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TOMOYO Linux Cross Reference
Linux/fs/btrfs/ctree.c

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  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 

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