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 static inline bool btree_node_lock_type(struct btree_trans *trans,
 132                                        struct btree_path *path,
 133                                        struct btree *b,
 134                                        struct bpos pos, unsigned level,
 135                                        enum six_lock_type type,
 136                                        six_lock_should_sleep_fn should_sleep_fn, void *p)
 137 {
 138         struct bch_fs *c = trans->c;
 139         u64 start_time;
 140         bool ret;
 141
 142         if (six_trylock_type(&b->c.lock, type))
 143                 return true;
 144
 145         start_time = local_clock();
 146
 147         trans->locking_path_idx = path->idx;
 148         trans->locking_pos      = pos;
 149         trans->locking_btree_id = path->btree_id;
 150         trans->locking_level    = level;
 151         trans->locking_lock_type = type;
 152         trans->locking          = b;
 153         ret = six_lock_type(&b->c.lock, type, should_sleep_fn, p) == 0;
 154         trans->locking = NULL;
 155
 156         if (ret)
 157                 bch2_time_stats_update(&c->times[lock_to_time_stat(type)], start_time);
 158
 159         return ret;
 160 }
 161
 162 /*
 163  * Lock a btree node if we already have it locked on one of our linked
 164  * iterators:
 165  */
 166 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 167                                              struct btree *b, unsigned level,
 168                                              enum btree_node_locked_type want)
 169 {
 170         struct btree_path *path;
 171
 172         trans_for_each_path(trans, path)
 173                 if (path->l[level].b == b &&
 174                     btree_node_locked_type(path, level) >= want) {
 175                         six_lock_increment(&b->c.lock, want);
 176                         return true;
 177                 }
 178
 179         return false;
 180 }
 181
 182 bool __bch2_btree_node_lock(struct btree_trans *, struct btree_path *,
 183                             struct btree *, struct bpos, unsigned,
 184                             enum six_lock_type,
 185                             six_lock_should_sleep_fn, void *,
 186                             unsigned long);
 187
 188 static inline bool btree_node_lock(struct btree_trans *trans,
 189                         struct btree_path *path,
 190                         struct btree *b, struct bpos pos, unsigned level,
 191                         enum six_lock_type type,
 192                         six_lock_should_sleep_fn should_sleep_fn, void *p,
 193                         unsigned long ip)
 194 {
 195         EBUG_ON(level >= BTREE_MAX_DEPTH);
 196         EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
 197
 198         return likely(six_trylock_type(&b->c.lock, type)) ||
 199                 btree_node_lock_increment(trans, b, level, type) ||
 200                 __bch2_btree_node_lock(trans, path, b, pos, level, type,
 201                                        should_sleep_fn, p, ip);
 202 }
 203
 204 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned);
 205
 206 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 207                                           struct btree_path *path, unsigned level)
 208 {
 209         EBUG_ON(btree_node_locked(path, level) &&
 210                 btree_node_locked_type(path, level) !=
 211                 __btree_lock_want(path, level));
 212
 213         return likely(btree_node_locked(path, level)) ||
 214                 __bch2_btree_node_relock(trans, path, level);
 215 }
 216
 217 /*
 218  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
 219  * succeed:
 220  */
 221 static inline void
 222 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 223                                      struct btree *b)
 224 {
 225         struct btree_path *linked;
 226
 227         EBUG_ON(path->l[b->c.level].b != b);
 228         EBUG_ON(path->l[b->c.level].lock_seq + 1 != b->c.lock.state.seq);
 229
 230         trans_for_each_path_with_node(trans, b, linked)
 231                 linked->l[b->c.level].lock_seq += 2;
 232
 233         six_unlock_write(&b->c.lock);
 234 }
 235
 236 void bch2_btree_node_unlock_write(struct btree_trans *,
 237                         struct btree_path *, struct btree *);
 238
 239 void __bch2_btree_node_lock_write(struct btree_trans *, struct btree *);
 240
 241 static inline void bch2_btree_node_lock_write(struct btree_trans *trans,
 242                                               struct btree_path *path,
 243                                               struct btree *b)
 244 {
 245         EBUG_ON(path->l[b->c.level].b != b);
 246         EBUG_ON(path->l[b->c.level].lock_seq != b->c.lock.state.seq);
 247         EBUG_ON(!btree_node_intent_locked(path, b->c.level));
 248
 249         if (unlikely(!six_trylock_write(&b->c.lock)))
 250                 __bch2_btree_node_lock_write(trans, b);
 251 }
 252
 253 #endif /* _BCACHEFS_BTREE_LOCKING_H */
 254
 255