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_iter *iter,
  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                 ((iter->nodes_locked >> level) & 1) +
  34                 ((iter->nodes_intent_locked >> level) & 1);
  35 }
  36
  37 static inline bool btree_node_intent_locked(struct btree_iter *iter,
  38                                             unsigned level)
  39 {
  40         return btree_node_locked_type(iter, level) == BTREE_NODE_INTENT_LOCKED;
  41 }
  42
  43 static inline bool btree_node_read_locked(struct btree_iter *iter,
  44                                           unsigned level)
  45 {
  46         return btree_node_locked_type(iter, level) == BTREE_NODE_READ_LOCKED;
  47 }
  48
  49 static inline bool btree_node_locked(struct btree_iter *iter, unsigned level)
  50 {
  51         return iter->nodes_locked & (1 << level);
  52 }
  53
  54 static inline void mark_btree_node_unlocked(struct btree_iter *iter,
  55                                             unsigned level)
  56 {
  57         iter->nodes_locked &= ~(1 << level);
  58         iter->nodes_intent_locked &= ~(1 << level);
  59 }
  60
  61 static inline void mark_btree_node_locked(struct btree_iter *iter,
  62                                           unsigned level,
  63                                           enum six_lock_type type)
  64 {
  65         /* relying on this to avoid a branch */
  66         BUILD_BUG_ON(SIX_LOCK_read   != 0);
  67         BUILD_BUG_ON(SIX_LOCK_intent != 1);
  68
  69         iter->nodes_locked |= 1 << level;
  70         iter->nodes_intent_locked |= type << level;
  71 }
  72
  73 static inline void mark_btree_node_intent_locked(struct btree_iter *iter,
  74                                                  unsigned level)
  75 {
  76         mark_btree_node_locked(iter, level, SIX_LOCK_intent);
  77 }
  78
  79 static inline enum six_lock_type __btree_lock_want(struct btree_iter *iter, int level)
  80 {
  81         return level < iter->locks_want
  82                 ? SIX_LOCK_intent
  83                 : SIX_LOCK_read;
  84 }
  85
  86 static inline enum btree_node_locked_type
  87 btree_lock_want(struct btree_iter *iter, int level)
  88 {
  89         if (level < iter->level)
  90                 return BTREE_NODE_UNLOCKED;
  91         if (level < iter->locks_want)
  92                 return BTREE_NODE_INTENT_LOCKED;
  93         if (level == iter->level)
  94                 return BTREE_NODE_READ_LOCKED;
  95         return BTREE_NODE_UNLOCKED;
  96 }
  97
  98 static inline void btree_node_unlock(struct btree_iter *iter, unsigned level)
  99 {
 100         int lock_type = btree_node_locked_type(iter, level);
 101
 102         EBUG_ON(level >= BTREE_MAX_DEPTH);
 103
 104         if (lock_type != BTREE_NODE_UNLOCKED)
 105                 six_unlock_type(&iter->l[level].b->c.lock, lock_type);
 106         mark_btree_node_unlocked(iter, level);
 107 }
 108
 109 static inline void __bch2_btree_iter_unlock(struct btree_iter *iter)
 110 {
 111         btree_iter_set_dirty(iter, BTREE_ITER_NEED_RELOCK);
 112
 113         while (iter->nodes_locked)
 114                 btree_node_unlock(iter, __ffs(iter->nodes_locked));
 115 }
 116
 117 static inline enum bch_time_stats lock_to_time_stat(enum six_lock_type type)
 118 {
 119         switch (type) {
 120         case SIX_LOCK_read:
 121                 return BCH_TIME_btree_lock_contended_read;
 122         case SIX_LOCK_intent:
 123                 return BCH_TIME_btree_lock_contended_intent;
 124         case SIX_LOCK_write:
 125                 return BCH_TIME_btree_lock_contended_write;
 126         default:
 127                 BUG();
 128         }
 129 }
 130
 131 /*
 132  * wrapper around six locks that just traces lock contended time
 133  */
 134 static inline void __btree_node_lock_type(struct bch_fs *c, struct btree *b,
 135                                           enum six_lock_type type)
 136 {
 137         u64 start_time = local_clock();
 138
 139         six_lock_type(&b->c.lock, type, NULL, NULL);
 140         bch2_time_stats_update(&c->times[lock_to_time_stat(type)], start_time);
 141 }
 142
 143 static inline void btree_node_lock_type(struct bch_fs *c, struct btree *b,
 144                                         enum six_lock_type type)
 145 {
 146         if (!six_trylock_type(&b->c.lock, type))
 147                 __btree_node_lock_type(c, b, type);
 148 }
 149
 150 /*
 151  * Lock a btree node if we already have it locked on one of our linked
 152  * iterators:
 153  */
 154 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 155                                              struct btree *b, unsigned level,
 156                                              enum btree_node_locked_type want)
 157 {
 158         struct btree_iter *iter;
 159
 160         trans_for_each_iter(trans, iter)
 161                 if (iter->l[level].b == b &&
 162                     btree_node_locked_type(iter, level) >= want) {
 163                         six_lock_increment(&b->c.lock, want);
 164                         return true;
 165                 }
 166
 167         return false;
 168 }
 169
 170 bool __bch2_btree_node_lock(struct btree *, struct bpos, unsigned,
 171                             struct btree_iter *, enum six_lock_type,
 172                             six_lock_should_sleep_fn, void *,
 173                             unsigned long);
 174
 175 static inline bool btree_node_lock(struct btree *b,
 176                         struct bpos pos, unsigned level,
 177                         struct btree_iter *iter,
 178                         enum six_lock_type type,
 179                         six_lock_should_sleep_fn should_sleep_fn, void *p,
 180                         unsigned long ip)
 181 {
 182         struct btree_trans *trans = iter->trans;
 183
 184         EBUG_ON(level >= BTREE_MAX_DEPTH);
 185         EBUG_ON(!(trans->iters_linked & (1ULL << iter->idx)));
 186
 187         return likely(six_trylock_type(&b->c.lock, type)) ||
 188                 btree_node_lock_increment(trans, b, level, type) ||
 189                 __bch2_btree_node_lock(b, pos, level, iter, type,
 190                                        should_sleep_fn, p, ip);
 191 }
 192
 193 bool __bch2_btree_node_relock(struct btree_iter *, unsigned);
 194
 195 static inline bool bch2_btree_node_relock(struct btree_iter *iter,
 196                                           unsigned level)
 197 {
 198         EBUG_ON(btree_node_locked(iter, level) &&
 199                 btree_node_locked_type(iter, level) !=
 200                 __btree_lock_want(iter, level));
 201
 202         return likely(btree_node_locked(iter, level)) ||
 203                 __bch2_btree_node_relock(iter, level);
 204 }
 205
 206 /*
 207  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 208  * succeed:
 209  */
 210 static inline void
 211 bch2_btree_node_unlock_write_inlined(struct btree *b, struct btree_iter *iter)
 212 {
 213         struct btree_iter *linked;
 214
 215         EBUG_ON(iter->l[b->c.level].b != b);
 216         EBUG_ON(iter->l[b->c.level].lock_seq + 1 != b->c.lock.state.seq);
 217
 218         trans_for_each_iter_with_node(iter->trans, b, linked)
 219                 linked->l[b->c.level].lock_seq += 2;
 220
 221         six_unlock_write(&b->c.lock);
 222 }
 223
 224 void bch2_btree_node_unlock_write(struct btree *, struct btree_iter *);
 225
 226 void __bch2_btree_node_lock_write(struct btree *, struct btree_iter *);
 227
 228 static inline void bch2_btree_node_lock_write(struct btree *b, struct btree_iter *iter)
 229 {
 230         EBUG_ON(iter->l[b->c.level].b != b);
 231         EBUG_ON(iter->l[b->c.level].lock_seq != b->c.lock.state.seq);
 232
 233         if (unlikely(!six_trylock_write(&b->c.lock)))
 234                 __bch2_btree_node_lock_write(b, iter);
 235 }
 236
 237 #endif /* _BCACHEFS_BTREE_LOCKING_H */
 238
 239