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diff --git a/c_src/libbcachefs/six.h b/c_src/libbcachefs/six.h
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-/* SPDX-License-Identifier: GPL-2.0 */
-
-#ifndef _LINUX_SIX_H
-#define _LINUX_SIX_H
-
-/**
- * DOC: SIX locks overview
- *
- * Shared/intent/exclusive locks: sleepable read/write locks, like rw semaphores
- * but with an additional state: read/shared, intent, exclusive/write
- *
- * The purpose of the intent state is to allow for greater concurrency on tree
- * structures without deadlocking. In general, a read can't be upgraded to a
- * write lock without deadlocking, so an operation that updates multiple nodes
- * will have to take write locks for the full duration of the operation.
- *
- * But by adding an intent state, which is exclusive with other intent locks but
- * not with readers, we can take intent locks at the start of the operation,
- * and then take write locks only for the actual update to each individual
- * nodes, without deadlocking.
- *
- * Example usage:
- *   six_lock_read(&foo->lock);
- *   six_unlock_read(&foo->lock);
- *
- * An intent lock must be held before taking a write lock:
- *   six_lock_intent(&foo->lock);
- *   six_lock_write(&foo->lock);
- *   six_unlock_write(&foo->lock);
- *   six_unlock_intent(&foo->lock);
- *
- * Other operations:
- *   six_trylock_read()
- *   six_trylock_intent()
- *   six_trylock_write()
- *
- *   six_lock_downgrade()	convert from intent to read
- *   six_lock_tryupgrade()	attempt to convert from read to intent, may fail
- *
- * There are also interfaces that take the lock type as an enum:
- *
- *   six_lock_type(&foo->lock, SIX_LOCK_read);
- *   six_trylock_convert(&foo->lock, SIX_LOCK_read, SIX_LOCK_intent)
- *   six_lock_type(&foo->lock, SIX_LOCK_write);
- *   six_unlock_type(&foo->lock, SIX_LOCK_write);
- *   six_unlock_type(&foo->lock, SIX_LOCK_intent);
- *
- * Lock sequence numbers - unlock(), relock():
- *
- *   Locks embed sequences numbers, which are incremented on write lock/unlock.
- *   This allows locks to be dropped and the retaken iff the state they protect
- *   hasn't changed; this makes it much easier to avoid holding locks while e.g.
- *   doing IO or allocating memory.
- *
- *   Example usage:
- *     six_lock_read(&foo->lock);
- *     u32 seq = six_lock_seq(&foo->lock);
- *     six_unlock_read(&foo->lock);
- *
- *     some_operation_that_may_block();
- *
- *     if (six_relock_read(&foo->lock, seq)) { ... }
- *
- *   If the relock operation succeeds, it is as if the lock was never unlocked.
- *
- * Reentrancy:
- *
- *   Six locks are not by themselves reentrant, but have counters for both the
- *   read and intent states that can be used to provide reentrancy by an upper
- *   layer that tracks held locks. If a lock is known to already be held in the
- *   read or intent state, six_lock_increment() can be used to bump the "lock
- *   held in this state" counter, increasing the number of unlock calls that
- *   will be required to fully unlock it.
- *
- *   Example usage:
- *     six_lock_read(&foo->lock);
- *     six_lock_increment(&foo->lock, SIX_LOCK_read);
- *     six_unlock_read(&foo->lock);
- *     six_unlock_read(&foo->lock);
- *   foo->lock is now fully unlocked.
- *
- *   Since the intent state supercedes read, it's legal to increment the read
- *   counter when holding an intent lock, but not the reverse.
- *
- *   A lock may only be held once for write: six_lock_increment(.., SIX_LOCK_write)
- *   is not legal.
- *
- * should_sleep_fn:
- *
- *   There is a six_lock() variant that takes a function pointer that is called
- *   immediately prior to schedule() when blocking, and may return an error to
- *   abort.
- *
- *   One possible use for this feature is when objects being locked are part of
- *   a cache and may reused, and lock ordering is based on a property of the
- *   object that will change when the object is reused - i.e. logical key order.
- *
- *   If looking up an object in the cache may race with object reuse, and lock
- *   ordering is required to prevent deadlock, object reuse may change the
- *   correct lock order for that object and cause a deadlock. should_sleep_fn
- *   can be used to check if the object is still the object we want and avoid
- *   this deadlock.
- *
- * Wait list entry interface:
- *
- *   There is a six_lock() variant, six_lock_waiter(), that takes a pointer to a
- *   wait list entry. By embedding six_lock_waiter into another object, and by
- *   traversing lock waitlists, it is then possible for an upper layer to
- *   implement full cycle detection for deadlock avoidance.
- *
- *   should_sleep_fn should be used for invoking the cycle detector, walking the
- *   graph of held locks to check for a deadlock. The upper layer must track
- *   held locks for each thread, and each thread's held locks must be reachable
- *   from its six_lock_waiter object.
- *
- *   six_lock_waiter() will add the wait object to the waitlist re-trying taking
- *   the lock, and before calling should_sleep_fn, and the wait object will not
- *   be removed from the waitlist until either the lock has been successfully
- *   acquired, or we aborted because should_sleep_fn returned an error.
- *
- *   Also, six_lock_waiter contains a timestamp, and waiters on a waitlist will
- *   have timestamps in strictly ascending order - this is so the timestamp can
- *   be used as a cursor for lock graph traverse.
- */
-
-#include <linux/lockdep.h>
-#include <linux/sched.h>
-#include <linux/types.h>
-
-enum six_lock_type {
-	SIX_LOCK_read,
-	SIX_LOCK_intent,
-	SIX_LOCK_write,
-};
-
-struct six_lock {
-	atomic_t		state;
-	u32			seq;
-	unsigned		intent_lock_recurse;
-	struct task_struct	*owner;
-	unsigned __percpu	*readers;
-	raw_spinlock_t		wait_lock;
-	struct list_head	wait_list;
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-	struct lockdep_map	dep_map;
-#endif
-};
-
-struct six_lock_waiter {
-	struct list_head	list;
-	struct task_struct	*task;
-	enum six_lock_type	lock_want;
-	bool			lock_acquired;
-	u64			start_time;
-};
-
-typedef int (*six_lock_should_sleep_fn)(struct six_lock *lock, void *);
-
-void six_lock_exit(struct six_lock *lock);
-
-enum six_lock_init_flags {
-	SIX_LOCK_INIT_PCPU	= 1U << 0,
-};
-
-void __six_lock_init(struct six_lock *lock, const char *name,
-		     struct lock_class_key *key, enum six_lock_init_flags flags);
-
-/**
- * six_lock_init - initialize a six lock
- * @lock:	lock to initialize
- * @flags:	optional flags, i.e. SIX_LOCK_INIT_PCPU
- */
-#define six_lock_init(lock, flags)					\
-do {									\
-	static struct lock_class_key __key;				\
-									\
-	__six_lock_init((lock), #lock, &__key, flags);			\
-} while (0)
-
-/**
- * six_lock_seq - obtain current lock sequence number
- * @lock:	six_lock to obtain sequence number for
- *
- * @lock should be held for read or intent, and not write
- *
- * By saving the lock sequence number, we can unlock @lock and then (typically
- * after some blocking operation) attempt to relock it: the relock will succeed
- * if the sequence number hasn't changed, meaning no write locks have been taken
- * and state corresponding to what @lock protects is still valid.
- */
-static inline u32 six_lock_seq(const struct six_lock *lock)
-{
-	return lock->seq;
-}
-
-bool six_trylock_ip(struct six_lock *lock, enum six_lock_type type, unsigned long ip);
-
-/**
- * six_trylock_type - attempt to take a six lock without blocking
- * @lock:	lock to take
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- *
- * Return: true on success, false on failure.
- */
-static inline bool six_trylock_type(struct six_lock *lock, enum six_lock_type type)
-{
-	return six_trylock_ip(lock, type, _THIS_IP_);
-}
-
-int six_lock_ip_waiter(struct six_lock *lock, enum six_lock_type type,
-		       struct six_lock_waiter *wait,
-		       six_lock_should_sleep_fn should_sleep_fn, void *p,
-		       unsigned long ip);
-
-/**
- * six_lock_waiter - take a lock, with full waitlist interface
- * @lock:	lock to take
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @wait:	pointer to wait object, which will be added to lock's waitlist
- * @should_sleep_fn: callback run after adding to waitlist, immediately prior
- *		to scheduling
- * @p:		passed through to @should_sleep_fn
- *
- * This is a convenience wrapper around six_lock_ip_waiter(), see that function
- * for full documentation.
- *
- * Return: 0 on success, or the return code from @should_sleep_fn on failure.
- */
-static inline int six_lock_waiter(struct six_lock *lock, enum six_lock_type type,
-				  struct six_lock_waiter *wait,
-				  six_lock_should_sleep_fn should_sleep_fn, void *p)
-{
-	return six_lock_ip_waiter(lock, type, wait, should_sleep_fn, p, _THIS_IP_);
-}
-
-/**
- * six_lock_ip - take a six lock lock
- * @lock:	lock to take
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @should_sleep_fn: callback run after adding to waitlist, immediately prior
- *		to scheduling
- * @p:		passed through to @should_sleep_fn
- * @ip:		ip parameter for lockdep/lockstat, i.e. _THIS_IP_
- *
- * Return: 0 on success, or the return code from @should_sleep_fn on failure.
- */
-static inline int six_lock_ip(struct six_lock *lock, enum six_lock_type type,
-			      six_lock_should_sleep_fn should_sleep_fn, void *p,
-			      unsigned long ip)
-{
-	struct six_lock_waiter wait;
-
-	return six_lock_ip_waiter(lock, type, &wait, should_sleep_fn, p, ip);
-}
-
-/**
- * six_lock_type - take a six lock lock
- * @lock:	lock to take
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @should_sleep_fn: callback run after adding to waitlist, immediately prior
- *		to scheduling
- * @p:		passed through to @should_sleep_fn
- *
- * Return: 0 on success, or the return code from @should_sleep_fn on failure.
- */
-static inline int six_lock_type(struct six_lock *lock, enum six_lock_type type,
-				six_lock_should_sleep_fn should_sleep_fn, void *p)
-{
-	struct six_lock_waiter wait;
-
-	return six_lock_ip_waiter(lock, type, &wait, should_sleep_fn, p, _THIS_IP_);
-}
-
-bool six_relock_ip(struct six_lock *lock, enum six_lock_type type,
-		   unsigned seq, unsigned long ip);
-
-/**
- * six_relock_type - attempt to re-take a lock that was held previously
- * @lock:	lock to take
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- * @seq:	lock sequence number obtained from six_lock_seq() while lock was
- *		held previously
- *
- * Return: true on success, false on failure.
- */
-static inline bool six_relock_type(struct six_lock *lock, enum six_lock_type type,
-				   unsigned seq)
-{
-	return six_relock_ip(lock, type, seq, _THIS_IP_);
-}
-
-void six_unlock_ip(struct six_lock *lock, enum six_lock_type type, unsigned long ip);
-
-/**
- * six_unlock_type - drop a six lock
- * @lock:	lock to unlock
- * @type:	SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write
- *
- * When a lock is held multiple times (because six_lock_incement()) was used),
- * this decrements the 'lock held' counter by one.
- *
- * For example:
- * six_lock_read(&foo->lock);				read count 1
- * six_lock_increment(&foo->lock, SIX_LOCK_read);	read count 2
- * six_lock_unlock(&foo->lock, SIX_LOCK_read);		read count 1
- * six_lock_unlock(&foo->lock, SIX_LOCK_read);		read count 0
- */
-static inline void six_unlock_type(struct six_lock *lock, enum six_lock_type type)
-{
-	six_unlock_ip(lock, type, _THIS_IP_);
-}
-
-#define __SIX_LOCK(type)						\
-static inline bool six_trylock_ip_##type(struct six_lock *lock, unsigned long ip)\
-{									\
-	return six_trylock_ip(lock, SIX_LOCK_##type, ip);		\
-}									\
-									\
-static inline bool six_trylock_##type(struct six_lock *lock)		\
-{									\
-	return six_trylock_ip(lock, SIX_LOCK_##type, _THIS_IP_);	\
-}									\
-									\
-static inline int six_lock_ip_waiter_##type(struct six_lock *lock,	\
-			   struct six_lock_waiter *wait,		\
-			   six_lock_should_sleep_fn should_sleep_fn, void *p,\
-			   unsigned long ip)				\
-{									\
-	return six_lock_ip_waiter(lock, SIX_LOCK_##type, wait, should_sleep_fn, p, ip);\
-}									\
-									\
-static inline int six_lock_ip_##type(struct six_lock *lock,		\
-		    six_lock_should_sleep_fn should_sleep_fn, void *p,	\
-		    unsigned long ip)					\
-{									\
-	return six_lock_ip(lock, SIX_LOCK_##type, should_sleep_fn, p, ip);\
-}									\
-									\
-static inline bool six_relock_ip_##type(struct six_lock *lock, u32 seq, unsigned long ip)\
-{									\
-	return six_relock_ip(lock, SIX_LOCK_##type, seq, ip);		\
-}									\
-									\
-static inline bool six_relock_##type(struct six_lock *lock, u32 seq)	\
-{									\
-	return six_relock_ip(lock, SIX_LOCK_##type, seq, _THIS_IP_);	\
-}									\
-									\
-static inline int six_lock_##type(struct six_lock *lock,		\
-				  six_lock_should_sleep_fn fn, void *p)\
-{									\
-	return six_lock_ip_##type(lock, fn, p, _THIS_IP_);		\
-}									\
-									\
-static inline void six_unlock_ip_##type(struct six_lock *lock, unsigned long ip)	\
-{									\
-	six_unlock_ip(lock, SIX_LOCK_##type, ip);			\
-}									\
-									\
-static inline void six_unlock_##type(struct six_lock *lock)		\
-{									\
-	six_unlock_ip(lock, SIX_LOCK_##type, _THIS_IP_);		\
-}
-
-__SIX_LOCK(read)
-__SIX_LOCK(intent)
-__SIX_LOCK(write)
-#undef __SIX_LOCK
-
-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);
-
-void six_lock_wakeup_all(struct six_lock *);
-
-struct six_lock_count {
-	unsigned n[3];
-};
-
-struct six_lock_count six_lock_counts(struct six_lock *);
-void six_lock_readers_add(struct six_lock *, int);
-
-#endif /* _LINUX_SIX_H */