[04/10] locking: export osq_lock()/osq_unlock()
diff mbox

Message ID 20180518101804.GB15403@kmo-pixel
State New
Headers show

Commit Message

Kent Overstreet May 18, 2018, 10:18 a.m. UTC
On Fri, May 18, 2018 at 11:52:04AM +0200, Peter Zijlstra wrote:
> On Fri, May 18, 2018 at 03:49:06AM -0400, Kent Overstreet wrote:
> 
> No.. and most certainly not without a _very_ good reason.

Ok, can I ask why?

Here's what it's for:

commit 61782bf71eef83919af100a9747d8d86dfdf3605
Author: Kent Overstreet <kent.overstreet@gmail.com>
Date:   Fri May 18 06:14:56 2018 -0400

    bcachefs: SIX locks (shared/intent/exclusive)
    
    New lock for bcachefs, like read/write locks but with a third state,
    intent.
    
    Intent locks conflict with each other, but not with read locks; taking a
    write lock requires first holding an intent lock.


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Comments

Peter Zijlstra May 18, 2018, 11:08 a.m. UTC | #1
On Fri, May 18, 2018 at 06:18:04AM -0400, Kent Overstreet wrote:
> On Fri, May 18, 2018 at 11:52:04AM +0200, Peter Zijlstra wrote:
> > On Fri, May 18, 2018 at 03:49:06AM -0400, Kent Overstreet wrote:
> > 
> > No.. and most certainly not without a _very_ good reason.
> 
> Ok, can I ask why?

Because it is an internal helper for lock implementations that want to
do optimistic spinning, it isn't a lock on its own and lacks several
things you would expect.

Using it is tricky and I don't trust random module authors to get 1+1
right, let alone use this thing correctly (no judgement on your code,
just in general).

> Here's what it's for:

I'll try and have a look soon :-) But does that really _have_ to live in
a module?
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Kent Overstreet May 18, 2018, 11:32 a.m. UTC | #2
On Fri, May 18, 2018 at 01:08:08PM +0200, Peter Zijlstra wrote:
> On Fri, May 18, 2018 at 06:18:04AM -0400, Kent Overstreet wrote:
> > On Fri, May 18, 2018 at 11:52:04AM +0200, Peter Zijlstra wrote:
> > > On Fri, May 18, 2018 at 03:49:06AM -0400, Kent Overstreet wrote:
> > > 
> > > No.. and most certainly not without a _very_ good reason.
> > 
> > Ok, can I ask why?
> 
> Because it is an internal helper for lock implementations that want to
> do optimistic spinning, it isn't a lock on its own and lacks several
> things you would expect.
> 
> Using it is tricky and I don't trust random module authors to get 1+1
> right, let alone use this thing correctly (no judgement on your code,
> just in general).

Yeah, that's true. I just modelled my usage on the rwsem code.

It does strike me that the whole optimistic spin algorithm
(mutex_optimistic_spin() and rwsem_optimistic_spin()) are ripe for factoring
out. They've been growing more optimizations I see, and the optimizations mostly
aren't specific to either locks.

> > Here's what it's for:
> 
> I'll try and have a look soon :-) But does that really _have_ to live in
> a module?

No, I'd be completely fine with moving six locks out of bcachefs, just don't
know that there'd be any other users. But I suppose we do have other filesystems
that use btrees, and that's what they're for.
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Peter Zijlstra May 18, 2018, 11:40 a.m. UTC | #3
On Fri, May 18, 2018 at 07:32:05AM -0400, Kent Overstreet wrote:
> It does strike me that the whole optimistic spin algorithm
> (mutex_optimistic_spin() and rwsem_optimistic_spin()) are ripe for factoring
> out. They've been growing more optimizations I see, and the optimizations mostly
> aren't specific to either locks.

There's a few unfortunate differences between the two; but yes it would
be good if we could reduce some of the duplication found there.

One of the distinct differences is that mutex (now) has the lock state
and owner in a single atomic word, while rwsem still tracks the owner in
a separate word and thus needs to account for 'inconsistent' owner
state.

And then there's warts such as ww_mutex and rwsem_owner_is_reader and
similar.
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Patch
diff mbox

diff --git a/fs/bcachefs/six.c b/fs/bcachefs/six.c
new file mode 100644
index 0000000000..afa59a476a
--- /dev/null
+++ b/fs/bcachefs/six.c
@@ -0,0 +1,516 @@ 
+
+#include <linux/log2.h>
+#include <linux/preempt.h>
+#include <linux/rcupdate.h>
+#include <linux/sched.h>
+#include <linux/sched/rt.h>
+
+#include "six.h"
+
+#define six_acquire(l, t)	lock_acquire(l, 0, t, 0, 0, NULL, _RET_IP_)
+#define six_release(l)		lock_release(l, 0, _RET_IP_)
+
+struct six_lock_vals {
+	/* Value we add to the lock in order to take the lock: */
+	u64			lock_val;
+
+	/* If the lock has this value (used as a mask), taking the lock fails: */
+	u64			lock_fail;
+
+	/* Value we add to the lock in order to release the lock: */
+	u64			unlock_val;
+
+	/* Mask that indicates lock is held for this type: */
+	u64			held_mask;
+
+	/* Waitlist we wakeup when releasing the lock: */
+	enum six_lock_type	unlock_wakeup;
+};
+
+#define __SIX_LOCK_HELD_read	__SIX_VAL(read_lock, ~0)
+#define __SIX_LOCK_HELD_intent	__SIX_VAL(intent_lock, ~0)
+#define __SIX_LOCK_HELD_write	__SIX_VAL(seq, 1)
+
+#define LOCK_VALS {							\
+	[SIX_LOCK_read] = {						\
+		.lock_val	= __SIX_VAL(read_lock, 1),		\
+		.lock_fail	= __SIX_LOCK_HELD_write,		\
+		.unlock_val	= -__SIX_VAL(read_lock, 1),		\
+		.held_mask	= __SIX_LOCK_HELD_read,			\
+		.unlock_wakeup	= SIX_LOCK_write,			\
+	},								\
+	[SIX_LOCK_intent] = {						\
+		.lock_val	= __SIX_VAL(intent_lock, 1),		\
+		.lock_fail	= __SIX_LOCK_HELD_intent,		\
+		.unlock_val	= -__SIX_VAL(intent_lock, 1),		\
+		.held_mask	= __SIX_LOCK_HELD_intent,		\
+		.unlock_wakeup	= SIX_LOCK_intent,			\
+	},								\
+	[SIX_LOCK_write] = {						\
+		.lock_val	= __SIX_VAL(seq, 1),			\
+		.lock_fail	= __SIX_LOCK_HELD_read,			\
+		.unlock_val	= __SIX_VAL(seq, 1),			\
+		.held_mask	= __SIX_LOCK_HELD_write,		\
+		.unlock_wakeup	= SIX_LOCK_read,			\
+	},								\
+}
+
+static inline void six_set_owner(struct six_lock *lock, enum six_lock_type type,
+				 union six_lock_state old)
+{
+	if (type != SIX_LOCK_intent)
+		return;
+
+	if (!old.intent_lock) {
+		EBUG_ON(lock->owner);
+		lock->owner = current;
+	} else {
+		EBUG_ON(lock->owner != current);
+	}
+}
+
+static inline void six_clear_owner(struct six_lock *lock, enum six_lock_type type)
+{
+	if (type != SIX_LOCK_intent)
+		return;
+
+	EBUG_ON(lock->owner != current);
+
+	if (lock->state.intent_lock == 1)
+		lock->owner = NULL;
+}
+
+static __always_inline bool do_six_trylock_type(struct six_lock *lock,
+						enum six_lock_type type)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+	union six_lock_state old;
+	u64 v = READ_ONCE(lock->state.v);
+
+	EBUG_ON(type == SIX_LOCK_write && lock->owner != current);
+
+	do {
+		old.v = v;
+
+		EBUG_ON(type == SIX_LOCK_write &&
+			((old.v & __SIX_LOCK_HELD_write) ||
+			 !(old.v & __SIX_LOCK_HELD_intent)));
+
+		if (old.v & l[type].lock_fail)
+			return false;
+	} while ((v = atomic64_cmpxchg_acquire(&lock->state.counter,
+				old.v,
+				old.v + l[type].lock_val)) != old.v);
+
+	six_set_owner(lock, type, old);
+	return true;
+}
+
+__always_inline __flatten
+static bool __six_trylock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	if (!do_six_trylock_type(lock, type))
+		return false;
+
+	six_acquire(&lock->dep_map, 1);
+	return true;
+}
+
+__always_inline __flatten
+static bool __six_relock_type(struct six_lock *lock, enum six_lock_type type,
+			      unsigned seq)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+	union six_lock_state old;
+	u64 v = READ_ONCE(lock->state.v);
+
+	do {
+		old.v = v;
+
+		if (old.seq != seq || old.v & l[type].lock_fail)
+			return false;
+	} while ((v = atomic64_cmpxchg_acquire(&lock->state.counter,
+				old.v,
+				old.v + l[type].lock_val)) != old.v);
+
+	six_set_owner(lock, type, old);
+	six_acquire(&lock->dep_map, 1);
+	return true;
+}
+
+struct six_lock_waiter {
+	struct list_head	list;
+	struct task_struct	*task;
+};
+
+/* This is probably up there with the more evil things I've done */
+#define waitlist_bitnr(id) ilog2((((union six_lock_state) { .waiters = 1 << (id) }).l))
+
+#ifdef CONFIG_LOCK_SPIN_ON_OWNER
+
+static inline int six_can_spin_on_owner(struct six_lock *lock)
+{
+	struct task_struct *owner;
+	int retval = 1;
+
+	if (need_resched())
+		return 0;
+
+	rcu_read_lock();
+	owner = READ_ONCE(lock->owner);
+	if (owner)
+		retval = owner->on_cpu;
+	rcu_read_unlock();
+	/*
+	 * if lock->owner is not set, the mutex owner may have just acquired
+	 * it and not set the owner yet or the mutex has been released.
+	 */
+	return retval;
+}
+
+static inline bool six_spin_on_owner(struct six_lock *lock,
+				     struct task_struct *owner)
+{
+	bool ret = true;
+
+	rcu_read_lock();
+	while (lock->owner == owner) {
+		/*
+		 * Ensure we emit the owner->on_cpu, dereference _after_
+		 * checking lock->owner still matches owner. If that fails,
+		 * owner might point to freed memory. If it still matches,
+		 * the rcu_read_lock() ensures the memory stays valid.
+		 */
+		barrier();
+
+		if (!owner->on_cpu || need_resched()) {
+			ret = false;
+			break;
+		}
+
+		cpu_relax();
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static inline bool six_optimistic_spin(struct six_lock *lock, enum six_lock_type type)
+{
+	struct task_struct *task = current;
+
+	if (type == SIX_LOCK_write)
+		return false;
+
+	preempt_disable();
+	if (!six_can_spin_on_owner(lock))
+		goto fail;
+
+	if (!osq_lock(&lock->osq))
+		goto fail;
+
+	while (1) {
+		struct task_struct *owner;
+
+		/*
+		 * If there's an owner, wait for it to either
+		 * release the lock or go to sleep.
+		 */
+		owner = READ_ONCE(lock->owner);
+		if (owner && !six_spin_on_owner(lock, owner))
+			break;
+
+		if (do_six_trylock_type(lock, type)) {
+			osq_unlock(&lock->osq);
+			preempt_enable();
+			return true;
+		}
+
+		/*
+		 * When there's no owner, we might have preempted between the
+		 * owner acquiring the lock and setting the owner field. If
+		 * we're an RT task that will live-lock because we won't let
+		 * the owner complete.
+		 */
+		if (!owner && (need_resched() || rt_task(task)))
+			break;
+
+		/*
+		 * The cpu_relax() call is a compiler barrier which forces
+		 * everything in this loop to be re-loaded. We don't need
+		 * memory barriers as we'll eventually observe the right
+		 * values at the cost of a few extra spins.
+		 */
+		cpu_relax();
+	}
+
+	osq_unlock(&lock->osq);
+fail:
+	preempt_enable();
+
+	/*
+	 * If we fell out of the spin path because of need_resched(),
+	 * reschedule now, before we try-lock again. This avoids getting
+	 * scheduled out right after we obtained the lock.
+	 */
+	if (need_resched())
+		schedule();
+
+	return false;
+}
+
+#else /* CONFIG_LOCK_SPIN_ON_OWNER */
+
+static inline bool six_optimistic_spin(struct six_lock *lock, enum six_lock_type type)
+{
+	return false;
+}
+
+#endif
+
+noinline
+static void __six_lock_type_slowpath(struct six_lock *lock, enum six_lock_type type)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+	union six_lock_state old, new;
+	struct six_lock_waiter wait;
+	u64 v;
+
+	if (six_optimistic_spin(lock, type))
+		return;
+
+	lock_contended(&lock->dep_map, _RET_IP_);
+
+	INIT_LIST_HEAD(&wait.list);
+	wait.task = current;
+
+	while (1) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (type == SIX_LOCK_write)
+			EBUG_ON(lock->owner != current);
+		else if (list_empty_careful(&wait.list)) {
+			raw_spin_lock(&lock->wait_lock);
+			list_add_tail(&wait.list, &lock->wait_list[type]);
+			raw_spin_unlock(&lock->wait_lock);
+		}
+
+		v = READ_ONCE(lock->state.v);
+		do {
+			new.v = old.v = v;
+
+			if (!(old.v & l[type].lock_fail))
+				new.v += l[type].lock_val;
+			else if (!(new.waiters & (1 << type)))
+				new.waiters |= 1 << type;
+			else
+				break; /* waiting bit already set */
+		} while ((v = atomic64_cmpxchg_acquire(&lock->state.counter,
+					old.v, new.v)) != old.v);
+
+		if (!(old.v & l[type].lock_fail))
+			break;
+
+		schedule();
+	}
+
+	six_set_owner(lock, type, old);
+
+	__set_current_state(TASK_RUNNING);
+
+	if (!list_empty_careful(&wait.list)) {
+		raw_spin_lock(&lock->wait_lock);
+		list_del_init(&wait.list);
+		raw_spin_unlock(&lock->wait_lock);
+	}
+}
+
+__always_inline
+static void __six_lock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	six_acquire(&lock->dep_map, 0);
+
+	if (!do_six_trylock_type(lock, type))
+		__six_lock_type_slowpath(lock, type);
+
+	lock_acquired(&lock->dep_map, _RET_IP_);
+}
+
+static inline void six_lock_wakeup(struct six_lock *lock,
+				   union six_lock_state state,
+				   unsigned waitlist_id)
+{
+	struct list_head *wait_list = &lock->wait_list[waitlist_id];
+	struct six_lock_waiter *w, *next;
+
+	if (waitlist_id == SIX_LOCK_write && state.read_lock)
+		return;
+
+	if (!(state.waiters & (1 << waitlist_id)))
+		return;
+
+	clear_bit(waitlist_bitnr(waitlist_id),
+		  (unsigned long *) &lock->state.v);
+
+	if (waitlist_id == SIX_LOCK_write) {
+		struct task_struct *p = READ_ONCE(lock->owner);
+
+		if (p)
+			wake_up_process(p);
+		return;
+	}
+
+	raw_spin_lock(&lock->wait_lock);
+
+	list_for_each_entry_safe(w, next, wait_list, list) {
+		list_del_init(&w->list);
+
+		if (wake_up_process(w->task) &&
+		    waitlist_id != SIX_LOCK_read) {
+			if (!list_empty(wait_list))
+				set_bit(waitlist_bitnr(waitlist_id),
+					(unsigned long *) &lock->state.v);
+			break;
+		}
+	}
+
+	raw_spin_unlock(&lock->wait_lock);
+}
+
+__always_inline __flatten
+static void __six_unlock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+	union six_lock_state state;
+
+	EBUG_ON(!(lock->state.v & l[type].held_mask));
+	EBUG_ON(type == SIX_LOCK_write &&
+		!(lock->state.v & __SIX_LOCK_HELD_intent));
+
+	six_clear_owner(lock, type);
+
+	state.v = atomic64_add_return_release(l[type].unlock_val,
+					      &lock->state.counter);
+	six_release(&lock->dep_map);
+	six_lock_wakeup(lock, state, l[type].unlock_wakeup);
+}
+
+#ifdef SIX_LOCK_SEPARATE_LOCKFNS
+
+#define __SIX_LOCK(type)						\
+bool six_trylock_##type(struct six_lock *lock)				\
+{									\
+	return __six_trylock_type(lock, SIX_LOCK_##type);		\
+}									\
+									\
+bool six_relock_##type(struct six_lock *lock, u32 seq)			\
+{									\
+	return __six_relock_type(lock, SIX_LOCK_##type, seq);		\
+}									\
+									\
+void six_lock_##type(struct six_lock *lock)				\
+{									\
+	__six_lock_type(lock, SIX_LOCK_##type);				\
+}									\
+									\
+void six_unlock_##type(struct six_lock *lock)				\
+{									\
+	__six_unlock_type(lock, SIX_LOCK_##type);			\
+}
+
+__SIX_LOCK(read)
+__SIX_LOCK(intent)
+__SIX_LOCK(write)
+
+#undef __SIX_LOCK
+
+#else
+
+bool six_trylock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	return __six_trylock_type(lock, type);
+}
+
+bool six_relock_type(struct six_lock *lock, enum six_lock_type type,
+		     unsigned seq)
+{
+	return __six_relock_type(lock, type, seq);
+
+}
+
+void six_lock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	__six_lock_type(lock, type);
+}
+
+void six_unlock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	__six_unlock_type(lock, type);
+}
+
+#endif
+
+/* Convert from intent to read: */
+void six_lock_downgrade(struct six_lock *lock)
+{
+	six_lock_increment(lock, SIX_LOCK_read);
+	six_unlock_intent(lock);
+}
+
+bool six_lock_tryupgrade(struct six_lock *lock)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+	union six_lock_state old, new;
+	u64 v = READ_ONCE(lock->state.v);
+
+	do {
+		new.v = old.v = v;
+
+		EBUG_ON(!(old.v & l[SIX_LOCK_read].held_mask));
+
+		new.v += l[SIX_LOCK_read].unlock_val;
+
+		if (new.v & l[SIX_LOCK_intent].lock_fail)
+			return false;
+
+		new.v += l[SIX_LOCK_intent].lock_val;
+	} while ((v = atomic64_cmpxchg_acquire(&lock->state.counter,
+				old.v, new.v)) != old.v);
+
+	six_set_owner(lock, SIX_LOCK_intent, old);
+	six_lock_wakeup(lock, new, l[SIX_LOCK_read].unlock_wakeup);
+
+	return true;
+}
+
+bool six_trylock_convert(struct six_lock *lock,
+			 enum six_lock_type from,
+			 enum six_lock_type to)
+{
+	EBUG_ON(to == SIX_LOCK_write || from == SIX_LOCK_write);
+
+	if (to == from)
+		return true;
+
+	if (to == SIX_LOCK_read) {
+		six_lock_downgrade(lock);
+		return true;
+	} else {
+		return six_lock_tryupgrade(lock);
+	}
+}
+
+/*
+ * Increment read/intent lock count, assuming we already have it read or intent
+ * locked:
+ */
+void six_lock_increment(struct six_lock *lock, enum six_lock_type type)
+{
+	const struct six_lock_vals l[] = LOCK_VALS;
+
+	EBUG_ON(type == SIX_LOCK_write);
+	six_acquire(&lock->dep_map, 0);
+
+	/* XXX: assert already locked, and that we don't overflow: */
+
+	atomic64_add(l[type].lock_val, &lock->state.counter);
+}
diff --git a/fs/bcachefs/six.h b/fs/bcachefs/six.h
new file mode 100644
index 0000000000..f518c64c40
--- /dev/null
+++ b/fs/bcachefs/six.h
@@ -0,0 +1,190 @@ 
+#ifndef _BCACHEFS_SIX_H
+#define _BCACHEFS_SIX_H
+
+#include <linux/lockdep.h>
+#include <linux/osq_lock.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+
+#include "util.h"
+
+#define SIX_LOCK_SEPARATE_LOCKFNS
+
+/*
+ * LOCK STATES:
+ *
+ * read, intent, write (i.e. shared/intent/exclusive, hence the name)
+ *
+ * read and write work as with normal read/write locks - a lock can have
+ * multiple readers, but write excludes reads and other write locks.
+ *
+ * Intent does not block read, but it does block other intent locks. The idea is
+ * by taking an intent lock, you can then later upgrade to a write lock without
+ * dropping your read lock and without deadlocking - because no other thread has
+ * the intent lock and thus no other thread could be trying to take the write
+ * lock.
+ */
+
+union six_lock_state {
+	struct {
+		atomic64_t	counter;
+	};
+
+	struct {
+		u64		v;
+	};
+
+	struct {
+		/* for waitlist_bitnr() */
+		unsigned long	l;
+	};
+
+	struct {
+		unsigned	read_lock:26;
+		unsigned	intent_lock:3;
+		unsigned	waiters:3;
+		/*
+		 * seq works much like in seqlocks: it's incremented every time
+		 * we lock and unlock for write.
+		 *
+		 * If it's odd write lock is held, even unlocked.
+		 *
+		 * Thus readers can unlock, and then lock again later iff it
+		 * hasn't been modified in the meantime.
+		 */
+		u32		seq;
+	};
+};
+
+#define SIX_LOCK_MAX_RECURSE	((1 << 3) - 1)
+
+enum six_lock_type {
+	SIX_LOCK_read,
+	SIX_LOCK_intent,
+	SIX_LOCK_write,
+};
+
+struct six_lock {
+	union six_lock_state	state;
+	struct task_struct	*owner;
+	struct optimistic_spin_queue osq;
+
+	raw_spinlock_t		wait_lock;
+	struct list_head	wait_list[2];
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map	dep_map;
+#endif
+};
+
+static __always_inline void __six_lock_init(struct six_lock *lock,
+					    const char *name,
+					    struct lock_class_key *key)
+{
+	atomic64_set(&lock->state.counter, 0);
+	raw_spin_lock_init(&lock->wait_lock);
+	INIT_LIST_HEAD(&lock->wait_list[SIX_LOCK_read]);
+	INIT_LIST_HEAD(&lock->wait_list[SIX_LOCK_intent]);
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	debug_check_no_locks_freed((void *) lock, sizeof(*lock));
+	lockdep_init_map(&lock->dep_map, name, key, 0);
+#endif
+}
+
+#define six_lock_init(lock)						\
+do {									\
+	static struct lock_class_key __key;				\
+									\
+	__six_lock_init((lock), #lock, &__key);				\
+} while (0)
+
+#define __SIX_VAL(field, _v)	(((union six_lock_state) { .field = _v }).v)
+
+#ifdef SIX_LOCK_SEPARATE_LOCKFNS
+
+#define __SIX_LOCK(type)						\
+bool six_trylock_##type(struct six_lock *);				\
+bool six_relock_##type(struct six_lock *, u32);				\
+void six_lock_##type(struct six_lock *);				\
+void six_unlock_##type(struct six_lock *);
+
+__SIX_LOCK(read)
+__SIX_LOCK(intent)
+__SIX_LOCK(write)
+#undef __SIX_LOCK
+
+#define SIX_LOCK_DISPATCH(type, fn, ...)			\
+	switch (type) {						\
+	case SIX_LOCK_read:					\
+		return fn##_read(__VA_ARGS__);			\
+	case SIX_LOCK_intent:					\
+		return fn##_intent(__VA_ARGS__);		\
+	case SIX_LOCK_write:					\
+		return fn##_write(__VA_ARGS__);			\
+	default:						\
+		BUG();						\
+	}
+
+static inline bool six_trylock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	SIX_LOCK_DISPATCH(type, six_trylock, lock);
+}
+
+static inline bool six_relock_type(struct six_lock *lock, enum six_lock_type type,
+		     unsigned seq)
+{
+	SIX_LOCK_DISPATCH(type, six_relock, lock, seq);
+}
+
+static inline void six_lock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	SIX_LOCK_DISPATCH(type, six_lock, lock);
+}
+
+static inline void six_unlock_type(struct six_lock *lock, enum six_lock_type type)
+{
+	SIX_LOCK_DISPATCH(type, six_unlock, lock);
+}
+
+#else
+
+bool six_trylock_type(struct six_lock *, enum six_lock_type);
+bool six_relock_type(struct six_lock *, enum six_lock_type, unsigned);
+void six_lock_type(struct six_lock *, enum six_lock_type);
+void six_unlock_type(struct six_lock *, enum six_lock_type);
+
+#define __SIX_LOCK(type)						\
+static __always_inline bool six_trylock_##type(struct six_lock *lock)	\
+{									\
+	return six_trylock_type(lock, SIX_LOCK_##type);			\
+}									\
+									\
+static __always_inline bool six_relock_##type(struct six_lock *lock, u32 seq)\
+{									\
+	return six_relock_type(lock, SIX_LOCK_##type, seq);		\
+}									\
+									\
+static __always_inline void six_lock_##type(struct six_lock *lock)	\
+{									\
+	six_lock_type(lock, SIX_LOCK_##type);				\
+}									\
+									\
+static __always_inline void six_unlock_##type(struct six_lock *lock)	\
+{									\
+	six_unlock_type(lock, SIX_LOCK_##type);				\
+}
+
+__SIX_LOCK(read)
+__SIX_LOCK(intent)
+__SIX_LOCK(write)
+#undef __SIX_LOCK
+
+#endif
+
+void six_lock_downgrade(struct six_lock *);
+bool six_lock_tryupgrade(struct six_lock *);
+bool six_trylock_convert(struct six_lock *, enum six_lock_type,
+			 enum six_lock_type);
+
+void six_lock_increment(struct six_lock *, enum six_lock_type);
+
+#endif /* _BCACHEFS_SIX_H */