Date: Mon, 11 Aug 2008 17:14:33 -0600
From: Jonathan Corbet <corbet@lwn.net>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>,
       "Serge E. Hallyn" <serue@us.ibm.com>,
       containers@lists.linux-foundation.org, Theodore Tso <tytso@mit.edu>,
       linux-kernel@vger.kernel.org
Subject: Re: checkpoint/restart ABI
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On Mon, 11 Aug 2008 23:47:49 +0200
Arnd Bergmann <arnd@arndb.de> wrote:

> The other problem that you really need to solve is interface
> stability. What you are creating is a binary representation
> of many kernel internal data structures, so in our common
> rules, you have to make sure that you remain forward and
> backward compatible. Simply saying that you need to run
> an identical kernel when restarting from a checkpoint is not
> enough IMHO.

OTOH, making one of these checkpoint files go into any 2.6.x kernel
seems like a very high bar, to the point, perhaps, of killing this
feature entirely.  

There could be a case for viewing sys_restore() as being a lot like
sys_init_module() - a view into kernel internals that goes beyond the
normal user-space ABI, and beyond the stability guarantee.  It might be
possible to create a certain amount of version portability with a
modversions-like mechanism, but it sure seems hard to do better than
that.

jon
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