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[198.145.29.99]) by mx.google.com with ESMTPS id s3si2805108pji.94.2019.06.07.12.54.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 07 Jun 2019 12:54:31 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=TANt56tM; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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?