On Fri, 14 Oct 2016, Fenghua Yu wrote:
> +struct task_move_callback {
> +     struct callback_head work;
> +     struct rdtgroup *rdtgrp;

Please align the struct members as you did everywhere else already.

> +};
> +
> +static void move_myself(struct callback_head *head)
> +{
> +     struct task_move_callback *callback;
> +     struct rdtgroup *rdtgrp;
> +
> +     callback = container_of(head, struct task_move_callback, work);
> +     rdtgrp = callback->rdtgrp;
> +
> +     /* Resource group might have been deleted before process runs */

        /*
         * If resource group was deleted before this task work callback
         * was invoked, then assign the task to root group and free the
         * resource group,
         */

> +     if (atomic_dec_and_test(&rdtgrp->waitcount) &&
> +         (rdtgrp->flags & RDT_DELETED)) {
> +             current->closid = 0;
> +             kfree(rdtgrp);
> +     }
> +
> +     kfree(callback);
> +}
> +
> +static int __rdtgroup_move_task(struct task_struct *tsk,
> +                             struct rdtgroup *rdtgrp)
> +{
> +     struct task_move_callback *callback;
> +     int ret;
> +
> +     callback = kzalloc(sizeof(*callback), GFP_KERNEL);
> +     if (!callback)
> +             return -ENOMEM;
> +     callback->work.func = move_myself;
> +     callback->rdtgrp = rdtgrp;

Lacks a comment:

        /*
         * Take a refcount, so rdtgrp cannot be freed before the
         * callback has been invoked
         */

> +     atomic_inc(&rdtgrp->waitcount);
> +     ret = task_work_add(tsk, &callback->work, true);
> +     if (ret) {


Lacks a comment as well:

                /*
                 * Task is exiting. Drop the refcount and free the callback.
                 * No need to check the refcount as the group cannot be
                 * deleted before the write function unlocks rdtgroup_mutex.
                 */

For you the comment might be obvious, but I had to lookup the world and
some more.

> +             atomic_dec(&rdtgrp->waitcount);
> +             kfree(callback);
> +     } else {
> +             tsk->closid = rdtgrp->closid;
> +     }
> +     return ret;

> +static int rdtgroup_task_write_permission(struct task_struct *task,
> +                                       struct kernfs_open_file *of)
> +{
> +     const struct cred *cred = current_cred();
> +     const struct cred *tcred = get_task_cred(task);
> +     int ret = 0;
> +
> +     /*
> +      * even if we're attaching all tasks in the thread group, we only

Sentences start with an uppercase letter.

> +      * need to check permissions on one of them.
> +      */
> +     if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
> +         !uid_eq(cred->euid, tcred->uid) &&
> +         !uid_eq(cred->euid, tcred->suid))
> +             ret = -EPERM;
> +
> +     put_cred(tcred);
> +     return ret;
> +}
> +
> +static int rdtgroup_move_task(pid_t pid, struct rdtgroup *rdtgrp,
> +                           struct kernfs_open_file *of)
> +{
> +     struct task_struct *tsk;
> +     int ret;
> +
> +     rcu_read_lock();
> +     if (pid) {
> +             tsk = find_task_by_vpid(pid);
> +             if (!tsk) {
> +                     ret = -ESRCH;
> +                     goto out_unlock_rcu;

This goto is pointless as this is the only user,

                        rcu_read_unlock()l
                        return -ESRCH;

> +             }
> +     } else {
> +             tsk = current;
> +     }

> @@ -559,6 +713,13 @@ static void rmdir_all_sub(void)
>  {
>       struct rdtgroup *rdtgrp;
>       struct list_head *l, *next;
> +     struct task_struct *p;
> +
> +     /* move all tasks to default resource group */
> +     read_lock(&tasklist_lock);
> +     for_each_process(p)
> +             p->closid = 0;
> +     read_unlock(&tasklist_lock);

Ok.

> +     /* Don't allow if there are processes in this group */
> +     read_lock(&tasklist_lock);
> +     for_each_process(p) {
> +             if (p->closid == rdtgrp->closid) {
> +                     read_unlock(&tasklist_lock);
> +                     rdtgroup_kn_unlock(kn);
> +                     return -EBUSY;
> +             }
> +     }
> +     read_unlock(&tasklist_lock);

I wonder, whether we should simply give those tasks back to the default
group, same as we do with the cpus.

Thanks,

        tglx

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