linux-kernel - Re: [PATCH 3/3] powerpc/pseries: Support compression of oops text via pstore

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Message-ID: <51CC08FC.6000301@linux.vnet.ibm.com>
Date:	Thu, 27 Jun 2013 15:12:20 +0530
From:	Aruna Balakrishnaiah <aruna@...ux.vnet.ibm.com>
To:	"Luck, Tony" <tony.luck@...el.com>
CC:	Kees Cook <keescook@...omium.org>,
	"jkenisto@...ux.vnet.ibm.com" <jkenisto@...ux.vnet.ibm.com>,
	Colin Cross <ccross@...roid.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Anton Vorontsov <cbouatmailru@...il.com>,
	"linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>,
	"paulus@...ba.org" <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	"mahesh@...ux.vnet.ibm.com" <mahesh@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/3] powerpc/pseries: Support compression of oops text
 via pstore

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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