From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9253D3F54A0 for ; Thu, 3 Sep 2026 06:36:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788417381; cv=none; b=SOYj9pSjV4nXWeL4W/Zwdf886JivMt8g1x+jrpT5rhKh7CXn4/4V94Ta5mB+WNm7Dq8bND71E3SGxr3E51Z2XY6zwgkkgJJVC0jl1tLHzHsfrHIwO4N1TtZAPOBGGdY+9keOWpSzUku35d7pK6b1j1xjRkUhACnTsK8nsK3gC3k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788417381; c=relaxed/simple; bh=/7zVF87+vSIaxGdnTGi6zl+USr7Ew+xcjHfJdu2PHXQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Iei1YW+F38glIGk/7o5+h/pL4JnmkVI66SgXkI2z35oAY2L8lVglDAWVHlZDddfaje80auFlRfcnnqncSK0f/DjVyNOB/HA+rZX/DOLkiHcwTR5msQn37VuMOcaVbnWMK3N7Byb8p5MLUx8MKHKpM7Xu3z6zwvrZBoOoSV7Ju4Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=BDPYwWUG; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="BDPYwWUG" X-Envelope-To: linux-doc@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=/7zVF87+vSIaxGdnTGi6zl+USr7Ew+xcjHfJdu2PHXQ=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788417371; v=1; x=1789022171; b=BDPYwWUG2Z6bRep3T0VLBuuKDahOxIhearwYCB9Uw1og7GYuVlylNKYFuk9DYYcpN79wzQxv Jzj5HFC8/TpHPwL4N387Usg237Go+wsjMcy9922gksnD2685r3sFTvRolNcm0p8lyA42w1yhfCR 2I4StrsLfzGRP/Q1GsSuYBDA= X-Envelope-To: linux-doc@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 8473698cd31aeb55; Thu, 03 Sep 2026 06:36:11 +0000 X-Mizu-Trace-ID: 8473698cd31aeb55 X-Migadu-Flow: FLOW_OUT Message-ID: <3775da0f-4068-4fc4-97a7-135eb975ec65@linux.dev> Date: Thu, 3 Sep 2026 14:36:01 +0800 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 04/11] mm/sparse-vmemmap: prepare DAX vmemmap population for section orders To: Muchun Song , Andrew Morton , David Hildenbrand , 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 , Nicholas Piggin , Christophe Leroy , Randy Dunlap References: <20260831075342.57563-1-songmuchun@bytedance.com> <20260831075342.57563-5-songmuchun@bytedance.com> From: Qi Zheng In-Reply-To: <20260831075342.57563-5-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/31/26 3:53 PM, Muchun Song wrote: > Device DAX still uses vmemmap_populate_compound_pages() to populate its > compound-page vmemmap mappings. That helper allocates the head and first > tail vmemmap pages explicitly, then reuses the first tail page for the > remaining tail page mappings. > > Device DAX is being moved to the section-based vmemmap optimization > infrastructure, but it cannot switch to the generic section-based > population path yet. Once a later patch records the DAX compound-page > geometry in the section order, DAX head and first-tail PFNs can look > optimizable to the generic helpers as well. > > Add a DAX-specific population flag for this transition. It keeps DAX > head/first-tail allocations on the normal vmemmap allocation path, while > preserving the existing page reference for reused DAX tail mappings. > > Signed-off-by: Muchun Song > --- > mm/sparse-vmemmap.c | 27 +++++++++++++++------------ > 1 file changed, 15 insertions(+), 12 deletions(-) > Acked-by: Qi Zheng Thanks, Qi