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(READ_ONCE(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 (READ_ONCE(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 = READ_ONCE(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  * Check whether bios must be queued in the device-mapper core rather
 462  * than here in the target.
 463  *
 464  * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
 465  * the same value then we are not between multipath_presuspend()
 466  * and multipath_resume() calls and we have no need to check
 467  * for the DMF_NOFLUSH_SUSPENDING flag.
 468  */
 469 static bool __must_push_back(struct multipath *m, unsigned long flags)
 470 {
 471         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
 472                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
 473                 dm_noflush_suspending(m->ti));
 474 }
 475
 476 /*
 477  * Following functions use READ_ONCE to get atomic access to
 478  * all m->flags to avoid taking spinlock
 479  */
 480 static bool must_push_back_rq(struct multipath *m)
 481 {
 482         unsigned long flags = READ_ONCE(m->flags);
 483         return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
 484 }
 485
 486 static bool must_push_back_bio(struct multipath *m)
 487 {
 488         unsigned long flags = READ_ONCE(m->flags);
 489         return __must_push_back(m, flags);
 490 }
 491
 492 /*
 493  * Map cloned requests (request-based multipath)
 494  */
 495 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 496                                    union map_info *map_context,
 497                                    struct request **__clone)
 498 {
 499         struct multipath *m = ti->private;
 500         size_t nr_bytes = blk_rq_bytes(rq);
 501         struct pgpath *pgpath;
 502         struct block_device *bdev;
 503         struct dm_mpath_io *mpio = get_mpio(map_context);
 504         struct request_queue *q;
 505         struct request *clone;
 506
 507         /* Do we need to select a new pgpath? */
 508         pgpath = READ_ONCE(m->current_pgpath);
 509         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 510                 pgpath = choose_pgpath(m, nr_bytes);
 511
 512         if (!pgpath) {
 513                 if (must_push_back_rq(m))
 514                         return DM_MAPIO_DELAY_REQUEUE;
 515                 dm_report_EIO(m);       /* Failed */
 516                 return DM_MAPIO_KILL;
 517         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 518                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 519                 if (pg_init_all_paths(m))
 520                         return DM_MAPIO_DELAY_REQUEUE;
 521                 return DM_MAPIO_REQUEUE;
 522         }
 523
 524         memset(mpio, 0, sizeof(*mpio));
 525         mpio->pgpath = pgpath;
 526         mpio->nr_bytes = nr_bytes;
 527
 528         bdev = pgpath->path.dev->bdev;
 529         q = bdev_get_queue(bdev);
 530         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
 531         if (IS_ERR(clone)) {
 532                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 533                 bool queue_dying = blk_queue_dying(q);
 534                 if (queue_dying) {
 535                         atomic_inc(&m->pg_init_in_progress);
 536                         activate_or_offline_path(pgpath);
 537                 }
 538                 return DM_MAPIO_DELAY_REQUEUE;
 539         }
 540         clone->bio = clone->biotail = NULL;
 541         clone->rq_disk = bdev->bd_disk;
 542         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 543         *__clone = clone;
 544
 545         if (pgpath->pg->ps.type->start_io)
 546                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 547                                               &pgpath->path,
 548                                               nr_bytes);
 549         return DM_MAPIO_REMAPPED;
 550 }
 551
 552 static void multipath_release_clone(struct request *clone)
 553 {
 554         blk_put_request(clone);
 555 }
 556
 557 /*
 558  * Map cloned bios (bio-based multipath)
 559  */
 560 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 561 {
 562         size_t nr_bytes = bio->bi_iter.bi_size;
 563         struct pgpath *pgpath;
 564         unsigned long flags;
 565         bool queue_io;
 566
 567         /* Do we need to select a new pgpath? */
 568         pgpath = READ_ONCE(m->current_pgpath);
 569         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 570         if (!pgpath || !queue_io)
 571                 pgpath = choose_pgpath(m, nr_bytes);
 572
 573         if ((pgpath && queue_io) ||
 574             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 575                 /* Queue for the daemon to resubmit */
 576                 spin_lock_irqsave(&m->lock, flags);
 577                 bio_list_add(&m->queued_bios, bio);
 578                 spin_unlock_irqrestore(&m->lock, flags);
 579                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 580                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 581                         pg_init_all_paths(m);
 582                 else if (!queue_io)
 583                         queue_work(kmultipathd, &m->process_queued_bios);
 584                 return DM_MAPIO_SUBMITTED;
 585         }
 586
 587         if (!pgpath) {
 588                 if (must_push_back_bio(m))
 589                         return DM_MAPIO_REQUEUE;
 590                 dm_report_EIO(m);
 591                 return DM_MAPIO_KILL;
 592         }
 593
 594         mpio->pgpath = pgpath;
 595         mpio->nr_bytes = nr_bytes;
 596
 597         bio->bi_status = 0;
 598         bio_set_dev(bio, pgpath->path.dev->bdev);
 599         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 600
 601         if (pgpath->pg->ps.type->start_io)
 602                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 603                                               &pgpath->path,
 604                                               nr_bytes);
 605         return DM_MAPIO_REMAPPED;
 606 }
 607
 608 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 609 {
 610         struct multipath *m = ti->private;
 611         struct dm_mpath_io *mpio = NULL;
 612
 613         multipath_init_per_bio_data(bio, &mpio, NULL);
 614
 615         return __multipath_map_bio(m, bio, mpio);
 616 }
 617
 618 static void process_queued_io_list(struct multipath *m)
 619 {
 620         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 621                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 622         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 623                 queue_work(kmultipathd, &m->process_queued_bios);
 624 }
 625
 626 static void process_queued_bios(struct work_struct *work)
 627 {
 628         int r;
 629         unsigned long flags;
 630         struct bio *bio;
 631         struct bio_list bios;
 632         struct blk_plug plug;
 633         struct multipath *m =
 634                 container_of(work, struct multipath, process_queued_bios);
 635
 636         bio_list_init(&bios);
 637
 638         spin_lock_irqsave(&m->lock, flags);
 639
 640         if (bio_list_empty(&m->queued_bios)) {
 641                 spin_unlock_irqrestore(&m->lock, flags);
 642                 return;
 643         }
 644
 645         bio_list_merge(&bios, &m->queued_bios);
 646         bio_list_init(&m->queued_bios);
 647
 648         spin_unlock_irqrestore(&m->lock, flags);
 649
 650         blk_start_plug(&plug);
 651         while ((bio = bio_list_pop(&bios))) {
 652                 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
 653                 switch (r) {
 654                 case DM_MAPIO_KILL:
 655                         bio->bi_status = BLK_STS_IOERR;
 656                         bio_endio(bio);
 657                         break;
 658                 case DM_MAPIO_REQUEUE:
 659                         bio->bi_status = BLK_STS_DM_REQUEUE;
 660                         bio_endio(bio);
 661                         break;
 662                 case DM_MAPIO_REMAPPED:
 663                         generic_make_request(bio);
 664                         break;
 665                 case 0:
 666                         break;
 667                 default:
 668                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 669                 }
 670         }
 671         blk_finish_plug(&plug);
 672 }
 673
 674 /*
 675  * If we run out of usable paths, should we queue I/O or error it?
 676  */
 677 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 678                             bool save_old_value)
 679 {
 680         unsigned long flags;
 681
 682         spin_lock_irqsave(&m->lock, flags);
 683         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 684                    (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 685                    (!save_old_value && queue_if_no_path));
 686         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 687         spin_unlock_irqrestore(&m->lock, flags);
 688
 689         if (!queue_if_no_path) {
 690                 dm_table_run_md_queue_async(m->ti->table);
 691                 process_queued_io_list(m);
 692         }
 693
 694         return 0;
 695 }
 696
 697 /*
 698  * An event is triggered whenever a path is taken out of use.
 699  * Includes path failure and PG bypass.
 700  */
 701 static void trigger_event(struct work_struct *work)
 702 {
 703         struct multipath *m =
 704                 container_of(work, struct multipath, trigger_event);
 705
 706         dm_table_event(m->ti->table);
 707 }
 708
 709 /*-----------------------------------------------------------------
 710  * Constructor/argument parsing:
 711  * <#multipath feature args> [<arg>]*
 712  * <#hw_handler args> [hw_handler [<arg>]*]
 713  * <#priority groups>
 714  * <initial priority group>
 715  *     [<selector> <#selector args> [<arg>]*
 716  *      <#paths> <#per-path selector args>
 717  *         [<path> [<arg>]* ]+ ]+
 718  *---------------------------------------------------------------*/
 719 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 720                                struct dm_target *ti)
 721 {
 722         int r;
 723         struct path_selector_type *pst;
 724         unsigned ps_argc;
 725
 726         static const struct dm_arg _args[] = {
 727                 {0, 1024, "invalid number of path selector args"},
 728         };
 729
 730         pst = dm_get_path_selector(dm_shift_arg(as));
 731         if (!pst) {
 732                 ti->error = "unknown path selector type";
 733                 return -EINVAL;
 734         }
 735
 736         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 737         if (r) {
 738                 dm_put_path_selector(pst);
 739                 return -EINVAL;
 740         }
 741
 742         r = pst->create(&pg->ps, ps_argc, as->argv);
 743         if (r) {
 744                 dm_put_path_selector(pst);
 745                 ti->error = "path selector constructor failed";
 746                 return r;
 747         }
 748
 749         pg->ps.type = pst;
 750         dm_consume_args(as, ps_argc);
 751
 752         return 0;
 753 }
 754
 755 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 756                                struct dm_target *ti)
 757 {
 758         int r;
 759         struct pgpath *p;
 760         struct multipath *m = ti->private;
 761         struct request_queue *q = NULL;
 762         const char *attached_handler_name;
 763
 764         /* we need at least a path arg */
 765         if (as->argc < 1) {
 766                 ti->error = "no device given";
 767                 return ERR_PTR(-EINVAL);
 768         }
 769
 770         p = alloc_pgpath();
 771         if (!p)
 772                 return ERR_PTR(-ENOMEM);
 773
 774         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 775                           &p->path.dev);
 776         if (r) {
 777                 ti->error = "error getting device";
 778                 goto bad;
 779         }
 780
 781         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 782                 q = bdev_get_queue(p->path.dev->bdev);
 783
 784         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 785 retain:
 786                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 787                 if (attached_handler_name) {
 788                         /*
 789                          * Clear any hw_handler_params associated with a
 790                          * handler that isn't already attached.
 791                          */
 792                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 793                                 kfree(m->hw_handler_params);
 794                                 m->hw_handler_params = NULL;
 795                         }
 796
 797                         /*
 798                          * Reset hw_handler_name to match the attached handler
 799                          *
 800                          * NB. This modifies the table line to show the actual
 801                          * handler instead of the original table passed in.
 802                          */
 803                         kfree(m->hw_handler_name);
 804                         m->hw_handler_name = attached_handler_name;
 805                 }
 806         }
 807
 808         if (m->hw_handler_name) {
 809                 r = scsi_dh_attach(q, m->hw_handler_name);
 810                 if (r == -EBUSY) {
 811                         char b[BDEVNAME_SIZE];
 812
 813                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 814                                 bdevname(p->path.dev->bdev, b));
 815                         goto retain;
 816                 }
 817                 if (r < 0) {
 818                         ti->error = "error attaching hardware handler";
 819                         dm_put_device(ti, p->path.dev);
 820                         goto bad;
 821                 }
 822
 823                 if (m->hw_handler_params) {
 824                         r = scsi_dh_set_params(q, m->hw_handler_params);
 825                         if (r < 0) {
 826                                 ti->error = "unable to set hardware "
 827                                                         "handler parameters";
 828                                 dm_put_device(ti, p->path.dev);
 829                                 goto bad;
 830                         }
 831                 }
 832         }
 833
 834         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 835         if (r) {
 836                 dm_put_device(ti, p->path.dev);
 837                 goto bad;
 838         }
 839
 840         return p;
 841
 842  bad:
 843         free_pgpath(p);
 844         return ERR_PTR(r);
 845 }
 846
 847 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 848                                                    struct multipath *m)
 849 {
 850         static const struct dm_arg _args[] = {
 851                 {1, 1024, "invalid number of paths"},
 852                 {0, 1024, "invalid number of selector args"}
 853         };
 854
 855         int r;
 856         unsigned i, nr_selector_args, nr_args;
 857         struct priority_group *pg;
 858         struct dm_target *ti = m->ti;
 859
 860         if (as->argc < 2) {
 861                 as->argc = 0;
 862                 ti->error = "not enough priority group arguments";
 863                 return ERR_PTR(-EINVAL);
 864         }
 865
 866         pg = alloc_priority_group();
 867         if (!pg) {
 868                 ti->error = "couldn't allocate priority group";
 869                 return ERR_PTR(-ENOMEM);
 870         }
 871         pg->m = m;
 872
 873         r = parse_path_selector(as, pg, ti);
 874         if (r)
 875                 goto bad;
 876
 877         /*
 878          * read the paths
 879          */
 880         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 881         if (r)
 882                 goto bad;
 883
 884         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 885         if (r)
 886                 goto bad;
 887
 888         nr_args = 1 + nr_selector_args;
 889         for (i = 0; i < pg->nr_pgpaths; i++) {
 890                 struct pgpath *pgpath;
 891                 struct dm_arg_set path_args;
 892
 893                 if (as->argc < nr_args) {
 894                         ti->error = "not enough path parameters";
 895                         r = -EINVAL;
 896                         goto bad;
 897                 }
 898
 899                 path_args.argc = nr_args;
 900                 path_args.argv = as->argv;
 901
 902                 pgpath = parse_path(&path_args, &pg->ps, ti);
 903                 if (IS_ERR(pgpath)) {
 904                         r = PTR_ERR(pgpath);
 905                         goto bad;
 906                 }
 907
 908                 pgpath->pg = pg;
 909                 list_add_tail(&pgpath->list, &pg->pgpaths);
 910                 dm_consume_args(as, nr_args);
 911         }
 912
 913         return pg;
 914
 915  bad:
 916         free_priority_group(pg, ti);
 917         return ERR_PTR(r);
 918 }
 919
 920 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 921 {
 922         unsigned hw_argc;
 923         int ret;
 924         struct dm_target *ti = m->ti;
 925
 926         static const struct dm_arg _args[] = {
 927                 {0, 1024, "invalid number of hardware handler args"},
 928         };
 929
 930         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 931                 return -EINVAL;
 932
 933         if (!hw_argc)
 934                 return 0;
 935
 936         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 937                 dm_consume_args(as, hw_argc);
 938                 DMERR("bio-based multipath doesn't allow hardware handler args");
 939                 return 0;
 940         }
 941
 942         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 943         if (!m->hw_handler_name)
 944                 return -EINVAL;
 945
 946         if (hw_argc > 1) {
 947                 char *p;
 948                 int i, j, len = 4;
 949
 950                 for (i = 0; i <= hw_argc - 2; i++)
 951                         len += strlen(as->argv[i]) + 1;
 952                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 953                 if (!p) {
 954                         ti->error = "memory allocation failed";
 955                         ret = -ENOMEM;
 956                         goto fail;
 957                 }
 958                 j = sprintf(p, "%d", hw_argc - 1);
 959                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 960                         j = sprintf(p, "%s", as->argv[i]);
 961         }
 962         dm_consume_args(as, hw_argc - 1);
 963
 964         return 0;
 965 fail:
 966         kfree(m->hw_handler_name);
 967         m->hw_handler_name = NULL;
 968         return ret;
 969 }
 970
 971 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 972 {
 973         int r;
 974         unsigned argc;
 975         struct dm_target *ti = m->ti;
 976         const char *arg_name;
 977
 978         static const struct dm_arg _args[] = {
 979                 {0, 8, "invalid number of feature args"},
 980                 {1, 50, "pg_init_retries must be between 1 and 50"},
 981                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 982         };
 983
 984         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 985         if (r)
 986                 return -EINVAL;
 987
 988         if (!argc)
 989                 return 0;
 990
 991         do {
 992                 arg_name = dm_shift_arg(as);
 993                 argc--;
 994
 995                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 996                         r = queue_if_no_path(m, true, false);
 997                         continue;
 998                 }
 999
1000                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1001                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1002                         continue;
1003                 }
1004
1005                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1006                     (argc >= 1)) {
1007                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1008                         argc--;
1009                         continue;
1010                 }
1011
1012                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1013                     (argc >= 1)) {
1014                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1015                         argc--;
1016                         continue;
1017                 }
1018
1019                 if (!strcasecmp(arg_name, "queue_mode") &&
1020                     (argc >= 1)) {
1021                         const char *queue_mode_name = dm_shift_arg(as);
1022
1023                         if (!strcasecmp(queue_mode_name, "bio"))
1024                                 m->queue_mode = DM_TYPE_BIO_BASED;
1025                         else if (!strcasecmp(queue_mode_name, "rq"))
1026                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1027                         else if (!strcasecmp(queue_mode_name, "mq"))
1028                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1029                         else {
1030                                 ti->error = "Unknown 'queue_mode' requested";
1031                                 r = -EINVAL;
1032                         }
1033                         argc--;
1034                         continue;
1035                 }
1036
1037                 ti->error = "Unrecognised multipath feature request";
1038                 r = -EINVAL;
1039         } while (argc && !r);
1040
1041         return r;
1042 }
1043
1044 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1045 {
1046         /* target arguments */
1047         static const struct dm_arg _args[] = {
1048                 {0, 1024, "invalid number of priority groups"},
1049                 {0, 1024, "invalid initial priority group number"},
1050         };
1051
1052         int r;
1053         struct multipath *m;
1054         struct dm_arg_set as;
1055         unsigned pg_count = 0;
1056         unsigned next_pg_num;
1057
1058         as.argc = argc;
1059         as.argv = argv;
1060
1061         m = alloc_multipath(ti);
1062         if (!m) {
1063                 ti->error = "can't allocate multipath";
1064                 return -EINVAL;
1065         }
1066
1067         r = parse_features(&as, m);
1068         if (r)
1069                 goto bad;
1070
1071         r = alloc_multipath_stage2(ti, m);
1072         if (r)
1073                 goto bad;
1074
1075         r = parse_hw_handler(&as, m);
1076         if (r)
1077                 goto bad;
1078
1079         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1080         if (r)
1081                 goto bad;
1082
1083         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1084         if (r)
1085                 goto bad;
1086
1087         if ((!m->nr_priority_groups && next_pg_num) ||
1088             (m->nr_priority_groups && !next_pg_num)) {
1089                 ti->error = "invalid initial priority group";
1090                 r = -EINVAL;
1091                 goto bad;
1092         }
1093
1094         /* parse the priority groups */
1095         while (as.argc) {
1096                 struct priority_group *pg;
1097                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1098
1099                 pg = parse_priority_group(&as, m);
1100                 if (IS_ERR(pg)) {
1101                         r = PTR_ERR(pg);
1102                         goto bad;
1103                 }
1104
1105                 nr_valid_paths += pg->nr_pgpaths;
1106                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1107
1108                 list_add_tail(&pg->list, &m->priority_groups);
1109                 pg_count++;
1110                 pg->pg_num = pg_count;
1111                 if (!--next_pg_num)
1112                         m->next_pg = pg;
1113         }
1114
1115         if (pg_count != m->nr_priority_groups) {
1116                 ti->error = "priority group count mismatch";
1117                 r = -EINVAL;
1118                 goto bad;
1119         }
1120
1121         ti->num_flush_bios = 1;
1122         ti->num_discard_bios = 1;
1123         ti->num_write_same_bios = 1;
1124         ti->num_write_zeroes_bios = 1;
1125         if (m->queue_mode == DM_TYPE_BIO_BASED)
1126                 ti->per_io_data_size = multipath_per_bio_data_size();
1127         else
1128                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1129
1130         return 0;
1131
1132  bad:
1133         free_multipath(m);
1134         return r;
1135 }
1136
1137 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1138 {
1139         DEFINE_WAIT(wait);
1140
1141         while (1) {
1142                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1143
1144                 if (!atomic_read(&m->pg_init_in_progress))
1145                         break;
1146
1147                 io_schedule();
1148         }
1149         finish_wait(&m->pg_init_wait, &wait);
1150 }
1151
1152 static void flush_multipath_work(struct multipath *m)
1153 {
1154         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1155         smp_mb__after_atomic();
1156
1157         flush_workqueue(kmpath_handlerd);
1158         multipath_wait_for_pg_init_completion(m);
1159         flush_workqueue(kmultipathd);
1160         flush_work(&m->trigger_event);
1161
1162         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1163         smp_mb__after_atomic();
1164 }
1165
1166 static void multipath_dtr(struct dm_target *ti)
1167 {
1168         struct multipath *m = ti->private;
1169
1170         flush_multipath_work(m);
1171         free_multipath(m);
1172 }
1173
1174 /*
1175  * Take a path out of use.
1176  */
1177 static int fail_path(struct pgpath *pgpath)
1178 {
1179         unsigned long flags;
1180         struct multipath *m = pgpath->pg->m;
1181
1182         spin_lock_irqsave(&m->lock, flags);
1183
1184         if (!pgpath->is_active)
1185                 goto out;
1186
1187         DMWARN("Failing path %s.", pgpath->path.dev->name);
1188
1189         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1190         pgpath->is_active = false;
1191         pgpath->fail_count++;
1192
1193         atomic_dec(&m->nr_valid_paths);
1194
1195         if (pgpath == m->current_pgpath)
1196                 m->current_pgpath = NULL;
1197
1198         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1199                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1200
1201         schedule_work(&m->trigger_event);
1202
1203 out:
1204         spin_unlock_irqrestore(&m->lock, flags);
1205
1206         return 0;
1207 }
1208
1209 /*
1210  * Reinstate a previously-failed path
1211  */
1212 static int reinstate_path(struct pgpath *pgpath)
1213 {
1214         int r = 0, run_queue = 0;
1215         unsigned long flags;
1216         struct multipath *m = pgpath->pg->m;
1217         unsigned nr_valid_paths;
1218
1219         spin_lock_irqsave(&m->lock, flags);
1220
1221         if (pgpath->is_active)
1222                 goto out;
1223
1224         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1225
1226         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1227         if (r)
1228                 goto out;
1229
1230         pgpath->is_active = true;
1231
1232         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1233         if (nr_valid_paths == 1) {
1234                 m->current_pgpath = NULL;
1235                 run_queue = 1;
1236         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1237                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1238                         atomic_inc(&m->pg_init_in_progress);
1239         }
1240
1241         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1242                        pgpath->path.dev->name, nr_valid_paths);
1243
1244         schedule_work(&m->trigger_event);
1245
1246 out:
1247         spin_unlock_irqrestore(&m->lock, flags);
1248         if (run_queue) {
1249                 dm_table_run_md_queue_async(m->ti->table);
1250                 process_queued_io_list(m);
1251         }
1252
1253         return r;
1254 }
1255
1256 /*
1257  * Fail or reinstate all paths that match the provided struct dm_dev.
1258  */
1259 static int action_dev(struct multipath *m, struct dm_dev *dev,
1260                       action_fn action)
1261 {
1262         int r = -EINVAL;
1263         struct pgpath *pgpath;
1264         struct priority_group *pg;
1265
1266         list_for_each_entry(pg, &m->priority_groups, list) {
1267                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1268                         if (pgpath->path.dev == dev)
1269                                 r = action(pgpath);
1270                 }
1271         }
1272
1273         return r;
1274 }
1275
1276 /*
1277  * Temporarily try to avoid having to use the specified PG
1278  */
1279 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1280                       bool bypassed)
1281 {
1282         unsigned long flags;
1283
1284         spin_lock_irqsave(&m->lock, flags);
1285
1286         pg->bypassed = bypassed;
1287         m->current_pgpath = NULL;
1288         m->current_pg = NULL;
1289
1290         spin_unlock_irqrestore(&m->lock, flags);
1291
1292         schedule_work(&m->trigger_event);
1293 }
1294
1295 /*
1296  * Switch to using the specified PG from the next I/O that gets mapped
1297  */
1298 static int switch_pg_num(struct multipath *m, const char *pgstr)
1299 {
1300         struct priority_group *pg;
1301         unsigned pgnum;
1302         unsigned long flags;
1303         char dummy;
1304
1305         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1306             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1307                 DMWARN("invalid PG number supplied to switch_pg_num");
1308                 return -EINVAL;
1309         }
1310
1311         spin_lock_irqsave(&m->lock, flags);
1312         list_for_each_entry(pg, &m->priority_groups, list) {
1313                 pg->bypassed = false;
1314                 if (--pgnum)
1315                         continue;
1316
1317                 m->current_pgpath = NULL;
1318                 m->current_pg = NULL;
1319                 m->next_pg = pg;
1320         }
1321         spin_unlock_irqrestore(&m->lock, flags);
1322
1323         schedule_work(&m->trigger_event);
1324         return 0;
1325 }
1326
1327 /*
1328  * Set/clear bypassed status of a PG.
1329  * PGs are numbered upwards from 1 in the order they were declared.
1330  */
1331 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1332 {
1333         struct priority_group *pg;
1334         unsigned pgnum;
1335         char dummy;
1336
1337         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1338             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1339                 DMWARN("invalid PG number supplied to bypass_pg");
1340                 return -EINVAL;
1341         }
1342
1343         list_for_each_entry(pg, &m->priority_groups, list) {
1344                 if (!--pgnum)
1345                         break;
1346         }
1347
1348         bypass_pg(m, pg, bypassed);
1349         return 0;
1350 }
1351
1352 /*
1353  * Should we retry pg_init immediately?
1354  */
1355 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1356 {
1357         unsigned long flags;
1358         bool limit_reached = false;
1359
1360         spin_lock_irqsave(&m->lock, flags);
1361
1362         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1363             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1364                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1365         else
1366                 limit_reached = true;
1367
1368         spin_unlock_irqrestore(&m->lock, flags);
1369
1370         return limit_reached;
1371 }
1372
1373 static void pg_init_done(void *data, int errors)
1374 {
1375         struct pgpath *pgpath = data;
1376         struct priority_group *pg = pgpath->pg;
1377         struct multipath *m = pg->m;
1378         unsigned long flags;
1379         bool delay_retry = false;
1380
1381         /* device or driver problems */
1382         switch (errors) {
1383         case SCSI_DH_OK:
1384                 break;
1385         case SCSI_DH_NOSYS:
1386                 if (!m->hw_handler_name) {
1387                         errors = 0;
1388                         break;
1389                 }
1390                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1391                       "Error %d.", m->hw_handler_name, errors);
1392                 /*
1393                  * Fail path for now, so we do not ping pong
1394                  */
1395                 fail_path(pgpath);
1396                 break;
1397         case SCSI_DH_DEV_TEMP_BUSY:
1398                 /*
1399                  * Probably doing something like FW upgrade on the
1400                  * controller so try the other pg.
1401                  */
1402                 bypass_pg(m, pg, true);
1403                 break;
1404         case SCSI_DH_RETRY:
1405                 /* Wait before retrying. */
1406                 delay_retry = 1;
1407                 /* fall through */
1408         case SCSI_DH_IMM_RETRY:
1409         case SCSI_DH_RES_TEMP_UNAVAIL:
1410                 if (pg_init_limit_reached(m, pgpath))
1411                         fail_path(pgpath);
1412                 errors = 0;
1413                 break;
1414         case SCSI_DH_DEV_OFFLINED:
1415         default:
1416                 /*
1417                  * We probably do not want to fail the path for a device
1418                  * error, but this is what the old dm did. In future
1419                  * patches we can do more advanced handling.
1420                  */
1421                 fail_path(pgpath);
1422         }
1423
1424         spin_lock_irqsave(&m->lock, flags);
1425         if (errors) {
1426                 if (pgpath == m->current_pgpath) {
1427                         DMERR("Could not failover device. Error %d.", errors);
1428                         m->current_pgpath = NULL;
1429                         m->current_pg = NULL;
1430                 }
1431         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1432                 pg->bypassed = false;
1433
1434         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1435                 /* Activations of other paths are still on going */
1436                 goto out;
1437
1438         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1439                 if (delay_retry)
1440                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1441                 else
1442                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1443
1444                 if (__pg_init_all_paths(m))
1445                         goto out;
1446         }
1447         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1448
1449         process_queued_io_list(m);
1450
1451         /*
1452          * Wake up any thread waiting to suspend.
1453          */
1454         wake_up(&m->pg_init_wait);
1455
1456 out:
1457         spin_unlock_irqrestore(&m->lock, flags);
1458 }
1459
1460 static void activate_or_offline_path(struct pgpath *pgpath)
1461 {
1462         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1463
1464         if (pgpath->is_active && !blk_queue_dying(q))
1465                 scsi_dh_activate(q, pg_init_done, pgpath);
1466         else
1467                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1468 }
1469
1470 static void activate_path_work(struct work_struct *work)
1471 {
1472         struct pgpath *pgpath =
1473                 container_of(work, struct pgpath, activate_path.work);
1474
1475         activate_or_offline_path(pgpath);
1476 }
1477
1478 static int noretry_error(blk_status_t error)
1479 {
1480         switch (error) {
1481         case BLK_STS_NOTSUPP:
1482         case BLK_STS_NOSPC:
1483         case BLK_STS_TARGET:
1484         case BLK_STS_NEXUS:
1485         case BLK_STS_MEDIUM:
1486                 return 1;
1487         }
1488
1489         /* Anything else could be a path failure, so should be retried */
1490         return 0;
1491 }
1492
1493 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1494                             blk_status_t error, union map_info *map_context)
1495 {
1496         struct dm_mpath_io *mpio = get_mpio(map_context);
1497         struct pgpath *pgpath = mpio->pgpath;
1498         int r = DM_ENDIO_DONE;
1499
1500         /*
1501          * We don't queue any clone request inside the multipath target
1502          * during end I/O handling, since those clone requests don't have
1503          * bio clones.  If we queue them inside the multipath target,
1504          * we need to make bio clones, that requires memory allocation.
1505          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1506          *  don't have bio clones.)
1507          * Instead of queueing the clone request here, we queue the original
1508          * request into dm core, which will remake a clone request and
1509          * clone bios for it and resubmit it later.
1510          */
1511         if (error && !noretry_error(error)) {
1512                 struct multipath *m = ti->private;
1513
1514                 r = DM_ENDIO_REQUEUE;
1515
1516                 if (pgpath)
1517                         fail_path(pgpath);
1518
1519                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1520                     !must_push_back_rq(m)) {
1521                         if (error == BLK_STS_IOERR)
1522                                 dm_report_EIO(m);
1523                         /* complete with the original error */
1524                         r = DM_ENDIO_DONE;
1525                 }
1526         }
1527
1528         if (pgpath) {
1529                 struct path_selector *ps = &pgpath->pg->ps;
1530
1531                 if (ps->type->end_io)
1532                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1533         }
1534
1535         return r;
1536 }
1537
1538 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1539                 blk_status_t *error)
1540 {
1541         struct multipath *m = ti->private;
1542         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1543         struct pgpath *pgpath = mpio->pgpath;
1544         unsigned long flags;
1545         int r = DM_ENDIO_DONE;
1546
1547         if (!*error || noretry_error(*error))
1548                 goto done;
1549
1550         if (pgpath)
1551                 fail_path(pgpath);
1552
1553         if (atomic_read(&m->nr_valid_paths) == 0 &&
1554             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1555                 if (must_push_back_bio(m)) {
1556                         r = DM_ENDIO_REQUEUE;
1557                 } else {
1558                         dm_report_EIO(m);
1559                         *error = BLK_STS_IOERR;
1560                 }
1561                 goto done;
1562         }
1563
1564         /* Queue for the daemon to resubmit */
1565         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1566
1567         spin_lock_irqsave(&m->lock, flags);
1568         bio_list_add(&m->queued_bios, clone);
1569         spin_unlock_irqrestore(&m->lock, flags);
1570         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1571                 queue_work(kmultipathd, &m->process_queued_bios);
1572
1573         r = DM_ENDIO_INCOMPLETE;
1574 done:
1575         if (pgpath) {
1576                 struct path_selector *ps = &pgpath->pg->ps;
1577
1578                 if (ps->type->end_io)
1579                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1580         }
1581
1582         return r;
1583 }
1584
1585 /*
1586  * Suspend can't complete until all the I/O is processed so if
1587  * the last path fails we must error any remaining I/O.
1588  * Note that if the freeze_bdev fails while suspending, the
1589  * queue_if_no_path state is lost - userspace should reset it.
1590  */
1591 static void multipath_presuspend(struct dm_target *ti)
1592 {
1593         struct multipath *m = ti->private;
1594
1595         queue_if_no_path(m, false, true);
1596 }
1597
1598 static void multipath_postsuspend(struct dm_target *ti)
1599 {
1600         struct multipath *m = ti->private;
1601
1602         mutex_lock(&m->work_mutex);
1603         flush_multipath_work(m);
1604         mutex_unlock(&m->work_mutex);
1605 }
1606
1607 /*
1608  * Restore the queue_if_no_path setting.
1609  */
1610 static void multipath_resume(struct dm_target *ti)
1611 {
1612         struct multipath *m = ti->private;
1613         unsigned long flags;
1614
1615         spin_lock_irqsave(&m->lock, flags);
1616         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1617                    test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1618         spin_unlock_irqrestore(&m->lock, flags);
1619 }
1620
1621 /*
1622  * Info output has the following format:
1623  * num_multipath_feature_args [multipath_feature_args]*
1624  * num_handler_status_args [handler_status_args]*
1625  * num_groups init_group_number
1626  *            [A|D|E num_ps_status_args [ps_status_args]*
1627  *             num_paths num_selector_args
1628  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1629  *
1630  * Table output has the following format (identical to the constructor string):
1631  * num_feature_args [features_args]*
1632  * num_handler_args hw_handler [hw_handler_args]*
1633  * num_groups init_group_number
1634  *     [priority selector-name num_ps_args [ps_args]*
1635  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1636  */
1637 static void multipath_status(struct dm_target *ti, status_type_t type,
1638                              unsigned status_flags, char *result, unsigned maxlen)
1639 {
1640         int sz = 0;
1641         unsigned long flags;
1642         struct multipath *m = ti->private;
1643         struct priority_group *pg;
1644         struct pgpath *p;
1645         unsigned pg_num;
1646         char state;
1647
1648         spin_lock_irqsave(&m->lock, flags);
1649
1650         /* Features */
1651         if (type == STATUSTYPE_INFO)
1652                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1653                        atomic_read(&m->pg_init_count));
1654         else {
1655                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1656                               (m->pg_init_retries > 0) * 2 +
1657                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1658                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1659                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1660
1661                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1662                         DMEMIT("queue_if_no_path ");
1663                 if (m->pg_init_retries)
1664                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1665                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1666                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1667                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1668                         DMEMIT("retain_attached_hw_handler ");
1669                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1670                         switch(m->queue_mode) {
1671                         case DM_TYPE_BIO_BASED:
1672                                 DMEMIT("queue_mode bio ");
1673                                 break;
1674                         case DM_TYPE_MQ_REQUEST_BASED:
1675                                 DMEMIT("queue_mode mq ");
1676                                 break;
1677                         default:
1678                                 WARN_ON_ONCE(true);
1679                                 break;
1680                         }
1681                 }
1682         }
1683
1684         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1685                 DMEMIT("0 ");
1686         else
1687                 DMEMIT("1 %s ", m->hw_handler_name);
1688
1689         DMEMIT("%u ", m->nr_priority_groups);
1690
1691         if (m->next_pg)
1692                 pg_num = m->next_pg->pg_num;
1693         else if (m->current_pg)
1694                 pg_num = m->current_pg->pg_num;
1695         else
1696                 pg_num = (m->nr_priority_groups ? 1 : 0);
1697
1698         DMEMIT("%u ", pg_num);
1699
1700         switch (type) {
1701         case STATUSTYPE_INFO:
1702                 list_for_each_entry(pg, &m->priority_groups, list) {
1703                         if (pg->bypassed)
1704                                 state = 'D';    /* Disabled */
1705                         else if (pg == m->current_pg)
1706                                 state = 'A';    /* Currently Active */
1707                         else
1708                                 state = 'E';    /* Enabled */
1709
1710                         DMEMIT("%c ", state);
1711
1712                         if (pg->ps.type->status)
1713                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1714                                                           result + sz,
1715                                                           maxlen - sz);
1716                         else
1717                                 DMEMIT("0 ");
1718
1719                         DMEMIT("%u %u ", pg->nr_pgpaths,
1720                                pg->ps.type->info_args);
1721
1722                         list_for_each_entry(p, &pg->pgpaths, list) {
1723                                 DMEMIT("%s %s %u ", p->path.dev->name,
1724                                        p->is_active ? "A" : "F",
1725                                        p->fail_count);
1726                                 if (pg->ps.type->status)
1727                                         sz += pg->ps.type->status(&pg->ps,
1728                                               &p->path, type, result + sz,
1729                                               maxlen - sz);
1730                         }
1731                 }
1732                 break;
1733
1734         case STATUSTYPE_TABLE:
1735                 list_for_each_entry(pg, &m->priority_groups, list) {
1736                         DMEMIT("%s ", pg->ps.type->name);
1737
1738                         if (pg->ps.type->status)
1739                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1740                                                           result + sz,
1741                                                           maxlen - sz);
1742                         else
1743                                 DMEMIT("0 ");
1744
1745                         DMEMIT("%u %u ", pg->nr_pgpaths,
1746                                pg->ps.type->table_args);
1747
1748                         list_for_each_entry(p, &pg->pgpaths, list) {
1749                                 DMEMIT("%s ", p->path.dev->name);
1750                                 if (pg->ps.type->status)
1751                                         sz += pg->ps.type->status(&pg->ps,
1752                                               &p->path, type, result + sz,
1753                                               maxlen - sz);
1754                         }
1755                 }
1756                 break;
1757         }
1758
1759         spin_unlock_irqrestore(&m->lock, flags);
1760 }
1761
1762 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1763 {
1764         int r = -EINVAL;
1765         struct dm_dev *dev;
1766         struct multipath *m = ti->private;
1767         action_fn action;
1768
1769         mutex_lock(&m->work_mutex);
1770
1771         if (dm_suspended(ti)) {
1772                 r = -EBUSY;
1773                 goto out;
1774         }
1775
1776         if (argc == 1) {
1777                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1778                         r = queue_if_no_path(m, true, false);
1779                         goto out;
1780                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1781                         r = queue_if_no_path(m, false, false);
1782                         goto out;
1783                 }
1784         }
1785
1786         if (argc != 2) {
1787                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1788                 goto out;
1789         }
1790
1791         if (!strcasecmp(argv[0], "disable_group")) {
1792                 r = bypass_pg_num(m, argv[1], true);
1793                 goto out;
1794         } else if (!strcasecmp(argv[0], "enable_group")) {
1795                 r = bypass_pg_num(m, argv[1], false);
1796                 goto out;
1797         } else if (!strcasecmp(argv[0], "switch_group")) {
1798                 r = switch_pg_num(m, argv[1]);
1799                 goto out;
1800         } else if (!strcasecmp(argv[0], "reinstate_path"))
1801                 action = reinstate_path;
1802         else if (!strcasecmp(argv[0], "fail_path"))
1803                 action = fail_path;
1804         else {
1805                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1806                 goto out;
1807         }
1808
1809         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1810         if (r) {
1811                 DMWARN("message: error getting device %s",
1812                        argv[1]);
1813                 goto out;
1814         }
1815
1816         r = action_dev(m, dev, action);
1817
1818         dm_put_device(ti, dev);
1819
1820 out:
1821         mutex_unlock(&m->work_mutex);
1822         return r;
1823 }
1824
1825 static int multipath_prepare_ioctl(struct dm_target *ti,
1826                 struct block_device **bdev, fmode_t *mode)
1827 {
1828         struct multipath *m = ti->private;
1829         struct pgpath *current_pgpath;
1830         int r;
1831
1832         current_pgpath = READ_ONCE(m->current_pgpath);
1833         if (!current_pgpath)
1834                 current_pgpath = choose_pgpath(m, 0);
1835
1836         if (current_pgpath) {
1837                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1838                         *bdev = current_pgpath->path.dev->bdev;
1839                         *mode = current_pgpath->path.dev->mode;
1840                         r = 0;
1841                 } else {
1842                         /* pg_init has not started or completed */
1843                         r = -ENOTCONN;
1844                 }
1845         } else {
1846                 /* No path is available */
1847                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1848                         r = -ENOTCONN;
1849                 else
1850                         r = -EIO;
1851         }
1852
1853         if (r == -ENOTCONN) {
1854                 if (!READ_ONCE(m->current_pg)) {
1855                         /* Path status changed, redo selection */
1856                         (void) choose_pgpath(m, 0);
1857                 }
1858                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1859                         pg_init_all_paths(m);
1860                 dm_table_run_md_queue_async(m->ti->table);
1861                 process_queued_io_list(m);
1862         }
1863
1864         /*
1865          * Only pass ioctls through if the device sizes match exactly.
1866          */
1867         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1868                 return 1;
1869         return r;
1870 }
1871
1872 static int multipath_iterate_devices(struct dm_target *ti,
1873                                      iterate_devices_callout_fn fn, void *data)
1874 {
1875         struct multipath *m = ti->private;
1876         struct priority_group *pg;
1877         struct pgpath *p;
1878         int ret = 0;
1879
1880         list_for_each_entry(pg, &m->priority_groups, list) {
1881                 list_for_each_entry(p, &pg->pgpaths, list) {
1882                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1883                         if (ret)
1884                                 goto out;
1885                 }
1886         }
1887
1888 out:
1889         return ret;
1890 }
1891
1892 static int pgpath_busy(struct pgpath *pgpath)
1893 {
1894         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1895
1896         return blk_lld_busy(q);
1897 }
1898
1899 /*
1900  * We return "busy", only when we can map I/Os but underlying devices
1901  * are busy (so even if we map I/Os now, the I/Os will wait on
1902  * the underlying queue).
1903  * In other words, if we want to kill I/Os or queue them inside us
1904  * due to map unavailability, we don't return "busy".  Otherwise,
1905  * dm core won't give us the I/Os and we can't do what we want.
1906  */
1907 static int multipath_busy(struct dm_target *ti)
1908 {
1909         bool busy = false, has_active = false;
1910         struct multipath *m = ti->private;
1911         struct priority_group *pg, *next_pg;
1912         struct pgpath *pgpath;
1913
1914         /* pg_init in progress */
1915         if (atomic_read(&m->pg_init_in_progress))
1916                 return true;
1917
1918         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1919         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1920                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1921
1922         /* Guess which priority_group will be used at next mapping time */
1923         pg = READ_ONCE(m->current_pg);
1924         next_pg = READ_ONCE(m->next_pg);
1925         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1926                 pg = next_pg;
1927
1928         if (!pg) {
1929                 /*
1930                  * We don't know which pg will be used at next mapping time.
1931                  * We don't call choose_pgpath() here to avoid to trigger
1932                  * pg_init just by busy checking.
1933                  * So we don't know whether underlying devices we will be using
1934                  * at next mapping time are busy or not. Just try mapping.
1935                  */
1936                 return busy;
1937         }
1938
1939         /*
1940          * If there is one non-busy active path at least, the path selector
1941          * will be able to select it. So we consider such a pg as not busy.
1942          */
1943         busy = true;
1944         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1945                 if (pgpath->is_active) {
1946                         has_active = true;
1947                         if (!pgpath_busy(pgpath)) {
1948                                 busy = false;
1949                                 break;
1950                         }
1951                 }
1952         }
1953
1954         if (!has_active) {
1955                 /*
1956                  * No active path in this pg, so this pg won't be used and
1957                  * the current_pg will be changed at next mapping time.
1958                  * We need to try mapping to determine it.
1959                  */
1960                 busy = false;
1961         }
1962
1963         return busy;
1964 }
1965
1966 /*-----------------------------------------------------------------
1967  * Module setup
1968  *---------------------------------------------------------------*/
1969 static struct target_type multipath_target = {
1970         .name = "multipath",
1971         .version = {1, 12, 0},
1972         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1973         .module = THIS_MODULE,
1974         .ctr = multipath_ctr,
1975         .dtr = multipath_dtr,
1976         .clone_and_map_rq = multipath_clone_and_map,
1977         .release_clone_rq = multipath_release_clone,
1978         .rq_end_io = multipath_end_io,
1979         .map = multipath_map_bio,
1980         .end_io = multipath_end_io_bio,
1981         .presuspend = multipath_presuspend,
1982         .postsuspend = multipath_postsuspend,
1983         .resume = multipath_resume,
1984         .status = multipath_status,
1985         .message = multipath_message,
1986         .prepare_ioctl = multipath_prepare_ioctl,
1987         .iterate_devices = multipath_iterate_devices,
1988         .busy = multipath_busy,
1989 };
1990
1991 static int __init dm_multipath_init(void)
1992 {
1993         int r;
1994
1995         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1996         if (!kmultipathd) {
1997                 DMERR("failed to create workqueue kmpathd");
1998                 r = -ENOMEM;
1999                 goto bad_alloc_kmultipathd;
2000         }
2001
2002         /*
2003          * A separate workqueue is used to handle the device handlers
2004          * to avoid overloading existing workqueue. Overloading the
2005          * old workqueue would also create a bottleneck in the
2006          * path of the storage hardware device activation.
2007          */
2008         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2009                                                   WQ_MEM_RECLAIM);
2010         if (!kmpath_handlerd) {
2011                 DMERR("failed to create workqueue kmpath_handlerd");
2012                 r = -ENOMEM;
2013                 goto bad_alloc_kmpath_handlerd;
2014         }
2015
2016         r = dm_register_target(&multipath_target);
2017         if (r < 0) {
2018                 DMERR("request-based register failed %d", r);
2019                 r = -EINVAL;
2020                 goto bad_register_target;
2021         }
2022
2023         return 0;
2024
2025 bad_register_target:
2026         destroy_workqueue(kmpath_handlerd);
2027 bad_alloc_kmpath_handlerd:
2028         destroy_workqueue(kmultipathd);
2029 bad_alloc_kmultipathd:
2030         return r;
2031 }
2032
2033 static void __exit dm_multipath_exit(void)
2034 {
2035         destroy_workqueue(kmpath_handlerd);
2036         destroy_workqueue(kmultipathd);
2037
2038         dm_unregister_target(&multipath_target);
2039 }
2040
2041 module_init(dm_multipath_init);
2042 module_exit(dm_multipath_exit);
2043
2044 MODULE_DESCRIPTION(DM_NAME " multipath target");
2045 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2046 MODULE_LICENSE("GPL");