The current code for multi-thread compression is not clear,
especially in the aspect of using lock. Refine the code
to make it clear.
Signed-off-by: Liang Li <liang.z.li@intel.com>
Message-Id: <1462433579-13691-8-git-send-email-liang.z.li@intel.com>
Signed-off-by: Amit Shah <amit.shah@redhat.com>