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Re: [dm-devel] [PATCH][RESEND+fixes] dm + sysfs

Hi Mike,

I've just been reading through this stuff, you've put a lot effort
into it.  I'm still really worried by how invasive it is to the core
dm code.  The current code is structured to support different
interfaces (eg. ioctl, dmfs).  I see sysfs as simply another user
interface, albeit a read only one, so it would be nice if it could be
written without embedding kobjects etc. in the core dm structs.  The
reason you're finding this hard to do is that I never intended for
people to run more than one interface at the same time, so there is no
update mechanism to inform the interfaces of any changes initiated by
a different interface.  Adding such a feature is not something I
wanted to do, since it will end up defining what it is possible to do
using a user interface, for example the ioctl interface supports 2
namespaces for devices (name, uuid), whereas dmsfs supports an
arbitrary number.  How should we map these onto each other ?

Can you come up with a list of events that your sysfs interface is
iterested in ?  eg. you are probably interested in a device rename, a
table load etc.  Once we have this list we can maybe let the
interfaces register callbacks for notification of these changes.

Hope this makes sense.

- Joe

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