cpumask: make nr_cpu_ids valid in all configurations.

nr_cpu_ids is the (badly named) runtime limit on possible CPU numbers;
ie. the variable version of NR_CPUS.

This makes is valid in all configs, including UP.

From: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Mike Travis <travis@sgi.com>
---
 include/linux/cpumask.h |    9 +++++++--
 init/main.c             |    7 +++++++
 2 files changed, 14 insertions(+), 2 deletions(-)

diff -r a8fed8d3197c include/linux/cpumask.h
--- a/include/linux/cpumask.h	Wed Oct 22 10:25:39 2008 +1100
+++ b/include/linux/cpumask.h	Wed Oct 22 10:43:15 2008 +1100
@@ -194,6 +194,13 @@ extern cpumask_t _unused_cpumask_arg_;
 #define cpus_addr(src) ((src).bits)
 /* End deprecated region. */
 
+#if NR_CPUS > 1
+/* Starts at NR_CPUS until we know better. */
+extern int nr_cpu_ids;
+#else
+#define nr_cpu_ids	NR_CPUS
+#endif
+
 static inline void cpumask_set_cpu(int cpu, volatile struct cpumask *dstp)
 {
 	set_bit(cpu, dstp->bits);
@@ -433,7 +440,6 @@ extern cpumask_t cpu_mask_all;
 
 #if NR_CPUS == 1
 
-#define nr_cpu_ids			1
 #define first_cpu(src)			({ (void)(src); 0; })
 #define next_cpu(n, src)		({ (void)(src); 1; })
 #define cpumask_next_and(n, srcp, andp)	({ (void)(srcp), (void)(andp); 1; })
@@ -446,7 +452,6 @@ extern cpumask_t cpu_mask_all;
 
 #else /* NR_CPUS > 1 */
 
-extern int nr_cpu_ids;
 int __first_cpu(const cpumask_t *srcp);
 int __next_cpu(int n, const cpumask_t *srcp);
 int cpumask_next_and(int n, const cpumask_t *srcp, const cpumask_t *andp);
diff -r a8fed8d3197c init/main.c
--- a/init/main.c	Wed Oct 22 10:25:39 2008 +1100
+++ b/init/main.c	Wed Oct 22 10:43:15 2008 +1100
@@ -372,6 +372,8 @@ EXPORT_SYMBOL(cpu_mask_all);
 #endif
 
 /* Setup number of possible processor ids */
+/* nr_cpu_ids is a real variable for SMP. */
+#ifndef nr_cpu_ids
 int nr_cpu_ids __read_mostly = NR_CPUS;
 EXPORT_SYMBOL(nr_cpu_ids);
 
@@ -385,6 +387,11 @@ static void __init setup_nr_cpu_ids(void
 
 	nr_cpu_ids = highest_cpu + 1;
 }
+#else
+void __init setup_nr_cpu_ids(void)
+{
+}
+#endif /* ... nr_cpu_ids is a constant. */
 
 #ifndef CONFIG_HAVE_SETUP_PER_CPU_AREA
 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;