86b7445193
bch2_btree_trans_to_text() is used to print btree_transactions owned by other threads; thus, it needs to be particularly careful. This fixes a null ptr deref caused by racing with the owning thread changing path->l[].b. Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
287 lines
7.7 KiB
C
287 lines
7.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHEFS_BTREE_LOCKING_H
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#define _BCACHEFS_BTREE_LOCKING_H
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/*
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* Only for internal btree use:
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*
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* The btree iterator tracks what locks it wants to take, and what locks it
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* currently has - here we have wrappers for locking/unlocking btree nodes and
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* updating the iterator state
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*/
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#include "btree_iter.h"
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#include "six.h"
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/* matches six lock types */
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enum btree_node_locked_type {
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BTREE_NODE_UNLOCKED = -1,
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BTREE_NODE_READ_LOCKED = SIX_LOCK_read,
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BTREE_NODE_INTENT_LOCKED = SIX_LOCK_intent,
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};
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static inline int btree_node_locked_type(struct btree_path *path,
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unsigned level)
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{
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/*
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* We're relying on the fact that if nodes_intent_locked is set
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* nodes_locked must be set as well, so that we can compute without
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* branches:
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*/
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return BTREE_NODE_UNLOCKED +
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((path->nodes_locked >> level) & 1) +
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((path->nodes_intent_locked >> level) & 1);
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}
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static inline bool btree_node_intent_locked(struct btree_path *path,
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unsigned level)
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{
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return btree_node_locked_type(path, level) == BTREE_NODE_INTENT_LOCKED;
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}
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static inline bool btree_node_read_locked(struct btree_path *path,
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unsigned level)
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{
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return btree_node_locked_type(path, level) == BTREE_NODE_READ_LOCKED;
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}
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static inline bool btree_node_locked(struct btree_path *path, unsigned level)
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{
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return path->nodes_locked & (1 << level);
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}
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static inline void mark_btree_node_unlocked(struct btree_path *path,
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unsigned level)
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{
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path->nodes_locked &= ~(1 << level);
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path->nodes_intent_locked &= ~(1 << level);
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}
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static inline void mark_btree_node_locked_noreset(struct btree_trans *trans,
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struct btree_path *path,
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unsigned level,
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enum six_lock_type type)
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{
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/* relying on this to avoid a branch */
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BUILD_BUG_ON(SIX_LOCK_read != 0);
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BUILD_BUG_ON(SIX_LOCK_intent != 1);
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path->nodes_locked |= 1 << level;
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path->nodes_intent_locked |= type << level;
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}
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static inline void mark_btree_node_locked(struct btree_trans *trans,
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struct btree_path *path,
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unsigned level,
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enum six_lock_type type)
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{
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mark_btree_node_locked_noreset(trans, path, level, type);
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#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
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path->l[level].lock_taken_time = ktime_get_ns();
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#endif
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}
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static inline void mark_btree_node_intent_locked(struct btree_trans *trans,
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struct btree_path *path,
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unsigned level)
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{
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mark_btree_node_locked_noreset(trans, path, level, SIX_LOCK_intent);
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}
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static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
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{
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return level < path->locks_want
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? SIX_LOCK_intent
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: SIX_LOCK_read;
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}
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static inline enum btree_node_locked_type
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btree_lock_want(struct btree_path *path, int level)
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{
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if (level < path->level)
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return BTREE_NODE_UNLOCKED;
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if (level < path->locks_want)
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return BTREE_NODE_INTENT_LOCKED;
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if (level == path->level)
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return BTREE_NODE_READ_LOCKED;
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return BTREE_NODE_UNLOCKED;
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}
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static inline void btree_node_unlock(struct btree_trans *trans,
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struct btree_path *path, unsigned level)
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{
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int lock_type = btree_node_locked_type(path, level);
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EBUG_ON(level >= BTREE_MAX_DEPTH);
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if (lock_type != BTREE_NODE_UNLOCKED) {
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six_unlock_type(&path->l[level].b->c.lock, lock_type);
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#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
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if (trans->lock_name_idx < BCH_LOCK_TIME_NR) {
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struct bch_fs *c = trans->c;
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__bch2_time_stats_update(&c->lock_held_stats.times[trans->lock_name_idx],
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path->l[level].lock_taken_time,
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ktime_get_ns());
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}
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#endif
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}
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mark_btree_node_unlocked(path, level);
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}
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static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
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struct btree_path *path)
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{
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btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);
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while (path->nodes_locked)
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btree_node_unlock(trans, path, __ffs(path->nodes_locked));
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}
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static inline enum bch_time_stats lock_to_time_stat(enum six_lock_type type)
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{
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switch (type) {
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case SIX_LOCK_read:
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return BCH_TIME_btree_lock_contended_read;
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case SIX_LOCK_intent:
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return BCH_TIME_btree_lock_contended_intent;
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case SIX_LOCK_write:
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return BCH_TIME_btree_lock_contended_write;
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default:
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BUG();
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}
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}
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static inline int btree_node_lock_type(struct btree_trans *trans,
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struct btree_path *path,
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struct btree *b,
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struct bpos pos, unsigned level,
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enum six_lock_type type,
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six_lock_should_sleep_fn should_sleep_fn, void *p)
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{
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struct bch_fs *c = trans->c;
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u64 start_time;
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int ret;
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if (six_trylock_type(&b->c.lock, type))
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return 0;
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start_time = local_clock();
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trans->locking_path_idx = path->idx;
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trans->locking_pos = pos;
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trans->locking_btree_id = path->btree_id;
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trans->locking_level = level;
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trans->locking_lock_type = type;
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trans->locking = &b->c;
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ret = six_lock_type(&b->c.lock, type, should_sleep_fn, p);
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trans->locking = NULL;
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if (ret)
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return ret;
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bch2_time_stats_update(&c->times[lock_to_time_stat(type)], start_time);
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return 0;
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}
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/*
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* Lock a btree node if we already have it locked on one of our linked
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* iterators:
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*/
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static inline bool btree_node_lock_increment(struct btree_trans *trans,
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struct btree *b, unsigned level,
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enum btree_node_locked_type want)
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{
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struct btree_path *path;
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trans_for_each_path(trans, path)
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if (path->l[level].b == b &&
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btree_node_locked_type(path, level) >= want) {
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six_lock_increment(&b->c.lock, want);
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return true;
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}
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return false;
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}
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int __bch2_btree_node_lock(struct btree_trans *, struct btree_path *,
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struct btree *, struct bpos, unsigned,
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enum six_lock_type,
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six_lock_should_sleep_fn, void *,
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unsigned long);
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static inline int btree_node_lock(struct btree_trans *trans,
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struct btree_path *path,
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struct btree *b, struct bpos pos, unsigned level,
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enum six_lock_type type,
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six_lock_should_sleep_fn should_sleep_fn, void *p,
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unsigned long ip)
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{
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int ret = 0;
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EBUG_ON(level >= BTREE_MAX_DEPTH);
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EBUG_ON(!(trans->paths_allocated & (1ULL << path->idx)));
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if (likely(six_trylock_type(&b->c.lock, type)) ||
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btree_node_lock_increment(trans, b, level, type) ||
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!(ret = __bch2_btree_node_lock(trans, path, b, pos, level, type,
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should_sleep_fn, p, ip))) {
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#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
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path->l[b->c.level].lock_taken_time = ktime_get_ns();
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#endif
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}
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return ret;
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}
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bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned);
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static inline bool bch2_btree_node_relock(struct btree_trans *trans,
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struct btree_path *path, unsigned level)
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{
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EBUG_ON(btree_node_locked(path, level) &&
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btree_node_locked_type(path, level) !=
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__btree_lock_want(path, level));
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return likely(btree_node_locked(path, level)) ||
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__bch2_btree_node_relock(trans, path, level);
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}
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/*
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* Updates the saved lock sequence number, so that bch2_btree_node_relock() will
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* succeed:
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*/
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static inline void
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bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
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struct btree *b)
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{
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struct btree_path *linked;
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EBUG_ON(path->l[b->c.level].b != b);
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EBUG_ON(path->l[b->c.level].lock_seq + 1 != b->c.lock.state.seq);
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trans_for_each_path_with_node(trans, b, linked)
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linked->l[b->c.level].lock_seq += 2;
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six_unlock_write(&b->c.lock);
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}
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void bch2_btree_node_unlock_write(struct btree_trans *,
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struct btree_path *, struct btree *);
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void __bch2_btree_node_lock_write(struct btree_trans *, struct btree *);
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static inline void bch2_btree_node_lock_write(struct btree_trans *trans,
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struct btree_path *path,
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struct btree *b)
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{
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EBUG_ON(path->l[b->c.level].b != b);
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EBUG_ON(path->l[b->c.level].lock_seq != b->c.lock.state.seq);
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EBUG_ON(!btree_node_intent_locked(path, b->c.level));
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if (unlikely(!six_trylock_write(&b->c.lock)))
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__bch2_btree_node_lock_write(trans, b);
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}
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#endif /* _BCACHEFS_BTREE_LOCKING_H */
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