fs/nfs_common/grace.c

   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  * @lm: who this grace period is for
  46  *
  47  * Call this function to state that the given lock manager is ready to
  48  * resume regular locking.  The grace period will not end until all lock
  49  * managers that called locks_start_grace() also call locks_end_grace().
  50  * Note that callers count on it being safe to call this more than once,
  51  * and the second call should be a no-op.
  52  */
  53 void
  54 locks_end_grace(struct lock_manager *lm)
  55 {
  56         spin_lock(&grace_lock);
  57         list_del_init(&lm->list);
  58         spin_unlock(&grace_lock);
  59 }
  60 EXPORT_SYMBOL_GPL(locks_end_grace);
  61
  62 static bool
  63 __state_in_grace(struct net *net, bool open)
  64 {
  65         struct list_head *grace_list = net_generic(net, grace_net_id);
  66         struct lock_manager *lm;
  67
  68         if (!open)
  69                 return !list_empty(grace_list);
  70
  71         spin_lock(&grace_lock);
  72         list_for_each_entry(lm, grace_list, list) {
  73                 if (lm->block_opens) {
  74                         spin_unlock(&grace_lock);
  75                         return true;
  76                 }
  77         }
  78         spin_unlock(&grace_lock);
  79         return false;
  80 }
  81
  82 /**
  83  * locks_in_grace
  84  * @net: network namespace
  85  *
  86  * Lock managers call this function to determine when it is OK for them
  87  * to answer ordinary lock requests, and when they should accept only
  88  * lock reclaims.
  89  */
  90 bool locks_in_grace(struct net *net)
  91 {
  92         return __state_in_grace(net, false);
  93 }
  94 EXPORT_SYMBOL_GPL(locks_in_grace);
  95
  96 bool opens_in_grace(struct net *net)
  97 {
  98         return __state_in_grace(net, true);
  99 }
 100 EXPORT_SYMBOL_GPL(opens_in_grace);
 101
 102 static int __net_init
 103 grace_init_net(struct net *net)
 104 {
 105         struct list_head *grace_list = net_generic(net, grace_net_id);
 106
 107         INIT_LIST_HEAD(grace_list);
 108         return 0;
 109 }
 110
 111 static void __net_exit
 112 grace_exit_net(struct net *net)
 113 {
 114         struct list_head *grace_list = net_generic(net, grace_net_id);
 115
 116         WARN_ONCE(!list_empty(grace_list),
 117                   "net %x %s: grace_list is not empty\n",
 118                   net->ns.inum, __func__);
 119 }
 120
 121 static struct pernet_operations grace_net_ops = {
 122         .init = grace_init_net,
 123         .exit = grace_exit_net,
 124         .id   = &grace_net_id,
 125         .size = sizeof(struct list_head),
 126 };
 127
 128 static int __init
 129 init_grace(void)
 130 {
 131         return register_pernet_subsys(&grace_net_ops);
 132 }
 133
 134 static void __exit
 135 exit_grace(void)
 136 {
 137         unregister_pernet_subsys(&grace_net_ops);
 138 }
 139
 140 MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
 141 MODULE_LICENSE("GPL");
 142 module_init(init_grace)
 143 module_exit(exit_grace)