[PATCH] Bug in MM_RB debugging

The code is seemingly trying to make sure that rb_next() brings us to
successive increasing vma entries.

But the two variables, prev and pend, used to perform these checks, are
never advanced.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Cc: Andrea Arcangeli <andrea@novell.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

@@ -299,6 +299,8 @@ static int browse_rb(struct rb_root *root)
 			printk("vm_end %lx < vm_start %lx\n", vma->vm_end, vma->vm_start);
 		i++;
 		pn = nd;
+		prev = vma->vm_start;
+		pend = vma->vm_end;
 	}
 	j = 0;
 	for (nd = pn; nd; nd = rb_prev(nd)) {