Interface changes to multisnap

Interface changes to multisnap

[Joe Thornber]

I've just pushed an interface change for multisnap.

From now on the 'new-thin' message to the pool target takes just one
argument, the id of the new device.  The size field has been dropped,
instead the new device has a zero size.

When a multisnap target is loaded it implicitly resizes the thin
device based on the size of the target.  Truncation will lose data
that is off the end of the new device immediately.

- Joe

https://github.com/jthornber/linux-2.6/tree/multisnap

Re: Interface changes to multisnap

[Joe Thornber]

On Mon, Jun 20, 2011 at 01:22:57PM +0100, Joe Thornber wrote:
> I've just pushed an interface change for multisnap.

Ignore the previous message, it turned out to be bogus.  So now
resizing is implemented as follows:

- new-thin still takes a size arg

  new-thin <id> <size in sectors>

- There is a resize message:

  resize <id> <size in sectors>

- The target length doesn't have to correspond to the size of the thin
  device.  Writes beyond the end will cause IO error.

- Multiple targets may point to the same thin device.  If you make
  more than one active then it is a user error.  Much like using a
  linear target to map multiple devices to the same physical disk.

- Joe