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/timer.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/delay.h>
  26 #include <scsi/scsi_dh.h>
  27 #include <linux/atomic.h>
  28 #include <linux/blk-mq.h>
  29
  30 #define DM_MSG_PREFIX "multipath"
  31 #define DM_PG_INIT_DELAY_MSECS 2000
  32 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  33 #define QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT 0
  34
  35 static unsigned long queue_if_no_path_timeout_secs = QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT;
  36
  37 /* Path properties */
  38 struct pgpath {
  39         struct list_head list;
  40
  41         struct priority_group *pg;      /* Owning PG */
  42         unsigned fail_count;            /* Cumulative failure count */
  43
  44         struct dm_path path;
  45         struct delayed_work activate_path;
  46
  47         bool is_active:1;               /* Path status */
  48 };
  49
  50 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  51
  52 /*
  53  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  54  * Each has a path selector which controls which path gets used.
  55  */
  56 struct priority_group {
  57         struct list_head list;
  58
  59         struct multipath *m;            /* Owning multipath instance */
  60         struct path_selector ps;
  61
  62         unsigned pg_num;                /* Reference number */
  63         unsigned nr_pgpaths;            /* Number of paths in PG */
  64         struct list_head pgpaths;
  65
  66         bool bypassed:1;                /* Temporarily bypass this PG? */
  67 };
  68
  69 /* Multipath context */
  70 struct multipath {
  71         unsigned long flags;            /* Multipath state flags */
  72
  73         spinlock_t lock;
  74         enum dm_queue_mode queue_mode;
  75
  76         struct pgpath *current_pgpath;
  77         struct priority_group *current_pg;
  78         struct priority_group *next_pg; /* Switch to this PG if set */
  79
  80         atomic_t nr_valid_paths;        /* Total number of usable paths */
  81         unsigned nr_priority_groups;
  82         struct list_head priority_groups;
  83
  84         const char *hw_handler_name;
  85         char *hw_handler_params;
  86         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  87         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  88         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  89         atomic_t pg_init_in_progress;   /* Only one pg_init allowed at once */
  90         atomic_t pg_init_count;         /* Number of times pg_init called */
  91
  92         struct mutex work_mutex;
  93         struct work_struct trigger_event;
  94         struct dm_target *ti;
  95
  96         struct work_struct process_queued_bios;
  97         struct bio_list queued_bios;
  98
  99         struct timer_list nopath_timer; /* Timeout for queue_if_no_path */
 100 };
 101
 102 /*
 103  * Context information attached to each io we process.
 104  */
 105 struct dm_mpath_io {
 106         struct pgpath *pgpath;
 107         size_t nr_bytes;
 108 };
 109
 110 typedef int (*action_fn) (struct pgpath *pgpath);
 111
 112 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 113 static void trigger_event(struct work_struct *work);
 114 static void activate_or_offline_path(struct pgpath *pgpath);
 115 static void activate_path_work(struct work_struct *work);
 116 static void process_queued_bios(struct work_struct *work);
 117 static void queue_if_no_path_timeout_work(struct timer_list *t);
 118
 119 /*-----------------------------------------------
 120  * Multipath state flags.
 121  *-----------------------------------------------*/
 122
 123 #define MPATHF_QUEUE_IO 0                       /* Must we queue all I/O? */
 124 #define MPATHF_QUEUE_IF_NO_PATH 1               /* Queue I/O if last path fails? */
 125 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2         /* Saved state during suspension */
 126 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3     /* If there's already a hw_handler present, don't change it. */
 127 #define MPATHF_PG_INIT_DISABLED 4               /* pg_init is not currently allowed */
 128 #define MPATHF_PG_INIT_REQUIRED 5               /* pg_init needs calling? */
 129 #define MPATHF_PG_INIT_DELAY_RETRY 6            /* Delay pg_init retry? */
 130
 131 static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
 132 {
 133         bool r = test_bit(MPATHF_bit, &m->flags);
 134
 135         if (r) {
 136                 unsigned long flags;
 137                 spin_lock_irqsave(&m->lock, flags);
 138                 r = test_bit(MPATHF_bit, &m->flags);
 139                 spin_unlock_irqrestore(&m->lock, flags);
 140         }
 141
 142         return r;
 143 }
 144
 145 /*-----------------------------------------------
 146  * Allocation routines
 147  *-----------------------------------------------*/
 148
 149 static struct pgpath *alloc_pgpath(void)
 150 {
 151         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 152
 153         if (!pgpath)
 154                 return NULL;
 155
 156         pgpath->is_active = true;
 157
 158         return pgpath;
 159 }
 160
 161 static void free_pgpath(struct pgpath *pgpath)
 162 {
 163         kfree(pgpath);
 164 }
 165
 166 static struct priority_group *alloc_priority_group(void)
 167 {
 168         struct priority_group *pg;
 169
 170         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 171
 172         if (pg)
 173                 INIT_LIST_HEAD(&pg->pgpaths);
 174
 175         return pg;
 176 }
 177
 178 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 179 {
 180         struct pgpath *pgpath, *tmp;
 181
 182         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 183                 list_del(&pgpath->list);
 184                 dm_put_device(ti, pgpath->path.dev);
 185                 free_pgpath(pgpath);
 186         }
 187 }
 188
 189 static void free_priority_group(struct priority_group *pg,
 190                                 struct dm_target *ti)
 191 {
 192         struct path_selector *ps = &pg->ps;
 193
 194         if (ps->type) {
 195                 ps->type->destroy(ps);
 196                 dm_put_path_selector(ps->type);
 197         }
 198
 199         free_pgpaths(&pg->pgpaths, ti);
 200         kfree(pg);
 201 }
 202
 203 static struct multipath *alloc_multipath(struct dm_target *ti)
 204 {
 205         struct multipath *m;
 206
 207         m = kzalloc(sizeof(*m), GFP_KERNEL);
 208         if (m) {
 209                 INIT_LIST_HEAD(&m->priority_groups);
 210                 spin_lock_init(&m->lock);
 211                 atomic_set(&m->nr_valid_paths, 0);
 212                 INIT_WORK(&m->trigger_event, trigger_event);
 213                 mutex_init(&m->work_mutex);
 214
 215                 m->queue_mode = DM_TYPE_NONE;
 216
 217                 m->ti = ti;
 218                 ti->private = m;
 219
 220                 timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
 221         }
 222
 223         return m;
 224 }
 225
 226 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 227 {
 228         if (m->queue_mode == DM_TYPE_NONE) {
 229                 m->queue_mode = DM_TYPE_REQUEST_BASED;
 230         } else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 231                 INIT_WORK(&m->process_queued_bios, process_queued_bios);
 232                 /*
 233                  * bio-based doesn't support any direct scsi_dh management;
 234                  * it just discovers if a scsi_dh is attached.
 235                  */
 236                 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 237         }
 238
 239         dm_table_set_type(ti->table, m->queue_mode);
 240
 241         /*
 242          * Init fields that are only used when a scsi_dh is attached
 243          * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 244          */
 245         set_bit(MPATHF_QUEUE_IO, &m->flags);
 246         atomic_set(&m->pg_init_in_progress, 0);
 247         atomic_set(&m->pg_init_count, 0);
 248         m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 249         init_waitqueue_head(&m->pg_init_wait);
 250
 251         return 0;
 252 }
 253
 254 static void free_multipath(struct multipath *m)
 255 {
 256         struct priority_group *pg, *tmp;
 257
 258         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 259                 list_del(&pg->list);
 260                 free_priority_group(pg, m->ti);
 261         }
 262
 263         kfree(m->hw_handler_name);
 264         kfree(m->hw_handler_params);
 265         mutex_destroy(&m->work_mutex);
 266         kfree(m);
 267 }
 268
 269 static struct dm_mpath_io *get_mpio(union map_info *info)
 270 {
 271         return info->ptr;
 272 }
 273
 274 static size_t multipath_per_bio_data_size(void)
 275 {
 276         return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 277 }
 278
 279 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 280 {
 281         return dm_per_bio_data(bio, multipath_per_bio_data_size());
 282 }
 283
 284 static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 285 {
 286         /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 287         void *bio_details = mpio + 1;
 288         return bio_details;
 289 }
 290
 291 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 292 {
 293         struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 294         struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 295
 296         mpio->nr_bytes = bio->bi_iter.bi_size;
 297         mpio->pgpath = NULL;
 298         *mpio_p = mpio;
 299
 300         dm_bio_record(bio_details, bio);
 301 }
 302
 303 /*-----------------------------------------------
 304  * Path selection
 305  *-----------------------------------------------*/
 306
 307 static int __pg_init_all_paths(struct multipath *m)
 308 {
 309         struct pgpath *pgpath;
 310         unsigned long pg_init_delay = 0;
 311
 312         lockdep_assert_held(&m->lock);
 313
 314         if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 315                 return 0;
 316
 317         atomic_inc(&m->pg_init_count);
 318         clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 319
 320         /* Check here to reset pg_init_required */
 321         if (!m->current_pg)
 322                 return 0;
 323
 324         if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 325                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 326                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 327         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 328                 /* Skip failed paths */
 329                 if (!pgpath->is_active)
 330                         continue;
 331                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 332                                        pg_init_delay))
 333                         atomic_inc(&m->pg_init_in_progress);
 334         }
 335         return atomic_read(&m->pg_init_in_progress);
 336 }
 337
 338 static int pg_init_all_paths(struct multipath *m)
 339 {
 340         int ret;
 341         unsigned long flags;
 342
 343         spin_lock_irqsave(&m->lock, flags);
 344         ret = __pg_init_all_paths(m);
 345         spin_unlock_irqrestore(&m->lock, flags);
 346
 347         return ret;
 348 }
 349
 350 static void __switch_pg(struct multipath *m, struct priority_group *pg)
 351 {
 352         lockdep_assert_held(&m->lock);
 353
 354         m->current_pg = pg;
 355
 356         /* Must we initialise the PG first, and queue I/O till it's ready? */
 357         if (m->hw_handler_name) {
 358                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 359                 set_bit(MPATHF_QUEUE_IO, &m->flags);
 360         } else {
 361                 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 362                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 363         }
 364
 365         atomic_set(&m->pg_init_count, 0);
 366 }
 367
 368 static struct pgpath *choose_path_in_pg(struct multipath *m,
 369                                         struct priority_group *pg,
 370                                         size_t nr_bytes)
 371 {
 372         unsigned long flags;
 373         struct dm_path *path;
 374         struct pgpath *pgpath;
 375
 376         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 377         if (!path)
 378                 return ERR_PTR(-ENXIO);
 379
 380         pgpath = path_to_pgpath(path);
 381
 382         if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 383                 /* Only update current_pgpath if pg changed */
 384                 spin_lock_irqsave(&m->lock, flags);
 385                 m->current_pgpath = pgpath;
 386                 __switch_pg(m, pg);
 387                 spin_unlock_irqrestore(&m->lock, flags);
 388         }
 389
 390         return pgpath;
 391 }
 392
 393 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 394 {
 395         unsigned long flags;
 396         struct priority_group *pg;
 397         struct pgpath *pgpath;
 398         unsigned bypassed = 1;
 399
 400         if (!atomic_read(&m->nr_valid_paths)) {
 401                 spin_lock_irqsave(&m->lock, flags);
 402                 clear_bit(MPATHF_QUEUE_IO, &m->flags);
 403                 spin_unlock_irqrestore(&m->lock, flags);
 404                 goto failed;
 405         }
 406
 407         /* Were we instructed to switch PG? */
 408         if (READ_ONCE(m->next_pg)) {
 409                 spin_lock_irqsave(&m->lock, flags);
 410                 pg = m->next_pg;
 411                 if (!pg) {
 412                         spin_unlock_irqrestore(&m->lock, flags);
 413                         goto check_current_pg;
 414                 }
 415                 m->next_pg = NULL;
 416                 spin_unlock_irqrestore(&m->lock, flags);
 417                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 418                 if (!IS_ERR_OR_NULL(pgpath))
 419                         return pgpath;
 420         }
 421
 422         /* Don't change PG until it has no remaining paths */
 423 check_current_pg:
 424         pg = READ_ONCE(m->current_pg);
 425         if (pg) {
 426                 pgpath = choose_path_in_pg(m, pg, nr_bytes);
 427                 if (!IS_ERR_OR_NULL(pgpath))
 428                         return pgpath;
 429         }
 430
 431         /*
 432          * Loop through priority groups until we find a valid path.
 433          * First time we skip PGs marked 'bypassed'.
 434          * Second time we only try the ones we skipped, but set
 435          * pg_init_delay_retry so we do not hammer controllers.
 436          */
 437         do {
 438                 list_for_each_entry(pg, &m->priority_groups, list) {
 439                         if (pg->bypassed == !!bypassed)
 440                                 continue;
 441                         pgpath = choose_path_in_pg(m, pg, nr_bytes);
 442                         if (!IS_ERR_OR_NULL(pgpath)) {
 443                                 if (!bypassed) {
 444                                         spin_lock_irqsave(&m->lock, flags);
 445                                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 446                                         spin_unlock_irqrestore(&m->lock, flags);
 447                                 }
 448                                 return pgpath;
 449                         }
 450                 }
 451         } while (bypassed--);
 452
 453 failed:
 454         spin_lock_irqsave(&m->lock, flags);
 455         m->current_pgpath = NULL;
 456         m->current_pg = NULL;
 457         spin_unlock_irqrestore(&m->lock, flags);
 458
 459         return NULL;
 460 }
 461
 462 /*
 463  * dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
 464  * report the function name and line number of the function from which
 465  * it has been invoked.
 466  */
 467 #define dm_report_EIO(m)                                                \
 468 do {                                                                    \
 469         DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 470                       dm_table_device_name((m)->ti->table),             \
 471                       test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),   \
 472                       test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 473                       dm_noflush_suspending((m)->ti));                  \
 474 } while (0)
 475
 476 /*
 477  * Check whether bios must be queued in the device-mapper core rather
 478  * than here in the target.
 479  */
 480 static bool __must_push_back(struct multipath *m)
 481 {
 482         return dm_noflush_suspending(m->ti);
 483 }
 484
 485 static bool must_push_back_rq(struct multipath *m)
 486 {
 487         unsigned long flags;
 488         bool ret;
 489
 490         spin_lock_irqsave(&m->lock, flags);
 491         ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
 492         spin_unlock_irqrestore(&m->lock, flags);
 493
 494         return ret;
 495 }
 496
 497 /*
 498  * Map cloned requests (request-based multipath)
 499  */
 500 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 501                                    union map_info *map_context,
 502                                    struct request **__clone)
 503 {
 504         struct multipath *m = ti->private;
 505         size_t nr_bytes = blk_rq_bytes(rq);
 506         struct pgpath *pgpath;
 507         struct block_device *bdev;
 508         struct dm_mpath_io *mpio = get_mpio(map_context);
 509         struct request_queue *q;
 510         struct request *clone;
 511
 512         /* Do we need to select a new pgpath? */
 513         pgpath = READ_ONCE(m->current_pgpath);
 514         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 515                 pgpath = choose_pgpath(m, nr_bytes);
 516
 517         if (!pgpath) {
 518                 if (must_push_back_rq(m))
 519                         return DM_MAPIO_DELAY_REQUEUE;
 520                 dm_report_EIO(m);       /* Failed */
 521                 return DM_MAPIO_KILL;
 522         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 523                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 524                 pg_init_all_paths(m);
 525                 return DM_MAPIO_DELAY_REQUEUE;
 526         }
 527
 528         mpio->pgpath = pgpath;
 529         mpio->nr_bytes = nr_bytes;
 530
 531         bdev = pgpath->path.dev->bdev;
 532         q = bdev_get_queue(bdev);
 533         clone = blk_mq_alloc_request(q, rq->cmd_flags | REQ_NOMERGE,
 534                         BLK_MQ_REQ_NOWAIT);
 535         if (IS_ERR(clone)) {
 536                 /* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 537                 if (blk_queue_dying(q)) {
 538                         atomic_inc(&m->pg_init_in_progress);
 539                         activate_or_offline_path(pgpath);
 540                         return DM_MAPIO_DELAY_REQUEUE;
 541                 }
 542
 543                 /*
 544                  * blk-mq's SCHED_RESTART can cover this requeue, so we
 545                  * needn't deal with it by DELAY_REQUEUE. More importantly,
 546                  * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 547                  * get the queue busy feedback (via BLK_STS_RESOURCE),
 548                  * otherwise I/O merging can suffer.
 549                  */
 550                 return DM_MAPIO_REQUEUE;
 551         }
 552         clone->bio = clone->biotail = NULL;
 553         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 554         *__clone = clone;
 555
 556         if (pgpath->pg->ps.type->start_io)
 557                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 558                                               &pgpath->path,
 559                                               nr_bytes);
 560         return DM_MAPIO_REMAPPED;
 561 }
 562
 563 static void multipath_release_clone(struct request *clone,
 564                                     union map_info *map_context)
 565 {
 566         if (unlikely(map_context)) {
 567                 /*
 568                  * non-NULL map_context means caller is still map
 569                  * method; must undo multipath_clone_and_map()
 570                  */
 571                 struct dm_mpath_io *mpio = get_mpio(map_context);
 572                 struct pgpath *pgpath = mpio->pgpath;
 573
 574                 if (pgpath && pgpath->pg->ps.type->end_io)
 575                         pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 576                                                     &pgpath->path,
 577                                                     mpio->nr_bytes,
 578                                                     clone->io_start_time_ns);
 579         }
 580
 581         blk_mq_free_request(clone);
 582 }
 583
 584 /*
 585  * Map cloned bios (bio-based multipath)
 586  */
 587
 588 static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
 589 {
 590         /* Queue for the daemon to resubmit */
 591         bio_list_add(&m->queued_bios, bio);
 592         if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
 593                 queue_work(kmultipathd, &m->process_queued_bios);
 594 }
 595
 596 static void multipath_queue_bio(struct multipath *m, struct bio *bio)
 597 {
 598         unsigned long flags;
 599
 600         spin_lock_irqsave(&m->lock, flags);
 601         __multipath_queue_bio(m, bio);
 602         spin_unlock_irqrestore(&m->lock, flags);
 603 }
 604
 605 static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 606 {
 607         struct pgpath *pgpath;
 608         unsigned long flags;
 609
 610         /* Do we need to select a new pgpath? */
 611         pgpath = READ_ONCE(m->current_pgpath);
 612         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 613                 pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 614
 615         if (!pgpath) {
 616                 spin_lock_irqsave(&m->lock, flags);
 617                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 618                         __multipath_queue_bio(m, bio);
 619                         pgpath = ERR_PTR(-EAGAIN);
 620                 }
 621                 spin_unlock_irqrestore(&m->lock, flags);
 622
 623         } else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 624                    mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 625                 multipath_queue_bio(m, bio);
 626                 pg_init_all_paths(m);
 627                 return ERR_PTR(-EAGAIN);
 628         }
 629
 630         return pgpath;
 631 }
 632
 633 static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 634                                struct dm_mpath_io *mpio)
 635 {
 636         struct pgpath *pgpath = __map_bio(m, bio);
 637
 638         if (IS_ERR(pgpath))
 639                 return DM_MAPIO_SUBMITTED;
 640
 641         if (!pgpath) {
 642                 if (__must_push_back(m))
 643                         return DM_MAPIO_REQUEUE;
 644                 dm_report_EIO(m);
 645                 return DM_MAPIO_KILL;
 646         }
 647
 648         mpio->pgpath = pgpath;
 649
 650         bio->bi_status = 0;
 651         bio_set_dev(bio, pgpath->path.dev->bdev);
 652         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 653
 654         if (pgpath->pg->ps.type->start_io)
 655                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 656                                               &pgpath->path,
 657                                               mpio->nr_bytes);
 658         return DM_MAPIO_REMAPPED;
 659 }
 660
 661 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 662 {
 663         struct multipath *m = ti->private;
 664         struct dm_mpath_io *mpio = NULL;
 665
 666         multipath_init_per_bio_data(bio, &mpio);
 667         return __multipath_map_bio(m, bio, mpio);
 668 }
 669
 670 static void process_queued_io_list(struct multipath *m)
 671 {
 672         if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 673                 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 674         else if (m->queue_mode == DM_TYPE_BIO_BASED)
 675                 queue_work(kmultipathd, &m->process_queued_bios);
 676 }
 677
 678 static void process_queued_bios(struct work_struct *work)
 679 {
 680         int r;
 681         unsigned long flags;
 682         struct bio *bio;
 683         struct bio_list bios;
 684         struct blk_plug plug;
 685         struct multipath *m =
 686                 container_of(work, struct multipath, process_queued_bios);
 687
 688         bio_list_init(&bios);
 689
 690         spin_lock_irqsave(&m->lock, flags);
 691
 692         if (bio_list_empty(&m->queued_bios)) {
 693                 spin_unlock_irqrestore(&m->lock, flags);
 694                 return;
 695         }
 696
 697         bio_list_merge(&bios, &m->queued_bios);
 698         bio_list_init(&m->queued_bios);
 699
 700         spin_unlock_irqrestore(&m->lock, flags);
 701
 702         blk_start_plug(&plug);
 703         while ((bio = bio_list_pop(&bios))) {
 704                 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 705                 dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 706                 r = __multipath_map_bio(m, bio, mpio);
 707                 switch (r) {
 708                 case DM_MAPIO_KILL:
 709                         bio->bi_status = BLK_STS_IOERR;
 710                         bio_endio(bio);
 711                         break;
 712                 case DM_MAPIO_REQUEUE:
 713                         bio->bi_status = BLK_STS_DM_REQUEUE;
 714                         bio_endio(bio);
 715                         break;
 716                 case DM_MAPIO_REMAPPED:
 717                         submit_bio_noacct(bio);
 718                         break;
 719                 case DM_MAPIO_SUBMITTED:
 720                         break;
 721                 default:
 722                         WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 723                 }
 724         }
 725         blk_finish_plug(&plug);
 726 }
 727
 728 /*
 729  * If we run out of usable paths, should we queue I/O or error it?
 730  */
 731 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 732                             bool save_old_value, const char *caller)
 733 {
 734         unsigned long flags;
 735         bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 736         const char *dm_dev_name = dm_table_device_name(m->ti->table);
 737
 738         DMDEBUG("%s: %s caller=%s queue_if_no_path=%d save_old_value=%d",
 739                 dm_dev_name, __func__, caller, queue_if_no_path, save_old_value);
 740
 741         spin_lock_irqsave(&m->lock, flags);
 742
 743         queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 744         saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 745
 746         if (save_old_value) {
 747                 if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 748                         DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 749                               dm_dev_name);
 750                 } else
 751                         assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 752         } else if (!queue_if_no_path && saved_queue_if_no_path_bit) {
 753                 /* due to "fail_if_no_path" message, need to honor it. */
 754                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 755         }
 756         assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 757
 758         DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 759                 dm_dev_name, __func__,
 760                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 761                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 762                 dm_noflush_suspending(m->ti));
 763
 764         spin_unlock_irqrestore(&m->lock, flags);
 765
 766         if (!queue_if_no_path) {
 767                 dm_table_run_md_queue_async(m->ti->table);
 768                 process_queued_io_list(m);
 769         }
 770
 771         return 0;
 772 }
 773
 774 /*
 775  * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 776  * process any queued I/O.
 777  */
 778 static void queue_if_no_path_timeout_work(struct timer_list *t)
 779 {
 780         struct multipath *m = from_timer(m, t, nopath_timer);
 781
 782         DMWARN("queue_if_no_path timeout on %s, failing queued IO",
 783                dm_table_device_name(m->ti->table));
 784         queue_if_no_path(m, false, false, __func__);
 785 }
 786
 787 /*
 788  * Enable the queue_if_no_path timeout if necessary.
 789  * Called with m->lock held.
 790  */
 791 static void enable_nopath_timeout(struct multipath *m)
 792 {
 793         unsigned long queue_if_no_path_timeout =
 794                 READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 795
 796         lockdep_assert_held(&m->lock);
 797
 798         if (queue_if_no_path_timeout > 0 &&
 799             atomic_read(&m->nr_valid_paths) == 0 &&
 800             test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 801                 mod_timer(&m->nopath_timer,
 802                           jiffies + queue_if_no_path_timeout);
 803         }
 804 }
 805
 806 static void disable_nopath_timeout(struct multipath *m)
 807 {
 808         del_timer_sync(&m->nopath_timer);
 809 }
 810
 811 /*
 812  * An event is triggered whenever a path is taken out of use.
 813  * Includes path failure and PG bypass.
 814  */
 815 static void trigger_event(struct work_struct *work)
 816 {
 817         struct multipath *m =
 818                 container_of(work, struct multipath, trigger_event);
 819
 820         dm_table_event(m->ti->table);
 821 }
 822
 823 /*-----------------------------------------------------------------
 824  * Constructor/argument parsing:
 825  * <#multipath feature args> [<arg>]*
 826  * <#hw_handler args> [hw_handler [<arg>]*]
 827  * <#priority groups>
 828  * <initial priority group>
 829  *     [<selector> <#selector args> [<arg>]*
 830  *      <#paths> <#per-path selector args>
 831  *         [<path> [<arg>]* ]+ ]+
 832  *---------------------------------------------------------------*/
 833 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 834                                struct dm_target *ti)
 835 {
 836         int r;
 837         struct path_selector_type *pst;
 838         unsigned ps_argc;
 839
 840         static const struct dm_arg _args[] = {
 841                 {0, 1024, "invalid number of path selector args"},
 842         };
 843
 844         pst = dm_get_path_selector(dm_shift_arg(as));
 845         if (!pst) {
 846                 ti->error = "unknown path selector type";
 847                 return -EINVAL;
 848         }
 849
 850         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 851         if (r) {
 852                 dm_put_path_selector(pst);
 853                 return -EINVAL;
 854         }
 855
 856         r = pst->create(&pg->ps, ps_argc, as->argv);
 857         if (r) {
 858                 dm_put_path_selector(pst);
 859                 ti->error = "path selector constructor failed";
 860                 return r;
 861         }
 862
 863         pg->ps.type = pst;
 864         dm_consume_args(as, ps_argc);
 865
 866         return 0;
 867 }
 868
 869 static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 870                          const char **attached_handler_name, char **error)
 871 {
 872         struct request_queue *q = bdev_get_queue(bdev);
 873         int r;
 874
 875         if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
 876 retain:
 877                 if (*attached_handler_name) {
 878                         /*
 879                          * Clear any hw_handler_params associated with a
 880                          * handler that isn't already attached.
 881                          */
 882                         if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 883                                 kfree(m->hw_handler_params);
 884                                 m->hw_handler_params = NULL;
 885                         }
 886
 887                         /*
 888                          * Reset hw_handler_name to match the attached handler
 889                          *
 890                          * NB. This modifies the table line to show the actual
 891                          * handler instead of the original table passed in.
 892                          */
 893                         kfree(m->hw_handler_name);
 894                         m->hw_handler_name = *attached_handler_name;
 895                         *attached_handler_name = NULL;
 896                 }
 897         }
 898
 899         if (m->hw_handler_name) {
 900                 r = scsi_dh_attach(q, m->hw_handler_name);
 901                 if (r == -EBUSY) {
 902                         DMINFO("retaining handler on device %pg", bdev);
 903                         goto retain;
 904                 }
 905                 if (r < 0) {
 906                         *error = "error attaching hardware handler";
 907                         return r;
 908                 }
 909
 910                 if (m->hw_handler_params) {
 911                         r = scsi_dh_set_params(q, m->hw_handler_params);
 912                         if (r < 0) {
 913                                 *error = "unable to set hardware handler parameters";
 914                                 return r;
 915                         }
 916                 }
 917         }
 918
 919         return 0;
 920 }
 921
 922 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 923                                  struct dm_target *ti)
 924 {
 925         int r;
 926         struct pgpath *p;
 927         struct multipath *m = ti->private;
 928         struct request_queue *q;
 929         const char *attached_handler_name = NULL;
 930
 931         /* we need at least a path arg */
 932         if (as->argc < 1) {
 933                 ti->error = "no device given";
 934                 return ERR_PTR(-EINVAL);
 935         }
 936
 937         p = alloc_pgpath();
 938         if (!p)
 939                 return ERR_PTR(-ENOMEM);
 940
 941         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 942                           &p->path.dev);
 943         if (r) {
 944                 ti->error = "error getting device";
 945                 goto bad;
 946         }
 947
 948         q = bdev_get_queue(p->path.dev->bdev);
 949         attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 950         if (attached_handler_name || m->hw_handler_name) {
 951                 INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 952                 r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 953                 kfree(attached_handler_name);
 954                 if (r) {
 955                         dm_put_device(ti, p->path.dev);
 956                         goto bad;
 957                 }
 958         }
 959
 960         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 961         if (r) {
 962                 dm_put_device(ti, p->path.dev);
 963                 goto bad;
 964         }
 965
 966         return p;
 967  bad:
 968         free_pgpath(p);
 969         return ERR_PTR(r);
 970 }
 971
 972 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 973                                                    struct multipath *m)
 974 {
 975         static const struct dm_arg _args[] = {
 976                 {1, 1024, "invalid number of paths"},
 977                 {0, 1024, "invalid number of selector args"}
 978         };
 979
 980         int r;
 981         unsigned i, nr_selector_args, nr_args;
 982         struct priority_group *pg;
 983         struct dm_target *ti = m->ti;
 984
 985         if (as->argc < 2) {
 986                 as->argc = 0;
 987                 ti->error = "not enough priority group arguments";
 988                 return ERR_PTR(-EINVAL);
 989         }
 990
 991         pg = alloc_priority_group();
 992         if (!pg) {
 993                 ti->error = "couldn't allocate priority group";
 994                 return ERR_PTR(-ENOMEM);
 995         }
 996         pg->m = m;
 997
 998         r = parse_path_selector(as, pg, ti);
 999         if (r)
1000                 goto bad;
1001
1002         /*
1003          * read the paths
1004          */
1005         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
1006         if (r)
1007                 goto bad;
1008
1009         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
1010         if (r)
1011                 goto bad;
1012
1013         nr_args = 1 + nr_selector_args;
1014         for (i = 0; i < pg->nr_pgpaths; i++) {
1015                 struct pgpath *pgpath;
1016                 struct dm_arg_set path_args;
1017
1018                 if (as->argc < nr_args) {
1019                         ti->error = "not enough path parameters";
1020                         r = -EINVAL;
1021                         goto bad;
1022                 }
1023
1024                 path_args.argc = nr_args;
1025                 path_args.argv = as->argv;
1026
1027                 pgpath = parse_path(&path_args, &pg->ps, ti);
1028                 if (IS_ERR(pgpath)) {
1029                         r = PTR_ERR(pgpath);
1030                         goto bad;
1031                 }
1032
1033                 pgpath->pg = pg;
1034                 list_add_tail(&pgpath->list, &pg->pgpaths);
1035                 dm_consume_args(as, nr_args);
1036         }
1037
1038         return pg;
1039
1040  bad:
1041         free_priority_group(pg, ti);
1042         return ERR_PTR(r);
1043 }
1044
1045 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1046 {
1047         unsigned hw_argc;
1048         int ret;
1049         struct dm_target *ti = m->ti;
1050
1051         static const struct dm_arg _args[] = {
1052                 {0, 1024, "invalid number of hardware handler args"},
1053         };
1054
1055         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1056                 return -EINVAL;
1057
1058         if (!hw_argc)
1059                 return 0;
1060
1061         if (m->queue_mode == DM_TYPE_BIO_BASED) {
1062                 dm_consume_args(as, hw_argc);
1063                 DMERR("bio-based multipath doesn't allow hardware handler args");
1064                 return 0;
1065         }
1066
1067         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1068         if (!m->hw_handler_name)
1069                 return -EINVAL;
1070
1071         if (hw_argc > 1) {
1072                 char *p;
1073                 int i, j, len = 4;
1074
1075                 for (i = 0; i <= hw_argc - 2; i++)
1076                         len += strlen(as->argv[i]) + 1;
1077                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1078                 if (!p) {
1079                         ti->error = "memory allocation failed";
1080                         ret = -ENOMEM;
1081                         goto fail;
1082                 }
1083                 j = sprintf(p, "%d", hw_argc - 1);
1084                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1085                         j = sprintf(p, "%s", as->argv[i]);
1086         }
1087         dm_consume_args(as, hw_argc - 1);
1088
1089         return 0;
1090 fail:
1091         kfree(m->hw_handler_name);
1092         m->hw_handler_name = NULL;
1093         return ret;
1094 }
1095
1096 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1097 {
1098         int r;
1099         unsigned argc;
1100         struct dm_target *ti = m->ti;
1101         const char *arg_name;
1102
1103         static const struct dm_arg _args[] = {
1104                 {0, 8, "invalid number of feature args"},
1105                 {1, 50, "pg_init_retries must be between 1 and 50"},
1106                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1107         };
1108
1109         r = dm_read_arg_group(_args, as, &argc, &ti->error);
1110         if (r)
1111                 return -EINVAL;
1112
1113         if (!argc)
1114                 return 0;
1115
1116         do {
1117                 arg_name = dm_shift_arg(as);
1118                 argc--;
1119
1120                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1121                         r = queue_if_no_path(m, true, false, __func__);
1122                         continue;
1123                 }
1124
1125                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1126                         set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1127                         continue;
1128                 }
1129
1130                 if (!strcasecmp(arg_name, "pg_init_retries") &&
1131                     (argc >= 1)) {
1132                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1133                         argc--;
1134                         continue;
1135                 }
1136
1137                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1138                     (argc >= 1)) {
1139                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1140                         argc--;
1141                         continue;
1142                 }
1143
1144                 if (!strcasecmp(arg_name, "queue_mode") &&
1145                     (argc >= 1)) {
1146                         const char *queue_mode_name = dm_shift_arg(as);
1147
1148                         if (!strcasecmp(queue_mode_name, "bio"))
1149                                 m->queue_mode = DM_TYPE_BIO_BASED;
1150                         else if (!strcasecmp(queue_mode_name, "rq") ||
1151                                  !strcasecmp(queue_mode_name, "mq"))
1152                                 m->queue_mode = DM_TYPE_REQUEST_BASED;
1153                         else {
1154                                 ti->error = "Unknown 'queue_mode' requested";
1155                                 r = -EINVAL;
1156                         }
1157                         argc--;
1158                         continue;
1159                 }
1160
1161                 ti->error = "Unrecognised multipath feature request";
1162                 r = -EINVAL;
1163         } while (argc && !r);
1164
1165         return r;
1166 }
1167
1168 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1169 {
1170         /* target arguments */
1171         static const struct dm_arg _args[] = {
1172                 {0, 1024, "invalid number of priority groups"},
1173                 {0, 1024, "invalid initial priority group number"},
1174         };
1175
1176         int r;
1177         struct multipath *m;
1178         struct dm_arg_set as;
1179         unsigned pg_count = 0;
1180         unsigned next_pg_num;
1181         unsigned long flags;
1182
1183         as.argc = argc;
1184         as.argv = argv;
1185
1186         m = alloc_multipath(ti);
1187         if (!m) {
1188                 ti->error = "can't allocate multipath";
1189                 return -EINVAL;
1190         }
1191
1192         r = parse_features(&as, m);
1193         if (r)
1194                 goto bad;
1195
1196         r = alloc_multipath_stage2(ti, m);
1197         if (r)
1198                 goto bad;
1199
1200         r = parse_hw_handler(&as, m);
1201         if (r)
1202                 goto bad;
1203
1204         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1205         if (r)
1206                 goto bad;
1207
1208         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1209         if (r)
1210                 goto bad;
1211
1212         if ((!m->nr_priority_groups && next_pg_num) ||
1213             (m->nr_priority_groups && !next_pg_num)) {
1214                 ti->error = "invalid initial priority group";
1215                 r = -EINVAL;
1216                 goto bad;
1217         }
1218
1219         /* parse the priority groups */
1220         while (as.argc) {
1221                 struct priority_group *pg;
1222                 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1223
1224                 pg = parse_priority_group(&as, m);
1225                 if (IS_ERR(pg)) {
1226                         r = PTR_ERR(pg);
1227                         goto bad;
1228                 }
1229
1230                 nr_valid_paths += pg->nr_pgpaths;
1231                 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1232
1233                 list_add_tail(&pg->list, &m->priority_groups);
1234                 pg_count++;
1235                 pg->pg_num = pg_count;
1236                 if (!--next_pg_num)
1237                         m->next_pg = pg;
1238         }
1239
1240         if (pg_count != m->nr_priority_groups) {
1241                 ti->error = "priority group count mismatch";
1242                 r = -EINVAL;
1243                 goto bad;
1244         }
1245
1246         spin_lock_irqsave(&m->lock, flags);
1247         enable_nopath_timeout(m);
1248         spin_unlock_irqrestore(&m->lock, flags);
1249
1250         ti->num_flush_bios = 1;
1251         ti->num_discard_bios = 1;
1252         ti->num_write_zeroes_bios = 1;
1253         if (m->queue_mode == DM_TYPE_BIO_BASED)
1254                 ti->per_io_data_size = multipath_per_bio_data_size();
1255         else
1256                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1257
1258         return 0;
1259
1260  bad:
1261         free_multipath(m);
1262         return r;
1263 }
1264
1265 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1266 {
1267         DEFINE_WAIT(wait);
1268
1269         while (1) {
1270                 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1271
1272                 if (!atomic_read(&m->pg_init_in_progress))
1273                         break;
1274
1275                 io_schedule();
1276         }
1277         finish_wait(&m->pg_init_wait, &wait);
1278 }
1279
1280 static void flush_multipath_work(struct multipath *m)
1281 {
1282         if (m->hw_handler_name) {
1283                 unsigned long flags;
1284
1285                 if (!atomic_read(&m->pg_init_in_progress))
1286                         goto skip;
1287
1288                 spin_lock_irqsave(&m->lock, flags);
1289                 if (atomic_read(&m->pg_init_in_progress) &&
1290                     !test_and_set_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) {
1291                         spin_unlock_irqrestore(&m->lock, flags);
1292
1293                         flush_workqueue(kmpath_handlerd);
1294                         multipath_wait_for_pg_init_completion(m);
1295
1296                         spin_lock_irqsave(&m->lock, flags);
1297                         clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1298                 }
1299                 spin_unlock_irqrestore(&m->lock, flags);
1300         }
1301 skip:
1302         if (m->queue_mode == DM_TYPE_BIO_BASED)
1303                 flush_work(&m->process_queued_bios);
1304         flush_work(&m->trigger_event);
1305 }
1306
1307 static void multipath_dtr(struct dm_target *ti)
1308 {
1309         struct multipath *m = ti->private;
1310
1311         disable_nopath_timeout(m);
1312         flush_multipath_work(m);
1313         free_multipath(m);
1314 }
1315
1316 /*
1317  * Take a path out of use.
1318  */
1319 static int fail_path(struct pgpath *pgpath)
1320 {
1321         unsigned long flags;
1322         struct multipath *m = pgpath->pg->m;
1323
1324         spin_lock_irqsave(&m->lock, flags);
1325
1326         if (!pgpath->is_active)
1327                 goto out;
1328
1329         DMWARN("%s: Failing path %s.",
1330                dm_table_device_name(m->ti->table),
1331                pgpath->path.dev->name);
1332
1333         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1334         pgpath->is_active = false;
1335         pgpath->fail_count++;
1336
1337         atomic_dec(&m->nr_valid_paths);
1338
1339         if (pgpath == m->current_pgpath)
1340                 m->current_pgpath = NULL;
1341
1342         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1343                        pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1344
1345         schedule_work(&m->trigger_event);
1346
1347         enable_nopath_timeout(m);
1348
1349 out:
1350         spin_unlock_irqrestore(&m->lock, flags);
1351
1352         return 0;
1353 }
1354
1355 /*
1356  * Reinstate a previously-failed path
1357  */
1358 static int reinstate_path(struct pgpath *pgpath)
1359 {
1360         int r = 0, run_queue = 0;
1361         unsigned long flags;
1362         struct multipath *m = pgpath->pg->m;
1363         unsigned nr_valid_paths;
1364
1365         spin_lock_irqsave(&m->lock, flags);
1366
1367         if (pgpath->is_active)
1368                 goto out;
1369
1370         DMWARN("%s: Reinstating path %s.",
1371                dm_table_device_name(m->ti->table),
1372                pgpath->path.dev->name);
1373
1374         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1375         if (r)
1376                 goto out;
1377
1378         pgpath->is_active = true;
1379
1380         nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1381         if (nr_valid_paths == 1) {
1382                 m->current_pgpath = NULL;
1383                 run_queue = 1;
1384         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1385                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1386                         atomic_inc(&m->pg_init_in_progress);
1387         }
1388
1389         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1390                        pgpath->path.dev->name, nr_valid_paths);
1391
1392         schedule_work(&m->trigger_event);
1393
1394 out:
1395         spin_unlock_irqrestore(&m->lock, flags);
1396         if (run_queue) {
1397                 dm_table_run_md_queue_async(m->ti->table);
1398                 process_queued_io_list(m);
1399         }
1400
1401         if (pgpath->is_active)
1402                 disable_nopath_timeout(m);
1403
1404         return r;
1405 }
1406
1407 /*
1408  * Fail or reinstate all paths that match the provided struct dm_dev.
1409  */
1410 static int action_dev(struct multipath *m, struct dm_dev *dev,
1411                       action_fn action)
1412 {
1413         int r = -EINVAL;
1414         struct pgpath *pgpath;
1415         struct priority_group *pg;
1416
1417         list_for_each_entry(pg, &m->priority_groups, list) {
1418                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1419                         if (pgpath->path.dev == dev)
1420                                 r = action(pgpath);
1421                 }
1422         }
1423
1424         return r;
1425 }
1426
1427 /*
1428  * Temporarily try to avoid having to use the specified PG
1429  */
1430 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1431                       bool bypassed)
1432 {
1433         unsigned long flags;
1434
1435         spin_lock_irqsave(&m->lock, flags);
1436
1437         pg->bypassed = bypassed;
1438         m->current_pgpath = NULL;
1439         m->current_pg = NULL;
1440
1441         spin_unlock_irqrestore(&m->lock, flags);
1442
1443         schedule_work(&m->trigger_event);
1444 }
1445
1446 /*
1447  * Switch to using the specified PG from the next I/O that gets mapped
1448  */
1449 static int switch_pg_num(struct multipath *m, const char *pgstr)
1450 {
1451         struct priority_group *pg;
1452         unsigned pgnum;
1453         unsigned long flags;
1454         char dummy;
1455
1456         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1457             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1458                 DMWARN("invalid PG number supplied to switch_pg_num");
1459                 return -EINVAL;
1460         }
1461
1462         spin_lock_irqsave(&m->lock, flags);
1463         list_for_each_entry(pg, &m->priority_groups, list) {
1464                 pg->bypassed = false;
1465                 if (--pgnum)
1466                         continue;
1467
1468                 m->current_pgpath = NULL;
1469                 m->current_pg = NULL;
1470                 m->next_pg = pg;
1471         }
1472         spin_unlock_irqrestore(&m->lock, flags);
1473
1474         schedule_work(&m->trigger_event);
1475         return 0;
1476 }
1477
1478 /*
1479  * Set/clear bypassed status of a PG.
1480  * PGs are numbered upwards from 1 in the order they were declared.
1481  */
1482 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1483 {
1484         struct priority_group *pg;
1485         unsigned pgnum;
1486         char dummy;
1487
1488         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1489             !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1490                 DMWARN("invalid PG number supplied to bypass_pg");
1491                 return -EINVAL;
1492         }
1493
1494         list_for_each_entry(pg, &m->priority_groups, list) {
1495                 if (!--pgnum)
1496                         break;
1497         }
1498
1499         bypass_pg(m, pg, bypassed);
1500         return 0;
1501 }
1502
1503 /*
1504  * Should we retry pg_init immediately?
1505  */
1506 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1507 {
1508         unsigned long flags;
1509         bool limit_reached = false;
1510
1511         spin_lock_irqsave(&m->lock, flags);
1512
1513         if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1514             !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1515                 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1516         else
1517                 limit_reached = true;
1518
1519         spin_unlock_irqrestore(&m->lock, flags);
1520
1521         return limit_reached;
1522 }
1523
1524 static void pg_init_done(void *data, int errors)
1525 {
1526         struct pgpath *pgpath = data;
1527         struct priority_group *pg = pgpath->pg;
1528         struct multipath *m = pg->m;
1529         unsigned long flags;
1530         bool delay_retry = false;
1531
1532         /* device or driver problems */
1533         switch (errors) {
1534         case SCSI_DH_OK:
1535                 break;
1536         case SCSI_DH_NOSYS:
1537                 if (!m->hw_handler_name) {
1538                         errors = 0;
1539                         break;
1540                 }
1541                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1542                       "Error %d.", m->hw_handler_name, errors);
1543                 /*
1544                  * Fail path for now, so we do not ping pong
1545                  */
1546                 fail_path(pgpath);
1547                 break;
1548         case SCSI_DH_DEV_TEMP_BUSY:
1549                 /*
1550                  * Probably doing something like FW upgrade on the
1551                  * controller so try the other pg.
1552                  */
1553                 bypass_pg(m, pg, true);
1554                 break;
1555         case SCSI_DH_RETRY:
1556                 /* Wait before retrying. */
1557                 delay_retry = true;
1558                 fallthrough;
1559         case SCSI_DH_IMM_RETRY:
1560         case SCSI_DH_RES_TEMP_UNAVAIL:
1561                 if (pg_init_limit_reached(m, pgpath))
1562                         fail_path(pgpath);
1563                 errors = 0;
1564                 break;
1565         case SCSI_DH_DEV_OFFLINED:
1566         default:
1567                 /*
1568                  * We probably do not want to fail the path for a device
1569                  * error, but this is what the old dm did. In future
1570                  * patches we can do more advanced handling.
1571                  */
1572                 fail_path(pgpath);
1573         }
1574
1575         spin_lock_irqsave(&m->lock, flags);
1576         if (errors) {
1577                 if (pgpath == m->current_pgpath) {
1578                         DMERR("Could not failover device. Error %d.", errors);
1579                         m->current_pgpath = NULL;
1580                         m->current_pg = NULL;
1581                 }
1582         } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1583                 pg->bypassed = false;
1584
1585         if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1586                 /* Activations of other paths are still on going */
1587                 goto out;
1588
1589         if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1590                 if (delay_retry)
1591                         set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1592                 else
1593                         clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1594
1595                 if (__pg_init_all_paths(m))
1596                         goto out;
1597         }
1598         clear_bit(MPATHF_QUEUE_IO, &m->flags);
1599
1600         process_queued_io_list(m);
1601
1602         /*
1603          * Wake up any thread waiting to suspend.
1604          */
1605         wake_up(&m->pg_init_wait);
1606
1607 out:
1608         spin_unlock_irqrestore(&m->lock, flags);
1609 }
1610
1611 static void activate_or_offline_path(struct pgpath *pgpath)
1612 {
1613         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1614
1615         if (pgpath->is_active && !blk_queue_dying(q))
1616                 scsi_dh_activate(q, pg_init_done, pgpath);
1617         else
1618                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1619 }
1620
1621 static void activate_path_work(struct work_struct *work)
1622 {
1623         struct pgpath *pgpath =
1624                 container_of(work, struct pgpath, activate_path.work);
1625
1626         activate_or_offline_path(pgpath);
1627 }
1628
1629 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1630                             blk_status_t error, union map_info *map_context)
1631 {
1632         struct dm_mpath_io *mpio = get_mpio(map_context);
1633         struct pgpath *pgpath = mpio->pgpath;
1634         int r = DM_ENDIO_DONE;
1635
1636         /*
1637          * We don't queue any clone request inside the multipath target
1638          * during end I/O handling, since those clone requests don't have
1639          * bio clones.  If we queue them inside the multipath target,
1640          * we need to make bio clones, that requires memory allocation.
1641          * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1642          *  don't have bio clones.)
1643          * Instead of queueing the clone request here, we queue the original
1644          * request into dm core, which will remake a clone request and
1645          * clone bios for it and resubmit it later.
1646          */
1647         if (error && blk_path_error(error)) {
1648                 struct multipath *m = ti->private;
1649
1650                 if (error == BLK_STS_RESOURCE)
1651                         r = DM_ENDIO_DELAY_REQUEUE;
1652                 else
1653                         r = DM_ENDIO_REQUEUE;
1654
1655                 if (pgpath)
1656                         fail_path(pgpath);
1657
1658                 if (!atomic_read(&m->nr_valid_paths) &&
1659                     !must_push_back_rq(m)) {
1660                         if (error == BLK_STS_IOERR)
1661                                 dm_report_EIO(m);
1662                         /* complete with the original error */
1663                         r = DM_ENDIO_DONE;
1664                 }
1665         }
1666
1667         if (pgpath) {
1668                 struct path_selector *ps = &pgpath->pg->ps;
1669
1670                 if (ps->type->end_io)
1671                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1672                                          clone->io_start_time_ns);
1673         }
1674
1675         return r;
1676 }
1677
1678 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1679                                 blk_status_t *error)
1680 {
1681         struct multipath *m = ti->private;
1682         struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1683         struct pgpath *pgpath = mpio->pgpath;
1684         unsigned long flags;
1685         int r = DM_ENDIO_DONE;
1686
1687         if (!*error || !blk_path_error(*error))
1688                 goto done;
1689
1690         if (pgpath)
1691                 fail_path(pgpath);
1692
1693         if (!atomic_read(&m->nr_valid_paths)) {
1694                 spin_lock_irqsave(&m->lock, flags);
1695                 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1696                         if (__must_push_back(m)) {
1697                                 r = DM_ENDIO_REQUEUE;
1698                         } else {
1699                                 dm_report_EIO(m);
1700                                 *error = BLK_STS_IOERR;
1701                         }
1702                         spin_unlock_irqrestore(&m->lock, flags);
1703                         goto done;
1704                 }
1705                 spin_unlock_irqrestore(&m->lock, flags);
1706         }
1707
1708         multipath_queue_bio(m, clone);
1709         r = DM_ENDIO_INCOMPLETE;
1710 done:
1711         if (pgpath) {
1712                 struct path_selector *ps = &pgpath->pg->ps;
1713
1714                 if (ps->type->end_io)
1715                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1716                                          dm_start_time_ns_from_clone(clone));
1717         }
1718
1719         return r;
1720 }
1721
1722 /*
1723  * Suspend with flush can't complete until all the I/O is processed
1724  * so if the last path fails we must error any remaining I/O.
1725  * - Note that if the freeze_bdev fails while suspending, the
1726  *   queue_if_no_path state is lost - userspace should reset it.
1727  * Otherwise, during noflush suspend, queue_if_no_path will not change.
1728  */
1729 static void multipath_presuspend(struct dm_target *ti)
1730 {
1731         struct multipath *m = ti->private;
1732
1733         /* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1734         if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1735                 queue_if_no_path(m, false, true, __func__);
1736 }
1737
1738 static void multipath_postsuspend(struct dm_target *ti)
1739 {
1740         struct multipath *m = ti->private;
1741
1742         mutex_lock(&m->work_mutex);
1743         flush_multipath_work(m);
1744         mutex_unlock(&m->work_mutex);
1745 }
1746
1747 /*
1748  * Restore the queue_if_no_path setting.
1749  */
1750 static void multipath_resume(struct dm_target *ti)
1751 {
1752         struct multipath *m = ti->private;
1753         unsigned long flags;
1754
1755         spin_lock_irqsave(&m->lock, flags);
1756         if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1757                 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1758                 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1759         }
1760
1761         DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1762                 dm_table_device_name(m->ti->table), __func__,
1763                 test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1764                 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1765
1766         spin_unlock_irqrestore(&m->lock, flags);
1767 }
1768
1769 /*
1770  * Info output has the following format:
1771  * num_multipath_feature_args [multipath_feature_args]*
1772  * num_handler_status_args [handler_status_args]*
1773  * num_groups init_group_number
1774  *            [A|D|E num_ps_status_args [ps_status_args]*
1775  *             num_paths num_selector_args
1776  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1777  *
1778  * Table output has the following format (identical to the constructor string):
1779  * num_feature_args [features_args]*
1780  * num_handler_args hw_handler [hw_handler_args]*
1781  * num_groups init_group_number
1782  *     [priority selector-name num_ps_args [ps_args]*
1783  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1784  */
1785 static void multipath_status(struct dm_target *ti, status_type_t type,
1786                              unsigned status_flags, char *result, unsigned maxlen)
1787 {
1788         int sz = 0, pg_counter, pgpath_counter;
1789         unsigned long flags;
1790         struct multipath *m = ti->private;
1791         struct priority_group *pg;
1792         struct pgpath *p;
1793         unsigned pg_num;
1794         char state;
1795
1796         spin_lock_irqsave(&m->lock, flags);
1797
1798         /* Features */
1799         if (type == STATUSTYPE_INFO)
1800                 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1801                        atomic_read(&m->pg_init_count));
1802         else {
1803                 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1804                               (m->pg_init_retries > 0) * 2 +
1805                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1806                               test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1807                               (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1808
1809                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1810                         DMEMIT("queue_if_no_path ");
1811                 if (m->pg_init_retries)
1812                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1813                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1814                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1815                 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1816                         DMEMIT("retain_attached_hw_handler ");
1817                 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1818                         switch(m->queue_mode) {
1819                         case DM_TYPE_BIO_BASED:
1820                                 DMEMIT("queue_mode bio ");
1821                                 break;
1822                         default:
1823                                 WARN_ON_ONCE(true);
1824                                 break;
1825                         }
1826                 }
1827         }
1828
1829         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1830                 DMEMIT("0 ");
1831         else
1832                 DMEMIT("1 %s ", m->hw_handler_name);
1833
1834         DMEMIT("%u ", m->nr_priority_groups);
1835
1836         if (m->next_pg)
1837                 pg_num = m->next_pg->pg_num;
1838         else if (m->current_pg)
1839                 pg_num = m->current_pg->pg_num;
1840         else
1841                 pg_num = (m->nr_priority_groups ? 1 : 0);
1842
1843         DMEMIT("%u ", pg_num);
1844
1845         switch (type) {
1846         case STATUSTYPE_INFO:
1847                 list_for_each_entry(pg, &m->priority_groups, list) {
1848                         if (pg->bypassed)
1849                                 state = 'D';    /* Disabled */
1850                         else if (pg == m->current_pg)
1851                                 state = 'A';    /* Currently Active */
1852                         else
1853                                 state = 'E';    /* Enabled */
1854
1855                         DMEMIT("%c ", state);
1856
1857                         if (pg->ps.type->status)
1858                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1859                                                           result + sz,
1860                                                           maxlen - sz);
1861                         else
1862                                 DMEMIT("0 ");
1863
1864                         DMEMIT("%u %u ", pg->nr_pgpaths,
1865                                pg->ps.type->info_args);
1866
1867                         list_for_each_entry(p, &pg->pgpaths, list) {
1868                                 DMEMIT("%s %s %u ", p->path.dev->name,
1869                                        p->is_active ? "A" : "F",
1870                                        p->fail_count);
1871                                 if (pg->ps.type->status)
1872                                         sz += pg->ps.type->status(&pg->ps,
1873                                               &p->path, type, result + sz,
1874                                               maxlen - sz);
1875                         }
1876                 }
1877                 break;
1878
1879         case STATUSTYPE_TABLE:
1880                 list_for_each_entry(pg, &m->priority_groups, list) {
1881                         DMEMIT("%s ", pg->ps.type->name);
1882
1883                         if (pg->ps.type->status)
1884                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1885                                                           result + sz,
1886                                                           maxlen - sz);
1887                         else
1888                                 DMEMIT("0 ");
1889
1890                         DMEMIT("%u %u ", pg->nr_pgpaths,
1891                                pg->ps.type->table_args);
1892
1893                         list_for_each_entry(p, &pg->pgpaths, list) {
1894                                 DMEMIT("%s ", p->path.dev->name);
1895                                 if (pg->ps.type->status)
1896                                         sz += pg->ps.type->status(&pg->ps,
1897                                               &p->path, type, result + sz,
1898                                               maxlen - sz);
1899                         }
1900                 }
1901                 break;
1902
1903         case STATUSTYPE_IMA:
1904                 sz = 0; /*reset the result pointer*/
1905
1906                 DMEMIT_TARGET_NAME_VERSION(ti->type);
1907                 DMEMIT(",nr_priority_groups=%u", m->nr_priority_groups);
1908
1909                 pg_counter = 0;
1910                 list_for_each_entry(pg, &m->priority_groups, list) {
1911                         if (pg->bypassed)
1912                                 state = 'D';    /* Disabled */
1913                         else if (pg == m->current_pg)
1914                                 state = 'A';    /* Currently Active */
1915                         else
1916                                 state = 'E';    /* Enabled */
1917                         DMEMIT(",pg_state_%d=%c", pg_counter, state);
1918                         DMEMIT(",nr_pgpaths_%d=%u", pg_counter, pg->nr_pgpaths);
1919                         DMEMIT(",path_selector_name_%d=%s", pg_counter, pg->ps.type->name);
1920
1921                         pgpath_counter = 0;
1922                         list_for_each_entry(p, &pg->pgpaths, list) {
1923                                 DMEMIT(",path_name_%d_%d=%s,is_active_%d_%d=%c,fail_count_%d_%d=%u",
1924                                        pg_counter, pgpath_counter, p->path.dev->name,
1925                                        pg_counter, pgpath_counter, p->is_active ? 'A' : 'F',
1926                                        pg_counter, pgpath_counter, p->fail_count);
1927                                 if (pg->ps.type->status) {
1928                                         DMEMIT(",path_selector_status_%d_%d=",
1929                                                pg_counter, pgpath_counter);
1930                                         sz += pg->ps.type->status(&pg->ps, &p->path,
1931                                                                   type, result + sz,
1932                                                                   maxlen - sz);
1933                                 }
1934                                 pgpath_counter++;
1935                         }
1936                         pg_counter++;
1937                 }
1938                 DMEMIT(";");
1939                 break;
1940         }
1941
1942         spin_unlock_irqrestore(&m->lock, flags);
1943 }
1944
1945 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1946                              char *result, unsigned maxlen)
1947 {
1948         int r = -EINVAL;
1949         struct dm_dev *dev;
1950         struct multipath *m = ti->private;
1951         action_fn action;
1952         unsigned long flags;
1953
1954         mutex_lock(&m->work_mutex);
1955
1956         if (dm_suspended(ti)) {
1957                 r = -EBUSY;
1958                 goto out;
1959         }
1960
1961         if (argc == 1) {
1962                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1963                         r = queue_if_no_path(m, true, false, __func__);
1964                         spin_lock_irqsave(&m->lock, flags);
1965                         enable_nopath_timeout(m);
1966                         spin_unlock_irqrestore(&m->lock, flags);
1967                         goto out;
1968                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1969                         r = queue_if_no_path(m, false, false, __func__);
1970                         disable_nopath_timeout(m);
1971                         goto out;
1972                 }
1973         }
1974
1975         if (argc != 2) {
1976                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1977                 goto out;
1978         }
1979
1980         if (!strcasecmp(argv[0], "disable_group")) {
1981                 r = bypass_pg_num(m, argv[1], true);
1982                 goto out;
1983         } else if (!strcasecmp(argv[0], "enable_group")) {
1984                 r = bypass_pg_num(m, argv[1], false);
1985                 goto out;
1986         } else if (!strcasecmp(argv[0], "switch_group")) {
1987                 r = switch_pg_num(m, argv[1]);
1988                 goto out;
1989         } else if (!strcasecmp(argv[0], "reinstate_path"))
1990                 action = reinstate_path;
1991         else if (!strcasecmp(argv[0], "fail_path"))
1992                 action = fail_path;
1993         else {
1994                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1995                 goto out;
1996         }
1997
1998         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1999         if (r) {
2000                 DMWARN("message: error getting device %s",
2001                        argv[1]);
2002                 goto out;
2003         }
2004
2005         r = action_dev(m, dev, action);
2006
2007         dm_put_device(ti, dev);
2008
2009 out:
2010         mutex_unlock(&m->work_mutex);
2011         return r;
2012 }
2013
2014 static int multipath_prepare_ioctl(struct dm_target *ti,
2015                                    struct block_device **bdev)
2016 {
2017         struct multipath *m = ti->private;
2018         struct pgpath *pgpath;
2019         unsigned long flags;
2020         int r;
2021
2022         pgpath = READ_ONCE(m->current_pgpath);
2023         if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
2024                 pgpath = choose_pgpath(m, 0);
2025
2026         if (pgpath) {
2027                 if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
2028                         *bdev = pgpath->path.dev->bdev;
2029                         r = 0;
2030                 } else {
2031                         /* pg_init has not started or completed */
2032                         r = -ENOTCONN;
2033                 }
2034         } else {
2035                 /* No path is available */
2036                 r = -EIO;
2037                 spin_lock_irqsave(&m->lock, flags);
2038                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2039                         r = -ENOTCONN;
2040                 spin_unlock_irqrestore(&m->lock, flags);
2041         }
2042
2043         if (r == -ENOTCONN) {
2044                 if (!READ_ONCE(m->current_pg)) {
2045                         /* Path status changed, redo selection */
2046                         (void) choose_pgpath(m, 0);
2047                 }
2048                 spin_lock_irqsave(&m->lock, flags);
2049                 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2050                         (void) __pg_init_all_paths(m);
2051                 spin_unlock_irqrestore(&m->lock, flags);
2052                 dm_table_run_md_queue_async(m->ti->table);
2053                 process_queued_io_list(m);
2054         }
2055
2056         /*
2057          * Only pass ioctls through if the device sizes match exactly.
2058          */
2059         if (!r && ti->len != bdev_nr_sectors((*bdev)))
2060                 return 1;
2061         return r;
2062 }
2063
2064 static int multipath_iterate_devices(struct dm_target *ti,
2065                                      iterate_devices_callout_fn fn, void *data)
2066 {
2067         struct multipath *m = ti->private;
2068         struct priority_group *pg;
2069         struct pgpath *p;
2070         int ret = 0;
2071
2072         list_for_each_entry(pg, &m->priority_groups, list) {
2073                 list_for_each_entry(p, &pg->pgpaths, list) {
2074                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2075                         if (ret)
2076                                 goto out;
2077                 }
2078         }
2079
2080 out:
2081         return ret;
2082 }
2083
2084 static int pgpath_busy(struct pgpath *pgpath)
2085 {
2086         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2087
2088         return blk_lld_busy(q);
2089 }
2090
2091 /*
2092  * We return "busy", only when we can map I/Os but underlying devices
2093  * are busy (so even if we map I/Os now, the I/Os will wait on
2094  * the underlying queue).
2095  * In other words, if we want to kill I/Os or queue them inside us
2096  * due to map unavailability, we don't return "busy".  Otherwise,
2097  * dm core won't give us the I/Os and we can't do what we want.
2098  */
2099 static int multipath_busy(struct dm_target *ti)
2100 {
2101         bool busy = false, has_active = false;
2102         struct multipath *m = ti->private;
2103         struct priority_group *pg, *next_pg;
2104         struct pgpath *pgpath;
2105
2106         /* pg_init in progress */
2107         if (atomic_read(&m->pg_init_in_progress))
2108                 return true;
2109
2110         /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2111         if (!atomic_read(&m->nr_valid_paths)) {
2112                 unsigned long flags;
2113                 spin_lock_irqsave(&m->lock, flags);
2114                 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2115                         spin_unlock_irqrestore(&m->lock, flags);
2116                         return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2117                 }
2118                 spin_unlock_irqrestore(&m->lock, flags);
2119         }
2120
2121         /* Guess which priority_group will be used at next mapping time */
2122         pg = READ_ONCE(m->current_pg);
2123         next_pg = READ_ONCE(m->next_pg);
2124         if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2125                 pg = next_pg;
2126
2127         if (!pg) {
2128                 /*
2129                  * We don't know which pg will be used at next mapping time.
2130                  * We don't call choose_pgpath() here to avoid to trigger
2131                  * pg_init just by busy checking.
2132                  * So we don't know whether underlying devices we will be using
2133                  * at next mapping time are busy or not. Just try mapping.
2134                  */
2135                 return busy;
2136         }
2137
2138         /*
2139          * If there is one non-busy active path at least, the path selector
2140          * will be able to select it. So we consider such a pg as not busy.
2141          */
2142         busy = true;
2143         list_for_each_entry(pgpath, &pg->pgpaths, list) {
2144                 if (pgpath->is_active) {
2145                         has_active = true;
2146                         if (!pgpath_busy(pgpath)) {
2147                                 busy = false;
2148                                 break;
2149                         }
2150                 }
2151         }
2152
2153         if (!has_active) {
2154                 /*
2155                  * No active path in this pg, so this pg won't be used and
2156                  * the current_pg will be changed at next mapping time.
2157                  * We need to try mapping to determine it.
2158                  */
2159                 busy = false;
2160         }
2161
2162         return busy;
2163 }
2164
2165 /*-----------------------------------------------------------------
2166  * Module setup
2167  *---------------------------------------------------------------*/
2168 static struct target_type multipath_target = {
2169         .name = "multipath",
2170         .version = {1, 14, 0},
2171         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2172                     DM_TARGET_PASSES_INTEGRITY,
2173         .module = THIS_MODULE,
2174         .ctr = multipath_ctr,
2175         .dtr = multipath_dtr,
2176         .clone_and_map_rq = multipath_clone_and_map,
2177         .release_clone_rq = multipath_release_clone,
2178         .rq_end_io = multipath_end_io,
2179         .map = multipath_map_bio,
2180         .end_io = multipath_end_io_bio,
2181         .presuspend = multipath_presuspend,
2182         .postsuspend = multipath_postsuspend,
2183         .resume = multipath_resume,
2184         .status = multipath_status,
2185         .message = multipath_message,
2186         .prepare_ioctl = multipath_prepare_ioctl,
2187         .iterate_devices = multipath_iterate_devices,
2188         .busy = multipath_busy,
2189 };
2190
2191 static int __init dm_multipath_init(void)
2192 {
2193         int r;
2194
2195         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2196         if (!kmultipathd) {
2197                 DMERR("failed to create workqueue kmpathd");
2198                 r = -ENOMEM;
2199                 goto bad_alloc_kmultipathd;
2200         }
2201
2202         /*
2203          * A separate workqueue is used to handle the device handlers
2204          * to avoid overloading existing workqueue. Overloading the
2205          * old workqueue would also create a bottleneck in the
2206          * path of the storage hardware device activation.
2207          */
2208         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2209                                                   WQ_MEM_RECLAIM);
2210         if (!kmpath_handlerd) {
2211                 DMERR("failed to create workqueue kmpath_handlerd");
2212                 r = -ENOMEM;
2213                 goto bad_alloc_kmpath_handlerd;
2214         }
2215
2216         r = dm_register_target(&multipath_target);
2217         if (r < 0) {
2218                 DMERR("request-based register failed %d", r);
2219                 r = -EINVAL;
2220                 goto bad_register_target;
2221         }
2222
2223         return 0;
2224
2225 bad_register_target:
2226         destroy_workqueue(kmpath_handlerd);
2227 bad_alloc_kmpath_handlerd:
2228         destroy_workqueue(kmultipathd);
2229 bad_alloc_kmultipathd:
2230         return r;
2231 }
2232
2233 static void __exit dm_multipath_exit(void)
2234 {
2235         destroy_workqueue(kmpath_handlerd);
2236         destroy_workqueue(kmultipathd);
2237
2238         dm_unregister_target(&multipath_target);
2239 }
2240
2241 module_init(dm_multipath_init);
2242 module_exit(dm_multipath_exit);
2243
2244 module_param_named(queue_if_no_path_timeout_secs,
2245                    queue_if_no_path_timeout_secs, ulong, S_IRUGO | S_IWUSR);
2246 MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2247
2248 MODULE_DESCRIPTION(DM_NAME " multipath target");
2249 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2250 MODULE_LICENSE("GPL");