[dm-devel] [PATCH 1/6] dm cache: cache shrinking support

[Alasdair G Kergon]

On Mon, Nov 11, 2013 at 06:06:26PM -0500, Mike Snitzer wrote:
> This really isn't even an "interface".  

It is an extension to the existing userspace-kernel interface: a size
reduction of an underlying device is detected on reload and triggers the
removal of metadata relating to the removed portion of the device.

Another interface might for example require a message to be sent to set
a threshold above which the device is 'cleaned' until there is no
metadata pointing beyond that point.  A subsequent reload using the
smaller underlying device would not then need to trigger any metadata
removal: it would already have been removed.

Alasdair