We currently have a CONFIG_USER_NS option. Just rename it 
into CONFIG_NAMESPACES_EXPERIMANTAL and move the init_user_ns
into user.c file to make the kernel compile and work without 
the namespaces support.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index b5f41d4..dda160c 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -17,7 +17,7 @@ struct user_namespace {
 
 extern struct user_namespace init_user_ns;
 
-#ifdef CONFIG_USER_NS
+#ifdef CONFIG_NAMESPACES_EXPERIMENTAL
 
 static inline struct user_namespace *get_user_ns(struct user_namespace *ns)
 {
diff --git a/init/Kconfig b/init/Kconfig
index 684ccfb..0db1c3b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -206,15 +206,6 @@ config TASK_IO_ACCOUNTING
 
 	  Say N if unsure.
 
-config USER_NS
-	bool "User Namespaces (EXPERIMENTAL)"
-	default n
-	depends on EXPERIMENTAL
-	help
-	  Support user namespaces.  This allows containers, i.e.
-	  vservers, to use user namespaces to provide different
-	  user info for different servers.  If unsure, say N.
-
 config AUDIT
 	bool "Auditing support"
 	depends on NET
diff --git a/kernel/Makefile b/kernel/Makefile
index 76f782f..5817bfe 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -4,7 +4,7 @@
 
 obj-y     = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
 	    exit.o itimer.o time.o softirq.o resource.o \
-	    sysctl.o capability.o ptrace.o timer.o user.o user_namespace.o \
+	    sysctl.o capability.o ptrace.o timer.o user.o \
 	    signal.o sys.o kmod.o workqueue.o pid.o \
 	    rcupdate.o extable.o params.o posix-timers.o \
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
@@ -50,6 +49,7 @@ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_KGDB) += kgdb.o
 obj-$(CONFIG_NAMESPACES) += utsname.o
+obj-$(CONFIG_NAMESPACES_EXPERIMENTAL) += user_namespace.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
diff --git a/kernel/user.c b/kernel/user.c
index b45f55f..d7c0831 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -17,6 +17,15 @@
 #include <linux/module.h>
 #include <linux/user_namespace.h>
 
+struct user_namespace init_user_ns = {
+	.kref = {
+		.refcount	= ATOMIC_INIT(2),
+	},
+	.root_user = &root_user,
+};
+
+EXPORT_SYMBOL_GPL(init_user_ns);
+
 /*
  * UID task count cache, to get fast user lookup in "alloc_uid"
  * when changing user ID's (ie setuid() and friends).
@@ -199,6 +208,7 @@ void switch_uid(struct user_struct *new_
 	suid_keys(current);
 }
 
+#ifdef CONFIG_NAMESPACES_EXPERIMENTAL
 void release_uids(struct user_namespace *ns)
 {
 	int i;
@@ -223,6 +233,7 @@ void release_uids(struct user_namespace 
 
 	free_uid(ns->root_user);
 }
+#endif
 
 static int __init uid_cache_init(void)
 {
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 7af90fc..4c90062 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -10,17 +10,6 @@
 #include <linux/nsproxy.h>
 #include <linux/user_namespace.h>
 
-struct user_namespace init_user_ns = {
-	.kref = {
-		.refcount	= ATOMIC_INIT(2),
-	},
-	.root_user = &root_user,
-};
-
-EXPORT_SYMBOL_GPL(init_user_ns);
-
-#ifdef CONFIG_USER_NS
-
 /*
  * Clone a new ns copying an original user ns, setting refcount to 1
  * @old_ns: namespace to clone
@@ -84,5 +73,3 @@ void free_user_ns(struct kref *kref)
 	release_uids(ns);
 	kfree(ns);
 }
-
-#endif /* CONFIG_USER_NS */

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