From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751495AbeEaWw7 (ORCPT ); Thu, 31 May 2018 18:52:59 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59854 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751135AbeEaWw6 (ORCPT ); Thu, 31 May 2018 18:52:58 -0400 Date: Thu, 31 May 2018 15:52:56 -0700 From: Andrew Morton To: "Kirill A. Shutemov" Cc: Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/shmem: Zero out unused vma fields in shmem_pseudo_vma_init() Message-Id: <20180531155256.a5f557c9e620a6d7e85e4ca1@linux-foundation.org> In-Reply-To: <20180531135602.20321-1-kirill.shutemov@linux.intel.com> References: <20180531135602.20321-1-kirill.shutemov@linux.intel.com> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 31 May 2018 16:56:02 +0300 "Kirill A. Shutemov" wrote: > shmem/tmpfs uses pseudo vma to allocate page with correct NUMA policy. > > The pseudo vma doesn't have vm_page_prot set. We are going to encode > encryption KeyID in vm_page_prot. Having garbage there causes problems. > > Zero out all unused fields in the pseudo vma. > So there are no known problems in the current mainline kernel? > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1404,10 +1404,9 @@ static void shmem_pseudo_vma_init(struct vm_area_struct *vma, > struct shmem_inode_info *info, pgoff_t index) > { > /* Create a pseudo vma that just contains the policy */ > - vma->vm_start = 0; > + memset(vma, 0, sizeof(*vma)); > /* Bias interleave by inode number to distribute better across nodes */ > vma->vm_pgoff = index + info->vfs_inode.i_ino; > - vma->vm_ops = NULL; > vma->vm_policy = mpol_shared_policy_lookup(&info->policy, index); > }