Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752794AbcJJOwJ (ORCPT ); Mon, 10 Oct 2016 10:52:09 -0400 Received: from mail-it0-f42.google.com ([209.85.214.42]:37846 "EHLO mail-it0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752119AbcJJOwH (ORCPT ); Mon, 10 Oct 2016 10:52:07 -0400 MIME-Version: 1.0 In-Reply-To: <20161010132542.GA17958@redhat.com> References: <1476102919-25112-1-git-send-email-tahsin@google.com> <20161010132542.GA17958@redhat.com> From: Tahsin Erdogan Date: Mon, 10 Oct 2016 07:52:05 -0700 Message-ID: Subject: Re: dm: free io_barrier after blk_cleanup_queue call To: Mike Snitzer Cc: Alasdair Kergon , dm-devel@redhat.com, Shaohua Li , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org 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: 539 Lines: 12 On Mon, Oct 10, 2016 at 6:25 AM, Mike Snitzer wrote: > I have to believe this was born out of code inspection rather than > actual need (due to crash, etc)? This got originated from several crashes I have seen with 4.3 kernel. The crashes were caused by null dereferencing of io_barrier->per_cpu_ref. The issue may no longer be relevant after commit c91852ff0815 ("dm: optimize dm_request_fn()") because conditions for accessing io_barrier may not longer exist. But fix should be considered for forked stable trees.