[PATCH v10 01/13] cgroup: Added cgroup_get_from_id

Muneendra
2021-04-28T05:35:51Z

Added a new function cgroup_get_from_id to retrieve the cgroup
associated with cgroup id.
Exported the same as this can be used by blk-cgorup.c

Added function declaration of cgroup_get_from_id in cgorup.h

This patch also exported the function cgroup_get_e_css
as this is getting used in blk-cgroup.h

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Muneendra <muneendra.kumar@broadcom.com>

---
v10:
No change

v9:
Addressed the issues reported by kernel test robot

v8:
No change

v7:
No change

v6:
No change

v5:
renamed the function cgroup_get_from_kernfs_id to
cgroup_get_from_id

v4:
No change

v3:
Exported the cgroup_get_e_css

v2:
New patch
---
include/linux/cgroup.h | 6 ++++++
kernel/cgroup/cgroup.c | 26 ++++++++++++++++++++++++++
2 files changed, 32 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 4f2f79de083e..d2eace88d9d1 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -696,6 +696,7 @@ static inline void cgroup_kthread_ready(void)
}

void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen);
+struct cgroup *cgroup_get_from_id(u64 id);
#else /* !CONFIG_CGROUPS */

struct cgroup_subsys_state;
@@ -743,6 +744,11 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task,

static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
{}
+
+static inline struct cgroup *cgroup_get_from_id(u64 id)
+{
+ return NULL;
+}
#endif /* !CONFIG_CGROUPS */

#ifdef CONFIG_CGROUPS
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 9153b20e5cc6..20e5424a8227 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -577,6 +577,7 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
rcu_read_unlock();
return css;
}
+EXPORT_SYMBOL_GPL(cgroup_get_e_css);

static void cgroup_get_live(struct cgroup *cgrp)
{
@@ -5768,6 +5769,31 @@ void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
kernfs_put(kn);
}

+/*
+ * cgroup_get_from_id : get the cgroup associated with cgroup id
+ * @id: cgroup id
+ * On success it returns the cgrp on failure it returns NULL
+ */
+struct cgroup *cgroup_get_from_id(u64 id)
+{
+ struct kernfs_node *kn;
+ struct cgroup *cgrp = NULL;
+
+ mutex_lock(&cgroup_mutex);
+ kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
+ if (!kn)
+ goto out_unlock;
+
+ cgrp = kn->priv;
+ if (cgroup_is_dead(cgrp) || !cgroup_tryget(cgrp))
+ cgrp = NULL;
+ kernfs_put(kn);
+out_unlock:
+ mutex_unlock(&cgroup_mutex);
+ return cgrp;
+}
+EXPORT_SYMBOL_GPL(cgroup_get_from_id);
+
/*
* proc_cgroup_show()
* - Print task's cgroup paths into seq_file, one line for each hierarchy
--
2.26.2