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 9D412364926 for ; Sun, 26 Jul 2026 12:00:51 +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=1785067252; cv=none; b=cYkwDB1cc2Zr9AYLwsk2c/5ImlSLQe0Ajq6ekPy725DEMC4SY1k79bAh1AtRP4jzxTBI0SSl+BUNoAQHtknGM60LpKTzRFXwenEW71M7vLry95Ssq+7SXKB7XKRVifqm8Wvot8gMlJbKXP/Pt/lVYT8iqI4CQLjGvvlLkcaacxY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785067252; c=relaxed/simple; bh=hZBGvm4CkfChWc9I2LXhaMapZEEU+vjWRpP/FoPeLLk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W4RpZSlrY6YQpAlZx7LJ2gNz57aiWR+fo+9TYvXVlz6BRsyT3laJZQBEJXLd35xAc6Sh83crB70vCA1AEFd8BM0jxqLbIjWgTvLexp4IuuVaQfoE5bxSJfcycQC36STBulIxiYz8xOOG9n3JLO01QLZR8E6vx+QkjJmKyDNmNCM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=aPF9uZhq; 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="aPF9uZhq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B22D31F000E9; Sun, 26 Jul 2026 12:00:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785067251; bh=DoxR8ELuXeNOxlH+kCD102bGDCegASpCTBfCOd1NHo0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aPF9uZhq+nVTcYThjzznxxGLD5O6t8B0vEmJJZ8aRCjxPVA7GS2tde23nBm0ZkP9G Bay3QyuVlQ+Ya5+OUb6fwVznwnCeR7IgC1mJmKMsANOVZYuU+nAvnrJSf6//Cf7oMD Jl3dh1lCRJbesyYG1rB3VQjf/TWJyHggLTbvtBXch3J765uB05m0noLv1kjeHcL9lU lZqwadeW71MXH2oUEPfSIZb0JHlxn2QiHULY7zf/2q8D2XYA1bQ3qCxZQ7z+epxs/M Ld8OHBDnXtUYbW1vZWqTDt2Zzt3JtYeGrout/A52/tAR/r0OgDIZrWWQL+BRsKHUiu BjVE9Pdz91FKQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Muchun Song , "Mike Rapoport (Microsoft)" , Oscar Salvador , "David Hildenbrand (Arm)" , "Liam R. Howlett" , "Aneesh Kumar K.V" , Joao Martins , Lorenzo Stoakes , Madhavan Srinivasan , Michael Ellerman , Michal Hocko , Nicholas Piggin , Suren Baghdasaryan , Vlastimil Babka , Andrew Morton , Sasha Levin Subject: [PATCH 6.12.y 2/2] mm/sparse-vmemmap: fix DAX vmemmap accounting with optimization Date: Sun, 26 Jul 2026 08:00:46 -0400 Message-ID: <20260726120046.4138231-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260726120046.4138231-1-sashal@kernel.org> References: <2026072034-upstream-sanctuary-dd7e@gregkh> <20260726120046.4138231-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Muchun Song [ Upstream commit 721a73e30c9e3e8fcffe1725bcede1bbd20b4918 ] 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 Signed-off-by: Sasha Levin --- mm/sparse-vmemmap.c | 34 ++++++++++++++++++++++++++++++---- 1 file changed, 30 insertions(+), 4 deletions(-) diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c index c9da0ea63f234a..8fe7ea9a1e18dc 100644 --- a/mm/sparse-vmemmap.c +++ b/mm/sparse-vmemmap.c @@ -539,6 +539,31 @@ 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) @@ -546,7 +571,7 @@ 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; } @@ -557,7 +582,7 @@ 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); } @@ -565,9 +590,10 @@ 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); } -- 2.53.0