From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 318D135B634 for ; Mon, 13 Apr 2026 18:41:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776105686; cv=none; b=bXChyzqDomeRBaiSZsdTchmtxTMJ0Xwuo+Nq+6Uh6jGHN/sAhtk6jIbhB/jATDaEACOfsM1OtwtCk5EOC1Q8AgpRV3/hlZQdwspW1f5O6v/UB+wkz3KOsinibORAYFs3Za67H8qfnii5cJFL+tOFOdWiPm6uetG3g+2r3o+j8KM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776105686; c=relaxed/simple; bh=Ag34EiRSRProjSszPBmIGU7K92Xfr0e+QDVz287fZs8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=c3t9pZlgupTUjnqDJWo56oXi8zq5/GlFEnswqnolCG3IvsNckkpnsJVw4rrm2Tvti42FrZ3doBD8K72N2FtL1uHLVIXi9qXVrJHGd4ru0+0nclsBCs+iezCVPwYoN6OmmJjy4YKuov6X3QbTpR3rSPXrIMRTprVaoFDRAZXxOug= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RYUiTIEB; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RYUiTIEB" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52627C2BCAF; Mon, 13 Apr 2026 18:41:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776105686; bh=Ag34EiRSRProjSszPBmIGU7K92Xfr0e+QDVz287fZs8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=RYUiTIEBiWUn3y/EkLaQ+B6or6WPDAJLf1CGVxYVwTegeS8M6EoDmczfXWKz0ZXOz 0+9etjUpPxVxm6h1D6hH6ELi0BENK6eMTe+EfabF0ADKvKCW9kJIwUAjXqMsEv/K1m o589wnQnYobBXyMAFP4ggd9Xoa1oeu6Bm2Di8fpJQCKBQcvyZ/gKGIwtidfpEQA17O 3zXGd2OlwjNvDVYdCbwlRlVWXcWTPStWTQnnpDld2QBNtqFDSk7x+JetUtJL/wwPVZ y3i5WrOphiKj9EZ/Ag3DqRTX/GyJaTBe+tkAp/xIQ//2KXChkz1ph2H3wZRDkubPFS 1HIUjTKc95cwQ== Message-ID: <2b51659e-5527-4e15-a0a8-41f30f589d07@kernel.org> Date: Mon, 13 Apr 2026 20:41:16 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 03/49] mm/sparse: fix vmemmap page accounting for HVOed DAX To: Muchun Song , Andrew Morton , Muchun Song , Oscar Salvador , Michael Ellerman , Madhavan Srinivasan Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Nicholas Piggin , Christophe Leroy , aneesh.kumar@linux.ibm.com, joao.m.martins@oracle.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20260405125240.2558577-1-songmuchun@bytedance.com> <20260405125240.2558577-4-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260405125240.2558577-4-songmuchun@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/5/26 14:51, Muchun Song wrote: > When HVO is enabled for DAX, the vmemmap page accounting is wrong since > it only accounts for non-HVO case. > > Fix the accounting by introducing section_vmemmap_pages() that returns > the exact number of vmemmap pages needed for the given pfn range. > > Fixes: 15995a352474 ("mm: report per-page metadata information") > Signed-off-by: Muchun Song > --- > mm/sparse-vmemmap.c | 30 ++++++++++++++++++++++++++---- > 1 file changed, 26 insertions(+), 4 deletions(-) > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > index 7aa9a97498eb..0ef96b1afbcc 100644 > --- a/mm/sparse-vmemmap.c > +++ b/mm/sparse-vmemmap.c > @@ -724,6 +724,27 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages) > return rc; > } > > +static int __meminit section_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, > + struct vmem_altmap *altmap, struct dev_pagemap *pgmap) > +{ > + unsigned int order = pgmap ? pgmap->vmemmap_shift : 0; > + unsigned long pages_per_compound = 1L << order; > + > + VM_BUG_ON(!IS_ALIGNED(pfn | nr_pages, min(pages_per_compound, PAGES_PER_SECTION))); > + VM_BUG_ON(pfn_to_section_nr(pfn) != pfn_to_section_nr(pfn + nr_pages - 1)); > + > + if (!vmemmap_can_optimize(altmap, pgmap)) > + return DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE); > + > + if (order < PFN_SECTION_SHIFT) > + return VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound; > + > + if (IS_ALIGNED(pfn, pages_per_compound)) > + return VMEMMAP_RESERVE_NR; This makes me wonder whether that is really the right place to update the counter. Can't we update the counter where we actually allocate/free the pages, so we don't have to re-calculate that? -- Cheers, David