From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100Ab2H1XBp (ORCPT ); Tue, 28 Aug 2012 19:01:45 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:48728 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807Ab2H1XBn (ORCPT ); Tue, 28 Aug 2012 19:01:43 -0400 Date: Tue, 28 Aug 2012 16:01:08 -0700 From: Kent Overstreet To: Tejun Heo Cc: linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, dm-devel@redhat.com, vgoyal@redhat.com, mpatocka@redhat.com, bharrosh@panasas.com, Jens Axboe Subject: Re: [PATCH v7 9/9] block: Avoid deadlocks with bio allocation by stacking drivers Message-ID: <20120828230108.GI1048@moria.home.lan> References: <1346175456-1572-1-git-send-email-koverstreet@google.com> <1346175456-1572-10-git-send-email-koverstreet@google.com> <20120828204910.GG24608@dhcp-172-17-108-109.mtv.corp.google.com> <20120828222800.GG1048@moria.home.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120828222800.GG1048@moria.home.lan> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 28, 2012 at 03:28:00PM -0700, Kent Overstreet wrote: > On Tue, Aug 28, 2012 at 01:49:10PM -0700, Tejun Heo wrote: > > Overall, I *think* this is correct but need to think more about it to > > be sure. > > Please do. As much time as I've spent staring at this kind of stuff, > I'm pretty sure I've got it correct but it still makes my head hurt to > work out all the various possible deadlocks. Hilarious thought: We're punting bios to a rescuer thread that's specific to a certain bio_set, right? What if we happen to punt bios from a different bio_set? And then the rescuer goes to resubmit those bios, and in the process they happen to have dependencies on the original bio_set... I think it's actually necessary to filter out only bios from the current bio_set to punt to the rescuer. God I love the block layer sometimes.