fs/erofs/erofs_fs.h - filogic/uboot - Gitiles

 /* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
 /*
  * 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

 #include <asm/unaligned.h>
 #include <fs.h>
 #include <part.h>
 #include <stdint.h>
 #include <compiler.h>

 #define EROFS_SUPER_MAGIC_V1    0xE0F5E1E2
 #define EROFS_SUPER_OFFSET      1024

 #define EROFS_FEATURE_COMPAT_SB_CHKSUM          0x00000001
 #define EROFS_FEATURE_COMPAT_MTIME              0x00000002

 /*
  * Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
  * be incompatible with this kernel version.
  */
 #define EROFS_FEATURE_INCOMPAT_ZERO_PADDING	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_ALL_FEATURE_INCOMPAT		\
 	(EROFS_FEATURE_INCOMPAT_ZERO_PADDING | \
 	 EROFS_FEATURE_INCOMPAT_COMPR_CFGS | \
 	 EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER | \
 	 EROFS_FEATURE_INCOMPAT_CHUNKED_FILE | \
 	 EROFS_FEATURE_INCOMPAT_DEVICE_TABLE | \
 	 EROFS_FEATURE_INCOMPAT_COMPR_HEAD2 | \
 	 EROFS_FEATURE_INCOMPAT_ZTAILPACKING | \
 	 EROFS_FEATURE_INCOMPAT_FRAGMENTS | \
 	 EROFS_FEATURE_INCOMPAT_DEDUPE | \
 	 EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES)

 #define EROFS_SB_EXTSLOT_SIZE	16

 struct erofs_deviceslot {
 	u8 tag[64];		/* digest(sha256), etc. */
 	__le32 blocks;		/* total fs blocks of this device */
 	__le32 mapped_blkaddr;	/* map starting at mapped_blkaddr */
 	u8 reserved[56];
 };

 #define EROFS_DEVT_SLOT_SIZE	sizeof(struct erofs_deviceslot)

 /* erofs on-disk super block (currently 128 bytes) */
 struct erofs_super_block {
 	__le32 magic;           /* file system magic number */
 	__le32 checksum;        /* crc32c(super_block) */
 	__le32 feature_compat;
 	__u8 blkszbits;         /* filesystem block size in bit shift */
 	__u8 sb_extslots;	/* superblock size = 128 + sb_extslots * 16 */

 	__le16 root_nid;	/* nid of root directory */
 	__le64 inos;            /* total valid ino # (== f_files - f_favail) */

 	__le64 build_time;      /* compact inode time derivation */
 	__le32 build_time_nsec;	/* compact inode time derivation in ns scale */
 	__le32 blocks;          /* used for statfs */
 	__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 reserved2[24];
 };

 /*
  * 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_BITS            1
 #define EROFS_I_DATALAYOUT_BITS         3

 #define EROFS_I_VERSION_BIT             0
 #define EROFS_I_DATALAYOUT_BIT          1

 #define EROFS_I_ALL	\
 	((1 << (EROFS_I_DATALAYOUT_BIT + EROFS_I_DATALAYOUT_BITS)) - 1)

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

 #define EROFS_CHUNK_FORMAT_ALL	\
 	(EROFS_CHUNK_FORMAT_BLKBITS_MASK | EROFS_CHUNK_FORMAT_INDEXES)

 /* 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 {
 	/* total compressed blocks for compressed inodes */
 	__le32 compressed_blocks;

 	/* block address for uncompressed flat inodes */
 	__le32 raw_blkaddr;

 	/* for device files, used to indicate old/new device # */
 	__le32 rdev;

 	/* for chunk-based files, it contains the summary info */
 	struct erofs_inode_chunk_info c;
 };

 /* 32-byte reduced form of an ondisk inode */
 struct erofs_inode_compact {
 	__le16 i_format;	/* inode format hints */

 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
 	__le16 i_xattr_icount;
 	__le16 i_mode;
 	__le16 i_nlink;
 	__le32 i_size;
 	__le32 i_reserved;
 	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_reserved2;
 };

 /* 64-byte complete form of an ondisk inode */
 struct erofs_inode_extended {
 	__le16 i_format;	/* inode format hints */

 /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
 	__le16 i_xattr_icount;
 	__le16 i_mode;
 	__le16 i_reserved;
 	__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_reserved;
 	__u8   h_shared_count;
 	__u8   h_reserved2[7];
 	__le32 h_shared_xattrs[0];      /* 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

 /* 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 */
 };

 /* long xattr name prefix */
 struct erofs_xattr_long_prefix {
 	__u8   base_index;	/* short xattr name prefix index */
 	char   infix[0];	/* infix apart from short prefix */
 };

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

 	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 indexes */
 struct erofs_inode_chunk_index {
 	__le16 advise;		/* always 0, don't care for now */
 	__le16 device_id;	/* back-end storage id (with bits masked) */
 	__le32 blkaddr;		/* start block address of this inode chunk */
 };

 /* 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;

 /* 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

 /* maximum supported size of a physical compression cluster */
 #define Z_EROFS_PCLUSTER_MAX_SIZE	(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_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)

 /*
  * 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.
  * bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
  * bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
  * bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
  * bit 4 : interlaced plain pcluster (0 - off; 1 - on)
  * bit 5 : fragment pcluster (0 - off; 1 - on)
  */
 #define Z_EROFS_ADVISE_COMPACTED_2B		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

 #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;
 		};
 	};
 	__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 3-6 : reserved;
 	 * bit 7   : move the whole file into packed inode or not.
 	 */
 	__u8	h_clusterbits;
 };

 /*
  * On-disk logical cluster type:
  *    0   - literal (uncompressed) lcluster
  *    1,3 - compressed lcluster (for HEAD lclusters)
  *    2   - compressed lcluster (for NONHEAD lclusters)
  *
  * In detail,
  *    0 - literal (uncompressed) lcluster,
  *        di_advise = 0
  *        di_clusterofs = the literal data offset of the lcluster
  *        di_blkaddr = the blkaddr of the literal pcluster
  *
  *    1,3 - compressed lcluster (for HEAD lclusters)
  *        di_advise = 1 or 3
  *        di_clusterofs = the decompressed data offset of the lcluster
  *        di_blkaddr = the blkaddr of the compressed pcluster
  *
  *    2 - compressed lcluster (for NONHEAD lclusters)
  *        di_advise = 2
  *        di_clusterofs =
  *           the decompressed data offset in its own HEAD lcluster
  *        di_u.delta[0] = distance to this HEAD lcluster
  *        di_u.delta[1] = distance to the next HEAD lcluster
  */
 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_BITS        2
 #define Z_EROFS_LI_LCLUSTER_TYPE_BIT         0

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

 /*
  * D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
  * compressed block count of a compressed extent (in logical clusters, aka.
  * block count of a pcluster).
  */
 #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 {
 		/* for the HEAD lclusters */
 		__le32 blkaddr;
 		/*
 		 * for the NONHEAD lclusters
 		 * [0] - distance to its HEAD lcluster
 		 * [1] - distance to the next HEAD lcluster
 		 */
 		__le16 delta[2];
 	} di_u;
 };

 #define Z_EROFS_FULL_INDEX_ALIGN(end)	\
 	(round_up(end, 8) + sizeof(struct z_erofs_map_header) + 8)

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

 	BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
 	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);

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

 #endif
	/* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
	/*
	* 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

	#include <asm/unaligned.h>
	#include <fs.h>
	#include <part.h>
	#include <stdint.h>
	#include <compiler.h>

	#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
	#define EROFS_SUPER_OFFSET 1024

	#define EROFS_FEATURE_COMPAT_SB_CHKSUM 0x00000001
	#define EROFS_FEATURE_COMPAT_MTIME 0x00000002

	/*
	* Any bits that aren't in EROFS_ALL_FEATURE_INCOMPAT should
	* be incompatible with this kernel version.
	*/
	#define EROFS_FEATURE_INCOMPAT_ZERO_PADDING 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_ALL_FEATURE_INCOMPAT \
	(EROFS_FEATURE_INCOMPAT_ZERO_PADDING \| \
	EROFS_FEATURE_INCOMPAT_COMPR_CFGS \| \
	EROFS_FEATURE_INCOMPAT_BIG_PCLUSTER \| \
	EROFS_FEATURE_INCOMPAT_CHUNKED_FILE \| \
	EROFS_FEATURE_INCOMPAT_DEVICE_TABLE \| \
	EROFS_FEATURE_INCOMPAT_COMPR_HEAD2 \| \
	EROFS_FEATURE_INCOMPAT_ZTAILPACKING \| \
	EROFS_FEATURE_INCOMPAT_FRAGMENTS \| \
	EROFS_FEATURE_INCOMPAT_DEDUPE \| \
	EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES)

	#define EROFS_SB_EXTSLOT_SIZE 16

	struct erofs_deviceslot {
	u8 tag[64]; /* digest(sha256), etc. */
	__le32 blocks; /* total fs blocks of this device */
	__le32 mapped_blkaddr; /* map starting at mapped_blkaddr */
	u8 reserved[56];
	};

	#define EROFS_DEVT_SLOT_SIZE sizeof(struct erofs_deviceslot)

	/* erofs on-disk super block (currently 128 bytes) */
	struct erofs_super_block {
	__le32 magic; /* file system magic number */
	__le32 checksum; /* crc32c(super_block) */
	__le32 feature_compat;
	__u8 blkszbits; /* filesystem block size in bit shift */
	__u8 sb_extslots; /* superblock size = 128 + sb_extslots * 16 */

	__le16 root_nid; /* nid of root directory */
	__le64 inos; /* total valid ino # (== f_files - f_favail) */

	__le64 build_time; /* compact inode time derivation */
	__le32 build_time_nsec; /* compact inode time derivation in ns scale */
	__le32 blocks; /* used for statfs */
	__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 reserved2[24];
	};

	/*
	* 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_BITS 1
	#define EROFS_I_DATALAYOUT_BITS 3

	#define EROFS_I_VERSION_BIT 0
	#define EROFS_I_DATALAYOUT_BIT 1

	#define EROFS_I_ALL \
	((1 << (EROFS_I_DATALAYOUT_BIT + EROFS_I_DATALAYOUT_BITS)) - 1)

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

	#define EROFS_CHUNK_FORMAT_ALL \
	(EROFS_CHUNK_FORMAT_BLKBITS_MASK \| EROFS_CHUNK_FORMAT_INDEXES)

	/* 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 {
	/* total compressed blocks for compressed inodes */
	__le32 compressed_blocks;

	/* block address for uncompressed flat inodes */
	__le32 raw_blkaddr;

	/* for device files, used to indicate old/new device # */
	__le32 rdev;

	/* for chunk-based files, it contains the summary info */
	struct erofs_inode_chunk_info c;
	};

	/* 32-byte reduced form of an ondisk inode */
	struct erofs_inode_compact {
	__le16 i_format; /* inode format hints */

	/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
	__le16 i_xattr_icount;
	__le16 i_mode;
	__le16 i_nlink;
	__le32 i_size;
	__le32 i_reserved;
	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_reserved2;
	};

	/* 64-byte complete form of an ondisk inode */
	struct erofs_inode_extended {
	__le16 i_format; /* inode format hints */

	/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
	__le16 i_xattr_icount;
	__le16 i_mode;
	__le16 i_reserved;
	__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_reserved;
	__u8 h_shared_count;
	__u8 h_reserved2[7];
	__le32 h_shared_xattrs[0]; /* 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

	/* 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 */
	};

	/* long xattr name prefix */
	struct erofs_xattr_long_prefix {
	__u8 base_index; /* short xattr name prefix index */
	char infix[0]; /* infix apart from short prefix */
	};

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

	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 indexes */
	struct erofs_inode_chunk_index {
	__le16 advise; /* always 0, don't care for now */
	__le16 device_id; /* back-end storage id (with bits masked) */
	__le32 blkaddr; /* start block address of this inode chunk */
	};

	/* 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;

	/* 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

	/* maximum supported size of a physical compression cluster */
	#define Z_EROFS_PCLUSTER_MAX_SIZE (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_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)

	/*
	* 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.
	* bit 1 : HEAD1 big pcluster (0 - off; 1 - on)
	* bit 2 : HEAD2 big pcluster (0 - off; 1 - on)
	* bit 3 : tailpacking inline pcluster (0 - off; 1 - on)
	* bit 4 : interlaced plain pcluster (0 - off; 1 - on)
	* bit 5 : fragment pcluster (0 - off; 1 - on)
	*/
	#define Z_EROFS_ADVISE_COMPACTED_2B 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

	#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;
	};
	};
	__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 3-6 : reserved;
	* bit 7 : move the whole file into packed inode or not.
	*/
	__u8 h_clusterbits;
	};

	/*
	* On-disk logical cluster type:
	* 0 - literal (uncompressed) lcluster
	* 1,3 - compressed lcluster (for HEAD lclusters)
	* 2 - compressed lcluster (for NONHEAD lclusters)
	*
	* In detail,
	* 0 - literal (uncompressed) lcluster,
	* di_advise = 0
	* di_clusterofs = the literal data offset of the lcluster
	* di_blkaddr = the blkaddr of the literal pcluster
	*
	* 1,3 - compressed lcluster (for HEAD lclusters)
	* di_advise = 1 or 3
	* di_clusterofs = the decompressed data offset of the lcluster
	* di_blkaddr = the blkaddr of the compressed pcluster
	*
	* 2 - compressed lcluster (for NONHEAD lclusters)
	* di_advise = 2
	* di_clusterofs =
	* the decompressed data offset in its own HEAD lcluster
	* di_u.delta[0] = distance to this HEAD lcluster
	* di_u.delta[1] = distance to the next HEAD lcluster
	*/
	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_BITS 2
	#define Z_EROFS_LI_LCLUSTER_TYPE_BIT 0

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

	/*
	* D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
	* compressed block count of a compressed extent (in logical clusters, aka.
	* block count of a pcluster).
	*/
	#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 {
	/* for the HEAD lclusters */
	__le32 blkaddr;
	/*
	* for the NONHEAD lclusters
	* [0] - distance to its HEAD lcluster
	* [1] - distance to the next HEAD lcluster
	*/
	__le16 delta[2];
	} di_u;
	};

	#define Z_EROFS_FULL_INDEX_ALIGN(end) \
	(round_up(end, 8) + sizeof(struct z_erofs_map_header) + 8)

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

	BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
	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);

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

	#endif