[PATCH -mm] add a kmem_cache for nsproxy objects

[Cedric Le Goater <clg@fr.ibm.com>]

It should improve performance in some scenarii where a lot of 
these nsproxy objects are created by unsharing namespaces. This is
a typical use of virtual servers that are being created or entered.

This is also a good tool to find leaks and gather statistics on
namespace usage.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
---
 kernel/nsproxy.c |   21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

Index: 2.6.22-rc4-mm2/kernel/nsproxy.c
===================================================================
--- 2.6.22-rc4-mm2.orig/kernel/nsproxy.c
+++ 2.6.22-rc4-mm2/kernel/nsproxy.c
@@ -21,6 +21,8 @@
 #include <linux/utsname.h>
 #include <linux/pid_namespace.h>
 
+static struct kmem_cache *nsproxy_cachep;
+
 struct nsproxy init_nsproxy = INIT_NSPROXY(init_nsproxy);
 
 static inline void get_nsproxy(struct nsproxy *ns)
@@ -43,9 +45,11 @@ static inline struct nsproxy *clone_nspr
 {
 	struct nsproxy *ns;
 
-	ns = kmemdup(orig, sizeof(struct nsproxy), GFP_KERNEL);
-	if (ns)
+	ns = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
+	if (ns) {
+		memcpy(ns, orig, sizeof(struct nsproxy));
 		atomic_set(&ns->count, 1);
+	}
 	return ns;
 }
 
@@ -109,7 +113,7 @@ out_uts:
 	if (new_nsp->mnt_ns)
 		put_mnt_ns(new_nsp->mnt_ns);
 out_ns:
-	kfree(new_nsp);
+	kmem_cache_free(nsproxy_cachep, new_nsp);
 	return ERR_PTR(err);
 }
 
@@ -160,7 +164,7 @@ void free_nsproxy(struct nsproxy *ns)
 		put_pid_ns(ns->pid_ns);
 	if (ns->user_ns)
 		put_user_ns(ns->user_ns);
-	kfree(ns);
+	kmem_cache_free(nsproxy_cachep, ns);
 }
 
 /*
@@ -191,3 +195,12 @@ int unshare_nsproxy_namespaces(unsigned 
 	}
 	return err;
 }
+
+static int __init nsproxy_cache_init(void)
+{
+	nsproxy_cachep = kmem_cache_create("nsproxy", sizeof(struct nsproxy),
+					   0, SLAB_PANIC, NULL, NULL);
+	return 0;
+}
+
+module_init(nsproxy_cache_init);