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/slab.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/highmem.h>
  23 #include "ctree.h"
  24 #include "disk-io.h"
  25 #include "transaction.h"
  26 #include "print-tree.h"
  27
  28 #define MAX_CSUM_ITEMS(r, size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
  29                                    sizeof(struct btrfs_item) * 2) / \
  30                                   size) - 1))
  31
  32 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
  33                                    sizeof(struct btrfs_ordered_sum)) / \
  34                                    sizeof(struct btrfs_sector_sum) * \
  35                                    (r)->sectorsize - (r)->sectorsize)
  36
  37 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  38                              struct btrfs_root *root,
  39                              u64 objectid, u64 pos,
  40                              u64 disk_offset, u64 disk_num_bytes,
  41                              u64 num_bytes, u64 offset, u64 ram_bytes,
  42                              u8 compression, u8 encryption, u16 other_encoding)
  43 {
  44         int ret = 0;
  45         struct btrfs_file_extent_item *item;
  46         struct btrfs_key file_key;
  47         struct btrfs_path *path;
  48         struct extent_buffer *leaf;
  49
  50         path = btrfs_alloc_path();
  51         if (!path)
  52                 return -ENOMEM;
  53         file_key.objectid = objectid;
  54         file_key.offset = pos;
  55         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  56
  57         path->leave_spinning = 1;
  58         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  59                                       sizeof(*item));
  60         if (ret < 0)
  61                 goto out;
  62         BUG_ON(ret);
  63         leaf = path->nodes[0];
  64         item = btrfs_item_ptr(leaf, path->slots[0],
  65                               struct btrfs_file_extent_item);
  66         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  67         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  68         btrfs_set_file_extent_offset(leaf, item, offset);
  69         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  70         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  71         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  72         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  73         btrfs_set_file_extent_compression(leaf, item, compression);
  74         btrfs_set_file_extent_encryption(leaf, item, encryption);
  75         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  76
  77         btrfs_mark_buffer_dirty(leaf);
  78 out:
  79         btrfs_free_path(path);
  80         return ret;
  81 }
  82
  83 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  84                                           struct btrfs_root *root,
  85                                           struct btrfs_path *path,
  86                                           u64 bytenr, int cow)
  87 {
  88         int ret;
  89         struct btrfs_key file_key;
  90         struct btrfs_key found_key;
  91         struct btrfs_csum_item *item;
  92         struct extent_buffer *leaf;
  93         u64 csum_offset = 0;
  94         u16 csum_size =
  95                 btrfs_super_csum_size(&root->fs_info->super_copy);
  96         int csums_in_item;
  97
  98         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  99         file_key.offset = bytenr;
 100         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 101         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 102         if (ret < 0)
 103                 goto fail;
 104         leaf = path->nodes[0];
 105         if (ret > 0) {
 106                 ret = 1;
 107                 if (path->slots[0] == 0)
 108                         goto fail;
 109                 path->slots[0]--;
 110                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 111                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 112                         goto fail;
 113
 114                 csum_offset = (bytenr - found_key.offset) >>
 115                                 root->fs_info->sb->s_blocksize_bits;
 116                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 117                 csums_in_item /= csum_size;
 118
 119                 if (csum_offset >= csums_in_item) {
 120                         ret = -EFBIG;
 121                         goto fail;
 122                 }
 123         }
 124         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 125         item = (struct btrfs_csum_item *)((unsigned char *)item +
 126                                           csum_offset * csum_size);
 127         return item;
 128 fail:
 129         if (ret > 0)
 130                 ret = -ENOENT;
 131         return ERR_PTR(ret);
 132 }
 133
 134
 135 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 136                              struct btrfs_root *root,
 137                              struct btrfs_path *path, u64 objectid,
 138                              u64 offset, int mod)
 139 {
 140         int ret;
 141         struct btrfs_key file_key;
 142         int ins_len = mod < 0 ? -1 : 0;
 143         int cow = mod != 0;
 144
 145         file_key.objectid = objectid;
 146         file_key.offset = offset;
 147         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 148         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 149         return ret;
 150 }
 151
 152
 153 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 154                                    struct inode *inode, struct bio *bio,
 155                                    u64 logical_offset, u32 *dst, int dio)
 156 {
 157         u32 sum;
 158         struct bio_vec *bvec = bio->bi_io_vec;
 159         int bio_index = 0;
 160         u64 offset = 0;
 161         u64 item_start_offset = 0;
 162         u64 item_last_offset = 0;
 163         u64 disk_bytenr;
 164         u32 diff;
 165         u16 csum_size =
 166                 btrfs_super_csum_size(&root->fs_info->super_copy);
 167         int ret;
 168         struct btrfs_path *path;
 169         struct btrfs_csum_item *item = NULL;
 170         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 171
 172         path = btrfs_alloc_path();
 173         if (!path)
 174                 return -ENOMEM;
 175         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 176                 path->reada = 2;
 177
 178         WARN_ON(bio->bi_vcnt <= 0);
 179
 180         disk_bytenr = (u64)bio->bi_sector << 9;
 181         if (dio)
 182                 offset = logical_offset;
 183         while (bio_index < bio->bi_vcnt) {
 184                 if (!dio)
 185                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 186                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 187                 if (ret == 0)
 188                         goto found;
 189
 190                 if (!item || disk_bytenr < item_start_offset ||
 191                     disk_bytenr >= item_last_offset) {
 192                         struct btrfs_key found_key;
 193                         u32 item_size;
 194
 195                         if (item)
 196                                 btrfs_release_path(path);
 197                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 198                                                  path, disk_bytenr, 0);
 199                         if (IS_ERR(item)) {
 200                                 ret = PTR_ERR(item);
 201                                 if (ret == -ENOENT || ret == -EFBIG)
 202                                         ret = 0;
 203                                 sum = 0;
 204                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 205                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 206                                         set_extent_bits(io_tree, offset,
 207                                                 offset + bvec->bv_len - 1,
 208                                                 EXTENT_NODATASUM, GFP_NOFS);
 209                                 } else {
 210                                         printk(KERN_INFO "btrfs no csum found "
 211                                                "for inode %llu start %llu\n",
 212                                                (unsigned long long)
 213                                                btrfs_ino(inode),
 214                                                (unsigned long long)offset);
 215                                 }
 216                                 item = NULL;
 217                                 btrfs_release_path(path);
 218                                 goto found;
 219                         }
 220                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 221                                               path->slots[0]);
 222
 223                         item_start_offset = found_key.offset;
 224                         item_size = btrfs_item_size_nr(path->nodes[0],
 225                                                        path->slots[0]);
 226                         item_last_offset = item_start_offset +
 227                                 (item_size / csum_size) *
 228                                 root->sectorsize;
 229                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 230                                               struct btrfs_csum_item);
 231                 }
 232                 /*
 233                  * this byte range must be able to fit inside
 234                  * a single leaf so it will also fit inside a u32
 235                  */
 236                 diff = disk_bytenr - item_start_offset;
 237                 diff = diff / root->sectorsize;
 238                 diff = diff * csum_size;
 239
 240                 read_extent_buffer(path->nodes[0], &sum,
 241                                    ((unsigned long)item) + diff,
 242                                    csum_size);
 243 found:
 244                 if (dst)
 245                         *dst++ = sum;
 246                 else
 247                         set_state_private(io_tree, offset, sum);
 248                 disk_bytenr += bvec->bv_len;
 249                 offset += bvec->bv_len;
 250                 bio_index++;
 251                 bvec++;
 252         }
 253         btrfs_free_path(path);
 254         return 0;
 255 }
 256
 257 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 258                           struct bio *bio, u32 *dst)
 259 {
 260         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 261 }
 262
 263 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 264                               struct bio *bio, u64 offset, u32 *dst)
 265 {
 266         return __btrfs_lookup_bio_sums(root, inode, bio, offset, dst, 1);
 267 }
 268
 269 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 270                              struct list_head *list, int search_commit)
 271 {
 272         struct btrfs_key key;
 273         struct btrfs_path *path;
 274         struct extent_buffer *leaf;
 275         struct btrfs_ordered_sum *sums;
 276         struct btrfs_sector_sum *sector_sum;
 277         struct btrfs_csum_item *item;
 278         unsigned long offset;
 279         int ret;
 280         size_t size;
 281         u64 csum_end;
 282         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 283
 284         path = btrfs_alloc_path();
 285         BUG_ON(!path);
 286
 287         if (search_commit) {
 288                 path->skip_locking = 1;
 289                 path->reada = 2;
 290                 path->search_commit_root = 1;
 291         }
 292
 293         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 294         key.offset = start;
 295         key.type = BTRFS_EXTENT_CSUM_KEY;
 296
 297         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 298         if (ret < 0)
 299                 goto fail;
 300         if (ret > 0 && path->slots[0] > 0) {
 301                 leaf = path->nodes[0];
 302                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 303                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 304                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 305                         offset = (start - key.offset) >>
 306                                  root->fs_info->sb->s_blocksize_bits;
 307                         if (offset * csum_size <
 308                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 309                                 path->slots[0]--;
 310                 }
 311         }
 312
 313         while (start <= end) {
 314                 leaf = path->nodes[0];
 315                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 316                         ret = btrfs_next_leaf(root, path);
 317                         if (ret < 0)
 318                                 goto fail;
 319                         if (ret > 0)
 320                                 break;
 321                         leaf = path->nodes[0];
 322                 }
 323
 324                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 325                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 326                     key.type != BTRFS_EXTENT_CSUM_KEY)
 327                         break;
 328
 329                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 330                 if (key.offset > end)
 331                         break;
 332
 333                 if (key.offset > start)
 334                         start = key.offset;
 335
 336                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 337                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 338                 if (csum_end <= start) {
 339                         path->slots[0]++;
 340                         continue;
 341                 }
 342
 343                 csum_end = min(csum_end, end + 1);
 344                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 345                                       struct btrfs_csum_item);
 346                 while (start < csum_end) {
 347                         size = min_t(size_t, csum_end - start,
 348                                         MAX_ORDERED_SUM_BYTES(root));
 349                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 350                                         GFP_NOFS);
 351                         BUG_ON(!sums);
 352
 353                         sector_sum = sums->sums;
 354                         sums->bytenr = start;
 355                         sums->len = size;
 356
 357                         offset = (start - key.offset) >>
 358                                 root->fs_info->sb->s_blocksize_bits;
 359                         offset *= csum_size;
 360
 361                         while (size > 0) {
 362                                 read_extent_buffer(path->nodes[0],
 363                                                 &sector_sum->sum,
 364                                                 ((unsigned long)item) +
 365                                                 offset, csum_size);
 366                                 sector_sum->bytenr = start;
 367
 368                                 size -= root->sectorsize;
 369                                 start += root->sectorsize;
 370                                 offset += csum_size;
 371                                 sector_sum++;
 372                         }
 373                         list_add_tail(&sums->list, list);
 374                 }
 375                 path->slots[0]++;
 376         }
 377         ret = 0;
 378 fail:
 379         btrfs_free_path(path);
 380         return ret;
 381 }
 382
 383 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 384                        struct bio *bio, u64 file_start, int contig)
 385 {
 386         struct btrfs_ordered_sum *sums;
 387         struct btrfs_sector_sum *sector_sum;
 388         struct btrfs_ordered_extent *ordered;
 389         char *data;
 390         struct bio_vec *bvec = bio->bi_io_vec;
 391         int bio_index = 0;
 392         unsigned long total_bytes = 0;
 393         unsigned long this_sum_bytes = 0;
 394         u64 offset;
 395         u64 disk_bytenr;
 396
 397         WARN_ON(bio->bi_vcnt <= 0);
 398         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 399         if (!sums)
 400                 return -ENOMEM;
 401
 402         sector_sum = sums->sums;
 403         disk_bytenr = (u64)bio->bi_sector << 9;
 404         sums->len = bio->bi_size;
 405         INIT_LIST_HEAD(&sums->list);
 406
 407         if (contig)
 408                 offset = file_start;
 409         else
 410                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 411
 412         ordered = btrfs_lookup_ordered_extent(inode, offset);
 413         BUG_ON(!ordered);
 414         sums->bytenr = ordered->start;
 415
 416         while (bio_index < bio->bi_vcnt) {
 417                 if (!contig)
 418                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 419
 420                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 421                     offset < ordered->file_offset)) {
 422                         unsigned long bytes_left;
 423                         sums->len = this_sum_bytes;
 424                         this_sum_bytes = 0;
 425                         btrfs_add_ordered_sum(inode, ordered, sums);
 426                         btrfs_put_ordered_extent(ordered);
 427
 428                         bytes_left = bio->bi_size - total_bytes;
 429
 430                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 431                                        GFP_NOFS);
 432                         BUG_ON(!sums);
 433                         sector_sum = sums->sums;
 434                         sums->len = bytes_left;
 435                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 436                         BUG_ON(!ordered);
 437                         sums->bytenr = ordered->start;
 438                 }
 439
 440                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 441                 sector_sum->sum = ~(u32)0;
 442                 sector_sum->sum = btrfs_csum_data(root,
 443                                                   data + bvec->bv_offset,
 444                                                   sector_sum->sum,
 445                                                   bvec->bv_len);
 446                 kunmap_atomic(data, KM_USER0);
 447                 btrfs_csum_final(sector_sum->sum,
 448                                  (char *)&sector_sum->sum);
 449                 sector_sum->bytenr = disk_bytenr;
 450
 451                 sector_sum++;
 452                 bio_index++;
 453                 total_bytes += bvec->bv_len;
 454                 this_sum_bytes += bvec->bv_len;
 455                 disk_bytenr += bvec->bv_len;
 456                 offset += bvec->bv_len;
 457                 bvec++;
 458         }
 459         this_sum_bytes = 0;
 460         btrfs_add_ordered_sum(inode, ordered, sums);
 461         btrfs_put_ordered_extent(ordered);
 462         return 0;
 463 }
 464
 465 /*
 466  * helper function for csum removal, this expects the
 467  * key to describe the csum pointed to by the path, and it expects
 468  * the csum to overlap the range [bytenr, len]
 469  *
 470  * The csum should not be entirely contained in the range and the
 471  * range should not be entirely contained in the csum.
 472  *
 473  * This calls btrfs_truncate_item with the correct args based on the
 474  * overlap, and fixes up the key as required.
 475  */
 476 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 477                                       struct btrfs_root *root,
 478                                       struct btrfs_path *path,
 479                                       struct btrfs_key *key,
 480                                       u64 bytenr, u64 len)
 481 {
 482         struct extent_buffer *leaf;
 483         u16 csum_size =
 484                 btrfs_super_csum_size(&root->fs_info->super_copy);
 485         u64 csum_end;
 486         u64 end_byte = bytenr + len;
 487         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 488         int ret;
 489
 490         leaf = path->nodes[0];
 491         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 492         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 493         csum_end += key->offset;
 494
 495         if (key->offset < bytenr && csum_end <= end_byte) {
 496                 /*
 497                  *         [ bytenr - len ]
 498                  *         [   ]
 499                  *   [csum     ]
 500                  *   A simple truncate off the end of the item
 501                  */
 502                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 503                 new_size *= csum_size;
 504                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 505         } else if (key->offset >= bytenr && csum_end > end_byte &&
 506                    end_byte > key->offset) {
 507                 /*
 508                  *         [ bytenr - len ]
 509                  *                 [ ]
 510                  *                 [csum     ]
 511                  * we need to truncate from the beginning of the csum
 512                  */
 513                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 514                 new_size *= csum_size;
 515
 516                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 517
 518                 key->offset = end_byte;
 519                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 520                 BUG_ON(ret);
 521         } else {
 522                 BUG();
 523         }
 524         return 0;
 525 }
 526
 527 /*
 528  * deletes the csum items from the csum tree for a given
 529  * range of bytes.
 530  */
 531 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 532                     struct btrfs_root *root, u64 bytenr, u64 len)
 533 {
 534         struct btrfs_path *path;
 535         struct btrfs_key key;
 536         u64 end_byte = bytenr + len;
 537         u64 csum_end;
 538         struct extent_buffer *leaf;
 539         int ret;
 540         u16 csum_size =
 541                 btrfs_super_csum_size(&root->fs_info->super_copy);
 542         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 543
 544         root = root->fs_info->csum_root;
 545
 546         path = btrfs_alloc_path();
 547         if (!path)
 548                 return -ENOMEM;
 549
 550         while (1) {
 551                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 552                 key.offset = end_byte - 1;
 553                 key.type = BTRFS_EXTENT_CSUM_KEY;
 554
 555                 path->leave_spinning = 1;
 556                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 557                 if (ret > 0) {
 558                         if (path->slots[0] == 0)
 559                                 break;
 560                         path->slots[0]--;
 561                 } else if (ret < 0) {
 562                         break;
 563                 }
 564
 565                 leaf = path->nodes[0];
 566                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 567
 568                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 569                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 570                         break;
 571                 }
 572
 573                 if (key.offset >= end_byte)
 574                         break;
 575
 576                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 577                 csum_end <<= blocksize_bits;
 578                 csum_end += key.offset;
 579
 580                 /* this csum ends before we start, we're done */
 581                 if (csum_end <= bytenr)
 582                         break;
 583
 584                 /* delete the entire item, it is inside our range */
 585                 if (key.offset >= bytenr && csum_end <= end_byte) {
 586                         ret = btrfs_del_item(trans, root, path);
 587                         if (ret)
 588                                 goto out;
 589                         if (key.offset == bytenr)
 590                                 break;
 591                 } else if (key.offset < bytenr && csum_end > end_byte) {
 592                         unsigned long offset;
 593                         unsigned long shift_len;
 594                         unsigned long item_offset;
 595                         /*
 596                          *        [ bytenr - len ]
 597                          *     [csum                ]
 598                          *
 599                          * Our bytes are in the middle of the csum,
 600                          * we need to split this item and insert a new one.
 601                          *
 602                          * But we can't drop the path because the
 603                          * csum could change, get removed, extended etc.
 604                          *
 605                          * The trick here is the max size of a csum item leaves
 606                          * enough room in the tree block for a single
 607                          * item header.  So, we split the item in place,
 608                          * adding a new header pointing to the existing
 609                          * bytes.  Then we loop around again and we have
 610                          * a nicely formed csum item that we can neatly
 611                          * truncate.
 612                          */
 613                         offset = (bytenr - key.offset) >> blocksize_bits;
 614                         offset *= csum_size;
 615
 616                         shift_len = (len >> blocksize_bits) * csum_size;
 617
 618                         item_offset = btrfs_item_ptr_offset(leaf,
 619                                                             path->slots[0]);
 620
 621                         memset_extent_buffer(leaf, 0, item_offset + offset,
 622                                              shift_len);
 623                         key.offset = bytenr;
 624
 625                         /*
 626                          * btrfs_split_item returns -EAGAIN when the
 627                          * item changed size or key
 628                          */
 629                         ret = btrfs_split_item(trans, root, path, &key, offset);
 630                         BUG_ON(ret && ret != -EAGAIN);
 631
 632                         key.offset = end_byte - 1;
 633                 } else {
 634                         ret = truncate_one_csum(trans, root, path,
 635                                                 &key, bytenr, len);
 636                         BUG_ON(ret);
 637                         if (key.offset < bytenr)
 638                                 break;
 639                 }
 640                 btrfs_release_path(path);
 641         }
 642         ret = 0;
 643 out:
 644         btrfs_free_path(path);
 645         return ret;
 646 }
 647
 648 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 649                            struct btrfs_root *root,
 650                            struct btrfs_ordered_sum *sums)
 651 {
 652         u64 bytenr;
 653         int ret;
 654         struct btrfs_key file_key;
 655         struct btrfs_key found_key;
 656         u64 next_offset;
 657         u64 total_bytes = 0;
 658         int found_next;
 659         struct btrfs_path *path;
 660         struct btrfs_csum_item *item;
 661         struct btrfs_csum_item *item_end;
 662         struct extent_buffer *leaf = NULL;
 663         u64 csum_offset;
 664         struct btrfs_sector_sum *sector_sum;
 665         u32 nritems;
 666         u32 ins_size;
 667         char *eb_map;
 668         char *eb_token;
 669         unsigned long map_len;
 670         unsigned long map_start;
 671         u16 csum_size =
 672                 btrfs_super_csum_size(&root->fs_info->super_copy);
 673
 674         path = btrfs_alloc_path();
 675         BUG_ON(!path);
 676         sector_sum = sums->sums;
 677 again:
 678         next_offset = (u64)-1;
 679         found_next = 0;
 680         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 681         file_key.offset = sector_sum->bytenr;
 682         bytenr = sector_sum->bytenr;
 683         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 684
 685         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 686         if (!IS_ERR(item)) {
 687                 leaf = path->nodes[0];
 688                 ret = 0;
 689                 goto found;
 690         }
 691         ret = PTR_ERR(item);
 692         if (ret != -EFBIG && ret != -ENOENT)
 693                 goto fail_unlock;
 694
 695         if (ret == -EFBIG) {
 696                 u32 item_size;
 697                 /* we found one, but it isn't big enough yet */
 698                 leaf = path->nodes[0];
 699                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 700                 if ((item_size / csum_size) >=
 701                     MAX_CSUM_ITEMS(root, csum_size)) {
 702                         /* already at max size, make a new one */
 703                         goto insert;
 704                 }
 705         } else {
 706                 int slot = path->slots[0] + 1;
 707                 /* we didn't find a csum item, insert one */
 708                 nritems = btrfs_header_nritems(path->nodes[0]);
 709                 if (path->slots[0] >= nritems - 1) {
 710                         ret = btrfs_next_leaf(root, path);
 711                         if (ret == 1)
 712                                 found_next = 1;
 713                         if (ret != 0)
 714                                 goto insert;
 715                         slot = 0;
 716                 }
 717                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 718                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 719                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 720                         found_next = 1;
 721                         goto insert;
 722                 }
 723                 next_offset = found_key.offset;
 724                 found_next = 1;
 725                 goto insert;
 726         }
 727
 728         /*
 729          * at this point, we know the tree has an item, but it isn't big
 730          * enough yet to put our csum in.  Grow it
 731          */
 732         btrfs_release_path(path);
 733         ret = btrfs_search_slot(trans, root, &file_key, path,
 734                                 csum_size, 1);
 735         if (ret < 0)
 736                 goto fail_unlock;
 737
 738         if (ret > 0) {
 739                 if (path->slots[0] == 0)
 740                         goto insert;
 741                 path->slots[0]--;
 742         }
 743
 744         leaf = path->nodes[0];
 745         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 746         csum_offset = (bytenr - found_key.offset) >>
 747                         root->fs_info->sb->s_blocksize_bits;
 748
 749         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 750             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 751             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 752                 goto insert;
 753         }
 754
 755         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 756             csum_size) {
 757                 u32 diff = (csum_offset + 1) * csum_size;
 758
 759                 /*
 760                  * is the item big enough already?  we dropped our lock
 761                  * before and need to recheck
 762                  */
 763                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 764                         goto csum;
 765
 766                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 767                 if (diff != csum_size)
 768                         goto insert;
 769
 770                 ret = btrfs_extend_item(trans, root, path, diff);
 771                 goto csum;
 772         }
 773
 774 insert:
 775         btrfs_release_path(path);
 776         csum_offset = 0;
 777         if (found_next) {
 778                 u64 tmp = total_bytes + root->sectorsize;
 779                 u64 next_sector = sector_sum->bytenr;
 780                 struct btrfs_sector_sum *next = sector_sum + 1;
 781
 782                 while (tmp < sums->len) {
 783                         if (next_sector + root->sectorsize != next->bytenr)
 784                                 break;
 785                         tmp += root->sectorsize;
 786                         next_sector = next->bytenr;
 787                         next++;
 788                 }
 789                 tmp = min(tmp, next_offset - file_key.offset);
 790                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 791                 tmp = max((u64)1, tmp);
 792                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 793                 ins_size = csum_size * tmp;
 794         } else {
 795                 ins_size = csum_size;
 796         }
 797         path->leave_spinning = 1;
 798         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 799                                       ins_size);
 800         path->leave_spinning = 0;
 801         if (ret < 0)
 802                 goto fail_unlock;
 803         if (ret != 0) {
 804                 WARN_ON(1);
 805                 goto fail_unlock;
 806         }
 807 csum:
 808         leaf = path->nodes[0];
 809         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 810         ret = 0;
 811         item = (struct btrfs_csum_item *)((unsigned char *)item +
 812                                           csum_offset * csum_size);
 813 found:
 814         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 815         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 816                                       btrfs_item_size_nr(leaf, path->slots[0]));
 817         eb_token = NULL;
 818 next_sector:
 819
 820         if (!eb_token ||
 821            (unsigned long)item + csum_size >= map_start + map_len) {
 822                 int err;
 823
 824                 if (eb_token)
 825                         unmap_extent_buffer(leaf, eb_token, KM_USER1);
 826                 eb_token = NULL;
 827                 err = map_private_extent_buffer(leaf, (unsigned long)item,
 828                                                 csum_size,
 829                                                 &eb_token, &eb_map,
 830                                                 &map_start, &map_len, KM_USER1);
 831                 if (err)
 832                         eb_token = NULL;
 833         }
 834         if (eb_token) {
 835                 memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
 836                        &sector_sum->sum, csum_size);
 837         } else {
 838                 write_extent_buffer(leaf, &sector_sum->sum,
 839                                     (unsigned long)item, csum_size);
 840         }
 841
 842         total_bytes += root->sectorsize;
 843         sector_sum++;
 844         if (total_bytes < sums->len) {
 845                 item = (struct btrfs_csum_item *)((char *)item +
 846                                                   csum_size);
 847                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 848                     sector_sum->bytenr) {
 849                         bytenr = sector_sum->bytenr;
 850                         goto next_sector;
 851                 }
 852         }
 853         if (eb_token) {
 854                 unmap_extent_buffer(leaf, eb_token, KM_USER1);
 855                 eb_token = NULL;
 856         }
 857         btrfs_mark_buffer_dirty(path->nodes[0]);
 858         if (total_bytes < sums->len) {
 859                 btrfs_release_path(path);
 860                 cond_resched();
 861                 goto again;
 862         }
 863 out:
 864         btrfs_free_path(path);
 865         return ret;
 866
 867 fail_unlock:
 868         goto out;
 869 }