From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D2FE3D810F for ; Fri, 2 Oct 2026 18:12:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790964770; cv=none; b=BciYTgA1rB6TfnkD0SyQCYpVj4Fp02jUFiTZvJzImBVGZVOv3MnB3djCoOYc8ef8O1Hy+vmPXsxsKuw2MZkjv1LnHd9Ne4vJ2UpPCe1JY2zgvYt+Zgt/HtDvbKaSUBtWuQ7EFzphIi/jCgwv84nm1kBIpvJs8UjgzjcpgJTr6JY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790964770; c=relaxed/simple; bh=k3+m/tfgIoEhYfQ9b1znZ7J4AsQ71/eGy/gtuGn78/I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=QObiGb+gMAz5PJz0LVlazwXmNxjDxS6Rx6r8E5dLzFcZlyOjV9DwizgnPbDema6g8xJQY6mla0zw/y7DGWxecrdOS/uJMaiwldVld4sUpZq08I1nN97dVxKtghOPZ5qj7G5DnBRwclyQyFVX/Q7C9eB9RYJM1jalBW/eCw9n76g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=V0REfLB+; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="V0REfLB+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C070F1F000FF; Fri, 2 Oct 2026 18:12:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790964768; bh=g8XGruUG1q9NlQK3HfsezWI4sNwg1U3GmGD0QRbensM=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=V0REfLB+j9fthMzAGcutHRNmRjr4fXKGl1aG9r8XK0w+Vy31R2L9pIYOOWtSZBw3U 7qyfwbDD83FmvTuz/gfIb24vWYjIoi/zze2L5JgCYcUWmqce1xusyI7j5+nqBM+MjO 27DBo08CWDgdEvumIyd2DotOo5ve2+0IFdtN0jqI5CGjcyLBNLz/3AZRwe7WVDsF2+ OldX0GA0jKKM+8yhQ8cXETn3mQMG47JK/JjJ2Y+VWgt70E9FZp7zqmkM8202/EeQot H5P/0nnTUDfDsBZfsNIws2Csfz0zHJOh9GPJm2AmOCw1tlEl4vfgYkJLZPYoZl6IZE j20D1JesWAFYQ== Date: Fri, 2 Oct 2026 20:12:40 +0200 From: Mike Rapoport To: Muchun Song 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 Subject: Re: [PATCH v3 6/6] mm/mm_init: add zone mismatch warning during page init Message-ID: References: <20260929053231.66085-1-songmuchun@bytedance.com> <20260929053231.66085-7-songmuchun@bytedance.com> <78D5D6AA-BE36-432C-B0F7-453F93DF18C0@linux.dev> <85941AA4-7E50-4AAE-BC05-0F443B21BE8B@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <85941AA4-7E50-4AAE-BC05-0F443B21BE8B@linux.dev> On Fri, Oct 02, 2026 at 05:56:40PM +0800, Muchun Song wrote: > > On Oct 2, 2026, at 16:22, Mike Rapoport wrote: > > >>>> 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(pfn)) && > >>>> + page_zone_id(page + VMEMMAP_OPTIMIZATION_NR_STRUCT_PAGES) != > >>>> + page_zone_id(page)); > >>> > >>> 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? > >> > >> 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 — right here, after vmemmap > >> population. > > > > 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—normally 64—is 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? While it feels really out of place in __init_single_page(), but having it memmap_init_range() close to the if that skips shared tail pages makes sense. What do you say? > [1] https://lore.kernel.org/20260513132044.41690-18-songmuchun@bytedance.com/ > > Thanks, > Muchun -- Sincerely yours, Mike.