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 work_struct flush_expired_bios;
  24         struct list_head delayed_bios;
  25         atomic_t may_delay;
  26         mempool_t *delayed_pool;
  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         struct bio *bio;
  43         unsigned long expires;
  44 };
  45
  46 static DEFINE_MUTEX(delayed_bios_lock);
  47
  48 static struct workqueue_struct *kdelayd_wq;
  49 static struct kmem_cache *delayed_cache;
  50
  51 static void handle_delayed_timer(unsigned long data)
  52 {
  53         struct delay_c *dc = (struct delay_c *)data;
  54
  55         queue_work(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                 generic_make_request(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         int 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                         list_del(&delayed->list);
  91                         bio_list_add(&flush_bios, delayed->bio);
  92                         if ((bio_data_dir(delayed->bio) == WRITE))
  93                                 delayed->context->writes--;
  94                         else
  95                                 delayed->context->reads--;
  96                         mempool_free(delayed, dc->delayed_pool);
  97                         continue;
  98                 }
  99
 100                 if (!start_timer) {
 101                         start_timer = 1;
 102                         next_expires = delayed->expires;
 103                 } else
 104                         next_expires = min(next_expires, delayed->expires);
 105         }
 106
 107         mutex_unlock(&delayed_bios_lock);
 108
 109         if (start_timer)
 110                 queue_timeout(dc, next_expires);
 111
 112         return bio_list_get(&flush_bios);
 113 }
 114
 115 static void flush_expired_bios(struct work_struct *work)
 116 {
 117         struct delay_c *dc;
 118
 119         dc = container_of(work, struct delay_c, flush_expired_bios);
 120         flush_bios(flush_delayed_bios(dc, 0));
 121 }
 122
 123 /*
 124  * Mapping parameters:
 125  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 126  *
 127  * With separate write parameters, the first set is only used for reads.
 128  * Delays are specified in milliseconds.
 129  */
 130 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 131 {
 132         struct delay_c *dc;
 133         unsigned long long tmpll;
 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         if (sscanf(argv[1], "%llu", &tmpll) != 1) {
 149                 ti->error = "Invalid device sector";
 150                 goto bad;
 151         }
 152         dc->start_read = tmpll;
 153
 154         if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
 155                 ti->error = "Invalid delay";
 156                 goto bad;
 157         }
 158
 159         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
 160                           &dc->dev_read)) {
 161                 ti->error = "Device lookup failed";
 162                 goto bad;
 163         }
 164
 165         dc->dev_write = NULL;
 166         if (argc == 3)
 167                 goto out;
 168
 169         if (sscanf(argv[4], "%llu", &tmpll) != 1) {
 170                 ti->error = "Invalid write device sector";
 171                 goto bad_dev_read;
 172         }
 173         dc->start_write = tmpll;
 174
 175         if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
 176                 ti->error = "Invalid write delay";
 177                 goto bad_dev_read;
 178         }
 179
 180         if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
 181                           &dc->dev_write)) {
 182                 ti->error = "Write device lookup failed";
 183                 goto bad_dev_read;
 184         }
 185
 186 out:
 187         dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
 188         if (!dc->delayed_pool) {
 189                 DMERR("Couldn't create delayed bio pool.");
 190                 goto bad_dev_write;
 191         }
 192
 193         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
 194
 195         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 196         INIT_LIST_HEAD(&dc->delayed_bios);
 197         mutex_init(&dc->timer_lock);
 198         atomic_set(&dc->may_delay, 1);
 199
 200         ti->num_flush_requests = 1;
 201         ti->private = dc;
 202         return 0;
 203
 204 bad_dev_write:
 205         if (dc->dev_write)
 206                 dm_put_device(ti, dc->dev_write);
 207 bad_dev_read:
 208         dm_put_device(ti, dc->dev_read);
 209 bad:
 210         kfree(dc);
 211         return -EINVAL;
 212 }
 213
 214 static void delay_dtr(struct dm_target *ti)
 215 {
 216         struct delay_c *dc = ti->private;
 217
 218         flush_workqueue(kdelayd_wq);
 219
 220         dm_put_device(ti, dc->dev_read);
 221
 222         if (dc->dev_write)
 223                 dm_put_device(ti, dc->dev_write);
 224
 225         mempool_destroy(dc->delayed_pool);
 226         kfree(dc);
 227 }
 228
 229 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 230 {
 231         struct dm_delay_info *delayed;
 232         unsigned long expires = 0;
 233
 234         if (!delay || !atomic_read(&dc->may_delay))
 235                 return 1;
 236
 237         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
 238
 239         delayed->context = dc;
 240         delayed->bio = bio;
 241         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 242
 243         mutex_lock(&delayed_bios_lock);
 244
 245         if (bio_data_dir(bio) == WRITE)
 246                 dc->writes++;
 247         else
 248                 dc->reads++;
 249
 250         list_add_tail(&delayed->list, &dc->delayed_bios);
 251
 252         mutex_unlock(&delayed_bios_lock);
 253
 254         queue_timeout(dc, expires);
 255
 256         return 0;
 257 }
 258
 259 static void delay_presuspend(struct dm_target *ti)
 260 {
 261         struct delay_c *dc = ti->private;
 262
 263         atomic_set(&dc->may_delay, 0);
 264         del_timer_sync(&dc->delay_timer);
 265         flush_bios(flush_delayed_bios(dc, 1));
 266 }
 267
 268 static void delay_resume(struct dm_target *ti)
 269 {
 270         struct delay_c *dc = ti->private;
 271
 272         atomic_set(&dc->may_delay, 1);
 273 }
 274
 275 static int delay_map(struct dm_target *ti, struct bio *bio,
 276                      union map_info *map_context)
 277 {
 278         struct delay_c *dc = ti->private;
 279
 280         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 281                 bio->bi_bdev = dc->dev_write->bdev;
 282                 if (bio_sectors(bio))
 283                         bio->bi_sector = dc->start_write +
 284                                          (bio->bi_sector - ti->begin);
 285
 286                 return delay_bio(dc, dc->write_delay, bio);
 287         }
 288
 289         bio->bi_bdev = dc->dev_read->bdev;
 290         bio->bi_sector = dc->start_read +
 291                          (bio->bi_sector - ti->begin);
 292
 293         return delay_bio(dc, dc->read_delay, bio);
 294 }
 295
 296 static int delay_status(struct dm_target *ti, status_type_t type,
 297                         char *result, unsigned maxlen)
 298 {
 299         struct delay_c *dc = ti->private;
 300         int sz = 0;
 301
 302         switch (type) {
 303         case STATUSTYPE_INFO:
 304                 DMEMIT("%u %u", dc->reads, dc->writes);
 305                 break;
 306
 307         case STATUSTYPE_TABLE:
 308                 DMEMIT("%s %llu %u", dc->dev_read->name,
 309                        (unsigned long long) dc->start_read,
 310                        dc->read_delay);
 311                 if (dc->dev_write)
 312                         DMEMIT(" %s %llu %u", dc->dev_write->name,
 313                                (unsigned long long) dc->start_write,
 314                                dc->write_delay);
 315                 break;
 316         }
 317
 318         return 0;
 319 }
 320
 321 static int delay_iterate_devices(struct dm_target *ti,
 322                                  iterate_devices_callout_fn fn, void *data)
 323 {
 324         struct delay_c *dc = ti->private;
 325         int ret = 0;
 326
 327         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 328         if (ret)
 329                 goto out;
 330
 331         if (dc->dev_write)
 332                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 333
 334 out:
 335         return ret;
 336 }
 337
 338 static struct target_type delay_target = {
 339         .name        = "delay",
 340         .version     = {1, 1, 0},
 341         .module      = THIS_MODULE,
 342         .ctr         = delay_ctr,
 343         .dtr         = delay_dtr,
 344         .map         = delay_map,
 345         .presuspend  = delay_presuspend,
 346         .resume      = delay_resume,
 347         .status      = delay_status,
 348         .iterate_devices = delay_iterate_devices,
 349 };
 350
 351 static int __init dm_delay_init(void)
 352 {
 353         int r = -ENOMEM;
 354
 355         kdelayd_wq = create_workqueue("kdelayd");
 356         if (!kdelayd_wq) {
 357                 DMERR("Couldn't start kdelayd");
 358                 goto bad_queue;
 359         }
 360
 361         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 362         if (!delayed_cache) {
 363                 DMERR("Couldn't create delayed bio cache.");
 364                 goto bad_memcache;
 365         }
 366
 367         r = dm_register_target(&delay_target);
 368         if (r < 0) {
 369                 DMERR("register failed %d", r);
 370                 goto bad_register;
 371         }
 372
 373         return 0;
 374
 375 bad_register:
 376         kmem_cache_destroy(delayed_cache);
 377 bad_memcache:
 378         destroy_workqueue(kdelayd_wq);
 379 bad_queue:
 380         return r;
 381 }
 382
 383 static void __exit dm_delay_exit(void)
 384 {
 385         dm_unregister_target(&delay_target);
 386         kmem_cache_destroy(delayed_cache);
 387         destroy_workqueue(kdelayd_wq);
 388 }
 389
 390 /* Module hooks */
 391 module_init(dm_delay_init);
 392 module_exit(dm_delay_exit);
 393
 394 MODULE_DESCRIPTION(DM_NAME " delay target");
 395 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 396 MODULE_LICENSE("GPL");