Changes from v1:
* make the NAMESPACES_EXPERIMENTAL selectable even in !EMBEDDED case

There were some questions like "do I need this on my cellphone"
in reply to different namespaces patches. Indeed, the namespaces
are not useful for most of the embedded systems, but the code
creating and releasing them weights a lot.

So I propose to add a config option which will help embedded
people to reduce the vmlinux size. This option simply compiles
out the namespaces cloning and releasing code *only*, but keeps
all the other logic untouched (e.g. the notion of init_ns).

When someone tries to clone some namespace with their support
turned off, he will receive an EINVAL error.

This patchset can save more than 2KB from the vmlinux when
turning the config option "NAMESPACES" to "n":

$ scripts/bloat-o-meter vmlinux-no-ns vmlinux-with-ns 
add/remove: 27/0 grow/shrink: 11/7 up/down: 2477/-340 (2137)
function                                     old     new   delta
copy_pid_ns                                    -     537    +537
copy_user_ns                                   -     181    +181
copy_ipcs                                      -     149    +149
zap_pid_ns_processes                           -     130    +130
copy_utsname                                   -     120    +120
shm_exit_ns                                    -     106    +106
sem_exit_ns                                    -     106    +106
msg_exit_ns                                    -     106    +106
freeary                                        -     100    +100
release_uids                                   -      95     +95
freeque                                        -      92     +92
free_nsproxy                                  48     123     +75
create_new_namespaces                        300     358     +58
free_pid_ns                                    -      56     +56
pid_namespaces_init                            -      48     +48
__sem_init_ns                                  -      45     +45
shm_init_ns                                    -      42     +42
sem_init_ns                                    -      42     +42
msg_init_ns                                    -      42     +42
__shm_init_ns                                  -      38     +38
__msg_init_ns                                  -      31     +31
sysvipc_proc_release                           5      35     +30
proc_kill_sb                                   5      35     +30
free_ipc_ns                                    -      30     +30
do_shm_rmid                                    -      29     +29
proc_set_super                                13      38     +25
shm_release                                   18      39     +21
put_pid                                       75      95     +20
alloc_pid                                    687     706     +19
pid_caches_mutex                               -      16     +16
free_user_ns                                   -      16     +16
sysvipc_proc_open                            100     111     +11
do_shmat                                     778     787      +9
pid_caches_lh                                  -       8      +8
free_uts_ns                                    -       5      +5
pid_ns_cachep                                  -       4      +4
__initcall_pid_namespaces_init6                -       4      +4
do_exit                                     1855    1856      +1
show_stat                                   1665    1661      -4
sys_shmctl                                  1934    1907     -27
msg_init                                      82      47     -35
shm_init                                      92      47     -45
sem_init                                      99      44     -55
sys_msgctl                                  1394    1311     -83
sys_semctl                                  2123    2032     -91

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

The option is called NAMESPACES. It can be selectable only
if EMBEDDED is chosen (this was Eric's requisition). When
the EMBEDDED is off namespaces will be on automatically.

One more option (NAMESPACES_EXPERIMENTAL) was added by 
Serge's request to move there all the namespaces that are 
not finished yet. Currently only the user and the network
namespaces are such. This option is selectable all the
time NAMESPACES are "y" regardless of EMBEDDED one.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Cedric Le Goater <clg@fr.ibm.com>

---

diff --git a/init/Kconfig b/init/Kconfig
index 6bb603a..67b1e41 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -390,6 +381,23 @@ config RELAY
 
 	  If unsure, say N.
 
+config NAMESPACES
+	bool "Namespaces support" if EMBEDDED
+	default !EMBEDDED
+	help
+	  Provides the way to make tasks work with different objects using
+	  the same id. For example same IPC id may refer to different objects
+	  or same user id or pid may refer to different tasks when used in
+	  different namespaces.
+
+config NAMESPACES_EXPERIMENTAL
+	bool "Add experimantal namespaces support"
+	depends on NAMESPACES && EXPERIMENTAL
+	default n
+	help
+	  Also include the support for the namespaces that are not fnished
+	  or well developed yet
+
 config BLK_DEV_INITRD
 	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 	depends on BROKEN || !FRV

Currently all the namespace management code is in the
kernel/utsname.c file, so just compile it out and make
stub in .h file.

The init namespace itself is in init/version.c and is
left in the kernel.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Cedric Le Goater <clg@fr.ibm.com>

---

diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 923db99..52b9116 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -35,6 +35,7 @@ struct new_utsname {
 #include <linux/sched.h>
 #include <linux/kref.h>
 #include <linux/nsproxy.h>
+#include <linux/err.h>
 #include <asm/atomic.h>
 
 struct uts_namespace {
@@ -43,6 +44,7 @@ struct uts_namespace {
 };
 extern struct uts_namespace init_uts_ns;
 
+#ifdef CONFIG_NAMESPACES
 static inline void get_uts_ns(struct uts_namespace *ns)
 {
 	kref_get(&ns->kref);
@@ -56,6 +58,25 @@ static inline void put_uts_ns(struct uts
 {
 	kref_put(&ns->kref, free_uts_ns);
 }
+#else
+static inline void get_uts_ns(struct uts_namespace *ns)
+{
+}
+
+static inline void put_uts_ns(struct uts_namespace *ns)
+{
+}
+
+static inline struct uts_namespace *copy_utsname(unsigned long flags,
+					struct uts_namespace *ns)
+{
+	if (flags & CLONE_NEWUTS)
+		return ERR_PTR(-EINVAL);
+
+	return ns;
+}
+#endif
+
 static inline struct new_utsname *utsname(void)
 {
 	return &current->nsproxy->uts_ns->name;
diff --git a/kernel/Makefile b/kernel/Makefile
index 76f782f..5817bfe 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -4,8 +4,7 @@
 	    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 \
-	    hrtimer.o rwsem.o latency.o nsproxy.o srcu.o \
-	    utsname.o notifier.o sysctl.o
+	    hrtimer.o rwsem.o latency.o nsproxy.o srcu.o notifier.o sysctl.o
 
 obj-$(CONFIG_SYSCTL) += sysctl_check.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
@@ -50,6 +49,7 @@ obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
 obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_KGDB) += kgdb.o
+obj-$(CONFIG_NAMESPACES) += utsname.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/

Currently all the IPC namespace management code is in 
ipc/util.c. I moved this code into ipc/namespace.c file
which is compiled out when needed.

The linux/ipc_namespace.h file is used to store the
prototypes of the functions in namespace.c and the stubs
for NAMESPACES=n case. This is done so, because the stub
for copy_ipc_namespace requires the knoweledge of the
CLONE_NEWIPC flag, which is in sched.h. But the linux/ipc.h
file itself in included into many many .c files via the
sys.h->sem.h sequence so adding the sched.h into it will
make all these .c depend on sched.h which is not that good.
On the other hand the knowledge about the namespaces stuff 
is required in 4 .c files only.

Besides, this patch compiles out some auxiliary functions
from ipc/sem.c, msg.c and shm.c files. It turned out that
moving these functions into namespaces.c is not that easy
because they use many other calls and macros from the original
file. Moving them would make this patch complicated. On the
other hand all these functions can be consolidated, so I
will make it separately a bit later.

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

---

diff --git a/include/linux/ipc.h b/include/linux/ipc.h
index 96988d1..b882610 100644
--- a/include/linux/ipc.h
+++ b/include/linux/ipc.h
@@ -100,56 +100,6 @@ struct kern_ipc_perm
 	void		*security;
 };
 
-struct ipc_ids;
-struct ipc_namespace {
-	struct kref	kref;
-	struct ipc_ids	*ids[3];
-
-	int		sem_ctls[4];
-	int		used_sems;
-
-	int		msg_ctlmax;
-	int		msg_ctlmnb;
-	int		msg_ctlmni;
-
-	size_t		shm_ctlmax;
-	size_t		shm_ctlall;
-	int		shm_ctlmni;
-	int		shm_tot;
-};
-
-extern struct ipc_namespace init_ipc_ns;
-
-#ifdef CONFIG_SYSVIPC
-#define INIT_IPC_NS(ns)		.ns		= &init_ipc_ns,
-extern void free_ipc_ns(struct kref *kref);
-extern struct ipc_namespace *copy_ipcs(unsigned long flags,
-						struct ipc_namespace *ns);
-#else
-#define INIT_IPC_NS(ns)
-static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
-						struct ipc_namespace *ns)
-{
-	return ns;
-}
-#endif
-
-static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
-{
-#ifdef CONFIG_SYSVIPC
-	if (ns)
-		kref_get(&ns->kref);
-#endif
-	return ns;
-}
-
-static inline void put_ipc_ns(struct ipc_namespace *ns)
-{
-#ifdef CONFIG_SYSVIPC
-	kref_put(&ns->kref, free_ipc_ns);
-#endif
-}
-
 #endif /* __KERNEL__ */
 
 #endif /* _LINUX_IPC_H */
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
new file mode 100644
index 0000000..3d8a516
--- /dev/null
+++ b/include/linux/ipc_namespace.h
@@ -0,0 +1,67 @@
+#ifndef __IPC_NAMESPACE_H__
+#define __IPC_NAMESPACE_H__
+
+#include <linux/err.h>
+
+struct ipc_ids;
+struct ipc_namespace {
+	struct kref	kref;
+	struct ipc_ids	*ids[3];
+
+	int		sem_ctls[4];
+	int		used_sems;
+
+	int		msg_ctlmax;
+	int		msg_ctlmnb;
+	int		msg_ctlmni;
+
+	size_t		shm_ctlmax;
+	size_t		shm_ctlall;
+	int		shm_ctlmni;
+	int		shm_tot;
+};
+
+extern struct ipc_namespace init_ipc_ns;
+
+#ifdef CONFIG_SYSVIPC
+#define INIT_IPC_NS(ns)		.ns		= &init_ipc_ns,
+#else
+#define INIT_IPC_NS(ns)
+#endif
+
+#if defined(CONFIG_SYSVIPC) && defined(CONFIG_NAMESPACES)
+extern void free_ipc_ns(struct kref *kref);
+extern struct ipc_namespace *copy_ipcs(unsigned long flags,
+						struct ipc_namespace *ns);
+
+static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
+{
+	if (ns)
+		kref_get(&ns->kref);
+	return ns;
+}
+
+static inline void put_ipc_ns(struct ipc_namespace *ns)
+{
+	kref_put(&ns->kref, free_ipc_ns);
+}
+#else
+static inline struct ipc_namespace *copy_ipcs(unsigned long flags,
+		struct ipc_namespace *ns)
+{
+	if (flags & CLONE_NEWIPC)
+		return ERR_PTR(-EINVAL);
+
+	return ns;
+}
+
+static inline struct ipc_namespace *get_ipc_ns(struct ipc_namespace *ns)
+{
+	return ns;
+}
+
+static inline void put_ipc_ns(struct ipc_namespace *ns)
+{
+}
+#endif
+#endif
diff --git a/ipc/Makefile b/ipc/Makefile
index b93bba6..d81fb35 100644
--- a/ipc/Makefile
+++ b/ipc/Makefile
@@ -7,4 +7,5 @@ obj-$(CONFIG_SYSVIPC) += util.o msgutil.
 obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o
 obj_mq-$(CONFIG_COMPAT) += compat_mq.o
 obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o $(obj_mq-y)
+obj-$(CONFIG_NAMESPACES) += namespace.o
 
diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index 79e24e8..7f4235b 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -14,6 +14,7 @@
 #include <linux/nsproxy.h>
 #include <linux/sysctl.h>
 #include <linux/uaccess.h>
+#include <linux/ipc_namespace.h>
 
 static void *get_ipc(ctl_table *table)
 {
diff --git a/ipc/msg.c b/ipc/msg.c
index b7274db..eb74965 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -36,6 +36,7 @@
 #include <linux/seq_file.h>
 #include <linux/mutex.h>
 #include <linux/nsproxy.h>
+#include <linux/ipc_namespace.h>
 
 #include <asm/current.h>
 #include <asm/uaccess.h>
@@ -92,6 +93,7 @@ static void __msg_init_ns(struct ipc_nam
 	ipc_init_ids(ids);
 }
 
+#ifdef CONFIG_NAMESPACES
 int msg_init_ns(struct ipc_namespace *ns)
 {
 	struct ipc_ids *ids;
@@ -127,6 +129,7 @@ void msg_exit_ns(struct ipc_namespace *n
 	kfree(ns->ids[IPC_MSG_IDS]);
 	ns->ids[IPC_MSG_IDS] = NULL;
 }
+#endif
 
 void __init msg_init(void)
 {
diff --git a/ipc/namespace.c b/ipc/namespace.c
new file mode 100644
index 0000000..cef1139
--- /dev/null
+++ b/ipc/namespace.c
@@ -0,0 +1,73 @@
+/*
+ * linux/ipc/namespace.c
+ * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
+ */
+
+#include <linux/ipc.h>
+#include <linux/msg.h>
+#include <linux/ipc_namespace.h>
+#include <linux/rcupdate.h>
+#include <linux/nsproxy.h>
+#include <linux/slab.h>
+
+#include "util.h"
+
+static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
+{
+	int err;
+	struct ipc_namespace *ns;
+
+	err = -ENOMEM;
+	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
+	if (ns == NULL)
+		goto err_mem;
+
+	err = sem_init_ns(ns);
+	if (err)
+		goto err_sem;
+	err = msg_init_ns(ns);
+	if (err)
+		goto err_msg;
+	err = shm_init_ns(ns);
+	if (err)
+		goto err_shm;
+
+	kref_init(&ns->kref);
+	return ns;
+
+err_shm:
+	msg_exit_ns(ns);
+err_msg:
+	sem_exit_ns(ns);
+err_sem:
+	kfree(ns);
+err_mem:
+	return ERR_PTR(err);
+}
+
+struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
+{
+	struct ipc_namespace *new_ns;
+
+	BUG_ON(!ns);
+	get_ipc_ns(ns);
+
+	if (!(flags & CLONE_NEWIPC))
+		return ns;
+
+	new_ns = clone_ipc_ns(ns);
+
+	put_ipc_ns(ns);
+	return new_ns;
+}
+
+void free_ipc_ns(struct kref *kref)
+{
+	struct ipc_namespace *ns;
+
+	ns = container_of(kref, struct ipc_namespace, kref);
+	sem_exit_ns(ns);
+	msg_exit_ns(ns);
+	shm_exit_ns(ns);
+	kfree(ns);
+}
diff --git a/ipc/sem.c b/ipc/sem.c
index 45c7e57..2e9f449 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -82,6 +82,7 @@
 #include <linux/seq_file.h>
 #include <linux/mutex.h>
 #include <linux/nsproxy.h>
+#include <linux/ipc_namespace.h>
 
 #include <asm/uaccess.h>
 #include "util.h"
@@ -130,6 +131,7 @@ static void __sem_init_ns(struct ipc_nam
 	ipc_init_ids(ids);
 }
 
+#ifdef CONFIG_NAMESPACES
 int sem_init_ns(struct ipc_namespace *ns)
 {
 	struct ipc_ids *ids;
@@ -165,6 +167,7 @@ void sem_exit_ns(struct ipc_namespace *n
 	kfree(ns->ids[IPC_SEM_IDS]);
 	ns->ids[IPC_SEM_IDS] = NULL;
 }
+#endif
 
 void __init sem_init (void)
 {
diff --git a/ipc/shm.c b/ipc/shm.c
index f28f2a3..2717cbc 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -38,6 +38,7 @@
 #include <linux/mutex.h>
 #include <linux/nsproxy.h>
 #include <linux/mount.h>
+#include <linux/ipc_namespace.h>
 
 #include <asm/uaccess.h>
 
@@ -97,6 +98,7 @@ static void do_shm_rmid(struct ipc_names
 		shm_destroy(ns, shp);
 }
 
+#ifdef CONFIG_NAMESPACES
 int shm_init_ns(struct ipc_namespace *ns)
 {
 	struct ipc_ids *ids;
@@ -132,6 +134,7 @@ void shm_exit_ns(struct ipc_namespace *n
 	kfree(ns->ids[IPC_SHM_IDS]);
 	ns->ids[IPC_SHM_IDS] = NULL;
 }
+#endif
 
 void __init shm_init (void)
 {
diff --git a/ipc/util.c b/ipc/util.c
index fd29246..44fb843 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -32,6 +32,7 @@
 #include <linux/proc_fs.h>
 #include <linux/audit.h>
 #include <linux/nsproxy.h>
+#include <linux/ipc_namespace.h>
 
 #include <asm/unistd.h>
 
@@ -50,66 +51,6 @@ struct ipc_namespace init_ipc_ns = {
 	},
 };
 
-static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
-{
-	int err;
-	struct ipc_namespace *ns;
-
-	err = -ENOMEM;
-	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
-	if (ns == NULL)
-		goto err_mem;
-
-	err = sem_init_ns(ns);
-	if (err)
-		goto err_sem;
-	err = msg_init_ns(ns);
-	if (err)
-		goto err_msg;
-	err = shm_init_ns(ns);
-	if (err)
-		goto err_shm;
-
-	kref_init(&ns->kref);
-	return ns;
-
-err_shm:
-	msg_exit_ns(ns);
-err_msg:
-	sem_exit_ns(ns);
-err_sem:
-	kfree(ns);
-err_mem:
-	return ERR_PTR(err);
-}
-
-struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
-{
-	struct ipc_namespace *new_ns;
-
-	BUG_ON(!ns);
-	get_ipc_ns(ns);
-
-	if (!(flags & CLONE_NEWIPC))
-		return ns;
-
-	new_ns = clone_ipc_ns(ns);
-
-	put_ipc_ns(ns);
-	return new_ns;
-}
-
-void free_ipc_ns(struct kref *kref)
-{
-	struct ipc_namespace *ns;
-
-	ns = container_of(kref, struct ipc_namespace, kref);
-	sem_exit_ns(ns);
-	msg_exit_ns(ns);
-	shm_exit_ns(ns);
-	kfree(ns);
-}
-
 /**
  *	ipc_init	-	initialise IPC subsystem
  *
diff --git a/ipc/util.h b/ipc/util.h
index 99414a3..8972402 100644
--- a/ipc/util.h
+++ b/ipc/util.h
@@ -20,6 +20,8 @@ void sem_init (void);
 void msg_init (void);
 void shm_init (void);
 
+struct ipc_namespace;
+
 int sem_init_ns(struct ipc_namespace *ns);
 int msg_init_ns(struct ipc_namespace *ns);
 int shm_init_ns(struct ipc_namespace *ns);
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index 31351cc..aac9b15 10064

We currently have a CONFIG_USER_NS option. Just rename it 
into CONFIG_NAMESPACES_EXPERIMENTAL 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>
Acked-by: Cedric Le Goater <clg@fr.ibm.com>

---

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 6bb603a..67b1e41 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 80fbe56..2f62cf4 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).
@@ -242,6 +251,7 @@ void switch_uid(struct user_struct *new_
 	suid_keys(current);
 }
 
+#ifdef CONFIG_NAMESPACES_EXPERIMENTAL
 void release_uids(struct user_namespace *ns)
 {
 	int i;
@@ -266,6 +276,7 @@ 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 */

For the same reasons as with the IPC namespaces, all the
prototypes and stuns go to the pid_namespace.h file. The
namespace management code itself is moved to the
pid_namespace.c file.

The pid_namespace cache is created inside an initcall,
i.e. a bit later than the pid hash is initialized. This
is OK for now - no code in kernel tries to clone new
pid namespaces before boot.

The zap_pid_namespace() function is expanded into a
BUG() when NAMESPACES is "n". This is normal as exiting
the init namespace (the only namespace in this case)
causes a panic() in exit_child_reaper() function anyway.

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

---

diff --git a/include/linux/pid.h b/include/linux/pid.h
index e29a900..e67b130 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -121,7 +121,8 @@ extern struct pid *find_ge_pid(int nr, s
 
 extern struct pid *alloc_pid(struct pid_namespace *ns);
 extern void FASTCALL(free_pid(struct pid *pid));
-extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);
+
+int next_pidmap(struct pid_namespace *pid_ns, int last);
 
 /*
  * the helpers to get the pid's id seen from different namespaces
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 0135c76..6d6bd18 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -6,6 +6,7 @@
 #include <linux/threads.h>
 #include <linux/nsproxy.h>
 #include <linux/kref.h>
+#include <linux/err.h>
 
 struct pidmap {
        atomic_t nr_free;
@@ -29,6 +30,7 @@ struct pid_namespace {
 
 extern struct pid_namespace init_pid_ns;
 
+#ifdef CONFIG_NAMESPACES
 static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
 {
 	if (ns != &init_pid_ns)
@@ -38,12 +40,37 @@ static inline struct pid_namespace *get_
 
 extern struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *ns);
 extern void free_pid_ns(struct kref *kref);
+extern void zap_pid_ns_processes(struct pid_namespace *pid_ns);
 
 static inline void put_pid_ns(struct pid_namespace *ns)
 {
 	if (ns != &init_pid_ns)
 		kref_put(&ns->kref, free_pid_ns);
 }
+#else
+static inline struct pid_namespace *get_pid_ns(struct pid_namespace *ns)
+{
+	return ns;
+}
+
+static inline void put_pid_ns(struct pid_namespace *ns)
+{
+}
+
+static inline struct pid_namespace *copy_pid_ns(unsigned long flags,
+		struct pid_namespace *ns)
+{
+	if (flags & CLONE_NEWPID)
+		return ERR_PTR(-EINVAL);
+
+	return ns;
+}
+
+static inline void zap_pid_ns_processes(struct pid_namespace *ns)
+{
+	BUG();
+}
+#endif
 
 static inline struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
 {
diff --git a/kernel/Makefile b/kernel/Makefile
index 76f782f..5817bfe 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -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-$(CONFIG_NAMESPACES) += pid_namespace.o
 obj-$(CONFIG_NAMESPACES_EXPERIMENTAL) += user_namespace.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
diff --git a/kernel/pid.c b/kernel/pid.c
index d7388d7..2411bc5 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -18,12 +18,6 @@
  * allocation scenario when all but one out of 1 million PIDs possible are
  * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
  * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
- *
- * Pid namespaces:
- *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
- *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
- *     Many thanks to Oleg Nesterov for comments and help
- *
  */
 
 #include <linux/mm.h>
@@ -34,14 +28,12 @@
 #include <linux/hash.h>
 #include <linux/pid_namespace.h>
 #include <linux/init_task.h>
-#include <linux/syscalls.h>
 
 #define pid_hashfn(nr, ns)	\
 	hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
 static struct hlist_head *pid_hash;
 static int pidhash_shift;
 struct pid init_struct_pid = INIT_STRUCT_PID;
-static struct kmem_cache *pid_ns_cachep;
 
 int pid_max = PID_MAX_DEFAULT;
 
@@ -181,7 +173,7 @@ static int alloc_pidmap(struct pid_names
 	return -1;
 }
 
-static int next_pidmap(struct pid_namespace *pid_ns, int last)
+int next_pidmap(struct pid_namespace *pid_ns, int last)
 {
 	int offset;
 	struct pidmap *map, *end;
@@ -487,178 +479,6 @@ struct pid *find_ge_pid(int nr, struct p
 }
 EXPORT_SYMBOL_GPL(find_get_pid);
 
-struct pid_cache {
-	int nr_ids;
-	char name[16];
-	struct kmem_cache *cachep;
-	struct list_head list;
-};
-
-static LIST_HEAD(pid_caches_lh);
-static DEFINE_MUTEX(pid_caches_mutex);
-
-/*
- * creates the kmem cache to allocate pids from.
- * @nr_ids: the number of numerical ids this pid will have to carry
- */
-
-static struct kmem_cache *create_pid_cachep(int nr_ids)
-{
-	struct pid_cache *pcache;
-	struct kmem_cache *cachep;
-
-	mutex_lock(&pid_caches_mutex);
-	list_for_each_entry (pcache, &pid_caches_lh, list)
-		if (pcache->nr_ids == nr_ids)
-			goto out;
-
-	pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
-	if (pcache == NULL)
-		goto err_alloc;
-
-	snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
-	cachep = kmem_cache_create(pcache->name,
-			sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
-			0, SLAB_HWCACHE_ALIGN, NULL);
-	if (cachep == NULL)
-		goto err_cachep;
-
-	pcache->nr_ids = nr_ids;
-	pcache->cachep = cachep;
-	list_add(&pcache->list, &pid_caches_lh);
-out:
-	mutex_unlock(&pid_caches_mutex);
-	return pcache->cachep;
-
-err_cachep:
-	kfree(pcache);
-err_alloc:
-	mutex_unlock(&pid_caches_mutex);
-	return NULL;
-}
-
-static struct pid_namespace *create_pid_namespace(int level)
-{
-	struct pid_namespace *ns;
-	int i;
-
-	ns = kmem_cache_alloc(pid_ns_cachep, GFP_KERNEL);
-	if (ns == NULL)
-		goto out;
-
-	ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-	if (!ns->pidmap[0].page)
-		goto out_free;
-
-	ns->pid_cachep = create_pid_cachep(level + 1);
-	if (ns->pid_cachep == NULL)
-		goto out_free_map;
-
-	kref_init(&ns->kref);
-	ns->last_pid = 0;
-	ns->child_reaper = NULL;
-	ns->level = level;
-
-	set_bit(0, ns->pidmap[0].page);
-	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
-
-	for (i = 1; i < PIDMAP_ENTRIES; i++) {
-		ns->pidmap[i].page = 0;
-		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
-	}
-
-	return ns;
-
-out_free_map:
-	kfree(ns->pidmap[0].page);
-out_free:
-	kmem_cache_free(pid_ns_cachep, ns);
-out:
-	return ERR_PTR(-ENOMEM);
-}
-
-static void destroy_pid_namespace(struct pid_namespace *ns)
-{
-	int i;
-
-	for (i = 0; i < PIDMAP_ENTRIES; i++)
-		kfree(ns->pidmap[i].page);
-	kmem_cache_free(pid_ns_cachep, ns);
-}
-
-struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
-{
-	struct pid_namespace *new_ns;
-
-	BUG_ON(!old_ns);
-	new_ns = get_pid_ns(old_ns);
-	if (!(flags & CLONE_NEWPID))
-		goto out;
-
-	new_ns = ERR_PTR(-EINVAL);
-	if (flags & CLONE_THREAD)
-		goto out_put;
-
-	new_ns = create_pid_namespace(old_ns->level + 1);
-	if (!IS_ERR(new_ns))
-		new_ns->parent = get_pid_ns(old_ns);
-
-out_put:
-	put_pid_ns(old_ns);
-out:
-	return new_ns;
-}
-
-void free_pid_ns(struct kref *kref)
-{
-	struct pid_namespace *ns, *parent;
-
-	ns = container_of(kref, struct pid_namespace, kref);
-
-	parent = ns->parent;
-	destroy_pid_namespace(ns);
-
-	if (parent != NULL)
-		put_pid_ns(parent);
-}
-
-void zap_pid_ns_processes(struct pid_namespace *pid_ns)
-{
-	int nr;
-	int rc;
-
-	/*
-	 * The last thread in the cgroup-init thread group is terminating.
-	 * Find remaining pid_ts in the namespace, signal and wait for them
-	 * to exit.
-	 *
-	 * Note:  This signals each threads in the namespace - even those that
-	 * 	  belong to the same thread group, To avoid this, we would have
-	 * 	  to walk the entire tasklist looking a processes in this
-	 * 	  namespace, but that could be unnecessarily expensive if the
-	 * 	  pid namespace has just a few processes. Or we need to
-	 * 	  maintain a tasklist for each pid namespace.
-	 *
-	 */
-	read_lock(&tasklist_lock);
-	nr = next_pidmap(pid_ns, 1);
-	while (nr > 0) {
-		kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
-		nr = next_pidmap(pid_ns, nr);
-	}
-	read_unlock(&tasklist_lock);
-
-	do {
-		clear_thread_flag(TIF_SIGPENDING);
-		rc = sys_wait4(-1, NULL, __WALL, NULL);
-	} while (rc != -ECHILD);
-
-
-	/* Child reaper for the pid namespace is going away */
-	pid_ns->child_reaper = NULL;
-	return;
-}
-
 /*
  * The pid hash table is scaled according to the amount of memory in the
  * machine.  From a minimum of 16 slots up to 4096 slots at one gigabyte or
@@ -691,9 +511,6 @@ void __init pidmap_init(void)
 	set_bit(0, init_pid_ns.pidmap[0].page);
 	atomic_dec(&init_pid_ns.pidmap[0].nr_free);
 
-	init_pid_ns.pid_cachep = create_pid_cachep(1);
-	if (init_pid_ns.pid_cachep == NULL)
-		panic("Can't create pid_1 cachep\n");
-
-	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
+	init_pid_ns.pid_cachep = kmem_cache_create("pid", sizeof(struct pid),
+			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
 }
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
new file mode 100644
index 0000000..2936923
--- /dev/null
+++ b/kernel/pid_namespace.c
@@ -0,0 +1,196 @@
+/*
+ * Pid namespaces
+ *
+ * Authors:
+ *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
+ *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
+ *     Many thanks to Oleg Nesterov for comments and help
+ *
+ */
+
+#include <linux/pid.h>
+#include <linux/pid_namespace.h>
+#include <linux/syscalls.h>
+
+#define BITS_PER_PAGE		(PAGE_SIZE*8)
+
+struct pid_cache {
+	int nr_ids;
+	char name[16];
+	struct kmem_cache

Quoting Pavel Emelyanov (xemul@openvz.org):
> The option is called NAMESPACES. It can be selectable only
> if EMBEDDED is chosen (this was Eric's requisition). When
> the EMBEDDED is off namespaces will be on automatically.
> 
> One more option (NAMESPACES_EXPERIMENTAL) was added by 
> Serge's request to move there all the namespaces that are 
> not finished yet. Currently only the user and the network
> namespaces are such. This option is selectable all the
> time NAMESPACES are "y" regardless of EMBEDDED one.
> 
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
> Acked-by: Cedric Le Goater <clg@fr.ibm.com>

Looks good.  Thanks.

Acked-by: Serge Hallyn <serue@us.ibm.com>

(for the whole set, just to save the list from a few emails)

-serge

> 
> ---
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index 6bb603a..67b1e41 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -390,6 +381,23 @@ config RELAY
> 
>  	  If unsure, say N.
> 
> +config NAMESPACES
> +	bool "Namespaces support" if EMBEDDED
> +	default !EMBEDDED
> +	help
> +	  Provides the way to make tasks work with different objects using
> +	  the same id. For example same IPC id may refer to different objects
> +	  or same user id or pid may refer to different tasks when used in
> +	  different namespaces.
> +
> +config NAMESPACES_EXPERIMENTAL
> +	bool "Add experimantal namespaces support"
> +	depends on NAMESPACES && EXPERIMENTAL
> +	default n
> +	help
> +	  Also include the support for the namespaces that are not fnished
> +	  or well developed yet
> +
>  config BLK_DEV_INITRD
>  	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
>  	depends on BROKEN || !FRV

Pavel Emelyanov wrote:
> Currently all the IPC namespace management code is in 
> ipc/util.c. I moved this code into ipc/namespace.c file
> which is compiled out when needed.
> 
> The linux/ipc_namespace.h file is used to store the
> prototypes of the functions in namespace.c and the stubs
> for NAMESPACES=n case. This is done so, because the stub
> for copy_ipc_namespace requires the knoweledge of the
> CLONE_NEWIPC flag, which is in sched.h. But the linux/ipc.h
> file itself in included into many many .c files via the
> sys.h->sem.h sequence so adding the sched.h into it will
> make all these .c depend on sched.h which is not that good.
> On the other hand the knowledge about the namespaces stuff 
> is required in 4 .c files only.
> 
> Besides, this patch compiles out some auxiliary functions
> from ipc/sem.c, msg.c and shm.c files. It turned out that
> moving these functions into namespaces.c is not that easy
> because they use many other calls and macros from the original
> file. Moving them would make this patch complicated. On the
> other hand all these functions can be consolidated, so I
> will make it separately a bit later.
> 
> Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

Fine with me.

Acked-by: Cedric Le Goater <clg@fr.ibm.com>

Thanks !

C.

On Mon, 01 Oct 2007 19:33:27 +0400 Pavel Emelyanov wrote:

> diff --git a/init/Kconfig b/init/Kconfig
> index 6bb603a..67b1e41 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -390,6 +381,23 @@ config RELAY
>  
>  	  If unsure, say N.
>  
> +config NAMESPACES
> +	bool "Namespaces support" if EMBEDDED
> +	default !EMBEDDED
> +	help
> +	  Provides the way to make tasks work with different objects using
> +	  the same id. For example same IPC id may refer to different objects
> +	  or same user id or pid may refer to different tasks when used in
> +	  different namespaces.
> +
> +config NAMESPACES_EXPERIMENTAL
> +	bool "Add experimantal namespaces support"

                  experimental

> +	depends on NAMESPACES && EXPERIMENTAL
> +	default n
> +	help
> +	  Also include the support for the namespaces that are not fnished

                                                                   finished

> +	  or well developed yet
> +
>  config BLK_DEV_INITRD
>  	bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
>  	depends on BROKEN || !FRV


---
~Randy