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a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790671478; b=d+xM5Yt6SNWTVvW8z8CNOBRZ2aaiVl0y3K0j91FvNir0Pr4FPLK2e2UuzwwyHEnm0vOTSI xYzUdF/uGu6fh+OvN22zCYzYL34C64tQH1m73uijuiIRS42bhC6mPgNqX/vh2ihtxZ9caa ilwcgzH3YHBk3CMbadsbMVe1mH6TLqI= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Fy7FxN0I; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 1EF9843C18; Tue, 29 Sep 2026 08:44:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D44961F00899; Tue, 29 Sep 2026 08:44:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790671477; bh=x4L/jE5ebP4VaIcoaqlRL5Ew3xtGuWL/copMvRUYC5A=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Fy7FxN0IlIRFzxaE9D0CVee2wD8aBYfBGhMpfSJ5mU35Z0HXsavQxNKOJ/ifFcHDB 7DPywdjuwW6jxeQxSR5zna3L6bplj4pTi5cOgmbWRH1DFbAy7Bta8TKii+fCWnJ/YT wd/VFXsLIIS0Lge88piuCgH9Vfj2px2o/oOOng34Htvac3JdTduprEAiqF9RthPeKe vnir0muq/qdyVBQ331EM0FEjj//JPAXixYRUTRPwd5drrOmrjXjgu1onPQ5bxjzvfP Q1lef2ekkipbtmQMDmSfMaZeuYVEQreTpQN4qaL/CjE9qJ/eCeJW0XbWijFyz94b8p 32SMVGda3PK1Q== Message-ID: <7b7f0ce6-6f67-4f98-9408-59e9d0716135@kernel.org> Date: Tue, 29 Sep 2026 10:44:31 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 09/12] powerpc/mm: switch device DAX to shared tail vmemmap pages To: Muchun Song , Andrew Morton , Oscar Salvador , Madhavan Srinivasan , Michael Ellerman , Jonathan Corbet Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, Muchun Song , Lorenzo Stoakes , Mike Rapoport , Qi Zheng , Nicholas Piggin , Christophe Leroy , Randy Dunlap , Lance Yang References: <20260927025441.741633-1-songmuchun@bytedance.com> <20260927025441.741633-10-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: E2072100006 X-Stat-Signature: qytiemm4m4mskwby7pze7dzp6ibrcf9j X-Rspam-User: X-HE-Tag: 1790671477-429327 X-HE-Meta: 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 Z+Uc4vlI mnajflyf1YKNocbzHNom99QmH/JH7tmk8g6agAj0IhEfSxg1qtEBaylm9GVSjkpvMqdmzG92Bj5TN93bSm8oam0DJYvXBws8cGbDYZpXaXuYqTYFSolHhomCC2YJg1Lu2Ayk7LZPQzHWLggCE3DTcIi7Ph7jDnstD0675QPK6n5bH3E0z1WAng+SWqhuZomWmal9ghKUORlD8FY9cPwraUCe/QBTKoYx9L9+mhPZclNG3zMDKfkGbme51gDZcKPK8RM1aGPYrMq3R7TOs0f1J8kloydcp9gmghzHsZN9KZ5/3XxFuP7pTzJ2Rsw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/27/26 04:54, Muchun Song wrote: > The powerpc radix compound vmemmap population path still finds a reusable > tail page by walking the vmemmap page tables. > > Switch it to the common vmemmap_shared_tail_page() helper instead, so it > can use the shared vmemmap page directly to simplify the code. > > This removes the powerpc-specific tail-page lookup and its fallback path > and aligns the device DAX vmemmap optimization path with HugeTLB. > > Signed-off-by: Muchun Song > --- I did not grasp all the complexity of the old approach, but what i read here all makes sense to me. Acked-by: David Hildenbrand (Arm) -- Cheers, David