drivers/md/dm-delay.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2005-2007 Red Hat GmbH
   4  *
   5  * A target that delays reads and/or writes and can send
   6  * them to different devices.
   7  *
   8  * This file is released under the GPL.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/blkdev.h>
  14 #include <linux/bio.h>
  15 #include <linux/slab.h>
  16 #include <linux/kthread.h>
  17
  18 #include <linux/device-mapper.h>
  19
  20 #define DM_MSG_PREFIX "delay"
  21
  22 struct delay_class {
  23         struct dm_dev *dev;
  24         sector_t start;
  25         unsigned int delay;
  26         unsigned int ops;
  27 };
  28
  29 struct delay_c {
  30         struct timer_list delay_timer;
  31         struct mutex timer_lock;
  32         struct workqueue_struct *kdelayd_wq;
  33         struct work_struct flush_expired_bios;
  34         struct list_head delayed_bios;
  35         struct task_struct *worker;
  36         atomic_t may_delay;
  37
  38         struct delay_class read;
  39         struct delay_class write;
  40         struct delay_class flush;
  41
  42         int argc;
  43 };
  44
  45 struct dm_delay_info {
  46         struct delay_c *context;
  47         struct delay_class *class;
  48         struct list_head list;
  49         unsigned long expires;
  50 };
  51
  52 static DEFINE_MUTEX(delayed_bios_lock);
  53
  54 static void handle_delayed_timer(struct timer_list *t)
  55 {
  56         struct delay_c *dc = from_timer(dc, t, delay_timer);
  57
  58         queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
  59 }
  60
  61 static void queue_timeout(struct delay_c *dc, unsigned long expires)
  62 {
  63         mutex_lock(&dc->timer_lock);
  64
  65         if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
  66                 mod_timer(&dc->delay_timer, expires);
  67
  68         mutex_unlock(&dc->timer_lock);
  69 }
  70
  71 static inline bool delay_is_fast(struct delay_c *dc)
  72 {
  73         return !!dc->worker;
  74 }
  75
  76 static void flush_delayed_bios_fast(struct delay_c *dc, bool flush_all)
  77 {
  78         struct dm_delay_info *delayed, *next;
  79
  80         mutex_lock(&delayed_bios_lock);
  81         list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
  82                 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
  83                         struct bio *bio = dm_bio_from_per_bio_data(delayed,
  84                                                 sizeof(struct dm_delay_info));
  85                         list_del(&delayed->list);
  86                         dm_submit_bio_remap(bio, NULL);
  87                         delayed->class->ops--;
  88                 }
  89         }
  90         mutex_unlock(&delayed_bios_lock);
  91 }
  92
  93 static int flush_worker_fn(void *data)
  94 {
  95         struct delay_c *dc = data;
  96
  97         while (1) {
  98                 flush_delayed_bios_fast(dc, false);
  99                 if (unlikely(list_empty(&dc->delayed_bios))) {
 100                         set_current_state(TASK_INTERRUPTIBLE);
 101                         schedule();
 102                 } else
 103                         cond_resched();
 104         }
 105
 106         return 0;
 107 }
 108
 109 static void flush_bios(struct bio *bio)
 110 {
 111         struct bio *n;
 112
 113         while (bio) {
 114                 n = bio->bi_next;
 115                 bio->bi_next = NULL;
 116                 dm_submit_bio_remap(bio, NULL);
 117                 bio = n;
 118         }
 119 }
 120
 121 static struct bio *flush_delayed_bios(struct delay_c *dc, bool flush_all)
 122 {
 123         struct dm_delay_info *delayed, *next;
 124         unsigned long next_expires = 0;
 125         unsigned long start_timer = 0;
 126         struct bio_list flush_bios = { };
 127
 128         mutex_lock(&delayed_bios_lock);
 129         list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
 130                 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
 131                         struct bio *bio = dm_bio_from_per_bio_data(delayed,
 132                                                 sizeof(struct dm_delay_info));
 133                         list_del(&delayed->list);
 134                         bio_list_add(&flush_bios, bio);
 135                         delayed->class->ops--;
 136                         continue;
 137                 }
 138
 139                 if (!start_timer) {
 140                         start_timer = 1;
 141                         next_expires = delayed->expires;
 142                 } else
 143                         next_expires = min(next_expires, delayed->expires);
 144         }
 145         mutex_unlock(&delayed_bios_lock);
 146
 147         if (start_timer)
 148                 queue_timeout(dc, next_expires);
 149
 150         return bio_list_get(&flush_bios);
 151 }
 152
 153 static void flush_expired_bios(struct work_struct *work)
 154 {
 155         struct delay_c *dc;
 156
 157         dc = container_of(work, struct delay_c, flush_expired_bios);
 158         if (delay_is_fast(dc))
 159                 flush_delayed_bios_fast(dc, false);
 160         else
 161                 flush_bios(flush_delayed_bios(dc, false));
 162 }
 163
 164 static void delay_dtr(struct dm_target *ti)
 165 {
 166         struct delay_c *dc = ti->private;
 167
 168         if (dc->kdelayd_wq)
 169                 destroy_workqueue(dc->kdelayd_wq);
 170
 171         if (dc->read.dev)
 172                 dm_put_device(ti, dc->read.dev);
 173         if (dc->write.dev)
 174                 dm_put_device(ti, dc->write.dev);
 175         if (dc->flush.dev)
 176                 dm_put_device(ti, dc->flush.dev);
 177         if (dc->worker)
 178                 kthread_stop(dc->worker);
 179
 180         if (!delay_is_fast(dc))
 181                 mutex_destroy(&dc->timer_lock);
 182
 183         kfree(dc);
 184 }
 185
 186 static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)
 187 {
 188         int ret;
 189         unsigned long long tmpll;
 190         char dummy;
 191
 192         if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
 193                 ti->error = "Invalid device sector";
 194                 return -EINVAL;
 195         }
 196         c->start = tmpll;
 197
 198         if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {
 199                 ti->error = "Invalid delay";
 200                 return -EINVAL;
 201         }
 202
 203         ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev);
 204         if (ret) {
 205                 ti->error = "Device lookup failed";
 206                 return ret;
 207         }
 208
 209         return 0;
 210 }
 211
 212 /*
 213  * Mapping parameters:
 214  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
 215  *
 216  * With separate write parameters, the first set is only used for reads.
 217  * Offsets are specified in sectors.
 218  * Delays are specified in milliseconds.
 219  */
 220 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 221 {
 222         struct delay_c *dc;
 223         int ret;
 224         unsigned int max_delay;
 225
 226         if (argc != 3 && argc != 6 && argc != 9) {
 227                 ti->error = "Requires exactly 3, 6 or 9 arguments";
 228                 return -EINVAL;
 229         }
 230
 231         dc = kzalloc(sizeof(*dc), GFP_KERNEL);
 232         if (!dc) {
 233                 ti->error = "Cannot allocate context";
 234                 return -ENOMEM;
 235         }
 236
 237         ti->private = dc;
 238         INIT_LIST_HEAD(&dc->delayed_bios);
 239         atomic_set(&dc->may_delay, 1);
 240         dc->argc = argc;
 241
 242         ret = delay_class_ctr(ti, &dc->read, argv);
 243         if (ret)
 244                 goto bad;
 245         max_delay = dc->read.delay;
 246
 247         if (argc == 3) {
 248                 ret = delay_class_ctr(ti, &dc->write, argv);
 249                 if (ret)
 250                         goto bad;
 251                 ret = delay_class_ctr(ti, &dc->flush, argv);
 252                 if (ret)
 253                         goto bad;
 254                 max_delay = max(max_delay, dc->write.delay);
 255                 max_delay = max(max_delay, dc->flush.delay);
 256                 goto out;
 257         }
 258
 259         ret = delay_class_ctr(ti, &dc->write, argv + 3);
 260         if (ret)
 261                 goto bad;
 262         if (argc == 6) {
 263                 ret = delay_class_ctr(ti, &dc->flush, argv + 3);
 264                 if (ret)
 265                         goto bad;
 266                 max_delay = max(max_delay, dc->flush.delay);
 267                 goto out;
 268         }
 269
 270         ret = delay_class_ctr(ti, &dc->flush, argv + 6);
 271         if (ret)
 272                 goto bad;
 273         max_delay = max(max_delay, dc->flush.delay);
 274
 275 out:
 276         if (max_delay < 50) {
 277                 /*
 278                  * In case of small requested delays, use kthread instead of
 279                  * timers and workqueue to achieve better latency.
 280                  */
 281                 dc->worker = kthread_create(&flush_worker_fn, dc,
 282                                             "dm-delay-flush-worker");
 283                 if (IS_ERR(dc->worker)) {
 284                         ret = PTR_ERR(dc->worker);
 285                         goto bad;
 286                 }
 287         } else {
 288                 timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
 289                 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
 290                 mutex_init(&dc->timer_lock);
 291                 dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
 292                 if (!dc->kdelayd_wq) {
 293                         ret = -EINVAL;
 294                         DMERR("Couldn't start kdelayd");
 295                         goto bad;
 296                 }
 297         }
 298
 299         ti->num_flush_bios = 1;
 300         ti->num_discard_bios = 1;
 301         ti->accounts_remapped_io = true;
 302         ti->per_io_data_size = sizeof(struct dm_delay_info);
 303         return 0;
 304
 305 bad:
 306         delay_dtr(ti);
 307         return ret;
 308 }
 309
 310 static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)
 311 {
 312         struct dm_delay_info *delayed;
 313         unsigned long expires = 0;
 314
 315         if (!c->delay || !atomic_read(&dc->may_delay))
 316                 return DM_MAPIO_REMAPPED;
 317
 318         delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 319
 320         delayed->context = dc;
 321         delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay);
 322
 323         mutex_lock(&delayed_bios_lock);
 324         c->ops++;
 325         list_add_tail(&delayed->list, &dc->delayed_bios);
 326         mutex_unlock(&delayed_bios_lock);
 327
 328         if (delay_is_fast(dc))
 329                 wake_up_process(dc->worker);
 330         else
 331                 queue_timeout(dc, expires);
 332
 333         return DM_MAPIO_SUBMITTED;
 334 }
 335
 336 static void delay_presuspend(struct dm_target *ti)
 337 {
 338         struct delay_c *dc = ti->private;
 339
 340         atomic_set(&dc->may_delay, 0);
 341
 342         if (delay_is_fast(dc))
 343                 flush_delayed_bios_fast(dc, true);
 344         else {
 345                 del_timer_sync(&dc->delay_timer);
 346                 flush_bios(flush_delayed_bios(dc, true));
 347         }
 348 }
 349
 350 static void delay_resume(struct dm_target *ti)
 351 {
 352         struct delay_c *dc = ti->private;
 353
 354         atomic_set(&dc->may_delay, 1);
 355 }
 356
 357 static int delay_map(struct dm_target *ti, struct bio *bio)
 358 {
 359         struct delay_c *dc = ti->private;
 360         struct delay_class *c;
 361         struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 362
 363         if (bio_data_dir(bio) == WRITE) {
 364                 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
 365                         c = &dc->flush;
 366                 else
 367                         c = &dc->write;
 368         } else {
 369                 c = &dc->read;
 370         }
 371         delayed->class = c;
 372         bio_set_dev(bio, c->dev->bdev);
 373         bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
 374
 375         return delay_bio(dc, c, bio);
 376 }
 377
 378 #define DMEMIT_DELAY_CLASS(c) \
 379         DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)
 380
 381 static void delay_status(struct dm_target *ti, status_type_t type,
 382                          unsigned int status_flags, char *result, unsigned int maxlen)
 383 {
 384         struct delay_c *dc = ti->private;
 385         int sz = 0;
 386
 387         switch (type) {
 388         case STATUSTYPE_INFO:
 389                 DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
 390                 break;
 391
 392         case STATUSTYPE_TABLE:
 393                 DMEMIT_DELAY_CLASS(&dc->read);
 394                 if (dc->argc >= 6) {
 395                         DMEMIT(" ");
 396                         DMEMIT_DELAY_CLASS(&dc->write);
 397                 }
 398                 if (dc->argc >= 9) {
 399                         DMEMIT(" ");
 400                         DMEMIT_DELAY_CLASS(&dc->flush);
 401                 }
 402                 break;
 403
 404         case STATUSTYPE_IMA:
 405                 *result = '\0';
 406                 break;
 407         }
 408 }
 409
 410 static int delay_iterate_devices(struct dm_target *ti,
 411                                  iterate_devices_callout_fn fn, void *data)
 412 {
 413         struct delay_c *dc = ti->private;
 414         int ret = 0;
 415
 416         ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);
 417         if (ret)
 418                 goto out;
 419         ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
 420         if (ret)
 421                 goto out;
 422         ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
 423         if (ret)
 424                 goto out;
 425
 426 out:
 427         return ret;
 428 }
 429
 430 static struct target_type delay_target = {
 431         .name        = "delay",
 432         .version     = {1, 4, 0},
 433         .features    = DM_TARGET_PASSES_INTEGRITY,
 434         .module      = THIS_MODULE,
 435         .ctr         = delay_ctr,
 436         .dtr         = delay_dtr,
 437         .map         = delay_map,
 438         .presuspend  = delay_presuspend,
 439         .resume      = delay_resume,
 440         .status      = delay_status,
 441         .iterate_devices = delay_iterate_devices,
 442 };
 443 module_dm(delay);
 444
 445 MODULE_DESCRIPTION(DM_NAME " delay target");
 446 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
 447 MODULE_LICENSE("GPL");