drivers/staging/erofs/erofs_fs.h

/* 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

/*
 * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
 * incompatible with this kernel version.
 */
#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 */

#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