[PATCH V2] mm/page: refine the calculation of highest possible node id

[Wei Yang <weiyang@linux.vnet.ibm.com>]

nr_node_ids records the highest possible node id, which is calculated by
scanning the bitmap node_states[N_POSSIBLE]. Current implementation scan
the bitmap from the beginning, which will scan the whole bitmap.

This patch reverse the order by scanning from the end with find_last_bit().

Signed-off-by: Wei Yang <weiyang@linux.vnet.ibm.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Tejun Heo <tj@kernel.org>

---
v2:
   Just call find_last_bit() on node_possible_map.
---
 mm/page_alloc.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 59248f4..f8d0a98 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5450,10 +5450,9 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 void __init setup_nr_node_ids(void)
 {
 	unsigned int node;
-	unsigned int highest = 0;
+	unsigned int highest;
 
-	for_each_node_mask(node, node_possible_map)
-		highest = node;
+	highest = find_last_bit(node_possible_map.bits, MAX_NUMNODES);
 	nr_node_ids = highest + 1;
 }
 #endif
-- 
1.7.9.5

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