Release 4.7 drivers/md/dm-path-selector.h

/*
 * Copyright (C) 2003 Sistina Software.
 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
 *
 * Module Author: Heinz Mauelshagen
 *
 * This file is released under the GPL.
 *
 * Path-Selector registration.
 */

#ifndef	DM_PATH_SELECTOR_H

#define	DM_PATH_SELECTOR_H

#include <linux/device-mapper.h>

#include "dm-mpath.h"

/*
 * We provide an abstraction for the code that chooses which path
 * to send some io down.
 */
struct path_selector_type;

struct path_selector {
	
struct path_selector_type *type;
	
void *context;
};

/* Information about a path selector type */

struct path_selector_type {
	
char *name;
	
struct module *module;

	
unsigned int table_args;
	
unsigned int info_args;

	/*
         * Constructs a path selector object, takes custom arguments
         */
	
int (*create) (struct path_selector *ps, unsigned argc, char **argv);
	
void (*destroy) (struct path_selector *ps);

	/*
         * Add an opaque path object, along with some selector specific
         * path args (eg, path priority).
         */
	
int (*add_path) (struct path_selector *ps, struct dm_path *path,
			 int argc, char **argv, char **error);

	/*
         * Chooses a path for this io, if no paths are available then
         * NULL will be returned.
         */
	
struct dm_path *(*select_path) (struct path_selector *ps,
					size_t nr_bytes);

	/*
         * Notify the selector that a path has failed.
         */
	
void (*fail_path) (struct path_selector *ps, struct dm_path *p);

	/*
         * Ask selector to reinstate a path.
         */
	
int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);

	/*
         * Table content based on parameters added in ps_add_path_fn
         * or path selector status
         */
	
int (*status) (struct path_selector *ps, struct dm_path *path,
		       status_type_t type, char *result, unsigned int maxlen);

	
int (*start_io) (struct path_selector *ps, struct dm_path *path,
			 size_t nr_bytes);
	
int (*end_io) (struct path_selector *ps, struct dm_path *path,
		       size_t nr_bytes);
};

/* Register a path selector */
int dm_register_path_selector(struct path_selector_type *type);

/* Unregister a path selector */
int dm_unregister_path_selector(struct path_selector_type *type);

/* Returns a registered path selector type */
struct path_selector_type *dm_get_path_selector(const char *name);

/* Releases a path selector  */
void dm_put_path_selector(struct path_selector_type *pst);

#endif
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Directory: drivers/md

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