Commit | Line | Data |
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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> | |
056075c7 | 17 | #include <linux/module.h> |
1da177e4 | 18 | |
72d94861 | 19 | #define DM_MSG_PREFIX "multipath round-robin" |
b0b477c7 | 20 | #define RR_MIN_IO 1000 |
21136f89 | 21 | #define RR_VERSION "1.1.0" |
72d94861 | 22 | |
1da177e4 LT |
23 | /*----------------------------------------------------------------- |
24 | * Path-handling code, paths are held in lists | |
25 | *---------------------------------------------------------------*/ | |
26 | struct path_info { | |
27 | struct list_head list; | |
c922d5f7 | 28 | struct dm_path *path; |
1da177e4 LT |
29 | unsigned repeat_count; |
30 | }; | |
31 | ||
32 | static void free_paths(struct list_head *paths) | |
33 | { | |
34 | struct path_info *pi, *next; | |
35 | ||
36 | list_for_each_entry_safe(pi, next, paths, list) { | |
37 | list_del(&pi->list); | |
38 | kfree(pi); | |
39 | } | |
40 | } | |
41 | ||
42 | /*----------------------------------------------------------------- | |
43 | * Round-robin selector | |
44 | *---------------------------------------------------------------*/ | |
45 | ||
1da177e4 LT |
46 | struct selector { |
47 | struct list_head valid_paths; | |
48 | struct list_head invalid_paths; | |
9659f811 | 49 | spinlock_t lock; |
b0b477c7 MS |
50 | struct dm_path * __percpu *current_path; |
51 | struct percpu_counter repeat_count; | |
1da177e4 LT |
52 | }; |
53 | ||
b0b477c7 MS |
54 | static void set_percpu_current_path(struct selector *s, struct dm_path *path) |
55 | { | |
56 | int cpu; | |
57 | ||
58 | for_each_possible_cpu(cpu) | |
59 | *per_cpu_ptr(s->current_path, cpu) = path; | |
60 | } | |
61 | ||
1da177e4 LT |
62 | static struct selector *alloc_selector(void) |
63 | { | |
64 | struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL); | |
65 | ||
b0b477c7 MS |
66 | if (!s) |
67 | return NULL; | |
68 | ||
69 | INIT_LIST_HEAD(&s->valid_paths); | |
70 | INIT_LIST_HEAD(&s->invalid_paths); | |
71 | spin_lock_init(&s->lock); | |
72 | ||
73 | s->current_path = alloc_percpu(struct dm_path *); | |
74 | if (!s->current_path) | |
75 | goto out_current_path; | |
76 | set_percpu_current_path(s, NULL); | |
77 | ||
78 | if (percpu_counter_init(&s->repeat_count, 0, GFP_KERNEL)) | |
79 | goto out_repeat_count; | |
1da177e4 LT |
80 | |
81 | return s; | |
b0b477c7 MS |
82 | |
83 | out_repeat_count: | |
84 | free_percpu(s->current_path); | |
85 | out_current_path: | |
86 | kfree(s); | |
87 | return NULL;; | |
1da177e4 LT |
88 | } |
89 | ||
90 | static int rr_create(struct path_selector *ps, unsigned argc, char **argv) | |
91 | { | |
92 | struct selector *s; | |
93 | ||
94 | s = alloc_selector(); | |
95 | if (!s) | |
96 | return -ENOMEM; | |
97 | ||
98 | ps->context = s; | |
99 | return 0; | |
100 | } | |
101 | ||
102 | static void rr_destroy(struct path_selector *ps) | |
103 | { | |
9659f811 | 104 | struct selector *s = ps->context; |
1da177e4 LT |
105 | |
106 | free_paths(&s->valid_paths); | |
107 | free_paths(&s->invalid_paths); | |
b0b477c7 MS |
108 | free_percpu(s->current_path); |
109 | percpu_counter_destroy(&s->repeat_count); | |
1da177e4 LT |
110 | kfree(s); |
111 | ps->context = NULL; | |
112 | } | |
113 | ||
c922d5f7 | 114 | static int rr_status(struct path_selector *ps, struct dm_path *path, |
1da177e4 LT |
115 | status_type_t type, char *result, unsigned int maxlen) |
116 | { | |
117 | struct path_info *pi; | |
118 | int sz = 0; | |
119 | ||
120 | if (!path) | |
121 | DMEMIT("0 "); | |
122 | else { | |
123 | switch(type) { | |
124 | case STATUSTYPE_INFO: | |
125 | break; | |
126 | case STATUSTYPE_TABLE: | |
127 | pi = path->pscontext; | |
128 | DMEMIT("%u ", pi->repeat_count); | |
129 | break; | |
130 | } | |
131 | } | |
132 | ||
133 | return sz; | |
134 | } | |
135 | ||
136 | /* | |
137 | * Called during initialisation to register each path with an | |
138 | * optional repeat_count. | |
139 | */ | |
c922d5f7 | 140 | static int rr_add_path(struct path_selector *ps, struct dm_path *path, |
1da177e4 LT |
141 | int argc, char **argv, char **error) |
142 | { | |
9659f811 | 143 | struct selector *s = ps->context; |
1da177e4 LT |
144 | struct path_info *pi; |
145 | unsigned repeat_count = RR_MIN_IO; | |
31998ef1 | 146 | char dummy; |
9659f811 | 147 | unsigned long flags; |
1da177e4 LT |
148 | |
149 | if (argc > 1) { | |
150 | *error = "round-robin ps: incorrect number of arguments"; | |
151 | return -EINVAL; | |
152 | } | |
153 | ||
154 | /* First path argument is number of I/Os before switching path */ | |
31998ef1 | 155 | if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) { |
1da177e4 LT |
156 | *error = "round-robin ps: invalid repeat count"; |
157 | return -EINVAL; | |
158 | } | |
159 | ||
160 | /* allocate the path */ | |
161 | pi = kmalloc(sizeof(*pi), GFP_KERNEL); | |
162 | if (!pi) { | |
163 | *error = "round-robin ps: Error allocating path context"; | |
164 | return -ENOMEM; | |
165 | } | |
166 | ||
167 | pi->path = path; | |
168 | pi->repeat_count = repeat_count; | |
169 | ||
170 | path->pscontext = pi; | |
171 | ||
9659f811 | 172 | spin_lock_irqsave(&s->lock, flags); |
5d55fdf9 | 173 | list_add_tail(&pi->list, &s->valid_paths); |
9659f811 | 174 | spin_unlock_irqrestore(&s->lock, flags); |
1da177e4 LT |
175 | |
176 | return 0; | |
177 | } | |
178 | ||
c922d5f7 | 179 | static void rr_fail_path(struct path_selector *ps, struct dm_path *p) |
1da177e4 | 180 | { |
9659f811 MS |
181 | unsigned long flags; |
182 | struct selector *s = ps->context; | |
1da177e4 LT |
183 | struct path_info *pi = p->pscontext; |
184 | ||
9659f811 | 185 | spin_lock_irqsave(&s->lock, flags); |
b0b477c7 MS |
186 | if (p == *this_cpu_ptr(s->current_path)) |
187 | set_percpu_current_path(s, NULL); | |
188 | ||
1da177e4 | 189 | list_move(&pi->list, &s->invalid_paths); |
9659f811 | 190 | spin_unlock_irqrestore(&s->lock, flags); |
1da177e4 LT |
191 | } |
192 | ||
c922d5f7 | 193 | static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p) |
1da177e4 | 194 | { |
9659f811 MS |
195 | unsigned long flags; |
196 | struct selector *s = ps->context; | |
1da177e4 LT |
197 | struct path_info *pi = p->pscontext; |
198 | ||
9659f811 | 199 | spin_lock_irqsave(&s->lock, flags); |
1da177e4 | 200 | list_move(&pi->list, &s->valid_paths); |
9659f811 | 201 | spin_unlock_irqrestore(&s->lock, flags); |
1da177e4 LT |
202 | |
203 | return 0; | |
204 | } | |
205 | ||
90a4323c | 206 | static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes) |
1da177e4 | 207 | { |
9659f811 MS |
208 | unsigned long flags; |
209 | struct selector *s = ps->context; | |
1da177e4 | 210 | struct path_info *pi = NULL; |
b0b477c7 MS |
211 | struct dm_path *current_path = NULL; |
212 | ||
213 | current_path = *this_cpu_ptr(s->current_path); | |
214 | if (current_path) { | |
215 | percpu_counter_dec(&s->repeat_count); | |
216 | if (percpu_counter_read_positive(&s->repeat_count) > 0) | |
217 | return current_path; | |
218 | } | |
1da177e4 | 219 | |
9659f811 | 220 | spin_lock_irqsave(&s->lock, flags); |
1da177e4 LT |
221 | if (!list_empty(&s->valid_paths)) { |
222 | pi = list_entry(s->valid_paths.next, struct path_info, list); | |
223 | list_move_tail(&pi->list, &s->valid_paths); | |
b0b477c7 MS |
224 | percpu_counter_set(&s->repeat_count, pi->repeat_count); |
225 | set_percpu_current_path(s, pi->path); | |
226 | current_path = pi->path; | |
1da177e4 | 227 | } |
9659f811 | 228 | spin_unlock_irqrestore(&s->lock, flags); |
1da177e4 | 229 | |
b0b477c7 | 230 | return current_path; |
1da177e4 LT |
231 | } |
232 | ||
233 | static struct path_selector_type rr_ps = { | |
234 | .name = "round-robin", | |
235 | .module = THIS_MODULE, | |
236 | .table_args = 1, | |
237 | .info_args = 0, | |
238 | .create = rr_create, | |
239 | .destroy = rr_destroy, | |
240 | .status = rr_status, | |
241 | .add_path = rr_add_path, | |
242 | .fail_path = rr_fail_path, | |
243 | .reinstate_path = rr_reinstate_path, | |
244 | .select_path = rr_select_path, | |
245 | }; | |
246 | ||
247 | static int __init dm_rr_init(void) | |
248 | { | |
249 | int r = dm_register_path_selector(&rr_ps); | |
250 | ||
251 | if (r < 0) | |
72d94861 | 252 | DMERR("register failed %d", r); |
1da177e4 | 253 | |
21136f89 | 254 | DMINFO("version " RR_VERSION " loaded"); |
1da177e4 LT |
255 | |
256 | return r; | |
257 | } | |
258 | ||
259 | static void __exit dm_rr_exit(void) | |
260 | { | |
261 | int r = dm_unregister_path_selector(&rr_ps); | |
262 | ||
263 | if (r < 0) | |
0cd33124 | 264 | DMERR("unregister failed %d", r); |
1da177e4 LT |
265 | } |
266 | ||
267 | module_init(dm_rr_init); | |
268 | module_exit(dm_rr_exit); | |
269 | ||
270 | MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector"); | |
271 | MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>"); | |
272 | MODULE_LICENSE("GPL"); |