Re: [PATCH v10 3/4] cgroups: allow a cgroup subsystem to reject a fork

[Aleksa Sarai <cyphar@cyphar.com>]

Hi Tejun,

>> +/* Ditto for the can_fork/cancel_fork/reapply_fork callbacks. */
>> +static int need_canfork_callback __read_mostly;
>> +static int need_cancelfork_callback __read_mostly;
>
> And given that the reason we have these masks is avoiding iteration in
> relatively hot paths.  Does cancelfork mask make sense?

Do you still want me to remove it? I only added it because it made the
callback code more consistent for cancel_fork and can_fork.

>> +void cgroup_cancel_fork(struct task_struct *child,
>> +                     void *ss_state[CGROUP_PREFORK_COUNT])
>> +{
>> +     struct cgroup_subsys *ss;
>> +     int i;
>> +
>> +     for_each_subsys_which(need_cancelfork_callback, ss, i) {
>> +             void *state = NULL;
>> +
>> +             if (CGROUP_PREFORK_START <= i && i < CGROUP_PREFORK_END)
>> +                     state = ss_state[i - CGROUP_PREFORK_START];
>
> Maybe we want a helper callback which does
>
>         if (CGROUP_PREFORK_START <= ssid && ssid < CGROUP_PREFORK_END)
>                 return &ss_state[ssid - CGROUP_PREFORK_START];
>         return NULL;

What would be a nice name for it? I can't think of anything better
than __get_ss_private() and __get_ss_privatep().

--
Aleksa Sarai (cyphar)
www.cyphar.com