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Commit ea085417 authored by Shaohui Zheng's avatar Shaohui Zheng Committed by Linus Torvalds
Browse files

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: default avatarShaohui Zheng <shaohui.zheng@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Li Haicheng <haicheng.li@intel.com>
Reviewed-by: default avatarWu Fengguang <fengguang.wu@intel.com>
Reviewed-by: default avatarKAMEZAWA 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a225a5cc

arch/x86/mm/init_64.c

+19 −0
Original line number Diff line number Diff line
@@ -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);