Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound-2.6
[linux-2.6] / drivers / md / dm-round-robin.c
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 #define DM_MSG_PREFIX "multipath round-robin"
18
19 /*-----------------------------------------------------------------
20  * Path-handling code, paths are held in lists
21  *---------------------------------------------------------------*/
22 struct path_info {
23         struct list_head list;
24         struct dm_path *path;
25         unsigned repeat_count;
26 };
27
28 static 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
44 struct selector {
45         struct list_head valid_paths;
46         struct list_head invalid_paths;
47 };
48
49 static 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
61 static 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
73 static 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
83 static int rr_status(struct path_selector *ps, struct dm_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  */
109 static int rr_add_path(struct path_selector *ps, struct dm_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_tail(&pi->list, &s->valid_paths);
140
141         return 0;
142 }
143
144 static void rr_fail_path(struct path_selector *ps, struct dm_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
152 static int rr_reinstate_path(struct path_selector *ps, struct dm_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
162 static struct dm_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
177 static 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
191 static int __init dm_rr_init(void)
192 {
193         int r = dm_register_path_selector(&rr_ps);
194
195         if (r < 0)
196                 DMERR("register failed %d", r);
197
198         DMINFO("version 1.0.0 loaded");
199
200         return r;
201 }
202
203 static void __exit dm_rr_exit(void)
204 {
205         int r = dm_unregister_path_selector(&rr_ps);
206
207         if (r < 0)
208                 DMERR("unregister failed %d", r);
209 }
210
211 module_init(dm_rr_init);
212 module_exit(dm_rr_exit);
213
214 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
215 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
216 MODULE_LICENSE("GPL");