--- /dev/null
+#ifndef _LINUX_KEY_H
+#define _LINUX_KEY_H
+
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <keyutils.h>
+
+struct user_key_payload {
+ size_t datalen; /* length of this data */
+ char data[0]; /* actual data */
+};
+
+struct key {
+ atomic_t usage; /* number of references */
+ key_serial_t serial; /* key serial number */
+ struct rw_semaphore sem; /* change vs change sem */
+ struct user_key_payload payload;
+};
+
+static inline const struct user_key_payload *user_key_payload(const struct key *key)
+{
+ return &key->payload;
+}
+
+static inline void key_put(struct key *key)
+{
+ if (atomic_dec_and_test(&key->usage))
+ free(key);
+}
+
+static inline struct key *__key_get(struct key *key)
+{
+ atomic_inc(&key->usage);
+ return key;
+}
+
+static inline struct key *key_get(struct key *key)
+{
+ return key ? __key_get(key) : key;
+}
+
+#endif /* _LINUX_KEY_H */