Btrfs: Integrate metadata reservation with start_transaction
[linux-2.6.git] / fs / btrfs / delayed-ref.c
1 /*
2  * Copyright (C) 2009 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
19 #include <linux/sched.h>
20 #include <linux/slab.h>
21 #include <linux/sort.h>
22 #include "ctree.h"
23 #include "delayed-ref.h"
24 #include "transaction.h"
25
26 /*
27  * delayed back reference update tracking.  For subvolume trees
28  * we queue up extent allocations and backref maintenance for
29  * delayed processing.   This avoids deep call chains where we
30  * add extents in the middle of btrfs_search_slot, and it allows
31  * us to buffer up frequently modified backrefs in an rb tree instead
32  * of hammering updates on the extent allocation tree.
33  */
34
35 /*
36  * compare two delayed tree backrefs with same bytenr and type
37  */
38 static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref2,
39                           struct btrfs_delayed_tree_ref *ref1)
40 {
41         if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
42                 if (ref1->root < ref2->root)
43                         return -1;
44                 if (ref1->root > ref2->root)
45                         return 1;
46         } else {
47                 if (ref1->parent < ref2->parent)
48                         return -1;
49                 if (ref1->parent > ref2->parent)
50                         return 1;
51         }
52         return 0;
53 }
54
55 /*
56  * compare two delayed data backrefs with same bytenr and type
57  */
58 static int comp_data_refs(struct btrfs_delayed_data_ref *ref2,
59                           struct btrfs_delayed_data_ref *ref1)
60 {
61         if (ref1->node.type == BTRFS_EXTENT_DATA_REF_KEY) {
62                 if (ref1->root < ref2->root)
63                         return -1;
64                 if (ref1->root > ref2->root)
65                         return 1;
66                 if (ref1->objectid < ref2->objectid)
67                         return -1;
68                 if (ref1->objectid > ref2->objectid)
69                         return 1;
70                 if (ref1->offset < ref2->offset)
71                         return -1;
72                 if (ref1->offset > ref2->offset)
73                         return 1;
74         } else {
75                 if (ref1->parent < ref2->parent)
76                         return -1;
77                 if (ref1->parent > ref2->parent)
78                         return 1;
79         }
80         return 0;
81 }
82
83 /*
84  * entries in the rb tree are ordered by the byte number of the extent,
85  * type of the delayed backrefs and content of delayed backrefs.
86  */
87 static int comp_entry(struct btrfs_delayed_ref_node *ref2,
88                       struct btrfs_delayed_ref_node *ref1)
89 {
90         if (ref1->bytenr < ref2->bytenr)
91                 return -1;
92         if (ref1->bytenr > ref2->bytenr)
93                 return 1;
94         if (ref1->is_head && ref2->is_head)
95                 return 0;
96         if (ref2->is_head)
97                 return -1;
98         if (ref1->is_head)
99                 return 1;
100         if (ref1->type < ref2->type)
101                 return -1;
102         if (ref1->type > ref2->type)
103                 return 1;
104         if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
105             ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
106                 return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
107                                       btrfs_delayed_node_to_tree_ref(ref1));
108         } else if (ref1->type == BTRFS_EXTENT_DATA_REF_KEY ||
109                    ref1->type == BTRFS_SHARED_DATA_REF_KEY) {
110                 return comp_data_refs(btrfs_delayed_node_to_data_ref(ref2),
111                                       btrfs_delayed_node_to_data_ref(ref1));
112         }
113         BUG();
114         return 0;
115 }
116
117 /*
118  * insert a new ref into the rbtree.  This returns any existing refs
119  * for the same (bytenr,parent) tuple, or NULL if the new node was properly
120  * inserted.
121  */
122 static struct btrfs_delayed_ref_node *tree_insert(struct rb_root *root,
123                                                   struct rb_node *node)
124 {
125         struct rb_node **p = &root->rb_node;
126         struct rb_node *parent_node = NULL;
127         struct btrfs_delayed_ref_node *entry;
128         struct btrfs_delayed_ref_node *ins;
129         int cmp;
130
131         ins = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
132         while (*p) {
133                 parent_node = *p;
134                 entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
135                                  rb_node);
136
137                 cmp = comp_entry(entry, ins);
138                 if (cmp < 0)
139                         p = &(*p)->rb_left;
140                 else if (cmp > 0)
141                         p = &(*p)->rb_right;
142                 else
143                         return entry;
144         }
145
146         rb_link_node(node, parent_node, p);
147         rb_insert_color(node, root);
148         return NULL;
149 }
150
151 /*
152  * find an head entry based on bytenr. This returns the delayed ref
153  * head if it was able to find one, or NULL if nothing was in that spot
154  */
155 static struct btrfs_delayed_ref_node *find_ref_head(struct rb_root *root,
156                                   u64 bytenr,
157                                   struct btrfs_delayed_ref_node **last)
158 {
159         struct rb_node *n = root->rb_node;
160         struct btrfs_delayed_ref_node *entry;
161         int cmp;
162
163         while (n) {
164                 entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
165                 WARN_ON(!entry->in_tree);
166                 if (last)
167                         *last = entry;
168
169                 if (bytenr < entry->bytenr)
170                         cmp = -1;
171                 else if (bytenr > entry->bytenr)
172                         cmp = 1;
173                 else if (!btrfs_delayed_ref_is_head(entry))
174                         cmp = 1;
175                 else
176                         cmp = 0;
177
178                 if (cmp < 0)
179                         n = n->rb_left;
180                 else if (cmp > 0)
181                         n = n->rb_right;
182                 else
183                         return entry;
184         }
185         return NULL;
186 }
187
188 int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
189                            struct btrfs_delayed_ref_head *head)
190 {
191         struct btrfs_delayed_ref_root *delayed_refs;
192
193         delayed_refs = &trans->transaction->delayed_refs;
194         assert_spin_locked(&delayed_refs->lock);
195         if (mutex_trylock(&head->mutex))
196                 return 0;
197
198         atomic_inc(&head->node.refs);
199         spin_unlock(&delayed_refs->lock);
200
201         mutex_lock(&head->mutex);
202         spin_lock(&delayed_refs->lock);
203         if (!head->node.in_tree) {
204                 mutex_unlock(&head->mutex);
205                 btrfs_put_delayed_ref(&head->node);
206                 return -EAGAIN;
207         }
208         btrfs_put_delayed_ref(&head->node);
209         return 0;
210 }
211
212 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
213                            struct list_head *cluster, u64 start)
214 {
215         int count = 0;
216         struct btrfs_delayed_ref_root *delayed_refs;
217         struct rb_node *node;
218         struct btrfs_delayed_ref_node *ref;
219         struct btrfs_delayed_ref_head *head;
220
221         delayed_refs = &trans->transaction->delayed_refs;
222         if (start == 0) {
223                 node = rb_first(&delayed_refs->root);
224         } else {
225                 ref = NULL;
226                 find_ref_head(&delayed_refs->root, start, &ref);
227                 if (ref) {
228                         struct btrfs_delayed_ref_node *tmp;
229
230                         node = rb_prev(&ref->rb_node);
231                         while (node) {
232                                 tmp = rb_entry(node,
233                                                struct btrfs_delayed_ref_node,
234                                                rb_node);
235                                 if (tmp->bytenr < start)
236                                         break;
237                                 ref = tmp;
238                                 node = rb_prev(&ref->rb_node);
239                         }
240                         node = &ref->rb_node;
241                 } else
242                         node = rb_first(&delayed_refs->root);
243         }
244 again:
245         while (node && count < 32) {
246                 ref = rb_entry(node, struct btrfs_delayed_ref_node, rb_node);
247                 if (btrfs_delayed_ref_is_head(ref)) {
248                         head = btrfs_delayed_node_to_head(ref);
249                         if (list_empty(&head->cluster)) {
250                                 list_add_tail(&head->cluster, cluster);
251                                 delayed_refs->run_delayed_start =
252                                         head->node.bytenr;
253                                 count++;
254
255                                 WARN_ON(delayed_refs->num_heads_ready == 0);
256                                 delayed_refs->num_heads_ready--;
257                         } else if (count) {
258                                 /* the goal of the clustering is to find extents
259                                  * that are likely to end up in the same extent
260                                  * leaf on disk.  So, we don't want them spread
261                                  * all over the tree.  Stop now if we've hit
262                                  * a head that was already in use
263                                  */
264                                 break;
265                         }
266                 }
267                 node = rb_next(node);
268         }
269         if (count) {
270                 return 0;
271         } else if (start) {
272                 /*
273                  * we've gone to the end of the rbtree without finding any
274                  * clusters.  start from the beginning and try again
275                  */
276                 start = 0;
277                 node = rb_first(&delayed_refs->root);
278                 goto again;
279         }
280         return 1;
281 }
282
283 /*
284  * This checks to see if there are any delayed refs in the
285  * btree for a given bytenr.  It returns one if it finds any
286  * and zero otherwise.
287  *
288  * If it only finds a head node, it returns 0.
289  *
290  * The idea is to use this when deciding if you can safely delete an
291  * extent from the extent allocation tree.  There may be a pending
292  * ref in the rbtree that adds or removes references, so as long as this
293  * returns one you need to leave the BTRFS_EXTENT_ITEM in the extent
294  * allocation tree.
295  */
296 int btrfs_delayed_ref_pending(struct btrfs_trans_handle *trans, u64 bytenr)
297 {
298         struct btrfs_delayed_ref_node *ref;
299         struct btrfs_delayed_ref_root *delayed_refs;
300         struct rb_node *prev_node;
301         int ret = 0;
302
303         delayed_refs = &trans->transaction->delayed_refs;
304         spin_lock(&delayed_refs->lock);
305
306         ref = find_ref_head(&delayed_refs->root, bytenr, NULL);
307         if (ref) {
308                 prev_node = rb_prev(&ref->rb_node);
309                 if (!prev_node)
310                         goto out;
311                 ref = rb_entry(prev_node, struct btrfs_delayed_ref_node,
312                                rb_node);
313                 if (ref->bytenr == bytenr)
314                         ret = 1;
315         }
316 out:
317         spin_unlock(&delayed_refs->lock);
318         return ret;
319 }
320
321 /*
322  * helper function to update an extent delayed ref in the
323  * rbtree.  existing and update must both have the same
324  * bytenr and parent
325  *
326  * This may free existing if the update cancels out whatever
327  * operation it was doing.
328  */
329 static noinline void
330 update_existing_ref(struct btrfs_trans_handle *trans,
331                     struct btrfs_delayed_ref_root *delayed_refs,
332                     struct btrfs_delayed_ref_node *existing,
333                     struct btrfs_delayed_ref_node *update)
334 {
335         if (update->action != existing->action) {
336                 /*
337                  * this is effectively undoing either an add or a
338                  * drop.  We decrement the ref_mod, and if it goes
339                  * down to zero we just delete the entry without
340                  * every changing the extent allocation tree.
341                  */
342                 existing->ref_mod--;
343                 if (existing->ref_mod == 0) {
344                         rb_erase(&existing->rb_node,
345                                  &delayed_refs->root);
346                         existing->in_tree = 0;
347                         btrfs_put_delayed_ref(existing);
348                         delayed_refs->num_entries--;
349                         if (trans->delayed_ref_updates)
350                                 trans->delayed_ref_updates--;
351                 } else {
352                         WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
353                                 existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
354                 }
355         } else {
356                 WARN_ON(existing->type == BTRFS_TREE_BLOCK_REF_KEY ||
357                         existing->type == BTRFS_SHARED_BLOCK_REF_KEY);
358                 /*
359                  * the action on the existing ref matches
360                  * the action on the ref we're trying to add.
361                  * Bump the ref_mod by one so the backref that
362                  * is eventually added/removed has the correct
363                  * reference count
364                  */
365                 existing->ref_mod += update->ref_mod;
366         }
367 }
368
369 /*
370  * helper function to update the accounting in the head ref
371  * existing and update must have the same bytenr
372  */
373 static noinline void
374 update_existing_head_ref(struct btrfs_delayed_ref_node *existing,
375                          struct btrfs_delayed_ref_node *update)
376 {
377         struct btrfs_delayed_ref_head *existing_ref;
378         struct btrfs_delayed_ref_head *ref;
379
380         existing_ref = btrfs_delayed_node_to_head(existing);
381         ref = btrfs_delayed_node_to_head(update);
382         BUG_ON(existing_ref->is_data != ref->is_data);
383
384         if (ref->must_insert_reserved) {
385                 /* if the extent was freed and then
386                  * reallocated before the delayed ref
387                  * entries were processed, we can end up
388                  * with an existing head ref without
389                  * the must_insert_reserved flag set.
390                  * Set it again here
391                  */
392                 existing_ref->must_insert_reserved = ref->must_insert_reserved;
393
394                 /*
395                  * update the num_bytes so we make sure the accounting
396                  * is done correctly
397                  */
398                 existing->num_bytes = update->num_bytes;
399
400         }
401
402         if (ref->extent_op) {
403                 if (!existing_ref->extent_op) {
404                         existing_ref->extent_op = ref->extent_op;
405                 } else {
406                         if (ref->extent_op->update_key) {
407                                 memcpy(&existing_ref->extent_op->key,
408                                        &ref->extent_op->key,
409                                        sizeof(ref->extent_op->key));
410                                 existing_ref->extent_op->update_key = 1;
411                         }
412                         if (ref->extent_op->update_flags) {
413                                 existing_ref->extent_op->flags_to_set |=
414                                         ref->extent_op->flags_to_set;
415                                 existing_ref->extent_op->update_flags = 1;
416                         }
417                         kfree(ref->extent_op);
418                 }
419         }
420         /*
421          * update the reference mod on the head to reflect this new operation
422          */
423         existing->ref_mod += update->ref_mod;
424 }
425
426 /*
427  * helper function to actually insert a head node into the rbtree.
428  * this does all the dirty work in terms of maintaining the correct
429  * overall modification count.
430  */
431 static noinline int add_delayed_ref_head(struct btrfs_trans_handle *trans,
432                                         struct btrfs_delayed_ref_node *ref,
433                                         u64 bytenr, u64 num_bytes,
434                                         int action, int is_data)
435 {
436         struct btrfs_delayed_ref_node *existing;
437         struct btrfs_delayed_ref_head *head_ref = NULL;
438         struct btrfs_delayed_ref_root *delayed_refs;
439         int count_mod = 1;
440         int must_insert_reserved = 0;
441
442         /*
443          * the head node stores the sum of all the mods, so dropping a ref
444          * should drop the sum in the head node by one.
445          */
446         if (action == BTRFS_UPDATE_DELAYED_HEAD)
447                 count_mod = 0;
448         else if (action == BTRFS_DROP_DELAYED_REF)
449                 count_mod = -1;
450
451         /*
452          * BTRFS_ADD_DELAYED_EXTENT means that we need to update
453          * the reserved accounting when the extent is finally added, or
454          * if a later modification deletes the delayed ref without ever
455          * inserting the extent into the extent allocation tree.
456          * ref->must_insert_reserved is the flag used to record
457          * that accounting mods are required.
458          *
459          * Once we record must_insert_reserved, switch the action to
460          * BTRFS_ADD_DELAYED_REF because other special casing is not required.
461          */
462         if (action == BTRFS_ADD_DELAYED_EXTENT)
463                 must_insert_reserved = 1;
464         else
465                 must_insert_reserved = 0;
466
467         delayed_refs = &trans->transaction->delayed_refs;
468
469         /* first set the basic ref node struct up */
470         atomic_set(&ref->refs, 1);
471         ref->bytenr = bytenr;
472         ref->num_bytes = num_bytes;
473         ref->ref_mod = count_mod;
474         ref->type  = 0;
475         ref->action  = 0;
476         ref->is_head = 1;
477         ref->in_tree = 1;
478
479         head_ref = btrfs_delayed_node_to_head(ref);
480         head_ref->must_insert_reserved = must_insert_reserved;
481         head_ref->is_data = is_data;
482
483         INIT_LIST_HEAD(&head_ref->cluster);
484         mutex_init(&head_ref->mutex);
485
486         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
487
488         if (existing) {
489                 update_existing_head_ref(existing, ref);
490                 /*
491                  * we've updated the existing ref, free the newly
492                  * allocated ref
493                  */
494                 kfree(ref);
495         } else {
496                 delayed_refs->num_heads++;
497                 delayed_refs->num_heads_ready++;
498                 delayed_refs->num_entries++;
499                 trans->delayed_ref_updates++;
500         }
501         return 0;
502 }
503
504 /*
505  * helper to insert a delayed tree ref into the rbtree.
506  */
507 static noinline int add_delayed_tree_ref(struct btrfs_trans_handle *trans,
508                                          struct btrfs_delayed_ref_node *ref,
509                                          u64 bytenr, u64 num_bytes, u64 parent,
510                                          u64 ref_root, int level, int action)
511 {
512         struct btrfs_delayed_ref_node *existing;
513         struct btrfs_delayed_tree_ref *full_ref;
514         struct btrfs_delayed_ref_root *delayed_refs;
515
516         if (action == BTRFS_ADD_DELAYED_EXTENT)
517                 action = BTRFS_ADD_DELAYED_REF;
518
519         delayed_refs = &trans->transaction->delayed_refs;
520
521         /* first set the basic ref node struct up */
522         atomic_set(&ref->refs, 1);
523         ref->bytenr = bytenr;
524         ref->num_bytes = num_bytes;
525         ref->ref_mod = 1;
526         ref->action = action;
527         ref->is_head = 0;
528         ref->in_tree = 1;
529
530         full_ref = btrfs_delayed_node_to_tree_ref(ref);
531         if (parent) {
532                 full_ref->parent = parent;
533                 ref->type = BTRFS_SHARED_BLOCK_REF_KEY;
534         } else {
535                 full_ref->root = ref_root;
536                 ref->type = BTRFS_TREE_BLOCK_REF_KEY;
537         }
538         full_ref->level = level;
539
540         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
541
542         if (existing) {
543                 update_existing_ref(trans, delayed_refs, existing, ref);
544                 /*
545                  * we've updated the existing ref, free the newly
546                  * allocated ref
547                  */
548                 kfree(ref);
549         } else {
550                 delayed_refs->num_entries++;
551                 trans->delayed_ref_updates++;
552         }
553         return 0;
554 }
555
556 /*
557  * helper to insert a delayed data ref into the rbtree.
558  */
559 static noinline int add_delayed_data_ref(struct btrfs_trans_handle *trans,
560                                          struct btrfs_delayed_ref_node *ref,
561                                          u64 bytenr, u64 num_bytes, u64 parent,
562                                          u64 ref_root, u64 owner, u64 offset,
563                                          int action)
564 {
565         struct btrfs_delayed_ref_node *existing;
566         struct btrfs_delayed_data_ref *full_ref;
567         struct btrfs_delayed_ref_root *delayed_refs;
568
569         if (action == BTRFS_ADD_DELAYED_EXTENT)
570                 action = BTRFS_ADD_DELAYED_REF;
571
572         delayed_refs = &trans->transaction->delayed_refs;
573
574         /* first set the basic ref node struct up */
575         atomic_set(&ref->refs, 1);
576         ref->bytenr = bytenr;
577         ref->num_bytes = num_bytes;
578         ref->ref_mod = 1;
579         ref->action = action;
580         ref->is_head = 0;
581         ref->in_tree = 1;
582
583         full_ref = btrfs_delayed_node_to_data_ref(ref);
584         if (parent) {
585                 full_ref->parent = parent;
586                 ref->type = BTRFS_SHARED_DATA_REF_KEY;
587         } else {
588                 full_ref->root = ref_root;
589                 ref->type = BTRFS_EXTENT_DATA_REF_KEY;
590         }
591         full_ref->objectid = owner;
592         full_ref->offset = offset;
593
594         existing = tree_insert(&delayed_refs->root, &ref->rb_node);
595
596         if (existing) {
597                 update_existing_ref(trans, delayed_refs, existing, ref);
598                 /*
599                  * we've updated the existing ref, free the newly
600                  * allocated ref
601                  */
602                 kfree(ref);
603         } else {
604                 delayed_refs->num_entries++;
605                 trans->delayed_ref_updates++;
606         }
607         return 0;
608 }
609
610 /*
611  * add a delayed tree ref.  This does all of the accounting required
612  * to make sure the delayed ref is eventually processed before this
613  * transaction commits.
614  */
615 int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
616                                u64 bytenr, u64 num_bytes, u64 parent,
617                                u64 ref_root,  int level, int action,
618                                struct btrfs_delayed_extent_op *extent_op)
619 {
620         struct btrfs_delayed_tree_ref *ref;
621         struct btrfs_delayed_ref_head *head_ref;
622         struct btrfs_delayed_ref_root *delayed_refs;
623         int ret;
624
625         BUG_ON(extent_op && extent_op->is_data);
626         ref = kmalloc(sizeof(*ref), GFP_NOFS);
627         if (!ref)
628                 return -ENOMEM;
629
630         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
631         if (!head_ref) {
632                 kfree(ref);
633                 return -ENOMEM;
634         }
635
636         head_ref->extent_op = extent_op;
637
638         delayed_refs = &trans->transaction->delayed_refs;
639         spin_lock(&delayed_refs->lock);
640
641         /*
642          * insert both the head node and the new ref without dropping
643          * the spin lock
644          */
645         ret = add_delayed_ref_head(trans, &head_ref->node, bytenr, num_bytes,
646                                    action, 0);
647         BUG_ON(ret);
648
649         ret = add_delayed_tree_ref(trans, &ref->node, bytenr, num_bytes,
650                                    parent, ref_root, level, action);
651         BUG_ON(ret);
652         spin_unlock(&delayed_refs->lock);
653         return 0;
654 }
655
656 /*
657  * add a delayed data ref. it's similar to btrfs_add_delayed_tree_ref.
658  */
659 int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
660                                u64 bytenr, u64 num_bytes,
661                                u64 parent, u64 ref_root,
662                                u64 owner, u64 offset, int action,
663                                struct btrfs_delayed_extent_op *extent_op)
664 {
665         struct btrfs_delayed_data_ref *ref;
666         struct btrfs_delayed_ref_head *head_ref;
667         struct btrfs_delayed_ref_root *delayed_refs;
668         int ret;
669
670         BUG_ON(extent_op && !extent_op->is_data);
671         ref = kmalloc(sizeof(*ref), GFP_NOFS);
672         if (!ref)
673                 return -ENOMEM;
674
675         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
676         if (!head_ref) {
677                 kfree(ref);
678                 return -ENOMEM;
679         }
680
681         head_ref->extent_op = extent_op;
682
683         delayed_refs = &trans->transaction->delayed_refs;
684         spin_lock(&delayed_refs->lock);
685
686         /*
687          * insert both the head node and the new ref without dropping
688          * the spin lock
689          */
690         ret = add_delayed_ref_head(trans, &head_ref->node, bytenr, num_bytes,
691                                    action, 1);
692         BUG_ON(ret);
693
694         ret = add_delayed_data_ref(trans, &ref->node, bytenr, num_bytes,
695                                    parent, ref_root, owner, offset, action);
696         BUG_ON(ret);
697         spin_unlock(&delayed_refs->lock);
698         return 0;
699 }
700
701 int btrfs_add_delayed_extent_op(struct btrfs_trans_handle *trans,
702                                 u64 bytenr, u64 num_bytes,
703                                 struct btrfs_delayed_extent_op *extent_op)
704 {
705         struct btrfs_delayed_ref_head *head_ref;
706         struct btrfs_delayed_ref_root *delayed_refs;
707         int ret;
708
709         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
710         if (!head_ref)
711                 return -ENOMEM;
712
713         head_ref->extent_op = extent_op;
714
715         delayed_refs = &trans->transaction->delayed_refs;
716         spin_lock(&delayed_refs->lock);
717
718         ret = add_delayed_ref_head(trans, &head_ref->node, bytenr,
719                                    num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
720                                    extent_op->is_data);
721         BUG_ON(ret);
722
723         spin_unlock(&delayed_refs->lock);
724         return 0;
725 }
726
727 /*
728  * this does a simple search for the head node for a given extent.
729  * It must be called with the delayed ref spinlock held, and it returns
730  * the head node if any where found, or NULL if not.
731  */
732 struct btrfs_delayed_ref_head *
733 btrfs_find_delayed_ref_head(struct btrfs_trans_handle *trans, u64 bytenr)
734 {
735         struct btrfs_delayed_ref_node *ref;
736         struct btrfs_delayed_ref_root *delayed_refs;
737
738         delayed_refs = &trans->transaction->delayed_refs;
739         ref = find_ref_head(&delayed_refs->root, bytenr, NULL);
740         if (ref)
741                 return btrfs_delayed_node_to_head(ref);
742         return NULL;
743 }
744
745 /*
746  * add a delayed ref to the tree.  This does all of the accounting required
747  * to make sure the delayed ref is eventually processed before this
748  * transaction commits.
749  *
750  * The main point of this call is to add and remove a backreference in a single
751  * shot, taking the lock only once, and only searching for the head node once.
752  *
753  * It is the same as doing a ref add and delete in two separate calls.
754  */
755 #if 0
756 int btrfs_update_delayed_ref(struct btrfs_trans_handle *trans,
757                           u64 bytenr, u64 num_bytes, u64 orig_parent,
758                           u64 parent, u64 orig_ref_root, u64 ref_root,
759                           u64 orig_ref_generation, u64 ref_generation,
760                           u64 owner_objectid, int pin)
761 {
762         struct btrfs_delayed_ref *ref;
763         struct btrfs_delayed_ref *old_ref;
764         struct btrfs_delayed_ref_head *head_ref;
765         struct btrfs_delayed_ref_root *delayed_refs;
766         int ret;
767
768         ref = kmalloc(sizeof(*ref), GFP_NOFS);
769         if (!ref)
770                 return -ENOMEM;
771
772         old_ref = kmalloc(sizeof(*old_ref), GFP_NOFS);
773         if (!old_ref) {
774                 kfree(ref);
775                 return -ENOMEM;
776         }
777
778         /*
779          * the parent = 0 case comes from cases where we don't actually
780          * know the parent yet.  It will get updated later via a add/drop
781          * pair.
782          */
783         if (parent == 0)
784                 parent = bytenr;
785         if (orig_parent == 0)
786                 orig_parent = bytenr;
787
788         head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
789         if (!head_ref) {
790                 kfree(ref);
791                 kfree(old_ref);
792                 return -ENOMEM;
793         }
794         delayed_refs = &trans->transaction->delayed_refs;
795         spin_lock(&delayed_refs->lock);
796
797         /*
798          * insert both the head node and the new ref without dropping
799          * the spin lock
800          */
801         ret = __btrfs_add_delayed_ref(trans, &head_ref->node, bytenr, num_bytes,
802                                       (u64)-1, 0, 0, 0,
803                                       BTRFS_UPDATE_DELAYED_HEAD, 0);
804         BUG_ON(ret);
805
806         ret = __btrfs_add_delayed_ref(trans, &ref->node, bytenr, num_bytes,
807                                       parent, ref_root, ref_generation,
808                                       owner_objectid, BTRFS_ADD_DELAYED_REF, 0);
809         BUG_ON(ret);
810
811         ret = __btrfs_add_delayed_ref(trans, &old_ref->node, bytenr, num_bytes,
812                                       orig_parent, orig_ref_root,
813                                       orig_ref_generation, owner_objectid,
814                                       BTRFS_DROP_DELAYED_REF, pin);
815         BUG_ON(ret);
816         spin_unlock(&delayed_refs->lock);
817         return 0;
818 }
819 #endif