From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 004E9FF885D for ; Tue, 28 Apr 2026 13:20:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 669396B0099; Tue, 28 Apr 2026 09:20:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 619A96B009B; Tue, 28 Apr 2026 09:20:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 509326B009D; Tue, 28 Apr 2026 09:20:50 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 3EF856B0099 for ; Tue, 28 Apr 2026 09:20:50 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id C42861B7218 for ; Tue, 28 Apr 2026 13:20:49 +0000 (UTC) X-FDA: 84708024618.04.F8CB221 Received: from out-177.mta1.migadu.com (out-177.mta1.migadu.com [95.215.58.177]) by imf15.hostedemail.com (Postfix) with ESMTP id C8E2EA000A for ; Tue, 28 Apr 2026 13:20:47 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=SuCOgAS4; spf=pass (imf15.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777382448; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=VQK83wzMxgtDx5zJs+rX80tqrYmQXtE7Gqa/54foH+M=; b=OhV8vxSNTBb15lGR4hwq6TI7HGyrzEYmP3fMldBmJDS52TyNoRZNybs3AHg0sIanEn90nM QGin36PAerDxb6nSE2b59dKT0E57eq2bvsJFyMzIBEOv1GSkPpjo1GmbuXwTYzU6uv2N+J 1dOGy0wY3LOEmuOYKmMTwutBQ3Wtytg= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=SuCOgAS4; spf=pass (imf15.hostedemail.com: domain of lance.yang@linux.dev designates 95.215.58.177 as permitted sender) smtp.mailfrom=lance.yang@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777382448; a=rsa-sha256; cv=none; b=7owH4wGkzvsDpbn35ny7VmgJKPDidONrpmelFZ0FzADkpV6gdQoXKh1AsllF6XVtUkfFDl n/058kY0peWWHIiaqhcOU8bBrJQBxOMOypKpGlu4WeO3vLHBmpKwdTXDuZY8LxZNK/d553 H8DmNImNmVlnKyssZCRTmgdwjQ1+c1g= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1777382445; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VQK83wzMxgtDx5zJs+rX80tqrYmQXtE7Gqa/54foH+M=; b=SuCOgAS4NzrmxBcKqLQ638tD3V02Ag8mN8/0M7capcdVTyJsCDDgenQZtxQTB4AUTX4YIF Zks1Lkqhz4DcxlukdWzarX/zlV6DV5yKyhodqiUSxXCOc2Noc/Xq71hZLkhOWE/kdIFcj4 vmBJt3djqbaM9XoBwIeaPLeZ8lXKk/w= From: Lance Yang To: david@kernel.org Cc: dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, rppt@kernel.org, jgg@ziepe.ca, baolu.lu@linux.intel.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org, Lance Yang Subject: Re: [PATCH] x86/mm: fix freeing of PMD-sized vmemmap pages Date: Tue, 28 Apr 2026 21:20:25 +0800 Message-Id: <20260428132025.86657-1-lance.yang@linux.dev> In-Reply-To: <20260428-vmemmap-v1-1-b2aa1e6db2c0@kernel.org> References: <20260428-vmemmap-v1-1-b2aa1e6db2c0@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: C8E2EA000A X-Rspamd-Server: rspam06 X-Stat-Signature: hwd6b8hgkaudndpidfdrgw91n1yf7no3 X-HE-Tag: 1777382447-541538 X-HE-Meta: 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 hdOag19H 2RRL1/Taym8leiBX2niyhc8s7sEwTelmK3cEVZrhPPVSMkaea7JgFzxiH9I4JpVjaO2j6ILV64XAlFBmZ+hzaVPPS56qGj+oJos5FJC8pyN4bMVfiJ0JdV6WLhi4k3rFz+Id9JsbV2KHZpSCC4LASW9VDZNfGBcqO3MorWaml7zAjrG144rvw3lqRE1b62EHn0BYWO0GMF+82fU2RAMfoBL+S6FoQPUbvfVsW4felTRsQ9gg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Apr 28, 2026 at 12:29:36PM +0200, David Hildenbrand (Arm) wrote: >In commit bf9e4e30f353 ("x86/mm: use pagetable_free()"), we switched >from freeing non-boot page tables through __free_pages() to >pagetable_free(). > >However, the function is also called to free vmemmap pages. > >Given that vmemmap pages are not page tables, already the page_ptdesc(page) >is wrong. But worse, pagetable_free() calls > > __free_pages(page, compound_order(page)); > >As vmemmap pages are not compound pages (see vmemmap_alloc_block()) -- >except for HVO, which doesn't apply here -- we will only free the first >page when freeing a PMD-sized vmemmap page, leaking the other ones. > >Fix it by properly decoupling pagetable and vmemmap freeing. >free_pagetable() no longer has to mess with SECTION_INFO, as only the >vmemmap is marked like that in register_page_bootmem_memmap(). > >While at it, just wire up the altmap parameter for remove_pte_table(). >Also, the indentation in remove_pmd_table() is messed up, let's fix that >while touching it. > >Note that we'll try to get rid of that bootmem info handling soon. For >now, we'll handle it similar to free_pagetable(), just avoiding the >ifdef. > >Fixes: bf9e4e30f353 ("x86/mm: use pagetable_free()") >Cc: stable@vger.kernel.org >Signed-off-by: David Hildenbrand (Arm) >--- >Reproduced and tested with a simple VM with a virtio-mem device, >repeatedly adding and removing memory. > >Found by code inspection while working on bootmem_info removal. >--- Cool! I just reproduced the leak with QEMU pc-dimm memory hotplug as well. Without the fix, nr_free_pages kept dropping after the hotplugged memory was removed again. With the fix applied, it stays stable over repeated add/remove cycles :) Tested-by: Lance Yang