fs/bcachefs/btree_locking.h - third_party/linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _BCACHEFS_BTREE_LOCKING_H
 #define _BCACHEFS_BTREE_LOCKING_H

 /*
  * Only for internal btree use:
  *
  * The btree iterator tracks what locks it wants to take, and what locks it
  * currently has - here we have wrappers for locking/unlocking btree nodes and
  * updating the iterator state
  */

 #include "btree_iter.h"
 #include "six.h"

 void bch2_btree_lock_init(struct btree_bkey_cached_common *, enum six_lock_init_flags);

 void bch2_trans_unlock_noassert(struct btree_trans *);

 static inline bool is_btree_node(struct btree_path *path, unsigned l)
 {
 	return l < BTREE_MAX_DEPTH && !IS_ERR_OR_NULL(path->l[l].b);
 }

 static inline struct btree_transaction_stats *btree_trans_stats(struct btree_trans *trans)
 {
 	return trans->fn_idx < ARRAY_SIZE(trans->c->btree_transaction_stats)
 		? &trans->c->btree_transaction_stats[trans->fn_idx]
 		: NULL;
 }

 /* matches six lock types */
 enum btree_node_locked_type {
 	BTREE_NODE_UNLOCKED		= -1,
 	BTREE_NODE_READ_LOCKED		= SIX_LOCK_read,
 	BTREE_NODE_INTENT_LOCKED	= SIX_LOCK_intent,
 	BTREE_NODE_WRITE_LOCKED		= SIX_LOCK_write,
 };

 static inline int btree_node_locked_type(struct btree_path *path,
 					 unsigned level)
 {
 	return BTREE_NODE_UNLOCKED + ((path->nodes_locked >> (level << 1)) & 3);
 }

 static inline bool btree_node_write_locked(struct btree_path *path, unsigned l)
 {
 	return btree_node_locked_type(path, l) == BTREE_NODE_WRITE_LOCKED;
 }

 static inline bool btree_node_intent_locked(struct btree_path *path, unsigned l)
 {
 	return btree_node_locked_type(path, l) == BTREE_NODE_INTENT_LOCKED;
 }

 static inline bool btree_node_read_locked(struct btree_path *path, unsigned l)
 {
 	return btree_node_locked_type(path, l) == BTREE_NODE_READ_LOCKED;
 }

 static inline bool btree_node_locked(struct btree_path *path, unsigned level)
 {
 	return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
 }

 static inline void mark_btree_node_locked_noreset(struct btree_path *path,
 						  unsigned level,
 						  enum btree_node_locked_type type)
 {
 	/* relying on this to avoid a branch */
 	BUILD_BUG_ON(SIX_LOCK_read   != 0);
 	BUILD_BUG_ON(SIX_LOCK_intent != 1);

 	path->nodes_locked &= ~(3U << (level << 1));
 	path->nodes_locked |= (type + 1) << (level << 1);
 }

 static inline void mark_btree_node_unlocked(struct btree_path *path,
 					    unsigned level)
 {
 	EBUG_ON(btree_node_write_locked(path, level));
 	mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
 }

 static inline void mark_btree_node_locked(struct btree_trans *trans,
 					  struct btree_path *path,
 					  unsigned level,
 					  enum btree_node_locked_type type)
 {
 	mark_btree_node_locked_noreset(path, level, (enum btree_node_locked_type) type);
 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 	path->l[level].lock_taken_time = local_clock();
 #endif
 }

 static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
 {
 	return level < path->locks_want
 		? SIX_LOCK_intent
 		: SIX_LOCK_read;
 }

 static inline enum btree_node_locked_type
 btree_lock_want(struct btree_path *path, int level)
 {
 	if (level < path->level)
 		return BTREE_NODE_UNLOCKED;
 	if (level < path->locks_want)
 		return BTREE_NODE_INTENT_LOCKED;
 	if (level == path->level)
 		return BTREE_NODE_READ_LOCKED;
 	return BTREE_NODE_UNLOCKED;
 }

 static void btree_trans_lock_hold_time_update(struct btree_trans *trans,
 					      struct btree_path *path, unsigned level)
 {
 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 	__bch2_time_stats_update(&btree_trans_stats(trans)->lock_hold_times,
 				 path->l[level].lock_taken_time,
 				 local_clock());
 #endif
 }

 /* unlock: */

 static inline void btree_node_unlock(struct btree_trans *trans,
 				     struct btree_path *path, unsigned level)
 {
 	int lock_type = btree_node_locked_type(path, level);

 	EBUG_ON(level >= BTREE_MAX_DEPTH);
 	EBUG_ON(lock_type == BTREE_NODE_WRITE_LOCKED);

 	if (lock_type != BTREE_NODE_UNLOCKED) {
 		six_unlock_type(&path->l[level].b->c.lock, lock_type);
 		btree_trans_lock_hold_time_update(trans, path, level);
 	}
 	mark_btree_node_unlocked(path, level);
 }

 static inline int btree_path_lowest_level_locked(struct btree_path *path)
 {
 	return __ffs(path->nodes_locked) >> 1;
 }

 static inline int btree_path_highest_level_locked(struct btree_path *path)
 {
 	return __fls(path->nodes_locked) >> 1;
 }

 static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
 					    struct btree_path *path)
 {
 	btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);

 	while (path->nodes_locked)
 		btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
 }

 /*
  * Updates the saved lock sequence number, so that bch2_btree_node_relock() will
  * succeed:
  */
 static inline void
 bch2_btree_node_unlock_write_inlined(struct btree_trans *trans, struct btree_path *path,
 				     struct btree *b)
 {
 	struct btree_path *linked;
 	unsigned i;

 	EBUG_ON(path->l[b->c.level].b != b);
 	EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
 	EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);

 	mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);

 	trans_for_each_path_with_node(trans, b, linked, i)
 		linked->l[b->c.level].lock_seq++;

 	six_unlock_write(&b->c.lock);
 }

 void bch2_btree_node_unlock_write(struct btree_trans *,
 			struct btree_path *, struct btree *);

 int bch2_six_check_for_deadlock(struct six_lock *lock, void *p);

 /* lock: */

 static inline void trans_set_locked(struct btree_trans *trans)
 {
 	if (!trans->locked) {
 		lock_acquire_exclusive(&trans->dep_map, 0, 0, NULL, _THIS_IP_);
 		trans->locked = true;
 		trans->last_unlock_ip = 0;

 		trans->pf_memalloc_nofs = (current->flags & PF_MEMALLOC_NOFS) != 0;
 		current->flags |= PF_MEMALLOC_NOFS;
 	}
 }

 static inline void trans_set_unlocked(struct btree_trans *trans)
 {
 	if (trans->locked) {
 		lock_release(&trans->dep_map, _THIS_IP_);
 		trans->locked = false;
 		trans->last_unlock_ip = _RET_IP_;

 		if (!trans->pf_memalloc_nofs)
 			current->flags &= ~PF_MEMALLOC_NOFS;
 	}
 }

 static inline int __btree_node_lock_nopath(struct btree_trans *trans,
 					 struct btree_bkey_cached_common *b,
 					 enum six_lock_type type,
 					 bool lock_may_not_fail,
 					 unsigned long ip)
 {
 	trans->lock_may_not_fail = lock_may_not_fail;
 	trans->lock_must_abort	= false;
 	trans->locking		= b;

 	int ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
 				     bch2_six_check_for_deadlock, trans, ip);
 	WRITE_ONCE(trans->locking, NULL);
 	WRITE_ONCE(trans->locking_wait.start_time, 0);

 	if (!ret)
 		trace_btree_path_lock(trans, _THIS_IP_, b);
 	return ret;
 }

 static inline int __must_check
 btree_node_lock_nopath(struct btree_trans *trans,
 		       struct btree_bkey_cached_common *b,
 		       enum six_lock_type type,
 		       unsigned long ip)
 {
 	return __btree_node_lock_nopath(trans, b, type, false, ip);
 }

 static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
 					 struct btree_bkey_cached_common *b,
 					 enum six_lock_type type)
 {
 	int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);

 	BUG_ON(ret);
 }

 /*
  * Lock a btree node if we already have it locked on one of our linked
  * iterators:
  */
 static inline bool btree_node_lock_increment(struct btree_trans *trans,
 					     struct btree_bkey_cached_common *b,
 					     unsigned level,
 					     enum btree_node_locked_type want)
 {
 	struct btree_path *path;
 	unsigned i;

 	trans_for_each_path(trans, path, i)
 		if (&path->l[level].b->c == b &&
 		    btree_node_locked_type(path, level) >= want) {
 			six_lock_increment(&b->lock, (enum six_lock_type) want);
 			return true;
 		}

 	return false;
 }

 static inline int btree_node_lock(struct btree_trans *trans,
 			struct btree_path *path,
 			struct btree_bkey_cached_common *b,
 			unsigned level,
 			enum six_lock_type type,
 			unsigned long ip)
 {
 	int ret = 0;

 	EBUG_ON(level >= BTREE_MAX_DEPTH);
 	bch2_trans_verify_not_unlocked(trans);

 	if (likely(six_trylock_type(&b->lock, type)) ||
 	    btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) ||
 	    !(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
 #ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
 		path->l[b->level].lock_taken_time = local_clock();
 #endif
 	}

 	return ret;
 }

 int __bch2_btree_node_lock_write(struct btree_trans *, struct btree_path *,
 				 struct btree_bkey_cached_common *b, bool);

 static inline int __btree_node_lock_write(struct btree_trans *trans,
 					  struct btree_path *path,
 					  struct btree_bkey_cached_common *b,
 					  bool lock_may_not_fail)
 {
 	EBUG_ON(&path->l[b->level].b->c != b);
 	EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
 	EBUG_ON(!btree_node_intent_locked(path, b->level));

 	/*
 	 * six locks are unfair, and read locks block while a thread wants a
 	 * write lock: thus, we need to tell the cycle detector we have a write
 	 * lock _before_ taking the lock:
 	 */
 	mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);

 	return likely(six_trylock_write(&b->lock))
 		? 0
 		: __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
 }

 static inline int __must_check
 bch2_btree_node_lock_write(struct btree_trans *trans,
 			   struct btree_path *path,
 			   struct btree_bkey_cached_common *b)
 {
 	return __btree_node_lock_write(trans, path, b, false);
 }

 void bch2_btree_node_lock_write_nofail(struct btree_trans *,
 				       struct btree_path *,
 				       struct btree_bkey_cached_common *);

 /* relock: */

 bool bch2_btree_path_relock_norestart(struct btree_trans *, struct btree_path *);
 int __bch2_btree_path_relock(struct btree_trans *,
 			     struct btree_path *, unsigned long);

 static inline int bch2_btree_path_relock(struct btree_trans *trans,
 				struct btree_path *path, unsigned long trace_ip)
 {
 	return btree_node_locked(path, path->level)
 		? 0
 		: __bch2_btree_path_relock(trans, path, trace_ip);
 }

 bool __bch2_btree_node_relock(struct btree_trans *, struct btree_path *, unsigned, bool trace);

 static inline bool bch2_btree_node_relock(struct btree_trans *trans,
 					  struct btree_path *path, unsigned level)
 {
 	EBUG_ON(btree_node_locked(path, level) &&
 		!btree_node_write_locked(path, level) &&
 		btree_node_locked_type(path, level) != __btree_lock_want(path, level));

 	return likely(btree_node_locked(path, level)) ||
 		(!IS_ERR_OR_NULL(path->l[level].b) &&
 		 __bch2_btree_node_relock(trans, path, level, true));
 }

 static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
 						  struct btree_path *path, unsigned level)
 {
 	EBUG_ON(btree_node_locked(path, level) &&
 		!btree_node_write_locked(path, level) &&
 		btree_node_locked_type(path, level) != __btree_lock_want(path, level));

 	return likely(btree_node_locked(path, level)) ||
 		(!IS_ERR_OR_NULL(path->l[level].b) &&
 		 __bch2_btree_node_relock(trans, path, level, false));
 }

 /* upgrade */

 bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *,
 			       struct btree_path *, unsigned,
 			       struct get_locks_fail *);

 bool __bch2_btree_path_upgrade(struct btree_trans *,
 			       struct btree_path *, unsigned,
 			       struct get_locks_fail *);

 static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
 					  struct btree_path *path,
 					  unsigned new_locks_want)
 {
 	struct get_locks_fail f = {};
 	unsigned old_locks_want = path->locks_want;

 	new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);

 	if (path->locks_want < new_locks_want
 	    ? __bch2_btree_path_upgrade(trans, path, new_locks_want, &f)
 	    : path->nodes_locked)
 		return 0;

 	trace_and_count(trans->c, trans_restart_upgrade, trans, _THIS_IP_, path,
 			old_locks_want, new_locks_want, &f);
 	return btree_trans_restart(trans, BCH_ERR_transaction_restart_upgrade);
 }

 /* misc: */

 static inline void btree_path_set_should_be_locked(struct btree_trans *trans, struct btree_path *path)
 {
 	EBUG_ON(!btree_node_locked(path, path->level));
 	EBUG_ON(path->uptodate);

 	path->should_be_locked = true;
 	trace_btree_path_should_be_locked(trans, path);
 }

 static inline void __btree_path_set_level_up(struct btree_trans *trans,
 				      struct btree_path *path,
 				      unsigned l)
 {
 	btree_node_unlock(trans, path, l);
 	path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
 }

 static inline void btree_path_set_level_up(struct btree_trans *trans,
 				    struct btree_path *path)
 {
 	__btree_path_set_level_up(trans, path, path->level++);
 	btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
 }

 /* debug */

 struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
 				struct btree_path *,
 				struct btree_bkey_cached_common *b,
 				unsigned);

 int bch2_check_for_deadlock(struct btree_trans *, struct printbuf *);

 #ifdef CONFIG_BCACHEFS_DEBUG
 void bch2_btree_path_verify_locks(struct btree_path *);
 void bch2_trans_verify_locks(struct btree_trans *);
 #else
 static inline void bch2_btree_path_verify_locks(struct btree_path *path) {}
 static inline void bch2_trans_verify_locks(struct btree_trans *trans) {}
 #endif

 #endif /* _BCACHEFS_BTREE_LOCKING_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef _BCACHEFS_BTREE_LOCKING_H
	#define _BCACHEFS_BTREE_LOCKING_H

	/*
	* Only for internal btree use:
	*
	* The btree iterator tracks what locks it wants to take, and what locks it
	* currently has - here we have wrappers for locking/unlocking btree nodes and
	* updating the iterator state
	*/

	#include "btree_iter.h"
	#include "six.h"

	void bch2_btree_lock_init(struct btree_bkey_cached_common *, enum six_lock_init_flags);

	void bch2_trans_unlock_noassert(struct btree_trans *);

	static inline bool is_btree_node(struct btree_path *path, unsigned l)
	{
	return l < BTREE_MAX_DEPTH && !IS_ERR_OR_NULL(path->l[l].b);
	}

	static inline struct btree_transaction_stats btree_trans_stats(struct btree_trans trans)
	{
	return trans->fn_idx < ARRAY_SIZE(trans->c->btree_transaction_stats)
	? &trans->c->btree_transaction_stats[trans->fn_idx]
	: NULL;
	}

	/* matches six lock types */
	enum btree_node_locked_type {
	BTREE_NODE_UNLOCKED = -1,
	BTREE_NODE_READ_LOCKED = SIX_LOCK_read,
	BTREE_NODE_INTENT_LOCKED = SIX_LOCK_intent,
	BTREE_NODE_WRITE_LOCKED = SIX_LOCK_write,
	};

	static inline int btree_node_locked_type(struct btree_path *path,
	unsigned level)
	{
	return BTREE_NODE_UNLOCKED + ((path->nodes_locked >> (level << 1)) & 3);
	}

	static inline bool btree_node_write_locked(struct btree_path *path, unsigned l)
	{
	return btree_node_locked_type(path, l) == BTREE_NODE_WRITE_LOCKED;
	}

	static inline bool btree_node_intent_locked(struct btree_path *path, unsigned l)
	{
	return btree_node_locked_type(path, l) == BTREE_NODE_INTENT_LOCKED;
	}

	static inline bool btree_node_read_locked(struct btree_path *path, unsigned l)
	{
	return btree_node_locked_type(path, l) == BTREE_NODE_READ_LOCKED;
	}

	static inline bool btree_node_locked(struct btree_path *path, unsigned level)
	{
	return btree_node_locked_type(path, level) != BTREE_NODE_UNLOCKED;
	}

	static inline void mark_btree_node_locked_noreset(struct btree_path *path,
	unsigned level,
	enum btree_node_locked_type type)
	{
	/* relying on this to avoid a branch */
	BUILD_BUG_ON(SIX_LOCK_read != 0);
	BUILD_BUG_ON(SIX_LOCK_intent != 1);

	path->nodes_locked &= ~(3U << (level << 1));
	path->nodes_locked \|= (type + 1) << (level << 1);
	}

	static inline void mark_btree_node_unlocked(struct btree_path *path,
	unsigned level)
	{
	EBUG_ON(btree_node_write_locked(path, level));
	mark_btree_node_locked_noreset(path, level, BTREE_NODE_UNLOCKED);
	}

	static inline void mark_btree_node_locked(struct btree_trans *trans,
	struct btree_path *path,
	unsigned level,
	enum btree_node_locked_type type)
	{
	mark_btree_node_locked_noreset(path, level, (enum btree_node_locked_type) type);
	#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
	path->l[level].lock_taken_time = local_clock();
	#endif
	}

	static inline enum six_lock_type __btree_lock_want(struct btree_path *path, int level)
	{
	return level < path->locks_want
	? SIX_LOCK_intent
	: SIX_LOCK_read;
	}

	static inline enum btree_node_locked_type
	btree_lock_want(struct btree_path *path, int level)
	{
	if (level < path->level)
	return BTREE_NODE_UNLOCKED;
	if (level < path->locks_want)
	return BTREE_NODE_INTENT_LOCKED;
	if (level == path->level)
	return BTREE_NODE_READ_LOCKED;
	return BTREE_NODE_UNLOCKED;
	}

	static void btree_trans_lock_hold_time_update(struct btree_trans *trans,
	struct btree_path *path, unsigned level)
	{
	#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
	__bch2_time_stats_update(&btree_trans_stats(trans)->lock_hold_times,
	path->l[level].lock_taken_time,
	local_clock());
	#endif
	}

	/* unlock: */

	static inline void btree_node_unlock(struct btree_trans *trans,
	struct btree_path *path, unsigned level)
	{
	int lock_type = btree_node_locked_type(path, level);

	EBUG_ON(level >= BTREE_MAX_DEPTH);
	EBUG_ON(lock_type == BTREE_NODE_WRITE_LOCKED);

	if (lock_type != BTREE_NODE_UNLOCKED) {
	six_unlock_type(&path->l[level].b->c.lock, lock_type);
	btree_trans_lock_hold_time_update(trans, path, level);
	}
	mark_btree_node_unlocked(path, level);
	}

	static inline int btree_path_lowest_level_locked(struct btree_path *path)
	{
	return __ffs(path->nodes_locked) >> 1;
	}

	static inline int btree_path_highest_level_locked(struct btree_path *path)
	{
	return __fls(path->nodes_locked) >> 1;
	}

	static inline void __bch2_btree_path_unlock(struct btree_trans *trans,
	struct btree_path *path)
	{
	btree_path_set_dirty(path, BTREE_ITER_NEED_RELOCK);

	while (path->nodes_locked)
	btree_node_unlock(trans, path, btree_path_lowest_level_locked(path));
	}

	/*
	* Updates the saved lock sequence number, so that bch2_btree_node_relock() will
	* succeed:
	*/
	static inline void
	bch2_btree_node_unlock_write_inlined(struct btree_trans trans, struct btree_path path,
	struct btree *b)
	{
	struct btree_path *linked;
	unsigned i;

	EBUG_ON(path->l[b->c.level].b != b);
	EBUG_ON(path->l[b->c.level].lock_seq != six_lock_seq(&b->c.lock));
	EBUG_ON(btree_node_locked_type(path, b->c.level) != SIX_LOCK_write);

	mark_btree_node_locked_noreset(path, b->c.level, BTREE_NODE_INTENT_LOCKED);

	trans_for_each_path_with_node(trans, b, linked, i)
	linked->l[b->c.level].lock_seq++;

	six_unlock_write(&b->c.lock);
	}

	void bch2_btree_node_unlock_write(struct btree_trans *,
	struct btree_path , struct btree );

	int bch2_six_check_for_deadlock(struct six_lock lock, void p);

	/* lock: */

	static inline void trans_set_locked(struct btree_trans *trans)
	{
	if (!trans->locked) {
	lock_acquire_exclusive(&trans->dep_map, 0, 0, NULL, _THIS_IP_);
	trans->locked = true;
	trans->last_unlock_ip = 0;

	trans->pf_memalloc_nofs = (current->flags & PF_MEMALLOC_NOFS) != 0;
	current->flags \|= PF_MEMALLOC_NOFS;
	}
	}

	static inline void trans_set_unlocked(struct btree_trans *trans)
	{
	if (trans->locked) {
	lock_release(&trans->dep_map, _THIS_IP_);
	trans->locked = false;
	trans->last_unlock_ip = _RET_IP_;

	if (!trans->pf_memalloc_nofs)
	current->flags &= ~PF_MEMALLOC_NOFS;
	}
	}

	static inline int __btree_node_lock_nopath(struct btree_trans *trans,
	struct btree_bkey_cached_common *b,
	enum six_lock_type type,
	bool lock_may_not_fail,
	unsigned long ip)
	{
	trans->lock_may_not_fail = lock_may_not_fail;
	trans->lock_must_abort = false;
	trans->locking = b;

	int ret = six_lock_ip_waiter(&b->lock, type, &trans->locking_wait,
	bch2_six_check_for_deadlock, trans, ip);
	WRITE_ONCE(trans->locking, NULL);
	WRITE_ONCE(trans->locking_wait.start_time, 0);

	if (!ret)
	trace_btree_path_lock(trans, _THIS_IP_, b);
	return ret;
	}

	static inline int __must_check
	btree_node_lock_nopath(struct btree_trans *trans,
	struct btree_bkey_cached_common *b,
	enum six_lock_type type,
	unsigned long ip)
	{
	return __btree_node_lock_nopath(trans, b, type, false, ip);
	}

	static inline void btree_node_lock_nopath_nofail(struct btree_trans *trans,
	struct btree_bkey_cached_common *b,
	enum six_lock_type type)
	{
	int ret = __btree_node_lock_nopath(trans, b, type, true, _THIS_IP_);

	BUG_ON(ret);
	}

	/*
	* Lock a btree node if we already have it locked on one of our linked
	* iterators:
	*/
	static inline bool btree_node_lock_increment(struct btree_trans *trans,
	struct btree_bkey_cached_common *b,
	unsigned level,
	enum btree_node_locked_type want)
	{
	struct btree_path *path;
	unsigned i;

	trans_for_each_path(trans, path, i)
	if (&path->l[level].b->c == b &&
	btree_node_locked_type(path, level) >= want) {
	six_lock_increment(&b->lock, (enum six_lock_type) want);
	return true;
	}

	return false;
	}

	static inline int btree_node_lock(struct btree_trans *trans,
	struct btree_path *path,
	struct btree_bkey_cached_common *b,
	unsigned level,
	enum six_lock_type type,
	unsigned long ip)
	{
	int ret = 0;

	EBUG_ON(level >= BTREE_MAX_DEPTH);
	bch2_trans_verify_not_unlocked(trans);

	if (likely(six_trylock_type(&b->lock, type)) \|\|
	btree_node_lock_increment(trans, b, level, (enum btree_node_locked_type) type) \|\|
	!(ret = btree_node_lock_nopath(trans, b, type, btree_path_ip_allocated(path)))) {
	#ifdef CONFIG_BCACHEFS_LOCK_TIME_STATS
	path->l[b->level].lock_taken_time = local_clock();
	#endif
	}

	return ret;
	}

	int __bch2_btree_node_lock_write(struct btree_trans , struct btree_path ,
	struct btree_bkey_cached_common *b, bool);

	static inline int __btree_node_lock_write(struct btree_trans *trans,
	struct btree_path *path,
	struct btree_bkey_cached_common *b,
	bool lock_may_not_fail)
	{
	EBUG_ON(&path->l[b->level].b->c != b);
	EBUG_ON(path->l[b->level].lock_seq != six_lock_seq(&b->lock));
	EBUG_ON(!btree_node_intent_locked(path, b->level));

	/*
	* six locks are unfair, and read locks block while a thread wants a
	* write lock: thus, we need to tell the cycle detector we have a write
	* lock _before_ taking the lock:
	*/
	mark_btree_node_locked_noreset(path, b->level, BTREE_NODE_WRITE_LOCKED);

	return likely(six_trylock_write(&b->lock))
	? 0
	: __bch2_btree_node_lock_write(trans, path, b, lock_may_not_fail);
	}

	static inline int __must_check
	bch2_btree_node_lock_write(struct btree_trans *trans,
	struct btree_path *path,
	struct btree_bkey_cached_common *b)
	{
	return __btree_node_lock_write(trans, path, b, false);
	}

	void bch2_btree_node_lock_write_nofail(struct btree_trans *,
	struct btree_path *,
	struct btree_bkey_cached_common *);

	/* relock: */

	bool bch2_btree_path_relock_norestart(struct btree_trans , struct btree_path );
	int __bch2_btree_path_relock(struct btree_trans *,
	struct btree_path *, unsigned long);

	static inline int bch2_btree_path_relock(struct btree_trans *trans,
	struct btree_path *path, unsigned long trace_ip)
	{
	return btree_node_locked(path, path->level)
	? 0
	: __bch2_btree_path_relock(trans, path, trace_ip);
	}

	bool __bch2_btree_node_relock(struct btree_trans , struct btree_path , unsigned, bool trace);

	static inline bool bch2_btree_node_relock(struct btree_trans *trans,
	struct btree_path *path, unsigned level)
	{
	EBUG_ON(btree_node_locked(path, level) &&
	!btree_node_write_locked(path, level) &&
	btree_node_locked_type(path, level) != __btree_lock_want(path, level));

	return likely(btree_node_locked(path, level)) \|\|
	(!IS_ERR_OR_NULL(path->l[level].b) &&
	__bch2_btree_node_relock(trans, path, level, true));
	}

	static inline bool bch2_btree_node_relock_notrace(struct btree_trans *trans,
	struct btree_path *path, unsigned level)
	{
	EBUG_ON(btree_node_locked(path, level) &&
	!btree_node_write_locked(path, level) &&
	btree_node_locked_type(path, level) != __btree_lock_want(path, level));

	return likely(btree_node_locked(path, level)) \|\|
	(!IS_ERR_OR_NULL(path->l[level].b) &&
	__bch2_btree_node_relock(trans, path, level, false));
	}

	/* upgrade */

	bool bch2_btree_path_upgrade_noupgrade_sibs(struct btree_trans *,
	struct btree_path *, unsigned,
	struct get_locks_fail *);

	bool __bch2_btree_path_upgrade(struct btree_trans *,
	struct btree_path *, unsigned,
	struct get_locks_fail *);

	static inline int bch2_btree_path_upgrade(struct btree_trans *trans,
	struct btree_path *path,
	unsigned new_locks_want)
	{
	struct get_locks_fail f = {};
	unsigned old_locks_want = path->locks_want;

	new_locks_want = min(new_locks_want, BTREE_MAX_DEPTH);

	if (path->locks_want < new_locks_want
	? __bch2_btree_path_upgrade(trans, path, new_locks_want, &f)
	: path->nodes_locked)
	return 0;

	trace_and_count(trans->c, trans_restart_upgrade, trans, _THIS_IP_, path,
	old_locks_want, new_locks_want, &f);
	return btree_trans_restart(trans, BCH_ERR_transaction_restart_upgrade);
	}

	/* misc: */

	static inline void btree_path_set_should_be_locked(struct btree_trans trans, struct btree_path path)
	{
	EBUG_ON(!btree_node_locked(path, path->level));
	EBUG_ON(path->uptodate);

	path->should_be_locked = true;
	trace_btree_path_should_be_locked(trans, path);
	}

	static inline void __btree_path_set_level_up(struct btree_trans *trans,
	struct btree_path *path,
	unsigned l)
	{
	btree_node_unlock(trans, path, l);
	path->l[l].b = ERR_PTR(-BCH_ERR_no_btree_node_up);
	}

	static inline void btree_path_set_level_up(struct btree_trans *trans,
	struct btree_path *path)
	{
	__btree_path_set_level_up(trans, path, path->level++);
	btree_path_set_dirty(path, BTREE_ITER_NEED_TRAVERSE);
	}

	/* debug */

	struct six_lock_count bch2_btree_node_lock_counts(struct btree_trans *,
	struct btree_path *,
	struct btree_bkey_cached_common *b,
	unsigned);

	int bch2_check_for_deadlock(struct btree_trans , struct printbuf );

	#ifdef CONFIG_BCACHEFS_DEBUG
	void bch2_btree_path_verify_locks(struct btree_path *);
	void bch2_trans_verify_locks(struct btree_trans *);
	#else
	static inline void bch2_btree_path_verify_locks(struct btree_path *path) {}
	static inline void bch2_trans_verify_locks(struct btree_trans *trans) {}
	#endif

	#endif /* _BCACHEFS_BTREE_LOCKING_H */