磁盘的超级块的结构体是啥

磁盘的超级块是一个重要的数据结构，它记录了文件系统的基本信息，包括文件系统的大小、块大小、inode 数量、块数量等信息。在 ext2、ext3、ext4 等文件系统中，超级块的结构体定义如下：

struct ext2_super_block {
    __le32 s_inodes_count;          /* Inodes count */
    __le32 s_blocks_count;          /* Blocks count */
    __le32 s_r_blocks_count;        /* Reserved blocks count */
    __le32 s_free_blocks_count;     /* Free blocks count */
    __le32 s_free_inodes_count;     /* Free inodes count */
    __le32 s_first_data_block;      /* First Data Block */
    __le32 s_log_block_size;        /* Block size */
    __le32 s_log_frag_size;         /* Fragment size */
    __le32 s_blocks_per_group;      /* # Blocks per group */
    __le32 s_frags_per_group;       /* # Fragments per group */
    __le32 s_inodes_per_group;      /* # Inodes per group */
    __le32 s_mtime;                 /* Mount time */
    __le32 s_wtime;                 /* Write time */
    __le16 s_mnt_count;             /* Mount count */
    __le16 s_max_mnt_count;         /* Maximal mount count */
    __le16 s_magic;                 /* Magic signature */
    __le16 s_state;                 /* File system state */
    __le16 s_errors;                /* Behaviour when detecting errors */
    __le16 s_minor_rev_level;       /* minor revision level */
    __le32 s_lastcheck;             /* time of last check */
    __le32 s_checkinterval;         /* max. time between checks */
    __le32 s_creator_os;            /* OS */
    __le32 s_rev_level;             /* Revision level */
    __le16 s_def_resuid;            /* Default uid for reserved blocks */
    __le16 s_def_resgid;            /* Default gid for reserved blocks */
    /*
     * These fields are for EXT2_DYNAMIC_REV superblocks only.
     *
     * Note: the difference between the compatible feature set and
     * the incompatible feature set is that if there is a bit set
     * in the incompatible feature set that the kernel doesn't
     * know about, it should refuse to mount the filesystem.
     *
     * e2fsck's requirements are more strict; if it doesn't know
     * about a feature in either the compatible or incompatible
     * feature set, it must abort and not try to meddle with
     * things it doesn't understand...
     */
    __le32 s_first_ino;             /* First non-reserved inode */
    __le16 s_inode_size;            /* size of inode structure */
    __le16 s_block_group_nr;        /* block group # of this superblock */
    __le32 s_feature_compat;        /* compatible feature set */
    __le32 s_feature_incompat;      /* incompatible feature set */
    __le32 s_feature_ro_compat;     /* readonly-compatible feature set */
    __u8   s_uuid[16];              /* 128-bit uuid for volume */
    char   s_volume_name[16];       /* volume name */
    char   s_last_mounted[64];      /* directory where last mounted */
    __le32 s_algorithm_usage_bitmap; /* For compression */
    /*
     * Performance hints.  Directory preallocation should only
     * happen if the EXT2_COMPAT_PREALLOC flag is on.
     */
    __u8   s_prealloc_blocks;       /* Nr of blocks to try to preallocate*/
    __u8   s_prealloc_dir_blocks;   /* Nr to preallocate for dirs */
    __u16  s_padding1;
    /*
     * Journaling support valid if EXT3_FEATURE_COMPAT_HAS_JOURNAL set.
     */
    __u8    s_journal_uuid[16];      /* uuid of journal superblock */
    __u32   s_journal_inum;          /* inode number of journal file */
    __u32   s_journal_dev;           /* device number of journal file */
    __u32   s_last_orphan;           /* start of list of inodes to delete */
    __u32   s_hash_seed[4];          /* HTREE hash seed */
    __u8    s_def_hash_version;      /* Default hash version to use */
    __u8    s_reserved_char_pad;
    __u16   s_reserved_word_pad;
    __le32  s_default_mount_opts;
    __le32  s_first_meta_bg;         /* First metablock block group */
    __u32   s_reserved[190];         /* Padding to the end of the block */
};