1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Common code for control of lockd and nfsv4 grace periods.
4 *
5 * Transplanted from lockd code
6 */
7
8#include <linux/module.h>
9#include <net/net_namespace.h>
10#include <net/netns/generic.h>
11#include <linux/fs.h>
12#include <linux/filelock.h>
13
14static unsigned int grace_net_id;
15static DEFINE_SPINLOCK(grace_lock);
16
17/**
18 * locks_start_grace
19 * @net: net namespace that this lock manager belongs to
20 * @lm: who this grace period is for
21 *
22 * A grace period is a period during which locks should not be given
23 * out.  Currently grace periods are only enforced by the two lock
24 * managers (lockd and nfsd), using the locks_in_grace() function to
25 * check when they are in a grace period.
26 *
27 * This function is called to start a grace period.
28 */
29void
30locks_start_grace(struct net *net, struct lock_manager *lm)
31{
32	struct list_head *grace_list = net_generic(net, grace_net_id);
33
34	spin_lock(&grace_lock);
35	if (list_empty(&lm->list))
36		list_add(&lm->list, grace_list);
37	else
38		WARN(1, "double list_add attempt detected in net %x %s\n",
39		     net->ns.inum, (net == &init_net) ? "(init_net)" : "");
40	spin_unlock(&grace_lock);
41}
42EXPORT_SYMBOL_GPL(locks_start_grace);
43
44/**
45 * locks_end_grace
46 * @lm: who this grace period is for
47 *
48 * Call this function to state that the given lock manager is ready to
49 * resume regular locking.  The grace period will not end until all lock
50 * managers that called locks_start_grace() also call locks_end_grace().
51 * Note that callers count on it being safe to call this more than once,
52 * and the second call should be a no-op.
53 */
54void
55locks_end_grace(struct lock_manager *lm)
56{
57	spin_lock(&grace_lock);
58	list_del_init(&lm->list);
59	spin_unlock(&grace_lock);
60}
61EXPORT_SYMBOL_GPL(locks_end_grace);
62
63static bool
64__state_in_grace(struct net *net, bool open)
65{
66	struct list_head *grace_list = net_generic(net, grace_net_id);
67	struct lock_manager *lm;
68
69	if (!open)
70		return !list_empty(grace_list);
71
72	spin_lock(&grace_lock);
73	list_for_each_entry(lm, grace_list, list) {
74		if (lm->block_opens) {
75			spin_unlock(&grace_lock);
76			return true;
77		}
78	}
79	spin_unlock(&grace_lock);
80	return false;
81}
82
83/**
84 * locks_in_grace
85 * @net: network namespace
86 *
87 * Lock managers call this function to determine when it is OK for them
88 * to answer ordinary lock requests, and when they should accept only
89 * lock reclaims.
90 */
91bool locks_in_grace(struct net *net)
92{
93	return __state_in_grace(net, false);
94}
95EXPORT_SYMBOL_GPL(locks_in_grace);
96
97bool opens_in_grace(struct net *net)
98{
99	return __state_in_grace(net, true);
100}
101EXPORT_SYMBOL_GPL(opens_in_grace);
102
103static int __net_init
104grace_init_net(struct net *net)
105{
106	struct list_head *grace_list = net_generic(net, grace_net_id);
107
108	INIT_LIST_HEAD(grace_list);
109	return 0;
110}
111
112static void __net_exit
113grace_exit_net(struct net *net)
114{
115	struct list_head *grace_list = net_generic(net, grace_net_id);
116
117	WARN_ONCE(!list_empty(grace_list),
118		  "net %x %s: grace_list is not empty\n",
119		  net->ns.inum, __func__);
120}
121
122static struct pernet_operations grace_net_ops = {
123	.init = grace_init_net,
124	.exit = grace_exit_net,
125	.id   = &grace_net_id,
126	.size = sizeof(struct list_head),
127};
128
129static int __init
130init_grace(void)
131{
132	return register_pernet_subsys(&grace_net_ops);
133}
134
135static void __exit
136exit_grace(void)
137{
138	unregister_pernet_subsys(&grace_net_ops);
139}
140
141MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
142MODULE_LICENSE("GPL");
143module_init(init_grace)
144module_exit(exit_grace)
145