1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 2008 Oracle. All rights reserved.
6 #include <linux/sched.h>
7 #include <linux/pagemap.h>
8 #include <linux/spinlock.h>
9 #include <linux/page-flags.h>
12 #include "extent_io.h"
15 #ifdef CONFIG_BTRFS_DEBUG
16 static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb)
18 WARN_ON(eb->spinning_writers);
19 eb->spinning_writers++;
22 static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb)
24 WARN_ON(eb->spinning_writers != 1);
25 eb->spinning_writers--;
28 static void btrfs_assert_no_spinning_writers(struct extent_buffer *eb)
30 WARN_ON(eb->spinning_writers);
33 static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb)
35 atomic_inc(&eb->spinning_readers);
38 static void btrfs_assert_spinning_readers_put(struct extent_buffer *eb)
40 WARN_ON(atomic_read(&eb->spinning_readers) == 0);
41 atomic_dec(&eb->spinning_readers);
44 static void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb)
46 atomic_inc(&eb->read_locks);
49 static void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb)
51 atomic_dec(&eb->read_locks);
54 static void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
56 BUG_ON(!atomic_read(&eb->read_locks));
59 static void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb)
64 static void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb)
69 void btrfs_assert_tree_locked(struct extent_buffer *eb)
71 BUG_ON(!eb->write_locks);
75 static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb) { }
76 static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb) { }
77 static void btrfs_assert_no_spinning_writers(struct extent_buffer *eb) { }
78 static void btrfs_assert_spinning_readers_put(struct extent_buffer *eb) { }
79 static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb) { }
80 static void btrfs_assert_tree_read_locked(struct extent_buffer *eb) { }
81 static void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb) { }
82 static void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb) { }
83 void btrfs_assert_tree_locked(struct extent_buffer *eb) { }
84 static void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb) { }
85 static void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb) { }
88 void btrfs_set_lock_blocking_read(struct extent_buffer *eb)
90 trace_btrfs_set_lock_blocking_read(eb);
92 * No lock is required. The lock owner may change if we have a read
93 * lock, but it won't change to or away from us. If we have the write
94 * lock, we are the owner and it'll never change.
96 if (eb->lock_nested && current->pid == eb->lock_owner)
98 btrfs_assert_tree_read_locked(eb);
99 atomic_inc(&eb->blocking_readers);
100 btrfs_assert_spinning_readers_put(eb);
101 read_unlock(&eb->lock);
104 void btrfs_set_lock_blocking_write(struct extent_buffer *eb)
106 trace_btrfs_set_lock_blocking_write(eb);
108 * No lock is required. The lock owner may change if we have a read
109 * lock, but it won't change to or away from us. If we have the write
110 * lock, we are the owner and it'll never change.
112 if (eb->lock_nested && current->pid == eb->lock_owner)
114 if (eb->blocking_writers == 0) {
115 btrfs_assert_spinning_writers_put(eb);
116 btrfs_assert_tree_locked(eb);
117 eb->blocking_writers++;
118 write_unlock(&eb->lock);
122 void btrfs_clear_lock_blocking_read(struct extent_buffer *eb)
124 trace_btrfs_clear_lock_blocking_read(eb);
126 * No lock is required. The lock owner may change if we have a read
127 * lock, but it won't change to or away from us. If we have the write
128 * lock, we are the owner and it'll never change.
130 if (eb->lock_nested && current->pid == eb->lock_owner)
132 BUG_ON(atomic_read(&eb->blocking_readers) == 0);
133 read_lock(&eb->lock);
134 btrfs_assert_spinning_readers_get(eb);
135 /* atomic_dec_and_test implies a barrier */
136 if (atomic_dec_and_test(&eb->blocking_readers))
137 cond_wake_up_nomb(&eb->read_lock_wq);
140 void btrfs_clear_lock_blocking_write(struct extent_buffer *eb)
142 trace_btrfs_clear_lock_blocking_write(eb);
144 * no lock is required. The lock owner may change if
145 * we have a read lock, but it won't change to or away
146 * from us. If we have the write lock, we are the owner
147 * and it'll never change.
149 if (eb->lock_nested && current->pid == eb->lock_owner)
151 write_lock(&eb->lock);
152 BUG_ON(eb->blocking_writers != 1);
153 btrfs_assert_spinning_writers_get(eb);
154 if (--eb->blocking_writers == 0)
155 cond_wake_up(&eb->write_lock_wq);
159 * take a spinning read lock. This will wait for any blocking
162 void btrfs_tree_read_lock(struct extent_buffer *eb)
166 if (trace_btrfs_tree_read_lock_enabled())
167 start_ns = ktime_get_ns();
169 read_lock(&eb->lock);
170 BUG_ON(eb->blocking_writers == 0 &&
171 current->pid == eb->lock_owner);
172 if (eb->blocking_writers && current->pid == eb->lock_owner) {
174 * This extent is already write-locked by our thread. We allow
175 * an additional read lock to be added because it's for the same
176 * thread. btrfs_find_all_roots() depends on this as it may be
177 * called on a partly (write-)locked tree.
179 BUG_ON(eb->lock_nested);
180 eb->lock_nested = true;
181 read_unlock(&eb->lock);
182 trace_btrfs_tree_read_lock(eb, start_ns);
185 if (eb->blocking_writers) {
186 read_unlock(&eb->lock);
187 wait_event(eb->write_lock_wq,
188 eb->blocking_writers == 0);
191 btrfs_assert_tree_read_locks_get(eb);
192 btrfs_assert_spinning_readers_get(eb);
193 trace_btrfs_tree_read_lock(eb, start_ns);
197 * take a spinning read lock.
198 * returns 1 if we get the read lock and 0 if we don't
199 * this won't wait for blocking writers
201 int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
203 if (eb->blocking_writers)
206 read_lock(&eb->lock);
207 if (eb->blocking_writers) {
208 read_unlock(&eb->lock);
211 btrfs_assert_tree_read_locks_get(eb);
212 btrfs_assert_spinning_readers_get(eb);
213 trace_btrfs_tree_read_lock_atomic(eb);
218 * returns 1 if we get the read lock and 0 if we don't
219 * this won't wait for blocking writers
221 int btrfs_try_tree_read_lock(struct extent_buffer *eb)
223 if (eb->blocking_writers)
226 if (!read_trylock(&eb->lock))
229 if (eb->blocking_writers) {
230 read_unlock(&eb->lock);
233 btrfs_assert_tree_read_locks_get(eb);
234 btrfs_assert_spinning_readers_get(eb);
235 trace_btrfs_try_tree_read_lock(eb);
240 * returns 1 if we get the read lock and 0 if we don't
241 * this won't wait for blocking writers or readers
243 int btrfs_try_tree_write_lock(struct extent_buffer *eb)
245 if (eb->blocking_writers || atomic_read(&eb->blocking_readers))
248 write_lock(&eb->lock);
249 if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) {
250 write_unlock(&eb->lock);
253 btrfs_assert_tree_write_locks_get(eb);
254 btrfs_assert_spinning_writers_get(eb);
255 eb->lock_owner = current->pid;
256 trace_btrfs_try_tree_write_lock(eb);
261 * drop a spinning read lock
263 void btrfs_tree_read_unlock(struct extent_buffer *eb)
265 trace_btrfs_tree_read_unlock(eb);
267 * if we're nested, we have the write lock. No new locking
268 * is needed as long as we are the lock owner.
269 * The write unlock will do a barrier for us, and the lock_nested
270 * field only matters to the lock owner.
272 if (eb->lock_nested && current->pid == eb->lock_owner) {
273 eb->lock_nested = false;
276 btrfs_assert_tree_read_locked(eb);
277 btrfs_assert_spinning_readers_put(eb);
278 btrfs_assert_tree_read_locks_put(eb);
279 read_unlock(&eb->lock);
283 * drop a blocking read lock
285 void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
287 trace_btrfs_tree_read_unlock_blocking(eb);
289 * if we're nested, we have the write lock. No new locking
290 * is needed as long as we are the lock owner.
291 * The write unlock will do a barrier for us, and the lock_nested
292 * field only matters to the lock owner.
294 if (eb->lock_nested && current->pid == eb->lock_owner) {
295 eb->lock_nested = false;
298 btrfs_assert_tree_read_locked(eb);
299 WARN_ON(atomic_read(&eb->blocking_readers) == 0);
300 /* atomic_dec_and_test implies a barrier */
301 if (atomic_dec_and_test(&eb->blocking_readers))
302 cond_wake_up_nomb(&eb->read_lock_wq);
303 btrfs_assert_tree_read_locks_put(eb);
307 * take a spinning write lock. This will wait for both
308 * blocking readers or writers
310 void btrfs_tree_lock(struct extent_buffer *eb)
314 if (trace_btrfs_tree_lock_enabled())
315 start_ns = ktime_get_ns();
317 WARN_ON(eb->lock_owner == current->pid);
319 wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
320 wait_event(eb->write_lock_wq, eb->blocking_writers == 0);
321 write_lock(&eb->lock);
322 if (atomic_read(&eb->blocking_readers) || eb->blocking_writers) {
323 write_unlock(&eb->lock);
326 btrfs_assert_spinning_writers_get(eb);
327 btrfs_assert_tree_write_locks_get(eb);
328 eb->lock_owner = current->pid;
329 trace_btrfs_tree_lock(eb, start_ns);
333 * drop a spinning or a blocking write lock.
335 void btrfs_tree_unlock(struct extent_buffer *eb)
337 int blockers = eb->blocking_writers;
339 BUG_ON(blockers > 1);
341 btrfs_assert_tree_locked(eb);
342 trace_btrfs_tree_unlock(eb);
344 btrfs_assert_tree_write_locks_put(eb);
347 btrfs_assert_no_spinning_writers(eb);
348 eb->blocking_writers--;
349 /* Use the lighter barrier after atomic */
350 smp_mb__after_atomic();
351 cond_wake_up_nomb(&eb->write_lock_wq);
353 btrfs_assert_spinning_writers_put(eb);
354 write_unlock(&eb->lock);