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