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