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 X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6B563C468BC for ; Fri, 7 Jun 2019 19:54:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4320D208E3 for ; Fri, 7 Jun 2019 19:54:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559937272; bh=8psQmUHD9luxI22nFWbQOgpTZfWDCb9IM6SP1Gb6RuE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=1tI6KBXPKtk9TA8YHyXerum3mWAeT9BldNlTDSP+S7ijXV93Ua+b+/9tqGJeQeups bdY2WcSHgi5mOBJSACK3T3WAnmTS6BdIr6AzkvYbyEP2WGJZd4nzv+GOu3YEzi9TVj AVgt93W9d8blFAycn0/x1L8oFQmRo5LkBaWt4Eow= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731255AbfFGTyb (ORCPT ); Fri, 7 Jun 2019 15:54:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:59446 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729241AbfFGTyb (ORCPT ); Fri, 7 Jun 2019 15:54:31 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 81E7D208C3; Fri, 7 Jun 2019 19:54:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559937270; bh=8psQmUHD9luxI22nFWbQOgpTZfWDCb9IM6SP1Gb6RuE=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=TANt56tMnGHGSeTHxg2W5Nga6u0fq8FsdWYmLcrlsCGA2NGsA2mQH36A8hsYaUQl7 PvF+FiSUc0fahikKKGkO11OQ4+xLKsQjmAxNlLOFaGKdbVX69LqoznlxnaXcFMOm0G NPbdjRpokmMR23+zPVRWYusaOBotEgcPCbhlQMLI= Date: Fri, 7 Jun 2019 12:54:30 -0700 From: Andrew Morton To: Dan Williams Cc: stable , Linux MM , linux-nvdimm , Linux Kernel Mailing List , Oscar Salvador , Michal Hocko Subject: Re: [PATCH v9 11/12] libnvdimm/pfn: Fix fsdax-mode namespace info-block zero-fields Message-Id: <20190607125430.81e63cd56590ab3fea37a635@linux-foundation.org> In-Reply-To: References: <155977186863.2443951.9036044808311959913.stgit@dwillia2-desk3.amr.corp.intel.com> <155977193862.2443951.10284714500308539570.stgit@dwillia2-desk3.amr.corp.intel.com> <20190606144643.4f3363db9499ebbf8f76e62e@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 6 Jun 2019 15:06:26 -0700 Dan Williams wrote: > On Thu, Jun 6, 2019 at 2:46 PM Andrew Morton wrote: > > > > On Wed, 05 Jun 2019 14:58:58 -0700 Dan Williams wrote: > > > > > At namespace creation time there is the potential for the "expected to > > > be zero" fields of a 'pfn' info-block to be filled with indeterminate > > > data. While the kernel buffer is zeroed on allocation it is immediately > > > overwritten by nd_pfn_validate() filling it with the current contents of > > > the on-media info-block location. For fields like, 'flags' and the > > > 'padding' it potentially means that future implementations can not rely > > > on those fields being zero. > > > > > > In preparation to stop using the 'start_pad' and 'end_trunc' fields for > > > section alignment, arrange for fields that are not explicitly > > > initialized to be guaranteed zero. Bump the minor version to indicate it > > > is safe to assume the 'padding' and 'flags' are zero. Otherwise, this > > > corruption is expected to benign since all other critical fields are > > > explicitly initialized. > > > > > > Fixes: 32ab0a3f5170 ("libnvdimm, pmem: 'struct page' for pmem") > > > Cc: > > > Signed-off-by: Dan Williams > > > > The cc:stable in [11/12] seems odd. Is this independent of the other > > patches? If so, shouldn't it be a standalone thing which can be > > prioritized? > > > > The cc: stable is about spreading this new policy to as many kernels > as possible not fixing an issue in those kernels. It's not until patch > 12 "libnvdimm/pfn: Stop padding pmem namespaces to section alignment" > as all previous kernel do initialize all fields. > > I'd be ok to drop that cc: stable, my concern is distros that somehow > pickup and backport patch 12 and miss patch 11. Could you please propose a changelog paragraph which explains all this to those who will be considering this patch for backports?