path: root/drivers/md/dm-vdo/encodings.h

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright 2023 Red Hat
 */

#ifndef VDO_ENCODINGS_H
#define VDO_ENCODINGS_H

#include <linux/blk_types.h>
#include <linux/crc32.h>
#include <linux/limits.h>
#include <linux/uuid.h>

#include "numeric.h"

#include "constants.h"
#include "types.h"

/*
 * An in-memory representation of a version number for versioned structures on disk.
 *
 * A version number consists of two portions, a major version and a minor version. Any format
 * change which does not require an explicit upgrade step from the previous version should
 * increment the minor version. Any format change which either requires an explicit upgrade step,
 * or is wholly incompatible (i.e. can not be upgraded to), should increment the major version, and
 * set the minor version to 0.
 */
struct version_number {
	u32 major_version;
	u32 minor_version;
};

/*
 * A packed, machine-independent, on-disk representation of a version_number. Both fields are
 * stored in little-endian byte order.
 */
struct packed_version_number {
	__le32 major_version;
	__le32 minor_version;
} __packed;

/* The registry of component ids for use in headers */
#define VDO_SUPER_BLOCK 0
#define VDO_LAYOUT 1
#define VDO_RECOVERY_JOURNAL 2
#define VDO_SLAB_DEPOT 3
#define VDO_BLOCK_MAP 4
#define VDO_GEOMETRY_BLOCK 5

/* The header for versioned data stored on disk. */
struct header {
	u32 id; /* The component this is a header for */
	struct version_number version; /* The version of the data format */
	size_t size; /* The size of the data following this header */
};

/* A packed, machine-independent, on-disk representation of a component header. */
struct packed_header {
	__le32 id;
	struct packed_version_number version;
	__le64 size;
} __packed;

enum {
	VDO_GEOMETRY_BLOCK_LOCATION = 0,
	VDO_GEOMETRY_MAGIC_NUMBER_SIZE = 8,
	VDO_DEFAULT_GEOMETRY_BLOCK_VERSION = 5,
};

struct index_config {
	u32 mem;
	u32 unused;
	bool sparse;
} __packed;

enum volume_region_id {
	VDO_INDEX_REGION = 0,
	VDO_DATA_REGION = 1,
	VDO_VOLUME_REGION_COUNT,
};

struct volume_region {
	/* The ID of the region */
	enum volume_region_id id;
	/*
	 * The absolute starting offset on the device. The region continues until the next region
	 * begins.
	 */
	physical_block_number_t start_block;
} __packed;

struct volume_geometry {
	/* For backwards compatibility */
	u32 unused;
	/* The nonce of this volume */
	nonce_t nonce;
	/* The uuid of this volume */
	uuid_t uuid;
	/* The block offset to be applied to bios */
	block_count_t bio_offset;
	/* The regions in ID order */
	struct volume_region regions[VDO_VOLUME_REGION_COUNT];
	/* The index config */
	struct index_config index_config;
} __packed;

/* This volume geometry struct is used for sizing only */
struct volume_geometry_4_0 {
	/* For backwards compatibility */
	u32 unused;
	/* The nonce of this volume */
	nonce_t nonce;
	/* The uuid of this volume */
	uuid_t uuid;
	/* The regions in ID order */
	struct volume_region regions[VDO_VOLUME_REGION_COUNT];
	/* The index config */
	struct index_config index_config;
} __packed;

extern const u8 VDO_GEOMETRY_MAGIC_NUMBER[VDO_GEOMETRY_MAGIC_NUMBER_SIZE + 1];

/**
 * DOC: Block map entries
 *
 * The entry for each logical block in the block map is encoded into five bytes, which saves space
 * in both the on-disk and in-memory layouts. It consists of the 36 low-order bits of a
 * physical_block_number_t (addressing 256 terabytes with a 4KB block size) and a 4-bit encoding of
 * a block_mapping_state.
 *
 * Of the 8 high bits of the 5-byte structure:
 *
 * Bits 7..4: The four highest bits of the 36-bit physical block number
 * Bits 3..0: The 4-bit block_mapping_state
 *
 * The following 4 bytes are the low order bytes of the physical block number, in little-endian
 * order.
 *
 * Conversion functions to and from a data location are provided.
 */
struct block_map_entry {
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
	unsigned mapping_state : 4;
	unsigned pbn_high_nibble : 4;
#else
	unsigned pbn_high_nibble : 4;
	unsigned mapping_state : 4;
#endif

	__le32 pbn_low_word;
} __packed;

struct block_map_page_header {
	__le64 nonce;
	__le64 pbn;

	/* May be non-zero on disk */
	u8 unused_long_word[8];

	/* Whether this page has been written twice to disk */
	bool initialized;

	/* Always zero on disk */
	u8 unused_byte1;

	/* May be non-zero on disk */
	u8 unused_byte2;
	u8 unused_byte3;