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         /*
 181          * the free space stuff is only read when it hasn't been
 182          * updated in the current transaction.  So, we can safely
 183          * read from the commit root and sidestep a nasty deadlock
 184          * between reading the free space cache and updating the csum tree.
 185          */
 186         if (btrfs_is_free_space_inode(root, inode))
 187                 path->search_commit_root = 1;
 188
 189         disk_bytenr = (u64)bio->bi_sector << 9;
 190         if (dio)
 191                 offset = logical_offset;
 192         while (bio_index < bio->bi_vcnt) {
 193                 if (!dio)
 194                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 195                 ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 196                 if (ret == 0)
 197                         goto found;
 198
 199                 if (!item || disk_bytenr < item_start_offset ||
 200                     disk_bytenr >= item_last_offset) {
 201                         struct btrfs_key found_key;
 202                         u32 item_size;
 203
 204                         if (item)
 205                                 btrfs_release_path(path);
 206                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 207                                                  path, disk_bytenr, 0);
 208                         if (IS_ERR(item)) {
 209                                 ret = PTR_ERR(item);
 210                                 if (ret == -ENOENT || ret == -EFBIG)
 211                                         ret = 0;
 212                                 sum = 0;
 213                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 214                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 215                                         set_extent_bits(io_tree, offset,
 216                                                 offset + bvec->bv_len - 1,
 217                                                 EXTENT_NODATASUM, GFP_NOFS);
 218                                 } else {
 219                                         printk(KERN_INFO "btrfs no csum found "
 220                                                "for inode %llu start %llu\n",
 221                                                (unsigned long long)
 222                                                btrfs_ino(inode),
 223                                                (unsigned long long)offset);
 224                                 }
 225                                 item = NULL;
 226                                 btrfs_release_path(path);
 227                                 goto found;
 228                         }
 229                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 230                                               path->slots[0]);
 231
 232                         item_start_offset = found_key.offset;
 233                         item_size = btrfs_item_size_nr(path->nodes[0],
 234                                                        path->slots[0]);
 235                         item_last_offset = item_start_offset +
 236                                 (item_size / csum_size) *
 237                                 root->sectorsize;
 238                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 239                                               struct btrfs_csum_item);
 240                 }
 241                 /*
 242                  * this byte range must be able to fit inside
 243                  * a single leaf so it will also fit inside a u32
 244                  */
 245                 diff = disk_bytenr - item_start_offset;
 246                 diff = diff / root->sectorsize;
 247                 diff = diff * csum_size;
 248
 249                 read_extent_buffer(path->nodes[0], &sum,
 250                                    ((unsigned long)item) + diff,
 251                                    csum_size);
 252 found:
 253                 if (dst)
 254                         *dst++ = sum;
 255                 else
 256                         set_state_private(io_tree, offset, sum);
 257                 disk_bytenr += bvec->bv_len;
 258                 offset += bvec->bv_len;
 259                 bio_index++;
 260                 bvec++;
 261         }
 262         btrfs_free_path(path);
 263         return 0;
 264 }
 265
 266 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 267                           struct bio *bio, u32 *dst)
 268 {
 269         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 270 }
 271
 272 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 273                               struct bio *bio, u64 offset, u32 *dst)
 274 {
 275         return __btrfs_lookup_bio_sums(root, inode, bio, offset, dst, 1);
 276 }
 277
 278 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 279                              struct list_head *list, int search_commit)
 280 {
 281         struct btrfs_key key;
 282         struct btrfs_path *path;
 283         struct extent_buffer *leaf;
 284         struct btrfs_ordered_sum *sums;
 285         struct btrfs_sector_sum *sector_sum;
 286         struct btrfs_csum_item *item;
 287         unsigned long offset;
 288         int ret;
 289         size_t size;
 290         u64 csum_end;
 291         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 292
 293         path = btrfs_alloc_path();
 294         BUG_ON(!path);
 295
 296         if (search_commit) {
 297                 path->skip_locking = 1;
 298                 path->reada = 2;
 299                 path->search_commit_root = 1;
 300         }
 301
 302         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 303         key.offset = start;
 304         key.type = BTRFS_EXTENT_CSUM_KEY;
 305
 306         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 307         if (ret < 0)
 308                 goto fail;
 309         if (ret > 0 && path->slots[0] > 0) {
 310                 leaf = path->nodes[0];
 311                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 312                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 313                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 314                         offset = (start - key.offset) >>
 315                                  root->fs_info->sb->s_blocksize_bits;
 316                         if (offset * csum_size <
 317                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 318                                 path->slots[0]--;
 319                 }
 320         }
 321
 322         while (start <= end) {
 323                 leaf = path->nodes[0];
 324                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 325                         ret = btrfs_next_leaf(root, path);
 326                         if (ret < 0)
 327                                 goto fail;
 328                         if (ret > 0)
 329                                 break;
 330                         leaf = path->nodes[0];
 331                 }
 332
 333                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 334                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 335                     key.type != BTRFS_EXTENT_CSUM_KEY)
 336                         break;
 337
 338                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 339                 if (key.offset > end)
 340                         break;
 341
 342                 if (key.offset > start)
 343                         start = key.offset;
 344
 345                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 346                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 347                 if (csum_end <= start) {
 348                         path->slots[0]++;
 349                         continue;
 350                 }
 351
 352                 csum_end = min(csum_end, end + 1);
 353                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 354                                       struct btrfs_csum_item);
 355                 while (start < csum_end) {
 356                         size = min_t(size_t, csum_end - start,
 357                                         MAX_ORDERED_SUM_BYTES(root));
 358                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 359                                         GFP_NOFS);
 360                         BUG_ON(!sums);
 361
 362                         sector_sum = sums->sums;
 363                         sums->bytenr = start;
 364                         sums->len = size;
 365
 366                         offset = (start - key.offset) >>
 367                                 root->fs_info->sb->s_blocksize_bits;
 368                         offset *= csum_size;
 369
 370                         while (size > 0) {
 371                                 read_extent_buffer(path->nodes[0],
 372                                                 &sector_sum->sum,
 373                                                 ((unsigned long)item) +
 374                                                 offset, csum_size);
 375                                 sector_sum->bytenr = start;
 376
 377                                 size -= root->sectorsize;
 378                                 start += root->sectorsize;
 379                                 offset += csum_size;
 380                                 sector_sum++;
 381                         }
 382                         list_add_tail(&sums->list, list);
 383                 }
 384                 path->slots[0]++;
 385         }
 386         ret = 0;
 387 fail:
 388         btrfs_free_path(path);
 389         return ret;
 390 }
 391
 392 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 393                        struct bio *bio, u64 file_start, int contig)
 394 {
 395         struct btrfs_ordered_sum *sums;
 396         struct btrfs_sector_sum *sector_sum;
 397         struct btrfs_ordered_extent *ordered;
 398         char *data;
 399         struct bio_vec *bvec = bio->bi_io_vec;
 400         int bio_index = 0;
 401         unsigned long total_bytes = 0;
 402         unsigned long this_sum_bytes = 0;
 403         u64 offset;
 404         u64 disk_bytenr;
 405
 406         WARN_ON(bio->bi_vcnt <= 0);
 407         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 408         if (!sums)
 409                 return -ENOMEM;
 410
 411         sector_sum = sums->sums;
 412         disk_bytenr = (u64)bio->bi_sector << 9;
 413         sums->len = bio->bi_size;
 414         INIT_LIST_HEAD(&sums->list);
 415
 416         if (contig)
 417                 offset = file_start;
 418         else
 419                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 420
 421         ordered = btrfs_lookup_ordered_extent(inode, offset);
 422         BUG_ON(!ordered);
 423         sums->bytenr = ordered->start;
 424
 425         while (bio_index < bio->bi_vcnt) {
 426                 if (!contig)
 427                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 428
 429                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 430                     offset < ordered->file_offset)) {
 431                         unsigned long bytes_left;
 432                         sums->len = this_sum_bytes;
 433                         this_sum_bytes = 0;
 434                         btrfs_add_ordered_sum(inode, ordered, sums);
 435                         btrfs_put_ordered_extent(ordered);
 436
 437                         bytes_left = bio->bi_size - total_bytes;
 438
 439                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 440                                        GFP_NOFS);
 441                         BUG_ON(!sums);
 442                         sector_sum = sums->sums;
 443                         sums->len = bytes_left;
 444                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 445                         BUG_ON(!ordered);
 446                         sums->bytenr = ordered->start;
 447                 }
 448
 449                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 450                 sector_sum->sum = ~(u32)0;
 451                 sector_sum->sum = btrfs_csum_data(root,
 452                                                   data + bvec->bv_offset,
 453                                                   sector_sum->sum,
 454                                                   bvec->bv_len);
 455                 kunmap_atomic(data, KM_USER0);
 456                 btrfs_csum_final(sector_sum->sum,
 457                                  (char *)&sector_sum->sum);
 458                 sector_sum->bytenr = disk_bytenr;
 459
 460                 sector_sum++;
 461                 bio_index++;
 462                 total_bytes += bvec->bv_len;
 463                 this_sum_bytes += bvec->bv_len;
 464                 disk_bytenr += bvec->bv_len;
 465                 offset += bvec->bv_len;
 466                 bvec++;
 467         }
 468         this_sum_bytes = 0;
 469         btrfs_add_ordered_sum(inode, ordered, sums);
 470         btrfs_put_ordered_extent(ordered);
 471         return 0;
 472 }
 473
 474 /*
 475  * helper function for csum removal, this expects the
 476  * key to describe the csum pointed to by the path, and it expects
 477  * the csum to overlap the range [bytenr, len]
 478  *
 479  * The csum should not be entirely contained in the range and the
 480  * range should not be entirely contained in the csum.
 481  *
 482  * This calls btrfs_truncate_item with the correct args based on the
 483  * overlap, and fixes up the key as required.
 484  */
 485 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 486                                       struct btrfs_root *root,
 487                                       struct btrfs_path *path,
 488                                       struct btrfs_key *key,
 489                                       u64 bytenr, u64 len)
 490 {
 491         struct extent_buffer *leaf;
 492         u16 csum_size =
 493                 btrfs_super_csum_size(&root->fs_info->super_copy);
 494         u64 csum_end;
 495         u64 end_byte = bytenr + len;
 496         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 497         int ret;
 498
 499         leaf = path->nodes[0];
 500         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 501         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 502         csum_end += key->offset;
 503
 504         if (key->offset < bytenr && csum_end <= end_byte) {
 505                 /*
 506                  *         [ bytenr - len ]
 507                  *         [   ]
 508                  *   [csum     ]
 509                  *   A simple truncate off the end of the item
 510                  */
 511                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 512                 new_size *= csum_size;
 513                 ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 514         } else if (key->offset >= bytenr && csum_end > end_byte &&
 515                    end_byte > key->offset) {
 516                 /*
 517                  *         [ bytenr - len ]
 518                  *                 [ ]
 519                  *                 [csum     ]
 520                  * we need to truncate from the beginning of the csum
 521                  */
 522                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 523                 new_size *= csum_size;
 524
 525                 ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 526
 527                 key->offset = end_byte;
 528                 ret = btrfs_set_item_key_safe(trans, root, path, key);
 529                 BUG_ON(ret);
 530         } else {
 531                 BUG();
 532         }
 533         return 0;
 534 }
 535
 536 /*
 537  * deletes the csum items from the csum tree for a given
 538  * range of bytes.
 539  */
 540 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 541                     struct btrfs_root *root, u64 bytenr, u64 len)
 542 {
 543         struct btrfs_path *path;
 544         struct btrfs_key key;
 545         u64 end_byte = bytenr + len;
 546         u64 csum_end;
 547         struct extent_buffer *leaf;
 548         int ret;
 549         u16 csum_size =
 550                 btrfs_super_csum_size(&root->fs_info->super_copy);
 551         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 552
 553         root = root->fs_info->csum_root;
 554
 555         path = btrfs_alloc_path();
 556         if (!path)
 557                 return -ENOMEM;
 558
 559         while (1) {
 560                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 561                 key.offset = end_byte - 1;
 562                 key.type = BTRFS_EXTENT_CSUM_KEY;
 563
 564                 path->leave_spinning = 1;
 565                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 566                 if (ret > 0) {
 567                         if (path->slots[0] == 0)
 568                                 break;
 569                         path->slots[0]--;
 570                 } else if (ret < 0) {
 571                         break;
 572                 }
 573
 574                 leaf = path->nodes[0];
 575                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 576
 577                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 578                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 579                         break;
 580                 }
 581
 582                 if (key.offset >= end_byte)
 583                         break;
 584
 585                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 586                 csum_end <<= blocksize_bits;
 587                 csum_end += key.offset;
 588
 589                 /* this csum ends before we start, we're done */
 590                 if (csum_end <= bytenr)
 591                         break;
 592
 593                 /* delete the entire item, it is inside our range */
 594                 if (key.offset >= bytenr && csum_end <= end_byte) {
 595                         ret = btrfs_del_item(trans, root, path);
 596                         if (ret)
 597                                 goto out;
 598                         if (key.offset == bytenr)
 599                                 break;
 600                 } else if (key.offset < bytenr && csum_end > end_byte) {
 601                         unsigned long offset;
 602                         unsigned long shift_len;
 603                         unsigned long item_offset;
 604                         /*
 605                          *        [ bytenr - len ]
 606                          *     [csum                ]
 607                          *
 608                          * Our bytes are in the middle of the csum,
 609                          * we need to split this item and insert a new one.
 610                          *
 611                          * But we can't drop the path because the
 612                          * csum could change, get removed, extended etc.
 613                          *
 614                          * The trick here is the max size of a csum item leaves
 615                          * enough room in the tree block for a single
 616                          * item header.  So, we split the item in place,
 617                          * adding a new header pointing to the existing
 618                          * bytes.  Then we loop around again and we have
 619                          * a nicely formed csum item that we can neatly
 620                          * truncate.
 621                          */
 622                         offset = (bytenr - key.offset) >> blocksize_bits;
 623                         offset *= csum_size;
 624
 625                         shift_len = (len >> blocksize_bits) * csum_size;
 626
 627                         item_offset = btrfs_item_ptr_offset(leaf,
 628                                                             path->slots[0]);
 629
 630                         memset_extent_buffer(leaf, 0, item_offset + offset,
 631                                              shift_len);
 632                         key.offset = bytenr;
 633
 634                         /*
 635                          * btrfs_split_item returns -EAGAIN when the
 636                          * item changed size or key
 637                          */
 638                         ret = btrfs_split_item(trans, root, path, &key, offset);
 639                         BUG_ON(ret && ret != -EAGAIN);
 640
 641                         key.offset = end_byte - 1;
 642                 } else {
 643                         ret = truncate_one_csum(trans, root, path,
 644                                                 &key, bytenr, len);
 645                         BUG_ON(ret);
 646                         if (key.offset < bytenr)
 647                                 break;
 648                 }
 649                 btrfs_release_path(path);
 650         }
 651         ret = 0;
 652 out:
 653         btrfs_free_path(path);
 654         return ret;
 655 }
 656
 657 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 658                            struct btrfs_root *root,
 659                            struct btrfs_ordered_sum *sums)
 660 {
 661         u64 bytenr;
 662         int ret;
 663         struct btrfs_key file_key;
 664         struct btrfs_key found_key;
 665         u64 next_offset;
 666         u64 total_bytes = 0;
 667         int found_next;
 668         struct btrfs_path *path;
 669         struct btrfs_csum_item *item;
 670         struct btrfs_csum_item *item_end;
 671         struct extent_buffer *leaf = NULL;
 672         u64 csum_offset;
 673         struct btrfs_sector_sum *sector_sum;
 674         u32 nritems;
 675         u32 ins_size;
 676         u16 csum_size =
 677                 btrfs_super_csum_size(&root->fs_info->super_copy);
 678
 679         path = btrfs_alloc_path();
 680         BUG_ON(!path);
 681         sector_sum = sums->sums;
 682 again:
 683         next_offset = (u64)-1;
 684         found_next = 0;
 685         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 686         file_key.offset = sector_sum->bytenr;
 687         bytenr = sector_sum->bytenr;
 688         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 689
 690         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 691         if (!IS_ERR(item)) {
 692                 leaf = path->nodes[0];
 693                 ret = 0;
 694                 goto found;
 695         }
 696         ret = PTR_ERR(item);
 697         if (ret != -EFBIG && ret != -ENOENT)
 698                 goto fail_unlock;
 699
 700         if (ret == -EFBIG) {
 701                 u32 item_size;
 702                 /* we found one, but it isn't big enough yet */
 703                 leaf = path->nodes[0];
 704                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 705                 if ((item_size / csum_size) >=
 706                     MAX_CSUM_ITEMS(root, csum_size)) {
 707                         /* already at max size, make a new one */
 708                         goto insert;
 709                 }
 710         } else {
 711                 int slot = path->slots[0] + 1;
 712                 /* we didn't find a csum item, insert one */
 713                 nritems = btrfs_header_nritems(path->nodes[0]);
 714                 if (path->slots[0] >= nritems - 1) {
 715                         ret = btrfs_next_leaf(root, path);
 716                         if (ret == 1)
 717                                 found_next = 1;
 718                         if (ret != 0)
 719                                 goto insert;
 720                         slot = 0;
 721                 }
 722                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 723                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 724                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 725                         found_next = 1;
 726                         goto insert;
 727                 }
 728                 next_offset = found_key.offset;
 729                 found_next = 1;
 730                 goto insert;
 731         }
 732
 733         /*
 734          * at this point, we know the tree has an item, but it isn't big
 735          * enough yet to put our csum in.  Grow it
 736          */
 737         btrfs_release_path(path);
 738         ret = btrfs_search_slot(trans, root, &file_key, path,
 739                                 csum_size, 1);
 740         if (ret < 0)
 741                 goto fail_unlock;
 742
 743         if (ret > 0) {
 744                 if (path->slots[0] == 0)
 745                         goto insert;
 746                 path->slots[0]--;
 747         }
 748
 749         leaf = path->nodes[0];
 750         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 751         csum_offset = (bytenr - found_key.offset) >>
 752                         root->fs_info->sb->s_blocksize_bits;
 753
 754         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 755             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 756             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 757                 goto insert;
 758         }
 759
 760         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 761             csum_size) {
 762                 u32 diff = (csum_offset + 1) * csum_size;
 763
 764                 /*
 765                  * is the item big enough already?  we dropped our lock
 766                  * before and need to recheck
 767                  */
 768                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 769                         goto csum;
 770
 771                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 772                 if (diff != csum_size)
 773                         goto insert;
 774
 775                 ret = btrfs_extend_item(trans, root, path, diff);
 776                 goto csum;
 777         }
 778
 779 insert:
 780         btrfs_release_path(path);
 781         csum_offset = 0;
 782         if (found_next) {
 783                 u64 tmp = total_bytes + root->sectorsize;
 784                 u64 next_sector = sector_sum->bytenr;
 785                 struct btrfs_sector_sum *next = sector_sum + 1;
 786
 787                 while (tmp < sums->len) {
 788                         if (next_sector + root->sectorsize != next->bytenr)
 789                                 break;
 790                         tmp += root->sectorsize;
 791                         next_sector = next->bytenr;
 792                         next++;
 793                 }
 794                 tmp = min(tmp, next_offset - file_key.offset);
 795                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 796                 tmp = max((u64)1, tmp);
 797                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 798                 ins_size = csum_size * tmp;
 799         } else {
 800                 ins_size = csum_size;
 801         }
 802         path->leave_spinning = 1;
 803         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 804                                       ins_size);
 805         path->leave_spinning = 0;
 806         if (ret < 0)
 807                 goto fail_unlock;
 808         if (ret != 0) {
 809                 WARN_ON(1);
 810                 goto fail_unlock;
 811         }
 812 csum:
 813         leaf = path->nodes[0];
 814         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 815         ret = 0;
 816         item = (struct btrfs_csum_item *)((unsigned char *)item +
 817                                           csum_offset * csum_size);
 818 found:
 819         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 820         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 821                                       btrfs_item_size_nr(leaf, path->slots[0]));
 822 next_sector:
 823
 824         write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item, csum_size);
 825
 826         total_bytes += root->sectorsize;
 827         sector_sum++;
 828         if (total_bytes < sums->len) {
 829                 item = (struct btrfs_csum_item *)((char *)item +
 830                                                   csum_size);
 831                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 832                     sector_sum->bytenr) {
 833                         bytenr = sector_sum->bytenr;
 834                         goto next_sector;
 835                 }
 836         }
 837
 838         btrfs_mark_buffer_dirty(path->nodes[0]);
 839         if (total_bytes < sums->len) {
 840                 btrfs_release_path(path);
 841                 cond_resched();
 842                 goto again;
 843         }
 844 out:
 845         btrfs_free_path(path);
 846         return ret;
 847
 848 fail_unlock:
 849         goto out;
 850 }