[PATCH] add child reaper to pid_namespace

Add a per pid_namespace child-reaper.  This is needed so processes are reaped
within the same pid space and do not spill over to the parent pid space.  Its
also needed so containers preserve existing semantic that pid == 1 would reap
orphaned children.

This is based on Eric Biederman's patch: http://lkml.org/lkml/2006/2/6/285

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 9 insertions, 3 deletions

diff --git a/include/linux/pid.h b/include/linux/pid.h
index 2c0007d17218..4dec047b1837 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -35,8 +35,9 @@ enum pid_type
  *
  * Holding a reference to struct pid solves both of these problems.
  * It is small so holding a reference does not consume a lot of
- * resources, and since a new struct pid is allocated when the numeric
- * pid value is reused we don't mistakenly refer to new processes.
+ * resources, and since a new struct pid is allocated when the numeric pid
+ * value is reused (when pids wrap around) we don't mistakenly refer to new
+ * processes.
  */
 
 struct pid
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index 76e7c6b2cf33..d2a9d419f01f 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -19,6 +19,7 @@ struct pid_namespace {
         struct kref kref;
         struct pidmap pidmap[PIDMAP_ENTRIES];
         int last_pid;
+        struct task_struct *child_reaper;
 };
 
 extern struct pid_namespace init_pid_ns;
@@ -36,4 +37,9 @@ static inline void put_pid_ns(struct pid_namespace *ns)
         kref_put(&ns->kref, free_pid_ns);
 }
 
+static inline struct task_struct *child_reaper(struct task_struct *tsk)
+{
+        return tsk->nsproxy->pid_ns->child_reaper;
+}
+
 #endif /* _LINUX_PID_NS_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6fec1d419714..f0317edea141 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1400,7 +1400,6 @@ extern NORET_TYPE void do_group_exit(int);
 extern void daemonize(const char *, ...);
 extern int allow_signal(int);
 extern int disallow_signal(int);
-extern struct task_struct *child_reaper;
 
 extern int do_execve(char *, char __user * __user *, char __user * __user *, struct pt_regs *);
 extern long do_fork(unsigned long, unsigned long, struct pt_regs *, unsigned long, int __user *, int __user *);