143 lines
3.3 KiB
C
143 lines
3.3 KiB
C
/*
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* Common code for control of lockd and nfsv4 grace periods.
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*
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* Transplanted from lockd code
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*/
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#include <linux/module.h>
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#include <net/net_namespace.h>
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#include <net/netns/generic.h>
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#include <linux/fs.h>
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static int grace_net_id;
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static DEFINE_SPINLOCK(grace_lock);
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/**
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* locks_start_grace
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* @net: net namespace that this lock manager belongs to
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* @lm: who this grace period is for
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*
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* A grace period is a period during which locks should not be given
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* out. Currently grace periods are only enforced by the two lock
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* managers (lockd and nfsd), using the locks_in_grace() function to
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* check when they are in a grace period.
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*
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* This function is called to start a grace period.
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*/
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void
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locks_start_grace(struct net *net, struct lock_manager *lm)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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spin_lock(&grace_lock);
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if (list_empty(&lm->list))
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list_add(&lm->list, grace_list);
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else
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WARN(1, "double list_add attempt detected in net %x %s\n",
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net->ns.inum, (net == &init_net) ? "(init_net)" : "");
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spin_unlock(&grace_lock);
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}
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EXPORT_SYMBOL_GPL(locks_start_grace);
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/**
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* locks_end_grace
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* @net: net namespace that this lock manager belongs to
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* @lm: who this grace period is for
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*
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* Call this function to state that the given lock manager is ready to
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* resume regular locking. The grace period will not end until all lock
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* managers that called locks_start_grace() also call locks_end_grace().
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* Note that callers count on it being safe to call this more than once,
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* and the second call should be a no-op.
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*/
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void
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locks_end_grace(struct lock_manager *lm)
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{
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spin_lock(&grace_lock);
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list_del_init(&lm->list);
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spin_unlock(&grace_lock);
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}
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EXPORT_SYMBOL_GPL(locks_end_grace);
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/**
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* locks_in_grace
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*
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* Lock managers call this function to determine when it is OK for them
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* to answer ordinary lock requests, and when they should accept only
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* lock reclaims.
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*/
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int
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__state_in_grace(struct net *net, bool open)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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struct lock_manager *lm;
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if (!open)
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return !list_empty(grace_list);
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spin_lock(&grace_lock);
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list_for_each_entry(lm, grace_list, list) {
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if (lm->block_opens) {
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spin_unlock(&grace_lock);
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return true;
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}
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}
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spin_unlock(&grace_lock);
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return false;
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}
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int locks_in_grace(struct net *net)
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{
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return __state_in_grace(net, 0);
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}
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EXPORT_SYMBOL_GPL(locks_in_grace);
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int opens_in_grace(struct net *net)
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{
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return __state_in_grace(net, 1);
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}
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EXPORT_SYMBOL_GPL(opens_in_grace);
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static int __net_init
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grace_init_net(struct net *net)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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INIT_LIST_HEAD(grace_list);
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return 0;
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}
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static void __net_exit
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grace_exit_net(struct net *net)
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{
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struct list_head *grace_list = net_generic(net, grace_net_id);
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WARN_ONCE(!list_empty(grace_list),
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"net %x %s: grace_list is not empty\n",
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net->ns.inum, __func__);
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}
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static struct pernet_operations grace_net_ops = {
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.init = grace_init_net,
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.exit = grace_exit_net,
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.id = &grace_net_id,
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.size = sizeof(struct list_head),
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};
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static int __init
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init_grace(void)
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{
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return register_pernet_subsys(&grace_net_ops);
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}
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static void __exit
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exit_grace(void)
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{
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unregister_pernet_subsys(&grace_net_ops);
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}
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MODULE_AUTHOR("Jeff Layton <jlayton@primarydata.com>");
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MODULE_LICENSE("GPL");
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module_init(init_grace)
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module_exit(exit_grace)
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