1/*
   2 * Copyright (C) 2003 Sistina Software Limited.
   3 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4 *
   5 * This file is released under the GPL.
   6 */
   7
   8#include <linux/device-mapper.h>
   9
  10#include "dm-rq.h"
  11#include "dm-bio-record.h"
  12#include "dm-path-selector.h"
  13#include "dm-uevent.h"
  14
  15#include <linux/blkdev.h>
  16#include <linux/ctype.h>
  17#include <linux/init.h>
  18#include <linux/mempool.h>
  19#include <linux/module.h>
  20#include <linux/pagemap.h>
  21#include <linux/slab.h>
  22#include <linux/time.h>
  23#include <linux/workqueue.h>
  24#include <linux/delay.h>
  25#include <scsi/scsi_dh.h>
  26#include <linux/atomic.h>
  27#include <linux/blk-mq.h>
  28
  29#define DM_MSG_PREFIX "multipath"
  30#define DM_PG_INIT_DELAY_MSECS 2000
  31#define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  32
  33/* Path properties */
  34struct pgpath {
  35	struct list_head list;
  36
  37	struct priority_group *pg;	/* Owning PG */
  38	unsigned fail_count;		/* Cumulative failure count */
  39
  40	struct dm_path path;
  41	struct delayed_work activate_path;
  42
  43	bool is_active:1;		/* Path status */
  44};
  45
  46#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  47
  48/*
  49 * Paths are grouped into Priority Groups and numbered from 1 upwards.
  50 * Each has a path selector which controls which path gets used.
  51 */
  52struct priority_group {
  53	struct list_head list;
  54
  55	struct multipath *m;		/* Owning multipath instance */
  56	struct path_selector ps;
  57
  58	unsigned pg_num;		/* Reference number */
  59	unsigned nr_pgpaths;		/* Number of paths in PG */
  60	struct list_head pgpaths;
  61
  62	bool bypassed:1;		/* Temporarily bypass this PG? */
  63};
  64
  65/* Multipath context */
  66struct multipath {
  67	unsigned long flags;		/* Multipath state flags */
  68
  69	spinlock_t lock;
  70	enum dm_queue_mode queue_mode;
  71
  72	struct pgpath *current_pgpath;
  73	struct priority_group *current_pg;
  74	struct priority_group *next_pg;	/* Switch to this PG if set */
  75
  76	atomic_t nr_valid_paths;	/* Total number of usable paths */
  77	unsigned nr_priority_groups;
  78	struct list_head priority_groups;
  79
  80	const char *hw_handler_name;
  81	char *hw_handler_params;
  82	wait_queue_head_t pg_init_wait;	/* Wait for pg_init completion */
  83	unsigned pg_init_retries;	/* Number of times to retry pg_init */
  84	unsigned pg_init_delay_msecs;	/* Number of msecs before pg_init retry */
  85	atomic_t pg_init_in_progress;	/* Only one pg_init allowed at once */
  86	atomic_t pg_init_count;		/* Number of times pg_init called */
  87
  88	struct mutex work_mutex;
  89	struct work_struct trigger_event;
  90	struct dm_target *ti;
  91
  92	struct work_struct process_queued_bios;
  93	struct bio_list queued_bios;
  94};
  95
  96/*
  97 * Context information attached to each io we process.
  98 */
  99struct dm_mpath_io {
 100	struct pgpath *pgpath;
 101	size_t nr_bytes;
 102};
 103
 104typedef int (*action_fn) (struct pgpath *pgpath);
 105
 106static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 107static void trigger_event(struct work_struct *work);
 108static void activate_or_offline_path(struct pgpath *pgpath);
 109static void activate_path_work(struct work_struct *work);
 110static void process_queued_bios(struct work_struct *work);
 111
 112/*-----------------------------------------------
 113 * Multipath state flags.
 114 *-----------------------------------------------*/
 115
 116#define MPATHF_QUEUE_IO 0			/* Must we queue all I/O? */
 117#define MPATHF_QUEUE_IF_NO_PATH 1		/* Queue I/O if last path fails? */
 118#define MPATHF_SAVED_QUEUE_IF_NO_PATH 2		/* Saved state during suspension */
 119#define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3	/* If there's already a hw_handler present, don't change it. */
 120#define MPATHF_PG_INIT_DISABLED 4		/* pg_init is not currently allowed */
 121#define MPATHF_PG_INIT_REQUIRED 5		/* pg_init needs calling? */
 122#define MPATHF_PG_INIT_DELAY_RETRY 6		/* Delay pg_init retry? */
 123
 124/*-----------------------------------------------
 125 * Allocation routines
 126 *-----------------------------------------------*/
 127
 128static struct pgpath *alloc_pgpath(void)
 129{
 130	struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 131
 132	if (!pgpath)
 133		return NULL;
 134
 135	pgpath->is_active = true;
 136
 137	return pgpath;
 138}
 139
 140static void free_pgpath(struct pgpath *pgpath)
 141{
 142	kfree(pgpath);
 143}
 144
 145static struct priority_group *alloc_priority_group(void)
 146{
 147	struct priority_group *pg;
 148
 149	pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 150
 151	if (pg)
 152		INIT_LIST_HEAD(&pg->pgpaths);
 153
 154	return pg;
 155}
 156
 157static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 158{
 159	struct pgpath *pgpath, *tmp;
 160
 161	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 162		list_del(&pgpath->list);
 163		dm_put_device(ti, pgpath->path.dev);
 164		free_pgpath(pgpath);
 165	}
 166}
 167
 168static void free_priority_group(struct priority_group *pg,
 169				struct dm_target *ti)
 170{
 171	struct path_selector *ps = &pg->ps;
 172
 173	if (ps->type) {
 174		ps->type->destroy(ps);
 175		dm_put_path_selector(ps->type);
 176	}
 177
 178	free_pgpaths(&pg->pgpaths, ti);
 179	kfree(pg);
 180}
 181
 182static struct multipath *alloc_multipath(struct dm_target *ti)
 183{
 184	struct multipath *m;
 185
 186	m = kzalloc(sizeof(*m), GFP_KERNEL);
 187	if (m) {
 188		INIT_LIST_HEAD(&m->priority_groups);
 189		spin_lock_init(&m->lock);
 190		atomic_set(&m->nr_valid_paths, 0);
 191		INIT_WORK(&m->trigger_event, trigger_event);
 192		mutex_init(&m->work_mutex);
 193
 194		m->queue_mode = DM_TYPE_NONE;
 195
 196		m->ti = ti;
 197		ti->private = m;
 198	}
 199
 200	return m;
 201}
 202
 203static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 204{
 205	if (m->queue_mode == DM_TYPE_NONE) {
 206		m->queue_mode = DM_TYPE_REQUEST_BASED;
 
 
 
 
 
 
 
 207	} else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 208		INIT_WORK(&m->process_queued_bios, process_queued_bios);
 209		/*
 210		 * bio-based doesn't support any direct scsi_dh management;
 211		 * it just discovers if a scsi_dh is attached.
 212		 */
 213		set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 214	}
 215
 216	dm_table_set_type(ti->table, m->queue_mode);
 217
 218	/*
 219	 * Init fields that are only used when a scsi_dh is attached
 220	 * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 221	 */
 222	set_bit(MPATHF_QUEUE_IO, &m->flags);
 223	atomic_set(&m->pg_init_in_progress, 0);
 224	atomic_set(&m->pg_init_count, 0);
 225	m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 226	init_waitqueue_head(&m->pg_init_wait);
 227
 228	return 0;
 229}
 230
 231static void free_multipath(struct multipath *m)
 232{
 233	struct priority_group *pg, *tmp;
 234
 235	list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 236		list_del(&pg->list);
 237		free_priority_group(pg, m->ti);
 238	}
 239
 240	kfree(m->hw_handler_name);
 241	kfree(m->hw_handler_params);
 242	mutex_destroy(&m->work_mutex);
 243	kfree(m);
 244}
 245
 246static struct dm_mpath_io *get_mpio(union map_info *info)
 247{
 248	return info->ptr;
 249}
 250
 251static size_t multipath_per_bio_data_size(void)
 252{
 253	return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 254}
 255
 256static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 257{
 258	return dm_per_bio_data(bio, multipath_per_bio_data_size());
 259}
 260
 261static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 262{
 263	/* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 264	void *bio_details = mpio + 1;
 265	return bio_details;
 266}
 267
 268static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 269{
 270	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 271	struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 272
 273	mpio->nr_bytes = bio->bi_iter.bi_size;
 274	mpio->pgpath = NULL;
 275	*mpio_p = mpio;
 276
 277	dm_bio_record(bio_details, bio);
 278}
 279
 280/*-----------------------------------------------
 281 * Path selection
 282 *-----------------------------------------------*/
 283
 284static int __pg_init_all_paths(struct multipath *m)
 285{
 286	struct pgpath *pgpath;
 287	unsigned long pg_init_delay = 0;
 288
 289	lockdep_assert_held(&m->lock);
 290
 291	if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 292		return 0;
 293
 294	atomic_inc(&m->pg_init_count);
 295	clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 296
 297	/* Check here to reset pg_init_required */
 298	if (!m->current_pg)
 299		return 0;
 300
 301	if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 302		pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 303						 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 304	list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 305		/* Skip failed paths */
 306		if (!pgpath->is_active)
 307			continue;
 308		if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 309				       pg_init_delay))
 310			atomic_inc(&m->pg_init_in_progress);
 311	}
 312	return atomic_read(&m->pg_init_in_progress);
 313}
 314
 315static int pg_init_all_paths(struct multipath *m)
 316{
 317	int ret;
 318	unsigned long flags;
 319
 320	spin_lock_irqsave(&m->lock, flags);
 321	ret = __pg_init_all_paths(m);
 322	spin_unlock_irqrestore(&m->lock, flags);
 323
 324	return ret;
 325}
 326
 327static void __switch_pg(struct multipath *m, struct priority_group *pg)
 328{
 329	m->current_pg = pg;
 330
 331	/* Must we initialise the PG first, and queue I/O till it's ready? */
 332	if (m->hw_handler_name) {
 333		set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 334		set_bit(MPATHF_QUEUE_IO, &m->flags);
 335	} else {
 336		clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 337		clear_bit(MPATHF_QUEUE_IO, &m->flags);
 338	}
 339
 340	atomic_set(&m->pg_init_count, 0);
 341}
 342
 343static struct pgpath *choose_path_in_pg(struct multipath *m,
 344					struct priority_group *pg,
 345					size_t nr_bytes)
 346{
 347	unsigned long flags;
 348	struct dm_path *path;
 349	struct pgpath *pgpath;
 350
 351	path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 352	if (!path)
 353		return ERR_PTR(-ENXIO);
 354
 355	pgpath = path_to_pgpath(path);
 356
 357	if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 358		/* Only update current_pgpath if pg changed */
 359		spin_lock_irqsave(&m->lock, flags);
 360		m->current_pgpath = pgpath;
 361		__switch_pg(m, pg);
 362		spin_unlock_irqrestore(&m->lock, flags);
 363	}
 364
 365	return pgpath;
 366}
 367
 368static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 369{
 370	unsigned long flags;
 371	struct priority_group *pg;
 372	struct pgpath *pgpath;
 373	unsigned bypassed = 1;
 374
 375	if (!atomic_read(&m->nr_valid_paths)) {
 376		clear_bit(MPATHF_QUEUE_IO, &m->flags);
 377		goto failed;
 378	}
 379
 380	/* Were we instructed to switch PG? */
 381	if (READ_ONCE(m->next_pg)) {
 382		spin_lock_irqsave(&m->lock, flags);
 383		pg = m->next_pg;
 384		if (!pg) {
 385			spin_unlock_irqrestore(&m->lock, flags);
 386			goto check_current_pg;
 387		}
 388		m->next_pg = NULL;
 389		spin_unlock_irqrestore(&m->lock, flags);
 390		pgpath = choose_path_in_pg(m, pg, nr_bytes);
 391		if (!IS_ERR_OR_NULL(pgpath))
 392			return pgpath;
 393	}
 394
 395	/* Don't change PG until it has no remaining paths */
 396check_current_pg:
 397	pg = READ_ONCE(m->current_pg);
 398	if (pg) {
 399		pgpath = choose_path_in_pg(m, pg, nr_bytes);
 400		if (!IS_ERR_OR_NULL(pgpath))
 401			return pgpath;
 402	}
 403
 404	/*
 405	 * Loop through priority groups until we find a valid path.
 406	 * First time we skip PGs marked 'bypassed'.
 407	 * Second time we only try the ones we skipped, but set
 408	 * pg_init_delay_retry so we do not hammer controllers.
 409	 */
 410	do {
 411		list_for_each_entry(pg, &m->priority_groups, list) {
 412			if (pg->bypassed == !!bypassed)
 413				continue;
 414			pgpath = choose_path_in_pg(m, pg, nr_bytes);
 415			if (!IS_ERR_OR_NULL(pgpath)) {
 416				if (!bypassed)
 417					set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 418				return pgpath;
 419			}
 420		}
 421	} while (bypassed--);
 422
 423failed:
 424	spin_lock_irqsave(&m->lock, flags);
 425	m->current_pgpath = NULL;
 426	m->current_pg = NULL;
 427	spin_unlock_irqrestore(&m->lock, flags);
 428
 429	return NULL;
 430}
 431
 432/*
 433 * dm_report_EIO() is a macro instead of a function to make pr_debug()
 434 * report the function name and line number of the function from which
 435 * it has been invoked.
 436 */
 437#define dm_report_EIO(m)						\
 438do {									\
 439	struct mapped_device *md = dm_table_get_md((m)->ti->table);	\
 440									\
 441	pr_debug("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d\n", \
 442		 dm_device_name(md),					\
 443		 test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),	\
 444		 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags),	\
 445		 dm_noflush_suspending((m)->ti));			\
 446} while (0)
 447
 448/*
 449 * Check whether bios must be queued in the device-mapper core rather
 450 * than here in the target.
 451 *
 452 * If MPATHF_QUEUE_IF_NO_PATH and MPATHF_SAVED_QUEUE_IF_NO_PATH hold
 453 * the same value then we are not between multipath_presuspend()
 454 * and multipath_resume() calls and we have no need to check
 455 * for the DMF_NOFLUSH_SUSPENDING flag.
 456 */
 457static bool __must_push_back(struct multipath *m, unsigned long flags)
 458{
 459	return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) !=
 460		 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &flags)) &&
 461		dm_noflush_suspending(m->ti));
 462}
 463
 464/*
 465 * Following functions use READ_ONCE to get atomic access to
 466 * all m->flags to avoid taking spinlock
 467 */
 468static bool must_push_back_rq(struct multipath *m)
 469{
 470	unsigned long flags = READ_ONCE(m->flags);
 471	return test_bit(MPATHF_QUEUE_IF_NO_PATH, &flags) || __must_push_back(m, flags);
 472}
 473
 474static bool must_push_back_bio(struct multipath *m)
 475{
 476	unsigned long flags = READ_ONCE(m->flags);
 477	return __must_push_back(m, flags);
 478}
 479
 480/*
 481 * Map cloned requests (request-based multipath)
 482 */
 483static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 484				   union map_info *map_context,
 485				   struct request **__clone)
 486{
 487	struct multipath *m = ti->private;
 488	size_t nr_bytes = blk_rq_bytes(rq);
 489	struct pgpath *pgpath;
 490	struct block_device *bdev;
 491	struct dm_mpath_io *mpio = get_mpio(map_context);
 492	struct request_queue *q;
 493	struct request *clone;
 494
 495	/* Do we need to select a new pgpath? */
 496	pgpath = READ_ONCE(m->current_pgpath);
 497	if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
 498		pgpath = choose_pgpath(m, nr_bytes);
 499
 500	if (!pgpath) {
 501		if (must_push_back_rq(m))
 502			return DM_MAPIO_DELAY_REQUEUE;
 503		dm_report_EIO(m);	/* Failed */
 504		return DM_MAPIO_KILL;
 505	} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
 506		   test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
 507		pg_init_all_paths(m);
 508		return DM_MAPIO_DELAY_REQUEUE;
 509	}
 510
 511	mpio->pgpath = pgpath;
 512	mpio->nr_bytes = nr_bytes;
 513
 514	bdev = pgpath->path.dev->bdev;
 515	q = bdev_get_queue(bdev);
 516	clone = blk_get_request(q, rq->cmd_flags | REQ_NOMERGE,
 517			BLK_MQ_REQ_NOWAIT);
 518	if (IS_ERR(clone)) {
 519		/* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 520		if (blk_queue_dying(q)) {
 521			atomic_inc(&m->pg_init_in_progress);
 522			activate_or_offline_path(pgpath);
 523			return DM_MAPIO_DELAY_REQUEUE;
 524		}
 525
 526		/*
 527		 * blk-mq's SCHED_RESTART can cover this requeue, so we
 528		 * needn't deal with it by DELAY_REQUEUE. More importantly,
 529		 * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 530		 * get the queue busy feedback (via BLK_STS_RESOURCE),
 531		 * otherwise I/O merging can suffer.
 532		 */
 533		return DM_MAPIO_REQUEUE;
 
 
 
 534	}
 535	clone->bio = clone->biotail = NULL;
 536	clone->rq_disk = bdev->bd_disk;
 537	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 538	*__clone = clone;
 539
 540	if (pgpath->pg->ps.type->start_io)
 541		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 542					      &pgpath->path,
 543					      nr_bytes);
 544	return DM_MAPIO_REMAPPED;
 545}
 546
 547static void multipath_release_clone(struct request *clone,
 548				    union map_info *map_context)
 549{
 550	if (unlikely(map_context)) {
 551		/*
 552		 * non-NULL map_context means caller is still map
 553		 * method; must undo multipath_clone_and_map()
 554		 */
 555		struct dm_mpath_io *mpio = get_mpio(map_context);
 556		struct pgpath *pgpath = mpio->pgpath;
 557
 558		if (pgpath && pgpath->pg->ps.type->end_io)
 559			pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 560						    &pgpath->path,
 561						    mpio->nr_bytes);
 562	}
 563
 564	blk_put_request(clone);
 565}
 566
 567/*
 568 * Map cloned bios (bio-based multipath)
 569 */
 570
 571static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 572{
 573	struct pgpath *pgpath;
 574	unsigned long flags;
 575	bool queue_io;
 576
 577	/* Do we need to select a new pgpath? */
 578	pgpath = READ_ONCE(m->current_pgpath);
 579	queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
 580	if (!pgpath || !queue_io)
 581		pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 582
 583	if ((pgpath && queue_io) ||
 584	    (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
 585		/* Queue for the daemon to resubmit */
 586		spin_lock_irqsave(&m->lock, flags);
 587		bio_list_add(&m->queued_bios, bio);
 588		spin_unlock_irqrestore(&m->lock, flags);
 589
 590		/* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
 591		if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
 592			pg_init_all_paths(m);
 593		else if (!queue_io)
 594			queue_work(kmultipathd, &m->process_queued_bios);
 595
 596		return ERR_PTR(-EAGAIN);
 597	}
 598
 599	return pgpath;
 600}
 601
 602static struct pgpath *__map_bio_fast(struct multipath *m, struct bio *bio)
 603{
 604	struct pgpath *pgpath;
 605	unsigned long flags;
 606
 607	/* Do we need to select a new pgpath? */
 608	/*
 609	 * FIXME: currently only switching path if no path (due to failure, etc)
 610	 * - which negates the point of using a path selector
 611	 */
 612	pgpath = READ_ONCE(m->current_pgpath);
 613	if (!pgpath)
 614		pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 615
 616	if (!pgpath) {
 617		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 618			/* Queue for the daemon to resubmit */
 619			spin_lock_irqsave(&m->lock, flags);
 620			bio_list_add(&m->queued_bios, bio);
 621			spin_unlock_irqrestore(&m->lock, flags);
 622			queue_work(kmultipathd, &m->process_queued_bios);
 623
 624			return ERR_PTR(-EAGAIN);
 625		}
 626		return NULL;
 627	}
 628
 629	return pgpath;
 630}
 631
 632static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 633			       struct dm_mpath_io *mpio)
 634{
 635	struct pgpath *pgpath;
 636
 637	if (!m->hw_handler_name)
 638		pgpath = __map_bio_fast(m, bio);
 639	else
 640		pgpath = __map_bio(m, bio);
 641
 642	if (IS_ERR(pgpath))
 643		return DM_MAPIO_SUBMITTED;
 644
 645	if (!pgpath) {
 646		if (must_push_back_bio(m))
 647			return DM_MAPIO_REQUEUE;
 648		dm_report_EIO(m);
 649		return DM_MAPIO_KILL;
 650	}
 651
 652	mpio->pgpath = pgpath;
 653
 654	bio->bi_status = 0;
 655	bio_set_dev(bio, pgpath->path.dev->bdev);
 656	bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 657
 658	if (pgpath->pg->ps.type->start_io)
 659		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 660					      &pgpath->path,
 661					      mpio->nr_bytes);
 662	return DM_MAPIO_REMAPPED;
 663}
 664
 665static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 666{
 667	struct multipath *m = ti->private;
 668	struct dm_mpath_io *mpio = NULL;
 669
 670	multipath_init_per_bio_data(bio, &mpio);
 671	return __multipath_map_bio(m, bio, mpio);
 672}
 673
 674static void process_queued_io_list(struct multipath *m)
 675{
 676	if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 677		dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 678	else if (m->queue_mode == DM_TYPE_BIO_BASED)
 679		queue_work(kmultipathd, &m->process_queued_bios);
 680}
 681
 682static void process_queued_bios(struct work_struct *work)
 683{
 684	int r;
 685	unsigned long flags;
 686	struct bio *bio;
 687	struct bio_list bios;
 688	struct blk_plug plug;
 689	struct multipath *m =
 690		container_of(work, struct multipath, process_queued_bios);
 691
 692	bio_list_init(&bios);
 693
 694	spin_lock_irqsave(&m->lock, flags);
 695
 696	if (bio_list_empty(&m->queued_bios)) {
 697		spin_unlock_irqrestore(&m->lock, flags);
 698		return;
 699	}
 700
 701	bio_list_merge(&bios, &m->queued_bios);
 702	bio_list_init(&m->queued_bios);
 703
 704	spin_unlock_irqrestore(&m->lock, flags);
 705
 706	blk_start_plug(&plug);
 707	while ((bio = bio_list_pop(&bios))) {
 708		struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 709		dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 710		r = __multipath_map_bio(m, bio, mpio);
 711		switch (r) {
 712		case DM_MAPIO_KILL:
 713			bio->bi_status = BLK_STS_IOERR;
 714			bio_endio(bio);
 715			break;
 716		case DM_MAPIO_REQUEUE:
 717			bio->bi_status = BLK_STS_DM_REQUEUE;
 718			bio_endio(bio);
 719			break;
 720		case DM_MAPIO_REMAPPED:
 721			generic_make_request(bio);
 722			break;
 723		case DM_MAPIO_SUBMITTED:
 724			break;
 725		default:
 726			WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 727		}
 728	}
 729	blk_finish_plug(&plug);
 730}
 731
 732/*
 733 * If we run out of usable paths, should we queue I/O or error it?
 734 */
 735static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 736			    bool save_old_value)
 737{
 738	unsigned long flags;
 739
 740	spin_lock_irqsave(&m->lock, flags);
 741	assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
 742		   (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
 743		   (!save_old_value && queue_if_no_path));
 744	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path);
 745	spin_unlock_irqrestore(&m->lock, flags);
 746
 747	if (!queue_if_no_path) {
 748		dm_table_run_md_queue_async(m->ti->table);
 749		process_queued_io_list(m);
 750	}
 751
 752	return 0;
 753}
 754
 755/*
 756 * An event is triggered whenever a path is taken out of use.
 757 * Includes path failure and PG bypass.
 758 */
 759static void trigger_event(struct work_struct *work)
 760{
 761	struct multipath *m =
 762		container_of(work, struct multipath, trigger_event);
 763
 764	dm_table_event(m->ti->table);
 765}
 766
 767/*-----------------------------------------------------------------
 768 * Constructor/argument parsing:
 769 * <#multipath feature args> [<arg>]*
 770 * <#hw_handler args> [hw_handler [<arg>]*]
 771 * <#priority groups>
 772 * <initial priority group>
 773 *     [<selector> <#selector args> [<arg>]*
 774 *      <#paths> <#per-path selector args>
 775 *         [<path> [<arg>]* ]+ ]+
 776 *---------------------------------------------------------------*/
 777static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 778			       struct dm_target *ti)
 779{
 780	int r;
 781	struct path_selector_type *pst;
 782	unsigned ps_argc;
 783
 784	static const struct dm_arg _args[] = {
 785		{0, 1024, "invalid number of path selector args"},
 786	};
 787
 788	pst = dm_get_path_selector(dm_shift_arg(as));
 789	if (!pst) {
 790		ti->error = "unknown path selector type";
 791		return -EINVAL;
 792	}
 793
 794	r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 795	if (r) {
 796		dm_put_path_selector(pst);
 797		return -EINVAL;
 798	}
 799
 800	r = pst->create(&pg->ps, ps_argc, as->argv);
 801	if (r) {
 802		dm_put_path_selector(pst);
 803		ti->error = "path selector constructor failed";
 804		return r;
 805	}
 806
 807	pg->ps.type = pst;
 808	dm_consume_args(as, ps_argc);
 809
 810	return 0;
 811}
 812
 813static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 814			 const char **attached_handler_name, char **error)
 815{
 816	struct request_queue *q = bdev_get_queue(bdev);
 817	int r;
 818
 819	if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
 820retain:
 821		if (*attached_handler_name) {
 822			/*
 823			 * Clear any hw_handler_params associated with a
 824			 * handler that isn't already attached.
 825			 */
 826			if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 827				kfree(m->hw_handler_params);
 828				m->hw_handler_params = NULL;
 829			}
 830
 831			/*
 832			 * Reset hw_handler_name to match the attached handler
 833			 *
 834			 * NB. This modifies the table line to show the actual
 835			 * handler instead of the original table passed in.
 836			 */
 837			kfree(m->hw_handler_name);
 838			m->hw_handler_name = *attached_handler_name;
 839			*attached_handler_name = NULL;
 840		}
 841	}
 842
 843	if (m->hw_handler_name) {
 844		r = scsi_dh_attach(q, m->hw_handler_name);
 845		if (r == -EBUSY) {
 846			char b[BDEVNAME_SIZE];
 847
 848			printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 849			       bdevname(bdev, b));
 850			goto retain;
 851		}
 852		if (r < 0) {
 853			*error = "error attaching hardware handler";
 854			return r;
 855		}
 856
 857		if (m->hw_handler_params) {
 858			r = scsi_dh_set_params(q, m->hw_handler_params);
 859			if (r < 0) {
 860				*error = "unable to set hardware handler parameters";
 861				return r;
 862			}
 863		}
 864	}
 865
 866	return 0;
 867}
 868
 869static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 870				 struct dm_target *ti)
 871{
 872	int r;
 873	struct pgpath *p;
 874	struct multipath *m = ti->private;
 875	struct request_queue *q;
 876	const char *attached_handler_name = NULL;
 877
 878	/* we need at least a path arg */
 879	if (as->argc < 1) {
 880		ti->error = "no device given";
 881		return ERR_PTR(-EINVAL);
 882	}
 883
 884	p = alloc_pgpath();
 885	if (!p)
 886		return ERR_PTR(-ENOMEM);
 887
 888	r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 889			  &p->path.dev);
 890	if (r) {
 891		ti->error = "error getting device";
 892		goto bad;
 893	}
 894
 895	q = bdev_get_queue(p->path.dev->bdev);
 896	attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 897	if (attached_handler_name || m->hw_handler_name) {
 898		INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 899		r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 900		kfree(attached_handler_name);
 901		if (r) {
 902			dm_put_device(ti, p->path.dev);
 903			goto bad;
 904		}
 905	}
 906
 907	r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 908	if (r) {
 909		dm_put_device(ti, p->path.dev);
 910		goto bad;
 911	}
 912
 913	return p;
 914 bad:
 915	free_pgpath(p);
 916	return ERR_PTR(r);
 917}
 918
 919static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 920						   struct multipath *m)
 921{
 922	static const struct dm_arg _args[] = {
 923		{1, 1024, "invalid number of paths"},
 924		{0, 1024, "invalid number of selector args"}
 925	};
 926
 927	int r;
 928	unsigned i, nr_selector_args, nr_args;
 929	struct priority_group *pg;
 930	struct dm_target *ti = m->ti;
 931
 932	if (as->argc < 2) {
 933		as->argc = 0;
 934		ti->error = "not enough priority group arguments";
 935		return ERR_PTR(-EINVAL);
 936	}
 937
 938	pg = alloc_priority_group();
 939	if (!pg) {
 940		ti->error = "couldn't allocate priority group";
 941		return ERR_PTR(-ENOMEM);
 942	}
 943	pg->m = m;
 944
 945	r = parse_path_selector(as, pg, ti);
 946	if (r)
 947		goto bad;
 948
 949	/*
 950	 * read the paths
 951	 */
 952	r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 953	if (r)
 954		goto bad;
 955
 956	r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 957	if (r)
 958		goto bad;
 959
 960	nr_args = 1 + nr_selector_args;
 961	for (i = 0; i < pg->nr_pgpaths; i++) {
 962		struct pgpath *pgpath;
 963		struct dm_arg_set path_args;
 964
 965		if (as->argc < nr_args) {
 966			ti->error = "not enough path parameters";
 967			r = -EINVAL;
 968			goto bad;
 969		}
 970
 971		path_args.argc = nr_args;
 972		path_args.argv = as->argv;
 973
 974		pgpath = parse_path(&path_args, &pg->ps, ti);
 975		if (IS_ERR(pgpath)) {
 976			r = PTR_ERR(pgpath);
 977			goto bad;
 978		}
 979
 980		pgpath->pg = pg;
 981		list_add_tail(&pgpath->list, &pg->pgpaths);
 982		dm_consume_args(as, nr_args);
 983	}
 984
 985	return pg;
 986
 987 bad:
 988	free_priority_group(pg, ti);
 989	return ERR_PTR(r);
 990}
 991
 992static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 993{
 994	unsigned hw_argc;
 995	int ret;
 996	struct dm_target *ti = m->ti;
 997
 998	static const struct dm_arg _args[] = {
 999		{0, 1024, "invalid number of hardware handler args"},
1000	};
1001
1002	if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1003		return -EINVAL;
1004
1005	if (!hw_argc)
1006		return 0;
1007
1008	if (m->queue_mode == DM_TYPE_BIO_BASED) {
1009		dm_consume_args(as, hw_argc);
1010		DMERR("bio-based multipath doesn't allow hardware handler args");
1011		return 0;
1012	}
1013
1014	m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1015	if (!m->hw_handler_name)
1016		return -EINVAL;
1017
1018	if (hw_argc > 1) {
1019		char *p;
1020		int i, j, len = 4;
1021
1022		for (i = 0; i <= hw_argc - 2; i++)
1023			len += strlen(as->argv[i]) + 1;
1024		p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1025		if (!p) {
1026			ti->error = "memory allocation failed";
1027			ret = -ENOMEM;
1028			goto fail;
1029		}
1030		j = sprintf(p, "%d", hw_argc - 1);
1031		for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1032			j = sprintf(p, "%s", as->argv[i]);
1033	}
1034	dm_consume_args(as, hw_argc - 1);
1035
1036	return 0;
1037fail:
1038	kfree(m->hw_handler_name);
1039	m->hw_handler_name = NULL;
1040	return ret;
1041}
1042
1043static int parse_features(struct dm_arg_set *as, struct multipath *m)
1044{
1045	int r;
1046	unsigned argc;
1047	struct dm_target *ti = m->ti;
1048	const char *arg_name;
1049
1050	static const struct dm_arg _args[] = {
1051		{0, 8, "invalid number of feature args"},
1052		{1, 50, "pg_init_retries must be between 1 and 50"},
1053		{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1054	};
1055
1056	r = dm_read_arg_group(_args, as, &argc, &ti->error);
1057	if (r)
1058		return -EINVAL;
1059
1060	if (!argc)
1061		return 0;
1062
1063	do {
1064		arg_name = dm_shift_arg(as);
1065		argc--;
1066
1067		if (!strcasecmp(arg_name, "queue_if_no_path")) {
1068			r = queue_if_no_path(m, true, false);
1069			continue;
1070		}
1071
1072		if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1073			set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1074			continue;
1075		}
1076
1077		if (!strcasecmp(arg_name, "pg_init_retries") &&
1078		    (argc >= 1)) {
1079			r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1080			argc--;
1081			continue;
1082		}
1083
1084		if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1085		    (argc >= 1)) {
1086			r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1087			argc--;
1088			continue;
1089		}
1090
1091		if (!strcasecmp(arg_name, "queue_mode") &&
1092		    (argc >= 1)) {
1093			const char *queue_mode_name = dm_shift_arg(as);
1094
1095			if (!strcasecmp(queue_mode_name, "bio"))
1096				m->queue_mode = DM_TYPE_BIO_BASED;
1097			else if (!strcasecmp(queue_mode_name, "rq") ||
1098				 !strcasecmp(queue_mode_name, "mq"))
1099				m->queue_mode = DM_TYPE_REQUEST_BASED;
 
 
1100			else {
1101				ti->error = "Unknown 'queue_mode' requested";
1102				r = -EINVAL;
1103			}
1104			argc--;
1105			continue;
1106		}
1107
1108		ti->error = "Unrecognised multipath feature request";
1109		r = -EINVAL;
1110	} while (argc && !r);
1111
1112	return r;
1113}
1114
1115static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1116{
1117	/* target arguments */
1118	static const struct dm_arg _args[] = {
1119		{0, 1024, "invalid number of priority groups"},
1120		{0, 1024, "invalid initial priority group number"},
1121	};
1122
1123	int r;
1124	struct multipath *m;
1125	struct dm_arg_set as;
1126	unsigned pg_count = 0;
1127	unsigned next_pg_num;
1128
1129	as.argc = argc;
1130	as.argv = argv;
1131
1132	m = alloc_multipath(ti);
1133	if (!m) {
1134		ti->error = "can't allocate multipath";
1135		return -EINVAL;
1136	}
1137
1138	r = parse_features(&as, m);
1139	if (r)
1140		goto bad;
1141
1142	r = alloc_multipath_stage2(ti, m);
1143	if (r)
1144		goto bad;
1145
1146	r = parse_hw_handler(&as, m);
1147	if (r)
1148		goto bad;
1149
1150	r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1151	if (r)
1152		goto bad;
1153
1154	r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1155	if (r)
1156		goto bad;
1157
1158	if ((!m->nr_priority_groups && next_pg_num) ||
1159	    (m->nr_priority_groups && !next_pg_num)) {
1160		ti->error = "invalid initial priority group";
1161		r = -EINVAL;
1162		goto bad;
1163	}
1164
1165	/* parse the priority groups */
1166	while (as.argc) {
1167		struct priority_group *pg;
1168		unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1169
1170		pg = parse_priority_group(&as, m);
1171		if (IS_ERR(pg)) {
1172			r = PTR_ERR(pg);
1173			goto bad;
1174		}
1175
1176		nr_valid_paths += pg->nr_pgpaths;
1177		atomic_set(&m->nr_valid_paths, nr_valid_paths);
1178
1179		list_add_tail(&pg->list, &m->priority_groups);
1180		pg_count++;
1181		pg->pg_num = pg_count;
1182		if (!--next_pg_num)
1183			m->next_pg = pg;
1184	}
1185
1186	if (pg_count != m->nr_priority_groups) {
1187		ti->error = "priority group count mismatch";
1188		r = -EINVAL;
1189		goto bad;
1190	}
1191
1192	ti->num_flush_bios = 1;
1193	ti->num_discard_bios = 1;
1194	ti->num_write_same_bios = 1;
1195	ti->num_write_zeroes_bios = 1;
1196	if (m->queue_mode == DM_TYPE_BIO_BASED)
1197		ti->per_io_data_size = multipath_per_bio_data_size();
1198	else
1199		ti->per_io_data_size = sizeof(struct dm_mpath_io);
1200
1201	return 0;
1202
1203 bad:
1204	free_multipath(m);
1205	return r;
1206}
1207
1208static void multipath_wait_for_pg_init_completion(struct multipath *m)
1209{
1210	DEFINE_WAIT(wait);
1211
1212	while (1) {
1213		prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1214
1215		if (!atomic_read(&m->pg_init_in_progress))
1216			break;
1217
1218		io_schedule();
1219	}
1220	finish_wait(&m->pg_init_wait, &wait);
1221}
1222
1223static void flush_multipath_work(struct multipath *m)
1224{
1225	if (m->hw_handler_name) {
1226		set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1227		smp_mb__after_atomic();
1228
1229		if (atomic_read(&m->pg_init_in_progress))
1230			flush_workqueue(kmpath_handlerd);
1231		multipath_wait_for_pg_init_completion(m);
1232
1233		clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1234		smp_mb__after_atomic();
1235	}
1236
1237	if (m->queue_mode == DM_TYPE_BIO_BASED)
1238		flush_work(&m->process_queued_bios);
1239	flush_work(&m->trigger_event);
1240}
1241
1242static void multipath_dtr(struct dm_target *ti)
1243{
1244	struct multipath *m = ti->private;
1245
1246	flush_multipath_work(m);
1247	free_multipath(m);
1248}
1249
1250/*
1251 * Take a path out of use.
1252 */
1253static int fail_path(struct pgpath *pgpath)
1254{
1255	unsigned long flags;
1256	struct multipath *m = pgpath->pg->m;
1257
1258	spin_lock_irqsave(&m->lock, flags);
1259
1260	if (!pgpath->is_active)
1261		goto out;
1262
1263	DMWARN("Failing path %s.", pgpath->path.dev->name);
1264
1265	pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1266	pgpath->is_active = false;
1267	pgpath->fail_count++;
1268
1269	atomic_dec(&m->nr_valid_paths);
1270
1271	if (pgpath == m->current_pgpath)
1272		m->current_pgpath = NULL;
1273
1274	dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1275		       pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1276
1277	schedule_work(&m->trigger_event);
1278
1279out:
1280	spin_unlock_irqrestore(&m->lock, flags);
1281
1282	return 0;
1283}
1284
1285/*
1286 * Reinstate a previously-failed path
1287 */
1288static int reinstate_path(struct pgpath *pgpath)
1289{
1290	int r = 0, run_queue = 0;
1291	unsigned long flags;
1292	struct multipath *m = pgpath->pg->m;
1293	unsigned nr_valid_paths;
1294
1295	spin_lock_irqsave(&m->lock, flags);
1296
1297	if (pgpath->is_active)
1298		goto out;
1299
1300	DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1301
1302	r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1303	if (r)
1304		goto out;
1305
1306	pgpath->is_active = true;
1307
1308	nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1309	if (nr_valid_paths == 1) {
1310		m->current_pgpath = NULL;
1311		run_queue = 1;
1312	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1313		if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1314			atomic_inc(&m->pg_init_in_progress);
1315	}
1316
1317	dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1318		       pgpath->path.dev->name, nr_valid_paths);
1319
1320	schedule_work(&m->trigger_event);
1321
1322out:
1323	spin_unlock_irqrestore(&m->lock, flags);
1324	if (run_queue) {
1325		dm_table_run_md_queue_async(m->ti->table);
1326		process_queued_io_list(m);
1327	}
1328
1329	return r;
1330}
1331
1332/*
1333 * Fail or reinstate all paths that match the provided struct dm_dev.
1334 */
1335static int action_dev(struct multipath *m, struct dm_dev *dev,
1336		      action_fn action)
1337{
1338	int r = -EINVAL;
1339	struct pgpath *pgpath;
1340	struct priority_group *pg;
1341
1342	list_for_each_entry(pg, &m->priority_groups, list) {
1343		list_for_each_entry(pgpath, &pg->pgpaths, list) {
1344			if (pgpath->path.dev == dev)
1345				r = action(pgpath);
1346		}
1347	}
1348
1349	return r;
1350}
1351
1352/*
1353 * Temporarily try to avoid having to use the specified PG
1354 */
1355static void bypass_pg(struct multipath *m, struct priority_group *pg,
1356		      bool bypassed)
1357{
1358	unsigned long flags;
1359
1360	spin_lock_irqsave(&m->lock, flags);
1361
1362	pg->bypassed = bypassed;
1363	m->current_pgpath = NULL;
1364	m->current_pg = NULL;
1365
1366	spin_unlock_irqrestore(&m->lock, flags);
1367
1368	schedule_work(&m->trigger_event);
1369}
1370
1371/*
1372 * Switch to using the specified PG from the next I/O that gets mapped
1373 */
1374static int switch_pg_num(struct multipath *m, const char *pgstr)
1375{
1376	struct priority_group *pg;
1377	unsigned pgnum;
1378	unsigned long flags;
1379	char dummy;
1380
1381	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1382	    !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1383		DMWARN("invalid PG number supplied to switch_pg_num");
1384		return -EINVAL;
1385	}
1386
1387	spin_lock_irqsave(&m->lock, flags);
1388	list_for_each_entry(pg, &m->priority_groups, list) {
1389		pg->bypassed = false;
1390		if (--pgnum)
1391			continue;
1392
1393		m->current_pgpath = NULL;
1394		m->current_pg = NULL;
1395		m->next_pg = pg;
1396	}
1397	spin_unlock_irqrestore(&m->lock, flags);
1398
1399	schedule_work(&m->trigger_event);
1400	return 0;
1401}
1402
1403/*
1404 * Set/clear bypassed status of a PG.
1405 * PGs are numbered upwards from 1 in the order they were declared.
1406 */
1407static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1408{
1409	struct priority_group *pg;
1410	unsigned pgnum;
1411	char dummy;
1412
1413	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1414	    !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1415		DMWARN("invalid PG number supplied to bypass_pg");
1416		return -EINVAL;
1417	}
1418
1419	list_for_each_entry(pg, &m->priority_groups, list) {
1420		if (!--pgnum)
1421			break;
1422	}
1423
1424	bypass_pg(m, pg, bypassed);
1425	return 0;
1426}
1427
1428/*
1429 * Should we retry pg_init immediately?
1430 */
1431static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1432{
1433	unsigned long flags;
1434	bool limit_reached = false;
1435
1436	spin_lock_irqsave(&m->lock, flags);
1437
1438	if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1439	    !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1440		set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1441	else
1442		limit_reached = true;
1443
1444	spin_unlock_irqrestore(&m->lock, flags);
1445
1446	return limit_reached;
1447}
1448
1449static void pg_init_done(void *data, int errors)
1450{
1451	struct pgpath *pgpath = data;
1452	struct priority_group *pg = pgpath->pg;
1453	struct multipath *m = pg->m;
1454	unsigned long flags;
1455	bool delay_retry = false;
1456
1457	/* device or driver problems */
1458	switch (errors) {
1459	case SCSI_DH_OK:
1460		break;
1461	case SCSI_DH_NOSYS:
1462		if (!m->hw_handler_name) {
1463			errors = 0;
1464			break;
1465		}
1466		DMERR("Could not failover the device: Handler scsi_dh_%s "
1467		      "Error %d.", m->hw_handler_name, errors);
1468		/*
1469		 * Fail path for now, so we do not ping pong
1470		 */
1471		fail_path(pgpath);
1472		break;
1473	case SCSI_DH_DEV_TEMP_BUSY:
1474		/*
1475		 * Probably doing something like FW upgrade on the
1476		 * controller so try the other pg.
1477		 */
1478		bypass_pg(m, pg, true);
1479		break;
1480	case SCSI_DH_RETRY:
1481		/* Wait before retrying. */
1482		delay_retry = 1;
1483		/* fall through */
1484	case SCSI_DH_IMM_RETRY:
1485	case SCSI_DH_RES_TEMP_UNAVAIL:
1486		if (pg_init_limit_reached(m, pgpath))
1487			fail_path(pgpath);
1488		errors = 0;
1489		break;
1490	case SCSI_DH_DEV_OFFLINED:
1491	default:
1492		/*
1493		 * We probably do not want to fail the path for a device
1494		 * error, but this is what the old dm did. In future
1495		 * patches we can do more advanced handling.
1496		 */
1497		fail_path(pgpath);
1498	}
1499
1500	spin_lock_irqsave(&m->lock, flags);
1501	if (errors) {
1502		if (pgpath == m->current_pgpath) {
1503			DMERR("Could not failover device. Error %d.", errors);
1504			m->current_pgpath = NULL;
1505			m->current_pg = NULL;
1506		}
1507	} else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1508		pg->bypassed = false;
1509
1510	if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1511		/* Activations of other paths are still on going */
1512		goto out;
1513
1514	if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1515		if (delay_retry)
1516			set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1517		else
1518			clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1519
1520		if (__pg_init_all_paths(m))
1521			goto out;
1522	}
1523	clear_bit(MPATHF_QUEUE_IO, &m->flags);
1524
1525	process_queued_io_list(m);
1526
1527	/*
1528	 * Wake up any thread waiting to suspend.
1529	 */
1530	wake_up(&m->pg_init_wait);
1531
1532out:
1533	spin_unlock_irqrestore(&m->lock, flags);
1534}
1535
1536static void activate_or_offline_path(struct pgpath *pgpath)
1537{
1538	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1539
1540	if (pgpath->is_active && !blk_queue_dying(q))
1541		scsi_dh_activate(q, pg_init_done, pgpath);
1542	else
1543		pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1544}
1545
1546static void activate_path_work(struct work_struct *work)
1547{
1548	struct pgpath *pgpath =
1549		container_of(work, struct pgpath, activate_path.work);
1550
1551	activate_or_offline_path(pgpath);
1552}
1553
1554static int multipath_end_io(struct dm_target *ti, struct request *clone,
1555			    blk_status_t error, union map_info *map_context)
1556{
1557	struct dm_mpath_io *mpio = get_mpio(map_context);
1558	struct pgpath *pgpath = mpio->pgpath;
1559	int r = DM_ENDIO_DONE;
1560
1561	/*
1562	 * We don't queue any clone request inside the multipath target
1563	 * during end I/O handling, since those clone requests don't have
1564	 * bio clones.  If we queue them inside the multipath target,
1565	 * we need to make bio clones, that requires memory allocation.
1566	 * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1567	 *  don't have bio clones.)
1568	 * Instead of queueing the clone request here, we queue the original
1569	 * request into dm core, which will remake a clone request and
1570	 * clone bios for it and resubmit it later.
1571	 */
1572	if (error && blk_path_error(error)) {
1573		struct multipath *m = ti->private;
1574
1575		if (error == BLK_STS_RESOURCE)
1576			r = DM_ENDIO_DELAY_REQUEUE;
1577		else
1578			r = DM_ENDIO_REQUEUE;
1579
1580		if (pgpath)
1581			fail_path(pgpath);
1582
1583		if (atomic_read(&m->nr_valid_paths) == 0 &&
1584		    !must_push_back_rq(m)) {
1585			if (error == BLK_STS_IOERR)
1586				dm_report_EIO(m);
1587			/* complete with the original error */
1588			r = DM_ENDIO_DONE;
1589		}
1590	}
1591
1592	if (pgpath) {
1593		struct path_selector *ps = &pgpath->pg->ps;
1594
1595		if (ps->type->end_io)
1596			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1597	}
1598
1599	return r;
1600}
1601
1602static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1603				blk_status_t *error)
1604{
1605	struct multipath *m = ti->private;
1606	struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1607	struct pgpath *pgpath = mpio->pgpath;
1608	unsigned long flags;
1609	int r = DM_ENDIO_DONE;
1610
1611	if (!*error || !blk_path_error(*error))
1612		goto done;
1613
1614	if (pgpath)
1615		fail_path(pgpath);
1616
1617	if (atomic_read(&m->nr_valid_paths) == 0 &&
1618	    !test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1619		if (must_push_back_bio(m)) {
1620			r = DM_ENDIO_REQUEUE;
1621		} else {
1622			dm_report_EIO(m);
1623			*error = BLK_STS_IOERR;
1624		}
1625		goto done;
1626	}
1627
1628	spin_lock_irqsave(&m->lock, flags);
1629	bio_list_add(&m->queued_bios, clone);
1630	spin_unlock_irqrestore(&m->lock, flags);
1631	if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1632		queue_work(kmultipathd, &m->process_queued_bios);
1633
1634	r = DM_ENDIO_INCOMPLETE;
1635done:
1636	if (pgpath) {
1637		struct path_selector *ps = &pgpath->pg->ps;
1638
1639		if (ps->type->end_io)
1640			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1641	}
1642
1643	return r;
1644}
1645
1646/*
1647 * Suspend can't complete until all the I/O is processed so if
1648 * the last path fails we must error any remaining I/O.
1649 * Note that if the freeze_bdev fails while suspending, the
1650 * queue_if_no_path state is lost - userspace should reset it.
1651 */
1652static void multipath_presuspend(struct dm_target *ti)
1653{
1654	struct multipath *m = ti->private;
1655
1656	queue_if_no_path(m, false, true);
1657}
1658
1659static void multipath_postsuspend(struct dm_target *ti)
1660{
1661	struct multipath *m = ti->private;
1662
1663	mutex_lock(&m->work_mutex);
1664	flush_multipath_work(m);
1665	mutex_unlock(&m->work_mutex);
1666}
1667
1668/*
1669 * Restore the queue_if_no_path setting.
1670 */
1671static void multipath_resume(struct dm_target *ti)
1672{
1673	struct multipath *m = ti->private;
1674	unsigned long flags;
1675
1676	spin_lock_irqsave(&m->lock, flags);
1677	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
1678		   test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1679	spin_unlock_irqrestore(&m->lock, flags);
1680}
1681
1682/*
1683 * Info output has the following format:
1684 * num_multipath_feature_args [multipath_feature_args]*
1685 * num_handler_status_args [handler_status_args]*
1686 * num_groups init_group_number
1687 *            [A|D|E num_ps_status_args [ps_status_args]*
1688 *             num_paths num_selector_args
1689 *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1690 *
1691 * Table output has the following format (identical to the constructor string):
1692 * num_feature_args [features_args]*
1693 * num_handler_args hw_handler [hw_handler_args]*
1694 * num_groups init_group_number
1695 *     [priority selector-name num_ps_args [ps_args]*
1696 *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1697 */
1698static void multipath_status(struct dm_target *ti, status_type_t type,
1699			     unsigned status_flags, char *result, unsigned maxlen)
1700{
1701	int sz = 0;
1702	unsigned long flags;
1703	struct multipath *m = ti->private;
1704	struct priority_group *pg;
1705	struct pgpath *p;
1706	unsigned pg_num;
1707	char state;
1708
1709	spin_lock_irqsave(&m->lock, flags);
1710
1711	/* Features */
1712	if (type == STATUSTYPE_INFO)
1713		DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1714		       atomic_read(&m->pg_init_count));
1715	else {
1716		DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1717			      (m->pg_init_retries > 0) * 2 +
1718			      (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1719			      test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1720			      (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1721
1722		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1723			DMEMIT("queue_if_no_path ");
1724		if (m->pg_init_retries)
1725			DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1726		if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1727			DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1728		if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1729			DMEMIT("retain_attached_hw_handler ");
1730		if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1731			switch(m->queue_mode) {
1732			case DM_TYPE_BIO_BASED:
1733				DMEMIT("queue_mode bio ");
1734				break;
 
 
 
1735			default:
1736				WARN_ON_ONCE(true);
1737				break;
1738			}
1739		}
1740	}
1741
1742	if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1743		DMEMIT("0 ");
1744	else
1745		DMEMIT("1 %s ", m->hw_handler_name);
1746
1747	DMEMIT("%u ", m->nr_priority_groups);
1748
1749	if (m->next_pg)
1750		pg_num = m->next_pg->pg_num;
1751	else if (m->current_pg)
1752		pg_num = m->current_pg->pg_num;
1753	else
1754		pg_num = (m->nr_priority_groups ? 1 : 0);
1755
1756	DMEMIT("%u ", pg_num);
1757
1758	switch (type) {
1759	case STATUSTYPE_INFO:
1760		list_for_each_entry(pg, &m->priority_groups, list) {
1761			if (pg->bypassed)
1762				state = 'D';	/* Disabled */
1763			else if (pg == m->current_pg)
1764				state = 'A';	/* Currently Active */
1765			else
1766				state = 'E';	/* Enabled */
1767
1768			DMEMIT("%c ", state);
1769
1770			if (pg->ps.type->status)
1771				sz += pg->ps.type->status(&pg->ps, NULL, type,
1772							  result + sz,
1773							  maxlen - sz);
1774			else
1775				DMEMIT("0 ");
1776
1777			DMEMIT("%u %u ", pg->nr_pgpaths,
1778			       pg->ps.type->info_args);
1779
1780			list_for_each_entry(p, &pg->pgpaths, list) {
1781				DMEMIT("%s %s %u ", p->path.dev->name,
1782				       p->is_active ? "A" : "F",
1783				       p->fail_count);
1784				if (pg->ps.type->status)
1785					sz += pg->ps.type->status(&pg->ps,
1786					      &p->path, type, result + sz,
1787					      maxlen - sz);
1788			}
1789		}
1790		break;
1791
1792	case STATUSTYPE_TABLE:
1793		list_for_each_entry(pg, &m->priority_groups, list) {
1794			DMEMIT("%s ", pg->ps.type->name);
1795
1796			if (pg->ps.type->status)
1797				sz += pg->ps.type->status(&pg->ps, NULL, type,
1798							  result + sz,
1799							  maxlen - sz);
1800			else
1801				DMEMIT("0 ");
1802
1803			DMEMIT("%u %u ", pg->nr_pgpaths,
1804			       pg->ps.type->table_args);
1805
1806			list_for_each_entry(p, &pg->pgpaths, list) {
1807				DMEMIT("%s ", p->path.dev->name);
1808				if (pg->ps.type->status)
1809					sz += pg->ps.type->status(&pg->ps,
1810					      &p->path, type, result + sz,
1811					      maxlen - sz);
1812			}
1813		}
1814		break;
1815	}
1816
1817	spin_unlock_irqrestore(&m->lock, flags);
1818}
1819
1820static int multipath_message(struct dm_target *ti, unsigned argc, char **argv,
1821			     char *result, unsigned maxlen)
1822{
1823	int r = -EINVAL;
1824	struct dm_dev *dev;
1825	struct multipath *m = ti->private;
1826	action_fn action;
1827
1828	mutex_lock(&m->work_mutex);
1829
1830	if (dm_suspended(ti)) {
1831		r = -EBUSY;
1832		goto out;
1833	}
1834
1835	if (argc == 1) {
1836		if (!strcasecmp(argv[0], "queue_if_no_path")) {
1837			r = queue_if_no_path(m, true, false);
1838			goto out;
1839		} else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1840			r = queue_if_no_path(m, false, false);
1841			goto out;
1842		}
1843	}
1844
1845	if (argc != 2) {
1846		DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1847		goto out;
1848	}
1849
1850	if (!strcasecmp(argv[0], "disable_group")) {
1851		r = bypass_pg_num(m, argv[1], true);
1852		goto out;
1853	} else if (!strcasecmp(argv[0], "enable_group")) {
1854		r = bypass_pg_num(m, argv[1], false);
1855		goto out;
1856	} else if (!strcasecmp(argv[0], "switch_group")) {
1857		r = switch_pg_num(m, argv[1]);
1858		goto out;
1859	} else if (!strcasecmp(argv[0], "reinstate_path"))
1860		action = reinstate_path;
1861	else if (!strcasecmp(argv[0], "fail_path"))
1862		action = fail_path;
1863	else {
1864		DMWARN("Unrecognised multipath message received: %s", argv[0]);
1865		goto out;
1866	}
1867
1868	r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1869	if (r) {
1870		DMWARN("message: error getting device %s",
1871		       argv[1]);
1872		goto out;
1873	}
1874
1875	r = action_dev(m, dev, action);
1876
1877	dm_put_device(ti, dev);
1878
1879out:
1880	mutex_unlock(&m->work_mutex);
1881	return r;
1882}
1883
1884static int multipath_prepare_ioctl(struct dm_target *ti,
1885				   struct block_device **bdev)
1886{
1887	struct multipath *m = ti->private;
1888	struct pgpath *current_pgpath;
1889	int r;
1890
1891	current_pgpath = READ_ONCE(m->current_pgpath);
1892	if (!current_pgpath)
1893		current_pgpath = choose_pgpath(m, 0);
1894
1895	if (current_pgpath) {
1896		if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1897			*bdev = current_pgpath->path.dev->bdev;
1898			r = 0;
1899		} else {
1900			/* pg_init has not started or completed */
1901			r = -ENOTCONN;
1902		}
1903	} else {
1904		/* No path is available */
1905		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1906			r = -ENOTCONN;
1907		else
1908			r = -EIO;
1909	}
1910
1911	if (r == -ENOTCONN) {
1912		if (!READ_ONCE(m->current_pg)) {
1913			/* Path status changed, redo selection */
1914			(void) choose_pgpath(m, 0);
1915		}
1916		if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1917			pg_init_all_paths(m);
1918		dm_table_run_md_queue_async(m->ti->table);
1919		process_queued_io_list(m);
1920	}
1921
1922	/*
1923	 * Only pass ioctls through if the device sizes match exactly.
1924	 */
1925	if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1926		return 1;
1927	return r;
1928}
1929
1930static int multipath_iterate_devices(struct dm_target *ti,
1931				     iterate_devices_callout_fn fn, void *data)
1932{
1933	struct multipath *m = ti->private;
1934	struct priority_group *pg;
1935	struct pgpath *p;
1936	int ret = 0;
1937
1938	list_for_each_entry(pg, &m->priority_groups, list) {
1939		list_for_each_entry(p, &pg->pgpaths, list) {
1940			ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1941			if (ret)
1942				goto out;
1943		}
1944	}
1945
1946out:
1947	return ret;
1948}
1949
1950static int pgpath_busy(struct pgpath *pgpath)
1951{
1952	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1953
1954	return blk_lld_busy(q);
1955}
1956
1957/*
1958 * We return "busy", only when we can map I/Os but underlying devices
1959 * are busy (so even if we map I/Os now, the I/Os will wait on
1960 * the underlying queue).
1961 * In other words, if we want to kill I/Os or queue them inside us
1962 * due to map unavailability, we don't return "busy".  Otherwise,
1963 * dm core won't give us the I/Os and we can't do what we want.
1964 */
1965static int multipath_busy(struct dm_target *ti)
1966{
1967	bool busy = false, has_active = false;
1968	struct multipath *m = ti->private;
1969	struct priority_group *pg, *next_pg;
1970	struct pgpath *pgpath;
1971
1972	/* pg_init in progress */
1973	if (atomic_read(&m->pg_init_in_progress))
1974		return true;
1975
1976	/* no paths available, for blk-mq: rely on IO mapping to delay requeue */
1977	if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1978		return (m->queue_mode != DM_TYPE_REQUEST_BASED);
1979
1980	/* Guess which priority_group will be used at next mapping time */
1981	pg = READ_ONCE(m->current_pg);
1982	next_pg = READ_ONCE(m->next_pg);
1983	if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
1984		pg = next_pg;
1985
1986	if (!pg) {
1987		/*
1988		 * We don't know which pg will be used at next mapping time.
1989		 * We don't call choose_pgpath() here to avoid to trigger
1990		 * pg_init just by busy checking.
1991		 * So we don't know whether underlying devices we will be using
1992		 * at next mapping time are busy or not. Just try mapping.
1993		 */
1994		return busy;
1995	}
1996
1997	/*
1998	 * If there is one non-busy active path at least, the path selector
1999	 * will be able to select it. So we consider such a pg as not busy.
2000	 */
2001	busy = true;
2002	list_for_each_entry(pgpath, &pg->pgpaths, list) {
2003		if (pgpath->is_active) {
2004			has_active = true;
2005			if (!pgpath_busy(pgpath)) {
2006				busy = false;
2007				break;
2008			}
2009		}
2010	}
2011
2012	if (!has_active) {
2013		/*
2014		 * No active path in this pg, so this pg won't be used and
2015		 * the current_pg will be changed at next mapping time.
2016		 * We need to try mapping to determine it.
2017		 */
2018		busy = false;
2019	}
2020
2021	return busy;
2022}
2023
2024/*-----------------------------------------------------------------
2025 * Module setup
2026 *---------------------------------------------------------------*/
2027static struct target_type multipath_target = {
2028	.name = "multipath",
2029	.version = {1, 13, 0},
2030	.features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2031		    DM_TARGET_PASSES_INTEGRITY,
2032	.module = THIS_MODULE,
2033	.ctr = multipath_ctr,
2034	.dtr = multipath_dtr,
2035	.clone_and_map_rq = multipath_clone_and_map,
2036	.release_clone_rq = multipath_release_clone,
2037	.rq_end_io = multipath_end_io,
2038	.map = multipath_map_bio,
2039	.end_io = multipath_end_io_bio,
2040	.presuspend = multipath_presuspend,
2041	.postsuspend = multipath_postsuspend,
2042	.resume = multipath_resume,
2043	.status = multipath_status,
2044	.message = multipath_message,
2045	.prepare_ioctl = multipath_prepare_ioctl,
2046	.iterate_devices = multipath_iterate_devices,
2047	.busy = multipath_busy,
2048};
2049
2050static int __init dm_multipath_init(void)
2051{
2052	int r;
2053
2054	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2055	if (!kmultipathd) {
2056		DMERR("failed to create workqueue kmpathd");
2057		r = -ENOMEM;
2058		goto bad_alloc_kmultipathd;
2059	}
2060
2061	/*
2062	 * A separate workqueue is used to handle the device handlers
2063	 * to avoid overloading existing workqueue. Overloading the
2064	 * old workqueue would also create a bottleneck in the
2065	 * path of the storage hardware device activation.
2066	 */
2067	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2068						  WQ_MEM_RECLAIM);
2069	if (!kmpath_handlerd) {
2070		DMERR("failed to create workqueue kmpath_handlerd");
2071		r = -ENOMEM;
2072		goto bad_alloc_kmpath_handlerd;
2073	}
2074
2075	r = dm_register_target(&multipath_target);
2076	if (r < 0) {
2077		DMERR("request-based register failed %d", r);
2078		r = -EINVAL;
2079		goto bad_register_target;
2080	}
2081
2082	return 0;
2083
2084bad_register_target:
2085	destroy_workqueue(kmpath_handlerd);
2086bad_alloc_kmpath_handlerd:
2087	destroy_workqueue(kmultipathd);
2088bad_alloc_kmultipathd:
2089	return r;
2090}
2091
2092static void __exit dm_multipath_exit(void)
2093{
2094	destroy_workqueue(kmpath_handlerd);
2095	destroy_workqueue(kmultipathd);
2096
2097	dm_unregister_target(&multipath_target);
2098}
2099
2100module_init(dm_multipath_init);
2101module_exit(dm_multipath_exit);
2102
2103MODULE_DESCRIPTION(DM_NAME " multipath target");
2104MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2105MODULE_LICENSE("GPL");