1 files changed, 143 insertions, 0 deletions
diff --git a/fs/nfs_common/grace.c b/fs/nfs_common/grace.c
new file mode 100644
index 000000000..26f2a50ec
--- /dev/null
+++ b/fs/nfs_common/grace.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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);
+
+	spin_lock(&grace_lock);
+	list_for_each_entry(lm, grace_list, list) {
+		if (lm->block_opens) {
+			spin_unlock(&grace_lock);
+			return true;
+		}
+	}
+	spin_unlock(&grace_lock);
+	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)