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 "dm.h"
  17 #include "dm-bio-list.h"
  18
  19 #define DM_MSG_PREFIX "delay"
  20
  21 struct delay_c {
  22         struct timer_list delay_timer;
  23         struct mutex timer_lock;
  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 workqueue_struct *kdelayd_wq;
  50 static struct kmem_cache *delayed_cache;
  51
  52 static void handle_delayed_timer(unsigned long data)
  53 {
  54         struct delay_c *dc = (struct delay_c *)data;
  55
  56         queue_work(kdelayd_wq, &dc->flush_expired_bios);
  57 }
  58
  59 static void queue_timeout(struct delay_c *dc, unsigned long expires)
  60 {
  61         mutex_lock(&dc->timer_lock);
  62
  63         if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
  64                 mod_timer(&dc->delay_timer, expires);
  65
  66         mutex_unlock(&dc->timer_lock);
  67 }
  68
  69 static void flush_bios(struct bio *bio)
  70 {
  71         struct bio *n;
  72
  73         while (bio) {
  74                 n = bio->bi_next;
  75                 bio->bi_next = NULL;
  76                 generic_make_request(bio);
  77                 bio = n;
  78         }
  79 }
  80
  81 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
  82 {
  83         struct dm_delay_info *delayed, *next;
  84         unsigned long next_expires = 0;
  85         int start_timer = 0;
  86         BIO_LIST(flush_bios);
  87
  88         mutex_lock(&delayed_bios_lock);
  89         list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
  90                 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
  91                         list_del(&delayed->list);
  92                         bio_list_add(&flush_bios, delayed->bio);
  93                         if ((bio_data_dir(delayed->bio) == WRITE))
  94                                 delayed->context->writes--;
  95                         else
  96                                 delayed->context->reads--;
  97                         mempool_free(delayed, dc->delayed_pool);
  98                         continue;
  99                 }
 100
 101                 if (!start_timer) {
 102                         start_timer = 1;
 103                         next_expires = delayed->expires;
 104                 } else
 105                         next_expires = min(next_expires, delayed->expires);
 106         }
 107
 108         mutex_unlock(&delayed_bios_lock);
 109
 110         if (start_timer)
 111                 queue_timeout(dc, next_expires);
 112
 113         return bio_list_get(&flush_bios);
 114 }
 115
 116 static void flush_expired_bios(struct work_struct *work)
 117 {
 118         struct delay_c *dc;
 119
 120         dc = container_of(work, struct delay_c, flush_expired_bios);
 121         flush_bios(flush_delayed_bios(dc, 0));
 122 }
 123
 124 /*
 125  * Mapping parameters:
 126  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 127  *
 128  * With separate write parameters, the first set is only used for reads.
 129  * Delays are specified in milliseconds.
 130  */
 131 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 132 {
 133         struct delay_c *dc;
 134         unsigned long long tmpll;
 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", &tmpll) != 1) {
 150                 ti->error = "Invalid device sector";
 151                 goto bad;
 152         }
 153         dc->start_read = tmpll;
 154
 155         if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
 156                 ti->error = "Invalid delay";
 157                 goto bad;
 158         }
 159
 160         if (dm_get_device(ti, argv[0], dc->start_read, ti->len,
 161                           dm_table_get_mode(ti->table), &dc->dev_read)) {
 162                 ti->error = "Device lookup failed";
 163                 goto bad;
 164         }
 165
 166         if (argc == 3) {
 167                 dc->dev_write = NULL;
 168                 goto out;
 169         }
 170
 171         if (sscanf(argv[4], "%llu", &tmpll) != 1) {
 172                 ti->error = "Invalid write device sector";
 173                 goto bad;
 174         }
 175         dc->start_write = tmpll;
 176
 177         if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
 178                 ti->error = "Invalid write delay";
 179                 goto bad;
 180         }
 181
 182         if (dm_get_device(ti, argv[3], dc->start_write, ti->len,
 183                           dm_table_get_mode(ti->table), &dc->dev_write)) {
 184                 ti->error = "Write device lookup failed";
 185                 dm_put_device(ti, dc->dev_read);
 186                 goto bad;
 187         }
 188
 189 out:
 190         dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
 191         if (!dc->delayed_pool) {
 192                 DMERR("Couldn't create delayed bio pool.");
 193                 goto bad;
 194         }
 195
 196         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
 197
 198         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 199         INIT_LIST_HEAD(&dc->delayed_bios);
 200         mutex_init(&dc->timer_lock);
 201         atomic_set(&dc->may_delay, 1);
 202
 203         ti->private = dc;
 204         return 0;
 205
 206 bad:
 207         kfree(dc);
 208         return -EINVAL;
 209 }
 210
 211 static void delay_dtr(struct dm_target *ti)
 212 {
 213         struct delay_c *dc = ti->private;
 214
 215         flush_workqueue(kdelayd_wq);
 216
 217         dm_put_device(ti, dc->dev_read);
 218
 219         if (dc->dev_write)
 220                 dm_put_device(ti, dc->dev_write);
 221
 222         mempool_destroy(dc->delayed_pool);
 223         kfree(dc);
 224 }
 225
 226 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 227 {
 228         struct dm_delay_info *delayed;
 229         unsigned long expires = 0;
 230
 231         if (!delay || !atomic_read(&dc->may_delay))
 232                 return 1;
 233
 234         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
 235
 236         delayed->context = dc;
 237         delayed->bio = bio;
 238         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 239
 240         mutex_lock(&delayed_bios_lock);
 241
 242         if (bio_data_dir(bio) == WRITE)
 243                 dc->writes++;
 244         else
 245                 dc->reads++;
 246
 247         list_add_tail(&delayed->list, &dc->delayed_bios);
 248
 249         mutex_unlock(&delayed_bios_lock);
 250
 251         queue_timeout(dc, expires);
 252
 253         return 0;
 254 }
 255
 256 static void delay_presuspend(struct dm_target *ti)
 257 {
 258         struct delay_c *dc = ti->private;
 259
 260         atomic_set(&dc->may_delay, 0);
 261         del_timer_sync(&dc->delay_timer);
 262         flush_bios(flush_delayed_bios(dc, 1));
 263 }
 264
 265 static void delay_resume(struct dm_target *ti)
 266 {
 267         struct delay_c *dc = ti->private;
 268
 269         atomic_set(&dc->may_delay, 1);
 270 }
 271
 272 static int delay_map(struct dm_target *ti, struct bio *bio,
 273                      union map_info *map_context)
 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                 bio->bi_sector = dc->start_write +
 280                                  (bio->bi_sector - ti->begin);
 281
 282                 return delay_bio(dc, dc->write_delay, bio);
 283         }
 284
 285         bio->bi_bdev = dc->dev_read->bdev;
 286         bio->bi_sector = dc->start_read +
 287                          (bio->bi_sector - ti->begin);
 288
 289         return delay_bio(dc, dc->read_delay, bio);
 290 }
 291
 292 static int delay_status(struct dm_target *ti, status_type_t type,
 293                         char *result, unsigned maxlen)
 294 {
 295         struct delay_c *dc = ti->private;
 296         int sz = 0;
 297
 298         switch (type) {
 299         case STATUSTYPE_INFO:
 300                 DMEMIT("%u %u", dc->reads, dc->writes);
 301                 break;
 302
 303         case STATUSTYPE_TABLE:
 304                 DMEMIT("%s %llu %u", dc->dev_read->name,
 305                        (unsigned long long) dc->start_read,
 306                        dc->read_delay);
 307                 if (dc->dev_write)
 308                         DMEMIT("%s %llu %u", dc->dev_write->name,
 309                                (unsigned long long) dc->start_write,
 310                                dc->write_delay);
 311                 break;
 312         }
 313
 314         return 0;
 315 }
 316
 317 static struct target_type delay_target = {
 318         .name        = "delay",
 319         .version     = {1, 0, 2},
 320         .module      = THIS_MODULE,
 321         .ctr         = delay_ctr,
 322         .dtr         = delay_dtr,
 323         .map         = delay_map,
 324         .presuspend  = delay_presuspend,
 325         .resume      = delay_resume,
 326         .status      = delay_status,
 327 };
 328
 329 static int __init dm_delay_init(void)
 330 {
 331         int r = -ENOMEM;
 332
 333         kdelayd_wq = create_workqueue("kdelayd");
 334         if (!kdelayd_wq) {
 335                 DMERR("Couldn't start kdelayd");
 336                 goto bad_queue;
 337         }
 338
 339         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 340         if (!delayed_cache) {
 341                 DMERR("Couldn't create delayed bio cache.");
 342                 goto bad_memcache;
 343         }
 344
 345         r = dm_register_target(&delay_target);
 346         if (r < 0) {
 347                 DMERR("register failed %d", r);
 348                 goto bad_register;
 349         }
 350
 351         return 0;
 352
 353 bad_register:
 354         kmem_cache_destroy(delayed_cache);
 355 bad_memcache:
 356         destroy_workqueue(kdelayd_wq);
 357 bad_queue:
 358         return r;
 359 }
 360
 361 static void __exit dm_delay_exit(void)
 362 {
 363         int r = dm_unregister_target(&delay_target);
 364
 365         if (r < 0)
 366                 DMERR("unregister failed %d", r);
 367
 368         kmem_cache_destroy(delayed_cache);
 369         destroy_workqueue(kdelayd_wq);
 370 }
 371
 372 /* Module hooks */
 373 module_init(dm_delay_init);
 374 module_exit(dm_delay_exit);
 375
 376 MODULE_DESCRIPTION(DM_NAME " delay target");
 377 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 378 MODULE_LICENSE("GPL");