On Wed, Aug 21 2013 at 10:40pm -0400,
Joe Jin <joe.jin@xxxxxxxxxx> wrote:
> On 08/21/13 23:06, Mike Snitzer wrote:
> > On Wed, Aug 21 2013 at 10:48am -0400,
> > Mikulas Patocka <mpatocka@xxxxxxxxxx> 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").
>
> Hi Mike,
>
> So far dmsetup support wipe_table:
> https://bugzilla.redhat.com/show_bug.cgi?id=742607
> As description in the bug Doc Text, "This could be useful, for example,
> if a long-running process keeps a device open after it has finished using
> it and you need to release the underlying devices before that process exits."
>
> After apply the commit, wipe_table no long works.
Well, it never _really_ worked even before that commit because it was
switching from request-based to bio-based. Some queued requests
could've easily slipped through the cracks.
But I now understand what it is you want to be able to do.
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
