From 37b000b640741132eddaa9fbeca1f988139ad7e2 Mon Sep 17 00:00:00 2001
From: Xishi Qiu <qiuxishi@huawei.com>
Date: Wed, 11 Sep 2013 14:21:41 -0700
Subject: [PATCH] mm/hotplug: remove unnecessary BUG_ON in __offline_pages()

I think we can remove "BUG_ON(start_pfn >= end_pfn)" in __offline_pages(),
because in memory_block_action() "nr_pages = PAGES_PER_SECTION * sections_per_block"
is always greater than 0.

memory_block_action()
	offline_pages()
		__offline_pages()
			BUG_ON(start_pfn >= end_pfn)

In v2.6.32, If info->length==0, this way may hit this BUG_ON().
acpi_memory_disable_device()
	remove_memory(info->start_addr, info->length)
			offline_pages()

A later Fujitsu patch renamed this function and the BUG_ON() is
unnecessary.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/memory_hotplug.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index ca1dd3aa5eee..8e333f953f08 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1472,7 +1472,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	struct zone *zone;
 	struct memory_notify arg;
 
-	BUG_ON(start_pfn >= end_pfn);
 	/* at least, alignment against pageblock is necessary */
 	if (!IS_ALIGNED(start_pfn, pageblock_nr_pages))
 		return -EINVAL;