EXT4_MIN_BLOCK_SIZE
# define EXT4_BLOCK_SIZE(s) (EXT4_MIN_BLOCK_SIZE << (s)->s_log_block_size)
#define EXT4_MAX_DESC_SIZE EXT4_MIN_BLOCK_SIZE
sb_block = 1 * EXT4_MIN_BLOCK_SIZE;
blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
if (blocksize != EXT4_MIN_BLOCK_SIZE) {
logical_sb_block = sbi->s_sb_block * EXT4_MIN_BLOCK_SIZE;
blocksize = EXT4_MIN_BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
logical_sb_block = sbi->s_sb_block * EXT4_MIN_BLOCK_SIZE;
sb_block = EXT4_MIN_BLOCK_SIZE / blocksize;
offset = EXT4_MIN_BLOCK_SIZE % blocksize;