From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f48.google.com (mail-wr1-f48.google.com [209.85.221.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 41E4D3AFB0E for ; Mon, 12 Oct 2026 11:15:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791803721; cv=none; b=eK4IiSNoyp+nzC1608ffquJzqCw8saWbWZoKEOyHd2/SUKvmq4EMuOLyqhQe42jwWiEk83a4Ee0JVmY2ytrUlhidaCZ343jxXYEAmyGYnpcjMAfJFpvcvUygXzhOSs9M1vkCyERB4F64fia38zj76gxCk6PQxqxJWZKKe15pLwc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791803721; c=relaxed/simple; bh=HdqTt+q/rfbcDE1yH9uRCugIMBEwtlrnLu6S9W7U8R0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nKRKpW7yv6M+6EMj4xdr5C9ma2H6xx/iunPPIxMTHps/XEkhjV+GKuECxB32u7ePdKvQNdC20ERlbsMeCsJzmeb42Cf7/rLbk/lbaauZzUasxzR08+2aAj74Jwy5i+gVvXQC+HAX9tMyda9NzJYGmGomATiG4UVKFMpN4lz/BdY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=h5nu7ddK; arc=none smtp.client-ip=209.85.221.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="h5nu7ddK" Received: by mail-wr1-f48.google.com with SMTP id ffacd0b85a97d-48b0ef9c76eso1454060f8f.0 for ; Mon, 12 Oct 2026 04:15:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791803718; x=1792408518; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=dOcvEm9msY+cl7KKbAZfMaogQnVH3/RbIaSfojxkTRo=; b=h5nu7ddK/nORjzfhtVUdNW0OJdY868u1dyHw35LvA5jcKRRM6xO0CmFU/IfAF/Z1US y2dRizCmATL95I/H81DPPSzZZzqRQDnY1wqW5iiEJIYOHAbYsF6eH792WtAh5SH8fNbJ QkKfCBDwPwSgOZURXMBo/oFeMLjo6DrH0M0Q1h5ijloVxirL/sC9+3AlU1qZKDdgFeva Q1TOJNVkYoGHrGXkHRNIPRvTdGbgxEjPXKCNVCjVDCmDkUSFLNbmeDNpRK748Un6I/3g +vYLIyIs/DCeG/+fAUWaCI1dxaw9/Rt4rUHh2SqszoWLywDVM11VB90iogVtlnhIqpPd IiNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791803718; x=1792408518; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=dOcvEm9msY+cl7KKbAZfMaogQnVH3/RbIaSfojxkTRo=; b=QNdDYOWxM5Slko3lGBzX9R6KxWWcsr0iG8TfHbYjNFFX9zttvVj8xtSj6xRoLCB9Hb o3Y7okZC2dOm7ar9mQhJliCj1FLISy+Xoqe7D4DekFg0EA7oiI9nqWpBznucHioO27fs j+VzWFS6b3gYtyVSBx9tCiIIRNr4S7/rdk8OWgiN2fzeIT4Jq+DnCRXgD2xTToHE6PdX xO32a/29QtDAlwIknyYLqkGaFbLo+mBjwSUH+UnC1zhHyFcVV3JgGBGhWVt9tym7UNlR axKPNlsq+P12BC2kaWJ59KhQug+hKbkXDq8EaA90ExLtsR1u+8jJCvVigxqnDsq8grBm oiKA== X-Forwarded-Encrypted: i=1; AKwUvBwQJgtwb+cuMS9S8N1FbIjg88eGH8Tg9eUII3aRie8jMEH1BPLNGxd6IgbXPbRpR2qHCPnrKqU=@vger.kernel.org X-Gm-Message-State: AFq9FYKlKFanRuFo5eQiR6CnKLmcJ5obkShl7HuezIzqVwDceKyQK8Vz SAr/lwskmLVfSU1VQgZ/8fxHnl0PolncoOpTMFYKZ3UAQgclpvtWs209 X-Gm-Gg: AYBFou0dgvg35Edk4t0Xp6tXf030dLnFL5coxR2o52L1A4XTJP1gOkHCQzLQgz5s3ai 9UlQTfe3/5v5hbUvkco3Eqie+PgXE46w03I4cuH+kH1cwn0IRxkzz8Sr4KoQAumM/dd1AOFj9UL xM0rmxXw0MCja9D9PrdWhE+xV8T5SgSaSxtxm3eekf7e9sMjKHPs2F/lw+X0nJ9DvVmPE5ZP3qC vPLmm1B3fT6puCGGC4s8fP/aIPF5XJ0ssBYCDUd8eFOav6bEaN8aQW23L+7W/mqv3LklybjM4Qi Cs9XmVhZgC3MFUdtv+DrroOVkMsirtWLfcmxeN6O29tEtCY6nHiWVPmhr4rweAOLRIzol/PvBka NOcQpW1EpIdYbJeisE0VLNECnPH2H1pOdnhGeMXJ/5WNJJXOzxzr/rHU1qe6tq2cXZvWbLHAnJb NZkveJWfo3xVX/YbDhonpba1W+dZNSfgT9tcAQ1CRFx2THYHgHDTuvirsmVZT9ho0uTo68aA== X-Received: by 2002:adf:e005:0:10b0:48d:dec7:974c with SMTP id ffacd0b85a97d-48ddec797bfmr346783f8f.7.1791803718021; Mon, 12 Oct 2026 04:15:18 -0700 (PDT) Received: from gmail.com ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48db94e33d2sm20034954f8f.9.2026.10.12.04.15.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Oct 2026 04:15:17 -0700 (PDT) Date: Mon, 12 Oct 2026 13:15:14 +0200 From: "Jose A. Perez de Azpillaga" To: Muchun Song Cc: Andrew Morton , 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, Muchun Song Subject: Re: [PATCH v2 1/4] mm: fix missing page-table destructor in pagetable_free() Message-ID: References: <20261010112457.49485-1-songmuchun@bytedance.com> <20261010112457.49485-2-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261010112457.49485-2-songmuchun@bytedance.com> 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. > > 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. > > Make pagetable_free() detect constructor-backed pages and run the > destructor before releasing their memory to fix the problem. > > Fixes: 49f599666420 ("mm: call ctor/dtor for kernel PTEs") > Cc: stable@vger.kernel.org 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? > Assisted-by: LLM > Signed-off-by: Muchun Song > --- > v2: > - Move destructor handling from x86 into pagetable_free() (suggested by > David Hildenbrand) > - Trim and update the commit message (requested by Dave Hansen) > --- > include/linux/mm.h | 37 ++++++++++++++++++++----------------- > 1 file changed, 20 insertions(+), 17 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 5cca90fc1df6..771a7d60b0a5 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3969,23 +3969,6 @@ static inline void pagetable_free_kernel(struct ptdesc *pt) > __pagetable_free(pt); > } > #endif > -/** > - * pagetable_free - Free pagetables > - * @pt: The page table descriptor > - * > - * pagetable_free frees the memory of all page tables described by a page > - * table descriptor and the memory for the descriptor itself. > - */ > -static inline void pagetable_free(struct ptdesc *pt) > -{ > - if (ptdesc_test_kernel(pt)) { > - ptdesc_clear_kernel(pt); > - pagetable_free_kernel(pt); > - } else { > - __pagetable_free(pt); > - } > -} > - > #if defined(CONFIG_SPLIT_PTE_PTLOCKS) > #if ALLOC_SPLIT_PTLOCKS > void __init ptlock_cache_init(void); > @@ -4078,6 +4061,26 @@ static inline void pagetable_dtor(struct ptdesc *ptdesc) > lruvec_stat_sub_folio(folio, NR_PAGETABLE); > } > > +/** > + * pagetable_free - Free pagetables > + * @pt: The page table descriptor > + * > + * pagetable_free frees the memory of all page tables described by a page > + * table descriptor and the memory for the descriptor itself. > + */ > +static inline void pagetable_free(struct ptdesc *pt) > +{ > + if (PageTable(ptdesc_page(pt))) > + pagetable_dtor(pt); > + > + if (ptdesc_test_kernel(pt)) { > + ptdesc_clear_kernel(pt); > + pagetable_free_kernel(pt); > + } else { > + __pagetable_free(pt); > + } > +} > + > static inline void pagetable_dtor_free(struct ptdesc *ptdesc) > { > pagetable_dtor(ptdesc); > -- > 2.54.0 > > -- cheers, jose a. p-a