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         mempool_t *delayed_pool;
  28
  29         struct dm_dev *dev_read;
  30         sector_t start_read;
  31         unsigned read_delay;
  32         unsigned reads;
  33
  34         struct dm_dev *dev_write;
  35         sector_t start_write;
  36         unsigned write_delay;
  37         unsigned writes;
  38 };
  39
  40 struct dm_delay_info {
  41         struct delay_c *context;
  42         struct list_head list;
  43         struct bio *bio;
  44         unsigned long expires;
  45 };
  46
  47 static DEFINE_MUTEX(delayed_bios_lock);
  48
  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(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                 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         dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 194         if (!dc->kdelayd_wq) {
 195                 DMERR("Couldn't start kdelayd");
 196                 goto bad_queue;
 197         }
 198
 199         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
 200
 201         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 202         INIT_LIST_HEAD(&dc->delayed_bios);
 203         mutex_init(&dc->timer_lock);
 204         atomic_set(&dc->may_delay, 1);
 205
 206         ti->num_flush_requests = 1;
 207         ti->num_discard_requests = 1;
 208         ti->private = dc;
 209         return 0;
 210
 211 bad_queue:
 212         mempool_destroy(dc->delayed_pool);
 213 bad_dev_write:
 214         if (dc->dev_write)
 215                 dm_put_device(ti, dc->dev_write);
 216 bad_dev_read:
 217         dm_put_device(ti, dc->dev_read);
 218 bad:
 219         kfree(dc);
 220         return -EINVAL;
 221 }
 222
 223 static void delay_dtr(struct dm_target *ti)
 224 {
 225         struct delay_c *dc = ti->private;
 226
 227         destroy_workqueue(dc->kdelayd_wq);
 228
 229         dm_put_device(ti, dc->dev_read);
 230
 231         if (dc->dev_write)
 232                 dm_put_device(ti, dc->dev_write);
 233
 234         mempool_destroy(dc->delayed_pool);
 235         kfree(dc);
 236 }
 237
 238 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 239 {
 240         struct dm_delay_info *delayed;
 241         unsigned long expires = 0;
 242
 243         if (!delay || !atomic_read(&dc->may_delay))
 244                 return 1;
 245
 246         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
 247
 248         delayed->context = dc;
 249         delayed->bio = bio;
 250         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 251
 252         mutex_lock(&delayed_bios_lock);
 253
 254         if (bio_data_dir(bio) == WRITE)
 255                 dc->writes++;
 256         else
 257                 dc->reads++;
 258
 259         list_add_tail(&delayed->list, &dc->delayed_bios);
 260
 261         mutex_unlock(&delayed_bios_lock);
 262
 263         queue_timeout(dc, expires);
 264
 265         return 0;
 266 }
 267
 268 static void delay_presuspend(struct dm_target *ti)
 269 {
 270         struct delay_c *dc = ti->private;
 271
 272         atomic_set(&dc->may_delay, 0);
 273         del_timer_sync(&dc->delay_timer);
 274         flush_bios(flush_delayed_bios(dc, 1));
 275 }
 276
 277 static void delay_resume(struct dm_target *ti)
 278 {
 279         struct delay_c *dc = ti->private;
 280
 281         atomic_set(&dc->may_delay, 1);
 282 }
 283
 284 static int delay_map(struct dm_target *ti, struct bio *bio,
 285                      union map_info *map_context)
 286 {
 287         struct delay_c *dc = ti->private;
 288
 289         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 290                 bio->bi_bdev = dc->dev_write->bdev;
 291                 if (bio_sectors(bio))
 292                         bio->bi_sector = dc->start_write +
 293                                          dm_target_offset(ti, bio->bi_sector);
 294
 295                 return delay_bio(dc, dc->write_delay, bio);
 296         }
 297
 298         bio->bi_bdev = dc->dev_read->bdev;
 299         bio->bi_sector = dc->start_read + dm_target_offset(ti, bio->bi_sector);
 300
 301         return delay_bio(dc, dc->read_delay, bio);
 302 }
 303
 304 static void delay_status(struct dm_target *ti, status_type_t type,
 305                          char *result, unsigned maxlen)
 306 {
 307         struct delay_c *dc = ti->private;
 308         int sz = 0;
 309
 310         switch (type) {
 311         case STATUSTYPE_INFO:
 312                 DMEMIT("%u %u", dc->reads, dc->writes);
 313                 break;
 314
 315         case STATUSTYPE_TABLE:
 316                 DMEMIT("%s %llu %u", dc->dev_read->name,
 317                        (unsigned long long) dc->start_read,
 318                        dc->read_delay);
 319                 if (dc->dev_write)
 320                         DMEMIT(" %s %llu %u", dc->dev_write->name,
 321                                (unsigned long long) dc->start_write,
 322                                dc->write_delay);
 323                 break;
 324         }
 325 }
 326
 327 static int delay_iterate_devices(struct dm_target *ti,
 328                                  iterate_devices_callout_fn fn, void *data)
 329 {
 330         struct delay_c *dc = ti->private;
 331         int ret = 0;
 332
 333         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 334         if (ret)
 335                 goto out;
 336
 337         if (dc->dev_write)
 338                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 339
 340 out:
 341         return ret;
 342 }
 343
 344 static struct target_type delay_target = {
 345         .name        = "delay",
 346         .version     = {1, 1, 1},
 347         .module      = THIS_MODULE,
 348         .ctr         = delay_ctr,
 349         .dtr         = delay_dtr,
 350         .map         = delay_map,
 351         .presuspend  = delay_presuspend,
 352         .resume      = delay_resume,
 353         .status      = delay_status,
 354         .iterate_devices = delay_iterate_devices,
 355 };
 356
 357 static int __init dm_delay_init(void)
 358 {
 359         int r = -ENOMEM;
 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         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 }
 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");