xref: /linux/fs/bcachefs/btree_locking.h (revision f7c595c9d9f4cce9ec335f0d3c5d875bb547f9d5) 
1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_BTREE_LOCKING_H
3 #define _BCACHEFS_BTREE_LOCKING_H
4 
5 /*
6  * Only for internal btree use:
7  *
8  * The btree iterator tracks what locks it wants to take, and what locks it
9  * currently has - here we have wrappers for locking/unlocking btree nodes and
10  * updating the iterator state
11  */
12 
13 #include "btree_iter.h"
14 #include "six.h"
15 
16 void bch2_btree_lock_init(struct btree_bkey_cached_common *, enum six_lock_init_flags, gfp_t gfp);
17 
18 void bch2_trans_unlock_write(struct btree_trans *);
19 
20 static inline bool is_btree_node(struct btree_path *path, unsigned l)
21 {
22 	return l < BTREE_MAX_DEPTH && !IS_ERR_OR_NULL(path->l[l].b);
23 }
24 
25 static inline struct btree_transaction_stats *btree_trans_stats(struct btree_trans *trans)
26 {
27 	return trans->fn_idx < ARRAY_SIZE(trans->c->btree_transaction_stats)
28 		? &trans->c->btree_transaction_stats[trans->fn_idx]
29 		: NULL;
30 }
31 
32 /* matches six lock types */
33 enum btree_node_locked_type {
34 	BTREE_NODE_UNLOCKED		= -1,
35 	BTREE_NODE_READ_LOCKED		= SIX_LOCK_read,
36 	BTREE_NODE_INTENT_LOCKED	= SIX_LOCK_intent,
37 	BTREE_NODE_WRITE_LOCKED		= SIX_LOCK_write,
38 };
39 
40 static inline int btree_node_locked_type(struct btree_path *path,
41 					 unsigned level)
42 {
43 	return BTREE_NODE_UNLOCKED + ((path->nodes_locked >> (level << 1)) & 3);
44 }
45 
46 static inline int btree_node_locked_type_nowrite(struct btree_path *path,
47 						 unsigned level)
48 {
49 	int have = btree_node_locked_type(path, level);
50 	return have == BTREE_NODE_WRITE_LOCKED
51 		? BTREE_NODE_INTENT_LOCKED
52 		: have;
53 }
54 
55 static inline bool btree_node_write_locked(struct btree_path *path, unsigned l)
56 {
57 	return btree_node_locked_type(path, l) == BTREE_NODE_WRITE_LOCKED;
58 }
59 
60 static inline bool btree_node_intent_locked(struct btree_path *path, unsigned l)
61 {
62 	return btree_node_locked_type(path, l) == BTREE_NODE_INTENT_LOCKED;
63 }
64 
65 static inline bool btree_node_read_locked(struct btree_path *path, unsigned l)
66 {
67 	return btree_node_locked_type(path, l) == BTREE_NODE_READ_LOCKED;
68 }
69 
70 static inline bool btree_node_locked(struct btree_path *path, unsigned level)
71 {
72 	return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
73 }
74 
75 static inline void mark_btree_node_locked_noreset(struct btree_path *path,
76 						  unsigned level,
77 						  enum btree_node_locked_type type)
78 {
79 	/* relying on this to avoid a branch */
80 	BUILD_BUG_ON(SIX_LOCK_read   != 0);
81 	BUILD_BUG_ON(SIX_LOCK_intent != 1);
82 
83 	path->nodes_locked &= ~(3U << (level << 1));
84 	path->nodes_locked |= (type + 1) << (level << 1);
85 }
86 
87 static inline void mark_btree_node_locked(struct btree_trans *trans,
88 					  struct btree_path *path,
89 					  unsigned level,
90 					  enum btree_node_locked_type type)
91 {
92 	mark_btree_node_locked_noreset(path, level, (enum btree_node_locked_type) type);
93 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
94 	path->l[level].lock_taken_time = local_clock();
95 #endif
96 }
97 
98 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
99 {
100 	return level < path->locks_want
101 		? SIX_LOCK_intent
102 		: SIX_LOCK_read;
103 }
104 
105 static inline enum btree_node_locked_type
106 btree_lock_want(struct btree_path *path, int level)
107 {
108 	if (level < path->level)
109 		return BTREE_NODE_UNLOCKED;
110 	if (level < path->locks_want)
111 		return BTREE_NODE_INTENT_LOCKED;
112 	if (level == path->level)
113 		return BTREE_NODE_READ_LOCKED;
114 	return BTREE_NODE_UNLOCKED;
115 }
116 
117 static void btree_trans_lock_hold_time_update(struct btree_trans *trans,
118 					      struct btree_path *path, unsigned level)
119 {
120 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
121 	__bch2_time_stats_update(&btree_trans_stats(trans)->lock_hold_times,
122 				 path->l[level].lock_taken_time,
123 				 local_clock());
124 #endif
125 }
126 
127 /* unlock: */
128 
129 void bch2_btree_node_unlock_write(struct btree_trans *,
130 			struct btree_path *, struct btree *);
131 
132 static inline void btree_node_unlock(struct btree_trans *trans,
133 				     struct btree_path *path, unsigned level)
134 {
135 	int lock_type = btree_node_locked_type(path, level);
136 
137 	EBUG_ON(level >= BTREE_MAX_DEPTH);
138 
139 	if (lock_type != BTREE_NODE_UNLOCKED) {
140 		if (unlikely(lock_type == BTREE_NODE_WRITE_LOCKED)) {
141 			bch2_btree_node_unlock_write(trans, path, path->l[level].b);
142 			lock_type = BTREE_NODE_INTENT_LOCKED;
143 		}
144 		six_unlock_type(&path->l[level].b->c.lock, lock_type);
145 		btree_trans_lock_hold_time_update(trans, path, level);
146 		mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
147 	}
148 }
149 
150 static inline int btree_path_lowest_level_locked(struct btree_path *path)
151 {
152 	return __ffs(path->nodes_locked) >> 1;
153 }
154 
155 static inline int btree_path_highest_level_locked(struct btree_path *path)
156 {
157 	return __fls(path->nodes_locked) >> 1;
158 }
159 
160 static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
161 					    struct btree_path *path)
162 {
163 	btree_path_set_dirty(trans, path, BTREE_ITER_NEED_RELOCK);
164 
165 	while (path->nodes_locked)
166 		btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
167 }
168 
169 /*
170  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
171  * succeed:
172  */
173 static inline void
174 __bch2_btree_node_unlock_write(struct btree_trans *trans, struct btree *b)
175 {
176 	if (!b->c.lock.write_lock_recurse) {
177 		struct btree_path *linked;
178 		unsigned i;
179 
180 		trans_for_each_path_with_node(trans, b, linked, i)
181 			linked->l[b->c.level].lock_seq++;
182 	}
183 
184 	six_unlock_write(&b->c.lock);
185 }
186 
187 static inline void
188 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
189 				     struct btree *b)
190 {
191 	EBUG_ON(path->l[b->c.level].b != b);
192 	EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
193 	EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);
194 
195 	mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);
196 	__bch2_btree_node_unlock_write(trans, b);
197 }
198 
199 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p);
200 
201 /* lock: */
202 
203 static inline void trans_set_locked(struct btree_trans *trans, bool try)
204 {
205 	if (!trans->locked) {
206 		lock_acquire_exclusive(&trans->dep_map, 0, try, NULL, _THIS_IP_);
207 		trans->locked = true;
208 		trans->last_unlock_ip = 0;
209 
210 		trans->pf_memalloc_nofs = (current->flags & PF_MEMALLOC_NOFS) != 0;
211 		current->flags |= PF_MEMALLOC_NOFS;
212 	}
213 }
214 
215 static inline void trans_set_unlocked(struct btree_trans *trans)
216 {
217 	if (trans->locked) {
218 		lock_release(&trans->dep_map, _THIS_IP_);
219 		trans->locked = false;
220 		trans->last_unlock_ip = _RET_IP_;
221 
222 		if (!trans->pf_memalloc_nofs)
223 			current->flags &= ~PF_MEMALLOC_NOFS;
224 	}
225 }
226 
227 static inline int __btree_node_lock_nopath(struct btree_trans *trans,
228 					 struct btree_bkey_cached_common *b,
229 					 enum six_lock_type type,
230 					 bool lock_may_not_fail,
231 					 unsigned long ip)
232 {
233 	trans->lock_may_not_fail = lock_may_not_fail;
234 	trans->lock_must_abort	= false;
235 	trans->locking		= b;
236 
237 	int ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
238 				     bch2_six_check_for_deadlock, trans, ip);
239 	WRITE_ONCE(trans->locking, NULL);
240 	WRITE_ONCE(trans->locking_wait.start_time, 0);
241 
242 	if (!ret)
243 		trace_btree_path_lock(trans, _THIS_IP_, b);
244 	return ret;
245 }
246 
247 static inline int __must_check
248 btree_node_lock_nopath(struct btree_trans *trans,
249 		       struct btree_bkey_cached_common *b,
250 		       enum six_lock_type type,
251 		       unsigned long ip)
252 {
253 	return __btree_node_lock_nopath(trans, b, type, false, ip);
254 }
255 
256 static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
257 					 struct btree_bkey_cached_common *b,
258 					 enum six_lock_type type)
259 {
260 	int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);
261 
262 	BUG_ON(ret);
263 }
264 
265 /*
266  * Lock a btree node if we already have it locked on one of our linked
267  * iterators:
268  */
269 static inline bool btree_node_lock_increment(struct btree_trans *trans,
270 					     struct btree_bkey_cached_common *b,
271 					     unsigned level,
272 					     enum btree_node_locked_type want)
273 {
274 	struct btree_path *path;
275 	unsigned i;
276 
277 	trans_for_each_path(trans, path, i)
278 		if (&path->l[level].b->c == b &&
279 		    btree_node_locked_type(path, level) >= want) {
280 			six_lock_increment(&b->lock, (enum six_lock_type) want);
281 			return true;
282 		}
283 
284 	return false;
285 }
286 
287 static inline int btree_node_lock(struct btree_trans *trans,
288 			struct btree_path *path,
289 			struct btree_bkey_cached_common *b,
290 			unsigned level,
291 			enum six_lock_type type,
292 			unsigned long ip)
293 {
294 	int ret = 0;
295 
296 	EBUG_ON(level >= BTREE_MAX_DEPTH);
297 	bch2_trans_verify_not_unlocked_or_in_restart(trans);
298 
299 	if (likely(six_trylock_type(&b->lock, type)) ||
300 	    btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||
301 	    !(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
302 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
303 		path->l[b->level].lock_taken_time = local_clock();
304 #endif
305 	}
306 
307 	return ret;
308 }
309 
310 int __bch2_btree_node_lock_write(struct btree_trans *, struct btree_path *,
311 				 struct btree_bkey_cached_common *b, bool);
312 
313 static inline int __btree_node_lock_write(struct btree_trans *trans,
314 					  struct btree_path *path,
315 					  struct btree_bkey_cached_common *b,
316 					  bool lock_may_not_fail)
317 {
318 	EBUG_ON(&path->l[b->level].b->c != b);
319 	EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
320 	EBUG_ON(!btree_node_intent_locked(path, b->level));
321 
322 	/*
323 	 * six locks are unfair, and read locks block while a thread wants a
324 	 * write lock: thus, we need to tell the cycle detector we have a write
325 	 * lock _before_ taking the lock:
326 	 */
327 	mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);
328 
329 	return likely(six_trylock_write(&b->lock))
330 		? 0
331 		: __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
332 }
333 
334 static inline int __must_check
335 bch2_btree_node_lock_write(struct btree_trans *trans,
336 			   struct btree_path *path,
337 			   struct btree_bkey_cached_common *b)
338 {
339 	return __btree_node_lock_write(trans, path, b, false);
340 }
341 
342 void bch2_btree_node_lock_write_nofail(struct btree_trans *,
343 				       struct btree_path *,
344 				       struct btree_bkey_cached_common *);
345 
346 /* relock: */
347 
348 bool bch2_btree_path_relock_norestart(struct btree_trans *, struct btree_path *);
349 int __bch2_btree_path_relock(struct btree_trans *,
350 			     struct btree_path *, unsigned long);
351 
352 static inline int bch2_btree_path_relock(struct btree_trans *trans,
353 				struct btree_path *path, unsigned long trace_ip)
354 {
355 	return btree_node_locked(path, path->level)
356 		? 0
357 		: __bch2_btree_path_relock(trans, path, trace_ip);
358 }
359 
360 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned, bool trace);
361 
362 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
363 					  struct btree_path *path, unsigned level)
364 {
365 	EBUG_ON(btree_node_locked(path, level) &&
366 		!btree_node_write_locked(path, level) &&
367 		btree_node_locked_type(path, level) != __btree_lock_want(path, level));
368 
369 	return likely(btree_node_locked(path, level)) ||
370 		(!IS_ERR_OR_NULL(path->l[level].b) &&
371 		 __bch2_btree_node_relock(trans, path, level, true));
372 }
373 
374 static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
375 						  struct btree_path *path, unsigned level)
376 {
377 	EBUG_ON(btree_node_locked(path, level) &&
378 		btree_node_locked_type_nowrite(path, level) !=
379 		__btree_lock_want(path, level));
380 
381 	return likely(btree_node_locked(path, level)) ||
382 		(!IS_ERR_OR_NULL(path->l[level].b) &&
383 		 __bch2_btree_node_relock(trans, path, level, false));
384 }
385 
386 /* upgrade */
387 
388 bool __bch2_btree_path_upgrade_norestart(struct btree_trans *, struct btree_path *, unsigned);
389 
390 static inline bool bch2_btree_path_upgrade_norestart(struct btree_trans *trans,
391 			       struct btree_path *path,
392 			       unsigned new_locks_want)
393 {
394 	return new_locks_want > path->locks_want
395 		? __bch2_btree_path_upgrade_norestart(trans, path, new_locks_want)
396 		: true;
397 }
398 
399 int __bch2_btree_path_upgrade(struct btree_trans *,
400 			      struct btree_path *, unsigned);
401 
402 static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
403 					  struct btree_path *path,
404 					  unsigned new_locks_want)
405 {
406 	new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);
407 
408 	return likely(path->locks_want >= new_locks_want && path->nodes_locked)
409 		? 0
410 		: __bch2_btree_path_upgrade(trans, path, new_locks_want);
411 }
412 
413 /* misc: */
414 
415 static inline void btree_path_set_should_be_locked(struct btree_trans *trans, struct btree_path *path)
416 {
417 	EBUG_ON(!btree_node_locked(path, path->level));
418 	EBUG_ON(path->uptodate);
419 
420 	if (!path->should_be_locked) {
421 		path->should_be_locked = true;
422 		trace_btree_path_should_be_locked(trans, path);
423 	}
424 }
425 
426 static inline void __btree_path_set_level_up(struct btree_trans *trans,
427 				      struct btree_path *path,
428 				      unsigned l)
429 {
430 	btree_node_unlock(trans, path, l);
431 	path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
432 }
433 
434 static inline void btree_path_set_level_up(struct btree_trans *trans,
435 				    struct btree_path *path)
436 {
437 	__btree_path_set_level_up(trans, path, path->level++);
438 	btree_path_set_dirty(trans, path, BTREE_ITER_NEED_TRAVERSE);
439 }
440 
441 /* debug */
442 
443 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
444 				struct btree_path *,
445 				struct btree_bkey_cached_common *b,
446 				unsigned);
447 
448 int bch2_check_for_deadlock(struct btree_trans *, struct printbuf *);
449 
450 void __bch2_btree_path_verify_locks(struct btree_trans *, struct btree_path *);
451 void __bch2_trans_verify_locks(struct btree_trans *);
452 
453 static inline void bch2_btree_path_verify_locks(struct btree_trans *trans,
454 						struct btree_path *path)
455 {
456 	if (static_branch_unlikely(&bch2_debug_check_btree_locking))
457 		__bch2_btree_path_verify_locks(trans, path);
458 }
459 
460 static inline void bch2_trans_verify_locks(struct btree_trans *trans)
461 {
462 	if (static_branch_unlikely(&bch2_debug_check_btree_locking))
463 		__bch2_trans_verify_locks(trans);
464 }
465 
466 #endif /* _BCACHEFS_BTREE_LOCKING_H */
467