1 /* 2 * Copyright (C) 2005-2007 Red Hat GmbH 3 * 4 * A target that delays reads and/or writes and can send 5 * them to different devices. 6 * 7 * This file is released under the GPL. 8 */ 9 10 #include <linux/module.h> 11 #include <linux/init.h> 12 #include <linux/blkdev.h> 13 #include <linux/bio.h> 14 #include <linux/slab.h> 15 16 #include "dm.h" 17 #include "dm-bio-list.h" 18 19 #define DM_MSG_PREFIX "delay" 20 21 struct delay_c { 22 struct timer_list delay_timer; 23 struct semaphore timer_lock; 24 struct work_struct flush_expired_bios; 25 struct list_head delayed_bios; 26 atomic_t may_delay; 27 mempool_t *delayed_pool; 28 29 struct dm_dev *dev_read; 30 sector_t start_read; 31 unsigned read_delay; 32 unsigned reads; 33 34 struct dm_dev *dev_write; 35 sector_t start_write; 36 unsigned write_delay; 37 unsigned writes; 38 }; 39 40 struct delay_info { 41 struct delay_c *context; 42 struct list_head list; 43 struct bio *bio; 44 unsigned long expires; 45 }; 46 47 static DEFINE_MUTEX(delayed_bios_lock); 48 49 static struct workqueue_struct *kdelayd_wq; 50 static struct kmem_cache *delayed_cache; 51 52 static void handle_delayed_timer(unsigned long data) 53 { 54 struct delay_c *dc = (struct delay_c *)data; 55 56 queue_work(kdelayd_wq, &dc->flush_expired_bios); 57 } 58 59 static void queue_timeout(struct delay_c *dc, unsigned long expires) 60 { 61 down(&dc->timer_lock); 62 63 if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires) 64 mod_timer(&dc->delay_timer, expires); 65 66 up(&dc->timer_lock); 67 } 68 69 static void flush_bios(struct bio *bio) 70 { 71 struct bio *n; 72 73 while (bio) { 74 n = bio->bi_next; 75 bio->bi_next = NULL; 76 generic_make_request(bio); 77 bio = n; 78 } 79 } 80 81 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all) 82 { 83 struct delay_info *delayed, *next; 84 unsigned long next_expires = 0; 85 int start_timer = 0; 86 BIO_LIST(flush_bios); 87 88 mutex_lock(&delayed_bios_lock); 89 list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) { 90 if (flush_all || time_after_eq(jiffies, delayed->expires)) { 91 list_del(&delayed->list); 92 bio_list_add(&flush_bios, delayed->bio); 93 if ((bio_data_dir(delayed->bio) == WRITE)) 94 delayed->context->writes--; 95 else 96 delayed->context->reads--; 97 mempool_free(delayed, dc->delayed_pool); 98 continue; 99 } 100 101 if (!start_timer) { 102 start_timer = 1; 103 next_expires = delayed->expires; 104 } else 105 next_expires = min(next_expires, delayed->expires); 106 } 107 108 mutex_unlock(&delayed_bios_lock); 109 110 if (start_timer) 111 queue_timeout(dc, next_expires); 112 113 return bio_list_get(&flush_bios); 114 } 115 116 static void flush_expired_bios(struct work_struct *work) 117 { 118 struct delay_c *dc; 119 120 dc = container_of(work, struct delay_c, flush_expired_bios); 121 flush_bios(flush_delayed_bios(dc, 0)); 122 } 123 124 /* 125 * Mapping parameters: 126 * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>] 127 * 128 * With separate write parameters, the first set is only used for reads. 129 * Delays are specified in milliseconds. 130 */ 131 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) 132 { 133 struct delay_c *dc; 134 unsigned long long tmpll; 135 136 if (argc != 3 && argc != 6) { 137 ti->error = "requires exactly 3 or 6 arguments"; 138 return -EINVAL; 139 } 140 141 dc = kmalloc(sizeof(*dc), GFP_KERNEL); 142 if (!dc) { 143 ti->error = "Cannot allocate context"; 144 return -ENOMEM; 145 } 146 147 dc->reads = dc->writes = 0; 148 149 if (sscanf(argv[1], "%llu", &tmpll) != 1) { 150 ti->error = "Invalid device sector"; 151 goto bad; 152 } 153 dc->start_read = tmpll; 154 155 if (sscanf(argv[2], "%u", &dc->read_delay) != 1) { 156 ti->error = "Invalid delay"; 157 goto bad; 158 } 159 160 if (dm_get_device(ti, argv[0], dc->start_read, ti->len, 161 dm_table_get_mode(ti->table), &dc->dev_read)) { 162 ti->error = "Device lookup failed"; 163 goto bad; 164 } 165 166 if (argc == 3) { 167 dc->dev_write = NULL; 168 goto out; 169 } 170 171 if (sscanf(argv[4], "%llu", &tmpll) != 1) { 172 ti->error = "Invalid write device sector"; 173 goto bad; 174 } 175 dc->start_write = tmpll; 176 177 if (sscanf(argv[5], "%u", &dc->write_delay) != 1) { 178 ti->error = "Invalid write delay"; 179 goto bad; 180 } 181 182 if (dm_get_device(ti, argv[3], dc->start_write, ti->len, 183 dm_table_get_mode(ti->table), &dc->dev_write)) { 184 ti->error = "Write device lookup failed"; 185 dm_put_device(ti, dc->dev_read); 186 goto bad; 187 } 188 189 out: 190 dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache); 191 if (!dc->delayed_pool) { 192 DMERR("Couldn't create delayed bio pool."); 193 goto bad; 194 } 195 196 init_timer(&dc->delay_timer); 197 dc->delay_timer.function = handle_delayed_timer; 198 dc->delay_timer.data = (unsigned long)dc; 199 200 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); 201 INIT_LIST_HEAD(&dc->delayed_bios); 202 init_MUTEX(&dc->timer_lock); 203 atomic_set(&dc->may_delay, 1); 204 205 ti->private = dc; 206 return 0; 207 208 bad: 209 kfree(dc); 210 return -EINVAL; 211 } 212 213 static void delay_dtr(struct dm_target *ti) 214 { 215 struct delay_c *dc = ti->private; 216 217 flush_workqueue(kdelayd_wq); 218 219 dm_put_device(ti, dc->dev_read); 220 221 if (dc->dev_write) 222 dm_put_device(ti, dc->dev_write); 223 224 mempool_destroy(dc->delayed_pool); 225 kfree(dc); 226 } 227 228 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio) 229 { 230 struct delay_info *delayed; 231 unsigned long expires = 0; 232 233 if (!delay || !atomic_read(&dc->may_delay)) 234 return 1; 235 236 delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO); 237 238 delayed->context = dc; 239 delayed->bio = bio; 240 delayed->expires = expires = jiffies + (delay * HZ / 1000); 241 242 mutex_lock(&delayed_bios_lock); 243 244 if (bio_data_dir(bio) == WRITE) 245 dc->writes++; 246 else 247 dc->reads++; 248 249 list_add_tail(&delayed->list, &dc->delayed_bios); 250 251 mutex_unlock(&delayed_bios_lock); 252 253 queue_timeout(dc, expires); 254 255 return 0; 256 } 257 258 static void delay_presuspend(struct dm_target *ti) 259 { 260 struct delay_c *dc = ti->private; 261 262 atomic_set(&dc->may_delay, 0); 263 del_timer_sync(&dc->delay_timer); 264 flush_bios(flush_delayed_bios(dc, 1)); 265 } 266 267 static void delay_resume(struct dm_target *ti) 268 { 269 struct delay_c *dc = ti->private; 270 271 atomic_set(&dc->may_delay, 1); 272 } 273 274 static int delay_map(struct dm_target *ti, struct bio *bio, 275 union map_info *map_context) 276 { 277 struct delay_c *dc = ti->private; 278 279 if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) { 280 bio->bi_bdev = dc->dev_write->bdev; 281 bio->bi_sector = dc->start_write + 282 (bio->bi_sector - ti->begin); 283 284 return delay_bio(dc, dc->write_delay, bio); 285 } 286 287 bio->bi_bdev = dc->dev_read->bdev; 288 bio->bi_sector = dc->start_read + 289 (bio->bi_sector - ti->begin); 290 291 return delay_bio(dc, dc->read_delay, bio); 292 } 293 294 static int delay_status(struct dm_target *ti, status_type_t type, 295 char *result, unsigned maxlen) 296 { 297 struct delay_c *dc = ti->private; 298 int sz = 0; 299 300 switch (type) { 301 case STATUSTYPE_INFO: 302 DMEMIT("%u %u", dc->reads, dc->writes); 303 break; 304 305 case STATUSTYPE_TABLE: 306 DMEMIT("%s %llu %u", dc->dev_read->name, 307 (unsigned long long) dc->start_read, 308 dc->read_delay); 309 if (dc->dev_write) 310 DMEMIT("%s %llu %u", dc->dev_write->name, 311 (unsigned long long) dc->start_write, 312 dc->write_delay); 313 break; 314 } 315 316 return 0; 317 } 318 319 static struct target_type delay_target = { 320 .name = "delay", 321 .version = {1, 0, 2}, 322 .module = THIS_MODULE, 323 .ctr = delay_ctr, 324 .dtr = delay_dtr, 325 .map = delay_map, 326 .presuspend = delay_presuspend, 327 .resume = delay_resume, 328 .status = delay_status, 329 }; 330 331 static int __init dm_delay_init(void) 332 { 333 int r = -ENOMEM; 334 335 kdelayd_wq = create_workqueue("kdelayd"); 336 if (!kdelayd_wq) { 337 DMERR("Couldn't start kdelayd"); 338 goto bad_queue; 339 } 340 341 delayed_cache = kmem_cache_create("dm-delay", 342 sizeof(struct delay_info), 343 __alignof__(struct delay_info), 344 0, NULL, NULL); 345 if (!delayed_cache) { 346 DMERR("Couldn't create delayed bio cache."); 347 goto bad_memcache; 348 } 349 350 r = dm_register_target(&delay_target); 351 if (r < 0) { 352 DMERR("register failed %d", r); 353 goto bad_register; 354 } 355 356 return 0; 357 358 bad_register: 359 kmem_cache_destroy(delayed_cache); 360 bad_memcache: 361 destroy_workqueue(kdelayd_wq); 362 bad_queue: 363 return r; 364 } 365 366 static void __exit dm_delay_exit(void) 367 { 368 int r = dm_unregister_target(&delay_target); 369 370 if (r < 0) 371 DMERR("unregister failed %d", r); 372 373 kmem_cache_destroy(delayed_cache); 374 destroy_workqueue(kdelayd_wq); 375 } 376 377 /* Module hooks */ 378 module_init(dm_delay_init); 379 module_exit(dm_delay_exit); 380 381 MODULE_DESCRIPTION(DM_NAME " delay target"); 382 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>"); 383 MODULE_LICENSE("GPL"); 384