1 files changed, 65 insertions, 0 deletions
diff --git a/fs/lockd/grace.c b/fs/lockd/grace.c
new file mode 100644
index 00000000000..6d1ee7204c8
--- /dev/null
+++ b/fs/lockd/grace.c
@@ -0,0 +1,65 @@
+/*
+ * Common code for control of lockd and nfsv4 grace periods.
+ */
+
+#include <linux/module.h>
+#include <linux/lockd/bind.h>
+#include <net/net_namespace.h>
+
+#include "netns.h"
+
+static DEFINE_SPINLOCK(grace_lock);
+
+/**
+ * locks_start_grace
+ * @lm: who this grace period is for
+ *
+ * A grace period is a period during which locks should not be given
+ * out.  Currently grace periods are only enforced by the two lock
+ * managers (lockd and nfsd), using the locks_in_grace() function to
+ * check when they are in a grace period.
+ *
+ * This function is called to start a grace period.
+ */
+void locks_start_grace(struct net *net, struct lock_manager *lm)
+{
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+	spin_lock(&grace_lock);
+	list_add(&lm->list, &ln->grace_list);
+	spin_unlock(&grace_lock);
+}
+EXPORT_SYMBOL_GPL(locks_start_grace);
+
+/**
+ * locks_end_grace
+ * @lm: who this grace period is for
+ *
+ * Call this function to state that the given lock manager is ready to
+ * resume regular locking.  The grace period will not end until all lock
+ * managers that called locks_start_grace() also call locks_end_grace().
+ * Note that callers count on it being safe to call this more than once,
+ * and the second call should be a no-op.
+ */
+void locks_end_grace(struct lock_manager *lm)
+{
+	spin_lock(&grace_lock);
+	list_del_init(&lm->list);
+	spin_unlock(&grace_lock);
+}
+EXPORT_SYMBOL_GPL(locks_end_grace);
+
+/**
+ * locks_in_grace
+ *
+ * Lock managers call this function to determine when it is OK for them
+ * to answer ordinary lock requests, and when they should accept only
+ * lock reclaims.
+ */
+int locks_in_grace(struct net *net)
+{
+	struct lockd_net *ln = net_generic(net, lockd_net_id);
+
+	return !list_empty(&ln->grace_list);
+}
+EXPORT_SYMBOL_GPL(locks_in_grace);