path: root/include/linux/device-mapper.h

/*
 * Copyright (C) 2001 Sistina Software (UK) Limited.
 * Copyright (C) 2004-2008 Red Hat, Inc. All rights reserved.
 *
 * This file is released under the LGPL.
 */

#ifndef _LINUX_DEVICE_MAPPER_H
#define _LINUX_DEVICE_MAPPER_H

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/math64.h>
#include <linux/ratelimit.h>

struct dm_dev;
struct dm_target;
struct dm_table;
struct mapped_device;
struct bio_vec;

/*
 * Type of table, mapped_device's mempool and request_queue
 */
enum dm_queue_mode {
	DM_TYPE_NONE		 = 0,
	DM_TYPE_BIO_BASED	 = 1,
	DM_TYPE_REQUEST_BASED	 = 2,
	DM_TYPE_MQ_REQUEST_BASED = 3,
	DM_TYPE_DAX_BIO_BASED	 = 4,
};

typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;

union map_info {
	void *ptr;
};

/*
 * In the constructor the target parameter will already have the
 * table, type, begin and len fields filled in.
 */
typedef int (*dm_ctr_fn) (struct dm_target *target,
			  unsigned int argc, char **argv);

/*
 * The destructor doesn't need to free the dm_target, just
 * anything hidden ti->private.
 */
typedef void (*dm_dtr_fn) (struct dm_target *ti);

/*
 * The map function must return:
 * < 0: error
 * = 0: The target will handle the io by resubmitting it later
 * = 1: simple remap complete
 * = 2: The target wants to push back the io
 */
typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio);
typedef int (*dm_clone_and_map_request_fn) (struct dm_target *ti,
					    struct request *rq,
					    union map_info *map_context,
					    struct request **clone);
typedef void (*dm_release_clone_request_fn) (struct request *clone);

/*
 * Returns:
 * < 0 : error (currently ignored)
 * 0   : ended successfully
 * 1   : for some reason the io has still not completed (eg,
 *       multipath target might want to requeue a failed io).
 * 2   : The target wants to push back the io
 */
typedef int (*dm_endio_fn) (struct dm_target *ti,
			    struct bio *bio, blk_status_t *error);
typedef int (*dm_request_endio_fn) (struct dm_target *ti,
				    struct request *clone, blk_status_t error,
				    union map_info *map_context);

typedef void (*dm_presuspend_fn) (struct dm_target *ti);
typedef void (*dm_presuspend_undo_fn) (struct dm_target *ti);
typedef void (*dm_postsuspend_fn) (struct dm_target *ti);
typedef int (*dm_preresume_fn) (struct dm_target *ti);
typedef void (*dm_resume_fn) (struct dm_target *ti);

typedef void (*dm_status_fn) (struct dm_target *ti, status_type_t status_type,
			      unsigned status_flags, char *result, unsigned maxlen);

typedef int (*dm_message_fn) (struct dm_target *ti, unsigned argc, char **argv);

typedef int (*dm_prepare_ioctl_fn) (struct dm_target *ti,
			    struct block_device **bdev, fmode_t *mode);

/*
 * These iteration functions are typically used to check (and combine)
 * properties of underlying devices.
 * E.g. Does at least one underlying device support flush?
 *      Does any underlying device not support WRITE_SAME?
 *
 * The callout function is called once for each contiguous section of
 * an underlying device.  State can be maintained in *data.
 * Return non-zero to stop iterating through any further devices.
 */
typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
					   struct dm_dev *dev,
					   sector_t start, sector_t len,
					   void *data);

/*
 * This function must iterate through each section of device used by the
 * target until it encounters a non-zero return code, which it then returns.
 * Returns zero if no callout returned non-zero.
 */
typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
				      iterate_devices_callout_fn fn,
				      void *data);

typedef void (*dm_io_hints_fn) (struct dm_target *ti,
				struct queue_limits *limits);

/*
 * Returns:
 *    0: The target can handle the next I/O immediately.
 *    1: The target can't handle the next I/O immediately.
 */
typedef int (*dm_busy_fn) (struct dm_target *ti);

/*
 * Returns:
 *  < 0 : error
 * >= 0 : the number of bytes accessible at the address
 */
typedef long (*dm_dax_direct_access_fn) (struct dm_target *ti, pgoff_t pgoff,
		long nr_pages, void **kaddr, pfn_t *pfn);
typedef size_t (*dm_dax_copy_from_iter_fn)(struct dm_target *ti, pgoff_t pgoff,
		void *addr, size_t bytes, struct iov_iter *i);
#define PAGE_SECTORS (PAGE_SIZE / 512)

void dm_error(const char *message);

struct dm_dev {
	struct block_device *bdev;
	struct dax_device *dax_dev;
	fmode_t mode;
	char name[16];
};

dev_t dm_get_dev_t(const char *path);

/*
 * Constructors should call these functions to ensure destination devices
 * are opened/closed correctly.
 */
int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
		  struct dm_dev **result);
void dm_put_device(struct dm_target *ti, struct dm_dev *d);

/*
 * Information about a target type
 */

struct target_type {
	uint64_t features;
	const char *name;
	struct module *module;
	unsigned version[3];
	dm_ctr_fn ctr;
	dm_dtr_fn dtr;
	dm_map_fn map;
	dm_clone_and_map_request_fn clone_and_map_rq;
	dm_release_clone_request_fn release_clone_rq;
	dm_endio_fn end_io;
	dm_request_endio_fn rq_end_io;
	dm_presuspend_fn presuspend;
	dm_presuspend_undo_fn presuspend_undo;
	dm_postsuspend_fn postsuspend;
	dm_preresume_fn preresume;
	dm_resume_fn resume;
	dm_status_fn status;
	dm_message_fn message;
	dm_prepare_ioctl_fn prepare_ioctl;
	dm_busy_fn busy;
	dm_iterate_devices_fn iterate_devices;
	dm_io_hints_fn io_hints;
	dm_dax_direct_access_fn direct_access;
	dm_dax_copy_from_iter_fn dax_copy_from_iter;

	/* For internal device-mapper use. */
	struct list_head list;
};

/*
 * Target features
 */

/*
 * Any table that contains an instance of this target must have only one.
 */
#define DM_TARGET_SINGLETON		0x00000001
#define dm_target_needs_singleton(type)	((type)->features & DM_TARGET_SINGLETON)

/*
 * Indicates that a target does not support read-only devices.
 */
#define DM_TARGET_ALWAYS_WRITEABLE	0x00000002
#define dm_target_always_writeable(type) \
		((type)->features & DM_TARGET_ALWAYS_WRITEABLE)

/*
 * Any device that contains a table with an instance of this target may never
 * have tables containing any different target type.
 */
#define DM_TARGET_IMMUTABLE		0x00000004
#define dm_target_is_immutable(type)	((type)->features & DM_TARGET_IMMUTABLE)

/*
 * Indicates that a target may replace any target; even immutable targets.
 * .map, .map_rq, .clone_and_map_rq and .release_clone_rq are all defined.
 */
#define DM_TARGET_WILDCARD		0x00000008
#define dm_target_is_wildcard(type)	((type)->features & DM_TARGET_WILDCARD)

/*
 * Some targets need to be sent the same WRITE bio severals times so
 * that they can send copies of it to different devices.  This function
 * examines any supplied bio and returns the number of copies of it the
 * target requires.
 */
typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio);

/*
 * A target implements own bio data integrity.
 */
#define DM_TARGET_INTEGRITY		0x00000010
#define dm_target_has_integrity(type)	((type)->features & DM_TARGET_INTEGRITY)

/*
 * A target passes integrity data to the lower device.
 */
#define DM_TARGET_PASSES_INTEGRITY	0x00000020
#define dm_target_passes_integrity(type) ((type)->features & DM_TARGET_PASSES_INTEGRITY)

/*
 * Indicates that a target supports host-managed zoned block devices.
 */
#define DM_TARGET_ZONED_HM		0x00000040
#define dm_target_supports_zoned_hm(type) ((type)->features & DM_TARGET_ZONED_HM)

struct dm_target {
	struct dm_table *table;
	struct target_type *type;

	/* target limits */
	sector_t begin;
	sector_t len;

	/* If non-zero, maximum size of I/O submitted to a target. */
	uint32_t max_io_len;

	/*
	 * A number of zero-length barrier bios that will be submitted
	 * to the target for the purpose of flushing cache.
	 *
	 * The bio number can be accessed with dm_bio_get_target_bio_nr.
	 * It is a responsibility of the target driver to remap these bios
	 * to the real underlying devices.
	 */
	unsigned num_flush_bios;

	/*
	 * The number of discard bios that will be submitted to the target.
	 * The bio number can be accessed with dm_bio_get_target_bio_nr.
	 */
	unsigned num_discard_bios;

	/*
	 * The number of WRITE SAME bios that will be submitted to the target.
	 * The bio number can be accessed with dm_bio_get_target_bio_nr.
	 */
	unsigned num_write_same_bios;

	/*
	 * The number of WRITE ZEROES bios that will be submitted to the target.
	 * The bio number can be accessed with dm_bio_get_target_bio_nr.
	 */
	unsigned num_write_zeroes_bios