fs/btrfs/relocation.c

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