blob: c5a16c5501227f1097a72ddcb85f6ef37be4bec2 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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 "dm.h"
13#include "dm-path-selector.h"
14
15#include <linux/slab.h>
16
Alasdair G Kergon72d94862006-06-26 00:27:35 -070017#define DM_MSG_PREFIX "multipath round-robin"
18
Linus Torvalds1da177e2005-04-16 15:20:36 -070019/*-----------------------------------------------------------------
20 * Path-handling code, paths are held in lists
21 *---------------------------------------------------------------*/
22struct path_info {
23 struct list_head list;
24 struct path *path;
25 unsigned repeat_count;
26};
27
28static void free_paths(struct list_head *paths)
29{
30 struct path_info *pi, *next;
31
32 list_for_each_entry_safe(pi, next, paths, list) {
33 list_del(&pi->list);
34 kfree(pi);
35 }
36}
37
38/*-----------------------------------------------------------------
39 * Round-robin selector
40 *---------------------------------------------------------------*/
41
42#define RR_MIN_IO 1000
43
44struct selector {
45 struct list_head valid_paths;
46 struct list_head invalid_paths;
47};
48
49static struct selector *alloc_selector(void)
50{
51 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
52
53 if (s) {
54 INIT_LIST_HEAD(&s->valid_paths);
55 INIT_LIST_HEAD(&s->invalid_paths);
56 }
57
58 return s;
59}
60
61static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
62{
63 struct selector *s;
64
65 s = alloc_selector();
66 if (!s)
67 return -ENOMEM;
68
69 ps->context = s;
70 return 0;
71}
72
73static void rr_destroy(struct path_selector *ps)
74{
75 struct selector *s = (struct selector *) ps->context;
76
77 free_paths(&s->valid_paths);
78 free_paths(&s->invalid_paths);
79 kfree(s);
80 ps->context = NULL;
81}
82
83static int rr_status(struct path_selector *ps, struct path *path,
84 status_type_t type, char *result, unsigned int maxlen)
85{
86 struct path_info *pi;
87 int sz = 0;
88
89 if (!path)
90 DMEMIT("0 ");
91 else {
92 switch(type) {
93 case STATUSTYPE_INFO:
94 break;
95 case STATUSTYPE_TABLE:
96 pi = path->pscontext;
97 DMEMIT("%u ", pi->repeat_count);
98 break;
99 }
100 }
101
102 return sz;
103}
104
105/*
106 * Called during initialisation to register each path with an
107 * optional repeat_count.
108 */
109static int rr_add_path(struct path_selector *ps, struct path *path,
110 int argc, char **argv, char **error)
111{
112 struct selector *s = (struct selector *) ps->context;
113 struct path_info *pi;
114 unsigned repeat_count = RR_MIN_IO;
115
116 if (argc > 1) {
117 *error = "round-robin ps: incorrect number of arguments";
118 return -EINVAL;
119 }
120
121 /* First path argument is number of I/Os before switching path */
122 if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
123 *error = "round-robin ps: invalid repeat count";
124 return -EINVAL;
125 }
126
127 /* allocate the path */
128 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
129 if (!pi) {
130 *error = "round-robin ps: Error allocating path context";
131 return -ENOMEM;
132 }
133
134 pi->path = path;
135 pi->repeat_count = repeat_count;
136
137 path->pscontext = pi;
138
139 list_add(&pi->list, &s->valid_paths);
140
141 return 0;
142}
143
144static void rr_fail_path(struct path_selector *ps, struct path *p)
145{
146 struct selector *s = (struct selector *) ps->context;
147 struct path_info *pi = p->pscontext;
148
149 list_move(&pi->list, &s->invalid_paths);
150}
151
152static int rr_reinstate_path(struct path_selector *ps, struct path *p)
153{
154 struct selector *s = (struct selector *) ps->context;
155 struct path_info *pi = p->pscontext;
156
157 list_move(&pi->list, &s->valid_paths);
158
159 return 0;
160}
161
162static struct path *rr_select_path(struct path_selector *ps,
163 unsigned *repeat_count)
164{
165 struct selector *s = (struct selector *) ps->context;
166 struct path_info *pi = NULL;
167
168 if (!list_empty(&s->valid_paths)) {
169 pi = list_entry(s->valid_paths.next, struct path_info, list);
170 list_move_tail(&pi->list, &s->valid_paths);
171 *repeat_count = pi->repeat_count;
172 }
173
174 return pi ? pi->path : NULL;
175}
176
177static struct path_selector_type rr_ps = {
178 .name = "round-robin",
179 .module = THIS_MODULE,
180 .table_args = 1,
181 .info_args = 0,
182 .create = rr_create,
183 .destroy = rr_destroy,
184 .status = rr_status,
185 .add_path = rr_add_path,
186 .fail_path = rr_fail_path,
187 .reinstate_path = rr_reinstate_path,
188 .select_path = rr_select_path,
189};
190
191static int __init dm_rr_init(void)
192{
193 int r = dm_register_path_selector(&rr_ps);
194
195 if (r < 0)
Alasdair G Kergon72d94862006-06-26 00:27:35 -0700196 DMERR("register failed %d", r);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197
Alasdair G Kergon72d94862006-06-26 00:27:35 -0700198 DMINFO("version 1.0.0 loaded");
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199
200 return r;
201}
202
203static void __exit dm_rr_exit(void)
204{
205 int r = dm_unregister_path_selector(&rr_ps);
206
207 if (r < 0)
208 DMERR("round-robin: unregister failed %d", r);
209}
210
211module_init(dm_rr_init);
212module_exit(dm_rr_exit);
213
214MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
215MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
216MODULE_LICENSE("GPL");