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         unsigned long flags;            /* Multipath state flags */
  68
  69         spinlock_t lock;
  70         enum dm_queue_mode queue_mode;
  71
  72         struct pgpath *current_pgpath;
  73         struct priority_group *current_pg;
  74         struct priority_group *next_pg; /* Switch to this PG if set */
  75
  76         atomic_t nr_valid_paths;        /* Total number of usable paths */
  77         unsigned nr_priority_groups;
  78         struct list_head priority_groups;
  79
  80         const char *hw_handler_name;
  81         char *hw_handler_params;
  82         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  83         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  84         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  85         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  86         atomic_t pg_init_count;         /* Number of times pg_init called */
  87
  88         struct mutex work_mutex;
  89         struct work_struct trigger_event;
  90         struct dm_target *ti;
  91
  92         struct work_struct process_queued_bios;
  93         struct bio_list queued_bios;
  94 };
  95
  96 /*
  97  * Context information attached to each io we process.
  98  */
  99 struct dm_mpath_io {
 100         struct pgpath *pgpath;
 101         size_t nr_bytes;
 102 };
 103
 104 typedef int (*action_fn) (struct pgpath *pgpath);
 105
 106 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 107 static void trigger_event(struct work_struct *work);
 108 static void activate_or_offline_path(struct pgpath *pgpath);
 109 static void activate_path_work(struct work_struct *work);
 110 static void process_queued_bios(struct work_struct *work);
 111
 112 /*-----------------------------------------------
 113  * Multipath state flags.
 114  *-----------------------------------------------*/
 115
 116 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 117 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 118 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 119 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 120 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 121 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 122 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 123
 124 /*-----------------------------------------------
 125  * Allocation routines
 126  *-----------------------------------------------*/
 127
 128 static struct pgpath *alloc_pgpath(void)
 129 {
 130         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 131
 132         if (!pgpath)
 133                 return NULL;
 134
 135         pgpath->is_active = true;
 136
 137         return pgpath;
 138 }
 139
 140 static void free_pgpath(struct pgpath *pgpath)
 141 {
 142         kfree(pgpath);
 143 }
 144
 145 static struct priority_group *alloc_priority_group(void)
 146 {
 147         struct priority_group *pg;
 148
 149         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 150
 151         if (pg)
 152                 INIT_LIST_HEAD(&pg->pgpaths);
 153
 154         return pg;
 155 }
 156
 157 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 158 {
 159         struct pgpath *pgpath, *tmp;
 160
 161         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 162                 list_del(&pgpath->list);
 163                 dm_put_device(ti, pgpath->path.dev);
 164                 free_pgpath(pgpath);
 165         }
 166 }
 167
 168 static void free_priority_group(struct priority_group *pg,
 169                                 struct dm_target *ti)
 170 {
 171         struct path_selector *ps = &pg->ps;
 172
 173         if (ps->type) {
 174                 ps->type->destroy(ps);
 175                 dm_put_path_selector(ps->type);
 176         }
 177
 178         free_pgpaths(&pg->pgpaths, ti);
 179         kfree(pg);
 180 }
 181
 182 static struct multipath *alloc_multipath(struct dm_target *ti)
 183 {
 184         struct multipath *m;
 185
 186         m = kzalloc(sizeof(*m), GFP_KERNEL);
 187         if (m) {
 188                 INIT_LIST_HEAD(&m->priority_groups);
 189                 spin_lock_init(&m->lock);
 190                 atomic_set(&m->nr_valid_paths, 0);
 191                 INIT_WORK(&m->trigger_event, trigger_event);
 192                 mutex_init(&m->work_mutex);
 193
 194                 m->queue_mode = DM_TYPE_NONE;
 195
 196                 m->ti = ti;
 197                 ti->private = m;
 198         }
 199
 200         return m;
 201 }
 202
 203 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 204 {
 205         if (m->queue_mode == DM_TYPE_NONE) {
 206                 /*
 207                  * Default to request-based.
 208                  */
 209                 if (dm_use_blk_mq(dm_table_get_md(ti->table)))
 210                         m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
 211                 else
 212                         m->queue_mode = DM_TYPE_REQUEST_BASED;
 213
 214         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 215                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 216                 /*
 217                  * bio-based doesn't support any direct scsi_dh management;
 218                  * it just discovers if a scsi_dh is attached.
 219                  */
 220                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 221         }
 222
 223         dm_table_set_type(ti->table, m->queue_mode);
 224
 225         /*
 226          * Init fields that are only used when a scsi_dh is attached
 227          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 228          */
 229         set_bit(MPATHF_QUEUE_IO, &m->flags);
 230         atomic_set(&m->pg_init_in_progress, 0);
 231         atomic_set(&m->pg_init_count, 0);
 232         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 233         init_waitqueue_head(&m->pg_init_wait);
 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         mutex_destroy(&m->work_mutex);
 250         kfree(m);
 251 }
 252
 253 static struct dm_mpath_io *get_mpio(union map_info *info)
 254 {
 255         return info->ptr;
 256 }
 257
 258 static size_t multipath_per_bio_data_size(void)
 259 {
 260         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 261 }
 262
 263 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 264 {
 265         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 266 }
 267
 268 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 269 {
 270         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 271         void *bio_details = mpio + 1;
 272         return bio_details;
 273 }
 274
 275 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 276 {
 277         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 278         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 279
 280         mpio->nr_bytes = bio->bi_iter.bi_size;
 281         mpio->pgpath = NULL;
 282         *mpio_p = mpio;
 283
 284         dm_bio_record(bio_details, bio);
 285 }
 286
 287 /*-----------------------------------------------
 288  * Path selection
 289  *-----------------------------------------------*/
 290
 291 static int __pg_init_all_paths(struct multipath *m)
 292 {
 293         struct pgpath *pgpath;
 294         unsigned long pg_init_delay = 0;
 295
 296         lockdep_assert_held(&m->lock);
 297
 298         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 299                 return 0;
 300
 301         atomic_inc(&m->pg_init_count);
 302         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 303
 304         /* Check here to reset pg_init_required */
 305         if (!m->current_pg)
 306                 return 0;
 307
 308         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 309                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 310                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 311         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 312                 /* Skip failed paths */
 313                 if (!pgpath->is_active)
 314                         continue;
 315                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 316                                        pg_init_delay))
 317                         atomic_inc(&m->pg_init_in_progress);
 318         }
 319         return atomic_read(&m->pg_init_in_progress);
 320 }
 321
 322 static int pg_init_all_paths(struct multipath *m)
 323 {
 324         int ret;
 325         unsigned long flags;
 326
 327         spin_lock_irqsave(&m->lock, flags);
 328         ret = __pg_init_all_paths(m);
 329         spin_unlock_irqrestore(&m->lock, flags);
 330
 331         return ret;
 332 }
 333
 334 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 335 {
 336         m->current_pg = pg;
 337
 338         /* Must we initialise the PG first, and queue I/O till it's ready? */
 339         if (m->hw_handler_name) {
 340                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 341                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 342         } else {
 343                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 344                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 345         }
 346
 347         atomic_set(&m->pg_init_count, 0);
 348 }
 349
 350 static struct pgpath *choose_path_in_pg(struct multipath *m,
 351                                         struct priority_group *pg,
 352                                         size_t nr_bytes)
 353 {
 354         unsigned long flags;
 355         struct dm_path *path;
 356         struct pgpath *pgpath;
 357
 358         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 359         if (!path)
 360                 return ERR_PTR(-ENXIO);
 361
 362         pgpath = path_to_pgpath(path);
 363
 364         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 365                 /* Only update current_pgpath if pg changed */
 366                 spin_lock_irqsave(&m->lock, flags);
 367                 m->current_pgpath = pgpath;
 368                 __switch_pg(m, pg);
 369                 spin_unlock_irqrestore(&m->lock, flags);
 370         }
 371
 372         return pgpath;
 373 }
 374
 375 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 376 {
 377         unsigned long flags;
 378         struct priority_group *pg;
 379         struct pgpath *pgpath;
 380         unsigned bypassed = 1;
 381
 382         if (!atomic_read(&m->nr_valid_paths)) {
 383                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 384                 goto failed;
 385         }
 386
 387         /* Were we instructed to switch PG? */
 388         if (READ_ONCE(m->next_pg)) {
 389                 spin_lock_irqsave(&m->lock, flags);
 390                 pg = m->next_pg;
 391                 if (!pg) {
 392                         spin_unlock_irqrestore(&m->lock, flags);
 393                         goto check_current_pg;
 394                 }
 395                 m->next_pg = NULL;
 396                 spin_unlock_irqrestore(&m->lock, flags);
 397                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 398                 if (!IS_ERR_OR_NULL(pgpath))
 399                         return pgpath;
 400         }
 401
 402         /* Don't change PG until it has no remaining paths */
 403 check_current_pg:
 404         pg = READ_ONCE(m->current_pg);
 405         if (pg) {
 406                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 407                 if (!IS_ERR_OR_NULL(pgpath))
 408                         return pgpath;
 409         }
 410
 411         /*
 412          * Loop through priority groups until we find a valid path.
 413          * First time we skip PGs marked 'bypassed'.
 414          * Second time we only try the ones we skipped, but set
 415          * pg_init_delay_retry so we do not hammer controllers.
 416          */
 417         do {
 418                 list_for_each_entry(pg, &m->priority_groups, list) {
 419                         if (pg->bypassed == !!bypassed)
 420                                 continue;
 421                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 422                         if (!IS_ERR_OR_NULL(pgpath)) {
 423                                 if (!bypassed)
 424                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 425                                 return pgpath;
 426                         }
 427                 }
 428         } while (bypassed--);
 429
 430 failed:
 431         spin_lock_irqsave(&m->lock, flags);
 432         m->current_pgpath = NULL;
 433         m->current_pg = NULL;
 434         spin_unlock_irqrestore(&m->lock, flags);
 435
 436         return NULL;
 437 }
 438
 439 /*
 440  * dm_report_EIO() is a macro instead of a function to make pr_debug()
 441  * report the function name and line number of the function from which
 442  * it has been invoked.
 443  */
 444 #define dm_report_EIO(m)                                                \
 445 do {                                                                    \
 446         struct mapped_device *md = dm_table_get_md((m)->ti->table);     \
 447                                                                         \
 448         pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 449                  dm_device_name(md),                                    \
 450                  test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),        \
 451                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),  \
 452                  dm_noflush_suspending((m)->ti));                       \
 453 } while (0)
 454
 455 /*
 456  * Check whether bios must be queued in the device-mapper core rather
 457  * than here in the target.
 458  *
 459  * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
 460  * the same value then we are not between multipath_presuspend()
 461  * and multipath_resume() calls and we have no need to check
 462  * for the DMF_NOFLUSH_SUSPENDING flag.
 463  */
 464 static bool __must_push_back(struct multipath *m, unsigned long flags)
 465 {
 466         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
 467                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
 468                 dm_noflush_suspending(m->ti));
 469 }
 470
 471 /*
 472  * Following functions use READ_ONCE to get atomic access to
 473  * all m->flags to avoid taking spinlock
 474  */
 475 static bool must_push_back_rq(struct multipath *m)
 476 {
 477         unsigned long flags = READ_ONCE(m->flags);
 478         return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
 479 }
 480
 481 static bool must_push_back_bio(struct multipath *m)
 482 {
 483         unsigned long flags = READ_ONCE(m->flags);
 484         return __must_push_back(m, flags);
 485 }
 486
 487 /*
 488  * Map cloned requests (request-based multipath)
 489  */
 490 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 491                                    union map_info *map_context,
 492                                    struct request **__clone)
 493 {
 494         struct multipath *m = ti->private;
 495         size_t nr_bytes = blk_rq_bytes(rq);
 496         struct pgpath *pgpath;
 497         struct block_device *bdev;
 498         struct dm_mpath_io *mpio = get_mpio(map_context);
 499         struct request_queue *q;
 500         struct request *clone;
 501
 502         /* Do we need to select a new pgpath? */
 503         pgpath = READ_ONCE(m->current_pgpath);
 504         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 505                 pgpath = choose_pgpath(m, nr_bytes);
 506
 507         if (!pgpath) {
 508                 if (must_push_back_rq(m))
 509                         return DM_MAPIO_DELAY_REQUEUE;
 510                 dm_report_EIO(m);       /* Failed */
 511                 return DM_MAPIO_KILL;
 512         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 513                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 514                 pg_init_all_paths(m);
 515                 return DM_MAPIO_DELAY_REQUEUE;
 516         }
 517
 518         mpio->pgpath = pgpath;
 519         mpio->nr_bytes = nr_bytes;
 520
 521         bdev = pgpath->path.dev->bdev;
 522         q = bdev_get_queue(bdev);
 523         clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE, GFP_ATOMIC);
 524         if (IS_ERR(clone)) {
 525                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 526                 if (blk_queue_dying(q)) {
 527                         atomic_inc(&m->pg_init_in_progress);
 528                         activate_or_offline_path(pgpath);
 529                         return DM_MAPIO_DELAY_REQUEUE;
 530                 }
 531
 532                 /*
 533                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 534                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 535                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 536                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 537                  * otherwise I/O merging can suffer.
 538                  */
 539                 if (q->mq_ops)
 540                         return DM_MAPIO_REQUEUE;
 541                 else
 542                         return DM_MAPIO_DELAY_REQUEUE;
 543         }
 544         clone->bio = clone->biotail = NULL;
 545         clone->rq_disk = bdev->bd_disk;
 546         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 547         *__clone = clone;
 548
 549         if (pgpath->pg->ps.type->start_io)
 550                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 551                                               &pgpath->path,
 552                                               nr_bytes);
 553         return DM_MAPIO_REMAPPED;
 554 }
 555
 556 static void multipath_release_clone(struct request *clone)
 557 {
 558         blk_put_request(clone);
 559 }
 560
 561 /*
 562  * Map cloned bios (bio-based multipath)
 563  */
 564
 565 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 566 {
 567         struct pgpath *pgpath;
 568         unsigned long flags;
 569         bool queue_io;
 570
 571         /* Do we need to select a new pgpath? */
 572         pgpath = READ_ONCE(m->current_pgpath);
 573         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 574         if (!pgpath || !queue_io)
 575                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 576
 577         if ((pgpath && queue_io) ||
 578             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 579                 /* Queue for the daemon to resubmit */
 580                 spin_lock_irqsave(&m->lock, flags);
 581                 bio_list_add(&m->queued_bios, bio);
 582                 spin_unlock_irqrestore(&m->lock, flags);
 583
 584                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 585                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 586                         pg_init_all_paths(m);
 587                 else if (!queue_io)
 588                         queue_work(kmultipathd, &m->process_queued_bios);
 589
 590                 return ERR_PTR(-EAGAIN);
 591         }
 592
 593         return pgpath;
 594 }
 595
 596 static struct pgpath *__map_bio_fast(struct multipath *m, struct bio *bio)
 597 {
 598         struct pgpath *pgpath;
 599         unsigned long flags;
 600
 601         /* Do we need to select a new pgpath? */
 602         /*
 603          * FIXME: currently only switching path if no path (due to failure, etc)
 604          * - which negates the point of using a path selector
 605          */
 606         pgpath = READ_ONCE(m->current_pgpath);
 607         if (!pgpath)
 608                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 609
 610         if (!pgpath) {
 611                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 612                         /* Queue for the daemon to resubmit */
 613                         spin_lock_irqsave(&m->lock, flags);
 614                         bio_list_add(&m->queued_bios, bio);
 615                         spin_unlock_irqrestore(&m->lock, flags);
 616                         queue_work(kmultipathd, &m->process_queued_bios);
 617
 618                         return ERR_PTR(-EAGAIN);
 619                 }
 620                 return NULL;
 621         }
 622
 623         return pgpath;
 624 }
 625
 626 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 627                                struct dm_mpath_io *mpio)
 628 {
 629         struct pgpath *pgpath;
 630
 631         if (!m->hw_handler_name)
 632                 pgpath = __map_bio_fast(m, bio);
 633         else
 634                 pgpath = __map_bio(m, bio);
 635
 636         if (IS_ERR(pgpath))
 637                 return DM_MAPIO_SUBMITTED;
 638
 639         if (!pgpath) {
 640                 if (must_push_back_bio(m))
 641                         return DM_MAPIO_REQUEUE;
 642                 dm_report_EIO(m);
 643                 return DM_MAPIO_KILL;
 644         }
 645
 646         mpio->pgpath = pgpath;
 647
 648         bio->bi_status = 0;
 649         bio_set_dev(bio, pgpath->path.dev->bdev);
 650         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 651
 652         if (pgpath->pg->ps.type->start_io)
 653                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 654                                               &pgpath->path,
 655                                               mpio->nr_bytes);
 656         return DM_MAPIO_REMAPPED;
 657 }
 658
 659 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 660 {
 661         struct multipath *m = ti->private;
 662         struct dm_mpath_io *mpio = NULL;
 663
 664         multipath_init_per_bio_data(bio, &mpio);
 665         return __multipath_map_bio(m, bio, mpio);
 666 }
 667
 668 static void process_queued_io_list(struct multipath *m)
 669 {
 670         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 671                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 672         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 673                 queue_work(kmultipathd, &m->process_queued_bios);
 674 }
 675
 676 static void process_queued_bios(struct work_struct *work)
 677 {
 678         int r;
 679         unsigned long flags;
 680         struct bio *bio;
 681         struct bio_list bios;
 682         struct blk_plug plug;
 683         struct multipath *m =
 684                 container_of(work, struct multipath, process_queued_bios);
 685
 686         bio_list_init(&bios);
 687
 688         spin_lock_irqsave(&m->lock, flags);
 689
 690         if (bio_list_empty(&m->queued_bios)) {
 691                 spin_unlock_irqrestore(&m->lock, flags);
 692                 return;
 693         }
 694
 695         bio_list_merge(&bios, &m->queued_bios);
 696         bio_list_init(&m->queued_bios);
 697
 698         spin_unlock_irqrestore(&m->lock, flags);
 699
 700         blk_start_plug(&plug);
 701         while ((bio = bio_list_pop(&bios))) {
 702                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 703                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 704                 r = __multipath_map_bio(m, bio, mpio);
 705                 switch (r) {
 706                 case DM_MAPIO_KILL:
 707                         bio->bi_status = BLK_STS_IOERR;
 708                         bio_endio(bio);
 709                         break;
 710                 case DM_MAPIO_REQUEUE:
 711                         bio->bi_status = BLK_STS_DM_REQUEUE;
 712                         bio_endio(bio);
 713                         break;
 714                 case DM_MAPIO_REMAPPED:
 715                         generic_make_request(bio);
 716                         break;
 717                 case 0:
 718                         break;
 719                 default:
 720                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 721                 }
 722         }
 723         blk_finish_plug(&plug);
 724 }
 725
 726 /*
 727  * If we run out of usable paths, should we queue I/O or error it?
 728  */
 729 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 730                             bool save_old_value)
 731 {
 732         unsigned long flags;
 733
 734         spin_lock_irqsave(&m->lock, flags);
 735         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 736                    (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 737                    (!save_old_value && queue_if_no_path));
 738         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 739         spin_unlock_irqrestore(&m->lock, flags);
 740
 741         if (!queue_if_no_path) {
 742                 dm_table_run_md_queue_async(m->ti->table);
 743                 process_queued_io_list(m);
 744         }
 745
 746         return 0;
 747 }
 748
 749 /*
 750  * An event is triggered whenever a path is taken out of use.
 751  * Includes path failure and PG bypass.
 752  */
 753 static void trigger_event(struct work_struct *work)
 754 {
 755         struct multipath *m =
 756                 container_of(work, struct multipath, trigger_event);
 757
 758         dm_table_event(m->ti->table);
 759 }
 760
 761 /*-----------------------------------------------------------------
 762  * Constructor/argument parsing:
 763  * <#multipath feature args> [<arg>]*
 764  * <#hw_handler args> [hw_handler [<arg>]*]
 765  * <#priority groups>
 766  * <initial priority group>
 767  *     [<selector> <#selector args> [<arg>]*
 768  *      <#paths> <#per-path selector args>
 769  *         [<path> [<arg>]* ]+ ]+
 770  *---------------------------------------------------------------*/
 771 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 772                                struct dm_target *ti)
 773 {
 774         int r;
 775         struct path_selector_type *pst;
 776         unsigned ps_argc;
 777
 778         static const struct dm_arg _args[] = {
 779                 {0, 1024, "invalid number of path selector args"},
 780         };
 781
 782         pst = dm_get_path_selector(dm_shift_arg(as));
 783         if (!pst) {
 784                 ti->error = "unknown path selector type";
 785                 return -EINVAL;
 786         }
 787
 788         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 789         if (r) {
 790                 dm_put_path_selector(pst);
 791                 return -EINVAL;
 792         }
 793
 794         r = pst->create(&pg->ps, ps_argc, as->argv);
 795         if (r) {
 796                 dm_put_path_selector(pst);
 797                 ti->error = "path selector constructor failed";
 798                 return r;
 799         }
 800
 801         pg->ps.type = pst;
 802         dm_consume_args(as, ps_argc);
 803
 804         return 0;
 805 }
 806
 807 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 808                          const char *attached_handler_name, char **error)
 809 {
 810         struct request_queue *q = bdev_get_queue(bdev);
 811         int r;
 812
 813         if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 814 retain:
 815                 if (attached_handler_name) {
 816                         /*
 817                          * Clear any hw_handler_params associated with a
 818                          * handler that isn't already attached.
 819                          */
 820                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 821                                 kfree(m->hw_handler_params);
 822                                 m->hw_handler_params = NULL;
 823                         }
 824
 825                         /*
 826                          * Reset hw_handler_name to match the attached handler
 827                          *
 828                          * NB. This modifies the table line to show the actual
 829                          * handler instead of the original table passed in.
 830                          */
 831                         kfree(m->hw_handler_name);
 832                         m->hw_handler_name = attached_handler_name;
 833                 }
 834         }
 835
 836         if (m->hw_handler_name) {
 837                 r = scsi_dh_attach(q, m->hw_handler_name);
 838                 if (r == -EBUSY) {
 839                         char b[BDEVNAME_SIZE];
 840
 841                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 842                                bdevname(bdev, b));
 843                         goto retain;
 844                 }
 845                 if (r < 0) {
 846                         *error = "error attaching hardware handler";
 847                         return r;
 848                 }
 849
 850                 if (m->hw_handler_params) {
 851                         r = scsi_dh_set_params(q, m->hw_handler_params);
 852                         if (r < 0) {
 853                                 *error = "unable to set hardware handler parameters";
 854                                 return r;
 855                         }
 856                 }
 857         }
 858
 859         return 0;
 860 }
 861
 862 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 863                                  struct dm_target *ti)
 864 {
 865         int r;
 866         struct pgpath *p;
 867         struct multipath *m = ti->private;
 868         struct request_queue *q;
 869         const char *attached_handler_name;
 870
 871         /* we need at least a path arg */
 872         if (as->argc < 1) {
 873                 ti->error = "no device given";
 874                 return ERR_PTR(-EINVAL);
 875         }
 876
 877         p = alloc_pgpath();
 878         if (!p)
 879                 return ERR_PTR(-ENOMEM);
 880
 881         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 882                           &p->path.dev);
 883         if (r) {
 884                 ti->error = "error getting device";
 885                 goto bad;
 886         }
 887
 888         q = bdev_get_queue(p->path.dev->bdev);
 889         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 890         if (attached_handler_name) {
 891                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 892                 r = setup_scsi_dh(p->path.dev->bdev, m, attached_handler_name, &ti->error);
 893                 if (r) {
 894                         dm_put_device(ti, p->path.dev);
 895                         goto bad;
 896                 }
 897         }
 898
 899         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 900         if (r) {
 901                 dm_put_device(ti, p->path.dev);
 902                 goto bad;
 903         }
 904
 905         return p;
 906  bad:
 907         free_pgpath(p);
 908         return ERR_PTR(r);
 909 }
 910
 911 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 912                                                    struct multipath *m)
 913 {
 914         static const struct dm_arg _args[] = {
 915                 {1, 1024, "invalid number of paths"},
 916                 {0, 1024, "invalid number of selector args"}
 917         };
 918
 919         int r;
 920         unsigned i, nr_selector_args, nr_args;
 921         struct priority_group *pg;
 922         struct dm_target *ti = m->ti;
 923
 924         if (as->argc < 2) {
 925                 as->argc = 0;
 926                 ti->error = "not enough priority group arguments";
 927                 return ERR_PTR(-EINVAL);
 928         }
 929
 930         pg = alloc_priority_group();
 931         if (!pg) {
 932                 ti->error = "couldn't allocate priority group";
 933                 return ERR_PTR(-ENOMEM);
 934         }
 935         pg->m = m;
 936
 937         r = parse_path_selector(as, pg, ti);
 938         if (r)
 939                 goto bad;
 940
 941         /*
 942          * read the paths
 943          */
 944         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 945         if (r)
 946                 goto bad;
 947
 948         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 949         if (r)
 950                 goto bad;
 951
 952         nr_args = 1 + nr_selector_args;
 953         for (i = 0; i < pg->nr_pgpaths; i++) {
 954                 struct pgpath *pgpath;
 955                 struct dm_arg_set path_args;
 956
 957                 if (as->argc < nr_args) {
 958                         ti->error = "not enough path parameters";
 959                         r = -EINVAL;
 960                         goto bad;
 961                 }
 962
 963                 path_args.argc = nr_args;
 964                 path_args.argv = as->argv;
 965
 966                 pgpath = parse_path(&path_args, &pg->ps, ti);
 967                 if (IS_ERR(pgpath)) {
 968                         r = PTR_ERR(pgpath);
 969                         goto bad;
 970                 }
 971
 972                 pgpath->pg = pg;
 973                 list_add_tail(&pgpath->list, &pg->pgpaths);
 974                 dm_consume_args(as, nr_args);
 975         }
 976
 977         return pg;
 978
 979  bad:
 980         free_priority_group(pg, ti);
 981         return ERR_PTR(r);
 982 }
 983
 984 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 985 {
 986         unsigned hw_argc;
 987         int ret;
 988         struct dm_target *ti = m->ti;
 989
 990         static const struct dm_arg _args[] = {
 991                 {0, 1024, "invalid number of hardware handler args"},
 992         };
 993
 994         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 995                 return -EINVAL;
 996
 997         if (!hw_argc)
 998                 return 0;
 999
1000         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1001                 dm_consume_args(as, hw_argc);
1002                 DMERR("bio-based multipath doesn't allow hardware handler args");
1003                 return 0;
1004         }
1005
1006         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1007         if (!m->hw_handler_name)
1008                 return -EINVAL;
1009
1010         if (hw_argc > 1) {
1011                 char *p;
1012                 int i, j, len = 4;
1013
1014                 for (i = 0; i <= hw_argc - 2; i++)
1015                         len += strlen(as->argv[i]) + 1;
1016                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1017                 if (!p) {
1018                         ti->error = "memory allocation failed";
1019                         ret = -ENOMEM;
1020                         goto fail;
1021                 }
1022                 j = sprintf(p, "%d", hw_argc - 1);
1023                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1024                         j = sprintf(p, "%s", as->argv[i]);
1025         }
1026         dm_consume_args(as, hw_argc - 1);
1027
1028         return 0;
1029 fail:
1030         kfree(m->hw_handler_name);
1031         m->hw_handler_name = NULL;
1032         return ret;
1033 }
1034
1035 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1036 {
1037         int r;
1038         unsigned argc;
1039         struct dm_target *ti = m->ti;
1040         const char *arg_name;
1041
1042         static const struct dm_arg _args[] = {
1043                 {0, 8, "invalid number of feature args"},
1044                 {1, 50, "pg_init_retries must be between 1 and 50"},
1045                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1046         };
1047
1048         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1049         if (r)
1050                 return -EINVAL;
1051
1052         if (!argc)
1053                 return 0;
1054
1055         do {
1056                 arg_name = dm_shift_arg(as);
1057                 argc--;
1058
1059                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1060                         r = queue_if_no_path(m, true, false);
1061                         continue;
1062                 }
1063
1064                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1065                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1066                         continue;
1067                 }
1068
1069                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1070                     (argc >= 1)) {
1071                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1072                         argc--;
1073                         continue;
1074                 }
1075
1076                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1077                     (argc >= 1)) {
1078                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1079                         argc--;
1080                         continue;
1081                 }
1082
1083                 if (!strcasecmp(arg_name, "queue_mode") &&
1084                     (argc >= 1)) {
1085                         const char *queue_mode_name = dm_shift_arg(as);
1086
1087                         if (!strcasecmp(queue_mode_name, "bio"))
1088                                 m->queue_mode = DM_TYPE_BIO_BASED;
1089                         else if (!strcasecmp(queue_mode_name, "rq"))
1090                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1091                         else if (!strcasecmp(queue_mode_name, "mq"))
1092                                 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1093                         else {
1094                                 ti->error = "Unknown 'queue_mode' requested";
1095                                 r = -EINVAL;
1096                         }
1097                         argc--;
1098                         continue;
1099                 }
1100
1101                 ti->error = "Unrecognised multipath feature request";
1102                 r = -EINVAL;
1103         } while (argc && !r);
1104
1105         return r;
1106 }
1107
1108 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1109 {
1110         /* target arguments */
1111         static const struct dm_arg _args[] = {
1112                 {0, 1024, "invalid number of priority groups"},
1113                 {0, 1024, "invalid initial priority group number"},
1114         };
1115
1116         int r;
1117         struct multipath *m;
1118         struct dm_arg_set as;
1119         unsigned pg_count = 0;
1120         unsigned next_pg_num;
1121
1122         as.argc = argc;
1123         as.argv = argv;
1124
1125         m = alloc_multipath(ti);
1126         if (!m) {
1127                 ti->error = "can't allocate multipath";
1128                 return -EINVAL;
1129         }
1130
1131         r = parse_features(&as, m);
1132         if (r)
1133                 goto bad;
1134
1135         r = alloc_multipath_stage2(ti, m);
1136         if (r)
1137                 goto bad;
1138
1139         r = parse_hw_handler(&as, m);
1140         if (r)
1141                 goto bad;
1142
1143         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1144         if (r)
1145                 goto bad;
1146
1147         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1148         if (r)
1149                 goto bad;
1150
1151         if ((!m->nr_priority_groups && next_pg_num) ||
1152             (m->nr_priority_groups && !next_pg_num)) {
1153                 ti->error = "invalid initial priority group";
1154                 r = -EINVAL;
1155                 goto bad;
1156         }
1157
1158         /* parse the priority groups */
1159         while (as.argc) {
1160                 struct priority_group *pg;
1161                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1162
1163                 pg = parse_priority_group(&as, m);
1164                 if (IS_ERR(pg)) {
1165                         r = PTR_ERR(pg);
1166                         goto bad;
1167                 }
1168
1169                 nr_valid_paths += pg->nr_pgpaths;
1170                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1171
1172                 list_add_tail(&pg->list, &m->priority_groups);
1173                 pg_count++;
1174                 pg->pg_num = pg_count;
1175                 if (!--next_pg_num)
1176                         m->next_pg = pg;
1177         }
1178
1179         if (pg_count != m->nr_priority_groups) {
1180                 ti->error = "priority group count mismatch";
1181                 r = -EINVAL;
1182                 goto bad;
1183         }
1184
1185         ti->num_flush_bios = 1;
1186         ti->num_discard_bios = 1;
1187         ti->num_write_same_bios = 1;
1188         ti->num_write_zeroes_bios = 1;
1189         if (m->queue_mode == DM_TYPE_BIO_BASED)
1190                 ti->per_io_data_size = multipath_per_bio_data_size();
1191         else
1192                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1193
1194         return 0;
1195
1196  bad:
1197         free_multipath(m);
1198         return r;
1199 }
1200
1201 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1202 {
1203         DEFINE_WAIT(wait);
1204
1205         while (1) {
1206                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1207
1208                 if (!atomic_read(&m->pg_init_in_progress))
1209                         break;
1210
1211                 io_schedule();
1212         }
1213         finish_wait(&m->pg_init_wait, &wait);
1214 }
1215
1216 static void flush_multipath_work(struct multipath *m)
1217 {
1218         if (m->hw_handler_name) {
1219                 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1220                 smp_mb__after_atomic();
1221
1222                 flush_workqueue(kmpath_handlerd);
1223                 multipath_wait_for_pg_init_completion(m);
1224
1225                 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1226                 smp_mb__after_atomic();
1227         }
1228
1229         flush_workqueue(kmultipathd);
1230         flush_work(&m->trigger_event);
1231 }
1232
1233 static void multipath_dtr(struct dm_target *ti)
1234 {
1235         struct multipath *m = ti->private;
1236
1237         flush_multipath_work(m);
1238         free_multipath(m);
1239 }
1240
1241 /*
1242  * Take a path out of use.
1243  */
1244 static int fail_path(struct pgpath *pgpath)
1245 {
1246         unsigned long flags;
1247         struct multipath *m = pgpath->pg->m;
1248
1249         spin_lock_irqsave(&m->lock, flags);
1250
1251         if (!pgpath->is_active)
1252                 goto out;
1253
1254         DMWARN("Failing path %s.", pgpath->path.dev->name);
1255
1256         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1257         pgpath->is_active = false;
1258         pgpath->fail_count++;
1259
1260         atomic_dec(&m->nr_valid_paths);
1261
1262         if (pgpath == m->current_pgpath)
1263                 m->current_pgpath = NULL;
1264
1265         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1266                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1267
1268         schedule_work(&m->trigger_event);
1269
1270 out:
1271         spin_unlock_irqrestore(&m->lock, flags);
1272
1273         return 0;
1274 }
1275
1276 /*
1277  * Reinstate a previously-failed path
1278  */
1279 static int reinstate_path(struct pgpath *pgpath)
1280 {
1281         int r = 0, run_queue = 0;
1282         unsigned long flags;
1283         struct multipath *m = pgpath->pg->m;
1284         unsigned nr_valid_paths;
1285
1286         spin_lock_irqsave(&m->lock, flags);
1287
1288         if (pgpath->is_active)
1289                 goto out;
1290
1291         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1292
1293         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1294         if (r)
1295                 goto out;
1296
1297         pgpath->is_active = true;
1298
1299         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1300         if (nr_valid_paths == 1) {
1301                 m->current_pgpath = NULL;
1302                 run_queue = 1;
1303         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1304                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1305                         atomic_inc(&m->pg_init_in_progress);
1306         }
1307
1308         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1309                        pgpath->path.dev->name, nr_valid_paths);
1310
1311         schedule_work(&m->trigger_event);
1312
1313 out:
1314         spin_unlock_irqrestore(&m->lock, flags);
1315         if (run_queue) {
1316                 dm_table_run_md_queue_async(m->ti->table);
1317                 process_queued_io_list(m);
1318         }
1319
1320         return r;
1321 }
1322
1323 /*
1324  * Fail or reinstate all paths that match the provided struct dm_dev.
1325  */
1326 static int action_dev(struct multipath *m, struct dm_dev *dev,
1327                       action_fn action)
1328 {
1329         int r = -EINVAL;
1330         struct pgpath *pgpath;
1331         struct priority_group *pg;
1332
1333         list_for_each_entry(pg, &m->priority_groups, list) {
1334                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1335                         if (pgpath->path.dev == dev)
1336                                 r = action(pgpath);
1337                 }
1338         }
1339
1340         return r;
1341 }
1342
1343 /*
1344  * Temporarily try to avoid having to use the specified PG
1345  */
1346 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1347                       bool bypassed)
1348 {
1349         unsigned long flags;
1350
1351         spin_lock_irqsave(&m->lock, flags);
1352
1353         pg->bypassed = bypassed;
1354         m->current_pgpath = NULL;
1355         m->current_pg = NULL;
1356
1357         spin_unlock_irqrestore(&m->lock, flags);
1358
1359         schedule_work(&m->trigger_event);
1360 }
1361
1362 /*
1363  * Switch to using the specified PG from the next I/O that gets mapped
1364  */
1365 static int switch_pg_num(struct multipath *m, const char *pgstr)
1366 {
1367         struct priority_group *pg;
1368         unsigned pgnum;
1369         unsigned long flags;
1370         char dummy;
1371
1372         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1373             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1374                 DMWARN("invalid PG number supplied to switch_pg_num");
1375                 return -EINVAL;
1376         }
1377
1378         spin_lock_irqsave(&m->lock, flags);
1379         list_for_each_entry(pg, &m->priority_groups, list) {
1380                 pg->bypassed = false;
1381                 if (--pgnum)
1382                         continue;
1383
1384                 m->current_pgpath = NULL;
1385                 m->current_pg = NULL;
1386                 m->next_pg = pg;
1387         }
1388         spin_unlock_irqrestore(&m->lock, flags);
1389
1390         schedule_work(&m->trigger_event);
1391         return 0;
1392 }
1393
1394 /*
1395  * Set/clear bypassed status of a PG.
1396  * PGs are numbered upwards from 1 in the order they were declared.
1397  */
1398 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1399 {
1400         struct priority_group *pg;
1401         unsigned pgnum;
1402         char dummy;
1403
1404         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1405             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1406                 DMWARN("invalid PG number supplied to bypass_pg");
1407                 return -EINVAL;
1408         }
1409
1410         list_for_each_entry(pg, &m->priority_groups, list) {
1411                 if (!--pgnum)
1412                         break;
1413         }
1414
1415         bypass_pg(m, pg, bypassed);
1416         return 0;
1417 }
1418
1419 /*
1420  * Should we retry pg_init immediately?
1421  */
1422 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1423 {
1424         unsigned long flags;
1425         bool limit_reached = false;
1426
1427         spin_lock_irqsave(&m->lock, flags);
1428
1429         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1430             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1431                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1432         else
1433                 limit_reached = true;
1434
1435         spin_unlock_irqrestore(&m->lock, flags);
1436
1437         return limit_reached;
1438 }
1439
1440 static void pg_init_done(void *data, int errors)
1441 {
1442         struct pgpath *pgpath = data;
1443         struct priority_group *pg = pgpath->pg;
1444         struct multipath *m = pg->m;
1445         unsigned long flags;
1446         bool delay_retry = false;
1447
1448         /* device or driver problems */
1449         switch (errors) {
1450         case SCSI_DH_OK:
1451                 break;
1452         case SCSI_DH_NOSYS:
1453                 if (!m->hw_handler_name) {
1454                         errors = 0;
1455                         break;
1456                 }
1457                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1458                       "Error %d.", m->hw_handler_name, errors);
1459                 /*
1460                  * Fail path for now, so we do not ping pong
1461                  */
1462                 fail_path(pgpath);
1463                 break;
1464         case SCSI_DH_DEV_TEMP_BUSY:
1465                 /*
1466                  * Probably doing something like FW upgrade on the
1467                  * controller so try the other pg.
1468                  */
1469                 bypass_pg(m, pg, true);
1470                 break;
1471         case SCSI_DH_RETRY:
1472                 /* Wait before retrying. */
1473                 delay_retry = 1;
1474                 /* fall through */
1475         case SCSI_DH_IMM_RETRY:
1476         case SCSI_DH_RES_TEMP_UNAVAIL:
1477                 if (pg_init_limit_reached(m, pgpath))
1478                         fail_path(pgpath);
1479                 errors = 0;
1480                 break;
1481         case SCSI_DH_DEV_OFFLINED:
1482         default:
1483                 /*
1484                  * We probably do not want to fail the path for a device
1485                  * error, but this is what the old dm did. In future
1486                  * patches we can do more advanced handling.
1487                  */
1488                 fail_path(pgpath);
1489         }
1490
1491         spin_lock_irqsave(&m->lock, flags);
1492         if (errors) {
1493                 if (pgpath == m->current_pgpath) {
1494                         DMERR("Could not failover device. Error %d.", errors);
1495                         m->current_pgpath = NULL;
1496                         m->current_pg = NULL;
1497                 }
1498         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1499                 pg->bypassed = false;
1500
1501         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1502                 /* Activations of other paths are still on going */
1503                 goto out;
1504
1505         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1506                 if (delay_retry)
1507                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1508                 else
1509                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1510
1511                 if (__pg_init_all_paths(m))
1512                         goto out;
1513         }
1514         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1515
1516         process_queued_io_list(m);
1517
1518         /*
1519          * Wake up any thread waiting to suspend.
1520          */
1521         wake_up(&m->pg_init_wait);
1522
1523 out:
1524         spin_unlock_irqrestore(&m->lock, flags);
1525 }
1526
1527 static void activate_or_offline_path(struct pgpath *pgpath)
1528 {
1529         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1530
1531         if (pgpath->is_active && !blk_queue_dying(q))
1532                 scsi_dh_activate(q, pg_init_done, pgpath);
1533         else
1534                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1535 }
1536
1537 static void activate_path_work(struct work_struct *work)
1538 {
1539         struct pgpath *pgpath =
1540                 container_of(work, struct pgpath, activate_path.work);
1541
1542         activate_or_offline_path(pgpath);
1543 }
1544
1545 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1546                             blk_status_t error, union map_info *map_context)
1547 {
1548         struct dm_mpath_io *mpio = get_mpio(map_context);
1549         struct pgpath *pgpath = mpio->pgpath;
1550         int r = DM_ENDIO_DONE;
1551
1552         /*
1553          * We don't queue any clone request inside the multipath target
1554          * during end I/O handling, since those clone requests don't have
1555          * bio clones.  If we queue them inside the multipath target,
1556          * we need to make bio clones, that requires memory allocation.
1557          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1558          *  don't have bio clones.)
1559          * Instead of queueing the clone request here, we queue the original
1560          * request into dm core, which will remake a clone request and
1561          * clone bios for it and resubmit it later.
1562          */
1563         if (error && blk_path_error(error)) {
1564                 struct multipath *m = ti->private;
1565
1566                 if (error == BLK_STS_RESOURCE)
1567                         r = DM_ENDIO_DELAY_REQUEUE;
1568                 else
1569                         r = DM_ENDIO_REQUEUE;
1570
1571                 if (pgpath)
1572                         fail_path(pgpath);
1573
1574                 if (atomic_read(&m->nr_valid_paths) == 0 &&
1575                     !must_push_back_rq(m)) {
1576                         if (error == BLK_STS_IOERR)
1577                                 dm_report_EIO(m);
1578                         /* complete with the original error */
1579                         r = DM_ENDIO_DONE;
1580                 }
1581         }
1582
1583         if (pgpath) {
1584                 struct path_selector *ps = &pgpath->pg->ps;
1585
1586                 if (ps->type->end_io)
1587                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1588         }
1589
1590         return r;
1591 }
1592
1593 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1594                                 blk_status_t *error)
1595 {
1596         struct multipath *m = ti->private;
1597         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1598         struct pgpath *pgpath = mpio->pgpath;
1599         unsigned long flags;
1600         int r = DM_ENDIO_DONE;
1601
1602         if (!*error || !blk_path_error(*error))
1603                 goto done;
1604
1605         if (pgpath)
1606                 fail_path(pgpath);
1607
1608         if (atomic_read(&m->nr_valid_paths) == 0 &&
1609             !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1610                 if (must_push_back_bio(m)) {
1611                         r = DM_ENDIO_REQUEUE;
1612                 } else {
1613                         dm_report_EIO(m);
1614                         *error = BLK_STS_IOERR;
1615                 }
1616                 goto done;
1617         }
1618
1619         spin_lock_irqsave(&m->lock, flags);
1620         bio_list_add(&m->queued_bios, clone);
1621         spin_unlock_irqrestore(&m->lock, flags);
1622         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1623                 queue_work(kmultipathd, &m->process_queued_bios);
1624
1625         r = DM_ENDIO_INCOMPLETE;
1626 done:
1627         if (pgpath) {
1628                 struct path_selector *ps = &pgpath->pg->ps;
1629
1630                 if (ps->type->end_io)
1631                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1632         }
1633
1634         return r;
1635 }
1636
1637 /*
1638  * Suspend can't complete until all the I/O is processed so if
1639  * the last path fails we must error any remaining I/O.
1640  * Note that if the freeze_bdev fails while suspending, the
1641  * queue_if_no_path state is lost - userspace should reset it.
1642  */
1643 static void multipath_presuspend(struct dm_target *ti)
1644 {
1645         struct multipath *m = ti->private;
1646
1647         queue_if_no_path(m, false, true);
1648 }
1649
1650 static void multipath_postsuspend(struct dm_target *ti)
1651 {
1652         struct multipath *m = ti->private;
1653
1654         mutex_lock(&m->work_mutex);
1655         flush_multipath_work(m);
1656         mutex_unlock(&m->work_mutex);
1657 }
1658
1659 /*
1660  * Restore the queue_if_no_path setting.
1661  */
1662 static void multipath_resume(struct dm_target *ti)
1663 {
1664         struct multipath *m = ti->private;
1665         unsigned long flags;
1666
1667         spin_lock_irqsave(&m->lock, flags);
1668         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1669                    test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1670         spin_unlock_irqrestore(&m->lock, flags);
1671 }
1672
1673 /*
1674  * Info output has the following format:
1675  * num_multipath_feature_args [multipath_feature_args]*
1676  * num_handler_status_args [handler_status_args]*
1677  * num_groups init_group_number
1678  *            [A|D|E num_ps_status_args [ps_status_args]*
1679  *             num_paths num_selector_args
1680  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1681  *
1682  * Table output has the following format (identical to the constructor string):
1683  * num_feature_args [features_args]*
1684  * num_handler_args hw_handler [hw_handler_args]*
1685  * num_groups init_group_number
1686  *     [priority selector-name num_ps_args [ps_args]*
1687  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1688  */
1689 static void multipath_status(struct dm_target *ti, status_type_t type,
1690                              unsigned status_flags, char *result, unsigned maxlen)
1691 {
1692         int sz = 0;
1693         unsigned long flags;
1694         struct multipath *m = ti->private;
1695         struct priority_group *pg;
1696         struct pgpath *p;
1697         unsigned pg_num;
1698         char state;
1699
1700         spin_lock_irqsave(&m->lock, flags);
1701
1702         /* Features */
1703         if (type == STATUSTYPE_INFO)
1704                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1705                        atomic_read(&m->pg_init_count));
1706         else {
1707                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1708                               (m->pg_init_retries > 0) * 2 +
1709                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1710                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1711                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1712
1713                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1714                         DMEMIT("queue_if_no_path ");
1715                 if (m->pg_init_retries)
1716                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1717                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1718                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1719                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1720                         DMEMIT("retain_attached_hw_handler ");
1721                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1722                         switch(m->queue_mode) {
1723                         case DM_TYPE_BIO_BASED:
1724                                 DMEMIT("queue_mode bio ");
1725                                 break;
1726                         case DM_TYPE_MQ_REQUEST_BASED:
1727                                 DMEMIT("queue_mode mq ");
1728                                 break;
1729                         default:
1730                                 WARN_ON_ONCE(true);
1731                                 break;
1732                         }
1733                 }
1734         }
1735
1736         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1737                 DMEMIT("0 ");
1738         else
1739                 DMEMIT("1 %s ", m->hw_handler_name);
1740
1741         DMEMIT("%u ", m->nr_priority_groups);
1742
1743         if (m->next_pg)
1744                 pg_num = m->next_pg->pg_num;
1745         else if (m->current_pg)
1746                 pg_num = m->current_pg->pg_num;
1747         else
1748                 pg_num = (m->nr_priority_groups ? 1 : 0);
1749
1750         DMEMIT("%u ", pg_num);
1751
1752         switch (type) {
1753         case STATUSTYPE_INFO:
1754                 list_for_each_entry(pg, &m->priority_groups, list) {
1755                         if (pg->bypassed)
1756                                 state = 'D';    /* Disabled */
1757                         else if (pg == m->current_pg)
1758                                 state = 'A';    /* Currently Active */
1759                         else
1760                                 state = 'E';    /* Enabled */
1761
1762                         DMEMIT("%c ", state);
1763
1764                         if (pg->ps.type->status)
1765                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1766                                                           result + sz,
1767                                                           maxlen - sz);
1768                         else
1769                                 DMEMIT("0 ");
1770
1771                         DMEMIT("%u %u ", pg->nr_pgpaths,
1772                                pg->ps.type->info_args);
1773
1774                         list_for_each_entry(p, &pg->pgpaths, list) {
1775                                 DMEMIT("%s %s %u ", p->path.dev->name,
1776                                        p->is_active ? "A" : "F",
1777                                        p->fail_count);
1778                                 if (pg->ps.type->status)
1779                                         sz += pg->ps.type->status(&pg->ps,
1780                                               &p->path, type, result + sz,
1781                                               maxlen - sz);
1782                         }
1783                 }
1784                 break;
1785
1786         case STATUSTYPE_TABLE:
1787                 list_for_each_entry(pg, &m->priority_groups, list) {
1788                         DMEMIT("%s ", pg->ps.type->name);
1789
1790                         if (pg->ps.type->status)
1791                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1792                                                           result + sz,
1793                                                           maxlen - sz);
1794                         else
1795                                 DMEMIT("0 ");
1796
1797                         DMEMIT("%u %u ", pg->nr_pgpaths,
1798                                pg->ps.type->table_args);
1799
1800                         list_for_each_entry(p, &pg->pgpaths, list) {
1801                                 DMEMIT("%s ", p->path.dev->name);
1802                                 if (pg->ps.type->status)
1803                                         sz += pg->ps.type->status(&pg->ps,
1804                                               &p->path, type, result + sz,
1805                                               maxlen - sz);
1806                         }
1807                 }
1808                 break;
1809         }
1810
1811         spin_unlock_irqrestore(&m->lock, flags);
1812 }
1813
1814 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1815 {
1816         int r = -EINVAL;
1817         struct dm_dev *dev;
1818         struct multipath *m = ti->private;
1819         action_fn action;
1820
1821         mutex_lock(&m->work_mutex);
1822
1823         if (dm_suspended(ti)) {
1824                 r = -EBUSY;
1825                 goto out;
1826         }
1827
1828         if (argc == 1) {
1829                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1830                         r = queue_if_no_path(m, true, false);
1831                         goto out;
1832                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1833                         r = queue_if_no_path(m, false, false);
1834                         goto out;
1835                 }
1836         }
1837
1838         if (argc != 2) {
1839                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1840                 goto out;
1841         }
1842
1843         if (!strcasecmp(argv[0], "disable_group")) {
1844                 r = bypass_pg_num(m, argv[1], true);
1845                 goto out;
1846         } else if (!strcasecmp(argv[0], "enable_group")) {
1847                 r = bypass_pg_num(m, argv[1], false);
1848                 goto out;
1849         } else if (!strcasecmp(argv[0], "switch_group")) {
1850                 r = switch_pg_num(m, argv[1]);
1851                 goto out;
1852         } else if (!strcasecmp(argv[0], "reinstate_path"))
1853                 action = reinstate_path;
1854         else if (!strcasecmp(argv[0], "fail_path"))
1855                 action = fail_path;
1856         else {
1857                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1858                 goto out;
1859         }
1860
1861         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1862         if (r) {
1863                 DMWARN("message: error getting device %s",
1864                        argv[1]);
1865                 goto out;
1866         }
1867
1868         r = action_dev(m, dev, action);
1869
1870         dm_put_device(ti, dev);
1871
1872 out:
1873         mutex_unlock(&m->work_mutex);
1874         return r;
1875 }
1876
1877 static int multipath_prepare_ioctl(struct dm_target *ti,
1878                 struct block_device **bdev, fmode_t *mode)
1879 {
1880         struct multipath *m = ti->private;
1881         struct pgpath *current_pgpath;
1882         int r;
1883
1884         current_pgpath = READ_ONCE(m->current_pgpath);
1885         if (!current_pgpath)
1886                 current_pgpath = choose_pgpath(m, 0);
1887
1888         if (current_pgpath) {
1889                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1890                         *bdev = current_pgpath->path.dev->bdev;
1891                         *mode = current_pgpath->path.dev->mode;
1892                         r = 0;
1893                 } else {
1894                         /* pg_init has not started or completed */
1895                         r = -ENOTCONN;
1896                 }
1897         } else {
1898                 /* No path is available */
1899                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1900                         r = -ENOTCONN;
1901                 else
1902                         r = -EIO;
1903         }
1904
1905         if (r == -ENOTCONN) {
1906                 if (!READ_ONCE(m->current_pg)) {
1907                         /* Path status changed, redo selection */
1908                         (void) choose_pgpath(m, 0);
1909                 }
1910                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1911                         pg_init_all_paths(m);
1912                 dm_table_run_md_queue_async(m->ti->table);
1913                 process_queued_io_list(m);
1914         }
1915
1916         /*
1917          * Only pass ioctls through if the device sizes match exactly.
1918          */
1919         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1920                 return 1;
1921         return r;
1922 }
1923
1924 static int multipath_iterate_devices(struct dm_target *ti,
1925                                      iterate_devices_callout_fn fn, void *data)
1926 {
1927         struct multipath *m = ti->private;
1928         struct priority_group *pg;
1929         struct pgpath *p;
1930         int ret = 0;
1931
1932         list_for_each_entry(pg, &m->priority_groups, list) {
1933                 list_for_each_entry(p, &pg->pgpaths, list) {
1934                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1935                         if (ret)
1936                                 goto out;
1937                 }
1938         }
1939
1940 out:
1941         return ret;
1942 }
1943
1944 static int pgpath_busy(struct pgpath *pgpath)
1945 {
1946         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1947
1948         return blk_lld_busy(q);
1949 }
1950
1951 /*
1952  * We return "busy", only when we can map I/Os but underlying devices
1953  * are busy (so even if we map I/Os now, the I/Os will wait on
1954  * the underlying queue).
1955  * In other words, if we want to kill I/Os or queue them inside us
1956  * due to map unavailability, we don't return "busy".  Otherwise,
1957  * dm core won't give us the I/Os and we can't do what we want.
1958  */
1959 static int multipath_busy(struct dm_target *ti)
1960 {
1961         bool busy = false, has_active = false;
1962         struct multipath *m = ti->private;
1963         struct priority_group *pg, *next_pg;
1964         struct pgpath *pgpath;
1965
1966         /* pg_init in progress */
1967         if (atomic_read(&m->pg_init_in_progress))
1968                 return true;
1969
1970         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1971         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1972                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
1973
1974         /* Guess which priority_group will be used at next mapping time */
1975         pg = READ_ONCE(m->current_pg);
1976         next_pg = READ_ONCE(m->next_pg);
1977         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1978                 pg = next_pg;
1979
1980         if (!pg) {
1981                 /*
1982                  * We don't know which pg will be used at next mapping time.
1983                  * We don't call choose_pgpath() here to avoid to trigger
1984                  * pg_init just by busy checking.
1985                  * So we don't know whether underlying devices we will be using
1986                  * at next mapping time are busy or not. Just try mapping.
1987                  */
1988                 return busy;
1989         }
1990
1991         /*
1992          * If there is one non-busy active path at least, the path selector
1993          * will be able to select it. So we consider such a pg as not busy.
1994          */
1995         busy = true;
1996         list_for_each_entry(pgpath, &pg->pgpaths, list) {
1997                 if (pgpath->is_active) {
1998                         has_active = true;
1999                         if (!pgpath_busy(pgpath)) {
2000                                 busy = false;
2001                                 break;
2002                         }
2003                 }
2004         }
2005
2006         if (!has_active) {
2007                 /*
2008                  * No active path in this pg, so this pg won't be used and
2009                  * the current_pg will be changed at next mapping time.
2010                  * We need to try mapping to determine it.
2011                  */
2012                 busy = false;
2013         }
2014
2015         return busy;
2016 }
2017
2018 /*-----------------------------------------------------------------
2019  * Module setup
2020  *---------------------------------------------------------------*/
2021 static struct target_type multipath_target = {
2022         .name = "multipath",
2023         .version = {1, 13, 0},
2024         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2025                     DM_TARGET_PASSES_INTEGRITY,
2026         .module = THIS_MODULE,
2027         .ctr = multipath_ctr,
2028         .dtr = multipath_dtr,
2029         .clone_and_map_rq = multipath_clone_and_map,
2030         .release_clone_rq = multipath_release_clone,
2031         .rq_end_io = multipath_end_io,
2032         .map = multipath_map_bio,
2033         .end_io = multipath_end_io_bio,
2034         .presuspend = multipath_presuspend,
2035         .postsuspend = multipath_postsuspend,
2036         .resume = multipath_resume,
2037         .status = multipath_status,
2038         .message = multipath_message,
2039         .prepare_ioctl = multipath_prepare_ioctl,
2040         .iterate_devices = multipath_iterate_devices,
2041         .busy = multipath_busy,
2042 };
2043
2044 static int __init dm_multipath_init(void)
2045 {
2046         int r;
2047
2048         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2049         if (!kmultipathd) {
2050                 DMERR("failed to create workqueue kmpathd");
2051                 r = -ENOMEM;
2052                 goto bad_alloc_kmultipathd;
2053         }
2054
2055         /*
2056          * A separate workqueue is used to handle the device handlers
2057          * to avoid overloading existing workqueue. Overloading the
2058          * old workqueue would also create a bottleneck in the
2059          * path of the storage hardware device activation.
2060          */
2061         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2062                                                   WQ_MEM_RECLAIM);
2063         if (!kmpath_handlerd) {
2064                 DMERR("failed to create workqueue kmpath_handlerd");
2065                 r = -ENOMEM;
2066                 goto bad_alloc_kmpath_handlerd;
2067         }
2068
2069         r = dm_register_target(&multipath_target);
2070         if (r < 0) {
2071                 DMERR("request-based register failed %d", r);
2072                 r = -EINVAL;
2073                 goto bad_register_target;
2074         }
2075
2076         return 0;
2077
2078 bad_register_target:
2079         destroy_workqueue(kmpath_handlerd);
2080 bad_alloc_kmpath_handlerd:
2081         destroy_workqueue(kmultipathd);
2082 bad_alloc_kmultipathd:
2083         return r;
2084 }
2085
2086 static void __exit dm_multipath_exit(void)
2087 {
2088         destroy_workqueue(kmpath_handlerd);
2089         destroy_workqueue(kmultipathd);
2090
2091         dm_unregister_target(&multipath_target);
2092 }
2093
2094 module_init(dm_multipath_init);
2095 module_exit(dm_multipath_exit);
2096
2097 MODULE_DESCRIPTION(DM_NAME " multipath target");
2098 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2099 MODULE_LICENSE("GPL");