[PATCH 3/3] powerpc/pseries: Support compression of oops text via pstore

[Luck, Tony]

> Introducing headersize in pstore_write() API would need changes at
> multiple places whereits being called. The idea is to move the
> compression support to pstore infrastructure so that other platforms
> could also make use of it.

Any thoughts on the back/forward compatibility as we switch to compressed
pstore data?   E.g. imagine I have a system installed with some Linux distribution
with a kernel too old to know about compressed pstore. I use that machine to
run the latest kernels that do compression ... and one fine day one of them crashes
hard - logging in compressed form to pstore. Now I boot my distro kernel to pick
up the pieces ... what do I see in /sys/fs/pstore/*? Some compressed files? Can I
read them with some tool?

This somewhat of a corner case - but not completely unrealistic ... I'd at least
like to be reassured that the old kernel won't choke when it sees the compressed
blobs.

-Tony