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, given a block number
  32  */
  33 void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr,
  34                 ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp)
  35 {
  36         struct ext4_super_block *es = EXT4_SB(sb)->s_es;
  37         ext4_grpblk_t offset;
  38
  39         blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
  40         offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb));
  41         if (offsetp)
  42                 *offsetp = offset;
  43         if (blockgrpp)
  44                 *blockgrpp = blocknr;
  45
  46 }
  47
  48 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  49                         ext4_group_t block_group)
  50 {
  51         ext4_group_t actual_group;
  52         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
  53         if (actual_group == block_group)
  54                 return 1;
  55         return 0;
  56 }
  57
  58 /* Return the number of clusters used for file system metadata; this
  59  * represents the overhead needed by the file system.
  60  */
  61 unsigned ext4_num_overhead_clusters(struct super_block *sb,
  62                                     ext4_group_t block_group,
  63                                     struct ext4_group_desc *gdp)
  64 {
  65         unsigned num_clusters;
  66         int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
  67         ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
  68         ext4_fsblk_t itbl_blk;
  69         struct ext4_sb_info *sbi = EXT4_SB(sb);
  70
  71         /* This is the number of clusters used by the superblock,
  72          * block group descriptors, and reserved block group
  73          * descriptor blocks */
  74         num_clusters = ext4_num_base_meta_clusters(sb, block_group);
  75
  76         /*
  77          * For the allocation bitmaps and inode table, we first need
  78          * to check to see if the block is in the block group.  If it
  79          * is, then check to see if the cluster is already accounted
  80          * for in the clusters used for the base metadata cluster, or
  81          * if we can increment the base metadata cluster to include
  82          * that block.  Otherwise, we will have to track the cluster
  83          * used for the allocation bitmap or inode table explicitly.
  84          * Normally all of these blocks are contiguous, so the special
  85          * case handling shouldn't be necessary except for *very*
  86          * unusual file system layouts.
  87          */
  88         if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
  89                 block_cluster = EXT4_B2C(sbi, (start -
  90                                                ext4_block_bitmap(sb, gdp)));
  91                 if (block_cluster < num_clusters)
  92                         block_cluster = -1;
  93                 else if (block_cluster == num_clusters) {
  94                         num_clusters++;
  95                         block_cluster = -1;
  96                 }
  97         }
  98
  99         if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
 100                 inode_cluster = EXT4_B2C(sbi,
 101                                          start - ext4_inode_bitmap(sb, gdp));
 102                 if (inode_cluster < num_clusters)
 103                         inode_cluster = -1;
 104                 else if (inode_cluster == num_clusters) {
 105                         num_clusters++;
 106                         inode_cluster = -1;
 107                 }
 108         }
 109
 110         itbl_blk = ext4_inode_table(sb, gdp);
 111         for (i = 0; i < sbi->s_itb_per_group; i++) {
 112                 if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
 113                         c = EXT4_B2C(sbi, start - itbl_blk + i);
 114                         if ((c < num_clusters) || (c == inode_cluster) ||
 115                             (c == block_cluster) || (c == itbl_cluster))
 116                                 continue;
 117                         if (c == num_clusters) {
 118                                 num_clusters++;
 119                                 continue;
 120                         }
 121                         num_clusters++;
 122                         itbl_cluster = c;
 123                 }
 124         }
 125
 126         if (block_cluster != -1)
 127                 num_clusters++;
 128         if (inode_cluster != -1)
 129                 num_clusters++;
 130
 131         return num_clusters;
 132 }
 133
 134 static unsigned int num_clusters_in_group(struct super_block *sb,
 135                                           ext4_group_t block_group)
 136 {
 137         unsigned int blocks;
 138
 139         if (block_group == ext4_get_groups_count(sb) - 1) {
 140                 /*
 141                  * Even though mke2fs always initializes the first and
 142                  * last group, just in case some other tool was used,
 143                  * we need to make sure we calculate the right free
 144                  * blocks.
 145                  */
 146                 blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
 147                         ext4_group_first_block_no(sb, block_group);
 148         } else
 149                 blocks = EXT4_BLOCKS_PER_GROUP(sb);
 150         return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
 151 }
 152
 153 /* Initializes an uninitialized block bitmap */
 154 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 155                             ext4_group_t block_group,
 156                             struct ext4_group_desc *gdp)
 157 {
 158         unsigned int bit, bit_max;
 159         struct ext4_sb_info *sbi = EXT4_SB(sb);
 160         ext4_fsblk_t start, tmp;
 161         int flex_bg = 0;
 162
 163         J_ASSERT_BH(bh, buffer_locked(bh));
 164
 165         /* If checksum is bad mark all blocks used to prevent allocation
 166          * essentially implementing a per-group read-only flag. */
 167         if (!ext4_group_desc_csum_verify(sbi, block_group, gdp)) {
 168                 ext4_error(sb, "Checksum bad for group %u", block_group);
 169                 ext4_free_blks_set(sb, gdp, 0);
 170                 ext4_free_inodes_set(sb, gdp, 0);
 171                 ext4_itable_unused_set(sb, gdp, 0);
 172                 memset(bh->b_data, 0xff, sb->s_blocksize);
 173                 return;
 174         }
 175         memset(bh->b_data, 0, sb->s_blocksize);
 176
 177         bit_max = ext4_num_base_meta_clusters(sb, block_group);
 178         for (bit = 0; bit < bit_max; bit++)
 179                 ext4_set_bit(bit, bh->b_data);
 180
 181         start = ext4_group_first_block_no(sb, block_group);
 182
 183         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 184                 flex_bg = 1;
 185
 186         /* Set bits for block and inode bitmaps, and inode table */
 187         tmp = ext4_block_bitmap(sb, gdp);
 188         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 189                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 190
 191         tmp = ext4_inode_bitmap(sb, gdp);
 192         if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 193                 ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 194
 195         tmp = ext4_inode_table(sb, gdp);
 196         for (; tmp < ext4_inode_table(sb, gdp) +
 197                      sbi->s_itb_per_group; tmp++) {
 198                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 199                         ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 200         }
 201
 202         /*
 203          * Also if the number of blocks within the group is less than
 204          * the blocksize * 8 ( which is the size of bitmap ), set rest
 205          * of the block bitmap to 1
 206          */
 207         ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
 208                              sb->s_blocksize * 8, bh->b_data);
 209 }
 210
 211 /* Return the number of free blocks in a block group.  It is used when
 212  * the block bitmap is uninitialized, so we can't just count the bits
 213  * in the bitmap. */
 214 unsigned ext4_free_blocks_after_init(struct super_block *sb,
 215                                      ext4_group_t block_group,
 216                                      struct ext4_group_desc *gdp)
 217 {
 218         return num_clusters_in_group(sb, block_group) -
 219                 ext4_num_overhead_clusters(sb, block_group, gdp);
 220 }
 221
 222 /*
 223  * The free blocks are managed by bitmaps.  A file system contains several
 224  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 225  * block for inodes, N blocks for the inode table and data blocks.
 226  *
 227  * The file system contains group descriptors which are located after the
 228  * super block.  Each descriptor contains the number of the bitmap block and
 229  * the free blocks count in the block.  The descriptors are loaded in memory
 230  * when a file system is mounted (see ext4_fill_super).
 231  */
 232
 233 /**
 234  * ext4_get_group_desc() -- load group descriptor from disk
 235  * @sb:                 super block
 236  * @block_group:        given block group
 237  * @bh:                 pointer to the buffer head to store the block
 238  *                      group descriptor
 239  */
 240 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 241                                              ext4_group_t block_group,
 242                                              struct buffer_head **bh)
 243 {
 244         unsigned int group_desc;
 245         unsigned int offset;
 246         ext4_group_t ngroups = ext4_get_groups_count(sb);
 247         struct ext4_group_desc *desc;
 248         struct ext4_sb_info *sbi = EXT4_SB(sb);
 249
 250         if (block_group >= ngroups) {
 251                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 252                            " groups_count = %u", block_group, ngroups);
 253
 254                 return NULL;
 255         }
 256
 257         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 258         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 259         if (!sbi->s_group_desc[group_desc]) {
 260                 ext4_error(sb, "Group descriptor not loaded - "
 261                            "block_group = %u, group_desc = %u, desc = %u",
 262                            block_group, group_desc, offset);
 263                 return NULL;
 264         }
 265
 266         desc = (struct ext4_group_desc *)(
 267                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 268                 offset * EXT4_DESC_SIZE(sb));
 269         if (bh)
 270                 *bh = sbi->s_group_desc[group_desc];
 271         return desc;
 272 }
 273
 274 static int ext4_valid_block_bitmap(struct super_block *sb,
 275                                         struct ext4_group_desc *desc,
 276                                         unsigned int block_group,
 277                                         struct buffer_head *bh)
 278 {
 279         ext4_grpblk_t offset;
 280         ext4_grpblk_t next_zero_bit;
 281         ext4_fsblk_t bitmap_blk;
 282         ext4_fsblk_t group_first_block;
 283
 284         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 285                 /* with FLEX_BG, the inode/block bitmaps and itable
 286                  * blocks may not be in the group at all
 287                  * so the bitmap validation will be skipped for those groups
 288                  * or it has to also read the block group where the bitmaps
 289                  * are located to verify they are set.
 290                  */
 291                 return 1;
 292         }
 293         group_first_block = ext4_group_first_block_no(sb, block_group);
 294
 295         /* check whether block bitmap block number is set */
 296         bitmap_blk = ext4_block_bitmap(sb, desc);
 297         offset = bitmap_blk - group_first_block;
 298         if (!ext4_test_bit(offset, bh->b_data))
 299                 /* bad block bitmap */
 300                 goto err_out;
 301
 302         /* check whether the inode bitmap block number is set */
 303         bitmap_blk = ext4_inode_bitmap(sb, desc);
 304         offset = bitmap_blk - group_first_block;
 305         if (!ext4_test_bit(offset, bh->b_data))
 306                 /* bad block bitmap */
 307                 goto err_out;
 308
 309         /* check whether the inode table block number is set */
 310         bitmap_blk = ext4_inode_table(sb, desc);
 311         offset = bitmap_blk - group_first_block;
 312         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 313                                 offset + EXT4_SB(sb)->s_itb_per_group,
 314                                 offset);
 315         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
 316                 /* good bitmap for inode tables */
 317                 return 1;
 318
 319 err_out:
 320         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
 321                         block_group, bitmap_blk);
 322         return 0;
 323 }
 324 /**
 325  * ext4_read_block_bitmap()
 326  * @sb:                 super block
 327  * @block_group:        given block group
 328  *
 329  * Read the bitmap for a given block_group,and validate the
 330  * bits for block/inode/inode tables are set in the bitmaps
 331  *
 332  * Return buffer_head on success or NULL in case of failure.
 333  */
 334 struct buffer_head *
 335 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 336 {
 337         struct ext4_group_desc *desc;
 338         struct buffer_head *bh = NULL;
 339         ext4_fsblk_t bitmap_blk;
 340
 341         desc = ext4_get_group_desc(sb, block_group, NULL);
 342         if (!desc)
 343                 return NULL;
 344         bitmap_blk = ext4_block_bitmap(sb, desc);
 345         bh = sb_getblk(sb, bitmap_blk);
 346         if (unlikely(!bh)) {
 347                 ext4_error(sb, "Cannot read block bitmap - "
 348                             "block_group = %u, block_bitmap = %llu",
 349                             block_group, bitmap_blk);
 350                 return NULL;
 351         }
 352
 353         if (bitmap_uptodate(bh))
 354                 return bh;
 355
 356         lock_buffer(bh);
 357         if (bitmap_uptodate(bh)) {
 358                 unlock_buffer(bh);
 359                 return bh;
 360         }
 361         ext4_lock_group(sb, block_group);
 362         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 363                 ext4_init_block_bitmap(sb, bh, block_group, desc);
 364                 set_bitmap_uptodate(bh);
 365                 set_buffer_uptodate(bh);
 366                 ext4_unlock_group(sb, block_group);
 367                 unlock_buffer(bh);
 368                 return bh;
 369         }
 370         ext4_unlock_group(sb, block_group);
 371         if (buffer_uptodate(bh)) {
 372                 /*
 373                  * if not uninit if bh is uptodate,
 374                  * bitmap is also uptodate
 375                  */
 376                 set_bitmap_uptodate(bh);
 377                 unlock_buffer(bh);
 378                 return bh;
 379         }
 380         /*
 381          * submit the buffer_head for read. We can
 382          * safely mark the bitmap as uptodate now.
 383          * We do it here so the bitmap uptodate bit
 384          * get set with buffer lock held.
 385          */
 386         trace_ext4_read_block_bitmap_load(sb, block_group);
 387         set_bitmap_uptodate(bh);
 388         if (bh_submit_read(bh) < 0) {
 389                 put_bh(bh);
 390                 ext4_error(sb, "Cannot read block bitmap - "
 391                             "block_group = %u, block_bitmap = %llu",
 392                             block_group, bitmap_blk);
 393                 return NULL;
 394         }
 395         ext4_valid_block_bitmap(sb, desc, block_group, bh);
 396         /*
 397          * file system mounted not to panic on error,
 398          * continue with corrupt bitmap
 399          */
 400         return bh;
 401 }
 402
 403 /**
 404  * ext4_has_free_blocks()
 405  * @sbi:        in-core super block structure.
 406  * @nblocks:    number of needed blocks
 407  *
 408  * Check if filesystem has nblocks free & available for allocation.
 409  * On success return 1, return 0 on failure.
 410  */
 411 static int ext4_has_free_blocks(struct ext4_sb_info *sbi,
 412                                 s64 nblocks, unsigned int flags)
 413 {
 414         s64 free_blocks, dirty_blocks, root_blocks;
 415         struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
 416         struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
 417
 418         free_blocks  = percpu_counter_read_positive(fbc);
 419         dirty_blocks = percpu_counter_read_positive(dbc);
 420         root_blocks = ext4_r_blocks_count(sbi->s_es);
 421
 422         if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
 423                                                 EXT4_FREEBLOCKS_WATERMARK) {
 424                 free_blocks  = percpu_counter_sum_positive(fbc);
 425                 dirty_blocks = percpu_counter_sum_positive(dbc);
 426         }
 427         /* Check whether we have space after
 428          * accounting for current dirty blocks & root reserved blocks.
 429          */
 430         if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
 431                 return 1;
 432
 433         /* Hm, nope.  Are (enough) root reserved blocks available? */
 434         if (sbi->s_resuid == current_fsuid() ||
 435             ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
 436             capable(CAP_SYS_RESOURCE) ||
 437                 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 438
 439                 if (free_blocks >= (nblocks + dirty_blocks))
 440                         return 1;
 441         }
 442
 443         return 0;
 444 }
 445
 446 int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
 447                            s64 nblocks, unsigned int flags)
 448 {
 449         if (ext4_has_free_blocks(sbi, nblocks, flags)) {
 450                 percpu_counter_add(&sbi->s_dirtyblocks_counter, nblocks);
 451                 return 0;
 452         } else
 453                 return -ENOSPC;
 454 }
 455
 456 /**
 457  * ext4_should_retry_alloc()
 458  * @sb:                 super block
 459  * @retries             number of attemps has been made
 460  *
 461  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 462  * it is profitable to retry the operation, this function will wait
 463  * for the current or committing transaction to complete, and then
 464  * return TRUE.
 465  *
 466  * if the total number of retries exceed three times, return FALSE.
 467  */
 468 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 469 {
 470         if (!ext4_has_free_blocks(EXT4_SB(sb), 1, 0) ||
 471             (*retries)++ > 3 ||
 472             !EXT4_SB(sb)->s_journal)
 473                 return 0;
 474
 475         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 476
 477         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 478 }
 479
 480 /*
 481  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 482  *
 483  * @handle:             handle to this transaction
 484  * @inode:              file inode
 485  * @goal:               given target block(filesystem wide)
 486  * @count:              pointer to total number of blocks needed
 487  * @errp:               error code
 488  *
 489  * Return 1st allocated block number on success, *count stores total account
 490  * error stores in errp pointer
 491  */
 492 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 493                                   ext4_fsblk_t goal, unsigned int flags,
 494                                   unsigned long *count, int *errp)
 495 {
 496         struct ext4_allocation_request ar;
 497         ext4_fsblk_t ret;
 498
 499         memset(&ar, 0, sizeof(ar));
 500         /* Fill with neighbour allocated blocks */
 501         ar.inode = inode;
 502         ar.goal = goal;
 503         ar.len = count ? *count : 1;
 504         ar.flags = flags;
 505
 506         ret = ext4_mb_new_blocks(handle, &ar, errp);
 507         if (count)
 508                 *count = ar.len;
 509         /*
 510          * Account for the allocated meta blocks.  We will never
 511          * fail EDQUOT for metdata, but we do account for it.
 512          */
 513         if (!(*errp) &&
 514             ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 515                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 516                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 517                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 518                 dquot_alloc_block_nofail(inode, ar.len);
 519         }
 520         return ret;
 521 }
 522
 523 /**
 524  * ext4_count_free_blocks() -- count filesystem free blocks
 525  * @sb:         superblock
 526  *
 527  * Adds up the number of free blocks from each block group.
 528  */
 529 ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
 530 {
 531         ext4_fsblk_t desc_count;
 532         struct ext4_group_desc *gdp;
 533         ext4_group_t i;
 534         ext4_group_t ngroups = ext4_get_groups_count(sb);
 535 #ifdef EXT4FS_DEBUG
 536         struct ext4_super_block *es;
 537         ext4_fsblk_t bitmap_count;
 538         unsigned int x;
 539         struct buffer_head *bitmap_bh = NULL;
 540
 541         es = EXT4_SB(sb)->s_es;
 542         desc_count = 0;
 543         bitmap_count = 0;
 544         gdp = NULL;
 545
 546         for (i = 0; i < ngroups; i++) {
 547                 gdp = ext4_get_group_desc(sb, i, NULL);
 548                 if (!gdp)
 549                         continue;
 550                 desc_count += ext4_free_blks_count(sb, gdp);
 551                 brelse(bitmap_bh);
 552                 bitmap_bh = ext4_read_block_bitmap(sb, i);
 553                 if (bitmap_bh == NULL)
 554                         continue;
 555
 556                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
 557                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 558                         i, ext4_free_blks_count(sb, gdp), x);
 559                 bitmap_count += x;
 560         }
 561         brelse(bitmap_bh);
 562         printk(KERN_DEBUG "ext4_count_free_blocks: stored = %llu"
 563                 ", computed = %llu, %llu\n", ext4_free_blocks_count(es),
 564                desc_count, bitmap_count);
 565         return bitmap_count;
 566 #else
 567         desc_count = 0;
 568         for (i = 0; i < ngroups; i++) {
 569                 gdp = ext4_get_group_desc(sb, i, NULL);
 570                 if (!gdp)
 571                         continue;
 572                 desc_count += ext4_free_blks_count(sb, gdp);
 573         }
 574
 575         return desc_count;
 576 #endif
 577 }
 578
 579 static inline int test_root(ext4_group_t a, int b)
 580 {
 581         int num = b;
 582
 583         while (a > num)
 584                 num *= b;
 585         return num == a;
 586 }
 587
 588 static int ext4_group_sparse(ext4_group_t group)
 589 {
 590         if (group <= 1)
 591                 return 1;
 592         if (!(group & 1))
 593                 return 0;
 594         return (test_root(group, 7) || test_root(group, 5) ||
 595                 test_root(group, 3));
 596 }
 597
 598 /**
 599  *      ext4_bg_has_super - number of blocks used by the superblock in group
 600  *      @sb: superblock for filesystem
 601  *      @group: group number to check
 602  *
 603  *      Return the number of blocks used by the superblock (primary or backup)
 604  *      in this group.  Currently this will be only 0 or 1.
 605  */
 606 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 607 {
 608         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 609                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 610                         !ext4_group_sparse(group))
 611                 return 0;
 612         return 1;
 613 }
 614
 615 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 616                                         ext4_group_t group)
 617 {
 618         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 619         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 620         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 621
 622         if (group == first || group == first + 1 || group == last)
 623                 return 1;
 624         return 0;
 625 }
 626
 627 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 628                                         ext4_group_t group)
 629 {
 630         if (!ext4_bg_has_super(sb, group))
 631                 return 0;
 632
 633         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 634                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 635         else
 636                 return EXT4_SB(sb)->s_gdb_count;
 637 }
 638
 639 /**
 640  *      ext4_bg_num_gdb - number of blocks used by the group table in group
 641  *      @sb: superblock for filesystem
 642  *      @group: group number to check
 643  *
 644  *      Return the number of blocks used by the group descriptor table
 645  *      (primary or backup) in this group.  In the future there may be a
 646  *      different number of descriptor blocks in each group.
 647  */
 648 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 649 {
 650         unsigned long first_meta_bg =
 651                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 652         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 653
 654         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 655                         metagroup < first_meta_bg)
 656                 return ext4_bg_num_gdb_nometa(sb, group);
 657
 658         return ext4_bg_num_gdb_meta(sb,group);
 659
 660 }
 661
 662 /*
 663  * This function returns the number of file system metadata clusters at
 664  * the beginning of a block group, including the reserved gdt blocks.
 665  */
 666 unsigned ext4_num_base_meta_clusters(struct super_block *sb,
 667                                      ext4_group_t block_group)
 668 {
 669         struct ext4_sb_info *sbi = EXT4_SB(sb);
 670         unsigned num;
 671
 672         /* Check for superblock and gdt backups in this group */
 673         num = ext4_bg_has_super(sb, block_group);
 674
 675         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 676             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 677                           sbi->s_desc_per_block) {
 678                 if (num) {
 679                         num += ext4_bg_num_gdb(sb, block_group);
 680                         num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 681                 }
 682         } else { /* For META_BG_BLOCK_GROUPS */
 683                 num += ext4_bg_num_gdb(sb, block_group);
 684         }
 685         return EXT4_NUM_B2C(sbi, num);
 686 }
 687 /**
 688  *      ext4_inode_to_goal_block - return a hint for block allocation
 689  *      @inode: inode for block allocation
 690  *
 691  *      Return the ideal location to start allocating blocks for a
 692  *      newly created inode.
 693  */
 694 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 695 {
 696         struct ext4_inode_info *ei = EXT4_I(inode);
 697         ext4_group_t block_group;
 698         ext4_grpblk_t colour;
 699         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 700         ext4_fsblk_t bg_start;
 701         ext4_fsblk_t last_block;
 702
 703         block_group = ei->i_block_group;
 704         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 705                 /*
 706                  * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 707                  * block groups per flexgroup, reserve the first block
 708                  * group for directories and special files.  Regular
 709                  * files will start at the second block group.  This
 710                  * tends to speed up directory access and improves
 711                  * fsck times.
 712                  */
 713                 block_group &= ~(flex_size-1);
 714                 if (S_ISREG(inode->i_mode))
 715                         block_group++;
 716         }
 717         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 718         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 719
 720         /*
 721          * If we are doing delayed allocation, we don't need take
 722          * colour into account.
 723          */
 724         if (test_opt(inode->i_sb, DELALLOC))
 725                 return bg_start;
 726
 727         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 728                 colour = (current->pid % 16) *
 729                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 730         else
 731                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 732         return bg_start + colour;
 733 }
 734