[PATCH v3 0/7] efi_pstore: multiple event logging support

[Seiji Aguchi]

Changelog

v2 -> v3
   - Create patches 6/7 and 7/7 to work with an existing format of variable name

v1 -> v2
   - Separate into 5 patches in accordance with Mike's comment
   - Erase an extra line of comment in patch 1/5

[Issue]

    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]

(1/7) efi_pstore: Check remaining space with QueryVariableInfo() before writing data

(2/7) efi_pstore: Add a logic erasing entries to an erase callback

(3/7) efi_pstore: Remove a logic erasing entries from a write callback to hold multiple logs

(4/7) efi_pstore: Add ctime to argument of erase callback

(5/7) efi_pstore: Change a format of a variable name by adding a sequence counter

(6/7) efi_pstore: Add a format check for an existing variable name at reading time

(7/7) efi_pstore: Add a format check for an existing variable name at erasing time

Detailed explanations are written in each patch.

 drivers/acpi/apei/erst.c   |   16 +++---
 drivers/firmware/efivars.c |  150 ++++++++++++++++++++++++++++++-------------
 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, 133 insertions(+), 69 deletions(-)

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