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 void pg_init_all_paths(struct multipath *m)
 376 {
 377         unsigned long flags;
 378
 379         spin_lock_irqsave(&m->lock, flags);
 380         __pg_init_all_paths(m);
 381         spin_unlock_irqrestore(&m->lock, flags);
 382 }
 383
 384 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 385 {
 386         m->current_pg = pg;
 387
 388         /* Must we initialise the PG first, and queue I/O till it's ready? */
 389         if (m->hw_handler_name) {
 390                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 391                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 392         } else {
 393                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 394                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 395         }
 396
 397         atomic_set(&m->pg_init_count, 0);
 398 }
 399
 400 static struct pgpath *choose_path_in_pg(struct multipath *m,
 401                                         struct priority_group *pg,
 402                                         size_t nr_bytes)
 403 {
 404         unsigned long flags;
 405         struct dm_path *path;
 406         struct pgpath *pgpath;
 407
 408         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 409         if (!path)
 410                 return ERR_PTR(-ENXIO);
 411
 412         pgpath = path_to_pgpath(path);
 413
 414         if (unlikely(lockless_dereference(m->current_pg) != pg)) {
 415                 /* Only update current_pgpath if pg changed */
 416                 spin_lock_irqsave(&m->lock, flags);
 417                 m->current_pgpath = pgpath;
 418                 __switch_pg(m, pg);
 419                 spin_unlock_irqrestore(&m->lock, flags);
 420         }
 421
 422         return pgpath;
 423 }
 424
 425 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 426 {
 427         unsigned long flags;
 428         struct priority_group *pg;
 429         struct pgpath *pgpath;
 430         bool bypassed = true;
 431
 432         if (!atomic_read(&m->nr_valid_paths)) {
 433                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 434                 goto failed;
 435         }
 436
 437         /* Were we instructed to switch PG? */
 438         if (lockless_dereference(m->next_pg)) {
 439                 spin_lock_irqsave(&m->lock, flags);
 440                 pg = m->next_pg;
 441                 if (!pg) {
 442                         spin_unlock_irqrestore(&m->lock, flags);
 443                         goto check_current_pg;
 444                 }
 445                 m->next_pg = NULL;
 446                 spin_unlock_irqrestore(&m->lock, flags);
 447                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 448                 if (!IS_ERR_OR_NULL(pgpath))
 449                         return pgpath;
 450         }
 451
 452         /* Don't change PG until it has no remaining paths */
 453 check_current_pg:
 454         pg = lockless_dereference(m->current_pg);
 455         if (pg) {
 456                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 457                 if (!IS_ERR_OR_NULL(pgpath))
 458                         return pgpath;
 459         }
 460
 461         /*
 462          * Loop through priority groups until we find a valid path.
 463          * First time we skip PGs marked 'bypassed'.
 464          * Second time we only try the ones we skipped, but set
 465          * pg_init_delay_retry so we do not hammer controllers.
 466          */
 467         do {
 468                 list_for_each_entry(pg, &m->priority_groups, list) {
 469                         if (pg->bypassed == bypassed)
 470                                 continue;
 471                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 472                         if (!IS_ERR_OR_NULL(pgpath)) {
 473                                 if (!bypassed)
 474                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 475                                 return pgpath;
 476                         }
 477                 }
 478         } while (bypassed--);
 479
 480 failed:
 481         spin_lock_irqsave(&m->lock, flags);
 482         m->current_pgpath = NULL;
 483         m->current_pg = NULL;
 484         spin_unlock_irqrestore(&m->lock, flags);
 485
 486         return NULL;
 487 }
 488
 489 /*
 490  * Check whether bios must be queued in the device-mapper core rather
 491  * than here in the target.
 492  *
 493  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 494  * same value then we are not between multipath_presuspend()
 495  * and multipath_resume() calls and we have no need to check
 496  * for the DMF_NOFLUSH_SUSPENDING flag.
 497  */
 498 static bool __must_push_back(struct multipath *m)
 499 {
 500         return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) !=
 501                  test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) &&
 502                 dm_noflush_suspending(m->ti));
 503 }
 504
 505 static bool must_push_back_rq(struct multipath *m)
 506 {
 507         bool r;
 508         unsigned long flags;
 509
 510         spin_lock_irqsave(&m->lock, flags);
 511         r = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) ||
 512              __must_push_back(m));
 513         spin_unlock_irqrestore(&m->lock, flags);
 514
 515         return r;
 516 }
 517
 518 static bool must_push_back_bio(struct multipath *m)
 519 {
 520         bool r;
 521         unsigned long flags;
 522
 523         spin_lock_irqsave(&m->lock, flags);
 524         r = __must_push_back(m);
 525         spin_unlock_irqrestore(&m->lock, flags);
 526
 527         return r;
 528 }
 529
 530 /*
 531  * Map cloned requests (request-based multipath)
 532  */
 533 static int __multipath_map(struct dm_target *ti, struct request *clone,
 534                            union map_info *map_context,
 535                            struct request *rq, struct request **__clone)
 536 {
 537         struct multipath *m = ti->private;
 538         int r = DM_MAPIO_REQUEUE;
 539         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 540         struct pgpath *pgpath;
 541         struct block_device *bdev;
 542         struct dm_mpath_io *mpio;
 543
 544         /* Do we need to select a new pgpath? */
 545         pgpath = lockless_dereference(m->current_pgpath);
 546         if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 547                 pgpath = choose_pgpath(m, nr_bytes);
 548
 549         if (!pgpath) {
 550                 if (must_push_back_rq(m))
 551                         return DM_MAPIO_DELAY_REQUEUE;
 552                 return -EIO;    /* Failed */
 553         } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 554                    test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 555                 pg_init_all_paths(m);
 556                 return r;
 557         }
 558
 559         mpio = set_mpio(m, map_context);
 560         if (!mpio)
 561                 /* ENOMEM, requeue */
 562                 return r;
 563
 564         mpio->pgpath = pgpath;
 565         mpio->nr_bytes = nr_bytes;
 566
 567         bdev = pgpath->path.dev->bdev;
 568
 569         if (clone) {
 570                 /*
 571                  * Old request-based interface: allocated clone is passed in.
 572                  * Used by: .request_fn stacked on .request_fn path(s).
 573                  */
 574                 clone->q = bdev_get_queue(bdev);
 575                 clone->rq_disk = bdev->bd_disk;
 576                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 577         } else {
 578                 /*
 579                  * blk-mq request-based interface; used by both:
 580                  * .request_fn stacked on blk-mq path(s) and
 581                  * blk-mq stacked on blk-mq path(s).
 582                  */
 583                 clone = blk_mq_alloc_request(bdev_get_queue(bdev),
 584                                              rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
 585                 if (IS_ERR(clone)) {
 586                         /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 587                         clear_request_fn_mpio(m, map_context);
 588                         return r;
 589                 }
 590                 clone->bio = clone->biotail = NULL;
 591                 clone->rq_disk = bdev->bd_disk;
 592                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 593                 *__clone = clone;
 594         }
 595
 596         if (pgpath->pg->ps.type->start_io)
 597                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 598                                               &pgpath->path,
 599                                               nr_bytes);
 600         return DM_MAPIO_REMAPPED;
 601 }
 602
 603 static int multipath_map(struct dm_target *ti, struct request *clone,
 604                          union map_info *map_context)
 605 {
 606         return __multipath_map(ti, clone, map_context, NULL, NULL);
 607 }
 608
 609 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 610                                    union map_info *map_context,
 611                                    struct request **clone)
 612 {
 613         return __multipath_map(ti, NULL, map_context, rq, clone);
 614 }
 615
 616 static void multipath_release_clone(struct request *clone)
 617 {
 618         blk_mq_free_request(clone);
 619 }
 620
 621 /*
 622  * Map cloned bios (bio-based multipath)
 623  */
 624 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
 625 {
 626         size_t nr_bytes = bio->bi_iter.bi_size;
 627         struct pgpath *pgpath;
 628         unsigned long flags;
 629         bool queue_io;
 630
 631         /* Do we need to select a new pgpath? */
 632         pgpath = lockless_dereference(m->current_pgpath);
 633         queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 634         if (!pgpath || !queue_io)
 635                 pgpath = choose_pgpath(m, nr_bytes);
 636
 637         if ((pgpath && queue_io) ||
 638             (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 639                 /* Queue for the daemon to resubmit */
 640                 spin_lock_irqsave(&m->lock, flags);
 641                 bio_list_add(&m->queued_bios, bio);
 642                 spin_unlock_irqrestore(&m->lock, flags);
 643                 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 644                 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 645                         pg_init_all_paths(m);
 646                 else if (!queue_io)
 647                         queue_work(kmultipathd, &m->process_queued_bios);
 648                 return DM_MAPIO_SUBMITTED;
 649         }
 650
 651         if (!pgpath) {
 652                 if (!must_push_back_bio(m))
 653                         return -EIO;
 654                 return DM_MAPIO_REQUEUE;
 655         }
 656
 657         mpio->pgpath = pgpath;
 658         mpio->nr_bytes = nr_bytes;
 659
 660         bio->bi_error = 0;
 661         bio->bi_bdev = pgpath->path.dev->bdev;
 662         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 663
 664         if (pgpath->pg->ps.type->start_io)
 665                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 666                                               &pgpath->path,
 667                                               nr_bytes);
 668         return DM_MAPIO_REMAPPED;
 669 }
 670
 671 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 672 {
 673         struct multipath *m = ti->private;
 674         struct dm_mpath_io *mpio = NULL;
 675
 676         multipath_init_per_bio_data(bio, &mpio, NULL);
 677
 678         return __multipath_map_bio(m, bio, mpio);
 679 }
 680
 681 static void process_queued_io_list(struct multipath *m)
 682 {
 683         if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
 684                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 685         else 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_io_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                          * Clear any hw_handler_params associated with a
 854                          * handler that isn't already attached.
 855                          */
 856                         if (m->hw_handler_name && strcmp(attached_handler_name, m->hw_handler_name)) {
 857                                 kfree(m->hw_handler_params);
 858                                 m->hw_handler_params = NULL;
 859                         }
 860
 861                         /*
 862                          * Reset hw_handler_name to match the attached handler
 863                          *
 864                          * NB. This modifies the table line to show the actual
 865                          * handler instead of the original table passed in.
 866                          */
 867                         kfree(m->hw_handler_name);
 868                         m->hw_handler_name = attached_handler_name;
 869                 }
 870         }
 871
 872         if (m->hw_handler_name) {
 873                 r = scsi_dh_attach(q, m->hw_handler_name);
 874                 if (r == -EBUSY) {
 875                         char b[BDEVNAME_SIZE];
 876
 877                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 878                                 bdevname(p->path.dev->bdev, b));
 879                         goto retain;
 880                 }
 881                 if (r < 0) {
 882                         ti->error = "error attaching hardware handler";
 883                         dm_put_device(ti, p->path.dev);
 884                         goto bad;
 885                 }
 886
 887                 if (m->hw_handler_params) {
 888                         r = scsi_dh_set_params(q, m->hw_handler_params);
 889                         if (r < 0) {
 890                                 ti->error = "unable to set hardware "
 891                                                         "handler parameters";
 892                                 dm_put_device(ti, p->path.dev);
 893                                 goto bad;
 894                         }
 895                 }
 896         }
 897
 898         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 899         if (r) {
 900                 dm_put_device(ti, p->path.dev);
 901                 goto bad;
 902         }
 903
 904         return p;
 905
 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 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 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 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 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         if (m->queue_mode == DM_TYPE_BIO_BASED)
1189                 ti->per_io_data_size = multipath_per_bio_data_size();
1190         else if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
1191                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1192
1193         return 0;
1194
1195  bad:
1196         free_multipath(m);
1197         return r;
1198 }
1199
1200 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1201 {
1202         DEFINE_WAIT(wait);
1203
1204         while (1) {
1205                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1206
1207                 if (!atomic_read(&m->pg_init_in_progress))
1208                         break;
1209
1210                 io_schedule();
1211         }
1212         finish_wait(&m->pg_init_wait, &wait);
1213 }
1214
1215 static void flush_multipath_work(struct multipath *m)
1216 {
1217         set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1218         smp_mb__after_atomic();
1219
1220         flush_workqueue(kmpath_handlerd);
1221         multipath_wait_for_pg_init_completion(m);
1222         flush_workqueue(kmultipathd);
1223         flush_work(&m->trigger_event);
1224
1225         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1226         smp_mb__after_atomic();
1227 }
1228
1229 static void multipath_dtr(struct dm_target *ti)
1230 {
1231         struct multipath *m = ti->private;
1232
1233         flush_multipath_work(m);
1234         free_multipath(m);
1235 }
1236
1237 /*
1238  * Take a path out of use.
1239  */
1240 static int fail_path(struct pgpath *pgpath)
1241 {
1242         unsigned long flags;
1243         struct multipath *m = pgpath->pg->m;
1244
1245         spin_lock_irqsave(&m->lock, flags);
1246
1247         if (!pgpath->is_active)
1248                 goto out;
1249
1250         DMWARN("Failing path %s.", pgpath->path.dev->name);
1251
1252         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1253         pgpath->is_active = false;
1254         pgpath->fail_count++;
1255
1256         atomic_dec(&m->nr_valid_paths);
1257
1258         if (pgpath == m->current_pgpath)
1259                 m->current_pgpath = NULL;
1260
1261         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1262                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1263
1264         schedule_work(&m->trigger_event);
1265
1266 out:
1267         spin_unlock_irqrestore(&m->lock, flags);
1268
1269         return 0;
1270 }
1271
1272 /*
1273  * Reinstate a previously-failed path
1274  */
1275 static int reinstate_path(struct pgpath *pgpath)
1276 {
1277         int r = 0, run_queue = 0;
1278         unsigned long flags;
1279         struct multipath *m = pgpath->pg->m;
1280         unsigned nr_valid_paths;
1281
1282         spin_lock_irqsave(&m->lock, flags);
1283
1284         if (pgpath->is_active)
1285                 goto out;
1286
1287         DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1288
1289         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1290         if (r)
1291                 goto out;
1292
1293         pgpath->is_active = true;
1294
1295         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1296         if (nr_valid_paths == 1) {
1297                 m->current_pgpath = NULL;
1298                 run_queue = 1;
1299         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1300                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1301                         atomic_inc(&m->pg_init_in_progress);
1302         }
1303
1304         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1305                        pgpath->path.dev->name, nr_valid_paths);
1306
1307         schedule_work(&m->trigger_event);
1308
1309 out:
1310         spin_unlock_irqrestore(&m->lock, flags);
1311         if (run_queue) {
1312                 dm_table_run_md_queue_async(m->ti->table);
1313                 process_queued_io_list(m);
1314         }
1315
1316         return r;
1317 }
1318
1319 /*
1320  * Fail or reinstate all paths that match the provided struct dm_dev.
1321  */
1322 static int action_dev(struct multipath *m, struct dm_dev *dev,
1323                       action_fn action)
1324 {
1325         int r = -EINVAL;
1326         struct pgpath *pgpath;
1327         struct priority_group *pg;
1328
1329         list_for_each_entry(pg, &m->priority_groups, list) {
1330                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1331                         if (pgpath->path.dev == dev)
1332                                 r = action(pgpath);
1333                 }
1334         }
1335
1336         return r;
1337 }
1338
1339 /*
1340  * Temporarily try to avoid having to use the specified PG
1341  */
1342 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1343                       bool bypassed)
1344 {
1345         unsigned long flags;
1346
1347         spin_lock_irqsave(&m->lock, flags);
1348
1349         pg->bypassed = bypassed;
1350         m->current_pgpath = NULL;
1351         m->current_pg = NULL;
1352
1353         spin_unlock_irqrestore(&m->lock, flags);
1354
1355         schedule_work(&m->trigger_event);
1356 }
1357
1358 /*
1359  * Switch to using the specified PG from the next I/O that gets mapped
1360  */
1361 static int switch_pg_num(struct multipath *m, const char *pgstr)
1362 {
1363         struct priority_group *pg;
1364         unsigned pgnum;
1365         unsigned long flags;
1366         char dummy;
1367
1368         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1369             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1370                 DMWARN("invalid PG number supplied to switch_pg_num");
1371                 return -EINVAL;
1372         }
1373
1374         spin_lock_irqsave(&m->lock, flags);
1375         list_for_each_entry(pg, &m->priority_groups, list) {
1376                 pg->bypassed = false;
1377                 if (--pgnum)
1378                         continue;
1379
1380                 m->current_pgpath = NULL;
1381                 m->current_pg = NULL;
1382                 m->next_pg = pg;
1383         }
1384         spin_unlock_irqrestore(&m->lock, flags);
1385
1386         schedule_work(&m->trigger_event);
1387         return 0;
1388 }
1389
1390 /*
1391  * Set/clear bypassed status of a PG.
1392  * PGs are numbered upwards from 1 in the order they were declared.
1393  */
1394 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1395 {
1396         struct priority_group *pg;
1397         unsigned pgnum;
1398         char dummy;
1399
1400         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1401             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1402                 DMWARN("invalid PG number supplied to bypass_pg");
1403                 return -EINVAL;
1404         }
1405
1406         list_for_each_entry(pg, &m->priority_groups, list) {
1407                 if (!--pgnum)
1408                         break;
1409         }
1410
1411         bypass_pg(m, pg, bypassed);
1412         return 0;
1413 }
1414
1415 /*
1416  * Should we retry pg_init immediately?
1417  */
1418 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1419 {
1420         unsigned long flags;
1421         bool limit_reached = false;
1422
1423         spin_lock_irqsave(&m->lock, flags);
1424
1425         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1426             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1427                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1428         else
1429                 limit_reached = true;
1430
1431         spin_unlock_irqrestore(&m->lock, flags);
1432
1433         return limit_reached;
1434 }
1435
1436 static void pg_init_done(void *data, int errors)
1437 {
1438         struct pgpath *pgpath = data;
1439         struct priority_group *pg = pgpath->pg;
1440         struct multipath *m = pg->m;
1441         unsigned long flags;
1442         bool delay_retry = false;
1443
1444         /* device or driver problems */
1445         switch (errors) {
1446         case SCSI_DH_OK:
1447                 break;
1448         case SCSI_DH_NOSYS:
1449                 if (!m->hw_handler_name) {
1450                         errors = 0;
1451                         break;
1452                 }
1453                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1454                       "Error %d.", m->hw_handler_name, errors);
1455                 /*
1456                  * Fail path for now, so we do not ping pong
1457                  */
1458                 fail_path(pgpath);
1459                 break;
1460         case SCSI_DH_DEV_TEMP_BUSY:
1461                 /*
1462                  * Probably doing something like FW upgrade on the
1463                  * controller so try the other pg.
1464                  */
1465                 bypass_pg(m, pg, true);
1466                 break;
1467         case SCSI_DH_RETRY:
1468                 /* Wait before retrying. */
1469                 delay_retry = 1;
1470         case SCSI_DH_IMM_RETRY:
1471         case SCSI_DH_RES_TEMP_UNAVAIL:
1472                 if (pg_init_limit_reached(m, pgpath))
1473                         fail_path(pgpath);
1474                 errors = 0;
1475                 break;
1476         case SCSI_DH_DEV_OFFLINED:
1477         default:
1478                 /*
1479                  * We probably do not want to fail the path for a device
1480                  * error, but this is what the old dm did. In future
1481                  * patches we can do more advanced handling.
1482                  */
1483                 fail_path(pgpath);
1484         }
1485
1486         spin_lock_irqsave(&m->lock, flags);
1487         if (errors) {
1488                 if (pgpath == m->current_pgpath) {
1489                         DMERR("Could not failover device. Error %d.", errors);
1490                         m->current_pgpath = NULL;
1491                         m->current_pg = NULL;
1492                 }
1493         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1494                 pg->bypassed = false;
1495
1496         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1497                 /* Activations of other paths are still on going */
1498                 goto out;
1499
1500         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1501                 if (delay_retry)
1502                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1503                 else
1504                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1505
1506                 if (__pg_init_all_paths(m))
1507                         goto out;
1508         }
1509         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1510
1511         process_queued_io_list(m);
1512
1513         /*
1514          * Wake up any thread waiting to suspend.
1515          */
1516         wake_up(&m->pg_init_wait);
1517
1518 out:
1519         spin_unlock_irqrestore(&m->lock, flags);
1520 }
1521
1522 static void activate_path(struct work_struct *work)
1523 {
1524         struct pgpath *pgpath =
1525                 container_of(work, struct pgpath, activate_path.work);
1526         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1527
1528         if (pgpath->is_active && !blk_queue_dying(q))
1529                 scsi_dh_activate(q, pg_init_done, pgpath);
1530         else
1531                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1532 }
1533
1534 static int noretry_error(int error)
1535 {
1536         switch (error) {
1537         case -EBADE:
1538                 /*
1539                  * EBADE signals an reservation conflict.
1540                  * We shouldn't fail the path here as we can communicate with
1541                  * the target.  We should failover to the next path, but in
1542                  * doing so we might be causing a ping-pong between paths.
1543                  * So just return the reservation conflict error.
1544                  */
1545         case -EOPNOTSUPP:
1546         case -EREMOTEIO:
1547         case -EILSEQ:
1548         case -ENODATA:
1549         case -ENOSPC:
1550                 return 1;
1551         }
1552
1553         /* Anything else could be a path failure, so should be retried */
1554         return 0;
1555 }
1556
1557 /*
1558  * end_io handling
1559  */
1560 static int do_end_io(struct multipath *m, struct request *clone,
1561                      int error, struct dm_mpath_io *mpio)
1562 {
1563         /*
1564          * We don't queue any clone request inside the multipath target
1565          * during end I/O handling, since those clone requests don't have
1566          * bio clones.  If we queue them inside the multipath target,
1567          * we need to make bio clones, that requires memory allocation.
1568          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1569          *  don't have bio clones.)
1570          * Instead of queueing the clone request here, we queue the original
1571          * request into dm core, which will remake a clone request and
1572          * clone bios for it and resubmit it later.
1573          */
1574         int r = DM_ENDIO_REQUEUE;
1575
1576         if (!error && !clone->errors)
1577                 return 0;       /* I/O complete */
1578
1579         if (noretry_error(error))
1580                 return error;
1581
1582         if (mpio->pgpath)
1583                 fail_path(mpio->pgpath);
1584
1585         if (!atomic_read(&m->nr_valid_paths)) {
1586                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1587                         if (!must_push_back_rq(m))
1588                                 r = -EIO;
1589                 }
1590         }
1591
1592         return r;
1593 }
1594
1595 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1596                             int error, union map_info *map_context)
1597 {
1598         struct multipath *m = ti->private;
1599         struct dm_mpath_io *mpio = get_mpio(map_context);
1600         struct pgpath *pgpath;
1601         struct path_selector *ps;
1602         int r;
1603
1604         BUG_ON(!mpio);
1605
1606         r = do_end_io(m, clone, error, mpio);
1607         pgpath = mpio->pgpath;
1608         if (pgpath) {
1609                 ps = &pgpath->pg->ps;
1610                 if (ps->type->end_io)
1611                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1612         }
1613         clear_request_fn_mpio(m, map_context);
1614
1615         return r;
1616 }
1617
1618 static int do_end_io_bio(struct multipath *m, struct bio *clone,
1619                          int error, struct dm_mpath_io *mpio)
1620 {
1621         unsigned long flags;
1622
1623         if (!error)
1624                 return 0;       /* I/O complete */
1625
1626         if (noretry_error(error))
1627                 return error;
1628
1629         if (mpio->pgpath)
1630                 fail_path(mpio->pgpath);
1631
1632         if (!atomic_read(&m->nr_valid_paths)) {
1633                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1634                         if (!must_push_back_bio(m))
1635                                 return -EIO;
1636                         return DM_ENDIO_REQUEUE;
1637                 }
1638         }
1639
1640         /* Queue for the daemon to resubmit */
1641         dm_bio_restore(get_bio_details_from_bio(clone), clone);
1642
1643         spin_lock_irqsave(&m->lock, flags);
1644         bio_list_add(&m->queued_bios, clone);
1645         spin_unlock_irqrestore(&m->lock, flags);
1646         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1647                 queue_work(kmultipathd, &m->process_queued_bios);
1648
1649         return DM_ENDIO_INCOMPLETE;
1650 }
1651
1652 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, int error)
1653 {
1654         struct multipath *m = ti->private;
1655         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1656         struct pgpath *pgpath;
1657         struct path_selector *ps;
1658         int r;
1659
1660         BUG_ON(!mpio);
1661
1662         r = do_end_io_bio(m, clone, error, mpio);
1663         pgpath = mpio->pgpath;
1664         if (pgpath) {
1665                 ps = &pgpath->pg->ps;
1666                 if (ps->type->end_io)
1667                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1668         }
1669
1670         return r;
1671 }
1672
1673 /*
1674  * Suspend can't complete until all the I/O is processed so if
1675  * the last path fails we must error any remaining I/O.
1676  * Note that if the freeze_bdev fails while suspending, the
1677  * queue_if_no_path state is lost - userspace should reset it.
1678  */
1679 static void multipath_presuspend(struct dm_target *ti)
1680 {
1681         struct multipath *m = ti->private;
1682
1683         queue_if_no_path(m, false, true);
1684 }
1685
1686 static void multipath_postsuspend(struct dm_target *ti)
1687 {
1688         struct multipath *m = ti->private;
1689
1690         mutex_lock(&m->work_mutex);
1691         flush_multipath_work(m);
1692         mutex_unlock(&m->work_mutex);
1693 }
1694
1695 /*
1696  * Restore the queue_if_no_path setting.
1697  */
1698 static void multipath_resume(struct dm_target *ti)
1699 {
1700         struct multipath *m = ti->private;
1701         unsigned long flags;
1702
1703         spin_lock_irqsave(&m->lock, flags);
1704         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags))
1705                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1706         else
1707                 clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1708         spin_unlock_irqrestore(&m->lock, flags);
1709 }
1710
1711 /*
1712  * Info output has the following format:
1713  * num_multipath_feature_args [multipath_feature_args]*
1714  * num_handler_status_args [handler_status_args]*
1715  * num_groups init_group_number
1716  *            [A|D|E num_ps_status_args [ps_status_args]*
1717  *             num_paths num_selector_args
1718  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1719  *
1720  * Table output has the following format (identical to the constructor string):
1721  * num_feature_args [features_args]*
1722  * num_handler_args hw_handler [hw_handler_args]*
1723  * num_groups init_group_number
1724  *     [priority selector-name num_ps_args [ps_args]*
1725  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1726  */
1727 static void multipath_status(struct dm_target *ti, status_type_t type,
1728                              unsigned status_flags, char *result, unsigned maxlen)
1729 {
1730         int sz = 0;
1731         unsigned long flags;
1732         struct multipath *m = ti->private;
1733         struct priority_group *pg;
1734         struct pgpath *p;
1735         unsigned pg_num;
1736         char state;
1737
1738         spin_lock_irqsave(&m->lock, flags);
1739
1740         /* Features */
1741         if (type == STATUSTYPE_INFO)
1742                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1743                        atomic_read(&m->pg_init_count));
1744         else {
1745                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1746                               (m->pg_init_retries > 0) * 2 +
1747                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1748                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1749                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1750
1751                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1752                         DMEMIT("queue_if_no_path ");
1753                 if (m->pg_init_retries)
1754                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1755                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1756                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1757                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1758                         DMEMIT("retain_attached_hw_handler ");
1759                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1760                         switch(m->queue_mode) {
1761                         case DM_TYPE_BIO_BASED:
1762                                 DMEMIT("queue_mode bio ");
1763                                 break;
1764                         case DM_TYPE_MQ_REQUEST_BASED:
1765                                 DMEMIT("queue_mode mq ");
1766                                 break;
1767                         }
1768                 }
1769         }
1770
1771         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1772                 DMEMIT("0 ");
1773         else
1774                 DMEMIT("1 %s ", m->hw_handler_name);
1775
1776         DMEMIT("%u ", m->nr_priority_groups);
1777
1778         if (m->next_pg)
1779                 pg_num = m->next_pg->pg_num;
1780         else if (m->current_pg)
1781                 pg_num = m->current_pg->pg_num;
1782         else
1783                 pg_num = (m->nr_priority_groups ? 1 : 0);
1784
1785         DMEMIT("%u ", pg_num);
1786
1787         switch (type) {
1788         case STATUSTYPE_INFO:
1789                 list_for_each_entry(pg, &m->priority_groups, list) {
1790                         if (pg->bypassed)
1791                                 state = 'D';    /* Disabled */
1792                         else if (pg == m->current_pg)
1793                                 state = 'A';    /* Currently Active */
1794                         else
1795                                 state = 'E';    /* Enabled */
1796
1797                         DMEMIT("%c ", state);
1798
1799                         if (pg->ps.type->status)
1800                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1801                                                           result + sz,
1802                                                           maxlen - sz);
1803                         else
1804                                 DMEMIT("0 ");
1805
1806                         DMEMIT("%u %u ", pg->nr_pgpaths,
1807                                pg->ps.type->info_args);
1808
1809                         list_for_each_entry(p, &pg->pgpaths, list) {
1810                                 DMEMIT("%s %s %u ", p->path.dev->name,
1811                                        p->is_active ? "A" : "F",
1812                                        p->fail_count);
1813                                 if (pg->ps.type->status)
1814                                         sz += pg->ps.type->status(&pg->ps,
1815                                               &p->path, type, result + sz,
1816                                               maxlen - sz);
1817                         }
1818                 }
1819                 break;
1820
1821         case STATUSTYPE_TABLE:
1822                 list_for_each_entry(pg, &m->priority_groups, list) {
1823                         DMEMIT("%s ", pg->ps.type->name);
1824
1825                         if (pg->ps.type->status)
1826                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1827                                                           result + sz,
1828                                                           maxlen - sz);
1829                         else
1830                                 DMEMIT("0 ");
1831
1832                         DMEMIT("%u %u ", pg->nr_pgpaths,
1833                                pg->ps.type->table_args);
1834
1835                         list_for_each_entry(p, &pg->pgpaths, list) {
1836                                 DMEMIT("%s ", p->path.dev->name);
1837                                 if (pg->ps.type->status)
1838                                         sz += pg->ps.type->status(&pg->ps,
1839                                               &p->path, type, result + sz,
1840                                               maxlen - sz);
1841                         }
1842                 }
1843                 break;
1844         }
1845
1846         spin_unlock_irqrestore(&m->lock, flags);
1847 }
1848
1849 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1850 {
1851         int r = -EINVAL;
1852         struct dm_dev *dev;
1853         struct multipath *m = ti->private;
1854         action_fn action;
1855
1856         mutex_lock(&m->work_mutex);
1857
1858         if (dm_suspended(ti)) {
1859                 r = -EBUSY;
1860                 goto out;
1861         }
1862
1863         if (argc == 1) {
1864                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1865                         r = queue_if_no_path(m, true, false);
1866                         goto out;
1867                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1868                         r = queue_if_no_path(m, false, false);
1869                         goto out;
1870                 }
1871         }
1872
1873         if (argc != 2) {
1874                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1875                 goto out;
1876         }
1877
1878         if (!strcasecmp(argv[0], "disable_group")) {
1879                 r = bypass_pg_num(m, argv[1], true);
1880                 goto out;
1881         } else if (!strcasecmp(argv[0], "enable_group")) {
1882                 r = bypass_pg_num(m, argv[1], false);
1883                 goto out;
1884         } else if (!strcasecmp(argv[0], "switch_group")) {
1885                 r = switch_pg_num(m, argv[1]);
1886                 goto out;
1887         } else if (!strcasecmp(argv[0], "reinstate_path"))
1888                 action = reinstate_path;
1889         else if (!strcasecmp(argv[0], "fail_path"))
1890                 action = fail_path;
1891         else {
1892                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1893                 goto out;
1894         }
1895
1896         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1897         if (r) {
1898                 DMWARN("message: error getting device %s",
1899                        argv[1]);
1900                 goto out;
1901         }
1902
1903         r = action_dev(m, dev, action);
1904
1905         dm_put_device(ti, dev);
1906
1907 out:
1908         mutex_unlock(&m->work_mutex);
1909         return r;
1910 }
1911
1912 static int multipath_prepare_ioctl(struct dm_target *ti,
1913                 struct block_device **bdev, fmode_t *mode)
1914 {
1915         struct multipath *m = ti->private;
1916         struct pgpath *current_pgpath;
1917         int r;
1918
1919         current_pgpath = lockless_dereference(m->current_pgpath);
1920         if (!current_pgpath)
1921                 current_pgpath = choose_pgpath(m, 0);
1922
1923         if (current_pgpath) {
1924                 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1925                         *bdev = current_pgpath->path.dev->bdev;
1926                         *mode = current_pgpath->path.dev->mode;
1927                         r = 0;
1928                 } else {
1929                         /* pg_init has not started or completed */
1930                         r = -ENOTCONN;
1931                 }
1932         } else {
1933                 /* No path is available */
1934                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1935                         r = -ENOTCONN;
1936                 else
1937                         r = -EIO;
1938         }
1939
1940         if (r == -ENOTCONN) {
1941                 if (!lockless_dereference(m->current_pg)) {
1942                         /* Path status changed, redo selection */
1943                         (void) choose_pgpath(m, 0);
1944                 }
1945                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1946                         pg_init_all_paths(m);
1947                 dm_table_run_md_queue_async(m->ti->table);
1948                 process_queued_io_list(m);
1949         }
1950
1951         /*
1952          * Only pass ioctls through if the device sizes match exactly.
1953          */
1954         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1955                 return 1;
1956         return r;
1957 }
1958
1959 static int multipath_iterate_devices(struct dm_target *ti,
1960                                      iterate_devices_callout_fn fn, void *data)
1961 {
1962         struct multipath *m = ti->private;
1963         struct priority_group *pg;
1964         struct pgpath *p;
1965         int ret = 0;
1966
1967         list_for_each_entry(pg, &m->priority_groups, list) {
1968                 list_for_each_entry(p, &pg->pgpaths, list) {
1969                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1970                         if (ret)
1971                                 goto out;
1972                 }
1973         }
1974
1975 out:
1976         return ret;
1977 }
1978
1979 static int pgpath_busy(struct pgpath *pgpath)
1980 {
1981         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1982
1983         return blk_lld_busy(q);
1984 }
1985
1986 /*
1987  * We return "busy", only when we can map I/Os but underlying devices
1988  * are busy (so even if we map I/Os now, the I/Os will wait on
1989  * the underlying queue).
1990  * In other words, if we want to kill I/Os or queue them inside us
1991  * due to map unavailability, we don't return "busy".  Otherwise,
1992  * dm core won't give us the I/Os and we can't do what we want.
1993  */
1994 static int multipath_busy(struct dm_target *ti)
1995 {
1996         bool busy = false, has_active = false;
1997         struct multipath *m = ti->private;
1998         struct priority_group *pg, *next_pg;
1999         struct pgpath *pgpath;
2000
2001         /* pg_init in progress */
2002         if (atomic_read(&m->pg_init_in_progress))
2003                 return true;
2004
2005         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2006         if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2007                 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
2008
2009         /* Guess which priority_group will be used at next mapping time */
2010         pg = lockless_dereference(m->current_pg);
2011         next_pg = lockless_dereference(m->next_pg);
2012         if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
2013                 pg = next_pg;
2014
2015         if (!pg) {
2016                 /*
2017                  * We don't know which pg will be used at next mapping time.
2018                  * We don't call choose_pgpath() here to avoid to trigger
2019                  * pg_init just by busy checking.
2020                  * So we don't know whether underlying devices we will be using
2021                  * at next mapping time are busy or not. Just try mapping.
2022                  */
2023                 return busy;
2024         }
2025
2026         /*
2027          * If there is one non-busy active path at least, the path selector
2028          * will be able to select it. So we consider such a pg as not busy.
2029          */
2030         busy = true;
2031         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2032                 if (pgpath->is_active) {
2033                         has_active = true;
2034                         if (!pgpath_busy(pgpath)) {
2035                                 busy = false;
2036                                 break;
2037                         }
2038                 }
2039         }
2040
2041         if (!has_active) {
2042                 /*
2043                  * No active path in this pg, so this pg won't be used and
2044                  * the current_pg will be changed at next mapping time.
2045                  * We need to try mapping to determine it.
2046                  */
2047                 busy = false;
2048         }
2049
2050         return busy;
2051 }
2052
2053 /*-----------------------------------------------------------------
2054  * Module setup
2055  *---------------------------------------------------------------*/
2056 static struct target_type multipath_target = {
2057         .name = "multipath",
2058         .version = {1, 12, 0},
2059         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
2060         .module = THIS_MODULE,
2061         .ctr = multipath_ctr,
2062         .dtr = multipath_dtr,
2063         .map_rq = multipath_map,
2064         .clone_and_map_rq = multipath_clone_and_map,
2065         .release_clone_rq = multipath_release_clone,
2066         .rq_end_io = multipath_end_io,
2067         .map = multipath_map_bio,
2068         .end_io = multipath_end_io_bio,
2069         .presuspend = multipath_presuspend,
2070         .postsuspend = multipath_postsuspend,
2071         .resume = multipath_resume,
2072         .status = multipath_status,
2073         .message = multipath_message,
2074         .prepare_ioctl = multipath_prepare_ioctl,
2075         .iterate_devices = multipath_iterate_devices,
2076         .busy = multipath_busy,
2077 };
2078
2079 static int __init dm_multipath_init(void)
2080 {
2081         int r;
2082
2083         /* allocate a slab for the dm_mpath_ios */
2084         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
2085         if (!_mpio_cache)
2086                 return -ENOMEM;
2087
2088         r = dm_register_target(&multipath_target);
2089         if (r < 0) {
2090                 DMERR("request-based register failed %d", r);
2091                 r = -EINVAL;
2092                 goto bad_register_target;
2093         }
2094
2095         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2096         if (!kmultipathd) {
2097                 DMERR("failed to create workqueue kmpathd");
2098                 r = -ENOMEM;
2099                 goto bad_alloc_kmultipathd;
2100         }
2101
2102         /*
2103          * A separate workqueue is used to handle the device handlers
2104          * to avoid overloading existing workqueue. Overloading the
2105          * old workqueue would also create a bottleneck in the
2106          * path of the storage hardware device activation.
2107          */
2108         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2109                                                   WQ_MEM_RECLAIM);
2110         if (!kmpath_handlerd) {
2111                 DMERR("failed to create workqueue kmpath_handlerd");
2112                 r = -ENOMEM;
2113                 goto bad_alloc_kmpath_handlerd;
2114         }
2115
2116         return 0;
2117
2118 bad_alloc_kmpath_handlerd:
2119         destroy_workqueue(kmultipathd);
2120 bad_alloc_kmultipathd:
2121         dm_unregister_target(&multipath_target);
2122 bad_register_target:
2123         kmem_cache_destroy(_mpio_cache);
2124
2125         return r;
2126 }
2127
2128 static void __exit dm_multipath_exit(void)
2129 {
2130         destroy_workqueue(kmpath_handlerd);
2131         destroy_workqueue(kmultipathd);
2132
2133         dm_unregister_target(&multipath_target);
2134         kmem_cache_destroy(_mpio_cache);
2135 }
2136
2137 module_init(dm_multipath_init);
2138 module_exit(dm_multipath_exit);
2139
2140 MODULE_DESCRIPTION(DM_NAME " multipath target");
2141 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2142 MODULE_LICENSE("GPL");