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 <linux/device-mapper.h> 17 18 #define DM_MSG_PREFIX "delay" 19 20 struct delay_class { 21 struct dm_dev *dev; 22 sector_t start; 23 unsigned delay; 24 unsigned ops; 25 }; 26 27 struct delay_c { 28 struct timer_list delay_timer; 29 struct mutex timer_lock; 30 struct workqueue_struct *kdelayd_wq; 31 struct work_struct flush_expired_bios; 32 struct list_head delayed_bios; 33 atomic_t may_delay; 34 35 struct delay_class read; 36 struct delay_class write; 37 struct delay_class flush; 38 39 int argc; 40 }; 41 42 struct dm_delay_info { 43 struct delay_c *context; 44 struct delay_class *class; 45 struct list_head list; 46 unsigned long expires; 47 }; 48 49 static DEFINE_MUTEX(delayed_bios_lock); 50 51 static void handle_delayed_timer(struct timer_list *t) 52 { 53 struct delay_c *dc = from_timer(dc, t, delay_timer); 54 55 queue_work(dc->kdelayd_wq, &dc->flush_expired_bios); 56 } 57 58 static void queue_timeout(struct delay_c *dc, unsigned long expires) 59 { 60 mutex_lock(&dc->timer_lock); 61 62 if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires) 63 mod_timer(&dc->delay_timer, expires); 64 65 mutex_unlock(&dc->timer_lock); 66 } 67 68 static void flush_bios(struct bio *bio) 69 { 70 struct bio *n; 71 72 while (bio) { 73 n = bio->bi_next; 74 bio->bi_next = NULL; 75 submit_bio_noacct(bio); 76 bio = n; 77 } 78 } 79 80 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all) 81 { 82 struct dm_delay_info *delayed, *next; 83 unsigned long next_expires = 0; 84 unsigned long start_timer = 0; 85 struct bio_list flush_bios = { }; 86 87 mutex_lock(&delayed_bios_lock); 88 list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) { 89 if (flush_all || time_after_eq(jiffies, delayed->expires)) { 90 struct bio *bio = dm_bio_from_per_bio_data(delayed, 91 sizeof(struct dm_delay_info)); 92 list_del(&delayed->list); 93 bio_list_add(&flush_bios, bio); 94 delayed->class->ops--; 95 continue; 96 } 97 98 if (!start_timer) { 99 start_timer = 1; 100 next_expires = delayed->expires; 101 } else 102 next_expires = min(next_expires, delayed->expires); 103 } 104 mutex_unlock(&delayed_bios_lock); 105 106 if (start_timer) 107 queue_timeout(dc, next_expires); 108 109 return bio_list_get(&flush_bios); 110 } 111 112 static void flush_expired_bios(struct work_struct *work) 113 { 114 struct delay_c *dc; 115 116 dc = container_of(work, struct delay_c, flush_expired_bios); 117 flush_bios(flush_delayed_bios(dc, 0)); 118 } 119 120 static void delay_dtr(struct dm_target *ti) 121 { 122 struct delay_c *dc = ti->private; 123 124 if (dc->kdelayd_wq) 125 destroy_workqueue(dc->kdelayd_wq); 126 127 if (dc->read.dev) 128 dm_put_device(ti, dc->read.dev); 129 if (dc->write.dev) 130 dm_put_device(ti, dc->write.dev); 131 if (dc->flush.dev) 132 dm_put_device(ti, dc->flush.dev); 133 134 mutex_destroy(&dc->timer_lock); 135 136 kfree(dc); 137 } 138 139 static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv) 140 { 141 int ret; 142 unsigned long long tmpll; 143 char dummy; 144 145 if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) { 146 ti->error = "Invalid device sector"; 147 return -EINVAL; 148 } 149 c->start = tmpll; 150 151 if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) { 152 ti->error = "Invalid delay"; 153 return -EINVAL; 154 } 155 156 ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev); 157 if (ret) { 158 ti->error = "Device lookup failed"; 159 return ret; 160 } 161 162 return 0; 163 } 164 165 /* 166 * Mapping parameters: 167 * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>] 168 * 169 * With separate write parameters, the first set is only used for reads. 170 * Offsets are specified in sectors. 171 * Delays are specified in milliseconds. 172 */ 173 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) 174 { 175 struct delay_c *dc; 176 int ret; 177 178 if (argc != 3 && argc != 6 && argc != 9) { 179 ti->error = "Requires exactly 3, 6 or 9 arguments"; 180 return -EINVAL; 181 } 182 183 dc = kzalloc(sizeof(*dc), GFP_KERNEL); 184 if (!dc) { 185 ti->error = "Cannot allocate context"; 186 return -ENOMEM; 187 } 188 189 ti->private = dc; 190 timer_setup(&dc->delay_timer, handle_delayed_timer, 0); 191 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); 192 INIT_LIST_HEAD(&dc->delayed_bios); 193 mutex_init(&dc->timer_lock); 194 atomic_set(&dc->may_delay, 1); 195 dc->argc = argc; 196 197 ret = delay_class_ctr(ti, &dc->read, argv); 198 if (ret) 199 goto bad; 200 201 if (argc == 3) { 202 ret = delay_class_ctr(ti, &dc->write, argv); 203 if (ret) 204 goto bad; 205 ret = delay_class_ctr(ti, &dc->flush, argv); 206 if (ret) 207 goto bad; 208 goto out; 209 } 210 211 ret = delay_class_ctr(ti, &dc->write, argv + 3); 212 if (ret) 213 goto bad; 214 if (argc == 6) { 215 ret = delay_class_ctr(ti, &dc->flush, argv + 3); 216 if (ret) 217 goto bad; 218 goto out; 219 } 220 221 ret = delay_class_ctr(ti, &dc->flush, argv + 6); 222 if (ret) 223 goto bad; 224 225 out: 226 dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0); 227 if (!dc->kdelayd_wq) { 228 ret = -EINVAL; 229 DMERR("Couldn't start kdelayd"); 230 goto bad; 231 } 232 233 ti->num_flush_bios = 1; 234 ti->num_discard_bios = 1; 235 ti->per_io_data_size = sizeof(struct dm_delay_info); 236 return 0; 237 238 bad: 239 delay_dtr(ti); 240 return ret; 241 } 242 243 static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) 244 { 245 struct dm_delay_info *delayed; 246 unsigned long expires = 0; 247 248 if (!c->delay || !atomic_read(&dc->may_delay)) 249 return DM_MAPIO_REMAPPED; 250 251 delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); 252 253 delayed->context = dc; 254 delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay); 255 256 mutex_lock(&delayed_bios_lock); 257 c->ops++; 258 list_add_tail(&delayed->list, &dc->delayed_bios); 259 mutex_unlock(&delayed_bios_lock); 260 261 queue_timeout(dc, expires); 262 263 return DM_MAPIO_SUBMITTED; 264 } 265 266 static void delay_presuspend(struct dm_target *ti) 267 { 268 struct delay_c *dc = ti->private; 269 270 atomic_set(&dc->may_delay, 0); 271 del_timer_sync(&dc->delay_timer); 272 flush_bios(flush_delayed_bios(dc, 1)); 273 } 274 275 static void delay_resume(struct dm_target *ti) 276 { 277 struct delay_c *dc = ti->private; 278 279 atomic_set(&dc->may_delay, 1); 280 } 281 282 static int delay_map(struct dm_target *ti, struct bio *bio) 283 { 284 struct delay_c *dc = ti->private; 285 struct delay_class *c; 286 struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info)); 287 288 if (bio_data_dir(bio) == WRITE) { 289 if (unlikely(bio->bi_opf & REQ_PREFLUSH)) 290 c = &dc->flush; 291 else 292 c = &dc->write; 293 } else { 294 c = &dc->read; 295 } 296 delayed->class = c; 297 bio_set_dev(bio, c->dev->bdev); 298 if (bio_sectors(bio)) 299 bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector); 300 301 return delay_bio(dc, c, bio); 302 } 303 304 #define DMEMIT_DELAY_CLASS(c) \ 305 DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay) 306 307 static void delay_status(struct dm_target *ti, status_type_t type, 308 unsigned status_flags, char *result, unsigned maxlen) 309 { 310 struct delay_c *dc = ti->private; 311 int sz = 0; 312 313 switch (type) { 314 case STATUSTYPE_INFO: 315 DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops); 316 break; 317 318 case STATUSTYPE_TABLE: 319 DMEMIT_DELAY_CLASS(&dc->read); 320 if (dc->argc >= 6) { 321 DMEMIT(" "); 322 DMEMIT_DELAY_CLASS(&dc->write); 323 } 324 if (dc->argc >= 9) { 325 DMEMIT(" "); 326 DMEMIT_DELAY_CLASS(&dc->flush); 327 } 328 break; 329 } 330 } 331 332 static int delay_iterate_devices(struct dm_target *ti, 333 iterate_devices_callout_fn fn, void *data) 334 { 335 struct delay_c *dc = ti->private; 336 int ret = 0; 337 338 ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data); 339 if (ret) 340 goto out; 341 ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data); 342 if (ret) 343 goto out; 344 ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data); 345 if (ret) 346 goto out; 347 348 out: 349 return ret; 350 } 351 352 static struct target_type delay_target = { 353 .name = "delay", 354 .version = {1, 2, 1}, 355 .features = DM_TARGET_PASSES_INTEGRITY, 356 .module = THIS_MODULE, 357 .ctr = delay_ctr, 358 .dtr = delay_dtr, 359 .map = delay_map, 360 .presuspend = delay_presuspend, 361 .resume = delay_resume, 362 .status = delay_status, 363 .iterate_devices = delay_iterate_devices, 364 }; 365 366 static int __init dm_delay_init(void) 367 { 368 int r; 369 370 r = dm_register_target(&delay_target); 371 if (r < 0) { 372 DMERR("register failed %d", r); 373 goto bad_register; 374 } 375 376 return 0; 377 378 bad_register: 379 return r; 380 } 381 382 static void __exit dm_delay_exit(void) 383 { 384 dm_unregister_target(&delay_target); 385 } 386 387 /* Module hooks */ 388 module_init(dm_delay_init); 389 module_exit(dm_delay_exit); 390 391 MODULE_DESCRIPTION(DM_NAME " delay target"); 392 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>"); 393 MODULE_LICENSE("GPL"); 394