Re: [dm-devel] Re: [RFC] device-mapper ioctl interface

[Kevin Corry <kevcorry@us.ibm.com>]

On Thursday 05 June 2003 12:00, Daniel Phillips wrote:
> On Thursday 05 June 2003 18:47, Kevin Corry wrote:
> > 2) Removing suspended devices. The current code (2.5.70) does not allow a
> > suspended device to be removed/unlinked from the ioctl interface, since
> > removing it would leave you with no way to resume it (and hence flush any
> > pending I/Os). Alasdair mentioned a couple of new ideas. One would be to
> > reload the device with an error-map and force it to resume, thus erroring
> > any pending I/Os and allowing the device to be removed. This seems a bit
> > heavy-handed.
>
> Which is the heavy-handed part?

The part about automatically reloading the table with an error map and forcing 
it to resume. It just seemed to me that user-space ought to be able to gather 
enough information to determine that a device needed to be resumed before it 
could be removed. Thus the kernel driver wouldn't be forced to implement such 
a policy.

Talking with Alasadair again, he mentioned a case I hadn't considered. Devices 
would now be created without a mapping and initially suspended. If some other 
error occurred, and you decided to just delete the device before loading a 
mapping, it would fail.  And having to resume a device with no mapping just 
to be able to delete it definitely seems odd.

So, it's not like I'm dead-set against this idea. I was just curious what the 
reasoning was behind this change.

-- 
Kevin Corry
kevcorry@us.ibm.com
http://evms.sourceforge.net/