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1/*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
4 *
5 * Module Author: Heinz Mauelshagen
6 *
7 * This file is released under the GPL.
8 *
9 * Round-robin path selector.
10 */
11
12#include <linux/device-mapper.h>
13
14#include "dm-path-selector.h"
15
16#include <linux/slab.h>
17#include <linux/module.h>
18
19#define DM_MSG_PREFIX "multipath round-robin"
20#define RR_MIN_IO 1000
21#define RR_VERSION "1.1.0"
22
23/*-----------------------------------------------------------------
24 * Path-handling code, paths are held in lists
25 *---------------------------------------------------------------*/
26struct path_info {
27 struct list_head list;
28 struct dm_path *path;
29 unsigned repeat_count;
30};
31
32static void free_paths(struct list_head *paths)
33{
34 struct path_info *pi, *next;
35
36 list_for_each_entry_safe(pi, next, paths, list) {
37 list_del(&pi->list);
38 kfree(pi);
39 }
40}
41
42/*-----------------------------------------------------------------
43 * Round-robin selector
44 *---------------------------------------------------------------*/
45
46struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
49 spinlock_t lock;
50 struct dm_path * __percpu *current_path;
51 struct percpu_counter repeat_count;
52};
53
54static void set_percpu_current_path(struct selector *s, struct dm_path *path)
55{
56 int cpu;
57
58 for_each_possible_cpu(cpu)
59 *per_cpu_ptr(s->current_path, cpu) = path;
60}
61
62static struct selector *alloc_selector(void)
63{
64 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
65
66 if (!s)
67 return NULL;
68
69 INIT_LIST_HEAD(&s->valid_paths);
70 INIT_LIST_HEAD(&s->invalid_paths);
71 spin_lock_init(&s->lock);
72
73 s->current_path = alloc_percpu(struct dm_path *);
74 if (!s->current_path)
75 goto out_current_path;
76 set_percpu_current_path(s, NULL);
77
78 if (percpu_counter_init(&s->repeat_count, 0, GFP_KERNEL))
79 goto out_repeat_count;
80
81 return s;
82
83out_repeat_count:
84 free_percpu(s->current_path);
85out_current_path:
86 kfree(s);
87 return NULL;;
88}
89
90static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
91{
92 struct selector *s;
93
94 s = alloc_selector();
95 if (!s)
96 return -ENOMEM;
97
98 ps->context = s;
99 return 0;
100}
101
102static void rr_destroy(struct path_selector *ps)
103{
104 struct selector *s = ps->context;
105
106 free_paths(&s->valid_paths);
107 free_paths(&s->invalid_paths);
108 free_percpu(s->current_path);
109 percpu_counter_destroy(&s->repeat_count);
110 kfree(s);
111 ps->context = NULL;
112}
113
114static int rr_status(struct path_selector *ps, struct dm_path *path,
115 status_type_t type, char *result, unsigned int maxlen)
116{
117 struct path_info *pi;
118 int sz = 0;
119
120 if (!path)
121 DMEMIT("0 ");
122 else {
123 switch(type) {
124 case STATUSTYPE_INFO:
125 break;
126 case STATUSTYPE_TABLE:
127 pi = path->pscontext;
128 DMEMIT("%u ", pi->repeat_count);
129 break;
130 }
131 }
132
133 return sz;
134}
135
136/*
137 * Called during initialisation to register each path with an
138 * optional repeat_count.
139 */
140static int rr_add_path(struct path_selector *ps, struct dm_path *path,
141 int argc, char **argv, char **error)
142{
143 struct selector *s = ps->context;
144 struct path_info *pi;
145 unsigned repeat_count = RR_MIN_IO;
146 char dummy;
147 unsigned long flags;
148
149 if (argc > 1) {
150 *error = "round-robin ps: incorrect number of arguments";
151 return -EINVAL;
152 }
153
154 /* First path argument is number of I/Os before switching path */
155 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
156 *error = "round-robin ps: invalid repeat count";
157 return -EINVAL;
158 }
159
160 /* allocate the path */
161 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
162 if (!pi) {
163 *error = "round-robin ps: Error allocating path context";
164 return -ENOMEM;
165 }
166
167 pi->path = path;
168 pi->repeat_count = repeat_count;
169
170 path->pscontext = pi;
171
172 spin_lock_irqsave(&s->lock, flags);
173 list_add_tail(&pi->list, &s->valid_paths);
174 spin_unlock_irqrestore(&s->lock, flags);
175
176 return 0;
177}
178
179static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
180{
181 unsigned long flags;
182 struct selector *s = ps->context;
183 struct path_info *pi = p->pscontext;
184
185 spin_lock_irqsave(&s->lock, flags);
186 if (p == *this_cpu_ptr(s->current_path))
187 set_percpu_current_path(s, NULL);
188
189 list_move(&pi->list, &s->invalid_paths);
190 spin_unlock_irqrestore(&s->lock, flags);
191}
192
193static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
194{
195 unsigned long flags;
196 struct selector *s = ps->context;
197 struct path_info *pi = p->pscontext;
198
199 spin_lock_irqsave(&s->lock, flags);
200 list_move(&pi->list, &s->valid_paths);
201 spin_unlock_irqrestore(&s->lock, flags);
202
203 return 0;
204}
205
206static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
207{
208 unsigned long flags;
209 struct selector *s = ps->context;
210 struct path_info *pi = NULL;
211 struct dm_path *current_path = NULL;
212
213 current_path = *this_cpu_ptr(s->current_path);
214 if (current_path) {
215 percpu_counter_dec(&s->repeat_count);
216 if (percpu_counter_read_positive(&s->repeat_count) > 0)
217 return current_path;
218 }
219
220 spin_lock_irqsave(&s->lock, flags);
221 if (!list_empty(&s->valid_paths)) {
222 pi = list_entry(s->valid_paths.next, struct path_info, list);
223 list_move_tail(&pi->list, &s->valid_paths);
224 percpu_counter_set(&s->repeat_count, pi->repeat_count);
225 set_percpu_current_path(s, pi->path);
226 current_path = pi->path;
227 }
228 spin_unlock_irqrestore(&s->lock, flags);
229
230 return current_path;
231}
232
233static struct path_selector_type rr_ps = {
234 .name = "round-robin",
235 .module = THIS_MODULE,
236 .table_args = 1,
237 .info_args = 0,
238 .create = rr_create,
239 .destroy = rr_destroy,
240 .status = rr_status,
241 .add_path = rr_add_path,
242 .fail_path = rr_fail_path,
243 .reinstate_path = rr_reinstate_path,
244 .select_path = rr_select_path,
245};
246
247static int __init dm_rr_init(void)
248{
249 int r = dm_register_path_selector(&rr_ps);
250
251 if (r < 0)
252 DMERR("register failed %d", r);
253
254 DMINFO("version " RR_VERSION " loaded");
255
256 return r;
257}
258
259static void __exit dm_rr_exit(void)
260{
261 int r = dm_unregister_path_selector(&rr_ps);
262
263 if (r < 0)
264 DMERR("unregister failed %d", r);
265}
266
267module_init(dm_rr_init);
268module_exit(dm_rr_exit);
269
270MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
271MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
272MODULE_LICENSE("GPL");
1/*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
4 *
5 * Module Author: Heinz Mauelshagen
6 *
7 * This file is released under the GPL.
8 *
9 * Round-robin path selector.
10 */
11
12#include <linux/device-mapper.h>
13
14#include "dm-path-selector.h"
15
16#include <linux/slab.h>
17#include <linux/module.h>
18
19#define DM_MSG_PREFIX "multipath round-robin"
20
21/*-----------------------------------------------------------------
22 * Path-handling code, paths are held in lists
23 *---------------------------------------------------------------*/
24struct path_info {
25 struct list_head list;
26 struct dm_path *path;
27 unsigned repeat_count;
28};
29
30static void free_paths(struct list_head *paths)
31{
32 struct path_info *pi, *next;
33
34 list_for_each_entry_safe(pi, next, paths, list) {
35 list_del(&pi->list);
36 kfree(pi);
37 }
38}
39
40/*-----------------------------------------------------------------
41 * Round-robin selector
42 *---------------------------------------------------------------*/
43
44#define RR_MIN_IO 1000
45
46struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
49};
50
51static struct selector *alloc_selector(void)
52{
53 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
54
55 if (s) {
56 INIT_LIST_HEAD(&s->valid_paths);
57 INIT_LIST_HEAD(&s->invalid_paths);
58 }
59
60 return s;
61}
62
63static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
64{
65 struct selector *s;
66
67 s = alloc_selector();
68 if (!s)
69 return -ENOMEM;
70
71 ps->context = s;
72 return 0;
73}
74
75static void rr_destroy(struct path_selector *ps)
76{
77 struct selector *s = (struct selector *) ps->context;
78
79 free_paths(&s->valid_paths);
80 free_paths(&s->invalid_paths);
81 kfree(s);
82 ps->context = NULL;
83}
84
85static int rr_status(struct path_selector *ps, struct dm_path *path,
86 status_type_t type, char *result, unsigned int maxlen)
87{
88 struct path_info *pi;
89 int sz = 0;
90
91 if (!path)
92 DMEMIT("0 ");
93 else {
94 switch(type) {
95 case STATUSTYPE_INFO:
96 break;
97 case STATUSTYPE_TABLE:
98 pi = path->pscontext;
99 DMEMIT("%u ", pi->repeat_count);
100 break;
101 }
102 }
103
104 return sz;
105}
106
107/*
108 * Called during initialisation to register each path with an
109 * optional repeat_count.
110 */
111static int rr_add_path(struct path_selector *ps, struct dm_path *path,
112 int argc, char **argv, char **error)
113{
114 struct selector *s = (struct selector *) ps->context;
115 struct path_info *pi;
116 unsigned repeat_count = RR_MIN_IO;
117 char dummy;
118
119 if (argc > 1) {
120 *error = "round-robin ps: incorrect number of arguments";
121 return -EINVAL;
122 }
123
124 /* First path argument is number of I/Os before switching path */
125 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
126 *error = "round-robin ps: invalid repeat count";
127 return -EINVAL;
128 }
129
130 /* allocate the path */
131 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
132 if (!pi) {
133 *error = "round-robin ps: Error allocating path context";
134 return -ENOMEM;
135 }
136
137 pi->path = path;
138 pi->repeat_count = repeat_count;
139
140 path->pscontext = pi;
141
142 list_add_tail(&pi->list, &s->valid_paths);
143
144 return 0;
145}
146
147static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
148{
149 struct selector *s = (struct selector *) ps->context;
150 struct path_info *pi = p->pscontext;
151
152 list_move(&pi->list, &s->invalid_paths);
153}
154
155static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
156{
157 struct selector *s = (struct selector *) ps->context;
158 struct path_info *pi = p->pscontext;
159
160 list_move(&pi->list, &s->valid_paths);
161
162 return 0;
163}
164
165static struct dm_path *rr_select_path(struct path_selector *ps,
166 unsigned *repeat_count, size_t nr_bytes)
167{
168 struct selector *s = (struct selector *) ps->context;
169 struct path_info *pi = NULL;
170
171 if (!list_empty(&s->valid_paths)) {
172 pi = list_entry(s->valid_paths.next, struct path_info, list);
173 list_move_tail(&pi->list, &s->valid_paths);
174 *repeat_count = pi->repeat_count;
175 }
176
177 return pi ? pi->path : NULL;
178}
179
180static struct path_selector_type rr_ps = {
181 .name = "round-robin",
182 .module = THIS_MODULE,
183 .table_args = 1,
184 .info_args = 0,
185 .create = rr_create,
186 .destroy = rr_destroy,
187 .status = rr_status,
188 .add_path = rr_add_path,
189 .fail_path = rr_fail_path,
190 .reinstate_path = rr_reinstate_path,
191 .select_path = rr_select_path,
192};
193
194static int __init dm_rr_init(void)
195{
196 int r = dm_register_path_selector(&rr_ps);
197
198 if (r < 0)
199 DMERR("register failed %d", r);
200
201 DMINFO("version 1.0.0 loaded");
202
203 return r;
204}
205
206static void __exit dm_rr_exit(void)
207{
208 int r = dm_unregister_path_selector(&rr_ps);
209
210 if (r < 0)
211 DMERR("unregister failed %d", r);
212}
213
214module_init(dm_rr_init);
215module_exit(dm_rr_exit);
216
217MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
218MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
219MODULE_LICENSE("GPL");