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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Mikulas Patocka586e80e2008-10-21 17:44:59 +010012#include <linux/device-mapper.h>
13
Linus Torvalds1da177e2005-04-16 15:20:36 -070014#include "dm-path-selector.h"
15
16#include <linux/slab.h>
Paul Gortmaker056075c2011-07-03 13:58:33 -040017#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070018
Alasdair G Kergon72d94862006-06-26 00:27:35 -070019#define DM_MSG_PREFIX "multipath round-robin"
Mike Snitzerb0b477c2016-02-17 15:04:05 -050020#define RR_MIN_IO 1000
Mike Snitzer21136f82016-02-10 11:58:45 -050021#define RR_VERSION "1.1.0"
Alasdair G Kergon72d94862006-06-26 00:27:35 -070022
Linus Torvalds1da177e2005-04-16 15:20:36 -070023/*-----------------------------------------------------------------
24 * Path-handling code, paths are held in lists
25 *---------------------------------------------------------------*/
26struct path_info {
27 struct list_head list;
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -080028 struct dm_path *path;
Linus Torvalds1da177e2005-04-16 15:20:36 -070029 unsigned repeat_count;
30};
31
32static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070046struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
Mike Snitzer9659f812016-02-15 14:25:00 -050049 spinlock_t lock;
Mike Snitzerb0b477c2016-02-17 15:04:05 -050050 struct dm_path * __percpu *current_path;
51 struct percpu_counter repeat_count;
Linus Torvalds1da177e2005-04-16 15:20:36 -070052};
53
Mike Snitzerb0b477c2016-02-17 15:04:05 -050054static 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
Linus Torvalds1da177e2005-04-16 15:20:36 -070062static struct selector *alloc_selector(void)
63{
64 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
65
Mike Snitzerb0b477c2016-02-17 15:04:05 -050066 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;
Linus Torvalds1da177e2005-04-16 15:20:36 -070080
81 return s;
Mike Snitzerb0b477c2016-02-17 15:04:05 -050082
83out_repeat_count:
84 free_percpu(s->current_path);
85out_current_path:
86 kfree(s);
87 return NULL;;
Linus Torvalds1da177e2005-04-16 15:20:36 -070088}
89
90static 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
102static void rr_destroy(struct path_selector *ps)
103{
Mike Snitzer9659f812016-02-15 14:25:00 -0500104 struct selector *s = ps->context;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105
106 free_paths(&s->valid_paths);
107 free_paths(&s->invalid_paths);
Mike Snitzerb0b477c2016-02-17 15:04:05 -0500108 free_percpu(s->current_path);
109 percpu_counter_destroy(&s->repeat_count);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700110 kfree(s);
111 ps->context = NULL;
112}
113
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -0800114static int rr_status(struct path_selector *ps, struct dm_path *path,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700115 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 */
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -0800140static int rr_add_path(struct path_selector *ps, struct dm_path *path,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141 int argc, char **argv, char **error)
142{
Mike Snitzer9659f812016-02-15 14:25:00 -0500143 struct selector *s = ps->context;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 struct path_info *pi;
145 unsigned repeat_count = RR_MIN_IO;
Mikulas Patocka31998ef2012-03-28 18:41:26 +0100146 char dummy;
Mike Snitzer9659f812016-02-15 14:25:00 -0500147 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148
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 */
Mikulas Patocka31998ef2012-03-28 18:41:26 +0100155 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 *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
Mike Snitzer9659f812016-02-15 14:25:00 -0500172 spin_lock_irqsave(&s->lock, flags);
Jonathan E Brassow5d55fdf2006-11-08 17:44:43 -0800173 list_add_tail(&pi->list, &s->valid_paths);
Mike Snitzer9659f812016-02-15 14:25:00 -0500174 spin_unlock_irqrestore(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175
176 return 0;
177}
178
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -0800179static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180{
Mike Snitzer9659f812016-02-15 14:25:00 -0500181 unsigned long flags;
182 struct selector *s = ps->context;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 struct path_info *pi = p->pscontext;
184
Mike Snitzer9659f812016-02-15 14:25:00 -0500185 spin_lock_irqsave(&s->lock, flags);
Mike Snitzerb0b477c2016-02-17 15:04:05 -0500186 if (p == *this_cpu_ptr(s->current_path))
187 set_percpu_current_path(s, NULL);
188
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 list_move(&pi->list, &s->invalid_paths);
Mike Snitzer9659f812016-02-15 14:25:00 -0500190 spin_unlock_irqrestore(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191}
192
Josef "Jeff" Sipekc922d5f2006-12-08 02:36:33 -0800193static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194{
Mike Snitzer9659f812016-02-15 14:25:00 -0500195 unsigned long flags;
196 struct selector *s = ps->context;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197 struct path_info *pi = p->pscontext;
198
Mike Snitzer9659f812016-02-15 14:25:00 -0500199 spin_lock_irqsave(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200 list_move(&pi->list, &s->valid_paths);
Mike Snitzer9659f812016-02-15 14:25:00 -0500201 spin_unlock_irqrestore(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202
203 return 0;
204}
205
Mike Snitzer90a43232016-02-17 21:29:17 -0500206static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207{
Mike Snitzer9659f812016-02-15 14:25:00 -0500208 unsigned long flags;
209 struct selector *s = ps->context;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 struct path_info *pi = NULL;
Mike Snitzerb0b477c2016-02-17 15:04:05 -0500211 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 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219
Mike Snitzer9659f812016-02-15 14:25:00 -0500220 spin_lock_irqsave(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700221 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);
Mike Snitzerb0b477c2016-02-17 15:04:05 -0500224 percpu_counter_set(&s->repeat_count, pi->repeat_count);
225 set_percpu_current_path(s, pi->path);
226 current_path = pi->path;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 }
Mike Snitzer9659f812016-02-15 14:25:00 -0500228 spin_unlock_irqrestore(&s->lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229
Mike Snitzerb0b477c2016-02-17 15:04:05 -0500230 return current_path;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231}
232
233static 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
247static int __init dm_rr_init(void)
248{
249 int r = dm_register_path_selector(&rr_ps);
250
251 if (r < 0)
Alasdair G Kergon72d94862006-06-26 00:27:35 -0700252 DMERR("register failed %d", r);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253
Mike Snitzer21136f82016-02-10 11:58:45 -0500254 DMINFO("version " RR_VERSION " loaded");
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255
256 return r;
257}
258
259static void __exit dm_rr_exit(void)
260{
261 int r = dm_unregister_path_selector(&rr_ps);
262
263 if (r < 0)
Alasdair G Kergon0cd33122007-07-12 17:27:01 +0100264 DMERR("unregister failed %d", r);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700265}
266
267module_init(dm_rr_init);
268module_exit(dm_rr_exit);
269
270MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
271MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
272MODULE_LICENSE("GPL");