drivers/md/dm-delay.c

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