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