/* constant dm_target structures for error, zero, linear, stripes etc. */
struct dm_target {
	int (*init)(struct dm_table_entry *, int argc, char **argv);
	int (*destroy)(struct dm_table_entry *);
	int (*strategy)(struct dm_table_entry *, struct buf *);
	int (*upcall)(struct dm_table_entry *, struct buf *);

	SLIST_ENTRY(dm_target) next;
};


struct dm_table_entry {
	struct dm_dev *dm_dev;		/* backlink */
	uint64_t start;
	uint64_t length;

	struct dm_target *target;
	void *target_config;
	SLIST_ENTRY(dm_table_entry) next;
};
SLIST(dm_table, dm_table_entry);


struct dm_pdev {
	struct vnode *pdev_vnode;
	int refcnt;
	SLIST_ENTRY(dm_pdev) next_pdev;
};
SLIST(dm_pdevs, pm_pdev);


struct dm_dev {
	char name[DM_NAME_LEN];
	char uuid[DM_UUID_LEN];

	int minor;
	uint32_t flags;

	kmutex_t dev_mtx;
	uint32_t event_nr;
	uint32_t ref_cnt;

	struct dm_pdev pdevs;

	int cur_active_table;
	struct dm_table tables[2];

	struct dm_dev_list upcalls;
	SLIST_NEXT(dm_dev) next_upcall;

	SLIST_NEXT(dm_dev) next_devlist;
};
SLIST(dm_dev_list, dm_dev) dm_devs;


/* for zero,error : dm_target->target_config == NULL */
/* for linear : */
struct target_linear_config {
	struct dm_pdev *pdev;
	uint64_t offset;
};


/* for mirror : */
struct target_mirror_config {
	struct dm_pdev *orig;
	struct dm_pdev *copies[MAX_MIRROR_COPIES];

	/* copied blocks bitmaps administration etc*/
	struct dm_pdev *log_pdev;	/* for administration */
	uint64_t log_regionsize;	/* blocksize of mirror */

	/* list of parts that still need copied etc.; run length encoded? */
	....
};


/* for snapshot : */
struct target_snapshot_config {
	struct dm_dev *orig;

	/* modified blocks bitmaps administration etc*/
	struct dm_pdev *log_pdev;
	uint64_t log_regionsize;
	/* list of sector renames to the log device */
	...
};