erofs_fs.h

/* SPDX-License-Identifier: MIT */
/*
 * EROFS (Enhanced ROM File System) on-disk format definition
 *
 * Copyright (C) 2017-2018 HUAWEI, Inc.
 *             https://www.huawei.com/
 * Copyright (C) 2021, Alibaba Cloud
 */
#ifndef __EROFS_FS_H
#define __EROFS_FS_H

/* to allow for x86 boot sectors and other oddities. */
#define EROFS_SUPER_OFFSET      1024

#define EROFS_FEATURE_COMPAT_SB_CHKSUM			0x00000001
#define EROFS_FEATURE_COMPAT_MTIME			0x00000002
#define EROFS_FEATURE_COMPAT_XATTR_FILTER		0x00000004
#define EROFS_FEATURE_COMPAT_SHARED_EA_IN_METABOX	0x00000008
#define EROFS_FEATURE_COMPAT_PLAIN_XATTR_PFX		0x00000010
#define EROFS_FEATURE_COMPAT_ISHARE_XATTRS		0x00000020

/*
 * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
 * be incompatible with this kernel version.
 */
#define EROFS_FEATURE_INCOMPAT_LZ4_0PADDING	0x00000001
#define EROFS_FEATURE_INCOMPAT_COMPR_CFGS	0x00000002
#define EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER	0x00000002
#define EROFS_FEATURE_INCOMPAT_CHUNKED_FILE	0x00000004
#define EROFS_FEATURE_INCOMPAT_DEVICE_TABLE	0x00000008
#define EROFS_FEATURE_INCOMPAT_COMPR_HEAD2	0x00000008
#define EROFS_FEATURE_INCOMPAT_ZTAILPACKING	0x00000010
#define EROFS_FEATURE_INCOMPAT_FRAGMENTS	0x00000020
#define EROFS_FEATURE_INCOMPAT_DEDUPE		0x00000020
#define EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES	0x00000040
#define EROFS_FEATURE_INCOMPAT_48BIT		0x00000080
#define EROFS_FEATURE_INCOMPAT_METABOX		0x00000100
#define EROFS_ALL_FEATURE_INCOMPAT		\
	((EROFS_FEATURE_INCOMPAT_METABOX << 1) - 1)

#define EROFS_SB_EXTSLOT_SIZE	16

struct erofs_deviceslot {
	u8 tag[64];		/* digest(sha256), etc. */
	__le32 blocks_lo;	/* total blocks count of this device */
	__le32 uniaddr_lo;	/* unified starting block of this device */
	__le32 blocks_hi;	/* total blocks count MSB */
	__le16 uniaddr_hi;	/* unified starting block MSB */
	u8 reserved[50];
};
#define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)

/* erofs on-disk super block (currently 144 bytes at maximum) */
struct erofs_super_block {
	__le32 magic;           /* file system magic number */
	__le32 checksum;        /* crc32c to avoid unexpected on-disk overlap */
	__le32 feature_compat;
	__u8 blkszbits;         /* filesystem block size in bit shift */
	__u8 sb_extslots;	/* superblock size = 128 + sb_extslots * 16 */
	union {
		__le16 rootnid_2b;	/* nid of root directory */
		__le16 blocks_hi;	/* (48BIT on) blocks count MSB */
	} __packed rb;
	__le64 inos;            /* total valid ino # (== f_files - f_favail) */
	__le64 epoch;		/* base seconds used for compact inodes */
	__le32 fixed_nsec;	/* fixed nanoseconds for compact inodes */
	__le32 blocks_lo;	/* blocks count LSB */
	__le32 meta_blkaddr;	/* start block address of metadata area */
	__le32 xattr_blkaddr;	/* start block address of shared xattr area */
	__u8 uuid[16];          /* 128-bit uuid for volume */
	__u8 volume_name[16];   /* volume name */
	__le32 feature_incompat;
	union {
		/* bitmap for available compression algorithms */
		__le16 available_compr_algs;
		/* customized sliding window size instead of 64k by default */
		__le16 lz4_max_distance;
	} __packed u1;
	__le16 extra_devices;	/* # of devices besides the primary device */
	__le16 devt_slotoff;	/* startoff = devt_slotoff * devt_slotsize */
	__u8 dirblkbits;	/* directory block size in bit shift */
	__u8 xattr_prefix_count;	/* # of long xattr name prefixes */
	__le32 xattr_prefix_start;	/* start of long xattr prefixes */
	__le64 packed_nid;	/* nid of the special packed inode */
	__u8 xattr_filter_reserved; /* reserved for xattr name filter */
	__u8 ishare_xattr_prefix_id;
	__u8 reserved[2];
	__le32 build_time;	/* seconds added to epoch for mkfs time */
	__le64 rootnid_8b;	/* (48BIT on) nid of root directory */
	__le64 reserved2;
	__le64 metabox_nid;     /* (METABOX on) nid of the metabox inode */
	__le64 reserved3;	/* [align to extslot 1] */
};

/*
 * EROFS inode datalayout (i_format in on-disk inode):
 * 0 - uncompressed flat inode without tail-packing inline data:
 * 1 - compressed inode with non-compact indexes:
 * 2 - uncompressed flat inode with tail-packing inline data:
 * 3 - compressed inode with compact indexes:
 * 4 - chunk-based inode with (optional) multi-device support:
 * 5~7 - reserved
 */
enum {
	EROFS_INODE_FLAT_PLAIN			= 0,
	EROFS_INODE_COMPRESSED_FULL		= 1,
	EROFS_INODE_FLAT_INLINE			= 2,
	EROFS_INODE_COMPRESSED_COMPACT		= 3,
	EROFS_INODE_CHUNK_BASED			= 4,
	EROFS_INODE_DATALAYOUT_MAX
};

static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
{
	return datamode == EROFS_INODE_COMPRESSED_COMPACT ||
		datamode == EROFS_INODE_COMPRESSED_FULL;
}

/* bit definitions of inode i_format */
#define EROFS_I_VERSION_MASK            0x01
#define EROFS_I_DATALAYOUT_MASK         0x07

#define EROFS_I_VERSION_BIT	0
#define EROFS_I_DATALAYOUT_BIT	1
#define EROFS_I_NLINK_1_BIT	4	/* non-directory compact inodes only */
#define EROFS_I_DOT_OMITTED_BIT	4	/* (directories) omit the `.` dirent */
#define EROFS_I_ALL		((1 << (EROFS_I_NLINK_1_BIT + 1)) - 1)

/* indicate chunk blkbits, thus 'chunksize = blocksize << chunk blkbits' */
#define EROFS_CHUNK_FORMAT_BLKBITS_MASK		0x001F
/* with chunk indexes or just a 4-byte block array */
#define EROFS_CHUNK_FORMAT_INDEXES		0x0020
#define EROFS_CHUNK_FORMAT_48BIT		0x0040

#define EROFS_CHUNK_FORMAT_ALL	((EROFS_CHUNK_FORMAT_48BIT << 1) - 1)

/* 32-byte on-disk inode */
#define EROFS_INODE_LAYOUT_COMPACT	0
/* 64-byte on-disk inode */
#define EROFS_INODE_LAYOUT_EXTENDED	1

struct erofs_inode_chunk_info {
	__le16 format;		/* chunk blkbits, etc. */
	__le16 reserved;
};

union erofs_inode_i_u {
	__le32 blocks_lo;	/* total blocks count (if compressed inodes) */
	__le32 startblk_lo;	/* starting block number (if flat inodes) */
	__le32 rdev;		/* device ID (if special inodes) */
	struct erofs_inode_chunk_info c;
};

union erofs_inode_i_nb {
	__le16 nlink;		/* if EROFS_I_NLINK_1_BIT is unset */
	__le16 blocks_hi;	/* total blocks count MSB */
	__le16 startblk_hi;	/* starting block number MSB */
} __packed;

/* 32-byte reduced form of an ondisk inode */
struct erofs_inode_compact {
	__le16 i_format;	/* inode format hints */
	__le16 i_xattr_icount;
	__le16 i_mode;
	union erofs_inode_i_nb i_nb;
	__le32 i_size;
	__le32 i_mtime;
	union erofs_inode_i_u i_u;

	__le32 i_ino;		/* only used for 32-bit stat compatibility */
	__le16 i_uid;
	__le16 i_gid;
	__le32 i_reserved;
};

/* 64-byte complete form of an ondisk inode */
struct erofs_inode_extended {
	__le16 i_format;	/* inode format hints */
	__le16 i_xattr_icount;
	__le16 i_mode;
	union erofs_inode_i_nb i_nb;
	__le64 i_size;
	union erofs_inode_i_u i_u;

	__le32 i_ino;		/* only used for 32-bit stat compatibility */
	__le32 i_uid;
	__le32 i_gid;
	__le64 i_mtime;
	__le32 i_mtime_nsec;
	__le32 i_nlink;
	__u8   i_reserved2[16];
};

/*
 * 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_name_filter;		/* bit value 1 indicates not-present */
	__u8   h_shared_count;
	__u8   h_reserved2[7];
	__le32 h_shared_xattrs[];       /* shared xattr id array */
};

/* 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

/*
 * bit 7 of e_name_index is set when it refers to a long xattr name prefix,
 * while the remained lower bits represent the index of the prefix.
 */
#define EROFS_XATTR_LONG_PREFIX		0x80
#define EROFS_XATTR_LONG_PREFIX_MASK	0x7f

#define EROFS_XATTR_FILTER_BITS		32
#define EROFS_XATTR_FILTER_DEFAULT	UINT32_MAX
#define EROFS_XATTR_FILTER_SEED		0x25BBE08F

/* 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[];        /* attribute name */
};

/* long xattr name prefix */
struct erofs_xattr_long_prefix {
	__u8   base_index;	/* short xattr name prefix index */
	char   infix[];		/* infix apart from short prefix */
};

static inline unsigned int erofs_xattr_ibody_size(__le16 i_xattr_icount)
{
	if (!i_xattr_icount)
		return 0;

	/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
	return sizeof(struct erofs_xattr_ibody_header) +
		sizeof(__u32) * (le16_to_cpu(i_xattr_icount) - 1);
}

#define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))

static inline unsigned int erofs_xattr_entry_size(struct erofs_xattr_entry *e)
{
	return EROFS_XATTR_ALIGN(sizeof(struct erofs_xattr_entry) +
				 e->e_name_len + le16_to_cpu(e->e_value_size));
}

/* represent a zeroed chunk (hole) */
#define EROFS_NULL_ADDR			-1

/* 4-byte block address array */
#define EROFS_BLOCK_MAP_ENTRY_SIZE	sizeof(__le32)

/* 8-byte inode chunk index */
struct erofs_inode_chunk_index {
	__le16 startblk_hi;	/* starting block number MSB */
	__le16 device_id;	/* back-end storage id (with bits masked) */
	__le32 startblk_lo;	/* starting block number of this chunk */
};

#define EROFS_DIRENT_NID_METABOX_BIT	63
#define EROFS_DIRENT_NID_MASK	(BIT_ULL(EROFS_DIRENT_NID_METABOX_BIT) - 1)

/* dirent sorts in alphabet order, thus we can do binary search */
struct erofs_dirent {
	__le64 nid;     /* node number */
	__le16 nameoff; /* start offset of file name */
	__u8 file_type; /* file type */
	__u8 reserved;  /* reserved */
} __packed;

/*
 * EROFS file types should match generic FT_* types and
 * it seems no need to add BUILD_BUG_ONs since potential
 * unmatchness will break other fses as well...
 */

#define EROFS_NAME_LEN      255

/* maximum supported encoded size of a physical compressed cluster */
#define Z_EROFS_PCLUSTER_MAX_SIZE	(1024 * 1024)

/* maximum supported decoded size of a physical compressed cluster */
#define Z_EROFS_PCLUSTER_MAX_DSIZE	(12 * 1024 * 1024)

/* available compression algorithm types (for h_algorithmtype) */
enum {
	Z_EROFS_COMPRESSION_LZ4		= 0,
	Z_EROFS_COMPRESSION_LZMA	= 1,
	Z_EROFS_COMPRESSION_DEFLATE	= 2,
	Z_EROFS_COMPRESSION_ZSTD	= 3,
	Z_EROFS_COMPRESSION_MAX
};
#define Z_EROFS_ALL_COMPR_ALGS		((1 << Z_EROFS_COMPRESSION_MAX) - 1)

/* 14 bytes (+ length field = 16 bytes) */
struct z_erofs_lz4_cfgs {
	__le16 max_distance;
	__le16 max_pclusterblks;
	u8 reserved[10];
} __packed;

/* 14 bytes (+ length field = 16 bytes) */
struct z_erofs_lzma_cfgs {
	__le32 dict_size;
	__le16 format;
	u8 reserved[8];
} __packed;

#define Z_EROFS_LZMA_MAX_DICT_SIZE	(8 * Z_EROFS_PCLUSTER_MAX_SIZE)

/* 6 bytes (+ length field = 8 bytes) */
struct z_erofs_deflate_cfgs {
	u8 windowbits;			/* 8..15 for DEFLATE */
	u8 reserved[5];
} __packed;

/* 6 bytes (+ length field = 8 bytes) */
struct z_erofs_zstd_cfgs {
	u8 format;
	u8 windowlog;           /* windowLog - ZSTD_WINDOWLOG_ABSOLUTEMIN(10) */
	u8 reserved[4];
} __packed;

#define Z_EROFS_ZSTD_MAX_DICT_SIZE      Z_EROFS_PCLUSTER_MAX_SIZE

/*
 * Enable COMPACTED_2B for EROFS_INODE_COMPRESSED_COMPACT inodes:
 *   4B (disabled) vs 4B+2B+4B (enabled)
 */
#define Z_EROFS_ADVISE_COMPACTED_2B		0x0001
/* Enable extent metadata for EROFS_INODE_COMPRESSED_FULL inodes */
#define Z_EROFS_ADVISE_EXTENTS			0x0001
#define Z_EROFS_ADVISE_BIG_PCLUSTER_1		0x0002
#define Z_EROFS_ADVISE_BIG_PCLUSTER_2		0x0004
#define Z_EROFS_ADVISE_INLINE_PCLUSTER		0x0008
#define Z_EROFS_ADVISE_INTERLACED_PCLUSTER	0x0010
#define Z_EROFS_ADVISE_FRAGMENT_PCLUSTER	0x0020
/* Indicate the record size for each extent if extent metadata is used */
#define Z_EROFS_ADVISE_EXTRECSZ_BIT		1
#define Z_EROFS_ADVISE_EXTRECSZ_MASK		0x3

#define Z_EROFS_FRAGMENT_INODE_BIT              7
struct z_erofs_map_header {
	union {
		/* fragment data offset in the packed inode */
		__le32  h_fragmentoff;
		struct {
			__le16  h_reserved1;
			/* indicates the encoded size of tailpacking data */
			__le16  h_idata_size;
		};
		__le32 h_extents_lo;	/* extent count LSB */
	};
	__le16	h_advise;
	union {
		struct {
			/* algorithm type (bit 0-3: HEAD1; bit 4-7: HEAD2) */
			__u8	h_algorithmtype;
			/*
			 * bit 0-3 : logical cluster bits - blkszbits
			 * bit 4-6 : reserved
			 * bit 7   : pack the whole file into packed inode
			 */
			__u8	h_clusterbits;
		} __packed;
		__le16 h_extents_hi;	/* extent count MSB */
	} __packed;
};

enum {
	Z_EROFS_LCLUSTER_TYPE_PLAIN	= 0,
	Z_EROFS_LCLUSTER_TYPE_HEAD1	= 1,
	Z_EROFS_LCLUSTER_TYPE_NONHEAD	= 2,
	Z_EROFS_LCLUSTER_TYPE_HEAD2	= 3,
	Z_EROFS_LCLUSTER_TYPE_MAX
};

#define Z_EROFS_LI_LCLUSTER_TYPE_MASK	(Z_EROFS_LCLUSTER_TYPE_MAX - 1)

/* (noncompact only, HEAD) This pcluster refers to partial decompressed data */
#define Z_EROFS_LI_PARTIAL_REF		(1 << 15)

/* Set on 1st non-head lcluster to store compressed block counti (in blocks) */
#define Z_EROFS_LI_D0_CBLKCNT		(1 << 11)

struct z_erofs_lcluster_index {
	__le16 di_advise;
	/* where to decompress in the head lcluster */
	__le16 di_clusterofs;

	union {
		__le32 blkaddr;		/* for the HEAD lclusters */
		/*
		 * [0] - distance to its HEAD lcluster
		 * [1] - distance to the next HEAD lcluster
		 */
		__le16 delta[2];	/* for the NONHEAD lclusters */
	} di_u;
};

#define Z_EROFS_MAP_HEADER_END(end)	\
	(ALIGN(end, 8) + sizeof(struct z_erofs_map_header))
#define Z_EROFS_FULL_INDEX_START(end)	(Z_EROFS_MAP_HEADER_END(end) + 8)

#define Z_EROFS_EXTENT_PLEN_PARTIAL	BIT(27)
#define Z_EROFS_EXTENT_PLEN_FMT_BIT	28
#define Z_EROFS_EXTENT_PLEN_MASK	((Z_EROFS_PCLUSTER_MAX_SIZE << 1) - 1)
struct z_erofs_extent {
	__le32 plen;		/* encoded length */
	__le32 pstart_lo;	/* physical offset */
	__le32 pstart_hi;	/* physical offset MSB */
	__le32 lstart_lo;	/* logical offset */
	__le32 lstart_hi;	/* logical offset MSB (>= 4GiB inodes) */
	__u8 reserved[12];	/* for future use */
};

static inline int z_erofs_extent_recsize(unsigned int advise)
{
	return 4 << ((advise >> Z_EROFS_ADVISE_EXTRECSZ_BIT) &
		Z_EROFS_ADVISE_EXTRECSZ_MASK);
}

/* check the EROFS on-disk layout strictly at compile time */
static inline void erofs_check_ondisk_layout_definitions(void)
{
	const __le64 fmh = *(__le64 *)&(struct z_erofs_map_header) {
		.h_clusterbits = 1 << Z_EROFS_FRAGMENT_INODE_BIT
	};

	BUILD_BUG_ON(sizeof(struct erofs_super_block) != 144);
	BUILD_BUG_ON(sizeof(struct erofs_inode_compact) != 32);
	BUILD_BUG_ON(sizeof(struct erofs_inode_extended) != 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_inode_chunk_info) != 4);
	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) != 8);
	BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
	BUILD_BUG_ON(sizeof(struct z_erofs_lcluster_index) != 8);
	BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
	/* keep in sync between 2 index structures for better extendibility */
	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) !=
		     sizeof(struct z_erofs_lcluster_index));
	BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);

	/* exclude old compiler versions like gcc 7.5.0 */
	BUILD_BUG_ON(__builtin_constant_p(fmh) ?
		     fmh != cpu_to_le64(1ULL << 63) : 0);
}

#endif