[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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