[Devel] Re: [PATCH 12/15] Miscelaneous stuff for pid namespaces

[sukadev at us.ibm.com]

Pavel Emelianov [xemul at openvz.org] wrote:
| This includes
|  * the headers dependency fix
|  * task_child_reaper() correct declaration
|  * fixes for is_global_init() and is_container_init()
| 
| Maybe this should come before all the other stuff...
| 
| Signed-off-by: Pavel Emelyanov <xemul at openvz.org>
| 
| ---
| 
| include/linux/pid_namespace.h |    4 ++--
| include/linux/sched.h         |    4 ++--
| kernel/pid.c                  |   16 +++++++++++++---
| 3 files changed, 17 insertions(+), 7 deletions(-)
| 
| diff -upr linux-2.6.23-rc1-mm1.orig/include/linux/pid_namespace.h 
| linux-2.6.23-rc1-mm1-7/include/linux/pid_namespace.h
| --- linux-2.6.23-rc1-mm1.orig/include/linux/pid_namespace.h	2007-07-26 
| 16:34:45.000000000 +0400
| +++ linux-2.6.23-rc1-mm1-7/include/linux/pid_namespace.h	2007-07-26 
| 16:36:36.000000000 +0400
| @@ -4,7 +4,6 @@
| #include <linux/sched.h>
| #include <linux/mm.h>
| #include <linux/threads.h>
| -#include <linux/pid.h>
| #include <linux/nsproxy.h>
| #include <linux/kref.h>
| 
| @@ -46,7 +53,8 @@ static inline struct pid_namespace *task
| 
| static inline struct task_struct *task_child_reaper(struct task_struct *tsk)
| {
| -	return init_pid_ns.child_reaper;
| +	BUG_ON(tsk != current);
| +	return tsk->nsproxy->pid_ns->child_reaper;
| }
| 
| #endif /* _LINUX_PID_NS_H */
| diff -upr linux-2.6.23-rc1-mm1.orig/include/linux/sched.h 
| linux-2.6.23-rc1-mm1-7/include/linux/sched.h
| --- linux-2.6.23-rc1-mm1.orig/include/linux/sched.h	2007-07-26 
| 16:34:45.000000000 +0400
| +++ linux-2.6.23-rc1-mm1-7/include/linux/sched.h	2007-07-26 
| 16:36:37.000000000 +0400
| @@ -1277,13 +1366,13 @@ static inline int pid_alive(struct task_
|  *
|  * TODO: We should inline this function after some cleanups in 
|  pid_namespace.h
|  */

We can now remove this TODO.

| -extern int is_global_init(struct task_struct *tsk);
| +extern int is_container_init(struct task_struct *tsk);
| 
| /*
|  * is_container_init:
|  * check whether in the task is init in its own pid namespace.
|  */

The function header describes is_container_init() but the function
is actually is_global_init(). The opp is true for the function
heaer of is_container_init() above.

| -static inline int is_container_init(struct task_struct *tsk)
| +static inline int is_global_init(struct task_struct *tsk)
| {
| 	return tsk->pid == 1;
| }
| diff -upr linux-2.6.23-rc1-mm1.orig/kernel/pid.c 
| linux-2.6.23-rc1-mm1-7/kernel/pid.c
| --- linux-2.6.23-rc1-mm1.orig/kernel/pid.c	2007-07-26 
| 16:34:45.000000000 +0400
| +++ linux-2.6.23-rc1-mm1-7/kernel/pid.c	2007-07-26 
| 16:36:37.000000000 +0400
| @@ -60,11 +62,21 @@ static inline int mk_pid(struct pid_name
| };
| EXPORT_SYMBOL(init_pid_ns);
| 
| -int is_global_init(struct task_struct *tsk)
| +int is_container_init(struct task_struct *tsk)
| {
| -	return tsk == init_pid_ns.child_reaper;
| +	int ret;

Initialize ret = 0 here would save a line of code below :-)

| +	struct pid *pid;
| +
| +	ret = 0;
| +	rcu_read_lock();
| +	pid = task_pid(tsk);
| +	if (pid != NULL && pid->numbers[pid->level].nr == 1)
| +		ret = 1;
| +	rcu_read_unlock();
| +
| +	return ret;
| }
| -EXPORT_SYMBOL(is_global_init);
| +EXPORT_SYMBOL(is_container_init);
| 
| /*
|  * Note: disable interrupts while the pidmap_lock is held as an