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
14 static unsigned int grace_net_id;
15 static 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 */
29 void
locks_start_grace(struct net * net,struct lock_manager * lm)30 locks_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 }
42 EXPORT_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 */
54 void
locks_end_grace(struct lock_manager * lm)55 locks_end_grace(struct lock_manager *lm)
56 {
57 spin_lock(&grace_lock);
58 list_del_init(&lm->list);
59 spin_unlock(&grace_lock);
60 }
61 EXPORT_SYMBOL_GPL(locks_end_grace);
62
63 static bool
__state_in_grace(struct net * net,bool open)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 */
locks_in_grace(struct net * net)91 bool locks_in_grace(struct net *net)
92 {
93 return __state_in_grace(net, false);
94 }
95 EXPORT_SYMBOL_GPL(locks_in_grace);
96
opens_in_grace(struct net * net)97 bool opens_in_grace(struct net *net)
98 {
99 return __state_in_grace(net, true);
100 }
101 EXPORT_SYMBOL_GPL(opens_in_grace);
102
103 static int __net_init
grace_init_net(struct net * net)104 grace_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
112 static void __net_exit
grace_exit_net(struct net * net)113 grace_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
122 static 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
129 static int __init
init_grace(void)130 init_grace(void)
131 {
132 return register_pernet_subsys(&grace_net_ops);
133 }
134
135 static void __exit
exit_grace(void)136 exit_grace(void)
137 {
138 unregister_pernet_subsys(&grace_net_ops);
139 }
140
141 MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
142 MODULE_LICENSE("GPL");
143 module_init(init_grace)
144 module_exit(exit_grace)
145
