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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Copyright (C) 2008 Oracle. All rights reserved.
4 */
5
6#ifndef BTRFS_DELAYED_REF_H
7#define BTRFS_DELAYED_REF_H
8
9#include <linux/refcount.h>
10
11/* these are the possible values of struct btrfs_delayed_ref_node->action */
12#define BTRFS_ADD_DELAYED_REF 1 /* add one backref to the tree */
13#define BTRFS_DROP_DELAYED_REF 2 /* delete one backref from the tree */
14#define BTRFS_ADD_DELAYED_EXTENT 3 /* record a full extent allocation */
15#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
16
17struct btrfs_delayed_ref_node {
18 struct rb_node ref_node;
19 /*
20 * If action is BTRFS_ADD_DELAYED_REF, also link this node to
21 * ref_head->ref_add_list, then we do not need to iterate the
22 * whole ref_head->ref_list to find BTRFS_ADD_DELAYED_REF nodes.
23 */
24 struct list_head add_list;
25
26 /* the starting bytenr of the extent */
27 u64 bytenr;
28
29 /* the size of the extent */
30 u64 num_bytes;
31
32 /* seq number to keep track of insertion order */
33 u64 seq;
34
35 /* ref count on this data structure */
36 refcount_t refs;
37
38 /*
39 * how many refs is this entry adding or deleting. For
40 * head refs, this may be a negative number because it is keeping
41 * track of the total mods done to the reference count.
42 * For individual refs, this will always be a positive number
43 *
44 * It may be more than one, since it is possible for a single
45 * parent to have more than one ref on an extent
46 */
47 int ref_mod;
48
49 unsigned int action:8;
50 unsigned int type:8;
51 /* is this node still in the rbtree? */
52 unsigned int is_head:1;
53 unsigned int in_tree:1;
54};
55
56struct btrfs_delayed_extent_op {
57 struct btrfs_disk_key key;
58 u8 level;
59 bool update_key;
60 bool update_flags;
61 bool is_data;
62 u64 flags_to_set;
63};
64
65/*
66 * the head refs are used to hold a lock on a given extent, which allows us
67 * to make sure that only one process is running the delayed refs
68 * at a time for a single extent. They also store the sum of all the
69 * reference count modifications we've queued up.
70 */
71struct btrfs_delayed_ref_head {
72 u64 bytenr;
73 u64 num_bytes;
74 refcount_t refs;
75 /*
76 * the mutex is held while running the refs, and it is also
77 * held when checking the sum of reference modifications.
78 */
79 struct mutex mutex;
80
81 spinlock_t lock;
82 struct rb_root_cached ref_tree;
83 /* accumulate add BTRFS_ADD_DELAYED_REF nodes to this ref_add_list. */
84 struct list_head ref_add_list;
85
86 struct rb_node href_node;
87
88 struct btrfs_delayed_extent_op *extent_op;
89
90 /*
91 * This is used to track the final ref_mod from all the refs associated
92 * with this head ref, this is not adjusted as delayed refs are run,
93 * this is meant to track if we need to do the csum accounting or not.
94 */
95 int total_ref_mod;
96
97 /*
98 * This is the current outstanding mod references for this bytenr. This
99 * is used with lookup_extent_info to get an accurate reference count
100 * for a bytenr, so it is adjusted as delayed refs are run so that any
101 * on disk reference count + ref_mod is accurate.
102 */
103 int ref_mod;
104
105 /*
106 * when a new extent is allocated, it is just reserved in memory
107 * The actual extent isn't inserted into the extent allocation tree
108 * until the delayed ref is processed. must_insert_reserved is
109 * used to flag a delayed ref so the accounting can be updated
110 * when a full insert is done.
111 *
112 * It is possible the extent will be freed before it is ever
113 * inserted into the extent allocation tree. In this case
114 * we need to update the in ram accounting to properly reflect
115 * the free has happened.
116 */
117 unsigned int must_insert_reserved:1;
118 unsigned int is_data:1;
119 unsigned int is_system:1;
120 unsigned int processing:1;
121};
122
123struct btrfs_delayed_tree_ref {
124 struct btrfs_delayed_ref_node node;
125 u64 root;
126 u64 parent;
127 int level;
128};
129
130struct btrfs_delayed_data_ref {
131 struct btrfs_delayed_ref_node node;
132 u64 root;
133 u64 parent;
134 u64 objectid;
135 u64 offset;
136};
137
138struct btrfs_delayed_ref_root {
139 /* head ref rbtree */
140 struct rb_root_cached href_root;
141
142 /* dirty extent records */
143 struct rb_root dirty_extent_root;
144
145 /* this spin lock protects the rbtree and the entries inside */
146 spinlock_t lock;
147
148 /* how many delayed ref updates we've queued, used by the
149 * throttling code
150 */
151 atomic_t num_entries;
152
153 /* total number of head nodes in tree */
154 unsigned long num_heads;
155
156 /* total number of head nodes ready for processing */
157 unsigned long num_heads_ready;
158
159 u64 pending_csums;
160
161 /*
162 * set when the tree is flushing before a transaction commit,
163 * used by the throttling code to decide if new updates need
164 * to be run right away
165 */
166 int flushing;
167
168 u64 run_delayed_start;
169
170 /*
171 * To make qgroup to skip given root.
172 * This is for snapshot, as btrfs_qgroup_inherit() will manually
173 * modify counters for snapshot and its source, so we should skip
174 * the snapshot in new_root/old_roots or it will get calculated twice
175 */
176 u64 qgroup_to_skip;
177};
178
179enum btrfs_ref_type {
180 BTRFS_REF_NOT_SET,
181 BTRFS_REF_DATA,
182 BTRFS_REF_METADATA,
183 BTRFS_REF_LAST,
184};
185
186struct btrfs_data_ref {
187 /* For EXTENT_DATA_REF */
188
189 /* Root which refers to this data extent */
190 u64 ref_root;
191
192 /* Inode which refers to this data extent */
193 u64 ino;
194
195 /*
196 * file_offset - extent_offset
197 *
198 * file_offset is the key.offset of the EXTENT_DATA key.
199 * extent_offset is btrfs_file_extent_offset() of the EXTENT_DATA data.
200 */
201 u64 offset;
202};
203
204struct btrfs_tree_ref {
205 /*
206 * Level of this tree block
207 *
208 * Shared for skinny (TREE_BLOCK_REF) and normal tree ref.
209 */
210 int level;
211
212 /*
213 * Root which refers to this tree block.
214 *
215 * For TREE_BLOCK_REF (skinny metadata, either inline or keyed)
216 */
217 u64 root;
218
219 /* For non-skinny metadata, no special member needed */
220};
221
222struct btrfs_ref {
223 enum btrfs_ref_type type;
224 int action;
225
226 /*
227 * Whether this extent should go through qgroup record.
228 *
229 * Normally false, but for certain cases like delayed subtree scan,
230 * setting this flag can hugely reduce qgroup overhead.
231 */
232 bool skip_qgroup;
233
234 /*
235 * Optional. For which root is this modification.
236 * Mostly used for qgroup optimization.
237 *
238 * When unset, data/tree ref init code will populate it.
239 * In certain cases, we're modifying reference for a different root.
240 * E.g. COW fs tree blocks for balance.
241 * In that case, tree_ref::root will be fs tree, but we're doing this
242 * for reloc tree, then we should set @real_root to reloc tree.
243 */
244 u64 real_root;
245 u64 bytenr;
246 u64 len;
247
248 /* Bytenr of the parent tree block */
249 u64 parent;
250 union {
251 struct btrfs_data_ref data_ref;
252 struct btrfs_tree_ref tree_ref;
253 };
254};
255
256extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
257extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
258extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
259extern struct kmem_cache *btrfs_delayed_extent_op_cachep;
260
261int __init btrfs_delayed_ref_init(void);
262void __cold btrfs_delayed_ref_exit(void);
263
264static inline void btrfs_init_generic_ref(struct btrfs_ref *generic_ref,
265 int action, u64 bytenr, u64 len, u64 parent)
266{
267 generic_ref->action = action;
268 generic_ref->bytenr = bytenr;
269 generic_ref->len = len;
270 generic_ref->parent = parent;
271}
272
273static inline void btrfs_init_tree_ref(struct btrfs_ref *generic_ref,
274 int level, u64 root)
275{
276 /* If @real_root not set, use @root as fallback */
277 if (!generic_ref->real_root)
278 generic_ref->real_root = root;
279 generic_ref->tree_ref.level = level;
280 generic_ref->tree_ref.root = root;
281 generic_ref->type = BTRFS_REF_METADATA;
282}
283
284static inline void btrfs_init_data_ref(struct btrfs_ref *generic_ref,
285 u64 ref_root, u64 ino, u64 offset)
286{
287 /* If @real_root not set, use @root as fallback */
288 if (!generic_ref->real_root)
289 generic_ref->real_root = ref_root;
290 generic_ref->data_ref.ref_root = ref_root;
291 generic_ref->data_ref.ino = ino;
292 generic_ref->data_ref.offset = offset;
293 generic_ref->type = BTRFS_REF_DATA;
294}
295
296static inline struct btrfs_delayed_extent_op *
297btrfs_alloc_delayed_extent_op(void)
298{
299 return kmem_cache_alloc(btrfs_delayed_extent_op_cachep, GFP_NOFS);
300}
301
302static inline void
303btrfs_free_delayed_extent_op(struct btrfs_delayed_extent_op *op)
304{
305 if (op)
306 kmem_cache_free(btrfs_delayed_extent_op_cachep, op);
307}
308
309static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
310{
311 WARN_ON(refcount_read(&ref->refs) == 0);
312 if (refcount_dec_and_test(&ref->refs)) {
313 WARN_ON(ref->in_tree);
314 switch (ref->type) {
315 case BTRFS_TREE_BLOCK_REF_KEY:
316 case BTRFS_SHARED_BLOCK_REF_KEY:
317 kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
318 break;
319 case BTRFS_EXTENT_DATA_REF_KEY:
320 case BTRFS_SHARED_DATA_REF_KEY:
321 kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
322 break;
323 default:
324 BUG();
325 }
326 }
327}
328
329static inline void btrfs_put_delayed_ref_head(struct btrfs_delayed_ref_head *head)
330{
331 if (refcount_dec_and_test(&head->refs))
332 kmem_cache_free(btrfs_delayed_ref_head_cachep, head);
333}
334
335int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
336 struct btrfs_ref *generic_ref,
337 struct btrfs_delayed_extent_op *extent_op,
338 int *old_ref_mod, int *new_ref_mod);
339int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
340 struct btrfs_ref *generic_ref,
341 u64 reserved, int *old_ref_mod,
342 int *new_ref_mod);
343int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
344 u64 bytenr, u64 num_bytes,
345 struct btrfs_delayed_extent_op *extent_op);
346void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
347 struct btrfs_delayed_ref_root *delayed_refs,
348 struct btrfs_delayed_ref_head *head);
349
350struct btrfs_delayed_ref_head *
351btrfs_find_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
352 u64 bytenr);
353int btrfs_delayed_ref_lock(struct btrfs_delayed_ref_root *delayed_refs,
354 struct btrfs_delayed_ref_head *head);
355static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
356{
357 mutex_unlock(&head->mutex);
358}
359void btrfs_delete_ref_head(struct btrfs_delayed_ref_root *delayed_refs,
360 struct btrfs_delayed_ref_head *head);
361
362struct btrfs_delayed_ref_head *btrfs_select_ref_head(
363 struct btrfs_delayed_ref_root *delayed_refs);
364
365int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq);
366
367void btrfs_delayed_refs_rsv_release(struct btrfs_fs_info *fs_info, int nr);
368void btrfs_update_delayed_refs_rsv(struct btrfs_trans_handle *trans);
369int btrfs_delayed_refs_rsv_refill(struct btrfs_fs_info *fs_info,
370 enum btrfs_reserve_flush_enum flush);
371void btrfs_migrate_to_delayed_refs_rsv(struct btrfs_fs_info *fs_info,
372 struct btrfs_block_rsv *src,
373 u64 num_bytes);
374int btrfs_should_throttle_delayed_refs(struct btrfs_trans_handle *trans);
375bool btrfs_check_space_for_delayed_refs(struct btrfs_fs_info *fs_info);
376
377/*
378 * helper functions to cast a node into its container
379 */
380static inline struct btrfs_delayed_tree_ref *
381btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
382{
383 return container_of(node, struct btrfs_delayed_tree_ref, node);
384}
385
386static inline struct btrfs_delayed_data_ref *
387btrfs_delayed_node_to_data_ref(struct btrfs_delayed_ref_node *node)
388{
389 return container_of(node, struct btrfs_delayed_data_ref, node);
390}
391
392#endif
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
21/* these are the possible values of struct btrfs_delayed_ref_node->action */
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 */
25#define BTRFS_UPDATE_DELAYED_HEAD 4 /* not changing ref count on head ref */
26
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 */
36struct btrfs_delayed_ref_node {
37 /*
38 * ref_head use rb tree, stored in ref_root->href.
39 * indexed by bytenr
40 */
41 struct rb_node rb_node;
42
43 /*data/tree ref use list, stored in ref_head->ref_list. */
44 struct list_head list;
45
46 /* the starting bytenr of the extent */
47 u64 bytenr;
48
49 /* the size of the extent */
50 u64 num_bytes;
51
52 /* seq number to keep track of insertion order */
53 u64 seq;
54
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
69 unsigned int action:8;
70 unsigned int type:8;
71 /* is this node still in the rbtree? */
72 unsigned int is_head:1;
73 unsigned int in_tree:1;
74};
75
76struct btrfs_delayed_extent_op {
77 struct btrfs_disk_key key;
78 u8 level;
79 bool update_key;
80 bool update_flags;
81 bool is_data;
82 u64 flags_to_set;
83};
84
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 */
91struct 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
100 spinlock_t lock;
101 struct list_head ref_list;
102
103 struct rb_node href_node;
104
105 struct btrfs_delayed_extent_op *extent_op;
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
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
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;
138 unsigned int is_data:1;
139 unsigned int processing:1;
140};
141
142struct btrfs_delayed_tree_ref {
143 struct btrfs_delayed_ref_node node;
144 u64 root;
145 u64 parent;
146 int level;
147};
148
149struct btrfs_delayed_data_ref {
150 struct btrfs_delayed_ref_node node;
151 u64 root;
152 u64 parent;
153 u64 objectid;
154 u64 offset;
155};
156
157struct btrfs_delayed_ref_root {
158 /* head ref rbtree */
159 struct rb_root href_root;
160
161 /* dirty extent records */
162 struct rb_root dirty_extent_root;
163
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 */
170 atomic_t num_entries;
171
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
178 u64 pending_csums;
179
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;
186
187 u64 run_delayed_start;
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;
196};
197
198extern struct kmem_cache *btrfs_delayed_ref_head_cachep;
199extern struct kmem_cache *btrfs_delayed_tree_ref_cachep;
200extern struct kmem_cache *btrfs_delayed_data_ref_cachep;
201extern struct kmem_cache *btrfs_delayed_extent_op_cachep;
202
203int btrfs_delayed_ref_init(void);
204void btrfs_delayed_ref_exit(void);
205
206static inline struct btrfs_delayed_extent_op *
207btrfs_alloc_delayed_extent_op(void)
208{
209 return kmem_cache_alloc(btrfs_delayed_extent_op_cachep, GFP_NOFS);
210}
211
212static inline void
213btrfs_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
219static 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);
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 }
239 }
240}
241
242int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
243 struct btrfs_trans_handle *trans,
244 u64 bytenr, u64 num_bytes, u64 parent,
245 u64 ref_root, int level, int action,
246 struct btrfs_delayed_extent_op *extent_op);
247int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
248 struct btrfs_trans_handle *trans,
249 u64 bytenr, u64 num_bytes,
250 u64 parent, u64 ref_root,
251 u64 owner, u64 offset, u64 reserved, int action,
252 struct btrfs_delayed_extent_op *extent_op);
253int 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);
256int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
257 struct btrfs_trans_handle *trans,
258 u64 bytenr, u64 num_bytes,
259 struct btrfs_delayed_extent_op *extent_op);
260void 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);
264
265struct btrfs_delayed_ref_head *
266btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr);
267int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
268 struct btrfs_delayed_ref_head *head);
269static inline void btrfs_delayed_ref_unlock(struct btrfs_delayed_ref_head *head)
270{
271 mutex_unlock(&head->mutex);
272}
273
274
275struct btrfs_delayed_ref_head *
276btrfs_select_ref_head(struct btrfs_trans_handle *trans);
277
278int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
279 struct btrfs_delayed_ref_root *delayed_refs,
280 u64 seq);
281
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 */
286static int btrfs_delayed_ref_is_head(struct btrfs_delayed_ref_node *node)
287{
288 return node->is_head;
289}
290
291/*
292 * helper functions to cast a node into its container
293 */
294static inline struct btrfs_delayed_tree_ref *
295btrfs_delayed_node_to_tree_ref(struct btrfs_delayed_ref_node *node)
296{
297 WARN_ON(btrfs_delayed_ref_is_head(node));
298 return container_of(node, struct btrfs_delayed_tree_ref, node);
299}
300
301static inline struct btrfs_delayed_data_ref *
302btrfs_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);
306}
307
308static inline struct btrfs_delayed_ref_head *
309btrfs_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);
313}
314#endif