linux-kernel - [RFC][PATCH 0/2] efi_pstore: multiple event logging support

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Message-ID: <A5ED84D3BB3A384992CBB9C77DEDA4D41386D0F8@USINDEM103.corp.hds.com>
Date:	Fri, 5 Oct 2012 19:00:14 +0000
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"mikew@...gle.com" <mikew@...gle.com>
CC:	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: [RFC][PATCH 0/2] efi_pstore: multiple event logging support

[Problem]

    Currently, efi_pstore driver simply overwrites existing panic messages in NVRAM.
    So, in the following scenario, we will lose 1st panic messages.

    1. kernel panics.
    2. efi_pstore is kicked and writes panic messages to NVRAM.
    3. system reboots.
    4. kernel panics again before a user checks the 1st panic messages in NVRAM.

[Solution]
   
   Solutions of this problem has been discussed among Tony, Matthew, Don, Mike and me.

   http://marc.info/?l=linux-kernel&m=134273270704586&w=2

   And there are two possible solutions right now.
     - First one is introducing some policy overwriting existing logs. 
     - Second one is simply holding multiple log without overwriting any entries. 

   We haven't decided the overwriting policy which is reasonable to all users yet. 
   But I believe we agree that just holding multiple logs is a reasonable way.

   We may need further discussions to find the possibility of introducing overwriting 
   policy, especially getting critical messages in multiple oops case.
   But I would like to begin with a simple and reasonable way to everyone.
   So, this patch takes an approach just holding multiple logs.

[Patch Description]

(1/2) efi_pstore: hold multiple logs
  This patch makes efi_pstore hold multiple logs.
  Once a critical message is logged, users can see it via /dev/pstore 
  without being influenced by subsequent events.

(2/2) efi_pstore: add a sequence counter to a variable name
  This patch fix an issue in case where multiple events happens in a short time  

Detailed explanations are written in each patch.

 drivers/acpi/apei/erst.c   |   16 +++---
 drivers/firmware/efivars.c |  106 ++++++++++++++++++++++++++++---------------
 fs/pstore/inode.c          |    7 ++-
 fs/pstore/internal.h       |    2 +-
 fs/pstore/platform.c       |   11 +++--
 fs/pstore/ram.c            |    9 ++--
 include/linux/efi.h        |    1 +
 include/linux/pstore.h     |    6 ++-
 8 files changed, 98 insertions(+), 60 deletions(-)

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