ladybird/Kernel/FileSystem/ext2_fs.h

/*
 *  linux/include/linux/ext2_fs.h
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/include/linux/minix_fs.h
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#ifndef _LINUX_EXT2_FS_H
#define _LINUX_EXT2_FS_H

#include "ext2_types.h" /* Changed from linux/types.h */

/*
 * The second extended filesystem constants/structures
 */

/*
 * Define EXT2_PREALLOCATE to preallocate data blocks for expanding files
 */
#define EXT2_PREALLOCATE
#define EXT2_DEFAULT_PREALLOC_BLOCKS 8

/*
 * The second extended file system version
 */
#define EXT2FS_DATE "95/08/09"
#define EXT2FS_VERSION "0.5b"

/*
 * Special inode numbers
 */
#define EXT2_BAD_INO 1         /* Bad blocks inode */
#define EXT2_ROOT_INO 2        /* Root inode */
#define EXT2_ACL_IDX_INO 3     /* ACL inode */
#define EXT2_ACL_DATA_INO 4    /* ACL inode */
#define EXT2_BOOT_LOADER_INO 5 /* Boot loader inode */
#define EXT2_UNDEL_DIR_INO 6   /* Undelete directory inode */
#define EXT2_RESIZE_INO 7      /* Reserved group descriptors inode */
#define EXT2_JOURNAL_INO 8     /* Journal inode */

/* First non-reserved inode for old ext2 filesystems */
#define EXT2_GOOD_OLD_FIRST_INO 11

/*
 * The second extended file system magic number
 */
#define EXT2_SUPER_MAGIC 0xEF53

#ifdef __KERNEL__
#    define EXT2_SB(sb) (&((sb)->u.ext2_sb))
#else
/* Assume that user mode programs are passing in an ext2fs superblock, not
 * a kernel struct super_block.  This will allow us to call the feature-test
 * macros from user land. */
#    define EXT2_SB(sb) (sb)
#endif

/*
 * Maximal count of links to a file
 */
#define EXT2_LINK_MAX 65000

/*
 * Macro-instructions used to manage several block sizes
 */
#define EXT2_MIN_BLOCK_LOG_SIZE 10 /* 1024 */
#define EXT2_MAX_BLOCK_LOG_SIZE 16 /* 65536 */
#define EXT2_MIN_BLOCK_SIZE (1 << EXT2_MIN_BLOCK_LOG_SIZE)
#define EXT2_MAX_BLOCK_SIZE (1 << EXT2_MAX_BLOCK_LOG_SIZE)
#ifdef __KERNEL__
#    define EXT2_BLOCK_SIZE(s) ((s)->s_blocksize)
#    define EXT2_BLOCK_SIZE_BITS(s) ((s)->s_blocksize_bits)
#    define EXT2_ADDR_PER_BLOCK_BITS(s) (EXT2_SB(s)->addr_per_block_bits)
#    define EXT2_INODE_SIZE(s) (EXT2_SB(s)->s_inode_size)
#    define EXT2_FIRST_INO(s) (EXT2_SB(s)->s_first_ino)
#else
#    define EXT2_BLOCK_SIZE(s) (EXT2_MIN_BLOCK_SIZE << (s)->s_log_block_size)
#    define EXT2_BLOCK_SIZE_BITS(s) ((s)->s_log_block_size + 10)
#    define EXT2_INODE_SIZE(s) (((s)->s_rev_level == EXT2_GOOD_OLD_REV) ? EXT2_GOOD_OLD_INODE_SIZE : (s)->s_inode_size)
#    define EXT2_FIRST_INO(s) (((s)->s_rev_level == EXT2_GOOD_OLD_REV) ? EXT2_GOOD_OLD_FIRST_INO : (s)->s_first_ino)
#endif
#define EXT2_ADDR_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s) / sizeof(__u32))

/*
 * Macro-instructions used to manage fragments
 */
#define EXT2_MIN_FRAG_SIZE EXT2_MIN_BLOCK_SIZE
#define EXT2_MAX_FRAG_SIZE EXT2_MAX_BLOCK_SIZE
#define EXT2_MIN_FRAG_LOG_SIZE EXT2_MIN_BLOCK_LOG_SIZE
#ifdef __KERNEL__
#    define EXT2_FRAG_SIZE(s) (EXT2_SB(s)->s_frag_size)
#    define EXT2_FRAGS_PER_BLOCK(s) (EXT2_SB(s)->s_frags_per_block)
#else
#    define EXT2_FRAG_SIZE(s) (EXT2_MIN_FRAG_SIZE << (s)->s_log_frag_size)
#    define EXT2_FRAGS_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s) / EXT2_FRAG_SIZE(s))
#endif

/*
 * ACL structures
 */
struct ext2_acl_header /* Header of Access Control Lists */
{
    __u32 aclh_size;
    __u32 aclh_file_count;
    __u32 aclh_acle_count;
    __u32 aclh_first_acle;
};

struct ext2_acl_entry /* Access Control List Entry */
{
    __u32 acle_size;
    __u16 acle_perms; /* Access permissions */
    __u16 acle_type;  /* Type of entry */
    __u16 acle_tag;   /* User or group identity */
    __u16 acle_pad1;
    __u32 acle_next; /* Pointer on next entry for the */
                     /* same inode or on next free entry */
};

/*
 * Structure of a blocks group descriptor
 */
struct ext2_group_desc {
    __u32 bg_block_bitmap;      /* Blocks bitmap block */
    __u32 bg_inode_bitmap;      /* Inodes bitmap block */
    __u32 bg_inode_table;       /* Inodes table block */
    __u16 bg_free_blocks_count; /* Free blocks count */
    __u16 bg_free_inodes_count; /* Free inodes count */
    __u16 bg_used_dirs_count;   /* Directories count */
    __u16 bg_flags;
    __u32 bg_reserved[2];
    __u16 bg_itable_unused; /* Unused inodes count */
    __u16 bg_checksum;      /* crc16(s_uuid+grouo_num+group_desc)*/
};

struct ext4_group_desc {
    __u32 bg_block_bitmap;      /* Blocks bitmap block */
    __u32 bg_inode_bitmap;      /* Inodes bitmap block */
    __u32 bg_inode_table;       /* Inodes table block */
    __u16 bg_free_blocks_count; /* Free blocks count */
    __u16 bg_free_inodes_count; /* Free inodes count */
    __u16 bg_used_dirs_count;   /* Directories count */
    __u16 bg_flags;
    __u32 bg_reserved[2];
    __u16 bg_itable_unused;        /* Unused inodes count */
    __u16 bg_checksum;             /* crc16(s_uuid+grouo_num+group_desc)*/
    __u32 bg_block_bitmap_hi;      /* Blocks bitmap block MSB */
    __u32 bg_inode_bitmap_hi;      /* Inodes bitmap block MSB */
    __u32 bg_inode_table_hi;       /* Inodes table block MSB */
    __u16 bg_free_blocks_count_hi; /* Free blocks count MSB */
    __u16 bg_free_inodes_count_hi; /* Free inodes count MSB */
    __u16 bg_used_dirs_count_hi;   /* Directories count MSB */
    __u16 bg_pad;
    __u32 bg_reserved2[3];
};

#define EXT2_BG_INODE_UNINIT 0x0001 /* Inode table/bitmap not initialized */
#define EXT2_BG_BLOCK_UNINIT 0x0002 /* Block bitmap not initialized */
#define EXT2_BG_INODE_ZEROED 0x0004 /* On-disk itable initialized to zero */

/*
 * Data structures used by the directory indexing feature
 *
 * Note: all of the multibyte integer fields are little endian.
 */

/*
 * Note: dx_root_info is laid out so that if it should somehow get
 * overlaid by a dirent the two low bits of the hash version will be
 * zero.  Therefore, the hash version mod 4 should never be 0.
 * Sincerely, the paranoia department.
 */
struct ext2_dx_root_info {
    __u32 reserved_zero;
    __u8 hash_version; /* 0 now, 1 at release */
    __u8 info_length;  /* 8 */
    __u8 indirect_levels;
    __u8 unused_flags;
};

#define EXT2_HASH_LEGACY 0
#define EXT2_HASH_HALF_MD4 1
#define EXT2_HASH_TEA 2
#define EXT2_HASH_LEGACY_UNSIGNED 3   /* reserved for userspace lib */
#define EXT2_HASH_HALF_MD4_UNSIGNED 4 /* reserved for userspace lib */
#define EXT2_HASH_TEA_UNSIGNED 5      /* reserved for userspace lib */

#define EXT2_HASH_FLAG_INCOMPAT 0x1

struct ext2_dx_entry {
    __u32 hash;
    __u32 block;
};

struct ext2_dx_countlimit {
    __u16 limit;
    __u16 count;
};

/*
 * Macro-instructions used to manage group descriptors
 */
#define EXT2_MIN_DESC_SIZE 32
#define EXT2_MIN_DESC_SIZE_64BIT 64
#define EXT2_MAX_DESC_SIZE EXT2_MIN_BLOCK_SIZE
#define EXT2_DESC_SIZE(s) \
    ((EXT2_SB(s)->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) ? (s)->s_desc_size : EXT2_MIN_DESC_SIZE)

#define EXT2_BLOCKS_PER_GROUP(s) (EXT2_SB(s)->s_blocks_per_group)
#define EXT2_INODES_PER_GROUP(s) (EXT2_SB(s)->s_inodes_per_group)
#define EXT2_INODES_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s) / EXT2_INODE_SIZE(s))
/* limits imposed by 16-bit value gd_free_{blocks,inode}_count */
#define EXT2_MAX_BLOCKS_PER_GROUP(s) ((1 << 16) - 8)
#define EXT2_MAX_INODES_PER_GROUP(s) ((1 << 16) - EXT2_INODES_PER_BLOCK(s))
#ifdef __KERNEL__
#    define EXT2_DESC_PER_BLOCK(s) (EXT2_SB(s)->s_desc_per_block)
#    define EXT2_DESC_PER_BLOCK_BITS(s) (EXT2_SB(s)->s_desc_per_block_bits)
#else
#    define EXT2_DESC_PER_BLOCK(s) (EXT2_BLOCK_SIZE(s) / EXT2_DESC_SIZE(s))
#endif

/*
 * Constants relative to the data blocks
 */
#define EXT2_NDIR_BLOCKS 12
#define EXT2_IND_BLOCK EXT2_NDIR_BLOCKS
#define EXT2_DIND_BLOCK (EXT2_IND_BLOCK + 1)
#define EXT2_TIND_BLOCK (EXT2_DIND_BLOCK + 1)
#define EXT2_N_BLOCKS (EXT2_TIND_BLOCK + 1)

/*
 * Inode flags
 */
#define EXT2_SECRM_FL 0x00000001     /* Secure deletion */
#define EXT2_UNRM_FL 0x00000002      /* Undelete */
#define EXT2_COMPR_FL 0x00000004     /* Compress file */
#define EXT2_SYNC_FL 0x00000008      /* Synchronous updates */
#define EXT2_IMMUTABLE_FL 0x00000010 /* Immutable file */
#define EXT2_APPEND_FL 0x00000020    /* writes to file may only append */
#define EXT2_NODUMP_FL 0x00000040    /* do not dump file */
#define EXT2_NOATIME_FL 0x00000080   /* do not update atime */
/* Reserved for compression usage... */
#define EXT2_DIRTY_FL 0x00000100
#define EXT2_COMPRBLK_FL 0x00000200 /* One or more compressed clusters */
#define EXT2_NOCOMPR_FL 0x00000400  /* Access raw compressed data */
#define EXT2_ECOMPR_FL 0x00000800   /* Compression error */
/* End compression flags --- maybe not all used */
#define EXT2_BTREE_FL 0x00001000 /* btree format dir */
#define EXT2_INDEX_FL 0x00001000 /* hash-indexed directory */
#define EXT2_IMAGIC_FL 0x00002000
#define EXT3_JOURNAL_DATA_FL 0x00004000 /* file data should be journaled */
#define EXT2_NOTAIL_FL 0x00008000       /* file tail should not be merged */
#define EXT2_DIRSYNC_FL 0x00010000      /* Synchronous directory modifications */
#define EXT2_TOPDIR_FL 0x00020000       /* Top of directory hierarchies*/
#define EXT4_HUGE_FILE_FL 0x00040000    /* Set to each huge file */
#define EXT4_EXTENTS_FL 0x00080000      /* Inode uses extents */
#define EXT2_RESERVED_FL 0x80000000     /* reserved for ext2 lib */

#define EXT2_FL_USER_VISIBLE 0x000BDFFF    /* User visible flags */
#define EXT2_FL_USER_MODIFIABLE 0x000080FF /* User modifiable flags */

/*
 * ioctl commands
 */

/* Used for online resize */
struct ext2_new_group_input {
    __u32 group;           /* Group number for this data */
    __u32 block_bitmap;    /* Absolute block number of block bitmap */
    __u32 inode_bitmap;    /* Absolute block number of inode bitmap */
    __u32 inode_table;     /* Absolute block number of inode table start */
    __u32 blocks_count;    /* Total number of blocks in this group */
    __u16 reserved_blocks; /* Number of reserved blocks in this group */
    __u16 unused;          /* Number of reserved GDT blocks in group */
};

struct ext4_new_group_input {
    __u32 group;           /* Group number for this data */
    __u64 block_bitmap;    /* Absolute block number of block bitmap */
    __u64 inode_bitmap;    /* Absolute block number of inode bitmap */
    __u64 inode_table;     /* Absolute block number of inode table start */
    __u32 blocks_count;    /* Total number of blocks in this group */
    __u16 reserved_blocks; /* Number of reserved blocks in this group */
    __u16 unused;
};

#ifdef __GNU__ /* Needed for the Hurd */
#    define _IOT_ext2_new_group_input _IOT(_IOTS(__u32), 5, _IOTS(__u16), 2, 0, 0)
#endif

#define EXT2_IOC_GETFLAGS _IOR('f', 1, long)
#define EXT2_IOC_SETFLAGS _IOW('f', 2, long)
#define EXT2_IOC_GETVERSION _IOR('v', 1, long)
#define EXT2_IOC_SETVERSION _IOW('v', 2, long)
#define EXT2_IOC_GETVERSION_NEW _IOR('f', 3, long)
#define EXT2_IOC_SETVERSION_NEW _IOW('f', 4, long)
#define EXT2_IOC_GROUP_EXTEND _IOW('f', 7, unsigned long)
#define EXT2_IOC_GROUP_ADD _IOW('f', 8, struct ext2_new_group_input)
#define EXT4_IOC_GROUP_ADD _IOW('f', 8, struct ext4_new_group_input)

/*
 * Structure of an inode on the disk
 */
struct ext2_inode {
    __u16 i_mode;        /* File mode */
    __u16 i_uid;         /* Low 16 bits of Owner Uid */
    __u32 i_size;        /* Size in bytes */
    __u32 i_atime;       /* Access time */
    __u32 i_ctime;       /* Inode change time */
    __u32 i_mtime;       /* Modification time */
    __u32 i_dtime;       /* Deletion Time */
    __u16 i_gid;         /* Low 16 bits of Group Id */
    __u16 i_links_count; /* Links count */
    __u32 i_blocks;      /* Blocks count */
    __u32 i_flags;       /* File flags */
    union {
        struct {
            __u32 l_i_version; /* was l_i_reserved1 */
        } linux1;
        struct {
            __u32 h_i_translator;
        } hurd1;
    } osd1;                       /* OS dependent 1 */
    __u32 i_block[EXT2_N_BLOCKS]; /* Pointers to blocks */
    __u32 i_generation;           /* File version (for NFS) */
    __u32 i_file_acl;             /* File ACL */
    __u32 i_dir_acl;              /* Directory ACL */
    __u32 i_faddr;                /* Fragment address */
    union {
        struct {
            __u16 l_i_blocks_hi;
            __u16 l_i_file_acl_high;
            __u16 l_i_uid_high; /* these 2 fields    */
            __u16 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 */
            __u16 h_i_mode_high;
            __u16 h_i_uid_high;
            __u16 h_i_gid_high;
            __u32 h_i_author;
        } hurd2;
    } osd2; /* OS dependent 2 */
};

/*
 * Permanent part of an large inode on the disk
 */
struct ext2_inode_large {
    __u16 i_mode;        /* File mode */
    __u16 i_uid;         /* Low 16 bits of Owner Uid */
    __u32 i_size;        /* Size in bytes */
    __u32 i_atime;       /* Access time */
    __u32 i_ctime;       /* Inode Change time */
    __u32 i_mtime;       /* Modification time */
    __u32 i_dtime;       /* Deletion Time */
    __u16 i_gid;         /* Low 16 bits of Group Id */
    __u16 i_links_count; /* Links count */
    __u32 i_blocks;      /* Blocks count */
    __u32 i_flags;       /* File flags */
    union {
        struct {
            __u32 l_i_version; /* was l_i_reserved1 */
        } linux1;
        struct {
            __u32 h_i_translator;
        } hurd1;
    } osd1;                       /* OS dependent 1 */
    __u32 i_block[EXT2_N_BLOCKS]; /* Pointers to blocks */
    __u32 i_generation;           /* File version (for NFS) */
    __u32 i_file_acl;             /* File ACL */
    __u32 i_dir_acl;              /* Directory ACL */
    __u32 i_faddr;                /* Fragment address */
    union {
        struct {
            __u16 l_i_blocks_hi;
            __u16 l_i_file_acl_high;
            __u16 l_i_uid_high; /* these 2 fields    */
            __u16 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 */
            __u16 h_i_mode_high;
            __u16 h_i_uid_high;
            __u16 h_i_gid_high;
            __u32 h_i_author;
        } hurd2;
    } osd2; /* OS dependent 2 */
    __u16 i_extra_isize;
    __u16 i_pad1;
    __u32 i_ctime_extra;  /* extra Change time (nsec << 2 | epoch) */
    __u32 i_mtime_extra;  /* extra Modification time (nsec << 2 | epoch) */
    __u32 i_atime_extra;  /* extra Access time (nsec << 2 | epoch) */
    __u32 i_crtime;       /* File creation time */
    __u32 i_crtime_extra; /* extra File creation time (nsec << 2 | epoch)*/
    __u32 i_version_hi;   /* high 32 bits for 64-bit version */
};

#define i_size_high i_dir_acl

#if defined(__KERNEL__) || defined(__linux__)
#    define i_reserved1 osd1.linux1.l_i_reserved1
#    define i_frag osd2.linux2.l_i_frag
#    define i_fsize osd2.linux2.l_i_fsize
#    define i_uid_low i_uid
#    define i_gid_low i_gid
#    define i_uid_high osd2.linux2.l_i_uid_high
#    define i_gid_high osd2.linux2.l_i_gid_high
#    define i_reserved2 osd2.linux2.l_i_reserved2
#else
#    if defined(__GNU__)

#        define i_translator osd1.hurd1.h_i_translator
#        define i_frag osd2.hurd2.h_i_frag;
#        define i_fsize osd2.hurd2.h_i_fsize;
#        define i_uid_high osd2.hurd2.h_i_uid_high
#        define i_gid_high osd2.hurd2.h_i_gid_high
#        define i_author osd2.hurd2.h_i_author

#    endif /* __GNU__ */
#endif     /* defined(__KERNEL__) || defined(__linux__) */

#define inode_uid(inode) ((inode).i_uid | (inode).osd2.linux2.l_i_uid_high << 16)
#define inode_gid(inode) ((inode).i_gid | (inode).osd2.linux2.l_i_gid_high << 16)
#define ext2fs_set_i_uid_high(inode, x) ((inode).osd2.linux2.l_i_uid_high = (x))
#define ext2fs_set_i_gid_high(inode, x) ((inode).osd2.linux2.l_i_gid_high = (x))

/*
 * File system states
 */
#define EXT2_VALID_FS 0x0001  /* Unmounted cleanly */
#define EXT2_ERROR_FS 0x0002  /* Errors detected */
#define EXT3_ORPHAN_FS 0x0004 /* Orphans being recovered */

/*
 * Misc. filesystem flags
 */
#define EXT2_FLAGS_SIGNED_HASH 0x0001   /* Signed dirhash in use */
#define EXT2_FLAGS_UNSIGNED_HASH 0x0002 /* Unsigned dirhash in use */
#define EXT2_FLAGS_TEST_FILESYS 0x0004  /* OK for use on development code */

/*
 * Mount flags
 */
#define EXT2_MOUNT_CHECK 0x0001        /* Do mount-time checks */
#define EXT2_MOUNT_GRPID 0x0004        /* Create files with directory's group */
#define EXT2_MOUNT_DEBUG 0x0008        /* Some debugging messages */
#define EXT2_MOUNT_ERRORS_CONT 0x0010  /* Continue on errors */
#define EXT2_MOUNT_ERRORS_RO 0x0020    /* Remount fs ro on errors */
#define EXT2_MOUNT_ERRORS_PANIC 0x0040 /* Panic on errors */
#define EXT2_MOUNT_MINIX_DF 0x0080     /* Mimics the Minix statfs */
#define EXT2_MOUNT_NO_UID32 0x0200     /* Disable 32-bit UIDs */

#define clear_opt(o, opt) o &= ~EXT2_MOUNT_##opt
#define set_opt(o, opt) o |= EXT2_MOUNT_##opt
#define test_opt(sb, opt) (EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_##opt)
/*
 * Maximal mount counts between two filesystem checks
 */
#define EXT2_DFL_MAX_MNT_COUNT 20 /* Allow 20 mounts */
#define EXT2_DFL_CHECKINTERVAL 0  /* Don't use interval check */

/*
 * Behavior when detecting errors
 */
#define EXT2_ERRORS_CONTINUE 1 /* Continue execution */
#define EXT2_ERRORS_RO 2       /* Remount fs read-only */
#define EXT2_ERRORS_PANIC 3    /* Panic */
#define EXT2_ERRORS_DEFAULT EXT2_ERRORS_CONTINUE

/*
 * Structure of the super block
 */
struct ext2_super_block {
    __u32 s_inodes_count;      /* Inodes count */
    __u32 s_blocks_count;      /* Blocks count */
    __u32 s_r_blocks_count;    /* Reserved blocks count */
    __u32 s_free_blocks_count; /* Free blocks count */
    __u32 s_free_inodes_count; /* Free inodes count */
    __u32 s_first_data_block;  /* First Data Block */
    __u32 s_log_block_size;    /* Block size */
    __s32 s_log_frag_size;     /* Fragment size */
    __u32 s_blocks_per_group;  /* # Blocks per group */
    __u32 s_frags_per_group;   /* # Fragments per group */
    __u32 s_inodes_per_group;  /* # Inodes per group */
    __u32 s_mtime;             /* Mount time */
    __u32 s_wtime;             /* Write time */
    __u16 s_mnt_count;         /* Mount count */
    __s16 s_max_mnt_count;     /* Maximal mount count */
    __u16 s_magic;             /* Magic signature */
    __u16 s_state;             /* File system state */
    __u16 s_errors;            /* Behavior when detecting errors */
    __u16 s_minor_rev_level;   /* minor revision level */
    __u32 s_lastcheck;         /* time of last check */
    __u32 s_checkinterval;     /* max. time between checks */
    __u32 s_creator_os;        /* OS */
    __u32 s_rev_level;         /* Revision level */
    __u16 s_def_resuid;        /* Default uid for reserved blocks */
    __u16 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...
	 */
    __u32 s_first_ino;              /* First non-reserved inode */
    __u16 s_inode_size;             /* size of inode structure */
    __u16 s_block_group_nr;         /* block group # of this superblock */
    __u32 s_feature_compat;         /* compatible feature set */
    __u32 s_feature_incompat;       /* incompatible feature set */
    __u32 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 */
    __u32 s_algorithm_usage_bitmap; /* For compression */
    /*
	 * Performance hints.  Directory preallocation should only
	 * happen if the EXT2_FEATURE_COMPAT_DIR_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_reserved_gdt_blocks; /* Per group table for online growth */
    /*
	 * Journaling support valid if EXT2_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_jnl_backup_type;  /* Default type of journal backup */
    __u16 s_desc_size;       /* Group desc. size: INCOMPAT_64BIT */
    __u32 s_default_mount_opts;
    __u32 s_first_meta_bg;      /* First metablock group */
    __u32 s_mkfs_time;          /* When the filesystem was created */
    __u32 s_jnl_blocks[17];     /* Backup of the journal inode */
    __u32 s_blocks_count_hi;    /* Blocks count high 32bits */
    __u32 s_r_blocks_count_hi;  /* Reserved blocks count high 32 bits*/
    __u32 s_free_blocks_hi;     /* Free blocks count */
    __u16 s_min_extra_isize;    /* All inodes have at least # bytes */
    __u16 s_want_extra_isize;   /* New inodes should reserve # bytes */
    __u32 s_flags;              /* Miscellaneous flags */
    __u16 s_raid_stride;        /* RAID stride */
    __u16 s_mmp_interval;       /* # seconds to wait in MMP checking */
    __u64 s_mmp_block;          /* Block for multi-mount protection */
    __u32 s_raid_stripe_width;  /* blocks on all data disks (N*stride)*/
    __u8 s_log_groups_per_flex; /* FLEX_BG group size */
    __u8 s_reserved_char_pad;
    __u16 s_reserved_pad;  /* Padding to next 32bits */
    __u32 s_reserved[162]; /* Padding to the end of the block */
};

/*
 * Codes for operating systems
 */
#define EXT2_OS_LINUX 0
#define EXT2_OS_HURD 1
#define EXT2_OBSO_OS_MASIX 2
#define EXT2_OS_FREEBSD 3
#define EXT2_OS_LITES 4

/*
 * Revision levels
 */
#define EXT2_GOOD_OLD_REV 0 /* The good old (original) format */
#define EXT2_DYNAMIC_REV 1  /* V2 format w/ dynamic inode sizes */

#define EXT2_CURRENT_REV EXT2_GOOD_OLD_REV
#define EXT2_MAX_SUPP_REV EXT2_DYNAMIC_REV

#define EXT2_GOOD_OLD_INODE_SIZE 128

/*
 * Journal inode backup types
 */
#define EXT3_JNL_BACKUP_BLOCKS 1

/*
 * Feature set definitions
 */

#define EXT2_HAS_COMPAT_FEATURE(sb, mask) \
    (EXT2_SB(sb)->s_feature_compat & (mask))
#define EXT2_HAS_RO_COMPAT_FEATURE(sb, mask) \
    (EXT2_SB(sb)->s_feature_ro_compat & (mask))
#define EXT2_HAS_INCOMPAT_FEATURE(sb, mask) \
    (EXT2_SB(sb)->s_feature_incompat & (mask))

#define EXT2_FEATURE_COMPAT_DIR_PREALLOC 0x0001
#define EXT2_FEATURE_COMPAT_IMAGIC_INODES 0x0002
#define EXT3_FEATURE_COMPAT_HAS_JOURNAL 0x0004
#define EXT2_FEATURE_COMPAT_EXT_ATTR 0x0008
#define EXT2_FEATURE_COMPAT_RESIZE_INODE 0x0010
#define EXT2_FEATURE_COMPAT_DIR_INDEX 0x0020
#define EXT2_FEATURE_COMPAT_LAZY_BG 0x0040

#define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER 0x0001
#define EXT2_FEATURE_RO_COMPAT_LARGE_FILE 0x0002
/* #define EXT2_FEATURE_RO_COMPAT_BTREE_DIR	0x0004 not used */
#define EXT4_FEATURE_RO_COMPAT_HUGE_FILE 0x0008
#define EXT4_FEATURE_RO_COMPAT_GDT_CSUM 0x0010
#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK 0x0020
#define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE 0x0040

#define EXT2_FEATURE_INCOMPAT_COMPRESSION 0x0001
#define EXT2_FEATURE_INCOMPAT_FILETYPE 0x0002
#define EXT3_FEATURE_INCOMPAT_RECOVER 0x0004     /* Needs recovery */
#define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV 0x0008 /* Journal device */
#define EXT2_FEATURE_INCOMPAT_META_BG 0x0010
#define EXT3_FEATURE_INCOMPAT_EXTENTS 0x0040
#define EXT4_FEATURE_INCOMPAT_64BIT 0x0080
#define EXT4_FEATURE_INCOMPAT_MMP 0x0100
#define EXT4_FEATURE_INCOMPAT_FLEX_BG 0x0200

#define EXT2_FEATURE_COMPAT_SUPP 0
#define EXT2_FEATURE_INCOMPAT_SUPP (EXT2_FEATURE_INCOMPAT_FILETYPE)
#define EXT2_FEATURE_RO_COMPAT_SUPP (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER | EXT2_FEATURE_RO_COMPAT_LARGE_FILE | EXT4_FEATURE_RO_COMPAT_DIR_NLINK | EXT2_FEATURE_RO_COMPAT_BTREE_DIR)

/*
 * Default values for user and/or group using reserved blocks
 */
#define EXT2_DEF_RESUID 0
#define EXT2_DEF_RESGID 0

/*
 * Default mount options
 */
#define EXT2_DEFM_DEBUG 0x0001
#define EXT2_DEFM_BSDGROUPS 0x0002
#define EXT2_DEFM_XATTR_USER 0x0004
#define EXT2_DEFM_ACL 0x0008
#define EXT2_DEFM_UID16 0x0010
#define EXT3_DEFM_JMODE 0x0060
#define EXT3_DEFM_JMODE_DATA 0x0020
#define EXT3_DEFM_JMODE_ORDERED 0x0040
#define EXT3_DEFM_JMODE_WBACK 0x0060

/*
 * Structure of a directory entry
 */
#define EXT2_NAME_LEN 255

struct ext2_dir_entry {
    __u32 inode;              /* Inode number */
    __u16 rec_len;            /* Directory entry length */
    __u16 name_len;           /* Name length */
    char name[EXT2_NAME_LEN]; /* Filename */
};

/*
 * The new version of the directory entry.  Since EXT2 structures are
 * stored in intel byte order, and the name_len field could never be
 * bigger than 255 chars, it's safe to reclaim the extra byte for the
 * file_type field.
 */
struct ext2_dir_entry_2 {
    __u32 inode;   /* Inode number */
    __u16 rec_len; /* Directory entry length */
    __u8 name_len; /* Name length */
    __u8 file_type;
    char name[EXT2_NAME_LEN]; /* Filename */
};

/*
 * Ext2 directory file types.  Only the low 3 bits are used.  The
 * other bits are reserved for now.
 */
#define EXT2_FT_UNKNOWN 0
#define EXT2_FT_REG_FILE 1
#define EXT2_FT_DIR 2
#define EXT2_FT_CHRDEV 3
#define EXT2_FT_BLKDEV 4
#define EXT2_FT_FIFO 5
#define EXT2_FT_SOCK 6
#define EXT2_FT_SYMLINK 7

#define EXT2_FT_MAX 8

/*
 * EXT2_DIR_PAD defines the directory entries boundaries
 *
 * NOTE: It must be a multiple of 4
 */
#define EXT2_DIR_PAD 4
#define EXT2_DIR_ROUND (EXT2_DIR_PAD - 1)
#define EXT2_DIR_REC_LEN(name_len) (((name_len) + 8 + EXT2_DIR_ROUND) & ~EXT2_DIR_ROUND)

/*
 * This structure will be used for multiple mount protection. It will be
 * written into the block number saved in the s_mmp_block field in the
 * superblock.
 */
#define EXT2_MMP_MAGIC 0x004D4D50   /* ASCII for MMP */
#define EXT2_MMP_CLEAN 0xFF4D4D50   /* Value of mmp_seq for clean unmount */
#define EXT2_MMP_FSCK_ON 0xE24D4D50 /* Value of mmp_seq when being fscked */

struct mmp_struct {
    __u32 mmp_magic;
    __u32 mmp_seq;
    __u64 mmp_time;
    char mmp_nodename[64];
    char mmp_bdevname[32];
    __u16 mmp_interval;
    __u16 mmp_pad1;
    __u32 mmp_pad2;
};

/*
 * Interval in number of seconds to update the MMP sequence number.
 */
#define EXT2_MMP_DEF_INTERVAL 5

#endif /* _LINUX_EXT2_FS_H */