1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
/*
* Copyright (C) 2003 Sistina Software.
* Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
*
* Module Author: Heinz Mauelshagen
*
* This file is released under the GPL.
*
* Round-robin path selector.
*/
#include "dm.h"
#include "dm-path-selector.h"
#include <linux/slab.h>
#define DM_MSG_PREFIX "multipath round-robin"
/*-----------------------------------------------------------------
* Path-handling code, paths are held in lists
*---------------------------------------------------------------*/
struct path_info {
struct list_head list;
struct path *path;
unsigned repeat_count;
};
static void free_paths(struct list_head *paths)
{
struct path_info *pi, *next;
list_for_each_entry_safe(pi, next, paths, list) {
list_del(&pi->list);
kfree(pi);
}
}
/*-----------------------------------------------------------------
* Round-robin selector
*---------------------------------------------------------------*/
#define RR_MIN_IO 1000
struct selector {
struct list_head valid_paths;
struct list_head invalid_paths;
};
static struct selector *alloc_selector(void)
{
struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
if (s) {
INIT_LIST_HEAD(&s->valid_paths);
INIT_LIST_HEAD(&s->invalid_paths);
}
return s;
}
static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
{
struct selector *s;
s = alloc_selector();
if (!s)
return -ENOMEM;
ps->context = s;
return 0;
}
static void rr_destroy(struct path_selector *ps)
{
struct selector *s = (struct selector *) ps->context;
free_paths(&s->valid_paths);
free_paths(&s->invalid_paths);
kfree(s);
ps->context = NULL;
}
static int rr_status(struct path_selector *ps, struct path *path,
status_type_t type, char *result, unsigned int maxlen)
{
struct path_info *pi;
int sz = 0;
if (!path)
DMEMIT("0 ");
else {
switch(type) {
case STATUSTYPE_INFO:
break;
case STATUSTYPE_TABLE:
pi = path->pscontext;
DMEMIT("%u ", pi->repeat_count);
break;
}
}
return sz;
}
/*
* Called during initialisation to register each path with an
* optional repeat_count.
*/
static int rr_add_path(struct path_selector *ps, struct path *path,
int argc, char **argv, char **error)
{
struct selector *s = (struct selector *) ps->context;
struct path_info *pi;
unsigned repeat_count = RR_MIN_IO;
if (argc > 1) {
*error = "round-robin ps: incorrect number of arguments";
return -EINVAL;
}
/* First path argument is number of I/Os before switching path */
if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
*error = "round-robin ps: invalid repeat count";
return -EINVAL;
}
/* allocate the path */
pi = kmalloc(sizeof(*pi), GFP_KERNEL);
if (!pi) {
*error = "round-robin ps: Error allocating path context";
return -ENOMEM;
}
pi->path = path;
pi->repeat_count = repeat_count;
path->pscontext = pi;
list_add(&pi->list, &s->valid_paths);
return 0;
}
static void rr_fail_path(struct path_selector *ps, struct path *p)
{
struct selector *s = (struct selector *) ps->context;
struct path_info *pi = p->pscontext;
list_move(&pi->list, &s->invalid_paths);
}
static int rr_reinstate_path(struct path_selector *ps, struct path *p)
{
struct selector *s = (struct selector *) ps->context;
struct path_info *pi = p->pscontext;
list_move(&pi->list, &s->valid_paths);
return 0;
}
static struct path *rr_select_path(struct path_selector *ps,
unsigned *repeat_count)
{
struct selector *s = (struct selector *) ps->context;
struct path_info *pi = NULL;
if (!list_empty(&s->valid_paths)) {
pi = list_entry(s->valid_paths.next, struct path_info, list);
list_move_tail(&pi->list, &s->valid_paths);
*repeat_count = pi->repeat_count;
}
return pi ? pi->path : NULL;
}
static struct path_selector_type rr_ps = {
.name = "round-robin",
.module = THIS_MODULE,
.table_args = 1,
.info_args = 0,
.create = rr_create,
.destroy = rr_destroy,
.status = rr_status,
.add_path = rr_add_path,
.fail_path = rr_fail_path,
.reinstate_path = rr_reinstate_path,
.select_path = rr_select_path,
};
static int __init dm_rr_init(void)
{
int r = dm_register_path_selector(&rr_ps);
if (r < 0)
DMERR("register failed %d", r);
DMINFO("version 1.0.0 loaded");
return r;
}
static void __exit dm_rr_exit(void)
{
int r = dm_unregister_path_selector(&rr_ps);
if (r < 0)
DMERR("round-robin: unregister failed %d", r);
}
module_init(dm_rr_init);
module_exit(dm_rr_exit);
MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");
|
