From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH v2] dm ioctl: allow change device target type to error Date: Wed, 21 Aug 2013 11:06:42 -0400 Message-ID: <20130821150547.GA10987@redhat.com> References: <5214CC25.1070307@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mikulas Patocka Cc: dm-devel@redhat.com, joe.jin@oracle.com, agk@redhat.com, linux-kernel@vger.kernel.org List-Id: dm-devel.ids On Wed, Aug 21 2013 at 10:48am -0400, Mikulas Patocka wrote: > > > On Wed, 21 Aug 2013, Joe Jin wrote: > > > commit a5664da "dm ioctl: make bio or request based device type immutable" > > prevented "dmsetup wape_table" change the target type to "error". > > That commit a5664da is there for a reason (it is not possible to change > bio-based device to request-based and vice versa) and I don't really see > how this patch is supposed to work. > > If there are bios that are in flight and that already passed through > blk_queue_bio, and you change the device from request-based to bio-based, > what are you going to do with them? - The patch doesn't do anything about > it. > > A better approach would be to create a new request-based target "error-rq" > and change the multipath target to "error-rq" target. That way, you don't > have to change device type from request based to bio based. My thoughts _exactly_. This patch is very confused. Joe, what are you looking to be able to do? Switch a dm-multipath device to error? Or allowing switching a target that has DM_TARGET_IMMUTABLE flag set to be switched to error target? The latter restriction was introduced with commit 36a0456fb ("dm table: add immutable feature"). Mike