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_path *path,
  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         path->nodes_locked |= 1 << level;
  70         path->nodes_intent_locked |= type << level;
  71 }
  72
  73 static inline void mark_btree_node_intent_locked(struct btree_path *path,
  74                                                  unsigned level)
  75 {
  76         mark_btree_node_locked(path, level, SIX_LOCK_intent);
  77 }
  78
  79 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
  80 {
  81         return level < path->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_path *path, int level)
  88 {
  89         if (level < path->level)
  90                 return BTREE_NODE_UNLOCKED;
  91         if (level < path->locks_want)
  92                 return BTREE_NODE_INTENT_LOCKED;
  93         if (level == path->level)
  94                 return BTREE_NODE_READ_LOCKED;
  95         return BTREE_NODE_UNLOCKED;
  96 }
  97
  98 static inline void btree_node_unlock(struct btree_path *path, unsigned level)
  99 {
 100         int lock_type = btree_node_locked_type(path, level);
 101
 102         EBUG_ON(level >= BTREE_MAX_DEPTH);
 103
 104         if (lock_type != BTREE_NODE_UNLOCKED)
 105                 six_unlock_type(&path->l[level].b->c.lock, lock_type);
 106         mark_btree_node_unlocked(path, level);
 107 }
 108
 109 static inline void __bch2_btree_path_unlock(struct btree_path *path)
 110 {
 111         btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
 112
 113         while (path->nodes_locked)
 114                 btree_node_unlock(path, __ffs(path->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_path *path;
 159
 160         trans_for_each_path(trans, path)
 161                 if (path->l[level].b == b &&
 162                     btree_node_locked_type(path, 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_trans *, struct btree_path *,
 171                             struct btree *, struct bpos, unsigned,
 172                             enum six_lock_type,
 173                             six_lock_should_sleep_fn, void *,
 174                             unsigned long);
 175
 176 static inline bool btree_node_lock(struct btree_trans *trans,
 177                         struct btree_path *path,
 178                         struct btree *b, struct bpos pos, unsigned level,
 179                         enum six_lock_type type,
 180                         six_lock_should_sleep_fn should_sleep_fn, void *p,
 181                         unsigned long ip)
 182 {
 183         EBUG_ON(level >= BTREE_MAX_DEPTH);
 184         EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
 185
 186         return likely(six_trylock_type(&b->c.lock, type)) ||
 187                 btree_node_lock_increment(trans, b, level, type) ||
 188                 __bch2_btree_node_lock(trans, path, b, pos, level, type,
 189                                        should_sleep_fn, p, ip);
 190 }
 191
 192 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned);
 193
 194 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 195                                           struct btree_path *path, unsigned level)
 196 {
 197         EBUG_ON(btree_node_locked(path, level) &&
 198                 btree_node_locked_type(path, level) !=
 199                 __btree_lock_want(path, level));
 200
 201         return likely(btree_node_locked(path, level)) ||
 202                 __bch2_btree_node_relock(trans, path, level);
 203 }
 204
 205 /*
 206  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 207  * succeed:
 208  */
 209 static inline void
 210 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 211                                      struct btree *b)
 212 {
 213         struct btree_path *linked;
 214
 215         EBUG_ON(path->l[b->c.level].b != b);
 216         EBUG_ON(path->l[b->c.level].lock_seq + 1 != b->c.lock.state.seq);
 217
 218         trans_for_each_path_with_node(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_trans *,
 225                         struct btree_path *, struct btree *);
 226
 227 void __bch2_btree_node_lock_write(struct btree_trans *, struct btree *);
 228
 229 static inline void bch2_btree_node_lock_write(struct btree_trans *trans,
 230                                               struct btree_path *path,
 231                                               struct btree *b)
 232 {
 233         EBUG_ON(path->l[b->c.level].b != b);
 234         EBUG_ON(path->l[b->c.level].lock_seq != b->c.lock.state.seq);
 235         EBUG_ON(!btree_node_intent_locked(path, b->c.level));
 236
 237         if (unlikely(!six_trylock_write(&b->c.lock)))
 238                 __bch2_btree_node_lock_write(trans, b);
 239 }
 240
 241 #endif /* _BCACHEFS_BTREE_LOCKING_H */
 242
 243