Root/fs/lockd/grace.c

1/*
2 * Common code for control of lockd and nfsv4 grace periods.
3 */
4
5#include <linux/module.h>
6#include <linux/lockd/bind.h>
7
8static LIST_HEAD(grace_list);
9static DEFINE_SPINLOCK(grace_lock);
10
11/**
12 * locks_start_grace
13 * @lm: who this grace period is for
14 *
15 * A grace period is a period during which locks should not be given
16 * out. Currently grace periods are only enforced by the two lock
17 * managers (lockd and nfsd), using the locks_in_grace() function to
18 * check when they are in a grace period.
19 *
20 * This function is called to start a grace period.
21 */
22void locks_start_grace(struct lock_manager *lm)
23{
24    spin_lock(&grace_lock);
25    list_add(&lm->list, &grace_list);
26    spin_unlock(&grace_lock);
27}
28EXPORT_SYMBOL_GPL(locks_start_grace);
29
30/**
31 * locks_end_grace
32 * @lm: who this grace period is for
33 *
34 * Call this function to state that the given lock manager is ready to
35 * resume regular locking. The grace period will not end until all lock
36 * managers that called locks_start_grace() also call locks_end_grace().
37 * Note that callers count on it being safe to call this more than once,
38 * and the second call should be a no-op.
39 */
40void locks_end_grace(struct lock_manager *lm)
41{
42    spin_lock(&grace_lock);
43    list_del_init(&lm->list);
44    spin_unlock(&grace_lock);
45}
46EXPORT_SYMBOL_GPL(locks_end_grace);
47
48/**
49 * locks_in_grace
50 *
51 * Lock managers call this function to determine when it is OK for them
52 * to answer ordinary lock requests, and when they should accept only
53 * lock reclaims.
54 */
55int locks_in_grace(void)
56{
57    return !list_empty(&grace_list);
58}
59EXPORT_SYMBOL_GPL(locks_in_grace);
60

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