diff mbox series

[v3,01/19] cgroup: Added cgroup_get_from_kernfs_id

Message ID 1604387903-20006-2-git-send-email-muneendra.kumar@broadcom.com
State Superseded
Headers show
Series [v3,01/19] cgroup: Added cgroup_get_from_kernfs_id | expand

Commit Message

Muneendra Kumar Nov. 3, 2020, 7:18 a.m. UTC 
Added a new function cgroup_get_from_kernfs_id  to retrieve the cgroup
associated with cgroup id.
It takes cgroupid as an argument and returns cgrp and on failure
it returns NULL.
Exported the same as this can be used by blk-cgorup.c

Added function declaration of cgroup_get_from_kernfs_id in cgorup.h
Exported the cgroup_get_e_css

Signed-off-by: Muneendra <muneendra.kumar@broadcom.com>

---
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(+)

Comments

Tejun Heo Nov. 9, 2020, 1:49 p.m. UTC | #1 
Hello,

Generally looks good to me. A few nits.

On Tue, Nov 03, 2020 at 12:48:05PM +0530, Muneendra wrote:
> Added a new function cgroup_get_from_kernfs_id  to retrieve the cgroup

> associated with cgroup id.

> It takes cgroupid as an argument and returns cgrp and on failure

> it returns NULL.

> Exported the same as this can be used by blk-cgorup.c


Can you please reflow the above paragraph?

> +struct cgroup *cgroup_get_from_kernfs_id(u64 id);


Let's just name it cgroup_get_from_id(). There's no other id. We can rename
cgroup_path_from_kernfs_id() later.

> +/*


/** starts a function comment.

> + * cgroup_get_from_kernfs_id : get the cgroup associated with cgroup id

> + * @id: cgroup id

> + * On success it returns the cgrp on failure it returns NULL

> + */


With the above nits updated, please feel free to add

Acked-by: Tejun Heo <tj@kernel.org>


Thanks.

-- 
tejun
diff mbox series

Patch

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 618838c48313..1741f02a41d6 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_kernfs_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 struct cgroup *cgroup_get_from_kernfs_id(u64 id)
+{
+	return NULL;
+}
 #endif /* !CONFIG_CGROUPS */
 
 #ifdef CONFIG_CGROUPS
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index dd247747ec14..53046deeb9ca 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -580,6 +580,7 @@  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)
 {
@@ -5803,6 +5804,31 @@  void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 	kernfs_put(kn);
 }
 
+/*
+ * cgroup_get_from_kernfs_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_kernfs_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_kernfs_id);
+
 /*
  * proc_cgroup_show()
  *  - Print task's cgroup paths into seq_file, one line for each hierarchy