File: delayed-ref.c

package info (click to toggle)
btrfs-progs 4.20.1-2
  • links: PTS, VCS
  • area: main
  • in suites: buster
  • size: 14,444 kB
  • sloc: ansic: 90,777; sh: 7,369; python: 1,256; makefile: 654
file content (607 lines) | stat: -rw-r--r-- 16,070 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2009 Oracle.  All rights reserved.
 */

#include "ctree.h"
#include "btrfs-list.h"
#include "delayed-ref.h"
#include "transaction.h"

/*
 * delayed back reference update tracking.  For subvolume trees
 * we queue up extent allocations and backref maintenance for
 * delayed processing.   This avoids deep call chains where we
 * add extents in the middle of btrfs_search_slot, and it allows
 * us to buffer up frequently modified backrefs in an rb tree instead
 * of hammering updates on the extent allocation tree.
 */

/*
 * compare two delayed tree backrefs with same bytenr and type
 */
static int comp_tree_refs(struct btrfs_delayed_tree_ref *ref1,
			  struct btrfs_delayed_tree_ref *ref2)
{
	if (ref1->node.type == BTRFS_TREE_BLOCK_REF_KEY) {
		if (ref1->root < ref2->root)
			return -1;
		if (ref1->root > ref2->root)
			return 1;
	} else {
		if (ref1->parent < ref2->parent)
			return -1;
		if (ref1->parent > ref2->parent)
			return 1;
	}
	return 0;
}

static int comp_refs(struct btrfs_delayed_ref_node *ref1,
		     struct btrfs_delayed_ref_node *ref2,
		     bool check_seq)
{
	int ret = 0;

	if (ref1->type < ref2->type)
		return -1;
	if (ref1->type > ref2->type)
		return 1;
	if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
	    ref1->type == BTRFS_SHARED_BLOCK_REF_KEY)
		ret = comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref1),
				     btrfs_delayed_node_to_tree_ref(ref2));
	else
		BUG();

	if (ret)
		return ret;
	if (check_seq) {
		if (ref1->seq < ref2->seq)
			return -1;
		if (ref1->seq > ref2->seq)
			return 1;
	}
	return 0;
}

/* insert a new ref to head ref rbtree */
static struct btrfs_delayed_ref_head *htree_insert(struct rb_root *root,
						   struct rb_node *node)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent_node = NULL;
	struct btrfs_delayed_ref_head *entry;
	struct btrfs_delayed_ref_head *ins;
	u64 bytenr;

	ins = rb_entry(node, struct btrfs_delayed_ref_head, href_node);
	bytenr = ins->bytenr;
	while (*p) {
		parent_node = *p;
		entry = rb_entry(parent_node, struct btrfs_delayed_ref_head,
				 href_node);

		if (bytenr < entry->bytenr)
			p = &(*p)->rb_left;
		else if (bytenr > entry->bytenr)
			p = &(*p)->rb_right;
		else
			return entry;
	}

	rb_link_node(node, parent_node, p);
	rb_insert_color(node, root);
	return NULL;
}

static struct btrfs_delayed_ref_node* tree_insert(struct rb_root *root,
		struct btrfs_delayed_ref_node *ins)
{
	struct rb_node **p = &root->rb_node;
	struct rb_node *node = &ins->ref_node;
	struct rb_node *parent_node = NULL;
	struct btrfs_delayed_ref_node *entry;

	while (*p) {
		int comp;

		parent_node = *p;
		entry = rb_entry(parent_node, struct btrfs_delayed_ref_node,
				 ref_node);
		comp = comp_refs(ins, entry, true);
		if (comp < 0)
			p = &(*p)->rb_left;
		else if (comp > 0)
			p = &(*p)->rb_right;
		else
			return entry;
	}

	rb_link_node(node, parent_node, p);
	rb_insert_color(node, root);
	return NULL;
}

/*
 * find an head entry based on bytenr. This returns the delayed ref
 * head if it was able to find one, or NULL if nothing was in that spot.
 * If return_bigger is given, the next bigger entry is returned if no exact
 * match is found.
 */
static struct btrfs_delayed_ref_head *
find_ref_head(struct rb_root *root, u64 bytenr,
	      int return_bigger)
{
	struct rb_node *n;
	struct btrfs_delayed_ref_head *entry;

	n = root->rb_node;
	entry = NULL;
	while (n) {
		entry = rb_entry(n, struct btrfs_delayed_ref_head, href_node);

		if (bytenr < entry->bytenr)
			n = n->rb_left;
		else if (bytenr > entry->bytenr)
			n = n->rb_right;
		else
			return entry;
	}
	if (entry && return_bigger) {
		if (bytenr > entry->bytenr) {
			n = rb_next(&entry->href_node);
			if (!n)
				n = rb_first(root);
			entry = rb_entry(n, struct btrfs_delayed_ref_head,
					 href_node);
			return entry;
		}
		return entry;
	}
	return NULL;
}

static inline void drop_delayed_ref(struct btrfs_trans_handle *trans,
				    struct btrfs_delayed_ref_root *delayed_refs,
				    struct btrfs_delayed_ref_head *head,
				    struct btrfs_delayed_ref_node *ref)
{
	rb_erase(&ref->ref_node, &head->ref_tree);
	RB_CLEAR_NODE(&ref->ref_node);
	if (!list_empty(&ref->add_list))
		list_del(&ref->add_list);
	ref->in_tree = 0;
	btrfs_put_delayed_ref(ref);
	if (trans->delayed_ref_updates)
		trans->delayed_ref_updates--;
}

static bool merge_ref(struct btrfs_trans_handle *trans,
		      struct btrfs_delayed_ref_root *delayed_refs,
		      struct btrfs_delayed_ref_head *head,
		      struct btrfs_delayed_ref_node *ref,
		      u64 seq)
{
	struct btrfs_delayed_ref_node *next;
	struct rb_node *node = rb_next(&ref->ref_node);
	bool done = false;

	while (!done && node) {
		int mod;

		next = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
		node = rb_next(node);
		if (seq && next->seq >= seq)
			break;
		if (comp_refs(ref, next, false))
			break;

		if (ref->action == next->action) {
			mod = next->ref_mod;
		} else {
			if (ref->ref_mod < next->ref_mod) {
				__swap(ref, next);
				done = true;
			}
			mod = -next->ref_mod;
		}

		drop_delayed_ref(trans, delayed_refs, head, next);
		ref->ref_mod += mod;
		if (ref->ref_mod == 0) {
			drop_delayed_ref(trans, delayed_refs, head, ref);
			done = true;
		} else {
			/*
			 * Can't have multiples of the same ref on a tree block.
			 */
			WARN_ON(ref->type == BTRFS_TREE_BLOCK_REF_KEY ||
				ref->type == BTRFS_SHARED_BLOCK_REF_KEY);
		}
	}

	return done;
}

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_node *ref;
	struct rb_node *node;

	if (RB_EMPTY_ROOT(&head->ref_tree))
		return;

	/* We don't have too many refs to merge for data. */
	if (head->is_data)
		return;

again:
	for (node = rb_first(&head->ref_tree); node; node = rb_next(node)) {
		ref = rb_entry(node, struct btrfs_delayed_ref_node, ref_node);
		if (merge_ref(trans, delayed_refs, head, ref, 0))
			goto again;
	}
}

struct btrfs_delayed_ref_head *
btrfs_select_ref_head(struct btrfs_trans_handle *trans)
{
	struct btrfs_delayed_ref_root *delayed_refs;
	struct btrfs_delayed_ref_head *head;
	u64 start;
	bool loop = false;

	delayed_refs = &trans->delayed_refs;

again:
	start = delayed_refs->run_delayed_start;
	head = find_ref_head(&delayed_refs->href_root, start, 1);
	if (!head && !loop) {
		delayed_refs->run_delayed_start = 0;
		start = 0;
		loop = true;
		head = find_ref_head(&delayed_refs->href_root, start, 1);
		if (!head)
			return NULL;
	} else if (!head && loop) {
		return NULL;
	}

	while (head->processing) {
		struct rb_node *node;

		node = rb_next(&head->href_node);
		if (!node) {
			if (loop)
				return NULL;
			delayed_refs->run_delayed_start = 0;
			start = 0;
			loop = true;
			goto again;
		}
		head = rb_entry(node, struct btrfs_delayed_ref_head,
				href_node);
	}

	head->processing = 1;
	WARN_ON(delayed_refs->num_heads_ready == 0);
	delayed_refs->num_heads_ready--;
	delayed_refs->run_delayed_start = head->bytenr +
		head->num_bytes;
	return head;
}

/*
 * Helper to insert the ref_node to the tail or merge with tail.
 *
 * Return 0 for insert.
 * Return >0 for merge.
 */
static int insert_delayed_ref(struct btrfs_trans_handle *trans,
			      struct btrfs_delayed_ref_root *root,
			      struct btrfs_delayed_ref_head *href,
			      struct btrfs_delayed_ref_node *ref)
{
	struct btrfs_delayed_ref_node *exist;
	int mod;
	int ret = 0;

	exist = tree_insert(&href->ref_tree, ref);
	if (!exist)
		goto inserted;

	/* Now we are sure we can merge */
	ret = 1;
	if (exist->action == ref->action) {
		mod = ref->ref_mod;
	} else {
		/* Need to change action */
		if (exist->ref_mod < ref->ref_mod) {
			exist->action = ref->action;
			mod = -exist->ref_mod;
			exist->ref_mod = ref->ref_mod;
			if (ref->action == BTRFS_ADD_DELAYED_REF)
				list_add_tail(&exist->add_list,
					      &href->ref_add_list);
			else if (ref->action == BTRFS_DROP_DELAYED_REF) {
				ASSERT(!list_empty(&exist->add_list));
				list_del(&exist->add_list);
			} else {
				ASSERT(0);
			}
		} else
			mod = -ref->ref_mod;
	}
	exist->ref_mod += mod;

	/* remove existing tail if its ref_mod is zero */
	if (exist->ref_mod == 0)
		drop_delayed_ref(trans, root, href, exist);
	return ret;
inserted:
	if (ref->action == BTRFS_ADD_DELAYED_REF)
		list_add_tail(&ref->add_list, &href->ref_add_list);
	trans->delayed_ref_updates++;
	return ret;
}

/*
 * helper function to update the accounting in the head ref
 * existing and update must have the same bytenr
 */
static noinline void
update_existing_head_ref(struct btrfs_delayed_ref_root *delayed_refs,
			 struct btrfs_delayed_ref_head *existing,
			 struct btrfs_delayed_ref_head *update,
			 int *old_ref_mod_ret)
{
	int old_ref_mod;

	BUG_ON(existing->is_data != update->is_data);

	if (update->must_insert_reserved) {
		/* if the extent was freed and then
		 * reallocated before the delayed ref
		 * entries were processed, we can end up
		 * with an existing head ref without
		 * the must_insert_reserved flag set.
		 * Set it again here
		 */
		existing->must_insert_reserved = update->must_insert_reserved;

		/*
		 * update the num_bytes so we make sure the accounting
		 * is done correctly
		 */
		existing->num_bytes = update->num_bytes;

	}

	if (update->extent_op) {
		if (!existing->extent_op) {
			existing->extent_op = update->extent_op;
		} else {
			if (update->extent_op->update_key) {
				memcpy(&existing->extent_op->key,
				       &update->extent_op->key,
				       sizeof(update->extent_op->key));
				existing->extent_op->update_key = true;
			}
			if (update->extent_op->update_flags) {
				existing->extent_op->flags_to_set |=
					update->extent_op->flags_to_set;
				existing->extent_op->update_flags = true;
			}
			btrfs_free_delayed_extent_op(update->extent_op);
		}
	}
	/*
	 * update the reference mod on the head to reflect this new operation,
	 * only need the lock for this case cause we could be processing it
	 * currently, for refs we just added we know we're a-ok.
	 */
	old_ref_mod = existing->total_ref_mod;
	if (old_ref_mod_ret)
		*old_ref_mod_ret = old_ref_mod;
	existing->ref_mod += update->ref_mod;
	existing->total_ref_mod += update->ref_mod;

}

static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
				  void *qrecord,
				  u64 bytenr, u64 num_bytes, u64 ref_root,
				  u64 reserved, int action, bool is_data,
				  bool is_system)
{
	int count_mod = 1;
	int must_insert_reserved = 0;

	/* If reserved is provided, it must be a data extent. */
	BUG_ON(!is_data && reserved);

	/*
	 * The head node stores the sum of all the mods, so dropping a ref
	 * should drop the sum in the head node by one.
	 */
	if (action == BTRFS_UPDATE_DELAYED_HEAD)
		count_mod = 0;
	else if (action == BTRFS_DROP_DELAYED_REF)
		count_mod = -1;

	/*
	 * BTRFS_ADD_DELAYED_EXTENT means that we need to update the reserved
	 * accounting when the extent is finally added, or if a later
	 * modification deletes the delayed ref without ever inserting the
	 * extent into the extent allocation tree.  ref->must_insert_reserved
	 * is the flag used to record that accounting mods are required.
	 *
	 * Once we record must_insert_reserved, switch the action to
	 * BTRFS_ADD_DELAYED_REF because other special casing is not required.
	 */
	if (action == BTRFS_ADD_DELAYED_EXTENT)
		must_insert_reserved = 1;
	else
		must_insert_reserved = 0;

	head_ref->refs = 1;
	head_ref->bytenr = bytenr;
	head_ref->num_bytes = num_bytes;
	head_ref->ref_mod = count_mod;
	head_ref->must_insert_reserved = must_insert_reserved;
	head_ref->is_data = is_data;
	head_ref->is_system = is_system;
	head_ref->ref_tree = RB_ROOT;
	INIT_LIST_HEAD(&head_ref->ref_add_list);
	RB_CLEAR_NODE(&head_ref->href_node);
	head_ref->processing = 0;
	head_ref->total_ref_mod = count_mod;
}

/*
 * helper function to actually insert a head node into the rbtree.
 * this does all the dirty work in terms of maintaining the correct
 * overall modification count.
 */
static noinline struct btrfs_delayed_ref_head *
add_delayed_ref_head(struct btrfs_trans_handle *trans,
		     struct btrfs_delayed_ref_head *head_ref,
		     void *qrecord,
		     int action, int *qrecord_inserted_ret,
		     int *old_ref_mod, int *new_ref_mod)
{
	struct btrfs_delayed_ref_head *existing;
	struct btrfs_delayed_ref_root *delayed_refs;

	delayed_refs = &trans->delayed_refs;

	existing = htree_insert(&delayed_refs->href_root, &head_ref->href_node);
	if (existing) {
		update_existing_head_ref(delayed_refs, existing, head_ref, old_ref_mod);
		/*
		 * we've updated the existing ref, free the newly
		 * allocated ref
		 */
		kfree(head_ref);
		head_ref = existing;
	} else {
		if (old_ref_mod)
			*old_ref_mod = 0;
		delayed_refs->num_heads++;
		delayed_refs->num_heads_ready++;
		trans->delayed_ref_updates++;
	}
	if (new_ref_mod)
		*new_ref_mod = head_ref->total_ref_mod;

	return head_ref;
}

/*
 * init_delayed_ref_common - Initialize the structure which represents a
 *			     modification to a an extent.
 *
 * @fs_info:    Internal to the mounted filesystem mount structure.
 *
 * @ref:	The structure which is going to be initialized.
 *
 * @bytenr:	The logical address of the extent for which a modification is
 *		going to be recorded.
 *
 * @num_bytes:  Size of the extent whose modification is being recorded.
 *
 * @ref_root:	The id of the root where this modification has originated, this
 *		can be either one of the well-known metadata trees or the
 *		subvolume id which references this extent.
 *
 * @action:	Can be one of BTRFS_ADD_DELAYED_REF/BTRFS_DROP_DELAYED_REF or
 *		BTRFS_ADD_DELAYED_EXTENT
 *
 * @ref_type:	Holds the type of the extent which is being recorded, can be
 *		one of BTRFS_SHARED_BLOCK_REF_KEY/BTRFS_TREE_BLOCK_REF_KEY
 *		when recording a metadata extent or BTRFS_SHARED_DATA_REF_KEY/
 *		BTRFS_EXTENT_DATA_REF_KEY when recording data extent
 */
static void init_delayed_ref_common(struct btrfs_fs_info *fs_info,
				    struct btrfs_delayed_ref_node *ref,
				    u64 bytenr, u64 num_bytes, u64 ref_root,
				    int action, u8 ref_type)
{
	if (action == BTRFS_ADD_DELAYED_EXTENT)
		action = BTRFS_ADD_DELAYED_REF;

	ref->refs = 1;
	ref->bytenr = bytenr;
	ref->num_bytes = num_bytes;
	ref->ref_mod = 1;
	ref->action = action;
	ref->is_head = 0;
	ref->in_tree = 1;
	ref->seq = 0;
	ref->type = ref_type;
	RB_CLEAR_NODE(&ref->ref_node);
	INIT_LIST_HEAD(&ref->add_list);
}

/*
 * add a delayed tree ref.  This does all of the accounting required
 * to make sure the delayed ref is eventually processed before this
 * transaction commits.
 */
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 *old_ref_mod, int *new_ref_mod)
{
	struct btrfs_delayed_tree_ref *ref;
	struct btrfs_delayed_ref_head *head_ref;
	struct btrfs_delayed_ref_root *delayed_refs;
	bool is_system = (ref_root == BTRFS_CHUNK_TREE_OBJECTID);
	int ret;
	u8 ref_type;

	BUG_ON(extent_op && extent_op->is_data);
	ref = kmalloc(sizeof(*ref), GFP_NOFS);
	if (!ref)
		return -ENOMEM;

	if (parent)
		ref_type = BTRFS_SHARED_BLOCK_REF_KEY;
	else
		ref_type = BTRFS_TREE_BLOCK_REF_KEY;
	init_delayed_ref_common(fs_info, &ref->node, bytenr, num_bytes,
				ref_root, action, ref_type);
	ref->root = ref_root;
	ref->parent = parent;
	ref->level = level;

	head_ref = kmalloc(sizeof(*head_ref), GFP_NOFS);
	if (!head_ref)
		goto free_ref;

	init_delayed_ref_head(head_ref, NULL, bytenr, num_bytes,
			      ref_root, 0, action, false, is_system);
	head_ref->extent_op = extent_op;

	delayed_refs = &trans->delayed_refs;

	head_ref = add_delayed_ref_head(trans, head_ref, NULL, action, NULL,
			old_ref_mod, new_ref_mod);

	ret = insert_delayed_ref(trans, delayed_refs, head_ref, &ref->node);

	if (ret > 0)
		kfree(ref);

	return 0;

free_ref:
	kfree(ref);

	return -ENOMEM;
}