sukadev@us.ibm.com wrote:
> Subject: Move alloc_pid call to copy_process
> 
> From: Sukadev Bhattiprolu <sukadev@us.ibm.com>
> 
> Move alloc_pid() into copy_process(). This will keep all pid and pid
> namespace code together and simplify error handling when we support
> multiple pid namespaces.

I haven't found this in patches, so I ask it here:

We clone a new task with CLONE_NEWPIDS flag. This task
allocates its PIDTYPE_PID pid and this pid happens in 
booth parent and child namespace. This is OK. Then new 
task attaches PIDTYPE_SID and PIDTYPE_PGID pids from parent
task. But these ones are in parent namespace only. 

Right? Is that good?

> Changelog: 
> 	- [Eric Biederman] Move the check of copy_process_type to alloc_pid()/
> 	  free_pid() and to avoid clutter in copy_process().
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
> ---
>  include/linux/pid.h |    7 ++++++-
>  kernel/fork.c       |   21 +++++++++++++--------
>  kernel/pid.c        |   10 +++++++++-
>  3 files changed, 28 insertions(+), 10 deletions(-)
> 
> Index: lx26-21-mm2/include/linux/pid.h
> ===================================================================
> --- lx26-21-mm2.orig/include/linux/pid.h	2007-05-22 16:59:40.000000000 -0700
> +++ lx26-21-mm2/include/linux/pid.h	2007-05-22 17:06:48.000000000 -0700
> @@ -3,6 +3,11 @@
>  
>  #include <linux/rcupdate.h>
>  
> +enum copy_process_type {
> +	COPY_NON_IDLE_PROCESS,
> +	COPY_IDLE_PROCESS,
> +};
> +
>  enum pid_type
>  {
>  	PIDTYPE_PID,
> @@ -95,7 +100,7 @@ extern struct pid *FASTCALL(find_pid(int
>  extern struct pid *find_get_pid(int nr);
>  extern struct pid *find_ge_pid(int nr);
>  
> -extern struct pid *alloc_pid(void);
> +extern struct pid *alloc_pid(enum copy_process_type);
>  extern void FASTCALL(free_pid(struct pid *pid));
>  
>  static inline pid_t pid_to_nr(struct pid *pid)
> Index: lx26-21-mm2/kernel/fork.c
> ===================================================================
> --- lx26-21-mm2.orig/kernel/fork.c	2007-05-22 16:59:41.000000000 -0700
> +++ lx26-21-mm2/kernel/fork.c	2007-05-22 17:06:48.000000000 -0700
> @@ -961,10 +961,11 @@ static struct task_struct *copy_process(
>  					unsigned long stack_size,
>  					int __user *parent_tidptr,
>  					int __user *child_tidptr,
> -					struct pid *pid)
> +					enum copy_process_type copy_src)
>  {
>  	int retval;
>  	struct task_struct *p = NULL;
> +	struct pid *pid;
>  
>  	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
>  		return ERR_PTR(-EINVAL);
> @@ -1025,6 +1026,10 @@ static struct task_struct *copy_process(
>  	if (p->binfmt && !try_module_get(p->binfmt->module))
>  		goto bad_fork_cleanup_put_domain;
>  
> +	pid = alloc_pid(copy_src);
> +	if (!pid)
> +		goto bad_fork_put_binfmt_module;
> +
>  	p->did_exec = 0;
>  	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
>  	copy_flags(clone_flags, p);
> @@ -1305,6 +1310,8 @@ bad_fork_cleanup_cpuset:
>  #endif
>  	cpuset_exit(p);
>  	delayacct_tsk_free(p);
> +	free_pid(pid);
> +bad_fork_put_binfmt_module:
>  	if (p->binfmt)
>  		module_put(p->binfmt->module);
>  bad_fork_cleanup_put_domain:
> @@ -1331,7 +1338,7 @@ struct task_struct * __cpuinit fork_idle
>  	struct pt_regs regs;
>  
>  	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL,
> -				&init_struct_pid);
> +				COPY_IDLE_PROCESS);
>  	if (!IS_ERR(task))
>  		init_idle(task, cpu);
>  
> @@ -1369,19 +1376,16 @@ long do_fork(unsigned long clone_flags,
>  {
>  	struct task_struct *p;
>  	int trace = 0;
> -	struct pid *pid = alloc_pid();
>  	long nr;
>  
> -	if (!pid)
> -		return -EAGAIN;
> -	nr = pid->nr;
>  	if (unlikely(current->ptrace)) {
>  		trace = fork_traceflag (clone_flags);
>  		if (trace)
>  			clone_flags |= CLONE_PTRACE;
>  	}
>  
> -	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
> +	p = copy_process(clone_flags, stack_start, regs, stack_size,
> +			parent_tidptr, child_tidptr, COPY_NON_IDLE_PROCESS);
>  	/*
>  	 * Do this prior waking up the new thread - the thread pointer
>  	 * might get invalid after that point, if the thread exits quickly.
> @@ -1389,6 +1393,8 @@ long do_fork(unsigned long clone_flags,
>  	if (!IS_ERR(p)) {
>  		struct completion vfork;
>  
> +		nr = pid_to_nr(task_pid(p));
> +
>  		if (clone_flags & CLONE_VFORK) {
>  			p->vfork_done = &vfork;
>  			init_completion(&vfork);
> @@ -1422,7 +1428,6 @@ long do_fork(unsigned long clone_flags,
>  			}
>  		}
>  	} else {
> -		free_pid(pid);
>  		nr = PTR_ERR(p);
>  	}
>  	return nr;
> Index: lx26-21-mm2/kernel/pid.c
> ===================================================================
> --- lx26-21-mm2.orig/kernel/pid.c	2007-05-22 16:59:46.000000000 -0700
> +++ lx26-21-mm2/kernel/pid.c	2007-05-22 17:06:48.000000000 -0700
> @@ -216,6 +216,10 @@ fastcall void free_pid(struct pid *pid)
>  	/* We can be called with write_lock_irq(&tasklist_lock) held */
>  	unsigned long flags;
>  
> +	/* check this here to keep copy_process() cleaner */
> +	if (unlikely(pid == &init_struct_pid))
> +		return;
> +
>  	spin_lock_irqsave(&pidmap_lock, flags);
>  	hlist_del_rcu(&pid->pid_chain);
>  	spin_unlock_irqrestore(&pidmap_lock, flags);
> @@ -224,12 +228,16 @@ fastcall void free_pid(struct pid *pid)
>  	call_rcu(&pid->rcu, delayed_put_pid);
>  }
>  
> -struct pid *alloc_pid(void)
> +struct pid *alloc_pid(enum copy_process_type copy_src)
>  {
>  	struct pid *pid;
>  	enum pid_type type;
>  	int nr = -1;
>  
> +	/* check this here to keep copy_process() cleaner */
> +	if (unlikely(copy_src == COPY_IDLE_PROCESS))
> +		return &init_struct_pid;
> +
>  	pid = kmem_cache_alloc(pid_cachep, GFP_KERNEL);
>  	if (!pid)
>  		goto out;
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