#define EXT4_GOOD_OLD_INODE_SIZE 128

...

#define EXT4_GOOD_OLD_REV    0    /* The good old (original) format */

...

/* s 一般是 super_block */

#define EXT4_INODE_SIZE(s)    (((s)->s_rev_level == EXT4_GOOD_OLD_REV) ? \

EXT4_GOOD_OLD_INODE_SIZE : \

(s)->s_inode_size) 

/*s_inode_size ：

sbi 是 ext4_sb_info ， sb=superblock

*/ 

if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {

　　sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;

　　sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;

} else {

　　sbi->s_inode_size = le16_to_cpu(es->s_inode_size);

　　sbi->s_first_ino = le32_to_cpu(es->s_first_ino);

...