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Thu, 22 Jan 2026 06:29:48 -0500 (EST) Date: Thu, 22 Jan 2026 11:29:43 +0000 From: Kiryl Shutsemau To: Zi Yan Cc: Andrew Morton , Muchun Song , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden , Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCHv4 05/14] mm: Rework compound_head() for power-of-2 sizeof(struct page) Message-ID: References: <20260121162253.2216580-1-kas@kernel.org> <20260121162253.2216580-6-kas@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 07F4C100007 X-Stat-Signature: p81qzho74m9min6ndifigc6168ug1px1 X-HE-Tag: 1769081392-910792 X-HE-Meta: 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 sYSgsN8B +8zNT 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: List-Subscribe: List-Unsubscribe: On Wed, Jan 21, 2026 at 12:12:13PM -0500, Zi Yan wrote: > > @@ -1244,8 +1244,8 @@ void snapshot_page(struct page_snapshot *ps, const struct page *page) > > again: > > memset(&ps->folio_snapshot, 0, sizeof(struct folio)); > > memcpy(&ps->page_snapshot, page, sizeof(*page)); > > - head = ps->page_snapshot.compound_info; > > - if ((head & 1) == 0) { > > + info = ps->page_snapshot.compound_info; > > + if ((info & 1) == 0) { > > This could be “if (!(info & 1))” like _compound_head(), right? Right. But I don't see why it has to change. -- Kiryl Shutsemau / Kirill A. Shutemov