From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-101.mta1.migadu.com [95.215.58.101]) (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 1E82747FB0C for ; Fri, 2 Oct 2026 09:57:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935025; cv=none; b=hDgiIryU/dDqQq9CHjhWQ8rJt4IKLTHoiFdAZKd7mTIXvSqEOpuTKvpmDROAZaFADdHZnDP1zbT1GJ9pgP1b19TqBFKgBHT3kUatSZlzdBpMPkd0uYHKgPJ0O8/ixa36l1g4ptLK62/oHUsi/EI2Szwzni2DKDy3lK2+5EWQ4os= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790935025; c=relaxed/simple; bh=roAk5SWvCfO6tRD7usWMkoWmhkjxdhsqx8L4kRhcClI=; h=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc: Message-Id:References:To; b=ZA++nYGVACqBfsYN/yU+hgS37UKolxQTTmurHarsHcs7LAhTRhbd+5g/bktINDIewtsG53/f9YrF930qRSejNiNNybXCeV9yO15mZ1DfFs7xVi9Dh3GQASRL3NONIYm+3GHtKEeoKJSfvelA56tMy+JHkwPA9e2FoSCstVd3Pp8= 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=nlTAQEKg; arc=none smtp.client-ip=95.215.58.101 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="nlTAQEKg" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=roAk5SWvCfO6tRD7usWMkoWmhkjxdhsqx8L4kRhcClI=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790935021; v=1; x=1791539821; b=nlTAQEKgfBTJ7beIvEZL1nlOX9yQBup7rkvDhDPQDEea763f1MOHHC2Yd87TRkN9nS7D09aY U6E7ts/3WBktQzF1GXnyYfUF+B+t/l6cN+GnL9NiG50MyBEScAtEwxt+SYUY2yToAtyxl0ItJj+ blBTN1dUBGX7UdkAHu9KHf28= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 12c54f5d308feb20; Fri, 02 Oct 2026 09:57:00 +0000 X-Mizu-Trace-ID: 12c54f5d308feb20 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=utf-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH v3 6/6] mm/mm_init: add zone mismatch warning during page init From: Muchun Song In-Reply-To: Date: Fri, 2 Oct 2026 17:56:40 +0800 Cc: Muchun Song , Madhavan Srinivasan , Andrew Morton , David Hildenbrand , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Ritesh Harjani , Shrikanth Hegde , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Qi Zheng , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Message-Id: <85941AA4-7E50-4AAE-BC05-0F443B21BE8B@linux.dev> References: <20260929053231.66085-1-songmuchun@bytedance.com> <20260929053231.66085-7-songmuchun@bytedance.com> <78D5D6AA-BE36-432C-B0F7-453F93DF18C0@linux.dev> To: Mike Rapoport X-Mailer: Apple Mail (2.3901.100.1.1.12) > On Oct 2, 2026, at 16:22, Mike Rapoport wrote: >=20 > On Fri, Oct 02, 2026 at 09:48:42AM +0800, Muchun Song wrote: >>=20 >>=20 >>> On Oct 1, 2026, at 22:42, Mike Rapoport wrote: >>>=20 >>> Hi Muchun, >>=20 >> Hi, >>=20 >>>=20 >>> On Tue, Sep 29, 2026 at 01:32:31PM +0800, Muchun Song wrote: >>>> For vmemmap-optimized sections, tail struct pages may be backed by >>>> shared vmemmap pages. Those shared pages must carry the same page = zone >>>> ID as the struct pages initialized for the section. >>>>=20 >>>> Warn in __init_single_page() if the shared tail page has a = different >>>> page_zone_id(), which would indicate inconsistent initialization. >>>>=20 >>>> Signed-off-by: Muchun Song >>>> Acked-by: Qi Zheng >>>> --- >>>> v3: >>>> - Collect Acked-by from Qi Zheng >>>>=20 >>>> v2: >>>> - New patch. >>>> --- >>>> mm/mm_init.c | 3 +++ >>>> 1 file changed, 3 insertions(+) >>>>=20 >>>> diff --git a/mm/mm_init.c b/mm/mm_init.c >>>> index 1650d6bc1211..bd02e8d06965 100644 >>>> --- a/mm/mm_init.c >>>> +++ b/mm/mm_init.c >>>> @@ -609,6 +609,9 @@ void __meminit __init_single_page(struct page = *page, unsigned long pfn, >>>> if (!is_highmem_idx(zone)) >>>> set_page_address(page, __va(pfn << PAGE_SHIFT)); >>>> #endif >>>> + = VM_WARN_ON_ONCE(vmemmap_optimizable_order(pfn_to_section_compound_order(pf= n)) && >>>> + page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) !=3D >>>> + page_zone_id(page)); >>>=20 >>> Hmm, page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES is initialized a = tad later >>> than page so it'll have stale data in the page->flags, won't it? >>=20 >> Lance is right. The shared tail struct pages are already initialized = by >> vmemmap_shared_tail_page() during vmemmap population, so they're not = stale. >> The head 64 struct pages are initialized later =E2=80=94 right here, = after vmemmap >> population. >=20 > Still it looks out of place here, can this check be done in = sparse-vmemmap > somehow? The struct page entries of a vmemmap-optimizable compound page are currently initialized in two stages. During vmemmap population, the shared tail entries are initialized first. The retained head area=E2=80=94normally 64=E2=80=94is initialized later = through __init_single_page(). This warning connects the two stages: while initializing the retained entries in the second stage, it verifies that their zone information is consistent with the shared entries initialized in the first stage. Therefore, the same check cannot be performed during vmemmap population. I am planning to first unify the HugeTLB and Device DAX compound-page initialization through a common helper [1]. Once that work is complete, maybe it will be easy to move the initialization of the retained head area into vmemmap population. With both the retained and shared entries initialized in the same stage, there will be no cross-stage inconsistency to check, and this warning can be removed. Would keeping the check here for now and removing it as part of that follow-up sound reasonable to you? [1] = https://lore.kernel.org/20260513132044.41690-18-songmuchun@bytedance.com/ Thanks, Muchun >=20 >> Thanks, >> Muchun >>=20 >>>=20 >>>> } >>>>=20 >>>> #ifdef CONFIG_NUMA >>>> --=20 >>>> 2.54.0 >>>>=20 >>>=20 >>> --=20 >>> Sincerely yours, >>> Mike. >>=20 >>=20 >=20 > --=20 > Sincerely yours, > Mike.