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_header_generation(reloc_root->commit_root) ==
 615             root->fs_info->running_transaction->transid)
 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)
1531                 return 0;
1532
1533         /*
1534          * The subvolume has reloc tree but the swap is finished, no need to
1535          * create/update the dead reloc tree
1536          */
1537         if (reloc_root_is_dead(root))
1538                 return 0;
1539
1540         /*
1541          * This is subtle but important.  We do not do
1542          * record_root_in_transaction for reloc roots, instead we record their
1543          * corresponding fs root, and then here we update the last trans for the
1544          * reloc root.  This means that we have to do this for the entire life
1545          * of the reloc root, regardless of which stage of the relocation we are
1546          * in.
1547          */
1548         if (root->reloc_root) {
1549                 reloc_root = root->reloc_root;
1550                 reloc_root->last_trans = trans->transid;
1551                 return 0;
1552         }
1553
1554         /*
1555          * We are merging reloc roots, we do not need new reloc trees.  Also
1556          * reloc trees never need their own reloc tree.
1557          */
1558         if (!rc->create_reloc_tree ||
1559             root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1560                 return 0;
1561
1562         if (!trans->reloc_reserved) {
1563                 rsv = trans->block_rsv;
1564                 trans->block_rsv = rc->block_rsv;
1565                 clear_rsv = 1;
1566         }
1567         reloc_root = create_reloc_root(trans, root, root->root_key.objectid);
1568         if (clear_rsv)
1569                 trans->block_rsv = rsv;
1570
1571         ret = __add_reloc_root(reloc_root);
1572         BUG_ON(ret < 0);
1573         root->reloc_root = btrfs_grab_root(reloc_root);
1574         return 0;
1575 }
1576
1577 /*
1578  * update root item of reloc tree
1579  */
1580 int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
1581                             struct btrfs_root *root)
1582 {
1583         struct btrfs_fs_info *fs_info = root->fs_info;
1584         struct btrfs_root *reloc_root;
1585         struct btrfs_root_item *root_item;
1586         int ret;
1587
1588         if (!have_reloc_root(root))
1589                 goto out;
1590
1591         reloc_root = root->reloc_root;
1592         root_item = &reloc_root->root_item;
1593
1594         /*
1595          * We are probably ok here, but __del_reloc_root() will drop its ref of
1596          * the root.  We have the ref for root->reloc_root, but just in case
1597          * hold it while we update the reloc root.
1598          */
1599         btrfs_grab_root(reloc_root);
1600
1601         /* root->reloc_root will stay until current relocation finished */
1602         if (fs_info->reloc_ctl->merge_reloc_tree &&
1603             btrfs_root_refs(root_item) == 0) {
1604                 set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
1605                 /*
1606                  * Mark the tree as dead before we change reloc_root so
1607                  * have_reloc_root will not touch it from now on.
1608                  */
1609                 smp_wmb();
1610                 __del_reloc_root(reloc_root);
1611         }
1612
1613         if (reloc_root->commit_root != reloc_root->node) {
1614                 __update_reloc_root(reloc_root);
1615                 btrfs_set_root_node(root_item, reloc_root->node);
1616                 free_extent_buffer(reloc_root->commit_root);
1617                 reloc_root->commit_root = btrfs_root_node(reloc_root);
1618         }
1619
1620         ret = btrfs_update_root(trans, fs_info->tree_root,
1621                                 &reloc_root->root_key, root_item);
1622         BUG_ON(ret);
1623         btrfs_put_root(reloc_root);
1624 out:
1625         return 0;
1626 }
1627
1628 /*
1629  * helper to find first cached inode with inode number >= objectid
1630  * in a subvolume
1631  */
1632 static struct inode *find_next_inode(struct btrfs_root *root, u64 objectid)
1633 {
1634         struct rb_node *node;
1635         struct rb_node *prev;
1636         struct btrfs_inode *entry;
1637         struct inode *inode;
1638
1639         spin_lock(&root->inode_lock);
1640 again:
1641         node = root->inode_tree.rb_node;
1642         prev = NULL;
1643         while (node) {
1644                 prev = node;
1645                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1646
1647                 if (objectid < btrfs_ino(entry))
1648                         node = node->rb_left;
1649                 else if (objectid > btrfs_ino(entry))
1650                         node = node->rb_right;
1651                 else
1652                         break;
1653         }
1654         if (!node) {
1655                 while (prev) {
1656                         entry = rb_entry(prev, struct btrfs_inode, rb_node);
1657                         if (objectid <= btrfs_ino(entry)) {
1658                                 node = prev;
1659                                 break;
1660                         }
1661                         prev = rb_next(prev);
1662                 }
1663         }
1664         while (node) {
1665                 entry = rb_entry(node, struct btrfs_inode, rb_node);
1666                 inode = igrab(&entry->vfs_inode);
1667                 if (inode) {
1668                         spin_unlock(&root->inode_lock);
1669                         return inode;
1670                 }
1671
1672                 objectid = btrfs_ino(entry) + 1;
1673                 if (cond_resched_lock(&root->inode_lock))
1674                         goto again;
1675
1676                 node = rb_next(node);
1677         }
1678         spin_unlock(&root->inode_lock);
1679         return NULL;
1680 }
1681
1682 static int in_block_group(u64 bytenr, struct btrfs_block_group *block_group)
1683 {
1684         if (bytenr >= block_group->start &&
1685             bytenr < block_group->start + block_group->length)
1686                 return 1;
1687         return 0;
1688 }
1689
1690 /*
1691  * get new location of data
1692  */
1693 static int get_new_location(struct inode *reloc_inode, u64 *new_bytenr,
1694                             u64 bytenr, u64 num_bytes)
1695 {
1696         struct btrfs_root *root = BTRFS_I(reloc_inode)->root;
1697         struct btrfs_path *path;
1698         struct btrfs_file_extent_item *fi;
1699         struct extent_buffer *leaf;
1700         int ret;
1701
1702         path = btrfs_alloc_path();
1703         if (!path)
1704                 return -ENOMEM;
1705
1706         bytenr -= BTRFS_I(reloc_inode)->index_cnt;
1707         ret = btrfs_lookup_file_extent(NULL, root, path,
1708                         btrfs_ino(BTRFS_I(reloc_inode)), bytenr, 0);
1709         if (ret < 0)
1710                 goto out;
1711         if (ret > 0) {
1712                 ret = -ENOENT;
1713                 goto out;
1714         }
1715
1716         leaf = path->nodes[0];
1717         fi = btrfs_item_ptr(leaf, path->slots[0],
1718                             struct btrfs_file_extent_item);
1719
1720         BUG_ON(btrfs_file_extent_offset(leaf, fi) ||
1721                btrfs_file_extent_compression(leaf, fi) ||
1722                btrfs_file_extent_encryption(leaf, fi) ||
1723                btrfs_file_extent_other_encoding(leaf, fi));
1724
1725         if (num_bytes != btrfs_file_extent_disk_num_bytes(leaf, fi)) {
1726                 ret = -EINVAL;
1727                 goto out;
1728         }
1729
1730         *new_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1731         ret = 0;
1732 out:
1733         btrfs_free_path(path);
1734         return ret;
1735 }
1736
1737 /*
1738  * update file extent items in the tree leaf to point to
1739  * the new locations.
1740  */
1741 static noinline_for_stack
1742 int replace_file_extents(struct btrfs_trans_handle *trans,
1743                          struct reloc_control *rc,
1744                          struct btrfs_root *root,
1745                          struct extent_buffer *leaf)
1746 {
1747         struct btrfs_fs_info *fs_info = root->fs_info;
1748         struct btrfs_key key;
1749         struct btrfs_file_extent_item *fi;
1750         struct inode *inode = NULL;
1751         u64 parent;
1752         u64 bytenr;
1753         u64 new_bytenr = 0;
1754         u64 num_bytes;
1755         u64 end;
1756         u32 nritems;
1757         u32 i;
1758         int ret = 0;
1759         int first = 1;
1760         int dirty = 0;
1761
1762         if (rc->stage != UPDATE_DATA_PTRS)
1763                 return 0;
1764
1765         /* reloc trees always use full backref */
1766         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID)
1767                 parent = leaf->start;
1768         else
1769                 parent = 0;
1770
1771         nritems = btrfs_header_nritems(leaf);
1772         for (i = 0; i < nritems; i++) {
1773                 struct btrfs_ref ref = { 0 };
1774
1775                 cond_resched();
1776                 btrfs_item_key_to_cpu(leaf, &key, i);
1777                 if (key.type != BTRFS_EXTENT_DATA_KEY)
1778                         continue;
1779                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
1780                 if (btrfs_file_extent_type(leaf, fi) ==
1781                     BTRFS_FILE_EXTENT_INLINE)
1782                         continue;
1783                 bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
1784                 num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
1785                 if (bytenr == 0)
1786                         continue;
1787                 if (!in_block_group(bytenr, rc->block_group))
1788                         continue;
1789
1790                 /*
1791                  * if we are modifying block in fs tree, wait for readpage
1792                  * to complete and drop the extent cache
1793                  */
1794                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
1795                         if (first) {
1796                                 inode = find_next_inode(root, key.objectid);
1797                                 first = 0;
1798                         } else if (inode && btrfs_ino(BTRFS_I(inode)) < key.objectid) {
1799                                 btrfs_add_delayed_iput(inode);
1800                                 inode = find_next_inode(root, key.objectid);
1801                         }
1802                         if (inode && btrfs_ino(BTRFS_I(inode)) == key.objectid) {
1803                                 end = key.offset +
1804                                       btrfs_file_extent_num_bytes(leaf, fi);
1805                                 WARN_ON(!IS_ALIGNED(key.offset,
1806                                                     fs_info->sectorsize));
1807                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
1808                                 end--;
1809                                 ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
1810                                                       key.offset, end);
1811                                 if (!ret)
1812                                         continue;
1813
1814                                 btrfs_drop_extent_cache(BTRFS_I(inode),
1815                                                 key.offset,     end, 1);
1816                                 unlock_extent(&BTRFS_I(inode)->io_tree,
1817                                               key.offset, end);
1818                         }
1819                 }
1820
1821                 ret = get_new_location(rc->data_inode, &new_bytenr,
1822                                        bytenr, num_bytes);
1823                 if (ret) {
1824                         /*
1825                          * Don't have to abort since we've not changed anything
1826                          * in the file extent yet.
1827                          */
1828                         break;
1829                 }
1830
1831                 btrfs_set_file_extent_disk_bytenr(leaf, fi, new_bytenr);
1832                 dirty = 1;
1833
1834                 key.offset -= btrfs_file_extent_offset(leaf, fi);
1835                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
1836                                        num_bytes, parent);
1837                 ref.real_root = root->root_key.objectid;
1838                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1839                                     key.objectid, key.offset);
1840                 ret = btrfs_inc_extent_ref(trans, &ref);
1841                 if (ret) {
1842                         btrfs_abort_transaction(trans, ret);
1843                         break;
1844                 }
1845
1846                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, bytenr,
1847                                        num_bytes, parent);
1848                 ref.real_root = root->root_key.objectid;
1849                 btrfs_init_data_ref(&ref, btrfs_header_owner(leaf),
1850                                     key.objectid, key.offset);
1851                 ret = btrfs_free_extent(trans, &ref);
1852                 if (ret) {
1853                         btrfs_abort_transaction(trans, ret);
1854                         break;
1855                 }
1856         }
1857         if (dirty)
1858                 btrfs_mark_buffer_dirty(leaf);
1859         if (inode)
1860                 btrfs_add_delayed_iput(inode);
1861         return ret;
1862 }
1863
1864 static noinline_for_stack
1865 int memcmp_node_keys(struct extent_buffer *eb, int slot,
1866                      struct btrfs_path *path, int level)
1867 {
1868         struct btrfs_disk_key key1;
1869         struct btrfs_disk_key key2;
1870         btrfs_node_key(eb, &key1, slot);
1871         btrfs_node_key(path->nodes[level], &key2, path->slots[level]);
1872         return memcmp(&key1, &key2, sizeof(key1));
1873 }
1874
1875 /*
1876  * try to replace tree blocks in fs tree with the new blocks
1877  * in reloc tree. tree blocks haven't been modified since the
1878  * reloc tree was create can be replaced.
1879  *
1880  * if a block was replaced, level of the block + 1 is returned.
1881  * if no block got replaced, 0 is returned. if there are other
1882  * errors, a negative error number is returned.
1883  */
1884 static noinline_for_stack
1885 int replace_path(struct btrfs_trans_handle *trans, struct reloc_control *rc,
1886                  struct btrfs_root *dest, struct btrfs_root *src,
1887                  struct btrfs_path *path, struct btrfs_key *next_key,
1888                  int lowest_level, int max_level)
1889 {
1890         struct btrfs_fs_info *fs_info = dest->fs_info;
1891         struct extent_buffer *eb;
1892         struct extent_buffer *parent;
1893         struct btrfs_ref ref = { 0 };
1894         struct btrfs_key key;
1895         u64 old_bytenr;
1896         u64 new_bytenr;
1897         u64 old_ptr_gen;
1898         u64 new_ptr_gen;
1899         u64 last_snapshot;
1900         u32 blocksize;
1901         int cow = 0;
1902         int level;
1903         int ret;
1904         int slot;
1905
1906         BUG_ON(src->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
1907         BUG_ON(dest->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID);
1908
1909         last_snapshot = btrfs_root_last_snapshot(&src->root_item);
1910 again:
1911         slot = path->slots[lowest_level];
1912         btrfs_node_key_to_cpu(path->nodes[lowest_level], &key, slot);
1913
1914         eb = btrfs_lock_root_node(dest);
1915         btrfs_set_lock_blocking_write(eb);
1916         level = btrfs_header_level(eb);
1917
1918         if (level < lowest_level) {
1919                 btrfs_tree_unlock(eb);
1920                 free_extent_buffer(eb);
1921                 return 0;
1922         }
1923
1924         if (cow) {
1925                 ret = btrfs_cow_block(trans, dest, eb, NULL, 0, &eb);
1926                 BUG_ON(ret);
1927         }
1928         btrfs_set_lock_blocking_write(eb);
1929
1930         if (next_key) {
1931                 next_key->objectid = (u64)-1;
1932                 next_key->type = (u8)-1;
1933                 next_key->offset = (u64)-1;
1934         }
1935
1936         parent = eb;
1937         while (1) {
1938                 struct btrfs_key first_key;
1939
1940                 level = btrfs_header_level(parent);
1941                 BUG_ON(level < lowest_level);
1942
1943                 ret = btrfs_bin_search(parent, &key, level, &slot);
1944                 if (ret < 0)
1945                         break;
1946                 if (ret && slot > 0)
1947                         slot--;
1948
1949                 if (next_key && slot + 1 < btrfs_header_nritems(parent))
1950                         btrfs_node_key_to_cpu(parent, next_key, slot + 1);
1951
1952                 old_bytenr = btrfs_node_blockptr(parent, slot);
1953                 blocksize = fs_info->nodesize;
1954                 old_ptr_gen = btrfs_node_ptr_generation(parent, slot);
1955                 btrfs_node_key_to_cpu(parent, &first_key, slot);
1956
1957                 if (level <= max_level) {
1958                         eb = path->nodes[level];
1959                         new_bytenr = btrfs_node_blockptr(eb,
1960                                                         path->slots[level]);
1961                         new_ptr_gen = btrfs_node_ptr_generation(eb,
1962                                                         path->slots[level]);
1963                 } else {
1964                         new_bytenr = 0;
1965                         new_ptr_gen = 0;
1966                 }
1967
1968                 if (WARN_ON(new_bytenr > 0 && new_bytenr == old_bytenr)) {
1969                         ret = level;
1970                         break;
1971                 }
1972
1973                 if (new_bytenr == 0 || old_ptr_gen > last_snapshot ||
1974                     memcmp_node_keys(parent, slot, path, level)) {
1975                         if (level <= lowest_level) {
1976                                 ret = 0;
1977                                 break;
1978                         }
1979
1980                         eb = read_tree_block(fs_info, old_bytenr, old_ptr_gen,
1981                                              level - 1, &first_key);
1982                         if (IS_ERR(eb)) {
1983                                 ret = PTR_ERR(eb);
1984                                 break;
1985                         } else if (!extent_buffer_uptodate(eb)) {
1986                                 ret = -EIO;
1987                                 free_extent_buffer(eb);
1988                                 break;
1989                         }
1990                         btrfs_tree_lock(eb);
1991                         if (cow) {
1992                                 ret = btrfs_cow_block(trans, dest, eb, parent,
1993                                                       slot, &eb);
1994                                 BUG_ON(ret);
1995                         }
1996                         btrfs_set_lock_blocking_write(eb);
1997
1998                         btrfs_tree_unlock(parent);
1999                         free_extent_buffer(parent);
2000
2001                         parent = eb;
2002                         continue;
2003                 }
2004
2005                 if (!cow) {
2006                         btrfs_tree_unlock(parent);
2007                         free_extent_buffer(parent);
2008                         cow = 1;
2009                         goto again;
2010                 }
2011
2012                 btrfs_node_key_to_cpu(path->nodes[level], &key,
2013                                       path->slots[level]);
2014                 btrfs_release_path(path);
2015
2016                 path->lowest_level = level;
2017                 ret = btrfs_search_slot(trans, src, &key, path, 0, 1);
2018                 path->lowest_level = 0;
2019                 BUG_ON(ret);
2020
2021                 /*
2022                  * Info qgroup to trace both subtrees.
2023                  *
2024                  * We must trace both trees.
2025                  * 1) Tree reloc subtree
2026                  *    If not traced, we will leak data numbers
2027                  * 2) Fs subtree
2028                  *    If not traced, we will double count old data
2029                  *
2030                  * We don't scan the subtree right now, but only record
2031                  * the swapped tree blocks.
2032                  * The real subtree rescan is delayed until we have new
2033                  * CoW on the subtree root node before transaction commit.
2034                  */
2035                 ret = btrfs_qgroup_add_swapped_blocks(trans, dest,
2036                                 rc->block_group, parent, slot,
2037                                 path->nodes[level], path->slots[level],
2038                                 last_snapshot);
2039                 if (ret < 0)
2040                         break;
2041                 /*
2042                  * swap blocks in fs tree and reloc tree.
2043                  */
2044                 btrfs_set_node_blockptr(parent, slot, new_bytenr);
2045                 btrfs_set_node_ptr_generation(parent, slot, new_ptr_gen);
2046                 btrfs_mark_buffer_dirty(parent);
2047
2048                 btrfs_set_node_blockptr(path->nodes[level],
2049                                         path->slots[level], old_bytenr);
2050                 btrfs_set_node_ptr_generation(path->nodes[level],
2051                                               path->slots[level], old_ptr_gen);
2052                 btrfs_mark_buffer_dirty(path->nodes[level]);
2053
2054                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, old_bytenr,
2055                                        blocksize, path->nodes[level]->start);
2056                 ref.skip_qgroup = true;
2057                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
2058                 ret = btrfs_inc_extent_ref(trans, &ref);
2059                 BUG_ON(ret);
2060                 btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF, new_bytenr,
2061                                        blocksize, 0);
2062                 ref.skip_qgroup = true;
2063                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
2064                 ret = btrfs_inc_extent_ref(trans, &ref);
2065                 BUG_ON(ret);
2066
2067                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, new_bytenr,
2068                                        blocksize, path->nodes[level]->start);
2069                 btrfs_init_tree_ref(&ref, level - 1, src->root_key.objectid);
2070                 ref.skip_qgroup = true;
2071                 ret = btrfs_free_extent(trans, &ref);
2072                 BUG_ON(ret);
2073
2074                 btrfs_init_generic_ref(&ref, BTRFS_DROP_DELAYED_REF, old_bytenr,
2075                                        blocksize, 0);
2076                 btrfs_init_tree_ref(&ref, level - 1, dest->root_key.objectid);
2077                 ref.skip_qgroup = true;
2078                 ret = btrfs_free_extent(trans, &ref);
2079                 BUG_ON(ret);
2080
2081                 btrfs_unlock_up_safe(path, 0);
2082
2083                 ret = level;
2084                 break;
2085         }
2086         btrfs_tree_unlock(parent);
2087         free_extent_buffer(parent);
2088         return ret;
2089 }
2090
2091 /*
2092  * helper to find next relocated block in reloc tree
2093  */
2094 static noinline_for_stack
2095 int walk_up_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2096                        int *level)
2097 {
2098         struct extent_buffer *eb;
2099         int i;
2100         u64 last_snapshot;
2101         u32 nritems;
2102
2103         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2104
2105         for (i = 0; i < *level; i++) {
2106                 free_extent_buffer(path->nodes[i]);
2107                 path->nodes[i] = NULL;
2108         }
2109
2110         for (i = *level; i < BTRFS_MAX_LEVEL && path->nodes[i]; i++) {
2111                 eb = path->nodes[i];
2112                 nritems = btrfs_header_nritems(eb);
2113                 while (path->slots[i] + 1 < nritems) {
2114                         path->slots[i]++;
2115                         if (btrfs_node_ptr_generation(eb, path->slots[i]) <=
2116                             last_snapshot)
2117                                 continue;
2118
2119                         *level = i;
2120                         return 0;
2121                 }
2122                 free_extent_buffer(path->nodes[i]);
2123                 path->nodes[i] = NULL;
2124         }
2125         return 1;
2126 }
2127
2128 /*
2129  * walk down reloc tree to find relocated block of lowest level
2130  */
2131 static noinline_for_stack
2132 int walk_down_reloc_tree(struct btrfs_root *root, struct btrfs_path *path,
2133                          int *level)
2134 {
2135         struct btrfs_fs_info *fs_info = root->fs_info;
2136         struct extent_buffer *eb = NULL;
2137         int i;
2138         u64 bytenr;
2139         u64 ptr_gen = 0;
2140         u64 last_snapshot;
2141         u32 nritems;
2142
2143         last_snapshot = btrfs_root_last_snapshot(&root->root_item);
2144
2145         for (i = *level; i > 0; i--) {
2146                 struct btrfs_key first_key;
2147
2148                 eb = path->nodes[i];
2149                 nritems = btrfs_header_nritems(eb);
2150                 while (path->slots[i] < nritems) {
2151                         ptr_gen = btrfs_node_ptr_generation(eb, path->slots[i]);
2152                         if (ptr_gen > last_snapshot)
2153                                 break;
2154                         path->slots[i]++;
2155                 }
2156                 if (path->slots[i] >= nritems) {
2157                         if (i == *level)
2158                                 break;
2159                         *level = i + 1;
2160                         return 0;
2161                 }
2162                 if (i == 1) {
2163                         *level = i;
2164                         return 0;
2165                 }
2166
2167                 bytenr = btrfs_node_blockptr(eb, path->slots[i]);
2168                 btrfs_node_key_to_cpu(eb, &first_key, path->slots[i]);
2169                 eb = read_tree_block(fs_info, bytenr, ptr_gen, i - 1,
2170                                      &first_key);
2171                 if (IS_ERR(eb)) {
2172                         return PTR_ERR(eb);
2173                 } else if (!extent_buffer_uptodate(eb)) {
2174                         free_extent_buffer(eb);
2175                         return -EIO;
2176                 }
2177                 BUG_ON(btrfs_header_level(eb) != i - 1);
2178                 path->nodes[i - 1] = eb;
2179                 path->slots[i - 1] = 0;
2180         }
2181         return 1;
2182 }
2183
2184 /*
2185  * invalidate extent cache for file extents whose key in range of
2186  * [min_key, max_key)
2187  */
2188 static int invalidate_extent_cache(struct btrfs_root *root,
2189                                    struct btrfs_key *min_key,
2190                                    struct btrfs_key *max_key)
2191 {
2192         struct btrfs_fs_info *fs_info = root->fs_info;
2193         struct inode *inode = NULL;
2194         u64 objectid;
2195         u64 start, end;
2196         u64 ino;
2197
2198         objectid = min_key->objectid;
2199         while (1) {
2200                 cond_resched();
2201                 iput(inode);
2202
2203                 if (objectid > max_key->objectid)
2204                         break;
2205
2206                 inode = find_next_inode(root, objectid);
2207                 if (!inode)
2208                         break;
2209                 ino = btrfs_ino(BTRFS_I(inode));
2210
2211                 if (ino > max_key->objectid) {
2212                         iput(inode);
2213                         break;
2214                 }
2215
2216                 objectid = ino + 1;
2217                 if (!S_ISREG(inode->i_mode))
2218                         continue;
2219
2220                 if (unlikely(min_key->objectid == ino)) {
2221                         if (min_key->type > BTRFS_EXTENT_DATA_KEY)
2222                                 continue;
2223                         if (min_key->type < BTRFS_EXTENT_DATA_KEY)
2224                                 start = 0;
2225                         else {
2226                                 start = min_key->offset;
2227                                 WARN_ON(!IS_ALIGNED(start, fs_info->sectorsize));
2228                         }
2229                 } else {
2230                         start = 0;
2231                 }
2232
2233                 if (unlikely(max_key->objectid == ino)) {
2234                         if (max_key->type < BTRFS_EXTENT_DATA_KEY)
2235                                 continue;
2236                         if (max_key->type > BTRFS_EXTENT_DATA_KEY) {
2237                                 end = (u64)-1;
2238                         } else {
2239                                 if (max_key->offset == 0)
2240                                         continue;
2241                                 end = max_key->offset;
2242                                 WARN_ON(!IS_ALIGNED(end, fs_info->sectorsize));
2243                                 end--;
2244                         }
2245                 } else {
2246                         end = (u64)-1;
2247                 }
2248
2249                 /* the lock_extent waits for readpage to complete */
2250                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
2251                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 1);
2252                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
2253         }
2254         return 0;
2255 }
2256
2257 static int find_next_key(struct btrfs_path *path, int level,
2258                          struct btrfs_key *key)
2259
2260 {
2261         while (level < BTRFS_MAX_LEVEL) {
2262                 if (!path->nodes[level])
2263                         break;
2264                 if (path->slots[level] + 1 <
2265                     btrfs_header_nritems(path->nodes[level])) {
2266                         btrfs_node_key_to_cpu(path->nodes[level], key,
2267                                               path->slots[level] + 1);
2268                         return 0;
2269                 }
2270                 level++;
2271         }
2272         return 1;
2273 }
2274
2275 /*
2276  * Insert current subvolume into reloc_control::dirty_subvol_roots
2277  */
2278 static void insert_dirty_subvol(struct btrfs_trans_handle *trans,
2279                                 struct reloc_control *rc,
2280                                 struct btrfs_root *root)
2281 {
2282         struct btrfs_root *reloc_root = root->reloc_root;
2283         struct btrfs_root_item *reloc_root_item;
2284
2285         /* @root must be a subvolume tree root with a valid reloc tree */
2286         ASSERT(root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID);
2287         ASSERT(reloc_root);
2288
2289         reloc_root_item = &reloc_root->root_item;
2290         memset(&reloc_root_item->drop_progress, 0,
2291                 sizeof(reloc_root_item->drop_progress));
2292         reloc_root_item->drop_level = 0;
2293         btrfs_set_root_refs(reloc_root_item, 0);
2294         btrfs_update_reloc_root(trans, root);
2295
2296         if (list_empty(&root->reloc_dirty_list)) {
2297                 btrfs_grab_root(root);
2298                 list_add_tail(&root->reloc_dirty_list, &rc->dirty_subvol_roots);
2299         }
2300 }
2301
2302 static int clean_dirty_subvols(struct reloc_control *rc)
2303 {
2304         struct btrfs_root *root;
2305         struct btrfs_root *next;
2306         int ret = 0;
2307         int ret2;
2308
2309         list_for_each_entry_safe(root, next, &rc->dirty_subvol_roots,
2310                                  reloc_dirty_list) {
2311                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID) {
2312                         /* Merged subvolume, cleanup its reloc root */
2313                         struct btrfs_root *reloc_root = root->reloc_root;
2314
2315                         list_del_init(&root->reloc_dirty_list);
2316                         root->reloc_root = NULL;
2317                         /*
2318                          * Need barrier to ensure clear_bit() only happens after
2319                          * root->reloc_root = NULL. Pairs with have_reloc_root.
2320                          */
2321                         smp_wmb();
2322                         clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
2323                         if (reloc_root) {
2324                                 /*
2325                                  * btrfs_drop_snapshot drops our ref we hold for
2326                                  * ->reloc_root.  If it fails however we must
2327                                  * drop the ref ourselves.
2328                                  */
2329                                 ret2 = btrfs_drop_snapshot(reloc_root, 0, 1);
2330                                 if (ret2 < 0) {
2331                                         btrfs_put_root(reloc_root);
2332                                         if (!ret)
2333                                                 ret = ret2;
2334                                 }
2335                         }
2336                         btrfs_put_root(root);
2337                 } else {
2338                         /* Orphan reloc tree, just clean it up */
2339                         ret2 = btrfs_drop_snapshot(root, 0, 1);
2340                         if (ret2 < 0) {
2341                                 btrfs_put_root(root);
2342                                 if (!ret)
2343                                         ret = ret2;
2344                         }
2345                 }
2346         }
2347         return ret;
2348 }
2349
2350 /*
2351  * merge the relocated tree blocks in reloc tree with corresponding
2352  * fs tree.
2353  */
2354 static noinline_for_stack int merge_reloc_root(struct reloc_control *rc,
2355                                                struct btrfs_root *root)
2356 {
2357         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2358         struct btrfs_key key;
2359         struct btrfs_key next_key;
2360         struct btrfs_trans_handle *trans = NULL;
2361         struct btrfs_root *reloc_root;
2362         struct btrfs_root_item *root_item;
2363         struct btrfs_path *path;
2364         struct extent_buffer *leaf;
2365         int level;
2366         int max_level;
2367         int replaced = 0;
2368         int ret;
2369         int err = 0;
2370         u32 min_reserved;
2371
2372         path = btrfs_alloc_path();
2373         if (!path)
2374                 return -ENOMEM;
2375         path->reada = READA_FORWARD;
2376
2377         reloc_root = root->reloc_root;
2378         root_item = &reloc_root->root_item;
2379
2380         if (btrfs_disk_key_objectid(&root_item->drop_progress) == 0) {
2381                 level = btrfs_root_level(root_item);
2382                 atomic_inc(&reloc_root->node->refs);
2383                 path->nodes[level] = reloc_root->node;
2384                 path->slots[level] = 0;
2385         } else {
2386                 btrfs_disk_key_to_cpu(&key, &root_item->drop_progress);
2387
2388                 level = root_item->drop_level;
2389                 BUG_ON(level == 0);
2390                 path->lowest_level = level;
2391                 ret = btrfs_search_slot(NULL, reloc_root, &key, path, 0, 0);
2392                 path->lowest_level = 0;
2393                 if (ret < 0) {
2394                         btrfs_free_path(path);
2395                         return ret;
2396                 }
2397
2398                 btrfs_node_key_to_cpu(path->nodes[level], &next_key,
2399                                       path->slots[level]);
2400                 WARN_ON(memcmp(&key, &next_key, sizeof(key)));
2401
2402                 btrfs_unlock_up_safe(path, 0);
2403         }
2404
2405         min_reserved = fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2406         memset(&next_key, 0, sizeof(next_key));
2407
2408         while (1) {
2409                 ret = btrfs_block_rsv_refill(root, rc->block_rsv, min_reserved,
2410                                              BTRFS_RESERVE_FLUSH_ALL);
2411                 if (ret) {
2412                         err = ret;
2413                         goto out;
2414                 }
2415                 trans = btrfs_start_transaction(root, 0);
2416                 if (IS_ERR(trans)) {
2417                         err = PTR_ERR(trans);
2418                         trans = NULL;
2419                         goto out;
2420                 }
2421
2422                 /*
2423                  * At this point we no longer have a reloc_control, so we can't
2424                  * depend on btrfs_init_reloc_root to update our last_trans.
2425                  *
2426                  * But that's ok, we started the trans handle on our
2427                  * corresponding fs_root, which means it's been added to the
2428                  * dirty list.  At commit time we'll still call
2429                  * btrfs_update_reloc_root() and update our root item
2430                  * appropriately.
2431                  */
2432                 reloc_root->last_trans = trans->transid;
2433                 trans->block_rsv = rc->block_rsv;
2434
2435                 replaced = 0;
2436                 max_level = level;
2437
2438                 ret = walk_down_reloc_tree(reloc_root, path, &level);
2439                 if (ret < 0) {
2440                         err = ret;
2441                         goto out;
2442                 }
2443                 if (ret > 0)
2444                         break;
2445
2446                 if (!find_next_key(path, level, &key) &&
2447                     btrfs_comp_cpu_keys(&next_key, &key) >= 0) {
2448                         ret = 0;
2449                 } else {
2450                         ret = replace_path(trans, rc, root, reloc_root, path,
2451                                            &next_key, level, max_level);
2452                 }
2453                 if (ret < 0) {
2454                         err = ret;
2455                         goto out;
2456                 }
2457
2458                 if (ret > 0) {
2459                         level = ret;
2460                         btrfs_node_key_to_cpu(path->nodes[level], &key,
2461                                               path->slots[level]);
2462                         replaced = 1;
2463                 }
2464
2465                 ret = walk_up_reloc_tree(reloc_root, path, &level);
2466                 if (ret > 0)
2467                         break;
2468
2469                 BUG_ON(level == 0);
2470                 /*
2471                  * save the merging progress in the drop_progress.
2472                  * this is OK since root refs == 1 in this case.
2473                  */
2474                 btrfs_node_key(path->nodes[level], &root_item->drop_progress,
2475                                path->slots[level]);
2476                 root_item->drop_level = level;
2477
2478                 btrfs_end_transaction_throttle(trans);
2479                 trans = NULL;
2480
2481                 btrfs_btree_balance_dirty(fs_info);
2482
2483                 if (replaced && rc->stage == UPDATE_DATA_PTRS)
2484                         invalidate_extent_cache(root, &key, &next_key);
2485         }
2486
2487         /*
2488          * handle the case only one block in the fs tree need to be
2489          * relocated and the block is tree root.
2490          */
2491         leaf = btrfs_lock_root_node(root);
2492         ret = btrfs_cow_block(trans, root, leaf, NULL, 0, &leaf);
2493         btrfs_tree_unlock(leaf);
2494         free_extent_buffer(leaf);
2495         if (ret < 0)
2496                 err = ret;
2497 out:
2498         btrfs_free_path(path);
2499
2500         if (err == 0)
2501                 insert_dirty_subvol(trans, rc, root);
2502
2503         if (trans)
2504                 btrfs_end_transaction_throttle(trans);
2505
2506         btrfs_btree_balance_dirty(fs_info);
2507
2508         if (replaced && rc->stage == UPDATE_DATA_PTRS)
2509                 invalidate_extent_cache(root, &key, &next_key);
2510
2511         return err;
2512 }
2513
2514 static noinline_for_stack
2515 int prepare_to_merge(struct reloc_control *rc, int err)
2516 {
2517         struct btrfs_root *root = rc->extent_root;
2518         struct btrfs_fs_info *fs_info = root->fs_info;
2519         struct btrfs_root *reloc_root;
2520         struct btrfs_trans_handle *trans;
2521         LIST_HEAD(reloc_roots);
2522         u64 num_bytes = 0;
2523         int ret;
2524
2525         mutex_lock(&fs_info->reloc_mutex);
2526         rc->merging_rsv_size += fs_info->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
2527         rc->merging_rsv_size += rc->nodes_relocated * 2;
2528         mutex_unlock(&fs_info->reloc_mutex);
2529
2530 again:
2531         if (!err) {
2532                 num_bytes = rc->merging_rsv_size;
2533                 ret = btrfs_block_rsv_add(root, rc->block_rsv, num_bytes,
2534                                           BTRFS_RESERVE_FLUSH_ALL);
2535                 if (ret)
2536                         err = ret;
2537         }
2538
2539         trans = btrfs_join_transaction(rc->extent_root);
2540         if (IS_ERR(trans)) {
2541                 if (!err)
2542                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2543                                                 num_bytes, NULL);
2544                 return PTR_ERR(trans);
2545         }
2546
2547         if (!err) {
2548                 if (num_bytes != rc->merging_rsv_size) {
2549                         btrfs_end_transaction(trans);
2550                         btrfs_block_rsv_release(fs_info, rc->block_rsv,
2551                                                 num_bytes, NULL);
2552                         goto again;
2553                 }
2554         }
2555
2556         rc->merge_reloc_tree = 1;
2557
2558         while (!list_empty(&rc->reloc_roots)) {
2559                 reloc_root = list_entry(rc->reloc_roots.next,
2560                                         struct btrfs_root, root_list);
2561                 list_del_init(&reloc_root->root_list);
2562
2563                 root = read_fs_root(fs_info, reloc_root->root_key.offset);
2564                 BUG_ON(IS_ERR(root));
2565                 BUG_ON(root->reloc_root != reloc_root);
2566
2567                 /*
2568                  * set reference count to 1, so btrfs_recover_relocation
2569                  * knows it should resumes merging
2570                  */
2571                 if (!err)
2572                         btrfs_set_root_refs(&reloc_root->root_item, 1);
2573                 btrfs_update_reloc_root(trans, root);
2574
2575                 list_add(&reloc_root->root_list, &reloc_roots);
2576                 btrfs_put_root(root);
2577         }
2578
2579         list_splice(&reloc_roots, &rc->reloc_roots);
2580
2581         if (!err)
2582                 btrfs_commit_transaction(trans);
2583         else
2584                 btrfs_end_transaction(trans);
2585         return err;
2586 }
2587
2588 static noinline_for_stack
2589 void free_reloc_roots(struct list_head *list)
2590 {
2591         struct btrfs_root *reloc_root;
2592
2593         while (!list_empty(list)) {
2594                 reloc_root = list_entry(list->next, struct btrfs_root,
2595                                         root_list);
2596                 __del_reloc_root(reloc_root);
2597         }
2598 }
2599
2600 static noinline_for_stack
2601 void merge_reloc_roots(struct reloc_control *rc)
2602 {
2603         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2604         struct btrfs_root *root;
2605         struct btrfs_root *reloc_root;
2606         LIST_HEAD(reloc_roots);
2607         int found = 0;
2608         int ret = 0;
2609 again:
2610         root = rc->extent_root;
2611
2612         /*
2613          * this serializes us with btrfs_record_root_in_transaction,
2614          * we have to make sure nobody is in the middle of
2615          * adding their roots to the list while we are
2616          * doing this splice
2617          */
2618         mutex_lock(&fs_info->reloc_mutex);
2619         list_splice_init(&rc->reloc_roots, &reloc_roots);
2620         mutex_unlock(&fs_info->reloc_mutex);
2621
2622         while (!list_empty(&reloc_roots)) {
2623                 found = 1;
2624                 reloc_root = list_entry(reloc_roots.next,
2625                                         struct btrfs_root, root_list);
2626
2627                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
2628                         root = read_fs_root(fs_info,
2629                                             reloc_root->root_key.offset);
2630                         BUG_ON(IS_ERR(root));
2631                         BUG_ON(root->reloc_root != reloc_root);
2632
2633                         ret = merge_reloc_root(rc, root);
2634                         btrfs_put_root(root);
2635                         if (ret) {
2636                                 if (list_empty(&reloc_root->root_list))
2637                                         list_add_tail(&reloc_root->root_list,
2638                                                       &reloc_roots);
2639                                 goto out;
2640                         }
2641                 } else {
2642                         list_del_init(&reloc_root->root_list);
2643                         /* Don't forget to queue this reloc root for cleanup */
2644                         list_add_tail(&reloc_root->reloc_dirty_list,
2645                                       &rc->dirty_subvol_roots);
2646                 }
2647         }
2648
2649         if (found) {
2650                 found = 0;
2651                 goto again;
2652         }
2653 out:
2654         if (ret) {
2655                 btrfs_handle_fs_error(fs_info, ret, NULL);
2656                 if (!list_empty(&reloc_roots))
2657                         free_reloc_roots(&reloc_roots);
2658
2659                 /* new reloc root may be added */
2660                 mutex_lock(&fs_info->reloc_mutex);
2661                 list_splice_init(&rc->reloc_roots, &reloc_roots);
2662                 mutex_unlock(&fs_info->reloc_mutex);
2663                 if (!list_empty(&reloc_roots))
2664                         free_reloc_roots(&reloc_roots);
2665         }
2666
2667         /*
2668          * We used to have
2669          *
2670          * BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
2671          *
2672          * here, but it's wrong.  If we fail to start the transaction in
2673          * prepare_to_merge() we will have only 0 ref reloc roots, none of which
2674          * have actually been removed from the reloc_root_tree rb tree.  This is
2675          * fine because we're bailing here, and we hold a reference on the root
2676          * for the list that holds it, so these roots will be cleaned up when we
2677          * do the reloc_dirty_list afterwards.  Meanwhile the root->reloc_root
2678          * will be cleaned up on unmount.
2679          *
2680          * The remaining nodes will be cleaned up by free_reloc_control.
2681          */
2682 }
2683
2684 static void free_block_list(struct rb_root *blocks)
2685 {
2686         struct tree_block *block;
2687         struct rb_node *rb_node;
2688         while ((rb_node = rb_first(blocks))) {
2689                 block = rb_entry(rb_node, struct tree_block, rb_node);
2690                 rb_erase(rb_node, blocks);
2691                 kfree(block);
2692         }
2693 }
2694
2695 static int record_reloc_root_in_trans(struct btrfs_trans_handle *trans,
2696                                       struct btrfs_root *reloc_root)
2697 {
2698         struct btrfs_fs_info *fs_info = reloc_root->fs_info;
2699         struct btrfs_root *root;
2700         int ret;
2701
2702         if (reloc_root->last_trans == trans->transid)
2703                 return 0;
2704
2705         root = read_fs_root(fs_info, reloc_root->root_key.offset);
2706         BUG_ON(IS_ERR(root));
2707         BUG_ON(root->reloc_root != reloc_root);
2708         ret = btrfs_record_root_in_trans(trans, root);
2709         btrfs_put_root(root);
2710
2711         return ret;
2712 }
2713
2714 static noinline_for_stack
2715 struct btrfs_root *select_reloc_root(struct btrfs_trans_handle *trans,
2716                                      struct reloc_control *rc,
2717                                      struct backref_node *node,
2718                                      struct backref_edge *edges[])
2719 {
2720         struct backref_node *next;
2721         struct btrfs_root *root;
2722         int index = 0;
2723
2724         next = node;
2725         while (1) {
2726                 cond_resched();
2727                 next = walk_up_backref(next, edges, &index);
2728                 root = next->root;
2729                 BUG_ON(!root);
2730                 BUG_ON(!test_bit(BTRFS_ROOT_REF_COWS, &root->state));
2731
2732                 if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) {
2733                         record_reloc_root_in_trans(trans, root);
2734                         break;
2735                 }
2736
2737                 btrfs_record_root_in_trans(trans, root);
2738                 root = root->reloc_root;
2739
2740                 if (next->new_bytenr != root->node->start) {
2741                         BUG_ON(next->new_bytenr);
2742                         BUG_ON(!list_empty(&next->list));
2743                         next->new_bytenr = root->node->start;
2744                         btrfs_put_root(next->root);
2745                         next->root = btrfs_grab_root(root);
2746                         ASSERT(next->root);
2747                         list_add_tail(&next->list,
2748                                       &rc->backref_cache.changed);
2749                         __mark_block_processed(rc, next);
2750                         break;
2751                 }
2752
2753                 WARN_ON(1);
2754                 root = NULL;
2755                 next = walk_down_backref(edges, &index);
2756                 if (!next || next->level <= node->level)
2757                         break;
2758         }
2759         if (!root)
2760                 return NULL;
2761
2762         next = node;
2763         /* setup backref node path for btrfs_reloc_cow_block */
2764         while (1) {
2765                 rc->backref_cache.path[next->level] = next;
2766                 if (--index < 0)
2767                         break;
2768                 next = edges[index]->node[UPPER];
2769         }
2770         return root;
2771 }
2772
2773 /*
2774  * select a tree root for relocation. return NULL if the block
2775  * is reference counted. we should use do_relocation() in this
2776  * case. return a tree root pointer if the block isn't reference
2777  * counted. return -ENOENT if the block is root of reloc tree.
2778  */
2779 static noinline_for_stack
2780 struct btrfs_root *select_one_root(struct backref_node *node)
2781 {
2782         struct backref_node *next;
2783         struct btrfs_root *root;
2784         struct btrfs_root *fs_root = NULL;
2785         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2786         int index = 0;
2787
2788         next = node;
2789         while (1) {
2790                 cond_resched();
2791                 next = walk_up_backref(next, edges, &index);
2792                 root = next->root;
2793                 BUG_ON(!root);
2794
2795                 /* no other choice for non-references counted tree */
2796                 if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
2797                         return root;
2798
2799                 if (root->root_key.objectid != BTRFS_TREE_RELOC_OBJECTID)
2800                         fs_root = root;
2801
2802                 if (next != node)
2803                         return NULL;
2804
2805                 next = walk_down_backref(edges, &index);
2806                 if (!next || next->level <= node->level)
2807                         break;
2808         }
2809
2810         if (!fs_root)
2811                 return ERR_PTR(-ENOENT);
2812         return fs_root;
2813 }
2814
2815 static noinline_for_stack
2816 u64 calcu_metadata_size(struct reloc_control *rc,
2817                         struct backref_node *node, int reserve)
2818 {
2819         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2820         struct backref_node *next = node;
2821         struct backref_edge *edge;
2822         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2823         u64 num_bytes = 0;
2824         int index = 0;
2825
2826         BUG_ON(reserve && node->processed);
2827
2828         while (next) {
2829                 cond_resched();
2830                 while (1) {
2831                         if (next->processed && (reserve || next != node))
2832                                 break;
2833
2834                         num_bytes += fs_info->nodesize;
2835
2836                         if (list_empty(&next->upper))
2837                                 break;
2838
2839                         edge = list_entry(next->upper.next,
2840                                           struct backref_edge, list[LOWER]);
2841                         edges[index++] = edge;
2842                         next = edge->node[UPPER];
2843                 }
2844                 next = walk_down_backref(edges, &index);
2845         }
2846         return num_bytes;
2847 }
2848
2849 static int reserve_metadata_space(struct btrfs_trans_handle *trans,
2850                                   struct reloc_control *rc,
2851                                   struct backref_node *node)
2852 {
2853         struct btrfs_root *root = rc->extent_root;
2854         struct btrfs_fs_info *fs_info = root->fs_info;
2855         u64 num_bytes;
2856         int ret;
2857         u64 tmp;
2858
2859         num_bytes = calcu_metadata_size(rc, node, 1) * 2;
2860
2861         trans->block_rsv = rc->block_rsv;
2862         rc->reserved_bytes += num_bytes;
2863
2864         /*
2865          * We are under a transaction here so we can only do limited flushing.
2866          * If we get an enospc just kick back -EAGAIN so we know to drop the
2867          * transaction and try to refill when we can flush all the things.
2868          */
2869         ret = btrfs_block_rsv_refill(root, rc->block_rsv, num_bytes,
2870                                 BTRFS_RESERVE_FLUSH_LIMIT);
2871         if (ret) {
2872                 tmp = fs_info->nodesize * RELOCATION_RESERVED_NODES;
2873                 while (tmp <= rc->reserved_bytes)
2874                         tmp <<= 1;
2875                 /*
2876                  * only one thread can access block_rsv at this point,
2877                  * so we don't need hold lock to protect block_rsv.
2878                  * we expand more reservation size here to allow enough
2879                  * space for relocation and we will return earlier in
2880                  * enospc case.
2881                  */
2882                 rc->block_rsv->size = tmp + fs_info->nodesize *
2883                                       RELOCATION_RESERVED_NODES;
2884                 return -EAGAIN;
2885         }
2886
2887         return 0;
2888 }
2889
2890 /*
2891  * relocate a block tree, and then update pointers in upper level
2892  * blocks that reference the block to point to the new location.
2893  *
2894  * if called by link_to_upper, the block has already been relocated.
2895  * in that case this function just updates pointers.
2896  */
2897 static int do_relocation(struct btrfs_trans_handle *trans,
2898                          struct reloc_control *rc,
2899                          struct backref_node *node,
2900                          struct btrfs_key *key,
2901                          struct btrfs_path *path, int lowest)
2902 {
2903         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
2904         struct backref_node *upper;
2905         struct backref_edge *edge;
2906         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
2907         struct btrfs_root *root;
2908         struct extent_buffer *eb;
2909         u32 blocksize;
2910         u64 bytenr;
2911         u64 generation;
2912         int slot;
2913         int ret;
2914         int err = 0;
2915
2916         BUG_ON(lowest && node->eb);
2917
2918         path->lowest_level = node->level + 1;
2919         rc->backref_cache.path[node->level] = node;
2920         list_for_each_entry(edge, &node->upper, list[LOWER]) {
2921                 struct btrfs_key first_key;
2922                 struct btrfs_ref ref = { 0 };
2923
2924                 cond_resched();
2925
2926                 upper = edge->node[UPPER];
2927                 root = select_reloc_root(trans, rc, upper, edges);
2928                 BUG_ON(!root);
2929
2930                 if (upper->eb && !upper->locked) {
2931                         if (!lowest) {
2932                                 ret = btrfs_bin_search(upper->eb, key,
2933                                                        upper->level, &slot);
2934                                 if (ret < 0) {
2935                                         err = ret;
2936                                         goto next;
2937                                 }
2938                                 BUG_ON(ret);
2939                                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2940                                 if (node->eb->start == bytenr)
2941                                         goto next;
2942                         }
2943                         drop_node_buffer(upper);
2944                 }
2945
2946                 if (!upper->eb) {
2947                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
2948                         if (ret) {
2949                                 if (ret < 0)
2950                                         err = ret;
2951                                 else
2952                                         err = -ENOENT;
2953
2954                                 btrfs_release_path(path);
2955                                 break;
2956                         }
2957
2958                         if (!upper->eb) {
2959                                 upper->eb = path->nodes[upper->level];
2960                                 path->nodes[upper->level] = NULL;
2961                         } else {
2962                                 BUG_ON(upper->eb != path->nodes[upper->level]);
2963                         }
2964
2965                         upper->locked = 1;
2966                         path->locks[upper->level] = 0;
2967
2968                         slot = path->slots[upper->level];
2969                         btrfs_release_path(path);
2970                 } else {
2971                         ret = btrfs_bin_search(upper->eb, key, upper->level,
2972                                                &slot);
2973                         if (ret < 0) {
2974                                 err = ret;
2975                                 goto next;
2976                         }
2977                         BUG_ON(ret);
2978                 }
2979
2980                 bytenr = btrfs_node_blockptr(upper->eb, slot);
2981                 if (lowest) {
2982                         if (bytenr != node->bytenr) {
2983                                 btrfs_err(root->fs_info,
2984                 "lowest leaf/node mismatch: bytenr %llu node->bytenr %llu slot %d upper %llu",
2985                                           bytenr, node->bytenr, slot,
2986                                           upper->eb->start);
2987                                 err = -EIO;
2988                                 goto next;
2989                         }
2990                 } else {
2991                         if (node->eb->start == bytenr)
2992                                 goto next;
2993                 }
2994
2995                 blocksize = root->fs_info->nodesize;
2996                 generation = btrfs_node_ptr_generation(upper->eb, slot);
2997                 btrfs_node_key_to_cpu(upper->eb, &first_key, slot);
2998                 eb = read_tree_block(fs_info, bytenr, generation,
2999                                      upper->level - 1, &first_key);
3000                 if (IS_ERR(eb)) {
3001                         err = PTR_ERR(eb);
3002                         goto next;
3003                 } else if (!extent_buffer_uptodate(eb)) {
3004                         free_extent_buffer(eb);
3005                         err = -EIO;
3006                         goto next;
3007                 }
3008                 btrfs_tree_lock(eb);
3009                 btrfs_set_lock_blocking_write(eb);
3010
3011                 if (!node->eb) {
3012                         ret = btrfs_cow_block(trans, root, eb, upper->eb,
3013                                               slot, &eb);
3014                         btrfs_tree_unlock(eb);
3015                         free_extent_buffer(eb);
3016                         if (ret < 0) {
3017                                 err = ret;
3018                                 goto next;
3019                         }
3020                         BUG_ON(node->eb != eb);
3021                 } else {
3022                         btrfs_set_node_blockptr(upper->eb, slot,
3023                                                 node->eb->start);
3024                         btrfs_set_node_ptr_generation(upper->eb, slot,
3025                                                       trans->transid);
3026                         btrfs_mark_buffer_dirty(upper->eb);
3027
3028                         btrfs_init_generic_ref(&ref, BTRFS_ADD_DELAYED_REF,
3029                                                node->eb->start, blocksize,
3030                                                upper->eb->start);
3031                         ref.real_root = root->root_key.objectid;
3032                         btrfs_init_tree_ref(&ref, node->level,
3033                                             btrfs_header_owner(upper->eb));
3034                         ret = btrfs_inc_extent_ref(trans, &ref);
3035                         BUG_ON(ret);
3036
3037                         ret = btrfs_drop_subtree(trans, root, eb, upper->eb);
3038                         BUG_ON(ret);
3039                 }
3040 next:
3041                 if (!upper->pending)
3042                         drop_node_buffer(upper);
3043                 else
3044                         unlock_node_buffer(upper);
3045                 if (err)
3046                         break;
3047         }
3048
3049         if (!err && node->pending) {
3050                 drop_node_buffer(node);
3051                 list_move_tail(&node->list, &rc->backref_cache.changed);
3052                 node->pending = 0;
3053         }
3054
3055         path->lowest_level = 0;
3056         BUG_ON(err == -ENOSPC);
3057         return err;
3058 }
3059
3060 static int link_to_upper(struct btrfs_trans_handle *trans,
3061                          struct reloc_control *rc,
3062                          struct backref_node *node,
3063                          struct btrfs_path *path)
3064 {
3065         struct btrfs_key key;
3066
3067         btrfs_node_key_to_cpu(node->eb, &key, 0);
3068         return do_relocation(trans, rc, node, &key, path, 0);
3069 }
3070
3071 static int finish_pending_nodes(struct btrfs_trans_handle *trans,
3072                                 struct reloc_control *rc,
3073                                 struct btrfs_path *path, int err)
3074 {
3075         LIST_HEAD(list);
3076         struct backref_cache *cache = &rc->backref_cache;
3077         struct backref_node *node;
3078         int level;
3079         int ret;
3080
3081         for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
3082                 while (!list_empty(&cache->pending[level])) {
3083                         node = list_entry(cache->pending[level].next,
3084                                           struct backref_node, list);
3085                         list_move_tail(&node->list, &list);
3086                         BUG_ON(!node->pending);
3087
3088                         if (!err) {
3089                                 ret = link_to_upper(trans, rc, node, path);
3090                                 if (ret < 0)
3091                                         err = ret;
3092                         }
3093                 }
3094                 list_splice_init(&list, &cache->pending[level]);
3095         }
3096         return err;
3097 }
3098
3099 static void mark_block_processed(struct reloc_control *rc,
3100                                  u64 bytenr, u32 blocksize)
3101 {
3102         set_extent_bits(&rc->processed_blocks, bytenr, bytenr + blocksize - 1,
3103                         EXTENT_DIRTY);
3104 }
3105
3106 static void __mark_block_processed(struct reloc_control *rc,
3107                                    struct backref_node *node)
3108 {
3109         u32 blocksize;
3110         if (node->level == 0 ||
3111             in_block_group(node->bytenr, rc->block_group)) {
3112                 blocksize = rc->extent_root->fs_info->nodesize;
3113                 mark_block_processed(rc, node->bytenr, blocksize);
3114         }
3115         node->processed = 1;
3116 }
3117
3118 /*
3119  * mark a block and all blocks directly/indirectly reference the block
3120  * as processed.
3121  */
3122 static void update_processed_blocks(struct reloc_control *rc,
3123                                     struct backref_node *node)
3124 {
3125         struct backref_node *next = node;
3126         struct backref_edge *edge;
3127         struct backref_edge *edges[BTRFS_MAX_LEVEL - 1];
3128         int index = 0;
3129
3130         while (next) {
3131                 cond_resched();
3132                 while (1) {
3133                         if (next->processed)
3134                                 break;
3135
3136                         __mark_block_processed(rc, next);
3137
3138                         if (list_empty(&next->upper))
3139                                 break;
3140
3141                         edge = list_entry(next->upper.next,
3142                                           struct backref_edge, list[LOWER]);
3143                         edges[index++] = edge;
3144                         next = edge->node[UPPER];
3145                 }
3146                 next = walk_down_backref(edges, &index);
3147         }
3148 }
3149
3150 static int tree_block_processed(u64 bytenr, struct reloc_control *rc)
3151 {
3152         u32 blocksize = rc->extent_root->fs_info->nodesize;
3153
3154         if (test_range_bit(&rc->processed_blocks, bytenr,
3155                            bytenr + blocksize - 1, EXTENT_DIRTY, 1, NULL))
3156                 return 1;
3157         return 0;
3158 }
3159
3160 static int get_tree_block_key(struct btrfs_fs_info *fs_info,
3161                               struct tree_block *block)
3162 {
3163         struct extent_buffer *eb;
3164
3165         eb = read_tree_block(fs_info, block->bytenr, block->key.offset,
3166                              block->level, NULL);
3167         if (IS_ERR(eb)) {
3168                 return PTR_ERR(eb);
3169         } else if (!extent_buffer_uptodate(eb)) {
3170                 free_extent_buffer(eb);
3171                 return -EIO;
3172         }
3173         if (block->level == 0)
3174                 btrfs_item_key_to_cpu(eb, &block->key, 0);
3175         else
3176                 btrfs_node_key_to_cpu(eb, &block->key, 0);
3177         free_extent_buffer(eb);
3178         block->key_ready = 1;
3179         return 0;
3180 }
3181
3182 /*
3183  * helper function to relocate a tree block
3184  */
3185 static int relocate_tree_block(struct btrfs_trans_handle *trans,
3186                                 struct reloc_control *rc,
3187                                 struct backref_node *node,
3188                                 struct btrfs_key *key,
3189                                 struct btrfs_path *path)
3190 {
3191         struct btrfs_root *root;
3192         int ret = 0;
3193
3194         if (!node)
3195                 return 0;
3196
3197         /*
3198          * If we fail here we want to drop our backref_node because we are going
3199          * to start over and regenerate the tree for it.
3200          */
3201         ret = reserve_metadata_space(trans, rc, node);
3202         if (ret)
3203                 goto out;
3204
3205         BUG_ON(node->processed);
3206         root = select_one_root(node);
3207         if (root == ERR_PTR(-ENOENT)) {
3208                 update_processed_blocks(rc, node);
3209                 goto out;
3210         }
3211
3212         if (root) {
3213                 if (test_bit(BTRFS_ROOT_REF_COWS, &root->state)) {
3214                         BUG_ON(node->new_bytenr);
3215                         BUG_ON(!list_empty(&node->list));
3216                         btrfs_record_root_in_trans(trans, root);
3217                         root = root->reloc_root;
3218                         node->new_bytenr = root->node->start;
3219                         btrfs_put_root(node->root);
3220                         node->root = btrfs_grab_root(root);
3221                         ASSERT(node->root);
3222                         list_add_tail(&node->list, &rc->backref_cache.changed);
3223                 } else {
3224                         path->lowest_level = node->level;
3225                         ret = btrfs_search_slot(trans, root, key, path, 0, 1);
3226                         btrfs_release_path(path);
3227                         if (ret > 0)
3228                                 ret = 0;
3229                 }
3230                 if (!ret)
3231                         update_processed_blocks(rc, node);
3232         } else {
3233                 ret = do_relocation(trans, rc, node, key, path, 1);
3234         }
3235 out:
3236         if (ret || node->level == 0 || node->cowonly)
3237                 remove_backref_node(&rc->backref_cache, node);
3238         return ret;
3239 }
3240
3241 /*
3242  * relocate a list of blocks
3243  */
3244 static noinline_for_stack
3245 int relocate_tree_blocks(struct btrfs_trans_handle *trans,
3246                          struct reloc_control *rc, struct rb_root *blocks)
3247 {
3248         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3249         struct backref_node *node;
3250         struct btrfs_path *path;
3251         struct tree_block *block;
3252         struct tree_block *next;
3253         int ret;
3254         int err = 0;
3255
3256         path = btrfs_alloc_path();
3257         if (!path) {
3258                 err = -ENOMEM;
3259                 goto out_free_blocks;
3260         }
3261
3262         /* Kick in readahead for tree blocks with missing keys */
3263         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3264                 if (!block->key_ready)
3265                         readahead_tree_block(fs_info, block->bytenr);
3266         }
3267
3268         /* Get first keys */
3269         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3270                 if (!block->key_ready) {
3271                         err = get_tree_block_key(fs_info, block);
3272                         if (err)
3273                                 goto out_free_path;
3274                 }
3275         }
3276
3277         /* Do tree relocation */
3278         rbtree_postorder_for_each_entry_safe(block, next, blocks, rb_node) {
3279                 node = build_backref_tree(rc, &block->key,
3280                                           block->level, block->bytenr);
3281                 if (IS_ERR(node)) {
3282                         err = PTR_ERR(node);
3283                         goto out;
3284                 }
3285
3286                 ret = relocate_tree_block(trans, rc, node, &block->key,
3287                                           path);
3288                 if (ret < 0) {
3289                         err = ret;
3290                         break;
3291                 }
3292         }
3293 out:
3294         err = finish_pending_nodes(trans, rc, path, err);
3295
3296 out_free_path:
3297         btrfs_free_path(path);
3298 out_free_blocks:
3299         free_block_list(blocks);
3300         return err;
3301 }
3302
3303 static noinline_for_stack
3304 int prealloc_file_extent_cluster(struct inode *inode,
3305                                  struct file_extent_cluster *cluster)
3306 {
3307         u64 alloc_hint = 0;
3308         u64 start;
3309         u64 end;
3310         u64 offset = BTRFS_I(inode)->index_cnt;
3311         u64 num_bytes;
3312         int nr = 0;
3313         int ret = 0;
3314         u64 prealloc_start = cluster->start - offset;
3315         u64 prealloc_end = cluster->end - offset;
3316         u64 cur_offset;
3317         struct extent_changeset *data_reserved = NULL;
3318
3319         BUG_ON(cluster->start != cluster->boundary[0]);
3320         inode_lock(inode);
3321
3322         ret = btrfs_check_data_free_space(inode, &data_reserved, prealloc_start,
3323                                           prealloc_end + 1 - prealloc_start);
3324         if (ret)
3325                 goto out;
3326
3327         cur_offset = prealloc_start;
3328         while (nr < cluster->nr) {
3329                 start = cluster->boundary[nr] - offset;
3330                 if (nr + 1 < cluster->nr)
3331                         end = cluster->boundary[nr + 1] - 1 - offset;
3332                 else
3333                         end = cluster->end - offset;
3334
3335                 lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3336                 num_bytes = end + 1 - start;
3337                 if (cur_offset < start)
3338                         btrfs_free_reserved_data_space(inode, data_reserved,
3339                                         cur_offset, start - cur_offset);
3340                 ret = btrfs_prealloc_file_range(inode, 0, start,
3341                                                 num_bytes, num_bytes,
3342                                                 end + 1, &alloc_hint);
3343                 cur_offset = end + 1;
3344                 unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3345                 if (ret)
3346                         break;
3347                 nr++;
3348         }
3349         if (cur_offset < prealloc_end)
3350                 btrfs_free_reserved_data_space(inode, data_reserved,
3351                                 cur_offset, prealloc_end + 1 - cur_offset);
3352 out:
3353         inode_unlock(inode);
3354         extent_changeset_free(data_reserved);
3355         return ret;
3356 }
3357
3358 static noinline_for_stack
3359 int setup_extent_mapping(struct inode *inode, u64 start, u64 end,
3360                          u64 block_start)
3361 {
3362         struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
3363         struct extent_map *em;
3364         int ret = 0;
3365
3366         em = alloc_extent_map();
3367         if (!em)
3368                 return -ENOMEM;
3369
3370         em->start = start;
3371         em->len = end + 1 - start;
3372         em->block_len = em->len;
3373         em->block_start = block_start;
3374         set_bit(EXTENT_FLAG_PINNED, &em->flags);
3375
3376         lock_extent(&BTRFS_I(inode)->io_tree, start, end);
3377         while (1) {
3378                 write_lock(&em_tree->lock);
3379                 ret = add_extent_mapping(em_tree, em, 0);
3380                 write_unlock(&em_tree->lock);
3381                 if (ret != -EEXIST) {
3382                         free_extent_map(em);
3383                         break;
3384                 }
3385                 btrfs_drop_extent_cache(BTRFS_I(inode), start, end, 0);
3386         }
3387         unlock_extent(&BTRFS_I(inode)->io_tree, start, end);
3388         return ret;
3389 }
3390
3391 /*
3392  * Allow error injection to test balance cancellation
3393  */
3394 int btrfs_should_cancel_balance(struct btrfs_fs_info *fs_info)
3395 {
3396         return atomic_read(&fs_info->balance_cancel_req);
3397 }
3398 ALLOW_ERROR_INJECTION(btrfs_should_cancel_balance, TRUE);
3399
3400 static int relocate_file_extent_cluster(struct inode *inode,
3401                                         struct file_extent_cluster *cluster)
3402 {
3403         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
3404         u64 page_start;
3405         u64 page_end;
3406         u64 offset = BTRFS_I(inode)->index_cnt;
3407         unsigned long index;
3408         unsigned long last_index;
3409         struct page *page;
3410         struct file_ra_state *ra;
3411         gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
3412         int nr = 0;
3413         int ret = 0;
3414
3415         if (!cluster->nr)
3416                 return 0;
3417
3418         ra = kzalloc(sizeof(*ra), GFP_NOFS);
3419         if (!ra)
3420                 return -ENOMEM;
3421
3422         ret = prealloc_file_extent_cluster(inode, cluster);
3423         if (ret)
3424                 goto out;
3425
3426         file_ra_state_init(ra, inode->i_mapping);
3427
3428         ret = setup_extent_mapping(inode, cluster->start - offset,
3429                                    cluster->end - offset, cluster->start);
3430         if (ret)
3431                 goto out;
3432
3433         index = (cluster->start - offset) >> PAGE_SHIFT;
3434         last_index = (cluster->end - offset) >> PAGE_SHIFT;
3435         while (index <= last_index) {
3436                 ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
3437                                 PAGE_SIZE);
3438                 if (ret)
3439                         goto out;
3440
3441                 page = find_lock_page(inode->i_mapping, index);
3442                 if (!page) {
3443                         page_cache_sync_readahead(inode->i_mapping,
3444                                                   ra, NULL, index,
3445                                                   last_index + 1 - index);
3446                         page = find_or_create_page(inode->i_mapping, index,
3447                                                    mask);
3448                         if (!page) {
3449                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3450                                                         PAGE_SIZE, true);
3451                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3452                                                         PAGE_SIZE);
3453                                 ret = -ENOMEM;
3454                                 goto out;
3455                         }
3456                 }
3457
3458                 if (PageReadahead(page)) {
3459                         page_cache_async_readahead(inode->i_mapping,
3460                                                    ra, NULL, page, index,
3461                                                    last_index + 1 - index);
3462                 }
3463
3464                 if (!PageUptodate(page)) {
3465                         btrfs_readpage(NULL, page);
3466                         lock_page(page);
3467                         if (!PageUptodate(page)) {
3468                                 unlock_page(page);
3469                                 put_page(page);
3470                                 btrfs_delalloc_release_metadata(BTRFS_I(inode),
3471                                                         PAGE_SIZE, true);
3472                                 btrfs_delalloc_release_extents(BTRFS_I(inode),
3473                                                                PAGE_SIZE);
3474                                 ret = -EIO;
3475                                 goto out;
3476                         }
3477                 }
3478
3479                 page_start = page_offset(page);
3480                 page_end = page_start + PAGE_SIZE - 1;
3481
3482                 lock_extent(&BTRFS_I(inode)->io_tree, page_start, page_end);
3483
3484                 set_page_extent_mapped(page);
3485
3486                 if (nr < cluster->nr &&
3487                     page_start + offset == cluster->boundary[nr]) {
3488                         set_extent_bits(&BTRFS_I(inode)->io_tree,
3489                                         page_start, page_end,
3490                                         EXTENT_BOUNDARY);
3491                         nr++;
3492                 }
3493
3494                 ret = btrfs_set_extent_delalloc(inode, page_start, page_end, 0,
3495                                                 NULL);
3496                 if (ret) {
3497                         unlock_page(page);
3498                         put_page(page);
3499                         btrfs_delalloc_release_metadata(BTRFS_I(inode),
3500                                                          PAGE_SIZE, true);
3501                         btrfs_delalloc_release_extents(BTRFS_I(inode),
3502                                                        PAGE_SIZE);
3503
3504                         clear_extent_bits(&BTRFS_I(inode)->io_tree,
3505                                           page_start, page_end,
3506                                           EXTENT_LOCKED | EXTENT_BOUNDARY);
3507                         goto out;
3508
3509                 }
3510                 set_page_dirty(page);
3511
3512                 unlock_extent(&BTRFS_I(inode)->io_tree,
3513                               page_start, page_end);
3514                 unlock_page(page);
3515                 put_page(page);
3516
3517                 index++;
3518                 btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
3519                 balance_dirty_pages_ratelimited(inode->i_mapping);
3520                 btrfs_throttle(fs_info);
3521                 if (btrfs_should_cancel_balance(fs_info)) {
3522                         ret = -ECANCELED;
3523                         goto out;
3524                 }
3525         }
3526         WARN_ON(nr != cluster->nr);
3527 out:
3528         kfree(ra);
3529         return ret;
3530 }
3531
3532 static noinline_for_stack
3533 int relocate_data_extent(struct inode *inode, struct btrfs_key *extent_key,
3534                          struct file_extent_cluster *cluster)
3535 {
3536         int ret;
3537
3538         if (cluster->nr > 0 && extent_key->objectid != cluster->end + 1) {
3539                 ret = relocate_file_extent_cluster(inode, cluster);
3540                 if (ret)
3541                         return ret;
3542                 cluster->nr = 0;
3543         }
3544
3545         if (!cluster->nr)
3546                 cluster->start = extent_key->objectid;
3547         else
3548                 BUG_ON(cluster->nr >= MAX_EXTENTS);
3549         cluster->end = extent_key->objectid + extent_key->offset - 1;
3550         cluster->boundary[cluster->nr] = extent_key->objectid;
3551         cluster->nr++;
3552
3553         if (cluster->nr >= MAX_EXTENTS) {
3554                 ret = relocate_file_extent_cluster(inode, cluster);
3555                 if (ret)
3556                         return ret;
3557                 cluster->nr = 0;
3558         }
3559         return 0;
3560 }
3561
3562 /*
3563  * helper to add a tree block to the list.
3564  * the major work is getting the generation and level of the block
3565  */
3566 static int add_tree_block(struct reloc_control *rc,
3567                           struct btrfs_key *extent_key,
3568                           struct btrfs_path *path,
3569                           struct rb_root *blocks)
3570 {
3571         struct extent_buffer *eb;
3572         struct btrfs_extent_item *ei;
3573         struct btrfs_tree_block_info *bi;
3574         struct tree_block *block;
3575         struct rb_node *rb_node;
3576         u32 item_size;
3577         int level = -1;
3578         u64 generation;
3579
3580         eb =  path->nodes[0];
3581         item_size = btrfs_item_size_nr(eb, path->slots[0]);
3582
3583         if (extent_key->type == BTRFS_METADATA_ITEM_KEY ||
3584             item_size >= sizeof(*ei) + sizeof(*bi)) {
3585                 ei = btrfs_item_ptr(eb, path->slots[0],
3586                                 struct btrfs_extent_item);
3587                 if (extent_key->type == BTRFS_EXTENT_ITEM_KEY) {
3588                         bi = (struct btrfs_tree_block_info *)(ei + 1);
3589                         level = btrfs_tree_block_level(eb, bi);
3590                 } else {
3591                         level = (int)extent_key->offset;
3592                 }
3593                 generation = btrfs_extent_generation(eb, ei);
3594         } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
3595                 btrfs_print_v0_err(eb->fs_info);
3596                 btrfs_handle_fs_error(eb->fs_info, -EINVAL, NULL);
3597                 return -EINVAL;
3598         } else {
3599                 BUG();
3600         }
3601
3602         btrfs_release_path(path);
3603
3604         BUG_ON(level == -1);
3605
3606         block = kmalloc(sizeof(*block), GFP_NOFS);
3607         if (!block)
3608                 return -ENOMEM;
3609
3610         block->bytenr = extent_key->objectid;
3611         block->key.objectid = rc->extent_root->fs_info->nodesize;
3612         block->key.offset = generation;
3613         block->level = level;
3614         block->key_ready = 0;
3615
3616         rb_node = tree_insert(blocks, block->bytenr, &block->rb_node);
3617         if (rb_node)
3618                 backref_tree_panic(rb_node, -EEXIST, block->bytenr);
3619
3620         return 0;
3621 }
3622
3623 /*
3624  * helper to add tree blocks for backref of type BTRFS_SHARED_DATA_REF_KEY
3625  */
3626 static int __add_tree_block(struct reloc_control *rc,
3627                             u64 bytenr, u32 blocksize,
3628                             struct rb_root *blocks)
3629 {
3630         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3631         struct btrfs_path *path;
3632         struct btrfs_key key;
3633         int ret;
3634         bool skinny = btrfs_fs_incompat(fs_info, SKINNY_METADATA);
3635
3636         if (tree_block_processed(bytenr, rc))
3637                 return 0;
3638
3639         if (tree_search(blocks, bytenr))
3640                 return 0;
3641
3642         path = btrfs_alloc_path();
3643         if (!path)
3644                 return -ENOMEM;
3645 again:
3646         key.objectid = bytenr;
3647         if (skinny) {
3648                 key.type = BTRFS_METADATA_ITEM_KEY;
3649                 key.offset = (u64)-1;
3650         } else {
3651                 key.type = BTRFS_EXTENT_ITEM_KEY;
3652                 key.offset = blocksize;
3653         }
3654
3655         path->search_commit_root = 1;
3656         path->skip_locking = 1;
3657         ret = btrfs_search_slot(NULL, rc->extent_root, &key, path, 0, 0);
3658         if (ret < 0)
3659                 goto out;
3660
3661         if (ret > 0 && skinny) {
3662                 if (path->slots[0]) {
3663                         path->slots[0]--;
3664                         btrfs_item_key_to_cpu(path->nodes[0], &key,
3665                                               path->slots[0]);
3666                         if (key.objectid == bytenr &&
3667                             (key.type == BTRFS_METADATA_ITEM_KEY ||
3668                              (key.type == BTRFS_EXTENT_ITEM_KEY &&
3669                               key.offset == blocksize)))
3670                                 ret = 0;
3671                 }
3672
3673                 if (ret) {
3674                         skinny = false;
3675                         btrfs_release_path(path);
3676                         goto again;
3677                 }
3678         }
3679         if (ret) {
3680                 ASSERT(ret == 1);
3681                 btrfs_print_leaf(path->nodes[0]);
3682                 btrfs_err(fs_info,
3683              "tree block extent item (%llu) is not found in extent tree",
3684                      bytenr);
3685                 WARN_ON(1);
3686                 ret = -EINVAL;
3687                 goto out;
3688         }
3689
3690         ret = add_tree_block(rc, &key, path, blocks);
3691 out:
3692         btrfs_free_path(path);
3693         return ret;
3694 }
3695
3696 static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
3697                                     struct btrfs_block_group *block_group,
3698                                     struct inode *inode,
3699                                     u64 ino)
3700 {
3701         struct btrfs_key key;
3702         struct btrfs_root *root = fs_info->tree_root;
3703         struct btrfs_trans_handle *trans;
3704         int ret = 0;
3705
3706         if (inode)
3707                 goto truncate;
3708
3709         key.objectid = ino;
3710         key.type = BTRFS_INODE_ITEM_KEY;
3711         key.offset = 0;
3712
3713         inode = btrfs_iget(fs_info->sb, &key, root);
3714         if (IS_ERR(inode))
3715                 return -ENOENT;
3716
3717 truncate:
3718         ret = btrfs_check_trunc_cache_free_space(fs_info,
3719                                                  &fs_info->global_block_rsv);
3720         if (ret)
3721                 goto out;
3722
3723         trans = btrfs_join_transaction(root);
3724         if (IS_ERR(trans)) {
3725                 ret = PTR_ERR(trans);
3726                 goto out;
3727         }
3728
3729         ret = btrfs_truncate_free_space_cache(trans, block_group, inode);
3730
3731         btrfs_end_transaction(trans);
3732         btrfs_btree_balance_dirty(fs_info);
3733 out:
3734         iput(inode);
3735         return ret;
3736 }
3737
3738 /*
3739  * Locate the free space cache EXTENT_DATA in root tree leaf and delete the
3740  * cache inode, to avoid free space cache data extent blocking data relocation.
3741  */
3742 static int delete_v1_space_cache(struct extent_buffer *leaf,
3743                                  struct btrfs_block_group *block_group,
3744                                  u64 data_bytenr)
3745 {
3746         u64 space_cache_ino;
3747         struct btrfs_file_extent_item *ei;
3748         struct btrfs_key key;
3749         bool found = false;
3750         int i;
3751         int ret;
3752
3753         if (btrfs_header_owner(leaf) != BTRFS_ROOT_TREE_OBJECTID)
3754                 return 0;
3755
3756         for (i = 0; i < btrfs_header_nritems(leaf); i++) {
3757                 btrfs_item_key_to_cpu(leaf, &key, i);
3758                 if (key.type != BTRFS_EXTENT_DATA_KEY)
3759                         continue;
3760                 ei = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
3761                 if (btrfs_file_extent_type(leaf, ei) == BTRFS_FILE_EXTENT_REG &&
3762                     btrfs_file_extent_disk_bytenr(leaf, ei) == data_bytenr) {
3763                         found = true;
3764                         space_cache_ino = key.objectid;
3765                         break;
3766                 }
3767         }
3768         if (!found)
3769                 return -ENOENT;
3770         ret = delete_block_group_cache(leaf->fs_info, block_group, NULL,
3771                                         space_cache_ino);
3772         return ret;
3773 }
3774
3775 /*
3776  * helper to find all tree blocks that reference a given data extent
3777  */
3778 static noinline_for_stack
3779 int add_data_references(struct reloc_control *rc,
3780                         struct btrfs_key *extent_key,
3781                         struct btrfs_path *path,
3782                         struct rb_root *blocks)
3783 {
3784         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3785         struct ulist *leaves = NULL;
3786         struct ulist_iterator leaf_uiter;
3787         struct ulist_node *ref_node = NULL;
3788         const u32 blocksize = fs_info->nodesize;
3789         int ret = 0;
3790
3791         btrfs_release_path(path);
3792         ret = btrfs_find_all_leafs(NULL, fs_info, extent_key->objectid,
3793                                    0, &leaves, NULL, true);
3794         if (ret < 0)
3795                 return ret;
3796
3797         ULIST_ITER_INIT(&leaf_uiter);
3798         while ((ref_node = ulist_next(leaves, &leaf_uiter))) {
3799                 struct extent_buffer *eb;
3800
3801                 eb = read_tree_block(fs_info, ref_node->val, 0, 0, NULL);
3802                 if (IS_ERR(eb)) {
3803                         ret = PTR_ERR(eb);
3804                         break;
3805                 }
3806                 ret = delete_v1_space_cache(eb, rc->block_group,
3807                                             extent_key->objectid);
3808                 free_extent_buffer(eb);
3809                 if (ret < 0)
3810                         break;
3811                 ret = __add_tree_block(rc, ref_node->val, blocksize, blocks);
3812                 if (ret < 0)
3813                         break;
3814         }
3815         if (ret < 0)
3816                 free_block_list(blocks);
3817         ulist_free(leaves);
3818         return ret;
3819 }
3820
3821 /*
3822  * helper to find next unprocessed extent
3823  */
3824 static noinline_for_stack
3825 int find_next_extent(struct reloc_control *rc, struct btrfs_path *path,
3826                      struct btrfs_key *extent_key)
3827 {
3828         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3829         struct btrfs_key key;
3830         struct extent_buffer *leaf;
3831         u64 start, end, last;
3832         int ret;
3833
3834         last = rc->block_group->start + rc->block_group->length;
3835         while (1) {
3836                 cond_resched();
3837                 if (rc->search_start >= last) {
3838                         ret = 1;
3839                         break;
3840                 }
3841
3842                 key.objectid = rc->search_start;
3843                 key.type = BTRFS_EXTENT_ITEM_KEY;
3844                 key.offset = 0;
3845
3846                 path->search_commit_root = 1;
3847                 path->skip_locking = 1;
3848                 ret = btrfs_search_slot(NULL, rc->extent_root, &key, path,
3849                                         0, 0);
3850                 if (ret < 0)
3851                         break;
3852 next:
3853                 leaf = path->nodes[0];
3854                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
3855                         ret = btrfs_next_leaf(rc->extent_root, path);
3856                         if (ret != 0)
3857                                 break;
3858                         leaf = path->nodes[0];
3859                 }
3860
3861                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
3862                 if (key.objectid >= last) {
3863                         ret = 1;
3864                         break;
3865                 }
3866
3867                 if (key.type != BTRFS_EXTENT_ITEM_KEY &&
3868                     key.type != BTRFS_METADATA_ITEM_KEY) {
3869                         path->slots[0]++;
3870                         goto next;
3871                 }
3872
3873                 if (key.type == BTRFS_EXTENT_ITEM_KEY &&
3874                     key.objectid + key.offset <= rc->search_start) {
3875                         path->slots[0]++;
3876                         goto next;
3877                 }
3878
3879                 if (key.type == BTRFS_METADATA_ITEM_KEY &&
3880                     key.objectid + fs_info->nodesize <=
3881                     rc->search_start) {
3882                         path->slots[0]++;
3883                         goto next;
3884                 }
3885
3886                 ret = find_first_extent_bit(&rc->processed_blocks,
3887                                             key.objectid, &start, &end,
3888                                             EXTENT_DIRTY, NULL);
3889
3890                 if (ret == 0 && start <= key.objectid) {
3891                         btrfs_release_path(path);
3892                         rc->search_start = end + 1;
3893                 } else {
3894                         if (key.type == BTRFS_EXTENT_ITEM_KEY)
3895                                 rc->search_start = key.objectid + key.offset;
3896                         else
3897                                 rc->search_start = key.objectid +
3898                                         fs_info->nodesize;
3899                         memcpy(extent_key, &key, sizeof(key));
3900                         return 0;
3901                 }
3902         }
3903         btrfs_release_path(path);
3904         return ret;
3905 }
3906
3907 static void set_reloc_control(struct reloc_control *rc)
3908 {
3909         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3910
3911         mutex_lock(&fs_info->reloc_mutex);
3912         fs_info->reloc_ctl = rc;
3913         mutex_unlock(&fs_info->reloc_mutex);
3914 }
3915
3916 static void unset_reloc_control(struct reloc_control *rc)
3917 {
3918         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3919
3920         mutex_lock(&fs_info->reloc_mutex);
3921         fs_info->reloc_ctl = NULL;
3922         mutex_unlock(&fs_info->reloc_mutex);
3923 }
3924
3925 static int check_extent_flags(u64 flags)
3926 {
3927         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3928             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3929                 return 1;
3930         if (!(flags & BTRFS_EXTENT_FLAG_DATA) &&
3931             !(flags & BTRFS_EXTENT_FLAG_TREE_BLOCK))
3932                 return 1;
3933         if ((flags & BTRFS_EXTENT_FLAG_DATA) &&
3934             (flags & BTRFS_BLOCK_FLAG_FULL_BACKREF))
3935                 return 1;
3936         return 0;
3937 }
3938
3939 static noinline_for_stack
3940 int prepare_to_relocate(struct reloc_control *rc)
3941 {
3942         struct btrfs_trans_handle *trans;
3943         int ret;
3944
3945         rc->block_rsv = btrfs_alloc_block_rsv(rc->extent_root->fs_info,
3946                                               BTRFS_BLOCK_RSV_TEMP);
3947         if (!rc->block_rsv)
3948                 return -ENOMEM;
3949
3950         memset(&rc->cluster, 0, sizeof(rc->cluster));
3951         rc->search_start = rc->block_group->start;
3952         rc->extents_found = 0;
3953         rc->nodes_relocated = 0;
3954         rc->merging_rsv_size = 0;
3955         rc->reserved_bytes = 0;
3956         rc->block_rsv->size = rc->extent_root->fs_info->nodesize *
3957                               RELOCATION_RESERVED_NODES;
3958         ret = btrfs_block_rsv_refill(rc->extent_root,
3959                                      rc->block_rsv, rc->block_rsv->size,
3960                                      BTRFS_RESERVE_FLUSH_ALL);
3961         if (ret)
3962                 return ret;
3963
3964         rc->create_reloc_tree = 1;
3965         set_reloc_control(rc);
3966
3967         trans = btrfs_join_transaction(rc->extent_root);
3968         if (IS_ERR(trans)) {
3969                 unset_reloc_control(rc);
3970                 /*
3971                  * extent tree is not a ref_cow tree and has no reloc_root to
3972                  * cleanup.  And callers are responsible to free the above
3973                  * block rsv.
3974                  */
3975                 return PTR_ERR(trans);
3976         }
3977         btrfs_commit_transaction(trans);
3978         return 0;
3979 }
3980
3981 static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
3982 {
3983         struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
3984         struct rb_root blocks = RB_ROOT;
3985         struct btrfs_key key;
3986         struct btrfs_trans_handle *trans = NULL;
3987         struct btrfs_path *path;
3988         struct btrfs_extent_item *ei;
3989         u64 flags;
3990         u32 item_size;
3991         int ret;
3992         int err = 0;
3993         int progress = 0;
3994
3995         path = btrfs_alloc_path();
3996         if (!path)
3997                 return -ENOMEM;
3998         path->reada = READA_FORWARD;
3999
4000         ret = prepare_to_relocate(rc);
4001         if (ret) {
4002                 err = ret;
4003                 goto out_free;
4004         }
4005
4006         while (1) {
4007                 rc->reserved_bytes = 0;
4008                 ret = btrfs_block_rsv_refill(rc->extent_root,
4009                                         rc->block_rsv, rc->block_rsv->size,
4010                                         BTRFS_RESERVE_FLUSH_ALL);
4011                 if (ret) {
4012                         err = ret;
4013                         break;
4014                 }
4015                 progress++;
4016                 trans = btrfs_start_transaction(rc->extent_root, 0);
4017                 if (IS_ERR(trans)) {
4018                         err = PTR_ERR(trans);
4019                         trans = NULL;
4020                         break;
4021                 }
4022 restart:
4023                 if (update_backref_cache(trans, &rc->backref_cache)) {
4024                         btrfs_end_transaction(trans);
4025                         trans = NULL;
4026                         continue;
4027                 }
4028
4029                 ret = find_next_extent(rc, path, &key);
4030                 if (ret < 0)
4031                         err = ret;
4032                 if (ret != 0)
4033                         break;
4034
4035                 rc->extents_found++;
4036
4037                 ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
4038                                     struct btrfs_extent_item);
4039                 item_size = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
4040                 if (item_size >= sizeof(*ei)) {
4041                         flags = btrfs_extent_flags(path->nodes[0], ei);
4042                         ret = check_extent_flags(flags);
4043                         BUG_ON(ret);
4044                 } else if (unlikely(item_size == sizeof(struct btrfs_extent_item_v0))) {
4045                         err = -EINVAL;
4046                         btrfs_print_v0_err(trans->fs_info);
4047                         btrfs_abort_transaction(trans, err);
4048                         break;
4049                 } else {
4050                         BUG();
4051                 }
4052
4053                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
4054                         ret = add_tree_block(rc, &key, path, &blocks);
4055                 } else if (rc->stage == UPDATE_DATA_PTRS &&
4056                            (flags & BTRFS_EXTENT_FLAG_DATA)) {
4057                         ret = add_data_references(rc, &key, path, &blocks);
4058                 } else {
4059                         btrfs_release_path(path);
4060                         ret = 0;
4061                 }
4062                 if (ret < 0) {
4063                         err = ret;
4064                         break;
4065                 }
4066
4067                 if (!RB_EMPTY_ROOT(&blocks)) {
4068                         ret = relocate_tree_blocks(trans, rc, &blocks);
4069                         if (ret < 0) {
4070                                 if (ret != -EAGAIN) {
4071                                         err = ret;
4072                                         break;
4073                                 }
4074                                 rc->extents_found--;
4075                                 rc->search_start = key.objectid;
4076                         }
4077                 }
4078
4079                 btrfs_end_transaction_throttle(trans);
4080                 btrfs_btree_balance_dirty(fs_info);
4081                 trans = NULL;
4082
4083                 if (rc->stage == MOVE_DATA_EXTENTS &&
4084                     (flags & BTRFS_EXTENT_FLAG_DATA)) {
4085                         rc->found_file_extent = 1;
4086                         ret = relocate_data_extent(rc->data_inode,
4087                                                    &key, &rc->cluster);
4088                         if (ret < 0) {
4089                                 err = ret;
4090                                 break;
4091                         }
4092                 }
4093                 if (btrfs_should_cancel_balance(fs_info)) {
4094                         err = -ECANCELED;
4095                         break;
4096                 }
4097         }
4098         if (trans && progress && err == -ENOSPC) {
4099                 ret = btrfs_force_chunk_alloc(trans, rc->block_group->flags);
4100                 if (ret == 1) {
4101                         err = 0;
4102                         progress = 0;
4103                         goto restart;
4104                 }
4105         }
4106
4107         btrfs_release_path(path);
4108         clear_extent_bits(&rc->processed_blocks, 0, (u64)-1, EXTENT_DIRTY);
4109
4110         if (trans) {
4111                 btrfs_end_transaction_throttle(trans);
4112                 btrfs_btree_balance_dirty(fs_info);
4113         }
4114
4115         if (!err) {
4116                 ret = relocate_file_extent_cluster(rc->data_inode,
4117                                                    &rc->cluster);
4118                 if (ret < 0)
4119                         err = ret;
4120         }
4121
4122         rc->create_reloc_tree = 0;
4123         set_reloc_control(rc);
4124
4125         backref_cache_cleanup(&rc->backref_cache);
4126         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
4127
4128         /*
4129          * Even in the case when the relocation is cancelled, we should all go
4130          * through prepare_to_merge() and merge_reloc_roots().
4131          *
4132          * For error (including cancelled balance), prepare_to_merge() will
4133          * mark all reloc trees orphan, then queue them for cleanup in
4134          * merge_reloc_roots()
4135          */
4136         err = prepare_to_merge(rc, err);
4137
4138         merge_reloc_roots(rc);
4139
4140         rc->merge_reloc_tree = 0;
4141         unset_reloc_control(rc);
4142         btrfs_block_rsv_release(fs_info, rc->block_rsv, (u64)-1, NULL);
4143
4144         /* get rid of pinned extents */
4145         trans = btrfs_join_transaction(rc->extent_root);
4146         if (IS_ERR(trans)) {
4147                 err = PTR_ERR(trans);
4148                 goto out_free;
4149         }
4150         btrfs_commit_transaction(trans);
4151 out_free:
4152         ret = clean_dirty_subvols(rc);
4153         if (ret < 0 && !err)
4154                 err = ret;
4155         btrfs_free_block_rsv(fs_info, rc->block_rsv);
4156         btrfs_free_path(path);
4157         return err;
4158 }
4159
4160 static int __insert_orphan_inode(struct btrfs_trans_handle *trans,
4161                                  struct btrfs_root *root, u64 objectid)
4162 {
4163         struct btrfs_path *path;
4164         struct btrfs_inode_item *item;
4165         struct extent_buffer *leaf;
4166         int ret;
4167
4168         path = btrfs_alloc_path();
4169         if (!path)
4170                 return -ENOMEM;
4171
4172         ret = btrfs_insert_empty_inode(trans, root, path, objectid);
4173         if (ret)
4174                 goto out;
4175
4176         leaf = path->nodes[0];
4177         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_inode_item);
4178         memzero_extent_buffer(leaf, (unsigned long)item, sizeof(*item));
4179         btrfs_set_inode_generation(leaf, item, 1);
4180         btrfs_set_inode_size(leaf, item, 0);
4181         btrfs_set_inode_mode(leaf, item, S_IFREG | 0600);
4182         btrfs_set_inode_flags(leaf, item, BTRFS_INODE_NOCOMPRESS |
4183                                           BTRFS_INODE_PREALLOC);
4184         btrfs_mark_buffer_dirty(leaf);
4185 out:
4186         btrfs_free_path(path);
4187         return ret;
4188 }
4189
4190 /*
4191  * helper to create inode for data relocation.
4192  * the inode is in data relocation tree and its link count is 0
4193  */
4194 static noinline_for_stack
4195 struct inode *create_reloc_inode(struct btrfs_fs_info *fs_info,
4196                                  struct btrfs_block_group *group)
4197 {
4198         struct inode *inode = NULL;
4199         struct btrfs_trans_handle *trans;
4200         struct btrfs_root *root;
4201         struct btrfs_key key;
4202         u64 objectid;
4203         int err = 0;
4204
4205         root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4206         if (IS_ERR(root))
4207                 return ERR_CAST(root);
4208
4209         trans = btrfs_start_transaction(root, 6);
4210         if (IS_ERR(trans)) {
4211                 btrfs_put_root(root);
4212                 return ERR_CAST(trans);
4213         }
4214
4215         err = btrfs_find_free_objectid(root, &objectid);
4216         if (err)
4217                 goto out;
4218
4219         err = __insert_orphan_inode(trans, root, objectid);
4220         BUG_ON(err);
4221
4222         key.objectid = objectid;
4223         key.type = BTRFS_INODE_ITEM_KEY;
4224         key.offset = 0;
4225         inode = btrfs_iget(fs_info->sb, &key, root);
4226         BUG_ON(IS_ERR(inode));
4227         BTRFS_I(inode)->index_cnt = group->start;
4228
4229         err = btrfs_orphan_add(trans, BTRFS_I(inode));
4230 out:
4231         btrfs_put_root(root);
4232         btrfs_end_transaction(trans);
4233         btrfs_btree_balance_dirty(fs_info);
4234         if (err) {
4235                 if (inode)
4236                         iput(inode);
4237                 inode = ERR_PTR(err);
4238         }
4239         return inode;
4240 }
4241
4242 static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
4243 {
4244         struct reloc_control *rc;
4245
4246         rc = kzalloc(sizeof(*rc), GFP_NOFS);
4247         if (!rc)
4248                 return NULL;
4249
4250         INIT_LIST_HEAD(&rc->reloc_roots);
4251         INIT_LIST_HEAD(&rc->dirty_subvol_roots);
4252         backref_cache_init(&rc->backref_cache);
4253         mapping_tree_init(&rc->reloc_root_tree);
4254         extent_io_tree_init(fs_info, &rc->processed_blocks,
4255                             IO_TREE_RELOC_BLOCKS, NULL);
4256         return rc;
4257 }
4258
4259 static void free_reloc_control(struct reloc_control *rc)
4260 {
4261         struct mapping_node *node, *tmp;
4262
4263         free_reloc_roots(&rc->reloc_roots);
4264         rbtree_postorder_for_each_entry_safe(node, tmp,
4265                         &rc->reloc_root_tree.rb_root, rb_node)
4266                 kfree(node);
4267
4268         kfree(rc);
4269 }
4270
4271 /*
4272  * Print the block group being relocated
4273  */
4274 static void describe_relocation(struct btrfs_fs_info *fs_info,
4275                                 struct btrfs_block_group *block_group)
4276 {
4277         char buf[128] = {'\0'};
4278
4279         btrfs_describe_block_groups(block_group->flags, buf, sizeof(buf));
4280
4281         btrfs_info(fs_info,
4282                    "relocating block group %llu flags %s",
4283                    block_group->start, buf);
4284 }
4285
4286 static const char *stage_to_string(int stage)
4287 {
4288         if (stage == MOVE_DATA_EXTENTS)
4289                 return "move data extents";
4290         if (stage == UPDATE_DATA_PTRS)
4291                 return "update data pointers";
4292         return "unknown";
4293 }
4294
4295 /*
4296  * function to relocate all extents in a block group.
4297  */
4298 int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
4299 {
4300         struct btrfs_block_group *bg;
4301         struct btrfs_root *extent_root = fs_info->extent_root;
4302         struct reloc_control *rc;
4303         struct inode *inode;
4304         struct btrfs_path *path;
4305         int ret;
4306         int rw = 0;
4307         int err = 0;
4308
4309         bg = btrfs_lookup_block_group(fs_info, group_start);
4310         if (!bg)
4311                 return -ENOENT;
4312
4313         if (btrfs_pinned_by_swapfile(fs_info, bg)) {
4314                 btrfs_put_block_group(bg);
4315                 return -ETXTBSY;
4316         }
4317
4318         rc = alloc_reloc_control(fs_info);
4319         if (!rc) {
4320                 btrfs_put_block_group(bg);
4321                 return -ENOMEM;
4322         }
4323
4324         rc->extent_root = extent_root;
4325         rc->block_group = bg;
4326
4327         ret = btrfs_inc_block_group_ro(rc->block_group, true);
4328         if (ret) {
4329                 err = ret;
4330                 goto out;
4331         }
4332         rw = 1;
4333
4334         path = btrfs_alloc_path();
4335         if (!path) {
4336                 err = -ENOMEM;
4337                 goto out;
4338         }
4339
4340         inode = lookup_free_space_inode(rc->block_group, path);
4341         btrfs_free_path(path);
4342
4343         if (!IS_ERR(inode))
4344                 ret = delete_block_group_cache(fs_info, rc->block_group, inode, 0);
4345         else
4346                 ret = PTR_ERR(inode);
4347
4348         if (ret && ret != -ENOENT) {
4349                 err = ret;
4350                 goto out;
4351         }
4352
4353         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
4354         if (IS_ERR(rc->data_inode)) {
4355                 err = PTR_ERR(rc->data_inode);
4356                 rc->data_inode = NULL;
4357                 goto out;
4358         }
4359
4360         describe_relocation(fs_info, rc->block_group);
4361
4362         btrfs_wait_block_group_reservations(rc->block_group);
4363         btrfs_wait_nocow_writers(rc->block_group);
4364         btrfs_wait_ordered_roots(fs_info, U64_MAX,
4365                                  rc->block_group->start,
4366                                  rc->block_group->length);
4367
4368         while (1) {
4369                 int finishes_stage;
4370
4371                 mutex_lock(&fs_info->cleaner_mutex);
4372                 ret = relocate_block_group(rc);
4373                 mutex_unlock(&fs_info->cleaner_mutex);
4374                 if (ret < 0)
4375                         err = ret;
4376
4377                 finishes_stage = rc->stage;
4378                 /*
4379                  * We may have gotten ENOSPC after we already dirtied some
4380                  * extents.  If writeout happens while we're relocating a
4381                  * different block group we could end up hitting the
4382                  * BUG_ON(rc->stage == UPDATE_DATA_PTRS) in
4383                  * btrfs_reloc_cow_block.  Make sure we write everything out
4384                  * properly so we don't trip over this problem, and then break
4385                  * out of the loop if we hit an error.
4386                  */
4387                 if (rc->stage == MOVE_DATA_EXTENTS && rc->found_file_extent) {
4388                         ret = btrfs_wait_ordered_range(rc->data_inode, 0,
4389                                                        (u64)-1);
4390                         if (ret)
4391                                 err = ret;
4392                         invalidate_mapping_pages(rc->data_inode->i_mapping,
4393                                                  0, -1);
4394                         rc->stage = UPDATE_DATA_PTRS;
4395                 }
4396
4397                 if (err < 0)
4398                         goto out;
4399
4400                 if (rc->extents_found == 0)
4401                         break;
4402
4403                 btrfs_info(fs_info, "found %llu extents, stage: %s",
4404                            rc->extents_found, stage_to_string(finishes_stage));
4405         }
4406
4407         WARN_ON(rc->block_group->pinned > 0);
4408         WARN_ON(rc->block_group->reserved > 0);
4409         WARN_ON(rc->block_group->used > 0);
4410 out:
4411         if (err && rw)
4412                 btrfs_dec_block_group_ro(rc->block_group);
4413         iput(rc->data_inode);
4414         btrfs_put_block_group(rc->block_group);
4415         free_reloc_control(rc);
4416         return err;
4417 }
4418
4419 static noinline_for_stack int mark_garbage_root(struct btrfs_root *root)
4420 {
4421         struct btrfs_fs_info *fs_info = root->fs_info;
4422         struct btrfs_trans_handle *trans;
4423         int ret, err;
4424
4425         trans = btrfs_start_transaction(fs_info->tree_root, 0);
4426         if (IS_ERR(trans))
4427                 return PTR_ERR(trans);
4428
4429         memset(&root->root_item.drop_progress, 0,
4430                 sizeof(root->root_item.drop_progress));
4431         root->root_item.drop_level = 0;
4432         btrfs_set_root_refs(&root->root_item, 0);
4433         ret = btrfs_update_root(trans, fs_info->tree_root,
4434                                 &root->root_key, &root->root_item);
4435
4436         err = btrfs_end_transaction(trans);
4437         if (err)
4438                 return err;
4439         return ret;
4440 }
4441
4442 /*
4443  * recover relocation interrupted by system crash.
4444  *
4445  * this function resumes merging reloc trees with corresponding fs trees.
4446  * this is important for keeping the sharing of tree blocks
4447  */
4448 int btrfs_recover_relocation(struct btrfs_root *root)
4449 {
4450         struct btrfs_fs_info *fs_info = root->fs_info;
4451         LIST_HEAD(reloc_roots);
4452         struct btrfs_key key;
4453         struct btrfs_root *fs_root;
4454         struct btrfs_root *reloc_root;
4455         struct btrfs_path *path;
4456         struct extent_buffer *leaf;
4457         struct reloc_control *rc = NULL;
4458         struct btrfs_trans_handle *trans;
4459         int ret;
4460         int err = 0;
4461
4462         path = btrfs_alloc_path();
4463         if (!path)
4464                 return -ENOMEM;
4465         path->reada = READA_BACK;
4466
4467         key.objectid = BTRFS_TREE_RELOC_OBJECTID;
4468         key.type = BTRFS_ROOT_ITEM_KEY;
4469         key.offset = (u64)-1;
4470
4471         while (1) {
4472                 ret = btrfs_search_slot(NULL, fs_info->tree_root, &key,
4473                                         path, 0, 0);
4474                 if (ret < 0) {
4475                         err = ret;
4476                         goto out;
4477                 }
4478                 if (ret > 0) {
4479                         if (path->slots[0] == 0)
4480                                 break;
4481                         path->slots[0]--;
4482                 }
4483                 leaf = path->nodes[0];
4484                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
4485                 btrfs_release_path(path);
4486
4487                 if (key.objectid != BTRFS_TREE_RELOC_OBJECTID ||
4488                     key.type != BTRFS_ROOT_ITEM_KEY)
4489                         break;
4490
4491                 reloc_root = btrfs_read_tree_root(root, &key);
4492                 if (IS_ERR(reloc_root)) {
4493                         err = PTR_ERR(reloc_root);
4494                         goto out;
4495                 }
4496
4497                 set_bit(BTRFS_ROOT_REF_COWS, &reloc_root->state);
4498                 list_add(&reloc_root->root_list, &reloc_roots);
4499
4500                 if (btrfs_root_refs(&reloc_root->root_item) > 0) {
4501                         fs_root = read_fs_root(fs_info,
4502                                                reloc_root->root_key.offset);
4503                         if (IS_ERR(fs_root)) {
4504                                 ret = PTR_ERR(fs_root);
4505                                 if (ret != -ENOENT) {
4506                                         err = ret;
4507                                         goto out;
4508                                 }
4509                                 ret = mark_garbage_root(reloc_root);
4510                                 if (ret < 0) {
4511                                         err = ret;
4512                                         goto out;
4513                                 }
4514                         } else {
4515                                 btrfs_put_root(fs_root);
4516                         }
4517                 }
4518
4519                 if (key.offset == 0)
4520                         break;
4521
4522                 key.offset--;
4523         }
4524         btrfs_release_path(path);
4525
4526         if (list_empty(&reloc_roots))
4527                 goto out;
4528
4529         rc = alloc_reloc_control(fs_info);
4530         if (!rc) {
4531                 err = -ENOMEM;
4532                 goto out;
4533         }
4534
4535         rc->extent_root = fs_info->extent_root;
4536
4537         set_reloc_control(rc);
4538
4539         trans = btrfs_join_transaction(rc->extent_root);
4540         if (IS_ERR(trans)) {
4541                 err = PTR_ERR(trans);
4542                 goto out_unset;
4543         }
4544
4545         rc->merge_reloc_tree = 1;
4546
4547         while (!list_empty(&reloc_roots)) {
4548                 reloc_root = list_entry(reloc_roots.next,
4549                                         struct btrfs_root, root_list);
4550                 list_del(&reloc_root->root_list);
4551
4552                 if (btrfs_root_refs(&reloc_root->root_item) == 0) {
4553                         list_add_tail(&reloc_root->root_list,
4554                                       &rc->reloc_roots);
4555                         continue;
4556                 }
4557
4558                 fs_root = read_fs_root(fs_info, reloc_root->root_key.offset);
4559                 if (IS_ERR(fs_root)) {
4560                         err = PTR_ERR(fs_root);
4561                         list_add_tail(&reloc_root->root_list, &reloc_roots);
4562                         goto out_unset;
4563                 }
4564
4565                 err = __add_reloc_root(reloc_root);
4566                 BUG_ON(err < 0); /* -ENOMEM or logic error */
4567                 fs_root->reloc_root = btrfs_grab_root(reloc_root);
4568                 btrfs_put_root(fs_root);
4569         }
4570
4571         err = btrfs_commit_transaction(trans);
4572         if (err)
4573                 goto out_unset;
4574
4575         merge_reloc_roots(rc);
4576
4577         unset_reloc_control(rc);
4578
4579         trans = btrfs_join_transaction(rc->extent_root);
4580         if (IS_ERR(trans)) {
4581                 err = PTR_ERR(trans);
4582                 goto out_clean;
4583         }
4584         err = btrfs_commit_transaction(trans);
4585 out_clean:
4586         ret = clean_dirty_subvols(rc);
4587         if (ret < 0 && !err)
4588                 err = ret;
4589 out_unset:
4590         unset_reloc_control(rc);
4591         free_reloc_control(rc);
4592 out:
4593         if (!list_empty(&reloc_roots))
4594                 free_reloc_roots(&reloc_roots);
4595
4596         btrfs_free_path(path);
4597
4598         if (err == 0) {
4599                 /* cleanup orphan inode in data relocation tree */
4600                 fs_root = read_fs_root(fs_info, BTRFS_DATA_RELOC_TREE_OBJECTID);
4601                 if (IS_ERR(fs_root)) {
4602                         err = PTR_ERR(fs_root);
4603                 } else {
4604                         err = btrfs_orphan_cleanup(fs_root);
4605                         btrfs_put_root(fs_root);
4606                 }
4607         }
4608         return err;
4609 }
4610
4611 /*
4612  * helper to add ordered checksum for data relocation.
4613  *
4614  * cloning checksum properly handles the nodatasum extents.
4615  * it also saves CPU time to re-calculate the checksum.
4616  */
4617 int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
4618 {
4619         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
4620         struct btrfs_ordered_sum *sums;
4621         struct btrfs_ordered_extent *ordered;
4622         int ret;
4623         u64 disk_bytenr;
4624         u64 new_bytenr;
4625         LIST_HEAD(list);
4626
4627         ordered = btrfs_lookup_ordered_extent(inode, file_pos);
4628         BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
4629
4630         disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
4631         ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
4632                                        disk_bytenr + len - 1, &list, 0);
4633         if (ret)
4634                 goto out;
4635
4636         while (!list_empty(&list)) {
4637                 sums = list_entry(list.next, struct btrfs_ordered_sum, list);
4638                 list_del_init(&sums->list);
4639
4640                 /*
4641                  * We need to offset the new_bytenr based on where the csum is.
4642                  * We need to do this because we will read in entire prealloc
4643                  * extents but we may have written to say the middle of the
4644                  * prealloc extent, so we need to make sure the csum goes with
4645                  * the right disk offset.
4646                  *
4647                  * We can do this because the data reloc inode refers strictly
4648                  * to the on disk bytes, so we don't have to worry about
4649                  * disk_len vs real len like with real inodes since it's all
4650                  * disk length.
4651                  */
4652                 new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
4653                 sums->bytenr = new_bytenr;
4654
4655                 btrfs_add_ordered_sum(ordered, sums);
4656         }
4657 out:
4658         btrfs_put_ordered_extent(ordered);
4659         return ret;
4660 }
4661
4662 int btrfs_reloc_cow_block(struct btrfs_trans_handle *trans,
4663                           struct btrfs_root *root, struct extent_buffer *buf,
4664                           struct extent_buffer *cow)
4665 {
4666         struct btrfs_fs_info *fs_info = root->fs_info;
4667         struct reloc_control *rc;
4668         struct backref_node *node;
4669         int first_cow = 0;
4670         int level;
4671         int ret = 0;
4672
4673         rc = fs_info->reloc_ctl;
4674         if (!rc)
4675                 return 0;
4676
4677         BUG_ON(rc->stage == UPDATE_DATA_PTRS &&
4678                root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID);
4679
4680         level = btrfs_header_level(buf);
4681         if (btrfs_header_generation(buf) <=
4682             btrfs_root_last_snapshot(&root->root_item))
4683                 first_cow = 1;
4684
4685         if (root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID &&
4686             rc->create_reloc_tree) {
4687                 WARN_ON(!first_cow && level == 0);
4688
4689                 node = rc->backref_cache.path[level];
4690                 BUG_ON(node->bytenr != buf->start &&
4691                        node->new_bytenr != buf->start);
4692
4693                 drop_node_buffer(node);
4694                 atomic_inc(&cow->refs);
4695                 node->eb = cow;
4696                 node->new_bytenr = cow->start;
4697
4698                 if (!node->pending) {
4699                         list_move_tail(&node->list,
4700                                        &rc->backref_cache.pending[level]);
4701                         node->pending = 1;
4702                 }
4703
4704                 if (first_cow)
4705                         __mark_block_processed(rc, node);
4706
4707                 if (first_cow && level > 0)
4708                         rc->nodes_relocated += buf->len;
4709         }
4710
4711         if (level == 0 && first_cow && rc->stage == UPDATE_DATA_PTRS)
4712                 ret = replace_file_extents(trans, rc, root, cow);
4713         return ret;
4714 }
4715
4716 /*
4717  * called before creating snapshot. it calculates metadata reservation
4718  * required for relocating tree blocks in the snapshot
4719  */
4720 void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
4721                               u64 *bytes_to_reserve)
4722 {
4723         struct btrfs_root *root = pending->root;
4724         struct reloc_control *rc = root->fs_info->reloc_ctl;
4725
4726         if (!rc || !have_reloc_root(root))
4727                 return;
4728
4729         if (!rc->merge_reloc_tree)
4730                 return;
4731
4732         root = root->reloc_root;
4733         BUG_ON(btrfs_root_refs(&root->root_item) == 0);
4734         /*
4735          * relocation is in the stage of merging trees. the space
4736          * used by merging a reloc tree is twice the size of
4737          * relocated tree nodes in the worst case. half for cowing
4738          * the reloc tree, half for cowing the fs tree. the space
4739          * used by cowing the reloc tree will be freed after the
4740          * tree is dropped. if we create snapshot, cowing the fs
4741          * tree may use more space than it frees. so we need
4742          * reserve extra space.
4743          */
4744         *bytes_to_reserve += rc->nodes_relocated;
4745 }
4746
4747 /*
4748  * called after snapshot is created. migrate block reservation
4749  * and create reloc root for the newly created snapshot
4750  *
4751  * This is similar to btrfs_init_reloc_root(), we come out of here with two
4752  * references held on the reloc_root, one for root->reloc_root and one for
4753  * rc->reloc_roots.
4754  */
4755 int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
4756                                struct btrfs_pending_snapshot *pending)
4757 {
4758         struct btrfs_root *root = pending->root;
4759         struct btrfs_root *reloc_root;
4760         struct btrfs_root *new_root;
4761         struct reloc_control *rc = root->fs_info->reloc_ctl;
4762         int ret;
4763
4764         if (!rc || !have_reloc_root(root))
4765                 return 0;
4766
4767         rc = root->fs_info->reloc_ctl;
4768         rc->merging_rsv_size += rc->nodes_relocated;
4769
4770         if (rc->merge_reloc_tree) {
4771                 ret = btrfs_block_rsv_migrate(&pending->block_rsv,
4772                                               rc->block_rsv,
4773                                               rc->nodes_relocated, true);
4774                 if (ret)
4775                         return ret;
4776         }
4777
4778         new_root = pending->snap;
4779         reloc_root = create_reloc_root(trans, root->reloc_root,
4780                                        new_root->root_key.objectid);
4781         if (IS_ERR(reloc_root))
4782                 return PTR_ERR(reloc_root);
4783
4784         ret = __add_reloc_root(reloc_root);
4785         BUG_ON(ret < 0);
4786         new_root->reloc_root = btrfs_grab_root(reloc_root);
4787
4788         if (rc->create_reloc_tree)
4789                 ret = clone_backref_node(trans, rc, root, reloc_root);
4790         return ret;
4791 }