fs/bcachefs/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 void bch2_trans_unlock_noassert(struct btree_trans *);
  19 void bch2_trans_unlock_write(struct btree_trans *);
  20
  21 static inline bool is_btree_node(struct btree_path *path, unsigned l)
  22 {
  23         return l < BTREE_MAX_DEPTH && !IS_ERR_OR_NULL(path->l[l].b);
  24 }
  25
  26 static inline struct btree_transaction_stats *btree_trans_stats(struct btree_trans *trans)
  27 {
  28         return trans->fn_idx < ARRAY_SIZE(trans->c->btree_transaction_stats)
  29                 ? &trans->c->btree_transaction_stats[trans->fn_idx]
  30                 : NULL;
  31 }
  32
  33 /* matches six lock types */
  34 enum btree_node_locked_type {
  35         BTREE_NODE_UNLOCKED             = -1,
  36         BTREE_NODE_READ_LOCKED          = SIX_LOCK_read,
  37         BTREE_NODE_INTENT_LOCKED        = SIX_LOCK_intent,
  38         BTREE_NODE_WRITE_LOCKED         = SIX_LOCK_write,
  39 };
  40
  41 static inline int btree_node_locked_type(struct btree_path *path,
  42                                          unsigned level)
  43 {
  44         return BTREE_NODE_UNLOCKED + ((path->nodes_locked >> (level << 1)) & 3);
  45 }
  46
  47 static inline bool btree_node_write_locked(struct btree_path *path, unsigned l)
  48 {
  49         return btree_node_locked_type(path, l) == BTREE_NODE_WRITE_LOCKED;
  50 }
  51
  52 static inline bool btree_node_intent_locked(struct btree_path *path, unsigned l)
  53 {
  54         return btree_node_locked_type(path, l) == BTREE_NODE_INTENT_LOCKED;
  55 }
  56
  57 static inline bool btree_node_read_locked(struct btree_path *path, unsigned l)
  58 {
  59         return btree_node_locked_type(path, l) == BTREE_NODE_READ_LOCKED;
  60 }
  61
  62 static inline bool btree_node_locked(struct btree_path *path, unsigned level)
  63 {
  64         return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
  65 }
  66
  67 static inline void mark_btree_node_locked_noreset(struct btree_path *path,
  68                                                   unsigned level,
  69                                                   enum btree_node_locked_type type)
  70 {
  71         /* relying on this to avoid a branch */
  72         BUILD_BUG_ON(SIX_LOCK_read   != 0);
  73         BUILD_BUG_ON(SIX_LOCK_intent != 1);
  74
  75         path->nodes_locked &= ~(3U << (level << 1));
  76         path->nodes_locked |= (type + 1) << (level << 1);
  77 }
  78
  79 static inline void mark_btree_node_locked(struct btree_trans *trans,
  80                                           struct btree_path *path,
  81                                           unsigned level,
  82                                           enum btree_node_locked_type type)
  83 {
  84         mark_btree_node_locked_noreset(path, level, (enum btree_node_locked_type) type);
  85 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
  86         path->l[level].lock_taken_time = local_clock();
  87 #endif
  88 }
  89
  90 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
  91 {
  92         return level < path->locks_want
  93                 ? SIX_LOCK_intent
  94                 : SIX_LOCK_read;
  95 }
  96
  97 static inline enum btree_node_locked_type
  98 btree_lock_want(struct btree_path *path, int level)
  99 {
 100         if (level < path->level)
 101                 return BTREE_NODE_UNLOCKED;
 102         if (level < path->locks_want)
 103                 return BTREE_NODE_INTENT_LOCKED;
 104         if (level == path->level)
 105                 return BTREE_NODE_READ_LOCKED;
 106         return BTREE_NODE_UNLOCKED;
 107 }
 108
 109 static void btree_trans_lock_hold_time_update(struct btree_trans *trans,
 110                                               struct btree_path *path, unsigned level)
 111 {
 112 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 113         __bch2_time_stats_update(&btree_trans_stats(trans)->lock_hold_times,
 114                                  path->l[level].lock_taken_time,
 115                                  local_clock());
 116 #endif
 117 }
 118
 119 /* unlock: */
 120
 121 void bch2_btree_node_unlock_write(struct btree_trans *,
 122                         struct btree_path *, struct btree *);
 123
 124 static inline void btree_node_unlock(struct btree_trans *trans,
 125                                      struct btree_path *path, unsigned level)
 126 {
 127         int lock_type = btree_node_locked_type(path, level);
 128
 129         EBUG_ON(level >= BTREE_MAX_DEPTH);
 130
 131         if (lock_type != BTREE_NODE_UNLOCKED) {
 132                 if (unlikely(lock_type == BTREE_NODE_WRITE_LOCKED)) {
 133                         bch2_btree_node_unlock_write(trans, path, path->l[level].b);
 134                         lock_type = BTREE_NODE_INTENT_LOCKED;
 135                 }
 136                 six_unlock_type(&path->l[level].b->c.lock, lock_type);
 137                 btree_trans_lock_hold_time_update(trans, path, level);
 138                 mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
 139         }
 140 }
 141
 142 static inline int btree_path_lowest_level_locked(struct btree_path *path)
 143 {
 144         return __ffs(path->nodes_locked) >> 1;
 145 }
 146
 147 static inline int btree_path_highest_level_locked(struct btree_path *path)
 148 {
 149         return __fls(path->nodes_locked) >> 1;
 150 }
 151
 152 static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
 153                                             struct btree_path *path)
 154 {
 155         btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
 156
 157         while (path->nodes_locked)
 158                 btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
 159 }
 160
 161 /*
 162  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 163  * succeed:
 164  */
 165 static inline void
 166 __bch2_btree_node_unlock_write(struct btree_trans *trans, struct btree *b)
 167 {
 168         if (!b->c.lock.write_lock_recurse) {
 169                 struct btree_path *linked;
 170                 unsigned i;
 171
 172                 trans_for_each_path_with_node(trans, b, linked, i)
 173                         linked->l[b->c.level].lock_seq++;
 174         }
 175
 176         six_unlock_write(&b->c.lock);
 177 }
 178
 179 static inline void
 180 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 181                                      struct btree *b)
 182 {
 183         EBUG_ON(path->l[b->c.level].b != b);
 184         EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
 185         EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);
 186
 187         mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);
 188         __bch2_btree_node_unlock_write(trans, b);
 189 }
 190
 191 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p);
 192
 193 /* lock: */
 194
 195 static inline void trans_set_locked(struct btree_trans *trans, bool try)
 196 {
 197         if (!trans->locked) {
 198                 lock_acquire_exclusive(&trans->dep_map, 0, try, NULL, _THIS_IP_);
 199                 trans->locked = true;
 200                 trans->last_unlock_ip = 0;
 201
 202                 trans->pf_memalloc_nofs = (current->flags & PF_MEMALLOC_NOFS) != 0;
 203                 current->flags |= PF_MEMALLOC_NOFS;
 204         }
 205 }
 206
 207 static inline void trans_set_unlocked(struct btree_trans *trans)
 208 {
 209         if (trans->locked) {
 210                 lock_release(&trans->dep_map, _THIS_IP_);
 211                 trans->locked = false;
 212                 trans->last_unlock_ip = _RET_IP_;
 213
 214                 if (!trans->pf_memalloc_nofs)
 215                         current->flags &= ~PF_MEMALLOC_NOFS;
 216         }
 217 }
 218
 219 static inline int __btree_node_lock_nopath(struct btree_trans *trans,
 220                                          struct btree_bkey_cached_common *b,
 221                                          enum six_lock_type type,
 222                                          bool lock_may_not_fail,
 223                                          unsigned long ip)
 224 {
 225         trans->lock_may_not_fail = lock_may_not_fail;
 226         trans->lock_must_abort  = false;
 227         trans->locking          = b;
 228
 229         int ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
 230                                      bch2_six_check_for_deadlock, trans, ip);
 231         WRITE_ONCE(trans->locking, NULL);
 232         WRITE_ONCE(trans->locking_wait.start_time, 0);
 233
 234         if (!ret)
 235                 trace_btree_path_lock(trans, _THIS_IP_, b);
 236         return ret;
 237 }
 238
 239 static inline int __must_check
 240 btree_node_lock_nopath(struct btree_trans *trans,
 241                        struct btree_bkey_cached_common *b,
 242                        enum six_lock_type type,
 243                        unsigned long ip)
 244 {
 245         return __btree_node_lock_nopath(trans, b, type, false, ip);
 246 }
 247
 248 static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
 249                                          struct btree_bkey_cached_common *b,
 250                                          enum six_lock_type type)
 251 {
 252         int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);
 253
 254         BUG_ON(ret);
 255 }
 256
 257 /*
 258  * Lock a btree node if we already have it locked on one of our linked
 259  * iterators:
 260  */
 261 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 262                                              struct btree_bkey_cached_common *b,
 263                                              unsigned level,
 264                                              enum btree_node_locked_type want)
 265 {
 266         struct btree_path *path;
 267         unsigned i;
 268
 269         trans_for_each_path(trans, path, i)
 270                 if (&path->l[level].b->c == b &&
 271                     btree_node_locked_type(path, level) >= want) {
 272                         six_lock_increment(&b->lock, (enum six_lock_type) want);
 273                         return true;
 274                 }
 275
 276         return false;
 277 }
 278
 279 static inline int btree_node_lock(struct btree_trans *trans,
 280                         struct btree_path *path,
 281                         struct btree_bkey_cached_common *b,
 282                         unsigned level,
 283                         enum six_lock_type type,
 284                         unsigned long ip)
 285 {
 286         int ret = 0;
 287
 288         EBUG_ON(level >= BTREE_MAX_DEPTH);
 289         bch2_trans_verify_not_unlocked_or_in_restart(trans);
 290
 291         if (likely(six_trylock_type(&b->lock, type)) ||
 292             btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||
 293             !(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
 294 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 295                 path->l[b->level].lock_taken_time = local_clock();
 296 #endif
 297         }
 298
 299         return ret;
 300 }
 301
 302 int __bch2_btree_node_lock_write(struct btree_trans *, struct btree_path *,
 303                                  struct btree_bkey_cached_common *b, bool);
 304
 305 static inline int __btree_node_lock_write(struct btree_trans *trans,
 306                                           struct btree_path *path,
 307                                           struct btree_bkey_cached_common *b,
 308                                           bool lock_may_not_fail)
 309 {
 310         EBUG_ON(&path->l[b->level].b->c != b);
 311         EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
 312         EBUG_ON(!btree_node_intent_locked(path, b->level));
 313
 314         /*
 315          * six locks are unfair, and read locks block while a thread wants a
 316          * write lock: thus, we need to tell the cycle detector we have a write
 317          * lock _before_ taking the lock:
 318          */
 319         mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);
 320
 321         return likely(six_trylock_write(&b->lock))
 322                 ? 0
 323                 : __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
 324 }
 325
 326 static inline int __must_check
 327 bch2_btree_node_lock_write(struct btree_trans *trans,
 328                            struct btree_path *path,
 329                            struct btree_bkey_cached_common *b)
 330 {
 331         return __btree_node_lock_write(trans, path, b, false);
 332 }
 333
 334 void bch2_btree_node_lock_write_nofail(struct btree_trans *,
 335                                        struct btree_path *,
 336                                        struct btree_bkey_cached_common *);
 337
 338 /* relock: */
 339
 340 bool bch2_btree_path_relock_norestart(struct btree_trans *, struct btree_path *);
 341 int __bch2_btree_path_relock(struct btree_trans *,
 342                              struct btree_path *, unsigned long);
 343
 344 static inline int bch2_btree_path_relock(struct btree_trans *trans,
 345                                 struct btree_path *path, unsigned long trace_ip)
 346 {
 347         return btree_node_locked(path, path->level)
 348                 ? 0
 349                 : __bch2_btree_path_relock(trans, path, trace_ip);
 350 }
 351
 352 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned, bool trace);
 353
 354 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 355                                           struct btree_path *path, unsigned level)
 356 {
 357         EBUG_ON(btree_node_locked(path, level) &&
 358                 !btree_node_write_locked(path, level) &&
 359                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 360
 361         return likely(btree_node_locked(path, level)) ||
 362                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 363                  __bch2_btree_node_relock(trans, path, level, true));
 364 }
 365
 366 static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
 367                                                   struct btree_path *path, unsigned level)
 368 {
 369         EBUG_ON(btree_node_locked(path, level) &&
 370                 !btree_node_write_locked(path, level) &&
 371                 btree_node_locked_type(path, level) != __btree_lock_want(path, level));
 372
 373         return likely(btree_node_locked(path, level)) ||
 374                 (!IS_ERR_OR_NULL(path->l[level].b) &&
 375                  __bch2_btree_node_relock(trans, path, level, false));
 376 }
 377
 378 /* upgrade */
 379
 380 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *,
 381                                struct btree_path *, unsigned,
 382                                struct get_locks_fail *);
 383
 384 bool __bch2_btree_path_upgrade(struct btree_trans *,
 385                                struct btree_path *, unsigned,
 386                                struct get_locks_fail *);
 387
 388 static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
 389                                           struct btree_path *path,
 390                                           unsigned new_locks_want)
 391 {
 392         struct get_locks_fail f = {};
 393         unsigned old_locks_want = path->locks_want;
 394
 395         new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);
 396
 397         if (path->locks_want < new_locks_want
 398             ? __bch2_btree_path_upgrade(trans, path, new_locks_want, &f)
 399             : path->nodes_locked)
 400                 return 0;
 401
 402         trace_and_count(trans->c, trans_restart_upgrade, trans, _THIS_IP_, path,
 403                         old_locks_want, new_locks_want, &f);
 404         return btree_trans_restart(trans, BCH_ERR_transaction_restart_upgrade);
 405 }
 406
 407 /* misc: */
 408
 409 static inline void btree_path_set_should_be_locked(struct btree_trans *trans, struct btree_path *path)
 410 {
 411         EBUG_ON(!btree_node_locked(path, path->level));
 412         EBUG_ON(path->uptodate);
 413
 414         path->should_be_locked = true;
 415         trace_btree_path_should_be_locked(trans, path);
 416 }
 417
 418 static inline void __btree_path_set_level_up(struct btree_trans *trans,
 419                                       struct btree_path *path,
 420                                       unsigned l)
 421 {
 422         btree_node_unlock(trans, path, l);
 423         path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
 424 }
 425
 426 static inline void btree_path_set_level_up(struct btree_trans *trans,
 427                                     struct btree_path *path)
 428 {
 429         __btree_path_set_level_up(trans, path, path->level++);
 430         btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 431 }
 432
 433 /* debug */
 434
 435 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
 436                                 struct btree_path *,
 437                                 struct btree_bkey_cached_common *b,
 438                                 unsigned);
 439
 440 int bch2_check_for_deadlock(struct btree_trans *, struct printbuf *);
 441
 442 #ifdef CONFIG_BCACHEFS_DEBUG
 443 void bch2_btree_path_verify_locks(struct btree_path *);
 444 void bch2_trans_verify_locks(struct btree_trans *);
 445 #else
 446 static inline void bch2_btree_path_verify_locks(struct btree_path *path) {}
 447 static inline void bch2_trans_verify_locks(struct btree_trans *trans) {}
 448 #endif
 449
 450 #endif /* _BCACHEFS_BTREE_LOCKING_H */