fs/btrfs/delayed-ref.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (C) 2008 Oracle.  All rights reserved.
  */

 #ifndef BTRFS_DELAYED_REF_H
 #define BTRFS_DELAYED_REF_H

 #include <linux/refcount.h>

 /* these are the possible values of struct btrfs_delayed_ref_node->action */
 #define BTRFS_ADD_DELAYED_REF    1 /* add one backref to the tree */
 #define BTRFS_DROP_DELAYED_REF   2 /* delete one backref from the tree */
 #define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
 #define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */

 struct btrfs_delayed_ref_node {
 	struct rb_node ref_node;
 	/*
 	 * If action is BTRFS_ADD_DELAYED_REF, also link this node to
 	 * ref_head->ref_add_list, then we do not need to iterate the
 	 * whole ref_head->ref_list to find BTRFS_ADD_DELAYED_REF nodes.
 	 */
 	struct list_head add_list;

 	/* the starting bytenr of the extent */
 	u64 bytenr;

 	/* the size of the extent */
 	u64 num_bytes;

 	/* seq number to keep track of insertion order */
 	u64 seq;

 	/* ref count on this data structure */
 	refcount_t refs;

 	/*
 	 * how many refs is this entry adding or deleting.  For
 	 * head refs, this may be a negative number because it is keeping
 	 * track of the total mods done to the reference count.
 	 * For individual refs, this will always be a positive number
 	 *
 	 * It may be more than one, since it is possible for a single
 	 * parent to have more than one ref on an extent
 	 */
 	int ref_mod;

 	unsigned int action:8;
 	unsigned int type:8;
 	/* is this node still in the rbtree? */
 	unsigned int is_head:1;
 	unsigned int in_tree:1;
 };

 struct btrfs_delayed_extent_op {
 	struct btrfs_disk_key key;
 	u8 level;
 	bool update_key;
 	bool update_flags;
 	bool is_data;
 	u64 flags_to_set;
 };

 /*
  * the head refs are used to hold a lock on a given extent, which allows us
  * to make sure that only one process is running the delayed refs
  * at a time for a single extent.  They also store the sum of all the
  * reference count modifications we've queued up.
  */
 struct btrfs_delayed_ref_head {
 	u64 bytenr;
 	u64 num_bytes;
 	refcount_t refs;
 	/*
 	 * the mutex is held while running the refs, and it is also
 	 * held when checking the sum of reference modifications.
 	 */
 	struct mutex mutex;

 	spinlock_t lock;
 	struct rb_root_cached ref_tree;
 	/* accumulate add BTRFS_ADD_DELAYED_REF nodes to this ref_add_list. */
 	struct list_head ref_add_list;

 	struct rb_node href_node;

 	struct btrfs_delayed_extent_op *extent_op;

 	/*
 	 * This is used to track the final ref_mod from all the refs associated
 	 * with this head ref, this is not adjusted as delayed refs are run,
 	 * this is meant to track if we need to do the csum accounting or not.
 	 */
 	int total_ref_mod;

 	/*
 	 * This is the current outstanding mod references for this bytenr.  This
 	 * is used with lookup_extent_info to get an accurate reference count
 	 * for a bytenr, so it is adjusted as delayed refs are run so that any
 	 * on disk reference count + ref_mod is accurate.
 	 */
 	int ref_mod;

 	/*
 	 * when a new extent is allocated, it is just reserved in memory
 	 * The actual extent isn't inserted into the extent allocation tree
 	 * until the delayed ref is processed.  must_insert_reserved is
 	 * used to flag a delayed ref so the accounting can be updated
 	 * when a full insert is done.
 	 *
 	 * It is possible the extent will be freed before it is ever
 	 * inserted into the extent allocation tree.  In this case
 	 * we need to update the in ram accounting to properly reflect
 	 * the free has happened.
 	 */
 	unsigned int must_insert_reserved:1;
 	unsigned int is_data:1;
 	unsigned int is_system:1;
 	unsigned int processing:1;
 };

 struct btrfs_delayed_tree_ref {
 	struct btrfs_delayed_ref_node node;
 	u64 root;
 	u64 parent;
 	int level;
 };

 struct btrfs_delayed_data_ref {
 	struct btrfs_delayed_ref_node node;
 	u64 root;
 	u64 parent;
 	u64 objectid;
 	u64 offset;
 };

 struct btrfs_delayed_ref_root {
 	/* head ref rbtree */
 	struct rb_root_cached href_root;

 	/* dirty extent records */
 	struct rb_root dirty_extent_root;

 	/* this spin lock protects the rbtree and the entries inside */
 	spinlock_t lock;

 	/* how many delayed ref updates we've queued, used by the
 	 * throttling code
 	 */
 	atomic_t num_entries;

 	/* total number of head nodes in tree */
 	unsigned long num_heads;

 	/* total number of head nodes ready for processing */
 	unsigned long num_heads_ready;

 	u64 pending_csums;

 	/*
 	 * set when the tree is flushing before a transaction commit,
 	 * used by the throttling code to decide if new updates need
 	 * to be run right away
 	 */
 	int flushing;

 	u64 run_delayed_start;

 	/*
 	 * To make qgroup to skip given root.
 	 * This is for snapshot, as btrfs_qgroup_inherit() will manually
 	 * modify counters for snapshot and its source, so we should skip
 	 * the snapshot in new_root/old_roots or it will get calculated twice
 	 */
 	u64 qgroup_to_skip;
 };

 enum btrfs_ref_type {
 	BTRFS_REF_NOT_SET,
 	BTRFS_REF_DATA,
 	BTRFS_REF_METADATA,
 	BTRFS_REF_LAST,
 };

 struct btrfs_data_ref {
 	/* For EXTENT_DATA_REF */

 	/* Root which refers to this data extent */
 	u64 ref_root;

 	/* Inode which refers to this data extent */
 	u64 ino;

 	/*
 	 * file_offset - extent_offset
 	 *
 	 * file_offset is the key.offset of the EXTENT_DATA key.
 	 * extent_offset is btrfs_file_extent_offset() of the EXTENT_DATA data.
 	 */
 	u64 offset;
 };

 struct btrfs_tree_ref {
 	/*
 	 * Level of this tree block
 	 *
 	 * Shared for skinny (TREE_BLOCK_REF) and normal tree ref.
 	 */
 	int level;

 	/*
 	 * Root which refers to this tree block.
 	 *
 	 * For TREE_BLOCK_REF (skinny metadata, either inline or keyed)
 	 */
 	u64 root;

 	/* For non-skinny metadata, no special member needed */
 };

 struct btrfs_ref {
 	enum btrfs_ref_type type;
 	int action;

 	/*
 	 * Whether this extent should go through qgroup record.
 	 *
 	 * Normally false, but for certain cases like delayed subtree scan,
 	 * setting this flag can hugely reduce qgroup overhead.
 	 */
 	bool skip_qgroup;

 	/*
 	 * Optional. For which root is this modification.
 	 * Mostly used for qgroup optimization.
 	 *
 	 * When unset, data/tree ref init code will populate it.
 	 * In certain cases, we're modifying reference for a different root.
 	 * E.g. COW fs tree blocks for balance.
 	 * In that case, tree_ref::root will be fs tree, but we're doing this
 	 * for reloc tree, then we should set @real_root to reloc tree.
 	 */
 	u64 real_root;
 	u64 bytenr;
 	u64 len;

 	/* Bytenr of the parent tree block */
 	u64 parent;
 	union {
 		struct btrfs_data_ref data_ref;
 		struct btrfs_tree_ref tree_ref;
 	};
 };

 extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
 extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
 extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
 extern struct kmem_cache *btrfs_delayed_extent_op_cachep;

 int __init btrfs_delayed_ref_init(void);
 void __cold btrfs_delayed_ref_exit(void);

 static inline void btrfs_init_generic_ref(struct btrfs_ref *generic_ref,
 				int action, u64 bytenr, u64 len, u64 parent)
 {
 	generic_ref->action = action;
 	generic_ref->bytenr = bytenr;
 	generic_ref->len = len;
 	generic_ref->parent = parent;
 }

 static inline void btrfs_init_tree_ref(struct btrfs_ref *generic_ref,
 				int level, u64 root)
 {
 	/* If @real_root not set, use @root as fallback */
 	if (!generic_ref->real_root)
 		generic_ref->real_root = root;
 	generic_ref->tree_ref.level = level;
 	generic_ref->tree_ref.root = root;
 	generic_ref->type = BTRFS_REF_METADATA;
 }

 static inline void btrfs_init_data_ref(struct btrfs_ref *generic_ref,
 				u64 ref_root, u64 ino, u64 offset)
 {
 	/* If @real_root not set, use @root as fallback */
 	if (!generic_ref->real_root)
 		generic_ref->real_root = ref_root;
 	generic_ref->data_ref.ref_root = ref_root;
 	generic_ref->data_ref.ino = ino;
 	generic_ref->data_ref.offset = offset;
 	generic_ref->type = BTRFS_REF_DATA;
 }

 static inline struct btrfs_delayed_extent_op *
 btrfs_alloc_delayed_extent_op(void)
 {
 	return kmem_cache_alloc(btrfs_delayed_extent_op_cachep, GFP_NOFS);
 }

 static inline void
 btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
 {
 	if (op)
 		kmem_cache_free(btrfs_delayed_extent_op_cachep, op);
 }

 static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
 {
 	WARN_ON(refcount_read(&ref->refs) == 0);
 	if (refcount_dec_and_test(&ref->refs)) {
 		WARN_ON(ref->in_tree);
 		switch (ref->type) {
 		case BTRFS_TREE_BLOCK_REF_KEY:
 		case BTRFS_SHARED_BLOCK_REF_KEY:
 			kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
 			break;
 		case BTRFS_EXTENT_DATA_REF_KEY:
 		case BTRFS_SHARED_DATA_REF_KEY:
 			kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
 			break;
 		default:
 			BUG();
 		}
 	}
 }

 static inline void btrfs_put_delayed_ref_head(struct btrfs_delayed_ref_head *head)
 {
 	if (refcount_dec_and_test(&head->refs))
 		kmem_cache_free(btrfs_delayed_ref_head_cachep, head);
 }

 int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
 			       struct btrfs_ref *generic_ref,
 			       struct btrfs_delayed_extent_op *extent_op,
 			       int *old_ref_mod, int *new_ref_mod);
 int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
 			       struct btrfs_ref *generic_ref,
 			       u64 reserved, int *old_ref_mod,
 			       int *new_ref_mod);
 int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
 				u64 bytenr, u64 num_bytes,
 				struct btrfs_delayed_extent_op *extent_op);
 void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
 			      struct btrfs_delayed_ref_root *delayed_refs,
 			      struct btrfs_delayed_ref_head *head);

 struct btrfs_delayed_ref_head *
 btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
 			    u64 bytenr);
 int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
 			   struct btrfs_delayed_ref_head *head);
 static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
 {
 	mutex_unlock(&head->mutex);
 }
 void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
 			   struct btrfs_delayed_ref_head *head);

 struct btrfs_delayed_ref_head *btrfs_select_ref_head(
 		struct btrfs_delayed_ref_root *delayed_refs);

 int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq);

 void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr);
 void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans);
 int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
 				  enum btrfs_reserve_flush_enum flush);
 void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
 				       struct btrfs_block_rsv *src,
 				       u64 num_bytes);
 int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans);
 bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info);

 /*
  * helper functions to cast a node into its container
  */
 static inline struct btrfs_delayed_tree_ref *
 btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
 {
 	return container_of(node, struct btrfs_delayed_tree_ref, node);
 }

 static inline struct btrfs_delayed_data_ref *
 btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
 {
 	return container_of(node, struct btrfs_delayed_data_ref, node);
 }

 #endif
	/* SPDX-License-Identifier: GPL-2.0 */
	/*
	* Copyright (C) 2008 Oracle. All rights reserved.
	*/

	#ifndef BTRFS_DELAYED_REF_H
	#define BTRFS_DELAYED_REF_H

	#include <linux/refcount.h>

	/* these are the possible values of struct btrfs_delayed_ref_node->action */
	#define BTRFS_ADD_DELAYED_REF 1 /* add one backref to the tree */
	#define BTRFS_DROP_DELAYED_REF 2 /* delete one backref from the tree */
	#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
	#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */

	struct btrfs_delayed_ref_node {
	struct rb_node ref_node;
	/*
	* If action is BTRFS_ADD_DELAYED_REF, also link this node to
	* ref_head->ref_add_list, then we do not need to iterate the
	* whole ref_head->ref_list to find BTRFS_ADD_DELAYED_REF nodes.
	*/
	struct list_head add_list;

	/* the starting bytenr of the extent */
	u64 bytenr;

	/* the size of the extent */
	u64 num_bytes;

	/* seq number to keep track of insertion order */
	u64 seq;

	/* ref count on this data structure */
	refcount_t refs;

	/*
	* how many refs is this entry adding or deleting. For
	* head refs, this may be a negative number because it is keeping
	* track of the total mods done to the reference count.
	* For individual refs, this will always be a positive number
	*
	* It may be more than one, since it is possible for a single
	* parent to have more than one ref on an extent
	*/
	int ref_mod;

	unsigned int action:8;
	unsigned int type:8;
	/* is this node still in the rbtree? */
	unsigned int is_head:1;
	unsigned int in_tree:1;
	};

	struct btrfs_delayed_extent_op {
	struct btrfs_disk_key key;
	u8 level;
	bool update_key;
	bool update_flags;
	bool is_data;
	u64 flags_to_set;
	};

	/*
	* the head refs are used to hold a lock on a given extent, which allows us
	* to make sure that only one process is running the delayed refs
	* at a time for a single extent. They also store the sum of all the
	* reference count modifications we've queued up.
	*/
	struct btrfs_delayed_ref_head {
	u64 bytenr;
	u64 num_bytes;
	refcount_t refs;
	/*
	* the mutex is held while running the refs, and it is also
	* held when checking the sum of reference modifications.
	*/
	struct mutex mutex;

	spinlock_t lock;
	struct rb_root_cached ref_tree;
	/* accumulate add BTRFS_ADD_DELAYED_REF nodes to this ref_add_list. */
	struct list_head ref_add_list;

	struct rb_node href_node;

	struct btrfs_delayed_extent_op *extent_op;

	/*
	* This is used to track the final ref_mod from all the refs associated
	* with this head ref, this is not adjusted as delayed refs are run,
	* this is meant to track if we need to do the csum accounting or not.
	*/
	int total_ref_mod;

	/*
	* This is the current outstanding mod references for this bytenr. This
	* is used with lookup_extent_info to get an accurate reference count
	* for a bytenr, so it is adjusted as delayed refs are run so that any
	* on disk reference count + ref_mod is accurate.
	*/
	int ref_mod;

	/*
	* when a new extent is allocated, it is just reserved in memory
	* The actual extent isn't inserted into the extent allocation tree
	* until the delayed ref is processed. must_insert_reserved is
	* used to flag a delayed ref so the accounting can be updated
	* when a full insert is done.
	*
	* It is possible the extent will be freed before it is ever
	* inserted into the extent allocation tree. In this case
	* we need to update the in ram accounting to properly reflect
	* the free has happened.
	*/
	unsigned int must_insert_reserved:1;
	unsigned int is_data:1;
	unsigned int is_system:1;
	unsigned int processing:1;
	};

	struct btrfs_delayed_tree_ref {
	struct btrfs_delayed_ref_node node;
	u64 root;
	u64 parent;
	int level;
	};

	struct btrfs_delayed_data_ref {
	struct btrfs_delayed_ref_node node;
	u64 root;
	u64 parent;
	u64 objectid;
	u64 offset;
	};

	struct btrfs_delayed_ref_root {
	/* head ref rbtree */
	struct rb_root_cached href_root;

	/* dirty extent records */
	struct rb_root dirty_extent_root;

	/* this spin lock protects the rbtree and the entries inside */
	spinlock_t lock;

	/* how many delayed ref updates we've queued, used by the
	* throttling code
	*/
	atomic_t num_entries;

	/* total number of head nodes in tree */
	unsigned long num_heads;

	/* total number of head nodes ready for processing */
	unsigned long num_heads_ready;

	u64 pending_csums;

	/*
	* set when the tree is flushing before a transaction commit,
	* used by the throttling code to decide if new updates need
	* to be run right away
	*/
	int flushing;

	u64 run_delayed_start;

	/*
	* To make qgroup to skip given root.
	* This is for snapshot, as btrfs_qgroup_inherit() will manually
	* modify counters for snapshot and its source, so we should skip
	* the snapshot in new_root/old_roots or it will get calculated twice
	*/
	u64 qgroup_to_skip;
	};

	enum btrfs_ref_type {
	BTRFS_REF_NOT_SET,
	BTRFS_REF_DATA,
	BTRFS_REF_METADATA,
	BTRFS_REF_LAST,
	};

	struct btrfs_data_ref {
	/* For EXTENT_DATA_REF */

	/* Root which refers to this data extent */
	u64 ref_root;

	/* Inode which refers to this data extent */
	u64 ino;

	/*
	* file_offset - extent_offset
	*
	* file_offset is the key.offset of the EXTENT_DATA key.
	* extent_offset is btrfs_file_extent_offset() of the EXTENT_DATA data.
	*/
	u64 offset;
	};

	struct btrfs_tree_ref {
	/*
	* Level of this tree block
	*
	* Shared for skinny (TREE_BLOCK_REF) and normal tree ref.
	*/
	int level;

	/*
	* Root which refers to this tree block.
	*
	* For TREE_BLOCK_REF (skinny metadata, either inline or keyed)
	*/
	u64 root;

	/* For non-skinny metadata, no special member needed */
	};

	struct btrfs_ref {
	enum btrfs_ref_type type;
	int action;

	/*
	* Whether this extent should go through qgroup record.
	*
	* Normally false, but for certain cases like delayed subtree scan,
	* setting this flag can hugely reduce qgroup overhead.
	*/
	bool skip_qgroup;

	/*
	* Optional. For which root is this modification.
	* Mostly used for qgroup optimization.
	*
	* When unset, data/tree ref init code will populate it.
	* In certain cases, we're modifying reference for a different root.
	* E.g. COW fs tree blocks for balance.
	* In that case, tree_ref::root will be fs tree, but we're doing this
	* for reloc tree, then we should set @real_root to reloc tree.
	*/
	u64 real_root;
	u64 bytenr;
	u64 len;

	/* Bytenr of the parent tree block */
	u64 parent;
	union {
	struct btrfs_data_ref data_ref;
	struct btrfs_tree_ref tree_ref;
	};
	};

	extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
	extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
	extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
	extern struct kmem_cache *btrfs_delayed_extent_op_cachep;

	int __init btrfs_delayed_ref_init(void);
	void __cold btrfs_delayed_ref_exit(void);

	static inline void btrfs_init_generic_ref(struct btrfs_ref *generic_ref,
	int action, u64 bytenr, u64 len, u64 parent)
	{
	generic_ref->action = action;
	generic_ref->bytenr = bytenr;
	generic_ref->len = len;
	generic_ref->parent = parent;
	}

	static inline void btrfs_init_tree_ref(struct btrfs_ref *generic_ref,
	int level, u64 root)
	{
	/* If @real_root not set, use @root as fallback */
	if (!generic_ref->real_root)
	generic_ref->real_root = root;
	generic_ref->tree_ref.level = level;
	generic_ref->tree_ref.root = root;
	generic_ref->type = BTRFS_REF_METADATA;
	}

	static inline void btrfs_init_data_ref(struct btrfs_ref *generic_ref,
	u64 ref_root, u64 ino, u64 offset)
	{
	/* If @real_root not set, use @root as fallback */
	if (!generic_ref->real_root)
	generic_ref->real_root = ref_root;
	generic_ref->data_ref.ref_root = ref_root;
	generic_ref->data_ref.ino = ino;
	generic_ref->data_ref.offset = offset;
	generic_ref->type = BTRFS_REF_DATA;
	}

	static inline struct btrfs_delayed_extent_op *
	btrfs_alloc_delayed_extent_op(void)
	{
	return kmem_cache_alloc(btrfs_delayed_extent_op_cachep, GFP_NOFS);
	}

	static inline void
	btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
	{
	if (op)
	kmem_cache_free(btrfs_delayed_extent_op_cachep, op);
	}

	static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
	{
	WARN_ON(refcount_read(&ref->refs) == 0);
	if (refcount_dec_and_test(&ref->refs)) {
	WARN_ON(ref->in_tree);
	switch (ref->type) {
	case BTRFS_TREE_BLOCK_REF_KEY:
	case BTRFS_SHARED_BLOCK_REF_KEY:
	kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
	break;
	case BTRFS_EXTENT_DATA_REF_KEY:
	case BTRFS_SHARED_DATA_REF_KEY:
	kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
	break;
	default:
	BUG();
	}
	}
	}

	static inline void btrfs_put_delayed_ref_head(struct btrfs_delayed_ref_head *head)
	{
	if (refcount_dec_and_test(&head->refs))
	kmem_cache_free(btrfs_delayed_ref_head_cachep, head);
	}

	int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
	struct btrfs_ref *generic_ref,
	struct btrfs_delayed_extent_op *extent_op,
	int old_ref_mod, int new_ref_mod);
	int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
	struct btrfs_ref *generic_ref,
	u64 reserved, int *old_ref_mod,
	int *new_ref_mod);
	int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
	u64 bytenr, u64 num_bytes,
	struct btrfs_delayed_extent_op *extent_op);
	void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
	struct btrfs_delayed_ref_root *delayed_refs,
	struct btrfs_delayed_ref_head *head);

	struct btrfs_delayed_ref_head *
	btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
	u64 bytenr);
	int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
	struct btrfs_delayed_ref_head *head);
	static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
	{
	mutex_unlock(&head->mutex);
	}
	void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
	struct btrfs_delayed_ref_head *head);

	struct btrfs_delayed_ref_head *btrfs_select_ref_head(
	struct btrfs_delayed_ref_root *delayed_refs);

	int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq);

	void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr);
	void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans);
	int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
	enum btrfs_reserve_flush_enum flush);
	void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
	struct btrfs_block_rsv *src,
	u64 num_bytes);
	int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans);
	bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info);

	/*
	* helper functions to cast a node into its container
	*/
	static inline struct btrfs_delayed_tree_ref *
	btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
	{
	return container_of(node, struct btrfs_delayed_tree_ref, node);
	}

	static inline struct btrfs_delayed_data_ref *
	btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
	{
	return container_of(node, struct btrfs_delayed_data_ref, node);
	}

	#endif