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Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5c6dd7ed26a7..cbb6314f1836 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5616,8 +5616,14 @@ struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
}
EXPORT_SYMBOL_GPL(css_lookup);
-/*
- * get corresponding css from file open on cgroupfs directory
+/**
+ * cgroup_css_from_dir - get corresponding css from file open on cgroup dir
+ * @f: directory file of interest
+ * @id: subsystem id of interest
+ *
+ * Must be called under RCU read lock. The caller is responsible for
+ * pinning the returned css if it needs to be accessed outside the RCU
+ * critical section.
*/
struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
{
@@ -5625,6 +5631,8 @@ struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
struct inode *inode;
struct cgroup_subsys_state *css;
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
inode = file_inode(f);
/* check in cgroup filesystem dir */
if (inode->i_op != &cgroup_dir_inode_operations)