Unike Suka's patches I don not limit the level of pid nesting
creating the caches on demand, depending on the namespace's level.

Each kmem cache is names "pid_<NR>", where <NR> is the level
of pid namespace and thus - the number of virtual pids in it.

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

---

 pid.c |   61 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 56 insertions(+), 5 deletions(-)

--- ./kernel/pid.c.ve10	2007-07-06 11:04:15.000000000 +0400
+++ ./kernel/pid.c	2007-07-06 11:04:48.000000000 +0400
@@ -32,7 +32,6 @@
 #define pid_hashfn(nr) hash_long((unsigned long)nr, pidhash_shift)
 static struct hlist_head *pid_hash;
 static int pidhash_shift;
-static struct kmem_cache *pid_cachep;
 struct pid init_struct_pid = INIT_STRUCT_PID;
 
 int pid_max = PID_MAX_DEFAULT;
@@ -179,11 +178,15 @@ static int next_pidmap(struct pid_namesp
 
 fastcall void put_pid(struct pid *pid)
 {
+	struct pid_namespace *ns;
+
 	if (!pid)
 		return;
+
+	ns = pid->numbers[0].ns;
 	if ((atomic_read(&pid->count) == 1) ||
 	     atomic_dec_and_test(&pid->count))
-		kmem_cache_free(pid_cachep, pid);
+		kmem_cache_free(ns->pid_cachep, pid);
 }
 EXPORT_SYMBOL_GPL(put_pid);
 
@@ -212,7 +215,7 @@ struct pid *alloc_pid(struct pid_namespa
 	enum pid_type type;
 	int nr = -1;
 
-	pid = kmem_cache_alloc(pid_cachep, GFP_KERNEL);
+	pid = kmem_cache_alloc(init_pid_ns.pid_cachep, GFP_KERNEL);
 	if (!pid)
 		goto out;
 
@@ -233,7 +236,7 @@ out:
 	return pid;
 
 out_free:
-	kmem_cache_free(pid_cachep, pid);
+	kmem_cache_free(init_pid_ns.pid_cachep, pid);
 	pid = NULL;
 	goto out;
 }
@@ -378,6 +381,52 @@ struct pid *find_ge_pid(int nr, struct p
 }
 EXPORT_SYMBOL_GPL(find_get_pid);
 
+struct pid_cache {
+	int level;
+	char name[16];
+	struct kmem_cache *cachep;
+	struct list_head lh;
+};
+
+static LIST_HEAD(pid_caches);
+static DEFINE_MUTEX(pid_cache_mutex);
+
+static struct kmem_cache *create_pid_cachep(int level)
+{
+	struct pid_cache *pc;
+	struct kmem_cache *cachep = NULL;
+
+	mutex_lock(&pid_cache_mutex);
+	list_for_each_entry (pc, &pid_caches, lh)
+		if (pc->level == level) {
+			cachep = pc->cachep;
+			goto out;
+		}
+
+	pc = kzalloc(sizeof(struct pid_cache), GFP_KERNEL);
+	if (pc == NULL)
+		goto out;
+
+	snprintf(pc->name, sizeof(pc->name), "pid_%d", level);
+	cachep = kmem_cache_create(pc->name,
+			sizeof(struct pid) + level * sizeof(struct pid_number),
+			0, SLAB_HWCACHE_ALIGN, NULL, NULL);
+	if (cachep == NULL)
+		goto out_free;
+
+	pc->cachep = cachep;
+	pc->level = level;
+	list_add(&pc->lh, &pid_caches);
+	pc = NULL;
+
+out_free:
+	if (pc != NULL)
+		kfree(pc);
+out:
+	mutex_unlock(&pid_cache_mutex);
+	return cachep;
+}
+
 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 {
 	BUG_ON(!old_ns);
@@ -425,5 +474,7 @@ void __init pidmap_init(void)
 	set_bit(0, init_pid_ns.pidmap[0].page);
 	atomic_dec(&init_pid_ns.pidmap[0].nr_free);
 
-	pid_cachep = KMEM_CACHE(pid, SLAB_PANIC);
+	init_pid_ns.pid_cachep = create_pid_cachep(0);
+	if (init_pid_ns.pid_cachep == NULL)
+		panic("Can't create pid cachep");
 }
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