+/*
+ * check already instantiated keys aren't going to be a problem
+ * - the caller must have called __key_link_begin()
+ * - don't need to call this for keys that were created since __key_link_begin()
+ * was called
+ */
+int __key_link_check_live_key(struct key *keyring, struct key *key)
+{
+ if (key->type == &key_type_keyring)
+ /* check that we aren't going to create a cycle by linking one
+ * keyring to another */
+ return keyring_detect_cycle(keyring, key);
+ return 0;
+}
+
+/*
+ * link a key into to a keyring
+ * - must be called with __key_link_begin() having being called
+ * - discard already extant link to matching key if there is one
+ */
+void __key_link(struct key *keyring, struct key *key,
+ struct keyring_list **_prealloc)
+{
+ struct keyring_list *klist, *nklist;
+
+ nklist = *_prealloc;
+ *_prealloc = NULL;
+
+ kenter("%d,%d,%p", keyring->serial, key->serial, nklist);
+
+ klist = rcu_dereference_protected(keyring->payload.subscriptions,
+ rwsem_is_locked(&keyring->sem));
+
+ atomic_inc(&key->usage);
+
+ /* there's a matching key we can displace or an empty slot in a newly
+ * allocated list we can fill */
+ if (nklist) {
+ kdebug("replace %hu/%hu/%hu",
+ nklist->delkey, nklist->nkeys, nklist->maxkeys);
+
+ nklist->keys[nklist->delkey] = key;
+
+ rcu_assign_pointer(keyring->payload.subscriptions, nklist);
+
+ /* dispose of the old keyring list and, if there was one, the
+ * displaced key */
+ if (klist) {
+ kdebug("dispose %hu/%hu/%hu",
+ klist->delkey, klist->nkeys, klist->maxkeys);
+ call_rcu(&klist->rcu, keyring_unlink_rcu_disposal);
+ }
+ } else {
+ /* there's sufficient slack space to append directly */
+ klist->keys[klist->nkeys] = key;
+ smp_wmb();
+ klist->nkeys++;
+ }
+}
+
+/*
+ * finish linking a key into to a keyring
+ * - must be called with __key_link_begin() having being called
+ */
+void __key_link_end(struct key *keyring, struct key_type *type,
+ struct keyring_list *prealloc)
+ __releases(&keyring->sem)
+{
+ BUG_ON(type == NULL);
+ BUG_ON(type->name == NULL);
+ kenter("%d,%s,%p", keyring->serial, type->name, prealloc);
+
+ if (type == &key_type_keyring)
+ up_write(&keyring_serialise_link_sem);
+
+ if (prealloc) {
+ kfree(prealloc);
+ key_payload_reserve(keyring,
+ keyring->datalen - KEYQUOTA_LINK_BYTES);
+ }
+ up_write(&keyring->sem);
+}