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_mpio(struct dm_mpath_io *mpio)
 268 {
 269         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 270         void *bio_details = mpio + 1;
 271         return bio_details;
 272 }
 273
 274 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 275 {
 276         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 277         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 278
 279         mpio->nr_bytes = bio->bi_iter.bi_size;
 280         mpio->pgpath = NULL;
 281         *mpio_p = mpio;
 282
 283         dm_bio_record(bio_details, bio);
 284 }
 285
 286 /*-----------------------------------------------
 287  * Path selection
 288  *-----------------------------------------------*/
 289
 290 static int __pg_init_all_paths(struct multipath *m)
 291 {
 292         struct pgpath *pgpath;
 293         unsigned long pg_init_delay = 0;
 294
 295         lockdep_assert_held(&m->lock);
 296
 297         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 298                 return 0;
 299
 300         atomic_inc(&m->pg_init_count);
 301         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 302
 303         /* Check here to reset pg_init_required */
 304         if (!m->current_pg)
 305                 return 0;
 306
 307         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 308                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 309                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 310         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 311                 /* Skip failed paths */
 312                 if (!pgpath->is_active)
 313                         continue;
 314                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 315                                        pg_init_delay))
 316                         atomic_inc(&m->pg_init_in_progress);
 317         }
 318         return atomic_read(&m->pg_init_in_progress);
 319 }
 320
 321 static int pg_init_all_paths(struct multipath *m)
 322 {
 323         int ret;
 324         unsigned long flags;
 325
 326         spin_lock_irqsave(&m->lock, flags);
 327         ret = __pg_init_all_paths(m);
 328         spin_unlock_irqrestore(&m->lock, flags);
 329
 330         return ret;
 331 }
 332
 333 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 334 {
 335         m->current_pg = pg;
 336
 337         /* Must we initialise the PG first, and queue I/O till it's ready? */
 338         if (m->hw_handler_name) {
 339                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 340                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 341         } else {
 342                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 343                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 344         }
 345
 346         atomic_set(&m->pg_init_count, 0);
 347 }
 348
 349 static struct pgpath *choose_path_in_pg(struct multipath *m,
 350                                         struct priority_group *pg,
 351                                         size_t nr_bytes)
 352 {
 353         unsigned long flags;
 354         struct dm_path *path;
 355         struct pgpath *pgpath;
 356
 357         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 358         if (!path)
 359                 return ERR_PTR(-ENXIO);
 360
 361         pgpath = path_to_pgpath(path);
 362
 363         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 364                 /* Only update current_pgpath if pg changed */
 365                 spin_lock_irqsave(&m->lock, flags);
 366                 m->current_pgpath = pgpath;
 367                 __switch_pg(m, pg);
 368                 spin_unlock_irqrestore(&m->lock, flags);
 369         }
 370
 371         return pgpath;
 372 }
 373
 374 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 375 {
 376         unsigned long flags;
 377         struct priority_group *pg;
 378         struct pgpath *pgpath;
 379         unsigned bypassed = 1;
 380
 381         if (!atomic_read(&m->nr_valid_paths)) {
 382                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 383                 goto failed;
 384         }
 385
 386         /* Were we instructed to switch PG? */
 387         if (READ_ONCE(m->next_pg)) {
 388                 spin_lock_irqsave(&m->lock, flags);
 389                 pg = m->next_pg;
 390                 if (!pg) {
 391                         spin_unlock_irqrestore(&m->lock, flags);
 392                         goto check_current_pg;
 393                 }
 394                 m->next_pg = NULL;
 395                 spin_unlock_irqrestore(&m->lock, flags);
 396                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 397                 if (!IS_ERR_OR_NULL(pgpath))
 398                         return pgpath;
 399         }
 400
 401         /* Don't change PG until it has no remaining paths */
 402 check_current_pg:
 403         pg = READ_ONCE(m->current_pg);
 404         if (pg) {
 405                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 406                 if (!IS_ERR_OR_NULL(pgpath))
 407                         return pgpath;
 408         }
 409
 410         /*
 411          * Loop through priority groups until we find a valid path.
 412          * First time we skip PGs marked 'bypassed'.
 413          * Second time we only try the ones we skipped, but set
 414          * pg_init_delay_retry so we do not hammer controllers.
 415          */
 416         do {
 417                 list_for_each_entry(pg, &m->priority_groups, list) {
 418                         if (pg->bypassed == !!bypassed)
 419                                 continue;
 420                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 421                         if (!IS_ERR_OR_NULL(pgpath)) {
 422                                 if (!bypassed)
 423                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 424                                 return pgpath;
 425                         }
 426                 }
 427         } while (bypassed--);
 428
 429 failed:
 430         spin_lock_irqsave(&m->lock, flags);
 431         m->current_pgpath = NULL;
 432         m->current_pg = NULL;
 433         spin_unlock_irqrestore(&m->lock, flags);
 434
 435         return NULL;
 436 }
 437
 438 /*
 439  * dm_report_EIO() is a macro instead of a function to make pr_debug()
 440  * report the function name and line number of the function from which
 441  * it has been invoked.
 442  */
 443 #define dm_report_EIO(m)                                                \
 444 do {                                                                    \
 445         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 446                                                                         \
 447         pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 448                  dm_device_name(md),                                    \
 449                  test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
 450                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
 451                  dm_noflush_suspending((m)->ti));                       \
 452 } while (0)
 453
 454 /*
 455  * Check whether bios must be queued in the device-mapper core rather
 456  * than here in the target.
 457  *
 458  * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
 459  * the same value then we are not between multipath_presuspend()
 460  * and multipath_resume() calls and we have no need to check
 461  * for the DMF_NOFLUSH_SUSPENDING flag.
 462  */
 463 static bool __must_push_back(struct multipath *m, unsigned long flags)
 464 {
 465         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
 466                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
 467                 dm_noflush_suspending(m->ti));
 468 }
 469
 470 /*
 471  * Following functions use READ_ONCE to get atomic access to
 472  * all m->flags to avoid taking spinlock
 473  */
 474 static bool must_push_back_rq(struct multipath *m)
 475 {
 476         unsigned long flags = READ_ONCE(m->flags);
 477         return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
 478 }
 479
 480 static bool must_push_back_bio(struct multipath *m)
 481 {
 482         unsigned long flags = READ_ONCE(m->flags);
 483         return __must_push_back(m, flags);
 484 }
 485
 486 /*
 487  * Map cloned requests (request-based multipath)
 488  */
 489 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 490                                    union map_info *map_context,
 491                                    struct request **__clone)
 492 {
 493         struct multipath *m = ti->private;
 494         size_t nr_bytes = blk_rq_bytes(rq);
 495         struct pgpath *pgpath;
 496         struct block_device *bdev;
 497         struct dm_mpath_io *mpio = get_mpio(map_context);
 498         struct request_queue *q;
 499         struct request *clone;
 500
 501         /* Do we need to select a new pgpath? */
 502         pgpath = READ_ONCE(m->current_pgpath);
 503         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 504                 pgpath = choose_pgpath(m, nr_bytes);
 505
 506         if (!pgpath) {
 507                 if (must_push_back_rq(m))
 508                         return DM_MAPIO_DELAY_REQUEUE;
 509                 dm_report_EIO(m);       /* Failed */
 510                 return DM_MAPIO_KILL;
 511         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 512                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 513                 if (pg_init_all_paths(m))
 514                         return DM_MAPIO_DELAY_REQUEUE;
 515                 return DM_MAPIO_REQUEUE;
 516         }
 517
 518         mpio->pgpath = pgpath;
 519         mpio->nr_bytes = nr_bytes;
 520
 521         bdev = pgpath->path.dev->bdev;
 522         q = bdev_get_queue(bdev);
 523         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
 524         if (IS_ERR(clone)) {
 525                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 526                 bool queue_dying = blk_queue_dying(q);
 527                 if (queue_dying) {
 528                         atomic_inc(&m->pg_init_in_progress);
 529                         activate_or_offline_path(pgpath);
 530                 }
 531                 return DM_MAPIO_DELAY_REQUEUE;
 532         }
 533         clone->bio = clone->biotail = NULL;
 534         clone->rq_disk = bdev->bd_disk;
 535         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 536         *__clone = clone;
 537
 538         if (pgpath->pg->ps.type->start_io)
 539                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 540                                               &pgpath->path,
 541                                               nr_bytes);
 542         return DM_MAPIO_REMAPPED;
 543 }
 544
 545 static void multipath_release_clone(struct request *clone)
 546 {
 547         blk_put_request(clone);
 548 }
 549
 550 /*
 551  * Map cloned bios (bio-based multipath)
 552  */
 553 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 554 {
 555         struct pgpath *pgpath;
 556         unsigned long flags;
 557         bool queue_io;
 558
 559         /* Do we need to select a new pgpath? */
 560         pgpath = READ_ONCE(m->current_pgpath);
 561         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 562         if (!pgpath || !queue_io)
 563                 pgpath = choose_pgpath(m, mpio->nr_bytes);
 564
 565         if ((pgpath && queue_io) ||
 566             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 567                 /* Queue for the daemon to resubmit */
 568                 spin_lock_irqsave(&m->lock, flags);
 569                 bio_list_add(&m->queued_bios, bio);
 570                 spin_unlock_irqrestore(&m->lock, flags);
 571                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 572                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 573                         pg_init_all_paths(m);
 574                 else if (!queue_io)
 575                         queue_work(kmultipathd, &m->process_queued_bios);
 576                 return DM_MAPIO_SUBMITTED;
 577         }
 578
 579         if (!pgpath) {
 580                 if (must_push_back_bio(m))
 581                         return DM_MAPIO_REQUEUE;
 582                 dm_report_EIO(m);
 583                 return DM_MAPIO_KILL;
 584         }
 585
 586         mpio->pgpath = pgpath;
 587
 588         bio->bi_status = 0;
 589         bio_set_dev(bio, pgpath->path.dev->bdev);
 590         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 591
 592         if (pgpath->pg->ps.type->start_io)
 593                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 594                                               &pgpath->path,
 595                                               mpio->nr_bytes);
 596         return DM_MAPIO_REMAPPED;
 597 }
 598
 599 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 600 {
 601         struct multipath *m = ti->private;
 602         struct dm_mpath_io *mpio = NULL;
 603
 604         multipath_init_per_bio_data(bio, &mpio);
 605         return __multipath_map_bio(m, bio, mpio);
 606 }
 607
 608 static void process_queued_io_list(struct multipath *m)
 609 {
 610         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 611                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 612         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 613                 queue_work(kmultipathd, &m->process_queued_bios);
 614 }
 615
 616 static void process_queued_bios(struct work_struct *work)
 617 {
 618         int r;
 619         unsigned long flags;
 620         struct bio *bio;
 621         struct bio_list bios;
 622         struct blk_plug plug;
 623         struct multipath *m =
 624                 container_of(work, struct multipath, process_queued_bios);
 625
 626         bio_list_init(&bios);
 627
 628         spin_lock_irqsave(&m->lock, flags);
 629
 630         if (bio_list_empty(&m->queued_bios)) {
 631                 spin_unlock_irqrestore(&m->lock, flags);
 632                 return;
 633         }
 634
 635         bio_list_merge(&bios, &m->queued_bios);
 636         bio_list_init(&m->queued_bios);
 637
 638         spin_unlock_irqrestore(&m->lock, flags);
 639
 640         blk_start_plug(&plug);
 641         while ((bio = bio_list_pop(&bios))) {
 642                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 643                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 644                 r = __multipath_map_bio(m, bio, mpio);
 645                 switch (r) {
 646                 case DM_MAPIO_KILL:
 647                         bio->bi_status = BLK_STS_IOERR;
 648                         bio_endio(bio);
 649                         break;
 650                 case DM_MAPIO_REQUEUE:
 651                         bio->bi_status = BLK_STS_DM_REQUEUE;
 652                         bio_endio(bio);
 653                         break;
 654                 case DM_MAPIO_REMAPPED:
 655                         generic_make_request(bio);
 656                         break;
 657                 case 0:
 658                         break;
 659                 default:
 660                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 661                 }
 662         }
 663         blk_finish_plug(&plug);
 664 }
 665
 666 /*
 667  * If we run out of usable paths, should we queue I/O or error it?
 668  */
 669 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 670                             bool save_old_value)
 671 {
 672         unsigned long flags;
 673
 674         spin_lock_irqsave(&m->lock, flags);
 675         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 676                    (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 677                    (!save_old_value && queue_if_no_path));
 678         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 679         spin_unlock_irqrestore(&m->lock, flags);
 680
 681         if (!queue_if_no_path) {
 682                 dm_table_run_md_queue_async(m->ti->table);
 683                 process_queued_io_list(m);
 684         }
 685
 686         return 0;
 687 }
 688
 689 /*
 690  * An event is triggered whenever a path is taken out of use.
 691  * Includes path failure and PG bypass.
 692  */
 693 static void trigger_event(struct work_struct *work)
 694 {
 695         struct multipath *m =
 696                 container_of(work, struct multipath, trigger_event);
 697
 698         dm_table_event(m->ti->table);
 699 }
 700
 701 /*-----------------------------------------------------------------
 702  * Constructor/argument parsing:
 703  * <#multipath feature args> [<arg>]*
 704  * <#hw_handler args> [hw_handler [<arg>]*]
 705  * <#priority groups>
 706  * <initial priority group>
 707  *     [<selector> <#selector args> [<arg>]*
 708  *      <#paths> <#per-path selector args>
 709  *         [<path> [<arg>]* ]+ ]+
 710  *---------------------------------------------------------------*/
 711 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 712                                struct dm_target *ti)
 713 {
 714         int r;
 715         struct path_selector_type *pst;
 716         unsigned ps_argc;
 717
 718         static const struct dm_arg _args[] = {
 719                 {0, 1024, "invalid number of path selector args"},
 720         };
 721
 722         pst = dm_get_path_selector(dm_shift_arg(as));
 723         if (!pst) {
 724                 ti->error = "unknown path selector type";
 725                 return -EINVAL;
 726         }
 727
 728         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 729         if (r) {
 730                 dm_put_path_selector(pst);
 731                 return -EINVAL;
 732         }
 733
 734         r = pst->create(&pg->ps, ps_argc, as->argv);
 735         if (r) {
 736                 dm_put_path_selector(pst);
 737                 ti->error = "path selector constructor failed";
 738                 return r;
 739         }
 740
 741         pg->ps.type = pst;
 742         dm_consume_args(as, ps_argc);
 743
 744         return 0;
 745 }
 746
 747 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 748                                struct dm_target *ti)
 749 {
 750         int r;
 751         struct pgpath *p;
 752         struct multipath *m = ti->private;
 753         struct request_queue *q = NULL;
 754         const char *attached_handler_name;
 755
 756         /* we need at least a path arg */
 757         if (as->argc < 1) {
 758                 ti->error = "no device given";
 759                 return ERR_PTR(-EINVAL);
 760         }
 761
 762         p = alloc_pgpath();
 763         if (!p)
 764                 return ERR_PTR(-ENOMEM);
 765
 766         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 767                           &p->path.dev);
 768         if (r) {
 769                 ti->error = "error getting device";
 770                 goto bad;
 771         }
 772
 773         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 774                 q = bdev_get_queue(p->path.dev->bdev);
 775
 776         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 777 retain:
 778                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 779                 if (attached_handler_name) {
 780                         /*
 781                          * Clear any hw_handler_params associated with a
 782                          * handler that isn't already attached.
 783                          */
 784                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 785                                 kfree(m->hw_handler_params);
 786                                 m->hw_handler_params = NULL;
 787                         }
 788
 789                         /*
 790                          * Reset hw_handler_name to match the attached handler
 791                          *
 792                          * NB. This modifies the table line to show the actual
 793                          * handler instead of the original table passed in.
 794                          */
 795                         kfree(m->hw_handler_name);
 796                         m->hw_handler_name = attached_handler_name;
 797                 }
 798         }
 799
 800         if (m->hw_handler_name) {
 801                 r = scsi_dh_attach(q, m->hw_handler_name);
 802                 if (r == -EBUSY) {
 803                         char b[BDEVNAME_SIZE];
 804
 805                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 806                                 bdevname(p->path.dev->bdev, b));
 807                         goto retain;
 808                 }
 809                 if (r < 0) {
 810                         ti->error = "error attaching hardware handler";
 811                         dm_put_device(ti, p->path.dev);
 812                         goto bad;
 813                 }
 814
 815                 if (m->hw_handler_params) {
 816                         r = scsi_dh_set_params(q, m->hw_handler_params);
 817                         if (r < 0) {
 818                                 ti->error = "unable to set hardware "
 819                                                         "handler parameters";
 820                                 dm_put_device(ti, p->path.dev);
 821                                 goto bad;
 822                         }
 823                 }
 824         }
 825
 826         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 827         if (r) {
 828                 dm_put_device(ti, p->path.dev);
 829                 goto bad;
 830         }
 831
 832         return p;
 833
 834  bad:
 835         free_pgpath(p);
 836         return ERR_PTR(r);
 837 }
 838
 839 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 840                                                    struct multipath *m)
 841 {
 842         static const struct dm_arg _args[] = {
 843                 {1, 1024, "invalid number of paths"},
 844                 {0, 1024, "invalid number of selector args"}
 845         };
 846
 847         int r;
 848         unsigned i, nr_selector_args, nr_args;
 849         struct priority_group *pg;
 850         struct dm_target *ti = m->ti;
 851
 852         if (as->argc < 2) {
 853                 as->argc = 0;
 854                 ti->error = "not enough priority group arguments";
 855                 return ERR_PTR(-EINVAL);
 856         }
 857
 858         pg = alloc_priority_group();
 859         if (!pg) {
 860                 ti->error = "couldn't allocate priority group";
 861                 return ERR_PTR(-ENOMEM);
 862         }
 863         pg->m = m;
 864
 865         r = parse_path_selector(as, pg, ti);
 866         if (r)
 867                 goto bad;
 868
 869         /*
 870          * read the paths
 871          */
 872         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 873         if (r)
 874                 goto bad;
 875
 876         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 877         if (r)
 878                 goto bad;
 879
 880         nr_args = 1 + nr_selector_args;
 881         for (i = 0; i < pg->nr_pgpaths; i++) {
 882                 struct pgpath *pgpath;
 883                 struct dm_arg_set path_args;
 884
 885                 if (as->argc < nr_args) {
 886                         ti->error = "not enough path parameters";
 887                         r = -EINVAL;
 888                         goto bad;
 889                 }
 890
 891                 path_args.argc = nr_args;
 892                 path_args.argv = as->argv;
 893
 894                 pgpath = parse_path(&path_args, &pg->ps, ti);
 895                 if (IS_ERR(pgpath)) {
 896                         r = PTR_ERR(pgpath);
 897                         goto bad;
 898                 }
 899
 900                 pgpath->pg = pg;
 901                 list_add_tail(&pgpath->list, &pg->pgpaths);
 902                 dm_consume_args(as, nr_args);
 903         }
 904
 905         return pg;
 906
 907  bad:
 908         free_priority_group(pg, ti);
 909         return ERR_PTR(r);
 910 }
 911
 912 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 913 {
 914         unsigned hw_argc;
 915         int ret;
 916         struct dm_target *ti = m->ti;
 917
 918         static const struct dm_arg _args[] = {
 919                 {0, 1024, "invalid number of hardware handler args"},
 920         };
 921
 922         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 923                 return -EINVAL;
 924
 925         if (!hw_argc)
 926                 return 0;
 927
 928         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 929                 dm_consume_args(as, hw_argc);
 930                 DMERR("bio-based multipath doesn't allow hardware handler args");
 931                 return 0;
 932         }
 933
 934         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 935         if (!m->hw_handler_name)
 936                 return -EINVAL;
 937
 938         if (hw_argc > 1) {
 939                 char *p;
 940                 int i, j, len = 4;
 941
 942                 for (i = 0; i <= hw_argc - 2; i++)
 943                         len += strlen(as->argv[i]) + 1;
 944                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 945                 if (!p) {
 946                         ti->error = "memory allocation failed";
 947                         ret = -ENOMEM;
 948                         goto fail;
 949                 }
 950                 j = sprintf(p, "%d", hw_argc - 1);
 951                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 952                         j = sprintf(p, "%s", as->argv[i]);
 953         }
 954         dm_consume_args(as, hw_argc - 1);
 955
 956         return 0;
 957 fail:
 958         kfree(m->hw_handler_name);
 959         m->hw_handler_name = NULL;
 960         return ret;
 961 }
 962
 963 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 964 {
 965         int r;
 966         unsigned argc;
 967         struct dm_target *ti = m->ti;
 968         const char *arg_name;
 969
 970         static const struct dm_arg _args[] = {
 971                 {0, 8, "invalid number of feature args"},
 972                 {1, 50, "pg_init_retries must be between 1 and 50"},
 973                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 974         };
 975
 976         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 977         if (r)
 978                 return -EINVAL;
 979
 980         if (!argc)
 981                 return 0;
 982
 983         do {
 984                 arg_name = dm_shift_arg(as);
 985                 argc--;
 986
 987                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 988                         r = queue_if_no_path(m, true, false);
 989                         continue;
 990                 }
 991
 992                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 993                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 994                         continue;
 995                 }
 996
 997                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 998                     (argc >= 1)) {
 999                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1000                         argc--;
1001                         continue;
1002                 }
1003
1004                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1005                     (argc >= 1)) {
1006                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1007                         argc--;
1008                         continue;
1009                 }
1010
1011                 if (!strcasecmp(arg_name, "queue_mode") &&
1012                     (argc >= 1)) {
1013                         const char *queue_mode_name = dm_shift_arg(as);
1014
1015                         if (!strcasecmp(queue_mode_name, "bio"))
1016                                 m->queue_mode = DM_TYPE_BIO_BASED;
1017                         else if (!strcasecmp(queue_mode_name, "rq"))
1018                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1019                         else if (!strcasecmp(queue_mode_name, "mq"))
1020                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1021                         else {
1022                                 ti->error = "Unknown 'queue_mode' requested";
1023                                 r = -EINVAL;
1024                         }
1025                         argc--;
1026                         continue;
1027                 }
1028
1029                 ti->error = "Unrecognised multipath feature request";
1030                 r = -EINVAL;
1031         } while (argc && !r);
1032
1033         return r;
1034 }
1035
1036 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1037 {
1038         /* target arguments */
1039         static const struct dm_arg _args[] = {
1040                 {0, 1024, "invalid number of priority groups"},
1041                 {0, 1024, "invalid initial priority group number"},
1042         };
1043
1044         int r;
1045         struct multipath *m;
1046         struct dm_arg_set as;
1047         unsigned pg_count = 0;
1048         unsigned next_pg_num;
1049
1050         as.argc = argc;
1051         as.argv = argv;
1052
1053         m = alloc_multipath(ti);
1054         if (!m) {
1055                 ti->error = "can't allocate multipath";
1056                 return -EINVAL;
1057         }
1058
1059         r = parse_features(&as, m);
1060         if (r)
1061                 goto bad;
1062
1063         r = alloc_multipath_stage2(ti, m);
1064         if (r)
1065                 goto bad;
1066
1067         r = parse_hw_handler(&as, m);
1068         if (r)
1069                 goto bad;
1070
1071         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1072         if (r)
1073                 goto bad;
1074
1075         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1076         if (r)
1077                 goto bad;
1078
1079         if ((!m->nr_priority_groups && next_pg_num) ||
1080             (m->nr_priority_groups && !next_pg_num)) {
1081                 ti->error = "invalid initial priority group";
1082                 r = -EINVAL;
1083                 goto bad;
1084         }
1085
1086         /* parse the priority groups */
1087         while (as.argc) {
1088                 struct priority_group *pg;
1089                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1090
1091                 pg = parse_priority_group(&as, m);
1092                 if (IS_ERR(pg)) {
1093                         r = PTR_ERR(pg);
1094                         goto bad;
1095                 }
1096
1097                 nr_valid_paths += pg->nr_pgpaths;
1098                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1099
1100                 list_add_tail(&pg->list, &m->priority_groups);
1101                 pg_count++;
1102                 pg->pg_num = pg_count;
1103                 if (!--next_pg_num)
1104                         m->next_pg = pg;
1105         }
1106
1107         if (pg_count != m->nr_priority_groups) {
1108                 ti->error = "priority group count mismatch";
1109                 r = -EINVAL;
1110                 goto bad;
1111         }
1112
1113         ti->num_flush_bios = 1;
1114         ti->num_discard_bios = 1;
1115         ti->num_write_same_bios = 1;
1116         ti->num_write_zeroes_bios = 1;
1117         if (m->queue_mode == DM_TYPE_BIO_BASED)
1118                 ti->per_io_data_size = multipath_per_bio_data_size();
1119         else
1120                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1121
1122         return 0;
1123
1124  bad:
1125         free_multipath(m);
1126         return r;
1127 }
1128
1129 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1130 {
1131         DEFINE_WAIT(wait);
1132
1133         while (1) {
1134                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1135
1136                 if (!atomic_read(&m->pg_init_in_progress))
1137                         break;
1138
1139                 io_schedule();
1140         }
1141         finish_wait(&m->pg_init_wait, &wait);
1142 }
1143
1144 static void flush_multipath_work(struct multipath *m)
1145 {
1146         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1147         smp_mb__after_atomic();
1148
1149         flush_workqueue(kmpath_handlerd);
1150         multipath_wait_for_pg_init_completion(m);
1151         flush_workqueue(kmultipathd);
1152         flush_work(&m->trigger_event);
1153
1154         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1155         smp_mb__after_atomic();
1156 }
1157
1158 static void multipath_dtr(struct dm_target *ti)
1159 {
1160         struct multipath *m = ti->private;
1161
1162         flush_multipath_work(m);
1163         free_multipath(m);
1164 }
1165
1166 /*
1167  * Take a path out of use.
1168  */
1169 static int fail_path(struct pgpath *pgpath)
1170 {
1171         unsigned long flags;
1172         struct multipath *m = pgpath->pg->m;
1173
1174         spin_lock_irqsave(&m->lock, flags);
1175
1176         if (!pgpath->is_active)
1177                 goto out;
1178
1179         DMWARN("Failing path %s.", pgpath->path.dev->name);
1180
1181         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1182         pgpath->is_active = false;
1183         pgpath->fail_count++;
1184
1185         atomic_dec(&m->nr_valid_paths);
1186
1187         if (pgpath == m->current_pgpath)
1188                 m->current_pgpath = NULL;
1189
1190         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1191                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1192
1193         schedule_work(&m->trigger_event);
1194
1195 out:
1196         spin_unlock_irqrestore(&m->lock, flags);
1197
1198         return 0;
1199 }
1200
1201 /*
1202  * Reinstate a previously-failed path
1203  */
1204 static int reinstate_path(struct pgpath *pgpath)
1205 {
1206         int r = 0, run_queue = 0;
1207         unsigned long flags;
1208         struct multipath *m = pgpath->pg->m;
1209         unsigned nr_valid_paths;
1210
1211         spin_lock_irqsave(&m->lock, flags);
1212
1213         if (pgpath->is_active)
1214                 goto out;
1215
1216         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1217
1218         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1219         if (r)
1220                 goto out;
1221
1222         pgpath->is_active = true;
1223
1224         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1225         if (nr_valid_paths == 1) {
1226                 m->current_pgpath = NULL;
1227                 run_queue = 1;
1228         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1229                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1230                         atomic_inc(&m->pg_init_in_progress);
1231         }
1232
1233         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1234                        pgpath->path.dev->name, nr_valid_paths);
1235
1236         schedule_work(&m->trigger_event);
1237
1238 out:
1239         spin_unlock_irqrestore(&m->lock, flags);
1240         if (run_queue) {
1241                 dm_table_run_md_queue_async(m->ti->table);
1242                 process_queued_io_list(m);
1243         }
1244
1245         return r;
1246 }
1247
1248 /*
1249  * Fail or reinstate all paths that match the provided struct dm_dev.
1250  */
1251 static int action_dev(struct multipath *m, struct dm_dev *dev,
1252                       action_fn action)
1253 {
1254         int r = -EINVAL;
1255         struct pgpath *pgpath;
1256         struct priority_group *pg;
1257
1258         list_for_each_entry(pg, &m->priority_groups, list) {
1259                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1260                         if (pgpath->path.dev == dev)
1261                                 r = action(pgpath);
1262                 }
1263         }
1264
1265         return r;
1266 }
1267
1268 /*
1269  * Temporarily try to avoid having to use the specified PG
1270  */
1271 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1272                       bool bypassed)
1273 {
1274         unsigned long flags;
1275
1276         spin_lock_irqsave(&m->lock, flags);
1277
1278         pg->bypassed = bypassed;
1279         m->current_pgpath = NULL;
1280         m->current_pg = NULL;
1281
1282         spin_unlock_irqrestore(&m->lock, flags);
1283
1284         schedule_work(&m->trigger_event);
1285 }
1286
1287 /*
1288  * Switch to using the specified PG from the next I/O that gets mapped
1289  */
1290 static int switch_pg_num(struct multipath *m, const char *pgstr)
1291 {
1292         struct priority_group *pg;
1293         unsigned pgnum;
1294         unsigned long flags;
1295         char dummy;
1296
1297         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1298             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1299                 DMWARN("invalid PG number supplied to switch_pg_num");
1300                 return -EINVAL;
1301         }
1302
1303         spin_lock_irqsave(&m->lock, flags);
1304         list_for_each_entry(pg, &m->priority_groups, list) {
1305                 pg->bypassed = false;
1306                 if (--pgnum)
1307                         continue;
1308
1309                 m->current_pgpath = NULL;
1310                 m->current_pg = NULL;
1311                 m->next_pg = pg;
1312         }
1313         spin_unlock_irqrestore(&m->lock, flags);
1314
1315         schedule_work(&m->trigger_event);
1316         return 0;
1317 }
1318
1319 /*
1320  * Set/clear bypassed status of a PG.
1321  * PGs are numbered upwards from 1 in the order they were declared.
1322  */
1323 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1324 {
1325         struct priority_group *pg;
1326         unsigned pgnum;
1327         char dummy;
1328
1329         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1330             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1331                 DMWARN("invalid PG number supplied to bypass_pg");
1332                 return -EINVAL;
1333         }
1334
1335         list_for_each_entry(pg, &m->priority_groups, list) {
1336                 if (!--pgnum)
1337                         break;
1338         }
1339
1340         bypass_pg(m, pg, bypassed);
1341         return 0;
1342 }
1343
1344 /*
1345  * Should we retry pg_init immediately?
1346  */
1347 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1348 {
1349         unsigned long flags;
1350         bool limit_reached = false;
1351
1352         spin_lock_irqsave(&m->lock, flags);
1353
1354         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1355             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1356                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1357         else
1358                 limit_reached = true;
1359
1360         spin_unlock_irqrestore(&m->lock, flags);
1361
1362         return limit_reached;
1363 }
1364
1365 static void pg_init_done(void *data, int errors)
1366 {
1367         struct pgpath *pgpath = data;
1368         struct priority_group *pg = pgpath->pg;
1369         struct multipath *m = pg->m;
1370         unsigned long flags;
1371         bool delay_retry = false;
1372
1373         /* device or driver problems */
1374         switch (errors) {
1375         case SCSI_DH_OK:
1376                 break;
1377         case SCSI_DH_NOSYS:
1378                 if (!m->hw_handler_name) {
1379                         errors = 0;
1380                         break;
1381                 }
1382                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1383                       "Error %d.", m->hw_handler_name, errors);
1384                 /*
1385                  * Fail path for now, so we do not ping pong
1386                  */
1387                 fail_path(pgpath);
1388                 break;
1389         case SCSI_DH_DEV_TEMP_BUSY:
1390                 /*
1391                  * Probably doing something like FW upgrade on the
1392                  * controller so try the other pg.
1393                  */
1394                 bypass_pg(m, pg, true);
1395                 break;
1396         case SCSI_DH_RETRY:
1397                 /* Wait before retrying. */
1398                 delay_retry = 1;
1399                 /* fall through */
1400         case SCSI_DH_IMM_RETRY:
1401         case SCSI_DH_RES_TEMP_UNAVAIL:
1402                 if (pg_init_limit_reached(m, pgpath))
1403                         fail_path(pgpath);
1404                 errors = 0;
1405                 break;
1406         case SCSI_DH_DEV_OFFLINED:
1407         default:
1408                 /*
1409                  * We probably do not want to fail the path for a device
1410                  * error, but this is what the old dm did. In future
1411                  * patches we can do more advanced handling.
1412                  */
1413                 fail_path(pgpath);
1414         }
1415
1416         spin_lock_irqsave(&m->lock, flags);
1417         if (errors) {
1418                 if (pgpath == m->current_pgpath) {
1419                         DMERR("Could not failover device. Error %d.", errors);
1420                         m->current_pgpath = NULL;
1421                         m->current_pg = NULL;
1422                 }
1423         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1424                 pg->bypassed = false;
1425
1426         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1427                 /* Activations of other paths are still on going */
1428                 goto out;
1429
1430         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1431                 if (delay_retry)
1432                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1433                 else
1434                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1435
1436                 if (__pg_init_all_paths(m))
1437                         goto out;
1438         }
1439         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1440
1441         process_queued_io_list(m);
1442
1443         /*
1444          * Wake up any thread waiting to suspend.
1445          */
1446         wake_up(&m->pg_init_wait);
1447
1448 out:
1449         spin_unlock_irqrestore(&m->lock, flags);
1450 }
1451
1452 static void activate_or_offline_path(struct pgpath *pgpath)
1453 {
1454         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1455
1456         if (pgpath->is_active && !blk_queue_dying(q))
1457                 scsi_dh_activate(q, pg_init_done, pgpath);
1458         else
1459                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1460 }
1461
1462 static void activate_path_work(struct work_struct *work)
1463 {
1464         struct pgpath *pgpath =
1465                 container_of(work, struct pgpath, activate_path.work);
1466
1467         activate_or_offline_path(pgpath);
1468 }
1469
1470 static int noretry_error(blk_status_t error)
1471 {
1472         switch (error) {
1473         case BLK_STS_NOTSUPP:
1474         case BLK_STS_NOSPC:
1475         case BLK_STS_TARGET:
1476         case BLK_STS_NEXUS:
1477         case BLK_STS_MEDIUM:
1478                 return 1;
1479         }
1480
1481         /* Anything else could be a path failure, so should be retried */
1482         return 0;
1483 }
1484
1485 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1486                             blk_status_t error, union map_info *map_context)
1487 {
1488         struct dm_mpath_io *mpio = get_mpio(map_context);
1489         struct pgpath *pgpath = mpio->pgpath;
1490         int r = DM_ENDIO_DONE;
1491
1492         /*
1493          * We don't queue any clone request inside the multipath target
1494          * during end I/O handling, since those clone requests don't have
1495          * bio clones.  If we queue them inside the multipath target,
1496          * we need to make bio clones, that requires memory allocation.
1497          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1498          *  don't have bio clones.)
1499          * Instead of queueing the clone request here, we queue the original
1500          * request into dm core, which will remake a clone request and
1501          * clone bios for it and resubmit it later.
1502          */
1503         if (error && !noretry_error(error)) {
1504                 struct multipath *m = ti->private;
1505
1506                 r = DM_ENDIO_REQUEUE;
1507
1508                 if (pgpath)
1509                         fail_path(pgpath);
1510
1511                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1512                     !must_push_back_rq(m)) {
1513                         if (error == BLK_STS_IOERR)
1514                                 dm_report_EIO(m);
1515                         /* complete with the original error */
1516                         r = DM_ENDIO_DONE;
1517                 }
1518         }
1519
1520         if (pgpath) {
1521                 struct path_selector *ps = &pgpath->pg->ps;
1522
1523                 if (ps->type->end_io)
1524                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1525         }
1526
1527         return r;
1528 }
1529
1530 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1531                 blk_status_t *error)
1532 {
1533         struct multipath *m = ti->private;
1534         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1535         struct pgpath *pgpath = mpio->pgpath;
1536         unsigned long flags;
1537         int r = DM_ENDIO_DONE;
1538
1539         if (!*error || noretry_error(*error))
1540                 goto done;
1541
1542         if (pgpath)
1543                 fail_path(pgpath);
1544
1545         if (atomic_read(&m->nr_valid_paths) == 0 &&
1546             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1547                 if (must_push_back_bio(m)) {
1548                         r = DM_ENDIO_REQUEUE;
1549                 } else {
1550                         dm_report_EIO(m);
1551                         *error = BLK_STS_IOERR;
1552                 }
1553                 goto done;
1554         }
1555
1556         spin_lock_irqsave(&m->lock, flags);
1557         bio_list_add(&m->queued_bios, clone);
1558         spin_unlock_irqrestore(&m->lock, flags);
1559         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1560                 queue_work(kmultipathd, &m->process_queued_bios);
1561
1562         r = DM_ENDIO_INCOMPLETE;
1563 done:
1564         if (pgpath) {
1565                 struct path_selector *ps = &pgpath->pg->ps;
1566
1567                 if (ps->type->end_io)
1568                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1569         }
1570
1571         return r;
1572 }
1573
1574 /*
1575  * Suspend can't complete until all the I/O is processed so if
1576  * the last path fails we must error any remaining I/O.
1577  * Note that if the freeze_bdev fails while suspending, the
1578  * queue_if_no_path state is lost - userspace should reset it.
1579  */
1580 static void multipath_presuspend(struct dm_target *ti)
1581 {
1582         struct multipath *m = ti->private;
1583
1584         queue_if_no_path(m, false, true);
1585 }
1586
1587 static void multipath_postsuspend(struct dm_target *ti)
1588 {
1589         struct multipath *m = ti->private;
1590
1591         mutex_lock(&m->work_mutex);
1592         flush_multipath_work(m);
1593         mutex_unlock(&m->work_mutex);
1594 }
1595
1596 /*
1597  * Restore the queue_if_no_path setting.
1598  */
1599 static void multipath_resume(struct dm_target *ti)
1600 {
1601         struct multipath *m = ti->private;
1602         unsigned long flags;
1603
1604         spin_lock_irqsave(&m->lock, flags);
1605         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1606                    test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1607         spin_unlock_irqrestore(&m->lock, flags);
1608 }
1609
1610 /*
1611  * Info output has the following format:
1612  * num_multipath_feature_args [multipath_feature_args]*
1613  * num_handler_status_args [handler_status_args]*
1614  * num_groups init_group_number
1615  *            [A|D|E num_ps_status_args [ps_status_args]*
1616  *             num_paths num_selector_args
1617  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1618  *
1619  * Table output has the following format (identical to the constructor string):
1620  * num_feature_args [features_args]*
1621  * num_handler_args hw_handler [hw_handler_args]*
1622  * num_groups init_group_number
1623  *     [priority selector-name num_ps_args [ps_args]*
1624  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1625  */
1626 static void multipath_status(struct dm_target *ti, status_type_t type,
1627                              unsigned status_flags, char *result, unsigned maxlen)
1628 {
1629         int sz = 0;
1630         unsigned long flags;
1631         struct multipath *m = ti->private;
1632         struct priority_group *pg;
1633         struct pgpath *p;
1634         unsigned pg_num;
1635         char state;
1636
1637         spin_lock_irqsave(&m->lock, flags);
1638
1639         /* Features */
1640         if (type == STATUSTYPE_INFO)
1641                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1642                        atomic_read(&m->pg_init_count));
1643         else {
1644                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1645                               (m->pg_init_retries > 0) * 2 +
1646                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1647                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1648                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1649
1650                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1651                         DMEMIT("queue_if_no_path ");
1652                 if (m->pg_init_retries)
1653                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1654                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1655                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1656                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1657                         DMEMIT("retain_attached_hw_handler ");
1658                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1659                         switch(m->queue_mode) {
1660                         case DM_TYPE_BIO_BASED:
1661                                 DMEMIT("queue_mode bio ");
1662                                 break;
1663                         case DM_TYPE_MQ_REQUEST_BASED:
1664                                 DMEMIT("queue_mode mq ");
1665                                 break;
1666                         default:
1667                                 WARN_ON_ONCE(true);
1668                                 break;
1669                         }
1670                 }
1671         }
1672
1673         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1674                 DMEMIT("0 ");
1675         else
1676                 DMEMIT("1 %s ", m->hw_handler_name);
1677
1678         DMEMIT("%u ", m->nr_priority_groups);
1679
1680         if (m->next_pg)
1681                 pg_num = m->next_pg->pg_num;
1682         else if (m->current_pg)
1683                 pg_num = m->current_pg->pg_num;
1684         else
1685                 pg_num = (m->nr_priority_groups ? 1 : 0);
1686
1687         DMEMIT("%u ", pg_num);
1688
1689         switch (type) {
1690         case STATUSTYPE_INFO:
1691                 list_for_each_entry(pg, &m->priority_groups, list) {
1692                         if (pg->bypassed)
1693                                 state = 'D';    /* Disabled */
1694                         else if (pg == m->current_pg)
1695                                 state = 'A';    /* Currently Active */
1696                         else
1697                                 state = 'E';    /* Enabled */
1698
1699                         DMEMIT("%c ", state);
1700
1701                         if (pg->ps.type->status)
1702                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1703                                                           result + sz,
1704                                                           maxlen - sz);
1705                         else
1706                                 DMEMIT("0 ");
1707
1708                         DMEMIT("%u %u ", pg->nr_pgpaths,
1709                                pg->ps.type->info_args);
1710
1711                         list_for_each_entry(p, &pg->pgpaths, list) {
1712                                 DMEMIT("%s %s %u ", p->path.dev->name,
1713                                        p->is_active ? "A" : "F",
1714                                        p->fail_count);
1715                                 if (pg->ps.type->status)
1716                                         sz += pg->ps.type->status(&pg->ps,
1717                                               &p->path, type, result + sz,
1718                                               maxlen - sz);
1719                         }
1720                 }
1721                 break;
1722
1723         case STATUSTYPE_TABLE:
1724                 list_for_each_entry(pg, &m->priority_groups, list) {
1725                         DMEMIT("%s ", pg->ps.type->name);
1726
1727                         if (pg->ps.type->status)
1728                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1729                                                           result + sz,
1730                                                           maxlen - sz);
1731                         else
1732                                 DMEMIT("0 ");
1733
1734                         DMEMIT("%u %u ", pg->nr_pgpaths,
1735                                pg->ps.type->table_args);
1736
1737                         list_for_each_entry(p, &pg->pgpaths, list) {
1738                                 DMEMIT("%s ", p->path.dev->name);
1739                                 if (pg->ps.type->status)
1740                                         sz += pg->ps.type->status(&pg->ps,
1741                                               &p->path, type, result + sz,
1742                                               maxlen - sz);
1743                         }
1744                 }
1745                 break;
1746         }
1747
1748         spin_unlock_irqrestore(&m->lock, flags);
1749 }
1750
1751 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1752 {
1753         int r = -EINVAL;
1754         struct dm_dev *dev;
1755         struct multipath *m = ti->private;
1756         action_fn action;
1757
1758         mutex_lock(&m->work_mutex);
1759
1760         if (dm_suspended(ti)) {
1761                 r = -EBUSY;
1762                 goto out;
1763         }
1764
1765         if (argc == 1) {
1766                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1767                         r = queue_if_no_path(m, true, false);
1768                         goto out;
1769                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1770                         r = queue_if_no_path(m, false, false);
1771                         goto out;
1772                 }
1773         }
1774
1775         if (argc != 2) {
1776                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1777                 goto out;
1778         }
1779
1780         if (!strcasecmp(argv[0], "disable_group")) {
1781                 r = bypass_pg_num(m, argv[1], true);
1782                 goto out;
1783         } else if (!strcasecmp(argv[0], "enable_group")) {
1784                 r = bypass_pg_num(m, argv[1], false);
1785                 goto out;
1786         } else if (!strcasecmp(argv[0], "switch_group")) {
1787                 r = switch_pg_num(m, argv[1]);
1788                 goto out;
1789         } else if (!strcasecmp(argv[0], "reinstate_path"))
1790                 action = reinstate_path;
1791         else if (!strcasecmp(argv[0], "fail_path"))
1792                 action = fail_path;
1793         else {
1794                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1795                 goto out;
1796         }
1797
1798         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1799         if (r) {
1800                 DMWARN("message: error getting device %s",
1801                        argv[1]);
1802                 goto out;
1803         }
1804
1805         r = action_dev(m, dev, action);
1806
1807         dm_put_device(ti, dev);
1808
1809 out:
1810         mutex_unlock(&m->work_mutex);
1811         return r;
1812 }
1813
1814 static int multipath_prepare_ioctl(struct dm_target *ti,
1815                 struct block_device **bdev, fmode_t *mode)
1816 {
1817         struct multipath *m = ti->private;
1818         struct pgpath *current_pgpath;
1819         int r;
1820
1821         current_pgpath = READ_ONCE(m->current_pgpath);
1822         if (!current_pgpath)
1823                 current_pgpath = choose_pgpath(m, 0);
1824
1825         if (current_pgpath) {
1826                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1827                         *bdev = current_pgpath->path.dev->bdev;
1828                         *mode = current_pgpath->path.dev->mode;
1829                         r = 0;
1830                 } else {
1831                         /* pg_init has not started or completed */
1832                         r = -ENOTCONN;
1833                 }
1834         } else {
1835                 /* No path is available */
1836                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1837                         r = -ENOTCONN;
1838                 else
1839                         r = -EIO;
1840         }
1841
1842         if (r == -ENOTCONN) {
1843                 if (!READ_ONCE(m->current_pg)) {
1844                         /* Path status changed, redo selection */
1845                         (void) choose_pgpath(m, 0);
1846                 }
1847                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1848                         pg_init_all_paths(m);
1849                 dm_table_run_md_queue_async(m->ti->table);
1850                 process_queued_io_list(m);
1851         }
1852
1853         /*
1854          * Only pass ioctls through if the device sizes match exactly.
1855          */
1856         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1857                 return 1;
1858         return r;
1859 }
1860
1861 static int multipath_iterate_devices(struct dm_target *ti,
1862                                      iterate_devices_callout_fn fn, void *data)
1863 {
1864         struct multipath *m = ti->private;
1865         struct priority_group *pg;
1866         struct pgpath *p;
1867         int ret = 0;
1868
1869         list_for_each_entry(pg, &m->priority_groups, list) {
1870                 list_for_each_entry(p, &pg->pgpaths, list) {
1871                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1872                         if (ret)
1873                                 goto out;
1874                 }
1875         }
1876
1877 out:
1878         return ret;
1879 }
1880
1881 static int pgpath_busy(struct pgpath *pgpath)
1882 {
1883         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1884
1885         return blk_lld_busy(q);
1886 }
1887
1888 /*
1889  * We return "busy", only when we can map I/Os but underlying devices
1890  * are busy (so even if we map I/Os now, the I/Os will wait on
1891  * the underlying queue).
1892  * In other words, if we want to kill I/Os or queue them inside us
1893  * due to map unavailability, we don't return "busy".  Otherwise,
1894  * dm core won't give us the I/Os and we can't do what we want.
1895  */
1896 static int multipath_busy(struct dm_target *ti)
1897 {
1898         bool busy = false, has_active = false;
1899         struct multipath *m = ti->private;
1900         struct priority_group *pg, *next_pg;
1901         struct pgpath *pgpath;
1902
1903         /* pg_init in progress */
1904         if (atomic_read(&m->pg_init_in_progress))
1905                 return true;
1906
1907         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1908         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1909                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1910
1911         /* Guess which priority_group will be used at next mapping time */
1912         pg = READ_ONCE(m->current_pg);
1913         next_pg = READ_ONCE(m->next_pg);
1914         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1915                 pg = next_pg;
1916
1917         if (!pg) {
1918                 /*
1919                  * We don't know which pg will be used at next mapping time.
1920                  * We don't call choose_pgpath() here to avoid to trigger
1921                  * pg_init just by busy checking.
1922                  * So we don't know whether underlying devices we will be using
1923                  * at next mapping time are busy or not. Just try mapping.
1924                  */
1925                 return busy;
1926         }
1927
1928         /*
1929          * If there is one non-busy active path at least, the path selector
1930          * will be able to select it. So we consider such a pg as not busy.
1931          */
1932         busy = true;
1933         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1934                 if (pgpath->is_active) {
1935                         has_active = true;
1936                         if (!pgpath_busy(pgpath)) {
1937                                 busy = false;
1938                                 break;
1939                         }
1940                 }
1941         }
1942
1943         if (!has_active) {
1944                 /*
1945                  * No active path in this pg, so this pg won't be used and
1946                  * the current_pg will be changed at next mapping time.
1947                  * We need to try mapping to determine it.
1948                  */
1949                 busy = false;
1950         }
1951
1952         return busy;
1953 }
1954
1955 /*-----------------------------------------------------------------
1956  * Module setup
1957  *---------------------------------------------------------------*/
1958 static struct target_type multipath_target = {
1959         .name = "multipath",
1960         .version = {1, 12, 0},
1961         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1962         .module = THIS_MODULE,
1963         .ctr = multipath_ctr,
1964         .dtr = multipath_dtr,
1965         .clone_and_map_rq = multipath_clone_and_map,
1966         .release_clone_rq = multipath_release_clone,
1967         .rq_end_io = multipath_end_io,
1968         .map = multipath_map_bio,
1969         .end_io = multipath_end_io_bio,
1970         .presuspend = multipath_presuspend,
1971         .postsuspend = multipath_postsuspend,
1972         .resume = multipath_resume,
1973         .status = multipath_status,
1974         .message = multipath_message,
1975         .prepare_ioctl = multipath_prepare_ioctl,
1976         .iterate_devices = multipath_iterate_devices,
1977         .busy = multipath_busy,
1978 };
1979
1980 static int __init dm_multipath_init(void)
1981 {
1982         int r;
1983
1984         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1985         if (!kmultipathd) {
1986                 DMERR("failed to create workqueue kmpathd");
1987                 r = -ENOMEM;
1988                 goto bad_alloc_kmultipathd;
1989         }
1990
1991         /*
1992          * A separate workqueue is used to handle the device handlers
1993          * to avoid overloading existing workqueue. Overloading the
1994          * old workqueue would also create a bottleneck in the
1995          * path of the storage hardware device activation.
1996          */
1997         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1998                                                   WQ_MEM_RECLAIM);
1999         if (!kmpath_handlerd) {
2000                 DMERR("failed to create workqueue kmpath_handlerd");
2001                 r = -ENOMEM;
2002                 goto bad_alloc_kmpath_handlerd;
2003         }
2004
2005         r = dm_register_target(&multipath_target);
2006         if (r < 0) {
2007                 DMERR("request-based register failed %d", r);
2008                 r = -EINVAL;
2009                 goto bad_register_target;
2010         }
2011
2012         return 0;
2013
2014 bad_register_target:
2015         destroy_workqueue(kmpath_handlerd);
2016 bad_alloc_kmpath_handlerd:
2017         destroy_workqueue(kmultipathd);
2018 bad_alloc_kmultipathd:
2019         return r;
2020 }
2021
2022 static void __exit dm_multipath_exit(void)
2023 {
2024         destroy_workqueue(kmpath_handlerd);
2025         destroy_workqueue(kmultipathd);
2026
2027         dm_unregister_target(&multipath_target);
2028 }
2029
2030 module_init(dm_multipath_init);
2031 module_exit(dm_multipath_exit);
2032
2033 MODULE_DESCRIPTION(DM_NAME " multipath target");
2034 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2035 MODULE_LICENSE("GPL");