code.delx.au - refind/blob - filesystems/fsw_ext4_disk.h

   1 /**
   2  * \file fsw_ext4_disk.h
   3  * ext4 file system on-disk structures.
   4  */
   5
   6 /*-
   7  * Copyright (c) 2012 Stefan Agner
   8  * Portions Copyright (c) 2006 Christoph Pfisterer
   9  * Portions Copyright (c) 1991-2012 by various Linux kernel contributors
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program; if not, write to the Free Software
  23  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  24  */
  25
  26 #ifndef _FSW_EXT4_DISK_H_
  27 #define _FSW_EXT4_DISK_H_
  28
  29 // types
  30
  31 typedef fsw_s8  __s8;
  32 typedef fsw_u8  __u8;
  33 typedef fsw_s16 __s16;
  34 typedef fsw_u16 __u16;
  35 typedef fsw_s32 __s32;
  36 typedef fsw_u32 __u32;
  37 typedef fsw_s64 __s64;
  38 typedef fsw_u64 __u64;
  39
  40 typedef __u16   __le16;
  41 typedef __u32   __le32;
  42 typedef __u64   __le64;
  43
  44 //
  45 // from Linux kernel, fs/ext4/ext4.h
  46 //
  47
  48 /*
  49  * Special inode numbers
  50  */
  51 #define EXT4_BAD_INO             1      /* Bad blocks inode */
  52 #define EXT4_ROOT_INO            2      /* Root inode */
  53 #define EXT4_USR_QUOTA_INO       3      /* User quota inode */
  54 #define EXT4_GRP_QUOTA_INO       4      /* Group quota inode */
  55 #define EXT4_BOOT_LOADER_INO     5      /* Boot loader inode */
  56 #define EXT4_UNDEL_DIR_INO       6      /* Undelete directory inode */
  57 #define EXT4_RESIZE_INO          7      /* Reserved group descriptors inode */
  58 #define EXT4_JOURNAL_INO         8      /* Journal inode */
  59
  60 /*
  61  * The second extended file system magic number
  62  */
  63 #define EXT4_SUPER_MAGIC        0xEF53
  64
  65 /*
  66  * Macro-instructions used to manage several block sizes
  67  */
  68 #define EXT4_MIN_BLOCK_SIZE             1024
  69 #define EXT4_MAX_BLOCK_SIZE             4096
  70 #define EXT4_MIN_BLOCK_LOG_SIZE           10
  71 #define EXT4_BLOCK_SIZE(s)              (EXT4_MIN_BLOCK_SIZE << (s)->s_log_block_size)
  72 #define EXT4_ADDR_PER_BLOCK(s)          (EXT4_BLOCK_SIZE(s) / sizeof (__u32))
  73 #define EXT4_BLOCK_SIZE_BITS(s)         ((s)->s_log_block_size + 10)
  74 #define EXT4_INODE_SIZE(s)      (((s)->s_rev_level == EXT4_GOOD_OLD_REV) ? \
  75                                  EXT4_GOOD_OLD_INODE_SIZE : \
  76                                  (s)->s_inode_size)
  77
  78 /*
  79  * Structure of a blocks group descriptor
  80  */
  81 struct ext4_group_desc
  82 {
  83         __le32  bg_block_bitmap_lo;     /* Blocks bitmap block */
  84         __le32  bg_inode_bitmap_lo;     /* Inodes bitmap block */
  85         __le32  bg_inode_table_lo;      /* Inodes table block */
  86         __le16  bg_free_blocks_count_lo;/* Free blocks count */
  87         __le16  bg_free_inodes_count_lo;/* Free inodes count */
  88         __le16  bg_used_dirs_count_lo;  /* Directories count */
  89         __le16  bg_flags;               /* EXT4_BG_flags (INODE_UNINIT, etc) */
  90         __le32  bg_exclude_bitmap_lo;   /* Exclude bitmap for snapshots */
  91         __le16  bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bbitmap) LE */
  92         __le16  bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+ibitmap) LE */
  93         __le16  bg_itable_unused_lo;    /* Unused inodes count */
  94         __le16  bg_checksum;            /* crc16(sb_uuid+group+desc) */
  95         __le32  bg_block_bitmap_hi;     /* Blocks bitmap block MSB */
  96         __le32  bg_inode_bitmap_hi;     /* Inodes bitmap block MSB */
  97         __le32  bg_inode_table_hi;      /* Inodes table block MSB */
  98         __le16  bg_free_blocks_count_hi;/* Free blocks count MSB */
  99         __le16  bg_free_inodes_count_hi;/* Free inodes count MSB */
 100         __le16  bg_used_dirs_count_hi;  /* Directories count MSB */
 101         __le16  bg_itable_unused_hi;    /* Unused inodes count MSB */
 102         __le32  bg_exclude_bitmap_hi;   /* Exclude bitmap block MSB */
 103         __le16  bg_block_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bbitmap) BE */
 104         __le16  bg_inode_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+ibitmap) BE */
 105         __u32   bg_reserved;
 106 };
 107
 108
 109 /*
 110  * Macro-instructions used to manage group descriptors
 111  */
 112 #define EXT4_MIN_DESC_SIZE              32
 113 #define EXT4_MIN_DESC_SIZE_64BIT        64
 114 #define EXT4_MAX_DESC_SIZE              EXT4_MIN_BLOCK_SIZE
 115 #define EXT4_DESC_SIZE(s)              ((s)->s_desc_size)
 116 #define EXT4_BLOCKS_PER_GROUP(s)       ((s)->s_blocks_per_group)
 117 #define EXT4_DESC_PER_BLOCK(s)         (EXT4_BLOCK_SIZE(s) / EXT4_DESC_SIZE(s))
 118 #define EXT4_INODES_PER_GROUP(s)       ((s)->s_inodes_per_group)
 119
 120 /*
 121  * Constants relative to the data blocks
 122  */
 123 #define EXT4_NDIR_BLOCKS                12
 124 #define EXT4_IND_BLOCK                  EXT4_NDIR_BLOCKS
 125 #define EXT4_DIND_BLOCK                 (EXT4_IND_BLOCK + 1)
 126 #define EXT4_TIND_BLOCK                 (EXT4_DIND_BLOCK + 1)
 127 #define EXT4_N_BLOCKS                   (EXT4_TIND_BLOCK + 1)
 128
 129 /*
 130  * Inode flags
 131  */
 132 #define EXT4_SECRM_FL                   0x00000001 /* Secure deletion */
 133 #define EXT4_UNRM_FL                    0x00000002 /* Undelete */
 134 #define EXT4_COMPR_FL                   0x00000004 /* Compress file */
 135 #define EXT4_SYNC_FL                    0x00000008 /* Synchronous updates */
 136 #define EXT4_IMMUTABLE_FL               0x00000010 /* Immutable file */
 137 #define EXT4_APPEND_FL                  0x00000020 /* writes to file may only append */
 138 #define EXT4_NODUMP_FL                  0x00000040 /* do not dump file */
 139 #define EXT4_NOATIME_FL                 0x00000080 /* do not update atime */
 140 /* Reserved for compression usage... */
 141 #define EXT4_DIRTY_FL                   0x00000100
 142 #define EXT4_COMPRBLK_FL                0x00000200 /* One or more compressed clusters */
 143 #define EXT4_NOCOMP_FL                  0x00000400 /* Don't compress */
 144 #define EXT4_ECOMPR_FL                  0x00000800 /* Compression error */
 145 /* End compression flags --- maybe not all used */
 146 #define EXT4_INDEX_FL                   0x00001000 /* hash-indexed directory */
 147 #define EXT4_IMAGIC_FL                  0x00002000 /* AFS directory */
 148 #define EXT4_JOURNAL_DATA_FL            0x00004000 /* Reserved for ext3 */
 149 #define EXT4_NOTAIL_FL                  0x00008000 /* file tail should not be merged */
 150 #define EXT4_DIRSYNC_FL                 0x00010000 /* dirsync behaviour (directories only) */
 151 #define EXT4_TOPDIR_FL                  0x00020000 /* Top of directory hierarchies*/
 152 #define EXT4_HUGE_FILE_FL               0x00040000 /* Set to each huge file */
 153 #define EXT4_EXTENTS_FL                 0x00080000 /* Inode uses extents */
 154 #define EXT4_EA_INODE_FL                0x00200000 /* Inode used for large EA */
 155 #define EXT4_EOFBLOCKS_FL               0x00400000 /* Blocks allocated beyond EOF */
 156 #define EXT4_RESERVED_FL                0x80000000 /* reserved for ext4 lib */
 157
 158 #define EXT4_FL_USER_VISIBLE            0x004BDFFF /* User visible flags */
 159 #define EXT4_FL_USER_MODIFIABLE         0x004B80FF /* User modifiable flags */
 160
 161
 162 /*
 163  * Structure of an inode on the disk
 164  */
 165 struct ext4_inode {
 166         __le16  i_mode;         /* File mode */
 167         __le16  i_uid;          /* Low 16 bits of Owner Uid */
 168         __le32  i_size_lo;      /* Size in bytes */
 169         __le32  i_atime;        /* Access time */
 170         __le32  i_ctime;        /* Inode Change time */
 171         __le32  i_mtime;        /* Modification time */
 172         __le32  i_dtime;        /* Deletion Time */
 173         __le16  i_gid;          /* Low 16 bits of Group Id */
 174         __le16  i_links_count;  /* Links count */
 175         __le32  i_blocks_lo;    /* Blocks count */
 176         __le32  i_flags;        /* File flags */
 177         union {
 178                 struct {
 179                         __le32  l_i_version;
 180                 } linux1;
 181                 struct {
 182                         __u32  h_i_translator;
 183                 } hurd1;
 184                 struct {
 185                         __u32  m_i_reserved1;
 186                 } masix1;
 187         } osd1;                         /* OS dependent 1 */
 188         __le32  i_block[EXT4_N_BLOCKS];/* Pointers to blocks */
 189         __le32  i_generation;   /* File version (for NFS) */
 190         __le32  i_file_acl_lo;  /* File ACL */
 191         __le32  i_size_high;
 192         __le32  i_obso_faddr;   /* Obsoleted fragment address */
 193         union {
 194                 struct {
 195                         __le16  l_i_blocks_high; /* were l_i_reserved1 */
 196                         __le16  l_i_file_acl_high;
 197                         __le16  l_i_uid_high;   /* these 2 fields */
 198                         __le16  l_i_gid_high;   /* were reserved2[0] */
 199                         __le16  l_i_checksum_lo;/* crc32c(uuid+inum+inode) LE */
 200                         __le16  l_i_reserved;
 201                 } linux2;
 202                 struct {
 203                         __le16  h_i_reserved1;  /* Obsoleted fragment number/size which are removed in ext4 */
 204                         __u16   h_i_mode_high;
 205                         __u16   h_i_uid_high;
 206                         __u16   h_i_gid_high;
 207                         __u32   h_i_author;
 208                 } hurd2;
 209                 struct {
 210                         __le16  h_i_reserved1;  /* Obsoleted fragment number/size which are removed in ext4 */
 211                         __le16  m_i_file_acl_high;
 212                         __u32   m_i_reserved2[2];
 213                 } masix2;
 214         } osd2;                         /* OS dependent 2 */
 215         __le16  i_extra_isize;
 216         __le16  i_checksum_hi;  /* crc32c(uuid+inum+inode) BE */
 217         __le32  i_ctime_extra;  /* extra Change time      (nsec << 2 | epoch) */
 218         __le32  i_mtime_extra;  /* extra Modification time(nsec << 2 | epoch) */
 219         __le32  i_atime_extra;  /* extra Access time      (nsec << 2 | epoch) */
 220         __le32  i_crtime;       /* File Creation time */
 221         __le32  i_crtime_extra; /* extra FileCreationtime (nsec << 2 | epoch) */
 222         __le32  i_version_hi;   /* high 32 bits for 64-bit version */
 223 };
 224
 225
 226 /*
 227  * Inode flags used for atomic set/get
 228  */
 229 enum {
 230         EXT4_INODE_SECRM        = 0,    /* Secure deletion */
 231         EXT4_INODE_UNRM         = 1,    /* Undelete */
 232         EXT4_INODE_COMPR        = 2,    /* Compress file */
 233         EXT4_INODE_SYNC         = 3,    /* Synchronous updates */
 234         EXT4_INODE_IMMUTABLE    = 4,    /* Immutable file */
 235         EXT4_INODE_APPEND       = 5,    /* writes to file may only append */
 236         EXT4_INODE_NODUMP       = 6,    /* do not dump file */
 237         EXT4_INODE_NOATIME      = 7,    /* do not update atime */
 238 /* Reserved for compression usage... */
 239         EXT4_INODE_DIRTY        = 8,
 240         EXT4_INODE_COMPRBLK     = 9,    /* One or more compressed clusters */
 241         EXT4_INODE_NOCOMPR      = 10,   /* Don't compress */
 242         EXT4_INODE_ECOMPR       = 11,   /* Compression error */
 243 /* End compression flags --- maybe not all used */
 244         EXT4_INODE_INDEX        = 12,   /* hash-indexed directory */
 245         EXT4_INODE_IMAGIC       = 13,   /* AFS directory */
 246         EXT4_INODE_JOURNAL_DATA = 14,   /* file data should be journaled */
 247         EXT4_INODE_NOTAIL       = 15,   /* file tail should not be merged */
 248         EXT4_INODE_DIRSYNC      = 16,   /* dirsync behaviour (directories only) */
 249         EXT4_INODE_TOPDIR       = 17,   /* Top of directory hierarchies*/
 250         EXT4_INODE_HUGE_FILE    = 18,   /* Set to each huge file */
 251         EXT4_INODE_EXTENTS      = 19,   /* Inode uses extents */
 252         EXT4_INODE_EA_INODE     = 21,   /* Inode used for large EA */
 253         EXT4_INODE_EOFBLOCKS    = 22,   /* Blocks allocated beyond EOF */
 254         EXT4_INODE_RESERVED     = 31,   /* reserved for ext4 lib */
 255 };
 256
 257 /*
 258  * Structure of the super block
 259  */
 260 struct ext4_super_block {
 261 /*00*/  __le32  s_inodes_count;         /* Inodes count */
 262         __le32  s_blocks_count_lo;      /* Blocks count */
 263         __le32  s_r_blocks_count_lo;    /* Reserved blocks count */
 264         __le32  s_free_blocks_count_lo; /* Free blocks count */
 265 /*10*/  __le32  s_free_inodes_count;    /* Free inodes count */
 266         __le32  s_first_data_block;     /* First Data Block */
 267         __le32  s_log_block_size;       /* Block size */
 268         __le32  s_log_cluster_size;     /* Allocation cluster size */
 269 /*20*/  __le32  s_blocks_per_group;     /* # Blocks per group */
 270         __le32  s_clusters_per_group;   /* # Clusters per group */
 271         __le32  s_inodes_per_group;     /* # Inodes per group */
 272         __le32  s_mtime;                /* Mount time */
 273 /*30*/  __le32  s_wtime;                /* Write time */
 274         __le16  s_mnt_count;            /* Mount count */
 275         __le16  s_max_mnt_count;        /* Maximal mount count */
 276         __le16  s_magic;                /* Magic signature */
 277         __le16  s_state;                /* File system state */
 278         __le16  s_errors;               /* Behaviour when detecting errors */
 279         __le16  s_minor_rev_level;      /* minor revision level */
 280 /*40*/  __le32  s_lastcheck;            /* time of last check */
 281         __le32  s_checkinterval;        /* max. time between checks */
 282         __le32  s_creator_os;           /* OS */
 283         __le32  s_rev_level;            /* Revision level */
 284 /*50*/  __le16  s_def_resuid;           /* Default uid for reserved blocks */
 285         __le16  s_def_resgid;           /* Default gid for reserved blocks */
 286         /*
 287          * These fields are for EXT4_DYNAMIC_REV superblocks only.
 288          *
 289          * Note: the difference between the compatible feature set and
 290          * the incompatible feature set is that if there is a bit set
 291          * in the incompatible feature set that the kernel doesn't
 292          * know about, it should refuse to mount the filesystem.
 293          *
 294          * e2fsck's requirements are more strict; if it doesn't know
 295          * about a feature in either the compatible or incompatible
 296          * feature set, it must abort and not try to meddle with
 297          * things it doesn't understand...
 298          */
 299         __le32  s_first_ino;            /* First non-reserved inode */
 300         __le16  s_inode_size;           /* size of inode structure */
 301         __le16  s_block_group_nr;       /* block group # of this superblock */
 302         __le32  s_feature_compat;       /* compatible feature set */
 303 /*60*/  __le32  s_feature_incompat;     /* incompatible feature set */
 304         __le32  s_feature_ro_compat;    /* readonly-compatible feature set */
 305 /*68*/  __u8    s_uuid[16];             /* 128-bit uuid for volume */
 306 /*78*/  char    s_volume_name[16];      /* volume name */
 307 /*88*/  char    s_last_mounted[64];     /* directory where last mounted */
 308 /*C8*/  __le32  s_algorithm_usage_bitmap; /* For compression */
 309         /*
 310          * Performance hints.  Directory preallocation should only
 311          * happen if the EXT4_FEATURE_COMPAT_DIR_PREALLOC flag is on.
 312          */
 313         __u8    s_prealloc_blocks;      /* Nr of blocks to try to preallocate*/
 314         __u8    s_prealloc_dir_blocks;  /* Nr to preallocate for dirs */
 315         __le16  s_reserved_gdt_blocks;  /* Per group desc for online growth */
 316         /*
 317          * Journaling support valid if EXT4_FEATURE_COMPAT_HAS_JOURNAL set.
 318          */
 319 /*D0*/  __u8    s_journal_uuid[16];     /* uuid of journal superblock */
 320 /*E0*/  __le32  s_journal_inum;         /* inode number of journal file */
 321         __le32  s_journal_dev;          /* device number of journal file */
 322         __le32  s_last_orphan;          /* start of list of inodes to delete */
 323         __le32  s_hash_seed[4];         /* HTREE hash seed */
 324         __u8    s_def_hash_version;     /* Default hash version to use */
 325         __u8    s_jnl_backup_type;
 326         __le16  s_desc_size;            /* size of group descriptor */
 327 /*100*/ __le32  s_default_mount_opts;
 328         __le32  s_first_meta_bg;        /* First metablock block group */
 329         __le32  s_mkfs_time;            /* When the filesystem was created */
 330         __le32  s_jnl_blocks[17];       /* Backup of the journal inode */
 331         /* 64bit support valid if EXT4_FEATURE_COMPAT_64BIT */
 332 /*150*/ __le32  s_blocks_count_hi;      /* Blocks count */
 333         __le32  s_r_blocks_count_hi;    /* Reserved blocks count */
 334         __le32  s_free_blocks_count_hi; /* Free blocks count */
 335         __le16  s_min_extra_isize;      /* All inodes have at least # bytes */
 336         __le16  s_want_extra_isize;     /* New inodes should reserve # bytes */
 337         __le32  s_flags;                /* Miscellaneous flags */
 338         __le16  s_raid_stride;          /* RAID stride */
 339         __le16  s_mmp_update_interval;  /* # seconds to wait in MMP checking */
 340         __le64  s_mmp_block;            /* Block for multi-mount protection */
 341         __le32  s_raid_stripe_width;    /* blocks on all data disks (N*stride)*/
 342         __u8    s_log_groups_per_flex;  /* FLEX_BG group size */
 343         __u8    s_checksum_type;        /* metadata checksum algorithm used */
 344         __le16  s_reserved_pad;
 345         __le64  s_kbytes_written;       /* nr of lifetime kilobytes written */
 346         __le32  s_snapshot_inum;        /* Inode number of active snapshot */
 347         __le32  s_snapshot_id;          /* sequential ID of active snapshot */
 348         __le64  s_snapshot_r_blocks_count; /* reserved blocks for active
 349                                               snapshot's future use */
 350         __le32  s_snapshot_list;        /* inode number of the head of the
 351                                            on-disk snapshot list */
 352 #define EXT4_S_ERR_START offsetof(struct ext4_super_block, s_error_count)
 353         __le32  s_error_count;          /* number of fs errors */
 354         __le32  s_first_error_time;     /* first time an error happened */
 355         __le32  s_first_error_ino;      /* inode involved in first error */
 356         __le64  s_first_error_block;    /* block involved of first error */
 357         __u8    s_first_error_func[32]; /* function where the error happened */
 358         __le32  s_first_error_line;     /* line number where error happened */
 359         __le32  s_last_error_time;      /* most recent time of an error */
 360         __le32  s_last_error_ino;       /* inode involved in last error */
 361         __le32  s_last_error_line;      /* line number where error happened */
 362         __le64  s_last_error_block;     /* block involved of last error */
 363         __u8    s_last_error_func[32];  /* function where the error happened */
 364 #define EXT4_S_ERR_END offsetof(struct ext4_super_block, s_mount_opts)
 365         __u8    s_mount_opts[64];
 366         __le32  s_usr_quota_inum;       /* inode for tracking user quota */
 367         __le32  s_grp_quota_inum;       /* inode for tracking group quota */
 368         __le32  s_overhead_clusters;    /* overhead blocks/clusters in fs */
 369         __le32  s_reserved[108];        /* Padding to the end of the block */
 370         __le32  s_checksum;             /* crc32c(superblock) */
 371 };
 372
 373 /*
 374  * Revision levels
 375  */
 376 #define EXT4_GOOD_OLD_REV       0       /* The good old (original) format */
 377 #define EXT4_DYNAMIC_REV        1       /* V2 format w/ dynamic inode sizes */
 378
 379 #define EXT4_CURRENT_REV        EXT4_GOOD_OLD_REV
 380 #define EXT4_MAX_SUPP_REV       EXT4_DYNAMIC_REV
 381
 382 #define EXT4_GOOD_OLD_INODE_SIZE 128
 383
 384 /*
 385  * Feature set definitions (only the once we need for read support)
 386  */
 387 #define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER     0x0001
 388
 389 #define EXT4_FEATURE_INCOMPAT_COMPRESSION       0x0001
 390 #define EXT4_FEATURE_INCOMPAT_FILETYPE          0x0002
 391 #define EXT4_FEATURE_INCOMPAT_RECOVER           0x0004 /* Needs recovery */
 392 #define EXT4_FEATURE_INCOMPAT_JOURNAL_DEV       0x0008 /* Journal device */
 393 #define EXT4_FEATURE_INCOMPAT_META_BG           0x0010
 394 #define EXT4_FEATURE_INCOMPAT_EXTENTS           0x0040 /* extents support */
 395 #define EXT4_FEATURE_INCOMPAT_64BIT             0x0080
 396 #define EXT4_FEATURE_INCOMPAT_MMP               0x0100
 397 #define EXT4_FEATURE_INCOMPAT_FLEX_BG           0x0200
 398 #define EXT4_FEATURE_INCOMPAT_EA_INODE          0x0400 /* EA in inode */
 399 #define EXT4_FEATURE_INCOMPAT_DIRDATA           0x1000 /* data in dirent */
 400 #define EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM  0x2000 /* use crc32c for bg */
 401 #define EXT4_FEATURE_INCOMPAT_LARGEDIR          0x4000 /* >2GB or 3-lvl htree */
 402 #define EXT4_FEATURE_INCOMPAT_INLINEDATA        0x8000 /* data in inode */
 403
 404 #define EXT4_FEATURE_INCOMPAT_SUPP      (EXT4_FEATURE_INCOMPAT_FILETYPE| \
 405                                          EXT4_FEATURE_INCOMPAT_RECOVER| \
 406                                          EXT4_FEATURE_INCOMPAT_META_BG| \
 407                                          EXT4_FEATURE_INCOMPAT_EXTENTS| \
 408                                          EXT4_FEATURE_INCOMPAT_64BIT| \
 409                                          EXT4_FEATURE_INCOMPAT_FLEX_BG| \
 410                                          EXT4_FEATURE_INCOMPAT_MMP)
 411
 412 /*
 413  * Structure of a directory entry
 414  */
 415 #define EXT4_NAME_LEN 255
 416
 417 struct ext4_dir_entry {
 418     __le32  inode;                  /* Inode number */
 419     __le16  rec_len;                /* Directory entry length */
 420     __u8    name_len;               /* Name length */
 421     __u8    file_type;
 422     char    name[EXT4_NAME_LEN];    /* File name */
 423 };
 424 // NOTE: The original Linux kernel header defines ext4_dir_entry with the original
 425 //  layout and ext4_dir_entry_2 with the revised layout. We simply use the revised one.
 426
 427 /*
 428  * Ext2 directory file types.  Only the low 3 bits are used.  The
 429  * other bits are reserved for now.
 430  */
 431 enum {
 432     EXT4_FT_UNKNOWN,
 433     EXT4_FT_REG_FILE,
 434     EXT4_FT_DIR,
 435     EXT4_FT_CHRDEV,
 436     EXT4_FT_BLKDEV,
 437     EXT4_FT_FIFO,
 438     EXT4_FT_SOCK,
 439     EXT4_FT_SYMLINK,
 440     EXT4_FT_MAX
 441 };
 442
 443 /*
 444  * ext4_inode has i_block array (60 bytes total).
 445  * The first 12 bytes store ext4_extent_header;
 446  * the remainder stores an array of ext4_extent.
 447  * For non-inode extent blocks, ext4_extent_tail
 448  * follows the array.
 449  */
 450
 451 /*
 452  * This is the extent tail on-disk structure.
 453  * All other extent structures are 12 bytes long.  It turns out that
 454  * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
 455  * covers all valid ext4 block sizes.  Therefore, this tail structure can be
 456  * crammed into the end of the block without having to rebalance the tree.
 457  */
 458 struct ext4_extent_tail {
 459         __le32  et_checksum;    /* crc32c(uuid+inum+extent_block) */
 460 };
 461
 462 /*
 463  * This is the extent on-disk structure.
 464  * It's used at the bottom of the tree.
 465  */
 466 struct ext4_extent {
 467         __le32  ee_block;       /* first logical block extent covers */
 468         __le16  ee_len;         /* number of blocks covered by extent */
 469         __le16  ee_start_hi;    /* high 16 bits of physical block */
 470         __le32  ee_start_lo;    /* low 32 bits of physical block */
 471 };
 472
 473 /*
 474  * This is index on-disk structure.
 475  * It's used at all the levels except the bottom.
 476  */
 477 struct ext4_extent_idx {
 478         __le32  ei_block;       /* index covers logical blocks from 'block' */
 479         __le32  ei_leaf_lo;     /* pointer to the physical block of the next *
 480                                  * level. leaf or next index could be there */
 481         __le16  ei_leaf_hi;     /* high 16 bits of physical block */
 482         __u16   ei_unused;
 483 };
 484
 485
 486 /*
 487  * Each block (leaves and indexes), even inode-stored has header.
 488  */
 489 struct ext4_extent_header {
 490         __le16  eh_magic;       /* probably will support different formats */
 491         __le16  eh_entries;     /* number of valid entries */
 492         __le16  eh_max;         /* capacity of store in entries */
 493         __le16  eh_depth;       /* has tree real underlying blocks? */
 494         __le32  eh_generation;  /* generation of the tree */
 495 };
 496
 497 #define EXT4_EXT_MAGIC          (0xf30a)
 498
 499
 500 #endif