[PATCH v3] include/linux/nodemask.h: Use nr_node_ids (not MAX_NUMNODES) in __nodemask_pr_numnodes()

[Waiman Long]

When viewing the /proc/<pid>/status file, one can see output lines like

  Cpus_allowed:	ffffffff,ffffffff,ffffffff
  Cpus_allowed_list:	0-95
  Mems_allowed:	00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,0000000f
  Mems_allowed_list:	0-3

The "Mems_allowed" line uses the "%*pb" format string while the
"Mems_allowed_list" line uses the "%*pbl" format string together with
the nodemask_pr_args() macro.

The "Mems_allowed" looks insane compared with the others.  It is because
the nodemask_pr_args() macro uses MAX_NUMNODES as the number of nodes
to iterate. The cpumask_pr_args() macro uses nr_cpu_ids instead of
MAX_CPUS. For nodes, there is a corresponding nr_node_ids.  So it makes
sense to use nr_node_ids instead to be consistent with "Cpus_allowed:".

With that change, the "Mems_allowed" line becomes sane again.

  Mems_allowed:	f

There are currently 10 call sites of nodemask_pr_args() in the kernel.
Of them, only cpuset_task_status_allowed() in kernel/cgroup/cpuset.c
uses the "%*pb" format string that will be affected by this change. That
cpuset function is called by proc_pid_status() only.

 v3: Fix build problem with MAX_NUMNODES=1.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
 include/linux/nodemask.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 5a30ad5..9e3a30d 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -98,6 +98,13 @@
 typedef struct { DECLARE_BITMAP(bits, MAX_NUMNODES); } nodemask_t;
 extern nodemask_t _unused_nodemask_arg_;
 
+#if MAX_NUMNODES > 1
+extern int nr_node_ids;
+extern int nr_online_nodes;
+#else
+#define nr_node_ids	MAX_NUMNODES
+#endif
+
 /**
  * nodemask_pr_args - printf args to output a nodemask
  * @maskp: nodemask to be printed
@@ -108,7 +115,7 @@
 				__nodemask_pr_bits(maskp)
 static inline unsigned int __nodemask_pr_numnodes(const nodemask_t *m)
 {
-	return m ? MAX_NUMNODES : 0;
+	return m ? nr_node_ids : 0;
 }
 static inline const unsigned long *__nodemask_pr_bits(const nodemask_t *m)
 {
@@ -444,9 +451,6 @@ static inline int next_memory_node(int nid)
 	return next_node(nid, node_states[N_MEMORY]);
 }
 
-extern int nr_node_ids;
-extern int nr_online_nodes;
-
 static inline void node_set_online(int nid)
 {
 	node_set_state(nid, N_ONLINE);
-- 
1.8.3.1