diff options
| -rw-r--r-- | include/linux/cgroup.h | 2 | ||||
| -rw-r--r-- | kernel/cgroup.c | 37 |
2 files changed, 39 insertions, 0 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 3a04aeb8b5a..9fd99f5e699 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -910,6 +910,8 @@ void css_task_iter_end(struct css_task_iter *it); int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); +struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, + struct cgroup_subsys *ss); struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, struct cgroup_subsys *ss); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 69f033582a1..bb263d0caab 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -277,6 +277,10 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, if (!(cgrp->root->subsys_mask & (1 << ss->id))) return NULL; + /* + * This function is used while updating css associations and thus + * can't test the csses directly. Use ->child_subsys_mask. + */ while (cgroup_parent(cgrp) && !(cgroup_parent(cgrp)->child_subsys_mask & (1 << ss->id))) cgrp = cgroup_parent(cgrp); @@ -284,6 +288,39 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, return cgroup_css(cgrp, ss); } +/** + * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem + * @cgrp: the cgroup of interest + * @ss: the subsystem of interest + * + * Find and get the effective css of @cgrp for @ss. The effective css is + * defined as the matching css of the nearest ancestor including self which + * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on, + * the root css is returned, so this function always returns a valid css. + * The returned css must be put using css_put(). + */ +struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp, + struct cgroup_subsys *ss) +{ + struct cgroup_subsys_state *css; + + rcu_read_lock(); + + do { + css = cgroup_css(cgrp, ss); + + if (css && css_tryget_online(css)) + goto out_unlock; + cgrp = cgroup_parent(cgrp); + } while (cgrp); + + css = init_css_set.subsys[ss->id]; + css_get(css); +out_unlock: + rcu_read_unlock(); + return css; +} + /* convenient tests for these bits */ static inline bool cgroup_is_dead(const struct cgroup *cgrp) { |