1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2003 Sistina Software.
4 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
5 *
6 * Module Author: Heinz Mauelshagen
7 *
8 * This file is released under the GPL.
9 *
10 * Round-robin path selector.
11 */
12
13#include <linux/device-mapper.h>
14
15#include "dm-path-selector.h"
16
17#include <linux/slab.h>
18#include <linux/module.h>
19
20#define DM_MSG_PREFIX "multipath round-robin"
21#define RR_MIN_IO     1
22#define RR_VERSION    "1.2.0"
23
24/*
25 *---------------------------------------------------------------
26 * Path-handling code, paths are held in lists
27 *---------------------------------------------------------------
28 */
29struct path_info {
30	struct list_head list;
31	struct dm_path *path;
32	unsigned int repeat_count;
33};
34
35static void free_paths(struct list_head *paths)
36{
37	struct path_info *pi, *next;
38
39	list_for_each_entry_safe(pi, next, paths, list) {
40		list_del(&pi->list);
41		kfree(pi);
42	}
43}
44
45/*
46 *---------------------------------------------------------------
47 * Round-robin selector
48 *---------------------------------------------------------------
49 */
50struct selector {
51	struct list_head valid_paths;
52	struct list_head invalid_paths;
53	spinlock_t lock;
54};
55
56static struct selector *alloc_selector(void)
57{
58	struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
59
60	if (s) {
61		INIT_LIST_HEAD(&s->valid_paths);
62		INIT_LIST_HEAD(&s->invalid_paths);
63		spin_lock_init(&s->lock);
64	}
65
66	return s;
67}
68
69static int rr_create(struct path_selector *ps, unsigned int argc, char **argv)
70{
71	struct selector *s;
72
73	s = alloc_selector();
74	if (!s)
75		return -ENOMEM;
76
77	ps->context = s;
78	return 0;
79}
80
81static void rr_destroy(struct path_selector *ps)
82{
83	struct selector *s = ps->context;
84
85	free_paths(&s->valid_paths);
86	free_paths(&s->invalid_paths);
87	kfree(s);
88	ps->context = NULL;
89}
90
91static int rr_status(struct path_selector *ps, struct dm_path *path,
92		     status_type_t type, char *result, unsigned int maxlen)
93{
94	struct path_info *pi;
95	int sz = 0;
96
97	if (!path)
98		DMEMIT("0 ");
99	else {
100		switch (type) {
101		case STATUSTYPE_INFO:
102			break;
103		case STATUSTYPE_TABLE:
104			pi = path->pscontext;
105			DMEMIT("%u ", pi->repeat_count);
106			break;
107
108		case STATUSTYPE_IMA:
109			*result = '\0';
110			break;
111		}
112	}
113
114	return sz;
115}
116
117/*
118 * Called during initialisation to register each path with an
119 * optional repeat_count.
120 */
121static int rr_add_path(struct path_selector *ps, struct dm_path *path,
122		       int argc, char **argv, char **error)
123{
124	struct selector *s = ps->context;
125	struct path_info *pi;
126	unsigned int repeat_count = RR_MIN_IO;
127	char dummy;
128	unsigned long flags;
129
130	if (argc > 1) {
131		*error = "round-robin ps: incorrect number of arguments";
132		return -EINVAL;
133	}
134
135	/* First path argument is number of I/Os before switching path */
136	if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
137		*error = "round-robin ps: invalid repeat count";
138		return -EINVAL;
139	}
140
141	if (repeat_count > 1) {
142		DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead");
143		repeat_count = 1;
144	}
145
146	/* allocate the path */
147	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
148	if (!pi) {
149		*error = "round-robin ps: Error allocating path context";
150		return -ENOMEM;
151	}
152
153	pi->path = path;
154	pi->repeat_count = repeat_count;
155
156	path->pscontext = pi;
157
158	spin_lock_irqsave(&s->lock, flags);
159	list_add_tail(&pi->list, &s->valid_paths);
160	spin_unlock_irqrestore(&s->lock, flags);
161
162	return 0;
163}
164
165static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
166{
167	unsigned long flags;
168	struct selector *s = ps->context;
169	struct path_info *pi = p->pscontext;
170
171	spin_lock_irqsave(&s->lock, flags);
172	list_move(&pi->list, &s->invalid_paths);
173	spin_unlock_irqrestore(&s->lock, flags);
174}
175
176static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
177{
178	unsigned long flags;
179	struct selector *s = ps->context;
180	struct path_info *pi = p->pscontext;
181
182	spin_lock_irqsave(&s->lock, flags);
183	list_move(&pi->list, &s->valid_paths);
184	spin_unlock_irqrestore(&s->lock, flags);
185
186	return 0;
187}
188
189static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
190{
191	unsigned long flags;
192	struct selector *s = ps->context;
193	struct path_info *pi = NULL;
194
195	spin_lock_irqsave(&s->lock, flags);
196	if (!list_empty(&s->valid_paths)) {
197		pi = list_entry(s->valid_paths.next, struct path_info, list);
198		list_move_tail(&pi->list, &s->valid_paths);
199	}
200	spin_unlock_irqrestore(&s->lock, flags);
201
202	return pi ? pi->path : NULL;
203}
204
205static struct path_selector_type rr_ps = {
206	.name = "round-robin",
207	.module = THIS_MODULE,
208	.table_args = 1,
209	.info_args = 0,
210	.create = rr_create,
211	.destroy = rr_destroy,
212	.status = rr_status,
213	.add_path = rr_add_path,
214	.fail_path = rr_fail_path,
215	.reinstate_path = rr_reinstate_path,
216	.select_path = rr_select_path,
217};
218
219static int __init dm_rr_init(void)
220{
221	int r = dm_register_path_selector(&rr_ps);
222
223	if (r < 0)
224		DMERR("register failed %d", r);
225
226	DMINFO("version " RR_VERSION " loaded");
227
228	return r;
229}
230
231static void __exit dm_rr_exit(void)
232{
233	int r = dm_unregister_path_selector(&rr_ps);
234
235	if (r < 0)
236		DMERR("unregister failed %d", r);
237}
238
239module_init(dm_rr_init);
240module_exit(dm_rr_exit);
241
242MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
243MODULE_AUTHOR("Sistina Software <dm-devel@lists.linux.dev>");
244MODULE_LICENSE("GPL");
245