namespaces: cleanup the code managed with the USER_NS option

Make the user_namespace.o compilation depend on this option and move the
init_user_ns into user.c file to make the kernel compile and work without the
namespaces support.  This make the user namespace code be organized similar to
other namespaces'.

Also mask the USER_NS option as "depend on NAMESPACES".

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 21 insertions, 24 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 47879a874966..2a6499d6f283 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -214,15 +214,6 @@ 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 PID_NS
         bool "PID Namespaces (EXPERIMENTAL)"
         default n
@@ -443,6 +434,14 @@ config IPC_NS
           In this namespace tasks work with IPC ids which correspond to
           different IPC objects in different namespaces
 
+config USER_NS
+        bool "User namespace (EXPERIMENTAL)"
+        depends on NAMESPACES && EXPERIMENTAL
+        help
+          This allows containers, i.e. vservers, to use user namespaces
+          to provide different user info for different servers.
+          If unsure, say N.
+
 config BLK_DEV_INITRD
         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
         depends on BROKEN || !FRV
diff --git a/kernel/Makefile b/kernel/Makefile
index 0f15bd409367..30a957a35c91 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 \
@@ -33,7 +33,6 @@ obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
-obj-$(CONFIG_UTS_NS) += utsname.o
 obj-$(CONFIG_PM) += power/
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
@@ -43,6 +42,8 @@ obj-$(CONFIG_CGROUPS) += cgroup.o
 obj-$(CONFIG_CGROUP_DEBUG) += cgroup_debug.o
 obj-$(CONFIG_CPUSETS) += cpuset.o
 obj-$(CONFIG_CGROUP_NS) += ns_cgroup.o
+obj-$(CONFIG_UTS_NS) += utsname.o
+obj-$(CONFIG_USER_NS) += user_namespace.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_RESOURCE_COUNTERS) += res_counter.o
 obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
diff --git a/kernel/user.c b/kernel/user.c
index bc1c48d35cb3..7d7900c5a1fd 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -17,6 +17,14 @@
 #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).
@@ -427,6 +435,7 @@ void switch_uid(struct user_struct *new_user)
         suid_keys(current);
 }
 
+#ifdef CONFIG_USER_NS
 void release_uids(struct user_namespace *ns)
 {
         int i;
@@ -451,6 +460,7 @@ void release_uids(struct user_namespace *ns)
 
         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 7af90fc4f0fd..4c9006275df7 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 */