--- a/mm/mmap.c~mm-check-rb_subtree_gap-correctness-fix
+++ a/mm/mmap.c
@@ -372,16 +372,25 @@ static int browse_rb(struct rb_root *roo
 	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
 		struct vm_area_struct *vma;
 		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
-		if (vma->vm_start < prev)
-			printk("vm_start %lx prev %lx\n", vma->vm_start, prev), bug = 1;
-		if (vma->vm_start < pend)
-			printk("vm_start %lx pend %lx\n", vma->vm_start, pend), bug = 1;
-		if (vma->vm_start > vma->vm_end)
-			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start), bug = 1;
-		if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma))
+		if (vma->vm_start < prev) {
+			printk("vm_start %lx prev %lx\n", vma->vm_start, prev);
+			bug = 1;
+		}
+		if (vma->vm_start < pend) {
+			printk("vm_start %lx pend %lx\n", vma->vm_start, pend);
+			bug = 1;
+		}
+		if (vma->vm_start > vma->vm_end) {
+			printk("vm_end %lx < vm_start %lx\n",
+				vma->vm_end, vma->vm_start);
+			bug = 1;
+		}
+		if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
 			printk("free gap %lx, correct %lx\n",
 			       vma->rb_subtree_gap,
-			       vma_compute_subtree_gap(vma)), bug = 1;
+			       vma_compute_subtree_gap(vma));
+			bug = 1;
+		}
 		i++;
 		pn = nd;
 		prev = vma->vm_start;
@@ -390,8 +399,10 @@ static int browse_rb(struct rb_root *roo
 	j = 0;
 	for (nd = pn; nd; nd = rb_prev(nd))
 		j++;
-	if (i != j)
-		printk("backwards %d, forwards %d\n", j, i), bug = 1;
+	if (i != j) {
+		printk("backwards %d, forwards %d\n", j, i);
+		bug = 1;
+	}
 	return bug ? -1 : i;
 }
 
@@ -411,14 +422,20 @@ void validate_mm(struct mm_struct *mm)
 		vma = vma->vm_next;
 		i++;
 	}
-	if (i != mm->map_count)
-		printk("map_count %d vm_next %d\n", mm->map_count, i), bug = 1;
-	if (highest_address != mm->highest_vm_end)
+	if (i != mm->map_count) {
+		printk("map_count %d vm_next %d\n", mm->map_count, i);
+		bug = 1;
+	}
+	if (highest_address != mm->highest_vm_end) {
 		printk("mm->highest_vm_end %lx, found %lx\n",
-		       mm->highest_vm_end, highest_address), bug = 1;
+		       mm->highest_vm_end, highest_address);
+		bug = 1;
+	}
 	i = browse_rb(&mm->mm_rb);
-	if (i != mm->map_count)
-		printk("map_count %d rb %d\n", mm->map_count, i), bug = 1;
+	if (i != mm->map_count) {
+		printk("map_count %d rb %d\n", mm->map_count, i);
+		bug = 1;
+	}
 	BUG_ON(bug);
 }
 #else