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staging: erofs: add on-disk layout
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This commit adds the on-disk layout header file of erofs.

Note that the on-disk layout is still WIP, and some fields are
reserved for the future use by design.

Any comments are welcome.

Thanks-to: Li Guifu <liguifu2@huawei.com>
Thanks-to: Sun Qiuyang <sunqiuyang@huawei.com>
Signed-off-by: Miao Xie <miaoxie@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Gao Xiang authored and Greg Kroah-Hartman committed Jul 27, 2018
1 parent a89bac0 commit aea1286
Showing 1 changed file with 266 additions and 0 deletions.
266 changes: 266 additions & 0 deletions drivers/staging/erofs/erofs_fs.h
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/* SPDX-License-Identifier: GPL-2.0 OR Apache-2.0
*
* linux/drivers/staging/erofs/erofs_fs.h
*
* Copyright (C) 2017-2018 HUAWEI, Inc.
* http://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*
* This file is dual-licensed; you may select either the GNU General Public
* License version 2 or Apache License, Version 2.0. See the file COPYING
* in the main directory of the Linux distribution for more details.
*/
#ifndef __EROFS_FS_H
#define __EROFS_FS_H

/* Enhanced(Extended) ROM File System */
#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
#define EROFS_SUPER_OFFSET 1024

struct erofs_super_block {
/* 0 */__le32 magic; /* in the little endian */
/* 4 */__le32 checksum; /* crc32c(super_block) */
/* 8 */__le32 features;
/* 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 */__u8 reserved2[48]; /* 128 bytes */
} __packed;

#define __EROFS_BIT(_prefix, _cur, _pre) enum { \
_prefix ## _cur ## _BIT = _prefix ## _pre ## _BIT + \
_prefix ## _pre ## _BITS }

/*
* erofs inode data mapping:
* 0 - inode plain without inline data A:
* inode, [xattrs], ... | ... | no-holed data
* 1 - inode VLE compression B:
* inode, [xattrs], extents ... | ...
* 2 - inode plain with inline data C:
* inode, [xattrs], last_inline_data, ... | ... | no-holed data
* 3~7 - reserved
*/
enum {
EROFS_INODE_LAYOUT_PLAIN,
EROFS_INODE_LAYOUT_COMPRESSION,
EROFS_INODE_LAYOUT_INLINE,
EROFS_INODE_LAYOUT_MAX
};
#define EROFS_I_VERSION_BITS 1
#define EROFS_I_DATA_MAPPING_BITS 3

#define EROFS_I_VERSION_BIT 0
__EROFS_BIT(EROFS_I_, DATA_MAPPING, VERSION);

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_checksum;
} __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 {
__le16 i_advise;

/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
__le16 i_xattr_icount;
__le16 i_mode;
__le16 i_reserved; /* 8 bytes */
__le64 i_size; /* 16 bytes */
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 */
__le32 i_ino; /* 24 bytes */

__le32 i_uid;
__le32 i_gid;
__le64 i_ctime; /* 32 bytes */
__le32 i_ctime_nsec;
__le32 i_nlink;
__u8 i_reserved2[12];
__le32 i_checksum; /* 64 bytes */
} __packed;

#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_checksum;
__u8 h_shared_count;
__u8 h_reserved[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))

/* have to be aligned with 8 bytes on disk */
struct erofs_extent_header {
__le32 eh_checksum;
__le32 eh_reserved[3];
} __packed;

/*
* 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)
*/
#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_EXTENT_ALIGN(size) round_up(size, \
sizeof(struct z_erofs_vle_decompressed_index))

/* 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 erofs_extent_header) != 16);
BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
}

#endif

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