fs/erofs/erofs_fs.h

   1 /* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
   2 /*
   3  * EROFS (Enhanced ROM File System) on-disk format definition
   4  *
   5  * Copyright (C) 2017-2018 HUAWEI, Inc.
   6  *             https://www.huawei.com/
   7  * Copyright (C) 2021, Alibaba Cloud
   8  */
   9 #ifndef __EROFS_FS_H
  10 #define __EROFS_FS_H
  11
  12 #define EROFS_SUPER_OFFSET      1024
  13
  14 #define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
  15 #define EROFS_FEATURE_COMPAT_MTIME              0x00000002
  16 #define EROFS_FEATURE_COMPAT_XATTR_FILTER       0x00000004
  17
  18 /*
  19  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
  20  * be incompatible with this kernel version.
  21  */
  22 #define EROFS_FEATURE_INCOMPAT_ZERO_PADDING     0x00000001
  23 #define EROFS_FEATURE_INCOMPAT_COMPR_CFGS       0x00000002
  24 #define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER     0x00000002
  25 #define EROFS_FEATURE_INCOMPAT_CHUNKED_FILE     0x00000004
  26 #define EROFS_FEATURE_INCOMPAT_DEVICE_TABLE     0x00000008
  27 #define EROFS_FEATURE_INCOMPAT_COMPR_HEAD2      0x00000008
  28 #define EROFS_FEATURE_INCOMPAT_ZTAILPACKING     0x00000010
  29 #define EROFS_FEATURE_INCOMPAT_FRAGMENTS        0x00000020
  30 #define EROFS_FEATURE_INCOMPAT_DEDUPE           0x00000020
  31 #define EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES   0x00000040
  32 #define EROFS_ALL_FEATURE_INCOMPAT              \
  33         (EROFS_FEATURE_INCOMPAT_ZERO_PADDING | \
  34          EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
  35          EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER | \
  36          EROFS_FEATURE_INCOMPAT_CHUNKED_FILE | \
  37          EROFS_FEATURE_INCOMPAT_DEVICE_TABLE | \
  38          EROFS_FEATURE_INCOMPAT_COMPR_HEAD2 | \
  39          EROFS_FEATURE_INCOMPAT_ZTAILPACKING | \
  40          EROFS_FEATURE_INCOMPAT_FRAGMENTS | \
  41          EROFS_FEATURE_INCOMPAT_DEDUPE | \
  42          EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES)
  43
  44 #define EROFS_SB_EXTSLOT_SIZE   16
  45
  46 struct erofs_deviceslot {
  47         u8 tag[64];             /* digest(sha256), etc. */
  48         __le32 blocks;          /* total fs blocks of this device */
  49         __le32 mapped_blkaddr;  /* map starting at mapped_blkaddr */
  50         u8 reserved[56];
  51 };
  52 #define EROFS_DEVT_SLOT_SIZE    sizeof(struct erofs_deviceslot)
  53
  54 /* erofs on-disk super block (currently 128 bytes) */
  55 struct erofs_super_block {
  56         __le32 magic;           /* file system magic number */
  57         __le32 checksum;        /* crc32c(super_block) */
  58         __le32 feature_compat;
  59         __u8 blkszbits;         /* filesystem block size in bit shift */
  60         __u8 sb_extslots;       /* superblock size = 128 + sb_extslots * 16 */
  61
  62         __le16 root_nid;        /* nid of root directory */
  63         __le64 inos;            /* total valid ino # (== f_files - f_favail) */
  64
  65         __le64 build_time;      /* compact inode time derivation */
  66         __le32 build_time_nsec; /* compact inode time derivation in ns scale */
  67         __le32 blocks;          /* used for statfs */
  68         __le32 meta_blkaddr;    /* start block address of metadata area */
  69         __le32 xattr_blkaddr;   /* start block address of shared xattr area */
  70         __u8 uuid[16];          /* 128-bit uuid for volume */
  71         __u8 volume_name[16];   /* volume name */
  72         __le32 feature_incompat;
  73         union {
  74                 /* bitmap for available compression algorithms */
  75                 __le16 available_compr_algs;
  76                 /* customized sliding window size instead of 64k by default */
  77                 __le16 lz4_max_distance;
  78         } __packed u1;
  79         __le16 extra_devices;   /* # of devices besides the primary device */
  80         __le16 devt_slotoff;    /* startoff = devt_slotoff * devt_slotsize */
  81         __u8 dirblkbits;        /* directory block size in bit shift */
  82         __u8 xattr_prefix_count;        /* # of long xattr name prefixes */
  83         __le32 xattr_prefix_start;      /* start of long xattr prefixes */
  84         __le64 packed_nid;      /* nid of the special packed inode */
  85         __u8 xattr_filter_reserved; /* reserved for xattr name filter */
  86         __u8 reserved2[23];
  87 };
  88
  89 /*
  90  * EROFS inode datalayout (i_format in on-disk inode):
  91  * 0 - uncompressed flat inode without tail-packing inline data:
  92  * 1 - compressed inode with non-compact indexes:
  93  * 2 - uncompressed flat inode with tail-packing inline data:
  94  * 3 - compressed inode with compact indexes:
  95  * 4 - chunk-based inode with (optional) multi-device support:
  96  * 5~7 - reserved
  97  */
  98 enum {
  99         EROFS_INODE_FLAT_PLAIN                  = 0,
 100         EROFS_INODE_COMPRESSED_FULL             = 1,
 101         EROFS_INODE_FLAT_INLINE                 = 2,
 102         EROFS_INODE_COMPRESSED_COMPACT          = 3,
 103         EROFS_INODE_CHUNK_BASED                 = 4,
 104         EROFS_INODE_DATALAYOUT_MAX
 105 };
 106
 107 static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
 108 {
 109         return datamode == EROFS_INODE_COMPRESSED_COMPACT ||
 110                 datamode == EROFS_INODE_COMPRESSED_FULL;
 111 }
 112
 113 /* bit definitions of inode i_format */
 114 #define EROFS_I_VERSION_MASK            0x01
 115 #define EROFS_I_DATALAYOUT_MASK         0x07
 116
 117 #define EROFS_I_VERSION_BIT             0
 118 #define EROFS_I_DATALAYOUT_BIT          1
 119 #define EROFS_I_ALL_BIT                 4
 120
 121 #define EROFS_I_ALL     ((1 << EROFS_I_ALL_BIT) - 1)
 122
 123 /* indicate chunk blkbits, thus 'chunksize = blocksize << chunk blkbits' */
 124 #define EROFS_CHUNK_FORMAT_BLKBITS_MASK         0x001F
 125 /* with chunk indexes or just a 4-byte blkaddr array */
 126 #define EROFS_CHUNK_FORMAT_INDEXES              0x0020
 127
 128 #define EROFS_CHUNK_FORMAT_ALL  \
 129         (EROFS_CHUNK_FORMAT_BLKBITS_MASK | EROFS_CHUNK_FORMAT_INDEXES)
 130
 131 /* 32-byte on-disk inode */
 132 #define EROFS_INODE_LAYOUT_COMPACT      0
 133 /* 64-byte on-disk inode */
 134 #define EROFS_INODE_LAYOUT_EXTENDED     1
 135
 136 struct erofs_inode_chunk_info {
 137         __le16 format;          /* chunk blkbits, etc. */
 138         __le16 reserved;
 139 };
 140
 141 union erofs_inode_i_u {
 142         /* total compressed blocks for compressed inodes */
 143         __le32 compressed_blocks;
 144
 145         /* block address for uncompressed flat inodes */
 146         __le32 raw_blkaddr;
 147
 148         /* for device files, used to indicate old/new device # */
 149         __le32 rdev;
 150
 151         /* for chunk-based files, it contains the summary info */
 152         struct erofs_inode_chunk_info c;
 153 };
 154
 155 /* 32-byte reduced form of an ondisk inode */
 156 struct erofs_inode_compact {
 157         __le16 i_format;        /* inode format hints */
 158
 159 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
 160         __le16 i_xattr_icount;
 161         __le16 i_mode;
 162         __le16 i_nlink;
 163         __le32 i_size;
 164         __le32 i_reserved;
 165         union erofs_inode_i_u i_u;
 166
 167         __le32 i_ino;           /* only used for 32-bit stat compatibility */
 168         __le16 i_uid;
 169         __le16 i_gid;
 170         __le32 i_reserved2;
 171 };
 172
 173 /* 64-byte complete form of an ondisk inode */
 174 struct erofs_inode_extended {
 175         __le16 i_format;        /* inode format hints */
 176
 177 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
 178         __le16 i_xattr_icount;
 179         __le16 i_mode;
 180         __le16 i_reserved;
 181         __le64 i_size;
 182         union erofs_inode_i_u i_u;
 183
 184         __le32 i_ino;           /* only used for 32-bit stat compatibility */
 185         __le32 i_uid;
 186         __le32 i_gid;
 187         __le64 i_mtime;
 188         __le32 i_mtime_nsec;
 189         __le32 i_nlink;
 190         __u8   i_reserved2[16];
 191 };
 192
 193 /*
 194  * inline xattrs (n == i_xattr_icount):
 195  * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
 196  *          12 bytes           /                   \
 197  *                            /                     \
 198  *                           /-----------------------\
 199  *                           |  erofs_xattr_entries+ |
 200  *                           +-----------------------+
 201  * inline xattrs must starts in erofs_xattr_ibody_header,
 202  * for read-only fs, no need to introduce h_refcount
 203  */
 204 struct erofs_xattr_ibody_header {
 205         __le32 h_name_filter;           /* bit value 1 indicates not-present */
 206         __u8   h_shared_count;
 207         __u8   h_reserved2[7];
 208         __le32 h_shared_xattrs[];       /* shared xattr id array */
 209 };
 210
 211 /* Name indexes */
 212 #define EROFS_XATTR_INDEX_USER              1
 213 #define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS  2
 214 #define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
 215 #define EROFS_XATTR_INDEX_TRUSTED           4
 216 #define EROFS_XATTR_INDEX_LUSTRE            5
 217 #define EROFS_XATTR_INDEX_SECURITY          6
 218
 219 /*
 220  * bit 7 of e_name_index is set when it refers to a long xattr name prefix,
 221  * while the remained lower bits represent the index of the prefix.
 222  */
 223 #define EROFS_XATTR_LONG_PREFIX         0x80
 224 #define EROFS_XATTR_LONG_PREFIX_MASK    0x7f
 225
 226 #define EROFS_XATTR_FILTER_BITS         32
 227 #define EROFS_XATTR_FILTER_DEFAULT      UINT32_MAX
 228 #define EROFS_XATTR_FILTER_SEED         0x25BBE08F
 229
 230 /* xattr entry (for both inline & shared xattrs) */
 231 struct erofs_xattr_entry {
 232         __u8   e_name_len;      /* length of name */
 233         __u8   e_name_index;    /* attribute name index */
 234         __le16 e_value_size;    /* size of attribute value */
 235         /* followed by e_name and e_value */
 236         char   e_name[];        /* attribute name */
 237 };
 238
 239 /* long xattr name prefix */
 240 struct erofs_xattr_long_prefix {
 241         __u8   base_index;      /* short xattr name prefix index */
 242         char   infix[];         /* infix apart from short prefix */
 243 };
 244
 245 static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount)
 246 {
 247         if (!i_xattr_icount)
 248                 return 0;
 249
 250         return sizeof(struct erofs_xattr_ibody_header) +
 251                 sizeof(__u32) * (le16_to_cpu(i_xattr_icount) - 1);
 252 }
 253
 254 #define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
 255
 256 static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
 257 {
 258         return EROFS_XATTR_ALIGN(sizeof(struct erofs_xattr_entry) +
 259                                  e->e_name_len + le16_to_cpu(e->e_value_size));
 260 }
 261
 262 /* represent a zeroed chunk (hole) */
 263 #define EROFS_NULL_ADDR                 -1
 264
 265 /* 4-byte block address array */
 266 #define EROFS_BLOCK_MAP_ENTRY_SIZE      sizeof(__le32)
 267
 268 /* 8-byte inode chunk indexes */
 269 struct erofs_inode_chunk_index {
 270         __le16 advise;          /* always 0, don't care for now */
 271         __le16 device_id;       /* back-end storage id (with bits masked) */
 272         __le32 blkaddr;         /* start block address of this inode chunk */
 273 };
 274
 275 /* dirent sorts in alphabet order, thus we can do binary search */
 276 struct erofs_dirent {
 277         __le64 nid;     /* node number */
 278         __le16 nameoff; /* start offset of file name */
 279         __u8 file_type; /* file type */
 280         __u8 reserved;  /* reserved */
 281 } __packed;
 282
 283 /*
 284  * EROFS file types should match generic FT_* types and
 285  * it seems no need to add BUILD_BUG_ONs since potential
 286  * unmatchness will break other fses as well...
 287  */
 288
 289 #define EROFS_NAME_LEN      255
 290
 291 /* maximum supported encoded size of a physical compressed cluster */
 292 #define Z_EROFS_PCLUSTER_MAX_SIZE       (1024 * 1024)
 293
 294 /* maximum supported decoded size of a physical compressed cluster */
 295 #define Z_EROFS_PCLUSTER_MAX_DSIZE      (12 * 1024 * 1024)
 296
 297 /* available compression algorithm types (for h_algorithmtype) */
 298 enum {
 299         Z_EROFS_COMPRESSION_LZ4         = 0,
 300         Z_EROFS_COMPRESSION_LZMA        = 1,
 301         Z_EROFS_COMPRESSION_DEFLATE     = 2,
 302         Z_EROFS_COMPRESSION_ZSTD        = 3,
 303         Z_EROFS_COMPRESSION_MAX
 304 };
 305 #define Z_EROFS_ALL_COMPR_ALGS          ((1 << Z_EROFS_COMPRESSION_MAX) - 1)
 306
 307 /* 14 bytes (+ length field = 16 bytes) */
 308 struct z_erofs_lz4_cfgs {
 309         __le16 max_distance;
 310         __le16 max_pclusterblks;
 311         u8 reserved[10];
 312 } __packed;
 313
 314 /* 14 bytes (+ length field = 16 bytes) */
 315 struct z_erofs_lzma_cfgs {
 316         __le32 dict_size;
 317         __le16 format;
 318         u8 reserved[8];
 319 } __packed;
 320
 321 #define Z_EROFS_LZMA_MAX_DICT_SIZE      (8 * Z_EROFS_PCLUSTER_MAX_SIZE)
 322
 323 /* 6 bytes (+ length field = 8 bytes) */
 324 struct z_erofs_deflate_cfgs {
 325         u8 windowbits;                  /* 8..15 for DEFLATE */
 326         u8 reserved[5];
 327 } __packed;
 328
 329 /* 6 bytes (+ length field = 8 bytes) */
 330 struct z_erofs_zstd_cfgs {
 331         u8 format;
 332         u8 windowlog;           /* windowLog - ZSTD_WINDOWLOG_ABSOLUTEMIN(10) */
 333         u8 reserved[4];
 334 } __packed;
 335
 336 #define Z_EROFS_ZSTD_MAX_DICT_SIZE      Z_EROFS_PCLUSTER_MAX_SIZE
 337
 338 /*
 339  * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
 340  *  e.g. for 4k logical cluster size,      4B        if compacted 2B is off;
 341  *                                  (4B) + 2B + (4B) if compacted 2B is on.
 342  * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
 343  * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
 344  * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
 345  * bit 4 : interlaced plain pcluster (0 - off; 1 - on)
 346  * bit 5 : fragment pcluster (0 - off; 1 - on)
 347  */
 348 #define Z_EROFS_ADVISE_COMPACTED_2B             0x0001
 349 #define Z_EROFS_ADVISE_BIG_PCLUSTER_1           0x0002
 350 #define Z_EROFS_ADVISE_BIG_PCLUSTER_2           0x0004
 351 #define Z_EROFS_ADVISE_INLINE_PCLUSTER          0x0008
 352 #define Z_EROFS_ADVISE_INTERLACED_PCLUSTER      0x0010
 353 #define Z_EROFS_ADVISE_FRAGMENT_PCLUSTER        0x0020
 354
 355 #define Z_EROFS_FRAGMENT_INODE_BIT              7
 356 struct z_erofs_map_header {
 357         union {
 358                 /* fragment data offset in the packed inode */
 359                 __le32  h_fragmentoff;
 360                 struct {
 361                         __le16  h_reserved1;
 362                         /* indicates the encoded size of tailpacking data */
 363                         __le16  h_idata_size;
 364                 };
 365         };
 366         __le16  h_advise;
 367         /*
 368          * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
 369          * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
 370          */
 371         __u8    h_algorithmtype;
 372         /*
 373          * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
 374          * bit 3-6 : reserved;
 375          * bit 7   : move the whole file into packed inode or not.
 376          */
 377         __u8    h_clusterbits;
 378 };
 379
 380 /*
 381  * On-disk logical cluster type:
 382  *    0   - literal (uncompressed) lcluster
 383  *    1,3 - compressed lcluster (for HEAD lclusters)
 384  *    2   - compressed lcluster (for NONHEAD lclusters)
 385  *
 386  * In detail,
 387  *    0 - literal (uncompressed) lcluster,
 388  *        di_advise = 0
 389  *        di_clusterofs = the literal data offset of the lcluster
 390  *        di_blkaddr = the blkaddr of the literal pcluster
 391  *
 392  *    1,3 - compressed lcluster (for HEAD lclusters)
 393  *        di_advise = 1 or 3
 394  *        di_clusterofs = the decompressed data offset of the lcluster
 395  *        di_blkaddr = the blkaddr of the compressed pcluster
 396  *
 397  *    2 - compressed lcluster (for NONHEAD lclusters)
 398  *        di_advise = 2
 399  *        di_clusterofs =
 400  *           the decompressed data offset in its own HEAD lcluster
 401  *        di_u.delta[0] = distance to this HEAD lcluster
 402  *        di_u.delta[1] = distance to the next HEAD lcluster
 403  */
 404 enum {
 405         Z_EROFS_LCLUSTER_TYPE_PLAIN     = 0,
 406         Z_EROFS_LCLUSTER_TYPE_HEAD1     = 1,
 407         Z_EROFS_LCLUSTER_TYPE_NONHEAD   = 2,
 408         Z_EROFS_LCLUSTER_TYPE_HEAD2     = 3,
 409         Z_EROFS_LCLUSTER_TYPE_MAX
 410 };
 411
 412 #define Z_EROFS_LI_LCLUSTER_TYPE_MASK   (Z_EROFS_LCLUSTER_TYPE_MAX - 1)
 413
 414 /* (noncompact only, HEAD) This pcluster refers to partial decompressed data */
 415 #define Z_EROFS_LI_PARTIAL_REF          (1 << 15)
 416
 417 /*
 418  * D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
 419  * compressed block count of a compressed extent (in logical clusters, aka.
 420  * block count of a pcluster).
 421  */
 422 #define Z_EROFS_LI_D0_CBLKCNT           (1 << 11)
 423
 424 struct z_erofs_lcluster_index {
 425         __le16 di_advise;
 426         /* where to decompress in the head lcluster */
 427         __le16 di_clusterofs;
 428
 429         union {
 430                 /* for the HEAD lclusters */
 431                 __le32 blkaddr;
 432                 /*
 433                  * for the NONHEAD lclusters
 434                  * [0] - distance to its HEAD lcluster
 435                  * [1] - distance to the next HEAD lcluster
 436                  */
 437                 __le16 delta[2];
 438         } di_u;
 439 };
 440
 441 #define Z_EROFS_FULL_INDEX_ALIGN(end)   \
 442         (ALIGN(end, 8) + sizeof(struct z_erofs_map_header) + 8)
 443
 444 /* check the EROFS on-disk layout strictly at compile time */
 445 static inline void erofs_check_ondisk_layout_definitions(void)
 446 {
 447         const __le64 fmh = *(__le64 *)&(struct z_erofs_map_header) {
 448                 .h_clusterbits = 1 << Z_EROFS_FRAGMENT_INODE_BIT
 449         };
 450
 451         BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
 452         BUILD_BUG_ON(sizeof(struct erofs_inode_compact) != 32);
 453         BUILD_BUG_ON(sizeof(struct erofs_inode_extended) != 64);
 454         BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
 455         BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
 456         BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_info) != 4);
 457         BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) != 8);
 458         BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
 459         BUILD_BUG_ON(sizeof(struct z_erofs_lcluster_index) != 8);
 460         BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
 461         /* keep in sync between 2 index structures for better extendibility */
 462         BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) !=
 463                      sizeof(struct z_erofs_lcluster_index));
 464         BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);
 465
 466         /* exclude old compiler versions like gcc 7.5.0 */
 467         BUILD_BUG_ON(__builtin_constant_p(fmh) ?
 468                      fmh != cpu_to_le64(1ULL << 63) : 0);
 469 }
 470
 471 #endif