idr: create idr_layer_cache at boot time

Avoid a possible kmem_cache_create() failure by creating idr_layer_cache
unconditionary at boot time rather than creating it on-demand when idr_init()
is called the first time.

This change also enables us to eliminate the check every time idr_init() is
called.

[akpm@linux-foundation.org: rename init_id_cache() to idr_init_cache()]
[akpm@linux-foundation.org: fix alpha build]
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

include/linux/idr.h

@@ -14,6 +14,7 @@
 
 #include <linux/types.h>
 #include <linux/bitops.h>
+#include <linux/init.h>
 
 #if BITS_PER_LONG == 32
 # define IDR_BITS 5
@@ -115,4 +116,6 @@ void ida_remove(struct ida *ida, int id);
 void ida_destroy(struct ida *ida);
 void ida_init(struct ida *ida);
 
+void __init idr_init_cache(void);
+
 #endif /* __IDR_H__ */

init/main.c

@@ -58,6 +58,7 @@
 #include <linux/kthread.h>
 #include <linux/sched.h>
 #include <linux/signal.h>
+#include <linux/idr.h>
 
 #include <asm/io.h>
 #include <asm/bugs.h>
@@ -637,6 +638,7 @@ asmlinkage void __init start_kernel(void)
 	enable_debug_pagealloc();
 	cpu_hotplug_init();
 	kmem_cache_init();
+	idr_init_cache();
 	setup_per_cpu_pageset();
 	numa_policy_init();
 	if (late_time_init)

lib/idr.c

@@ -585,12 +585,11 @@ static void idr_cache_ctor(struct kmem_cache *idr_layer_cache, void *idr_layer)
 	memset(idr_layer, 0, sizeof(struct idr_layer));
 }
 
-static  int init_id_cache(void)
+void __init idr_init_cache(void)
 {
-	if (!idr_layer_cache)
 	idr_layer_cache = kmem_cache_create("idr_layer_cache",
-			sizeof(struct idr_layer), 0, 0, idr_cache_ctor);
-	return 0;
+				sizeof(struct idr_layer), 0, SLAB_PANIC,
+				idr_cache_ctor);
 }
 
 /**
@@ -602,7 +601,6 @@ static  int init_id_cache(void)
  */
 void idr_init(struct idr *idp)
 {
-	init_id_cache();
 	memset(idp, 0, sizeof(struct idr));
 	spin_lock_init(&idp->lock);
 }