From: Cedric Le Goater <clg@fr.ibm.com>

This patch adds a hashtable of nsproxy using the nsproxy as a key. 
init_nsproxy is hashed at init with key 0. This is considered to be 
the 'host' nsproxy.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
---
 include/linux/nsproxy.h |    3 +++
 kernel/nsproxy.c        |   43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

Index: 2.6.19-rc6-mm2/include/linux/nsproxy.h
===================================================================
--- 2.6.19-rc6-mm2.orig/include/linux/nsproxy.h
+++ 2.6.19-rc6-mm2/include/linux/nsproxy.h
@@ -2,6 +2,7 @@
 #define _LINUX_NSPROXY_H
 
 #include <linux/spinlock.h>
+#include <linux/list.h>
 
 struct task_struct;
 
@@ -34,6 +35,8 @@ struct nsproxy {
 	struct pid_namespace *pid_ns;
 	struct net_namespace *net_ns;
 	struct user_namespace *user_ns;
+
+	struct hlist_node ns_hash_node;
 };
 extern struct nsproxy init_nsproxy;
 
Index: 2.6.19-rc6-mm2/kernel/nsproxy.c
===================================================================
--- 2.6.19-rc6-mm2.orig/kernel/nsproxy.c
+++ 2.6.19-rc6-mm2/kernel/nsproxy.c
@@ -22,6 +22,15 @@
 #include <linux/pid_namespace.h>
 #include <linux/net_namespace.h>
 
+#define NS_HASH_BITS 		3 /* this might need some configuration */
+#define NS_HASH_SIZE		(1 << NS_HASH_BITS)
+#define NS_HASH_MASK		(NS_HASH_SIZE - 1)
+#define ns_hashfn(id)		(((id >> NS_HASH_BITS) + id) & NS_HASH_MASK)
+#define ns_hash_head(id)	&ns_hash[ns_hashfn(id)]
+
+static struct hlist_head ns_hash[NS_HASH_SIZE];
+static DEFINE_SPINLOCK(ns_hash_lock);
+
 struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
 
 static inline void get_nsproxy(struct nsproxy *ns)
@@ -190,3 +199,37 @@ void put_nsproxy(struct nsproxy *ns)
 		free_nsproxy(ns);
 	}
 }
+
+/*
+ * This routine must be called with the ns_hash spin_locked
+ */
+static inline struct nsproxy *ns_hash_find(int id)
+{
+	struct hlist_node *elem;
+	struct nsproxy *ns;
+
+	hlist_for_each_entry(ns, elem, ns_hash_head(id), ns_hash_node) {
+		if (ns->id == id) {
+			get_nsproxy(ns);
+			return ns;
+		}
+	}
+
+	return NULL;
+}
+
+static int __init nshash_init(void)
+{
+	int i;
+
+	for (i = 0; i < NS_HASH_SIZE; ++i)
+		INIT_HLIST_HEAD(&ns_hash[i]);
+
+	spin_lock_irq(&ns_hash_lock);
+	hlist_add_head(&init_nsproxy.ns_hash_node, ns_hash_head(0));
+	spin_unlock_irq(&ns_hash_lock);
+
+	return 0;
+}
+
+module_init(nshash_init);

-- 
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