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

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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>
This commit is contained in:
Yinghai Lu 2011-05-01 19:12:04 +02:00 committed by Ingo Molnar
parent e20a2d205c
commit 2be19102b7
1 changed files with 1 additions and 1 deletions
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2
arch/x86/mm/numa_64.c
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@ -306,7 +306,7 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
bi->end = min(bi->end, high); bi->end = min(bi->end, high);
/* and there's no empty block */ /* and there's no empty block */
if (bi->start == bi->end) { if (bi->start >= bi->end) {
numa_remove_memblk_from(i--, mi); numa_remove_memblk_from(i--, mi);
continue; continue;
} }