This is the implementation of move_pid_to_ns (see [PATCH 15/28])

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

---

 pid.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 58 insertions(+)

--- ./kernel/pid.c.flatclone	2007-06-15 15:26:23.000000000 +0400
+++ ./kernel/pid.c	2007-06-15 15:28:22.000000000 +0400
@@ -331,6 +331,48 @@ struct pid * fastcall find_pid_ns(int nr
 	return (ns == &init_pid_ns ?
 			find_global_pid(nr) : find_virtual_pid(nr, ns));
 }
+
+static inline int move_pid_to_ns(struct pid *pid, struct pid_namespace *ns)
+{
+	int vnr;
+
+	/*
+	 * the pid is in this ns already. e.g. this may happen if
+	 * the task has equal pid and pgid
+	 */
+	if (pid->ns == ns)
+		return 0;
+
+	BUG_ON(pid->ns != &init_pid_ns);
+
+	vnr = alloc_pidmap(ns);
+	if (vnr < 0)
+		return -ENOMEM;
+
+	get_pid_ns(ns);
+	pid->vnr = vnr;
+	pid->ns = ns;
+	spin_lock_irq(&pidmap_lock);
+	hlist_add_head_rcu(&pid->vpid_chain,
+			&vpid_hash[vpid_hashfn(vnr, ns)]);
+	spin_unlock_irq(&pidmap_lock);
+	return 0;
+}
+
+static inline void del_pid_from_ns(struct pid *pid, struct pid_namespace *ns)
+{
+	if (pid->ns == &init_pid_ns)
+		return;
+
+	spin_lock_irq(&pidmap_lock);
+	hlist_del_rcu(&pid->vpid_chain);
+	spin_unlock_irq(&pidmap_lock);
+
+	free_pidmap(ns, pid->vnr);
+	put_pid_ns(pid->ns);
+	pid->vnr = pid->nr;
+	pid->ns = &init_pid_ns;
+}
 #endif
 #endif
 
@@ -588,6 +630,15 @@ struct pid_namespace *copy_pid_ns(int fl
 	if (!(flags & CLONE_NEWPIDS))
 		goto out;
 
+#ifdef CONFIG_PID_NS_FLAT
+	/*
+	 * flat model doen't allow to create the nested namespaces
+	 */
+	new_ns = ERR_PTR(-EINVAL);
+	if (old_ns != &init_pid_ns)
+		goto out_put;
+#endif
+
 	new_ns = ERR_PTR(-EBUSY);
 	if (!alone_in_pgrp(current))
 		goto out_put;
@@ -646,6 +697,13 @@ out_pgid:
 out_sid:
 	del_pid_from_ns(task_pid(tsk), ns);
 out_pid:
+#ifdef CONFIG_PID_NS_FLAT
+	/*
+	 * this cannot happen if we use flat pid namespaces as we try to
+	 * allocate the very first pid from the pidmap with one page in it
+	 */
+	BUG();
+#endif
 	return err;
 }
 #else
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