linux/fs/ext4/balloc.c
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   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
  26static 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 */
  36void 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
  52static 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 */
  65unsigned 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
 138static 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 */
 158void 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                return;
 179        }
 180        memset(bh->b_data, 0, sb->s_blocksize);
 181
 182        bit_max = ext4_num_base_meta_clusters(sb, block_group);
 183        for (bit = 0; bit < bit_max; bit++)
 184                ext4_set_bit(bit, bh->b_data);
 185
 186        start = ext4_group_first_block_no(sb, block_group);
 187
 188        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
 189                flex_bg = 1;
 190
 191        /* Set bits for block and inode bitmaps, and inode table */
 192        tmp = ext4_block_bitmap(sb, gdp);
 193        if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 194                ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 195
 196        tmp = ext4_inode_bitmap(sb, gdp);
 197        if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 198                ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 199
 200        tmp = ext4_inode_table(sb, gdp);
 201        for (; tmp < ext4_inode_table(sb, gdp) +
 202                     sbi->s_itb_per_group; tmp++) {
 203                if (!flex_bg || ext4_block_in_group(sb, tmp, block_group))
 204                        ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data);
 205        }
 206
 207        /*
 208         * Also if the number of blocks within the group is less than
 209         * the blocksize * 8 ( which is the size of bitmap ), set rest
 210         * of the block bitmap to 1
 211         */
 212        ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
 213                             sb->s_blocksize * 8, bh->b_data);
 214        ext4_block_bitmap_csum_set(sb, block_group, gdp, bh);
 215        ext4_group_desc_csum_set(sb, block_group, gdp);
 216}
 217
 218/* Return the number of free blocks in a block group.  It is used when
 219 * the block bitmap is uninitialized, so we can't just count the bits
 220 * in the bitmap. */
 221unsigned ext4_free_clusters_after_init(struct super_block *sb,
 222                                       ext4_group_t block_group,
 223                                       struct ext4_group_desc *gdp)
 224{
 225        return num_clusters_in_group(sb, block_group) - 
 226                ext4_num_overhead_clusters(sb, block_group, gdp);
 227}
 228
 229/*
 230 * The free blocks are managed by bitmaps.  A file system contains several
 231 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 232 * block for inodes, N blocks for the inode table and data blocks.
 233 *
 234 * The file system contains group descriptors which are located after the
 235 * super block.  Each descriptor contains the number of the bitmap block and
 236 * the free blocks count in the block.  The descriptors are loaded in memory
 237 * when a file system is mounted (see ext4_fill_super).
 238 */
 239
 240/**
 241 * ext4_get_group_desc() -- load group descriptor from disk
 242 * @sb:                 super block
 243 * @block_group:        given block group
 244 * @bh:                 pointer to the buffer head to store the block
 245 *                      group descriptor
 246 */
 247struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 248                                             ext4_group_t block_group,
 249                                             struct buffer_head **bh)
 250{
 251        unsigned int group_desc;
 252        unsigned int offset;
 253        ext4_group_t ngroups = ext4_get_groups_count(sb);
 254        struct ext4_group_desc *desc;
 255        struct ext4_sb_info *sbi = EXT4_SB(sb);
 256
 257        if (block_group >= ngroups) {
 258                ext4_error(sb, "block_group >= groups_count - block_group = %u,"
 259                           " groups_count = %u", block_group, ngroups);
 260
 261                return NULL;
 262        }
 263
 264        group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
 265        offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
 266        if (!sbi->s_group_desc[group_desc]) {
 267                ext4_error(sb, "Group descriptor not loaded - "
 268                           "block_group = %u, group_desc = %u, desc = %u",
 269                           block_group, group_desc, offset);
 270                return NULL;
 271        }
 272
 273        desc = (struct ext4_group_desc *)(
 274                (__u8 *)sbi->s_group_desc[group_desc]->b_data +
 275                offset * EXT4_DESC_SIZE(sb));
 276        if (bh)
 277                *bh = sbi->s_group_desc[group_desc];
 278        return desc;
 279}
 280
 281/*
 282 * Return the block number which was discovered to be invalid, or 0 if
 283 * the block bitmap is valid.
 284 */
 285static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
 286                                            struct ext4_group_desc *desc,
 287                                            unsigned int block_group,
 288                                            struct buffer_head *bh)
 289{
 290        ext4_grpblk_t offset;
 291        ext4_grpblk_t next_zero_bit;
 292        ext4_fsblk_t blk;
 293        ext4_fsblk_t group_first_block;
 294
 295        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 296                /* with FLEX_BG, the inode/block bitmaps and itable
 297                 * blocks may not be in the group at all
 298                 * so the bitmap validation will be skipped for those groups
 299                 * or it has to also read the block group where the bitmaps
 300                 * are located to verify they are set.
 301                 */
 302                return 0;
 303        }
 304        group_first_block = ext4_group_first_block_no(sb, block_group);
 305
 306        /* check whether block bitmap block number is set */
 307        blk = ext4_block_bitmap(sb, desc);
 308        offset = blk - group_first_block;
 309        if (!ext4_test_bit(offset, bh->b_data))
 310                /* bad block bitmap */
 311                return blk;
 312
 313        /* check whether the inode bitmap block number is set */
 314        blk = ext4_inode_bitmap(sb, desc);
 315        offset = blk - group_first_block;
 316        if (!ext4_test_bit(offset, bh->b_data))
 317                /* bad block bitmap */
 318                return blk;
 319
 320        /* check whether the inode table block number is set */
 321        blk = ext4_inode_table(sb, desc);
 322        offset = blk - group_first_block;
 323        next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 324                                offset + EXT4_SB(sb)->s_itb_per_group,
 325                                offset);
 326        if (next_zero_bit < offset + EXT4_SB(sb)->s_itb_per_group)
 327                /* bad bitmap for inode tables */
 328                return blk;
 329        return 0;
 330}
 331
 332void ext4_validate_block_bitmap(struct super_block *sb,
 333                               struct ext4_group_desc *desc,
 334                               unsigned int block_group,
 335                               struct buffer_head *bh)
 336{
 337        ext4_fsblk_t    blk;
 338
 339        if (buffer_verified(bh))
 340                return;
 341
 342        ext4_lock_group(sb, block_group);
 343        blk = ext4_valid_block_bitmap(sb, desc, block_group, bh);
 344        if (unlikely(blk != 0)) {
 345                ext4_unlock_group(sb, block_group);
 346                ext4_error(sb, "bg %u: block %llu: invalid block bitmap",
 347                           block_group, blk);
 348                return;
 349        }
 350        if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
 351                        desc, bh))) {
 352                ext4_unlock_group(sb, block_group);
 353                ext4_error(sb, "bg %u: bad block bitmap checksum", block_group);
 354                return;
 355        }
 356        set_buffer_verified(bh);
 357        ext4_unlock_group(sb, block_group);
 358}
 359
 360/**
 361 * ext4_read_block_bitmap()
 362 * @sb:                 super block
 363 * @block_group:        given block group
 364 *
 365 * Read the bitmap for a given block_group,and validate the
 366 * bits for block/inode/inode tables are set in the bitmaps
 367 *
 368 * Return buffer_head on success or NULL in case of failure.
 369 */
 370struct buffer_head *
 371ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
 372{
 373        struct ext4_group_desc *desc;
 374        struct buffer_head *bh;
 375        ext4_fsblk_t bitmap_blk;
 376
 377        desc = ext4_get_group_desc(sb, block_group, NULL);
 378        if (!desc)
 379                return NULL;
 380        bitmap_blk = ext4_block_bitmap(sb, desc);
 381        bh = sb_getblk(sb, bitmap_blk);
 382        if (unlikely(!bh)) {
 383                ext4_error(sb, "Cannot get buffer for block bitmap - "
 384                           "block_group = %u, block_bitmap = %llu",
 385                           block_group, bitmap_blk);
 386                return NULL;
 387        }
 388
 389        if (bitmap_uptodate(bh))
 390                goto verify;
 391
 392        lock_buffer(bh);
 393        if (bitmap_uptodate(bh)) {
 394                unlock_buffer(bh);
 395                goto verify;
 396        }
 397        ext4_lock_group(sb, block_group);
 398        if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 399                ext4_init_block_bitmap(sb, bh, block_group, desc);
 400                set_bitmap_uptodate(bh);
 401                set_buffer_uptodate(bh);
 402                ext4_unlock_group(sb, block_group);
 403                unlock_buffer(bh);
 404                return bh;
 405        }
 406        ext4_unlock_group(sb, block_group);
 407        if (buffer_uptodate(bh)) {
 408                /*
 409                 * if not uninit if bh is uptodate,
 410                 * bitmap is also uptodate
 411                 */
 412                set_bitmap_uptodate(bh);
 413                unlock_buffer(bh);
 414                goto verify;
 415        }
 416        /*
 417         * submit the buffer_head for reading
 418         */
 419        set_buffer_new(bh);
 420        trace_ext4_read_block_bitmap_load(sb, block_group);
 421        bh->b_end_io = ext4_end_bitmap_read;
 422        get_bh(bh);
 423        submit_bh(READ, bh);
 424        return bh;
 425verify:
 426        ext4_validate_block_bitmap(sb, desc, block_group, bh);
 427        return bh;
 428}
 429
 430/* Returns 0 on success, 1 on error */
 431int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
 432                           struct buffer_head *bh)
 433{
 434        struct ext4_group_desc *desc;
 435
 436        if (!buffer_new(bh))
 437                return 0;
 438        desc = ext4_get_group_desc(sb, block_group, NULL);
 439        if (!desc)
 440                return 1;
 441        wait_on_buffer(bh);
 442        if (!buffer_uptodate(bh)) {
 443                ext4_error(sb, "Cannot read block bitmap - "
 444                           "block_group = %u, block_bitmap = %llu",
 445                           block_group, (unsigned long long) bh->b_blocknr);
 446                return 1;
 447        }
 448        clear_buffer_new(bh);
 449        /* Panic or remount fs read-only if block bitmap is invalid */
 450        ext4_validate_block_bitmap(sb, desc, block_group, bh);
 451        return 0;
 452}
 453
 454struct buffer_head *
 455ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 456{
 457        struct buffer_head *bh;
 458
 459        bh = ext4_read_block_bitmap_nowait(sb, block_group);
 460        if (ext4_wait_block_bitmap(sb, block_group, bh)) {
 461                put_bh(bh);
 462                return NULL;
 463        }
 464        return bh;
 465}
 466
 467/**
 468 * ext4_has_free_clusters()
 469 * @sbi:        in-core super block structure.
 470 * @nclusters:  number of needed blocks
 471 * @flags:      flags from ext4_mb_new_blocks()
 472 *
 473 * Check if filesystem has nclusters free & available for allocation.
 474 * On success return 1, return 0 on failure.
 475 */
 476static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
 477                                  s64 nclusters, unsigned int flags)
 478{
 479        s64 free_clusters, dirty_clusters, root_clusters;
 480        struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
 481        struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
 482
 483        free_clusters  = percpu_counter_read_positive(fcc);
 484        dirty_clusters = percpu_counter_read_positive(dcc);
 485        root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
 486
 487        if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
 488                                        EXT4_FREECLUSTERS_WATERMARK) {
 489                free_clusters  = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
 490                dirty_clusters = percpu_counter_sum_positive(dcc);
 491        }
 492        /* Check whether we have space after accounting for current
 493         * dirty clusters & root reserved clusters.
 494         */
 495        if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
 496                return 1;
 497
 498        /* Hm, nope.  Are (enough) root reserved clusters available? */
 499        if (uid_eq(sbi->s_resuid, current_fsuid()) ||
 500            (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) ||
 501            capable(CAP_SYS_RESOURCE) ||
 502                (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 503
 504                if (free_clusters >= (nclusters + dirty_clusters))
 505                        return 1;
 506        }
 507
 508        return 0;
 509}
 510
 511int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
 512                             s64 nclusters, unsigned int flags)
 513{
 514        if (ext4_has_free_clusters(sbi, nclusters, flags)) {
 515                percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
 516                return 0;
 517        } else
 518                return -ENOSPC;
 519}
 520
 521/**
 522 * ext4_should_retry_alloc()
 523 * @sb:                 super block
 524 * @retries             number of attemps has been made
 525 *
 526 * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 527 * it is profitable to retry the operation, this function will wait
 528 * for the current or committing transaction to complete, and then
 529 * return TRUE.
 530 *
 531 * if the total number of retries exceed three times, return FALSE.
 532 */
 533int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 534{
 535        if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
 536            (*retries)++ > 3 ||
 537            !EXT4_SB(sb)->s_journal)
 538                return 0;
 539
 540        jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 541
 542        return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 543}
 544
 545/*
 546 * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 547 *
 548 * @handle:             handle to this transaction
 549 * @inode:              file inode
 550 * @goal:               given target block(filesystem wide)
 551 * @count:              pointer to total number of clusters needed
 552 * @errp:               error code
 553 *
 554 * Return 1st allocated block number on success, *count stores total account
 555 * error stores in errp pointer
 556 */
 557ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 558                                  ext4_fsblk_t goal, unsigned int flags,
 559                                  unsigned long *count, int *errp)
 560{
 561        struct ext4_allocation_request ar;
 562        ext4_fsblk_t ret;
 563
 564        memset(&ar, 0, sizeof(ar));
 565        /* Fill with neighbour allocated blocks */
 566        ar.inode = inode;
 567        ar.goal = goal;
 568        ar.len = count ? *count : 1;
 569        ar.flags = flags;
 570
 571        ret = ext4_mb_new_blocks(handle, &ar, errp);
 572        if (count)
 573                *count = ar.len;
 574        /*
 575         * Account for the allocated meta blocks.  We will never
 576         * fail EDQUOT for metdata, but we do account for it.
 577         */
 578        if (!(*errp) &&
 579            ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 580                spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 581                EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 582                spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 583                dquot_alloc_block_nofail(inode,
 584                                EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
 585        }
 586        return ret;
 587}
 588
 589/**
 590 * ext4_count_free_clusters() -- count filesystem free clusters
 591 * @sb:         superblock
 592 *
 593 * Adds up the number of free clusters from each block group.
 594 */
 595ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
 596{
 597        ext4_fsblk_t desc_count;
 598        struct ext4_group_desc *gdp;
 599        ext4_group_t i;
 600        ext4_group_t ngroups = ext4_get_groups_count(sb);
 601#ifdef EXT4FS_DEBUG
 602        struct ext4_super_block *es;
 603        ext4_fsblk_t bitmap_count;
 604        unsigned int x;
 605        struct buffer_head *bitmap_bh = NULL;
 606
 607        es = EXT4_SB(sb)->s_es;
 608        desc_count = 0;
 609        bitmap_count = 0;
 610        gdp = NULL;
 611
 612        for (i = 0; i < ngroups; i++) {
 613                gdp = ext4_get_group_desc(sb, i, NULL);
 614                if (!gdp)
 615                        continue;
 616                desc_count += ext4_free_group_clusters(sb, gdp);
 617                brelse(bitmap_bh);
 618                bitmap_bh = ext4_read_block_bitmap(sb, i);
 619                if (bitmap_bh == NULL)
 620                        continue;
 621
 622                x = ext4_count_free(bitmap_bh->b_data,
 623                                    EXT4_BLOCKS_PER_GROUP(sb) / 8);
 624                printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 625                        i, ext4_free_group_clusters(sb, gdp), x);
 626                bitmap_count += x;
 627        }
 628        brelse(bitmap_bh);
 629        printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
 630               ", computed = %llu, %llu\n",
 631               EXT4_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
 632               desc_count, bitmap_count);
 633        return bitmap_count;
 634#else
 635        desc_count = 0;
 636        for (i = 0; i < ngroups; i++) {
 637                gdp = ext4_get_group_desc(sb, i, NULL);
 638                if (!gdp)
 639                        continue;
 640                desc_count += ext4_free_group_clusters(sb, gdp);
 641        }
 642
 643        return desc_count;
 644#endif
 645}
 646
 647static inline int test_root(ext4_group_t a, int b)
 648{
 649        int num = b;
 650
 651        while (a > num)
 652                num *= b;
 653        return num == a;
 654}
 655
 656static int ext4_group_sparse(ext4_group_t group)
 657{
 658        if (group <= 1)
 659                return 1;
 660        if (!(group & 1))
 661                return 0;
 662        return (test_root(group, 7) || test_root(group, 5) ||
 663                test_root(group, 3));
 664}
 665
 666/**
 667 *      ext4_bg_has_super - number of blocks used by the superblock in group
 668 *      @sb: superblock for filesystem
 669 *      @group: group number to check
 670 *
 671 *      Return the number of blocks used by the superblock (primary or backup)
 672 *      in this group.  Currently this will be only 0 or 1.
 673 */
 674int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 675{
 676        if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 677                                EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 678                        !ext4_group_sparse(group))
 679                return 0;
 680        return 1;
 681}
 682
 683static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 684                                        ext4_group_t group)
 685{
 686        unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 687        ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 688        ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 689
 690        if (group == first || group == first + 1 || group == last)
 691                return 1;
 692        return 0;
 693}
 694
 695static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 696                                        ext4_group_t group)
 697{
 698        if (!ext4_bg_has_super(sb, group))
 699                return 0;
 700
 701        if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 702                return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 703        else
 704                return EXT4_SB(sb)->s_gdb_count;
 705}
 706
 707/**
 708 *      ext4_bg_num_gdb - number of blocks used by the group table in group
 709 *      @sb: superblock for filesystem
 710 *      @group: group number to check
 711 *
 712 *      Return the number of blocks used by the group descriptor table
 713 *      (primary or backup) in this group.  In the future there may be a
 714 *      different number of descriptor blocks in each group.
 715 */
 716unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 717{
 718        unsigned long first_meta_bg =
 719                        le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 720        unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 721
 722        if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 723                        metagroup < first_meta_bg)
 724                return ext4_bg_num_gdb_nometa(sb, group);
 725
 726        return ext4_bg_num_gdb_meta(sb,group);
 727
 728}
 729
 730/*
 731 * This function returns the number of file system metadata clusters at
 732 * the beginning of a block group, including the reserved gdt blocks.
 733 */
 734static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
 735                                     ext4_group_t block_group)
 736{
 737        struct ext4_sb_info *sbi = EXT4_SB(sb);
 738        unsigned num;
 739
 740        /* Check for superblock and gdt backups in this group */
 741        num = ext4_bg_has_super(sb, block_group);
 742
 743        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 744            block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 745                          sbi->s_desc_per_block) {
 746                if (num) {
 747                        num += ext4_bg_num_gdb(sb, block_group);
 748                        num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 749                }
 750        } else { /* For META_BG_BLOCK_GROUPS */
 751                num += ext4_bg_num_gdb(sb, block_group);
 752        }
 753        return EXT4_NUM_B2C(sbi, num);
 754}
 755/**
 756 *      ext4_inode_to_goal_block - return a hint for block allocation
 757 *      @inode: inode for block allocation
 758 *
 759 *      Return the ideal location to start allocating blocks for a
 760 *      newly created inode.
 761 */
 762ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 763{
 764        struct ext4_inode_info *ei = EXT4_I(inode);
 765        ext4_group_t block_group;
 766        ext4_grpblk_t colour;
 767        int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 768        ext4_fsblk_t bg_start;
 769        ext4_fsblk_t last_block;
 770
 771        block_group = ei->i_block_group;
 772        if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 773                /*
 774                 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 775                 * block groups per flexgroup, reserve the first block
 776                 * group for directories and special files.  Regular
 777                 * files will start at the second block group.  This
 778                 * tends to speed up directory access and improves
 779                 * fsck times.
 780                 */
 781                block_group &= ~(flex_size-1);
 782                if (S_ISREG(inode->i_mode))
 783                        block_group++;
 784        }
 785        bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 786        last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 787
 788        /*
 789         * If we are doing delayed allocation, we don't need take
 790         * colour into account.
 791         */
 792        if (test_opt(inode->i_sb, DELALLOC))
 793                return bg_start;
 794
 795        if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 796                colour = (current->pid % 16) *
 797                        (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 798        else
 799                colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 800        return bg_start + colour;
 801}
 802
 803
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