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 <linux/six.h>
  14
  15 #include "btree_iter.h"
  16
  17 /* matches six lock types */
  18 enum btree_node_locked_type {
  19         BTREE_NODE_UNLOCKED             = -1,
  20         BTREE_NODE_READ_LOCKED          = SIX_LOCK_read,
  21         BTREE_NODE_INTENT_LOCKED        = SIX_LOCK_intent,
  22 };
  23
  24 static inline int btree_node_locked_type(struct btree_path *path,
  25                                          unsigned level)
  26 {
  27         /*
  28          * We're relying on the fact that if nodes_intent_locked is set
  29          * nodes_locked must be set as well, so that we can compute without
  30          * branches:
  31          */
  32         return BTREE_NODE_UNLOCKED +
  33                 ((path->nodes_locked >> level) & 1) +
  34                 ((path->nodes_intent_locked >> level) & 1);
  35 }
  36
  37 static inline bool btree_node_intent_locked(struct btree_path *path,
  38                                             unsigned level)
  39 {
  40         return btree_node_locked_type(path, level) == BTREE_NODE_INTENT_LOCKED;
  41 }
  42
  43 static inline bool btree_node_read_locked(struct btree_path *path,
  44                                           unsigned level)
  45 {
  46         return btree_node_locked_type(path, level) == BTREE_NODE_READ_LOCKED;
  47 }
  48
  49 static inline bool btree_node_locked(struct btree_path *path, unsigned level)
  50 {
  51         return path->nodes_locked & (1 << level);
  52 }
  53
  54 static inline void mark_btree_node_unlocked(struct btree_path *path,
  55                                             unsigned level)
  56 {
  57         path->nodes_locked &= ~(1 << level);
  58         path->nodes_intent_locked &= ~(1 << level);
  59 }
  60
  61 static inline void mark_btree_node_locked(struct btree_trans *trans,
  62                                           struct btree_path *path,
  63                                           unsigned level,
  64                                           enum six_lock_type type)
  65 {
  66         /* relying on this to avoid a branch */
  67         BUILD_BUG_ON(SIX_LOCK_read   != 0);
  68         BUILD_BUG_ON(SIX_LOCK_intent != 1);
  69
  70         BUG_ON(trans->in_traverse_all && path->sorted_idx > trans->traverse_all_idx);
  71
  72         path->nodes_locked |= 1 << level;
  73         path->nodes_intent_locked |= type << level;
  74 }
  75
  76 static inline void mark_btree_node_intent_locked(struct btree_trans *trans,
  77                                                  struct btree_path *path,
  78                                                  unsigned level)
  79 {
  80         mark_btree_node_locked(trans, path, level, SIX_LOCK_intent);
  81 }
  82
  83 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
  84 {
  85         return level < path->locks_want
  86                 ? SIX_LOCK_intent
  87                 : SIX_LOCK_read;
  88 }
  89
  90 static inline enum btree_node_locked_type
  91 btree_lock_want(struct btree_path *path, int level)
  92 {
  93         if (level < path->level)
  94                 return BTREE_NODE_UNLOCKED;
  95         if (level < path->locks_want)
  96                 return BTREE_NODE_INTENT_LOCKED;
  97         if (level == path->level)
  98                 return BTREE_NODE_READ_LOCKED;
  99         return BTREE_NODE_UNLOCKED;
 100 }
 101
 102 static inline void btree_node_unlock(struct btree_path *path, unsigned level)
 103 {
 104         int lock_type = btree_node_locked_type(path, level);
 105
 106         EBUG_ON(level >= BTREE_MAX_DEPTH);
 107
 108         if (lock_type != BTREE_NODE_UNLOCKED)
 109                 six_unlock_type(&path->l[level].b->c.lock, lock_type);
 110         mark_btree_node_unlocked(path, level);
 111 }
 112
 113 static inline void __bch2_btree_path_unlock(struct btree_path *path)
 114 {
 115         btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
 116
 117         while (path->nodes_locked)
 118                 btree_node_unlock(path, __ffs(path->nodes_locked));
 119 }
 120
 121 static inline enum bch_time_stats lock_to_time_stat(enum six_lock_type type)
 122 {
 123         switch (type) {
 124         case SIX_LOCK_read:
 125                 return BCH_TIME_btree_lock_contended_read;
 126         case SIX_LOCK_intent:
 127                 return BCH_TIME_btree_lock_contended_intent;
 128         case SIX_LOCK_write:
 129                 return BCH_TIME_btree_lock_contended_write;
 130         default:
 131                 BUG();
 132         }
 133 }
 134
 135 static inline bool btree_node_lock_type(struct btree_trans *trans,
 136                                        struct btree_path *path,
 137                                        struct btree *b,
 138                                        struct bpos pos, unsigned level,
 139                                        enum six_lock_type type,
 140                                        six_lock_should_sleep_fn should_sleep_fn, void *p)
 141 {
 142         struct bch_fs *c = trans->c;
 143         u64 start_time;
 144         bool ret;
 145
 146         if (six_trylock_type(&b->c.lock, type))
 147                 return true;
 148
 149         start_time = local_clock();
 150
 151         trans->locking_path_idx = path->idx;
 152         trans->locking_pos      = pos;
 153         trans->locking_btree_id = path->btree_id;
 154         trans->locking_level    = level;
 155         trans->locking_lock_type = type;
 156         trans->locking          = b;
 157         ret = six_lock_type(&b->c.lock, type, should_sleep_fn, p) == 0;
 158         trans->locking = NULL;
 159
 160         if (ret)
 161                 bch2_time_stats_update(&c->times[lock_to_time_stat(type)], start_time);
 162
 163         return ret;
 164 }
 165
 166 /*
 167  * Lock a btree node if we already have it locked on one of our linked
 168  * iterators:
 169  */
 170 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 171                                              struct btree *b, unsigned level,
 172                                              enum btree_node_locked_type want)
 173 {
 174         struct btree_path *path;
 175
 176         trans_for_each_path(trans, path)
 177                 if (path->l[level].b == b &&
 178                     btree_node_locked_type(path, level) >= want) {
 179                         six_lock_increment(&b->c.lock, want);
 180                         return true;
 181                 }
 182
 183         return false;
 184 }
 185
 186 bool __bch2_btree_node_lock(struct btree_trans *, struct btree_path *,
 187                             struct btree *, struct bpos, unsigned,
 188                             enum six_lock_type,
 189                             six_lock_should_sleep_fn, void *,
 190                             unsigned long);
 191
 192 static inline bool btree_node_lock(struct btree_trans *trans,
 193                         struct btree_path *path,
 194                         struct btree *b, struct bpos pos, unsigned level,
 195                         enum six_lock_type type,
 196                         six_lock_should_sleep_fn should_sleep_fn, void *p,
 197                         unsigned long ip)
 198 {
 199         EBUG_ON(level >= BTREE_MAX_DEPTH);
 200         EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
 201
 202         return likely(six_trylock_type(&b->c.lock, type)) ||
 203                 btree_node_lock_increment(trans, b, level, type) ||
 204                 __bch2_btree_node_lock(trans, path, b, pos, level, type,
 205                                        should_sleep_fn, p, ip);
 206 }
 207
 208 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned);
 209
 210 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 211                                           struct btree_path *path, unsigned level)
 212 {
 213         EBUG_ON(btree_node_locked(path, level) &&
 214                 btree_node_locked_type(path, level) !=
 215                 __btree_lock_want(path, level));
 216
 217         return likely(btree_node_locked(path, level)) ||
 218                 __bch2_btree_node_relock(trans, path, level);
 219 }
 220
 221 /*
 222  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 223  * succeed:
 224  */
 225 static inline void
 226 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 227                                      struct btree *b)
 228 {
 229         struct btree_path *linked;
 230
 231         EBUG_ON(path->l[b->c.level].b != b);
 232         EBUG_ON(path->l[b->c.level].lock_seq + 1 != b->c.lock.state.seq);
 233
 234         trans_for_each_path_with_node(trans, b, linked)
 235                 linked->l[b->c.level].lock_seq += 2;
 236
 237         six_unlock_write(&b->c.lock);
 238 }
 239
 240 void bch2_btree_node_unlock_write(struct btree_trans *,
 241                         struct btree_path *, struct btree *);
 242
 243 void __bch2_btree_node_lock_write(struct btree_trans *, struct btree *);
 244
 245 static inline void bch2_btree_node_lock_write(struct btree_trans *trans,
 246                                               struct btree_path *path,
 247                                               struct btree *b)
 248 {
 249         EBUG_ON(path->l[b->c.level].b != b);
 250         EBUG_ON(path->l[b->c.level].lock_seq != b->c.lock.state.seq);
 251         EBUG_ON(!btree_node_intent_locked(path, b->c.level));
 252
 253         if (unlikely(!six_trylock_write(&b->c.lock)))
 254                 __bch2_btree_node_lock_write(trans, b);
 255 }
 256
 257 #endif /* _BCACHEFS_BTREE_LOCKING_H */
 258
 259