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Mon, 14 Aug 2023 21:31:31 -0700 (PDT) MIME-Version: 1.0 References: <20230815032645.1393700-1-willy@infradead.org> <20230815032645.1393700-9-willy@infradead.org> In-Reply-To: <20230815032645.1393700-9-willy@infradead.org> From: Yosry Ahmed Date: Mon, 14 Aug 2023 21:30:54 -0700 Message-ID: Subject: Re: [PATCH 8/9] mm: Rearrange page flags To: "Matthew Wilcox (Oracle)" Cc: Andrew Morton , Jens Axboe , io-uring@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: DFE6480017 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: ggquqrznzsjskw76ziysgows3cf11rao X-HE-Tag: 1692073892-911880 X-HE-Meta: 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 9OeVkjT+ FgtQ5wBylQEoXxZwd4j7AH/YIq7Wh3+jDU/J/pAxErjfh7xkCFyBILYjP+1pvVpDBBgIZlF6MS0r91ZMpL3mcpcfPYtob7cCIW4RlXx+CmEJIbSLm5ZiPuN27GMFhrteTUITKVm4hKMLfQYCK+ctkOX4PGwiktQJdqGHq3pV44AYSr46/EzlpLwRVmcTj7UDTzoLt4FeyZFo4UWjU0VXfaZgpFlqk6461AM0uLQTgHNBs+xSn0WiWZt48QaQQSr+MJa3S6HVZCCDesWRQbrWzXgC8nyrGpDDSOPnvTzmsP/gAvzhWWKuwoCxsQp/0+qLma8+Jc1xtDSTgof8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.005116, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 14, 2023 at 8:27=E2=80=AFPM Matthew Wilcox (Oracle) wrote: > > Move PG_writeback into bottom byte so that it can use PG_waiters in a > later patch. Move PG_head into bottom byte as well to match with where > 'order' is moving next. Sorry if that's obvious, but why do we want to move PG_head to where 'order' is moving? I thought we would want to avoid an overlap to avoid mistaking the first tail page of a high-order compound page as a head page?