LXR linux/fs/nfs_common/grace.c

   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
  12static unsigned int grace_net_id;
  13static 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 */
  27void
  28locks_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        if (list_empty(&lm->list))
  34                list_add(&lm->list, grace_list);
  35        else
  36                WARN(1, "double list_add attempt detected in net %x %s\n",
  37                     net->ns.inum, (net == &init_net) ? "(init_net)" : "");
  38        spin_unlock(&grace_lock);
  39}
  40EXPORT_SYMBOL_GPL(locks_start_grace);
  41
  42/**
  43 * locks_end_grace
  44 * @net: net namespace that this lock manager belongs to
  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 */
  53void
  54locks_end_grace(struct lock_manager *lm)
  55{
  56        spin_lock(&grace_lock);
  57        list_del_init(&lm->list);
  58        spin_unlock(&grace_lock);
  59}
  60EXPORT_SYMBOL_GPL(locks_end_grace);
  61
  62static 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        list_for_each_entry(lm, grace_list, list) {
  72                if (lm->block_opens)
  73                        return true;
  74        }
  75        return false;
  76}
  77
  78/**
  79 * locks_in_grace
  80 *
  81 * Lock managers call this function to determine when it is OK for them
  82 * to answer ordinary lock requests, and when they should accept only
  83 * lock reclaims.
  84 */
  85bool locks_in_grace(struct net *net)
  86{
  87        return __state_in_grace(net, false);
  88}
  89EXPORT_SYMBOL_GPL(locks_in_grace);
  90
  91bool opens_in_grace(struct net *net)
  92{
  93        return __state_in_grace(net, true);
  94}
  95EXPORT_SYMBOL_GPL(opens_in_grace);
  96
  97static int __net_init
  98grace_init_net(struct net *net)
  99{
 100        struct list_head *grace_list = net_generic(net, grace_net_id);
 101
 102        INIT_LIST_HEAD(grace_list);
 103        return 0;
 104}
 105
 106static void __net_exit
 107grace_exit_net(struct net *net)
 108{
 109        struct list_head *grace_list = net_generic(net, grace_net_id);
 110
 111        WARN_ONCE(!list_empty(grace_list),
 112                  "net %x %s: grace_list is not empty\n",
 113                  net->ns.inum, __func__);
 114}
 115
 116static struct pernet_operations grace_net_ops = {
 117        .init = grace_init_net,
 118        .exit = grace_exit_net,
 119        .id   = &grace_net_id,
 120        .size = sizeof(struct list_head),
 121};
 122
 123static int __init
 124init_grace(void)
 125{
 126        return register_pernet_subsys(&grace_net_ops);
 127}
 128
 129static void __exit
 130exit_grace(void)
 131{
 132        unregister_pernet_subsys(&grace_net_ops);
 133}
 134
 135MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
 136MODULE_LICENSE("GPL");
 137module_init(init_grace)
 138module_exit(exit_grace)
 139