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 ext4_num_base_meta_clusters(struct super_block *sb,
  27                                             ext4_group_t block_group);
  28 /*
  29  * balloc.c contains the blocks allocation and deallocation routines
  30  */
  31
  32 /*
  33  * Calculate the block group number and offset into the block/cluster
  34  * allocation bitmap, 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                 EXT4_SB(sb)->s_cluster_bits;
  45         if (offsetp)
  46                 *offsetp = offset;
  47         if (blockgrpp)
  48                 *blockgrpp = blocknr;
  49
  50 }
  51
  52 static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block,
  53                         ext4_group_t block_group)
  54 {
  55         ext4_group_t actual_group;
  56         ext4_get_group_no_and_offset(sb, block, &actual_group, NULL);
  57         if (actual_group == block_group)
  58                 return 1;
  59         return 0;
  60 }
  61
  62 /* Return the number of clusters used for file system metadata; this
  63  * represents the overhead needed by the file system.
  64  */
  65 unsigned ext4_num_overhead_clusters(struct super_block *sb,
  66                                     ext4_group_t block_group,
  67                                     struct ext4_group_desc *gdp)
  68 {
  69         unsigned num_clusters;
  70         int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c;
  71         ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group);
  72         ext4_fsblk_t itbl_blk;
  73         struct ext4_sb_info *sbi = EXT4_SB(sb);
  74
  75         /* This is the number of clusters used by the superblock,
  76          * block group descriptors, and reserved block group
  77          * descriptor blocks */
  78         num_clusters = ext4_num_base_meta_clusters(sb, block_group);
  79
  80         /*
  81          * For the allocation bitmaps and inode table, we first need
  82          * to check to see if the block is in the block group.  If it
  83          * is, then check to see if the cluster is already accounted
  84          * for in the clusters used for the base metadata cluster, or
  85          * if we can increment the base metadata cluster to include
  86          * that block.  Otherwise, we will have to track the cluster
  87          * used for the allocation bitmap or inode table explicitly.
  88          * Normally all of these blocks are contiguous, so the special
  89          * case handling shouldn't be necessary except for *very*
  90          * unusual file system layouts.
  91          */
  92         if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) {
  93                 block_cluster = EXT4_B2C(sbi,
  94                                          ext4_block_bitmap(sb, gdp) - start);
  95                 if (block_cluster < num_clusters)
  96                         block_cluster = -1;
  97                 else if (block_cluster == num_clusters) {
  98                         num_clusters++;
  99                         block_cluster = -1;
 100                 }
 101         }
 102
 103         if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) {
 104                 inode_cluster = EXT4_B2C(sbi,
 105                                          ext4_inode_bitmap(sb, gdp) - start);
 106                 if (inode_cluster < num_clusters)
 107                         inode_cluster = -1;
 108                 else if (inode_cluster == num_clusters) {
 109                         num_clusters++;
 110                         inode_cluster = -1;
 111                 }
 112         }
 113
 114         itbl_blk = ext4_inode_table(sb, gdp);
 115         for (i = 0; i < sbi->s_itb_per_group; i++) {
 116                 if (ext4_block_in_group(sb, itbl_blk + i, block_group)) {
 117                         c = EXT4_B2C(sbi, itbl_blk + i - start);
 118                         if ((c < num_clusters) || (c == inode_cluster) ||
 119                             (c == block_cluster) || (c == itbl_cluster))
 120                                 continue;
 121                         if (c == num_clusters) {
 122                                 num_clusters++;
 123                                 continue;
 124                         }
 125                         num_clusters++;
 126                         itbl_cluster = c;
 127                 }
 128         }
 129
 130         if (block_cluster != -1)
 131                 num_clusters++;
 132         if (inode_cluster != -1)
 133                 num_clusters++;
 134
 135         return num_clusters;
 136 }
 137
 138 static unsigned int num_clusters_in_group(struct super_block *sb,
 139                                           ext4_group_t block_group)
 140 {
 141         unsigned int blocks;
 142
 143         if (block_group == ext4_get_groups_count(sb) - 1) {
 144                 /*
 145                  * Even though mke2fs always initializes the first and
 146                  * last group, just in case some other tool was used,
 147                  * we need to make sure we calculate the right free
 148                  * blocks.
 149                  */
 150                 blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) -
 151                         ext4_group_first_block_no(sb, block_group);
 152         } else
 153                 blocks = EXT4_BLOCKS_PER_GROUP(sb);
 154         return EXT4_NUM_B2C(EXT4_SB(sb), blocks);
 155 }
 156
 157 /* Initializes an uninitialized block bitmap */
 158 void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
 159                             ext4_group_t block_group,
 160                             struct ext4_group_desc *gdp)
 161 {
 162         unsigned int bit, bit_max;
 163         struct ext4_sb_info *sbi = EXT4_SB(sb);
 164         ext4_fsblk_t start, tmp;
 165         int flex_bg = 0;
 166
 167         J_ASSERT_BH(bh, buffer_locked(bh));
 168
 169         /* If checksum is bad mark all blocks used to prevent allocation
 170          * essentially implementing a per-group read-only flag. */
 171         if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) {
 172                 ext4_error(sb, "Checksum bad for group %u", block_group);
 173                 ext4_free_group_clusters_set(sb, gdp, 0);
 174                 ext4_free_inodes_set(sb, gdp, 0);
 175                 ext4_itable_unused_set(sb, gdp, 0);
 176                 memset(bh->b_data, 0xff, sb->s_blocksize);
 177                 ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
 178                                            EXT4_BLOCKS_PER_GROUP(sb) / 8);
 179                 return;
 180         }
 181         memset(bh->b_data, 0, sb->s_blocksize);
 182
 183         bit_max = ext4_num_base_meta_clusters(sb, block_group);
 184         for (bit = 0; bit < bit_max; bit++)
 185                 ext4_set_bit(bit, bh->b_data);
 186
 187         start = ext4_group_first_block_no(sb, block_group);
 188
 189         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 190                 flex_bg = 1;
 191
 192         /* Set bits for block and inode bitmaps, and inode table */
 193         tmp = ext4_block_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_bitmap(sb, gdp);
 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         tmp = ext4_inode_table(sb, gdp);
 202         for (; tmp < ext4_inode_table(sb, gdp) +
 203                      sbi->s_itb_per_group; tmp++) {
 204                 if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 205                         ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 206         }
 207
 208         /*
 209          * Also if the number of blocks within the group is less than
 210          * the blocksize * 8 ( which is the size of bitmap ), set rest
 211          * of the block bitmap to 1
 212          */
 213         ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
 214                              sb->s_blocksize * 8, bh->b_data);
 215         ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
 216                                    EXT4_BLOCKS_PER_GROUP(sb) / 8);
 217         ext4_group_desc_csum_set(sb, block_group, gdp);
 218 }
 219
 220 /* Return the number of free blocks in a block group.  It is used when
 221  * the block bitmap is uninitialized, so we can't just count the bits
 222  * in the bitmap. */
 223 unsigned ext4_free_clusters_after_init(struct super_block *sb,
 224                                        ext4_group_t block_group,
 225                                        struct ext4_group_desc *gdp)
 226 {
 227         return num_clusters_in_group(sb, block_group) -
 228                 ext4_num_overhead_clusters(sb, block_group, gdp);
 229 }
 230
 231 /*
 232  * The free blocks are managed by bitmaps.  A file system contains several
 233  * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 234  * block for inodes, N blocks for the inode table and data blocks.
 235  *
 236  * The file system contains group descriptors which are located after the
 237  * super block.  Each descriptor contains the number of the bitmap block and
 238  * the free blocks count in the block.  The descriptors are loaded in memory
 239  * when a file system is mounted (see ext4_fill_super).
 240  */
 241
 242 /**
 243  * ext4_get_group_desc() -- load group descriptor from disk
 244  * @sb:                 super block
 245  * @block_group:        given block group
 246  * @bh:                 pointer to the buffer head to store the block
 247  *                      group descriptor
 248  */
 249 struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 250                                              ext4_group_t block_group,
 251                                              struct buffer_head **bh)
 252 {
 253         unsigned int group_desc;
 254         unsigned int offset;
 255         ext4_group_t ngroups = ext4_get_groups_count(sb);
 256         struct ext4_group_desc *desc;
 257         struct ext4_sb_info *sbi = EXT4_SB(sb);
 258
 259         if (block_group >= ngroups) {
 260                 ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 261                            " groups_count = %u", block_group, ngroups);
 262
 263                 return NULL;
 264         }
 265
 266         group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 267         offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 268         if (!sbi->s_group_desc[group_desc]) {
 269                 ext4_error(sb, "Group descriptor not loaded - "
 270                            "block_group = %u, group_desc = %u, desc = %u",
 271                            block_group, group_desc, offset);
 272                 return NULL;
 273         }
 274
 275         desc = (struct ext4_group_desc *)(
 276                 (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 277                 offset * EXT4_DESC_SIZE(sb));
 278         if (bh)
 279                 *bh = sbi->s_group_desc[group_desc];
 280         return desc;
 281 }
 282
 283 static int ext4_valid_block_bitmap(struct super_block *sb,
 284                                    struct ext4_group_desc *desc,
 285                                    unsigned int block_group,
 286                                    struct buffer_head *bh)
 287 {
 288         ext4_grpblk_t offset;
 289         ext4_grpblk_t next_zero_bit;
 290         ext4_fsblk_t bitmap_blk;
 291         ext4_fsblk_t group_first_block;
 292
 293         if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 294                 /* with FLEX_BG, the inode/block bitmaps and itable
 295                  * blocks may not be in the group at all
 296                  * so the bitmap validation will be skipped for those groups
 297                  * or it has to also read the block group where the bitmaps
 298                  * are located to verify they are set.
 299                  */
 300                 return 1;
 301         }
 302         group_first_block = ext4_group_first_block_no(sb, block_group);
 303
 304         /* check whether block bitmap block number is set */
 305         bitmap_blk = ext4_block_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 bitmap block number is set */
 312         bitmap_blk = ext4_inode_bitmap(sb, desc);
 313         offset = bitmap_blk - group_first_block;
 314         if (!ext4_test_bit(offset, bh->b_data))
 315                 /* bad block bitmap */
 316                 goto err_out;
 317
 318         /* check whether the inode table block number is set */
 319         bitmap_blk = ext4_inode_table(sb, desc);
 320         offset = bitmap_blk - group_first_block;
 321         next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 322                                 offset + EXT4_SB(sb)->s_itb_per_group,
 323                                 offset);
 324         if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
 325                 /* good bitmap for inode tables */
 326                 return 1;
 327
 328 err_out:
 329         ext4_error(sb, "Invalid block bitmap - block_group = %d, block = %llu",
 330                         block_group, bitmap_blk);
 331         return 0;
 332 }
 333
 334 void ext4_validate_block_bitmap(struct super_block *sb,
 335                                struct ext4_group_desc *desc,
 336                                unsigned int block_group,
 337                                struct buffer_head *bh)
 338 {
 339         if (buffer_verified(bh))
 340                 return;
 341
 342         ext4_lock_group(sb, block_group);
 343         if (ext4_valid_block_bitmap(sb, desc, block_group, bh) &&
 344             ext4_block_bitmap_csum_verify(sb, block_group, desc, bh,
 345                                           EXT4_BLOCKS_PER_GROUP(sb) / 8))
 346                 set_buffer_verified(bh);
 347         ext4_unlock_group(sb, block_group);
 348 }
 349
 350 /**
 351  * ext4_read_block_bitmap()
 352  * @sb:                 super block
 353  * @block_group:        given block group
 354  *
 355  * Read the bitmap for a given block_group,and validate the
 356  * bits for block/inode/inode tables are set in the bitmaps
 357  *
 358  * Return buffer_head on success or NULL in case of failure.
 359  */
 360 struct buffer_head *
 361 ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
 362 {
 363         struct ext4_group_desc *desc;
 364         struct buffer_head *bh;
 365         ext4_fsblk_t bitmap_blk;
 366
 367         desc = ext4_get_group_desc(sb, block_group, NULL);
 368         if (!desc)
 369                 return NULL;
 370         bitmap_blk = ext4_block_bitmap(sb, desc);
 371         bh = sb_getblk(sb, bitmap_blk);
 372         if (unlikely(!bh)) {
 373                 ext4_error(sb, "Cannot get buffer for block bitmap - "
 374                            "block_group = %u, block_bitmap = %llu",
 375                            block_group, bitmap_blk);
 376                 return NULL;
 377         }
 378
 379         if (bitmap_uptodate(bh))
 380                 goto verify;
 381
 382         lock_buffer(bh);
 383         if (bitmap_uptodate(bh)) {
 384                 unlock_buffer(bh);
 385                 goto verify;
 386         }
 387         ext4_lock_group(sb, block_group);
 388         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 389                 ext4_init_block_bitmap(sb, bh, block_group, desc);
 390                 set_bitmap_uptodate(bh);
 391                 set_buffer_uptodate(bh);
 392                 ext4_unlock_group(sb, block_group);
 393                 unlock_buffer(bh);
 394                 return bh;
 395         }
 396         ext4_unlock_group(sb, block_group);
 397         if (buffer_uptodate(bh)) {
 398                 /*
 399                  * if not uninit if bh is uptodate,
 400                  * bitmap is also uptodate
 401                  */
 402                 set_bitmap_uptodate(bh);
 403                 unlock_buffer(bh);
 404                 goto verify;
 405         }
 406         /*
 407          * submit the buffer_head for reading
 408          */
 409         set_buffer_new(bh);
 410         trace_ext4_read_block_bitmap_load(sb, block_group);
 411         bh->b_end_io = ext4_end_bitmap_read;
 412         get_bh(bh);
 413         submit_bh(READ, bh);
 414         return bh;
 415 verify:
 416         ext4_validate_block_bitmap(sb, desc, block_group, bh);
 417         return bh;
 418 }
 419
 420 /* Returns 0 on success, 1 on error */
 421 int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
 422                            struct buffer_head *bh)
 423 {
 424         struct ext4_group_desc *desc;
 425
 426         if (!buffer_new(bh))
 427                 return 0;
 428         desc = ext4_get_group_desc(sb, block_group, NULL);
 429         if (!desc)
 430                 return 1;
 431         wait_on_buffer(bh);
 432         if (!buffer_uptodate(bh)) {
 433                 ext4_error(sb, "Cannot read block bitmap - "
 434                            "block_group = %u, block_bitmap = %llu",
 435                            block_group, (unsigned long long) bh->b_blocknr);
 436                 return 1;
 437         }
 438         clear_buffer_new(bh);
 439         /* Panic or remount fs read-only if block bitmap is invalid */
 440         ext4_validate_block_bitmap(sb, desc, block_group, bh);
 441         return 0;
 442 }
 443
 444 struct buffer_head *
 445 ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 446 {
 447         struct buffer_head *bh;
 448
 449         bh = ext4_read_block_bitmap_nowait(sb, block_group);
 450         if (ext4_wait_block_bitmap(sb, block_group, bh)) {
 451                 put_bh(bh);
 452                 return NULL;
 453         }
 454         return bh;
 455 }
 456
 457 /**
 458  * ext4_has_free_clusters()
 459  * @sbi:        in-core super block structure.
 460  * @nclusters:  number of needed blocks
 461  * @flags:      flags from ext4_mb_new_blocks()
 462  *
 463  * Check if filesystem has nclusters free & available for allocation.
 464  * On success return 1, return 0 on failure.
 465  */
 466 static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
 467                                   s64 nclusters, unsigned int flags)
 468 {
 469         s64 free_clusters, dirty_clusters, root_clusters;
 470         struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
 471         struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
 472
 473         free_clusters  = percpu_counter_read_positive(fcc);
 474         dirty_clusters = percpu_counter_read_positive(dcc);
 475         root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
 476
 477         if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
 478                                         EXT4_FREECLUSTERS_WATERMARK) {
 479                 free_clusters  = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
 480                 dirty_clusters = percpu_counter_sum_positive(dcc);
 481         }
 482         /* Check whether we have space after accounting for current
 483          * dirty clusters & root reserved clusters.
 484          */
 485         if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
 486                 return 1;
 487
 488         /* Hm, nope.  Are (enough) root reserved clusters available? */
 489         if (uid_eq(sbi->s_resuid, current_fsuid()) ||
 490             (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) ||
 491             capable(CAP_SYS_RESOURCE) ||
 492                 (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 493
 494                 if (free_clusters >= (nclusters + dirty_clusters))
 495                         return 1;
 496         }
 497
 498         return 0;
 499 }
 500
 501 int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
 502                              s64 nclusters, unsigned int flags)
 503 {
 504         if (ext4_has_free_clusters(sbi, nclusters, flags)) {
 505                 percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
 506                 return 0;
 507         } else
 508                 return -ENOSPC;
 509 }
 510
 511 /**
 512  * ext4_should_retry_alloc()
 513  * @sb:                 super block
 514  * @retries             number of attemps has been made
 515  *
 516  * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 517  * it is profitable to retry the operation, this function will wait
 518  * for the current or committing transaction to complete, and then
 519  * return TRUE.
 520  *
 521  * if the total number of retries exceed three times, return FALSE.
 522  */
 523 int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 524 {
 525         if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
 526             (*retries)++ > 3 ||
 527             !EXT4_SB(sb)->s_journal)
 528                 return 0;
 529
 530         jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 531
 532         return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 533 }
 534
 535 /*
 536  * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 537  *
 538  * @handle:             handle to this transaction
 539  * @inode:              file inode
 540  * @goal:               given target block(filesystem wide)
 541  * @count:              pointer to total number of clusters needed
 542  * @errp:               error code
 543  *
 544  * Return 1st allocated block number on success, *count stores total account
 545  * error stores in errp pointer
 546  */
 547 ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 548                                   ext4_fsblk_t goal, unsigned int flags,
 549                                   unsigned long *count, int *errp)
 550 {
 551         struct ext4_allocation_request ar;
 552         ext4_fsblk_t ret;
 553
 554         memset(&ar, 0, sizeof(ar));
 555         /* Fill with neighbour allocated blocks */
 556         ar.inode = inode;
 557         ar.goal = goal;
 558         ar.len = count ? *count : 1;
 559         ar.flags = flags;
 560
 561         ret = ext4_mb_new_blocks(handle, &ar, errp);
 562         if (count)
 563                 *count = ar.len;
 564         /*
 565          * Account for the allocated meta blocks.  We will never
 566          * fail EDQUOT for metdata, but we do account for it.
 567          */
 568         if (!(*errp) &&
 569             ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 570                 spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 571                 EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 572                 spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 573                 dquot_alloc_block_nofail(inode,
 574                                 EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
 575         }
 576         return ret;
 577 }
 578
 579 /**
 580  * ext4_count_free_clusters() -- count filesystem free clusters
 581  * @sb:         superblock
 582  *
 583  * Adds up the number of free clusters from each block group.
 584  */
 585 ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
 586 {
 587         ext4_fsblk_t desc_count;
 588         struct ext4_group_desc *gdp;
 589         ext4_group_t i;
 590         ext4_group_t ngroups = ext4_get_groups_count(sb);
 591 #ifdef EXT4FS_DEBUG
 592         struct ext4_super_block *es;
 593         ext4_fsblk_t bitmap_count;
 594         unsigned int x;
 595         struct buffer_head *bitmap_bh = NULL;
 596
 597         es = EXT4_SB(sb)->s_es;
 598         desc_count = 0;
 599         bitmap_count = 0;
 600         gdp = NULL;
 601
 602         for (i = 0; i < ngroups; i++) {
 603                 gdp = ext4_get_group_desc(sb, i, NULL);
 604                 if (!gdp)
 605                         continue;
 606                 desc_count += ext4_free_group_clusters(sb, gdp);
 607                 brelse(bitmap_bh);
 608                 bitmap_bh = ext4_read_block_bitmap(sb, i);
 609                 if (bitmap_bh == NULL)
 610                         continue;
 611
 612                 x = ext4_count_free(bitmap_bh, sb->s_blocksize);
 613                 printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 614                         i, ext4_free_group_clusters(sb, gdp), x);
 615                 bitmap_count += x;
 616         }
 617         brelse(bitmap_bh);
 618         printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
 619                ", computed = %llu, %llu\n",
 620                EXT4_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
 621                desc_count, bitmap_count);
 622         return bitmap_count;
 623 #else
 624         desc_count = 0;
 625         for (i = 0; i < ngroups; i++) {
 626                 gdp = ext4_get_group_desc(sb, i, NULL);
 627                 if (!gdp)
 628                         continue;
 629                 desc_count += ext4_free_group_clusters(sb, gdp);
 630         }
 631
 632         return desc_count;
 633 #endif
 634 }
 635
 636 static inline int test_root(ext4_group_t a, int b)
 637 {
 638         int num = b;
 639
 640         while (a > num)
 641                 num *= b;
 642         return num == a;
 643 }
 644
 645 static int ext4_group_sparse(ext4_group_t group)
 646 {
 647         if (group <= 1)
 648                 return 1;
 649         if (!(group & 1))
 650                 return 0;
 651         return (test_root(group, 7) || test_root(group, 5) ||
 652                 test_root(group, 3));
 653 }
 654
 655 /**
 656  *      ext4_bg_has_super - number of blocks used by the superblock in group
 657  *      @sb: superblock for filesystem
 658  *      @group: group number to check
 659  *
 660  *      Return the number of blocks used by the superblock (primary or backup)
 661  *      in this group.  Currently this will be only 0 or 1.
 662  */
 663 int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 664 {
 665         if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 666                                 EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 667                         !ext4_group_sparse(group))
 668                 return 0;
 669         return 1;
 670 }
 671
 672 static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 673                                         ext4_group_t group)
 674 {
 675         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 676         ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 677         ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 678
 679         if (group == first || group == first + 1 || group == last)
 680                 return 1;
 681         return 0;
 682 }
 683
 684 static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 685                                         ext4_group_t group)
 686 {
 687         if (!ext4_bg_has_super(sb, group))
 688                 return 0;
 689
 690         if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 691                 return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 692         else
 693                 return EXT4_SB(sb)->s_gdb_count;
 694 }
 695
 696 /**
 697  *      ext4_bg_num_gdb - number of blocks used by the group table in group
 698  *      @sb: superblock for filesystem
 699  *      @group: group number to check
 700  *
 701  *      Return the number of blocks used by the group descriptor table
 702  *      (primary or backup) in this group.  In the future there may be a
 703  *      different number of descriptor blocks in each group.
 704  */
 705 unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 706 {
 707         unsigned long first_meta_bg =
 708                         le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 709         unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 710
 711         if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 712                         metagroup < first_meta_bg)
 713                 return ext4_bg_num_gdb_nometa(sb, group);
 714
 715         return ext4_bg_num_gdb_meta(sb,group);
 716
 717 }
 718
 719 /*
 720  * This function returns the number of file system metadata clusters at
 721  * the beginning of a block group, including the reserved gdt blocks.
 722  */
 723 static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
 724                                      ext4_group_t block_group)
 725 {
 726         struct ext4_sb_info *sbi = EXT4_SB(sb);
 727         unsigned num;
 728
 729         /* Check for superblock and gdt backups in this group */
 730         num = ext4_bg_has_super(sb, block_group);
 731
 732         if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 733             block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 734                           sbi->s_desc_per_block) {
 735                 if (num) {
 736                         num += ext4_bg_num_gdb(sb, block_group);
 737                         num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 738                 }
 739         } else { /* For META_BG_BLOCK_GROUPS */
 740                 num += ext4_bg_num_gdb(sb, block_group);
 741         }
 742         return EXT4_NUM_B2C(sbi, num);
 743 }
 744 /**
 745  *      ext4_inode_to_goal_block - return a hint for block allocation
 746  *      @inode: inode for block allocation
 747  *
 748  *      Return the ideal location to start allocating blocks for a
 749  *      newly created inode.
 750  */
 751 ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 752 {
 753         struct ext4_inode_info *ei = EXT4_I(inode);
 754         ext4_group_t block_group;
 755         ext4_grpblk_t colour;
 756         int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 757         ext4_fsblk_t bg_start;
 758         ext4_fsblk_t last_block;
 759
 760         block_group = ei->i_block_group;
 761         if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 762                 /*
 763                  * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 764                  * block groups per flexgroup, reserve the first block
 765                  * group for directories and special files.  Regular
 766                  * files will start at the second block group.  This
 767                  * tends to speed up directory access and improves
 768                  * fsck times.
 769                  */
 770                 block_group &= ~(flex_size-1);
 771                 if (S_ISREG(inode->i_mode))
 772                         block_group++;
 773         }
 774         bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 775         last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 776
 777         /*
 778          * If we are doing delayed allocation, we don't need take
 779          * colour into account.
 780          */
 781         if (test_opt(inode->i_sb, DELALLOC))
 782                 return bg_start;
 783
 784         if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 785                 colour = (current->pid % 16) *
 786                         (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 787         else
 788                 colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 789         return bg_start + colour;
 790 }
 791