cgroup: Add a new helper for cgroup1 hierarchy

A new helper is added for cgroup1 hierarchy:

- task_get_cgroup1
  Acquires the associated cgroup of a task within a specific cgroup1
  hierarchy. The cgroup1 hierarchy is identified by its hierarchy ID.

This helper function is added to facilitate the tracing of tasks within
a particular container or cgroup dir in BPF programs. It's important to
note that this helper is designed specifically for cgroup1 only.

tj: Use irsqsave/restore as suggested by Hou Tao <houtao@huaweicloud.com>.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Hou Tao <houtao@huaweicloud.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 0ef0af6..34aaf0e 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -69,6 +69,7 @@ struct css_task_iter {
 extern struct file_system_type cgroup_fs_type;
 extern struct cgroup_root cgrp_dfl_root;
 extern struct css_set init_css_set;
+extern spinlock_t css_set_lock;
 
 #define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
 #include <linux/cgroup_subsys.h>
@@ -386,7 +387,6 @@ static inline void cgroup_unlock(void)
  * as locks used during the cgroup_subsys::attach() methods.
  */
 #ifdef CONFIG_PROVE_RCU
-extern spinlock_t css_set_lock;
 #define task_css_set_check(task, __c)                                  \
        rcu_dereference_check((task)->cgroups,                          \
                rcu_read_lock_sched_held() ||                           \
@@ -853,4 +853,6 @@ static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
 
 #endif /* CONFIG_CGROUP_BPF */
 
+struct cgroup *task_get_cgroup1(struct task_struct *tsk, int hierarchy_id);
+
 #endif /* _LINUX_CGROUP_H */

diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h
index 5e17f01..520b90d 100644 (file)
--- a/kernel/cgroup/cgroup-internal.h
+++ b/kernel/cgroup/cgroup-internal.h
@@ -164,7 +164,6 @@ struct cgroup_mgctx {
 #define DEFINE_CGROUP_MGCTX(name)                                              \
        struct cgroup_mgctx name = CGROUP_MGCTX_INIT(name)
 
-extern spinlock_t css_set_lock;
 extern struct cgroup_subsys *cgroup_subsys[];
 extern struct list_head cgroup_roots;
 

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 76db6c6..04d11a7 100644 (file)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1262,6 +1262,40 @@ int cgroup1_get_tree(struct fs_context *fc)
        return ret;
 }
 
+/**
+ * task_get_cgroup1 - Acquires the associated cgroup of a task within a
+ * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
+ * hierarchy ID.
+ * @tsk: The target task
+ * @hierarchy_id: The ID of a cgroup1 hierarchy
+ *
+ * On success, the cgroup is returned. On failure, ERR_PTR is returned.
+ * We limit it to cgroup1 only.
+ */
+struct cgroup *task_get_cgroup1(struct task_struct *tsk, int hierarchy_id)
+{
+       struct cgroup *cgrp = ERR_PTR(-ENOENT);
+       struct cgroup_root *root;
+       unsigned long flags;
+
+       rcu_read_lock();
+       for_each_root(root) {
+               /* cgroup1 only*/
+               if (root == &cgrp_dfl_root)
+                       continue;
+               if (root->hierarchy_id != hierarchy_id)
+                       continue;
+               spin_lock_irqsave(&css_set_lock, flags);
+               cgrp = task_cgroup_from_root(tsk, root);
+               if (!cgrp || !cgroup_tryget(cgrp))
+                       cgrp = ERR_PTR(-ENOENT);
+               spin_unlock_irqrestore(&css_set_lock, flags);
+               break;
+       }
+       rcu_read_unlock();
+       return cgrp;
+}
+
 static int __init cgroup1_wq_init(void)
 {
        /*