Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-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 /*-----------------------------------------------------------------
18  * Path-handling code, paths are held in lists
19  *---------------------------------------------------------------*/
20 struct path_info {
21         struct list_head list;
22         struct path *path;
23         unsigned repeat_count;
24 };
25
26 static 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
42 struct selector {
43         struct list_head valid_paths;
44         struct list_head invalid_paths;
45 };
46
47 static 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
59 static 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
71 static 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
81 static 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  */
107 static 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
142 static 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
150 static 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
160 static 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
175 static 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
189 static 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
201 static 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
209 module_init(dm_rr_init);
210 module_exit(dm_rr_exit);
211
212 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
213 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
214 MODULE_LICENSE("GPL");