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
18 #define DM_MSG_PREFIX "multipath round-robin"
19
20 /*-----------------------------------------------------------------
21 * Path-handling code, paths are held in lists
22 *---------------------------------------------------------------*/
23 struct path_info {
24 struct list_head list;
25 struct dm_path *path;
26 unsigned repeat_count;
27 };
28
free_paths(struct list_head * paths)29 static void free_paths(struct list_head *paths)
30 {
31 struct path_info *pi, *next;
32
33 list_for_each_entry_safe(pi, next, paths, list) {
34 list_del(&pi->list);
35 kfree(pi);
36 }
37 }
38
39 /*-----------------------------------------------------------------
40 * Round-robin selector
41 *---------------------------------------------------------------*/
42
43 #define RR_MIN_IO 1000
44
45 struct selector {
46 struct list_head valid_paths;
47 struct list_head invalid_paths;
48 };
49
alloc_selector(void)50 static struct selector *alloc_selector(void)
51 {
52 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
53
54 if (s) {
55 INIT_LIST_HEAD(&s->valid_paths);
56 INIT_LIST_HEAD(&s->invalid_paths);
57 }
58
59 return s;
60 }
61
rr_create(struct path_selector * ps,unsigned argc,char ** argv)62 static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
63 {
64 struct selector *s;
65
66 s = alloc_selector();
67 if (!s)
68 return -ENOMEM;
69
70 ps->context = s;
71 return 0;
72 }
73
rr_destroy(struct path_selector * ps)74 static void rr_destroy(struct path_selector *ps)
75 {
76 struct selector *s = (struct selector *) ps->context;
77
78 free_paths(&s->valid_paths);
79 free_paths(&s->invalid_paths);
80 kfree(s);
81 ps->context = NULL;
82 }
83
rr_status(struct path_selector * ps,struct dm_path * path,status_type_t type,char * result,unsigned int maxlen)84 static int rr_status(struct path_selector *ps, struct dm_path *path,
85 status_type_t type, char *result, unsigned int maxlen)
86 {
87 struct path_info *pi;
88 int sz = 0;
89
90 if (!path)
91 DMEMIT("0 ");
92 else {
93 switch(type) {
94 case STATUSTYPE_INFO:
95 break;
96 case STATUSTYPE_TABLE:
97 pi = path->pscontext;
98 DMEMIT("%u ", pi->repeat_count);
99 break;
100 }
101 }
102
103 return sz;
104 }
105
106 /*
107 * Called during initialisation to register each path with an
108 * optional repeat_count.
109 */
rr_add_path(struct path_selector * ps,struct dm_path * path,int argc,char ** argv,char ** error)110 static int rr_add_path(struct path_selector *ps, struct dm_path *path,
111 int argc, char **argv, char **error)
112 {
113 struct selector *s = (struct selector *) ps->context;
114 struct path_info *pi;
115 unsigned repeat_count = RR_MIN_IO;
116
117 if (argc > 1) {
118 *error = "round-robin ps: incorrect number of arguments";
119 return -EINVAL;
120 }
121
122 /* First path argument is number of I/Os before switching path */
123 if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
124 *error = "round-robin ps: invalid repeat count";
125 return -EINVAL;
126 }
127
128 /* allocate the path */
129 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
130 if (!pi) {
131 *error = "round-robin ps: Error allocating path context";
132 return -ENOMEM;
133 }
134
135 pi->path = path;
136 pi->repeat_count = repeat_count;
137
138 path->pscontext = pi;
139
140 list_add_tail(&pi->list, &s->valid_paths);
141
142 return 0;
143 }
144
rr_fail_path(struct path_selector * ps,struct dm_path * p)145 static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
146 {
147 struct selector *s = (struct selector *) ps->context;
148 struct path_info *pi = p->pscontext;
149
150 list_move(&pi->list, &s->invalid_paths);
151 }
152
rr_reinstate_path(struct path_selector * ps,struct dm_path * p)153 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
154 {
155 struct selector *s = (struct selector *) ps->context;
156 struct path_info *pi = p->pscontext;
157
158 list_move(&pi->list, &s->valid_paths);
159
160 return 0;
161 }
162
rr_select_path(struct path_selector * ps,unsigned * repeat_count)163 static struct dm_path *rr_select_path(struct path_selector *ps,
164 unsigned *repeat_count)
165 {
166 struct selector *s = (struct selector *) ps->context;
167 struct path_info *pi = NULL;
168
169 if (!list_empty(&s->valid_paths)) {
170 pi = list_entry(s->valid_paths.next, struct path_info, list);
171 list_move_tail(&pi->list, &s->valid_paths);
172 *repeat_count = pi->repeat_count;
173 }
174
175 return pi ? pi->path : NULL;
176 }
177
178 static struct path_selector_type rr_ps = {
179 .name = "round-robin",
180 .module = THIS_MODULE,
181 .table_args = 1,
182 .info_args = 0,
183 .create = rr_create,
184 .destroy = rr_destroy,
185 .status = rr_status,
186 .add_path = rr_add_path,
187 .fail_path = rr_fail_path,
188 .reinstate_path = rr_reinstate_path,
189 .select_path = rr_select_path,
190 };
191
dm_rr_init(void)192 static int __init dm_rr_init(void)
193 {
194 int r = dm_register_path_selector(&rr_ps);
195
196 if (r < 0)
197 DMERR("register failed %d", r);
198
199 DMINFO("version 1.0.0 loaded");
200
201 return r;
202 }
203
dm_rr_exit(void)204 static void __exit dm_rr_exit(void)
205 {
206 int r = dm_unregister_path_selector(&rr_ps);
207
208 if (r < 0)
209 DMERR("unregister failed %d", r);
210 }
211
212 module_init(dm_rr_init);
213 module_exit(dm_rr_exit);
214
215 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
216 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
217 MODULE_LICENSE("GPL");
218