Quoting Matt Roper (2018-02-01 19:53:11)
> Drivers will need to save/restore the appropriate cgroup data for the process
> submitting a driver request. Add an interface for drivers to determine the
> cgroup for the userspace process submitting a driver request.
>
> Cc: Tejun Heo <t...@kernel.org>
> Cc: cgro...@vger.kernel.org
> Signed-off-by: Matt Roper <matthew.d.ro...@intel.com>
> ---
> include/linux/cgroup.h | 6 ++++++
> kernel/cgroup/cgroup_driver.c | 24 ++++++++++++++++++++++++
> 2 files changed, 30 insertions(+)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 0ba1374122c7..05ebfb97bcde 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -842,6 +842,7 @@ void cgroup_driver_release(struct cgroup_driver *drv);
> struct cgroup_driver_data * cgroup_driver_get_data(struct cgroup_driver *drv,
> struct cgroup *cgrp,
> bool *is_new);
> +struct cgroup *cgroup_for_driver_process(struct pid *pid);
>
> #else /* !CONFIG_CGROUP_DRIVER */
>
> @@ -857,6 +858,11 @@ cgroup_driver_get_data(struct cgroup_driver *drv,
> {
> return ERR_PTR(-EINVAL);
> }
> +static inline struct cgroup *
> +cgroup_for_driver_process(struct pid *pid)
> +{
> + return NULL;
> +}
>
> #endif /* !CONFIG_CGROUP_DRIVER */
>
> diff --git a/kernel/cgroup/cgroup_driver.c b/kernel/cgroup/cgroup_driver.c
> index 0d893395dc7b..4f870cbb9212 100644
> --- a/kernel/cgroup/cgroup_driver.c
> +++ b/kernel/cgroup/cgroup_driver.c
> @@ -128,3 +128,27 @@ cgroup_driver_get_data(struct cgroup_driver *drv,
> return data;
> }
> EXPORT_SYMBOL(cgroup_driver_get_data);
> +
> +/**
> + * cgroup_for_driver_process - return the cgroup for a process
> + * @pid: process to lookup cgroup for
> + *
> + * Returns the cgroup from the v2 hierarchy that a process belongs to.
> + * This function is intended to be called from drivers and will obtain
> + * the necessary cgroup locks.
> + *
> + * RETURNS:
> + * Process' cgroup in the default (v2) hierarchy
> + */
> +struct cgroup *
> +cgroup_for_driver_process(struct pid *pid)
> +{
> + struct task_struct *task = pid_task(pid, PIDTYPE_PID);
> +
> + mutex_lock(&cgroup_mutex);
> + spin_lock_irq(&css_set_lock);
> + task_cgroup_from_root(task, &cgrp_dfl_root);
> + spin_unlock_irq(&css_set_lock);
> + mutex_unlock(&cgroup_mutex);
Gut feeling says use task = get_pid_task(); if (!task) return NULL and
put_task_struct(task); for safety.
Shouldn't there be a return here?
> +}
-Chris
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