srcu: Move rcu_init_levelspread() to rcu_tree_node.h

This commit moves the rcu_init_levelspread() function from
kernel/rcu/tree.c to kernel/rcu/rcu.h so that SRCU can access it.  This is
another step towards enabling SRCU to create its own combining tree.
This commit is code-movement only, give or take knock-on adjustments.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

include/linux/rcu_node_tree.h

@@ -96,7 +96,4 @@
 # error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
 #endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
 
-extern int rcu_num_lvls;
-extern int rcu_num_nodes;
-
 #endif /* __LINUX_RCU_NODE_TREE_H */

kernel/rcu/rcu.h

@@ -190,4 +190,40 @@ void rcu_test_sync_prims(void);
  */
 extern void resched_cpu(int cpu);
 
+#if defined(SRCU) || !defined(TINY_RCU)
+
+#include <linux/rcu_node_tree.h>
+
+extern int rcu_num_lvls;
+extern int rcu_num_nodes;
+static bool rcu_fanout_exact;
+static int rcu_fanout_leaf;
+
+/*
+ * Compute the per-level fanout, either using the exact fanout specified
+ * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
+ */
+static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
+{
+	int i;
+
+	if (rcu_fanout_exact) {
+		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
+		for (i = rcu_num_lvls - 2; i >= 0; i--)
+			levelspread[i] = RCU_FANOUT;
+	} else {
+		int ccur;
+		int cprv;
+
+		cprv = nr_cpu_ids;
+		for (i = rcu_num_lvls - 1; i >= 0; i--) {
+			ccur = levelcnt[i];
+			levelspread[i] = (cprv + ccur - 1) / ccur;
+			cprv = ccur;
+		}
+	}
+}
+
+#endif /* #if defined(SRCU) || !defined(TINY_RCU) */
+
 #endif /* __LINUX_RCU_H */

kernel/rcu/srcu.c

@@ -36,6 +36,7 @@
 #include <linux/delay.h>
 #include <linux/srcu.h>
 
+#include <linux/rcu_node_tree.h>
 #include "rcu.h"
 
 static int init_srcu_struct_fields(struct srcu_struct *sp)

kernel/rcu/tree.c

@@ -3951,31 +3951,6 @@ void rcu_scheduler_starting(void)
 	rcu_test_sync_prims();
 }
 
-/*
- * Compute the per-level fanout, either using the exact fanout specified
- * or balancing the tree, depending on the rcu_fanout_exact boot parameter.
- */
-static void __init rcu_init_levelspread(int *levelspread, const int *levelcnt)
-{
-	int i;
-
-	if (rcu_fanout_exact) {
-		levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
-		for (i = rcu_num_lvls - 2; i >= 0; i--)
-			levelspread[i] = RCU_FANOUT;
-	} else {
-		int ccur;
-		int cprv;
-
-		cprv = nr_cpu_ids;
-		for (i = rcu_num_lvls - 1; i >= 0; i--) {
-			ccur = levelcnt[i];
-			levelspread[i] = (cprv + ccur - 1) / ccur;
-			cprv = ccur;
-		}
-	}
-}
-
 /*
  * Helper function for rcu_init() that initializes one rcu_state structure.
  */

kernel/rcu/tree_trace.c

@@ -45,6 +45,7 @@
 
 #define RCU_TREE_NONCORE
 #include "tree.h"
+#include "rcu.h"
 
 static int r_open(struct inode *inode, struct file *file,
 					const struct seq_operations *op)