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
  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         unsigned long expires;
  43 };
  44
  45 static DEFINE_MUTEX(delayed_bios_lock);
  46
  47 static void handle_delayed_timer(unsigned long data)
  48 {
  49         struct delay_c *dc = (struct delay_c *)data;
  50
  51         queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
  52 }
  53
  54 static void queue_timeout(struct delay_c *dc, unsigned long expires)
  55 {
  56         mutex_lock(&dc->timer_lock);
  57
  58         if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
  59                 mod_timer(&dc->delay_timer, expires);
  60
  61         mutex_unlock(&dc->timer_lock);
  62 }
  63
  64 static void flush_bios(struct bio *bio)
  65 {
  66         struct bio *n;
  67
  68         while (bio) {
  69                 n = bio->bi_next;
  70                 bio->bi_next = NULL;
  71                 generic_make_request(bio);
  72                 bio = n;
  73         }
  74 }
  75
  76 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
  77 {
  78         struct dm_delay_info *delayed, *next;
  79         unsigned long next_expires = 0;
  80         int start_timer = 0;
  81         struct bio_list flush_bios = { };
  82
  83         mutex_lock(&delayed_bios_lock);
  84         list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
  85                 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
  86                         struct bio *bio = dm_bio_from_per_bio_data(delayed,
  87                                                 sizeof(struct dm_delay_info));
  88                         list_del(&delayed->list);
  89                         bio_list_add(&flush_bios, bio);
  90                         if ((bio_data_dir(bio) == WRITE))
  91                                 delayed->context->writes--;
  92                         else
  93                                 delayed->context->reads--;
  94                         continue;
  95                 }
  96
  97                 if (!start_timer) {
  98                         start_timer = 1;
  99                         next_expires = delayed->expires;
 100                 } else
 101                         next_expires = min(next_expires, delayed->expires);
 102         }
 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 /*
 121  * Mapping parameters:
 122  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 123  *
 124  * With separate write parameters, the first set is only used for reads.
 125  * Delays are specified in milliseconds.
 126  */
 127 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 128 {
 129         struct delay_c *dc;
 130         unsigned long long tmpll;
 131         char dummy;
 132
 133         if (argc != 3 && argc != 6) {
 134                 ti->error = "requires exactly 3 or 6 arguments";
 135                 return -EINVAL;
 136         }
 137
 138         dc = kmalloc(sizeof(*dc), GFP_KERNEL);
 139         if (!dc) {
 140                 ti->error = "Cannot allocate context";
 141                 return -ENOMEM;
 142         }
 143
 144         dc->reads = dc->writes = 0;
 145
 146         if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1) {
 147                 ti->error = "Invalid device sector";
 148                 goto bad;
 149         }
 150         dc->start_read = tmpll;
 151
 152         if (sscanf(argv[2], "%u%c", &dc->read_delay, &dummy) != 1) {
 153                 ti->error = "Invalid delay";
 154                 goto bad;
 155         }
 156
 157         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
 158                           &dc->dev_read)) {
 159                 ti->error = "Device lookup failed";
 160                 goto bad;
 161         }
 162
 163         dc->dev_write = NULL;
 164         if (argc == 3)
 165                 goto out;
 166
 167         if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1) {
 168                 ti->error = "Invalid write device sector";
 169                 goto bad_dev_read;
 170         }
 171         dc->start_write = tmpll;
 172
 173         if (sscanf(argv[5], "%u%c", &dc->write_delay, &dummy) != 1) {
 174                 ti->error = "Invalid write delay";
 175                 goto bad_dev_read;
 176         }
 177
 178         if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
 179                           &dc->dev_write)) {
 180                 ti->error = "Write device lookup failed";
 181                 goto bad_dev_read;
 182         }
 183
 184 out:
 185         dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 186         if (!dc->kdelayd_wq) {
 187                 DMERR("Couldn't start kdelayd");
 188                 goto bad_queue;
 189         }
 190
 191         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
 192
 193         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 194         INIT_LIST_HEAD(&dc->delayed_bios);
 195         mutex_init(&dc->timer_lock);
 196         atomic_set(&dc->may_delay, 1);
 197
 198         ti->num_flush_bios = 1;
 199         ti->num_discard_bios = 1;
 200         ti->per_bio_data_size = sizeof(struct dm_delay_info);
 201         ti->private = dc;
 202         return 0;
 203
 204 bad_queue:
 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         destroy_workqueue(dc->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         kfree(dc);
 226 }
 227
 228 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 229 {
 230         struct dm_delay_info *delayed;
 231         unsigned long expires = 0;
 232
 233         if (!delay || !atomic_read(&dc->may_delay))
 234                 return 1;
 235
 236         delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 237
 238         delayed->context = dc;
 239         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 240
 241         mutex_lock(&delayed_bios_lock);
 242
 243         if (bio_data_dir(bio) == WRITE)
 244                 dc->writes++;
 245         else
 246                 dc->reads++;
 247
 248         list_add_tail(&delayed->list, &dc->delayed_bios);
 249
 250         mutex_unlock(&delayed_bios_lock);
 251
 252         queue_timeout(dc, expires);
 253
 254         return 0;
 255 }
 256
 257 static void delay_presuspend(struct dm_target *ti)
 258 {
 259         struct delay_c *dc = ti->private;
 260
 261         atomic_set(&dc->may_delay, 0);
 262         del_timer_sync(&dc->delay_timer);
 263         flush_bios(flush_delayed_bios(dc, 1));
 264 }
 265
 266 static void delay_resume(struct dm_target *ti)
 267 {
 268         struct delay_c *dc = ti->private;
 269
 270         atomic_set(&dc->may_delay, 1);
 271 }
 272
 273 static int delay_map(struct dm_target *ti, struct bio *bio)
 274 {
 275         struct delay_c *dc = ti->private;
 276
 277         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 278                 bio->bi_bdev = dc->dev_write->bdev;
 279                 if (bio_sectors(bio))
 280                         bio->bi_iter.bi_sector = dc->start_write +
 281                                 dm_target_offset(ti, bio->bi_iter.bi_sector);
 282
 283                 return delay_bio(dc, dc->write_delay, bio);
 284         }
 285
 286         bio->bi_bdev = dc->dev_read->bdev;
 287         bio->bi_iter.bi_sector = dc->start_read +
 288                 dm_target_offset(ti, bio->bi_iter.bi_sector);
 289
 290         return delay_bio(dc, dc->read_delay, bio);
 291 }
 292
 293 static void delay_status(struct dm_target *ti, status_type_t type,
 294                          unsigned status_flags, char *result, unsigned maxlen)
 295 {
 296         struct delay_c *dc = ti->private;
 297         int sz = 0;
 298
 299         switch (type) {
 300         case STATUSTYPE_INFO:
 301                 DMEMIT("%u %u", dc->reads, dc->writes);
 302                 break;
 303
 304         case STATUSTYPE_TABLE:
 305                 DMEMIT("%s %llu %u", dc->dev_read->name,
 306                        (unsigned long long) dc->start_read,
 307                        dc->read_delay);
 308                 if (dc->dev_write)
 309                         DMEMIT(" %s %llu %u", dc->dev_write->name,
 310                                (unsigned long long) dc->start_write,
 311                                dc->write_delay);
 312                 break;
 313         }
 314 }
 315
 316 static int delay_iterate_devices(struct dm_target *ti,
 317                                  iterate_devices_callout_fn fn, void *data)
 318 {
 319         struct delay_c *dc = ti->private;
 320         int ret = 0;
 321
 322         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
 323         if (ret)
 324                 goto out;
 325
 326         if (dc->dev_write)
 327                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
 328
 329 out:
 330         return ret;
 331 }
 332
 333 static struct target_type delay_target = {
 334         .name        = "delay",
 335         .version     = {1, 2, 1},
 336         .module      = THIS_MODULE,
 337         .ctr         = delay_ctr,
 338         .dtr         = delay_dtr,
 339         .map         = delay_map,
 340         .presuspend  = delay_presuspend,
 341         .resume      = delay_resume,
 342         .status      = delay_status,
 343         .iterate_devices = delay_iterate_devices,
 344 };
 345
 346 static int __init dm_delay_init(void)
 347 {
 348         int r;
 349
 350         r = dm_register_target(&delay_target);
 351         if (r < 0) {
 352                 DMERR("register failed %d", r);
 353                 goto bad_register;
 354         }
 355
 356         return 0;
 357
 358 bad_register:
 359         return r;
 360 }
 361
 362 static void __exit dm_delay_exit(void)
 363 {
 364         dm_unregister_target(&delay_target);
 365 }
 366
 367 /* Module hooks */
 368 module_init(dm_delay_init);
 369 module_exit(dm_delay_exit);
 370
 371 MODULE_DESCRIPTION(DM_NAME " delay target");
 372 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 373 MODULE_LICENSE("GPL");