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/*
* Common code for control of lockd and nfsv4 grace periods.
*
* Transplanted from lockd code
*/
#include <linux/module.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <linux/fs.h>
static unsigned int grace_net_id;
static DEFINE_SPINLOCK(grace_lock);
/**
* locks_start_grace
* @net: net namespace that this lock manager belongs to
* @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.
*/
void
locks_start_grace(struct net *net, struct lock_manager *lm)
{
struct list_head *grace_list = net_generic(net, grace_net_id);
spin_lock(&grace_lock);
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)" : "");
spin_unlock(&grace_lock);
}
EXPORT_SYMBOL_GPL(locks_start_grace);
/**
* locks_end_grace
* @net: net namespace that this lock manager belongs to
* @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.
*/
void
locks_end_grace(struct lock_manager *lm)
{
spin_lock(&grace_lock);
list_del_init(&lm->list);
spin_unlock(&grace_lock);
}
EXPORT_SYMBOL_GPL(locks_end_grace);
static bool
__state_in_grace(struct net *net, bool open)
{
struct list_head *grace_list = net_generic(net, grace_net_id);
struct lock_manager *lm;
if (!open)
return !list_empty(grace_list);
spin_lock(&grace_lock);
list_for_each_entry(lm, grace_list, list) {
if (lm->block_opens) {
spin_unlock(&grace_lock);
return true;
}
}
spin_unlock(&grace_lock);
return false;
}
/**
* 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.
*/
bool locks_in_grace(struct net *net)
{
return __state_in_grace(net, false);
}
EXPORT_SYMBOL_GPL(locks_in_grace);
bool opens_in_grace(struct net *net)
{
return __state_in_grace(net, true);
}
EXPORT_SYMBOL_GPL(opens_in_grace);
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);
WARN_ONCE(!list_empty(grace_list),
"net %x %s: grace_list is not empty\n",
net->ns.inum, __func__);
}
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)
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