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c1d7c514 | 1 | // SPDX-License-Identifier: GPL-2.0 |
925baedd CM |
2 | /* |
3 | * Copyright (C) 2008 Oracle. All rights reserved. | |
925baedd | 4 | */ |
c1d7c514 | 5 | |
925baedd | 6 | #include <linux/sched.h> |
925baedd CM |
7 | #include <linux/pagemap.h> |
8 | #include <linux/spinlock.h> | |
9 | #include <linux/page-flags.h> | |
4881ee5a | 10 | #include <asm/bug.h> |
925baedd CM |
11 | #include "ctree.h" |
12 | #include "extent_io.h" | |
13 | #include "locking.h" | |
14 | ||
e4e9fd0f DS |
15 | #ifdef CONFIG_BTRFS_DEBUG |
16 | static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb) | |
17 | { | |
f3dc24c5 DS |
18 | WARN_ON(eb->spinning_writers); |
19 | eb->spinning_writers++; | |
e4e9fd0f DS |
20 | } |
21 | ||
22 | static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb) | |
23 | { | |
f3dc24c5 DS |
24 | WARN_ON(eb->spinning_writers != 1); |
25 | eb->spinning_writers--; | |
e4e9fd0f DS |
26 | } |
27 | ||
28 | static void btrfs_assert_no_spinning_writers(struct extent_buffer *eb) | |
29 | { | |
f3dc24c5 | 30 | WARN_ON(eb->spinning_writers); |
e4e9fd0f DS |
31 | } |
32 | ||
225948de DS |
33 | static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb) |
34 | { | |
35 | atomic_inc(&eb->spinning_readers); | |
36 | } | |
37 | ||
38 | static void btrfs_assert_spinning_readers_put(struct extent_buffer *eb) | |
39 | { | |
40 | WARN_ON(atomic_read(&eb->spinning_readers) == 0); | |
41 | atomic_dec(&eb->spinning_readers); | |
42 | } | |
43 | ||
58a2ddae DS |
44 | static void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb) |
45 | { | |
46 | atomic_inc(&eb->read_locks); | |
47 | } | |
48 | ||
49 | static void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb) | |
50 | { | |
51 | atomic_dec(&eb->read_locks); | |
52 | } | |
53 | ||
54 | static void btrfs_assert_tree_read_locked(struct extent_buffer *eb) | |
55 | { | |
56 | BUG_ON(!atomic_read(&eb->read_locks)); | |
57 | } | |
58 | ||
e3f15388 DS |
59 | static void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb) |
60 | { | |
00801ae4 | 61 | eb->write_locks++; |
e3f15388 DS |
62 | } |
63 | ||
64 | static void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb) | |
65 | { | |
00801ae4 | 66 | eb->write_locks--; |
e3f15388 DS |
67 | } |
68 | ||
69 | void btrfs_assert_tree_locked(struct extent_buffer *eb) | |
70 | { | |
00801ae4 | 71 | BUG_ON(!eb->write_locks); |
e3f15388 DS |
72 | } |
73 | ||
e4e9fd0f DS |
74 | #else |
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) { } | |
225948de DS |
78 | static void btrfs_assert_spinning_readers_put(struct extent_buffer *eb) { } |
79 | static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb) { } | |
58a2ddae DS |
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) { } | |
e3f15388 DS |
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) { } | |
e4e9fd0f DS |
86 | #endif |
87 | ||
b95be2d9 DS |
88 | void btrfs_set_lock_blocking_read(struct extent_buffer *eb) |
89 | { | |
31aab402 | 90 | trace_btrfs_set_lock_blocking_read(eb); |
b95be2d9 DS |
91 | /* |
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. | |
95 | */ | |
96 | if (eb->lock_nested && current->pid == eb->lock_owner) | |
97 | return; | |
98 | btrfs_assert_tree_read_locked(eb); | |
99 | atomic_inc(&eb->blocking_readers); | |
afd495a8 | 100 | btrfs_assert_spinning_readers_put(eb); |
b95be2d9 DS |
101 | read_unlock(&eb->lock); |
102 | } | |
103 | ||
104 | void btrfs_set_lock_blocking_write(struct extent_buffer *eb) | |
925baedd | 105 | { |
31aab402 | 106 | trace_btrfs_set_lock_blocking_write(eb); |
ea4ebde0 | 107 | /* |
b95be2d9 DS |
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. | |
ea4ebde0 CM |
111 | */ |
112 | if (eb->lock_nested && current->pid == eb->lock_owner) | |
113 | return; | |
06297d8c | 114 | if (eb->blocking_writers == 0) { |
843ccf9f | 115 | btrfs_assert_spinning_writers_put(eb); |
b95be2d9 | 116 | btrfs_assert_tree_locked(eb); |
06297d8c | 117 | eb->blocking_writers++; |
b95be2d9 | 118 | write_unlock(&eb->lock); |
b4ce94de | 119 | } |
b4ce94de | 120 | } |
f9efa9c7 | 121 | |
aa12c027 DS |
122 | void btrfs_clear_lock_blocking_read(struct extent_buffer *eb) |
123 | { | |
31aab402 | 124 | trace_btrfs_clear_lock_blocking_read(eb); |
aa12c027 DS |
125 | /* |
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. | |
129 | */ | |
130 | if (eb->lock_nested && current->pid == eb->lock_owner) | |
131 | return; | |
132 | BUG_ON(atomic_read(&eb->blocking_readers) == 0); | |
133 | read_lock(&eb->lock); | |
afd495a8 | 134 | btrfs_assert_spinning_readers_get(eb); |
aa12c027 DS |
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); | |
138 | } | |
139 | ||
140 | void btrfs_clear_lock_blocking_write(struct extent_buffer *eb) | |
b4ce94de | 141 | { |
31aab402 | 142 | trace_btrfs_clear_lock_blocking_write(eb); |
ea4ebde0 CM |
143 | /* |
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. | |
148 | */ | |
149 | if (eb->lock_nested && current->pid == eb->lock_owner) | |
150 | return; | |
aa12c027 | 151 | write_lock(&eb->lock); |
06297d8c | 152 | BUG_ON(eb->blocking_writers != 1); |
843ccf9f | 153 | btrfs_assert_spinning_writers_get(eb); |
06297d8c DS |
154 | if (--eb->blocking_writers == 0) |
155 | cond_wake_up(&eb->write_lock_wq); | |
b4ce94de CM |
156 | } |
157 | ||
158 | /* | |
bd681513 CM |
159 | * take a spinning read lock. This will wait for any blocking |
160 | * writers | |
b4ce94de | 161 | */ |
bd681513 | 162 | void btrfs_tree_read_lock(struct extent_buffer *eb) |
b4ce94de | 163 | { |
34e73cc9 QW |
164 | u64 start_ns = 0; |
165 | ||
166 | if (trace_btrfs_tree_read_lock_enabled()) | |
167 | start_ns = ktime_get_ns(); | |
bd681513 | 168 | again: |
5b25f70f | 169 | read_lock(&eb->lock); |
06297d8c DS |
170 | BUG_ON(eb->blocking_writers == 0 && |
171 | current->pid == eb->lock_owner); | |
172 | if (eb->blocking_writers && current->pid == eb->lock_owner) { | |
5b25f70f AJ |
173 | /* |
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. | |
178 | */ | |
179 | BUG_ON(eb->lock_nested); | |
ed1b4ed7 | 180 | eb->lock_nested = true; |
5b25f70f | 181 | read_unlock(&eb->lock); |
34e73cc9 | 182 | trace_btrfs_tree_read_lock(eb, start_ns); |
5b25f70f AJ |
183 | return; |
184 | } | |
06297d8c | 185 | if (eb->blocking_writers) { |
bd681513 | 186 | read_unlock(&eb->lock); |
39f9d028 | 187 | wait_event(eb->write_lock_wq, |
06297d8c | 188 | eb->blocking_writers == 0); |
bd681513 | 189 | goto again; |
b4ce94de | 190 | } |
5c9c799a | 191 | btrfs_assert_tree_read_locks_get(eb); |
afd495a8 | 192 | btrfs_assert_spinning_readers_get(eb); |
34e73cc9 | 193 | trace_btrfs_tree_read_lock(eb, start_ns); |
b4ce94de CM |
194 | } |
195 | ||
f82c458a CM |
196 | /* |
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 | |
200 | */ | |
201 | int btrfs_tree_read_lock_atomic(struct extent_buffer *eb) | |
202 | { | |
06297d8c | 203 | if (eb->blocking_writers) |
f82c458a CM |
204 | return 0; |
205 | ||
206 | read_lock(&eb->lock); | |
06297d8c | 207 | if (eb->blocking_writers) { |
f82c458a CM |
208 | read_unlock(&eb->lock); |
209 | return 0; | |
210 | } | |
5c9c799a | 211 | btrfs_assert_tree_read_locks_get(eb); |
afd495a8 | 212 | btrfs_assert_spinning_readers_get(eb); |
31aab402 | 213 | trace_btrfs_tree_read_lock_atomic(eb); |
f82c458a CM |
214 | return 1; |
215 | } | |
216 | ||
b4ce94de | 217 | /* |
bd681513 CM |
218 | * returns 1 if we get the read lock and 0 if we don't |
219 | * this won't wait for blocking writers | |
b4ce94de | 220 | */ |
bd681513 | 221 | int btrfs_try_tree_read_lock(struct extent_buffer *eb) |
b4ce94de | 222 | { |
06297d8c | 223 | if (eb->blocking_writers) |
bd681513 | 224 | return 0; |
b4ce94de | 225 | |
ea4ebde0 CM |
226 | if (!read_trylock(&eb->lock)) |
227 | return 0; | |
228 | ||
06297d8c | 229 | if (eb->blocking_writers) { |
bd681513 CM |
230 | read_unlock(&eb->lock); |
231 | return 0; | |
b9473439 | 232 | } |
5c9c799a | 233 | btrfs_assert_tree_read_locks_get(eb); |
afd495a8 | 234 | btrfs_assert_spinning_readers_get(eb); |
31aab402 | 235 | trace_btrfs_try_tree_read_lock(eb); |
bd681513 | 236 | return 1; |
b4ce94de CM |
237 | } |
238 | ||
239 | /* | |
bd681513 CM |
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 | |
b4ce94de | 242 | */ |
bd681513 | 243 | int btrfs_try_tree_write_lock(struct extent_buffer *eb) |
b4ce94de | 244 | { |
06297d8c | 245 | if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) |
bd681513 | 246 | return 0; |
ea4ebde0 | 247 | |
f82c458a | 248 | write_lock(&eb->lock); |
06297d8c | 249 | if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) { |
bd681513 CM |
250 | write_unlock(&eb->lock); |
251 | return 0; | |
252 | } | |
c79adfc0 | 253 | btrfs_assert_tree_write_locks_get(eb); |
843ccf9f | 254 | btrfs_assert_spinning_writers_get(eb); |
5b25f70f | 255 | eb->lock_owner = current->pid; |
31aab402 | 256 | trace_btrfs_try_tree_write_lock(eb); |
b4ce94de CM |
257 | return 1; |
258 | } | |
259 | ||
260 | /* | |
bd681513 CM |
261 | * drop a spinning read lock |
262 | */ | |
263 | void btrfs_tree_read_unlock(struct extent_buffer *eb) | |
264 | { | |
31aab402 | 265 | trace_btrfs_tree_read_unlock(eb); |
ea4ebde0 CM |
266 | /* |
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. | |
271 | */ | |
272 | if (eb->lock_nested && current->pid == eb->lock_owner) { | |
ed1b4ed7 | 273 | eb->lock_nested = false; |
ea4ebde0 | 274 | return; |
5b25f70f | 275 | } |
bd681513 | 276 | btrfs_assert_tree_read_locked(eb); |
afd495a8 | 277 | btrfs_assert_spinning_readers_put(eb); |
5c9c799a | 278 | btrfs_assert_tree_read_locks_put(eb); |
bd681513 CM |
279 | read_unlock(&eb->lock); |
280 | } | |
281 | ||
282 | /* | |
283 | * drop a blocking read lock | |
284 | */ | |
285 | void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb) | |
286 | { | |
31aab402 | 287 | trace_btrfs_tree_read_unlock_blocking(eb); |
ea4ebde0 CM |
288 | /* |
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. | |
293 | */ | |
294 | if (eb->lock_nested && current->pid == eb->lock_owner) { | |
ed1b4ed7 | 295 | eb->lock_nested = false; |
ea4ebde0 | 296 | return; |
5b25f70f | 297 | } |
bd681513 CM |
298 | btrfs_assert_tree_read_locked(eb); |
299 | WARN_ON(atomic_read(&eb->blocking_readers) == 0); | |
093258e6 DS |
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); | |
5c9c799a | 303 | btrfs_assert_tree_read_locks_put(eb); |
bd681513 CM |
304 | } |
305 | ||
306 | /* | |
307 | * take a spinning write lock. This will wait for both | |
308 | * blocking readers or writers | |
b4ce94de | 309 | */ |
143bede5 | 310 | void btrfs_tree_lock(struct extent_buffer *eb) |
b4ce94de | 311 | { |
34e73cc9 QW |
312 | u64 start_ns = 0; |
313 | ||
314 | if (trace_btrfs_tree_lock_enabled()) | |
315 | start_ns = ktime_get_ns(); | |
316 | ||
166f66d0 | 317 | WARN_ON(eb->lock_owner == current->pid); |
bd681513 CM |
318 | again: |
319 | wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0); | |
06297d8c | 320 | wait_event(eb->write_lock_wq, eb->blocking_writers == 0); |
bd681513 | 321 | write_lock(&eb->lock); |
06297d8c | 322 | if (atomic_read(&eb->blocking_readers) || eb->blocking_writers) { |
bd681513 | 323 | write_unlock(&eb->lock); |
bd681513 CM |
324 | goto again; |
325 | } | |
843ccf9f | 326 | btrfs_assert_spinning_writers_get(eb); |
c79adfc0 | 327 | btrfs_assert_tree_write_locks_get(eb); |
5b25f70f | 328 | eb->lock_owner = current->pid; |
34e73cc9 | 329 | trace_btrfs_tree_lock(eb, start_ns); |
925baedd CM |
330 | } |
331 | ||
bd681513 CM |
332 | /* |
333 | * drop a spinning or a blocking write lock. | |
334 | */ | |
143bede5 | 335 | void btrfs_tree_unlock(struct extent_buffer *eb) |
925baedd | 336 | { |
06297d8c | 337 | int blockers = eb->blocking_writers; |
bd681513 CM |
338 | |
339 | BUG_ON(blockers > 1); | |
340 | ||
341 | btrfs_assert_tree_locked(eb); | |
31aab402 | 342 | trace_btrfs_tree_unlock(eb); |
ea4ebde0 | 343 | eb->lock_owner = 0; |
c79adfc0 | 344 | btrfs_assert_tree_write_locks_put(eb); |
bd681513 CM |
345 | |
346 | if (blockers) { | |
843ccf9f | 347 | btrfs_assert_no_spinning_writers(eb); |
06297d8c | 348 | eb->blocking_writers--; |
6e7ca09b NB |
349 | /* |
350 | * We need to order modifying blocking_writers above with | |
351 | * actually waking up the sleepers to ensure they see the | |
352 | * updated value of blocking_writers | |
353 | */ | |
354 | cond_wake_up(&eb->write_lock_wq); | |
bd681513 | 355 | } else { |
843ccf9f | 356 | btrfs_assert_spinning_writers_put(eb); |
bd681513 CM |
357 | write_unlock(&eb->lock); |
358 | } | |
925baedd | 359 | } |