git.sesse.net Git - bcachefs-tools-debian/blob - libbcachefs/btree_locking.h

   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);
  17
  18 #ifdef CONFIG_LOCKDEP
  19 void bch2_assert_btree_nodes_not_locked(void);
  20 #else
  21 static inline void bch2_assert_btree_nodes_not_locked(void) {}
  22 #endif
  23
  24 void bch2_trans_unlock_noassert(struct btree_trans *);
  25
  26 static inline bool is_btree_node(struct btree_path *path, unsigned l)
  27 {
  28         return l < BTREE_MAX_DEPTH && !IS_ERR_OR_NULL(path->l[l].b);
  29 }
  30
  31 static inline struct btree_transaction_stats *btree_trans_stats(struct btree_trans *trans)
  32 {
  33         return trans->fn_idx < ARRAY_SIZE(trans->c->btree_transaction_stats)
  34                 ? &trans->c->btree_transaction_stats[trans->fn_idx]
  35                 : NULL;
  36 }
  37
  38 /* matches six lock types */
  39 enum btree_node_locked_type {
  40         BTREE_NODE_UNLOCKED             = -1,
  41         BTREE_NODE_READ_LOCKED          = SIX_LOCK_read,
  42         BTREE_NODE_INTENT_LOCKED        = SIX_LOCK_intent,
  43         BTREE_NODE_WRITE_LOCKED         = SIX_LOCK_write,
  44 };
  45
  46 static inline int btree_node_locked_type(struct btree_path *path,
  47                                          unsigned level)
  48 {
  49         return BTREE_NODE_UNLOCKED + ((path->nodes_locked >> (level << 1)) & 3);
  50 }
  51
  52 static inline bool btree_node_write_locked(struct btree_path *path, unsigned l)
  53 {
  54         return btree_node_locked_type(path, l) == BTREE_NODE_WRITE_LOCKED;
  55 }
  56
  57 static inline bool btree_node_intent_locked(struct btree_path *path, unsigned l)
  58 {
  59         return btree_node_locked_type(path, l) == BTREE_NODE_INTENT_LOCKED;
  60 }
  61
  62 static inline bool btree_node_read_locked(struct btree_path *path, unsigned l)
  63 {
  64         return btree_node_locked_type(path, l) == BTREE_NODE_READ_LOCKED;
  65 }
  66
  67 static inline bool btree_node_locked(struct btree_path *path, unsigned level)
  68 {
  69         return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
  70 }
  71
  72 static inline void mark_btree_node_locked_noreset(struct btree_path *path,
  73                                                   unsigned level,
  74                                                   enum btree_node_locked_type type)
  75 {
  76         /* relying on this to avoid a branch */
  77         BUILD_BUG_ON(SIX_LOCK_read   != 0);
  78         BUILD_BUG_ON(SIX_LOCK_intent != 1);
  79
  80         path->nodes_locked &= ~(3U << (level << 1));
  81         path->nodes_locked |= (type + 1) << (level << 1);
  82 }
  83
  84 static inline void mark_btree_node_unlocked(struct btree_path *path,
  85                                             unsigned level)
  86 {
  87         EBUG_ON(btree_node_write_locked(path, level));
  88         mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
  89 }
  90
  91 static inline void mark_btree_node_locked(struct btree_trans *trans,
  92                                           struct btree_path *path,
  93                                           unsigned level,
  94                                           enum btree_node_locked_type type)
  95 {
  96         mark_btree_node_locked_noreset(path, level, (enum btree_node_locked_type) type);
  97 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
  98         path->l[level].lock_taken_time = local_clock();
  99 #endif
 100 }
 101
 102 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
 103 {
 104         return level < path->locks_want
 105                 ? SIX_LOCK_intent
 106                 : SIX_LOCK_read;
 107 }
 108
 109 static inline enum btree_node_locked_type
 110 btree_lock_want(struct btree_path *path, int level)
 111 {
 112         if (level < path->level)
 113                 return BTREE_NODE_UNLOCKED;
 114         if (level < path->locks_want)
 115                 return BTREE_NODE_INTENT_LOCKED;
 116         if (level == path->level)
 117                 return BTREE_NODE_READ_LOCKED;
 118         return BTREE_NODE_UNLOCKED;
 119 }
 120
 121 static void btree_trans_lock_hold_time_update(struct btree_trans *trans,
 122                                               struct btree_path *path, unsigned level)
 123 {
 124 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 125         struct btree_transaction_stats *s = btree_trans_stats(trans);
 126
 127         if (s)
 128                 __bch2_time_stats_update(&s->lock_hold_times,
 129                                          path->l[level].lock_taken_time,
 130                                          local_clock());
 131 #endif
 132 }
 133
 134 /* unlock: */
 135
 136 static inline void btree_node_unlock(struct btree_trans *trans,
 137                                      struct btree_path *path, unsigned level)
 138 {
 139         int lock_type = btree_node_locked_type(path, level);
 140
 141         EBUG_ON(level >= BTREE_MAX_DEPTH);
 142
 143         if (lock_type != BTREE_NODE_UNLOCKED) {
 144                 six_unlock_type(&path->l[level].b->c.lock, lock_type);
 145                 btree_trans_lock_hold_time_update(trans, path, level);
 146         }
 147         mark_btree_node_unlocked(path, level);
 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(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_inlined(struct btree_trans *trans, struct btree_path *path,
 175                                      struct btree *b)
 176 {
 177         struct btree_path *linked;
 178
 179         EBUG_ON(path->l[b->c.level].b != b);
 180         EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
 181         EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);
 182
 183         mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);
 184
 185         trans_for_each_path_with_node(trans, b, linked)
 186                 linked->l[b->c.level].lock_seq++;
 187
 188         six_unlock_write(&b->c.lock);
 189 }
 190
 191 void bch2_btree_node_unlock_write(struct btree_trans *,
 192                         struct btree_path *, struct btree *);
 193
 194 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p);
 195
 196 /* lock: */
 197
 198 static inline int __btree_node_lock_nopath(struct btree_trans *trans,
 199                                          struct btree_bkey_cached_common *b,
 200                                          enum six_lock_type type,
 201                                          bool lock_may_not_fail,
 202                                          unsigned long ip)
 203 {
 204         int ret;
 205
 206         trans->lock_may_not_fail = lock_may_not_fail;
 207         trans->lock_must_abort  = false;
 208         trans->locking          = b;
 209
 210         ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
 211                                  bch2_six_check_for_deadlock, trans, ip);
 212         WRITE_ONCE(trans->locking, NULL);
 213         WRITE_ONCE(trans->locking_wait.start_time, 0);
 214         return ret;
 215 }
 216
 217 static inline int __must_check
 218 btree_node_lock_nopath(struct btree_trans *trans,
 219                        struct btree_bkey_cached_common *b,
 220                        enum six_lock_type type,
 221                        unsigned long ip)
 222 {
 223         return __btree_node_lock_nopath(trans, b, type, false, ip);
 224 }
 225
 226 static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
 227                                          struct btree_bkey_cached_common *b,
 228                                          enum six_lock_type type)
 229 {
 230         int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);
 231
 232         BUG_ON(ret);
 233 }
 234
 235 /*
 236  * Lock a btree node if we already have it locked on one of our linked
 237  * iterators:
 238  */
 239 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 240                                              struct btree_bkey_cached_common *b,
 241                                              unsigned level,
 242                                              enum btree_node_locked_type want)
 243 {
 244         struct btree_path *path;
 245
 246         trans_for_each_path(trans, path)
 247                 if (&path->l[level].b->c == b &&
 248                     btree_node_locked_type(path, level) >= want) {
 249                         six_lock_increment(&b->lock, (enum six_lock_type) want);
 250                         return true;
 251                 }
 252
 253         return false;
 254 }
 255
 256 static inline int btree_node_lock(struct btree_trans *trans,
 257                         struct btree_path *path,
 258                         struct btree_bkey_cached_common *b,
 259                         unsigned level,
 260                         enum six_lock_type type,
 261                         unsigned long ip)
 262 {
 263         int ret = 0;
 264
 265         EBUG_ON(level >= BTREE_MAX_DEPTH);
 266         EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
 267
 268         if (likely(six_trylock_type(&b->lock, type)) ||
 269             btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||
 270             !(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
 271 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 272                 path->l[b->level].lock_taken_time = local_clock();
 273 #endif
 274         }
 275
 276         return ret;
 277 }
 278
 279 int __bch2_btree_node_lock_write(struct btree_trans *, struct btree_path *,
 280                                  struct btree_bkey_cached_common *b, bool);
 281
 282 static inline int __btree_node_lock_write(struct btree_trans *trans,
 283                                           struct btree_path *path,
 284                                           struct btree_bkey_cached_common *b,
 285                                           bool lock_may_not_fail)
 286 {
 287         EBUG_ON(&path->l[b->level].b->c != b);
 288         EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
 289         EBUG_ON(!btree_node_intent_locked(path, b->level));
 290
 291         /*
 292          * six locks are unfair, and read locks block while a thread wants a
 293          * write lock: thus, we need to tell the cycle detector we have a write
 294          * lock _before_ taking the lock:
 295          */
 296         mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);
 297
 298         return likely(six_trylock_write(&b->lock))
 299                 ? 0
 300                 : __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
 301 }
 302
 303 static inline int __must_check
 304 bch2_btree_node_lock_write(struct btree_trans *trans,
 305                            struct btree_path *path,
 306                            struct btree_bkey_cached_common *b)
 307 {
 308         return __btree_node_lock_write(trans, path, b, false);
 309 }
 310
 311 void bch2_btree_node_lock_write_nofail(struct btree_trans *,
 312                                        struct btree_path *,
 313                                        struct btree_bkey_cached_common *);
 314
 315 /* relock: */
 316
 317 bool bch2_btree_path_relock_norestart(struct btree_trans *,
 318                                       struct btree_path *, unsigned long);
 319 int __bch2_btree_path_relock(struct btree_trans *,
 320                              struct btree_path *, unsigned long);
 321
 322 static inline int bch2_btree_path_relock(struct btree_trans *trans,
 323                                 struct btree_path *path, unsigned long trace_ip)
 324 {
 325         return btree_node_locked(path, path->level)
 326                 ? 0
 327                 : __bch2_btree_path_relock(trans, path, trace_ip);
 328 }
 329
 330 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned, bool trace);
 331
 332 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 333                                           struct btree_path *path, unsigned level)
 334 {
 335         EBUG_ON(btree_node_locked(path, level) &&
 336                 !btree_node_write_locked(path, level) &&
 337                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 338
 339         return likely(btree_node_locked(path, level)) ||
 340                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 341                  __bch2_btree_node_relock(trans, path, level, true));
 342 }
 343
 344 static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
 345                                                   struct btree_path *path, unsigned level)
 346 {
 347         EBUG_ON(btree_node_locked(path, level) &&
 348                 !btree_node_write_locked(path, level) &&
 349                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 350
 351         return likely(btree_node_locked(path, level)) ||
 352                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 353                  __bch2_btree_node_relock(trans, path, level, false));
 354 }
 355
 356 /* upgrade */
 357
 358 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *,
 359                                struct btree_path *, unsigned);
 360 bool __bch2_btree_path_upgrade(struct btree_trans *,
 361                                struct btree_path *, unsigned);
 362
 363 static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
 364                                           struct btree_path *path,
 365                                           unsigned new_locks_want)
 366 {
 367         unsigned old_locks_want = path->locks_want;
 368
 369         new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);
 370
 371         if (path->locks_want < new_locks_want
 372             ? __bch2_btree_path_upgrade(trans, path, new_locks_want)
 373             : path->uptodate == BTREE_ITER_UPTODATE)
 374                 return 0;
 375
 376         trace_and_count(trans->c, trans_restart_upgrade, trans, _THIS_IP_, path,
 377                         old_locks_want, new_locks_want);
 378         return btree_trans_restart(trans, BCH_ERR_transaction_restart_upgrade);
 379 }
 380
 381 /* misc: */
 382
 383 static inline void btree_path_set_should_be_locked(struct btree_path *path)
 384 {
 385         EBUG_ON(!btree_node_locked(path, path->level));
 386         EBUG_ON(path->uptodate);
 387
 388         path->should_be_locked = true;
 389 }
 390
 391 static inline void __btree_path_set_level_up(struct btree_trans *trans,
 392                                       struct btree_path *path,
 393                                       unsigned l)
 394 {
 395         btree_node_unlock(trans, path, l);
 396         path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
 397 }
 398
 399 static inline void btree_path_set_level_up(struct btree_trans *trans,
 400                                     struct btree_path *path)
 401 {
 402         __btree_path_set_level_up(trans, path, path->level++);
 403         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 404 }
 405
 406 /* debug */
 407
 408 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
 409                                 struct btree_path *,
 410                                 struct btree_bkey_cached_common *b,
 411                                 unsigned);
 412
 413 int bch2_check_for_deadlock(struct btree_trans *, struct printbuf *);
 414
 415 #ifdef CONFIG_BCACHEFS_DEBUG
 416 void bch2_btree_path_verify_locks(struct btree_path *);
 417 void bch2_trans_verify_locks(struct btree_trans *);
 418 #else
 419 static inline void bch2_btree_path_verify_locks(struct btree_path *path) {}
 420 static inline void bch2_trans_verify_locks(struct btree_trans *trans) {}
 421 #endif
 422
 423 #endif /* _BCACHEFS_BTREE_LOCKING_H */