ceph: message pools

The msgpool is a basic mempool_t-like structure to preallocate
messages we expect to receive over the wire.  This ensures we have the
necessary memory preallocated to process replies to requests, or to
process unsolicited messages from various servers.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --cc fs/ceph/msgpool.c
Simple merge

diff --cc fs/ceph/msgpool.h
Simple merge