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SubjectRe: [PATCH v3 1/2] pid: Replace pid bitmap implementation with IDR API
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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.
 
>   tmp = ns;
>   pid->level = ns->level;
> +
>   for (i = ns->level; i >= 0; i--) {
> - nr = alloc_pidmap(tmp);
> + int pid_min = 1;
> + idr_preload(GFP_KERNEL);
> + spin_lock_irq(&pidmap_lock);
> +
> + /*
> +  * init really needs pid 1, but after reaching the
> maximum
> +  * wrap back to RESERVED_PIDS
> +  */
> + if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
> + pid_min = RESERVED_PIDS;
> +
> + /*
> +  * allocate a NULL pointer so that find_pid_ns can't
> +  * find pid that is not fully initialized
> +  */

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

/* Make the PID visible to find_pid_ns. */

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

Everything else looks great to me.

Reviewed-by: Rik van Riel <riel@redhat.com>

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