From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-115.mta0.migadu.com [91.218.175.115]) (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 1BF673B71CF for ; Sat, 5 Sep 2026 08:20:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.115 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788596452; cv=none; b=ZX1ZcfmePxzMc93vZBovZtHCsEX78MB/oHr/g70p8N/PlU8qrcCyLIRn7kaJLV23ZF1oMUq6LO7f+rpu9JADfZ+DBcPQaciaaqtTGMJoihlFJdsRGSE5VhHgIT4Vw6J+hODN0kVoGBkhdPADR42P/sVo261qeJMKS7zjaHQn9xA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788596452; c=relaxed/simple; bh=cWv2OsYaUjRAleYfGIeSk6xvjxd4wSnUJO1edGPXAD0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=guzKTNuyNsqlb+aGSOqCmRpuX5nXwFDrXm48IpRVBGMg0WAhdKW0NAHvV4UpCVFKttnlaJ3413HpxhEUigXinFLarTceaQ1m3YB9YtK4C6Cm2Zp4+Yxj0Ul/uzZD5xe1JhChZv07j2rKmXZVRgJy0U94Wf/VAneSfnJ1aq1nFq4= 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=IicFwOJs; arc=none smtp.client-ip=91.218.175.115 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="IicFwOJs" X-Envelope-To: linux-doc@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=cWv2OsYaUjRAleYfGIeSk6xvjxd4wSnUJO1edGPXAD0=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1788596436; v=1; x=1789201236; b=IicFwOJs2CPlLipHw597EH7HUKwox4Ly1bXjZpWkeBf20n4MKLPELD2P97Zjm95kLCmKluvD 1ZqczU3Ai3D+CEGD3NGVKwsE5idxGTNEzXLfZFFxgGoKVas590lbIivGqKDe2bMx88ZNhU6NUGr 90fHICjD9DlHQXAGAONWs1mI= X-Envelope-To: linux-doc@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 1b4d3cf39591adcd; Sat, 05 Sep 2026 08:20:25 +0000 X-Mizu-Trace-ID: 1b4d3cf39591adcd X-Migadu-Flow: FLOW_OUT Message-ID: <1143901c-5036-4b79-8135-21ce57075136@linux.dev> Date: Sat, 5 Sep 2026 16:20:16 +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 05/11] mm/sparse-vmemmap: set section order for device DAX 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> <20260831075342.57563-6-songmuchun@bytedance.com> From: Qi Zheng In-Reply-To: <20260831075342.57563-6-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Muchun, On 8/31/26 3:53 PM, Muchun Song wrote: > Device DAX can use vmemmap optimization only when a full section is > populated with a compound-page geometry. Record that geometry in the > section order before populating the section, so later vmemmap accounting > and population decisions can use the section state directly. > > Clear the section order when the section becomes empty again. Also reject > partial additions to a section that already has optimized vmemmap mappings, > because a section cannot safely mix optimized and ordinary vmemmap layouts. Perhaps we should explain why they cannot be safely mixed. > > Partial additions continue to use ordinary vmemmap population, so they do > not save vmemmap memory. Such additions are uncommon, and the lost saving > is negligible. > > Signed-off-by: Muchun Song > --- > mm/mm_init.c | 13 ++++--------- > mm/sparse-vmemmap.c | 16 ++++++++++++---- > 2 files changed, 16 insertions(+), 13 deletions(-) > Also, the issue sashiko reported looks like it was pre-existing, not introduced by this patch. So: Acked-by: Qi Zheng Thanks, Qi