Re: [RFC PATCH 05/11] mm/mempolicy: modify set_mempolicy_home_node to take a task argument

Michal Hocko
2023-11-28T14:07:50Z

On Wed 22-11-23 16:11:54, Gregory Price wrote:
[...]
> +
> + /*
> + * Behavior when task == current allows a task modifying itself
> + * to bypass the check in get_task_mm and acquire the mm directly
> + */
> + if (task == current) {
> + mm = task->mm;
> + mmget(mm);
> + } else
> + mm = get_task_mm(task);

Similar question as in the previous patch. When is a kthread legit to do
manipulate borrowed mm memory policy?

> +
> + if (!mm)
> + return -ENODEV;

Is this an expected error? No mm means task dying and mm has been
already released. Should we simply return ESRCH wouldbe a better error
code IMO. This should never happen for the current task so it sould be
safe to add.

--
Michal Hocko
SUSE Labs