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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
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 "dm.h"
13#include "dm-path-selector.h"
14
15#include <linux/slab.h>
16
17/*-----------------------------------------------------------------
18 * Path-handling code, paths are held in lists
19 *---------------------------------------------------------------*/
20struct path_info {
21 struct list_head list;
22 struct path *path;
23 unsigned repeat_count;
24};
25
26static void free_paths(struct list_head *paths)
27{
28 struct path_info *pi, *next;
29
30 list_for_each_entry_safe(pi, next, paths, list) {
31 list_del(&pi->list);
32 kfree(pi);
33 }
34}
35
36/*-----------------------------------------------------------------
37 * Round-robin selector
38 *---------------------------------------------------------------*/
39
40#define RR_MIN_IO 1000
41
42struct selector {
43 struct list_head valid_paths;
44 struct list_head invalid_paths;
45};
46
47static struct selector *alloc_selector(void)
48{
49 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
50
51 if (s) {
52 INIT_LIST_HEAD(&s->valid_paths);
53 INIT_LIST_HEAD(&s->invalid_paths);
54 }
55
56 return s;
57}
58
59static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
60{
61 struct selector *s;
62
63 s = alloc_selector();
64 if (!s)
65 return -ENOMEM;
66
67 ps->context = s;
68 return 0;
69}
70
71static void rr_destroy(struct path_selector *ps)
72{
73 struct selector *s = (struct selector *) ps->context;
74
75 free_paths(&s->valid_paths);
76 free_paths(&s->invalid_paths);
77 kfree(s);
78 ps->context = NULL;
79}
80
81static int rr_status(struct path_selector *ps, struct path *path,
82 status_type_t type, char *result, unsigned int maxlen)
83{
84 struct path_info *pi;
85 int sz = 0;
86
87 if (!path)
88 DMEMIT("0 ");
89 else {
90 switch(type) {
91 case STATUSTYPE_INFO:
92 break;
93 case STATUSTYPE_TABLE:
94 pi = path->pscontext;
95 DMEMIT("%u ", pi->repeat_count);
96 break;
97 }
98 }
99
100 return sz;
101}
102
103/*
104 * Called during initialisation to register each path with an
105 * optional repeat_count.
106 */
107static int rr_add_path(struct path_selector *ps, struct path *path,
108 int argc, char **argv, char **error)
109{
110 struct selector *s = (struct selector *) ps->context;
111 struct path_info *pi;
112 unsigned repeat_count = RR_MIN_IO;
113
114 if (argc > 1) {
115 *error = "round-robin ps: incorrect number of arguments";
116 return -EINVAL;
117 }
118
119 /* First path argument is number of I/Os before switching path */
120 if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
121 *error = "round-robin ps: invalid repeat count";
122 return -EINVAL;
123 }
124
125 /* allocate the path */
126 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
127 if (!pi) {
128 *error = "round-robin ps: Error allocating path context";
129 return -ENOMEM;
130 }
131
132 pi->path = path;
133 pi->repeat_count = repeat_count;
134
135 path->pscontext = pi;
136
137 list_add(&pi->list, &s->valid_paths);
138
139 return 0;
140}
141
142static void rr_fail_path(struct path_selector *ps, struct path *p)
143{
144 struct selector *s = (struct selector *) ps->context;
145 struct path_info *pi = p->pscontext;
146
147 list_move(&pi->list, &s->invalid_paths);
148}
149
150static int rr_reinstate_path(struct path_selector *ps, struct path *p)
151{
152 struct selector *s = (struct selector *) ps->context;
153 struct path_info *pi = p->pscontext;
154
155 list_move(&pi->list, &s->valid_paths);
156
157 return 0;
158}
159
160static struct path *rr_select_path(struct path_selector *ps,
161 unsigned *repeat_count)
162{
163 struct selector *s = (struct selector *) ps->context;
164 struct path_info *pi = NULL;
165
166 if (!list_empty(&s->valid_paths)) {
167 pi = list_entry(s->valid_paths.next, struct path_info, list);
168 list_move_tail(&pi->list, &s->valid_paths);
169 *repeat_count = pi->repeat_count;
170 }
171
172 return pi ? pi->path : NULL;
173}
174
175static struct path_selector_type rr_ps = {
176 .name = "round-robin",
177 .module = THIS_MODULE,
178 .table_args = 1,
179 .info_args = 0,
180 .create = rr_create,
181 .destroy = rr_destroy,
182 .status = rr_status,
183 .add_path = rr_add_path,
184 .fail_path = rr_fail_path,
185 .reinstate_path = rr_reinstate_path,
186 .select_path = rr_select_path,
187};
188
189static int __init dm_rr_init(void)
190{
191 int r = dm_register_path_selector(&rr_ps);
192
193 if (r < 0)
194 DMERR("round-robin: register failed %d", r);
195
196 DMINFO("dm-round-robin version 1.0.0 loaded");
197
198 return r;
199}
200
201static void __exit dm_rr_exit(void)
202{
203 int r = dm_unregister_path_selector(&rr_ps);
204
205 if (r < 0)
206 DMERR("round-robin: unregister failed %d", r);
207}
208
209module_init(dm_rr_init);
210module_exit(dm_rr_exit);
211
212MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
213MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
214MODULE_LICENSE("GPL");