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 23BFB42981C for ; Mon, 20 Jul 2026 14:21:53 +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=1784557315; cv=none; b=mx5X2L14tsPH1pFDnbslDVdcODjsZhpe2MGZIiQyPpCZJmoox1CoLthHLqIezxD1bcw8p6cDsMz7OlHLMm5HotWY1xkiIRUHZzbsIsG9M1GvQw33A6uyPNsQhYypcA2mf/5O1Zil1uQ/ZUEVbAoSy/T4nxQ1fZIb1DSTgkpdXdk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784557315; c=relaxed/simple; bh=+7NystvdXzMr6NM8Dw4/ScxJMsYOwnZE9UgxU837Cig=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=M6tu3A/58qXrbFwqzCheOTiqR25wjHnZrdDpYu+5Q2wybOaTaIpzcNk5Gcz9j2HXaxOgIKmWsQIISdCxewmGlGqns7uISnBjA8nMZajFkF4FkuQfjMBZmfGzDNNBX/Z83VAPL/IfdoVYioxSavvTWItnjdl3N1xpBtV8fdj4Ryg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eHFnKc1j; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="eHFnKc1j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 558391F000E9; Mon, 20 Jul 2026 14:21:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784557313; bh=lA6Os9I7nAVPHLTpQ6TwlEoRXYbLN7HPI/E0Lo1XHVk=; h=Subject:To:Cc:From:Date; b=eHFnKc1jk04hUeVKVRVbSElIuqj7OVjJ8m73cBlwVP4JxEHKivZIgGza/lx3oWkp5 iCM6zXKeEnWYjkAAhLc8huYfl2WNp2P7Dg9oH5eCJrKf7u+SkHUvPUC2kUEhIVDcbp xfZfopYFjESvGHIsBzEDoquTxufvIKLiyOLrhcec= Subject: FAILED: patch "[PATCH] mm/sparse-vmemmap: fix DAX vmemmap accounting with" failed to apply to 6.18-stable tree To: muchun.song@linux.dev,akpm@linux-foundation.org,aneesh.kumar@linux.ibm.com,david@kernel.org,joao.m.martins@oracle.com,liam@infradead.org,ljs@kernel.org,maddy@linux.ibm.com,mhocko@suse.com,mpe@ellerman.id.au,npiggin@gmail.com,osalvador@suse.de,rppt@kernel.org,songmuchun@bytedance.com,stable@vger.kernel.org,surenb@google.com,vbabka@kernel.org Cc: From: Date: Mon, 20 Jul 2026 16:21:34 +0200 Message-ID: <2026072034-plow-sliceable-b741@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.18-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y git checkout FETCH_HEAD git cherry-pick -x 721a73e30c9e3e8fcffe1725bcede1bbd20b4918 # git commit -s git send-email --to '' --in-reply-to '2026072034-plow-sliceable-b741@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From 721a73e30c9e3e8fcffe1725bcede1bbd20b4918 Mon Sep 17 00:00:00 2001 From: Muchun Song Date: Tue, 28 Apr 2026 16:18:53 +0800 Subject: [PATCH] mm/sparse-vmemmap: fix DAX vmemmap accounting with optimization 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_nr_vmemmap_pages(), which returns the exact vmemmap page count for a given pfn range based on whether optimization is in effect. Link: https://lore.kernel.org/20260428081855.1249045-5-songmuchun@bytedance.com Fixes: 15995a352474 ("mm: report per-page metadata information") Signed-off-by: Muchun Song Acked-by: Mike Rapoport (Microsoft) Acked-by: Oscar Salvador Acked-by: David Hildenbrand (Arm) Acked-by: Liam R. Howlett Cc: "Aneesh Kumar K.V" Cc: Joao Martins Cc: Lorenzo Stoakes Cc: Madhavan Srinivasan Cc: Michael Ellerman Cc: Michal Hocko Cc: Nicholas Piggin Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index eafb7c6eb71e..112ccf9c71ca 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -647,6 +647,31 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) } } +static int __meminit section_nr_vmemmap_pages(unsigned long pfn, unsigned long nr_pages, + struct vmem_altmap *altmap, struct dev_pagemap *pgmap) +{ + const unsigned int order = pgmap ? pgmap->vmemmap_shift : 0; + const unsigned long pages_per_compound = 1UL << order; + + VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SUBSECTION)); + VM_WARN_ON_ONCE(nr_pages > PAGES_PER_SECTION); + + if (!vmemmap_can_optimize(altmap, pgmap)) + return DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE); + + if (order < PFN_SECTION_SHIFT) { + VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, pages_per_compound)); + return VMEMMAP_RESERVE_NR * nr_pages / pages_per_compound; + } + + VM_WARN_ON_ONCE(!IS_ALIGNED(pfn | nr_pages, PAGES_PER_SECTION)); + + 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) @@ -654,7 +679,7 @@ 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_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap)); return page; } @@ -665,7 +690,7 @@ 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_nr_vmemmap_pages(pfn, nr_pages, altmap, pgmap)); vmemmap_free(start, end, altmap); } @@ -673,9 +698,10 @@ static void free_map_bootmem(struct page *memmap) { 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_nr_vmemmap_pages(pfn, PAGES_PER_SECTION, + NULL, NULL)); vmemmap_free(start, end, NULL); }