grace.c 3.24 KB
Newer Older
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 10
#include <net/netns/generic.h>
#include <linux/fs.h>
11

12
static unsigned int grace_net_id;
13 14 15 16
static DEFINE_SPINLOCK(grace_lock);

/**
 * locks_start_grace
17
 * @net: net namespace that this lock manager belongs to
18 19 20 21 22 23 24 25 26
 * @lm: who this grace period is for
 *
 * A grace period is a period during which locks should not be given
 * out.  Currently grace periods are only enforced by the two lock
 * managers (lockd and nfsd), using the locks_in_grace() function to
 * check when they are in a grace period.
 *
 * This function is called to start a grace period.
 */
27 28
void
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 34 35 36 37
	if (list_empty(&lm->list))
		list_add(&lm->list, grace_list);
	else
		WARN(1, "double list_add attempt detected in net %x %s\n",
		     net->ns.inum, (net == &init_net) ? "(init_net)" : "");
38 39 40 41 42 43
	spin_unlock(&grace_lock);
}
EXPORT_SYMBOL_GPL(locks_start_grace);

/**
 * locks_end_grace
44
 * @net: net namespace that this lock manager belongs to
45 46 47 48 49 50 51 52
 * @lm: who this grace period is for
 *
 * Call this function to state that the given lock manager is ready to
 * resume regular locking.  The grace period will not end until all lock
 * managers that called locks_start_grace() also call locks_end_grace().
 * Note that callers count on it being safe to call this more than once,
 * and the second call should be a no-op.
 */
53 54
void
locks_end_grace(struct lock_manager *lm)
55 56 57 58 59 60 61 62 63 64 65 66 67 68
{
	spin_lock(&grace_lock);
	list_del_init(&lm->list);
	spin_unlock(&grace_lock);
}
EXPORT_SYMBOL_GPL(locks_end_grace);

/**
 * locks_in_grace
 *
 * Lock managers call this function to determine when it is OK for them
 * to answer ordinary lock requests, and when they should accept only
 * lock reclaims.
 */
69
int
70
__state_in_grace(struct net *net, bool open)
71
{
72
	struct list_head *grace_list = net_generic(net, grace_net_id);
73
	struct lock_manager *lm;
74

75 76 77 78 79 80 81 82 83 84 85 86 87
	if (!open)
		return !list_empty(grace_list);

	list_for_each_entry(lm, grace_list, list) {
		if (lm->block_opens)
			return true;
	}
	return false;
}

int locks_in_grace(struct net *net)
{
	return __state_in_grace(net, 0);
88 89
}
EXPORT_SYMBOL_GPL(locks_in_grace);
90

91 92 93 94 95 96
int opens_in_grace(struct net *net)
{
	return __state_in_grace(net, 1);
}
EXPORT_SYMBOL_GPL(opens_in_grace);

97 98 99 100 101 102 103 104 105 106 107 108 109 110
static int __net_init
grace_init_net(struct net *net)
{
	struct list_head *grace_list = net_generic(net, grace_net_id);

	INIT_LIST_HEAD(grace_list);
	return 0;
}

static void __net_exit
grace_exit_net(struct net *net)
{
	struct list_head *grace_list = net_generic(net, grace_net_id);

111 112 113
	WARN_ONCE(!list_empty(grace_list),
		  "net %x %s: grace_list is not empty\n",
		  net->ns.inum, __func__);
114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138
}

static struct pernet_operations grace_net_ops = {
	.init = grace_init_net,
	.exit = grace_exit_net,
	.id   = &grace_net_id,
	.size = sizeof(struct list_head),
};

static int __init
init_grace(void)
{
	return register_pernet_subsys(&grace_net_ops);
}

static void __exit
exit_grace(void)
{
	unregister_pernet_subsys(&grace_net_ops);
}

MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
MODULE_LICENSE("GPL");
module_init(init_grace)
module_exit(exit_grace)