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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Copyright (C) 2008 Oracle. All rights reserved.
4 */
5
6#ifndef BTRFS_LOCKING_H
7#define BTRFS_LOCKING_H
8
9#include <linux/atomic.h>
10#include <linux/wait.h>
11#include <linux/percpu_counter.h>
12#include "extent_io.h"
13
14#define BTRFS_WRITE_LOCK 1
15#define BTRFS_READ_LOCK 2
16
17/*
18 * We are limited in number of subclasses by MAX_LOCKDEP_SUBCLASSES, which at
19 * the time of this patch is 8, which is how many we use. Keep this in mind if
20 * you decide you want to add another subclass.
21 */
22enum btrfs_lock_nesting {
23 BTRFS_NESTING_NORMAL,
24
25 /*
26 * When we COW a block we are holding the lock on the original block,
27 * and since our lockdep maps are rootid+level, this confuses lockdep
28 * when we lock the newly allocated COW'd block. Handle this by having
29 * a subclass for COW'ed blocks so that lockdep doesn't complain.
30 */
31 BTRFS_NESTING_COW,
32
33 /*
34 * Oftentimes we need to lock adjacent nodes on the same level while
35 * still holding the lock on the original node we searched to, such as
36 * for searching forward or for split/balance.
37 *
38 * Because of this we need to indicate to lockdep that this is
39 * acceptable by having a different subclass for each of these
40 * operations.
41 */
42 BTRFS_NESTING_LEFT,
43 BTRFS_NESTING_RIGHT,
44
45 /*
46 * When splitting we will be holding a lock on the left/right node when
47 * we need to cow that node, thus we need a new set of subclasses for
48 * these two operations.
49 */
50 BTRFS_NESTING_LEFT_COW,
51 BTRFS_NESTING_RIGHT_COW,
52
53 /*
54 * When splitting we may push nodes to the left or right, but still use
55 * the subsequent nodes in our path, keeping our locks on those adjacent
56 * blocks. Thus when we go to allocate a new split block we've already
57 * used up all of our available subclasses, so this subclass exists to
58 * handle this case where we need to allocate a new split block.
59 */
60 BTRFS_NESTING_SPLIT,
61
62 /*
63 * When promoting a new block to a root we need to have a special
64 * subclass so we don't confuse lockdep, as it will appear that we are
65 * locking a higher level node before a lower level one. Copying also
66 * has this problem as it appears we're locking the same block again
67 * when we make a snapshot of an existing root.
68 */
69 BTRFS_NESTING_NEW_ROOT,
70
71 /*
72 * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so
73 * add this in here and add a static_assert to keep us from going over
74 * the limit. As of this writing we're limited to 8, and we're
75 * definitely using 8, hence this check to keep us from messing up in
76 * the future.
77 */
78 BTRFS_NESTING_MAX,
79};
80
81enum btrfs_lockdep_trans_states {
82 BTRFS_LOCKDEP_TRANS_COMMIT_PREP,
83 BTRFS_LOCKDEP_TRANS_UNBLOCKED,
84 BTRFS_LOCKDEP_TRANS_SUPER_COMMITTED,
85 BTRFS_LOCKDEP_TRANS_COMPLETED,
86};
87
88/*
89 * Lockdep annotation for wait events.
90 *
91 * @owner: The struct where the lockdep map is defined
92 * @lock: The lockdep map corresponding to a wait event
93 *
94 * This macro is used to annotate a wait event. In this case a thread acquires
95 * the lockdep map as writer (exclusive lock) because it has to block until all
96 * the threads that hold the lock as readers signal the condition for the wait
97 * event and release their locks.
98 */
99#define btrfs_might_wait_for_event(owner, lock) \
100 do { \
101 rwsem_acquire(&owner->lock##_map, 0, 0, _THIS_IP_); \
102 rwsem_release(&owner->lock##_map, _THIS_IP_); \
103 } while (0)
104
105/*
106 * Protection for the resource/condition of a wait event.
107 *
108 * @owner: The struct where the lockdep map is defined
109 * @lock: The lockdep map corresponding to a wait event
110 *
111 * Many threads can modify the condition for the wait event at the same time
112 * and signal the threads that block on the wait event. The threads that modify
113 * the condition and do the signaling acquire the lock as readers (shared
114 * lock).
115 */
116#define btrfs_lockdep_acquire(owner, lock) \
117 rwsem_acquire_read(&owner->lock##_map, 0, 0, _THIS_IP_)
118
119/*
120 * Used after signaling the condition for a wait event to release the lockdep
121 * map held by a reader thread.
122 */
123#define btrfs_lockdep_release(owner, lock) \
124 rwsem_release(&owner->lock##_map, _THIS_IP_)
125
126/*
127 * Macros for the transaction states wait events, similar to the generic wait
128 * event macros.
129 */
130#define btrfs_might_wait_for_state(owner, i) \
131 do { \
132 rwsem_acquire(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_); \
133 rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_); \
134 } while (0)
135
136#define btrfs_trans_state_lockdep_acquire(owner, i) \
137 rwsem_acquire_read(&owner->btrfs_state_change_map[i], 0, 0, _THIS_IP_)
138
139#define btrfs_trans_state_lockdep_release(owner, i) \
140 rwsem_release(&owner->btrfs_state_change_map[i], _THIS_IP_)
141
142/* Initialization of the lockdep map */
143#define btrfs_lockdep_init_map(owner, lock) \
144 do { \
145 static struct lock_class_key lock##_key; \
146 lockdep_init_map(&owner->lock##_map, #lock, &lock##_key, 0); \
147 } while (0)
148
149/* Initialization of the transaction states lockdep maps. */
150#define btrfs_state_lockdep_init_map(owner, lock, state) \
151 do { \
152 static struct lock_class_key lock##_key; \
153 lockdep_init_map(&owner->btrfs_state_change_map[state], #lock, \
154 &lock##_key, 0); \
155 } while (0)
156
157static_assert(BTRFS_NESTING_MAX <= MAX_LOCKDEP_SUBCLASSES,
158 "too many lock subclasses defined");
159
160struct btrfs_path;
161
162void __btrfs_tree_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest);
163void btrfs_tree_lock(struct extent_buffer *eb);
164void btrfs_tree_unlock(struct extent_buffer *eb);
165
166void __btrfs_tree_read_lock(struct extent_buffer *eb, enum btrfs_lock_nesting nest);
167void btrfs_tree_read_lock(struct extent_buffer *eb);
168void btrfs_tree_read_unlock(struct extent_buffer *eb);
169int btrfs_try_tree_read_lock(struct extent_buffer *eb);
170int btrfs_try_tree_write_lock(struct extent_buffer *eb);
171struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);
172struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root);
173struct extent_buffer *btrfs_try_read_lock_root_node(struct btrfs_root *root);
174
175#ifdef CONFIG_BTRFS_DEBUG
176static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb)
177{
178 lockdep_assert_held_write(&eb->lock);
179}
180#else
181static inline void btrfs_assert_tree_write_locked(struct extent_buffer *eb) { }
182#endif
183
184void btrfs_unlock_up_safe(struct btrfs_path *path, int level);
185
186static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
187{
188 if (rw == BTRFS_WRITE_LOCK)
189 btrfs_tree_unlock(eb);
190 else if (rw == BTRFS_READ_LOCK)
191 btrfs_tree_read_unlock(eb);
192 else
193 BUG();
194}
195
196struct btrfs_drew_lock {
197 atomic_t readers;
198 atomic_t writers;
199 wait_queue_head_t pending_writers;
200 wait_queue_head_t pending_readers;
201};
202
203void btrfs_drew_lock_init(struct btrfs_drew_lock *lock);
204void btrfs_drew_write_lock(struct btrfs_drew_lock *lock);
205bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock);
206void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock);
207void btrfs_drew_read_lock(struct btrfs_drew_lock *lock);
208void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock);
209
210#ifdef CONFIG_DEBUG_LOCK_ALLOC
211void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int level);
212void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb);
213#else
214static inline void btrfs_set_buffer_lockdep_class(u64 objectid,
215 struct extent_buffer *eb, int level)
216{
217}
218static inline void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root,
219 struct extent_buffer *eb)
220{
221}
222#endif
223
224#endif
1/*
2 * Copyright (C) 2008 Oracle. All rights reserved.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public
6 * License v2 as published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public
14 * License along with this program; if not, write to the
15 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
16 * Boston, MA 021110-1307, USA.
17 */
18
19#ifndef __BTRFS_LOCKING_
20#define __BTRFS_LOCKING_
21
22#define BTRFS_WRITE_LOCK 1
23#define BTRFS_READ_LOCK 2
24#define BTRFS_WRITE_LOCK_BLOCKING 3
25#define BTRFS_READ_LOCK_BLOCKING 4
26
27void btrfs_tree_lock(struct extent_buffer *eb);
28void btrfs_tree_unlock(struct extent_buffer *eb);
29int btrfs_try_spin_lock(struct extent_buffer *eb);
30
31void btrfs_tree_read_lock(struct extent_buffer *eb);
32void btrfs_tree_read_unlock(struct extent_buffer *eb);
33void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb);
34void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw);
35void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw);
36void btrfs_assert_tree_locked(struct extent_buffer *eb);
37int btrfs_try_tree_read_lock(struct extent_buffer *eb);
38int btrfs_try_tree_write_lock(struct extent_buffer *eb);
39
40static inline void btrfs_tree_unlock_rw(struct extent_buffer *eb, int rw)
41{
42 if (rw == BTRFS_WRITE_LOCK || rw == BTRFS_WRITE_LOCK_BLOCKING)
43 btrfs_tree_unlock(eb);
44 else if (rw == BTRFS_READ_LOCK_BLOCKING)
45 btrfs_tree_read_unlock_blocking(eb);
46 else if (rw == BTRFS_READ_LOCK)
47 btrfs_tree_read_unlock(eb);
48 else
49 BUG();
50}
51
52static inline void btrfs_set_lock_blocking(struct extent_buffer *eb)
53{
54 btrfs_set_lock_blocking_rw(eb, BTRFS_WRITE_LOCK);
55}
56
57static inline void btrfs_clear_lock_blocking(struct extent_buffer *eb)
58{
59 btrfs_clear_lock_blocking_rw(eb, BTRFS_WRITE_LOCK_BLOCKING);
60}
61#endif