1/*
2 * Common code for control of lockd and nfsv4 grace periods.
3 *
4 * Transplanted from lockd code
5 */
6
7#include <linux/module.h>
8#include <net/net_namespace.h>
9#include <net/netns/generic.h>
10#include <linux/fs.h>
11
12static int grace_net_id;
13static DEFINE_SPINLOCK(grace_lock);
14
15/**
16 * locks_start_grace
17 * @net: net namespace that this lock manager belongs to
18 * @lm: who this grace period is for
19 *
20 * A grace period is a period during which locks should not be given
21 * out.  Currently grace periods are only enforced by the two lock
22 * managers (lockd and nfsd), using the locks_in_grace() function to
23 * check when they are in a grace period.
24 *
25 * This function is called to start a grace period.
26 */
27void
28locks_start_grace(struct net *net, struct lock_manager *lm)
29{
30	struct list_head *grace_list = net_generic(net, grace_net_id);
31
32	spin_lock(&grace_lock);
33	list_add(&lm->list, grace_list);
34	spin_unlock(&grace_lock);
35}
36EXPORT_SYMBOL_GPL(locks_start_grace);
37
38/**
39 * locks_end_grace
40 * @net: net namespace that this lock manager belongs to
41 * @lm: who this grace period is for
42 *
43 * Call this function to state that the given lock manager is ready to
44 * resume regular locking.  The grace period will not end until all lock
45 * managers that called locks_start_grace() also call locks_end_grace().
46 * Note that callers count on it being safe to call this more than once,
47 * and the second call should be a no-op.
48 */
49void
50locks_end_grace(struct lock_manager *lm)
51{
52	spin_lock(&grace_lock);
53	list_del_init(&lm->list);
54	spin_unlock(&grace_lock);
55}
56EXPORT_SYMBOL_GPL(locks_end_grace);
57
58/**
59 * locks_in_grace
60 *
61 * Lock managers call this function to determine when it is OK for them
62 * to answer ordinary lock requests, and when they should accept only
63 * lock reclaims.
64 */
65int
66locks_in_grace(struct net *net)
67{
68	struct list_head *grace_list = net_generic(net, grace_net_id);
69
70	return !list_empty(grace_list);
71}
72EXPORT_SYMBOL_GPL(locks_in_grace);
73
74static int __net_init
75grace_init_net(struct net *net)
76{
77	struct list_head *grace_list = net_generic(net, grace_net_id);
78
79	INIT_LIST_HEAD(grace_list);
80	return 0;
81}
82
83static void __net_exit
84grace_exit_net(struct net *net)
85{
86	struct list_head *grace_list = net_generic(net, grace_net_id);
87
88	BUG_ON(!list_empty(grace_list));
89}
90
91static struct pernet_operations grace_net_ops = {
92	.init = grace_init_net,
93	.exit = grace_exit_net,
94	.id   = &grace_net_id,
95	.size = sizeof(struct list_head),
96};
97
98static int __init
99init_grace(void)
100{
101	return register_pernet_subsys(&grace_net_ops);
102}
103
104static void __exit
105exit_grace(void)
106{
107	unregister_pernet_subsys(&grace_net_ops);
108}
109
110MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
111MODULE_LICENSE("GPL");
112module_init(init_grace)
113module_exit(exit_grace)
114