staging/lustre/clio: Solve a race in cl_lock_put
staging/lustre/clio: Solve a race in cl_lock_put

It's not atomic to check the last reference and state of cl_lock
in cl_lock_put(). This can cause a problem that an using lock is
freed, if the process is preempted between atomic_dec_and_test()
and (lock->cll_state == CLS_FREEING).

This problem can be solved by holding a refcount by coh_locks. In
this case, it can be sure that if the lock refcount reaches zero,
nobody else can have any chance to use it again.

Signed-off-by: Jinshan Xiong <4f9c0b864b7f9eb8a22fd0e8ad685c34bbc01268@intel.com>
Reviewed-on: http://review.whamcloud.com/9881
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4558
Reviewed-by: Bobi Jam <5e451d3f5f035e14a83905a8d5b052763fc3f4cb@gmail.com>
Reviewed-by: Lai Siyao <3de0ff1f562be7153cd883e1be3e88580ec32e8b@intel.com>
Signed-off-by: Oleg Drokin <65b2ca07820e940f66d8901813c729ec10a548f5@intel.com>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs