drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include "dm-rq.h"
  11 #include "dm-bio-record.h"
  12 #include "dm-path-selector.h"
  13 #include "dm-uevent.h"
  14
  15 #include <linux/blkdev.h>
  16 #include <linux/ctype.h>
  17 #include <linux/init.h>
  18 #include <linux/mempool.h>
  19 #include <linux/module.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/slab.h>
  22 #include <linux/time.h>
  23 #include <linux/workqueue.h>
  24 #include <linux/delay.h>
  25 #include <scsi/scsi_dh.h>
  26 #include <linux/atomic.h>
  27 #include <linux/blk-mq.h>
  28
  29 #define DM_MSG_PREFIX "multipath"
  30 #define DM_PG_INIT_DELAY_MSECS 2000
  31 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  32
  33 /* Path properties */
  34 struct pgpath {
  35         struct list_head list;
  36
  37         struct priority_group *pg;      /* Owning PG */
  38         unsigned fail_count;            /* Cumulative failure count */
  39
  40         struct dm_path path;
  41         struct delayed_work activate_path;
  42
  43         bool is_active:1;               /* Path status */
  44 };
  45
  46 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  47
  48 /*
  49  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  50  * Each has a path selector which controls which path gets used.
  51  */
  52 struct priority_group {
  53         struct list_head list;
  54
  55         struct multipath *m;            /* Owning multipath instance */
  56         struct path_selector ps;
  57
  58         unsigned pg_num;                /* Reference number */
  59         unsigned nr_pgpaths;            /* Number of paths in PG */
  60         struct list_head pgpaths;
  61
  62         bool bypassed:1;                /* Temporarily bypass this PG? */
  63 };
  64
  65 /* Multipath context */
  66 struct multipath {
  67         struct list_head list;
  68         struct dm_target *ti;
  69
  70         const char *hw_handler_name;
  71         char *hw_handler_params;
  72
  73         spinlock_t lock;
  74
  75         unsigned nr_priority_groups;
  76         struct list_head priority_groups;
  77
  78         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  79
  80         struct pgpath *current_pgpath;
  81         struct priority_group *current_pg;
  82         struct priority_group *next_pg; /* Switch to this PG if set */
  83
  84         unsigned long flags;            /* Multipath state flags */
  85
  86         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  87         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  88
  89         atomic_t nr_valid_paths;        /* Total number of usable paths */
  90         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  91         atomic_t pg_init_count;         /* Number of times pg_init called */
  92
  93         enum dm_queue_mode queue_mode;
  94
  95         struct mutex work_mutex;
  96         struct work_struct trigger_event;
  97
  98         struct work_struct process_queued_bios;
  99         struct bio_list queued_bios;
 100 };
 101
 102 /*
 103  * Context information attached to each io we process.
 104  */
 105 struct dm_mpath_io {
 106         struct pgpath *pgpath;
 107         size_t nr_bytes;
 108 };
 109
 110 typedef int (*action_fn) (struct pgpath *pgpath);
 111
 112 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 113 static void trigger_event(struct work_struct *work);
 114 static void activate_or_offline_path(struct pgpath *pgpath);
 115 static void activate_path_work(struct work_struct *work);
 116 static void process_queued_bios(struct work_struct *work);
 117
 118 /*-----------------------------------------------
 119  * Multipath state flags.
 120  *-----------------------------------------------*/
 121
 122 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 123 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 124 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 125 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 126 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 127 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 128 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 129
 130 /*-----------------------------------------------
 131  * Allocation routines
 132  *-----------------------------------------------*/
 133
 134 static struct pgpath *alloc_pgpath(void)
 135 {
 136         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 137
 138         if (pgpath) {
 139                 pgpath->is_active = true;
 140                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path_work);
 141         }
 142
 143         return pgpath;
 144 }
 145
 146 static void free_pgpath(struct pgpath *pgpath)
 147 {
 148         kfree(pgpath);
 149 }
 150
 151 static struct priority_group *alloc_priority_group(void)
 152 {
 153         struct priority_group *pg;
 154
 155         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 156
 157         if (pg)
 158                 INIT_LIST_HEAD(&pg->pgpaths);
 159
 160         return pg;
 161 }
 162
 163 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 164 {
 165         struct pgpath *pgpath, *tmp;
 166
 167         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 168                 list_del(&pgpath->list);
 169                 dm_put_device(ti, pgpath->path.dev);
 170                 free_pgpath(pgpath);
 171         }
 172 }
 173
 174 static void free_priority_group(struct priority_group *pg,
 175                                 struct dm_target *ti)
 176 {
 177         struct path_selector *ps = &pg->ps;
 178
 179         if (ps->type) {
 180                 ps->type->destroy(ps);
 181                 dm_put_path_selector(ps->type);
 182         }
 183
 184         free_pgpaths(&pg->pgpaths, ti);
 185         kfree(pg);
 186 }
 187
 188 static struct multipath *alloc_multipath(struct dm_target *ti)
 189 {
 190         struct multipath *m;
 191
 192         m = kzalloc(sizeof(*m), GFP_KERNEL);
 193         if (m) {
 194                 INIT_LIST_HEAD(&m->priority_groups);
 195                 spin_lock_init(&m->lock);
 196                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 197                 atomic_set(&m->nr_valid_paths, 0);
 198                 atomic_set(&m->pg_init_in_progress, 0);
 199                 atomic_set(&m->pg_init_count, 0);
 200                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 201                 INIT_WORK(&m->trigger_event, trigger_event);
 202                 init_waitqueue_head(&m->pg_init_wait);
 203                 mutex_init(&m->work_mutex);
 204
 205                 m->queue_mode = DM_TYPE_NONE;
 206
 207                 m->ti = ti;
 208                 ti->private = m;
 209         }
 210
 211         return m;
 212 }
 213
 214 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 215 {
 216         if (m->queue_mode == DM_TYPE_NONE) {
 217                 /*
 218                  * Default to request-based.
 219                  */
 220                 if (dm_use_blk_mq(dm_table_get_md(ti->table)))
 221                         m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
 222                 else
 223                         m->queue_mode = DM_TYPE_REQUEST_BASED;
 224         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 225                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 226                 /*
 227                  * bio-based doesn't support any direct scsi_dh management;
 228                  * it just discovers if a scsi_dh is attached.
 229                  */
 230                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 231         }
 232
 233         dm_table_set_type(ti->table, m->queue_mode);
 234
 235         return 0;
 236 }
 237
 238 static void free_multipath(struct multipath *m)
 239 {
 240         struct priority_group *pg, *tmp;
 241
 242         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 243                 list_del(&pg->list);
 244                 free_priority_group(pg, m->ti);
 245         }
 246
 247         kfree(m->hw_handler_name);
 248         kfree(m->hw_handler_params);
 249         kfree(m);
 250 }
 251
 252 static struct dm_mpath_io *get_mpio(union map_info *info)
 253 {
 254         return info->ptr;
 255 }
 256
 257 static size_t multipath_per_bio_data_size(void)
 258 {
 259         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 260 }
 261
 262 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 263 {
 264         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 265 }
 266
 267 static struct dm_bio_details *get_bio_details_from_bio(struct bio *bio)
 268 {
 269         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 270         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 271         void *bio_details = mpio + 1;
 272
 273         return bio_details;
 274 }
 275
 276 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p,
 277                                         struct dm_bio_details **bio_details_p)
 278 {
 279         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 280         struct dm_bio_details *bio_details = get_bio_details_from_bio(bio);
 281
 282         memset(mpio, 0, sizeof(*mpio));
 283         memset(bio_details, 0, sizeof(*bio_details));
 284         dm_bio_record(bio_details, bio);
 285
 286         if (mpio_p)
 287                 *mpio_p = mpio;
 288         if (bio_details_p)
 289                 *bio_details_p = bio_details;
 290 }
 291
 292 /*-----------------------------------------------
 293  * Path selection
 294  *-----------------------------------------------*/
 295
 296 static int __pg_init_all_paths(struct multipath *m)
 297 {
 298         struct pgpath *pgpath;
 299         unsigned long pg_init_delay = 0;
 300
 301         lockdep_assert_held(&m->lock);
 302
 303         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 304                 return 0;
 305
 306         atomic_inc(&m->pg_init_count);
 307         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 308
 309         /* Check here to reset pg_init_required */
 310         if (!m->current_pg)
 311                 return 0;
 312
 313         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 314                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 315                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 316         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 317                 /* Skip failed paths */
 318                 if (!pgpath->is_active)
 319                         continue;
 320                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 321                                        pg_init_delay))
 322                         atomic_inc(&m->pg_init_in_progress);
 323         }
 324         return atomic_read(&m->pg_init_in_progress);
 325 }
 326
 327 static int pg_init_all_paths(struct multipath *m)
 328 {
 329         int ret;
 330         unsigned long flags;
 331
 332         spin_lock_irqsave(&m->lock, flags);
 333         ret = __pg_init_all_paths(m);
 334         spin_unlock_irqrestore(&m->lock, flags);
 335
 336         return ret;
 337 }
 338
 339 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 340 {
 341         m->current_pg = pg;
 342
 343         /* Must we initialise the PG first, and queue I/O till it's ready? */
 344         if (m->hw_handler_name) {
 345                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 346                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 347         } else {
 348                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 349                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 350         }
 351
 352         atomic_set(&m->pg_init_count, 0);
 353 }
 354
 355 static struct pgpath *choose_path_in_pg(struct multipath *m,
 356                                         struct priority_group *pg,
 357                                         size_t nr_bytes)
 358 {
 359         unsigned long flags;
 360         struct dm_path *path;
 361         struct pgpath *pgpath;
 362
 363         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 364         if (!path)
 365                 return ERR_PTR(-ENXIO);
 366
 367         pgpath = path_to_pgpath(path);
 368
 369         if (unlikely(lockless_dereference(m->current_pg) != pg)) {
 370                 /* Only update current_pgpath if pg changed */
 371                 spin_lock_irqsave(&m->lock, flags);
 372                 m->current_pgpath = pgpath;
 373                 __switch_pg(m, pg);
 374                 spin_unlock_irqrestore(&m->lock, flags);
 375         }
 376
 377         return pgpath;
 378 }
 379
 380 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 381 {
 382         unsigned long flags;
 383         struct priority_group *pg;
 384         struct pgpath *pgpath;
 385         unsigned bypassed = 1;
 386
 387         if (!atomic_read(&m->nr_valid_paths)) {
 388                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 389                 goto failed;
 390         }
 391
 392         /* Were we instructed to switch PG? */
 393         if (lockless_dereference(m->next_pg)) {
 394                 spin_lock_irqsave(&m->lock, flags);
 395                 pg = m->next_pg;
 396                 if (!pg) {
 397                         spin_unlock_irqrestore(&m->lock, flags);
 398                         goto check_current_pg;
 399                 }
 400                 m->next_pg = NULL;
 401                 spin_unlock_irqrestore(&m->lock, flags);
 402                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 403                 if (!IS_ERR_OR_NULL(pgpath))
 404                         return pgpath;
 405         }
 406
 407         /* Don't change PG until it has no remaining paths */
 408 check_current_pg:
 409         pg = lockless_dereference(m->current_pg);
 410         if (pg) {
 411                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 412                 if (!IS_ERR_OR_NULL(pgpath))
 413                         return pgpath;
 414         }
 415
 416         /*
 417          * Loop through priority groups until we find a valid path.
 418          * First time we skip PGs marked 'bypassed'.
 419          * Second time we only try the ones we skipped, but set
 420          * pg_init_delay_retry so we do not hammer controllers.
 421          */
 422         do {
 423                 list_for_each_entry(pg, &m->priority_groups, list) {
 424                         if (pg->bypassed == !!bypassed)
 425                                 continue;
 426                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 427                         if (!IS_ERR_OR_NULL(pgpath)) {
 428                                 if (!bypassed)
 429                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 430                                 return pgpath;
 431                         }
 432                 }
 433         } while (bypassed--);
 434
 435 failed:
 436         spin_lock_irqsave(&m->lock, flags);
 437         m->current_pgpath = NULL;
 438         m->current_pg = NULL;
 439         spin_unlock_irqrestore(&m->lock, flags);
 440
 441         return NULL;
 442 }
 443
 444 /*
 445  * dm_report_EIO() is a macro instead of a function to make pr_debug()
 446  * report the function name and line number of the function from which
 447  * it has been invoked.
 448  */
 449 #define dm_report_EIO(m)                                                \
 450 do {                                                                    \
 451         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 452                                                                         \
 453         pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 454                  dm_device_name(md),                                    \
 455                  test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
 456                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
 457                  dm_noflush_suspending((m)->ti));                       \
 458 } while (0)
 459
 460 /*
 461  * Map cloned requests (request-based multipath)
 462  */
 463 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 464                                    union map_info *map_context,
 465                                    struct request **__clone)
 466 {
 467         struct multipath *m = ti->private;
 468         size_t nr_bytes = blk_rq_bytes(rq);
 469         struct pgpath *pgpath;
 470         struct block_device *bdev;
 471         struct dm_mpath_io *mpio = get_mpio(map_context);
 472         struct request_queue *q;
 473         struct request *clone;
 474
 475         /* Do we need to select a new pgpath? */
 476         pgpath = lockless_dereference(m->current_pgpath);
 477         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 478                 pgpath = choose_pgpath(m, nr_bytes);
 479
 480         if (!pgpath) {
 481                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 482                         return DM_MAPIO_DELAY_REQUEUE;
 483                 dm_report_EIO(m);       /* Failed */
 484                 return DM_MAPIO_KILL;
 485         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 486                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 487                 if (pg_init_all_paths(m))
 488                         return DM_MAPIO_DELAY_REQUEUE;
 489                 return DM_MAPIO_REQUEUE;
 490         }
 491
 492         memset(mpio, 0, sizeof(*mpio));
 493         mpio->pgpath = pgpath;
 494         mpio->nr_bytes = nr_bytes;
 495
 496         bdev = pgpath->path.dev->bdev;
 497         q = bdev_get_queue(bdev);
 498         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
 499         if (IS_ERR(clone)) {
 500                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 501                 bool queue_dying = blk_queue_dying(q);
 502                 DMERR_LIMIT("blk_get_request() returned %ld%s - requeuing",
 503                             PTR_ERR(clone), queue_dying ? " (path offline)" : "");
 504                 if (queue_dying) {
 505                         atomic_inc(&m->pg_init_in_progress);
 506                         activate_or_offline_path(pgpath);
 507                 }
 508                 return DM_MAPIO_DELAY_REQUEUE;
 509         }
 510         clone->bio = clone->biotail = NULL;
 511         clone->rq_disk = bdev->bd_disk;
 512         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 513         *__clone = clone;
 514
 515         if (pgpath->pg->ps.type->start_io)
 516                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 517                                               &pgpath->path,
 518                                               nr_bytes);
 519         return DM_MAPIO_REMAPPED;
 520 }
 521
 522 static void multipath_release_clone(struct request *clone)
 523 {
 524         blk_put_request(clone);
 525 }
 526
 527 /*
 528  * Map cloned bios (bio-based multipath)
 529  */
 530 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 531 {
 532         size_t nr_bytes = bio->bi_iter.bi_size;
 533         struct pgpath *pgpath;
 534         unsigned long flags;
 535         bool queue_io;
 536
 537         /* Do we need to select a new pgpath? */
 538         pgpath = lockless_dereference(m->current_pgpath);
 539         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 540         if (!pgpath || !queue_io)
 541                 pgpath = choose_pgpath(m, nr_bytes);
 542
 543         if ((pgpath && queue_io) ||
 544             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 545                 /* Queue for the daemon to resubmit */
 546                 spin_lock_irqsave(&m->lock, flags);
 547                 bio_list_add(&m->queued_bios, bio);
 548                 spin_unlock_irqrestore(&m->lock, flags);
 549                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 550                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 551                         pg_init_all_paths(m);
 552                 else if (!queue_io)
 553                         queue_work(kmultipathd, &m->process_queued_bios);
 554                 return DM_MAPIO_SUBMITTED;
 555         }
 556
 557         if (!pgpath) {
 558                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 559                         return DM_MAPIO_REQUEUE;
 560                 dm_report_EIO(m);
 561                 return DM_MAPIO_KILL;
 562         }
 563
 564         mpio->pgpath = pgpath;
 565         mpio->nr_bytes = nr_bytes;
 566
 567         bio->bi_status = 0;
 568         bio_set_dev(bio, pgpath->path.dev->bdev);
 569         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 570
 571         if (pgpath->pg->ps.type->start_io)
 572                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 573                                               &pgpath->path,
 574                                               nr_bytes);
 575         return DM_MAPIO_REMAPPED;
 576 }
 577
 578 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 579 {
 580         struct multipath *m = ti->private;
 581         struct dm_mpath_io *mpio = NULL;
 582
 583         multipath_init_per_bio_data(bio, &mpio, NULL);
 584
 585         return __multipath_map_bio(m, bio, mpio);
 586 }
 587
 588 static void process_queued_io_list(struct multipath *m)
 589 {
 590         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 591                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 592         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 593                 queue_work(kmultipathd, &m->process_queued_bios);
 594 }
 595
 596 static void process_queued_bios(struct work_struct *work)
 597 {
 598         int r;
 599         unsigned long flags;
 600         struct bio *bio;
 601         struct bio_list bios;
 602         struct blk_plug plug;
 603         struct multipath *m =
 604                 container_of(work, struct multipath, process_queued_bios);
 605
 606         bio_list_init(&bios);
 607
 608         spin_lock_irqsave(&m->lock, flags);
 609
 610         if (bio_list_empty(&m->queued_bios)) {
 611                 spin_unlock_irqrestore(&m->lock, flags);
 612                 return;
 613         }
 614
 615         bio_list_merge(&bios, &m->queued_bios);
 616         bio_list_init(&m->queued_bios);
 617
 618         spin_unlock_irqrestore(&m->lock, flags);
 619
 620         blk_start_plug(&plug);
 621         while ((bio = bio_list_pop(&bios))) {
 622                 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
 623                 switch (r) {
 624                 case DM_MAPIO_KILL:
 625                         bio->bi_status = BLK_STS_IOERR;
 626                         bio_endio(bio);
 627                         break;
 628                 case DM_MAPIO_REQUEUE:
 629                         bio->bi_status = BLK_STS_DM_REQUEUE;
 630                         bio_endio(bio);
 631                         break;
 632                 case DM_MAPIO_REMAPPED:
 633                         generic_make_request(bio);
 634                         break;
 635                 case 0:
 636                         break;
 637                 default:
 638                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 639                 }
 640         }
 641         blk_finish_plug(&plug);
 642 }
 643
 644 static void assign_bit(bool value, long nr, unsigned long *addr)
 645 {
 646         if (value)
 647                 set_bit(nr, addr);
 648         else
 649                 clear_bit(nr, addr);
 650 }
 651
 652 /*
 653  * If we run out of usable paths, should we queue I/O or error it?
 654  */
 655 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 656                             bool save_old_value)
 657 {
 658         unsigned long flags;
 659
 660         spin_lock_irqsave(&m->lock, flags);
 661         assign_bit((save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 662                    (!save_old_value && queue_if_no_path),
 663                    MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 664         assign_bit(queue_if_no_path || dm_noflush_suspending(m->ti),
 665                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 666         spin_unlock_irqrestore(&m->lock, flags);
 667
 668         if (!queue_if_no_path) {
 669                 dm_table_run_md_queue_async(m->ti->table);
 670                 process_queued_io_list(m);
 671         }
 672
 673         return 0;
 674 }
 675
 676 /*
 677  * An event is triggered whenever a path is taken out of use.
 678  * Includes path failure and PG bypass.
 679  */
 680 static void trigger_event(struct work_struct *work)
 681 {
 682         struct multipath *m =
 683                 container_of(work, struct multipath, trigger_event);
 684
 685         dm_table_event(m->ti->table);
 686 }
 687
 688 /*-----------------------------------------------------------------
 689  * Constructor/argument parsing:
 690  * <#multipath feature args> [<arg>]*
 691  * <#hw_handler args> [hw_handler [<arg>]*]
 692  * <#priority groups>
 693  * <initial priority group>
 694  *     [<selector> <#selector args> [<arg>]*
 695  *      <#paths> <#per-path selector args>
 696  *         [<path> [<arg>]* ]+ ]+
 697  *---------------------------------------------------------------*/
 698 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 699                                struct dm_target *ti)
 700 {
 701         int r;
 702         struct path_selector_type *pst;
 703         unsigned ps_argc;
 704
 705         static const struct dm_arg _args[] = {
 706                 {0, 1024, "invalid number of path selector args"},
 707         };
 708
 709         pst = dm_get_path_selector(dm_shift_arg(as));
 710         if (!pst) {
 711                 ti->error = "unknown path selector type";
 712                 return -EINVAL;
 713         }
 714
 715         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 716         if (r) {
 717                 dm_put_path_selector(pst);
 718                 return -EINVAL;
 719         }
 720
 721         r = pst->create(&pg->ps, ps_argc, as->argv);
 722         if (r) {
 723                 dm_put_path_selector(pst);
 724                 ti->error = "path selector constructor failed";
 725                 return r;
 726         }
 727
 728         pg->ps.type = pst;
 729         dm_consume_args(as, ps_argc);
 730
 731         return 0;
 732 }
 733
 734 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 735                                struct dm_target *ti)
 736 {
 737         int r;
 738         struct pgpath *p;
 739         struct multipath *m = ti->private;
 740         struct request_queue *q = NULL;
 741         const char *attached_handler_name;
 742
 743         /* we need at least a path arg */
 744         if (as->argc < 1) {
 745                 ti->error = "no device given";
 746                 return ERR_PTR(-EINVAL);
 747         }
 748
 749         p = alloc_pgpath();
 750         if (!p)
 751                 return ERR_PTR(-ENOMEM);
 752
 753         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 754                           &p->path.dev);
 755         if (r) {
 756                 ti->error = "error getting device";
 757                 goto bad;
 758         }
 759
 760         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 761                 q = bdev_get_queue(p->path.dev->bdev);
 762
 763         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 764 retain:
 765                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 766                 if (attached_handler_name) {
 767                         /*
 768                          * Clear any hw_handler_params associated with a
 769                          * handler that isn't already attached.
 770                          */
 771                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 772                                 kfree(m->hw_handler_params);
 773                                 m->hw_handler_params = NULL;
 774                         }
 775
 776                         /*
 777                          * Reset hw_handler_name to match the attached handler
 778                          *
 779                          * NB. This modifies the table line to show the actual
 780                          * handler instead of the original table passed in.
 781                          */
 782                         kfree(m->hw_handler_name);
 783                         m->hw_handler_name = attached_handler_name;
 784                 }
 785         }
 786
 787         if (m->hw_handler_name) {
 788                 r = scsi_dh_attach(q, m->hw_handler_name);
 789                 if (r == -EBUSY) {
 790                         char b[BDEVNAME_SIZE];
 791
 792                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 793                                 bdevname(p->path.dev->bdev, b));
 794                         goto retain;
 795                 }
 796                 if (r < 0) {
 797                         ti->error = "error attaching hardware handler";
 798                         dm_put_device(ti, p->path.dev);
 799                         goto bad;
 800                 }
 801
 802                 if (m->hw_handler_params) {
 803                         r = scsi_dh_set_params(q, m->hw_handler_params);
 804                         if (r < 0) {
 805                                 ti->error = "unable to set hardware "
 806                                                         "handler parameters";
 807                                 dm_put_device(ti, p->path.dev);
 808                                 goto bad;
 809                         }
 810                 }
 811         }
 812
 813         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 814         if (r) {
 815                 dm_put_device(ti, p->path.dev);
 816                 goto bad;
 817         }
 818
 819         return p;
 820
 821  bad:
 822         free_pgpath(p);
 823         return ERR_PTR(r);
 824 }
 825
 826 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 827                                                    struct multipath *m)
 828 {
 829         static const struct dm_arg _args[] = {
 830                 {1, 1024, "invalid number of paths"},
 831                 {0, 1024, "invalid number of selector args"}
 832         };
 833
 834         int r;
 835         unsigned i, nr_selector_args, nr_args;
 836         struct priority_group *pg;
 837         struct dm_target *ti = m->ti;
 838
 839         if (as->argc < 2) {
 840                 as->argc = 0;
 841                 ti->error = "not enough priority group arguments";
 842                 return ERR_PTR(-EINVAL);
 843         }
 844
 845         pg = alloc_priority_group();
 846         if (!pg) {
 847                 ti->error = "couldn't allocate priority group";
 848                 return ERR_PTR(-ENOMEM);
 849         }
 850         pg->m = m;
 851
 852         r = parse_path_selector(as, pg, ti);
 853         if (r)
 854                 goto bad;
 855
 856         /*
 857          * read the paths
 858          */
 859         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 860         if (r)
 861                 goto bad;
 862
 863         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 864         if (r)
 865                 goto bad;
 866
 867         nr_args = 1 + nr_selector_args;
 868         for (i = 0; i < pg->nr_pgpaths; i++) {
 869                 struct pgpath *pgpath;
 870                 struct dm_arg_set path_args;
 871
 872                 if (as->argc < nr_args) {
 873                         ti->error = "not enough path parameters";
 874                         r = -EINVAL;
 875                         goto bad;
 876                 }
 877
 878                 path_args.argc = nr_args;
 879                 path_args.argv = as->argv;
 880
 881                 pgpath = parse_path(&path_args, &pg->ps, ti);
 882                 if (IS_ERR(pgpath)) {
 883                         r = PTR_ERR(pgpath);
 884                         goto bad;
 885                 }
 886
 887                 pgpath->pg = pg;
 888                 list_add_tail(&pgpath->list, &pg->pgpaths);
 889                 dm_consume_args(as, nr_args);
 890         }
 891
 892         return pg;
 893
 894  bad:
 895         free_priority_group(pg, ti);
 896         return ERR_PTR(r);
 897 }
 898
 899 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 900 {
 901         unsigned hw_argc;
 902         int ret;
 903         struct dm_target *ti = m->ti;
 904
 905         static const struct dm_arg _args[] = {
 906                 {0, 1024, "invalid number of hardware handler args"},
 907         };
 908
 909         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 910                 return -EINVAL;
 911
 912         if (!hw_argc)
 913                 return 0;
 914
 915         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 916                 dm_consume_args(as, hw_argc);
 917                 DMERR("bio-based multipath doesn't allow hardware handler args");
 918                 return 0;
 919         }
 920
 921         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 922         if (!m->hw_handler_name)
 923                 return -EINVAL;
 924
 925         if (hw_argc > 1) {
 926                 char *p;
 927                 int i, j, len = 4;
 928
 929                 for (i = 0; i <= hw_argc - 2; i++)
 930                         len += strlen(as->argv[i]) + 1;
 931                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 932                 if (!p) {
 933                         ti->error = "memory allocation failed";
 934                         ret = -ENOMEM;
 935                         goto fail;
 936                 }
 937                 j = sprintf(p, "%d", hw_argc - 1);
 938                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 939                         j = sprintf(p, "%s", as->argv[i]);
 940         }
 941         dm_consume_args(as, hw_argc - 1);
 942
 943         return 0;
 944 fail:
 945         kfree(m->hw_handler_name);
 946         m->hw_handler_name = NULL;
 947         return ret;
 948 }
 949
 950 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 951 {
 952         int r;
 953         unsigned argc;
 954         struct dm_target *ti = m->ti;
 955         const char *arg_name;
 956
 957         static const struct dm_arg _args[] = {
 958                 {0, 8, "invalid number of feature args"},
 959                 {1, 50, "pg_init_retries must be between 1 and 50"},
 960                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 961         };
 962
 963         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 964         if (r)
 965                 return -EINVAL;
 966
 967         if (!argc)
 968                 return 0;
 969
 970         do {
 971                 arg_name = dm_shift_arg(as);
 972                 argc--;
 973
 974                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 975                         r = queue_if_no_path(m, true, false);
 976                         continue;
 977                 }
 978
 979                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 980                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 981                         continue;
 982                 }
 983
 984                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 985                     (argc >= 1)) {
 986                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 987                         argc--;
 988                         continue;
 989                 }
 990
 991                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 992                     (argc >= 1)) {
 993                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 994                         argc--;
 995                         continue;
 996                 }
 997
 998                 if (!strcasecmp(arg_name, "queue_mode") &&
 999                     (argc >= 1)) {
1000                         const char *queue_mode_name = dm_shift_arg(as);
1001
1002                         if (!strcasecmp(queue_mode_name, "bio"))
1003                                 m->queue_mode = DM_TYPE_BIO_BASED;
1004                         else if (!strcasecmp(queue_mode_name, "rq"))
1005                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1006                         else if (!strcasecmp(queue_mode_name, "mq"))
1007                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1008                         else {
1009                                 ti->error = "Unknown 'queue_mode' requested";
1010                                 r = -EINVAL;
1011                         }
1012                         argc--;
1013                         continue;
1014                 }
1015
1016                 ti->error = "Unrecognised multipath feature request";
1017                 r = -EINVAL;
1018         } while (argc && !r);
1019
1020         return r;
1021 }
1022
1023 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1024 {
1025         /* target arguments */
1026         static const struct dm_arg _args[] = {
1027                 {0, 1024, "invalid number of priority groups"},
1028                 {0, 1024, "invalid initial priority group number"},
1029         };
1030
1031         int r;
1032         struct multipath *m;
1033         struct dm_arg_set as;
1034         unsigned pg_count = 0;
1035         unsigned next_pg_num;
1036
1037         as.argc = argc;
1038         as.argv = argv;
1039
1040         m = alloc_multipath(ti);
1041         if (!m) {
1042                 ti->error = "can't allocate multipath";
1043                 return -EINVAL;
1044         }
1045
1046         r = parse_features(&as, m);
1047         if (r)
1048                 goto bad;
1049
1050         r = alloc_multipath_stage2(ti, m);
1051         if (r)
1052                 goto bad;
1053
1054         r = parse_hw_handler(&as, m);
1055         if (r)
1056                 goto bad;
1057
1058         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1059         if (r)
1060                 goto bad;
1061
1062         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1063         if (r)
1064                 goto bad;
1065
1066         if ((!m->nr_priority_groups && next_pg_num) ||
1067             (m->nr_priority_groups && !next_pg_num)) {
1068                 ti->error = "invalid initial priority group";
1069                 r = -EINVAL;
1070                 goto bad;
1071         }
1072
1073         /* parse the priority groups */
1074         while (as.argc) {
1075                 struct priority_group *pg;
1076                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1077
1078                 pg = parse_priority_group(&as, m);
1079                 if (IS_ERR(pg)) {
1080                         r = PTR_ERR(pg);
1081                         goto bad;
1082                 }
1083
1084                 nr_valid_paths += pg->nr_pgpaths;
1085                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1086
1087                 list_add_tail(&pg->list, &m->priority_groups);
1088                 pg_count++;
1089                 pg->pg_num = pg_count;
1090                 if (!--next_pg_num)
1091                         m->next_pg = pg;
1092         }
1093
1094         if (pg_count != m->nr_priority_groups) {
1095                 ti->error = "priority group count mismatch";
1096                 r = -EINVAL;
1097                 goto bad;
1098         }
1099
1100         ti->num_flush_bios = 1;
1101         ti->num_discard_bios = 1;
1102         ti->num_write_same_bios = 1;
1103         ti->num_write_zeroes_bios = 1;
1104         if (m->queue_mode == DM_TYPE_BIO_BASED)
1105                 ti->per_io_data_size = multipath_per_bio_data_size();
1106         else
1107                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1108
1109         return 0;
1110
1111  bad:
1112         free_multipath(m);
1113         return r;
1114 }
1115
1116 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1117 {
1118         DEFINE_WAIT(wait);
1119
1120         while (1) {
1121                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1122
1123                 if (!atomic_read(&m->pg_init_in_progress))
1124                         break;
1125
1126                 io_schedule();
1127         }
1128         finish_wait(&m->pg_init_wait, &wait);
1129 }
1130
1131 static void flush_multipath_work(struct multipath *m)
1132 {
1133         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1134         smp_mb__after_atomic();
1135
1136         flush_workqueue(kmpath_handlerd);
1137         multipath_wait_for_pg_init_completion(m);
1138         flush_workqueue(kmultipathd);
1139         flush_work(&m->trigger_event);
1140
1141         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1142         smp_mb__after_atomic();
1143 }
1144
1145 static void multipath_dtr(struct dm_target *ti)
1146 {
1147         struct multipath *m = ti->private;
1148
1149         flush_multipath_work(m);
1150         free_multipath(m);
1151 }
1152
1153 /*
1154  * Take a path out of use.
1155  */
1156 static int fail_path(struct pgpath *pgpath)
1157 {
1158         unsigned long flags;
1159         struct multipath *m = pgpath->pg->m;
1160
1161         spin_lock_irqsave(&m->lock, flags);
1162
1163         if (!pgpath->is_active)
1164                 goto out;
1165
1166         DMWARN("Failing path %s.", pgpath->path.dev->name);
1167
1168         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1169         pgpath->is_active = false;
1170         pgpath->fail_count++;
1171
1172         atomic_dec(&m->nr_valid_paths);
1173
1174         if (pgpath == m->current_pgpath)
1175                 m->current_pgpath = NULL;
1176
1177         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1178                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1179
1180         schedule_work(&m->trigger_event);
1181
1182 out:
1183         spin_unlock_irqrestore(&m->lock, flags);
1184
1185         return 0;
1186 }
1187
1188 /*
1189  * Reinstate a previously-failed path
1190  */
1191 static int reinstate_path(struct pgpath *pgpath)
1192 {
1193         int r = 0, run_queue = 0;
1194         unsigned long flags;
1195         struct multipath *m = pgpath->pg->m;
1196         unsigned nr_valid_paths;
1197
1198         spin_lock_irqsave(&m->lock, flags);
1199
1200         if (pgpath->is_active)
1201                 goto out;
1202
1203         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1204
1205         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1206         if (r)
1207                 goto out;
1208
1209         pgpath->is_active = true;
1210
1211         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1212         if (nr_valid_paths == 1) {
1213                 m->current_pgpath = NULL;
1214                 run_queue = 1;
1215         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1216                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1217                         atomic_inc(&m->pg_init_in_progress);
1218         }
1219
1220         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1221                        pgpath->path.dev->name, nr_valid_paths);
1222
1223         schedule_work(&m->trigger_event);
1224
1225 out:
1226         spin_unlock_irqrestore(&m->lock, flags);
1227         if (run_queue) {
1228                 dm_table_run_md_queue_async(m->ti->table);
1229                 process_queued_io_list(m);
1230         }
1231
1232         return r;
1233 }
1234
1235 /*
1236  * Fail or reinstate all paths that match the provided struct dm_dev.
1237  */
1238 static int action_dev(struct multipath *m, struct dm_dev *dev,
1239                       action_fn action)
1240 {
1241         int r = -EINVAL;
1242         struct pgpath *pgpath;
1243         struct priority_group *pg;
1244
1245         list_for_each_entry(pg, &m->priority_groups, list) {
1246                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1247                         if (pgpath->path.dev == dev)
1248                                 r = action(pgpath);
1249                 }
1250         }
1251
1252         return r;
1253 }
1254
1255 /*
1256  * Temporarily try to avoid having to use the specified PG
1257  */
1258 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1259                       bool bypassed)
1260 {
1261         unsigned long flags;
1262
1263         spin_lock_irqsave(&m->lock, flags);
1264
1265         pg->bypassed = bypassed;
1266         m->current_pgpath = NULL;
1267         m->current_pg = NULL;
1268
1269         spin_unlock_irqrestore(&m->lock, flags);
1270
1271         schedule_work(&m->trigger_event);
1272 }
1273
1274 /*
1275  * Switch to using the specified PG from the next I/O that gets mapped
1276  */
1277 static int switch_pg_num(struct multipath *m, const char *pgstr)
1278 {
1279         struct priority_group *pg;
1280         unsigned pgnum;
1281         unsigned long flags;
1282         char dummy;
1283
1284         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1285             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1286                 DMWARN("invalid PG number supplied to switch_pg_num");
1287                 return -EINVAL;
1288         }
1289
1290         spin_lock_irqsave(&m->lock, flags);
1291         list_for_each_entry(pg, &m->priority_groups, list) {
1292                 pg->bypassed = false;
1293                 if (--pgnum)
1294                         continue;
1295
1296                 m->current_pgpath = NULL;
1297                 m->current_pg = NULL;
1298                 m->next_pg = pg;
1299         }
1300         spin_unlock_irqrestore(&m->lock, flags);
1301
1302         schedule_work(&m->trigger_event);
1303         return 0;
1304 }
1305
1306 /*
1307  * Set/clear bypassed status of a PG.
1308  * PGs are numbered upwards from 1 in the order they were declared.
1309  */
1310 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1311 {
1312         struct priority_group *pg;
1313         unsigned pgnum;
1314         char dummy;
1315
1316         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1317             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1318                 DMWARN("invalid PG number supplied to bypass_pg");
1319                 return -EINVAL;
1320         }
1321
1322         list_for_each_entry(pg, &m->priority_groups, list) {
1323                 if (!--pgnum)
1324                         break;
1325         }
1326
1327         bypass_pg(m, pg, bypassed);
1328         return 0;
1329 }
1330
1331 /*
1332  * Should we retry pg_init immediately?
1333  */
1334 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1335 {
1336         unsigned long flags;
1337         bool limit_reached = false;
1338
1339         spin_lock_irqsave(&m->lock, flags);
1340
1341         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1342             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1343                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1344         else
1345                 limit_reached = true;
1346
1347         spin_unlock_irqrestore(&m->lock, flags);
1348
1349         return limit_reached;
1350 }
1351
1352 static void pg_init_done(void *data, int errors)
1353 {
1354         struct pgpath *pgpath = data;
1355         struct priority_group *pg = pgpath->pg;
1356         struct multipath *m = pg->m;
1357         unsigned long flags;
1358         bool delay_retry = false;
1359
1360         /* device or driver problems */
1361         switch (errors) {
1362         case SCSI_DH_OK:
1363                 break;
1364         case SCSI_DH_NOSYS:
1365                 if (!m->hw_handler_name) {
1366                         errors = 0;
1367                         break;
1368                 }
1369                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1370                       "Error %d.", m->hw_handler_name, errors);
1371                 /*
1372                  * Fail path for now, so we do not ping pong
1373                  */
1374                 fail_path(pgpath);
1375                 break;
1376         case SCSI_DH_DEV_TEMP_BUSY:
1377                 /*
1378                  * Probably doing something like FW upgrade on the
1379                  * controller so try the other pg.
1380                  */
1381                 bypass_pg(m, pg, true);
1382                 break;
1383         case SCSI_DH_RETRY:
1384                 /* Wait before retrying. */
1385                 delay_retry = 1;
1386                 /* fall through */
1387         case SCSI_DH_IMM_RETRY:
1388         case SCSI_DH_RES_TEMP_UNAVAIL:
1389                 if (pg_init_limit_reached(m, pgpath))
1390                         fail_path(pgpath);
1391                 errors = 0;
1392                 break;
1393         case SCSI_DH_DEV_OFFLINED:
1394         default:
1395                 /*
1396                  * We probably do not want to fail the path for a device
1397                  * error, but this is what the old dm did. In future
1398                  * patches we can do more advanced handling.
1399                  */
1400                 fail_path(pgpath);
1401         }
1402
1403         spin_lock_irqsave(&m->lock, flags);
1404         if (errors) {
1405                 if (pgpath == m->current_pgpath) {
1406                         DMERR("Could not failover device. Error %d.", errors);
1407                         m->current_pgpath = NULL;
1408                         m->current_pg = NULL;
1409                 }
1410         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1411                 pg->bypassed = false;
1412
1413         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1414                 /* Activations of other paths are still on going */
1415                 goto out;
1416
1417         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1418                 if (delay_retry)
1419                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1420                 else
1421                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1422
1423                 if (__pg_init_all_paths(m))
1424                         goto out;
1425         }
1426         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1427
1428         process_queued_io_list(m);
1429
1430         /*
1431          * Wake up any thread waiting to suspend.
1432          */
1433         wake_up(&m->pg_init_wait);
1434
1435 out:
1436         spin_unlock_irqrestore(&m->lock, flags);
1437 }
1438
1439 static void activate_or_offline_path(struct pgpath *pgpath)
1440 {
1441         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1442
1443         if (pgpath->is_active && !blk_queue_dying(q))
1444                 scsi_dh_activate(q, pg_init_done, pgpath);
1445         else
1446                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1447 }
1448
1449 static void activate_path_work(struct work_struct *work)
1450 {
1451         struct pgpath *pgpath =
1452                 container_of(work, struct pgpath, activate_path.work);
1453
1454         activate_or_offline_path(pgpath);
1455 }
1456
1457 static int noretry_error(blk_status_t error)
1458 {
1459         switch (error) {
1460         case BLK_STS_NOTSUPP:
1461         case BLK_STS_NOSPC:
1462         case BLK_STS_TARGET:
1463         case BLK_STS_NEXUS:
1464         case BLK_STS_MEDIUM:
1465                 return 1;
1466         }
1467
1468         /* Anything else could be a path failure, so should be retried */
1469         return 0;
1470 }
1471
1472 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1473                             blk_status_t error, union map_info *map_context)
1474 {
1475         struct dm_mpath_io *mpio = get_mpio(map_context);
1476         struct pgpath *pgpath = mpio->pgpath;
1477         int r = DM_ENDIO_DONE;
1478
1479         /*
1480          * We don't queue any clone request inside the multipath target
1481          * during end I/O handling, since those clone requests don't have
1482          * bio clones.  If we queue them inside the multipath target,
1483          * we need to make bio clones, that requires memory allocation.
1484          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1485          *  don't have bio clones.)
1486          * Instead of queueing the clone request here, we queue the original
1487          * request into dm core, which will remake a clone request and
1488          * clone bios for it and resubmit it later.
1489          */
1490         if (error && !noretry_error(error)) {
1491                 struct multipath *m = ti->private;
1492
1493                 r = DM_ENDIO_REQUEUE;
1494
1495                 if (pgpath)
1496                         fail_path(pgpath);
1497
1498                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1499                     !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1500                         if (error == BLK_STS_IOERR)
1501                                 dm_report_EIO(m);
1502                         /* complete with the original error */
1503                         r = DM_ENDIO_DONE;
1504                 }
1505         }
1506
1507         if (pgpath) {
1508                 struct path_selector *ps = &pgpath->pg->ps;
1509
1510                 if (ps->type->end_io)
1511                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1512         }
1513
1514         return r;
1515 }
1516
1517 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1518                 blk_status_t *error)
1519 {
1520         struct multipath *m = ti->private;
1521         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1522         struct pgpath *pgpath = mpio->pgpath;
1523         unsigned long flags;
1524         int r = DM_ENDIO_DONE;
1525
1526         if (!*error || noretry_error(*error))
1527                 goto done;
1528
1529         if (pgpath)
1530                 fail_path(pgpath);
1531
1532         if (atomic_read(&m->nr_valid_paths) == 0 &&
1533             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1534                 dm_report_EIO(m);
1535                 *error = BLK_STS_IOERR;
1536                 goto done;
1537         }
1538
1539         /* Queue for the daemon to resubmit */
1540         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1541
1542         spin_lock_irqsave(&m->lock, flags);
1543         bio_list_add(&m->queued_bios, clone);
1544         spin_unlock_irqrestore(&m->lock, flags);
1545         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1546                 queue_work(kmultipathd, &m->process_queued_bios);
1547
1548         r = DM_ENDIO_INCOMPLETE;
1549 done:
1550         if (pgpath) {
1551                 struct path_selector *ps = &pgpath->pg->ps;
1552
1553                 if (ps->type->end_io)
1554                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1555         }
1556
1557         return r;
1558 }
1559
1560 /*
1561  * Suspend can't complete until all the I/O is processed so if
1562  * the last path fails we must error any remaining I/O.
1563  * Note that if the freeze_bdev fails while suspending, the
1564  * queue_if_no_path state is lost - userspace should reset it.
1565  */
1566 static void multipath_presuspend(struct dm_target *ti)
1567 {
1568         struct multipath *m = ti->private;
1569
1570         queue_if_no_path(m, false, true);
1571 }
1572
1573 static void multipath_postsuspend(struct dm_target *ti)
1574 {
1575         struct multipath *m = ti->private;
1576
1577         mutex_lock(&m->work_mutex);
1578         flush_multipath_work(m);
1579         mutex_unlock(&m->work_mutex);
1580 }
1581
1582 /*
1583  * Restore the queue_if_no_path setting.
1584  */
1585 static void multipath_resume(struct dm_target *ti)
1586 {
1587         struct multipath *m = ti->private;
1588         unsigned long flags;
1589
1590         spin_lock_irqsave(&m->lock, flags);
1591         assign_bit(test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
1592                    MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1593         spin_unlock_irqrestore(&m->lock, flags);
1594 }
1595
1596 /*
1597  * Info output has the following format:
1598  * num_multipath_feature_args [multipath_feature_args]*
1599  * num_handler_status_args [handler_status_args]*
1600  * num_groups init_group_number
1601  *            [A|D|E num_ps_status_args [ps_status_args]*
1602  *             num_paths num_selector_args
1603  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1604  *
1605  * Table output has the following format (identical to the constructor string):
1606  * num_feature_args [features_args]*
1607  * num_handler_args hw_handler [hw_handler_args]*
1608  * num_groups init_group_number
1609  *     [priority selector-name num_ps_args [ps_args]*
1610  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1611  */
1612 static void multipath_status(struct dm_target *ti, status_type_t type,
1613                              unsigned status_flags, char *result, unsigned maxlen)
1614 {
1615         int sz = 0;
1616         unsigned long flags;
1617         struct multipath *m = ti->private;
1618         struct priority_group *pg;
1619         struct pgpath *p;
1620         unsigned pg_num;
1621         char state;
1622
1623         spin_lock_irqsave(&m->lock, flags);
1624
1625         /* Features */
1626         if (type == STATUSTYPE_INFO)
1627                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1628                        atomic_read(&m->pg_init_count));
1629         else {
1630                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1631                               (m->pg_init_retries > 0) * 2 +
1632                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1633                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1634                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1635
1636                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1637                         DMEMIT("queue_if_no_path ");
1638                 if (m->pg_init_retries)
1639                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1640                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1641                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1642                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1643                         DMEMIT("retain_attached_hw_handler ");
1644                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1645                         switch(m->queue_mode) {
1646                         case DM_TYPE_BIO_BASED:
1647                                 DMEMIT("queue_mode bio ");
1648                                 break;
1649                         case DM_TYPE_MQ_REQUEST_BASED:
1650                                 DMEMIT("queue_mode mq ");
1651                                 break;
1652                         default:
1653                                 WARN_ON_ONCE(true);
1654                                 break;
1655                         }
1656                 }
1657         }
1658
1659         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1660                 DMEMIT("0 ");
1661         else
1662                 DMEMIT("1 %s ", m->hw_handler_name);
1663
1664         DMEMIT("%u ", m->nr_priority_groups);
1665
1666         if (m->next_pg)
1667                 pg_num = m->next_pg->pg_num;
1668         else if (m->current_pg)
1669                 pg_num = m->current_pg->pg_num;
1670         else
1671                 pg_num = (m->nr_priority_groups ? 1 : 0);
1672
1673         DMEMIT("%u ", pg_num);
1674
1675         switch (type) {
1676         case STATUSTYPE_INFO:
1677                 list_for_each_entry(pg, &m->priority_groups, list) {
1678                         if (pg->bypassed)
1679                                 state = 'D';    /* Disabled */
1680                         else if (pg == m->current_pg)
1681                                 state = 'A';    /* Currently Active */
1682                         else
1683                                 state = 'E';    /* Enabled */
1684
1685                         DMEMIT("%c ", state);
1686
1687                         if (pg->ps.type->status)
1688                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1689                                                           result + sz,
1690                                                           maxlen - sz);
1691                         else
1692                                 DMEMIT("0 ");
1693
1694                         DMEMIT("%u %u ", pg->nr_pgpaths,
1695                                pg->ps.type->info_args);
1696
1697                         list_for_each_entry(p, &pg->pgpaths, list) {
1698                                 DMEMIT("%s %s %u ", p->path.dev->name,
1699                                        p->is_active ? "A" : "F",
1700                                        p->fail_count);
1701                                 if (pg->ps.type->status)
1702                                         sz += pg->ps.type->status(&pg->ps,
1703                                               &p->path, type, result + sz,
1704                                               maxlen - sz);
1705                         }
1706                 }
1707                 break;
1708
1709         case STATUSTYPE_TABLE:
1710                 list_for_each_entry(pg, &m->priority_groups, list) {
1711                         DMEMIT("%s ", pg->ps.type->name);
1712
1713                         if (pg->ps.type->status)
1714                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1715                                                           result + sz,
1716                                                           maxlen - sz);
1717                         else
1718                                 DMEMIT("0 ");
1719
1720                         DMEMIT("%u %u ", pg->nr_pgpaths,
1721                                pg->ps.type->table_args);
1722
1723                         list_for_each_entry(p, &pg->pgpaths, list) {
1724                                 DMEMIT("%s ", p->path.dev->name);
1725                                 if (pg->ps.type->status)
1726                                         sz += pg->ps.type->status(&pg->ps,
1727                                               &p->path, type, result + sz,
1728                                               maxlen - sz);
1729                         }
1730                 }
1731                 break;
1732         }
1733
1734         spin_unlock_irqrestore(&m->lock, flags);
1735 }
1736
1737 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1738 {
1739         int r = -EINVAL;
1740         struct dm_dev *dev;
1741         struct multipath *m = ti->private;
1742         action_fn action;
1743
1744         mutex_lock(&m->work_mutex);
1745
1746         if (dm_suspended(ti)) {
1747                 r = -EBUSY;
1748                 goto out;
1749         }
1750
1751         if (argc == 1) {
1752                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1753                         r = queue_if_no_path(m, true, false);
1754                         goto out;
1755                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1756                         r = queue_if_no_path(m, false, false);
1757                         goto out;
1758                 }
1759         }
1760
1761         if (argc != 2) {
1762                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1763                 goto out;
1764         }
1765
1766         if (!strcasecmp(argv[0], "disable_group")) {
1767                 r = bypass_pg_num(m, argv[1], true);
1768                 goto out;
1769         } else if (!strcasecmp(argv[0], "enable_group")) {
1770                 r = bypass_pg_num(m, argv[1], false);
1771                 goto out;
1772         } else if (!strcasecmp(argv[0], "switch_group")) {
1773                 r = switch_pg_num(m, argv[1]);
1774                 goto out;
1775         } else if (!strcasecmp(argv[0], "reinstate_path"))
1776                 action = reinstate_path;
1777         else if (!strcasecmp(argv[0], "fail_path"))
1778                 action = fail_path;
1779         else {
1780                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1781                 goto out;
1782         }
1783
1784         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1785         if (r) {
1786                 DMWARN("message: error getting device %s",
1787                        argv[1]);
1788                 goto out;
1789         }
1790
1791         r = action_dev(m, dev, action);
1792
1793         dm_put_device(ti, dev);
1794
1795 out:
1796         mutex_unlock(&m->work_mutex);
1797         return r;
1798 }
1799
1800 static int multipath_prepare_ioctl(struct dm_target *ti,
1801                 struct block_device **bdev, fmode_t *mode)
1802 {
1803         struct multipath *m = ti->private;
1804         struct pgpath *current_pgpath;
1805         int r;
1806
1807         current_pgpath = lockless_dereference(m->current_pgpath);
1808         if (!current_pgpath)
1809                 current_pgpath = choose_pgpath(m, 0);
1810
1811         if (current_pgpath) {
1812                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1813                         *bdev = current_pgpath->path.dev->bdev;
1814                         *mode = current_pgpath->path.dev->mode;
1815                         r = 0;
1816                 } else {
1817                         /* pg_init has not started or completed */
1818                         r = -ENOTCONN;
1819                 }
1820         } else {
1821                 /* No path is available */
1822                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1823                         r = -ENOTCONN;
1824                 else
1825                         r = -EIO;
1826         }
1827
1828         if (r == -ENOTCONN) {
1829                 if (!lockless_dereference(m->current_pg)) {
1830                         /* Path status changed, redo selection */
1831                         (void) choose_pgpath(m, 0);
1832                 }
1833                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1834                         pg_init_all_paths(m);
1835                 dm_table_run_md_queue_async(m->ti->table);
1836                 process_queued_io_list(m);
1837         }
1838
1839         /*
1840          * Only pass ioctls through if the device sizes match exactly.
1841          */
1842         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1843                 return 1;
1844         return r;
1845 }
1846
1847 static int multipath_iterate_devices(struct dm_target *ti,
1848                                      iterate_devices_callout_fn fn, void *data)
1849 {
1850         struct multipath *m = ti->private;
1851         struct priority_group *pg;
1852         struct pgpath *p;
1853         int ret = 0;
1854
1855         list_for_each_entry(pg, &m->priority_groups, list) {
1856                 list_for_each_entry(p, &pg->pgpaths, list) {
1857                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1858                         if (ret)
1859                                 goto out;
1860                 }
1861         }
1862
1863 out:
1864         return ret;
1865 }
1866
1867 static int pgpath_busy(struct pgpath *pgpath)
1868 {
1869         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1870
1871         return blk_lld_busy(q);
1872 }
1873
1874 /*
1875  * We return "busy", only when we can map I/Os but underlying devices
1876  * are busy (so even if we map I/Os now, the I/Os will wait on
1877  * the underlying queue).
1878  * In other words, if we want to kill I/Os or queue them inside us
1879  * due to map unavailability, we don't return "busy".  Otherwise,
1880  * dm core won't give us the I/Os and we can't do what we want.
1881  */
1882 static int multipath_busy(struct dm_target *ti)
1883 {
1884         bool busy = false, has_active = false;
1885         struct multipath *m = ti->private;
1886         struct priority_group *pg, *next_pg;
1887         struct pgpath *pgpath;
1888
1889         /* pg_init in progress */
1890         if (atomic_read(&m->pg_init_in_progress))
1891                 return true;
1892
1893         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1894         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1895                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1896
1897         /* Guess which priority_group will be used at next mapping time */
1898         pg = lockless_dereference(m->current_pg);
1899         next_pg = lockless_dereference(m->next_pg);
1900         if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
1901                 pg = next_pg;
1902
1903         if (!pg) {
1904                 /*
1905                  * We don't know which pg will be used at next mapping time.
1906                  * We don't call choose_pgpath() here to avoid to trigger
1907                  * pg_init just by busy checking.
1908                  * So we don't know whether underlying devices we will be using
1909                  * at next mapping time are busy or not. Just try mapping.
1910                  */
1911                 return busy;
1912         }
1913
1914         /*
1915          * If there is one non-busy active path at least, the path selector
1916          * will be able to select it. So we consider such a pg as not busy.
1917          */
1918         busy = true;
1919         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1920                 if (pgpath->is_active) {
1921                         has_active = true;
1922                         if (!pgpath_busy(pgpath)) {
1923                                 busy = false;
1924                                 break;
1925                         }
1926                 }
1927         }
1928
1929         if (!has_active) {
1930                 /*
1931                  * No active path in this pg, so this pg won't be used and
1932                  * the current_pg will be changed at next mapping time.
1933                  * We need to try mapping to determine it.
1934                  */
1935                 busy = false;
1936         }
1937
1938         return busy;
1939 }
1940
1941 /*-----------------------------------------------------------------
1942  * Module setup
1943  *---------------------------------------------------------------*/
1944 static struct target_type multipath_target = {
1945         .name = "multipath",
1946         .version = {1, 12, 0},
1947         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1948         .module = THIS_MODULE,
1949         .ctr = multipath_ctr,
1950         .dtr = multipath_dtr,
1951         .clone_and_map_rq = multipath_clone_and_map,
1952         .release_clone_rq = multipath_release_clone,
1953         .rq_end_io = multipath_end_io,
1954         .map = multipath_map_bio,
1955         .end_io = multipath_end_io_bio,
1956         .presuspend = multipath_presuspend,
1957         .postsuspend = multipath_postsuspend,
1958         .resume = multipath_resume,
1959         .status = multipath_status,
1960         .message = multipath_message,
1961         .prepare_ioctl = multipath_prepare_ioctl,
1962         .iterate_devices = multipath_iterate_devices,
1963         .busy = multipath_busy,
1964 };
1965
1966 static int __init dm_multipath_init(void)
1967 {
1968         int r;
1969
1970         r = dm_register_target(&multipath_target);
1971         if (r < 0) {
1972                 DMERR("request-based register failed %d", r);
1973                 r = -EINVAL;
1974                 goto bad_register_target;
1975         }
1976
1977         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1978         if (!kmultipathd) {
1979                 DMERR("failed to create workqueue kmpathd");
1980                 r = -ENOMEM;
1981                 goto bad_alloc_kmultipathd;
1982         }
1983
1984         /*
1985          * A separate workqueue is used to handle the device handlers
1986          * to avoid overloading existing workqueue. Overloading the
1987          * old workqueue would also create a bottleneck in the
1988          * path of the storage hardware device activation.
1989          */
1990         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1991                                                   WQ_MEM_RECLAIM);
1992         if (!kmpath_handlerd) {
1993                 DMERR("failed to create workqueue kmpath_handlerd");
1994                 r = -ENOMEM;
1995                 goto bad_alloc_kmpath_handlerd;
1996         }
1997
1998         return 0;
1999
2000 bad_alloc_kmpath_handlerd:
2001         destroy_workqueue(kmultipathd);
2002 bad_alloc_kmultipathd:
2003         dm_unregister_target(&multipath_target);
2004 bad_register_target:
2005         return r;
2006 }
2007
2008 static void __exit dm_multipath_exit(void)
2009 {
2010         destroy_workqueue(kmpath_handlerd);
2011         destroy_workqueue(kmultipathd);
2012
2013         dm_unregister_target(&multipath_target);
2014 }
2015
2016 module_init(dm_multipath_init);
2017 module_exit(dm_multipath_exit);
2018
2019 MODULE_DESCRIPTION(DM_NAME " multipath target");
2020 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2021 MODULE_LICENSE("GPL");