task_work: cleanup notification modes

A previous commit changed the notification mode from true/false to an
int, allowing notify-no, notify-yes, or signal-notify. This was
backwards compatible in the sense that any existing true/false user
would translate to either 0 (on notification sent) or 1, the latter
which mapped to TWA_RESUME. TWA_SIGNAL was assigned a value of 2.

Clean this up properly, and define a proper enum for the notification
mode. Now we have:

- TWA_NONE. This is 0, same as before the original change, meaning no
  notification requested.
- TWA_RESUME. This is 1, same as before the original change, meaning
  that we use TIF_NOTIFY_RESUME.
- TWA_SIGNAL. This uses TIF_SIGPENDING/JOBCTL_TASK_WORK for the
  notification.

Clean up all the callers, switching their 0/1/false/true to using the
appropriate TWA_* mode for notifications.

Fixes: e91b481623 ("task_work: teach task_work_add() to do signal_wake_up()")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/task_work.h

@@ -13,9 +13,14 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
 	twork->func = func;
 }
 
-#define TWA_RESUME	1
-#define TWA_SIGNAL	2
-int task_work_add(struct task_struct *task, struct callback_head *twork, int);
+enum task_work_notify_mode {
+	TWA_NONE,
+	TWA_RESUME,
+	TWA_SIGNAL,
+};
+
+int task_work_add(struct task_struct *task, struct callback_head *twork,
+			enum task_work_notify_mode mode);
 
 struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
 void task_work_run(void);