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); /* Can't happen */
  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 = btrfs_super_csum_size(root->fs_info->super_copy);
  95         int csums_in_item;
  96
  97         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  98         file_key.offset = bytenr;
  99         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 100         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 101         if (ret < 0)
 102                 goto fail;
 103         leaf = path->nodes[0];
 104         if (ret > 0) {
 105                 ret = 1;
 106                 if (path->slots[0] == 0)
 107                         goto fail;
 108                 path->slots[0]--;
 109                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 110                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 111                         goto fail;
 112
 113                 csum_offset = (bytenr - found_key.offset) >>
 114                                 root->fs_info->sb->s_blocksize_bits;
 115                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 116                 csums_in_item /= csum_size;
 117
 118                 if (csum_offset >= csums_in_item) {
 119                         ret = -EFBIG;
 120                         goto fail;
 121                 }
 122         }
 123         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 124         item = (struct btrfs_csum_item *)((unsigned char *)item +
 125                                           csum_offset * csum_size);
 126         return item;
 127 fail:
 128         if (ret > 0)
 129                 ret = -ENOENT;
 130         return ERR_PTR(ret);
 131 }
 132
 133
 134 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 135                              struct btrfs_root *root,
 136                              struct btrfs_path *path, u64 objectid,
 137                              u64 offset, int mod)
 138 {
 139         int ret;
 140         struct btrfs_key file_key;
 141         int ins_len = mod < 0 ? -1 : 0;
 142         int cow = mod != 0;
 143
 144         file_key.objectid = objectid;
 145         file_key.offset = offset;
 146         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 147         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 148         return ret;
 149 }
 150
 151
 152 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 153                                    struct inode *inode, struct bio *bio,
 154                                    u64 logical_offset, u32 *dst, int dio)
 155 {
 156         u32 sum;
 157         struct bio_vec *bvec = bio->bi_io_vec;
 158         int bio_index = 0;
 159         u64 offset = 0;
 160         u64 item_start_offset = 0;
 161         u64 item_last_offset = 0;
 162         u64 disk_bytenr;
 163         u32 diff;
 164         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 165         int ret;
 166         struct btrfs_path *path;
 167         struct btrfs_csum_item *item = NULL;
 168         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 169
 170         path = btrfs_alloc_path();
 171         if (!path)
 172                 return -ENOMEM;
 173         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 174                 path->reada = 2;
 175
 176         WARN_ON(bio->bi_vcnt <= 0);
 177
 178         /*
 179          * the free space stuff is only read when it hasn't been
 180          * updated in the current transaction.  So, we can safely
 181          * read from the commit root and sidestep a nasty deadlock
 182          * between reading the free space cache and updating the csum tree.
 183          */
 184         if (btrfs_is_free_space_inode(root, inode)) {
 185                 path->search_commit_root = 1;
 186                 path->skip_locking = 1;
 187         }
 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         LIST_HEAD(tmplist);
 288         unsigned long offset;
 289         int ret;
 290         size_t size;
 291         u64 csum_end;
 292         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 293
 294         path = btrfs_alloc_path();
 295         if (!path)
 296                 return -ENOMEM;
 297
 298         if (search_commit) {
 299                 path->skip_locking = 1;
 300                 path->reada = 2;
 301                 path->search_commit_root = 1;
 302         }
 303
 304         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 305         key.offset = start;
 306         key.type = BTRFS_EXTENT_CSUM_KEY;
 307
 308         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 309         if (ret < 0)
 310                 goto fail;
 311         if (ret > 0 && path->slots[0] > 0) {
 312                 leaf = path->nodes[0];
 313                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 314                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 315                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 316                         offset = (start - key.offset) >>
 317                                  root->fs_info->sb->s_blocksize_bits;
 318                         if (offset * csum_size <
 319                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 320                                 path->slots[0]--;
 321                 }
 322         }
 323
 324         while (start <= end) {
 325                 leaf = path->nodes[0];
 326                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 327                         ret = btrfs_next_leaf(root, path);
 328                         if (ret < 0)
 329                                 goto fail;
 330                         if (ret > 0)
 331                                 break;
 332                         leaf = path->nodes[0];
 333                 }
 334
 335                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 336                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 337                     key.type != BTRFS_EXTENT_CSUM_KEY)
 338                         break;
 339
 340                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 341                 if (key.offset > end)
 342                         break;
 343
 344                 if (key.offset > start)
 345                         start = key.offset;
 346
 347                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 348                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 349                 if (csum_end <= start) {
 350                         path->slots[0]++;
 351                         continue;
 352                 }
 353
 354                 csum_end = min(csum_end, end + 1);
 355                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 356                                       struct btrfs_csum_item);
 357                 while (start < csum_end) {
 358                         size = min_t(size_t, csum_end - start,
 359                                         MAX_ORDERED_SUM_BYTES(root));
 360                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 361                                         GFP_NOFS);
 362                         if (!sums) {
 363                                 ret = -ENOMEM;
 364                                 goto fail;
 365                         }
 366
 367                         sector_sum = sums->sums;
 368                         sums->bytenr = start;
 369                         sums->len = size;
 370
 371                         offset = (start - key.offset) >>
 372                                 root->fs_info->sb->s_blocksize_bits;
 373                         offset *= csum_size;
 374
 375                         while (size > 0) {
 376                                 read_extent_buffer(path->nodes[0],
 377                                                 &sector_sum->sum,
 378                                                 ((unsigned long)item) +
 379                                                 offset, csum_size);
 380                                 sector_sum->bytenr = start;
 381
 382                                 size -= root->sectorsize;
 383                                 start += root->sectorsize;
 384                                 offset += csum_size;
 385                                 sector_sum++;
 386                         }
 387                         list_add_tail(&sums->list, &tmplist);
 388                 }
 389                 path->slots[0]++;
 390         }
 391         ret = 0;
 392 fail:
 393         while (ret < 0 && !list_empty(&tmplist)) {
 394                 sums = list_entry(&tmplist, struct btrfs_ordered_sum, list);
 395                 list_del(&sums->list);
 396                 kfree(sums);
 397         }
 398         list_splice_tail(&tmplist, list);
 399
 400         btrfs_free_path(path);
 401         return ret;
 402 }
 403
 404 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 405                        struct bio *bio, u64 file_start, int contig)
 406 {
 407         struct btrfs_ordered_sum *sums;
 408         struct btrfs_sector_sum *sector_sum;
 409         struct btrfs_ordered_extent *ordered;
 410         char *data;
 411         struct bio_vec *bvec = bio->bi_io_vec;
 412         int bio_index = 0;
 413         unsigned long total_bytes = 0;
 414         unsigned long this_sum_bytes = 0;
 415         u64 offset;
 416         u64 disk_bytenr;
 417
 418         WARN_ON(bio->bi_vcnt <= 0);
 419         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 420         if (!sums)
 421                 return -ENOMEM;
 422
 423         sector_sum = sums->sums;
 424         disk_bytenr = (u64)bio->bi_sector << 9;
 425         sums->len = bio->bi_size;
 426         INIT_LIST_HEAD(&sums->list);
 427
 428         if (contig)
 429                 offset = file_start;
 430         else
 431                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 432
 433         ordered = btrfs_lookup_ordered_extent(inode, offset);
 434         BUG_ON(!ordered); /* Logic error */
 435         sums->bytenr = ordered->start;
 436
 437         while (bio_index < bio->bi_vcnt) {
 438                 if (!contig)
 439                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 440
 441                 if (!contig && (offset >= ordered->file_offset + ordered->len ||
 442                     offset < ordered->file_offset)) {
 443                         unsigned long bytes_left;
 444                         sums->len = this_sum_bytes;
 445                         this_sum_bytes = 0;
 446                         btrfs_add_ordered_sum(inode, ordered, sums);
 447                         btrfs_put_ordered_extent(ordered);
 448
 449                         bytes_left = bio->bi_size - total_bytes;
 450
 451                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 452                                        GFP_NOFS);
 453                         BUG_ON(!sums); /* -ENOMEM */
 454                         sector_sum = sums->sums;
 455                         sums->len = bytes_left;
 456                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 457                         BUG_ON(!ordered); /* Logic error */
 458                         sums->bytenr = ordered->start;
 459                 }
 460
 461                 data = kmap_atomic(bvec->bv_page, KM_USER0);
 462                 sector_sum->sum = ~(u32)0;
 463                 sector_sum->sum = btrfs_csum_data(root,
 464                                                   data + bvec->bv_offset,
 465                                                   sector_sum->sum,
 466                                                   bvec->bv_len);
 467                 kunmap_atomic(data, KM_USER0);
 468                 btrfs_csum_final(sector_sum->sum,
 469                                  (char *)&sector_sum->sum);
 470                 sector_sum->bytenr = disk_bytenr;
 471
 472                 sector_sum++;
 473                 bio_index++;
 474                 total_bytes += bvec->bv_len;
 475                 this_sum_bytes += bvec->bv_len;
 476                 disk_bytenr += bvec->bv_len;
 477                 offset += bvec->bv_len;
 478                 bvec++;
 479         }
 480         this_sum_bytes = 0;
 481         btrfs_add_ordered_sum(inode, ordered, sums);
 482         btrfs_put_ordered_extent(ordered);
 483         return 0;
 484 }
 485
 486 /*
 487  * helper function for csum removal, this expects the
 488  * key to describe the csum pointed to by the path, and it expects
 489  * the csum to overlap the range [bytenr, len]
 490  *
 491  * The csum should not be entirely contained in the range and the
 492  * range should not be entirely contained in the csum.
 493  *
 494  * This calls btrfs_truncate_item with the correct args based on the
 495  * overlap, and fixes up the key as required.
 496  */
 497 static noinline void truncate_one_csum(struct btrfs_trans_handle *trans,
 498                                        struct btrfs_root *root,
 499                                        struct btrfs_path *path,
 500                                        struct btrfs_key *key,
 501                                        u64 bytenr, u64 len)
 502 {
 503         struct extent_buffer *leaf;
 504         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 505         u64 csum_end;
 506         u64 end_byte = bytenr + len;
 507         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 508
 509         leaf = path->nodes[0];
 510         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 511         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 512         csum_end += key->offset;
 513
 514         if (key->offset < bytenr && csum_end <= end_byte) {
 515                 /*
 516                  *         [ bytenr - len ]
 517                  *         [   ]
 518                  *   [csum     ]
 519                  *   A simple truncate off the end of the item
 520                  */
 521                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 522                 new_size *= csum_size;
 523                 btrfs_truncate_item(trans, root, path, new_size, 1);
 524         } else if (key->offset >= bytenr && csum_end > end_byte &&
 525                    end_byte > key->offset) {
 526                 /*
 527                  *         [ bytenr - len ]
 528                  *                 [ ]
 529                  *                 [csum     ]
 530                  * we need to truncate from the beginning of the csum
 531                  */
 532                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 533                 new_size *= csum_size;
 534
 535                 btrfs_truncate_item(trans, root, path, new_size, 0);
 536
 537                 key->offset = end_byte;
 538                 btrfs_set_item_key_safe(trans, root, path, key);
 539         } else {
 540                 BUG();
 541         }
 542 }
 543
 544 /*
 545  * deletes the csum items from the csum tree for a given
 546  * range of bytes.
 547  */
 548 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 549                     struct btrfs_root *root, u64 bytenr, u64 len)
 550 {
 551         struct btrfs_path *path;
 552         struct btrfs_key key;
 553         u64 end_byte = bytenr + len;
 554         u64 csum_end;
 555         struct extent_buffer *leaf;
 556         int ret;
 557         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 558         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 559
 560         root = root->fs_info->csum_root;
 561
 562         path = btrfs_alloc_path();
 563         if (!path)
 564                 return -ENOMEM;
 565
 566         while (1) {
 567                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 568                 key.offset = end_byte - 1;
 569                 key.type = BTRFS_EXTENT_CSUM_KEY;
 570
 571                 path->leave_spinning = 1;
 572                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 573                 if (ret > 0) {
 574                         if (path->slots[0] == 0)
 575                                 break;
 576                         path->slots[0]--;
 577                 } else if (ret < 0) {
 578                         break;
 579                 }
 580
 581                 leaf = path->nodes[0];
 582                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 583
 584                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 585                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 586                         break;
 587                 }
 588
 589                 if (key.offset >= end_byte)
 590                         break;
 591
 592                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 593                 csum_end <<= blocksize_bits;
 594                 csum_end += key.offset;
 595
 596                 /* this csum ends before we start, we're done */
 597                 if (csum_end <= bytenr)
 598                         break;
 599
 600                 /* delete the entire item, it is inside our range */
 601                 if (key.offset >= bytenr && csum_end <= end_byte) {
 602                         ret = btrfs_del_item(trans, root, path);
 603                         if (ret)
 604                                 goto out;
 605                         if (key.offset == bytenr)
 606                                 break;
 607                 } else if (key.offset < bytenr && csum_end > end_byte) {
 608                         unsigned long offset;
 609                         unsigned long shift_len;
 610                         unsigned long item_offset;
 611                         /*
 612                          *        [ bytenr - len ]
 613                          *     [csum                ]
 614                          *
 615                          * Our bytes are in the middle of the csum,
 616                          * we need to split this item and insert a new one.
 617                          *
 618                          * But we can't drop the path because the
 619                          * csum could change, get removed, extended etc.
 620                          *
 621                          * The trick here is the max size of a csum item leaves
 622                          * enough room in the tree block for a single
 623                          * item header.  So, we split the item in place,
 624                          * adding a new header pointing to the existing
 625                          * bytes.  Then we loop around again and we have
 626                          * a nicely formed csum item that we can neatly
 627                          * truncate.
 628                          */
 629                         offset = (bytenr - key.offset) >> blocksize_bits;
 630                         offset *= csum_size;
 631
 632                         shift_len = (len >> blocksize_bits) * csum_size;
 633
 634                         item_offset = btrfs_item_ptr_offset(leaf,
 635                                                             path->slots[0]);
 636
 637                         memset_extent_buffer(leaf, 0, item_offset + offset,
 638                                              shift_len);
 639                         key.offset = bytenr;
 640
 641                         /*
 642                          * btrfs_split_item returns -EAGAIN when the
 643                          * item changed size or key
 644                          */
 645                         ret = btrfs_split_item(trans, root, path, &key, offset);
 646                         if (ret && ret != -EAGAIN) {
 647                                 btrfs_abort_transaction(trans, root, ret);
 648                                 goto out;
 649                         }
 650
 651                         key.offset = end_byte - 1;
 652                 } else {
 653                         truncate_one_csum(trans, root, path, &key, bytenr, len);
 654                         if (key.offset < bytenr)
 655                                 break;
 656                 }
 657                 btrfs_release_path(path);
 658         }
 659         ret = 0;
 660 out:
 661         btrfs_free_path(path);
 662         return ret;
 663 }
 664
 665 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 666                            struct btrfs_root *root,
 667                            struct btrfs_ordered_sum *sums)
 668 {
 669         u64 bytenr;
 670         int ret;
 671         struct btrfs_key file_key;
 672         struct btrfs_key found_key;
 673         u64 next_offset;
 674         u64 total_bytes = 0;
 675         int found_next;
 676         struct btrfs_path *path;
 677         struct btrfs_csum_item *item;
 678         struct btrfs_csum_item *item_end;
 679         struct extent_buffer *leaf = NULL;
 680         u64 csum_offset;
 681         struct btrfs_sector_sum *sector_sum;
 682         u32 nritems;
 683         u32 ins_size;
 684         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 685
 686         path = btrfs_alloc_path();
 687         if (!path)
 688                 return -ENOMEM;
 689
 690         sector_sum = sums->sums;
 691 again:
 692         next_offset = (u64)-1;
 693         found_next = 0;
 694         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 695         file_key.offset = sector_sum->bytenr;
 696         bytenr = sector_sum->bytenr;
 697         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 698
 699         item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 700         if (!IS_ERR(item)) {
 701                 leaf = path->nodes[0];
 702                 ret = 0;
 703                 goto found;
 704         }
 705         ret = PTR_ERR(item);
 706         if (ret != -EFBIG && ret != -ENOENT)
 707                 goto fail_unlock;
 708
 709         if (ret == -EFBIG) {
 710                 u32 item_size;
 711                 /* we found one, but it isn't big enough yet */
 712                 leaf = path->nodes[0];
 713                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 714                 if ((item_size / csum_size) >=
 715                     MAX_CSUM_ITEMS(root, csum_size)) {
 716                         /* already at max size, make a new one */
 717                         goto insert;
 718                 }
 719         } else {
 720                 int slot = path->slots[0] + 1;
 721                 /* we didn't find a csum item, insert one */
 722                 nritems = btrfs_header_nritems(path->nodes[0]);
 723                 if (path->slots[0] >= nritems - 1) {
 724                         ret = btrfs_next_leaf(root, path);
 725                         if (ret == 1)
 726                                 found_next = 1;
 727                         if (ret != 0)
 728                                 goto insert;
 729                         slot = 0;
 730                 }
 731                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 732                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 733                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 734                         found_next = 1;
 735                         goto insert;
 736                 }
 737                 next_offset = found_key.offset;
 738                 found_next = 1;
 739                 goto insert;
 740         }
 741
 742         /*
 743          * at this point, we know the tree has an item, but it isn't big
 744          * enough yet to put our csum in.  Grow it
 745          */
 746         btrfs_release_path(path);
 747         ret = btrfs_search_slot(trans, root, &file_key, path,
 748                                 csum_size, 1);
 749         if (ret < 0)
 750                 goto fail_unlock;
 751
 752         if (ret > 0) {
 753                 if (path->slots[0] == 0)
 754                         goto insert;
 755                 path->slots[0]--;
 756         }
 757
 758         leaf = path->nodes[0];
 759         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 760         csum_offset = (bytenr - found_key.offset) >>
 761                         root->fs_info->sb->s_blocksize_bits;
 762
 763         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 764             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 765             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 766                 goto insert;
 767         }
 768
 769         if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 770             csum_size) {
 771                 u32 diff = (csum_offset + 1) * csum_size;
 772
 773                 /*
 774                  * is the item big enough already?  we dropped our lock
 775                  * before and need to recheck
 776                  */
 777                 if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 778                         goto csum;
 779
 780                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 781                 if (diff != csum_size)
 782                         goto insert;
 783
 784                 btrfs_extend_item(trans, root, path, diff);
 785                 goto csum;
 786         }
 787
 788 insert:
 789         btrfs_release_path(path);
 790         csum_offset = 0;
 791         if (found_next) {
 792                 u64 tmp = total_bytes + root->sectorsize;
 793                 u64 next_sector = sector_sum->bytenr;
 794                 struct btrfs_sector_sum *next = sector_sum + 1;
 795
 796                 while (tmp < sums->len) {
 797                         if (next_sector + root->sectorsize != next->bytenr)
 798                                 break;
 799                         tmp += root->sectorsize;
 800                         next_sector = next->bytenr;
 801                         next++;
 802                 }
 803                 tmp = min(tmp, next_offset - file_key.offset);
 804                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 805                 tmp = max((u64)1, tmp);
 806                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 807                 ins_size = csum_size * tmp;
 808         } else {
 809                 ins_size = csum_size;
 810         }
 811         path->leave_spinning = 1;
 812         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 813                                       ins_size);
 814         path->leave_spinning = 0;
 815         if (ret < 0)
 816                 goto fail_unlock;
 817         if (ret != 0) {
 818                 WARN_ON(1);
 819                 goto fail_unlock;
 820         }
 821 csum:
 822         leaf = path->nodes[0];
 823         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 824         ret = 0;
 825         item = (struct btrfs_csum_item *)((unsigned char *)item +
 826                                           csum_offset * csum_size);
 827 found:
 828         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 829         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 830                                       btrfs_item_size_nr(leaf, path->slots[0]));
 831 next_sector:
 832
 833         write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item, csum_size);
 834
 835         total_bytes += root->sectorsize;
 836         sector_sum++;
 837         if (total_bytes < sums->len) {
 838                 item = (struct btrfs_csum_item *)((char *)item +
 839                                                   csum_size);
 840                 if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 841                     sector_sum->bytenr) {
 842                         bytenr = sector_sum->bytenr;
 843                         goto next_sector;
 844                 }
 845         }
 846
 847         btrfs_mark_buffer_dirty(path->nodes[0]);
 848         if (total_bytes < sums->len) {
 849                 btrfs_release_path(path);
 850                 cond_resched();
 851                 goto again;
 852         }
 853 out:
 854         btrfs_free_path(path);
 855         return ret;
 856
 857 fail_unlock:
 858         goto out;
 859 }