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 <linux/error-injection.h>
  13 #include "ctree.h"
  14 #include "disk-io.h"
  15 #include "transaction.h"
  16 #include "volumes.h"
  17 #include "locking.h"
  18 #include "btrfs_inode.h"
  19 #include "async-thread.h"
  20 #include "free-space-cache.h"
  21 #include "qgroup.h"
  22 #include "print-tree.h"
  23 #include "delalloc-space.h"
  24 #include "block-group.h"
  25 #include "backref.h"
  26 #include "misc.h"
  27
  28 /*
  29  * Relocation overview
  30  *
  31  * [What does relocation do]
  32  *
  33  * The objective of relocation is to relocate all extents of the target block
  34  * group to other block groups.
  35  * This is utilized by resize (shrink only), profile converting, compacting
  36  * space, or balance routine to spread chunks over devices.
  37  *
  38  *              Before          |               After
  39  * ------------------------------------------------------------------
  40  *  BG A: 10 data extents       | BG A: deleted
  41  *  BG B:  2 data extents       | BG B: 10 data extents (2 old + 8 relocated)
  42  *  BG C:  1 extents            | BG C:  3 data extents (1 old + 2 relocated)
  43  *
  44  * [How does relocation work]
  45  *
  46  * 1.   Mark the target block group read-only
  47  *      New extents won't be allocated from the target block group.
  48  *
  49  * 2.1  Record each extent in the target block group
  50  *      To build a proper map of extents to be relocated.
  51  *
  52  * 2.2  Build data reloc tree and reloc trees
  53  *      Data reloc tree will contain an inode, recording all newly relocated
  54  *      data extents.
  55  *      There will be only one data reloc tree for one data block group.
  56  *
  57  *      Reloc tree will be a special snapshot of its source tree, containing
  58  *      relocated tree blocks.
  59  *      Each tree referring to a tree block in target block group will get its
  60  *      reloc tree built.
  61  *
  62  * 2.3  Swap source tree with its corresponding reloc tree
  63  *      Each involved tree only refers to new extents after swap.
  64  *
  65  * 3.   Cleanup reloc trees and data reloc tree.
  66  *      As old extents in the target block group are still referenced by reloc
  67  *      trees, we need to clean them up before really freeing the target block
  68  *      group.
  69  *
  70  * The main complexity is in steps 2.2 and 2.3.
  71  *
  72  * The entry point of relocation is relocate_block_group() function.
  73  */
  74
  75 #define RELOCATION_RESERVED_NODES       256
  76 /*
  77  * map address of tree root to tree
  78  */
  79 struct mapping_node {
  80         struct {
  81                 struct rb_node rb_node;
  82                 u64 bytenr;
  83         }; /* Use rb_simle_node for search/insert */
  84         void *data;
  85 };
  86
  87 struct mapping_tree {
  88         struct rb_root rb_root;
  89         spinlock_t lock;
  90 };
  91
  92 /*
  93  * present a tree block to process
  94  */
  95 struct tree_block {
  96         struct {
  97                 struct rb_node rb_node;
  98                 u64 bytenr;
  99         }; /* Use rb_simple_node for search/insert */
 100         u64 owner;
 101         struct btrfs_key key;
 102         unsigned int level:8;
 103         unsigned int key_ready:1;
 104 };
 105
 106 #define MAX_EXTENTS 128
 107
 108 struct file_extent_cluster {
 109         u64 start;
 110         u64 end;
 111         u64 boundary[MAX_EXTENTS];
 112         unsigned int nr;
 113 };
 114
 115 struct reloc_control {
 116         /* block group to relocate */
 117         struct btrfs_block_group *block_group;
 118         /* extent tree */
 119         struct btrfs_root *extent_root;
 120         /* inode for moving data */
 121         struct inode *data_inode;
 122
 123         struct btrfs_block_rsv *block_rsv;
 124
 125         struct btrfs_backref_cache backref_cache;
 126
 127         struct file_extent_cluster cluster;
 128         /* tree blocks have been processed */
 129         struct extent_io_tree processed_blocks;
 130         /* map start of tree root to corresponding reloc tree */
 131         struct mapping_tree reloc_root_tree;
 132         /* list of reloc trees */
 133         struct list_head reloc_roots;
 134         /* list of subvolume trees that get relocated */
 135         struct list_head dirty_subvol_roots;
 136         /* size of metadata reservation for merging reloc trees */
 137         u64 merging_rsv_size;
 138         /* size of relocated tree nodes */
 139         u64 nodes_relocated;
 140         /* reserved size for block group relocation*/
 141         u64 reserved_bytes;
 142
 143         u64 search_start;
 144         u64 extents_found;
 145
 146         unsigned int stage:8;
 147         unsigned int create_reloc_tree:1;
 148         unsigned int merge_reloc_tree:1;
 149         unsigned int found_file_extent:1;
 150 };
 151
 152 /* stages of data relocation */
 153 #define MOVE_DATA_EXTENTS       0
 154 #define UPDATE_DATA_PTRS        1
 155
 156 static void mark_block_processed(struct reloc_control *rc,
 157                                  struct btrfs_backref_node *node)
 158 {
 159         u32 blocksize;
 160
 161         if (node->level == 0 ||
 162             in_range(node->bytenr, rc->block_group->start,
 163                      rc->block_group->length)) {
 164                 blocksize = rc->extent_root->fs_info->nodesize;
 165                 set_extent_bits(&rc->processed_blocks, node->bytenr,
 166                                 node->bytenr + blocksize - 1, EXTENT_DIRTY);
 167         }
 168         node->processed = 1;
 169 }
 170
 171
 172 static void mapping_tree_init(struct mapping_tree *tree)
 173 {
 174         tree->rb_root = RB_ROOT;
 175         spin_lock_init(&tree->lock);
 176 }
 177
 178 /*
 179  * walk up backref nodes until reach node presents tree root
 180  */
 181 static struct btrfs_backref_node *walk_up_backref(
 182                 struct btrfs_backref_node *node,
 183                 struct btrfs_backref_edge *edges[], int *index)
 184 {
 185         struct btrfs_backref_edge *edge;
 186         int idx = *index;
 187
 188         while (!list_empty(&node->upper)) {
 189                 edge = list_entry(node->upper.next,
 190                                   struct btrfs_backref_edge, list[LOWER]);
 191                 edges[idx++] = edge;
 192                 node = edge->node[UPPER];
 193         }
 194         BUG_ON(node->detached);
 195         *index = idx;
 196         return node;
 197 }
 198
 199 /*
 200  * walk down backref nodes to find start of next reference path
 201  */
 202 static struct btrfs_backref_node *walk_down_backref(
 203                 struct btrfs_backref_edge *edges[], int *index)
 204 {
 205         struct btrfs_backref_edge *edge;
 206         struct btrfs_backref_node *lower;
 207         int idx = *index;
 208
 209         while (idx > 0) {
 210                 edge = edges[idx - 1];
 211                 lower = edge->node[LOWER];
 212                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 213                         idx--;
 214                         continue;
 215                 }
 216                 edge = list_entry(edge->list[LOWER].next,
 217                                   struct btrfs_backref_edge, list[LOWER]);
 218                 edges[idx - 1] = edge;
 219                 *index = idx;
 220                 return edge->node[UPPER];
 221         }
 222         *index = 0;
 223         return NULL;
 224 }
 225
 226 static void update_backref_node(struct btrfs_backref_cache *cache,
 227                                 struct btrfs_backref_node *node, u64 bytenr)
 228 {
 229         struct rb_node *rb_node;
 230         rb_erase(&node->rb_node, &cache->rb_root);
 231         node->bytenr = bytenr;
 232         rb_node = rb_simple_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 233         if (rb_node)
 234                 btrfs_backref_panic(cache->fs_info, bytenr, -EEXIST);
 235 }
 236
 237 /*
 238  * update backref cache after a transaction commit
 239  */
 240 static int update_backref_cache(struct btrfs_trans_handle *trans,
 241                                 struct btrfs_backref_cache *cache)
 242 {
 243         struct btrfs_backref_node *node;
 244         int level = 0;
 245
 246         if (cache->last_trans == 0) {
 247                 cache->last_trans = trans->transid;
 248                 return 0;
 249         }
 250
 251         if (cache->last_trans == trans->transid)
 252                 return 0;
 253
 254         /*
 255          * detached nodes are used to avoid unnecessary backref
 256          * lookup. transaction commit changes the extent tree.
 257          * so the detached nodes are no longer useful.
 258          */
 259         while (!list_empty(&cache->detached)) {
 260                 node = list_entry(cache->detached.next,
 261                                   struct btrfs_backref_node, list);
 262                 btrfs_backref_cleanup_node(cache, node);
 263         }
 264
 265         while (!list_empty(&cache->changed)) {
 266                 node = list_entry(cache->changed.next,
 267                                   struct btrfs_backref_node, list);
 268                 list_del_init(&node->list);
 269                 BUG_ON(node->pending);
 270                 update_backref_node(cache, node, node->new_bytenr);
 271         }
 272
 273         /*
 274          * some nodes can be left in the pending list if there were
 275          * errors during processing the pending nodes.
 276          */
 277         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 278                 list_for_each_entry(node, &cache->pending[level], list) {
 279                         BUG_ON(!node->pending);
 280                         if (node->bytenr == node->new_bytenr)
 281                                 continue;
 282                         update_backref_node(cache, node, node->new_bytenr);
 283                 }
 284         }
 285
 286         cache->last_trans = 0;
 287         return 1;
 288 }
 289
 290 static bool reloc_root_is_dead(struct btrfs_root *root)
 291 {
 292         /*
 293          * Pair with set_bit/clear_bit in clean_dirty_subvols and
 294          * btrfs_update_reloc_root. We need to see the updated bit before
 295          * trying to access reloc_root
 296          */
 297         smp_rmb();
 298         if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
 299                 return true;
 300         return false;
 301 }
 302
 303 /*
 304  * Check if this subvolume tree has valid reloc tree.
 305  *
 306  * Reloc tree after swap is considered dead, thus not considered as valid.
 307  * This is enough for most callers, as they don't distinguish dead reloc root
 308  * from no reloc root.  But btrfs_should_ignore_reloc_root() below is a
 309  * special case.
 310  */
 311 static bool have_reloc_root(struct btrfs_root *root)
 312 {
 313         if (reloc_root_is_dead(root))
 314                 return false;
 315         if (!root->reloc_root)
 316                 return false;
 317         return true;
 318 }
 319
 320 int btrfs_should_ignore_reloc_root(struct btrfs_root *root)
 321 {
 322         struct btrfs_root *reloc_root;
 323
 324         if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
 325                 return 0;
 326
 327         /* This root has been merged with its reloc tree, we can ignore it */
 328         if (reloc_root_is_dead(root))
 329                 return 1;
 330
 331         reloc_root = root->reloc_root;
 332         if (!reloc_root)
 333                 return 0;
 334
 335         if (btrfs_header_generation(reloc_root->commit_root) ==
 336             root->fs_info->running_transaction->transid)
 337                 return 0;
 338         /*
 339          * if there is reloc tree and it was created in previous
 340          * transaction backref lookup can find the reloc tree,
 341          * so backref node for the fs tree root is useless for
 342          * relocation.
 343          */
 344         return 1;
 345 }
 346
 347 /*
 348  * find reloc tree by address of tree root
 349  */
 350 struct btrfs_root *find_reloc_root(struct btrfs_fs_info *fs_info, u64 bytenr)
 351 {
 352         struct reloc_control *rc = fs_info->reloc_ctl;
 353         struct rb_node *rb_node;
 354         struct mapping_node *node;
 355         struct btrfs_root *root = NULL;
 356
 357         ASSERT(rc);
 358         spin_lock(&rc->reloc_root_tree.lock);
 359         rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root, bytenr);
 360         if (rb_node) {
 361                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 362                 root = (struct btrfs_root *)node->data;
 363         }
 364         spin_unlock(&rc->reloc_root_tree.lock);
 365         return btrfs_grab_root(root);
 366 }
 367
 368 /*
 369  * For useless nodes, do two major clean ups:
 370  *
 371  * - Cleanup the children edges and nodes
 372  *   If child node is also orphan (no parent) during cleanup, then the child
 373  *   node will also be cleaned up.
 374  *
 375  * - Freeing up leaves (level 0), keeps nodes detached
 376  *   For nodes, the node is still cached as "detached"
 377  *
 378  * Return false if @node is not in the @useless_nodes list.
 379  * Return true if @node is in the @useless_nodes list.
 380  */
 381 static bool handle_useless_nodes(struct reloc_control *rc,
 382                                  struct btrfs_backref_node *node)
 383 {
 384         struct btrfs_backref_cache *cache = &rc->backref_cache;
 385         struct list_head *useless_node = &cache->useless_node;
 386         bool ret = false;
 387
 388         while (!list_empty(useless_node)) {
 389                 struct btrfs_backref_node *cur;
 390
 391                 cur = list_first_entry(useless_node, struct btrfs_backref_node,
 392                                  list);
 393                 list_del_init(&cur->list);
 394
 395                 /* Only tree root nodes can be added to @useless_nodes */
 396                 ASSERT(list_empty(&cur->upper));
 397
 398                 if (cur == node)
 399                         ret = true;
 400
 401                 /* The node is the lowest node */
 402                 if (cur->lowest) {
 403                         list_del_init(&cur->lower);
 404                         cur->lowest = 0;
 405                 }
 406
 407                 /* Cleanup the lower edges */
 408                 while (!list_empty(&cur->lower)) {
 409                         struct btrfs_backref_edge *edge;
 410                         struct btrfs_backref_node *lower;
 411
 412                         edge = list_entry(cur->lower.next,
 413                                         struct btrfs_backref_edge, list[UPPER]);
 414                         list_del(&edge->list[UPPER]);
 415                         list_del(&edge->list[LOWER]);
 416                         lower = edge->node[LOWER];
 417                         btrfs_backref_free_edge(cache, edge);
 418
 419                         /* Child node is also orphan, queue for cleanup */
 420                         if (list_empty(&lower->upper))
 421                                 list_add(&lower->list, useless_node);
 422                 }
 423                 /* Mark this block processed for relocation */
 424                 mark_block_processed(rc, cur);
 425
 426                 /*
 427                  * Backref nodes for tree leaves are deleted from the cache.
 428                  * Backref nodes for upper level tree blocks are left in the
 429                  * cache to avoid unnecessary backref lookup.
 430                  */
 431                 if (cur->level > 0) {
 432                         list_add(&cur->list, &cache->detached);
 433                         cur->detached = 1;
 434                 } else {
 435                         rb_erase(&cur->rb_node, &cache->rb_root);
 436                         btrfs_backref_free_node(cache, cur);
 437                 }
 438         }
 439         return ret;
 440 }
 441
 442 /*
 443  * Build backref tree for a given tree block. Root of the backref tree
 444  * corresponds the tree block, leaves of the backref tree correspond roots of
 445  * b-trees that reference the tree block.
 446  *
 447  * The basic idea of this function is check backrefs of a given block to find
 448  * upper level blocks that reference the block, and then check backrefs of
 449  * these upper level blocks recursively. The recursion stops when tree root is
 450  * reached or backrefs for the block is cached.
 451  *
 452  * NOTE: if we find that backrefs for a block are cached, we know backrefs for
 453  * all upper level blocks that directly/indirectly reference the block are also
 454  * cached.
 455  */
 456 static noinline_for_stack struct btrfs_backref_node *build_backref_tree(
 457                         struct reloc_control *rc, struct btrfs_key *node_key,
 458                         int level, u64 bytenr)
 459 {
 460         struct btrfs_backref_iter *iter;
 461         struct btrfs_backref_cache *cache = &rc->backref_cache;
 462         /* For searching parent of TREE_BLOCK_REF */
 463         struct btrfs_path *path;
 464         struct btrfs_backref_node *cur;
 465         struct btrfs_backref_node *node = NULL;
 466         struct btrfs_backref_edge *edge;
 467         int ret;
 468         int err = 0;
 469
 470         iter = btrfs_backref_iter_alloc(rc->extent_root->fs_info, GFP_NOFS);
 471         if (!iter)
 472                 return ERR_PTR(-ENOMEM);
 473         path = btrfs_alloc_path();
 474         if (!path) {
 475                 err = -ENOMEM;
 476                 goto out;
 477         }
 478
 479         node = btrfs_backref_alloc_node(cache, bytenr, level);
 480         if (!node) {
 481                 err = -ENOMEM;
 482                 goto out;
 483         }
 484
 485         node->lowest = 1;
 486         cur = node;
 487
 488         /* Breadth-first search to build backref cache */
 489         do {
 490                 ret = btrfs_backref_add_tree_node(cache, path, iter, node_key,
 491                                                   cur);
 492                 if (ret < 0) {
 493                         err = ret;
 494                         goto out;
 495                 }
 496                 edge = list_first_entry_or_null(&cache->pending_edge,
 497                                 struct btrfs_backref_edge, list[UPPER]);
 498                 /*
 499                  * The pending list isn't empty, take the first block to
 500                  * process
 501                  */
 502                 if (edge) {
 503                         list_del_init(&edge->list[UPPER]);
 504                         cur = edge->node[UPPER];
 505                 }
 506         } while (edge);
 507
 508         /* Finish the upper linkage of newly added edges/nodes */
 509         ret = btrfs_backref_finish_upper_links(cache, node);
 510         if (ret < 0) {
 511                 err = ret;
 512                 goto out;
 513         }
 514
 515         if (handle_useless_nodes(rc, node))
 516                 node = NULL;
 517 out:
 518         btrfs_backref_iter_free(iter);
 519         btrfs_free_path(path);
 520         if (err) {
 521                 btrfs_backref_error_cleanup(cache, node);
 522                 return ERR_PTR(err);
 523         }
 524         ASSERT(!node || !node->detached);
 525         ASSERT(list_empty(&cache->useless_node) &&
 526                list_empty(&cache->pending_edge));
 527         return node;
 528 }
 529
 530 /*
 531  * helper to add backref node for the newly created snapshot.
 532  * the backref node is created by cloning backref node that
 533  * corresponds to root of source tree
 534  */
 535 static int clone_backref_node(struct btrfs_trans_handle *trans,
 536                               struct reloc_control *rc,
 537                               struct btrfs_root *src,
 538                               struct btrfs_root *dest)
 539 {
 540         struct btrfs_root *reloc_root = src->reloc_root;
 541         struct btrfs_backref_cache *cache = &rc->backref_cache;
 542         struct btrfs_backref_node *node = NULL;
 543         struct btrfs_backref_node *new_node;
 544         struct btrfs_backref_edge *edge;
 545         struct btrfs_backref_edge *new_edge;
 546         struct rb_node *rb_node;
 547
 548         if (cache->last_trans > 0)
 549                 update_backref_cache(trans, cache);
 550
 551         rb_node = rb_simple_search(&cache->rb_root, src->commit_root->start);
 552         if (rb_node) {
 553                 node = rb_entry(rb_node, struct btrfs_backref_node, rb_node);
 554                 if (node->detached)
 555                         node = NULL;
 556                 else
 557                         BUG_ON(node->new_bytenr != reloc_root->node->start);
 558         }
 559
 560         if (!node) {
 561                 rb_node = rb_simple_search(&cache->rb_root,
 562                                            reloc_root->commit_root->start);
 563                 if (rb_node) {
 564                         node = rb_entry(rb_node, struct btrfs_backref_node,
 565                                         rb_node);
 566                         BUG_ON(node->detached);
 567                 }
 568         }
 569
 570         if (!node)
 571                 return 0;
 572
 573         new_node = btrfs_backref_alloc_node(cache, dest->node->start,
 574                                             node->level);
 575         if (!new_node)
 576                 return -ENOMEM;
 577
 578         new_node->lowest = node->lowest;
 579         new_node->checked = 1;
 580         new_node->root = btrfs_grab_root(dest);
 581         ASSERT(new_node->root);
 582
 583         if (!node->lowest) {
 584                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
 585                         new_edge = btrfs_backref_alloc_edge(cache);
 586                         if (!new_edge)
 587                                 goto fail;
 588
 589                         btrfs_backref_link_edge(new_edge, edge->node[LOWER],
 590                                                 new_node, LINK_UPPER);
 591                 }
 592         } else {
 593                 list_add_tail(&new_node->lower, &cache->leaves);
 594         }
 595
 596         rb_node = rb_simple_insert(&cache->rb_root, new_node->bytenr,
 597                                    &new_node->rb_node);
 598         if (rb_node)
 599                 btrfs_backref_panic(trans->fs_info, new_node->bytenr, -EEXIST);
 600
 601         if (!new_node->lowest) {
 602                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
 603                         list_add_tail(&new_edge->list[LOWER],
 604                                       &new_edge->node[LOWER]->upper);
 605                 }
 606         }
 607         return 0;
 608 fail:
 609         while (!list_empty(&new_node->lower)) {
 610                 new_edge = list_entry(new_node->lower.next,
 611                                       struct btrfs_backref_edge, list[UPPER]);
 612                 list_del(&new_edge->list[UPPER]);
 613                 btrfs_backref_free_edge(cache, new_edge);
 614         }
 615         btrfs_backref_free_node(cache, new_node);
 616         return -ENOMEM;
 617 }
 618
 619 /*
 620  * helper to add 'address of tree root -> reloc tree' mapping
 621  */
 622 static int __must_check __add_reloc_root(struct btrfs_root *root)
 623 {
 624         struct btrfs_fs_info *fs_info = root->fs_info;
 625         struct rb_node *rb_node;
 626         struct mapping_node *node;
 627         struct reloc_control *rc = fs_info->reloc_ctl;
 628
 629         node = kmalloc(sizeof(*node), GFP_NOFS);
 630         if (!node)
 631                 return -ENOMEM;
 632
 633         node->bytenr = root->commit_root->start;
 634         node->data = root;
 635
 636         spin_lock(&rc->reloc_root_tree.lock);
 637         rb_node = rb_simple_insert(&rc->reloc_root_tree.rb_root,
 638                                    node->bytenr, &node->rb_node);
 639         spin_unlock(&rc->reloc_root_tree.lock);
 640         if (rb_node) {
 641                 btrfs_panic(fs_info, -EEXIST,
 642                             "Duplicate root found for start=%llu while inserting into relocation tree",
 643                             node->bytenr);
 644         }
 645
 646         list_add_tail(&root->root_list, &rc->reloc_roots);
 647         return 0;
 648 }
 649
 650 /*
 651  * helper to delete the 'address of tree root -> reloc tree'
 652  * mapping
 653  */
 654 static void __del_reloc_root(struct btrfs_root *root)
 655 {
 656         struct btrfs_fs_info *fs_info = root->fs_info;
 657         struct rb_node *rb_node;
 658         struct mapping_node *node = NULL;
 659         struct reloc_control *rc = fs_info->reloc_ctl;
 660         bool put_ref = false;
 661
 662         if (rc && root->node) {
 663                 spin_lock(&rc->reloc_root_tree.lock);
 664                 rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root,
 665                                            root->commit_root->start);
 666                 if (rb_node) {
 667                         node = rb_entry(rb_node, struct mapping_node, rb_node);
 668                         rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
 669                         RB_CLEAR_NODE(&node->rb_node);
 670                 }
 671                 spin_unlock(&rc->reloc_root_tree.lock);
 672                 ASSERT(!node || (struct btrfs_root *)node->data == root);
 673         }
 674
 675         /*
 676          * We only put the reloc root here if it's on the list.  There's a lot
 677          * of places where the pattern is to splice the rc->reloc_roots, process
 678          * the reloc roots, and then add the reloc root back onto
 679          * rc->reloc_roots.  If we call __del_reloc_root while it's off of the
 680          * list we don't want the reference being dropped, because the guy
 681          * messing with the list is in charge of the reference.
 682          */
 683         spin_lock(&fs_info->trans_lock);
 684         if (!list_empty(&root->root_list)) {
 685                 put_ref = true;
 686                 list_del_init(&root->root_list);
 687         }
 688         spin_unlock(&fs_info->trans_lock);
 689         if (put_ref)
 690                 btrfs_put_root(root);
 691         kfree(node);
 692 }
 693
 694 /*
 695  * helper to update the 'address of tree root -> reloc tree'
 696  * mapping
 697  */
 698 static int __update_reloc_root(struct btrfs_root *root)
 699 {
 700         struct btrfs_fs_info *fs_info = root->fs_info;
 701         struct rb_node *rb_node;
 702         struct mapping_node *node = NULL;
 703         struct reloc_control *rc = fs_info->reloc_ctl;
 704
 705         spin_lock(&rc->reloc_root_tree.lock);
 706         rb_node = rb_simple_search(&rc->reloc_root_tree.rb_root,
 707                                    root->commit_root->start);
 708         if (rb_node) {
 709                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 710                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
 711         }
 712         spin_unlock(&rc->reloc_root_tree.lock);
 713
 714         if (!node)
 715                 return 0;
 716         BUG_ON((struct btrfs_root *)node->data != root);
 717
 718         spin_lock(&rc->reloc_root_tree.lock);
 719         node->bytenr = root->node->start;
 720         rb_node = rb_simple_insert(&rc->reloc_root_tree.rb_root,
 721                                    node->bytenr, &node->rb_node);
 722         spin_unlock(&rc->reloc_root_tree.lock);
 723         if (rb_node)
 724                 btrfs_backref_panic(fs_info, node->bytenr, -EEXIST);
 725         return 0;
 726 }
 727
 728 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
 729                                         struct btrfs_root *root, u64 objectid)
 730 {
 731         struct btrfs_fs_info *fs_info = root->fs_info;
 732         struct btrfs_root *reloc_root;
 733         struct extent_buffer *eb;
 734         struct btrfs_root_item *root_item;
 735         struct btrfs_key root_key;
 736         int ret;
 737
 738         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
 739         BUG_ON(!root_item);
 740
 741         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
 742         root_key.type = BTRFS_ROOT_ITEM_KEY;
 743         root_key.offset = objectid;
 744
 745         if (root->root_key.objectid == objectid) {
 746                 u64 commit_root_gen;
 747
 748                 /* called by btrfs_init_reloc_root */
 749                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
 750                                       BTRFS_TREE_RELOC_OBJECTID);
 751                 BUG_ON(ret);
 752                 /*
 753                  * Set the last_snapshot field to the generation of the commit
 754                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
 755                  * correctly (returns true) when the relocation root is created
 756                  * either inside the critical section of a transaction commit
 757                  * (through transaction.c:qgroup_account_snapshot()) and when
 758                  * it's created before the transaction commit is started.
 759                  */
 760                 commit_root_gen = btrfs_header_generation(root->commit_root);
 761                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
 762         } else {
 763                 /*
 764                  * called by btrfs_reloc_post_snapshot_hook.
 765                  * the source tree is a reloc tree, all tree blocks
 766                  * modified after it was created have RELOC flag
 767                  * set in their headers. so it's OK to not update
 768                  * the 'last_snapshot'.
 769                  */
 770                 ret = btrfs_copy_root(trans, root, root->node, &eb,
 771                                       BTRFS_TREE_RELOC_OBJECTID);
 772                 BUG_ON(ret);
 773         }
 774
 775         memcpy(root_item, &root->root_item, sizeof(*root_item));
 776         btrfs_set_root_bytenr(root_item, eb->start);
 777         btrfs_set_root_level(root_item, btrfs_header_level(eb));
 778         btrfs_set_root_generation(root_item, trans->transid);
 779
 780         if (root->root_key.objectid == objectid) {
 781                 btrfs_set_root_refs(root_item, 0);
 782                 memset(&root_item->drop_progress, 0,
 783                        sizeof(struct btrfs_disk_key));
 784                 btrfs_set_root_drop_level(root_item, 0);
 785         }
 786
 787         btrfs_tree_unlock(eb);
 788         free_extent_buffer(eb);
 789
 790         ret = btrfs_insert_root(trans, fs_info->tree_root,
 791                                 &root_key, root_item);
 792         BUG_ON(ret);
 793         kfree(root_item);
 794
 795         reloc_root = btrfs_read_tree_root(fs_info->tree_root, &root_key);
 796         BUG_ON(IS_ERR(reloc_root));
 797         set_bit(BTRFS_ROOT_SHAREABLE, &reloc_root->state);
 798         reloc_root->last_trans = trans->transid;
 799         return reloc_root;
 800 }
 801
 802 /*
 803  * create reloc tree for a given fs tree. reloc tree is just a
 804  * snapshot of the fs tree with special root objectid.
 805  *
 806  * The reloc_root comes out of here with two references, one for
 807  * root->reloc_root, and another for being on the rc->reloc_roots list.
 808  */
 809 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
 810                           struct btrfs_root *root)
 811 {
 812         struct btrfs_fs_info *fs_info = root->fs_info;
 813         struct btrfs_root *reloc_root;
 814         struct reloc_control *rc = fs_info->reloc_ctl;
 815         struct btrfs_block_rsv *rsv;
 816         int clear_rsv = 0;
 817         int ret;
 818
 819         if (!rc)
 820                 return 0;
 821
 822         /*
 823          * The subvolume has reloc tree but the swap is finished, no need to
 824          * create/update the dead reloc tree
 825          */
 826         if (reloc_root_is_dead(root))
 827                 return 0;
 828
 829         /*
 830          * This is subtle but important.  We do not do
 831          * record_root_in_transaction for reloc roots, instead we record their
 832          * corresponding fs root, and then here we update the last trans for the
 833          * reloc root.  This means that we have to do this for the entire life
 834          * of the reloc root, regardless of which stage of the relocation we are
 835          * in.
 836          */
 837         if (root->reloc_root) {
 838                 reloc_root = root->reloc_root;
 839                 reloc_root->last_trans = trans->transid;
 840                 return 0;
 841         }
 842
 843         /*
 844          * We are merging reloc roots, we do not need new reloc trees.  Also
 845          * reloc trees never need their own reloc tree.
 846          */
 847         if (!rc->create_reloc_tree ||
 848             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
 849                 return 0;
 850
 851         if (!trans->reloc_reserved) {
 852                 rsv = trans->block_rsv;
 853                 trans->block_rsv = rc->block_rsv;
 854                 clear_rsv = 1;
 855         }
 856         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
 857         if (clear_rsv)
 858                 trans->block_rsv = rsv;
 859
 860         ret = __add_reloc_root(reloc_root);
 861         BUG_ON(ret < 0);
 862         root->reloc_root = btrfs_grab_root(reloc_root);
 863         return 0;
 864 }
 865
 866 /*
 867  * update root item of reloc tree
 868  */
 869 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
 870                             struct btrfs_root *root)
 871 {
 872         struct btrfs_fs_info *fs_info = root->fs_info;
 873         struct btrfs_root *reloc_root;
 874         struct btrfs_root_item *root_item;
 875         int ret;
 876
 877         if (!have_reloc_root(root))
 878                 goto out;
 879
 880         reloc_root = root->reloc_root;
 881         root_item = &reloc_root->root_item;
 882
 883         /*
 884          * We are probably ok here, but __del_reloc_root() will drop its ref of
 885          * the root.  We have the ref for root->reloc_root, but just in case
 886          * hold it while we update the reloc root.
 887          */
 888         btrfs_grab_root(reloc_root);
 889
 890         /* root->reloc_root will stay until current relocation finished */
 891         if (fs_info->reloc_ctl->merge_reloc_tree &&
 892             btrfs_root_refs(root_item) == 0) {
 893                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
 894                 /*
 895                  * Mark the tree as dead before we change reloc_root so
 896                  * have_reloc_root will not touch it from now on.
 897                  */
 898                 smp_wmb();
 899                 __del_reloc_root(reloc_root);
 900         }
 901
 902         if (reloc_root->commit_root != reloc_root->node) {
 903                 __update_reloc_root(reloc_root);
 904                 btrfs_set_root_node(root_item, reloc_root->node);
 905                 free_extent_buffer(reloc_root->commit_root);
 906                 reloc_root->commit_root = btrfs_root_node(reloc_root);
 907         }
 908
 909         ret = btrfs_update_root(trans, fs_info->tree_root,
 910                                 &reloc_root->root_key, root_item);
 911         BUG_ON(ret);
 912         btrfs_put_root(reloc_root);
 913 out:
 914         return 0;
 915 }
 916
 917 /*
 918  * helper to find first cached inode with inode number >= objectid
 919  * in a subvolume
 920  */
 921 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
 922 {
 923         struct rb_node *node;
 924         struct rb_node *prev;
 925         struct btrfs_inode *entry;
 926         struct inode *inode;
 927
 928         spin_lock(&root->inode_lock);
 929 again:
 930         node = root->inode_tree.rb_node;
 931         prev = NULL;
 932         while (node) {
 933                 prev = node;
 934                 entry = rb_entry(node, struct btrfs_inode, rb_node);
 935
 936                 if (objectid < btrfs_ino(entry))
 937                         node = node->rb_left;
 938                 else if (objectid > btrfs_ino(entry))
 939                         node = node->rb_right;
 940                 else
 941                         break;
 942         }
 943         if (!node) {
 944                 while (prev) {
 945                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
 946                         if (objectid <= btrfs_ino(entry)) {
 947                                 node = prev;
 948                                 break;
 949                         }
 950                         prev = rb_next(prev);
 951                 }
 952         }
 953         while (node) {
 954                 entry = rb_entry(node, struct btrfs_inode, rb_node);
 955                 inode = igrab(&entry->vfs_inode);
 956                 if (inode) {
 957                         spin_unlock(&root->inode_lock);
 958                         return inode;
 959                 }
 960
 961                 objectid = btrfs_ino(entry) + 1;
 962                 if (cond_resched_lock(&root->inode_lock))
 963                         goto again;
 964
 965                 node = rb_next(node);
 966         }
 967         spin_unlock(&root->inode_lock);
 968         return NULL;
 969 }
 970
 971 /*
 972  * get new location of data
 973  */
 974 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
 975                             u64 bytenr, u64 num_bytes)
 976 {
 977         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
 978         struct btrfs_path *path;
 979         struct btrfs_file_extent_item *fi;
 980         struct extent_buffer *leaf;
 981         int ret;
 982
 983         path = btrfs_alloc_path();
 984         if (!path)
 985                 return -ENOMEM;
 986
 987         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
 988         ret = btrfs_lookup_file_extent(NULL, root, path,
 989                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
 990         if (ret < 0)
 991                 goto out;
 992         if (ret > 0) {
 993                 ret = -ENOENT;
 994                 goto out;
 995         }
 996
 997         leaf = path->nodes[0];
 998         fi = btrfs_item_ptr(leaf, path->slots[0],
 999                             struct btrfs_file_extent_item);
1000
1001         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1002                btrfs_file_extent_compression(leaf, fi) ||
1003                btrfs_file_extent_encryption(leaf, fi) ||
1004                btrfs_file_extent_other_encoding(leaf, fi));
1005
1006         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1007                 ret = -EINVAL;
1008                 goto out;
1009         }
1010
1011         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1012         ret = 0;
1013 out:
1014         btrfs_free_path(path);
1015         return ret;
1016 }
1017
1018 /*
1019  * update file extent items in the tree leaf to point to
1020  * the new locations.
1021  */
1022 static noinline_for_stack
1023 int replace_file_extents(struct btrfs_trans_handle *trans,
1024                          struct reloc_control *rc,
1025                          struct btrfs_root *root,
1026                          struct extent_buffer *leaf)
1027 {
1028         struct btrfs_fs_info *fs_info = root->fs_info;
1029         struct btrfs_key key;
1030         struct btrfs_file_extent_item *fi;
1031         struct inode *inode = NULL;
1032         u64 parent;
1033         u64 bytenr;
1034         u64 new_bytenr = 0;
1035         u64 num_bytes;
1036         u64 end;
1037         u32 nritems;
1038         u32 i;
1039         int ret = 0;
1040         int first = 1;
1041         int dirty = 0;
1042
1043         if (rc->stage != UPDATE_DATA_PTRS)
1044                 return 0;
1045
1046         /* reloc trees always use full backref */
1047         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1048                 parent = leaf->start;
1049         else
1050                 parent = 0;
1051
1052         nritems = btrfs_header_nritems(leaf);
1053         for (i = 0; i < nritems; i++) {
1054                 struct btrfs_ref ref = { 0 };
1055
1056                 cond_resched();
1057                 btrfs_item_key_to_cpu(leaf, &key, i);
1058                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1059                         continue;
1060                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1061                 if (btrfs_file_extent_type(leaf, fi) ==
1062                     BTRFS_FILE_EXTENT_INLINE)
1063                         continue;
1064                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1065                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1066                 if (bytenr == 0)
1067                         continue;
1068                 if (!in_range(bytenr, rc->block_group->start,
1069                               rc->block_group->length))
1070                         continue;
1071
1072                 /*
1073                  * if we are modifying block in fs tree, wait for readpage
1074                  * to complete and drop the extent cache
1075                  */
1076                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1077                         if (first) {
1078                                 inode = find_next_inode(root, key.objectid);
1079                                 first = 0;
1080                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1081                                 btrfs_add_delayed_iput(inode);
1082                                 inode = find_next_inode(root, key.objectid);
1083                         }
1084                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1085                                 end = key.offset +
1086                                       btrfs_file_extent_num_bytes(leaf, fi);
1087                                 WARN_ON(!IS_ALIGNED(key.offset,
1088                                                     fs_info->sectorsize));
1089                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1090                                 end--;
1091                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1092                                                       key.offset, end);
1093                                 if (!ret)
1094                                         continue;
1095
1096                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1097                                                 key.offset,     end, 1);
1098                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1099                                               key.offset, end);
1100                         }
1101                 }
1102
1103                 ret = get_new_location(rc->data_inode, &new_bytenr,
1104                                        bytenr, num_bytes);
1105                 if (ret) {
1106                         /*
1107                          * Don't have to abort since we've not changed anything
1108                          * in the file extent yet.
1109                          */
1110                         break;
1111                 }
1112
1113                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1114                 dirty = 1;
1115
1116                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1117                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1118                                        num_bytes, parent);
1119                 ref.real_root = root->root_key.objectid;
1120                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1121                                     key.objectid, key.offset);
1122                 ret = btrfs_inc_extent_ref(trans, &ref);
1123                 if (ret) {
1124                         btrfs_abort_transaction(trans, ret);
1125                         break;
1126                 }
1127
1128                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1129                                        num_bytes, parent);
1130                 ref.real_root = root->root_key.objectid;
1131                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1132                                     key.objectid, key.offset);
1133                 ret = btrfs_free_extent(trans, &ref);
1134                 if (ret) {
1135                         btrfs_abort_transaction(trans, ret);
1136                         break;
1137                 }
1138         }
1139         if (dirty)
1140                 btrfs_mark_buffer_dirty(leaf);
1141         if (inode)
1142                 btrfs_add_delayed_iput(inode);
1143         return ret;
1144 }
1145
1146 static noinline_for_stack
1147 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1148                      struct btrfs_path *path, int level)
1149 {
1150         struct btrfs_disk_key key1;
1151         struct btrfs_disk_key key2;
1152         btrfs_node_key(eb, &key1, slot);
1153         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1154         return memcmp(&key1, &key2, sizeof(key1));
1155 }
1156
1157 /*
1158  * try to replace tree blocks in fs tree with the new blocks
1159  * in reloc tree. tree blocks haven't been modified since the
1160  * reloc tree was create can be replaced.
1161  *
1162  * if a block was replaced, level of the block + 1 is returned.
1163  * if no block got replaced, 0 is returned. if there are other
1164  * errors, a negative error number is returned.
1165  */
1166 static noinline_for_stack
1167 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1168                  struct btrfs_root *dest, struct btrfs_root *src,
1169                  struct btrfs_path *path, struct btrfs_key *next_key,
1170                  int lowest_level, int max_level)
1171 {
1172         struct btrfs_fs_info *fs_info = dest->fs_info;
1173         struct extent_buffer *eb;
1174         struct extent_buffer *parent;
1175         struct btrfs_ref ref = { 0 };
1176         struct btrfs_key key;
1177         u64 old_bytenr;
1178         u64 new_bytenr;
1179         u64 old_ptr_gen;
1180         u64 new_ptr_gen;
1181         u64 last_snapshot;
1182         u32 blocksize;
1183         int cow = 0;
1184         int level;
1185         int ret;
1186         int slot;
1187
1188         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1189         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1190
1191         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1192 again:
1193         slot = path->slots[lowest_level];
1194         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1195
1196         eb = btrfs_lock_root_node(dest);
1197         level = btrfs_header_level(eb);
1198
1199         if (level < lowest_level) {
1200                 btrfs_tree_unlock(eb);
1201                 free_extent_buffer(eb);
1202                 return 0;
1203         }
1204
1205         if (cow) {
1206                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb,
1207                                       BTRFS_NESTING_COW);
1208                 BUG_ON(ret);
1209         }
1210
1211         if (next_key) {
1212                 next_key->objectid = (u64)-1;
1213                 next_key->type = (u8)-1;
1214                 next_key->offset = (u64)-1;
1215         }
1216
1217         parent = eb;
1218         while (1) {
1219                 level = btrfs_header_level(parent);
1220                 BUG_ON(level < lowest_level);
1221
1222                 ret = btrfs_bin_search(parent, &key, &slot);
1223                 if (ret < 0)
1224                         break;
1225                 if (ret && slot > 0)
1226                         slot--;
1227
1228                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1229                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1230
1231                 old_bytenr = btrfs_node_blockptr(parent, slot);
1232                 blocksize = fs_info->nodesize;
1233                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1234
1235                 if (level <= max_level) {
1236                         eb = path->nodes[level];
1237                         new_bytenr = btrfs_node_blockptr(eb,
1238                                                         path->slots[level]);
1239                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1240                                                         path->slots[level]);
1241                 } else {
1242                         new_bytenr = 0;
1243                         new_ptr_gen = 0;
1244                 }
1245
1246                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1247                         ret = level;
1248                         break;
1249                 }
1250
1251                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1252                     memcmp_node_keys(parent, slot, path, level)) {
1253                         if (level <= lowest_level) {
1254                                 ret = 0;
1255                                 break;
1256                         }
1257
1258                         eb = btrfs_read_node_slot(parent, slot);
1259                         if (IS_ERR(eb)) {
1260                                 ret = PTR_ERR(eb);
1261                                 break;
1262                         }
1263                         btrfs_tree_lock(eb);
1264                         if (cow) {
1265                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1266                                                       slot, &eb,
1267                                                       BTRFS_NESTING_COW);
1268                                 BUG_ON(ret);
1269                         }
1270
1271                         btrfs_tree_unlock(parent);
1272                         free_extent_buffer(parent);
1273
1274                         parent = eb;
1275                         continue;
1276                 }
1277
1278                 if (!cow) {
1279                         btrfs_tree_unlock(parent);
1280                         free_extent_buffer(parent);
1281                         cow = 1;
1282                         goto again;
1283                 }
1284
1285                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1286                                       path->slots[level]);
1287                 btrfs_release_path(path);
1288
1289                 path->lowest_level = level;
1290                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
1291                 path->lowest_level = 0;
1292                 BUG_ON(ret);
1293
1294                 /*
1295                  * Info qgroup to trace both subtrees.
1296                  *
1297                  * We must trace both trees.
1298                  * 1) Tree reloc subtree
1299                  *    If not traced, we will leak data numbers
1300                  * 2) Fs subtree
1301                  *    If not traced, we will double count old data
1302                  *
1303                  * We don't scan the subtree right now, but only record
1304                  * the swapped tree blocks.
1305                  * The real subtree rescan is delayed until we have new
1306                  * CoW on the subtree root node before transaction commit.
1307                  */
1308                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
1309                                 rc->block_group, parent, slot,
1310                                 path->nodes[level], path->slots[level],
1311                                 last_snapshot);
1312                 if (ret < 0)
1313                         break;
1314                 /*
1315                  * swap blocks in fs tree and reloc tree.
1316                  */
1317                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
1318                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
1319                 btrfs_mark_buffer_dirty(parent);
1320
1321                 btrfs_set_node_blockptr(path->nodes[level],
1322                                         path->slots[level], old_bytenr);
1323                 btrfs_set_node_ptr_generation(path->nodes[level],
1324                                               path->slots[level], old_ptr_gen);
1325                 btrfs_mark_buffer_dirty(path->nodes[level]);
1326
1327                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
1328                                        blocksize, path->nodes[level]->start);
1329                 ref.skip_qgroup = true;
1330                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1331                 ret = btrfs_inc_extent_ref(trans, &ref);
1332                 BUG_ON(ret);
1333                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1334                                        blocksize, 0);
1335                 ref.skip_qgroup = true;
1336                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1337                 ret = btrfs_inc_extent_ref(trans, &ref);
1338                 BUG_ON(ret);
1339
1340                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
1341                                        blocksize, path->nodes[level]->start);
1342                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
1343                 ref.skip_qgroup = true;
1344                 ret = btrfs_free_extent(trans, &ref);
1345                 BUG_ON(ret);
1346
1347                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
1348                                        blocksize, 0);
1349                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
1350                 ref.skip_qgroup = true;
1351                 ret = btrfs_free_extent(trans, &ref);
1352                 BUG_ON(ret);
1353
1354                 btrfs_unlock_up_safe(path, 0);
1355
1356                 ret = level;
1357                 break;
1358         }
1359         btrfs_tree_unlock(parent);
1360         free_extent_buffer(parent);
1361         return ret;
1362 }
1363
1364 /*
1365  * helper to find next relocated block in reloc tree
1366  */
1367 static noinline_for_stack
1368 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1369                        int *level)
1370 {
1371         struct extent_buffer *eb;
1372         int i;
1373         u64 last_snapshot;
1374         u32 nritems;
1375
1376         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1377
1378         for (i = 0; i < *level; i++) {
1379                 free_extent_buffer(path->nodes[i]);
1380                 path->nodes[i] = NULL;
1381         }
1382
1383         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
1384                 eb = path->nodes[i];
1385                 nritems = btrfs_header_nritems(eb);
1386                 while (path->slots[i] + 1 < nritems) {
1387                         path->slots[i]++;
1388                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
1389                             last_snapshot)
1390                                 continue;
1391
1392                         *level = i;
1393                         return 0;
1394                 }
1395                 free_extent_buffer(path->nodes[i]);
1396                 path->nodes[i] = NULL;
1397         }
1398         return 1;
1399 }
1400
1401 /*
1402  * walk down reloc tree to find relocated block of lowest level
1403  */
1404 static noinline_for_stack
1405 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
1406                          int *level)
1407 {
1408         struct extent_buffer *eb = NULL;
1409         int i;
1410         u64 ptr_gen = 0;
1411         u64 last_snapshot;
1412         u32 nritems;
1413
1414         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
1415
1416         for (i = *level; i > 0; i--) {
1417                 eb = path->nodes[i];
1418                 nritems = btrfs_header_nritems(eb);
1419                 while (path->slots[i] < nritems) {
1420                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
1421                         if (ptr_gen > last_snapshot)
1422                                 break;
1423                         path->slots[i]++;
1424                 }
1425                 if (path->slots[i] >= nritems) {
1426                         if (i == *level)
1427                                 break;
1428                         *level = i + 1;
1429                         return 0;
1430                 }
1431                 if (i == 1) {
1432                         *level = i;
1433                         return 0;
1434                 }
1435
1436                 eb = btrfs_read_node_slot(eb, path->slots[i]);
1437                 if (IS_ERR(eb))
1438                         return PTR_ERR(eb);
1439                 BUG_ON(btrfs_header_level(eb) != i - 1);
1440                 path->nodes[i - 1] = eb;
1441                 path->slots[i - 1] = 0;
1442         }
1443         return 1;
1444 }
1445
1446 /*
1447  * invalidate extent cache for file extents whose key in range of
1448  * [min_key, max_key)
1449  */
1450 static int invalidate_extent_cache(struct btrfs_root *root,
1451                                    struct btrfs_key *min_key,
1452                                    struct btrfs_key *max_key)
1453 {
1454         struct btrfs_fs_info *fs_info = root->fs_info;
1455         struct inode *inode = NULL;
1456         u64 objectid;
1457         u64 start, end;
1458         u64 ino;
1459
1460         objectid = min_key->objectid;
1461         while (1) {
1462                 cond_resched();
1463                 iput(inode);
1464
1465                 if (objectid > max_key->objectid)
1466                         break;
1467
1468                 inode = find_next_inode(root, objectid);
1469                 if (!inode)
1470                         break;
1471                 ino = btrfs_ino(BTRFS_I(inode));
1472
1473                 if (ino > max_key->objectid) {
1474                         iput(inode);
1475                         break;
1476                 }
1477
1478                 objectid = ino + 1;
1479                 if (!S_ISREG(inode->i_mode))
1480                         continue;
1481
1482                 if (unlikely(min_key->objectid == ino)) {
1483                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
1484                                 continue;
1485                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
1486                                 start = 0;
1487                         else {
1488                                 start = min_key->offset;
1489                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
1490                         }
1491                 } else {
1492                         start = 0;
1493                 }
1494
1495                 if (unlikely(max_key->objectid == ino)) {
1496                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
1497                                 continue;
1498                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
1499                                 end = (u64)-1;
1500                         } else {
1501                                 if (max_key->offset == 0)
1502                                         continue;
1503                                 end = max_key->offset;
1504                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1505                                 end--;
1506                         }
1507                 } else {
1508                         end = (u64)-1;
1509                 }
1510
1511                 /* the lock_extent waits for readpage to complete */
1512                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
1513                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
1514                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
1515         }
1516         return 0;
1517 }
1518
1519 static int find_next_key(struct btrfs_path *path, int level,
1520                          struct btrfs_key *key)
1521
1522 {
1523         while (level < BTRFS_MAX_LEVEL) {
1524                 if (!path->nodes[level])
1525                         break;
1526                 if (path->slots[level] + 1 <
1527                     btrfs_header_nritems(path->nodes[level])) {
1528                         btrfs_node_key_to_cpu(path->nodes[level], key,
1529                                               path->slots[level] + 1);
1530                         return 0;
1531                 }
1532                 level++;
1533         }
1534         return 1;
1535 }
1536
1537 /*
1538  * Insert current subvolume into reloc_control::dirty_subvol_roots
1539  */
1540 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
1541                                 struct reloc_control *rc,
1542                                 struct btrfs_root *root)
1543 {
1544         struct btrfs_root *reloc_root = root->reloc_root;
1545         struct btrfs_root_item *reloc_root_item;
1546
1547         /* @root must be a subvolume tree root with a valid reloc tree */
1548         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1549         ASSERT(reloc_root);
1550
1551         reloc_root_item = &reloc_root->root_item;
1552         memset(&reloc_root_item->drop_progress, 0,
1553                 sizeof(reloc_root_item->drop_progress));
1554         btrfs_set_root_drop_level(reloc_root_item, 0);
1555         btrfs_set_root_refs(reloc_root_item, 0);
1556         btrfs_update_reloc_root(trans, root);
1557
1558         if (list_empty(&root->reloc_dirty_list)) {
1559                 btrfs_grab_root(root);
1560                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
1561         }
1562 }
1563
1564 static int clean_dirty_subvols(struct reloc_control *rc)
1565 {
1566         struct btrfs_root *root;
1567         struct btrfs_root *next;
1568         int ret = 0;
1569         int ret2;
1570
1571         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
1572                                  reloc_dirty_list) {
1573                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1574                         /* Merged subvolume, cleanup its reloc root */
1575                         struct btrfs_root *reloc_root = root->reloc_root;
1576
1577                         list_del_init(&root->reloc_dirty_list);
1578                         root->reloc_root = NULL;
1579                         /*
1580                          * Need barrier to ensure clear_bit() only happens after
1581                          * root->reloc_root = NULL. Pairs with have_reloc_root.
1582                          */
1583                         smp_wmb();
1584                         clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1585                         if (reloc_root) {
1586                                 /*
1587                                  * btrfs_drop_snapshot drops our ref we hold for
1588                                  * ->reloc_root.  If it fails however we must
1589                                  * drop the ref ourselves.
1590                                  */
1591                                 ret2 = btrfs_drop_snapshot(reloc_root, 0, 1);
1592                                 if (ret2 < 0) {
1593                                         btrfs_put_root(reloc_root);
1594                                         if (!ret)
1595                                                 ret = ret2;
1596                                 }
1597                         }
1598                         btrfs_put_root(root);
1599                 } else {
1600                         /* Orphan reloc tree, just clean it up */
1601                         ret2 = btrfs_drop_snapshot(root, 0, 1);
1602                         if (ret2 < 0) {
1603                                 btrfs_put_root(root);
1604                                 if (!ret)
1605                                         ret = ret2;
1606                         }
1607                 }
1608         }
1609         return ret;
1610 }
1611
1612 /*
1613  * merge the relocated tree blocks in reloc tree with corresponding
1614  * fs tree.
1615  */
1616 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
1617                                                struct btrfs_root *root)
1618 {
1619         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
1620         struct btrfs_key key;
1621         struct btrfs_key next_key;
1622         struct btrfs_trans_handle *trans = NULL;
1623         struct btrfs_root *reloc_root;
1624         struct btrfs_root_item *root_item;
1625         struct btrfs_path *path;
1626         struct extent_buffer *leaf;
1627         int reserve_level;
1628         int level;
1629         int max_level;
1630         int replaced = 0;
1631         int ret = 0;
1632         u32 min_reserved;
1633
1634         path = btrfs_alloc_path();
1635         if (!path)
1636                 return -ENOMEM;
1637         path->reada = READA_FORWARD;
1638
1639         reloc_root = root->reloc_root;
1640         root_item = &reloc_root->root_item;
1641
1642         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
1643                 level = btrfs_root_level(root_item);
1644                 atomic_inc(&reloc_root->node->refs);
1645                 path->nodes[level] = reloc_root->node;
1646                 path->slots[level] = 0;
1647         } else {
1648                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
1649
1650                 level = btrfs_root_drop_level(root_item);
1651                 BUG_ON(level == 0);
1652                 path->lowest_level = level;
1653                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
1654                 path->lowest_level = 0;
1655                 if (ret < 0) {
1656                         btrfs_free_path(path);
1657                         return ret;
1658                 }
1659
1660                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
1661                                       path->slots[level]);
1662                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
1663
1664                 btrfs_unlock_up_safe(path, 0);
1665         }
1666
1667         /*
1668          * In merge_reloc_root(), we modify the upper level pointer to swap the
1669          * tree blocks between reloc tree and subvolume tree.  Thus for tree
1670          * block COW, we COW at most from level 1 to root level for each tree.
1671          *
1672          * Thus the needed metadata size is at most root_level * nodesize,
1673          * and * 2 since we have two trees to COW.
1674          */
1675         reserve_level = max_t(int, 1, btrfs_root_level(root_item));
1676         min_reserved = fs_info->nodesize * reserve_level * 2;
1677         memset(&next_key, 0, sizeof(next_key));
1678
1679         while (1) {
1680                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
1681                                              BTRFS_RESERVE_FLUSH_LIMIT);
1682                 if (ret)
1683                         goto out;
1684                 trans = btrfs_start_transaction(root, 0);
1685                 if (IS_ERR(trans)) {
1686                         ret = PTR_ERR(trans);
1687                         trans = NULL;
1688                         goto out;
1689                 }
1690
1691                 /*
1692                  * At this point we no longer have a reloc_control, so we can't
1693                  * depend on btrfs_init_reloc_root to update our last_trans.
1694                  *
1695                  * But that's ok, we started the trans handle on our
1696                  * corresponding fs_root, which means it's been added to the
1697                  * dirty list.  At commit time we'll still call
1698                  * btrfs_update_reloc_root() and update our root item
1699                  * appropriately.
1700                  */
1701                 reloc_root->last_trans = trans->transid;
1702                 trans->block_rsv = rc->block_rsv;
1703
1704                 replaced = 0;
1705                 max_level = level;
1706
1707                 ret = walk_down_reloc_tree(reloc_root, path, &level);
1708                 if (ret < 0)
1709                         goto out;
1710                 if (ret > 0)
1711                         break;
1712
1713                 if (!find_next_key(path, level, &key) &&
1714                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
1715                         ret = 0;
1716                 } else {
1717                         ret = replace_path(trans, rc, root, reloc_root, path,
1718                                            &next_key, level, max_level);
1719                 }
1720                 if (ret < 0)
1721                         goto out;
1722                 if (ret > 0) {
1723                         level = ret;
1724                         btrfs_node_key_to_cpu(path->nodes[level], &key,
1725                                               path->slots[level]);
1726                         replaced = 1;
1727                 }
1728
1729                 ret = walk_up_reloc_tree(reloc_root, path, &level);
1730                 if (ret > 0)
1731                         break;
1732
1733                 BUG_ON(level == 0);
1734                 /*
1735                  * save the merging progress in the drop_progress.
1736                  * this is OK since root refs == 1 in this case.
1737                  */
1738                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
1739                                path->slots[level]);
1740                 btrfs_set_root_drop_level(root_item, level);
1741
1742                 btrfs_end_transaction_throttle(trans);
1743                 trans = NULL;
1744
1745                 btrfs_btree_balance_dirty(fs_info);
1746
1747                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
1748                         invalidate_extent_cache(root, &key, &next_key);
1749         }
1750
1751         /*
1752          * handle the case only one block in the fs tree need to be
1753          * relocated and the block is tree root.
1754          */
1755         leaf = btrfs_lock_root_node(root);
1756         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf,
1757                               BTRFS_NESTING_COW);
1758         btrfs_tree_unlock(leaf);
1759         free_extent_buffer(leaf);
1760 out:
1761         btrfs_free_path(path);
1762
1763         if (ret == 0)
1764                 insert_dirty_subvol(trans, rc, root);
1765
1766         if (trans)
1767                 btrfs_end_transaction_throttle(trans);
1768
1769         btrfs_btree_balance_dirty(fs_info);
1770
1771         if (replaced && rc->stage == UPDATE_DATA_PTRS)
1772                 invalidate_extent_cache(root, &key, &next_key);
1773
1774         return ret;
1775 }
1776
1777 static noinline_for_stack
1778 int prepare_to_merge(struct reloc_control *rc, int err)
1779 {
1780         struct btrfs_root *root = rc->extent_root;
1781         struct btrfs_fs_info *fs_info = root->fs_info;
1782         struct btrfs_root *reloc_root;
1783         struct btrfs_trans_handle *trans;
1784         LIST_HEAD(reloc_roots);
1785         u64 num_bytes = 0;
1786         int ret;
1787
1788         mutex_lock(&fs_info->reloc_mutex);
1789         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
1790         rc->merging_rsv_size += rc->nodes_relocated * 2;
1791         mutex_unlock(&fs_info->reloc_mutex);
1792
1793 again:
1794         if (!err) {
1795                 num_bytes = rc->merging_rsv_size;
1796                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
1797                                           BTRFS_RESERVE_FLUSH_ALL);
1798                 if (ret)
1799                         err = ret;
1800         }
1801
1802         trans = btrfs_join_transaction(rc->extent_root);
1803         if (IS_ERR(trans)) {
1804                 if (!err)
1805                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
1806                                                 num_bytes, NULL);
1807                 return PTR_ERR(trans);
1808         }
1809
1810         if (!err) {
1811                 if (num_bytes != rc->merging_rsv_size) {
1812                         btrfs_end_transaction(trans);
1813                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
1814                                                 num_bytes, NULL);
1815                         goto again;
1816                 }
1817         }
1818
1819         rc->merge_reloc_tree = 1;
1820
1821         while (!list_empty(&rc->reloc_roots)) {
1822                 reloc_root = list_entry(rc->reloc_roots.next,
1823                                         struct btrfs_root, root_list);
1824                 list_del_init(&reloc_root->root_list);
1825
1826                 root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset,
1827                                 false);
1828                 BUG_ON(IS_ERR(root));
1829                 BUG_ON(root->reloc_root != reloc_root);
1830
1831                 /*
1832                  * set reference count to 1, so btrfs_recover_relocation
1833                  * knows it should resumes merging
1834                  */
1835                 if (!err)
1836                         btrfs_set_root_refs(&reloc_root->root_item, 1);
1837                 btrfs_update_reloc_root(trans, root);
1838
1839                 list_add(&reloc_root->root_list, &reloc_roots);
1840                 btrfs_put_root(root);
1841         }
1842
1843         list_splice(&reloc_roots, &rc->reloc_roots);
1844
1845         if (!err)
1846                 btrfs_commit_transaction(trans);
1847         else
1848                 btrfs_end_transaction(trans);
1849         return err;
1850 }
1851
1852 static noinline_for_stack
1853 void free_reloc_roots(struct list_head *list)
1854 {
1855         struct btrfs_root *reloc_root, *tmp;
1856
1857         list_for_each_entry_safe(reloc_root, tmp, list, root_list)
1858                 __del_reloc_root(reloc_root);
1859 }
1860
1861 static noinline_for_stack
1862 void merge_reloc_roots(struct reloc_control *rc)
1863 {
1864         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
1865         struct btrfs_root *root;
1866         struct btrfs_root *reloc_root;
1867         LIST_HEAD(reloc_roots);
1868         int found = 0;
1869         int ret = 0;
1870 again:
1871         root = rc->extent_root;
1872
1873         /*
1874          * this serializes us with btrfs_record_root_in_transaction,
1875          * we have to make sure nobody is in the middle of
1876          * adding their roots to the list while we are
1877          * doing this splice
1878          */
1879         mutex_lock(&fs_info->reloc_mutex);
1880         list_splice_init(&rc->reloc_roots, &reloc_roots);
1881         mutex_unlock(&fs_info->reloc_mutex);
1882
1883         while (!list_empty(&reloc_roots)) {
1884                 found = 1;
1885                 reloc_root = list_entry(reloc_roots.next,
1886                                         struct btrfs_root, root_list);
1887
1888                 root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset,
1889                                          false);
1890                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
1891                         BUG_ON(IS_ERR(root));
1892                         BUG_ON(root->reloc_root != reloc_root);
1893                         ret = merge_reloc_root(rc, root);
1894                         btrfs_put_root(root);
1895                         if (ret) {
1896                                 if (list_empty(&reloc_root->root_list))
1897                                         list_add_tail(&reloc_root->root_list,
1898                                                       &reloc_roots);
1899                                 goto out;
1900                         }
1901                 } else {
1902                         if (!IS_ERR(root)) {
1903                                 if (root->reloc_root == reloc_root) {
1904                                         root->reloc_root = NULL;
1905                                         btrfs_put_root(reloc_root);
1906                                 }
1907                                 clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE,
1908                                           &root->state);
1909                                 btrfs_put_root(root);
1910                         }
1911
1912                         list_del_init(&reloc_root->root_list);
1913                         /* Don't forget to queue this reloc root for cleanup */
1914                         list_add_tail(&reloc_root->reloc_dirty_list,
1915                                       &rc->dirty_subvol_roots);
1916                 }
1917         }
1918
1919         if (found) {
1920                 found = 0;
1921                 goto again;
1922         }
1923 out:
1924         if (ret) {
1925                 btrfs_handle_fs_error(fs_info, ret, NULL);
1926                 free_reloc_roots(&reloc_roots);
1927
1928                 /* new reloc root may be added */
1929                 mutex_lock(&fs_info->reloc_mutex);
1930                 list_splice_init(&rc->reloc_roots, &reloc_roots);
1931                 mutex_unlock(&fs_info->reloc_mutex);
1932                 free_reloc_roots(&reloc_roots);
1933         }
1934
1935         /*
1936          * We used to have
1937          *
1938          * BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
1939          *
1940          * here, but it's wrong.  If we fail to start the transaction in
1941          * prepare_to_merge() we will have only 0 ref reloc roots, none of which
1942          * have actually been removed from the reloc_root_tree rb tree.  This is
1943          * fine because we're bailing here, and we hold a reference on the root
1944          * for the list that holds it, so these roots will be cleaned up when we
1945          * do the reloc_dirty_list afterwards.  Meanwhile the root->reloc_root
1946          * will be cleaned up on unmount.
1947          *
1948          * The remaining nodes will be cleaned up by free_reloc_control.
1949          */
1950 }
1951
1952 static void free_block_list(struct rb_root *blocks)
1953 {
1954         struct tree_block *block;
1955         struct rb_node *rb_node;
1956         while ((rb_node = rb_first(blocks))) {
1957                 block = rb_entry(rb_node, struct tree_block, rb_node);
1958                 rb_erase(rb_node, blocks);
1959                 kfree(block);
1960         }
1961 }
1962
1963 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
1964                                       struct btrfs_root *reloc_root)
1965 {
1966         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
1967         struct btrfs_root *root;
1968         int ret;
1969
1970         if (reloc_root->last_trans == trans->transid)
1971                 return 0;
1972
1973         root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset, false);
1974         BUG_ON(IS_ERR(root));
1975         BUG_ON(root->reloc_root != reloc_root);
1976         ret = btrfs_record_root_in_trans(trans, root);
1977         btrfs_put_root(root);
1978
1979         return ret;
1980 }
1981
1982 static noinline_for_stack
1983 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
1984                                      struct reloc_control *rc,
1985                                      struct btrfs_backref_node *node,
1986                                      struct btrfs_backref_edge *edges[])
1987 {
1988         struct btrfs_backref_node *next;
1989         struct btrfs_root *root;
1990         int index = 0;
1991
1992         next = node;
1993         while (1) {
1994                 cond_resched();
1995                 next = walk_up_backref(next, edges, &index);
1996                 root = next->root;
1997                 BUG_ON(!root);
1998                 BUG_ON(!test_bit(BTRFS_ROOT_SHAREABLE, &root->state));
1999
2000                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2001                         record_reloc_root_in_trans(trans, root);
2002                         break;
2003                 }
2004
2005                 btrfs_record_root_in_trans(trans, root);
2006                 root = root->reloc_root;
2007
2008                 if (next->new_bytenr != root->node->start) {
2009                         BUG_ON(next->new_bytenr);
2010                         BUG_ON(!list_empty(&next->list));
2011                         next->new_bytenr = root->node->start;
2012                         btrfs_put_root(next->root);
2013                         next->root = btrfs_grab_root(root);
2014                         ASSERT(next->root);
2015                         list_add_tail(&next->list,
2016                                       &rc->backref_cache.changed);
2017                         mark_block_processed(rc, next);
2018                         break;
2019                 }
2020
2021                 WARN_ON(1);
2022                 root = NULL;
2023                 next = walk_down_backref(edges, &index);
2024                 if (!next || next->level <= node->level)
2025                         break;
2026         }
2027         if (!root)
2028                 return NULL;
2029
2030         next = node;
2031         /* setup backref node path for btrfs_reloc_cow_block */
2032         while (1) {
2033                 rc->backref_cache.path[next->level] = next;
2034                 if (--index < 0)
2035                         break;
2036                 next = edges[index]->node[UPPER];
2037         }
2038         return root;
2039 }
2040
2041 /*
2042  * Select a tree root for relocation.
2043  *
2044  * Return NULL if the block is not shareable. We should use do_relocation() in
2045  * this case.
2046  *
2047  * Return a tree root pointer if the block is shareable.
2048  * Return -ENOENT if the block is root of reloc tree.
2049  */
2050 static noinline_for_stack
2051 struct btrfs_root *select_one_root(struct btrfs_backref_node *node)
2052 {
2053         struct btrfs_backref_node *next;
2054         struct btrfs_root *root;
2055         struct btrfs_root *fs_root = NULL;
2056         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2057         int index = 0;
2058
2059         next = node;
2060         while (1) {
2061                 cond_resched();
2062                 next = walk_up_backref(next, edges, &index);
2063                 root = next->root;
2064                 BUG_ON(!root);
2065
2066                 /* No other choice for non-shareable tree */
2067                 if (!test_bit(BTRFS_ROOT_SHAREABLE, &root->state))
2068                         return root;
2069
2070                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2071                         fs_root = root;
2072
2073                 if (next != node)
2074                         return NULL;
2075
2076                 next = walk_down_backref(edges, &index);
2077                 if (!next || next->level <= node->level)
2078                         break;
2079         }
2080
2081         if (!fs_root)
2082                 return ERR_PTR(-ENOENT);
2083         return fs_root;
2084 }
2085
2086 static noinline_for_stack
2087 u64 calcu_metadata_size(struct reloc_control *rc,
2088                         struct btrfs_backref_node *node, int reserve)
2089 {
2090         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2091         struct btrfs_backref_node *next = node;
2092         struct btrfs_backref_edge *edge;
2093         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2094         u64 num_bytes = 0;
2095         int index = 0;
2096
2097         BUG_ON(reserve && node->processed);
2098
2099         while (next) {
2100                 cond_resched();
2101                 while (1) {
2102                         if (next->processed && (reserve || next != node))
2103                                 break;
2104
2105                         num_bytes += fs_info->nodesize;
2106
2107                         if (list_empty(&next->upper))
2108                                 break;
2109
2110                         edge = list_entry(next->upper.next,
2111                                         struct btrfs_backref_edge, list[LOWER]);
2112                         edges[index++] = edge;
2113                         next = edge->node[UPPER];
2114                 }
2115                 next = walk_down_backref(edges, &index);
2116         }
2117         return num_bytes;
2118 }
2119
2120 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2121                                   struct reloc_control *rc,
2122                                   struct btrfs_backref_node *node)
2123 {
2124         struct btrfs_root *root = rc->extent_root;
2125         struct btrfs_fs_info *fs_info = root->fs_info;
2126         u64 num_bytes;
2127         int ret;
2128         u64 tmp;
2129
2130         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2131
2132         trans->block_rsv = rc->block_rsv;
2133         rc->reserved_bytes += num_bytes;
2134
2135         /*
2136          * We are under a transaction here so we can only do limited flushing.
2137          * If we get an enospc just kick back -EAGAIN so we know to drop the
2138          * transaction and try to refill when we can flush all the things.
2139          */
2140         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2141                                 BTRFS_RESERVE_FLUSH_LIMIT);
2142         if (ret) {
2143                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2144                 while (tmp <= rc->reserved_bytes)
2145                         tmp <<= 1;
2146                 /*
2147                  * only one thread can access block_rsv at this point,
2148                  * so we don't need hold lock to protect block_rsv.
2149                  * we expand more reservation size here to allow enough
2150                  * space for relocation and we will return earlier in
2151                  * enospc case.
2152                  */
2153                 rc->block_rsv->size = tmp + fs_info->nodesize *
2154                                       RELOCATION_RESERVED_NODES;
2155                 return -EAGAIN;
2156         }
2157
2158         return 0;
2159 }
2160
2161 /*
2162  * relocate a block tree, and then update pointers in upper level
2163  * blocks that reference the block to point to the new location.
2164  *
2165  * if called by link_to_upper, the block has already been relocated.
2166  * in that case this function just updates pointers.
2167  */
2168 static int do_relocation(struct btrfs_trans_handle *trans,
2169                          struct reloc_control *rc,
2170                          struct btrfs_backref_node *node,
2171                          struct btrfs_key *key,
2172                          struct btrfs_path *path, int lowest)
2173 {
2174         struct btrfs_backref_node *upper;
2175         struct btrfs_backref_edge *edge;
2176         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2177         struct btrfs_root *root;
2178         struct extent_buffer *eb;
2179         u32 blocksize;
2180         u64 bytenr;
2181         int slot;
2182         int ret = 0;
2183
2184         BUG_ON(lowest && node->eb);
2185
2186         path->lowest_level = node->level + 1;
2187         rc->backref_cache.path[node->level] = node;
2188         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2189                 struct btrfs_ref ref = { 0 };
2190
2191                 cond_resched();
2192
2193                 upper = edge->node[UPPER];
2194                 root = select_reloc_root(trans, rc, upper, edges);
2195                 BUG_ON(!root);
2196
2197                 if (upper->eb && !upper->locked) {
2198                         if (!lowest) {
2199                                 ret = btrfs_bin_search(upper->eb, key, &slot);
2200                                 if (ret < 0)
2201                                         goto next;
2202                                 BUG_ON(ret);
2203                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2204                                 if (node->eb->start == bytenr)
2205                                         goto next;
2206                         }
2207                         btrfs_backref_drop_node_buffer(upper);
2208                 }
2209
2210                 if (!upper->eb) {
2211                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2212                         if (ret) {
2213                                 if (ret > 0)
2214                                         ret = -ENOENT;
2215
2216                                 btrfs_release_path(path);
2217                                 break;
2218                         }
2219
2220                         if (!upper->eb) {
2221                                 upper->eb = path->nodes[upper->level];
2222                                 path->nodes[upper->level] = NULL;
2223                         } else {
2224                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2225                         }
2226
2227                         upper->locked = 1;
2228                         path->locks[upper->level] = 0;
2229
2230                         slot = path->slots[upper->level];
2231                         btrfs_release_path(path);
2232                 } else {
2233                         ret = btrfs_bin_search(upper->eb, key, &slot);
2234                         if (ret < 0)
2235                                 goto next;
2236                         BUG_ON(ret);
2237                 }
2238
2239                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2240                 if (lowest) {
2241                         if (bytenr != node->bytenr) {
2242                                 btrfs_err(root->fs_info,
2243                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2244                                           bytenr, node->bytenr, slot,
2245                                           upper->eb->start);
2246                                 ret = -EIO;
2247                                 goto next;
2248                         }
2249                 } else {
2250                         if (node->eb->start == bytenr)
2251                                 goto next;
2252                 }
2253
2254                 blocksize = root->fs_info->nodesize;
2255                 eb = btrfs_read_node_slot(upper->eb, slot);
2256                 if (IS_ERR(eb)) {
2257                         ret = PTR_ERR(eb);
2258                         goto next;
2259                 }
2260                 btrfs_tree_lock(eb);
2261
2262                 if (!node->eb) {
2263                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2264                                               slot, &eb, BTRFS_NESTING_COW);
2265                         btrfs_tree_unlock(eb);
2266                         free_extent_buffer(eb);
2267                         if (ret < 0)
2268                                 goto next;
2269                         BUG_ON(node->eb != eb);
2270                 } else {
2271                         btrfs_set_node_blockptr(upper->eb, slot,
2272                                                 node->eb->start);
2273                         btrfs_set_node_ptr_generation(upper->eb, slot,
2274                                                       trans->transid);
2275                         btrfs_mark_buffer_dirty(upper->eb);
2276
2277                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
2278                                                node->eb->start, blocksize,
2279                                                upper->eb->start);
2280                         ref.real_root = root->root_key.objectid;
2281                         btrfs_init_tree_ref(&ref, node->level,
2282                                             btrfs_header_owner(upper->eb));
2283                         ret = btrfs_inc_extent_ref(trans, &ref);
2284                         BUG_ON(ret);
2285
2286                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
2287                         BUG_ON(ret);
2288                 }
2289 next:
2290                 if (!upper->pending)
2291                         btrfs_backref_drop_node_buffer(upper);
2292                 else
2293                         btrfs_backref_unlock_node_buffer(upper);
2294                 if (ret)
2295                         break;
2296         }
2297
2298         if (!ret && node->pending) {
2299                 btrfs_backref_drop_node_buffer(node);
2300                 list_move_tail(&node->list, &rc->backref_cache.changed);
2301                 node->pending = 0;
2302         }
2303
2304         path->lowest_level = 0;
2305         BUG_ON(ret == -ENOSPC);
2306         return ret;
2307 }
2308
2309 static int link_to_upper(struct btrfs_trans_handle *trans,
2310                          struct reloc_control *rc,
2311                          struct btrfs_backref_node *node,
2312                          struct btrfs_path *path)
2313 {
2314         struct btrfs_key key;
2315
2316         btrfs_node_key_to_cpu(node->eb, &key, 0);
2317         return do_relocation(trans, rc, node, &key, path, 0);
2318 }
2319
2320 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
2321                                 struct reloc_control *rc,
2322                                 struct btrfs_path *path, int err)
2323 {
2324         LIST_HEAD(list);
2325         struct btrfs_backref_cache *cache = &rc->backref_cache;
2326         struct btrfs_backref_node *node;
2327         int level;
2328         int ret;
2329
2330         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
2331                 while (!list_empty(&cache->pending[level])) {
2332                         node = list_entry(cache->pending[level].next,
2333                                           struct btrfs_backref_node, list);
2334                         list_move_tail(&node->list, &list);
2335                         BUG_ON(!node->pending);
2336
2337                         if (!err) {
2338                                 ret = link_to_upper(trans, rc, node, path);
2339                                 if (ret < 0)
2340                                         err = ret;
2341                         }
2342                 }
2343                 list_splice_init(&list, &cache->pending[level]);
2344         }
2345         return err;
2346 }
2347
2348 /*
2349  * mark a block and all blocks directly/indirectly reference the block
2350  * as processed.
2351  */
2352 static void update_processed_blocks(struct reloc_control *rc,
2353                                     struct btrfs_backref_node *node)
2354 {
2355         struct btrfs_backref_node *next = node;
2356         struct btrfs_backref_edge *edge;
2357         struct btrfs_backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2358         int index = 0;
2359
2360         while (next) {
2361                 cond_resched();
2362                 while (1) {
2363                         if (next->processed)
2364                                 break;
2365
2366                         mark_block_processed(rc, next);
2367
2368                         if (list_empty(&next->upper))
2369                                 break;
2370
2371                         edge = list_entry(next->upper.next,
2372                                         struct btrfs_backref_edge, list[LOWER]);
2373                         edges[index++] = edge;
2374                         next = edge->node[UPPER];
2375                 }
2376                 next = walk_down_backref(edges, &index);
2377         }
2378 }
2379
2380 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
2381 {
2382         u32 blocksize = rc->extent_root->fs_info->nodesize;
2383
2384         if (test_range_bit(&rc->processed_blocks, bytenr,
2385                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
2386                 return 1;
2387         return 0;
2388 }
2389
2390 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
2391                               struct tree_block *block)
2392 {
2393         struct extent_buffer *eb;
2394
2395         eb = read_tree_block(fs_info, block->bytenr, block->owner,
2396                              block->key.offset, block->level, NULL);
2397         if (IS_ERR(eb)) {
2398                 return PTR_ERR(eb);
2399         } else if (!extent_buffer_uptodate(eb)) {
2400                 free_extent_buffer(eb);
2401                 return -EIO;
2402         }
2403         if (block->level == 0)
2404                 btrfs_item_key_to_cpu(eb, &block->key, 0);
2405         else
2406                 btrfs_node_key_to_cpu(eb, &block->key, 0);
2407         free_extent_buffer(eb);
2408         block->key_ready = 1;
2409         return 0;
2410 }
2411
2412 /*
2413  * helper function to relocate a tree block
2414  */
2415 static int relocate_tree_block(struct btrfs_trans_handle *trans,
2416                                 struct reloc_control *rc,
2417                                 struct btrfs_backref_node *node,
2418                                 struct btrfs_key *key,
2419                                 struct btrfs_path *path)
2420 {
2421         struct btrfs_root *root;
2422         int ret = 0;
2423
2424         if (!node)
2425                 return 0;
2426
2427         /*
2428          * If we fail here we want to drop our backref_node because we are going
2429          * to start over and regenerate the tree for it.
2430          */
2431         ret = reserve_metadata_space(trans, rc, node);
2432         if (ret)
2433                 goto out;
2434
2435         BUG_ON(node->processed);
2436         root = select_one_root(node);
2437         if (root == ERR_PTR(-ENOENT)) {
2438                 update_processed_blocks(rc, node);
2439                 goto out;
2440         }
2441
2442         if (root) {
2443                 if (test_bit(BTRFS_ROOT_SHAREABLE, &root->state)) {
2444                         BUG_ON(node->new_bytenr);
2445                         BUG_ON(!list_empty(&node->list));
2446                         btrfs_record_root_in_trans(trans, root);
2447                         root = root->reloc_root;
2448                         node->new_bytenr = root->node->start;
2449                         btrfs_put_root(node->root);
2450                         node->root = btrfs_grab_root(root);
2451                         ASSERT(node->root);
2452                         list_add_tail(&node->list, &rc->backref_cache.changed);
2453                 } else {
2454                         path->lowest_level = node->level;
2455                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2456                         btrfs_release_path(path);
2457                         if (ret > 0)
2458                                 ret = 0;
2459                 }
2460                 if (!ret)
2461                         update_processed_blocks(rc, node);
2462         } else {
2463                 ret = do_relocation(trans, rc, node, key, path, 1);
2464         }
2465 out:
2466         if (ret || node->level == 0 || node->cowonly)
2467                 btrfs_backref_cleanup_node(&rc->backref_cache, node);
2468         return ret;
2469 }
2470
2471 /*
2472  * relocate a list of blocks
2473  */
2474 static noinline_for_stack
2475 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
2476                          struct reloc_control *rc, struct rb_root *blocks)
2477 {
2478         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2479         struct btrfs_backref_node *node;
2480         struct btrfs_path *path;
2481         struct tree_block *block;
2482         struct tree_block *next;
2483         int ret;
2484         int err = 0;
2485
2486         path = btrfs_alloc_path();
2487         if (!path) {
2488                 err = -ENOMEM;
2489                 goto out_free_blocks;
2490         }
2491
2492         /* Kick in readahead for tree blocks with missing keys */
2493         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2494                 if (!block->key_ready)
2495                         btrfs_readahead_tree_block(fs_info, block->bytenr,
2496                                                    block->owner, 0,
2497                                                    block->level);
2498         }
2499
2500         /* Get first keys */
2501         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2502                 if (!block->key_ready) {
2503                         err = get_tree_block_key(fs_info, block);
2504                         if (err)
2505                                 goto out_free_path;
2506                 }
2507         }
2508
2509         /* Do tree relocation */
2510         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
2511                 node = build_backref_tree(rc, &block->key,
2512                                           block->level, block->bytenr);
2513                 if (IS_ERR(node)) {
2514                         err = PTR_ERR(node);
2515                         goto out;
2516                 }
2517
2518                 ret = relocate_tree_block(trans, rc, node, &block->key,
2519                                           path);
2520                 if (ret < 0) {
2521                         err = ret;
2522                         break;
2523                 }
2524         }
2525 out:
2526         err = finish_pending_nodes(trans, rc, path, err);
2527
2528 out_free_path:
2529         btrfs_free_path(path);
2530 out_free_blocks:
2531         free_block_list(blocks);
2532         return err;
2533 }
2534
2535 static noinline_for_stack int prealloc_file_extent_cluster(
2536                                 struct btrfs_inode *inode,
2537                                 struct file_extent_cluster *cluster)
2538 {
2539         u64 alloc_hint = 0;
2540         u64 start;
2541         u64 end;
2542         u64 offset = inode->index_cnt;
2543         u64 num_bytes;
2544         int nr;
2545         int ret = 0;
2546         u64 prealloc_start = cluster->start - offset;
2547         u64 prealloc_end = cluster->end - offset;
2548         u64 cur_offset = prealloc_start;
2549
2550         BUG_ON(cluster->start != cluster->boundary[0]);
2551         ret = btrfs_alloc_data_chunk_ondemand(inode,
2552                                               prealloc_end + 1 - prealloc_start);
2553         if (ret)
2554                 return ret;
2555
2556         /*
2557          * On a zoned filesystem, we cannot preallocate the file region.
2558          * Instead, we dirty and fiemap_write the region.
2559          */
2560         if (btrfs_is_zoned(inode->root->fs_info)) {
2561                 struct btrfs_root *root = inode->root;
2562                 struct btrfs_trans_handle *trans;
2563
2564                 end = cluster->end - offset + 1;
2565                 trans = btrfs_start_transaction(root, 1);
2566                 if (IS_ERR(trans))
2567                         return PTR_ERR(trans);
2568
2569                 inode->vfs_inode.i_ctime = current_time(&inode->vfs_inode);
2570                 i_size_write(&inode->vfs_inode, end);
2571                 ret = btrfs_update_inode(trans, root, inode);
2572                 if (ret) {
2573                         btrfs_abort_transaction(trans, ret);
2574                         btrfs_end_transaction(trans);
2575                         return ret;
2576                 }
2577
2578                 return btrfs_end_transaction(trans);
2579         }
2580
2581         inode_lock(&inode->vfs_inode);
2582         for (nr = 0; nr < cluster->nr; nr++) {
2583                 start = cluster->boundary[nr] - offset;
2584                 if (nr + 1 < cluster->nr)
2585                         end = cluster->boundary[nr + 1] - 1 - offset;
2586                 else
2587                         end = cluster->end - offset;
2588
2589                 lock_extent(&inode->io_tree, start, end);
2590                 num_bytes = end + 1 - start;
2591                 ret = btrfs_prealloc_file_range(&inode->vfs_inode, 0, start,
2592                                                 num_bytes, num_bytes,
2593                                                 end + 1, &alloc_hint);
2594                 cur_offset = end + 1;
2595                 unlock_extent(&inode->io_tree, start, end);
2596                 if (ret)
2597                         break;
2598         }
2599         inode_unlock(&inode->vfs_inode);
2600
2601         if (cur_offset < prealloc_end)
2602                 btrfs_free_reserved_data_space_noquota(inode->root->fs_info,
2603                                                prealloc_end + 1 - cur_offset);
2604         return ret;
2605 }
2606
2607 static noinline_for_stack
2608 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
2609                          u64 block_start)
2610 {
2611         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
2612         struct extent_map *em;
2613         int ret = 0;
2614
2615         em = alloc_extent_map();
2616         if (!em)
2617                 return -ENOMEM;
2618
2619         em->start = start;
2620         em->len = end + 1 - start;
2621         em->block_len = em->len;
2622         em->block_start = block_start;
2623         set_bit(EXTENT_FLAG_PINNED, &em->flags);
2624
2625         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2626         while (1) {
2627                 write_lock(&em_tree->lock);
2628                 ret = add_extent_mapping(em_tree, em, 0);
2629                 write_unlock(&em_tree->lock);
2630                 if (ret != -EEXIST) {
2631                         free_extent_map(em);
2632                         break;
2633                 }
2634                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
2635         }
2636         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2637         return ret;
2638 }
2639
2640 /*
2641  * Allow error injection to test balance cancellation
2642  */
2643 noinline int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
2644 {
2645         return atomic_read(&fs_info->balance_cancel_req) ||
2646                 fatal_signal_pending(current);
2647 }
2648 ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
2649
2650 static int relocate_file_extent_cluster(struct inode *inode,
2651                                         struct file_extent_cluster *cluster)
2652 {
2653         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
2654         u64 page_start;
2655         u64 page_end;
2656         u64 offset = BTRFS_I(inode)->index_cnt;
2657         unsigned long index;
2658         unsigned long last_index;
2659         struct page *page;
2660         struct file_ra_state *ra;
2661         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
2662         int nr = 0;
2663         int ret = 0;
2664
2665         if (!cluster->nr)
2666                 return 0;
2667
2668         ra = kzalloc(sizeof(*ra), GFP_NOFS);
2669         if (!ra)
2670                 return -ENOMEM;
2671
2672         ret = prealloc_file_extent_cluster(BTRFS_I(inode), cluster);
2673         if (ret)
2674                 goto out;
2675
2676         file_ra_state_init(ra, inode->i_mapping);
2677
2678         ret = setup_extent_mapping(inode, cluster->start - offset,
2679                                    cluster->end - offset, cluster->start);
2680         if (ret)
2681                 goto out;
2682
2683         index = (cluster->start - offset) >> PAGE_SHIFT;
2684         last_index = (cluster->end - offset) >> PAGE_SHIFT;
2685         while (index <= last_index) {
2686                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
2687                                 PAGE_SIZE);
2688                 if (ret)
2689                         goto out;
2690
2691                 page = find_lock_page(inode->i_mapping, index);
2692                 if (!page) {
2693                         page_cache_sync_readahead(inode->i_mapping,
2694                                                   ra, NULL, index,
2695                                                   last_index + 1 - index);
2696                         page = find_or_create_page(inode->i_mapping, index,
2697                                                    mask);
2698                         if (!page) {
2699                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
2700                                                         PAGE_SIZE, true);
2701                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
2702                                                         PAGE_SIZE);
2703                                 ret = -ENOMEM;
2704                                 goto out;
2705                         }
2706                 }
2707                 ret = set_page_extent_mapped(page);
2708                 if (ret < 0) {
2709                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
2710                                                         PAGE_SIZE, true);
2711                         btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
2712                         unlock_page(page);
2713                         put_page(page);
2714                         goto out;
2715                 }
2716
2717                 if (PageReadahead(page)) {
2718                         page_cache_async_readahead(inode->i_mapping,
2719                                                    ra, NULL, page, index,
2720                                                    last_index + 1 - index);
2721                 }
2722
2723                 if (!PageUptodate(page)) {
2724                         btrfs_readpage(NULL, page);
2725                         lock_page(page);
2726                         if (!PageUptodate(page)) {
2727                                 unlock_page(page);
2728                                 put_page(page);
2729                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
2730                                                         PAGE_SIZE, true);
2731                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
2732                                                                PAGE_SIZE);
2733                                 ret = -EIO;
2734                                 goto out;
2735                         }
2736                 }
2737
2738                 page_start = page_offset(page);
2739                 page_end = page_start + PAGE_SIZE - 1;
2740
2741                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
2742
2743                 if (nr < cluster->nr &&
2744                     page_start + offset == cluster->boundary[nr]) {
2745                         set_extent_bits(&BTRFS_I(inode)->io_tree,
2746                                         page_start, page_end,
2747                                         EXTENT_BOUNDARY);
2748                         nr++;
2749                 }
2750
2751                 ret = btrfs_set_extent_delalloc(BTRFS_I(inode), page_start,
2752                                                 page_end, 0, NULL);
2753                 if (ret) {
2754                         unlock_page(page);
2755                         put_page(page);
2756                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
2757                                                          PAGE_SIZE, true);
2758                         btrfs_delalloc_release_extents(BTRFS_I(inode),
2759                                                        PAGE_SIZE);
2760
2761                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
2762                                           page_start, page_end,
2763                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
2764                         goto out;
2765
2766                 }
2767                 set_page_dirty(page);
2768
2769                 unlock_extent(&BTRFS_I(inode)->io_tree,
2770                               page_start, page_end);
2771                 unlock_page(page);
2772                 put_page(page);
2773
2774                 index++;
2775                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
2776                 balance_dirty_pages_ratelimited(inode->i_mapping);
2777                 btrfs_throttle(fs_info);
2778                 if (btrfs_should_cancel_balance(fs_info)) {
2779                         ret = -ECANCELED;
2780                         goto out;
2781                 }
2782         }
2783         WARN_ON(nr != cluster->nr);
2784         if (btrfs_is_zoned(fs_info) && !ret)
2785                 ret = btrfs_wait_ordered_range(inode, 0, (u64)-1);
2786 out:
2787         kfree(ra);
2788         return ret;
2789 }
2790
2791 static noinline_for_stack
2792 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
2793                          struct file_extent_cluster *cluster)
2794 {
2795         int ret;
2796
2797         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
2798                 ret = relocate_file_extent_cluster(inode, cluster);
2799                 if (ret)
2800                         return ret;
2801                 cluster->nr = 0;
2802         }
2803
2804         if (!cluster->nr)
2805                 cluster->start = extent_key->objectid;
2806         else
2807                 BUG_ON(cluster->nr >= MAX_EXTENTS);
2808         cluster->end = extent_key->objectid + extent_key->offset - 1;
2809         cluster->boundary[cluster->nr] = extent_key->objectid;
2810         cluster->nr++;
2811
2812         if (cluster->nr >= MAX_EXTENTS) {
2813                 ret = relocate_file_extent_cluster(inode, cluster);
2814                 if (ret)
2815                         return ret;
2816                 cluster->nr = 0;
2817         }
2818         return 0;
2819 }
2820
2821 /*
2822  * helper to add a tree block to the list.
2823  * the major work is getting the generation and level of the block
2824  */
2825 static int add_tree_block(struct reloc_control *rc,
2826                           struct btrfs_key *extent_key,
2827                           struct btrfs_path *path,
2828                           struct rb_root *blocks)
2829 {
2830         struct extent_buffer *eb;
2831         struct btrfs_extent_item *ei;
2832         struct btrfs_tree_block_info *bi;
2833         struct tree_block *block;
2834         struct rb_node *rb_node;
2835         u32 item_size;
2836         int level = -1;
2837         u64 generation;
2838         u64 owner = 0;
2839
2840         eb =  path->nodes[0];
2841         item_size = btrfs_item_size_nr(eb, path->slots[0]);
2842
2843         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
2844             item_size >= sizeof(*ei) + sizeof(*bi)) {
2845                 unsigned long ptr = 0, end;
2846
2847                 ei = btrfs_item_ptr(eb, path->slots[0],
2848                                 struct btrfs_extent_item);
2849                 end = (unsigned long)ei + item_size;
2850                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
2851                         bi = (struct btrfs_tree_block_info *)(ei + 1);
2852                         level = btrfs_tree_block_level(eb, bi);
2853                         ptr = (unsigned long)(bi + 1);
2854                 } else {
2855                         level = (int)extent_key->offset;
2856                         ptr = (unsigned long)(ei + 1);
2857                 }
2858                 generation = btrfs_extent_generation(eb, ei);
2859
2860                 /*
2861                  * We're reading random blocks without knowing their owner ahead
2862                  * of time.  This is ok most of the time, as all reloc roots and
2863                  * fs roots have the same lock type.  However normal trees do
2864                  * not, and the only way to know ahead of time is to read the
2865                  * inline ref offset.  We know it's an fs root if
2866                  *
2867                  * 1. There's more than one ref.
2868                  * 2. There's a SHARED_DATA_REF_KEY set.
2869                  * 3. FULL_BACKREF is set on the flags.
2870                  *
2871                  * Otherwise it's safe to assume that the ref offset == the
2872                  * owner of this block, so we can use that when calling
2873                  * read_tree_block.
2874                  */
2875                 if (btrfs_extent_refs(eb, ei) == 1 &&
2876                     !(btrfs_extent_flags(eb, ei) &
2877                       BTRFS_BLOCK_FLAG_FULL_BACKREF) &&
2878                     ptr < end) {
2879                         struct btrfs_extent_inline_ref *iref;
2880                         int type;
2881
2882                         iref = (struct btrfs_extent_inline_ref *)ptr;
2883                         type = btrfs_get_extent_inline_ref_type(eb, iref,
2884                                                         BTRFS_REF_TYPE_BLOCK);
2885                         if (type == BTRFS_REF_TYPE_INVALID)
2886                                 return -EINVAL;
2887                         if (type == BTRFS_TREE_BLOCK_REF_KEY)
2888                                 owner = btrfs_extent_inline_ref_offset(eb, iref);
2889                 }
2890         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
2891                 btrfs_print_v0_err(eb->fs_info);
2892                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
2893                 return -EINVAL;
2894         } else {
2895                 BUG();
2896         }
2897
2898         btrfs_release_path(path);
2899
2900         BUG_ON(level == -1);
2901
2902         block = kmalloc(sizeof(*block), GFP_NOFS);
2903         if (!block)
2904                 return -ENOMEM;
2905
2906         block->bytenr = extent_key->objectid;
2907         block->key.objectid = rc->extent_root->fs_info->nodesize;
2908         block->key.offset = generation;
2909         block->level = level;
2910         block->key_ready = 0;
2911         block->owner = owner;
2912
2913         rb_node = rb_simple_insert(blocks, block->bytenr, &block->rb_node);
2914         if (rb_node)
2915                 btrfs_backref_panic(rc->extent_root->fs_info, block->bytenr,
2916                                     -EEXIST);
2917
2918         return 0;
2919 }
2920
2921 /*
2922  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
2923  */
2924 static int __add_tree_block(struct reloc_control *rc,
2925                             u64 bytenr, u32 blocksize,
2926                             struct rb_root *blocks)
2927 {
2928         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2929         struct btrfs_path *path;
2930         struct btrfs_key key;
2931         int ret;
2932         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
2933
2934         if (tree_block_processed(bytenr, rc))
2935                 return 0;
2936
2937         if (rb_simple_search(blocks, bytenr))
2938                 return 0;
2939
2940         path = btrfs_alloc_path();
2941         if (!path)
2942                 return -ENOMEM;
2943 again:
2944         key.objectid = bytenr;
2945         if (skinny) {
2946                 key.type = BTRFS_METADATA_ITEM_KEY;
2947                 key.offset = (u64)-1;
2948         } else {
2949                 key.type = BTRFS_EXTENT_ITEM_KEY;
2950                 key.offset = blocksize;
2951         }
2952
2953         path->search_commit_root = 1;
2954         path->skip_locking = 1;
2955         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
2956         if (ret < 0)
2957                 goto out;
2958
2959         if (ret > 0 && skinny) {
2960                 if (path->slots[0]) {
2961                         path->slots[0]--;
2962                         btrfs_item_key_to_cpu(path->nodes[0], &key,
2963                                               path->slots[0]);
2964                         if (key.objectid == bytenr &&
2965                             (key.type == BTRFS_METADATA_ITEM_KEY ||
2966                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
2967                               key.offset == blocksize)))
2968                                 ret = 0;
2969                 }
2970
2971                 if (ret) {
2972                         skinny = false;
2973                         btrfs_release_path(path);
2974                         goto again;
2975                 }
2976         }
2977         if (ret) {
2978                 ASSERT(ret == 1);
2979                 btrfs_print_leaf(path->nodes[0]);
2980                 btrfs_err(fs_info,
2981              "tree block extent item (%llu) is not found in extent tree",
2982                      bytenr);
2983                 WARN_ON(1);
2984                 ret = -EINVAL;
2985                 goto out;
2986         }
2987
2988         ret = add_tree_block(rc, &key, path, blocks);
2989 out:
2990         btrfs_free_path(path);
2991         return ret;
2992 }
2993
2994 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
2995                                     struct btrfs_block_group *block_group,
2996                                     struct inode *inode,
2997                                     u64 ino)
2998 {
2999         struct btrfs_root *root = fs_info->tree_root;
3000         struct btrfs_trans_handle *trans;
3001         int ret = 0;
3002
3003         if (inode)
3004                 goto truncate;
3005
3006         inode = btrfs_iget(fs_info->sb, ino, root);
3007         if (IS_ERR(inode))
3008                 return -ENOENT;
3009
3010 truncate:
3011         ret = btrfs_check_trunc_cache_free_space(fs_info,
3012                                                  &fs_info->global_block_rsv);
3013         if (ret)
3014                 goto out;
3015
3016         trans = btrfs_join_transaction(root);
3017         if (IS_ERR(trans)) {
3018                 ret = PTR_ERR(trans);
3019                 goto out;
3020         }
3021
3022         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3023
3024         btrfs_end_transaction(trans);
3025         btrfs_btree_balance_dirty(fs_info);
3026 out:
3027         iput(inode);
3028         return ret;
3029 }
3030
3031 /*
3032  * Locate the free space cache EXTENT_DATA in root tree leaf and delete the
3033  * cache inode, to avoid free space cache data extent blocking data relocation.
3034  */
3035 static int delete_v1_space_cache(struct extent_buffer *leaf,
3036                                  struct btrfs_block_group *block_group,
3037                                  u64 data_bytenr)
3038 {
3039         u64 space_cache_ino;
3040         struct btrfs_file_extent_item *ei;
3041         struct btrfs_key key;
3042         bool found = false;
3043         int i;
3044         int ret;
3045
3046         if (btrfs_header_owner(leaf) != BTRFS_ROOT_TREE_OBJECTID)
3047                 return 0;
3048
3049         for (i = 0; i < btrfs_header_nritems(leaf); i++) {
3050                 u8 type;
3051
3052                 btrfs_item_key_to_cpu(leaf, &key, i);
3053                 if (key.type != BTRFS_EXTENT_DATA_KEY)
3054                         continue;
3055                 ei = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
3056                 type = btrfs_file_extent_type(leaf, ei);
3057
3058                 if ((type == BTRFS_FILE_EXTENT_REG ||
3059                      type == BTRFS_FILE_EXTENT_PREALLOC) &&
3060                     btrfs_file_extent_disk_bytenr(leaf, ei) == data_bytenr) {
3061                         found = true;
3062                         space_cache_ino = key.objectid;
3063                         break;
3064                 }
3065         }
3066         if (!found)
3067                 return -ENOENT;
3068         ret = delete_block_group_cache(leaf->fs_info, block_group, NULL,
3069                                         space_cache_ino);
3070         return ret;
3071 }
3072
3073 /*
3074  * helper to find all tree blocks that reference a given data extent
3075  */
3076 static noinline_for_stack
3077 int add_data_references(struct reloc_control *rc,
3078                         struct btrfs_key *extent_key,
3079                         struct btrfs_path *path,
3080                         struct rb_root *blocks)
3081 {
3082         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3083         struct ulist *leaves = NULL;
3084         struct ulist_iterator leaf_uiter;
3085         struct ulist_node *ref_node = NULL;
3086         const u32 blocksize = fs_info->nodesize;
3087         int ret = 0;
3088
3089         btrfs_release_path(path);
3090         ret = btrfs_find_all_leafs(NULL, fs_info, extent_key->objectid,
3091                                    0, &leaves, NULL, true);
3092         if (ret < 0)
3093                 return ret;
3094
3095         ULIST_ITER_INIT(&leaf_uiter);
3096         while ((ref_node = ulist_next(leaves, &leaf_uiter))) {
3097                 struct extent_buffer *eb;
3098
3099                 eb = read_tree_block(fs_info, ref_node->val, 0, 0, 0, NULL);
3100                 if (IS_ERR(eb)) {
3101                         ret = PTR_ERR(eb);
3102                         break;
3103                 }
3104                 ret = delete_v1_space_cache(eb, rc->block_group,
3105                                             extent_key->objectid);
3106                 free_extent_buffer(eb);
3107                 if (ret < 0)
3108                         break;
3109                 ret = __add_tree_block(rc, ref_node->val, blocksize, blocks);
3110                 if (ret < 0)
3111                         break;
3112         }
3113         if (ret < 0)
3114                 free_block_list(blocks);
3115         ulist_free(leaves);
3116         return ret;
3117 }
3118
3119 /*
3120  * helper to find next unprocessed extent
3121  */
3122 static noinline_for_stack
3123 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3124                      struct btrfs_key *extent_key)
3125 {
3126         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3127         struct btrfs_key key;
3128         struct extent_buffer *leaf;
3129         u64 start, end, last;
3130         int ret;
3131
3132         last = rc->block_group->start + rc->block_group->length;
3133         while (1) {
3134                 cond_resched();
3135                 if (rc->search_start >= last) {
3136                         ret = 1;
3137                         break;
3138                 }
3139
3140                 key.objectid = rc->search_start;
3141                 key.type = BTRFS_EXTENT_ITEM_KEY;
3142                 key.offset = 0;
3143
3144                 path->search_commit_root = 1;
3145                 path->skip_locking = 1;
3146                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3147                                         0, 0);
3148                 if (ret < 0)
3149                         break;
3150 next:
3151                 leaf = path->nodes[0];
3152                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3153                         ret = btrfs_next_leaf(rc->extent_root, path);
3154                         if (ret != 0)
3155                                 break;
3156                         leaf = path->nodes[0];
3157                 }
3158
3159                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3160                 if (key.objectid >= last) {
3161                         ret = 1;
3162                         break;
3163                 }
3164
3165                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3166                     key.type != BTRFS_METADATA_ITEM_KEY) {
3167                         path->slots[0]++;
3168                         goto next;
3169                 }
3170
3171                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3172                     key.objectid + key.offset <= rc->search_start) {
3173                         path->slots[0]++;
3174                         goto next;
3175                 }
3176
3177                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3178                     key.objectid + fs_info->nodesize <=
3179                     rc->search_start) {
3180                         path->slots[0]++;
3181                         goto next;
3182                 }
3183
3184                 ret = find_first_extent_bit(&rc->processed_blocks,
3185                                             key.objectid, &start, &end,
3186                                             EXTENT_DIRTY, NULL);
3187
3188                 if (ret == 0 && start <= key.objectid) {
3189                         btrfs_release_path(path);
3190                         rc->search_start = end + 1;
3191                 } else {
3192                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3193                                 rc->search_start = key.objectid + key.offset;
3194                         else
3195                                 rc->search_start = key.objectid +
3196                                         fs_info->nodesize;
3197                         memcpy(extent_key, &key, sizeof(key));
3198                         return 0;
3199                 }
3200         }
3201         btrfs_release_path(path);
3202         return ret;
3203 }
3204
3205 static void set_reloc_control(struct reloc_control *rc)
3206 {
3207         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3208
3209         mutex_lock(&fs_info->reloc_mutex);
3210         fs_info->reloc_ctl = rc;
3211         mutex_unlock(&fs_info->reloc_mutex);
3212 }
3213
3214 static void unset_reloc_control(struct reloc_control *rc)
3215 {
3216         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3217
3218         mutex_lock(&fs_info->reloc_mutex);
3219         fs_info->reloc_ctl = NULL;
3220         mutex_unlock(&fs_info->reloc_mutex);
3221 }
3222
3223 static int check_extent_flags(u64 flags)
3224 {
3225         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3226             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3227                 return 1;
3228         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3229             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3230                 return 1;
3231         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3232             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3233                 return 1;
3234         return 0;
3235 }
3236
3237 static noinline_for_stack
3238 int prepare_to_relocate(struct reloc_control *rc)
3239 {
3240         struct btrfs_trans_handle *trans;
3241         int ret;
3242
3243         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3244                                               BTRFS_BLOCK_RSV_TEMP);
3245         if (!rc->block_rsv)
3246                 return -ENOMEM;
3247
3248         memset(&rc->cluster, 0, sizeof(rc->cluster));
3249         rc->search_start = rc->block_group->start;
3250         rc->extents_found = 0;
3251         rc->nodes_relocated = 0;
3252         rc->merging_rsv_size = 0;
3253         rc->reserved_bytes = 0;
3254         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
3255                               RELOCATION_RESERVED_NODES;
3256         ret = btrfs_block_rsv_refill(rc->extent_root,
3257                                      rc->block_rsv, rc->block_rsv->size,
3258                                      BTRFS_RESERVE_FLUSH_ALL);
3259         if (ret)
3260                 return ret;
3261
3262         rc->create_reloc_tree = 1;
3263         set_reloc_control(rc);
3264
3265         trans = btrfs_join_transaction(rc->extent_root);
3266         if (IS_ERR(trans)) {
3267                 unset_reloc_control(rc);
3268                 /*
3269                  * extent tree is not a ref_cow tree and has no reloc_root to
3270                  * cleanup.  And callers are responsible to free the above
3271                  * block rsv.
3272                  */
3273                 return PTR_ERR(trans);
3274         }
3275         btrfs_commit_transaction(trans);
3276         return 0;
3277 }
3278
3279 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3280 {
3281         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3282         struct rb_root blocks = RB_ROOT;
3283         struct btrfs_key key;
3284         struct btrfs_trans_handle *trans = NULL;
3285         struct btrfs_path *path;
3286         struct btrfs_extent_item *ei;
3287         u64 flags;
3288         u32 item_size;
3289         int ret;
3290         int err = 0;
3291         int progress = 0;
3292
3293         path = btrfs_alloc_path();
3294         if (!path)
3295                 return -ENOMEM;
3296         path->reada = READA_FORWARD;
3297
3298         ret = prepare_to_relocate(rc);
3299         if (ret) {
3300                 err = ret;
3301                 goto out_free;
3302         }
3303
3304         while (1) {
3305                 rc->reserved_bytes = 0;
3306                 ret = btrfs_block_rsv_refill(rc->extent_root,
3307                                         rc->block_rsv, rc->block_rsv->size,
3308                                         BTRFS_RESERVE_FLUSH_ALL);
3309                 if (ret) {
3310                         err = ret;
3311                         break;
3312                 }
3313                 progress++;
3314                 trans = btrfs_start_transaction(rc->extent_root, 0);
3315                 if (IS_ERR(trans)) {
3316                         err = PTR_ERR(trans);
3317                         trans = NULL;
3318                         break;
3319                 }
3320 restart:
3321                 if (update_backref_cache(trans, &rc->backref_cache)) {
3322                         btrfs_end_transaction(trans);
3323                         trans = NULL;
3324                         continue;
3325                 }
3326
3327                 ret = find_next_extent(rc, path, &key);
3328                 if (ret < 0)
3329                         err = ret;
3330                 if (ret != 0)
3331                         break;
3332
3333                 rc->extents_found++;
3334
3335                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
3336                                     struct btrfs_extent_item);
3337                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
3338                 if (item_size >= sizeof(*ei)) {
3339                         flags = btrfs_extent_flags(path->nodes[0], ei);
3340                         ret = check_extent_flags(flags);
3341                         BUG_ON(ret);
3342                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3343                         err = -EINVAL;
3344                         btrfs_print_v0_err(trans->fs_info);
3345                         btrfs_abort_transaction(trans, err);
3346                         break;
3347                 } else {
3348                         BUG();
3349                 }
3350
3351                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
3352                         ret = add_tree_block(rc, &key, path, &blocks);
3353                 } else if (rc->stage == UPDATE_DATA_PTRS &&
3354                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
3355                         ret = add_data_references(rc, &key, path, &blocks);
3356                 } else {
3357                         btrfs_release_path(path);
3358                         ret = 0;
3359                 }
3360                 if (ret < 0) {
3361                         err = ret;
3362                         break;
3363                 }
3364
3365                 if (!RB_EMPTY_ROOT(&blocks)) {
3366                         ret = relocate_tree_blocks(trans, rc, &blocks);
3367                         if (ret < 0) {
3368                                 if (ret != -EAGAIN) {
3369                                         err = ret;
3370                                         break;
3371                                 }
3372                                 rc->extents_found--;
3373                                 rc->search_start = key.objectid;
3374                         }
3375                 }
3376
3377                 btrfs_end_transaction_throttle(trans);
3378                 btrfs_btree_balance_dirty(fs_info);
3379                 trans = NULL;
3380
3381                 if (rc->stage == MOVE_DATA_EXTENTS &&
3382                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
3383                         rc->found_file_extent = 1;
3384                         ret = relocate_data_extent(rc->data_inode,
3385                                                    &key, &rc->cluster);
3386                         if (ret < 0) {
3387                                 err = ret;
3388                                 break;
3389                         }
3390                 }
3391                 if (btrfs_should_cancel_balance(fs_info)) {
3392                         err = -ECANCELED;
3393                         break;
3394                 }
3395         }
3396         if (trans && progress && err == -ENOSPC) {
3397                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
3398                 if (ret == 1) {
3399                         err = 0;
3400                         progress = 0;
3401                         goto restart;
3402                 }
3403         }
3404
3405         btrfs_release_path(path);
3406         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
3407
3408         if (trans) {
3409                 btrfs_end_transaction_throttle(trans);
3410                 btrfs_btree_balance_dirty(fs_info);
3411         }
3412
3413         if (!err) {
3414                 ret = relocate_file_extent_cluster(rc->data_inode,
3415                                                    &rc->cluster);
3416                 if (ret < 0)
3417                         err = ret;
3418         }
3419
3420         rc->create_reloc_tree = 0;
3421         set_reloc_control(rc);
3422
3423         btrfs_backref_release_cache(&rc->backref_cache);
3424         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
3425
3426         /*
3427          * Even in the case when the relocation is cancelled, we should all go
3428          * through prepare_to_merge() and merge_reloc_roots().
3429          *
3430          * For error (including cancelled balance), prepare_to_merge() will
3431          * mark all reloc trees orphan, then queue them for cleanup in
3432          * merge_reloc_roots()
3433          */
3434         err = prepare_to_merge(rc, err);
3435
3436         merge_reloc_roots(rc);
3437
3438         rc->merge_reloc_tree = 0;
3439         unset_reloc_control(rc);
3440         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
3441
3442         /* get rid of pinned extents */
3443         trans = btrfs_join_transaction(rc->extent_root);
3444         if (IS_ERR(trans)) {
3445                 err = PTR_ERR(trans);
3446                 goto out_free;
3447         }
3448         btrfs_commit_transaction(trans);
3449 out_free:
3450         ret = clean_dirty_subvols(rc);
3451         if (ret < 0 && !err)
3452                 err = ret;
3453         btrfs_free_block_rsv(fs_info, rc->block_rsv);
3454         btrfs_free_path(path);
3455         return err;
3456 }
3457
3458 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
3459                                  struct btrfs_root *root, u64 objectid)
3460 {
3461         struct btrfs_path *path;
3462         struct btrfs_inode_item *item;
3463         struct extent_buffer *leaf;
3464         u64 flags = BTRFS_INODE_NOCOMPRESS | BTRFS_INODE_PREALLOC;
3465         int ret;
3466
3467         if (btrfs_is_zoned(trans->fs_info))
3468                 flags &= ~BTRFS_INODE_PREALLOC;
3469
3470         path = btrfs_alloc_path();
3471         if (!path)
3472                 return -ENOMEM;
3473
3474         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
3475         if (ret)
3476                 goto out;
3477
3478         leaf = path->nodes[0];
3479         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
3480         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
3481         btrfs_set_inode_generation(leaf, item, 1);
3482         btrfs_set_inode_size(leaf, item, 0);
3483         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
3484         btrfs_set_inode_flags(leaf, item, flags);
3485         btrfs_mark_buffer_dirty(leaf);
3486 out:
3487         btrfs_free_path(path);
3488         return ret;
3489 }
3490
3491 /*
3492  * helper to create inode for data relocation.
3493  * the inode is in data relocation tree and its link count is 0
3494  */
3495 static noinline_for_stack
3496 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
3497                                  struct btrfs_block_group *group)
3498 {
3499         struct inode *inode = NULL;
3500         struct btrfs_trans_handle *trans;
3501         struct btrfs_root *root;
3502         u64 objectid;
3503         int err = 0;
3504
3505         root = btrfs_grab_root(fs_info->data_reloc_root);
3506         trans = btrfs_start_transaction(root, 6);
3507         if (IS_ERR(trans)) {
3508                 btrfs_put_root(root);
3509                 return ERR_CAST(trans);
3510         }
3511
3512         err = btrfs_get_free_objectid(root, &objectid);
3513         if (err)
3514                 goto out;
3515
3516         err = __insert_orphan_inode(trans, root, objectid);
3517         BUG_ON(err);
3518
3519         inode = btrfs_iget(fs_info->sb, objectid, root);
3520         BUG_ON(IS_ERR(inode));
3521         BTRFS_I(inode)->index_cnt = group->start;
3522
3523         err = btrfs_orphan_add(trans, BTRFS_I(inode));
3524 out:
3525         btrfs_put_root(root);
3526         btrfs_end_transaction(trans);
3527         btrfs_btree_balance_dirty(fs_info);
3528         if (err) {
3529                 if (inode)
3530                         iput(inode);
3531                 inode = ERR_PTR(err);
3532         }
3533         return inode;
3534 }
3535
3536 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
3537 {
3538         struct reloc_control *rc;
3539
3540         rc = kzalloc(sizeof(*rc), GFP_NOFS);
3541         if (!rc)
3542                 return NULL;
3543
3544         INIT_LIST_HEAD(&rc->reloc_roots);
3545         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
3546         btrfs_backref_init_cache(fs_info, &rc->backref_cache, 1);
3547         mapping_tree_init(&rc->reloc_root_tree);
3548         extent_io_tree_init(fs_info, &rc->processed_blocks,
3549                             IO_TREE_RELOC_BLOCKS, NULL);
3550         return rc;
3551 }
3552
3553 static void free_reloc_control(struct reloc_control *rc)
3554 {
3555         struct mapping_node *node, *tmp;
3556
3557         free_reloc_roots(&rc->reloc_roots);
3558         rbtree_postorder_for_each_entry_safe(node, tmp,
3559                         &rc->reloc_root_tree.rb_root, rb_node)
3560                 kfree(node);
3561
3562         kfree(rc);
3563 }
3564
3565 /*
3566  * Print the block group being relocated
3567  */
3568 static void describe_relocation(struct btrfs_fs_info *fs_info,
3569                                 struct btrfs_block_group *block_group)
3570 {
3571         char buf[128] = {'\0'};
3572
3573         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
3574
3575         btrfs_info(fs_info,
3576                    "relocating block group %llu flags %s",
3577                    block_group->start, buf);
3578 }
3579
3580 static const char *stage_to_string(int stage)
3581 {
3582         if (stage == MOVE_DATA_EXTENTS)
3583                 return "move data extents";
3584         if (stage == UPDATE_DATA_PTRS)
3585                 return "update data pointers";
3586         return "unknown";
3587 }
3588
3589 /*
3590  * function to relocate all extents in a block group.
3591  */
3592 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
3593 {
3594         struct btrfs_block_group *bg;
3595         struct btrfs_root *extent_root = fs_info->extent_root;
3596         struct reloc_control *rc;
3597         struct inode *inode;
3598         struct btrfs_path *path;
3599         int ret;
3600         int rw = 0;
3601         int err = 0;
3602
3603         bg = btrfs_lookup_block_group(fs_info, group_start);
3604         if (!bg)
3605                 return -ENOENT;
3606
3607         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
3608                 btrfs_put_block_group(bg);
3609                 return -ETXTBSY;
3610         }
3611
3612         rc = alloc_reloc_control(fs_info);
3613         if (!rc) {
3614                 btrfs_put_block_group(bg);
3615                 return -ENOMEM;
3616         }
3617
3618         rc->extent_root = extent_root;
3619         rc->block_group = bg;
3620
3621         ret = btrfs_inc_block_group_ro(rc->block_group, true);
3622         if (ret) {
3623                 err = ret;
3624                 goto out;
3625         }
3626         rw = 1;
3627
3628         path = btrfs_alloc_path();
3629         if (!path) {
3630                 err = -ENOMEM;
3631                 goto out;
3632         }
3633
3634         inode = lookup_free_space_inode(rc->block_group, path);
3635         btrfs_free_path(path);
3636
3637         if (!IS_ERR(inode))
3638                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
3639         else
3640                 ret = PTR_ERR(inode);
3641
3642         if (ret && ret != -ENOENT) {
3643                 err = ret;
3644                 goto out;
3645         }
3646
3647         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
3648         if (IS_ERR(rc->data_inode)) {
3649                 err = PTR_ERR(rc->data_inode);
3650                 rc->data_inode = NULL;
3651                 goto out;
3652         }
3653
3654         describe_relocation(fs_info, rc->block_group);
3655
3656         btrfs_wait_block_group_reservations(rc->block_group);
3657         btrfs_wait_nocow_writers(rc->block_group);
3658         btrfs_wait_ordered_roots(fs_info, U64_MAX,
3659                                  rc->block_group->start,
3660                                  rc->block_group->length);
3661
3662         while (1) {
3663                 int finishes_stage;
3664
3665                 mutex_lock(&fs_info->cleaner_mutex);
3666                 ret = relocate_block_group(rc);
3667                 mutex_unlock(&fs_info->cleaner_mutex);
3668                 if (ret < 0)
3669                         err = ret;
3670
3671                 finishes_stage = rc->stage;
3672                 /*
3673                  * We may have gotten ENOSPC after we already dirtied some
3674                  * extents.  If writeout happens while we're relocating a
3675                  * different block group we could end up hitting the
3676                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
3677                  * btrfs_reloc_cow_block.  Make sure we write everything out
3678                  * properly so we don't trip over this problem, and then break
3679                  * out of the loop if we hit an error.
3680                  */
3681                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
3682                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
3683                                                        (u64)-1);
3684                         if (ret)
3685                                 err = ret;
3686                         invalidate_mapping_pages(rc->data_inode->i_mapping,
3687                                                  0, -1);
3688                         rc->stage = UPDATE_DATA_PTRS;
3689                 }
3690
3691                 if (err < 0)
3692                         goto out;
3693
3694                 if (rc->extents_found == 0)
3695                         break;
3696
3697                 btrfs_info(fs_info, "found %llu extents, stage: %s",
3698                            rc->extents_found, stage_to_string(finishes_stage));
3699         }
3700
3701         WARN_ON(rc->block_group->pinned > 0);
3702         WARN_ON(rc->block_group->reserved > 0);
3703         WARN_ON(rc->block_group->used > 0);
3704 out:
3705         if (err && rw)
3706                 btrfs_dec_block_group_ro(rc->block_group);
3707         iput(rc->data_inode);
3708         btrfs_put_block_group(rc->block_group);
3709         free_reloc_control(rc);
3710         return err;
3711 }
3712
3713 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
3714 {
3715         struct btrfs_fs_info *fs_info = root->fs_info;
3716         struct btrfs_trans_handle *trans;
3717         int ret, err;
3718
3719         trans = btrfs_start_transaction(fs_info->tree_root, 0);
3720         if (IS_ERR(trans))
3721                 return PTR_ERR(trans);
3722
3723         memset(&root->root_item.drop_progress, 0,
3724                 sizeof(root->root_item.drop_progress));
3725         btrfs_set_root_drop_level(&root->root_item, 0);
3726         btrfs_set_root_refs(&root->root_item, 0);
3727         ret = btrfs_update_root(trans, fs_info->tree_root,
3728                                 &root->root_key, &root->root_item);
3729
3730         err = btrfs_end_transaction(trans);
3731         if (err)
3732                 return err;
3733         return ret;
3734 }
3735
3736 /*
3737  * recover relocation interrupted by system crash.
3738  *
3739  * this function resumes merging reloc trees with corresponding fs trees.
3740  * this is important for keeping the sharing of tree blocks
3741  */
3742 int btrfs_recover_relocation(struct btrfs_root *root)
3743 {
3744         struct btrfs_fs_info *fs_info = root->fs_info;
3745         LIST_HEAD(reloc_roots);
3746         struct btrfs_key key;
3747         struct btrfs_root *fs_root;
3748         struct btrfs_root *reloc_root;
3749         struct btrfs_path *path;
3750         struct extent_buffer *leaf;
3751         struct reloc_control *rc = NULL;
3752         struct btrfs_trans_handle *trans;
3753         int ret;
3754         int err = 0;
3755
3756         path = btrfs_alloc_path();
3757         if (!path)
3758                 return -ENOMEM;
3759         path->reada = READA_BACK;
3760
3761         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
3762         key.type = BTRFS_ROOT_ITEM_KEY;
3763         key.offset = (u64)-1;
3764
3765         while (1) {
3766                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
3767                                         path, 0, 0);
3768                 if (ret < 0) {
3769                         err = ret;
3770                         goto out;
3771                 }
3772                 if (ret > 0) {
3773                         if (path->slots[0] == 0)
3774                                 break;
3775                         path->slots[0]--;
3776                 }
3777                 leaf = path->nodes[0];
3778                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3779                 btrfs_release_path(path);
3780
3781                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
3782                     key.type != BTRFS_ROOT_ITEM_KEY)
3783                         break;
3784
3785                 reloc_root = btrfs_read_tree_root(root, &key);
3786                 if (IS_ERR(reloc_root)) {
3787                         err = PTR_ERR(reloc_root);
3788                         goto out;
3789                 }
3790
3791                 set_bit(BTRFS_ROOT_SHAREABLE, &reloc_root->state);
3792                 list_add(&reloc_root->root_list, &reloc_roots);
3793
3794                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
3795                         fs_root = btrfs_get_fs_root(fs_info,
3796                                         reloc_root->root_key.offset, false);
3797                         if (IS_ERR(fs_root)) {
3798                                 ret = PTR_ERR(fs_root);
3799                                 if (ret != -ENOENT) {
3800                                         err = ret;
3801                                         goto out;
3802                                 }
3803                                 ret = mark_garbage_root(reloc_root);
3804                                 if (ret < 0) {
3805                                         err = ret;
3806                                         goto out;
3807                                 }
3808                         } else {
3809                                 btrfs_put_root(fs_root);
3810                         }
3811                 }
3812
3813                 if (key.offset == 0)
3814                         break;
3815
3816                 key.offset--;
3817         }
3818         btrfs_release_path(path);
3819
3820         if (list_empty(&reloc_roots))
3821                 goto out;
3822
3823         rc = alloc_reloc_control(fs_info);
3824         if (!rc) {
3825                 err = -ENOMEM;
3826                 goto out;
3827         }
3828
3829         rc->extent_root = fs_info->extent_root;
3830
3831         set_reloc_control(rc);
3832
3833         trans = btrfs_join_transaction(rc->extent_root);
3834         if (IS_ERR(trans)) {
3835                 err = PTR_ERR(trans);
3836                 goto out_unset;
3837         }
3838
3839         rc->merge_reloc_tree = 1;
3840
3841         while (!list_empty(&reloc_roots)) {
3842                 reloc_root = list_entry(reloc_roots.next,
3843                                         struct btrfs_root, root_list);
3844                 list_del(&reloc_root->root_list);
3845
3846                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
3847                         list_add_tail(&reloc_root->root_list,
3848                                       &rc->reloc_roots);
3849                         continue;
3850                 }
3851
3852                 fs_root = btrfs_get_fs_root(fs_info, reloc_root->root_key.offset,
3853                                             false);
3854                 if (IS_ERR(fs_root)) {
3855                         err = PTR_ERR(fs_root);
3856                         list_add_tail(&reloc_root->root_list, &reloc_roots);
3857                         btrfs_end_transaction(trans);
3858                         goto out_unset;
3859                 }
3860
3861                 err = __add_reloc_root(reloc_root);
3862                 BUG_ON(err < 0); /* -ENOMEM or logic error */
3863                 fs_root->reloc_root = btrfs_grab_root(reloc_root);
3864                 btrfs_put_root(fs_root);
3865         }
3866
3867         err = btrfs_commit_transaction(trans);
3868         if (err)
3869                 goto out_unset;
3870
3871         merge_reloc_roots(rc);
3872
3873         unset_reloc_control(rc);
3874
3875         trans = btrfs_join_transaction(rc->extent_root);
3876         if (IS_ERR(trans)) {
3877                 err = PTR_ERR(trans);
3878                 goto out_clean;
3879         }
3880         err = btrfs_commit_transaction(trans);
3881 out_clean:
3882         ret = clean_dirty_subvols(rc);
3883         if (ret < 0 && !err)
3884                 err = ret;
3885 out_unset:
3886         unset_reloc_control(rc);
3887         free_reloc_control(rc);
3888 out:
3889         free_reloc_roots(&reloc_roots);
3890
3891         btrfs_free_path(path);
3892
3893         if (err == 0) {
3894                 /* cleanup orphan inode in data relocation tree */
3895                 fs_root = btrfs_grab_root(fs_info->data_reloc_root);
3896                 ASSERT(fs_root);
3897                 err = btrfs_orphan_cleanup(fs_root);
3898                 btrfs_put_root(fs_root);
3899         }
3900         return err;
3901 }
3902
3903 /*
3904  * helper to add ordered checksum for data relocation.
3905  *
3906  * cloning checksum properly handles the nodatasum extents.
3907  * it also saves CPU time to re-calculate the checksum.
3908  */
3909 int btrfs_reloc_clone_csums(struct btrfs_inode *inode, u64 file_pos, u64 len)
3910 {
3911         struct btrfs_fs_info *fs_info = inode->root->fs_info;
3912         struct btrfs_ordered_sum *sums;
3913         struct btrfs_ordered_extent *ordered;
3914         int ret;
3915         u64 disk_bytenr;
3916         u64 new_bytenr;
3917         LIST_HEAD(list);
3918
3919         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
3920         BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
3921
3922         disk_bytenr = file_pos + inode->index_cnt;
3923         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
3924                                        disk_bytenr + len - 1, &list, 0);
3925         if (ret)
3926                 goto out;
3927
3928         while (!list_empty(&list)) {
3929                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
3930                 list_del_init(&sums->list);
3931
3932                 /*
3933                  * We need to offset the new_bytenr based on where the csum is.
3934                  * We need to do this because we will read in entire prealloc
3935                  * extents but we may have written to say the middle of the
3936                  * prealloc extent, so we need to make sure the csum goes with
3937                  * the right disk offset.
3938                  *
3939                  * We can do this because the data reloc inode refers strictly
3940                  * to the on disk bytes, so we don't have to worry about
3941                  * disk_len vs real len like with real inodes since it's all
3942                  * disk length.
3943                  */
3944                 new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
3945                 sums->bytenr = new_bytenr;
3946
3947                 btrfs_add_ordered_sum(ordered, sums);
3948         }
3949 out:
3950         btrfs_put_ordered_extent(ordered);
3951         return ret;
3952 }
3953
3954 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
3955                           struct btrfs_root *root, struct extent_buffer *buf,
3956                           struct extent_buffer *cow)
3957 {
3958         struct btrfs_fs_info *fs_info = root->fs_info;
3959         struct reloc_control *rc;
3960         struct btrfs_backref_node *node;
3961         int first_cow = 0;
3962         int level;
3963         int ret = 0;
3964
3965         rc = fs_info->reloc_ctl;
3966         if (!rc)
3967                 return 0;
3968
3969         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
3970                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
3971
3972         level = btrfs_header_level(buf);
3973         if (btrfs_header_generation(buf) <=
3974             btrfs_root_last_snapshot(&root->root_item))
3975                 first_cow = 1;
3976
3977         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
3978             rc->create_reloc_tree) {
3979                 WARN_ON(!first_cow && level == 0);
3980
3981                 node = rc->backref_cache.path[level];
3982                 BUG_ON(node->bytenr != buf->start &&
3983                        node->new_bytenr != buf->start);
3984
3985                 btrfs_backref_drop_node_buffer(node);
3986                 atomic_inc(&cow->refs);
3987                 node->eb = cow;
3988                 node->new_bytenr = cow->start;
3989
3990                 if (!node->pending) {
3991                         list_move_tail(&node->list,
3992                                        &rc->backref_cache.pending[level]);
3993                         node->pending = 1;
3994                 }
3995
3996                 if (first_cow)
3997                         mark_block_processed(rc, node);
3998
3999                 if (first_cow && level > 0)
4000                         rc->nodes_relocated += buf->len;
4001         }
4002
4003         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4004                 ret = replace_file_extents(trans, rc, root, cow);
4005         return ret;
4006 }
4007
4008 /*
4009  * called before creating snapshot. it calculates metadata reservation
4010  * required for relocating tree blocks in the snapshot
4011  */
4012 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4013                               u64 *bytes_to_reserve)
4014 {
4015         struct btrfs_root *root = pending->root;
4016         struct reloc_control *rc = root->fs_info->reloc_ctl;
4017
4018         if (!rc || !have_reloc_root(root))
4019                 return;
4020
4021         if (!rc->merge_reloc_tree)
4022                 return;
4023
4024         root = root->reloc_root;
4025         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4026         /*
4027          * relocation is in the stage of merging trees. the space
4028          * used by merging a reloc tree is twice the size of
4029          * relocated tree nodes in the worst case. half for cowing
4030          * the reloc tree, half for cowing the fs tree. the space
4031          * used by cowing the reloc tree will be freed after the
4032          * tree is dropped. if we create snapshot, cowing the fs
4033          * tree may use more space than it frees. so we need
4034          * reserve extra space.
4035          */
4036         *bytes_to_reserve += rc->nodes_relocated;
4037 }
4038
4039 /*
4040  * called after snapshot is created. migrate block reservation
4041  * and create reloc root for the newly created snapshot
4042  *
4043  * This is similar to btrfs_init_reloc_root(), we come out of here with two
4044  * references held on the reloc_root, one for root->reloc_root and one for
4045  * rc->reloc_roots.
4046  */
4047 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4048                                struct btrfs_pending_snapshot *pending)
4049 {
4050         struct btrfs_root *root = pending->root;
4051         struct btrfs_root *reloc_root;
4052         struct btrfs_root *new_root;
4053         struct reloc_control *rc = root->fs_info->reloc_ctl;
4054         int ret;
4055
4056         if (!rc || !have_reloc_root(root))
4057                 return 0;
4058
4059         rc = root->fs_info->reloc_ctl;
4060         rc->merging_rsv_size += rc->nodes_relocated;
4061
4062         if (rc->merge_reloc_tree) {
4063                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4064                                               rc->block_rsv,
4065                                               rc->nodes_relocated, true);
4066                 if (ret)
4067                         return ret;
4068         }
4069
4070         new_root = pending->snap;
4071         reloc_root = create_reloc_root(trans, root->reloc_root,
4072                                        new_root->root_key.objectid);
4073         if (IS_ERR(reloc_root))
4074                 return PTR_ERR(reloc_root);
4075
4076         ret = __add_reloc_root(reloc_root);
4077         BUG_ON(ret < 0);
4078         new_root->reloc_root = btrfs_grab_root(reloc_root);
4079
4080         if (rc->create_reloc_tree)
4081                 ret = clone_backref_node(trans, rc, root, reloc_root);
4082         return ret;
4083 }