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_class {
  21         struct dm_dev *dev;
  22         sector_t start;
  23         unsigned delay;
  24         unsigned ops;
  25 };
  26
  27 struct delay_c {
  28         struct timer_list delay_timer;
  29         struct mutex timer_lock;
  30         struct workqueue_struct *kdelayd_wq;
  31         struct work_struct flush_expired_bios;
  32         struct list_head delayed_bios;
  33         atomic_t may_delay;
  34
  35         struct delay_class read;
  36         struct delay_class write;
  37         struct delay_class flush;
  38
  39         int argc;
  40 };
  41
  42 struct dm_delay_info {
  43         struct delay_c *context;
  44         struct delay_class *class;
  45         struct list_head list;
  46         unsigned long expires;
  47 };
  48
  49 static DEFINE_MUTEX(delayed_bios_lock);
  50
  51 static void handle_delayed_timer(struct timer_list *t)
  52 {
  53         struct delay_c *dc = from_timer(dc, t, delay_timer);
  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         unsigned long 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                         struct bio *bio = dm_bio_from_per_bio_data(delayed,
  91                                                 sizeof(struct dm_delay_info));
  92                         list_del(&delayed->list);
  93                         bio_list_add(&flush_bios, bio);
  94                         delayed->class->ops--;
  95                         continue;
  96                 }
  97
  98                 if (!start_timer) {
  99                         start_timer = 1;
 100                         next_expires = delayed->expires;
 101                 } else
 102                         next_expires = min(next_expires, delayed->expires);
 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 static void delay_dtr(struct dm_target *ti)
 121 {
 122         struct delay_c *dc = ti->private;
 123
 124         destroy_workqueue(dc->kdelayd_wq);
 125
 126         if (dc->read.dev)
 127                 dm_put_device(ti, dc->read.dev);
 128         if (dc->write.dev)
 129                 dm_put_device(ti, dc->write.dev);
 130         if (dc->flush.dev)
 131                 dm_put_device(ti, dc->flush.dev);
 132
 133         mutex_destroy(&dc->timer_lock);
 134
 135         kfree(dc);
 136 }
 137
 138 static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)
 139 {
 140         int ret;
 141         unsigned long long tmpll;
 142         char dummy;
 143
 144         if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
 145                 ti->error = "Invalid device sector";
 146                 return -EINVAL;
 147         }
 148         c->start = tmpll;
 149
 150         if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {
 151                 ti->error = "Invalid delay";
 152                 return -EINVAL;
 153         }
 154
 155         ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev);
 156         if (ret) {
 157                 ti->error = "Device lookup failed";
 158                 return ret;
 159         }
 160
 161         return 0;
 162 }
 163
 164 /*
 165  * Mapping parameters:
 166  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 167  *
 168  * With separate write parameters, the first set is only used for reads.
 169  * Offsets are specified in sectors.
 170  * Delays are specified in milliseconds.
 171  */
 172 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 173 {
 174         struct delay_c *dc;
 175         int ret;
 176
 177         if (argc != 3 && argc != 6 && argc != 9) {
 178                 ti->error = "Requires exactly 3, 6 or 9 arguments";
 179                 return -EINVAL;
 180         }
 181
 182         dc = kzalloc(sizeof(*dc), GFP_KERNEL);
 183         if (!dc) {
 184                 ti->error = "Cannot allocate context";
 185                 return -ENOMEM;
 186         }
 187
 188         ti->private = dc;
 189         timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
 190         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 191         INIT_LIST_HEAD(&dc->delayed_bios);
 192         mutex_init(&dc->timer_lock);
 193         atomic_set(&dc->may_delay, 1);
 194         dc->argc = argc;
 195
 196         ret = delay_class_ctr(ti, &dc->read, argv);
 197         if (ret)
 198                 goto bad;
 199
 200         if (argc == 3) {
 201                 ret = delay_class_ctr(ti, &dc->write, argv);
 202                 if (ret)
 203                         goto bad;
 204                 ret = delay_class_ctr(ti, &dc->flush, argv);
 205                 if (ret)
 206                         goto bad;
 207                 goto out;
 208         }
 209
 210         ret = delay_class_ctr(ti, &dc->write, argv + 3);
 211         if (ret)
 212                 goto bad;
 213         if (argc == 6) {
 214                 ret = delay_class_ctr(ti, &dc->flush, argv + 3);
 215                 if (ret)
 216                         goto bad;
 217                 goto out;
 218         }
 219
 220         ret = delay_class_ctr(ti, &dc->flush, argv + 6);
 221         if (ret)
 222                 goto bad;
 223
 224 out:
 225         dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 226         if (!dc->kdelayd_wq) {
 227                 ret = -EINVAL;
 228                 DMERR("Couldn't start kdelayd");
 229                 goto bad;
 230         }
 231
 232         ti->num_flush_bios = 1;
 233         ti->num_discard_bios = 1;
 234         ti->per_io_data_size = sizeof(struct dm_delay_info);
 235         return 0;
 236
 237 bad:
 238         delay_dtr(ti);
 239         return ret;
 240 }
 241
 242 static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)
 243 {
 244         struct dm_delay_info *delayed;
 245         unsigned long expires = 0;
 246
 247         if (!c->delay || !atomic_read(&dc->may_delay))
 248                 return DM_MAPIO_REMAPPED;
 249
 250         delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 251
 252         delayed->context = dc;
 253         delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay);
 254
 255         mutex_lock(&delayed_bios_lock);
 256         c->ops++;
 257         list_add_tail(&delayed->list, &dc->delayed_bios);
 258         mutex_unlock(&delayed_bios_lock);
 259
 260         queue_timeout(dc, expires);
 261
 262         return DM_MAPIO_SUBMITTED;
 263 }
 264
 265 static void delay_presuspend(struct dm_target *ti)
 266 {
 267         struct delay_c *dc = ti->private;
 268
 269         atomic_set(&dc->may_delay, 0);
 270         del_timer_sync(&dc->delay_timer);
 271         flush_bios(flush_delayed_bios(dc, 1));
 272 }
 273
 274 static void delay_resume(struct dm_target *ti)
 275 {
 276         struct delay_c *dc = ti->private;
 277
 278         atomic_set(&dc->may_delay, 1);
 279 }
 280
 281 static int delay_map(struct dm_target *ti, struct bio *bio)
 282 {
 283         struct delay_c *dc = ti->private;
 284         struct delay_class *c;
 285         struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 286
 287         if (bio_data_dir(bio) == WRITE) {
 288                 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
 289                         c = &dc->flush;
 290                 else
 291                         c = &dc->write;
 292         } else {
 293                 c = &dc->read;
 294         }
 295         delayed->class = c;
 296         bio_set_dev(bio, c->dev->bdev);
 297         if (bio_sectors(bio))
 298                 bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
 299
 300         return delay_bio(dc, c, bio);
 301 }
 302
 303 #define DMEMIT_DELAY_CLASS(c) \
 304         DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)
 305
 306 static void delay_status(struct dm_target *ti, status_type_t type,
 307                          unsigned status_flags, char *result, unsigned maxlen)
 308 {
 309         struct delay_c *dc = ti->private;
 310         int sz = 0;
 311
 312         switch (type) {
 313         case STATUSTYPE_INFO:
 314                 DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
 315                 break;
 316
 317         case STATUSTYPE_TABLE:
 318                 DMEMIT_DELAY_CLASS(&dc->read);
 319                 if (dc->argc >= 6) {
 320                         DMEMIT(" ");
 321                         DMEMIT_DELAY_CLASS(&dc->write);
 322                 }
 323                 if (dc->argc >= 9) {
 324                         DMEMIT(" ");
 325                         DMEMIT_DELAY_CLASS(&dc->flush);
 326                 }
 327                 break;
 328         }
 329 }
 330
 331 static int delay_iterate_devices(struct dm_target *ti,
 332                                  iterate_devices_callout_fn fn, void *data)
 333 {
 334         struct delay_c *dc = ti->private;
 335         int ret = 0;
 336
 337         ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);
 338         if (ret)
 339                 goto out;
 340         ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
 341         if (ret)
 342                 goto out;
 343         ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
 344         if (ret)
 345                 goto out;
 346
 347 out:
 348         return ret;
 349 }
 350
 351 static struct target_type delay_target = {
 352         .name        = "delay",
 353         .version     = {1, 2, 1},
 354         .features    = DM_TARGET_PASSES_INTEGRITY,
 355         .module      = THIS_MODULE,
 356         .ctr         = delay_ctr,
 357         .dtr         = delay_dtr,
 358         .map         = delay_map,
 359         .presuspend  = delay_presuspend,
 360         .resume      = delay_resume,
 361         .status      = delay_status,
 362         .iterate_devices = delay_iterate_devices,
 363 };
 364
 365 static int __init dm_delay_init(void)
 366 {
 367         int r;
 368
 369         r = dm_register_target(&delay_target);
 370         if (r < 0) {
 371                 DMERR("register failed %d", r);
 372                 goto bad_register;
 373         }
 374
 375         return 0;
 376
 377 bad_register:
 378         return r;
 379 }
 380
 381 static void __exit dm_delay_exit(void)
 382 {
 383         dm_unregister_target(&delay_target);
 384 }
 385
 386 /* Module hooks */
 387 module_init(dm_delay_init);
 388 module_exit(dm_delay_exit);
 389
 390 MODULE_DESCRIPTION(DM_NAME " delay target");
 391 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 392 MODULE_LICENSE("GPL");