git.sesse.net Git - bcachefs-tools-debian/blob - c_src/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         __bch2_time_stats_update(&btree_trans_stats(trans)->lock_hold_times,
 126                                  path->l[level].lock_taken_time,
 127                                  local_clock());
 128 #endif
 129 }
 130
 131 /* unlock: */
 132
 133 static inline void btree_node_unlock(struct btree_trans *trans,
 134                                      struct btree_path *path, unsigned level)
 135 {
 136         int lock_type = btree_node_locked_type(path, level);
 137
 138         EBUG_ON(level >= BTREE_MAX_DEPTH);
 139
 140         if (lock_type != BTREE_NODE_UNLOCKED) {
 141                 six_unlock_type(&path->l[level].b->c.lock, lock_type);
 142                 btree_trans_lock_hold_time_update(trans, path, level);
 143         }
 144         mark_btree_node_unlocked(path, level);
 145 }
 146
 147 static inline int btree_path_lowest_level_locked(struct btree_path *path)
 148 {
 149         return __ffs(path->nodes_locked) >> 1;
 150 }
 151
 152 static inline int btree_path_highest_level_locked(struct btree_path *path)
 153 {
 154         return __fls(path->nodes_locked) >> 1;
 155 }
 156
 157 static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
 158                                             struct btree_path *path)
 159 {
 160         btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
 161
 162         while (path->nodes_locked)
 163                 btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
 164 }
 165
 166 /*
 167  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 168  * succeed:
 169  */
 170 static inline void
 171 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 172                                      struct btree *b)
 173 {
 174         struct btree_path *linked;
 175         unsigned i;
 176
 177         EBUG_ON(path->l[b->c.level].b != b);
 178         EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
 179         EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);
 180
 181         mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);
 182
 183         trans_for_each_path_with_node(trans, b, linked, i)
 184                 linked->l[b->c.level].lock_seq++;
 185
 186         six_unlock_write(&b->c.lock);
 187 }
 188
 189 void bch2_btree_node_unlock_write(struct btree_trans *,
 190                         struct btree_path *, struct btree *);
 191
 192 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p);
 193
 194 /* lock: */
 195
 196 static inline int __btree_node_lock_nopath(struct btree_trans *trans,
 197                                          struct btree_bkey_cached_common *b,
 198                                          enum six_lock_type type,
 199                                          bool lock_may_not_fail,
 200                                          unsigned long ip)
 201 {
 202         int ret;
 203
 204         trans->lock_may_not_fail = lock_may_not_fail;
 205         trans->lock_must_abort  = false;
 206         trans->locking          = b;
 207
 208         ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
 209                                  bch2_six_check_for_deadlock, trans, ip);
 210         WRITE_ONCE(trans->locking, NULL);
 211         WRITE_ONCE(trans->locking_wait.start_time, 0);
 212         return ret;
 213 }
 214
 215 static inline int __must_check
 216 btree_node_lock_nopath(struct btree_trans *trans,
 217                        struct btree_bkey_cached_common *b,
 218                        enum six_lock_type type,
 219                        unsigned long ip)
 220 {
 221         return __btree_node_lock_nopath(trans, b, type, false, ip);
 222 }
 223
 224 static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
 225                                          struct btree_bkey_cached_common *b,
 226                                          enum six_lock_type type)
 227 {
 228         int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);
 229
 230         BUG_ON(ret);
 231 }
 232
 233 /*
 234  * Lock a btree node if we already have it locked on one of our linked
 235  * iterators:
 236  */
 237 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 238                                              struct btree_bkey_cached_common *b,
 239                                              unsigned level,
 240                                              enum btree_node_locked_type want)
 241 {
 242         struct btree_path *path;
 243         unsigned i;
 244
 245         trans_for_each_path(trans, path, i)
 246                 if (&path->l[level].b->c == b &&
 247                     btree_node_locked_type(path, level) >= want) {
 248                         six_lock_increment(&b->lock, (enum six_lock_type) want);
 249                         return true;
 250                 }
 251
 252         return false;
 253 }
 254
 255 static inline int btree_node_lock(struct btree_trans *trans,
 256                         struct btree_path *path,
 257                         struct btree_bkey_cached_common *b,
 258                         unsigned level,
 259                         enum six_lock_type type,
 260                         unsigned long ip)
 261 {
 262         int ret = 0;
 263
 264         EBUG_ON(level >= BTREE_MAX_DEPTH);
 265
 266         if (likely(six_trylock_type(&b->lock, type)) ||
 267             btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||
 268             !(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
 269 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 270                 path->l[b->level].lock_taken_time = local_clock();
 271 #endif
 272         }
 273
 274         return ret;
 275 }
 276
 277 int __bch2_btree_node_lock_write(struct btree_trans *, struct btree_path *,
 278                                  struct btree_bkey_cached_common *b, bool);
 279
 280 static inline int __btree_node_lock_write(struct btree_trans *trans,
 281                                           struct btree_path *path,
 282                                           struct btree_bkey_cached_common *b,
 283                                           bool lock_may_not_fail)
 284 {
 285         EBUG_ON(&path->l[b->level].b->c != b);
 286         EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
 287         EBUG_ON(!btree_node_intent_locked(path, b->level));
 288
 289         /*
 290          * six locks are unfair, and read locks block while a thread wants a
 291          * write lock: thus, we need to tell the cycle detector we have a write
 292          * lock _before_ taking the lock:
 293          */
 294         mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);
 295
 296         return likely(six_trylock_write(&b->lock))
 297                 ? 0
 298                 : __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
 299 }
 300
 301 static inline int __must_check
 302 bch2_btree_node_lock_write(struct btree_trans *trans,
 303                            struct btree_path *path,
 304                            struct btree_bkey_cached_common *b)
 305 {
 306         return __btree_node_lock_write(trans, path, b, false);
 307 }
 308
 309 void bch2_btree_node_lock_write_nofail(struct btree_trans *,
 310                                        struct btree_path *,
 311                                        struct btree_bkey_cached_common *);
 312
 313 /* relock: */
 314
 315 bool bch2_btree_path_relock_norestart(struct btree_trans *,
 316                                       struct btree_path *, unsigned long);
 317 int __bch2_btree_path_relock(struct btree_trans *,
 318                              struct btree_path *, unsigned long);
 319
 320 static inline int bch2_btree_path_relock(struct btree_trans *trans,
 321                                 struct btree_path *path, unsigned long trace_ip)
 322 {
 323         return btree_node_locked(path, path->level)
 324                 ? 0
 325                 : __bch2_btree_path_relock(trans, path, trace_ip);
 326 }
 327
 328 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned, bool trace);
 329
 330 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 331                                           struct btree_path *path, unsigned level)
 332 {
 333         EBUG_ON(btree_node_locked(path, level) &&
 334                 !btree_node_write_locked(path, level) &&
 335                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 336
 337         return likely(btree_node_locked(path, level)) ||
 338                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 339                  __bch2_btree_node_relock(trans, path, level, true));
 340 }
 341
 342 static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
 343                                                   struct btree_path *path, unsigned level)
 344 {
 345         EBUG_ON(btree_node_locked(path, level) &&
 346                 !btree_node_write_locked(path, level) &&
 347                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 348
 349         return likely(btree_node_locked(path, level)) ||
 350                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 351                  __bch2_btree_node_relock(trans, path, level, false));
 352 }
 353
 354 /* upgrade */
 355
 356
 357 struct get_locks_fail {
 358         unsigned        l;
 359         struct btree    *b;
 360 };
 361
 362 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *,
 363                                struct btree_path *, unsigned,
 364                                struct get_locks_fail *);
 365
 366 bool __bch2_btree_path_upgrade(struct btree_trans *,
 367                                struct btree_path *, unsigned,
 368                                struct get_locks_fail *);
 369
 370 static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
 371                                           struct btree_path *path,
 372                                           unsigned new_locks_want)
 373 {
 374         struct get_locks_fail f;
 375         unsigned old_locks_want = path->locks_want;
 376
 377         new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);
 378
 379         if (path->locks_want < new_locks_want
 380             ? __bch2_btree_path_upgrade(trans, path, new_locks_want, &f)
 381             : path->uptodate == BTREE_ITER_UPTODATE)
 382                 return 0;
 383
 384         trace_and_count(trans->c, trans_restart_upgrade, trans, _THIS_IP_, path,
 385                         old_locks_want, new_locks_want, &f);
 386         return btree_trans_restart(trans, BCH_ERR_transaction_restart_upgrade);
 387 }
 388
 389 /* misc: */
 390
 391 static inline void btree_path_set_should_be_locked(struct btree_path *path)
 392 {
 393         EBUG_ON(!btree_node_locked(path, path->level));
 394         EBUG_ON(path->uptodate);
 395
 396         path->should_be_locked = true;
 397 }
 398
 399 static inline void __btree_path_set_level_up(struct btree_trans *trans,
 400                                       struct btree_path *path,
 401                                       unsigned l)
 402 {
 403         btree_node_unlock(trans, path, l);
 404         path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
 405 }
 406
 407 static inline void btree_path_set_level_up(struct btree_trans *trans,
 408                                     struct btree_path *path)
 409 {
 410         __btree_path_set_level_up(trans, path, path->level++);
 411         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 412 }
 413
 414 /* debug */
 415
 416 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
 417                                 struct btree_path *,
 418                                 struct btree_bkey_cached_common *b,
 419                                 unsigned);
 420
 421 int bch2_check_for_deadlock(struct btree_trans *, struct printbuf *);
 422
 423 #ifdef CONFIG_BCACHEFS_DEBUG
 424 void bch2_btree_path_verify_locks(struct btree_path *);
 425 void bch2_trans_verify_locks(struct btree_trans *);
 426 #else
 427 static inline void bch2_btree_path_verify_locks(struct btree_path *path) {}
 428 static inline void bch2_trans_verify_locks(struct btree_trans *trans) {}
 429 #endif
 430
 431 #endif /* _BCACHEFS_BTREE_LOCKING_H */