v4.19.13 snapshot.
diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
new file mode 100644
index 0000000..5be08f0
--- /dev/null
+++ b/fs/nfs_common/grace.c
@@ -0,0 +1,138 @@
+/*
+ * Common code for control of lockd and nfsv4 grace periods.
+ *
+ * Transplanted from lockd code
+ */
+
+#include <linux/module.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+#include <linux/fs.h>
+
+static unsigned int grace_net_id;
+static DEFINE_SPINLOCK(grace_lock);
+
+/**
+ * locks_start_grace
+ * @net: net namespace that this lock manager belongs to
+ * @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 list_head *grace_list = net_generic(net, grace_net_id);
+
+ spin_lock(&grace_lock);
+ if (list_empty(&lm->list))
+ list_add(&lm->list, grace_list);
+ else
+ WARN(1, "double list_add attempt detected in net %x %s\n",
+ net->ns.inum, (net == &init_net) ? "(init_net)" : "");
+ spin_unlock(&grace_lock);
+}
+EXPORT_SYMBOL_GPL(locks_start_grace);
+
+/**
+ * locks_end_grace
+ * @net: net namespace that this lock manager belongs to
+ * @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);
+
+static bool
+__state_in_grace(struct net *net, bool open)
+{
+ struct list_head *grace_list = net_generic(net, grace_net_id);
+ struct lock_manager *lm;
+
+ if (!open)
+ return !list_empty(grace_list);
+
+ list_for_each_entry(lm, grace_list, list) {
+ if (lm->block_opens)
+ return true;
+ }
+ return false;
+}
+
+/**
+ * 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.
+ */
+bool locks_in_grace(struct net *net)
+{
+ return __state_in_grace(net, false);
+}
+EXPORT_SYMBOL_GPL(locks_in_grace);
+
+bool opens_in_grace(struct net *net)
+{
+ return __state_in_grace(net, true);
+}
+EXPORT_SYMBOL_GPL(opens_in_grace);
+
+static int __net_init
+grace_init_net(struct net *net)
+{
+ struct list_head *grace_list = net_generic(net, grace_net_id);
+
+ INIT_LIST_HEAD(grace_list);
+ return 0;
+}
+
+static void __net_exit
+grace_exit_net(struct net *net)
+{
+ struct list_head *grace_list = net_generic(net, grace_net_id);
+
+ WARN_ONCE(!list_empty(grace_list),
+ "net %x %s: grace_list is not empty\n",
+ net->ns.inum, __func__);
+}
+
+static struct pernet_operations grace_net_ops = {
+ .init = grace_init_net,
+ .exit = grace_exit_net,
+ .id = &grace_net_id,
+ .size = sizeof(struct list_head),
+};
+
+static int __init
+init_grace(void)
+{
+ return register_pernet_subsys(&grace_net_ops);
+}
+
+static void __exit
+exit_grace(void)
+{
+ unregister_pernet_subsys(&grace_net_ops);
+}
+
+MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
+MODULE_LICENSE("GPL");
+module_init(init_grace)
+module_exit(exit_grace)