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 */
29 struct path_info {
30 struct list_head list;
31 struct dm_path *path;
32 unsigned int repeat_count;
33 };
34
free_paths(struct list_head * paths)35 static 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 */
50 struct selector {
51 struct list_head valid_paths;
52 struct list_head invalid_paths;
53 spinlock_t lock;
54 };
55
alloc_selector(void)56 static 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
rr_create(struct path_selector * ps,unsigned int argc,char ** argv)69 static 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
rr_destroy(struct path_selector * ps)81 static 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
rr_status(struct path_selector * ps,struct dm_path * path,status_type_t type,char * result,unsigned int maxlen)91 static 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 */
rr_add_path(struct path_selector * ps,struct dm_path * path,int argc,char ** argv,char ** error)121 static 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
rr_fail_path(struct path_selector * ps,struct dm_path * p)165 static 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
rr_reinstate_path(struct path_selector * ps,struct dm_path * p)176 static 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
rr_select_path(struct path_selector * ps,size_t nr_bytes)189 static 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
205 static 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
dm_rr_init(void)219 static 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
dm_rr_exit(void)231 static 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
239 module_init(dm_rr_init);
240 module_exit(dm_rr_exit);
241
242 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
243 MODULE_AUTHOR("Sistina Software <dm-devel@lists.linux.dev>");
244 MODULE_LICENSE("GPL");
245