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) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
  29                                    sizeof(struct btrfs_item) * 2) / \
  30                                   size) - 1))
  31
  32 #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
  33                                        PAGE_CACHE_SIZE))
  34
  35 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
  36                                    sizeof(struct btrfs_ordered_sum)) / \
  37                                    sizeof(u32) * (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 static struct btrfs_csum_item *
  86 btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  87                   struct btrfs_root *root,
  88                   struct btrfs_path *path,
  89                   u64 bytenr, int cow)
  90 {
  91         int ret;
  92         struct btrfs_key file_key;
  93         struct btrfs_key found_key;
  94         struct btrfs_csum_item *item;
  95         struct extent_buffer *leaf;
  96         u64 csum_offset = 0;
  97         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
  98         int csums_in_item;
  99
 100         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 101         file_key.offset = bytenr;
 102         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 103         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 104         if (ret < 0)
 105                 goto fail;
 106         leaf = path->nodes[0];
 107         if (ret > 0) {
 108                 ret = 1;
 109                 if (path->slots[0] == 0)
 110                         goto fail;
 111                 path->slots[0]--;
 112                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 113                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 114                         goto fail;
 115
 116                 csum_offset = (bytenr - found_key.offset) >>
 117                                 root->fs_info->sb->s_blocksize_bits;
 118                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 119                 csums_in_item /= csum_size;
 120
 121                 if (csum_offset == csums_in_item) {
 122                         ret = -EFBIG;
 123                         goto fail;
 124                 } else if (csum_offset > csums_in_item) {
 125                         goto fail;
 126                 }
 127         }
 128         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 129         item = (struct btrfs_csum_item *)((unsigned char *)item +
 130                                           csum_offset * csum_size);
 131         return item;
 132 fail:
 133         if (ret > 0)
 134                 ret = -ENOENT;
 135         return ERR_PTR(ret);
 136 }
 137
 138 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 139                              struct btrfs_root *root,
 140                              struct btrfs_path *path, u64 objectid,
 141                              u64 offset, int mod)
 142 {
 143         int ret;
 144         struct btrfs_key file_key;
 145         int ins_len = mod < 0 ? -1 : 0;
 146         int cow = mod != 0;
 147
 148         file_key.objectid = objectid;
 149         file_key.offset = offset;
 150         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 151         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 152         return ret;
 153 }
 154
 155 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 156                                    struct inode *inode, struct bio *bio,
 157                                    u64 logical_offset, u32 *dst, int dio)
 158 {
 159         u32 sum[16];
 160         int len;
 161         struct bio_vec *bvec = bio->bi_io_vec;
 162         int bio_index = 0;
 163         u64 offset = 0;
 164         u64 item_start_offset = 0;
 165         u64 item_last_offset = 0;
 166         u64 disk_bytenr;
 167         u32 diff;
 168         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 169         int count;
 170         struct btrfs_path *path;
 171         struct btrfs_csum_item *item = NULL;
 172         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 173
 174         path = btrfs_alloc_path();
 175         if (!path)
 176                 return -ENOMEM;
 177         if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 178                 path->reada = 2;
 179
 180         WARN_ON(bio->bi_vcnt <= 0);
 181
 182         /*
 183          * the free space stuff is only read when it hasn't been
 184          * updated in the current transaction.  So, we can safely
 185          * read from the commit root and sidestep a nasty deadlock
 186          * between reading the free space cache and updating the csum tree.
 187          */
 188         if (btrfs_is_free_space_inode(inode)) {
 189                 path->search_commit_root = 1;
 190                 path->skip_locking = 1;
 191         }
 192
 193         disk_bytenr = (u64)bio->bi_sector << 9;
 194         if (dio)
 195                 offset = logical_offset;
 196         while (bio_index < bio->bi_vcnt) {
 197                 len = min_t(int, ARRAY_SIZE(sum), bio->bi_vcnt - bio_index);
 198                 if (!dio)
 199                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 200                 count = btrfs_find_ordered_sum(inode, offset, disk_bytenr, sum,
 201                                                len);
 202                 if (count)
 203                         goto found;
 204
 205                 if (!item || disk_bytenr < item_start_offset ||
 206                     disk_bytenr >= item_last_offset) {
 207                         struct btrfs_key found_key;
 208                         u32 item_size;
 209
 210                         if (item)
 211                                 btrfs_release_path(path);
 212                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 213                                                  path, disk_bytenr, 0);
 214                         if (IS_ERR(item)) {
 215                                 count = 1;
 216                                 sum[0] = 0;
 217                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 218                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 219                                         set_extent_bits(io_tree, offset,
 220                                                 offset + bvec->bv_len - 1,
 221                                                 EXTENT_NODATASUM, GFP_NOFS);
 222                                 } else {
 223                                         printk(KERN_INFO "btrfs no csum found "
 224                                                "for inode %llu start %llu\n",
 225                                                (unsigned long long)
 226                                                btrfs_ino(inode),
 227                                                (unsigned long long)offset);
 228                                 }
 229                                 item = NULL;
 230                                 btrfs_release_path(path);
 231                                 goto found;
 232                         }
 233                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 234                                               path->slots[0]);
 235
 236                         item_start_offset = found_key.offset;
 237                         item_size = btrfs_item_size_nr(path->nodes[0],
 238                                                        path->slots[0]);
 239                         item_last_offset = item_start_offset +
 240                                 (item_size / csum_size) *
 241                                 root->sectorsize;
 242                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 243                                               struct btrfs_csum_item);
 244                 }
 245                 /*
 246                  * this byte range must be able to fit inside
 247                  * a single leaf so it will also fit inside a u32
 248                  */
 249                 diff = disk_bytenr - item_start_offset;
 250                 diff = diff / root->sectorsize;
 251                 diff = diff * csum_size;
 252                 count = min_t(int, len, (item_last_offset - disk_bytenr) >>
 253                                         inode->i_sb->s_blocksize_bits);
 254                 read_extent_buffer(path->nodes[0], sum,
 255                                    ((unsigned long)item) + diff,
 256                                    csum_size * count);
 257 found:
 258                 if (dst) {
 259                         memcpy(dst, sum, count * csum_size);
 260                         dst += count;
 261                 } else {
 262                         if (dio)
 263                                 extent_cache_csums_dio(io_tree, offset, sum,
 264                                                        count);
 265                         else
 266                                 extent_cache_csums(io_tree, bio, bio_index, sum,
 267                                             count);
 268                 }
 269                 while (count--) {
 270                         disk_bytenr += bvec->bv_len;
 271                         offset += bvec->bv_len;
 272                         bio_index++;
 273                         bvec++;
 274                 }
 275         }
 276         btrfs_free_path(path);
 277         return 0;
 278 }
 279
 280 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 281                           struct bio *bio, u32 *dst)
 282 {
 283         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 284 }
 285
 286 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 287                               struct bio *bio, u64 offset)
 288 {
 289         return __btrfs_lookup_bio_sums(root, inode, bio, offset, NULL, 1);
 290 }
 291
 292 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 293                              struct list_head *list, int search_commit)
 294 {
 295         struct btrfs_key key;
 296         struct btrfs_path *path;
 297         struct extent_buffer *leaf;
 298         struct btrfs_ordered_sum *sums;
 299         struct btrfs_csum_item *item;
 300         LIST_HEAD(tmplist);
 301         unsigned long offset;
 302         int ret;
 303         size_t size;
 304         u64 csum_end;
 305         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 306
 307         path = btrfs_alloc_path();
 308         if (!path)
 309                 return -ENOMEM;
 310
 311         if (search_commit) {
 312                 path->skip_locking = 1;
 313                 path->reada = 2;
 314                 path->search_commit_root = 1;
 315         }
 316
 317         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 318         key.offset = start;
 319         key.type = BTRFS_EXTENT_CSUM_KEY;
 320
 321         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 322         if (ret < 0)
 323                 goto fail;
 324         if (ret > 0 && path->slots[0] > 0) {
 325                 leaf = path->nodes[0];
 326                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 327                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 328                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 329                         offset = (start - key.offset) >>
 330                                  root->fs_info->sb->s_blocksize_bits;
 331                         if (offset * csum_size <
 332                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 333                                 path->slots[0]--;
 334                 }
 335         }
 336
 337         while (start <= end) {
 338                 leaf = path->nodes[0];
 339                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 340                         ret = btrfs_next_leaf(root, path);
 341                         if (ret < 0)
 342                                 goto fail;
 343                         if (ret > 0)
 344                                 break;
 345                         leaf = path->nodes[0];
 346                 }
 347
 348                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 349                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 350                     key.type != BTRFS_EXTENT_CSUM_KEY ||
 351                     key.offset > end)
 352                         break;
 353
 354                 if (key.offset > start)
 355                         start = key.offset;
 356
 357                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 358                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 359                 if (csum_end <= start) {
 360                         path->slots[0]++;
 361                         continue;
 362                 }
 363
 364                 csum_end = min(csum_end, end + 1);
 365                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 366                                       struct btrfs_csum_item);
 367                 while (start < csum_end) {
 368                         size = min_t(size_t, csum_end - start,
 369                                      MAX_ORDERED_SUM_BYTES(root));
 370                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 371                                        GFP_NOFS);
 372                         if (!sums) {
 373                                 ret = -ENOMEM;
 374                                 goto fail;
 375                         }
 376
 377                         sums->bytenr = start;
 378                         sums->len = (int)size;
 379
 380                         offset = (start - key.offset) >>
 381                                 root->fs_info->sb->s_blocksize_bits;
 382                         offset *= csum_size;
 383                         size >>= root->fs_info->sb->s_blocksize_bits;
 384
 385                         read_extent_buffer(path->nodes[0],
 386                                            sums->sums,
 387                                            ((unsigned long)item) + offset,
 388                                            csum_size * size);
 389
 390                         start += root->sectorsize * size;
 391                         list_add_tail(&sums->list, &tmplist);
 392                 }
 393                 path->slots[0]++;
 394         }
 395         ret = 0;
 396 fail:
 397         while (ret < 0 && !list_empty(&tmplist)) {
 398                 sums = list_entry(&tmplist, struct btrfs_ordered_sum, list);
 399                 list_del(&sums->list);
 400                 kfree(sums);
 401         }
 402         list_splice_tail(&tmplist, list);
 403
 404         btrfs_free_path(path);
 405         return ret;
 406 }
 407
 408 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 409                        struct bio *bio, u64 file_start, int contig)
 410 {
 411         struct btrfs_ordered_sum *sums;
 412         struct btrfs_ordered_extent *ordered;
 413         char *data;
 414         struct bio_vec *bvec = bio->bi_io_vec;
 415         int bio_index = 0;
 416         int index;
 417         unsigned long total_bytes = 0;
 418         unsigned long this_sum_bytes = 0;
 419         u64 offset;
 420
 421         WARN_ON(bio->bi_vcnt <= 0);
 422         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 423         if (!sums)
 424                 return -ENOMEM;
 425
 426         sums->len = bio->bi_size;
 427         INIT_LIST_HEAD(&sums->list);
 428
 429         if (contig)
 430                 offset = file_start;
 431         else
 432                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 433
 434         ordered = btrfs_lookup_ordered_extent(inode, offset);
 435         BUG_ON(!ordered); /* Logic error */
 436         sums->bytenr = (u64)bio->bi_sector << 9;
 437         index = 0;
 438
 439         while (bio_index < bio->bi_vcnt) {
 440                 if (!contig)
 441                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 442
 443                 if (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                         sums->len = bytes_left;
 457                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 458                         BUG_ON(!ordered); /* Logic error */
 459                         sums->bytenr = ((u64)bio->bi_sector << 9) +
 460                                        total_bytes;
 461                         index = 0;
 462                 }
 463
 464                 data = kmap_atomic(bvec->bv_page);
 465                 sums->sums[index] = ~(u32)0;
 466                 sums->sums[index] = btrfs_csum_data(data + bvec->bv_offset,
 467                                                     sums->sums[index],
 468                                                     bvec->bv_len);
 469                 kunmap_atomic(data);
 470                 btrfs_csum_final(sums->sums[index],
 471                                  (char *)(sums->sums + index));
 472
 473                 bio_index++;
 474                 index++;
 475                 total_bytes += bvec->bv_len;
 476                 this_sum_bytes += 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_root *root,
 498                                        struct btrfs_path *path,
 499                                        struct btrfs_key *key,
 500                                        u64 bytenr, u64 len)
 501 {
 502         struct extent_buffer *leaf;
 503         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 504         u64 csum_end;
 505         u64 end_byte = bytenr + len;
 506         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 507
 508         leaf = path->nodes[0];
 509         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 510         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 511         csum_end += key->offset;
 512
 513         if (key->offset < bytenr && csum_end <= end_byte) {
 514                 /*
 515                  *         [ bytenr - len ]
 516                  *         [   ]
 517                  *   [csum     ]
 518                  *   A simple truncate off the end of the item
 519                  */
 520                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 521                 new_size *= csum_size;
 522                 btrfs_truncate_item(root, path, new_size, 1);
 523         } else if (key->offset >= bytenr && csum_end > end_byte &&
 524                    end_byte > key->offset) {
 525                 /*
 526                  *         [ bytenr - len ]
 527                  *                 [ ]
 528                  *                 [csum     ]
 529                  * we need to truncate from the beginning of the csum
 530                  */
 531                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 532                 new_size *= csum_size;
 533
 534                 btrfs_truncate_item(root, path, new_size, 0);
 535
 536                 key->offset = end_byte;
 537                 btrfs_set_item_key_safe(root, path, key);
 538         } else {
 539                 BUG();
 540         }
 541 }
 542
 543 /*
 544  * deletes the csum items from the csum tree for a given
 545  * range of bytes.
 546  */
 547 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 548                     struct btrfs_root *root, u64 bytenr, u64 len)
 549 {
 550         struct btrfs_path *path;
 551         struct btrfs_key key;
 552         u64 end_byte = bytenr + len;
 553         u64 csum_end;
 554         struct extent_buffer *leaf;
 555         int ret;
 556         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 557         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 558
 559         root = root->fs_info->csum_root;
 560
 561         path = btrfs_alloc_path();
 562         if (!path)
 563                 return -ENOMEM;
 564
 565         while (1) {
 566                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 567                 key.offset = end_byte - 1;
 568                 key.type = BTRFS_EXTENT_CSUM_KEY;
 569
 570                 path->leave_spinning = 1;
 571                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 572                 if (ret > 0) {
 573                         if (path->slots[0] == 0)
 574                                 break;
 575                         path->slots[0]--;
 576                 } else if (ret < 0) {
 577                         break;
 578                 }
 579
 580                 leaf = path->nodes[0];
 581                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 582
 583                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 584                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 585                         break;
 586                 }
 587
 588                 if (key.offset >= end_byte)
 589                         break;
 590
 591                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 592                 csum_end <<= blocksize_bits;
 593                 csum_end += key.offset;
 594
 595                 /* this csum ends before we start, we're done */
 596                 if (csum_end <= bytenr)
 597                         break;
 598
 599                 /* delete the entire item, it is inside our range */
 600                 if (key.offset >= bytenr && csum_end <= end_byte) {
 601                         ret = btrfs_del_item(trans, root, path);
 602                         if (ret)
 603                                 goto out;
 604                         if (key.offset == bytenr)
 605                                 break;
 606                 } else if (key.offset < bytenr && csum_end > end_byte) {
 607                         unsigned long offset;
 608                         unsigned long shift_len;
 609                         unsigned long item_offset;
 610                         /*
 611                          *        [ bytenr - len ]
 612                          *     [csum                ]
 613                          *
 614                          * Our bytes are in the middle of the csum,
 615                          * we need to split this item and insert a new one.
 616                          *
 617                          * But we can't drop the path because the
 618                          * csum could change, get removed, extended etc.
 619                          *
 620                          * The trick here is the max size of a csum item leaves
 621                          * enough room in the tree block for a single
 622                          * item header.  So, we split the item in place,
 623                          * adding a new header pointing to the existing
 624                          * bytes.  Then we loop around again and we have
 625                          * a nicely formed csum item that we can neatly
 626                          * truncate.
 627                          */
 628                         offset = (bytenr - key.offset) >> blocksize_bits;
 629                         offset *= csum_size;
 630
 631                         shift_len = (len >> blocksize_bits) * csum_size;
 632
 633                         item_offset = btrfs_item_ptr_offset(leaf,
 634                                                             path->slots[0]);
 635
 636                         memset_extent_buffer(leaf, 0, item_offset + offset,
 637                                              shift_len);
 638                         key.offset = bytenr;
 639
 640                         /*
 641                          * btrfs_split_item returns -EAGAIN when the
 642                          * item changed size or key
 643                          */
 644                         ret = btrfs_split_item(trans, root, path, &key, offset);
 645                         if (ret && ret != -EAGAIN) {
 646                                 btrfs_abort_transaction(trans, root, ret);
 647                                 goto out;
 648                         }
 649
 650                         key.offset = end_byte - 1;
 651                 } else {
 652                         truncate_one_csum(root, path, &key, bytenr, len);
 653                         if (key.offset < bytenr)
 654                                 break;
 655                 }
 656                 btrfs_release_path(path);
 657         }
 658         ret = 0;
 659 out:
 660         btrfs_free_path(path);
 661         return ret;
 662 }
 663
 664 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 665                            struct btrfs_root *root,
 666                            struct btrfs_ordered_sum *sums)
 667 {
 668         struct btrfs_key file_key;
 669         struct btrfs_key found_key;
 670         struct btrfs_path *path;
 671         struct btrfs_csum_item *item;
 672         struct btrfs_csum_item *item_end;
 673         struct extent_buffer *leaf = NULL;
 674         u64 next_offset;
 675         u64 total_bytes = 0;
 676         u64 csum_offset;
 677         u64 bytenr;
 678         u32 nritems;
 679         u32 ins_size;
 680         int index = 0;
 681         int found_next;
 682         int ret;
 683         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 684
 685         path = btrfs_alloc_path();
 686         if (!path)
 687                 return -ENOMEM;
 688 again:
 689         next_offset = (u64)-1;
 690         found_next = 0;
 691         bytenr = sums->bytenr + total_bytes;
 692         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 693         file_key.offset = bytenr;
 694         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 695
 696         item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
 697         if (!IS_ERR(item)) {
 698                 ret = 0;
 699                 leaf = path->nodes[0];
 700                 item_end = btrfs_item_ptr(leaf, path->slots[0],
 701                                           struct btrfs_csum_item);
 702                 item_end = (struct btrfs_csum_item *)((char *)item_end +
 703                            btrfs_item_size_nr(leaf, path->slots[0]));
 704                 goto found;
 705         }
 706         ret = PTR_ERR(item);
 707         if (ret != -EFBIG && ret != -ENOENT)
 708                 goto fail_unlock;
 709
 710         if (ret == -EFBIG) {
 711                 u32 item_size;
 712                 /* we found one, but it isn't big enough yet */
 713                 leaf = path->nodes[0];
 714                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 715                 if ((item_size / csum_size) >=
 716                     MAX_CSUM_ITEMS(root, csum_size)) {
 717                         /* already at max size, make a new one */
 718                         goto insert;
 719                 }
 720         } else {
 721                 int slot = path->slots[0] + 1;
 722                 /* we didn't find a csum item, insert one */
 723                 nritems = btrfs_header_nritems(path->nodes[0]);
 724                 if (path->slots[0] >= nritems - 1) {
 725                         ret = btrfs_next_leaf(root, path);
 726                         if (ret == 1)
 727                                 found_next = 1;
 728                         if (ret != 0)
 729                                 goto insert;
 730                         slot = 0;
 731                 }
 732                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 733                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 734                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 735                         found_next = 1;
 736                         goto insert;
 737                 }
 738                 next_offset = found_key.offset;
 739                 found_next = 1;
 740                 goto insert;
 741         }
 742
 743         /*
 744          * at this point, we know the tree has an item, but it isn't big
 745          * enough yet to put our csum in.  Grow it
 746          */
 747         btrfs_release_path(path);
 748         ret = btrfs_search_slot(trans, root, &file_key, path,
 749                                 csum_size, 1);
 750         if (ret < 0)
 751                 goto fail_unlock;
 752
 753         if (ret > 0) {
 754                 if (path->slots[0] == 0)
 755                         goto insert;
 756                 path->slots[0]--;
 757         }
 758
 759         leaf = path->nodes[0];
 760         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 761         csum_offset = (bytenr - found_key.offset) >>
 762                         root->fs_info->sb->s_blocksize_bits;
 763
 764         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 765             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 766             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 767                 goto insert;
 768         }
 769
 770         if (csum_offset == btrfs_item_size_nr(leaf, path->slots[0]) /
 771             csum_size) {
 772                 int extend_nr;
 773                 u64 tmp;
 774                 u32 diff;
 775                 u32 free_space;
 776
 777                 if (btrfs_leaf_free_space(root, leaf) <
 778                                  sizeof(struct btrfs_item) + csum_size * 2)
 779                         goto insert;
 780
 781                 free_space = btrfs_leaf_free_space(root, leaf) -
 782                                          sizeof(struct btrfs_item) - csum_size;
 783                 tmp = sums->len - total_bytes;
 784                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 785                 WARN_ON(tmp < 1);
 786
 787                 extend_nr = max_t(int, 1, (int)tmp);
 788                 diff = (csum_offset + extend_nr) * csum_size;
 789                 diff = min(diff, MAX_CSUM_ITEMS(root, csum_size) * csum_size);
 790
 791                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 792                 diff = min(free_space, diff);
 793                 diff /= csum_size;
 794                 diff *= csum_size;
 795
 796                 btrfs_extend_item(root, path, diff);
 797                 ret = 0;
 798                 goto csum;
 799         }
 800
 801 insert:
 802         btrfs_release_path(path);
 803         csum_offset = 0;
 804         if (found_next) {
 805                 u64 tmp;
 806
 807                 tmp = sums->len - total_bytes;
 808                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 809                 tmp = min(tmp, (next_offset - file_key.offset) >>
 810                                          root->fs_info->sb->s_blocksize_bits);
 811
 812                 tmp = max((u64)1, tmp);
 813                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 814                 ins_size = csum_size * tmp;
 815         } else {
 816                 ins_size = csum_size;
 817         }
 818         path->leave_spinning = 1;
 819         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 820                                       ins_size);
 821         path->leave_spinning = 0;
 822         if (ret < 0)
 823                 goto fail_unlock;
 824         if (ret != 0) {
 825                 WARN_ON(1);
 826                 goto fail_unlock;
 827         }
 828         leaf = path->nodes[0];
 829 csum:
 830         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 831         item_end = (struct btrfs_csum_item *)((unsigned char *)item +
 832                                       btrfs_item_size_nr(leaf, path->slots[0]));
 833         item = (struct btrfs_csum_item *)((unsigned char *)item +
 834                                           csum_offset * csum_size);
 835 found:
 836         ins_size = (u32)(sums->len - total_bytes) >>
 837                    root->fs_info->sb->s_blocksize_bits;
 838         ins_size *= csum_size;
 839         ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
 840                               ins_size);
 841         write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
 842                             ins_size);
 843
 844         ins_size /= csum_size;
 845         total_bytes += ins_size * root->sectorsize;
 846         index += ins_size;
 847
 848         btrfs_mark_buffer_dirty(path->nodes[0]);
 849         if (total_bytes < sums->len) {
 850                 btrfs_release_path(path);
 851                 cond_resched();
 852                 goto again;
 853         }
 854 out:
 855         btrfs_free_path(path);
 856         return ret;
 857
 858 fail_unlock:
 859         goto out;
 860 }