linux-kernel - [PATCH x86,mm] fix pgt_buf

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Date:	Thu, 08 Sep 2011 17:33:55 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Tejun Heo <tj@...nel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Stephen Wilson <wilsons@...rt.ca>
Subject: [PATCH x86,mm]  fix pgt_buf_end when memory hotplug


When I test memory hotplug, such message is always outputted when hot-adding
a memory block:

initial kernel pagetable allocation wasted ffffffffffffffff pages

This message comes from init_memory_mapping(), it shows "pgt_buf_end" is
incorrect here, and I found it was caused by alloc_low_page().

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index bbaaa00..e138e0a 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -317,7 +317,7 @@ void __init cleanup_highmap(void)
 
 static __ref void *alloc_low_page(unsigned long *phys)
 {
-	unsigned long pfn = pgt_buf_end++;
+	unsigned long pfn;
 	void *adr;
 
 	if (after_bootmem) {
@@ -327,6 +327,7 @@ static __ref void *alloc_low_page(unsigned long *phys)
 		return adr;
 	}
 
+	pfn = pgt_buf_end++;
 	if (pfn >= pgt_buf_top)
 		panic("alloc_low_page: ran out of memory");
 
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