Merge branch 'samsung-fixes-4' of git://github.com/kgene/linux-samsung
[linux-btrfs-devel.git] / fs / btrfs / locking.c
blobd77b67c4b275731417c11e04ad38b3dc9c4d456b
1 /*
2 * Copyright (C) 2008 Oracle. All rights reserved.
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.
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.
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.
18 #include <linux/sched.h>
19 #include <linux/pagemap.h>
20 #include <linux/spinlock.h>
21 #include <linux/page-flags.h>
22 #include <asm/bug.h>
23 #include "ctree.h"
24 #include "extent_io.h"
25 #include "locking.h"
27 void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
30 * if we currently have a spinning reader or writer lock
31 * (indicated by the rw flag) this will bump the count
32 * of blocking holders and drop the spinlock.
34 void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw)
36 if (rw == BTRFS_WRITE_LOCK) {
37 if (atomic_read(&eb->blocking_writers) == 0) {
38 WARN_ON(atomic_read(&eb->spinning_writers) != 1);
39 atomic_dec(&eb->spinning_writers);
40 btrfs_assert_tree_locked(eb);
41 atomic_inc(&eb->blocking_writers);
42 write_unlock(&eb->lock);
44 } else if (rw == BTRFS_READ_LOCK) {
45 btrfs_assert_tree_read_locked(eb);
46 atomic_inc(&eb->blocking_readers);
47 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
48 atomic_dec(&eb->spinning_readers);
49 read_unlock(&eb->lock);
51 return;
55 * if we currently have a blocking lock, take the spinlock
56 * and drop our blocking count
58 void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
60 if (rw == BTRFS_WRITE_LOCK_BLOCKING) {
61 BUG_ON(atomic_read(&eb->blocking_writers) != 1);
62 write_lock(&eb->lock);
63 WARN_ON(atomic_read(&eb->spinning_writers));
64 atomic_inc(&eb->spinning_writers);
65 if (atomic_dec_and_test(&eb->blocking_writers))
66 wake_up(&eb->write_lock_wq);
67 } else if (rw == BTRFS_READ_LOCK_BLOCKING) {
68 BUG_ON(atomic_read(&eb->blocking_readers) == 0);
69 read_lock(&eb->lock);
70 atomic_inc(&eb->spinning_readers);
71 if (atomic_dec_and_test(&eb->blocking_readers))
72 wake_up(&eb->read_lock_wq);
74 return;
78 * take a spinning read lock. This will wait for any blocking
79 * writers
81 void btrfs_tree_read_lock(struct extent_buffer *eb)
83 again:
84 wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
85 read_lock(&eb->lock);
86 if (atomic_read(&eb->blocking_writers)) {
87 read_unlock(&eb->lock);
88 wait_event(eb->write_lock_wq,
89 atomic_read(&eb->blocking_writers) == 0);
90 goto again;
92 atomic_inc(&eb->read_locks);
93 atomic_inc(&eb->spinning_readers);
97 * returns 1 if we get the read lock and 0 if we don't
98 * this won't wait for blocking writers
100 int btrfs_try_tree_read_lock(struct extent_buffer *eb)
102 if (atomic_read(&eb->blocking_writers))
103 return 0;
105 read_lock(&eb->lock);
106 if (atomic_read(&eb->blocking_writers)) {
107 read_unlock(&eb->lock);
108 return 0;
110 atomic_inc(&eb->read_locks);
111 atomic_inc(&eb->spinning_readers);
112 return 1;
116 * returns 1 if we get the read lock and 0 if we don't
117 * this won't wait for blocking writers or readers
119 int btrfs_try_tree_write_lock(struct extent_buffer *eb)
121 if (atomic_read(&eb->blocking_writers) ||
122 atomic_read(&eb->blocking_readers))
123 return 0;
124 write_lock(&eb->lock);
125 if (atomic_read(&eb->blocking_writers) ||
126 atomic_read(&eb->blocking_readers)) {
127 write_unlock(&eb->lock);
128 return 0;
130 atomic_inc(&eb->write_locks);
131 atomic_inc(&eb->spinning_writers);
132 return 1;
136 * drop a spinning read lock
138 void btrfs_tree_read_unlock(struct extent_buffer *eb)
140 btrfs_assert_tree_read_locked(eb);
141 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
142 atomic_dec(&eb->spinning_readers);
143 atomic_dec(&eb->read_locks);
144 read_unlock(&eb->lock);
148 * drop a blocking read lock
150 void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
152 btrfs_assert_tree_read_locked(eb);
153 WARN_ON(atomic_read(&eb->blocking_readers) == 0);
154 if (atomic_dec_and_test(&eb->blocking_readers))
155 wake_up(&eb->read_lock_wq);
156 atomic_dec(&eb->read_locks);
160 * take a spinning write lock. This will wait for both
161 * blocking readers or writers
163 int btrfs_tree_lock(struct extent_buffer *eb)
165 again:
166 wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
167 wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
168 write_lock(&eb->lock);
169 if (atomic_read(&eb->blocking_readers)) {
170 write_unlock(&eb->lock);
171 wait_event(eb->read_lock_wq,
172 atomic_read(&eb->blocking_readers) == 0);
173 goto again;
175 if (atomic_read(&eb->blocking_writers)) {
176 write_unlock(&eb->lock);
177 wait_event(eb->write_lock_wq,
178 atomic_read(&eb->blocking_writers) == 0);
179 goto again;
181 WARN_ON(atomic_read(&eb->spinning_writers));
182 atomic_inc(&eb->spinning_writers);
183 atomic_inc(&eb->write_locks);
184 return 0;
188 * drop a spinning or a blocking write lock.
190 int btrfs_tree_unlock(struct extent_buffer *eb)
192 int blockers = atomic_read(&eb->blocking_writers);
194 BUG_ON(blockers > 1);
196 btrfs_assert_tree_locked(eb);
197 atomic_dec(&eb->write_locks);
199 if (blockers) {
200 WARN_ON(atomic_read(&eb->spinning_writers));
201 atomic_dec(&eb->blocking_writers);
202 smp_wmb();
203 wake_up(&eb->write_lock_wq);
204 } else {
205 WARN_ON(atomic_read(&eb->spinning_writers) != 1);
206 atomic_dec(&eb->spinning_writers);
207 write_unlock(&eb->lock);
209 return 0;
212 void btrfs_assert_tree_locked(struct extent_buffer *eb)
214 BUG_ON(!atomic_read(&eb->write_locks));
217 void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
219 BUG_ON(!atomic_read(&eb->read_locks));