17  * Lockdep class keys for extent_buffer->lock's in this root.  For a given
27  * Lock-nesting across peer nodes is always done with the immediate parent
93 	lockdep_set_class_and_name(&eb->lock, &ks->keys[level], ks->names[level]);  in btrfs_set_buffer_lockdep_class()
124  * - try-lock semantics for readers and writers
131  * btrfs_tree_read_lock_nested - lock extent buffer for read
135  * This takes the read lock on the extent buffer, using the specified nesting
145 	down_read_nested(&eb->lock, nest);  in btrfs_tree_read_lock_nested()
150  * Try-lock for read.
156 	if (down_read_trylock(&eb->lock)) {  in btrfs_try_tree_read_lock()
164  * Release read lock.
169 	up_read(&eb->lock);  in btrfs_tree_read_unlock()
173  * Lock eb for write.
175  * @eb:		the eb to lock
176  * @nest:	the nesting to use for the lock
178  * Returns with the eb->lock write locked.
181 	__acquires(&eb->lock)  in btrfs_tree_lock_nested()
188 	down_write_nested(&eb->lock, nest);  in btrfs_tree_lock_nested()
194  * Release the write lock.
200 	up_write(&eb->lock);  in btrfs_tree_unlock()
207  * btrfs_search_slot will keep the lock held on higher nodes in a few corner
231  * we end up with a lock on the root node.
233  * Return: root extent buffer with write lock held
254  * we end up with a lock on the root node.
256  * Return: root extent buffer with read lock held
277  * nowait mode until we end up with a lock on the root node or returning to
280  * Return: root extent buffer with read lock held or -EAGAIN.
304  * DREW stands for double-reader-writer-exclusion lock. It's used in situation
308  * writer both race to acquire their respective sides of the lock the writer
309  * would yield its lock as soon as it detects a concurrent reader. Additionally
311  * acquire the lock.
314 void btrfs_drew_lock_init(struct btrfs_drew_lock *lock)  in btrfs_drew_lock_init()  argument
316 	atomic_set(&lock->readers, 0);  in btrfs_drew_lock_init()
317 	atomic_set(&lock->writers, 0);  in btrfs_drew_lock_init()
318 	init_waitqueue_head(&lock->pending_readers);  in btrfs_drew_lock_init()
319 	init_waitqueue_head(&lock->pending_writers);  in btrfs_drew_lock_init()
323 bool btrfs_drew_try_write_lock(struct btrfs_drew_lock *lock)  in btrfs_drew_try_write_lock()  argument
325 	if (atomic_read(&lock->readers))  in btrfs_drew_try_write_lock()
328 	atomic_inc(&lock->writers);  in btrfs_drew_try_write_lock()
332 	if (atomic_read(&lock->readers)) {  in btrfs_drew_try_write_lock()
333 		btrfs_drew_write_unlock(lock);  in btrfs_drew_try_write_lock()
340 void btrfs_drew_write_lock(struct btrfs_drew_lock *lock)  in btrfs_drew_write_lock()  argument
343 		if (btrfs_drew_try_write_lock(lock))  in btrfs_drew_write_lock()
345 		wait_event(lock->pending_writers, !atomic_read(&lock->readers));  in btrfs_drew_write_lock()
349 void btrfs_drew_write_unlock(struct btrfs_drew_lock *lock)  in btrfs_drew_write_unlock()  argument
355 	if (atomic_dec_and_test(&lock->writers))  in btrfs_drew_write_unlock()
356 		wake_up(&lock->pending_readers);  in btrfs_drew_write_unlock()
359 void btrfs_drew_read_lock(struct btrfs_drew_lock *lock)  in btrfs_drew_read_lock()  argument
361 	atomic_inc(&lock->readers);  in btrfs_drew_read_lock()
371 	wait_event(lock->pending_readers, atomic_read(&lock->writers) == 0);  in btrfs_drew_read_lock()
374 void btrfs_drew_read_unlock(struct btrfs_drew_lock *lock)  in btrfs_drew_read_unlock()  argument
380 	if (atomic_dec_and_test(&lock->readers))  in btrfs_drew_read_unlock()
381 		wake_up(&lock->pending_writers);  in btrfs_drew_read_unlock()