[PATCH] nodemask: use nr_node_ids instead of MAX_NUMNODES in __nodemask_pr_numnodes()

[lirongqing]

From: Li RongQing <lirongqing@xxxxxxxxx>

__nodemask_pr_numnodes() returns MAX_NUMNODES, a compile-time constant,
as the width for '%*pb[l]' nodemask printing. On systems with few NUMA
nodes this produces excessive zero-padding, e.g. with MAX_NUMNODES=1024
but only 2 nodes:

  Mems_allowed: 00000000,00000000,...,00000003  (32 groups)

Use nr_node_ids (the runtime highest-node-id + 1) instead, matching the
behavior of cpumask_pr_args() which uses nr_cpu_ids:

  Mems_allowed: 00000003

Move the nr_node_ids declaration earlier in the file (guarded by
__nodemask_pr_numnodes(), and remove the now-duplicate declarations.

Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
---
 include/linux/nodemask.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index b842aa5..35269ea 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -95,6 +95,12 @@
 
 extern nodemask_t _unused_nodemask_arg_;
 
+#if MAX_NUMNODES > 1
+extern unsigned int nr_node_ids;
+#else
+#define nr_node_ids		1U
+#endif
+
 /**
  * nodemask_pr_args - printf args to output a nodemask
  * @maskp: nodemask to be printed
@@ -105,7 +111,7 @@ extern nodemask_t _unused_nodemask_arg_;
 				__nodemask_pr_bits(maskp)
 static __always_inline unsigned int __nodemask_pr_numnodes(const nodemask_t *m)
 {
-	return m ? MAX_NUMNODES : 0;
+	return m ? nr_node_ids : 0;
 }
 static __always_inline const unsigned long *__nodemask_pr_bits(const nodemask_t *m)
 {
@@ -438,7 +444,6 @@ static __always_inline unsigned int next_memory_node(int nid)
 	return next_node(nid, node_states[N_MEMORY]);
 }
 
-extern unsigned int nr_node_ids;
 extern unsigned int nr_online_nodes;
 
 static __always_inline void node_set_online(int nid)
@@ -480,7 +485,6 @@ static __always_inline int num_node_state(enum node_states state)
 #define first_memory_node	0
 #define next_online_node(nid)	(MAX_NUMNODES)
 #define next_memory_node(nid)	(MAX_NUMNODES)
-#define nr_node_ids		1U
 #define nr_online_nodes		1U
 
 #define node_set_online(node)	   node_set_state((node), N_ONLINE)
-- 
2.9.4