[PATCH] Fix crash-on-boot in init_l440gx SMP

ioremap_nocache() doesn't need to check for physical address
wraps because __ioremap() has already done that;
fix calculation of npages to handle non-aligned phys_addr;

arch/i386/mm/ioremap.c

@@ -190,16 +190,27 @@ void * __ioremap(unsigned long phys_addr, unsigned long size, unsigned long flag
 
 void *ioremap_nocache (unsigned long phys_addr, unsigned long size)
 {
+	unsigned long last_addr;
 	void *p = __ioremap(phys_addr, size, _PAGE_PCD);
 	if (!p) 
 		return p; 
 
-	if (phys_addr + size < virt_to_phys(high_memory)) { 
+	/* Guaranteed to be > phys_addr, as per __ioremap() */
+	last_addr = phys_addr + size - 1;
+
+	if (last_addr < virt_to_phys(high_memory)) { 
 		struct page *ppage = virt_to_page(__va(phys_addr));		
-		unsigned long npages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+		unsigned long npages;
+
+		phys_addr &= PAGE_MASK;
+
+		/* This might overflow and become zero.. */
+		last_addr = PAGE_ALIGN(last_addr);
 
-		BUG_ON(phys_addr+size > (unsigned long)high_memory);
-		BUG_ON(phys_addr + size < phys_addr);
+		/* .. but that's ok, because modulo-2**n arithmetic will make
+	 	* the page-aligned "last - first" come out right.
+	 	*/
+		npages = (last_addr - phys_addr) >> PAGE_SHIFT;
 
 		if (change_page_attr(ppage, npages, PAGE_KERNEL_NOCACHE) < 0) { 
 			iounmap(p);