KEYS: Define a __key_get() wrapper to use rather than atomic_inc()

Define a __key_get() wrapper to use rather than atomic_inc() on the key usage
count as this makes it easier to hook in refcount error debugging.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index e68a3e0..68548ea 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -235,7 +235,7 @@
 		if (IS_ERR(keyring))
 			return PTR_ERR(keyring);
 	} else {
-		atomic_inc(&keyring->usage);
+		__key_get(keyring);
 	}
 
 	/* install the keyring */
@@ -544,7 +544,7 @@
 		}
 
 		key = ctx.cred->thread_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -562,7 +562,7 @@
 		}
 
 		key = ctx.cred->process_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -593,7 +593,7 @@
 
 		rcu_read_lock();
 		key = rcu_dereference(ctx.cred->session_keyring);
-		atomic_inc(&key->usage);
+		__key_get(key);
 		rcu_read_unlock();
 		key_ref = make_key_ref(key, 1);
 		break;
@@ -606,7 +606,7 @@
 		}
 
 		key = ctx.cred->user->uid_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -618,7 +618,7 @@
 		}
 
 		key = ctx.cred->user->session_keyring;
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -632,7 +632,7 @@
 		if (!key)
 			goto error;
 
-		atomic_inc(&key->usage);
+		__key_get(key);
 		key_ref = make_key_ref(key, 1);
 		break;
 
@@ -648,7 +648,7 @@
 		} else {
 			rka = ctx.cred->request_key_auth->payload.data;
 			key = rka->dest_keyring;
-			atomic_inc(&key->usage);
+			__key_get(key);
 		}
 		up_read(&ctx.cred->request_key_auth->sem);
 		if (!key)