Created a function for setting timeouts on keys

The keyctl_set_timeout function isn't exported to other parts of the
kernel, but I want to use it for the NFS idmapper.  I already have the
key, but I wanted a generic way to set the timeout.
Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/key.h

@@ -276,6 +276,8 @@ static inline key_serial_t key_serial(const struct key *key)
 	return key ? key->serial : 0;
 }
 
+extern void key_set_timeout(struct key *, unsigned);
+
 /**
  * key_is_instantiated - Determine if a key has been positively instantiated
  * @key: The key to check.

security/keys/key.c

@@ -671,6 +671,26 @@ struct key_type *key_type_lookup(const char *type)
 	return ktype;
 }
 
+void key_set_timeout(struct key *key, unsigned timeout)
+{
+	struct timespec now;
+	time_t expiry = 0;
+
+	/* make the changes with the locks held to prevent races */
+	down_write(&key->sem);
+
+	if (timeout > 0) {
+		now = current_kernel_time();
+		expiry = now.tv_sec + timeout;
+	}
+
+	key->expiry = expiry;
+	key_schedule_gc(key->expiry + key_gc_delay);
+
+	up_write(&key->sem);
+}
+EXPORT_SYMBOL_GPL(key_set_timeout);
+
 /*
  * Unlock a key type locked by key_type_lookup().
  */

security/keys/keyctl.c

@@ -14,6 +14,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/syscalls.h>
+#include <linux/key.h>
 #include <linux/keyctl.h>
 #include <linux/fs.h>
 #include <linux/capability.h>
@@ -1244,10 +1245,8 @@ long keyctl_set_reqkey_keyring(int reqkey_defl)
  */
 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 {
-	struct timespec now;
 	struct key *key, *instkey;
 	key_ref_t key_ref;
-	time_t expiry;
 	long ret;
 
 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
@@ -1273,20 +1272,7 @@ long keyctl_set_timeout(key_serial_t id, unsigned timeout)
 
 okay:
 	key = key_ref_to_ptr(key_ref);
-
-	/* make the changes with the locks held to prevent races */
-	down_write(&key->sem);
-
-	expiry = 0;
-	if (timeout > 0) {
-		now = current_kernel_time();
-		expiry = now.tv_sec + timeout;
-	}
-
-	key->expiry = expiry;
-	key_schedule_gc(key->expiry + key_gc_delay);
-
-	up_write(&key->sem);
+	key_set_timeout(key, timeout);
 	key_put(key);
 
 	ret = 0;