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    Subject[PATCH v6 01/24] erofs: add on-disk layout
    Date
    This commit adds the on-disk layout header file of erofs.
    On-disk format is compatible with erofs-staging added in 4.19.

    In addition, add EROFS_SUPER_MAGIC_V1 to magic.h.

    Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
    ---
    fs/erofs/erofs_fs.h | 316 +++++++++++++++++++++++++++++++++++++
    include/uapi/linux/magic.h | 1 +
    2 files changed, 317 insertions(+)
    create mode 100644 fs/erofs/erofs_fs.h

    diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
    new file mode 100644
    index 000000000000..b307060dd220
    --- /dev/null
    +++ b/fs/erofs/erofs_fs.h
    @@ -0,0 +1,316 @@
    +/* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
    +/*
    + * linux/fs/erofs/erofs_fs.h
    + *
    + * Copyright (C) 2017-2018 HUAWEI, Inc.
    + * http://www.huawei.com/
    + * Created by Gao Xiang <gaoxiang25@huawei.com>
    + */
    +#ifndef __EROFS_FS_H
    +#define __EROFS_FS_H
    +
    +/* Enhanced(Extended) ROM File System */
    +#define EROFS_SUPER_OFFSET 1024
    +
    +/*
    + * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
    + * incompatible with this kernel version.
    + */
    +#define EROFS_REQUIREMENT_LZ4_0PADDING 0x00000001
    +#define EROFS_ALL_REQUIREMENTS 0
    +
    +struct erofs_super_block {
    +/* 0 */__le32 magic; /* in the little endian */
    +/* 4 */__le32 checksum; /* crc32c(super_block) */
    +/* 8 */__le32 features; /* (aka. feature_compat) */
    +/* 12 */__u8 blkszbits; /* support block_size == PAGE_SIZE only */
    +/* 13 */__u8 reserved;
    +
    +/* 14 */__le16 root_nid;
    +/* 16 */__le64 inos; /* total valid ino # (== f_files - f_favail) */
    +
    +/* 24 */__le64 build_time; /* inode v1 time derivation */
    +/* 32 */__le32 build_time_nsec;
    +/* 36 */__le32 blocks; /* used for statfs */
    +/* 40 */__le32 meta_blkaddr;
    +/* 44 */__le32 xattr_blkaddr;
    +/* 48 */__u8 uuid[16]; /* 128-bit uuid for volume */
    +/* 64 */__u8 volume_name[16]; /* volume name */
    +/* 80 */__le32 requirements; /* (aka. feature_incompat) */
    +
    +/* 84 */__u8 reserved2[44];
    +} __packed; /* 128 bytes */
    +
    +/*
    + * erofs inode data mapping:
    + * 0 - inode plain without inline data A:
    + * inode, [xattrs], ... | ... | no-holed data
    + * 1 - inode VLE compression B (legacy):
    + * inode, [xattrs], extents ... | ...
    + * 2 - inode plain with inline data C:
    + * inode, [xattrs], last_inline_data, ... | ... | no-holed data
    + * 3 - inode compression D:
    + * inode, [xattrs], map_header, extents ... | ...
    + * 4~7 - reserved
    + */
    +enum {
    + EROFS_INODE_FLAT_PLAIN,
    + EROFS_INODE_FLAT_COMPRESSION_LEGACY,
    + EROFS_INODE_FLAT_INLINE,
    + EROFS_INODE_FLAT_COMPRESSION,
    + EROFS_INODE_LAYOUT_MAX
    +};
    +
    +static bool erofs_inode_is_data_compressed(unsigned int datamode)
    +{
    + if (datamode == EROFS_INODE_FLAT_COMPRESSION)
    + return true;
    + return datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
    +}
    +
    +/* bit definitions of inode i_advise */
    +#define EROFS_I_VERSION_BITS 1
    +#define EROFS_I_DATA_MAPPING_BITS 3
    +
    +#define EROFS_I_VERSION_BIT 0
    +#define EROFS_I_DATA_MAPPING_BIT 1
    +
    +struct erofs_inode_v1 {
    +/* 0 */__le16 i_advise;
    +
    +/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
    +/* 2 */__le16 i_xattr_icount;
    +/* 4 */__le16 i_mode;
    +/* 6 */__le16 i_nlink;
    +/* 8 */__le32 i_size;
    +/* 12 */__le32 i_reserved;
    +/* 16 */union {
    + /* file total compressed blocks for data mapping 1 */
    + __le32 compressed_blocks;
    + __le32 raw_blkaddr;
    +
    + /* for device files, used to indicate old/new device # */
    + __le32 rdev;
    + } i_u __packed;
    +/* 20 */__le32 i_ino; /* only used for 32-bit stat compatibility */
    +/* 24 */__le16 i_uid;
    +/* 26 */__le16 i_gid;
    +/* 28 */__le32 i_reserved2;
    +} __packed;
    +
    +/* 32 bytes on-disk inode */
    +#define EROFS_INODE_LAYOUT_V1 0
    +/* 64 bytes on-disk inode */
    +#define EROFS_INODE_LAYOUT_V2 1
    +
    +struct erofs_inode_v2 {
    +/* 0 */__le16 i_advise;
    +
    +/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
    +/* 2 */__le16 i_xattr_icount;
    +/* 4 */__le16 i_mode;
    +/* 6 */__le16 i_reserved;
    +/* 8 */__le64 i_size;
    +/* 16 */union {
    + /* file total compressed blocks for data mapping 1 */
    + __le32 compressed_blocks;
    + __le32 raw_blkaddr;
    +
    + /* for device files, used to indicate old/new device # */
    + __le32 rdev;
    + } i_u __packed;
    +
    + /* only used for 32-bit stat compatibility */
    +/* 20 */__le32 i_ino;
    +
    +/* 24 */__le32 i_uid;
    +/* 28 */__le32 i_gid;
    +/* 32 */__le64 i_ctime;
    +/* 40 */__le32 i_ctime_nsec;
    +/* 44 */__le32 i_nlink;
    +/* 48 */__u8 i_reserved2[16];
    +} __packed; /* 64 bytes */
    +
    +#define EROFS_MAX_SHARED_XATTRS (128)
    +/* h_shared_count between 129 ... 255 are special # */
    +#define EROFS_SHARED_XATTR_EXTENT (255)
    +
    +/*
    + * inline xattrs (n == i_xattr_icount):
    + * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
    + * 12 bytes / \
    + * / \
    + * /-----------------------\
    + * | erofs_xattr_entries+ |
    + * +-----------------------+
    + * inline xattrs must starts in erofs_xattr_ibody_header,
    + * for read-only fs, no need to introduce h_refcount
    + */
    +struct erofs_xattr_ibody_header {
    + __le32 h_reserved;
    + __u8 h_shared_count;
    + __u8 h_reserved2[7];
    + __le32 h_shared_xattrs[0]; /* shared xattr id array */
    +} __packed;
    +
    +/* Name indexes */
    +#define EROFS_XATTR_INDEX_USER 1
    +#define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS 2
    +#define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
    +#define EROFS_XATTR_INDEX_TRUSTED 4
    +#define EROFS_XATTR_INDEX_LUSTRE 5
    +#define EROFS_XATTR_INDEX_SECURITY 6
    +
    +/* xattr entry (for both inline & shared xattrs) */
    +struct erofs_xattr_entry {
    + __u8 e_name_len; /* length of name */
    + __u8 e_name_index; /* attribute name index */
    + __le16 e_value_size; /* size of attribute value */
    + /* followed by e_name and e_value */
    + char e_name[0]; /* attribute name */
    +} __packed;
    +
    +#define ondisk_xattr_ibody_size(count) ({\
    + u32 __count = le16_to_cpu(count); \
    + ((__count) == 0) ? 0 : \
    + sizeof(struct erofs_xattr_ibody_header) + \
    + sizeof(__u32) * ((__count) - 1); })
    +
    +#define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
    +#define EROFS_XATTR_ENTRY_SIZE(entry) EROFS_XATTR_ALIGN( \
    + sizeof(struct erofs_xattr_entry) + \
    + (entry)->e_name_len + le16_to_cpu((entry)->e_value_size))
    +
    +/* available compression algorithm types */
    +enum {
    + Z_EROFS_COMPRESSION_LZ4,
    + Z_EROFS_COMPRESSION_MAX
    +};
    +
    +/*
    + * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
    + * e.g. for 4k logical cluster size, 4B if compacted 2B is off;
    + * (4B) + 2B + (4B) if compacted 2B is on.
    + */
    +#define Z_EROFS_ADVISE_COMPACTED_2B_BIT 0
    +
    +#define Z_EROFS_ADVISE_COMPACTED_2B (1 << Z_EROFS_ADVISE_COMPACTED_2B_BIT)
    +
    +struct z_erofs_map_header {
    + __le32 h_reserved1;
    + __le16 h_advise;
    + /*
    + * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
    + * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
    + */
    + __u8 h_algorithmtype;
    + /*
    + * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
    + * bit 3-4 : (physical - logical) cluster bits of head 1:
    + * For example, if logical clustersize = 4096, 1 for 8192.
    + * bit 5-7 : (physical - logical) cluster bits of head 2.
    + */
    + __u8 h_clusterbits;
    +};
    +
    +#define Z_EROFS_VLE_LEGACY_HEADER_PADDING 8
    +
    +/*
    + * Z_EROFS Variable-sized Logical Extent cluster type:
    + * 0 - literal (uncompressed) cluster
    + * 1 - compressed cluster (for the head logical cluster)
    + * 2 - compressed cluster (for the other logical clusters)
    + *
    + * In detail,
    + * 0 - literal (uncompressed) cluster,
    + * di_advise = 0
    + * di_clusterofs = the literal data offset of the cluster
    + * di_blkaddr = the blkaddr of the literal cluster
    + *
    + * 1 - compressed cluster (for the head logical cluster)
    + * di_advise = 1
    + * di_clusterofs = the decompressed data offset of the cluster
    + * di_blkaddr = the blkaddr of the compressed cluster
    + *
    + * 2 - compressed cluster (for the other logical clusters)
    + * di_advise = 2
    + * di_clusterofs =
    + * the decompressed data offset in its own head cluster
    + * di_u.delta[0] = distance to its corresponding head cluster
    + * di_u.delta[1] = distance to its corresponding tail cluster
    + * (di_advise could be 0, 1 or 2)
    + */
    +enum {
    + Z_EROFS_VLE_CLUSTER_TYPE_PLAIN,
    + Z_EROFS_VLE_CLUSTER_TYPE_HEAD,
    + Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD,
    + Z_EROFS_VLE_CLUSTER_TYPE_RESERVED,
    + Z_EROFS_VLE_CLUSTER_TYPE_MAX
    +};
    +
    +#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS 2
    +#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT 0
    +
    +struct z_erofs_vle_decompressed_index {
    + __le16 di_advise;
    + /* where to decompress in the head cluster */
    + __le16 di_clusterofs;
    +
    + union {
    + /* for the head cluster */
    + __le32 blkaddr;
    + /*
    + * for the rest clusters
    + * eg. for 4k page-sized cluster, maximum 4K*64k = 256M)
    + * [0] - pointing to the head cluster
    + * [1] - pointing to the tail cluster
    + */
    + __le16 delta[2];
    + } di_u __packed; /* 8 bytes */
    +} __packed;
    +
    +#define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
    + (round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
    + sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)
    +
    +/* dirent sorts in alphabet order, thus we can do binary search */
    +struct erofs_dirent {
    + __le64 nid; /* 0, node number */
    + __le16 nameoff; /* 8, start offset of file name */
    + __u8 file_type; /* 10, file type */
    + __u8 reserved; /* 11, reserved */
    +} __packed;
    +
    +/* file types used in inode_info->flags */
    +enum {
    + EROFS_FT_UNKNOWN,
    + EROFS_FT_REG_FILE,
    + EROFS_FT_DIR,
    + EROFS_FT_CHRDEV,
    + EROFS_FT_BLKDEV,
    + EROFS_FT_FIFO,
    + EROFS_FT_SOCK,
    + EROFS_FT_SYMLINK,
    + EROFS_FT_MAX
    +};
    +
    +#define EROFS_NAME_LEN 255
    +
    +/* check the EROFS on-disk layout strictly at compile time */
    +static inline void erofs_check_ondisk_layout_definitions(void)
    +{
    + BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
    + BUILD_BUG_ON(sizeof(struct erofs_inode_v1) != 32);
    + BUILD_BUG_ON(sizeof(struct erofs_inode_v2) != 64);
    + BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
    + BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
    + BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
    + BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
    + BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
    +
    + BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
    + Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
    +}
    +
    +#endif
    +
    diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
    index 1274c692e59c..903cc2d2750b 100644
    --- a/include/uapi/linux/magic.h
    +++ b/include/uapi/linux/magic.h
    @@ -19,6 +19,7 @@
    #define SQUASHFS_MAGIC 0x73717368
    #define ECRYPTFS_SUPER_MAGIC 0xf15f
    #define EFS_SUPER_MAGIC 0x414A53
    +#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
    #define EXT2_SUPER_MAGIC 0xEF53
    #define EXT3_SUPER_MAGIC 0xEF53
    #define XENFS_SUPER_MAGIC 0xabba1974
    --
    2.17.1
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