linux/fs/btrfs/backref.c
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   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 <linux/vmalloc.h>
  20#include "ctree.h"
  21#include "disk-io.h"
  22#include "backref.h"
  23#include "ulist.h"
  24#include "transaction.h"
  25#include "delayed-ref.h"
  26#include "locking.h"
  27
  28struct extent_inode_elem {
  29        u64 inum;
  30        u64 offset;
  31        struct extent_inode_elem *next;
  32};
  33
  34static int check_extent_in_eb(struct btrfs_key *key, struct extent_buffer *eb,
  35                                struct btrfs_file_extent_item *fi,
  36                                u64 extent_item_pos,
  37                                struct extent_inode_elem **eie)
  38{
  39        u64 data_offset;
  40        u64 data_len;
  41        struct extent_inode_elem *e;
  42
  43        data_offset = btrfs_file_extent_offset(eb, fi);
  44        data_len = btrfs_file_extent_num_bytes(eb, fi);
  45
  46        if (extent_item_pos < data_offset ||
  47            extent_item_pos >= data_offset + data_len)
  48                return 1;
  49
  50        e = kmalloc(sizeof(*e), GFP_NOFS);
  51        if (!e)
  52                return -ENOMEM;
  53
  54        e->next = *eie;
  55        e->inum = key->objectid;
  56        e->offset = key->offset + (extent_item_pos - data_offset);
  57        *eie = e;
  58
  59        return 0;
  60}
  61
  62static int find_extent_in_eb(struct extent_buffer *eb, u64 wanted_disk_byte,
  63                                u64 extent_item_pos,
  64                                struct extent_inode_elem **eie)
  65{
  66        u64 disk_byte;
  67        struct btrfs_key key;
  68        struct btrfs_file_extent_item *fi;
  69        int slot;
  70        int nritems;
  71        int extent_type;
  72        int ret;
  73
  74        /*
  75         * from the shared data ref, we only have the leaf but we need
  76         * the key. thus, we must look into all items and see that we
  77         * find one (some) with a reference to our extent item.
  78         */
  79        nritems = btrfs_header_nritems(eb);
  80        for (slot = 0; slot < nritems; ++slot) {
  81                btrfs_item_key_to_cpu(eb, &key, slot);
  82                if (key.type != BTRFS_EXTENT_DATA_KEY)
  83                        continue;
  84                fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
  85                extent_type = btrfs_file_extent_type(eb, fi);
  86                if (extent_type == BTRFS_FILE_EXTENT_INLINE)
  87                        continue;
  88                /* don't skip BTRFS_FILE_EXTENT_PREALLOC, we can handle that */
  89                disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
  90                if (disk_byte != wanted_disk_byte)
  91                        continue;
  92
  93                ret = check_extent_in_eb(&key, eb, fi, extent_item_pos, eie);
  94                if (ret < 0)
  95                        return ret;
  96        }
  97
  98        return 0;
  99}
 100
 101/*
 102 * this structure records all encountered refs on the way up to the root
 103 */
 104struct __prelim_ref {
 105        struct list_head list;
 106        u64 root_id;
 107        struct btrfs_key key_for_search;
 108        int level;
 109        int count;
 110        struct extent_inode_elem *inode_list;
 111        u64 parent;
 112        u64 wanted_disk_byte;
 113};
 114
 115/*
 116 * the rules for all callers of this function are:
 117 * - obtaining the parent is the goal
 118 * - if you add a key, you must know that it is a correct key
 119 * - if you cannot add the parent or a correct key, then we will look into the
 120 *   block later to set a correct key
 121 *
 122 * delayed refs
 123 * ============
 124 *        backref type | shared | indirect | shared | indirect
 125 * information         |   tree |     tree |   data |     data
 126 * --------------------+--------+----------+--------+----------
 127 *      parent logical |    y   |     -    |    -   |     -
 128 *      key to resolve |    -   |     y    |    y   |     y
 129 *  tree block logical |    -   |     -    |    -   |     -
 130 *  root for resolving |    y   |     y    |    y   |     y
 131 *
 132 * - column 1:       we've the parent -> done
 133 * - column 2, 3, 4: we use the key to find the parent
 134 *
 135 * on disk refs (inline or keyed)
 136 * ==============================
 137 *        backref type | shared | indirect | shared | indirect
 138 * information         |   tree |     tree |   data |     data
 139 * --------------------+--------+----------+--------+----------
 140 *      parent logical |    y   |     -    |    y   |     -
 141 *      key to resolve |    -   |     -    |    -   |     y
 142 *  tree block logical |    y   |     y    |    y   |     y
 143 *  root for resolving |    -   |     y    |    y   |     y
 144 *
 145 * - column 1, 3: we've the parent -> done
 146 * - column 2:    we take the first key from the block to find the parent
 147 *                (see __add_missing_keys)
 148 * - column 4:    we use the key to find the parent
 149 *
 150 * additional information that's available but not required to find the parent
 151 * block might help in merging entries to gain some speed.
 152 */
 153
 154static int __add_prelim_ref(struct list_head *head, u64 root_id,
 155                            struct btrfs_key *key, int level,
 156                            u64 parent, u64 wanted_disk_byte, int count)
 157{
 158        struct __prelim_ref *ref;
 159
 160        /* in case we're adding delayed refs, we're holding the refs spinlock */
 161        ref = kmalloc(sizeof(*ref), GFP_ATOMIC);
 162        if (!ref)
 163                return -ENOMEM;
 164
 165        ref->root_id = root_id;
 166        if (key)
 167                ref->key_for_search = *key;
 168        else
 169                memset(&ref->key_for_search, 0, sizeof(ref->key_for_search));
 170
 171        ref->inode_list = NULL;
 172        ref->level = level;
 173        ref->count = count;
 174        ref->parent = parent;
 175        ref->wanted_disk_byte = wanted_disk_byte;
 176        list_add_tail(&ref->list, head);
 177
 178        return 0;
 179}
 180
 181static int add_all_parents(struct btrfs_root *root, struct btrfs_path *path,
 182                                struct ulist *parents, int level,
 183                                struct btrfs_key *key_for_search, u64 time_seq,
 184                                u64 wanted_disk_byte,
 185                                const u64 *extent_item_pos)
 186{
 187        int ret = 0;
 188        int slot;
 189        struct extent_buffer *eb;
 190        struct btrfs_key key;
 191        struct btrfs_file_extent_item *fi;
 192        struct extent_inode_elem *eie = NULL;
 193        u64 disk_byte;
 194
 195        if (level != 0) {
 196                eb = path->nodes[level];
 197                ret = ulist_add(parents, eb->start, 0, GFP_NOFS);
 198                if (ret < 0)
 199                        return ret;
 200                return 0;
 201        }
 202
 203        /*
 204         * We normally enter this function with the path already pointing to
 205         * the first item to check. But sometimes, we may enter it with
 206         * slot==nritems. In that case, go to the next leaf before we continue.
 207         */
 208        if (path->slots[0] >= btrfs_header_nritems(path->nodes[0]))
 209                ret = btrfs_next_old_leaf(root, path, time_seq);
 210
 211        while (!ret) {
 212                eb = path->nodes[0];
 213                slot = path->slots[0];
 214
 215                btrfs_item_key_to_cpu(eb, &key, slot);
 216
 217                if (key.objectid != key_for_search->objectid ||
 218                    key.type != BTRFS_EXTENT_DATA_KEY)
 219                        break;
 220
 221                fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 222                disk_byte = btrfs_file_extent_disk_bytenr(eb, fi);
 223
 224                if (disk_byte == wanted_disk_byte) {
 225                        eie = NULL;
 226                        if (extent_item_pos) {
 227                                ret = check_extent_in_eb(&key, eb, fi,
 228                                                *extent_item_pos,
 229                                                &eie);
 230                                if (ret < 0)
 231                                        break;
 232                        }
 233                        if (!ret) {
 234                                ret = ulist_add(parents, eb->start,
 235                                                (uintptr_t)eie, GFP_NOFS);
 236                                if (ret < 0)
 237                                        break;
 238                                if (!extent_item_pos) {
 239                                        ret = btrfs_next_old_leaf(root, path,
 240                                                        time_seq);
 241                                        continue;
 242                                }
 243                        }
 244                }
 245                ret = btrfs_next_old_item(root, path, time_seq);
 246        }
 247
 248        if (ret > 0)
 249                ret = 0;
 250        return ret;
 251}
 252
 253/*
 254 * resolve an indirect backref in the form (root_id, key, level)
 255 * to a logical address
 256 */
 257static int __resolve_indirect_ref(struct btrfs_fs_info *fs_info,
 258                                        int search_commit_root,
 259                                        u64 time_seq,
 260                                        struct __prelim_ref *ref,
 261                                        struct ulist *parents,
 262                                        const u64 *extent_item_pos)
 263{
 264        struct btrfs_path *path;
 265        struct btrfs_root *root;
 266        struct btrfs_key root_key;
 267        struct extent_buffer *eb;
 268        int ret = 0;
 269        int root_level;
 270        int level = ref->level;
 271
 272        path = btrfs_alloc_path();
 273        if (!path)
 274                return -ENOMEM;
 275        path->search_commit_root = !!search_commit_root;
 276
 277        root_key.objectid = ref->root_id;
 278        root_key.type = BTRFS_ROOT_ITEM_KEY;
 279        root_key.offset = (u64)-1;
 280        root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 281        if (IS_ERR(root)) {
 282                ret = PTR_ERR(root);
 283                goto out;
 284        }
 285
 286        root_level = btrfs_old_root_level(root, time_seq);
 287
 288        if (root_level + 1 == level)
 289                goto out;
 290
 291        path->lowest_level = level;
 292        ret = btrfs_search_old_slot(root, &ref->key_for_search, path, time_seq);
 293        pr_debug("search slot in root %llu (level %d, ref count %d) returned "
 294                 "%d for key (%llu %u %llu)\n",
 295                 (unsigned long long)ref->root_id, level, ref->count, ret,
 296                 (unsigned long long)ref->key_for_search.objectid,
 297                 ref->key_for_search.type,
 298                 (unsigned long long)ref->key_for_search.offset);
 299        if (ret < 0)
 300                goto out;
 301
 302        eb = path->nodes[level];
 303        while (!eb) {
 304                if (!level) {
 305                        WARN_ON(1);
 306                        ret = 1;
 307                        goto out;
 308                }
 309                level--;
 310                eb = path->nodes[level];
 311        }
 312
 313        ret = add_all_parents(root, path, parents, level, &ref->key_for_search,
 314                                time_seq, ref->wanted_disk_byte,
 315                                extent_item_pos);
 316out:
 317        btrfs_free_path(path);
 318        return ret;
 319}
 320
 321/*
 322 * resolve all indirect backrefs from the list
 323 */
 324static int __resolve_indirect_refs(struct btrfs_fs_info *fs_info,
 325                                   int search_commit_root, u64 time_seq,
 326                                   struct list_head *head,
 327                                   const u64 *extent_item_pos)
 328{
 329        int err;
 330        int ret = 0;
 331        struct __prelim_ref *ref;
 332        struct __prelim_ref *ref_safe;
 333        struct __prelim_ref *new_ref;
 334        struct ulist *parents;
 335        struct ulist_node *node;
 336        struct ulist_iterator uiter;
 337
 338        parents = ulist_alloc(GFP_NOFS);
 339        if (!parents)
 340                return -ENOMEM;
 341
 342        /*
 343         * _safe allows us to insert directly after the current item without
 344         * iterating over the newly inserted items.
 345         * we're also allowed to re-assign ref during iteration.
 346         */
 347        list_for_each_entry_safe(ref, ref_safe, head, list) {
 348                if (ref->parent)        /* already direct */
 349                        continue;
 350                if (ref->count == 0)
 351                        continue;
 352                err = __resolve_indirect_ref(fs_info, search_commit_root,
 353                                             time_seq, ref, parents,
 354                                             extent_item_pos);
 355                if (err) {
 356                        if (ret == 0)
 357                                ret = err;
 358                        continue;
 359                }
 360
 361                /* we put the first parent into the ref at hand */
 362                ULIST_ITER_INIT(&uiter);
 363                node = ulist_next(parents, &uiter);
 364                ref->parent = node ? node->val : 0;
 365                ref->inode_list = node ?
 366                        (struct extent_inode_elem *)(uintptr_t)node->aux : 0;
 367
 368                /* additional parents require new refs being added here */
 369                while ((node = ulist_next(parents, &uiter))) {
 370                        new_ref = kmalloc(sizeof(*new_ref), GFP_NOFS);
 371                        if (!new_ref) {
 372                                ret = -ENOMEM;
 373                                break;
 374                        }
 375                        memcpy(new_ref, ref, sizeof(*ref));
 376                        new_ref->parent = node->val;
 377                        new_ref->inode_list = (struct extent_inode_elem *)
 378                                                        (uintptr_t)node->aux;
 379                        list_add(&new_ref->list, &ref->list);
 380                }
 381                ulist_reinit(parents);
 382        }
 383
 384        ulist_free(parents);
 385        return ret;
 386}
 387
 388static inline int ref_for_same_block(struct __prelim_ref *ref1,
 389                                     struct __prelim_ref *ref2)
 390{
 391        if (ref1->level != ref2->level)
 392                return 0;
 393        if (ref1->root_id != ref2->root_id)
 394                return 0;
 395        if (ref1->key_for_search.type != ref2->key_for_search.type)
 396                return 0;
 397        if (ref1->key_for_search.objectid != ref2->key_for_search.objectid)
 398                return 0;
 399        if (ref1->key_for_search.offset != ref2->key_for_search.offset)
 400                return 0;
 401        if (ref1->parent != ref2->parent)
 402                return 0;
 403
 404        return 1;
 405}
 406
 407/*
 408 * read tree blocks and add keys where required.
 409 */
 410static int __add_missing_keys(struct btrfs_fs_info *fs_info,
 411                              struct list_head *head)
 412{
 413        struct list_head *pos;
 414        struct extent_buffer *eb;
 415
 416        list_for_each(pos, head) {
 417                struct __prelim_ref *ref;
 418                ref = list_entry(pos, struct __prelim_ref, list);
 419
 420                if (ref->parent)
 421                        continue;
 422                if (ref->key_for_search.type)
 423                        continue;
 424                BUG_ON(!ref->wanted_disk_byte);
 425                eb = read_tree_block(fs_info->tree_root, ref->wanted_disk_byte,
 426                                     fs_info->tree_root->leafsize, 0);
 427                BUG_ON(!eb);
 428                btrfs_tree_read_lock(eb);
 429                if (btrfs_header_level(eb) == 0)
 430                        btrfs_item_key_to_cpu(eb, &ref->key_for_search, 0);
 431                else
 432                        btrfs_node_key_to_cpu(eb, &ref->key_for_search, 0);
 433                btrfs_tree_read_unlock(eb);
 434                free_extent_buffer(eb);
 435        }
 436        return 0;
 437}
 438
 439/*
 440 * merge two lists of backrefs and adjust counts accordingly
 441 *
 442 * mode = 1: merge identical keys, if key is set
 443 *    FIXME: if we add more keys in __add_prelim_ref, we can merge more here.
 444 *           additionally, we could even add a key range for the blocks we
 445 *           looked into to merge even more (-> replace unresolved refs by those
 446 *           having a parent).
 447 * mode = 2: merge identical parents
 448 */
 449static int __merge_refs(struct list_head *head, int mode)
 450{
 451        struct list_head *pos1;
 452
 453        list_for_each(pos1, head) {
 454                struct list_head *n2;
 455                struct list_head *pos2;
 456                struct __prelim_ref *ref1;
 457
 458                ref1 = list_entry(pos1, struct __prelim_ref, list);
 459
 460                for (pos2 = pos1->next, n2 = pos2->next; pos2 != head;
 461                     pos2 = n2, n2 = pos2->next) {
 462                        struct __prelim_ref *ref2;
 463                        struct __prelim_ref *xchg;
 464
 465                        ref2 = list_entry(pos2, struct __prelim_ref, list);
 466
 467                        if (mode == 1) {
 468                                if (!ref_for_same_block(ref1, ref2))
 469                                        continue;
 470                                if (!ref1->parent && ref2->parent) {
 471                                        xchg = ref1;
 472                                        ref1 = ref2;
 473                                        ref2 = xchg;
 474                                }
 475                                ref1->count += ref2->count;
 476                        } else {
 477                                if (ref1->parent != ref2->parent)
 478                                        continue;
 479                                ref1->count += ref2->count;
 480                        }
 481                        list_del(&ref2->list);
 482                        kfree(ref2);
 483                }
 484
 485        }
 486        return 0;
 487}
 488
 489/*
 490 * add all currently queued delayed refs from this head whose seq nr is
 491 * smaller or equal that seq to the list
 492 */
 493static int __add_delayed_refs(struct btrfs_delayed_ref_head *head, u64 seq,
 494                              struct list_head *prefs)
 495{
 496        struct btrfs_delayed_extent_op *extent_op = head->extent_op;
 497        struct rb_node *n = &head->node.rb_node;
 498        struct btrfs_key key;
 499        struct btrfs_key op_key = {0};
 500        int sgn;
 501        int ret = 0;
 502
 503        if (extent_op && extent_op->update_key)
 504                btrfs_disk_key_to_cpu(&op_key, &extent_op->key);
 505
 506        while ((n = rb_prev(n))) {
 507                struct btrfs_delayed_ref_node *node;
 508                node = rb_entry(n, struct btrfs_delayed_ref_node,
 509                                rb_node);
 510                if (node->bytenr != head->node.bytenr)
 511                        break;
 512                WARN_ON(node->is_head);
 513
 514                if (node->seq > seq)
 515                        continue;
 516
 517                switch (node->action) {
 518                case BTRFS_ADD_DELAYED_EXTENT:
 519                case BTRFS_UPDATE_DELAYED_HEAD:
 520                        WARN_ON(1);
 521                        continue;
 522                case BTRFS_ADD_DELAYED_REF:
 523                        sgn = 1;
 524                        break;
 525                case BTRFS_DROP_DELAYED_REF:
 526                        sgn = -1;
 527                        break;
 528                default:
 529                        BUG_ON(1);
 530                }
 531                switch (node->type) {
 532                case BTRFS_TREE_BLOCK_REF_KEY: {
 533                        struct btrfs_delayed_tree_ref *ref;
 534
 535                        ref = btrfs_delayed_node_to_tree_ref(node);
 536                        ret = __add_prelim_ref(prefs, ref->root, &op_key,
 537                                               ref->level + 1, 0, node->bytenr,
 538                                               node->ref_mod * sgn);
 539                        break;
 540                }
 541                case BTRFS_SHARED_BLOCK_REF_KEY: {
 542                        struct btrfs_delayed_tree_ref *ref;
 543
 544                        ref = btrfs_delayed_node_to_tree_ref(node);
 545                        ret = __add_prelim_ref(prefs, ref->root, NULL,
 546                                               ref->level + 1, ref->parent,
 547                                               node->bytenr,
 548                                               node->ref_mod * sgn);
 549                        break;
 550                }
 551                case BTRFS_EXTENT_DATA_REF_KEY: {
 552                        struct btrfs_delayed_data_ref *ref;
 553                        ref = btrfs_delayed_node_to_data_ref(node);
 554
 555                        key.objectid = ref->objectid;
 556                        key.type = BTRFS_EXTENT_DATA_KEY;
 557                        key.offset = ref->offset;
 558                        ret = __add_prelim_ref(prefs, ref->root, &key, 0, 0,
 559                                               node->bytenr,
 560                                               node->ref_mod * sgn);
 561                        break;
 562                }
 563                case BTRFS_SHARED_DATA_REF_KEY: {
 564                        struct btrfs_delayed_data_ref *ref;
 565
 566                        ref = btrfs_delayed_node_to_data_ref(node);
 567
 568                        key.objectid = ref->objectid;
 569                        key.type = BTRFS_EXTENT_DATA_KEY;
 570                        key.offset = ref->offset;
 571                        ret = __add_prelim_ref(prefs, ref->root, &key, 0,
 572                                               ref->parent, node->bytenr,
 573                                               node->ref_mod * sgn);
 574                        break;
 575                }
 576                default:
 577                        WARN_ON(1);
 578                }
 579                BUG_ON(ret);
 580        }
 581
 582        return 0;
 583}
 584
 585/*
 586 * add all inline backrefs for bytenr to the list
 587 */
 588static int __add_inline_refs(struct btrfs_fs_info *fs_info,
 589                             struct btrfs_path *path, u64 bytenr,
 590                             int *info_level, struct list_head *prefs)
 591{
 592        int ret = 0;
 593        int slot;
 594        struct extent_buffer *leaf;
 595        struct btrfs_key key;
 596        unsigned long ptr;
 597        unsigned long end;
 598        struct btrfs_extent_item *ei;
 599        u64 flags;
 600        u64 item_size;
 601
 602        /*
 603         * enumerate all inline refs
 604         */
 605        leaf = path->nodes[0];
 606        slot = path->slots[0];
 607
 608        item_size = btrfs_item_size_nr(leaf, slot);
 609        BUG_ON(item_size < sizeof(*ei));
 610
 611        ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
 612        flags = btrfs_extent_flags(leaf, ei);
 613
 614        ptr = (unsigned long)(ei + 1);
 615        end = (unsigned long)ei + item_size;
 616
 617        if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 618                struct btrfs_tree_block_info *info;
 619
 620                info = (struct btrfs_tree_block_info *)ptr;
 621                *info_level = btrfs_tree_block_level(leaf, info);
 622                ptr += sizeof(struct btrfs_tree_block_info);
 623                BUG_ON(ptr > end);
 624        } else {
 625                BUG_ON(!(flags & BTRFS_EXTENT_FLAG_DATA));
 626        }
 627
 628        while (ptr < end) {
 629                struct btrfs_extent_inline_ref *iref;
 630                u64 offset;
 631                int type;
 632
 633                iref = (struct btrfs_extent_inline_ref *)ptr;
 634                type = btrfs_extent_inline_ref_type(leaf, iref);
 635                offset = btrfs_extent_inline_ref_offset(leaf, iref);
 636
 637                switch (type) {
 638                case BTRFS_SHARED_BLOCK_REF_KEY:
 639                        ret = __add_prelim_ref(prefs, 0, NULL,
 640                                                *info_level + 1, offset,
 641                                                bytenr, 1);
 642                        break;
 643                case BTRFS_SHARED_DATA_REF_KEY: {
 644                        struct btrfs_shared_data_ref *sdref;
 645                        int count;
 646
 647                        sdref = (struct btrfs_shared_data_ref *)(iref + 1);
 648                        count = btrfs_shared_data_ref_count(leaf, sdref);
 649                        ret = __add_prelim_ref(prefs, 0, NULL, 0, offset,
 650                                               bytenr, count);
 651                        break;
 652                }
 653                case BTRFS_TREE_BLOCK_REF_KEY:
 654                        ret = __add_prelim_ref(prefs, offset, NULL,
 655                                               *info_level + 1, 0,
 656                                               bytenr, 1);
 657                        break;
 658                case BTRFS_EXTENT_DATA_REF_KEY: {
 659                        struct btrfs_extent_data_ref *dref;
 660                        int count;
 661                        u64 root;
 662
 663                        dref = (struct btrfs_extent_data_ref *)(&iref->offset);
 664                        count = btrfs_extent_data_ref_count(leaf, dref);
 665                        key.objectid = btrfs_extent_data_ref_objectid(leaf,
 666                                                                      dref);
 667                        key.type = BTRFS_EXTENT_DATA_KEY;
 668                        key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 669                        root = btrfs_extent_data_ref_root(leaf, dref);
 670                        ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 671                                               bytenr, count);
 672                        break;
 673                }
 674                default:
 675                        WARN_ON(1);
 676                }
 677                BUG_ON(ret);
 678                ptr += btrfs_extent_inline_ref_size(type);
 679        }
 680
 681        return 0;
 682}
 683
 684/*
 685 * add all non-inline backrefs for bytenr to the list
 686 */
 687static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
 688                            struct btrfs_path *path, u64 bytenr,
 689                            int info_level, struct list_head *prefs)
 690{
 691        struct btrfs_root *extent_root = fs_info->extent_root;
 692        int ret;
 693        int slot;
 694        struct extent_buffer *leaf;
 695        struct btrfs_key key;
 696
 697        while (1) {
 698                ret = btrfs_next_item(extent_root, path);
 699                if (ret < 0)
 700                        break;
 701                if (ret) {
 702                        ret = 0;
 703                        break;
 704                }
 705
 706                slot = path->slots[0];
 707                leaf = path->nodes[0];
 708                btrfs_item_key_to_cpu(leaf, &key, slot);
 709
 710                if (key.objectid != bytenr)
 711                        break;
 712                if (key.type < BTRFS_TREE_BLOCK_REF_KEY)
 713                        continue;
 714                if (key.type > BTRFS_SHARED_DATA_REF_KEY)
 715                        break;
 716
 717                switch (key.type) {
 718                case BTRFS_SHARED_BLOCK_REF_KEY:
 719                        ret = __add_prelim_ref(prefs, 0, NULL,
 720                                                info_level + 1, key.offset,
 721                                                bytenr, 1);
 722                        break;
 723                case BTRFS_SHARED_DATA_REF_KEY: {
 724                        struct btrfs_shared_data_ref *sdref;
 725                        int count;
 726
 727                        sdref = btrfs_item_ptr(leaf, slot,
 728                                              struct btrfs_shared_data_ref);
 729                        count = btrfs_shared_data_ref_count(leaf, sdref);
 730                        ret = __add_prelim_ref(prefs, 0, NULL, 0, key.offset,
 731                                                bytenr, count);
 732                        break;
 733                }
 734                case BTRFS_TREE_BLOCK_REF_KEY:
 735                        ret = __add_prelim_ref(prefs, key.offset, NULL,
 736                                               info_level + 1, 0,
 737                                               bytenr, 1);
 738                        break;
 739                case BTRFS_EXTENT_DATA_REF_KEY: {
 740                        struct btrfs_extent_data_ref *dref;
 741                        int count;
 742                        u64 root;
 743
 744                        dref = btrfs_item_ptr(leaf, slot,
 745                                              struct btrfs_extent_data_ref);
 746                        count = btrfs_extent_data_ref_count(leaf, dref);
 747                        key.objectid = btrfs_extent_data_ref_objectid(leaf,
 748                                                                      dref);
 749                        key.type = BTRFS_EXTENT_DATA_KEY;
 750                        key.offset = btrfs_extent_data_ref_offset(leaf, dref);
 751                        root = btrfs_extent_data_ref_root(leaf, dref);
 752                        ret = __add_prelim_ref(prefs, root, &key, 0, 0,
 753                                               bytenr, count);
 754                        break;
 755                }
 756                default:
 757                        WARN_ON(1);
 758                }
 759                BUG_ON(ret);
 760        }
 761
 762        return ret;
 763}
 764
 765/*
 766 * this adds all existing backrefs (inline backrefs, backrefs and delayed
 767 * refs) for the given bytenr to the refs list, merges duplicates and resolves
 768 * indirect refs to their parent bytenr.
 769 * When roots are found, they're added to the roots list
 770 *
 771 * FIXME some caching might speed things up
 772 */
 773static int find_parent_nodes(struct btrfs_trans_handle *trans,
 774                             struct btrfs_fs_info *fs_info, u64 bytenr,
 775                             u64 time_seq, struct ulist *refs,
 776                             struct ulist *roots, const u64 *extent_item_pos)
 777{
 778        struct btrfs_key key;
 779        struct btrfs_path *path;
 780        struct btrfs_delayed_ref_root *delayed_refs = NULL;
 781        struct btrfs_delayed_ref_head *head;
 782        int info_level = 0;
 783        int ret;
 784        int search_commit_root = (trans == BTRFS_BACKREF_SEARCH_COMMIT_ROOT);
 785        struct list_head prefs_delayed;
 786        struct list_head prefs;
 787        struct __prelim_ref *ref;
 788
 789        INIT_LIST_HEAD(&prefs);
 790        INIT_LIST_HEAD(&prefs_delayed);
 791
 792        key.objectid = bytenr;
 793        key.type = BTRFS_EXTENT_ITEM_KEY;
 794        key.offset = (u64)-1;
 795
 796        path = btrfs_alloc_path();
 797        if (!path)
 798                return -ENOMEM;
 799        path->search_commit_root = !!search_commit_root;
 800
 801        /*
 802         * grab both a lock on the path and a lock on the delayed ref head.
 803         * We need both to get a consistent picture of how the refs look
 804         * at a specified point in time
 805         */
 806again:
 807        head = NULL;
 808
 809        ret = btrfs_search_slot(trans, fs_info->extent_root, &key, path, 0, 0);
 810        if (ret < 0)
 811                goto out;
 812        BUG_ON(ret == 0);
 813
 814        if (trans != BTRFS_BACKREF_SEARCH_COMMIT_ROOT) {
 815                /*
 816                 * look if there are updates for this ref queued and lock the
 817                 * head
 818                 */
 819                delayed_refs = &trans->transaction->delayed_refs;
 820                spin_lock(&delayed_refs->lock);
 821                head = btrfs_find_delayed_ref_head(trans, bytenr);
 822                if (head) {
 823                        if (!mutex_trylock(&head->mutex)) {
 824                                atomic_inc(&head->node.refs);
 825                                spin_unlock(&delayed_refs->lock);
 826
 827                                btrfs_release_path(path);
 828
 829                                /*
 830                                 * Mutex was contended, block until it's
 831                                 * released and try again
 832                                 */
 833                                mutex_lock(&head->mutex);
 834                                mutex_unlock(&head->mutex);
 835                                btrfs_put_delayed_ref(&head->node);
 836                                goto again;
 837                        }
 838                        ret = __add_delayed_refs(head, time_seq,
 839                                                 &prefs_delayed);
 840                        mutex_unlock(&head->mutex);
 841                        if (ret) {
 842                                spin_unlock(&delayed_refs->lock);
 843                                goto out;
 844                        }
 845                }
 846                spin_unlock(&delayed_refs->lock);
 847        }
 848
 849        if (path->slots[0]) {
 850                struct extent_buffer *leaf;
 851                int slot;
 852
 853                path->slots[0]--;
 854                leaf = path->nodes[0];
 855                slot = path->slots[0];
 856                btrfs_item_key_to_cpu(leaf, &key, slot);
 857                if (key.objectid == bytenr &&
 858                    key.type == BTRFS_EXTENT_ITEM_KEY) {
 859                        ret = __add_inline_refs(fs_info, path, bytenr,
 860                                                &info_level, &prefs);
 861                        if (ret)
 862                                goto out;
 863                        ret = __add_keyed_refs(fs_info, path, bytenr,
 864                                               info_level, &prefs);
 865                        if (ret)
 866                                goto out;
 867                }
 868        }
 869        btrfs_release_path(path);
 870
 871        list_splice_init(&prefs_delayed, &prefs);
 872
 873        ret = __add_missing_keys(fs_info, &prefs);
 874        if (ret)
 875                goto out;
 876
 877        ret = __merge_refs(&prefs, 1);
 878        if (ret)
 879                goto out;
 880
 881        ret = __resolve_indirect_refs(fs_info, search_commit_root, time_seq,
 882                                      &prefs, extent_item_pos);
 883        if (ret)
 884                goto out;
 885
 886        ret = __merge_refs(&prefs, 2);
 887        if (ret)
 888                goto out;
 889
 890        while (!list_empty(&prefs)) {
 891                ref = list_first_entry(&prefs, struct __prelim_ref, list);
 892                list_del(&ref->list);
 893                if (ref->count < 0)
 894                        WARN_ON(1);
 895                if (ref->count && ref->root_id && ref->parent == 0) {
 896                        /* no parent == root of tree */
 897                        ret = ulist_add(roots, ref->root_id, 0, GFP_NOFS);
 898                        BUG_ON(ret < 0);
 899                }
 900                if (ref->count && ref->parent) {
 901                        struct extent_inode_elem *eie = NULL;
 902                        if (extent_item_pos && !ref->inode_list) {
 903                                u32 bsz;
 904                                struct extent_buffer *eb;
 905                                bsz = btrfs_level_size(fs_info->extent_root,
 906                                                        info_level);
 907                                eb = read_tree_block(fs_info->extent_root,
 908                                                           ref->parent, bsz, 0);
 909                                BUG_ON(!eb);
 910                                ret = find_extent_in_eb(eb, bytenr,
 911                                                        *extent_item_pos, &eie);
 912                                ref->inode_list = eie;
 913                                free_extent_buffer(eb);
 914                        }
 915                        ret = ulist_add_merge(refs, ref->parent,
 916                                              (uintptr_t)ref->inode_list,
 917                                              (u64 *)&eie, GFP_NOFS);
 918                        if (!ret && extent_item_pos) {
 919                                /*
 920                                 * we've recorded that parent, so we must extend
 921                                 * its inode list here
 922                                 */
 923                                BUG_ON(!eie);
 924                                while (eie->next)
 925                                        eie = eie->next;
 926                                eie->next = ref->inode_list;
 927                        }
 928                        BUG_ON(ret < 0);
 929                }
 930                kfree(ref);
 931        }
 932
 933out:
 934        btrfs_free_path(path);
 935        while (!list_empty(&prefs)) {
 936                ref = list_first_entry(&prefs, struct __prelim_ref, list);
 937                list_del(&ref->list);
 938                kfree(ref);
 939        }
 940        while (!list_empty(&prefs_delayed)) {
 941                ref = list_first_entry(&prefs_delayed, struct __prelim_ref,
 942                                       list);
 943                list_del(&ref->list);
 944                kfree(ref);
 945        }
 946
 947        return ret;
 948}
 949
 950static void free_leaf_list(struct ulist *blocks)
 951{
 952        struct ulist_node *node = NULL;
 953        struct extent_inode_elem *eie;
 954        struct extent_inode_elem *eie_next;
 955        struct ulist_iterator uiter;
 956
 957        ULIST_ITER_INIT(&uiter);
 958        while ((node = ulist_next(blocks, &uiter))) {
 959                if (!node->aux)
 960                        continue;
 961                eie = (struct extent_inode_elem *)(uintptr_t)node->aux;
 962                for (; eie; eie = eie_next) {
 963                        eie_next = eie->next;
 964                        kfree(eie);
 965                }
 966                node->aux = 0;
 967        }
 968
 969        ulist_free(blocks);
 970}
 971
 972/*
 973 * Finds all leafs with a reference to the specified combination of bytenr and
 974 * offset. key_list_head will point to a list of corresponding keys (caller must
 975 * free each list element). The leafs will be stored in the leafs ulist, which
 976 * must be freed with ulist_free.
 977 *
 978 * returns 0 on success, <0 on error
 979 */
 980static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
 981                                struct btrfs_fs_info *fs_info, u64 bytenr,
 982                                u64 time_seq, struct ulist **leafs,
 983                                const u64 *extent_item_pos)
 984{
 985        struct ulist *tmp;
 986        int ret;
 987
 988        tmp = ulist_alloc(GFP_NOFS);
 989        if (!tmp)
 990                return -ENOMEM;
 991        *leafs = ulist_alloc(GFP_NOFS);
 992        if (!*leafs) {
 993                ulist_free(tmp);
 994                return -ENOMEM;
 995        }
 996
 997        ret = find_parent_nodes(trans, fs_info, bytenr,
 998                                time_seq, *leafs, tmp, extent_item_pos);
 999        ulist_free(tmp);
1000
1001        if (ret < 0 && ret != -ENOENT) {
1002                free_leaf_list(*leafs);
1003                return ret;
1004        }
1005
1006        return 0;
1007}
1008
1009/*
1010 * walk all backrefs for a given extent to find all roots that reference this
1011 * extent. Walking a backref means finding all extents that reference this
1012 * extent and in turn walk the backrefs of those, too. Naturally this is a
1013 * recursive process, but here it is implemented in an iterative fashion: We
1014 * find all referencing extents for the extent in question and put them on a
1015 * list. In turn, we find all referencing extents for those, further appending
1016 * to the list. The way we iterate the list allows adding more elements after
1017 * the current while iterating. The process stops when we reach the end of the
1018 * list. Found roots are added to the roots list.
1019 *
1020 * returns 0 on success, < 0 on error.
1021 */
1022int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
1023                                struct btrfs_fs_info *fs_info, u64 bytenr,
1024                                u64 time_seq, struct ulist **roots)
1025{
1026        struct ulist *tmp;
1027        struct ulist_node *node = NULL;
1028        struct ulist_iterator uiter;
1029        int ret;
1030
1031        tmp = ulist_alloc(GFP_NOFS);
1032        if (!tmp)
1033                return -ENOMEM;
1034        *roots = ulist_alloc(GFP_NOFS);
1035        if (!*roots) {
1036                ulist_free(tmp);
1037                return -ENOMEM;
1038        }
1039
1040        ULIST_ITER_INIT(&uiter);
1041        while (1) {
1042                ret = find_parent_nodes(trans, fs_info, bytenr,
1043                                        time_seq, tmp, *roots, NULL);
1044                if (ret < 0 && ret != -ENOENT) {
1045                        ulist_free(tmp);
1046                        ulist_free(*roots);
1047                        return ret;
1048                }
1049                node = ulist_next(tmp, &uiter);
1050                if (!node)
1051                        break;
1052                bytenr = node->val;
1053        }
1054
1055        ulist_free(tmp);
1056        return 0;
1057}
1058
1059
1060static int __inode_info(u64 inum, u64 ioff, u8 key_type,
1061                        struct btrfs_root *fs_root, struct btrfs_path *path,
1062                        struct btrfs_key *found_key)
1063{
1064        int ret;
1065        struct btrfs_key key;
1066        struct extent_buffer *eb;
1067
1068        key.type = key_type;
1069        key.objectid = inum;
1070        key.offset = ioff;
1071
1072        ret = btrfs_search_slot(NULL, fs_root, &key, path, 0, 0);
1073        if (ret < 0)
1074                return ret;
1075
1076        eb = path->nodes[0];
1077        if (ret && path->slots[0] >= btrfs_header_nritems(eb)) {
1078                ret = btrfs_next_leaf(fs_root, path);
1079                if (ret)
1080                        return ret;
1081                eb = path->nodes[0];
1082        }
1083
1084        btrfs_item_key_to_cpu(eb, found_key, path->slots[0]);
1085        if (found_key->type != key.type || found_key->objectid != key.objectid)
1086                return 1;
1087
1088        return 0;
1089}
1090
1091/*
1092 * this makes the path point to (inum INODE_ITEM ioff)
1093 */
1094int inode_item_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1095                        struct btrfs_path *path)
1096{
1097        struct btrfs_key key;
1098        return __inode_info(inum, ioff, BTRFS_INODE_ITEM_KEY, fs_root, path,
1099                                &key);
1100}
1101
1102static int inode_ref_info(u64 inum, u64 ioff, struct btrfs_root *fs_root,
1103                                struct btrfs_path *path,
1104                                struct btrfs_key *found_key)
1105{
1106        return __inode_info(inum, ioff, BTRFS_INODE_REF_KEY, fs_root, path,
1107                                found_key);
1108}
1109
1110int btrfs_find_one_extref(struct btrfs_root *root, u64 inode_objectid,
1111                          u64 start_off, struct btrfs_path *path,
1112                          struct btrfs_inode_extref **ret_extref,
1113                          u64 *found_off)
1114{
1115        int ret, slot;
1116        struct btrfs_key key;
1117        struct btrfs_key found_key;
1118        struct btrfs_inode_extref *extref;
1119        struct extent_buffer *leaf;
1120        unsigned long ptr;
1121
1122        key.objectid = inode_objectid;
1123        btrfs_set_key_type(&key, BTRFS_INODE_EXTREF_KEY);
1124        key.offset = start_off;
1125
1126        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1127        if (ret < 0)
1128                return ret;
1129
1130        while (1) {
1131                leaf = path->nodes[0];
1132                slot = path->slots[0];
1133                if (slot >= btrfs_header_nritems(leaf)) {
1134                        /*
1135                         * If the item at offset is not found,
1136                         * btrfs_search_slot will point us to the slot
1137                         * where it should be inserted. In our case
1138                         * that will be the slot directly before the
1139                         * next INODE_REF_KEY_V2 item. In the case
1140                         * that we're pointing to the last slot in a
1141                         * leaf, we must move one leaf over.
1142                         */
1143                        ret = btrfs_next_leaf(root, path);
1144                        if (ret) {
1145                                if (ret >= 1)
1146                                        ret = -ENOENT;
1147                                break;
1148                        }
1149                        continue;
1150                }
1151
1152                btrfs_item_key_to_cpu(leaf, &found_key, slot);
1153
1154                /*
1155                 * Check that we're still looking at an extended ref key for
1156                 * this particular objectid. If we have different
1157                 * objectid or type then there are no more to be found
1158                 * in the tree and we can exit.
1159                 */
1160                ret = -ENOENT;
1161                if (found_key.objectid != inode_objectid)
1162                        break;
1163                if (btrfs_key_type(&found_key) != BTRFS_INODE_EXTREF_KEY)
1164                        break;
1165
1166                ret = 0;
1167                ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1168                extref = (struct btrfs_inode_extref *)ptr;
1169                *ret_extref = extref;
1170                if (found_off)
1171                        *found_off = found_key.offset;
1172                break;
1173        }
1174
1175        return ret;
1176}
1177
1178char *btrfs_ref_to_path(struct btrfs_root *fs_root, struct btrfs_path *path,
1179                        u32 name_len, unsigned long name_off,
1180                        struct extent_buffer *eb_in, u64 parent,
1181                        char *dest, u32 size)
1182{
1183        int slot;
1184        u64 next_inum;
1185        int ret;
1186        s64 bytes_left = ((s64)size) - 1;
1187        struct extent_buffer *eb = eb_in;
1188        struct btrfs_key found_key;
1189        int leave_spinning = path->leave_spinning;
1190        struct btrfs_inode_ref *iref;
1191
1192        if (bytes_left >= 0)
1193                dest[bytes_left] = '\0';
1194
1195        path->leave_spinning = 1;
1196        while (1) {
1197                bytes_left -= name_len;
1198                if (bytes_left >= 0)
1199                        read_extent_buffer(eb, dest + bytes_left,
1200                                           name_off, name_len);
1201                if (eb != eb_in) {
1202                        btrfs_tree_read_unlock_blocking(eb);
1203                        free_extent_buffer(eb);
1204                }
1205                ret = inode_ref_info(parent, 0, fs_root, path, &found_key);
1206                if (ret > 0)
1207                        ret = -ENOENT;
1208                if (ret)
1209                        break;
1210
1211                next_inum = found_key.offset;
1212
1213                /* regular exit ahead */
1214                if (parent == next_inum)
1215                        break;
1216
1217                slot = path->slots[0];
1218                eb = path->nodes[0];
1219                /* make sure we can use eb after releasing the path */
1220                if (eb != eb_in) {
1221                        atomic_inc(&eb->refs);
1222                        btrfs_tree_read_lock(eb);
1223                        btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1224                }
1225                btrfs_release_path(path);
1226                iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1227
1228                name_len = btrfs_inode_ref_name_len(eb, iref);
1229                name_off = (unsigned long)(iref + 1);
1230
1231                parent = next_inum;
1232                --bytes_left;
1233                if (bytes_left >= 0)
1234                        dest[bytes_left] = '/';
1235        }
1236
1237        btrfs_release_path(path);
1238        path->leave_spinning = leave_spinning;
1239
1240        if (ret)
1241                return ERR_PTR(ret);
1242
1243        return dest + bytes_left;
1244}
1245
1246/*
1247 * this iterates to turn a btrfs_inode_ref into a full filesystem path. elements
1248 * of the path are separated by '/' and the path is guaranteed to be
1249 * 0-terminated. the path is only given within the current file system.
1250 * Therefore, it never starts with a '/'. the caller is responsible to provide
1251 * "size" bytes in "dest". the dest buffer will be filled backwards. finally,
1252 * the start point of the resulting string is returned. this pointer is within
1253 * dest, normally.
1254 * in case the path buffer would overflow, the pointer is decremented further
1255 * as if output was written to the buffer, though no more output is actually
1256 * generated. that way, the caller can determine how much space would be
1257 * required for the path to fit into the buffer. in that case, the returned
1258 * value will be smaller than dest. callers must check this!
1259 */
1260char *btrfs_iref_to_path(struct btrfs_root *fs_root,
1261                         struct btrfs_path *path,
1262                         struct btrfs_inode_ref *iref,
1263                         struct extent_buffer *eb_in, u64 parent,
1264                         char *dest, u32 size)
1265{
1266        return btrfs_ref_to_path(fs_root, path,
1267                                 btrfs_inode_ref_name_len(eb_in, iref),
1268                                 (unsigned long)(iref + 1),
1269                                 eb_in, parent, dest, size);
1270}
1271
1272/*
1273 * this makes the path point to (logical EXTENT_ITEM *)
1274 * returns BTRFS_EXTENT_FLAG_DATA for data, BTRFS_EXTENT_FLAG_TREE_BLOCK for
1275 * tree blocks and <0 on error.
1276 */
1277int extent_from_logical(struct btrfs_fs_info *fs_info, u64 logical,
1278                        struct btrfs_path *path, struct btrfs_key *found_key,
1279                        u64 *flags_ret)
1280{
1281        int ret;
1282        u64 flags;
1283        u32 item_size;
1284        struct extent_buffer *eb;
1285        struct btrfs_extent_item *ei;
1286        struct btrfs_key key;
1287
1288        key.type = BTRFS_EXTENT_ITEM_KEY;
1289        key.objectid = logical;
1290        key.offset = (u64)-1;
1291
1292        ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, path, 0, 0);
1293        if (ret < 0)
1294                return ret;
1295        ret = btrfs_previous_item(fs_info->extent_root, path,
1296                                        0, BTRFS_EXTENT_ITEM_KEY);
1297        if (ret < 0)
1298                return ret;
1299
1300        btrfs_item_key_to_cpu(path->nodes[0], found_key, path->slots[0]);
1301        if (found_key->type != BTRFS_EXTENT_ITEM_KEY ||
1302            found_key->objectid > logical ||
1303            found_key->objectid + found_key->offset <= logical) {
1304                pr_debug("logical %llu is not within any extent\n",
1305                         (unsigned long long)logical);
1306                return -ENOENT;
1307        }
1308
1309        eb = path->nodes[0];
1310        item_size = btrfs_item_size_nr(eb, path->slots[0]);
1311        BUG_ON(item_size < sizeof(*ei));
1312
1313        ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
1314        flags = btrfs_extent_flags(eb, ei);
1315
1316        pr_debug("logical %llu is at position %llu within the extent (%llu "
1317                 "EXTENT_ITEM %llu) flags %#llx size %u\n",
1318                 (unsigned long long)logical,
1319                 (unsigned long long)(logical - found_key->objectid),
1320                 (unsigned long long)found_key->objectid,
1321                 (unsigned long long)found_key->offset,
1322                 (unsigned long long)flags, item_size);
1323
1324        WARN_ON(!flags_ret);
1325        if (flags_ret) {
1326                if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1327                        *flags_ret = BTRFS_EXTENT_FLAG_TREE_BLOCK;
1328                else if (flags & BTRFS_EXTENT_FLAG_DATA)
1329                        *flags_ret = BTRFS_EXTENT_FLAG_DATA;
1330                else
1331                        BUG_ON(1);
1332                return 0;
1333        }
1334
1335        return -EIO;
1336}
1337
1338/*
1339 * helper function to iterate extent inline refs. ptr must point to a 0 value
1340 * for the first call and may be modified. it is used to track state.
1341 * if more refs exist, 0 is returned and the next call to
1342 * __get_extent_inline_ref must pass the modified ptr parameter to get the
1343 * next ref. after the last ref was processed, 1 is returned.
1344 * returns <0 on error
1345 */
1346static int __get_extent_inline_ref(unsigned long *ptr, struct extent_buffer *eb,
1347                                struct btrfs_extent_item *ei, u32 item_size,
1348                                struct btrfs_extent_inline_ref **out_eiref,
1349                                int *out_type)
1350{
1351        unsigned long end;
1352        u64 flags;
1353        struct btrfs_tree_block_info *info;
1354
1355        if (!*ptr) {
1356                /* first call */
1357                flags = btrfs_extent_flags(eb, ei);
1358                if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1359                        info = (struct btrfs_tree_block_info *)(ei + 1);
1360                        *out_eiref =
1361                                (struct btrfs_extent_inline_ref *)(info + 1);
1362                } else {
1363                        *out_eiref = (struct btrfs_extent_inline_ref *)(ei + 1);
1364                }
1365                *ptr = (unsigned long)*out_eiref;
1366                if ((void *)*ptr >= (void *)ei + item_size)
1367                        return -ENOENT;
1368        }
1369
1370        end = (unsigned long)ei + item_size;
1371        *out_eiref = (struct btrfs_extent_inline_ref *)*ptr;
1372        *out_type = btrfs_extent_inline_ref_type(eb, *out_eiref);
1373
1374        *ptr += btrfs_extent_inline_ref_size(*out_type);
1375        WARN_ON(*ptr > end);
1376        if (*ptr == end)
1377                return 1; /* last */
1378
1379        return 0;
1380}
1381
1382/*
1383 * reads the tree block backref for an extent. tree level and root are returned
1384 * through out_level and out_root. ptr must point to a 0 value for the first
1385 * call and may be modified (see __get_extent_inline_ref comment).
1386 * returns 0 if data was provided, 1 if there was no more data to provide or
1387 * <0 on error.
1388 */
1389int tree_backref_for_extent(unsigned long *ptr, struct extent_buffer *eb,
1390                                struct btrfs_extent_item *ei, u32 item_size,
1391                                u64 *out_root, u8 *out_level)
1392{
1393        int ret;
1394        int type;
1395        struct btrfs_tree_block_info *info;
1396        struct btrfs_extent_inline_ref *eiref;
1397
1398        if (*ptr == (unsigned long)-1)
1399                return 1;
1400
1401        while (1) {
1402                ret = __get_extent_inline_ref(ptr, eb, ei, item_size,
1403                                                &eiref, &type);
1404                if (ret < 0)
1405                        return ret;
1406
1407                if (type == BTRFS_TREE_BLOCK_REF_KEY ||
1408                    type == BTRFS_SHARED_BLOCK_REF_KEY)
1409                        break;
1410
1411                if (ret == 1)
1412                        return 1;
1413        }
1414
1415        /* we can treat both ref types equally here */
1416        info = (struct btrfs_tree_block_info *)(ei + 1);
1417        *out_root = btrfs_extent_inline_ref_offset(eb, eiref);
1418        *out_level = btrfs_tree_block_level(eb, info);
1419
1420        if (ret == 1)
1421                *ptr = (unsigned long)-1;
1422
1423        return 0;
1424}
1425
1426static int iterate_leaf_refs(struct extent_inode_elem *inode_list,
1427                                u64 root, u64 extent_item_objectid,
1428                                iterate_extent_inodes_t *iterate, void *ctx)
1429{
1430        struct extent_inode_elem *eie;
1431        int ret = 0;
1432
1433        for (eie = inode_list; eie; eie = eie->next) {
1434                pr_debug("ref for %llu resolved, key (%llu EXTEND_DATA %llu), "
1435                         "root %llu\n", extent_item_objectid,
1436                         eie->inum, eie->offset, root);
1437                ret = iterate(eie->inum, eie->offset, root, ctx);
1438                if (ret) {
1439                        pr_debug("stopping iteration for %llu due to ret=%d\n",
1440                                 extent_item_objectid, ret);
1441                        break;
1442                }
1443        }
1444
1445        return ret;
1446}
1447
1448/*
1449 * calls iterate() for every inode that references the extent identified by
1450 * the given parameters.
1451 * when the iterator function returns a non-zero value, iteration stops.
1452 */
1453int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
1454                                u64 extent_item_objectid, u64 extent_item_pos,
1455                                int search_commit_root,
1456                                iterate_extent_inodes_t *iterate, void *ctx)
1457{
1458        int ret;
1459        struct list_head data_refs = LIST_HEAD_INIT(data_refs);
1460        struct list_head shared_refs = LIST_HEAD_INIT(shared_refs);
1461        struct btrfs_trans_handle *trans;
1462        struct ulist *refs = NULL;
1463        struct ulist *roots = NULL;
1464        struct ulist_node *ref_node = NULL;
1465        struct ulist_node *root_node = NULL;
1466        struct seq_list tree_mod_seq_elem = {};
1467        struct ulist_iterator ref_uiter;
1468        struct ulist_iterator root_uiter;
1469
1470        pr_debug("resolving all inodes for extent %llu\n",
1471                        extent_item_objectid);
1472
1473        if (search_commit_root) {
1474                trans = BTRFS_BACKREF_SEARCH_COMMIT_ROOT;
1475        } else {
1476                trans = btrfs_join_transaction(fs_info->extent_root);
1477                if (IS_ERR(trans))
1478                        return PTR_ERR(trans);
1479                btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1480        }
1481
1482        ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
1483                                   tree_mod_seq_elem.seq, &refs,
1484                                   &extent_item_pos);
1485        if (ret)
1486                goto out;
1487
1488        ULIST_ITER_INIT(&ref_uiter);
1489        while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
1490                ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
1491                                           tree_mod_seq_elem.seq, &roots);
1492                if (ret)
1493                        break;
1494                ULIST_ITER_INIT(&root_uiter);
1495                while (!ret && (root_node = ulist_next(roots, &root_uiter))) {
1496                        pr_debug("root %llu references leaf %llu, data list "
1497                                 "%#llx\n", root_node->val, ref_node->val,
1498                                 (long long)ref_node->aux);
1499                        ret = iterate_leaf_refs((struct extent_inode_elem *)
1500                                                (uintptr_t)ref_node->aux,
1501                                                root_node->val,
1502                                                extent_item_objectid,
1503                                                iterate, ctx);
1504                }
1505                ulist_free(roots);
1506                roots = NULL;
1507        }
1508
1509        free_leaf_list(refs);
1510        ulist_free(roots);
1511out:
1512        if (!search_commit_root) {
1513                btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
1514                btrfs_end_transaction(trans, fs_info->extent_root);
1515        }
1516
1517        return ret;
1518}
1519
1520int iterate_inodes_from_logical(u64 logical, struct btrfs_fs_info *fs_info,
1521                                struct btrfs_path *path,
1522                                iterate_extent_inodes_t *iterate, void *ctx)
1523{
1524        int ret;
1525        u64 extent_item_pos;
1526        u64 flags = 0;
1527        struct btrfs_key found_key;
1528        int search_commit_root = path->search_commit_root;
1529
1530        ret = extent_from_logical(fs_info, logical, path, &found_key, &flags);
1531        btrfs_release_path(path);
1532        if (ret < 0)
1533                return ret;
1534        if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1535                return -EINVAL;
1536
1537        extent_item_pos = logical - found_key.objectid;
1538        ret = iterate_extent_inodes(fs_info, found_key.objectid,
1539                                        extent_item_pos, search_commit_root,
1540                                        iterate, ctx);
1541
1542        return ret;
1543}
1544
1545typedef int (iterate_irefs_t)(u64 parent, u32 name_len, unsigned long name_off,
1546                              struct extent_buffer *eb, void *ctx);
1547
1548static int iterate_inode_refs(u64 inum, struct btrfs_root *fs_root,
1549                              struct btrfs_path *path,
1550                              iterate_irefs_t *iterate, void *ctx)
1551{
1552        int ret = 0;
1553        int slot;
1554        u32 cur;
1555        u32 len;
1556        u32 name_len;
1557        u64 parent = 0;
1558        int found = 0;
1559        struct extent_buffer *eb;
1560        struct btrfs_item *item;
1561        struct btrfs_inode_ref *iref;
1562        struct btrfs_key found_key;
1563
1564        while (!ret) {
1565                path->leave_spinning = 1;
1566                ret = inode_ref_info(inum, parent ? parent+1 : 0, fs_root, path,
1567                                     &found_key);
1568                if (ret < 0)
1569                        break;
1570                if (ret) {
1571                        ret = found ? 0 : -ENOENT;
1572                        break;
1573                }
1574                ++found;
1575
1576                parent = found_key.offset;
1577                slot = path->slots[0];
1578                eb = path->nodes[0];
1579                /* make sure we can use eb after releasing the path */
1580                atomic_inc(&eb->refs);
1581                btrfs_tree_read_lock(eb);
1582                btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1583                btrfs_release_path(path);
1584
1585                item = btrfs_item_nr(eb, slot);
1586                iref = btrfs_item_ptr(eb, slot, struct btrfs_inode_ref);
1587
1588                for (cur = 0; cur < btrfs_item_size(eb, item); cur += len) {
1589                        name_len = btrfs_inode_ref_name_len(eb, iref);
1590                        /* path must be released before calling iterate()! */
1591                        pr_debug("following ref at offset %u for inode %llu in "
1592                                 "tree %llu\n", cur,
1593                                 (unsigned long long)found_key.objectid,
1594                                 (unsigned long long)fs_root->objectid);
1595                        ret = iterate(parent, name_len,
1596                                      (unsigned long)(iref + 1), eb, ctx);
1597                        if (ret)
1598                                break;
1599                        len = sizeof(*iref) + name_len;
1600                        iref = (struct btrfs_inode_ref *)((char *)iref + len);
1601                }
1602                btrfs_tree_read_unlock_blocking(eb);
1603                free_extent_buffer(eb);
1604        }
1605
1606        btrfs_release_path(path);
1607
1608        return ret;
1609}
1610
1611static int iterate_inode_extrefs(u64 inum, struct btrfs_root *fs_root,
1612                                 struct btrfs_path *path,
1613                                 iterate_irefs_t *iterate, void *ctx)
1614{
1615        int ret;
1616        int slot;
1617        u64 offset = 0;
1618        u64 parent;
1619        int found = 0;
1620        struct extent_buffer *eb;
1621        struct btrfs_inode_extref *extref;
1622        struct extent_buffer *leaf;
1623        u32 item_size;
1624        u32 cur_offset;
1625        unsigned long ptr;
1626
1627        while (1) {
1628                ret = btrfs_find_one_extref(fs_root, inum, offset, path, &extref,
1629                                            &offset);
1630                if (ret < 0)
1631                        break;
1632                if (ret) {
1633                        ret = found ? 0 : -ENOENT;
1634                        break;
1635                }
1636                ++found;
1637
1638                slot = path->slots[0];
1639                eb = path->nodes[0];
1640                /* make sure we can use eb after releasing the path */
1641                atomic_inc(&eb->refs);
1642
1643                btrfs_tree_read_lock(eb);
1644                btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
1645                btrfs_release_path(path);
1646
1647                leaf = path->nodes[0];
1648                item_size = btrfs_item_size_nr(leaf, path->slots[0]);
1649                ptr = btrfs_item_ptr_offset(leaf, path->slots[0]);
1650                cur_offset = 0;
1651
1652                while (cur_offset < item_size) {
1653                        u32 name_len;
1654
1655                        extref = (struct btrfs_inode_extref *)(ptr + cur_offset);
1656                        parent = btrfs_inode_extref_parent(eb, extref);
1657                        name_len = btrfs_inode_extref_name_len(eb, extref);
1658                        ret = iterate(parent, name_len,
1659                                      (unsigned long)&extref->name, eb, ctx);
1660                        if (ret)
1661                                break;
1662
1663                        cur_offset += btrfs_inode_extref_name_len(leaf, extref);
1664                        cur_offset += sizeof(*extref);
1665                }
1666                btrfs_tree_read_unlock_blocking(eb);
1667                free_extent_buffer(eb);
1668
1669                offset++;
1670        }
1671
1672        btrfs_release_path(path);
1673
1674        return ret;
1675}
1676
1677static int iterate_irefs(u64 inum, struct btrfs_root *fs_root,
1678                         struct btrfs_path *path, iterate_irefs_t *iterate,
1679                         void *ctx)
1680{
1681        int ret;
1682        int found_refs = 0;
1683
1684        ret = iterate_inode_refs(inum, fs_root, path, iterate, ctx);
1685        if (!ret)
1686                ++found_refs;
1687        else if (ret != -ENOENT)
1688                return ret;
1689
1690        ret = iterate_inode_extrefs(inum, fs_root, path, iterate, ctx);
1691        if (ret == -ENOENT && found_refs)
1692                return 0;
1693
1694        return ret;
1695}
1696
1697/*
1698 * returns 0 if the path could be dumped (probably truncated)
1699 * returns <0 in case of an error
1700 */
1701static int inode_to_path(u64 inum, u32 name_len, unsigned long name_off,
1702                         struct extent_buffer *eb, void *ctx)
1703{
1704        struct inode_fs_paths *ipath = ctx;
1705        char *fspath;
1706        char *fspath_min;
1707        int i = ipath->fspath->elem_cnt;
1708        const int s_ptr = sizeof(char *);
1709        u32 bytes_left;
1710
1711        bytes_left = ipath->fspath->bytes_left > s_ptr ?
1712                                        ipath->fspath->bytes_left - s_ptr : 0;
1713
1714        fspath_min = (char *)ipath->fspath->val + (i + 1) * s_ptr;
1715        fspath = btrfs_ref_to_path(ipath->fs_root, ipath->btrfs_path, name_len,
1716                                   name_off, eb, inum, fspath_min, bytes_left);
1717        if (IS_ERR(fspath))
1718                return PTR_ERR(fspath);
1719
1720        if (fspath > fspath_min) {
1721                ipath->fspath->val[i] = (u64)(unsigned long)fspath;
1722                ++ipath->fspath->elem_cnt;
1723                ipath->fspath->bytes_left = fspath - fspath_min;
1724        } else {
1725                ++ipath->fspath->elem_missed;
1726                ipath->fspath->bytes_missing += fspath_min - fspath;
1727                ipath->fspath->bytes_left = 0;
1728        }
1729
1730        return 0;
1731}
1732
1733/*
1734 * this dumps all file system paths to the inode into the ipath struct, provided
1735 * is has been created large enough. each path is zero-terminated and accessed
1736 * from ipath->fspath->val[i].
1737 * when it returns, there are ipath->fspath->elem_cnt number of paths available
1738 * in ipath->fspath->val[]. when the allocated space wasn't sufficient, the
1739 * number of missed paths in recored in ipath->fspath->elem_missed, otherwise,
1740 * it's zero. ipath->fspath->bytes_missing holds the number of bytes that would
1741 * have been needed to return all paths.
1742 */
1743int paths_from_inode(u64 inum, struct inode_fs_paths *ipath)
1744{
1745        return iterate_irefs(inum, ipath->fs_root, ipath->btrfs_path,
1746                             inode_to_path, ipath);
1747}
1748
1749struct btrfs_data_container *init_data_container(u32 total_bytes)
1750{
1751        struct btrfs_data_container *data;
1752        size_t alloc_bytes;
1753
1754        alloc_bytes = max_t(size_t, total_bytes, sizeof(*data));
1755        data = vmalloc(alloc_bytes);
1756        if (!data)
1757                return ERR_PTR(-ENOMEM);
1758
1759        if (total_bytes >= sizeof(*data)) {
1760                data->bytes_left = total_bytes - sizeof(*data);
1761                data->bytes_missing = 0;
1762        } else {
1763                data->bytes_missing = sizeof(*data) - total_bytes;
1764                data->bytes_left = 0;
1765        }
1766
1767        data->elem_cnt = 0;
1768        data->elem_missed = 0;
1769
1770        return data;
1771}
1772
1773/*
1774 * allocates space to return multiple file system paths for an inode.
1775 * total_bytes to allocate are passed, note that space usable for actual path
1776 * information will be total_bytes - sizeof(struct inode_fs_paths).
1777 * the returned pointer must be freed with free_ipath() in the end.
1778 */
1779struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
1780                                        struct btrfs_path *path)
1781{
1782        struct inode_fs_paths *ifp;
1783        struct btrfs_data_container *fspath;
1784
1785        fspath = init_data_container(total_bytes);
1786        if (IS_ERR(fspath))
1787                return (void *)fspath;
1788
1789        ifp = kmalloc(sizeof(*ifp), GFP_NOFS);
1790        if (!ifp) {
1791                kfree(fspath);
1792                return ERR_PTR(-ENOMEM);
1793        }
1794
1795        ifp->btrfs_path = path;
1796        ifp->fspath = fspath;
1797        ifp->fs_root = fs_root;
1798
1799        return ifp;
1800}
1801
1802void free_ipath(struct inode_fs_paths *ipath)
1803{
1804        if (!ipath)
1805                return;
1806        vfree(ipath->fspath);
1807        kfree(ipath);
1808}
1809
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