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 1
21#define RR_VERSION "1.2.0"
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};
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 }
105
106 return sz;
107}
108
109/*
110 * Called during initialisation to register each path with an
111 * optional repeat_count.
112 */
113static int rr_add_path(struct path_selector *ps, struct dm_path *path,
114 int argc, char **argv, char **error)
115{
116 struct selector *s = ps->context;
117 struct path_info *pi;
118 unsigned repeat_count = RR_MIN_IO;
119 char dummy;
120 unsigned long flags;
121
122 if (argc > 1) {
123 *error = "round-robin ps: incorrect number of arguments";
124 return -EINVAL;
125 }
126
127 /* First path argument is number of I/Os before switching path */
128 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
129 *error = "round-robin ps: invalid repeat count";
130 return -EINVAL;
131 }
132
133 if (repeat_count > 1) {
134 DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead");
135 repeat_count = 1;
136 }
137
138 /* allocate the path */
139 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
140 if (!pi) {
141 *error = "round-robin ps: Error allocating path context";
142 return -ENOMEM;
143 }
144
145 pi->path = path;
146 pi->repeat_count = repeat_count;
147
148 path->pscontext = pi;
149
150 spin_lock_irqsave(&s->lock, flags);
151 list_add_tail(&pi->list, &s->valid_paths);
152 spin_unlock_irqrestore(&s->lock, flags);
153
154 return 0;
155}
156
157static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
158{
159 unsigned long flags;
160 struct selector *s = ps->context;
161 struct path_info *pi = p->pscontext;
162
163 spin_lock_irqsave(&s->lock, flags);
164 list_move(&pi->list, &s->invalid_paths);
165 spin_unlock_irqrestore(&s->lock, flags);
166}
167
168static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
169{
170 unsigned long flags;
171 struct selector *s = ps->context;
172 struct path_info *pi = p->pscontext;
173
174 spin_lock_irqsave(&s->lock, flags);
175 list_move(&pi->list, &s->valid_paths);
176 spin_unlock_irqrestore(&s->lock, flags);
177
178 return 0;
179}
180
181static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
182{
183 unsigned long flags;
184 struct selector *s = ps->context;
185 struct path_info *pi = NULL;
186
187 spin_lock_irqsave(&s->lock, flags);
188 if (!list_empty(&s->valid_paths)) {
189 pi = list_entry(s->valid_paths.next, struct path_info, list);
190 list_move_tail(&pi->list, &s->valid_paths);
191 }
192 spin_unlock_irqrestore(&s->lock, flags);
193
194 return pi ? pi->path : NULL;
195}
196
197static struct path_selector_type rr_ps = {
198 .name = "round-robin",
199 .module = THIS_MODULE,
200 .table_args = 1,
201 .info_args = 0,
202 .create = rr_create,
203 .destroy = rr_destroy,
204 .status = rr_status,
205 .add_path = rr_add_path,
206 .fail_path = rr_fail_path,
207 .reinstate_path = rr_reinstate_path,
208 .select_path = rr_select_path,
209};
210
211static int __init dm_rr_init(void)
212{
213 int r = dm_register_path_selector(&rr_ps);
214
215 if (r < 0)
216 DMERR("register failed %d", r);
217
218 DMINFO("version " RR_VERSION " loaded");
219
220 return r;
221}
222
223static void __exit dm_rr_exit(void)
224{
225 int r = dm_unregister_path_selector(&rr_ps);
226
227 if (r < 0)
228 DMERR("unregister failed %d", r);
229}
230
231module_init(dm_rr_init);
232module_exit(dm_rr_exit);
233
234MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
235MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
236MODULE_LICENSE("GPL");
237