Re: [PATCH 3/7] [PATCH] Add target_pid parameter to alloc_pidmap()

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Sukadev Bhattiprolu (sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org):
> 
> From: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
> Date: Mon, 4 May 2009 01:17:41 -0700
> Subject: [PATCH 3/7] [PATCH] Add target_pid parameter to alloc_pidmap()
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>

How about

#define TARGET_PID_UNSPECIFIED 0

or something to pass to alloc_pidmap() from alloc_pid()?
Up to you....  More importantly:

> ---
>  kernel/pid.c |   28 ++++++++++++++++++++++++++--
>  1 files changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/pid.c b/kernel/pid.c
> index fd72ad9..93406c6 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -147,12 +147,36 @@ static int alloc_pidmap_page(struct pidmap *map)
>  	return 0;
>  }
> 
> -static int alloc_pidmap(struct pid_namespace *pid_ns)
> +static int set_pidmap(struct pid_namespace *pid_ns, int pid)
> +{
> +	int offset;
> +	struct pidmap *map;
> +
> +	if (pid >= pid_max)
> +		return -EINVAL;

what about pid < 0?

> +
> +	offset = pid & BITS_PER_PAGE_MASK;
> +	map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
> +
> +	if (alloc_pidmap_page(map))
> +		return -ENOMEM;
> +
> +	if (test_and_set_bit(offset, map->page))
> +		return -EBUSY;
> +
> +	atomic_dec(&map->nr_free);
> +	return pid;
> +}
> +
> +static int alloc_pidmap(struct pid_namespace *pid_ns, int target_pid)
>  {
>  	int i, offset, max_scan, pid, last = pid_ns->last_pid;
>  	struct pidmap *map;
>  	int rc = -EAGAIN;
> 
> +	if (target_pid)
> +		return set_pidmap(pid_ns, target_pid);
> +
>  	pid = last + 1;
>  	if (pid >= pid_max)
>  		pid = RESERVED_PIDS;
> @@ -269,7 +293,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
> 
>  	tmp = ns;
>  	for (i = ns->level; i >= 0; i--) {
> -		nr = alloc_pidmap(tmp);
> +		nr = alloc_pidmap(tmp, 0);
>  		if (nr < 0)
>  			goto out_free;
> 
> -- 
> 1.5.2.5