Re: [PATCH v3 1/2] pid: Replace pid bitmap implementation with IDR API

[Rik van Riel]

On Fri, 2017-10-06 at 07:53 -0400, Gargi Sharma wrote:

> @@ -308,8 +165,28 @@ struct pid *alloc_pid(struct pid_namespace *ns)

The code looks like it addresses all of Oleg's comments now, but the
comments could be a little clearer, IMHO.
Â
> Â	tmp = ns;
> Â	pid->level = ns->level;
> +
> Â	for (i = ns->level; i >= 0; i--) {
> -		nr = alloc_pidmap(tmp);
> +		int pid_min = 1;
> +		idr_preload(GFP_KERNEL);
> +		spin_lock_irq(&pidmap_lock);
> +
> +		/*
> +		Â* init really needs pid 1, but after reaching the
> maximum
> +		Â* wrap back to RESERVED_PIDS
> +		Â*/
> +		if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
> +			pid_min = RESERVED_PIDS;
> +
> +		/*
> +		Â* allocate a NULL pointer so that find_pid_ns can't
> +		Â* find pid that is not fully initialized
> +		Â*/

		/*
		 * Store a null pointer so find_pid_ns does not find		 *
a partially initialized PID (see below).
		 */

> +		nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
> +				ÂÂÂÂÂÂpid_max, GFP_ATOMIC);
> +		spin_unlock_irq(&pidmap_lock);
> +		idr_preload_end();
> +
> Â		if (nr < 0) {
> Â			retval = nr;
> Â			goto out_free;
> @@ -339,6 +216,7 @@ struct pid *alloc_pid(struct pid_namespace *ns)
> Â	for ( ; upid >= pid->numbers; --upid) {
> Â		hlist_add_head_rcu(&upid->pid_chain,
> Â				&pid_hash[pid_hashfn(upid->nr, upid-
> >ns)]);

		/* Make the PID visible to find_pid_ns. */

> +		idr_replace(&upid->ns->idr, pid, upid->nr);
> Â		upid->ns->nr_hashed++;
> Â	}
> Â	spin_unlock_irq(&pidmap_lock);
> 

Everything else looks great to me.

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

-- 
All Rights Reversed.

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