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

Version: ~ [ linux-5.5-rc1 ] ~ [ linux-5.4.2 ] ~ [ linux-5.3.15 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.88 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.158 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.206 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.206 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.140 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.78 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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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 
 35 /*
 36  * backref_node, mapping_node and tree_block start with this
 37  */
 38 struct tree_entry {
 39         struct rb_node rb_node;
 40         u64 bytenr;
 41 };
 42 
 43 /*
 44  * present a tree block in the backref cache
 45  */
 46 struct backref_node {
 47         struct rb_node rb_node;
 48         u64 bytenr;
 49 
 50         u64 new_bytenr;
 51         /* objectid of tree block owner, can be not uptodate */
 52         u64 owner;
 53         /* link to pending, changed or detached list */
 54         struct list_head list;
 55         /* list of upper level blocks reference this block */
 56         struct list_head upper;
 57         /* list of child blocks in the cache */
 58         struct list_head lower;
 59         /* NULL if this node is not tree root */
 60         struct btrfs_root *root;
 61         /* extent buffer got by COW the block */
 62         struct extent_buffer *eb;
 63         /* level of tree block */
 64         unsigned int level:8;
 65         /* is the block in non-reference counted tree */
 66         unsigned int cowonly:1;
 67         /* 1 if no child node in the cache */
 68         unsigned int lowest:1;
 69         /* is the extent buffer locked */
 70         unsigned int locked:1;
 71         /* has the block been processed */
 72         unsigned int processed:1;
 73         /* have backrefs of this block been checked */
 74         unsigned int checked:1;
 75         /*
 76          * 1 if corresponding block has been cowed but some upper
 77          * level block pointers may not point to the new location
 78          */
 79         unsigned int pending:1;
 80         /*
 81          * 1 if the backref node isn't connected to any other
 82          * backref node.
 83          */
 84         unsigned int detached:1;
 85 };
 86 
 87 /*
 88  * present a block pointer in the backref cache
 89  */
 90 struct backref_edge {
 91         struct list_head list[2];
 92         struct backref_node *node[2];
 93 };
 94 
 95 #define LOWER   0
 96 #define UPPER   1
 97 
 98 struct backref_cache {
 99         /* red black tree of all backref nodes in the cache */
100         struct rb_root rb_root;
101         /* for passing backref nodes to btrfs_reloc_cow_block */
102         struct backref_node *path[BTRFS_MAX_LEVEL];
103         /*
104          * list of blocks that have been cowed but some block
105          * pointers in upper level blocks may not reflect the
106          * new location
107          */
108         struct list_head pending[BTRFS_MAX_LEVEL];
109         /* list of backref nodes with no child node */
110         struct list_head leaves;
111         /* list of blocks that have been cowed in current transaction */
112         struct list_head changed;
113         /* list of detached backref node. */
114         struct list_head detached;
115 
116         u64 last_trans;
117 
118         int nr_nodes;
119         int nr_edges;
120 };
121 
122 /*
123  * map address of tree root to tree
124  */
125 struct mapping_node {
126         struct rb_node rb_node;
127         u64 bytenr;
128         void *data;
129 };
130 
131 struct mapping_tree {
132         struct rb_root rb_root;
133         spinlock_t lock;
134 };
135 
136 /*
137  * present a tree block to process
138  */
139 struct tree_block {
140         struct rb_node rb_node;
141         u64 bytenr;
142         struct btrfs_key key;
143         unsigned int level:8;
144         unsigned int key_ready:1;
145 };
146 
147 #define MAX_EXTENTS 128
148 
149 struct file_extent_cluster {
150         u64 start;
151         u64 end;
152         u64 boundary[MAX_EXTENTS];
153         unsigned int nr;
154 };
155 
156 struct reloc_control {
157         /* block group to relocate */
158         struct btrfs_block_group_cache *block_group;
159         /* extent tree */
160         struct btrfs_root *extent_root;
161         /* inode for moving data */
162         struct inode *data_inode;
163 
164         struct btrfs_block_rsv *block_rsv;
165 
166         struct backref_cache backref_cache;
167 
168         struct file_extent_cluster cluster;
169         /* tree blocks have been processed */
170         struct extent_io_tree processed_blocks;
171         /* map start of tree root to corresponding reloc tree */
172         struct mapping_tree reloc_root_tree;
173         /* list of reloc trees */
174         struct list_head reloc_roots;
175         /* size of metadata reservation for merging reloc trees */
176         u64 merging_rsv_size;
177         /* size of relocated tree nodes */
178         u64 nodes_relocated;
179 
180         u64 search_start;
181         u64 extents_found;
182 
183         unsigned int stage:8;
184         unsigned int create_reloc_tree:1;
185         unsigned int merge_reloc_tree:1;
186         unsigned int found_file_extent:1;
187         unsigned int commit_transaction:1;
188 };
189 
190 /* stages of data relocation */
191 #define MOVE_DATA_EXTENTS       0
192 #define UPDATE_DATA_PTRS        1
193 
194 static void remove_backref_node(struct backref_cache *cache,
195                                 struct backref_node *node);
196 static void __mark_block_processed(struct reloc_control *rc,
197                                    struct backref_node *node);
198 
199 static void mapping_tree_init(struct mapping_tree *tree)
200 {
201         tree->rb_root = RB_ROOT;
202         spin_lock_init(&tree->lock);
203 }
204 
205 static void backref_cache_init(struct backref_cache *cache)
206 {
207         int i;
208         cache->rb_root = RB_ROOT;
209         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
210                 INIT_LIST_HEAD(&cache->pending[i]);
211         INIT_LIST_HEAD(&cache->changed);
212         INIT_LIST_HEAD(&cache->detached);
213         INIT_LIST_HEAD(&cache->leaves);
214 }
215 
216 static void backref_cache_cleanup(struct backref_cache *cache)
217 {
218         struct backref_node *node;
219         int i;
220 
221         while (!list_empty(&cache->detached)) {
222                 node = list_entry(cache->detached.next,
223                                   struct backref_node, list);
224                 remove_backref_node(cache, node);
225         }
226 
227         while (!list_empty(&cache->leaves)) {
228                 node = list_entry(cache->leaves.next,
229                                   struct backref_node, lower);
230                 remove_backref_node(cache, node);
231         }
232 
233         cache->last_trans = 0;
234 
235         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
236                 BUG_ON(!list_empty(&cache->pending[i]));
237         BUG_ON(!list_empty(&cache->changed));
238         BUG_ON(!list_empty(&cache->detached));
239         BUG_ON(!RB_EMPTY_ROOT(&cache->rb_root));
240         BUG_ON(cache->nr_nodes);
241         BUG_ON(cache->nr_edges);
242 }
243 
244 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
245 {
246         struct backref_node *node;
247 
248         node = kzalloc(sizeof(*node), GFP_NOFS);
249         if (node) {
250                 INIT_LIST_HEAD(&node->list);
251                 INIT_LIST_HEAD(&node->upper);
252                 INIT_LIST_HEAD(&node->lower);
253                 RB_CLEAR_NODE(&node->rb_node);
254                 cache->nr_nodes++;
255         }
256         return node;
257 }
258 
259 static void free_backref_node(struct backref_cache *cache,
260                               struct backref_node *node)
261 {
262         if (node) {
263                 cache->nr_nodes--;
264                 kfree(node);
265         }
266 }
267 
268 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
269 {
270         struct backref_edge *edge;
271 
272         edge = kzalloc(sizeof(*edge), GFP_NOFS);
273         if (edge)
274                 cache->nr_edges++;
275         return edge;
276 }
277 
278 static void free_backref_edge(struct backref_cache *cache,
279                               struct backref_edge *edge)
280 {
281         if (edge) {
282                 cache->nr_edges--;
283                 kfree(edge);
284         }
285 }
286 
287 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
288                                    struct rb_node *node)
289 {
290         struct rb_node **p = &root->rb_node;
291         struct rb_node *parent = NULL;
292         struct tree_entry *entry;
293 
294         while (*p) {
295                 parent = *p;
296                 entry = rb_entry(parent, struct tree_entry, rb_node);
297 
298                 if (bytenr < entry->bytenr)
299                         p = &(*p)->rb_left;
300                 else if (bytenr > entry->bytenr)
301                         p = &(*p)->rb_right;
302                 else
303                         return parent;
304         }
305 
306         rb_link_node(node, parent, p);
307         rb_insert_color(node, root);
308         return NULL;
309 }
310 
311 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
312 {
313         struct rb_node *n = root->rb_node;
314         struct tree_entry *entry;
315 
316         while (n) {
317                 entry = rb_entry(n, struct tree_entry, rb_node);
318 
319                 if (bytenr < entry->bytenr)
320                         n = n->rb_left;
321                 else if (bytenr > entry->bytenr)
322                         n = n->rb_right;
323                 else
324                         return n;
325         }
326         return NULL;
327 }
328 
329 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
330 {
331 
332         struct btrfs_fs_info *fs_info = NULL;
333         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
334                                               rb_node);
335         if (bnode->root)
336                 fs_info = bnode->root->fs_info;
337         btrfs_panic(fs_info, errno, "Inconsistency in backref cache "
338                     "found at offset %llu\n", (unsigned long long)bytenr);
339 }
340 
341 /*
342  * walk up backref nodes until reach node presents tree root
343  */
344 static struct backref_node *walk_up_backref(struct backref_node *node,
345                                             struct backref_edge *edges[],
346                                             int *index)
347 {
348         struct backref_edge *edge;
349         int idx = *index;
350 
351         while (!list_empty(&node->upper)) {
352                 edge = list_entry(node->upper.next,
353                                   struct backref_edge, list[LOWER]);
354                 edges[idx++] = edge;
355                 node = edge->node[UPPER];
356         }
357         BUG_ON(node->detached);
358         *index = idx;
359         return node;
360 }
361 
362 /*
363  * walk down backref nodes to find start of next reference path
364  */
365 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
366                                               int *index)
367 {
368         struct backref_edge *edge;
369         struct backref_node *lower;
370         int idx = *index;
371 
372         while (idx > 0) {
373                 edge = edges[idx - 1];
374                 lower = edge->node[LOWER];
375                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
376                         idx--;
377                         continue;
378                 }
379                 edge = list_entry(edge->list[LOWER].next,
380                                   struct backref_edge, list[LOWER]);
381                 edges[idx - 1] = edge;
382                 *index = idx;
383                 return edge->node[UPPER];
384         }
385         *index = 0;
386         return NULL;
387 }
388 
389 static void unlock_node_buffer(struct backref_node *node)
390 {
391         if (node->locked) {
392                 btrfs_tree_unlock(node->eb);
393                 node->locked = 0;
394         }
395 }
396 
397 static void drop_node_buffer(struct backref_node *node)
398 {
399         if (node->eb) {
400                 unlock_node_buffer(node);
401                 free_extent_buffer(node->eb);
402                 node->eb = NULL;
403         }
404 }
405 
406 static void drop_backref_node(struct backref_cache *tree,
407                               struct backref_node *node)
408 {
409         BUG_ON(!list_empty(&node->upper));
410 
411         drop_node_buffer(node);
412         list_del(&node->list);
413         list_del(&node->lower);
414         if (!RB_EMPTY_NODE(&node->rb_node))
415                 rb_erase(&node->rb_node, &tree->rb_root);
416         free_backref_node(tree, node);
417 }
418 
419 /*
420  * remove a backref node from the backref cache
421  */
422 static void remove_backref_node(struct backref_cache *cache,
423                                 struct backref_node *node)
424 {
425         struct backref_node *upper;
426         struct backref_edge *edge;
427 
428         if (!node)
429                 return;
430 
431         BUG_ON(!node->lowest && !node->detached);
432         while (!list_empty(&node->upper)) {
433                 edge = list_entry(node->upper.next, struct backref_edge,
434                                   list[LOWER]);
435                 upper = edge->node[UPPER];
436                 list_del(&edge->list[LOWER]);
437                 list_del(&edge->list[UPPER]);
438                 free_backref_edge(cache, edge);
439 
440                 if (RB_EMPTY_NODE(&upper->rb_node)) {
441                         BUG_ON(!list_empty(&node->upper));
442                         drop_backref_node(cache, node);
443                         node = upper;
444                         node->lowest = 1;
445                         continue;
446                 }
447                 /*
448                  * add the node to leaf node list if no other
449                  * child block cached.
450                  */
451                 if (list_empty(&upper->lower)) {
452                         list_add_tail(&upper->lower, &cache->leaves);
453                         upper->lowest = 1;
454                 }
455         }
456 
457         drop_backref_node(cache, node);
458 }
459 
460 static void update_backref_node(struct backref_cache *cache,
461                                 struct backref_node *node, u64 bytenr)
462 {
463         struct rb_node *rb_node;
464         rb_erase(&node->rb_node, &cache->rb_root);
465         node->bytenr = bytenr;
466         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
467         if (rb_node)
468                 backref_tree_panic(rb_node, -EEXIST, bytenr);
469 }
470 
471 /*
472  * update backref cache after a transaction commit
473  */
474 static int update_backref_cache(struct btrfs_trans_handle *trans,
475                                 struct backref_cache *cache)
476 {
477         struct backref_node *node;
478         int level = 0;
479 
480         if (cache->last_trans == 0) {
481                 cache->last_trans = trans->transid;
482                 return 0;
483         }
484 
485         if (cache->last_trans == trans->transid)
486                 return 0;
487 
488         /*
489          * detached nodes are used to avoid unnecessary backref
490          * lookup. transaction commit changes the extent tree.
491          * so the detached nodes are no longer useful.
492          */
493         while (!list_empty(&cache->detached)) {
494                 node = list_entry(cache->detached.next,
495                                   struct backref_node, list);
496                 remove_backref_node(cache, node);
497         }
498 
499         while (!list_empty(&cache->changed)) {
500                 node = list_entry(cache->changed.next,
501                                   struct backref_node, list);
502                 list_del_init(&node->list);
503                 BUG_ON(node->pending);
504                 update_backref_node(cache, node, node->new_bytenr);
505         }
506 
507         /*
508          * some nodes can be left in the pending list if there were
509          * errors during processing the pending nodes.
510          */
511         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
512                 list_for_each_entry(node, &cache->pending[level], list) {
513                         BUG_ON(!node->pending);
514                         if (node->bytenr == node->new_bytenr)
515                                 continue;
516                         update_backref_node(cache, node, node->new_bytenr);
517                 }
518         }
519 
520         cache->last_trans = 0;
521         return 1;
522 }
523 
524 
525 static int should_ignore_root(struct btrfs_root *root)
526 {
527         struct btrfs_root *reloc_root;
528 
529         if (!root->ref_cows)
530                 return 0;
531 
532         reloc_root = root->reloc_root;
533         if (!reloc_root)
534                 return 0;
535 
536         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
537             root->fs_info->running_transaction->transid - 1)
538                 return 0;
539         /*
540          * if there is reloc tree and it was created in previous
541          * transaction backref lookup can find the reloc tree,
542          * so backref node for the fs tree root is useless for
543          * relocation.
544          */
545         return 1;
546 }
547 /*
548  * find reloc tree by address of tree root
549  */
550 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
551                                           u64 bytenr)
552 {
553         struct rb_node *rb_node;
554         struct mapping_node *node;
555         struct btrfs_root *root = NULL;
556 
557         spin_lock(&rc->reloc_root_tree.lock);
558         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
559         if (rb_node) {
560                 node = rb_entry(rb_node, struct mapping_node, rb_node);
561                 root = (struct btrfs_root *)node->data;
562         }
563         spin_unlock(&rc->reloc_root_tree.lock);
564         return root;
565 }
566 
567 static int is_cowonly_root(u64 root_objectid)
568 {
569         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
570             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
571             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
572             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
573             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
574             root_objectid == BTRFS_CSUM_TREE_OBJECTID)
575                 return 1;
576         return 0;
577 }
578 
579 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
580                                         u64 root_objectid)
581 {
582         struct btrfs_key key;
583 
584         key.objectid = root_objectid;
585         key.type = BTRFS_ROOT_ITEM_KEY;
586         if (is_cowonly_root(root_objectid))
587                 key.offset = 0;
588         else
589                 key.offset = (u64)-1;
590 
591         return btrfs_read_fs_root_no_name(fs_info, &key);
592 }
593 
594 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
595 static noinline_for_stack
596 struct btrfs_root *find_tree_root(struct reloc_control *rc,
597                                   struct extent_buffer *leaf,
598                                   struct btrfs_extent_ref_v0 *ref0)
599 {
600         struct btrfs_root *root;
601         u64 root_objectid = btrfs_ref_root_v0(leaf, ref0);
602         u64 generation = btrfs_ref_generation_v0(leaf, ref0);
603 
604         BUG_ON(root_objectid == BTRFS_TREE_RELOC_OBJECTID);
605 
606         root = read_fs_root(rc->extent_root->fs_info, root_objectid);
607         BUG_ON(IS_ERR(root));
608 
609         if (root->ref_cows &&
610             generation != btrfs_root_generation(&root->root_item))
611                 return NULL;
612 
613         return root;
614 }
615 #endif
616 
617 static noinline_for_stack
618 int find_inline_backref(struct extent_buffer *leaf, int slot,
619                         unsigned long *ptr, unsigned long *end)
620 {
621         struct btrfs_key key;
622         struct btrfs_extent_item *ei;
623         struct btrfs_tree_block_info *bi;
624         u32 item_size;
625 
626         btrfs_item_key_to_cpu(leaf, &key, slot);
627 
628         item_size = btrfs_item_size_nr(leaf, slot);
629 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
630         if (item_size < sizeof(*ei)) {
631                 WARN_ON(item_size != sizeof(struct btrfs_extent_item_v0));
632                 return 1;
633         }
634 #endif
635         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
636         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
637                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
638 
639         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
640             item_size <= sizeof(*ei) + sizeof(*bi)) {
641                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
642                 return 1;
643         }
644 
645         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
646                 bi = (struct btrfs_tree_block_info *)(ei + 1);
647                 *ptr = (unsigned long)(bi + 1);
648         } else {
649                 *ptr = (unsigned long)(ei + 1);
650         }
651         *end = (unsigned long)ei + item_size;
652         return 0;
653 }
654 
655 /*
656  * build backref tree for a given tree block. root of the backref tree
657  * corresponds the tree block, leaves of the backref tree correspond
658  * roots of b-trees that reference the tree block.
659  *
660  * the basic idea of this function is check backrefs of a given block
661  * to find upper level blocks that refernece the block, and then check
662  * bakcrefs of these upper level blocks recursively. the recursion stop
663  * when tree root is reached or backrefs for the block is cached.
664  *
665  * NOTE: if we find backrefs for a block are cached, we know backrefs
666  * for all upper level blocks that directly/indirectly reference the
667  * block are also cached.
668  */
669 static noinline_for_stack
670 struct backref_node *build_backref_tree(struct reloc_control *rc,
671                                         struct btrfs_key *node_key,
672                                         int level, u64 bytenr)
673 {
674         struct backref_cache *cache = &rc->backref_cache;
675         struct btrfs_path *path1;
676         struct btrfs_path *path2;
677         struct extent_buffer *eb;
678         struct btrfs_root *root;
679         struct backref_node *cur;
680         struct backref_node *upper;
681         struct backref_node *lower;
682         struct backref_node *node = NULL;
683         struct backref_node *exist = NULL;
684         struct backref_edge *edge;
685         struct rb_node *rb_node;
686         struct btrfs_key key;
687         unsigned long end;
688         unsigned long ptr;
689         LIST_HEAD(list);
690         LIST_HEAD(useless);
691         int cowonly;
692         int ret;
693         int err = 0;
694         bool need_check = true;
695 
696         path1 = btrfs_alloc_path();
697         path2 = btrfs_alloc_path();
698         if (!path1 || !path2) {
699                 err = -ENOMEM;
700                 goto out;
701         }
702         path1->reada = 1;
703         path2->reada = 2;
704 
705         node = alloc_backref_node(cache);
706         if (!node) {
707                 err = -ENOMEM;
708                 goto out;
709         }
710 
711         node->bytenr = bytenr;
712         node->level = level;
713         node->lowest = 1;
714         cur = node;
715 again:
716         end = 0;
717         ptr = 0;
718         key.objectid = cur->bytenr;
719         key.type = BTRFS_METADATA_ITEM_KEY;
720         key.offset = (u64)-1;
721 
722         path1->search_commit_root = 1;
723         path1->skip_locking = 1;
724         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
725                                 0, 0);
726         if (ret < 0) {
727                 err = ret;
728                 goto out;
729         }
730         BUG_ON(!ret || !path1->slots[0]);
731 
732         path1->slots[0]--;
733 
734         WARN_ON(cur->checked);
735         if (!list_empty(&cur->upper)) {
736                 /*
737                  * the backref was added previously when processing
738                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
739                  */
740                 BUG_ON(!list_is_singular(&cur->upper));
741                 edge = list_entry(cur->upper.next, struct backref_edge,
742                                   list[LOWER]);
743                 BUG_ON(!list_empty(&edge->list[UPPER]));
744                 exist = edge->node[UPPER];
745                 /*
746                  * add the upper level block to pending list if we need
747                  * check its backrefs
748                  */
749                 if (!exist->checked)
750                         list_add_tail(&edge->list[UPPER], &list);
751         } else {
752                 exist = NULL;
753         }
754 
755         while (1) {
756                 cond_resched();
757                 eb = path1->nodes[0];
758 
759                 if (ptr >= end) {
760                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
761                                 ret = btrfs_next_leaf(rc->extent_root, path1);
762                                 if (ret < 0) {
763                                         err = ret;
764                                         goto out;
765                                 }
766                                 if (ret > 0)
767                                         break;
768                                 eb = path1->nodes[0];
769                         }
770 
771                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
772                         if (key.objectid != cur->bytenr) {
773                                 WARN_ON(exist);
774                                 break;
775                         }
776 
777                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
778                             key.type == BTRFS_METADATA_ITEM_KEY) {
779                                 ret = find_inline_backref(eb, path1->slots[0],
780                                                           &ptr, &end);
781                                 if (ret)
782                                         goto next;
783                         }
784                 }
785 
786                 if (ptr < end) {
787                         /* update key for inline back ref */
788                         struct btrfs_extent_inline_ref *iref;
789                         iref = (struct btrfs_extent_inline_ref *)ptr;
790                         key.type = btrfs_extent_inline_ref_type(eb, iref);
791                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
792                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
793                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
794                 }
795 
796                 if (exist &&
797                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
798                       exist->owner == key.offset) ||
799                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
800                       exist->bytenr == key.offset))) {
801                         exist = NULL;
802                         goto next;
803                 }
804 
805 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
806                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY ||
807                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
808                         if (key.type == BTRFS_EXTENT_REF_V0_KEY) {
809                                 struct btrfs_extent_ref_v0 *ref0;
810                                 ref0 = btrfs_item_ptr(eb, path1->slots[0],
811                                                 struct btrfs_extent_ref_v0);
812                                 if (key.objectid == key.offset) {
813                                         root = find_tree_root(rc, eb, ref0);
814                                         if (root && !should_ignore_root(root))
815                                                 cur->root = root;
816                                         else
817                                                 list_add(&cur->list, &useless);
818                                         break;
819                                 }
820                                 if (is_cowonly_root(btrfs_ref_root_v0(eb,
821                                                                       ref0)))
822                                         cur->cowonly = 1;
823                         }
824 #else
825                 BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
826                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
827 #endif
828                         if (key.objectid == key.offset) {
829                                 /*
830                                  * only root blocks of reloc trees use
831                                  * backref of this type.
832                                  */
833                                 root = find_reloc_root(rc, cur->bytenr);
834                                 BUG_ON(!root);
835                                 cur->root = root;
836                                 break;
837                         }
838 
839                         edge = alloc_backref_edge(cache);
840                         if (!edge) {
841                                 err = -ENOMEM;
842                                 goto out;
843                         }
844                         rb_node = tree_search(&cache->rb_root, key.offset);
845                         if (!rb_node) {
846                                 upper = alloc_backref_node(cache);
847                                 if (!upper) {
848                                         free_backref_edge(cache, edge);
849                                         err = -ENOMEM;
850                                         goto out;
851                                 }
852                                 upper->bytenr = key.offset;
853                                 upper->level = cur->level + 1;
854                                 /*
855                                  *  backrefs for the upper level block isn't
856                                  *  cached, add the block to pending list
857                                  */
858                                 list_add_tail(&edge->list[UPPER], &list);
859                         } else {
860                                 upper = rb_entry(rb_node, struct backref_node,
861                                                  rb_node);
862                                 BUG_ON(!upper->checked);
863                                 INIT_LIST_HEAD(&edge->list[UPPER]);
864                         }
865                         list_add_tail(&edge->list[LOWER], &cur->upper);
866                         edge->node[LOWER] = cur;
867                         edge->node[UPPER] = upper;
868 
869                         goto next;
870                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
871                         goto next;
872                 }
873 
874                 /* key.type == BTRFS_TREE_BLOCK_REF_KEY */
875                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
876                 if (IS_ERR(root)) {
877                         err = PTR_ERR(root);
878                         goto out;
879                 }
880 
881                 if (!root->ref_cows)
882                         cur->cowonly = 1;
883 
884                 if (btrfs_root_level(&root->root_item) == cur->level) {
885                         /* tree root */
886                         BUG_ON(btrfs_root_bytenr(&root->root_item) !=
887                                cur->bytenr);
888                         if (should_ignore_root(root))
889                                 list_add(&cur->list, &useless);
890                         else
891                                 cur->root = root;
892                         break;
893                 }
894 
895                 level = cur->level + 1;
896 
897                 /*
898                  * searching the tree to find upper level blocks
899                  * reference the block.
900                  */
901                 path2->search_commit_root = 1;
902                 path2->skip_locking = 1;
903                 path2->lowest_level = level;
904                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
905                 path2->lowest_level = 0;
906                 if (ret < 0) {
907                         err = ret;
908                         goto out;
909                 }
910                 if (ret > 0 && path2->slots[level] > 0)
911                         path2->slots[level]--;
912 
913                 eb = path2->nodes[level];
914                 WARN_ON(btrfs_node_blockptr(eb, path2->slots[level]) !=
915                         cur->bytenr);
916 
917                 lower = cur;
918                 need_check = true;
919                 for (; level < BTRFS_MAX_LEVEL; level++) {
920                         if (!path2->nodes[level]) {
921                                 BUG_ON(btrfs_root_bytenr(&root->root_item) !=
922                                        lower->bytenr);
923                                 if (should_ignore_root(root))
924                                         list_add(&lower->list, &useless);
925                                 else
926                                         lower->root = root;
927                                 break;
928                         }
929 
930                         edge = alloc_backref_edge(cache);
931                         if (!edge) {
932                                 err = -ENOMEM;
933                                 goto out;
934                         }
935 
936                         eb = path2->nodes[level];
937                         rb_node = tree_search(&cache->rb_root, eb->start);
938                         if (!rb_node) {
939                                 upper = alloc_backref_node(cache);
940                                 if (!upper) {
941                                         free_backref_edge(cache, edge);
942                                         err = -ENOMEM;
943                                         goto out;
944                                 }
945                                 upper->bytenr = eb->start;
946                                 upper->owner = btrfs_header_owner(eb);
947                                 upper->level = lower->level + 1;
948                                 if (!root->ref_cows)
949                                         upper->cowonly = 1;
950 
951                                 /*
952                                  * if we know the block isn't shared
953                                  * we can void checking its backrefs.
954                                  */
955                                 if (btrfs_block_can_be_shared(root, eb))
956                                         upper->checked = 0;
957                                 else
958                                         upper->checked = 1;
959 
960                                 /*
961                                  * add the block to pending list if we
962                                  * need check its backrefs, we only do this once
963                                  * while walking up a tree as we will catch
964                                  * anything else later on.
965                                  */
966                                 if (!upper->checked && need_check) {
967                                         need_check = false;
968                                         list_add_tail(&edge->list[UPPER],
969                                                       &list);
970                                 } else
971                                         INIT_LIST_HEAD(&edge->list[UPPER]);
972                         } else {
973                                 upper = rb_entry(rb_node, struct backref_node,
974                                                  rb_node);
975                                 BUG_ON(!upper->checked);
976                                 INIT_LIST_HEAD(&edge->list[UPPER]);
977                                 if (!upper->owner)
978                                         upper->owner = btrfs_header_owner(eb);
979                         }
980                         list_add_tail(&edge->list[LOWER], &lower->upper);
981                         edge->node[LOWER] = lower;
982                         edge->node[UPPER] = upper;
983 
984                         if (rb_node)
985                                 break;
986                         lower = upper;
987                         upper = NULL;
988                 }
989                 btrfs_release_path(path2);
990 next:
991                 if (ptr < end) {
992                         ptr += btrfs_extent_inline_ref_size(key.type);
993                         if (ptr >= end) {
994                                 WARN_ON(ptr > end);
995                                 ptr = 0;
996                                 end = 0;
997                         }
998                 }
999                 if (ptr >= end)
1000                         path1->slots[0]++;
1001         }
1002         btrfs_release_path(path1);
1003 
1004         cur->checked = 1;
1005         WARN_ON(exist);
1006 
1007         /* the pending list isn't empty, take the first block to process */
1008         if (!list_empty(&list)) {
1009                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1010                 list_del_init(&edge->list[UPPER]);
1011                 cur = edge->node[UPPER];
1012                 goto again;
1013         }
1014 
1015         /*
1016          * everything goes well, connect backref nodes and insert backref nodes
1017          * into the cache.
1018          */
1019         BUG_ON(!node->checked);
1020         cowonly = node->cowonly;
1021         if (!cowonly) {
1022                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1023                                       &node->rb_node);
1024                 if (rb_node)
1025                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1026                 list_add_tail(&node->lower, &cache->leaves);
1027         }
1028 
1029         list_for_each_entry(edge, &node->upper, list[LOWER])
1030                 list_add_tail(&edge->list[UPPER], &list);
1031 
1032         while (!list_empty(&list)) {
1033                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1034                 list_del_init(&edge->list[UPPER]);
1035                 upper = edge->node[UPPER];
1036                 if (upper->detached) {
1037                         list_del(&edge->list[LOWER]);
1038                         lower = edge->node[LOWER];
1039                         free_backref_edge(cache, edge);
1040                         if (list_empty(&lower->upper))
1041                                 list_add(&lower->list, &useless);
1042                         continue;
1043                 }
1044 
1045                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1046                         if (upper->lowest) {
1047                                 list_del_init(&upper->lower);
1048                                 upper->lowest = 0;
1049                         }
1050 
1051                         list_add_tail(&edge->list[UPPER], &upper->lower);
1052                         continue;
1053                 }
1054 
1055                 BUG_ON(!upper->checked);
1056                 BUG_ON(cowonly != upper->cowonly);
1057                 if (!cowonly) {
1058                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1059                                               &upper->rb_node);
1060                         if (rb_node)
1061                                 backref_tree_panic(rb_node, -EEXIST,
1062                                                    upper->bytenr);
1063                 }
1064 
1065                 list_add_tail(&edge->list[UPPER], &upper->lower);
1066 
1067                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1068                         list_add_tail(&edge->list[UPPER], &list);
1069         }
1070         /*
1071          * process useless backref nodes. backref nodes for tree leaves
1072          * are deleted from the cache. backref nodes for upper level
1073          * tree blocks are left in the cache to avoid unnecessary backref
1074          * lookup.
1075          */
1076         while (!list_empty(&useless)) {
1077                 upper = list_entry(useless.next, struct backref_node, list);
1078                 list_del_init(&upper->list);
1079                 BUG_ON(!list_empty(&upper->upper));
1080                 if (upper == node)
1081                         node = NULL;
1082                 if (upper->lowest) {
1083                         list_del_init(&upper->lower);
1084                         upper->lowest = 0;
1085                 }
1086                 while (!list_empty(&upper->lower)) {
1087                         edge = list_entry(upper->lower.next,
1088                                           struct backref_edge, list[UPPER]);
1089                         list_del(&edge->list[UPPER]);
1090                         list_del(&edge->list[LOWER]);
1091                         lower = edge->node[LOWER];
1092                         free_backref_edge(cache, edge);
1093 
1094                         if (list_empty(&lower->upper))
1095                                 list_add(&lower->list, &useless);
1096                 }
1097                 __mark_block_processed(rc, upper);
1098                 if (upper->level > 0) {
1099                         list_add(&upper->list, &cache->detached);
1100                         upper->detached = 1;
1101                 } else {
1102                         rb_erase(&upper->rb_node, &cache->rb_root);
1103                         free_backref_node(cache, upper);
1104                 }
1105         }
1106 out:
1107         btrfs_free_path(path1);
1108         btrfs_free_path(path2);
1109         if (err) {
1110                 while (!list_empty(&useless)) {
1111                         lower = list_entry(useless.next,
1112                                            struct backref_node, upper);
1113                         list_del_init(&lower->upper);
1114                 }
1115                 upper = node;
1116                 INIT_LIST_HEAD(&list);
1117                 while (upper) {
1118                         if (RB_EMPTY_NODE(&upper->rb_node)) {
1119                                 list_splice_tail(&upper->upper, &list);
1120                                 free_backref_node(cache, upper);
1121                         }
1122 
1123                         if (list_empty(&list))
1124                                 break;
1125 
1126                         edge = list_entry(list.next, struct backref_edge,
1127                                           list[LOWER]);
1128                         list_del(&edge->list[LOWER]);
1129                         upper = edge->node[UPPER];
1130                         free_backref_edge(cache, edge);
1131                 }
1132                 return ERR_PTR(err);
1133         }
1134         BUG_ON(node && node->detached);
1135         return node;
1136 }
1137 
1138 /*
1139  * helper to add backref node for the newly created snapshot.
1140  * the backref node is created by cloning backref node that
1141  * corresponds to root of source tree
1142  */
1143 static int clone_backref_node(struct btrfs_trans_handle *trans,
1144                               struct reloc_control *rc,
1145                               struct btrfs_root *src,
1146                               struct btrfs_root *dest)
1147 {
1148         struct btrfs_root *reloc_root = src->reloc_root;
1149         struct backref_cache *cache = &rc->backref_cache;
1150         struct backref_node *node = NULL;
1151         struct backref_node *new_node;
1152         struct backref_edge *edge;
1153         struct backref_edge *new_edge;
1154         struct rb_node *rb_node;
1155 
1156         if (cache->last_trans > 0)
1157                 update_backref_cache(trans, cache);
1158 
1159         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1160         if (rb_node) {
1161                 node = rb_entry(rb_node, struct backref_node, rb_node);
1162                 if (node->detached)
1163                         node = NULL;
1164                 else
1165                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1166         }
1167 
1168         if (!node) {
1169                 rb_node = tree_search(&cache->rb_root,
1170                                       reloc_root->commit_root->start);
1171                 if (rb_node) {
1172                         node = rb_entry(rb_node, struct backref_node,
1173                                         rb_node);
1174                         BUG_ON(node->detached);
1175                 }
1176         }
1177 
1178         if (!node)
1179                 return 0;
1180 
1181         new_node = alloc_backref_node(cache);
1182         if (!new_node)
1183                 return -ENOMEM;
1184 
1185         new_node->bytenr = dest->node->start;
1186         new_node->level = node->level;
1187         new_node->lowest = node->lowest;
1188         new_node->checked = 1;
1189         new_node->root = dest;
1190 
1191         if (!node->lowest) {
1192                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1193                         new_edge = alloc_backref_edge(cache);
1194                         if (!new_edge)
1195                                 goto fail;
1196 
1197                         new_edge->node[UPPER] = new_node;
1198                         new_edge->node[LOWER] = edge->node[LOWER];
1199                         list_add_tail(&new_edge->list[UPPER],
1200                                       &new_node->lower);
1201                 }
1202         } else {
1203                 list_add_tail(&new_node->lower, &cache->leaves);
1204         }
1205 
1206         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1207                               &new_node->rb_node);
1208         if (rb_node)
1209                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1210 
1211         if (!new_node->lowest) {
1212                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1213                         list_add_tail(&new_edge->list[LOWER],
1214                                       &new_edge->node[LOWER]->upper);
1215                 }
1216         }
1217         return 0;
1218 fail:
1219         while (!list_empty(&new_node->lower)) {
1220                 new_edge = list_entry(new_node->lower.next,
1221                                       struct backref_edge, list[UPPER]);
1222                 list_del(&new_edge->list[UPPER]);
1223                 free_backref_edge(cache, new_edge);
1224         }
1225         free_backref_node(cache, new_node);
1226         return -ENOMEM;
1227 }
1228 
1229 /*
1230  * helper to add 'address of tree root -> reloc tree' mapping
1231  */
1232 static int __must_check __add_reloc_root(struct btrfs_root *root)
1233 {
1234         struct rb_node *rb_node;
1235         struct mapping_node *node;
1236         struct reloc_control *rc = root->fs_info->reloc_ctl;
1237 
1238         node = kmalloc(sizeof(*node), GFP_NOFS);
1239         if (!node)
1240                 return -ENOMEM;
1241 
1242         node->bytenr = root->node->start;
1243         node->data = root;
1244 
1245         spin_lock(&rc->reloc_root_tree.lock);
1246         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1247                               node->bytenr, &node->rb_node);
1248         spin_unlock(&rc->reloc_root_tree.lock);
1249         if (rb_node) {
1250                 btrfs_panic(root->fs_info, -EEXIST, "Duplicate root found "
1251                             "for start=%llu while inserting into relocation "
1252                             "tree\n", node->bytenr);
1253                 kfree(node);
1254                 return -EEXIST;
1255         }
1256 
1257         list_add_tail(&root->root_list, &rc->reloc_roots);
1258         return 0;
1259 }
1260 
1261 /*
1262  * helper to update/delete the 'address of tree root -> reloc tree'
1263  * mapping
1264  */
1265 static int __update_reloc_root(struct btrfs_root *root, int del)
1266 {
1267         struct rb_node *rb_node;
1268         struct mapping_node *node = NULL;
1269         struct reloc_control *rc = root->fs_info->reloc_ctl;
1270 
1271         spin_lock(&rc->reloc_root_tree.lock);
1272         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1273                               root->commit_root->start);
1274         if (rb_node) {
1275                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1276                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1277         }
1278         spin_unlock(&rc->reloc_root_tree.lock);
1279 
1280         if (!node)
1281                 return 0;
1282         BUG_ON((struct btrfs_root *)node->data != root);
1283 
1284         if (!del) {
1285                 spin_lock(&rc->reloc_root_tree.lock);
1286                 node->bytenr = root->node->start;
1287                 rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1288                                       node->bytenr, &node->rb_node);
1289                 spin_unlock(&rc->reloc_root_tree.lock);
1290                 if (rb_node)
1291                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1292         } else {
1293                 spin_lock(&root->fs_info->trans_lock);
1294                 list_del_init(&root->root_list);
1295                 spin_unlock(&root->fs_info->trans_lock);
1296                 kfree(node);
1297         }
1298         return 0;
1299 }
1300 
1301 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1302                                         struct btrfs_root *root, u64 objectid)
1303 {
1304         struct btrfs_root *reloc_root;
1305         struct extent_buffer *eb;
1306         struct btrfs_root_item *root_item;
1307         struct btrfs_key root_key;
1308         u64 last_snap = 0;
1309         int ret;
1310 
1311         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1312         BUG_ON(!root_item);
1313 
1314         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1315         root_key.type = BTRFS_ROOT_ITEM_KEY;
1316         root_key.offset = objectid;
1317 
1318         if (root->root_key.objectid == objectid) {
1319                 /* called by btrfs_init_reloc_root */
1320                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1321                                       BTRFS_TREE_RELOC_OBJECTID);
1322                 BUG_ON(ret);
1323 
1324                 last_snap = btrfs_root_last_snapshot(&root->root_item);
1325                 btrfs_set_root_last_snapshot(&root->root_item,
1326                                              trans->transid - 1);
1327         } else {
1328                 /*
1329                  * called by btrfs_reloc_post_snapshot_hook.
1330                  * the source tree is a reloc tree, all tree blocks
1331                  * modified after it was created have RELOC flag
1332                  * set in their headers. so it's OK to not update
1333                  * the 'last_snapshot'.
1334                  */
1335                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1336                                       BTRFS_TREE_RELOC_OBJECTID);
1337                 BUG_ON(ret);
1338         }
1339 
1340         memcpy(root_item, &root->root_item, sizeof(*root_item));
1341         btrfs_set_root_bytenr(root_item, eb->start);
1342         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1343         btrfs_set_root_generation(root_item, trans->transid);
1344 
1345         if (root->root_key.objectid == objectid) {
1346                 btrfs_set_root_refs(root_item, 0);
1347                 memset(&root_item->drop_progress, 0,
1348                        sizeof(struct btrfs_disk_key));
1349                 root_item->drop_level = 0;
1350                 /*
1351                  * abuse rtransid, it is safe because it is impossible to
1352                  * receive data into a relocation tree.
1353                  */
1354                 btrfs_set_root_rtransid(root_item, last_snap);
1355                 btrfs_set_root_otransid(root_item, trans->transid);
1356         }
1357 
1358         btrfs_tree_unlock(eb);
1359         free_extent_buffer(eb);
1360 
1361         ret = btrfs_insert_root(trans, root->fs_info->tree_root,
1362                                 &root_key, root_item);
1363         BUG_ON(ret);
1364         kfree(root_item);
1365 
1366         reloc_root = btrfs_read_fs_root(root->fs_info->tree_root, &root_key);
1367         BUG_ON(IS_ERR(reloc_root));
1368         reloc_root->last_trans = trans->transid;
1369         return reloc_root;
1370 }
1371 
1372 /*
1373  * create reloc tree for a given fs tree. reloc tree is just a
1374  * snapshot of the fs tree with special root objectid.
1375  */
1376 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1377                           struct btrfs_root *root)
1378 {
1379         struct btrfs_root *reloc_root;
1380         struct reloc_control *rc = root->fs_info->reloc_ctl;
1381         int clear_rsv = 0;
1382         int ret;
1383 
1384         if (root->reloc_root) {
1385                 reloc_root = root->reloc_root;
1386                 reloc_root->last_trans = trans->transid;
1387                 return 0;
1388         }
1389 
1390         if (!rc || !rc->create_reloc_tree ||
1391             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1392                 return 0;
1393 
1394         if (!trans->block_rsv) {
1395                 trans->block_rsv = rc->block_rsv;
1396                 clear_rsv = 1;
1397         }
1398         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1399         if (clear_rsv)
1400                 trans->block_rsv = NULL;
1401 
1402         ret = __add_reloc_root(reloc_root);
1403         BUG_ON(ret < 0);
1404         root->reloc_root = reloc_root;
1405         return 0;
1406 }
1407 
1408 /*
1409  * update root item of reloc tree
1410  */
1411 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1412                             struct btrfs_root *root)
1413 {
1414         struct btrfs_root *reloc_root;
1415         struct btrfs_root_item *root_item;
1416         int del = 0;
1417         int ret;
1418 
1419         if (!root->reloc_root)
1420                 goto out;
1421 
1422         reloc_root = root->reloc_root;
1423         root_item = &reloc_root->root_item;
1424 
1425         if (root->fs_info->reloc_ctl->merge_reloc_tree &&
1426             btrfs_root_refs(root_item) == 0) {
1427                 root->reloc_root = NULL;
1428                 del = 1;
1429         }
1430 
1431         __update_reloc_root(reloc_root, del);
1432 
1433         if (reloc_root->commit_root != reloc_root->node) {
1434                 btrfs_set_root_node(root_item, reloc_root->node);
1435                 free_extent_buffer(reloc_root->commit_root);
1436                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1437         }
1438 
1439         ret = btrfs_update_root(trans, root->fs_info->tree_root,
1440                                 &reloc_root->root_key, root_item);
1441         BUG_ON(ret);
1442 
1443 out:
1444         return 0;
1445 }
1446 
1447 /*
1448  * helper to find first cached inode with inode number >= objectid
1449  * in a subvolume
1450  */
1451 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1452 {
1453         struct rb_node *node;
1454         struct rb_node *prev;
1455         struct btrfs_inode *entry;
1456         struct inode *inode;
1457 
1458         spin_lock(&root->inode_lock);
1459 again:
1460         node = root->inode_tree.rb_node;
1461         prev = NULL;
1462         while (node) {
1463                 prev = node;
1464                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1465 
1466                 if (objectid < btrfs_ino(&entry->vfs_inode))
1467                         node = node->rb_left;
1468                 else if (objectid > btrfs_ino(&entry->vfs_inode))
1469                         node = node->rb_right;
1470                 else
1471                         break;
1472         }
1473         if (!node) {
1474                 while (prev) {
1475                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1476                         if (objectid <= btrfs_ino(&entry->vfs_inode)) {
1477                                 node = prev;
1478                                 break;
1479                         }
1480                         prev = rb_next(prev);
1481                 }
1482         }
1483         while (node) {
1484                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1485                 inode = igrab(&entry->vfs_inode);
1486                 if (inode) {
1487                         spin_unlock(&root->inode_lock);
1488                         return inode;
1489                 }
1490 
1491                 objectid = btrfs_ino(&entry->vfs_inode) + 1;
1492                 if (cond_resched_lock(&root->inode_lock))
1493                         goto again;
1494 
1495                 node = rb_next(node);
1496         }
1497         spin_unlock(&root->inode_lock);
1498         return NULL;
1499 }
1500 
1501 static int in_block_group(u64 bytenr,
1502                           struct btrfs_block_group_cache *block_group)
1503 {
1504         if (bytenr >= block_group->key.objectid &&
1505             bytenr < block_group->key.objectid + block_group->key.offset)
1506                 return 1;
1507         return 0;
1508 }
1509 
1510 /*
1511  * get new location of data
1512  */
1513 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1514                             u64 bytenr, u64 num_bytes)
1515 {
1516         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1517         struct btrfs_path *path;
1518         struct btrfs_file_extent_item *fi;
1519         struct extent_buffer *leaf;
1520         int ret;
1521 
1522         path = btrfs_alloc_path();
1523         if (!path)
1524                 return -ENOMEM;
1525 
1526         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1527         ret = btrfs_lookup_file_extent(NULL, root, path, btrfs_ino(reloc_inode),
1528                                        bytenr, 0);
1529         if (ret < 0)
1530                 goto out;
1531         if (ret > 0) {
1532                 ret = -ENOENT;
1533                 goto out;
1534         }
1535 
1536         leaf = path->nodes[0];
1537         fi = btrfs_item_ptr(leaf, path->slots[0],
1538                             struct btrfs_file_extent_item);
1539 
1540         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1541                btrfs_file_extent_compression(leaf, fi) ||
1542                btrfs_file_extent_encryption(leaf, fi) ||
1543                btrfs_file_extent_other_encoding(leaf, fi));
1544 
1545         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1546                 ret = 1;
1547                 goto out;
1548         }
1549 
1550         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1551         ret = 0;
1552 out:
1553         btrfs_free_path(path);
1554         return ret;
1555 }
1556 
1557 /*
1558  * update file extent items in the tree leaf to point to
1559  * the new locations.
1560  */
1561 static noinline_for_stack
1562 int replace_file_extents(struct btrfs_trans_handle *trans,
1563                          struct reloc_control *rc,
1564                          struct btrfs_root *root,
1565                          struct extent_buffer *leaf)
1566 {
1567         struct btrfs_key key;
1568         struct btrfs_file_extent_item *fi;
1569         struct inode *inode = NULL;
1570         u64 parent;
1571         u64 bytenr;
1572         u64 new_bytenr = 0;
1573         u64 num_bytes;
1574         u64 end;
1575         u32 nritems;
1576         u32 i;
1577         int ret;
1578         int first = 1;
1579         int dirty = 0;
1580 
1581         if (rc->stage != UPDATE_DATA_PTRS)
1582                 return 0;
1583 
1584         /* reloc trees always use full backref */
1585         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1586                 parent = leaf->start;
1587         else
1588                 parent = 0;
1589 
1590         nritems = btrfs_header_nritems(leaf);
1591         for (i = 0; i < nritems; i++) {
1592                 cond_resched();
1593                 btrfs_item_key_to_cpu(leaf, &key, i);
1594                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1595                         continue;
1596                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1597                 if (btrfs_file_extent_type(leaf, fi) ==
1598                     BTRFS_FILE_EXTENT_INLINE)
1599                         continue;
1600                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1601                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1602                 if (bytenr == 0)
1603                         continue;
1604                 if (!in_block_group(bytenr, rc->block_group))
1605                         continue;
1606 
1607                 /*
1608                  * if we are modifying block in fs tree, wait for readpage
1609                  * to complete and drop the extent cache
1610                  */
1611                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1612                         if (first) {
1613                                 inode = find_next_inode(root, key.objectid);
1614                                 first = 0;
1615                         } else if (inode && btrfs_ino(inode) < key.objectid) {
1616                                 btrfs_add_delayed_iput(inode);
1617                                 inode = find_next_inode(root, key.objectid);
1618                         }
1619                         if (inode && btrfs_ino(inode) == key.objectid) {
1620                                 end = key.offset +
1621                                       btrfs_file_extent_num_bytes(leaf, fi);
1622                                 WARN_ON(!IS_ALIGNED(key.offset,
1623                                                     root->sectorsize));
1624                                 WARN_ON(!IS_ALIGNED(end, root->sectorsize));
1625                                 end--;
1626                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1627                                                       key.offset, end);
1628                                 if (!ret)
1629                                         continue;
1630 
1631                                 btrfs_drop_extent_cache(inode, key.offset, end,
1632                                                         1);
1633                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1634                                               key.offset, end);
1635                         }
1636                 }
1637 
1638                 ret = get_new_location(rc->data_inode, &new_bytenr,
1639                                        bytenr, num_bytes);
1640                 if (ret > 0) {
1641                         WARN_ON(1);
1642                         continue;
1643                 }
1644                 BUG_ON(ret < 0);
1645 
1646                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1647                 dirty = 1;
1648 
1649                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1650                 ret = btrfs_inc_extent_ref(trans, root, new_bytenr,
1651                                            num_bytes, parent,
1652                                            btrfs_header_owner(leaf),
1653                                            key.objectid, key.offset, 1);
1654                 BUG_ON(ret);
1655 
1656                 ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
1657                                         parent, btrfs_header_owner(leaf),
1658                                         key.objectid, key.offset, 1);
1659                 BUG_ON(ret);
1660         }
1661         if (dirty)
1662                 btrfs_mark_buffer_dirty(leaf);
1663         if (inode)
1664                 btrfs_add_delayed_iput(inode);
1665         return 0;
1666 }
1667 
1668 static noinline_for_stack
1669 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1670                      struct btrfs_path *path, int level)
1671 {
1672         struct btrfs_disk_key key1;
1673         struct btrfs_disk_key key2;
1674         btrfs_node_key(eb, &key1, slot);
1675         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1676         return memcmp(&key1, &key2, sizeof(key1));
1677 }
1678 
1679 /*
1680  * try to replace tree blocks in fs tree with the new blocks
1681  * in reloc tree. tree blocks haven't been modified since the
1682  * reloc tree was create can be replaced.
1683  *
1684  * if a block was replaced, level of the block + 1 is returned.
1685  * if no block got replaced, 0 is returned. if there are other
1686  * errors, a negative error number is returned.
1687  */
1688 static noinline_for_stack
1689 int replace_path(struct btrfs_trans_handle *trans,
1690                  struct btrfs_root *dest, struct btrfs_root *src,
1691                  struct btrfs_path *path, struct btrfs_key *next_key,
1692                  int lowest_level, int max_level)
1693 {
1694         struct extent_buffer *eb;
1695         struct extent_buffer *parent;
1696         struct btrfs_key key;
1697         u64 old_bytenr;
1698         u64 new_bytenr;
1699         u64 old_ptr_gen;
1700         u64 new_ptr_gen;
1701         u64 last_snapshot;
1702         u32 blocksize;
1703         int cow = 0;
1704         int level;
1705         int ret;
1706         int slot;
1707 
1708         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1709         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1710 
1711         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1712 again:
1713         slot = path->slots[lowest_level];
1714         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1715 
1716         eb = btrfs_lock_root_node(dest);
1717         btrfs_set_lock_blocking(eb);
1718         level = btrfs_header_level(eb);
1719 
1720         if (level < lowest_level) {
1721                 btrfs_tree_unlock(eb);
1722                 free_extent_buffer(eb);
1723                 return 0;
1724         }
1725 
1726         if (cow) {
1727                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1728                 BUG_ON(ret);
1729         }
1730         btrfs_set_lock_blocking(eb);
1731 
1732         if (next_key) {
1733                 next_key->objectid = (u64)-1;
1734                 next_key->type = (u8)-1;
1735                 next_key->offset = (u64)-1;
1736         }
1737 
1738         parent = eb;
1739         while (1) {
1740                 level = btrfs_header_level(parent);
1741                 BUG_ON(level < lowest_level);
1742 
1743                 ret = btrfs_bin_search(parent, &key, level, &slot);
1744                 if (ret && slot > 0)
1745                         slot--;
1746 
1747                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1748                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1749 
1750                 old_bytenr = btrfs_node_blockptr(parent, slot);
1751                 blocksize = btrfs_level_size(dest, level - 1);
1752                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1753 
1754                 if (level <= max_level) {
1755                         eb = path->nodes[level];
1756                         new_bytenr = btrfs_node_blockptr(eb,
1757                                                         path->slots[level]);
1758                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1759                                                         path->slots[level]);
1760                 } else {
1761                         new_bytenr = 0;
1762                         new_ptr_gen = 0;
1763                 }
1764 
1765                 if (new_bytenr > 0 && new_bytenr == old_bytenr) {
1766                         WARN_ON(1);
1767                         ret = level;
1768                         break;
1769                 }
1770 
1771                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1772                     memcmp_node_keys(parent, slot, path, level)) {
1773                         if (level <= lowest_level) {
1774                                 ret = 0;
1775                                 break;
1776                         }
1777 
1778                         eb = read_tree_block(dest, old_bytenr, blocksize,
1779                                              old_ptr_gen);
1780                         if (!eb || !extent_buffer_uptodate(eb)) {
1781                                 ret = (!eb) ? -ENOMEM : -EIO;
1782                                 free_extent_buffer(eb);
1783                                 break;
1784                         }
1785                         btrfs_tree_lock(eb);
1786                         if (cow) {
1787                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1788                                                       slot, &eb);
1789                                 BUG_ON(ret);
1790                         }
1791                         btrfs_set_lock_blocking(eb);
1792 
1793                         btrfs_tree_unlock(parent);
1794                         free_extent_buffer(parent);
1795 
1796                         parent = eb;
1797                         continue;
1798                 }
1799 
1800                 if (!cow) {
1801                         btrfs_tree_unlock(parent);
1802                         free_extent_buffer(parent);
1803                         cow = 1;
1804                         goto again;
1805                 }
1806 
1807                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1808                                       path->slots[level]);
1809                 btrfs_release_path(path);
1810 
1811                 path->lowest_level = level;
1812                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1813                 path->lowest_level = 0;
1814                 BUG_ON(ret);
1815 
1816                 /*
1817                  * swap blocks in fs tree and reloc tree.
1818                  */
1819                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1820                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1821                 btrfs_mark_buffer_dirty(parent);
1822 
1823                 btrfs_set_node_blockptr(path->nodes[level],
1824                                         path->slots[level], old_bytenr);
1825                 btrfs_set_node_ptr_generation(path->nodes[level],
1826                                               path->slots[level], old_ptr_gen);
1827                 btrfs_mark_buffer_dirty(path->nodes[level]);
1828 
1829                 ret = btrfs_inc_extent_ref(trans, src, old_bytenr, blocksize,
1830                                         path->nodes[level]->start,
1831                                         src->root_key.objectid, level - 1, 0,
1832                                         1);
1833                 BUG_ON(ret);
1834                 ret = btrfs_inc_extent_ref(trans, dest, new_bytenr, blocksize,
1835                                         0, dest->root_key.objectid, level - 1,
1836                                         0, 1);
1837                 BUG_ON(ret);
1838 
1839                 ret = btrfs_free_extent(trans, src, new_bytenr, blocksize,
1840                                         path->nodes[level]->start,
1841                                         src->root_key.objectid, level - 1, 0,
1842                                         1);
1843                 BUG_ON(ret);
1844 
1845                 ret = btrfs_free_extent(trans, dest, old_bytenr, blocksize,
1846                                         0, dest->root_key.objectid, level - 1,
1847                                         0, 1);
1848                 BUG_ON(ret);
1849 
1850                 btrfs_unlock_up_safe(path, 0);
1851 
1852                 ret = level;
1853                 break;
1854         }
1855         btrfs_tree_unlock(parent);
1856         free_extent_buffer(parent);
1857         return ret;
1858 }
1859 
1860 /*
1861  * helper to find next relocated block in reloc tree
1862  */
1863 static noinline_for_stack
1864 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1865                        int *level)
1866 {
1867         struct extent_buffer *eb;
1868         int i;
1869         u64 last_snapshot;
1870         u32 nritems;
1871 
1872         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1873 
1874         for (i = 0; i < *level; i++) {
1875                 free_extent_buffer(path->nodes[i]);
1876                 path->nodes[i] = NULL;
1877         }
1878 
1879         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1880                 eb = path->nodes[i];
1881                 nritems = btrfs_header_nritems(eb);
1882                 while (path->slots[i] + 1 < nritems) {
1883                         path->slots[i]++;
1884                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
1885                             last_snapshot)
1886                                 continue;
1887 
1888                         *level = i;
1889                         return 0;
1890                 }
1891                 free_extent_buffer(path->nodes[i]);
1892                 path->nodes[i] = NULL;
1893         }
1894         return 1;
1895 }
1896 
1897 /*
1898  * walk down reloc tree to find relocated block of lowest level
1899  */
1900 static noinline_for_stack
1901 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1902                          int *level)
1903 {
1904         struct extent_buffer *eb = NULL;
1905         int i;
1906         u64 bytenr;
1907         u64 ptr_gen = 0;
1908         u64 last_snapshot;
1909         u32 blocksize;
1910         u32 nritems;
1911 
1912         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1913 
1914         for (i = *level; i > 0; i--) {
1915                 eb = path->nodes[i];
1916                 nritems = btrfs_header_nritems(eb);
1917                 while (path->slots[i] < nritems) {
1918                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
1919                         if (ptr_gen > last_snapshot)
1920                                 break;
1921                         path->slots[i]++;
1922                 }
1923                 if (path->slots[i] >= nritems) {
1924                         if (i == *level)
1925                                 break;
1926                         *level = i + 1;
1927                         return 0;
1928                 }
1929                 if (i == 1) {
1930                         *level = i;
1931                         return 0;
1932                 }
1933 
1934                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
1935                 blocksize = btrfs_level_size(root, i - 1);
1936                 eb = read_tree_block(root, bytenr, blocksize, ptr_gen);
1937                 if (!eb || !extent_buffer_uptodate(eb)) {
1938                         free_extent_buffer(eb);
1939                         return -EIO;
1940                 }
1941                 BUG_ON(btrfs_header_level(eb) != i - 1);
1942                 path->nodes[i - 1] = eb;
1943                 path->slots[i - 1] = 0;
1944         }
1945         return 1;
1946 }
1947 
1948 /*
1949  * invalidate extent cache for file extents whose key in range of
1950  * [min_key, max_key)
1951  */
1952 static int invalidate_extent_cache(struct btrfs_root *root,
1953                                    struct btrfs_key *min_key,
1954                                    struct btrfs_key *max_key)
1955 {
1956         struct inode *inode = NULL;
1957         u64 objectid;
1958         u64 start, end;
1959         u64 ino;
1960 
1961         objectid = min_key->objectid;
1962         while (1) {
1963                 cond_resched();
1964                 iput(inode);
1965 
1966                 if (objectid > max_key->objectid)
1967                         break;
1968 
1969                 inode = find_next_inode(root, objectid);
1970                 if (!inode)
1971                         break;
1972                 ino = btrfs_ino(inode);
1973 
1974                 if (ino > max_key->objectid) {
1975                         iput(inode);
1976                         break;
1977                 }
1978 
1979                 objectid = ino + 1;
1980                 if (!S_ISREG(inode->i_mode))
1981                         continue;
1982 
1983                 if (unlikely(min_key->objectid == ino)) {
1984                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
1985                                 continue;
1986                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
1987                                 start = 0;
1988                         else {
1989                                 start = min_key->offset;
1990                                 WARN_ON(!IS_ALIGNED(start, root->sectorsize));
1991                         }
1992                 } else {
1993                         start = 0;
1994                 }
1995 
1996                 if (unlikely(max_key->objectid == ino)) {
1997                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
1998                                 continue;
1999                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2000                                 end = (u64)-1;
2001                         } else {
2002                                 if (max_key->offset == 0)
2003                                         continue;
2004                                 end = max_key->offset;
2005                                 WARN_ON(!IS_ALIGNED(end, root->sectorsize));
2006                                 end--;
2007                         }
2008                 } else {
2009                         end = (u64)-1;
2010                 }
2011 
2012                 /* the lock_extent waits for readpage to complete */
2013                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2014                 btrfs_drop_extent_cache(inode, start, end, 1);
2015                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2016         }
2017         return 0;
2018 }
2019 
2020 static int find_next_key(struct btrfs_path *path, int level,
2021                          struct btrfs_key *key)
2022 
2023 {
2024         while (level < BTRFS_MAX_LEVEL) {
2025                 if (!path->nodes[level])
2026                         break;
2027                 if (path->slots[level] + 1 <
2028                     btrfs_header_nritems(path->nodes[level])) {
2029                         btrfs_node_key_to_cpu(path->nodes[level], key,
2030                                               path->slots[level] + 1);
2031                         return 0;
2032                 }
2033                 level++;
2034         }
2035         return 1;
2036 }
2037 
2038 /*
2039  * merge the relocated tree blocks in reloc tree with corresponding
2040  * fs tree.
2041  */
2042 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2043                                                struct btrfs_root *root)
2044 {
2045         LIST_HEAD(inode_list);
2046         struct btrfs_key key;
2047         struct btrfs_key next_key;
2048         struct btrfs_trans_handle *trans;
2049         struct btrfs_root *reloc_root;
2050         struct btrfs_root_item *root_item;
2051         struct btrfs_path *path;
2052         struct extent_buffer *leaf;
2053         int level;
2054         int max_level;
2055         int replaced = 0;
2056         int ret;
2057         int err = 0;
2058         u32 min_reserved;
2059 
2060         path = btrfs_alloc_path();
2061         if (!path)
2062                 return -ENOMEM;
2063         path->reada = 1;
2064 
2065         reloc_root = root->reloc_root;
2066         root_item = &reloc_root->root_item;
2067 
2068         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2069                 level = btrfs_root_level(root_item);
2070                 extent_buffer_get(reloc_root->node);
2071                 path->nodes[level] = reloc_root->node;
2072                 path->slots[level] = 0;
2073         } else {
2074                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2075 
2076                 level = root_item->drop_level;
2077                 BUG_ON(level == 0);
2078                 path->lowest_level = level;
2079                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2080                 path->lowest_level = 0;
2081                 if (ret < 0) {
2082                         btrfs_free_path(path);
2083                         return ret;
2084                 }
2085 
2086                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2087                                       path->slots[level]);
2088                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2089 
2090                 btrfs_unlock_up_safe(path, 0);
2091         }
2092 
2093         min_reserved = root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2094         memset(&next_key, 0, sizeof(next_key));
2095 
2096         while (1) {
2097                 trans = btrfs_start_transaction(root, 0);
2098                 BUG_ON(IS_ERR(trans));
2099                 trans->block_rsv = rc->block_rsv;
2100 
2101                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2102                                              BTRFS_RESERVE_FLUSH_ALL);
2103                 if (ret) {
2104                         BUG_ON(ret != -EAGAIN);
2105                         ret = btrfs_commit_transaction(trans, root);
2106                         BUG_ON(ret);
2107                         continue;
2108                 }
2109 
2110                 replaced = 0;
2111                 max_level = level;
2112 
2113                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2114                 if (ret < 0) {
2115                         err = ret;
2116                         goto out;
2117                 }
2118                 if (ret > 0)
2119                         break;
2120 
2121                 if (!find_next_key(path, level, &key) &&
2122                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2123                         ret = 0;
2124                 } else {
2125                         ret = replace_path(trans, root, reloc_root, path,
2126                                            &next_key, level, max_level);
2127                 }
2128                 if (ret < 0) {
2129                         err = ret;
2130                         goto out;
2131                 }
2132 
2133                 if (ret > 0) {
2134                         level = ret;
2135                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2136                                               path->slots[level]);
2137                         replaced = 1;
2138                 }
2139 
2140                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2141                 if (ret > 0)
2142                         break;
2143 
2144                 BUG_ON(level == 0);
2145                 /*
2146                  * save the merging progress in the drop_progress.
2147                  * this is OK since root refs == 1 in this case.
2148                  */
2149                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2150                                path->slots[level]);
2151                 root_item->drop_level = level;
2152 
2153                 btrfs_end_transaction_throttle(trans, root);
2154 
2155                 btrfs_btree_balance_dirty(root);
2156 
2157                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2158                         invalidate_extent_cache(root, &key, &next_key);
2159         }
2160 
2161         /*
2162          * handle the case only one block in the fs tree need to be
2163          * relocated and the block is tree root.
2164          */
2165         leaf = btrfs_lock_root_node(root);
2166         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2167         btrfs_tree_unlock(leaf);
2168         free_extent_buffer(leaf);
2169         if (ret < 0)
2170                 err = ret;
2171 out:
2172         btrfs_free_path(path);
2173 
2174         if (err == 0) {
2175                 memset(&root_item->drop_progress, 0,
2176                        sizeof(root_item->drop_progress));
2177                 root_item->drop_level = 0;
2178                 btrfs_set_root_refs(root_item, 0);
2179                 btrfs_update_reloc_root(trans, root);
2180         }
2181 
2182         btrfs_end_transaction_throttle(trans, root);
2183 
2184         btrfs_btree_balance_dirty(root);
2185 
2186         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2187                 invalidate_extent_cache(root, &key, &next_key);
2188 
2189         return err;
2190 }
2191 
2192 static noinline_for_stack
2193 int prepare_to_merge(struct reloc_control *rc, int err)
2194 {
2195         struct btrfs_root *root = rc->extent_root;
2196         struct btrfs_root *reloc_root;
2197         struct btrfs_trans_handle *trans;
2198         LIST_HEAD(reloc_roots);
2199         u64 num_bytes = 0;
2200         int ret;
2201 
2202         mutex_lock(&root->fs_info->reloc_mutex);
2203         rc->merging_rsv_size += root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2204         rc->merging_rsv_size += rc->nodes_relocated * 2;
2205         mutex_unlock(&root->fs_info->reloc_mutex);
2206 
2207 again:
2208         if (!err) {
2209                 num_bytes = rc->merging_rsv_size;
2210                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2211                                           BTRFS_RESERVE_FLUSH_ALL);
2212                 if (ret)
2213                         err = ret;
2214         }
2215 
2216         trans = btrfs_join_transaction(rc->extent_root);
2217         if (IS_ERR(trans)) {
2218                 if (!err)
2219                         btrfs_block_rsv_release(rc->extent_root,
2220                                                 rc->block_rsv, num_bytes);
2221                 return PTR_ERR(trans);
2222         }
2223 
2224         if (!err) {
2225                 if (num_bytes != rc->merging_rsv_size) {
2226                         btrfs_end_transaction(trans, rc->extent_root);
2227                         btrfs_block_rsv_release(rc->extent_root,
2228                                                 rc->block_rsv, num_bytes);
2229                         goto again;
2230                 }
2231         }
2232 
2233         rc->merge_reloc_tree = 1;
2234 
2235         while (!list_empty(&rc->reloc_roots)) {
2236                 reloc_root = list_entry(rc->reloc_roots.next,
2237                                         struct btrfs_root, root_list);
2238                 list_del_init(&reloc_root->root_list);
2239 
2240                 root = read_fs_root(reloc_root->fs_info,
2241                                     reloc_root->root_key.offset);
2242                 BUG_ON(IS_ERR(root));
2243                 BUG_ON(root->reloc_root != reloc_root);
2244 
2245                 /*
2246                  * set reference count to 1, so btrfs_recover_relocation
2247                  * knows it should resumes merging
2248                  */
2249                 if (!err)
2250                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2251                 btrfs_update_reloc_root(trans, root);
2252 
2253                 list_add(&reloc_root->root_list, &reloc_roots);
2254         }
2255 
2256         list_splice(&reloc_roots, &rc->reloc_roots);
2257 
2258         if (!err)
2259                 btrfs_commit_transaction(trans, rc->extent_root);
2260         else
2261                 btrfs_end_transaction(trans, rc->extent_root);
2262         return err;
2263 }
2264 
2265 static noinline_for_stack
2266 void free_reloc_roots(struct list_head *list)
2267 {
2268         struct btrfs_root *reloc_root;
2269 
2270         while (!list_empty(list)) {
2271                 reloc_root = list_entry(list->next, struct btrfs_root,
2272                                         root_list);
2273                 __update_reloc_root(reloc_root, 1);
2274                 free_extent_buffer(reloc_root->node);
2275                 free_extent_buffer(reloc_root->commit_root);
2276                 kfree(reloc_root);
2277         }
2278 }
2279 
2280 static noinline_for_stack
2281 int merge_reloc_roots(struct reloc_control *rc)
2282 {
2283         struct btrfs_trans_handle *trans;
2284         struct btrfs_root *root;
2285         struct btrfs_root *reloc_root;
2286         u64 last_snap;
2287         u64 otransid;
2288         u64 objectid;
2289         LIST_HEAD(reloc_roots);
2290         int found = 0;
2291         int ret = 0;
2292 again:
2293         root = rc->extent_root;
2294 
2295         /*
2296          * this serializes us with btrfs_record_root_in_transaction,
2297          * we have to make sure nobody is in the middle of
2298          * adding their roots to the list while we are
2299          * doing this splice
2300          */
2301         mutex_lock(&root->fs_info->reloc_mutex);
2302         list_splice_init(&rc->reloc_roots, &reloc_roots);
2303         mutex_unlock(&root->fs_info->reloc_mutex);
2304 
2305         while (!list_empty(&reloc_roots)) {
2306                 found = 1;
2307                 reloc_root = list_entry(reloc_roots.next,
2308                                         struct btrfs_root, root_list);
2309 
2310                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2311                         root = read_fs_root(reloc_root->fs_info,
2312                                             reloc_root->root_key.offset);
2313                         BUG_ON(IS_ERR(root));
2314                         BUG_ON(root->reloc_root != reloc_root);
2315 
2316                         ret = merge_reloc_root(rc, root);
2317                         if (ret)
2318                                 goto out;
2319                 } else {
2320                         list_del_init(&reloc_root->root_list);
2321                 }
2322 
2323                 /*
2324                  * we keep the old last snapshod transid in rtranid when we
2325                  * created the relocation tree.
2326                  */
2327                 last_snap = btrfs_root_rtransid(&reloc_root->root_item);
2328                 otransid = btrfs_root_otransid(&reloc_root->root_item);
2329                 objectid = reloc_root->root_key.offset;
2330 
2331                 ret = btrfs_drop_snapshot(reloc_root, rc->block_rsv, 0, 1);
2332                 if (ret < 0) {
2333                         if (list_empty(&reloc_root->root_list))
2334                                 list_add_tail(&reloc_root->root_list,
2335                                               &reloc_roots);
2336                         goto out;
2337                 } else if (!ret) {
2338                         /*
2339                          * recover the last snapshot tranid to avoid
2340                          * the space balance break NOCOW.
2341                          */
2342                         root = read_fs_root(rc->extent_root->fs_info,
2343                                             objectid);
2344                         if (IS_ERR(root))
2345                                 continue;
2346 
2347                         if (btrfs_root_refs(&root->root_item) == 0)
2348                                 continue;
2349 
2350                         trans = btrfs_join_transaction(root);
2351                         BUG_ON(IS_ERR(trans));
2352 
2353                         /* Check if the fs/file tree was snapshoted or not. */
2354                         if (btrfs_root_last_snapshot(&root->root_item) ==
2355                             otransid - 1)
2356                                 btrfs_set_root_last_snapshot(&root->root_item,
2357                                                              last_snap);
2358                                 
2359                         btrfs_end_transaction(trans, root);
2360                 }
2361         }
2362 
2363         if (found) {
2364                 found = 0;
2365                 goto again;
2366         }
2367 out:
2368         if (ret) {
2369                 btrfs_std_error(root->fs_info, ret);
2370                 if (!list_empty(&reloc_roots))
2371                         free_reloc_roots(&reloc_roots);
2372         }
2373 
2374         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2375         return ret;
2376 }
2377 
2378 static void free_block_list(struct rb_root *blocks)
2379 {
2380         struct tree_block *block;
2381         struct rb_node *rb_node;
2382         while ((rb_node = rb_first(blocks))) {
2383                 block = rb_entry(rb_node, struct tree_block, rb_node);
2384                 rb_erase(rb_node, blocks);
2385                 kfree(block);
2386         }
2387 }
2388 
2389 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2390                                       struct btrfs_root *reloc_root)
2391 {
2392         struct btrfs_root *root;
2393 
2394         if (reloc_root->last_trans == trans->transid)
2395                 return 0;
2396 
2397         root = read_fs_root(reloc_root->fs_info, reloc_root->root_key.offset);
2398         BUG_ON(IS_ERR(root));
2399         BUG_ON(root->reloc_root != reloc_root);
2400 
2401         return btrfs_record_root_in_trans(trans, root);
2402 }
2403 
2404 static noinline_for_stack
2405 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2406                                      struct reloc_control *rc,
2407                                      struct backref_node *node,
2408                                      struct backref_edge *edges[], int *nr)
2409 {
2410         struct backref_node *next;
2411         struct btrfs_root *root;
2412         int index = 0;
2413 
2414         next = node;
2415         while (1) {
2416                 cond_resched();
2417                 next = walk_up_backref(next, edges, &index);
2418                 root = next->root;
2419                 BUG_ON(!root);
2420                 BUG_ON(!root->ref_cows);
2421 
2422                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2423                         record_reloc_root_in_trans(trans, root);
2424                         break;
2425                 }
2426 
2427                 btrfs_record_root_in_trans(trans, root);
2428                 root = root->reloc_root;
2429 
2430                 if (next->new_bytenr != root->node->start) {
2431                         BUG_ON(next->new_bytenr);
2432                         BUG_ON(!list_empty(&next->list));
2433                         next->new_bytenr = root->node->start;
2434                         next->root = root;
2435                         list_add_tail(&next->list,
2436                                       &rc->backref_cache.changed);
2437                         __mark_block_processed(rc, next);
2438                         break;
2439                 }
2440 
2441                 WARN_ON(1);
2442                 root = NULL;
2443                 next = walk_down_backref(edges, &index);
2444                 if (!next || next->level <= node->level)
2445                         break;
2446         }
2447         if (!root)
2448                 return NULL;
2449 
2450         *nr = index;
2451         next = node;
2452         /* setup backref node path for btrfs_reloc_cow_block */
2453         while (1) {
2454                 rc->backref_cache.path[next->level] = next;
2455                 if (--index < 0)
2456                         break;
2457                 next = edges[index]->node[UPPER];
2458         }
2459         return root;
2460 }
2461 
2462 /*
2463  * select a tree root for relocation. return NULL if the block
2464  * is reference counted. we should use do_relocation() in this
2465  * case. return a tree root pointer if the block isn't reference
2466  * counted. return -ENOENT if the block is root of reloc tree.
2467  */
2468 static noinline_for_stack
2469 struct btrfs_root *select_one_root(struct btrfs_trans_handle *trans,
2470                                    struct backref_node *node)
2471 {
2472         struct backref_node *next;
2473         struct btrfs_root *root;
2474         struct btrfs_root *fs_root = NULL;
2475         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2476         int index = 0;
2477 
2478         next = node;
2479         while (1) {
2480                 cond_resched();
2481                 next = walk_up_backref(next, edges, &index);
2482                 root = next->root;
2483                 BUG_ON(!root);
2484 
2485                 /* no other choice for non-references counted tree */
2486                 if (!root->ref_cows)
2487                         return root;
2488 
2489                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2490                         fs_root = root;
2491 
2492                 if (next != node)
2493                         return NULL;
2494 
2495                 next = walk_down_backref(edges, &index);
2496                 if (!next || next->level <= node->level)
2497                         break;
2498         }
2499 
2500         if (!fs_root)
2501                 return ERR_PTR(-ENOENT);
2502         return fs_root;
2503 }
2504 
2505 static noinline_for_stack
2506 u64 calcu_metadata_size(struct reloc_control *rc,
2507                         struct backref_node *node, int reserve)
2508 {
2509         struct backref_node *next = node;
2510         struct backref_edge *edge;
2511         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2512         u64 num_bytes = 0;
2513         int index = 0;
2514 
2515         BUG_ON(reserve && node->processed);
2516 
2517         while (next) {
2518                 cond_resched();
2519                 while (1) {
2520                         if (next->processed && (reserve || next != node))
2521                                 break;
2522 
2523                         num_bytes += btrfs_level_size(rc->extent_root,
2524                                                       next->level);
2525 
2526                         if (list_empty(&next->upper))
2527                                 break;
2528 
2529                         edge = list_entry(next->upper.next,
2530                                           struct backref_edge, list[LOWER]);
2531                         edges[index++] = edge;
2532                         next = edge->node[UPPER];
2533                 }
2534                 next = walk_down_backref(edges, &index);
2535         }
2536         return num_bytes;
2537 }
2538 
2539 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2540                                   struct reloc_control *rc,
2541                                   struct backref_node *node)
2542 {
2543         struct btrfs_root *root = rc->extent_root;
2544         u64 num_bytes;
2545         int ret;
2546 
2547         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2548 
2549         trans->block_rsv = rc->block_rsv;
2550         ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2551                                   BTRFS_RESERVE_FLUSH_ALL);
2552         if (ret) {
2553                 if (ret == -EAGAIN)
2554                         rc->commit_transaction = 1;
2555                 return ret;
2556         }
2557 
2558         return 0;
2559 }
2560 
2561 static void release_metadata_space(struct reloc_control *rc,
2562                                    struct backref_node *node)
2563 {
2564         u64 num_bytes = calcu_metadata_size(rc, node, 0) * 2;
2565         btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, num_bytes);
2566 }
2567 
2568 /*
2569  * relocate a block tree, and then update pointers in upper level
2570  * blocks that reference the block to point to the new location.
2571  *
2572  * if called by link_to_upper, the block has already been relocated.
2573  * in that case this function just updates pointers.
2574  */
2575 static int do_relocation(struct btrfs_trans_handle *trans,
2576                          struct reloc_control *rc,
2577                          struct backref_node *node,
2578                          struct btrfs_key *key,
2579                          struct btrfs_path *path, int lowest)
2580 {
2581         struct backref_node *upper;
2582         struct backref_edge *edge;
2583         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2584         struct btrfs_root *root;
2585         struct extent_buffer *eb;
2586         u32 blocksize;
2587         u64 bytenr;
2588         u64 generation;
2589         int nr;
2590         int slot;
2591         int ret;
2592         int err = 0;
2593 
2594         BUG_ON(lowest && node->eb);
2595 
2596         path->lowest_level = node->level + 1;
2597         rc->backref_cache.path[node->level] = node;
2598         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2599                 cond_resched();
2600 
2601                 upper = edge->node[UPPER];
2602                 root = select_reloc_root(trans, rc, upper, edges, &nr);
2603                 BUG_ON(!root);
2604 
2605                 if (upper->eb && !upper->locked) {
2606                         if (!lowest) {
2607                                 ret = btrfs_bin_search(upper->eb, key,
2608                                                        upper->level, &slot);
2609                                 BUG_ON(ret);
2610                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2611                                 if (node->eb->start == bytenr)
2612                                         goto next;
2613                         }
2614                         drop_node_buffer(upper);
2615                 }
2616 
2617                 if (!upper->eb) {
2618                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2619                         if (ret < 0) {
2620                                 err = ret;
2621                                 break;
2622                         }
2623                         BUG_ON(ret > 0);
2624 
2625                         if (!upper->eb) {
2626                                 upper->eb = path->nodes[upper->level];
2627                                 path->nodes[upper->level] = NULL;
2628                         } else {
2629                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2630                         }
2631 
2632                         upper->locked = 1;
2633                         path->locks[upper->level] = 0;
2634 
2635                         slot = path->slots[upper->level];
2636                         btrfs_release_path(path);
2637                 } else {
2638                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2639                                                &slot);
2640                         BUG_ON(ret);
2641                 }
2642 
2643                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2644                 if (lowest) {
2645                         BUG_ON(bytenr != node->bytenr);
2646                 } else {
2647                         if (node->eb->start == bytenr)
2648                                 goto next;
2649                 }
2650 
2651                 blocksize = btrfs_level_size(root, node->level);
2652                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2653                 eb = read_tree_block(root, bytenr, blocksize, generation);
2654                 if (!eb || !extent_buffer_uptodate(eb)) {
2655                         free_extent_buffer(eb);
2656                         err = -EIO;
2657                         goto next;
2658                 }
2659                 btrfs_tree_lock(eb);
2660                 btrfs_set_lock_blocking(eb);
2661 
2662                 if (!node->eb) {
2663                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2664                                               slot, &eb);
2665                         btrfs_tree_unlock(eb);
2666                         free_extent_buffer(eb);
2667                         if (ret < 0) {
2668                                 err = ret;
2669                                 goto next;
2670                         }
2671                         BUG_ON(node->eb != eb);
2672                 } else {
2673                         btrfs_set_node_blockptr(upper->eb, slot,
2674                                                 node->eb->start);
2675                         btrfs_set_node_ptr_generation(upper->eb, slot,
2676                                                       trans->transid);
2677                         btrfs_mark_buffer_dirty(upper->eb);
2678 
2679                         ret = btrfs_inc_extent_ref(trans, root,
2680                                                 node->eb->start, blocksize,
2681                                                 upper->eb->start,
2682                                                 btrfs_header_owner(upper->eb),
2683                                                 node->level, 0, 1);
2684                         BUG_ON(ret);
2685 
2686                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2687                         BUG_ON(ret);
2688                 }
2689 next:
2690                 if (!upper->pending)
2691                         drop_node_buffer(upper);
2692                 else
2693                         unlock_node_buffer(upper);
2694                 if (err)
2695                         break;
2696         }
2697 
2698         if (!err && node->pending) {
2699                 drop_node_buffer(node);
2700                 list_move_tail(&node->list, &rc->backref_cache.changed);
2701                 node->pending = 0;
2702         }
2703 
2704         path->lowest_level = 0;
2705         BUG_ON(err == -ENOSPC);
2706         return err;
2707 }
2708 
2709 static int link_to_upper(struct btrfs_trans_handle *trans,
2710                          struct reloc_control *rc,
2711                          struct backref_node *node,
2712                          struct btrfs_path *path)
2713 {
2714         struct btrfs_key key;
2715 
2716         btrfs_node_key_to_cpu(node->eb, &key, 0);
2717         return do_relocation(trans, rc, node, &key, path, 0);
2718 }
2719 
2720 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2721                                 struct reloc_control *rc,
2722                                 struct btrfs_path *path, int err)
2723 {
2724         LIST_HEAD(list);
2725         struct backref_cache *cache = &rc->backref_cache;
2726         struct backref_node *node;
2727         int level;
2728         int ret;
2729 
2730         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2731                 while (!list_empty(&cache->pending[level])) {
2732                         node = list_entry(cache->pending[level].next,
2733                                           struct backref_node, list);
2734                         list_move_tail(&node->list, &list);
2735                         BUG_ON(!node->pending);
2736 
2737                         if (!err) {
2738                                 ret = link_to_upper(trans, rc, node, path);
2739                                 if (ret < 0)
2740                                         err = ret;
2741                         }
2742                 }
2743                 list_splice_init(&list, &cache->pending[level]);
2744         }
2745         return err;
2746 }
2747 
2748 static void mark_block_processed(struct reloc_control *rc,
2749                                  u64 bytenr, u32 blocksize)
2750 {
2751         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2752                         EXTENT_DIRTY, GFP_NOFS);
2753 }
2754 
2755 static void __mark_block_processed(struct reloc_control *rc,
2756                                    struct backref_node *node)
2757 {
2758         u32 blocksize;
2759         if (node->level == 0 ||
2760             in_block_group(node->bytenr, rc->block_group)) {
2761                 blocksize = btrfs_level_size(rc->extent_root, node->level);
2762                 mark_block_processed(rc, node->bytenr, blocksize);
2763         }
2764         node->processed = 1;
2765 }
2766 
2767 /*
2768  * mark a block and all blocks directly/indirectly reference the block
2769  * as processed.
2770  */
2771 static void update_processed_blocks(struct reloc_control *rc,
2772                                     struct backref_node *node)
2773 {
2774         struct backref_node *next = node;
2775         struct backref_edge *edge;
2776         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2777         int index = 0;
2778 
2779         while (next) {
2780                 cond_resched();
2781                 while (1) {
2782                         if (next->processed)
2783                                 break;
2784 
2785                         __mark_block_processed(rc, next);
2786 
2787                         if (list_empty(&next->upper))
2788                                 break;
2789 
2790                         edge = list_entry(next->upper.next,
2791                                           struct backref_edge, list[LOWER]);
2792                         edges[index++] = edge;
2793                         next = edge->node[UPPER];
2794                 }
2795                 next = walk_down_backref(edges, &index);
2796         }
2797 }
2798 
2799 static int tree_block_processed(u64 bytenr, u32 blocksize,
2800                                 struct reloc_control *rc)
2801 {
2802         if (test_range_bit(&rc->processed_blocks, bytenr,
2803                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2804                 return 1;
2805         return 0;
2806 }
2807 
2808 static int get_tree_block_key(struct reloc_control *rc,
2809                               struct tree_block *block)
2810 {
2811         struct extent_buffer *eb;
2812 
2813         BUG_ON(block->key_ready);
2814         eb = read_tree_block(rc->extent_root, block->bytenr,
2815                              block->key.objectid, block->key.offset);
2816         if (!eb || !extent_buffer_uptodate(eb)) {
2817                 free_extent_buffer(eb);
2818                 return -EIO;
2819         }
2820         WARN_ON(btrfs_header_level(eb) != block->level);
2821         if (block->level == 0)
2822                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2823         else
2824                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2825         free_extent_buffer(eb);
2826         block->key_ready = 1;
2827         return 0;
2828 }
2829 
2830 static int reada_tree_block(struct reloc_control *rc,
2831                             struct tree_block *block)
2832 {
2833         BUG_ON(block->key_ready);
2834         if (block->key.type == BTRFS_METADATA_ITEM_KEY)
2835                 readahead_tree_block(rc->extent_root, block->bytenr,
2836                                      block->key.objectid,
2837                                      rc->extent_root->leafsize);
2838         else
2839                 readahead_tree_block(rc->extent_root, block->bytenr,
2840                                      block->key.objectid, block->key.offset);
2841         return 0;
2842 }
2843 
2844 /*
2845  * helper function to relocate a tree block
2846  */
2847 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2848                                 struct reloc_control *rc,
2849                                 struct backref_node *node,
2850                                 struct btrfs_key *key,
2851                                 struct btrfs_path *path)
2852 {
2853         struct btrfs_root *root;
2854         int release = 0;
2855         int ret = 0;
2856 
2857         if (!node)
2858                 return 0;
2859 
2860         BUG_ON(node->processed);
2861         root = select_one_root(trans, node);
2862         if (root == ERR_PTR(-ENOENT)) {
2863                 update_processed_blocks(rc, node);
2864                 goto out;
2865         }
2866 
2867         if (!root || root->ref_cows) {
2868                 ret = reserve_metadata_space(trans, rc, node);
2869                 if (ret)
2870                         goto out;
2871                 release = 1;
2872         }
2873 
2874         if (root) {
2875                 if (root->ref_cows) {
2876                         BUG_ON(node->new_bytenr);
2877                         BUG_ON(!list_empty(&node->list));
2878                         btrfs_record_root_in_trans(trans, root);
2879                         root = root->reloc_root;
2880                         node->new_bytenr = root->node->start;
2881                         node->root = root;
2882                         list_add_tail(&node->list, &rc->backref_cache.changed);
2883                 } else {
2884                         path->lowest_level = node->level;
2885                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2886                         btrfs_release_path(path);
2887                         if (ret > 0)
2888                                 ret = 0;
2889                 }
2890                 if (!ret)
2891                         update_processed_blocks(rc, node);
2892         } else {
2893                 ret = do_relocation(trans, rc, node, key, path, 1);
2894         }
2895 out:
2896         if (ret || node->level == 0 || node->cowonly) {
2897                 if (release)
2898                         release_metadata_space(rc, node);
2899                 remove_backref_node(&rc->backref_cache, node);
2900         }
2901         return ret;
2902 }
2903 
2904 /*
2905  * relocate a list of blocks
2906  */
2907 static noinline_for_stack
2908 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
2909                          struct reloc_control *rc, struct rb_root *blocks)
2910 {
2911         struct backref_node *node;
2912         struct btrfs_path *path;
2913         struct tree_block *block;
2914         struct rb_node *rb_node;
2915         int ret;
2916         int err = 0;
2917 
2918         path = btrfs_alloc_path();
2919         if (!path) {
2920                 err = -ENOMEM;
2921                 goto out_free_blocks;
2922         }
2923 
2924         rb_node = rb_first(blocks);
2925         while (rb_node) {
2926                 block = rb_entry(rb_node, struct tree_block, rb_node);
2927                 if (!block->key_ready)
2928                         reada_tree_block(rc, block);
2929                 rb_node = rb_next(rb_node);
2930         }
2931 
2932         rb_node = rb_first(blocks);
2933         while (rb_node) {
2934                 block = rb_entry(rb_node, struct tree_block, rb_node);
2935                 if (!block->key_ready) {
2936                         err = get_tree_block_key(rc, block);
2937                         if (err)
2938                                 goto out_free_path;
2939                 }
2940                 rb_node = rb_next(rb_node);
2941         }
2942 
2943         rb_node = rb_first(blocks);
2944         while (rb_node) {
2945                 block = rb_entry(rb_node, struct tree_block, rb_node);
2946 
2947                 node = build_backref_tree(rc, &block->key,
2948                                           block->level, block->bytenr);
2949                 if (IS_ERR(node)) {
2950                         err = PTR_ERR(node);
2951                         goto out;
2952                 }
2953 
2954                 ret = relocate_tree_block(trans, rc, node, &block->key,
2955                                           path);
2956                 if (ret < 0) {
2957                         if (ret != -EAGAIN || rb_node == rb_first(blocks))
2958                                 err = ret;
2959                         goto out;
2960                 }
2961                 rb_node = rb_next(rb_node);
2962         }
2963 out:
2964         err = finish_pending_nodes(trans, rc, path, err);
2965 
2966 out_free_path:
2967         btrfs_free_path(path);
2968 out_free_blocks:
2969         free_block_list(blocks);
2970         return err;
2971 }
2972 
2973 static noinline_for_stack
2974 int prealloc_file_extent_cluster(struct inode *inode,
2975                                  struct file_extent_cluster *cluster)
2976 {
2977         u64 alloc_hint = 0;
2978         u64 start;
2979         u64 end;
2980         u64 offset = BTRFS_I(inode)->index_cnt;
2981         u64 num_bytes;
2982         int nr = 0;
2983         int ret = 0;
2984 
2985         BUG_ON(cluster->start != cluster->boundary[0]);
2986         mutex_lock(&inode->i_mutex);
2987 
2988         ret = btrfs_check_data_free_space(inode, cluster->end +
2989                                           1 - cluster->start);
2990         if (ret)
2991                 goto out;
2992 
2993         while (nr < cluster->nr) {
2994                 start = cluster->boundary[nr] - offset;
2995                 if (nr + 1 < cluster->nr)
2996                         end = cluster->boundary[nr + 1] - 1 - offset;
2997                 else
2998                         end = cluster->end - offset;
2999 
3000                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3001                 num_bytes = end + 1 - start;
3002                 ret = btrfs_prealloc_file_range(inode, 0, start,
3003                                                 num_bytes, num_bytes,
3004                                                 end + 1, &alloc_hint);
3005                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3006                 if (ret)
3007                         break;
3008                 nr++;
3009         }
3010         btrfs_free_reserved_data_space(inode, cluster->end +
3011                                        1 - cluster->start);
3012 out:
3013         mutex_unlock(&inode->i_mutex);
3014         return ret;
3015 }
3016 
3017 static noinline_for_stack
3018 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3019                          u64 block_start)
3020 {
3021         struct btrfs_root *root = BTRFS_I(inode)->root;
3022         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3023         struct extent_map *em;
3024         int ret = 0;
3025 
3026         em = alloc_extent_map();
3027         if (!em)
3028                 return -ENOMEM;
3029 
3030         em->start = start;
3031         em->len = end + 1 - start;
3032         em->block_len = em->len;
3033         em->block_start = block_start;
3034         em->bdev = root->fs_info->fs_devices->latest_bdev;
3035         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3036 
3037         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3038         while (1) {
3039                 write_lock(&em_tree->lock);
3040                 ret = add_extent_mapping(em_tree, em, 0);
3041                 write_unlock(&em_tree->lock);
3042                 if (ret != -EEXIST) {
3043                         free_extent_map(em);
3044                         break;
3045                 }
3046                 btrfs_drop_extent_cache(inode, start, end, 0);
3047         }
3048         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3049         return ret;
3050 }
3051 
3052 static int relocate_file_extent_cluster(struct inode *inode,
3053                                         struct file_extent_cluster *cluster)
3054 {
3055         u64 page_start;
3056         u64 page_end;
3057         u64 offset = BTRFS_I(inode)->index_cnt;
3058         unsigned long index;
3059         unsigned long last_index;
3060         struct page *page;
3061         struct file_ra_state *ra;
3062         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3063         int nr = 0;
3064         int ret = 0;
3065 
3066         if (!cluster->nr)
3067                 return 0;
3068 
3069         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3070         if (!ra)
3071                 return -ENOMEM;
3072 
3073         ret = prealloc_file_extent_cluster(inode, cluster);
3074         if (ret)
3075                 goto out;
3076 
3077         file_ra_state_init(ra, inode->i_mapping);
3078 
3079         ret = setup_extent_mapping(inode, cluster->start - offset,
3080                                    cluster->end - offset, cluster->start);
3081         if (ret)
3082                 goto out;
3083 
3084         index = (cluster->start - offset) >> PAGE_CACHE_SHIFT;
3085         last_index = (cluster->end - offset) >> PAGE_CACHE_SHIFT;
3086         while (index <= last_index) {
3087                 ret = btrfs_delalloc_reserve_metadata(inode, PAGE_CACHE_SIZE);
3088                 if (ret)
3089                         goto out;
3090 
3091                 page = find_lock_page(inode->i_mapping, index);
3092                 if (!page) {
3093                         page_cache_sync_readahead(inode->i_mapping,
3094                                                   ra, NULL, index,
3095                                                   last_index + 1 - index);
3096                         page = find_or_create_page(inode->i_mapping, index,
3097                                                    mask);
3098                         if (!page) {
3099                                 btrfs_delalloc_release_metadata(inode,
3100                                                         PAGE_CACHE_SIZE);
3101                                 ret = -ENOMEM;
3102                                 goto out;
3103                         }
3104                 }
3105 
3106                 if (PageReadahead(page)) {
3107                         page_cache_async_readahead(inode->i_mapping,
3108                                                    ra, NULL, page, index,
3109                                                    last_index + 1 - index);
3110                 }
3111 
3112                 if (!PageUptodate(page)) {
3113                         btrfs_readpage(NULL, page);
3114                         lock_page(page);
3115                         if (!PageUptodate(page)) {
3116                                 unlock_page(page);
3117                                 page_cache_release(page);
3118                                 btrfs_delalloc_release_metadata(inode,
3119                                                         PAGE_CACHE_SIZE);
3120                                 ret = -EIO;
3121                                 goto out;
3122                         }
3123                 }
3124 
3125                 page_start = page_offset(page);
3126                 page_end = page_start + PAGE_CACHE_SIZE - 1;
3127 
3128                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3129 
3130                 set_page_extent_mapped(page);
3131 
3132                 if (nr < cluster->nr &&
3133                     page_start + offset == cluster->boundary[nr]) {
3134                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3135                                         page_start, page_end,
3136                                         EXTENT_BOUNDARY, GFP_NOFS);
3137                         nr++;
3138                 }
3139 
3140                 btrfs_set_extent_delalloc(inode, page_start, page_end, NULL);
3141                 set_page_dirty(page);
3142 
3143                 unlock_extent(&BTRFS_I(inode)->io_tree,
3144                               page_start, page_end);
3145                 unlock_page(page);
3146                 page_cache_release(page);
3147 
3148                 index++;
3149                 balance_dirty_pages_ratelimited(inode->i_mapping);
3150                 btrfs_throttle(BTRFS_I(inode)->root);
3151         }
3152         WARN_ON(nr != cluster->nr);
3153 out:
3154         kfree(ra);
3155         return ret;
3156 }
3157 
3158 static noinline_for_stack
3159 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3160                          struct file_extent_cluster *cluster)
3161 {
3162         int ret;
3163 
3164         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3165                 ret = relocate_file_extent_cluster(inode, cluster);
3166                 if (ret)
3167                         return ret;
3168                 cluster->nr = 0;
3169         }
3170 
3171         if (!cluster->nr)
3172                 cluster->start = extent_key->objectid;
3173         else
3174                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3175         cluster->end = extent_key->objectid + extent_key->offset - 1;
3176         cluster->boundary[cluster->nr] = extent_key->objectid;
3177         cluster->nr++;
3178 
3179         if (cluster->nr >= MAX_EXTENTS) {
3180                 ret = relocate_file_extent_cluster(inode, cluster);
3181                 if (ret)
3182                         return ret;
3183                 cluster->nr = 0;
3184         }
3185         return 0;
3186 }
3187 
3188 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3189 static int get_ref_objectid_v0(struct reloc_control *rc,
3190                                struct btrfs_path *path,
3191                                struct btrfs_key *extent_key,
3192                                u64 *ref_objectid, int *path_change)
3193 {
3194         struct btrfs_key key;
3195         struct extent_buffer *leaf;
3196         struct btrfs_extent_ref_v0 *ref0;
3197         int ret;
3198         int slot;
3199 
3200         leaf = path->nodes[0];
3201         slot = path->slots[0];
3202         while (1) {
3203                 if (slot >= btrfs_header_nritems(leaf)) {
3204                         ret = btrfs_next_leaf(rc->extent_root, path);
3205                         if (ret < 0)
3206                                 return ret;
3207                         BUG_ON(ret > 0);
3208                         leaf = path->nodes[0];
3209                         slot = path->slots[0];
3210                         if (path_change)
3211                                 *path_change = 1;
3212                 }
3213                 btrfs_item_key_to_cpu(leaf, &key, slot);
3214                 if (key.objectid != extent_key->objectid)
3215                         return -ENOENT;
3216 
3217                 if (key.type != BTRFS_EXTENT_REF_V0_KEY) {
3218                         slot++;
3219                         continue;
3220                 }
3221                 ref0 = btrfs_item_ptr(leaf, slot,
3222                                 struct btrfs_extent_ref_v0);
3223                 *ref_objectid = btrfs_ref_objectid_v0(leaf, ref0);
3224                 break;
3225         }
3226         return 0;
3227 }
3228 #endif
3229 
3230 /*
3231  * helper to add a tree block to the list.
3232  * the major work is getting the generation and level of the block
3233  */
3234 static int add_tree_block(struct reloc_control *rc,
3235                           struct btrfs_key *extent_key,
3236                           struct btrfs_path *path,
3237                           struct rb_root *blocks)
3238 {
3239         struct extent_buffer *eb;
3240         struct btrfs_extent_item *ei;
3241         struct btrfs_tree_block_info *bi;
3242         struct tree_block *block;
3243         struct rb_node *rb_node;
3244         u32 item_size;
3245         int level = -1;
3246         int generation;
3247 
3248         eb =  path->nodes[0];
3249         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3250 
3251         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3252             item_size >= sizeof(*ei) + sizeof(*bi)) {
3253                 ei = btrfs_item_ptr(eb, path->slots[0],
3254                                 struct btrfs_extent_item);
3255                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3256                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3257                         level = btrfs_tree_block_level(eb, bi);
3258                 } else {
3259                         level = (int)extent_key->offset;
3260                 }
3261                 generation = btrfs_extent_generation(eb, ei);
3262         } else {
3263 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3264                 u64 ref_owner;
3265                 int ret;
3266 
3267                 BUG_ON(item_size != sizeof(struct btrfs_extent_item_v0));
3268                 ret = get_ref_objectid_v0(rc, path, extent_key,
3269                                           &ref_owner, NULL);
3270                 if (ret < 0)
3271                         return ret;
3272                 BUG_ON(ref_owner >= BTRFS_MAX_LEVEL);
3273                 level = (int)ref_owner;
3274                 /* FIXME: get real generation */
3275                 generation = 0;
3276 #else
3277                 BUG();
3278 #endif
3279         }
3280 
3281         btrfs_release_path(path);
3282 
3283         BUG_ON(level == -1);
3284 
3285         block = kmalloc(sizeof(*block), GFP_NOFS);
3286         if (!block)
3287                 return -ENOMEM;
3288 
3289         block->bytenr = extent_key->objectid;
3290         block->key.objectid = rc->extent_root->leafsize;
3291         block->key.offset = generation;
3292         block->level = level;
3293         block->key_ready = 0;
3294 
3295         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3296         if (rb_node)
3297                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3298 
3299         return 0;
3300 }
3301 
3302 /*
3303  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3304  */
3305 static int __add_tree_block(struct reloc_control *rc,
3306                             u64 bytenr, u32 blocksize,
3307                             struct rb_root *blocks)
3308 {
3309         struct btrfs_path *path;
3310         struct btrfs_key key;
3311         int ret;
3312         bool skinny = btrfs_fs_incompat(rc->extent_root->fs_info,
3313                                         SKINNY_METADATA);
3314 
3315         if (tree_block_processed(bytenr, blocksize, rc))
3316                 return 0;
3317 
3318         if (tree_search(blocks, bytenr))
3319                 return 0;
3320 
3321         path = btrfs_alloc_path();
3322         if (!path)
3323                 return -ENOMEM;
3324 again:
3325         key.objectid = bytenr;
3326         if (skinny) {
3327                 key.type = BTRFS_METADATA_ITEM_KEY;
3328                 key.offset = (u64)-1;
3329         } else {
3330                 key.type = BTRFS_EXTENT_ITEM_KEY;
3331                 key.offset = blocksize;
3332         }
3333 
3334         path->search_commit_root = 1;
3335         path->skip_locking = 1;
3336         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3337         if (ret < 0)
3338                 goto out;
3339 
3340         if (ret > 0 && skinny) {
3341                 if (path->slots[0]) {
3342                         path->slots[0]--;
3343                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3344                                               path->slots[0]);
3345                         if (key.objectid == bytenr &&
3346                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3347                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3348                               key.offset == blocksize)))
3349                                 ret = 0;
3350                 }
3351 
3352                 if (ret) {
3353                         skinny = false;
3354                         btrfs_release_path(path);
3355                         goto again;
3356                 }
3357         }
3358         BUG_ON(ret);
3359 
3360         ret = add_tree_block(rc, &key, path, blocks);
3361 out:
3362         btrfs_free_path(path);
3363         return ret;
3364 }
3365 
3366 /*
3367  * helper to check if the block use full backrefs for pointers in it
3368  */
3369 static int block_use_full_backref(struct reloc_control *rc,
3370                                   struct extent_buffer *eb)
3371 {
3372         u64 flags;
3373         int ret;
3374 
3375         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3376             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3377                 return 1;
3378 
3379         ret = btrfs_lookup_extent_info(NULL, rc->extent_root,
3380                                        eb->start, btrfs_header_level(eb), 1,
3381                                        NULL, &flags);
3382         BUG_ON(ret);
3383 
3384         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3385                 ret = 1;
3386         else
3387                 ret = 0;
3388         return ret;
3389 }
3390 
3391 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3392                                     struct inode *inode, u64 ino)
3393 {
3394         struct btrfs_key key;
3395         struct btrfs_path *path;
3396         struct btrfs_root *root = fs_info->tree_root;
3397         struct btrfs_trans_handle *trans;
3398         int ret = 0;
3399 
3400         if (inode)
3401                 goto truncate;
3402 
3403         key.objectid = ino;
3404         key.type = BTRFS_INODE_ITEM_KEY;
3405         key.offset = 0;
3406 
3407         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
3408         if (IS_ERR(inode) || is_bad_inode(inode)) {
3409                 if (!IS_ERR(inode))
3410                         iput(inode);
3411                 return -ENOENT;
3412         }
3413 
3414 truncate:
3415         ret = btrfs_check_trunc_cache_free_space(root,
3416                                                  &fs_info->global_block_rsv);
3417         if (ret)
3418                 goto out;
3419 
3420         path = btrfs_alloc_path();
3421         if (!path) {
3422                 ret = -ENOMEM;
3423                 goto out;
3424         }
3425 
3426         trans = btrfs_join_transaction(root);
3427         if (IS_ERR(trans)) {
3428                 btrfs_free_path(path);
3429                 ret = PTR_ERR(trans);
3430                 goto out;
3431         }
3432 
3433         ret = btrfs_truncate_free_space_cache(root, trans, path, inode);
3434 
3435         btrfs_free_path(path);
3436         btrfs_end_transaction(trans, root);
3437         btrfs_btree_balance_dirty(root);
3438 out:
3439         iput(inode);
3440         return ret;
3441 }
3442 
3443 /*
3444  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3445  * this function scans fs tree to find blocks reference the data extent
3446  */
3447 static int find_data_references(struct reloc_control *rc,
3448                                 struct btrfs_key *extent_key,
3449                                 struct extent_buffer *leaf,
3450                                 struct btrfs_extent_data_ref *ref,
3451                                 struct rb_root *blocks)
3452 {
3453         struct btrfs_path *path;
3454         struct tree_block *block;
3455         struct btrfs_root *root;
3456         struct btrfs_file_extent_item *fi;
3457         struct rb_node *rb_node;
3458         struct btrfs_key key;
3459         u64 ref_root;
3460         u64 ref_objectid;
3461         u64 ref_offset;
3462         u32 ref_count;
3463         u32 nritems;
3464         int err = 0;
3465         int added = 0;
3466         int counted;
3467         int ret;
3468 
3469         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3470         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3471         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3472         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3473 
3474         /*
3475          * This is an extent belonging to the free space cache, lets just delete
3476          * it and redo the search.
3477          */
3478         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3479                 ret = delete_block_group_cache(rc->extent_root->fs_info,
3480                                                NULL, ref_objectid);
3481                 if (ret != -ENOENT)
3482                         return ret;
3483                 ret = 0;
3484         }
3485 
3486         path = btrfs_alloc_path();
3487         if (!path)
3488                 return -ENOMEM;
3489         path->reada = 1;
3490 
3491         root = read_fs_root(rc->extent_root->fs_info, ref_root);
3492         if (IS_ERR(root)) {
3493                 err = PTR_ERR(root);
3494                 goto out;
3495         }
3496 
3497         key.objectid = ref_objectid;
3498         key.type = BTRFS_EXTENT_DATA_KEY;
3499         if (ref_offset > ((u64)-1 << 32))
3500                 key.offset = 0;
3501         else
3502                 key.offset = ref_offset;
3503 
3504         path->search_commit_root = 1;
3505         path->skip_locking = 1;
3506         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3507         if (ret < 0) {
3508                 err = ret;
3509                 goto out;
3510         }
3511 
3512         leaf = path->nodes[0];
3513         nritems = btrfs_header_nritems(leaf);
3514         /*
3515          * the references in tree blocks that use full backrefs
3516          * are not counted in
3517          */
3518         if (block_use_full_backref(rc, leaf))
3519                 counted = 0;
3520         else
3521                 counted = 1;
3522         rb_node = tree_search(blocks, leaf->start);
3523         if (rb_node) {
3524                 if (counted)
3525                         added = 1;
3526                 else
3527                         path->slots[0] = nritems;
3528         }
3529 
3530         while (ref_count > 0) {
3531                 while (path->slots[0] >= nritems) {
3532                         ret = btrfs_next_leaf(root, path);
3533                         if (ret < 0) {
3534                                 err = ret;
3535                                 goto out;
3536                         }
3537                         if (ret > 0) {
3538                                 WARN_ON(1);
3539                                 goto out;
3540                         }
3541 
3542                         leaf = path->nodes[0];
3543                         nritems = btrfs_header_nritems(leaf);
3544                         added = 0;
3545 
3546                         if (block_use_full_backref(rc, leaf))
3547                                 counted = 0;
3548                         else
3549                                 counted = 1;
3550                         rb_node = tree_search(blocks, leaf->start);
3551                         if (rb_node) {
3552                                 if (counted)
3553                                         added = 1;
3554                                 else
3555                                         path->slots[0] = nritems;
3556                         }
3557                 }
3558 
3559                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3560                 if (key.objectid != ref_objectid ||
3561                     key.type != BTRFS_EXTENT_DATA_KEY) {
3562                         WARN_ON(1);
3563                         break;
3564                 }
3565 
3566                 fi = btrfs_item_ptr(leaf, path->slots[0],
3567                                     struct btrfs_file_extent_item);
3568 
3569                 if (btrfs_file_extent_type(leaf, fi) ==
3570                     BTRFS_FILE_EXTENT_INLINE)
3571                         goto next;
3572 
3573                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3574                     extent_key->objectid)
3575                         goto next;
3576 
3577                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3578                 if (key.offset != ref_offset)
3579                         goto next;
3580 
3581                 if (counted)
3582                         ref_count--;
3583                 if (added)
3584                         goto next;
3585 
3586                 if (!tree_block_processed(leaf->start, leaf->len, rc)) {
3587                         block = kmalloc(sizeof(*block), GFP_NOFS);
3588                         if (!block) {
3589                                 err = -ENOMEM;
3590                                 break;
3591                         }
3592                         block->bytenr = leaf->start;
3593                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3594                         block->level = 0;
3595                         block->key_ready = 1;
3596                         rb_node = tree_insert(blocks, block->bytenr,
3597                                               &block->rb_node);
3598                         if (rb_node)
3599                                 backref_tree_panic(rb_node, -EEXIST,
3600                                                    block->bytenr);
3601                 }
3602                 if (counted)
3603                         added = 1;
3604                 else
3605                         path->slots[0] = nritems;
3606 next:
3607                 path->slots[0]++;
3608 
3609         }
3610 out:
3611         btrfs_free_path(path);
3612         return err;
3613 }
3614 
3615 /*
3616  * helper to find all tree blocks that reference a given data extent
3617  */
3618 static noinline_for_stack
3619 int add_data_references(struct reloc_control *rc,
3620                         struct btrfs_key *extent_key,
3621                         struct btrfs_path *path,
3622                         struct rb_root *blocks)
3623 {
3624         struct btrfs_key key;
3625         struct extent_buffer *eb;
3626         struct btrfs_extent_data_ref *dref;
3627         struct btrfs_extent_inline_ref *iref;
3628         unsigned long ptr;
3629         unsigned long end;
3630         u32 blocksize = btrfs_level_size(rc->extent_root, 0);
3631         int ret;
3632         int err = 0;
3633 
3634         eb = path->nodes[0];
3635         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3636         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3637 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3638         if (ptr + sizeof(struct btrfs_extent_item_v0) == end)
3639                 ptr = end;
3640         else
3641 #endif
3642                 ptr += sizeof(struct btrfs_extent_item);
3643 
3644         while (ptr < end) {
3645                 iref = (struct btrfs_extent_inline_ref *)ptr;
3646                 key.type = btrfs_extent_inline_ref_type(eb, iref);
3647                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3648                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3649                         ret = __add_tree_block(rc, key.offset, blocksize,
3650                                                blocks);
3651                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3652                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3653                         ret = find_data_references(rc, extent_key,
3654                                                    eb, dref, blocks);
3655                 } else {
3656                         BUG();
3657                 }
3658                 ptr += btrfs_extent_inline_ref_size(key.type);
3659         }
3660         WARN_ON(ptr > end);
3661 
3662         while (1) {
3663                 cond_resched();
3664                 eb = path->nodes[0];
3665                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3666                         ret = btrfs_next_leaf(rc->extent_root, path);
3667                         if (ret < 0) {
3668                                 err = ret;
3669                                 break;
3670                         }
3671                         if (ret > 0)
3672                                 break;
3673                         eb = path->nodes[0];
3674                 }
3675 
3676                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3677                 if (key.objectid != extent_key->objectid)
3678                         break;
3679 
3680 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3681                 if (key.type == BTRFS_SHARED_DATA_REF_KEY ||
3682                     key.type == BTRFS_EXTENT_REF_V0_KEY) {
3683 #else
3684                 BUG_ON(key.type == BTRFS_EXTENT_REF_V0_KEY);
3685                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3686 #endif
3687                         ret = __add_tree_block(rc, key.offset, blocksize,
3688                                                blocks);
3689                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3690                         dref = btrfs_item_ptr(eb, path->slots[0],
3691                                               struct btrfs_extent_data_ref);
3692                         ret = find_data_references(rc, extent_key,
3693                                                    eb, dref, blocks);
3694                 } else {
3695                         ret = 0;
3696                 }
3697                 if (ret) {
3698                         err = ret;
3699                         break;
3700                 }
3701                 path->slots[0]++;
3702         }
3703         btrfs_release_path(path);
3704         if (err)
3705                 free_block_list(blocks);
3706         return err;
3707 }
3708 
3709 /*
3710  * helper to find next unprocessed extent
3711  */
3712 static noinline_for_stack
3713 int find_next_extent(struct btrfs_trans_handle *trans,
3714                      struct reloc_control *rc, struct btrfs_path *path,
3715                      struct btrfs_key *extent_key)
3716 {
3717         struct btrfs_key key;
3718         struct extent_buffer *leaf;
3719         u64 start, end, last;
3720         int ret;
3721 
3722         last = rc->block_group->key.objectid + rc->block_group->key.offset;
3723         while (1) {
3724                 cond_resched();
3725                 if (rc->search_start >= last) {
3726                         ret = 1;
3727                         break;
3728                 }
3729 
3730                 key.objectid = rc->search_start;
3731                 key.type = BTRFS_EXTENT_ITEM_KEY;
3732                 key.offset = 0;
3733 
3734                 path->search_commit_root = 1;
3735                 path->skip_locking = 1;
3736                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3737                                         0, 0);
3738                 if (ret < 0)
3739                         break;
3740 next:
3741                 leaf = path->nodes[0];
3742                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3743                         ret = btrfs_next_leaf(rc->extent_root, path);
3744                         if (ret != 0)
3745                                 break;
3746                         leaf = path->nodes[0];
3747                 }
3748 
3749                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3750                 if (key.objectid >= last) {
3751                         ret = 1;
3752                         break;
3753                 }
3754 
3755                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3756                     key.type != BTRFS_METADATA_ITEM_KEY) {
3757                         path->slots[0]++;
3758                         goto next;
3759                 }
3760 
3761                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3762                     key.objectid + key.offset <= rc->search_start) {
3763                         path->slots[0]++;
3764                         goto next;
3765                 }
3766 
3767                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3768                     key.objectid + rc->extent_root->leafsize <=
3769                     rc->search_start) {
3770                         path->slots[0]++;
3771                         goto next;
3772                 }
3773 
3774                 ret = find_first_extent_bit(&rc->processed_blocks,
3775                                             key.objectid, &start, &end,
3776                                             EXTENT_DIRTY, NULL);
3777 
3778                 if (ret == 0 && start <= key.objectid) {
3779                         btrfs_release_path(path);
3780                         rc->search_start = end + 1;
3781                 } else {
3782                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3783                                 rc->search_start = key.objectid + key.offset;
3784                         else
3785                                 rc->search_start = key.objectid +
3786                                         rc->extent_root->leafsize;
3787                         memcpy(extent_key, &key, sizeof(key));
3788                         return 0;
3789                 }
3790         }
3791         btrfs_release_path(path);
3792         return ret;
3793 }
3794 
3795 static void set_reloc_control(struct reloc_control *rc)
3796 {
3797         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3798 
3799         mutex_lock(&fs_info->reloc_mutex);
3800         fs_info->reloc_ctl = rc;
3801         mutex_unlock(&fs_info->reloc_mutex);
3802 }
3803 
3804 static void unset_reloc_control(struct reloc_control *rc)
3805 {
3806         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3807 
3808         mutex_lock(&fs_info->reloc_mutex);
3809         fs_info->reloc_ctl = NULL;
3810         mutex_unlock(&fs_info->reloc_mutex);
3811 }
3812 
3813 static int check_extent_flags(u64 flags)
3814 {
3815         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3816             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3817                 return 1;
3818         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3819             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3820                 return 1;
3821         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3822             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3823                 return 1;
3824         return 0;
3825 }
3826 
3827 static noinline_for_stack
3828 int prepare_to_relocate(struct reloc_control *rc)
3829 {
3830         struct btrfs_trans_handle *trans;
3831         int ret;
3832 
3833         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root,
3834                                               BTRFS_BLOCK_RSV_TEMP);
3835         if (!rc->block_rsv)
3836                 return -ENOMEM;
3837 
3838         /*
3839          * reserve some space for creating reloc trees.
3840          * btrfs_init_reloc_root will use them when there
3841          * is no reservation in transaction handle.
3842          */
3843         ret = btrfs_block_rsv_add(rc->extent_root, rc->block_rsv,
3844                                   rc->extent_root->nodesize * 256,
3845                                   BTRFS_RESERVE_FLUSH_ALL);
3846         if (ret)
3847                 return ret;
3848 
3849         memset(&rc->cluster, 0, sizeof(rc->cluster));
3850         rc->search_start = rc->block_group->key.objectid;
3851         rc->extents_found = 0;
3852         rc->nodes_relocated = 0;
3853         rc->merging_rsv_size = 0;
3854 
3855         rc->create_reloc_tree = 1;
3856         set_reloc_control(rc);
3857 
3858         trans = btrfs_join_transaction(rc->extent_root);
3859         if (IS_ERR(trans)) {
3860                 unset_reloc_control(rc);
3861                 /*
3862                  * extent tree is not a ref_cow tree and has no reloc_root to
3863                  * cleanup.  And callers are responsible to free the above
3864                  * block rsv.
3865                  */
3866                 return PTR_ERR(trans);
3867         }
3868         btrfs_commit_transaction(trans, rc->extent_root);
3869         return 0;
3870 }
3871 
3872 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3873 {
3874         struct rb_root blocks = RB_ROOT;
3875         struct btrfs_key key;
3876         struct btrfs_trans_handle *trans = NULL;
3877         struct btrfs_path *path;
3878         struct btrfs_extent_item *ei;
3879         u64 flags;
3880         u32 item_size;
3881         int ret;
3882         int err = 0;
3883         int progress = 0;
3884 
3885         path = btrfs_alloc_path();
3886         if (!path)
3887                 return -ENOMEM;
3888         path->reada = 1;
3889 
3890         ret = prepare_to_relocate(rc);
3891         if (ret) {
3892                 err = ret;
3893                 goto out_free;
3894         }
3895 
3896         while (1) {
3897                 progress++;
3898                 trans = btrfs_start_transaction(rc->extent_root, 0);
3899                 if (IS_ERR(trans)) {
3900                         err = PTR_ERR(trans);
3901                         trans = NULL;
3902                         break;
3903                 }
3904 restart:
3905                 if (update_backref_cache(trans, &rc->backref_cache)) {
3906                         btrfs_end_transaction(trans, rc->extent_root);
3907                         continue;
3908                 }
3909 
3910                 ret = find_next_extent(trans, rc, path, &key);
3911                 if (ret < 0)
3912                         err = ret;
3913                 if (ret != 0)
3914                         break;
3915 
3916                 rc->extents_found++;
3917 
3918                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
3919                                     struct btrfs_extent_item);
3920                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
3921                 if (item_size >= sizeof(*ei)) {
3922                         flags = btrfs_extent_flags(path->nodes[0], ei);
3923                         ret = check_extent_flags(flags);
3924                         BUG_ON(ret);
3925 
3926                 } else {
3927 #ifdef BTRFS_COMPAT_EXTENT_TREE_V0
3928                         u64 ref_owner;
3929                         int path_change = 0;
3930 
3931                         BUG_ON(item_size !=
3932                                sizeof(struct btrfs_extent_item_v0));
3933                         ret = get_ref_objectid_v0(rc, path, &key, &ref_owner,
3934                                                   &path_change);
3935                         if (ref_owner < BTRFS_FIRST_FREE_OBJECTID)
3936                                 flags = BTRFS_EXTENT_FLAG_TREE_BLOCK;
3937                         else
3938                                 flags = BTRFS_EXTENT_FLAG_DATA;
3939 
3940                         if (path_change) {
3941                                 btrfs_release_path(path);
3942 
3943                                 path->search_commit_root = 1;
3944                                 path->skip_locking = 1;
3945                                 ret = btrfs_search_slot(NULL, rc->extent_root,
3946                                                         &key, path, 0, 0);
3947                                 if (ret < 0) {
3948                                         err = ret;
3949                                         break;
3950                                 }
3951                                 BUG_ON(ret > 0);
3952                         }
3953 #else
3954                         BUG();
3955 #endif
3956                 }
3957 
3958                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
3959                         ret = add_tree_block(rc, &key, path, &blocks);
3960                 } else if (rc->stage == UPDATE_DATA_PTRS &&
3961                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
3962                         ret = add_data_references(rc, &key, path, &blocks);
3963                 } else {
3964                         btrfs_release_path(path);
3965                         ret = 0;
3966                 }
3967                 if (ret < 0) {
3968                         err = ret;
3969                         break;
3970                 }
3971 
3972                 if (!RB_EMPTY_ROOT(&blocks)) {
3973                         ret = relocate_tree_blocks(trans, rc, &blocks);
3974                         if (ret < 0) {
3975                                 if (ret != -EAGAIN) {
3976                                         err = ret;
3977                                         break;
3978                                 }
3979                                 rc->extents_found--;
3980                                 rc->search_start = key.objectid;
3981                         }
3982                 }
3983 
3984                 ret = btrfs_block_rsv_check(rc->extent_root, rc->block_rsv, 5);
3985                 if (ret < 0) {
3986                         if (ret != -ENOSPC) {
3987                                 err = ret;
3988                                 WARN_ON(1);
3989                                 break;
3990                         }
3991                         rc->commit_transaction = 1;
3992                 }
3993 
3994                 if (rc->commit_transaction) {
3995                         rc->commit_transaction = 0;
3996                         ret = btrfs_commit_transaction(trans, rc->extent_root);
3997                         BUG_ON(ret);
3998                 } else {
3999                         btrfs_end_transaction_throttle(trans, rc->extent_root);
4000                         btrfs_btree_balance_dirty(rc->extent_root);
4001                 }
4002                 trans = NULL;
4003 
4004                 if (rc->stage == MOVE_DATA_EXTENTS &&
4005                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4006                         rc->found_file_extent = 1;
4007                         ret = relocate_data_extent(rc->data_inode,
4008                                                    &key, &rc->cluster);
4009                         if (ret < 0) {
4010                                 err = ret;
4011                                 break;
4012                         }
4013                 }
4014         }
4015         if (trans && progress && err == -ENOSPC) {
4016                 ret = btrfs_force_chunk_alloc(trans, rc->extent_root,
4017                                               rc->block_group->flags);
4018                 if (ret == 0) {
4019                         err = 0;
4020                         progress = 0;
4021                         goto restart;
4022                 }
4023         }
4024 
4025         btrfs_release_path(path);
4026         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY,
4027                           GFP_NOFS);
4028 
4029         if (trans) {
4030                 btrfs_end_transaction_throttle(trans, rc->extent_root);
4031                 btrfs_btree_balance_dirty(rc->extent_root);
4032         }
4033 
4034         if (!err) {
4035                 ret = relocate_file_extent_cluster(rc->data_inode,
4036                                                    &rc->cluster);
4037                 if (ret < 0)
4038                         err = ret;
4039         }
4040 
4041         rc->create_reloc_tree = 0;
4042         set_reloc_control(rc);
4043 
4044         backref_cache_cleanup(&rc->backref_cache);
4045         btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, (u64)-1);
4046 
4047         err = prepare_to_merge(rc, err);
4048 
4049         merge_reloc_roots(rc);
4050 
4051         rc->merge_reloc_tree = 0;
4052         unset_reloc_control(rc);
4053         btrfs_block_rsv_release(rc->extent_root, rc->block_rsv, (u64)-1);
4054 
4055         /* get rid of pinned extents */
4056         trans = btrfs_join_transaction(rc->extent_root);
4057         if (IS_ERR(trans))
4058                 err = PTR_ERR(trans);
4059         else
4060                 btrfs_commit_transaction(trans, rc->extent_root);
4061 out_free:
4062         btrfs_free_block_rsv(rc->extent_root, rc->block_rsv);
4063         btrfs_free_path(path);
4064         return err;
4065 }
4066 
4067 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4068                                  struct btrfs_root *root, u64 objectid)
4069 {
4070         struct btrfs_path *path;
4071         struct btrfs_inode_item *item;
4072         struct extent_buffer *leaf;
4073         int ret;
4074 
4075         path = btrfs_alloc_path();
4076         if (!path)
4077                 return -ENOMEM;
4078 
4079         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4080         if (ret)
4081                 goto out;
4082 
4083         leaf = path->nodes[0];
4084         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4085         memset_extent_buffer(leaf, 0, (unsigned long)item, sizeof(*item));
4086         btrfs_set_inode_generation(leaf, item, 1);
4087         btrfs_set_inode_size(leaf, item, 0);
4088         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4089         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4090                                           BTRFS_INODE_PREALLOC);
4091         btrfs_mark_buffer_dirty(leaf);
4092         btrfs_release_path(path);
4093 out:
4094         btrfs_free_path(path);
4095         return ret;
4096 }
4097 
4098 /*
4099  * helper to create inode for data relocation.
4100  * the inode is in data relocation tree and its link count is 0
4101  */
4102 static noinline_for_stack
4103 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4104                                  struct btrfs_block_group_cache *group)
4105 {
4106         struct inode *inode = NULL;
4107         struct btrfs_trans_handle *trans;
4108         struct btrfs_root *root;
4109         struct btrfs_key key;
4110         u64 objectid = BTRFS_FIRST_FREE_OBJECTID;
4111         int err = 0;
4112 
4113         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4114         if (IS_ERR(root))
4115                 return ERR_CAST(root);
4116 
4117         trans = btrfs_start_transaction(root, 6);
4118         if (IS_ERR(trans))
4119                 return ERR_CAST(trans);
4120 
4121         err = btrfs_find_free_objectid(root, &objectid);
4122         if (err)
4123                 goto out;
4124 
4125         err = __insert_orphan_inode(trans, root, objectid);
4126         BUG_ON(err);
4127 
4128         key.objectid = objectid;
4129         key.type = BTRFS_INODE_ITEM_KEY;
4130         key.offset = 0;
4131         inode = btrfs_iget(root->fs_info->sb, &key, root, NULL);
4132         BUG_ON(IS_ERR(inode) || is_bad_inode(inode));
4133         BTRFS_I(inode)->index_cnt = group->key.objectid;
4134 
4135         err = btrfs_orphan_add(trans, inode);
4136 out:
4137         btrfs_end_transaction(trans, root);
4138         btrfs_btree_balance_dirty(root);
4139         if (err) {
4140                 if (inode)
4141                         iput(inode);
4142                 inode = ERR_PTR(err);
4143         }
4144         return inode;
4145 }
4146 
4147 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4148 {
4149         struct reloc_control *rc;
4150 
4151         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4152         if (!rc)
4153                 return NULL;
4154 
4155         INIT_LIST_HEAD(&rc->reloc_roots);
4156         backref_cache_init(&rc->backref_cache);
4157         mapping_tree_init(&rc->reloc_root_tree);
4158         extent_io_tree_init(&rc->processed_blocks,
4159                             fs_info->btree_inode->i_mapping);
4160         return rc;
4161 }
4162 
4163 /*
4164  * function to relocate all extents in a block group.
4165  */
4166 int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
4167 {
4168         struct btrfs_fs_info *fs_info = extent_root->fs_info;
4169         struct reloc_control *rc;
4170         struct inode *inode;
4171         struct btrfs_path *path;
4172         int ret;
4173         int rw = 0;
4174         int err = 0;
4175 
4176         rc = alloc_reloc_control(fs_info);
4177         if (!rc)
4178                 return -ENOMEM;
4179 
4180         rc->extent_root = extent_root;
4181 
4182         rc->block_group = btrfs_lookup_block_group(fs_info, group_start);
4183         BUG_ON(!rc->block_group);
4184 
4185         if (!rc->block_group->ro) {
4186                 ret = btrfs_set_block_group_ro(extent_root, rc->block_group);
4187                 if (ret) {
4188                         err = ret;
4189                         goto out;
4190                 }
4191                 rw = 1;
4192         }
4193 
4194         path = btrfs_alloc_path();
4195         if (!path) {
4196                 err = -ENOMEM;
4197                 goto out;
4198         }
4199 
4200         inode = lookup_free_space_inode(fs_info->tree_root, rc->block_group,
4201                                         path);
4202         btrfs_free_path(path);
4203 
4204         if (!IS_ERR(inode))
4205                 ret = delete_block_group_cache(fs_info, inode, 0);
4206         else
4207                 ret = PTR_ERR(inode);
4208 
4209         if (ret && ret != -ENOENT) {
4210                 err = ret;
4211                 goto out;
4212         }
4213 
4214         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4215         if (IS_ERR(rc->data_inode)) {
4216                 err = PTR_ERR(rc->data_inode);
4217                 rc->data_inode = NULL;
4218                 goto out;
4219         }
4220 
4221         printk(KERN_INFO "btrfs: relocating block group %llu flags %llu\n",
4222                (unsigned long long)rc->block_group->key.objectid,
4223                (unsigned long long)rc->block_group->flags);
4224 
4225         ret = btrfs_start_all_delalloc_inodes(fs_info, 0);
4226         if (ret < 0) {
4227                 err = ret;
4228                 goto out;
4229         }
4230         btrfs_wait_all_ordered_extents(fs_info, 0);
4231 
4232         while (1) {
4233                 mutex_lock(&fs_info->cleaner_mutex);
4234                 ret = relocate_block_group(rc);
4235                 mutex_unlock(&fs_info->cleaner_mutex);
4236                 if (ret < 0) {
4237                         err = ret;
4238                         goto out;
4239                 }
4240 
4241                 if (rc->extents_found == 0)
4242                         break;
4243 
4244                 printk(KERN_INFO "btrfs: found %llu extents\n",
4245                         (unsigned long long)rc->extents_found);
4246 
4247                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4248                         btrfs_wait_ordered_range(rc->data_inode, 0, (u64)-1);
4249                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4250                                                  0, -1);
4251                         rc->stage = UPDATE_DATA_PTRS;
4252                 }
4253         }
4254 
4255         filemap_write_and_wait_range(fs_info->btree_inode->i_mapping,
4256                                      rc->block_group->key.objectid,
4257                                      rc->block_group->key.objectid +
4258                                      rc->block_group->key.offset - 1);
4259 
4260         WARN_ON(rc->block_group->pinned > 0);
4261         WARN_ON(rc->block_group->reserved > 0);
4262         WARN_ON(btrfs_block_group_used(&rc->block_group->item) > 0);
4263 out:
4264         if (err && rw)
4265                 btrfs_set_block_group_rw(extent_root, rc->block_group);
4266         iput(rc->data_inode);
4267         btrfs_put_block_group(rc->block_group);
4268         kfree(rc);
4269         return err;
4270 }
4271 
4272 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4273 {
4274         struct btrfs_trans_handle *trans;
4275         int ret, err;
4276 
4277         trans = btrfs_start_transaction(root->fs_info->tree_root, 0);
4278         if (IS_ERR(trans))
4279                 return PTR_ERR(trans);
4280 
4281         memset(&root->root_item.drop_progress, 0,
4282                 sizeof(root->root_item.drop_progress));
4283         root->root_item.drop_level = 0;
4284         btrfs_set_root_refs(&root->root_item, 0);
4285         ret = btrfs_update_root(trans, root->fs_info->tree_root,
4286                                 &root->root_key, &root->root_item);
4287 
4288         err = btrfs_end_transaction(trans, root->fs_info->tree_root);
4289         if (err)
4290                 return err;
4291         return ret;
4292 }
4293 
4294 /*
4295  * recover relocation interrupted by system crash.
4296  *
4297  * this function resumes merging reloc trees with corresponding fs trees.
4298  * this is important for keeping the sharing of tree blocks
4299  */
4300 int btrfs_recover_relocation(struct btrfs_root *root)
4301 {
4302         LIST_HEAD(reloc_roots);
4303         struct btrfs_key key;
4304         struct btrfs_root *fs_root;
4305         struct btrfs_root *reloc_root;
4306         struct btrfs_path *path;
4307         struct extent_buffer *leaf;
4308         struct reloc_control *rc = NULL;
4309         struct btrfs_trans_handle *trans;
4310         int ret;
4311         int err = 0;
4312 
4313         path = btrfs_alloc_path();
4314         if (!path)
4315                 return -ENOMEM;
4316         path->reada = -1;
4317 
4318         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4319         key.type = BTRFS_ROOT_ITEM_KEY;
4320         key.offset = (u64)-1;
4321 
4322         while (1) {
4323                 ret = btrfs_search_slot(NULL, root->fs_info->tree_root, &key,
4324                                         path, 0, 0);
4325                 if (ret < 0) {
4326                         err = ret;
4327                         goto out;
4328                 }
4329                 if (ret > 0) {
4330                         if (path->slots[0] == 0)
4331                                 break;
4332                         path->slots[0]--;
4333                 }
4334                 leaf = path->nodes[0];
4335                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4336                 btrfs_release_path(path);
4337 
4338                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4339                     key.type != BTRFS_ROOT_ITEM_KEY)
4340                         break;
4341 
4342                 reloc_root = btrfs_read_fs_root(root, &key);
4343                 if (IS_ERR(reloc_root)) {
4344                         err = PTR_ERR(reloc_root);
4345                         goto out;
4346                 }
4347 
4348                 list_add(&reloc_root->root_list, &reloc_roots);
4349 
4350                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4351                         fs_root = read_fs_root(root->fs_info,
4352                                                reloc_root->root_key.offset);
4353                         if (IS_ERR(fs_root)) {
4354                                 ret = PTR_ERR(fs_root);
4355                                 if (ret != -ENOENT) {
4356                                         err = ret;
4357                                         goto out;
4358                                 }
4359                                 ret = mark_garbage_root(reloc_root);
4360                                 if (ret < 0) {
4361                                         err = ret;
4362                                         goto out;
4363                                 }
4364                         }
4365                 }
4366 
4367                 if (key.offset == 0)
4368                         break;
4369 
4370                 key.offset--;
4371         }
4372         btrfs_release_path(path);
4373 
4374         if (list_empty(&reloc_roots))
4375                 goto out;
4376 
4377         rc = alloc_reloc_control(root->fs_info);
4378         if (!rc) {
4379                 err = -ENOMEM;
4380                 goto out;
4381         }
4382 
4383         rc->extent_root = root->fs_info->extent_root;
4384 
4385         set_reloc_control(rc);
4386 
4387         trans = btrfs_join_transaction(rc->extent_root);
4388         if (IS_ERR(trans)) {
4389                 unset_reloc_control(rc);
4390                 err = PTR_ERR(trans);
4391                 goto out_free;
4392         }
4393 
4394         rc->merge_reloc_tree = 1;
4395 
4396         while (!list_empty(&reloc_roots)) {
4397                 reloc_root = list_entry(reloc_roots.next,
4398                                         struct btrfs_root, root_list);
4399                 list_del(&reloc_root->root_list);
4400 
4401                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4402                         list_add_tail(&reloc_root->root_list,
4403                                       &rc->reloc_roots);
4404                         continue;
4405                 }
4406 
4407                 fs_root = read_fs_root(root->fs_info,
4408                                        reloc_root->root_key.offset);
4409                 if (IS_ERR(fs_root)) {
4410                         err = PTR_ERR(fs_root);
4411                         goto out_free;
4412                 }
4413 
4414                 err = __add_reloc_root(reloc_root);
4415                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4416                 fs_root->reloc_root = reloc_root;
4417         }
4418 
4419         err = btrfs_commit_transaction(trans, rc->extent_root);
4420         if (err)
4421                 goto out_free;
4422 
4423         merge_reloc_roots(rc);
4424 
4425         unset_reloc_control(rc);
4426 
4427         trans = btrfs_join_transaction(rc->extent_root);
4428         if (IS_ERR(trans))
4429                 err = PTR_ERR(trans);
4430         else
4431                 err = btrfs_commit_transaction(trans, rc->extent_root);
4432 out_free:
4433         kfree(rc);
4434 out:
4435         if (!list_empty(&reloc_roots))
4436                 free_reloc_roots(&reloc_roots);
4437 
4438         btrfs_free_path(path);
4439 
4440         if (err == 0) {
4441                 /* cleanup orphan inode in data relocation tree */
4442                 fs_root = read_fs_root(root->fs_info,
4443                                        BTRFS_DATA_RELOC_TREE_OBJECTID);
4444                 if (IS_ERR(fs_root))
4445                         err = PTR_ERR(fs_root);
4446                 else
4447                         err = btrfs_orphan_cleanup(fs_root);
4448         }
4449         return err;
4450 }
4451 
4452 /*
4453  * helper to add ordered checksum for data relocation.
4454  *
4455  * cloning checksum properly handles the nodatasum extents.
4456  * it also saves CPU time to re-calculate the checksum.
4457  */
4458 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4459 {
4460         struct btrfs_ordered_sum *sums;
4461         struct btrfs_ordered_extent *ordered;
4462         struct btrfs_root *root = BTRFS_I(inode)->root;
4463         int ret;
4464         u64 disk_bytenr;
4465         u64 new_bytenr;
4466         LIST_HEAD(list);
4467 
4468         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4469         BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
4470 
4471         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4472         ret = btrfs_lookup_csums_range(root->fs_info->csum_root, disk_bytenr,
4473                                        disk_bytenr + len - 1, &list, 0);
4474         if (ret)
4475                 goto out;
4476 
4477         while (!list_empty(&list)) {
4478                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4479                 list_del_init(&sums->list);
4480 
4481                 /*
4482                  * We need to offset the new_bytenr based on where the csum is.
4483                  * We need to do this because we will read in entire prealloc
4484                  * extents but we may have written to say the middle of the
4485                  * prealloc extent, so we need to make sure the csum goes with
4486                  * the right disk offset.
4487                  *
4488                  * We can do this because the data reloc inode refers strictly
4489                  * to the on disk bytes, so we don't have to worry about
4490                  * disk_len vs real len like with real inodes since it's all
4491                  * disk length.
4492                  */
4493                 new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
4494                 sums->bytenr = new_bytenr;
4495 
4496                 btrfs_add_ordered_sum(inode, ordered, sums);
4497         }
4498 out:
4499         btrfs_put_ordered_extent(ordered);
4500         return ret;
4501 }
4502 
4503 void btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4504                            struct btrfs_root *root, struct extent_buffer *buf,
4505                            struct extent_buffer *cow)
4506 {
4507         struct reloc_control *rc;
4508         struct backref_node *node;
4509         int first_cow = 0;
4510         int level;
4511         int ret;
4512 
4513         rc = root->fs_info->reloc_ctl;
4514         if (!rc)
4515                 return;
4516 
4517         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4518                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4519 
4520         level = btrfs_header_level(buf);
4521         if (btrfs_header_generation(buf) <=
4522             btrfs_root_last_snapshot(&root->root_item))
4523                 first_cow = 1;
4524 
4525         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4526             rc->create_reloc_tree) {
4527                 WARN_ON(!first_cow && level == 0);
4528 
4529                 node = rc->backref_cache.path[level];
4530                 BUG_ON(node->bytenr != buf->start &&
4531                        node->new_bytenr != buf->start);
4532 
4533                 drop_node_buffer(node);
4534                 extent_buffer_get(cow);
4535                 node->eb = cow;
4536                 node->new_bytenr = cow->start;
4537 
4538                 if (!node->pending) {
4539                         list_move_tail(&node->list,
4540                                        &rc->backref_cache.pending[level]);
4541                         node->pending = 1;
4542                 }
4543 
4544                 if (first_cow)
4545                         __mark_block_processed(rc, node);
4546 
4547                 if (first_cow && level > 0)
4548                         rc->nodes_relocated += buf->len;
4549         }
4550 
4551         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS) {
4552                 ret = replace_file_extents(trans, rc, root, cow);
4553                 BUG_ON(ret);
4554         }
4555 }
4556 
4557 /*
4558  * called before creating snapshot. it calculates metadata reservation
4559  * requried for relocating tree blocks in the snapshot
4560  */
4561 void btrfs_reloc_pre_snapshot(struct btrfs_trans_handle *trans,
4562                               struct btrfs_pending_snapshot *pending,
4563                               u64 *bytes_to_reserve)
4564 {
4565         struct btrfs_root *root;
4566         struct reloc_control *rc;
4567 
4568         root = pending->root;
4569         if (!root->reloc_root)
4570                 return;
4571 
4572         rc = root->fs_info->reloc_ctl;
4573         if (!rc->merge_reloc_tree)
4574                 return;
4575 
4576         root = root->reloc_root;
4577         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4578         /*
4579          * relocation is in the stage of merging trees. the space
4580          * used by merging a reloc tree is twice the size of
4581          * relocated tree nodes in the worst case. half for cowing
4582          * the reloc tree, half for cowing the fs tree. the space
4583          * used by cowing the reloc tree will be freed after the
4584          * tree is dropped. if we create snapshot, cowing the fs
4585          * tree may use more space than it frees. so we need
4586          * reserve extra space.
4587          */
4588         *bytes_to_reserve += rc->nodes_relocated;
4589 }
4590 
4591 /*
4592  * called after snapshot is created. migrate block reservation
4593  * and create reloc root for the newly created snapshot
4594  */
4595 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4596                                struct btrfs_pending_snapshot *pending)
4597 {
4598         struct btrfs_root *root = pending->root;
4599         struct btrfs_root *reloc_root;
4600         struct btrfs_root *new_root;
4601         struct reloc_control *rc;
4602         int ret;
4603 
4604         if (!root->reloc_root)
4605                 return 0;
4606 
4607         rc = root->fs_info->reloc_ctl;
4608         rc->merging_rsv_size += rc->nodes_relocated;
4609 
4610         if (rc->merge_reloc_tree) {
4611                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4612                                               rc->block_rsv,
4613                                               rc->nodes_relocated);
4614                 if (ret)
4615                         return ret;
4616         }
4617 
4618         new_root = pending->snap;
4619         reloc_root = create_reloc_root(trans, root->reloc_root,
4620                                        new_root->root_key.objectid);
4621         if (IS_ERR(reloc_root))
4622                 return PTR_ERR(reloc_root);
4623 
4624         ret = __add_reloc_root(reloc_root);
4625         BUG_ON(ret < 0);
4626         new_root->reloc_root = reloc_root;
4627 
4628         if (rc->create_reloc_tree)
4629                 ret = clone_backref_node(trans, rc, root, reloc_root);
4630         return ret;
4631 }
4632 

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