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 F0694339360; Mon, 12 Oct 2026 13:27:33 +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=1791811655; cv=none; b=EyrjBgyCncrO1P8dYdXOewurwOaiAUjqTgOEuypNmzdAAp6dDNl22nH88qkHSkVWUqtoRO0eoK0OLfSu0pR5vYE0cpRdreWsYjZI3IpBayBkwB07yOekI4owpskMgTzT83Wkkt6ouBa9l7ALIfLmANdumonspvTlu1AlGwe5uRc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791811655; c=relaxed/simple; bh=EMAsdNyiURLBpk9FYtaLDI0O6pceU8Tte2UoXCbKcMs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=pOLwPhOPKhTPABgcDyLji56lWuB3u6J5NS7xN671e/bYVDxijLfb0t0TxrwMcx0tCyFx1mNl98AvXlx531qIfk9uRhXhSSrV7ppl/MHroBrO/kUTHk/f+3bB5zV4VZ1piBFFZbn8VjNIPesNW6K4hmni66o3Q6OErPyi1D6XKms= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h+BEp3hE; 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="h+BEp3hE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B5781F0089B; Mon, 12 Oct 2026 13:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791811653; bh=mqbvsZSYJL1Y0+A59bOb/XHgebVZKcusk4yArMBC290=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=h+BEp3hED2E0t7oun5QTzPFxYlzk8K02LAR1RNB0ToQTnQqjgYdWzs+nzz9W9b2bd bT+OPcuZJRbU/r5Mrnxzo8YX4VZBGdQciwtrAxOhNdv65GQ8YC4HA/OCpBnoQ/akS6 +Hoh7vNe8fF/PjR749ofV44TdW7pkptiUn/9DK/Rfd1s2lBf01ZVCkySBvkRbW+Lnc zD10e1pIDa41mD2jHiNZ4rpC58X5vL6L22whLxjDivnC0RUGm3Zf5umuF5BNUORxSk 0hbvromI8XB3qlj1JlndvU0++4iSr7HwXXiuyxSBr3HYudxNDWcTaVHXM6e5Td8gQO NM9DIcNwTjbsQ== Message-ID: <919fcaa9-5ebe-4940-b4fc-59ea0c655ec3@kernel.org> Date: Mon, 12 Oct 2026 15:27:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] mm: fix missing page-table destructor in pagetable_free() To: Muchun Song , Andrew Morton Cc: 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 References: <20261010112457.49485-1-songmuchun@bytedance.com> <20261010112457.49485-2-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/10/26 13:24, 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 > 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); We do have static inline void pagetable_dtor_free(struct ptdesc *ptdesc) { pagetable_dtor(ptdesc); pagetable_free(ptdesc); } ... can we now get rid of pagetable_dtor_free() and simply use pagetable_free() ? (separate cleanup) > + > + if (ptdesc_test_kernel(pt)) { > + ptdesc_clear_kernel(pt); > + pagetable_free_kernel(pt); > + } else { > + __pagetable_free(pt); > + } This goes into the right direction. I'm still confused, but the less freeing functions we have the better. Acked-by: David Hildenbrand (Arm) -- Cheers, David