1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2003 Sistina Software. 4 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved. 5 * 6 * Module Author: Heinz Mauelshagen 7 * 8 * This file is released under the GPL. 9 * 10 * Round-robin path selector. 11 */ 12 13 #include <linux/device-mapper.h> 14 15 #include "dm-path-selector.h" 16 17 #include <linux/slab.h> 18 #include <linux/module.h> 19 20 #define DM_MSG_PREFIX "multipath round-robin" 21 #define RR_MIN_IO 1 22 #define RR_VERSION "1.2.0" 23 24 /* 25 *--------------------------------------------------------------- 26 * Path-handling code, paths are held in lists 27 *--------------------------------------------------------------- 28 */ 29 struct path_info { 30 struct list_head list; 31 struct dm_path *path; 32 unsigned int repeat_count; 33 }; 34 35 static void free_paths(struct list_head *paths) 36 { 37 struct path_info *pi, *next; 38 39 list_for_each_entry_safe(pi, next, paths, list) { 40 list_del(&pi->list); 41 kfree(pi); 42 } 43 } 44 45 /* 46 *--------------------------------------------------------------- 47 * Round-robin selector 48 *--------------------------------------------------------------- 49 */ 50 struct selector { 51 struct list_head valid_paths; 52 struct list_head invalid_paths; 53 spinlock_t lock; 54 }; 55 56 static struct selector *alloc_selector(void) 57 { 58 struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL); 59 60 if (s) { 61 INIT_LIST_HEAD(&s->valid_paths); 62 INIT_LIST_HEAD(&s->invalid_paths); 63 spin_lock_init(&s->lock); 64 } 65 66 return s; 67 } 68 69 static int rr_create(struct path_selector *ps, unsigned int argc, char **argv) 70 { 71 struct selector *s; 72 73 s = alloc_selector(); 74 if (!s) 75 return -ENOMEM; 76 77 ps->context = s; 78 return 0; 79 } 80 81 static void rr_destroy(struct path_selector *ps) 82 { 83 struct selector *s = ps->context; 84 85 free_paths(&s->valid_paths); 86 free_paths(&s->invalid_paths); 87 kfree(s); 88 ps->context = NULL; 89 } 90 91 static int rr_status(struct path_selector *ps, struct dm_path *path, 92 status_type_t type, char *result, unsigned int maxlen) 93 { 94 struct path_info *pi; 95 int sz = 0; 96 97 if (!path) 98 DMEMIT("0 "); 99 else { 100 switch (type) { 101 case STATUSTYPE_INFO: 102 break; 103 case STATUSTYPE_TABLE: 104 pi = path->pscontext; 105 DMEMIT("%u ", pi->repeat_count); 106 break; 107 108 case STATUSTYPE_IMA: 109 *result = '\0'; 110 break; 111 } 112 } 113 114 return sz; 115 } 116 117 /* 118 * Called during initialisation to register each path with an 119 * optional repeat_count. 120 */ 121 static int rr_add_path(struct path_selector *ps, struct dm_path *path, 122 int argc, char **argv, char **error) 123 { 124 struct selector *s = ps->context; 125 struct path_info *pi; 126 unsigned int repeat_count = RR_MIN_IO; 127 char dummy; 128 unsigned long flags; 129 130 if (argc > 1) { 131 *error = "round-robin ps: incorrect number of arguments"; 132 return -EINVAL; 133 } 134 135 /* First path argument is number of I/Os before switching path */ 136 if ((argc == 1) && (sscanf(argv[0], "%u%c", &repeat_count, &dummy) != 1)) { 137 *error = "round-robin ps: invalid repeat count"; 138 return -EINVAL; 139 } 140 141 if (repeat_count > 1) { 142 DMWARN_LIMIT("repeat_count > 1 is deprecated, using 1 instead"); 143 repeat_count = 1; 144 } 145 146 /* allocate the path */ 147 pi = kmalloc(sizeof(*pi), GFP_KERNEL); 148 if (!pi) { 149 *error = "round-robin ps: Error allocating path context"; 150 return -ENOMEM; 151 } 152 153 pi->path = path; 154 pi->repeat_count = repeat_count; 155 156 path->pscontext = pi; 157 158 spin_lock_irqsave(&s->lock, flags); 159 list_add_tail(&pi->list, &s->valid_paths); 160 spin_unlock_irqrestore(&s->lock, flags); 161 162 return 0; 163 } 164 165 static void rr_fail_path(struct path_selector *ps, struct dm_path *p) 166 { 167 unsigned long flags; 168 struct selector *s = ps->context; 169 struct path_info *pi = p->pscontext; 170 171 spin_lock_irqsave(&s->lock, flags); 172 list_move(&pi->list, &s->invalid_paths); 173 spin_unlock_irqrestore(&s->lock, flags); 174 } 175 176 static int rr_reinstate_path(struct path_selector *ps, struct dm_path *p) 177 { 178 unsigned long flags; 179 struct selector *s = ps->context; 180 struct path_info *pi = p->pscontext; 181 182 spin_lock_irqsave(&s->lock, flags); 183 list_move(&pi->list, &s->valid_paths); 184 spin_unlock_irqrestore(&s->lock, flags); 185 186 return 0; 187 } 188 189 static struct dm_path *rr_select_path(struct path_selector *ps, size_t nr_bytes) 190 { 191 unsigned long flags; 192 struct selector *s = ps->context; 193 struct path_info *pi = NULL; 194 195 spin_lock_irqsave(&s->lock, flags); 196 if (!list_empty(&s->valid_paths)) { 197 pi = list_entry(s->valid_paths.next, struct path_info, list); 198 list_move_tail(&pi->list, &s->valid_paths); 199 } 200 spin_unlock_irqrestore(&s->lock, flags); 201 202 return pi ? pi->path : NULL; 203 } 204 205 static struct path_selector_type rr_ps = { 206 .name = "round-robin", 207 .module = THIS_MODULE, 208 .table_args = 1, 209 .info_args = 0, 210 .create = rr_create, 211 .destroy = rr_destroy, 212 .status = rr_status, 213 .add_path = rr_add_path, 214 .fail_path = rr_fail_path, 215 .reinstate_path = rr_reinstate_path, 216 .select_path = rr_select_path, 217 }; 218 219 static int __init dm_rr_init(void) 220 { 221 int r = dm_register_path_selector(&rr_ps); 222 223 if (r < 0) 224 DMERR("register failed %d", r); 225 226 DMINFO("version " RR_VERSION " loaded"); 227 228 return r; 229 } 230 231 static void __exit dm_rr_exit(void) 232 { 233 int r = dm_unregister_path_selector(&rr_ps); 234 235 if (r < 0) 236 DMERR("unregister failed %d", r); 237 } 238 239 module_init(dm_rr_init); 240 module_exit(dm_rr_exit); 241 242 MODULE_DESCRIPTION(DM_NAME " round-robin multipath path selector"); 243 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>"); 244 MODULE_LICENSE("GPL"); 245