memory hotplug: fix a bug on /dev/mem for 64-bit kernels

Newly added memory can not be accessed via /dev/mem, because we do not
update the variables high_memory, max_pfn and max_low_pfn.

Add a function update_end_of_memory_vars() to update these variables for
64-bit kernels.

[akpm@linux-foundation.org: simplify comment]
Signed-off-by: Shaohui Zheng <shaohui.zheng@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Li Haicheng <haicheng.li@intel.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5198b9bb34ef8eb86da0be3e6962a2456d4f9d64..69ddfbd911357534125bc5bb300776562a747ad8 100644 (file)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -49,6 +49,7 @@
 #include <asm/numa.h>
 #include <asm/cacheflush.h>
 #include <asm/init.h>
+#include <linux/bootmem.h>
 
 static unsigned long dma_reserve __initdata;
 
@@ -615,6 +616,21 @@ void __init paging_init(void)
  * Memory hotplug specific functions
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
+/*
+ * After memory hotplug the variables max_pfn, max_low_pfn and high_memory need
+ * updating.
+ */
+static void  update_end_of_memory_vars(u64 start, u64 size)
+{
+       unsigned long end_pfn = PFN_UP(start + size);
+
+       if (end_pfn > max_pfn) {
+               max_pfn = end_pfn;
+               max_low_pfn = end_pfn;
+               high_memory = (void *)__va(max_pfn * PAGE_SIZE - 1) + 1;
+       }
+}
+
 /*
  * Memory is added always to NORMAL zone. This means you will never get
  * additional DMA/DMA32 memory.
@@ -634,6 +650,9 @@ int arch_add_memory(int nid, u64 start, u64 size)
        ret = __add_pages(nid, zone, start_pfn, nr_pages);
        WARN_ON_ONCE(ret);
 
+       /* update max_pfn, max_low_pfn and high_memory */
+       update_end_of_memory_vars(start, size);
+
        return ret;
 }
 EXPORT_SYMBOL_GPL(arch_add_memory);