mm/page_alloc: Use migrate_disable() in drain_local_pages_wq()

The drain_local_pages_wq() uses preempt_disable() to ensure that there
will be no CPU migration while drain_local_pages() is invoked which
might happen if the CPU is going down.
drain_local_pages() acquires a sleeping lock on RT which can not be
acquired with disabled preemption.

Use migrate_disable() instead of preempt_disable(): On RT it ensures
that the CPU won't go down and on !RT it is replaced with
preempt_disable().

Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Alexander Winkowski <[email protected]>

mm/page_alloc.c

@@ -2668,9 +2668,9 @@ static void drain_local_pages_wq(struct work_struct *work)
 	 * cpu which is allright but we also have to make sure to not move to
 	 * a different one.
 	 */
-	preempt_disable();
+	migrate_disable();
 	drain_local_pages(drain->zone);
-	preempt_enable();
+	migrate_enable();
 }
 
 /*