On Mon, Dec 07, 2015 at 05:38:50PM -0500, Tejun Heo wrote:
> Implement cgroup_get_from_path() using kernfs_walk_and_get() which
> obtains a default hierarchy cgroup from its path. This will be used
> to allow cgroup path based matching from outside cgroup proper -
> e.g. networking and perf.
Hi Tejun,
I'm trying to figure out how to handle this in the cgroup ns patchset.
Is this going to be purely used internally? From the user i see in
this patchset it looks like I should leave it be (and have @path always
be absolute) Is that right?
thanks,
-serge
> v2: Add EXPORT_SYMBOL_GPL(cgroup_get_from_path).
>
> Signed-off-by: Tejun Heo <t...@kernel.org>
> ---
> include/linux/cgroup.h | 7 +++++++
> kernel/cgroup.c | 39 ++++++++++++++++++++++++++++++++++-----
> 2 files changed, 41 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index b5ee2c4..4c3ffab 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -81,6 +81,8 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup
> *cgroup,
> struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
> struct cgroup_subsys
> *ss);
>
> +struct cgroup *cgroup_get_from_path(const char *path);
> +
> int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
> int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
>
> @@ -351,6 +353,11 @@ static inline void css_put_many(struct
> cgroup_subsys_state *css, unsigned int n)
> percpu_ref_put_many(&css->refcnt, n);
> }
>
> +static inline void cgroup_put(struct cgroup *cgrp)
> +{
> + css_put(&cgrp->self);
> +}
> +
> /**
> * task_css_set_check - obtain a task's css_set with extra access conditions
> * @task: the task to obtain css_set for
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 3190040..3db5e8f 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -434,11 +434,6 @@ static bool cgroup_tryget(struct cgroup *cgrp)
> return css_tryget(&cgrp->self);
> }
>
> -static void cgroup_put(struct cgroup *cgrp)
> -{
> - css_put(&cgrp->self);
> -}
> -
> struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
> {
> struct cgroup *cgrp = of->kn->parent->priv;
> @@ -5753,6 +5748,40 @@ struct cgroup_subsys_state *css_from_id(int id, struct
> cgroup_subsys *ss)
> return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
> }
>
> +/**
> + * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy
> path
> + * @path: path on the default hierarchy
> + *
> + * Find the cgroup at @path on the default hierarchy, increment its
> + * reference count and return it. Returns pointer to the found cgroup on
> + * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR)
> + * if @path points to a non-directory.
> + */
> +struct cgroup *cgroup_get_from_path(const char *path)
> +{
> + struct kernfs_node *kn;
> + struct cgroup *cgrp;
> +
> + mutex_lock(&cgroup_mutex);
> +
> + kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
> + if (kn) {
> + if (kernfs_type(kn) == KERNFS_DIR) {
> + cgrp = kn->priv;
> + cgroup_get(cgrp);
> + } else {
> + cgrp = ERR_PTR(-ENOTDIR);
> + }
> + kernfs_put(kn);
> + } else {
> + cgrp = ERR_PTR(-ENOENT);
> + }
> +
> + mutex_unlock(&cgroup_mutex);
> + return cgrp;
> +}
> +EXPORT_SYMBOL_GPL(cgroup_get_from_path);
> +
> #ifdef CONFIG_CGROUP_DEBUG
> static struct cgroup_subsys_state *
> debug_css_alloc(struct cgroup_subsys_state *parent_css)
> --
> 2.5.0
>
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