mm/swap: Convert to percpu locked

Replace global locks (get_cpu + local_irq_save) with "local_locks()".
Currently there is one of for "rotate" and one for "swap".

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 33d7808..eb57892 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6559,7 +6559,9 @@
 	int cpu = (unsigned long)hcpu;
 
 	if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) {
+		local_lock_irq_on(swapvec_lock, cpu);
 		lru_add_drain_cpu(cpu);
+		local_unlock_irq_on(swapvec_lock, cpu);
 		drain_pages(cpu);
 
 		/*