1 /* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
3 * EROFS (Enhanced ROM File System) on-disk format definition
5 * Copyright (C) 2017-2018 HUAWEI, Inc.
6 * https://www.huawei.com/
7 * Created by Gao Xiang <gaoxiang25@huawei.com>
12 #define EROFS_SUPER_OFFSET 1024
14 #define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
17 * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
18 * be incompatible with this kernel version.
20 #define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING 0x00000001
21 #define EROFS_FEATURE_INCOMPAT_COMPR_CFGS 0x00000002
22 #define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER 0x00000002
23 #define EROFS_ALL_FEATURE_INCOMPAT \
24 (EROFS_FEATURE_INCOMPAT_LZ4_0PADDING | \
25 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
26 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER)
28 #define EROFS_SB_EXTSLOT_SIZE 16
30 /* erofs on-disk super block (currently 128 bytes) */
31 struct erofs_super_block {
32 __le32 magic; /* file system magic number */
33 __le32 checksum; /* crc32c(super_block) */
34 __le32 feature_compat;
35 __u8 blkszbits; /* support block_size == PAGE_SIZE only */
36 __u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */
38 __le16 root_nid; /* nid of root directory */
39 __le64 inos; /* total valid ino # (== f_files - f_favail) */
41 __le64 build_time; /* inode v1 time derivation */
42 __le32 build_time_nsec; /* inode v1 time derivation in nano scale */
43 __le32 blocks; /* used for statfs */
44 __le32 meta_blkaddr; /* start block address of metadata area */
45 __le32 xattr_blkaddr; /* start block address of shared xattr area */
46 __u8 uuid[16]; /* 128-bit uuid for volume */
47 __u8 volume_name[16]; /* volume name */
48 __le32 feature_incompat;
50 /* bitmap for available compression algorithms */
51 __le16 available_compr_algs;
52 /* customized sliding window size instead of 64k by default */
53 __le16 lz4_max_distance;
59 * erofs inode datalayout (i_format in on-disk inode):
60 * 0 - inode plain without inline data A:
61 * inode, [xattrs], ... | ... | no-holed data
62 * 1 - inode VLE compression B (legacy):
63 * inode, [xattrs], extents ... | ...
64 * 2 - inode plain with inline data C:
65 * inode, [xattrs], last_inline_data, ... | ... | no-holed data
66 * 3 - inode compression D:
67 * inode, [xattrs], map_header, extents ... | ...
71 EROFS_INODE_FLAT_PLAIN = 0,
72 EROFS_INODE_FLAT_COMPRESSION_LEGACY = 1,
73 EROFS_INODE_FLAT_INLINE = 2,
74 EROFS_INODE_FLAT_COMPRESSION = 3,
75 EROFS_INODE_DATALAYOUT_MAX
78 static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
80 return datamode == EROFS_INODE_FLAT_COMPRESSION ||
81 datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
84 /* bit definitions of inode i_advise */
85 #define EROFS_I_VERSION_BITS 1
86 #define EROFS_I_DATALAYOUT_BITS 3
88 #define EROFS_I_VERSION_BIT 0
89 #define EROFS_I_DATALAYOUT_BIT 1
92 ((1 << (EROFS_I_DATALAYOUT_BIT + EROFS_I_DATALAYOUT_BITS)) - 1)
94 /* 32-byte reduced form of an ondisk inode */
95 struct erofs_inode_compact {
96 __le16 i_format; /* inode format hints */
98 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
99 __le16 i_xattr_icount;
105 /* file total compressed blocks for data mapping 1 */
106 __le32 compressed_blocks;
109 /* for device files, used to indicate old/new device # */
112 __le32 i_ino; /* only used for 32-bit stat compatibility */
118 /* 32 bytes on-disk inode */
119 #define EROFS_INODE_LAYOUT_COMPACT 0
120 /* 64 bytes on-disk inode */
121 #define EROFS_INODE_LAYOUT_EXTENDED 1
123 /* 64-byte complete form of an ondisk inode */
124 struct erofs_inode_extended {
125 __le16 i_format; /* inode format hints */
127 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
128 __le16 i_xattr_icount;
133 /* file total compressed blocks for data mapping 1 */
134 __le32 compressed_blocks;
137 /* for device files, used to indicate old/new device # */
141 /* only used for 32-bit stat compatibility */
149 __u8 i_reserved2[16];
152 #define EROFS_MAX_SHARED_XATTRS (128)
153 /* h_shared_count between 129 ... 255 are special # */
154 #define EROFS_SHARED_XATTR_EXTENT (255)
157 * inline xattrs (n == i_xattr_icount):
158 * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
161 * /-----------------------\
162 * | erofs_xattr_entries+ |
163 * +-----------------------+
164 * inline xattrs must starts in erofs_xattr_ibody_header,
165 * for read-only fs, no need to introduce h_refcount
167 struct erofs_xattr_ibody_header {
171 __le32 h_shared_xattrs[0]; /* shared xattr id array */
175 #define EROFS_XATTR_INDEX_USER 1
176 #define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS 2
177 #define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
178 #define EROFS_XATTR_INDEX_TRUSTED 4
179 #define EROFS_XATTR_INDEX_LUSTRE 5
180 #define EROFS_XATTR_INDEX_SECURITY 6
182 /* xattr entry (for both inline & shared xattrs) */
183 struct erofs_xattr_entry {
184 __u8 e_name_len; /* length of name */
185 __u8 e_name_index; /* attribute name index */
186 __le16 e_value_size; /* size of attribute value */
187 /* followed by e_name and e_value */
188 char e_name[0]; /* attribute name */
191 static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount)
196 return sizeof(struct erofs_xattr_ibody_header) +
197 sizeof(__u32) * (le16_to_cpu(i_xattr_icount) - 1);
200 #define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
202 static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
204 return EROFS_XATTR_ALIGN(sizeof(struct erofs_xattr_entry) +
205 e->e_name_len + le16_to_cpu(e->e_value_size));
208 /* maximum supported size of a physical compression cluster */
209 #define Z_EROFS_PCLUSTER_MAX_SIZE (1024 * 1024)
211 /* available compression algorithm types (for h_algorithmtype) */
213 Z_EROFS_COMPRESSION_LZ4 = 0,
214 Z_EROFS_COMPRESSION_MAX
216 #define Z_EROFS_ALL_COMPR_ALGS (1 << (Z_EROFS_COMPRESSION_MAX - 1))
218 /* 14 bytes (+ length field = 16 bytes) */
219 struct z_erofs_lz4_cfgs {
221 __le16 max_pclusterblks;
226 * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
227 * e.g. for 4k logical cluster size, 4B if compacted 2B is off;
228 * (4B) + 2B + (4B) if compacted 2B is on.
229 * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
230 * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
232 #define Z_EROFS_ADVISE_COMPACTED_2B 0x0001
233 #define Z_EROFS_ADVISE_BIG_PCLUSTER_1 0x0002
234 #define Z_EROFS_ADVISE_BIG_PCLUSTER_2 0x0004
236 struct z_erofs_map_header {
240 * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
241 * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
243 __u8 h_algorithmtype;
245 * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
246 * bit 3-7 : reserved.
251 #define Z_EROFS_VLE_LEGACY_HEADER_PADDING 8
254 * Fixed-sized output compression ondisk Logical Extent cluster type:
255 * 0 - literal (uncompressed) cluster
256 * 1 - compressed cluster (for the head logical cluster)
257 * 2 - compressed cluster (for the other logical clusters)
260 * 0 - literal (uncompressed) cluster,
262 * di_clusterofs = the literal data offset of the cluster
263 * di_blkaddr = the blkaddr of the literal cluster
265 * 1 - compressed cluster (for the head logical cluster)
267 * di_clusterofs = the decompressed data offset of the cluster
268 * di_blkaddr = the blkaddr of the compressed cluster
270 * 2 - compressed cluster (for the other logical clusters)
273 * the decompressed data offset in its own head cluster
274 * di_u.delta[0] = distance to its corresponding head cluster
275 * di_u.delta[1] = distance to its corresponding tail cluster
276 * (di_advise could be 0, 1 or 2)
279 Z_EROFS_VLE_CLUSTER_TYPE_PLAIN = 0,
280 Z_EROFS_VLE_CLUSTER_TYPE_HEAD = 1,
281 Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD = 2,
282 Z_EROFS_VLE_CLUSTER_TYPE_RESERVED = 3,
283 Z_EROFS_VLE_CLUSTER_TYPE_MAX
286 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS 2
287 #define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT 0
290 * D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
291 * compressed block count of a compressed extent (in logical clusters, aka.
292 * block count of a pcluster).
294 #define Z_EROFS_VLE_DI_D0_CBLKCNT (1 << 11)
296 struct z_erofs_vle_decompressed_index {
298 /* where to decompress in the head cluster */
299 __le16 di_clusterofs;
302 /* for the head cluster */
305 * for the rest clusters
306 * eg. for 4k page-sized cluster, maximum 4K*64k = 256M)
307 * [0] - pointing to the head cluster
308 * [1] - pointing to the tail cluster
314 #define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
315 (round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
316 sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)
318 /* dirent sorts in alphabet order, thus we can do binary search */
319 struct erofs_dirent {
320 __le64 nid; /* node number */
321 __le16 nameoff; /* start offset of file name */
322 __u8 file_type; /* file type */
323 __u8 reserved; /* reserved */
327 * EROFS file types should match generic FT_* types and
328 * it seems no need to add BUILD_BUG_ONs since potential
329 * unmatchness will break other fses as well...
332 #define EROFS_NAME_LEN 255
334 /* check the EROFS on-disk layout strictly at compile time */
335 static inline void erofs_check_ondisk_layout_definitions(void)
337 BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
338 BUILD_BUG_ON(sizeof(struct erofs_inode_compact) != 32);
339 BUILD_BUG_ON(sizeof(struct erofs_inode_extended) != 64);
340 BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
341 BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
342 BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
343 BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
344 BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
346 BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
347 Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);