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 /*
  27  * balloc.c contains the blocks allocation and deallocation routines
  28  */
  29
  30 /*
  31  * Calculate the block group number and offset into the block/cluster
  32  * allocation bitmap, given a block number
  33  */
  34 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
  35                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
  36 {
  37         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  38         ext4_grpblk_t offset;
  39
  40         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
  41         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >>
  42                 EXT4_SB(sb)->s_cluster_bits;
  43         if (offsetp)
  44                 *offsetp = offset;
  45         if (blockgrpp)
  46                 *blockgrpp = blocknr;
  47
  48 }
  49
  50 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  51                         ext4_group_t block_group)
  52 {
  53         ext4_group_t actual_group;
  54         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
  55         if (actual_group == block_group)
  56                 return 1;
  57         return 0;
  58 }
  59
  60 /* Return the number of clusters used for file system metadata; this
  61  * represents the overhead needed by the file system.
  62  */
  63 unsigned ext4_num_overhead_clusters(struct super_block *sb,
  64                                     ext4_group_t block_group,
  65                                     struct ext4_group_desc *gdp)
  66 {
  67         unsigned num_clusters;
  68         int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
  69         ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
  70         ext4_fsblk_t itbl_blk;
  71         struct ext4_sb_info *sbi = EXT4_SB(sb);
  72
  73         /* This is the number of clusters used by the superblock,
  74          * block group descriptors, and reserved block group
  75          * descriptor blocks */
  76         num_clusters = ext4_num_base_meta_clusters(sb, block_group);
  77
  78         /*
  79          * For the allocation bitmaps and inode table, we first need
  80          * to check to see if the block is in the block group.  If it
  81          * is, then check to see if the cluster is already accounted
  82          * for in the clusters used for the base metadata cluster, or
  83          * if we can increment the base metadata cluster to include
  84          * that block.  Otherwise, we will have to track the cluster
  85          * used for the allocation bitmap or inode table explicitly.
  86          * Normally all of these blocks are contiguous, so the special
  87          * case handling shouldn't be necessary except for *very*
  88          * unusual file system layouts.
  89          */
  90         if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
  91                 block_cluster = EXT4_B2C(sbi, (start -
  92                                                ext4_block_bitmap(sb, gdp)));
  93                 if (block_cluster < num_clusters)
  94                         block_cluster = -1;
  95                 else if (block_cluster == num_clusters) {
  96                         num_clusters++;
  97                         block_cluster = -1;
  98                 }
  99         }
 100
 101         if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
 102                 inode_cluster = EXT4_B2C(sbi,
 103                                          start - ext4_inode_bitmap(sb, gdp));
 104                 if (inode_cluster < num_clusters)
 105                         inode_cluster = -1;
 106                 else if (inode_cluster == num_clusters) {
 107                         num_clusters++;
 108                         inode_cluster = -1;
 109                 }
 110         }
 111
 112         itbl_blk = ext4_inode_table(sb, gdp);
 113         for (i = 0; i < sbi->s_itb_per_group; i++) {
 114                 if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
 115                         c = EXT4_B2C(sbi, start - itbl_blk + i);
 116                         if ((c < num_clusters) || (c == inode_cluster) ||
 117                             (c == block_cluster) || (c == itbl_cluster))
 118                                 continue;
 119                         if (c == num_clusters) {
 120                                 num_clusters++;
 121                                 continue;
 122                         }
 123                         num_clusters++;
 124                         itbl_cluster = c;
 125                 }
 126         }
 127
 128         if (block_cluster != -1)
 129                 num_clusters++;
 130         if (inode_cluster != -1)
 131                 num_clusters++;
 132
 133         return num_clusters;
 134 }
 135
 136 static unsigned int num_clusters_in_group(struct super_block *sb,
 137                                           ext4_group_t block_group)
 138 {
 139         unsigned int blocks;
 140
 141         if (block_group == ext4_get_groups_count(sb) - 1) {
 142                 /*
 143                  * Even though mke2fs always initializes the first and
 144                  * last group, just in case some other tool was used,
 145                  * we need to make sure we calculate the right free
 146                  * blocks.
 147                  */
 148                 blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
 149                         ext4_group_first_block_no(sb, block_group);
 150         } else
 151                 blocks = EXT4_BLOCKS_PER_GROUP(sb);
 152         return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
 153 }
 154
 155 /* Initializes an uninitialized block bitmap */
 156 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 157                             ext4_group_t block_group,
 158                             struct ext4_group_desc *gdp)
 159 {
 160         unsigned int bit, bit_max;
 161         struct ext4_sb_info *sbi = EXT4_SB(sb);
 162         ext4_fsblk_t start, tmp;
 163         int flex_bg = 0;
 164
 165         J_ASSERT_BH(bh, buffer_locked(bh));
 166
 167         /* If checksum is bad mark all blocks used to prevent allocation
 168          * essentially implementing a per-group read-only flag. */
 169         if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
 170                 ext4_error(sb, "Checksum bad for group %u", block_group);
 171                 ext4_free_group_clusters_set(sb, gdp, 0);
 172                 ext4_free_inodes_set(sb, gdp, 0);
 173                 ext4_itable_unused_set(sb, gdp, 0);
 174                 memset(bh->b_data, 0xff, sb->s_blocksize);
 175                 return;
 176         }
 177         memset(bh->b_data, 0, sb->s_blocksize);
 178
 179         bit_max = ext4_num_base_meta_clusters(sb, block_group);
 180         for (bit = 0; bit < bit_max; bit++)
 181                 ext4_set_bit(bit, bh->b_data);
 182
 183         start = ext4_group_first_block_no(sb, block_group);
 184
 185         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 186                 flex_bg = 1;
 187
 188         /* Set bits for block and inode bitmaps, and inode table */
 189         tmp = ext4_block_bitmap(sb, gdp);
 190         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 191                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 192
 193         tmp = ext4_inode_bitmap(sb, gdp);
 194         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 195                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 196
 197         tmp = ext4_inode_table(sb, gdp);
 198         for (; tmp < ext4_inode_table(sb, gdp) +
 199                      sbi->s_itb_per_group; tmp++) {
 200                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 201                         ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 202         }
 203
 204         /*
 205          * Also if the number of blocks within the group is less than
 206          * the blocksize * 8 ( which is the size of bitmap ), set rest
 207          * of the block bitmap to 1
 208          */
 209         ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
 210                              sb->s_blocksize * 8, bh->b_data);
 211 }
 212
 213 /* Return the number of free blocks in a block group.  It is used when
 214  * the block bitmap is uninitialized, so we can't just count the bits
 215  * in the bitmap. */
 216 unsigned ext4_free_clusters_after_init(struct super_block *sb,
 217                                        ext4_group_t block_group,
 218                                        struct ext4_group_desc *gdp)
 219 {
 220         return num_clusters_in_group(sb, block_group) -
 221                 ext4_num_overhead_clusters(sb, block_group, gdp);
 222 }
 223
 224 /*
 225  * The free blocks are managed by bitmaps.  A file system contains several
 226  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 227  * block for inodes, N blocks for the inode table and data blocks.
 228  *
 229  * The file system contains group descriptors which are located after the
 230  * super block.  Each descriptor contains the number of the bitmap block and
 231  * the free blocks count in the block.  The descriptors are loaded in memory
 232  * when a file system is mounted (see ext4_fill_super).
 233  */
 234
 235 /**
 236  * ext4_get_group_desc() -- load group descriptor from disk
 237  * @sb:                 super block
 238  * @block_group:        given block group
 239  * @bh:                 pointer to the buffer head to store the block
 240  *                      group descriptor
 241  */
 242 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 243                                              ext4_group_t block_group,
 244                                              struct buffer_head **bh)
 245 {
 246         unsigned int group_desc;
 247         unsigned int offset;
 248         ext4_group_t ngroups = ext4_get_groups_count(sb);
 249         struct ext4_group_desc *desc;
 250         struct ext4_sb_info *sbi = EXT4_SB(sb);
 251
 252         if (block_group >= ngroups) {
 253                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 254                            " groups_count = %u", block_group, ngroups);
 255
 256                 return NULL;
 257         }
 258
 259         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 260         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 261         if (!sbi->s_group_desc[group_desc]) {
 262                 ext4_error(sb, "Group descriptor not loaded - "
 263                            "block_group = %u, group_desc = %u, desc = %u",
 264                            block_group, group_desc, offset);
 265                 return NULL;
 266         }
 267
 268         desc = (struct ext4_group_desc *)(
 269                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 270                 offset * EXT4_DESC_SIZE(sb));
 271         if (bh)
 272                 *bh = sbi->s_group_desc[group_desc];
 273         return desc;
 274 }
 275
 276 static int ext4_valid_block_bitmap(struct super_block *sb,
 277                                         struct ext4_group_desc *desc,
 278                                         unsigned int block_group,
 279                                         struct buffer_head *bh)
 280 {
 281         ext4_grpblk_t offset;
 282         ext4_grpblk_t next_zero_bit;
 283         ext4_fsblk_t bitmap_blk;
 284         ext4_fsblk_t group_first_block;
 285
 286         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 287                 /* with FLEX_BG, the inode/block bitmaps and itable
 288                  * blocks may not be in the group at all
 289                  * so the bitmap validation will be skipped for those groups
 290                  * or it has to also read the block group where the bitmaps
 291                  * are located to verify they are set.
 292                  */
 293                 return 1;
 294         }
 295         group_first_block = ext4_group_first_block_no(sb, block_group);
 296
 297         /* check whether block bitmap block number is set */
 298         bitmap_blk = ext4_block_bitmap(sb, desc);
 299         offset = bitmap_blk - group_first_block;
 300         if (!ext4_test_bit(offset, bh->b_data))
 301                 /* bad block bitmap */
 302                 goto err_out;
 303
 304         /* check whether the inode bitmap block number is set */
 305         bitmap_blk = ext4_inode_bitmap(sb, desc);
 306         offset = bitmap_blk - group_first_block;
 307         if (!ext4_test_bit(offset, bh->b_data))
 308                 /* bad block bitmap */
 309                 goto err_out;
 310
 311         /* check whether the inode table block number is set */
 312         bitmap_blk = ext4_inode_table(sb, desc);
 313         offset = bitmap_blk - group_first_block;
 314         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 315                                 offset + EXT4_SB(sb)->s_itb_per_group,
 316                                 offset);
 317         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
 318                 /* good bitmap for inode tables */
 319                 return 1;
 320
 321 err_out:
 322         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
 323                         block_group, bitmap_blk);
 324         return 0;
 325 }
 326 /**
 327  * ext4_read_block_bitmap()
 328  * @sb:                 super block
 329  * @block_group:        given block group
 330  *
 331  * Read the bitmap for a given block_group,and validate the
 332  * bits for block/inode/inode tables are set in the bitmaps
 333  *
 334  * Return buffer_head on success or NULL in case of failure.
 335  */
 336 struct buffer_head *
 337 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 338 {
 339         struct ext4_group_desc *desc;
 340         struct buffer_head *bh = NULL;
 341         ext4_fsblk_t bitmap_blk;
 342
 343         desc = ext4_get_group_desc(sb, block_group, NULL);
 344         if (!desc)
 345                 return NULL;
 346         bitmap_blk = ext4_block_bitmap(sb, desc);
 347         bh = sb_getblk(sb, bitmap_blk);
 348         if (unlikely(!bh)) {
 349                 ext4_error(sb, "Cannot read block bitmap - "
 350                             "block_group = %u, block_bitmap = %llu",
 351                             block_group, bitmap_blk);
 352                 return NULL;
 353         }
 354
 355         if (bitmap_uptodate(bh))
 356                 return bh;
 357
 358         lock_buffer(bh);
 359         if (bitmap_uptodate(bh)) {
 360                 unlock_buffer(bh);
 361                 return bh;
 362         }
 363         ext4_lock_group(sb, block_group);
 364         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 365                 ext4_init_block_bitmap(sb, bh, block_group, desc);
 366                 set_bitmap_uptodate(bh);
 367                 set_buffer_uptodate(bh);
 368                 ext4_unlock_group(sb, block_group);
 369                 unlock_buffer(bh);
 370                 return bh;
 371         }
 372         ext4_unlock_group(sb, block_group);
 373         if (buffer_uptodate(bh)) {
 374                 /*
 375                  * if not uninit if bh is uptodate,
 376                  * bitmap is also uptodate
 377                  */
 378                 set_bitmap_uptodate(bh);
 379                 unlock_buffer(bh);
 380                 return bh;
 381         }
 382         /*
 383          * submit the buffer_head for read. We can
 384          * safely mark the bitmap as uptodate now.
 385          * We do it here so the bitmap uptodate bit
 386          * get set with buffer lock held.
 387          */
 388         trace_ext4_read_block_bitmap_load(sb, block_group);
 389         set_bitmap_uptodate(bh);
 390         if (bh_submit_read(bh) < 0) {
 391                 put_bh(bh);
 392                 ext4_error(sb, "Cannot read block bitmap - "
 393                             "block_group = %u, block_bitmap = %llu",
 394                             block_group, bitmap_blk);
 395                 return NULL;
 396         }
 397         ext4_valid_block_bitmap(sb, desc, block_group, bh);
 398         /*
 399          * file system mounted not to panic on error,
 400          * continue with corrupt bitmap
 401          */
 402         return bh;
 403 }
 404
 405 /**
 406  * ext4_has_free_clusters()
 407  * @sbi:        in-core super block structure.
 408  * @nclusters:  number of needed blocks
 409  * @flags:      flags from ext4_mb_new_blocks()
 410  *
 411  * Check if filesystem has nclusters free & available for allocation.
 412  * On success return 1, return 0 on failure.
 413  */
 414 static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
 415                                   s64 nclusters, unsigned int flags)
 416 {
 417         s64 free_clusters, dirty_clusters, root_clusters;
 418         struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
 419         struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
 420
 421         free_clusters  = percpu_counter_read_positive(fcc);
 422         dirty_clusters = percpu_counter_read_positive(dcc);
 423         root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
 424
 425         if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
 426                                         EXT4_FREECLUSTERS_WATERMARK) {
 427                 free_clusters  = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
 428                 dirty_clusters = percpu_counter_sum_positive(dcc);
 429         }
 430         /* Check whether we have space after accounting for current
 431          * dirty clusters & root reserved clusters.
 432          */
 433         if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
 434                 return 1;
 435
 436         /* Hm, nope.  Are (enough) root reserved clusters available? */
 437         if (sbi->s_resuid == current_fsuid() ||
 438             ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
 439             capable(CAP_SYS_RESOURCE) ||
 440                 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 441
 442                 if (free_clusters >= (nclusters + dirty_clusters))
 443                         return 1;
 444         }
 445
 446         return 0;
 447 }
 448
 449 int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
 450                              s64 nclusters, unsigned int flags)
 451 {
 452         if (ext4_has_free_clusters(sbi, nclusters, flags)) {
 453                 percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
 454                 return 0;
 455         } else
 456                 return -ENOSPC;
 457 }
 458
 459 /**
 460  * ext4_should_retry_alloc()
 461  * @sb:                 super block
 462  * @retries             number of attemps has been made
 463  *
 464  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 465  * it is profitable to retry the operation, this function will wait
 466  * for the current or committing transaction to complete, and then
 467  * return TRUE.
 468  *
 469  * if the total number of retries exceed three times, return FALSE.
 470  */
 471 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 472 {
 473         if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
 474             (*retries)++ > 3 ||
 475             !EXT4_SB(sb)->s_journal)
 476                 return 0;
 477
 478         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 479
 480         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 481 }
 482
 483 /*
 484  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 485  *
 486  * @handle:             handle to this transaction
 487  * @inode:              file inode
 488  * @goal:               given target block(filesystem wide)
 489  * @count:              pointer to total number of clusters needed
 490  * @errp:               error code
 491  *
 492  * Return 1st allocated block number on success, *count stores total account
 493  * error stores in errp pointer
 494  */
 495 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 496                                   ext4_fsblk_t goal, unsigned int flags,
 497                                   unsigned long *count, int *errp)
 498 {
 499         struct ext4_allocation_request ar;
 500         ext4_fsblk_t ret;
 501
 502         memset(&ar, 0, sizeof(ar));
 503         /* Fill with neighbour allocated blocks */
 504         ar.inode = inode;
 505         ar.goal = goal;
 506         ar.len = count ? *count : 1;
 507         ar.flags = flags;
 508
 509         ret = ext4_mb_new_blocks(handle, &ar, errp);
 510         if (count)
 511                 *count = ar.len;
 512         /*
 513          * Account for the allocated meta blocks.  We will never
 514          * fail EDQUOT for metdata, but we do account for it.
 515          */
 516         if (!(*errp) &&
 517             ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 518                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 519                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 520                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 521                 dquot_alloc_block_nofail(inode,
 522                                 EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
 523         }
 524         return ret;
 525 }
 526
 527 /**
 528  * ext4_count_free_clusters() -- count filesystem free clusters
 529  * @sb:         superblock
 530  *
 531  * Adds up the number of free clusters from each block group.
 532  */
 533 ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
 534 {
 535         ext4_fsblk_t desc_count;
 536         struct ext4_group_desc *gdp;
 537         ext4_group_t i;
 538         ext4_group_t ngroups = ext4_get_groups_count(sb);
 539 #ifdef EXT4FS_DEBUG
 540         struct ext4_super_block *es;
 541         ext4_fsblk_t bitmap_count;
 542         unsigned int x;
 543         struct buffer_head *bitmap_bh = NULL;
 544
 545         es = EXT4_SB(sb)->s_es;
 546         desc_count = 0;
 547         bitmap_count = 0;
 548         gdp = NULL;
 549
 550         for (i = 0; i < ngroups; i++) {
 551                 gdp = ext4_get_group_desc(sb, i, NULL);
 552                 if (!gdp)
 553                         continue;
 554                 desc_count += ext4_free_group_clusters(sb, gdp);
 555                 brelse(bitmap_bh);
 556                 bitmap_bh = ext4_read_block_bitmap(sb, i);
 557                 if (bitmap_bh == NULL)
 558                         continue;
 559
 560                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
 561                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 562                         i, ext4_free_group_clusters(sb, gdp), x);
 563                 bitmap_count += x;
 564         }
 565         brelse(bitmap_bh);
 566         printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
 567                ", computed = %llu, %llu\n",
 568                EXT4_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
 569                desc_count, bitmap_count);
 570         return bitmap_count;
 571 #else
 572         desc_count = 0;
 573         for (i = 0; i < ngroups; i++) {
 574                 gdp = ext4_get_group_desc(sb, i, NULL);
 575                 if (!gdp)
 576                         continue;
 577                 desc_count += ext4_free_group_clusters(sb, gdp);
 578         }
 579
 580         return desc_count;
 581 #endif
 582 }
 583
 584 static inline int test_root(ext4_group_t a, int b)
 585 {
 586         int num = b;
 587
 588         while (a > num)
 589                 num *= b;
 590         return num == a;
 591 }
 592
 593 static int ext4_group_sparse(ext4_group_t group)
 594 {
 595         if (group <= 1)
 596                 return 1;
 597         if (!(group & 1))
 598                 return 0;
 599         return (test_root(group, 7) || test_root(group, 5) ||
 600                 test_root(group, 3));
 601 }
 602
 603 /**
 604  *      ext4_bg_has_super - number of blocks used by the superblock in group
 605  *      @sb: superblock for filesystem
 606  *      @group: group number to check
 607  *
 608  *      Return the number of blocks used by the superblock (primary or backup)
 609  *      in this group.  Currently this will be only 0 or 1.
 610  */
 611 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 612 {
 613         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 614                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 615                         !ext4_group_sparse(group))
 616                 return 0;
 617         return 1;
 618 }
 619
 620 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 621                                         ext4_group_t group)
 622 {
 623         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 624         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 625         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 626
 627         if (group == first || group == first + 1 || group == last)
 628                 return 1;
 629         return 0;
 630 }
 631
 632 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 633                                         ext4_group_t group)
 634 {
 635         if (!ext4_bg_has_super(sb, group))
 636                 return 0;
 637
 638         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 639                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 640         else
 641                 return EXT4_SB(sb)->s_gdb_count;
 642 }
 643
 644 /**
 645  *      ext4_bg_num_gdb - number of blocks used by the group table in group
 646  *      @sb: superblock for filesystem
 647  *      @group: group number to check
 648  *
 649  *      Return the number of blocks used by the group descriptor table
 650  *      (primary or backup) in this group.  In the future there may be a
 651  *      different number of descriptor blocks in each group.
 652  */
 653 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 654 {
 655         unsigned long first_meta_bg =
 656                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 657         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 658
 659         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 660                         metagroup < first_meta_bg)
 661                 return ext4_bg_num_gdb_nometa(sb, group);
 662
 663         return ext4_bg_num_gdb_meta(sb,group);
 664
 665 }
 666
 667 /*
 668  * This function returns the number of file system metadata clusters at
 669  * the beginning of a block group, including the reserved gdt blocks.
 670  */
 671 unsigned ext4_num_base_meta_clusters(struct super_block *sb,
 672                                      ext4_group_t block_group)
 673 {
 674         struct ext4_sb_info *sbi = EXT4_SB(sb);
 675         unsigned num;
 676
 677         /* Check for superblock and gdt backups in this group */
 678         num = ext4_bg_has_super(sb, block_group);
 679
 680         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 681             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 682                           sbi->s_desc_per_block) {
 683                 if (num) {
 684                         num += ext4_bg_num_gdb(sb, block_group);
 685                         num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 686                 }
 687         } else { /* For META_BG_BLOCK_GROUPS */
 688                 num += ext4_bg_num_gdb(sb, block_group);
 689         }
 690         return EXT4_NUM_B2C(sbi, num);
 691 }
 692 /**
 693  *      ext4_inode_to_goal_block - return a hint for block allocation
 694  *      @inode: inode for block allocation
 695  *
 696  *      Return the ideal location to start allocating blocks for a
 697  *      newly created inode.
 698  */
 699 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 700 {
 701         struct ext4_inode_info *ei = EXT4_I(inode);
 702         ext4_group_t block_group;
 703         ext4_grpblk_t colour;
 704         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 705         ext4_fsblk_t bg_start;
 706         ext4_fsblk_t last_block;
 707
 708         block_group = ei->i_block_group;
 709         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 710                 /*
 711                  * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 712                  * block groups per flexgroup, reserve the first block
 713                  * group for directories and special files.  Regular
 714                  * files will start at the second block group.  This
 715                  * tends to speed up directory access and improves
 716                  * fsck times.
 717                  */
 718                 block_group &= ~(flex_size-1);
 719                 if (S_ISREG(inode->i_mode))
 720                         block_group++;
 721         }
 722         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 723         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 724
 725         /*
 726          * If we are doing delayed allocation, we don't need take
 727          * colour into account.
 728          */
 729         if (test_opt(inode->i_sb, DELALLOC))
 730                 return bg_start;
 731
 732         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 733                 colour = (current->pid % 16) *
 734                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 735         else
 736                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 737         return bg_start + colour;
 738 }
 739