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SubjectRe: [RFC][PATCH 0/2]efi_pstore: Avoid missing panic message in NVRAM
On Tue, Jul 03, 2012 at 11:33:57PM +0000, Seiji Aguchi wrote:
> [Problem]
> Current efi_pstore simply overwrites existing entries in NVRAM.
> So, if 2nd panic happens before a user checks 1st panic message, 1st panic message will be lost.

I thought the rule was entries do not get overwritten until they are
deleted first. Perhaps that is just an APEI thing, but it seems like that
should be a good rule for EFI too.

Mainly because there is very little userspace apps that actually clear the
old error records. So this could become a common problem.

Unless we are implementing a flight recorder option which explicitly
states overwrite older entries?

Cheers,
Don

>
> [Solution]
> To avoid missing 1st panic message, this patch introduce a rule checking if existing entries in NRAM are erasable to efi_pstore.
>
> [Patch Descriptions]
>
> [PATCH 1/2] Duplicate a shared code between write and erase callbacks
>
> Currently, efi_pstore driver shares a code erasing existing entries in NVRAM with write and erase callbacks.
> But there some cases we should avoid erasing existing entries in write callback. (Please see PATCH 2/2).
> This patch duplicates the code so that write and erase callbacks work independently.
>
>
> [PATCH 2/2] write callback: Check if existing entry is erasable
>
> this patch introduce a rule checking if existing entries in NRAM are erasable to efi_pstore.
> With this patch, if previous event is panic, efi_pstore never overwrite it.
>
>
> drivers/firmware/efivars.c | 94 +++++++++++++++++++++++++++++++++++++++++++-
> fs/pstore/platform.c | 4 +-
> include/linux/pstore.h | 5 ++
> 3 files changed, 99 insertions(+), 4 deletions(-)
>
> Seiji


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