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1da177e4 LT |
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 | ||
586e80e6 MP |
12 | #include <linux/device-mapper.h> |
13 | ||
1da177e4 LT |
14 | #include "dm-path-selector.h" |
15 | ||
16 | #include <linux/slab.h> | |
17 | ||
72d94861 AK |
18 | #define DM_MSG_PREFIX "multipath round-robin" |
19 | ||
1da177e4 LT |
20 | /*----------------------------------------------------------------- |
21 | * Path-handling code, paths are held in lists | |
22 | *---------------------------------------------------------------*/ | |
23 | struct path_info { | |
24 | struct list_head list; | |
c922d5f7 | 25 | struct dm_path *path; |
1da177e4 LT |
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 | ||
c922d5f7 | 84 | static int rr_status(struct path_selector *ps, struct dm_path *path, |
1da177e4 LT |
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 | */ | |
c922d5f7 | 110 | static int rr_add_path(struct path_selector *ps, struct dm_path *path, |
1da177e4 LT |
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 | ||
5d55fdf9 | 140 | list_add_tail(&pi->list, &s->valid_paths); |
1da177e4 LT |
141 | |
142 | return 0; | |
143 | } | |
144 | ||
c922d5f7 | 145 | static void rr_fail_path(struct path_selector *ps, struct dm_path *p) |
1da177e4 LT |
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 | ||
c922d5f7 | 153 | static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p) |
1da177e4 LT |
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 | ||
c922d5f7 | 163 | static struct dm_path *rr_select_path(struct path_selector *ps, |
1da177e4 LT |
164 | unsigned *repeat_count) |
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) | |
72d94861 | 197 | DMERR("register failed %d", r); |
1da177e4 | 198 | |
72d94861 | 199 | DMINFO("version 1.0.0 loaded"); |
1da177e4 LT |
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) | |
0cd33124 | 209 | DMERR("unregister failed %d", r); |
1da177e4 LT |
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"); |