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

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  1 /*
  2  * Copyright (C) 2009 Oracle.  All rights reserved.
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public
  6  * License v2 as published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 11  * General Public License for more details.
 12  *
 13  * You should have received a copy of the GNU General Public
 14  * License along with this program; if not, write to the
 15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 16  * Boston, MA 021110-1307, USA.
 17  */
 18 
 19 #include <linux/sched.h>
 20 #include <linux/pagemap.h>
 21 #include <linux/writeback.h>
 22 #include <linux/blkdev.h>
 23 #include <linux/rbtree.h>
 24 #include <linux/slab.h>
 25 #include "ctree.h"
 26 #include "disk-io.h"
 27 #include "transaction.h"
 28 #include "volumes.h"
 29 #include "locking.h"
 30 #include "btrfs_inode.h"
 31 #include "async-thread.h"
 32 #include "free-space-cache.h"
 33 #include "inode-map.h"
 34 #include "qgroup.h"
 35 #include "print-tree.h"
 36 
 37 /*
 38  * backref_node, mapping_node and tree_block start with this
 39  */
 40 struct tree_entry {
 41         struct rb_node rb_node;
 42         u64 bytenr;
 43 };
 44 
 45 /*
 46  * present a tree block in the backref cache
 47  */
 48 struct backref_node {
 49         struct rb_node rb_node;
 50         u64 bytenr;
 51 
 52         u64 new_bytenr;
 53         /* objectid of tree block owner, can be not uptodate */
 54         u64 owner;
 55         /* link to pending, changed or detached list */
 56         struct list_head list;
 57         /* list of upper level blocks reference this block */
 58         struct list_head upper;
 59         /* list of child blocks in the cache */
 60         struct list_head lower;
 61         /* NULL if this node is not tree root */
 62         struct btrfs_root *root;
 63         /* extent buffer got by COW the block */
 64         struct extent_buffer *eb;
 65         /* level of tree block */
 66         unsigned int level:8;
 67         /* is the block in non-reference counted tree */
 68         unsigned int cowonly:1;
 69         /* 1 if no child node in the cache */
 70         unsigned int lowest:1;
 71         /* is the extent buffer locked */
 72         unsigned int locked:1;
 73         /* has the block been processed */
 74         unsigned int processed:1;
 75         /* have backrefs of this block been checked */
 76         unsigned int checked:1;
 77         /*
 78          * 1 if corresponding block has been cowed but some upper
 79          * level block pointers may not point to the new location
 80          */
 81         unsigned int pending:1;
 82         /*
 83          * 1 if the backref node isn't connected to any other
 84          * backref node.
 85          */
 86         unsigned int detached:1;
 87 };
 88 
 89 /*
 90  * present a block pointer in the backref cache
 91  */
 92 struct backref_edge {
 93         struct list_head list[2];
 94         struct backref_node *node[2];
 95 };
 96 
 97 #define LOWER   0
 98 #define UPPER   1
 99 #define RELOCATION_RESERVED_NODES       256
100 
101 struct backref_cache {
102         /* red black tree of all backref nodes in the cache */
103         struct rb_root rb_root;
104         /* for passing backref nodes to btrfs_reloc_cow_block */
105         struct backref_node *path[BTRFS_MAX_LEVEL];
106         /*
107          * list of blocks that have been cowed but some block
108          * pointers in upper level blocks may not reflect the
109          * new location
110          */
111         struct list_head pending[BTRFS_MAX_LEVEL];
112         /* list of backref nodes with no child node */
113         struct list_head leaves;
114         /* list of blocks that have been cowed in current transaction */
115         struct list_head changed;
116         /* list of detached backref node. */
117         struct list_head detached;
118 
119         u64 last_trans;
120 
121         int nr_nodes;
122         int nr_edges;
123 };
124 
125 /*
126  * map address of tree root to tree
127  */
128 struct mapping_node {
129         struct rb_node rb_node;
130         u64 bytenr;
131         void *data;
132 };
133 
134 struct mapping_tree {
135         struct rb_root rb_root;
136         spinlock_t lock;
137 };
138 
139 /*
140  * present a tree block to process
141  */
142 struct tree_block {
143         struct rb_node rb_node;
144         u64 bytenr;
145         struct btrfs_key key;
146         unsigned int level:8;
147         unsigned int key_ready:1;
148 };
149 
150 #define MAX_EXTENTS 128
151 
152 struct file_extent_cluster {
153         u64 start;
154         u64 end;
155         u64 boundary[MAX_EXTENTS];
156         unsigned int nr;
157 };
158 
159 struct reloc_control {
160         /* block group to relocate */
161         struct btrfs_block_group_cache *block_group;
162         /* extent tree */
163         struct btrfs_root *extent_root;
164         /* inode for moving data */
165         struct inode *data_inode;
166 
167         struct btrfs_block_rsv *block_rsv;
168 
169         struct backref_cache backref_cache;
170 
171         struct file_extent_cluster cluster;
172         /* tree blocks have been processed */
173         struct extent_io_tree processed_blocks;
174         /* map start of tree root to corresponding reloc tree */
175         struct mapping_tree reloc_root_tree;
176         /* list of reloc trees */
177         struct list_head reloc_roots;
178         /* size of metadata reservation for merging reloc trees */
179         u64 merging_rsv_size;
180         /* size of relocated tree nodes */
181         u64 nodes_relocated;
182         /* reserved size for block group relocation*/
183         u64 reserved_bytes;
184 
185         u64 search_start;
186         u64 extents_found;
187 
188         unsigned int stage:8;
189         unsigned int create_reloc_tree:1;
190         unsigned int merge_reloc_tree:1;
191         unsigned int found_file_extent:1;
192 };
193 
194 /* stages of data relocation */
195 #define MOVE_DATA_EXTENTS       0
196 #define UPDATE_DATA_PTRS        1
197 
198 static void remove_backref_node(struct backref_cache *cache,
199                                 struct backref_node *node);
200 static void __mark_block_processed(struct reloc_control *rc,
201                                    struct backref_node *node);
202 
203 static void mapping_tree_init(struct mapping_tree *tree)
204 {
205         tree->rb_root = RB_ROOT;
206         spin_lock_init(&tree->lock);
207 }
208 
209 static void backref_cache_init(struct backref_cache *cache)
210 {
211         int i;
212         cache->rb_root = RB_ROOT;
213         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
214                 INIT_LIST_HEAD(&cache->pending[i]);
215         INIT_LIST_HEAD(&cache->changed);
216         INIT_LIST_HEAD(&cache->detached);
217         INIT_LIST_HEAD(&cache->leaves);
218 }
219 
220 static void backref_cache_cleanup(struct backref_cache *cache)
221 {
222         struct backref_node *node;
223         int i;
224 
225         while (!list_empty(&cache->detached)) {
226                 node = list_entry(cache->detached.next,
227                                   struct backref_node, list);
228                 remove_backref_node(cache, node);
229         }
230 
231         while (!list_empty(&cache->leaves)) {
232                 node = list_entry(cache->leaves.next,
233                                   struct backref_node, lower);
234                 remove_backref_node(cache, node);
235         }
236 
237         cache->last_trans = 0;
238 
239         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
240                 ASSERT(list_empty(&cache->pending[i]));
241         ASSERT(list_empty(&cache->changed));
242         ASSERT(list_empty(&cache->detached));
243         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
244         ASSERT(!cache->nr_nodes);
245         ASSERT(!cache->nr_edges);
246 }
247 
248 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
249 {
250         struct backref_node *node;
251 
252         node = kzalloc(sizeof(*node), GFP_NOFS);
253         if (node) {
254                 INIT_LIST_HEAD(&node->list);
255                 INIT_LIST_HEAD(&node->upper);
256                 INIT_LIST_HEAD(&node->lower);
257                 RB_CLEAR_NODE(&node->rb_node);
258                 cache->nr_nodes++;
259         }
260         return node;
261 }
262 
263 static void free_backref_node(struct backref_cache *cache,
264                               struct backref_node *node)
265 {
266         if (node) {
267                 cache->nr_nodes--;
268                 kfree(node);
269         }
270 }
271 
272 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
273 {
274         struct backref_edge *edge;
275 
276         edge = kzalloc(sizeof(*edge), GFP_NOFS);
277         if (edge)
278                 cache->nr_edges++;
279         return edge;
280 }
281 
282 static void free_backref_edge(struct backref_cache *cache,
283                               struct backref_edge *edge)
284 {
285         if (edge) {
286                 cache->nr_edges--;
287                 kfree(edge);
288         }
289 }
290 
291 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
292                                    struct rb_node *node)
293 {
294         struct rb_node **p = &root->rb_node;
295         struct rb_node *parent = NULL;
296         struct tree_entry *entry;
297 
298         while (*p) {
299                 parent = *p;
300                 entry = rb_entry(parent, struct tree_entry, rb_node);
301 
302                 if (bytenr < entry->bytenr)
303                         p = &(*p)->rb_left;
304                 else if (bytenr > entry->bytenr)
305                         p = &(*p)->rb_right;
306                 else
307                         return parent;
308         }
309 
310         rb_link_node(node, parent, p);
311         rb_insert_color(node, root);
312         return NULL;
313 }
314 
315 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
316 {
317         struct rb_node *n = root->rb_node;
318         struct tree_entry *entry;
319 
320         while (n) {
321                 entry = rb_entry(n, struct tree_entry, rb_node);
322 
323                 if (bytenr < entry->bytenr)
324                         n = n->rb_left;
325                 else if (bytenr > entry->bytenr)
326                         n = n->rb_right;
327                 else
328                         return n;
329         }
330         return NULL;
331 }
332 
333 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
334 {
335 
336         struct btrfs_fs_info *fs_info = NULL;
337         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
338                                               rb_node);
339         if (bnode->root)
340                 fs_info = bnode->root->fs_info;
341         btrfs_panic(fs_info, errno,
342                     "Inconsistency in backref cache found at offset %llu",
343                     bytenr);
344 }
345 
346 /*
347  * walk up backref nodes until reach node presents tree root
348  */
349 static struct backref_node *walk_up_backref(struct backref_node *node,
350                                             struct backref_edge *edges[],
351                                             int *index)
352 {
353         struct backref_edge *edge;
354         int idx = *index;
355 
356         while (!list_empty(&node->upper)) {
357                 edge = list_entry(node->upper.next,
358                                   struct backref_edge, list[LOWER]);
359                 edges[idx++] = edge;
360                 node = edge->node[UPPER];
361         }
362         BUG_ON(node->detached);
363         *index = idx;
364         return node;
365 }
366 
367 /*
368  * walk down backref nodes to find start of next reference path
369  */
370 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
371                                               int *index)
372 {
373         struct backref_edge *edge;
374         struct backref_node *lower;
375         int idx = *index;
376 
377         while (idx > 0) {
378                 edge = edges[idx - 1];
379                 lower = edge->node[LOWER];
380                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
381                         idx--;
382                         continue;
383                 }
384                 edge = list_entry(edge->list[LOWER].next,
385                                   struct backref_edge, list[LOWER]);
386                 edges[idx - 1] = edge;
387                 *index = idx;
388                 return edge->node[UPPER];
389         }
390         *index = 0;
391         return NULL;
392 }
393 
394 static void unlock_node_buffer(struct backref_node *node)
395 {
396         if (node->locked) {
397                 btrfs_tree_unlock(node->eb);
398                 node->locked = 0;
399         }
400 }
401 
402 static void drop_node_buffer(struct backref_node *node)
403 {
404         if (node->eb) {
405                 unlock_node_buffer(node);
406                 free_extent_buffer(node->eb);
407                 node->eb = NULL;
408         }
409 }
410 
411 static void drop_backref_node(struct backref_cache *tree,
412                               struct backref_node *node)
413 {
414         BUG_ON(!list_empty(&node->upper));
415 
416         drop_node_buffer(node);
417         list_del(&node->list);
418         list_del(&node->lower);
419         if (!RB_EMPTY_NODE(&node->rb_node))
420                 rb_erase(&node->rb_node, &tree->rb_root);
421         free_backref_node(tree, node);
422 }
423 
424 /*
425  * remove a backref node from the backref cache
426  */
427 static void remove_backref_node(struct backref_cache *cache,
428                                 struct backref_node *node)
429 {
430         struct backref_node *upper;
431         struct backref_edge *edge;
432 
433         if (!node)
434                 return;
435 
436         BUG_ON(!node->lowest && !node->detached);
437         while (!list_empty(&node->upper)) {
438                 edge = list_entry(node->upper.next, struct backref_edge,
439                                   list[LOWER]);
440                 upper = edge->node[UPPER];
441                 list_del(&edge->list[LOWER]);
442                 list_del(&edge->list[UPPER]);
443                 free_backref_edge(cache, edge);
444 
445                 if (RB_EMPTY_NODE(&upper->rb_node)) {
446                         BUG_ON(!list_empty(&node->upper));
447                         drop_backref_node(cache, node);
448                         node = upper;
449                         node->lowest = 1;
450                         continue;
451                 }
452                 /*
453                  * add the node to leaf node list if no other
454                  * child block cached.
455                  */
456                 if (list_empty(&upper->lower)) {
457                         list_add_tail(&upper->lower, &cache->leaves);
458                         upper->lowest = 1;
459                 }
460         }
461 
462         drop_backref_node(cache, node);
463 }
464 
465 static void update_backref_node(struct backref_cache *cache,
466                                 struct backref_node *node, u64 bytenr)
467 {
468         struct rb_node *rb_node;
469         rb_erase(&node->rb_node, &cache->rb_root);
470         node->bytenr = bytenr;
471         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
472         if (rb_node)
473                 backref_tree_panic(rb_node, -EEXIST, bytenr);
474 }
475 
476 /*
477  * update backref cache after a transaction commit
478  */
479 static int update_backref_cache(struct btrfs_trans_handle *trans,
480                                 struct backref_cache *cache)
481 {
482         struct backref_node *node;
483         int level = 0;
484 
485         if (cache->last_trans == 0) {
486                 cache->last_trans = trans->transid;
487                 return 0;
488         }
489 
490         if (cache->last_trans == trans->transid)
491                 return 0;
492 
493         /*
494          * detached nodes are used to avoid unnecessary backref
495          * lookup. transaction commit changes the extent tree.
496          * so the detached nodes are no longer useful.
497          */
498         while (!list_empty(&cache->detached)) {
499                 node = list_entry(cache->detached.next,
500                                   struct backref_node, list);
501                 remove_backref_node(cache, node);
502         }
503 
504         while (!list_empty(&cache->changed)) {
505                 node = list_entry(cache->changed.next,
506                                   struct backref_node, list);
507                 list_del_init(&node->list);
508                 BUG_ON(node->pending);
509                 update_backref_node(cache, node, node->new_bytenr);
510         }
511 
512         /*
513          * some nodes can be left in the pending list if there were
514          * errors during processing the pending nodes.
515          */
516         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
517                 list_for_each_entry(node, &cache->pending[level], list) {
518                         BUG_ON(!node->pending);
519                         if (node->bytenr == node->new_bytenr)
520                                 continue;
521                         update_backref_node(cache, node, node->new_bytenr);
522                 }
523         }
524 
525         cache->last_trans = 0;
526         return 1;
527 }
528 
529 
530 static int should_ignore_root(struct btrfs_root *root)
531 {
532         struct btrfs_root *reloc_root;
533 
534         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
535                 return 0;
536 
537         reloc_root = root->reloc_root;
538         if (!reloc_root)
539                 return 0;
540 
541         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
542             root->fs_info->running_transaction->transid - 1)
543                 return 0;
544         /*
545          * if there is reloc tree and it was created in previous
546          * transaction backref lookup can find the reloc tree,
547          * so backref node for the fs tree root is useless for
548          * relocation.
549          */
550         return 1;
551 }
552 /*
553  * find reloc tree by address of tree root
554  */
555 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
556                                           u64 bytenr)
557 {
558         struct rb_node *rb_node;
559         struct mapping_node *node;
560         struct btrfs_root *root = NULL;
561 
562         spin_lock(&rc->reloc_root_tree.lock);
563         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
564         if (rb_node) {
565                 node = rb_entry(rb_node, struct mapping_node, rb_node);
566                 root = (struct btrfs_root *)node->data;
567         }
568         spin_unlock(&rc->reloc_root_tree.lock);
569         return root;
570 }
571 
572 static int is_cowonly_root(u64 root_objectid)
573 {
574         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
575             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
576             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
577             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
578             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
579             root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
580             root_objectid == BTRFS_UUID_TREE_OBJECTID ||
581             root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
582             root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
583                 return 1;
584         return 0;
585 }
586 
587 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
588                                         u64 root_objectid)
589 {
590         struct btrfs_key key;
591 
592         key.objectid = root_objectid;
593         key.type = BTRFS_ROOT_ITEM_KEY;
594         if (is_cowonly_root(root_objectid))
595                 key.offset = 0;
596         else
597                 key.offset = (u64)-1;
598 
599         return btrfs_get_fs_root(fs_info, &key, false);
600 }
601 
602 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
603 static noinline_for_stack
604 struct btrfs_root *find_tree_root(struct reloc_control *rc,
605                                   struct extent_buffer *leaf,
606                                   struct btrfs_extent_ref_v0 *ref0)
607 {
608         struct btrfs_root *root;
609         u64 root_objectid = btrfs_ref_root_v0(leaf, ref0);
610         u64 generation = btrfs_ref_generation_v0(leaf, ref0);
611 
612         BUG_ON(root_objectid == BTRFS_TREE_RELOC_OBJECTID);
613 
614         root = read_fs_root(rc->extent_root->fs_info, root_objectid);
615         BUG_ON(IS_ERR(root));
616 
617         if (test_bit(BTRFS_ROOT_REF_COWS, &root->state) &&
618             generation != btrfs_root_generation(&root->root_item))
619                 return NULL;
620 
621         return root;
622 }
623 #endif
624 
625 static noinline_for_stack
626 int find_inline_backref(struct extent_buffer *leaf, int slot,
627                         unsigned long *ptr, unsigned long *end)
628 {
629         struct btrfs_key key;
630         struct btrfs_extent_item *ei;
631         struct btrfs_tree_block_info *bi;
632         u32 item_size;
633 
634         btrfs_item_key_to_cpu(leaf, &key, slot);
635 
636         item_size = btrfs_item_size_nr(leaf, slot);
637 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
638         if (item_size < sizeof(*ei)) {
639                 WARN_ON(item_size != sizeof(struct btrfs_extent_item_v0));
640                 return 1;
641         }
642 #endif
643         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
644         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
645                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
646 
647         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
648             item_size <= sizeof(*ei) + sizeof(*bi)) {
649                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
650                 return 1;
651         }
652         if (key.type == BTRFS_METADATA_ITEM_KEY &&
653             item_size <= sizeof(*ei)) {
654                 WARN_ON(item_size < sizeof(*ei));
655                 return 1;
656         }
657 
658         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
659                 bi = (struct btrfs_tree_block_info *)(ei + 1);
660                 *ptr = (unsigned long)(bi + 1);
661         } else {
662                 *ptr = (unsigned long)(ei + 1);
663         }
664         *end = (unsigned long)ei + item_size;
665         return 0;
666 }
667 
668 /*
669  * build backref tree for a given tree block. root of the backref tree
670  * corresponds the tree block, leaves of the backref tree correspond
671  * roots of b-trees that reference the tree block.
672  *
673  * the basic idea of this function is check backrefs of a given block
674  * to find upper level blocks that reference the block, and then check
675  * backrefs of these upper level blocks recursively. the recursion stop
676  * when tree root is reached or backrefs for the block is cached.
677  *
678  * NOTE: if we find backrefs for a block are cached, we know backrefs
679  * for all upper level blocks that directly/indirectly reference the
680  * block are also cached.
681  */
682 static noinline_for_stack
683 struct backref_node *build_backref_tree(struct reloc_control *rc,
684                                         struct btrfs_key *node_key,
685                                         int level, u64 bytenr)
686 {
687         struct backref_cache *cache = &rc->backref_cache;
688         struct btrfs_path *path1;
689         struct btrfs_path *path2;
690         struct extent_buffer *eb;
691         struct btrfs_root *root;
692         struct backref_node *cur;
693         struct backref_node *upper;
694         struct backref_node *lower;
695         struct backref_node *node = NULL;
696         struct backref_node *exist = NULL;
697         struct backref_edge *edge;
698         struct rb_node *rb_node;
699         struct btrfs_key key;
700         unsigned long end;
701         unsigned long ptr;
702         LIST_HEAD(list);
703         LIST_HEAD(useless);
704         int cowonly;
705         int ret;
706         int err = 0;
707         bool need_check = true;
708 
709         path1 = btrfs_alloc_path();
710         path2 = btrfs_alloc_path();
711         if (!path1 || !path2) {
712                 err = -ENOMEM;
713                 goto out;
714         }
715         path1->reada = READA_FORWARD;
716         path2->reada = READA_FORWARD;
717 
718         node = alloc_backref_node(cache);
719         if (!node) {
720                 err = -ENOMEM;
721                 goto out;
722         }
723 
724         node->bytenr = bytenr;
725         node->level = level;
726         node->lowest = 1;
727         cur = node;
728 again:
729         end = 0;
730         ptr = 0;
731         key.objectid = cur->bytenr;
732         key.type = BTRFS_METADATA_ITEM_KEY;
733         key.offset = (u64)-1;
734 
735         path1->search_commit_root = 1;
736         path1->skip_locking = 1;
737         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
738                                 0, 0);
739         if (ret < 0) {
740                 err = ret;
741                 goto out;
742         }
743         ASSERT(ret);
744         ASSERT(path1->slots[0]);
745 
746         path1->slots[0]--;
747 
748         WARN_ON(cur->checked);
749         if (!list_empty(&cur->upper)) {
750                 /*
751                  * the backref was added previously when processing
752                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
753                  */
754                 ASSERT(list_is_singular(&cur->upper));
755                 edge = list_entry(cur->upper.next, struct backref_edge,
756                                   list[LOWER]);
757                 ASSERT(list_empty(&edge->list[UPPER]));
758                 exist = edge->node[UPPER];
759                 /*
760                  * add the upper level block to pending list if we need
761                  * check its backrefs
762                  */
763                 if (!exist->checked)
764                         list_add_tail(&edge->list[UPPER], &list);
765         } else {
766                 exist = NULL;
767         }
768 
769         while (1) {
770                 cond_resched();
771                 eb = path1->nodes[0];
772 
773                 if (ptr >= end) {
774                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
775                                 ret = btrfs_next_leaf(rc->extent_root, path1);
776                                 if (ret < 0) {
777                                         err = ret;
778                                         goto out;
779                                 }
780                                 if (ret > 0)
781                                         break;
782                                 eb = path1->nodes[0];
783                         }
784 
785                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
786                         if (key.objectid != cur->bytenr) {
787                                 WARN_ON(exist);
788                                 break;
789                         }
790 
791                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
792                             key.type == BTRFS_METADATA_ITEM_KEY) {
793                                 ret = find_inline_backref(eb, path1->slots[0],
794                                                           &ptr, &end);
795                                 if (ret)
796                                         goto next;
797                         }
798                 }
799 
800                 if (ptr < end) {
801                         /* update key for inline back ref */
802                         struct btrfs_extent_inline_ref *iref;
803                         int type;
804                         iref = (struct btrfs_extent_inline_ref *)ptr;
805                         type = btrfs_get_extent_inline_ref_type(eb, iref,
806                                                         BTRFS_REF_TYPE_BLOCK);
807                         if (type == BTRFS_REF_TYPE_INVALID) {
808                                 err = -EINVAL;
809                                 goto out;
810                         }
811                         key.type = type;
812                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
813 
814                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
815                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
816                 }
817 
818                 if (exist &&
819                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
820                       exist->owner == key.offset) ||
821                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
822                       exist->bytenr == key.offset))) {
823                         exist = NULL;
824                         goto next;
825                 }
826 
827 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
828                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY ||
829                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
830                         if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
831                                 struct btrfs_extent_ref_v0 *ref0;
832                                 ref0 = btrfs_item_ptr(eb, path1->slots[0],
833                                                 struct btrfs_extent_ref_v0);
834                                 if (key.objectid == key.offset) {
835                                         root = find_tree_root(rc, eb, ref0);
836                                         if (root && !should_ignore_root(root))
837                                                 cur->root = root;
838                                         else
839                                                 list_add(&cur->list, &useless);
840                                         break;
841                                 }
842                                 if (is_cowonly_root(btrfs_ref_root_v0(eb,
843                                                                       ref0)))
844                                         cur->cowonly = 1;
845                         }
846 #else
847                 ASSERT(key.type != BTRFS_EXTENT_REF_V0_KEY);
848                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
849 #endif
850                         if (key.objectid == key.offset) {
851                                 /*
852                                  * only root blocks of reloc trees use
853                                  * backref of this type.
854                                  */
855                                 root = find_reloc_root(rc, cur->bytenr);
856                                 ASSERT(root);
857                                 cur->root = root;
858                                 break;
859                         }
860 
861                         edge = alloc_backref_edge(cache);
862                         if (!edge) {
863                                 err = -ENOMEM;
864                                 goto out;
865                         }
866                         rb_node = tree_search(&cache->rb_root, key.offset);
867                         if (!rb_node) {
868                                 upper = alloc_backref_node(cache);
869                                 if (!upper) {
870                                         free_backref_edge(cache, edge);
871                                         err = -ENOMEM;
872                                         goto out;
873                                 }
874                                 upper->bytenr = key.offset;
875                                 upper->level = cur->level + 1;
876                                 /*
877                                  *  backrefs for the upper level block isn't
878                                  *  cached, add the block to pending list
879                                  */
880                                 list_add_tail(&edge->list[UPPER], &list);
881                         } else {
882                                 upper = rb_entry(rb_node, struct backref_node,
883                                                  rb_node);
884                                 ASSERT(upper->checked);
885                                 INIT_LIST_HEAD(&edge->list[UPPER]);
886                         }
887                         list_add_tail(&edge->list[LOWER], &cur->upper);
888                         edge->node[LOWER] = cur;
889                         edge->node[UPPER] = upper;
890 
891                         goto next;
892                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
893                         goto next;
894                 }
895 
896                 /* key.type == BTRFS_TREE_BLOCK_REF_KEY */
897                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
898                 if (IS_ERR(root)) {
899                         err = PTR_ERR(root);
900                         goto out;
901                 }
902 
903                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
904                         cur->cowonly = 1;
905 
906                 if (btrfs_root_level(&root->root_item) == cur->level) {
907                         /* tree root */
908                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
909                                cur->bytenr);
910                         if (should_ignore_root(root))
911                                 list_add(&cur->list, &useless);
912                         else
913                                 cur->root = root;
914                         break;
915                 }
916 
917                 level = cur->level + 1;
918 
919                 /*
920                  * searching the tree to find upper level blocks
921                  * reference the block.
922                  */
923                 path2->search_commit_root = 1;
924                 path2->skip_locking = 1;
925                 path2->lowest_level = level;
926                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
927                 path2->lowest_level = 0;
928                 if (ret < 0) {
929                         err = ret;
930                         goto out;
931                 }
932                 if (ret > 0 && path2->slots[level] > 0)
933                         path2->slots[level]--;
934 
935                 eb = path2->nodes[level];
936                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
937                     cur->bytenr) {
938                         btrfs_err(root->fs_info,
939         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
940                                   cur->bytenr, level - 1, root->objectid,
941                                   node_key->objectid, node_key->type,
942                                   node_key->offset);
943                         err = -ENOENT;
944                         goto out;
945                 }
946                 lower = cur;
947                 need_check = true;
948                 for (; level < BTRFS_MAX_LEVEL; level++) {
949                         if (!path2->nodes[level]) {
950                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
951                                        lower->bytenr);
952                                 if (should_ignore_root(root))
953                                         list_add(&lower->list, &useless);
954                                 else
955                                         lower->root = root;
956                                 break;
957                         }
958 
959                         edge = alloc_backref_edge(cache);
960                         if (!edge) {
961                                 err = -ENOMEM;
962                                 goto out;
963                         }
964 
965                         eb = path2->nodes[level];
966                         rb_node = tree_search(&cache->rb_root, eb->start);
967                         if (!rb_node) {
968                                 upper = alloc_backref_node(cache);
969                                 if (!upper) {
970                                         free_backref_edge(cache, edge);
971                                         err = -ENOMEM;
972                                         goto out;
973                                 }
974                                 upper->bytenr = eb->start;
975                                 upper->owner = btrfs_header_owner(eb);
976                                 upper->level = lower->level + 1;
977                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
978                                               &root->state))
979                                         upper->cowonly = 1;
980 
981                                 /*
982                                  * if we know the block isn't shared
983                                  * we can void checking its backrefs.
984                                  */
985                                 if (btrfs_block_can_be_shared(root, eb))
986                                         upper->checked = 0;
987                                 else
988                                         upper->checked = 1;
989 
990                                 /*
991                                  * add the block to pending list if we
992                                  * need check its backrefs, we only do this once
993                                  * while walking up a tree as we will catch
994                                  * anything else later on.
995                                  */
996                                 if (!upper->checked && need_check) {
997                                         need_check = false;
998                                         list_add_tail(&edge->list[UPPER],
999                                                       &list);
1000                                 } else {
1001                                         if (upper->checked)
1002                                                 need_check = true;
1003                                         INIT_LIST_HEAD(&edge->list[UPPER]);
1004                                 }
1005                         } else {
1006                                 upper = rb_entry(rb_node, struct backref_node,
1007                                                  rb_node);
1008                                 ASSERT(upper->checked);
1009                                 INIT_LIST_HEAD(&edge->list[UPPER]);
1010                                 if (!upper->owner)
1011                                         upper->owner = btrfs_header_owner(eb);
1012                         }
1013                         list_add_tail(&edge->list[LOWER], &lower->upper);
1014                         edge->node[LOWER] = lower;
1015                         edge->node[UPPER] = upper;
1016 
1017                         if (rb_node)
1018                                 break;
1019                         lower = upper;
1020                         upper = NULL;
1021                 }
1022                 btrfs_release_path(path2);
1023 next:
1024                 if (ptr < end) {
1025                         ptr += btrfs_extent_inline_ref_size(key.type);
1026                         if (ptr >= end) {
1027                                 WARN_ON(ptr > end);
1028                                 ptr = 0;
1029                                 end = 0;
1030                         }
1031                 }
1032                 if (ptr >= end)
1033                         path1->slots[0]++;
1034         }
1035         btrfs_release_path(path1);
1036 
1037         cur->checked = 1;
1038         WARN_ON(exist);
1039 
1040         /* the pending list isn't empty, take the first block to process */
1041         if (!list_empty(&list)) {
1042                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1043                 list_del_init(&edge->list[UPPER]);
1044                 cur = edge->node[UPPER];
1045                 goto again;
1046         }
1047 
1048         /*
1049          * everything goes well, connect backref nodes and insert backref nodes
1050          * into the cache.
1051          */
1052         ASSERT(node->checked);
1053         cowonly = node->cowonly;
1054         if (!cowonly) {
1055                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1056                                       &node->rb_node);
1057                 if (rb_node)
1058                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1059                 list_add_tail(&node->lower, &cache->leaves);
1060         }
1061 
1062         list_for_each_entry(edge, &node->upper, list[LOWER])
1063                 list_add_tail(&edge->list[UPPER], &list);
1064 
1065         while (!list_empty(&list)) {
1066                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1067                 list_del_init(&edge->list[UPPER]);
1068                 upper = edge->node[UPPER];
1069                 if (upper->detached) {
1070                         list_del(&edge->list[LOWER]);
1071                         lower = edge->node[LOWER];
1072                         free_backref_edge(cache, edge);
1073                         if (list_empty(&lower->upper))
1074                                 list_add(&lower->list, &useless);
1075                         continue;
1076                 }
1077 
1078                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1079                         if (upper->lowest) {
1080                                 list_del_init(&upper->lower);
1081                                 upper->lowest = 0;
1082                         }
1083 
1084                         list_add_tail(&edge->list[UPPER], &upper->lower);
1085                         continue;
1086                 }
1087 
1088                 if (!upper->checked) {
1089                         /*
1090                          * Still want to blow up for developers since this is a
1091                          * logic bug.
1092                          */
1093                         ASSERT(0);
1094                         err = -EINVAL;
1095                         goto out;
1096                 }
1097                 if (cowonly != upper->cowonly) {
1098                         ASSERT(0);
1099                         err = -EINVAL;
1100                         goto out;
1101                 }
1102 
1103                 if (!cowonly) {
1104                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1105                                               &upper->rb_node);
1106                         if (rb_node)
1107                                 backref_tree_panic(rb_node, -EEXIST,
1108                                                    upper->bytenr);
1109                 }
1110 
1111                 list_add_tail(&edge->list[UPPER], &upper->lower);
1112 
1113                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1114                         list_add_tail(&edge->list[UPPER], &list);
1115         }
1116         /*
1117          * process useless backref nodes. backref nodes for tree leaves
1118          * are deleted from the cache. backref nodes for upper level
1119          * tree blocks are left in the cache to avoid unnecessary backref
1120          * lookup.
1121          */
1122         while (!list_empty(&useless)) {
1123                 upper = list_entry(useless.next, struct backref_node, list);
1124                 list_del_init(&upper->list);
1125                 ASSERT(list_empty(&upper->upper));
1126                 if (upper == node)
1127                         node = NULL;
1128                 if (upper->lowest) {
1129                         list_del_init(&upper->lower);
1130                         upper->lowest = 0;
1131                 }
1132                 while (!list_empty(&upper->lower)) {
1133                         edge = list_entry(upper->lower.next,
1134                                           struct backref_edge, list[UPPER]);
1135                         list_del(&edge->list[UPPER]);
1136                         list_del(&edge->list[LOWER]);
1137                         lower = edge->node[LOWER];
1138                         free_backref_edge(cache, edge);
1139 
1140                         if (list_empty(&lower->upper))
1141                                 list_add(&lower->list, &useless);
1142                 }
1143                 __mark_block_processed(rc, upper);
1144                 if (upper->level > 0) {
1145                         list_add(&upper->list, &cache->detached);
1146                         upper->detached = 1;
1147                 } else {
1148                         rb_erase(&upper->rb_node, &cache->rb_root);
1149                         free_backref_node(cache, upper);
1150                 }
1151         }
1152 out:
1153         btrfs_free_path(path1);
1154         btrfs_free_path(path2);
1155         if (err) {
1156                 while (!list_empty(&useless)) {
1157                         lower = list_entry(useless.next,
1158                                            struct backref_node, list);
1159                         list_del_init(&lower->list);
1160                 }
1161                 while (!list_empty(&list)) {
1162                         edge = list_first_entry(&list, struct backref_edge,
1163                                                 list[UPPER]);
1164                         list_del(&edge->list[UPPER]);
1165                         list_del(&edge->list[LOWER]);
1166                         lower = edge->node[LOWER];
1167                         upper = edge->node[UPPER];
1168                         free_backref_edge(cache, edge);
1169 
1170                         /*
1171                          * Lower is no longer linked to any upper backref nodes
1172                          * and isn't in the cache, we can free it ourselves.
1173                          */
1174                         if (list_empty(&lower->upper) &&
1175                             RB_EMPTY_NODE(&lower->rb_node))
1176                                 list_add(&lower->list, &useless);
1177 
1178                         if (!RB_EMPTY_NODE(&upper->rb_node))
1179                                 continue;
1180 
1181                         /* Add this guy's upper edges to the list to process */
1182                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1183                                 list_add_tail(&edge->list[UPPER], &list);
1184                         if (list_empty(&upper->upper))
1185                                 list_add(&upper->list, &useless);
1186                 }
1187 
1188                 while (!list_empty(&useless)) {
1189                         lower = list_entry(useless.next,
1190                                            struct backref_node, list);
1191                         list_del_init(&lower->list);
1192                         if (lower == node)
1193                                 node = NULL;
1194                         free_backref_node(cache, lower);
1195                 }
1196 
1197                 free_backref_node(cache, node);
1198                 return ERR_PTR(err);
1199         }
1200         ASSERT(!node || !node->detached);
1201         return node;
1202 }
1203 
1204 /*
1205  * helper to add backref node for the newly created snapshot.
1206  * the backref node is created by cloning backref node that
1207  * corresponds to root of source tree
1208  */
1209 static int clone_backref_node(struct btrfs_trans_handle *trans,
1210                               struct reloc_control *rc,
1211                               struct btrfs_root *src,
1212                               struct btrfs_root *dest)
1213 {
1214         struct btrfs_root *reloc_root = src->reloc_root;
1215         struct backref_cache *cache = &rc->backref_cache;
1216         struct backref_node *node = NULL;
1217         struct backref_node *new_node;
1218         struct backref_edge *edge;
1219         struct backref_edge *new_edge;
1220         struct rb_node *rb_node;
1221 
1222         if (cache->last_trans > 0)
1223                 update_backref_cache(trans, cache);
1224 
1225         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1226         if (rb_node) {
1227                 node = rb_entry(rb_node, struct backref_node, rb_node);
1228                 if (node->detached)
1229                         node = NULL;
1230                 else
1231                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1232         }
1233 
1234         if (!node) {
1235                 rb_node = tree_search(&cache->rb_root,
1236                                       reloc_root->commit_root->start);
1237                 if (rb_node) {
1238                         node = rb_entry(rb_node, struct backref_node,
1239                                         rb_node);
1240                         BUG_ON(node->detached);
1241                 }
1242         }
1243 
1244         if (!node)
1245                 return 0;
1246 
1247         new_node = alloc_backref_node(cache);
1248         if (!new_node)
1249                 return -ENOMEM;
1250 
1251         new_node->bytenr = dest->node->start;
1252         new_node->level = node->level;
1253         new_node->lowest = node->lowest;
1254         new_node->checked = 1;
1255         new_node->root = dest;
1256 
1257         if (!node->lowest) {
1258                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1259                         new_edge = alloc_backref_edge(cache);
1260                         if (!new_edge)
1261                                 goto fail;
1262 
1263                         new_edge->node[UPPER] = new_node;
1264                         new_edge->node[LOWER] = edge->node[LOWER];
1265                         list_add_tail(&new_edge->list[UPPER],
1266                                       &new_node->lower);
1267                 }
1268         } else {
1269                 list_add_tail(&new_node->lower, &cache->leaves);
1270         }
1271 
1272         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1273                               &new_node->rb_node);
1274         if (rb_node)
1275                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1276 
1277         if (!new_node->lowest) {
1278                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1279                         list_add_tail(&new_edge->list[LOWER],
1280                                       &new_edge->node[LOWER]->upper);
1281                 }
1282         }
1283         return 0;
1284 fail:
1285         while (!list_empty(&new_node->lower)) {
1286                 new_edge = list_entry(new_node->lower.next,
1287                                       struct backref_edge, list[UPPER]);
1288                 list_del(&new_edge->list[UPPER]);
1289                 free_backref_edge(cache, new_edge);
1290         }
1291         free_backref_node(cache, new_node);
1292         return -ENOMEM;
1293 }
1294 
1295 /*
1296  * helper to add 'address of tree root -> reloc tree' mapping
1297  */
1298 static int __must_check __add_reloc_root(struct btrfs_root *root)
1299 {
1300         struct btrfs_fs_info *fs_info = root->fs_info;
1301         struct rb_node *rb_node;
1302         struct mapping_node *node;
1303         struct reloc_control *rc = fs_info->reloc_ctl;
1304 
1305         node = kmalloc(sizeof(*node), GFP_NOFS);
1306         if (!node)
1307                 return -ENOMEM;
1308 
1309         node->bytenr = root->node->start;
1310         node->data = root;
1311 
1312         spin_lock(&rc->reloc_root_tree.lock);
1313         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1314                               node->bytenr, &node->rb_node);
1315         spin_unlock(&rc->reloc_root_tree.lock);
1316         if (rb_node) {
1317                 btrfs_panic(fs_info, -EEXIST,
1318                             "Duplicate root found for start=%llu while inserting into relocation tree",
1319                             node->bytenr);
1320         }
1321 
1322         list_add_tail(&root->root_list, &rc->reloc_roots);
1323         return 0;
1324 }
1325 
1326 /*
1327  * helper to delete the 'address of tree root -> reloc tree'
1328  * mapping
1329  */
1330 static void __del_reloc_root(struct btrfs_root *root)
1331 {
1332         struct btrfs_fs_info *fs_info = root->fs_info;
1333         struct rb_node *rb_node;
1334         struct mapping_node *node = NULL;
1335         struct reloc_control *rc = fs_info->reloc_ctl;
1336 
1337         spin_lock(&rc->reloc_root_tree.lock);
1338         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1339                               root->node->start);
1340         if (rb_node) {
1341                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1342                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1343         }
1344         spin_unlock(&rc->reloc_root_tree.lock);
1345 
1346         if (!node)
1347                 return;
1348         BUG_ON((struct btrfs_root *)node->data != root);
1349 
1350         spin_lock(&fs_info->trans_lock);
1351         list_del_init(&root->root_list);
1352         spin_unlock(&fs_info->trans_lock);
1353         kfree(node);
1354 }
1355 
1356 /*
1357  * helper to update the 'address of tree root -> reloc tree'
1358  * mapping
1359  */
1360 static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)
1361 {
1362         struct btrfs_fs_info *fs_info = root->fs_info;
1363         struct rb_node *rb_node;
1364         struct mapping_node *node = NULL;
1365         struct reloc_control *rc = fs_info->reloc_ctl;
1366 
1367         spin_lock(&rc->reloc_root_tree.lock);
1368         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1369                               root->node->start);
1370         if (rb_node) {
1371                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1372                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1373         }
1374         spin_unlock(&rc->reloc_root_tree.lock);
1375 
1376         if (!node)
1377                 return 0;
1378         BUG_ON((struct btrfs_root *)node->data != root);
1379 
1380         spin_lock(&rc->reloc_root_tree.lock);
1381         node->bytenr = new_bytenr;
1382         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1383                               node->bytenr, &node->rb_node);
1384         spin_unlock(&rc->reloc_root_tree.lock);
1385         if (rb_node)
1386                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1387         return 0;
1388 }
1389 
1390 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1391                                         struct btrfs_root *root, u64 objectid)
1392 {
1393         struct btrfs_fs_info *fs_info = root->fs_info;
1394         struct btrfs_root *reloc_root;
1395         struct extent_buffer *eb;
1396         struct btrfs_root_item *root_item;
1397         struct btrfs_key root_key;
1398         int ret;
1399 
1400         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1401         BUG_ON(!root_item);
1402 
1403         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1404         root_key.type = BTRFS_ROOT_ITEM_KEY;
1405         root_key.offset = objectid;
1406 
1407         if (root->root_key.objectid == objectid) {
1408                 u64 commit_root_gen;
1409 
1410                 /* called by btrfs_init_reloc_root */
1411                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1412                                       BTRFS_TREE_RELOC_OBJECTID);
1413                 BUG_ON(ret);
1414                 /*
1415                  * Set the last_snapshot field to the generation of the commit
1416                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
1417                  * correctly (returns true) when the relocation root is created
1418                  * either inside the critical section of a transaction commit
1419                  * (through transaction.c:qgroup_account_snapshot()) and when
1420                  * it's created before the transaction commit is started.
1421                  */
1422                 commit_root_gen = btrfs_header_generation(root->commit_root);
1423                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
1424         } else {
1425                 /*
1426                  * called by btrfs_reloc_post_snapshot_hook.
1427                  * the source tree is a reloc tree, all tree blocks
1428                  * modified after it was created have RELOC flag
1429                  * set in their headers. so it's OK to not update
1430                  * the 'last_snapshot'.
1431                  */
1432                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1433                                       BTRFS_TREE_RELOC_OBJECTID);
1434                 BUG_ON(ret);
1435         }
1436 
1437         memcpy(root_item, &root->root_item, sizeof(*root_item));
1438         btrfs_set_root_bytenr(root_item, eb->start);
1439         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1440         btrfs_set_root_generation(root_item, trans->transid);
1441 
1442         if (root->root_key.objectid == objectid) {
1443                 btrfs_set_root_refs(root_item, 0);
1444                 memset(&root_item->drop_progress, 0,
1445                        sizeof(struct btrfs_disk_key));
1446                 root_item->drop_level = 0;
1447         }
1448 
1449         btrfs_tree_unlock(eb);
1450         free_extent_buffer(eb);
1451 
1452         ret = btrfs_insert_root(trans, fs_info->tree_root,
1453                                 &root_key, root_item);
1454         BUG_ON(ret);
1455         kfree(root_item);
1456 
1457         reloc_root = btrfs_read_fs_root(fs_info->tree_root, &root_key);
1458         BUG_ON(IS_ERR(reloc_root));
1459         reloc_root->last_trans = trans->transid;
1460         return reloc_root;
1461 }
1462 
1463 /*
1464  * create reloc tree for a given fs tree. reloc tree is just a
1465  * snapshot of the fs tree with special root objectid.
1466  */
1467 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1468                           struct btrfs_root *root)
1469 {
1470         struct btrfs_fs_info *fs_info = root->fs_info;
1471         struct btrfs_root *reloc_root;
1472         struct reloc_control *rc = fs_info->reloc_ctl;
1473         struct btrfs_block_rsv *rsv;
1474         int clear_rsv = 0;
1475         int ret;
1476 
1477         if (root->reloc_root) {
1478                 reloc_root = root->reloc_root;
1479                 reloc_root->last_trans = trans->transid;
1480                 return 0;
1481         }
1482 
1483         if (!rc || !rc->create_reloc_tree ||
1484             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1485                 return 0;
1486 
1487         if (!trans->reloc_reserved) {
1488                 rsv = trans->block_rsv;
1489                 trans->block_rsv = rc->block_rsv;
1490                 clear_rsv = 1;
1491         }
1492         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1493         if (clear_rsv)
1494                 trans->block_rsv = rsv;
1495 
1496         ret = __add_reloc_root(reloc_root);
1497         BUG_ON(ret < 0);
1498         root->reloc_root = reloc_root;
1499         return 0;
1500 }
1501 
1502 /*
1503  * update root item of reloc tree
1504  */
1505 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1506                             struct btrfs_root *root)
1507 {
1508         struct btrfs_fs_info *fs_info = root->fs_info;
1509         struct btrfs_root *reloc_root;
1510         struct btrfs_root_item *root_item;
1511         int ret;
1512 
1513         if (!root->reloc_root)
1514                 goto out;
1515 
1516         reloc_root = root->reloc_root;
1517         root_item = &reloc_root->root_item;
1518 
1519         if (fs_info->reloc_ctl->merge_reloc_tree &&
1520             btrfs_root_refs(root_item) == 0) {
1521                 root->reloc_root = NULL;
1522                 __del_reloc_root(reloc_root);
1523         }
1524 
1525         if (reloc_root->commit_root != reloc_root->node) {
1526                 btrfs_set_root_node(root_item, reloc_root->node);
1527                 free_extent_buffer(reloc_root->commit_root);
1528                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1529         }
1530 
1531         ret = btrfs_update_root(trans, fs_info->tree_root,
1532                                 &reloc_root->root_key, root_item);
1533         BUG_ON(ret);
1534 
1535 out:
1536         return 0;
1537 }
1538 
1539 /*
1540  * helper to find first cached inode with inode number >= objectid
1541  * in a subvolume
1542  */
1543 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1544 {
1545         struct rb_node *node;
1546         struct rb_node *prev;
1547         struct btrfs_inode *entry;
1548         struct inode *inode;
1549 
1550         spin_lock(&root->inode_lock);
1551 again:
1552         node = root->inode_tree.rb_node;
1553         prev = NULL;
1554         while (node) {
1555                 prev = node;
1556                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1557 
1558                 if (objectid < btrfs_ino(entry))
1559                         node = node->rb_left;
1560                 else if (objectid > btrfs_ino(entry))
1561                         node = node->rb_right;
1562                 else
1563                         break;
1564         }
1565         if (!node) {
1566                 while (prev) {
1567                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1568                         if (objectid <= btrfs_ino(entry)) {
1569                                 node = prev;
1570                                 break;
1571                         }
1572                         prev = rb_next(prev);
1573                 }
1574         }
1575         while (node) {
1576                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1577                 inode = igrab(&entry->vfs_inode);
1578                 if (inode) {
1579                         spin_unlock(&root->inode_lock);
1580                         return inode;
1581                 }
1582 
1583                 objectid = btrfs_ino(entry) + 1;
1584                 if (cond_resched_lock(&root->inode_lock))
1585                         goto again;
1586 
1587                 node = rb_next(node);
1588         }
1589         spin_unlock(&root->inode_lock);
1590         return NULL;
1591 }
1592 
1593 static int in_block_group(u64 bytenr,
1594                           struct btrfs_block_group_cache *block_group)
1595 {
1596         if (bytenr >= block_group->key.objectid &&
1597             bytenr < block_group->key.objectid + block_group->key.offset)
1598                 return 1;
1599         return 0;
1600 }
1601 
1602 /*
1603  * get new location of data
1604  */
1605 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1606                             u64 bytenr, u64 num_bytes)
1607 {
1608         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1609         struct btrfs_path *path;
1610         struct btrfs_file_extent_item *fi;
1611         struct extent_buffer *leaf;
1612         int ret;
1613 
1614         path = btrfs_alloc_path();
1615         if (!path)
1616                 return -ENOMEM;
1617 
1618         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1619         ret = btrfs_lookup_file_extent(NULL, root, path,
1620                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1621         if (ret < 0)
1622                 goto out;
1623         if (ret > 0) {
1624                 ret = -ENOENT;
1625                 goto out;
1626         }
1627 
1628         leaf = path->nodes[0];
1629         fi = btrfs_item_ptr(leaf, path->slots[0],
1630                             struct btrfs_file_extent_item);
1631 
1632         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1633                btrfs_file_extent_compression(leaf, fi) ||
1634                btrfs_file_extent_encryption(leaf, fi) ||
1635                btrfs_file_extent_other_encoding(leaf, fi));
1636 
1637         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1638                 ret = -EINVAL;
1639                 goto out;
1640         }
1641 
1642         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1643         ret = 0;
1644 out:
1645         btrfs_free_path(path);
1646         return ret;
1647 }
1648 
1649 /*
1650  * update file extent items in the tree leaf to point to
1651  * the new locations.
1652  */
1653 static noinline_for_stack
1654 int replace_file_extents(struct btrfs_trans_handle *trans,
1655                          struct reloc_control *rc,
1656                          struct btrfs_root *root,
1657                          struct extent_buffer *leaf)
1658 {
1659         struct btrfs_fs_info *fs_info = root->fs_info;
1660         struct btrfs_key key;
1661         struct btrfs_file_extent_item *fi;
1662         struct inode *inode = NULL;
1663         u64 parent;
1664         u64 bytenr;
1665         u64 new_bytenr = 0;
1666         u64 num_bytes;
1667         u64 end;
1668         u32 nritems;
1669         u32 i;
1670         int ret = 0;
1671         int first = 1;
1672         int dirty = 0;
1673 
1674         if (rc->stage != UPDATE_DATA_PTRS)
1675                 return 0;
1676 
1677         /* reloc trees always use full backref */
1678         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1679                 parent = leaf->start;
1680         else
1681                 parent = 0;
1682 
1683         nritems = btrfs_header_nritems(leaf);
1684         for (i = 0; i < nritems; i++) {
1685                 cond_resched();
1686                 btrfs_item_key_to_cpu(leaf, &key, i);
1687                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1688                         continue;
1689                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1690                 if (btrfs_file_extent_type(leaf, fi) ==
1691                     BTRFS_FILE_EXTENT_INLINE)
1692                         continue;
1693                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1694                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1695                 if (bytenr == 0)
1696                         continue;
1697                 if (!in_block_group(bytenr, rc->block_group))
1698                         continue;
1699 
1700                 /*
1701                  * if we are modifying block in fs tree, wait for readpage
1702                  * to complete and drop the extent cache
1703                  */
1704                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1705                         if (first) {
1706                                 inode = find_next_inode(root, key.objectid);
1707                                 first = 0;
1708                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1709                                 btrfs_add_delayed_iput(inode);
1710                                 inode = find_next_inode(root, key.objectid);
1711                         }
1712                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1713                                 end = key.offset +
1714                                       btrfs_file_extent_num_bytes(leaf, fi);
1715                                 WARN_ON(!IS_ALIGNED(key.offset,
1716                                                     fs_info->sectorsize));
1717                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1718                                 end--;
1719                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1720                                                       key.offset, end);
1721                                 if (!ret)
1722                                         continue;
1723 
1724                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1725                                                 key.offset,     end, 1);
1726                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1727                                               key.offset, end);
1728                         }
1729                 }
1730 
1731                 ret = get_new_location(rc->data_inode, &new_bytenr,
1732                                        bytenr, num_bytes);
1733                 if (ret) {
1734                         /*
1735                          * Don't have to abort since we've not changed anything
1736                          * in the file extent yet.
1737                          */
1738                         break;
1739                 }
1740 
1741                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1742                 dirty = 1;
1743 
1744                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1745                 ret = btrfs_inc_extent_ref(trans, root, new_bytenr,
1746                                            num_bytes, parent,
1747                                            btrfs_header_owner(leaf),
1748                                            key.objectid, key.offset);
1749                 if (ret) {
1750                         btrfs_abort_transaction(trans, ret);
1751                         break;
1752                 }
1753 
1754                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
1755                                         parent, btrfs_header_owner(leaf),
1756                                         key.objectid, key.offset);
1757                 if (ret) {
1758                         btrfs_abort_transaction(trans, ret);
1759                         break;
1760                 }
1761         }
1762         if (dirty)
1763                 btrfs_mark_buffer_dirty(leaf);
1764         if (inode)
1765                 btrfs_add_delayed_iput(inode);
1766         return ret;
1767 }
1768 
1769 static noinline_for_stack
1770 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1771                      struct btrfs_path *path, int level)
1772 {
1773         struct btrfs_disk_key key1;
1774         struct btrfs_disk_key key2;
1775         btrfs_node_key(eb, &key1, slot);
1776         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1777         return memcmp(&key1, &key2, sizeof(key1));
1778 }
1779 
1780 /*
1781  * try to replace tree blocks in fs tree with the new blocks
1782  * in reloc tree. tree blocks haven't been modified since the
1783  * reloc tree was create can be replaced.
1784  *
1785  * if a block was replaced, level of the block + 1 is returned.
1786  * if no block got replaced, 0 is returned. if there are other
1787  * errors, a negative error number is returned.
1788  */
1789 static noinline_for_stack
1790 int replace_path(struct btrfs_trans_handle *trans,
1791                  struct btrfs_root *dest, struct btrfs_root *src,
1792                  struct btrfs_path *path, struct btrfs_key *next_key,
1793                  int lowest_level, int max_level)
1794 {
1795         struct btrfs_fs_info *fs_info = dest->fs_info;
1796         struct extent_buffer *eb;
1797         struct extent_buffer *parent;
1798         struct btrfs_key key;
1799         u64 old_bytenr;
1800         u64 new_bytenr;
1801         u64 old_ptr_gen;
1802         u64 new_ptr_gen;
1803         u64 last_snapshot;
1804         u32 blocksize;
1805         int cow = 0;
1806         int level;
1807         int ret;
1808         int slot;
1809 
1810         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1811         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1812 
1813         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1814 again:
1815         slot = path->slots[lowest_level];
1816         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1817 
1818         eb = btrfs_lock_root_node(dest);
1819         btrfs_set_lock_blocking(eb);
1820         level = btrfs_header_level(eb);
1821 
1822         if (level < lowest_level) {
1823                 btrfs_tree_unlock(eb);
1824                 free_extent_buffer(eb);
1825                 return 0;
1826         }
1827 
1828         if (cow) {
1829                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1830                 BUG_ON(ret);
1831         }
1832         btrfs_set_lock_blocking(eb);
1833 
1834         if (next_key) {
1835                 next_key->objectid = (u64)-1;
1836                 next_key->type = (u8)-1;
1837                 next_key->offset = (u64)-1;
1838         }
1839 
1840         parent = eb;
1841         while (1) {
1842                 level = btrfs_header_level(parent);
1843                 BUG_ON(level < lowest_level);
1844 
1845                 ret = btrfs_bin_search(parent, &key, level, &slot);
1846                 if (ret && slot > 0)
1847                         slot--;
1848 
1849                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1850                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1851 
1852                 old_bytenr = btrfs_node_blockptr(parent, slot);
1853                 blocksize = fs_info->nodesize;
1854                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1855 
1856                 if (level <= max_level) {
1857                         eb = path->nodes[level];
1858                         new_bytenr = btrfs_node_blockptr(eb,
1859                                                         path->slots[level]);
1860                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1861                                                         path->slots[level]);
1862                 } else {
1863                         new_bytenr = 0;
1864                         new_ptr_gen = 0;
1865                 }
1866 
1867                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1868                         ret = level;
1869                         break;
1870                 }
1871 
1872                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1873                     memcmp_node_keys(parent, slot, path, level)) {
1874                         if (level <= lowest_level) {
1875                                 ret = 0;
1876                                 break;
1877                         }
1878 
1879                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen);
1880                         if (IS_ERR(eb)) {
1881                                 ret = PTR_ERR(eb);
1882                                 break;
1883                         } else if (!extent_buffer_uptodate(eb)) {
1884                                 ret = -EIO;
1885                                 free_extent_buffer(eb);
1886                                 break;
1887                         }
1888                         btrfs_tree_lock(eb);
1889                         if (cow) {
1890                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1891                                                       slot, &eb);
1892                                 BUG_ON(ret);
1893                         }
1894                         btrfs_set_lock_blocking(eb);
1895 
1896                         btrfs_tree_unlock(parent);
1897                         free_extent_buffer(parent);
1898 
1899                         parent = eb;
1900                         continue;
1901                 }
1902 
1903                 if (!cow) {
1904                         btrfs_tree_unlock(parent);
1905                         free_extent_buffer(parent);
1906                         cow = 1;
1907                         goto again;
1908                 }
1909 
1910                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1911                                       path->slots[level]);
1912                 btrfs_release_path(path);
1913 
1914                 path->lowest_level = level;
1915                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1916                 path->lowest_level = 0;
1917                 BUG_ON(ret);
1918 
1919                 /*
1920                  * Info qgroup to trace both subtrees.
1921                  *
1922                  * We must trace both trees.
1923                  * 1) Tree reloc subtree
1924                  *    If not traced, we will leak data numbers
1925                  * 2) Fs subtree
1926                  *    If not traced, we will double count old data
1927                  *    and tree block numbers, if current trans doesn't free
1928                  *    data reloc tree inode.
1929                  */
1930                 ret = btrfs_qgroup_trace_subtree(trans, src, parent,
1931                                 btrfs_header_generation(parent),
1932                                 btrfs_header_level(parent));
1933                 if (ret < 0)
1934                         break;
1935                 ret = btrfs_qgroup_trace_subtree(trans, dest,
1936                                 path->nodes[level],
1937                                 btrfs_header_generation(path->nodes[level]),
1938                                 btrfs_header_level(path->nodes[level]));
1939                 if (ret < 0)
1940                         break;
1941 
1942                 /*
1943                  * swap blocks in fs tree and reloc tree.
1944                  */
1945                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1946                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1947                 btrfs_mark_buffer_dirty(parent);
1948 
1949                 btrfs_set_node_blockptr(path->nodes[level],
1950                                         path->slots[level], old_bytenr);
1951                 btrfs_set_node_ptr_generation(path->nodes[level],
1952                                               path->slots[level], old_ptr_gen);
1953                 btrfs_mark_buffer_dirty(path->nodes[level]);
1954 
1955                 ret = btrfs_inc_extent_ref(trans, src, old_bytenr,
1956                                         blocksize, path->nodes[level]->start,
1957                                         src->root_key.objectid, level - 1, 0);
1958                 BUG_ON(ret);
1959                 ret = btrfs_inc_extent_ref(trans, dest, new_bytenr,
1960                                         blocksize, 0, dest->root_key.objectid,
1961                                         level - 1, 0);
1962                 BUG_ON(ret);
1963 
1964                 ret = btrfs_free_extent(trans, src, new_bytenr, blocksize,
1965                                         path->nodes[level]->start,
1966                                         src->root_key.objectid, level - 1, 0);
1967                 BUG_ON(ret);
1968 
1969                 ret = btrfs_free_extent(trans, dest, old_bytenr, blocksize,
1970                                         0, dest->root_key.objectid, level - 1,
1971                                         0);
1972                 BUG_ON(ret);
1973 
1974                 btrfs_unlock_up_safe(path, 0);
1975 
1976                 ret = level;
1977                 break;
1978         }
1979         btrfs_tree_unlock(parent);
1980         free_extent_buffer(parent);
1981         return ret;
1982 }
1983 
1984 /*
1985  * helper to find next relocated block in reloc tree
1986  */
1987 static noinline_for_stack
1988 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1989                        int *level)
1990 {
1991         struct extent_buffer *eb;
1992         int i;
1993         u64 last_snapshot;
1994         u32 nritems;
1995 
1996         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1997 
1998         for (i = 0; i < *level; i++) {
1999                 free_extent_buffer(path->nodes[i]);
2000                 path->nodes[i] = NULL;
2001         }
2002 
2003         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
2004                 eb = path->nodes[i];
2005                 nritems = btrfs_header_nritems(eb);
2006                 while (path->slots[i] + 1 < nritems) {
2007                         path->slots[i]++;
2008                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
2009                             last_snapshot)
2010                                 continue;
2011 
2012                         *level = i;
2013                         return 0;
2014                 }
2015                 free_extent_buffer(path->nodes[i]);
2016                 path->nodes[i] = NULL;
2017         }
2018         return 1;
2019 }
2020 
2021 /*
2022  * walk down reloc tree to find relocated block of lowest level
2023  */
2024 static noinline_for_stack
2025 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2026                          int *level)
2027 {
2028         struct btrfs_fs_info *fs_info = root->fs_info;
2029         struct extent_buffer *eb = NULL;
2030         int i;
2031         u64 bytenr;
2032         u64 ptr_gen = 0;
2033         u64 last_snapshot;
2034         u32 nritems;
2035 
2036         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2037 
2038         for (i = *level; i > 0; i--) {
2039                 eb = path->nodes[i];
2040                 nritems = btrfs_header_nritems(eb);
2041                 while (path->slots[i] < nritems) {
2042                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2043                         if (ptr_gen > last_snapshot)
2044                                 break;
2045                         path->slots[i]++;
2046                 }
2047                 if (path->slots[i] >= nritems) {
2048                         if (i == *level)
2049                                 break;
2050                         *level = i + 1;
2051                         return 0;
2052                 }
2053                 if (i == 1) {
2054                         *level = i;
2055                         return 0;
2056                 }
2057 
2058                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2059                 eb = read_tree_block(fs_info, bytenr, ptr_gen);
2060                 if (IS_ERR(eb)) {
2061                         return PTR_ERR(eb);
2062                 } else if (!extent_buffer_uptodate(eb)) {
2063                         free_extent_buffer(eb);
2064                         return -EIO;
2065                 }
2066                 BUG_ON(btrfs_header_level(eb) != i - 1);
2067                 path->nodes[i - 1] = eb;
2068                 path->slots[i - 1] = 0;
2069         }
2070         return 1;
2071 }
2072 
2073 /*
2074  * invalidate extent cache for file extents whose key in range of
2075  * [min_key, max_key)
2076  */
2077 static int invalidate_extent_cache(struct btrfs_root *root,
2078                                    struct btrfs_key *min_key,
2079                                    struct btrfs_key *max_key)
2080 {
2081         struct btrfs_fs_info *fs_info = root->fs_info;
2082         struct inode *inode = NULL;
2083         u64 objectid;
2084         u64 start, end;
2085         u64 ino;
2086 
2087         objectid = min_key->objectid;
2088         while (1) {
2089                 cond_resched();
2090                 iput(inode);
2091 
2092                 if (objectid > max_key->objectid)
2093                         break;
2094 
2095                 inode = find_next_inode(root, objectid);
2096                 if (!inode)
2097                         break;
2098                 ino = btrfs_ino(BTRFS_I(inode));
2099 
2100                 if (ino > max_key->objectid) {
2101                         iput(inode);
2102                         break;
2103                 }
2104 
2105                 objectid = ino + 1;
2106                 if (!S_ISREG(inode->i_mode))
2107                         continue;
2108 
2109                 if (unlikely(min_key->objectid == ino)) {
2110                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2111                                 continue;
2112                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2113                                 start = 0;
2114                         else {
2115                                 start = min_key->offset;
2116                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2117                         }
2118                 } else {
2119                         start = 0;
2120                 }
2121 
2122                 if (unlikely(max_key->objectid == ino)) {
2123                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2124                                 continue;
2125                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2126                                 end = (u64)-1;
2127                         } else {
2128                                 if (max_key->offset == 0)
2129                                         continue;
2130                                 end = max_key->offset;
2131                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2132                                 end--;
2133                         }
2134                 } else {
2135                         end = (u64)-1;
2136                 }
2137 
2138                 /* the lock_extent waits for readpage to complete */
2139                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2140                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2141                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2142         }
2143         return 0;
2144 }
2145 
2146 static int find_next_key(struct btrfs_path *path, int level,
2147                          struct btrfs_key *key)
2148 
2149 {
2150         while (level < BTRFS_MAX_LEVEL) {
2151                 if (!path->nodes[level])
2152                         break;
2153                 if (path->slots[level] + 1 <
2154                     btrfs_header_nritems(path->nodes[level])) {
2155                         btrfs_node_key_to_cpu(path->nodes[level], key,
2156                                               path->slots[level] + 1);
2157                         return 0;
2158                 }
2159                 level++;
2160         }
2161         return 1;
2162 }
2163 
2164 /*
2165  * merge the relocated tree blocks in reloc tree with corresponding
2166  * fs tree.
2167  */
2168 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2169                                                struct btrfs_root *root)
2170 {
2171         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2172         LIST_HEAD(inode_list);
2173         struct btrfs_key key;
2174         struct btrfs_key next_key;
2175         struct btrfs_trans_handle *trans = NULL;
2176         struct btrfs_root *reloc_root;
2177         struct btrfs_root_item *root_item;
2178         struct btrfs_path *path;
2179         struct extent_buffer *leaf;
2180         int level;
2181         int max_level;
2182         int replaced = 0;
2183         int ret;
2184         int err = 0;
2185         u32 min_reserved;
2186 
2187         path = btrfs_alloc_path();
2188         if (!path)
2189                 return -ENOMEM;
2190         path->reada = READA_FORWARD;
2191 
2192         reloc_root = root->reloc_root;
2193         root_item = &reloc_root->root_item;
2194 
2195         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2196                 level = btrfs_root_level(root_item);
2197                 extent_buffer_get(reloc_root->node);
2198                 path->nodes[level] = reloc_root->node;
2199                 path->slots[level] = 0;
2200         } else {
2201                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2202 
2203                 level = root_item->drop_level;
2204                 BUG_ON(level == 0);
2205                 path->lowest_level = level;
2206                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2207                 path->lowest_level = 0;
2208                 if (ret < 0) {
2209                         btrfs_free_path(path);
2210                         return ret;
2211                 }
2212 
2213                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2214                                       path->slots[level]);
2215                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2216 
2217                 btrfs_unlock_up_safe(path, 0);
2218         }
2219 
2220         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2221         memset(&next_key, 0, sizeof(next_key));
2222 
2223         while (1) {
2224                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2225                                              BTRFS_RESERVE_FLUSH_ALL);
2226                 if (ret) {
2227                         err = ret;
2228                         goto out;
2229                 }
2230                 trans = btrfs_start_transaction(root, 0);
2231                 if (IS_ERR(trans)) {
2232                         err = PTR_ERR(trans);
2233                         trans = NULL;
2234                         goto out;
2235                 }
2236                 trans->block_rsv = rc->block_rsv;
2237 
2238                 replaced = 0;
2239                 max_level = level;
2240 
2241                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2242                 if (ret < 0) {
2243                         err = ret;
2244                         goto out;
2245                 }
2246                 if (ret > 0)
2247                         break;
2248 
2249                 if (!find_next_key(path, level, &key) &&
2250                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2251                         ret = 0;
2252                 } else {
2253                         ret = replace_path(trans, root, reloc_root, path,
2254                                            &next_key, level, max_level);
2255                 }
2256                 if (ret < 0) {
2257                         err = ret;
2258                         goto out;
2259                 }
2260 
2261                 if (ret > 0) {
2262                         level = ret;
2263                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2264                                               path->slots[level]);
2265                         replaced = 1;
2266                 }
2267 
2268                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2269                 if (ret > 0)
2270                         break;
2271 
2272                 BUG_ON(level == 0);
2273                 /*
2274                  * save the merging progress in the drop_progress.
2275                  * this is OK since root refs == 1 in this case.
2276                  */
2277                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2278                                path->slots[level]);
2279                 root_item->drop_level = level;
2280 
2281                 btrfs_end_transaction_throttle(trans);
2282                 trans = NULL;
2283 
2284                 btrfs_btree_balance_dirty(fs_info);
2285 
2286                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2287                         invalidate_extent_cache(root, &key, &next_key);
2288         }
2289 
2290         /*
2291          * handle the case only one block in the fs tree need to be
2292          * relocated and the block is tree root.
2293          */
2294         leaf = btrfs_lock_root_node(root);
2295         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2296         btrfs_tree_unlock(leaf);
2297         free_extent_buffer(leaf);
2298         if (ret < 0)
2299                 err = ret;
2300 out:
2301         btrfs_free_path(path);
2302 
2303         if (err == 0) {
2304                 memset(&root_item->drop_progress, 0,
2305                        sizeof(root_item->drop_progress));
2306                 root_item->drop_level = 0;
2307                 btrfs_set_root_refs(root_item, 0);
2308                 btrfs_update_reloc_root(trans, root);
2309         }
2310 
2311         if (trans)
2312                 btrfs_end_transaction_throttle(trans);
2313 
2314         btrfs_btree_balance_dirty(fs_info);
2315 
2316         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2317                 invalidate_extent_cache(root, &key, &next_key);
2318 
2319         return err;
2320 }
2321 
2322 static noinline_for_stack
2323 int prepare_to_merge(struct reloc_control *rc, int err)
2324 {
2325         struct btrfs_root *root = rc->extent_root;
2326         struct btrfs_fs_info *fs_info = root->fs_info;
2327         struct btrfs_root *reloc_root;
2328         struct btrfs_trans_handle *trans;
2329         LIST_HEAD(reloc_roots);
2330         u64 num_bytes = 0;
2331         int ret;
2332 
2333         mutex_lock(&fs_info->reloc_mutex);
2334         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2335         rc->merging_rsv_size += rc->nodes_relocated * 2;
2336         mutex_unlock(&fs_info->reloc_mutex);
2337 
2338 again:
2339         if (!err) {
2340                 num_bytes = rc->merging_rsv_size;
2341                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2342                                           BTRFS_RESERVE_FLUSH_ALL);
2343                 if (ret)
2344                         err = ret;
2345         }
2346 
2347         trans = btrfs_join_transaction(rc->extent_root);
2348         if (IS_ERR(trans)) {
2349                 if (!err)
2350                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2351                                                 num_bytes);
2352                 return PTR_ERR(trans);
2353         }
2354 
2355         if (!err) {
2356                 if (num_bytes != rc->merging_rsv_size) {
2357                         btrfs_end_transaction(trans);
2358                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2359                                                 num_bytes);
2360                         goto again;
2361                 }
2362         }
2363 
2364         rc->merge_reloc_tree = 1;
2365 
2366         while (!list_empty(&rc->reloc_roots)) {
2367                 reloc_root = list_entry(rc->reloc_roots.next,
2368                                         struct btrfs_root, root_list);
2369                 list_del_init(&reloc_root->root_list);
2370 
2371                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2372                 BUG_ON(IS_ERR(root));
2373                 BUG_ON(root->reloc_root != reloc_root);
2374 
2375                 /*
2376                  * set reference count to 1, so btrfs_recover_relocation
2377                  * knows it should resumes merging
2378                  */
2379                 if (!err)
2380                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2381                 btrfs_update_reloc_root(trans, root);
2382 
2383                 list_add(&reloc_root->root_list, &reloc_roots);
2384         }
2385 
2386         list_splice(&reloc_roots, &rc->reloc_roots);
2387 
2388         if (!err)
2389                 btrfs_commit_transaction(trans);
2390         else
2391                 btrfs_end_transaction(trans);
2392         return err;
2393 }
2394 
2395 static noinline_for_stack
2396 void free_reloc_roots(struct list_head *list)
2397 {
2398         struct btrfs_root *reloc_root;
2399 
2400         while (!list_empty(list)) {
2401                 reloc_root = list_entry(list->next, struct btrfs_root,
2402                                         root_list);
2403                 __del_reloc_root(reloc_root);
2404                 free_extent_buffer(reloc_root->node);
2405                 free_extent_buffer(reloc_root->commit_root);
2406                 reloc_root->node = NULL;
2407                 reloc_root->commit_root = NULL;
2408         }
2409 }
2410 
2411 static noinline_for_stack
2412 void merge_reloc_roots(struct reloc_control *rc)
2413 {
2414         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2415         struct btrfs_root *root;
2416         struct btrfs_root *reloc_root;
2417         LIST_HEAD(reloc_roots);
2418         int found = 0;
2419         int ret = 0;
2420 again:
2421         root = rc->extent_root;
2422 
2423         /*
2424          * this serializes us with btrfs_record_root_in_transaction,
2425          * we have to make sure nobody is in the middle of
2426          * adding their roots to the list while we are
2427          * doing this splice
2428          */
2429         mutex_lock(&fs_info->reloc_mutex);
2430         list_splice_init(&rc->reloc_roots, &reloc_roots);
2431         mutex_unlock(&fs_info->reloc_mutex);
2432 
2433         while (!list_empty(&reloc_roots)) {
2434                 found = 1;
2435                 reloc_root = list_entry(reloc_roots.next,
2436                                         struct btrfs_root, root_list);
2437 
2438                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2439                         root = read_fs_root(fs_info,
2440                                             reloc_root->root_key.offset);
2441                         BUG_ON(IS_ERR(root));
2442                         BUG_ON(root->reloc_root != reloc_root);
2443 
2444                         ret = merge_reloc_root(rc, root);
2445                         if (ret) {
2446                                 if (list_empty(&reloc_root->root_list))
2447                                         list_add_tail(&reloc_root->root_list,
2448                                                       &reloc_roots);
2449                                 goto out;
2450                         }
2451                 } else {
2452                         list_del_init(&reloc_root->root_list);
2453                 }
2454 
2455                 ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
2456                 if (ret < 0) {
2457                         if (list_empty(&reloc_root->root_list))
2458                                 list_add_tail(&reloc_root->root_list,
2459                                               &reloc_roots);
2460                         goto out;
2461                 }
2462         }
2463 
2464         if (found) {
2465                 found = 0;
2466                 goto again;
2467         }
2468 out:
2469         if (ret) {
2470                 btrfs_handle_fs_error(fs_info, ret, NULL);
2471                 if (!list_empty(&reloc_roots))
2472                         free_reloc_roots(&reloc_roots);
2473 
2474                 /* new reloc root may be added */
2475                 mutex_lock(&fs_info->reloc_mutex);
2476                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2477                 mutex_unlock(&fs_info->reloc_mutex);
2478                 if (!list_empty(&reloc_roots))
2479                         free_reloc_roots(&reloc_roots);
2480         }
2481 
2482         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2483 }
2484 
2485 static void free_block_list(struct rb_root *blocks)
2486 {
2487         struct tree_block *block;
2488         struct rb_node *rb_node;
2489         while ((rb_node = rb_first(blocks))) {
2490                 block = rb_entry(rb_node, struct tree_block, rb_node);
2491                 rb_erase(rb_node, blocks);
2492                 kfree(block);
2493         }
2494 }
2495 
2496 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2497                                       struct btrfs_root *reloc_root)
2498 {
2499         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2500         struct btrfs_root *root;
2501 
2502         if (reloc_root->last_trans == trans->transid)
2503                 return 0;
2504 
2505         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2506         BUG_ON(IS_ERR(root));
2507         BUG_ON(root->reloc_root != reloc_root);
2508 
2509         return btrfs_record_root_in_trans(trans, root);
2510 }
2511 
2512 static noinline_for_stack
2513 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2514                                      struct reloc_control *rc,
2515                                      struct backref_node *node,
2516                                      struct backref_edge *edges[])
2517 {
2518         struct backref_node *next;
2519         struct btrfs_root *root;
2520         int index = 0;
2521 
2522         next = node;
2523         while (1) {
2524                 cond_resched();
2525                 next = walk_up_backref(next, edges, &index);
2526                 root = next->root;
2527                 BUG_ON(!root);
2528                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2529 
2530                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2531                         record_reloc_root_in_trans(trans, root);
2532                         break;
2533                 }
2534 
2535                 btrfs_record_root_in_trans(trans, root);
2536                 root = root->reloc_root;
2537 
2538                 if (next->new_bytenr != root->node->start) {
2539                         BUG_ON(next->new_bytenr);
2540                         BUG_ON(!list_empty(&next->list));
2541                         next->new_bytenr = root->node->start;
2542                         next->root = root;
2543                         list_add_tail(&next->list,
2544                                       &rc->backref_cache.changed);
2545                         __mark_block_processed(rc, next);
2546                         break;
2547                 }
2548 
2549                 WARN_ON(1);
2550                 root = NULL;
2551                 next = walk_down_backref(edges, &index);
2552                 if (!next || next->level <= node->level)
2553                         break;
2554         }
2555         if (!root)
2556                 return NULL;
2557 
2558         next = node;
2559         /* setup backref node path for btrfs_reloc_cow_block */
2560         while (1) {
2561                 rc->backref_cache.path[next->level] = next;
2562                 if (--index < 0)
2563                         break;
2564                 next = edges[index]->node[UPPER];
2565         }
2566         return root;
2567 }
2568 
2569 /*
2570  * select a tree root for relocation. return NULL if the block
2571  * is reference counted. we should use do_relocation() in this
2572  * case. return a tree root pointer if the block isn't reference
2573  * counted. return -ENOENT if the block is root of reloc tree.
2574  */
2575 static noinline_for_stack
2576 struct btrfs_root *select_one_root(struct backref_node *node)
2577 {
2578         struct backref_node *next;
2579         struct btrfs_root *root;
2580         struct btrfs_root *fs_root = NULL;
2581         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2582         int index = 0;
2583 
2584         next = node;
2585         while (1) {
2586                 cond_resched();
2587                 next = walk_up_backref(next, edges, &index);
2588                 root = next->root;
2589                 BUG_ON(!root);
2590 
2591                 /* no other choice for non-references counted tree */
2592                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2593                         return root;
2594 
2595                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2596                         fs_root = root;
2597 
2598                 if (next != node)
2599                         return NULL;
2600 
2601                 next = walk_down_backref(edges, &index);
2602                 if (!next || next->level <= node->level)
2603                         break;
2604         }
2605 
2606         if (!fs_root)
2607                 return ERR_PTR(-ENOENT);
2608         return fs_root;
2609 }
2610 
2611 static noinline_for_stack
2612 u64 calcu_metadata_size(struct reloc_control *rc,
2613                         struct backref_node *node, int reserve)
2614 {
2615         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2616         struct backref_node *next = node;
2617         struct backref_edge *edge;
2618         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2619         u64 num_bytes = 0;
2620         int index = 0;
2621 
2622         BUG_ON(reserve && node->processed);
2623 
2624         while (next) {
2625                 cond_resched();
2626                 while (1) {
2627                         if (next->processed && (reserve || next != node))
2628                                 break;
2629 
2630                         num_bytes += fs_info->nodesize;
2631 
2632                         if (list_empty(&next->upper))
2633                                 break;
2634 
2635                         edge = list_entry(next->upper.next,
2636                                           struct backref_edge, list[LOWER]);
2637                         edges[index++] = edge;
2638                         next = edge->node[UPPER];
2639                 }
2640                 next = walk_down_backref(edges, &index);
2641         }
2642         return num_bytes;
2643 }
2644 
2645 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2646                                   struct reloc_control *rc,
2647                                   struct backref_node *node)
2648 {
2649         struct btrfs_root *root = rc->extent_root;
2650         struct btrfs_fs_info *fs_info = root->fs_info;
2651         u64 num_bytes;
2652         int ret;
2653         u64 tmp;
2654 
2655         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2656 
2657         trans->block_rsv = rc->block_rsv;
2658         rc->reserved_bytes += num_bytes;
2659 
2660         /*
2661          * We are under a transaction here so we can only do limited flushing.
2662          * If we get an enospc just kick back -EAGAIN so we know to drop the
2663          * transaction and try to refill when we can flush all the things.
2664          */
2665         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2666                                 BTRFS_RESERVE_FLUSH_LIMIT);
2667         if (ret) {
2668                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2669                 while (tmp <= rc->reserved_bytes)
2670                         tmp <<= 1;
2671                 /*
2672                  * only one thread can access block_rsv at this point,
2673                  * so we don't need hold lock to protect block_rsv.
2674                  * we expand more reservation size here to allow enough
2675                  * space for relocation and we will return eailer in
2676                  * enospc case.
2677                  */
2678                 rc->block_rsv->size = tmp + fs_info->nodesize *
2679                                       RELOCATION_RESERVED_NODES;
2680                 return -EAGAIN;
2681         }
2682 
2683         return 0;
2684 }
2685 
2686 /*
2687  * relocate a block tree, and then update pointers in upper level
2688  * blocks that reference the block to point to the new location.
2689  *
2690  * if called by link_to_upper, the block has already been relocated.
2691  * in that case this function just updates pointers.
2692  */
2693 static int do_relocation(struct btrfs_trans_handle *trans,
2694                          struct reloc_control *rc,
2695                          struct backref_node *node,
2696                          struct btrfs_key *key,
2697                          struct btrfs_path *path, int lowest)
2698 {
2699         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2700         struct backref_node *upper;
2701         struct backref_edge *edge;
2702         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2703         struct btrfs_root *root;
2704         struct extent_buffer *eb;
2705         u32 blocksize;
2706         u64 bytenr;
2707         u64 generation;
2708         int slot;
2709         int ret;
2710         int err = 0;
2711 
2712         BUG_ON(lowest && node->eb);
2713 
2714         path->lowest_level = node->level + 1;
2715         rc->backref_cache.path[node->level] = node;
2716         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2717                 cond_resched();
2718 
2719                 upper = edge->node[UPPER];
2720                 root = select_reloc_root(trans, rc, upper, edges);
2721                 BUG_ON(!root);
2722 
2723                 if (upper->eb && !upper->locked) {
2724                         if (!lowest) {
2725                                 ret = btrfs_bin_search(upper->eb, key,
2726                                                        upper->level, &slot);
2727                                 BUG_ON(ret);
2728                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2729                                 if (node->eb->start == bytenr)
2730                                         goto next;
2731                         }
2732                         drop_node_buffer(upper);
2733                 }
2734 
2735                 if (!upper->eb) {
2736                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2737                         if (ret) {
2738                                 if (ret < 0)
2739                                         err = ret;
2740                                 else
2741                                         err = -ENOENT;
2742 
2743                                 btrfs_release_path(path);
2744                                 break;
2745                         }
2746 
2747                         if (!upper->eb) {
2748                                 upper->eb = path->nodes[upper->level];
2749                                 path->nodes[upper->level] = NULL;
2750                         } else {
2751                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2752                         }
2753 
2754                         upper->locked = 1;
2755                         path->locks[upper->level] = 0;
2756 
2757                         slot = path->slots[upper->level];
2758                         btrfs_release_path(path);
2759                 } else {
2760                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2761                                                &slot);
2762                         BUG_ON(ret);
2763                 }
2764 
2765                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2766                 if (lowest) {
2767                         if (bytenr != node->bytenr) {
2768                                 btrfs_err(root->fs_info,
2769                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2770                                           bytenr, node->bytenr, slot,
2771                                           upper->eb->start);
2772                                 err = -EIO;
2773                                 goto next;
2774                         }
2775                 } else {
2776                         if (node->eb->start == bytenr)
2777                                 goto next;
2778                 }
2779 
2780                 blocksize = root->fs_info->nodesize;
2781                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2782                 eb = read_tree_block(fs_info, bytenr, generation);
2783                 if (IS_ERR(eb)) {
2784                         err = PTR_ERR(eb);
2785                         goto next;
2786                 } else if (!extent_buffer_uptodate(eb)) {
2787                         free_extent_buffer(eb);
2788                         err = -EIO;
2789                         goto next;
2790                 }
2791                 btrfs_tree_lock(eb);
2792                 btrfs_set_lock_blocking(eb);
2793 
2794                 if (!node->eb) {
2795                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2796                                               slot, &eb);
2797                         btrfs_tree_unlock(eb);
2798                         free_extent_buffer(eb);
2799                         if (ret < 0) {
2800                                 err = ret;
2801                                 goto next;
2802                         }
2803                         BUG_ON(node->eb != eb);
2804                 } else {
2805                         btrfs_set_node_blockptr(upper->eb, slot,
2806                                                 node->eb->start);
2807                         btrfs_set_node_ptr_generation(upper->eb, slot,
2808                                                       trans->transid);
2809                         btrfs_mark_buffer_dirty(upper->eb);
2810 
2811                         ret = btrfs_inc_extent_ref(trans, root,
2812                                                 node->eb->start, blocksize,
2813                                                 upper->eb->start,
2814                                                 btrfs_header_owner(upper->eb),
2815                                                 node->level, 0);
2816                         BUG_ON(ret);
2817 
2818                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2819                         BUG_ON(ret);
2820                 }
2821 next:
2822                 if (!upper->pending)
2823                         drop_node_buffer(upper);
2824                 else
2825                         unlock_node_buffer(upper);
2826                 if (err)
2827                         break;
2828         }
2829 
2830         if (!err && node->pending) {
2831                 drop_node_buffer(node);
2832                 list_move_tail(&node->list, &rc->backref_cache.changed);
2833                 node->pending = 0;
2834         }
2835 
2836         path->lowest_level = 0;
2837         BUG_ON(err == -ENOSPC);
2838         return err;
2839 }
2840 
2841 static int link_to_upper(struct btrfs_trans_handle *trans,
2842                          struct reloc_control *rc,
2843                          struct backref_node *node,
2844                          struct btrfs_path *path)
2845 {
2846         struct btrfs_key key;
2847 
2848         btrfs_node_key_to_cpu(node->eb, &key, 0);
2849         return do_relocation(trans, rc, node, &key, path, 0);
2850 }
2851 
2852 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2853                                 struct reloc_control *rc,
2854                                 struct btrfs_path *path, int err)
2855 {
2856         LIST_HEAD(list);
2857         struct backref_cache *cache = &rc->backref_cache;
2858         struct backref_node *node;
2859         int level;
2860         int ret;
2861 
2862         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2863                 while (!list_empty(&cache->pending[level])) {
2864                         node = list_entry(cache->pending[level].next,
2865                                           struct backref_node, list);
2866                         list_move_tail(&node->list, &list);
2867                         BUG_ON(!node->pending);
2868 
2869                         if (!err) {
2870                                 ret = link_to_upper(trans, rc, node, path);
2871                                 if (ret < 0)
2872                                         err = ret;
2873                         }
2874                 }
2875                 list_splice_init(&list, &cache->pending[level]);
2876         }
2877         return err;
2878 }
2879 
2880 static void mark_block_processed(struct reloc_control *rc,
2881                                  u64 bytenr, u32 blocksize)
2882 {
2883         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2884                         EXTENT_DIRTY);
2885 }
2886 
2887 static void __mark_block_processed(struct reloc_control *rc,
2888                                    struct backref_node *node)
2889 {
2890         u32 blocksize;
2891         if (node->level == 0 ||
2892             in_block_group(node->bytenr, rc->block_group)) {
2893                 blocksize = rc->extent_root->fs_info->nodesize;
2894                 mark_block_processed(rc, node->bytenr, blocksize);
2895         }
2896         node->processed = 1;
2897 }
2898 
2899 /*
2900  * mark a block and all blocks directly/indirectly reference the block
2901  * as processed.
2902  */
2903 static void update_processed_blocks(struct reloc_control *rc,
2904                                     struct backref_node *node)
2905 {
2906         struct backref_node *next = node;
2907         struct backref_edge *edge;
2908         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2909         int index = 0;
2910 
2911         while (next) {
2912                 cond_resched();
2913                 while (1) {
2914                         if (next->processed)
2915                                 break;
2916 
2917                         __mark_block_processed(rc, next);
2918 
2919                         if (list_empty(&next->upper))
2920                                 break;
2921 
2922                         edge = list_entry(next->upper.next,
2923                                           struct backref_edge, list[LOWER]);
2924                         edges[index++] = edge;
2925                         next = edge->node[UPPER];
2926                 }
2927                 next = walk_down_backref(edges, &index);
2928         }
2929 }
2930 
2931 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2932 {
2933         u32 blocksize = rc->extent_root->fs_info->nodesize;
2934 
2935         if (test_range_bit(&rc->processed_blocks, bytenr,
2936                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2937                 return 1;
2938         return 0;
2939 }
2940 
2941 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
2942                               struct tree_block *block)
2943 {
2944         struct extent_buffer *eb;
2945 
2946         BUG_ON(block->key_ready);
2947         eb = read_tree_block(fs_info, block->bytenr, block->key.offset);
2948         if (IS_ERR(eb)) {
2949                 return PTR_ERR(eb);
2950         } else if (!extent_buffer_uptodate(eb)) {
2951                 free_extent_buffer(eb);
2952                 return -EIO;
2953         }
2954         WARN_ON(btrfs_header_level(eb) != block->level);
2955         if (block->level == 0)
2956                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2957         else
2958                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2959         free_extent_buffer(eb);
2960         block->key_ready = 1;
2961         return 0;
2962 }
2963 
2964 /*
2965  * helper function to relocate a tree block
2966  */
2967 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2968                                 struct reloc_control *rc,
2969                                 struct backref_node *node,
2970                                 struct btrfs_key *key,
2971                                 struct btrfs_path *path)
2972 {
2973         struct btrfs_root *root;
2974         int ret = 0;
2975 
2976         if (!node)
2977                 return 0;
2978 
2979         BUG_ON(node->processed);
2980         root = select_one_root(node);
2981         if (root == ERR_PTR(-ENOENT)) {
2982                 update_processed_blocks(rc, node);
2983                 goto out;
2984         }
2985 
2986         if (!root || test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2987                 ret = reserve_metadata_space(trans, rc, node);
2988                 if (ret)
2989                         goto out;
2990         }
2991 
2992         if (root) {
2993                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
2994                         BUG_ON(node->new_bytenr);
2995                         BUG_ON(!list_empty(&node->list));
2996                         btrfs_record_root_in_trans(trans, root);
2997                         root = root->reloc_root;
2998                         node->new_bytenr = root->node->start;
2999                         node->root = root;
3000                         list_add_tail(&node->list, &rc->backref_cache.changed);
3001                 } else {
3002                         path->lowest_level = node->level;
3003                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3004                         btrfs_release_path(path);
3005                         if (ret > 0)
3006                                 ret = 0;
3007                 }
3008                 if (!ret)
3009                         update_processed_blocks(rc, node);
3010         } else {
3011                 ret = do_relocation(trans, rc, node, key, path, 1);
3012         }
3013 out:
3014         if (ret || node->level == 0 || node->cowonly)
3015                 remove_backref_node(&rc->backref_cache, node);
3016         return ret;
3017 }
3018 
3019 /*
3020  * relocate a list of blocks
3021  */
3022 static noinline_for_stack
3023 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3024                          struct reloc_control *rc, struct rb_root *blocks)
3025 {
3026         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3027         struct backref_node *node;
3028         struct btrfs_path *path;
3029         struct tree_block *block;
3030         struct rb_node *rb_node;
3031         int ret;
3032         int err = 0;
3033 
3034         path = btrfs_alloc_path();
3035         if (!path) {
3036                 err = -ENOMEM;
3037                 goto out_free_blocks;
3038         }
3039 
3040         rb_node = rb_first(blocks);
3041         while (rb_node) {
3042                 block = rb_entry(rb_node, struct tree_block, rb_node);
3043                 if (!block->key_ready)
3044                         readahead_tree_block(fs_info, block->bytenr);
3045                 rb_node = rb_next(rb_node);
3046         }
3047 
3048         rb_node = rb_first(blocks);
3049         while (rb_node) {
3050                 block = rb_entry(rb_node, struct tree_block, rb_node);
3051                 if (!block->key_ready) {
3052                         err = get_tree_block_key(fs_info, block);
3053                         if (err)
3054                                 goto out_free_path;
3055                 }
3056                 rb_node = rb_next(rb_node);
3057         }
3058 
3059         rb_node = rb_first(blocks);
3060         while (rb_node) {
3061                 block = rb_entry(rb_node, struct tree_block, rb_node);
3062 
3063                 node = build_backref_tree(rc, &block->key,
3064                                           block->level, block->bytenr);
3065                 if (IS_ERR(node)) {
3066                         err = PTR_ERR(node);
3067                         goto out;
3068                 }
3069 
3070                 ret = relocate_tree_block(trans, rc, node, &block->key,
3071                                           path);
3072                 if (ret < 0) {
3073                         if (ret != -EAGAIN || rb_node == rb_first(blocks))
3074                                 err = ret;
3075                         goto out;
3076                 }
3077                 rb_node = rb_next(rb_node);
3078         }
3079 out:
3080         err = finish_pending_nodes(trans, rc, path, err);
3081 
3082 out_free_path:
3083         btrfs_free_path(path);
3084 out_free_blocks:
3085         free_block_list(blocks);
3086         return err;
3087 }
3088 
3089 static noinline_for_stack
3090 int prealloc_file_extent_cluster(struct inode *inode,
3091                                  struct file_extent_cluster *cluster)
3092 {
3093         u64 alloc_hint = 0;
3094         u64 start;
3095         u64 end;
3096         u64 offset = BTRFS_I(inode)->index_cnt;
3097         u64 num_bytes;
3098         int nr = 0;
3099         int ret = 0;
3100         u64 prealloc_start = cluster->start - offset;
3101         u64 prealloc_end = cluster->end - offset;
3102         u64 cur_offset;
3103         struct extent_changeset *data_reserved = NULL;
3104 
3105         BUG_ON(cluster->start != cluster->boundary[0]);
3106         inode_lock(inode);
3107 
3108         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3109                                           prealloc_end + 1 - prealloc_start);
3110         if (ret)
3111                 goto out;
3112 
3113         cur_offset = prealloc_start;
3114         while (nr < cluster->nr) {
3115                 start = cluster->boundary[nr] - offset;
3116                 if (nr + 1 < cluster->nr)
3117                         end = cluster->boundary[nr + 1] - 1 - offset;
3118                 else
3119                         end = cluster->end - offset;
3120 
3121                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3122                 num_bytes = end + 1 - start;
3123                 if (cur_offset < start)
3124                         btrfs_free_reserved_data_space(inode, data_reserved,
3125                                         cur_offset, start - cur_offset);
3126                 ret = btrfs_prealloc_file_range(inode, 0, start,
3127                                                 num_bytes, num_bytes,
3128                                                 end + 1, &alloc_hint);
3129                 cur_offset = end + 1;
3130                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3131                 if (ret)
3132                         break;
3133                 nr++;
3134         }
3135         if (cur_offset < prealloc_end)
3136                 btrfs_free_reserved_data_space(inode, data_reserved,
3137                                 cur_offset, prealloc_end + 1 - cur_offset);
3138 out:
3139         inode_unlock(inode);
3140         extent_changeset_free(data_reserved);
3141         return ret;
3142 }
3143 
3144 static noinline_for_stack
3145 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3146                          u64 block_start)
3147 {
3148         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3149         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3150         struct extent_map *em;
3151         int ret = 0;
3152 
3153         em = alloc_extent_map();
3154         if (!em)
3155                 return -ENOMEM;
3156 
3157         em->start = start;
3158         em->len = end + 1 - start;
3159         em->block_len = em->len;
3160         em->block_start = block_start;
3161         em->bdev = fs_info->fs_devices->latest_bdev;
3162         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3163 
3164         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3165         while (1) {
3166                 write_lock(&em_tree->lock);
3167                 ret = add_extent_mapping(em_tree, em, 0);
3168                 write_unlock(&em_tree->lock);
3169                 if (ret != -EEXIST) {
3170                         free_extent_map(em);
3171                         break;
3172                 }
3173                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3174         }
3175         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3176         return ret;
3177 }
3178 
3179 static int relocate_file_extent_cluster(struct inode *inode,
3180                                         struct file_extent_cluster *cluster)
3181 {
3182         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3183         u64 page_start;
3184         u64 page_end;
3185         u64 offset = BTRFS_I(inode)->index_cnt;
3186         unsigned long index;
3187         unsigned long last_index;
3188         struct page *page;
3189         struct file_ra_state *ra;
3190         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3191         int nr = 0;
3192         int ret = 0;
3193 
3194         if (!cluster->nr)
3195                 return 0;
3196 
3197         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3198         if (!ra)
3199                 return -ENOMEM;
3200 
3201         ret = prealloc_file_extent_cluster(inode, cluster);
3202         if (ret)
3203                 goto out;
3204 
3205         file_ra_state_init(ra, inode->i_mapping);
3206 
3207         ret = setup_extent_mapping(inode, cluster->start - offset,
3208                                    cluster->end - offset, cluster->start);
3209         if (ret)
3210                 goto out;
3211 
3212         index = (cluster->start - offset) >> PAGE_SHIFT;
3213         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3214         while (index <= last_index) {
3215                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3216                                 PAGE_SIZE);
3217                 if (ret)
3218                         goto out;
3219 
3220                 page = find_lock_page(inode->i_mapping, index);
3221                 if (!page) {
3222                         page_cache_sync_readahead(inode->i_mapping,
3223                                                   ra, NULL, index,
3224                                                   last_index + 1 - index);
3225                         page = find_or_create_page(inode->i_mapping, index,
3226                                                    mask);
3227                         if (!page) {
3228                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3229                                                         PAGE_SIZE);
3230                                 ret = -ENOMEM;
3231                                 goto out;
3232                         }
3233                 }
3234 
3235                 if (PageReadahead(page)) {
3236                         page_cache_async_readahead(inode->i_mapping,
3237                                                    ra, NULL, page, index,
3238                                                    last_index + 1 - index);
3239                 }
3240 
3241                 if (!PageUptodate(page)) {
3242                         btrfs_readpage(NULL, page);
3243                         lock_page(page);
3244                         if (!PageUptodate(page)) {
3245                                 unlock_page(page);
3246                                 put_page(page);
3247                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3248                                                         PAGE_SIZE);
3249                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3250                                                                PAGE_SIZE);
3251                                 ret = -EIO;
3252                                 goto out;
3253                         }
3254                 }
3255 
3256                 page_start = page_offset(page);
3257                 page_end = page_start + PAGE_SIZE - 1;
3258 
3259                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3260 
3261                 set_page_extent_mapped(page);
3262 
3263                 if (nr < cluster->nr &&
3264                     page_start + offset == cluster->boundary[nr]) {
3265                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3266                                         page_start, page_end,
3267                                         EXTENT_BOUNDARY);
3268                         nr++;
3269                 }
3270 
3271                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3272                                                 NULL, 0);
3273                 if (ret) {
3274                         unlock_page(page);
3275                         put_page(page);
3276                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3277                                                          PAGE_SIZE);
3278                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3279                                                        PAGE_SIZE);
3280 
3281                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3282                                           page_start, page_end,
3283                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3284                         goto out;
3285 
3286                 }
3287                 set_page_dirty(page);
3288 
3289                 unlock_extent(&BTRFS_I(inode)->io_tree,
3290                               page_start, page_end);
3291                 unlock_page(page);
3292                 put_page(page);
3293 
3294                 index++;
3295                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
3296                 balance_dirty_pages_ratelimited(inode->i_mapping);
3297                 btrfs_throttle(fs_info);
3298         }
3299         WARN_ON(nr != cluster->nr);
3300 out:
3301         kfree(ra);
3302         return ret;
3303 }
3304 
3305 static noinline_for_stack
3306 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3307                          struct file_extent_cluster *cluster)
3308 {
3309         int ret;
3310 
3311         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3312                 ret = relocate_file_extent_cluster(inode, cluster);
3313                 if (ret)
3314                         return ret;
3315                 cluster->nr = 0;
3316         }
3317 
3318         if (!cluster->nr)
3319                 cluster->start = extent_key->objectid;
3320         else
3321                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3322         cluster->end = extent_key->objectid + extent_key->offset - 1;
3323         cluster->boundary[cluster->nr] = extent_key->objectid;
3324         cluster->nr++;
3325 
3326         if (cluster->nr >= MAX_EXTENTS) {
3327                 ret = relocate_file_extent_cluster(inode, cluster);
3328                 if (ret)
3329                         return ret;
3330                 cluster->nr = 0;
3331         }
3332         return 0;
3333 }
3334 
3335 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3336 static int get_ref_objectid_v0(struct reloc_control *rc,
3337                                struct btrfs_path *path,
3338                                struct btrfs_key *extent_key,
3339                                u64 *ref_objectid, int *path_change)
3340 {
3341         struct btrfs_key key;
3342         struct extent_buffer *leaf;
3343         struct btrfs_extent_ref_v0 *ref0;
3344         int ret;
3345         int slot;
3346 
3347         leaf = path->nodes[0];
3348         slot = path->slots[0];
3349         while (1) {
3350                 if (slot >= btrfs_header_nritems(leaf)) {
3351                         ret = btrfs_next_leaf(rc->extent_root, path);
3352                         if (ret < 0)
3353                                 return ret;
3354                         BUG_ON(ret > 0);
3355                         leaf = path->nodes[0];
3356                         slot = path->slots[0];
3357                         if (path_change)
3358                                 *path_change = 1;
3359                 }
3360                 btrfs_item_key_to_cpu(leaf, &key, slot);
3361                 if (key.objectid != extent_key->objectid)
3362                         return -ENOENT;
3363 
3364                 if (key.type != BTRFS_EXTENT_REF_V0_KEY) {
3365                         slot++;
3366                         continue;
3367                 }
3368                 ref0 = btrfs_item_ptr(leaf, slot,
3369                                 struct btrfs_extent_ref_v0);
3370                 *ref_objectid = btrfs_ref_objectid_v0(leaf, ref0);
3371                 break;
3372         }
3373         return 0;
3374 }
3375 #endif
3376 
3377 /*
3378  * helper to add a tree block to the list.
3379  * the major work is getting the generation and level of the block
3380  */
3381 static int add_tree_block(struct reloc_control *rc,
3382                           struct btrfs_key *extent_key,
3383                           struct btrfs_path *path,
3384                           struct rb_root *blocks)
3385 {
3386         struct extent_buffer *eb;
3387         struct btrfs_extent_item *ei;
3388         struct btrfs_tree_block_info *bi;
3389         struct tree_block *block;
3390         struct rb_node *rb_node;
3391         u32 item_size;
3392         int level = -1;
3393         u64 generation;
3394 
3395         eb =  path->nodes[0];
3396         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3397 
3398         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3399             item_size >= sizeof(*ei) + sizeof(*bi)) {
3400                 ei = btrfs_item_ptr(eb, path->slots[0],
3401                                 struct btrfs_extent_item);
3402                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3403                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3404                         level = btrfs_tree_block_level(eb, bi);
3405                 } else {
3406                         level = (int)extent_key->offset;
3407                 }
3408                 generation = btrfs_extent_generation(eb, ei);
3409         } else {
3410 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3411                 u64 ref_owner;
3412                 int ret;
3413 
3414                 BUG_ON(item_size != sizeof(struct btrfs_extent_item_v0));
3415                 ret = get_ref_objectid_v0(rc, path, extent_key,
3416                                           &ref_owner, NULL);
3417                 if (ret < 0)
3418                         return ret;
3419                 BUG_ON(ref_owner >= BTRFS_MAX_LEVEL);
3420                 level = (int)ref_owner;
3421                 /* FIXME: get real generation */
3422                 generation = 0;
3423 #else
3424                 BUG();
3425 #endif
3426         }
3427 
3428         btrfs_release_path(path);
3429 
3430         BUG_ON(level == -1);
3431 
3432         block = kmalloc(sizeof(*block), GFP_NOFS);
3433         if (!block)
3434                 return -ENOMEM;
3435 
3436         block->bytenr = extent_key->objectid;
3437         block->key.objectid = rc->extent_root->fs_info->nodesize;
3438         block->key.offset = generation;
3439         block->level = level;
3440         block->key_ready = 0;
3441 
3442         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3443         if (rb_node)
3444                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3445 
3446         return 0;
3447 }
3448 
3449 /*
3450  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3451  */
3452 static int __add_tree_block(struct reloc_control *rc,
3453                             u64 bytenr, u32 blocksize,
3454                             struct rb_root *blocks)
3455 {
3456         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3457         struct btrfs_path *path;
3458         struct btrfs_key key;
3459         int ret;
3460         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3461 
3462         if (tree_block_processed(bytenr, rc))
3463                 return 0;
3464 
3465         if (tree_search(blocks, bytenr))
3466                 return 0;
3467 
3468         path = btrfs_alloc_path();
3469         if (!path)
3470                 return -ENOMEM;
3471 again:
3472         key.objectid = bytenr;
3473         if (skinny) {
3474                 key.type = BTRFS_METADATA_ITEM_KEY;
3475                 key.offset = (u64)-1;
3476         } else {
3477                 key.type = BTRFS_EXTENT_ITEM_KEY;
3478                 key.offset = blocksize;
3479         }
3480 
3481         path->search_commit_root = 1;
3482         path->skip_locking = 1;
3483         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3484         if (ret < 0)
3485                 goto out;
3486 
3487         if (ret > 0 && skinny) {
3488                 if (path->slots[0]) {
3489                         path->slots[0]--;
3490                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3491                                               path->slots[0]);
3492                         if (key.objectid == bytenr &&
3493                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3494                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3495                               key.offset == blocksize)))
3496                                 ret = 0;
3497                 }
3498 
3499                 if (ret) {
3500                         skinny = false;
3501                         btrfs_release_path(path);
3502                         goto again;
3503                 }
3504         }
3505         if (ret) {
3506                 ASSERT(ret == 1);
3507                 btrfs_print_leaf(path->nodes[0]);
3508                 btrfs_err(fs_info,
3509              "tree block extent item (%llu) is not found in extent tree",
3510                      bytenr);
3511                 WARN_ON(1);
3512                 ret = -EINVAL;
3513                 goto out;
3514         }
3515 
3516         ret = add_tree_block(rc, &key, path, blocks);
3517 out:
3518         btrfs_free_path(path);
3519         return ret;
3520 }
3521 
3522 /*
3523  * helper to check if the block use full backrefs for pointers in it
3524  */
3525 static int block_use_full_backref(struct reloc_control *rc,
3526                                   struct extent_buffer *eb)
3527 {
3528         u64 flags;
3529         int ret;
3530 
3531         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3532             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3533                 return 1;
3534 
3535         ret = btrfs_lookup_extent_info(NULL, rc->extent_root->fs_info,
3536                                        eb->start, btrfs_header_level(eb), 1,
3537                                        NULL, &flags);
3538         BUG_ON(ret);
3539 
3540         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3541                 ret = 1;
3542         else
3543                 ret = 0;
3544         return ret;
3545 }
3546 
3547 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3548                                     struct btrfs_block_group_cache *block_group,
3549                                     struct inode *inode,
3550                                     u64 ino)
3551 {
3552         struct btrfs_key key;
3553         struct btrfs_root *root = fs_info->tree_root;
3554         struct btrfs_trans_handle *trans;
3555         int ret = 0;
3556 
3557         if (inode)
3558                 goto truncate;
3559 
3560         key.objectid = ino;
3561         key.type = BTRFS_INODE_ITEM_KEY;
3562         key.offset = 0;
3563 
3564         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
3565         if (IS_ERR(inode) || is_bad_inode(inode)) {
3566                 if (!IS_ERR(inode))
3567                         iput(inode);
3568                 return -ENOENT;
3569         }
3570 
3571 truncate:
3572         ret = btrfs_check_trunc_cache_free_space(fs_info,
3573                                                  &fs_info->global_block_rsv);
3574         if (ret)
3575                 goto out;
3576 
3577         trans = btrfs_join_transaction(root);
3578         if (IS_ERR(trans)) {
3579                 ret = PTR_ERR(trans);
3580                 goto out;
3581         }
3582 
3583         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3584 
3585         btrfs_end_transaction(trans);
3586         btrfs_btree_balance_dirty(fs_info);
3587 out:
3588         iput(inode);
3589         return ret;
3590 }
3591 
3592 /*
3593  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3594  * this function scans fs tree to find blocks reference the data extent
3595  */
3596 static int find_data_references(struct reloc_control *rc,
3597                                 struct btrfs_key *extent_key,
3598                                 struct extent_buffer *leaf,
3599                                 struct btrfs_extent_data_ref *ref,
3600                                 struct rb_root *blocks)
3601 {
3602         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3603         struct btrfs_path *path;
3604         struct tree_block *block;
3605         struct btrfs_root *root;
3606         struct btrfs_file_extent_item *fi;
3607         struct rb_node *rb_node;
3608         struct btrfs_key key;
3609         u64 ref_root;
3610         u64 ref_objectid;
3611         u64 ref_offset;
3612         u32 ref_count;
3613         u32 nritems;
3614         int err = 0;
3615         int added = 0;
3616         int counted;
3617         int ret;
3618 
3619         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3620         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3621         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3622         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3623 
3624         /*
3625          * This is an extent belonging to the free space cache, lets just delete
3626          * it and redo the search.
3627          */
3628         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3629                 ret = delete_block_group_cache(fs_info, rc->block_group,
3630                                                NULL, ref_objectid);
3631                 if (ret != -ENOENT)
3632                         return ret;
3633                 ret = 0;
3634         }
3635 
3636         path = btrfs_alloc_path();
3637         if (!path)
3638                 return -ENOMEM;
3639         path->reada = READA_FORWARD;
3640 
3641         root = read_fs_root(fs_info, ref_root);
3642         if (IS_ERR(root)) {
3643                 err = PTR_ERR(root);
3644                 goto out;
3645         }
3646 
3647         key.objectid = ref_objectid;
3648         key.type = BTRFS_EXTENT_DATA_KEY;
3649         if (ref_offset > ((u64)-1 << 32))
3650                 key.offset = 0;
3651         else
3652                 key.offset = ref_offset;
3653 
3654         path->search_commit_root = 1;
3655         path->skip_locking = 1;
3656         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3657         if (ret < 0) {
3658                 err = ret;
3659                 goto out;
3660         }
3661 
3662         leaf = path->nodes[0];
3663         nritems = btrfs_header_nritems(leaf);
3664         /*
3665          * the references in tree blocks that use full backrefs
3666          * are not counted in
3667          */
3668         if (block_use_full_backref(rc, leaf))
3669                 counted = 0;
3670         else
3671                 counted = 1;
3672         rb_node = tree_search(blocks, leaf->start);
3673         if (rb_node) {
3674                 if (counted)
3675                         added = 1;
3676                 else
3677                         path->slots[0] = nritems;
3678         }
3679 
3680         while (ref_count > 0) {
3681                 while (path->slots[0] >= nritems) {
3682                         ret = btrfs_next_leaf(root, path);
3683                         if (ret < 0) {
3684                                 err = ret;
3685                                 goto out;
3686                         }
3687                         if (WARN_ON(ret > 0))
3688                                 goto out;
3689 
3690                         leaf = path->nodes[0];
3691                         nritems = btrfs_header_nritems(leaf);
3692                         added = 0;
3693 
3694                         if (block_use_full_backref(rc, leaf))
3695                                 counted = 0;
3696                         else
3697                                 counted = 1;
3698                         rb_node = tree_search(blocks, leaf->start);
3699                         if (rb_node) {
3700                                 if (counted)
3701                                         added = 1;
3702                                 else
3703                                         path->slots[0] = nritems;
3704                         }
3705                 }
3706 
3707                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3708                 if (WARN_ON(key.objectid != ref_objectid ||
3709                     key.type != BTRFS_EXTENT_DATA_KEY))
3710                         break;
3711 
3712                 fi = btrfs_item_ptr(leaf, path->slots[0],
3713                                     struct btrfs_file_extent_item);
3714 
3715                 if (btrfs_file_extent_type(leaf, fi) ==
3716                     BTRFS_FILE_EXTENT_INLINE)
3717                         goto next;
3718 
3719                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3720                     extent_key->objectid)
3721                         goto next;
3722 
3723                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3724                 if (key.offset != ref_offset)
3725                         goto next;
3726 
3727                 if (counted)
3728                         ref_count--;
3729                 if (added)
3730                         goto next;
3731 
3732                 if (!tree_block_processed(leaf->start, rc)) {
3733                         block = kmalloc(sizeof(*block), GFP_NOFS);
3734                         if (!block) {
3735                                 err = -ENOMEM;
3736                                 break;
3737                         }
3738                         block->bytenr = leaf->start;
3739                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3740                         block->level = 0;
3741                         block->key_ready = 1;
3742                         rb_node = tree_insert(blocks, block->bytenr,
3743                                               &block->rb_node);
3744                         if (rb_node)
3745                                 backref_tree_panic(rb_node, -EEXIST,
3746                                                    block->bytenr);
3747                 }
3748                 if (counted)
3749                         added = 1;
3750                 else
3751                         path->slots[0] = nritems;
3752 next:
3753                 path->slots[0]++;
3754 
3755         }
3756 out:
3757         btrfs_free_path(path);
3758         return err;
3759 }
3760 
3761 /*
3762  * helper to find all tree blocks that reference a given data extent
3763  */
3764 static noinline_for_stack
3765 int add_data_references(struct reloc_control *rc,
3766                         struct btrfs_key *extent_key,
3767                         struct btrfs_path *path,
3768                         struct rb_root *blocks)
3769 {
3770         struct btrfs_key key;
3771         struct extent_buffer *eb;
3772         struct btrfs_extent_data_ref *dref;
3773         struct btrfs_extent_inline_ref *iref;
3774         unsigned long ptr;
3775         unsigned long end;
3776         u32 blocksize = rc->extent_root->fs_info->nodesize;
3777         int ret = 0;
3778         int err = 0;
3779 
3780         eb = path->nodes[0];
3781         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3782         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3783 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3784         if (ptr + sizeof(struct btrfs_extent_item_v0) == end)
3785                 ptr = end;
3786         else
3787 #endif
3788                 ptr += sizeof(struct btrfs_extent_item);
3789 
3790         while (ptr < end) {
3791                 iref = (struct btrfs_extent_inline_ref *)ptr;
3792                 key.type = btrfs_get_extent_inline_ref_type(eb, iref,
3793                                                         BTRFS_REF_TYPE_DATA);
3794                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3795                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3796                         ret = __add_tree_block(rc, key.offset, blocksize,
3797                                                blocks);
3798                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3799                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3800                         ret = find_data_references(rc, extent_key,
3801                                                    eb, dref, blocks);
3802                 } else {
3803                         ret = -EINVAL;
3804                         btrfs_err(rc->extent_root->fs_info,
3805                      "extent %llu slot %d has an invalid inline ref type",
3806                              eb->start, path->slots[0]);
3807                 }
3808                 if (ret) {
3809                         err = ret;
3810                         goto out;
3811                 }
3812                 ptr += btrfs_extent_inline_ref_size(key.type);
3813         }
3814         WARN_ON(ptr > end);
3815 
3816         while (1) {
3817                 cond_resched();
3818                 eb = path->nodes[0];
3819                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3820                         ret = btrfs_next_leaf(rc->extent_root, path);
3821                         if (ret < 0) {
3822                                 err = ret;
3823                                 break;
3824                         }
3825                         if (ret > 0)
3826                                 break;
3827                         eb = path->nodes[0];
3828                 }
3829 
3830                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3831                 if (key.objectid != extent_key->objectid)
3832                         break;
3833 
3834 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3835                 if (key.type == BTRFS_SHARED_DATA_REF_KEY ||
3836                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
3837 #else
3838                 BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
3839                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3840 #endif
3841                         ret = __add_tree_block(rc, key.offset, blocksize,
3842                                                blocks);
3843                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3844                         dref = btrfs_item_ptr(eb, path->slots[0],
3845                                               struct btrfs_extent_data_ref);
3846                         ret = find_data_references(rc, extent_key,
3847                                                    eb, dref, blocks);
3848                 } else {
3849                         ret = 0;
3850                 }
3851                 if (ret) {
3852                         err = ret;
3853                         break;
3854                 }
3855                 path->slots[0]++;
3856         }
3857 out:
3858         btrfs_release_path(path);
3859         if (err)
3860                 free_block_list(blocks);
3861         return err;
3862 }
3863 
3864 /*
3865  * helper to find next unprocessed extent
3866  */
3867 static noinline_for_stack
3868 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3869                      struct btrfs_key *extent_key)
3870 {
3871         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3872         struct btrfs_key key;
3873         struct extent_buffer *leaf;
3874         u64 start, end, last;
3875         int ret;
3876 
3877         last = rc->block_group->key.objectid + rc->block_group->key.offset;
3878         while (1) {
3879                 cond_resched();
3880                 if (rc->search_start >= last) {
3881                         ret = 1;
3882                         break;
3883                 }
3884 
3885                 key.objectid = rc->search_start;
3886                 key.type = BTRFS_EXTENT_ITEM_KEY;
3887                 key.offset = 0;
3888 
3889                 path->search_commit_root = 1;
3890                 path->skip_locking = 1;
3891                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3892                                         0, 0);
3893                 if (ret < 0)
3894                         break;
3895 next:
3896                 leaf = path->nodes[0];
3897                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3898                         ret = btrfs_next_leaf(rc->extent_root, path);
3899                         if (ret != 0)
3900                                 break;
3901                         leaf = path->nodes[0];
3902                 }
3903 
3904                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3905                 if (key.objectid >= last) {
3906                         ret = 1;
3907                         break;
3908                 }
3909 
3910                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3911                     key.type != BTRFS_METADATA_ITEM_KEY) {
3912                         path->slots[0]++;
3913                         goto next;
3914                 }
3915 
3916                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3917                     key.objectid + key.offset <= rc->search_start) {
3918                         path->slots[0]++;
3919                         goto next;
3920                 }
3921 
3922                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3923                     key.objectid + fs_info->nodesize <=
3924                     rc->search_start) {
3925                         path->slots[0]++;
3926                         goto next;
3927                 }
3928 
3929                 ret = find_first_extent_bit(&rc->processed_blocks,
3930                                             key.objectid, &start, &end,
3931                                             EXTENT_DIRTY, NULL);
3932 
3933                 if (ret == 0 && start <= key.objectid) {
3934                         btrfs_release_path(path);
3935                         rc->search_start = end + 1;
3936                 } else {
3937                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3938                                 rc->search_start = key.objectid + key.offset;
3939                         else
3940                                 rc->search_start = key.objectid +
3941                                         fs_info->nodesize;
3942                         memcpy(extent_key, &key, sizeof(key));
3943                         return 0;
3944                 }
3945         }
3946         btrfs_release_path(path);
3947         return ret;
3948 }
3949 
3950 static void set_reloc_control(struct reloc_control *rc)
3951 {
3952         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3953 
3954         mutex_lock(&fs_info->reloc_mutex);
3955         fs_info->reloc_ctl = rc;
3956         mutex_unlock(&fs_info->reloc_mutex);
3957 }
3958 
3959 static void unset_reloc_control(struct reloc_control *rc)
3960 {
3961         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3962 
3963         mutex_lock(&fs_info->reloc_mutex);
3964         fs_info->reloc_ctl = NULL;
3965         mutex_unlock(&fs_info->reloc_mutex);
3966 }
3967 
3968 static int check_extent_flags(u64 flags)
3969 {
3970         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3971             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3972                 return 1;
3973         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3974             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3975                 return 1;
3976         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3977             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3978                 return 1;
3979         return 0;
3980 }
3981 
3982 static noinline_for_stack
3983 int prepare_to_relocate(struct reloc_control *rc)
3984 {
3985         struct btrfs_trans_handle *trans;
3986         int ret;
3987 
3988         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3989                                               BTRFS_BLOCK_RSV_TEMP);
3990         if (!rc->block_rsv)
3991                 return -ENOMEM;
3992 
3993         memset(&rc->cluster, 0, sizeof(rc->cluster));
3994         rc->search_start = rc->block_group->key.objectid;
3995         rc->extents_found = 0;
3996         rc->nodes_relocated = 0;
3997         rc->merging_rsv_size = 0;
3998         rc->reserved_bytes = 0;
3999         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
4000                               RELOCATION_RESERVED_NODES;
4001         ret = btrfs_block_rsv_refill(rc->extent_root,
4002                                      rc->block_rsv, rc->block_rsv->size,
4003                                      BTRFS_RESERVE_FLUSH_ALL);
4004         if (ret)
4005                 return ret;
4006 
4007         rc->create_reloc_tree = 1;
4008         set_reloc_control(rc);
4009 
4010         trans = btrfs_join_transaction(rc->extent_root);
4011         if (IS_ERR(trans)) {
4012                 unset_reloc_control(rc);
4013                 /*
4014                  * extent tree is not a ref_cow tree and has no reloc_root to
4015                  * cleanup.  And callers are responsible to free the above
4016                  * block rsv.
4017                  */
4018                 return PTR_ERR(trans);
4019         }
4020         btrfs_commit_transaction(trans);
4021         return 0;
4022 }
4023 
4024 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
4025 {
4026         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
4027         struct rb_root blocks = RB_ROOT;
4028         struct btrfs_key key;
4029         struct btrfs_trans_handle *trans = NULL;
4030         struct btrfs_path *path;
4031         struct btrfs_extent_item *ei;
4032         u64 flags;
4033         u32 item_size;
4034         int ret;
4035         int err = 0;
4036         int progress = 0;
4037 
4038         path = btrfs_alloc_path();
4039         if (!path)
4040                 return -ENOMEM;
4041         path->reada = READA_FORWARD;
4042 
4043         ret = prepare_to_relocate(rc);
4044         if (ret) {
4045                 err = ret;
4046                 goto out_free;
4047         }
4048 
4049         while (1) {
4050                 rc->reserved_bytes = 0;
4051                 ret = btrfs_block_rsv_refill(rc->extent_root,
4052                                         rc->block_rsv, rc->block_rsv->size,
4053                                         BTRFS_RESERVE_FLUSH_ALL);
4054                 if (ret) {
4055                         err = ret;
4056                         break;
4057                 }
4058                 progress++;
4059                 trans = btrfs_start_transaction(rc->extent_root, 0);
4060                 if (IS_ERR(trans)) {
4061                         err = PTR_ERR(trans);
4062                         trans = NULL;
4063                         break;
4064                 }
4065 restart:
4066                 if (update_backref_cache(trans, &rc->backref_cache)) {
4067                         btrfs_end_transaction(trans);
4068                         continue;
4069                 }
4070 
4071                 ret = find_next_extent(rc, path, &key);
4072                 if (ret < 0)
4073                         err = ret;
4074                 if (ret != 0)
4075                         break;
4076 
4077                 rc->extents_found++;
4078 
4079                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4080                                     struct btrfs_extent_item);
4081                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4082                 if (item_size >= sizeof(*ei)) {
4083                         flags = btrfs_extent_flags(path->nodes[0], ei);
4084                         ret = check_extent_flags(flags);
4085                         BUG_ON(ret);
4086 
4087                 } else {
4088 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
4089                         u64 ref_owner;
4090                         int path_change = 0;
4091 
4092                         BUG_ON(item_size !=
4093                                sizeof(struct btrfs_extent_item_v0));
4094                         ret = get_ref_objectid_v0(rc, path, &key, &ref_owner,
4095                                                   &path_change);
4096                         if (ret < 0) {
4097                                 err = ret;
4098                                 break;
4099                         }
4100                         if (ref_owner < BTRFS_FIRST_FREE_OBJECTID)
4101                                 flags = BTRFS_EXTENT_FLAG_TREE_BLOCK;
4102                         else
4103                                 flags = BTRFS_EXTENT_FLAG_DATA;
4104 
4105                         if (path_change) {
4106                                 btrfs_release_path(path);
4107 
4108                                 path->search_commit_root = 1;
4109                                 path->skip_locking = 1;
4110                                 ret = btrfs_search_slot(NULL, rc->extent_root,
4111                                                         &key, path, 0, 0);
4112                                 if (ret < 0) {
4113                                         err = ret;
4114                                         break;
4115                                 }
4116                                 BUG_ON(ret > 0);
4117                         }
4118 #else
4119                         BUG();
4120 #endif
4121                 }
4122 
4123                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4124                         ret = add_tree_block(rc, &key, path, &blocks);
4125                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4126                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4127                         ret = add_data_references(rc, &key, path, &blocks);
4128                 } else {
4129                         btrfs_release_path(path);
4130                         ret = 0;
4131                 }
4132                 if (ret < 0) {
4133                         err = ret;
4134                         break;
4135                 }
4136 
4137                 if (!RB_EMPTY_ROOT(&blocks)) {
4138                         ret = relocate_tree_blocks(trans, rc, &blocks);
4139                         if (ret < 0) {
4140                                 /*
4141                                  * if we fail to relocate tree blocks, force to update
4142                                  * backref cache when committing transaction.
4143                                  */
4144                                 rc->backref_cache.last_trans = trans->transid - 1;
4145 
4146                                 if (ret != -EAGAIN) {
4147                                         err = ret;
4148                                         break;
4149                                 }
4150                                 rc->extents_found--;
4151                                 rc->search_start = key.objectid;
4152                         }
4153                 }
4154 
4155                 btrfs_end_transaction_throttle(trans);
4156                 btrfs_btree_balance_dirty(fs_info);
4157                 trans = NULL;
4158 
4159                 if (rc->stage == MOVE_DATA_EXTENTS &&
4160                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4161                         rc->found_file_extent = 1;
4162                         ret = relocate_data_extent(rc->data_inode,
4163                                                    &key, &rc->cluster);
4164                         if (ret < 0) {
4165                                 err = ret;
4166                                 break;
4167                         }
4168                 }
4169         }
4170         if (trans && progress && err == -ENOSPC) {
4171                 ret = btrfs_force_chunk_alloc(trans, fs_info,
4172                                               rc->block_group->flags);
4173                 if (ret == 1) {
4174                         err = 0;
4175                         progress = 0;
4176                         goto restart;
4177                 }
4178         }
4179 
4180         btrfs_release_path(path);
4181         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4182 
4183         if (trans) {
4184                 btrfs_end_transaction_throttle(trans);
4185                 btrfs_btree_balance_dirty(fs_info);
4186         }
4187 
4188         if (!err) {
4189                 ret = relocate_file_extent_cluster(rc->data_inode,
4190                                                    &rc->cluster);
4191                 if (ret < 0)
4192                         err = ret;
4193         }
4194 
4195         rc->create_reloc_tree = 0;
4196         set_reloc_control(rc);
4197 
4198         backref_cache_cleanup(&rc->backref_cache);
4199         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4200 
4201         err = prepare_to_merge(rc, err);
4202 
4203         merge_reloc_roots(rc);
4204 
4205         rc->merge_reloc_tree = 0;
4206         unset_reloc_control(rc);
4207         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4208 
4209         /* get rid of pinned extents */
4210         trans = btrfs_join_transaction(rc->extent_root);
4211         if (IS_ERR(trans)) {
4212                 err = PTR_ERR(trans);
4213                 goto out_free;
4214         }
4215         btrfs_commit_transaction(trans);
4216 out_free:
4217         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4218         btrfs_free_path(path);
4219         return err;
4220 }
4221 
4222 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4223                                  struct btrfs_root *root, u64 objectid)
4224 {
4225         struct btrfs_path *path;
4226         struct btrfs_inode_item *item;
4227         struct extent_buffer *leaf;
4228         int ret;
4229 
4230         path = btrfs_alloc_path();
4231         if (!path)
4232                 return -ENOMEM;
4233 
4234         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4235         if (ret)
4236                 goto out;
4237 
4238         leaf = path->nodes[0];
4239         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4240         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4241         btrfs_set_inode_generation(leaf, item, 1);
4242         btrfs_set_inode_size(leaf, item, 0);
4243         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4244         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4245                                           BTRFS_INODE_PREALLOC);
4246         btrfs_mark_buffer_dirty(leaf);
4247 out:
4248         btrfs_free_path(path);
4249         return ret;
4250 }
4251 
4252 /*
4253  * helper to create inode for data relocation.
4254  * the inode is in data relocation tree and its link count is 0
4255  */
4256 static noinline_for_stack
4257 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4258                                  struct btrfs_block_group_cache *group)
4259 {
4260         struct inode *inode = NULL;
4261         struct btrfs_trans_handle *trans;
4262         struct btrfs_root *root;
4263         struct btrfs_key key;
4264         u64 objectid;
4265         int err = 0;
4266 
4267         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4268         if (IS_ERR(root))
4269                 return ERR_CAST(root);
4270 
4271         trans = btrfs_start_transaction(root, 6);
4272         if (IS_ERR(trans))
4273                 return ERR_CAST(trans);
4274 
4275         err = btrfs_find_free_objectid(root, &objectid);
4276         if (err)
4277                 goto out;
4278 
4279         err = __insert_orphan_inode(trans, root, objectid);
4280         BUG_ON(err);
4281 
4282         key.objectid = objectid;
4283         key.type = BTRFS_INODE_ITEM_KEY;
4284         key.offset = 0;
4285         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
4286         BUG_ON(IS_ERR(inode) || is_bad_inode(inode));
4287         BTRFS_I(inode)->index_cnt = group->key.objectid;
4288 
4289         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4290 out:
4291         btrfs_end_transaction(trans);
4292         btrfs_btree_balance_dirty(fs_info);
4293         if (err) {
4294                 if (inode)
4295                         iput(inode);
4296                 inode = ERR_PTR(err);
4297         }
4298         return inode;
4299 }
4300 
4301 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4302 {
4303         struct reloc_control *rc;
4304 
4305         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4306         if (!rc)
4307                 return NULL;
4308 
4309         INIT_LIST_HEAD(&rc->reloc_roots);
4310         backref_cache_init(&rc->backref_cache);
4311         mapping_tree_init(&rc->reloc_root_tree);
4312         extent_io_tree_init(&rc->processed_blocks, NULL);
4313         return rc;
4314 }
4315 
4316 /*
4317  * Print the block group being relocated
4318  */
4319 static void describe_relocation(struct btrfs_fs_info *fs_info,
4320                                 struct btrfs_block_group_cache *block_group)
4321 {
4322         char buf[128];          /* prefixed by a '|' that'll be dropped */
4323         u64 flags = block_group->flags;
4324 
4325         /* Shouldn't happen */
4326         if (!flags) {
4327                 strcpy(buf, "|NONE");
4328         } else {
4329                 char *bp = buf;
4330 
4331 #define DESCRIBE_FLAG(f, d) \
4332                 if (flags & BTRFS_BLOCK_GROUP_##f) { \
4333                         bp += snprintf(bp, buf - bp + sizeof(buf), "|%s", d); \
4334                         flags &= ~BTRFS_BLOCK_GROUP_##f; \
4335                 }
4336                 DESCRIBE_FLAG(DATA,     "data");
4337                 DESCRIBE_FLAG(SYSTEM,   "system");
4338                 DESCRIBE_FLAG(METADATA, "metadata");
4339                 DESCRIBE_FLAG(RAID0,    "raid0");
4340                 DESCRIBE_FLAG(RAID1,    "raid1");
4341                 DESCRIBE_FLAG(DUP,      "dup");
4342                 DESCRIBE_FLAG(RAID10,   "raid10");
4343                 DESCRIBE_FLAG(RAID5,    "raid5");
4344                 DESCRIBE_FLAG(RAID6,    "raid6");
4345                 if (flags)
4346                         snprintf(buf, buf - bp + sizeof(buf), "|0x%llx", flags);
4347 #undef DESCRIBE_FLAG
4348         }
4349 
4350         btrfs_info(fs_info,
4351                    "relocating block group %llu flags %s",
4352                    block_group->key.objectid, buf + 1);
4353 }
4354 
4355 /*
4356  * function to relocate all extents in a block group.
4357  */
4358 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4359 {
4360         struct btrfs_root *extent_root = fs_info->extent_root;
4361         struct reloc_control *rc;
4362         struct inode *inode;
4363         struct btrfs_path *path;
4364         int ret;
4365         int rw = 0;
4366         int err = 0;
4367 
4368         rc = alloc_reloc_control(fs_info);
4369         if (!rc)
4370                 return -ENOMEM;
4371 
4372         rc->extent_root = extent_root;
4373 
4374         rc->block_group = btrfs_lookup_block_group(fs_info, group_start);
4375         BUG_ON(!rc->block_group);
4376 
4377         ret = btrfs_inc_block_group_ro(fs_info, rc->block_group);
4378         if (ret) {
4379                 err = ret;
4380                 goto out;
4381         }
4382         rw = 1;
4383 
4384         path = btrfs_alloc_path();
4385         if (!path) {
4386                 err = -ENOMEM;
4387                 goto out;
4388         }
4389 
4390         inode = lookup_free_space_inode(fs_info, rc->block_group, path);
4391         btrfs_free_path(path);
4392 
4393         if (!IS_ERR(inode))
4394                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4395         else
4396                 ret = PTR_ERR(inode);
4397 
4398         if (ret && ret != -ENOENT) {
4399                 err = ret;
4400                 goto out;
4401         }
4402 
4403         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4404         if (IS_ERR(rc->data_inode)) {
4405                 err = PTR_ERR(rc->data_inode);
4406                 rc->data_inode = NULL;
4407                 goto out;
4408         }
4409 
4410         describe_relocation(fs_info, rc->block_group);
4411 
4412         btrfs_wait_block_group_reservations(rc->block_group);
4413         btrfs_wait_nocow_writers(rc->block_group);
4414         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4415                                  rc->block_group->key.objectid,
4416                                  rc->block_group->key.offset);
4417 
4418         while (1) {
4419                 mutex_lock(&fs_info->cleaner_mutex);
4420                 ret = relocate_block_group(rc);
4421                 mutex_unlock(&fs_info->cleaner_mutex);
4422                 if (ret < 0) {
4423                         err = ret;
4424                         goto out;
4425                 }
4426 
4427                 if (rc->extents_found == 0)
4428                         break;
4429 
4430                 btrfs_info(fs_info, "found %llu extents", rc->extents_found);
4431 
4432                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4433                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4434                                                        (u64)-1);
4435                         if (ret) {
4436                                 err = ret;
4437                                 goto out;
4438                         }
4439                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4440                                                  0, -1);
4441                         rc->stage = UPDATE_DATA_PTRS;
4442                 }
4443         }
4444 
4445         WARN_ON(rc->block_group->pinned > 0);
4446         WARN_ON(rc->block_group->reserved > 0);
4447         WARN_ON(btrfs_block_group_used(&rc->block_group->item) > 0);
4448 out:
4449         if (err && rw)
4450                 btrfs_dec_block_group_ro(rc->block_group);
4451         iput(rc->data_inode);
4452         btrfs_put_block_group(rc->block_group);
4453         kfree(rc);
4454         return err;
4455 }
4456 
4457 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4458 {
4459         struct btrfs_fs_info *fs_info = root->fs_info;
4460         struct btrfs_trans_handle *trans;
4461         int ret, err;
4462 
4463         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4464         if (IS_ERR(trans))
4465                 return PTR_ERR(trans);
4466 
4467         memset(&root->root_item.drop_progress, 0,
4468                 sizeof(root->root_item.drop_progress));
4469         root->root_item.drop_level = 0;
4470         btrfs_set_root_refs(&root->root_item, 0);
4471         ret = btrfs_update_root(trans, fs_info->tree_root,
4472                                 &root->root_key, &root->root_item);
4473 
4474         err = btrfs_end_transaction(trans);
4475         if (err)
4476                 return err;
4477         return ret;
4478 }
4479 
4480 /*
4481  * recover relocation interrupted by system crash.
4482  *
4483  * this function resumes merging reloc trees with corresponding fs trees.
4484  * this is important for keeping the sharing of tree blocks
4485  */
4486 int btrfs_recover_relocation(struct btrfs_root *root)
4487 {
4488         struct btrfs_fs_info *fs_info = root->fs_info;
4489         LIST_HEAD(reloc_roots);
4490         struct btrfs_key key;
4491         struct btrfs_root *fs_root;
4492         struct btrfs_root *reloc_root;
4493         struct btrfs_path *path;
4494         struct extent_buffer *leaf;
4495         struct reloc_control *rc = NULL;
4496         struct btrfs_trans_handle *trans;
4497         int ret;
4498         int err = 0;
4499 
4500         path = btrfs_alloc_path();
4501         if (!path)
4502                 return -ENOMEM;
4503         path->reada = READA_BACK;
4504 
4505         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4506         key.type = BTRFS_ROOT_ITEM_KEY;
4507         key.offset = (u64)-1;
4508 
4509         while (1) {
4510                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4511                                         path, 0, 0);
4512                 if (ret < 0) {
4513                         err = ret;
4514                         goto out;
4515                 }
4516                 if (ret > 0) {
4517                         if (path->slots[0] == 0)
4518                                 break;
4519                         path->slots[0]--;
4520                 }
4521                 leaf = path->nodes[0];
4522                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4523                 btrfs_release_path(path);
4524 
4525                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4526                     key.type != BTRFS_ROOT_ITEM_KEY)
4527                         break;
4528 
4529                 reloc_root = btrfs_read_fs_root(root, &key);
4530                 if (IS_ERR(reloc_root)) {
4531                         err = PTR_ERR(reloc_root);
4532                         goto out;
4533                 }
4534 
4535                 list_add(&reloc_root->root_list, &reloc_roots);
4536 
4537                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4538                         fs_root = read_fs_root(fs_info,
4539                                                reloc_root->root_key.offset);
4540                         if (IS_ERR(fs_root)) {
4541                                 ret = PTR_ERR(fs_root);
4542                                 if (ret != -ENOENT) {
4543                                         err = ret;
4544                                         goto out;
4545                                 }
4546                                 ret = mark_garbage_root(reloc_root);
4547                                 if (ret < 0) {
4548                                         err = ret;
4549                                         goto out;
4550                                 }
4551                         }
4552                 }
4553 
4554                 if (key.offset == 0)
4555                         break;
4556 
4557                 key.offset--;
4558         }
4559         btrfs_release_path(path);
4560 
4561         if (list_empty(&reloc_roots))
4562                 goto out;
4563 
4564         rc = alloc_reloc_control(fs_info);
4565         if (!rc) {
4566                 err = -ENOMEM;
4567                 goto out;
4568         }
4569 
4570         rc->extent_root = fs_info->extent_root;
4571 
4572         set_reloc_control(rc);
4573 
4574         trans = btrfs_join_transaction(rc->extent_root);
4575         if (IS_ERR(trans)) {
4576                 unset_reloc_control(rc);
4577                 err = PTR_ERR(trans);
4578                 goto out_free;
4579         }
4580 
4581         rc->merge_reloc_tree = 1;
4582 
4583         while (!list_empty(&reloc_roots)) {
4584                 reloc_root = list_entry(reloc_roots.next,
4585                                         struct btrfs_root, root_list);
4586                 list_del(&reloc_root->root_list);
4587 
4588                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4589                         list_add_tail(&reloc_root->root_list,
4590                                       &rc->reloc_roots);
4591                         continue;
4592                 }
4593 
4594                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4595                 if (IS_ERR(fs_root)) {
4596                         err = PTR_ERR(fs_root);
4597                         goto out_free;
4598                 }
4599 
4600                 err = __add_reloc_root(reloc_root);
4601                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4602                 fs_root->reloc_root = reloc_root;
4603         }
4604 
4605         err = btrfs_commit_transaction(trans);
4606         if (err)
4607                 goto out_free;
4608 
4609         merge_reloc_roots(rc);
4610 
4611         unset_reloc_control(rc);
4612 
4613         trans = btrfs_join_transaction(rc->extent_root);
4614         if (IS_ERR(trans)) {
4615                 err = PTR_ERR(trans);
4616                 goto out_free;
4617         }
4618         err = btrfs_commit_transaction(trans);
4619 out_free:
4620         kfree(rc);
4621 out:
4622         if (!list_empty(&reloc_roots))
4623                 free_reloc_roots(&reloc_roots);
4624 
4625         btrfs_free_path(path);
4626 
4627         if (err == 0) {
4628                 /* cleanup orphan inode in data relocation tree */
4629                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4630                 if (IS_ERR(fs_root))
4631                         err = PTR_ERR(fs_root);
4632                 else
4633                         err = btrfs_orphan_cleanup(fs_root);
4634         }
4635         return err;
4636 }
4637 
4638 /*
4639  * helper to add ordered checksum for data relocation.
4640  *
4641  * cloning checksum properly handles the nodatasum extents.
4642  * it also saves CPU time to re-calculate the checksum.
4643  */
4644 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4645 {
4646         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4647         struct btrfs_ordered_sum *sums;
4648         struct btrfs_ordered_extent *ordered;
4649         int ret;
4650         u64 disk_bytenr;
4651         u64 new_bytenr;
4652         LIST_HEAD(list);
4653 
4654         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4655         BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
4656 
4657         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4658         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4659                                        disk_bytenr + len - 1, &list, 0);
4660         if (ret)
4661                 goto out;
4662 
4663         while (!list_empty(&list)) {
4664                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4665                 list_del_init(&sums->list);
4666 
4667                 /*
4668                  * We need to offset the new_bytenr based on where the csum is.
4669                  * We need to do this because we will read in entire prealloc
4670                  * extents but we may have written to say the middle of the
4671                  * prealloc extent, so we need to make sure the csum goes with
4672                  * the right disk offset.
4673                  *
4674                  * We can do this because the data reloc inode refers strictly
4675                  * to the on disk bytes, so we don't have to worry about
4676                  * disk_len vs real len like with real inodes since it's all
4677                  * disk length.
4678                  */
4679                 new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
4680                 sums->bytenr = new_bytenr;
4681 
4682                 btrfs_add_ordered_sum(inode, ordered, sums);
4683         }
4684 out:
4685         btrfs_put_ordered_extent(ordered);
4686         return ret;
4687 }
4688 
4689 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4690                           struct btrfs_root *root, struct extent_buffer *buf,
4691                           struct extent_buffer *cow)
4692 {
4693         struct btrfs_fs_info *fs_info = root->fs_info;
4694         struct reloc_control *rc;
4695         struct backref_node *node;
4696         int first_cow = 0;
4697         int level;
4698         int ret = 0;
4699 
4700         rc = fs_info->reloc_ctl;
4701         if (!rc)
4702                 return 0;
4703 
4704         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4705                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4706 
4707         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
4708                 if (buf == root->node)
4709                         __update_reloc_root(root, cow->start);
4710         }
4711 
4712         level = btrfs_header_level(buf);
4713         if (btrfs_header_generation(buf) <=
4714             btrfs_root_last_snapshot(&root->root_item))
4715                 first_cow = 1;
4716 
4717         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4718             rc->create_reloc_tree) {
4719                 WARN_ON(!first_cow && level == 0);
4720 
4721                 node = rc->backref_cache.path[level];
4722                 BUG_ON(node->bytenr != buf->start &&
4723                        node->new_bytenr != buf->start);
4724 
4725                 drop_node_buffer(node);
4726                 extent_buffer_get(cow);
4727                 node->eb = cow;
4728                 node->new_bytenr = cow->start;
4729 
4730                 if (!node->pending) {
4731                         list_move_tail(&node->list,
4732                                        &rc->backref_cache.pending[level]);
4733                         node->pending = 1;
4734                 }
4735 
4736                 if (first_cow)
4737                         __mark_block_processed(rc, node);
4738 
4739                 if (first_cow && level > 0)
4740                         rc->nodes_relocated += buf->len;
4741         }
4742 
4743         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4744                 ret = replace_file_extents(trans, rc, root, cow);
4745         return ret;
4746 }
4747 
4748 /*
4749  * called before creating snapshot. it calculates metadata reservation
4750  * required for relocating tree blocks in the snapshot
4751  */
4752 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4753                               u64 *bytes_to_reserve)
4754 {
4755         struct btrfs_root *root;
4756         struct reloc_control *rc;
4757 
4758         root = pending->root;
4759         if (!root->reloc_root)
4760                 return;
4761 
4762         rc = root->fs_info->reloc_ctl;
4763         if (!rc->merge_reloc_tree)
4764                 return;
4765 
4766         root = root->reloc_root;
4767         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4768         /*
4769          * relocation is in the stage of merging trees. the space
4770          * used by merging a reloc tree is twice the size of
4771          * relocated tree nodes in the worst case. half for cowing
4772          * the reloc tree, half for cowing the fs tree. the space
4773          * used by cowing the reloc tree will be freed after the
4774          * tree is dropped. if we create snapshot, cowing the fs
4775          * tree may use more space than it frees. so we need
4776          * reserve extra space.
4777          */
4778         *bytes_to_reserve += rc->nodes_relocated;
4779 }
4780 
4781 /*
4782  * called after snapshot is created. migrate block reservation
4783  * and create reloc root for the newly created snapshot
4784  */
4785 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4786                                struct btrfs_pending_snapshot *pending)
4787 {
4788         struct btrfs_root *root = pending->root;
4789         struct btrfs_root *reloc_root;
4790         struct btrfs_root *new_root;
4791         struct reloc_control *rc;
4792         int ret;
4793 
4794         if (!root->reloc_root)
4795                 return 0;
4796 
4797         rc = root->fs_info->reloc_ctl;
4798         rc->merging_rsv_size += rc->nodes_relocated;
4799 
4800         if (rc->merge_reloc_tree) {
4801                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4802                                               rc->block_rsv,
4803                                               rc->nodes_relocated, 1);
4804                 if (ret)
4805                         return ret;
4806         }
4807 
4808         new_root = pending->snap;
4809         reloc_root = create_reloc_root(trans, root->reloc_root,
4810                                        new_root->root_key.objectid);
4811         if (IS_ERR(reloc_root))
4812                 return PTR_ERR(reloc_root);
4813 
4814         ret = __add_reloc_root(reloc_root);
4815         BUG_ON(ret < 0);
4816         new_root->reloc_root = reloc_root;
4817 
4818         if (rc->create_reloc_tree)
4819                 ret = clone_backref_node(trans, rc, root, reloc_root);
4820         return ret;
4821 }
4822 

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