/* * linux/fs/ext4/balloc.c * * Copyright (C) 1992, 1993, 1994, 1995 * Remy Card (card@masi.ibp.fr) * Laboratoire MASI - Institut Blaise Pascal * Universite Pierre et Marie Curie (Paris VI) * * Enhanced block allocation by Stephen Tweedie (sct@redhat.com), 1993 * Big-endian to little-endian byte-swapping/bitmaps by * David S. Miller (davem@caip.rutgers.edu), 1995 */ #include <linux/time.h> #include <linux/capability.h> #include <linux/fs.h> #include <linux/jbd2.h> #include <linux/quotaops.h> #include <linux/buffer_head.h> #include "ext4.h" #include "ext4_jbd2.h" #include "mballoc.h" #include <trace/events/ext4.h> static unsigned ext4_num_base_meta_clusters(struct super_block *sb, ext4_group_t block_group); /* * balloc.c contains the blocks allocation and deallocation routines */ /* * Calculate the block group number and offset into the block/cluster * allocation bitmap, given a block number */ void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr, ext4_group_t *blockgrpp, ext4_grpblk_t *offsetp) { struct ext4_super_block *es = EXT4_SB(sb)->s_es; ext4_grpblk_t offset; blocknr = blocknr - le32_to_cpu(es->s_first_data_block); offset = do_div(blocknr, EXT4_BLOCKS_PER_GROUP(sb)) >> EXT4_SB(sb)->s_cluster_bits; if (offsetp) *offsetp = offset; if (blockgrpp) *blockgrpp = blocknr; } static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block, ext4_group_t block_group) { ext4_group_t actual_group; ext4_get_group_no_and_offset(sb, block, &actual_group, NULL); if (actual_group == block_group) return 1; return 0; } /* Return the number of clusters used for file system metadata; this * represents the overhead needed by the file system. */ unsigned ext4_num_overhead_clusters(struct super_block *sb, ext4_group_t block_group, struct ext4_group_desc *gdp) { unsigned num_clusters; int block_cluster = -1, inode_cluster = -1, itbl_cluster = -1, i, c; ext4_fsblk_t start = ext4_group_first_block_no(sb, block_group); ext4_fsblk_t itbl_blk; struct ext4_sb_info *sbi = EXT4_SB(sb); /* This is the number of clusters used by the superblock, * block group descriptors, and reserved block group * descriptor blocks */ num_clusters = ext4_num_base_meta_clusters(sb, block_group); /* * For the allocation bitmaps and inode table, we first need * to check to see if the block is in the block group. If it * is, then check to see if the cluster is already accounted * for in the clusters used for the base metadata cluster, or * if we can increment the base metadata cluster to include * that block. Otherwise, we will have to track the cluster * used for the allocation bitmap or inode table explicitly. * Normally all of these blocks are contiguous, so the special * case handling shouldn't be necessary except for *very* * unusual file system layouts. */ if (ext4_block_in_group(sb, ext4_block_bitmap(sb, gdp), block_group)) { block_cluster = EXT4_B2C(sbi, ext4_block_bitmap(sb, gdp) - start); if (block_cluster < num_clusters) block_cluster = -1; else if (block_cluster == num_clusters) { num_clusters++; block_cluster = -1; } } if (ext4_block_in_group(sb, ext4_inode_bitmap(sb, gdp), block_group)) { inode_cluster = EXT4_B2C(sbi, ext4_inode_bitmap(sb, gdp) - start); if (inode_cluster < num_clusters) inode_cluster = -1; else if (inode_cluster == num_clusters) { num_clusters++; inode_cluster = -1; } } itbl_blk = ext4_inode_table(sb, gdp); for (i = 0; i < sbi->s_itb_per_group; i++) { if (ext4_block_in_group(sb, itbl_blk + i, block_group)) { c = EXT4_B2C(sbi, itbl_blk + i - start); if ((c < num_clusters) || (c == inode_cluster) || (c == block_cluster) || (c == itbl_cluster)) continue; if (c == num_clusters) { num_clusters++; continue; } num_clusters++; itbl_cluster = c; } } if (block_cluster != -1) num_clusters++; if (inode_cluster != -1) num_clusters++; return num_clusters; } static unsigned int num_clusters_in_group(struct super_block *sb, ext4_group_t block_group) { unsigned int blocks; if (block_group == ext4_get_groups_count(sb) - 1) { /* * Even though mke2fs always initializes the first and * last group, just in case some other tool was used, * we need to make sure we calculate the right free * blocks. */ blocks = ext4_blocks_count(EXT4_SB(sb)->s_es) - ext4_group_first_block_no(sb, block_group); } else blocks = EXT4_BLOCKS_PER_GROUP(sb); return EXT4_NUM_B2C(EXT4_SB(sb), blocks); } /* Initializes an uninitialized block bitmap */ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh, ext4_group_t block_group, struct ext4_group_desc *gdp) { unsigned int bit, bit_max; struct ext4_sb_info *sbi = EXT4_SB(sb); ext4_fsblk_t start, tmp; int flex_bg = 0; J_ASSERT_BH(bh, buffer_locked(bh)); /* If checksum is bad mark all blocks used to prevent allocation * essentially implementing a per-group read-only flag. */ if (!ext4_group_desc_csum_verify(sb, block_group, gdp)) { ext4_error(sb, "Checksum bad for group %u", block_group); ext4_free_group_clusters_set(sb, gdp, 0); ext4_free_inodes_set(sb, gdp, 0); ext4_itable_unused_set(sb, gdp, 0); memset(bh->b_data, 0xff, sb->s_blocksize); ext4_block_bitmap_csum_set(sb, block_group, gdp, bh); return; } memset(bh->b_data, 0, sb->s_blocksize); bit_max = ext4_num_base_meta_clusters(sb, block_group); for (bit = 0; bit < bit_max; bit++) ext4_set_bit(bit, bh->b_data); start = ext4_group_first_block_no(sb, block_group); if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) flex_bg = 1; /* Set bits for block and inode bitmaps, and inode table */ tmp = ext4_block_bitmap(sb, gdp); if (!flex_bg || ext4_block_in_group(sb, tmp, block_group)) ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data); tmp = ext4_inode_bitmap(sb, gdp); if (!flex_bg || ext4_block_in_group(sb, tmp, block_group)) ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data); tmp = ext4_inode_table(sb, gdp); for (; tmp < ext4_inode_table(sb, gdp) + sbi->s_itb_per_group; tmp++) { if (!flex_bg || ext4_block_in_group(sb, tmp, block_group)) ext4_set_bit(EXT4_B2C(sbi, tmp - start), bh->b_data); } /* * Also if the number of blocks within the group is less than * the blocksize * 8 ( which is the size of bitmap ), set rest * of the block bitmap to 1 */ ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group), sb->s_blocksize * 8, bh->b_data); ext4_block_bitmap_csum_set(sb, block_group, gdp, bh); ext4_group_desc_csum_set(sb, block_group, gdp); } /* Return the number of free blocks in a block group. It is used when * the block bitmap is uninitialized, so we can't just count the bits * in the bitmap. */ unsigned ext4_free_clusters_after_init(struct super_block *sb, ext4_group_t block_group, struct ext4_group_desc *gdp) { return num_clusters_in_group(sb, block_group) - ext4_num_overhead_clusters(sb, block_group, gdp); } /* * The free blocks are managed by bitmaps. A file system contains several * blocks groups. Each group contains 1 bitmap block for blocks, 1 bitmap * block for inodes, N blocks for the inode table and data blocks. * * The file system contains group descriptors which are located after the * super block. Each descriptor contains the number of the bitmap block and * the free blocks count in the block. The descriptors are loaded in memory * when a file system is mounted (see ext4_fill_super). */ /** * ext4_get_group_desc() -- load group descriptor from disk * @sb: super block * @block_group: given block group * @bh: pointer to the buffer head to store the block * group descriptor */ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb, ext4_group_t block_group, struct buffer_head **bh) { unsigned int group_desc; unsigned int offset; ext4_group_t ngroups = ext4_get_groups_count(sb); struct ext4_group_desc *desc; struct ext4_sb_info *sbi = EXT4_SB(sb); if (block_group >= ngroups) { ext4_error(sb, "block_group >= groups_count - block_group = %u," " groups_count = %u", block_group, ngroups); return NULL; } group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb); offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1); if (!sbi->s_group_desc[group_desc]) { ext4_error(sb, "Group descriptor not loaded - " "block_group = %u, group_desc = %u, desc = %u", block_group, group_desc, offset); return NULL; } desc = (struct ext4_group_desc *)( (__u8 *)sbi->s_group_desc[group_desc]->b_data + offset * EXT4_DESC_SIZE(sb)); if (bh) *bh = sbi->s_group_desc[group_desc]; return desc; } /* * Return the block number which was discovered to be invalid, or 0 if * the block bitmap is valid. */ static ext4_fsblk_t ext4_valid_block_bitmap(struct super_block *sb, struct ext4_group_desc *desc, unsigned int block_group, struct buffer_head *bh) { ext4_grpblk_t offset; ext4_grpblk_t next_zero_bit; ext4_fsblk_t blk; ext4_fsblk_t group_first_block; if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) { /* with FLEX_BG, the inode/block bitmaps and itable * blocks may not be in the group at all * so the bitmap validation will be skipped for those groups * or it has to also read the block group where the bitmaps * are located to verify they are set. */ return 0; } group_first_block = ext4_group_first_block_no(sb, block_group); /* check whether block bitmap block number is set */ blk = ext4_block_bitmap(sb, desc); offset = blk - group_first_block; if (!ext4_test_bit(offset, bh->b_data)) /* bad block bitmap */ return blk; /* check whether the inode bitmap block number is set */ blk = ext4_inode_bitmap(sb, desc); offset = blk - group_first_block; if (!ext4_test_bit(offset, bh->b_data)) /* bad block bitmap */ return blk; /* check whether the inode table block number is set */ blk = ext4_inode_table(sb, desc); offset = blk - group_first_block; next_zero_bit = ext4_find_next_zero_bit(bh->b_data, offset + EXT4_SB(sb)->s_itb_per_group, offset); if (next_zero_bit < offset + EXT4_SB(sb)->s_itb_per_group) /* bad bitmap for inode tables */ return blk; return 0; } void ext4_validate_block_bitmap(struct super_block *sb, struct ext4_group_desc *desc, unsigned int block_group, struct buffer_head *bh) { ext4_fsblk_t blk; if (buffer_verified(bh)) return; ext4_lock_group(sb, block_group); blk = ext4_valid_block_bitmap(sb, desc, block_group, bh); if (unlikely(blk != 0)) { ext4_unlock_group(sb, block_group); ext4_error(sb, "bg %u: block %llu: invalid block bitmap", block_group, blk); return; } if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group, desc, bh))) { ext4_unlock_group(sb, block_group); ext4_error(sb, "bg %u: bad block bitmap checksum", block_group); return; } set_buffer_verified(bh); ext4_unlock_group(sb, block_group); } /** * ext4_read_block_bitmap_nowait() * @sb: super block * @block_group: given block group * * Read the bitmap for a given block_group,and validate the * bits for block/inode/inode tables are set in the bitmaps * * Return buffer_head on success or NULL in case of failure. */ struct buffer_head * ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group) { struct ext4_group_desc *desc; struct buffer_head *bh; ext4_fsblk_t bitmap_blk; desc = ext4_get_group_desc(sb, block_group, NULL); if (!desc) return NULL; bitmap_blk = ext4_block_bitmap(sb, desc); bh = sb_getblk(sb, bitmap_blk); if (unlikely(!bh)) { ext4_error(sb, "Cannot get buffer for block bitmap - " "block_group = %u, block_bitmap = %llu", block_group, bitmap_blk); return NULL; } if (bitmap_uptodate(bh)) goto verify; lock_buffer(bh); if (bitmap_uptodate(bh)) { unlock_buffer(bh); goto verify; } ext4_lock_group(sb, block_group); if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { ext4_init_block_bitmap(sb, bh, block_group, desc); set_bitmap_uptodate(bh); set_buffer_uptodate(bh); ext4_unlock_group(sb, block_group); unlock_buffer(bh); return bh; } ext4_unlock_group(sb, block_group); if (buffer_uptodate(bh)) { /* * if not uninit if bh is uptodate, * bitmap is also uptodate */ set_bitmap_uptodate(bh); unlock_buffer(bh); goto verify; } /* * submit the buffer_head for reading */ set_buffer_new(bh); trace_ext4_read_block_bitmap_load(sb, block_group); bh->b_end_io = ext4_end_bitmap_read; get_bh(bh); submit_bh(READ, bh); return bh; verify: ext4_validate_block_bitmap(sb, desc, block_group, bh); return bh; } /* Returns 0 on success, 1 on error */ int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group, struct buffer_head *bh) { struct ext4_group_desc *desc; if (!buffer_new(bh)) return 0; desc = ext4_get_group_desc(sb, block_group, NULL); if (!desc) return 1; wait_on_buffer(bh); if (!buffer_uptodate(bh)) { ext4_error(sb, "Cannot read block bitmap - " "block_group = %u, block_bitmap = %llu", block_group, (unsigned long long) bh->b_blocknr); return 1; } clear_buffer_new(bh); /* Panic or remount fs read-only if block bitmap is invalid */ ext4_validate_block_bitmap(sb, desc, block_group, bh); return 0; } struct buffer_head * ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group) { struct buffer_head *bh; bh = ext4_read_block_bitmap_nowait(sb, block_group); if (!bh) return NULL; if (ext4_wait_block_bitmap(sb, block_group, bh)) { put_bh(bh); return NULL; } return bh; } /** * ext4_has_free_clusters() * @sbi: in-core super block structure. * @nclusters: number of needed blocks * @flags: flags from ext4_mb_new_blocks() * * Check if filesystem has nclusters free & available for allocation. * On success return 1, return 0 on failure. */ static int ext4_has_free_clusters(struct ext4_sb_info *sbi, s64 nclusters, unsigned int flags) { s64 free_clusters, dirty_clusters, root_clusters; struct percpu_counter *fcc = &sbi->s_freeclusters_counter; struct percpu_counter *dcc = &sbi->s_dirtyclusters_counter; free_clusters = percpu_counter_read_positive(fcc); dirty_clusters = percpu_counter_read_positive(dcc); /* * r_blocks_count should always be multiple of the cluster ratio so * we are safe to do a plane bit shift only. */ root_clusters = ext4_r_blocks_count(sbi->s_es) >> sbi->s_cluster_bits; if (free_clusters - (nclusters + root_clusters + dirty_clusters) < EXT4_FREECLUSTERS_WATERMARK) { free_clusters = percpu_counter_sum_positive(fcc); dirty_clusters = percpu_counter_sum_positive(dcc); } /* Check whether we have space after accounting for current * dirty clusters & root reserved clusters. */ if (free_clusters >= ((root_clusters + nclusters) + dirty_clusters)) return 1; /* Hm, nope. Are (enough) root reserved clusters available? */ if (uid_eq(sbi->s_resuid, current_fsuid()) || (!gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) && in_group_p(sbi->s_resgid)) || capable(CAP_SYS_RESOURCE) || (flags & EXT4_MB_USE_ROOT_BLOCKS)) { if (free_clusters >= (nclusters + dirty_clusters)) return 1; } return 0; } int ext4_claim_free_clusters(struct ext4_sb_info *sbi, s64 nclusters, unsigned int flags) { if (ext4_has_free_clusters(sbi, nclusters, flags)) { percpu_counter_add(&sbi->s_dirtyclusters_counter, nclusters); return 0; } else return -ENOSPC; } /** * ext4_should_retry_alloc() * @sb: super block * @retries number of attemps has been made * * ext4_should_retry_alloc() is called when ENOSPC is returned, and if * it is profitable to retry the operation, this function will wait * for the current or committing transaction to complete, and then * return TRUE. * * if the total number of retries exceed three times, return FALSE. */ int ext4_should_retry_alloc(struct super_block *sb, int *retries) { if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) || (*retries)++ > 3 || !EXT4_SB(sb)->s_journal) return 0; jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id); return jbd2_journal_force_commit_nested(EXT4_SB(sb)->s_journal); } /* * ext4_new_meta_blocks() -- allocate block for meta data (indexing) blocks * * @handle: handle to this transaction * @inode: file inode * @goal: given target block(filesystem wide) * @count: pointer to total number of clusters needed * @errp: error code * * Return 1st allocated block number on success, *count stores total account * error stores in errp pointer */ ext4_fsblk_t ext4_new_meta_blocks(handle_t *handle, struct inode *inode, ext4_fsblk_t goal, unsigned int flags, unsigned long *count, int *errp) { struct ext4_allocation_request ar; ext4_fsblk_t ret; memset(&ar, 0, sizeof(ar)); /* Fill with neighbour allocated blocks */ ar.inode = inode; ar.goal = goal; ar.len = count ? *count : 1; ar.flags = flags; ret = ext4_mb_new_blocks(handle, &ar, errp); if (count) *count = ar.len; /* * Account for the allocated meta blocks. We will never * fail EDQUOT for metdata, but we do account for it. */ if (!(*errp) && ext4_test_inode_state(inode, EXT4_STATE_DELALLOC_RESERVED)) { spin_lock(&EXT4_I(inode)->i_block_reservation_lock); EXT4_I(inode)->i_allocated_meta_blocks += ar.len; spin_unlock(&EXT4_I(inode)->i_block_reservation_lock); dquot_alloc_block_nofail(inode, EXT4_C2B(EXT4_SB(inode->i_sb), ar.len)); } return ret; } /** * ext4_count_free_clusters() -- count filesystem free clusters * @sb: superblock * * Adds up the number of free clusters from each block group. */ ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb) { ext4_fsblk_t desc_count; struct ext4_group_desc *gdp; ext4_group_t i; ext4_group_t ngroups = ext4_get_groups_count(sb); #ifdef EXT4FS_DEBUG struct ext4_super_block *es; ext4_fsblk_t bitmap_count; unsigned int x; struct buffer_head *bitmap_bh = NULL; es = EXT4_SB(sb)->s_es; desc_count = 0; bitmap_count = 0; gdp = NULL; for (i = 0; i < ngroups; i++) { gdp = ext4_get_group_desc(sb, i, NULL); if (!gdp) continue; desc_count += ext4_free_group_clusters(sb, gdp); brelse(bitmap_bh); bitmap_bh = ext4_read_block_bitmap(sb, i); if (bitmap_bh == NULL) continue; x = ext4_count_free(bitmap_bh->b_data, EXT4_BLOCKS_PER_GROUP(sb) / 8); printk(KERN_DEBUG "group %u: stored = %d, counted = %u\n", i, ext4_free_group_clusters(sb, gdp), x); bitmap_count += x; } brelse(bitmap_bh); printk(KERN_DEBUG "ext4_count_free_clusters: stored = %llu" ", computed = %llu, %llu\n", EXT4_NUM_B2C(EXT4_SB(sb), ext4_free_blocks_count(es)), desc_count, bitmap_count); return bitmap_count; #else desc_count = 0; for (i = 0; i < ngroups; i++) { gdp = ext4_get_group_desc(sb, i, NULL); if (!gdp) continue; desc_count += ext4_free_group_clusters(sb, gdp); } return desc_count; #endif } static inline int test_root(ext4_group_t a, int b) { int num = b; while (a > num) num *= b; return num == a; } static int ext4_group_sparse(ext4_group_t group) { if (group <= 1) return 1; if (!(group & 1)) return 0; return (test_root(group, 7) || test_root(group, 5) || test_root(group, 3)); } /** * ext4_bg_has_super - number of blocks used by the superblock in group * @sb: superblock for filesystem * @group: group number to check * * Return the number of blocks used by the superblock (primary or backup) * in this group. Currently this will be only 0 or 1. */ int ext4_bg_has_super(struct super_block *sb, ext4_group_t group) { if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER) && !ext4_group_sparse(group)) return 0; return 1; } static unsigned long ext4_bg_num_gdb_meta(struct super_block *sb, ext4_group_t group) { unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb); ext4_group_t first = metagroup * EXT4_DESC_PER_BLOCK(sb); ext4_group_t last = first + EXT4_DESC_PER_BLOCK(sb) - 1; if (group == first || group == first + 1 || group == last) return 1; return 0; } static unsigned long ext4_bg_num_gdb_nometa(struct super_block *sb, ext4_group_t group) { if (!ext4_bg_has_super(sb, group)) return 0; if (EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG)) return le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg); else return EXT4_SB(sb)->s_gdb_count; } /** * ext4_bg_num_gdb - number of blocks used by the group table in group * @sb: superblock for filesystem * @group: group number to check * * Return the number of blocks used by the group descriptor table * (primary or backup) in this group. In the future there may be a * different number of descriptor blocks in each group. */ unsigned long ext4_bg_num_gdb(struct super_block *sb, ext4_group_t group) { unsigned long first_meta_bg = le32_to_cpu(EXT4_SB(sb)->s_es->s_first_meta_bg); unsigned long metagroup = group / EXT4_DESC_PER_BLOCK(sb); if (!EXT4_HAS_INCOMPAT_FEATURE(sb,EXT4_FEATURE_INCOMPAT_META_BG) || metagroup < first_meta_bg) return ext4_bg_num_gdb_nometa(sb, group); return ext4_bg_num_gdb_meta(sb,group); } /* * This function returns the number of file system metadata clusters at * the beginning of a block group, including the reserved gdt blocks. */ static unsigned ext4_num_base_meta_clusters(struct super_block *sb, ext4_group_t block_group) { struct ext4_sb_info *sbi = EXT4_SB(sb); unsigned num; /* Check for superblock and gdt backups in this group */ num = ext4_bg_has_super(sb, block_group); if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) || block_group < le32_to_cpu(sbi->s_es->s_first_meta_bg) * sbi->s_desc_per_block) { if (num) { num += ext4_bg_num_gdb(sb, block_group); num += le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks); } } else { /* For META_BG_BLOCK_GROUPS */ num += ext4_bg_num_gdb(sb, block_group); } return EXT4_NUM_B2C(sbi, num); } /** * ext4_inode_to_goal_block - return a hint for block allocation * @inode: inode for block allocation * * Return the ideal location to start allocating blocks for a * newly created inode. */ ext4_fsblk_t ext4_inode_to_goal_block(struct inode *inode) { struct ext4_inode_info *ei = EXT4_I(inode); ext4_group_t block_group; ext4_grpblk_t colour; int flex_size = ext4_flex_bg_size(EXT4_SB(inode->i_sb)); ext4_fsblk_t bg_start; ext4_fsblk_t last_block; block_group = ei->i_block_group; if (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) { /* * If there are at least EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME * block groups per flexgroup, reserve the first block * group for directories and special files. Regular * files will start at the second block group. This * tends to speed up directory access and improves * fsck times. */ block_group &= ~(flex_size-1); if (S_ISREG(inode->i_mode)) block_group++; } bg_start = ext4_group_first_block_no(inode->i_sb, block_group); last_block = ext4_blocks_count(EXT4_SB(inode->i_sb)->s_es) - 1; /* * If we are doing delayed allocation, we don't need take * colour into account. */ if (test_opt(inode->i_sb, DELALLOC)) return bg_start; if (bg_start + EXT4_BLOCKS_PER_GROUP(inode->i_sb) <= last_block) colour = (current->pid % 16) * (EXT4_BLOCKS_PER_GROUP(inode->i_sb) / 16); else colour = (current->pid % 16) * ((last_block - bg_start) / 16); return bg_start + colour; }