dm crypt: optionally support discard requests
[linux-2.6.git] / 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 <linux/device-mapper.h>
13
14 #include "dm-path-selector.h"
15
16 #include <linux/slab.h>
17
18 #define DM_MSG_PREFIX "multipath round-robin"
19
20 /*-----------------------------------------------------------------
21  * Path-handling code, paths are held in lists
22  *---------------------------------------------------------------*/
23 struct path_info {
24         struct list_head list;
25         struct dm_path *path;
26         unsigned repeat_count;
27 };
28
29 static void free_paths(struct list_head *paths)
30 {
31         struct path_info *pi, *next;
32
33         list_for_each_entry_safe(pi, next, paths, list) {
34                 list_del(&pi->list);
35                 kfree(pi);
36         }
37 }
38
39 /*-----------------------------------------------------------------
40  * Round-robin selector
41  *---------------------------------------------------------------*/
42
43 #define RR_MIN_IO               1000
44
45 struct selector {
46         struct list_head valid_paths;
47         struct list_head invalid_paths;
48 };
49
50 static struct selector *alloc_selector(void)
51 {
52         struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
53
54         if (s) {
55                 INIT_LIST_HEAD(&s->valid_paths);
56                 INIT_LIST_HEAD(&s->invalid_paths);
57         }
58
59         return s;
60 }
61
62 static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
63 {
64         struct selector *s;
65
66         s = alloc_selector();
67         if (!s)
68                 return -ENOMEM;
69
70         ps->context = s;
71         return 0;
72 }
73
74 static void rr_destroy(struct path_selector *ps)
75 {
76         struct selector *s = (struct selector *) ps->context;
77
78         free_paths(&s->valid_paths);
79         free_paths(&s->invalid_paths);
80         kfree(s);
81         ps->context = NULL;
82 }
83
84 static int rr_status(struct path_selector *ps, struct dm_path *path,
85                      status_type_t type, char *result, unsigned int maxlen)
86 {
87         struct path_info *pi;
88         int sz = 0;
89
90         if (!path)
91                 DMEMIT("0 ");
92         else {
93                 switch(type) {
94                 case STATUSTYPE_INFO:
95                         break;
96                 case STATUSTYPE_TABLE:
97                         pi = path->pscontext;
98                         DMEMIT("%u ", pi->repeat_count);
99                         break;
100                 }
101         }
102
103         return sz;
104 }
105
106 /*
107  * Called during initialisation to register each path with an
108  * optional repeat_count.
109  */
110 static int rr_add_path(struct path_selector *ps, struct dm_path *path,
111                        int argc, char **argv, char **error)
112 {
113         struct selector *s = (struct selector *) ps->context;
114         struct path_info *pi;
115         unsigned repeat_count = RR_MIN_IO;
116
117         if (argc > 1) {
118                 *error = "round-robin ps: incorrect number of arguments";
119                 return -EINVAL;
120         }
121
122         /* First path argument is number of I/Os before switching path */
123         if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
124                 *error = "round-robin ps: invalid repeat count";
125                 return -EINVAL;
126         }
127
128         /* allocate the path */
129         pi = kmalloc(sizeof(*pi), GFP_KERNEL);
130         if (!pi) {
131                 *error = "round-robin ps: Error allocating path context";
132                 return -ENOMEM;
133         }
134
135         pi->path = path;
136         pi->repeat_count = repeat_count;
137
138         path->pscontext = pi;
139
140         list_add_tail(&pi->list, &s->valid_paths);
141
142         return 0;
143 }
144
145 static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
146 {
147         struct selector *s = (struct selector *) ps->context;
148         struct path_info *pi = p->pscontext;
149
150         list_move(&pi->list, &s->invalid_paths);
151 }
152
153 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
154 {
155         struct selector *s = (struct selector *) ps->context;
156         struct path_info *pi = p->pscontext;
157
158         list_move(&pi->list, &s->valid_paths);
159
160         return 0;
161 }
162
163 static struct dm_path *rr_select_path(struct path_selector *ps,
164                                       unsigned *repeat_count, size_t nr_bytes)
165 {
166         struct selector *s = (struct selector *) ps->context;
167         struct path_info *pi = NULL;
168
169         if (!list_empty(&s->valid_paths)) {
170                 pi = list_entry(s->valid_paths.next, struct path_info, list);
171                 list_move_tail(&pi->list, &s->valid_paths);
172                 *repeat_count = pi->repeat_count;
173         }
174
175         return pi ? pi->path : NULL;
176 }
177
178 static struct path_selector_type rr_ps = {
179         .name = "round-robin",
180         .module = THIS_MODULE,
181         .table_args = 1,
182         .info_args = 0,
183         .create = rr_create,
184         .destroy = rr_destroy,
185         .status = rr_status,
186         .add_path = rr_add_path,
187         .fail_path = rr_fail_path,
188         .reinstate_path = rr_reinstate_path,
189         .select_path = rr_select_path,
190 };
191
192 static int __init dm_rr_init(void)
193 {
194         int r = dm_register_path_selector(&rr_ps);
195
196         if (r < 0)
197                 DMERR("register failed %d", r);
198
199         DMINFO("version 1.0.0 loaded");
200
201         return r;
202 }
203
204 static void __exit dm_rr_exit(void)
205 {
206         int r = dm_unregister_path_selector(&rr_ps);
207
208         if (r < 0)
209                 DMERR("unregister failed %d", r);
210 }
211
212 module_init(dm_rr_init);
213 module_exit(dm_rr_exit);
214
215 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
216 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
217 MODULE_LICENSE("GPL");