Kirill A. Shutemov