From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752592Ab1JLWRj (ORCPT ); Wed, 12 Oct 2011 18:17:39 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:64999 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751790Ab1JLWRh (ORCPT ); Wed, 12 Oct 2011 18:17:37 -0400 Date: Wed, 12 Oct 2011 15:17:32 -0700 From: Tejun Heo To: Jeff Moyer Cc: linux-kernel@vger.kernel.org, jaxboe@fusionio.com, christophe@saout.de, dm-devel@redhat.com, msnitzer@redhat.com Subject: Re: [PATCH 1/2] blk-flush: move the queue kick into blk_insert_cloned_request Message-ID: <20111012221732.GH6281@google.com> References: <1318454562-25291-1-git-send-email-jmoyer@redhat.com> <1318454562-25291-2-git-send-email-jmoyer@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1318454562-25291-2-git-send-email-jmoyer@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 12, 2011 at 05:22:41PM -0400, Jeff Moyer wrote: > A dm-multipath user reported[1] a problem when trying to boot > a kernel with commit 4853abaae7e4a2af938115ce9071ef8684fb7af4 > (block: fix flush machinery for stacking drivers with differring > flush flags) applied. It turns out that an empty flush request > can be sent into blk_insert_flush. When the BUG_ON was fixed > to allow for this, I/O on the underlying device would stall. The > reason is that blk_insert_cloned_request does not kick the queue. > In the aforementioned commit, I had added a special case to > kick the queue if data was sent down but the queue flags did > not require a flush. A better solution is to push the queue > kick up into blk_insert_cloned_request. > > This patch, along with a follow-on which fixes the BUG_ON, fixes > the issue reported. > > [1] http://www.redhat.com/archives/dm-devel/2011-September/msg00154.html > > Reported-by: Christophe Saout > Signed-off-by: Jeff Moyer Acked-by: Tejun Heo Thank you for fixing this, but one curiosity, what happens for !flush cloned requests? Is someone else responsible for kicking the queue? -- tejun