From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 993A3156991; Fri, 24 Jan 2025 07:58:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737705495; cv=none; b=gjvspu3BPgycMRjuL+4WPMFg4zhKOlkyKo/mnmX2DerAPP4bfHZLTpX5diRiGTBdVffKyp34V3IppvirtaRc5a7yQ4Ovw7R+FhZot6JbrcDRhFMpCDiO+ADW8W0MuJpHzfCHNo+RZQB+sjHkUgNhv/1YrXto+U/d7SNNnzSwV/M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737705495; c=relaxed/simple; bh=dOOYMgxR5dJ6D6pdPdoRQuEu0PiWlbYN0Z4O2pdURPU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AlF8eAzr54frCfhDgA3P/lLJyjLUt5M4CgQvJrQ5VmzN/ZPMUBT5y3O5N+pP6BeYT/NyTHqx5cegxG1Ke1aC5T+Jj8SBMbX9mmooWtx2b6+vy55Mu8i3YeTS8fc/e9rBYomATC8kaEQGzfxZjau5hyeeDRcWr4goowQrVPqERRM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C2952497; Thu, 23 Jan 2025 23:58:40 -0800 (PST) Received: from [10.57.95.170] (unknown [10.57.95.170]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D9EAD3F5A1; Thu, 23 Jan 2025 23:58:10 -0800 (PST) Message-ID: Date: Fri, 24 Jan 2025 08:58:07 +0100 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] s390/mm: Add missing ctor/dtor on page table upgrade To: Alexander Gordeev , Qi Zheng , Gerald Schaefer , Heiko Carstens Cc: linux-mm@kvack.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton References: <20250123160349.200154-1-agordeev@linux.ibm.com> Content-Language: en-GB From: Kevin Brodsky In-Reply-To: <20250123160349.200154-1-agordeev@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 23/01/2025 17:03, Alexander Gordeev wrote: > Commit 78966b550289 ("s390: pgtable: add statistics for PUD and P4D > level page table") misses the call to pagetable_p4d_ctor() against > a newly allocated P4D table in crst_table_upgrade(); > > Commit 68c601de75d8 ("mm: introduce ctor/dtor at PGD level") misses > the call to pagetable_pgd_ctor() against a newly allocated PGD and > the call to pagetable_dtor() against a newly allocated P4D that is > about to be freed on crst_table_upgrade() PGD upgrade fail path. > > The missed constructors and destructor break (at least) the page > table accounting when a process memory space is upgraded. > > Reported-by: Heiko Carstens > Closes: https://lore.kernel.org/all/20250122074954.8685-A-hca@linux.ibm.com/ > Suggested-by: Heiko Carstens > Fixes: 78966b550289 ("s390: pgtable: add statistics for PUD and P4D level page table") > Fixes: 68c601de75d8 ("mm: introduce ctor/dtor at PGD level") > Signed-off-by: Alexander Gordeev > --- > The patch is against: > > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git next-20250123 > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm mm-stable Thank you for putting together this patch! I was completely unaware of this "upgrade" path on s390. > --- > arch/s390/mm/pgalloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c > index a4e761902093..d33f55b7ee98 100644 > --- a/arch/s390/mm/pgalloc.c > +++ b/arch/s390/mm/pgalloc.c > @@ -88,12 +88,14 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end) > if (unlikely(!p4d)) > goto err_p4d; > crst_table_init(p4d, _REGION2_ENTRY_EMPTY); > + pagetable_p4d_ctor(virt_to_ptdesc(p4d)); This block seems to be equivalent to p4d_alloc_one(), maybe it would be preferable to just call p4d_alloc_one() here to avoid further mismatches in the future (and reduce duplication)? > } > if (end > _REGION1_SIZE) { > pgd = crst_table_alloc(mm); > if (unlikely(!pgd)) > goto err_pgd; > crst_table_init(pgd, _REGION1_ENTRY_EMPTY); > + pagetable_pgd_ctor(virt_to_ptdesc(pgd)); I was hoping this might be equivalent to pgd_alloc() but it does not include a call to crst_table_init(). Since adding it would be apparently undesirable (having read the other thread), it seems reasonable to add the explicit constructor call. > } > > spin_lock_bh(&mm->page_table_lock); > @@ -130,6 +132,7 @@ int crst_table_upgrade(struct mm_struct *mm, unsigned long end) > return 0; > > err_pgd: > + pagetable_dtor(virt_to_ptdesc(p4d)); > crst_table_free(mm, p4d); Similarly, this could be a call to p4d_free(). - Kevin > err_p4d: > return -ENOMEM;