xref: /linux/fs/btrfs/ctree.c (revision 2ba9268dd603d23e17643437b2246acb6844953b)
1 /*
2  * Copyright (C) 2007,2008 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 
19 #include <linux/sched.h>
20 #include <linux/slab.h>
21 #include <linux/rbtree.h>
22 #include "ctree.h"
23 #include "disk-io.h"
24 #include "transaction.h"
25 #include "print-tree.h"
26 #include "locking.h"
27 
28 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
29 		      *root, struct btrfs_path *path, int level);
30 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
31 		      *root, struct btrfs_key *ins_key,
32 		      struct btrfs_path *path, int data_size, int extend);
33 static int push_node_left(struct btrfs_trans_handle *trans,
34 			  struct btrfs_root *root, struct extent_buffer *dst,
35 			  struct extent_buffer *src, int empty);
36 static int balance_node_right(struct btrfs_trans_handle *trans,
37 			      struct btrfs_root *root,
38 			      struct extent_buffer *dst_buf,
39 			      struct extent_buffer *src_buf);
40 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
41 		    int level, int slot);
42 static int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
43 				 struct extent_buffer *eb);
44 
45 struct btrfs_path *btrfs_alloc_path(void)
46 {
47 	struct btrfs_path *path;
48 	path = kmem_cache_zalloc(btrfs_path_cachep, GFP_NOFS);
49 	return path;
50 }
51 
52 /*
53  * set all locked nodes in the path to blocking locks.  This should
54  * be done before scheduling
55  */
56 noinline void btrfs_set_path_blocking(struct btrfs_path *p)
57 {
58 	int i;
59 	for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
60 		if (!p->nodes[i] || !p->locks[i])
61 			continue;
62 		btrfs_set_lock_blocking_rw(p->nodes[i], p->locks[i]);
63 		if (p->locks[i] == BTRFS_READ_LOCK)
64 			p->locks[i] = BTRFS_READ_LOCK_BLOCKING;
65 		else if (p->locks[i] == BTRFS_WRITE_LOCK)
66 			p->locks[i] = BTRFS_WRITE_LOCK_BLOCKING;
67 	}
68 }
69 
70 /*
71  * reset all the locked nodes in the patch to spinning locks.
72  *
73  * held is used to keep lockdep happy, when lockdep is enabled
74  * we set held to a blocking lock before we go around and
75  * retake all the spinlocks in the path.  You can safely use NULL
76  * for held
77  */
78 noinline void btrfs_clear_path_blocking(struct btrfs_path *p,
79 					struct extent_buffer *held, int held_rw)
80 {
81 	int i;
82 
83 	if (held) {
84 		btrfs_set_lock_blocking_rw(held, held_rw);
85 		if (held_rw == BTRFS_WRITE_LOCK)
86 			held_rw = BTRFS_WRITE_LOCK_BLOCKING;
87 		else if (held_rw == BTRFS_READ_LOCK)
88 			held_rw = BTRFS_READ_LOCK_BLOCKING;
89 	}
90 	btrfs_set_path_blocking(p);
91 
92 	for (i = BTRFS_MAX_LEVEL - 1; i >= 0; i--) {
93 		if (p->nodes[i] && p->locks[i]) {
94 			btrfs_clear_lock_blocking_rw(p->nodes[i], p->locks[i]);
95 			if (p->locks[i] == BTRFS_WRITE_LOCK_BLOCKING)
96 				p->locks[i] = BTRFS_WRITE_LOCK;
97 			else if (p->locks[i] == BTRFS_READ_LOCK_BLOCKING)
98 				p->locks[i] = BTRFS_READ_LOCK;
99 		}
100 	}
101 
102 	if (held)
103 		btrfs_clear_lock_blocking_rw(held, held_rw);
104 }
105 
106 /* this also releases the path */
107 void btrfs_free_path(struct btrfs_path *p)
108 {
109 	if (!p)
110 		return;
111 	btrfs_release_path(p);
112 	kmem_cache_free(btrfs_path_cachep, p);
113 }
114 
115 /*
116  * path release drops references on the extent buffers in the path
117  * and it drops any locks held by this path
118  *
119  * It is safe to call this on paths that no locks or extent buffers held.
120  */
121 noinline void btrfs_release_path(struct btrfs_path *p)
122 {
123 	int i;
124 
125 	for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
126 		p->slots[i] = 0;
127 		if (!p->nodes[i])
128 			continue;
129 		if (p->locks[i]) {
130 			btrfs_tree_unlock_rw(p->nodes[i], p->locks[i]);
131 			p->locks[i] = 0;
132 		}
133 		free_extent_buffer(p->nodes[i]);
134 		p->nodes[i] = NULL;
135 	}
136 }
137 
138 /*
139  * safely gets a reference on the root node of a tree.  A lock
140  * is not taken, so a concurrent writer may put a different node
141  * at the root of the tree.  See btrfs_lock_root_node for the
142  * looping required.
143  *
144  * The extent buffer returned by this has a reference taken, so
145  * it won't disappear.  It may stop being the root of the tree
146  * at any time because there are no locks held.
147  */
148 struct extent_buffer *btrfs_root_node(struct btrfs_root *root)
149 {
150 	struct extent_buffer *eb;
151 
152 	while (1) {
153 		rcu_read_lock();
154 		eb = rcu_dereference(root->node);
155 
156 		/*
157 		 * RCU really hurts here, we could free up the root node because
158 		 * it was cow'ed but we may not get the new root node yet so do
159 		 * the inc_not_zero dance and if it doesn't work then
160 		 * synchronize_rcu and try again.
161 		 */
162 		if (atomic_inc_not_zero(&eb->refs)) {
163 			rcu_read_unlock();
164 			break;
165 		}
166 		rcu_read_unlock();
167 		synchronize_rcu();
168 	}
169 	return eb;
170 }
171 
172 /* loop around taking references on and locking the root node of the
173  * tree until you end up with a lock on the root.  A locked buffer
174  * is returned, with a reference held.
175  */
176 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
177 {
178 	struct extent_buffer *eb;
179 
180 	while (1) {
181 		eb = btrfs_root_node(root);
182 		btrfs_tree_lock(eb);
183 		if (eb == root->node)
184 			break;
185 		btrfs_tree_unlock(eb);
186 		free_extent_buffer(eb);
187 	}
188 	return eb;
189 }
190 
191 /* loop around taking references on and locking the root node of the
192  * tree until you end up with a lock on the root.  A locked buffer
193  * is returned, with a reference held.
194  */
195 static struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
196 {
197 	struct extent_buffer *eb;
198 
199 	while (1) {
200 		eb = btrfs_root_node(root);
201 		btrfs_tree_read_lock(eb);
202 		if (eb == root->node)
203 			break;
204 		btrfs_tree_read_unlock(eb);
205 		free_extent_buffer(eb);
206 	}
207 	return eb;
208 }
209 
210 /* cowonly root (everything not a reference counted cow subvolume), just get
211  * put onto a simple dirty list.  transaction.c walks this to make sure they
212  * get properly updated on disk.
213  */
214 static void add_root_to_dirty_list(struct btrfs_root *root)
215 {
216 	if (test_bit(BTRFS_ROOT_DIRTY, &root->state) ||
217 	    !test_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state))
218 		return;
219 
220 	spin_lock(&root->fs_info->trans_lock);
221 	if (!test_and_set_bit(BTRFS_ROOT_DIRTY, &root->state)) {
222 		/* Want the extent tree to be the last on the list */
223 		if (root->objectid == BTRFS_EXTENT_TREE_OBJECTID)
224 			list_move_tail(&root->dirty_list,
225 				       &root->fs_info->dirty_cowonly_roots);
226 		else
227 			list_move(&root->dirty_list,
228 				  &root->fs_info->dirty_cowonly_roots);
229 	}
230 	spin_unlock(&root->fs_info->trans_lock);
231 }
232 
233 /*
234  * used by snapshot creation to make a copy of a root for a tree with
235  * a given objectid.  The buffer with the new root node is returned in
236  * cow_ret, and this func returns zero on success or a negative error code.
237  */
238 int btrfs_copy_root(struct btrfs_trans_handle *trans,
239 		      struct btrfs_root *root,
240 		      struct extent_buffer *buf,
241 		      struct extent_buffer **cow_ret, u64 new_root_objectid)
242 {
243 	struct extent_buffer *cow;
244 	int ret = 0;
245 	int level;
246 	struct btrfs_disk_key disk_key;
247 
248 	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
249 		trans->transid != root->fs_info->running_transaction->transid);
250 	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
251 		trans->transid != root->last_trans);
252 
253 	level = btrfs_header_level(buf);
254 	if (level == 0)
255 		btrfs_item_key(buf, &disk_key, 0);
256 	else
257 		btrfs_node_key(buf, &disk_key, 0);
258 
259 	cow = btrfs_alloc_tree_block(trans, root, 0, new_root_objectid,
260 			&disk_key, level, buf->start, 0);
261 	if (IS_ERR(cow))
262 		return PTR_ERR(cow);
263 
264 	copy_extent_buffer(cow, buf, 0, 0, cow->len);
265 	btrfs_set_header_bytenr(cow, cow->start);
266 	btrfs_set_header_generation(cow, trans->transid);
267 	btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
268 	btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
269 				     BTRFS_HEADER_FLAG_RELOC);
270 	if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
271 		btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
272 	else
273 		btrfs_set_header_owner(cow, new_root_objectid);
274 
275 	write_extent_buffer(cow, root->fs_info->fsid, btrfs_header_fsid(),
276 			    BTRFS_FSID_SIZE);
277 
278 	WARN_ON(btrfs_header_generation(buf) > trans->transid);
279 	if (new_root_objectid == BTRFS_TREE_RELOC_OBJECTID)
280 		ret = btrfs_inc_ref(trans, root, cow, 1);
281 	else
282 		ret = btrfs_inc_ref(trans, root, cow, 0);
283 
284 	if (ret)
285 		return ret;
286 
287 	btrfs_mark_buffer_dirty(cow);
288 	*cow_ret = cow;
289 	return 0;
290 }
291 
292 enum mod_log_op {
293 	MOD_LOG_KEY_REPLACE,
294 	MOD_LOG_KEY_ADD,
295 	MOD_LOG_KEY_REMOVE,
296 	MOD_LOG_KEY_REMOVE_WHILE_FREEING,
297 	MOD_LOG_KEY_REMOVE_WHILE_MOVING,
298 	MOD_LOG_MOVE_KEYS,
299 	MOD_LOG_ROOT_REPLACE,
300 };
301 
302 struct tree_mod_move {
303 	int dst_slot;
304 	int nr_items;
305 };
306 
307 struct tree_mod_root {
308 	u64 logical;
309 	u8 level;
310 };
311 
312 struct tree_mod_elem {
313 	struct rb_node node;
314 	u64 index;		/* shifted logical */
315 	u64 seq;
316 	enum mod_log_op op;
317 
318 	/* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
319 	int slot;
320 
321 	/* this is used for MOD_LOG_KEY* and MOD_LOG_ROOT_REPLACE */
322 	u64 generation;
323 
324 	/* those are used for op == MOD_LOG_KEY_{REPLACE,REMOVE} */
325 	struct btrfs_disk_key key;
326 	u64 blockptr;
327 
328 	/* this is used for op == MOD_LOG_MOVE_KEYS */
329 	struct tree_mod_move move;
330 
331 	/* this is used for op == MOD_LOG_ROOT_REPLACE */
332 	struct tree_mod_root old_root;
333 };
334 
335 static inline void tree_mod_log_read_lock(struct btrfs_fs_info *fs_info)
336 {
337 	read_lock(&fs_info->tree_mod_log_lock);
338 }
339 
340 static inline void tree_mod_log_read_unlock(struct btrfs_fs_info *fs_info)
341 {
342 	read_unlock(&fs_info->tree_mod_log_lock);
343 }
344 
345 static inline void tree_mod_log_write_lock(struct btrfs_fs_info *fs_info)
346 {
347 	write_lock(&fs_info->tree_mod_log_lock);
348 }
349 
350 static inline void tree_mod_log_write_unlock(struct btrfs_fs_info *fs_info)
351 {
352 	write_unlock(&fs_info->tree_mod_log_lock);
353 }
354 
355 /*
356  * Pull a new tree mod seq number for our operation.
357  */
358 static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
359 {
360 	return atomic64_inc_return(&fs_info->tree_mod_seq);
361 }
362 
363 /*
364  * This adds a new blocker to the tree mod log's blocker list if the @elem
365  * passed does not already have a sequence number set. So when a caller expects
366  * to record tree modifications, it should ensure to set elem->seq to zero
367  * before calling btrfs_get_tree_mod_seq.
368  * Returns a fresh, unused tree log modification sequence number, even if no new
369  * blocker was added.
370  */
371 u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
372 			   struct seq_list *elem)
373 {
374 	tree_mod_log_write_lock(fs_info);
375 	spin_lock(&fs_info->tree_mod_seq_lock);
376 	if (!elem->seq) {
377 		elem->seq = btrfs_inc_tree_mod_seq(fs_info);
378 		list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
379 	}
380 	spin_unlock(&fs_info->tree_mod_seq_lock);
381 	tree_mod_log_write_unlock(fs_info);
382 
383 	return elem->seq;
384 }
385 
386 void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
387 			    struct seq_list *elem)
388 {
389 	struct rb_root *tm_root;
390 	struct rb_node *node;
391 	struct rb_node *next;
392 	struct seq_list *cur_elem;
393 	struct tree_mod_elem *tm;
394 	u64 min_seq = (u64)-1;
395 	u64 seq_putting = elem->seq;
396 
397 	if (!seq_putting)
398 		return;
399 
400 	spin_lock(&fs_info->tree_mod_seq_lock);
401 	list_del(&elem->list);
402 	elem->seq = 0;
403 
404 	list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
405 		if (cur_elem->seq < min_seq) {
406 			if (seq_putting > cur_elem->seq) {
407 				/*
408 				 * blocker with lower sequence number exists, we
409 				 * cannot remove anything from the log
410 				 */
411 				spin_unlock(&fs_info->tree_mod_seq_lock);
412 				return;
413 			}
414 			min_seq = cur_elem->seq;
415 		}
416 	}
417 	spin_unlock(&fs_info->tree_mod_seq_lock);
418 
419 	/*
420 	 * anything that's lower than the lowest existing (read: blocked)
421 	 * sequence number can be removed from the tree.
422 	 */
423 	tree_mod_log_write_lock(fs_info);
424 	tm_root = &fs_info->tree_mod_log;
425 	for (node = rb_first(tm_root); node; node = next) {
426 		next = rb_next(node);
427 		tm = container_of(node, struct tree_mod_elem, node);
428 		if (tm->seq > min_seq)
429 			continue;
430 		rb_erase(node, tm_root);
431 		kfree(tm);
432 	}
433 	tree_mod_log_write_unlock(fs_info);
434 }
435 
436 /*
437  * key order of the log:
438  *       index -> sequence
439  *
440  * the index is the shifted logical of the *new* root node for root replace
441  * operations, or the shifted logical of the affected block for all other
442  * operations.
443  *
444  * Note: must be called with write lock (tree_mod_log_write_lock).
445  */
446 static noinline int
447 __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
448 {
449 	struct rb_root *tm_root;
450 	struct rb_node **new;
451 	struct rb_node *parent = NULL;
452 	struct tree_mod_elem *cur;
453 
454 	BUG_ON(!tm);
455 
456 	tm->seq = btrfs_inc_tree_mod_seq(fs_info);
457 
458 	tm_root = &fs_info->tree_mod_log;
459 	new = &tm_root->rb_node;
460 	while (*new) {
461 		cur = container_of(*new, struct tree_mod_elem, node);
462 		parent = *new;
463 		if (cur->index < tm->index)
464 			new = &((*new)->rb_left);
465 		else if (cur->index > tm->index)
466 			new = &((*new)->rb_right);
467 		else if (cur->seq < tm->seq)
468 			new = &((*new)->rb_left);
469 		else if (cur->seq > tm->seq)
470 			new = &((*new)->rb_right);
471 		else
472 			return -EEXIST;
473 	}
474 
475 	rb_link_node(&tm->node, parent, new);
476 	rb_insert_color(&tm->node, tm_root);
477 	return 0;
478 }
479 
480 /*
481  * Determines if logging can be omitted. Returns 1 if it can. Otherwise, it
482  * returns zero with the tree_mod_log_lock acquired. The caller must hold
483  * this until all tree mod log insertions are recorded in the rb tree and then
484  * call tree_mod_log_write_unlock() to release.
485  */
486 static inline int tree_mod_dont_log(struct btrfs_fs_info *fs_info,
487 				    struct extent_buffer *eb) {
488 	smp_mb();
489 	if (list_empty(&(fs_info)->tree_mod_seq_list))
490 		return 1;
491 	if (eb && btrfs_header_level(eb) == 0)
492 		return 1;
493 
494 	tree_mod_log_write_lock(fs_info);
495 	if (list_empty(&(fs_info)->tree_mod_seq_list)) {
496 		tree_mod_log_write_unlock(fs_info);
497 		return 1;
498 	}
499 
500 	return 0;
501 }
502 
503 /* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
504 static inline int tree_mod_need_log(const struct btrfs_fs_info *fs_info,
505 				    struct extent_buffer *eb)
506 {
507 	smp_mb();
508 	if (list_empty(&(fs_info)->tree_mod_seq_list))
509 		return 0;
510 	if (eb && btrfs_header_level(eb) == 0)
511 		return 0;
512 
513 	return 1;
514 }
515 
516 static struct tree_mod_elem *
517 alloc_tree_mod_elem(struct extent_buffer *eb, int slot,
518 		    enum mod_log_op op, gfp_t flags)
519 {
520 	struct tree_mod_elem *tm;
521 
522 	tm = kzalloc(sizeof(*tm), flags);
523 	if (!tm)
524 		return NULL;
525 
526 	tm->index = eb->start >> PAGE_CACHE_SHIFT;
527 	if (op != MOD_LOG_KEY_ADD) {
528 		btrfs_node_key(eb, &tm->key, slot);
529 		tm->blockptr = btrfs_node_blockptr(eb, slot);
530 	}
531 	tm->op = op;
532 	tm->slot = slot;
533 	tm->generation = btrfs_node_ptr_generation(eb, slot);
534 	RB_CLEAR_NODE(&tm->node);
535 
536 	return tm;
537 }
538 
539 static noinline int
540 tree_mod_log_insert_key(struct btrfs_fs_info *fs_info,
541 			struct extent_buffer *eb, int slot,
542 			enum mod_log_op op, gfp_t flags)
543 {
544 	struct tree_mod_elem *tm;
545 	int ret;
546 
547 	if (!tree_mod_need_log(fs_info, eb))
548 		return 0;
549 
550 	tm = alloc_tree_mod_elem(eb, slot, op, flags);
551 	if (!tm)
552 		return -ENOMEM;
553 
554 	if (tree_mod_dont_log(fs_info, eb)) {
555 		kfree(tm);
556 		return 0;
557 	}
558 
559 	ret = __tree_mod_log_insert(fs_info, tm);
560 	tree_mod_log_write_unlock(fs_info);
561 	if (ret)
562 		kfree(tm);
563 
564 	return ret;
565 }
566 
567 static noinline int
568 tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
569 			 struct extent_buffer *eb, int dst_slot, int src_slot,
570 			 int nr_items, gfp_t flags)
571 {
572 	struct tree_mod_elem *tm = NULL;
573 	struct tree_mod_elem **tm_list = NULL;
574 	int ret = 0;
575 	int i;
576 	int locked = 0;
577 
578 	if (!tree_mod_need_log(fs_info, eb))
579 		return 0;
580 
581 	tm_list = kzalloc(nr_items * sizeof(struct tree_mod_elem *), flags);
582 	if (!tm_list)
583 		return -ENOMEM;
584 
585 	tm = kzalloc(sizeof(*tm), flags);
586 	if (!tm) {
587 		ret = -ENOMEM;
588 		goto free_tms;
589 	}
590 
591 	tm->index = eb->start >> PAGE_CACHE_SHIFT;
592 	tm->slot = src_slot;
593 	tm->move.dst_slot = dst_slot;
594 	tm->move.nr_items = nr_items;
595 	tm->op = MOD_LOG_MOVE_KEYS;
596 
597 	for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
598 		tm_list[i] = alloc_tree_mod_elem(eb, i + dst_slot,
599 		    MOD_LOG_KEY_REMOVE_WHILE_MOVING, flags);
600 		if (!tm_list[i]) {
601 			ret = -ENOMEM;
602 			goto free_tms;
603 		}
604 	}
605 
606 	if (tree_mod_dont_log(fs_info, eb))
607 		goto free_tms;
608 	locked = 1;
609 
610 	/*
611 	 * When we override something during the move, we log these removals.
612 	 * This can only happen when we move towards the beginning of the
613 	 * buffer, i.e. dst_slot < src_slot.
614 	 */
615 	for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
616 		ret = __tree_mod_log_insert(fs_info, tm_list[i]);
617 		if (ret)
618 			goto free_tms;
619 	}
620 
621 	ret = __tree_mod_log_insert(fs_info, tm);
622 	if (ret)
623 		goto free_tms;
624 	tree_mod_log_write_unlock(fs_info);
625 	kfree(tm_list);
626 
627 	return 0;
628 free_tms:
629 	for (i = 0; i < nr_items; i++) {
630 		if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
631 			rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
632 		kfree(tm_list[i]);
633 	}
634 	if (locked)
635 		tree_mod_log_write_unlock(fs_info);
636 	kfree(tm_list);
637 	kfree(tm);
638 
639 	return ret;
640 }
641 
642 static inline int
643 __tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
644 		       struct tree_mod_elem **tm_list,
645 		       int nritems)
646 {
647 	int i, j;
648 	int ret;
649 
650 	for (i = nritems - 1; i >= 0; i--) {
651 		ret = __tree_mod_log_insert(fs_info, tm_list[i]);
652 		if (ret) {
653 			for (j = nritems - 1; j > i; j--)
654 				rb_erase(&tm_list[j]->node,
655 					 &fs_info->tree_mod_log);
656 			return ret;
657 		}
658 	}
659 
660 	return 0;
661 }
662 
663 static noinline int
664 tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
665 			 struct extent_buffer *old_root,
666 			 struct extent_buffer *new_root, gfp_t flags,
667 			 int log_removal)
668 {
669 	struct tree_mod_elem *tm = NULL;
670 	struct tree_mod_elem **tm_list = NULL;
671 	int nritems = 0;
672 	int ret = 0;
673 	int i;
674 
675 	if (!tree_mod_need_log(fs_info, NULL))
676 		return 0;
677 
678 	if (log_removal && btrfs_header_level(old_root) > 0) {
679 		nritems = btrfs_header_nritems(old_root);
680 		tm_list = kzalloc(nritems * sizeof(struct tree_mod_elem *),
681 				  flags);
682 		if (!tm_list) {
683 			ret = -ENOMEM;
684 			goto free_tms;
685 		}
686 		for (i = 0; i < nritems; i++) {
687 			tm_list[i] = alloc_tree_mod_elem(old_root, i,
688 			    MOD_LOG_KEY_REMOVE_WHILE_FREEING, flags);
689 			if (!tm_list[i]) {
690 				ret = -ENOMEM;
691 				goto free_tms;
692 			}
693 		}
694 	}
695 
696 	tm = kzalloc(sizeof(*tm), flags);
697 	if (!tm) {
698 		ret = -ENOMEM;
699 		goto free_tms;
700 	}
701 
702 	tm->index = new_root->start >> PAGE_CACHE_SHIFT;
703 	tm->old_root.logical = old_root->start;
704 	tm->old_root.level = btrfs_header_level(old_root);
705 	tm->generation = btrfs_header_generation(old_root);
706 	tm->op = MOD_LOG_ROOT_REPLACE;
707 
708 	if (tree_mod_dont_log(fs_info, NULL))
709 		goto free_tms;
710 
711 	if (tm_list)
712 		ret = __tree_mod_log_free_eb(fs_info, tm_list, nritems);
713 	if (!ret)
714 		ret = __tree_mod_log_insert(fs_info, tm);
715 
716 	tree_mod_log_write_unlock(fs_info);
717 	if (ret)
718 		goto free_tms;
719 	kfree(tm_list);
720 
721 	return ret;
722 
723 free_tms:
724 	if (tm_list) {
725 		for (i = 0; i < nritems; i++)
726 			kfree(tm_list[i]);
727 		kfree(tm_list);
728 	}
729 	kfree(tm);
730 
731 	return ret;
732 }
733 
734 static struct tree_mod_elem *
735 __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
736 		      int smallest)
737 {
738 	struct rb_root *tm_root;
739 	struct rb_node *node;
740 	struct tree_mod_elem *cur = NULL;
741 	struct tree_mod_elem *found = NULL;
742 	u64 index = start >> PAGE_CACHE_SHIFT;
743 
744 	tree_mod_log_read_lock(fs_info);
745 	tm_root = &fs_info->tree_mod_log;
746 	node = tm_root->rb_node;
747 	while (node) {
748 		cur = container_of(node, struct tree_mod_elem, node);
749 		if (cur->index < index) {
750 			node = node->rb_left;
751 		} else if (cur->index > index) {
752 			node = node->rb_right;
753 		} else if (cur->seq < min_seq) {
754 			node = node->rb_left;
755 		} else if (!smallest) {
756 			/* we want the node with the highest seq */
757 			if (found)
758 				BUG_ON(found->seq > cur->seq);
759 			found = cur;
760 			node = node->rb_left;
761 		} else if (cur->seq > min_seq) {
762 			/* we want the node with the smallest seq */
763 			if (found)
764 				BUG_ON(found->seq < cur->seq);
765 			found = cur;
766 			node = node->rb_right;
767 		} else {
768 			found = cur;
769 			break;
770 		}
771 	}
772 	tree_mod_log_read_unlock(fs_info);
773 
774 	return found;
775 }
776 
777 /*
778  * this returns the element from the log with the smallest time sequence
779  * value that's in the log (the oldest log item). any element with a time
780  * sequence lower than min_seq will be ignored.
781  */
782 static struct tree_mod_elem *
783 tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info, u64 start,
784 			   u64 min_seq)
785 {
786 	return __tree_mod_log_search(fs_info, start, min_seq, 1);
787 }
788 
789 /*
790  * this returns the element from the log with the largest time sequence
791  * value that's in the log (the most recent log item). any element with
792  * a time sequence lower than min_seq will be ignored.
793  */
794 static struct tree_mod_elem *
795 tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
796 {
797 	return __tree_mod_log_search(fs_info, start, min_seq, 0);
798 }
799 
800 static noinline int
801 tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
802 		     struct extent_buffer *src, unsigned long dst_offset,
803 		     unsigned long src_offset, int nr_items)
804 {
805 	int ret = 0;
806 	struct tree_mod_elem **tm_list = NULL;
807 	struct tree_mod_elem **tm_list_add, **tm_list_rem;
808 	int i;
809 	int locked = 0;
810 
811 	if (!tree_mod_need_log(fs_info, NULL))
812 		return 0;
813 
814 	if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
815 		return 0;
816 
817 	tm_list = kzalloc(nr_items * 2 * sizeof(struct tree_mod_elem *),
818 			  GFP_NOFS);
819 	if (!tm_list)
820 		return -ENOMEM;
821 
822 	tm_list_add = tm_list;
823 	tm_list_rem = tm_list + nr_items;
824 	for (i = 0; i < nr_items; i++) {
825 		tm_list_rem[i] = alloc_tree_mod_elem(src, i + src_offset,
826 		    MOD_LOG_KEY_REMOVE, GFP_NOFS);
827 		if (!tm_list_rem[i]) {
828 			ret = -ENOMEM;
829 			goto free_tms;
830 		}
831 
832 		tm_list_add[i] = alloc_tree_mod_elem(dst, i + dst_offset,
833 		    MOD_LOG_KEY_ADD, GFP_NOFS);
834 		if (!tm_list_add[i]) {
835 			ret = -ENOMEM;
836 			goto free_tms;
837 		}
838 	}
839 
840 	if (tree_mod_dont_log(fs_info, NULL))
841 		goto free_tms;
842 	locked = 1;
843 
844 	for (i = 0; i < nr_items; i++) {
845 		ret = __tree_mod_log_insert(fs_info, tm_list_rem[i]);
846 		if (ret)
847 			goto free_tms;
848 		ret = __tree_mod_log_insert(fs_info, tm_list_add[i]);
849 		if (ret)
850 			goto free_tms;
851 	}
852 
853 	tree_mod_log_write_unlock(fs_info);
854 	kfree(tm_list);
855 
856 	return 0;
857 
858 free_tms:
859 	for (i = 0; i < nr_items * 2; i++) {
860 		if (tm_list[i] && !RB_EMPTY_NODE(&tm_list[i]->node))
861 			rb_erase(&tm_list[i]->node, &fs_info->tree_mod_log);
862 		kfree(tm_list[i]);
863 	}
864 	if (locked)
865 		tree_mod_log_write_unlock(fs_info);
866 	kfree(tm_list);
867 
868 	return ret;
869 }
870 
871 static inline void
872 tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
873 		     int dst_offset, int src_offset, int nr_items)
874 {
875 	int ret;
876 	ret = tree_mod_log_insert_move(fs_info, dst, dst_offset, src_offset,
877 				       nr_items, GFP_NOFS);
878 	BUG_ON(ret < 0);
879 }
880 
881 static noinline void
882 tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
883 			  struct extent_buffer *eb, int slot, int atomic)
884 {
885 	int ret;
886 
887 	ret = tree_mod_log_insert_key(fs_info, eb, slot,
888 					MOD_LOG_KEY_REPLACE,
889 					atomic ? GFP_ATOMIC : GFP_NOFS);
890 	BUG_ON(ret < 0);
891 }
892 
893 static noinline int
894 tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
895 {
896 	struct tree_mod_elem **tm_list = NULL;
897 	int nritems = 0;
898 	int i;
899 	int ret = 0;
900 
901 	if (btrfs_header_level(eb) == 0)
902 		return 0;
903 
904 	if (!tree_mod_need_log(fs_info, NULL))
905 		return 0;
906 
907 	nritems = btrfs_header_nritems(eb);
908 	tm_list = kzalloc(nritems * sizeof(struct tree_mod_elem *),
909 			  GFP_NOFS);
910 	if (!tm_list)
911 		return -ENOMEM;
912 
913 	for (i = 0; i < nritems; i++) {
914 		tm_list[i] = alloc_tree_mod_elem(eb, i,
915 		    MOD_LOG_KEY_REMOVE_WHILE_FREEING, GFP_NOFS);
916 		if (!tm_list[i]) {
917 			ret = -ENOMEM;
918 			goto free_tms;
919 		}
920 	}
921 
922 	if (tree_mod_dont_log(fs_info, eb))
923 		goto free_tms;
924 
925 	ret = __tree_mod_log_free_eb(fs_info, tm_list, nritems);
926 	tree_mod_log_write_unlock(fs_info);
927 	if (ret)
928 		goto free_tms;
929 	kfree(tm_list);
930 
931 	return 0;
932 
933 free_tms:
934 	for (i = 0; i < nritems; i++)
935 		kfree(tm_list[i]);
936 	kfree(tm_list);
937 
938 	return ret;
939 }
940 
941 static noinline void
942 tree_mod_log_set_root_pointer(struct btrfs_root *root,
943 			      struct extent_buffer *new_root_node,
944 			      int log_removal)
945 {
946 	int ret;
947 	ret = tree_mod_log_insert_root(root->fs_info, root->node,
948 				       new_root_node, GFP_NOFS, log_removal);
949 	BUG_ON(ret < 0);
950 }
951 
952 /*
953  * check if the tree block can be shared by multiple trees
954  */
955 int btrfs_block_can_be_shared(struct btrfs_root *root,
956 			      struct extent_buffer *buf)
957 {
958 	/*
959 	 * Tree blocks not in refernece counted trees and tree roots
960 	 * are never shared. If a block was allocated after the last
961 	 * snapshot and the block was not allocated by tree relocation,
962 	 * we know the block is not shared.
963 	 */
964 	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
965 	    buf != root->node && buf != root->commit_root &&
966 	    (btrfs_header_generation(buf) <=
967 	     btrfs_root_last_snapshot(&root->root_item) ||
968 	     btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)))
969 		return 1;
970 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
971 	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
972 	    btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
973 		return 1;
974 #endif
975 	return 0;
976 }
977 
978 static noinline int update_ref_for_cow(struct btrfs_trans_handle *trans,
979 				       struct btrfs_root *root,
980 				       struct extent_buffer *buf,
981 				       struct extent_buffer *cow,
982 				       int *last_ref)
983 {
984 	u64 refs;
985 	u64 owner;
986 	u64 flags;
987 	u64 new_flags = 0;
988 	int ret;
989 
990 	/*
991 	 * Backrefs update rules:
992 	 *
993 	 * Always use full backrefs for extent pointers in tree block
994 	 * allocated by tree relocation.
995 	 *
996 	 * If a shared tree block is no longer referenced by its owner
997 	 * tree (btrfs_header_owner(buf) == root->root_key.objectid),
998 	 * use full backrefs for extent pointers in tree block.
999 	 *
1000 	 * If a tree block is been relocating
1001 	 * (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID),
1002 	 * use full backrefs for extent pointers in tree block.
1003 	 * The reason for this is some operations (such as drop tree)
1004 	 * are only allowed for blocks use full backrefs.
1005 	 */
1006 
1007 	if (btrfs_block_can_be_shared(root, buf)) {
1008 		ret = btrfs_lookup_extent_info(trans, root, buf->start,
1009 					       btrfs_header_level(buf), 1,
1010 					       &refs, &flags);
1011 		if (ret)
1012 			return ret;
1013 		if (refs == 0) {
1014 			ret = -EROFS;
1015 			btrfs_std_error(root->fs_info, ret);
1016 			return ret;
1017 		}
1018 	} else {
1019 		refs = 1;
1020 		if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1021 		    btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1022 			flags = BTRFS_BLOCK_FLAG_FULL_BACKREF;
1023 		else
1024 			flags = 0;
1025 	}
1026 
1027 	owner = btrfs_header_owner(buf);
1028 	BUG_ON(owner == BTRFS_TREE_RELOC_OBJECTID &&
1029 	       !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF));
1030 
1031 	if (refs > 1) {
1032 		if ((owner == root->root_key.objectid ||
1033 		     root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) &&
1034 		    !(flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)) {
1035 			ret = btrfs_inc_ref(trans, root, buf, 1);
1036 			BUG_ON(ret); /* -ENOMEM */
1037 
1038 			if (root->root_key.objectid ==
1039 			    BTRFS_TREE_RELOC_OBJECTID) {
1040 				ret = btrfs_dec_ref(trans, root, buf, 0);
1041 				BUG_ON(ret); /* -ENOMEM */
1042 				ret = btrfs_inc_ref(trans, root, cow, 1);
1043 				BUG_ON(ret); /* -ENOMEM */
1044 			}
1045 			new_flags |= BTRFS_BLOCK_FLAG_FULL_BACKREF;
1046 		} else {
1047 
1048 			if (root->root_key.objectid ==
1049 			    BTRFS_TREE_RELOC_OBJECTID)
1050 				ret = btrfs_inc_ref(trans, root, cow, 1);
1051 			else
1052 				ret = btrfs_inc_ref(trans, root, cow, 0);
1053 			BUG_ON(ret); /* -ENOMEM */
1054 		}
1055 		if (new_flags != 0) {
1056 			int level = btrfs_header_level(buf);
1057 
1058 			ret = btrfs_set_disk_extent_flags(trans, root,
1059 							  buf->start,
1060 							  buf->len,
1061 							  new_flags, level, 0);
1062 			if (ret)
1063 				return ret;
1064 		}
1065 	} else {
1066 		if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF) {
1067 			if (root->root_key.objectid ==
1068 			    BTRFS_TREE_RELOC_OBJECTID)
1069 				ret = btrfs_inc_ref(trans, root, cow, 1);
1070 			else
1071 				ret = btrfs_inc_ref(trans, root, cow, 0);
1072 			BUG_ON(ret); /* -ENOMEM */
1073 			ret = btrfs_dec_ref(trans, root, buf, 1);
1074 			BUG_ON(ret); /* -ENOMEM */
1075 		}
1076 		clean_tree_block(trans, root, buf);
1077 		*last_ref = 1;
1078 	}
1079 	return 0;
1080 }
1081 
1082 /*
1083  * does the dirty work in cow of a single block.  The parent block (if
1084  * supplied) is updated to point to the new cow copy.  The new buffer is marked
1085  * dirty and returned locked.  If you modify the block it needs to be marked
1086  * dirty again.
1087  *
1088  * search_start -- an allocation hint for the new block
1089  *
1090  * empty_size -- a hint that you plan on doing more cow.  This is the size in
1091  * bytes the allocator should try to find free next to the block it returns.
1092  * This is just a hint and may be ignored by the allocator.
1093  */
1094 static noinline int __btrfs_cow_block(struct btrfs_trans_handle *trans,
1095 			     struct btrfs_root *root,
1096 			     struct extent_buffer *buf,
1097 			     struct extent_buffer *parent, int parent_slot,
1098 			     struct extent_buffer **cow_ret,
1099 			     u64 search_start, u64 empty_size)
1100 {
1101 	struct btrfs_disk_key disk_key;
1102 	struct extent_buffer *cow;
1103 	int level, ret;
1104 	int last_ref = 0;
1105 	int unlock_orig = 0;
1106 	u64 parent_start;
1107 
1108 	if (*cow_ret == buf)
1109 		unlock_orig = 1;
1110 
1111 	btrfs_assert_tree_locked(buf);
1112 
1113 	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1114 		trans->transid != root->fs_info->running_transaction->transid);
1115 	WARN_ON(test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
1116 		trans->transid != root->last_trans);
1117 
1118 	level = btrfs_header_level(buf);
1119 
1120 	if (level == 0)
1121 		btrfs_item_key(buf, &disk_key, 0);
1122 	else
1123 		btrfs_node_key(buf, &disk_key, 0);
1124 
1125 	if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
1126 		if (parent)
1127 			parent_start = parent->start;
1128 		else
1129 			parent_start = 0;
1130 	} else
1131 		parent_start = 0;
1132 
1133 	cow = btrfs_alloc_tree_block(trans, root, parent_start,
1134 			root->root_key.objectid, &disk_key, level,
1135 			search_start, empty_size);
1136 	if (IS_ERR(cow))
1137 		return PTR_ERR(cow);
1138 
1139 	/* cow is set to blocking by btrfs_init_new_buffer */
1140 
1141 	copy_extent_buffer(cow, buf, 0, 0, cow->len);
1142 	btrfs_set_header_bytenr(cow, cow->start);
1143 	btrfs_set_header_generation(cow, trans->transid);
1144 	btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
1145 	btrfs_clear_header_flag(cow, BTRFS_HEADER_FLAG_WRITTEN |
1146 				     BTRFS_HEADER_FLAG_RELOC);
1147 	if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1148 		btrfs_set_header_flag(cow, BTRFS_HEADER_FLAG_RELOC);
1149 	else
1150 		btrfs_set_header_owner(cow, root->root_key.objectid);
1151 
1152 	write_extent_buffer(cow, root->fs_info->fsid, btrfs_header_fsid(),
1153 			    BTRFS_FSID_SIZE);
1154 
1155 	ret = update_ref_for_cow(trans, root, buf, cow, &last_ref);
1156 	if (ret) {
1157 		btrfs_abort_transaction(trans, root, ret);
1158 		return ret;
1159 	}
1160 
1161 	if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
1162 		ret = btrfs_reloc_cow_block(trans, root, buf, cow);
1163 		if (ret)
1164 			return ret;
1165 	}
1166 
1167 	if (buf == root->node) {
1168 		WARN_ON(parent && parent != buf);
1169 		if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID ||
1170 		    btrfs_header_backref_rev(buf) < BTRFS_MIXED_BACKREF_REV)
1171 			parent_start = buf->start;
1172 		else
1173 			parent_start = 0;
1174 
1175 		extent_buffer_get(cow);
1176 		tree_mod_log_set_root_pointer(root, cow, 1);
1177 		rcu_assign_pointer(root->node, cow);
1178 
1179 		btrfs_free_tree_block(trans, root, buf, parent_start,
1180 				      last_ref);
1181 		free_extent_buffer(buf);
1182 		add_root_to_dirty_list(root);
1183 	} else {
1184 		if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1185 			parent_start = parent->start;
1186 		else
1187 			parent_start = 0;
1188 
1189 		WARN_ON(trans->transid != btrfs_header_generation(parent));
1190 		tree_mod_log_insert_key(root->fs_info, parent, parent_slot,
1191 					MOD_LOG_KEY_REPLACE, GFP_NOFS);
1192 		btrfs_set_node_blockptr(parent, parent_slot,
1193 					cow->start);
1194 		btrfs_set_node_ptr_generation(parent, parent_slot,
1195 					      trans->transid);
1196 		btrfs_mark_buffer_dirty(parent);
1197 		if (last_ref) {
1198 			ret = tree_mod_log_free_eb(root->fs_info, buf);
1199 			if (ret) {
1200 				btrfs_abort_transaction(trans, root, ret);
1201 				return ret;
1202 			}
1203 		}
1204 		btrfs_free_tree_block(trans, root, buf, parent_start,
1205 				      last_ref);
1206 	}
1207 	if (unlock_orig)
1208 		btrfs_tree_unlock(buf);
1209 	free_extent_buffer_stale(buf);
1210 	btrfs_mark_buffer_dirty(cow);
1211 	*cow_ret = cow;
1212 	return 0;
1213 }
1214 
1215 /*
1216  * returns the logical address of the oldest predecessor of the given root.
1217  * entries older than time_seq are ignored.
1218  */
1219 static struct tree_mod_elem *
1220 __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
1221 			   struct extent_buffer *eb_root, u64 time_seq)
1222 {
1223 	struct tree_mod_elem *tm;
1224 	struct tree_mod_elem *found = NULL;
1225 	u64 root_logical = eb_root->start;
1226 	int looped = 0;
1227 
1228 	if (!time_seq)
1229 		return NULL;
1230 
1231 	/*
1232 	 * the very last operation that's logged for a root is the replacement
1233 	 * operation (if it is replaced at all). this has the index of the *new*
1234 	 * root, making it the very first operation that's logged for this root.
1235 	 */
1236 	while (1) {
1237 		tm = tree_mod_log_search_oldest(fs_info, root_logical,
1238 						time_seq);
1239 		if (!looped && !tm)
1240 			return NULL;
1241 		/*
1242 		 * if there are no tree operation for the oldest root, we simply
1243 		 * return it. this should only happen if that (old) root is at
1244 		 * level 0.
1245 		 */
1246 		if (!tm)
1247 			break;
1248 
1249 		/*
1250 		 * if there's an operation that's not a root replacement, we
1251 		 * found the oldest version of our root. normally, we'll find a
1252 		 * MOD_LOG_KEY_REMOVE_WHILE_FREEING operation here.
1253 		 */
1254 		if (tm->op != MOD_LOG_ROOT_REPLACE)
1255 			break;
1256 
1257 		found = tm;
1258 		root_logical = tm->old_root.logical;
1259 		looped = 1;
1260 	}
1261 
1262 	/* if there's no old root to return, return what we found instead */
1263 	if (!found)
1264 		found = tm;
1265 
1266 	return found;
1267 }
1268 
1269 /*
1270  * tm is a pointer to the first operation to rewind within eb. then, all
1271  * previous operations will be rewinded (until we reach something older than
1272  * time_seq).
1273  */
1274 static void
1275 __tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
1276 		      u64 time_seq, struct tree_mod_elem *first_tm)
1277 {
1278 	u32 n;
1279 	struct rb_node *next;
1280 	struct tree_mod_elem *tm = first_tm;
1281 	unsigned long o_dst;
1282 	unsigned long o_src;
1283 	unsigned long p_size = sizeof(struct btrfs_key_ptr);
1284 
1285 	n = btrfs_header_nritems(eb);
1286 	tree_mod_log_read_lock(fs_info);
1287 	while (tm && tm->seq >= time_seq) {
1288 		/*
1289 		 * all the operations are recorded with the operator used for
1290 		 * the modification. as we're going backwards, we do the
1291 		 * opposite of each operation here.
1292 		 */
1293 		switch (tm->op) {
1294 		case MOD_LOG_KEY_REMOVE_WHILE_FREEING:
1295 			BUG_ON(tm->slot < n);
1296 			/* Fallthrough */
1297 		case MOD_LOG_KEY_REMOVE_WHILE_MOVING:
1298 		case MOD_LOG_KEY_REMOVE:
1299 			btrfs_set_node_key(eb, &tm->key, tm->slot);
1300 			btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1301 			btrfs_set_node_ptr_generation(eb, tm->slot,
1302 						      tm->generation);
1303 			n++;
1304 			break;
1305 		case MOD_LOG_KEY_REPLACE:
1306 			BUG_ON(tm->slot >= n);
1307 			btrfs_set_node_key(eb, &tm->key, tm->slot);
1308 			btrfs_set_node_blockptr(eb, tm->slot, tm->blockptr);
1309 			btrfs_set_node_ptr_generation(eb, tm->slot,
1310 						      tm->generation);
1311 			break;
1312 		case MOD_LOG_KEY_ADD:
1313 			/* if a move operation is needed it's in the log */
1314 			n--;
1315 			break;
1316 		case MOD_LOG_MOVE_KEYS:
1317 			o_dst = btrfs_node_key_ptr_offset(tm->slot);
1318 			o_src = btrfs_node_key_ptr_offset(tm->move.dst_slot);
1319 			memmove_extent_buffer(eb, o_dst, o_src,
1320 					      tm->move.nr_items * p_size);
1321 			break;
1322 		case MOD_LOG_ROOT_REPLACE:
1323 			/*
1324 			 * this operation is special. for roots, this must be
1325 			 * handled explicitly before rewinding.
1326 			 * for non-roots, this operation may exist if the node
1327 			 * was a root: root A -> child B; then A gets empty and
1328 			 * B is promoted to the new root. in the mod log, we'll
1329 			 * have a root-replace operation for B, a tree block
1330 			 * that is no root. we simply ignore that operation.
1331 			 */
1332 			break;
1333 		}
1334 		next = rb_next(&tm->node);
1335 		if (!next)
1336 			break;
1337 		tm = container_of(next, struct tree_mod_elem, node);
1338 		if (tm->index != first_tm->index)
1339 			break;
1340 	}
1341 	tree_mod_log_read_unlock(fs_info);
1342 	btrfs_set_header_nritems(eb, n);
1343 }
1344 
1345 /*
1346  * Called with eb read locked. If the buffer cannot be rewinded, the same buffer
1347  * is returned. If rewind operations happen, a fresh buffer is returned. The
1348  * returned buffer is always read-locked. If the returned buffer is not the
1349  * input buffer, the lock on the input buffer is released and the input buffer
1350  * is freed (its refcount is decremented).
1351  */
1352 static struct extent_buffer *
1353 tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct btrfs_path *path,
1354 		    struct extent_buffer *eb, u64 time_seq)
1355 {
1356 	struct extent_buffer *eb_rewin;
1357 	struct tree_mod_elem *tm;
1358 
1359 	if (!time_seq)
1360 		return eb;
1361 
1362 	if (btrfs_header_level(eb) == 0)
1363 		return eb;
1364 
1365 	tm = tree_mod_log_search(fs_info, eb->start, time_seq);
1366 	if (!tm)
1367 		return eb;
1368 
1369 	btrfs_set_path_blocking(path);
1370 	btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1371 
1372 	if (tm->op == MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1373 		BUG_ON(tm->slot != 0);
1374 		eb_rewin = alloc_dummy_extent_buffer(fs_info, eb->start);
1375 		if (!eb_rewin) {
1376 			btrfs_tree_read_unlock_blocking(eb);
1377 			free_extent_buffer(eb);
1378 			return NULL;
1379 		}
1380 		btrfs_set_header_bytenr(eb_rewin, eb->start);
1381 		btrfs_set_header_backref_rev(eb_rewin,
1382 					     btrfs_header_backref_rev(eb));
1383 		btrfs_set_header_owner(eb_rewin, btrfs_header_owner(eb));
1384 		btrfs_set_header_level(eb_rewin, btrfs_header_level(eb));
1385 	} else {
1386 		eb_rewin = btrfs_clone_extent_buffer(eb);
1387 		if (!eb_rewin) {
1388 			btrfs_tree_read_unlock_blocking(eb);
1389 			free_extent_buffer(eb);
1390 			return NULL;
1391 		}
1392 	}
1393 
1394 	btrfs_clear_path_blocking(path, NULL, BTRFS_READ_LOCK);
1395 	btrfs_tree_read_unlock_blocking(eb);
1396 	free_extent_buffer(eb);
1397 
1398 	extent_buffer_get(eb_rewin);
1399 	btrfs_tree_read_lock(eb_rewin);
1400 	__tree_mod_log_rewind(fs_info, eb_rewin, time_seq, tm);
1401 	WARN_ON(btrfs_header_nritems(eb_rewin) >
1402 		BTRFS_NODEPTRS_PER_BLOCK(fs_info->tree_root));
1403 
1404 	return eb_rewin;
1405 }
1406 
1407 /*
1408  * get_old_root() rewinds the state of @root's root node to the given @time_seq
1409  * value. If there are no changes, the current root->root_node is returned. If
1410  * anything changed in between, there's a fresh buffer allocated on which the
1411  * rewind operations are done. In any case, the returned buffer is read locked.
1412  * Returns NULL on error (with no locks held).
1413  */
1414 static inline struct extent_buffer *
1415 get_old_root(struct btrfs_root *root, u64 time_seq)
1416 {
1417 	struct tree_mod_elem *tm;
1418 	struct extent_buffer *eb = NULL;
1419 	struct extent_buffer *eb_root;
1420 	struct extent_buffer *old;
1421 	struct tree_mod_root *old_root = NULL;
1422 	u64 old_generation = 0;
1423 	u64 logical;
1424 
1425 	eb_root = btrfs_read_lock_root_node(root);
1426 	tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
1427 	if (!tm)
1428 		return eb_root;
1429 
1430 	if (tm->op == MOD_LOG_ROOT_REPLACE) {
1431 		old_root = &tm->old_root;
1432 		old_generation = tm->generation;
1433 		logical = old_root->logical;
1434 	} else {
1435 		logical = eb_root->start;
1436 	}
1437 
1438 	tm = tree_mod_log_search(root->fs_info, logical, time_seq);
1439 	if (old_root && tm && tm->op != MOD_LOG_KEY_REMOVE_WHILE_FREEING) {
1440 		btrfs_tree_read_unlock(eb_root);
1441 		free_extent_buffer(eb_root);
1442 		old = read_tree_block(root, logical, 0);
1443 		if (WARN_ON(!old || !extent_buffer_uptodate(old))) {
1444 			free_extent_buffer(old);
1445 			btrfs_warn(root->fs_info,
1446 				"failed to read tree block %llu from get_old_root", logical);
1447 		} else {
1448 			eb = btrfs_clone_extent_buffer(old);
1449 			free_extent_buffer(old);
1450 		}
1451 	} else if (old_root) {
1452 		btrfs_tree_read_unlock(eb_root);
1453 		free_extent_buffer(eb_root);
1454 		eb = alloc_dummy_extent_buffer(root->fs_info, logical);
1455 	} else {
1456 		btrfs_set_lock_blocking_rw(eb_root, BTRFS_READ_LOCK);
1457 		eb = btrfs_clone_extent_buffer(eb_root);
1458 		btrfs_tree_read_unlock_blocking(eb_root);
1459 		free_extent_buffer(eb_root);
1460 	}
1461 
1462 	if (!eb)
1463 		return NULL;
1464 	extent_buffer_get(eb);
1465 	btrfs_tree_read_lock(eb);
1466 	if (old_root) {
1467 		btrfs_set_header_bytenr(eb, eb->start);
1468 		btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
1469 		btrfs_set_header_owner(eb, btrfs_header_owner(eb_root));
1470 		btrfs_set_header_level(eb, old_root->level);
1471 		btrfs_set_header_generation(eb, old_generation);
1472 	}
1473 	if (tm)
1474 		__tree_mod_log_rewind(root->fs_info, eb, time_seq, tm);
1475 	else
1476 		WARN_ON(btrfs_header_level(eb) != 0);
1477 	WARN_ON(btrfs_header_nritems(eb) > BTRFS_NODEPTRS_PER_BLOCK(root));
1478 
1479 	return eb;
1480 }
1481 
1482 int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
1483 {
1484 	struct tree_mod_elem *tm;
1485 	int level;
1486 	struct extent_buffer *eb_root = btrfs_root_node(root);
1487 
1488 	tm = __tree_mod_log_oldest_root(root->fs_info, eb_root, time_seq);
1489 	if (tm && tm->op == MOD_LOG_ROOT_REPLACE) {
1490 		level = tm->old_root.level;
1491 	} else {
1492 		level = btrfs_header_level(eb_root);
1493 	}
1494 	free_extent_buffer(eb_root);
1495 
1496 	return level;
1497 }
1498 
1499 static inline int should_cow_block(struct btrfs_trans_handle *trans,
1500 				   struct btrfs_root *root,
1501 				   struct extent_buffer *buf)
1502 {
1503 	if (btrfs_test_is_dummy_root(root))
1504 		return 0;
1505 
1506 	/* ensure we can see the force_cow */
1507 	smp_rmb();
1508 
1509 	/*
1510 	 * We do not need to cow a block if
1511 	 * 1) this block is not created or changed in this transaction;
1512 	 * 2) this block does not belong to TREE_RELOC tree;
1513 	 * 3) the root is not forced COW.
1514 	 *
1515 	 * What is forced COW:
1516 	 *    when we create snapshot during commiting the transaction,
1517 	 *    after we've finished coping src root, we must COW the shared
1518 	 *    block to ensure the metadata consistency.
1519 	 */
1520 	if (btrfs_header_generation(buf) == trans->transid &&
1521 	    !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&
1522 	    !(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID &&
1523 	      btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) &&
1524 	    !test_bit(BTRFS_ROOT_FORCE_COW, &root->state))
1525 		return 0;
1526 	return 1;
1527 }
1528 
1529 /*
1530  * cows a single block, see __btrfs_cow_block for the real work.
1531  * This version of it has extra checks so that a block isn't cow'd more than
1532  * once per transaction, as long as it hasn't been written yet
1533  */
1534 noinline int btrfs_cow_block(struct btrfs_trans_handle *trans,
1535 		    struct btrfs_root *root, struct extent_buffer *buf,
1536 		    struct extent_buffer *parent, int parent_slot,
1537 		    struct extent_buffer **cow_ret)
1538 {
1539 	u64 search_start;
1540 	int ret;
1541 
1542 	if (trans->transaction != root->fs_info->running_transaction)
1543 		WARN(1, KERN_CRIT "trans %llu running %llu\n",
1544 		       trans->transid,
1545 		       root->fs_info->running_transaction->transid);
1546 
1547 	if (trans->transid != root->fs_info->generation)
1548 		WARN(1, KERN_CRIT "trans %llu running %llu\n",
1549 		       trans->transid, root->fs_info->generation);
1550 
1551 	if (!should_cow_block(trans, root, buf)) {
1552 		*cow_ret = buf;
1553 		return 0;
1554 	}
1555 
1556 	search_start = buf->start & ~((u64)(1024 * 1024 * 1024) - 1);
1557 
1558 	if (parent)
1559 		btrfs_set_lock_blocking(parent);
1560 	btrfs_set_lock_blocking(buf);
1561 
1562 	ret = __btrfs_cow_block(trans, root, buf, parent,
1563 				 parent_slot, cow_ret, search_start, 0);
1564 
1565 	trace_btrfs_cow_block(root, buf, *cow_ret);
1566 
1567 	return ret;
1568 }
1569 
1570 /*
1571  * helper function for defrag to decide if two blocks pointed to by a
1572  * node are actually close by
1573  */
1574 static int close_blocks(u64 blocknr, u64 other, u32 blocksize)
1575 {
1576 	if (blocknr < other && other - (blocknr + blocksize) < 32768)
1577 		return 1;
1578 	if (blocknr > other && blocknr - (other + blocksize) < 32768)
1579 		return 1;
1580 	return 0;
1581 }
1582 
1583 /*
1584  * compare two keys in a memcmp fashion
1585  */
1586 static int comp_keys(struct btrfs_disk_key *disk, struct btrfs_key *k2)
1587 {
1588 	struct btrfs_key k1;
1589 
1590 	btrfs_disk_key_to_cpu(&k1, disk);
1591 
1592 	return btrfs_comp_cpu_keys(&k1, k2);
1593 }
1594 
1595 /*
1596  * same as comp_keys only with two btrfs_key's
1597  */
1598 int btrfs_comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2)
1599 {
1600 	if (k1->objectid > k2->objectid)
1601 		return 1;
1602 	if (k1->objectid < k2->objectid)
1603 		return -1;
1604 	if (k1->type > k2->type)
1605 		return 1;
1606 	if (k1->type < k2->type)
1607 		return -1;
1608 	if (k1->offset > k2->offset)
1609 		return 1;
1610 	if (k1->offset < k2->offset)
1611 		return -1;
1612 	return 0;
1613 }
1614 
1615 /*
1616  * this is used by the defrag code to go through all the
1617  * leaves pointed to by a node and reallocate them so that
1618  * disk order is close to key order
1619  */
1620 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
1621 		       struct btrfs_root *root, struct extent_buffer *parent,
1622 		       int start_slot, u64 *last_ret,
1623 		       struct btrfs_key *progress)
1624 {
1625 	struct extent_buffer *cur;
1626 	u64 blocknr;
1627 	u64 gen;
1628 	u64 search_start = *last_ret;
1629 	u64 last_block = 0;
1630 	u64 other;
1631 	u32 parent_nritems;
1632 	int end_slot;
1633 	int i;
1634 	int err = 0;
1635 	int parent_level;
1636 	int uptodate;
1637 	u32 blocksize;
1638 	int progress_passed = 0;
1639 	struct btrfs_disk_key disk_key;
1640 
1641 	parent_level = btrfs_header_level(parent);
1642 
1643 	WARN_ON(trans->transaction != root->fs_info->running_transaction);
1644 	WARN_ON(trans->transid != root->fs_info->generation);
1645 
1646 	parent_nritems = btrfs_header_nritems(parent);
1647 	blocksize = root->nodesize;
1648 	end_slot = parent_nritems - 1;
1649 
1650 	if (parent_nritems <= 1)
1651 		return 0;
1652 
1653 	btrfs_set_lock_blocking(parent);
1654 
1655 	for (i = start_slot; i <= end_slot; i++) {
1656 		int close = 1;
1657 
1658 		btrfs_node_key(parent, &disk_key, i);
1659 		if (!progress_passed && comp_keys(&disk_key, progress) < 0)
1660 			continue;
1661 
1662 		progress_passed = 1;
1663 		blocknr = btrfs_node_blockptr(parent, i);
1664 		gen = btrfs_node_ptr_generation(parent, i);
1665 		if (last_block == 0)
1666 			last_block = blocknr;
1667 
1668 		if (i > 0) {
1669 			other = btrfs_node_blockptr(parent, i - 1);
1670 			close = close_blocks(blocknr, other, blocksize);
1671 		}
1672 		if (!close && i < end_slot) {
1673 			other = btrfs_node_blockptr(parent, i + 1);
1674 			close = close_blocks(blocknr, other, blocksize);
1675 		}
1676 		if (close) {
1677 			last_block = blocknr;
1678 			continue;
1679 		}
1680 
1681 		cur = btrfs_find_tree_block(root, blocknr);
1682 		if (cur)
1683 			uptodate = btrfs_buffer_uptodate(cur, gen, 0);
1684 		else
1685 			uptodate = 0;
1686 		if (!cur || !uptodate) {
1687 			if (!cur) {
1688 				cur = read_tree_block(root, blocknr, gen);
1689 				if (!cur || !extent_buffer_uptodate(cur)) {
1690 					free_extent_buffer(cur);
1691 					return -EIO;
1692 				}
1693 			} else if (!uptodate) {
1694 				err = btrfs_read_buffer(cur, gen);
1695 				if (err) {
1696 					free_extent_buffer(cur);
1697 					return err;
1698 				}
1699 			}
1700 		}
1701 		if (search_start == 0)
1702 			search_start = last_block;
1703 
1704 		btrfs_tree_lock(cur);
1705 		btrfs_set_lock_blocking(cur);
1706 		err = __btrfs_cow_block(trans, root, cur, parent, i,
1707 					&cur, search_start,
1708 					min(16 * blocksize,
1709 					    (end_slot - i) * blocksize));
1710 		if (err) {
1711 			btrfs_tree_unlock(cur);
1712 			free_extent_buffer(cur);
1713 			break;
1714 		}
1715 		search_start = cur->start;
1716 		last_block = cur->start;
1717 		*last_ret = search_start;
1718 		btrfs_tree_unlock(cur);
1719 		free_extent_buffer(cur);
1720 	}
1721 	return err;
1722 }
1723 
1724 /*
1725  * The leaf data grows from end-to-front in the node.
1726  * this returns the address of the start of the last item,
1727  * which is the stop of the leaf data stack
1728  */
1729 static inline unsigned int leaf_data_end(struct btrfs_root *root,
1730 					 struct extent_buffer *leaf)
1731 {
1732 	u32 nr = btrfs_header_nritems(leaf);
1733 	if (nr == 0)
1734 		return BTRFS_LEAF_DATA_SIZE(root);
1735 	return btrfs_item_offset_nr(leaf, nr - 1);
1736 }
1737 
1738 
1739 /*
1740  * search for key in the extent_buffer.  The items start at offset p,
1741  * and they are item_size apart.  There are 'max' items in p.
1742  *
1743  * the slot in the array is returned via slot, and it points to
1744  * the place where you would insert key if it is not found in
1745  * the array.
1746  *
1747  * slot may point to max if the key is bigger than all of the keys
1748  */
1749 static noinline int generic_bin_search(struct extent_buffer *eb,
1750 				       unsigned long p,
1751 				       int item_size, struct btrfs_key *key,
1752 				       int max, int *slot)
1753 {
1754 	int low = 0;
1755 	int high = max;
1756 	int mid;
1757 	int ret;
1758 	struct btrfs_disk_key *tmp = NULL;
1759 	struct btrfs_disk_key unaligned;
1760 	unsigned long offset;
1761 	char *kaddr = NULL;
1762 	unsigned long map_start = 0;
1763 	unsigned long map_len = 0;
1764 	int err;
1765 
1766 	while (low < high) {
1767 		mid = (low + high) / 2;
1768 		offset = p + mid * item_size;
1769 
1770 		if (!kaddr || offset < map_start ||
1771 		    (offset + sizeof(struct btrfs_disk_key)) >
1772 		    map_start + map_len) {
1773 
1774 			err = map_private_extent_buffer(eb, offset,
1775 						sizeof(struct btrfs_disk_key),
1776 						&kaddr, &map_start, &map_len);
1777 
1778 			if (!err) {
1779 				tmp = (struct btrfs_disk_key *)(kaddr + offset -
1780 							map_start);
1781 			} else {
1782 				read_extent_buffer(eb, &unaligned,
1783 						   offset, sizeof(unaligned));
1784 				tmp = &unaligned;
1785 			}
1786 
1787 		} else {
1788 			tmp = (struct btrfs_disk_key *)(kaddr + offset -
1789 							map_start);
1790 		}
1791 		ret = comp_keys(tmp, key);
1792 
1793 		if (ret < 0)
1794 			low = mid + 1;
1795 		else if (ret > 0)
1796 			high = mid;
1797 		else {
1798 			*slot = mid;
1799 			return 0;
1800 		}
1801 	}
1802 	*slot = low;
1803 	return 1;
1804 }
1805 
1806 /*
1807  * simple bin_search frontend that does the right thing for
1808  * leaves vs nodes
1809  */
1810 static int bin_search(struct extent_buffer *eb, struct btrfs_key *key,
1811 		      int level, int *slot)
1812 {
1813 	if (level == 0)
1814 		return generic_bin_search(eb,
1815 					  offsetof(struct btrfs_leaf, items),
1816 					  sizeof(struct btrfs_item),
1817 					  key, btrfs_header_nritems(eb),
1818 					  slot);
1819 	else
1820 		return generic_bin_search(eb,
1821 					  offsetof(struct btrfs_node, ptrs),
1822 					  sizeof(struct btrfs_key_ptr),
1823 					  key, btrfs_header_nritems(eb),
1824 					  slot);
1825 }
1826 
1827 int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
1828 		     int level, int *slot)
1829 {
1830 	return bin_search(eb, key, level, slot);
1831 }
1832 
1833 static void root_add_used(struct btrfs_root *root, u32 size)
1834 {
1835 	spin_lock(&root->accounting_lock);
1836 	btrfs_set_root_used(&root->root_item,
1837 			    btrfs_root_used(&root->root_item) + size);
1838 	spin_unlock(&root->accounting_lock);
1839 }
1840 
1841 static void root_sub_used(struct btrfs_root *root, u32 size)
1842 {
1843 	spin_lock(&root->accounting_lock);
1844 	btrfs_set_root_used(&root->root_item,
1845 			    btrfs_root_used(&root->root_item) - size);
1846 	spin_unlock(&root->accounting_lock);
1847 }
1848 
1849 /* given a node and slot number, this reads the blocks it points to.  The
1850  * extent buffer is returned with a reference taken (but unlocked).
1851  * NULL is returned on error.
1852  */
1853 static noinline struct extent_buffer *read_node_slot(struct btrfs_root *root,
1854 				   struct extent_buffer *parent, int slot)
1855 {
1856 	int level = btrfs_header_level(parent);
1857 	struct extent_buffer *eb;
1858 
1859 	if (slot < 0)
1860 		return NULL;
1861 	if (slot >= btrfs_header_nritems(parent))
1862 		return NULL;
1863 
1864 	BUG_ON(level == 0);
1865 
1866 	eb = read_tree_block(root, btrfs_node_blockptr(parent, slot),
1867 			     btrfs_node_ptr_generation(parent, slot));
1868 	if (eb && !extent_buffer_uptodate(eb)) {
1869 		free_extent_buffer(eb);
1870 		eb = NULL;
1871 	}
1872 
1873 	return eb;
1874 }
1875 
1876 /*
1877  * node level balancing, used to make sure nodes are in proper order for
1878  * item deletion.  We balance from the top down, so we have to make sure
1879  * that a deletion won't leave an node completely empty later on.
1880  */
1881 static noinline int balance_level(struct btrfs_trans_handle *trans,
1882 			 struct btrfs_root *root,
1883 			 struct btrfs_path *path, int level)
1884 {
1885 	struct extent_buffer *right = NULL;
1886 	struct extent_buffer *mid;
1887 	struct extent_buffer *left = NULL;
1888 	struct extent_buffer *parent = NULL;
1889 	int ret = 0;
1890 	int wret;
1891 	int pslot;
1892 	int orig_slot = path->slots[level];
1893 	u64 orig_ptr;
1894 
1895 	if (level == 0)
1896 		return 0;
1897 
1898 	mid = path->nodes[level];
1899 
1900 	WARN_ON(path->locks[level] != BTRFS_WRITE_LOCK &&
1901 		path->locks[level] != BTRFS_WRITE_LOCK_BLOCKING);
1902 	WARN_ON(btrfs_header_generation(mid) != trans->transid);
1903 
1904 	orig_ptr = btrfs_node_blockptr(mid, orig_slot);
1905 
1906 	if (level < BTRFS_MAX_LEVEL - 1) {
1907 		parent = path->nodes[level + 1];
1908 		pslot = path->slots[level + 1];
1909 	}
1910 
1911 	/*
1912 	 * deal with the case where there is only one pointer in the root
1913 	 * by promoting the node below to a root
1914 	 */
1915 	if (!parent) {
1916 		struct extent_buffer *child;
1917 
1918 		if (btrfs_header_nritems(mid) != 1)
1919 			return 0;
1920 
1921 		/* promote the child to a root */
1922 		child = read_node_slot(root, mid, 0);
1923 		if (!child) {
1924 			ret = -EROFS;
1925 			btrfs_std_error(root->fs_info, ret);
1926 			goto enospc;
1927 		}
1928 
1929 		btrfs_tree_lock(child);
1930 		btrfs_set_lock_blocking(child);
1931 		ret = btrfs_cow_block(trans, root, child, mid, 0, &child);
1932 		if (ret) {
1933 			btrfs_tree_unlock(child);
1934 			free_extent_buffer(child);
1935 			goto enospc;
1936 		}
1937 
1938 		tree_mod_log_set_root_pointer(root, child, 1);
1939 		rcu_assign_pointer(root->node, child);
1940 
1941 		add_root_to_dirty_list(root);
1942 		btrfs_tree_unlock(child);
1943 
1944 		path->locks[level] = 0;
1945 		path->nodes[level] = NULL;
1946 		clean_tree_block(trans, root, mid);
1947 		btrfs_tree_unlock(mid);
1948 		/* once for the path */
1949 		free_extent_buffer(mid);
1950 
1951 		root_sub_used(root, mid->len);
1952 		btrfs_free_tree_block(trans, root, mid, 0, 1);
1953 		/* once for the root ptr */
1954 		free_extent_buffer_stale(mid);
1955 		return 0;
1956 	}
1957 	if (btrfs_header_nritems(mid) >
1958 	    BTRFS_NODEPTRS_PER_BLOCK(root) / 4)
1959 		return 0;
1960 
1961 	left = read_node_slot(root, parent, pslot - 1);
1962 	if (left) {
1963 		btrfs_tree_lock(left);
1964 		btrfs_set_lock_blocking(left);
1965 		wret = btrfs_cow_block(trans, root, left,
1966 				       parent, pslot - 1, &left);
1967 		if (wret) {
1968 			ret = wret;
1969 			goto enospc;
1970 		}
1971 	}
1972 	right = read_node_slot(root, parent, pslot + 1);
1973 	if (right) {
1974 		btrfs_tree_lock(right);
1975 		btrfs_set_lock_blocking(right);
1976 		wret = btrfs_cow_block(trans, root, right,
1977 				       parent, pslot + 1, &right);
1978 		if (wret) {
1979 			ret = wret;
1980 			goto enospc;
1981 		}
1982 	}
1983 
1984 	/* first, try to make some room in the middle buffer */
1985 	if (left) {
1986 		orig_slot += btrfs_header_nritems(left);
1987 		wret = push_node_left(trans, root, left, mid, 1);
1988 		if (wret < 0)
1989 			ret = wret;
1990 	}
1991 
1992 	/*
1993 	 * then try to empty the right most buffer into the middle
1994 	 */
1995 	if (right) {
1996 		wret = push_node_left(trans, root, mid, right, 1);
1997 		if (wret < 0 && wret != -ENOSPC)
1998 			ret = wret;
1999 		if (btrfs_header_nritems(right) == 0) {
2000 			clean_tree_block(trans, root, right);
2001 			btrfs_tree_unlock(right);
2002 			del_ptr(root, path, level + 1, pslot + 1);
2003 			root_sub_used(root, right->len);
2004 			btrfs_free_tree_block(trans, root, right, 0, 1);
2005 			free_extent_buffer_stale(right);
2006 			right = NULL;
2007 		} else {
2008 			struct btrfs_disk_key right_key;
2009 			btrfs_node_key(right, &right_key, 0);
2010 			tree_mod_log_set_node_key(root->fs_info, parent,
2011 						  pslot + 1, 0);
2012 			btrfs_set_node_key(parent, &right_key, pslot + 1);
2013 			btrfs_mark_buffer_dirty(parent);
2014 		}
2015 	}
2016 	if (btrfs_header_nritems(mid) == 1) {
2017 		/*
2018 		 * we're not allowed to leave a node with one item in the
2019 		 * tree during a delete.  A deletion from lower in the tree
2020 		 * could try to delete the only pointer in this node.
2021 		 * So, pull some keys from the left.
2022 		 * There has to be a left pointer at this point because
2023 		 * otherwise we would have pulled some pointers from the
2024 		 * right
2025 		 */
2026 		if (!left) {
2027 			ret = -EROFS;
2028 			btrfs_std_error(root->fs_info, ret);
2029 			goto enospc;
2030 		}
2031 		wret = balance_node_right(trans, root, mid, left);
2032 		if (wret < 0) {
2033 			ret = wret;
2034 			goto enospc;
2035 		}
2036 		if (wret == 1) {
2037 			wret = push_node_left(trans, root, left, mid, 1);
2038 			if (wret < 0)
2039 				ret = wret;
2040 		}
2041 		BUG_ON(wret == 1);
2042 	}
2043 	if (btrfs_header_nritems(mid) == 0) {
2044 		clean_tree_block(trans, root, mid);
2045 		btrfs_tree_unlock(mid);
2046 		del_ptr(root, path, level + 1, pslot);
2047 		root_sub_used(root, mid->len);
2048 		btrfs_free_tree_block(trans, root, mid, 0, 1);
2049 		free_extent_buffer_stale(mid);
2050 		mid = NULL;
2051 	} else {
2052 		/* update the parent key to reflect our changes */
2053 		struct btrfs_disk_key mid_key;
2054 		btrfs_node_key(mid, &mid_key, 0);
2055 		tree_mod_log_set_node_key(root->fs_info, parent,
2056 					  pslot, 0);
2057 		btrfs_set_node_key(parent, &mid_key, pslot);
2058 		btrfs_mark_buffer_dirty(parent);
2059 	}
2060 
2061 	/* update the path */
2062 	if (left) {
2063 		if (btrfs_header_nritems(left) > orig_slot) {
2064 			extent_buffer_get(left);
2065 			/* left was locked after cow */
2066 			path->nodes[level] = left;
2067 			path->slots[level + 1] -= 1;
2068 			path->slots[level] = orig_slot;
2069 			if (mid) {
2070 				btrfs_tree_unlock(mid);
2071 				free_extent_buffer(mid);
2072 			}
2073 		} else {
2074 			orig_slot -= btrfs_header_nritems(left);
2075 			path->slots[level] = orig_slot;
2076 		}
2077 	}
2078 	/* double check we haven't messed things up */
2079 	if (orig_ptr !=
2080 	    btrfs_node_blockptr(path->nodes[level], path->slots[level]))
2081 		BUG();
2082 enospc:
2083 	if (right) {
2084 		btrfs_tree_unlock(right);
2085 		free_extent_buffer(right);
2086 	}
2087 	if (left) {
2088 		if (path->nodes[level] != left)
2089 			btrfs_tree_unlock(left);
2090 		free_extent_buffer(left);
2091 	}
2092 	return ret;
2093 }
2094 
2095 /* Node balancing for insertion.  Here we only split or push nodes around
2096  * when they are completely full.  This is also done top down, so we
2097  * have to be pessimistic.
2098  */
2099 static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
2100 					  struct btrfs_root *root,
2101 					  struct btrfs_path *path, int level)
2102 {
2103 	struct extent_buffer *right = NULL;
2104 	struct extent_buffer *mid;
2105 	struct extent_buffer *left = NULL;
2106 	struct extent_buffer *parent = NULL;
2107 	int ret = 0;
2108 	int wret;
2109 	int pslot;
2110 	int orig_slot = path->slots[level];
2111 
2112 	if (level == 0)
2113 		return 1;
2114 
2115 	mid = path->nodes[level];
2116 	WARN_ON(btrfs_header_generation(mid) != trans->transid);
2117 
2118 	if (level < BTRFS_MAX_LEVEL - 1) {
2119 		parent = path->nodes[level + 1];
2120 		pslot = path->slots[level + 1];
2121 	}
2122 
2123 	if (!parent)
2124 		return 1;
2125 
2126 	left = read_node_slot(root, parent, pslot - 1);
2127 
2128 	/* first, try to make some room in the middle buffer */
2129 	if (left) {
2130 		u32 left_nr;
2131 
2132 		btrfs_tree_lock(left);
2133 		btrfs_set_lock_blocking(left);
2134 
2135 		left_nr = btrfs_header_nritems(left);
2136 		if (left_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
2137 			wret = 1;
2138 		} else {
2139 			ret = btrfs_cow_block(trans, root, left, parent,
2140 					      pslot - 1, &left);
2141 			if (ret)
2142 				wret = 1;
2143 			else {
2144 				wret = push_node_left(trans, root,
2145 						      left, mid, 0);
2146 			}
2147 		}
2148 		if (wret < 0)
2149 			ret = wret;
2150 		if (wret == 0) {
2151 			struct btrfs_disk_key disk_key;
2152 			orig_slot += left_nr;
2153 			btrfs_node_key(mid, &disk_key, 0);
2154 			tree_mod_log_set_node_key(root->fs_info, parent,
2155 						  pslot, 0);
2156 			btrfs_set_node_key(parent, &disk_key, pslot);
2157 			btrfs_mark_buffer_dirty(parent);
2158 			if (btrfs_header_nritems(left) > orig_slot) {
2159 				path->nodes[level] = left;
2160 				path->slots[level + 1] -= 1;
2161 				path->slots[level] = orig_slot;
2162 				btrfs_tree_unlock(mid);
2163 				free_extent_buffer(mid);
2164 			} else {
2165 				orig_slot -=
2166 					btrfs_header_nritems(left);
2167 				path->slots[level] = orig_slot;
2168 				btrfs_tree_unlock(left);
2169 				free_extent_buffer(left);
2170 			}
2171 			return 0;
2172 		}
2173 		btrfs_tree_unlock(left);
2174 		free_extent_buffer(left);
2175 	}
2176 	right = read_node_slot(root, parent, pslot + 1);
2177 
2178 	/*
2179 	 * then try to empty the right most buffer into the middle
2180 	 */
2181 	if (right) {
2182 		u32 right_nr;
2183 
2184 		btrfs_tree_lock(right);
2185 		btrfs_set_lock_blocking(right);
2186 
2187 		right_nr = btrfs_header_nritems(right);
2188 		if (right_nr >= BTRFS_NODEPTRS_PER_BLOCK(root) - 1) {
2189 			wret = 1;
2190 		} else {
2191 			ret = btrfs_cow_block(trans, root, right,
2192 					      parent, pslot + 1,
2193 					      &right);
2194 			if (ret)
2195 				wret = 1;
2196 			else {
2197 				wret = balance_node_right(trans, root,
2198 							  right, mid);
2199 			}
2200 		}
2201 		if (wret < 0)
2202 			ret = wret;
2203 		if (wret == 0) {
2204 			struct btrfs_disk_key disk_key;
2205 
2206 			btrfs_node_key(right, &disk_key, 0);
2207 			tree_mod_log_set_node_key(root->fs_info, parent,
2208 						  pslot + 1, 0);
2209 			btrfs_set_node_key(parent, &disk_key, pslot + 1);
2210 			btrfs_mark_buffer_dirty(parent);
2211 
2212 			if (btrfs_header_nritems(mid) <= orig_slot) {
2213 				path->nodes[level] = right;
2214 				path->slots[level + 1] += 1;
2215 				path->slots[level] = orig_slot -
2216 					btrfs_header_nritems(mid);
2217 				btrfs_tree_unlock(mid);
2218 				free_extent_buffer(mid);
2219 			} else {
2220 				btrfs_tree_unlock(right);
2221 				free_extent_buffer(right);
2222 			}
2223 			return 0;
2224 		}
2225 		btrfs_tree_unlock(right);
2226 		free_extent_buffer(right);
2227 	}
2228 	return 1;
2229 }
2230 
2231 /*
2232  * readahead one full node of leaves, finding things that are close
2233  * to the block in 'slot', and triggering ra on them.
2234  */
2235 static void reada_for_search(struct btrfs_root *root,
2236 			     struct btrfs_path *path,
2237 			     int level, int slot, u64 objectid)
2238 {
2239 	struct extent_buffer *node;
2240 	struct btrfs_disk_key disk_key;
2241 	u32 nritems;
2242 	u64 search;
2243 	u64 target;
2244 	u64 nread = 0;
2245 	u64 gen;
2246 	int direction = path->reada;
2247 	struct extent_buffer *eb;
2248 	u32 nr;
2249 	u32 blocksize;
2250 	u32 nscan = 0;
2251 
2252 	if (level != 1)
2253 		return;
2254 
2255 	if (!path->nodes[level])
2256 		return;
2257 
2258 	node = path->nodes[level];
2259 
2260 	search = btrfs_node_blockptr(node, slot);
2261 	blocksize = root->nodesize;
2262 	eb = btrfs_find_tree_block(root, search);
2263 	if (eb) {
2264 		free_extent_buffer(eb);
2265 		return;
2266 	}
2267 
2268 	target = search;
2269 
2270 	nritems = btrfs_header_nritems(node);
2271 	nr = slot;
2272 
2273 	while (1) {
2274 		if (direction < 0) {
2275 			if (nr == 0)
2276 				break;
2277 			nr--;
2278 		} else if (direction > 0) {
2279 			nr++;
2280 			if (nr >= nritems)
2281 				break;
2282 		}
2283 		if (path->reada < 0 && objectid) {
2284 			btrfs_node_key(node, &disk_key, nr);
2285 			if (btrfs_disk_key_objectid(&disk_key) != objectid)
2286 				break;
2287 		}
2288 		search = btrfs_node_blockptr(node, nr);
2289 		if ((search <= target && target - search <= 65536) ||
2290 		    (search > target && search - target <= 65536)) {
2291 			gen = btrfs_node_ptr_generation(node, nr);
2292 			readahead_tree_block(root, search);
2293 			nread += blocksize;
2294 		}
2295 		nscan++;
2296 		if ((nread > 65536 || nscan > 32))
2297 			break;
2298 	}
2299 }
2300 
2301 static noinline void reada_for_balance(struct btrfs_root *root,
2302 				       struct btrfs_path *path, int level)
2303 {
2304 	int slot;
2305 	int nritems;
2306 	struct extent_buffer *parent;
2307 	struct extent_buffer *eb;
2308 	u64 gen;
2309 	u64 block1 = 0;
2310 	u64 block2 = 0;
2311 
2312 	parent = path->nodes[level + 1];
2313 	if (!parent)
2314 		return;
2315 
2316 	nritems = btrfs_header_nritems(parent);
2317 	slot = path->slots[level + 1];
2318 
2319 	if (slot > 0) {
2320 		block1 = btrfs_node_blockptr(parent, slot - 1);
2321 		gen = btrfs_node_ptr_generation(parent, slot - 1);
2322 		eb = btrfs_find_tree_block(root, block1);
2323 		/*
2324 		 * if we get -eagain from btrfs_buffer_uptodate, we
2325 		 * don't want to return eagain here.  That will loop
2326 		 * forever
2327 		 */
2328 		if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2329 			block1 = 0;
2330 		free_extent_buffer(eb);
2331 	}
2332 	if (slot + 1 < nritems) {
2333 		block2 = btrfs_node_blockptr(parent, slot + 1);
2334 		gen = btrfs_node_ptr_generation(parent, slot + 1);
2335 		eb = btrfs_find_tree_block(root, block2);
2336 		if (eb && btrfs_buffer_uptodate(eb, gen, 1) != 0)
2337 			block2 = 0;
2338 		free_extent_buffer(eb);
2339 	}
2340 
2341 	if (block1)
2342 		readahead_tree_block(root, block1);
2343 	if (block2)
2344 		readahead_tree_block(root, block2);
2345 }
2346 
2347 
2348 /*
2349  * when we walk down the tree, it is usually safe to unlock the higher layers
2350  * in the tree.  The exceptions are when our path goes through slot 0, because
2351  * operations on the tree might require changing key pointers higher up in the
2352  * tree.
2353  *
2354  * callers might also have set path->keep_locks, which tells this code to keep
2355  * the lock if the path points to the last slot in the block.  This is part of
2356  * walking through the tree, and selecting the next slot in the higher block.
2357  *
2358  * lowest_unlock sets the lowest level in the tree we're allowed to unlock.  so
2359  * if lowest_unlock is 1, level 0 won't be unlocked
2360  */
2361 static noinline void unlock_up(struct btrfs_path *path, int level,
2362 			       int lowest_unlock, int min_write_lock_level,
2363 			       int *write_lock_level)
2364 {
2365 	int i;
2366 	int skip_level = level;
2367 	int no_skips = 0;
2368 	struct extent_buffer *t;
2369 
2370 	for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2371 		if (!path->nodes[i])
2372 			break;
2373 		if (!path->locks[i])
2374 			break;
2375 		if (!no_skips && path->slots[i] == 0) {
2376 			skip_level = i + 1;
2377 			continue;
2378 		}
2379 		if (!no_skips && path->keep_locks) {
2380 			u32 nritems;
2381 			t = path->nodes[i];
2382 			nritems = btrfs_header_nritems(t);
2383 			if (nritems < 1 || path->slots[i] >= nritems - 1) {
2384 				skip_level = i + 1;
2385 				continue;
2386 			}
2387 		}
2388 		if (skip_level < i && i >= lowest_unlock)
2389 			no_skips = 1;
2390 
2391 		t = path->nodes[i];
2392 		if (i >= lowest_unlock && i > skip_level && path->locks[i]) {
2393 			btrfs_tree_unlock_rw(t, path->locks[i]);
2394 			path->locks[i] = 0;
2395 			if (write_lock_level &&
2396 			    i > min_write_lock_level &&
2397 			    i <= *write_lock_level) {
2398 				*write_lock_level = i - 1;
2399 			}
2400 		}
2401 	}
2402 }
2403 
2404 /*
2405  * This releases any locks held in the path starting at level and
2406  * going all the way up to the root.
2407  *
2408  * btrfs_search_slot will keep the lock held on higher nodes in a few
2409  * corner cases, such as COW of the block at slot zero in the node.  This
2410  * ignores those rules, and it should only be called when there are no
2411  * more updates to be done higher up in the tree.
2412  */
2413 noinline void btrfs_unlock_up_safe(struct btrfs_path *path, int level)
2414 {
2415 	int i;
2416 
2417 	if (path->keep_locks)
2418 		return;
2419 
2420 	for (i = level; i < BTRFS_MAX_LEVEL; i++) {
2421 		if (!path->nodes[i])
2422 			continue;
2423 		if (!path->locks[i])
2424 			continue;
2425 		btrfs_tree_unlock_rw(path->nodes[i], path->locks[i]);
2426 		path->locks[i] = 0;
2427 	}
2428 }
2429 
2430 /*
2431  * helper function for btrfs_search_slot.  The goal is to find a block
2432  * in cache without setting the path to blocking.  If we find the block
2433  * we return zero and the path is unchanged.
2434  *
2435  * If we can't find the block, we set the path blocking and do some
2436  * reada.  -EAGAIN is returned and the search must be repeated.
2437  */
2438 static int
2439 read_block_for_search(struct btrfs_trans_handle *trans,
2440 		       struct btrfs_root *root, struct btrfs_path *p,
2441 		       struct extent_buffer **eb_ret, int level, int slot,
2442 		       struct btrfs_key *key, u64 time_seq)
2443 {
2444 	u64 blocknr;
2445 	u64 gen;
2446 	struct extent_buffer *b = *eb_ret;
2447 	struct extent_buffer *tmp;
2448 	int ret;
2449 
2450 	blocknr = btrfs_node_blockptr(b, slot);
2451 	gen = btrfs_node_ptr_generation(b, slot);
2452 
2453 	tmp = btrfs_find_tree_block(root, blocknr);
2454 	if (tmp) {
2455 		/* first we do an atomic uptodate check */
2456 		if (btrfs_buffer_uptodate(tmp, gen, 1) > 0) {
2457 			*eb_ret = tmp;
2458 			return 0;
2459 		}
2460 
2461 		/* the pages were up to date, but we failed
2462 		 * the generation number check.  Do a full
2463 		 * read for the generation number that is correct.
2464 		 * We must do this without dropping locks so
2465 		 * we can trust our generation number
2466 		 */
2467 		btrfs_set_path_blocking(p);
2468 
2469 		/* now we're allowed to do a blocking uptodate check */
2470 		ret = btrfs_read_buffer(tmp, gen);
2471 		if (!ret) {
2472 			*eb_ret = tmp;
2473 			return 0;
2474 		}
2475 		free_extent_buffer(tmp);
2476 		btrfs_release_path(p);
2477 		return -EIO;
2478 	}
2479 
2480 	/*
2481 	 * reduce lock contention at high levels
2482 	 * of the btree by dropping locks before
2483 	 * we read.  Don't release the lock on the current
2484 	 * level because we need to walk this node to figure
2485 	 * out which blocks to read.
2486 	 */
2487 	btrfs_unlock_up_safe(p, level + 1);
2488 	btrfs_set_path_blocking(p);
2489 
2490 	free_extent_buffer(tmp);
2491 	if (p->reada)
2492 		reada_for_search(root, p, level, slot, key->objectid);
2493 
2494 	btrfs_release_path(p);
2495 
2496 	ret = -EAGAIN;
2497 	tmp = read_tree_block(root, blocknr, 0);
2498 	if (tmp) {
2499 		/*
2500 		 * If the read above didn't mark this buffer up to date,
2501 		 * it will never end up being up to date.  Set ret to EIO now
2502 		 * and give up so that our caller doesn't loop forever
2503 		 * on our EAGAINs.
2504 		 */
2505 		if (!btrfs_buffer_uptodate(tmp, 0, 0))
2506 			ret = -EIO;
2507 		free_extent_buffer(tmp);
2508 	}
2509 	return ret;
2510 }
2511 
2512 /*
2513  * helper function for btrfs_search_slot.  This does all of the checks
2514  * for node-level blocks and does any balancing required based on
2515  * the ins_len.
2516  *
2517  * If no extra work was required, zero is returned.  If we had to
2518  * drop the path, -EAGAIN is returned and btrfs_search_slot must
2519  * start over
2520  */
2521 static int
2522 setup_nodes_for_search(struct btrfs_trans_handle *trans,
2523 		       struct btrfs_root *root, struct btrfs_path *p,
2524 		       struct extent_buffer *b, int level, int ins_len,
2525 		       int *write_lock_level)
2526 {
2527 	int ret;
2528 	if ((p->search_for_split || ins_len > 0) && btrfs_header_nritems(b) >=
2529 	    BTRFS_NODEPTRS_PER_BLOCK(root) - 3) {
2530 		int sret;
2531 
2532 		if (*write_lock_level < level + 1) {
2533 			*write_lock_level = level + 1;
2534 			btrfs_release_path(p);
2535 			goto again;
2536 		}
2537 
2538 		btrfs_set_path_blocking(p);
2539 		reada_for_balance(root, p, level);
2540 		sret = split_node(trans, root, p, level);
2541 		btrfs_clear_path_blocking(p, NULL, 0);
2542 
2543 		BUG_ON(sret > 0);
2544 		if (sret) {
2545 			ret = sret;
2546 			goto done;
2547 		}
2548 		b = p->nodes[level];
2549 	} else if (ins_len < 0 && btrfs_header_nritems(b) <
2550 		   BTRFS_NODEPTRS_PER_BLOCK(root) / 2) {
2551 		int sret;
2552 
2553 		if (*write_lock_level < level + 1) {
2554 			*write_lock_level = level + 1;
2555 			btrfs_release_path(p);
2556 			goto again;
2557 		}
2558 
2559 		btrfs_set_path_blocking(p);
2560 		reada_for_balance(root, p, level);
2561 		sret = balance_level(trans, root, p, level);
2562 		btrfs_clear_path_blocking(p, NULL, 0);
2563 
2564 		if (sret) {
2565 			ret = sret;
2566 			goto done;
2567 		}
2568 		b = p->nodes[level];
2569 		if (!b) {
2570 			btrfs_release_path(p);
2571 			goto again;
2572 		}
2573 		BUG_ON(btrfs_header_nritems(b) == 1);
2574 	}
2575 	return 0;
2576 
2577 again:
2578 	ret = -EAGAIN;
2579 done:
2580 	return ret;
2581 }
2582 
2583 static void key_search_validate(struct extent_buffer *b,
2584 				struct btrfs_key *key,
2585 				int level)
2586 {
2587 #ifdef CONFIG_BTRFS_ASSERT
2588 	struct btrfs_disk_key disk_key;
2589 
2590 	btrfs_cpu_key_to_disk(&disk_key, key);
2591 
2592 	if (level == 0)
2593 		ASSERT(!memcmp_extent_buffer(b, &disk_key,
2594 		    offsetof(struct btrfs_leaf, items[0].key),
2595 		    sizeof(disk_key)));
2596 	else
2597 		ASSERT(!memcmp_extent_buffer(b, &disk_key,
2598 		    offsetof(struct btrfs_node, ptrs[0].key),
2599 		    sizeof(disk_key)));
2600 #endif
2601 }
2602 
2603 static int key_search(struct extent_buffer *b, struct btrfs_key *key,
2604 		      int level, int *prev_cmp, int *slot)
2605 {
2606 	if (*prev_cmp != 0) {
2607 		*prev_cmp = bin_search(b, key, level, slot);
2608 		return *prev_cmp;
2609 	}
2610 
2611 	key_search_validate(b, key, level);
2612 	*slot = 0;
2613 
2614 	return 0;
2615 }
2616 
2617 int btrfs_find_item(struct btrfs_root *fs_root, struct btrfs_path *path,
2618 		u64 iobjectid, u64 ioff, u8 key_type,
2619 		struct btrfs_key *found_key)
2620 {
2621 	int ret;
2622 	struct btrfs_key key;
2623 	struct extent_buffer *eb;
2624 
2625 	ASSERT(path);
2626 	ASSERT(found_key);
2627 
2628 	key.type = key_type;
2629 	key.objectid = iobjectid;
2630 	key.offset = ioff;
2631 
2632 	ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
2633 	if (ret < 0)
2634 		return ret;
2635 
2636 	eb = path->nodes[0];
2637 	if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
2638 		ret = btrfs_next_leaf(fs_root, path);
2639 		if (ret)
2640 			return ret;
2641 		eb = path->nodes[0];
2642 	}
2643 
2644 	btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
2645 	if (found_key->type != key.type ||
2646 			found_key->objectid != key.objectid)
2647 		return 1;
2648 
2649 	return 0;
2650 }
2651 
2652 /*
2653  * look for key in the tree.  path is filled in with nodes along the way
2654  * if key is found, we return zero and you can find the item in the leaf
2655  * level of the path (level 0)
2656  *
2657  * If the key isn't found, the path points to the slot where it should
2658  * be inserted, and 1 is returned.  If there are other errors during the
2659  * search a negative error number is returned.
2660  *
2661  * if ins_len > 0, nodes and leaves will be split as we walk down the
2662  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
2663  * possible)
2664  */
2665 int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
2666 		      *root, struct btrfs_key *key, struct btrfs_path *p, int
2667 		      ins_len, int cow)
2668 {
2669 	struct extent_buffer *b;
2670 	int slot;
2671 	int ret;
2672 	int err;
2673 	int level;
2674 	int lowest_unlock = 1;
2675 	int root_lock;
2676 	/* everything at write_lock_level or lower must be write locked */
2677 	int write_lock_level = 0;
2678 	u8 lowest_level = 0;
2679 	int min_write_lock_level;
2680 	int prev_cmp;
2681 
2682 	lowest_level = p->lowest_level;
2683 	WARN_ON(lowest_level && ins_len > 0);
2684 	WARN_ON(p->nodes[0] != NULL);
2685 	BUG_ON(!cow && ins_len);
2686 
2687 	if (ins_len < 0) {
2688 		lowest_unlock = 2;
2689 
2690 		/* when we are removing items, we might have to go up to level
2691 		 * two as we update tree pointers  Make sure we keep write
2692 		 * for those levels as well
2693 		 */
2694 		write_lock_level = 2;
2695 	} else if (ins_len > 0) {
2696 		/*
2697 		 * for inserting items, make sure we have a write lock on
2698 		 * level 1 so we can update keys
2699 		 */
2700 		write_lock_level = 1;
2701 	}
2702 
2703 	if (!cow)
2704 		write_lock_level = -1;
2705 
2706 	if (cow && (p->keep_locks || p->lowest_level))
2707 		write_lock_level = BTRFS_MAX_LEVEL;
2708 
2709 	min_write_lock_level = write_lock_level;
2710 
2711 again:
2712 	prev_cmp = -1;
2713 	/*
2714 	 * we try very hard to do read locks on the root
2715 	 */
2716 	root_lock = BTRFS_READ_LOCK;
2717 	level = 0;
2718 	if (p->search_commit_root) {
2719 		/*
2720 		 * the commit roots are read only
2721 		 * so we always do read locks
2722 		 */
2723 		if (p->need_commit_sem)
2724 			down_read(&root->fs_info->commit_root_sem);
2725 		b = root->commit_root;
2726 		extent_buffer_get(b);
2727 		level = btrfs_header_level(b);
2728 		if (p->need_commit_sem)
2729 			up_read(&root->fs_info->commit_root_sem);
2730 		if (!p->skip_locking)
2731 			btrfs_tree_read_lock(b);
2732 	} else {
2733 		if (p->skip_locking) {
2734 			b = btrfs_root_node(root);
2735 			level = btrfs_header_level(b);
2736 		} else {
2737 			/* we don't know the level of the root node
2738 			 * until we actually have it read locked
2739 			 */
2740 			b = btrfs_read_lock_root_node(root);
2741 			level = btrfs_header_level(b);
2742 			if (level <= write_lock_level) {
2743 				/* whoops, must trade for write lock */
2744 				btrfs_tree_read_unlock(b);
2745 				free_extent_buffer(b);
2746 				b = btrfs_lock_root_node(root);
2747 				root_lock = BTRFS_WRITE_LOCK;
2748 
2749 				/* the level might have changed, check again */
2750 				level = btrfs_header_level(b);
2751 			}
2752 		}
2753 	}
2754 	p->nodes[level] = b;
2755 	if (!p->skip_locking)
2756 		p->locks[level] = root_lock;
2757 
2758 	while (b) {
2759 		level = btrfs_header_level(b);
2760 
2761 		/*
2762 		 * setup the path here so we can release it under lock
2763 		 * contention with the cow code
2764 		 */
2765 		if (cow) {
2766 			/*
2767 			 * if we don't really need to cow this block
2768 			 * then we don't want to set the path blocking,
2769 			 * so we test it here
2770 			 */
2771 			if (!should_cow_block(trans, root, b))
2772 				goto cow_done;
2773 
2774 			/*
2775 			 * must have write locks on this node and the
2776 			 * parent
2777 			 */
2778 			if (level > write_lock_level ||
2779 			    (level + 1 > write_lock_level &&
2780 			    level + 1 < BTRFS_MAX_LEVEL &&
2781 			    p->nodes[level + 1])) {
2782 				write_lock_level = level + 1;
2783 				btrfs_release_path(p);
2784 				goto again;
2785 			}
2786 
2787 			btrfs_set_path_blocking(p);
2788 			err = btrfs_cow_block(trans, root, b,
2789 					      p->nodes[level + 1],
2790 					      p->slots[level + 1], &b);
2791 			if (err) {
2792 				ret = err;
2793 				goto done;
2794 			}
2795 		}
2796 cow_done:
2797 		p->nodes[level] = b;
2798 		btrfs_clear_path_blocking(p, NULL, 0);
2799 
2800 		/*
2801 		 * we have a lock on b and as long as we aren't changing
2802 		 * the tree, there is no way to for the items in b to change.
2803 		 * It is safe to drop the lock on our parent before we
2804 		 * go through the expensive btree search on b.
2805 		 *
2806 		 * If we're inserting or deleting (ins_len != 0), then we might
2807 		 * be changing slot zero, which may require changing the parent.
2808 		 * So, we can't drop the lock until after we know which slot
2809 		 * we're operating on.
2810 		 */
2811 		if (!ins_len && !p->keep_locks) {
2812 			int u = level + 1;
2813 
2814 			if (u < BTRFS_MAX_LEVEL && p->locks[u]) {
2815 				btrfs_tree_unlock_rw(p->nodes[u], p->locks[u]);
2816 				p->locks[u] = 0;
2817 			}
2818 		}
2819 
2820 		ret = key_search(b, key, level, &prev_cmp, &slot);
2821 
2822 		if (level != 0) {
2823 			int dec = 0;
2824 			if (ret && slot > 0) {
2825 				dec = 1;
2826 				slot -= 1;
2827 			}
2828 			p->slots[level] = slot;
2829 			err = setup_nodes_for_search(trans, root, p, b, level,
2830 					     ins_len, &write_lock_level);
2831 			if (err == -EAGAIN)
2832 				goto again;
2833 			if (err) {
2834 				ret = err;
2835 				goto done;
2836 			}
2837 			b = p->nodes[level];
2838 			slot = p->slots[level];
2839 
2840 			/*
2841 			 * slot 0 is special, if we change the key
2842 			 * we have to update the parent pointer
2843 			 * which means we must have a write lock
2844 			 * on the parent
2845 			 */
2846 			if (slot == 0 && ins_len &&
2847 			    write_lock_level < level + 1) {
2848 				write_lock_level = level + 1;
2849 				btrfs_release_path(p);
2850 				goto again;
2851 			}
2852 
2853 			unlock_up(p, level, lowest_unlock,
2854 				  min_write_lock_level, &write_lock_level);
2855 
2856 			if (level == lowest_level) {
2857 				if (dec)
2858 					p->slots[level]++;
2859 				goto done;
2860 			}
2861 
2862 			err = read_block_for_search(trans, root, p,
2863 						    &b, level, slot, key, 0);
2864 			if (err == -EAGAIN)
2865 				goto again;
2866 			if (err) {
2867 				ret = err;
2868 				goto done;
2869 			}
2870 
2871 			if (!p->skip_locking) {
2872 				level = btrfs_header_level(b);
2873 				if (level <= write_lock_level) {
2874 					err = btrfs_try_tree_write_lock(b);
2875 					if (!err) {
2876 						btrfs_set_path_blocking(p);
2877 						btrfs_tree_lock(b);
2878 						btrfs_clear_path_blocking(p, b,
2879 								  BTRFS_WRITE_LOCK);
2880 					}
2881 					p->locks[level] = BTRFS_WRITE_LOCK;
2882 				} else {
2883 					err = btrfs_tree_read_lock_atomic(b);
2884 					if (!err) {
2885 						btrfs_set_path_blocking(p);
2886 						btrfs_tree_read_lock(b);
2887 						btrfs_clear_path_blocking(p, b,
2888 								  BTRFS_READ_LOCK);
2889 					}
2890 					p->locks[level] = BTRFS_READ_LOCK;
2891 				}
2892 				p->nodes[level] = b;
2893 			}
2894 		} else {
2895 			p->slots[level] = slot;
2896 			if (ins_len > 0 &&
2897 			    btrfs_leaf_free_space(root, b) < ins_len) {
2898 				if (write_lock_level < 1) {
2899 					write_lock_level = 1;
2900 					btrfs_release_path(p);
2901 					goto again;
2902 				}
2903 
2904 				btrfs_set_path_blocking(p);
2905 				err = split_leaf(trans, root, key,
2906 						 p, ins_len, ret == 0);
2907 				btrfs_clear_path_blocking(p, NULL, 0);
2908 
2909 				BUG_ON(err > 0);
2910 				if (err) {
2911 					ret = err;
2912 					goto done;
2913 				}
2914 			}
2915 			if (!p->search_for_split)
2916 				unlock_up(p, level, lowest_unlock,
2917 					  min_write_lock_level, &write_lock_level);
2918 			goto done;
2919 		}
2920 	}
2921 	ret = 1;
2922 done:
2923 	/*
2924 	 * we don't really know what they plan on doing with the path
2925 	 * from here on, so for now just mark it as blocking
2926 	 */
2927 	if (!p->leave_spinning)
2928 		btrfs_set_path_blocking(p);
2929 	if (ret < 0 && !p->skip_release_on_error)
2930 		btrfs_release_path(p);
2931 	return ret;
2932 }
2933 
2934 /*
2935  * Like btrfs_search_slot, this looks for a key in the given tree. It uses the
2936  * current state of the tree together with the operations recorded in the tree
2937  * modification log to search for the key in a previous version of this tree, as
2938  * denoted by the time_seq parameter.
2939  *
2940  * Naturally, there is no support for insert, delete or cow operations.
2941  *
2942  * The resulting path and return value will be set up as if we called
2943  * btrfs_search_slot at that point in time with ins_len and cow both set to 0.
2944  */
2945 int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key,
2946 			  struct btrfs_path *p, u64 time_seq)
2947 {
2948 	struct extent_buffer *b;
2949 	int slot;
2950 	int ret;
2951 	int err;
2952 	int level;
2953 	int lowest_unlock = 1;
2954 	u8 lowest_level = 0;
2955 	int prev_cmp = -1;
2956 
2957 	lowest_level = p->lowest_level;
2958 	WARN_ON(p->nodes[0] != NULL);
2959 
2960 	if (p->search_commit_root) {
2961 		BUG_ON(time_seq);
2962 		return btrfs_search_slot(NULL, root, key, p, 0, 0);
2963 	}
2964 
2965 again:
2966 	b = get_old_root(root, time_seq);
2967 	level = btrfs_header_level(b);
2968 	p->locks[level] = BTRFS_READ_LOCK;
2969 
2970 	while (b) {
2971 		level = btrfs_header_level(b);
2972 		p->nodes[level] = b;
2973 		btrfs_clear_path_blocking(p, NULL, 0);
2974 
2975 		/*
2976 		 * we have a lock on b and as long as we aren't changing
2977 		 * the tree, there is no way to for the items in b to change.
2978 		 * It is safe to drop the lock on our parent before we
2979 		 * go through the expensive btree search on b.
2980 		 */
2981 		btrfs_unlock_up_safe(p, level + 1);
2982 
2983 		/*
2984 		 * Since we can unwind eb's we want to do a real search every
2985 		 * time.
2986 		 */
2987 		prev_cmp = -1;
2988 		ret = key_search(b, key, level, &prev_cmp, &slot);
2989 
2990 		if (level != 0) {
2991 			int dec = 0;
2992 			if (ret && slot > 0) {
2993 				dec = 1;
2994 				slot -= 1;
2995 			}
2996 			p->slots[level] = slot;
2997 			unlock_up(p, level, lowest_unlock, 0, NULL);
2998 
2999 			if (level == lowest_level) {
3000 				if (dec)
3001 					p->slots[level]++;
3002 				goto done;
3003 			}
3004 
3005 			err = read_block_for_search(NULL, root, p, &b, level,
3006 						    slot, key, time_seq);
3007 			if (err == -EAGAIN)
3008 				goto again;
3009 			if (err) {
3010 				ret = err;
3011 				goto done;
3012 			}
3013 
3014 			level = btrfs_header_level(b);
3015 			err = btrfs_tree_read_lock_atomic(b);
3016 			if (!err) {
3017 				btrfs_set_path_blocking(p);
3018 				btrfs_tree_read_lock(b);
3019 				btrfs_clear_path_blocking(p, b,
3020 							  BTRFS_READ_LOCK);
3021 			}
3022 			b = tree_mod_log_rewind(root->fs_info, p, b, time_seq);
3023 			if (!b) {
3024 				ret = -ENOMEM;
3025 				goto done;
3026 			}
3027 			p->locks[level] = BTRFS_READ_LOCK;
3028 			p->nodes[level] = b;
3029 		} else {
3030 			p->slots[level] = slot;
3031 			unlock_up(p, level, lowest_unlock, 0, NULL);
3032 			goto done;
3033 		}
3034 	}
3035 	ret = 1;
3036 done:
3037 	if (!p->leave_spinning)
3038 		btrfs_set_path_blocking(p);
3039 	if (ret < 0)
3040 		btrfs_release_path(p);
3041 
3042 	return ret;
3043 }
3044 
3045 /*
3046  * helper to use instead of search slot if no exact match is needed but
3047  * instead the next or previous item should be returned.
3048  * When find_higher is true, the next higher item is returned, the next lower
3049  * otherwise.
3050  * When return_any and find_higher are both true, and no higher item is found,
3051  * return the next lower instead.
3052  * When return_any is true and find_higher is false, and no lower item is found,
3053  * return the next higher instead.
3054  * It returns 0 if any item is found, 1 if none is found (tree empty), and
3055  * < 0 on error
3056  */
3057 int btrfs_search_slot_for_read(struct btrfs_root *root,
3058 			       struct btrfs_key *key, struct btrfs_path *p,
3059 			       int find_higher, int return_any)
3060 {
3061 	int ret;
3062 	struct extent_buffer *leaf;
3063 
3064 again:
3065 	ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
3066 	if (ret <= 0)
3067 		return ret;
3068 	/*
3069 	 * a return value of 1 means the path is at the position where the
3070 	 * item should be inserted. Normally this is the next bigger item,
3071 	 * but in case the previous item is the last in a leaf, path points
3072 	 * to the first free slot in the previous leaf, i.e. at an invalid
3073 	 * item.
3074 	 */
3075 	leaf = p->nodes[0];
3076 
3077 	if (find_higher) {
3078 		if (p->slots[0] >= btrfs_header_nritems(leaf)) {
3079 			ret = btrfs_next_leaf(root, p);
3080 			if (ret <= 0)
3081 				return ret;
3082 			if (!return_any)
3083 				return 1;
3084 			/*
3085 			 * no higher item found, return the next
3086 			 * lower instead
3087 			 */
3088 			return_any = 0;
3089 			find_higher = 0;
3090 			btrfs_release_path(p);
3091 			goto again;
3092 		}
3093 	} else {
3094 		if (p->slots[0] == 0) {
3095 			ret = btrfs_prev_leaf(root, p);
3096 			if (ret < 0)
3097 				return ret;
3098 			if (!ret) {
3099 				leaf = p->nodes[0];
3100 				if (p->slots[0] == btrfs_header_nritems(leaf))
3101 					p->slots[0]--;
3102 				return 0;
3103 			}
3104 			if (!return_any)
3105 				return 1;
3106 			/*
3107 			 * no lower item found, return the next
3108 			 * higher instead
3109 			 */
3110 			return_any = 0;
3111 			find_higher = 1;
3112 			btrfs_release_path(p);
3113 			goto again;
3114 		} else {
3115 			--p->slots[0];
3116 		}
3117 	}
3118 	return 0;
3119 }
3120 
3121 /*
3122  * adjust the pointers going up the tree, starting at level
3123  * making sure the right key of each node is points to 'key'.
3124  * This is used after shifting pointers to the left, so it stops
3125  * fixing up pointers when a given leaf/node is not in slot 0 of the
3126  * higher levels
3127  *
3128  */
3129 static void fixup_low_keys(struct btrfs_root *root, struct btrfs_path *path,
3130 			   struct btrfs_disk_key *key, int level)
3131 {
3132 	int i;
3133 	struct extent_buffer *t;
3134 
3135 	for (i = level; i < BTRFS_MAX_LEVEL; i++) {
3136 		int tslot = path->slots[i];
3137 		if (!path->nodes[i])
3138 			break;
3139 		t = path->nodes[i];
3140 		tree_mod_log_set_node_key(root->fs_info, t, tslot, 1);
3141 		btrfs_set_node_key(t, key, tslot);
3142 		btrfs_mark_buffer_dirty(path->nodes[i]);
3143 		if (tslot != 0)
3144 			break;
3145 	}
3146 }
3147 
3148 /*
3149  * update item key.
3150  *
3151  * This function isn't completely safe. It's the caller's responsibility
3152  * that the new key won't break the order
3153  */
3154 void btrfs_set_item_key_safe(struct btrfs_root *root, struct btrfs_path *path,
3155 			     struct btrfs_key *new_key)
3156 {
3157 	struct btrfs_disk_key disk_key;
3158 	struct extent_buffer *eb;
3159 	int slot;
3160 
3161 	eb = path->nodes[0];
3162 	slot = path->slots[0];
3163 	if (slot > 0) {
3164 		btrfs_item_key(eb, &disk_key, slot - 1);
3165 		BUG_ON(comp_keys(&disk_key, new_key) >= 0);
3166 	}
3167 	if (slot < btrfs_header_nritems(eb) - 1) {
3168 		btrfs_item_key(eb, &disk_key, slot + 1);
3169 		BUG_ON(comp_keys(&disk_key, new_key) <= 0);
3170 	}
3171 
3172 	btrfs_cpu_key_to_disk(&disk_key, new_key);
3173 	btrfs_set_item_key(eb, &disk_key, slot);
3174 	btrfs_mark_buffer_dirty(eb);
3175 	if (slot == 0)
3176 		fixup_low_keys(root, path, &disk_key, 1);
3177 }
3178 
3179 /*
3180  * try to push data from one node into the next node left in the
3181  * tree.
3182  *
3183  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
3184  * error, and > 0 if there was no room in the left hand block.
3185  */
3186 static int push_node_left(struct btrfs_trans_handle *trans,
3187 			  struct btrfs_root *root, struct extent_buffer *dst,
3188 			  struct extent_buffer *src, int empty)
3189 {
3190 	int push_items = 0;
3191 	int src_nritems;
3192 	int dst_nritems;
3193 	int ret = 0;
3194 
3195 	src_nritems = btrfs_header_nritems(src);
3196 	dst_nritems = btrfs_header_nritems(dst);
3197 	push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
3198 	WARN_ON(btrfs_header_generation(src) != trans->transid);
3199 	WARN_ON(btrfs_header_generation(dst) != trans->transid);
3200 
3201 	if (!empty && src_nritems <= 8)
3202 		return 1;
3203 
3204 	if (push_items <= 0)
3205 		return 1;
3206 
3207 	if (empty) {
3208 		push_items = min(src_nritems, push_items);
3209 		if (push_items < src_nritems) {
3210 			/* leave at least 8 pointers in the node if
3211 			 * we aren't going to empty it
3212 			 */
3213 			if (src_nritems - push_items < 8) {
3214 				if (push_items <= 8)
3215 					return 1;
3216 				push_items -= 8;
3217 			}
3218 		}
3219 	} else
3220 		push_items = min(src_nritems - 8, push_items);
3221 
3222 	ret = tree_mod_log_eb_copy(root->fs_info, dst, src, dst_nritems, 0,
3223 				   push_items);
3224 	if (ret) {
3225 		btrfs_abort_transaction(trans, root, ret);
3226 		return ret;
3227 	}
3228 	copy_extent_buffer(dst, src,
3229 			   btrfs_node_key_ptr_offset(dst_nritems),
3230 			   btrfs_node_key_ptr_offset(0),
3231 			   push_items * sizeof(struct btrfs_key_ptr));
3232 
3233 	if (push_items < src_nritems) {
3234 		/*
3235 		 * don't call tree_mod_log_eb_move here, key removal was already
3236 		 * fully logged by tree_mod_log_eb_copy above.
3237 		 */
3238 		memmove_extent_buffer(src, btrfs_node_key_ptr_offset(0),
3239 				      btrfs_node_key_ptr_offset(push_items),
3240 				      (src_nritems - push_items) *
3241 				      sizeof(struct btrfs_key_ptr));
3242 	}
3243 	btrfs_set_header_nritems(src, src_nritems - push_items);
3244 	btrfs_set_header_nritems(dst, dst_nritems + push_items);
3245 	btrfs_mark_buffer_dirty(src);
3246 	btrfs_mark_buffer_dirty(dst);
3247 
3248 	return ret;
3249 }
3250 
3251 /*
3252  * try to push data from one node into the next node right in the
3253  * tree.
3254  *
3255  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
3256  * error, and > 0 if there was no room in the right hand block.
3257  *
3258  * this will  only push up to 1/2 the contents of the left node over
3259  */
3260 static int balance_node_right(struct btrfs_trans_handle *trans,
3261 			      struct btrfs_root *root,
3262 			      struct extent_buffer *dst,
3263 			      struct extent_buffer *src)
3264 {
3265 	int push_items = 0;
3266 	int max_push;
3267 	int src_nritems;
3268 	int dst_nritems;
3269 	int ret = 0;
3270 
3271 	WARN_ON(btrfs_header_generation(src) != trans->transid);
3272 	WARN_ON(btrfs_header_generation(dst) != trans->transid);
3273 
3274 	src_nritems = btrfs_header_nritems(src);
3275 	dst_nritems = btrfs_header_nritems(dst);
3276 	push_items = BTRFS_NODEPTRS_PER_BLOCK(root) - dst_nritems;
3277 	if (push_items <= 0)
3278 		return 1;
3279 
3280 	if (src_nritems < 4)
3281 		return 1;
3282 
3283 	max_push = src_nritems / 2 + 1;
3284 	/* don't try to empty the node */
3285 	if (max_push >= src_nritems)
3286 		return 1;
3287 
3288 	if (max_push < push_items)
3289 		push_items = max_push;
3290 
3291 	tree_mod_log_eb_move(root->fs_info, dst, push_items, 0, dst_nritems);
3292 	memmove_extent_buffer(dst, btrfs_node_key_ptr_offset(push_items),
3293 				      btrfs_node_key_ptr_offset(0),
3294 				      (dst_nritems) *
3295 				      sizeof(struct btrfs_key_ptr));
3296 
3297 	ret = tree_mod_log_eb_copy(root->fs_info, dst, src, 0,
3298 				   src_nritems - push_items, push_items);
3299 	if (ret) {
3300 		btrfs_abort_transaction(trans, root, ret);
3301 		return ret;
3302 	}
3303 	copy_extent_buffer(dst, src,
3304 			   btrfs_node_key_ptr_offset(0),
3305 			   btrfs_node_key_ptr_offset(src_nritems - push_items),
3306 			   push_items * sizeof(struct btrfs_key_ptr));
3307 
3308 	btrfs_set_header_nritems(src, src_nritems - push_items);
3309 	btrfs_set_header_nritems(dst, dst_nritems + push_items);
3310 
3311 	btrfs_mark_buffer_dirty(src);
3312 	btrfs_mark_buffer_dirty(dst);
3313 
3314 	return ret;
3315 }
3316 
3317 /*
3318  * helper function to insert a new root level in the tree.
3319  * A new node is allocated, and a single item is inserted to
3320  * point to the existing root
3321  *
3322  * returns zero on success or < 0 on failure.
3323  */
3324 static noinline int insert_new_root(struct btrfs_trans_handle *trans,
3325 			   struct btrfs_root *root,
3326 			   struct btrfs_path *path, int level)
3327 {
3328 	u64 lower_gen;
3329 	struct extent_buffer *lower;
3330 	struct extent_buffer *c;
3331 	struct extent_buffer *old;
3332 	struct btrfs_disk_key lower_key;
3333 
3334 	BUG_ON(path->nodes[level]);
3335 	BUG_ON(path->nodes[level-1] != root->node);
3336 
3337 	lower = path->nodes[level-1];
3338 	if (level == 1)
3339 		btrfs_item_key(lower, &lower_key, 0);
3340 	else
3341 		btrfs_node_key(lower, &lower_key, 0);
3342 
3343 	c = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3344 				   &lower_key, level, root->node->start, 0);
3345 	if (IS_ERR(c))
3346 		return PTR_ERR(c);
3347 
3348 	root_add_used(root, root->nodesize);
3349 
3350 	memset_extent_buffer(c, 0, 0, sizeof(struct btrfs_header));
3351 	btrfs_set_header_nritems(c, 1);
3352 	btrfs_set_header_level(c, level);
3353 	btrfs_set_header_bytenr(c, c->start);
3354 	btrfs_set_header_generation(c, trans->transid);
3355 	btrfs_set_header_backref_rev(c, BTRFS_MIXED_BACKREF_REV);
3356 	btrfs_set_header_owner(c, root->root_key.objectid);
3357 
3358 	write_extent_buffer(c, root->fs_info->fsid, btrfs_header_fsid(),
3359 			    BTRFS_FSID_SIZE);
3360 
3361 	write_extent_buffer(c, root->fs_info->chunk_tree_uuid,
3362 			    btrfs_header_chunk_tree_uuid(c), BTRFS_UUID_SIZE);
3363 
3364 	btrfs_set_node_key(c, &lower_key, 0);
3365 	btrfs_set_node_blockptr(c, 0, lower->start);
3366 	lower_gen = btrfs_header_generation(lower);
3367 	WARN_ON(lower_gen != trans->transid);
3368 
3369 	btrfs_set_node_ptr_generation(c, 0, lower_gen);
3370 
3371 	btrfs_mark_buffer_dirty(c);
3372 
3373 	old = root->node;
3374 	tree_mod_log_set_root_pointer(root, c, 0);
3375 	rcu_assign_pointer(root->node, c);
3376 
3377 	/* the super has an extra ref to root->node */
3378 	free_extent_buffer(old);
3379 
3380 	add_root_to_dirty_list(root);
3381 	extent_buffer_get(c);
3382 	path->nodes[level] = c;
3383 	path->locks[level] = BTRFS_WRITE_LOCK_BLOCKING;
3384 	path->slots[level] = 0;
3385 	return 0;
3386 }
3387 
3388 /*
3389  * worker function to insert a single pointer in a node.
3390  * the node should have enough room for the pointer already
3391  *
3392  * slot and level indicate where you want the key to go, and
3393  * blocknr is the block the key points to.
3394  */
3395 static void insert_ptr(struct btrfs_trans_handle *trans,
3396 		       struct btrfs_root *root, struct btrfs_path *path,
3397 		       struct btrfs_disk_key *key, u64 bytenr,
3398 		       int slot, int level)
3399 {
3400 	struct extent_buffer *lower;
3401 	int nritems;
3402 	int ret;
3403 
3404 	BUG_ON(!path->nodes[level]);
3405 	btrfs_assert_tree_locked(path->nodes[level]);
3406 	lower = path->nodes[level];
3407 	nritems = btrfs_header_nritems(lower);
3408 	BUG_ON(slot > nritems);
3409 	BUG_ON(nritems == BTRFS_NODEPTRS_PER_BLOCK(root));
3410 	if (slot != nritems) {
3411 		if (level)
3412 			tree_mod_log_eb_move(root->fs_info, lower, slot + 1,
3413 					     slot, nritems - slot);
3414 		memmove_extent_buffer(lower,
3415 			      btrfs_node_key_ptr_offset(slot + 1),
3416 			      btrfs_node_key_ptr_offset(slot),
3417 			      (nritems - slot) * sizeof(struct btrfs_key_ptr));
3418 	}
3419 	if (level) {
3420 		ret = tree_mod_log_insert_key(root->fs_info, lower, slot,
3421 					      MOD_LOG_KEY_ADD, GFP_NOFS);
3422 		BUG_ON(ret < 0);
3423 	}
3424 	btrfs_set_node_key(lower, key, slot);
3425 	btrfs_set_node_blockptr(lower, slot, bytenr);
3426 	WARN_ON(trans->transid == 0);
3427 	btrfs_set_node_ptr_generation(lower, slot, trans->transid);
3428 	btrfs_set_header_nritems(lower, nritems + 1);
3429 	btrfs_mark_buffer_dirty(lower);
3430 }
3431 
3432 /*
3433  * split the node at the specified level in path in two.
3434  * The path is corrected to point to the appropriate node after the split
3435  *
3436  * Before splitting this tries to make some room in the node by pushing
3437  * left and right, if either one works, it returns right away.
3438  *
3439  * returns 0 on success and < 0 on failure
3440  */
3441 static noinline int split_node(struct btrfs_trans_handle *trans,
3442 			       struct btrfs_root *root,
3443 			       struct btrfs_path *path, int level)
3444 {
3445 	struct extent_buffer *c;
3446 	struct extent_buffer *split;
3447 	struct btrfs_disk_key disk_key;
3448 	int mid;
3449 	int ret;
3450 	u32 c_nritems;
3451 
3452 	c = path->nodes[level];
3453 	WARN_ON(btrfs_header_generation(c) != trans->transid);
3454 	if (c == root->node) {
3455 		/*
3456 		 * trying to split the root, lets make a new one
3457 		 *
3458 		 * tree mod log: We don't log_removal old root in
3459 		 * insert_new_root, because that root buffer will be kept as a
3460 		 * normal node. We are going to log removal of half of the
3461 		 * elements below with tree_mod_log_eb_copy. We're holding a
3462 		 * tree lock on the buffer, which is why we cannot race with
3463 		 * other tree_mod_log users.
3464 		 */
3465 		ret = insert_new_root(trans, root, path, level + 1);
3466 		if (ret)
3467 			return ret;
3468 	} else {
3469 		ret = push_nodes_for_insert(trans, root, path, level);
3470 		c = path->nodes[level];
3471 		if (!ret && btrfs_header_nritems(c) <
3472 		    BTRFS_NODEPTRS_PER_BLOCK(root) - 3)
3473 			return 0;
3474 		if (ret < 0)
3475 			return ret;
3476 	}
3477 
3478 	c_nritems = btrfs_header_nritems(c);
3479 	mid = (c_nritems + 1) / 2;
3480 	btrfs_node_key(c, &disk_key, mid);
3481 
3482 	split = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
3483 			&disk_key, level, c->start, 0);
3484 	if (IS_ERR(split))
3485 		return PTR_ERR(split);
3486 
3487 	root_add_used(root, root->nodesize);
3488 
3489 	memset_extent_buffer(split, 0, 0, sizeof(struct btrfs_header));
3490 	btrfs_set_header_level(split, btrfs_header_level(c));
3491 	btrfs_set_header_bytenr(split, split->start);
3492 	btrfs_set_header_generation(split, trans->transid);
3493 	btrfs_set_header_backref_rev(split, BTRFS_MIXED_BACKREF_REV);
3494 	btrfs_set_header_owner(split, root->root_key.objectid);
3495 	write_extent_buffer(split, root->fs_info->fsid,
3496 			    btrfs_header_fsid(), BTRFS_FSID_SIZE);
3497 	write_extent_buffer(split, root->fs_info->chunk_tree_uuid,
3498 			    btrfs_header_chunk_tree_uuid(split),
3499 			    BTRFS_UUID_SIZE);
3500 
3501 	ret = tree_mod_log_eb_copy(root->fs_info, split, c, 0,
3502 				   mid, c_nritems - mid);
3503 	if (ret) {
3504 		btrfs_abort_transaction(trans, root, ret);
3505 		return ret;
3506 	}
3507 	copy_extent_buffer(split, c,
3508 			   btrfs_node_key_ptr_offset(0),
3509 			   btrfs_node_key_ptr_offset(mid),
3510 			   (c_nritems - mid) * sizeof(struct btrfs_key_ptr));
3511 	btrfs_set_header_nritems(split, c_nritems - mid);
3512 	btrfs_set_header_nritems(c, mid);
3513 	ret = 0;
3514 
3515 	btrfs_mark_buffer_dirty(c);
3516 	btrfs_mark_buffer_dirty(split);
3517 
3518 	insert_ptr(trans, root, path, &disk_key, split->start,
3519 		   path->slots[level + 1] + 1, level + 1);
3520 
3521 	if (path->slots[level] >= mid) {
3522 		path->slots[level] -= mid;
3523 		btrfs_tree_unlock(c);
3524 		free_extent_buffer(c);
3525 		path->nodes[level] = split;
3526 		path->slots[level + 1] += 1;
3527 	} else {
3528 		btrfs_tree_unlock(split);
3529 		free_extent_buffer(split);
3530 	}
3531 	return ret;
3532 }
3533 
3534 /*
3535  * how many bytes are required to store the items in a leaf.  start
3536  * and nr indicate which items in the leaf to check.  This totals up the
3537  * space used both by the item structs and the item data
3538  */
3539 static int leaf_space_used(struct extent_buffer *l, int start, int nr)
3540 {
3541 	struct btrfs_item *start_item;
3542 	struct btrfs_item *end_item;
3543 	struct btrfs_map_token token;
3544 	int data_len;
3545 	int nritems = btrfs_header_nritems(l);
3546 	int end = min(nritems, start + nr) - 1;
3547 
3548 	if (!nr)
3549 		return 0;
3550 	btrfs_init_map_token(&token);
3551 	start_item = btrfs_item_nr(start);
3552 	end_item = btrfs_item_nr(end);
3553 	data_len = btrfs_token_item_offset(l, start_item, &token) +
3554 		btrfs_token_item_size(l, start_item, &token);
3555 	data_len = data_len - btrfs_token_item_offset(l, end_item, &token);
3556 	data_len += sizeof(struct btrfs_item) * nr;
3557 	WARN_ON(data_len < 0);
3558 	return data_len;
3559 }
3560 
3561 /*
3562  * The space between the end of the leaf items and
3563  * the start of the leaf data.  IOW, how much room
3564  * the leaf has left for both items and data
3565  */
3566 noinline int btrfs_leaf_free_space(struct btrfs_root *root,
3567 				   struct extent_buffer *leaf)
3568 {
3569 	int nritems = btrfs_header_nritems(leaf);
3570 	int ret;
3571 	ret = BTRFS_LEAF_DATA_SIZE(root) - leaf_space_used(leaf, 0, nritems);
3572 	if (ret < 0) {
3573 		btrfs_crit(root->fs_info,
3574 			"leaf free space ret %d, leaf data size %lu, used %d nritems %d",
3575 		       ret, (unsigned long) BTRFS_LEAF_DATA_SIZE(root),
3576 		       leaf_space_used(leaf, 0, nritems), nritems);
3577 	}
3578 	return ret;
3579 }
3580 
3581 /*
3582  * min slot controls the lowest index we're willing to push to the
3583  * right.  We'll push up to and including min_slot, but no lower
3584  */
3585 static noinline int __push_leaf_right(struct btrfs_trans_handle *trans,
3586 				      struct btrfs_root *root,
3587 				      struct btrfs_path *path,
3588 				      int data_size, int empty,
3589 				      struct extent_buffer *right,
3590 				      int free_space, u32 left_nritems,
3591 				      u32 min_slot)
3592 {
3593 	struct extent_buffer *left = path->nodes[0];
3594 	struct extent_buffer *upper = path->nodes[1];
3595 	struct btrfs_map_token token;
3596 	struct btrfs_disk_key disk_key;
3597 	int slot;
3598 	u32 i;
3599 	int push_space = 0;
3600 	int push_items = 0;
3601 	struct btrfs_item *item;
3602 	u32 nr;
3603 	u32 right_nritems;
3604 	u32 data_end;
3605 	u32 this_item_size;
3606 
3607 	btrfs_init_map_token(&token);
3608 
3609 	if (empty)
3610 		nr = 0;
3611 	else
3612 		nr = max_t(u32, 1, min_slot);
3613 
3614 	if (path->slots[0] >= left_nritems)
3615 		push_space += data_size;
3616 
3617 	slot = path->slots[1];
3618 	i = left_nritems - 1;
3619 	while (i >= nr) {
3620 		item = btrfs_item_nr(i);
3621 
3622 		if (!empty && push_items > 0) {
3623 			if (path->slots[0] > i)
3624 				break;
3625 			if (path->slots[0] == i) {
3626 				int space = btrfs_leaf_free_space(root, left);
3627 				if (space + push_space * 2 > free_space)
3628 					break;
3629 			}
3630 		}
3631 
3632 		if (path->slots[0] == i)
3633 			push_space += data_size;
3634 
3635 		this_item_size = btrfs_item_size(left, item);
3636 		if (this_item_size + sizeof(*item) + push_space > free_space)
3637 			break;
3638 
3639 		push_items++;
3640 		push_space += this_item_size + sizeof(*item);
3641 		if (i == 0)
3642 			break;
3643 		i--;
3644 	}
3645 
3646 	if (push_items == 0)
3647 		goto out_unlock;
3648 
3649 	WARN_ON(!empty && push_items == left_nritems);
3650 
3651 	/* push left to right */
3652 	right_nritems = btrfs_header_nritems(right);
3653 
3654 	push_space = btrfs_item_end_nr(left, left_nritems - push_items);
3655 	push_space -= leaf_data_end(root, left);
3656 
3657 	/* make room in the right data area */
3658 	data_end = leaf_data_end(root, right);
3659 	memmove_extent_buffer(right,
3660 			      btrfs_leaf_data(right) + data_end - push_space,
3661 			      btrfs_leaf_data(right) + data_end,
3662 			      BTRFS_LEAF_DATA_SIZE(root) - data_end);
3663 
3664 	/* copy from the left data area */
3665 	copy_extent_buffer(right, left, btrfs_leaf_data(right) +
3666 		     BTRFS_LEAF_DATA_SIZE(root) - push_space,
3667 		     btrfs_leaf_data(left) + leaf_data_end(root, left),
3668 		     push_space);
3669 
3670 	memmove_extent_buffer(right, btrfs_item_nr_offset(push_items),
3671 			      btrfs_item_nr_offset(0),
3672 			      right_nritems * sizeof(struct btrfs_item));
3673 
3674 	/* copy the items from left to right */
3675 	copy_extent_buffer(right, left, btrfs_item_nr_offset(0),
3676 		   btrfs_item_nr_offset(left_nritems - push_items),
3677 		   push_items * sizeof(struct btrfs_item));
3678 
3679 	/* update the item pointers */
3680 	right_nritems += push_items;
3681 	btrfs_set_header_nritems(right, right_nritems);
3682 	push_space = BTRFS_LEAF_DATA_SIZE(root);
3683 	for (i = 0; i < right_nritems; i++) {
3684 		item = btrfs_item_nr(i);
3685 		push_space -= btrfs_token_item_size(right, item, &token);
3686 		btrfs_set_token_item_offset(right, item, push_space, &token);
3687 	}
3688 
3689 	left_nritems -= push_items;
3690 	btrfs_set_header_nritems(left, left_nritems);
3691 
3692 	if (left_nritems)
3693 		btrfs_mark_buffer_dirty(left);
3694 	else
3695 		clean_tree_block(trans, root, left);
3696 
3697 	btrfs_mark_buffer_dirty(right);
3698 
3699 	btrfs_item_key(right, &disk_key, 0);
3700 	btrfs_set_node_key(upper, &disk_key, slot + 1);
3701 	btrfs_mark_buffer_dirty(upper);
3702 
3703 	/* then fixup the leaf pointer in the path */
3704 	if (path->slots[0] >= left_nritems) {
3705 		path->slots[0] -= left_nritems;
3706 		if (btrfs_header_nritems(path->nodes[0]) == 0)
3707 			clean_tree_block(trans, root, path->nodes[0]);
3708 		btrfs_tree_unlock(path->nodes[0]);
3709 		free_extent_buffer(path->nodes[0]);
3710 		path->nodes[0] = right;
3711 		path->slots[1] += 1;
3712 	} else {
3713 		btrfs_tree_unlock(right);
3714 		free_extent_buffer(right);
3715 	}
3716 	return 0;
3717 
3718 out_unlock:
3719 	btrfs_tree_unlock(right);
3720 	free_extent_buffer(right);
3721 	return 1;
3722 }
3723 
3724 /*
3725  * push some data in the path leaf to the right, trying to free up at
3726  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3727  *
3728  * returns 1 if the push failed because the other node didn't have enough
3729  * room, 0 if everything worked out and < 0 if there were major errors.
3730  *
3731  * this will push starting from min_slot to the end of the leaf.  It won't
3732  * push any slot lower than min_slot
3733  */
3734 static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root
3735 			   *root, struct btrfs_path *path,
3736 			   int min_data_size, int data_size,
3737 			   int empty, u32 min_slot)
3738 {
3739 	struct extent_buffer *left = path->nodes[0];
3740 	struct extent_buffer *right;
3741 	struct extent_buffer *upper;
3742 	int slot;
3743 	int free_space;
3744 	u32 left_nritems;
3745 	int ret;
3746 
3747 	if (!path->nodes[1])
3748 		return 1;
3749 
3750 	slot = path->slots[1];
3751 	upper = path->nodes[1];
3752 	if (slot >= btrfs_header_nritems(upper) - 1)
3753 		return 1;
3754 
3755 	btrfs_assert_tree_locked(path->nodes[1]);
3756 
3757 	right = read_node_slot(root, upper, slot + 1);
3758 	if (right == NULL)
3759 		return 1;
3760 
3761 	btrfs_tree_lock(right);
3762 	btrfs_set_lock_blocking(right);
3763 
3764 	free_space = btrfs_leaf_free_space(root, right);
3765 	if (free_space < data_size)
3766 		goto out_unlock;
3767 
3768 	/* cow and double check */
3769 	ret = btrfs_cow_block(trans, root, right, upper,
3770 			      slot + 1, &right);
3771 	if (ret)
3772 		goto out_unlock;
3773 
3774 	free_space = btrfs_leaf_free_space(root, right);
3775 	if (free_space < data_size)
3776 		goto out_unlock;
3777 
3778 	left_nritems = btrfs_header_nritems(left);
3779 	if (left_nritems == 0)
3780 		goto out_unlock;
3781 
3782 	if (path->slots[0] == left_nritems && !empty) {
3783 		/* Key greater than all keys in the leaf, right neighbor has
3784 		 * enough room for it and we're not emptying our leaf to delete
3785 		 * it, therefore use right neighbor to insert the new item and
3786 		 * no need to touch/dirty our left leaft. */
3787 		btrfs_tree_unlock(left);
3788 		free_extent_buffer(left);
3789 		path->nodes[0] = right;
3790 		path->slots[0] = 0;
3791 		path->slots[1]++;
3792 		return 0;
3793 	}
3794 
3795 	return __push_leaf_right(trans, root, path, min_data_size, empty,
3796 				right, free_space, left_nritems, min_slot);
3797 out_unlock:
3798 	btrfs_tree_unlock(right);
3799 	free_extent_buffer(right);
3800 	return 1;
3801 }
3802 
3803 /*
3804  * push some data in the path leaf to the left, trying to free up at
3805  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3806  *
3807  * max_slot can put a limit on how far into the leaf we'll push items.  The
3808  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us do all the
3809  * items
3810  */
3811 static noinline int __push_leaf_left(struct btrfs_trans_handle *trans,
3812 				     struct btrfs_root *root,
3813 				     struct btrfs_path *path, int data_size,
3814 				     int empty, struct extent_buffer *left,
3815 				     int free_space, u32 right_nritems,
3816 				     u32 max_slot)
3817 {
3818 	struct btrfs_disk_key disk_key;
3819 	struct extent_buffer *right = path->nodes[0];
3820 	int i;
3821 	int push_space = 0;
3822 	int push_items = 0;
3823 	struct btrfs_item *item;
3824 	u32 old_left_nritems;
3825 	u32 nr;
3826 	int ret = 0;
3827 	u32 this_item_size;
3828 	u32 old_left_item_size;
3829 	struct btrfs_map_token token;
3830 
3831 	btrfs_init_map_token(&token);
3832 
3833 	if (empty)
3834 		nr = min(right_nritems, max_slot);
3835 	else
3836 		nr = min(right_nritems - 1, max_slot);
3837 
3838 	for (i = 0; i < nr; i++) {
3839 		item = btrfs_item_nr(i);
3840 
3841 		if (!empty && push_items > 0) {
3842 			if (path->slots[0] < i)
3843 				break;
3844 			if (path->slots[0] == i) {
3845 				int space = btrfs_leaf_free_space(root, right);
3846 				if (space + push_space * 2 > free_space)
3847 					break;
3848 			}
3849 		}
3850 
3851 		if (path->slots[0] == i)
3852 			push_space += data_size;
3853 
3854 		this_item_size = btrfs_item_size(right, item);
3855 		if (this_item_size + sizeof(*item) + push_space > free_space)
3856 			break;
3857 
3858 		push_items++;
3859 		push_space += this_item_size + sizeof(*item);
3860 	}
3861 
3862 	if (push_items == 0) {
3863 		ret = 1;
3864 		goto out;
3865 	}
3866 	WARN_ON(!empty && push_items == btrfs_header_nritems(right));
3867 
3868 	/* push data from right to left */
3869 	copy_extent_buffer(left, right,
3870 			   btrfs_item_nr_offset(btrfs_header_nritems(left)),
3871 			   btrfs_item_nr_offset(0),
3872 			   push_items * sizeof(struct btrfs_item));
3873 
3874 	push_space = BTRFS_LEAF_DATA_SIZE(root) -
3875 		     btrfs_item_offset_nr(right, push_items - 1);
3876 
3877 	copy_extent_buffer(left, right, btrfs_leaf_data(left) +
3878 		     leaf_data_end(root, left) - push_space,
3879 		     btrfs_leaf_data(right) +
3880 		     btrfs_item_offset_nr(right, push_items - 1),
3881 		     push_space);
3882 	old_left_nritems = btrfs_header_nritems(left);
3883 	BUG_ON(old_left_nritems <= 0);
3884 
3885 	old_left_item_size = btrfs_item_offset_nr(left, old_left_nritems - 1);
3886 	for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
3887 		u32 ioff;
3888 
3889 		item = btrfs_item_nr(i);
3890 
3891 		ioff = btrfs_token_item_offset(left, item, &token);
3892 		btrfs_set_token_item_offset(left, item,
3893 		      ioff - (BTRFS_LEAF_DATA_SIZE(root) - old_left_item_size),
3894 		      &token);
3895 	}
3896 	btrfs_set_header_nritems(left, old_left_nritems + push_items);
3897 
3898 	/* fixup right node */
3899 	if (push_items > right_nritems)
3900 		WARN(1, KERN_CRIT "push items %d nr %u\n", push_items,
3901 		       right_nritems);
3902 
3903 	if (push_items < right_nritems) {
3904 		push_space = btrfs_item_offset_nr(right, push_items - 1) -
3905 						  leaf_data_end(root, right);
3906 		memmove_extent_buffer(right, btrfs_leaf_data(right) +
3907 				      BTRFS_LEAF_DATA_SIZE(root) - push_space,
3908 				      btrfs_leaf_data(right) +
3909 				      leaf_data_end(root, right), push_space);
3910 
3911 		memmove_extent_buffer(right, btrfs_item_nr_offset(0),
3912 			      btrfs_item_nr_offset(push_items),
3913 			     (btrfs_header_nritems(right) - push_items) *
3914 			     sizeof(struct btrfs_item));
3915 	}
3916 	right_nritems -= push_items;
3917 	btrfs_set_header_nritems(right, right_nritems);
3918 	push_space = BTRFS_LEAF_DATA_SIZE(root);
3919 	for (i = 0; i < right_nritems; i++) {
3920 		item = btrfs_item_nr(i);
3921 
3922 		push_space = push_space - btrfs_token_item_size(right,
3923 								item, &token);
3924 		btrfs_set_token_item_offset(right, item, push_space, &token);
3925 	}
3926 
3927 	btrfs_mark_buffer_dirty(left);
3928 	if (right_nritems)
3929 		btrfs_mark_buffer_dirty(right);
3930 	else
3931 		clean_tree_block(trans, root, right);
3932 
3933 	btrfs_item_key(right, &disk_key, 0);
3934 	fixup_low_keys(root, path, &disk_key, 1);
3935 
3936 	/* then fixup the leaf pointer in the path */
3937 	if (path->slots[0] < push_items) {
3938 		path->slots[0] += old_left_nritems;
3939 		btrfs_tree_unlock(path->nodes[0]);
3940 		free_extent_buffer(path->nodes[0]);
3941 		path->nodes[0] = left;
3942 		path->slots[1] -= 1;
3943 	} else {
3944 		btrfs_tree_unlock(left);
3945 		free_extent_buffer(left);
3946 		path->slots[0] -= push_items;
3947 	}
3948 	BUG_ON(path->slots[0] < 0);
3949 	return ret;
3950 out:
3951 	btrfs_tree_unlock(left);
3952 	free_extent_buffer(left);
3953 	return ret;
3954 }
3955 
3956 /*
3957  * push some data in the path leaf to the left, trying to free up at
3958  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
3959  *
3960  * max_slot can put a limit on how far into the leaf we'll push items.  The
3961  * item at 'max_slot' won't be touched.  Use (u32)-1 to make us push all the
3962  * items
3963  */
3964 static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
3965 			  *root, struct btrfs_path *path, int min_data_size,
3966 			  int data_size, int empty, u32 max_slot)
3967 {
3968 	struct extent_buffer *right = path->nodes[0];
3969 	struct extent_buffer *left;
3970 	int slot;
3971 	int free_space;
3972 	u32 right_nritems;
3973 	int ret = 0;
3974 
3975 	slot = path->slots[1];
3976 	if (slot == 0)
3977 		return 1;
3978 	if (!path->nodes[1])
3979 		return 1;
3980 
3981 	right_nritems = btrfs_header_nritems(right);
3982 	if (right_nritems == 0)
3983 		return 1;
3984 
3985 	btrfs_assert_tree_locked(path->nodes[1]);
3986 
3987 	left = read_node_slot(root, path->nodes[1], slot - 1);
3988 	if (left == NULL)
3989 		return 1;
3990 
3991 	btrfs_tree_lock(left);
3992 	btrfs_set_lock_blocking(left);
3993 
3994 	free_space = btrfs_leaf_free_space(root, left);
3995 	if (free_space < data_size) {
3996 		ret = 1;
3997 		goto out;
3998 	}
3999 
4000 	/* cow and double check */
4001 	ret = btrfs_cow_block(trans, root, left,
4002 			      path->nodes[1], slot - 1, &left);
4003 	if (ret) {
4004 		/* we hit -ENOSPC, but it isn't fatal here */
4005 		if (ret == -ENOSPC)
4006 			ret = 1;
4007 		goto out;
4008 	}
4009 
4010 	free_space = btrfs_leaf_free_space(root, left);
4011 	if (free_space < data_size) {
4012 		ret = 1;
4013 		goto out;
4014 	}
4015 
4016 	return __push_leaf_left(trans, root, path, min_data_size,
4017 			       empty, left, free_space, right_nritems,
4018 			       max_slot);
4019 out:
4020 	btrfs_tree_unlock(left);
4021 	free_extent_buffer(left);
4022 	return ret;
4023 }
4024 
4025 /*
4026  * split the path's leaf in two, making sure there is at least data_size
4027  * available for the resulting leaf level of the path.
4028  */
4029 static noinline void copy_for_split(struct btrfs_trans_handle *trans,
4030 				    struct btrfs_root *root,
4031 				    struct btrfs_path *path,
4032 				    struct extent_buffer *l,
4033 				    struct extent_buffer *right,
4034 				    int slot, int mid, int nritems)
4035 {
4036 	int data_copy_size;
4037 	int rt_data_off;
4038 	int i;
4039 	struct btrfs_disk_key disk_key;
4040 	struct btrfs_map_token token;
4041 
4042 	btrfs_init_map_token(&token);
4043 
4044 	nritems = nritems - mid;
4045 	btrfs_set_header_nritems(right, nritems);
4046 	data_copy_size = btrfs_item_end_nr(l, mid) - leaf_data_end(root, l);
4047 
4048 	copy_extent_buffer(right, l, btrfs_item_nr_offset(0),
4049 			   btrfs_item_nr_offset(mid),
4050 			   nritems * sizeof(struct btrfs_item));
4051 
4052 	copy_extent_buffer(right, l,
4053 		     btrfs_leaf_data(right) + BTRFS_LEAF_DATA_SIZE(root) -
4054 		     data_copy_size, btrfs_leaf_data(l) +
4055 		     leaf_data_end(root, l), data_copy_size);
4056 
4057 	rt_data_off = BTRFS_LEAF_DATA_SIZE(root) -
4058 		      btrfs_item_end_nr(l, mid);
4059 
4060 	for (i = 0; i < nritems; i++) {
4061 		struct btrfs_item *item = btrfs_item_nr(i);
4062 		u32 ioff;
4063 
4064 		ioff = btrfs_token_item_offset(right, item, &token);
4065 		btrfs_set_token_item_offset(right, item,
4066 					    ioff + rt_data_off, &token);
4067 	}
4068 
4069 	btrfs_set_header_nritems(l, mid);
4070 	btrfs_item_key(right, &disk_key, 0);
4071 	insert_ptr(trans, root, path, &disk_key, right->start,
4072 		   path->slots[1] + 1, 1);
4073 
4074 	btrfs_mark_buffer_dirty(right);
4075 	btrfs_mark_buffer_dirty(l);
4076 	BUG_ON(path->slots[0] != slot);
4077 
4078 	if (mid <= slot) {
4079 		btrfs_tree_unlock(path->nodes[0]);
4080 		free_extent_buffer(path->nodes[0]);
4081 		path->nodes[0] = right;
4082 		path->slots[0] -= mid;
4083 		path->slots[1] += 1;
4084 	} else {
4085 		btrfs_tree_unlock(right);
4086 		free_extent_buffer(right);
4087 	}
4088 
4089 	BUG_ON(path->slots[0] < 0);
4090 }
4091 
4092 /*
4093  * double splits happen when we need to insert a big item in the middle
4094  * of a leaf.  A double split can leave us with 3 mostly empty leaves:
4095  * leaf: [ slots 0 - N] [ our target ] [ N + 1 - total in leaf ]
4096  *          A                 B                 C
4097  *
4098  * We avoid this by trying to push the items on either side of our target
4099  * into the adjacent leaves.  If all goes well we can avoid the double split
4100  * completely.
4101  */
4102 static noinline int push_for_double_split(struct btrfs_trans_handle *trans,
4103 					  struct btrfs_root *root,
4104 					  struct btrfs_path *path,
4105 					  int data_size)
4106 {
4107 	int ret;
4108 	int progress = 0;
4109 	int slot;
4110 	u32 nritems;
4111 	int space_needed = data_size;
4112 
4113 	slot = path->slots[0];
4114 	if (slot < btrfs_header_nritems(path->nodes[0]))
4115 		space_needed -= btrfs_leaf_free_space(root, path->nodes[0]);
4116 
4117 	/*
4118 	 * try to push all the items after our slot into the
4119 	 * right leaf
4120 	 */
4121 	ret = push_leaf_right(trans, root, path, 1, space_needed, 0, slot);
4122 	if (ret < 0)
4123 		return ret;
4124 
4125 	if (ret == 0)
4126 		progress++;
4127 
4128 	nritems = btrfs_header_nritems(path->nodes[0]);
4129 	/*
4130 	 * our goal is to get our slot at the start or end of a leaf.  If
4131 	 * we've done so we're done
4132 	 */
4133 	if (path->slots[0] == 0 || path->slots[0] == nritems)
4134 		return 0;
4135 
4136 	if (btrfs_leaf_free_space(root, path->nodes[0]) >= data_size)
4137 		return 0;
4138 
4139 	/* try to push all the items before our slot into the next leaf */
4140 	slot = path->slots[0];
4141 	ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot);
4142 	if (ret < 0)
4143 		return ret;
4144 
4145 	if (ret == 0)
4146 		progress++;
4147 
4148 	if (progress)
4149 		return 0;
4150 	return 1;
4151 }
4152 
4153 /*
4154  * split the path's leaf in two, making sure there is at least data_size
4155  * available for the resulting leaf level of the path.
4156  *
4157  * returns 0 if all went well and < 0 on failure.
4158  */
4159 static noinline int split_leaf(struct btrfs_trans_handle *trans,
4160 			       struct btrfs_root *root,
4161 			       struct btrfs_key *ins_key,
4162 			       struct btrfs_path *path, int data_size,
4163 			       int extend)
4164 {
4165 	struct btrfs_disk_key disk_key;
4166 	struct extent_buffer *l;
4167 	u32 nritems;
4168 	int mid;
4169 	int slot;
4170 	struct extent_buffer *right;
4171 	int ret = 0;
4172 	int wret;
4173 	int split;
4174 	int num_doubles = 0;
4175 	int tried_avoid_double = 0;
4176 
4177 	l = path->nodes[0];
4178 	slot = path->slots[0];
4179 	if (extend && data_size + btrfs_item_size_nr(l, slot) +
4180 	    sizeof(struct btrfs_item) > BTRFS_LEAF_DATA_SIZE(root))
4181 		return -EOVERFLOW;
4182 
4183 	/* first try to make some room by pushing left and right */
4184 	if (data_size && path->nodes[1]) {
4185 		int space_needed = data_size;
4186 
4187 		if (slot < btrfs_header_nritems(l))
4188 			space_needed -= btrfs_leaf_free_space(root, l);
4189 
4190 		wret = push_leaf_right(trans, root, path, space_needed,
4191 				       space_needed, 0, 0);
4192 		if (wret < 0)
4193 			return wret;
4194 		if (wret) {
4195 			wret = push_leaf_left(trans, root, path, space_needed,
4196 					      space_needed, 0, (u32)-1);
4197 			if (wret < 0)
4198 				return wret;
4199 		}
4200 		l = path->nodes[0];
4201 
4202 		/* did the pushes work? */
4203 		if (btrfs_leaf_free_space(root, l) >= data_size)
4204 			return 0;
4205 	}
4206 
4207 	if (!path->nodes[1]) {
4208 		ret = insert_new_root(trans, root, path, 1);
4209 		if (ret)
4210 			return ret;
4211 	}
4212 again:
4213 	split = 1;
4214 	l = path->nodes[0];
4215 	slot = path->slots[0];
4216 	nritems = btrfs_header_nritems(l);
4217 	mid = (nritems + 1) / 2;
4218 
4219 	if (mid <= slot) {
4220 		if (nritems == 1 ||
4221 		    leaf_space_used(l, mid, nritems - mid) + data_size >
4222 			BTRFS_LEAF_DATA_SIZE(root)) {
4223 			if (slot >= nritems) {
4224 				split = 0;
4225 			} else {
4226 				mid = slot;
4227 				if (mid != nritems &&
4228 				    leaf_space_used(l, mid, nritems - mid) +
4229 				    data_size > BTRFS_LEAF_DATA_SIZE(root)) {
4230 					if (data_size && !tried_avoid_double)
4231 						goto push_for_double;
4232 					split = 2;
4233 				}
4234 			}
4235 		}
4236 	} else {
4237 		if (leaf_space_used(l, 0, mid) + data_size >
4238 			BTRFS_LEAF_DATA_SIZE(root)) {
4239 			if (!extend && data_size && slot == 0) {
4240 				split = 0;
4241 			} else if ((extend || !data_size) && slot == 0) {
4242 				mid = 1;
4243 			} else {
4244 				mid = slot;
4245 				if (mid != nritems &&
4246 				    leaf_space_used(l, mid, nritems - mid) +
4247 				    data_size > BTRFS_LEAF_DATA_SIZE(root)) {
4248 					if (data_size && !tried_avoid_double)
4249 						goto push_for_double;
4250 					split = 2;
4251 				}
4252 			}
4253 		}
4254 	}
4255 
4256 	if (split == 0)
4257 		btrfs_cpu_key_to_disk(&disk_key, ins_key);
4258 	else
4259 		btrfs_item_key(l, &disk_key, mid);
4260 
4261 	right = btrfs_alloc_tree_block(trans, root, 0, root->root_key.objectid,
4262 			&disk_key, 0, l->start, 0);
4263 	if (IS_ERR(right))
4264 		return PTR_ERR(right);
4265 
4266 	root_add_used(root, root->nodesize);
4267 
4268 	memset_extent_buffer(right, 0, 0, sizeof(struct btrfs_header));
4269 	btrfs_set_header_bytenr(right, right->start);
4270 	btrfs_set_header_generation(right, trans->transid);
4271 	btrfs_set_header_backref_rev(right, BTRFS_MIXED_BACKREF_REV);
4272 	btrfs_set_header_owner(right, root->root_key.objectid);
4273 	btrfs_set_header_level(right, 0);
4274 	write_extent_buffer(right, root->fs_info->fsid,
4275 			    btrfs_header_fsid(), BTRFS_FSID_SIZE);
4276 
4277 	write_extent_buffer(right, root->fs_info->chunk_tree_uuid,
4278 			    btrfs_header_chunk_tree_uuid(right),
4279 			    BTRFS_UUID_SIZE);
4280 
4281 	if (split == 0) {
4282 		if (mid <= slot) {
4283 			btrfs_set_header_nritems(right, 0);
4284 			insert_ptr(trans, root, path, &disk_key, right->start,
4285 				   path->slots[1] + 1, 1);
4286 			btrfs_tree_unlock(path->nodes[0]);
4287 			free_extent_buffer(path->nodes[0]);
4288 			path->nodes[0] = right;
4289 			path->slots[0] = 0;
4290 			path->slots[1] += 1;
4291 		} else {
4292 			btrfs_set_header_nritems(right, 0);
4293 			insert_ptr(trans, root, path, &disk_key, right->start,
4294 					  path->slots[1], 1);
4295 			btrfs_tree_unlock(path->nodes[0]);
4296 			free_extent_buffer(path->nodes[0]);
4297 			path->nodes[0] = right;
4298 			path->slots[0] = 0;
4299 			if (path->slots[1] == 0)
4300 				fixup_low_keys(root, path, &disk_key, 1);
4301 		}
4302 		btrfs_mark_buffer_dirty(right);
4303 		return ret;
4304 	}
4305 
4306 	copy_for_split(trans, root, path, l, right, slot, mid, nritems);
4307 
4308 	if (split == 2) {
4309 		BUG_ON(num_doubles != 0);
4310 		num_doubles++;
4311 		goto again;
4312 	}
4313 
4314 	return 0;
4315 
4316 push_for_double:
4317 	push_for_double_split(trans, root, path, data_size);
4318 	tried_avoid_double = 1;
4319 	if (btrfs_leaf_free_space(root, path->nodes[0]) >= data_size)
4320 		return 0;
4321 	goto again;
4322 }
4323 
4324 static noinline int setup_leaf_for_split(struct btrfs_trans_handle *trans,
4325 					 struct btrfs_root *root,
4326 					 struct btrfs_path *path, int ins_len)
4327 {
4328 	struct btrfs_key key;
4329 	struct extent_buffer *leaf;
4330 	struct btrfs_file_extent_item *fi;
4331 	u64 extent_len = 0;
4332 	u32 item_size;
4333 	int ret;
4334 
4335 	leaf = path->nodes[0];
4336 	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4337 
4338 	BUG_ON(key.type != BTRFS_EXTENT_DATA_KEY &&
4339 	       key.type != BTRFS_EXTENT_CSUM_KEY);
4340 
4341 	if (btrfs_leaf_free_space(root, leaf) >= ins_len)
4342 		return 0;
4343 
4344 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4345 	if (key.type == BTRFS_EXTENT_DATA_KEY) {
4346 		fi = btrfs_item_ptr(leaf, path->slots[0],
4347 				    struct btrfs_file_extent_item);
4348 		extent_len = btrfs_file_extent_num_bytes(leaf, fi);
4349 	}
4350 	btrfs_release_path(path);
4351 
4352 	path->keep_locks = 1;
4353 	path->search_for_split = 1;
4354 	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
4355 	path->search_for_split = 0;
4356 	if (ret > 0)
4357 		ret = -EAGAIN;
4358 	if (ret < 0)
4359 		goto err;
4360 
4361 	ret = -EAGAIN;
4362 	leaf = path->nodes[0];
4363 	/* if our item isn't there, return now */
4364 	if (item_size != btrfs_item_size_nr(leaf, path->slots[0]))
4365 		goto err;
4366 
4367 	/* the leaf has  changed, it now has room.  return now */
4368 	if (btrfs_leaf_free_space(root, path->nodes[0]) >= ins_len)
4369 		goto err;
4370 
4371 	if (key.type == BTRFS_EXTENT_DATA_KEY) {
4372 		fi = btrfs_item_ptr(leaf, path->slots[0],
4373 				    struct btrfs_file_extent_item);
4374 		if (extent_len != btrfs_file_extent_num_bytes(leaf, fi))
4375 			goto err;
4376 	}
4377 
4378 	btrfs_set_path_blocking(path);
4379 	ret = split_leaf(trans, root, &key, path, ins_len, 1);
4380 	if (ret)
4381 		goto err;
4382 
4383 	path->keep_locks = 0;
4384 	btrfs_unlock_up_safe(path, 1);
4385 	return 0;
4386 err:
4387 	path->keep_locks = 0;
4388 	return ret;
4389 }
4390 
4391 static noinline int split_item(struct btrfs_trans_handle *trans,
4392 			       struct btrfs_root *root,
4393 			       struct btrfs_path *path,
4394 			       struct btrfs_key *new_key,
4395 			       unsigned long split_offset)
4396 {
4397 	struct extent_buffer *leaf;
4398 	struct btrfs_item *item;
4399 	struct btrfs_item *new_item;
4400 	int slot;
4401 	char *buf;
4402 	u32 nritems;
4403 	u32 item_size;
4404 	u32 orig_offset;
4405 	struct btrfs_disk_key disk_key;
4406 
4407 	leaf = path->nodes[0];
4408 	BUG_ON(btrfs_leaf_free_space(root, leaf) < sizeof(struct btrfs_item));
4409 
4410 	btrfs_set_path_blocking(path);
4411 
4412 	item = btrfs_item_nr(path->slots[0]);
4413 	orig_offset = btrfs_item_offset(leaf, item);
4414 	item_size = btrfs_item_size(leaf, item);
4415 
4416 	buf = kmalloc(item_size, GFP_NOFS);
4417 	if (!buf)
4418 		return -ENOMEM;
4419 
4420 	read_extent_buffer(leaf, buf, btrfs_item_ptr_offset(leaf,
4421 			    path->slots[0]), item_size);
4422 
4423 	slot = path->slots[0] + 1;
4424 	nritems = btrfs_header_nritems(leaf);
4425 	if (slot != nritems) {
4426 		/* shift the items */
4427 		memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + 1),
4428 				btrfs_item_nr_offset(slot),
4429 				(nritems - slot) * sizeof(struct btrfs_item));
4430 	}
4431 
4432 	btrfs_cpu_key_to_disk(&disk_key, new_key);
4433 	btrfs_set_item_key(leaf, &disk_key, slot);
4434 
4435 	new_item = btrfs_item_nr(slot);
4436 
4437 	btrfs_set_item_offset(leaf, new_item, orig_offset);
4438 	btrfs_set_item_size(leaf, new_item, item_size - split_offset);
4439 
4440 	btrfs_set_item_offset(leaf, item,
4441 			      orig_offset + item_size - split_offset);
4442 	btrfs_set_item_size(leaf, item, split_offset);
4443 
4444 	btrfs_set_header_nritems(leaf, nritems + 1);
4445 
4446 	/* write the data for the start of the original item */
4447 	write_extent_buffer(leaf, buf,
4448 			    btrfs_item_ptr_offset(leaf, path->slots[0]),
4449 			    split_offset);
4450 
4451 	/* write the data for the new item */
4452 	write_extent_buffer(leaf, buf + split_offset,
4453 			    btrfs_item_ptr_offset(leaf, slot),
4454 			    item_size - split_offset);
4455 	btrfs_mark_buffer_dirty(leaf);
4456 
4457 	BUG_ON(btrfs_leaf_free_space(root, leaf) < 0);
4458 	kfree(buf);
4459 	return 0;
4460 }
4461 
4462 /*
4463  * This function splits a single item into two items,
4464  * giving 'new_key' to the new item and splitting the
4465  * old one at split_offset (from the start of the item).
4466  *
4467  * The path may be released by this operation.  After
4468  * the split, the path is pointing to the old item.  The
4469  * new item is going to be in the same node as the old one.
4470  *
4471  * Note, the item being split must be smaller enough to live alone on
4472  * a tree block with room for one extra struct btrfs_item
4473  *
4474  * This allows us to split the item in place, keeping a lock on the
4475  * leaf the entire time.
4476  */
4477 int btrfs_split_item(struct btrfs_trans_handle *trans,
4478 		     struct btrfs_root *root,
4479 		     struct btrfs_path *path,
4480 		     struct btrfs_key *new_key,
4481 		     unsigned long split_offset)
4482 {
4483 	int ret;
4484 	ret = setup_leaf_for_split(trans, root, path,
4485 				   sizeof(struct btrfs_item));
4486 	if (ret)
4487 		return ret;
4488 
4489 	ret = split_item(trans, root, path, new_key, split_offset);
4490 	return ret;
4491 }
4492 
4493 /*
4494  * This function duplicate a item, giving 'new_key' to the new item.
4495  * It guarantees both items live in the same tree leaf and the new item
4496  * is contiguous with the original item.
4497  *
4498  * This allows us to split file extent in place, keeping a lock on the
4499  * leaf the entire time.
4500  */
4501 int btrfs_duplicate_item(struct btrfs_trans_handle *trans,
4502 			 struct btrfs_root *root,
4503 			 struct btrfs_path *path,
4504 			 struct btrfs_key *new_key)
4505 {
4506 	struct extent_buffer *leaf;
4507 	int ret;
4508 	u32 item_size;
4509 
4510 	leaf = path->nodes[0];
4511 	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
4512 	ret = setup_leaf_for_split(trans, root, path,
4513 				   item_size + sizeof(struct btrfs_item));
4514 	if (ret)
4515 		return ret;
4516 
4517 	path->slots[0]++;
4518 	setup_items_for_insert(root, path, new_key, &item_size,
4519 			       item_size, item_size +
4520 			       sizeof(struct btrfs_item), 1);
4521 	leaf = path->nodes[0];
4522 	memcpy_extent_buffer(leaf,
4523 			     btrfs_item_ptr_offset(leaf, path->slots[0]),
4524 			     btrfs_item_ptr_offset(leaf, path->slots[0] - 1),
4525 			     item_size);
4526 	return 0;
4527 }
4528 
4529 /*
4530  * make the item pointed to by the path smaller.  new_size indicates
4531  * how small to make it, and from_end tells us if we just chop bytes
4532  * off the end of the item or if we shift the item to chop bytes off
4533  * the front.
4534  */
4535 void btrfs_truncate_item(struct btrfs_root *root, struct btrfs_path *path,
4536 			 u32 new_size, int from_end)
4537 {
4538 	int slot;
4539 	struct extent_buffer *leaf;
4540 	struct btrfs_item *item;
4541 	u32 nritems;
4542 	unsigned int data_end;
4543 	unsigned int old_data_start;
4544 	unsigned int old_size;
4545 	unsigned int size_diff;
4546 	int i;
4547 	struct btrfs_map_token token;
4548 
4549 	btrfs_init_map_token(&token);
4550 
4551 	leaf = path->nodes[0];
4552 	slot = path->slots[0];
4553 
4554 	old_size = btrfs_item_size_nr(leaf, slot);
4555 	if (old_size == new_size)
4556 		return;
4557 
4558 	nritems = btrfs_header_nritems(leaf);
4559 	data_end = leaf_data_end(root, leaf);
4560 
4561 	old_data_start = btrfs_item_offset_nr(leaf, slot);
4562 
4563 	size_diff = old_size - new_size;
4564 
4565 	BUG_ON(slot < 0);
4566 	BUG_ON(slot >= nritems);
4567 
4568 	/*
4569 	 * item0..itemN ... dataN.offset..dataN.size .. data0.size
4570 	 */
4571 	/* first correct the data pointers */
4572 	for (i = slot; i < nritems; i++) {
4573 		u32 ioff;
4574 		item = btrfs_item_nr(i);
4575 
4576 		ioff = btrfs_token_item_offset(leaf, item, &token);
4577 		btrfs_set_token_item_offset(leaf, item,
4578 					    ioff + size_diff, &token);
4579 	}
4580 
4581 	/* shift the data */
4582 	if (from_end) {
4583 		memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
4584 			      data_end + size_diff, btrfs_leaf_data(leaf) +
4585 			      data_end, old_data_start + new_size - data_end);
4586 	} else {
4587 		struct btrfs_disk_key disk_key;
4588 		u64 offset;
4589 
4590 		btrfs_item_key(leaf, &disk_key, slot);
4591 
4592 		if (btrfs_disk_key_type(&disk_key) == BTRFS_EXTENT_DATA_KEY) {
4593 			unsigned long ptr;
4594 			struct btrfs_file_extent_item *fi;
4595 
4596 			fi = btrfs_item_ptr(leaf, slot,
4597 					    struct btrfs_file_extent_item);
4598 			fi = (struct btrfs_file_extent_item *)(
4599 			     (unsigned long)fi - size_diff);
4600 
4601 			if (btrfs_file_extent_type(leaf, fi) ==
4602 			    BTRFS_FILE_EXTENT_INLINE) {
4603 				ptr = btrfs_item_ptr_offset(leaf, slot);
4604 				memmove_extent_buffer(leaf, ptr,
4605 				      (unsigned long)fi,
4606 				      BTRFS_FILE_EXTENT_INLINE_DATA_START);
4607 			}
4608 		}
4609 
4610 		memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
4611 			      data_end + size_diff, btrfs_leaf_data(leaf) +
4612 			      data_end, old_data_start - data_end);
4613 
4614 		offset = btrfs_disk_key_offset(&disk_key);
4615 		btrfs_set_disk_key_offset(&disk_key, offset + size_diff);
4616 		btrfs_set_item_key(leaf, &disk_key, slot);
4617 		if (slot == 0)
4618 			fixup_low_keys(root, path, &disk_key, 1);
4619 	}
4620 
4621 	item = btrfs_item_nr(slot);
4622 	btrfs_set_item_size(leaf, item, new_size);
4623 	btrfs_mark_buffer_dirty(leaf);
4624 
4625 	if (btrfs_leaf_free_space(root, leaf) < 0) {
4626 		btrfs_print_leaf(root, leaf);
4627 		BUG();
4628 	}
4629 }
4630 
4631 /*
4632  * make the item pointed to by the path bigger, data_size is the added size.
4633  */
4634 void btrfs_extend_item(struct btrfs_root *root, struct btrfs_path *path,
4635 		       u32 data_size)
4636 {
4637 	int slot;
4638 	struct extent_buffer *leaf;
4639 	struct btrfs_item *item;
4640 	u32 nritems;
4641 	unsigned int data_end;
4642 	unsigned int old_data;
4643 	unsigned int old_size;
4644 	int i;
4645 	struct btrfs_map_token token;
4646 
4647 	btrfs_init_map_token(&token);
4648 
4649 	leaf = path->nodes[0];
4650 
4651 	nritems = btrfs_header_nritems(leaf);
4652 	data_end = leaf_data_end(root, leaf);
4653 
4654 	if (btrfs_leaf_free_space(root, leaf) < data_size) {
4655 		btrfs_print_leaf(root, leaf);
4656 		BUG();
4657 	}
4658 	slot = path->slots[0];
4659 	old_data = btrfs_item_end_nr(leaf, slot);
4660 
4661 	BUG_ON(slot < 0);
4662 	if (slot >= nritems) {
4663 		btrfs_print_leaf(root, leaf);
4664 		btrfs_crit(root->fs_info, "slot %d too large, nritems %d",
4665 		       slot, nritems);
4666 		BUG_ON(1);
4667 	}
4668 
4669 	/*
4670 	 * item0..itemN ... dataN.offset..dataN.size .. data0.size
4671 	 */
4672 	/* first correct the data pointers */
4673 	for (i = slot; i < nritems; i++) {
4674 		u32 ioff;
4675 		item = btrfs_item_nr(i);
4676 
4677 		ioff = btrfs_token_item_offset(leaf, item, &token);
4678 		btrfs_set_token_item_offset(leaf, item,
4679 					    ioff - data_size, &token);
4680 	}
4681 
4682 	/* shift the data */
4683 	memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
4684 		      data_end - data_size, btrfs_leaf_data(leaf) +
4685 		      data_end, old_data - data_end);
4686 
4687 	data_end = old_data;
4688 	old_size = btrfs_item_size_nr(leaf, slot);
4689 	item = btrfs_item_nr(slot);
4690 	btrfs_set_item_size(leaf, item, old_size + data_size);
4691 	btrfs_mark_buffer_dirty(leaf);
4692 
4693 	if (btrfs_leaf_free_space(root, leaf) < 0) {
4694 		btrfs_print_leaf(root, leaf);
4695 		BUG();
4696 	}
4697 }
4698 
4699 /*
4700  * this is a helper for btrfs_insert_empty_items, the main goal here is
4701  * to save stack depth by doing the bulk of the work in a function
4702  * that doesn't call btrfs_search_slot
4703  */
4704 void setup_items_for_insert(struct btrfs_root *root, struct btrfs_path *path,
4705 			    struct btrfs_key *cpu_key, u32 *data_size,
4706 			    u32 total_data, u32 total_size, int nr)
4707 {
4708 	struct btrfs_item *item;
4709 	int i;
4710 	u32 nritems;
4711 	unsigned int data_end;
4712 	struct btrfs_disk_key disk_key;
4713 	struct extent_buffer *leaf;
4714 	int slot;
4715 	struct btrfs_map_token token;
4716 
4717 	if (path->slots[0] == 0) {
4718 		btrfs_cpu_key_to_disk(&disk_key, cpu_key);
4719 		fixup_low_keys(root, path, &disk_key, 1);
4720 	}
4721 	btrfs_unlock_up_safe(path, 1);
4722 
4723 	btrfs_init_map_token(&token);
4724 
4725 	leaf = path->nodes[0];
4726 	slot = path->slots[0];
4727 
4728 	nritems = btrfs_header_nritems(leaf);
4729 	data_end = leaf_data_end(root, leaf);
4730 
4731 	if (btrfs_leaf_free_space(root, leaf) < total_size) {
4732 		btrfs_print_leaf(root, leaf);
4733 		btrfs_crit(root->fs_info, "not enough freespace need %u have %d",
4734 		       total_size, btrfs_leaf_free_space(root, leaf));
4735 		BUG();
4736 	}
4737 
4738 	if (slot != nritems) {
4739 		unsigned int old_data = btrfs_item_end_nr(leaf, slot);
4740 
4741 		if (old_data < data_end) {
4742 			btrfs_print_leaf(root, leaf);
4743 			btrfs_crit(root->fs_info, "slot %d old_data %d data_end %d",
4744 			       slot, old_data, data_end);
4745 			BUG_ON(1);
4746 		}
4747 		/*
4748 		 * item0..itemN ... dataN.offset..dataN.size .. data0.size
4749 		 */
4750 		/* first correct the data pointers */
4751 		for (i = slot; i < nritems; i++) {
4752 			u32 ioff;
4753 
4754 			item = btrfs_item_nr( i);
4755 			ioff = btrfs_token_item_offset(leaf, item, &token);
4756 			btrfs_set_token_item_offset(leaf, item,
4757 						    ioff - total_data, &token);
4758 		}
4759 		/* shift the items */
4760 		memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot + nr),
4761 			      btrfs_item_nr_offset(slot),
4762 			      (nritems - slot) * sizeof(struct btrfs_item));
4763 
4764 		/* shift the data */
4765 		memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
4766 			      data_end - total_data, btrfs_leaf_data(leaf) +
4767 			      data_end, old_data - data_end);
4768 		data_end = old_data;
4769 	}
4770 
4771 	/* setup the item for the new data */
4772 	for (i = 0; i < nr; i++) {
4773 		btrfs_cpu_key_to_disk(&disk_key, cpu_key + i);
4774 		btrfs_set_item_key(leaf, &disk_key, slot + i);
4775 		item = btrfs_item_nr(slot + i);
4776 		btrfs_set_token_item_offset(leaf, item,
4777 					    data_end - data_size[i], &token);
4778 		data_end -= data_size[i];
4779 		btrfs_set_token_item_size(leaf, item, data_size[i], &token);
4780 	}
4781 
4782 	btrfs_set_header_nritems(leaf, nritems + nr);
4783 	btrfs_mark_buffer_dirty(leaf);
4784 
4785 	if (btrfs_leaf_free_space(root, leaf) < 0) {
4786 		btrfs_print_leaf(root, leaf);
4787 		BUG();
4788 	}
4789 }
4790 
4791 /*
4792  * Given a key and some data, insert items into the tree.
4793  * This does all the path init required, making room in the tree if needed.
4794  */
4795 int btrfs_insert_empty_items(struct btrfs_trans_handle *trans,
4796 			    struct btrfs_root *root,
4797 			    struct btrfs_path *path,
4798 			    struct btrfs_key *cpu_key, u32 *data_size,
4799 			    int nr)
4800 {
4801 	int ret = 0;
4802 	int slot;
4803 	int i;
4804 	u32 total_size = 0;
4805 	u32 total_data = 0;
4806 
4807 	for (i = 0; i < nr; i++)
4808 		total_data += data_size[i];
4809 
4810 	total_size = total_data + (nr * sizeof(struct btrfs_item));
4811 	ret = btrfs_search_slot(trans, root, cpu_key, path, total_size, 1);
4812 	if (ret == 0)
4813 		return -EEXIST;
4814 	if (ret < 0)
4815 		return ret;
4816 
4817 	slot = path->slots[0];
4818 	BUG_ON(slot < 0);
4819 
4820 	setup_items_for_insert(root, path, cpu_key, data_size,
4821 			       total_data, total_size, nr);
4822 	return 0;
4823 }
4824 
4825 /*
4826  * Given a key and some data, insert an item into the tree.
4827  * This does all the path init required, making room in the tree if needed.
4828  */
4829 int btrfs_insert_item(struct btrfs_trans_handle *trans, struct btrfs_root
4830 		      *root, struct btrfs_key *cpu_key, void *data, u32
4831 		      data_size)
4832 {
4833 	int ret = 0;
4834 	struct btrfs_path *path;
4835 	struct extent_buffer *leaf;
4836 	unsigned long ptr;
4837 
4838 	path = btrfs_alloc_path();
4839 	if (!path)
4840 		return -ENOMEM;
4841 	ret = btrfs_insert_empty_item(trans, root, path, cpu_key, data_size);
4842 	if (!ret) {
4843 		leaf = path->nodes[0];
4844 		ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
4845 		write_extent_buffer(leaf, data, ptr, data_size);
4846 		btrfs_mark_buffer_dirty(leaf);
4847 	}
4848 	btrfs_free_path(path);
4849 	return ret;
4850 }
4851 
4852 /*
4853  * delete the pointer from a given node.
4854  *
4855  * the tree should have been previously balanced so the deletion does not
4856  * empty a node.
4857  */
4858 static void del_ptr(struct btrfs_root *root, struct btrfs_path *path,
4859 		    int level, int slot)
4860 {
4861 	struct extent_buffer *parent = path->nodes[level];
4862 	u32 nritems;
4863 	int ret;
4864 
4865 	nritems = btrfs_header_nritems(parent);
4866 	if (slot != nritems - 1) {
4867 		if (level)
4868 			tree_mod_log_eb_move(root->fs_info, parent, slot,
4869 					     slot + 1, nritems - slot - 1);
4870 		memmove_extent_buffer(parent,
4871 			      btrfs_node_key_ptr_offset(slot),
4872 			      btrfs_node_key_ptr_offset(slot + 1),
4873 			      sizeof(struct btrfs_key_ptr) *
4874 			      (nritems - slot - 1));
4875 	} else if (level) {
4876 		ret = tree_mod_log_insert_key(root->fs_info, parent, slot,
4877 					      MOD_LOG_KEY_REMOVE, GFP_NOFS);
4878 		BUG_ON(ret < 0);
4879 	}
4880 
4881 	nritems--;
4882 	btrfs_set_header_nritems(parent, nritems);
4883 	if (nritems == 0 && parent == root->node) {
4884 		BUG_ON(btrfs_header_level(root->node) != 1);
4885 		/* just turn the root into a leaf and break */
4886 		btrfs_set_header_level(root->node, 0);
4887 	} else if (slot == 0) {
4888 		struct btrfs_disk_key disk_key;
4889 
4890 		btrfs_node_key(parent, &disk_key, 0);
4891 		fixup_low_keys(root, path, &disk_key, level + 1);
4892 	}
4893 	btrfs_mark_buffer_dirty(parent);
4894 }
4895 
4896 /*
4897  * a helper function to delete the leaf pointed to by path->slots[1] and
4898  * path->nodes[1].
4899  *
4900  * This deletes the pointer in path->nodes[1] and frees the leaf
4901  * block extent.  zero is returned if it all worked out, < 0 otherwise.
4902  *
4903  * The path must have already been setup for deleting the leaf, including
4904  * all the proper balancing.  path->nodes[1] must be locked.
4905  */
4906 static noinline void btrfs_del_leaf(struct btrfs_trans_handle *trans,
4907 				    struct btrfs_root *root,
4908 				    struct btrfs_path *path,
4909 				    struct extent_buffer *leaf)
4910 {
4911 	WARN_ON(btrfs_header_generation(leaf) != trans->transid);
4912 	del_ptr(root, path, 1, path->slots[1]);
4913 
4914 	/*
4915 	 * btrfs_free_extent is expensive, we want to make sure we
4916 	 * aren't holding any locks when we call it
4917 	 */
4918 	btrfs_unlock_up_safe(path, 0);
4919 
4920 	root_sub_used(root, leaf->len);
4921 
4922 	extent_buffer_get(leaf);
4923 	btrfs_free_tree_block(trans, root, leaf, 0, 1);
4924 	free_extent_buffer_stale(leaf);
4925 }
4926 /*
4927  * delete the item at the leaf level in path.  If that empties
4928  * the leaf, remove it from the tree
4929  */
4930 int btrfs_del_items(struct btrfs_trans_handle *trans, struct btrfs_root *root,
4931 		    struct btrfs_path *path, int slot, int nr)
4932 {
4933 	struct extent_buffer *leaf;
4934 	struct btrfs_item *item;
4935 	int last_off;
4936 	int dsize = 0;
4937 	int ret = 0;
4938 	int wret;
4939 	int i;
4940 	u32 nritems;
4941 	struct btrfs_map_token token;
4942 
4943 	btrfs_init_map_token(&token);
4944 
4945 	leaf = path->nodes[0];
4946 	last_off = btrfs_item_offset_nr(leaf, slot + nr - 1);
4947 
4948 	for (i = 0; i < nr; i++)
4949 		dsize += btrfs_item_size_nr(leaf, slot + i);
4950 
4951 	nritems = btrfs_header_nritems(leaf);
4952 
4953 	if (slot + nr != nritems) {
4954 		int data_end = leaf_data_end(root, leaf);
4955 
4956 		memmove_extent_buffer(leaf, btrfs_leaf_data(leaf) +
4957 			      data_end + dsize,
4958 			      btrfs_leaf_data(leaf) + data_end,
4959 			      last_off - data_end);
4960 
4961 		for (i = slot + nr; i < nritems; i++) {
4962 			u32 ioff;
4963 
4964 			item = btrfs_item_nr(i);
4965 			ioff = btrfs_token_item_offset(leaf, item, &token);
4966 			btrfs_set_token_item_offset(leaf, item,
4967 						    ioff + dsize, &token);
4968 		}
4969 
4970 		memmove_extent_buffer(leaf, btrfs_item_nr_offset(slot),
4971 			      btrfs_item_nr_offset(slot + nr),
4972 			      sizeof(struct btrfs_item) *
4973 			      (nritems - slot - nr));
4974 	}
4975 	btrfs_set_header_nritems(leaf, nritems - nr);
4976 	nritems -= nr;
4977 
4978 	/* delete the leaf if we've emptied it */
4979 	if (nritems == 0) {
4980 		if (leaf == root->node) {
4981 			btrfs_set_header_level(leaf, 0);
4982 		} else {
4983 			btrfs_set_path_blocking(path);
4984 			clean_tree_block(trans, root, leaf);
4985 			btrfs_del_leaf(trans, root, path, leaf);
4986 		}
4987 	} else {
4988 		int used = leaf_space_used(leaf, 0, nritems);
4989 		if (slot == 0) {
4990 			struct btrfs_disk_key disk_key;
4991 
4992 			btrfs_item_key(leaf, &disk_key, 0);
4993 			fixup_low_keys(root, path, &disk_key, 1);
4994 		}
4995 
4996 		/* delete the leaf if it is mostly empty */
4997 		if (used < BTRFS_LEAF_DATA_SIZE(root) / 3) {
4998 			/* push_leaf_left fixes the path.
4999 			 * make sure the path still points to our leaf
5000 			 * for possible call to del_ptr below
5001 			 */
5002 			slot = path->slots[1];
5003 			extent_buffer_get(leaf);
5004 
5005 			btrfs_set_path_blocking(path);
5006 			wret = push_leaf_left(trans, root, path, 1, 1,
5007 					      1, (u32)-1);
5008 			if (wret < 0 && wret != -ENOSPC)
5009 				ret = wret;
5010 
5011 			if (path->nodes[0] == leaf &&
5012 			    btrfs_header_nritems(leaf)) {
5013 				wret = push_leaf_right(trans, root, path, 1,
5014 						       1, 1, 0);
5015 				if (wret < 0 && wret != -ENOSPC)
5016 					ret = wret;
5017 			}
5018 
5019 			if (btrfs_header_nritems(leaf) == 0) {
5020 				path->slots[1] = slot;
5021 				btrfs_del_leaf(trans, root, path, leaf);
5022 				free_extent_buffer(leaf);
5023 				ret = 0;
5024 			} else {
5025 				/* if we're still in the path, make sure
5026 				 * we're dirty.  Otherwise, one of the
5027 				 * push_leaf functions must have already
5028 				 * dirtied this buffer
5029 				 */
5030 				if (path->nodes[0] == leaf)
5031 					btrfs_mark_buffer_dirty(leaf);
5032 				free_extent_buffer(leaf);
5033 			}
5034 		} else {
5035 			btrfs_mark_buffer_dirty(leaf);
5036 		}
5037 	}
5038 	return ret;
5039 }
5040 
5041 /*
5042  * search the tree again to find a leaf with lesser keys
5043  * returns 0 if it found something or 1 if there are no lesser leaves.
5044  * returns < 0 on io errors.
5045  *
5046  * This may release the path, and so you may lose any locks held at the
5047  * time you call it.
5048  */
5049 int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
5050 {
5051 	struct btrfs_key key;
5052 	struct btrfs_disk_key found_key;
5053 	int ret;
5054 
5055 	btrfs_item_key_to_cpu(path->nodes[0], &key, 0);
5056 
5057 	if (key.offset > 0) {
5058 		key.offset--;
5059 	} else if (key.type > 0) {
5060 		key.type--;
5061 		key.offset = (u64)-1;
5062 	} else if (key.objectid > 0) {
5063 		key.objectid--;
5064 		key.type = (u8)-1;
5065 		key.offset = (u64)-1;
5066 	} else {
5067 		return 1;
5068 	}
5069 
5070 	btrfs_release_path(path);
5071 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5072 	if (ret < 0)
5073 		return ret;
5074 	btrfs_item_key(path->nodes[0], &found_key, 0);
5075 	ret = comp_keys(&found_key, &key);
5076 	/*
5077 	 * We might have had an item with the previous key in the tree right
5078 	 * before we released our path. And after we released our path, that
5079 	 * item might have been pushed to the first slot (0) of the leaf we
5080 	 * were holding due to a tree balance. Alternatively, an item with the
5081 	 * previous key can exist as the only element of a leaf (big fat item).
5082 	 * Therefore account for these 2 cases, so that our callers (like
5083 	 * btrfs_previous_item) don't miss an existing item with a key matching
5084 	 * the previous key we computed above.
5085 	 */
5086 	if (ret <= 0)
5087 		return 0;
5088 	return 1;
5089 }
5090 
5091 /*
5092  * A helper function to walk down the tree starting at min_key, and looking
5093  * for nodes or leaves that are have a minimum transaction id.
5094  * This is used by the btree defrag code, and tree logging
5095  *
5096  * This does not cow, but it does stuff the starting key it finds back
5097  * into min_key, so you can call btrfs_search_slot with cow=1 on the
5098  * key and get a writable path.
5099  *
5100  * This does lock as it descends, and path->keep_locks should be set
5101  * to 1 by the caller.
5102  *
5103  * This honors path->lowest_level to prevent descent past a given level
5104  * of the tree.
5105  *
5106  * min_trans indicates the oldest transaction that you are interested
5107  * in walking through.  Any nodes or leaves older than min_trans are
5108  * skipped over (without reading them).
5109  *
5110  * returns zero if something useful was found, < 0 on error and 1 if there
5111  * was nothing in the tree that matched the search criteria.
5112  */
5113 int btrfs_search_forward(struct btrfs_root *root, struct btrfs_key *min_key,
5114 			 struct btrfs_path *path,
5115 			 u64 min_trans)
5116 {
5117 	struct extent_buffer *cur;
5118 	struct btrfs_key found_key;
5119 	int slot;
5120 	int sret;
5121 	u32 nritems;
5122 	int level;
5123 	int ret = 1;
5124 	int keep_locks = path->keep_locks;
5125 
5126 	path->keep_locks = 1;
5127 again:
5128 	cur = btrfs_read_lock_root_node(root);
5129 	level = btrfs_header_level(cur);
5130 	WARN_ON(path->nodes[level]);
5131 	path->nodes[level] = cur;
5132 	path->locks[level] = BTRFS_READ_LOCK;
5133 
5134 	if (btrfs_header_generation(cur) < min_trans) {
5135 		ret = 1;
5136 		goto out;
5137 	}
5138 	while (1) {
5139 		nritems = btrfs_header_nritems(cur);
5140 		level = btrfs_header_level(cur);
5141 		sret = bin_search(cur, min_key, level, &slot);
5142 
5143 		/* at the lowest level, we're done, setup the path and exit */
5144 		if (level == path->lowest_level) {
5145 			if (slot >= nritems)
5146 				goto find_next_key;
5147 			ret = 0;
5148 			path->slots[level] = slot;
5149 			btrfs_item_key_to_cpu(cur, &found_key, slot);
5150 			goto out;
5151 		}
5152 		if (sret && slot > 0)
5153 			slot--;
5154 		/*
5155 		 * check this node pointer against the min_trans parameters.
5156 		 * If it is too old, old, skip to the next one.
5157 		 */
5158 		while (slot < nritems) {
5159 			u64 gen;
5160 
5161 			gen = btrfs_node_ptr_generation(cur, slot);
5162 			if (gen < min_trans) {
5163 				slot++;
5164 				continue;
5165 			}
5166 			break;
5167 		}
5168 find_next_key:
5169 		/*
5170 		 * we didn't find a candidate key in this node, walk forward
5171 		 * and find another one
5172 		 */
5173 		if (slot >= nritems) {
5174 			path->slots[level] = slot;
5175 			btrfs_set_path_blocking(path);
5176 			sret = btrfs_find_next_key(root, path, min_key, level,
5177 						  min_trans);
5178 			if (sret == 0) {
5179 				btrfs_release_path(path);
5180 				goto again;
5181 			} else {
5182 				goto out;
5183 			}
5184 		}
5185 		/* save our key for returning back */
5186 		btrfs_node_key_to_cpu(cur, &found_key, slot);
5187 		path->slots[level] = slot;
5188 		if (level == path->lowest_level) {
5189 			ret = 0;
5190 			goto out;
5191 		}
5192 		btrfs_set_path_blocking(path);
5193 		cur = read_node_slot(root, cur, slot);
5194 		BUG_ON(!cur); /* -ENOMEM */
5195 
5196 		btrfs_tree_read_lock(cur);
5197 
5198 		path->locks[level - 1] = BTRFS_READ_LOCK;
5199 		path->nodes[level - 1] = cur;
5200 		unlock_up(path, level, 1, 0, NULL);
5201 		btrfs_clear_path_blocking(path, NULL, 0);
5202 	}
5203 out:
5204 	path->keep_locks = keep_locks;
5205 	if (ret == 0) {
5206 		btrfs_unlock_up_safe(path, path->lowest_level + 1);
5207 		btrfs_set_path_blocking(path);
5208 		memcpy(min_key, &found_key, sizeof(found_key));
5209 	}
5210 	return ret;
5211 }
5212 
5213 static void tree_move_down(struct btrfs_root *root,
5214 			   struct btrfs_path *path,
5215 			   int *level, int root_level)
5216 {
5217 	BUG_ON(*level == 0);
5218 	path->nodes[*level - 1] = read_node_slot(root, path->nodes[*level],
5219 					path->slots[*level]);
5220 	path->slots[*level - 1] = 0;
5221 	(*level)--;
5222 }
5223 
5224 static int tree_move_next_or_upnext(struct btrfs_root *root,
5225 				    struct btrfs_path *path,
5226 				    int *level, int root_level)
5227 {
5228 	int ret = 0;
5229 	int nritems;
5230 	nritems = btrfs_header_nritems(path->nodes[*level]);
5231 
5232 	path->slots[*level]++;
5233 
5234 	while (path->slots[*level] >= nritems) {
5235 		if (*level == root_level)
5236 			return -1;
5237 
5238 		/* move upnext */
5239 		path->slots[*level] = 0;
5240 		free_extent_buffer(path->nodes[*level]);
5241 		path->nodes[*level] = NULL;
5242 		(*level)++;
5243 		path->slots[*level]++;
5244 
5245 		nritems = btrfs_header_nritems(path->nodes[*level]);
5246 		ret = 1;
5247 	}
5248 	return ret;
5249 }
5250 
5251 /*
5252  * Returns 1 if it had to move up and next. 0 is returned if it moved only next
5253  * or down.
5254  */
5255 static int tree_advance(struct btrfs_root *root,
5256 			struct btrfs_path *path,
5257 			int *level, int root_level,
5258 			int allow_down,
5259 			struct btrfs_key *key)
5260 {
5261 	int ret;
5262 
5263 	if (*level == 0 || !allow_down) {
5264 		ret = tree_move_next_or_upnext(root, path, level, root_level);
5265 	} else {
5266 		tree_move_down(root, path, level, root_level);
5267 		ret = 0;
5268 	}
5269 	if (ret >= 0) {
5270 		if (*level == 0)
5271 			btrfs_item_key_to_cpu(path->nodes[*level], key,
5272 					path->slots[*level]);
5273 		else
5274 			btrfs_node_key_to_cpu(path->nodes[*level], key,
5275 					path->slots[*level]);
5276 	}
5277 	return ret;
5278 }
5279 
5280 static int tree_compare_item(struct btrfs_root *left_root,
5281 			     struct btrfs_path *left_path,
5282 			     struct btrfs_path *right_path,
5283 			     char *tmp_buf)
5284 {
5285 	int cmp;
5286 	int len1, len2;
5287 	unsigned long off1, off2;
5288 
5289 	len1 = btrfs_item_size_nr(left_path->nodes[0], left_path->slots[0]);
5290 	len2 = btrfs_item_size_nr(right_path->nodes[0], right_path->slots[0]);
5291 	if (len1 != len2)
5292 		return 1;
5293 
5294 	off1 = btrfs_item_ptr_offset(left_path->nodes[0], left_path->slots[0]);
5295 	off2 = btrfs_item_ptr_offset(right_path->nodes[0],
5296 				right_path->slots[0]);
5297 
5298 	read_extent_buffer(left_path->nodes[0], tmp_buf, off1, len1);
5299 
5300 	cmp = memcmp_extent_buffer(right_path->nodes[0], tmp_buf, off2, len1);
5301 	if (cmp)
5302 		return 1;
5303 	return 0;
5304 }
5305 
5306 #define ADVANCE 1
5307 #define ADVANCE_ONLY_NEXT -1
5308 
5309 /*
5310  * This function compares two trees and calls the provided callback for
5311  * every changed/new/deleted item it finds.
5312  * If shared tree blocks are encountered, whole subtrees are skipped, making
5313  * the compare pretty fast on snapshotted subvolumes.
5314  *
5315  * This currently works on commit roots only. As commit roots are read only,
5316  * we don't do any locking. The commit roots are protected with transactions.
5317  * Transactions are ended and rejoined when a commit is tried in between.
5318  *
5319  * This function checks for modifications done to the trees while comparing.
5320  * If it detects a change, it aborts immediately.
5321  */
5322 int btrfs_compare_trees(struct btrfs_root *left_root,
5323 			struct btrfs_root *right_root,
5324 			btrfs_changed_cb_t changed_cb, void *ctx)
5325 {
5326 	int ret;
5327 	int cmp;
5328 	struct btrfs_path *left_path = NULL;
5329 	struct btrfs_path *right_path = NULL;
5330 	struct btrfs_key left_key;
5331 	struct btrfs_key right_key;
5332 	char *tmp_buf = NULL;
5333 	int left_root_level;
5334 	int right_root_level;
5335 	int left_level;
5336 	int right_level;
5337 	int left_end_reached;
5338 	int right_end_reached;
5339 	int advance_left;
5340 	int advance_right;
5341 	u64 left_blockptr;
5342 	u64 right_blockptr;
5343 	u64 left_gen;
5344 	u64 right_gen;
5345 
5346 	left_path = btrfs_alloc_path();
5347 	if (!left_path) {
5348 		ret = -ENOMEM;
5349 		goto out;
5350 	}
5351 	right_path = btrfs_alloc_path();
5352 	if (!right_path) {
5353 		ret = -ENOMEM;
5354 		goto out;
5355 	}
5356 
5357 	tmp_buf = kmalloc(left_root->nodesize, GFP_NOFS);
5358 	if (!tmp_buf) {
5359 		ret = -ENOMEM;
5360 		goto out;
5361 	}
5362 
5363 	left_path->search_commit_root = 1;
5364 	left_path->skip_locking = 1;
5365 	right_path->search_commit_root = 1;
5366 	right_path->skip_locking = 1;
5367 
5368 	/*
5369 	 * Strategy: Go to the first items of both trees. Then do
5370 	 *
5371 	 * If both trees are at level 0
5372 	 *   Compare keys of current items
5373 	 *     If left < right treat left item as new, advance left tree
5374 	 *       and repeat
5375 	 *     If left > right treat right item as deleted, advance right tree
5376 	 *       and repeat
5377 	 *     If left == right do deep compare of items, treat as changed if
5378 	 *       needed, advance both trees and repeat
5379 	 * If both trees are at the same level but not at level 0
5380 	 *   Compare keys of current nodes/leafs
5381 	 *     If left < right advance left tree and repeat
5382 	 *     If left > right advance right tree and repeat
5383 	 *     If left == right compare blockptrs of the next nodes/leafs
5384 	 *       If they match advance both trees but stay at the same level
5385 	 *         and repeat
5386 	 *       If they don't match advance both trees while allowing to go
5387 	 *         deeper and repeat
5388 	 * If tree levels are different
5389 	 *   Advance the tree that needs it and repeat
5390 	 *
5391 	 * Advancing a tree means:
5392 	 *   If we are at level 0, try to go to the next slot. If that's not
5393 	 *   possible, go one level up and repeat. Stop when we found a level
5394 	 *   where we could go to the next slot. We may at this point be on a
5395 	 *   node or a leaf.
5396 	 *
5397 	 *   If we are not at level 0 and not on shared tree blocks, go one
5398 	 *   level deeper.
5399 	 *
5400 	 *   If we are not at level 0 and on shared tree blocks, go one slot to
5401 	 *   the right if possible or go up and right.
5402 	 */
5403 
5404 	down_read(&left_root->fs_info->commit_root_sem);
5405 	left_level = btrfs_header_level(left_root->commit_root);
5406 	left_root_level = left_level;
5407 	left_path->nodes[left_level] = left_root->commit_root;
5408 	extent_buffer_get(left_path->nodes[left_level]);
5409 
5410 	right_level = btrfs_header_level(right_root->commit_root);
5411 	right_root_level = right_level;
5412 	right_path->nodes[right_level] = right_root->commit_root;
5413 	extent_buffer_get(right_path->nodes[right_level]);
5414 	up_read(&left_root->fs_info->commit_root_sem);
5415 
5416 	if (left_level == 0)
5417 		btrfs_item_key_to_cpu(left_path->nodes[left_level],
5418 				&left_key, left_path->slots[left_level]);
5419 	else
5420 		btrfs_node_key_to_cpu(left_path->nodes[left_level],
5421 				&left_key, left_path->slots[left_level]);
5422 	if (right_level == 0)
5423 		btrfs_item_key_to_cpu(right_path->nodes[right_level],
5424 				&right_key, right_path->slots[right_level]);
5425 	else
5426 		btrfs_node_key_to_cpu(right_path->nodes[right_level],
5427 				&right_key, right_path->slots[right_level]);
5428 
5429 	left_end_reached = right_end_reached = 0;
5430 	advance_left = advance_right = 0;
5431 
5432 	while (1) {
5433 		if (advance_left && !left_end_reached) {
5434 			ret = tree_advance(left_root, left_path, &left_level,
5435 					left_root_level,
5436 					advance_left != ADVANCE_ONLY_NEXT,
5437 					&left_key);
5438 			if (ret < 0)
5439 				left_end_reached = ADVANCE;
5440 			advance_left = 0;
5441 		}
5442 		if (advance_right && !right_end_reached) {
5443 			ret = tree_advance(right_root, right_path, &right_level,
5444 					right_root_level,
5445 					advance_right != ADVANCE_ONLY_NEXT,
5446 					&right_key);
5447 			if (ret < 0)
5448 				right_end_reached = ADVANCE;
5449 			advance_right = 0;
5450 		}
5451 
5452 		if (left_end_reached && right_end_reached) {
5453 			ret = 0;
5454 			goto out;
5455 		} else if (left_end_reached) {
5456 			if (right_level == 0) {
5457 				ret = changed_cb(left_root, right_root,
5458 						left_path, right_path,
5459 						&right_key,
5460 						BTRFS_COMPARE_TREE_DELETED,
5461 						ctx);
5462 				if (ret < 0)
5463 					goto out;
5464 			}
5465 			advance_right = ADVANCE;
5466 			continue;
5467 		} else if (right_end_reached) {
5468 			if (left_level == 0) {
5469 				ret = changed_cb(left_root, right_root,
5470 						left_path, right_path,
5471 						&left_key,
5472 						BTRFS_COMPARE_TREE_NEW,
5473 						ctx);
5474 				if (ret < 0)
5475 					goto out;
5476 			}
5477 			advance_left = ADVANCE;
5478 			continue;
5479 		}
5480 
5481 		if (left_level == 0 && right_level == 0) {
5482 			cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5483 			if (cmp < 0) {
5484 				ret = changed_cb(left_root, right_root,
5485 						left_path, right_path,
5486 						&left_key,
5487 						BTRFS_COMPARE_TREE_NEW,
5488 						ctx);
5489 				if (ret < 0)
5490 					goto out;
5491 				advance_left = ADVANCE;
5492 			} else if (cmp > 0) {
5493 				ret = changed_cb(left_root, right_root,
5494 						left_path, right_path,
5495 						&right_key,
5496 						BTRFS_COMPARE_TREE_DELETED,
5497 						ctx);
5498 				if (ret < 0)
5499 					goto out;
5500 				advance_right = ADVANCE;
5501 			} else {
5502 				enum btrfs_compare_tree_result result;
5503 
5504 				WARN_ON(!extent_buffer_uptodate(left_path->nodes[0]));
5505 				ret = tree_compare_item(left_root, left_path,
5506 						right_path, tmp_buf);
5507 				if (ret)
5508 					result = BTRFS_COMPARE_TREE_CHANGED;
5509 				else
5510 					result = BTRFS_COMPARE_TREE_SAME;
5511 				ret = changed_cb(left_root, right_root,
5512 						 left_path, right_path,
5513 						 &left_key, result, ctx);
5514 				if (ret < 0)
5515 					goto out;
5516 				advance_left = ADVANCE;
5517 				advance_right = ADVANCE;
5518 			}
5519 		} else if (left_level == right_level) {
5520 			cmp = btrfs_comp_cpu_keys(&left_key, &right_key);
5521 			if (cmp < 0) {
5522 				advance_left = ADVANCE;
5523 			} else if (cmp > 0) {
5524 				advance_right = ADVANCE;
5525 			} else {
5526 				left_blockptr = btrfs_node_blockptr(
5527 						left_path->nodes[left_level],
5528 						left_path->slots[left_level]);
5529 				right_blockptr = btrfs_node_blockptr(
5530 						right_path->nodes[right_level],
5531 						right_path->slots[right_level]);
5532 				left_gen = btrfs_node_ptr_generation(
5533 						left_path->nodes[left_level],
5534 						left_path->slots[left_level]);
5535 				right_gen = btrfs_node_ptr_generation(
5536 						right_path->nodes[right_level],
5537 						right_path->slots[right_level]);
5538 				if (left_blockptr == right_blockptr &&
5539 				    left_gen == right_gen) {
5540 					/*
5541 					 * As we're on a shared block, don't
5542 					 * allow to go deeper.
5543 					 */
5544 					advance_left = ADVANCE_ONLY_NEXT;
5545 					advance_right = ADVANCE_ONLY_NEXT;
5546 				} else {
5547 					advance_left = ADVANCE;
5548 					advance_right = ADVANCE;
5549 				}
5550 			}
5551 		} else if (left_level < right_level) {
5552 			advance_right = ADVANCE;
5553 		} else {
5554 			advance_left = ADVANCE;
5555 		}
5556 	}
5557 
5558 out:
5559 	btrfs_free_path(left_path);
5560 	btrfs_free_path(right_path);
5561 	kfree(tmp_buf);
5562 	return ret;
5563 }
5564 
5565 /*
5566  * this is similar to btrfs_next_leaf, but does not try to preserve
5567  * and fixup the path.  It looks for and returns the next key in the
5568  * tree based on the current path and the min_trans parameters.
5569  *
5570  * 0 is returned if another key is found, < 0 if there are any errors
5571  * and 1 is returned if there are no higher keys in the tree
5572  *
5573  * path->keep_locks should be set to 1 on the search made before
5574  * calling this function.
5575  */
5576 int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
5577 			struct btrfs_key *key, int level, u64 min_trans)
5578 {
5579 	int slot;
5580 	struct extent_buffer *c;
5581 
5582 	WARN_ON(!path->keep_locks);
5583 	while (level < BTRFS_MAX_LEVEL) {
5584 		if (!path->nodes[level])
5585 			return 1;
5586 
5587 		slot = path->slots[level] + 1;
5588 		c = path->nodes[level];
5589 next:
5590 		if (slot >= btrfs_header_nritems(c)) {
5591 			int ret;
5592 			int orig_lowest;
5593 			struct btrfs_key cur_key;
5594 			if (level + 1 >= BTRFS_MAX_LEVEL ||
5595 			    !path->nodes[level + 1])
5596 				return 1;
5597 
5598 			if (path->locks[level + 1]) {
5599 				level++;
5600 				continue;
5601 			}
5602 
5603 			slot = btrfs_header_nritems(c) - 1;
5604 			if (level == 0)
5605 				btrfs_item_key_to_cpu(c, &cur_key, slot);
5606 			else
5607 				btrfs_node_key_to_cpu(c, &cur_key, slot);
5608 
5609 			orig_lowest = path->lowest_level;
5610 			btrfs_release_path(path);
5611 			path->lowest_level = level;
5612 			ret = btrfs_search_slot(NULL, root, &cur_key, path,
5613 						0, 0);
5614 			path->lowest_level = orig_lowest;
5615 			if (ret < 0)
5616 				return ret;
5617 
5618 			c = path->nodes[level];
5619 			slot = path->slots[level];
5620 			if (ret == 0)
5621 				slot++;
5622 			goto next;
5623 		}
5624 
5625 		if (level == 0)
5626 			btrfs_item_key_to_cpu(c, key, slot);
5627 		else {
5628 			u64 gen = btrfs_node_ptr_generation(c, slot);
5629 
5630 			if (gen < min_trans) {
5631 				slot++;
5632 				goto next;
5633 			}
5634 			btrfs_node_key_to_cpu(c, key, slot);
5635 		}
5636 		return 0;
5637 	}
5638 	return 1;
5639 }
5640 
5641 /*
5642  * search the tree again to find a leaf with greater keys
5643  * returns 0 if it found something or 1 if there are no greater leaves.
5644  * returns < 0 on io errors.
5645  */
5646 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
5647 {
5648 	return btrfs_next_old_leaf(root, path, 0);
5649 }
5650 
5651 int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
5652 			u64 time_seq)
5653 {
5654 	int slot;
5655 	int level;
5656 	struct extent_buffer *c;
5657 	struct extent_buffer *next;
5658 	struct btrfs_key key;
5659 	u32 nritems;
5660 	int ret;
5661 	int old_spinning = path->leave_spinning;
5662 	int next_rw_lock = 0;
5663 
5664 	nritems = btrfs_header_nritems(path->nodes[0]);
5665 	if (nritems == 0)
5666 		return 1;
5667 
5668 	btrfs_item_key_to_cpu(path->nodes[0], &key, nritems - 1);
5669 again:
5670 	level = 1;
5671 	next = NULL;
5672 	next_rw_lock = 0;
5673 	btrfs_release_path(path);
5674 
5675 	path->keep_locks = 1;
5676 	path->leave_spinning = 1;
5677 
5678 	if (time_seq)
5679 		ret = btrfs_search_old_slot(root, &key, path, time_seq);
5680 	else
5681 		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
5682 	path->keep_locks = 0;
5683 
5684 	if (ret < 0)
5685 		return ret;
5686 
5687 	nritems = btrfs_header_nritems(path->nodes[0]);
5688 	/*
5689 	 * by releasing the path above we dropped all our locks.  A balance
5690 	 * could have added more items next to the key that used to be
5691 	 * at the very end of the block.  So, check again here and
5692 	 * advance the path if there are now more items available.
5693 	 */
5694 	if (nritems > 0 && path->slots[0] < nritems - 1) {
5695 		if (ret == 0)
5696 			path->slots[0]++;
5697 		ret = 0;
5698 		goto done;
5699 	}
5700 	/*
5701 	 * So the above check misses one case:
5702 	 * - after releasing the path above, someone has removed the item that
5703 	 *   used to be at the very end of the block, and balance between leafs
5704 	 *   gets another one with bigger key.offset to replace it.
5705 	 *
5706 	 * This one should be returned as well, or we can get leaf corruption
5707 	 * later(esp. in __btrfs_drop_extents()).
5708 	 *
5709 	 * And a bit more explanation about this check,
5710 	 * with ret > 0, the key isn't found, the path points to the slot
5711 	 * where it should be inserted, so the path->slots[0] item must be the
5712 	 * bigger one.
5713 	 */
5714 	if (nritems > 0 && ret > 0 && path->slots[0] == nritems - 1) {
5715 		ret = 0;
5716 		goto done;
5717 	}
5718 
5719 	while (level < BTRFS_MAX_LEVEL) {
5720 		if (!path->nodes[level]) {
5721 			ret = 1;
5722 			goto done;
5723 		}
5724 
5725 		slot = path->slots[level] + 1;
5726 		c = path->nodes[level];
5727 		if (slot >= btrfs_header_nritems(c)) {
5728 			level++;
5729 			if (level == BTRFS_MAX_LEVEL) {
5730 				ret = 1;
5731 				goto done;
5732 			}
5733 			continue;
5734 		}
5735 
5736 		if (next) {
5737 			btrfs_tree_unlock_rw(next, next_rw_lock);
5738 			free_extent_buffer(next);
5739 		}
5740 
5741 		next = c;
5742 		next_rw_lock = path->locks[level];
5743 		ret = read_block_for_search(NULL, root, path, &next, level,
5744 					    slot, &key, 0);
5745 		if (ret == -EAGAIN)
5746 			goto again;
5747 
5748 		if (ret < 0) {
5749 			btrfs_release_path(path);
5750 			goto done;
5751 		}
5752 
5753 		if (!path->skip_locking) {
5754 			ret = btrfs_try_tree_read_lock(next);
5755 			if (!ret && time_seq) {
5756 				/*
5757 				 * If we don't get the lock, we may be racing
5758 				 * with push_leaf_left, holding that lock while
5759 				 * itself waiting for the leaf we've currently
5760 				 * locked. To solve this situation, we give up
5761 				 * on our lock and cycle.
5762 				 */
5763 				free_extent_buffer(next);
5764 				btrfs_release_path(path);
5765 				cond_resched();
5766 				goto again;
5767 			}
5768 			if (!ret) {
5769 				btrfs_set_path_blocking(path);
5770 				btrfs_tree_read_lock(next);
5771 				btrfs_clear_path_blocking(path, next,
5772 							  BTRFS_READ_LOCK);
5773 			}
5774 			next_rw_lock = BTRFS_READ_LOCK;
5775 		}
5776 		break;
5777 	}
5778 	path->slots[level] = slot;
5779 	while (1) {
5780 		level--;
5781 		c = path->nodes[level];
5782 		if (path->locks[level])
5783 			btrfs_tree_unlock_rw(c, path->locks[level]);
5784 
5785 		free_extent_buffer(c);
5786 		path->nodes[level] = next;
5787 		path->slots[level] = 0;
5788 		if (!path->skip_locking)
5789 			path->locks[level] = next_rw_lock;
5790 		if (!level)
5791 			break;
5792 
5793 		ret = read_block_for_search(NULL, root, path, &next, level,
5794 					    0, &key, 0);
5795 		if (ret == -EAGAIN)
5796 			goto again;
5797 
5798 		if (ret < 0) {
5799 			btrfs_release_path(path);
5800 			goto done;
5801 		}
5802 
5803 		if (!path->skip_locking) {
5804 			ret = btrfs_try_tree_read_lock(next);
5805 			if (!ret) {
5806 				btrfs_set_path_blocking(path);
5807 				btrfs_tree_read_lock(next);
5808 				btrfs_clear_path_blocking(path, next,
5809 							  BTRFS_READ_LOCK);
5810 			}
5811 			next_rw_lock = BTRFS_READ_LOCK;
5812 		}
5813 	}
5814 	ret = 0;
5815 done:
5816 	unlock_up(path, 0, 1, 0, NULL);
5817 	path->leave_spinning = old_spinning;
5818 	if (!old_spinning)
5819 		btrfs_set_path_blocking(path);
5820 
5821 	return ret;
5822 }
5823 
5824 /*
5825  * this uses btrfs_prev_leaf to walk backwards in the tree, and keeps
5826  * searching until it gets past min_objectid or finds an item of 'type'
5827  *
5828  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5829  */
5830 int btrfs_previous_item(struct btrfs_root *root,
5831 			struct btrfs_path *path, u64 min_objectid,
5832 			int type)
5833 {
5834 	struct btrfs_key found_key;
5835 	struct extent_buffer *leaf;
5836 	u32 nritems;
5837 	int ret;
5838 
5839 	while (1) {
5840 		if (path->slots[0] == 0) {
5841 			btrfs_set_path_blocking(path);
5842 			ret = btrfs_prev_leaf(root, path);
5843 			if (ret != 0)
5844 				return ret;
5845 		} else {
5846 			path->slots[0]--;
5847 		}
5848 		leaf = path->nodes[0];
5849 		nritems = btrfs_header_nritems(leaf);
5850 		if (nritems == 0)
5851 			return 1;
5852 		if (path->slots[0] == nritems)
5853 			path->slots[0]--;
5854 
5855 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5856 		if (found_key.objectid < min_objectid)
5857 			break;
5858 		if (found_key.type == type)
5859 			return 0;
5860 		if (found_key.objectid == min_objectid &&
5861 		    found_key.type < type)
5862 			break;
5863 	}
5864 	return 1;
5865 }
5866 
5867 /*
5868  * search in extent tree to find a previous Metadata/Data extent item with
5869  * min objecitd.
5870  *
5871  * returns 0 if something is found, 1 if nothing was found and < 0 on error
5872  */
5873 int btrfs_previous_extent_item(struct btrfs_root *root,
5874 			struct btrfs_path *path, u64 min_objectid)
5875 {
5876 	struct btrfs_key found_key;
5877 	struct extent_buffer *leaf;
5878 	u32 nritems;
5879 	int ret;
5880 
5881 	while (1) {
5882 		if (path->slots[0] == 0) {
5883 			btrfs_set_path_blocking(path);
5884 			ret = btrfs_prev_leaf(root, path);
5885 			if (ret != 0)
5886 				return ret;
5887 		} else {
5888 			path->slots[0]--;
5889 		}
5890 		leaf = path->nodes[0];
5891 		nritems = btrfs_header_nritems(leaf);
5892 		if (nritems == 0)
5893 			return 1;
5894 		if (path->slots[0] == nritems)
5895 			path->slots[0]--;
5896 
5897 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
5898 		if (found_key.objectid < min_objectid)
5899 			break;
5900 		if (found_key.type == BTRFS_EXTENT_ITEM_KEY ||
5901 		    found_key.type == BTRFS_METADATA_ITEM_KEY)
5902 			return 0;
5903 		if (found_key.objectid == min_objectid &&
5904 		    found_key.type < BTRFS_EXTENT_ITEM_KEY)
5905 			break;
5906 	}
5907 	return 1;
5908 }
5909