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         unsigned queue_mode;
  94
  95         /*
  96          * We must use a mempool of dm_mpath_io structs so that we
  97          * can resubmit bios on error.
  98          */
  99         mempool_t *mpio_pool;
 100
 101         struct mutex work_mutex;
 102         struct work_struct trigger_event;
 103
 104         struct work_struct process_queued_bios;
 105         struct bio_list queued_bios;
 106 };
 107
 108 /*
 109  * Context information attached to each io we process.
 110  */
 111 struct dm_mpath_io {
 112         struct pgpath *pgpath;
 113         size_t nr_bytes;
 114 };
 115
 116 typedef int (*action_fn) (struct pgpath *pgpath);
 117
 118 static struct kmem_cache *_mpio_cache;
 119
 120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 121 static void trigger_event(struct work_struct *work);
 122 static void activate_path(struct work_struct *work);
 123 static void process_queued_bios(struct work_struct *work);
 124
 125 /*-----------------------------------------------
 126  * Multipath state flags.
 127  *-----------------------------------------------*/
 128
 129 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 130 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 131 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 132 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 133 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 134 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 135 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 136
 137 /*-----------------------------------------------
 138  * Allocation routines
 139  *-----------------------------------------------*/
 140
 141 static struct pgpath *alloc_pgpath(void)
 142 {
 143         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 144
 145         if (pgpath) {
 146                 pgpath->is_active = true;
 147                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 148         }
 149
 150         return pgpath;
 151 }
 152
 153 static void free_pgpath(struct pgpath *pgpath)
 154 {
 155         kfree(pgpath);
 156 }
 157
 158 static struct priority_group *alloc_priority_group(void)
 159 {
 160         struct priority_group *pg;
 161
 162         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 163
 164         if (pg)
 165                 INIT_LIST_HEAD(&pg->pgpaths);
 166
 167         return pg;
 168 }
 169
 170 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 171 {
 172         struct pgpath *pgpath, *tmp;
 173
 174         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 175                 list_del(&pgpath->list);
 176                 dm_put_device(ti, pgpath->path.dev);
 177                 free_pgpath(pgpath);
 178         }
 179 }
 180
 181 static void free_priority_group(struct priority_group *pg,
 182                                 struct dm_target *ti)
 183 {
 184         struct path_selector *ps = &pg->ps;
 185
 186         if (ps->type) {
 187                 ps->type->destroy(ps);
 188                 dm_put_path_selector(ps->type);
 189         }
 190
 191         free_pgpaths(&pg->pgpaths, ti);
 192         kfree(pg);
 193 }
 194
 195 static struct multipath *alloc_multipath(struct dm_target *ti)
 196 {
 197         struct multipath *m;
 198
 199         m = kzalloc(sizeof(*m), GFP_KERNEL);
 200         if (m) {
 201                 INIT_LIST_HEAD(&m->priority_groups);
 202                 spin_lock_init(&m->lock);
 203                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 204                 atomic_set(&m->nr_valid_paths, 0);
 205                 atomic_set(&m->pg_init_in_progress, 0);
 206                 atomic_set(&m->pg_init_count, 0);
 207                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 208                 INIT_WORK(&m->trigger_event, trigger_event);
 209                 init_waitqueue_head(&m->pg_init_wait);
 210                 mutex_init(&m->work_mutex);
 211
 212                 m->mpio_pool = NULL;
 213                 m->queue_mode = DM_TYPE_NONE;
 214
 215                 m->ti = ti;
 216                 ti->private = m;
 217         }
 218
 219         return m;
 220 }
 221
 222 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 223 {
 224         if (m->queue_mode == DM_TYPE_NONE) {
 225                 /*
 226                  * Default to request-based.
 227                  */
 228                 if (dm_use_blk_mq(dm_table_get_md(ti->table)))
 229                         m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
 230                 else
 231                         m->queue_mode = DM_TYPE_REQUEST_BASED;
 232         }
 233
 234         if (m->queue_mode == DM_TYPE_REQUEST_BASED) {
 235                 unsigned min_ios = dm_get_reserved_rq_based_ios();
 236
 237                 m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 238                 if (!m->mpio_pool)
 239                         return -ENOMEM;
 240         }
 241         else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 242                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 243                 /*
 244                  * bio-based doesn't support any direct scsi_dh management;
 245                  * it just discovers if a scsi_dh is attached.
 246                  */
 247                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 248         }
 249
 250         dm_table_set_type(ti->table, m->queue_mode);
 251
 252         return 0;
 253 }
 254
 255 static void free_multipath(struct multipath *m)
 256 {
 257         struct priority_group *pg, *tmp;
 258
 259         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 260                 list_del(&pg->list);
 261                 free_priority_group(pg, m->ti);
 262         }
 263
 264         kfree(m->hw_handler_name);
 265         kfree(m->hw_handler_params);
 266         mempool_destroy(m->mpio_pool);
 267         kfree(m);
 268 }
 269
 270 static struct dm_mpath_io *get_mpio(union map_info *info)
 271 {
 272         return info->ptr;
 273 }
 274
 275 static struct dm_mpath_io *set_mpio(struct multipath *m, union map_info *info)
 276 {
 277         struct dm_mpath_io *mpio;
 278
 279         if (!m->mpio_pool) {
 280                 /* Use blk-mq pdu memory requested via per_io_data_size */
 281                 mpio = get_mpio(info);
 282                 memset(mpio, 0, sizeof(*mpio));
 283                 return mpio;
 284         }
 285
 286         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 287         if (!mpio)
 288                 return NULL;
 289
 290         memset(mpio, 0, sizeof(*mpio));
 291         info->ptr = mpio;
 292
 293         return mpio;
 294 }
 295
 296 static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
 297 {
 298         /* Only needed for non blk-mq (.request_fn) multipath */
 299         if (m->mpio_pool) {
 300                 struct dm_mpath_io *mpio = info->ptr;
 301
 302                 info->ptr = NULL;
 303                 mempool_free(mpio, m->mpio_pool);
 304         }
 305 }
 306
 307 static size_t multipath_per_bio_data_size(void)
 308 {
 309         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 310 }
 311
 312 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 313 {
 314         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 315 }
 316
 317 static struct dm_bio_details *get_bio_details_from_bio(struct bio *bio)
 318 {
 319         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 320         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 321         void *bio_details = mpio + 1;
 322
 323         return bio_details;
 324 }
 325
 326 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p,
 327                                         struct dm_bio_details **bio_details_p)
 328 {
 329         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 330         struct dm_bio_details *bio_details = get_bio_details_from_bio(bio);
 331
 332         memset(mpio, 0, sizeof(*mpio));
 333         memset(bio_details, 0, sizeof(*bio_details));
 334         dm_bio_record(bio_details, bio);
 335
 336         if (mpio_p)
 337                 *mpio_p = mpio;
 338         if (bio_details_p)
 339                 *bio_details_p = bio_details;
 340 }
 341
 342 /*-----------------------------------------------
 343  * Path selection
 344  *-----------------------------------------------*/
 345
 346 static int __pg_init_all_paths(struct multipath *m)
 347 {
 348         struct pgpath *pgpath;
 349         unsigned long pg_init_delay = 0;
 350
 351         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 352                 return 0;
 353
 354         atomic_inc(&m->pg_init_count);
 355         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 356
 357         /* Check here to reset pg_init_required */
 358         if (!m->current_pg)
 359                 return 0;
 360
 361         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 362                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 363                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 364         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 365                 /* Skip failed paths */
 366                 if (!pgpath->is_active)
 367                         continue;
 368                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 369                                        pg_init_delay))
 370                         atomic_inc(&m->pg_init_in_progress);
 371         }
 372         return atomic_read(&m->pg_init_in_progress);
 373 }
 374
 375 static int pg_init_all_paths(struct multipath *m)
 376 {
 377         int r;
 378         unsigned long flags;
 379
 380         spin_lock_irqsave(&m->lock, flags);
 381         r = __pg_init_all_paths(m);
 382         spin_unlock_irqrestore(&m->lock, flags);
 383
 384         return r;
 385 }
 386
 387 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 388 {
 389         m->current_pg = pg;
 390
 391         /* Must we initialise the PG first, and queue I/O till it's ready? */
 392         if (m->hw_handler_name) {
 393                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 394                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 395         } else {
 396                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 397                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 398         }
 399
 400         atomic_set(&m->pg_init_count, 0);
 401 }
 402
 403 static struct pgpath *choose_path_in_pg(struct multipath *m,
 404                                         struct priority_group *pg,
 405                                         size_t nr_bytes)
 406 {
 407         unsigned long flags;
 408         struct dm_path *path;
 409         struct pgpath *pgpath;
 410
 411         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 412         if (!path)
 413                 return ERR_PTR(-ENXIO);
 414
 415         pgpath = path_to_pgpath(path);
 416
 417         if (unlikely(lockless_dereference(m->current_pg) != pg)) {
 418                 /* Only update current_pgpath if pg changed */
 419                 spin_lock_irqsave(&m->lock, flags);
 420                 m->current_pgpath = pgpath;
 421                 __switch_pg(m, pg);
 422                 spin_unlock_irqrestore(&m->lock, flags);
 423         }
 424
 425         return pgpath;
 426 }
 427
 428 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 429 {
 430         unsigned long flags;
 431         struct priority_group *pg;
 432         struct pgpath *pgpath;
 433         bool bypassed = true;
 434
 435         if (!atomic_read(&m->nr_valid_paths)) {
 436                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 437                 goto failed;
 438         }
 439
 440         /* Were we instructed to switch PG? */
 441         if (lockless_dereference(m->next_pg)) {
 442                 spin_lock_irqsave(&m->lock, flags);
 443                 pg = m->next_pg;
 444                 if (!pg) {
 445                         spin_unlock_irqrestore(&m->lock, flags);
 446                         goto check_current_pg;
 447                 }
 448                 m->next_pg = NULL;
 449                 spin_unlock_irqrestore(&m->lock, flags);
 450                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 451                 if (!IS_ERR_OR_NULL(pgpath))
 452                         return pgpath;
 453         }
 454
 455         /* Don't change PG until it has no remaining paths */
 456 check_current_pg:
 457         pg = lockless_dereference(m->current_pg);
 458         if (pg) {
 459                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 460                 if (!IS_ERR_OR_NULL(pgpath))
 461                         return pgpath;
 462         }
 463
 464         /*
 465          * Loop through priority groups until we find a valid path.
 466          * First time we skip PGs marked 'bypassed'.
 467          * Second time we only try the ones we skipped, but set
 468          * pg_init_delay_retry so we do not hammer controllers.
 469          */
 470         do {
 471                 list_for_each_entry(pg, &m->priority_groups, list) {
 472                         if (pg->bypassed == bypassed)
 473                                 continue;
 474                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 475                         if (!IS_ERR_OR_NULL(pgpath)) {
 476                                 if (!bypassed)
 477                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 478                                 return pgpath;
 479                         }
 480                 }
 481         } while (bypassed--);
 482
 483 failed:
 484         spin_lock_irqsave(&m->lock, flags);
 485         m->current_pgpath = NULL;
 486         m->current_pg = NULL;
 487         spin_unlock_irqrestore(&m->lock, flags);
 488
 489         return NULL;
 490 }
 491
 492 /*
 493  * Check whether bios must be queued in the device-mapper core rather
 494  * than here in the target.
 495  *
 496  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 497  * same value then we are not between multipath_presuspend()
 498  * and multipath_resume() calls and we have no need to check
 499  * for the DMF_NOFLUSH_SUSPENDING flag.
 500  */
 501 static bool __must_push_back(struct multipath *m)
 502 {
 503         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) !=
 504                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) &&
 505                 dm_noflush_suspending(m->ti));
 506 }
 507
 508 static bool must_push_back_rq(struct multipath *m)
 509 {
 510         bool r;
 511         unsigned long flags;
 512
 513         spin_lock_irqsave(&m->lock, flags);
 514         r = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) ||
 515              __must_push_back(m));
 516         spin_unlock_irqrestore(&m->lock, flags);
 517
 518         return r;
 519 }
 520
 521 static bool must_push_back_bio(struct multipath *m)
 522 {
 523         bool r;
 524         unsigned long flags;
 525
 526         spin_lock_irqsave(&m->lock, flags);
 527         r = __must_push_back(m);
 528         spin_unlock_irqrestore(&m->lock, flags);
 529
 530         return r;
 531 }
 532
 533 /*
 534  * Map cloned requests (request-based multipath)
 535  */
 536 static int __multipath_map(struct dm_target *ti, struct request *clone,
 537                            union map_info *map_context,
 538                            struct request *rq, struct request **__clone)
 539 {
 540         struct multipath *m = ti->private;
 541         int r = DM_MAPIO_REQUEUE;
 542         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 543         struct pgpath *pgpath;
 544         struct block_device *bdev;
 545         struct dm_mpath_io *mpio;
 546
 547         /* Do we need to select a new pgpath? */
 548         pgpath = lockless_dereference(m->current_pgpath);
 549         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 550                 pgpath = choose_pgpath(m, nr_bytes);
 551
 552         if (!pgpath) {
 553                 if (!must_push_back_rq(m))
 554                         r = -EIO;       /* Failed */
 555                 return r;
 556         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 557                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 558                 pg_init_all_paths(m);
 559                 return r;
 560         }
 561
 562         mpio = set_mpio(m, map_context);
 563         if (!mpio)
 564                 /* ENOMEM, requeue */
 565                 return r;
 566
 567         mpio->pgpath = pgpath;
 568         mpio->nr_bytes = nr_bytes;
 569
 570         bdev = pgpath->path.dev->bdev;
 571
 572         if (clone) {
 573                 /*
 574                  * Old request-based interface: allocated clone is passed in.
 575                  * Used by: .request_fn stacked on .request_fn path(s).
 576                  */
 577                 clone->q = bdev_get_queue(bdev);
 578                 clone->rq_disk = bdev->bd_disk;
 579                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 580         } else {
 581                 /*
 582                  * blk-mq request-based interface; used by both:
 583                  * .request_fn stacked on blk-mq path(s) and
 584                  * blk-mq stacked on blk-mq path(s).
 585                  */
 586                 *__clone = blk_mq_alloc_request(bdev_get_queue(bdev),
 587                                                 rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
 588                 if (IS_ERR(*__clone)) {
 589                         /* ENOMEM, requeue */
 590                         clear_request_fn_mpio(m, map_context);
 591                         return r;
 592                 }
 593                 (*__clone)->bio = (*__clone)->biotail = NULL;
 594                 (*__clone)->rq_disk = bdev->bd_disk;
 595                 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 596         }
 597
 598         if (pgpath->pg->ps.type->start_io)
 599                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 600                                               &pgpath->path,
 601                                               nr_bytes);
 602         return DM_MAPIO_REMAPPED;
 603 }
 604
 605 static int multipath_map(struct dm_target *ti, struct request *clone,
 606                          union map_info *map_context)
 607 {
 608         return __multipath_map(ti, clone, map_context, NULL, NULL);
 609 }
 610
 611 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 612                                    union map_info *map_context,
 613                                    struct request **clone)
 614 {
 615         return __multipath_map(ti, NULL, map_context, rq, clone);
 616 }
 617
 618 static void multipath_release_clone(struct request *clone)
 619 {
 620         blk_mq_free_request(clone);
 621 }
 622
 623 /*
 624  * Map cloned bios (bio-based multipath)
 625  */
 626 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 627 {
 628         size_t nr_bytes = bio->bi_iter.bi_size;
 629         struct pgpath *pgpath;
 630         unsigned long flags;
 631         bool queue_io;
 632
 633         /* Do we need to select a new pgpath? */
 634         pgpath = lockless_dereference(m->current_pgpath);
 635         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 636         if (!pgpath || !queue_io)
 637                 pgpath = choose_pgpath(m, nr_bytes);
 638
 639         if ((pgpath && queue_io) ||
 640             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 641                 /* Queue for the daemon to resubmit */
 642                 spin_lock_irqsave(&m->lock, flags);
 643                 bio_list_add(&m->queued_bios, bio);
 644                 spin_unlock_irqrestore(&m->lock, flags);
 645                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 646                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 647                         pg_init_all_paths(m);
 648                 else if (!queue_io)
 649                         queue_work(kmultipathd, &m->process_queued_bios);
 650                 return DM_MAPIO_SUBMITTED;
 651         }
 652
 653         if (!pgpath) {
 654                 if (!must_push_back_bio(m))
 655                         return -EIO;
 656                 return DM_MAPIO_REQUEUE;
 657         }
 658
 659         mpio->pgpath = pgpath;
 660         mpio->nr_bytes = nr_bytes;
 661
 662         bio->bi_error = 0;
 663         bio->bi_bdev = pgpath->path.dev->bdev;
 664         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 665
 666         if (pgpath->pg->ps.type->start_io)
 667                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 668                                               &pgpath->path,
 669                                               nr_bytes);
 670         return DM_MAPIO_REMAPPED;
 671 }
 672
 673 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 674 {
 675         struct multipath *m = ti->private;
 676         struct dm_mpath_io *mpio = NULL;
 677
 678         multipath_init_per_bio_data(bio, &mpio, NULL);
 679
 680         return __multipath_map_bio(m, bio, mpio);
 681 }
 682
 683 static void process_queued_bios_list(struct multipath *m)
 684 {
 685         if (m->queue_mode == DM_TYPE_BIO_BASED)
 686                 queue_work(kmultipathd, &m->process_queued_bios);
 687 }
 688
 689 static void process_queued_bios(struct work_struct *work)
 690 {
 691         int r;
 692         unsigned long flags;
 693         struct bio *bio;
 694         struct bio_list bios;
 695         struct blk_plug plug;
 696         struct multipath *m =
 697                 container_of(work, struct multipath, process_queued_bios);
 698
 699         bio_list_init(&bios);
 700
 701         spin_lock_irqsave(&m->lock, flags);
 702
 703         if (bio_list_empty(&m->queued_bios)) {
 704                 spin_unlock_irqrestore(&m->lock, flags);
 705                 return;
 706         }
 707
 708         bio_list_merge(&bios, &m->queued_bios);
 709         bio_list_init(&m->queued_bios);
 710
 711         spin_unlock_irqrestore(&m->lock, flags);
 712
 713         blk_start_plug(&plug);
 714         while ((bio = bio_list_pop(&bios))) {
 715                 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
 716                 if (r < 0 || r == DM_MAPIO_REQUEUE) {
 717                         bio->bi_error = r;
 718                         bio_endio(bio);
 719                 } else if (r == DM_MAPIO_REMAPPED)
 720                         generic_make_request(bio);
 721         }
 722         blk_finish_plug(&plug);
 723 }
 724
 725 /*
 726  * If we run out of usable paths, should we queue I/O or error it?
 727  */
 728 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 729                             bool save_old_value)
 730 {
 731         unsigned long flags;
 732
 733         spin_lock_irqsave(&m->lock, flags);
 734
 735         if (save_old_value) {
 736                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
 737                         set_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 738                 else
 739                         clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 740         } else {
 741                 if (queue_if_no_path)
 742                         set_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 743                 else
 744                         clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 745         }
 746         if (queue_if_no_path)
 747                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 748         else
 749                 clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 750
 751         spin_unlock_irqrestore(&m->lock, flags);
 752
 753         if (!queue_if_no_path) {
 754                 dm_table_run_md_queue_async(m->ti->table);
 755                 process_queued_bios_list(m);
 756         }
 757
 758         return 0;
 759 }
 760
 761 /*
 762  * An event is triggered whenever a path is taken out of use.
 763  * Includes path failure and PG bypass.
 764  */
 765 static void trigger_event(struct work_struct *work)
 766 {
 767         struct multipath *m =
 768                 container_of(work, struct multipath, trigger_event);
 769
 770         dm_table_event(m->ti->table);
 771 }
 772
 773 /*-----------------------------------------------------------------
 774  * Constructor/argument parsing:
 775  * <#multipath feature args> [<arg>]*
 776  * <#hw_handler args> [hw_handler [<arg>]*]
 777  * <#priority groups>
 778  * <initial priority group>
 779  *     [<selector> <#selector args> [<arg>]*
 780  *      <#paths> <#per-path selector args>
 781  *         [<path> [<arg>]* ]+ ]+
 782  *---------------------------------------------------------------*/
 783 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 784                                struct dm_target *ti)
 785 {
 786         int r;
 787         struct path_selector_type *pst;
 788         unsigned ps_argc;
 789
 790         static struct dm_arg _args[] = {
 791                 {0, 1024, "invalid number of path selector args"},
 792         };
 793
 794         pst = dm_get_path_selector(dm_shift_arg(as));
 795         if (!pst) {
 796                 ti->error = "unknown path selector type";
 797                 return -EINVAL;
 798         }
 799
 800         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 801         if (r) {
 802                 dm_put_path_selector(pst);
 803                 return -EINVAL;
 804         }
 805
 806         r = pst->create(&pg->ps, ps_argc, as->argv);
 807         if (r) {
 808                 dm_put_path_selector(pst);
 809                 ti->error = "path selector constructor failed";
 810                 return r;
 811         }
 812
 813         pg->ps.type = pst;
 814         dm_consume_args(as, ps_argc);
 815
 816         return 0;
 817 }
 818
 819 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 820                                struct dm_target *ti)
 821 {
 822         int r;
 823         struct pgpath *p;
 824         struct multipath *m = ti->private;
 825         struct request_queue *q = NULL;
 826         const char *attached_handler_name;
 827
 828         /* we need at least a path arg */
 829         if (as->argc < 1) {
 830                 ti->error = "no device given";
 831                 return ERR_PTR(-EINVAL);
 832         }
 833
 834         p = alloc_pgpath();
 835         if (!p)
 836                 return ERR_PTR(-ENOMEM);
 837
 838         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 839                           &p->path.dev);
 840         if (r) {
 841                 ti->error = "error getting device";
 842                 goto bad;
 843         }
 844
 845         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
 846                 q = bdev_get_queue(p->path.dev->bdev);
 847
 848         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 849 retain:
 850                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 851                 if (attached_handler_name) {
 852                         /*
 853                          * Reset hw_handler_name to match the attached handler
 854                          * and clear any hw_handler_params associated with the
 855                          * ignored handler.
 856                          *
 857                          * NB. This modifies the table line to show the actual
 858                          * handler instead of the original table passed in.
 859                          */
 860                         kfree(m->hw_handler_name);
 861                         m->hw_handler_name = attached_handler_name;
 862
 863                         kfree(m->hw_handler_params);
 864                         m->hw_handler_params = NULL;
 865                 }
 866         }
 867
 868         if (m->hw_handler_name) {
 869                 r = scsi_dh_attach(q, m->hw_handler_name);
 870                 if (r == -EBUSY) {
 871                         char b[BDEVNAME_SIZE];
 872
 873                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 874                                 bdevname(p->path.dev->bdev, b));
 875                         goto retain;
 876                 }
 877                 if (r < 0) {
 878                         ti->error = "error attaching hardware handler";
 879                         dm_put_device(ti, p->path.dev);
 880                         goto bad;
 881                 }
 882
 883                 if (m->hw_handler_params) {
 884                         r = scsi_dh_set_params(q, m->hw_handler_params);
 885                         if (r < 0) {
 886                                 ti->error = "unable to set hardware "
 887                                                         "handler parameters";
 888                                 dm_put_device(ti, p->path.dev);
 889                                 goto bad;
 890                         }
 891                 }
 892         }
 893
 894         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 895         if (r) {
 896                 dm_put_device(ti, p->path.dev);
 897                 goto bad;
 898         }
 899
 900         return p;
 901
 902  bad:
 903         free_pgpath(p);
 904         return ERR_PTR(r);
 905 }
 906
 907 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 908                                                    struct multipath *m)
 909 {
 910         static struct dm_arg _args[] = {
 911                 {1, 1024, "invalid number of paths"},
 912                 {0, 1024, "invalid number of selector args"}
 913         };
 914
 915         int r;
 916         unsigned i, nr_selector_args, nr_args;
 917         struct priority_group *pg;
 918         struct dm_target *ti = m->ti;
 919
 920         if (as->argc < 2) {
 921                 as->argc = 0;
 922                 ti->error = "not enough priority group arguments";
 923                 return ERR_PTR(-EINVAL);
 924         }
 925
 926         pg = alloc_priority_group();
 927         if (!pg) {
 928                 ti->error = "couldn't allocate priority group";
 929                 return ERR_PTR(-ENOMEM);
 930         }
 931         pg->m = m;
 932
 933         r = parse_path_selector(as, pg, ti);
 934         if (r)
 935                 goto bad;
 936
 937         /*
 938          * read the paths
 939          */
 940         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 941         if (r)
 942                 goto bad;
 943
 944         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 945         if (r)
 946                 goto bad;
 947
 948         nr_args = 1 + nr_selector_args;
 949         for (i = 0; i < pg->nr_pgpaths; i++) {
 950                 struct pgpath *pgpath;
 951                 struct dm_arg_set path_args;
 952
 953                 if (as->argc < nr_args) {
 954                         ti->error = "not enough path parameters";
 955                         r = -EINVAL;
 956                         goto bad;
 957                 }
 958
 959                 path_args.argc = nr_args;
 960                 path_args.argv = as->argv;
 961
 962                 pgpath = parse_path(&path_args, &pg->ps, ti);
 963                 if (IS_ERR(pgpath)) {
 964                         r = PTR_ERR(pgpath);
 965                         goto bad;
 966                 }
 967
 968                 pgpath->pg = pg;
 969                 list_add_tail(&pgpath->list, &pg->pgpaths);
 970                 dm_consume_args(as, nr_args);
 971         }
 972
 973         return pg;
 974
 975  bad:
 976         free_priority_group(pg, ti);
 977         return ERR_PTR(r);
 978 }
 979
 980 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 981 {
 982         unsigned hw_argc;
 983         int ret;
 984         struct dm_target *ti = m->ti;
 985
 986         static struct dm_arg _args[] = {
 987                 {0, 1024, "invalid number of hardware handler args"},
 988         };
 989
 990         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 991                 return -EINVAL;
 992
 993         if (!hw_argc)
 994                 return 0;
 995
 996         if (m->queue_mode == DM_TYPE_BIO_BASED) {
 997                 dm_consume_args(as, hw_argc);
 998                 DMERR("bio-based multipath doesn't allow hardware handler args");
 999                 return 0;
1000         }
1001
1002         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1003
1004         if (hw_argc > 1) {
1005                 char *p;
1006                 int i, j, len = 4;
1007
1008                 for (i = 0; i <= hw_argc - 2; i++)
1009                         len += strlen(as->argv[i]) + 1;
1010                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1011                 if (!p) {
1012                         ti->error = "memory allocation failed";
1013                         ret = -ENOMEM;
1014                         goto fail;
1015                 }
1016                 j = sprintf(p, "%d", hw_argc - 1);
1017                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1018                         j = sprintf(p, "%s", as->argv[i]);
1019         }
1020         dm_consume_args(as, hw_argc - 1);
1021
1022         return 0;
1023 fail:
1024         kfree(m->hw_handler_name);
1025         m->hw_handler_name = NULL;
1026         return ret;
1027 }
1028
1029 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1030 {
1031         int r;
1032         unsigned argc;
1033         struct dm_target *ti = m->ti;
1034         const char *arg_name;
1035
1036         static struct dm_arg _args[] = {
1037                 {0, 8, "invalid number of feature args"},
1038                 {1, 50, "pg_init_retries must be between 1 and 50"},
1039                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1040         };
1041
1042         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1043         if (r)
1044                 return -EINVAL;
1045
1046         if (!argc)
1047                 return 0;
1048
1049         do {
1050                 arg_name = dm_shift_arg(as);
1051                 argc--;
1052
1053                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1054                         r = queue_if_no_path(m, true, false);
1055                         continue;
1056                 }
1057
1058                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1059                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1060                         continue;
1061                 }
1062
1063                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1064                     (argc >= 1)) {
1065                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1066                         argc--;
1067                         continue;
1068                 }
1069
1070                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1071                     (argc >= 1)) {
1072                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1073                         argc--;
1074                         continue;
1075                 }
1076
1077                 if (!strcasecmp(arg_name, "queue_mode") &&
1078                     (argc >= 1)) {
1079                         const char *queue_mode_name = dm_shift_arg(as);
1080
1081                         if (!strcasecmp(queue_mode_name, "bio"))
1082                                 m->queue_mode = DM_TYPE_BIO_BASED;
1083                         else if (!strcasecmp(queue_mode_name, "rq"))
1084                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1085                         else if (!strcasecmp(queue_mode_name, "mq"))
1086                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1087                         else {
1088                                 ti->error = "Unknown 'queue_mode' requested";
1089                                 r = -EINVAL;
1090                         }
1091                         argc--;
1092                         continue;
1093                 }
1094
1095                 ti->error = "Unrecognised multipath feature request";
1096                 r = -EINVAL;
1097         } while (argc && !r);
1098
1099         return r;
1100 }
1101
1102 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1103 {
1104         /* target arguments */
1105         static struct dm_arg _args[] = {
1106                 {0, 1024, "invalid number of priority groups"},
1107                 {0, 1024, "invalid initial priority group number"},
1108         };
1109
1110         int r;
1111         struct multipath *m;
1112         struct dm_arg_set as;
1113         unsigned pg_count = 0;
1114         unsigned next_pg_num;
1115
1116         as.argc = argc;
1117         as.argv = argv;
1118
1119         m = alloc_multipath(ti);
1120         if (!m) {
1121                 ti->error = "can't allocate multipath";
1122                 return -EINVAL;
1123         }
1124
1125         r = parse_features(&as, m);
1126         if (r)
1127                 goto bad;
1128
1129         r = alloc_multipath_stage2(ti, m);
1130         if (r)
1131                 goto bad;
1132
1133         r = parse_hw_handler(&as, m);
1134         if (r)
1135                 goto bad;
1136
1137         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1138         if (r)
1139                 goto bad;
1140
1141         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1142         if (r)
1143                 goto bad;
1144
1145         if ((!m->nr_priority_groups && next_pg_num) ||
1146             (m->nr_priority_groups && !next_pg_num)) {
1147                 ti->error = "invalid initial priority group";
1148                 r = -EINVAL;
1149                 goto bad;
1150         }
1151
1152         /* parse the priority groups */
1153         while (as.argc) {
1154                 struct priority_group *pg;
1155                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1156
1157                 pg = parse_priority_group(&as, m);
1158                 if (IS_ERR(pg)) {
1159                         r = PTR_ERR(pg);
1160                         goto bad;
1161                 }
1162
1163                 nr_valid_paths += pg->nr_pgpaths;
1164                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1165
1166                 list_add_tail(&pg->list, &m->priority_groups);
1167                 pg_count++;
1168                 pg->pg_num = pg_count;
1169                 if (!--next_pg_num)
1170                         m->next_pg = pg;
1171         }
1172
1173         if (pg_count != m->nr_priority_groups) {
1174                 ti->error = "priority group count mismatch";
1175                 r = -EINVAL;
1176                 goto bad;
1177         }
1178
1179         ti->num_flush_bios = 1;
1180         ti->num_discard_bios = 1;
1181         ti->num_write_same_bios = 1;
1182         if (m->queue_mode == DM_TYPE_BIO_BASED)
1183                 ti->per_io_data_size = multipath_per_bio_data_size();
1184         else if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
1185                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1186
1187         return 0;
1188
1189  bad:
1190         free_multipath(m);
1191         return r;
1192 }
1193
1194 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1195 {
1196         DECLARE_WAITQUEUE(wait, current);
1197
1198         add_wait_queue(&m->pg_init_wait, &wait);
1199
1200         while (1) {
1201                 set_current_state(TASK_UNINTERRUPTIBLE);
1202
1203                 if (!atomic_read(&m->pg_init_in_progress))
1204                         break;
1205
1206                 io_schedule();
1207         }
1208         set_current_state(TASK_RUNNING);
1209
1210         remove_wait_queue(&m->pg_init_wait, &wait);
1211 }
1212
1213 static void flush_multipath_work(struct multipath *m)
1214 {
1215         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1216         smp_mb__after_atomic();
1217
1218         flush_workqueue(kmpath_handlerd);
1219         multipath_wait_for_pg_init_completion(m);
1220         flush_workqueue(kmultipathd);
1221         flush_work(&m->trigger_event);
1222
1223         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1224         smp_mb__after_atomic();
1225 }
1226
1227 static void multipath_dtr(struct dm_target *ti)
1228 {
1229         struct multipath *m = ti->private;
1230
1231         flush_multipath_work(m);
1232         free_multipath(m);
1233 }
1234
1235 /*
1236  * Take a path out of use.
1237  */
1238 static int fail_path(struct pgpath *pgpath)
1239 {
1240         unsigned long flags;
1241         struct multipath *m = pgpath->pg->m;
1242
1243         spin_lock_irqsave(&m->lock, flags);
1244
1245         if (!pgpath->is_active)
1246                 goto out;
1247
1248         DMWARN("Failing path %s.", pgpath->path.dev->name);
1249
1250         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1251         pgpath->is_active = false;
1252         pgpath->fail_count++;
1253
1254         atomic_dec(&m->nr_valid_paths);
1255
1256         if (pgpath == m->current_pgpath)
1257                 m->current_pgpath = NULL;
1258
1259         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1260                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1261
1262         schedule_work(&m->trigger_event);
1263
1264 out:
1265         spin_unlock_irqrestore(&m->lock, flags);
1266
1267         return 0;
1268 }
1269
1270 /*
1271  * Reinstate a previously-failed path
1272  */
1273 static int reinstate_path(struct pgpath *pgpath)
1274 {
1275         int r = 0, run_queue = 0;
1276         unsigned long flags;
1277         struct multipath *m = pgpath->pg->m;
1278         unsigned nr_valid_paths;
1279
1280         spin_lock_irqsave(&m->lock, flags);
1281
1282         if (pgpath->is_active)
1283                 goto out;
1284
1285         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1286
1287         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1288         if (r)
1289                 goto out;
1290
1291         pgpath->is_active = true;
1292
1293         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1294         if (nr_valid_paths == 1) {
1295                 m->current_pgpath = NULL;
1296                 run_queue = 1;
1297         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1298                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1299                         atomic_inc(&m->pg_init_in_progress);
1300         }
1301
1302         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1303                        pgpath->path.dev->name, nr_valid_paths);
1304
1305         schedule_work(&m->trigger_event);
1306
1307 out:
1308         spin_unlock_irqrestore(&m->lock, flags);
1309         if (run_queue) {
1310                 dm_table_run_md_queue_async(m->ti->table);
1311                 process_queued_bios_list(m);
1312         }
1313
1314         return r;
1315 }
1316
1317 /*
1318  * Fail or reinstate all paths that match the provided struct dm_dev.
1319  */
1320 static int action_dev(struct multipath *m, struct dm_dev *dev,
1321                       action_fn action)
1322 {
1323         int r = -EINVAL;
1324         struct pgpath *pgpath;
1325         struct priority_group *pg;
1326
1327         list_for_each_entry(pg, &m->priority_groups, list) {
1328                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1329                         if (pgpath->path.dev == dev)
1330                                 r = action(pgpath);
1331                 }
1332         }
1333
1334         return r;
1335 }
1336
1337 /*
1338  * Temporarily try to avoid having to use the specified PG
1339  */
1340 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1341                       bool bypassed)
1342 {
1343         unsigned long flags;
1344
1345         spin_lock_irqsave(&m->lock, flags);
1346
1347         pg->bypassed = bypassed;
1348         m->current_pgpath = NULL;
1349         m->current_pg = NULL;
1350
1351         spin_unlock_irqrestore(&m->lock, flags);
1352
1353         schedule_work(&m->trigger_event);
1354 }
1355
1356 /*
1357  * Switch to using the specified PG from the next I/O that gets mapped
1358  */
1359 static int switch_pg_num(struct multipath *m, const char *pgstr)
1360 {
1361         struct priority_group *pg;
1362         unsigned pgnum;
1363         unsigned long flags;
1364         char dummy;
1365
1366         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1367             (pgnum > m->nr_priority_groups)) {
1368                 DMWARN("invalid PG number supplied to switch_pg_num");
1369                 return -EINVAL;
1370         }
1371
1372         spin_lock_irqsave(&m->lock, flags);
1373         list_for_each_entry(pg, &m->priority_groups, list) {
1374                 pg->bypassed = false;
1375                 if (--pgnum)
1376                         continue;
1377
1378                 m->current_pgpath = NULL;
1379                 m->current_pg = NULL;
1380                 m->next_pg = pg;
1381         }
1382         spin_unlock_irqrestore(&m->lock, flags);
1383
1384         schedule_work(&m->trigger_event);
1385         return 0;
1386 }
1387
1388 /*
1389  * Set/clear bypassed status of a PG.
1390  * PGs are numbered upwards from 1 in the order they were declared.
1391  */
1392 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1393 {
1394         struct priority_group *pg;
1395         unsigned pgnum;
1396         char dummy;
1397
1398         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1399             (pgnum > m->nr_priority_groups)) {
1400                 DMWARN("invalid PG number supplied to bypass_pg");
1401                 return -EINVAL;
1402         }
1403
1404         list_for_each_entry(pg, &m->priority_groups, list) {
1405                 if (!--pgnum)
1406                         break;
1407         }
1408
1409         bypass_pg(m, pg, bypassed);
1410         return 0;
1411 }
1412
1413 /*
1414  * Should we retry pg_init immediately?
1415  */
1416 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1417 {
1418         unsigned long flags;
1419         bool limit_reached = false;
1420
1421         spin_lock_irqsave(&m->lock, flags);
1422
1423         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1424             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1425                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1426         else
1427                 limit_reached = true;
1428
1429         spin_unlock_irqrestore(&m->lock, flags);
1430
1431         return limit_reached;
1432 }
1433
1434 static void pg_init_done(void *data, int errors)
1435 {
1436         struct pgpath *pgpath = data;
1437         struct priority_group *pg = pgpath->pg;
1438         struct multipath *m = pg->m;
1439         unsigned long flags;
1440         bool delay_retry = false;
1441
1442         /* device or driver problems */
1443         switch (errors) {
1444         case SCSI_DH_OK:
1445                 break;
1446         case SCSI_DH_NOSYS:
1447                 if (!m->hw_handler_name) {
1448                         errors = 0;
1449                         break;
1450                 }
1451                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1452                       "Error %d.", m->hw_handler_name, errors);
1453                 /*
1454                  * Fail path for now, so we do not ping pong
1455                  */
1456                 fail_path(pgpath);
1457                 break;
1458         case SCSI_DH_DEV_TEMP_BUSY:
1459                 /*
1460                  * Probably doing something like FW upgrade on the
1461                  * controller so try the other pg.
1462                  */
1463                 bypass_pg(m, pg, true);
1464                 break;
1465         case SCSI_DH_RETRY:
1466                 /* Wait before retrying. */
1467                 delay_retry = 1;
1468         case SCSI_DH_IMM_RETRY:
1469         case SCSI_DH_RES_TEMP_UNAVAIL:
1470                 if (pg_init_limit_reached(m, pgpath))
1471                         fail_path(pgpath);
1472                 errors = 0;
1473                 break;
1474         case SCSI_DH_DEV_OFFLINED:
1475         default:
1476                 /*
1477                  * We probably do not want to fail the path for a device
1478                  * error, but this is what the old dm did. In future
1479                  * patches we can do more advanced handling.
1480                  */
1481                 fail_path(pgpath);
1482         }
1483
1484         spin_lock_irqsave(&m->lock, flags);
1485         if (errors) {
1486                 if (pgpath == m->current_pgpath) {
1487                         DMERR("Could not failover device. Error %d.", errors);
1488                         m->current_pgpath = NULL;
1489                         m->current_pg = NULL;
1490                 }
1491         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1492                 pg->bypassed = false;
1493
1494         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1495                 /* Activations of other paths are still on going */
1496                 goto out;
1497
1498         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1499                 if (delay_retry)
1500                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1501                 else
1502                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1503
1504                 if (__pg_init_all_paths(m))
1505                         goto out;
1506         }
1507         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1508
1509         process_queued_bios_list(m);
1510
1511         /*
1512          * Wake up any thread waiting to suspend.
1513          */
1514         wake_up(&m->pg_init_wait);
1515
1516 out:
1517         spin_unlock_irqrestore(&m->lock, flags);
1518 }
1519
1520 static void activate_path(struct work_struct *work)
1521 {
1522         struct pgpath *pgpath =
1523                 container_of(work, struct pgpath, activate_path.work);
1524
1525         if (pgpath->is_active)
1526                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1527                                  pg_init_done, pgpath);
1528         else
1529                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1530 }
1531
1532 static int noretry_error(int error)
1533 {
1534         switch (error) {
1535         case -EOPNOTSUPP:
1536         case -EREMOTEIO:
1537         case -EILSEQ:
1538         case -ENODATA:
1539         case -ENOSPC:
1540                 return 1;
1541         }
1542
1543         /* Anything else could be a path failure, so should be retried */
1544         return 0;
1545 }
1546
1547 /*
1548  * end_io handling
1549  */
1550 static int do_end_io(struct multipath *m, struct request *clone,
1551                      int error, struct dm_mpath_io *mpio)
1552 {
1553         /*
1554          * We don't queue any clone request inside the multipath target
1555          * during end I/O handling, since those clone requests don't have
1556          * bio clones.  If we queue them inside the multipath target,
1557          * we need to make bio clones, that requires memory allocation.
1558          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1559          *  don't have bio clones.)
1560          * Instead of queueing the clone request here, we queue the original
1561          * request into dm core, which will remake a clone request and
1562          * clone bios for it and resubmit it later.
1563          */
1564         int r = DM_ENDIO_REQUEUE;
1565
1566         if (!error && !clone->errors)
1567                 return 0;       /* I/O complete */
1568
1569         if (noretry_error(error))
1570                 return error;
1571
1572         if (mpio->pgpath)
1573                 fail_path(mpio->pgpath);
1574
1575         if (!atomic_read(&m->nr_valid_paths)) {
1576                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1577                         if (!must_push_back_rq(m))
1578                                 r = -EIO;
1579                 } else {
1580                         if (error == -EBADE)
1581                                 r = error;
1582                 }
1583         }
1584
1585         return r;
1586 }
1587
1588 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1589                             int error, union map_info *map_context)
1590 {
1591         struct multipath *m = ti->private;
1592         struct dm_mpath_io *mpio = get_mpio(map_context);
1593         struct pgpath *pgpath;
1594         struct path_selector *ps;
1595         int r;
1596
1597         BUG_ON(!mpio);
1598
1599         r = do_end_io(m, clone, error, mpio);
1600         pgpath = mpio->pgpath;
1601         if (pgpath) {
1602                 ps = &pgpath->pg->ps;
1603                 if (ps->type->end_io)
1604                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1605         }
1606         clear_request_fn_mpio(m, map_context);
1607
1608         return r;
1609 }
1610
1611 static int do_end_io_bio(struct multipath *m, struct bio *clone,
1612                          int error, struct dm_mpath_io *mpio)
1613 {
1614         unsigned long flags;
1615
1616         if (!error)
1617                 return 0;       /* I/O complete */
1618
1619         if (noretry_error(error))
1620                 return error;
1621
1622         if (mpio->pgpath)
1623                 fail_path(mpio->pgpath);
1624
1625         if (!atomic_read(&m->nr_valid_paths)) {
1626                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1627                         if (!must_push_back_bio(m))
1628                                 return -EIO;
1629                         return DM_ENDIO_REQUEUE;
1630                 } else {
1631                         if (error == -EBADE)
1632                                 return error;
1633                 }
1634         }
1635
1636         /* Queue for the daemon to resubmit */
1637         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1638
1639         spin_lock_irqsave(&m->lock, flags);
1640         bio_list_add(&m->queued_bios, clone);
1641         spin_unlock_irqrestore(&m->lock, flags);
1642         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1643                 queue_work(kmultipathd, &m->process_queued_bios);
1644
1645         return DM_ENDIO_INCOMPLETE;
1646 }
1647
1648 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, int error)
1649 {
1650         struct multipath *m = ti->private;
1651         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1652         struct pgpath *pgpath;
1653         struct path_selector *ps;
1654         int r;
1655
1656         BUG_ON(!mpio);
1657
1658         r = do_end_io_bio(m, clone, error, mpio);
1659         pgpath = mpio->pgpath;
1660         if (pgpath) {
1661                 ps = &pgpath->pg->ps;
1662                 if (ps->type->end_io)
1663                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1664         }
1665
1666         return r;
1667 }
1668
1669 /*
1670  * Suspend can't complete until all the I/O is processed so if
1671  * the last path fails we must error any remaining I/O.
1672  * Note that if the freeze_bdev fails while suspending, the
1673  * queue_if_no_path state is lost - userspace should reset it.
1674  */
1675 static void multipath_presuspend(struct dm_target *ti)
1676 {
1677         struct multipath *m = ti->private;
1678
1679         queue_if_no_path(m, false, true);
1680 }
1681
1682 static void multipath_postsuspend(struct dm_target *ti)
1683 {
1684         struct multipath *m = ti->private;
1685
1686         mutex_lock(&m->work_mutex);
1687         flush_multipath_work(m);
1688         mutex_unlock(&m->work_mutex);
1689 }
1690
1691 /*
1692  * Restore the queue_if_no_path setting.
1693  */
1694 static void multipath_resume(struct dm_target *ti)
1695 {
1696         struct multipath *m = ti->private;
1697         unsigned long flags;
1698
1699         spin_lock_irqsave(&m->lock, flags);
1700         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags))
1701                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1702         else
1703                 clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1704         spin_unlock_irqrestore(&m->lock, flags);
1705 }
1706
1707 /*
1708  * Info output has the following format:
1709  * num_multipath_feature_args [multipath_feature_args]*
1710  * num_handler_status_args [handler_status_args]*
1711  * num_groups init_group_number
1712  *            [A|D|E num_ps_status_args [ps_status_args]*
1713  *             num_paths num_selector_args
1714  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1715  *
1716  * Table output has the following format (identical to the constructor string):
1717  * num_feature_args [features_args]*
1718  * num_handler_args hw_handler [hw_handler_args]*
1719  * num_groups init_group_number
1720  *     [priority selector-name num_ps_args [ps_args]*
1721  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1722  */
1723 static void multipath_status(struct dm_target *ti, status_type_t type,
1724                              unsigned status_flags, char *result, unsigned maxlen)
1725 {
1726         int sz = 0;
1727         unsigned long flags;
1728         struct multipath *m = ti->private;
1729         struct priority_group *pg;
1730         struct pgpath *p;
1731         unsigned pg_num;
1732         char state;
1733
1734         spin_lock_irqsave(&m->lock, flags);
1735
1736         /* Features */
1737         if (type == STATUSTYPE_INFO)
1738                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1739                        atomic_read(&m->pg_init_count));
1740         else {
1741                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1742                               (m->pg_init_retries > 0) * 2 +
1743                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1744                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1745                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1746
1747                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1748                         DMEMIT("queue_if_no_path ");
1749                 if (m->pg_init_retries)
1750                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1751                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1752                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1753                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1754                         DMEMIT("retain_attached_hw_handler ");
1755                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1756                         switch(m->queue_mode) {
1757                         case DM_TYPE_BIO_BASED:
1758                                 DMEMIT("queue_mode bio ");
1759                                 break;
1760                         case DM_TYPE_MQ_REQUEST_BASED:
1761                                 DMEMIT("queue_mode mq ");
1762                                 break;
1763                         }
1764                 }
1765         }
1766
1767         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1768                 DMEMIT("0 ");
1769         else
1770                 DMEMIT("1 %s ", m->hw_handler_name);
1771
1772         DMEMIT("%u ", m->nr_priority_groups);
1773
1774         if (m->next_pg)
1775                 pg_num = m->next_pg->pg_num;
1776         else if (m->current_pg)
1777                 pg_num = m->current_pg->pg_num;
1778         else
1779                 pg_num = (m->nr_priority_groups ? 1 : 0);
1780
1781         DMEMIT("%u ", pg_num);
1782
1783         switch (type) {
1784         case STATUSTYPE_INFO:
1785                 list_for_each_entry(pg, &m->priority_groups, list) {
1786                         if (pg->bypassed)
1787                                 state = 'D';    /* Disabled */
1788                         else if (pg == m->current_pg)
1789                                 state = 'A';    /* Currently Active */
1790                         else
1791                                 state = 'E';    /* Enabled */
1792
1793                         DMEMIT("%c ", state);
1794
1795                         if (pg->ps.type->status)
1796                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1797                                                           result + sz,
1798                                                           maxlen - sz);
1799                         else
1800                                 DMEMIT("0 ");
1801
1802                         DMEMIT("%u %u ", pg->nr_pgpaths,
1803                                pg->ps.type->info_args);
1804
1805                         list_for_each_entry(p, &pg->pgpaths, list) {
1806                                 DMEMIT("%s %s %u ", p->path.dev->name,
1807                                        p->is_active ? "A" : "F",
1808                                        p->fail_count);
1809                                 if (pg->ps.type->status)
1810                                         sz += pg->ps.type->status(&pg->ps,
1811                                               &p->path, type, result + sz,
1812                                               maxlen - sz);
1813                         }
1814                 }
1815                 break;
1816
1817         case STATUSTYPE_TABLE:
1818                 list_for_each_entry(pg, &m->priority_groups, list) {
1819                         DMEMIT("%s ", pg->ps.type->name);
1820
1821                         if (pg->ps.type->status)
1822                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1823                                                           result + sz,
1824                                                           maxlen - sz);
1825                         else
1826                                 DMEMIT("0 ");
1827
1828                         DMEMIT("%u %u ", pg->nr_pgpaths,
1829                                pg->ps.type->table_args);
1830
1831                         list_for_each_entry(p, &pg->pgpaths, list) {
1832                                 DMEMIT("%s ", p->path.dev->name);
1833                                 if (pg->ps.type->status)
1834                                         sz += pg->ps.type->status(&pg->ps,
1835                                               &p->path, type, result + sz,
1836                                               maxlen - sz);
1837                         }
1838                 }
1839                 break;
1840         }
1841
1842         spin_unlock_irqrestore(&m->lock, flags);
1843 }
1844
1845 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1846 {
1847         int r = -EINVAL;
1848         struct dm_dev *dev;
1849         struct multipath *m = ti->private;
1850         action_fn action;
1851
1852         mutex_lock(&m->work_mutex);
1853
1854         if (dm_suspended(ti)) {
1855                 r = -EBUSY;
1856                 goto out;
1857         }
1858
1859         if (argc == 1) {
1860                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1861                         r = queue_if_no_path(m, true, false);
1862                         goto out;
1863                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1864                         r = queue_if_no_path(m, false, false);
1865                         goto out;
1866                 }
1867         }
1868
1869         if (argc != 2) {
1870                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1871                 goto out;
1872         }
1873
1874         if (!strcasecmp(argv[0], "disable_group")) {
1875                 r = bypass_pg_num(m, argv[1], true);
1876                 goto out;
1877         } else if (!strcasecmp(argv[0], "enable_group")) {
1878                 r = bypass_pg_num(m, argv[1], false);
1879                 goto out;
1880         } else if (!strcasecmp(argv[0], "switch_group")) {
1881                 r = switch_pg_num(m, argv[1]);
1882                 goto out;
1883         } else if (!strcasecmp(argv[0], "reinstate_path"))
1884                 action = reinstate_path;
1885         else if (!strcasecmp(argv[0], "fail_path"))
1886                 action = fail_path;
1887         else {
1888                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1889                 goto out;
1890         }
1891
1892         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1893         if (r) {
1894                 DMWARN("message: error getting device %s",
1895                        argv[1]);
1896                 goto out;
1897         }
1898
1899         r = action_dev(m, dev, action);
1900
1901         dm_put_device(ti, dev);
1902
1903 out:
1904         mutex_unlock(&m->work_mutex);
1905         return r;
1906 }
1907
1908 static int multipath_prepare_ioctl(struct dm_target *ti,
1909                 struct block_device **bdev, fmode_t *mode)
1910 {
1911         struct multipath *m = ti->private;
1912         struct pgpath *current_pgpath;
1913         int r;
1914
1915         current_pgpath = lockless_dereference(m->current_pgpath);
1916         if (!current_pgpath)
1917                 current_pgpath = choose_pgpath(m, 0);
1918
1919         if (current_pgpath) {
1920                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1921                         *bdev = current_pgpath->path.dev->bdev;
1922                         *mode = current_pgpath->path.dev->mode;
1923                         r = 0;
1924                 } else {
1925                         /* pg_init has not started or completed */
1926                         r = -ENOTCONN;
1927                 }
1928         } else {
1929                 /* No path is available */
1930                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1931                         r = -ENOTCONN;
1932                 else
1933                         r = -EIO;
1934         }
1935
1936         if (r == -ENOTCONN) {
1937                 if (!lockless_dereference(m->current_pg)) {
1938                         /* Path status changed, redo selection */
1939                         (void) choose_pgpath(m, 0);
1940                 }
1941                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1942                         pg_init_all_paths(m);
1943                 dm_table_run_md_queue_async(m->ti->table);
1944                 process_queued_bios_list(m);
1945         }
1946
1947         /*
1948          * Only pass ioctls through if the device sizes match exactly.
1949          */
1950         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1951                 return 1;
1952         return r;
1953 }
1954
1955 static int multipath_iterate_devices(struct dm_target *ti,
1956                                      iterate_devices_callout_fn fn, void *data)
1957 {
1958         struct multipath *m = ti->private;
1959         struct priority_group *pg;
1960         struct pgpath *p;
1961         int ret = 0;
1962
1963         list_for_each_entry(pg, &m->priority_groups, list) {
1964                 list_for_each_entry(p, &pg->pgpaths, list) {
1965                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1966                         if (ret)
1967                                 goto out;
1968                 }
1969         }
1970
1971 out:
1972         return ret;
1973 }
1974
1975 static int pgpath_busy(struct pgpath *pgpath)
1976 {
1977         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1978
1979         return blk_lld_busy(q);
1980 }
1981
1982 /*
1983  * We return "busy", only when we can map I/Os but underlying devices
1984  * are busy (so even if we map I/Os now, the I/Os will wait on
1985  * the underlying queue).
1986  * In other words, if we want to kill I/Os or queue them inside us
1987  * due to map unavailability, we don't return "busy".  Otherwise,
1988  * dm core won't give us the I/Os and we can't do what we want.
1989  */
1990 static int multipath_busy(struct dm_target *ti)
1991 {
1992         bool busy = false, has_active = false;
1993         struct multipath *m = ti->private;
1994         struct priority_group *pg, *next_pg;
1995         struct pgpath *pgpath;
1996
1997         /* pg_init in progress or no paths available */
1998         if (atomic_read(&m->pg_init_in_progress) ||
1999             (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)))
2000                 return true;
2001
2002         /* Guess which priority_group will be used at next mapping time */
2003         pg = lockless_dereference(m->current_pg);
2004         next_pg = lockless_dereference(m->next_pg);
2005         if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
2006                 pg = next_pg;
2007
2008         if (!pg) {
2009                 /*
2010                  * We don't know which pg will be used at next mapping time.
2011                  * We don't call choose_pgpath() here to avoid to trigger
2012                  * pg_init just by busy checking.
2013                  * So we don't know whether underlying devices we will be using
2014                  * at next mapping time are busy or not. Just try mapping.
2015                  */
2016                 return busy;
2017         }
2018
2019         /*
2020          * If there is one non-busy active path at least, the path selector
2021          * will be able to select it. So we consider such a pg as not busy.
2022          */
2023         busy = true;
2024         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2025                 if (pgpath->is_active) {
2026                         has_active = true;
2027                         if (!pgpath_busy(pgpath)) {
2028                                 busy = false;
2029                                 break;
2030                         }
2031                 }
2032         }
2033
2034         if (!has_active) {
2035                 /*
2036                  * No active path in this pg, so this pg won't be used and
2037                  * the current_pg will be changed at next mapping time.
2038                  * We need to try mapping to determine it.
2039                  */
2040                 busy = false;
2041         }
2042
2043         return busy;
2044 }
2045
2046 /*-----------------------------------------------------------------
2047  * Module setup
2048  *---------------------------------------------------------------*/
2049 static struct target_type multipath_target = {
2050         .name = "multipath",
2051         .version = {1, 12, 0},
2052         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
2053         .module = THIS_MODULE,
2054         .ctr = multipath_ctr,
2055         .dtr = multipath_dtr,
2056         .map_rq = multipath_map,
2057         .clone_and_map_rq = multipath_clone_and_map,
2058         .release_clone_rq = multipath_release_clone,
2059         .rq_end_io = multipath_end_io,
2060         .map = multipath_map_bio,
2061         .end_io = multipath_end_io_bio,
2062         .presuspend = multipath_presuspend,
2063         .postsuspend = multipath_postsuspend,
2064         .resume = multipath_resume,
2065         .status = multipath_status,
2066         .message = multipath_message,
2067         .prepare_ioctl = multipath_prepare_ioctl,
2068         .iterate_devices = multipath_iterate_devices,
2069         .busy = multipath_busy,
2070 };
2071
2072 static int __init dm_multipath_init(void)
2073 {
2074         int r;
2075
2076         /* allocate a slab for the dm_mpath_ios */
2077         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
2078         if (!_mpio_cache)
2079                 return -ENOMEM;
2080
2081         r = dm_register_target(&multipath_target);
2082         if (r < 0) {
2083                 DMERR("request-based register failed %d", r);
2084                 r = -EINVAL;
2085                 goto bad_register_target;
2086         }
2087
2088         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2089         if (!kmultipathd) {
2090                 DMERR("failed to create workqueue kmpathd");
2091                 r = -ENOMEM;
2092                 goto bad_alloc_kmultipathd;
2093         }
2094
2095         /*
2096          * A separate workqueue is used to handle the device handlers
2097          * to avoid overloading existing workqueue. Overloading the
2098          * old workqueue would also create a bottleneck in the
2099          * path of the storage hardware device activation.
2100          */
2101         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2102                                                   WQ_MEM_RECLAIM);
2103         if (!kmpath_handlerd) {
2104                 DMERR("failed to create workqueue kmpath_handlerd");
2105                 r = -ENOMEM;
2106                 goto bad_alloc_kmpath_handlerd;
2107         }
2108
2109         return 0;
2110
2111 bad_alloc_kmpath_handlerd:
2112         destroy_workqueue(kmultipathd);
2113 bad_alloc_kmultipathd:
2114         dm_unregister_target(&multipath_target);
2115 bad_register_target:
2116         kmem_cache_destroy(_mpio_cache);
2117
2118         return r;
2119 }
2120
2121 static void __exit dm_multipath_exit(void)
2122 {
2123         destroy_workqueue(kmpath_handlerd);
2124         destroy_workqueue(kmultipathd);
2125
2126         dm_unregister_target(&multipath_target);
2127         kmem_cache_destroy(_mpio_cache);
2128 }
2129
2130 module_init(dm_multipath_init);
2131 module_exit(dm_multipath_exit);
2132
2133 MODULE_DESCRIPTION(DM_NAME " multipath target");
2134 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2135 MODULE_LICENSE("GPL");