1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
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
139
140
141
142
143
144
145
146
147
148
149
150
151
152
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2022-2023 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <djwong@kernel.org>
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_ag.h"
#include "xfs_trace.h"
/*
* Use a static key here to reduce the overhead of xfs_drain_rele. If the
* compiler supports jump labels, the static branch will be replaced by a nop
* sled when there are no xfs_drain_wait callers. Online fsck is currently
* the only caller, so this is a reasonable tradeoff.
*
* Note: Patching the kernel code requires taking the cpu hotplug lock. Other
* parts of the kernel allocate memory with that lock held, which means that
* XFS callers cannot hold any locks that might be used by memory reclaim or
* writeback when calling the static_branch_{inc,dec} functions.
*/
static DEFINE_STATIC_KEY_FALSE(xfs_drain_waiter_gate);
void
xfs_drain_wait_disable(void)
{
static_branch_dec(&xfs_drain_waiter_gate);
}
void
xfs_drain_wait_enable(void)
{
static_branch_inc(&xfs_drain_waiter_gate);
}
void
xfs_defer_drain_init(
struct xfs_defer_drain *dr)
{
atomic_set(&dr->dr_count, 0);
init_waitqueue_head(&dr->dr_waiters);
}
void
xfs_defer_drain_free(struct xfs_defer_drain *dr)
{
ASSERT(atomic_read(&dr->dr_count) == 0);
}
/* Increase the pending intent count. */
static inline void xfs_defer_drain_grab(struct xfs_defer_drain *dr)
{
atomic_inc(&dr->dr_count);
}
static inline bool has_waiters(struct wait_queue_head *wq_head)
{
/*
* This memory barrier is paired with the one in set_current_state on
* the waiting side.
*/
smp_mb__after_atomic();
return waitqueue_active(wq_head);
}
/* Decrease the pending intent count, and wake any waiters, if appropriate. */
static inline void xfs_defer_drain_rele(struct xfs_defer_drain *dr)
{
if (atomic_dec_and_test(&dr->dr_count) &&
static_branch_unlikely(&xfs_drain_waiter_gate) &&
has_waiters(&dr->dr_waiters))
wake_up(&dr->dr_waiters);
}
/* Are there intents pending? */
static inline bool xfs_defer_drain_busy(struct xfs_defer_drain *dr)
{
return atomic_read(&dr->dr_count) > 0;
}
/*
* Wait for the pending intent count for a drain to hit zero.
*
* Callers must not hold any locks that would prevent intents from being
* finished.
*/
static inline int xfs_defer_drain_wait(struct xfs_defer_drain *dr)
{
return wait_event_killable(dr->dr_waiters, !xfs_defer_drain_busy(dr));
}
/*
* Get a passive reference to the group that contains a fsbno and declare an
* intent to update its metadata.
*
* Other threads that need exclusive access can decide to back off if they see
* declared intentions.
*/
struct xfs_group *
xfs_group_intent_get(
struct xfs_mount *mp,
xfs_fsblock_t fsbno,
enum xfs_group_type type)
{
struct xfs_group *xg;
xg = xfs_group_get_by_fsb(mp, fsbno, type);
if (!xg)
return NULL;
trace_xfs_group_intent_hold(xg, __return_address);
xfs_defer_drain_grab(&xg->xg_intents_drain);
return xg;
}
/*
* Release our intent to update this groups metadata, and then release our
* passive ref to it.
*/
void
xfs_group_intent_put(
struct xfs_group *xg)
{
trace_xfs_group_intent_rele(xg, __return_address);
xfs_defer_drain_rele(&xg->xg_intents_drain);
xfs_group_put(xg);
}
/*
* Wait for the intent update count for this AG to hit zero.
* Callers must not hold any AG header buffers.
*/
int
xfs_group_intent_drain(
struct xfs_group *xg)
{
trace_xfs_group_wait_intents(xg, __return_address);
return xfs_defer_drain_wait(&xg->xg_intents_drain);
}
/*
* Has anyone declared an intent to update this group?
*/
bool
xfs_group_intent_busy(
struct xfs_group *xg)
{
return xfs_defer_drain_busy(&xg->xg_intents_drain);
}
|
