1/*
 2 * Copyright (C) 2003 Sistina Software.
 3 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
 4 *
 5 * Module Author: Heinz Mauelshagen
 6 *
 7 * This file is released under the GPL.
 8 *
 9 * Path-Selector registration.
10 */
11
12#ifndef	DM_PATH_SELECTOR_H
13#define	DM_PATH_SELECTOR_H
14
15#include <linux/device-mapper.h>
16
17#include "dm-mpath.h"
18
19/*
20 * We provide an abstraction for the code that chooses which path
21 * to send some io down.
22 */
23struct path_selector_type;
24struct path_selector {
25	struct path_selector_type *type;
26	void *context;
27};
28
 
 
 
 
 
 
 
 
 
 
 
 
 
 
29/* Information about a path selector type */
30struct path_selector_type {
31	char *name;
32	struct module *module;
33
 
34	unsigned int table_args;
35	unsigned int info_args;
36
37	/*
38	 * Constructs a path selector object, takes custom arguments
39	 */
40	int (*create) (struct path_selector *ps, unsigned argc, char **argv);
41	void (*destroy) (struct path_selector *ps);
42
43	/*
44	 * Add an opaque path object, along with some selector specific
45	 * path args (eg, path priority).
46	 */
47	int (*add_path) (struct path_selector *ps, struct dm_path *path,
48			 int argc, char **argv, char **error);
49
50	/*
51	 * Chooses a path for this io, if no paths are available then
52	 * NULL will be returned.
53	 */
54	struct dm_path *(*select_path) (struct path_selector *ps,
55					size_t nr_bytes);
56
57	/*
58	 * Notify the selector that a path has failed.
59	 */
60	void (*fail_path) (struct path_selector *ps, struct dm_path *p);
61
62	/*
63	 * Ask selector to reinstate a path.
64	 */
65	int (*reinstate_path) (struct path_selector *ps, struct dm_path *p);
66
67	/*
68	 * Table content based on parameters added in ps_add_path_fn
69	 * or path selector status
70	 */
71	int (*status) (struct path_selector *ps, struct dm_path *path,
72		       status_type_t type, char *result, unsigned int maxlen);
73
74	int (*start_io) (struct path_selector *ps, struct dm_path *path,
75			 size_t nr_bytes);
76	int (*end_io) (struct path_selector *ps, struct dm_path *path,
77		       size_t nr_bytes, u64 start_time);
78};
79
80/* Register a path selector */
81int dm_register_path_selector(struct path_selector_type *type);
82
83/* Unregister a path selector */
84int dm_unregister_path_selector(struct path_selector_type *type);
85
86/* Returns a registered path selector type */
87struct path_selector_type *dm_get_path_selector(const char *name);
88
89/* Releases a path selector  */
90void dm_put_path_selector(struct path_selector_type *pst);
91
92#endif

  1/* SPDX-License-Identifier: GPL-2.0-only */
  2/*
  3 * Copyright (C) 2003 Sistina Software.
  4 * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
  5 *
  6 * Module Author: Heinz Mauelshagen
  7 *
  8 * This file is released under the GPL.
  9 *
 10 * Path-Selector registration.
 11 */
 12
 13#ifndef	DM_PATH_SELECTOR_H
 14#define	DM_PATH_SELECTOR_H
 15
 16#include <linux/device-mapper.h>
 17
 18#include "dm-mpath.h"
 19
 20/*
 21 * We provide an abstraction for the code that chooses which path
 22 * to send some io down.
 23 */
 24struct path_selector_type;
 25struct path_selector {
 26	struct path_selector_type *type;
 27	void *context;
 28};
 29
 30/*
 31 * If a path selector uses this flag, a high resolution timer is used
 32 * (via ktime_get_ns) to account for IO start time in BIO-based mpath.
 33 * This improves performance of some path selectors (i.e. HST), in
 34 * exchange for slightly higher overhead when submitting the BIO.
 35 * The extra cost is usually offset by improved path selection for
 36 * some benchmarks.
 37 *
 38 * This has no effect for request-based mpath, since it already uses a
 39 * higher precision timer by default.
 40 */
 41#define DM_PS_USE_HR_TIMER		0x00000001
 42#define dm_ps_use_hr_timer(type)	((type)->features & DM_PS_USE_HR_TIMER)
 43
 44/* Information about a path selector type */
 45struct path_selector_type {
 46	char *name;
 47	struct module *module;
 48
 49	unsigned int features;
 50	unsigned int table_args;
 51	unsigned int info_args;
 52
 53	/*
 54	 * Constructs a path selector object, takes custom arguments
 55	 */
 56	int (*create)(struct path_selector *ps, unsigned int argc, char **argv);
 57	void (*destroy)(struct path_selector *ps);
 58
 59	/*
 60	 * Add an opaque path object, along with some selector specific
 61	 * path args (eg, path priority).
 62	 */
 63	int (*add_path)(struct path_selector *ps, struct dm_path *path,
 64			int argc, char **argv, char **error);
 65
 66	/*
 67	 * Chooses a path for this io, if no paths are available then
 68	 * NULL will be returned.
 69	 */
 70	struct dm_path *(*select_path)(struct path_selector *ps, size_t nr_bytes);
 
 71
 72	/*
 73	 * Notify the selector that a path has failed.
 74	 */
 75	void (*fail_path)(struct path_selector *ps, struct dm_path *p);
 76
 77	/*
 78	 * Ask selector to reinstate a path.
 79	 */
 80	int (*reinstate_path)(struct path_selector *ps, struct dm_path *p);
 81
 82	/*
 83	 * Table content based on parameters added in ps_add_path_fn
 84	 * or path selector status
 85	 */
 86	int (*status)(struct path_selector *ps, struct dm_path *path,
 87		      status_type_t type, char *result, unsigned int maxlen);
 88
 89	int (*start_io)(struct path_selector *ps, struct dm_path *path,
 90			size_t nr_bytes);
 91	int (*end_io)(struct path_selector *ps, struct dm_path *path,
 92		      size_t nr_bytes, u64 start_time);
 93};
 94
 95/* Register a path selector */
 96int dm_register_path_selector(struct path_selector_type *type);
 97
 98/* Unregister a path selector */
 99int dm_unregister_path_selector(struct path_selector_type *type);
100
101/* Returns a registered path selector type */
102struct path_selector_type *dm_get_path_selector(const char *name);
103
104/* Releases a path selector  */
105void dm_put_path_selector(struct path_selector_type *pst);
106
107#endif