From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f169.google.com (mail-pl1-f169.google.com [209.85.214.169]) (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 C64A336604A for ; Wed, 15 Apr 2026 11:14:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776251681; cv=none; b=NeXA8Wu4nLQacLmdtd4p1VNr5DvlIx2sbJten/ISjqb0/2XNygg3GUfZJVVhm/45e0TViWKH98m7xzHMC6fYPLrKlmJ3vWepBneLN+U0Iu5LVx0XpGX699XHm93IBSs1DF6YQvkd5RtGaW10aseqMzGRRZ4O83mQrAmp/67mVME= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776251681; c=relaxed/simple; bh=4EoFcxXiqyz1WVaO4esUREYa5gKezgAPn/lvIA/IdgU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=hKIm3ESsLKyV+HOGkxRJk4hcMAhx6lk9MOPIdW7+sLu7kxnj3ndkd+9yrlrskAvqgDJhgxljluMMU20UT/TOqjJPIZN5qjMIgrTL1QGoMCTQTxsiX6BiTYyseyJ16JUMTWbzkQyiTP0I7qflmhaigIbW2MFVfyfdPHJtk0tyBEA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=bGscesIW; arc=none smtp.client-ip=209.85.214.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="bGscesIW" Received: by mail-pl1-f169.google.com with SMTP id d9443c01a7336-2b4583f0a1aso21441015ad.3 for ; Wed, 15 Apr 2026 04:14:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance.com; s=google; t=1776251679; x=1776856479; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=vC2b62MaZVNGL0bmie++eHoqVNtyAoC7qXucopPxUdw=; b=bGscesIWWodblw+E81BqGt+r/I12Eo7OloSdJsyF8gzS9iC5LrZ0cNHRv2JZ6njHQ3 PNC56+X4Y7/QrXp2yLibl8YnP06zRxKPfh8CzS/JCUXxsVxKog+F0kPWsSWQ72uAQwnQ Ohlsf/VyrpopyZPOqItevVdDAbUIL66tmjFujxEqKrUOKWJ43O7BfYAjJ38bbs/xmOkm pT3CalwFBhA1RiGRAUiXdyUUHfQ2Wmgn9S/M9GJhwMMZAL9ABHWiCPlHzKzhQBhTRNpo YUrmQ4ABw7kfTEQP8Y9KKe732+ZWKJtHeMnMwNSvVxXGPw7URgu+zOJhui1/MaXnW+Hy hfrw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1776251679; x=1776856479; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=vC2b62MaZVNGL0bmie++eHoqVNtyAoC7qXucopPxUdw=; b=qacPKs6s3ttRKaBgz4fQvMZD4Ffnm8jiE6ump052tcW3jzjgXDDb+D4z74aUQ5Epes HoY/49vv3PWp+bsZ5gRI64ecu1gqMeH/Amsx50a5VVbDSWUygKXmf/JUFaU5NzTvxhQC eUgGVxvSWF8r2XWhRUA1Ahj4XGKnnsc+k3n2UNO75x6LwrbeMid/bah5t3wm5akW3i6V SqidClkzEgUrFN+Kw98h9sMDcCuUtB5mFKPJND8gt0+ip8T3k6jI1jaf1Bt4vAbIGotI 4g7KU7AJrVumQUQOGCiC4FnaXFxbQuyw78afovCcaeWltiDVRtd4ivySv9byRMpAhEX1 MRcA== X-Forwarded-Encrypted: i=1; AFNElJ/L7RHUpH83NPUF4Yp7JwTUbttlYYTC4J76dw+6fDvgXgwfZnXa9eC7FlWIW23UVMJTPfd6I/xq4vfd4Vo=@vger.kernel.org X-Gm-Message-State: AOJu0Yx/p/d3Hz+nfGFPI7cuLwIF6a4tlKfwC9E+9HutO25r5P0HkkHo Hj/HKScCIKDW8uHR4TFb4NRvNZ5GVvDttN71EkjDNMclAJAylEGAwEabeA0JlQDSBJE= X-Gm-Gg: AeBDies8EqMdm/gG2B+J4Y2jK/WHUi7bjsAwaqjhc0LF7wwzFTpu3BpZoHQuBQOGeBj uxsdE6TYq+HY/5azQ87rXMiZ+cgIT17lgaArwDi6Ip+dZR15fdaEpEx6Z4xSa6vH4tjqKa1TEGC Og/HzcQfET0mc+PS6r/N0g/M6SIm7Gx7hGaXhfamM0a7tHOCTmFDOyzllpL+Z611qoNl28QNWXm Mbdqa1v339cd400peU8/rsb7o5xHDAf0E8SAgdNpvS76McEcKEM5Gqw1Zp/8BDxN8Vhr9G1qgTW UNlB7bZTk7ZKAlALvs5YWgPGdBeWgiPllunEyd5zoSxTzftApS7AR1HTqxckKHENypBHyFqPUup /HLbAGLjVdPP2vmM48Lnm+9g450KE8XTheB6oaQfmkjVpGps1JWUPHTwmJNcAznMRod2dX3nxUb W1UydHZs1Uv5CGdXF13Chk+EIQqDdlw6GZfnwxR+W2cRs= X-Received: by 2002:a17:903:249:b0:2ae:6192:8d78 with SMTP id d9443c01a7336-2b2d59411dbmr209611585ad.1.1776251679043; Wed, 15 Apr 2026 04:14:39 -0700 (PDT) Received: from n232-176-004.byted.org ([36.110.163.96]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b477fd3724sm19509485ad.0.2026.04.15.04.14.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2026 04:14:38 -0700 (PDT) From: Muchun Song To: Andrew Morton , David Hildenbrand , 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, Muchun Song Subject: [PATCH v2 3/6] mm/sparse-vmemmap: Fix DAX vmemmap accounting with optimization Date: Wed, 15 Apr 2026 19:14:09 +0800 Message-Id: <20260415111412.1003526-4-songmuchun@bytedance.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20260415111412.1003526-1-songmuchun@bytedance.com> References: <20260415111412.1003526-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When vmemmap optimization is enabled for DAX, the nr_memmap_pages counter in /proc/vmstat is incorrect. The current code always accounts for the full, non-optimized vmemmap size, but vmemmap optimization reduces the actual number of vmemmap pages by reusing tail pages. This causes the system to overcount vmemmap usage, leading to inaccurate page statistics in /proc/vmstat. Fix this by introducing section_vmemmap_pages(), which returns the exact vmemmap page count for a given pfn range based on whether optimization is in effect. Fixes: 15995a352474 ("mm: report per-page metadata information") Signed-off-by: Muchun Song --- mm/sparse-vmemmap.c | 32 ++++++++++++++++++++++++++++---- 1 file changed, 28 insertions(+), 4 deletions(-) diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index 40290fbc1db4..05e3e2b94e32 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -652,6 +652,29 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) } } +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_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, min(pages_per_compound, + PAGES_PER_SECTION))); + VM_WARN_ON_ONCE(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; + + return 0; +} + static struct page * __meminit populate_section_memmap(unsigned long pfn, unsigned long nr_pages, int nid, struct vmem_altmap *altmap, struct dev_pagemap *pgmap) @@ -659,7 +682,7 @@ static struct page * __meminit populate_section_memmap(unsigned long pfn, struct page *page = __populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap); - memmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)); + memmap_pages_add(section_vmemmap_pages(pfn, nr_pages, altmap, pgmap)); return page; } @@ -670,7 +693,7 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages, unsigned long start = (unsigned long) pfn_to_page(pfn); unsigned long end = start + nr_pages * sizeof(struct page); - memmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE))); + memmap_pages_add(-section_vmemmap_pages(pfn, nr_pages, altmap, pgmap)); vmemmap_free(start, end, altmap); } @@ -679,9 +702,10 @@ static void free_map_bootmem(struct page *memmap, struct vmem_altmap *altmap, { unsigned long start = (unsigned long)memmap; unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION); + unsigned long pfn = page_to_pfn(memmap); - memmap_boot_pages_add(-1L * (DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page), - PAGE_SIZE))); + memmap_boot_pages_add(-section_vmemmap_pages(pfn, PAGES_PER_SECTION, + altmap, pgmap)); vmemmap_free(start, end, NULL); } -- 2.20.1