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  * Created by Gao Xiang <gaoxiang25@huawei.com>
   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
  16 /*
  17  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
  18  * be incompatible with this kernel version.
  19  */
  20 #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING     0x00000001
  21 #define EROFS_ALL_FEATURE_INCOMPAT              EROFS_FEATURE_INCOMPAT_LZ4_0PADDING
  22
  23 /* 128-byte erofs on-disk super block */
  24 struct erofs_super_block {
  25         __le32 magic;           /* file system magic number */
  26         __le32 checksum;        /* crc32c(super_block) */
  27         __le32 feature_compat;
  28         __u8 blkszbits;         /* support block_size == PAGE_SIZE only */
  29         __u8 reserved;
  30
  31         __le16 root_nid;        /* nid of root directory */
  32         __le64 inos;            /* total valid ino # (== f_files - f_favail) */
  33
  34         __le64 build_time;      /* inode v1 time derivation */
  35         __le32 build_time_nsec; /* inode v1 time derivation in nano scale */
  36         __le32 blocks;          /* used for statfs */
  37         __le32 meta_blkaddr;    /* start block address of metadata area */
  38         __le32 xattr_blkaddr;   /* start block address of shared xattr area */
  39         __u8 uuid[16];          /* 128-bit uuid for volume */
  40         __u8 volume_name[16];   /* volume name */
  41         __le32 feature_incompat;
  42         __u8 reserved2[44];
  43 };
  44
  45 /*
  46  * erofs inode datalayout (i_format in on-disk inode):
  47  * 0 - inode plain without inline data A:
  48  * inode, [xattrs], ... | ... | no-holed data
  49  * 1 - inode VLE compression B (legacy):
  50  * inode, [xattrs], extents ... | ...
  51  * 2 - inode plain with inline data C:
  52  * inode, [xattrs], last_inline_data, ... | ... | no-holed data
  53  * 3 - inode compression D:
  54  * inode, [xattrs], map_header, extents ... | ...
  55  * 4~7 - reserved
  56  */
  57 enum {
  58         EROFS_INODE_FLAT_PLAIN                  = 0,
  59         EROFS_INODE_FLAT_COMPRESSION_LEGACY     = 1,
  60         EROFS_INODE_FLAT_INLINE                 = 2,
  61         EROFS_INODE_FLAT_COMPRESSION            = 3,
  62         EROFS_INODE_DATALAYOUT_MAX
  63 };
  64
  65 static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
  66 {
  67         return datamode == EROFS_INODE_FLAT_COMPRESSION ||
  68                 datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
  69 }
  70
  71 /* bit definitions of inode i_advise */
  72 #define EROFS_I_VERSION_BITS            1
  73 #define EROFS_I_DATALAYOUT_BITS         3
  74
  75 #define EROFS_I_VERSION_BIT             0
  76 #define EROFS_I_DATALAYOUT_BIT          1
  77
  78 /* 32-byte reduced form of an ondisk inode */
  79 struct erofs_inode_compact {
  80         __le16 i_format;        /* inode format hints */
  81
  82 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
  83         __le16 i_xattr_icount;
  84         __le16 i_mode;
  85         __le16 i_nlink;
  86         __le32 i_size;
  87         __le32 i_reserved;
  88         union {
  89                 /* file total compressed blocks for data mapping 1 */
  90                 __le32 compressed_blocks;
  91                 __le32 raw_blkaddr;
  92
  93                 /* for device files, used to indicate old/new device # */
  94                 __le32 rdev;
  95         } i_u;
  96         __le32 i_ino;           /* only used for 32-bit stat compatibility */
  97         __le16 i_uid;
  98         __le16 i_gid;
  99         __le32 i_reserved2;
 100 };
 101
 102 /* 32 bytes on-disk inode */
 103 #define EROFS_INODE_LAYOUT_COMPACT      0
 104 /* 64 bytes on-disk inode */
 105 #define EROFS_INODE_LAYOUT_EXTENDED     1
 106
 107 /* 64-byte complete form of an ondisk inode */
 108 struct erofs_inode_extended {
 109         __le16 i_format;        /* inode format hints */
 110
 111 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
 112         __le16 i_xattr_icount;
 113         __le16 i_mode;
 114         __le16 i_reserved;
 115         __le64 i_size;
 116         union {
 117                 /* file total compressed blocks for data mapping 1 */
 118                 __le32 compressed_blocks;
 119                 __le32 raw_blkaddr;
 120
 121                 /* for device files, used to indicate old/new device # */
 122                 __le32 rdev;
 123         } i_u;
 124
 125         /* only used for 32-bit stat compatibility */
 126         __le32 i_ino;
 127
 128         __le32 i_uid;
 129         __le32 i_gid;
 130         __le64 i_ctime;
 131         __le32 i_ctime_nsec;
 132         __le32 i_nlink;
 133         __u8   i_reserved2[16];
 134 };
 135
 136 #define EROFS_MAX_SHARED_XATTRS         (128)
 137 /* h_shared_count between 129 ... 255 are special # */
 138 #define EROFS_SHARED_XATTR_EXTENT       (255)
 139
 140 /*
 141  * inline xattrs (n == i_xattr_icount):
 142  * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
 143  *          12 bytes           /                   \
 144  *                            /                     \
 145  *                           /-----------------------\
 146  *                           |  erofs_xattr_entries+ |
 147  *                           +-----------------------+
 148  * inline xattrs must starts in erofs_xattr_ibody_header,
 149  * for read-only fs, no need to introduce h_refcount
 150  */
 151 struct erofs_xattr_ibody_header {
 152         __le32 h_reserved;
 153         __u8   h_shared_count;
 154         __u8   h_reserved2[7];
 155         __le32 h_shared_xattrs[0];      /* shared xattr id array */
 156 };
 157
 158 /* Name indexes */
 159 #define EROFS_XATTR_INDEX_USER              1
 160 #define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS  2
 161 #define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
 162 #define EROFS_XATTR_INDEX_TRUSTED           4
 163 #define EROFS_XATTR_INDEX_LUSTRE            5
 164 #define EROFS_XATTR_INDEX_SECURITY          6
 165
 166 /* xattr entry (for both inline & shared xattrs) */
 167 struct erofs_xattr_entry {
 168         __u8   e_name_len;      /* length of name */
 169         __u8   e_name_index;    /* attribute name index */
 170         __le16 e_value_size;    /* size of attribute value */
 171         /* followed by e_name and e_value */
 172         char   e_name[0];       /* attribute name */
 173 };
 174
 175 static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount)
 176 {
 177         if (!i_xattr_icount)
 178                 return 0;
 179
 180         return sizeof(struct erofs_xattr_ibody_header) +
 181                 sizeof(__u32) * (le16_to_cpu(i_xattr_icount) - 1);
 182 }
 183
 184 #define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
 185
 186 static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
 187 {
 188         return EROFS_XATTR_ALIGN(sizeof(struct erofs_xattr_entry) +
 189                                  e->e_name_len + le16_to_cpu(e->e_value_size));
 190 }
 191
 192 /* available compression algorithm types (for h_algorithmtype) */
 193 enum {
 194         Z_EROFS_COMPRESSION_LZ4 = 0,
 195         Z_EROFS_COMPRESSION_MAX
 196 };
 197
 198 /*
 199  * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
 200  *  e.g. for 4k logical cluster size,      4B        if compacted 2B is off;
 201  *                                  (4B) + 2B + (4B) if compacted 2B is on.
 202  */
 203 #define Z_EROFS_ADVISE_COMPACTED_2B_BIT         0
 204
 205 #define Z_EROFS_ADVISE_COMPACTED_2B     (1 << Z_EROFS_ADVISE_COMPACTED_2B_BIT)
 206
 207 struct z_erofs_map_header {
 208         __le32  h_reserved1;
 209         __le16  h_advise;
 210         /*
 211          * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
 212          * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
 213          */
 214         __u8    h_algorithmtype;
 215         /*
 216          * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
 217          * bit 3-4 : (physical - logical) cluster bits of head 1:
 218          *       For example, if logical clustersize = 4096, 1 for 8192.
 219          * bit 5-7 : (physical - logical) cluster bits of head 2.
 220          */
 221         __u8    h_clusterbits;
 222 };
 223
 224 #define Z_EROFS_VLE_LEGACY_HEADER_PADDING       8
 225
 226 /*
 227  * Fixed-sized output compression ondisk Logical Extent cluster type:
 228  *    0 - literal (uncompressed) cluster
 229  *    1 - compressed cluster (for the head logical cluster)
 230  *    2 - compressed cluster (for the other logical clusters)
 231  *
 232  * In detail,
 233  *    0 - literal (uncompressed) cluster,
 234  *        di_advise = 0
 235  *        di_clusterofs = the literal data offset of the cluster
 236  *        di_blkaddr = the blkaddr of the literal cluster
 237  *
 238  *    1 - compressed cluster (for the head logical cluster)
 239  *        di_advise = 1
 240  *        di_clusterofs = the decompressed data offset of the cluster
 241  *        di_blkaddr = the blkaddr of the compressed cluster
 242  *
 243  *    2 - compressed cluster (for the other logical clusters)
 244  *        di_advise = 2
 245  *        di_clusterofs =
 246  *           the decompressed data offset in its own head cluster
 247  *        di_u.delta[0] = distance to its corresponding head cluster
 248  *        di_u.delta[1] = distance to its corresponding tail cluster
 249  *                (di_advise could be 0, 1 or 2)
 250  */
 251 enum {
 252         Z_EROFS_VLE_CLUSTER_TYPE_PLAIN          = 0,
 253         Z_EROFS_VLE_CLUSTER_TYPE_HEAD           = 1,
 254         Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD        = 2,
 255         Z_EROFS_VLE_CLUSTER_TYPE_RESERVED       = 3,
 256         Z_EROFS_VLE_CLUSTER_TYPE_MAX
 257 };
 258
 259 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS        2
 260 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT         0
 261
 262 struct z_erofs_vle_decompressed_index {
 263         __le16 di_advise;
 264         /* where to decompress in the head cluster */
 265         __le16 di_clusterofs;
 266
 267         union {
 268                 /* for the head cluster */
 269                 __le32 blkaddr;
 270                 /*
 271                  * for the rest clusters
 272                  * eg. for 4k page-sized cluster, maximum 4K*64k = 256M)
 273                  * [0] - pointing to the head cluster
 274                  * [1] - pointing to the tail cluster
 275                  */
 276                 __le16 delta[2];
 277         } di_u;
 278 };
 279
 280 #define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
 281         (round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
 282          sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)
 283
 284 /* dirent sorts in alphabet order, thus we can do binary search */
 285 struct erofs_dirent {
 286         __le64 nid;     /* node number */
 287         __le16 nameoff; /* start offset of file name */
 288         __u8 file_type; /* file type */
 289         __u8 reserved;  /* reserved */
 290 } __packed;
 291
 292 /*
 293  * EROFS file types should match generic FT_* types and
 294  * it seems no need to add BUILD_BUG_ONs since potential
 295  * unmatchness will break other fses as well...
 296  */
 297
 298 #define EROFS_NAME_LEN      255
 299
 300 /* check the EROFS on-disk layout strictly at compile time */
 301 static inline void erofs_check_ondisk_layout_definitions(void)
 302 {
 303         BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
 304         BUILD_BUG_ON(sizeof(struct erofs_inode_compact) != 32);
 305         BUILD_BUG_ON(sizeof(struct erofs_inode_extended) != 64);
 306         BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
 307         BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
 308         BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
 309         BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
 310         BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
 311
 312         BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
 313                      Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
 314 }
 315
 316 #endif
 317