Changes from v1:
- Allocate compression workspace during initialisation as
per Tony's suggestion
- Copy the recent messages from big_oops_buf to psinfo->buf
when compression fails, since the printk buffer
would be fetched for compression calling it again when
compression fails would have moved the iterator of
printk buffer which results in fetching old contents.
The patchset adds compression and decompression support to pstore.
As the non-volatile storage space is limited, adding compression
support results in capturing more data within limited space.
Size of dmesg file in a powerpc/pseries box with nvram's
oops partition (to store oops-log) size 4k:
dmesg-nvram-1: ~ 4k (3980)
dmesg-nvram-1: ~8.8k (8844)
Writing to persistent store
Compression will reduce the size of oops/panic report to atmost 45% of its
original size. (Based on experiments done while providing compression
to nvram by Jim keniston).
Hence buffer of size ( (100/45 approx 2.22) * is
The compression parameters selected based on some experiments:
compression_level = 6, window_bits = 12, memory_level = 4 achieved a
Data is compressed from the bigger buffer to registered buffer which is
returned to backends.
Pstore will indicate that with a flag 'compressed' which is passed to
Using this flag, backends will add a flag in their header to indicate the
is compressed or not while writing to persistent store.
Reading from persistent store
When backends read data from persistent store it will use the flag added by
while writing to persistent store to determine if the data is compressed or
Using the information, it will set the flag in pstore's read call back.
Pstore will decompress the data based on the flag and writes decompressed
to the file.
Have tested the patches on powerpc/pseries.
Needs testing with erst backend, efivars and persistent ram.
Aruna Balakrishnaiah (11):
powerpc/pseries: Remove (de)compression in nvram with pstore enabled
pstore: Add new argument 'compressed' in pstore write callback
pstore/Kconfig: Select ZLIB_DEFLATE and ZLIB_INFLATE when PSTORE is
pstore: Add compression support to pstore
pstore: Introduce new argument 'compressed' in the read callback
pstore: Add decompression support to pstore
pstore: Add file extension to pstore file if compressed
powerpc/pseries: Read and write to the 'compressed' flag of pstore
erst: Read and write to the 'compressed' flag of pstore
efi-pstore: Read and write to the 'compressed' flag of pstore
pstore/ram: Read and write to the 'compressed' flag of pstore
arch/powerpc/platforms/pseries/nvram.c | 112 +++--------------
drivers/acpi/apei/erst.c | 21 ++-
drivers/firmware/efi/efi-pstore.c | 27 +++-
fs/pstore/Kconfig | 2
fs/pstore/inode.c | 7 +
fs/pstore/internal.h | 5 -
fs/pstore/platform.c | 212
fs/pstore/ram.c | 41 +++++-
include/linux/pstore.h | 6 -
9 files changed, 299 insertions(+), 134 deletions(-)