Replace list operation with RCU primitives and replace
down_read()/up_read() with srcu_read_lock()/srcu_read_unlock().
Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: NSerge Hallyn <serue@us.ibm.com>
Signed-off-by: NJames Morris <jmorris@namei.org>