[PATCH 5/5] Move the PID namespace under the option

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

For the same reasons as with the IPC namespaces, all the
prototypes and stubs 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 PID_NS 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-GEFAQzZX7r8dnm+yROfE0A@public.gmane.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, struct pid_namespace *);
 
 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..a07fcf6 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_PID_NS
 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_pid_ns(struct pid_namespace *ns)
 
 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/init/Kconfig b/init/Kconfig
index 1ec7009..de7f5c9 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -422,6 +422,14 @@ config USER_NS
 	  to provide different user info for different servers.
 	  If unsure, say N.
 
+config PID_NS
+	bool "PID namespace"
+	depends on NAMESPACES
+	help
+	  Suport process id namespaces.  This allows having multiple
+	  process with the same pid as long as they are in different
+	  pid namespaces.  This is a building block of containers.
+
 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 4c137b5..bc0dd65 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -50,6 +50,7 @@ obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_KGDB) += kgdb.o
 obj-$(CONFIG_UTS_NS) += utsname.o
 obj-$(CONFIG_USER_NS) += user_namespace.o
+obj-$(CONFIG_PID_NS) += pid_namespace.o
 obj-$(CONFIG_SYSFS) += ksysfs.o
 obj-$(CONFIG_DETECT_SOFTLOCKUP) += softlockup.o
 obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
diff --git a/kernel/pid.c b/kernel/pid.c
index d1db36b..c51eee9 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-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>, OpenVZ, SWsoft Inc.
- *    (C) 2007 Sukadev Bhattiprolu <sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, 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_namespace *pid_ns)
 	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 pid_namespace *ns)
 }
 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-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>, OpenVZ, SWsoft Inc.
+ *    (C) 2007 Sukadev Bhattiprolu <sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, 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 *cachep;
+	struct list_head list;
+};
+
+static LIST_HEAD(pid_caches_lh);
+static DEFINE_MUTEX(pid_caches_mutex);
+static struct kmem_cache *pid_ns_cachep;
+
+/*
+ * 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;
+}
+
+static __init int pid_namespaces_init(void)
+{
+	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
+	return 0;
+}
+
+__initcall(pid_namespaces_init);
-- 
1.5.3.4