lib/ext2fs/ext2_fs.h

   1 /*
   2  *  linux/include/linux/ext2_fs.h
   3  *
   4  * Copyright (C) 1992, 1993, 1994, 1995
   5  * Remy Card (card@masi.ibp.fr)
   6  * Laboratoire MASI - Institut Blaise Pascal
   7  * Universite Pierre et Marie Curie (Paris VI)
   8  *
   9  *  from
  10  *
  11  *  linux/include/linux/minix_fs.h
  12  *
  13  *  Copyright (C) 1991, 1992  Linus Torvalds
  14  */
  15
  16 #ifndef _LINUX_EXT2_FS_H
  17 #define _LINUX_EXT2_FS_H
  18
  19 #include <ext2fs/ext2_types.h>          /* Changed from linux/types.h */
  20
  21 /*
  22  * The second extended filesystem constants/structures
  23  */
  24
  25 /*
  26  * Define EXT2FS_DEBUG to produce debug messages
  27  */
  28 #undef EXT2FS_DEBUG
  29
  30 /*
  31  * Define EXT2_PREALLOCATE to preallocate data blocks for expanding files
  32  */
  33 #define EXT2_PREALLOCATE
  34 #define EXT2_DEFAULT_PREALLOC_BLOCKS    8
  35
  36 /*
  37  * The second extended file system version
  38  */
  39 #define EXT2FS_DATE             "95/08/09"
  40 #define EXT2FS_VERSION          "0.5b"
  41
  42 /*
  43  * Special inode numbers
  44  */
  45 #define EXT2_BAD_INO             1      /* Bad blocks inode */
  46 #define EXT2_ROOT_INO            2      /* Root inode */
  47 #define EXT4_USR_QUOTA_INO       3      /* User quota inode */
  48 #define EXT4_GRP_QUOTA_INO       4      /* Group quota inode */
  49 #define EXT2_BOOT_LOADER_INO     5      /* Boot loader inode */
  50 #define EXT2_UNDEL_DIR_INO       6      /* Undelete directory inode */
  51 #define EXT2_RESIZE_INO          7      /* Reserved group descriptors inode */
  52 #define EXT2_JOURNAL_INO         8      /* Journal inode */
  53 #define EXT2_EXCLUDE_INO         9      /* The "exclude" inode, for snapshots */
  54 #define EXT4_REPLICA_INO        10      /* Used by non-upstream feature */
  55
  56 /* First non-reserved inode for old ext2 filesystems */
  57 #define EXT2_GOOD_OLD_FIRST_INO 11
  58
  59 /*
  60  * The second extended file system magic number
  61  */
  62 #define EXT2_SUPER_MAGIC        0xEF53
  63
  64 #ifdef __KERNEL__
  65 #define EXT2_SB(sb)     (&((sb)->u.ext2_sb))
  66 #else
  67 /* Assume that user mode programs are passing in an ext2fs superblock, not
  68  * a kernel struct super_block.  This will allow us to call the feature-test
  69  * macros from user land. */
  70 #define EXT2_SB(sb)     (sb)
  71 #endif
  72
  73 /*
  74  * Maximal count of links to a file
  75  */
  76 #define EXT2_LINK_MAX           65000
  77
  78 /*
  79  * Macro-instructions used to manage several block sizes
  80  */
  81 #define EXT2_MIN_BLOCK_LOG_SIZE         10      /* 1024 */
  82 #define EXT2_MAX_BLOCK_LOG_SIZE         16      /* 65536 */
  83 #define EXT2_MIN_BLOCK_SIZE     (1 << EXT2_MIN_BLOCK_LOG_SIZE)
  84 #define EXT2_MAX_BLOCK_SIZE     (1 << EXT2_MAX_BLOCK_LOG_SIZE)
  85 #ifdef __KERNEL__
  86 #define EXT2_BLOCK_SIZE(s)      ((s)->s_blocksize)
  87 #define EXT2_BLOCK_SIZE_BITS(s) ((s)->s_blocksize_bits)
  88 #define EXT2_ADDR_PER_BLOCK_BITS(s)     (EXT2_SB(s)->addr_per_block_bits)
  89 #define EXT2_INODE_SIZE(s)      (EXT2_SB(s)->s_inode_size)
  90 #define EXT2_FIRST_INO(s)       (EXT2_SB(s)->s_first_ino)
  91 #else
  92 #define EXT2_BLOCK_SIZE(s)      (EXT2_MIN_BLOCK_SIZE << (s)->s_log_block_size)
  93 #define EXT2_BLOCK_SIZE_BITS(s) ((s)->s_log_block_size + 10)
  94 #define EXT2_INODE_SIZE(s)      (((s)->s_rev_level == EXT2_GOOD_OLD_REV) ? \
  95                                  EXT2_GOOD_OLD_INODE_SIZE : (s)->s_inode_size)
  96 #define EXT2_FIRST_INO(s)       (((s)->s_rev_level == EXT2_GOOD_OLD_REV) ? \
  97                                  EXT2_GOOD_OLD_FIRST_INO : (s)->s_first_ino)
  98 #endif
  99 #define EXT2_ADDR_PER_BLOCK(s)  (EXT2_BLOCK_SIZE(s) / sizeof(__u32))
 100
 101 /*
 102  * Macro-instructions used to manage allocation clusters
 103  */
 104 #define EXT2_MIN_CLUSTER_LOG_SIZE       EXT2_MIN_BLOCK_LOG_SIZE
 105 #define EXT2_MAX_CLUSTER_LOG_SIZE       29      /* 512MB  */
 106 #define EXT2_MIN_CLUSTER_SIZE           EXT2_MIN_BLOCK_SIZE
 107 #define EXT2_MAX_CLUSTER_SIZE           (1 << EXT2_MAX_CLUSTER_LOG_SIZE)
 108 #define EXT2_CLUSTER_SIZE(s)            (EXT2_MIN_BLOCK_SIZE << \
 109                                                 (s)->s_log_cluster_size)
 110 #define EXT2_CLUSTER_SIZE_BITS(s)       ((s)->s_log_cluster_size + 10)
 111
 112 /*
 113  * Macro-instructions used to manage fragments
 114  *
 115  * Note: for backwards compatibility only, for the dump program.
 116  * Ext2/3/4 will never support fragments....
 117  */
 118 #define EXT2_MIN_FRAG_SIZE              EXT2_MIN_BLOCK_SIZE
 119 #define EXT2_MAX_FRAG_SIZE              EXT2_MAX_BLOCK_SIZE
 120 #define EXT2_MIN_FRAG_LOG_SIZE          EXT2_MIN_BLOCK_LOG_SIZE
 121 #define EXT2_FRAG_SIZE(s)               EXT2_BLOCK_SIZE(s)
 122 #define EXT2_FRAGS_PER_BLOCK(s)         1
 123
 124 /*
 125  * ACL structures
 126  */
 127 struct ext2_acl_header  /* Header of Access Control Lists */
 128 {
 129         __u32   aclh_size;
 130         __u32   aclh_file_count;
 131         __u32   aclh_acle_count;
 132         __u32   aclh_first_acle;
 133 };
 134
 135 struct ext2_acl_entry   /* Access Control List Entry */
 136 {
 137         __u32   acle_size;
 138         __u16   acle_perms;     /* Access permissions */
 139         __u16   acle_type;      /* Type of entry */
 140         __u16   acle_tag;       /* User or group identity */
 141         __u16   acle_pad1;
 142         __u32   acle_next;      /* Pointer on next entry for the */
 143                                         /* same inode or on next free entry */
 144 };
 145
 146 /*
 147  * Structure of a blocks group descriptor
 148  */
 149 struct ext2_group_desc
 150 {
 151         __u32   bg_block_bitmap;        /* Blocks bitmap block */
 152         __u32   bg_inode_bitmap;        /* Inodes bitmap block */
 153         __u32   bg_inode_table;         /* Inodes table block */
 154         __u16   bg_free_blocks_count;   /* Free blocks count */
 155         __u16   bg_free_inodes_count;   /* Free inodes count */
 156         __u16   bg_used_dirs_count;     /* Directories count */
 157         __u16   bg_flags;
 158         __u32   bg_exclude_bitmap_lo;   /* Exclude bitmap for snapshots */
 159         __u16   bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
 160         __u16   bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
 161         __u16   bg_itable_unused;       /* Unused inodes count */
 162         __u16   bg_checksum;            /* crc16(s_uuid+group_num+group_desc)*/
 163 };
 164
 165 /*
 166  * Structure of a blocks group descriptor
 167  */
 168 struct ext4_group_desc
 169 {
 170         __u32   bg_block_bitmap;        /* Blocks bitmap block */
 171         __u32   bg_inode_bitmap;        /* Inodes bitmap block */
 172         __u32   bg_inode_table;         /* Inodes table block */
 173         __u16   bg_free_blocks_count;   /* Free blocks count */
 174         __u16   bg_free_inodes_count;   /* Free inodes count */
 175         __u16   bg_used_dirs_count;     /* Directories count */
 176         __u16   bg_flags;               /* EXT4_BG_flags (INODE_UNINIT, etc) */
 177         __u32   bg_exclude_bitmap_lo;   /* Exclude bitmap for snapshots */
 178         __u16   bg_block_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
 179         __u16   bg_inode_bitmap_csum_lo;/* crc32c(s_uuid+grp_num+bitmap) LSB */
 180         __u16   bg_itable_unused;       /* Unused inodes count */
 181         __u16   bg_checksum;            /* crc16(sb_uuid+group+desc) */
 182         __u32   bg_block_bitmap_hi;     /* Blocks bitmap block MSB */
 183         __u32   bg_inode_bitmap_hi;     /* Inodes bitmap block MSB */
 184         __u32   bg_inode_table_hi;      /* Inodes table block MSB */
 185         __u16   bg_free_blocks_count_hi;/* Free blocks count MSB */
 186         __u16   bg_free_inodes_count_hi;/* Free inodes count MSB */
 187         __u16   bg_used_dirs_count_hi;  /* Directories count MSB */
 188         __u16   bg_itable_unused_hi;    /* Unused inodes count MSB */
 189         __u32   bg_exclude_bitmap_hi;   /* Exclude bitmap block MSB */
 190         __u16   bg_block_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bitmap) MSB */
 191         __u16   bg_inode_bitmap_csum_hi;/* crc32c(s_uuid+grp_num+bitmap) MSB */
 192         __u32   bg_reserved;
 193 };
 194
 195 #define EXT4_BG_INODE_BITMAP_CSUM_HI_END        \
 196         (offsetof(struct ext4_group_desc, bg_inode_bitmap_csum_hi) + \
 197          sizeof(__u16))
 198 #define EXT4_BG_BLOCK_BITMAP_CSUM_HI_LOCATION   \
 199         (offsetof(struct ext4_group_desc, bg_block_bitmap_csum_hi) + \
 200          sizeof(__u16))
 201
 202 #define EXT2_BG_INODE_UNINIT    0x0001 /* Inode table/bitmap not initialized */
 203 #define EXT2_BG_BLOCK_UNINIT    0x0002 /* Block bitmap not initialized */
 204 #define EXT2_BG_INODE_ZEROED    0x0004 /* On-disk itable initialized to zero */
 205
 206 /*
 207  * Data structures used by the directory indexing feature
 208  *
 209  * Note: all of the multibyte integer fields are little endian.
 210  */
 211
 212 /*
 213  * Note: dx_root_info is laid out so that if it should somehow get
 214  * overlaid by a dirent the two low bits of the hash version will be
 215  * zero.  Therefore, the hash version mod 4 should never be 0.
 216  * Sincerely, the paranoia department.
 217  */
 218 struct ext2_dx_root_info {
 219         __u32 reserved_zero;
 220         __u8 hash_version; /* 0 now, 1 at release */
 221         __u8 info_length; /* 8 */
 222         __u8 indirect_levels;
 223         __u8 unused_flags;
 224 };
 225
 226 #define EXT2_HASH_LEGACY                0
 227 #define EXT2_HASH_HALF_MD4              1
 228 #define EXT2_HASH_TEA                   2
 229 #define EXT2_HASH_LEGACY_UNSIGNED       3 /* reserved for userspace lib */
 230 #define EXT2_HASH_HALF_MD4_UNSIGNED     4 /* reserved for userspace lib */
 231 #define EXT2_HASH_TEA_UNSIGNED          5 /* reserved for userspace lib */
 232
 233 #define EXT2_HASH_FLAG_INCOMPAT 0x1
 234
 235 struct ext2_dx_entry {
 236         __u32 hash;
 237         __u32 block;
 238 };
 239
 240 struct ext2_dx_countlimit {
 241         __u16 limit;
 242         __u16 count;
 243 };
 244
 245 /*
 246  * This goes at the end of each htree block.
 247  */
 248 struct ext2_dx_tail {
 249         __u32 dt_reserved;
 250         __u32 dt_checksum;      /* crc32c(uuid+inum+dxblock) */
 251 };
 252
 253 /*
 254  * Macro-instructions used to manage group descriptors
 255  */
 256 #define EXT2_MIN_DESC_SIZE             32
 257 #define EXT2_MIN_DESC_SIZE_64BIT       64
 258 #define EXT2_MAX_DESC_SIZE             EXT2_MIN_BLOCK_SIZE
 259 #define EXT2_DESC_SIZE(s)                                                \
 260        ((EXT2_SB(s)->s_feature_incompat & EXT4_FEATURE_INCOMPAT_64BIT) ? \
 261         (s)->s_desc_size : EXT2_MIN_DESC_SIZE)
 262
 263 #define EXT2_BLOCKS_PER_GROUP(s)        (EXT2_SB(s)->s_blocks_per_group)
 264 #define EXT2_INODES_PER_GROUP(s)        (EXT2_SB(s)->s_inodes_per_group)
 265 #define EXT2_CLUSTERS_PER_GROUP(s)      (EXT2_SB(s)->s_clusters_per_group)
 266 #define EXT2_INODES_PER_BLOCK(s)        (EXT2_BLOCK_SIZE(s)/EXT2_INODE_SIZE(s))
 267 /* limits imposed by 16-bit value gd_free_{blocks,inode}_count */
 268 #define EXT2_MAX_BLOCKS_PER_GROUP(s)    ((((unsigned) 1 << 16) - 8) *   \
 269                                          (EXT2_CLUSTER_SIZE(s) / \
 270                                           EXT2_BLOCK_SIZE(s)))
 271 #define EXT2_MAX_CLUSTERS_PER_GROUP(s)  (((unsigned) 1 << 16) - 8)
 272 #define EXT2_MAX_INODES_PER_GROUP(s)    (((unsigned) 1 << 16) - \
 273                                          EXT2_INODES_PER_BLOCK(s))
 274 #ifdef __KERNEL__
 275 #define EXT2_DESC_PER_BLOCK(s)          (EXT2_SB(s)->s_desc_per_block)
 276 #define EXT2_DESC_PER_BLOCK_BITS(s)     (EXT2_SB(s)->s_desc_per_block_bits)
 277 #else
 278 #define EXT2_DESC_PER_BLOCK(s)          (EXT2_BLOCK_SIZE(s) / EXT2_DESC_SIZE(s))
 279 #endif
 280
 281 /*
 282  * Constants relative to the data blocks
 283  */
 284 #define EXT2_NDIR_BLOCKS                12
 285 #define EXT2_IND_BLOCK                  EXT2_NDIR_BLOCKS
 286 #define EXT2_DIND_BLOCK                 (EXT2_IND_BLOCK + 1)
 287 #define EXT2_TIND_BLOCK                 (EXT2_DIND_BLOCK + 1)
 288 #define EXT2_N_BLOCKS                   (EXT2_TIND_BLOCK + 1)
 289
 290 /*
 291  * Inode flags
 292  */
 293 #define EXT2_SECRM_FL                   0x00000001 /* Secure deletion */
 294 #define EXT2_UNRM_FL                    0x00000002 /* Undelete */
 295 #define EXT2_COMPR_FL                   0x00000004 /* Compress file */
 296 #define EXT2_SYNC_FL                    0x00000008 /* Synchronous updates */
 297 #define EXT2_IMMUTABLE_FL               0x00000010 /* Immutable file */
 298 #define EXT2_APPEND_FL                  0x00000020 /* writes to file may only append */
 299 #define EXT2_NODUMP_FL                  0x00000040 /* do not dump file */
 300 #define EXT2_NOATIME_FL                 0x00000080 /* do not update atime */
 301 /* Reserved for compression usage... */
 302 #define EXT2_DIRTY_FL                   0x00000100
 303 #define EXT2_COMPRBLK_FL                0x00000200 /* One or more compressed clusters */
 304 #define EXT2_NOCOMPR_FL                 0x00000400 /* Access raw compressed data */
 305 #define EXT2_ECOMPR_FL                  0x00000800 /* Compression error */
 306 /* End compression flags --- maybe not all used */
 307 #define EXT2_BTREE_FL                   0x00001000 /* btree format dir */
 308 #define EXT2_INDEX_FL                   0x00001000 /* hash-indexed directory */
 309 #define EXT2_IMAGIC_FL                  0x00002000
 310 #define EXT3_JOURNAL_DATA_FL            0x00004000 /* file data should be journaled */
 311 #define EXT2_NOTAIL_FL                  0x00008000 /* file tail should not be merged */
 312 #define EXT2_DIRSYNC_FL                 0x00010000 /* Synchronous directory modifications */
 313 #define EXT2_TOPDIR_FL                  0x00020000 /* Top of directory hierarchies*/
 314 #define EXT4_HUGE_FILE_FL               0x00040000 /* Set to each huge file */
 315 #define EXT4_EXTENTS_FL                 0x00080000 /* Inode uses extents */
 316 #define EXT4_EA_INODE_FL                0x00200000 /* Inode used for large EA */
 317 /* EXT4_EOFBLOCKS_FL 0x00400000 was here */
 318 #define FS_NOCOW_FL                     0x00800000 /* Do not cow file */
 319 #define EXT4_SNAPFILE_FL                0x01000000  /* Inode is a snapshot */
 320 #define EXT4_SNAPFILE_DELETED_FL        0x04000000  /* Snapshot is being deleted */
 321 #define EXT4_SNAPFILE_SHRUNK_FL         0x08000000  /* Snapshot shrink has completed */
 322 #define EXT4_INLINE_DATA_FL             0x10000000 /* Inode has inline data */
 323 #define EXT2_RESERVED_FL                0x80000000 /* reserved for ext2 lib */
 324
 325 #define EXT2_FL_USER_VISIBLE            0x004BDFFF /* User visible flags */
 326 #define EXT2_FL_USER_MODIFIABLE         0x004B80FF /* User modifiable flags */
 327
 328 /*
 329  * ioctl commands
 330  */
 331
 332 /* Used for online resize */
 333 struct ext2_new_group_input {
 334         __u32 group;            /* Group number for this data */
 335         __u32 block_bitmap;     /* Absolute block number of block bitmap */
 336         __u32 inode_bitmap;     /* Absolute block number of inode bitmap */
 337         __u32 inode_table;      /* Absolute block number of inode table start */
 338         __u32 blocks_count;     /* Total number of blocks in this group */
 339         __u16 reserved_blocks;  /* Number of reserved blocks in this group */
 340         __u16 unused;           /* Number of reserved GDT blocks in group */
 341 };
 342
 343 struct ext4_new_group_input {
 344         __u32 group;            /* Group number for this data */
 345         __u64 block_bitmap;     /* Absolute block number of block bitmap */
 346         __u64 inode_bitmap;     /* Absolute block number of inode bitmap */
 347         __u64 inode_table;      /* Absolute block number of inode table start */
 348         __u32 blocks_count;     /* Total number of blocks in this group */
 349         __u16 reserved_blocks;  /* Number of reserved blocks in this group */
 350         __u16 unused;
 351 };
 352
 353 #ifdef __GNU__                  /* Needed for the Hurd */
 354 #define _IOT_ext2_new_group_input _IOT (_IOTS(__u32), 5, _IOTS(__u16), 2, 0, 0)
 355 #endif
 356
 357 #define EXT2_IOC_GETFLAGS               _IOR('f', 1, long)
 358 #define EXT2_IOC_SETFLAGS               _IOW('f', 2, long)
 359 #define EXT2_IOC_GETVERSION             _IOR('v', 1, long)
 360 #define EXT2_IOC_SETVERSION             _IOW('v', 2, long)
 361 #define EXT2_IOC_GETVERSION_NEW         _IOR('f', 3, long)
 362 #define EXT2_IOC_SETVERSION_NEW         _IOW('f', 4, long)
 363 #define EXT2_IOC_GROUP_EXTEND           _IOW('f', 7, unsigned long)
 364 #define EXT2_IOC_GROUP_ADD              _IOW('f', 8,struct ext2_new_group_input)
 365 #define EXT4_IOC_GROUP_ADD              _IOW('f', 8,struct ext4_new_group_input)
 366 #define EXT4_IOC_RESIZE_FS              _IOW('f', 16, __u64)
 367
 368 /*
 369  * Structure of an inode on the disk
 370  */
 371 struct ext2_inode {
 372         __u16   i_mode;         /* File mode */
 373         __u16   i_uid;          /* Low 16 bits of Owner Uid */
 374         __u32   i_size;         /* Size in bytes */
 375         __u32   i_atime;        /* Access time */
 376         __u32   i_ctime;        /* Inode change time */
 377         __u32   i_mtime;        /* Modification time */
 378         __u32   i_dtime;        /* Deletion Time */
 379         __u16   i_gid;          /* Low 16 bits of Group Id */
 380         __u16   i_links_count;  /* Links count */
 381         __u32   i_blocks;       /* Blocks count */
 382         __u32   i_flags;        /* File flags */
 383         union {
 384                 struct {
 385                         __u32   l_i_version; /* was l_i_reserved1 */
 386                 } linux1;
 387                 struct {
 388                         __u32  h_i_translator;
 389                 } hurd1;
 390         } osd1;                         /* OS dependent 1 */
 391         __u32   i_block[EXT2_N_BLOCKS];/* Pointers to blocks */
 392         __u32   i_generation;   /* File version (for NFS) */
 393         __u32   i_file_acl;     /* File ACL */
 394         __u32   i_size_high;    /* Formerly i_dir_acl, directory ACL */
 395         __u32   i_faddr;        /* Fragment address */
 396         union {
 397                 struct {
 398                         __u16   l_i_blocks_hi;
 399                         __u16   l_i_file_acl_high;
 400                         __u16   l_i_uid_high;   /* these 2 fields    */
 401                         __u16   l_i_gid_high;   /* were reserved2[0] */
 402                         __u16   l_i_checksum_lo; /* crc32c(uuid+inum+inode) */
 403                         __u16   l_i_reserved;
 404                 } linux2;
 405                 struct {
 406                         __u8    h_i_frag;       /* Fragment number */
 407                         __u8    h_i_fsize;      /* Fragment size */
 408                         __u16   h_i_mode_high;
 409                         __u16   h_i_uid_high;
 410                         __u16   h_i_gid_high;
 411                         __u32   h_i_author;
 412                 } hurd2;
 413         } osd2;                         /* OS dependent 2 */
 414 };
 415
 416 /*
 417  * Permanent part of an large inode on the disk
 418  */
 419 struct ext2_inode_large {
 420         __u16   i_mode;         /* File mode */
 421         __u16   i_uid;          /* Low 16 bits of Owner Uid */
 422         __u32   i_size;         /* Size in bytes */
 423         __u32   i_atime;        /* Access time */
 424         __u32   i_ctime;        /* Inode Change time */
 425         __u32   i_mtime;        /* Modification time */
 426         __u32   i_dtime;        /* Deletion Time */
 427         __u16   i_gid;          /* Low 16 bits of Group Id */
 428         __u16   i_links_count;  /* Links count */
 429         __u32   i_blocks;       /* Blocks count */
 430         __u32   i_flags;        /* File flags */
 431         union {
 432                 struct {
 433                         __u32   l_i_version; /* was l_i_reserved1 */
 434                 } linux1;
 435                 struct {
 436                         __u32  h_i_translator;
 437                 } hurd1;
 438         } osd1;                         /* OS dependent 1 */
 439         __u32   i_block[EXT2_N_BLOCKS];/* Pointers to blocks */
 440         __u32   i_generation;   /* File version (for NFS) */
 441         __u32   i_file_acl;     /* File ACL */
 442         __u32   i_size_high;    /* Formerly i_dir_acl, directory ACL */
 443         __u32   i_faddr;        /* Fragment address */
 444         union {
 445                 struct {
 446                         __u16   l_i_blocks_hi;
 447                         __u16   l_i_file_acl_high;
 448                         __u16   l_i_uid_high;   /* these 2 fields    */
 449                         __u16   l_i_gid_high;   /* were reserved2[0] */
 450                         __u16   l_i_checksum_lo; /* crc32c(uuid+inum+inode) */
 451                         __u16   l_i_reserved;
 452                 } linux2;
 453                 struct {
 454                         __u8    h_i_frag;       /* Fragment number */
 455                         __u8    h_i_fsize;      /* Fragment size */
 456                         __u16   h_i_mode_high;
 457                         __u16   h_i_uid_high;
 458                         __u16   h_i_gid_high;
 459                         __u32   h_i_author;
 460                 } hurd2;
 461         } osd2;                         /* OS dependent 2 */
 462         __u16   i_extra_isize;
 463         __u16   i_checksum_hi;  /* crc32c(uuid+inum+inode) */
 464         __u32   i_ctime_extra;  /* extra Change time (nsec << 2 | epoch) */
 465         __u32   i_mtime_extra;  /* extra Modification time (nsec << 2 | epoch) */
 466         __u32   i_atime_extra;  /* extra Access time (nsec << 2 | epoch) */
 467         __u32   i_crtime;       /* File creation time */
 468         __u32   i_crtime_extra; /* extra File creation time (nsec << 2 | epoch)*/
 469         __u32   i_version_hi;   /* high 32 bits for 64-bit version */
 470 };
 471
 472 #define EXT4_INODE_CSUM_HI_EXTRA_END    \
 473         (offsetof(struct ext2_inode_large, i_checksum_hi) + sizeof(__u16) - \
 474          EXT2_GOOD_OLD_INODE_SIZE)
 475
 476 #define i_dir_acl       i_size_high
 477
 478 #define i_checksum_lo   osd2.linux2.l_i_checksum_lo
 479
 480 #if defined(__KERNEL__) || defined(__linux__)
 481 #define i_reserved1     osd1.linux1.l_i_reserved1
 482 #define i_frag          osd2.linux2.l_i_frag
 483 #define i_fsize         osd2.linux2.l_i_fsize
 484 #define i_uid_low       i_uid
 485 #define i_gid_low       i_gid
 486 #define i_uid_high      osd2.linux2.l_i_uid_high
 487 #define i_gid_high      osd2.linux2.l_i_gid_high
 488 #else
 489 #if defined(__GNU__)
 490
 491 #define i_translator    osd1.hurd1.h_i_translator
 492 #define i_frag          osd2.hurd2.h_i_frag;
 493 #define i_fsize         osd2.hurd2.h_i_fsize;
 494 #define i_uid_high      osd2.hurd2.h_i_uid_high
 495 #define i_gid_high      osd2.hurd2.h_i_gid_high
 496 #define i_author        osd2.hurd2.h_i_author
 497
 498 #endif  /* __GNU__ */
 499 #endif  /* defined(__KERNEL__) || defined(__linux__) */
 500
 501 #define inode_uid(inode)        ((inode).i_uid | (inode).osd2.linux2.l_i_uid_high << 16)
 502 #define inode_gid(inode)        ((inode).i_gid | (inode).osd2.linux2.l_i_gid_high << 16)
 503 #define ext2fs_set_i_uid_high(inode,x) ((inode).osd2.linux2.l_i_uid_high = (x))
 504 #define ext2fs_set_i_gid_high(inode,x) ((inode).osd2.linux2.l_i_gid_high = (x))
 505
 506 /*
 507  * File system states
 508  */
 509 #define EXT2_VALID_FS                   0x0001  /* Unmounted cleanly */
 510 #define EXT2_ERROR_FS                   0x0002  /* Errors detected */
 511 #define EXT3_ORPHAN_FS                  0x0004  /* Orphans being recovered */
 512
 513 /*
 514  * Misc. filesystem flags
 515  */
 516 #define EXT2_FLAGS_SIGNED_HASH          0x0001  /* Signed dirhash in use */
 517 #define EXT2_FLAGS_UNSIGNED_HASH        0x0002  /* Unsigned dirhash in use */
 518 #define EXT2_FLAGS_TEST_FILESYS         0x0004  /* OK for use on development code */
 519 #define EXT2_FLAGS_IS_SNAPSHOT          0x0010  /* This is a snapshot image */
 520 #define EXT2_FLAGS_FIX_SNAPSHOT         0x0020  /* Snapshot inodes corrupted */
 521 #define EXT2_FLAGS_FIX_EXCLUDE          0x0040  /* Exclude bitmaps corrupted */
 522
 523 /*
 524  * Mount flags
 525  */
 526 #define EXT2_MOUNT_CHECK                0x0001  /* Do mount-time checks */
 527 #define EXT2_MOUNT_GRPID                0x0004  /* Create files with directory's group */
 528 #define EXT2_MOUNT_DEBUG                0x0008  /* Some debugging messages */
 529 #define EXT2_MOUNT_ERRORS_CONT          0x0010  /* Continue on errors */
 530 #define EXT2_MOUNT_ERRORS_RO            0x0020  /* Remount fs ro on errors */
 531 #define EXT2_MOUNT_ERRORS_PANIC         0x0040  /* Panic on errors */
 532 #define EXT2_MOUNT_MINIX_DF             0x0080  /* Mimics the Minix statfs */
 533 #define EXT2_MOUNT_NO_UID32             0x0200  /* Disable 32-bit UIDs */
 534
 535 #define clear_opt(o, opt)               o &= ~EXT2_MOUNT_##opt
 536 #define set_opt(o, opt)                 o |= EXT2_MOUNT_##opt
 537 #define test_opt(sb, opt)               (EXT2_SB(sb)->s_mount_opt & \
 538                                          EXT2_MOUNT_##opt)
 539 /*
 540  * Maximal mount counts between two filesystem checks
 541  */
 542 #define EXT2_DFL_MAX_MNT_COUNT          20      /* Allow 20 mounts */
 543 #define EXT2_DFL_CHECKINTERVAL          0       /* Don't use interval check */
 544
 545 /*
 546  * Behaviour when detecting errors
 547  */
 548 #define EXT2_ERRORS_CONTINUE            1       /* Continue execution */
 549 #define EXT2_ERRORS_RO                  2       /* Remount fs read-only */
 550 #define EXT2_ERRORS_PANIC               3       /* Panic */
 551 #define EXT2_ERRORS_DEFAULT             EXT2_ERRORS_CONTINUE
 552
 553 #if (__GNUC__ >= 4)
 554 #define ext4_offsetof(TYPE,MEMBER) __builtin_offsetof(TYPE,MEMBER)
 555 #else
 556 #define ext4_offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
 557 #endif
 558
 559 /* Metadata checksum algorithms */
 560 #define EXT2_CRC32C_CHKSUM              1
 561
 562 /*
 563  * Structure of the super block
 564  */
 565 struct ext2_super_block {
 566         __u32   s_inodes_count;         /* Inodes count */
 567         __u32   s_blocks_count;         /* Blocks count */
 568         __u32   s_r_blocks_count;       /* Reserved blocks count */
 569         __u32   s_free_blocks_count;    /* Free blocks count */
 570         __u32   s_free_inodes_count;    /* Free inodes count */
 571         __u32   s_first_data_block;     /* First Data Block */
 572         __u32   s_log_block_size;       /* Block size */
 573         __u32   s_log_cluster_size;     /* Allocation cluster size */
 574         __u32   s_blocks_per_group;     /* # Blocks per group */
 575         __u32   s_clusters_per_group;   /* # Fragments per group */
 576         __u32   s_inodes_per_group;     /* # Inodes per group */
 577         __u32   s_mtime;                /* Mount time */
 578         __u32   s_wtime;                /* Write time */
 579         __u16   s_mnt_count;            /* Mount count */
 580         __s16   s_max_mnt_count;        /* Maximal mount count */
 581         __u16   s_magic;                /* Magic signature */
 582         __u16   s_state;                /* File system state */
 583         __u16   s_errors;               /* Behaviour when detecting errors */
 584         __u16   s_minor_rev_level;      /* minor revision level */
 585         __u32   s_lastcheck;            /* time of last check */
 586         __u32   s_checkinterval;        /* max. time between checks */
 587         __u32   s_creator_os;           /* OS */
 588         __u32   s_rev_level;            /* Revision level */
 589         __u16   s_def_resuid;           /* Default uid for reserved blocks */
 590         __u16   s_def_resgid;           /* Default gid for reserved blocks */
 591         /*
 592          * These fields are for EXT2_DYNAMIC_REV superblocks only.
 593          *
 594          * Note: the difference between the compatible feature set and
 595          * the incompatible feature set is that if there is a bit set
 596          * in the incompatible feature set that the kernel doesn't
 597          * know about, it should refuse to mount the filesystem.
 598          *
 599          * e2fsck's requirements are more strict; if it doesn't know
 600          * about a feature in either the compatible or incompatible
 601          * feature set, it must abort and not try to meddle with
 602          * things it doesn't understand...
 603          */
 604         __u32   s_first_ino;            /* First non-reserved inode */
 605         __u16   s_inode_size;           /* size of inode structure */
 606         __u16   s_block_group_nr;       /* block group # of this superblock */
 607         __u32   s_feature_compat;       /* compatible feature set */
 608         __u32   s_feature_incompat;     /* incompatible feature set */
 609         __u32   s_feature_ro_compat;    /* readonly-compatible feature set */
 610         __u8    s_uuid[16];             /* 128-bit uuid for volume */
 611         char    s_volume_name[16];      /* volume name */
 612         char    s_last_mounted[64];     /* directory where last mounted */
 613         __u32   s_algorithm_usage_bitmap; /* For compression */
 614         /*
 615          * Performance hints.  Directory preallocation should only
 616          * happen if the EXT2_FEATURE_COMPAT_DIR_PREALLOC flag is on.
 617          */
 618         __u8    s_prealloc_blocks;      /* Nr of blocks to try to preallocate*/
 619         __u8    s_prealloc_dir_blocks;  /* Nr to preallocate for dirs */
 620         __u16   s_reserved_gdt_blocks;  /* Per group table for online growth */
 621         /*
 622          * Journaling support valid if EXT2_FEATURE_COMPAT_HAS_JOURNAL set.
 623          */
 624         __u8    s_journal_uuid[16];     /* uuid of journal superblock */
 625         __u32   s_journal_inum;         /* inode number of journal file */
 626         __u32   s_journal_dev;          /* device number of journal file */
 627         __u32   s_last_orphan;          /* start of list of inodes to delete */
 628         __u32   s_hash_seed[4];         /* HTREE hash seed */
 629         __u8    s_def_hash_version;     /* Default hash version to use */
 630         __u8    s_jnl_backup_type;      /* Default type of journal backup */
 631         __u16   s_desc_size;            /* Group desc. size: INCOMPAT_64BIT */
 632         __u32   s_default_mount_opts;
 633         __u32   s_first_meta_bg;        /* First metablock group */
 634         __u32   s_mkfs_time;            /* When the filesystem was created */
 635         __u32   s_jnl_blocks[17];       /* Backup of the journal inode */
 636         __u32   s_blocks_count_hi;      /* Blocks count high 32bits */
 637         __u32   s_r_blocks_count_hi;    /* Reserved blocks count high 32 bits*/
 638         __u32   s_free_blocks_hi;       /* Free blocks count */
 639         __u16   s_min_extra_isize;      /* All inodes have at least # bytes */
 640         __u16   s_want_extra_isize;     /* New inodes should reserve # bytes */
 641         __u32   s_flags;                /* Miscellaneous flags */
 642         __u16   s_raid_stride;          /* RAID stride */
 643         __u16   s_mmp_update_interval;  /* # seconds to wait in MMP checking */
 644         __u64   s_mmp_block;            /* Block for multi-mount protection */
 645         __u32   s_raid_stripe_width;    /* blocks on all data disks (N*stride)*/
 646         __u8    s_log_groups_per_flex;  /* FLEX_BG group size */
 647         __u8    s_checksum_type;        /* metadata checksum algorithm */
 648         __u16   s_reserved_pad;         /* Padding to next 32bits */
 649         __u64   s_kbytes_written;       /* nr of lifetime kilobytes written */
 650         __u32   s_snapshot_inum;        /* Inode number of active snapshot */
 651         __u32   s_snapshot_id;          /* sequential ID of active snapshot */
 652         __u64   s_snapshot_r_blocks_count; /* reserved blocks for active
 653                                               snapshot's future use */
 654         __u32   s_snapshot_list;        /* inode number of the head of the on-disk snapshot list */
 655 #define EXT4_S_ERR_START ext4_offsetof(struct ext2_super_block, s_error_count)
 656         __u32   s_error_count;          /* number of fs errors */
 657         __u32   s_first_error_time;     /* first time an error happened */
 658         __u32   s_first_error_ino;      /* inode involved in first error */
 659         __u64   s_first_error_block;    /* block involved of first error */
 660         __u8    s_first_error_func[32]; /* function where the error happened */
 661         __u32   s_first_error_line;     /* line number where error happened */
 662         __u32   s_last_error_time;      /* most recent time of an error */
 663         __u32   s_last_error_ino;       /* inode involved in last error */
 664         __u32   s_last_error_line;      /* line number where error happened */
 665         __u64   s_last_error_block;     /* block involved of last error */
 666         __u8    s_last_error_func[32];  /* function where the error happened */
 667 #define EXT4_S_ERR_END ext4_offsetof(struct ext2_super_block, s_mount_opts)
 668         __u8    s_mount_opts[64];
 669         __u32   s_usr_quota_inum;       /* inode number of user quota file */
 670         __u32   s_grp_quota_inum;       /* inode number of group quota file */
 671         __u32   s_overhead_blocks;      /* overhead blocks/clusters in fs */
 672         __u32   s_backup_bgs[2];        /* If sparse_super2 enabled */
 673         __u32   s_reserved[106];        /* Padding to the end of the block */
 674         __u32   s_checksum;             /* crc32c(superblock) */
 675 };
 676
 677 #define EXT4_S_ERR_LEN (EXT4_S_ERR_END - EXT4_S_ERR_START)
 678
 679 /*
 680  * Codes for operating systems
 681  */
 682 #define EXT2_OS_LINUX           0
 683 #define EXT2_OS_HURD            1
 684 #define EXT2_OBSO_OS_MASIX      2
 685 #define EXT2_OS_FREEBSD         3
 686 #define EXT2_OS_LITES           4
 687
 688 /*
 689  * Revision levels
 690  */
 691 #define EXT2_GOOD_OLD_REV       0       /* The good old (original) format */
 692 #define EXT2_DYNAMIC_REV        1       /* V2 format w/ dynamic inode sizes */
 693
 694 #define EXT2_CURRENT_REV        EXT2_GOOD_OLD_REV
 695 #define EXT2_MAX_SUPP_REV       EXT2_DYNAMIC_REV
 696
 697 #define EXT2_GOOD_OLD_INODE_SIZE 128
 698
 699 /*
 700  * Journal inode backup types
 701  */
 702 #define EXT3_JNL_BACKUP_BLOCKS  1
 703
 704 /*
 705  * Feature set definitions
 706  */
 707
 708 #define EXT2_HAS_COMPAT_FEATURE(sb,mask)                        \
 709         ( EXT2_SB(sb)->s_feature_compat & (mask) )
 710 #define EXT2_HAS_RO_COMPAT_FEATURE(sb,mask)                     \
 711         ( EXT2_SB(sb)->s_feature_ro_compat & (mask) )
 712 #define EXT2_HAS_INCOMPAT_FEATURE(sb,mask)                      \
 713         ( EXT2_SB(sb)->s_feature_incompat & (mask) )
 714
 715 #define EXT2_FEATURE_COMPAT_DIR_PREALLOC        0x0001
 716 #define EXT2_FEATURE_COMPAT_IMAGIC_INODES       0x0002
 717 #define EXT3_FEATURE_COMPAT_HAS_JOURNAL         0x0004
 718 #define EXT2_FEATURE_COMPAT_EXT_ATTR            0x0008
 719 #define EXT2_FEATURE_COMPAT_RESIZE_INODE        0x0010
 720 #define EXT2_FEATURE_COMPAT_DIR_INDEX           0x0020
 721 #define EXT2_FEATURE_COMPAT_LAZY_BG             0x0040
 722 /* #define EXT2_FEATURE_COMPAT_EXCLUDE_INODE    0x0080 not used, legacy */
 723 #define EXT2_FEATURE_COMPAT_EXCLUDE_BITMAP      0x0100
 724 #define EXT4_FEATURE_COMPAT_SPARSE_SUPER2       0x0200
 725
 726
 727 #define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER     0x0001
 728 #define EXT2_FEATURE_RO_COMPAT_LARGE_FILE       0x0002
 729 /* #define EXT2_FEATURE_RO_COMPAT_BTREE_DIR     0x0004 not used */
 730 #define EXT4_FEATURE_RO_COMPAT_HUGE_FILE        0x0008
 731 #define EXT4_FEATURE_RO_COMPAT_GDT_CSUM         0x0010
 732 #define EXT4_FEATURE_RO_COMPAT_DIR_NLINK        0x0020
 733 #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE      0x0040
 734 #define EXT4_FEATURE_RO_COMPAT_HAS_SNAPSHOT     0x0080
 735 #define EXT4_FEATURE_RO_COMPAT_QUOTA            0x0100
 736 #define EXT4_FEATURE_RO_COMPAT_BIGALLOC         0x0200
 737 /*
 738  * METADATA_CSUM implies GDT_CSUM.  When METADATA_CSUM is set, group
 739  * descriptor checksums use the same algorithm as all other data
 740  * structures' checksums.
 741  */
 742 #define EXT4_FEATURE_RO_COMPAT_METADATA_CSUM    0x0400
 743 #define EXT4_FEATURE_RO_COMPAT_REPLICA          0x0800
 744
 745 #define EXT2_FEATURE_INCOMPAT_COMPRESSION       0x0001
 746 #define EXT2_FEATURE_INCOMPAT_FILETYPE          0x0002
 747 #define EXT3_FEATURE_INCOMPAT_RECOVER           0x0004 /* Needs recovery */
 748 #define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV       0x0008 /* Journal device */
 749 #define EXT2_FEATURE_INCOMPAT_META_BG           0x0010
 750 #define EXT3_FEATURE_INCOMPAT_EXTENTS           0x0040
 751 #define EXT4_FEATURE_INCOMPAT_64BIT             0x0080
 752 #define EXT4_FEATURE_INCOMPAT_MMP               0x0100
 753 #define EXT4_FEATURE_INCOMPAT_FLEX_BG           0x0200
 754 #define EXT4_FEATURE_INCOMPAT_EA_INODE          0x0400
 755 #define EXT4_FEATURE_INCOMPAT_DIRDATA           0x1000
 756 /* 0x2000 was EXT4_FEATURE_INCOMPAT_BG_USE_META_CSUM but this was never used */
 757 #define EXT4_FEATURE_INCOMPAT_LARGEDIR          0x4000 /* >2GB or 3-lvl htree */
 758 #define EXT4_FEATURE_INCOMPAT_INLINE_DATA       0x8000 /* data in inode */
 759
 760 #define EXT2_FEATURE_COMPAT_SUPP        0
 761 #define EXT2_FEATURE_INCOMPAT_SUPP    (EXT2_FEATURE_INCOMPAT_FILETYPE| \
 762                                        EXT4_FEATURE_INCOMPAT_MMP)
 763 #define EXT2_FEATURE_RO_COMPAT_SUPP     (EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
 764                                          EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
 765                                          EXT4_FEATURE_RO_COMPAT_DIR_NLINK| \
 766                                          EXT2_FEATURE_RO_COMPAT_BTREE_DIR)
 767
 768 /*
 769  * Default values for user and/or group using reserved blocks
 770  */
 771 #define EXT2_DEF_RESUID         0
 772 #define EXT2_DEF_RESGID         0
 773
 774 /*
 775  * Default mount options
 776  */
 777 #define EXT2_DEFM_DEBUG         0x0001
 778 #define EXT2_DEFM_BSDGROUPS     0x0002
 779 #define EXT2_DEFM_XATTR_USER    0x0004
 780 #define EXT2_DEFM_ACL           0x0008
 781 #define EXT2_DEFM_UID16         0x0010
 782 #define EXT3_DEFM_JMODE         0x0060
 783 #define EXT3_DEFM_JMODE_DATA    0x0020
 784 #define EXT3_DEFM_JMODE_ORDERED 0x0040
 785 #define EXT3_DEFM_JMODE_WBACK   0x0060
 786 #define EXT4_DEFM_NOBARRIER     0x0100
 787 #define EXT4_DEFM_BLOCK_VALIDITY 0x0200
 788 #define EXT4_DEFM_DISCARD       0x0400
 789 #define EXT4_DEFM_NODELALLOC    0x0800
 790
 791 /*
 792  * Structure of a directory entry
 793  */
 794 #define EXT2_NAME_LEN 255
 795
 796 struct ext2_dir_entry {
 797         __u32   inode;                  /* Inode number */
 798         __u16   rec_len;                /* Directory entry length */
 799         __u16   name_len;               /* Name length */
 800         char    name[EXT2_NAME_LEN];    /* File name */
 801 };
 802
 803 /*
 804  * The new version of the directory entry.  Since EXT2 structures are
 805  * stored in intel byte order, and the name_len field could never be
 806  * bigger than 255 chars, it's safe to reclaim the extra byte for the
 807  * file_type field.
 808  *
 809  * This structure is deprecated due to endianity issues. Please use struct
 810  * ext2_dir_entry and accessor functions
 811  *   ext2fs_dirent_name_len
 812  *   ext2fs_dirent_set_name_len
 813  *   ext2fs_dirent_file_type
 814  *   ext2fs_dirent_set_file_type
 815  * to get and set name_len and file_type fields.
 816  */
 817 struct ext2_dir_entry_2 {
 818         __u32   inode;                  /* Inode number */
 819         __u16   rec_len;                /* Directory entry length */
 820         __u8    name_len;               /* Name length */
 821         __u8    file_type;
 822         char    name[EXT2_NAME_LEN];    /* File name */
 823 };
 824
 825 /*
 826  * This is a bogus directory entry at the end of each leaf block that
 827  * records checksums.
 828  */
 829 struct ext2_dir_entry_tail {
 830         __u32   det_reserved_zero1;     /* Pretend to be unused */
 831         __u16   det_rec_len;            /* 12 */
 832         __u16   det_reserved_name_len;  /* 0xDE00, fake namelen/filetype */
 833         __u32   det_checksum;           /* crc32c(uuid+inode+dirent) */
 834 };
 835
 836 /*
 837  * Ext2 directory file types.  Only the low 3 bits are used.  The
 838  * other bits are reserved for now.
 839  */
 840 #define EXT2_FT_UNKNOWN         0
 841 #define EXT2_FT_REG_FILE        1
 842 #define EXT2_FT_DIR             2
 843 #define EXT2_FT_CHRDEV          3
 844 #define EXT2_FT_BLKDEV          4
 845 #define EXT2_FT_FIFO            5
 846 #define EXT2_FT_SOCK            6
 847 #define EXT2_FT_SYMLINK         7
 848
 849 #define EXT2_FT_MAX             8
 850
 851 /*
 852  * Annoyingly, e2fsprogs always swab16s ext2_dir_entry.name_len, so we
 853  * have to build ext2_dir_entry_tail with that assumption too.  This
 854  * constant helps to build the dir_entry_tail to look like it has an
 855  * "invalid" file type.
 856  */
 857 #define EXT2_DIR_NAME_LEN_CSUM  0xDE00
 858
 859 /*
 860  * EXT2_DIR_PAD defines the directory entries boundaries
 861  *
 862  * NOTE: It must be a multiple of 4
 863  */
 864 #define EXT2_DIR_PAD                    4
 865 #define EXT2_DIR_ROUND                  (EXT2_DIR_PAD - 1)
 866 #define EXT2_DIR_REC_LEN(name_len)      (((name_len) + 8 + EXT2_DIR_ROUND) & \
 867                                          ~EXT2_DIR_ROUND)
 868
 869 /*
 870  * This structure is used for multiple mount protection. It is written
 871  * into the block number saved in the s_mmp_block field in the superblock.
 872  * Programs that check MMP should assume that if SEQ_FSCK (or any unknown
 873  * code above SEQ_MAX) is present then it is NOT safe to use the filesystem,
 874  * regardless of how old the timestamp is.
 875  *
 876  * The timestamp in the MMP structure will be updated by e2fsck at some
 877  * arbitary intervals (start of passes, after every few groups of inodes
 878  * in pass1 and pass1b).  There is no guarantee that e2fsck is updating
 879  * the MMP block in a timely manner, and the updates it does are purely
 880  * for the convenience of the sysadmin and not for automatic validation.
 881  *
 882  * Note: Only the mmp_seq value is used to determine whether the MMP block
 883  *      is being updated.  The mmp_time, mmp_nodename, and mmp_bdevname
 884  *      fields are only for informational purposes for the administrator,
 885  *      due to clock skew between nodes and hostname HA service takeover.
 886  */
 887 #define EXT4_MMP_MAGIC     0x004D4D50U /* ASCII for MMP */
 888 #define EXT4_MMP_SEQ_CLEAN 0xFF4D4D50U /* mmp_seq value for clean unmount */
 889 #define EXT4_MMP_SEQ_FSCK  0xE24D4D50U /* mmp_seq value when being fscked */
 890 #define EXT4_MMP_SEQ_MAX   0xE24D4D4FU /* maximum valid mmp_seq value */
 891
 892 struct mmp_struct {
 893         __u32   mmp_magic;              /* Magic number for MMP */
 894         __u32   mmp_seq;                /* Sequence no. updated periodically */
 895         __u64   mmp_time;               /* Time last updated */
 896         char    mmp_nodename[64];       /* Node which last updated MMP block */
 897         char    mmp_bdevname[32];       /* Bdev which last updated MMP block */
 898         __u16   mmp_check_interval;     /* Changed mmp_check_interval */
 899         __u16   mmp_pad1;
 900         __u32   mmp_pad2[226];
 901         __u32   mmp_checksum;           /* crc32c(uuid+mmp_block) */
 902 };
 903
 904 /*
 905  * Default interval for MMP update in seconds.
 906  */
 907 #define EXT4_MMP_UPDATE_INTERVAL        5
 908
 909 /*
 910  * Maximum interval for MMP update in seconds.
 911  */
 912 #define EXT4_MMP_MAX_UPDATE_INTERVAL    300
 913
 914 /*
 915  * Minimum interval for MMP checking in seconds.
 916  */
 917 #define EXT4_MMP_MIN_CHECK_INTERVAL     5
 918
 919 /*
 920  * Minimum size of inline data.
 921  */
 922 #define EXT4_MIN_INLINE_DATA_SIZE       ((sizeof(__u32) * EXT2_N_BLOCKS))
 923
 924 /*
 925  * Size of a parent inode in inline data directory.
 926  */
 927 #define EXT4_INLINE_DATA_DOTDOT_SIZE    (4)
 928
 929 #endif  /* _LINUX_EXT2_FS_H */