Re: [PATCH 3/3] powerpc/pseries: Support compression of oops textvia pstore

From: Aruna Balakrishnaiah
Date: Thu Jun 27 2013 - 05:42:39 EST


Hi Tony,

On Tuesday 25 June 2013 09:32 PM, Luck, Tony wrote:
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.

openssl command line tool can be used to decompress the compressed data of
the pstore file in the above scenario.

Usage:

cat <file> | openssl zlib -d

-Tony


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