Ext2文件系统中的数据结构

1、Ext2文件系统的结构：

2、硬盘上面各个数据结构的定义：

2.1 超结块

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 */
__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 */
__u8    s_prealloc_blocks;      /* Nr of blocks to try to preallocate*/
__u8    s_prealloc_dir_blocks;  /* Nr to preallocate for dirs */
__u16   s_padding1;
__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 */
};

2.2 块组

struct ext2_group_desc
{
__le32  bg_block_bitmap;        /* Blocks bitmap block */
__le32  bg_inode_bitmap;        /* Inodes bitmap block */
__le32  bg_inode_table;         /* Inodes table block */
__le16  bg_free_blocks_count;   /* Free blocks count */
__le16  bg_free_inodes_count;   /* Free inodes count */
__le16  bg_used_dirs_count;     /* Directories count */
__le16  bg_pad;
__le32  bg_reserved[3];
};

2.3 inode

struct ext2_inode {
__le16  i_mode;         /* File mode */
__le16  i_uid;          /* Low 16 bits of Owner Uid */
__le32  i_size;         /* Size in bytes */
__le32  i_atime;        /* Access time */
__le32  i_ctime;        /* Creation time */
__le32  i_mtime;        /* Modification time */
__le32  i_dtime;        /* Deletion Time */
__le16  i_gid;          /* Low 16 bits of Group Id */
__le16  i_links_count;  /* Links count */
__le32  i_blocks;       /* Blocks count */
__le32  i_flags;        /* File flags */
union {
struct {
__le32  l_i_reserved1;
} linux1;
struct {
__le32  h_i_translator;
} hurd1;
struct {
__le32  m_i_reserved1;
} masix1;
} osd1;                         /* OS dependent 1 */
__le32  i_block[EXT2_N_BLOCKS];/* Pointers to blocks */
__le32  i_generation;   /* File version (for NFS) */
__le32  i_file_acl;     /* File ACL */
__le32  i_dir_acl;      /* Directory ACL */
__le32  i_faddr;        /* Fragment address */
union {
struct {
__u8    l_i_frag;       /* Fragment number */
__u8    l_i_fsize;      /* Fragment size */
__u16   i_pad1;
__le16  l_i_uid_high;   /* these 2 fields    */
__le16  l_i_gid_high;   /* were reserved2[0] */
__u32   l_i_reserved2;
} linux2;
struct {
__u8    h_i_frag;       /* Fragment number */
__u8    h_i_fsize;      /* Fragment size */
__le16  h_i_mode_high;
__le16  h_i_uid_high;
__le16  h_i_gid_high;
__le32  h_i_author;
} hurd2;
struct {
__u8    m_i_frag;       /* Fragment number */
__u8    m_i_fsize;      /* Fragment size */
__u16   m_pad1;
__u32   m_i_reserved2[2];
} masix2;
} osd2;                         /* OS dependent 2 */
};

2.4 目录

struct ext2_dir_entry_2 {
__le32  inode;                  /* Inode number */
__le16  rec_len;                /* Directory entry length */
__u8    name_len;               /* Name length */
__u8    file_type;
char    name[EXT2_NAME_LEN];    /* File name */
};

3、内存中对应的结构

struct ext2_sb_info {
unsigned long s_frag_size;      /* Size of a fragment in bytes */
unsigned long s_frags_per_block;/* Number of fragments per block */
unsigned long s_inodes_per_block;/* Number of inodes per block */
unsigned long s_frags_per_group;/* Number of fragments in a group */
unsigned long s_blocks_per_group;/* Number of blocks in a group */
unsigned long s_inodes_per_group;/* Number of inodes in a group */
unsigned long s_itb_per_group;  /* Number of inode table blocks per group */
unsigned long s_gdb_count;      /* Number of group descriptor blocks */
unsigned long s_desc_per_block; /* Number of group descriptors per block */
unsigned long s_groups_count;   /* Number of groups in the fs */
unsigned long s_overhead_last;  /* Last calculated overhead */
unsigned long s_blocks_last;    /* Last seen block count */
struct buffer_head * s_sbh;     /* Buffer containing the super block */
struct ext2_super_block * s_es; /* Pointer to the super block in the buffer */
struct buffer_head ** s_group_desc;
unsigned long  s_mount_opt;
unsigned long s_sb_block;
uid_t s_resuid;
gid_t s_resgid;
unsigned short s_mount_state;
unsigned short s_pad;
int s_addr_per_block_bits;
int s_desc_per_block_bits;
int s_inode_size;
int s_first_ino;
spinlock_t s_next_gen_lock;
u32 s_next_generation;
unsigned long s_dir_count;
u8 *s_debts;
struct percpu_counter s_freeblocks_counter;
struct percpu_counter s_freeinodes_counter;
struct percpu_counter s_dirs_counter;
struct blockgroup_lock s_blockgroup_lock;
spinlock_t s_rsv_window_lock;/* root of the per fs reservation window tree */
struct rb_root s_rsv_window_root;
struct ext2_reserve_window_node s_rsv_window_head;
};