linux-kernel - [PATCH] mm,x86: fix span coverage in e820_all

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Message-ID: <52A6D9B0.7040506@huawei.com>
Date:	Tue, 10 Dec 2013 17:06:56 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<x86@...nel.org>, <linn@...com>, <penberg@...nel.org>,
	<yinghai@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, <linux-mm@...ck.org>
CC:	Xishi Qiu <qiuxishi@...wei.com>
Subject: [PATCH] mm,x86: fix span coverage in e820_all_mapped()

In the following case, e820_all_mapped() will return 1.
A < start < B-1 and B < end < C, it means <start, end> spans two regions.
<start, end>:	        [start - end]
e820 addr:	    ...[A - B-1][B - C]...

Signed-off-by: Xishi Qiu <qiuxishi@...wei.com>
---
 arch/x86/kernel/e820.c |   15 +++------------
 1 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 174da5f..31ecab2 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -85,20 +85,11 @@ int __init e820_all_mapped(u64 start, u64 end, unsigned type)
 
 		if (type && ei->type != type)
 			continue;
-		/* is the region (part) in overlap with the current region ?*/
+		/* is the region (part) in overlap with the current region ? */
 		if (ei->addr >= end || ei->addr + ei->size <= start)
 			continue;
-
-		/* if the region is at the beginning of <start,end> we move
-		 * start to the end of the region since it's ok until there
-		 */
-		if (ei->addr <= start)
-			start = ei->addr + ei->size;
-		/*
-		 * if start is now at or beyond end, we're done, full
-		 * coverage
-		 */
-		if (start >= end)
+		/* is the region full coverage of <start, end> ? */
+		if (ei->addr <= start && ei->addr + ei->size >= end)
 			return 1;
 	}
 	return 0;
-- 
1.7.1


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