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 "inode-map.h"
  22 #include "qgroup.h"
  23 #include "print-tree.h"
  24 #include "delalloc-space.h"
  25 #include "block-group.h"
  26 #include "backref.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 /*
  76  * backref_node, mapping_node and tree_block start with this
  77  */
  78 struct tree_entry {
  79         struct rb_node rb_node;
  80         u64 bytenr;
  81 };
  82
  83 /*
  84  * present a tree block in the backref cache
  85  */
  86 struct backref_node {
  87         struct rb_node rb_node;
  88         u64 bytenr;
  89
  90         u64 new_bytenr;
  91         /* objectid of tree block owner, can be not uptodate */
  92         u64 owner;
  93         /* link to pending, changed or detached list */
  94         struct list_head list;
  95         /* list of upper level blocks reference this block */
  96         struct list_head upper;
  97         /* list of child blocks in the cache */
  98         struct list_head lower;
  99         /* NULL if this node is not tree root */
 100         struct btrfs_root *root;
 101         /* extent buffer got by COW the block */
 102         struct extent_buffer *eb;
 103         /* level of tree block */
 104         unsigned int level:8;
 105         /* is the block in non-reference counted tree */
 106         unsigned int cowonly:1;
 107         /* 1 if no child node in the cache */
 108         unsigned int lowest:1;
 109         /* is the extent buffer locked */
 110         unsigned int locked:1;
 111         /* has the block been processed */
 112         unsigned int processed:1;
 113         /* have backrefs of this block been checked */
 114         unsigned int checked:1;
 115         /*
 116          * 1 if corresponding block has been cowed but some upper
 117          * level block pointers may not point to the new location
 118          */
 119         unsigned int pending:1;
 120         /*
 121          * 1 if the backref node isn't connected to any other
 122          * backref node.
 123          */
 124         unsigned int detached:1;
 125 };
 126
 127 /*
 128  * present a block pointer in the backref cache
 129  */
 130 struct backref_edge {
 131         struct list_head list[2];
 132         struct backref_node *node[2];
 133 };
 134
 135 #define LOWER   0
 136 #define UPPER   1
 137 #define RELOCATION_RESERVED_NODES       256
 138
 139 struct backref_cache {
 140         /* red black tree of all backref nodes in the cache */
 141         struct rb_root rb_root;
 142         /* for passing backref nodes to btrfs_reloc_cow_block */
 143         struct backref_node *path[BTRFS_MAX_LEVEL];
 144         /*
 145          * list of blocks that have been cowed but some block
 146          * pointers in upper level blocks may not reflect the
 147          * new location
 148          */
 149         struct list_head pending[BTRFS_MAX_LEVEL];
 150         /* list of backref nodes with no child node */
 151         struct list_head leaves;
 152         /* list of blocks that have been cowed in current transaction */
 153         struct list_head changed;
 154         /* list of detached backref node. */
 155         struct list_head detached;
 156
 157         u64 last_trans;
 158
 159         int nr_nodes;
 160         int nr_edges;
 161 };
 162
 163 /*
 164  * map address of tree root to tree
 165  */
 166 struct mapping_node {
 167         struct rb_node rb_node;
 168         u64 bytenr;
 169         void *data;
 170 };
 171
 172 struct mapping_tree {
 173         struct rb_root rb_root;
 174         spinlock_t lock;
 175 };
 176
 177 /*
 178  * present a tree block to process
 179  */
 180 struct tree_block {
 181         struct rb_node rb_node;
 182         u64 bytenr;
 183         struct btrfs_key key;
 184         unsigned int level:8;
 185         unsigned int key_ready:1;
 186 };
 187
 188 #define MAX_EXTENTS 128
 189
 190 struct file_extent_cluster {
 191         u64 start;
 192         u64 end;
 193         u64 boundary[MAX_EXTENTS];
 194         unsigned int nr;
 195 };
 196
 197 struct reloc_control {
 198         /* block group to relocate */
 199         struct btrfs_block_group *block_group;
 200         /* extent tree */
 201         struct btrfs_root *extent_root;
 202         /* inode for moving data */
 203         struct inode *data_inode;
 204
 205         struct btrfs_block_rsv *block_rsv;
 206
 207         struct backref_cache backref_cache;
 208
 209         struct file_extent_cluster cluster;
 210         /* tree blocks have been processed */
 211         struct extent_io_tree processed_blocks;
 212         /* map start of tree root to corresponding reloc tree */
 213         struct mapping_tree reloc_root_tree;
 214         /* list of reloc trees */
 215         struct list_head reloc_roots;
 216         /* list of subvolume trees that get relocated */
 217         struct list_head dirty_subvol_roots;
 218         /* size of metadata reservation for merging reloc trees */
 219         u64 merging_rsv_size;
 220         /* size of relocated tree nodes */
 221         u64 nodes_relocated;
 222         /* reserved size for block group relocation*/
 223         u64 reserved_bytes;
 224
 225         u64 search_start;
 226         u64 extents_found;
 227
 228         unsigned int stage:8;
 229         unsigned int create_reloc_tree:1;
 230         unsigned int merge_reloc_tree:1;
 231         unsigned int found_file_extent:1;
 232 };
 233
 234 /* stages of data relocation */
 235 #define MOVE_DATA_EXTENTS       0
 236 #define UPDATE_DATA_PTRS        1
 237
 238 static void remove_backref_node(struct backref_cache *cache,
 239                                 struct backref_node *node);
 240 static void __mark_block_processed(struct reloc_control *rc,
 241                                    struct backref_node *node);
 242
 243 static void mapping_tree_init(struct mapping_tree *tree)
 244 {
 245         tree->rb_root = RB_ROOT;
 246         spin_lock_init(&tree->lock);
 247 }
 248
 249 static void backref_cache_init(struct backref_cache *cache)
 250 {
 251         int i;
 252         cache->rb_root = RB_ROOT;
 253         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 254                 INIT_LIST_HEAD(&cache->pending[i]);
 255         INIT_LIST_HEAD(&cache->changed);
 256         INIT_LIST_HEAD(&cache->detached);
 257         INIT_LIST_HEAD(&cache->leaves);
 258 }
 259
 260 static void backref_cache_cleanup(struct backref_cache *cache)
 261 {
 262         struct backref_node *node;
 263         int i;
 264
 265         while (!list_empty(&cache->detached)) {
 266                 node = list_entry(cache->detached.next,
 267                                   struct backref_node, list);
 268                 remove_backref_node(cache, node);
 269         }
 270
 271         while (!list_empty(&cache->leaves)) {
 272                 node = list_entry(cache->leaves.next,
 273                                   struct backref_node, lower);
 274                 remove_backref_node(cache, node);
 275         }
 276
 277         cache->last_trans = 0;
 278
 279         for (i = 0; i < BTRFS_MAX_LEVEL; i++)
 280                 ASSERT(list_empty(&cache->pending[i]));
 281         ASSERT(list_empty(&cache->changed));
 282         ASSERT(list_empty(&cache->detached));
 283         ASSERT(RB_EMPTY_ROOT(&cache->rb_root));
 284         ASSERT(!cache->nr_nodes);
 285         ASSERT(!cache->nr_edges);
 286 }
 287
 288 static struct backref_node *alloc_backref_node(struct backref_cache *cache)
 289 {
 290         struct backref_node *node;
 291
 292         node = kzalloc(sizeof(*node), GFP_NOFS);
 293         if (node) {
 294                 INIT_LIST_HEAD(&node->list);
 295                 INIT_LIST_HEAD(&node->upper);
 296                 INIT_LIST_HEAD(&node->lower);
 297                 RB_CLEAR_NODE(&node->rb_node);
 298                 cache->nr_nodes++;
 299         }
 300         return node;
 301 }
 302
 303 static void free_backref_node(struct backref_cache *cache,
 304                               struct backref_node *node)
 305 {
 306         if (node) {
 307                 cache->nr_nodes--;
 308                 btrfs_put_root(node->root);
 309                 kfree(node);
 310         }
 311 }
 312
 313 static struct backref_edge *alloc_backref_edge(struct backref_cache *cache)
 314 {
 315         struct backref_edge *edge;
 316
 317         edge = kzalloc(sizeof(*edge), GFP_NOFS);
 318         if (edge)
 319                 cache->nr_edges++;
 320         return edge;
 321 }
 322
 323 static void free_backref_edge(struct backref_cache *cache,
 324                               struct backref_edge *edge)
 325 {
 326         if (edge) {
 327                 cache->nr_edges--;
 328                 kfree(edge);
 329         }
 330 }
 331
 332 static struct rb_node *tree_insert(struct rb_root *root, u64 bytenr,
 333                                    struct rb_node *node)
 334 {
 335         struct rb_node **p = &root->rb_node;
 336         struct rb_node *parent = NULL;
 337         struct tree_entry *entry;
 338
 339         while (*p) {
 340                 parent = *p;
 341                 entry = rb_entry(parent, struct tree_entry, rb_node);
 342
 343                 if (bytenr < entry->bytenr)
 344                         p = &(*p)->rb_left;
 345                 else if (bytenr > entry->bytenr)
 346                         p = &(*p)->rb_right;
 347                 else
 348                         return parent;
 349         }
 350
 351         rb_link_node(node, parent, p);
 352         rb_insert_color(node, root);
 353         return NULL;
 354 }
 355
 356 static struct rb_node *tree_search(struct rb_root *root, u64 bytenr)
 357 {
 358         struct rb_node *n = root->rb_node;
 359         struct tree_entry *entry;
 360
 361         while (n) {
 362                 entry = rb_entry(n, struct tree_entry, rb_node);
 363
 364                 if (bytenr < entry->bytenr)
 365                         n = n->rb_left;
 366                 else if (bytenr > entry->bytenr)
 367                         n = n->rb_right;
 368                 else
 369                         return n;
 370         }
 371         return NULL;
 372 }
 373
 374 static void backref_tree_panic(struct rb_node *rb_node, int errno, u64 bytenr)
 375 {
 376
 377         struct btrfs_fs_info *fs_info = NULL;
 378         struct backref_node *bnode = rb_entry(rb_node, struct backref_node,
 379                                               rb_node);
 380         if (bnode->root)
 381                 fs_info = bnode->root->fs_info;
 382         btrfs_panic(fs_info, errno,
 383                     "Inconsistency in backref cache found at offset %llu",
 384                     bytenr);
 385 }
 386
 387 /*
 388  * walk up backref nodes until reach node presents tree root
 389  */
 390 static struct backref_node *walk_up_backref(struct backref_node *node,
 391                                             struct backref_edge *edges[],
 392                                             int *index)
 393 {
 394         struct backref_edge *edge;
 395         int idx = *index;
 396
 397         while (!list_empty(&node->upper)) {
 398                 edge = list_entry(node->upper.next,
 399                                   struct backref_edge, list[LOWER]);
 400                 edges[idx++] = edge;
 401                 node = edge->node[UPPER];
 402         }
 403         BUG_ON(node->detached);
 404         *index = idx;
 405         return node;
 406 }
 407
 408 /*
 409  * walk down backref nodes to find start of next reference path
 410  */
 411 static struct backref_node *walk_down_backref(struct backref_edge *edges[],
 412                                               int *index)
 413 {
 414         struct backref_edge *edge;
 415         struct backref_node *lower;
 416         int idx = *index;
 417
 418         while (idx > 0) {
 419                 edge = edges[idx - 1];
 420                 lower = edge->node[LOWER];
 421                 if (list_is_last(&edge->list[LOWER], &lower->upper)) {
 422                         idx--;
 423                         continue;
 424                 }
 425                 edge = list_entry(edge->list[LOWER].next,
 426                                   struct backref_edge, list[LOWER]);
 427                 edges[idx - 1] = edge;
 428                 *index = idx;
 429                 return edge->node[UPPER];
 430         }
 431         *index = 0;
 432         return NULL;
 433 }
 434
 435 static void unlock_node_buffer(struct backref_node *node)
 436 {
 437         if (node->locked) {
 438                 btrfs_tree_unlock(node->eb);
 439                 node->locked = 0;
 440         }
 441 }
 442
 443 static void drop_node_buffer(struct backref_node *node)
 444 {
 445         if (node->eb) {
 446                 unlock_node_buffer(node);
 447                 free_extent_buffer(node->eb);
 448                 node->eb = NULL;
 449         }
 450 }
 451
 452 static void drop_backref_node(struct backref_cache *tree,
 453                               struct backref_node *node)
 454 {
 455         BUG_ON(!list_empty(&node->upper));
 456
 457         drop_node_buffer(node);
 458         list_del(&node->list);
 459         list_del(&node->lower);
 460         if (!RB_EMPTY_NODE(&node->rb_node))
 461                 rb_erase(&node->rb_node, &tree->rb_root);
 462         free_backref_node(tree, node);
 463 }
 464
 465 /*
 466  * remove a backref node from the backref cache
 467  */
 468 static void remove_backref_node(struct backref_cache *cache,
 469                                 struct backref_node *node)
 470 {
 471         struct backref_node *upper;
 472         struct backref_edge *edge;
 473
 474         if (!node)
 475                 return;
 476
 477         BUG_ON(!node->lowest && !node->detached);
 478         while (!list_empty(&node->upper)) {
 479                 edge = list_entry(node->upper.next, struct backref_edge,
 480                                   list[LOWER]);
 481                 upper = edge->node[UPPER];
 482                 list_del(&edge->list[LOWER]);
 483                 list_del(&edge->list[UPPER]);
 484                 free_backref_edge(cache, edge);
 485
 486                 if (RB_EMPTY_NODE(&upper->rb_node)) {
 487                         BUG_ON(!list_empty(&node->upper));
 488                         drop_backref_node(cache, node);
 489                         node = upper;
 490                         node->lowest = 1;
 491                         continue;
 492                 }
 493                 /*
 494                  * add the node to leaf node list if no other
 495                  * child block cached.
 496                  */
 497                 if (list_empty(&upper->lower)) {
 498                         list_add_tail(&upper->lower, &cache->leaves);
 499                         upper->lowest = 1;
 500                 }
 501         }
 502
 503         drop_backref_node(cache, node);
 504 }
 505
 506 static void update_backref_node(struct backref_cache *cache,
 507                                 struct backref_node *node, u64 bytenr)
 508 {
 509         struct rb_node *rb_node;
 510         rb_erase(&node->rb_node, &cache->rb_root);
 511         node->bytenr = bytenr;
 512         rb_node = tree_insert(&cache->rb_root, node->bytenr, &node->rb_node);
 513         if (rb_node)
 514                 backref_tree_panic(rb_node, -EEXIST, bytenr);
 515 }
 516
 517 /*
 518  * update backref cache after a transaction commit
 519  */
 520 static int update_backref_cache(struct btrfs_trans_handle *trans,
 521                                 struct backref_cache *cache)
 522 {
 523         struct backref_node *node;
 524         int level = 0;
 525
 526         if (cache->last_trans == 0) {
 527                 cache->last_trans = trans->transid;
 528                 return 0;
 529         }
 530
 531         if (cache->last_trans == trans->transid)
 532                 return 0;
 533
 534         /*
 535          * detached nodes are used to avoid unnecessary backref
 536          * lookup. transaction commit changes the extent tree.
 537          * so the detached nodes are no longer useful.
 538          */
 539         while (!list_empty(&cache->detached)) {
 540                 node = list_entry(cache->detached.next,
 541                                   struct backref_node, list);
 542                 remove_backref_node(cache, node);
 543         }
 544
 545         while (!list_empty(&cache->changed)) {
 546                 node = list_entry(cache->changed.next,
 547                                   struct backref_node, list);
 548                 list_del_init(&node->list);
 549                 BUG_ON(node->pending);
 550                 update_backref_node(cache, node, node->new_bytenr);
 551         }
 552
 553         /*
 554          * some nodes can be left in the pending list if there were
 555          * errors during processing the pending nodes.
 556          */
 557         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
 558                 list_for_each_entry(node, &cache->pending[level], list) {
 559                         BUG_ON(!node->pending);
 560                         if (node->bytenr == node->new_bytenr)
 561                                 continue;
 562                         update_backref_node(cache, node, node->new_bytenr);
 563                 }
 564         }
 565
 566         cache->last_trans = 0;
 567         return 1;
 568 }
 569
 570 static bool reloc_root_is_dead(struct btrfs_root *root)
 571 {
 572         /*
 573          * Pair with set_bit/clear_bit in clean_dirty_subvols and
 574          * btrfs_update_reloc_root. We need to see the updated bit before
 575          * trying to access reloc_root
 576          */
 577         smp_rmb();
 578         if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
 579                 return true;
 580         return false;
 581 }
 582
 583 /*
 584  * Check if this subvolume tree has valid reloc tree.
 585  *
 586  * Reloc tree after swap is considered dead, thus not considered as valid.
 587  * This is enough for most callers, as they don't distinguish dead reloc root
 588  * from no reloc root.  But should_ignore_root() below is a special case.
 589  */
 590 static bool have_reloc_root(struct btrfs_root *root)
 591 {
 592         if (reloc_root_is_dead(root))
 593                 return false;
 594         if (!root->reloc_root)
 595                 return false;
 596         return true;
 597 }
 598
 599 static int should_ignore_root(struct btrfs_root *root)
 600 {
 601         struct btrfs_root *reloc_root;
 602
 603         if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 604                 return 0;
 605
 606         /* This root has been merged with its reloc tree, we can ignore it */
 607         if (reloc_root_is_dead(root))
 608                 return 1;
 609
 610         reloc_root = root->reloc_root;
 611         if (!reloc_root)
 612                 return 0;
 613
 614         if (btrfs_root_last_snapshot(&reloc_root->root_item) ==
 615             root->fs_info->running_transaction->transid - 1)
 616                 return 0;
 617         /*
 618          * if there is reloc tree and it was created in previous
 619          * transaction backref lookup can find the reloc tree,
 620          * so backref node for the fs tree root is useless for
 621          * relocation.
 622          */
 623         return 1;
 624 }
 625 /*
 626  * find reloc tree by address of tree root
 627  */
 628 static struct btrfs_root *find_reloc_root(struct reloc_control *rc,
 629                                           u64 bytenr)
 630 {
 631         struct rb_node *rb_node;
 632         struct mapping_node *node;
 633         struct btrfs_root *root = NULL;
 634
 635         spin_lock(&rc->reloc_root_tree.lock);
 636         rb_node = tree_search(&rc->reloc_root_tree.rb_root, bytenr);
 637         if (rb_node) {
 638                 node = rb_entry(rb_node, struct mapping_node, rb_node);
 639                 root = (struct btrfs_root *)node->data;
 640         }
 641         spin_unlock(&rc->reloc_root_tree.lock);
 642         return btrfs_grab_root(root);
 643 }
 644
 645 static struct btrfs_root *read_fs_root(struct btrfs_fs_info *fs_info,
 646                                         u64 root_objectid)
 647 {
 648         struct btrfs_key key;
 649
 650         key.objectid = root_objectid;
 651         key.type = BTRFS_ROOT_ITEM_KEY;
 652         key.offset = (u64)-1;
 653
 654         return btrfs_get_fs_root(fs_info, &key, false);
 655 }
 656
 657 static noinline_for_stack
 658 int find_inline_backref(struct extent_buffer *leaf, int slot,
 659                         unsigned long *ptr, unsigned long *end)
 660 {
 661         struct btrfs_key key;
 662         struct btrfs_extent_item *ei;
 663         struct btrfs_tree_block_info *bi;
 664         u32 item_size;
 665
 666         btrfs_item_key_to_cpu(leaf, &key, slot);
 667
 668         item_size = btrfs_item_size_nr(leaf, slot);
 669         if (item_size < sizeof(*ei)) {
 670                 btrfs_print_v0_err(leaf->fs_info);
 671                 btrfs_handle_fs_error(leaf->fs_info, -EINVAL, NULL);
 672                 return 1;
 673         }
 674         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 675         WARN_ON(!(btrfs_extent_flags(leaf, ei) &
 676                   BTRFS_EXTENT_FLAG_TREE_BLOCK));
 677
 678         if (key.type == BTRFS_EXTENT_ITEM_KEY &&
 679             item_size <= sizeof(*ei) + sizeof(*bi)) {
 680                 WARN_ON(item_size < sizeof(*ei) + sizeof(*bi));
 681                 return 1;
 682         }
 683         if (key.type == BTRFS_METADATA_ITEM_KEY &&
 684             item_size <= sizeof(*ei)) {
 685                 WARN_ON(item_size < sizeof(*ei));
 686                 return 1;
 687         }
 688
 689         if (key.type == BTRFS_EXTENT_ITEM_KEY) {
 690                 bi = (struct btrfs_tree_block_info *)(ei + 1);
 691                 *ptr = (unsigned long)(bi + 1);
 692         } else {
 693                 *ptr = (unsigned long)(ei + 1);
 694         }
 695         *end = (unsigned long)ei + item_size;
 696         return 0;
 697 }
 698
 699 /*
 700  * build backref tree for a given tree block. root of the backref tree
 701  * corresponds the tree block, leaves of the backref tree correspond
 702  * roots of b-trees that reference the tree block.
 703  *
 704  * the basic idea of this function is check backrefs of a given block
 705  * to find upper level blocks that reference the block, and then check
 706  * backrefs of these upper level blocks recursively. the recursion stop
 707  * when tree root is reached or backrefs for the block is cached.
 708  *
 709  * NOTE: if we find backrefs for a block are cached, we know backrefs
 710  * for all upper level blocks that directly/indirectly reference the
 711  * block are also cached.
 712  */
 713 static noinline_for_stack
 714 struct backref_node *build_backref_tree(struct reloc_control *rc,
 715                                         struct btrfs_key *node_key,
 716                                         int level, u64 bytenr)
 717 {
 718         struct backref_cache *cache = &rc->backref_cache;
 719         struct btrfs_path *path1; /* For searching extent root */
 720         struct btrfs_path *path2; /* For searching parent of TREE_BLOCK_REF */
 721         struct extent_buffer *eb;
 722         struct btrfs_root *root;
 723         struct backref_node *cur;
 724         struct backref_node *upper;
 725         struct backref_node *lower;
 726         struct backref_node *node = NULL;
 727         struct backref_node *exist = NULL;
 728         struct backref_edge *edge;
 729         struct rb_node *rb_node;
 730         struct btrfs_key key;
 731         unsigned long end;
 732         unsigned long ptr;
 733         LIST_HEAD(list); /* Pending edge list, upper node needs to be checked */
 734         LIST_HEAD(useless);
 735         int cowonly;
 736         int ret;
 737         int err = 0;
 738         bool need_check = true;
 739
 740         path1 = btrfs_alloc_path();
 741         path2 = btrfs_alloc_path();
 742         if (!path1 || !path2) {
 743                 err = -ENOMEM;
 744                 goto out;
 745         }
 746
 747         node = alloc_backref_node(cache);
 748         if (!node) {
 749                 err = -ENOMEM;
 750                 goto out;
 751         }
 752
 753         node->bytenr = bytenr;
 754         node->level = level;
 755         node->lowest = 1;
 756         cur = node;
 757 again:
 758         end = 0;
 759         ptr = 0;
 760         key.objectid = cur->bytenr;
 761         key.type = BTRFS_METADATA_ITEM_KEY;
 762         key.offset = (u64)-1;
 763
 764         path1->search_commit_root = 1;
 765         path1->skip_locking = 1;
 766         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path1,
 767                                 0, 0);
 768         if (ret < 0) {
 769                 err = ret;
 770                 goto out;
 771         }
 772         ASSERT(ret);
 773         ASSERT(path1->slots[0]);
 774
 775         path1->slots[0]--;
 776
 777         WARN_ON(cur->checked);
 778         if (!list_empty(&cur->upper)) {
 779                 /*
 780                  * the backref was added previously when processing
 781                  * backref of type BTRFS_TREE_BLOCK_REF_KEY
 782                  */
 783                 ASSERT(list_is_singular(&cur->upper));
 784                 edge = list_entry(cur->upper.next, struct backref_edge,
 785                                   list[LOWER]);
 786                 ASSERT(list_empty(&edge->list[UPPER]));
 787                 exist = edge->node[UPPER];
 788                 /*
 789                  * add the upper level block to pending list if we need
 790                  * check its backrefs
 791                  */
 792                 if (!exist->checked)
 793                         list_add_tail(&edge->list[UPPER], &list);
 794         } else {
 795                 exist = NULL;
 796         }
 797
 798         while (1) {
 799                 cond_resched();
 800                 eb = path1->nodes[0];
 801
 802                 if (ptr >= end) {
 803                         if (path1->slots[0] >= btrfs_header_nritems(eb)) {
 804                                 ret = btrfs_next_leaf(rc->extent_root, path1);
 805                                 if (ret < 0) {
 806                                         err = ret;
 807                                         goto out;
 808                                 }
 809                                 if (ret > 0)
 810                                         break;
 811                                 eb = path1->nodes[0];
 812                         }
 813
 814                         btrfs_item_key_to_cpu(eb, &key, path1->slots[0]);
 815                         if (key.objectid != cur->bytenr) {
 816                                 WARN_ON(exist);
 817                                 break;
 818                         }
 819
 820                         if (key.type == BTRFS_EXTENT_ITEM_KEY ||
 821                             key.type == BTRFS_METADATA_ITEM_KEY) {
 822                                 ret = find_inline_backref(eb, path1->slots[0],
 823                                                           &ptr, &end);
 824                                 if (ret)
 825                                         goto next;
 826                         }
 827                 }
 828
 829                 if (ptr < end) {
 830                         /* update key for inline back ref */
 831                         struct btrfs_extent_inline_ref *iref;
 832                         int type;
 833                         iref = (struct btrfs_extent_inline_ref *)ptr;
 834                         type = btrfs_get_extent_inline_ref_type(eb, iref,
 835                                                         BTRFS_REF_TYPE_BLOCK);
 836                         if (type == BTRFS_REF_TYPE_INVALID) {
 837                                 err = -EUCLEAN;
 838                                 goto out;
 839                         }
 840                         key.type = type;
 841                         key.offset = btrfs_extent_inline_ref_offset(eb, iref);
 842
 843                         WARN_ON(key.type != BTRFS_TREE_BLOCK_REF_KEY &&
 844                                 key.type != BTRFS_SHARED_BLOCK_REF_KEY);
 845                 }
 846
 847                 /*
 848                  * Parent node found and matches current inline ref, no need to
 849                  * rebuild this node for this inline ref.
 850                  */
 851                 if (exist &&
 852                     ((key.type == BTRFS_TREE_BLOCK_REF_KEY &&
 853                       exist->owner == key.offset) ||
 854                      (key.type == BTRFS_SHARED_BLOCK_REF_KEY &&
 855                       exist->bytenr == key.offset))) {
 856                         exist = NULL;
 857                         goto next;
 858                 }
 859
 860                 /* SHARED_BLOCK_REF means key.offset is the parent bytenr */
 861                 if (key.type == BTRFS_SHARED_BLOCK_REF_KEY) {
 862                         if (key.objectid == key.offset) {
 863                                 /*
 864                                  * Only root blocks of reloc trees use backref
 865                                  * pointing to itself.
 866                                  */
 867                                 root = find_reloc_root(rc, cur->bytenr);
 868                                 ASSERT(root);
 869                                 cur->root = root;
 870                                 break;
 871                         }
 872
 873                         edge = alloc_backref_edge(cache);
 874                         if (!edge) {
 875                                 err = -ENOMEM;
 876                                 goto out;
 877                         }
 878                         rb_node = tree_search(&cache->rb_root, key.offset);
 879                         if (!rb_node) {
 880                                 upper = alloc_backref_node(cache);
 881                                 if (!upper) {
 882                                         free_backref_edge(cache, edge);
 883                                         err = -ENOMEM;
 884                                         goto out;
 885                                 }
 886                                 upper->bytenr = key.offset;
 887                                 upper->level = cur->level + 1;
 888                                 /*
 889                                  *  backrefs for the upper level block isn't
 890                                  *  cached, add the block to pending list
 891                                  */
 892                                 list_add_tail(&edge->list[UPPER], &list);
 893                         } else {
 894                                 upper = rb_entry(rb_node, struct backref_node,
 895                                                  rb_node);
 896                                 ASSERT(upper->checked);
 897                                 INIT_LIST_HEAD(&edge->list[UPPER]);
 898                         }
 899                         list_add_tail(&edge->list[LOWER], &cur->upper);
 900                         edge->node[LOWER] = cur;
 901                         edge->node[UPPER] = upper;
 902
 903                         goto next;
 904                 } else if (unlikely(key.type == BTRFS_EXTENT_REF_V0_KEY)) {
 905                         err = -EINVAL;
 906                         btrfs_print_v0_err(rc->extent_root->fs_info);
 907                         btrfs_handle_fs_error(rc->extent_root->fs_info, err,
 908                                               NULL);
 909                         goto out;
 910                 } else if (key.type != BTRFS_TREE_BLOCK_REF_KEY) {
 911                         goto next;
 912                 }
 913
 914                 /*
 915                  * key.type == BTRFS_TREE_BLOCK_REF_KEY, inline ref offset
 916                  * means the root objectid. We need to search the tree to get
 917                  * its parent bytenr.
 918                  */
 919                 root = read_fs_root(rc->extent_root->fs_info, key.offset);
 920                 if (IS_ERR(root)) {
 921                         err = PTR_ERR(root);
 922                         goto out;
 923                 }
 924
 925                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 926                         cur->cowonly = 1;
 927
 928                 if (btrfs_root_level(&root->root_item) == cur->level) {
 929                         /* tree root */
 930                         ASSERT(btrfs_root_bytenr(&root->root_item) ==
 931                                cur->bytenr);
 932                         if (should_ignore_root(root)) {
 933                                 btrfs_put_root(root);
 934                                 list_add(&cur->list, &useless);
 935                         } else {
 936                                 cur->root = root;
 937                         }
 938                         break;
 939                 }
 940
 941                 level = cur->level + 1;
 942
 943                 /* Search the tree to find parent blocks referring the block. */
 944                 path2->search_commit_root = 1;
 945                 path2->skip_locking = 1;
 946                 path2->lowest_level = level;
 947                 ret = btrfs_search_slot(NULL, root, node_key, path2, 0, 0);
 948                 path2->lowest_level = 0;
 949                 if (ret < 0) {
 950                         btrfs_put_root(root);
 951                         err = ret;
 952                         goto out;
 953                 }
 954                 if (ret > 0 && path2->slots[level] > 0)
 955                         path2->slots[level]--;
 956
 957                 eb = path2->nodes[level];
 958                 if (btrfs_node_blockptr(eb, path2->slots[level]) !=
 959                     cur->bytenr) {
 960                         btrfs_err(root->fs_info,
 961         "couldn't find block (%llu) (level %d) in tree (%llu) with key (%llu %u %llu)",
 962                                   cur->bytenr, level - 1,
 963                                   root->root_key.objectid,
 964                                   node_key->objectid, node_key->type,
 965                                   node_key->offset);
 966                         btrfs_put_root(root);
 967                         err = -ENOENT;
 968                         goto out;
 969                 }
 970                 lower = cur;
 971                 need_check = true;
 972
 973                 /* Add all nodes and edges in the path */
 974                 for (; level < BTRFS_MAX_LEVEL; level++) {
 975                         if (!path2->nodes[level]) {
 976                                 ASSERT(btrfs_root_bytenr(&root->root_item) ==
 977                                        lower->bytenr);
 978                                 if (should_ignore_root(root)) {
 979                                         btrfs_put_root(root);
 980                                         list_add(&lower->list, &useless);
 981                                 } else {
 982                                         lower->root = root;
 983                                 }
 984                                 break;
 985                         }
 986
 987                         edge = alloc_backref_edge(cache);
 988                         if (!edge) {
 989                                 btrfs_put_root(root);
 990                                 err = -ENOMEM;
 991                                 goto out;
 992                         }
 993
 994                         eb = path2->nodes[level];
 995                         rb_node = tree_search(&cache->rb_root, eb->start);
 996                         if (!rb_node) {
 997                                 upper = alloc_backref_node(cache);
 998                                 if (!upper) {
 999                                         btrfs_put_root(root);
1000                                         free_backref_edge(cache, edge);
1001                                         err = -ENOMEM;
1002                                         goto out;
1003                                 }
1004                                 upper->bytenr = eb->start;
1005                                 upper->owner = btrfs_header_owner(eb);
1006                                 upper->level = lower->level + 1;
1007                                 if (!test_bit(BTRFS_ROOT_REF_COWS,
1008                                               &root->state))
1009                                         upper->cowonly = 1;
1010
1011                                 /*
1012                                  * if we know the block isn't shared
1013                                  * we can void checking its backrefs.
1014                                  */
1015                                 if (btrfs_block_can_be_shared(root, eb))
1016                                         upper->checked = 0;
1017                                 else
1018                                         upper->checked = 1;
1019
1020                                 /*
1021                                  * add the block to pending list if we
1022                                  * need check its backrefs, we only do this once
1023                                  * while walking up a tree as we will catch
1024                                  * anything else later on.
1025                                  */
1026                                 if (!upper->checked && need_check) {
1027                                         need_check = false;
1028                                         list_add_tail(&edge->list[UPPER],
1029                                                       &list);
1030                                 } else {
1031                                         if (upper->checked)
1032                                                 need_check = true;
1033                                         INIT_LIST_HEAD(&edge->list[UPPER]);
1034                                 }
1035                         } else {
1036                                 upper = rb_entry(rb_node, struct backref_node,
1037                                                  rb_node);
1038                                 ASSERT(upper->checked);
1039                                 INIT_LIST_HEAD(&edge->list[UPPER]);
1040                                 if (!upper->owner)
1041                                         upper->owner = btrfs_header_owner(eb);
1042                         }
1043                         list_add_tail(&edge->list[LOWER], &lower->upper);
1044                         edge->node[LOWER] = lower;
1045                         edge->node[UPPER] = upper;
1046
1047                         if (rb_node) {
1048                                 btrfs_put_root(root);
1049                                 break;
1050                         }
1051                         lower = upper;
1052                         upper = NULL;
1053                 }
1054                 btrfs_release_path(path2);
1055 next:
1056                 if (ptr < end) {
1057                         ptr += btrfs_extent_inline_ref_size(key.type);
1058                         if (ptr >= end) {
1059                                 WARN_ON(ptr > end);
1060                                 ptr = 0;
1061                                 end = 0;
1062                         }
1063                 }
1064                 if (ptr >= end)
1065                         path1->slots[0]++;
1066         }
1067         btrfs_release_path(path1);
1068
1069         cur->checked = 1;
1070         WARN_ON(exist);
1071
1072         /* the pending list isn't empty, take the first block to process */
1073         if (!list_empty(&list)) {
1074                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1075                 list_del_init(&edge->list[UPPER]);
1076                 cur = edge->node[UPPER];
1077                 goto again;
1078         }
1079
1080         /*
1081          * everything goes well, connect backref nodes and insert backref nodes
1082          * into the cache.
1083          */
1084         ASSERT(node->checked);
1085         cowonly = node->cowonly;
1086         if (!cowonly) {
1087                 rb_node = tree_insert(&cache->rb_root, node->bytenr,
1088                                       &node->rb_node);
1089                 if (rb_node)
1090                         backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1091                 list_add_tail(&node->lower, &cache->leaves);
1092         }
1093
1094         list_for_each_entry(edge, &node->upper, list[LOWER])
1095                 list_add_tail(&edge->list[UPPER], &list);
1096
1097         while (!list_empty(&list)) {
1098                 edge = list_entry(list.next, struct backref_edge, list[UPPER]);
1099                 list_del_init(&edge->list[UPPER]);
1100                 upper = edge->node[UPPER];
1101                 if (upper->detached) {
1102                         list_del(&edge->list[LOWER]);
1103                         lower = edge->node[LOWER];
1104                         free_backref_edge(cache, edge);
1105                         if (list_empty(&lower->upper))
1106                                 list_add(&lower->list, &useless);
1107                         continue;
1108                 }
1109
1110                 if (!RB_EMPTY_NODE(&upper->rb_node)) {
1111                         if (upper->lowest) {
1112                                 list_del_init(&upper->lower);
1113                                 upper->lowest = 0;
1114                         }
1115
1116                         list_add_tail(&edge->list[UPPER], &upper->lower);
1117                         continue;
1118                 }
1119
1120                 if (!upper->checked) {
1121                         /*
1122                          * Still want to blow up for developers since this is a
1123                          * logic bug.
1124                          */
1125                         ASSERT(0);
1126                         err = -EINVAL;
1127                         goto out;
1128                 }
1129                 if (cowonly != upper->cowonly) {
1130                         ASSERT(0);
1131                         err = -EINVAL;
1132                         goto out;
1133                 }
1134
1135                 if (!cowonly) {
1136                         rb_node = tree_insert(&cache->rb_root, upper->bytenr,
1137                                               &upper->rb_node);
1138                         if (rb_node)
1139                                 backref_tree_panic(rb_node, -EEXIST,
1140                                                    upper->bytenr);
1141                 }
1142
1143                 list_add_tail(&edge->list[UPPER], &upper->lower);
1144
1145                 list_for_each_entry(edge, &upper->upper, list[LOWER])
1146                         list_add_tail(&edge->list[UPPER], &list);
1147         }
1148         /*
1149          * process useless backref nodes. backref nodes for tree leaves
1150          * are deleted from the cache. backref nodes for upper level
1151          * tree blocks are left in the cache to avoid unnecessary backref
1152          * lookup.
1153          */
1154         while (!list_empty(&useless)) {
1155                 upper = list_entry(useless.next, struct backref_node, list);
1156                 list_del_init(&upper->list);
1157                 ASSERT(list_empty(&upper->upper));
1158                 if (upper == node)
1159                         node = NULL;
1160                 if (upper->lowest) {
1161                         list_del_init(&upper->lower);
1162                         upper->lowest = 0;
1163                 }
1164                 while (!list_empty(&upper->lower)) {
1165                         edge = list_entry(upper->lower.next,
1166                                           struct backref_edge, list[UPPER]);
1167                         list_del(&edge->list[UPPER]);
1168                         list_del(&edge->list[LOWER]);
1169                         lower = edge->node[LOWER];
1170                         free_backref_edge(cache, edge);
1171
1172                         if (list_empty(&lower->upper))
1173                                 list_add(&lower->list, &useless);
1174                 }
1175                 __mark_block_processed(rc, upper);
1176                 if (upper->level > 0) {
1177                         list_add(&upper->list, &cache->detached);
1178                         upper->detached = 1;
1179                 } else {
1180                         rb_erase(&upper->rb_node, &cache->rb_root);
1181                         free_backref_node(cache, upper);
1182                 }
1183         }
1184 out:
1185         btrfs_free_path(path1);
1186         btrfs_free_path(path2);
1187         if (err) {
1188                 while (!list_empty(&useless)) {
1189                         lower = list_entry(useless.next,
1190                                            struct backref_node, list);
1191                         list_del_init(&lower->list);
1192                 }
1193                 while (!list_empty(&list)) {
1194                         edge = list_first_entry(&list, struct backref_edge,
1195                                                 list[UPPER]);
1196                         list_del(&edge->list[UPPER]);
1197                         list_del(&edge->list[LOWER]);
1198                         lower = edge->node[LOWER];
1199                         upper = edge->node[UPPER];
1200                         free_backref_edge(cache, edge);
1201
1202                         /*
1203                          * Lower is no longer linked to any upper backref nodes
1204                          * and isn't in the cache, we can free it ourselves.
1205                          */
1206                         if (list_empty(&lower->upper) &&
1207                             RB_EMPTY_NODE(&lower->rb_node))
1208                                 list_add(&lower->list, &useless);
1209
1210                         if (!RB_EMPTY_NODE(&upper->rb_node))
1211                                 continue;
1212
1213                         /* Add this guy's upper edges to the list to process */
1214                         list_for_each_entry(edge, &upper->upper, list[LOWER])
1215                                 list_add_tail(&edge->list[UPPER], &list);
1216                         if (list_empty(&upper->upper))
1217                                 list_add(&upper->list, &useless);
1218                 }
1219
1220                 while (!list_empty(&useless)) {
1221                         lower = list_entry(useless.next,
1222                                            struct backref_node, list);
1223                         list_del_init(&lower->list);
1224                         if (lower == node)
1225                                 node = NULL;
1226                         free_backref_node(cache, lower);
1227                 }
1228
1229                 remove_backref_node(cache, node);
1230                 return ERR_PTR(err);
1231         }
1232         ASSERT(!node || !node->detached);
1233         return node;
1234 }
1235
1236 /*
1237  * helper to add backref node for the newly created snapshot.
1238  * the backref node is created by cloning backref node that
1239  * corresponds to root of source tree
1240  */
1241 static int clone_backref_node(struct btrfs_trans_handle *trans,
1242                               struct reloc_control *rc,
1243                               struct btrfs_root *src,
1244                               struct btrfs_root *dest)
1245 {
1246         struct btrfs_root *reloc_root = src->reloc_root;
1247         struct backref_cache *cache = &rc->backref_cache;
1248         struct backref_node *node = NULL;
1249         struct backref_node *new_node;
1250         struct backref_edge *edge;
1251         struct backref_edge *new_edge;
1252         struct rb_node *rb_node;
1253
1254         if (cache->last_trans > 0)
1255                 update_backref_cache(trans, cache);
1256
1257         rb_node = tree_search(&cache->rb_root, src->commit_root->start);
1258         if (rb_node) {
1259                 node = rb_entry(rb_node, struct backref_node, rb_node);
1260                 if (node->detached)
1261                         node = NULL;
1262                 else
1263                         BUG_ON(node->new_bytenr != reloc_root->node->start);
1264         }
1265
1266         if (!node) {
1267                 rb_node = tree_search(&cache->rb_root,
1268                                       reloc_root->commit_root->start);
1269                 if (rb_node) {
1270                         node = rb_entry(rb_node, struct backref_node,
1271                                         rb_node);
1272                         BUG_ON(node->detached);
1273                 }
1274         }
1275
1276         if (!node)
1277                 return 0;
1278
1279         new_node = alloc_backref_node(cache);
1280         if (!new_node)
1281                 return -ENOMEM;
1282
1283         new_node->bytenr = dest->node->start;
1284         new_node->level = node->level;
1285         new_node->lowest = node->lowest;
1286         new_node->checked = 1;
1287         new_node->root = btrfs_grab_root(dest);
1288         ASSERT(new_node->root);
1289
1290         if (!node->lowest) {
1291                 list_for_each_entry(edge, &node->lower, list[UPPER]) {
1292                         new_edge = alloc_backref_edge(cache);
1293                         if (!new_edge)
1294                                 goto fail;
1295
1296                         new_edge->node[UPPER] = new_node;
1297                         new_edge->node[LOWER] = edge->node[LOWER];
1298                         list_add_tail(&new_edge->list[UPPER],
1299                                       &new_node->lower);
1300                 }
1301         } else {
1302                 list_add_tail(&new_node->lower, &cache->leaves);
1303         }
1304
1305         rb_node = tree_insert(&cache->rb_root, new_node->bytenr,
1306                               &new_node->rb_node);
1307         if (rb_node)
1308                 backref_tree_panic(rb_node, -EEXIST, new_node->bytenr);
1309
1310         if (!new_node->lowest) {
1311                 list_for_each_entry(new_edge, &new_node->lower, list[UPPER]) {
1312                         list_add_tail(&new_edge->list[LOWER],
1313                                       &new_edge->node[LOWER]->upper);
1314                 }
1315         }
1316         return 0;
1317 fail:
1318         while (!list_empty(&new_node->lower)) {
1319                 new_edge = list_entry(new_node->lower.next,
1320                                       struct backref_edge, list[UPPER]);
1321                 list_del(&new_edge->list[UPPER]);
1322                 free_backref_edge(cache, new_edge);
1323         }
1324         free_backref_node(cache, new_node);
1325         return -ENOMEM;
1326 }
1327
1328 /*
1329  * helper to add 'address of tree root -> reloc tree' mapping
1330  */
1331 static int __must_check __add_reloc_root(struct btrfs_root *root)
1332 {
1333         struct btrfs_fs_info *fs_info = root->fs_info;
1334         struct rb_node *rb_node;
1335         struct mapping_node *node;
1336         struct reloc_control *rc = fs_info->reloc_ctl;
1337
1338         node = kmalloc(sizeof(*node), GFP_NOFS);
1339         if (!node)
1340                 return -ENOMEM;
1341
1342         node->bytenr = root->commit_root->start;
1343         node->data = root;
1344
1345         spin_lock(&rc->reloc_root_tree.lock);
1346         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1347                               node->bytenr, &node->rb_node);
1348         spin_unlock(&rc->reloc_root_tree.lock);
1349         if (rb_node) {
1350                 btrfs_panic(fs_info, -EEXIST,
1351                             "Duplicate root found for start=%llu while inserting into relocation tree",
1352                             node->bytenr);
1353         }
1354
1355         list_add_tail(&root->root_list, &rc->reloc_roots);
1356         return 0;
1357 }
1358
1359 /*
1360  * helper to delete the 'address of tree root -> reloc tree'
1361  * mapping
1362  */
1363 static void __del_reloc_root(struct btrfs_root *root)
1364 {
1365         struct btrfs_fs_info *fs_info = root->fs_info;
1366         struct rb_node *rb_node;
1367         struct mapping_node *node = NULL;
1368         struct reloc_control *rc = fs_info->reloc_ctl;
1369         bool put_ref = false;
1370
1371         if (rc && root->node) {
1372                 spin_lock(&rc->reloc_root_tree.lock);
1373                 rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1374                                       root->commit_root->start);
1375                 if (rb_node) {
1376                         node = rb_entry(rb_node, struct mapping_node, rb_node);
1377                         rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1378                         RB_CLEAR_NODE(&node->rb_node);
1379                 }
1380                 spin_unlock(&rc->reloc_root_tree.lock);
1381                 if (!node)
1382                         return;
1383                 BUG_ON((struct btrfs_root *)node->data != root);
1384         }
1385
1386         /*
1387          * We only put the reloc root here if it's on the list.  There's a lot
1388          * of places where the pattern is to splice the rc->reloc_roots, process
1389          * the reloc roots, and then add the reloc root back onto
1390          * rc->reloc_roots.  If we call __del_reloc_root while it's off of the
1391          * list we don't want the reference being dropped, because the guy
1392          * messing with the list is in charge of the reference.
1393          */
1394         spin_lock(&fs_info->trans_lock);
1395         if (!list_empty(&root->root_list)) {
1396                 put_ref = true;
1397                 list_del_init(&root->root_list);
1398         }
1399         spin_unlock(&fs_info->trans_lock);
1400         if (put_ref)
1401                 btrfs_put_root(root);
1402         kfree(node);
1403 }
1404
1405 /*
1406  * helper to update the 'address of tree root -> reloc tree'
1407  * mapping
1408  */
1409 static int __update_reloc_root(struct btrfs_root *root)
1410 {
1411         struct btrfs_fs_info *fs_info = root->fs_info;
1412         struct rb_node *rb_node;
1413         struct mapping_node *node = NULL;
1414         struct reloc_control *rc = fs_info->reloc_ctl;
1415
1416         spin_lock(&rc->reloc_root_tree.lock);
1417         rb_node = tree_search(&rc->reloc_root_tree.rb_root,
1418                               root->commit_root->start);
1419         if (rb_node) {
1420                 node = rb_entry(rb_node, struct mapping_node, rb_node);
1421                 rb_erase(&node->rb_node, &rc->reloc_root_tree.rb_root);
1422         }
1423         spin_unlock(&rc->reloc_root_tree.lock);
1424
1425         if (!node)
1426                 return 0;
1427         BUG_ON((struct btrfs_root *)node->data != root);
1428
1429         spin_lock(&rc->reloc_root_tree.lock);
1430         node->bytenr = root->node->start;
1431         rb_node = tree_insert(&rc->reloc_root_tree.rb_root,
1432                               node->bytenr, &node->rb_node);
1433         spin_unlock(&rc->reloc_root_tree.lock);
1434         if (rb_node)
1435                 backref_tree_panic(rb_node, -EEXIST, node->bytenr);
1436         return 0;
1437 }
1438
1439 static struct btrfs_root *create_reloc_root(struct btrfs_trans_handle *trans,
1440                                         struct btrfs_root *root, u64 objectid)
1441 {
1442         struct btrfs_fs_info *fs_info = root->fs_info;
1443         struct btrfs_root *reloc_root;
1444         struct extent_buffer *eb;
1445         struct btrfs_root_item *root_item;
1446         struct btrfs_key root_key;
1447         int ret;
1448
1449         root_item = kmalloc(sizeof(*root_item), GFP_NOFS);
1450         BUG_ON(!root_item);
1451
1452         root_key.objectid = BTRFS_TREE_RELOC_OBJECTID;
1453         root_key.type = BTRFS_ROOT_ITEM_KEY;
1454         root_key.offset = objectid;
1455
1456         if (root->root_key.objectid == objectid) {
1457                 u64 commit_root_gen;
1458
1459                 /* called by btrfs_init_reloc_root */
1460                 ret = btrfs_copy_root(trans, root, root->commit_root, &eb,
1461                                       BTRFS_TREE_RELOC_OBJECTID);
1462                 BUG_ON(ret);
1463                 /*
1464                  * Set the last_snapshot field to the generation of the commit
1465                  * root - like this ctree.c:btrfs_block_can_be_shared() behaves
1466                  * correctly (returns true) when the relocation root is created
1467                  * either inside the critical section of a transaction commit
1468                  * (through transaction.c:qgroup_account_snapshot()) and when
1469                  * it's created before the transaction commit is started.
1470                  */
1471                 commit_root_gen = btrfs_header_generation(root->commit_root);
1472                 btrfs_set_root_last_snapshot(&root->root_item, commit_root_gen);
1473         } else {
1474                 /*
1475                  * called by btrfs_reloc_post_snapshot_hook.
1476                  * the source tree is a reloc tree, all tree blocks
1477                  * modified after it was created have RELOC flag
1478                  * set in their headers. so it's OK to not update
1479                  * the 'last_snapshot'.
1480                  */
1481                 ret = btrfs_copy_root(trans, root, root->node, &eb,
1482                                       BTRFS_TREE_RELOC_OBJECTID);
1483                 BUG_ON(ret);
1484         }
1485
1486         memcpy(root_item, &root->root_item, sizeof(*root_item));
1487         btrfs_set_root_bytenr(root_item, eb->start);
1488         btrfs_set_root_level(root_item, btrfs_header_level(eb));
1489         btrfs_set_root_generation(root_item, trans->transid);
1490
1491         if (root->root_key.objectid == objectid) {
1492                 btrfs_set_root_refs(root_item, 0);
1493                 memset(&root_item->drop_progress, 0,
1494                        sizeof(struct btrfs_disk_key));
1495                 root_item->drop_level = 0;
1496         }
1497
1498         btrfs_tree_unlock(eb);
1499         free_extent_buffer(eb);
1500
1501         ret = btrfs_insert_root(trans, fs_info->tree_root,
1502                                 &root_key, root_item);
1503         BUG_ON(ret);
1504         kfree(root_item);
1505
1506         reloc_root = btrfs_read_tree_root(fs_info->tree_root, &root_key);
1507         BUG_ON(IS_ERR(reloc_root));
1508         set_bit(BTRFS_ROOT_REF_COWS, &reloc_root->state);
1509         reloc_root->last_trans = trans->transid;
1510         return reloc_root;
1511 }
1512
1513 /*
1514  * create reloc tree for a given fs tree. reloc tree is just a
1515  * snapshot of the fs tree with special root objectid.
1516  *
1517  * The reloc_root comes out of here with two references, one for
1518  * root->reloc_root, and another for being on the rc->reloc_roots list.
1519  */
1520 int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
1521                           struct btrfs_root *root)
1522 {
1523         struct btrfs_fs_info *fs_info = root->fs_info;
1524         struct btrfs_root *reloc_root;
1525         struct reloc_control *rc = fs_info->reloc_ctl;
1526         struct btrfs_block_rsv *rsv;
1527         int clear_rsv = 0;
1528         int ret;
1529
1530         if (!rc || !rc->create_reloc_tree ||
1531             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1532                 return 0;
1533
1534         /*
1535          * The subvolume has reloc tree but the swap is finished, no need to
1536          * create/update the dead reloc tree
1537          */
1538         if (reloc_root_is_dead(root))
1539                 return 0;
1540
1541         if (root->reloc_root) {
1542                 reloc_root = root->reloc_root;
1543                 reloc_root->last_trans = trans->transid;
1544                 return 0;
1545         }
1546
1547         if (!trans->reloc_reserved) {
1548                 rsv = trans->block_rsv;
1549                 trans->block_rsv = rc->block_rsv;
1550                 clear_rsv = 1;
1551         }
1552         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1553         if (clear_rsv)
1554                 trans->block_rsv = rsv;
1555
1556         ret = __add_reloc_root(reloc_root);
1557         BUG_ON(ret < 0);
1558         root->reloc_root = btrfs_grab_root(reloc_root);
1559         return 0;
1560 }
1561
1562 /*
1563  * update root item of reloc tree
1564  */
1565 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1566                             struct btrfs_root *root)
1567 {
1568         struct btrfs_fs_info *fs_info = root->fs_info;
1569         struct btrfs_root *reloc_root;
1570         struct btrfs_root_item *root_item;
1571         int ret;
1572
1573         if (!have_reloc_root(root))
1574                 goto out;
1575
1576         reloc_root = root->reloc_root;
1577         root_item = &reloc_root->root_item;
1578
1579         /*
1580          * We are probably ok here, but __del_reloc_root() will drop its ref of
1581          * the root.  We have the ref for root->reloc_root, but just in case
1582          * hold it while we update the reloc root.
1583          */
1584         btrfs_grab_root(reloc_root);
1585
1586         /* root->reloc_root will stay until current relocation finished */
1587         if (fs_info->reloc_ctl->merge_reloc_tree &&
1588             btrfs_root_refs(root_item) == 0) {
1589                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1590                 /*
1591                  * Mark the tree as dead before we change reloc_root so
1592                  * have_reloc_root will not touch it from now on.
1593                  */
1594                 smp_wmb();
1595                 __del_reloc_root(reloc_root);
1596         }
1597
1598         if (reloc_root->commit_root != reloc_root->node) {
1599                 __update_reloc_root(reloc_root);
1600                 btrfs_set_root_node(root_item, reloc_root->node);
1601                 free_extent_buffer(reloc_root->commit_root);
1602                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1603         }
1604
1605         ret = btrfs_update_root(trans, fs_info->tree_root,
1606                                 &reloc_root->root_key, root_item);
1607         BUG_ON(ret);
1608         btrfs_put_root(reloc_root);
1609 out:
1610         return 0;
1611 }
1612
1613 /*
1614  * helper to find first cached inode with inode number >= objectid
1615  * in a subvolume
1616  */
1617 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1618 {
1619         struct rb_node *node;
1620         struct rb_node *prev;
1621         struct btrfs_inode *entry;
1622         struct inode *inode;
1623
1624         spin_lock(&root->inode_lock);
1625 again:
1626         node = root->inode_tree.rb_node;
1627         prev = NULL;
1628         while (node) {
1629                 prev = node;
1630                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1631
1632                 if (objectid < btrfs_ino(entry))
1633                         node = node->rb_left;
1634                 else if (objectid > btrfs_ino(entry))
1635                         node = node->rb_right;
1636                 else
1637                         break;
1638         }
1639         if (!node) {
1640                 while (prev) {
1641                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1642                         if (objectid <= btrfs_ino(entry)) {
1643                                 node = prev;
1644                                 break;
1645                         }
1646                         prev = rb_next(prev);
1647                 }
1648         }
1649         while (node) {
1650                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1651                 inode = igrab(&entry->vfs_inode);
1652                 if (inode) {
1653                         spin_unlock(&root->inode_lock);
1654                         return inode;
1655                 }
1656
1657                 objectid = btrfs_ino(entry) + 1;
1658                 if (cond_resched_lock(&root->inode_lock))
1659                         goto again;
1660
1661                 node = rb_next(node);
1662         }
1663         spin_unlock(&root->inode_lock);
1664         return NULL;
1665 }
1666
1667 static int in_block_group(u64 bytenr, struct btrfs_block_group *block_group)
1668 {
1669         if (bytenr >= block_group->start &&
1670             bytenr < block_group->start + block_group->length)
1671                 return 1;
1672         return 0;
1673 }
1674
1675 /*
1676  * get new location of data
1677  */
1678 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1679                             u64 bytenr, u64 num_bytes)
1680 {
1681         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1682         struct btrfs_path *path;
1683         struct btrfs_file_extent_item *fi;
1684         struct extent_buffer *leaf;
1685         int ret;
1686
1687         path = btrfs_alloc_path();
1688         if (!path)
1689                 return -ENOMEM;
1690
1691         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1692         ret = btrfs_lookup_file_extent(NULL, root, path,
1693                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1694         if (ret < 0)
1695                 goto out;
1696         if (ret > 0) {
1697                 ret = -ENOENT;
1698                 goto out;
1699         }
1700
1701         leaf = path->nodes[0];
1702         fi = btrfs_item_ptr(leaf, path->slots[0],
1703                             struct btrfs_file_extent_item);
1704
1705         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1706                btrfs_file_extent_compression(leaf, fi) ||
1707                btrfs_file_extent_encryption(leaf, fi) ||
1708                btrfs_file_extent_other_encoding(leaf, fi));
1709
1710         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1711                 ret = -EINVAL;
1712                 goto out;
1713         }
1714
1715         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1716         ret = 0;
1717 out:
1718         btrfs_free_path(path);
1719         return ret;
1720 }
1721
1722 /*
1723  * update file extent items in the tree leaf to point to
1724  * the new locations.
1725  */
1726 static noinline_for_stack
1727 int replace_file_extents(struct btrfs_trans_handle *trans,
1728                          struct reloc_control *rc,
1729                          struct btrfs_root *root,
1730                          struct extent_buffer *leaf)
1731 {
1732         struct btrfs_fs_info *fs_info = root->fs_info;
1733         struct btrfs_key key;
1734         struct btrfs_file_extent_item *fi;
1735         struct inode *inode = NULL;
1736         u64 parent;
1737         u64 bytenr;
1738         u64 new_bytenr = 0;
1739         u64 num_bytes;
1740         u64 end;
1741         u32 nritems;
1742         u32 i;
1743         int ret = 0;
1744         int first = 1;
1745         int dirty = 0;
1746
1747         if (rc->stage != UPDATE_DATA_PTRS)
1748                 return 0;
1749
1750         /* reloc trees always use full backref */
1751         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1752                 parent = leaf->start;
1753         else
1754                 parent = 0;
1755
1756         nritems = btrfs_header_nritems(leaf);
1757         for (i = 0; i < nritems; i++) {
1758                 struct btrfs_ref ref = { 0 };
1759
1760                 cond_resched();
1761                 btrfs_item_key_to_cpu(leaf, &key, i);
1762                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1763                         continue;
1764                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1765                 if (btrfs_file_extent_type(leaf, fi) ==
1766                     BTRFS_FILE_EXTENT_INLINE)
1767                         continue;
1768                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1769                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1770                 if (bytenr == 0)
1771                         continue;
1772                 if (!in_block_group(bytenr, rc->block_group))
1773                         continue;
1774
1775                 /*
1776                  * if we are modifying block in fs tree, wait for readpage
1777                  * to complete and drop the extent cache
1778                  */
1779                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1780                         if (first) {
1781                                 inode = find_next_inode(root, key.objectid);
1782                                 first = 0;
1783                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1784                                 btrfs_add_delayed_iput(inode);
1785                                 inode = find_next_inode(root, key.objectid);
1786                         }
1787                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1788                                 end = key.offset +
1789                                       btrfs_file_extent_num_bytes(leaf, fi);
1790                                 WARN_ON(!IS_ALIGNED(key.offset,
1791                                                     fs_info->sectorsize));
1792                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1793                                 end--;
1794                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1795                                                       key.offset, end);
1796                                 if (!ret)
1797                                         continue;
1798
1799                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1800                                                 key.offset,     end, 1);
1801                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1802                                               key.offset, end);
1803                         }
1804                 }
1805
1806                 ret = get_new_location(rc->data_inode, &new_bytenr,
1807                                        bytenr, num_bytes);
1808                 if (ret) {
1809                         /*
1810                          * Don't have to abort since we've not changed anything
1811                          * in the file extent yet.
1812                          */
1813                         break;
1814                 }
1815
1816                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1817                 dirty = 1;
1818
1819                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1820                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1821                                        num_bytes, parent);
1822                 ref.real_root = root->root_key.objectid;
1823                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1824                                     key.objectid, key.offset);
1825                 ret = btrfs_inc_extent_ref(trans, &ref);
1826                 if (ret) {
1827                         btrfs_abort_transaction(trans, ret);
1828                         break;
1829                 }
1830
1831                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1832                                        num_bytes, parent);
1833                 ref.real_root = root->root_key.objectid;
1834                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1835                                     key.objectid, key.offset);
1836                 ret = btrfs_free_extent(trans, &ref);
1837                 if (ret) {
1838                         btrfs_abort_transaction(trans, ret);
1839                         break;
1840                 }
1841         }
1842         if (dirty)
1843                 btrfs_mark_buffer_dirty(leaf);
1844         if (inode)
1845                 btrfs_add_delayed_iput(inode);
1846         return ret;
1847 }
1848
1849 static noinline_for_stack
1850 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1851                      struct btrfs_path *path, int level)
1852 {
1853         struct btrfs_disk_key key1;
1854         struct btrfs_disk_key key2;
1855         btrfs_node_key(eb, &key1, slot);
1856         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1857         return memcmp(&key1, &key2, sizeof(key1));
1858 }
1859
1860 /*
1861  * try to replace tree blocks in fs tree with the new blocks
1862  * in reloc tree. tree blocks haven't been modified since the
1863  * reloc tree was create can be replaced.
1864  *
1865  * if a block was replaced, level of the block + 1 is returned.
1866  * if no block got replaced, 0 is returned. if there are other
1867  * errors, a negative error number is returned.
1868  */
1869 static noinline_for_stack
1870 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1871                  struct btrfs_root *dest, struct btrfs_root *src,
1872                  struct btrfs_path *path, struct btrfs_key *next_key,
1873                  int lowest_level, int max_level)
1874 {
1875         struct btrfs_fs_info *fs_info = dest->fs_info;
1876         struct extent_buffer *eb;
1877         struct extent_buffer *parent;
1878         struct btrfs_ref ref = { 0 };
1879         struct btrfs_key key;
1880         u64 old_bytenr;
1881         u64 new_bytenr;
1882         u64 old_ptr_gen;
1883         u64 new_ptr_gen;
1884         u64 last_snapshot;
1885         u32 blocksize;
1886         int cow = 0;
1887         int level;
1888         int ret;
1889         int slot;
1890
1891         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1892         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1893
1894         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1895 again:
1896         slot = path->slots[lowest_level];
1897         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1898
1899         eb = btrfs_lock_root_node(dest);
1900         btrfs_set_lock_blocking_write(eb);
1901         level = btrfs_header_level(eb);
1902
1903         if (level < lowest_level) {
1904                 btrfs_tree_unlock(eb);
1905                 free_extent_buffer(eb);
1906                 return 0;
1907         }
1908
1909         if (cow) {
1910                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1911                 BUG_ON(ret);
1912         }
1913         btrfs_set_lock_blocking_write(eb);
1914
1915         if (next_key) {
1916                 next_key->objectid = (u64)-1;
1917                 next_key->type = (u8)-1;
1918                 next_key->offset = (u64)-1;
1919         }
1920
1921         parent = eb;
1922         while (1) {
1923                 struct btrfs_key first_key;
1924
1925                 level = btrfs_header_level(parent);
1926                 BUG_ON(level < lowest_level);
1927
1928                 ret = btrfs_bin_search(parent, &key, level, &slot);
1929                 if (ret < 0)
1930                         break;
1931                 if (ret && slot > 0)
1932                         slot--;
1933
1934                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1935                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1936
1937                 old_bytenr = btrfs_node_blockptr(parent, slot);
1938                 blocksize = fs_info->nodesize;
1939                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1940                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1941
1942                 if (level <= max_level) {
1943                         eb = path->nodes[level];
1944                         new_bytenr = btrfs_node_blockptr(eb,
1945                                                         path->slots[level]);
1946                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1947                                                         path->slots[level]);
1948                 } else {
1949                         new_bytenr = 0;
1950                         new_ptr_gen = 0;
1951                 }
1952
1953                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1954                         ret = level;
1955                         break;
1956                 }
1957
1958                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1959                     memcmp_node_keys(parent, slot, path, level)) {
1960                         if (level <= lowest_level) {
1961                                 ret = 0;
1962                                 break;
1963                         }
1964
1965                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1966                                              level - 1, &first_key);
1967                         if (IS_ERR(eb)) {
1968                                 ret = PTR_ERR(eb);
1969                                 break;
1970                         } else if (!extent_buffer_uptodate(eb)) {
1971                                 ret = -EIO;
1972                                 free_extent_buffer(eb);
1973                                 break;
1974                         }
1975                         btrfs_tree_lock(eb);
1976                         if (cow) {
1977                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1978                                                       slot, &eb);
1979                                 BUG_ON(ret);
1980                         }
1981                         btrfs_set_lock_blocking_write(eb);
1982
1983                         btrfs_tree_unlock(parent);
1984                         free_extent_buffer(parent);
1985
1986                         parent = eb;
1987                         continue;
1988                 }
1989
1990                 if (!cow) {
1991                         btrfs_tree_unlock(parent);
1992                         free_extent_buffer(parent);
1993                         cow = 1;
1994                         goto again;
1995                 }
1996
1997                 btrfs_node_key_to_cpu(path->nodes[level], &key,
1998                                       path->slots[level]);
1999                 btrfs_release_path(path);
2000
2001                 path->lowest_level = level;
2002                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
2003                 path->lowest_level = 0;
2004                 BUG_ON(ret);
2005
2006                 /*
2007                  * Info qgroup to trace both subtrees.
2008                  *
2009                  * We must trace both trees.
2010                  * 1) Tree reloc subtree
2011                  *    If not traced, we will leak data numbers
2012                  * 2) Fs subtree
2013                  *    If not traced, we will double count old data
2014                  *
2015                  * We don't scan the subtree right now, but only record
2016                  * the swapped tree blocks.
2017                  * The real subtree rescan is delayed until we have new
2018                  * CoW on the subtree root node before transaction commit.
2019                  */
2020                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
2021                                 rc->block_group, parent, slot,
2022                                 path->nodes[level], path->slots[level],
2023                                 last_snapshot);
2024                 if (ret < 0)
2025                         break;
2026                 /*
2027                  * swap blocks in fs tree and reloc tree.
2028                  */
2029                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
2030                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
2031                 btrfs_mark_buffer_dirty(parent);
2032
2033                 btrfs_set_node_blockptr(path->nodes[level],
2034                                         path->slots[level], old_bytenr);
2035                 btrfs_set_node_ptr_generation(path->nodes[level],
2036                                               path->slots[level], old_ptr_gen);
2037                 btrfs_mark_buffer_dirty(path->nodes[level]);
2038
2039                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
2040                                        blocksize, path->nodes[level]->start);
2041                 ref.skip_qgroup = true;
2042                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
2043                 ret = btrfs_inc_extent_ref(trans, &ref);
2044                 BUG_ON(ret);
2045                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
2046                                        blocksize, 0);
2047                 ref.skip_qgroup = true;
2048                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
2049                 ret = btrfs_inc_extent_ref(trans, &ref);
2050                 BUG_ON(ret);
2051
2052                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
2053                                        blocksize, path->nodes[level]->start);
2054                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
2055                 ref.skip_qgroup = true;
2056                 ret = btrfs_free_extent(trans, &ref);
2057                 BUG_ON(ret);
2058
2059                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
2060                                        blocksize, 0);
2061                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
2062                 ref.skip_qgroup = true;
2063                 ret = btrfs_free_extent(trans, &ref);
2064                 BUG_ON(ret);
2065
2066                 btrfs_unlock_up_safe(path, 0);
2067
2068                 ret = level;
2069                 break;
2070         }
2071         btrfs_tree_unlock(parent);
2072         free_extent_buffer(parent);
2073         return ret;
2074 }
2075
2076 /*
2077  * helper to find next relocated block in reloc tree
2078  */
2079 static noinline_for_stack
2080 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2081                        int *level)
2082 {
2083         struct extent_buffer *eb;
2084         int i;
2085         u64 last_snapshot;
2086         u32 nritems;
2087
2088         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2089
2090         for (i = 0; i < *level; i++) {
2091                 free_extent_buffer(path->nodes[i]);
2092                 path->nodes[i] = NULL;
2093         }
2094
2095         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
2096                 eb = path->nodes[i];
2097                 nritems = btrfs_header_nritems(eb);
2098                 while (path->slots[i] + 1 < nritems) {
2099                         path->slots[i]++;
2100                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
2101                             last_snapshot)
2102                                 continue;
2103
2104                         *level = i;
2105                         return 0;
2106                 }
2107                 free_extent_buffer(path->nodes[i]);
2108                 path->nodes[i] = NULL;
2109         }
2110         return 1;
2111 }
2112
2113 /*
2114  * walk down reloc tree to find relocated block of lowest level
2115  */
2116 static noinline_for_stack
2117 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2118                          int *level)
2119 {
2120         struct btrfs_fs_info *fs_info = root->fs_info;
2121         struct extent_buffer *eb = NULL;
2122         int i;
2123         u64 bytenr;
2124         u64 ptr_gen = 0;
2125         u64 last_snapshot;
2126         u32 nritems;
2127
2128         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2129
2130         for (i = *level; i > 0; i--) {
2131                 struct btrfs_key first_key;
2132
2133                 eb = path->nodes[i];
2134                 nritems = btrfs_header_nritems(eb);
2135                 while (path->slots[i] < nritems) {
2136                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2137                         if (ptr_gen > last_snapshot)
2138                                 break;
2139                         path->slots[i]++;
2140                 }
2141                 if (path->slots[i] >= nritems) {
2142                         if (i == *level)
2143                                 break;
2144                         *level = i + 1;
2145                         return 0;
2146                 }
2147                 if (i == 1) {
2148                         *level = i;
2149                         return 0;
2150                 }
2151
2152                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2153                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
2154                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
2155                                      &first_key);
2156                 if (IS_ERR(eb)) {
2157                         return PTR_ERR(eb);
2158                 } else if (!extent_buffer_uptodate(eb)) {
2159                         free_extent_buffer(eb);
2160                         return -EIO;
2161                 }
2162                 BUG_ON(btrfs_header_level(eb) != i - 1);
2163                 path->nodes[i - 1] = eb;
2164                 path->slots[i - 1] = 0;
2165         }
2166         return 1;
2167 }
2168
2169 /*
2170  * invalidate extent cache for file extents whose key in range of
2171  * [min_key, max_key)
2172  */
2173 static int invalidate_extent_cache(struct btrfs_root *root,
2174                                    struct btrfs_key *min_key,
2175                                    struct btrfs_key *max_key)
2176 {
2177         struct btrfs_fs_info *fs_info = root->fs_info;
2178         struct inode *inode = NULL;
2179         u64 objectid;
2180         u64 start, end;
2181         u64 ino;
2182
2183         objectid = min_key->objectid;
2184         while (1) {
2185                 cond_resched();
2186                 iput(inode);
2187
2188                 if (objectid > max_key->objectid)
2189                         break;
2190
2191                 inode = find_next_inode(root, objectid);
2192                 if (!inode)
2193                         break;
2194                 ino = btrfs_ino(BTRFS_I(inode));
2195
2196                 if (ino > max_key->objectid) {
2197                         iput(inode);
2198                         break;
2199                 }
2200
2201                 objectid = ino + 1;
2202                 if (!S_ISREG(inode->i_mode))
2203                         continue;
2204
2205                 if (unlikely(min_key->objectid == ino)) {
2206                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2207                                 continue;
2208                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2209                                 start = 0;
2210                         else {
2211                                 start = min_key->offset;
2212                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2213                         }
2214                 } else {
2215                         start = 0;
2216                 }
2217
2218                 if (unlikely(max_key->objectid == ino)) {
2219                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2220                                 continue;
2221                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2222                                 end = (u64)-1;
2223                         } else {
2224                                 if (max_key->offset == 0)
2225                                         continue;
2226                                 end = max_key->offset;
2227                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2228                                 end--;
2229                         }
2230                 } else {
2231                         end = (u64)-1;
2232                 }
2233
2234                 /* the lock_extent waits for readpage to complete */
2235                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2236                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2237                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2238         }
2239         return 0;
2240 }
2241
2242 static int find_next_key(struct btrfs_path *path, int level,
2243                          struct btrfs_key *key)
2244
2245 {
2246         while (level < BTRFS_MAX_LEVEL) {
2247                 if (!path->nodes[level])
2248                         break;
2249                 if (path->slots[level] + 1 <
2250                     btrfs_header_nritems(path->nodes[level])) {
2251                         btrfs_node_key_to_cpu(path->nodes[level], key,
2252                                               path->slots[level] + 1);
2253                         return 0;
2254                 }
2255                 level++;
2256         }
2257         return 1;
2258 }
2259
2260 /*
2261  * Insert current subvolume into reloc_control::dirty_subvol_roots
2262  */
2263 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
2264                                 struct reloc_control *rc,
2265                                 struct btrfs_root *root)
2266 {
2267         struct btrfs_root *reloc_root = root->reloc_root;
2268         struct btrfs_root_item *reloc_root_item;
2269
2270         /* @root must be a subvolume tree root with a valid reloc tree */
2271         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
2272         ASSERT(reloc_root);
2273
2274         reloc_root_item = &reloc_root->root_item;
2275         memset(&reloc_root_item->drop_progress, 0,
2276                 sizeof(reloc_root_item->drop_progress));
2277         reloc_root_item->drop_level = 0;
2278         btrfs_set_root_refs(reloc_root_item, 0);
2279         btrfs_update_reloc_root(trans, root);
2280
2281         if (list_empty(&root->reloc_dirty_list)) {
2282                 btrfs_grab_root(root);
2283                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
2284         }
2285 }
2286
2287 static int clean_dirty_subvols(struct reloc_control *rc)
2288 {
2289         struct btrfs_root *root;
2290         struct btrfs_root *next;
2291         int ret = 0;
2292         int ret2;
2293
2294         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
2295                                  reloc_dirty_list) {
2296                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
2297                         /* Merged subvolume, cleanup its reloc root */
2298                         struct btrfs_root *reloc_root = root->reloc_root;
2299
2300                         list_del_init(&root->reloc_dirty_list);
2301                         root->reloc_root = NULL;
2302                         /*
2303                          * Need barrier to ensure clear_bit() only happens after
2304                          * root->reloc_root = NULL. Pairs with have_reloc_root.
2305                          */
2306                         smp_wmb();
2307                         clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
2308                         if (reloc_root) {
2309                                 /*
2310                                  * btrfs_drop_snapshot drops our ref we hold for
2311                                  * ->reloc_root.  If it fails however we must
2312                                  * drop the ref ourselves.
2313                                  */
2314                                 ret2 = btrfs_drop_snapshot(reloc_root, 0, 1);
2315                                 if (ret2 < 0) {
2316                                         btrfs_put_root(reloc_root);
2317                                         if (!ret)
2318                                                 ret = ret2;
2319                                 }
2320                         }
2321                         btrfs_put_root(root);
2322                 } else {
2323                         /* Orphan reloc tree, just clean it up */
2324                         ret2 = btrfs_drop_snapshot(root, 0, 1);
2325                         if (ret2 < 0) {
2326                                 btrfs_put_root(root);
2327                                 if (!ret)
2328                                         ret = ret2;
2329                         }
2330                 }
2331         }
2332         return ret;
2333 }
2334
2335 /*
2336  * merge the relocated tree blocks in reloc tree with corresponding
2337  * fs tree.
2338  */
2339 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2340                                                struct btrfs_root *root)
2341 {
2342         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2343         struct btrfs_key key;
2344         struct btrfs_key next_key;
2345         struct btrfs_trans_handle *trans = NULL;
2346         struct btrfs_root *reloc_root;
2347         struct btrfs_root_item *root_item;
2348         struct btrfs_path *path;
2349         struct extent_buffer *leaf;
2350         int level;
2351         int max_level;
2352         int replaced = 0;
2353         int ret;
2354         int err = 0;
2355         u32 min_reserved;
2356
2357         path = btrfs_alloc_path();
2358         if (!path)
2359                 return -ENOMEM;
2360         path->reada = READA_FORWARD;
2361
2362         reloc_root = root->reloc_root;
2363         root_item = &reloc_root->root_item;
2364
2365         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2366                 level = btrfs_root_level(root_item);
2367                 atomic_inc(&reloc_root->node->refs);
2368                 path->nodes[level] = reloc_root->node;
2369                 path->slots[level] = 0;
2370         } else {
2371                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2372
2373                 level = root_item->drop_level;
2374                 BUG_ON(level == 0);
2375                 path->lowest_level = level;
2376                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2377                 path->lowest_level = 0;
2378                 if (ret < 0) {
2379                         btrfs_free_path(path);
2380                         return ret;
2381                 }
2382
2383                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2384                                       path->slots[level]);
2385                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2386
2387                 btrfs_unlock_up_safe(path, 0);
2388         }
2389
2390         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2391         memset(&next_key, 0, sizeof(next_key));
2392
2393         while (1) {
2394                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2395                                              BTRFS_RESERVE_FLUSH_ALL);
2396                 if (ret) {
2397                         err = ret;
2398                         goto out;
2399                 }
2400                 trans = btrfs_start_transaction(root, 0);
2401                 if (IS_ERR(trans)) {
2402                         err = PTR_ERR(trans);
2403                         trans = NULL;
2404                         goto out;
2405                 }
2406
2407                 /*
2408                  * At this point we no longer have a reloc_control, so we can't
2409                  * depend on btrfs_init_reloc_root to update our last_trans.
2410                  *
2411                  * But that's ok, we started the trans handle on our
2412                  * corresponding fs_root, which means it's been added to the
2413                  * dirty list.  At commit time we'll still call
2414                  * btrfs_update_reloc_root() and update our root item
2415                  * appropriately.
2416                  */
2417                 reloc_root->last_trans = trans->transid;
2418                 trans->block_rsv = rc->block_rsv;
2419
2420                 replaced = 0;
2421                 max_level = level;
2422
2423                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2424                 if (ret < 0) {
2425                         err = ret;
2426                         goto out;
2427                 }
2428                 if (ret > 0)
2429                         break;
2430
2431                 if (!find_next_key(path, level, &key) &&
2432                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2433                         ret = 0;
2434                 } else {
2435                         ret = replace_path(trans, rc, root, reloc_root, path,
2436                                            &next_key, level, max_level);
2437                 }
2438                 if (ret < 0) {
2439                         err = ret;
2440                         goto out;
2441                 }
2442
2443                 if (ret > 0) {
2444                         level = ret;
2445                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2446                                               path->slots[level]);
2447                         replaced = 1;
2448                 }
2449
2450                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2451                 if (ret > 0)
2452                         break;
2453
2454                 BUG_ON(level == 0);
2455                 /*
2456                  * save the merging progress in the drop_progress.
2457                  * this is OK since root refs == 1 in this case.
2458                  */
2459                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2460                                path->slots[level]);
2461                 root_item->drop_level = level;
2462
2463                 btrfs_end_transaction_throttle(trans);
2464                 trans = NULL;
2465
2466                 btrfs_btree_balance_dirty(fs_info);
2467
2468                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2469                         invalidate_extent_cache(root, &key, &next_key);
2470         }
2471
2472         /*
2473          * handle the case only one block in the fs tree need to be
2474          * relocated and the block is tree root.
2475          */
2476         leaf = btrfs_lock_root_node(root);
2477         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2478         btrfs_tree_unlock(leaf);
2479         free_extent_buffer(leaf);
2480         if (ret < 0)
2481                 err = ret;
2482 out:
2483         btrfs_free_path(path);
2484
2485         if (err == 0)
2486                 insert_dirty_subvol(trans, rc, root);
2487
2488         if (trans)
2489                 btrfs_end_transaction_throttle(trans);
2490
2491         btrfs_btree_balance_dirty(fs_info);
2492
2493         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2494                 invalidate_extent_cache(root, &key, &next_key);
2495
2496         return err;
2497 }
2498
2499 static noinline_for_stack
2500 int prepare_to_merge(struct reloc_control *rc, int err)
2501 {
2502         struct btrfs_root *root = rc->extent_root;
2503         struct btrfs_fs_info *fs_info = root->fs_info;
2504         struct btrfs_root *reloc_root;
2505         struct btrfs_trans_handle *trans;
2506         LIST_HEAD(reloc_roots);
2507         u64 num_bytes = 0;
2508         int ret;
2509
2510         mutex_lock(&fs_info->reloc_mutex);
2511         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2512         rc->merging_rsv_size += rc->nodes_relocated * 2;
2513         mutex_unlock(&fs_info->reloc_mutex);
2514
2515 again:
2516         if (!err) {
2517                 num_bytes = rc->merging_rsv_size;
2518                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2519                                           BTRFS_RESERVE_FLUSH_ALL);
2520                 if (ret)
2521                         err = ret;
2522         }
2523
2524         trans = btrfs_join_transaction(rc->extent_root);
2525         if (IS_ERR(trans)) {
2526                 if (!err)
2527                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2528                                                 num_bytes, NULL);
2529                 return PTR_ERR(trans);
2530         }
2531
2532         if (!err) {
2533                 if (num_bytes != rc->merging_rsv_size) {
2534                         btrfs_end_transaction(trans);
2535                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2536                                                 num_bytes, NULL);
2537                         goto again;
2538                 }
2539         }
2540
2541         rc->merge_reloc_tree = 1;
2542
2543         while (!list_empty(&rc->reloc_roots)) {
2544                 reloc_root = list_entry(rc->reloc_roots.next,
2545                                         struct btrfs_root, root_list);
2546                 list_del_init(&reloc_root->root_list);
2547
2548                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2549                 BUG_ON(IS_ERR(root));
2550                 BUG_ON(root->reloc_root != reloc_root);
2551
2552                 /*
2553                  * set reference count to 1, so btrfs_recover_relocation
2554                  * knows it should resumes merging
2555                  */
2556                 if (!err)
2557                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2558                 btrfs_update_reloc_root(trans, root);
2559
2560                 list_add(&reloc_root->root_list, &reloc_roots);
2561                 btrfs_put_root(root);
2562         }
2563
2564         list_splice(&reloc_roots, &rc->reloc_roots);
2565
2566         if (!err)
2567                 btrfs_commit_transaction(trans);
2568         else
2569                 btrfs_end_transaction(trans);
2570         return err;
2571 }
2572
2573 static noinline_for_stack
2574 void free_reloc_roots(struct list_head *list)
2575 {
2576         struct btrfs_root *reloc_root;
2577
2578         while (!list_empty(list)) {
2579                 reloc_root = list_entry(list->next, struct btrfs_root,
2580                                         root_list);
2581                 __del_reloc_root(reloc_root);
2582         }
2583 }
2584
2585 static noinline_for_stack
2586 void merge_reloc_roots(struct reloc_control *rc)
2587 {
2588         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2589         struct btrfs_root *root;
2590         struct btrfs_root *reloc_root;
2591         LIST_HEAD(reloc_roots);
2592         int found = 0;
2593         int ret = 0;
2594 again:
2595         root = rc->extent_root;
2596
2597         /*
2598          * this serializes us with btrfs_record_root_in_transaction,
2599          * we have to make sure nobody is in the middle of
2600          * adding their roots to the list while we are
2601          * doing this splice
2602          */
2603         mutex_lock(&fs_info->reloc_mutex);
2604         list_splice_init(&rc->reloc_roots, &reloc_roots);
2605         mutex_unlock(&fs_info->reloc_mutex);
2606
2607         while (!list_empty(&reloc_roots)) {
2608                 found = 1;
2609                 reloc_root = list_entry(reloc_roots.next,
2610                                         struct btrfs_root, root_list);
2611
2612                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2613                         root = read_fs_root(fs_info,
2614                                             reloc_root->root_key.offset);
2615                         BUG_ON(IS_ERR(root));
2616                         BUG_ON(root->reloc_root != reloc_root);
2617
2618                         ret = merge_reloc_root(rc, root);
2619                         btrfs_put_root(root);
2620                         if (ret) {
2621                                 if (list_empty(&reloc_root->root_list))
2622                                         list_add_tail(&reloc_root->root_list,
2623                                                       &reloc_roots);
2624                                 goto out;
2625                         }
2626                 } else {
2627                         list_del_init(&reloc_root->root_list);
2628                         /* Don't forget to queue this reloc root for cleanup */
2629                         list_add_tail(&reloc_root->reloc_dirty_list,
2630                                       &rc->dirty_subvol_roots);
2631                 }
2632         }
2633
2634         if (found) {
2635                 found = 0;
2636                 goto again;
2637         }
2638 out:
2639         if (ret) {
2640                 btrfs_handle_fs_error(fs_info, ret, NULL);
2641                 if (!list_empty(&reloc_roots))
2642                         free_reloc_roots(&reloc_roots);
2643
2644                 /* new reloc root may be added */
2645                 mutex_lock(&fs_info->reloc_mutex);
2646                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2647                 mutex_unlock(&fs_info->reloc_mutex);
2648                 if (!list_empty(&reloc_roots))
2649                         free_reloc_roots(&reloc_roots);
2650         }
2651
2652         /*
2653          * We used to have
2654          *
2655          * BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2656          *
2657          * here, but it's wrong.  If we fail to start the transaction in
2658          * prepare_to_merge() we will have only 0 ref reloc roots, none of which
2659          * have actually been removed from the reloc_root_tree rb tree.  This is
2660          * fine because we're bailing here, and we hold a reference on the root
2661          * for the list that holds it, so these roots will be cleaned up when we
2662          * do the reloc_dirty_list afterwards.  Meanwhile the root->reloc_root
2663          * will be cleaned up on unmount.
2664          *
2665          * The remaining nodes will be cleaned up by free_reloc_control.
2666          */
2667 }
2668
2669 static void free_block_list(struct rb_root *blocks)
2670 {
2671         struct tree_block *block;
2672         struct rb_node *rb_node;
2673         while ((rb_node = rb_first(blocks))) {
2674                 block = rb_entry(rb_node, struct tree_block, rb_node);
2675                 rb_erase(rb_node, blocks);
2676                 kfree(block);
2677         }
2678 }
2679
2680 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2681                                       struct btrfs_root *reloc_root)
2682 {
2683         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2684         struct btrfs_root *root;
2685         int ret;
2686
2687         if (reloc_root->last_trans == trans->transid)
2688                 return 0;
2689
2690         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2691         BUG_ON(IS_ERR(root));
2692         BUG_ON(root->reloc_root != reloc_root);
2693         ret = btrfs_record_root_in_trans(trans, root);
2694         btrfs_put_root(root);
2695
2696         return ret;
2697 }
2698
2699 static noinline_for_stack
2700 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2701                                      struct reloc_control *rc,
2702                                      struct backref_node *node,
2703                                      struct backref_edge *edges[])
2704 {
2705         struct backref_node *next;
2706         struct btrfs_root *root;
2707         int index = 0;
2708
2709         next = node;
2710         while (1) {
2711                 cond_resched();
2712                 next = walk_up_backref(next, edges, &index);
2713                 root = next->root;
2714                 BUG_ON(!root);
2715                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2716
2717                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2718                         record_reloc_root_in_trans(trans, root);
2719                         break;
2720                 }
2721
2722                 btrfs_record_root_in_trans(trans, root);
2723                 root = root->reloc_root;
2724
2725                 if (next->new_bytenr != root->node->start) {
2726                         BUG_ON(next->new_bytenr);
2727                         BUG_ON(!list_empty(&next->list));
2728                         next->new_bytenr = root->node->start;
2729                         btrfs_put_root(next->root);
2730                         next->root = btrfs_grab_root(root);
2731                         ASSERT(next->root);
2732                         list_add_tail(&next->list,
2733                                       &rc->backref_cache.changed);
2734                         __mark_block_processed(rc, next);
2735                         break;
2736                 }
2737
2738                 WARN_ON(1);
2739                 root = NULL;
2740                 next = walk_down_backref(edges, &index);
2741                 if (!next || next->level <= node->level)
2742                         break;
2743         }
2744         if (!root)
2745                 return NULL;
2746
2747         next = node;
2748         /* setup backref node path for btrfs_reloc_cow_block */
2749         while (1) {
2750                 rc->backref_cache.path[next->level] = next;
2751                 if (--index < 0)
2752                         break;
2753                 next = edges[index]->node[UPPER];
2754         }
2755         return root;
2756 }
2757
2758 /*
2759  * select a tree root for relocation. return NULL if the block
2760  * is reference counted. we should use do_relocation() in this
2761  * case. return a tree root pointer if the block isn't reference
2762  * counted. return -ENOENT if the block is root of reloc tree.
2763  */
2764 static noinline_for_stack
2765 struct btrfs_root *select_one_root(struct backref_node *node)
2766 {
2767         struct backref_node *next;
2768         struct btrfs_root *root;
2769         struct btrfs_root *fs_root = NULL;
2770         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2771         int index = 0;
2772
2773         next = node;
2774         while (1) {
2775                 cond_resched();
2776                 next = walk_up_backref(next, edges, &index);
2777                 root = next->root;
2778                 BUG_ON(!root);
2779
2780                 /* no other choice for non-references counted tree */
2781                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2782                         return root;
2783
2784                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2785                         fs_root = root;
2786
2787                 if (next != node)
2788                         return NULL;
2789
2790                 next = walk_down_backref(edges, &index);
2791                 if (!next || next->level <= node->level)
2792                         break;
2793         }
2794
2795         if (!fs_root)
2796                 return ERR_PTR(-ENOENT);
2797         return fs_root;
2798 }
2799
2800 static noinline_for_stack
2801 u64 calcu_metadata_size(struct reloc_control *rc,
2802                         struct backref_node *node, int reserve)
2803 {
2804         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2805         struct backref_node *next = node;
2806         struct backref_edge *edge;
2807         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2808         u64 num_bytes = 0;
2809         int index = 0;
2810
2811         BUG_ON(reserve && node->processed);
2812
2813         while (next) {
2814                 cond_resched();
2815                 while (1) {
2816                         if (next->processed && (reserve || next != node))
2817                                 break;
2818
2819                         num_bytes += fs_info->nodesize;
2820
2821                         if (list_empty(&next->upper))
2822                                 break;
2823
2824                         edge = list_entry(next->upper.next,
2825                                           struct backref_edge, list[LOWER]);
2826                         edges[index++] = edge;
2827                         next = edge->node[UPPER];
2828                 }
2829                 next = walk_down_backref(edges, &index);
2830         }
2831         return num_bytes;
2832 }
2833
2834 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2835                                   struct reloc_control *rc,
2836                                   struct backref_node *node)
2837 {
2838         struct btrfs_root *root = rc->extent_root;
2839         struct btrfs_fs_info *fs_info = root->fs_info;
2840         u64 num_bytes;
2841         int ret;
2842         u64 tmp;
2843
2844         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2845
2846         trans->block_rsv = rc->block_rsv;
2847         rc->reserved_bytes += num_bytes;
2848
2849         /*
2850          * We are under a transaction here so we can only do limited flushing.
2851          * If we get an enospc just kick back -EAGAIN so we know to drop the
2852          * transaction and try to refill when we can flush all the things.
2853          */
2854         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2855                                 BTRFS_RESERVE_FLUSH_LIMIT);
2856         if (ret) {
2857                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2858                 while (tmp <= rc->reserved_bytes)
2859                         tmp <<= 1;
2860                 /*
2861                  * only one thread can access block_rsv at this point,
2862                  * so we don't need hold lock to protect block_rsv.
2863                  * we expand more reservation size here to allow enough
2864                  * space for relocation and we will return earlier in
2865                  * enospc case.
2866                  */
2867                 rc->block_rsv->size = tmp + fs_info->nodesize *
2868                                       RELOCATION_RESERVED_NODES;
2869                 return -EAGAIN;
2870         }
2871
2872         return 0;
2873 }
2874
2875 /*
2876  * relocate a block tree, and then update pointers in upper level
2877  * blocks that reference the block to point to the new location.
2878  *
2879  * if called by link_to_upper, the block has already been relocated.
2880  * in that case this function just updates pointers.
2881  */
2882 static int do_relocation(struct btrfs_trans_handle *trans,
2883                          struct reloc_control *rc,
2884                          struct backref_node *node,
2885                          struct btrfs_key *key,
2886                          struct btrfs_path *path, int lowest)
2887 {
2888         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2889         struct backref_node *upper;
2890         struct backref_edge *edge;
2891         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2892         struct btrfs_root *root;
2893         struct extent_buffer *eb;
2894         u32 blocksize;
2895         u64 bytenr;
2896         u64 generation;
2897         int slot;
2898         int ret;
2899         int err = 0;
2900
2901         BUG_ON(lowest && node->eb);
2902
2903         path->lowest_level = node->level + 1;
2904         rc->backref_cache.path[node->level] = node;
2905         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2906                 struct btrfs_key first_key;
2907                 struct btrfs_ref ref = { 0 };
2908
2909                 cond_resched();
2910
2911                 upper = edge->node[UPPER];
2912                 root = select_reloc_root(trans, rc, upper, edges);
2913                 BUG_ON(!root);
2914
2915                 if (upper->eb && !upper->locked) {
2916                         if (!lowest) {
2917                                 ret = btrfs_bin_search(upper->eb, key,
2918                                                        upper->level, &slot);
2919                                 if (ret < 0) {
2920                                         err = ret;
2921                                         goto next;
2922                                 }
2923                                 BUG_ON(ret);
2924                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2925                                 if (node->eb->start == bytenr)
2926                                         goto next;
2927                         }
2928                         drop_node_buffer(upper);
2929                 }
2930
2931                 if (!upper->eb) {
2932                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2933                         if (ret) {
2934                                 if (ret < 0)
2935                                         err = ret;
2936                                 else
2937                                         err = -ENOENT;
2938
2939                                 btrfs_release_path(path);
2940                                 break;
2941                         }
2942
2943                         if (!upper->eb) {
2944                                 upper->eb = path->nodes[upper->level];
2945                                 path->nodes[upper->level] = NULL;
2946                         } else {
2947                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2948                         }
2949
2950                         upper->locked = 1;
2951                         path->locks[upper->level] = 0;
2952
2953                         slot = path->slots[upper->level];
2954                         btrfs_release_path(path);
2955                 } else {
2956                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2957                                                &slot);
2958                         if (ret < 0) {
2959                                 err = ret;
2960                                 goto next;
2961                         }
2962                         BUG_ON(ret);
2963                 }
2964
2965                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2966                 if (lowest) {
2967                         if (bytenr != node->bytenr) {
2968                                 btrfs_err(root->fs_info,
2969                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2970                                           bytenr, node->bytenr, slot,
2971                                           upper->eb->start);
2972                                 err = -EIO;
2973                                 goto next;
2974                         }
2975                 } else {
2976                         if (node->eb->start == bytenr)
2977                                 goto next;
2978                 }
2979
2980                 blocksize = root->fs_info->nodesize;
2981                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2982                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2983                 eb = read_tree_block(fs_info, bytenr, generation,
2984                                      upper->level - 1, &first_key);
2985                 if (IS_ERR(eb)) {
2986                         err = PTR_ERR(eb);
2987                         goto next;
2988                 } else if (!extent_buffer_uptodate(eb)) {
2989                         free_extent_buffer(eb);
2990                         err = -EIO;
2991                         goto next;
2992                 }
2993                 btrfs_tree_lock(eb);
2994                 btrfs_set_lock_blocking_write(eb);
2995
2996                 if (!node->eb) {
2997                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
2998                                               slot, &eb);
2999                         btrfs_tree_unlock(eb);
3000                         free_extent_buffer(eb);
3001                         if (ret < 0) {
3002                                 err = ret;
3003                                 goto next;
3004                         }
3005                         BUG_ON(node->eb != eb);
3006                 } else {
3007                         btrfs_set_node_blockptr(upper->eb, slot,
3008                                                 node->eb->start);
3009                         btrfs_set_node_ptr_generation(upper->eb, slot,
3010                                                       trans->transid);
3011                         btrfs_mark_buffer_dirty(upper->eb);
3012
3013                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
3014                                                node->eb->start, blocksize,
3015                                                upper->eb->start);
3016                         ref.real_root = root->root_key.objectid;
3017                         btrfs_init_tree_ref(&ref, node->level,
3018                                             btrfs_header_owner(upper->eb));
3019                         ret = btrfs_inc_extent_ref(trans, &ref);
3020                         BUG_ON(ret);
3021
3022                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
3023                         BUG_ON(ret);
3024                 }
3025 next:
3026                 if (!upper->pending)
3027                         drop_node_buffer(upper);
3028                 else
3029                         unlock_node_buffer(upper);
3030                 if (err)
3031                         break;
3032         }
3033
3034         if (!err && node->pending) {
3035                 drop_node_buffer(node);
3036                 list_move_tail(&node->list, &rc->backref_cache.changed);
3037                 node->pending = 0;
3038         }
3039
3040         path->lowest_level = 0;
3041         BUG_ON(err == -ENOSPC);
3042         return err;
3043 }
3044
3045 static int link_to_upper(struct btrfs_trans_handle *trans,
3046                          struct reloc_control *rc,
3047                          struct backref_node *node,
3048                          struct btrfs_path *path)
3049 {
3050         struct btrfs_key key;
3051
3052         btrfs_node_key_to_cpu(node->eb, &key, 0);
3053         return do_relocation(trans, rc, node, &key, path, 0);
3054 }
3055
3056 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
3057                                 struct reloc_control *rc,
3058                                 struct btrfs_path *path, int err)
3059 {
3060         LIST_HEAD(list);
3061         struct backref_cache *cache = &rc->backref_cache;
3062         struct backref_node *node;
3063         int level;
3064         int ret;
3065
3066         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
3067                 while (!list_empty(&cache->pending[level])) {
3068                         node = list_entry(cache->pending[level].next,
3069                                           struct backref_node, list);
3070                         list_move_tail(&node->list, &list);
3071                         BUG_ON(!node->pending);
3072
3073                         if (!err) {
3074                                 ret = link_to_upper(trans, rc, node, path);
3075                                 if (ret < 0)
3076                                         err = ret;
3077                         }
3078                 }
3079                 list_splice_init(&list, &cache->pending[level]);
3080         }
3081         return err;
3082 }
3083
3084 static void mark_block_processed(struct reloc_control *rc,
3085                                  u64 bytenr, u32 blocksize)
3086 {
3087         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
3088                         EXTENT_DIRTY);
3089 }
3090
3091 static void __mark_block_processed(struct reloc_control *rc,
3092                                    struct backref_node *node)
3093 {
3094         u32 blocksize;
3095         if (node->level == 0 ||
3096             in_block_group(node->bytenr, rc->block_group)) {
3097                 blocksize = rc->extent_root->fs_info->nodesize;
3098                 mark_block_processed(rc, node->bytenr, blocksize);
3099         }
3100         node->processed = 1;
3101 }
3102
3103 /*
3104  * mark a block and all blocks directly/indirectly reference the block
3105  * as processed.
3106  */
3107 static void update_processed_blocks(struct reloc_control *rc,
3108                                     struct backref_node *node)
3109 {
3110         struct backref_node *next = node;
3111         struct backref_edge *edge;
3112         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
3113         int index = 0;
3114
3115         while (next) {
3116                 cond_resched();
3117                 while (1) {
3118                         if (next->processed)
3119                                 break;
3120
3121                         __mark_block_processed(rc, next);
3122
3123                         if (list_empty(&next->upper))
3124                                 break;
3125
3126                         edge = list_entry(next->upper.next,
3127                                           struct backref_edge, list[LOWER]);
3128                         edges[index++] = edge;
3129                         next = edge->node[UPPER];
3130                 }
3131                 next = walk_down_backref(edges, &index);
3132         }
3133 }
3134
3135 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
3136 {
3137         u32 blocksize = rc->extent_root->fs_info->nodesize;
3138
3139         if (test_range_bit(&rc->processed_blocks, bytenr,
3140                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
3141                 return 1;
3142         return 0;
3143 }
3144
3145 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
3146                               struct tree_block *block)
3147 {
3148         struct extent_buffer *eb;
3149
3150         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
3151                              block->level, NULL);
3152         if (IS_ERR(eb)) {
3153                 return PTR_ERR(eb);
3154         } else if (!extent_buffer_uptodate(eb)) {
3155                 free_extent_buffer(eb);
3156                 return -EIO;
3157         }
3158         if (block->level == 0)
3159                 btrfs_item_key_to_cpu(eb, &block->key, 0);
3160         else
3161                 btrfs_node_key_to_cpu(eb, &block->key, 0);
3162         free_extent_buffer(eb);
3163         block->key_ready = 1;
3164         return 0;
3165 }
3166
3167 /*
3168  * helper function to relocate a tree block
3169  */
3170 static int relocate_tree_block(struct btrfs_trans_handle *trans,
3171                                 struct reloc_control *rc,
3172                                 struct backref_node *node,
3173                                 struct btrfs_key *key,
3174                                 struct btrfs_path *path)
3175 {
3176         struct btrfs_root *root;
3177         int ret = 0;
3178
3179         if (!node)
3180                 return 0;
3181
3182         /*
3183          * If we fail here we want to drop our backref_node because we are going
3184          * to start over and regenerate the tree for it.
3185          */
3186         ret = reserve_metadata_space(trans, rc, node);
3187         if (ret)
3188                 goto out;
3189
3190         BUG_ON(node->processed);
3191         root = select_one_root(node);
3192         if (root == ERR_PTR(-ENOENT)) {
3193                 update_processed_blocks(rc, node);
3194                 goto out;
3195         }
3196
3197         if (root) {
3198                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3199                         BUG_ON(node->new_bytenr);
3200                         BUG_ON(!list_empty(&node->list));
3201                         btrfs_record_root_in_trans(trans, root);
3202                         root = root->reloc_root;
3203                         node->new_bytenr = root->node->start;
3204                         btrfs_put_root(node->root);
3205                         node->root = btrfs_grab_root(root);
3206                         ASSERT(node->root);
3207                         list_add_tail(&node->list, &rc->backref_cache.changed);
3208                 } else {
3209                         path->lowest_level = node->level;
3210                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3211                         btrfs_release_path(path);
3212                         if (ret > 0)
3213                                 ret = 0;
3214                 }
3215                 if (!ret)
3216                         update_processed_blocks(rc, node);
3217         } else {
3218                 ret = do_relocation(trans, rc, node, key, path, 1);
3219         }
3220 out:
3221         if (ret || node->level == 0 || node->cowonly)
3222                 remove_backref_node(&rc->backref_cache, node);
3223         return ret;
3224 }
3225
3226 /*
3227  * relocate a list of blocks
3228  */
3229 static noinline_for_stack
3230 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3231                          struct reloc_control *rc, struct rb_root *blocks)
3232 {
3233         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3234         struct backref_node *node;
3235         struct btrfs_path *path;
3236         struct tree_block *block;
3237         struct tree_block *next;
3238         int ret;
3239         int err = 0;
3240
3241         path = btrfs_alloc_path();
3242         if (!path) {
3243                 err = -ENOMEM;
3244                 goto out_free_blocks;
3245         }
3246
3247         /* Kick in readahead for tree blocks with missing keys */
3248         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3249                 if (!block->key_ready)
3250                         readahead_tree_block(fs_info, block->bytenr);
3251         }
3252
3253         /* Get first keys */
3254         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3255                 if (!block->key_ready) {
3256                         err = get_tree_block_key(fs_info, block);
3257                         if (err)
3258                                 goto out_free_path;
3259                 }
3260         }
3261
3262         /* Do tree relocation */
3263         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3264                 node = build_backref_tree(rc, &block->key,
3265                                           block->level, block->bytenr);
3266                 if (IS_ERR(node)) {
3267                         err = PTR_ERR(node);
3268                         goto out;
3269                 }
3270
3271                 ret = relocate_tree_block(trans, rc, node, &block->key,
3272                                           path);
3273                 if (ret < 0) {
3274                         err = ret;
3275                         break;
3276                 }
3277         }
3278 out:
3279         err = finish_pending_nodes(trans, rc, path, err);
3280
3281 out_free_path:
3282         btrfs_free_path(path);
3283 out_free_blocks:
3284         free_block_list(blocks);
3285         return err;
3286 }
3287
3288 static noinline_for_stack
3289 int prealloc_file_extent_cluster(struct inode *inode,
3290                                  struct file_extent_cluster *cluster)
3291 {
3292         u64 alloc_hint = 0;
3293         u64 start;
3294         u64 end;
3295         u64 offset = BTRFS_I(inode)->index_cnt;
3296         u64 num_bytes;
3297         int nr = 0;
3298         int ret = 0;
3299         u64 prealloc_start = cluster->start - offset;
3300         u64 prealloc_end = cluster->end - offset;
3301         u64 cur_offset;
3302         struct extent_changeset *data_reserved = NULL;
3303
3304         BUG_ON(cluster->start != cluster->boundary[0]);
3305         inode_lock(inode);
3306
3307         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3308                                           prealloc_end + 1 - prealloc_start);
3309         if (ret)
3310                 goto out;
3311
3312         cur_offset = prealloc_start;
3313         while (nr < cluster->nr) {
3314                 start = cluster->boundary[nr] - offset;
3315                 if (nr + 1 < cluster->nr)
3316                         end = cluster->boundary[nr + 1] - 1 - offset;
3317                 else
3318                         end = cluster->end - offset;
3319
3320                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3321                 num_bytes = end + 1 - start;
3322                 if (cur_offset < start)
3323                         btrfs_free_reserved_data_space(inode, data_reserved,
3324                                         cur_offset, start - cur_offset);
3325                 ret = btrfs_prealloc_file_range(inode, 0, start,
3326                                                 num_bytes, num_bytes,
3327                                                 end + 1, &alloc_hint);
3328                 cur_offset = end + 1;
3329                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3330                 if (ret)
3331                         break;
3332                 nr++;
3333         }
3334         if (cur_offset < prealloc_end)
3335                 btrfs_free_reserved_data_space(inode, data_reserved,
3336                                 cur_offset, prealloc_end + 1 - cur_offset);
3337 out:
3338         inode_unlock(inode);
3339         extent_changeset_free(data_reserved);
3340         return ret;
3341 }
3342
3343 static noinline_for_stack
3344 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3345                          u64 block_start)
3346 {
3347         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3348         struct extent_map *em;
3349         int ret = 0;
3350
3351         em = alloc_extent_map();
3352         if (!em)
3353                 return -ENOMEM;
3354
3355         em->start = start;
3356         em->len = end + 1 - start;
3357         em->block_len = em->len;
3358         em->block_start = block_start;
3359         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3360
3361         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3362         while (1) {
3363                 write_lock(&em_tree->lock);
3364                 ret = add_extent_mapping(em_tree, em, 0);
3365                 write_unlock(&em_tree->lock);
3366                 if (ret != -EEXIST) {
3367                         free_extent_map(em);
3368                         break;
3369                 }
3370                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3371         }
3372         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3373         return ret;
3374 }
3375
3376 /*
3377  * Allow error injection to test balance cancellation
3378  */
3379 int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
3380 {
3381         return atomic_read(&fs_info->balance_cancel_req);
3382 }
3383 ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
3384
3385 static int relocate_file_extent_cluster(struct inode *inode,
3386                                         struct file_extent_cluster *cluster)
3387 {
3388         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3389         u64 page_start;
3390         u64 page_end;
3391         u64 offset = BTRFS_I(inode)->index_cnt;
3392         unsigned long index;
3393         unsigned long last_index;
3394         struct page *page;
3395         struct file_ra_state *ra;
3396         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3397         int nr = 0;
3398         int ret = 0;
3399
3400         if (!cluster->nr)
3401                 return 0;
3402
3403         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3404         if (!ra)
3405                 return -ENOMEM;
3406
3407         ret = prealloc_file_extent_cluster(inode, cluster);
3408         if (ret)
3409                 goto out;
3410
3411         file_ra_state_init(ra, inode->i_mapping);
3412
3413         ret = setup_extent_mapping(inode, cluster->start - offset,
3414                                    cluster->end - offset, cluster->start);
3415         if (ret)
3416                 goto out;
3417
3418         index = (cluster->start - offset) >> PAGE_SHIFT;
3419         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3420         while (index <= last_index) {
3421                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3422                                 PAGE_SIZE);
3423                 if (ret)
3424                         goto out;
3425
3426                 page = find_lock_page(inode->i_mapping, index);
3427                 if (!page) {
3428                         page_cache_sync_readahead(inode->i_mapping,
3429                                                   ra, NULL, index,
3430                                                   last_index + 1 - index);
3431                         page = find_or_create_page(inode->i_mapping, index,
3432                                                    mask);
3433                         if (!page) {
3434                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3435                                                         PAGE_SIZE, true);
3436                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3437                                                         PAGE_SIZE);
3438                                 ret = -ENOMEM;
3439                                 goto out;
3440                         }
3441                 }
3442
3443                 if (PageReadahead(page)) {
3444                         page_cache_async_readahead(inode->i_mapping,
3445                                                    ra, NULL, page, index,
3446                                                    last_index + 1 - index);
3447                 }
3448
3449                 if (!PageUptodate(page)) {
3450                         btrfs_readpage(NULL, page);
3451                         lock_page(page);
3452                         if (!PageUptodate(page)) {
3453                                 unlock_page(page);
3454                                 put_page(page);
3455                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3456                                                         PAGE_SIZE, true);
3457                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3458                                                                PAGE_SIZE);
3459                                 ret = -EIO;
3460                                 goto out;
3461                         }
3462                 }
3463
3464                 page_start = page_offset(page);
3465                 page_end = page_start + PAGE_SIZE - 1;
3466
3467                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3468
3469                 set_page_extent_mapped(page);
3470
3471                 if (nr < cluster->nr &&
3472                     page_start + offset == cluster->boundary[nr]) {
3473                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3474                                         page_start, page_end,
3475                                         EXTENT_BOUNDARY);
3476                         nr++;
3477                 }
3478
3479                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3480                                                 NULL);
3481                 if (ret) {
3482                         unlock_page(page);
3483                         put_page(page);
3484                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3485                                                          PAGE_SIZE, true);
3486                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3487                                                        PAGE_SIZE);
3488
3489                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3490                                           page_start, page_end,
3491                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3492                         goto out;
3493
3494                 }
3495                 set_page_dirty(page);
3496
3497                 unlock_extent(&BTRFS_I(inode)->io_tree,
3498                               page_start, page_end);
3499                 unlock_page(page);
3500                 put_page(page);
3501
3502                 index++;
3503                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
3504                 balance_dirty_pages_ratelimited(inode->i_mapping);
3505                 btrfs_throttle(fs_info);
3506                 if (btrfs_should_cancel_balance(fs_info)) {
3507                         ret = -ECANCELED;
3508                         goto out;
3509                 }
3510         }
3511         WARN_ON(nr != cluster->nr);
3512 out:
3513         kfree(ra);
3514         return ret;
3515 }
3516
3517 static noinline_for_stack
3518 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3519                          struct file_extent_cluster *cluster)
3520 {
3521         int ret;
3522
3523         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3524                 ret = relocate_file_extent_cluster(inode, cluster);
3525                 if (ret)
3526                         return ret;
3527                 cluster->nr = 0;
3528         }
3529
3530         if (!cluster->nr)
3531                 cluster->start = extent_key->objectid;
3532         else
3533                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3534         cluster->end = extent_key->objectid + extent_key->offset - 1;
3535         cluster->boundary[cluster->nr] = extent_key->objectid;
3536         cluster->nr++;
3537
3538         if (cluster->nr >= MAX_EXTENTS) {
3539                 ret = relocate_file_extent_cluster(inode, cluster);
3540                 if (ret)
3541                         return ret;
3542                 cluster->nr = 0;
3543         }
3544         return 0;
3545 }
3546
3547 /*
3548  * helper to add a tree block to the list.
3549  * the major work is getting the generation and level of the block
3550  */
3551 static int add_tree_block(struct reloc_control *rc,
3552                           struct btrfs_key *extent_key,
3553                           struct btrfs_path *path,
3554                           struct rb_root *blocks)
3555 {
3556         struct extent_buffer *eb;
3557         struct btrfs_extent_item *ei;
3558         struct btrfs_tree_block_info *bi;
3559         struct tree_block *block;
3560         struct rb_node *rb_node;
3561         u32 item_size;
3562         int level = -1;
3563         u64 generation;
3564
3565         eb =  path->nodes[0];
3566         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3567
3568         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3569             item_size >= sizeof(*ei) + sizeof(*bi)) {
3570                 ei = btrfs_item_ptr(eb, path->slots[0],
3571                                 struct btrfs_extent_item);
3572                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3573                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3574                         level = btrfs_tree_block_level(eb, bi);
3575                 } else {
3576                         level = (int)extent_key->offset;
3577                 }
3578                 generation = btrfs_extent_generation(eb, ei);
3579         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3580                 btrfs_print_v0_err(eb->fs_info);
3581                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3582                 return -EINVAL;
3583         } else {
3584                 BUG();
3585         }
3586
3587         btrfs_release_path(path);
3588
3589         BUG_ON(level == -1);
3590
3591         block = kmalloc(sizeof(*block), GFP_NOFS);
3592         if (!block)
3593                 return -ENOMEM;
3594
3595         block->bytenr = extent_key->objectid;
3596         block->key.objectid = rc->extent_root->fs_info->nodesize;
3597         block->key.offset = generation;
3598         block->level = level;
3599         block->key_ready = 0;
3600
3601         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3602         if (rb_node)
3603                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3604
3605         return 0;
3606 }
3607
3608 /*
3609  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3610  */
3611 static int __add_tree_block(struct reloc_control *rc,
3612                             u64 bytenr, u32 blocksize,
3613                             struct rb_root *blocks)
3614 {
3615         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3616         struct btrfs_path *path;
3617         struct btrfs_key key;
3618         int ret;
3619         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3620
3621         if (tree_block_processed(bytenr, rc))
3622                 return 0;
3623
3624         if (tree_search(blocks, bytenr))
3625                 return 0;
3626
3627         path = btrfs_alloc_path();
3628         if (!path)
3629                 return -ENOMEM;
3630 again:
3631         key.objectid = bytenr;
3632         if (skinny) {
3633                 key.type = BTRFS_METADATA_ITEM_KEY;
3634                 key.offset = (u64)-1;
3635         } else {
3636                 key.type = BTRFS_EXTENT_ITEM_KEY;
3637                 key.offset = blocksize;
3638         }
3639
3640         path->search_commit_root = 1;
3641         path->skip_locking = 1;
3642         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3643         if (ret < 0)
3644                 goto out;
3645
3646         if (ret > 0 && skinny) {
3647                 if (path->slots[0]) {
3648                         path->slots[0]--;
3649                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3650                                               path->slots[0]);
3651                         if (key.objectid == bytenr &&
3652                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3653                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3654                               key.offset == blocksize)))
3655                                 ret = 0;
3656                 }
3657
3658                 if (ret) {
3659                         skinny = false;
3660                         btrfs_release_path(path);
3661                         goto again;
3662                 }
3663         }
3664         if (ret) {
3665                 ASSERT(ret == 1);
3666                 btrfs_print_leaf(path->nodes[0]);
3667                 btrfs_err(fs_info,
3668              "tree block extent item (%llu) is not found in extent tree",
3669                      bytenr);
3670                 WARN_ON(1);
3671                 ret = -EINVAL;
3672                 goto out;
3673         }
3674
3675         ret = add_tree_block(rc, &key, path, blocks);
3676 out:
3677         btrfs_free_path(path);
3678         return ret;
3679 }
3680
3681 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3682                                     struct btrfs_block_group *block_group,
3683                                     struct inode *inode,
3684                                     u64 ino)
3685 {
3686         struct btrfs_key key;
3687         struct btrfs_root *root = fs_info->tree_root;
3688         struct btrfs_trans_handle *trans;
3689         int ret = 0;
3690
3691         if (inode)
3692                 goto truncate;
3693
3694         key.objectid = ino;
3695         key.type = BTRFS_INODE_ITEM_KEY;
3696         key.offset = 0;
3697
3698         inode = btrfs_iget(fs_info->sb, &key, root);
3699         if (IS_ERR(inode))
3700                 return -ENOENT;
3701
3702 truncate:
3703         ret = btrfs_check_trunc_cache_free_space(fs_info,
3704                                                  &fs_info->global_block_rsv);
3705         if (ret)
3706                 goto out;
3707
3708         trans = btrfs_join_transaction(root);
3709         if (IS_ERR(trans)) {
3710                 ret = PTR_ERR(trans);
3711                 goto out;
3712         }
3713
3714         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3715
3716         btrfs_end_transaction(trans);
3717         btrfs_btree_balance_dirty(fs_info);
3718 out:
3719         iput(inode);
3720         return ret;
3721 }
3722
3723 /*
3724  * Locate the free space cache EXTENT_DATA in root tree leaf and delete the
3725  * cache inode, to avoid free space cache data extent blocking data relocation.
3726  */
3727 static int delete_v1_space_cache(struct extent_buffer *leaf,
3728                                  struct btrfs_block_group *block_group,
3729                                  u64 data_bytenr)
3730 {
3731         u64 space_cache_ino;
3732         struct btrfs_file_extent_item *ei;
3733         struct btrfs_key key;
3734         bool found = false;
3735         int i;
3736         int ret;
3737
3738         if (btrfs_header_owner(leaf) != BTRFS_ROOT_TREE_OBJECTID)
3739                 return 0;
3740
3741         for (i = 0; i < btrfs_header_nritems(leaf); i++) {
3742                 btrfs_item_key_to_cpu(leaf, &key, i);
3743                 if (key.type != BTRFS_EXTENT_DATA_KEY)
3744                         continue;
3745                 ei = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
3746                 if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_REG &&
3747                     btrfs_file_extent_disk_bytenr(leaf, ei) == data_bytenr) {
3748                         found = true;
3749                         space_cache_ino = key.objectid;
3750                         break;
3751                 }
3752         }
3753         if (!found)
3754                 return -ENOENT;
3755         ret = delete_block_group_cache(leaf->fs_info, block_group, NULL,
3756                                         space_cache_ino);
3757         return ret;
3758 }
3759
3760 /*
3761  * helper to find all tree blocks that reference a given data extent
3762  */
3763 static noinline_for_stack
3764 int add_data_references(struct reloc_control *rc,
3765                         struct btrfs_key *extent_key,
3766                         struct btrfs_path *path,
3767                         struct rb_root *blocks)
3768 {
3769         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3770         struct ulist *leaves = NULL;
3771         struct ulist_iterator leaf_uiter;
3772         struct ulist_node *ref_node = NULL;
3773         const u32 blocksize = fs_info->nodesize;
3774         int ret = 0;
3775
3776         btrfs_release_path(path);
3777         ret = btrfs_find_all_leafs(NULL, fs_info, extent_key->objectid,
3778                                    0, &leaves, NULL, true);
3779         if (ret < 0)
3780                 return ret;
3781
3782         ULIST_ITER_INIT(&leaf_uiter);
3783         while ((ref_node = ulist_next(leaves, &leaf_uiter))) {
3784                 struct extent_buffer *eb;
3785
3786                 eb = read_tree_block(fs_info, ref_node->val, 0, 0, NULL);
3787                 if (IS_ERR(eb)) {
3788                         ret = PTR_ERR(eb);
3789                         break;
3790                 }
3791                 ret = delete_v1_space_cache(eb, rc->block_group,
3792                                             extent_key->objectid);
3793                 free_extent_buffer(eb);
3794                 if (ret < 0)
3795                         break;
3796                 ret = __add_tree_block(rc, ref_node->val, blocksize, blocks);
3797                 if (ret < 0)
3798                         break;
3799         }
3800         if (ret < 0)
3801                 free_block_list(blocks);
3802         ulist_free(leaves);
3803         return ret;
3804 }
3805
3806 /*
3807  * helper to find next unprocessed extent
3808  */
3809 static noinline_for_stack
3810 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3811                      struct btrfs_key *extent_key)
3812 {
3813         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3814         struct btrfs_key key;
3815         struct extent_buffer *leaf;
3816         u64 start, end, last;
3817         int ret;
3818
3819         last = rc->block_group->start + rc->block_group->length;
3820         while (1) {
3821                 cond_resched();
3822                 if (rc->search_start >= last) {
3823                         ret = 1;
3824                         break;
3825                 }
3826
3827                 key.objectid = rc->search_start;
3828                 key.type = BTRFS_EXTENT_ITEM_KEY;
3829                 key.offset = 0;
3830
3831                 path->search_commit_root = 1;
3832                 path->skip_locking = 1;
3833                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3834                                         0, 0);
3835                 if (ret < 0)
3836                         break;
3837 next:
3838                 leaf = path->nodes[0];
3839                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3840                         ret = btrfs_next_leaf(rc->extent_root, path);
3841                         if (ret != 0)
3842                                 break;
3843                         leaf = path->nodes[0];
3844                 }
3845
3846                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3847                 if (key.objectid >= last) {
3848                         ret = 1;
3849                         break;
3850                 }
3851
3852                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3853                     key.type != BTRFS_METADATA_ITEM_KEY) {
3854                         path->slots[0]++;
3855                         goto next;
3856                 }
3857
3858                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3859                     key.objectid + key.offset <= rc->search_start) {
3860                         path->slots[0]++;
3861                         goto next;
3862                 }
3863
3864                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3865                     key.objectid + fs_info->nodesize <=
3866                     rc->search_start) {
3867                         path->slots[0]++;
3868                         goto next;
3869                 }
3870
3871                 ret = find_first_extent_bit(&rc->processed_blocks,
3872                                             key.objectid, &start, &end,
3873                                             EXTENT_DIRTY, NULL);
3874
3875                 if (ret == 0 && start <= key.objectid) {
3876                         btrfs_release_path(path);
3877                         rc->search_start = end + 1;
3878                 } else {
3879                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3880                                 rc->search_start = key.objectid + key.offset;
3881                         else
3882                                 rc->search_start = key.objectid +
3883                                         fs_info->nodesize;
3884                         memcpy(extent_key, &key, sizeof(key));
3885                         return 0;
3886                 }
3887         }
3888         btrfs_release_path(path);
3889         return ret;
3890 }
3891
3892 static void set_reloc_control(struct reloc_control *rc)
3893 {
3894         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3895
3896         mutex_lock(&fs_info->reloc_mutex);
3897         fs_info->reloc_ctl = rc;
3898         mutex_unlock(&fs_info->reloc_mutex);
3899 }
3900
3901 static void unset_reloc_control(struct reloc_control *rc)
3902 {
3903         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3904
3905         mutex_lock(&fs_info->reloc_mutex);
3906         fs_info->reloc_ctl = NULL;
3907         mutex_unlock(&fs_info->reloc_mutex);
3908 }
3909
3910 static int check_extent_flags(u64 flags)
3911 {
3912         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3913             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3914                 return 1;
3915         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3916             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3917                 return 1;
3918         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3919             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3920                 return 1;
3921         return 0;
3922 }
3923
3924 static noinline_for_stack
3925 int prepare_to_relocate(struct reloc_control *rc)
3926 {
3927         struct btrfs_trans_handle *trans;
3928         int ret;
3929
3930         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3931                                               BTRFS_BLOCK_RSV_TEMP);
3932         if (!rc->block_rsv)
3933                 return -ENOMEM;
3934
3935         memset(&rc->cluster, 0, sizeof(rc->cluster));
3936         rc->search_start = rc->block_group->start;
3937         rc->extents_found = 0;
3938         rc->nodes_relocated = 0;
3939         rc->merging_rsv_size = 0;
3940         rc->reserved_bytes = 0;
3941         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
3942                               RELOCATION_RESERVED_NODES;
3943         ret = btrfs_block_rsv_refill(rc->extent_root,
3944                                      rc->block_rsv, rc->block_rsv->size,
3945                                      BTRFS_RESERVE_FLUSH_ALL);
3946         if (ret)
3947                 return ret;
3948
3949         rc->create_reloc_tree = 1;
3950         set_reloc_control(rc);
3951
3952         trans = btrfs_join_transaction(rc->extent_root);
3953         if (IS_ERR(trans)) {
3954                 unset_reloc_control(rc);
3955                 /*
3956                  * extent tree is not a ref_cow tree and has no reloc_root to
3957                  * cleanup.  And callers are responsible to free the above
3958                  * block rsv.
3959                  */
3960                 return PTR_ERR(trans);
3961         }
3962         btrfs_commit_transaction(trans);
3963         return 0;
3964 }
3965
3966 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3967 {
3968         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3969         struct rb_root blocks = RB_ROOT;
3970         struct btrfs_key key;
3971         struct btrfs_trans_handle *trans = NULL;
3972         struct btrfs_path *path;
3973         struct btrfs_extent_item *ei;
3974         u64 flags;
3975         u32 item_size;
3976         int ret;
3977         int err = 0;
3978         int progress = 0;
3979
3980         path = btrfs_alloc_path();
3981         if (!path)
3982                 return -ENOMEM;
3983         path->reada = READA_FORWARD;
3984
3985         ret = prepare_to_relocate(rc);
3986         if (ret) {
3987                 err = ret;
3988                 goto out_free;
3989         }
3990
3991         while (1) {
3992                 rc->reserved_bytes = 0;
3993                 ret = btrfs_block_rsv_refill(rc->extent_root,
3994                                         rc->block_rsv, rc->block_rsv->size,
3995                                         BTRFS_RESERVE_FLUSH_ALL);
3996                 if (ret) {
3997                         err = ret;
3998                         break;
3999                 }
4000                 progress++;
4001                 trans = btrfs_start_transaction(rc->extent_root, 0);
4002                 if (IS_ERR(trans)) {
4003                         err = PTR_ERR(trans);
4004                         trans = NULL;
4005                         break;
4006                 }
4007 restart:
4008                 if (update_backref_cache(trans, &rc->backref_cache)) {
4009                         btrfs_end_transaction(trans);
4010                         trans = NULL;
4011                         continue;
4012                 }
4013
4014                 ret = find_next_extent(rc, path, &key);
4015                 if (ret < 0)
4016                         err = ret;
4017                 if (ret != 0)
4018                         break;
4019
4020                 rc->extents_found++;
4021
4022                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4023                                     struct btrfs_extent_item);
4024                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4025                 if (item_size >= sizeof(*ei)) {
4026                         flags = btrfs_extent_flags(path->nodes[0], ei);
4027                         ret = check_extent_flags(flags);
4028                         BUG_ON(ret);
4029                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
4030                         err = -EINVAL;
4031                         btrfs_print_v0_err(trans->fs_info);
4032                         btrfs_abort_transaction(trans, err);
4033                         break;
4034                 } else {
4035                         BUG();
4036                 }
4037
4038                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4039                         ret = add_tree_block(rc, &key, path, &blocks);
4040                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4041                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4042                         ret = add_data_references(rc, &key, path, &blocks);
4043                 } else {
4044                         btrfs_release_path(path);
4045                         ret = 0;
4046                 }
4047                 if (ret < 0) {
4048                         err = ret;
4049                         break;
4050                 }
4051
4052                 if (!RB_EMPTY_ROOT(&blocks)) {
4053                         ret = relocate_tree_blocks(trans, rc, &blocks);
4054                         if (ret < 0) {
4055                                 if (ret != -EAGAIN) {
4056                                         err = ret;
4057                                         break;
4058                                 }
4059                                 rc->extents_found--;
4060                                 rc->search_start = key.objectid;
4061                         }
4062                 }
4063
4064                 btrfs_end_transaction_throttle(trans);
4065                 btrfs_btree_balance_dirty(fs_info);
4066                 trans = NULL;
4067
4068                 if (rc->stage == MOVE_DATA_EXTENTS &&
4069                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4070                         rc->found_file_extent = 1;
4071                         ret = relocate_data_extent(rc->data_inode,
4072                                                    &key, &rc->cluster);
4073                         if (ret < 0) {
4074                                 err = ret;
4075                                 break;
4076                         }
4077                 }
4078                 if (btrfs_should_cancel_balance(fs_info)) {
4079                         err = -ECANCELED;
4080                         break;
4081                 }
4082         }
4083         if (trans && progress && err == -ENOSPC) {
4084                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
4085                 if (ret == 1) {
4086                         err = 0;
4087                         progress = 0;
4088                         goto restart;
4089                 }
4090         }
4091
4092         btrfs_release_path(path);
4093         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4094
4095         if (trans) {
4096                 btrfs_end_transaction_throttle(trans);
4097                 btrfs_btree_balance_dirty(fs_info);
4098         }
4099
4100         if (!err) {
4101                 ret = relocate_file_extent_cluster(rc->data_inode,
4102                                                    &rc->cluster);
4103                 if (ret < 0)
4104                         err = ret;
4105         }
4106
4107         rc->create_reloc_tree = 0;
4108         set_reloc_control(rc);
4109
4110         backref_cache_cleanup(&rc->backref_cache);
4111         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
4112
4113         /*
4114          * Even in the case when the relocation is cancelled, we should all go
4115          * through prepare_to_merge() and merge_reloc_roots().
4116          *
4117          * For error (including cancelled balance), prepare_to_merge() will
4118          * mark all reloc trees orphan, then queue them for cleanup in
4119          * merge_reloc_roots()
4120          */
4121         err = prepare_to_merge(rc, err);
4122
4123         merge_reloc_roots(rc);
4124
4125         rc->merge_reloc_tree = 0;
4126         unset_reloc_control(rc);
4127         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
4128
4129         /* get rid of pinned extents */
4130         trans = btrfs_join_transaction(rc->extent_root);
4131         if (IS_ERR(trans)) {
4132                 err = PTR_ERR(trans);
4133                 goto out_free;
4134         }
4135         btrfs_commit_transaction(trans);
4136 out_free:
4137         ret = clean_dirty_subvols(rc);
4138         if (ret < 0 && !err)
4139                 err = ret;
4140         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4141         btrfs_free_path(path);
4142         return err;
4143 }
4144
4145 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4146                                  struct btrfs_root *root, u64 objectid)
4147 {
4148         struct btrfs_path *path;
4149         struct btrfs_inode_item *item;
4150         struct extent_buffer *leaf;
4151         int ret;
4152
4153         path = btrfs_alloc_path();
4154         if (!path)
4155                 return -ENOMEM;
4156
4157         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4158         if (ret)
4159                 goto out;
4160
4161         leaf = path->nodes[0];
4162         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4163         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4164         btrfs_set_inode_generation(leaf, item, 1);
4165         btrfs_set_inode_size(leaf, item, 0);
4166         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4167         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4168                                           BTRFS_INODE_PREALLOC);
4169         btrfs_mark_buffer_dirty(leaf);
4170 out:
4171         btrfs_free_path(path);
4172         return ret;
4173 }
4174
4175 /*
4176  * helper to create inode for data relocation.
4177  * the inode is in data relocation tree and its link count is 0
4178  */
4179 static noinline_for_stack
4180 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4181                                  struct btrfs_block_group *group)
4182 {
4183         struct inode *inode = NULL;
4184         struct btrfs_trans_handle *trans;
4185         struct btrfs_root *root;
4186         struct btrfs_key key;
4187         u64 objectid;
4188         int err = 0;
4189
4190         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4191         if (IS_ERR(root))
4192                 return ERR_CAST(root);
4193
4194         trans = btrfs_start_transaction(root, 6);
4195         if (IS_ERR(trans)) {
4196                 btrfs_put_root(root);
4197                 return ERR_CAST(trans);
4198         }
4199
4200         err = btrfs_find_free_objectid(root, &objectid);
4201         if (err)
4202                 goto out;
4203
4204         err = __insert_orphan_inode(trans, root, objectid);
4205         BUG_ON(err);
4206
4207         key.objectid = objectid;
4208         key.type = BTRFS_INODE_ITEM_KEY;
4209         key.offset = 0;
4210         inode = btrfs_iget(fs_info->sb, &key, root);
4211         BUG_ON(IS_ERR(inode));
4212         BTRFS_I(inode)->index_cnt = group->start;
4213
4214         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4215 out:
4216         btrfs_put_root(root);
4217         btrfs_end_transaction(trans);
4218         btrfs_btree_balance_dirty(fs_info);
4219         if (err) {
4220                 if (inode)
4221                         iput(inode);
4222                 inode = ERR_PTR(err);
4223         }
4224         return inode;
4225 }
4226
4227 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4228 {
4229         struct reloc_control *rc;
4230
4231         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4232         if (!rc)
4233                 return NULL;
4234
4235         INIT_LIST_HEAD(&rc->reloc_roots);
4236         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
4237         backref_cache_init(&rc->backref_cache);
4238         mapping_tree_init(&rc->reloc_root_tree);
4239         extent_io_tree_init(fs_info, &rc->processed_blocks,
4240                             IO_TREE_RELOC_BLOCKS, NULL);
4241         return rc;
4242 }
4243
4244 static void free_reloc_control(struct reloc_control *rc)
4245 {
4246         struct mapping_node *node, *tmp;
4247
4248         free_reloc_roots(&rc->reloc_roots);
4249         rbtree_postorder_for_each_entry_safe(node, tmp,
4250                         &rc->reloc_root_tree.rb_root, rb_node)
4251                 kfree(node);
4252
4253         kfree(rc);
4254 }
4255
4256 /*
4257  * Print the block group being relocated
4258  */
4259 static void describe_relocation(struct btrfs_fs_info *fs_info,
4260                                 struct btrfs_block_group *block_group)
4261 {
4262         char buf[128] = {'\0'};
4263
4264         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
4265
4266         btrfs_info(fs_info,
4267                    "relocating block group %llu flags %s",
4268                    block_group->start, buf);
4269 }
4270
4271 static const char *stage_to_string(int stage)
4272 {
4273         if (stage == MOVE_DATA_EXTENTS)
4274                 return "move data extents";
4275         if (stage == UPDATE_DATA_PTRS)
4276                 return "update data pointers";
4277         return "unknown";
4278 }
4279
4280 /*
4281  * function to relocate all extents in a block group.
4282  */
4283 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4284 {
4285         struct btrfs_block_group *bg;
4286         struct btrfs_root *extent_root = fs_info->extent_root;
4287         struct reloc_control *rc;
4288         struct inode *inode;
4289         struct btrfs_path *path;
4290         int ret;
4291         int rw = 0;
4292         int err = 0;
4293
4294         bg = btrfs_lookup_block_group(fs_info, group_start);
4295         if (!bg)
4296                 return -ENOENT;
4297
4298         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
4299                 btrfs_put_block_group(bg);
4300                 return -ETXTBSY;
4301         }
4302
4303         rc = alloc_reloc_control(fs_info);
4304         if (!rc) {
4305                 btrfs_put_block_group(bg);
4306                 return -ENOMEM;
4307         }
4308
4309         rc->extent_root = extent_root;
4310         rc->block_group = bg;
4311
4312         ret = btrfs_inc_block_group_ro(rc->block_group, true);
4313         if (ret) {
4314                 err = ret;
4315                 goto out;
4316         }
4317         rw = 1;
4318
4319         path = btrfs_alloc_path();
4320         if (!path) {
4321                 err = -ENOMEM;
4322                 goto out;
4323         }
4324
4325         inode = lookup_free_space_inode(rc->block_group, path);
4326         btrfs_free_path(path);
4327
4328         if (!IS_ERR(inode))
4329                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4330         else
4331                 ret = PTR_ERR(inode);
4332
4333         if (ret && ret != -ENOENT) {
4334                 err = ret;
4335                 goto out;
4336         }
4337
4338         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4339         if (IS_ERR(rc->data_inode)) {
4340                 err = PTR_ERR(rc->data_inode);
4341                 rc->data_inode = NULL;
4342                 goto out;
4343         }
4344
4345         describe_relocation(fs_info, rc->block_group);
4346
4347         btrfs_wait_block_group_reservations(rc->block_group);
4348         btrfs_wait_nocow_writers(rc->block_group);
4349         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4350                                  rc->block_group->start,
4351                                  rc->block_group->length);
4352
4353         while (1) {
4354                 int finishes_stage;
4355
4356                 mutex_lock(&fs_info->cleaner_mutex);
4357                 ret = relocate_block_group(rc);
4358                 mutex_unlock(&fs_info->cleaner_mutex);
4359                 if (ret < 0)
4360                         err = ret;
4361
4362                 finishes_stage = rc->stage;
4363                 /*
4364                  * We may have gotten ENOSPC after we already dirtied some
4365                  * extents.  If writeout happens while we're relocating a
4366                  * different block group we could end up hitting the
4367                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
4368                  * btrfs_reloc_cow_block.  Make sure we write everything out
4369                  * properly so we don't trip over this problem, and then break
4370                  * out of the loop if we hit an error.
4371                  */
4372                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4373                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4374                                                        (u64)-1);
4375                         if (ret)
4376                                 err = ret;
4377                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4378                                                  0, -1);
4379                         rc->stage = UPDATE_DATA_PTRS;
4380                 }
4381
4382                 if (err < 0)
4383                         goto out;
4384
4385                 if (rc->extents_found == 0)
4386                         break;
4387
4388                 btrfs_info(fs_info, "found %llu extents, stage: %s",
4389                            rc->extents_found, stage_to_string(finishes_stage));
4390         }
4391
4392         WARN_ON(rc->block_group->pinned > 0);
4393         WARN_ON(rc->block_group->reserved > 0);
4394         WARN_ON(rc->block_group->used > 0);
4395 out:
4396         if (err && rw)
4397                 btrfs_dec_block_group_ro(rc->block_group);
4398         iput(rc->data_inode);
4399         btrfs_put_block_group(rc->block_group);
4400         free_reloc_control(rc);
4401         return err;
4402 }
4403
4404 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4405 {
4406         struct btrfs_fs_info *fs_info = root->fs_info;
4407         struct btrfs_trans_handle *trans;
4408         int ret, err;
4409
4410         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4411         if (IS_ERR(trans))
4412                 return PTR_ERR(trans);
4413
4414         memset(&root->root_item.drop_progress, 0,
4415                 sizeof(root->root_item.drop_progress));
4416         root->root_item.drop_level = 0;
4417         btrfs_set_root_refs(&root->root_item, 0);
4418         ret = btrfs_update_root(trans, fs_info->tree_root,
4419                                 &root->root_key, &root->root_item);
4420
4421         err = btrfs_end_transaction(trans);
4422         if (err)
4423                 return err;
4424         return ret;
4425 }
4426
4427 /*
4428  * recover relocation interrupted by system crash.
4429  *
4430  * this function resumes merging reloc trees with corresponding fs trees.
4431  * this is important for keeping the sharing of tree blocks
4432  */
4433 int btrfs_recover_relocation(struct btrfs_root *root)
4434 {
4435         struct btrfs_fs_info *fs_info = root->fs_info;
4436         LIST_HEAD(reloc_roots);
4437         struct btrfs_key key;
4438         struct btrfs_root *fs_root;
4439         struct btrfs_root *reloc_root;
4440         struct btrfs_path *path;
4441         struct extent_buffer *leaf;
4442         struct reloc_control *rc = NULL;
4443         struct btrfs_trans_handle *trans;
4444         int ret;
4445         int err = 0;
4446
4447         path = btrfs_alloc_path();
4448         if (!path)
4449                 return -ENOMEM;
4450         path->reada = READA_BACK;
4451
4452         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4453         key.type = BTRFS_ROOT_ITEM_KEY;
4454         key.offset = (u64)-1;
4455
4456         while (1) {
4457                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4458                                         path, 0, 0);
4459                 if (ret < 0) {
4460                         err = ret;
4461                         goto out;
4462                 }
4463                 if (ret > 0) {
4464                         if (path->slots[0] == 0)
4465                                 break;
4466                         path->slots[0]--;
4467                 }
4468                 leaf = path->nodes[0];
4469                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4470                 btrfs_release_path(path);
4471
4472                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4473                     key.type != BTRFS_ROOT_ITEM_KEY)
4474                         break;
4475
4476                 reloc_root = btrfs_read_tree_root(root, &key);
4477                 if (IS_ERR(reloc_root)) {
4478                         err = PTR_ERR(reloc_root);
4479                         goto out;
4480                 }
4481
4482                 set_bit(BTRFS_ROOT_REF_COWS, &reloc_root->state);
4483                 list_add(&reloc_root->root_list, &reloc_roots);
4484
4485                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4486                         fs_root = read_fs_root(fs_info,
4487                                                reloc_root->root_key.offset);
4488                         if (IS_ERR(fs_root)) {
4489                                 ret = PTR_ERR(fs_root);
4490                                 if (ret != -ENOENT) {
4491                                         err = ret;
4492                                         goto out;
4493                                 }
4494                                 ret = mark_garbage_root(reloc_root);
4495                                 if (ret < 0) {
4496                                         err = ret;
4497                                         goto out;
4498                                 }
4499                         } else {
4500                                 btrfs_put_root(fs_root);
4501                         }
4502                 }
4503
4504                 if (key.offset == 0)
4505                         break;
4506
4507                 key.offset--;
4508         }
4509         btrfs_release_path(path);
4510
4511         if (list_empty(&reloc_roots))
4512                 goto out;
4513
4514         rc = alloc_reloc_control(fs_info);
4515         if (!rc) {
4516                 err = -ENOMEM;
4517                 goto out;
4518         }
4519
4520         rc->extent_root = fs_info->extent_root;
4521
4522         set_reloc_control(rc);
4523
4524         trans = btrfs_join_transaction(rc->extent_root);
4525         if (IS_ERR(trans)) {
4526                 err = PTR_ERR(trans);
4527                 goto out_unset;
4528         }
4529
4530         rc->merge_reloc_tree = 1;
4531
4532         while (!list_empty(&reloc_roots)) {
4533                 reloc_root = list_entry(reloc_roots.next,
4534                                         struct btrfs_root, root_list);
4535                 list_del(&reloc_root->root_list);
4536
4537                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4538                         list_add_tail(&reloc_root->root_list,
4539                                       &rc->reloc_roots);
4540                         continue;
4541                 }
4542
4543                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4544                 if (IS_ERR(fs_root)) {
4545                         err = PTR_ERR(fs_root);
4546                         list_add_tail(&reloc_root->root_list, &reloc_roots);
4547                         goto out_unset;
4548                 }
4549
4550                 err = __add_reloc_root(reloc_root);
4551                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4552                 fs_root->reloc_root = btrfs_grab_root(reloc_root);
4553                 btrfs_put_root(fs_root);
4554         }
4555
4556         err = btrfs_commit_transaction(trans);
4557         if (err)
4558                 goto out_unset;
4559
4560         merge_reloc_roots(rc);
4561
4562         unset_reloc_control(rc);
4563
4564         trans = btrfs_join_transaction(rc->extent_root);
4565         if (IS_ERR(trans)) {
4566                 err = PTR_ERR(trans);
4567                 goto out_clean;
4568         }
4569         err = btrfs_commit_transaction(trans);
4570 out_clean:
4571         ret = clean_dirty_subvols(rc);
4572         if (ret < 0 && !err)
4573                 err = ret;
4574 out_unset:
4575         unset_reloc_control(rc);
4576         free_reloc_control(rc);
4577 out:
4578         if (!list_empty(&reloc_roots))
4579                 free_reloc_roots(&reloc_roots);
4580
4581         btrfs_free_path(path);
4582
4583         if (err == 0) {
4584                 /* cleanup orphan inode in data relocation tree */
4585                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4586                 if (IS_ERR(fs_root)) {
4587                         err = PTR_ERR(fs_root);
4588                 } else {
4589                         err = btrfs_orphan_cleanup(fs_root);
4590                         btrfs_put_root(fs_root);
4591                 }
4592         }
4593         return err;
4594 }
4595
4596 /*
4597  * helper to add ordered checksum for data relocation.
4598  *
4599  * cloning checksum properly handles the nodatasum extents.
4600  * it also saves CPU time to re-calculate the checksum.
4601  */
4602 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4603 {
4604         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4605         struct btrfs_ordered_sum *sums;
4606         struct btrfs_ordered_extent *ordered;
4607         int ret;
4608         u64 disk_bytenr;
4609         u64 new_bytenr;
4610         LIST_HEAD(list);
4611
4612         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4613         BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
4614
4615         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4616         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4617                                        disk_bytenr + len - 1, &list, 0);
4618         if (ret)
4619                 goto out;
4620
4621         while (!list_empty(&list)) {
4622                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4623                 list_del_init(&sums->list);
4624
4625                 /*
4626                  * We need to offset the new_bytenr based on where the csum is.
4627                  * We need to do this because we will read in entire prealloc
4628                  * extents but we may have written to say the middle of the
4629                  * prealloc extent, so we need to make sure the csum goes with
4630                  * the right disk offset.
4631                  *
4632                  * We can do this because the data reloc inode refers strictly
4633                  * to the on disk bytes, so we don't have to worry about
4634                  * disk_len vs real len like with real inodes since it's all
4635                  * disk length.
4636                  */
4637                 new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
4638                 sums->bytenr = new_bytenr;
4639
4640                 btrfs_add_ordered_sum(ordered, sums);
4641         }
4642 out:
4643         btrfs_put_ordered_extent(ordered);
4644         return ret;
4645 }
4646
4647 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4648                           struct btrfs_root *root, struct extent_buffer *buf,
4649                           struct extent_buffer *cow)
4650 {
4651         struct btrfs_fs_info *fs_info = root->fs_info;
4652         struct reloc_control *rc;
4653         struct backref_node *node;
4654         int first_cow = 0;
4655         int level;
4656         int ret = 0;
4657
4658         rc = fs_info->reloc_ctl;
4659         if (!rc)
4660                 return 0;
4661
4662         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4663                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4664
4665         level = btrfs_header_level(buf);
4666         if (btrfs_header_generation(buf) <=
4667             btrfs_root_last_snapshot(&root->root_item))
4668                 first_cow = 1;
4669
4670         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4671             rc->create_reloc_tree) {
4672                 WARN_ON(!first_cow && level == 0);
4673
4674                 node = rc->backref_cache.path[level];
4675                 BUG_ON(node->bytenr != buf->start &&
4676                        node->new_bytenr != buf->start);
4677
4678                 drop_node_buffer(node);
4679                 atomic_inc(&cow->refs);
4680                 node->eb = cow;
4681                 node->new_bytenr = cow->start;
4682
4683                 if (!node->pending) {
4684                         list_move_tail(&node->list,
4685                                        &rc->backref_cache.pending[level]);
4686                         node->pending = 1;
4687                 }
4688
4689                 if (first_cow)
4690                         __mark_block_processed(rc, node);
4691
4692                 if (first_cow && level > 0)
4693                         rc->nodes_relocated += buf->len;
4694         }
4695
4696         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4697                 ret = replace_file_extents(trans, rc, root, cow);
4698         return ret;
4699 }
4700
4701 /*
4702  * called before creating snapshot. it calculates metadata reservation
4703  * required for relocating tree blocks in the snapshot
4704  */
4705 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4706                               u64 *bytes_to_reserve)
4707 {
4708         struct btrfs_root *root = pending->root;
4709         struct reloc_control *rc = root->fs_info->reloc_ctl;
4710
4711         if (!rc || !have_reloc_root(root))
4712                 return;
4713
4714         if (!rc->merge_reloc_tree)
4715                 return;
4716
4717         root = root->reloc_root;
4718         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4719         /*
4720          * relocation is in the stage of merging trees. the space
4721          * used by merging a reloc tree is twice the size of
4722          * relocated tree nodes in the worst case. half for cowing
4723          * the reloc tree, half for cowing the fs tree. the space
4724          * used by cowing the reloc tree will be freed after the
4725          * tree is dropped. if we create snapshot, cowing the fs
4726          * tree may use more space than it frees. so we need
4727          * reserve extra space.
4728          */
4729         *bytes_to_reserve += rc->nodes_relocated;
4730 }
4731
4732 /*
4733  * called after snapshot is created. migrate block reservation
4734  * and create reloc root for the newly created snapshot
4735  *
4736  * This is similar to btrfs_init_reloc_root(), we come out of here with two
4737  * references held on the reloc_root, one for root->reloc_root and one for
4738  * rc->reloc_roots.
4739  */
4740 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4741                                struct btrfs_pending_snapshot *pending)
4742 {
4743         struct btrfs_root *root = pending->root;
4744         struct btrfs_root *reloc_root;
4745         struct btrfs_root *new_root;
4746         struct reloc_control *rc = root->fs_info->reloc_ctl;
4747         int ret;
4748
4749         if (!rc || !have_reloc_root(root))
4750                 return 0;
4751
4752         rc = root->fs_info->reloc_ctl;
4753         rc->merging_rsv_size += rc->nodes_relocated;
4754
4755         if (rc->merge_reloc_tree) {
4756                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4757                                               rc->block_rsv,
4758                                               rc->nodes_relocated, true);
4759                 if (ret)
4760                         return ret;
4761         }
4762
4763         new_root = pending->snap;
4764         reloc_root = create_reloc_root(trans, root->reloc_root,
4765                                        new_root->root_key.objectid);
4766         if (IS_ERR(reloc_root))
4767                 return PTR_ERR(reloc_root);
4768
4769         ret = __add_reloc_root(reloc_root);
4770         BUG_ON(ret < 0);
4771         new_root->reloc_root = btrfs_grab_root(reloc_root);
4772
4773         if (rc->create_reloc_tree)
4774                 ret = clone_backref_node(trans, rc, root, reloc_root);
4775         return ret;
4776 }