Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost
[cris-mirror.git] / drivers / md / dm-round-robin.c
blobbdbb7e6e8212bfc050cadbfa42cb1fbabe03bc54
1 /*
2 * Copyright (C) 2003 Sistina Software.
3 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
5 * Module Author: Heinz Mauelshagen
7 * This file is released under the GPL.
9 * Round-robin path selector.
12 #include <linux/device-mapper.h>
14 #include "dm-path-selector.h"
16 #include <linux/slab.h>
17 #include <linux/module.h>
19 #define DM_MSG_PREFIX "multipath round-robin"
20 #define RR_MIN_IO 1
21 #define RR_VERSION "1.2.0"
23 /*-----------------------------------------------------------------
24 * Path-handling code, paths are held in lists
25 *---------------------------------------------------------------*/
26 struct path_info {
27 struct list_head list;
28 struct dm_path *path;
29 unsigned repeat_count;
32 static void free_paths(struct list_head *paths)
34 struct path_info *pi, *next;
36 list_for_each_entry_safe(pi, next, paths, list) {
37 list_del(&pi->list);
38 kfree(pi);
42 /*-----------------------------------------------------------------
43 * Round-robin selector
44 *---------------------------------------------------------------*/
46 struct selector {
47 struct list_head valid_paths;
48 struct list_head invalid_paths;
49 spinlock_t lock;
52 static struct selector *alloc_selector(void)
54 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
56 if (s) {
57 INIT_LIST_HEAD(&s->valid_paths);
58 INIT_LIST_HEAD(&s->invalid_paths);
59 spin_lock_init(&s->lock);
62 return s;
65 static int rr_create(struct path_selector *ps, unsigned argc, char **argv)
67 struct selector *s;
69 s = alloc_selector();
70 if (!s)
71 return -ENOMEM;
73 ps->context = s;
74 return 0;
77 static void rr_destroy(struct path_selector *ps)
79 struct selector *s = ps->context;
81 free_paths(&s->valid_paths);
82 free_paths(&s->invalid_paths);
83 kfree(s);
84 ps->context = NULL;
87 static int rr_status(struct path_selector *ps, struct dm_path *path,
88 status_type_t type, char *result, unsigned int maxlen)
90 struct path_info *pi;
91 int sz = 0;
93 if (!path)
94 DMEMIT("0 ");
95 else {
96 switch(type) {
97 case STATUSTYPE_INFO:
98 break;
99 case STATUSTYPE_TABLE:
100 pi = path->pscontext;
101 DMEMIT("%u ", pi->repeat_count);
102 break;
106 return sz;
110 * Called during initialisation to register each path with an
111 * optional repeat_count.
113 static int rr_add_path(struct path_selector *ps, struct dm_path *path,
114 int argc, char **argv, char **error)
116 struct selector *s = ps->context;
117 struct path_info *pi;
118 unsigned repeat_count = RR_MIN_IO;
119 char dummy;
120 unsigned long flags;
122 if (argc > 1) {
123 *error = "round-robin ps: incorrect number of arguments";
124 return -EINVAL;
127 /* First path argument is number of I/Os before switching path */
128 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) {
129 *error = "round-robin ps: invalid repeat count";
130 return -EINVAL;
133 if (repeat_count > 1) {
134 DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead");
135 repeat_count = 1;
138 /* allocate the path */
139 pi = kmalloc(sizeof(*pi), GFP_KERNEL);
140 if (!pi) {
141 *error = "round-robin ps: Error allocating path context";
142 return -ENOMEM;
145 pi->path = path;
146 pi->repeat_count = repeat_count;
148 path->pscontext = pi;
150 spin_lock_irqsave(&s->lock, flags);
151 list_add_tail(&pi->list, &s->valid_paths);
152 spin_unlock_irqrestore(&s->lock, flags);
154 return 0;
157 static void rr_fail_path(struct path_selector *ps, struct dm_path *p)
159 unsigned long flags;
160 struct selector *s = ps->context;
161 struct path_info *pi = p->pscontext;
163 spin_lock_irqsave(&s->lock, flags);
164 list_move(&pi->list, &s->invalid_paths);
165 spin_unlock_irqrestore(&s->lock, flags);
168 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p)
170 unsigned long flags;
171 struct selector *s = ps->context;
172 struct path_info *pi = p->pscontext;
174 spin_lock_irqsave(&s->lock, flags);
175 list_move(&pi->list, &s->valid_paths);
176 spin_unlock_irqrestore(&s->lock, flags);
178 return 0;
181 static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes)
183 unsigned long flags;
184 struct selector *s = ps->context;
185 struct path_info *pi = NULL;
187 spin_lock_irqsave(&s->lock, flags);
188 if (!list_empty(&s->valid_paths)) {
189 pi = list_entry(s->valid_paths.next, struct path_info, list);
190 list_move_tail(&pi->list, &s->valid_paths);
192 spin_unlock_irqrestore(&s->lock, flags);
194 return pi ? pi->path : NULL;
197 static struct path_selector_type rr_ps = {
198 .name = "round-robin",
199 .module = THIS_MODULE,
200 .table_args = 1,
201 .info_args = 0,
202 .create = rr_create,
203 .destroy = rr_destroy,
204 .status = rr_status,
205 .add_path = rr_add_path,
206 .fail_path = rr_fail_path,
207 .reinstate_path = rr_reinstate_path,
208 .select_path = rr_select_path,
211 static int __init dm_rr_init(void)
213 int r = dm_register_path_selector(&rr_ps);
215 if (r < 0)
216 DMERR("register failed %d", r);
218 DMINFO("version " RR_VERSION " loaded");
220 return r;
223 static void __exit dm_rr_exit(void)
225 int r = dm_unregister_path_selector(&rr_ps);
227 if (r < 0)
228 DMERR("unregister failed %d", r);
231 module_init(dm_rr_init);
232 module_exit(dm_rr_exit);
234 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector");
235 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
236 MODULE_LICENSE("GPL");