From 65513f34449eedb6b84c24a3583266534c1627e4 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 11 Mar 2013 17:09:55 +0100
Subject: [PATCH 2/6] x86/highmem: add a "already used pte" check

This is a copy from kmap_atomic_prot().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/mm/iomap_32.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -65,6 +65,8 @@ void *kmap_atomic_prot_pfn(unsigned long
 	type = kmap_atomic_idx_push();
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
+	WARN_ON(!pte_none(*(kmap_pte - idx)));
+
 #ifdef CONFIG_PREEMPT_RT_FULL
 	current->kmap_pte[type] = pte;
 #endif