On Fri, 14 Jul 2017, Gargi Sharma wrote:
> In pid_alloc function, idr_preload function is used along with
> idr_alloc_cyclic.
> idr_alloc_cyclic is used instead of idr_alloc because we might want to
> reuse the unassigned integers. The rest of the code is same as the previous
> alloc_pid, which puts the pid allocated onto the task list. After the flag
> out_free, ids are removed from the idr entry using idr_remove function.
> Inside free_pid() deleting from rcu hash list is same as before.
> The only change is instead of removing entry from pidmap, allocated
> number is now deleted from the idr entry.
>
> Signed-off-by: Gargi Sharma <gs051095@xxxxxxxxx>
> ---
> kernel/pid.c | 26 +++++++++++++++++++++-----
> 1 file changed, 21 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/pid.c b/kernel/pid.c
> index fd1cde1..5060266 100644
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -287,8 +287,14 @@ void free_pid(struct pid *pid)
> }
> spin_unlock_irqrestore(&pidmap_lock, flags);
>
> - for (i = 0; i <= pid->level; i++)
> - free_pidmap(pid->numbers + i);
> + for (i = 0; i <= pid->level; i++) {
> + struct upid *upid = pid->numbers + i;
> + struct pid_namespace *ns = upid->ns;
> +
> + mutex_lock(&ns->idr_mutex_lock);
> + idr_remove(ns->idr, upid->nr);
> + mutex_unlock(&ns->idr_mutex_lock);
> + }
>
> call_rcu(&pid->rcu, delayed_put_pid);
> }
> @@ -309,7 +315,15 @@ struct pid *alloc_pid(struct pid_namespace *ns)
> tmp = ns;
> pid->level = ns->level;
> for (i = ns->level; i >= 0; i--) {
> - nr = alloc_pidmap(tmp);
> + idr_preload(GFP_KERNEL);
> +
> + mutex_lock(&ns->idr_mutex_lock);
> + nr = idr_alloc_cyclic(tmp->idr, ns, RESERVED_PIDS,
> + pid_max, GFP_KERNEL);
> +
> + mutex_unlock(&ns->idr_mutex_lock);
> + idr_preload_end();
> +
> if (nr < 0) {
> retval = nr;
> goto out_free;
> @@ -350,8 +364,10 @@ struct pid *alloc_pid(struct pid_namespace *ns)
> put_pid_ns(ns);
>
> out_free:
> - while (++i <= ns->level)
> - free_pidmap(pid->numbers + i);
> + while (++i <= ns->level) {
> + idr_remove(ns->idr, (pid->numbers + i)->nr);
> + mutex_unlock(&ns->idr_mutex_lock);
It doesn't look right to call mutex_unlock multiple times in a lopo on the
same value.
julia
> + }
>
> kmem_cache_free(ns->pid_cachep, pid);
> return ERR_PTR(retval);
> --
> 2.7.4
>
>
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