[tip:x86/urgent] x86, NUMA: Fix empty memblk detection in numa_cleanup_meminfo()

[tip-bot for Yinghai Lu <yinghai@kernel.org>]

Commit-ID:  2be19102b71c1a45d37fec50303791daa1a06869
Gitweb:     http://git.kernel.org/tip/2be19102b71c1a45d37fec50303791daa1a06869
Author:     Yinghai Lu <yinghai@kernel.org>
AuthorDate: Sun, 1 May 2011 19:12:04 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Sun, 1 May 2011 19:15:11 +0200

x86, NUMA: Fix empty memblk detection in numa_cleanup_meminfo()

numa_cleanup_meminfo() trims each memblk between low (0) and
high (max_pfn) limits and discards empty ones.  However, the
emptiness detection incorrectly used equality test.  If the
start of a memblk is higher than max_pfn, it is empty but fails
the equality test and doesn't get discarded.

The condition triggers when max_pfn is lower than start of a
NUMA node and results in memory misconfiguration - leading to
WARN_ON()s and other funnies.  The bug was discovered in devel
branch where 32bit too uses this code path for NUMA init.  If a
node is above the addressing limit, max_pfn ends up lower than
the node triggering this problem.

The failure hasn't been observed on x86-64 but is still possible
with broken hardware e820/NUMA info.  As the fix is very low
risk, it would be better to apply it even for 64bit.

Fix it by using >= instead of ==.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
[ Extracted the actual fix from the original patch and rewrote patch description. ]
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20110501171204.GO29280@htj.dyndns.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/mm/numa_64.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index e8c00cc..85b52fc 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -306,7 +306,7 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
 		bi->end = min(bi->end, high);
 
 		/* and there's no empty block */
-		if (bi->start == bi->end) {
+		if (bi->start >= bi->end) {
 			numa_remove_memblk_from(i--, mi);
 			continue;
 		}