linux/drivers/md/dm-delay.c
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   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
  20struct delay_class {
  21        struct dm_dev *dev;
  22        sector_t start;
  23        unsigned delay;
  24        unsigned ops;
  25};
  26
  27struct 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
  42struct dm_delay_info {
  43        struct delay_c *context;
  44        struct delay_class *class;
  45        struct list_head list;
  46        unsigned long expires;
  47};
  48
  49static DEFINE_MUTEX(delayed_bios_lock);
  50
  51static 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
  58static 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
  68static 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
  80static 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
 112static 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
 120static void delay_dtr(struct dm_target *ti)
 121{
 122        struct delay_c *dc = ti->private;
 123
 124        if (dc->kdelayd_wq)
 125                destroy_workqueue(dc->kdelayd_wq);
 126
 127        if (dc->read.dev)
 128                dm_put_device(ti, dc->read.dev);
 129        if (dc->write.dev)
 130                dm_put_device(ti, dc->write.dev);
 131        if (dc->flush.dev)
 132                dm_put_device(ti, dc->flush.dev);
 133
 134        mutex_destroy(&dc->timer_lock);
 135
 136        kfree(dc);
 137}
 138
 139static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)
 140{
 141        int ret;
 142        unsigned long long tmpll;
 143        char dummy;
 144
 145        if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
 146                ti->error = "Invalid device sector";
 147                return -EINVAL;
 148        }
 149        c->start = tmpll;
 150
 151        if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {
 152                ti->error = "Invalid delay";
 153                return -EINVAL;
 154        }
 155
 156        ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev);
 157        if (ret) {
 158                ti->error = "Device lookup failed";
 159                return ret;
 160        }
 161
 162        return 0;
 163}
 164
 165/*
 166 * Mapping parameters:
 167 *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 168 *
 169 * With separate write parameters, the first set is only used for reads.
 170 * Offsets are specified in sectors.
 171 * Delays are specified in milliseconds.
 172 */
 173static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 174{
 175        struct delay_c *dc;
 176        int ret;
 177
 178        if (argc != 3 && argc != 6 && argc != 9) {
 179                ti->error = "Requires exactly 3, 6 or 9 arguments";
 180                return -EINVAL;
 181        }
 182
 183        dc = kzalloc(sizeof(*dc), GFP_KERNEL);
 184        if (!dc) {
 185                ti->error = "Cannot allocate context";
 186                return -ENOMEM;
 187        }
 188
 189        ti->private = dc;
 190        timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
 191        INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 192        INIT_LIST_HEAD(&dc->delayed_bios);
 193        mutex_init(&dc->timer_lock);
 194        atomic_set(&dc->may_delay, 1);
 195        dc->argc = argc;
 196
 197        ret = delay_class_ctr(ti, &dc->read, argv);
 198        if (ret)
 199                goto bad;
 200
 201        if (argc == 3) {
 202                ret = delay_class_ctr(ti, &dc->write, argv);
 203                if (ret)
 204                        goto bad;
 205                ret = delay_class_ctr(ti, &dc->flush, argv);
 206                if (ret)
 207                        goto bad;
 208                goto out;
 209        }
 210
 211        ret = delay_class_ctr(ti, &dc->write, argv + 3);
 212        if (ret)
 213                goto bad;
 214        if (argc == 6) {
 215                ret = delay_class_ctr(ti, &dc->flush, argv + 3);
 216                if (ret)
 217                        goto bad;
 218                goto out;
 219        }
 220
 221        ret = delay_class_ctr(ti, &dc->flush, argv + 6);
 222        if (ret)
 223                goto bad;
 224
 225out:
 226        dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 227        if (!dc->kdelayd_wq) {
 228                ret = -EINVAL;
 229                DMERR("Couldn't start kdelayd");
 230                goto bad;
 231        }
 232
 233        ti->num_flush_bios = 1;
 234        ti->num_discard_bios = 1;
 235        ti->per_io_data_size = sizeof(struct dm_delay_info);
 236        return 0;
 237
 238bad:
 239        delay_dtr(ti);
 240        return ret;
 241}
 242
 243static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)
 244{
 245        struct dm_delay_info *delayed;
 246        unsigned long expires = 0;
 247
 248        if (!c->delay || !atomic_read(&dc->may_delay))
 249                return DM_MAPIO_REMAPPED;
 250
 251        delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 252
 253        delayed->context = dc;
 254        delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay);
 255
 256        mutex_lock(&delayed_bios_lock);
 257        c->ops++;
 258        list_add_tail(&delayed->list, &dc->delayed_bios);
 259        mutex_unlock(&delayed_bios_lock);
 260
 261        queue_timeout(dc, expires);
 262
 263        return DM_MAPIO_SUBMITTED;
 264}
 265
 266static void delay_presuspend(struct dm_target *ti)
 267{
 268        struct delay_c *dc = ti->private;
 269
 270        atomic_set(&dc->may_delay, 0);
 271        del_timer_sync(&dc->delay_timer);
 272        flush_bios(flush_delayed_bios(dc, 1));
 273}
 274
 275static void delay_resume(struct dm_target *ti)
 276{
 277        struct delay_c *dc = ti->private;
 278
 279        atomic_set(&dc->may_delay, 1);
 280}
 281
 282static int delay_map(struct dm_target *ti, struct bio *bio)
 283{
 284        struct delay_c *dc = ti->private;
 285        struct delay_class *c;
 286        struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 287
 288        if (bio_data_dir(bio) == WRITE) {
 289                if (unlikely(bio->bi_opf & REQ_PREFLUSH))
 290                        c = &dc->flush;
 291                else
 292                        c = &dc->write;
 293        } else {
 294                c = &dc->read;
 295        }
 296        delayed->class = c;
 297        bio_set_dev(bio, c->dev->bdev);
 298        if (bio_sectors(bio))
 299                bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
 300
 301        return delay_bio(dc, c, bio);
 302}
 303
 304#define DMEMIT_DELAY_CLASS(c) \
 305        DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)
 306
 307static void delay_status(struct dm_target *ti, status_type_t type,
 308                         unsigned status_flags, char *result, unsigned maxlen)
 309{
 310        struct delay_c *dc = ti->private;
 311        int sz = 0;
 312
 313        switch (type) {
 314        case STATUSTYPE_INFO:
 315                DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
 316                break;
 317
 318        case STATUSTYPE_TABLE:
 319                DMEMIT_DELAY_CLASS(&dc->read);
 320                if (dc->argc >= 6) {
 321                        DMEMIT(" ");
 322                        DMEMIT_DELAY_CLASS(&dc->write);
 323                }
 324                if (dc->argc >= 9) {
 325                        DMEMIT(" ");
 326                        DMEMIT_DELAY_CLASS(&dc->flush);
 327                }
 328                break;
 329        }
 330}
 331
 332static int delay_iterate_devices(struct dm_target *ti,
 333                                 iterate_devices_callout_fn fn, void *data)
 334{
 335        struct delay_c *dc = ti->private;
 336        int ret = 0;
 337
 338        ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);
 339        if (ret)
 340                goto out;
 341        ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
 342        if (ret)
 343                goto out;
 344        ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
 345        if (ret)
 346                goto out;
 347
 348out:
 349        return ret;
 350}
 351
 352static struct target_type delay_target = {
 353        .name        = "delay",
 354        .version     = {1, 2, 1},
 355        .features    = DM_TARGET_PASSES_INTEGRITY,
 356        .module      = THIS_MODULE,
 357        .ctr         = delay_ctr,
 358        .dtr         = delay_dtr,
 359        .map         = delay_map,
 360        .presuspend  = delay_presuspend,
 361        .resume      = delay_resume,
 362        .status      = delay_status,
 363        .iterate_devices = delay_iterate_devices,
 364};
 365
 366static int __init dm_delay_init(void)
 367{
 368        int r;
 369
 370        r = dm_register_target(&delay_target);
 371        if (r < 0) {
 372                DMERR("register failed %d", r);
 373                goto bad_register;
 374        }
 375
 376        return 0;
 377
 378bad_register:
 379        return r;
 380}
 381
 382static void __exit dm_delay_exit(void)
 383{
 384        dm_unregister_target(&delay_target);
 385}
 386
 387/* Module hooks */
 388module_init(dm_delay_init);
 389module_exit(dm_delay_exit);
 390
 391MODULE_DESCRIPTION(DM_NAME " delay target");
 392MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 393MODULE_LICENSE("GPL");
 394