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 |
30 | locks_start_grace(struct net *net, struct lock_manager *lm) |
31 | { |
32 | struct list_head *grace_list = net_generic(net, id: grace_net_id); |
33 | |
34 | spin_lock(lock: &grace_lock); |
35 | if (list_empty(head: &lm->list)) |
36 | list_add(new: &lm->list, head: 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(lock: &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 |
55 | locks_end_grace(struct lock_manager *lm) |
56 | { |
57 | spin_lock(lock: &grace_lock); |
58 | list_del_init(entry: &lm->list); |
59 | spin_unlock(lock: &grace_lock); |
60 | } |
61 | EXPORT_SYMBOL_GPL(locks_end_grace); |
62 | |
63 | static bool |
64 | __state_in_grace(struct net *net, bool open) |
65 | { |
66 | struct list_head *grace_list = net_generic(net, id: grace_net_id); |
67 | struct lock_manager *lm; |
68 | |
69 | if (!open) |
70 | return !list_empty(head: grace_list); |
71 | |
72 | spin_lock(lock: &grace_lock); |
73 | list_for_each_entry(lm, grace_list, list) { |
74 | if (lm->block_opens) { |
75 | spin_unlock(lock: &grace_lock); |
76 | return true; |
77 | } |
78 | } |
79 | spin_unlock(lock: &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 | */ |
91 | bool locks_in_grace(struct net *net) |
92 | { |
93 | return __state_in_grace(net, open: false); |
94 | } |
95 | EXPORT_SYMBOL_GPL(locks_in_grace); |
96 | |
97 | bool opens_in_grace(struct net *net) |
98 | { |
99 | return __state_in_grace(net, open: true); |
100 | } |
101 | EXPORT_SYMBOL_GPL(opens_in_grace); |
102 | |
103 | static int __net_init |
104 | grace_init_net(struct net *net) |
105 | { |
106 | struct list_head *grace_list = net_generic(net, id: grace_net_id); |
107 | |
108 | INIT_LIST_HEAD(list: grace_list); |
109 | return 0; |
110 | } |
111 | |
112 | static void __net_exit |
113 | grace_exit_net(struct net *net) |
114 | { |
115 | struct list_head *grace_list = net_generic(net, id: 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 |
130 | init_grace(void) |
131 | { |
132 | return register_pernet_subsys(&grace_net_ops); |
133 | } |
134 | |
135 | static void __exit |
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 | |