path: root/drivers/md/dm-cache-metadata.c

/*
 * Copyright (C) 2012 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-cache-metadata.h"

#include "persistent-data/dm-array.h"
#include "persistent-data/dm-bitset.h"
#include "persistent-data/dm-space-map.h"
#include "persistent-data/dm-space-map-disk.h"
#include "persistent-data/dm-transaction-manager.h"

#include <linux/device-mapper.h>

/*----------------------------------------------------------------*/

#define DM_MSG_PREFIX   "cache metadata"

#define CACHE_SUPERBLOCK_MAGIC 06142003
#define CACHE_SUPERBLOCK_LOCATION 0

/*
 * defines a range of metadata versions that this module can handle.
 */
#define MIN_CACHE_VERSION 1
#define MAX_CACHE_VERSION 1

#define CACHE_METADATA_CACHE_SIZE 64

/*
 *  3 for btree insert +
 *  2 for btree lookup used within space map
 */
#define CACHE_MAX_CONCURRENT_LOCKS 5
#define SPACE_MAP_ROOT_SIZE 128

enum superblock_flag_bits {
	/* for spotting crashes that would invalidate the dirty bitset */
	CLEAN_SHUTDOWN,
};

/*
 * Each mapping from cache block -> origin block carries a set of flags.
 */
enum mapping_bits {
	/*
	 * A valid mapping.  Because we're using an array we clear this
	 * flag for an non existant mapping.
	 */
	M_VALID = 1,

	/*
	 * The data on the cache is different from that on the origin.
	 */
	M_DIRTY = 2
};

struct cache_disk_superblock {
	__le32 csum;
	__le32 flags;
	__le64 blocknr;

	__u8 uuid[16];
	__le64 magic;
	__le32 version;

	__u8 policy_name[CACHE_POLICY_NAME_SIZE];
	__le32 policy_hint_size;

	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
	__le64 mapping_root;
	__le64 hint_root;

	__le64 discard_root;
	__le64 discard_block_size;
	__le64 discard_nr_blocks;

	__le32 data_block_size;
	__le32 metadata_block_size;
	__le32 cache_blocks;

	__le32 compat_flags;
	__le32 compat_ro_flags;
	__le32 incompat_flags;

	__le32 read_hits;
	__le32 read_misses;
	__le32 write_hits;
	__le32 write_misses;

	__le32 policy_version[CACHE_POLICY_VERSION_SIZE];
} __packed;

struct dm_cache_metadata {
	atomic_t ref_count;
	struct list_head list;

	struct block_device *bdev;
	struct dm_block_manager *bm;
	struct dm_space_map *metadata_sm;
	struct dm_transaction_manager *tm;

	struct dm_array_info info;
	struct dm_array_info hint_info;
	struct dm_disk_bitset discard_info;

	struct rw_semaphore root_lock;
	dm_block_t root;
	dm_block_t hint_root;
	dm_block_t discard_root;

	sector_t discard_block_size;
	dm_dblock_t discard_nr_blocks;

	sector_t data_block_size;
	dm_cblock_t cache_blocks;
	bool changed:1;
	bool clean_when_opened:1;

	char policy_name[CACHE_POLICY_NAME_SIZE];
	unsigned policy_version[CACHE_POLICY_VERSION_SIZE];
	size_t policy_hint_size;
	struct dm_cache_statistics stats;

	/*
	 * Reading the space map root can fail, so we read it into this
	 * buffer before the superblock is locked and updated.
	 */
	__u8 metadata_space_map_root[SPACE_MAP_ROOT_SIZE];
};

/*-------------------------------------------------------------------