1
2
3
4
5
6
7
8
9
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 1
21#define RR_VERSION "1.2.0"
22
23
24
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
44
45
46struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
49 spinlock_t lock;
50};
51
52static struct selector *alloc_selector(void)
53{
54 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
55
56 if (s) {
57 INIT_LIST_HEAD(&s->valid_paths);
58 INIT_LIST_HEAD(&s->invalid_paths);
59 spin_lock_init(&s->lock);
60 }
61
62 return s;
63}
64
65static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
66{
67 struct selector *s;
68
69 s = alloc_selector();
70 if (!s)
71 return -ENOMEM;
72
73 ps->context = s;
74 return 0;
75}
76
77static void rr_destroy(struct path_selector *ps)
78{
79 struct selector *s = ps->context;
80
81 free_paths(&s->valid_paths);
82 free_paths(&s->invalid_paths);
83 kfree(s);
84 ps->context = NULL;
85}
86
87static int rr_status(struct path_selector *ps, struct dm_path *path,
88 status_type_t type, char *result, unsigned int maxlen)
89{
90 struct path_info *pi;
91 int sz = 0;
92
93 if (!path)
94 DMEMIT("0 ");
95 else {
96 switch(type) {
97 case STATUSTYPE_INFO:
98 break;
99 case STATUSTYPE_TABLE:
100 pi = path->pscontext;
101 DMEMIT("%u ", pi->repeat_count);
102 break;
103
104 case STATUSTYPE_IMA:
105 *result = '\0';
106 break;
107 }
108 }
109
110 return sz;
111}
112
113
114
115
116
117static int rr_add_path(struct path_selector *ps, struct dm_path *path,
118 int argc, char **argv, char **error)
119{
120 struct selector *s = ps->context;
121 struct path_info *pi;
122 unsigned repeat_count = RR_MIN_IO;
123 char dummy;
124 unsigned long flags;
125
126 if (argc > 1) {
127 *error = "round-robin ps: incorrect number of arguments";
128 return -EINVAL;
129 }
130
131
132 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
133 *error = "round-robin ps: invalid repeat count";
134 return -EINVAL;
135 }
136
137 if (repeat_count > 1) {
138 DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead");
139 repeat_count = 1;
140 }
141
142
143 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
144 if (!pi) {
145 *error = "round-robin ps: Error allocating path context";
146 return -ENOMEM;
147 }
148
149 pi->path = path;
150 pi->repeat_count = repeat_count;
151
152 path->pscontext = pi;
153
154 spin_lock_irqsave(&s->lock, flags);
155 list_add_tail(&pi->list, &s->valid_paths);
156 spin_unlock_irqrestore(&s->lock, flags);
157
158 return 0;
159}
160
161static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
162{
163 unsigned long flags;
164 struct selector *s = ps->context;
165 struct path_info *pi = p->pscontext;
166
167 spin_lock_irqsave(&s->lock, flags);
168 list_move(&pi->list, &s->invalid_paths);
169 spin_unlock_irqrestore(&s->lock, flags);
170}
171
172static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
173{
174 unsigned long flags;
175 struct selector *s = ps->context;
176 struct path_info *pi = p->pscontext;
177
178 spin_lock_irqsave(&s->lock, flags);
179 list_move(&pi->list, &s->valid_paths);
180 spin_unlock_irqrestore(&s->lock, flags);
181
182 return 0;
183}
184
185static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
186{
187 unsigned long flags;
188 struct selector *s = ps->context;
189 struct path_info *pi = NULL;
190
191 spin_lock_irqsave(&s->lock, flags);
192 if (!list_empty(&s->valid_paths)) {
193 pi = list_entry(s->valid_paths.next, struct path_info, list);
194 list_move_tail(&pi->list, &s->valid_paths);
195 }
196 spin_unlock_irqrestore(&s->lock, flags);
197
198 return pi ? pi->path : NULL;
199}
200
201static struct path_selector_type rr_ps = {
202 .name = "round-robin",
203 .module = THIS_MODULE,
204 .table_args = 1,
205 .info_args = 0,
206 .create = rr_create,
207 .destroy = rr_destroy,
208 .status = rr_status,
209 .add_path = rr_add_path,
210 .fail_path = rr_fail_path,
211 .reinstate_path = rr_reinstate_path,
212 .select_path = rr_select_path,
213};
214
215static int __init dm_rr_init(void)
216{
217 int r = dm_register_path_selector(&rr_ps);
218
219 if (r < 0)
220 DMERR("register failed %d", r);
221
222 DMINFO("version " RR_VERSION " loaded");
223
224 return r;
225}
226
227static void __exit dm_rr_exit(void)
228{
229 int r = dm_unregister_path_selector(&rr_ps);
230
231 if (r < 0)
232 DMERR("unregister failed %d", r);
233}
234
235module_init(dm_rr_init);
236module_exit(dm_rr_exit);
237
238MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
239MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
240MODULE_LICENSE("GPL");
241
