Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933945AbcJMTYi (ORCPT ); Thu, 13 Oct 2016 15:24:38 -0400 Received: from mail-oi0-f54.google.com ([209.85.218.54]:35072 "EHLO mail-oi0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933778AbcJMTYa (ORCPT ); Thu, 13 Oct 2016 15:24:30 -0400 MIME-Version: 1.0 In-Reply-To: <1476382494.20881.58.camel@hpe.com> References: <1476374061-9080-1-git-send-email-toshi.kani@hpe.com> <1476374787.20881.34.camel@hpe.com> <1476382494.20881.58.camel@hpe.com> From: Dan Williams Date: Thu, 13 Oct 2016 12:24:29 -0700 Message-ID: Subject: Re: [PATCH] pmem: report error on clear poison failure To: "Kani, Toshimitsu" Cc: "linux-kernel@vger.kernel.org" , "linux-nvdimm@lists.01.org" , "Verma, Vishal L" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2096 Lines: 51 On Thu, Oct 13, 2016 at 11:16 AM, Kani, Toshimitsu wrote: > On Thu, 2016-10-13 at 10:22 -0700, Dan Williams wrote: >> On Thu, Oct 13, 2016 at 9:08 AM, Kani, Toshimitsu > > wrote: >> > >> > On Thu, 2016-10-13 at 09:01 -0700, Dan Williams wrote: >> > > >> > > On Thu, Oct 13, 2016 at 8:54 AM, Toshi Kani >> > > wrote: >> > > > >> > > > >> > > > ACPI Clear Uncorrectable Error DSM function may fail or may be >> > > > unsupported on a platform. pmem_clear_poison() returns without >> > > > clearing badblocks in such cases, which leads to a silent data >> > > > corruption. >> > > > >> > > > Change pmem_do_bvec() and pmem_clear_poison() to return -EIO >> > > > so that filesystem can log an error message. >> > > >> > > What's the silent data corruption scenario? If the clear poison >> > > fails I'm assuming that the poison will still be notified on the >> > > next >> > > read. >> > >> > I agree that the data is eventually read, but there is no guranteed >> > that when it is read soon enough, i.e. user might not access to the >> > data for a long time. >> >> ...but that's the same behavior for errors that we don't yet know >> about. That said, we indeed know that the write failed. I'd feel >> better about this patch if the justification / impact was clearer in >> the changelog, because "silent data corruption" is not the impact. > > Agreed. How about the following descritpion? > > === > ACPI Clear Uncorrectable Error DSM function may fail or may be > unsupported on a platform. pmem_clear_poison() returns without > clearing badblocks in such cases. This failure is detected at > the next read (-EIO). > > This behavior can lead to an issue when user keeps writing but > does not read immedicately. For instance, flight recorder file > may be only read when it is necessary for troubleshooting. > > Change pmem_do_bvec() and pmem_clear_poison() to return -EIO > so that filesystem can log an error message on a write error. > === Looks good, thanks Toshi. I'll update the nvdimm.git branches after -rc1 is out.