Pileus Git - ~andy/linux/blob - 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 "volumes.h"
  27 #include "print-tree.h"
  28
  29 #define __MAX_CSUM_ITEMS(r, size) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
  30                                    sizeof(struct btrfs_item) * 2) / \
  31                                   size) - 1))
  32
  33 #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
  34                                        PAGE_CACHE_SIZE))
  35
  36 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
  37                                    sizeof(struct btrfs_ordered_sum)) / \
  38                                    sizeof(u32) * (r)->sectorsize)
  39
  40 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
  41                              struct btrfs_root *root,
  42                              u64 objectid, u64 pos,
  43                              u64 disk_offset, u64 disk_num_bytes,
  44                              u64 num_bytes, u64 offset, u64 ram_bytes,
  45                              u8 compression, u8 encryption, u16 other_encoding)
  46 {
  47         int ret = 0;
  48         struct btrfs_file_extent_item *item;
  49         struct btrfs_key file_key;
  50         struct btrfs_path *path;
  51         struct extent_buffer *leaf;
  52
  53         path = btrfs_alloc_path();
  54         if (!path)
  55                 return -ENOMEM;
  56         file_key.objectid = objectid;
  57         file_key.offset = pos;
  58         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
  59
  60         path->leave_spinning = 1;
  61         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  62                                       sizeof(*item));
  63         if (ret < 0)
  64                 goto out;
  65         BUG_ON(ret); /* Can't happen */
  66         leaf = path->nodes[0];
  67         item = btrfs_item_ptr(leaf, path->slots[0],
  68                               struct btrfs_file_extent_item);
  69         btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
  70         btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
  71         btrfs_set_file_extent_offset(leaf, item, offset);
  72         btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
  73         btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
  74         btrfs_set_file_extent_generation(leaf, item, trans->transid);
  75         btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
  76         btrfs_set_file_extent_compression(leaf, item, compression);
  77         btrfs_set_file_extent_encryption(leaf, item, encryption);
  78         btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
  79
  80         btrfs_mark_buffer_dirty(leaf);
  81 out:
  82         btrfs_free_path(path);
  83         return ret;
  84 }
  85
  86 static struct btrfs_csum_item *
  87 btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  88                   struct btrfs_root *root,
  89                   struct btrfs_path *path,
  90                   u64 bytenr, int cow)
  91 {
  92         int ret;
  93         struct btrfs_key file_key;
  94         struct btrfs_key found_key;
  95         struct btrfs_csum_item *item;
  96         struct extent_buffer *leaf;
  97         u64 csum_offset = 0;
  98         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
  99         int csums_in_item;
 100
 101         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 102         file_key.offset = bytenr;
 103         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 104         ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 105         if (ret < 0)
 106                 goto fail;
 107         leaf = path->nodes[0];
 108         if (ret > 0) {
 109                 ret = 1;
 110                 if (path->slots[0] == 0)
 111                         goto fail;
 112                 path->slots[0]--;
 113                 btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 114                 if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 115                         goto fail;
 116
 117                 csum_offset = (bytenr - found_key.offset) >>
 118                                 root->fs_info->sb->s_blocksize_bits;
 119                 csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 120                 csums_in_item /= csum_size;
 121
 122                 if (csum_offset == csums_in_item) {
 123                         ret = -EFBIG;
 124                         goto fail;
 125                 } else if (csum_offset > csums_in_item) {
 126                         goto fail;
 127                 }
 128         }
 129         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 130         item = (struct btrfs_csum_item *)((unsigned char *)item +
 131                                           csum_offset * csum_size);
 132         return item;
 133 fail:
 134         if (ret > 0)
 135                 ret = -ENOENT;
 136         return ERR_PTR(ret);
 137 }
 138
 139 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 140                              struct btrfs_root *root,
 141                              struct btrfs_path *path, u64 objectid,
 142                              u64 offset, int mod)
 143 {
 144         int ret;
 145         struct btrfs_key file_key;
 146         int ins_len = mod < 0 ? -1 : 0;
 147         int cow = mod != 0;
 148
 149         file_key.objectid = objectid;
 150         file_key.offset = offset;
 151         btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 152         ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 153         return ret;
 154 }
 155
 156 static void btrfs_io_bio_endio_readpage(struct btrfs_io_bio *bio, int err)
 157 {
 158         kfree(bio->csum_allocated);
 159 }
 160
 161 static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 162                                    struct inode *inode, struct bio *bio,
 163                                    u64 logical_offset, u32 *dst, int dio)
 164 {
 165         struct bio_vec *bvec = bio->bi_io_vec;
 166         struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
 167         struct btrfs_csum_item *item = NULL;
 168         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 169         struct btrfs_path *path;
 170         u8 *csum;
 171         u64 offset = 0;
 172         u64 item_start_offset = 0;
 173         u64 item_last_offset = 0;
 174         u64 disk_bytenr;
 175         u32 diff;
 176         int nblocks;
 177         int bio_index = 0;
 178         int count;
 179         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 180
 181         path = btrfs_alloc_path();
 182         if (!path)
 183                 return -ENOMEM;
 184
 185         nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
 186         if (!dst) {
 187                 if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {
 188                         btrfs_bio->csum_allocated = kmalloc(nblocks * csum_size,
 189                                                             GFP_NOFS);
 190                         if (!btrfs_bio->csum_allocated) {
 191                                 btrfs_free_path(path);
 192                                 return -ENOMEM;
 193                         }
 194                         btrfs_bio->csum = btrfs_bio->csum_allocated;
 195                         btrfs_bio->end_io = btrfs_io_bio_endio_readpage;
 196                 } else {
 197                         btrfs_bio->csum = btrfs_bio->csum_inline;
 198                 }
 199                 csum = btrfs_bio->csum;
 200         } else {
 201                 csum = (u8 *)dst;
 202         }
 203
 204         if (bio->bi_iter.bi_size > PAGE_CACHE_SIZE * 8)
 205                 path->reada = 2;
 206
 207         WARN_ON(bio->bi_vcnt <= 0);
 208
 209         /*
 210          * the free space stuff is only read when it hasn't been
 211          * updated in the current transaction.  So, we can safely
 212          * read from the commit root and sidestep a nasty deadlock
 213          * between reading the free space cache and updating the csum tree.
 214          */
 215         if (btrfs_is_free_space_inode(inode)) {
 216                 path->search_commit_root = 1;
 217                 path->skip_locking = 1;
 218         }
 219
 220         disk_bytenr = (u64)bio->bi_iter.bi_sector << 9;
 221         if (dio)
 222                 offset = logical_offset;
 223         while (bio_index < bio->bi_vcnt) {
 224                 if (!dio)
 225                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 226                 count = btrfs_find_ordered_sum(inode, offset, disk_bytenr,
 227                                                (u32 *)csum, nblocks);
 228                 if (count)
 229                         goto found;
 230
 231                 if (!item || disk_bytenr < item_start_offset ||
 232                     disk_bytenr >= item_last_offset) {
 233                         struct btrfs_key found_key;
 234                         u32 item_size;
 235
 236                         if (item)
 237                                 btrfs_release_path(path);
 238                         item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 239                                                  path, disk_bytenr, 0);
 240                         if (IS_ERR(item)) {
 241                                 count = 1;
 242                                 memset(csum, 0, csum_size);
 243                                 if (BTRFS_I(inode)->root->root_key.objectid ==
 244                                     BTRFS_DATA_RELOC_TREE_OBJECTID) {
 245                                         set_extent_bits(io_tree, offset,
 246                                                 offset + bvec->bv_len - 1,
 247                                                 EXTENT_NODATASUM, GFP_NOFS);
 248                                 } else {
 249                                         btrfs_info(BTRFS_I(inode)->root->fs_info,
 250                                                    "no csum found for inode %llu start %llu",
 251                                                btrfs_ino(inode), offset);
 252                                 }
 253                                 item = NULL;
 254                                 btrfs_release_path(path);
 255                                 goto found;
 256                         }
 257                         btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 258                                               path->slots[0]);
 259
 260                         item_start_offset = found_key.offset;
 261                         item_size = btrfs_item_size_nr(path->nodes[0],
 262                                                        path->slots[0]);
 263                         item_last_offset = item_start_offset +
 264                                 (item_size / csum_size) *
 265                                 root->sectorsize;
 266                         item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 267                                               struct btrfs_csum_item);
 268                 }
 269                 /*
 270                  * this byte range must be able to fit inside
 271                  * a single leaf so it will also fit inside a u32
 272                  */
 273                 diff = disk_bytenr - item_start_offset;
 274                 diff = diff / root->sectorsize;
 275                 diff = diff * csum_size;
 276                 count = min_t(int, nblocks, (item_last_offset - disk_bytenr) >>
 277                                             inode->i_sb->s_blocksize_bits);
 278                 read_extent_buffer(path->nodes[0], csum,
 279                                    ((unsigned long)item) + diff,
 280                                    csum_size * count);
 281 found:
 282                 csum += count * csum_size;
 283                 nblocks -= count;
 284                 while (count--) {
 285                         disk_bytenr += bvec->bv_len;
 286                         offset += bvec->bv_len;
 287                         bio_index++;
 288                         bvec++;
 289                 }
 290         }
 291         btrfs_free_path(path);
 292         return 0;
 293 }
 294
 295 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 296                           struct bio *bio, u32 *dst)
 297 {
 298         return __btrfs_lookup_bio_sums(root, inode, bio, 0, dst, 0);
 299 }
 300
 301 int btrfs_lookup_bio_sums_dio(struct btrfs_root *root, struct inode *inode,
 302                               struct btrfs_dio_private *dip, struct bio *bio,
 303                               u64 offset)
 304 {
 305         int len = (bio->bi_iter.bi_sector << 9) - dip->disk_bytenr;
 306         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 307         int ret;
 308
 309         len >>= inode->i_sb->s_blocksize_bits;
 310         len *= csum_size;
 311
 312         ret = __btrfs_lookup_bio_sums(root, inode, bio, offset,
 313                                       (u32 *)(dip->csum + len), 1);
 314         return ret;
 315 }
 316
 317 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 318                              struct list_head *list, int search_commit)
 319 {
 320         struct btrfs_key key;
 321         struct btrfs_path *path;
 322         struct extent_buffer *leaf;
 323         struct btrfs_ordered_sum *sums;
 324         struct btrfs_csum_item *item;
 325         LIST_HEAD(tmplist);
 326         unsigned long offset;
 327         int ret;
 328         size_t size;
 329         u64 csum_end;
 330         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 331
 332         ASSERT(start == ALIGN(start, root->sectorsize) &&
 333                (end + 1) == ALIGN(end + 1, root->sectorsize));
 334
 335         path = btrfs_alloc_path();
 336         if (!path)
 337                 return -ENOMEM;
 338
 339         if (search_commit) {
 340                 path->skip_locking = 1;
 341                 path->reada = 2;
 342                 path->search_commit_root = 1;
 343         }
 344
 345         key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 346         key.offset = start;
 347         key.type = BTRFS_EXTENT_CSUM_KEY;
 348
 349         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 350         if (ret < 0)
 351                 goto fail;
 352         if (ret > 0 && path->slots[0] > 0) {
 353                 leaf = path->nodes[0];
 354                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 355                 if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 356                     key.type == BTRFS_EXTENT_CSUM_KEY) {
 357                         offset = (start - key.offset) >>
 358                                  root->fs_info->sb->s_blocksize_bits;
 359                         if (offset * csum_size <
 360                             btrfs_item_size_nr(leaf, path->slots[0] - 1))
 361                                 path->slots[0]--;
 362                 }
 363         }
 364
 365         while (start <= end) {
 366                 leaf = path->nodes[0];
 367                 if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 368                         ret = btrfs_next_leaf(root, path);
 369                         if (ret < 0)
 370                                 goto fail;
 371                         if (ret > 0)
 372                                 break;
 373                         leaf = path->nodes[0];
 374                 }
 375
 376                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 377                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 378                     key.type != BTRFS_EXTENT_CSUM_KEY ||
 379                     key.offset > end)
 380                         break;
 381
 382                 if (key.offset > start)
 383                         start = key.offset;
 384
 385                 size = btrfs_item_size_nr(leaf, path->slots[0]);
 386                 csum_end = key.offset + (size / csum_size) * root->sectorsize;
 387                 if (csum_end <= start) {
 388                         path->slots[0]++;
 389                         continue;
 390                 }
 391
 392                 csum_end = min(csum_end, end + 1);
 393                 item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 394                                       struct btrfs_csum_item);
 395                 while (start < csum_end) {
 396                         size = min_t(size_t, csum_end - start,
 397                                      MAX_ORDERED_SUM_BYTES(root));
 398                         sums = kzalloc(btrfs_ordered_sum_size(root, size),
 399                                        GFP_NOFS);
 400                         if (!sums) {
 401                                 ret = -ENOMEM;
 402                                 goto fail;
 403                         }
 404
 405                         sums->bytenr = start;
 406                         sums->len = (int)size;
 407
 408                         offset = (start - key.offset) >>
 409                                 root->fs_info->sb->s_blocksize_bits;
 410                         offset *= csum_size;
 411                         size >>= root->fs_info->sb->s_blocksize_bits;
 412
 413                         read_extent_buffer(path->nodes[0],
 414                                            sums->sums,
 415                                            ((unsigned long)item) + offset,
 416                                            csum_size * size);
 417
 418                         start += root->sectorsize * size;
 419                         list_add_tail(&sums->list, &tmplist);
 420                 }
 421                 path->slots[0]++;
 422         }
 423         ret = 0;
 424 fail:
 425         while (ret < 0 && !list_empty(&tmplist)) {
 426                 sums = list_entry(&tmplist, struct btrfs_ordered_sum, list);
 427                 list_del(&sums->list);
 428                 kfree(sums);
 429         }
 430         list_splice_tail(&tmplist, list);
 431
 432         btrfs_free_path(path);
 433         return ret;
 434 }
 435
 436 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 437                        struct bio *bio, u64 file_start, int contig)
 438 {
 439         struct btrfs_ordered_sum *sums;
 440         struct btrfs_ordered_extent *ordered;
 441         char *data;
 442         struct bio_vec *bvec = bio->bi_io_vec;
 443         int bio_index = 0;
 444         int index;
 445         unsigned long total_bytes = 0;
 446         unsigned long this_sum_bytes = 0;
 447         u64 offset;
 448
 449         WARN_ON(bio->bi_vcnt <= 0);
 450         sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_iter.bi_size),
 451                        GFP_NOFS);
 452         if (!sums)
 453                 return -ENOMEM;
 454
 455         sums->len = bio->bi_iter.bi_size;
 456         INIT_LIST_HEAD(&sums->list);
 457
 458         if (contig)
 459                 offset = file_start;
 460         else
 461                 offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 462
 463         ordered = btrfs_lookup_ordered_extent(inode, offset);
 464         BUG_ON(!ordered); /* Logic error */
 465         sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
 466         index = 0;
 467
 468         while (bio_index < bio->bi_vcnt) {
 469                 if (!contig)
 470                         offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 471
 472                 if (offset >= ordered->file_offset + ordered->len ||
 473                     offset < ordered->file_offset) {
 474                         unsigned long bytes_left;
 475                         sums->len = this_sum_bytes;
 476                         this_sum_bytes = 0;
 477                         btrfs_add_ordered_sum(inode, ordered, sums);
 478                         btrfs_put_ordered_extent(ordered);
 479
 480                         bytes_left = bio->bi_iter.bi_size - total_bytes;
 481
 482                         sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 483                                        GFP_NOFS);
 484                         BUG_ON(!sums); /* -ENOMEM */
 485                         sums->len = bytes_left;
 486                         ordered = btrfs_lookup_ordered_extent(inode, offset);
 487                         BUG_ON(!ordered); /* Logic error */
 488                         sums->bytenr = ((u64)bio->bi_iter.bi_sector << 9) +
 489                                        total_bytes;
 490                         index = 0;
 491                 }
 492
 493                 data = kmap_atomic(bvec->bv_page);
 494                 sums->sums[index] = ~(u32)0;
 495                 sums->sums[index] = btrfs_csum_data(data + bvec->bv_offset,
 496                                                     sums->sums[index],
 497                                                     bvec->bv_len);
 498                 kunmap_atomic(data);
 499                 btrfs_csum_final(sums->sums[index],
 500                                  (char *)(sums->sums + index));
 501
 502                 bio_index++;
 503                 index++;
 504                 total_bytes += bvec->bv_len;
 505                 this_sum_bytes += bvec->bv_len;
 506                 offset += bvec->bv_len;
 507                 bvec++;
 508         }
 509         this_sum_bytes = 0;
 510         btrfs_add_ordered_sum(inode, ordered, sums);
 511         btrfs_put_ordered_extent(ordered);
 512         return 0;
 513 }
 514
 515 /*
 516  * helper function for csum removal, this expects the
 517  * key to describe the csum pointed to by the path, and it expects
 518  * the csum to overlap the range [bytenr, len]
 519  *
 520  * The csum should not be entirely contained in the range and the
 521  * range should not be entirely contained in the csum.
 522  *
 523  * This calls btrfs_truncate_item with the correct args based on the
 524  * overlap, and fixes up the key as required.
 525  */
 526 static noinline void truncate_one_csum(struct btrfs_root *root,
 527                                        struct btrfs_path *path,
 528                                        struct btrfs_key *key,
 529                                        u64 bytenr, u64 len)
 530 {
 531         struct extent_buffer *leaf;
 532         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 533         u64 csum_end;
 534         u64 end_byte = bytenr + len;
 535         u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 536
 537         leaf = path->nodes[0];
 538         csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 539         csum_end <<= root->fs_info->sb->s_blocksize_bits;
 540         csum_end += key->offset;
 541
 542         if (key->offset < bytenr && csum_end <= end_byte) {
 543                 /*
 544                  *         [ bytenr - len ]
 545                  *         [   ]
 546                  *   [csum     ]
 547                  *   A simple truncate off the end of the item
 548                  */
 549                 u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 550                 new_size *= csum_size;
 551                 btrfs_truncate_item(root, path, new_size, 1);
 552         } else if (key->offset >= bytenr && csum_end > end_byte &&
 553                    end_byte > key->offset) {
 554                 /*
 555                  *         [ bytenr - len ]
 556                  *                 [ ]
 557                  *                 [csum     ]
 558                  * we need to truncate from the beginning of the csum
 559                  */
 560                 u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 561                 new_size *= csum_size;
 562
 563                 btrfs_truncate_item(root, path, new_size, 0);
 564
 565                 key->offset = end_byte;
 566                 btrfs_set_item_key_safe(root, path, key);
 567         } else {
 568                 BUG();
 569         }
 570 }
 571
 572 /*
 573  * deletes the csum items from the csum tree for a given
 574  * range of bytes.
 575  */
 576 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 577                     struct btrfs_root *root, u64 bytenr, u64 len)
 578 {
 579         struct btrfs_path *path;
 580         struct btrfs_key key;
 581         u64 end_byte = bytenr + len;
 582         u64 csum_end;
 583         struct extent_buffer *leaf;
 584         int ret;
 585         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 586         int blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 587
 588         root = root->fs_info->csum_root;
 589
 590         path = btrfs_alloc_path();
 591         if (!path)
 592                 return -ENOMEM;
 593
 594         while (1) {
 595                 key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 596                 key.offset = end_byte - 1;
 597                 key.type = BTRFS_EXTENT_CSUM_KEY;
 598
 599                 path->leave_spinning = 1;
 600                 ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 601                 if (ret > 0) {
 602                         if (path->slots[0] == 0)
 603                                 break;
 604                         path->slots[0]--;
 605                 } else if (ret < 0) {
 606                         break;
 607                 }
 608
 609                 leaf = path->nodes[0];
 610                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 611
 612                 if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 613                     key.type != BTRFS_EXTENT_CSUM_KEY) {
 614                         break;
 615                 }
 616
 617                 if (key.offset >= end_byte)
 618                         break;
 619
 620                 csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 621                 csum_end <<= blocksize_bits;
 622                 csum_end += key.offset;
 623
 624                 /* this csum ends before we start, we're done */
 625                 if (csum_end <= bytenr)
 626                         break;
 627
 628                 /* delete the entire item, it is inside our range */
 629                 if (key.offset >= bytenr && csum_end <= end_byte) {
 630                         ret = btrfs_del_item(trans, root, path);
 631                         if (ret)
 632                                 goto out;
 633                         if (key.offset == bytenr)
 634                                 break;
 635                 } else if (key.offset < bytenr && csum_end > end_byte) {
 636                         unsigned long offset;
 637                         unsigned long shift_len;
 638                         unsigned long item_offset;
 639                         /*
 640                          *        [ bytenr - len ]
 641                          *     [csum                ]
 642                          *
 643                          * Our bytes are in the middle of the csum,
 644                          * we need to split this item and insert a new one.
 645                          *
 646                          * But we can't drop the path because the
 647                          * csum could change, get removed, extended etc.
 648                          *
 649                          * The trick here is the max size of a csum item leaves
 650                          * enough room in the tree block for a single
 651                          * item header.  So, we split the item in place,
 652                          * adding a new header pointing to the existing
 653                          * bytes.  Then we loop around again and we have
 654                          * a nicely formed csum item that we can neatly
 655                          * truncate.
 656                          */
 657                         offset = (bytenr - key.offset) >> blocksize_bits;
 658                         offset *= csum_size;
 659
 660                         shift_len = (len >> blocksize_bits) * csum_size;
 661
 662                         item_offset = btrfs_item_ptr_offset(leaf,
 663                                                             path->slots[0]);
 664
 665                         memset_extent_buffer(leaf, 0, item_offset + offset,
 666                                              shift_len);
 667                         key.offset = bytenr;
 668
 669                         /*
 670                          * btrfs_split_item returns -EAGAIN when the
 671                          * item changed size or key
 672                          */
 673                         ret = btrfs_split_item(trans, root, path, &key, offset);
 674                         if (ret && ret != -EAGAIN) {
 675                                 btrfs_abort_transaction(trans, root, ret);
 676                                 goto out;
 677                         }
 678
 679                         key.offset = end_byte - 1;
 680                 } else {
 681                         truncate_one_csum(root, path, &key, bytenr, len);
 682                         if (key.offset < bytenr)
 683                                 break;
 684                 }
 685                 btrfs_release_path(path);
 686         }
 687         ret = 0;
 688 out:
 689         btrfs_free_path(path);
 690         return ret;
 691 }
 692
 693 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 694                            struct btrfs_root *root,
 695                            struct btrfs_ordered_sum *sums)
 696 {
 697         struct btrfs_key file_key;
 698         struct btrfs_key found_key;
 699         struct btrfs_path *path;
 700         struct btrfs_csum_item *item;
 701         struct btrfs_csum_item *item_end;
 702         struct extent_buffer *leaf = NULL;
 703         u64 next_offset;
 704         u64 total_bytes = 0;
 705         u64 csum_offset;
 706         u64 bytenr;
 707         u32 nritems;
 708         u32 ins_size;
 709         int index = 0;
 710         int found_next;
 711         int ret;
 712         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 713
 714         path = btrfs_alloc_path();
 715         if (!path)
 716                 return -ENOMEM;
 717 again:
 718         next_offset = (u64)-1;
 719         found_next = 0;
 720         bytenr = sums->bytenr + total_bytes;
 721         file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 722         file_key.offset = bytenr;
 723         btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 724
 725         item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
 726         if (!IS_ERR(item)) {
 727                 ret = 0;
 728                 leaf = path->nodes[0];
 729                 item_end = btrfs_item_ptr(leaf, path->slots[0],
 730                                           struct btrfs_csum_item);
 731                 item_end = (struct btrfs_csum_item *)((char *)item_end +
 732                            btrfs_item_size_nr(leaf, path->slots[0]));
 733                 goto found;
 734         }
 735         ret = PTR_ERR(item);
 736         if (ret != -EFBIG && ret != -ENOENT)
 737                 goto fail_unlock;
 738
 739         if (ret == -EFBIG) {
 740                 u32 item_size;
 741                 /* we found one, but it isn't big enough yet */
 742                 leaf = path->nodes[0];
 743                 item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 744                 if ((item_size / csum_size) >=
 745                     MAX_CSUM_ITEMS(root, csum_size)) {
 746                         /* already at max size, make a new one */
 747                         goto insert;
 748                 }
 749         } else {
 750                 int slot = path->slots[0] + 1;
 751                 /* we didn't find a csum item, insert one */
 752                 nritems = btrfs_header_nritems(path->nodes[0]);
 753                 if (path->slots[0] >= nritems - 1) {
 754                         ret = btrfs_next_leaf(root, path);
 755                         if (ret == 1)
 756                                 found_next = 1;
 757                         if (ret != 0)
 758                                 goto insert;
 759                         slot = 0;
 760                 }
 761                 btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 762                 if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 763                     found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 764                         found_next = 1;
 765                         goto insert;
 766                 }
 767                 next_offset = found_key.offset;
 768                 found_next = 1;
 769                 goto insert;
 770         }
 771
 772         /*
 773          * at this point, we know the tree has an item, but it isn't big
 774          * enough yet to put our csum in.  Grow it
 775          */
 776         btrfs_release_path(path);
 777         ret = btrfs_search_slot(trans, root, &file_key, path,
 778                                 csum_size, 1);
 779         if (ret < 0)
 780                 goto fail_unlock;
 781
 782         if (ret > 0) {
 783                 if (path->slots[0] == 0)
 784                         goto insert;
 785                 path->slots[0]--;
 786         }
 787
 788         leaf = path->nodes[0];
 789         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 790         csum_offset = (bytenr - found_key.offset) >>
 791                         root->fs_info->sb->s_blocksize_bits;
 792
 793         if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 794             found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 795             csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 796                 goto insert;
 797         }
 798
 799         if (csum_offset == btrfs_item_size_nr(leaf, path->slots[0]) /
 800             csum_size) {
 801                 int extend_nr;
 802                 u64 tmp;
 803                 u32 diff;
 804                 u32 free_space;
 805
 806                 if (btrfs_leaf_free_space(root, leaf) <
 807                                  sizeof(struct btrfs_item) + csum_size * 2)
 808                         goto insert;
 809
 810                 free_space = btrfs_leaf_free_space(root, leaf) -
 811                                          sizeof(struct btrfs_item) - csum_size;
 812                 tmp = sums->len - total_bytes;
 813                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 814                 WARN_ON(tmp < 1);
 815
 816                 extend_nr = max_t(int, 1, (int)tmp);
 817                 diff = (csum_offset + extend_nr) * csum_size;
 818                 diff = min(diff, MAX_CSUM_ITEMS(root, csum_size) * csum_size);
 819
 820                 diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 821                 diff = min(free_space, diff);
 822                 diff /= csum_size;
 823                 diff *= csum_size;
 824
 825                 btrfs_extend_item(root, path, diff);
 826                 ret = 0;
 827                 goto csum;
 828         }
 829
 830 insert:
 831         btrfs_release_path(path);
 832         csum_offset = 0;
 833         if (found_next) {
 834                 u64 tmp;
 835
 836                 tmp = sums->len - total_bytes;
 837                 tmp >>= root->fs_info->sb->s_blocksize_bits;
 838                 tmp = min(tmp, (next_offset - file_key.offset) >>
 839                                          root->fs_info->sb->s_blocksize_bits);
 840
 841                 tmp = max((u64)1, tmp);
 842                 tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 843                 ins_size = csum_size * tmp;
 844         } else {
 845                 ins_size = csum_size;
 846         }
 847         path->leave_spinning = 1;
 848         ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 849                                       ins_size);
 850         path->leave_spinning = 0;
 851         if (ret < 0)
 852                 goto fail_unlock;
 853         if (WARN_ON(ret != 0))
 854                 goto fail_unlock;
 855         leaf = path->nodes[0];
 856 csum:
 857         item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 858         item_end = (struct btrfs_csum_item *)((unsigned char *)item +
 859                                       btrfs_item_size_nr(leaf, path->slots[0]));
 860         item = (struct btrfs_csum_item *)((unsigned char *)item +
 861                                           csum_offset * csum_size);
 862 found:
 863         ins_size = (u32)(sums->len - total_bytes) >>
 864                    root->fs_info->sb->s_blocksize_bits;
 865         ins_size *= csum_size;
 866         ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
 867                               ins_size);
 868         write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
 869                             ins_size);
 870
 871         ins_size /= csum_size;
 872         total_bytes += ins_size * root->sectorsize;
 873         index += ins_size;
 874
 875         btrfs_mark_buffer_dirty(path->nodes[0]);
 876         if (total_bytes < sums->len) {
 877                 btrfs_release_path(path);
 878                 cond_resched();
 879                 goto again;
 880         }
 881 out:
 882         btrfs_free_path(path);
 883         return ret;
 884
 885 fail_unlock:
 886         goto out;
 887 }