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         char dummy;
 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%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         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
 161                           &dc->dev_read)) {
 162                 ti->error = "Device lookup failed";
 163                 goto bad;
 164         }
 165
 166         dc->dev_write = NULL;
 167         if (argc == 3)
 168                 goto out;
 169
 170         if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1) {
 171                 ti->error = "Invalid write device sector";
 172                 goto bad_dev_read;
 173         }
 174         dc->start_write = tmpll;
 175
 176         if (sscanf(argv[5], "%u%c", &dc->write_delay, &dummy) != 1) {
 177                 ti->error = "Invalid write delay";
 178                 goto bad_dev_read;
 179         }
 180
 181         if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
 182                           &dc->dev_write)) {
 183                 ti->error = "Write device lookup failed";
 184                 goto bad_dev_read;
 185         }
 186
 187 out:
 188         dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
 189         if (!dc->delayed_pool) {
 190                 DMERR("Couldn't create delayed bio pool.");
 191                 goto bad_dev_write;
 192         }
 193
 194         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
 195
 196         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 197         INIT_LIST_HEAD(&dc->delayed_bios);
 198         mutex_init(&dc->timer_lock);
 199         atomic_set(&dc->may_delay, 1);
 200
 201         ti->num_flush_bios = 1;
 202         ti->num_discard_bios = 1;
 203         ti->private = dc;
 204         return 0;
 205
 206 bad_dev_write:
 207         if (dc->dev_write)
 208                 dm_put_device(ti, dc->dev_write);
 209 bad_dev_read:
 210         dm_put_device(ti, dc->dev_read);
 211 bad:
 212         kfree(dc);
 213         return -EINVAL;
 214 }
 215
 216 static void delay_dtr(struct dm_target *ti)
 217 {
 218         struct delay_c *dc = ti->private;
 219
 220         flush_workqueue(kdelayd_wq);
 221
 222         dm_put_device(ti, dc->dev_read);
 223
 224         if (dc->dev_write)
 225                 dm_put_device(ti, dc->dev_write);
 226
 227         mempool_destroy(dc->delayed_pool);
 228         kfree(dc);
 229 }
 230
 231 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 232 {
 233         struct dm_delay_info *delayed;
 234         unsigned long expires = 0;
 235
 236         if (!delay || !atomic_read(&dc->may_delay))
 237                 return 1;
 238
 239         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
 240
 241         delayed->context = dc;
 242         delayed->bio = bio;
 243         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 244
 245         mutex_lock(&delayed_bios_lock);
 246
 247         if (bio_data_dir(bio) == WRITE)
 248                 dc->writes++;
 249         else
 250                 dc->reads++;
 251
 252         list_add_tail(&delayed->list, &dc->delayed_bios);
 253
 254         mutex_unlock(&delayed_bios_lock);
 255
 256         queue_timeout(dc, expires);
 257
 258         return 0;
 259 }
 260
 261 static void delay_presuspend(struct dm_target *ti)
 262 {
 263         struct delay_c *dc = ti->private;
 264
 265         atomic_set(&dc->may_delay, 0);
 266         del_timer_sync(&dc->delay_timer);
 267         flush_bios(flush_delayed_bios(dc, 1));
 268 }
 269
 270 static void delay_resume(struct dm_target *ti)
 271 {
 272         struct delay_c *dc = ti->private;
 273
 274         atomic_set(&dc->may_delay, 1);
 275 }
 276
 277 static int delay_map(struct dm_target *ti, struct bio *bio)
 278 {
 279         struct delay_c *dc = ti->private;
 280
 281         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 282                 bio->bi_bdev = dc->dev_write->bdev;
 283                 if (bio_sectors(bio))
 284                         bio->bi_sector = dc->start_write +
 285                                          dm_target_offset(ti, bio->bi_sector);
 286
 287                 return delay_bio(dc, dc->write_delay, bio);
 288         }
 289
 290         bio->bi_bdev = dc->dev_read->bdev;
 291         bio->bi_sector = dc->start_read + dm_target_offset(ti, bio->bi_sector);
 292
 293         return delay_bio(dc, dc->read_delay, bio);
 294 }
 295
 296 static void delay_status(struct dm_target *ti, status_type_t type,
 297                          unsigned status_flags, 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
 319 static int delay_iterate_devices(struct dm_target *ti,
 320                                  iterate_devices_callout_fn fn, void *data)
 321 {
 322         struct delay_c *dc = ti->private;
 323         int ret = 0;
 324
 325         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 326         if (ret)
 327                 goto out;
 328
 329         if (dc->dev_write)
 330                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 331
 332 out:
 333         return ret;
 334 }
 335
 336 static struct target_type delay_target = {
 337         .name        = "delay",
 338         .version     = {1, 2, 1},
 339         .module      = THIS_MODULE,
 340         .ctr         = delay_ctr,
 341         .dtr         = delay_dtr,
 342         .map         = delay_map,
 343         .presuspend  = delay_presuspend,
 344         .resume      = delay_resume,
 345         .status      = delay_status,
 346         .iterate_devices = delay_iterate_devices,
 347 };
 348
 349 static int __init dm_delay_init(void)
 350 {
 351         int r = -ENOMEM;
 352
 353         kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 354         if (!kdelayd_wq) {
 355                 DMERR("Couldn't start kdelayd");
 356                 goto bad_queue;
 357         }
 358
 359         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 360         if (!delayed_cache) {
 361                 DMERR("Couldn't create delayed bio cache.");
 362                 goto bad_memcache;
 363         }
 364
 365         r = dm_register_target(&delay_target);
 366         if (r < 0) {
 367                 DMERR("register failed %d", r);
 368                 goto bad_register;
 369         }
 370
 371         return 0;
 372
 373 bad_register:
 374         kmem_cache_destroy(delayed_cache);
 375 bad_memcache:
 376         destroy_workqueue(kdelayd_wq);
 377 bad_queue:
 378         return r;
 379 }
 380
 381 static void __exit dm_delay_exit(void)
 382 {
 383         dm_unregister_target(&delay_target);
 384         kmem_cache_destroy(delayed_cache);
 385         destroy_workqueue(kdelayd_wq);
 386 }
 387
 388 /* Module hooks */
 389 module_init(dm_delay_init);
 390 module_exit(dm_delay_exit);
 391
 392 MODULE_DESCRIPTION(DM_NAME " delay target");
 393 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 394 MODULE_LICENSE("GPL");