1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 61a6ac8fa8f..5c660c77f03 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -426,20 +426,18 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 		 * p2m are consistent.
 		 */
 		if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-			unsigned long p;
-			struct page   *scratch_page = get_balloon_scratch_page();
-
 			if (!PageHighMem(page)) {
+				struct page *scratch_page = get_balloon_scratch_page();
+
 				ret = HYPERVISOR_update_va_mapping(
 						(unsigned long)__va(pfn << PAGE_SHIFT),
 						pfn_pte(page_to_pfn(scratch_page),
 							PAGE_KERNEL_RO), 0);
 				BUG_ON(ret);
-			}
-			p = page_to_pfn(scratch_page);
-			__set_phys_to_machine(pfn, pfn_to_mfn(p));
 
-			put_balloon_scratch_page();
+				put_balloon_scratch_page();
+			}
+			__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 		}
 #endif
 
@@ -604,19 +602,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
 	}
 }
 
+static int alloc_balloon_scratch_page(int cpu)
+{
+	if (per_cpu(balloon_scratch_page, cpu) != NULL)
+		return 0;
+
+	per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
+	if (per_cpu(balloon_scratch_page, cpu) == NULL) {
+		pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+
 static int balloon_cpu_notify(struct notifier_block *self,
 				    unsigned long action, void *hcpu)
 {
 	int cpu = (long)hcpu;
 	switch (action) {
 	case CPU_UP_PREPARE:
-		if (per_cpu(balloon_scratch_page, cpu) != NULL)
-			break;
-		per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
-		if (per_cpu(balloon_scratch_page, cpu) == NULL) {
-			pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+		if (alloc_balloon_scratch_page(cpu))
 			return NOTIFY_BAD;
-		}
 		break;
 	default:
 		break;
@@ -636,15 +644,17 @@ static int __init balloon_init(void)
 		return -ENODEV;
 
 	if (!xen_feature(XENFEAT_auto_translated_physmap)) {
-		for_each_online_cpu(cpu)
-		{
-			per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
-			if (per_cpu(balloon_scratch_page, cpu) == NULL) {
-				pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+		register_cpu_notifier(&balloon_cpu_notifier);
+
+		get_online_cpus();
+		for_each_online_cpu(cpu) {
+			if (alloc_balloon_scratch_page(cpu)) {
+				put_online_cpus();
+				unregister_cpu_notifier(&balloon_cpu_notifier);
 				return -ENOMEM;
 			}
 		}
-		register_cpu_notifier(&balloon_cpu_notifier);
+		put_online_cpus();
 	}
 
 	pr_info("Initialising balloon driver\n");