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         struct 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         dc->dev_write = NULL;
 167         if (argc == 3)
 168                 goto out;
 169
 170         if (sscanf(argv[4], "%llu", &tmpll) != 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", &dc->write_delay) != 1) {
 177                 ti->error = "Invalid write delay";
 178                 goto bad_dev_read;
 179         }
 180
 181         if (dm_get_device(ti, argv[3], dc->start_write, ti->len,
 182                           dm_table_get_mode(ti->table), &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->private = dc;
 202         return 0;
 203
 204 bad_dev_write:
 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         flush_workqueue(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         mempool_destroy(dc->delayed_pool);
 226         kfree(dc);
 227 }
 228
 229 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
 230 {
 231         struct dm_delay_info *delayed;
 232         unsigned long expires = 0;
 233
 234         if (!delay || !atomic_read(&dc->may_delay))
 235                 return 1;
 236
 237         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
 238
 239         delayed->context = dc;
 240         delayed->bio = bio;
 241         delayed->expires = expires = jiffies + (delay * HZ / 1000);
 242
 243         mutex_lock(&delayed_bios_lock);
 244
 245         if (bio_data_dir(bio) == WRITE)
 246                 dc->writes++;
 247         else
 248                 dc->reads++;
 249
 250         list_add_tail(&delayed->list, &dc->delayed_bios);
 251
 252         mutex_unlock(&delayed_bios_lock);
 253
 254         queue_timeout(dc, expires);
 255
 256         return 0;
 257 }
 258
 259 static void delay_presuspend(struct dm_target *ti)
 260 {
 261         struct delay_c *dc = ti->private;
 262
 263         atomic_set(&dc->may_delay, 0);
 264         del_timer_sync(&dc->delay_timer);
 265         flush_bios(flush_delayed_bios(dc, 1));
 266 }
 267
 268 static void delay_resume(struct dm_target *ti)
 269 {
 270         struct delay_c *dc = ti->private;
 271
 272         atomic_set(&dc->may_delay, 1);
 273 }
 274
 275 static int delay_map(struct dm_target *ti, struct bio *bio,
 276                      union map_info *map_context)
 277 {
 278         struct delay_c *dc = ti->private;
 279
 280         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
 281                 bio->bi_bdev = dc->dev_write->bdev;
 282                 bio->bi_sector = dc->start_write +
 283                                  (bio->bi_sector - ti->begin);
 284
 285                 return delay_bio(dc, dc->write_delay, bio);
 286         }
 287
 288         bio->bi_bdev = dc->dev_read->bdev;
 289         bio->bi_sector = dc->start_read +
 290                          (bio->bi_sector - ti->begin);
 291
 292         return delay_bio(dc, dc->read_delay, bio);
 293 }
 294
 295 static int delay_status(struct dm_target *ti, status_type_t type,
 296                         char *result, unsigned maxlen)
 297 {
 298         struct delay_c *dc = ti->private;
 299         int sz = 0;
 300
 301         switch (type) {
 302         case STATUSTYPE_INFO:
 303                 DMEMIT("%u %u", dc->reads, dc->writes);
 304                 break;
 305
 306         case STATUSTYPE_TABLE:
 307                 DMEMIT("%s %llu %u", dc->dev_read->name,
 308                        (unsigned long long) dc->start_read,
 309                        dc->read_delay);
 310                 if (dc->dev_write)
 311                         DMEMIT(" %s %llu %u", dc->dev_write->name,
 312                                (unsigned long long) dc->start_write,
 313                                dc->write_delay);
 314                 break;
 315         }
 316
 317         return 0;
 318 }
 319
 320 static struct target_type delay_target = {
 321         .name        = "delay",
 322         .version     = {1, 0, 2},
 323         .module      = THIS_MODULE,
 324         .ctr         = delay_ctr,
 325         .dtr         = delay_dtr,
 326         .map         = delay_map,
 327         .presuspend  = delay_presuspend,
 328         .resume      = delay_resume,
 329         .status      = delay_status,
 330 };
 331
 332 static int __init dm_delay_init(void)
 333 {
 334         int r = -ENOMEM;
 335
 336         kdelayd_wq = create_workqueue("kdelayd");
 337         if (!kdelayd_wq) {
 338                 DMERR("Couldn't start kdelayd");
 339                 goto bad_queue;
 340         }
 341
 342         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
 343         if (!delayed_cache) {
 344                 DMERR("Couldn't create delayed bio cache.");
 345                 goto bad_memcache;
 346         }
 347
 348         r = dm_register_target(&delay_target);
 349         if (r < 0) {
 350                 DMERR("register failed %d", r);
 351                 goto bad_register;
 352         }
 353
 354         return 0;
 355
 356 bad_register:
 357         kmem_cache_destroy(delayed_cache);
 358 bad_memcache:
 359         destroy_workqueue(kdelayd_wq);
 360 bad_queue:
 361         return r;
 362 }
 363
 364 static void __exit dm_delay_exit(void)
 365 {
 366         int r = dm_unregister_target(&delay_target);
 367
 368         if (r < 0)
 369                 DMERR("unregister failed %d", r);
 370
 371         kmem_cache_destroy(delayed_cache);
 372         destroy_workqueue(kdelayd_wq);
 373 }
 374
 375 /* Module hooks */
 376 module_init(dm_delay_init);
 377 module_exit(dm_delay_exit);
 378
 379 MODULE_DESCRIPTION(DM_NAME " delay target");
 380 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 381 MODULE_LICENSE("GPL");