[PATCH v4 RESEND 2/3] mm/sparse: more check on mem_section number

[Gavin Shan <shangw@linux.vnet.ibm.com>]

Function __section_nr() was implemented to retrieve the corresponding
memory section number according to its descriptor. It's possible that
the specified memory section descriptor isn't existing in the global
array. So here to add more check on that and report error for wrong
case.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
---
 mm/sparse.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index d882e88..51950de 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -130,6 +130,8 @@ int __section_nr(struct mem_section* ms)
 		     break;
 	}
 
+	VM_BUG_ON(root_nr == NR_SECTION_ROOTS);
+
 	return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
 }
 
-- 
1.7.5.4

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