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>

1 files changed, 10 insertions, 0 deletions

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)
 {