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 *---------------------------------------------------------------*/
24 struct path_info {
25 struct list_head list;
26 struct dm_path *path;
27 unsigned repeat_count;
28 };
29
free_paths(struct list_head * paths)30 static 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
46 struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
49 };
50
alloc_selector(void)51 static 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
rr_create(struct path_selector * ps,unsigned argc,char ** argv)63 static 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
rr_destroy(struct path_selector * ps)75 static 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
rr_status(struct path_selector * ps,struct dm_path * path,status_type_t type,char * result,unsigned int maxlen)85 static 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 */
rr_add_path(struct path_selector * ps,struct dm_path * path,int argc,char ** argv,char ** error)111 static 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
118 if (argc > 1) {
119 *error = "round-robin ps: incorrect number of arguments";
120 return -EINVAL;
121 }
122
123 /* First path argument is number of I/Os before switching path */
124 if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
125 *error = "round-robin ps: invalid repeat count";
126 return -EINVAL;
127 }
128
129 /* allocate the path */
130 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
131 if (!pi) {
132 *error = "round-robin ps: Error allocating path context";
133 return -ENOMEM;
134 }
135
136 pi->path = path;
137 pi->repeat_count = repeat_count;
138
139 path->pscontext = pi;
140
141 list_add_tail(&pi->list, &s->valid_paths);
142
143 return 0;
144 }
145
rr_fail_path(struct path_selector * ps,struct dm_path * p)146 static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
147 {
148 struct selector *s = (struct selector *) ps->context;
149 struct path_info *pi = p->pscontext;
150
151 list_move(&pi->list, &s->invalid_paths);
152 }
153
rr_reinstate_path(struct path_selector * ps,struct dm_path * p)154 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
155 {
156 struct selector *s = (struct selector *) ps->context;
157 struct path_info *pi = p->pscontext;
158
159 list_move(&pi->list, &s->valid_paths);
160
161 return 0;
162 }
163
rr_select_path(struct path_selector * ps,unsigned * repeat_count,size_t nr_bytes)164 static struct dm_path *rr_select_path(struct path_selector *ps,
165 unsigned *repeat_count, size_t nr_bytes)
166 {
167 struct selector *s = (struct selector *) ps->context;
168 struct path_info *pi = NULL;
169
170 if (!list_empty(&s->valid_paths)) {
171 pi = list_entry(s->valid_paths.next, struct path_info, list);
172 list_move_tail(&pi->list, &s->valid_paths);
173 *repeat_count = pi->repeat_count;
174 }
175
176 return pi ? pi->path : NULL;
177 }
178
179 static struct path_selector_type rr_ps = {
180 .name = "round-robin",
181 .module = THIS_MODULE,
182 .table_args = 1,
183 .info_args = 0,
184 .create = rr_create,
185 .destroy = rr_destroy,
186 .status = rr_status,
187 .add_path = rr_add_path,
188 .fail_path = rr_fail_path,
189 .reinstate_path = rr_reinstate_path,
190 .select_path = rr_select_path,
191 };
192
dm_rr_init(void)193 static int __init dm_rr_init(void)
194 {
195 int r = dm_register_path_selector(&rr_ps);
196
197 if (r < 0)
198 DMERR("register failed %d", r);
199
200 DMINFO("version 1.0.0 loaded");
201
202 return r;
203 }
204
dm_rr_exit(void)205 static void __exit dm_rr_exit(void)
206 {
207 int r = dm_unregister_path_selector(&rr_ps);
208
209 if (r < 0)
210 DMERR("unregister failed %d", r);
211 }
212
213 module_init(dm_rr_init);
214 module_exit(dm_rr_exit);
215
216 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
217 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
218 MODULE_LICENSE("GPL");
219