[dm-devel] dm thin: relax hard limit on the maximum size of a metadata device

Joe Thornber thornber at redhat.com
Tue Mar 6 10:09:53 UTC 2012

On Mon, Mar 05, 2012 at 09:04:21AM -0500, Mike Snitzer wrote:
> On Mon, Mar 05 2012 at  5:21am -0500,
> Joe Thornber <thornber at redhat.com> wrote:
> > Hi Mike,
> > 
> > My concerns are:
> > 
> > i) The current behaviour is upstream; by changing this aren't you
> >    making the tools writers life more complicated rather than less by
> >    making them support both interfaces?
> It is an incremental improvement.  Allows the kernel to be forgiving.
> How does this impact some tool that took the special care to limit the
> size of the device to METADATA_DEV_MAX_SECTORS (which is < 16G)?

You're making this change to make life easier for tool writers, yet
tool writers still have to support the existing 3.2 kernel and deal
with the 16G limit.

> Whatever the tools may be doing is not my concern.  Ideally the users
> and tool authors understand that 16G is insane for thinp metadata.  But
> in the event that they use 16G would you rather we reject them?

Yes, I would rather reject, than let people think they had 32G of
metadata.  It also forces the tool writers to do something sane.

I don't feel strongly enough about this to keep arguing.  So consider
this an ACK and see if you can get it past Alasdair.

- Joe

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