linux-kernel - [PATCH v4] include/linux/nodemask.h: Use nr_node_ids (not MAX_NUMNODES) in __nodemask_pr

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Date:   Fri, 21 Dec 2018 10:20:31 -0500
From:   Waiman Long <longman@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Oscar Salvador <osalvador@...e.de>,
        Tejun Heo <tj@...nel.org>, Waiman Long <longman@...hat.com>
Subject: [PATCH v4] include/linux/nodemask.h: Use nr_node_ids (not MAX_NUMNODES) in __nodemask_pr_numnodes()

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.

 v4: Fix build problem with MAX_NUMNODES=1.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/nodemask.h | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 5a30ad5..2fc99ac 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -98,6 +98,14 @@
 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	1
+#define nr_online_nodes	1
+#endif
+
 /**
  * nodemask_pr_args - printf args to output a nodemask
  * @maskp: nodemask to be printed
@@ -108,7 +116,7 @@
 				__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 +452,6 @@ 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);
@@ -485,8 +490,6 @@ static inline int num_node_state(enum node_states state)
 #define first_online_node	0
 #define first_memory_node	0
 #define next_online_node(nid)	(MAX_NUMNODES)
-#define nr_node_ids		1
-#define nr_online_nodes		1
 
 #define node_set_online(node)	   node_set_state((node), N_ONLINE)
 #define node_set_offline(node)	   node_clear_state((node), N_ONLINE)
-- 
1.8.3.1