[linux.git] / fs / btrfs / delayed-ref.h

/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#ifndef __DELAYED_REF__
#define __DELAYED_REF__

/* 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 */

/*
 * XXX: Qu: I really hate the design that ref_head and tree/data ref shares the
 * same ref_node structure.
 * Ref_head is in a higher logic level than tree/data ref, and duplicated
 * bytenr/num_bytes in ref_node is really a waste or memory, they should be
 * referred from ref_head.
 * This gets more disgusting after we use list to store tree/data ref in
 * ref_head. Must clean this mess up later.
 */
struct btrfs_delayed_ref_node {
	/*
	 * ref_head use rb tree, stored in ref_root->href.
	 * indexed by bytenr
	 */
	struct rb_node rb_node;

	/*data/tree ref use list, stored in ref_head->ref_list. */
	struct list_head 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 */
	atomic_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 {
	struct btrfs_delayed_ref_node node;

	/*
	 * 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 list_head ref_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;

	/*
	 * For qgroup reserved space freeing.
	 *
	 * ref_root and reserved will be recorded after
	 * BTRFS_ADD_DELAYED_EXTENT is called.
	 * And will be used to free reserved qgroup space at
	 * run_delayed_refs() time.
	 */
	u64 qgroup_ref_root;
	u64 qgroup_reserved;

	/*
	 * 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 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 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 manully
	 * 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;
};

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 btrfs_delayed_ref_init(void);
void btrfs_delayed_ref_exit(void);

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(atomic_read(&ref->refs) == 0);
	if (atomic_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;
		case 0:
			kmem_cache_free(btrfs_delayed_ref_head_cachep, ref);
			break;
		default:
			BUG();
		}
	}
}

int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
			       struct btrfs_trans_handle *trans,
			       u64 bytenr, u64 num_bytes, u64 parent,
			       u64 ref_root, int level, int action,
			       struct btrfs_delayed_extent_op *extent_op);
int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
			       struct btrfs_trans_handle *trans,
			       u64 bytenr, u64 num_bytes,
			       u64 parent, u64 ref_root,
			       u64 owner, u64 offset, u64 reserved, int action,
			       struct btrfs_delayed_extent_op *extent_op);
int btrfs_add_delayed_qgroup_reserve(struct btrfs_fs_info *fs_info,
				     struct btrfs_trans_handle *trans,
				     u64 ref_root, u64 bytenr, u64 num_bytes);
int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
				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_fs_info *fs_info,
			      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_trans_handle *trans, u64 bytenr);
int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
			   struct btrfs_delayed_ref_head *head);
static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
{
	mutex_unlock(&head->mutex);
}


struct btrfs_delayed_ref_head *
btrfs_select_ref_head(struct btrfs_trans_handle *trans);

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

/*
 * a node might live in a head or a regular ref, this lets you
 * test for the proper type to use.
 */
static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
{
	return node->is_head;
}

/*
 * 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)
{
	WARN_ON(btrfs_delayed_ref_is_head(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)
{
	WARN_ON(btrfs_delayed_ref_is_head(node));
	return container_of(node, struct btrfs_delayed_data_ref, node);
}

static inline struct btrfs_delayed_ref_head *
btrfs_delayed_node_to_head(struct btrfs_delayed_ref_node *node)
{
	WARN_ON(!btrfs_delayed_ref_is_head(node));
	return container_of(node, struct btrfs_delayed_ref_head, node);
}
#endif
Commit	Line	Data
56bec294 CM	1	/*
	2	* Copyright (C) 2008 Oracle. All rights reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or
	5	* modify it under the terms of the GNU General Public
	6	* License v2 as published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful,
	9	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	11	* General Public License for more details.
	12	*
	13	* You should have received a copy of the GNU General Public
	14	* License along with this program; if not, write to the
	15	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	16	* Boston, MA 021110-1307, USA.
	17	*/
	18	#ifndef __DELAYED_REF__
	19	#define __DELAYED_REF__
	20
44a075bd	21	/* these are the possible values of struct btrfs_delayed_ref_node->action */
56bec294 CM	22	#define BTRFS_ADD_DELAYED_REF 1 /* add one backref to the tree */
	23	#define BTRFS_DROP_DELAYED_REF 2 /* delete one backref from the tree */
	24	#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
1a81af4d	25	#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
56bec294	26
c6fc2454 QW	27	/*
	28	* XXX: Qu: I really hate the design that ref_head and tree/data ref shares the
	29	* same ref_node structure.
	30	* Ref_head is in a higher logic level than tree/data ref, and duplicated
	31	* bytenr/num_bytes in ref_node is really a waste or memory, they should be
	32	* referred from ref_head.
	33	* This gets more disgusting after we use list to store tree/data ref in
	34	* ref_head. Must clean this mess up later.
	35	*/
56bec294	36	struct btrfs_delayed_ref_node {
c6fc2454 QW	37	/*
	38	* ref_head use rb tree, stored in ref_root->href.
	39	* indexed by bytenr
	40	*/
56bec294 CM	41	struct rb_node rb_node;
56bec294 CM	42
c6fc2454 QW	43	/data/tree ref use list, stored in ref_head->ref_list. /
	44	struct list_head list;
	45
56bec294 CM	46	/* the starting bytenr of the extent */
	47	u64 bytenr;
	48
56bec294 CM	49	/* the size of the extent */
	50	u64 num_bytes;
	51
00f04b88 AJ	52	/* seq number to keep track of insertion order */
	53	u64 seq;
	54
56bec294 CM	55	/* ref count on this data structure */
	56	atomic_t refs;
	57
	58	/*
	59	* how many refs is this entry adding or deleting. For
	60	* head refs, this may be a negative number because it is keeping
	61	* track of the total mods done to the reference count.
	62	* For individual refs, this will always be a positive number
	63	*
	64	* It may be more than one, since it is possible for a single
	65	* parent to have more than one ref on an extent
	66	*/
	67	int ref_mod;
	68
5d4f98a2 YZ	69	unsigned int action:8;
5d4f98a2 YZ	70	unsigned int type:8;
56bec294	71	/* is this node still in the rbtree? */
5d4f98a2	72	unsigned int is_head:1;
56bec294 CM	73	unsigned int in_tree:1;
	74	};
	75
5d4f98a2 YZ	76	struct btrfs_delayed_extent_op {
5d4f98a2 YZ	77	struct btrfs_disk_key key;
35b3ad50 DS	78	u8 level;
	79	bool update_key;
	80	bool update_flags;
	81	bool is_data;
5d4f98a2	82	u64 flags_to_set;
5d4f98a2 YZ	83	};
5d4f98a2 YZ	84
56bec294 CM	85	/*
	86	* the head refs are used to hold a lock on a given extent, which allows us
	87	* to make sure that only one process is running the delayed refs
	88	* at a time for a single extent. They also store the sum of all the
	89	* reference count modifications we've queued up.
	90	*/
	91	struct btrfs_delayed_ref_head {
	92	struct btrfs_delayed_ref_node node;
	93
	94	/*
	95	* the mutex is held while running the refs, and it is also
	96	* held when checking the sum of reference modifications.
	97	*/
	98	struct mutex mutex;
	99
d7df2c79	100	spinlock_t lock;
c6fc2454	101	struct list_head ref_list;
c3e69d58	102
c46effa6 LB	103	struct rb_node href_node;
c46effa6 LB	104
5d4f98a2	105	struct btrfs_delayed_extent_op *extent_op;
1262133b JB	106
	107	/*
	108	* This is used to track the final ref_mod from all the refs associated
	109	* with this head ref, this is not adjusted as delayed refs are run,
	110	* this is meant to track if we need to do the csum accounting or not.
	111	*/
	112	int total_ref_mod;
	113
f64d5ca8 QW	114	/*
	115	* For qgroup reserved space freeing.
	116	*
	117	* ref_root and reserved will be recorded after
	118	* BTRFS_ADD_DELAYED_EXTENT is called.
	119	* And will be used to free reserved qgroup space at
	120	* run_delayed_refs() time.
	121	*/
	122	u64 qgroup_ref_root;
	123	u64 qgroup_reserved;
	124
56bec294 CM	125	/*
	126	* when a new extent is allocated, it is just reserved in memory
	127	* The actual extent isn't inserted into the extent allocation tree
	128	* until the delayed ref is processed. must_insert_reserved is
	129	* used to flag a delayed ref so the accounting can be updated
	130	* when a full insert is done.
	131	*
	132	* It is possible the extent will be freed before it is ever
	133	* inserted into the extent allocation tree. In this case
	134	* we need to update the in ram accounting to properly reflect
	135	* the free has happened.
	136	*/
	137	unsigned int must_insert_reserved:1;
5d4f98a2	138	unsigned int is_data:1;
d7df2c79	139	unsigned int processing:1;
56bec294 CM	140	};
56bec294 CM	141
5d4f98a2	142	struct btrfs_delayed_tree_ref {
56bec294	143	struct btrfs_delayed_ref_node node;
eebe063b AJ	144	u64 root;
eebe063b AJ	145	u64 parent;
5d4f98a2 YZ	146	int level;
5d4f98a2 YZ	147	};
56bec294	148
5d4f98a2 YZ	149	struct btrfs_delayed_data_ref {
5d4f98a2 YZ	150	struct btrfs_delayed_ref_node node;
eebe063b AJ	151	u64 root;
eebe063b AJ	152	u64 parent;
5d4f98a2 YZ	153	u64 objectid;
5d4f98a2 YZ	154	u64 offset;
56bec294 CM	155	};
	156
	157	struct btrfs_delayed_ref_root {
c46effa6 LB	158	/* head ref rbtree */
	159	struct rb_root href_root;
	160
3368d001 QW	161	/* dirty extent records */
	162	struct rb_root dirty_extent_root;
	163
56bec294 CM	164	/* this spin lock protects the rbtree and the entries inside */
	165	spinlock_t lock;
	166
	167	/* how many delayed ref updates we've queued, used by the
	168	* throttling code
	169	*/
d7df2c79	170	atomic_t num_entries;
56bec294	171
c3e69d58 CM	172	/* total number of head nodes in tree */
	173	unsigned long num_heads;
	174
	175	/* total number of head nodes ready for processing */
	176	unsigned long num_heads_ready;
	177
1262133b JB	178	u64 pending_csums;
1262133b JB	179
56bec294 CM	180	/*
	181	* set when the tree is flushing before a transaction commit,
	182	* used by the throttling code to decide if new updates need
	183	* to be run right away
	184	*/
	185	int flushing;
c3e69d58 CM	186
c3e69d58 CM	187	u64 run_delayed_start;
9086db86 QW	188
	189	/*
	190	* To make qgroup to skip given root.
	191	* This is for snapshot, as btrfs_qgroup_inherit() will manully
	192	* modify counters for snapshot and its source, so we should skip
	193	* the snapshot in new_root/old_roots or it will get calculated twice
	194	*/
	195	u64 qgroup_to_skip;
56bec294 CM	196	};
56bec294 CM	197
78a6184a MX	198	extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
	199	extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
	200	extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
	201	extern struct kmem_cache *btrfs_delayed_extent_op_cachep;
	202
	203	int btrfs_delayed_ref_init(void);
	204	void btrfs_delayed_ref_exit(void);
	205
	206	static inline struct btrfs_delayed_extent_op *
	207	btrfs_alloc_delayed_extent_op(void)
	208	{
	209	return kmem_cache_alloc(btrfs_delayed_extent_op_cachep, GFP_NOFS);
	210	}
	211
	212	static inline void
	213	btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
	214	{
	215	if (op)
	216	kmem_cache_free(btrfs_delayed_extent_op_cachep, op);
	217	}
	218
56bec294 CM	219	static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
	220	{
	221	WARN_ON(atomic_read(&ref->refs) == 0);
	222	if (atomic_dec_and_test(&ref->refs)) {
	223	WARN_ON(ref->in_tree);
78a6184a MX	224	switch (ref->type) {
	225	case BTRFS_TREE_BLOCK_REF_KEY:
	226	case BTRFS_SHARED_BLOCK_REF_KEY:
	227	kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
	228	break;
	229	case BTRFS_EXTENT_DATA_REF_KEY:
	230	case BTRFS_SHARED_DATA_REF_KEY:
	231	kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
	232	break;
	233	case 0:
	234	kmem_cache_free(btrfs_delayed_ref_head_cachep, ref);
	235	break;
	236	default:
	237	BUG();
	238	}
56bec294 CM	239	}
	240	}
	241
66d7e7f0 AJ	242	int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
66d7e7f0 AJ	243	struct btrfs_trans_handle *trans,
5d4f98a2 YZ	244	u64 bytenr, u64 num_bytes, u64 parent,
5d4f98a2 YZ	245	u64 ref_root, int level, int action,
b06c4bf5	246	struct btrfs_delayed_extent_op *extent_op);
66d7e7f0 AJ	247	int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
66d7e7f0 AJ	248	struct btrfs_trans_handle *trans,
5d4f98a2 YZ	249	u64 bytenr, u64 num_bytes,
5d4f98a2 YZ	250	u64 parent, u64 ref_root,
5846a3c2	251	u64 owner, u64 offset, u64 reserved, int action,
b06c4bf5	252	struct btrfs_delayed_extent_op *extent_op);
f64d5ca8 QW	253	int btrfs_add_delayed_qgroup_reserve(struct btrfs_fs_info *fs_info,
	254	struct btrfs_trans_handle *trans,
	255	u64 ref_root, u64 bytenr, u64 num_bytes);
66d7e7f0 AJ	256	int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
66d7e7f0 AJ	257	struct btrfs_trans_handle *trans,
5d4f98a2 YZ	258	u64 bytenr, u64 num_bytes,
5d4f98a2 YZ	259	struct btrfs_delayed_extent_op *extent_op);
ae1e206b JB	260	void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
	261	struct btrfs_fs_info *fs_info,
	262	struct btrfs_delayed_ref_root *delayed_refs,
	263	struct btrfs_delayed_ref_head *head);
56bec294	264
1887be66 CM	265	struct btrfs_delayed_ref_head *
1887be66 CM	266	btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr);
c3e69d58 CM	267	int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
c3e69d58 CM	268	struct btrfs_delayed_ref_head *head);
093486c4 MX	269	static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
	270	{
	271	mutex_unlock(&head->mutex);
	272	}
	273
d7df2c79 JB	274
	275	struct btrfs_delayed_ref_head *
	276	btrfs_select_ref_head(struct btrfs_trans_handle *trans);
00f04b88	277
097b8a7c JS	278	int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
097b8a7c JS	279	struct btrfs_delayed_ref_root *delayed_refs,
00f04b88 AJ	280	u64 seq);
00f04b88 AJ	281
56bec294 CM	282	/*
	283	* a node might live in a head or a regular ref, this lets you
	284	* test for the proper type to use.
	285	*/
	286	static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
	287	{
5d4f98a2	288	return node->is_head;
56bec294 CM	289	}
	290
	291	/*
	292	* helper functions to cast a node into its container
	293	*/
5d4f98a2 YZ	294	static inline struct btrfs_delayed_tree_ref *
5d4f98a2 YZ	295	btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
56bec294 CM	296	{
56bec294 CM	297	WARN_ON(btrfs_delayed_ref_is_head(node));
5d4f98a2 YZ	298	return container_of(node, struct btrfs_delayed_tree_ref, node);
5d4f98a2 YZ	299	}
56bec294	300
5d4f98a2 YZ	301	static inline struct btrfs_delayed_data_ref *
	302	btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
	303	{
	304	WARN_ON(btrfs_delayed_ref_is_head(node));
	305	return container_of(node, struct btrfs_delayed_data_ref, node);
56bec294 CM	306	}
	307
	308	static inline struct btrfs_delayed_ref_head *
	309	btrfs_delayed_node_to_head(struct btrfs_delayed_ref_node *node)
	310	{
	311	WARN_ON(!btrfs_delayed_ref_is_head(node));
	312	return container_of(node, struct btrfs_delayed_ref_head, node);
56bec294 CM	313	}
56bec294 CM	314	#endif