fs/btrfs/file-item.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  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/bio.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/highmem.h>
  22 #include "ctree.h"
  23 #include "disk-io.h"
  24 #include "transaction.h"
  25 #include "print-tree.h"
  26
  27 #define MAX_CSUM_ITEMS(r, size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
  28                                    sizeof(struct btrfs_item) * 2) / \
  29                                   size) - 1))
  30 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  31                              struct btrfs_root *root,
  32                              u64 objectid, u64 pos,
  33                              u64 disk_offset, u64 disk_num_bytes,
  34                              u64 num_bytes, u64 offset, u64 ram_bytes,
  35                              u8 compression, u8 encryption, u16 other_encoding)
  36 {
  37         int ret = 0;
  38         struct btrfs_file_extent_item *item;
  39         struct btrfs_key file_key;
  40         struct btrfs_path *path;
  41         struct extent_buffer *leaf;
  42
  43         path = btrfs_alloc_path();
  44         BUG_ON(!path);
  45         file_key.objectid = objectid;
  46         file_key.offset = pos;
  47         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  48
  49         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  50                                       sizeof(*item));
  51         if (ret < 0)
  52                 goto out;
  53         BUG_ON(ret);
  54         leaf = path->nodes[0];
  55         item = btrfs_item_ptr(leaf, path->slots[0],
  56                               struct btrfs_file_extent_item);
  57         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  58         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  59         btrfs_set_file_extent_offset(leaf, item, offset);
  60         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  61         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  62         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  63         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  64         btrfs_set_file_extent_compression(leaf, item, compression);
  65         btrfs_set_file_extent_encryption(leaf, item, encryption);
  66         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  67
  68         btrfs_mark_buffer_dirty(leaf);
  69 out:
  70         btrfs_free_path(path);
  71         return ret;
  72 }
  73
  74 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  75                                           struct btrfs_root *root,
  76                                           struct btrfs_path *path,
  77                                           u64 bytenr, int cow)
  78 {
  79         int ret;
  80         struct btrfs_key file_key;
  81         struct btrfs_key found_key;
  82         struct btrfs_csum_item *item;
  83         struct extent_buffer *leaf;
  84         u64 csum_offset = 0;
  85         u16 csum_size =
  86                 btrfs_super_csum_size(&root->fs_info->super_copy);
  87         int csums_in_item;
  88
  89         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  90         file_key.offset = bytenr;
  91         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
  92         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
  93         if (ret < 0)
  94                 goto fail;
  95         leaf = path->nodes[0];
  96         if (ret > 0) {
  97                 ret = 1;
  98                 if (path->slots[0] == 0)
  99                         goto fail;
 100                 path->slots[0]--;
 101                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 102                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 103                         goto fail;
 104
 105                 csum_offset = (bytenr - found_key.offset) >>
 106                                 root->fs_info->sb->s_blocksize_bits;
 107                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 108                 csums_in_item /= csum_size;
 109
 110                 if (csum_offset >= csums_in_item) {
 111                         ret = -EFBIG;
 112                         goto fail;
 113                 }
 114         }
 115         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 116         item = (struct btrfs_csum_item *)((unsigned char *)item +
 117                                           csum_offset * csum_size);
 118         return item;
 119 fail:
 120         if (ret > 0)
 121                 ret = -ENOENT;
 122         return ERR_PTR(ret);
 123 }
 124
 125
 126 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 127                              struct btrfs_root *root,
 128                              struct btrfs_path *path, u64 objectid,
 129                              u64 offset, int mod)
 130 {
 131         int ret;
 132         struct btrfs_key file_key;
 133         int ins_len = mod < 0 ? -1 : 0;
 134         int cow = mod != 0;
 135
 136         file_key.objectid = objectid;
 137         file_key.offset = offset;
 138         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 139         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 140         return ret;
 141 }
 142
 143
 144 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 145                           struct bio *bio, u32 *dst)
 146 {
 147         u32 sum;
 148         struct bio_vec *bvec = bio->bi_io_vec;
 149         int bio_index = 0;
 150         u64 offset;
 151         u64 item_start_offset = 0;
 152         u64 item_last_offset = 0;
 153         u64 disk_bytenr;
 154         u32 diff;
 155         u16 csum_size =
 156                 btrfs_super_csum_size(&root->fs_info->super_copy);
 157         int ret;
 158         struct btrfs_path *path;
 159         struct btrfs_csum_item *item = NULL;
 160         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 161
 162         path = btrfs_alloc_path();
 163         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 164                 path->reada = 2;
 165
 166         WARN_ON(bio->bi_vcnt <= 0);
 167
 168         disk_bytenr = (u64)bio->bi_sector << 9;
 169         while (bio_index < bio->bi_vcnt) {
 170                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 171                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 172                 if (ret == 0)
 173                         goto found;
 174
 175                 if (!item || disk_bytenr < item_start_offset ||
 176                     disk_bytenr >= item_last_offset) {
 177                         struct btrfs_key found_key;
 178                         u32 item_size;
 179
 180                         if (item)
 181                                 btrfs_release_path(root, path);
 182                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 183                                                  path, disk_bytenr, 0);
 184                         if (IS_ERR(item)) {
 185                                 ret = PTR_ERR(item);
 186                                 if (ret == -ENOENT || ret == -EFBIG)
 187                                         ret = 0;
 188                                 sum = 0;
 189                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 190                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 191                                         set_extent_bits(io_tree, offset,
 192                                                 offset + bvec->bv_len - 1,
 193                                                 EXTENT_NODATASUM, GFP_NOFS);
 194                                 } else {
 195                                         printk(KERN_INFO "btrfs no csum found "
 196                                                "for inode %lu start %llu\n",
 197                                                inode->i_ino,
 198                                                (unsigned long long)offset);
 199                                 }
 200                                 item = NULL;
 201                                 btrfs_release_path(root, path);
 202                                 goto found;
 203                         }
 204                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 205                                               path->slots[0]);
 206
 207                         item_start_offset = found_key.offset;
 208                         item_size = btrfs_item_size_nr(path->nodes[0],
 209                                                        path->slots[0]);
 210                         item_last_offset = item_start_offset +
 211                                 (item_size / csum_size) *
 212                                 root->sectorsize;
 213                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 214                                               struct btrfs_csum_item);
 215                 }
 216                 /*
 217                  * this byte range must be able to fit inside
 218                  * a single leaf so it will also fit inside a u32
 219                  */
 220                 diff = disk_bytenr - item_start_offset;
 221                 diff = diff / root->sectorsize;
 222                 diff = diff * csum_size;
 223
 224                 read_extent_buffer(path->nodes[0], &sum,
 225                                    ((unsigned long)item) + diff,
 226                                    csum_size);
 227 found:
 228                 if (dst)
 229                         *dst++ = sum;
 230                 else
 231                         set_state_private(io_tree, offset, sum);
 232                 disk_bytenr += bvec->bv_len;
 233                 bio_index++;
 234                 bvec++;
 235         }
 236         btrfs_free_path(path);
 237         return 0;
 238 }
 239
 240 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 241                              struct list_head *list)
 242 {
 243         struct btrfs_key key;
 244         struct btrfs_path *path;
 245         struct extent_buffer *leaf;
 246         struct btrfs_ordered_sum *sums;
 247         struct btrfs_sector_sum *sector_sum;
 248         struct btrfs_csum_item *item;
 249         unsigned long offset;
 250         int ret;
 251         size_t size;
 252         u64 csum_end;
 253         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 254
 255         path = btrfs_alloc_path();
 256         BUG_ON(!path);
 257
 258         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 259         key.offset = start;
 260         key.type = BTRFS_EXTENT_CSUM_KEY;
 261
 262         ret = btrfs_search_slot(NULL, root->fs_info->csum_root,
 263                                 &key, path, 0, 0);
 264         if (ret < 0)
 265                 goto fail;
 266         if (ret > 0 && path->slots[0] > 0) {
 267                 leaf = path->nodes[0];
 268                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 269                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 270                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 271                         offset = (start - key.offset) >>
 272                                  root->fs_info->sb->s_blocksize_bits;
 273                         if (offset * csum_size <
 274                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 275                                 path->slots[0]--;
 276                 }
 277         }
 278
 279         while (start <= end) {
 280                 leaf = path->nodes[0];
 281                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 282                         ret = btrfs_next_leaf(root->fs_info->csum_root, path);
 283                         if (ret < 0)
 284                                 goto fail;
 285                         if (ret > 0)
 286                                 break;
 287                         leaf = path->nodes[0];
 288                 }
 289
 290                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 291                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 292                     key.type != BTRFS_EXTENT_CSUM_KEY)
 293                         break;
 294
 295                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 296                 if (key.offset > end)
 297                         break;
 298
 299                 if (key.offset > start)
 300                         start = key.offset;
 301
 302                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 303                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 304                 if (csum_end <= start) {
 305                         path->slots[0]++;
 306                         continue;
 307                 }
 308
 309                 size = min(csum_end, end + 1) - start;
 310                 sums = kzalloc(btrfs_ordered_sum_size(root, size), GFP_NOFS);
 311                 BUG_ON(!sums);
 312
 313                 sector_sum = sums->sums;
 314                 sums->bytenr = start;
 315                 sums->len = size;
 316
 317                 offset = (start - key.offset) >>
 318                          root->fs_info->sb->s_blocksize_bits;
 319                 offset *= csum_size;
 320
 321                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 322                                       struct btrfs_csum_item);
 323                 while (size > 0) {
 324                         read_extent_buffer(path->nodes[0], &sector_sum->sum,
 325                                            ((unsigned long)item) + offset,
 326                                            csum_size);
 327                         sector_sum->bytenr = start;
 328
 329                         size -= root->sectorsize;
 330                         start += root->sectorsize;
 331                         offset += csum_size;
 332                         sector_sum++;
 333                 }
 334                 list_add_tail(&sums->list, list);
 335
 336                 path->slots[0]++;
 337         }
 338         ret = 0;
 339 fail:
 340         btrfs_free_path(path);
 341         return ret;
 342 }
 343
 344 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 345                        struct bio *bio, u64 file_start, int contig)
 346 {
 347         struct btrfs_ordered_sum *sums;
 348         struct btrfs_sector_sum *sector_sum;
 349         struct btrfs_ordered_extent *ordered;
 350         char *data;
 351         struct bio_vec *bvec = bio->bi_io_vec;
 352         int bio_index = 0;
 353         unsigned long total_bytes = 0;
 354         unsigned long this_sum_bytes = 0;
 355         u64 offset;
 356         u64 disk_bytenr;
 357
 358         WARN_ON(bio->bi_vcnt <= 0);
 359         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 360         if (!sums)
 361                 return -ENOMEM;
 362
 363         sector_sum = sums->sums;
 364         disk_bytenr = (u64)bio->bi_sector << 9;
 365         sums->len = bio->bi_size;
 366         INIT_LIST_HEAD(&sums->list);
 367
 368         if (contig)
 369                 offset = file_start;
 370         else
 371                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 372
 373         ordered = btrfs_lookup_ordered_extent(inode, offset);
 374         BUG_ON(!ordered);
 375         sums->bytenr = ordered->start;
 376
 377         while (bio_index < bio->bi_vcnt) {
 378                 if (!contig)
 379                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 380
 381                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 382                     offset < ordered->file_offset)) {
 383                         unsigned long bytes_left;
 384                         sums->len = this_sum_bytes;
 385                         this_sum_bytes = 0;
 386                         btrfs_add_ordered_sum(inode, ordered, sums);
 387                         btrfs_put_ordered_extent(ordered);
 388
 389                         bytes_left = bio->bi_size - total_bytes;
 390
 391                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 392                                        GFP_NOFS);
 393                         BUG_ON(!sums);
 394                         sector_sum = sums->sums;
 395                         sums->len = bytes_left;
 396                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 397                         BUG_ON(!ordered);
 398                         sums->bytenr = ordered->start;
 399                 }
 400
 401                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 402                 sector_sum->sum = ~(u32)0;
 403                 sector_sum->sum = btrfs_csum_data(root,
 404                                                   data + bvec->bv_offset,
 405                                                   sector_sum->sum,
 406                                                   bvec->bv_len);
 407                 kunmap_atomic(data, KM_USER0);
 408                 btrfs_csum_final(sector_sum->sum,
 409                                  (char *)&sector_sum->sum);
 410                 sector_sum->bytenr = disk_bytenr;
 411
 412                 sector_sum++;
 413                 bio_index++;
 414                 total_bytes += bvec->bv_len;
 415                 this_sum_bytes += bvec->bv_len;
 416                 disk_bytenr += bvec->bv_len;
 417                 offset += bvec->bv_len;
 418                 bvec++;
 419         }
 420         this_sum_bytes = 0;
 421         btrfs_add_ordered_sum(inode, ordered, sums);
 422         btrfs_put_ordered_extent(ordered);
 423         return 0;
 424 }
 425
 426 /*
 427  * helper function for csum removal, this expects the
 428  * key to describe the csum pointed to by the path, and it expects
 429  * the csum to overlap the range [bytenr, len]
 430  *
 431  * The csum should not be entirely contained in the range and the
 432  * range should not be entirely contained in the csum.
 433  *
 434  * This calls btrfs_truncate_item with the correct args based on the
 435  * overlap, and fixes up the key as required.
 436  */
 437 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 438                                       struct btrfs_root *root,
 439                                       struct btrfs_path *path,
 440                                       struct btrfs_key *key,
 441                                       u64 bytenr, u64 len)
 442 {
 443         struct extent_buffer *leaf;
 444         u16 csum_size =
 445                 btrfs_super_csum_size(&root->fs_info->super_copy);
 446         u64 csum_end;
 447         u64 end_byte = bytenr + len;
 448         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 449         int ret;
 450
 451         leaf = path->nodes[0];
 452         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 453         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 454         csum_end += key->offset;
 455
 456         if (key->offset < bytenr && csum_end <= end_byte) {
 457                 /*
 458                  *         [ bytenr - len ]
 459                  *         [   ]
 460                  *   [csum     ]
 461                  *   A simple truncate off the end of the item
 462                  */
 463                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 464                 new_size *= csum_size;
 465                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 466                 BUG_ON(ret);
 467         } else if (key->offset >= bytenr && csum_end > end_byte &&
 468                    end_byte > key->offset) {
 469                 /*
 470                  *         [ bytenr - len ]
 471                  *                 [ ]
 472                  *                 [csum     ]
 473                  * we need to truncate from the beginning of the csum
 474                  */
 475                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 476                 new_size *= csum_size;
 477
 478                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 479                 BUG_ON(ret);
 480
 481                 key->offset = end_byte;
 482                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 483                 BUG_ON(ret);
 484         } else {
 485                 BUG();
 486         }
 487         return 0;
 488 }
 489
 490 /*
 491  * deletes the csum items from the csum tree for a given
 492  * range of bytes.
 493  */
 494 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 495                     struct btrfs_root *root, u64 bytenr, u64 len)
 496 {
 497         struct btrfs_path *path;
 498         struct btrfs_key key;
 499         u64 end_byte = bytenr + len;
 500         u64 csum_end;
 501         struct extent_buffer *leaf;
 502         int ret;
 503         u16 csum_size =
 504                 btrfs_super_csum_size(&root->fs_info->super_copy);
 505         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 506
 507         root = root->fs_info->csum_root;
 508
 509         path = btrfs_alloc_path();
 510
 511         while (1) {
 512                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 513                 key.offset = end_byte - 1;
 514                 key.type = BTRFS_EXTENT_CSUM_KEY;
 515
 516                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 517                 if (ret > 0) {
 518                         if (path->slots[0] == 0)
 519                                 goto out;
 520                         path->slots[0]--;
 521                 }
 522                 leaf = path->nodes[0];
 523                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 524
 525                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 526                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 527                         break;
 528                 }
 529
 530                 if (key.offset >= end_byte)
 531                         break;
 532
 533                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 534                 csum_end <<= blocksize_bits;
 535                 csum_end += key.offset;
 536
 537                 /* this csum ends before we start, we're done */
 538                 if (csum_end <= bytenr)
 539                         break;
 540
 541                 /* delete the entire item, it is inside our range */
 542                 if (key.offset >= bytenr && csum_end <= end_byte) {
 543                         ret = btrfs_del_item(trans, root, path);
 544                         BUG_ON(ret);
 545                         if (key.offset == bytenr)
 546                                 break;
 547                 } else if (key.offset < bytenr && csum_end > end_byte) {
 548                         unsigned long offset;
 549                         unsigned long shift_len;
 550                         unsigned long item_offset;
 551                         /*
 552                          *        [ bytenr - len ]
 553                          *     [csum                ]
 554                          *
 555                          * Our bytes are in the middle of the csum,
 556                          * we need to split this item and insert a new one.
 557                          *
 558                          * But we can't drop the path because the
 559                          * csum could change, get removed, extended etc.
 560                          *
 561                          * The trick here is the max size of a csum item leaves
 562                          * enough room in the tree block for a single
 563                          * item header.  So, we split the item in place,
 564                          * adding a new header pointing to the existing
 565                          * bytes.  Then we loop around again and we have
 566                          * a nicely formed csum item that we can neatly
 567                          * truncate.
 568                          */
 569                         offset = (bytenr - key.offset) >> blocksize_bits;
 570                         offset *= csum_size;
 571
 572                         shift_len = (len >> blocksize_bits) * csum_size;
 573
 574                         item_offset = btrfs_item_ptr_offset(leaf,
 575                                                             path->slots[0]);
 576
 577                         memset_extent_buffer(leaf, 0, item_offset + offset,
 578                                              shift_len);
 579                         key.offset = bytenr;
 580
 581                         /*
 582                          * btrfs_split_item returns -EAGAIN when the
 583                          * item changed size or key
 584                          */
 585                         ret = btrfs_split_item(trans, root, path, &key, offset);
 586                         BUG_ON(ret && ret != -EAGAIN);
 587
 588                         key.offset = end_byte - 1;
 589                 } else {
 590                         ret = truncate_one_csum(trans, root, path,
 591                                                 &key, bytenr, len);
 592                         BUG_ON(ret);
 593                         if (key.offset < bytenr)
 594                                 break;
 595                 }
 596                 btrfs_release_path(root, path);
 597         }
 598 out:
 599         btrfs_free_path(path);
 600         return 0;
 601 }
 602
 603 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 604                            struct btrfs_root *root,
 605                            struct btrfs_ordered_sum *sums)
 606 {
 607         u64 bytenr;
 608         int ret;
 609         struct btrfs_key file_key;
 610         struct btrfs_key found_key;
 611         u64 next_offset;
 612         u64 total_bytes = 0;
 613         int found_next;
 614         struct btrfs_path *path;
 615         struct btrfs_csum_item *item;
 616         struct btrfs_csum_item *item_end;
 617         struct extent_buffer *leaf = NULL;
 618         u64 csum_offset;
 619         struct btrfs_sector_sum *sector_sum;
 620         u32 nritems;
 621         u32 ins_size;
 622         char *eb_map;
 623         char *eb_token;
 624         unsigned long map_len;
 625         unsigned long map_start;
 626         u16 csum_size =
 627                 btrfs_super_csum_size(&root->fs_info->super_copy);
 628
 629         path = btrfs_alloc_path();
 630         BUG_ON(!path);
 631         sector_sum = sums->sums;
 632 again:
 633         next_offset = (u64)-1;
 634         found_next = 0;
 635         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 636         file_key.offset = sector_sum->bytenr;
 637         bytenr = sector_sum->bytenr;
 638         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 639
 640         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 641         if (!IS_ERR(item)) {
 642                 leaf = path->nodes[0];
 643                 ret = 0;
 644                 goto found;
 645         }
 646         ret = PTR_ERR(item);
 647         if (ret == -EFBIG) {
 648                 u32 item_size;
 649                 /* we found one, but it isn't big enough yet */
 650                 leaf = path->nodes[0];
 651                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 652                 if ((item_size / csum_size) >=
 653                     MAX_CSUM_ITEMS(root, csum_size)) {
 654                         /* already at max size, make a new one */
 655                         goto insert;
 656                 }
 657         } else {
 658                 int slot = path->slots[0] + 1;
 659                 /* we didn't find a csum item, insert one */
 660                 nritems = btrfs_header_nritems(path->nodes[0]);
 661                 if (path->slots[0] >= nritems - 1) {
 662                         ret = btrfs_next_leaf(root, path);
 663                         if (ret == 1)
 664                                 found_next = 1;
 665                         if (ret != 0)
 666                                 goto insert;
 667                         slot = 0;
 668                 }
 669                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 670                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 671                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 672                         found_next = 1;
 673                         goto insert;
 674                 }
 675                 next_offset = found_key.offset;
 676                 found_next = 1;
 677                 goto insert;
 678         }
 679
 680         /*
 681          * at this point, we know the tree has an item, but it isn't big
 682          * enough yet to put our csum in.  Grow it
 683          */
 684         btrfs_release_path(root, path);
 685         ret = btrfs_search_slot(trans, root, &file_key, path,
 686                                 csum_size, 1);
 687         if (ret < 0)
 688                 goto fail_unlock;
 689
 690         if (ret > 0) {
 691                 if (path->slots[0] == 0)
 692                         goto insert;
 693                 path->slots[0]--;
 694         }
 695
 696         leaf = path->nodes[0];
 697         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 698         csum_offset = (bytenr - found_key.offset) >>
 699                         root->fs_info->sb->s_blocksize_bits;
 700
 701         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 702             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 703             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 704                 goto insert;
 705         }
 706
 707         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 708             csum_size) {
 709                 u32 diff = (csum_offset + 1) * csum_size;
 710
 711                 /*
 712                  * is the item big enough already?  we dropped our lock
 713                  * before and need to recheck
 714                  */
 715                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 716                         goto csum;
 717
 718                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 719                 if (diff != csum_size)
 720                         goto insert;
 721
 722                 ret = btrfs_extend_item(trans, root, path, diff);
 723                 BUG_ON(ret);
 724                 goto csum;
 725         }
 726
 727 insert:
 728         btrfs_release_path(root, path);
 729         csum_offset = 0;
 730         if (found_next) {
 731                 u64 tmp = total_bytes + root->sectorsize;
 732                 u64 next_sector = sector_sum->bytenr;
 733                 struct btrfs_sector_sum *next = sector_sum + 1;
 734
 735                 while (tmp < sums->len) {
 736                         if (next_sector + root->sectorsize != next->bytenr)
 737                                 break;
 738                         tmp += root->sectorsize;
 739                         next_sector = next->bytenr;
 740                         next++;
 741                 }
 742                 tmp = min(tmp, next_offset - file_key.offset);
 743                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 744                 tmp = max((u64)1, tmp);
 745                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 746                 ins_size = csum_size * tmp;
 747         } else {
 748                 ins_size = csum_size;
 749         }
 750         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 751                                       ins_size);
 752         if (ret < 0)
 753                 goto fail_unlock;
 754         if (ret != 0) {
 755                 WARN_ON(1);
 756                 goto fail_unlock;
 757         }
 758 csum:
 759         leaf = path->nodes[0];
 760         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 761         ret = 0;
 762         item = (struct btrfs_csum_item *)((unsigned char *)item +
 763                                           csum_offset * csum_size);
 764 found:
 765         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 766         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 767                                       btrfs_item_size_nr(leaf, path->slots[0]));
 768         eb_token = NULL;
 769         cond_resched();
 770 next_sector:
 771
 772         if (!eb_token ||
 773            (unsigned long)item + csum_size >= map_start + map_len) {
 774                 int err;
 775
 776                 if (eb_token)
 777                         unmap_extent_buffer(leaf, eb_token, KM_USER1);
 778                 eb_token = NULL;
 779                 err = map_private_extent_buffer(leaf, (unsigned long)item,
 780                                                 csum_size,
 781                                                 &eb_token, &eb_map,
 782                                                 &map_start, &map_len, KM_USER1);
 783                 if (err)
 784                         eb_token = NULL;
 785         }
 786         if (eb_token) {
 787                 memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
 788                        &sector_sum->sum, csum_size);
 789         } else {
 790                 write_extent_buffer(leaf, &sector_sum->sum,
 791                                     (unsigned long)item, csum_size);
 792         }
 793
 794         total_bytes += root->sectorsize;
 795         sector_sum++;
 796         if (total_bytes < sums->len) {
 797                 item = (struct btrfs_csum_item *)((char *)item +
 798                                                   csum_size);
 799                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 800                     sector_sum->bytenr) {
 801                         bytenr = sector_sum->bytenr;
 802                         goto next_sector;
 803                 }
 804         }
 805         if (eb_token) {
 806                 unmap_extent_buffer(leaf, eb_token, KM_USER1);
 807                 eb_token = NULL;
 808         }
 809         btrfs_mark_buffer_dirty(path->nodes[0]);
 810         cond_resched();
 811         if (total_bytes < sums->len) {
 812                 btrfs_release_path(root, path);
 813                 goto again;
 814         }
 815 out:
 816         btrfs_free_path(path);
 817         return ret;
 818
 819 fail_unlock:
 820         goto out;
 821 }