(resubmit) relay interface bugfixes and early logging support

Thanks to Andrea Righi for pointing out an error in patch number 2. I resubmitted the whole patch series because there were some problems reported by scripts/checkpatch.pl.

I apologize for any inconvenience caused.

Eduard - Gabriel Munteanu (3):
relay: Fix 4 off-by-one errors occuring when writing to a CPU buffer.
relay: Fix race condition which occurs when reading across CPUs.
relay: Add buffer-only channels; useful for early logging.

 Documentation/filesystems/relay.txt |   11 +++
 include/linux/relay.h               |   19 ++++--
 kernel/relay.c                      |  136 ++++++++++++++++++++++++++---------
 3 files changed, 127 insertions(+), 39 deletions(-)