futex: add wake_data to struct futex_q

With handling multiple futex_q for waitv, we cannot easily go from the
futex_q to data related to that request or queue. Add a wake_data
argument that belongs to the wake handler assigned.
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

kernel/futex/futex.h

@@ -148,6 +148,7 @@ typedef void (futex_wake_fn)(struct wake_q_head *wake_q, struct futex_q *q);
  * @task:		the task waiting on the futex
  * @lock_ptr:		the hash bucket lock
  * @wake:		the wake handler for this queue
+ * @wake_data:		data associated with the wake handler
  * @key:		the key the futex is hashed on
  * @pi_state:		optional priority inheritance state
  * @rt_waiter:		rt_waiter storage for use with requeue_pi
@@ -173,6 +174,7 @@ struct futex_q {
 	struct task_struct *task;
 	spinlock_t *lock_ptr;
 	futex_wake_fn *wake;
+	void *wake_data;
 	union futex_key key;
 	struct futex_pi_state *pi_state;
 	struct rt_mutex_waiter *rt_waiter;