x86: xen: use smp_call_function_many()

Impact: use new API, remove cpumask from stack.

Change smp_call_function_mask() callers to smp_call_function_many().

This removes a cpumask from the stack, and falls back should allocating
the cpumask var fail (only possible with CONFIG_CPUMASKS_OFFSTACK).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
Cc: jeremy@xensource.com

arch/x86/xen/mmu.c

@@ -1079,7 +1079,7 @@ static void drop_other_mm_ref(void *info)
 
 static void xen_drop_mm_ref(struct mm_struct *mm)
 {
-	cpumask_t mask;
+	cpumask_var_t mask;
 	unsigned cpu;
 
 	if (current->active_mm == mm) {
@@ -1091,7 +1091,16 @@ static void xen_drop_mm_ref(struct mm_struct *mm)
 	}
 
 	/* Get the "official" set of cpus referring to our pagetable. */
-	mask = mm->cpu_vm_mask;
+	if (!alloc_cpumask_var(&mask, GFP_ATOMIC)) {
+		for_each_online_cpu(cpu) {
+			if (!cpumask_test_cpu(cpu, &mm->cpu_vm_mask)
+			    && per_cpu(xen_current_cr3, cpu) != __pa(mm->pgd))
+				continue;
+			smp_call_function_single(cpu, drop_other_mm_ref, mm, 1);
+		}
+		return;
+	}
+	cpumask_copy(mask, &mm->cpu_vm_mask);
 
 	/* It's possible that a vcpu may have a stale reference to our
 	   cr3, because its in lazy mode, and it hasn't yet flushed
@@ -1100,11 +1109,12 @@ static void xen_drop_mm_ref(struct mm_struct *mm)
 	   if needed. */
 	for_each_online_cpu(cpu) {
 		if (per_cpu(xen_current_cr3, cpu) == __pa(mm->pgd))
-			cpu_set(cpu, mask);
+			cpumask_set_cpu(cpu, mask);
 	}
 
-	if (!cpus_empty(mask))
-		smp_call_function_mask(mask, drop_other_mm_ref, mm, 1);
+	if (!cpumask_empty(mask))
+		smp_call_function_many(mask, drop_other_mm_ref, mm, 1);
+	free_cpumask_var(mask);
 }
 #else
 static void xen_drop_mm_ref(struct mm_struct *mm)