fs/btrfs/backref.c

   1 /*
   2  * Copyright (C) 2011 STRATO.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include "ctree.h"
  20 #include "disk-io.h"
  21 #include "backref.h"
  22 #include "ulist.h"
  23 #include "transaction.h"
  24 #include "delayed-ref.h"
  25 #include "locking.h"
  26
  27 struct extent_inode_elem {
  28         u64 inum;
  29         u64 offset;
  30         struct extent_inode_elem *next;
  31 };
  32
  33 static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
  34                                 struct btrfs_file_extent_item *fi,
  35                                 u64 extent_item_pos,
  36                                 struct extent_inode_elem **eie)
  37 {
  38         u64 data_offset;
  39         u64 data_len;
  40         struct extent_inode_elem *e;
  41
  42         data_offset = btrfs_file_extent_offset(eb, fi);
  43         data_len = btrfs_file_extent_num_bytes(eb, fi);
  44
  45         if (extent_item_pos < data_offset ||
  46             extent_item_pos >= data_offset + data_len)
  47                 return 1;
  48
  49         e = kmalloc(sizeof(*e), GFP_NOFS);
  50         if (!e)
  51                 return -ENOMEM;
  52
  53         e->next = *eie;
  54         e->inum = key->objectid;
  55         e->offset = key->offset + (extent_item_pos - data_offset);
  56         *eie = e;
  57
  58         return 0;
  59 }
  60
  61 static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
  62                                 u64 extent_item_pos,
  63                                 struct extent_inode_elem **eie)
  64 {
  65         u64 disk_byte;
  66         struct btrfs_key key;
  67         struct btrfs_file_extent_item *fi;
  68         int slot;
  69         int nritems;
  70         int extent_type;
  71         int ret;
  72
  73         /*
  74          * from the shared data ref, we only have the leaf but we need
  75          * the key. thus, we must look into all items and see that we
  76          * find one (some) with a reference to our extent item.
  77          */
  78         nritems = btrfs_header_nritems(eb);
  79         for (slot = 0; slot < nritems; ++slot) {
  80                 btrfs_item_key_to_cpu(eb, &key, slot);
  81                 if (key.type != BTRFS_EXTENT_DATA_KEY)
  82                         continue;
  83                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
  84                 extent_type = btrfs_file_extent_type(eb, fi);
  85                 if (extent_type == BTRFS_FILE_EXTENT_INLINE)
  86                         continue;
  87                 /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
  88                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
  89                 if (disk_byte != wanted_disk_byte)
  90                         continue;
  91
  92                 ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
  93                 if (ret < 0)
  94                         return ret;
  95         }
  96
  97         return 0;
  98 }
  99
 100 /*
 101  * this structure records all encountered refs on the way up to the root
 102  */
 103 struct __prelim_ref {
 104         struct list_head list;
 105         u64 root_id;
 106         struct btrfs_key key_for_search;
 107         int level;
 108         int count;
 109         struct extent_inode_elem *inode_list;
 110         u64 parent;
 111         u64 wanted_disk_byte;
 112 };
 113
 114 /*
 115  * the rules for all callers of this function are:
 116  * - obtaining the parent is the goal
 117  * - if you add a key, you must know that it is a correct key
 118  * - if you cannot add the parent or a correct key, then we will look into the
 119  *   block later to set a correct key
 120  *
 121  * delayed refs
 122  * ============
 123  *        backref type | shared | indirect | shared | indirect
 124  * information         |   tree |     tree |   data |     data
 125  * --------------------+--------+----------+--------+----------
 126  *      parent logical |    y   |     -    |    -   |     -
 127  *      key to resolve |    -   |     y    |    y   |     y
 128  *  tree block logical |    -   |     -    |    -   |     -
 129  *  root for resolving |    y   |     y    |    y   |     y
 130  *
 131  * - column 1:       we've the parent -> done
 132  * - column 2, 3, 4: we use the key to find the parent
 133  *
 134  * on disk refs (inline or keyed)
 135  * ==============================
 136  *        backref type | shared | indirect | shared | indirect
 137  * information         |   tree |     tree |   data |     data
 138  * --------------------+--------+----------+--------+----------
 139  *      parent logical |    y   |     -    |    y   |     -
 140  *      key to resolve |    -   |     -    |    -   |     y
 141  *  tree block logical |    y   |     y    |    y   |     y
 142  *  root for resolving |    -   |     y    |    y   |     y
 143  *
 144  * - column 1, 3: we've the parent -> done
 145  * - column 2:    we take the first key from the block to find the parent
 146  *                (see __add_missing_keys)
 147  * - column 4:    we use the key to find the parent
 148  *
 149  * additional information that's available but not required to find the parent
 150  * block might help in merging entries to gain some speed.
 151  */
 152
 153 static int __add_prelim_ref(struct list_head *head, u64 root_id,
 154                             struct btrfs_key *key, int level,
 155                             u64 parent, u64 wanted_disk_byte, int count)
 156 {
 157         struct __prelim_ref *ref;
 158
 159         /* in case we're adding delayed refs, we're holding the refs spinlock */
 160         ref = kmalloc(sizeof(*ref), GFP_ATOMIC);
 161         if (!ref)
 162                 return -ENOMEM;
 163
 164         ref->root_id = root_id;
 165         if (key)
 166                 ref->key_for_search = *key;
 167         else
 168                 memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 169
 170         ref->inode_list = NULL;
 171         ref->level = level;
 172         ref->count = count;
 173         ref->parent = parent;
 174         ref->wanted_disk_byte = wanted_disk_byte;
 175         list_add_tail(&ref->list, head);
 176
 177         return 0;
 178 }
 179
 180 static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 181                                 struct ulist *parents, int level,
 182                                 struct btrfs_key *key_for_search, u64 time_seq,
 183                                 u64 wanted_disk_byte,
 184                                 const u64 *extent_item_pos)
 185 {
 186         int ret = 0;
 187         int slot;
 188         struct extent_buffer *eb;
 189         struct btrfs_key key;
 190         struct btrfs_file_extent_item *fi;
 191         struct extent_inode_elem *eie = NULL;
 192         u64 disk_byte;
 193
 194         if (level != 0) {
 195                 eb = path->nodes[level];
 196                 ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 197                 if (ret < 0)
 198                         return ret;
 199                 return 0;
 200         }
 201
 202         /*
 203          * We normally enter this function with the path already pointing to
 204          * the first item to check. But sometimes, we may enter it with
 205          * slot==nritems. In that case, go to the next leaf before we continue.
 206          */
 207         if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
 208                 ret = btrfs_next_old_leaf(root, path, time_seq);
 209
 210         while (!ret) {
 211                 eb = path->nodes[0];
 212                 slot = path->slots[0];
 213
 214                 btrfs_item_key_to_cpu(eb, &key, slot);
 215
 216                 if (key.objectid != key_for_search->objectid ||
 217                     key.type != BTRFS_EXTENT_DATA_KEY)
 218                         break;
 219
 220                 fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 221                 disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 222
 223                 if (disk_byte == wanted_disk_byte) {
 224                         eie = NULL;
 225                         if (extent_item_pos) {
 226                                 ret = check_extent_in_eb(&key, eb, fi,
 227                                                 *extent_item_pos,
 228                                                 &eie);
 229                                 if (ret < 0)
 230                                         break;
 231                         }
 232                         if (!ret) {
 233                                 ret = ulist_add(parents, eb->start,
 234                                                 (unsigned long)eie, GFP_NOFS);
 235                                 if (ret < 0)
 236                                         break;
 237                                 if (!extent_item_pos) {
 238                                         ret = btrfs_next_old_leaf(root, path,
 239                                                         time_seq);
 240                                         continue;
 241                                 }
 242                         }
 243                 }
 244                 ret = btrfs_next_old_item(root, path, time_seq);
 245         }
 246
 247         if (ret > 0)
 248                 ret = 0;
 249         return ret;
 250 }
 251
 252 /*
 253  * resolve an indirect backref in the form (root_id, key, level)
 254  * to a logical address
 255  */
 256 static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 257                                         int search_commit_root,
 258                                         u64 time_seq,
 259                                         struct __prelim_ref *ref,
 260                                         struct ulist *parents,
 261                                         const u64 *extent_item_pos)
 262 {
 263         struct btrfs_path *path;
 264         struct btrfs_root *root;
 265         struct btrfs_key root_key;
 266         struct extent_buffer *eb;
 267         int ret = 0;
 268         int root_level;
 269         int level = ref->level;
 270
 271         path = btrfs_alloc_path();
 272         if (!path)
 273                 return -ENOMEM;
 274         path->search_commit_root = !!search_commit_root;
 275
 276         root_key.objectid = ref->root_id;
 277         root_key.type = BTRFS_ROOT_ITEM_KEY;
 278         root_key.offset = (u64)-1;
 279         root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 280         if (IS_ERR(root)) {
 281                 ret = PTR_ERR(root);
 282                 goto out;
 283         }
 284
 285         rcu_read_lock();
 286         root_level = btrfs_header_level(root->node);
 287         rcu_read_unlock();
 288
 289         if (root_level + 1 == level)
 290                 goto out;
 291
 292         path->lowest_level = level;
 293         ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
 294         pr_debug("search slot in root %llu (level %d, ref count %d) returned "
 295                  "%d for key (%llu %u %llu)\n",
 296                  (unsigned long long)ref->root_id, level, ref->count, ret,
 297                  (unsigned long long)ref->key_for_search.objectid,
 298                  ref->key_for_search.type,
 299                  (unsigned long long)ref->key_for_search.offset);
 300         if (ret < 0)
 301                 goto out;
 302
 303         eb = path->nodes[level];
 304         while (!eb) {
 305                 if (!level) {
 306                         WARN_ON(1);
 307                         ret = 1;
 308                         goto out;
 309                 }
 310                 level--;
 311                 eb = path->nodes[level];
 312         }
 313
 314         ret = add_all_parents(root, path, parents, level, &ref->key_for_search,
 315                                 time_seq, ref->wanted_disk_byte,
 316                                 extent_item_pos);
 317 out:
 318         btrfs_free_path(path);
 319         return ret;
 320 }
 321
 322 /*
 323  * resolve all indirect backrefs from the list
 324  */
 325 static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 326                                    int search_commit_root, u64 time_seq,
 327                                    struct list_head *head,
 328                                    const u64 *extent_item_pos)
 329 {
 330         int err;
 331         int ret = 0;
 332         struct __prelim_ref *ref;
 333         struct __prelim_ref *ref_safe;
 334         struct __prelim_ref *new_ref;
 335         struct ulist *parents;
 336         struct ulist_node *node;
 337         struct ulist_iterator uiter;
 338
 339         parents = ulist_alloc(GFP_NOFS);
 340         if (!parents)
 341                 return -ENOMEM;
 342
 343         /*
 344          * _safe allows us to insert directly after the current item without
 345          * iterating over the newly inserted items.
 346          * we're also allowed to re-assign ref during iteration.
 347          */
 348         list_for_each_entry_safe(ref, ref_safe, head, list) {
 349                 if (ref->parent)        /* already direct */
 350                         continue;
 351                 if (ref->count == 0)
 352                         continue;
 353                 err = __resolve_indirect_ref(fs_info, search_commit_root,
 354                                              time_seq, ref, parents,
 355                                              extent_item_pos);
 356                 if (err) {
 357                         if (ret == 0)
 358                                 ret = err;
 359                         continue;
 360                 }
 361
 362                 /* we put the first parent into the ref at hand */
 363                 ULIST_ITER_INIT(&uiter);
 364                 node = ulist_next(parents, &uiter);
 365                 ref->parent = node ? node->val : 0;
 366                 ref->inode_list =
 367                         node ? (struct extent_inode_elem *)node->aux : 0;
 368
 369                 /* additional parents require new refs being added here */
 370                 while ((node = ulist_next(parents, &uiter))) {
 371                         new_ref = kmalloc(sizeof(*new_ref), GFP_NOFS);
 372                         if (!new_ref) {
 373                                 ret = -ENOMEM;
 374                                 break;
 375                         }
 376                         memcpy(new_ref, ref, sizeof(*ref));
 377                         new_ref->parent = node->val;
 378                         new_ref->inode_list =
 379                                         (struct extent_inode_elem *)node->aux;
 380                         list_add(&new_ref->list, &ref->list);
 381                 }
 382                 ulist_reinit(parents);
 383         }
 384
 385         ulist_free(parents);
 386         return ret;
 387 }
 388
 389 static inline int ref_for_same_block(struct __prelim_ref *ref1,
 390                                      struct __prelim_ref *ref2)
 391 {
 392         if (ref1->level != ref2->level)
 393                 return 0;
 394         if (ref1->root_id != ref2->root_id)
 395                 return 0;
 396         if (ref1->key_for_search.type != ref2->key_for_search.type)
 397                 return 0;
 398         if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
 399                 return 0;
 400         if (ref1->key_for_search.offset != ref2->key_for_search.offset)
 401                 return 0;
 402         if (ref1->parent != ref2->parent)
 403                 return 0;
 404
 405         return 1;
 406 }
 407
 408 /*
 409  * read tree blocks and add keys where required.
 410  */
 411 static int __add_missing_keys(struct btrfs_fs_info *fs_info,
 412                               struct list_head *head)
 413 {
 414         struct list_head *pos;
 415         struct extent_buffer *eb;
 416
 417         list_for_each(pos, head) {
 418                 struct __prelim_ref *ref;
 419                 ref = list_entry(pos, struct __prelim_ref, list);
 420
 421                 if (ref->parent)
 422                         continue;
 423                 if (ref->key_for_search.type)
 424                         continue;
 425                 BUG_ON(!ref->wanted_disk_byte);
 426                 eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
 427                                      fs_info->tree_root->leafsize, 0);
 428                 BUG_ON(!eb);
 429                 btrfs_tree_read_lock(eb);
 430                 if (btrfs_header_level(eb) == 0)
 431                         btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 432                 else
 433                         btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 434                 btrfs_tree_read_unlock(eb);
 435                 free_extent_buffer(eb);
 436         }
 437         return 0;
 438 }
 439
 440 /*
 441  * merge two lists of backrefs and adjust counts accordingly
 442  *
 443  * mode = 1: merge identical keys, if key is set
 444  *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
 445  *           additionally, we could even add a key range for the blocks we
 446  *           looked into to merge even more (-> replace unresolved refs by those
 447  *           having a parent).
 448  * mode = 2: merge identical parents
 449  */
 450 static int __merge_refs(struct list_head *head, int mode)
 451 {
 452         struct list_head *pos1;
 453
 454         list_for_each(pos1, head) {
 455                 struct list_head *n2;
 456                 struct list_head *pos2;
 457                 struct __prelim_ref *ref1;
 458
 459                 ref1 = list_entry(pos1, struct __prelim_ref, list);
 460
 461                 for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
 462                      pos2 = n2, n2 = pos2->next) {
 463                         struct __prelim_ref *ref2;
 464                         struct __prelim_ref *xchg;
 465
 466                         ref2 = list_entry(pos2, struct __prelim_ref, list);
 467
 468                         if (mode == 1) {
 469                                 if (!ref_for_same_block(ref1, ref2))
 470                                         continue;
 471                                 if (!ref1->parent && ref2->parent) {
 472                                         xchg = ref1;
 473                                         ref1 = ref2;
 474                                         ref2 = xchg;
 475                                 }
 476                                 ref1->count += ref2->count;
 477                         } else {
 478                                 if (ref1->parent != ref2->parent)
 479                                         continue;
 480                                 ref1->count += ref2->count;
 481                         }
 482                         list_del(&ref2->list);
 483                         kfree(ref2);
 484                 }
 485
 486         }
 487         return 0;
 488 }
 489
 490 /*
 491  * add all currently queued delayed refs from this head whose seq nr is
 492  * smaller or equal that seq to the list
 493  */
 494 static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 495                               struct list_head *prefs)
 496 {
 497         struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 498         struct rb_node *n = &head->node.rb_node;
 499         struct btrfs_key key;
 500         struct btrfs_key op_key = {0};
 501         int sgn;
 502         int ret = 0;
 503
 504         if (extent_op && extent_op->update_key)
 505                 btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 506
 507         while ((n = rb_prev(n))) {
 508                 struct btrfs_delayed_ref_node *node;
 509                 node = rb_entry(n, struct btrfs_delayed_ref_node,
 510                                 rb_node);
 511                 if (node->bytenr != head->node.bytenr)
 512                         break;
 513                 WARN_ON(node->is_head);
 514
 515                 if (node->seq > seq)
 516                         continue;
 517
 518                 switch (node->action) {
 519                 case BTRFS_ADD_DELAYED_EXTENT:
 520                 case BTRFS_UPDATE_DELAYED_HEAD:
 521                         WARN_ON(1);
 522                         continue;
 523                 case BTRFS_ADD_DELAYED_REF:
 524                         sgn = 1;
 525                         break;
 526                 case BTRFS_DROP_DELAYED_REF:
 527                         sgn = -1;
 528                         break;
 529                 default:
 530                         BUG_ON(1);
 531                 }
 532                 switch (node->type) {
 533                 case BTRFS_TREE_BLOCK_REF_KEY: {
 534                         struct btrfs_delayed_tree_ref *ref;
 535
 536                         ref = btrfs_delayed_node_to_tree_ref(node);
 537                         ret = __add_prelim_ref(prefs, ref->root, &op_key,
 538                                                ref->level + 1, 0, node->bytenr,
 539                                                node->ref_mod * sgn);
 540                         break;
 541                 }
 542                 case BTRFS_SHARED_BLOCK_REF_KEY: {
 543                         struct btrfs_delayed_tree_ref *ref;
 544
 545                         ref = btrfs_delayed_node_to_tree_ref(node);
 546                         ret = __add_prelim_ref(prefs, ref->root, NULL,
 547                                                ref->level + 1, ref->parent,
 548                                                node->bytenr,
 549                                                node->ref_mod * sgn);
 550                         break;
 551                 }
 552                 case BTRFS_EXTENT_DATA_REF_KEY: {
 553                         struct btrfs_delayed_data_ref *ref;
 554                         ref = btrfs_delayed_node_to_data_ref(node);
 555
 556                         key.objectid = ref->objectid;
 557                         key.type = BTRFS_EXTENT_DATA_KEY;
 558                         key.offset = ref->offset;
 559                         ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
 560                                                node->bytenr,
 561                                                node->ref_mod * sgn);
 562                         break;
 563                 }
 564                 case BTRFS_SHARED_DATA_REF_KEY: {
 565                         struct btrfs_delayed_data_ref *ref;
 566
 567                         ref = btrfs_delayed_node_to_data_ref(node);
 568
 569                         key.objectid = ref->objectid;
 570                         key.type = BTRFS_EXTENT_DATA_KEY;
 571                         key.offset = ref->offset;
 572                         ret = __add_prelim_ref(prefs, ref->root, &key, 0,
 573                                                ref->parent, node->bytenr,
 574                                                node->ref_mod * sgn);
 575                         break;
 576                 }
 577                 default:
 578                         WARN_ON(1);
 579                 }
 580                 BUG_ON(ret);
 581         }
 582
 583         return 0;
 584 }
 585
 586 /*
 587  * add all inline backrefs for bytenr to the list
 588  */
 589 static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 590                              struct btrfs_path *path, u64 bytenr,
 591                              int *info_level, struct list_head *prefs)
 592 {
 593         int ret = 0;
 594         int slot;
 595         struct extent_buffer *leaf;
 596         struct btrfs_key key;
 597         unsigned long ptr;
 598         unsigned long end;
 599         struct btrfs_extent_item *ei;
 600         u64 flags;
 601         u64 item_size;
 602
 603         /*
 604          * enumerate all inline refs
 605          */
 606         leaf = path->nodes[0];
 607         slot = path->slots[0];
 608
 609         item_size = btrfs_item_size_nr(leaf, slot);
 610         BUG_ON(item_size < sizeof(*ei));
 611
 612         ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 613         flags = btrfs_extent_flags(leaf, ei);
 614
 615         ptr = (unsigned long)(ei + 1);
 616         end = (unsigned long)ei + item_size;
 617
 618         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 619                 struct btrfs_tree_block_info *info;
 620
 621                 info = (struct btrfs_tree_block_info *)ptr;
 622                 *info_level = btrfs_tree_block_level(leaf, info);
 623                 ptr += sizeof(struct btrfs_tree_block_info);
 624                 BUG_ON(ptr > end);
 625         } else {
 626                 BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 627         }
 628
 629         while (ptr < end) {
 630                 struct btrfs_extent_inline_ref *iref;
 631                 u64 offset;
 632                 int type;
 633
 634                 iref = (struct btrfs_extent_inline_ref *)ptr;
 635                 type = btrfs_extent_inline_ref_type(leaf, iref);
 636                 offset = btrfs_extent_inline_ref_offset(leaf, iref);
 637
 638                 switch (type) {
 639                 case BTRFS_SHARED_BLOCK_REF_KEY:
 640                         ret = __add_prelim_ref(prefs, 0, NULL,
 641                                                 *info_level + 1, offset,
 642                                                 bytenr, 1);
 643                         break;
 644                 case BTRFS_SHARED_DATA_REF_KEY: {
 645                         struct btrfs_shared_data_ref *sdref;
 646                         int count;
 647
 648                         sdref = (struct btrfs_shared_data_ref *)(iref + 1);
 649                         count = btrfs_shared_data_ref_count(leaf, sdref);
 650                         ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
 651                                                bytenr, count);
 652                         break;
 653                 }
 654                 case BTRFS_TREE_BLOCK_REF_KEY:
 655                         ret = __add_prelim_ref(prefs, offset, NULL,
 656                                                *info_level + 1, 0,
 657                                                bytenr, 1);
 658                         break;
 659                 case BTRFS_EXTENT_DATA_REF_KEY: {
 660                         struct btrfs_extent_data_ref *dref;
 661                         int count;
 662                         u64 root;
 663
 664                         dref = (struct btrfs_extent_data_ref *)(&iref->offset);
 665                         count = btrfs_extent_data_ref_count(leaf, dref);
 666                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 667                                                                       dref);
 668                         key.type = BTRFS_EXTENT_DATA_KEY;
 669                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 670                         root = btrfs_extent_data_ref_root(leaf, dref);
 671                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 672                                                bytenr, count);
 673                         break;
 674                 }
 675                 default:
 676                         WARN_ON(1);
 677                 }
 678                 BUG_ON(ret);
 679                 ptr += btrfs_extent_inline_ref_size(type);
 680         }
 681
 682         return 0;
 683 }
 684
 685 /*
 686  * add all non-inline backrefs for bytenr to the list
 687  */
 688 static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
 689                             struct btrfs_path *path, u64 bytenr,
 690                             int info_level, struct list_head *prefs)
 691 {
 692         struct btrfs_root *extent_root = fs_info->extent_root;
 693         int ret;
 694         int slot;
 695         struct extent_buffer *leaf;
 696         struct btrfs_key key;
 697
 698         while (1) {
 699                 ret = btrfs_next_item(extent_root, path);
 700                 if (ret < 0)
 701                         break;
 702                 if (ret) {
 703                         ret = 0;
 704                         break;
 705                 }
 706
 707                 slot = path->slots[0];
 708                 leaf = path->nodes[0];
 709                 btrfs_item_key_to_cpu(leaf, &key, slot);
 710
 711                 if (key.objectid != bytenr)
 712                         break;
 713                 if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
 714                         continue;
 715                 if (key.type > BTRFS_SHARED_DATA_REF_KEY)
 716                         break;
 717
 718                 switch (key.type) {
 719                 case BTRFS_SHARED_BLOCK_REF_KEY:
 720                         ret = __add_prelim_ref(prefs, 0, NULL,
 721                                                 info_level + 1, key.offset,
 722                                                 bytenr, 1);
 723                         break;
 724                 case BTRFS_SHARED_DATA_REF_KEY: {
 725                         struct btrfs_shared_data_ref *sdref;
 726                         int count;
 727
 728                         sdref = btrfs_item_ptr(leaf, slot,
 729                                               struct btrfs_shared_data_ref);
 730                         count = btrfs_shared_data_ref_count(leaf, sdref);
 731                         ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 732                                                 bytenr, count);
 733                         break;
 734                 }
 735                 case BTRFS_TREE_BLOCK_REF_KEY:
 736                         ret = __add_prelim_ref(prefs, key.offset, NULL,
 737                                                info_level + 1, 0,
 738                                                bytenr, 1);
 739                         break;
 740                 case BTRFS_EXTENT_DATA_REF_KEY: {
 741                         struct btrfs_extent_data_ref *dref;
 742                         int count;
 743                         u64 root;
 744
 745                         dref = btrfs_item_ptr(leaf, slot,
 746                                               struct btrfs_extent_data_ref);
 747                         count = btrfs_extent_data_ref_count(leaf, dref);
 748                         key.objectid = btrfs_extent_data_ref_objectid(leaf,
 749                                                                       dref);
 750                         key.type = BTRFS_EXTENT_DATA_KEY;
 751                         key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 752                         root = btrfs_extent_data_ref_root(leaf, dref);
 753                         ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 754                                                bytenr, count);
 755                         break;
 756                 }
 757                 default:
 758                         WARN_ON(1);
 759                 }
 760                 BUG_ON(ret);
 761         }
 762
 763         return ret;
 764 }
 765
 766 /*
 767  * this adds all existing backrefs (inline backrefs, backrefs and delayed
 768  * refs) for the given bytenr to the refs list, merges duplicates and resolves
 769  * indirect refs to their parent bytenr.
 770  * When roots are found, they're added to the roots list
 771  *
 772  * FIXME some caching might speed things up
 773  */
 774 static int find_parent_nodes(struct btrfs_trans_handle *trans,
 775                              struct btrfs_fs_info *fs_info, u64 bytenr,
 776                              u64 time_seq, struct ulist *refs,
 777                              struct ulist *roots, const u64 *extent_item_pos)
 778 {
 779         struct btrfs_key key;
 780         struct btrfs_path *path;
 781         struct btrfs_delayed_ref_root *delayed_refs = NULL;
 782         struct btrfs_delayed_ref_head *head;
 783         int info_level = 0;
 784         int ret;
 785         int search_commit_root = (trans == BTRFS_BACKREF_SEARCH_COMMIT_ROOT);
 786         struct list_head prefs_delayed;
 787         struct list_head prefs;
 788         struct __prelim_ref *ref;
 789
 790         INIT_LIST_HEAD(&prefs);
 791         INIT_LIST_HEAD(&prefs_delayed);
 792
 793         key.objectid = bytenr;
 794         key.type = BTRFS_EXTENT_ITEM_KEY;
 795         key.offset = (u64)-1;
 796
 797         path = btrfs_alloc_path();
 798         if (!path)
 799                 return -ENOMEM;
 800         path->search_commit_root = !!search_commit_root;
 801
 802         /*
 803          * grab both a lock on the path and a lock on the delayed ref head.
 804          * We need both to get a consistent picture of how the refs look
 805          * at a specified point in time
 806          */
 807 again:
 808         head = NULL;
 809
 810         ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 811         if (ret < 0)
 812                 goto out;
 813         BUG_ON(ret == 0);
 814
 815         if (trans != BTRFS_BACKREF_SEARCH_COMMIT_ROOT) {
 816                 /*
 817                  * look if there are updates for this ref queued and lock the
 818                  * head
 819                  */
 820                 delayed_refs = &trans->transaction->delayed_refs;
 821                 spin_lock(&delayed_refs->lock);
 822                 head = btrfs_find_delayed_ref_head(trans, bytenr);
 823                 if (head) {
 824                         if (!mutex_trylock(&head->mutex)) {
 825                                 atomic_inc(&head->node.refs);
 826                                 spin_unlock(&delayed_refs->lock);
 827
 828                                 btrfs_release_path(path);
 829
 830                                 /*
 831                                  * Mutex was contended, block until it's
 832                                  * released and try again
 833                                  */
 834                                 mutex_lock(&head->mutex);
 835                                 mutex_unlock(&head->mutex);
 836                                 btrfs_put_delayed_ref(&head->node);
 837                                 goto again;
 838                         }
 839                         ret = __add_delayed_refs(head, time_seq,
 840                                                  &prefs_delayed);
 841                         mutex_unlock(&head->mutex);
 842                         if (ret) {
 843                                 spin_unlock(&delayed_refs->lock);
 844                                 goto out;
 845                         }
 846                 }
 847                 spin_unlock(&delayed_refs->lock);
 848         }
 849
 850         if (path->slots[0]) {
 851                 struct extent_buffer *leaf;
 852                 int slot;
 853
 854                 path->slots[0]--;
 855                 leaf = path->nodes[0];
 856                 slot = path->slots[0];
 857                 btrfs_item_key_to_cpu(leaf, &key, slot);
 858                 if (key.objectid == bytenr &&
 859                     key.type == BTRFS_EXTENT_ITEM_KEY) {
 860                         ret = __add_inline_refs(fs_info, path, bytenr,
 861                                                 &info_level, &prefs);
 862                         if (ret)
 863                                 goto out;
 864                         ret = __add_keyed_refs(fs_info, path, bytenr,
 865                                                info_level, &prefs);
 866                         if (ret)
 867                                 goto out;
 868                 }
 869         }
 870         btrfs_release_path(path);
 871
 872         list_splice_init(&prefs_delayed, &prefs);
 873
 874         ret = __add_missing_keys(fs_info, &prefs);
 875         if (ret)
 876                 goto out;
 877
 878         ret = __merge_refs(&prefs, 1);
 879         if (ret)
 880                 goto out;
 881
 882         ret = __resolve_indirect_refs(fs_info, search_commit_root, time_seq,
 883                                       &prefs, extent_item_pos);
 884         if (ret)
 885                 goto out;
 886
 887         ret = __merge_refs(&prefs, 2);
 888         if (ret)
 889                 goto out;
 890
 891         while (!list_empty(&prefs)) {
 892                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
 893                 list_del(&ref->list);
 894                 if (ref->count < 0)
 895                         WARN_ON(1);
 896                 if (ref->count && ref->root_id && ref->parent == 0) {
 897                         /* no parent == root of tree */
 898                         ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
 899                         BUG_ON(ret < 0);
 900                 }
 901                 if (ref->count && ref->parent) {
 902                         struct extent_inode_elem *eie = NULL;
 903                         if (extent_item_pos && !ref->inode_list) {
 904                                 u32 bsz;
 905                                 struct extent_buffer *eb;
 906                                 bsz = btrfs_level_size(fs_info->extent_root,
 907                                                         info_level);
 908                                 eb = read_tree_block(fs_info->extent_root,
 909                                                            ref->parent, bsz, 0);
 910                                 BUG_ON(!eb);
 911                                 ret = find_extent_in_eb(eb, bytenr,
 912                                                         *extent_item_pos, &eie);
 913                                 ref->inode_list = eie;
 914                                 free_extent_buffer(eb);
 915                         }
 916                         ret = ulist_add_merge(refs, ref->parent,
 917                                               (unsigned long)ref->inode_list,
 918                                               (unsigned long *)&eie, GFP_NOFS);
 919                         if (!ret && extent_item_pos) {
 920                                 /*
 921                                  * we've recorded that parent, so we must extend
 922                                  * its inode list here
 923                                  */
 924                                 BUG_ON(!eie);
 925                                 while (eie->next)
 926                                         eie = eie->next;
 927                                 eie->next = ref->inode_list;
 928                         }
 929                         BUG_ON(ret < 0);
 930                 }
 931                 kfree(ref);
 932         }
 933
 934 out:
 935         btrfs_free_path(path);
 936         while (!list_empty(&prefs)) {
 937                 ref = list_first_entry(&prefs, struct __prelim_ref, list);
 938                 list_del(&ref->list);
 939                 kfree(ref);
 940         }
 941         while (!list_empty(&prefs_delayed)) {
 942                 ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
 943                                        list);
 944                 list_del(&ref->list);
 945                 kfree(ref);
 946         }
 947
 948         return ret;
 949 }
 950
 951 static void free_leaf_list(struct ulist *blocks)
 952 {
 953         struct ulist_node *node = NULL;
 954         struct extent_inode_elem *eie;
 955         struct extent_inode_elem *eie_next;
 956         struct ulist_iterator uiter;
 957
 958         ULIST_ITER_INIT(&uiter);
 959         while ((node = ulist_next(blocks, &uiter))) {
 960                 if (!node->aux)
 961                         continue;
 962                 eie = (struct extent_inode_elem *)node->aux;
 963                 for (; eie; eie = eie_next) {
 964                         eie_next = eie->next;
 965                         kfree(eie);
 966                 }
 967                 node->aux = 0;
 968         }
 969
 970         ulist_free(blocks);
 971 }
 972
 973 /*
 974  * Finds all leafs with a reference to the specified combination of bytenr and
 975  * offset. key_list_head will point to a list of corresponding keys (caller must
 976  * free each list element). The leafs will be stored in the leafs ulist, which
 977  * must be freed with ulist_free.
 978  *
 979  * returns 0 on success, <0 on error
 980  */
 981 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
 982                                 struct btrfs_fs_info *fs_info, u64 bytenr,
 983                                 u64 time_seq, struct ulist **leafs,
 984                                 const u64 *extent_item_pos)
 985 {
 986         struct ulist *tmp;
 987         int ret;
 988
 989         tmp = ulist_alloc(GFP_NOFS);
 990         if (!tmp)
 991                 return -ENOMEM;
 992         *leafs = ulist_alloc(GFP_NOFS);
 993         if (!*leafs) {
 994                 ulist_free(tmp);
 995                 return -ENOMEM;
 996         }
 997
 998         ret = find_parent_nodes(trans, fs_info, bytenr,
 999                                 time_seq, *leafs, tmp, extent_item_pos);
1000         ulist_free(tmp);
1001
1002         if (ret < 0 && ret != -ENOENT) {
1003                 free_leaf_list(*leafs);
1004                 return ret;
1005         }
1006
1007         return 0;
1008 }
1009
1010 /*
1011  * walk all backrefs for a given extent to find all roots that reference this
1012  * extent. Walking a backref means finding all extents that reference this
1013  * extent and in turn walk the backrefs of those, too. Naturally this is a
1014  * recursive process, but here it is implemented in an iterative fashion: We
1015  * find all referencing extents for the extent in question and put them on a
1016  * list. In turn, we find all referencing extents for those, further appending
1017  * to the list. The way we iterate the list allows adding more elements after
1018  * the current while iterating. The process stops when we reach the end of the
1019  * list. Found roots are added to the roots list.
1020  *
1021  * returns 0 on success, < 0 on error.
1022  */
1023 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1024                                 struct btrfs_fs_info *fs_info, u64 bytenr,
1025                                 u64 time_seq, struct ulist **roots)
1026 {
1027         struct ulist *tmp;
1028         struct ulist_node *node = NULL;
1029         struct ulist_iterator uiter;
1030         int ret;
1031
1032         tmp = ulist_alloc(GFP_NOFS);
1033         if (!tmp)
1034                 return -ENOMEM;
1035         *roots = ulist_alloc(GFP_NOFS);
1036         if (!*roots) {
1037                 ulist_free(tmp);
1038                 return -ENOMEM;
1039         }
1040
1041         ULIST_ITER_INIT(&uiter);
1042         while (1) {
1043                 ret = find_parent_nodes(trans, fs_info, bytenr,
1044                                         time_seq, tmp, *roots, NULL);
1045                 if (ret < 0 && ret != -ENOENT) {
1046                         ulist_free(tmp);
1047                         ulist_free(*roots);
1048                         return ret;
1049                 }
1050                 node = ulist_next(tmp, &uiter);
1051                 if (!node)
1052                         break;
1053                 bytenr = node->val;
1054         }
1055
1056         ulist_free(tmp);
1057         return 0;
1058 }
1059
1060
1061 static int __inode_info(u64 inum, u64 ioff, u8 key_type,
1062                         struct btrfs_root *fs_root, struct btrfs_path *path,
1063                         struct btrfs_key *found_key)
1064 {
1065         int ret;
1066         struct btrfs_key key;
1067         struct extent_buffer *eb;
1068
1069         key.type = key_type;
1070         key.objectid = inum;
1071         key.offset = ioff;
1072
1073         ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
1074         if (ret < 0)
1075                 return ret;
1076
1077         eb = path->nodes[0];
1078         if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
1079                 ret = btrfs_next_leaf(fs_root, path);
1080                 if (ret)
1081                         return ret;
1082                 eb = path->nodes[0];
1083         }
1084
1085         btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
1086         if (found_key->type != key.type || found_key->objectid != key.objectid)
1087                 return 1;
1088
1089         return 0;
1090 }
1091
1092 /*
1093  * this makes the path point to (inum INODE_ITEM ioff)
1094  */
1095 int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1096                         struct btrfs_path *path)
1097 {
1098         struct btrfs_key key;
1099         return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
1100                                 &key);
1101 }
1102
1103 static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1104                                 struct btrfs_path *path,
1105                                 struct btrfs_key *found_key)
1106 {
1107         return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
1108                                 found_key);
1109 }
1110
1111 /*
1112  * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
1113  * of the path are separated by '/' and the path is guaranteed to be
1114  * 0-terminated. the path is only given within the current file system.
1115  * Therefore, it never starts with a '/'. the caller is responsible to provide
1116  * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1117  * the start point of the resulting string is returned. this pointer is within
1118  * dest, normally.
1119  * in case the path buffer would overflow, the pointer is decremented further
1120  * as if output was written to the buffer, though no more output is actually
1121  * generated. that way, the caller can determine how much space would be
1122  * required for the path to fit into the buffer. in that case, the returned
1123  * value will be smaller than dest. callers must check this!
1124  */
1125 char *btrfs_iref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1126                          struct btrfs_inode_ref *iref,
1127                          struct extent_buffer *eb_in, u64 parent,
1128                          char *dest, u32 size)
1129 {
1130         u32 len;
1131         int slot;
1132         u64 next_inum;
1133         int ret;
1134         s64 bytes_left = size - 1;
1135         struct extent_buffer *eb = eb_in;
1136         struct btrfs_key found_key;
1137         int leave_spinning = path->leave_spinning;
1138
1139         if (bytes_left >= 0)
1140                 dest[bytes_left] = '\0';
1141
1142         path->leave_spinning = 1;
1143         while (1) {
1144                 len = btrfs_inode_ref_name_len(eb, iref);
1145                 bytes_left -= len;
1146                 if (bytes_left >= 0)
1147                         read_extent_buffer(eb, dest + bytes_left,
1148                                                 (unsigned long)(iref + 1), len);
1149                 if (eb != eb_in) {
1150                         btrfs_tree_read_unlock_blocking(eb);
1151                         free_extent_buffer(eb);
1152                 }
1153                 ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1154                 if (ret > 0)
1155                         ret = -ENOENT;
1156                 if (ret)
1157                         break;
1158                 next_inum = found_key.offset;
1159
1160                 /* regular exit ahead */
1161                 if (parent == next_inum)
1162                         break;
1163
1164                 slot = path->slots[0];
1165                 eb = path->nodes[0];
1166                 /* make sure we can use eb after releasing the path */
1167                 if (eb != eb_in) {
1168                         atomic_inc(&eb->refs);
1169                         btrfs_tree_read_lock(eb);
1170                         btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1171                 }
1172                 btrfs_release_path(path);
1173
1174                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1175                 parent = next_inum;
1176                 --bytes_left;
1177                 if (bytes_left >= 0)
1178                         dest[bytes_left] = '/';
1179         }
1180
1181         btrfs_release_path(path);
1182         path->leave_spinning = leave_spinning;
1183
1184         if (ret)
1185                 return ERR_PTR(ret);
1186
1187         return dest + bytes_left;
1188 }
1189
1190 /*
1191  * this makes the path point to (logical EXTENT_ITEM *)
1192  * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1193  * tree blocks and <0 on error.
1194  */
1195 int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1196                         struct btrfs_path *path, struct btrfs_key *found_key)
1197 {
1198         int ret;
1199         u64 flags;
1200         u32 item_size;
1201         struct extent_buffer *eb;
1202         struct btrfs_extent_item *ei;
1203         struct btrfs_key key;
1204
1205         key.type = BTRFS_EXTENT_ITEM_KEY;
1206         key.objectid = logical;
1207         key.offset = (u64)-1;
1208
1209         ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1210         if (ret < 0)
1211                 return ret;
1212         ret = btrfs_previous_item(fs_info->extent_root, path,
1213                                         0, BTRFS_EXTENT_ITEM_KEY);
1214         if (ret < 0)
1215                 return ret;
1216
1217         btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1218         if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
1219             found_key->objectid > logical ||
1220             found_key->objectid + found_key->offset <= logical) {
1221                 pr_debug("logical %llu is not within any extent\n",
1222                          (unsigned long long)logical);
1223                 return -ENOENT;
1224         }
1225
1226         eb = path->nodes[0];
1227         item_size = btrfs_item_size_nr(eb, path->slots[0]);
1228         BUG_ON(item_size < sizeof(*ei));
1229
1230         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1231         flags = btrfs_extent_flags(eb, ei);
1232
1233         pr_debug("logical %llu is at position %llu within the extent (%llu "
1234                  "EXTENT_ITEM %llu) flags %#llx size %u\n",
1235                  (unsigned long long)logical,
1236                  (unsigned long long)(logical - found_key->objectid),
1237                  (unsigned long long)found_key->objectid,
1238                  (unsigned long long)found_key->offset,
1239                  (unsigned long long)flags, item_size);
1240         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1241                 return BTRFS_EXTENT_FLAG_TREE_BLOCK;
1242         if (flags & BTRFS_EXTENT_FLAG_DATA)
1243                 return BTRFS_EXTENT_FLAG_DATA;
1244
1245         return -EIO;
1246 }
1247
1248 /*
1249  * helper function to iterate extent inline refs. ptr must point to a 0 value
1250  * for the first call and may be modified. it is used to track state.
1251  * if more refs exist, 0 is returned and the next call to
1252  * __get_extent_inline_ref must pass the modified ptr parameter to get the
1253  * next ref. after the last ref was processed, 1 is returned.
1254  * returns <0 on error
1255  */
1256 static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1257                                 struct btrfs_extent_item *ei, u32 item_size,
1258                                 struct btrfs_extent_inline_ref **out_eiref,
1259                                 int *out_type)
1260 {
1261         unsigned long end;
1262         u64 flags;
1263         struct btrfs_tree_block_info *info;
1264
1265         if (!*ptr) {
1266                 /* first call */
1267                 flags = btrfs_extent_flags(eb, ei);
1268                 if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1269                         info = (struct btrfs_tree_block_info *)(ei + 1);
1270                         *out_eiref =
1271                                 (struct btrfs_extent_inline_ref *)(info + 1);
1272                 } else {
1273                         *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1274                 }
1275                 *ptr = (unsigned long)*out_eiref;
1276                 if ((void *)*ptr >= (void *)ei + item_size)
1277                         return -ENOENT;
1278         }
1279
1280         end = (unsigned long)ei + item_size;
1281         *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1282         *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1283
1284         *ptr += btrfs_extent_inline_ref_size(*out_type);
1285         WARN_ON(*ptr > end);
1286         if (*ptr == end)
1287                 return 1; /* last */
1288
1289         return 0;
1290 }
1291
1292 /*
1293  * reads the tree block backref for an extent. tree level and root are returned
1294  * through out_level and out_root. ptr must point to a 0 value for the first
1295  * call and may be modified (see __get_extent_inline_ref comment).
1296  * returns 0 if data was provided, 1 if there was no more data to provide or
1297  * <0 on error.
1298  */
1299 int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1300                                 struct btrfs_extent_item *ei, u32 item_size,
1301                                 u64 *out_root, u8 *out_level)
1302 {
1303         int ret;
1304         int type;
1305         struct btrfs_tree_block_info *info;
1306         struct btrfs_extent_inline_ref *eiref;
1307
1308         if (*ptr == (unsigned long)-1)
1309                 return 1;
1310
1311         while (1) {
1312                 ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1313                                                 &eiref, &type);
1314                 if (ret < 0)
1315                         return ret;
1316
1317                 if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1318                     type == BTRFS_SHARED_BLOCK_REF_KEY)
1319                         break;
1320
1321                 if (ret == 1)
1322                         return 1;
1323         }
1324
1325         /* we can treat both ref types equally here */
1326         info = (struct btrfs_tree_block_info *)(ei + 1);
1327         *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1328         *out_level = btrfs_tree_block_level(eb, info);
1329
1330         if (ret == 1)
1331                 *ptr = (unsigned long)-1;
1332
1333         return 0;
1334 }
1335
1336 static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1337                                 u64 root, u64 extent_item_objectid,
1338                                 iterate_extent_inodes_t *iterate, void *ctx)
1339 {
1340         struct extent_inode_elem *eie;
1341         int ret = 0;
1342
1343         for (eie = inode_list; eie; eie = eie->next) {
1344                 pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1345                          "root %llu\n", extent_item_objectid,
1346                          eie->inum, eie->offset, root);
1347                 ret = iterate(eie->inum, eie->offset, root, ctx);
1348                 if (ret) {
1349                         pr_debug("stopping iteration for %llu due to ret=%d\n",
1350                                  extent_item_objectid, ret);
1351                         break;
1352                 }
1353         }
1354
1355         return ret;
1356 }
1357
1358 /*
1359  * calls iterate() for every inode that references the extent identified by
1360  * the given parameters.
1361  * when the iterator function returns a non-zero value, iteration stops.
1362  */
1363 int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1364                                 u64 extent_item_objectid, u64 extent_item_pos,
1365                                 int search_commit_root,
1366                                 iterate_extent_inodes_t *iterate, void *ctx)
1367 {
1368         int ret;
1369         struct list_head data_refs = LIST_HEAD_INIT(data_refs);
1370         struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
1371         struct btrfs_trans_handle *trans;
1372         struct ulist *refs = NULL;
1373         struct ulist *roots = NULL;
1374         struct ulist_node *ref_node = NULL;
1375         struct ulist_node *root_node = NULL;
1376         struct seq_list tree_mod_seq_elem = {};
1377         struct ulist_iterator ref_uiter;
1378         struct ulist_iterator root_uiter;
1379
1380         pr_debug("resolving all inodes for extent %llu\n",
1381                         extent_item_objectid);
1382
1383         if (search_commit_root) {
1384                 trans = BTRFS_BACKREF_SEARCH_COMMIT_ROOT;
1385         } else {
1386                 trans = btrfs_join_transaction(fs_info->extent_root);
1387                 if (IS_ERR(trans))
1388                         return PTR_ERR(trans);
1389                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1390         }
1391
1392         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1393                                    tree_mod_seq_elem.seq, &refs,
1394                                    &extent_item_pos);
1395         if (ret)
1396                 goto out;
1397
1398         ULIST_ITER_INIT(&ref_uiter);
1399         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1400                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1401                                            tree_mod_seq_elem.seq, &roots);
1402                 if (ret)
1403                         break;
1404                 ULIST_ITER_INIT(&root_uiter);
1405                 while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1406                         pr_debug("root %llu references leaf %llu, data list "
1407                                  "%#lx\n", root_node->val, ref_node->val,
1408                                  ref_node->aux);
1409                         ret = iterate_leaf_refs(
1410                                 (struct extent_inode_elem *)ref_node->aux,
1411                                 root_node->val, extent_item_objectid,
1412                                 iterate, ctx);
1413                 }
1414                 ulist_free(roots);
1415                 roots = NULL;
1416         }
1417
1418         free_leaf_list(refs);
1419         ulist_free(roots);
1420 out:
1421         if (!search_commit_root) {
1422                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1423                 btrfs_end_transaction(trans, fs_info->extent_root);
1424         }
1425
1426         return ret;
1427 }
1428
1429 int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1430                                 struct btrfs_path *path,
1431                                 iterate_extent_inodes_t *iterate, void *ctx)
1432 {
1433         int ret;
1434         u64 extent_item_pos;
1435         struct btrfs_key found_key;
1436         int search_commit_root = path->search_commit_root;
1437
1438         ret = extent_from_logical(fs_info, logical, path,
1439                                         &found_key);
1440         btrfs_release_path(path);
1441         if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1442                 ret = -EINVAL;
1443         if (ret < 0)
1444                 return ret;
1445
1446         extent_item_pos = logical - found_key.objectid;
1447         ret = iterate_extent_inodes(fs_info, found_key.objectid,
1448                                         extent_item_pos, search_commit_root,
1449                                         iterate, ctx);
1450
1451         return ret;
1452 }
1453
1454 static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1455                                 struct btrfs_path *path,
1456                                 iterate_irefs_t *iterate, void *ctx)
1457 {
1458         int ret = 0;
1459         int slot;
1460         u32 cur;
1461         u32 len;
1462         u32 name_len;
1463         u64 parent = 0;
1464         int found = 0;
1465         struct extent_buffer *eb;
1466         struct btrfs_item *item;
1467         struct btrfs_inode_ref *iref;
1468         struct btrfs_key found_key;
1469
1470         while (!ret) {
1471                 path->leave_spinning = 1;
1472                 ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1473                                         &found_key);
1474                 if (ret < 0)
1475                         break;
1476                 if (ret) {
1477                         ret = found ? 0 : -ENOENT;
1478                         break;
1479                 }
1480                 ++found;
1481
1482                 parent = found_key.offset;
1483                 slot = path->slots[0];
1484                 eb = path->nodes[0];
1485                 /* make sure we can use eb after releasing the path */
1486                 atomic_inc(&eb->refs);
1487                 btrfs_tree_read_lock(eb);
1488                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1489                 btrfs_release_path(path);
1490
1491                 item = btrfs_item_nr(eb, slot);
1492                 iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1493
1494                 for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1495                         name_len = btrfs_inode_ref_name_len(eb, iref);
1496                         /* path must be released before calling iterate()! */
1497                         pr_debug("following ref at offset %u for inode %llu in "
1498                                  "tree %llu\n", cur,
1499                                  (unsigned long long)found_key.objectid,
1500                                  (unsigned long long)fs_root->objectid);
1501                         ret = iterate(parent, iref, eb, ctx);
1502                         if (ret)
1503                                 break;
1504                         len = sizeof(*iref) + name_len;
1505                         iref = (struct btrfs_inode_ref *)((char *)iref + len);
1506                 }
1507                 btrfs_tree_read_unlock_blocking(eb);
1508                 free_extent_buffer(eb);
1509         }
1510
1511         btrfs_release_path(path);
1512
1513         return ret;
1514 }
1515
1516 /*
1517  * returns 0 if the path could be dumped (probably truncated)
1518  * returns <0 in case of an error
1519  */
1520 static int inode_to_path(u64 inum, struct btrfs_inode_ref *iref,
1521                                 struct extent_buffer *eb, void *ctx)
1522 {
1523         struct inode_fs_paths *ipath = ctx;
1524         char *fspath;
1525         char *fspath_min;
1526         int i = ipath->fspath->elem_cnt;
1527         const int s_ptr = sizeof(char *);
1528         u32 bytes_left;
1529
1530         bytes_left = ipath->fspath->bytes_left > s_ptr ?
1531                                         ipath->fspath->bytes_left - s_ptr : 0;
1532
1533         fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1534         fspath = btrfs_iref_to_path(ipath->fs_root, ipath->btrfs_path, iref, eb,
1535                                 inum, fspath_min, bytes_left);
1536         if (IS_ERR(fspath))
1537                 return PTR_ERR(fspath);
1538
1539         if (fspath > fspath_min) {
1540                 pr_debug("path resolved: %s\n", fspath);
1541                 ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1542                 ++ipath->fspath->elem_cnt;
1543                 ipath->fspath->bytes_left = fspath - fspath_min;
1544         } else {
1545                 pr_debug("missed path, not enough space. missing bytes: %lu, "
1546                          "constructed so far: %s\n",
1547                          (unsigned long)(fspath_min - fspath), fspath_min);
1548                 ++ipath->fspath->elem_missed;
1549                 ipath->fspath->bytes_missing += fspath_min - fspath;
1550                 ipath->fspath->bytes_left = 0;
1551         }
1552
1553         return 0;
1554 }
1555
1556 /*
1557  * this dumps all file system paths to the inode into the ipath struct, provided
1558  * is has been created large enough. each path is zero-terminated and accessed
1559  * from ipath->fspath->val[i].
1560  * when it returns, there are ipath->fspath->elem_cnt number of paths available
1561  * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1562  * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1563  * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1564  * have been needed to return all paths.
1565  */
1566 int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1567 {
1568         return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1569                                 inode_to_path, ipath);
1570 }
1571
1572 struct btrfs_data_container *init_data_container(u32 total_bytes)
1573 {
1574         struct btrfs_data_container *data;
1575         size_t alloc_bytes;
1576
1577         alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1578         data = kmalloc(alloc_bytes, GFP_NOFS);
1579         if (!data)
1580                 return ERR_PTR(-ENOMEM);
1581
1582         if (total_bytes >= sizeof(*data)) {
1583                 data->bytes_left = total_bytes - sizeof(*data);
1584                 data->bytes_missing = 0;
1585         } else {
1586                 data->bytes_missing = sizeof(*data) - total_bytes;
1587                 data->bytes_left = 0;
1588         }
1589
1590         data->elem_cnt = 0;
1591         data->elem_missed = 0;
1592
1593         return data;
1594 }
1595
1596 /*
1597  * allocates space to return multiple file system paths for an inode.
1598  * total_bytes to allocate are passed, note that space usable for actual path
1599  * information will be total_bytes - sizeof(struct inode_fs_paths).
1600  * the returned pointer must be freed with free_ipath() in the end.
1601  */
1602 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1603                                         struct btrfs_path *path)
1604 {
1605         struct inode_fs_paths *ifp;
1606         struct btrfs_data_container *fspath;
1607
1608         fspath = init_data_container(total_bytes);
1609         if (IS_ERR(fspath))
1610                 return (void *)fspath;
1611
1612         ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1613         if (!ifp) {
1614                 kfree(fspath);
1615                 return ERR_PTR(-ENOMEM);
1616         }
1617
1618         ifp->btrfs_path = path;
1619         ifp->fspath = fspath;
1620         ifp->fs_root = fs_root;
1621
1622         return ifp;
1623 }
1624
1625 void free_ipath(struct inode_fs_paths *ipath)
1626 {
1627         if (!ipath)
1628                 return;
1629         kfree(ipath->fspath);
1630         kfree(ipath);
1631 }