[Vserver] [RFC][PATCH 9/9] actually use the vpid in the child

This implements the actual inheritance of the container id from the parent
as well as the actual modification to sys_getpid().

You can demonstrate that it works by doing the following with your shell:

        echo 99 > /proc/$$/task/$$/child_container_id

And running the following (horribly buggy) program. The first and second
getpid() will return different values.

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>

char bufa[1000];
char bufb[1000];
int main(void)
{
        int i,j;
        int pida, pidb;
        int fd;
        int res;

        pida = getpid();
        sprintf(bufb, "cat /proc/%d/task/%d/container_id", pida, pida);
        system(bufb);

        sprintf(bufa, "/proc/%d/task/%d/vpid", pida, pida);
        fd = open(bufa, O_RDWR);
        write(fd, "11179", 6);
        close(fd);

        pidb = getpid();
        printf("pida: %d\n", pida);
        printf("pidb: %d\n", pidb);
        sprintf(bufb, "cat /proc/%d/task/%d/vpid", pida, pida);
        system(bufb);
}

---
 linux-2.6.14-rc5-dave/include/linux/sched.h |    6 ++++++
 linux-2.6.14-rc5-dave/kernel/fork.c         |    3 +++
 linux-2.6.14-rc5-dave/kernel/timer.c        |    2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)
diff -puN include/linux/sched.h~D0-use-vpid include/linux/sched.h
--- linux-2.6.14-rc5/include/linux/sched.h~D0-use-vpid	2005-10-24 17:55:41.000000000 +0200
+++ linux-2.6.14-rc5-dave/include/linux/sched.h	2005-10-24 17:55:41.000000000 +0200
@@ -841,6 +841,12 @@ static inline pid_t get_kernel_pid(const
 {
 	return p->__pid;
 }
+static inline pid_t get_user_pid(const struct task_struct *p)
+{
+	if (!p->container_id)
+		return p->__pid;
+	return p->vpid;
+}
 
 static inline pid_t get_kernel_tgid(const struct task_struct *p)
 {
diff -puN kernel/fork.c~D0-use-vpid kernel/fork.c
--- linux-2.6.14-rc5/kernel/fork.c~D0-use-vpid	2005-10-24 17:55:41.000000000 +0200
+++ linux-2.6.14-rc5-dave/kernel/fork.c	2005-10-24 17:55:41.000000000 +0200
@@ -937,6 +937,7 @@ static task_t *copy_process(unsigned lon
 	p->did_exec = 0;
 	copy_flags(clone_flags, p);
 	p->__pid = pid;
+	p->vpid = p->__pid;
 	retval = -EFAULT;
 	if (clone_flags & CLONE_PARENT_SETTID)
 		if (put_user(get_kernel_pid(p), parent_tidptr))
@@ -987,6 +988,8 @@ static task_t *copy_process(unsigned lon
 	p->__tgid = get_kernel_pid(p);
 	if (clone_flags & CLONE_THREAD)
 		p->__tgid = get_kernel_tgid(current);
+	p->container_id = current->child_container_id;
+	p->child_container_id = current->child_container_id;
 
 	if ((retval = security_task_alloc(p)))
 		goto bad_fork_cleanup_policy;
diff -puN kernel/timer.c~D0-use-vpid kernel/timer.c
--- linux-2.6.14-rc5/kernel/timer.c~D0-use-vpid	2005-10-24 17:55:41.000000000 +0200
+++ linux-2.6.14-rc5-dave/kernel/timer.c	2005-10-24 17:55:41.000000000 +0200
@@ -996,7 +996,7 @@ asmlinkage unsigned long sys_alarm(unsig
  */
 asmlinkage long sys_getpid(void)
 {
-	return get_kernel_pid(current);
+	return get_user_pid(current);
 }
 
 /*
_
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