staging/lustre/llite: Solve a race to access lli_has_smd in read case

staging/lustre/llite: Solve a race to access lli_has_smd in read case

In vvp_io_read_lock(), it used to decide if to add read lock by
checking lli_has_smd. Accessing lli_has_smd is racy when an empty
file is turned into raid0, therefore, it may result in read requests
are issued without corresponding lock.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/12139
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5062
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>