linux-kernel - Re: [Patch - Resend v4] Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

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Date:	Mon, 1 Feb 2010 20:22:02 +0800
From:	Shaohui Zheng <shaohui.zheng@...el.com>
To:	Wu Fengguang <fengguang.wu@...el.com>, akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org, y-goto@...fujitsu.com,
	haveblue@...ibm.com, kamezawa.hiroyu@...fujitsu.com,
	ak@...ux.intel.com, fengguang.wu@...el.com, hpa@...nel.org,
	haicheng.li@...el.com, shaohui.zheng@...ux.intel.com
Subject: Re: [Patch - Resend v4] Memory-Hotplug: Fix the bug on interface
 /dev/mem for 64-bit kernel

On Mon, Feb 01, 2010 at 12:41:24PM +0800, Wu Fengguang wrote:
> Shaohui,
> 
> Some style nitpicks..
> 
> >  #ifdef CONFIG_MEMORY_HOTPLUG
> > +/**
> 
> Should use /* here. 
Agree.
> 
> > + * After memory hotplug, the variable max_pfn, max_low_pfn and high_memory will
> > + * be affected, it will be updated in this function.
> > + */
> > +static inline void __meminit update_end_of_memory_vars(u64 start,
> 
> The "inline" and "__meminit" are both redundant here.
will remove both.
> 
> > +		max_low_pfn = max_pfn = end_pfn;
> 
> One assignment per line is preferred.
will change to 2 statements.
> 
> Thanks,
> Fengguang

Memory-Hotplug: Fix the bug on interface /dev/mem for 64-bit kernel

The new added memory can not be access by interface /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 
kernel.

CC: Andi Kleen <ak@...ux.intel.com>
CC: Li Haicheng <haicheng.li@...el.com>
Reviewed-by: Wu Fengguang <fengguang.wu@...el.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Signed-off-by: Shaohui Zheng <shaohui.zheng@...el.com>
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 5198b9b..e1c9202 100644
--- 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;
 
@@ -616,6 +617,21 @@ void __init paging_init(void)
  */
 #ifdef CONFIG_MEMORY_HOTPLUG
 /*
+ * After memory hotplug, the variables max_pfn, max_low_pfn and high_memory will
+ * be affected, they will be updated in this function.
+ */
+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);
-- 
Thanks & Regards,
Shaohui


View attachment "memory-hotplug-fix-the-bug-on-interface-dev-mem-v5.patch" of type "text/x-diff" (1763 bytes)