[PATCH 5/15] Introduce struct upid

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

From: Sukadev Bhattiprolu <sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

Since task will be visible from different pid namespaces each of them
have to be addressed by multiple pids. struct upid is to store the
information about which id refers to which namespace.

The constuciton looks like this. Each struct pid carried the reference
counter and the list of tasks attached to this pid. At its end it has
a variable length array of struct upid-s. Each struct upid has a numerical
id (pid itself), pointer to the namespace, this ID is valid in and is
hashed into a pid_hash for searching the pids.

Signed-off-by: Sukadev Bhattiprolu <sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>

---

 init_task.h |    9 ++++++---
 pid.h       |   12 +++++++++---
 2 files changed, 15 insertions(+), 6 deletions(-)

diff -upr linux-2.6.23-rc1-mm1.orig/include/linux/init_task.h linux-2.6.23-rc1-mm1-7/include/linux/init_task.h
--- linux-2.6.23-rc1-mm1.orig/include/linux/init_task.h	2007-07-26 16:34:45.000000000 +0400
+++ linux-2.6.23-rc1-mm1-7/include/linux/init_task.h	2007-07-26 16:36:36.000000000 +0400
@@ -93,15 +93,18 @@ extern struct group_info init_groups;
 
 #define INIT_STRUCT_PID {						\
 	.count 		= ATOMIC_INIT(1),				\
-	.nr		= 0, 						\
-	/* Don't put this struct pid in pid_hash */			\
-	.pid_chain	= { .next = NULL, .pprev = NULL },		\
 	.tasks		= {						\
 		{ .first = &init_task.pids[PIDTYPE_PID].node },		\
 		{ .first = &init_task.pids[PIDTYPE_PGID].node },	\
 		{ .first = &init_task.pids[PIDTYPE_SID].node },		\
 	},								\
 	.rcu		= RCU_HEAD_INIT,				\
+	.level		= 0,						\
+	.numbers	= { {						\
+		.nr		= 0,					\
+		.ns		= &init_pid_ns,				\
+		.pid_chain	= { .next = NULL, .pprev = NULL },	\
+	}, }								\
 }
 
 #define INIT_PID_LINK(type) 					\
diff -upr linux-2.6.23-rc1-mm1.orig/include/linux/pid.h linux-2.6.23-rc1-mm1-7/include/linux/pid.h
--- linux-2.6.23-rc1-mm1.orig/include/linux/pid.h	2007-07-26 16:34:45.000000000 +0400
+++ linux-2.6.23-rc1-mm1-7/include/linux/pid.h	2007-07-26 16:36:37.000000000 +0400
@@ -40,15 +40,21 @@ enum pid_type
  * processes.
  */
 
-struct pid
-{
-	atomic_t count;
+struct upid {
 	/* Try to keep pid_chain in the same cacheline as nr for find_pid */
 	int nr;
+	struct pid_namespace *ns;
 	struct hlist_node pid_chain;
+};
+
+struct pid
+{
+	atomic_t count;
 	/* lists of tasks that use this pid */
 	struct hlist_head tasks[PIDTYPE_MAX];
 	struct rcu_head rcu;
+	int level;
+	struct upid numbers[1];
 };
 
 extern struct pid init_struct_pid;