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