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TOMOYO Linux Cross Reference
Linux/fs/nfs_common/grace.c

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  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 
 13 static unsigned int grace_net_id;
 14 static DEFINE_SPINLOCK(grace_lock);
 15 
 16 /**
 17  * locks_start_grace
 18  * @net: net namespace that this lock manager belongs to
 19  * @lm: who this grace period is for
 20  *
 21  * A grace period is a period during which locks should not be given
 22  * out.  Currently grace periods are only enforced by the two lock
 23  * managers (lockd and nfsd), using the locks_in_grace() function to
 24  * check when they are in a grace period.
 25  *
 26  * This function is called to start a grace period.
 27  */
 28 void
 29 locks_start_grace(struct net *net, struct lock_manager *lm)
 30 {
 31         struct list_head *grace_list = net_generic(net, grace_net_id);
 32 
 33         spin_lock(&grace_lock);
 34         if (list_empty(&lm->list))
 35                 list_add(&lm->list, grace_list);
 36         else
 37                 WARN(1, "double list_add attempt detected in net %x %s\n",
 38                      net->ns.inum, (net == &init_net) ? "(init_net)" : "");
 39         spin_unlock(&grace_lock);
 40 }
 41 EXPORT_SYMBOL_GPL(locks_start_grace);
 42 
 43 /**
 44  * locks_end_grace
 45  * @net: net namespace that this lock manager belongs to
 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(&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
 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         list_for_each_entry(lm, grace_list, list) {
 73                 if (lm->block_opens)
 74                         return true;
 75         }
 76         return false;
 77 }
 78 
 79 /**
 80  * locks_in_grace
 81  *
 82  * Lock managers call this function to determine when it is OK for them
 83  * to answer ordinary lock requests, and when they should accept only
 84  * lock reclaims.
 85  */
 86 bool locks_in_grace(struct net *net)
 87 {
 88         return __state_in_grace(net, false);
 89 }
 90 EXPORT_SYMBOL_GPL(locks_in_grace);
 91 
 92 bool opens_in_grace(struct net *net)
 93 {
 94         return __state_in_grace(net, true);
 95 }
 96 EXPORT_SYMBOL_GPL(opens_in_grace);
 97 
 98 static int __net_init
 99 grace_init_net(struct net *net)
100 {
101         struct list_head *grace_list = net_generic(net, grace_net_id);
102 
103         INIT_LIST_HEAD(grace_list);
104         return 0;
105 }
106 
107 static void __net_exit
108 grace_exit_net(struct net *net)
109 {
110         struct list_head *grace_list = net_generic(net, grace_net_id);
111 
112         WARN_ONCE(!list_empty(grace_list),
113                   "net %x %s: grace_list is not empty\n",
114                   net->ns.inum, __func__);
115 }
116 
117 static struct pernet_operations grace_net_ops = {
118         .init = grace_init_net,
119         .exit = grace_exit_net,
120         .id   = &grace_net_id,
121         .size = sizeof(struct list_head),
122 };
123 
124 static int __init
125 init_grace(void)
126 {
127         return register_pernet_subsys(&grace_net_ops);
128 }
129 
130 static void __exit
131 exit_grace(void)
132 {
133         unregister_pernet_subsys(&grace_net_ops);
134 }
135 
136 MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
137 MODULE_LICENSE("GPL");
138 module_init(init_grace)
139 module_exit(exit_grace)
140 

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