drivers/md/dm-mpath.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2003 Sistina Software Limited.
   4  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   5  *
   6  * This file is released under the GPL.
   7  */
   8
   9 #include <linux/device-mapper.h>
  10
  11 #include "dm-rq.h"
  12 #include "dm-bio-record.h"
  13 #include "dm-path-selector.h"
  14 #include "dm-uevent.h"
  15
  16 #include <linux/blkdev.h>
  17 #include <linux/ctype.h>
  18 #include <linux/init.h>
  19 #include <linux/mempool.h>
  20 #include <linux/module.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/slab.h>
  23 #include <linux/time.h>
  24 #include <linux/timer.h>
  25 #include <linux/workqueue.h>
  26 #include <linux/delay.h>
  27 #include <scsi/scsi_dh.h>
  28 #include <linux/atomic.h>
  29 #include <linux/blk-mq.h>
  30
  31 #define DM_MSG_PREFIX "multipath"
  32 #define DM_PG_INIT_DELAY_MSECS 2000
  33 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned int) -1)
  34 #define QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT 0
  35
  36 static unsigned long queue_if_no_path_timeout_secs = QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT;
  37
  38 /* Path properties */
  39 struct pgpath {
  40         struct list_head list;
  41
  42         struct priority_group *pg;      /* Owning PG */
  43         unsigned int fail_count;                /* Cumulative failure count */
  44
  45         struct dm_path path;
  46         struct delayed_work activate_path;
  47
  48         bool is_active:1;               /* Path status */
  49 };
  50
  51 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  52
  53 /*
  54  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  55  * Each has a path selector which controls which path gets used.
  56  */
  57 struct priority_group {
  58         struct list_head list;
  59
  60         struct multipath *m;            /* Owning multipath instance */
  61         struct path_selector ps;
  62
  63         unsigned int pg_num;            /* Reference number */
  64         unsigned int nr_pgpaths;                /* Number of paths in PG */
  65         struct list_head pgpaths;
  66
  67         bool bypassed:1;                /* Temporarily bypass this PG? */
  68 };
  69
  70 /* Multipath context */
  71 struct multipath {
  72         unsigned long flags;            /* Multipath state flags */
  73
  74         spinlock_t lock;
  75         enum dm_queue_mode queue_mode;
  76
  77         struct pgpath *current_pgpath;
  78         struct priority_group *current_pg;
  79         struct priority_group *next_pg; /* Switch to this PG if set */
  80
  81         atomic_t nr_valid_paths;        /* Total number of usable paths */
  82         unsigned int nr_priority_groups;
  83         struct list_head priority_groups;
  84
  85         const char *hw_handler_name;
  86         char *hw_handler_params;
  87         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  88         unsigned int pg_init_retries;   /* Number of times to retry pg_init */
  89         unsigned int pg_init_delay_msecs;       /* Number of msecs before pg_init retry */
  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         struct mutex work_mutex;
  94         struct work_struct trigger_event;
  95         struct dm_target *ti;
  96
  97         struct work_struct process_queued_bios;
  98         struct bio_list queued_bios;
  99
 100         struct timer_list nopath_timer; /* Timeout for queue_if_no_path */
 101 };
 102
 103 /*
 104  * Context information attached to each io we process.
 105  */
 106 struct dm_mpath_io {
 107         struct pgpath *pgpath;
 108         size_t nr_bytes;
 109         u64 start_time_ns;
 110 };
 111
 112 typedef int (*action_fn) (struct pgpath *pgpath);
 113
 114 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 115 static void trigger_event(struct work_struct *work);
 116 static void activate_or_offline_path(struct pgpath *pgpath);
 117 static void activate_path_work(struct work_struct *work);
 118 static void process_queued_bios(struct work_struct *work);
 119 static void queue_if_no_path_timeout_work(struct timer_list *t);
 120
 121 /*
 122  *-----------------------------------------------
 123  * Multipath state flags.
 124  *-----------------------------------------------
 125  */
 126 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 127 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 128 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 129 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 130 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 131 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 132 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 133
 134 static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
 135 {
 136         bool r = test_bit(MPATHF_bit, &m->flags);
 137
 138         if (r) {
 139                 unsigned long flags;
 140                 spin_lock_irqsave(&m->lock, flags);
 141                 r = test_bit(MPATHF_bit, &m->flags);
 142                 spin_unlock_irqrestore(&m->lock, flags);
 143         }
 144
 145         return r;
 146 }
 147
 148 /*
 149  *-----------------------------------------------
 150  * Allocation routines
 151  *-----------------------------------------------
 152  */
 153 static struct pgpath *alloc_pgpath(void)
 154 {
 155         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 156
 157         if (!pgpath)
 158                 return NULL;
 159
 160         pgpath->is_active = true;
 161
 162         return pgpath;
 163 }
 164
 165 static void free_pgpath(struct pgpath *pgpath)
 166 {
 167         kfree(pgpath);
 168 }
 169
 170 static struct priority_group *alloc_priority_group(void)
 171 {
 172         struct priority_group *pg;
 173
 174         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 175
 176         if (pg)
 177                 INIT_LIST_HEAD(&pg->pgpaths);
 178
 179         return pg;
 180 }
 181
 182 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 183 {
 184         struct pgpath *pgpath, *tmp;
 185
 186         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 187                 list_del(&pgpath->list);
 188                 dm_put_device(ti, pgpath->path.dev);
 189                 free_pgpath(pgpath);
 190         }
 191 }
 192
 193 static void free_priority_group(struct priority_group *pg,
 194                                 struct dm_target *ti)
 195 {
 196         struct path_selector *ps = &pg->ps;
 197
 198         if (ps->type) {
 199                 ps->type->destroy(ps);
 200                 dm_put_path_selector(ps->type);
 201         }
 202
 203         free_pgpaths(&pg->pgpaths, ti);
 204         kfree(pg);
 205 }
 206
 207 static struct multipath *alloc_multipath(struct dm_target *ti)
 208 {
 209         struct multipath *m;
 210
 211         m = kzalloc(sizeof(*m), GFP_KERNEL);
 212         if (m) {
 213                 INIT_LIST_HEAD(&m->priority_groups);
 214                 spin_lock_init(&m->lock);
 215                 atomic_set(&m->nr_valid_paths, 0);
 216                 INIT_WORK(&m->trigger_event, trigger_event);
 217                 mutex_init(&m->work_mutex);
 218
 219                 m->queue_mode = DM_TYPE_NONE;
 220
 221                 m->ti = ti;
 222                 ti->private = m;
 223
 224                 timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
 225         }
 226
 227         return m;
 228 }
 229
 230 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 231 {
 232         if (m->queue_mode == DM_TYPE_NONE) {
 233                 m->queue_mode = DM_TYPE_REQUEST_BASED;
 234         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 235                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 236                 /*
 237                  * bio-based doesn't support any direct scsi_dh management;
 238                  * it just discovers if a scsi_dh is attached.
 239                  */
 240                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 241         }
 242
 243         dm_table_set_type(ti->table, m->queue_mode);
 244
 245         /*
 246          * Init fields that are only used when a scsi_dh is attached
 247          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 248          */
 249         set_bit(MPATHF_QUEUE_IO, &m->flags);
 250         atomic_set(&m->pg_init_in_progress, 0);
 251         atomic_set(&m->pg_init_count, 0);
 252         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 253         init_waitqueue_head(&m->pg_init_wait);
 254
 255         return 0;
 256 }
 257
 258 static void free_multipath(struct multipath *m)
 259 {
 260         struct priority_group *pg, *tmp;
 261
 262         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 263                 list_del(&pg->list);
 264                 free_priority_group(pg, m->ti);
 265         }
 266
 267         kfree(m->hw_handler_name);
 268         kfree(m->hw_handler_params);
 269         mutex_destroy(&m->work_mutex);
 270         kfree(m);
 271 }
 272
 273 static struct dm_mpath_io *get_mpio(union map_info *info)
 274 {
 275         return info->ptr;
 276 }
 277
 278 static size_t multipath_per_bio_data_size(void)
 279 {
 280         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 281 }
 282
 283 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 284 {
 285         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 286 }
 287
 288 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 289 {
 290         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 291         void *bio_details = mpio + 1;
 292         return bio_details;
 293 }
 294
 295 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 296 {
 297         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 298         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 299
 300         mpio->nr_bytes = bio->bi_iter.bi_size;
 301         mpio->pgpath = NULL;
 302         mpio->start_time_ns = 0;
 303         *mpio_p = mpio;
 304
 305         dm_bio_record(bio_details, bio);
 306 }
 307
 308 /*
 309  *-----------------------------------------------
 310  * Path selection
 311  *-----------------------------------------------
 312  */
 313 static int __pg_init_all_paths(struct multipath *m)
 314 {
 315         struct pgpath *pgpath;
 316         unsigned long pg_init_delay = 0;
 317
 318         lockdep_assert_held(&m->lock);
 319
 320         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 321                 return 0;
 322
 323         atomic_inc(&m->pg_init_count);
 324         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 325
 326         /* Check here to reset pg_init_required */
 327         if (!m->current_pg)
 328                 return 0;
 329
 330         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 331                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 332                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 333         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 334                 /* Skip failed paths */
 335                 if (!pgpath->is_active)
 336                         continue;
 337                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 338                                        pg_init_delay))
 339                         atomic_inc(&m->pg_init_in_progress);
 340         }
 341         return atomic_read(&m->pg_init_in_progress);
 342 }
 343
 344 static int pg_init_all_paths(struct multipath *m)
 345 {
 346         int ret;
 347         unsigned long flags;
 348
 349         spin_lock_irqsave(&m->lock, flags);
 350         ret = __pg_init_all_paths(m);
 351         spin_unlock_irqrestore(&m->lock, flags);
 352
 353         return ret;
 354 }
 355
 356 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 357 {
 358         lockdep_assert_held(&m->lock);
 359
 360         m->current_pg = pg;
 361
 362         /* Must we initialise the PG first, and queue I/O till it's ready? */
 363         if (m->hw_handler_name) {
 364                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 365                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 366         } else {
 367                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 368                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 369         }
 370
 371         atomic_set(&m->pg_init_count, 0);
 372 }
 373
 374 static struct pgpath *choose_path_in_pg(struct multipath *m,
 375                                         struct priority_group *pg,
 376                                         size_t nr_bytes)
 377 {
 378         unsigned long flags;
 379         struct dm_path *path;
 380         struct pgpath *pgpath;
 381
 382         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 383         if (!path)
 384                 return ERR_PTR(-ENXIO);
 385
 386         pgpath = path_to_pgpath(path);
 387
 388         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 389                 /* Only update current_pgpath if pg changed */
 390                 spin_lock_irqsave(&m->lock, flags);
 391                 m->current_pgpath = pgpath;
 392                 __switch_pg(m, pg);
 393                 spin_unlock_irqrestore(&m->lock, flags);
 394         }
 395
 396         return pgpath;
 397 }
 398
 399 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 400 {
 401         unsigned long flags;
 402         struct priority_group *pg;
 403         struct pgpath *pgpath;
 404         unsigned int bypassed = 1;
 405
 406         if (!atomic_read(&m->nr_valid_paths)) {
 407                 spin_lock_irqsave(&m->lock, flags);
 408                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 409                 spin_unlock_irqrestore(&m->lock, flags);
 410                 goto failed;
 411         }
 412
 413         /* Were we instructed to switch PG? */
 414         if (READ_ONCE(m->next_pg)) {
 415                 spin_lock_irqsave(&m->lock, flags);
 416                 pg = m->next_pg;
 417                 if (!pg) {
 418                         spin_unlock_irqrestore(&m->lock, flags);
 419                         goto check_current_pg;
 420                 }
 421                 m->next_pg = NULL;
 422                 spin_unlock_irqrestore(&m->lock, flags);
 423                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 424                 if (!IS_ERR_OR_NULL(pgpath))
 425                         return pgpath;
 426         }
 427
 428         /* Don't change PG until it has no remaining paths */
 429 check_current_pg:
 430         pg = READ_ONCE(m->current_pg);
 431         if (pg) {
 432                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 433                 if (!IS_ERR_OR_NULL(pgpath))
 434                         return pgpath;
 435         }
 436
 437         /*
 438          * Loop through priority groups until we find a valid path.
 439          * First time we skip PGs marked 'bypassed'.
 440          * Second time we only try the ones we skipped, but set
 441          * pg_init_delay_retry so we do not hammer controllers.
 442          */
 443         do {
 444                 list_for_each_entry(pg, &m->priority_groups, list) {
 445                         if (pg->bypassed == !!bypassed)
 446                                 continue;
 447                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 448                         if (!IS_ERR_OR_NULL(pgpath)) {
 449                                 if (!bypassed) {
 450                                         spin_lock_irqsave(&m->lock, flags);
 451                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 452                                         spin_unlock_irqrestore(&m->lock, flags);
 453                                 }
 454                                 return pgpath;
 455                         }
 456                 }
 457         } while (bypassed--);
 458
 459 failed:
 460         spin_lock_irqsave(&m->lock, flags);
 461         m->current_pgpath = NULL;
 462         m->current_pg = NULL;
 463         spin_unlock_irqrestore(&m->lock, flags);
 464
 465         return NULL;
 466 }
 467
 468 /*
 469  * dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
 470  * report the function name and line number of the function from which
 471  * it has been invoked.
 472  */
 473 #define dm_report_EIO(m)                                                \
 474 do {                                                                    \
 475         DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 476                       dm_table_device_name((m)->ti->table),             \
 477                       test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),   \
 478                       test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 479                       dm_noflush_suspending((m)->ti));                  \
 480 } while (0)
 481
 482 /*
 483  * Check whether bios must be queued in the device-mapper core rather
 484  * than here in the target.
 485  */
 486 static bool __must_push_back(struct multipath *m)
 487 {
 488         return dm_noflush_suspending(m->ti);
 489 }
 490
 491 static bool must_push_back_rq(struct multipath *m)
 492 {
 493         unsigned long flags;
 494         bool ret;
 495
 496         spin_lock_irqsave(&m->lock, flags);
 497         ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
 498         spin_unlock_irqrestore(&m->lock, flags);
 499
 500         return ret;
 501 }
 502
 503 /*
 504  * Map cloned requests (request-based multipath)
 505  */
 506 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 507                                    union map_info *map_context,
 508                                    struct request **__clone)
 509 {
 510         struct multipath *m = ti->private;
 511         size_t nr_bytes = blk_rq_bytes(rq);
 512         struct pgpath *pgpath;
 513         struct block_device *bdev;
 514         struct dm_mpath_io *mpio = get_mpio(map_context);
 515         struct request_queue *q;
 516         struct request *clone;
 517
 518         /* Do we need to select a new pgpath? */
 519         pgpath = READ_ONCE(m->current_pgpath);
 520         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 521                 pgpath = choose_pgpath(m, nr_bytes);
 522
 523         if (!pgpath) {
 524                 if (must_push_back_rq(m))
 525                         return DM_MAPIO_DELAY_REQUEUE;
 526                 dm_report_EIO(m);       /* Failed */
 527                 return DM_MAPIO_KILL;
 528         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 529                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 530                 pg_init_all_paths(m);
 531                 return DM_MAPIO_DELAY_REQUEUE;
 532         }
 533
 534         mpio->pgpath = pgpath;
 535         mpio->nr_bytes = nr_bytes;
 536
 537         bdev = pgpath->path.dev->bdev;
 538         q = bdev_get_queue(bdev);
 539         clone = blk_mq_alloc_request(q, rq->cmd_flags | REQ_NOMERGE,
 540                         BLK_MQ_REQ_NOWAIT);
 541         if (IS_ERR(clone)) {
 542                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 543                 if (blk_queue_dying(q)) {
 544                         atomic_inc(&m->pg_init_in_progress);
 545                         activate_or_offline_path(pgpath);
 546                         return DM_MAPIO_DELAY_REQUEUE;
 547                 }
 548
 549                 /*
 550                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 551                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 552                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 553                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 554                  * otherwise I/O merging can suffer.
 555                  */
 556                 return DM_MAPIO_REQUEUE;
 557         }
 558         clone->bio = clone->biotail = NULL;
 559         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 560         *__clone = clone;
 561
 562         if (pgpath->pg->ps.type->start_io)
 563                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 564                                               &pgpath->path,
 565                                               nr_bytes);
 566         return DM_MAPIO_REMAPPED;
 567 }
 568
 569 static void multipath_release_clone(struct request *clone,
 570                                     union map_info *map_context)
 571 {
 572         if (unlikely(map_context)) {
 573                 /*
 574                  * non-NULL map_context means caller is still map
 575                  * method; must undo multipath_clone_and_map()
 576                  */
 577                 struct dm_mpath_io *mpio = get_mpio(map_context);
 578                 struct pgpath *pgpath = mpio->pgpath;
 579
 580                 if (pgpath && pgpath->pg->ps.type->end_io)
 581                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 582                                                     &pgpath->path,
 583                                                     mpio->nr_bytes,
 584                                                     clone->io_start_time_ns);
 585         }
 586
 587         blk_mq_free_request(clone);
 588 }
 589
 590 /*
 591  * Map cloned bios (bio-based multipath)
 592  */
 593
 594 static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
 595 {
 596         /* Queue for the daemon to resubmit */
 597         bio_list_add(&m->queued_bios, bio);
 598         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
 599                 queue_work(kmultipathd, &m->process_queued_bios);
 600 }
 601
 602 static void multipath_queue_bio(struct multipath *m, struct bio *bio)
 603 {
 604         unsigned long flags;
 605
 606         spin_lock_irqsave(&m->lock, flags);
 607         __multipath_queue_bio(m, bio);
 608         spin_unlock_irqrestore(&m->lock, flags);
 609 }
 610
 611 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 612 {
 613         struct pgpath *pgpath;
 614         unsigned long flags;
 615
 616         /* Do we need to select a new pgpath? */
 617         pgpath = READ_ONCE(m->current_pgpath);
 618         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 619                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 620
 621         if (!pgpath) {
 622                 spin_lock_irqsave(&m->lock, flags);
 623                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 624                         __multipath_queue_bio(m, bio);
 625                         pgpath = ERR_PTR(-EAGAIN);
 626                 }
 627                 spin_unlock_irqrestore(&m->lock, flags);
 628
 629         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 630                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 631                 multipath_queue_bio(m, bio);
 632                 pg_init_all_paths(m);
 633                 return ERR_PTR(-EAGAIN);
 634         }
 635
 636         return pgpath;
 637 }
 638
 639 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 640                                struct dm_mpath_io *mpio)
 641 {
 642         struct pgpath *pgpath = __map_bio(m, bio);
 643
 644         if (IS_ERR(pgpath))
 645                 return DM_MAPIO_SUBMITTED;
 646
 647         if (!pgpath) {
 648                 if (__must_push_back(m))
 649                         return DM_MAPIO_REQUEUE;
 650                 dm_report_EIO(m);
 651                 return DM_MAPIO_KILL;
 652         }
 653
 654         mpio->pgpath = pgpath;
 655
 656         if (dm_ps_use_hr_timer(pgpath->pg->ps.type))
 657                 mpio->start_time_ns = ktime_get_ns();
 658
 659         bio->bi_status = 0;
 660         bio_set_dev(bio, pgpath->path.dev->bdev);
 661         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 662
 663         if (pgpath->pg->ps.type->start_io)
 664                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 665                                               &pgpath->path,
 666                                               mpio->nr_bytes);
 667         return DM_MAPIO_REMAPPED;
 668 }
 669
 670 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 671 {
 672         struct multipath *m = ti->private;
 673         struct dm_mpath_io *mpio = NULL;
 674
 675         multipath_init_per_bio_data(bio, &mpio);
 676         return __multipath_map_bio(m, bio, mpio);
 677 }
 678
 679 static void process_queued_io_list(struct multipath *m)
 680 {
 681         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 682                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 683         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 684                 queue_work(kmultipathd, &m->process_queued_bios);
 685 }
 686
 687 static void process_queued_bios(struct work_struct *work)
 688 {
 689         int r;
 690         unsigned long flags;
 691         struct bio *bio;
 692         struct bio_list bios;
 693         struct blk_plug plug;
 694         struct multipath *m =
 695                 container_of(work, struct multipath, process_queued_bios);
 696
 697         bio_list_init(&bios);
 698
 699         spin_lock_irqsave(&m->lock, flags);
 700
 701         if (bio_list_empty(&m->queued_bios)) {
 702                 spin_unlock_irqrestore(&m->lock, flags);
 703                 return;
 704         }
 705
 706         bio_list_merge(&bios, &m->queued_bios);
 707         bio_list_init(&m->queued_bios);
 708
 709         spin_unlock_irqrestore(&m->lock, flags);
 710
 711         blk_start_plug(&plug);
 712         while ((bio = bio_list_pop(&bios))) {
 713                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 714                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 715                 r = __multipath_map_bio(m, bio, mpio);
 716                 switch (r) {
 717                 case DM_MAPIO_KILL:
 718                         bio->bi_status = BLK_STS_IOERR;
 719                         bio_endio(bio);
 720                         break;
 721                 case DM_MAPIO_REQUEUE:
 722                         bio->bi_status = BLK_STS_DM_REQUEUE;
 723                         bio_endio(bio);
 724                         break;
 725                 case DM_MAPIO_REMAPPED:
 726                         submit_bio_noacct(bio);
 727                         break;
 728                 case DM_MAPIO_SUBMITTED:
 729                         break;
 730                 default:
 731                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 732                 }
 733         }
 734         blk_finish_plug(&plug);
 735 }
 736
 737 /*
 738  * If we run out of usable paths, should we queue I/O or error it?
 739  */
 740 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 741                             bool save_old_value, const char *caller)
 742 {
 743         unsigned long flags;
 744         bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 745         const char *dm_dev_name = dm_table_device_name(m->ti->table);
 746
 747         DMDEBUG("%s: %s caller=%s queue_if_no_path=%d save_old_value=%d",
 748                 dm_dev_name, __func__, caller, queue_if_no_path, save_old_value);
 749
 750         spin_lock_irqsave(&m->lock, flags);
 751
 752         queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 753         saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 754
 755         if (save_old_value) {
 756                 if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 757                         DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 758                               dm_dev_name);
 759                 } else
 760                         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 761         } else if (!queue_if_no_path && saved_queue_if_no_path_bit) {
 762                 /* due to "fail_if_no_path" message, need to honor it. */
 763                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 764         }
 765         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 766
 767         DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 768                 dm_dev_name, __func__,
 769                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 770                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 771                 dm_noflush_suspending(m->ti));
 772
 773         spin_unlock_irqrestore(&m->lock, flags);
 774
 775         if (!queue_if_no_path) {
 776                 dm_table_run_md_queue_async(m->ti->table);
 777                 process_queued_io_list(m);
 778         }
 779
 780         return 0;
 781 }
 782
 783 /*
 784  * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 785  * process any queued I/O.
 786  */
 787 static void queue_if_no_path_timeout_work(struct timer_list *t)
 788 {
 789         struct multipath *m = from_timer(m, t, nopath_timer);
 790
 791         DMWARN("queue_if_no_path timeout on %s, failing queued IO",
 792                dm_table_device_name(m->ti->table));
 793         queue_if_no_path(m, false, false, __func__);
 794 }
 795
 796 /*
 797  * Enable the queue_if_no_path timeout if necessary.
 798  * Called with m->lock held.
 799  */
 800 static void enable_nopath_timeout(struct multipath *m)
 801 {
 802         unsigned long queue_if_no_path_timeout =
 803                 READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 804
 805         lockdep_assert_held(&m->lock);
 806
 807         if (queue_if_no_path_timeout > 0 &&
 808             atomic_read(&m->nr_valid_paths) == 0 &&
 809             test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 810                 mod_timer(&m->nopath_timer,
 811                           jiffies + queue_if_no_path_timeout);
 812         }
 813 }
 814
 815 static void disable_nopath_timeout(struct multipath *m)
 816 {
 817         del_timer_sync(&m->nopath_timer);
 818 }
 819
 820 /*
 821  * An event is triggered whenever a path is taken out of use.
 822  * Includes path failure and PG bypass.
 823  */
 824 static void trigger_event(struct work_struct *work)
 825 {
 826         struct multipath *m =
 827                 container_of(work, struct multipath, trigger_event);
 828
 829         dm_table_event(m->ti->table);
 830 }
 831
 832 /*
 833  *---------------------------------------------------------------
 834  * Constructor/argument parsing:
 835  * <#multipath feature args> [<arg>]*
 836  * <#hw_handler args> [hw_handler [<arg>]*]
 837  * <#priority groups>
 838  * <initial priority group>
 839  *     [<selector> <#selector args> [<arg>]*
 840  *      <#paths> <#per-path selector args>
 841  *         [<path> [<arg>]* ]+ ]+
 842  *---------------------------------------------------------------
 843  */
 844 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 845                                struct dm_target *ti)
 846 {
 847         int r;
 848         struct path_selector_type *pst;
 849         unsigned int ps_argc;
 850
 851         static const struct dm_arg _args[] = {
 852                 {0, 1024, "invalid number of path selector args"},
 853         };
 854
 855         pst = dm_get_path_selector(dm_shift_arg(as));
 856         if (!pst) {
 857                 ti->error = "unknown path selector type";
 858                 return -EINVAL;
 859         }
 860
 861         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 862         if (r) {
 863                 dm_put_path_selector(pst);
 864                 return -EINVAL;
 865         }
 866
 867         r = pst->create(&pg->ps, ps_argc, as->argv);
 868         if (r) {
 869                 dm_put_path_selector(pst);
 870                 ti->error = "path selector constructor failed";
 871                 return r;
 872         }
 873
 874         pg->ps.type = pst;
 875         dm_consume_args(as, ps_argc);
 876
 877         return 0;
 878 }
 879
 880 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 881                          const char **attached_handler_name, char **error)
 882 {
 883         struct request_queue *q = bdev_get_queue(bdev);
 884         int r;
 885
 886         if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
 887 retain:
 888                 if (*attached_handler_name) {
 889                         /*
 890                          * Clear any hw_handler_params associated with a
 891                          * handler that isn't already attached.
 892                          */
 893                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 894                                 kfree(m->hw_handler_params);
 895                                 m->hw_handler_params = NULL;
 896                         }
 897
 898                         /*
 899                          * Reset hw_handler_name to match the attached handler
 900                          *
 901                          * NB. This modifies the table line to show the actual
 902                          * handler instead of the original table passed in.
 903                          */
 904                         kfree(m->hw_handler_name);
 905                         m->hw_handler_name = *attached_handler_name;
 906                         *attached_handler_name = NULL;
 907                 }
 908         }
 909
 910         if (m->hw_handler_name) {
 911                 r = scsi_dh_attach(q, m->hw_handler_name);
 912                 if (r == -EBUSY) {
 913                         DMINFO("retaining handler on device %pg", bdev);
 914                         goto retain;
 915                 }
 916                 if (r < 0) {
 917                         *error = "error attaching hardware handler";
 918                         return r;
 919                 }
 920
 921                 if (m->hw_handler_params) {
 922                         r = scsi_dh_set_params(q, m->hw_handler_params);
 923                         if (r < 0) {
 924                                 *error = "unable to set hardware handler parameters";
 925                                 return r;
 926                         }
 927                 }
 928         }
 929
 930         return 0;
 931 }
 932
 933 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 934                                  struct dm_target *ti)
 935 {
 936         int r;
 937         struct pgpath *p;
 938         struct multipath *m = ti->private;
 939         struct request_queue *q;
 940         const char *attached_handler_name = NULL;
 941
 942         /* we need at least a path arg */
 943         if (as->argc < 1) {
 944                 ti->error = "no device given";
 945                 return ERR_PTR(-EINVAL);
 946         }
 947
 948         p = alloc_pgpath();
 949         if (!p)
 950                 return ERR_PTR(-ENOMEM);
 951
 952         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 953                           &p->path.dev);
 954         if (r) {
 955                 ti->error = "error getting device";
 956                 goto bad;
 957         }
 958
 959         q = bdev_get_queue(p->path.dev->bdev);
 960         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 961         if (attached_handler_name || m->hw_handler_name) {
 962                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 963                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 964                 kfree(attached_handler_name);
 965                 if (r) {
 966                         dm_put_device(ti, p->path.dev);
 967                         goto bad;
 968                 }
 969         }
 970
 971         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 972         if (r) {
 973                 dm_put_device(ti, p->path.dev);
 974                 goto bad;
 975         }
 976
 977         return p;
 978  bad:
 979         free_pgpath(p);
 980         return ERR_PTR(r);
 981 }
 982
 983 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 984                                                    struct multipath *m)
 985 {
 986         static const struct dm_arg _args[] = {
 987                 {1, 1024, "invalid number of paths"},
 988                 {0, 1024, "invalid number of selector args"}
 989         };
 990
 991         int r;
 992         unsigned int i, nr_selector_args, nr_args;
 993         struct priority_group *pg;
 994         struct dm_target *ti = m->ti;
 995
 996         if (as->argc < 2) {
 997                 as->argc = 0;
 998                 ti->error = "not enough priority group arguments";
 999                 return ERR_PTR(-EINVAL);
1000         }
1001
1002         pg = alloc_priority_group();
1003         if (!pg) {
1004                 ti->error = "couldn't allocate priority group";
1005                 return ERR_PTR(-ENOMEM);
1006         }
1007         pg->m = m;
1008
1009         r = parse_path_selector(as, pg, ti);
1010         if (r)
1011                 goto bad;
1012
1013         /*
1014          * read the paths
1015          */
1016         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
1017         if (r)
1018                 goto bad;
1019
1020         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
1021         if (r)
1022                 goto bad;
1023
1024         nr_args = 1 + nr_selector_args;
1025         for (i = 0; i < pg->nr_pgpaths; i++) {
1026                 struct pgpath *pgpath;
1027                 struct dm_arg_set path_args;
1028
1029                 if (as->argc < nr_args) {
1030                         ti->error = "not enough path parameters";
1031                         r = -EINVAL;
1032                         goto bad;
1033                 }
1034
1035                 path_args.argc = nr_args;
1036                 path_args.argv = as->argv;
1037
1038                 pgpath = parse_path(&path_args, &pg->ps, ti);
1039                 if (IS_ERR(pgpath)) {
1040                         r = PTR_ERR(pgpath);
1041                         goto bad;
1042                 }
1043
1044                 pgpath->pg = pg;
1045                 list_add_tail(&pgpath->list, &pg->pgpaths);
1046                 dm_consume_args(as, nr_args);
1047         }
1048
1049         return pg;
1050
1051  bad:
1052         free_priority_group(pg, ti);
1053         return ERR_PTR(r);
1054 }
1055
1056 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1057 {
1058         unsigned int hw_argc;
1059         int ret;
1060         struct dm_target *ti = m->ti;
1061
1062         static const struct dm_arg _args[] = {
1063                 {0, 1024, "invalid number of hardware handler args"},
1064         };
1065
1066         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1067                 return -EINVAL;
1068
1069         if (!hw_argc)
1070                 return 0;
1071
1072         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1073                 dm_consume_args(as, hw_argc);
1074                 DMERR("bio-based multipath doesn't allow hardware handler args");
1075                 return 0;
1076         }
1077
1078         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1079         if (!m->hw_handler_name)
1080                 return -EINVAL;
1081
1082         if (hw_argc > 1) {
1083                 char *p;
1084                 int i, j, len = 4;
1085
1086                 for (i = 0; i <= hw_argc - 2; i++)
1087                         len += strlen(as->argv[i]) + 1;
1088                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1089                 if (!p) {
1090                         ti->error = "memory allocation failed";
1091                         ret = -ENOMEM;
1092                         goto fail;
1093                 }
1094                 j = sprintf(p, "%d", hw_argc - 1);
1095                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1096                         j = sprintf(p, "%s", as->argv[i]);
1097         }
1098         dm_consume_args(as, hw_argc - 1);
1099
1100         return 0;
1101 fail:
1102         kfree(m->hw_handler_name);
1103         m->hw_handler_name = NULL;
1104         return ret;
1105 }
1106
1107 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1108 {
1109         int r;
1110         unsigned int argc;
1111         struct dm_target *ti = m->ti;
1112         const char *arg_name;
1113
1114         static const struct dm_arg _args[] = {
1115                 {0, 8, "invalid number of feature args"},
1116                 {1, 50, "pg_init_retries must be between 1 and 50"},
1117                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1118         };
1119
1120         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1121         if (r)
1122                 return -EINVAL;
1123
1124         if (!argc)
1125                 return 0;
1126
1127         do {
1128                 arg_name = dm_shift_arg(as);
1129                 argc--;
1130
1131                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1132                         r = queue_if_no_path(m, true, false, __func__);
1133                         continue;
1134                 }
1135
1136                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1137                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1138                         continue;
1139                 }
1140
1141                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1142                     (argc >= 1)) {
1143                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1144                         argc--;
1145                         continue;
1146                 }
1147
1148                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1149                     (argc >= 1)) {
1150                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1151                         argc--;
1152                         continue;
1153                 }
1154
1155                 if (!strcasecmp(arg_name, "queue_mode") &&
1156                     (argc >= 1)) {
1157                         const char *queue_mode_name = dm_shift_arg(as);
1158
1159                         if (!strcasecmp(queue_mode_name, "bio"))
1160                                 m->queue_mode = DM_TYPE_BIO_BASED;
1161                         else if (!strcasecmp(queue_mode_name, "rq") ||
1162                                  !strcasecmp(queue_mode_name, "mq"))
1163                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1164                         else {
1165                                 ti->error = "Unknown 'queue_mode' requested";
1166                                 r = -EINVAL;
1167                         }
1168                         argc--;
1169                         continue;
1170                 }
1171
1172                 ti->error = "Unrecognised multipath feature request";
1173                 r = -EINVAL;
1174         } while (argc && !r);
1175
1176         return r;
1177 }
1178
1179 static int multipath_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1180 {
1181         /* target arguments */
1182         static const struct dm_arg _args[] = {
1183                 {0, 1024, "invalid number of priority groups"},
1184                 {0, 1024, "invalid initial priority group number"},
1185         };
1186
1187         int r;
1188         struct multipath *m;
1189         struct dm_arg_set as;
1190         unsigned int pg_count = 0;
1191         unsigned int next_pg_num;
1192         unsigned long flags;
1193
1194         as.argc = argc;
1195         as.argv = argv;
1196
1197         m = alloc_multipath(ti);
1198         if (!m) {
1199                 ti->error = "can't allocate multipath";
1200                 return -EINVAL;
1201         }
1202
1203         r = parse_features(&as, m);
1204         if (r)
1205                 goto bad;
1206
1207         r = alloc_multipath_stage2(ti, m);
1208         if (r)
1209                 goto bad;
1210
1211         r = parse_hw_handler(&as, m);
1212         if (r)
1213                 goto bad;
1214
1215         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1216         if (r)
1217                 goto bad;
1218
1219         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1220         if (r)
1221                 goto bad;
1222
1223         if ((!m->nr_priority_groups && next_pg_num) ||
1224             (m->nr_priority_groups && !next_pg_num)) {
1225                 ti->error = "invalid initial priority group";
1226                 r = -EINVAL;
1227                 goto bad;
1228         }
1229
1230         /* parse the priority groups */
1231         while (as.argc) {
1232                 struct priority_group *pg;
1233                 unsigned int nr_valid_paths = atomic_read(&m->nr_valid_paths);
1234
1235                 pg = parse_priority_group(&as, m);
1236                 if (IS_ERR(pg)) {
1237                         r = PTR_ERR(pg);
1238                         goto bad;
1239                 }
1240
1241                 nr_valid_paths += pg->nr_pgpaths;
1242                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1243
1244                 list_add_tail(&pg->list, &m->priority_groups);
1245                 pg_count++;
1246                 pg->pg_num = pg_count;
1247                 if (!--next_pg_num)
1248                         m->next_pg = pg;
1249         }
1250
1251         if (pg_count != m->nr_priority_groups) {
1252                 ti->error = "priority group count mismatch";
1253                 r = -EINVAL;
1254                 goto bad;
1255         }
1256
1257         spin_lock_irqsave(&m->lock, flags);
1258         enable_nopath_timeout(m);
1259         spin_unlock_irqrestore(&m->lock, flags);
1260
1261         ti->num_flush_bios = 1;
1262         ti->num_discard_bios = 1;
1263         ti->num_write_zeroes_bios = 1;
1264         if (m->queue_mode == DM_TYPE_BIO_BASED)
1265                 ti->per_io_data_size = multipath_per_bio_data_size();
1266         else
1267                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1268
1269         return 0;
1270
1271  bad:
1272         free_multipath(m);
1273         return r;
1274 }
1275
1276 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1277 {
1278         DEFINE_WAIT(wait);
1279
1280         while (1) {
1281                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1282
1283                 if (!atomic_read(&m->pg_init_in_progress))
1284                         break;
1285
1286                 io_schedule();
1287         }
1288         finish_wait(&m->pg_init_wait, &wait);
1289 }
1290
1291 static void flush_multipath_work(struct multipath *m)
1292 {
1293         if (m->hw_handler_name) {
1294                 unsigned long flags;
1295
1296                 if (!atomic_read(&m->pg_init_in_progress))
1297                         goto skip;
1298
1299                 spin_lock_irqsave(&m->lock, flags);
1300                 if (atomic_read(&m->pg_init_in_progress) &&
1301                     !test_and_set_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) {
1302                         spin_unlock_irqrestore(&m->lock, flags);
1303
1304                         flush_workqueue(kmpath_handlerd);
1305                         multipath_wait_for_pg_init_completion(m);
1306
1307                         spin_lock_irqsave(&m->lock, flags);
1308                         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1309                 }
1310                 spin_unlock_irqrestore(&m->lock, flags);
1311         }
1312 skip:
1313         if (m->queue_mode == DM_TYPE_BIO_BASED)
1314                 flush_work(&m->process_queued_bios);
1315         flush_work(&m->trigger_event);
1316 }
1317
1318 static void multipath_dtr(struct dm_target *ti)
1319 {
1320         struct multipath *m = ti->private;
1321
1322         disable_nopath_timeout(m);
1323         flush_multipath_work(m);
1324         free_multipath(m);
1325 }
1326
1327 /*
1328  * Take a path out of use.
1329  */
1330 static int fail_path(struct pgpath *pgpath)
1331 {
1332         unsigned long flags;
1333         struct multipath *m = pgpath->pg->m;
1334
1335         spin_lock_irqsave(&m->lock, flags);
1336
1337         if (!pgpath->is_active)
1338                 goto out;
1339
1340         DMWARN("%s: Failing path %s.",
1341                dm_table_device_name(m->ti->table),
1342                pgpath->path.dev->name);
1343
1344         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1345         pgpath->is_active = false;
1346         pgpath->fail_count++;
1347
1348         atomic_dec(&m->nr_valid_paths);
1349
1350         if (pgpath == m->current_pgpath)
1351                 m->current_pgpath = NULL;
1352
1353         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1354                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1355
1356         schedule_work(&m->trigger_event);
1357
1358         enable_nopath_timeout(m);
1359
1360 out:
1361         spin_unlock_irqrestore(&m->lock, flags);
1362
1363         return 0;
1364 }
1365
1366 /*
1367  * Reinstate a previously-failed path
1368  */
1369 static int reinstate_path(struct pgpath *pgpath)
1370 {
1371         int r = 0, run_queue = 0;
1372         unsigned long flags;
1373         struct multipath *m = pgpath->pg->m;
1374         unsigned int nr_valid_paths;
1375
1376         spin_lock_irqsave(&m->lock, flags);
1377
1378         if (pgpath->is_active)
1379                 goto out;
1380
1381         DMWARN("%s: Reinstating path %s.",
1382                dm_table_device_name(m->ti->table),
1383                pgpath->path.dev->name);
1384
1385         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1386         if (r)
1387                 goto out;
1388
1389         pgpath->is_active = true;
1390
1391         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1392         if (nr_valid_paths == 1) {
1393                 m->current_pgpath = NULL;
1394                 run_queue = 1;
1395         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1396                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1397                         atomic_inc(&m->pg_init_in_progress);
1398         }
1399
1400         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1401                        pgpath->path.dev->name, nr_valid_paths);
1402
1403         schedule_work(&m->trigger_event);
1404
1405 out:
1406         spin_unlock_irqrestore(&m->lock, flags);
1407         if (run_queue) {
1408                 dm_table_run_md_queue_async(m->ti->table);
1409                 process_queued_io_list(m);
1410         }
1411
1412         if (pgpath->is_active)
1413                 disable_nopath_timeout(m);
1414
1415         return r;
1416 }
1417
1418 /*
1419  * Fail or reinstate all paths that match the provided struct dm_dev.
1420  */
1421 static int action_dev(struct multipath *m, struct dm_dev *dev,
1422                       action_fn action)
1423 {
1424         int r = -EINVAL;
1425         struct pgpath *pgpath;
1426         struct priority_group *pg;
1427
1428         list_for_each_entry(pg, &m->priority_groups, list) {
1429                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1430                         if (pgpath->path.dev == dev)
1431                                 r = action(pgpath);
1432                 }
1433         }
1434
1435         return r;
1436 }
1437
1438 /*
1439  * Temporarily try to avoid having to use the specified PG
1440  */
1441 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1442                       bool bypassed)
1443 {
1444         unsigned long flags;
1445
1446         spin_lock_irqsave(&m->lock, flags);
1447
1448         pg->bypassed = bypassed;
1449         m->current_pgpath = NULL;
1450         m->current_pg = NULL;
1451
1452         spin_unlock_irqrestore(&m->lock, flags);
1453
1454         schedule_work(&m->trigger_event);
1455 }
1456
1457 /*
1458  * Switch to using the specified PG from the next I/O that gets mapped
1459  */
1460 static int switch_pg_num(struct multipath *m, const char *pgstr)
1461 {
1462         struct priority_group *pg;
1463         unsigned int pgnum;
1464         unsigned long flags;
1465         char dummy;
1466
1467         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1468             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1469                 DMWARN("invalid PG number supplied to switch_pg_num");
1470                 return -EINVAL;
1471         }
1472
1473         spin_lock_irqsave(&m->lock, flags);
1474         list_for_each_entry(pg, &m->priority_groups, list) {
1475                 pg->bypassed = false;
1476                 if (--pgnum)
1477                         continue;
1478
1479                 m->current_pgpath = NULL;
1480                 m->current_pg = NULL;
1481                 m->next_pg = pg;
1482         }
1483         spin_unlock_irqrestore(&m->lock, flags);
1484
1485         schedule_work(&m->trigger_event);
1486         return 0;
1487 }
1488
1489 /*
1490  * Set/clear bypassed status of a PG.
1491  * PGs are numbered upwards from 1 in the order they were declared.
1492  */
1493 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1494 {
1495         struct priority_group *pg;
1496         unsigned int pgnum;
1497         char dummy;
1498
1499         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1500             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1501                 DMWARN("invalid PG number supplied to bypass_pg");
1502                 return -EINVAL;
1503         }
1504
1505         list_for_each_entry(pg, &m->priority_groups, list) {
1506                 if (!--pgnum)
1507                         break;
1508         }
1509
1510         bypass_pg(m, pg, bypassed);
1511         return 0;
1512 }
1513
1514 /*
1515  * Should we retry pg_init immediately?
1516  */
1517 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1518 {
1519         unsigned long flags;
1520         bool limit_reached = false;
1521
1522         spin_lock_irqsave(&m->lock, flags);
1523
1524         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1525             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1526                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1527         else
1528                 limit_reached = true;
1529
1530         spin_unlock_irqrestore(&m->lock, flags);
1531
1532         return limit_reached;
1533 }
1534
1535 static void pg_init_done(void *data, int errors)
1536 {
1537         struct pgpath *pgpath = data;
1538         struct priority_group *pg = pgpath->pg;
1539         struct multipath *m = pg->m;
1540         unsigned long flags;
1541         bool delay_retry = false;
1542
1543         /* device or driver problems */
1544         switch (errors) {
1545         case SCSI_DH_OK:
1546                 break;
1547         case SCSI_DH_NOSYS:
1548                 if (!m->hw_handler_name) {
1549                         errors = 0;
1550                         break;
1551                 }
1552                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1553                       "Error %d.", m->hw_handler_name, errors);
1554                 /*
1555                  * Fail path for now, so we do not ping pong
1556                  */
1557                 fail_path(pgpath);
1558                 break;
1559         case SCSI_DH_DEV_TEMP_BUSY:
1560                 /*
1561                  * Probably doing something like FW upgrade on the
1562                  * controller so try the other pg.
1563                  */
1564                 bypass_pg(m, pg, true);
1565                 break;
1566         case SCSI_DH_RETRY:
1567                 /* Wait before retrying. */
1568                 delay_retry = true;
1569                 fallthrough;
1570         case SCSI_DH_IMM_RETRY:
1571         case SCSI_DH_RES_TEMP_UNAVAIL:
1572                 if (pg_init_limit_reached(m, pgpath))
1573                         fail_path(pgpath);
1574                 errors = 0;
1575                 break;
1576         case SCSI_DH_DEV_OFFLINED:
1577         default:
1578                 /*
1579                  * We probably do not want to fail the path for a device
1580                  * error, but this is what the old dm did. In future
1581                  * patches we can do more advanced handling.
1582                  */
1583                 fail_path(pgpath);
1584         }
1585
1586         spin_lock_irqsave(&m->lock, flags);
1587         if (errors) {
1588                 if (pgpath == m->current_pgpath) {
1589                         DMERR("Could not failover device. Error %d.", errors);
1590                         m->current_pgpath = NULL;
1591                         m->current_pg = NULL;
1592                 }
1593         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1594                 pg->bypassed = false;
1595
1596         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1597                 /* Activations of other paths are still on going */
1598                 goto out;
1599
1600         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1601                 if (delay_retry)
1602                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1603                 else
1604                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1605
1606                 if (__pg_init_all_paths(m))
1607                         goto out;
1608         }
1609         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1610
1611         process_queued_io_list(m);
1612
1613         /*
1614          * Wake up any thread waiting to suspend.
1615          */
1616         wake_up(&m->pg_init_wait);
1617
1618 out:
1619         spin_unlock_irqrestore(&m->lock, flags);
1620 }
1621
1622 static void activate_or_offline_path(struct pgpath *pgpath)
1623 {
1624         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1625
1626         if (pgpath->is_active && !blk_queue_dying(q))
1627                 scsi_dh_activate(q, pg_init_done, pgpath);
1628         else
1629                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1630 }
1631
1632 static void activate_path_work(struct work_struct *work)
1633 {
1634         struct pgpath *pgpath =
1635                 container_of(work, struct pgpath, activate_path.work);
1636
1637         activate_or_offline_path(pgpath);
1638 }
1639
1640 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1641                             blk_status_t error, union map_info *map_context)
1642 {
1643         struct dm_mpath_io *mpio = get_mpio(map_context);
1644         struct pgpath *pgpath = mpio->pgpath;
1645         int r = DM_ENDIO_DONE;
1646
1647         /*
1648          * We don't queue any clone request inside the multipath target
1649          * during end I/O handling, since those clone requests don't have
1650          * bio clones.  If we queue them inside the multipath target,
1651          * we need to make bio clones, that requires memory allocation.
1652          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1653          *  don't have bio clones.)
1654          * Instead of queueing the clone request here, we queue the original
1655          * request into dm core, which will remake a clone request and
1656          * clone bios for it and resubmit it later.
1657          */
1658         if (error && blk_path_error(error)) {
1659                 struct multipath *m = ti->private;
1660
1661                 if (error == BLK_STS_RESOURCE)
1662                         r = DM_ENDIO_DELAY_REQUEUE;
1663                 else
1664                         r = DM_ENDIO_REQUEUE;
1665
1666                 if (pgpath)
1667                         fail_path(pgpath);
1668
1669                 if (!atomic_read(&m->nr_valid_paths) &&
1670                     !must_push_back_rq(m)) {
1671                         if (error == BLK_STS_IOERR)
1672                                 dm_report_EIO(m);
1673                         /* complete with the original error */
1674                         r = DM_ENDIO_DONE;
1675                 }
1676         }
1677
1678         if (pgpath) {
1679                 struct path_selector *ps = &pgpath->pg->ps;
1680
1681                 if (ps->type->end_io)
1682                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1683                                          clone->io_start_time_ns);
1684         }
1685
1686         return r;
1687 }
1688
1689 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1690                                 blk_status_t *error)
1691 {
1692         struct multipath *m = ti->private;
1693         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1694         struct pgpath *pgpath = mpio->pgpath;
1695         unsigned long flags;
1696         int r = DM_ENDIO_DONE;
1697
1698         if (!*error || !blk_path_error(*error))
1699                 goto done;
1700
1701         if (pgpath)
1702                 fail_path(pgpath);
1703
1704         if (!atomic_read(&m->nr_valid_paths)) {
1705                 spin_lock_irqsave(&m->lock, flags);
1706                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1707                         if (__must_push_back(m)) {
1708                                 r = DM_ENDIO_REQUEUE;
1709                         } else {
1710                                 dm_report_EIO(m);
1711                                 *error = BLK_STS_IOERR;
1712                         }
1713                         spin_unlock_irqrestore(&m->lock, flags);
1714                         goto done;
1715                 }
1716                 spin_unlock_irqrestore(&m->lock, flags);
1717         }
1718
1719         multipath_queue_bio(m, clone);
1720         r = DM_ENDIO_INCOMPLETE;
1721 done:
1722         if (pgpath) {
1723                 struct path_selector *ps = &pgpath->pg->ps;
1724
1725                 if (ps->type->end_io)
1726                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1727                                          (mpio->start_time_ns ?:
1728                                           dm_start_time_ns_from_clone(clone)));
1729         }
1730
1731         return r;
1732 }
1733
1734 /*
1735  * Suspend with flush can't complete until all the I/O is processed
1736  * so if the last path fails we must error any remaining I/O.
1737  * - Note that if the freeze_bdev fails while suspending, the
1738  *   queue_if_no_path state is lost - userspace should reset it.
1739  * Otherwise, during noflush suspend, queue_if_no_path will not change.
1740  */
1741 static void multipath_presuspend(struct dm_target *ti)
1742 {
1743         struct multipath *m = ti->private;
1744
1745         /* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1746         if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1747                 queue_if_no_path(m, false, true, __func__);
1748 }
1749
1750 static void multipath_postsuspend(struct dm_target *ti)
1751 {
1752         struct multipath *m = ti->private;
1753
1754         mutex_lock(&m->work_mutex);
1755         flush_multipath_work(m);
1756         mutex_unlock(&m->work_mutex);
1757 }
1758
1759 /*
1760  * Restore the queue_if_no_path setting.
1761  */
1762 static void multipath_resume(struct dm_target *ti)
1763 {
1764         struct multipath *m = ti->private;
1765         unsigned long flags;
1766
1767         spin_lock_irqsave(&m->lock, flags);
1768         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1769                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1770                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1771         }
1772
1773         DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1774                 dm_table_device_name(m->ti->table), __func__,
1775                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1776                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1777
1778         spin_unlock_irqrestore(&m->lock, flags);
1779 }
1780
1781 /*
1782  * Info output has the following format:
1783  * num_multipath_feature_args [multipath_feature_args]*
1784  * num_handler_status_args [handler_status_args]*
1785  * num_groups init_group_number
1786  *            [A|D|E num_ps_status_args [ps_status_args]*
1787  *             num_paths num_selector_args
1788  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1789  *
1790  * Table output has the following format (identical to the constructor string):
1791  * num_feature_args [features_args]*
1792  * num_handler_args hw_handler [hw_handler_args]*
1793  * num_groups init_group_number
1794  *     [priority selector-name num_ps_args [ps_args]*
1795  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1796  */
1797 static void multipath_status(struct dm_target *ti, status_type_t type,
1798                              unsigned int status_flags, char *result, unsigned int maxlen)
1799 {
1800         int sz = 0, pg_counter, pgpath_counter;
1801         unsigned long flags;
1802         struct multipath *m = ti->private;
1803         struct priority_group *pg;
1804         struct pgpath *p;
1805         unsigned int pg_num;
1806         char state;
1807
1808         spin_lock_irqsave(&m->lock, flags);
1809
1810         /* Features */
1811         if (type == STATUSTYPE_INFO)
1812                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1813                        atomic_read(&m->pg_init_count));
1814         else {
1815                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1816                               (m->pg_init_retries > 0) * 2 +
1817                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1818                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1819                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1820
1821                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1822                         DMEMIT("queue_if_no_path ");
1823                 if (m->pg_init_retries)
1824                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1825                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1826                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1827                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1828                         DMEMIT("retain_attached_hw_handler ");
1829                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1830                         switch (m->queue_mode) {
1831                         case DM_TYPE_BIO_BASED:
1832                                 DMEMIT("queue_mode bio ");
1833                                 break;
1834                         default:
1835                                 WARN_ON_ONCE(true);
1836                                 break;
1837                         }
1838                 }
1839         }
1840
1841         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1842                 DMEMIT("0 ");
1843         else
1844                 DMEMIT("1 %s ", m->hw_handler_name);
1845
1846         DMEMIT("%u ", m->nr_priority_groups);
1847
1848         if (m->next_pg)
1849                 pg_num = m->next_pg->pg_num;
1850         else if (m->current_pg)
1851                 pg_num = m->current_pg->pg_num;
1852         else
1853                 pg_num = (m->nr_priority_groups ? 1 : 0);
1854
1855         DMEMIT("%u ", pg_num);
1856
1857         switch (type) {
1858         case STATUSTYPE_INFO:
1859                 list_for_each_entry(pg, &m->priority_groups, list) {
1860                         if (pg->bypassed)
1861                                 state = 'D';    /* Disabled */
1862                         else if (pg == m->current_pg)
1863                                 state = 'A';    /* Currently Active */
1864                         else
1865                                 state = 'E';    /* Enabled */
1866
1867                         DMEMIT("%c ", state);
1868
1869                         if (pg->ps.type->status)
1870                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1871                                                           result + sz,
1872                                                           maxlen - sz);
1873                         else
1874                                 DMEMIT("0 ");
1875
1876                         DMEMIT("%u %u ", pg->nr_pgpaths,
1877                                pg->ps.type->info_args);
1878
1879                         list_for_each_entry(p, &pg->pgpaths, list) {
1880                                 DMEMIT("%s %s %u ", p->path.dev->name,
1881                                        p->is_active ? "A" : "F",
1882                                        p->fail_count);
1883                                 if (pg->ps.type->status)
1884                                         sz += pg->ps.type->status(&pg->ps,
1885                                               &p->path, type, result + sz,
1886                                               maxlen - sz);
1887                         }
1888                 }
1889                 break;
1890
1891         case STATUSTYPE_TABLE:
1892                 list_for_each_entry(pg, &m->priority_groups, list) {
1893                         DMEMIT("%s ", pg->ps.type->name);
1894
1895                         if (pg->ps.type->status)
1896                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1897                                                           result + sz,
1898                                                           maxlen - sz);
1899                         else
1900                                 DMEMIT("0 ");
1901
1902                         DMEMIT("%u %u ", pg->nr_pgpaths,
1903                                pg->ps.type->table_args);
1904
1905                         list_for_each_entry(p, &pg->pgpaths, list) {
1906                                 DMEMIT("%s ", p->path.dev->name);
1907                                 if (pg->ps.type->status)
1908                                         sz += pg->ps.type->status(&pg->ps,
1909                                               &p->path, type, result + sz,
1910                                               maxlen - sz);
1911                         }
1912                 }
1913                 break;
1914
1915         case STATUSTYPE_IMA:
1916                 sz = 0; /*reset the result pointer*/
1917
1918                 DMEMIT_TARGET_NAME_VERSION(ti->type);
1919                 DMEMIT(",nr_priority_groups=%u", m->nr_priority_groups);
1920
1921                 pg_counter = 0;
1922                 list_for_each_entry(pg, &m->priority_groups, list) {
1923                         if (pg->bypassed)
1924                                 state = 'D';    /* Disabled */
1925                         else if (pg == m->current_pg)
1926                                 state = 'A';    /* Currently Active */
1927                         else
1928                                 state = 'E';    /* Enabled */
1929                         DMEMIT(",pg_state_%d=%c", pg_counter, state);
1930                         DMEMIT(",nr_pgpaths_%d=%u", pg_counter, pg->nr_pgpaths);
1931                         DMEMIT(",path_selector_name_%d=%s", pg_counter, pg->ps.type->name);
1932
1933                         pgpath_counter = 0;
1934                         list_for_each_entry(p, &pg->pgpaths, list) {
1935                                 DMEMIT(",path_name_%d_%d=%s,is_active_%d_%d=%c,fail_count_%d_%d=%u",
1936                                        pg_counter, pgpath_counter, p->path.dev->name,
1937                                        pg_counter, pgpath_counter, p->is_active ? 'A' : 'F',
1938                                        pg_counter, pgpath_counter, p->fail_count);
1939                                 if (pg->ps.type->status) {
1940                                         DMEMIT(",path_selector_status_%d_%d=",
1941                                                pg_counter, pgpath_counter);
1942                                         sz += pg->ps.type->status(&pg->ps, &p->path,
1943                                                                   type, result + sz,
1944                                                                   maxlen - sz);
1945                                 }
1946                                 pgpath_counter++;
1947                         }
1948                         pg_counter++;
1949                 }
1950                 DMEMIT(";");
1951                 break;
1952         }
1953
1954         spin_unlock_irqrestore(&m->lock, flags);
1955 }
1956
1957 static int multipath_message(struct dm_target *ti, unsigned int argc, char **argv,
1958                              char *result, unsigned int maxlen)
1959 {
1960         int r = -EINVAL;
1961         struct dm_dev *dev;
1962         struct multipath *m = ti->private;
1963         action_fn action;
1964         unsigned long flags;
1965
1966         mutex_lock(&m->work_mutex);
1967
1968         if (dm_suspended(ti)) {
1969                 r = -EBUSY;
1970                 goto out;
1971         }
1972
1973         if (argc == 1) {
1974                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1975                         r = queue_if_no_path(m, true, false, __func__);
1976                         spin_lock_irqsave(&m->lock, flags);
1977                         enable_nopath_timeout(m);
1978                         spin_unlock_irqrestore(&m->lock, flags);
1979                         goto out;
1980                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1981                         r = queue_if_no_path(m, false, false, __func__);
1982                         disable_nopath_timeout(m);
1983                         goto out;
1984                 }
1985         }
1986
1987         if (argc != 2) {
1988                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1989                 goto out;
1990         }
1991
1992         if (!strcasecmp(argv[0], "disable_group")) {
1993                 r = bypass_pg_num(m, argv[1], true);
1994                 goto out;
1995         } else if (!strcasecmp(argv[0], "enable_group")) {
1996                 r = bypass_pg_num(m, argv[1], false);
1997                 goto out;
1998         } else if (!strcasecmp(argv[0], "switch_group")) {
1999                 r = switch_pg_num(m, argv[1]);
2000                 goto out;
2001         } else if (!strcasecmp(argv[0], "reinstate_path"))
2002                 action = reinstate_path;
2003         else if (!strcasecmp(argv[0], "fail_path"))
2004                 action = fail_path;
2005         else {
2006                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
2007                 goto out;
2008         }
2009
2010         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
2011         if (r) {
2012                 DMWARN("message: error getting device %s",
2013                        argv[1]);
2014                 goto out;
2015         }
2016
2017         r = action_dev(m, dev, action);
2018
2019         dm_put_device(ti, dev);
2020
2021 out:
2022         mutex_unlock(&m->work_mutex);
2023         return r;
2024 }
2025
2026 static int multipath_prepare_ioctl(struct dm_target *ti,
2027                                    struct block_device **bdev)
2028 {
2029         struct multipath *m = ti->private;
2030         struct pgpath *pgpath;
2031         unsigned long flags;
2032         int r;
2033
2034         pgpath = READ_ONCE(m->current_pgpath);
2035         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
2036                 pgpath = choose_pgpath(m, 0);
2037
2038         if (pgpath) {
2039                 if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
2040                         *bdev = pgpath->path.dev->bdev;
2041                         r = 0;
2042                 } else {
2043                         /* pg_init has not started or completed */
2044                         r = -ENOTCONN;
2045                 }
2046         } else {
2047                 /* No path is available */
2048                 r = -EIO;
2049                 spin_lock_irqsave(&m->lock, flags);
2050                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2051                         r = -ENOTCONN;
2052                 spin_unlock_irqrestore(&m->lock, flags);
2053         }
2054
2055         if (r == -ENOTCONN) {
2056                 if (!READ_ONCE(m->current_pg)) {
2057                         /* Path status changed, redo selection */
2058                         (void) choose_pgpath(m, 0);
2059                 }
2060                 spin_lock_irqsave(&m->lock, flags);
2061                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2062                         (void) __pg_init_all_paths(m);
2063                 spin_unlock_irqrestore(&m->lock, flags);
2064                 dm_table_run_md_queue_async(m->ti->table);
2065                 process_queued_io_list(m);
2066         }
2067
2068         /*
2069          * Only pass ioctls through if the device sizes match exactly.
2070          */
2071         if (!r && ti->len != bdev_nr_sectors((*bdev)))
2072                 return 1;
2073         return r;
2074 }
2075
2076 static int multipath_iterate_devices(struct dm_target *ti,
2077                                      iterate_devices_callout_fn fn, void *data)
2078 {
2079         struct multipath *m = ti->private;
2080         struct priority_group *pg;
2081         struct pgpath *p;
2082         int ret = 0;
2083
2084         list_for_each_entry(pg, &m->priority_groups, list) {
2085                 list_for_each_entry(p, &pg->pgpaths, list) {
2086                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2087                         if (ret)
2088                                 goto out;
2089                 }
2090         }
2091
2092 out:
2093         return ret;
2094 }
2095
2096 static int pgpath_busy(struct pgpath *pgpath)
2097 {
2098         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2099
2100         return blk_lld_busy(q);
2101 }
2102
2103 /*
2104  * We return "busy", only when we can map I/Os but underlying devices
2105  * are busy (so even if we map I/Os now, the I/Os will wait on
2106  * the underlying queue).
2107  * In other words, if we want to kill I/Os or queue them inside us
2108  * due to map unavailability, we don't return "busy".  Otherwise,
2109  * dm core won't give us the I/Os and we can't do what we want.
2110  */
2111 static int multipath_busy(struct dm_target *ti)
2112 {
2113         bool busy = false, has_active = false;
2114         struct multipath *m = ti->private;
2115         struct priority_group *pg, *next_pg;
2116         struct pgpath *pgpath;
2117
2118         /* pg_init in progress */
2119         if (atomic_read(&m->pg_init_in_progress))
2120                 return true;
2121
2122         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2123         if (!atomic_read(&m->nr_valid_paths)) {
2124                 unsigned long flags;
2125                 spin_lock_irqsave(&m->lock, flags);
2126                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2127                         spin_unlock_irqrestore(&m->lock, flags);
2128                         return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2129                 }
2130                 spin_unlock_irqrestore(&m->lock, flags);
2131         }
2132
2133         /* Guess which priority_group will be used at next mapping time */
2134         pg = READ_ONCE(m->current_pg);
2135         next_pg = READ_ONCE(m->next_pg);
2136         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2137                 pg = next_pg;
2138
2139         if (!pg) {
2140                 /*
2141                  * We don't know which pg will be used at next mapping time.
2142                  * We don't call choose_pgpath() here to avoid to trigger
2143                  * pg_init just by busy checking.
2144                  * So we don't know whether underlying devices we will be using
2145                  * at next mapping time are busy or not. Just try mapping.
2146                  */
2147                 return busy;
2148         }
2149
2150         /*
2151          * If there is one non-busy active path at least, the path selector
2152          * will be able to select it. So we consider such a pg as not busy.
2153          */
2154         busy = true;
2155         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2156                 if (pgpath->is_active) {
2157                         has_active = true;
2158                         if (!pgpath_busy(pgpath)) {
2159                                 busy = false;
2160                                 break;
2161                         }
2162                 }
2163         }
2164
2165         if (!has_active) {
2166                 /*
2167                  * No active path in this pg, so this pg won't be used and
2168                  * the current_pg will be changed at next mapping time.
2169                  * We need to try mapping to determine it.
2170                  */
2171                 busy = false;
2172         }
2173
2174         return busy;
2175 }
2176
2177 /*
2178  *---------------------------------------------------------------
2179  * Module setup
2180  *---------------------------------------------------------------
2181  */
2182 static struct target_type multipath_target = {
2183         .name = "multipath",
2184         .version = {1, 14, 0},
2185         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2186                     DM_TARGET_PASSES_INTEGRITY,
2187         .module = THIS_MODULE,
2188         .ctr = multipath_ctr,
2189         .dtr = multipath_dtr,
2190         .clone_and_map_rq = multipath_clone_and_map,
2191         .release_clone_rq = multipath_release_clone,
2192         .rq_end_io = multipath_end_io,
2193         .map = multipath_map_bio,
2194         .end_io = multipath_end_io_bio,
2195         .presuspend = multipath_presuspend,
2196         .postsuspend = multipath_postsuspend,
2197         .resume = multipath_resume,
2198         .status = multipath_status,
2199         .message = multipath_message,
2200         .prepare_ioctl = multipath_prepare_ioctl,
2201         .iterate_devices = multipath_iterate_devices,
2202         .busy = multipath_busy,
2203 };
2204
2205 static int __init dm_multipath_init(void)
2206 {
2207         int r;
2208
2209         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2210         if (!kmultipathd) {
2211                 DMERR("failed to create workqueue kmpathd");
2212                 r = -ENOMEM;
2213                 goto bad_alloc_kmultipathd;
2214         }
2215
2216         /*
2217          * A separate workqueue is used to handle the device handlers
2218          * to avoid overloading existing workqueue. Overloading the
2219          * old workqueue would also create a bottleneck in the
2220          * path of the storage hardware device activation.
2221          */
2222         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2223                                                   WQ_MEM_RECLAIM);
2224         if (!kmpath_handlerd) {
2225                 DMERR("failed to create workqueue kmpath_handlerd");
2226                 r = -ENOMEM;
2227                 goto bad_alloc_kmpath_handlerd;
2228         }
2229
2230         r = dm_register_target(&multipath_target);
2231         if (r < 0) {
2232                 DMERR("request-based register failed %d", r);
2233                 r = -EINVAL;
2234                 goto bad_register_target;
2235         }
2236
2237         return 0;
2238
2239 bad_register_target:
2240         destroy_workqueue(kmpath_handlerd);
2241 bad_alloc_kmpath_handlerd:
2242         destroy_workqueue(kmultipathd);
2243 bad_alloc_kmultipathd:
2244         return r;
2245 }
2246
2247 static void __exit dm_multipath_exit(void)
2248 {
2249         destroy_workqueue(kmpath_handlerd);
2250         destroy_workqueue(kmultipathd);
2251
2252         dm_unregister_target(&multipath_target);
2253 }
2254
2255 module_init(dm_multipath_init);
2256 module_exit(dm_multipath_exit);
2257
2258 module_param_named(queue_if_no_path_timeout_secs,
2259                    queue_if_no_path_timeout_secs, ulong, S_IRUGO | S_IWUSR);
2260 MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2261
2262 MODULE_DESCRIPTION(DM_NAME " multipath target");
2263 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2264 MODULE_LICENSE("GPL");