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; }
/** * 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; }
/** * 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); }