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 #include <trace/events/ext4.h>
  25
  26 static unsigned int num_base_meta_blocks(struct super_block *sb,
  27                                          ext4_group_t block_group);
  28
  29 /*
  30  * balloc.c contains the blocks allocation and deallocation routines
  31  */
  32
  33 /*
  34  * Calculate the block group number and offset, given a block number
  35  */
  36 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
  37                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
  38 {
  39         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  40         ext4_grpblk_t offset;
  41
  42         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
  43         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
  44         if (offsetp)
  45                 *offsetp = offset;
  46         if (blockgrpp)
  47                 *blockgrpp = blocknr;
  48
  49 }
  50
  51 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  52                         ext4_group_t block_group)
  53 {
  54         ext4_group_t actual_group;
  55         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
  56         if (actual_group == block_group)
  57                 return 1;
  58         return 0;
  59 }
  60
  61 static int ext4_group_used_meta_blocks(struct super_block *sb,
  62                                        ext4_group_t block_group,
  63                                        struct ext4_group_desc *gdp)
  64 {
  65         ext4_fsblk_t tmp;
  66         struct ext4_sb_info *sbi = EXT4_SB(sb);
  67         /* block bitmap, inode bitmap, and inode table blocks */
  68         int used_blocks = sbi->s_itb_per_group + 2;
  69
  70         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
  71                 if (!ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp),
  72                                         block_group))
  73                         used_blocks--;
  74
  75                 if (!ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp),
  76                                         block_group))
  77                         used_blocks--;
  78
  79                 tmp = ext4_inode_table(sb, gdp);
  80                 for (; tmp < ext4_inode_table(sb, gdp) +
  81                                 sbi->s_itb_per_group; tmp++) {
  82                         if (!ext4_block_in_group(sb, tmp, block_group))
  83                                 used_blocks -= 1;
  84                 }
  85         }
  86         return used_blocks;
  87 }
  88
  89 static unsigned int num_blocks_in_group(struct super_block *sb,
  90                                         ext4_group_t block_group)
  91 {
  92         if (block_group == ext4_get_groups_count(sb) - 1) {
  93                 /*
  94                  * Even though mke2fs always initializes the first and
  95                  * last group, just in case some other tool was used,
  96                  * we need to make sure we calculate the right free
  97                  * blocks.
  98                  */
  99                 return ext4_blocks_count(EXT4_SB(sb)->s_es) -
 100                         ext4_group_first_block_no(sb, block_group);
 101         } else
 102                 return EXT4_BLOCKS_PER_GROUP(sb);
 103 }
 104
 105 /* Initializes an uninitialized block bitmap */
 106 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 107                             ext4_group_t block_group,
 108                             struct ext4_group_desc *gdp)
 109 {
 110         unsigned int bit, bit_max = num_base_meta_blocks(sb, block_group);
 111         struct ext4_sb_info *sbi = EXT4_SB(sb);
 112         ext4_fsblk_t start, tmp;
 113         int flex_bg = 0;
 114
 115         J_ASSERT_BH(bh, buffer_locked(bh));
 116
 117         /* If checksum is bad mark all blocks used to prevent allocation
 118          * essentially implementing a per-group read-only flag. */
 119         if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
 120                 ext4_error(sb, "Checksum bad for group %u", block_group);
 121                 ext4_free_blks_set(sb, gdp, 0);
 122                 ext4_free_inodes_set(sb, gdp, 0);
 123                 ext4_itable_unused_set(sb, gdp, 0);
 124                 memset(bh->b_data, 0xff, sb->s_blocksize);
 125                 return;
 126         }
 127         memset(bh->b_data, 0, sb->s_blocksize);
 128
 129         for (bit = 0; bit < bit_max; bit++)
 130                 ext4_set_bit(bit, bh->b_data);
 131
 132         start = ext4_group_first_block_no(sb, block_group);
 133
 134         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 135                 flex_bg = 1;
 136
 137         /* Set bits for block and inode bitmaps, and inode table */
 138         tmp = ext4_block_bitmap(sb, gdp);
 139         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 140                 ext4_set_bit(tmp - start, bh->b_data);
 141
 142         tmp = ext4_inode_bitmap(sb, gdp);
 143         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 144                 ext4_set_bit(tmp - start, bh->b_data);
 145
 146         tmp = ext4_inode_table(sb, gdp);
 147         for (; tmp < ext4_inode_table(sb, gdp) +
 148                      sbi->s_itb_per_group; tmp++) {
 149                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 150                         ext4_set_bit(tmp - start, bh->b_data);
 151         }
 152         /*
 153          * Also if the number of blocks within the group is less than
 154          * the blocksize * 8 ( which is the size of bitmap ), set rest
 155          * of the block bitmap to 1
 156          */
 157         ext4_mark_bitmap_end(num_blocks_in_group(sb, block_group),
 158                              sb->s_blocksize * 8, bh->b_data);
 159 }
 160
 161 /* Return the number of free blocks in a block group.  It is used when
 162  * the block bitmap is uninitialized, so we can't just count the bits
 163  * in the bitmap. */
 164 unsigned ext4_free_blocks_after_init(struct super_block *sb,
 165                                      ext4_group_t block_group,
 166                                      struct ext4_group_desc *gdp)
 167 {
 168         return num_blocks_in_group(sb, block_group) -
 169                 num_base_meta_blocks(sb, block_group) -
 170                 ext4_group_used_meta_blocks(sb, block_group, gdp);
 171 }
 172
 173 /*
 174  * The free blocks are managed by bitmaps.  A file system contains several
 175  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 176  * block for inodes, N blocks for the inode table and data blocks.
 177  *
 178  * The file system contains group descriptors which are located after the
 179  * super block.  Each descriptor contains the number of the bitmap block and
 180  * the free blocks count in the block.  The descriptors are loaded in memory
 181  * when a file system is mounted (see ext4_fill_super).
 182  */
 183
 184 /**
 185  * ext4_get_group_desc() -- load group descriptor from disk
 186  * @sb:                 super block
 187  * @block_group:        given block group
 188  * @bh:                 pointer to the buffer head to store the block
 189  *                      group descriptor
 190  */
 191 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 192                                              ext4_group_t block_group,
 193                                              struct buffer_head **bh)
 194 {
 195         unsigned int group_desc;
 196         unsigned int offset;
 197         ext4_group_t ngroups = ext4_get_groups_count(sb);
 198         struct ext4_group_desc *desc;
 199         struct ext4_sb_info *sbi = EXT4_SB(sb);
 200
 201         if (block_group >= ngroups) {
 202                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 203                            " groups_count = %u", block_group, ngroups);
 204
 205                 return NULL;
 206         }
 207
 208         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 209         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 210         if (!sbi->s_group_desc[group_desc]) {
 211                 ext4_error(sb, "Group descriptor not loaded - "
 212                            "block_group = %u, group_desc = %u, desc = %u",
 213                            block_group, group_desc, offset);
 214                 return NULL;
 215         }
 216
 217         desc = (struct ext4_group_desc *)(
 218                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 219                 offset * EXT4_DESC_SIZE(sb));
 220         if (bh)
 221                 *bh = sbi->s_group_desc[group_desc];
 222         return desc;
 223 }
 224
 225 static int ext4_valid_block_bitmap(struct super_block *sb,
 226                                         struct ext4_group_desc *desc,
 227                                         unsigned int block_group,
 228                                         struct buffer_head *bh)
 229 {
 230         ext4_grpblk_t offset;
 231         ext4_grpblk_t next_zero_bit;
 232         ext4_fsblk_t bitmap_blk;
 233         ext4_fsblk_t group_first_block;
 234
 235         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 236                 /* with FLEX_BG, the inode/block bitmaps and itable
 237                  * blocks may not be in the group at all
 238                  * so the bitmap validation will be skipped for those groups
 239                  * or it has to also read the block group where the bitmaps
 240                  * are located to verify they are set.
 241                  */
 242                 return 1;
 243         }
 244         group_first_block = ext4_group_first_block_no(sb, block_group);
 245
 246         /* check whether block bitmap block number is set */
 247         bitmap_blk = ext4_block_bitmap(sb, desc);
 248         offset = bitmap_blk - group_first_block;
 249         if (!ext4_test_bit(offset, bh->b_data))
 250                 /* bad block bitmap */
 251                 goto err_out;
 252
 253         /* check whether the inode bitmap block number is set */
 254         bitmap_blk = ext4_inode_bitmap(sb, desc);
 255         offset = bitmap_blk - group_first_block;
 256         if (!ext4_test_bit(offset, bh->b_data))
 257                 /* bad block bitmap */
 258                 goto err_out;
 259
 260         /* check whether the inode table block number is set */
 261         bitmap_blk = ext4_inode_table(sb, desc);
 262         offset = bitmap_blk - group_first_block;
 263         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 264                                 offset + EXT4_SB(sb)->s_itb_per_group,
 265                                 offset);
 266         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
 267                 /* good bitmap for inode tables */
 268                 return 1;
 269
 270 err_out:
 271         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
 272                         block_group, bitmap_blk);
 273         return 0;
 274 }
 275 /**
 276  * ext4_read_block_bitmap()
 277  * @sb:                 super block
 278  * @block_group:        given block group
 279  *
 280  * Read the bitmap for a given block_group,and validate the
 281  * bits for block/inode/inode tables are set in the bitmaps
 282  *
 283  * Return buffer_head on success or NULL in case of failure.
 284  */
 285 struct buffer_head *
 286 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 287 {
 288         struct ext4_group_desc *desc;
 289         struct buffer_head *bh = NULL;
 290         ext4_fsblk_t bitmap_blk;
 291
 292         desc = ext4_get_group_desc(sb, block_group, NULL);
 293         if (!desc)
 294                 return NULL;
 295         bitmap_blk = ext4_block_bitmap(sb, desc);
 296         bh = sb_getblk(sb, bitmap_blk);
 297         if (unlikely(!bh)) {
 298                 ext4_error(sb, "Cannot read block bitmap - "
 299                             "block_group = %u, block_bitmap = %llu",
 300                             block_group, bitmap_blk);
 301                 return NULL;
 302         }
 303
 304         if (bitmap_uptodate(bh))
 305                 return bh;
 306
 307         lock_buffer(bh);
 308         if (bitmap_uptodate(bh)) {
 309                 unlock_buffer(bh);
 310                 return bh;
 311         }
 312         ext4_lock_group(sb, block_group);
 313         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 314                 ext4_init_block_bitmap(sb, bh, block_group, desc);
 315                 set_bitmap_uptodate(bh);
 316                 set_buffer_uptodate(bh);
 317                 ext4_unlock_group(sb, block_group);
 318                 unlock_buffer(bh);
 319                 return bh;
 320         }
 321         ext4_unlock_group(sb, block_group);
 322         if (buffer_uptodate(bh)) {
 323                 /*
 324                  * if not uninit if bh is uptodate,
 325                  * bitmap is also uptodate
 326                  */
 327                 set_bitmap_uptodate(bh);
 328                 unlock_buffer(bh);
 329                 return bh;
 330         }
 331         /*
 332          * submit the buffer_head for read. We can
 333          * safely mark the bitmap as uptodate now.
 334          * We do it here so the bitmap uptodate bit
 335          * get set with buffer lock held.
 336          */
 337         trace_ext4_read_block_bitmap_load(sb, block_group);
 338         set_bitmap_uptodate(bh);
 339         if (bh_submit_read(bh) < 0) {
 340                 put_bh(bh);
 341                 ext4_error(sb, "Cannot read block bitmap - "
 342                             "block_group = %u, block_bitmap = %llu",
 343                             block_group, bitmap_blk);
 344                 return NULL;
 345         }
 346         ext4_valid_block_bitmap(sb, desc, block_group, bh);
 347         /*
 348          * file system mounted not to panic on error,
 349          * continue with corrupt bitmap
 350          */
 351         return bh;
 352 }
 353
 354 /**
 355  * ext4_has_free_blocks()
 356  * @sbi:        in-core super block structure.
 357  * @nblocks:    number of needed blocks
 358  *
 359  * Check if filesystem has nblocks free & available for allocation.
 360  * On success return 1, return 0 on failure.
 361  */
 362 static int ext4_has_free_blocks(struct ext4_sb_info *sbi,
 363                                 s64 nblocks, unsigned int flags)
 364 {
 365         s64 free_blocks, dirty_blocks, root_blocks;
 366         struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
 367         struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
 368
 369         free_blocks  = percpu_counter_read_positive(fbc);
 370         dirty_blocks = percpu_counter_read_positive(dbc);
 371         root_blocks = ext4_r_blocks_count(sbi->s_es);
 372
 373         if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
 374                                                 EXT4_FREEBLOCKS_WATERMARK) {
 375                 free_blocks  = percpu_counter_sum_positive(fbc);
 376                 dirty_blocks = percpu_counter_sum_positive(dbc);
 377         }
 378         /* Check whether we have space after
 379          * accounting for current dirty blocks & root reserved blocks.
 380          */
 381         if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
 382                 return 1;
 383
 384         /* Hm, nope.  Are (enough) root reserved blocks available? */
 385         if (sbi->s_resuid == current_fsuid() ||
 386             ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
 387             capable(CAP_SYS_RESOURCE) ||
 388                 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 389
 390                 if (free_blocks >= (nblocks + dirty_blocks))
 391                         return 1;
 392         }
 393
 394         return 0;
 395 }
 396
 397 int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
 398                            s64 nblocks, unsigned int flags)
 399 {
 400         if (ext4_has_free_blocks(sbi, nblocks, flags)) {
 401                 percpu_counter_add(&sbi->s_dirtyblocks_counter, nblocks);
 402                 return 0;
 403         } else
 404                 return -ENOSPC;
 405 }
 406
 407 /**
 408  * ext4_should_retry_alloc()
 409  * @sb:                 super block
 410  * @retries             number of attemps has been made
 411  *
 412  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 413  * it is profitable to retry the operation, this function will wait
 414  * for the current or committing transaction to complete, and then
 415  * return TRUE.
 416  *
 417  * if the total number of retries exceed three times, return FALSE.
 418  */
 419 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 420 {
 421         if (!ext4_has_free_blocks(EXT4_SB(sb), 1, 0) ||
 422             (*retries)++ > 3 ||
 423             !EXT4_SB(sb)->s_journal)
 424                 return 0;
 425
 426         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 427
 428         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 429 }
 430
 431 /*
 432  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 433  *
 434  * @handle:             handle to this transaction
 435  * @inode:              file inode
 436  * @goal:               given target block(filesystem wide)
 437  * @count:              pointer to total number of blocks needed
 438  * @errp:               error code
 439  *
 440  * Return 1st allocated block number on success, *count stores total account
 441  * error stores in errp pointer
 442  */
 443 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 444                                   ext4_fsblk_t goal, unsigned int flags,
 445                                   unsigned long *count, int *errp)
 446 {
 447         struct ext4_allocation_request ar;
 448         ext4_fsblk_t ret;
 449
 450         memset(&ar, 0, sizeof(ar));
 451         /* Fill with neighbour allocated blocks */
 452         ar.inode = inode;
 453         ar.goal = goal;
 454         ar.len = count ? *count : 1;
 455         ar.flags = flags;
 456
 457         ret = ext4_mb_new_blocks(handle, &ar, errp);
 458         if (count)
 459                 *count = ar.len;
 460         /*
 461          * Account for the allocated meta blocks.  We will never
 462          * fail EDQUOT for metdata, but we do account for it.
 463          */
 464         if (!(*errp) &&
 465             ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 466                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 467                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 468                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 469                 dquot_alloc_block_nofail(inode, ar.len);
 470         }
 471         return ret;
 472 }
 473
 474 /**
 475  * ext4_count_free_blocks() -- count filesystem free blocks
 476  * @sb:         superblock
 477  *
 478  * Adds up the number of free blocks from each block group.
 479  */
 480 ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
 481 {
 482         ext4_fsblk_t desc_count;
 483         struct ext4_group_desc *gdp;
 484         ext4_group_t i;
 485         ext4_group_t ngroups = ext4_get_groups_count(sb);
 486 #ifdef EXT4FS_DEBUG
 487         struct ext4_super_block *es;
 488         ext4_fsblk_t bitmap_count;
 489         unsigned int x;
 490         struct buffer_head *bitmap_bh = NULL;
 491
 492         es = EXT4_SB(sb)->s_es;
 493         desc_count = 0;
 494         bitmap_count = 0;
 495         gdp = NULL;
 496
 497         for (i = 0; i < ngroups; i++) {
 498                 gdp = ext4_get_group_desc(sb, i, NULL);
 499                 if (!gdp)
 500                         continue;
 501                 desc_count += ext4_free_blks_count(sb, gdp);
 502                 brelse(bitmap_bh);
 503                 bitmap_bh = ext4_read_block_bitmap(sb, i);
 504                 if (bitmap_bh == NULL)
 505                         continue;
 506
 507                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
 508                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 509                         i, ext4_free_blks_count(sb, gdp), x);
 510                 bitmap_count += x;
 511         }
 512         brelse(bitmap_bh);
 513         printk(KERN_DEBUG "ext4_count_free_blocks: stored = %llu"
 514                 ", computed = %llu, %llu\n", ext4_free_blocks_count(es),
 515                desc_count, bitmap_count);
 516         return bitmap_count;
 517 #else
 518         desc_count = 0;
 519         for (i = 0; i < ngroups; i++) {
 520                 gdp = ext4_get_group_desc(sb, i, NULL);
 521                 if (!gdp)
 522                         continue;
 523                 desc_count += ext4_free_blks_count(sb, gdp);
 524         }
 525
 526         return desc_count;
 527 #endif
 528 }
 529
 530 static inline int test_root(ext4_group_t a, int b)
 531 {
 532         int num = b;
 533
 534         while (a > num)
 535                 num *= b;
 536         return num == a;
 537 }
 538
 539 static int ext4_group_sparse(ext4_group_t group)
 540 {
 541         if (group <= 1)
 542                 return 1;
 543         if (!(group & 1))
 544                 return 0;
 545         return (test_root(group, 7) || test_root(group, 5) ||
 546                 test_root(group, 3));
 547 }
 548
 549 /**
 550  *      ext4_bg_has_super - number of blocks used by the superblock in group
 551  *      @sb: superblock for filesystem
 552  *      @group: group number to check
 553  *
 554  *      Return the number of blocks used by the superblock (primary or backup)
 555  *      in this group.  Currently this will be only 0 or 1.
 556  */
 557 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 558 {
 559         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 560                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 561                         !ext4_group_sparse(group))
 562                 return 0;
 563         return 1;
 564 }
 565
 566 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 567                                         ext4_group_t group)
 568 {
 569         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 570         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 571         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 572
 573         if (group == first || group == first + 1 || group == last)
 574                 return 1;
 575         return 0;
 576 }
 577
 578 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 579                                         ext4_group_t group)
 580 {
 581         if (!ext4_bg_has_super(sb, group))
 582                 return 0;
 583
 584         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 585                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 586         else
 587                 return EXT4_SB(sb)->s_gdb_count;
 588 }
 589
 590 /**
 591  *      ext4_bg_num_gdb - number of blocks used by the group table in group
 592  *      @sb: superblock for filesystem
 593  *      @group: group number to check
 594  *
 595  *      Return the number of blocks used by the group descriptor table
 596  *      (primary or backup) in this group.  In the future there may be a
 597  *      different number of descriptor blocks in each group.
 598  */
 599 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 600 {
 601         unsigned long first_meta_bg =
 602                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 603         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 604
 605         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 606                         metagroup < first_meta_bg)
 607                 return ext4_bg_num_gdb_nometa(sb, group);
 608
 609         return ext4_bg_num_gdb_meta(sb,group);
 610
 611 }
 612
 613 /*
 614  * This function returns the number of file system metadata blocks at
 615  * the beginning of a block group, including the reserved gdt blocks.
 616  */
 617 static unsigned int num_base_meta_blocks(struct super_block *sb,
 618                                          ext4_group_t block_group)
 619 {
 620         struct ext4_sb_info *sbi = EXT4_SB(sb);
 621         int num;
 622
 623         /* Check for superblock and gdt backups in this group */
 624         num = ext4_bg_has_super(sb, block_group);
 625
 626         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 627             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 628                           sbi->s_desc_per_block) {
 629                 if (num) {
 630                         num += ext4_bg_num_gdb(sb, block_group);
 631                         num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 632                 }
 633         } else { /* For META_BG_BLOCK_GROUPS */
 634                 num += ext4_bg_num_gdb(sb, block_group);
 635         }
 636         return num;
 637 }
 638 /**
 639  *      ext4_inode_to_goal_block - return a hint for block allocation
 640  *      @inode: inode for block allocation
 641  *
 642  *      Return the ideal location to start allocating blocks for a
 643  *      newly created inode.
 644  */
 645 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 646 {
 647         struct ext4_inode_info *ei = EXT4_I(inode);
 648         ext4_group_t block_group;
 649         ext4_grpblk_t colour;
 650         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 651         ext4_fsblk_t bg_start;
 652         ext4_fsblk_t last_block;
 653
 654         block_group = ei->i_block_group;
 655         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 656                 /*
 657                  * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 658                  * block groups per flexgroup, reserve the first block
 659                  * group for directories and special files.  Regular
 660                  * files will start at the second block group.  This
 661                  * tends to speed up directory access and improves
 662                  * fsck times.
 663                  */
 664                 block_group &= ~(flex_size-1);
 665                 if (S_ISREG(inode->i_mode))
 666                         block_group++;
 667         }
 668         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 669         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 670
 671         /*
 672          * If we are doing delayed allocation, we don't need take
 673          * colour into account.
 674          */
 675         if (test_opt(inode->i_sb, DELALLOC))
 676                 return bg_start;
 677
 678         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 679                 colour = (current->pid % 16) *
 680                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 681         else
 682                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 683         return bg_start + colour;
 684 }
 685