fs/btrfs/relocation.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2009 Oracle.  All rights reserved.
   4  */
   5
   6 #include <linux/sched.h>
   7 #include <linux/pagemap.h>
   8 #include <linux/writeback.h>
   9 #include <linux/blkdev.h>
  10 #include <linux/rbtree.h>
  11 #include <linux/slab.h>
  12 #include "ctree.h"
  13 #include "disk-io.h"
  14 #include "transaction.h"
  15 #include "volumes.h"
  16 #include "locking.h"
  17 #include "btrfs_inode.h"
  18 #include "async-thread.h"
  19 #include "free-space-cache.h"
  20 #include "inode-map.h"
  21 #include "qgroup.h"
  22 #include "print-tree.h"
  23
  24 /*
  25  * backref_node, mapping_node and tree_block start with this
  26  */
  27 struct tree_entry {
  28         struct rb_node rb_node;
  29         u64 bytenr;
  30 };
  31
  32 /*
  33  * present a tree block in the backref cache
  34  */
  35 struct backref_node {
  36         struct rb_node rb_node;
  37         u64 bytenr;
  38
  39         u64 new_bytenr;
  40         /* objectid of tree block owner, can be not uptodate */
  41         u64 owner;
  42         /* link to pending, changed or detached list */
  43         struct list_head list;
  44         /* list of upper level blocks reference this block */
  45         struct list_head upper;
  46         /* list of child blocks in the cache */
  47         struct list_head lower;
  48         /* NULL if this node is not tree root */
  49         struct btrfs_root *root;
  50         /* extent buffer got by COW the block */
  51         struct extent_buffer *eb;
  52         /* level of tree block */
  53         unsigned int level:8;
  54         /* is the block in non-reference counted tree */
  55         unsigned int cowonly:1;
  56         /* 1 if no child node in the cache */
  57         unsigned int lowest:1;
  58         /* is the extent buffer locked */
  59         unsigned int locked:1;
  60         /* has the block been processed */
  61         unsigned int processed:1;
  62         /* have backrefs of this block been checked */
  63         unsigned int checked:1;
  64         /*
  65          * 1 if corresponding block has been cowed but some upper
  66          * level block pointers may not point to the new location
  67          */
  68         unsigned int pending:1;
  69         /*
  70          * 1 if the backref node isn't connected to any other
  71          * backref node.
  72          */
  73         unsigned int detached:1;
  74 };
  75
  76 /*
  77  * present a block pointer in the backref cache
  78  */
  79 struct backref_edge {
  80         struct list_head list[2];
  81         struct backref_node *node[2];
  82 };
  83
  84 #define LOWER   0
  85 #define UPPER   1
  86 #define RELOCATION_RESERVED_NODES       256
  87
  88 struct backref_cache {
  89         /* red black tree of all backref nodes in the cache */
  90         struct rb_root rb_root;
  91         /* for passing backref nodes to btrfs_reloc_cow_block */
  92         struct backref_node *path[BTRFS_MAX_LEVEL];
  93         /*
  94          * list of blocks that have been cowed but some block
  95          * pointers in upper level blocks may not reflect the
  96          * new location
  97          */
  98         struct list_head pending[BTRFS_MAX_LEVEL];
  99         /* list of backref nodes with no child node */
 100         struct list_head leaves;
 101         /* list of blocks that have been cowed in current transaction */
 102         struct list_head changed;
 103         /* list of detached backref node. */
 104         struct list_head detached;
 105
 106         u64 last_trans;
 107
 108         int nr_nodes;
 109         int nr_edges;
 110 };
 111
 112 /*
 113  * map address of tree root to tree
 114  */
 115 struct mapping_node {
 116         struct rb_node rb_node;
 117         u64 bytenr;
 118         void *data;
 119 };
 120
 121 struct mapping_tree {
 122         struct rb_root rb_root;
 123         spinlock_t lock;
 124 };
 125
 126 /*
 127  * present a tree block to process
 128  */
 129 struct tree_block {
 130         struct rb_node rb_node;
 131         u64 bytenr;
 132         struct btrfs_key key;
 133         unsigned int level:8;
 134         unsigned int key_ready:1;
 135 };
 136
 137 #define MAX_EXTENTS 128
 138
 139 struct file_extent_cluster {
 140         u64 start;
 141         u64 end;
 142         u64 boundary[MAX_EXTENTS];
 143         unsigned int nr;
 144 };
 145
 146 struct reloc_control {
 147         /* block group to relocate */
 148         struct btrfs_block_group_cache *block_group;
 149         /* extent tree */
 150         struct btrfs_root *extent_root;
 151         /* inode for moving data */
 152         struct inode *data_inode;
 153
 154         struct btrfs_block_rsv *block_rsv;
 155
 156         struct backref_cache backref_cache;
 157
 158         struct file_extent_cluster cluster;
 159         /* tree blocks have been processed */
 160         struct extent_io_tree processed_blocks;
 161         /* map start of tree root to corresponding reloc tree */
 162         struct mapping_tree reloc_root_tree;
 163         /* list of reloc trees */
 164         struct list_head reloc_roots;
 165         /* list of subvolume trees that get relocated */
 166         struct list_head dirty_subvol_roots;
 167         /* size of metadata reservation for merging reloc trees */
 168         u64 merging_rsv_size;
 169         /* size of relocated tree nodes */
 170         u64 nodes_relocated;
 171         /* reserved size for block group relocation*/
 172         u64 reserved_bytes;
 173
 174         u64 search_start;
 175         u64 extents_found;
 176
 177         unsigned int stage:8;
 178         unsigned int create_reloc_tree:1;
 179         unsigned int merge_reloc_tree:1;
 180         unsigned int found_file_extent:1;
 181 };
 182
 183 /* stages of data relocation */
 184 #define MOVE_DATA_EXTENTS       0
 185 #define UPDATE_DATA_PTRS        1
 186
 187 static void remove_backref_node(struct backref_cache *cache,
 188                                 struct backref_node *node);
 189 static void __mark_block_processed(struct reloc_control *rc,
 190                                    struct backref_node *node);
 191
 192 static void mapping_tree_init(struct mapping_tree *tree)
 193 {
 194         tree->rb_root = RB_ROOT;
 195         spin_lock_init(&tree->lock);
 196 }
 197
 198 static void backref_cache_init(struct backref_cache *cache)
 199 {
 200         int i;
 201         cache->rb_root = RB_ROOT;
 202         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 203                 INIT_LIST_HEAD(&cache->pending[i]);
 204         INIT_LIST_HEAD(&cache->changed);
 205         INIT_LIST_HEAD(&cache->detached);
 206         INIT_LIST_HEAD(&cache->leaves);
 207 }
 208
 209 static void backref_cache_cleanup(struct backref_cache *cache)
 210 {
 211         struct backref_node *node;
 212         int i;
 213
 214         while (!list_empty(&cache->detached)) {
 215                 node = list_entry(cache->detached.next,
 216                                   struct backref_node, list);
 217                 remove_backref_node(cache, node);
 218         }
 219
 220         while (!list_empty(&cache->leaves)) {
 221                 node = list_entry(cache->leaves.next,
 222                                   struct backref_node, lower);
 223                 remove_backref_node(cache, node);
 224         }
 225
 226         cache->last_trans = 0;
 227
 228         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 229                 ASSERT(list_empty(&cache->pending[i]));
 230         ASSERT(list_empty(&cache->changed));
 231         ASSERT(list_empty(&cache->detached));
 232         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
 233         ASSERT(!cache->nr_nodes);
 234         ASSERT(!cache->nr_edges);
 235 }
 236
 237 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
 238 {
 239         struct backref_node *node;
 240
 241         node = kzalloc(sizeof(*node), GFP_NOFS);
 242         if (node) {
 243                 INIT_LIST_HEAD(&node->list);
 244                 INIT_LIST_HEAD(&node->upper);
 245                 INIT_LIST_HEAD(&node->lower);
 246                 RB_CLEAR_NODE(&node->rb_node);
 247                 cache->nr_nodes++;
 248         }
 249         return node;
 250 }
 251
 252 static void free_backref_node(struct backref_cache *cache,
 253                               struct backref_node *node)
 254 {
 255         if (node) {
 256                 cache->nr_nodes--;
 257                 kfree(node);
 258         }
 259 }
 260
 261 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
 262 {
 263         struct backref_edge *edge;
 264
 265         edge = kzalloc(sizeof(*edge), GFP_NOFS);
 266         if (edge)
 267                 cache->nr_edges++;
 268         return edge;
 269 }
 270
 271 static void free_backref_edge(struct backref_cache *cache,
 272                               struct backref_edge *edge)
 273 {
 274         if (edge) {
 275                 cache->nr_edges--;
 276                 kfree(edge);
 277         }
 278 }
 279
 280 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 281                                    struct rb_node *node)
 282 {
 283         struct rb_node **p = &root->rb_node;
 284         struct rb_node *parent = NULL;
 285         struct tree_entry *entry;
 286
 287         while (*p) {
 288                 parent = *p;
 289                 entry = rb_entry(parent, struct tree_entry, rb_node);
 290
 291                 if (bytenr < entry->bytenr)
 292                         p = &(*p)->rb_left;
 293                 else if (bytenr > entry->bytenr)
 294                         p = &(*p)->rb_right;
 295                 else
 296                         return parent;
 297         }
 298
 299         rb_link_node(node, parent, p);
 300         rb_insert_color(node, root);
 301         return NULL;
 302 }
 303
 304 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 305 {
 306         struct rb_node *n = root->rb_node;
 307         struct tree_entry *entry;
 308
 309         while (n) {
 310                 entry = rb_entry(n, struct tree_entry, rb_node);
 311
 312                 if (bytenr < entry->bytenr)
 313                         n = n->rb_left;
 314                 else if (bytenr > entry->bytenr)
 315                         n = n->rb_right;
 316                 else
 317                         return n;
 318         }
 319         return NULL;
 320 }
 321
 322 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
 323 {
 324
 325         struct btrfs_fs_info *fs_info = NULL;
 326         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
 327                                               rb_node);
 328         if (bnode->root)
 329                 fs_info = bnode->root->fs_info;
 330         btrfs_panic(fs_info, errno,
 331                     "Inconsistency in backref cache found at offset %llu",
 332                     bytenr);
 333 }
 334
 335 /*
 336  * walk up backref nodes until reach node presents tree root
 337  */
 338 static struct backref_node *walk_up_backref(struct backref_node *node,
 339                                             struct backref_edge *edges[],
 340                                             int *index)
 341 {
 342         struct backref_edge *edge;
 343         int idx = *index;
 344
 345         while (!list_empty(&node->upper)) {
 346                 edge = list_entry(node->upper.next,
 347                                   struct backref_edge, list[LOWER]);
 348                 edges[idx++] = edge;
 349                 node = edge->node[UPPER];
 350         }
 351         BUG_ON(node->detached);
 352         *index = idx;
 353         return node;
 354 }
 355
 356 /*
 357  * walk down backref nodes to find start of next reference path
 358  */
 359 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
 360                                               int *index)
 361 {
 362         struct backref_edge *edge;
 363         struct backref_node *lower;
 364         int idx = *index;
 365
 366         while (idx > 0) {
 367                 edge = edges[idx - 1];
 368                 lower = edge->node[LOWER];
 369                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 370                         idx--;
 371                         continue;
 372                 }
 373                 edge = list_entry(edge->list[LOWER].next,
 374                                   struct backref_edge, list[LOWER]);
 375                 edges[idx - 1] = edge;
 376                 *index = idx;
 377                 return edge->node[UPPER];
 378         }
 379         *index = 0;
 380         return NULL;
 381 }
 382
 383 static void unlock_node_buffer(struct backref_node *node)
 384 {
 385         if (node->locked) {
 386                 btrfs_tree_unlock(node->eb);
 387                 node->locked = 0;
 388         }
 389 }
 390
 391 static void drop_node_buffer(struct backref_node *node)
 392 {
 393         if (node->eb) {
 394                 unlock_node_buffer(node);
 395                 free_extent_buffer(node->eb);
 396                 node->eb = NULL;
 397         }
 398 }
 399
 400 static void drop_backref_node(struct backref_cache *tree,
 401                               struct backref_node *node)
 402 {
 403         BUG_ON(!list_empty(&node->upper));
 404
 405         drop_node_buffer(node);
 406         list_del(&node->list);
 407         list_del(&node->lower);
 408         if (!RB_EMPTY_NODE(&node->rb_node))
 409                 rb_erase(&node->rb_node, &tree->rb_root);
 410         free_backref_node(tree, node);
 411 }
 412
 413 /*
 414  * remove a backref node from the backref cache
 415  */
 416 static void remove_backref_node(struct backref_cache *cache,
 417                                 struct backref_node *node)
 418 {
 419         struct backref_node *upper;
 420         struct backref_edge *edge;
 421
 422         if (!node)
 423                 return;
 424
 425         BUG_ON(!node->lowest && !node->detached);
 426         while (!list_empty(&node->upper)) {
 427                 edge = list_entry(node->upper.next, struct backref_edge,
 428                                   list[LOWER]);
 429                 upper = edge->node[UPPER];
 430                 list_del(&edge->list[LOWER]);
 431                 list_del(&edge->list[UPPER]);
 432                 free_backref_edge(cache, edge);
 433
 434                 if (RB_EMPTY_NODE(&upper->rb_node)) {
 435                         BUG_ON(!list_empty(&node->upper));
 436                         drop_backref_node(cache, node);
 437                         node = upper;
 438                         node->lowest = 1;
 439                         continue;
 440                 }
 441                 /*
 442                  * add the node to leaf node list if no other
 443                  * child block cached.
 444                  */
 445                 if (list_empty(&upper->lower)) {
 446                         list_add_tail(&upper->lower, &cache->leaves);
 447                         upper->lowest = 1;
 448                 }
 449         }
 450
 451         drop_backref_node(cache, node);
 452 }
 453
 454 static void update_backref_node(struct backref_cache *cache,
 455                                 struct backref_node *node, u64 bytenr)
 456 {
 457         struct rb_node *rb_node;
 458         rb_erase(&node->rb_node, &cache->rb_root);
 459         node->bytenr = bytenr;
 460         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 461         if (rb_node)
 462                 backref_tree_panic(rb_node, -EEXIST, bytenr);
 463 }
 464
 465 /*
 466  * update backref cache after a transaction commit
 467  */
 468 static int update_backref_cache(struct btrfs_trans_handle *trans,
 469                                 struct backref_cache *cache)
 470 {
 471         struct backref_node *node;
 472         int level = 0;
 473
 474         if (cache->last_trans == 0) {
 475                 cache->last_trans = trans->transid;
 476                 return 0;
 477         }
 478
 479         if (cache->last_trans == trans->transid)
 480                 return 0;
 481
 482         /*
 483          * detached nodes are used to avoid unnecessary backref
 484          * lookup. transaction commit changes the extent tree.
 485          * so the detached nodes are no longer useful.
 486          */
 487         while (!list_empty(&cache->detached)) {
 488                 node = list_entry(cache->detached.next,
 489                                   struct backref_node, list);
 490                 remove_backref_node(cache, node);
 491         }
 492
 493         while (!list_empty(&cache->changed)) {
 494                 node = list_entry(cache->changed.next,
 495                                   struct backref_node, list);
 496                 list_del_init(&node->list);
 497                 BUG_ON(node->pending);
 498                 update_backref_node(cache, node, node->new_bytenr);
 499         }
 500
 501         /*
 502          * some nodes can be left in the pending list if there were
 503          * errors during processing the pending nodes.
 504          */
 505         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 506                 list_for_each_entry(node, &cache->pending[level], list) {
 507                         BUG_ON(!node->pending);
 508                         if (node->bytenr == node->new_bytenr)
 509                                 continue;
 510                         update_backref_node(cache, node, node->new_bytenr);
 511                 }
 512         }
 513
 514         cache->last_trans = 0;
 515         return 1;
 516 }
 517
 518
 519 static int should_ignore_root(struct btrfs_root *root)
 520 {
 521         struct btrfs_root *reloc_root;
 522
 523         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 524                 return 0;
 525
 526         reloc_root = root->reloc_root;
 527         if (!reloc_root)
 528                 return 0;
 529
 530         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
 531             root->fs_info->running_transaction->transid - 1)
 532                 return 0;
 533         /*
 534          * if there is reloc tree and it was created in previous
 535          * transaction backref lookup can find the reloc tree,
 536          * so backref node for the fs tree root is useless for
 537          * relocation.
 538          */
 539         return 1;
 540 }
 541 /*
 542  * find reloc tree by address of tree root
 543  */
 544 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
 545                                           u64 bytenr)
 546 {
 547         struct rb_node *rb_node;
 548         struct mapping_node *node;
 549         struct btrfs_root *root = NULL;
 550
 551         spin_lock(&rc->reloc_root_tree.lock);
 552         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
 553         if (rb_node) {
 554                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 555                 root = (struct btrfs_root *)node->data;
 556         }
 557         spin_unlock(&rc->reloc_root_tree.lock);
 558         return root;
 559 }
 560
 561 static int is_cowonly_root(u64 root_objectid)
 562 {
 563         if (root_objectid == BTRFS_ROOT_TREE_OBJECTID ||
 564             root_objectid == BTRFS_EXTENT_TREE_OBJECTID ||
 565             root_objectid == BTRFS_CHUNK_TREE_OBJECTID ||
 566             root_objectid == BTRFS_DEV_TREE_OBJECTID ||
 567             root_objectid == BTRFS_TREE_LOG_OBJECTID ||
 568             root_objectid == BTRFS_CSUM_TREE_OBJECTID ||
 569             root_objectid == BTRFS_UUID_TREE_OBJECTID ||
 570             root_objectid == BTRFS_QUOTA_TREE_OBJECTID ||
 571             root_objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
 572                 return 1;
 573         return 0;
 574 }
 575
 576 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 577                                         u64 root_objectid)
 578 {
 579         struct btrfs_key key;
 580
 581         key.objectid = root_objectid;
 582         key.type = BTRFS_ROOT_ITEM_KEY;
 583         if (is_cowonly_root(root_objectid))
 584                 key.offset = 0;
 585         else
 586                 key.offset = (u64)-1;
 587
 588         return btrfs_get_fs_root(fs_info, &key, false);
 589 }
 590
 591 static noinline_for_stack
 592 int find_inline_backref(struct extent_buffer *leaf, int slot,
 593                         unsigned long *ptr, unsigned long *end)
 594 {
 595         struct btrfs_key key;
 596         struct btrfs_extent_item *ei;
 597         struct btrfs_tree_block_info *bi;
 598         u32 item_size;
 599
 600         btrfs_item_key_to_cpu(leaf, &key, slot);
 601
 602         item_size = btrfs_item_size_nr(leaf, slot);
 603         if (item_size < sizeof(*ei)) {
 604                 btrfs_print_v0_err(leaf->fs_info);
 605                 btrfs_handle_fs_error(leaf->fs_info, -EINVAL, NULL);
 606                 return 1;
 607         }
 608         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 609         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
 610                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
 611
 612         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
 613             item_size <= sizeof(*ei) + sizeof(*bi)) {
 614                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
 615                 return 1;
 616         }
 617         if (key.type == BTRFS_METADATA_ITEM_KEY &&
 618             item_size <= sizeof(*ei)) {
 619                 WARN_ON(item_size < sizeof(*ei));
 620                 return 1;
 621         }
 622
 623         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
 624                 bi = (struct btrfs_tree_block_info *)(ei + 1);
 625                 *ptr = (unsigned long)(bi + 1);
 626         } else {
 627                 *ptr = (unsigned long)(ei + 1);
 628         }
 629         *end = (unsigned long)ei + item_size;
 630         return 0;
 631 }
 632
 633 /*
 634  * build backref tree for a given tree block. root of the backref tree
 635  * corresponds the tree block, leaves of the backref tree correspond
 636  * roots of b-trees that reference the tree block.
 637  *
 638  * the basic idea of this function is check backrefs of a given block
 639  * to find upper level blocks that reference the block, and then check
 640  * backrefs of these upper level blocks recursively. the recursion stop
 641  * when tree root is reached or backrefs for the block is cached.
 642  *
 643  * NOTE: if we find backrefs for a block are cached, we know backrefs
 644  * for all upper level blocks that directly/indirectly reference the
 645  * block are also cached.
 646  */
 647 static noinline_for_stack
 648 struct backref_node *build_backref_tree(struct reloc_control *rc,
 649                                         struct btrfs_key *node_key,
 650                                         int level, u64 bytenr)
 651 {
 652         struct backref_cache *cache = &rc->backref_cache;
 653         struct btrfs_path *path1; /* For searching extent root */
 654         struct btrfs_path *path2; /* For searching parent of TREE_BLOCK_REF */
 655         struct extent_buffer *eb;
 656         struct btrfs_root *root;
 657         struct backref_node *cur;
 658         struct backref_node *upper;
 659         struct backref_node *lower;
 660         struct backref_node *node = NULL;
 661         struct backref_node *exist = NULL;
 662         struct backref_edge *edge;
 663         struct rb_node *rb_node;
 664         struct btrfs_key key;
 665         unsigned long end;
 666         unsigned long ptr;
 667         LIST_HEAD(list); /* Pending edge list, upper node needs to be checked */
 668         LIST_HEAD(useless);
 669         int cowonly;
 670         int ret;
 671         int err = 0;
 672         bool need_check = true;
 673
 674         path1 = btrfs_alloc_path();
 675         path2 = btrfs_alloc_path();
 676         if (!path1 || !path2) {
 677                 err = -ENOMEM;
 678                 goto out;
 679         }
 680         path1->reada = READA_FORWARD;
 681         path2->reada = READA_FORWARD;
 682
 683         node = alloc_backref_node(cache);
 684         if (!node) {
 685                 err = -ENOMEM;
 686                 goto out;
 687         }
 688
 689         node->bytenr = bytenr;
 690         node->level = level;
 691         node->lowest = 1;
 692         cur = node;
 693 again:
 694         end = 0;
 695         ptr = 0;
 696         key.objectid = cur->bytenr;
 697         key.type = BTRFS_METADATA_ITEM_KEY;
 698         key.offset = (u64)-1;
 699
 700         path1->search_commit_root = 1;
 701         path1->skip_locking = 1;
 702         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
 703                                 0, 0);
 704         if (ret < 0) {
 705                 err = ret;
 706                 goto out;
 707         }
 708         ASSERT(ret);
 709         ASSERT(path1->slots[0]);
 710
 711         path1->slots[0]--;
 712
 713         WARN_ON(cur->checked);
 714         if (!list_empty(&cur->upper)) {
 715                 /*
 716                  * the backref was added previously when processing
 717                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
 718                  */
 719                 ASSERT(list_is_singular(&cur->upper));
 720                 edge = list_entry(cur->upper.next, struct backref_edge,
 721                                   list[LOWER]);
 722                 ASSERT(list_empty(&edge->list[UPPER]));
 723                 exist = edge->node[UPPER];
 724                 /*
 725                  * add the upper level block to pending list if we need
 726                  * check its backrefs
 727                  */
 728                 if (!exist->checked)
 729                         list_add_tail(&edge->list[UPPER], &list);
 730         } else {
 731                 exist = NULL;
 732         }
 733
 734         while (1) {
 735                 cond_resched();
 736                 eb = path1->nodes[0];
 737
 738                 if (ptr >= end) {
 739                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
 740                                 ret = btrfs_next_leaf(rc->extent_root, path1);
 741                                 if (ret < 0) {
 742                                         err = ret;
 743                                         goto out;
 744                                 }
 745                                 if (ret > 0)
 746                                         break;
 747                                 eb = path1->nodes[0];
 748                         }
 749
 750                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
 751                         if (key.objectid != cur->bytenr) {
 752                                 WARN_ON(exist);
 753                                 break;
 754                         }
 755
 756                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
 757                             key.type == BTRFS_METADATA_ITEM_KEY) {
 758                                 ret = find_inline_backref(eb, path1->slots[0],
 759                                                           &ptr, &end);
 760                                 if (ret)
 761                                         goto next;
 762                         }
 763                 }
 764
 765                 if (ptr < end) {
 766                         /* update key for inline back ref */
 767                         struct btrfs_extent_inline_ref *iref;
 768                         int type;
 769                         iref = (struct btrfs_extent_inline_ref *)ptr;
 770                         type = btrfs_get_extent_inline_ref_type(eb, iref,
 771                                                         BTRFS_REF_TYPE_BLOCK);
 772                         if (type == BTRFS_REF_TYPE_INVALID) {
 773                                 err = -EUCLEAN;
 774                                 goto out;
 775                         }
 776                         key.type = type;
 777                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
 778
 779                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
 780                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
 781                 }
 782
 783                 /*
 784                  * Parent node found and matches current inline ref, no need to
 785                  * rebuild this node for this inline ref.
 786                  */
 787                 if (exist &&
 788                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
 789                       exist->owner == key.offset) ||
 790                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
 791                       exist->bytenr == key.offset))) {
 792                         exist = NULL;
 793                         goto next;
 794                 }
 795
 796                 /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
 797                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
 798                         if (key.objectid == key.offset) {
 799                                 /*
 800                                  * Only root blocks of reloc trees use backref
 801                                  * pointing to itself.
 802                                  */
 803                                 root = find_reloc_root(rc, cur->bytenr);
 804                                 ASSERT(root);
 805                                 cur->root = root;
 806                                 break;
 807                         }
 808
 809                         edge = alloc_backref_edge(cache);
 810                         if (!edge) {
 811                                 err = -ENOMEM;
 812                                 goto out;
 813                         }
 814                         rb_node = tree_search(&cache->rb_root, key.offset);
 815                         if (!rb_node) {
 816                                 upper = alloc_backref_node(cache);
 817                                 if (!upper) {
 818                                         free_backref_edge(cache, edge);
 819                                         err = -ENOMEM;
 820                                         goto out;
 821                                 }
 822                                 upper->bytenr = key.offset;
 823                                 upper->level = cur->level + 1;
 824                                 /*
 825                                  *  backrefs for the upper level block isn't
 826                                  *  cached, add the block to pending list
 827                                  */
 828                                 list_add_tail(&edge->list[UPPER], &list);
 829                         } else {
 830                                 upper = rb_entry(rb_node, struct backref_node,
 831                                                  rb_node);
 832                                 ASSERT(upper->checked);
 833                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 834                         }
 835                         list_add_tail(&edge->list[LOWER], &cur->upper);
 836                         edge->node[LOWER] = cur;
 837                         edge->node[UPPER] = upper;
 838
 839                         goto next;
 840                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
 841                         err = -EINVAL;
 842                         btrfs_print_v0_err(rc->extent_root->fs_info);
 843                         btrfs_handle_fs_error(rc->extent_root->fs_info, err,
 844                                               NULL);
 845                         goto out;
 846                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
 847                         goto next;
 848                 }
 849
 850                 /*
 851                  * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref offset
 852                  * means the root objectid. We need to search the tree to get
 853                  * its parent bytenr.
 854                  */
 855                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
 856                 if (IS_ERR(root)) {
 857                         err = PTR_ERR(root);
 858                         goto out;
 859                 }
 860
 861                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 862                         cur->cowonly = 1;
 863
 864                 if (btrfs_root_level(&root->root_item) == cur->level) {
 865                         /* tree root */
 866                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
 867                                cur->bytenr);
 868                         if (should_ignore_root(root))
 869                                 list_add(&cur->list, &useless);
 870                         else
 871                                 cur->root = root;
 872                         break;
 873                 }
 874
 875                 level = cur->level + 1;
 876
 877                 /* Search the tree to find parent blocks referring the block. */
 878                 path2->search_commit_root = 1;
 879                 path2->skip_locking = 1;
 880                 path2->lowest_level = level;
 881                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
 882                 path2->lowest_level = 0;
 883                 if (ret < 0) {
 884                         err = ret;
 885                         goto out;
 886                 }
 887                 if (ret > 0 && path2->slots[level] > 0)
 888                         path2->slots[level]--;
 889
 890                 eb = path2->nodes[level];
 891                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
 892                     cur->bytenr) {
 893                         btrfs_err(root->fs_info,
 894         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
 895                                   cur->bytenr, level - 1,
 896                                   root->root_key.objectid,
 897                                   node_key->objectid, node_key->type,
 898                                   node_key->offset);
 899                         err = -ENOENT;
 900                         goto out;
 901                 }
 902                 lower = cur;
 903                 need_check = true;
 904
 905                 /* Add all nodes and edges in the path */
 906                 for (; level < BTRFS_MAX_LEVEL; level++) {
 907                         if (!path2->nodes[level]) {
 908                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
 909                                        lower->bytenr);
 910                                 if (should_ignore_root(root))
 911                                         list_add(&lower->list, &useless);
 912                                 else
 913                                         lower->root = root;
 914                                 break;
 915                         }
 916
 917                         edge = alloc_backref_edge(cache);
 918                         if (!edge) {
 919                                 err = -ENOMEM;
 920                                 goto out;
 921                         }
 922
 923                         eb = path2->nodes[level];
 924                         rb_node = tree_search(&cache->rb_root, eb->start);
 925                         if (!rb_node) {
 926                                 upper = alloc_backref_node(cache);
 927                                 if (!upper) {
 928                                         free_backref_edge(cache, edge);
 929                                         err = -ENOMEM;
 930                                         goto out;
 931                                 }
 932                                 upper->bytenr = eb->start;
 933                                 upper->owner = btrfs_header_owner(eb);
 934                                 upper->level = lower->level + 1;
 935                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
 936                                               &root->state))
 937                                         upper->cowonly = 1;
 938
 939                                 /*
 940                                  * if we know the block isn't shared
 941                                  * we can void checking its backrefs.
 942                                  */
 943                                 if (btrfs_block_can_be_shared(root, eb))
 944                                         upper->checked = 0;
 945                                 else
 946                                         upper->checked = 1;
 947
 948                                 /*
 949                                  * add the block to pending list if we
 950                                  * need check its backrefs, we only do this once
 951                                  * while walking up a tree as we will catch
 952                                  * anything else later on.
 953                                  */
 954                                 if (!upper->checked && need_check) {
 955                                         need_check = false;
 956                                         list_add_tail(&edge->list[UPPER],
 957                                                       &list);
 958                                 } else {
 959                                         if (upper->checked)
 960                                                 need_check = true;
 961                                         INIT_LIST_HEAD(&edge->list[UPPER]);
 962                                 }
 963                         } else {
 964                                 upper = rb_entry(rb_node, struct backref_node,
 965                                                  rb_node);
 966                                 ASSERT(upper->checked);
 967                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 968                                 if (!upper->owner)
 969                                         upper->owner = btrfs_header_owner(eb);
 970                         }
 971                         list_add_tail(&edge->list[LOWER], &lower->upper);
 972                         edge->node[LOWER] = lower;
 973                         edge->node[UPPER] = upper;
 974
 975                         if (rb_node)
 976                                 break;
 977                         lower = upper;
 978                         upper = NULL;
 979                 }
 980                 btrfs_release_path(path2);
 981 next:
 982                 if (ptr < end) {
 983                         ptr += btrfs_extent_inline_ref_size(key.type);
 984                         if (ptr >= end) {
 985                                 WARN_ON(ptr > end);
 986                                 ptr = 0;
 987                                 end = 0;
 988                         }
 989                 }
 990                 if (ptr >= end)
 991                         path1->slots[0]++;
 992         }
 993         btrfs_release_path(path1);
 994
 995         cur->checked = 1;
 996         WARN_ON(exist);
 997
 998         /* the pending list isn't empty, take the first block to process */
 999         if (!list_empty(&list)) {
1000                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1001                 list_del_init(&edge->list[UPPER]);
1002                 cur = edge->node[UPPER];
1003                 goto again;
1004         }
1005
1006         /*
1007          * everything goes well, connect backref nodes and insert backref nodes
1008          * into the cache.
1009          */
1010         ASSERT(node->checked);
1011         cowonly = node->cowonly;
1012         if (!cowonly) {
1013                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1014                                       &node->rb_node);
1015                 if (rb_node)
1016                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1017                 list_add_tail(&node->lower, &cache->leaves);
1018         }
1019
1020         list_for_each_entry(edge, &node->upper, list[LOWER])
1021                 list_add_tail(&edge->list[UPPER], &list);
1022
1023         while (!list_empty(&list)) {
1024                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1025                 list_del_init(&edge->list[UPPER]);
1026                 upper = edge->node[UPPER];
1027                 if (upper->detached) {
1028                         list_del(&edge->list[LOWER]);
1029                         lower = edge->node[LOWER];
1030                         free_backref_edge(cache, edge);
1031                         if (list_empty(&lower->upper))
1032                                 list_add(&lower->list, &useless);
1033                         continue;
1034                 }
1035
1036                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1037                         if (upper->lowest) {
1038                                 list_del_init(&upper->lower);
1039                                 upper->lowest = 0;
1040                         }
1041
1042                         list_add_tail(&edge->list[UPPER], &upper->lower);
1043                         continue;
1044                 }
1045
1046                 if (!upper->checked) {
1047                         /*
1048                          * Still want to blow up for developers since this is a
1049                          * logic bug.
1050                          */
1051                         ASSERT(0);
1052                         err = -EINVAL;
1053                         goto out;
1054                 }
1055                 if (cowonly != upper->cowonly) {
1056                         ASSERT(0);
1057                         err = -EINVAL;
1058                         goto out;
1059                 }
1060
1061                 if (!cowonly) {
1062                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1063                                               &upper->rb_node);
1064                         if (rb_node)
1065                                 backref_tree_panic(rb_node, -EEXIST,
1066                                                    upper->bytenr);
1067                 }
1068
1069                 list_add_tail(&edge->list[UPPER], &upper->lower);
1070
1071                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1072                         list_add_tail(&edge->list[UPPER], &list);
1073         }
1074         /*
1075          * process useless backref nodes. backref nodes for tree leaves
1076          * are deleted from the cache. backref nodes for upper level
1077          * tree blocks are left in the cache to avoid unnecessary backref
1078          * lookup.
1079          */
1080         while (!list_empty(&useless)) {
1081                 upper = list_entry(useless.next, struct backref_node, list);
1082                 list_del_init(&upper->list);
1083                 ASSERT(list_empty(&upper->upper));
1084                 if (upper == node)
1085                         node = NULL;
1086                 if (upper->lowest) {
1087                         list_del_init(&upper->lower);
1088                         upper->lowest = 0;
1089                 }
1090                 while (!list_empty(&upper->lower)) {
1091                         edge = list_entry(upper->lower.next,
1092                                           struct backref_edge, list[UPPER]);
1093                         list_del(&edge->list[UPPER]);
1094                         list_del(&edge->list[LOWER]);
1095                         lower = edge->node[LOWER];
1096                         free_backref_edge(cache, edge);
1097
1098                         if (list_empty(&lower->upper))
1099                                 list_add(&lower->list, &useless);
1100                 }
1101                 __mark_block_processed(rc, upper);
1102                 if (upper->level > 0) {
1103                         list_add(&upper->list, &cache->detached);
1104                         upper->detached = 1;
1105                 } else {
1106                         rb_erase(&upper->rb_node, &cache->rb_root);
1107                         free_backref_node(cache, upper);
1108                 }
1109         }
1110 out:
1111         btrfs_free_path(path1);
1112         btrfs_free_path(path2);
1113         if (err) {
1114                 while (!list_empty(&useless)) {
1115                         lower = list_entry(useless.next,
1116                                            struct backref_node, list);
1117                         list_del_init(&lower->list);
1118                 }
1119                 while (!list_empty(&list)) {
1120                         edge = list_first_entry(&list, struct backref_edge,
1121                                                 list[UPPER]);
1122                         list_del(&edge->list[UPPER]);
1123                         list_del(&edge->list[LOWER]);
1124                         lower = edge->node[LOWER];
1125                         upper = edge->node[UPPER];
1126                         free_backref_edge(cache, edge);
1127
1128                         /*
1129                          * Lower is no longer linked to any upper backref nodes
1130                          * and isn't in the cache, we can free it ourselves.
1131                          */
1132                         if (list_empty(&lower->upper) &&
1133                             RB_EMPTY_NODE(&lower->rb_node))
1134                                 list_add(&lower->list, &useless);
1135
1136                         if (!RB_EMPTY_NODE(&upper->rb_node))
1137                                 continue;
1138
1139                         /* Add this guy's upper edges to the list to process */
1140                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1141                                 list_add_tail(&edge->list[UPPER], &list);
1142                         if (list_empty(&upper->upper))
1143                                 list_add(&upper->list, &useless);
1144                 }
1145
1146                 while (!list_empty(&useless)) {
1147                         lower = list_entry(useless.next,
1148                                            struct backref_node, list);
1149                         list_del_init(&lower->list);
1150                         if (lower == node)
1151                                 node = NULL;
1152                         free_backref_node(cache, lower);
1153                 }
1154
1155                 free_backref_node(cache, node);
1156                 return ERR_PTR(err);
1157         }
1158         ASSERT(!node || !node->detached);
1159         return node;
1160 }
1161
1162 /*
1163  * helper to add backref node for the newly created snapshot.
1164  * the backref node is created by cloning backref node that
1165  * corresponds to root of source tree
1166  */
1167 static int clone_backref_node(struct btrfs_trans_handle *trans,
1168                               struct reloc_control *rc,
1169                               struct btrfs_root *src,
1170                               struct btrfs_root *dest)
1171 {
1172         struct btrfs_root *reloc_root = src->reloc_root;
1173         struct backref_cache *cache = &rc->backref_cache;
1174         struct backref_node *node = NULL;
1175         struct backref_node *new_node;
1176         struct backref_edge *edge;
1177         struct backref_edge *new_edge;
1178         struct rb_node *rb_node;
1179
1180         if (cache->last_trans > 0)
1181                 update_backref_cache(trans, cache);
1182
1183         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1184         if (rb_node) {
1185                 node = rb_entry(rb_node, struct backref_node, rb_node);
1186                 if (node->detached)
1187                         node = NULL;
1188                 else
1189                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1190         }
1191
1192         if (!node) {
1193                 rb_node = tree_search(&cache->rb_root,
1194                                       reloc_root->commit_root->start);
1195                 if (rb_node) {
1196                         node = rb_entry(rb_node, struct backref_node,
1197                                         rb_node);
1198                         BUG_ON(node->detached);
1199                 }
1200         }
1201
1202         if (!node)
1203                 return 0;
1204
1205         new_node = alloc_backref_node(cache);
1206         if (!new_node)
1207                 return -ENOMEM;
1208
1209         new_node->bytenr = dest->node->start;
1210         new_node->level = node->level;
1211         new_node->lowest = node->lowest;
1212         new_node->checked = 1;
1213         new_node->root = dest;
1214
1215         if (!node->lowest) {
1216                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1217                         new_edge = alloc_backref_edge(cache);
1218                         if (!new_edge)
1219                                 goto fail;
1220
1221                         new_edge->node[UPPER] = new_node;
1222                         new_edge->node[LOWER] = edge->node[LOWER];
1223                         list_add_tail(&new_edge->list[UPPER],
1224                                       &new_node->lower);
1225                 }
1226         } else {
1227                 list_add_tail(&new_node->lower, &cache->leaves);
1228         }
1229
1230         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1231                               &new_node->rb_node);
1232         if (rb_node)
1233                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1234
1235         if (!new_node->lowest) {
1236                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1237                         list_add_tail(&new_edge->list[LOWER],
1238                                       &new_edge->node[LOWER]->upper);
1239                 }
1240         }
1241         return 0;
1242 fail:
1243         while (!list_empty(&new_node->lower)) {
1244                 new_edge = list_entry(new_node->lower.next,
1245                                       struct backref_edge, list[UPPER]);
1246                 list_del(&new_edge->list[UPPER]);
1247                 free_backref_edge(cache, new_edge);
1248         }
1249         free_backref_node(cache, new_node);
1250         return -ENOMEM;
1251 }
1252
1253 /*
1254  * helper to add 'address of tree root -> reloc tree' mapping
1255  */
1256 static int __must_check __add_reloc_root(struct btrfs_root *root)
1257 {
1258         struct btrfs_fs_info *fs_info = root->fs_info;
1259         struct rb_node *rb_node;
1260         struct mapping_node *node;
1261         struct reloc_control *rc = fs_info->reloc_ctl;
1262
1263         node = kmalloc(sizeof(*node), GFP_NOFS);
1264         if (!node)
1265                 return -ENOMEM;
1266
1267         node->bytenr = root->node->start;
1268         node->data = root;
1269
1270         spin_lock(&rc->reloc_root_tree.lock);
1271         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1272                               node->bytenr, &node->rb_node);
1273         spin_unlock(&rc->reloc_root_tree.lock);
1274         if (rb_node) {
1275                 btrfs_panic(fs_info, -EEXIST,
1276                             "Duplicate root found for start=%llu while inserting into relocation tree",
1277                             node->bytenr);
1278         }
1279
1280         list_add_tail(&root->root_list, &rc->reloc_roots);
1281         return 0;
1282 }
1283
1284 /*
1285  * helper to delete the 'address of tree root -> reloc tree'
1286  * mapping
1287  */
1288 static void __del_reloc_root(struct btrfs_root *root)
1289 {
1290         struct btrfs_fs_info *fs_info = root->fs_info;
1291         struct rb_node *rb_node;
1292         struct mapping_node *node = NULL;
1293         struct reloc_control *rc = fs_info->reloc_ctl;
1294
1295         if (rc && root->node) {
1296                 spin_lock(&rc->reloc_root_tree.lock);
1297                 rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1298                                       root->node->start);
1299                 if (rb_node) {
1300                         node = rb_entry(rb_node, struct mapping_node, rb_node);
1301                         rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1302                 }
1303                 spin_unlock(&rc->reloc_root_tree.lock);
1304                 if (!node)
1305                         return;
1306                 BUG_ON((struct btrfs_root *)node->data != root);
1307         }
1308
1309         spin_lock(&fs_info->trans_lock);
1310         list_del_init(&root->root_list);
1311         spin_unlock(&fs_info->trans_lock);
1312         kfree(node);
1313 }
1314
1315 /*
1316  * helper to update the 'address of tree root -> reloc tree'
1317  * mapping
1318  */
1319 static int __update_reloc_root(struct btrfs_root *root, u64 new_bytenr)
1320 {
1321         struct btrfs_fs_info *fs_info = root->fs_info;
1322         struct rb_node *rb_node;
1323         struct mapping_node *node = NULL;
1324         struct reloc_control *rc = fs_info->reloc_ctl;
1325
1326         spin_lock(&rc->reloc_root_tree.lock);
1327         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1328                               root->node->start);
1329         if (rb_node) {
1330                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1331                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1332         }
1333         spin_unlock(&rc->reloc_root_tree.lock);
1334
1335         if (!node)
1336                 return 0;
1337         BUG_ON((struct btrfs_root *)node->data != root);
1338
1339         spin_lock(&rc->reloc_root_tree.lock);
1340         node->bytenr = new_bytenr;
1341         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1342                               node->bytenr, &node->rb_node);
1343         spin_unlock(&rc->reloc_root_tree.lock);
1344         if (rb_node)
1345                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1346         return 0;
1347 }
1348
1349 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1350                                         struct btrfs_root *root, u64 objectid)
1351 {
1352         struct btrfs_fs_info *fs_info = root->fs_info;
1353         struct btrfs_root *reloc_root;
1354         struct extent_buffer *eb;
1355         struct btrfs_root_item *root_item;
1356         struct btrfs_key root_key;
1357         int ret;
1358
1359         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1360         BUG_ON(!root_item);
1361
1362         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1363         root_key.type = BTRFS_ROOT_ITEM_KEY;
1364         root_key.offset = objectid;
1365
1366         if (root->root_key.objectid == objectid) {
1367                 u64 commit_root_gen;
1368
1369                 /* called by btrfs_init_reloc_root */
1370                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1371                                       BTRFS_TREE_RELOC_OBJECTID);
1372                 BUG_ON(ret);
1373                 /*
1374                  * Set the last_snapshot field to the generation of the commit
1375                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
1376                  * correctly (returns true) when the relocation root is created
1377                  * either inside the critical section of a transaction commit
1378                  * (through transaction.c:qgroup_account_snapshot()) and when
1379                  * it's created before the transaction commit is started.
1380                  */
1381                 commit_root_gen = btrfs_header_generation(root->commit_root);
1382                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
1383         } else {
1384                 /*
1385                  * called by btrfs_reloc_post_snapshot_hook.
1386                  * the source tree is a reloc tree, all tree blocks
1387                  * modified after it was created have RELOC flag
1388                  * set in their headers. so it's OK to not update
1389                  * the 'last_snapshot'.
1390                  */
1391                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1392                                       BTRFS_TREE_RELOC_OBJECTID);
1393                 BUG_ON(ret);
1394         }
1395
1396         memcpy(root_item, &root->root_item, sizeof(*root_item));
1397         btrfs_set_root_bytenr(root_item, eb->start);
1398         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1399         btrfs_set_root_generation(root_item, trans->transid);
1400
1401         if (root->root_key.objectid == objectid) {
1402                 btrfs_set_root_refs(root_item, 0);
1403                 memset(&root_item->drop_progress, 0,
1404                        sizeof(struct btrfs_disk_key));
1405                 root_item->drop_level = 0;
1406         }
1407
1408         btrfs_tree_unlock(eb);
1409         free_extent_buffer(eb);
1410
1411         ret = btrfs_insert_root(trans, fs_info->tree_root,
1412                                 &root_key, root_item);
1413         BUG_ON(ret);
1414         kfree(root_item);
1415
1416         reloc_root = btrfs_read_fs_root(fs_info->tree_root, &root_key);
1417         BUG_ON(IS_ERR(reloc_root));
1418         reloc_root->last_trans = trans->transid;
1419         return reloc_root;
1420 }
1421
1422 /*
1423  * create reloc tree for a given fs tree. reloc tree is just a
1424  * snapshot of the fs tree with special root objectid.
1425  */
1426 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1427                           struct btrfs_root *root)
1428 {
1429         struct btrfs_fs_info *fs_info = root->fs_info;
1430         struct btrfs_root *reloc_root;
1431         struct reloc_control *rc = fs_info->reloc_ctl;
1432         struct btrfs_block_rsv *rsv;
1433         int clear_rsv = 0;
1434         int ret;
1435
1436         if (root->reloc_root) {
1437                 reloc_root = root->reloc_root;
1438                 reloc_root->last_trans = trans->transid;
1439                 return 0;
1440         }
1441
1442         if (!rc || !rc->create_reloc_tree ||
1443             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1444                 return 0;
1445
1446         if (!trans->reloc_reserved) {
1447                 rsv = trans->block_rsv;
1448                 trans->block_rsv = rc->block_rsv;
1449                 clear_rsv = 1;
1450         }
1451         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1452         if (clear_rsv)
1453                 trans->block_rsv = rsv;
1454
1455         ret = __add_reloc_root(reloc_root);
1456         BUG_ON(ret < 0);
1457         root->reloc_root = reloc_root;
1458         return 0;
1459 }
1460
1461 /*
1462  * update root item of reloc tree
1463  */
1464 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1465                             struct btrfs_root *root)
1466 {
1467         struct btrfs_fs_info *fs_info = root->fs_info;
1468         struct btrfs_root *reloc_root;
1469         struct btrfs_root_item *root_item;
1470         int ret;
1471
1472         if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state) ||
1473             !root->reloc_root)
1474                 goto out;
1475
1476         reloc_root = root->reloc_root;
1477         root_item = &reloc_root->root_item;
1478
1479         /* root->reloc_root will stay until current relocation finished */
1480         if (fs_info->reloc_ctl->merge_reloc_tree &&
1481             btrfs_root_refs(root_item) == 0) {
1482                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1483                 __del_reloc_root(reloc_root);
1484         }
1485
1486         if (reloc_root->commit_root != reloc_root->node) {
1487                 btrfs_set_root_node(root_item, reloc_root->node);
1488                 free_extent_buffer(reloc_root->commit_root);
1489                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1490         }
1491
1492         ret = btrfs_update_root(trans, fs_info->tree_root,
1493                                 &reloc_root->root_key, root_item);
1494         BUG_ON(ret);
1495
1496 out:
1497         return 0;
1498 }
1499
1500 /*
1501  * helper to find first cached inode with inode number >= objectid
1502  * in a subvolume
1503  */
1504 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1505 {
1506         struct rb_node *node;
1507         struct rb_node *prev;
1508         struct btrfs_inode *entry;
1509         struct inode *inode;
1510
1511         spin_lock(&root->inode_lock);
1512 again:
1513         node = root->inode_tree.rb_node;
1514         prev = NULL;
1515         while (node) {
1516                 prev = node;
1517                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1518
1519                 if (objectid < btrfs_ino(entry))
1520                         node = node->rb_left;
1521                 else if (objectid > btrfs_ino(entry))
1522                         node = node->rb_right;
1523                 else
1524                         break;
1525         }
1526         if (!node) {
1527                 while (prev) {
1528                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1529                         if (objectid <= btrfs_ino(entry)) {
1530                                 node = prev;
1531                                 break;
1532                         }
1533                         prev = rb_next(prev);
1534                 }
1535         }
1536         while (node) {
1537                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1538                 inode = igrab(&entry->vfs_inode);
1539                 if (inode) {
1540                         spin_unlock(&root->inode_lock);
1541                         return inode;
1542                 }
1543
1544                 objectid = btrfs_ino(entry) + 1;
1545                 if (cond_resched_lock(&root->inode_lock))
1546                         goto again;
1547
1548                 node = rb_next(node);
1549         }
1550         spin_unlock(&root->inode_lock);
1551         return NULL;
1552 }
1553
1554 static int in_block_group(u64 bytenr,
1555                           struct btrfs_block_group_cache *block_group)
1556 {
1557         if (bytenr >= block_group->key.objectid &&
1558             bytenr < block_group->key.objectid + block_group->key.offset)
1559                 return 1;
1560         return 0;
1561 }
1562
1563 /*
1564  * get new location of data
1565  */
1566 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1567                             u64 bytenr, u64 num_bytes)
1568 {
1569         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1570         struct btrfs_path *path;
1571         struct btrfs_file_extent_item *fi;
1572         struct extent_buffer *leaf;
1573         int ret;
1574
1575         path = btrfs_alloc_path();
1576         if (!path)
1577                 return -ENOMEM;
1578
1579         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1580         ret = btrfs_lookup_file_extent(NULL, root, path,
1581                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1582         if (ret < 0)
1583                 goto out;
1584         if (ret > 0) {
1585                 ret = -ENOENT;
1586                 goto out;
1587         }
1588
1589         leaf = path->nodes[0];
1590         fi = btrfs_item_ptr(leaf, path->slots[0],
1591                             struct btrfs_file_extent_item);
1592
1593         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1594                btrfs_file_extent_compression(leaf, fi) ||
1595                btrfs_file_extent_encryption(leaf, fi) ||
1596                btrfs_file_extent_other_encoding(leaf, fi));
1597
1598         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1599                 ret = -EINVAL;
1600                 goto out;
1601         }
1602
1603         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1604         ret = 0;
1605 out:
1606         btrfs_free_path(path);
1607         return ret;
1608 }
1609
1610 /*
1611  * update file extent items in the tree leaf to point to
1612  * the new locations.
1613  */
1614 static noinline_for_stack
1615 int replace_file_extents(struct btrfs_trans_handle *trans,
1616                          struct reloc_control *rc,
1617                          struct btrfs_root *root,
1618                          struct extent_buffer *leaf)
1619 {
1620         struct btrfs_fs_info *fs_info = root->fs_info;
1621         struct btrfs_key key;
1622         struct btrfs_file_extent_item *fi;
1623         struct inode *inode = NULL;
1624         u64 parent;
1625         u64 bytenr;
1626         u64 new_bytenr = 0;
1627         u64 num_bytes;
1628         u64 end;
1629         u32 nritems;
1630         u32 i;
1631         int ret = 0;
1632         int first = 1;
1633         int dirty = 0;
1634
1635         if (rc->stage != UPDATE_DATA_PTRS)
1636                 return 0;
1637
1638         /* reloc trees always use full backref */
1639         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1640                 parent = leaf->start;
1641         else
1642                 parent = 0;
1643
1644         nritems = btrfs_header_nritems(leaf);
1645         for (i = 0; i < nritems; i++) {
1646                 struct btrfs_ref ref = { 0 };
1647
1648                 cond_resched();
1649                 btrfs_item_key_to_cpu(leaf, &key, i);
1650                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1651                         continue;
1652                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1653                 if (btrfs_file_extent_type(leaf, fi) ==
1654                     BTRFS_FILE_EXTENT_INLINE)
1655                         continue;
1656                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1657                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1658                 if (bytenr == 0)
1659                         continue;
1660                 if (!in_block_group(bytenr, rc->block_group))
1661                         continue;
1662
1663                 /*
1664                  * if we are modifying block in fs tree, wait for readpage
1665                  * to complete and drop the extent cache
1666                  */
1667                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1668                         if (first) {
1669                                 inode = find_next_inode(root, key.objectid);
1670                                 first = 0;
1671                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1672                                 btrfs_add_delayed_iput(inode);
1673                                 inode = find_next_inode(root, key.objectid);
1674                         }
1675                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1676                                 end = key.offset +
1677                                       btrfs_file_extent_num_bytes(leaf, fi);
1678                                 WARN_ON(!IS_ALIGNED(key.offset,
1679                                                     fs_info->sectorsize));
1680                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1681                                 end--;
1682                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1683                                                       key.offset, end);
1684                                 if (!ret)
1685                                         continue;
1686
1687                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1688                                                 key.offset,     end, 1);
1689                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1690                                               key.offset, end);
1691                         }
1692                 }
1693
1694                 ret = get_new_location(rc->data_inode, &new_bytenr,
1695                                        bytenr, num_bytes);
1696                 if (ret) {
1697                         /*
1698                          * Don't have to abort since we've not changed anything
1699                          * in the file extent yet.
1700                          */
1701                         break;
1702                 }
1703
1704                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1705                 dirty = 1;
1706
1707                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1708                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1709                                        num_bytes, parent);
1710                 ref.real_root = root->root_key.objectid;
1711                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1712                                     key.objectid, key.offset);
1713                 ret = btrfs_inc_extent_ref(trans, &ref);
1714                 if (ret) {
1715                         btrfs_abort_transaction(trans, ret);
1716                         break;
1717                 }
1718
1719                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1720                                        num_bytes, parent);
1721                 ref.real_root = root->root_key.objectid;
1722                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1723                                     key.objectid, key.offset);
1724                 ret = btrfs_free_extent(trans, &ref);
1725                 if (ret) {
1726                         btrfs_abort_transaction(trans, ret);
1727                         break;
1728                 }
1729         }
1730         if (dirty)
1731                 btrfs_mark_buffer_dirty(leaf);
1732         if (inode)
1733                 btrfs_add_delayed_iput(inode);
1734         return ret;
1735 }
1736
1737 static noinline_for_stack
1738 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1739                      struct btrfs_path *path, int level)
1740 {
1741         struct btrfs_disk_key key1;
1742         struct btrfs_disk_key key2;
1743         btrfs_node_key(eb, &key1, slot);
1744         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1745         return memcmp(&key1, &key2, sizeof(key1));
1746 }
1747
1748 /*
1749  * try to replace tree blocks in fs tree with the new blocks
1750  * in reloc tree. tree blocks haven't been modified since the
1751  * reloc tree was create can be replaced.
1752  *
1753  * if a block was replaced, level of the block + 1 is returned.
1754  * if no block got replaced, 0 is returned. if there are other
1755  * errors, a negative error number is returned.
1756  */
1757 static noinline_for_stack
1758 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1759                  struct btrfs_root *dest, struct btrfs_root *src,
1760                  struct btrfs_path *path, struct btrfs_key *next_key,
1761                  int lowest_level, int max_level)
1762 {
1763         struct btrfs_fs_info *fs_info = dest->fs_info;
1764         struct extent_buffer *eb;
1765         struct extent_buffer *parent;
1766         struct btrfs_ref ref = { 0 };
1767         struct btrfs_key key;
1768         u64 old_bytenr;
1769         u64 new_bytenr;
1770         u64 old_ptr_gen;
1771         u64 new_ptr_gen;
1772         u64 last_snapshot;
1773         u32 blocksize;
1774         int cow = 0;
1775         int level;
1776         int ret;
1777         int slot;
1778
1779         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1780         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1781
1782         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1783 again:
1784         slot = path->slots[lowest_level];
1785         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1786
1787         eb = btrfs_lock_root_node(dest);
1788         btrfs_set_lock_blocking_write(eb);
1789         level = btrfs_header_level(eb);
1790
1791         if (level < lowest_level) {
1792                 btrfs_tree_unlock(eb);
1793                 free_extent_buffer(eb);
1794                 return 0;
1795         }
1796
1797         if (cow) {
1798                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1799                 BUG_ON(ret);
1800         }
1801         btrfs_set_lock_blocking_write(eb);
1802
1803         if (next_key) {
1804                 next_key->objectid = (u64)-1;
1805                 next_key->type = (u8)-1;
1806                 next_key->offset = (u64)-1;
1807         }
1808
1809         parent = eb;
1810         while (1) {
1811                 struct btrfs_key first_key;
1812
1813                 level = btrfs_header_level(parent);
1814                 BUG_ON(level < lowest_level);
1815
1816                 ret = btrfs_bin_search(parent, &key, level, &slot);
1817                 if (ret < 0)
1818                         break;
1819                 if (ret && slot > 0)
1820                         slot--;
1821
1822                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1823                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1824
1825                 old_bytenr = btrfs_node_blockptr(parent, slot);
1826                 blocksize = fs_info->nodesize;
1827                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1828                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1829
1830                 if (level <= max_level) {
1831                         eb = path->nodes[level];
1832                         new_bytenr = btrfs_node_blockptr(eb,
1833                                                         path->slots[level]);
1834                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1835                                                         path->slots[level]);
1836                 } else {
1837                         new_bytenr = 0;
1838                         new_ptr_gen = 0;
1839                 }
1840
1841                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1842                         ret = level;
1843                         break;
1844                 }
1845
1846                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1847                     memcmp_node_keys(parent, slot, path, level)) {
1848                         if (level <= lowest_level) {
1849                                 ret = 0;
1850                                 break;
1851                         }
1852
1853                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1854                                              level - 1, &first_key);
1855                         if (IS_ERR(eb)) {
1856                                 ret = PTR_ERR(eb);
1857                                 break;
1858                         } else if (!extent_buffer_uptodate(eb)) {
1859                                 ret = -EIO;
1860                                 free_extent_buffer(eb);
1861                                 break;
1862                         }
1863                         btrfs_tree_lock(eb);
1864                         if (cow) {
1865                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1866                                                       slot, &eb);
1867                                 BUG_ON(ret);
1868                         }
1869                         btrfs_set_lock_blocking_write(eb);
1870
1871                         btrfs_tree_unlock(parent);
1872                         free_extent_buffer(parent);
1873
1874                         parent = eb;
1875                         continue;
1876                 }
1877
1878                 if (!cow) {
1879                         btrfs_tree_unlock(parent);
1880                         free_extent_buffer(parent);
1881                         cow = 1;
1882                         goto again;
1883                 }
1884
1885                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1886                                       path->slots[level]);
1887                 btrfs_release_path(path);
1888
1889                 path->lowest_level = level;
1890                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1891                 path->lowest_level = 0;
1892                 BUG_ON(ret);
1893
1894                 /*
1895                  * Info qgroup to trace both subtrees.
1896                  *
1897                  * We must trace both trees.
1898                  * 1) Tree reloc subtree
1899                  *    If not traced, we will leak data numbers
1900                  * 2) Fs subtree
1901                  *    If not traced, we will double count old data
1902                  *
1903                  * We don't scan the subtree right now, but only record
1904                  * the swapped tree blocks.
1905                  * The real subtree rescan is delayed until we have new
1906                  * CoW on the subtree root node before transaction commit.
1907                  */
1908                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
1909                                 rc->block_group, parent, slot,
1910                                 path->nodes[level], path->slots[level],
1911                                 last_snapshot);
1912                 if (ret < 0)
1913                         break;
1914                 /*
1915                  * swap blocks in fs tree and reloc tree.
1916                  */
1917                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1918                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1919                 btrfs_mark_buffer_dirty(parent);
1920
1921                 btrfs_set_node_blockptr(path->nodes[level],
1922                                         path->slots[level], old_bytenr);
1923                 btrfs_set_node_ptr_generation(path->nodes[level],
1924                                               path->slots[level], old_ptr_gen);
1925                 btrfs_mark_buffer_dirty(path->nodes[level]);
1926
1927                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
1928                                        blocksize, path->nodes[level]->start);
1929                 ref.skip_qgroup = true;
1930                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1931                 ret = btrfs_inc_extent_ref(trans, &ref);
1932                 BUG_ON(ret);
1933                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1934                                        blocksize, 0);
1935                 ref.skip_qgroup = true;
1936                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1937                 ret = btrfs_inc_extent_ref(trans, &ref);
1938                 BUG_ON(ret);
1939
1940                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
1941                                        blocksize, path->nodes[level]->start);
1942                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1943                 ref.skip_qgroup = true;
1944                 ret = btrfs_free_extent(trans, &ref);
1945                 BUG_ON(ret);
1946
1947                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
1948                                        blocksize, 0);
1949                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1950                 ref.skip_qgroup = true;
1951                 ret = btrfs_free_extent(trans, &ref);
1952                 BUG_ON(ret);
1953
1954                 btrfs_unlock_up_safe(path, 0);
1955
1956                 ret = level;
1957                 break;
1958         }
1959         btrfs_tree_unlock(parent);
1960         free_extent_buffer(parent);
1961         return ret;
1962 }
1963
1964 /*
1965  * helper to find next relocated block in reloc tree
1966  */
1967 static noinline_for_stack
1968 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1969                        int *level)
1970 {
1971         struct extent_buffer *eb;
1972         int i;
1973         u64 last_snapshot;
1974         u32 nritems;
1975
1976         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1977
1978         for (i = 0; i < *level; i++) {
1979                 free_extent_buffer(path->nodes[i]);
1980                 path->nodes[i] = NULL;
1981         }
1982
1983         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1984                 eb = path->nodes[i];
1985                 nritems = btrfs_header_nritems(eb);
1986                 while (path->slots[i] + 1 < nritems) {
1987                         path->slots[i]++;
1988                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
1989                             last_snapshot)
1990                                 continue;
1991
1992                         *level = i;
1993                         return 0;
1994                 }
1995                 free_extent_buffer(path->nodes[i]);
1996                 path->nodes[i] = NULL;
1997         }
1998         return 1;
1999 }
2000
2001 /*
2002  * walk down reloc tree to find relocated block of lowest level
2003  */
2004 static noinline_for_stack
2005 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2006                          int *level)
2007 {
2008         struct btrfs_fs_info *fs_info = root->fs_info;
2009         struct extent_buffer *eb = NULL;
2010         int i;
2011         u64 bytenr;
2012         u64 ptr_gen = 0;
2013         u64 last_snapshot;
2014         u32 nritems;
2015
2016         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2017
2018         for (i = *level; i > 0; i--) {
2019                 struct btrfs_key first_key;
2020
2021                 eb = path->nodes[i];
2022                 nritems = btrfs_header_nritems(eb);
2023                 while (path->slots[i] < nritems) {
2024                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2025                         if (ptr_gen > last_snapshot)
2026                                 break;
2027                         path->slots[i]++;
2028                 }
2029                 if (path->slots[i] >= nritems) {
2030                         if (i == *level)
2031                                 break;
2032                         *level = i + 1;
2033                         return 0;
2034                 }
2035                 if (i == 1) {
2036                         *level = i;
2037                         return 0;
2038                 }
2039
2040                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2041                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
2042                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
2043                                      &first_key);
2044                 if (IS_ERR(eb)) {
2045                         return PTR_ERR(eb);
2046                 } else if (!extent_buffer_uptodate(eb)) {
2047                         free_extent_buffer(eb);
2048                         return -EIO;
2049                 }
2050                 BUG_ON(btrfs_header_level(eb) != i - 1);
2051                 path->nodes[i - 1] = eb;
2052                 path->slots[i - 1] = 0;
2053         }
2054         return 1;
2055 }
2056
2057 /*
2058  * invalidate extent cache for file extents whose key in range of
2059  * [min_key, max_key)
2060  */
2061 static int invalidate_extent_cache(struct btrfs_root *root,
2062                                    struct btrfs_key *min_key,
2063                                    struct btrfs_key *max_key)
2064 {
2065         struct btrfs_fs_info *fs_info = root->fs_info;
2066         struct inode *inode = NULL;
2067         u64 objectid;
2068         u64 start, end;
2069         u64 ino;
2070
2071         objectid = min_key->objectid;
2072         while (1) {
2073                 cond_resched();
2074                 iput(inode);
2075
2076                 if (objectid > max_key->objectid)
2077                         break;
2078
2079                 inode = find_next_inode(root, objectid);
2080                 if (!inode)
2081                         break;
2082                 ino = btrfs_ino(BTRFS_I(inode));
2083
2084                 if (ino > max_key->objectid) {
2085                         iput(inode);
2086                         break;
2087                 }
2088
2089                 objectid = ino + 1;
2090                 if (!S_ISREG(inode->i_mode))
2091                         continue;
2092
2093                 if (unlikely(min_key->objectid == ino)) {
2094                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2095                                 continue;
2096                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2097                                 start = 0;
2098                         else {
2099                                 start = min_key->offset;
2100                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2101                         }
2102                 } else {
2103                         start = 0;
2104                 }
2105
2106                 if (unlikely(max_key->objectid == ino)) {
2107                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2108                                 continue;
2109                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2110                                 end = (u64)-1;
2111                         } else {
2112                                 if (max_key->offset == 0)
2113                                         continue;
2114                                 end = max_key->offset;
2115                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2116                                 end--;
2117                         }
2118                 } else {
2119                         end = (u64)-1;
2120                 }
2121
2122                 /* the lock_extent waits for readpage to complete */
2123                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2124                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2125                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2126         }
2127         return 0;
2128 }
2129
2130 static int find_next_key(struct btrfs_path *path, int level,
2131                          struct btrfs_key *key)
2132
2133 {
2134         while (level < BTRFS_MAX_LEVEL) {
2135                 if (!path->nodes[level])
2136                         break;
2137                 if (path->slots[level] + 1 <
2138                     btrfs_header_nritems(path->nodes[level])) {
2139                         btrfs_node_key_to_cpu(path->nodes[level], key,
2140                                               path->slots[level] + 1);
2141                         return 0;
2142                 }
2143                 level++;
2144         }
2145         return 1;
2146 }
2147
2148 /*
2149  * Insert current subvolume into reloc_control::dirty_subvol_roots
2150  */
2151 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
2152                                 struct reloc_control *rc,
2153                                 struct btrfs_root *root)
2154 {
2155         struct btrfs_root *reloc_root = root->reloc_root;
2156         struct btrfs_root_item *reloc_root_item;
2157
2158         /* @root must be a subvolume tree root with a valid reloc tree */
2159         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
2160         ASSERT(reloc_root);
2161
2162         reloc_root_item = &reloc_root->root_item;
2163         memset(&reloc_root_item->drop_progress, 0,
2164                 sizeof(reloc_root_item->drop_progress));
2165         reloc_root_item->drop_level = 0;
2166         btrfs_set_root_refs(reloc_root_item, 0);
2167         btrfs_update_reloc_root(trans, root);
2168
2169         if (list_empty(&root->reloc_dirty_list)) {
2170                 btrfs_grab_fs_root(root);
2171                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
2172         }
2173 }
2174
2175 static int clean_dirty_subvols(struct reloc_control *rc)
2176 {
2177         struct btrfs_root *root;
2178         struct btrfs_root *next;
2179         int ret = 0;
2180
2181         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
2182                                  reloc_dirty_list) {
2183                 struct btrfs_root *reloc_root = root->reloc_root;
2184
2185                 clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
2186                 list_del_init(&root->reloc_dirty_list);
2187                 root->reloc_root = NULL;
2188                 if (reloc_root) {
2189                         int ret2;
2190
2191                         ret2 = btrfs_drop_snapshot(reloc_root, NULL, 0, 1);
2192                         if (ret2 < 0 && !ret)
2193                                 ret = ret2;
2194                 }
2195                 btrfs_put_fs_root(root);
2196         }
2197         return ret;
2198 }
2199
2200 /*
2201  * merge the relocated tree blocks in reloc tree with corresponding
2202  * fs tree.
2203  */
2204 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2205                                                struct btrfs_root *root)
2206 {
2207         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2208         struct btrfs_key key;
2209         struct btrfs_key next_key;
2210         struct btrfs_trans_handle *trans = NULL;
2211         struct btrfs_root *reloc_root;
2212         struct btrfs_root_item *root_item;
2213         struct btrfs_path *path;
2214         struct extent_buffer *leaf;
2215         int level;
2216         int max_level;
2217         int replaced = 0;
2218         int ret;
2219         int err = 0;
2220         u32 min_reserved;
2221
2222         path = btrfs_alloc_path();
2223         if (!path)
2224                 return -ENOMEM;
2225         path->reada = READA_FORWARD;
2226
2227         reloc_root = root->reloc_root;
2228         root_item = &reloc_root->root_item;
2229
2230         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2231                 level = btrfs_root_level(root_item);
2232                 extent_buffer_get(reloc_root->node);
2233                 path->nodes[level] = reloc_root->node;
2234                 path->slots[level] = 0;
2235         } else {
2236                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2237
2238                 level = root_item->drop_level;
2239                 BUG_ON(level == 0);
2240                 path->lowest_level = level;
2241                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2242                 path->lowest_level = 0;
2243                 if (ret < 0) {
2244                         btrfs_free_path(path);
2245                         return ret;
2246                 }
2247
2248                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2249                                       path->slots[level]);
2250                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2251
2252                 btrfs_unlock_up_safe(path, 0);
2253         }
2254
2255         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2256         memset(&next_key, 0, sizeof(next_key));
2257
2258         while (1) {
2259                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2260                                              BTRFS_RESERVE_FLUSH_ALL);
2261                 if (ret) {
2262                         err = ret;
2263                         goto out;
2264                 }
2265                 trans = btrfs_start_transaction(root, 0);
2266                 if (IS_ERR(trans)) {
2267                         err = PTR_ERR(trans);
2268                         trans = NULL;
2269                         goto out;
2270                 }
2271                 trans->block_rsv = rc->block_rsv;
2272
2273                 replaced = 0;
2274                 max_level = level;
2275
2276                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2277                 if (ret < 0) {
2278                         err = ret;
2279                         goto out;
2280                 }
2281                 if (ret > 0)
2282                         break;
2283
2284                 if (!find_next_key(path, level, &key) &&
2285                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2286                         ret = 0;
2287                 } else {
2288                         ret = replace_path(trans, rc, root, reloc_root, path,
2289                                            &next_key, level, max_level);
2290                 }
2291                 if (ret < 0) {
2292                         err = ret;
2293                         goto out;
2294                 }
2295
2296                 if (ret > 0) {
2297                         level = ret;
2298                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2299                                               path->slots[level]);
2300                         replaced = 1;
2301                 }
2302
2303                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2304                 if (ret > 0)
2305                         break;
2306
2307                 BUG_ON(level == 0);
2308                 /*
2309                  * save the merging progress in the drop_progress.
2310                  * this is OK since root refs == 1 in this case.
2311                  */
2312                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2313                                path->slots[level]);
2314                 root_item->drop_level = level;
2315
2316                 btrfs_end_transaction_throttle(trans);
2317                 trans = NULL;
2318
2319                 btrfs_btree_balance_dirty(fs_info);
2320
2321                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2322                         invalidate_extent_cache(root, &key, &next_key);
2323         }
2324
2325         /*
2326          * handle the case only one block in the fs tree need to be
2327          * relocated and the block is tree root.
2328          */
2329         leaf = btrfs_lock_root_node(root);
2330         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2331         btrfs_tree_unlock(leaf);
2332         free_extent_buffer(leaf);
2333         if (ret < 0)
2334                 err = ret;
2335 out:
2336         btrfs_free_path(path);
2337
2338         if (err == 0)
2339                 insert_dirty_subvol(trans, rc, root);
2340
2341         if (trans)
2342                 btrfs_end_transaction_throttle(trans);
2343
2344         btrfs_btree_balance_dirty(fs_info);
2345
2346         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2347                 invalidate_extent_cache(root, &key, &next_key);
2348
2349         return err;
2350 }
2351
2352 static noinline_for_stack
2353 int prepare_to_merge(struct reloc_control *rc, int err)
2354 {
2355         struct btrfs_root *root = rc->extent_root;
2356         struct btrfs_fs_info *fs_info = root->fs_info;
2357         struct btrfs_root *reloc_root;
2358         struct btrfs_trans_handle *trans;
2359         LIST_HEAD(reloc_roots);
2360         u64 num_bytes = 0;
2361         int ret;
2362
2363         mutex_lock(&fs_info->reloc_mutex);
2364         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2365         rc->merging_rsv_size += rc->nodes_relocated * 2;
2366         mutex_unlock(&fs_info->reloc_mutex);
2367
2368 again:
2369         if (!err) {
2370                 num_bytes = rc->merging_rsv_size;
2371                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2372                                           BTRFS_RESERVE_FLUSH_ALL);
2373                 if (ret)
2374                         err = ret;
2375         }
2376
2377         trans = btrfs_join_transaction(rc->extent_root);
2378         if (IS_ERR(trans)) {
2379                 if (!err)
2380                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2381                                                 num_bytes);
2382                 return PTR_ERR(trans);
2383         }
2384
2385         if (!err) {
2386                 if (num_bytes != rc->merging_rsv_size) {
2387                         btrfs_end_transaction(trans);
2388                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2389                                                 num_bytes);
2390                         goto again;
2391                 }
2392         }
2393
2394         rc->merge_reloc_tree = 1;
2395
2396         while (!list_empty(&rc->reloc_roots)) {
2397                 reloc_root = list_entry(rc->reloc_roots.next,
2398                                         struct btrfs_root, root_list);
2399                 list_del_init(&reloc_root->root_list);
2400
2401                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2402                 BUG_ON(IS_ERR(root));
2403                 BUG_ON(root->reloc_root != reloc_root);
2404
2405                 /*
2406                  * set reference count to 1, so btrfs_recover_relocation
2407                  * knows it should resumes merging
2408                  */
2409                 if (!err)
2410                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2411                 btrfs_update_reloc_root(trans, root);
2412
2413                 list_add(&reloc_root->root_list, &reloc_roots);
2414         }
2415
2416         list_splice(&reloc_roots, &rc->reloc_roots);
2417
2418         if (!err)
2419                 btrfs_commit_transaction(trans);
2420         else
2421                 btrfs_end_transaction(trans);
2422         return err;
2423 }
2424
2425 static noinline_for_stack
2426 void free_reloc_roots(struct list_head *list)
2427 {
2428         struct btrfs_root *reloc_root;
2429
2430         while (!list_empty(list)) {
2431                 reloc_root = list_entry(list->next, struct btrfs_root,
2432                                         root_list);
2433                 __del_reloc_root(reloc_root);
2434                 free_extent_buffer(reloc_root->node);
2435                 free_extent_buffer(reloc_root->commit_root);
2436                 reloc_root->node = NULL;
2437                 reloc_root->commit_root = NULL;
2438         }
2439 }
2440
2441 static noinline_for_stack
2442 void merge_reloc_roots(struct reloc_control *rc)
2443 {
2444         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2445         struct btrfs_root *root;
2446         struct btrfs_root *reloc_root;
2447         LIST_HEAD(reloc_roots);
2448         int found = 0;
2449         int ret = 0;
2450 again:
2451         root = rc->extent_root;
2452
2453         /*
2454          * this serializes us with btrfs_record_root_in_transaction,
2455          * we have to make sure nobody is in the middle of
2456          * adding their roots to the list while we are
2457          * doing this splice
2458          */
2459         mutex_lock(&fs_info->reloc_mutex);
2460         list_splice_init(&rc->reloc_roots, &reloc_roots);
2461         mutex_unlock(&fs_info->reloc_mutex);
2462
2463         while (!list_empty(&reloc_roots)) {
2464                 found = 1;
2465                 reloc_root = list_entry(reloc_roots.next,
2466                                         struct btrfs_root, root_list);
2467
2468                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2469                         root = read_fs_root(fs_info,
2470                                             reloc_root->root_key.offset);
2471                         BUG_ON(IS_ERR(root));
2472                         BUG_ON(root->reloc_root != reloc_root);
2473
2474                         ret = merge_reloc_root(rc, root);
2475                         if (ret) {
2476                                 if (list_empty(&reloc_root->root_list))
2477                                         list_add_tail(&reloc_root->root_list,
2478                                                       &reloc_roots);
2479                                 goto out;
2480                         }
2481                 } else {
2482                         list_del_init(&reloc_root->root_list);
2483                 }
2484         }
2485
2486         if (found) {
2487                 found = 0;
2488                 goto again;
2489         }
2490 out:
2491         if (ret) {
2492                 btrfs_handle_fs_error(fs_info, ret, NULL);
2493                 if (!list_empty(&reloc_roots))
2494                         free_reloc_roots(&reloc_roots);
2495
2496                 /* new reloc root may be added */
2497                 mutex_lock(&fs_info->reloc_mutex);
2498                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2499                 mutex_unlock(&fs_info->reloc_mutex);
2500                 if (!list_empty(&reloc_roots))
2501                         free_reloc_roots(&reloc_roots);
2502         }
2503
2504         BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2505 }
2506
2507 static void free_block_list(struct rb_root *blocks)
2508 {
2509         struct tree_block *block;
2510         struct rb_node *rb_node;
2511         while ((rb_node = rb_first(blocks))) {
2512                 block = rb_entry(rb_node, struct tree_block, rb_node);
2513                 rb_erase(rb_node, blocks);
2514                 kfree(block);
2515         }
2516 }
2517
2518 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2519                                       struct btrfs_root *reloc_root)
2520 {
2521         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2522         struct btrfs_root *root;
2523
2524         if (reloc_root->last_trans == trans->transid)
2525                 return 0;
2526
2527         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2528         BUG_ON(IS_ERR(root));
2529         BUG_ON(root->reloc_root != reloc_root);
2530
2531         return btrfs_record_root_in_trans(trans, root);
2532 }
2533
2534 static noinline_for_stack
2535 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2536                                      struct reloc_control *rc,
2537                                      struct backref_node *node,
2538                                      struct backref_edge *edges[])
2539 {
2540         struct backref_node *next;
2541         struct btrfs_root *root;
2542         int index = 0;
2543
2544         next = node;
2545         while (1) {
2546                 cond_resched();
2547                 next = walk_up_backref(next, edges, &index);
2548                 root = next->root;
2549                 BUG_ON(!root);
2550                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2551
2552                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2553                         record_reloc_root_in_trans(trans, root);
2554                         break;
2555                 }
2556
2557                 btrfs_record_root_in_trans(trans, root);
2558                 root = root->reloc_root;
2559
2560                 if (next->new_bytenr != root->node->start) {
2561                         BUG_ON(next->new_bytenr);
2562                         BUG_ON(!list_empty(&next->list));
2563                         next->new_bytenr = root->node->start;
2564                         next->root = root;
2565                         list_add_tail(&next->list,
2566                                       &rc->backref_cache.changed);
2567                         __mark_block_processed(rc, next);
2568                         break;
2569                 }
2570
2571                 WARN_ON(1);
2572                 root = NULL;
2573                 next = walk_down_backref(edges, &index);
2574                 if (!next || next->level <= node->level)
2575                         break;
2576         }
2577         if (!root)
2578                 return NULL;
2579
2580         next = node;
2581         /* setup backref node path for btrfs_reloc_cow_block */
2582         while (1) {
2583                 rc->backref_cache.path[next->level] = next;
2584                 if (--index < 0)
2585                         break;
2586                 next = edges[index]->node[UPPER];
2587         }
2588         return root;
2589 }
2590
2591 /*
2592  * select a tree root for relocation. return NULL if the block
2593  * is reference counted. we should use do_relocation() in this
2594  * case. return a tree root pointer if the block isn't reference
2595  * counted. return -ENOENT if the block is root of reloc tree.
2596  */
2597 static noinline_for_stack
2598 struct btrfs_root *select_one_root(struct backref_node *node)
2599 {
2600         struct backref_node *next;
2601         struct btrfs_root *root;
2602         struct btrfs_root *fs_root = NULL;
2603         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2604         int index = 0;
2605
2606         next = node;
2607         while (1) {
2608                 cond_resched();
2609                 next = walk_up_backref(next, edges, &index);
2610                 root = next->root;
2611                 BUG_ON(!root);
2612
2613                 /* no other choice for non-references counted tree */
2614                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2615                         return root;
2616
2617                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2618                         fs_root = root;
2619
2620                 if (next != node)
2621                         return NULL;
2622
2623                 next = walk_down_backref(edges, &index);
2624                 if (!next || next->level <= node->level)
2625                         break;
2626         }
2627
2628         if (!fs_root)
2629                 return ERR_PTR(-ENOENT);
2630         return fs_root;
2631 }
2632
2633 static noinline_for_stack
2634 u64 calcu_metadata_size(struct reloc_control *rc,
2635                         struct backref_node *node, int reserve)
2636 {
2637         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2638         struct backref_node *next = node;
2639         struct backref_edge *edge;
2640         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2641         u64 num_bytes = 0;
2642         int index = 0;
2643
2644         BUG_ON(reserve && node->processed);
2645
2646         while (next) {
2647                 cond_resched();
2648                 while (1) {
2649                         if (next->processed && (reserve || next != node))
2650                                 break;
2651
2652                         num_bytes += fs_info->nodesize;
2653
2654                         if (list_empty(&next->upper))
2655                                 break;
2656
2657                         edge = list_entry(next->upper.next,
2658                                           struct backref_edge, list[LOWER]);
2659                         edges[index++] = edge;
2660                         next = edge->node[UPPER];
2661                 }
2662                 next = walk_down_backref(edges, &index);
2663         }
2664         return num_bytes;
2665 }
2666
2667 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2668                                   struct reloc_control *rc,
2669                                   struct backref_node *node)
2670 {
2671         struct btrfs_root *root = rc->extent_root;
2672         struct btrfs_fs_info *fs_info = root->fs_info;
2673         u64 num_bytes;
2674         int ret;
2675         u64 tmp;
2676
2677         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2678
2679         trans->block_rsv = rc->block_rsv;
2680         rc->reserved_bytes += num_bytes;
2681
2682         /*
2683          * We are under a transaction here so we can only do limited flushing.
2684          * If we get an enospc just kick back -EAGAIN so we know to drop the
2685          * transaction and try to refill when we can flush all the things.
2686          */
2687         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2688                                 BTRFS_RESERVE_FLUSH_LIMIT);
2689         if (ret) {
2690                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2691                 while (tmp <= rc->reserved_bytes)
2692                         tmp <<= 1;
2693                 /*
2694                  * only one thread can access block_rsv at this point,
2695                  * so we don't need hold lock to protect block_rsv.
2696                  * we expand more reservation size here to allow enough
2697                  * space for relocation and we will return earlier in
2698                  * enospc case.
2699                  */
2700                 rc->block_rsv->size = tmp + fs_info->nodesize *
2701                                       RELOCATION_RESERVED_NODES;
2702                 return -EAGAIN;
2703         }
2704
2705         return 0;
2706 }
2707
2708 /*
2709  * relocate a block tree, and then update pointers in upper level
2710  * blocks that reference the block to point to the new location.
2711  *
2712  * if called by link_to_upper, the block has already been relocated.
2713  * in that case this function just updates pointers.
2714  */
2715 static int do_relocation(struct btrfs_trans_handle *trans,
2716                          struct reloc_control *rc,
2717                          struct backref_node *node,
2718                          struct btrfs_key *key,
2719                          struct btrfs_path *path, int lowest)
2720 {
2721         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2722         struct backref_node *upper;
2723         struct backref_edge *edge;
2724         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2725         struct btrfs_root *root;
2726         struct extent_buffer *eb;
2727         u32 blocksize;
2728         u64 bytenr;
2729         u64 generation;
2730         int slot;
2731         int ret;
2732         int err = 0;
2733
2734         BUG_ON(lowest && node->eb);
2735
2736         path->lowest_level = node->level + 1;
2737         rc->backref_cache.path[node->level] = node;
2738         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2739                 struct btrfs_key first_key;
2740                 struct btrfs_ref ref = { 0 };
2741
2742                 cond_resched();
2743
2744                 upper = edge->node[UPPER];
2745                 root = select_reloc_root(trans, rc, upper, edges);
2746                 BUG_ON(!root);
2747
2748                 if (upper->eb && !upper->locked) {
2749                         if (!lowest) {
2750                                 ret = btrfs_bin_search(upper->eb, key,
2751                                                        upper->level, &slot);
2752                                 if (ret < 0) {
2753                                         err = ret;
2754                                         goto next;
2755                                 }
2756                                 BUG_ON(ret);
2757                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2758                                 if (node->eb->start == bytenr)
2759                                         goto next;
2760                         }
2761                         drop_node_buffer(upper);
2762                 }
2763
2764                 if (!upper->eb) {
2765                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2766                         if (ret) {
2767                                 if (ret < 0)
2768                                         err = ret;
2769                                 else
2770                                         err = -ENOENT;
2771
2772                                 btrfs_release_path(path);
2773                                 break;
2774                         }
2775
2776                         if (!upper->eb) {
2777                                 upper->eb = path->nodes[upper->level];
2778                                 path->nodes[upper->level] = NULL;
2779                         } else {
2780                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2781                         }
2782
2783                         upper->locked = 1;
2784                         path->locks[upper->level] = 0;
2785
2786                         slot = path->slots[upper->level];
2787                         btrfs_release_path(path);
2788                 } else {
2789                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2790                                                &slot);
2791                         if (ret < 0) {
2792                                 err = ret;
2793                                 goto next;
2794                         }
2795                         BUG_ON(ret);
2796                 }
2797
2798                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2799                 if (lowest) {
2800                         if (bytenr != node->bytenr) {
2801                                 btrfs_err(root->fs_info,
2802                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2803                                           bytenr, node->bytenr, slot,
2804                                           upper->eb->start);
2805                                 err = -EIO;
2806                                 goto next;
2807                         }
2808                 } else {
2809                         if (node->eb->start == bytenr)
2810                                 goto next;
2811                 }
2812
2813                 blocksize = root->fs_info->nodesize;
2814                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2815                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2816                 eb = read_tree_block(fs_info, bytenr, generation,
2817                                      upper->level - 1, &first_key);
2818                 if (IS_ERR(eb)) {
2819                         err = PTR_ERR(eb);
2820                         goto next;
2821                 } else if (!extent_buffer_uptodate(eb)) {
2822                         free_extent_buffer(eb);
2823                         err = -EIO;
2824                         goto next;
2825                 }
2826                 btrfs_tree_lock(eb);
2827                 btrfs_set_lock_blocking_write(eb);
2828
2829                 if (!node->eb) {
2830                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2831                                               slot, &eb);
2832                         btrfs_tree_unlock(eb);
2833                         free_extent_buffer(eb);
2834                         if (ret < 0) {
2835                                 err = ret;
2836                                 goto next;
2837                         }
2838                         BUG_ON(node->eb != eb);
2839                 } else {
2840                         btrfs_set_node_blockptr(upper->eb, slot,
2841                                                 node->eb->start);
2842                         btrfs_set_node_ptr_generation(upper->eb, slot,
2843                                                       trans->transid);
2844                         btrfs_mark_buffer_dirty(upper->eb);
2845
2846                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
2847                                                node->eb->start, blocksize,
2848                                                upper->eb->start);
2849                         ref.real_root = root->root_key.objectid;
2850                         btrfs_init_tree_ref(&ref, node->level,
2851                                             btrfs_header_owner(upper->eb));
2852                         ret = btrfs_inc_extent_ref(trans, &ref);
2853                         BUG_ON(ret);
2854
2855                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2856                         BUG_ON(ret);
2857                 }
2858 next:
2859                 if (!upper->pending)
2860                         drop_node_buffer(upper);
2861                 else
2862                         unlock_node_buffer(upper);
2863                 if (err)
2864                         break;
2865         }
2866
2867         if (!err && node->pending) {
2868                 drop_node_buffer(node);
2869                 list_move_tail(&node->list, &rc->backref_cache.changed);
2870                 node->pending = 0;
2871         }
2872
2873         path->lowest_level = 0;
2874         BUG_ON(err == -ENOSPC);
2875         return err;
2876 }
2877
2878 static int link_to_upper(struct btrfs_trans_handle *trans,
2879                          struct reloc_control *rc,
2880                          struct backref_node *node,
2881                          struct btrfs_path *path)
2882 {
2883         struct btrfs_key key;
2884
2885         btrfs_node_key_to_cpu(node->eb, &key, 0);
2886         return do_relocation(trans, rc, node, &key, path, 0);
2887 }
2888
2889 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2890                                 struct reloc_control *rc,
2891                                 struct btrfs_path *path, int err)
2892 {
2893         LIST_HEAD(list);
2894         struct backref_cache *cache = &rc->backref_cache;
2895         struct backref_node *node;
2896         int level;
2897         int ret;
2898
2899         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2900                 while (!list_empty(&cache->pending[level])) {
2901                         node = list_entry(cache->pending[level].next,
2902                                           struct backref_node, list);
2903                         list_move_tail(&node->list, &list);
2904                         BUG_ON(!node->pending);
2905
2906                         if (!err) {
2907                                 ret = link_to_upper(trans, rc, node, path);
2908                                 if (ret < 0)
2909                                         err = ret;
2910                         }
2911                 }
2912                 list_splice_init(&list, &cache->pending[level]);
2913         }
2914         return err;
2915 }
2916
2917 static void mark_block_processed(struct reloc_control *rc,
2918                                  u64 bytenr, u32 blocksize)
2919 {
2920         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
2921                         EXTENT_DIRTY);
2922 }
2923
2924 static void __mark_block_processed(struct reloc_control *rc,
2925                                    struct backref_node *node)
2926 {
2927         u32 blocksize;
2928         if (node->level == 0 ||
2929             in_block_group(node->bytenr, rc->block_group)) {
2930                 blocksize = rc->extent_root->fs_info->nodesize;
2931                 mark_block_processed(rc, node->bytenr, blocksize);
2932         }
2933         node->processed = 1;
2934 }
2935
2936 /*
2937  * mark a block and all blocks directly/indirectly reference the block
2938  * as processed.
2939  */
2940 static void update_processed_blocks(struct reloc_control *rc,
2941                                     struct backref_node *node)
2942 {
2943         struct backref_node *next = node;
2944         struct backref_edge *edge;
2945         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2946         int index = 0;
2947
2948         while (next) {
2949                 cond_resched();
2950                 while (1) {
2951                         if (next->processed)
2952                                 break;
2953
2954                         __mark_block_processed(rc, next);
2955
2956                         if (list_empty(&next->upper))
2957                                 break;
2958
2959                         edge = list_entry(next->upper.next,
2960                                           struct backref_edge, list[LOWER]);
2961                         edges[index++] = edge;
2962                         next = edge->node[UPPER];
2963                 }
2964                 next = walk_down_backref(edges, &index);
2965         }
2966 }
2967
2968 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2969 {
2970         u32 blocksize = rc->extent_root->fs_info->nodesize;
2971
2972         if (test_range_bit(&rc->processed_blocks, bytenr,
2973                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2974                 return 1;
2975         return 0;
2976 }
2977
2978 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
2979                               struct tree_block *block)
2980 {
2981         struct extent_buffer *eb;
2982
2983         BUG_ON(block->key_ready);
2984         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
2985                              block->level, NULL);
2986         if (IS_ERR(eb)) {
2987                 return PTR_ERR(eb);
2988         } else if (!extent_buffer_uptodate(eb)) {
2989                 free_extent_buffer(eb);
2990                 return -EIO;
2991         }
2992         if (block->level == 0)
2993                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2994         else
2995                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2996         free_extent_buffer(eb);
2997         block->key_ready = 1;
2998         return 0;
2999 }
3000
3001 /*
3002  * helper function to relocate a tree block
3003  */
3004 static int relocate_tree_block(struct btrfs_trans_handle *trans,
3005                                 struct reloc_control *rc,
3006                                 struct backref_node *node,
3007                                 struct btrfs_key *key,
3008                                 struct btrfs_path *path)
3009 {
3010         struct btrfs_root *root;
3011         int ret = 0;
3012
3013         if (!node)
3014                 return 0;
3015
3016         BUG_ON(node->processed);
3017         root = select_one_root(node);
3018         if (root == ERR_PTR(-ENOENT)) {
3019                 update_processed_blocks(rc, node);
3020                 goto out;
3021         }
3022
3023         if (!root || test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3024                 ret = reserve_metadata_space(trans, rc, node);
3025                 if (ret)
3026                         goto out;
3027         }
3028
3029         if (root) {
3030                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3031                         BUG_ON(node->new_bytenr);
3032                         BUG_ON(!list_empty(&node->list));
3033                         btrfs_record_root_in_trans(trans, root);
3034                         root = root->reloc_root;
3035                         node->new_bytenr = root->node->start;
3036                         node->root = root;
3037                         list_add_tail(&node->list, &rc->backref_cache.changed);
3038                 } else {
3039                         path->lowest_level = node->level;
3040                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3041                         btrfs_release_path(path);
3042                         if (ret > 0)
3043                                 ret = 0;
3044                 }
3045                 if (!ret)
3046                         update_processed_blocks(rc, node);
3047         } else {
3048                 ret = do_relocation(trans, rc, node, key, path, 1);
3049         }
3050 out:
3051         if (ret || node->level == 0 || node->cowonly)
3052                 remove_backref_node(&rc->backref_cache, node);
3053         return ret;
3054 }
3055
3056 /*
3057  * relocate a list of blocks
3058  */
3059 static noinline_for_stack
3060 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3061                          struct reloc_control *rc, struct rb_root *blocks)
3062 {
3063         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3064         struct backref_node *node;
3065         struct btrfs_path *path;
3066         struct tree_block *block;
3067         struct tree_block *next;
3068         int ret;
3069         int err = 0;
3070
3071         path = btrfs_alloc_path();
3072         if (!path) {
3073                 err = -ENOMEM;
3074                 goto out_free_blocks;
3075         }
3076
3077         /* Kick in readahead for tree blocks with missing keys */
3078         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3079                 if (!block->key_ready)
3080                         readahead_tree_block(fs_info, block->bytenr);
3081         }
3082
3083         /* Get first keys */
3084         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3085                 if (!block->key_ready) {
3086                         err = get_tree_block_key(fs_info, block);
3087                         if (err)
3088                                 goto out_free_path;
3089                 }
3090         }
3091
3092         /* Do tree relocation */
3093         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3094                 node = build_backref_tree(rc, &block->key,
3095                                           block->level, block->bytenr);
3096                 if (IS_ERR(node)) {
3097                         err = PTR_ERR(node);
3098                         goto out;
3099                 }
3100
3101                 ret = relocate_tree_block(trans, rc, node, &block->key,
3102                                           path);
3103                 if (ret < 0) {
3104                         if (ret != -EAGAIN || &block->rb_node == rb_first(blocks))
3105                                 err = ret;
3106                         goto out;
3107                 }
3108         }
3109 out:
3110         err = finish_pending_nodes(trans, rc, path, err);
3111
3112 out_free_path:
3113         btrfs_free_path(path);
3114 out_free_blocks:
3115         free_block_list(blocks);
3116         return err;
3117 }
3118
3119 static noinline_for_stack
3120 int prealloc_file_extent_cluster(struct inode *inode,
3121                                  struct file_extent_cluster *cluster)
3122 {
3123         u64 alloc_hint = 0;
3124         u64 start;
3125         u64 end;
3126         u64 offset = BTRFS_I(inode)->index_cnt;
3127         u64 num_bytes;
3128         int nr = 0;
3129         int ret = 0;
3130         u64 prealloc_start = cluster->start - offset;
3131         u64 prealloc_end = cluster->end - offset;
3132         u64 cur_offset;
3133         struct extent_changeset *data_reserved = NULL;
3134
3135         BUG_ON(cluster->start != cluster->boundary[0]);
3136         inode_lock(inode);
3137
3138         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3139                                           prealloc_end + 1 - prealloc_start);
3140         if (ret)
3141                 goto out;
3142
3143         cur_offset = prealloc_start;
3144         while (nr < cluster->nr) {
3145                 start = cluster->boundary[nr] - offset;
3146                 if (nr + 1 < cluster->nr)
3147                         end = cluster->boundary[nr + 1] - 1 - offset;
3148                 else
3149                         end = cluster->end - offset;
3150
3151                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3152                 num_bytes = end + 1 - start;
3153                 if (cur_offset < start)
3154                         btrfs_free_reserved_data_space(inode, data_reserved,
3155                                         cur_offset, start - cur_offset);
3156                 ret = btrfs_prealloc_file_range(inode, 0, start,
3157                                                 num_bytes, num_bytes,
3158                                                 end + 1, &alloc_hint);
3159                 cur_offset = end + 1;
3160                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3161                 if (ret)
3162                         break;
3163                 nr++;
3164         }
3165         if (cur_offset < prealloc_end)
3166                 btrfs_free_reserved_data_space(inode, data_reserved,
3167                                 cur_offset, prealloc_end + 1 - cur_offset);
3168 out:
3169         inode_unlock(inode);
3170         extent_changeset_free(data_reserved);
3171         return ret;
3172 }
3173
3174 static noinline_for_stack
3175 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3176                          u64 block_start)
3177 {
3178         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3179         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3180         struct extent_map *em;
3181         int ret = 0;
3182
3183         em = alloc_extent_map();
3184         if (!em)
3185                 return -ENOMEM;
3186
3187         em->start = start;
3188         em->len = end + 1 - start;
3189         em->block_len = em->len;
3190         em->block_start = block_start;
3191         em->bdev = fs_info->fs_devices->latest_bdev;
3192         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3193
3194         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3195         while (1) {
3196                 write_lock(&em_tree->lock);
3197                 ret = add_extent_mapping(em_tree, em, 0);
3198                 write_unlock(&em_tree->lock);
3199                 if (ret != -EEXIST) {
3200                         free_extent_map(em);
3201                         break;
3202                 }
3203                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3204         }
3205         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3206         return ret;
3207 }
3208
3209 static int relocate_file_extent_cluster(struct inode *inode,
3210                                         struct file_extent_cluster *cluster)
3211 {
3212         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3213         u64 page_start;
3214         u64 page_end;
3215         u64 offset = BTRFS_I(inode)->index_cnt;
3216         unsigned long index;
3217         unsigned long last_index;
3218         struct page *page;
3219         struct file_ra_state *ra;
3220         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3221         int nr = 0;
3222         int ret = 0;
3223
3224         if (!cluster->nr)
3225                 return 0;
3226
3227         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3228         if (!ra)
3229                 return -ENOMEM;
3230
3231         ret = prealloc_file_extent_cluster(inode, cluster);
3232         if (ret)
3233                 goto out;
3234
3235         file_ra_state_init(ra, inode->i_mapping);
3236
3237         ret = setup_extent_mapping(inode, cluster->start - offset,
3238                                    cluster->end - offset, cluster->start);
3239         if (ret)
3240                 goto out;
3241
3242         index = (cluster->start - offset) >> PAGE_SHIFT;
3243         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3244         while (index <= last_index) {
3245                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3246                                 PAGE_SIZE);
3247                 if (ret)
3248                         goto out;
3249
3250                 page = find_lock_page(inode->i_mapping, index);
3251                 if (!page) {
3252                         page_cache_sync_readahead(inode->i_mapping,
3253                                                   ra, NULL, index,
3254                                                   last_index + 1 - index);
3255                         page = find_or_create_page(inode->i_mapping, index,
3256                                                    mask);
3257                         if (!page) {
3258                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3259                                                         PAGE_SIZE, true);
3260                                 ret = -ENOMEM;
3261                                 goto out;
3262                         }
3263                 }
3264
3265                 if (PageReadahead(page)) {
3266                         page_cache_async_readahead(inode->i_mapping,
3267                                                    ra, NULL, page, index,
3268                                                    last_index + 1 - index);
3269                 }
3270
3271                 if (!PageUptodate(page)) {
3272                         btrfs_readpage(NULL, page);
3273                         lock_page(page);
3274                         if (!PageUptodate(page)) {
3275                                 unlock_page(page);
3276                                 put_page(page);
3277                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3278                                                         PAGE_SIZE, true);
3279                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3280                                                                PAGE_SIZE, true);
3281                                 ret = -EIO;
3282                                 goto out;
3283                         }
3284                 }
3285
3286                 page_start = page_offset(page);
3287                 page_end = page_start + PAGE_SIZE - 1;
3288
3289                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3290
3291                 set_page_extent_mapped(page);
3292
3293                 if (nr < cluster->nr &&
3294                     page_start + offset == cluster->boundary[nr]) {
3295                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3296                                         page_start, page_end,
3297                                         EXTENT_BOUNDARY);
3298                         nr++;
3299                 }
3300
3301                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3302                                                 NULL, 0);
3303                 if (ret) {
3304                         unlock_page(page);
3305                         put_page(page);
3306                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3307                                                          PAGE_SIZE, true);
3308                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3309                                                        PAGE_SIZE, true);
3310
3311                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3312                                           page_start, page_end,
3313                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3314                         goto out;
3315
3316                 }
3317                 set_page_dirty(page);
3318
3319                 unlock_extent(&BTRFS_I(inode)->io_tree,
3320                               page_start, page_end);
3321                 unlock_page(page);
3322                 put_page(page);
3323
3324                 index++;
3325                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE,
3326                                                false);
3327                 balance_dirty_pages_ratelimited(inode->i_mapping);
3328                 btrfs_throttle(fs_info);
3329         }
3330         WARN_ON(nr != cluster->nr);
3331 out:
3332         kfree(ra);
3333         return ret;
3334 }
3335
3336 static noinline_for_stack
3337 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3338                          struct file_extent_cluster *cluster)
3339 {
3340         int ret;
3341
3342         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3343                 ret = relocate_file_extent_cluster(inode, cluster);
3344                 if (ret)
3345                         return ret;
3346                 cluster->nr = 0;
3347         }
3348
3349         if (!cluster->nr)
3350                 cluster->start = extent_key->objectid;
3351         else
3352                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3353         cluster->end = extent_key->objectid + extent_key->offset - 1;
3354         cluster->boundary[cluster->nr] = extent_key->objectid;
3355         cluster->nr++;
3356
3357         if (cluster->nr >= MAX_EXTENTS) {
3358                 ret = relocate_file_extent_cluster(inode, cluster);
3359                 if (ret)
3360                         return ret;
3361                 cluster->nr = 0;
3362         }
3363         return 0;
3364 }
3365
3366 /*
3367  * helper to add a tree block to the list.
3368  * the major work is getting the generation and level of the block
3369  */
3370 static int add_tree_block(struct reloc_control *rc,
3371                           struct btrfs_key *extent_key,
3372                           struct btrfs_path *path,
3373                           struct rb_root *blocks)
3374 {
3375         struct extent_buffer *eb;
3376         struct btrfs_extent_item *ei;
3377         struct btrfs_tree_block_info *bi;
3378         struct tree_block *block;
3379         struct rb_node *rb_node;
3380         u32 item_size;
3381         int level = -1;
3382         u64 generation;
3383
3384         eb =  path->nodes[0];
3385         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3386
3387         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3388             item_size >= sizeof(*ei) + sizeof(*bi)) {
3389                 ei = btrfs_item_ptr(eb, path->slots[0],
3390                                 struct btrfs_extent_item);
3391                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3392                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3393                         level = btrfs_tree_block_level(eb, bi);
3394                 } else {
3395                         level = (int)extent_key->offset;
3396                 }
3397                 generation = btrfs_extent_generation(eb, ei);
3398         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3399                 btrfs_print_v0_err(eb->fs_info);
3400                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3401                 return -EINVAL;
3402         } else {
3403                 BUG();
3404         }
3405
3406         btrfs_release_path(path);
3407
3408         BUG_ON(level == -1);
3409
3410         block = kmalloc(sizeof(*block), GFP_NOFS);
3411         if (!block)
3412                 return -ENOMEM;
3413
3414         block->bytenr = extent_key->objectid;
3415         block->key.objectid = rc->extent_root->fs_info->nodesize;
3416         block->key.offset = generation;
3417         block->level = level;
3418         block->key_ready = 0;
3419
3420         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3421         if (rb_node)
3422                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3423
3424         return 0;
3425 }
3426
3427 /*
3428  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3429  */
3430 static int __add_tree_block(struct reloc_control *rc,
3431                             u64 bytenr, u32 blocksize,
3432                             struct rb_root *blocks)
3433 {
3434         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3435         struct btrfs_path *path;
3436         struct btrfs_key key;
3437         int ret;
3438         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3439
3440         if (tree_block_processed(bytenr, rc))
3441                 return 0;
3442
3443         if (tree_search(blocks, bytenr))
3444                 return 0;
3445
3446         path = btrfs_alloc_path();
3447         if (!path)
3448                 return -ENOMEM;
3449 again:
3450         key.objectid = bytenr;
3451         if (skinny) {
3452                 key.type = BTRFS_METADATA_ITEM_KEY;
3453                 key.offset = (u64)-1;
3454         } else {
3455                 key.type = BTRFS_EXTENT_ITEM_KEY;
3456                 key.offset = blocksize;
3457         }
3458
3459         path->search_commit_root = 1;
3460         path->skip_locking = 1;
3461         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3462         if (ret < 0)
3463                 goto out;
3464
3465         if (ret > 0 && skinny) {
3466                 if (path->slots[0]) {
3467                         path->slots[0]--;
3468                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3469                                               path->slots[0]);
3470                         if (key.objectid == bytenr &&
3471                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3472                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3473                               key.offset == blocksize)))
3474                                 ret = 0;
3475                 }
3476
3477                 if (ret) {
3478                         skinny = false;
3479                         btrfs_release_path(path);
3480                         goto again;
3481                 }
3482         }
3483         if (ret) {
3484                 ASSERT(ret == 1);
3485                 btrfs_print_leaf(path->nodes[0]);
3486                 btrfs_err(fs_info,
3487              "tree block extent item (%llu) is not found in extent tree",
3488                      bytenr);
3489                 WARN_ON(1);
3490                 ret = -EINVAL;
3491                 goto out;
3492         }
3493
3494         ret = add_tree_block(rc, &key, path, blocks);
3495 out:
3496         btrfs_free_path(path);
3497         return ret;
3498 }
3499
3500 /*
3501  * helper to check if the block use full backrefs for pointers in it
3502  */
3503 static int block_use_full_backref(struct reloc_control *rc,
3504                                   struct extent_buffer *eb)
3505 {
3506         u64 flags;
3507         int ret;
3508
3509         if (btrfs_header_flag(eb, BTRFS_HEADER_FLAG_RELOC) ||
3510             btrfs_header_backref_rev(eb) < BTRFS_MIXED_BACKREF_REV)
3511                 return 1;
3512
3513         ret = btrfs_lookup_extent_info(NULL, rc->extent_root->fs_info,
3514                                        eb->start, btrfs_header_level(eb), 1,
3515                                        NULL, &flags);
3516         BUG_ON(ret);
3517
3518         if (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF)
3519                 ret = 1;
3520         else
3521                 ret = 0;
3522         return ret;
3523 }
3524
3525 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3526                                     struct btrfs_block_group_cache *block_group,
3527                                     struct inode *inode,
3528                                     u64 ino)
3529 {
3530         struct btrfs_key key;
3531         struct btrfs_root *root = fs_info->tree_root;
3532         struct btrfs_trans_handle *trans;
3533         int ret = 0;
3534
3535         if (inode)
3536                 goto truncate;
3537
3538         key.objectid = ino;
3539         key.type = BTRFS_INODE_ITEM_KEY;
3540         key.offset = 0;
3541
3542         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
3543         if (IS_ERR(inode))
3544                 return -ENOENT;
3545
3546 truncate:
3547         ret = btrfs_check_trunc_cache_free_space(fs_info,
3548                                                  &fs_info->global_block_rsv);
3549         if (ret)
3550                 goto out;
3551
3552         trans = btrfs_join_transaction(root);
3553         if (IS_ERR(trans)) {
3554                 ret = PTR_ERR(trans);
3555                 goto out;
3556         }
3557
3558         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3559
3560         btrfs_end_transaction(trans);
3561         btrfs_btree_balance_dirty(fs_info);
3562 out:
3563         iput(inode);
3564         return ret;
3565 }
3566
3567 /*
3568  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
3569  * this function scans fs tree to find blocks reference the data extent
3570  */
3571 static int find_data_references(struct reloc_control *rc,
3572                                 struct btrfs_key *extent_key,
3573                                 struct extent_buffer *leaf,
3574                                 struct btrfs_extent_data_ref *ref,
3575                                 struct rb_root *blocks)
3576 {
3577         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3578         struct btrfs_path *path;
3579         struct tree_block *block;
3580         struct btrfs_root *root;
3581         struct btrfs_file_extent_item *fi;
3582         struct rb_node *rb_node;
3583         struct btrfs_key key;
3584         u64 ref_root;
3585         u64 ref_objectid;
3586         u64 ref_offset;
3587         u32 ref_count;
3588         u32 nritems;
3589         int err = 0;
3590         int added = 0;
3591         int counted;
3592         int ret;
3593
3594         ref_root = btrfs_extent_data_ref_root(leaf, ref);
3595         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
3596         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
3597         ref_count = btrfs_extent_data_ref_count(leaf, ref);
3598
3599         /*
3600          * This is an extent belonging to the free space cache, lets just delete
3601          * it and redo the search.
3602          */
3603         if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
3604                 ret = delete_block_group_cache(fs_info, rc->block_group,
3605                                                NULL, ref_objectid);
3606                 if (ret != -ENOENT)
3607                         return ret;
3608                 ret = 0;
3609         }
3610
3611         path = btrfs_alloc_path();
3612         if (!path)
3613                 return -ENOMEM;
3614         path->reada = READA_FORWARD;
3615
3616         root = read_fs_root(fs_info, ref_root);
3617         if (IS_ERR(root)) {
3618                 err = PTR_ERR(root);
3619                 goto out;
3620         }
3621
3622         key.objectid = ref_objectid;
3623         key.type = BTRFS_EXTENT_DATA_KEY;
3624         if (ref_offset > ((u64)-1 << 32))
3625                 key.offset = 0;
3626         else
3627                 key.offset = ref_offset;
3628
3629         path->search_commit_root = 1;
3630         path->skip_locking = 1;
3631         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
3632         if (ret < 0) {
3633                 err = ret;
3634                 goto out;
3635         }
3636
3637         leaf = path->nodes[0];
3638         nritems = btrfs_header_nritems(leaf);
3639         /*
3640          * the references in tree blocks that use full backrefs
3641          * are not counted in
3642          */
3643         if (block_use_full_backref(rc, leaf))
3644                 counted = 0;
3645         else
3646                 counted = 1;
3647         rb_node = tree_search(blocks, leaf->start);
3648         if (rb_node) {
3649                 if (counted)
3650                         added = 1;
3651                 else
3652                         path->slots[0] = nritems;
3653         }
3654
3655         while (ref_count > 0) {
3656                 while (path->slots[0] >= nritems) {
3657                         ret = btrfs_next_leaf(root, path);
3658                         if (ret < 0) {
3659                                 err = ret;
3660                                 goto out;
3661                         }
3662                         if (WARN_ON(ret > 0))
3663                                 goto out;
3664
3665                         leaf = path->nodes[0];
3666                         nritems = btrfs_header_nritems(leaf);
3667                         added = 0;
3668
3669                         if (block_use_full_backref(rc, leaf))
3670                                 counted = 0;
3671                         else
3672                                 counted = 1;
3673                         rb_node = tree_search(blocks, leaf->start);
3674                         if (rb_node) {
3675                                 if (counted)
3676                                         added = 1;
3677                                 else
3678                                         path->slots[0] = nritems;
3679                         }
3680                 }
3681
3682                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3683                 if (WARN_ON(key.objectid != ref_objectid ||
3684                     key.type != BTRFS_EXTENT_DATA_KEY))
3685                         break;
3686
3687                 fi = btrfs_item_ptr(leaf, path->slots[0],
3688                                     struct btrfs_file_extent_item);
3689
3690                 if (btrfs_file_extent_type(leaf, fi) ==
3691                     BTRFS_FILE_EXTENT_INLINE)
3692                         goto next;
3693
3694                 if (btrfs_file_extent_disk_bytenr(leaf, fi) !=
3695                     extent_key->objectid)
3696                         goto next;
3697
3698                 key.offset -= btrfs_file_extent_offset(leaf, fi);
3699                 if (key.offset != ref_offset)
3700                         goto next;
3701
3702                 if (counted)
3703                         ref_count--;
3704                 if (added)
3705                         goto next;
3706
3707                 if (!tree_block_processed(leaf->start, rc)) {
3708                         block = kmalloc(sizeof(*block), GFP_NOFS);
3709                         if (!block) {
3710                                 err = -ENOMEM;
3711                                 break;
3712                         }
3713                         block->bytenr = leaf->start;
3714                         btrfs_item_key_to_cpu(leaf, &block->key, 0);
3715                         block->level = 0;
3716                         block->key_ready = 1;
3717                         rb_node = tree_insert(blocks, block->bytenr,
3718                                               &block->rb_node);
3719                         if (rb_node)
3720                                 backref_tree_panic(rb_node, -EEXIST,
3721                                                    block->bytenr);
3722                 }
3723                 if (counted)
3724                         added = 1;
3725                 else
3726                         path->slots[0] = nritems;
3727 next:
3728                 path->slots[0]++;
3729
3730         }
3731 out:
3732         btrfs_free_path(path);
3733         return err;
3734 }
3735
3736 /*
3737  * helper to find all tree blocks that reference a given data extent
3738  */
3739 static noinline_for_stack
3740 int add_data_references(struct reloc_control *rc,
3741                         struct btrfs_key *extent_key,
3742                         struct btrfs_path *path,
3743                         struct rb_root *blocks)
3744 {
3745         struct btrfs_key key;
3746         struct extent_buffer *eb;
3747         struct btrfs_extent_data_ref *dref;
3748         struct btrfs_extent_inline_ref *iref;
3749         unsigned long ptr;
3750         unsigned long end;
3751         u32 blocksize = rc->extent_root->fs_info->nodesize;
3752         int ret = 0;
3753         int err = 0;
3754
3755         eb = path->nodes[0];
3756         ptr = btrfs_item_ptr_offset(eb, path->slots[0]);
3757         end = ptr + btrfs_item_size_nr(eb, path->slots[0]);
3758         ptr += sizeof(struct btrfs_extent_item);
3759
3760         while (ptr < end) {
3761                 iref = (struct btrfs_extent_inline_ref *)ptr;
3762                 key.type = btrfs_get_extent_inline_ref_type(eb, iref,
3763                                                         BTRFS_REF_TYPE_DATA);
3764                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3765                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
3766                         ret = __add_tree_block(rc, key.offset, blocksize,
3767                                                blocks);
3768                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3769                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
3770                         ret = find_data_references(rc, extent_key,
3771                                                    eb, dref, blocks);
3772                 } else {
3773                         ret = -EUCLEAN;
3774                         btrfs_err(rc->extent_root->fs_info,
3775                      "extent %llu slot %d has an invalid inline ref type",
3776                              eb->start, path->slots[0]);
3777                 }
3778                 if (ret) {
3779                         err = ret;
3780                         goto out;
3781                 }
3782                 ptr += btrfs_extent_inline_ref_size(key.type);
3783         }
3784         WARN_ON(ptr > end);
3785
3786         while (1) {
3787                 cond_resched();
3788                 eb = path->nodes[0];
3789                 if (path->slots[0] >= btrfs_header_nritems(eb)) {
3790                         ret = btrfs_next_leaf(rc->extent_root, path);
3791                         if (ret < 0) {
3792                                 err = ret;
3793                                 break;
3794                         }
3795                         if (ret > 0)
3796                                 break;
3797                         eb = path->nodes[0];
3798                 }
3799
3800                 btrfs_item_key_to_cpu(eb, &key, path->slots[0]);
3801                 if (key.objectid != extent_key->objectid)
3802                         break;
3803
3804                 if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
3805                         ret = __add_tree_block(rc, key.offset, blocksize,
3806                                                blocks);
3807                 } else if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
3808                         dref = btrfs_item_ptr(eb, path->slots[0],
3809                                               struct btrfs_extent_data_ref);
3810                         ret = find_data_references(rc, extent_key,
3811                                                    eb, dref, blocks);
3812                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
3813                         btrfs_print_v0_err(eb->fs_info);
3814                         btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3815                         ret = -EINVAL;
3816                 } else {
3817                         ret = 0;
3818                 }
3819                 if (ret) {
3820                         err = ret;
3821                         break;
3822                 }
3823                 path->slots[0]++;
3824         }
3825 out:
3826         btrfs_release_path(path);
3827         if (err)
3828                 free_block_list(blocks);
3829         return err;
3830 }
3831
3832 /*
3833  * helper to find next unprocessed extent
3834  */
3835 static noinline_for_stack
3836 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3837                      struct btrfs_key *extent_key)
3838 {
3839         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3840         struct btrfs_key key;
3841         struct extent_buffer *leaf;
3842         u64 start, end, last;
3843         int ret;
3844
3845         last = rc->block_group->key.objectid + rc->block_group->key.offset;
3846         while (1) {
3847                 cond_resched();
3848                 if (rc->search_start >= last) {
3849                         ret = 1;
3850                         break;
3851                 }
3852
3853                 key.objectid = rc->search_start;
3854                 key.type = BTRFS_EXTENT_ITEM_KEY;
3855                 key.offset = 0;
3856
3857                 path->search_commit_root = 1;
3858                 path->skip_locking = 1;
3859                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3860                                         0, 0);
3861                 if (ret < 0)
3862                         break;
3863 next:
3864                 leaf = path->nodes[0];
3865                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3866                         ret = btrfs_next_leaf(rc->extent_root, path);
3867                         if (ret != 0)
3868                                 break;
3869                         leaf = path->nodes[0];
3870                 }
3871
3872                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3873                 if (key.objectid >= last) {
3874                         ret = 1;
3875                         break;
3876                 }
3877
3878                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3879                     key.type != BTRFS_METADATA_ITEM_KEY) {
3880                         path->slots[0]++;
3881                         goto next;
3882                 }
3883
3884                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3885                     key.objectid + key.offset <= rc->search_start) {
3886                         path->slots[0]++;
3887                         goto next;
3888                 }
3889
3890                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3891                     key.objectid + fs_info->nodesize <=
3892                     rc->search_start) {
3893                         path->slots[0]++;
3894                         goto next;
3895                 }
3896
3897                 ret = find_first_extent_bit(&rc->processed_blocks,
3898                                             key.objectid, &start, &end,
3899                                             EXTENT_DIRTY, NULL);
3900
3901                 if (ret == 0 && start <= key.objectid) {
3902                         btrfs_release_path(path);
3903                         rc->search_start = end + 1;
3904                 } else {
3905                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3906                                 rc->search_start = key.objectid + key.offset;
3907                         else
3908                                 rc->search_start = key.objectid +
3909                                         fs_info->nodesize;
3910                         memcpy(extent_key, &key, sizeof(key));
3911                         return 0;
3912                 }
3913         }
3914         btrfs_release_path(path);
3915         return ret;
3916 }
3917
3918 static void set_reloc_control(struct reloc_control *rc)
3919 {
3920         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3921
3922         mutex_lock(&fs_info->reloc_mutex);
3923         fs_info->reloc_ctl = rc;
3924         mutex_unlock(&fs_info->reloc_mutex);
3925 }
3926
3927 static void unset_reloc_control(struct reloc_control *rc)
3928 {
3929         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3930
3931         mutex_lock(&fs_info->reloc_mutex);
3932         fs_info->reloc_ctl = NULL;
3933         mutex_unlock(&fs_info->reloc_mutex);
3934 }
3935
3936 static int check_extent_flags(u64 flags)
3937 {
3938         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3939             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3940                 return 1;
3941         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3942             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3943                 return 1;
3944         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3945             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3946                 return 1;
3947         return 0;
3948 }
3949
3950 static noinline_for_stack
3951 int prepare_to_relocate(struct reloc_control *rc)
3952 {
3953         struct btrfs_trans_handle *trans;
3954         int ret;
3955
3956         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3957                                               BTRFS_BLOCK_RSV_TEMP);
3958         if (!rc->block_rsv)
3959                 return -ENOMEM;
3960
3961         memset(&rc->cluster, 0, sizeof(rc->cluster));
3962         rc->search_start = rc->block_group->key.objectid;
3963         rc->extents_found = 0;
3964         rc->nodes_relocated = 0;
3965         rc->merging_rsv_size = 0;
3966         rc->reserved_bytes = 0;
3967         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
3968                               RELOCATION_RESERVED_NODES;
3969         ret = btrfs_block_rsv_refill(rc->extent_root,
3970                                      rc->block_rsv, rc->block_rsv->size,
3971                                      BTRFS_RESERVE_FLUSH_ALL);
3972         if (ret)
3973                 return ret;
3974
3975         rc->create_reloc_tree = 1;
3976         set_reloc_control(rc);
3977
3978         trans = btrfs_join_transaction(rc->extent_root);
3979         if (IS_ERR(trans)) {
3980                 unset_reloc_control(rc);
3981                 /*
3982                  * extent tree is not a ref_cow tree and has no reloc_root to
3983                  * cleanup.  And callers are responsible to free the above
3984                  * block rsv.
3985                  */
3986                 return PTR_ERR(trans);
3987         }
3988         btrfs_commit_transaction(trans);
3989         return 0;
3990 }
3991
3992 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3993 {
3994         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3995         struct rb_root blocks = RB_ROOT;
3996         struct btrfs_key key;
3997         struct btrfs_trans_handle *trans = NULL;
3998         struct btrfs_path *path;
3999         struct btrfs_extent_item *ei;
4000         u64 flags;
4001         u32 item_size;
4002         int ret;
4003         int err = 0;
4004         int progress = 0;
4005
4006         path = btrfs_alloc_path();
4007         if (!path)
4008                 return -ENOMEM;
4009         path->reada = READA_FORWARD;
4010
4011         ret = prepare_to_relocate(rc);
4012         if (ret) {
4013                 err = ret;
4014                 goto out_free;
4015         }
4016
4017         while (1) {
4018                 rc->reserved_bytes = 0;
4019                 ret = btrfs_block_rsv_refill(rc->extent_root,
4020                                         rc->block_rsv, rc->block_rsv->size,
4021                                         BTRFS_RESERVE_FLUSH_ALL);
4022                 if (ret) {
4023                         err = ret;
4024                         break;
4025                 }
4026                 progress++;
4027                 trans = btrfs_start_transaction(rc->extent_root, 0);
4028                 if (IS_ERR(trans)) {
4029                         err = PTR_ERR(trans);
4030                         trans = NULL;
4031                         break;
4032                 }
4033 restart:
4034                 if (update_backref_cache(trans, &rc->backref_cache)) {
4035                         btrfs_end_transaction(trans);
4036                         trans = NULL;
4037                         continue;
4038                 }
4039
4040                 ret = find_next_extent(rc, path, &key);
4041                 if (ret < 0)
4042                         err = ret;
4043                 if (ret != 0)
4044                         break;
4045
4046                 rc->extents_found++;
4047
4048                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4049                                     struct btrfs_extent_item);
4050                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4051                 if (item_size >= sizeof(*ei)) {
4052                         flags = btrfs_extent_flags(path->nodes[0], ei);
4053                         ret = check_extent_flags(flags);
4054                         BUG_ON(ret);
4055                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
4056                         err = -EINVAL;
4057                         btrfs_print_v0_err(trans->fs_info);
4058                         btrfs_abort_transaction(trans, err);
4059                         break;
4060                 } else {
4061                         BUG();
4062                 }
4063
4064                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4065                         ret = add_tree_block(rc, &key, path, &blocks);
4066                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4067                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4068                         ret = add_data_references(rc, &key, path, &blocks);
4069                 } else {
4070                         btrfs_release_path(path);
4071                         ret = 0;
4072                 }
4073                 if (ret < 0) {
4074                         err = ret;
4075                         break;
4076                 }
4077
4078                 if (!RB_EMPTY_ROOT(&blocks)) {
4079                         ret = relocate_tree_blocks(trans, rc, &blocks);
4080                         if (ret < 0) {
4081                                 /*
4082                                  * if we fail to relocate tree blocks, force to update
4083                                  * backref cache when committing transaction.
4084                                  */
4085                                 rc->backref_cache.last_trans = trans->transid - 1;
4086
4087                                 if (ret != -EAGAIN) {
4088                                         err = ret;
4089                                         break;
4090                                 }
4091                                 rc->extents_found--;
4092                                 rc->search_start = key.objectid;
4093                         }
4094                 }
4095
4096                 btrfs_end_transaction_throttle(trans);
4097                 btrfs_btree_balance_dirty(fs_info);
4098                 trans = NULL;
4099
4100                 if (rc->stage == MOVE_DATA_EXTENTS &&
4101                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4102                         rc->found_file_extent = 1;
4103                         ret = relocate_data_extent(rc->data_inode,
4104                                                    &key, &rc->cluster);
4105                         if (ret < 0) {
4106                                 err = ret;
4107                                 break;
4108                         }
4109                 }
4110         }
4111         if (trans && progress && err == -ENOSPC) {
4112                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
4113                 if (ret == 1) {
4114                         err = 0;
4115                         progress = 0;
4116                         goto restart;
4117                 }
4118         }
4119
4120         btrfs_release_path(path);
4121         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4122
4123         if (trans) {
4124                 btrfs_end_transaction_throttle(trans);
4125                 btrfs_btree_balance_dirty(fs_info);
4126         }
4127
4128         if (!err) {
4129                 ret = relocate_file_extent_cluster(rc->data_inode,
4130                                                    &rc->cluster);
4131                 if (ret < 0)
4132                         err = ret;
4133         }
4134
4135         rc->create_reloc_tree = 0;
4136         set_reloc_control(rc);
4137
4138         backref_cache_cleanup(&rc->backref_cache);
4139         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4140
4141         err = prepare_to_merge(rc, err);
4142
4143         merge_reloc_roots(rc);
4144
4145         rc->merge_reloc_tree = 0;
4146         unset_reloc_control(rc);
4147         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1);
4148
4149         /* get rid of pinned extents */
4150         trans = btrfs_join_transaction(rc->extent_root);
4151         if (IS_ERR(trans)) {
4152                 err = PTR_ERR(trans);
4153                 goto out_free;
4154         }
4155         btrfs_commit_transaction(trans);
4156         ret = clean_dirty_subvols(rc);
4157         if (ret < 0 && !err)
4158                 err = ret;
4159 out_free:
4160         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4161         btrfs_free_path(path);
4162         return err;
4163 }
4164
4165 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4166                                  struct btrfs_root *root, u64 objectid)
4167 {
4168         struct btrfs_path *path;
4169         struct btrfs_inode_item *item;
4170         struct extent_buffer *leaf;
4171         int ret;
4172
4173         path = btrfs_alloc_path();
4174         if (!path)
4175                 return -ENOMEM;
4176
4177         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4178         if (ret)
4179                 goto out;
4180
4181         leaf = path->nodes[0];
4182         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4183         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4184         btrfs_set_inode_generation(leaf, item, 1);
4185         btrfs_set_inode_size(leaf, item, 0);
4186         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4187         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4188                                           BTRFS_INODE_PREALLOC);
4189         btrfs_mark_buffer_dirty(leaf);
4190 out:
4191         btrfs_free_path(path);
4192         return ret;
4193 }
4194
4195 /*
4196  * helper to create inode for data relocation.
4197  * the inode is in data relocation tree and its link count is 0
4198  */
4199 static noinline_for_stack
4200 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4201                                  struct btrfs_block_group_cache *group)
4202 {
4203         struct inode *inode = NULL;
4204         struct btrfs_trans_handle *trans;
4205         struct btrfs_root *root;
4206         struct btrfs_key key;
4207         u64 objectid;
4208         int err = 0;
4209
4210         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4211         if (IS_ERR(root))
4212                 return ERR_CAST(root);
4213
4214         trans = btrfs_start_transaction(root, 6);
4215         if (IS_ERR(trans))
4216                 return ERR_CAST(trans);
4217
4218         err = btrfs_find_free_objectid(root, &objectid);
4219         if (err)
4220                 goto out;
4221
4222         err = __insert_orphan_inode(trans, root, objectid);
4223         BUG_ON(err);
4224
4225         key.objectid = objectid;
4226         key.type = BTRFS_INODE_ITEM_KEY;
4227         key.offset = 0;
4228         inode = btrfs_iget(fs_info->sb, &key, root, NULL);
4229         BUG_ON(IS_ERR(inode));
4230         BTRFS_I(inode)->index_cnt = group->key.objectid;
4231
4232         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4233 out:
4234         btrfs_end_transaction(trans);
4235         btrfs_btree_balance_dirty(fs_info);
4236         if (err) {
4237                 if (inode)
4238                         iput(inode);
4239                 inode = ERR_PTR(err);
4240         }
4241         return inode;
4242 }
4243
4244 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4245 {
4246         struct reloc_control *rc;
4247
4248         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4249         if (!rc)
4250                 return NULL;
4251
4252         INIT_LIST_HEAD(&rc->reloc_roots);
4253         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
4254         backref_cache_init(&rc->backref_cache);
4255         mapping_tree_init(&rc->reloc_root_tree);
4256         extent_io_tree_init(fs_info, &rc->processed_blocks,
4257                             IO_TREE_RELOC_BLOCKS, NULL);
4258         return rc;
4259 }
4260
4261 /*
4262  * Print the block group being relocated
4263  */
4264 static void describe_relocation(struct btrfs_fs_info *fs_info,
4265                                 struct btrfs_block_group_cache *block_group)
4266 {
4267         char buf[128] = {'\0'};
4268
4269         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
4270
4271         btrfs_info(fs_info,
4272                    "relocating block group %llu flags %s",
4273                    block_group->key.objectid, buf);
4274 }
4275
4276 /*
4277  * function to relocate all extents in a block group.
4278  */
4279 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4280 {
4281         struct btrfs_block_group_cache *bg;
4282         struct btrfs_root *extent_root = fs_info->extent_root;
4283         struct reloc_control *rc;
4284         struct inode *inode;
4285         struct btrfs_path *path;
4286         int ret;
4287         int rw = 0;
4288         int err = 0;
4289
4290         bg = btrfs_lookup_block_group(fs_info, group_start);
4291         if (!bg)
4292                 return -ENOENT;
4293
4294         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
4295                 btrfs_put_block_group(bg);
4296                 return -ETXTBSY;
4297         }
4298
4299         rc = alloc_reloc_control(fs_info);
4300         if (!rc) {
4301                 btrfs_put_block_group(bg);
4302                 return -ENOMEM;
4303         }
4304
4305         rc->extent_root = extent_root;
4306         rc->block_group = bg;
4307
4308         ret = btrfs_inc_block_group_ro(rc->block_group);
4309         if (ret) {
4310                 err = ret;
4311                 goto out;
4312         }
4313         rw = 1;
4314
4315         path = btrfs_alloc_path();
4316         if (!path) {
4317                 err = -ENOMEM;
4318                 goto out;
4319         }
4320
4321         inode = lookup_free_space_inode(rc->block_group, path);
4322         btrfs_free_path(path);
4323
4324         if (!IS_ERR(inode))
4325                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4326         else
4327                 ret = PTR_ERR(inode);
4328
4329         if (ret && ret != -ENOENT) {
4330                 err = ret;
4331                 goto out;
4332         }
4333
4334         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4335         if (IS_ERR(rc->data_inode)) {
4336                 err = PTR_ERR(rc->data_inode);
4337                 rc->data_inode = NULL;
4338                 goto out;
4339         }
4340
4341         describe_relocation(fs_info, rc->block_group);
4342
4343         btrfs_wait_block_group_reservations(rc->block_group);
4344         btrfs_wait_nocow_writers(rc->block_group);
4345         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4346                                  rc->block_group->key.objectid,
4347                                  rc->block_group->key.offset);
4348
4349         while (1) {
4350                 mutex_lock(&fs_info->cleaner_mutex);
4351                 ret = relocate_block_group(rc);
4352                 mutex_unlock(&fs_info->cleaner_mutex);
4353                 if (ret < 0)
4354                         err = ret;
4355
4356                 /*
4357                  * We may have gotten ENOSPC after we already dirtied some
4358                  * extents.  If writeout happens while we're relocating a
4359                  * different block group we could end up hitting the
4360                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
4361                  * btrfs_reloc_cow_block.  Make sure we write everything out
4362                  * properly so we don't trip over this problem, and then break
4363                  * out of the loop if we hit an error.
4364                  */
4365                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4366                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4367                                                        (u64)-1);
4368                         if (ret)
4369                                 err = ret;
4370                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4371                                                  0, -1);
4372                         rc->stage = UPDATE_DATA_PTRS;
4373                 }
4374
4375                 if (err < 0)
4376                         goto out;
4377
4378                 if (rc->extents_found == 0)
4379                         break;
4380
4381                 btrfs_info(fs_info, "found %llu extents", rc->extents_found);
4382
4383         }
4384
4385         WARN_ON(rc->block_group->pinned > 0);
4386         WARN_ON(rc->block_group->reserved > 0);
4387         WARN_ON(btrfs_block_group_used(&rc->block_group->item) > 0);
4388 out:
4389         if (err && rw)
4390                 btrfs_dec_block_group_ro(rc->block_group);
4391         iput(rc->data_inode);
4392         btrfs_put_block_group(rc->block_group);
4393         kfree(rc);
4394         return err;
4395 }
4396
4397 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4398 {
4399         struct btrfs_fs_info *fs_info = root->fs_info;
4400         struct btrfs_trans_handle *trans;
4401         int ret, err;
4402
4403         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4404         if (IS_ERR(trans))
4405                 return PTR_ERR(trans);
4406
4407         memset(&root->root_item.drop_progress, 0,
4408                 sizeof(root->root_item.drop_progress));
4409         root->root_item.drop_level = 0;
4410         btrfs_set_root_refs(&root->root_item, 0);
4411         ret = btrfs_update_root(trans, fs_info->tree_root,
4412                                 &root->root_key, &root->root_item);
4413
4414         err = btrfs_end_transaction(trans);
4415         if (err)
4416                 return err;
4417         return ret;
4418 }
4419
4420 /*
4421  * recover relocation interrupted by system crash.
4422  *
4423  * this function resumes merging reloc trees with corresponding fs trees.
4424  * this is important for keeping the sharing of tree blocks
4425  */
4426 int btrfs_recover_relocation(struct btrfs_root *root)
4427 {
4428         struct btrfs_fs_info *fs_info = root->fs_info;
4429         LIST_HEAD(reloc_roots);
4430         struct btrfs_key key;
4431         struct btrfs_root *fs_root;
4432         struct btrfs_root *reloc_root;
4433         struct btrfs_path *path;
4434         struct extent_buffer *leaf;
4435         struct reloc_control *rc = NULL;
4436         struct btrfs_trans_handle *trans;
4437         int ret;
4438         int err = 0;
4439
4440         path = btrfs_alloc_path();
4441         if (!path)
4442                 return -ENOMEM;
4443         path->reada = READA_BACK;
4444
4445         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4446         key.type = BTRFS_ROOT_ITEM_KEY;
4447         key.offset = (u64)-1;
4448
4449         while (1) {
4450                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4451                                         path, 0, 0);
4452                 if (ret < 0) {
4453                         err = ret;
4454                         goto out;
4455                 }
4456                 if (ret > 0) {
4457                         if (path->slots[0] == 0)
4458                                 break;
4459                         path->slots[0]--;
4460                 }
4461                 leaf = path->nodes[0];
4462                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4463                 btrfs_release_path(path);
4464
4465                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4466                     key.type != BTRFS_ROOT_ITEM_KEY)
4467                         break;
4468
4469                 reloc_root = btrfs_read_fs_root(root, &key);
4470                 if (IS_ERR(reloc_root)) {
4471                         err = PTR_ERR(reloc_root);
4472                         goto out;
4473                 }
4474
4475                 list_add(&reloc_root->root_list, &reloc_roots);
4476
4477                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4478                         fs_root = read_fs_root(fs_info,
4479                                                reloc_root->root_key.offset);
4480                         if (IS_ERR(fs_root)) {
4481                                 ret = PTR_ERR(fs_root);
4482                                 if (ret != -ENOENT) {
4483                                         err = ret;
4484                                         goto out;
4485                                 }
4486                                 ret = mark_garbage_root(reloc_root);
4487                                 if (ret < 0) {
4488                                         err = ret;
4489                                         goto out;
4490                                 }
4491                         }
4492                 }
4493
4494                 if (key.offset == 0)
4495                         break;
4496
4497                 key.offset--;
4498         }
4499         btrfs_release_path(path);
4500
4501         if (list_empty(&reloc_roots))
4502                 goto out;
4503
4504         rc = alloc_reloc_control(fs_info);
4505         if (!rc) {
4506                 err = -ENOMEM;
4507                 goto out;
4508         }
4509
4510         rc->extent_root = fs_info->extent_root;
4511
4512         set_reloc_control(rc);
4513
4514         trans = btrfs_join_transaction(rc->extent_root);
4515         if (IS_ERR(trans)) {
4516                 unset_reloc_control(rc);
4517                 err = PTR_ERR(trans);
4518                 goto out_free;
4519         }
4520
4521         rc->merge_reloc_tree = 1;
4522
4523         while (!list_empty(&reloc_roots)) {
4524                 reloc_root = list_entry(reloc_roots.next,
4525                                         struct btrfs_root, root_list);
4526                 list_del(&reloc_root->root_list);
4527
4528                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4529                         list_add_tail(&reloc_root->root_list,
4530                                       &rc->reloc_roots);
4531                         continue;
4532                 }
4533
4534                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4535                 if (IS_ERR(fs_root)) {
4536                         err = PTR_ERR(fs_root);
4537                         goto out_free;
4538                 }
4539
4540                 err = __add_reloc_root(reloc_root);
4541                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4542                 fs_root->reloc_root = reloc_root;
4543         }
4544
4545         err = btrfs_commit_transaction(trans);
4546         if (err)
4547                 goto out_free;
4548
4549         merge_reloc_roots(rc);
4550
4551         unset_reloc_control(rc);
4552
4553         trans = btrfs_join_transaction(rc->extent_root);
4554         if (IS_ERR(trans)) {
4555                 err = PTR_ERR(trans);
4556                 goto out_free;
4557         }
4558         err = btrfs_commit_transaction(trans);
4559
4560         ret = clean_dirty_subvols(rc);
4561         if (ret < 0 && !err)
4562                 err = ret;
4563 out_free:
4564         kfree(rc);
4565 out:
4566         if (!list_empty(&reloc_roots))
4567                 free_reloc_roots(&reloc_roots);
4568
4569         btrfs_free_path(path);
4570
4571         if (err == 0) {
4572                 /* cleanup orphan inode in data relocation tree */
4573                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4574                 if (IS_ERR(fs_root))
4575                         err = PTR_ERR(fs_root);
4576                 else
4577                         err = btrfs_orphan_cleanup(fs_root);
4578         }
4579         return err;
4580 }
4581
4582 /*
4583  * helper to add ordered checksum for data relocation.
4584  *
4585  * cloning checksum properly handles the nodatasum extents.
4586  * it also saves CPU time to re-calculate the checksum.
4587  */
4588 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4589 {
4590         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4591         struct btrfs_ordered_sum *sums;
4592         struct btrfs_ordered_extent *ordered;
4593         int ret;
4594         u64 disk_bytenr;
4595         u64 new_bytenr;
4596         LIST_HEAD(list);
4597
4598         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4599         BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
4600
4601         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4602         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4603                                        disk_bytenr + len - 1, &list, 0);
4604         if (ret)
4605                 goto out;
4606
4607         while (!list_empty(&list)) {
4608                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4609                 list_del_init(&sums->list);
4610
4611                 /*
4612                  * We need to offset the new_bytenr based on where the csum is.
4613                  * We need to do this because we will read in entire prealloc
4614                  * extents but we may have written to say the middle of the
4615                  * prealloc extent, so we need to make sure the csum goes with
4616                  * the right disk offset.
4617                  *
4618                  * We can do this because the data reloc inode refers strictly
4619                  * to the on disk bytes, so we don't have to worry about
4620                  * disk_len vs real len like with real inodes since it's all
4621                  * disk length.
4622                  */
4623                 new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
4624                 sums->bytenr = new_bytenr;
4625
4626                 btrfs_add_ordered_sum(ordered, sums);
4627         }
4628 out:
4629         btrfs_put_ordered_extent(ordered);
4630         return ret;
4631 }
4632
4633 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4634                           struct btrfs_root *root, struct extent_buffer *buf,
4635                           struct extent_buffer *cow)
4636 {
4637         struct btrfs_fs_info *fs_info = root->fs_info;
4638         struct reloc_control *rc;
4639         struct backref_node *node;
4640         int first_cow = 0;
4641         int level;
4642         int ret = 0;
4643
4644         rc = fs_info->reloc_ctl;
4645         if (!rc)
4646                 return 0;
4647
4648         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4649                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4650
4651         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
4652                 if (buf == root->node)
4653                         __update_reloc_root(root, cow->start);
4654         }
4655
4656         level = btrfs_header_level(buf);
4657         if (btrfs_header_generation(buf) <=
4658             btrfs_root_last_snapshot(&root->root_item))
4659                 first_cow = 1;
4660
4661         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4662             rc->create_reloc_tree) {
4663                 WARN_ON(!first_cow && level == 0);
4664
4665                 node = rc->backref_cache.path[level];
4666                 BUG_ON(node->bytenr != buf->start &&
4667                        node->new_bytenr != buf->start);
4668
4669                 drop_node_buffer(node);
4670                 extent_buffer_get(cow);
4671                 node->eb = cow;
4672                 node->new_bytenr = cow->start;
4673
4674                 if (!node->pending) {
4675                         list_move_tail(&node->list,
4676                                        &rc->backref_cache.pending[level]);
4677                         node->pending = 1;
4678                 }
4679
4680                 if (first_cow)
4681                         __mark_block_processed(rc, node);
4682
4683                 if (first_cow && level > 0)
4684                         rc->nodes_relocated += buf->len;
4685         }
4686
4687         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4688                 ret = replace_file_extents(trans, rc, root, cow);
4689         return ret;
4690 }
4691
4692 /*
4693  * called before creating snapshot. it calculates metadata reservation
4694  * required for relocating tree blocks in the snapshot
4695  */
4696 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4697                               u64 *bytes_to_reserve)
4698 {
4699         struct btrfs_root *root = pending->root;
4700         struct reloc_control *rc = root->fs_info->reloc_ctl;
4701
4702         if (!root->reloc_root || !rc)
4703                 return;
4704
4705         if (!rc->merge_reloc_tree)
4706                 return;
4707
4708         root = root->reloc_root;
4709         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4710         /*
4711          * relocation is in the stage of merging trees. the space
4712          * used by merging a reloc tree is twice the size of
4713          * relocated tree nodes in the worst case. half for cowing
4714          * the reloc tree, half for cowing the fs tree. the space
4715          * used by cowing the reloc tree will be freed after the
4716          * tree is dropped. if we create snapshot, cowing the fs
4717          * tree may use more space than it frees. so we need
4718          * reserve extra space.
4719          */
4720         *bytes_to_reserve += rc->nodes_relocated;
4721 }
4722
4723 /*
4724  * called after snapshot is created. migrate block reservation
4725  * and create reloc root for the newly created snapshot
4726  */
4727 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4728                                struct btrfs_pending_snapshot *pending)
4729 {
4730         struct btrfs_root *root = pending->root;
4731         struct btrfs_root *reloc_root;
4732         struct btrfs_root *new_root;
4733         struct reloc_control *rc = root->fs_info->reloc_ctl;
4734         int ret;
4735
4736         if (!root->reloc_root || !rc)
4737                 return 0;
4738
4739         rc = root->fs_info->reloc_ctl;
4740         rc->merging_rsv_size += rc->nodes_relocated;
4741
4742         if (rc->merge_reloc_tree) {
4743                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4744                                               rc->block_rsv,
4745                                               rc->nodes_relocated, true);
4746                 if (ret)
4747                         return ret;
4748         }
4749
4750         new_root = pending->snap;
4751         reloc_root = create_reloc_root(trans, root->reloc_root,
4752                                        new_root->root_key.objectid);
4753         if (IS_ERR(reloc_root))
4754                 return PTR_ERR(reloc_root);
4755
4756         ret = __add_reloc_root(reloc_root);
4757         BUG_ON(ret < 0);
4758         new_root->reloc_root = reloc_root;
4759
4760         if (rc->create_reloc_tree)
4761                 ret = clone_backref_node(trans, rc, root, reloc_root);
4762         return ret;
4763 }