[{"id":3677604,"web_url":"http://patchwork.ozlabs.org/comment/3677604/","msgid":"","date":"2026-04-15T11:26:48","subject":"Re: [PATCH v2 1/6] mm/sparse-vmemmap: Fix vmemmap accounting\n underflow","submitter":{"id":84878,"url":"http://patchwork.ozlabs.org/api/people/84878/","name":"Muchun Song","email":"muchun.song@linux.dev"},"content":"> On Apr 15, 2026, at 19:14, Muchun Song wrote:\n> \n> In section_activate(), if populate_section_memmap() fails, the error\n> handling path calls section_deactivate() to roll back the state. This\n> causes a vmemmap accounting imbalance.\n> \n> Since commit c3576889d87b (\"mm: fix accounting of memmap pages\"),\n> memmap pages are accounted for only after populate_section_memmap()\n> succeeds. However, the failure path unconditionally calls\n> section_deactivate(), which decreases the vmemmap count. Consequently,\n> a failure in populate_section_memmap() leads to an accounting underflow,\n> incorrectly reducing the system's tracked vmemmap usage.\n> \n> Fix this more thoroughly by moving all accounting calls into the lower\n> level functions that actually perform the vmemmap allocation and freeing:\n> \n> - populate_section_memmap() accounts for newly allocated vmemmap pages\n> - depopulate_section_memmap() unaccounts when vmemmap is freed\n> - free_map_bootmem() handles early bootmem section accounting\n\nSorry, this line was forgotten to be deleted. The subsequent modification\nof free_map_bootmem() is a separate cleanup.","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=xJrY84Ru;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; helo=lists.ozlabs.org;\n envelope-from=linuxppc-dev+bounces-19771-incoming=patchwork.ozlabs.org@lists.ozlabs.org;\n receiver=patchwork.ozlabs.org)","lists.ozlabs.org;\n arc=none smtp.remote-ip=95.215.58.182","lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev","lists.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=xJrY84Ru;\n\tdkim-atps=neutral","lists.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=linux.dev\n (client-ip=95.215.58.182; helo=out-182.mta1.migadu.com;\n envelope-from=muchun.song@linux.dev; receiver=lists.ozlabs.org)"],"Received":["from lists.ozlabs.org (lists.ozlabs.org\n [IPv6:2404:9400:21b9:f100::1])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519)\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4fwf5T6ySrz1yHM\n\tfor ; Wed, 15 Apr 2026 21:27:57 +1000 (AEST)","from boromir.ozlabs.org (localhost [127.0.0.1])\n\tby lists.ozlabs.org (Postfix) with ESMTP id 4fwf5T1r9rz2yvh;\n\tWed, 15 Apr 2026 21:27:57 +1000 (AEST)","from out-182.mta1.migadu.com (out-182.mta1.migadu.com\n [95.215.58.182])\n\t(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n\t key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest\n SHA256)\n\t(No client certificate requested)\n\tby lists.ozlabs.org (Postfix) with ESMTPS id 4fwf5S2sj1z2yrM\n\tfor ; Wed, 15 Apr 2026 21:27:54 +1000 (AEST)"],"ARC-Seal":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1776252477;\n\tcv=none;\n b=aLF7SU6CIfkifXz6g4vkQFG1M8m8P9O84ReprQBVWOttFWJftRPXenGbcfA4VW5ujkxBfKuuLv15yBimef5WtrAncULiREZPBnlewGJ4AvjxQNj159mrAM96qKs4SzYWYUaGfZm92ooYpDtNRabUAB86psZmgeRQYswhQNcIgo10Ii86mXF4hq/HBdSO5BH4s1cxMn5K62a0VZImFM0zJbnjegMt0f5ElMgGyobh/hxhKB2M/k0h2gqun6QYGlNLgi5SQZ7wu7XtvWq/1npYvWZf5c84AoGQTuFYeJ8vhqv18rc+4lwEFsr4tOS7aBZRy5TqTtZDhfWiWW675Ia2JA==","ARC-Message-Signature":"i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707;\n\tt=1776252477; c=relaxed/relaxed;\n\tbh=W/nLB/pOMgjoGvlQGXIaocK5El7h3zMc3A4XsLzA8T8=;\n\th=Content-Type:Mime-Version:Subject:From:In-Reply-To:Date:Cc:\n\t Message-Id:References:To;\n b=am+rg2At08oeTOB5fjiwxJ4DDHJjcJRygGs7ARKQGQIZPU6KVGShTQRYG0YzPVoWHKJAXC2ZHlKitJcaygKGXL9zhK0sF49QHRwPFQvXRJehQ/rDmPilK1Co6VEN7E3VkKG+D9fAobCLmv1A5mwmQllHPoqRork2aB0eemg52mUphTFpxr2he7N5xgfd+s5L3gRAPs3A1B49CXOqaSGsx3wTX/L/+2mvzUiQyaYgRo7oJyhhVQAk8izeK4ggB5PF+mpNwxWLUfRFC4fOt4BG/Cufg2Rk7SoEuv7K4NAewTD7LBIR9EZgs5ADqSv4O3nkXju9xp6lzbT+kXBl6FFddw==","ARC-Authentication-Results":"i=1; lists.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=linux.dev; dkim=pass (1024-bit key;\n unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256\n header.s=key1 header.b=xJrY84Ru; dkim-atps=neutral;\n spf=pass (client-ip=95.215.58.182; helo=out-182.mta1.migadu.com;\n envelope-from=muchun.song@linux.dev;\n receiver=lists.ozlabs.org) smtp.mailfrom=linux.dev","Content-Type":"text/plain;\n\tcharset=us-ascii","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1;\n\tt=1776252455;\n\th=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n\t to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n\t content-transfer-encoding:content-transfer-encoding:\n\t in-reply-to:in-reply-to:references:references;\n\tbh=W/nLB/pOMgjoGvlQGXIaocK5El7h3zMc3A4XsLzA8T8=;\n\tb=xJrY84RuBgIzMfpV05/ao1QOksPa1LC3ottI+Y1uuNWVW70HEumJHngYbP3o5OEt/C56hI\n\tuMW9yrXZxypuR+c2t0uc5yyOqnLbnd/Nf8ksTgexH2Db8sypIHKqUu+glCUB9ga/1C3cLn\n\tESgtvYFhLGm6TvsP2fq9gT/wvtp4TWI=","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","Mime-Version":"1.0 (Mac OS X Mail 16.0 \\(3864.500.181\\))","Subject":"Re: [PATCH v2 1/6] mm/sparse-vmemmap: Fix vmemmap accounting\n underflow","X-Report-Abuse":"Please report any abuse attempt to abuse@migadu.com and\n include these headers.","From":"Muchun Song ","In-Reply-To":"<20260415111412.1003526-2-songmuchun@bytedance.com>","Date":"Wed, 15 Apr 2026 19:26:48 +0800","Cc":"Andrew Morton ,\n David Hildenbrand ,\n Oscar Salvador ,\n Michael Ellerman ,\n Madhavan Srinivasan ,\n Lorenzo Stoakes ,\n \"Liam R . Howlett\" ,\n Vlastimil Babka ,\n Mike Rapoport ,\n Suren Baghdasaryan ,\n Michal Hocko ,\n Nicholas Piggin ,\n Christophe Leroy ,\n aneesh.kumar@linux.ibm.com,\n joao.m.martins@oracle.com,\n linux-mm@kvack.org,\n linuxppc-dev@lists.ozlabs.org,\n linux-kernel@vger.kernel.org","Content-Transfer-Encoding":"7bit","Message-Id":"","References":"<20260415111412.1003526-1-songmuchun@bytedance.com>\n <20260415111412.1003526-2-songmuchun@bytedance.com>","To":"Muchun Song ","X-Migadu-Flow":"FLOW_OUT","X-Spam-Status":"No, score=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID,\n\tDKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}},{"id":3677744,"web_url":"http://patchwork.ozlabs.org/comment/3677744/","msgid":"","date":"2026-04-15T15:53:25","subject":"Re: [PATCH v2 1/6] mm/sparse-vmemmap: Fix vmemmap accounting\n underflow","submitter":{"id":77733,"url":"http://patchwork.ozlabs.org/api/people/77733/","name":"Mike Rapoport","email":"rppt@kernel.org"},"content":"On Wed, Apr 15, 2026 at 07:14:07PM +0800, Muchun Song wrote:\n> In section_activate(), if populate_section_memmap() fails, the error\n> handling path calls section_deactivate() to roll back the state. This\n> causes a vmemmap accounting imbalance.\n> \n> Since commit c3576889d87b (\"mm: fix accounting of memmap pages\"),\n> memmap pages are accounted for only after populate_section_memmap()\n> succeeds. However, the failure path unconditionally calls\n> section_deactivate(), which decreases the vmemmap count. Consequently,\n> a failure in populate_section_memmap() leads to an accounting underflow,\n> incorrectly reducing the system's tracked vmemmap usage.\n> \n> Fix this more thoroughly by moving all accounting calls into the lower\n> level functions that actually perform the vmemmap allocation and freeing:\n> \n> - populate_section_memmap() accounts for newly allocated vmemmap pages\n> - depopulate_section_memmap() unaccounts when vmemmap is freed\n> - free_map_bootmem() handles early bootmem section accounting\n> \n> This ensures proper accounting in all code paths, including error\n> handling and early section cases.\n> \n> Fixes: c3576889d87b (\"mm: fix accounting of memmap pages\")\n> Signed-off-by: Muchun Song \n\nAcked-by: Mike Rapoport (Microsoft) \n\n> ---\n> mm/sparse-vmemmap.c | 20 ++++++++++++--------\n> 1 file changed, 12 insertions(+), 8 deletions(-)\n> \n> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c\n> index 6eadb9d116e4..a7b11248b989 100644\n> --- a/mm/sparse-vmemmap.c\n> +++ b/mm/sparse-vmemmap.c\n> @@ -656,7 +656,12 @@ static struct page * __meminit populate_section_memmap(unsigned long pfn,\n> \t\tunsigned long nr_pages, int nid, struct vmem_altmap *altmap,\n> \t\tstruct dev_pagemap *pgmap)\n> {\n> -\treturn __populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);\n> +\tstruct page *page = __populate_section_memmap(pfn, nr_pages, nid, altmap,\n> +\t\t\t\t\t\t pgmap);\n> +\n> +\tmemmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));\n> +\n> +\treturn page;\n> }\n> \n> static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,\n> @@ -665,13 +670,17 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,\n> \tunsigned long start = (unsigned long) pfn_to_page(pfn);\n> \tunsigned long end = start + nr_pages * sizeof(struct page);\n> \n> +\tmemmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)));\n> \tvmemmap_free(start, end, altmap);\n> }\n> +\n> static void free_map_bootmem(struct page *memmap)\n> {\n> \tunsigned long start = (unsigned long)memmap;\n> \tunsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);\n> \n> +\tmemmap_boot_pages_add(-1L * (DIV_ROUND_UP(PAGES_PER_SECTION * sizeof(struct page),\n> +\t\t\t\t\t\t PAGE_SIZE)));\n> \tvmemmap_free(start, end, NULL);\n> }\n> \n> @@ -774,14 +783,10 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,\n> \t * The memmap of early sections is always fully populated. See\n> \t * section_activate() and pfn_valid() .\n> \t */\n> -\tif (!section_is_early) {\n> -\t\tmemmap_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE)));\n> +\tif (!section_is_early)\n> \t\tdepopulate_section_memmap(pfn, nr_pages, altmap);\n> -\t} else if (memmap) {\n> -\t\tmemmap_boot_pages_add(-1L * (DIV_ROUND_UP(nr_pages * sizeof(struct page),\n> -\t\t\t\t\t\t\t PAGE_SIZE)));\n> +\telse if (memmap)\n> \t\tfree_map_bootmem(memmap);\n> -\t}\n> \n> \tif (empty)\n> \t\tms->section_mem_map = (unsigned long)NULL;\n> @@ -826,7 +831,6 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,\n> \t\tsection_deactivate(pfn, nr_pages, altmap);\n> \t\treturn ERR_PTR(-ENOMEM);\n> \t}\n> -\tmemmap_pages_add(DIV_ROUND_UP(nr_pages * sizeof(struct page), PAGE_SIZE));\n> \n> \treturn memmap;\n> }\n> -- \n> 2.20.1\n>","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256\n header.s=k20201202 header.b=DlGLUOug;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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Howlett\" ,\n\tVlastimil Babka ,\n\tSuren Baghdasaryan ,\n\tMichal Hocko , Nicholas Piggin ,\n\tChristophe Leroy , aneesh.kumar@linux.ibm.com,\n\tjoao.m.martins@oracle.com, linux-mm@kvack.org,\n\tlinuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org","Subject":"Re: [PATCH v2 1/6] mm/sparse-vmemmap: Fix vmemmap accounting\n underflow","Message-ID":"","References":"<20260415111412.1003526-1-songmuchun@bytedance.com>\n <20260415111412.1003526-2-songmuchun@bytedance.com>","X-Mailing-List":"linuxppc-dev@lists.ozlabs.org","List-Id":"","List-Help":"","List-Owner":"","List-Post":"","List-Archive":",\n ","List-Subscribe":",\n ,\n ","List-Unsubscribe":"","Precedence":"list","MIME-Version":"1.0","Content-Type":"text/plain; charset=us-ascii","Content-Disposition":"inline","In-Reply-To":"<20260415111412.1003526-2-songmuchun@bytedance.com>","X-Spam-Status":"No, score=-0.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,\n\tDKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,SPF_HELO_NONE,SPF_PASS\n\tautolearn=disabled version=4.0.1 OzLabs 8","X-Spam-Checker-Version":"SpamAssassin 4.0.1 (2024-03-25) on lists.ozlabs.org"}}]