We need to use rcu_read_lock/unlock to avoid potential
race.
Reported-by: NShaohua Li <shli@fb.com>
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>