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_requests = 1;
 202         ti->num_discard_requests = 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                      union map_info *map_context)
 279 {
 280         struct delay_c *dc = ti->private;
 281
 282         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 283                 bio->bi_bdev = dc->dev_write->bdev;
 284                 if (bio_sectors(bio))
 285                         bio->bi_sector = dc->start_write +
 286                                          dm_target_offset(ti, bio->bi_sector);
 287
 288                 return delay_bio(dc, dc->write_delay, bio);
 289         }
 290
 291         bio->bi_bdev = dc->dev_read->bdev;
 292         bio->bi_sector = dc->start_read + dm_target_offset(ti, bio->bi_sector);
 293
 294         return delay_bio(dc, dc->read_delay, bio);
 295 }
 296
 297 static int delay_status(struct dm_target *ti, status_type_t type,
 298                         char *result, unsigned maxlen)
 299 {
 300         struct delay_c *dc = ti->private;
 301         int sz = 0;
 302
 303         switch (type) {
 304         case STATUSTYPE_INFO:
 305                 DMEMIT("%u %u", dc->reads, dc->writes);
 306                 break;
 307
 308         case STATUSTYPE_TABLE:
 309                 DMEMIT("%s %llu %u", dc->dev_read->name,
 310                        (unsigned long long) dc->start_read,
 311                        dc->read_delay);
 312                 if (dc->dev_write)
 313                         DMEMIT(" %s %llu %u", dc->dev_write->name,
 314                                (unsigned long long) dc->start_write,
 315                                dc->write_delay);
 316                 break;
 317         }
 318
 319         return 0;
 320 }
 321
 322 static int delay_iterate_devices(struct dm_target *ti,
 323                                  iterate_devices_callout_fn fn, void *data)
 324 {
 325         struct delay_c *dc = ti->private;
 326         int ret = 0;
 327
 328         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 329         if (ret)
 330                 goto out;
 331
 332         if (dc->dev_write)
 333                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 334
 335 out:
 336         return ret;
 337 }
 338
 339 static struct target_type delay_target = {
 340         .name        = "delay",
 341         .version     = {1, 1, 0},
 342         .module      = THIS_MODULE,
 343         .ctr         = delay_ctr,
 344         .dtr         = delay_dtr,
 345         .map         = delay_map,
 346         .presuspend  = delay_presuspend,
 347         .resume      = delay_resume,
 348         .status      = delay_status,
 349         .iterate_devices = delay_iterate_devices,
 350 };
 351
 352 static int __init dm_delay_init(void)
 353 {
 354         int r = -ENOMEM;
 355
 356         kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 357         if (!kdelayd_wq) {
 358                 DMERR("Couldn't start kdelayd");
 359                 goto bad_queue;
 360         }
 361
 362         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 363         if (!delayed_cache) {
 364                 DMERR("Couldn't create delayed bio cache.");
 365                 goto bad_memcache;
 366         }
 367
 368         r = dm_register_target(&delay_target);
 369         if (r < 0) {
 370                 DMERR("register failed %d", r);
 371                 goto bad_register;
 372         }
 373
 374         return 0;
 375
 376 bad_register:
 377         kmem_cache_destroy(delayed_cache);
 378 bad_memcache:
 379         destroy_workqueue(kdelayd_wq);
 380 bad_queue:
 381         return r;
 382 }
 383
 384 static void __exit dm_delay_exit(void)
 385 {
 386         dm_unregister_target(&delay_target);
 387         kmem_cache_destroy(delayed_cache);
 388         destroy_workqueue(kdelayd_wq);
 389 }
 390
 391 /* Module hooks */
 392 module_init(dm_delay_init);
 393 module_exit(dm_delay_exit);
 394
 395 MODULE_DESCRIPTION(DM_NAME " delay target");
 396 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 397 MODULE_LICENSE("GPL");