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                                           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. */
 223unsigned 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 */
 249struct 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/*
 284 * Return the block number which was discovered to be invalid, or 0 if
 285 * the block bitmap is valid.
 286 */
 287static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb,
 288                                            struct ext4_group_desc *desc,
 289                                            unsigned int block_group,
 290                                            struct buffer_head *bh)
 291{
 292        ext4_grpblk_t offset;
 293        ext4_grpblk_t next_zero_bit;
 294        ext4_fsblk_t blk;
 295        ext4_fsblk_t group_first_block;
 296
 297        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
 298                /* with FLEX_BG, the inode/block bitmaps and itable
 299                 * blocks may not be in the group at all
 300                 * so the bitmap validation will be skipped for those groups
 301                 * or it has to also read the block group where the bitmaps
 302                 * are located to verify they are set.
 303                 */
 304                return 0;
 305        }
 306        group_first_block = ext4_group_first_block_no(sb, block_group);
 307
 308        /* check whether block bitmap block number is set */
 309        blk = ext4_block_bitmap(sb, desc);
 310        offset = blk - group_first_block;
 311        if (!ext4_test_bit(offset, bh->b_data))
 312                /* bad block bitmap */
 313                return blk;
 314
 315        /* check whether the inode bitmap block number is set */
 316        blk = ext4_inode_bitmap(sb, desc);
 317        offset = blk - group_first_block;
 318        if (!ext4_test_bit(offset, bh->b_data))
 319                /* bad block bitmap */
 320                return blk;
 321
 322        /* check whether the inode table block number is set */
 323        blk = ext4_inode_table(sb, desc);
 324        offset = blk - group_first_block;
 325        next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
 326                                offset + EXT4_SB(sb)->s_itb_per_group,
 327                                offset);
 328        if (next_zero_bit < offset + EXT4_SB(sb)->s_itb_per_group)
 329                /* bad bitmap for inode tables */
 330                return blk;
 331        return 0;
 332}
 333
 334void 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        ext4_fsblk_t    blk;
 340
 341        if (buffer_verified(bh))
 342                return;
 343
 344        ext4_lock_group(sb, block_group);
 345        blk = ext4_valid_block_bitmap(sb, desc, block_group, bh);
 346        if (unlikely(blk != 0)) {
 347                ext4_unlock_group(sb, block_group);
 348                ext4_error(sb, "bg %u: block %llu: invalid block bitmap",
 349                           block_group, blk);
 350                return;
 351        }
 352        if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
 353                        desc, bh, EXT4_BLOCKS_PER_GROUP(sb) / 8))) {
 354                ext4_unlock_group(sb, block_group);
 355                ext4_error(sb, "bg %u: bad block bitmap checksum", block_group);
 356                return;
 357        }
 358        set_buffer_verified(bh);
 359        ext4_unlock_group(sb, block_group);
 360}
 361
 362/**
 363 * ext4_read_block_bitmap()
 364 * @sb:                 super block
 365 * @block_group:        given block group
 366 *
 367 * Read the bitmap for a given block_group,and validate the
 368 * bits for block/inode/inode tables are set in the bitmaps
 369 *
 370 * Return buffer_head on success or NULL in case of failure.
 371 */
 372struct buffer_head *
 373ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
 374{
 375        struct ext4_group_desc *desc;
 376        struct buffer_head *bh;
 377        ext4_fsblk_t bitmap_blk;
 378
 379        desc = ext4_get_group_desc(sb, block_group, NULL);
 380        if (!desc)
 381                return NULL;
 382        bitmap_blk = ext4_block_bitmap(sb, desc);
 383        bh = sb_getblk(sb, bitmap_blk);
 384        if (unlikely(!bh)) {
 385                ext4_error(sb, "Cannot get buffer for block bitmap - "
 386                           "block_group = %u, block_bitmap = %llu",
 387                           block_group, bitmap_blk);
 388                return NULL;
 389        }
 390
 391        if (bitmap_uptodate(bh))
 392                goto verify;
 393
 394        lock_buffer(bh);
 395        if (bitmap_uptodate(bh)) {
 396                unlock_buffer(bh);
 397                goto verify;
 398        }
 399        ext4_lock_group(sb, block_group);
 400        if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
 401                ext4_init_block_bitmap(sb, bh, block_group, desc);
 402                set_bitmap_uptodate(bh);
 403                set_buffer_uptodate(bh);
 404                ext4_unlock_group(sb, block_group);
 405                unlock_buffer(bh);
 406                return bh;
 407        }
 408        ext4_unlock_group(sb, block_group);
 409        if (buffer_uptodate(bh)) {
 410                /*
 411                 * if not uninit if bh is uptodate,
 412                 * bitmap is also uptodate
 413                 */
 414                set_bitmap_uptodate(bh);
 415                unlock_buffer(bh);
 416                goto verify;
 417        }
 418        /*
 419         * submit the buffer_head for reading
 420         */
 421        set_buffer_new(bh);
 422        trace_ext4_read_block_bitmap_load(sb, block_group);
 423        bh->b_end_io = ext4_end_bitmap_read;
 424        get_bh(bh);
 425        submit_bh(READ, bh);
 426        return bh;
 427verify:
 428        ext4_validate_block_bitmap(sb, desc, block_group, bh);
 429        return bh;
 430}
 431
 432/* Returns 0 on success, 1 on error */
 433int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
 434                           struct buffer_head *bh)
 435{
 436        struct ext4_group_desc *desc;
 437
 438        if (!buffer_new(bh))
 439                return 0;
 440        desc = ext4_get_group_desc(sb, block_group, NULL);
 441        if (!desc)
 442                return 1;
 443        wait_on_buffer(bh);
 444        if (!buffer_uptodate(bh)) {
 445                ext4_error(sb, "Cannot read block bitmap - "
 446                           "block_group = %u, block_bitmap = %llu",
 447                           block_group, (unsigned long long) bh->b_blocknr);
 448                return 1;
 449        }
 450        clear_buffer_new(bh);
 451        /* Panic or remount fs read-only if block bitmap is invalid */
 452        ext4_validate_block_bitmap(sb, desc, block_group, bh);
 453        return 0;
 454}
 455
 456struct buffer_head *
 457ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
 458{
 459        struct buffer_head *bh;
 460
 461        bh = ext4_read_block_bitmap_nowait(sb, block_group);
 462        if (ext4_wait_block_bitmap(sb, block_group, bh)) {
 463                put_bh(bh);
 464                return NULL;
 465        }
 466        return bh;
 467}
 468
 469/**
 470 * ext4_has_free_clusters()
 471 * @sbi:        in-core super block structure.
 472 * @nclusters:  number of needed blocks
 473 * @flags:      flags from ext4_mb_new_blocks()
 474 *
 475 * Check if filesystem has nclusters free & available for allocation.
 476 * On success return 1, return 0 on failure.
 477 */
 478static int ext4_has_free_clusters(struct ext4_sb_info *sbi,
 479                                  s64 nclusters, unsigned int flags)
 480{
 481        s64 free_clusters, dirty_clusters, root_clusters;
 482        struct percpu_counter *fcc = &sbi->s_freeclusters_counter;
 483        struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter;
 484
 485        free_clusters  = percpu_counter_read_positive(fcc);
 486        dirty_clusters = percpu_counter_read_positive(dcc);
 487        root_clusters = EXT4_B2C(sbi, ext4_r_blocks_count(sbi->s_es));
 488
 489        if (free_clusters - (nclusters + root_clusters + dirty_clusters) <
 490                                        EXT4_FREECLUSTERS_WATERMARK) {
 491                free_clusters  = EXT4_C2B(sbi, percpu_counter_sum_positive(fcc));
 492                dirty_clusters = percpu_counter_sum_positive(dcc);
 493        }
 494        /* Check whether we have space after accounting for current
 495         * dirty clusters & root reserved clusters.
 496         */
 497        if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters))
 498                return 1;
 499
 500        /* Hm, nope.  Are (enough) root reserved clusters available? */
 501        if (uid_eq(sbi->s_resuid, current_fsuid()) ||
 502            (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) ||
 503            capable(CAP_SYS_RESOURCE) ||
 504                (flags & EXT4_MB_USE_ROOT_BLOCKS)) {
 505
 506                if (free_clusters >= (nclusters + dirty_clusters))
 507                        return 1;
 508        }
 509
 510        return 0;
 511}
 512
 513int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
 514                             s64 nclusters, unsigned int flags)
 515{
 516        if (ext4_has_free_clusters(sbi, nclusters, flags)) {
 517                percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters);
 518                return 0;
 519        } else
 520                return -ENOSPC;
 521}
 522
 523/**
 524 * ext4_should_retry_alloc()
 525 * @sb:                 super block
 526 * @retries             number of attemps has been made
 527 *
 528 * ext4_should_retry_alloc() is called when ENOSPC is returned, and if
 529 * it is profitable to retry the operation, this function will wait
 530 * for the current or committing transaction to complete, and then
 531 * return TRUE.
 532 *
 533 * if the total number of retries exceed three times, return FALSE.
 534 */
 535int ext4_should_retry_alloc(struct super_block *sb, int *retries)
 536{
 537        if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
 538            (*retries)++ > 3 ||
 539            !EXT4_SB(sb)->s_journal)
 540                return 0;
 541
 542        jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);
 543
 544        return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal);
 545}
 546
 547/*
 548 * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks
 549 *
 550 * @handle:             handle to this transaction
 551 * @inode:              file inode
 552 * @goal:               given target block(filesystem wide)
 553 * @count:              pointer to total number of clusters needed
 554 * @errp:               error code
 555 *
 556 * Return 1st allocated block number on success, *count stores total account
 557 * error stores in errp pointer
 558 */
 559ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode,
 560                                  ext4_fsblk_t goal, unsigned int flags,
 561                                  unsigned long *count, int *errp)
 562{
 563        struct ext4_allocation_request ar;
 564        ext4_fsblk_t ret;
 565
 566        memset(&ar, 0, sizeof(ar));
 567        /* Fill with neighbour allocated blocks */
 568        ar.inode = inode;
 569        ar.goal = goal;
 570        ar.len = count ? *count : 1;
 571        ar.flags = flags;
 572
 573        ret = ext4_mb_new_blocks(handle, &ar, errp);
 574        if (count)
 575                *count = ar.len;
 576        /*
 577         * Account for the allocated meta blocks.  We will never
 578         * fail EDQUOT for metdata, but we do account for it.
 579         */
 580        if (!(*errp) &&
 581            ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) {
 582                spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
 583                EXT4_I(inode)->i_allocated_meta_blocks += ar.len;
 584                spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
 585                dquot_alloc_block_nofail(inode,
 586                                EXT4_C2B(EXT4_SB(inode->i_sb), ar.len));
 587        }
 588        return ret;
 589}
 590
 591/**
 592 * ext4_count_free_clusters() -- count filesystem free clusters
 593 * @sb:         superblock
 594 *
 595 * Adds up the number of free clusters from each block group.
 596 */
 597ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)
 598{
 599        ext4_fsblk_t desc_count;
 600        struct ext4_group_desc *gdp;
 601        ext4_group_t i;
 602        ext4_group_t ngroups = ext4_get_groups_count(sb);
 603#ifdef EXT4FS_DEBUG
 604        struct ext4_super_block *es;
 605        ext4_fsblk_t bitmap_count;
 606        unsigned int x;
 607        struct buffer_head *bitmap_bh = NULL;
 608
 609        es = EXT4_SB(sb)->s_es;
 610        desc_count = 0;
 611        bitmap_count = 0;
 612        gdp = NULL;
 613
 614        for (i = 0; i < ngroups; i++) {
 615                gdp = ext4_get_group_desc(sb, i, NULL);
 616                if (!gdp)
 617                        continue;
 618                desc_count += ext4_free_group_clusters(sb, gdp);
 619                brelse(bitmap_bh);
 620                bitmap_bh = ext4_read_block_bitmap(sb, i);
 621                if (bitmap_bh == NULL)
 622                        continue;
 623
 624                x = ext4_count_free(bitmap_bh->b_data,
 625                                    EXT4_BLOCKS_PER_GROUP(sb) / 8);
 626                printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n",
 627                        i, ext4_free_group_clusters(sb, gdp), x);
 628                bitmap_count += x;
 629        }
 630        brelse(bitmap_bh);
 631        printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu"
 632               ", computed = %llu, %llu\n",
 633               EXT4_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)),
 634               desc_count, bitmap_count);
 635        return bitmap_count;
 636#else
 637        desc_count = 0;
 638        for (i = 0; i < ngroups; i++) {
 639                gdp = ext4_get_group_desc(sb, i, NULL);
 640                if (!gdp)
 641                        continue;
 642                desc_count += ext4_free_group_clusters(sb, gdp);
 643        }
 644
 645        return desc_count;
 646#endif
 647}
 648
 649static inline int test_root(ext4_group_t a, int b)
 650{
 651        int num = b;
 652
 653        while (a > num)
 654                num *= b;
 655        return num == a;
 656}
 657
 658static int ext4_group_sparse(ext4_group_t group)
 659{
 660        if (group <= 1)
 661                return 1;
 662        if (!(group & 1))
 663                return 0;
 664        return (test_root(group, 7) || test_root(group, 5) ||
 665                test_root(group, 3));
 666}
 667
 668/**
 669 *      ext4_bg_has_super - number of blocks used by the superblock in group
 670 *      @sb: superblock for filesystem
 671 *      @group: group number to check
 672 *
 673 *      Return the number of blocks used by the superblock (primary or backup)
 674 *      in this group.  Currently this will be only 0 or 1.
 675 */
 676int ext4_bg_has_super(struct super_block *sb, ext4_group_t group)
 677{
 678        if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
 679                                EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
 680                        !ext4_group_sparse(group))
 681                return 0;
 682        return 1;
 683}
 684
 685static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb,
 686                                        ext4_group_t group)
 687{
 688        unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 689        ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb);
 690        ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1;
 691
 692        if (group == first || group == first + 1 || group == last)
 693                return 1;
 694        return 0;
 695}
 696
 697static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb,
 698                                        ext4_group_t group)
 699{
 700        if (!ext4_bg_has_super(sb, group))
 701                return 0;
 702
 703        if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG))
 704                return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 705        else
 706                return EXT4_SB(sb)->s_gdb_count;
 707}
 708
 709/**
 710 *      ext4_bg_num_gdb - number of blocks used by the group table in group
 711 *      @sb: superblock for filesystem
 712 *      @group: group number to check
 713 *
 714 *      Return the number of blocks used by the group descriptor table
 715 *      (primary or backup) in this group.  In the future there may be a
 716 *      different number of descriptor blocks in each group.
 717 */
 718unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group)
 719{
 720        unsigned long first_meta_bg =
 721                        le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg);
 722        unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb);
 723
 724        if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) ||
 725                        metagroup < first_meta_bg)
 726                return ext4_bg_num_gdb_nometa(sb, group);
 727
 728        return ext4_bg_num_gdb_meta(sb,group);
 729
 730}
 731
 732/*
 733 * This function returns the number of file system metadata clusters at
 734 * the beginning of a block group, including the reserved gdt blocks.
 735 */
 736static unsigned ext4_num_base_meta_clusters(struct super_block *sb,
 737                                     ext4_group_t block_group)
 738{
 739        struct ext4_sb_info *sbi = EXT4_SB(sb);
 740        unsigned num;
 741
 742        /* Check for superblock and gdt backups in this group */
 743        num = ext4_bg_has_super(sb, block_group);
 744
 745        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
 746            block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) *
 747                          sbi->s_desc_per_block) {
 748                if (num) {
 749                        num += ext4_bg_num_gdb(sb, block_group);
 750                        num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 751                }
 752        } else { /* For META_BG_BLOCK_GROUPS */
 753                num += ext4_bg_num_gdb(sb, block_group);
 754        }
 755        return EXT4_NUM_B2C(sbi, num);
 756}
 757/**
 758 *      ext4_inode_to_goal_block - return a hint for block allocation
 759 *      @inode: inode for block allocation
 760 *
 761 *      Return the ideal location to start allocating blocks for a
 762 *      newly created inode.
 763 */
 764ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode)
 765{
 766        struct ext4_inode_info *ei = EXT4_I(inode);
 767        ext4_group_t block_group;
 768        ext4_grpblk_t colour;
 769        int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb));
 770        ext4_fsblk_t bg_start;
 771        ext4_fsblk_t last_block;
 772
 773        block_group = ei->i_block_group;
 774        if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) {
 775                /*
 776                 * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME
 777                 * block groups per flexgroup, reserve the first block
 778                 * group for directories and special files.  Regular
 779                 * files will start at the second block group.  This
 780                 * tends to speed up directory access and improves
 781                 * fsck times.
 782                 */
 783                block_group &= ~(flex_size-1);
 784                if (S_ISREG(inode->i_mode))
 785                        block_group++;
 786        }
 787        bg_start = ext4_group_first_block_no(inode->i_sb, block_group);
 788        last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1;
 789
 790        /*
 791         * If we are doing delayed allocation, we don't need take
 792         * colour into account.
 793         */
 794        if (test_opt(inode->i_sb, DELALLOC))
 795                return bg_start;
 796
 797        if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block)
 798                colour = (current->pid % 16) *
 799                        (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16);
 800        else
 801                colour = (current->pid % 16) * ((last_block - bg_start) / 16);
 802        return bg_start + colour;
 803}
 804
 805
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