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").
Mike
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