[RFC][PATCH 1/6] Add struct pid_nr

[sukadev at us.ibm.com]

From: Cedric Le Goater <clg at fr.ibm.com>
Subject: [RFC][PATCH 1/6] Add struct pid_nr

Define struct pid_nr and some helper functions that will be used in
subsequent patches.

Changelog:
	- [Serge Hallyn comment]: Remove (!pid_nr) check in free_pid_nr()

Signed-off-by: Cedric Le Goater <clg at fr.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>

---
 include/linux/pid.h |   21 +++++++++++++++++
 kernel/pid.c        |   64 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)

Index: lx26-20-mm2b/include/linux/pid.h
===================================================================
--- lx26-20-mm2b.orig/include/linux/pid.h	2007-03-09 18:13:04.000000000 -0800
+++ lx26-20-mm2b/include/linux/pid.h	2007-03-09 18:27:51.000000000 -0800
@@ -11,6 +11,23 @@ enum pid_type
 	PIDTYPE_MAX
 };
 
+struct pid_namespace;
+
+/*
+ * A struct pid_nr holds a process identifier (or pid->nr) for a given
+ * pid namespace.
+ *
+ * A list of struct pid_nr is stored in the struct pid. this list is
+ * used to get the process identifier associated with the pid
+ * namespace it is being seen from.
+ */
+struct pid_nr
+{
+	struct hlist_node node;
+	int nr;
+	struct pid_namespace* pid_ns;
+};
+
 /*
  * What is struct pid?
  *
@@ -72,6 +89,7 @@ extern struct task_struct *FASTCALL(get_
 						enum pid_type));
 
 extern struct pid *get_task_pid(struct task_struct *task, enum pid_type type);
+extern void free_pidmap_pid_nr(struct pid_nr *);
 
 /*
  * attach_pid() and detach_pid() must be called with the tasklist_lock
@@ -95,6 +113,9 @@ extern struct pid *FASTCALL(find_pid(int
 extern struct pid *find_get_pid(int nr);
 extern struct pid *find_ge_pid(int nr);
 
+extern int attach_pid_nr(struct pid *pid, struct pid_nr *pid_nr);
+extern void free_pid_nr(struct pid_nr *pid_nr);
+extern struct pid_nr *alloc_pid_nr(struct pid_namespace *pid_ns);
 extern struct pid *alloc_pid(void);
 extern void FASTCALL(free_pid(struct pid *pid));
 
Index: lx26-20-mm2b/kernel/pid.c
===================================================================
--- lx26-20-mm2b.orig/kernel/pid.c	2007-03-09 18:13:04.000000000 -0800
+++ lx26-20-mm2b/kernel/pid.c	2007-03-09 18:27:51.000000000 -0800
@@ -33,6 +33,7 @@
 static struct hlist_head *pid_hash;
 static int pidhash_shift;
 static struct kmem_cache *pid_cachep;
+static struct kmem_cache *pid_nr_cachep;
 struct pid init_struct_pid = INIT_STRUCT_PID;
 
 int pid_max = PID_MAX_DEFAULT;
@@ -190,6 +191,12 @@ static void delayed_put_pid(struct rcu_h
 	put_pid(pid);
 }
 
+void free_pid_nr(struct pid_nr *pid_nr)
+{
+	put_pid_ns(pid_nr->pid_ns);
+	kmem_cache_free(pid_nr_cachep, pid_nr);
+}
+
 fastcall void free_pid(struct pid *pid)
 {
 	/* We can be called with write_lock_irq(&tasklist_lock) held */
@@ -203,6 +210,59 @@ fastcall void free_pid(struct pid *pid)
 	call_rcu(&pid->rcu, delayed_put_pid);
 }
 
+struct pid_nr *alloc_pid_nr(struct pid_namespace *pid_ns)
+{
+	struct pid_nr* pid_nr;
+
+	pid_nr = kmem_cache_alloc(pid_nr_cachep, GFP_KERNEL);
+	if (!pid_nr)
+		return pid_nr;
+
+	INIT_HLIST_NODE(&pid_nr->node);
+	pid_nr->nr = -1;
+	get_pid_ns(pid_ns);
+	pid_nr->pid_ns = pid_ns;
+
+	return pid_nr;
+}
+
+void free_pidmap_pid_nr(struct pid_nr *pid_nr)
+{
+        free_pidmap(pid_nr->pid_ns, pid_nr->nr);
+        free_pid_nr(pid_nr);
+}
+
+static struct pid_nr *alloc_pidmap_pid_nr(struct pid_namespace *pid_ns)
+{
+        int nr;
+        struct pid_nr *pid_nr;
+
+        nr = alloc_pidmap(pid_ns);
+        if (nr < 0)
+                return NULL;
+
+        pid_nr = alloc_pid_nr(pid_ns);
+        if (!pid_nr)
+                goto out_free_pidmap;
+
+        pid_nr->nr = nr;
+
+        return pid_nr;
+
+out_free_pidmap:
+        free_pidmap(pid_ns, nr);
+
+        return NULL;
+}
+
+int attach_pid_nr(struct pid *pid, struct pid_nr *pid_nr)
+{
+	spin_lock(&pid->lock);
+	hlist_add_head_rcu(&pid_nr->node, &pid->pid_nrs);
+	spin_unlock(&pid->lock);
+	return 0;
+}
+
 struct pid *alloc_pid(void)
 {
 	struct pid *pid;
@@ -420,4 +480,8 @@ void __init pidmap_init(void)
 	pid_cachep = kmem_cache_create("pid", sizeof(struct pid),
 					__alignof__(struct pid),
 					SLAB_PANIC, NULL, NULL);
+
+	pid_nr_cachep = kmem_cache_create("pid_nr", sizeof(struct pid_nr),
+					  __alignof__(struct pid_nr),
+					  SLAB_PANIC, NULL, NULL);
 }