fs/ext4/balloc.c

   1 /*
   2  *  linux/fs/ext4/balloc.c
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993
  10  *  Big-endian to little-endian byte-swapping/bitmaps by
  11  *        David S. Miller (davem@caip.rutgers.edu), 1995
  12  */
  13
  14 #include <linux/time.h>
  15 #include <linux/capability.h>
  16 #include <linux/fs.h>
  17 #include <linux/jbd2.h>
  18 #include <linux/quotaops.h>
  19 #include <linux/buffer_head.h>
  20 #include "ext4.h"
  21 #include "ext4_jbd2.h"
  22 #include "mballoc.h"
  23
  24 /*
  25  * balloc.c contains the blocks allocation and deallocation routines
  26  */
  27
  28 /*
  29  * Calculate the block group number and offset, given a block number
  30  */
  31 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
  32                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
  33 {
  34         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  35         ext4_grpblk_t offset;
  36
  37         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
  38         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
  39         if (offsetp)
  40                 *offsetp = offset;
  41         if (blockgrpp)
  42                 *blockgrpp = blocknr;
  43
  44 }
  45
  46 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  47                         ext4_group_t block_group)
  48 {
  49         ext4_group_t actual_group;
  50         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
  51         if (actual_group == block_group)
  52                 return 1;
  53         return 0;
  54 }
  55
  56 static int ext4_group_used_meta_blocks(struct super_block *sb,
  57                                        ext4_group_t block_group,
  58                                        struct ext4_group_desc *gdp)
  59 {
  60         ext4_fsblk_t tmp;
  61         struct ext4_sb_info *sbi = EXT4_SB(sb);
  62         /* block bitmap, inode bitmap, and inode table blocks */
  63         int used_blocks = sbi->s_itb_per_group + 2;
  64
  65         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
  66                 if (!ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp),
  67                                         block_group))
  68                         used_blocks--;
  69
  70                 if (!ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp),
  71                                         block_group))
  72                         used_blocks--;
  73
  74                 tmp = ext4_inode_table(sb, gdp);
  75                 for (; tmp < ext4_inode_table(sb, gdp) +
  76                                 sbi->s_itb_per_group; tmp++) {
  77                         if (!ext4_block_in_group(sb, tmp, block_group))
  78                                 used_blocks -= 1;
  79                 }
  80         }
  81         return used_blocks;
  82 }
  83
  84 /* Initializes an uninitialized block bitmap if given, and returns the
  85  * number of blocks free in the group. */
  86 unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
  87                  ext4_group_t block_group, struct ext4_group_desc *gdp)
  88 {
  89         int bit, bit_max;
  90         ext4_group_t ngroups = ext4_get_groups_count(sb);
  91         unsigned free_blocks, group_blocks;
  92         struct ext4_sb_info *sbi = EXT4_SB(sb);
  93
  94         if (bh) {
  95                 J_ASSERT_BH(bh, buffer_locked(bh));
  96
  97                 /* If checksum is bad mark all blocks used to prevent allocation
  98                  * essentially implementing a per-group read-only flag. */
  99                 if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
 100                         ext4_error(sb, "Checksum bad for group %u",
 101                                         block_group);
 102                         ext4_free_blks_set(sb, gdp, 0);
 103                         ext4_free_inodes_set(sb, gdp, 0);
 104                         ext4_itable_unused_set(sb, gdp, 0);
 105                         memset(bh->b_data, 0xff, sb->s_blocksize);
 106                         return 0;
 107                 }
 108                 memset(bh->b_data, 0, sb->s_blocksize);
 109         }
 110
 111         /* Check for superblock and gdt backups in this group */
 112         bit_max = ext4_bg_has_super(sb, block_group);
 113
 114         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 115             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 116                           sbi->s_desc_per_block) {
 117                 if (bit_max) {
 118                         bit_max += ext4_bg_num_gdb(sb, block_group);
 119                         bit_max +=
 120                                 le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 121                 }
 122         } else { /* For META_BG_BLOCK_GROUPS */
 123                 bit_max += ext4_bg_num_gdb(sb, block_group);
 124         }
 125
 126         if (block_group == ngroups - 1) {
 127                 /*
 128                  * Even though mke2fs always initialize first and last group
 129                  * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
 130                  * to make sure we calculate the right free blocks
 131                  */
 132                 group_blocks = ext4_blocks_count(sbi->s_es) -
 133                         ext4_group_first_block_no(sb, ngroups - 1);
 134         } else {
 135                 group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
 136         }
 137
 138         free_blocks = group_blocks - bit_max;
 139
 140         if (bh) {
 141                 ext4_fsblk_t start, tmp;
 142                 int flex_bg = 0;
 143
 144                 for (bit = 0; bit < bit_max; bit++)
 145                         ext4_set_bit(bit, bh->b_data);
 146
 147                 start = ext4_group_first_block_no(sb, block_group);
 148
 149                 if (EXT4_HAS_INCOMPAT_FEATURE(sb,
 150                                               EXT4_FEATURE_INCOMPAT_FLEX_BG))
 151                         flex_bg = 1;
 152
 153                 /* Set bits for block and inode bitmaps, and inode table */
 154                 tmp = ext4_block_bitmap(sb, gdp);
 155                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 156                         ext4_set_bit(tmp - start, bh->b_data);
 157
 158                 tmp = ext4_inode_bitmap(sb, gdp);
 159                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 160                         ext4_set_bit(tmp - start, bh->b_data);
 161
 162                 tmp = ext4_inode_table(sb, gdp);
 163                 for (; tmp < ext4_inode_table(sb, gdp) +
 164                                 sbi->s_itb_per_group; tmp++) {
 165                         if (!flex_bg ||
 166                                 ext4_block_in_group(sb, tmp, block_group))
 167                                 ext4_set_bit(tmp - start, bh->b_data);
 168                 }
 169                 /*
 170                  * Also if the number of blocks within the group is
 171                  * less than the blocksize * 8 ( which is the size
 172                  * of bitmap ), set rest of the block bitmap to 1
 173                  */
 174                 ext4_mark_bitmap_end(group_blocks, sb->s_blocksize * 8,
 175                                      bh->b_data);
 176         }
 177         return free_blocks - ext4_group_used_meta_blocks(sb, block_group, gdp);
 178 }
 179
 180
 181 /*
 182  * The free blocks are managed by bitmaps.  A file system contains several
 183  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 184  * block for inodes, N blocks for the inode table and data blocks.
 185  *
 186  * The file system contains group descriptors which are located after the
 187  * super block.  Each descriptor contains the number of the bitmap block and
 188  * the free blocks count in the block.  The descriptors are loaded in memory
 189  * when a file system is mounted (see ext4_fill_super).
 190  */
 191
 192 /**
 193  * ext4_get_group_desc() -- load group descriptor from disk
 194  * @sb:                 super block
 195  * @block_group:        given block group
 196  * @bh:                 pointer to the buffer head to store the block
 197  *                      group descriptor
 198  */
 199 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 200                                              ext4_group_t block_group,
 201                                              struct buffer_head **bh)
 202 {
 203         unsigned int group_desc;
 204         unsigned int offset;
 205         ext4_group_t ngroups = ext4_get_groups_count(sb);
 206         struct ext4_group_desc *desc;
 207         struct ext4_sb_info *sbi = EXT4_SB(sb);
 208
 209         if (block_group >= ngroups) {
 210                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 211                            " groups_count = %u", block_group, ngroups);
 212
 213                 return NULL;
 214         }
 215
 216         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 217         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 218         if (!sbi->s_group_desc[group_desc]) {
 219                 ext4_error(sb, "Group descriptor not loaded - "
 220                            "block_group = %u, group_desc = %u, desc = %u",
 221                            block_group, group_desc, offset);
 222                 return NULL;
 223         }
 224
 225         desc = (struct ext4_group_desc *)(
 226                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 227                 offset * EXT4_DESC_SIZE(sb));
 228         if (bh)
 229                 *bh = sbi->s_group_desc[group_desc];
 230         return desc;
 231 }
 232
 233 static int ext4_valid_block_bitmap(struct super_block *sb,
 234                                         struct ext4_group_desc *desc,
 235                                         unsigned int block_group,
 236                                         struct buffer_head *bh)
 237 {
 238         ext4_grpblk_t offset;
 239         ext4_grpblk_t next_zero_bit;
 240         ext4_fsblk_t bitmap_blk;
 241         ext4_fsblk_t group_first_block;
 242
 243         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 244                 /* with FLEX_BG, the inode/block bitmaps and itable
 245                  * blocks may not be in the group at all
 246                  * so the bitmap validation will be skipped for those groups
 247                  * or it has to also read the block group where the bitmaps
 248                  * are located to verify they are set.
 249                  */
 250                 return 1;
 251         }
 252         group_first_block = ext4_group_first_block_no(sb, block_group);
 253
 254         /* check whether block bitmap block number is set */
 255         bitmap_blk = ext4_block_bitmap(sb, desc);
 256         offset = bitmap_blk - group_first_block;
 257         if (!ext4_test_bit(offset, bh->b_data))
 258                 /* bad block bitmap */
 259                 goto err_out;
 260
 261         /* check whether the inode bitmap block number is set */
 262         bitmap_blk = ext4_inode_bitmap(sb, desc);
 263         offset = bitmap_blk - group_first_block;
 264         if (!ext4_test_bit(offset, bh->b_data))
 265                 /* bad block bitmap */
 266                 goto err_out;
 267
 268         /* check whether the inode table block number is set */
 269         bitmap_blk = ext4_inode_table(sb, desc);
 270         offset = bitmap_blk - group_first_block;
 271         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 272                                 offset + EXT4_SB(sb)->s_itb_per_group,
 273                                 offset);
 274         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
 275                 /* good bitmap for inode tables */
 276                 return 1;
 277
 278 err_out:
 279         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
 280                         block_group, bitmap_blk);
 281         return 0;
 282 }
 283 /**
 284  * ext4_read_block_bitmap()
 285  * @sb:                 super block
 286  * @block_group:        given block group
 287  *
 288  * Read the bitmap for a given block_group,and validate the
 289  * bits for block/inode/inode tables are set in the bitmaps
 290  *
 291  * Return buffer_head on success or NULL in case of failure.
 292  */
 293 struct buffer_head *
 294 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 295 {
 296         struct ext4_group_desc *desc;
 297         struct buffer_head *bh = NULL;
 298         ext4_fsblk_t bitmap_blk;
 299
 300         desc = ext4_get_group_desc(sb, block_group, NULL);
 301         if (!desc)
 302                 return NULL;
 303         bitmap_blk = ext4_block_bitmap(sb, desc);
 304         bh = sb_getblk(sb, bitmap_blk);
 305         if (unlikely(!bh)) {
 306                 ext4_error(sb, "Cannot read block bitmap - "
 307                             "block_group = %u, block_bitmap = %llu",
 308                             block_group, bitmap_blk);
 309                 return NULL;
 310         }
 311
 312         if (bitmap_uptodate(bh))
 313                 return bh;
 314
 315         lock_buffer(bh);
 316         if (bitmap_uptodate(bh)) {
 317                 unlock_buffer(bh);
 318                 return bh;
 319         }
 320         ext4_lock_group(sb, block_group);
 321         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 322                 ext4_init_block_bitmap(sb, bh, block_group, desc);
 323                 set_bitmap_uptodate(bh);
 324                 set_buffer_uptodate(bh);
 325                 ext4_unlock_group(sb, block_group);
 326                 unlock_buffer(bh);
 327                 return bh;
 328         }
 329         ext4_unlock_group(sb, block_group);
 330         if (buffer_uptodate(bh)) {
 331                 /*
 332                  * if not uninit if bh is uptodate,
 333                  * bitmap is also uptodate
 334                  */
 335                 set_bitmap_uptodate(bh);
 336                 unlock_buffer(bh);
 337                 return bh;
 338         }
 339         /*
 340          * submit the buffer_head for read. We can
 341          * safely mark the bitmap as uptodate now.
 342          * We do it here so the bitmap uptodate bit
 343          * get set with buffer lock held.
 344          */
 345         set_bitmap_uptodate(bh);
 346         if (bh_submit_read(bh) < 0) {
 347                 put_bh(bh);
 348                 ext4_error(sb, "Cannot read block bitmap - "
 349                             "block_group = %u, block_bitmap = %llu",
 350                             block_group, bitmap_blk);
 351                 return NULL;
 352         }
 353         ext4_valid_block_bitmap(sb, desc, block_group, bh);
 354         /*
 355          * file system mounted not to panic on error,
 356          * continue with corrupt bitmap
 357          */
 358         return bh;
 359 }
 360
 361 /**
 362  * ext4_add_groupblocks() -- Add given blocks to an existing group
 363  * @handle:                     handle to this transaction
 364  * @sb:                         super block
 365  * @block:                      start physcial block to add to the block group
 366  * @count:                      number of blocks to free
 367  *
 368  * This marks the blocks as free in the bitmap. We ask the
 369  * mballoc to reload the buddy after this by setting group
 370  * EXT4_GROUP_INFO_NEED_INIT_BIT flag
 371  */
 372 void ext4_add_groupblocks(handle_t *handle, struct super_block *sb,
 373                          ext4_fsblk_t block, unsigned long count)
 374 {
 375         struct buffer_head *bitmap_bh = NULL;
 376         struct buffer_head *gd_bh;
 377         ext4_group_t block_group;
 378         ext4_grpblk_t bit;
 379         unsigned int i;
 380         struct ext4_group_desc *desc;
 381         struct ext4_sb_info *sbi = EXT4_SB(sb);
 382         int err = 0, ret, blk_free_count;
 383         ext4_grpblk_t blocks_freed;
 384         struct ext4_group_info *grp;
 385
 386         ext4_debug("Adding block(s) %llu-%llu\n", block, block + count - 1);
 387
 388         ext4_get_group_no_and_offset(sb, block, &block_group, &bit);
 389         grp = ext4_get_group_info(sb, block_group);
 390         /*
 391          * Check to see if we are freeing blocks across a group
 392          * boundary.
 393          */
 394         if (bit + count > EXT4_BLOCKS_PER_GROUP(sb)) {
 395                 goto error_return;
 396         }
 397         bitmap_bh = ext4_read_block_bitmap(sb, block_group);
 398         if (!bitmap_bh)
 399                 goto error_return;
 400         desc = ext4_get_group_desc(sb, block_group, &gd_bh);
 401         if (!desc)
 402                 goto error_return;
 403
 404         if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
 405             in_range(ext4_inode_bitmap(sb, desc), block, count) ||
 406             in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
 407             in_range(block + count - 1, ext4_inode_table(sb, desc),
 408                      sbi->s_itb_per_group)) {
 409                 ext4_error(sb, "Adding blocks in system zones - "
 410                            "Block = %llu, count = %lu",
 411                            block, count);
 412                 goto error_return;
 413         }
 414
 415         /*
 416          * We are about to add blocks to the bitmap,
 417          * so we need undo access.
 418          */
 419         BUFFER_TRACE(bitmap_bh, "getting undo access");
 420         err = ext4_journal_get_undo_access(handle, bitmap_bh);
 421         if (err)
 422                 goto error_return;
 423
 424         /*
 425          * We are about to modify some metadata.  Call the journal APIs
 426          * to unshare ->b_data if a currently-committing transaction is
 427          * using it
 428          */
 429         BUFFER_TRACE(gd_bh, "get_write_access");
 430         err = ext4_journal_get_write_access(handle, gd_bh);
 431         if (err)
 432                 goto error_return;
 433         /*
 434          * make sure we don't allow a parallel init on other groups in the
 435          * same buddy cache
 436          */
 437         down_write(&grp->alloc_sem);
 438         for (i = 0, blocks_freed = 0; i < count; i++) {
 439                 BUFFER_TRACE(bitmap_bh, "clear bit");
 440                 if (!ext4_clear_bit_atomic(ext4_group_lock_ptr(sb, block_group),
 441                                                 bit + i, bitmap_bh->b_data)) {
 442                         ext4_error(sb, "bit already cleared for block %llu",
 443                                    (ext4_fsblk_t)(block + i));
 444                         BUFFER_TRACE(bitmap_bh, "bit already cleared");
 445                 } else {
 446                         blocks_freed++;
 447                 }
 448         }
 449         ext4_lock_group(sb, block_group);
 450         blk_free_count = blocks_freed + ext4_free_blks_count(sb, desc);
 451         ext4_free_blks_set(sb, desc, blk_free_count);
 452         desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
 453         ext4_unlock_group(sb, block_group);
 454         percpu_counter_add(&sbi->s_freeblocks_counter, blocks_freed);
 455
 456         if (sbi->s_log_groups_per_flex) {
 457                 ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
 458                 atomic_add(blocks_freed,
 459                            &sbi->s_flex_groups[flex_group].free_blocks);
 460         }
 461         /*
 462          * request to reload the buddy with the
 463          * new bitmap information
 464          */
 465         set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
 466         grp->bb_free += blocks_freed;
 467         up_write(&grp->alloc_sem);
 468
 469         /* We dirtied the bitmap block */
 470         BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
 471         err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
 472
 473         /* And the group descriptor block */
 474         BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
 475         ret = ext4_handle_dirty_metadata(handle, NULL, gd_bh);
 476         if (!err)
 477                 err = ret;
 478
 479 error_return:
 480         brelse(bitmap_bh);
 481         ext4_std_error(sb, err);
 482         return;
 483 }
 484
 485 /**
 486  * ext4_has_free_blocks()
 487  * @sbi:        in-core super block structure.
 488  * @nblocks:    number of needed blocks
 489  *
 490  * Check if filesystem has nblocks free & available for allocation.
 491  * On success return 1, return 0 on failure.
 492  */
 493 static int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
 494 {
 495         s64 free_blocks, dirty_blocks, root_blocks;
 496         struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
 497         struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
 498
 499         free_blocks  = percpu_counter_read_positive(fbc);
 500         dirty_blocks = percpu_counter_read_positive(dbc);
 501         root_blocks = ext4_r_blocks_count(sbi->s_es);
 502
 503         if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
 504                                                 EXT4_FREEBLOCKS_WATERMARK) {
 505                 free_blocks  = percpu_counter_sum_positive(fbc);
 506                 dirty_blocks = percpu_counter_sum_positive(dbc);
 507                 if (dirty_blocks < 0) {
 508                         printk(KERN_CRIT "Dirty block accounting "
 509                                         "went wrong %lld\n",
 510                                         (long long)dirty_blocks);
 511                 }
 512         }
 513         /* Check whether we have space after
 514          * accounting for current dirty blocks & root reserved blocks.
 515          */
 516         if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
 517                 return 1;
 518
 519         /* Hm, nope.  Are (enough) root reserved blocks available? */
 520         if (sbi->s_resuid == current_fsuid() ||
 521             ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
 522             capable(CAP_SYS_RESOURCE)) {
 523                 if (free_blocks >= (nblocks + dirty_blocks))
 524                         return 1;
 525         }
 526
 527         return 0;
 528 }
 529
 530 int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
 531                                                 s64 nblocks)
 532 {
 533         if (ext4_has_free_blocks(sbi, nblocks)) {
 534                 percpu_counter_add(&sbi->s_dirtyblocks_counter, nblocks);
 535                 return 0;
 536         } else
 537                 return -ENOSPC;
 538 }
 539
 540 /**
 541  * ext4_should_retry_alloc()
 542  * @sb:                 super block
 543  * @retries             number of attemps has been made
 544  *
 545  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 546  * it is profitable to retry the operation, this function will wait
 547  * for the current or commiting transaction to complete, and then
 548  * return TRUE.
 549  *
 550  * if the total number of retries exceed three times, return FALSE.
 551  */
 552 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 553 {
 554         if (!ext4_has_free_blocks(EXT4_SB(sb), 1) ||
 555             (*retries)++ > 3 ||
 556             !EXT4_SB(sb)->s_journal)
 557                 return 0;
 558
 559         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 560
 561         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 562 }
 563
 564 /*
 565  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 566  *
 567  * @handle:             handle to this transaction
 568  * @inode:              file inode
 569  * @goal:               given target block(filesystem wide)
 570  * @count:              pointer to total number of blocks needed
 571  * @errp:               error code
 572  *
 573  * Return 1st allocated block number on success, *count stores total account
 574  * error stores in errp pointer
 575  */
 576 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 577                 ext4_fsblk_t goal, unsigned long *count, int *errp)
 578 {
 579         struct ext4_allocation_request ar;
 580         ext4_fsblk_t ret;
 581
 582         memset(&ar, 0, sizeof(ar));
 583         /* Fill with neighbour allocated blocks */
 584         ar.inode = inode;
 585         ar.goal = goal;
 586         ar.len = count ? *count : 1;
 587
 588         ret = ext4_mb_new_blocks(handle, &ar, errp);
 589         if (count)
 590                 *count = ar.len;
 591         /*
 592          * Account for the allocated meta blocks.  We will never
 593          * fail EDQUOT for metdata, but we do account for it.
 594          */
 595         if (!(*errp) && EXT4_I(inode)->i_delalloc_reserved_flag) {
 596                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 597                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 598                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 599                 dquot_alloc_block_nofail(inode, ar.len);
 600         }
 601         return ret;
 602 }
 603
 604 /**
 605  * ext4_count_free_blocks() -- count filesystem free blocks
 606  * @sb:         superblock
 607  *
 608  * Adds up the number of free blocks from each block group.
 609  */
 610 ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
 611 {
 612         ext4_fsblk_t desc_count;
 613         struct ext4_group_desc *gdp;
 614         ext4_group_t i;
 615         ext4_group_t ngroups = ext4_get_groups_count(sb);
 616 #ifdef EXT4FS_DEBUG
 617         struct ext4_super_block *es;
 618         ext4_fsblk_t bitmap_count;
 619         unsigned int x;
 620         struct buffer_head *bitmap_bh = NULL;
 621
 622         es = EXT4_SB(sb)->s_es;
 623         desc_count = 0;
 624         bitmap_count = 0;
 625         gdp = NULL;
 626
 627         for (i = 0; i < ngroups; i++) {
 628                 gdp = ext4_get_group_desc(sb, i, NULL);
 629                 if (!gdp)
 630                         continue;
 631                 desc_count += ext4_free_blks_count(sb, gdp);
 632                 brelse(bitmap_bh);
 633                 bitmap_bh = ext4_read_block_bitmap(sb, i);
 634                 if (bitmap_bh == NULL)
 635                         continue;
 636
 637                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
 638                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 639                         i, ext4_free_blks_count(sb, gdp), x);
 640                 bitmap_count += x;
 641         }
 642         brelse(bitmap_bh);
 643         printk(KERN_DEBUG "ext4_count_free_blocks: stored = %llu"
 644                 ", computed = %llu, %llu\n", ext4_free_blocks_count(es),
 645                desc_count, bitmap_count);
 646         return bitmap_count;
 647 #else
 648         desc_count = 0;
 649         for (i = 0; i < ngroups; i++) {
 650                 gdp = ext4_get_group_desc(sb, i, NULL);
 651                 if (!gdp)
 652                         continue;
 653                 desc_count += ext4_free_blks_count(sb, gdp);
 654         }
 655
 656         return desc_count;
 657 #endif
 658 }
 659
 660 static inline int test_root(ext4_group_t a, int b)
 661 {
 662         int num = b;
 663
 664         while (a > num)
 665                 num *= b;
 666         return num == a;
 667 }
 668
 669 static int ext4_group_sparse(ext4_group_t group)
 670 {
 671         if (group <= 1)
 672                 return 1;
 673         if (!(group & 1))
 674                 return 0;
 675         return (test_root(group, 7) || test_root(group, 5) ||
 676                 test_root(group, 3));
 677 }
 678
 679 /**
 680  *      ext4_bg_has_super - number of blocks used by the superblock in group
 681  *      @sb: superblock for filesystem
 682  *      @group: group number to check
 683  *
 684  *      Return the number of blocks used by the superblock (primary or backup)
 685  *      in this group.  Currently this will be only 0 or 1.
 686  */
 687 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 688 {
 689         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 690                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 691                         !ext4_group_sparse(group))
 692                 return 0;
 693         return 1;
 694 }
 695
 696 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 697                                         ext4_group_t group)
 698 {
 699         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 700         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 701         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 702
 703         if (group == first || group == first + 1 || group == last)
 704                 return 1;
 705         return 0;
 706 }
 707
 708 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 709                                         ext4_group_t group)
 710 {
 711         if (!ext4_bg_has_super(sb, group))
 712                 return 0;
 713
 714         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 715                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 716         else
 717                 return EXT4_SB(sb)->s_gdb_count;
 718 }
 719
 720 /**
 721  *      ext4_bg_num_gdb - number of blocks used by the group table in group
 722  *      @sb: superblock for filesystem
 723  *      @group: group number to check
 724  *
 725  *      Return the number of blocks used by the group descriptor table
 726  *      (primary or backup) in this group.  In the future there may be a
 727  *      different number of descriptor blocks in each group.
 728  */
 729 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 730 {
 731         unsigned long first_meta_bg =
 732                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 733         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 734
 735         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 736                         metagroup < first_meta_bg)
 737                 return ext4_bg_num_gdb_nometa(sb, group);
 738
 739         return ext4_bg_num_gdb_meta(sb,group);
 740
 741 }
 742