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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 36FF1CC6B0E for ; Tue, 13 Oct 2026 06:34:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:To:References:Message-Id: Content-Transfer-Encoding:Cc:Date:In-Reply-To:From:Subject:Mime-Version: Content-Type:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=x3TJ+nLYXw+aqTgNhbnY0u+0hp8FGUc5AIcm44+MuiU=; b=lqT3LSuUupa5Fc3SriHreh6xtf Ionq/WxcU42N02DR0422WeW7e+ICDm4ygL47wlbLA1U+p2TKRoZedHc9zuK14Cwg/AymxPEZVKXbo nEQjvV4/1VFbx1PlChAdWYF6Mni2qKQooY8989wBRUS8kHY9jhpYYikKpaDf8DpYW4pmPyS67OQBM eWdfrrj+pggBS33UaAZNfKniZF6+h1qOOYFpHPTvnpdRBTkfAbhloXunzjuR5vyoc0kCMuT4HrczO TyiDvm9D3NuGLmsaj+/XdvgRNbgQmdrEw47UHtlgssiT9pQbrtchcj9x7ltjYdPm5HQUS0dmCRx3J khKfvyJw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGW5Y-0000000C9Zs-3t3t; Tue, 13 Oct 2026 06:34:16 +0000 Received: from out-37.mta0.migadu.com ([2001:41d0:1004:224b::25] helo=mta0.migadu.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xGW5U-0000000C9Yc-0VhG for linux-arm-kernel@lists.infradead.org; Tue, 13 Oct 2026 06:34:14 +0000 X-Envelope-To: linux-arm-kernel@lists.infradead.org DKIM-Signature: a=rsa-sha256; bh=x3TJ+nLYXw+aqTgNhbnY0u+0hp8FGUc5AIcm44+MuiU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791873249; v=1; x=1792478049; b=jPEz53G9zFtMf7S7MMA3ep20v99EcICky/EP9W6meqhELt5OpbuudGf6WopZUAQNGX9cbUKp oL5ue2WlC4wtiqVIRa6KGdXuVmtzRp5adDL+7FzQKnKieXPXu4d223bjJvrQA680vlem2AgFhI7 Sdrm3rr1ohq7fHe9xPgdcgq0= X-Envelope-To: linux-arm-kernel@lists.infradead.org Received: by smtp.migadu.com with ESMTPS id 4af039548b386c01; Tue, 13 Oct 2026 06:34:09 +0000 X-Mizu-Trace-ID: 4af039548b386c01 X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3901.100.1.1.12\)) Subject: Re: [PATCH v2 1/4] mm: fix missing page-table destructor in pagetable_free() From: Muchun Song In-Reply-To: <3ab63358-8bbe-4457-b21c-bb81bca804cc@gmail.com> Date: Tue, 13 Oct 2026 14:33:49 +0800 Cc: Andrew Morton , Muchun Song , David Hildenbrand , Oscar Salvador , Dave Hansen , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , =?utf-8?B?QmrDtnJuIFTDtnBlbA==?= , Catalin Marinas , Will Deacon , Mark Rutland , Kevin Brodsky , Alexander Gordeev , Alistair Popple , linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <2B2F2818-9309-450B-A2A4-9F53D802F1C6@linux.dev> References: <20261010112457.49485-1-songmuchun@bytedance.com> <20261010112457.49485-2-songmuchun@bytedance.com> <145CD5DC-6457-4E1E-8B9D-AE7D1EDB0AB8@linux.dev> <3ab63358-8bbe-4457-b21c-bb81bca804cc@gmail.com> To: "Jose A. Perez de Azpillaga" X-Mailer: Apple Mail (2.3901.100.1.1.12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261012_233412_292822_79A3A5EA X-CRM114-Status: GOOD ( 13.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > On Oct 13, 2026, at 01:21, Jose A. Perez de Azpillaga = wrote: >=20 > On 10/12/26 2:55 PM, Muchun Song wrote: >>=20 >>=20 >>> On Oct 12, 2026, at 19:15, Jose A. Perez de Azpillaga = wrote: >>>=20 >>> On Sat, Oct 10, 2026 at 07:24:54PM +0800, Muchun Song wrote: >>>> Since commit 49f599666420 ("mm: call ctor/dtor for kernel PTEs"), >>>> pte_alloc_one_kernel() runs the page-table constructor for kernel = PTE >>>> tables. >>>>=20 >>>> HVO (HugeTLB Vmemmap Optimization) uses pte_alloc_one_kernel() when >>>> splitting a PMD. Restoring the vmemmap backing pages does not = collapse >>>> the PTE table, so a later memory hot-remove eventually frees it = through >>>> pagetable_free() on x86-64. That releases the page without running = the >>>> matching destructor and leaves NR_PAGETABLE elevated. >>>>=20 >>>> Make pagetable_free() detect constructor-backed pages and run the >>>> destructor before releasing their memory to fix the problem. >>>>=20 >>>> Fixes: 49f599666420 ("mm: call ctor/dtor for kernel PTEs") >>>> Cc: stable@vger.kernel.org >>>=20 >>> is the x86 case covered for 6.16-6.18? as far as I can see, x86 >>> free_pagetable() only uses pagetable_free() since bf9e4e30f353 >>> ("x86/mm: use pagetable_free()") in v6.19, so the backport wouldn't >>> change anything there. or am I missing something? >>=20 >> Yes, you are absolutely right =E2=80=94 thanks for catching this. >>=20 >> I double-checked and indeed x86's free_pagetable() only starts using >> pagetable_free() since bf9e4e30f353 ("x86/mm: use pagetable_free()"), >> which landed in v6.19. So for 6.16-6.18 the prerequisite is not = present >> and the backport would be a no-op there. >>=20 >> The correct trailer is: >>=20 >> Cc: # 6.16-6.18: bf9e4e30f353: x86/mm: use = pagetable_free() >=20 > also, bf9e4e30f353 alone leaks PMD-sized vmemmap pages on those trees, > it needs 39406c05f8f1 ("x86/mm: Fix freeing of PMD-sized vmemmap = pages") > as well :) Yeah, you are so meticulous. >=20 > Reviewed-by: Jose A. Perez de Azpillaga >=20 Thanks. > --=20 > cheers, > jose a. p-a