1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * Copyright (C) 2003 Sistina Software Limited.
   4 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   5 *
   6 * This file is released under the GPL.
   7 */
   8
   9#include <linux/device-mapper.h>
  10
  11#include "dm-rq.h"
  12#include "dm-bio-record.h"
  13#include "dm-path-selector.h"
  14#include "dm-uevent.h"
  15
  16#include <linux/blkdev.h>
  17#include <linux/ctype.h>
  18#include <linux/init.h>
  19#include <linux/mempool.h>
  20#include <linux/module.h>
  21#include <linux/pagemap.h>
  22#include <linux/slab.h>
  23#include <linux/time.h>
  24#include <linux/timer.h>
  25#include <linux/workqueue.h>
  26#include <linux/delay.h>
  27#include <scsi/scsi_dh.h>
  28#include <linux/atomic.h>
  29#include <linux/blk-mq.h>
  30
  31static struct workqueue_struct *dm_mpath_wq;
  32
  33#define DM_MSG_PREFIX "multipath"
  34#define DM_PG_INIT_DELAY_MSECS 2000
  35#define DM_PG_INIT_DELAY_DEFAULT ((unsigned int) -1)
  36#define QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT 0
  37
  38static unsigned long queue_if_no_path_timeout_secs = QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT;
  39
  40/* Path properties */
  41struct pgpath {
  42	struct list_head list;
  43
  44	struct priority_group *pg;	/* Owning PG */
  45	unsigned int fail_count;		/* Cumulative failure count */
  46
  47	struct dm_path path;
  48	struct delayed_work activate_path;
  49
  50	bool is_active:1;		/* Path status */
  51};
  52
  53#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  54
  55/*
  56 * Paths are grouped into Priority Groups and numbered from 1 upwards.
  57 * Each has a path selector which controls which path gets used.
  58 */
  59struct priority_group {
  60	struct list_head list;
  61
  62	struct multipath *m;		/* Owning multipath instance */
  63	struct path_selector ps;
  64
  65	unsigned int pg_num;		/* Reference number */
  66	unsigned int nr_pgpaths;		/* Number of paths in PG */
  67	struct list_head pgpaths;
  68
  69	bool bypassed:1;		/* Temporarily bypass this PG? */
  70};
  71
  72/* Multipath context */
  73struct multipath {
  74	unsigned long flags;		/* Multipath state flags */
  75
  76	spinlock_t lock;
  77	enum dm_queue_mode queue_mode;
  78
  79	struct pgpath *current_pgpath;
  80	struct priority_group *current_pg;
  81	struct priority_group *next_pg;	/* Switch to this PG if set */
  82
  83	atomic_t nr_valid_paths;	/* Total number of usable paths */
  84	unsigned int nr_priority_groups;
  85	struct list_head priority_groups;
  86
  87	const char *hw_handler_name;
  88	char *hw_handler_params;
  89	wait_queue_head_t pg_init_wait;	/* Wait for pg_init completion */
  90	unsigned int pg_init_retries;	/* Number of times to retry pg_init */
  91	unsigned int pg_init_delay_msecs;	/* Number of msecs before pg_init retry */
  92	atomic_t pg_init_in_progress;	/* Only one pg_init allowed at once */
  93	atomic_t pg_init_count;		/* Number of times pg_init called */
  94
  95	struct mutex work_mutex;
  96	struct work_struct trigger_event;
  97	struct dm_target *ti;
  98
  99	struct work_struct process_queued_bios;
 100	struct bio_list queued_bios;
 101
 102	struct timer_list nopath_timer;	/* Timeout for queue_if_no_path */
 103};
 104
 105/*
 106 * Context information attached to each io we process.
 107 */
 108struct dm_mpath_io {
 109	struct pgpath *pgpath;
 110	size_t nr_bytes;
 111	u64 start_time_ns;
 112};
 113
 114typedef int (*action_fn) (struct pgpath *pgpath);
 115
 116static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 117static void trigger_event(struct work_struct *work);
 118static void activate_or_offline_path(struct pgpath *pgpath);
 119static void activate_path_work(struct work_struct *work);
 120static void process_queued_bios(struct work_struct *work);
 121static void queue_if_no_path_timeout_work(struct timer_list *t);
 122
 123/*
 124 *-----------------------------------------------
 125 * Multipath state flags.
 126 *-----------------------------------------------
 127 */
 128#define MPATHF_QUEUE_IO 0			/* Must we queue all I/O? */
 129#define MPATHF_QUEUE_IF_NO_PATH 1		/* Queue I/O if last path fails? */
 130#define MPATHF_SAVED_QUEUE_IF_NO_PATH 2		/* Saved state during suspension */
 131#define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3	/* If there's already a hw_handler present, don't change it. */
 132#define MPATHF_PG_INIT_DISABLED 4		/* pg_init is not currently allowed */
 133#define MPATHF_PG_INIT_REQUIRED 5		/* pg_init needs calling? */
 134#define MPATHF_PG_INIT_DELAY_RETRY 6		/* Delay pg_init retry? */
 135
 136static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
 137{
 138	bool r = test_bit(MPATHF_bit, &m->flags);
 139
 140	if (r) {
 141		unsigned long flags;
 142
 143		spin_lock_irqsave(&m->lock, flags);
 144		r = test_bit(MPATHF_bit, &m->flags);
 145		spin_unlock_irqrestore(&m->lock, flags);
 146	}
 147
 148	return r;
 149}
 150
 151/*
 152 *-----------------------------------------------
 153 * Allocation routines
 154 *-----------------------------------------------
 155 */
 156static struct pgpath *alloc_pgpath(void)
 157{
 158	struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 159
 160	if (!pgpath)
 161		return NULL;
 162
 163	pgpath->is_active = true;
 164
 165	return pgpath;
 166}
 167
 168static void free_pgpath(struct pgpath *pgpath)
 169{
 170	kfree(pgpath);
 171}
 172
 173static struct priority_group *alloc_priority_group(void)
 174{
 175	struct priority_group *pg;
 176
 177	pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 178
 179	if (pg)
 180		INIT_LIST_HEAD(&pg->pgpaths);
 181
 182	return pg;
 183}
 184
 185static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 186{
 187	struct pgpath *pgpath, *tmp;
 188
 189	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 190		list_del(&pgpath->list);
 191		dm_put_device(ti, pgpath->path.dev);
 192		free_pgpath(pgpath);
 193	}
 194}
 195
 196static void free_priority_group(struct priority_group *pg,
 197				struct dm_target *ti)
 198{
 199	struct path_selector *ps = &pg->ps;
 200
 201	if (ps->type) {
 202		ps->type->destroy(ps);
 203		dm_put_path_selector(ps->type);
 204	}
 205
 206	free_pgpaths(&pg->pgpaths, ti);
 207	kfree(pg);
 208}
 209
 210static struct multipath *alloc_multipath(struct dm_target *ti)
 211{
 212	struct multipath *m;
 213
 214	m = kzalloc(sizeof(*m), GFP_KERNEL);
 215	if (m) {
 216		INIT_LIST_HEAD(&m->priority_groups);
 217		spin_lock_init(&m->lock);
 218		atomic_set(&m->nr_valid_paths, 0);
 219		INIT_WORK(&m->trigger_event, trigger_event);
 220		mutex_init(&m->work_mutex);
 221
 222		m->queue_mode = DM_TYPE_NONE;
 223
 224		m->ti = ti;
 225		ti->private = m;
 226
 227		timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
 228	}
 229
 230	return m;
 231}
 232
 233static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
 234{
 235	if (m->queue_mode == DM_TYPE_NONE) {
 236		m->queue_mode = DM_TYPE_REQUEST_BASED;
 237	} else if (m->queue_mode == DM_TYPE_BIO_BASED) {
 238		INIT_WORK(&m->process_queued_bios, process_queued_bios);
 239		/*
 240		 * bio-based doesn't support any direct scsi_dh management;
 241		 * it just discovers if a scsi_dh is attached.
 242		 */
 243		set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
 244	}
 245
 246	dm_table_set_type(ti->table, m->queue_mode);
 247
 248	/*
 249	 * Init fields that are only used when a scsi_dh is attached
 250	 * - must do this unconditionally (really doesn't hurt non-SCSI uses)
 251	 */
 252	set_bit(MPATHF_QUEUE_IO, &m->flags);
 253	atomic_set(&m->pg_init_in_progress, 0);
 254	atomic_set(&m->pg_init_count, 0);
 255	m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 256	init_waitqueue_head(&m->pg_init_wait);
 257
 258	return 0;
 259}
 260
 261static void free_multipath(struct multipath *m)
 262{
 263	struct priority_group *pg, *tmp;
 264
 265	list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 266		list_del(&pg->list);
 267		free_priority_group(pg, m->ti);
 268	}
 269
 270	kfree(m->hw_handler_name);
 271	kfree(m->hw_handler_params);
 272	mutex_destroy(&m->work_mutex);
 273	kfree(m);
 274}
 275
 276static struct dm_mpath_io *get_mpio(union map_info *info)
 277{
 278	return info->ptr;
 279}
 280
 281static size_t multipath_per_bio_data_size(void)
 282{
 283	return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
 284}
 285
 286static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
 287{
 288	return dm_per_bio_data(bio, multipath_per_bio_data_size());
 289}
 290
 291static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
 292{
 293	/* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
 294	void *bio_details = mpio + 1;
 295	return bio_details;
 296}
 297
 298static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
 299{
 300	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 301	struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
 302
 303	mpio->nr_bytes = bio->bi_iter.bi_size;
 304	mpio->pgpath = NULL;
 305	mpio->start_time_ns = 0;
 306	*mpio_p = mpio;
 307
 308	dm_bio_record(bio_details, bio);
 309}
 310
 311/*
 312 *-----------------------------------------------
 313 * Path selection
 314 *-----------------------------------------------
 315 */
 316static int __pg_init_all_paths(struct multipath *m)
 317{
 318	struct pgpath *pgpath;
 319	unsigned long pg_init_delay = 0;
 320
 321	lockdep_assert_held(&m->lock);
 322
 323	if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
 324		return 0;
 325
 326	atomic_inc(&m->pg_init_count);
 327	clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 328
 329	/* Check here to reset pg_init_required */
 330	if (!m->current_pg)
 331		return 0;
 332
 333	if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
 334		pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 335						 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 336	list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 337		/* Skip failed paths */
 338		if (!pgpath->is_active)
 339			continue;
 340		if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 341				       pg_init_delay))
 342			atomic_inc(&m->pg_init_in_progress);
 343	}
 344	return atomic_read(&m->pg_init_in_progress);
 345}
 346
 347static int pg_init_all_paths(struct multipath *m)
 348{
 349	int ret;
 350	unsigned long flags;
 351
 352	spin_lock_irqsave(&m->lock, flags);
 353	ret = __pg_init_all_paths(m);
 354	spin_unlock_irqrestore(&m->lock, flags);
 355
 356	return ret;
 357}
 358
 359static void __switch_pg(struct multipath *m, struct priority_group *pg)
 360{
 361	lockdep_assert_held(&m->lock);
 362
 363	m->current_pg = pg;
 364
 365	/* Must we initialise the PG first, and queue I/O till it's ready? */
 366	if (m->hw_handler_name) {
 367		set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 368		set_bit(MPATHF_QUEUE_IO, &m->flags);
 369	} else {
 370		clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
 371		clear_bit(MPATHF_QUEUE_IO, &m->flags);
 372	}
 373
 374	atomic_set(&m->pg_init_count, 0);
 375}
 376
 377static struct pgpath *choose_path_in_pg(struct multipath *m,
 378					struct priority_group *pg,
 379					size_t nr_bytes)
 380{
 381	unsigned long flags;
 382	struct dm_path *path;
 383	struct pgpath *pgpath;
 384
 385	path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 386	if (!path)
 387		return ERR_PTR(-ENXIO);
 388
 389	pgpath = path_to_pgpath(path);
 390
 391	if (unlikely(READ_ONCE(m->current_pg) != pg)) {
 392		/* Only update current_pgpath if pg changed */
 393		spin_lock_irqsave(&m->lock, flags);
 394		m->current_pgpath = pgpath;
 395		__switch_pg(m, pg);
 396		spin_unlock_irqrestore(&m->lock, flags);
 397	}
 398
 399	return pgpath;
 400}
 401
 402static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
 403{
 404	unsigned long flags;
 405	struct priority_group *pg;
 406	struct pgpath *pgpath;
 407	unsigned int bypassed = 1;
 408
 409	if (!atomic_read(&m->nr_valid_paths)) {
 410		spin_lock_irqsave(&m->lock, flags);
 411		clear_bit(MPATHF_QUEUE_IO, &m->flags);
 412		spin_unlock_irqrestore(&m->lock, flags);
 413		goto failed;
 414	}
 415
 416	/* Were we instructed to switch PG? */
 417	if (READ_ONCE(m->next_pg)) {
 418		spin_lock_irqsave(&m->lock, flags);
 419		pg = m->next_pg;
 420		if (!pg) {
 421			spin_unlock_irqrestore(&m->lock, flags);
 422			goto check_current_pg;
 423		}
 424		m->next_pg = NULL;
 425		spin_unlock_irqrestore(&m->lock, flags);
 426		pgpath = choose_path_in_pg(m, pg, nr_bytes);
 427		if (!IS_ERR_OR_NULL(pgpath))
 428			return pgpath;
 429	}
 430
 431	/* Don't change PG until it has no remaining paths */
 432check_current_pg:
 433	pg = READ_ONCE(m->current_pg);
 434	if (pg) {
 435		pgpath = choose_path_in_pg(m, pg, nr_bytes);
 436		if (!IS_ERR_OR_NULL(pgpath))
 437			return pgpath;
 438	}
 439
 440	/*
 441	 * Loop through priority groups until we find a valid path.
 442	 * First time we skip PGs marked 'bypassed'.
 443	 * Second time we only try the ones we skipped, but set
 444	 * pg_init_delay_retry so we do not hammer controllers.
 445	 */
 446	do {
 447		list_for_each_entry(pg, &m->priority_groups, list) {
 448			if (pg->bypassed == !!bypassed)
 449				continue;
 450			pgpath = choose_path_in_pg(m, pg, nr_bytes);
 451			if (!IS_ERR_OR_NULL(pgpath)) {
 452				if (!bypassed) {
 453					spin_lock_irqsave(&m->lock, flags);
 454					set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
 455					spin_unlock_irqrestore(&m->lock, flags);
 456				}
 457				return pgpath;
 458			}
 459		}
 460	} while (bypassed--);
 461
 462failed:
 463	spin_lock_irqsave(&m->lock, flags);
 464	m->current_pgpath = NULL;
 465	m->current_pg = NULL;
 466	spin_unlock_irqrestore(&m->lock, flags);
 467
 468	return NULL;
 469}
 470
 471/*
 472 * dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
 473 * report the function name and line number of the function from which
 474 * it has been invoked.
 475 */
 476#define dm_report_EIO(m)						\
 477	DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
 478		      dm_table_device_name((m)->ti->table),		\
 479		      test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags),	\
 480		      test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
 481		      dm_noflush_suspending((m)->ti))
 482
 483/*
 484 * Check whether bios must be queued in the device-mapper core rather
 485 * than here in the target.
 486 */
 487static bool __must_push_back(struct multipath *m)
 488{
 489	return dm_noflush_suspending(m->ti);
 490}
 491
 492static bool must_push_back_rq(struct multipath *m)
 493{
 494	unsigned long flags;
 495	bool ret;
 496
 497	spin_lock_irqsave(&m->lock, flags);
 498	ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
 499	spin_unlock_irqrestore(&m->lock, flags);
 500
 501	return ret;
 502}
 503
 504/*
 505 * Map cloned requests (request-based multipath)
 506 */
 507static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 508				   union map_info *map_context,
 509				   struct request **__clone)
 510{
 511	struct multipath *m = ti->private;
 512	size_t nr_bytes = blk_rq_bytes(rq);
 513	struct pgpath *pgpath;
 514	struct block_device *bdev;
 515	struct dm_mpath_io *mpio = get_mpio(map_context);
 516	struct request_queue *q;
 517	struct request *clone;
 518
 519	/* Do we need to select a new pgpath? */
 520	pgpath = READ_ONCE(m->current_pgpath);
 521	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 522		pgpath = choose_pgpath(m, nr_bytes);
 523
 524	if (!pgpath) {
 525		if (must_push_back_rq(m))
 526			return DM_MAPIO_DELAY_REQUEUE;
 527		dm_report_EIO(m);	/* Failed */
 528		return DM_MAPIO_KILL;
 529	} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 530		   mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 531		pg_init_all_paths(m);
 532		return DM_MAPIO_DELAY_REQUEUE;
 533	}
 534
 535	mpio->pgpath = pgpath;
 536	mpio->nr_bytes = nr_bytes;
 537
 538	bdev = pgpath->path.dev->bdev;
 539	q = bdev_get_queue(bdev);
 540	clone = blk_mq_alloc_request(q, rq->cmd_flags | REQ_NOMERGE,
 541			BLK_MQ_REQ_NOWAIT);
 542	if (IS_ERR(clone)) {
 543		/* EBUSY, ENODEV or EWOULDBLOCK: requeue */
 544		if (blk_queue_dying(q)) {
 545			atomic_inc(&m->pg_init_in_progress);
 546			activate_or_offline_path(pgpath);
 547			return DM_MAPIO_DELAY_REQUEUE;
 548		}
 549
 550		/*
 551		 * blk-mq's SCHED_RESTART can cover this requeue, so we
 552		 * needn't deal with it by DELAY_REQUEUE. More importantly,
 553		 * we have to return DM_MAPIO_REQUEUE so that blk-mq can
 554		 * get the queue busy feedback (via BLK_STS_RESOURCE),
 555		 * otherwise I/O merging can suffer.
 556		 */
 557		return DM_MAPIO_REQUEUE;
 558	}
 559	clone->bio = clone->biotail = NULL;
 560	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 561	*__clone = clone;
 562
 563	if (pgpath->pg->ps.type->start_io)
 564		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 565					      &pgpath->path,
 566					      nr_bytes);
 567	return DM_MAPIO_REMAPPED;
 568}
 569
 570static void multipath_release_clone(struct request *clone,
 571				    union map_info *map_context)
 572{
 573	if (unlikely(map_context)) {
 574		/*
 575		 * non-NULL map_context means caller is still map
 576		 * method; must undo multipath_clone_and_map()
 577		 */
 578		struct dm_mpath_io *mpio = get_mpio(map_context);
 579		struct pgpath *pgpath = mpio->pgpath;
 580
 581		if (pgpath && pgpath->pg->ps.type->end_io)
 582			pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
 583						    &pgpath->path,
 584						    mpio->nr_bytes,
 585						    clone->io_start_time_ns);
 586	}
 587
 588	blk_mq_free_request(clone);
 589}
 590
 591/*
 592 * Map cloned bios (bio-based multipath)
 593 */
 594
 595static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
 596{
 597	/* Queue for the daemon to resubmit */
 598	bio_list_add(&m->queued_bios, bio);
 599	if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
 600		queue_work(kmultipathd, &m->process_queued_bios);
 601}
 602
 603static void multipath_queue_bio(struct multipath *m, struct bio *bio)
 604{
 605	unsigned long flags;
 606
 607	spin_lock_irqsave(&m->lock, flags);
 608	__multipath_queue_bio(m, bio);
 609	spin_unlock_irqrestore(&m->lock, flags);
 610}
 611
 612static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
 613{
 614	struct pgpath *pgpath;
 615	unsigned long flags;
 616
 617	/* Do we need to select a new pgpath? */
 618	pgpath = READ_ONCE(m->current_pgpath);
 619	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
 620		pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
 621
 622	if (!pgpath) {
 623		spin_lock_irqsave(&m->lock, flags);
 624		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 625			__multipath_queue_bio(m, bio);
 626			pgpath = ERR_PTR(-EAGAIN);
 627		}
 628		spin_unlock_irqrestore(&m->lock, flags);
 629
 630	} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
 631		   mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
 632		multipath_queue_bio(m, bio);
 633		pg_init_all_paths(m);
 634		return ERR_PTR(-EAGAIN);
 635	}
 636
 637	return pgpath;
 638}
 639
 640static int __multipath_map_bio(struct multipath *m, struct bio *bio,
 641			       struct dm_mpath_io *mpio)
 642{
 643	struct pgpath *pgpath = __map_bio(m, bio);
 644
 645	if (IS_ERR(pgpath))
 646		return DM_MAPIO_SUBMITTED;
 647
 648	if (!pgpath) {
 649		if (__must_push_back(m))
 650			return DM_MAPIO_REQUEUE;
 651		dm_report_EIO(m);
 652		return DM_MAPIO_KILL;
 653	}
 654
 655	mpio->pgpath = pgpath;
 656
 657	if (dm_ps_use_hr_timer(pgpath->pg->ps.type))
 658		mpio->start_time_ns = ktime_get_ns();
 659
 660	bio->bi_status = 0;
 661	bio_set_dev(bio, pgpath->path.dev->bdev);
 662	bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 663
 664	if (pgpath->pg->ps.type->start_io)
 665		pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 666					      &pgpath->path,
 667					      mpio->nr_bytes);
 668	return DM_MAPIO_REMAPPED;
 669}
 670
 671static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
 672{
 673	struct multipath *m = ti->private;
 674	struct dm_mpath_io *mpio = NULL;
 675
 676	multipath_init_per_bio_data(bio, &mpio);
 677	return __multipath_map_bio(m, bio, mpio);
 678}
 679
 680static void process_queued_io_list(struct multipath *m)
 681{
 682	if (m->queue_mode == DM_TYPE_REQUEST_BASED)
 683		dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
 684	else if (m->queue_mode == DM_TYPE_BIO_BASED)
 685		queue_work(kmultipathd, &m->process_queued_bios);
 686}
 687
 688static void process_queued_bios(struct work_struct *work)
 689{
 690	int r;
 691	unsigned long flags;
 692	struct bio *bio;
 693	struct bio_list bios;
 694	struct blk_plug plug;
 695	struct multipath *m =
 696		container_of(work, struct multipath, process_queued_bios);
 697
 698	bio_list_init(&bios);
 699
 700	spin_lock_irqsave(&m->lock, flags);
 701
 702	if (bio_list_empty(&m->queued_bios)) {
 703		spin_unlock_irqrestore(&m->lock, flags);
 704		return;
 705	}
 706
 707	bio_list_merge_init(&bios, &m->queued_bios);
 
 708
 709	spin_unlock_irqrestore(&m->lock, flags);
 710
 711	blk_start_plug(&plug);
 712	while ((bio = bio_list_pop(&bios))) {
 713		struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
 714
 715		dm_bio_restore(get_bio_details_from_mpio(mpio), bio);
 716		r = __multipath_map_bio(m, bio, mpio);
 717		switch (r) {
 718		case DM_MAPIO_KILL:
 719			bio->bi_status = BLK_STS_IOERR;
 720			bio_endio(bio);
 721			break;
 722		case DM_MAPIO_REQUEUE:
 723			bio->bi_status = BLK_STS_DM_REQUEUE;
 724			bio_endio(bio);
 725			break;
 726		case DM_MAPIO_REMAPPED:
 727			submit_bio_noacct(bio);
 728			break;
 729		case DM_MAPIO_SUBMITTED:
 730			break;
 731		default:
 732			WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
 733		}
 734	}
 735	blk_finish_plug(&plug);
 736}
 737
 738/*
 739 * If we run out of usable paths, should we queue I/O or error it?
 740 */
 741static int queue_if_no_path(struct multipath *m, bool f_queue_if_no_path,
 742			    bool save_old_value, const char *caller)
 743{
 744	unsigned long flags;
 745	bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
 746	const char *dm_dev_name = dm_table_device_name(m->ti->table);
 747
 748	DMDEBUG("%s: %s caller=%s f_queue_if_no_path=%d save_old_value=%d",
 749		dm_dev_name, __func__, caller, f_queue_if_no_path, save_old_value);
 750
 751	spin_lock_irqsave(&m->lock, flags);
 752
 753	queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
 754	saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 755
 756	if (save_old_value) {
 757		if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
 758			DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
 759			      dm_dev_name);
 760		} else
 761			assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
 762	} else if (!f_queue_if_no_path && saved_queue_if_no_path_bit) {
 763		/* due to "fail_if_no_path" message, need to honor it. */
 764		clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
 765	}
 766	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, f_queue_if_no_path);
 767
 768	DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
 769		dm_dev_name, __func__,
 770		test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
 771		test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
 772		dm_noflush_suspending(m->ti));
 773
 774	spin_unlock_irqrestore(&m->lock, flags);
 775
 776	if (!f_queue_if_no_path) {
 777		dm_table_run_md_queue_async(m->ti->table);
 778		process_queued_io_list(m);
 779	}
 780
 781	return 0;
 782}
 783
 784/*
 785 * If the queue_if_no_path timeout fires, turn off queue_if_no_path and
 786 * process any queued I/O.
 787 */
 788static void queue_if_no_path_timeout_work(struct timer_list *t)
 789{
 790	struct multipath *m = from_timer(m, t, nopath_timer);
 791
 792	DMWARN("queue_if_no_path timeout on %s, failing queued IO",
 793	       dm_table_device_name(m->ti->table));
 794	queue_if_no_path(m, false, false, __func__);
 795}
 796
 797/*
 798 * Enable the queue_if_no_path timeout if necessary.
 799 * Called with m->lock held.
 800 */
 801static void enable_nopath_timeout(struct multipath *m)
 802{
 803	unsigned long queue_if_no_path_timeout =
 804		READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
 805
 806	lockdep_assert_held(&m->lock);
 807
 808	if (queue_if_no_path_timeout > 0 &&
 809	    atomic_read(&m->nr_valid_paths) == 0 &&
 810	    test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
 811		mod_timer(&m->nopath_timer,
 812			  jiffies + queue_if_no_path_timeout);
 813	}
 814}
 815
 816static void disable_nopath_timeout(struct multipath *m)
 817{
 818	del_timer_sync(&m->nopath_timer);
 819}
 820
 821/*
 822 * An event is triggered whenever a path is taken out of use.
 823 * Includes path failure and PG bypass.
 824 */
 825static void trigger_event(struct work_struct *work)
 826{
 827	struct multipath *m =
 828		container_of(work, struct multipath, trigger_event);
 829
 830	dm_table_event(m->ti->table);
 831}
 832
 833/*
 834 *---------------------------------------------------------------
 835 * Constructor/argument parsing:
 836 * <#multipath feature args> [<arg>]*
 837 * <#hw_handler args> [hw_handler [<arg>]*]
 838 * <#priority groups>
 839 * <initial priority group>
 840 *     [<selector> <#selector args> [<arg>]*
 841 *      <#paths> <#per-path selector args>
 842 *         [<path> [<arg>]* ]+ ]+
 843 *---------------------------------------------------------------
 844 */
 845static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 846			       struct dm_target *ti)
 847{
 848	int r;
 849	struct path_selector_type *pst;
 850	unsigned int ps_argc;
 851
 852	static const struct dm_arg _args[] = {
 853		{0, 1024, "invalid number of path selector args"},
 854	};
 855
 856	pst = dm_get_path_selector(dm_shift_arg(as));
 857	if (!pst) {
 858		ti->error = "unknown path selector type";
 859		return -EINVAL;
 860	}
 861
 862	r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 863	if (r) {
 864		dm_put_path_selector(pst);
 865		return -EINVAL;
 866	}
 867
 868	r = pst->create(&pg->ps, ps_argc, as->argv);
 869	if (r) {
 870		dm_put_path_selector(pst);
 871		ti->error = "path selector constructor failed";
 872		return r;
 873	}
 874
 875	pg->ps.type = pst;
 876	dm_consume_args(as, ps_argc);
 877
 878	return 0;
 879}
 880
 881static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
 882			 const char **attached_handler_name, char **error)
 883{
 884	struct request_queue *q = bdev_get_queue(bdev);
 885	int r;
 886
 887	if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
 888retain:
 889		if (*attached_handler_name) {
 890			/*
 891			 * Clear any hw_handler_params associated with a
 892			 * handler that isn't already attached.
 893			 */
 894			if (m->hw_handler_name && strcmp(*attached_handler_name, m->hw_handler_name)) {
 895				kfree(m->hw_handler_params);
 896				m->hw_handler_params = NULL;
 897			}
 898
 899			/*
 900			 * Reset hw_handler_name to match the attached handler
 901			 *
 902			 * NB. This modifies the table line to show the actual
 903			 * handler instead of the original table passed in.
 904			 */
 905			kfree(m->hw_handler_name);
 906			m->hw_handler_name = *attached_handler_name;
 907			*attached_handler_name = NULL;
 908		}
 909	}
 910
 911	if (m->hw_handler_name) {
 912		r = scsi_dh_attach(q, m->hw_handler_name);
 913		if (r == -EBUSY) {
 914			DMINFO("retaining handler on device %pg", bdev);
 915			goto retain;
 916		}
 917		if (r < 0) {
 918			*error = "error attaching hardware handler";
 919			return r;
 920		}
 921
 922		if (m->hw_handler_params) {
 923			r = scsi_dh_set_params(q, m->hw_handler_params);
 924			if (r < 0) {
 925				*error = "unable to set hardware handler parameters";
 926				return r;
 927			}
 928		}
 929	}
 930
 931	return 0;
 932}
 933
 934static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 935				 struct dm_target *ti)
 936{
 937	int r;
 938	struct pgpath *p;
 939	struct multipath *m = ti->private;
 940	struct request_queue *q;
 941	const char *attached_handler_name = NULL;
 942
 943	/* we need at least a path arg */
 944	if (as->argc < 1) {
 945		ti->error = "no device given";
 946		return ERR_PTR(-EINVAL);
 947	}
 948
 949	p = alloc_pgpath();
 950	if (!p)
 951		return ERR_PTR(-ENOMEM);
 952
 953	r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 954			  &p->path.dev);
 955	if (r) {
 956		ti->error = "error getting device";
 957		goto bad;
 958	}
 959
 960	q = bdev_get_queue(p->path.dev->bdev);
 961	attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 962	if (attached_handler_name || m->hw_handler_name) {
 963		INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
 964		r = setup_scsi_dh(p->path.dev->bdev, m, &attached_handler_name, &ti->error);
 965		kfree(attached_handler_name);
 966		if (r) {
 967			dm_put_device(ti, p->path.dev);
 968			goto bad;
 969		}
 970	}
 971
 972	r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 973	if (r) {
 974		dm_put_device(ti, p->path.dev);
 975		goto bad;
 976	}
 977
 978	return p;
 979 bad:
 980	free_pgpath(p);
 981	return ERR_PTR(r);
 982}
 983
 984static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 985						   struct multipath *m)
 986{
 987	static const struct dm_arg _args[] = {
 988		{1, 1024, "invalid number of paths"},
 989		{0, 1024, "invalid number of selector args"}
 990	};
 991
 992	int r;
 993	unsigned int i, nr_selector_args, nr_args;
 994	struct priority_group *pg;
 995	struct dm_target *ti = m->ti;
 996
 997	if (as->argc < 2) {
 998		as->argc = 0;
 999		ti->error = "not enough priority group arguments";
1000		return ERR_PTR(-EINVAL);
1001	}
1002
1003	pg = alloc_priority_group();
1004	if (!pg) {
1005		ti->error = "couldn't allocate priority group";
1006		return ERR_PTR(-ENOMEM);
1007	}
1008	pg->m = m;
1009
1010	r = parse_path_selector(as, pg, ti);
1011	if (r)
1012		goto bad;
1013
1014	/*
1015	 * read the paths
1016	 */
1017	r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
1018	if (r)
1019		goto bad;
1020
1021	r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
1022	if (r)
1023		goto bad;
1024
1025	nr_args = 1 + nr_selector_args;
1026	for (i = 0; i < pg->nr_pgpaths; i++) {
1027		struct pgpath *pgpath;
1028		struct dm_arg_set path_args;
1029
1030		if (as->argc < nr_args) {
1031			ti->error = "not enough path parameters";
1032			r = -EINVAL;
1033			goto bad;
1034		}
1035
1036		path_args.argc = nr_args;
1037		path_args.argv = as->argv;
1038
1039		pgpath = parse_path(&path_args, &pg->ps, ti);
1040		if (IS_ERR(pgpath)) {
1041			r = PTR_ERR(pgpath);
1042			goto bad;
1043		}
1044
1045		pgpath->pg = pg;
1046		list_add_tail(&pgpath->list, &pg->pgpaths);
1047		dm_consume_args(as, nr_args);
1048	}
1049
1050	return pg;
1051
1052 bad:
1053	free_priority_group(pg, ti);
1054	return ERR_PTR(r);
1055}
1056
1057static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1058{
1059	unsigned int hw_argc;
1060	int ret;
1061	struct dm_target *ti = m->ti;
1062
1063	static const struct dm_arg _args[] = {
1064		{0, 1024, "invalid number of hardware handler args"},
1065	};
1066
1067	if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
1068		return -EINVAL;
1069
1070	if (!hw_argc)
1071		return 0;
1072
1073	if (m->queue_mode == DM_TYPE_BIO_BASED) {
1074		dm_consume_args(as, hw_argc);
1075		DMERR("bio-based multipath doesn't allow hardware handler args");
1076		return 0;
1077	}
1078
1079	m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1080	if (!m->hw_handler_name)
1081		return -EINVAL;
1082
1083	if (hw_argc > 1) {
1084		char *p;
1085		int i, j, len = 4;
1086
1087		for (i = 0; i <= hw_argc - 2; i++)
1088			len += strlen(as->argv[i]) + 1;
1089		p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1090		if (!p) {
1091			ti->error = "memory allocation failed";
1092			ret = -ENOMEM;
1093			goto fail;
1094		}
1095		j = sprintf(p, "%d", hw_argc - 1);
1096		for (i = 0, p += j + 1; i <= hw_argc - 2; i++, p += j + 1)
1097			j = sprintf(p, "%s", as->argv[i]);
1098	}
1099	dm_consume_args(as, hw_argc - 1);
1100
1101	return 0;
1102fail:
1103	kfree(m->hw_handler_name);
1104	m->hw_handler_name = NULL;
1105	return ret;
1106}
1107
1108static int parse_features(struct dm_arg_set *as, struct multipath *m)
1109{
1110	int r;
1111	unsigned int argc;
1112	struct dm_target *ti = m->ti;
1113	const char *arg_name;
1114
1115	static const struct dm_arg _args[] = {
1116		{0, 8, "invalid number of feature args"},
1117		{1, 50, "pg_init_retries must be between 1 and 50"},
1118		{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1119	};
1120
1121	r = dm_read_arg_group(_args, as, &argc, &ti->error);
1122	if (r)
1123		return -EINVAL;
1124
1125	if (!argc)
1126		return 0;
1127
1128	do {
1129		arg_name = dm_shift_arg(as);
1130		argc--;
1131
1132		if (!strcasecmp(arg_name, "queue_if_no_path")) {
1133			r = queue_if_no_path(m, true, false, __func__);
1134			continue;
1135		}
1136
1137		if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1138			set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1139			continue;
1140		}
1141
1142		if (!strcasecmp(arg_name, "pg_init_retries") &&
1143		    (argc >= 1)) {
1144			r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1145			argc--;
1146			continue;
1147		}
1148
1149		if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1150		    (argc >= 1)) {
1151			r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1152			argc--;
1153			continue;
1154		}
1155
1156		if (!strcasecmp(arg_name, "queue_mode") &&
1157		    (argc >= 1)) {
1158			const char *queue_mode_name = dm_shift_arg(as);
1159
1160			if (!strcasecmp(queue_mode_name, "bio"))
1161				m->queue_mode = DM_TYPE_BIO_BASED;
1162			else if (!strcasecmp(queue_mode_name, "rq") ||
1163				 !strcasecmp(queue_mode_name, "mq"))
1164				m->queue_mode = DM_TYPE_REQUEST_BASED;
1165			else {
1166				ti->error = "Unknown 'queue_mode' requested";
1167				r = -EINVAL;
1168			}
1169			argc--;
1170			continue;
1171		}
1172
1173		ti->error = "Unrecognised multipath feature request";
1174		r = -EINVAL;
1175	} while (argc && !r);
1176
1177	return r;
1178}
1179
1180static int multipath_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1181{
1182	/* target arguments */
1183	static const struct dm_arg _args[] = {
1184		{0, 1024, "invalid number of priority groups"},
1185		{0, 1024, "invalid initial priority group number"},
1186	};
1187
1188	int r;
1189	struct multipath *m;
1190	struct dm_arg_set as;
1191	unsigned int pg_count = 0;
1192	unsigned int next_pg_num;
1193	unsigned long flags;
1194
1195	as.argc = argc;
1196	as.argv = argv;
1197
1198	m = alloc_multipath(ti);
1199	if (!m) {
1200		ti->error = "can't allocate multipath";
1201		return -EINVAL;
1202	}
1203
1204	r = parse_features(&as, m);
1205	if (r)
1206		goto bad;
1207
1208	r = alloc_multipath_stage2(ti, m);
1209	if (r)
1210		goto bad;
1211
1212	r = parse_hw_handler(&as, m);
1213	if (r)
1214		goto bad;
1215
1216	r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1217	if (r)
1218		goto bad;
1219
1220	r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1221	if (r)
1222		goto bad;
1223
1224	if ((!m->nr_priority_groups && next_pg_num) ||
1225	    (m->nr_priority_groups && !next_pg_num)) {
1226		ti->error = "invalid initial priority group";
1227		r = -EINVAL;
1228		goto bad;
1229	}
1230
1231	/* parse the priority groups */
1232	while (as.argc) {
1233		struct priority_group *pg;
1234		unsigned int nr_valid_paths = atomic_read(&m->nr_valid_paths);
1235
1236		pg = parse_priority_group(&as, m);
1237		if (IS_ERR(pg)) {
1238			r = PTR_ERR(pg);
1239			goto bad;
1240		}
1241
1242		nr_valid_paths += pg->nr_pgpaths;
1243		atomic_set(&m->nr_valid_paths, nr_valid_paths);
1244
1245		list_add_tail(&pg->list, &m->priority_groups);
1246		pg_count++;
1247		pg->pg_num = pg_count;
1248		if (!--next_pg_num)
1249			m->next_pg = pg;
1250	}
1251
1252	if (pg_count != m->nr_priority_groups) {
1253		ti->error = "priority group count mismatch";
1254		r = -EINVAL;
1255		goto bad;
1256	}
1257
1258	spin_lock_irqsave(&m->lock, flags);
1259	enable_nopath_timeout(m);
1260	spin_unlock_irqrestore(&m->lock, flags);
1261
1262	ti->num_flush_bios = 1;
1263	ti->num_discard_bios = 1;
1264	ti->num_write_zeroes_bios = 1;
1265	if (m->queue_mode == DM_TYPE_BIO_BASED)
1266		ti->per_io_data_size = multipath_per_bio_data_size();
1267	else
1268		ti->per_io_data_size = sizeof(struct dm_mpath_io);
1269
1270	return 0;
1271
1272 bad:
1273	free_multipath(m);
1274	return r;
1275}
1276
1277static void multipath_wait_for_pg_init_completion(struct multipath *m)
1278{
1279	DEFINE_WAIT(wait);
1280
1281	while (1) {
1282		prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1283
1284		if (!atomic_read(&m->pg_init_in_progress))
1285			break;
1286
1287		io_schedule();
1288	}
1289	finish_wait(&m->pg_init_wait, &wait);
1290}
1291
1292static void flush_multipath_work(struct multipath *m)
1293{
1294	if (m->hw_handler_name) {
1295		unsigned long flags;
1296
1297		if (!atomic_read(&m->pg_init_in_progress))
1298			goto skip;
1299
1300		spin_lock_irqsave(&m->lock, flags);
1301		if (atomic_read(&m->pg_init_in_progress) &&
1302		    !test_and_set_bit(MPATHF_PG_INIT_DISABLED, &m->flags)) {
1303			spin_unlock_irqrestore(&m->lock, flags);
1304
1305			flush_workqueue(kmpath_handlerd);
1306			multipath_wait_for_pg_init_completion(m);
1307
1308			spin_lock_irqsave(&m->lock, flags);
1309			clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1310		}
1311		spin_unlock_irqrestore(&m->lock, flags);
1312	}
1313skip:
1314	if (m->queue_mode == DM_TYPE_BIO_BASED)
1315		flush_work(&m->process_queued_bios);
1316	flush_work(&m->trigger_event);
1317}
1318
1319static void multipath_dtr(struct dm_target *ti)
1320{
1321	struct multipath *m = ti->private;
1322
1323	disable_nopath_timeout(m);
1324	flush_multipath_work(m);
1325	free_multipath(m);
1326}
1327
1328/*
1329 * Take a path out of use.
1330 */
1331static int fail_path(struct pgpath *pgpath)
1332{
1333	unsigned long flags;
1334	struct multipath *m = pgpath->pg->m;
1335
1336	spin_lock_irqsave(&m->lock, flags);
1337
1338	if (!pgpath->is_active)
1339		goto out;
1340
1341	DMWARN("%s: Failing path %s.",
1342	       dm_table_device_name(m->ti->table),
1343	       pgpath->path.dev->name);
1344
1345	pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1346	pgpath->is_active = false;
1347	pgpath->fail_count++;
1348
1349	atomic_dec(&m->nr_valid_paths);
1350
1351	if (pgpath == m->current_pgpath)
1352		m->current_pgpath = NULL;
1353
1354	dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1355		       pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1356
1357	queue_work(dm_mpath_wq, &m->trigger_event);
1358
1359	enable_nopath_timeout(m);
1360
1361out:
1362	spin_unlock_irqrestore(&m->lock, flags);
1363
1364	return 0;
1365}
1366
1367/*
1368 * Reinstate a previously-failed path
1369 */
1370static int reinstate_path(struct pgpath *pgpath)
1371{
1372	int r = 0, run_queue = 0;
1373	unsigned long flags;
1374	struct multipath *m = pgpath->pg->m;
1375	unsigned int nr_valid_paths;
1376
1377	spin_lock_irqsave(&m->lock, flags);
1378
1379	if (pgpath->is_active)
1380		goto out;
1381
1382	DMWARN("%s: Reinstating path %s.",
1383	       dm_table_device_name(m->ti->table),
1384	       pgpath->path.dev->name);
1385
1386	r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1387	if (r)
1388		goto out;
1389
1390	pgpath->is_active = true;
1391
1392	nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1393	if (nr_valid_paths == 1) {
1394		m->current_pgpath = NULL;
1395		run_queue = 1;
1396	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1397		if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1398			atomic_inc(&m->pg_init_in_progress);
1399	}
1400
1401	dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1402		       pgpath->path.dev->name, nr_valid_paths);
1403
1404	schedule_work(&m->trigger_event);
1405
1406out:
1407	spin_unlock_irqrestore(&m->lock, flags);
1408	if (run_queue) {
1409		dm_table_run_md_queue_async(m->ti->table);
1410		process_queued_io_list(m);
1411	}
1412
1413	if (pgpath->is_active)
1414		disable_nopath_timeout(m);
1415
1416	return r;
1417}
1418
1419/*
1420 * Fail or reinstate all paths that match the provided struct dm_dev.
1421 */
1422static int action_dev(struct multipath *m, dev_t dev, action_fn action)
 
1423{
1424	int r = -EINVAL;
1425	struct pgpath *pgpath;
1426	struct priority_group *pg;
1427
1428	list_for_each_entry(pg, &m->priority_groups, list) {
1429		list_for_each_entry(pgpath, &pg->pgpaths, list) {
1430			if (pgpath->path.dev->bdev->bd_dev == dev)
1431				r = action(pgpath);
1432		}
1433	}
1434
1435	return r;
1436}
1437
1438/*
1439 * Temporarily try to avoid having to use the specified PG
1440 */
1441static void bypass_pg(struct multipath *m, struct priority_group *pg,
1442		      bool bypassed)
1443{
1444	unsigned long flags;
1445
1446	spin_lock_irqsave(&m->lock, flags);
1447
1448	pg->bypassed = bypassed;
1449	m->current_pgpath = NULL;
1450	m->current_pg = NULL;
1451
1452	spin_unlock_irqrestore(&m->lock, flags);
1453
1454	schedule_work(&m->trigger_event);
1455}
1456
1457/*
1458 * Switch to using the specified PG from the next I/O that gets mapped
1459 */
1460static int switch_pg_num(struct multipath *m, const char *pgstr)
1461{
1462	struct priority_group *pg;
1463	unsigned int pgnum;
1464	unsigned long flags;
1465	char dummy;
1466
1467	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1468	    !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1469		DMWARN("invalid PG number supplied to %s", __func__);
1470		return -EINVAL;
1471	}
1472
1473	spin_lock_irqsave(&m->lock, flags);
1474	list_for_each_entry(pg, &m->priority_groups, list) {
1475		pg->bypassed = false;
1476		if (--pgnum)
1477			continue;
1478
1479		m->current_pgpath = NULL;
1480		m->current_pg = NULL;
1481		m->next_pg = pg;
1482	}
1483	spin_unlock_irqrestore(&m->lock, flags);
1484
1485	schedule_work(&m->trigger_event);
1486	return 0;
1487}
1488
1489/*
1490 * Set/clear bypassed status of a PG.
1491 * PGs are numbered upwards from 1 in the order they were declared.
1492 */
1493static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1494{
1495	struct priority_group *pg;
1496	unsigned int pgnum;
1497	char dummy;
1498
1499	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1500	    !m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1501		DMWARN("invalid PG number supplied to bypass_pg");
1502		return -EINVAL;
1503	}
1504
1505	list_for_each_entry(pg, &m->priority_groups, list) {
1506		if (!--pgnum)
1507			break;
1508	}
1509
1510	bypass_pg(m, pg, bypassed);
1511	return 0;
1512}
1513
1514/*
1515 * Should we retry pg_init immediately?
1516 */
1517static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1518{
1519	unsigned long flags;
1520	bool limit_reached = false;
1521
1522	spin_lock_irqsave(&m->lock, flags);
1523
1524	if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1525	    !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1526		set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1527	else
1528		limit_reached = true;
1529
1530	spin_unlock_irqrestore(&m->lock, flags);
1531
1532	return limit_reached;
1533}
1534
1535static void pg_init_done(void *data, int errors)
1536{
1537	struct pgpath *pgpath = data;
1538	struct priority_group *pg = pgpath->pg;
1539	struct multipath *m = pg->m;
1540	unsigned long flags;
1541	bool delay_retry = false;
1542
1543	/* device or driver problems */
1544	switch (errors) {
1545	case SCSI_DH_OK:
1546		break;
1547	case SCSI_DH_NOSYS:
1548		if (!m->hw_handler_name) {
1549			errors = 0;
1550			break;
1551		}
1552		DMERR("Could not failover the device: Handler scsi_dh_%s "
1553		      "Error %d.", m->hw_handler_name, errors);
1554		/*
1555		 * Fail path for now, so we do not ping pong
1556		 */
1557		fail_path(pgpath);
1558		break;
1559	case SCSI_DH_DEV_TEMP_BUSY:
1560		/*
1561		 * Probably doing something like FW upgrade on the
1562		 * controller so try the other pg.
1563		 */
1564		bypass_pg(m, pg, true);
1565		break;
1566	case SCSI_DH_RETRY:
1567		/* Wait before retrying. */
1568		delay_retry = true;
1569		fallthrough;
1570	case SCSI_DH_IMM_RETRY:
1571	case SCSI_DH_RES_TEMP_UNAVAIL:
1572		if (pg_init_limit_reached(m, pgpath))
1573			fail_path(pgpath);
1574		errors = 0;
1575		break;
1576	case SCSI_DH_DEV_OFFLINED:
1577	default:
1578		/*
1579		 * We probably do not want to fail the path for a device
1580		 * error, but this is what the old dm did. In future
1581		 * patches we can do more advanced handling.
1582		 */
1583		fail_path(pgpath);
1584	}
1585
1586	spin_lock_irqsave(&m->lock, flags);
1587	if (errors) {
1588		if (pgpath == m->current_pgpath) {
1589			DMERR("Could not failover device. Error %d.", errors);
1590			m->current_pgpath = NULL;
1591			m->current_pg = NULL;
1592		}
1593	} else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1594		pg->bypassed = false;
1595
1596	if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1597		/* Activations of other paths are still on going */
1598		goto out;
1599
1600	if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1601		if (delay_retry)
1602			set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1603		else
1604			clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1605
1606		if (__pg_init_all_paths(m))
1607			goto out;
1608	}
1609	clear_bit(MPATHF_QUEUE_IO, &m->flags);
1610
1611	process_queued_io_list(m);
1612
1613	/*
1614	 * Wake up any thread waiting to suspend.
1615	 */
1616	wake_up(&m->pg_init_wait);
1617
1618out:
1619	spin_unlock_irqrestore(&m->lock, flags);
1620}
1621
1622static void activate_or_offline_path(struct pgpath *pgpath)
1623{
1624	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1625
1626	if (pgpath->is_active && !blk_queue_dying(q))
1627		scsi_dh_activate(q, pg_init_done, pgpath);
1628	else
1629		pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1630}
1631
1632static void activate_path_work(struct work_struct *work)
1633{
1634	struct pgpath *pgpath =
1635		container_of(work, struct pgpath, activate_path.work);
1636
1637	activate_or_offline_path(pgpath);
1638}
1639
1640static int multipath_end_io(struct dm_target *ti, struct request *clone,
1641			    blk_status_t error, union map_info *map_context)
1642{
1643	struct dm_mpath_io *mpio = get_mpio(map_context);
1644	struct pgpath *pgpath = mpio->pgpath;
1645	int r = DM_ENDIO_DONE;
1646
1647	/*
1648	 * We don't queue any clone request inside the multipath target
1649	 * during end I/O handling, since those clone requests don't have
1650	 * bio clones.  If we queue them inside the multipath target,
1651	 * we need to make bio clones, that requires memory allocation.
1652	 * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1653	 *  don't have bio clones.)
1654	 * Instead of queueing the clone request here, we queue the original
1655	 * request into dm core, which will remake a clone request and
1656	 * clone bios for it and resubmit it later.
1657	 */
1658	if (error && blk_path_error(error)) {
1659		struct multipath *m = ti->private;
1660
1661		if (error == BLK_STS_RESOURCE)
1662			r = DM_ENDIO_DELAY_REQUEUE;
1663		else
1664			r = DM_ENDIO_REQUEUE;
1665
1666		if (pgpath)
1667			fail_path(pgpath);
1668
1669		if (!atomic_read(&m->nr_valid_paths) &&
1670		    !must_push_back_rq(m)) {
1671			if (error == BLK_STS_IOERR)
1672				dm_report_EIO(m);
1673			/* complete with the original error */
1674			r = DM_ENDIO_DONE;
1675		}
1676	}
1677
1678	if (pgpath) {
1679		struct path_selector *ps = &pgpath->pg->ps;
1680
1681		if (ps->type->end_io)
1682			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1683					 clone->io_start_time_ns);
1684	}
1685
1686	return r;
1687}
1688
1689static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1690				blk_status_t *error)
1691{
1692	struct multipath *m = ti->private;
1693	struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1694	struct pgpath *pgpath = mpio->pgpath;
1695	unsigned long flags;
1696	int r = DM_ENDIO_DONE;
1697
1698	if (!*error || !blk_path_error(*error))
1699		goto done;
1700
1701	if (pgpath)
1702		fail_path(pgpath);
1703
1704	if (!atomic_read(&m->nr_valid_paths)) {
1705		spin_lock_irqsave(&m->lock, flags);
1706		if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1707			if (__must_push_back(m)) {
1708				r = DM_ENDIO_REQUEUE;
1709			} else {
1710				dm_report_EIO(m);
1711				*error = BLK_STS_IOERR;
1712			}
1713			spin_unlock_irqrestore(&m->lock, flags);
1714			goto done;
1715		}
1716		spin_unlock_irqrestore(&m->lock, flags);
1717	}
1718
1719	multipath_queue_bio(m, clone);
1720	r = DM_ENDIO_INCOMPLETE;
1721done:
1722	if (pgpath) {
1723		struct path_selector *ps = &pgpath->pg->ps;
1724
1725		if (ps->type->end_io)
1726			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1727					 (mpio->start_time_ns ?:
1728					  dm_start_time_ns_from_clone(clone)));
1729	}
1730
1731	return r;
1732}
1733
1734/*
1735 * Suspend with flush can't complete until all the I/O is processed
1736 * so if the last path fails we must error any remaining I/O.
1737 * - Note that if the freeze_bdev fails while suspending, the
1738 *   queue_if_no_path state is lost - userspace should reset it.
1739 * Otherwise, during noflush suspend, queue_if_no_path will not change.
1740 */
1741static void multipath_presuspend(struct dm_target *ti)
1742{
1743	struct multipath *m = ti->private;
1744
1745	/* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1746	if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(m->ti))
1747		queue_if_no_path(m, false, true, __func__);
1748}
1749
1750static void multipath_postsuspend(struct dm_target *ti)
1751{
1752	struct multipath *m = ti->private;
1753
1754	mutex_lock(&m->work_mutex);
1755	flush_multipath_work(m);
1756	mutex_unlock(&m->work_mutex);
1757}
1758
1759/*
1760 * Restore the queue_if_no_path setting.
1761 */
1762static void multipath_resume(struct dm_target *ti)
1763{
1764	struct multipath *m = ti->private;
1765	unsigned long flags;
1766
1767	spin_lock_irqsave(&m->lock, flags);
1768	if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1769		set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1770		clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
1771	}
1772
1773	DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1774		dm_table_device_name(m->ti->table), __func__,
1775		test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1776		test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1777
1778	spin_unlock_irqrestore(&m->lock, flags);
1779}
1780
1781/*
1782 * Info output has the following format:
1783 * num_multipath_feature_args [multipath_feature_args]*
1784 * num_handler_status_args [handler_status_args]*
1785 * num_groups init_group_number
1786 *            [A|D|E num_ps_status_args [ps_status_args]*
1787 *             num_paths num_selector_args
1788 *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1789 *
1790 * Table output has the following format (identical to the constructor string):
1791 * num_feature_args [features_args]*
1792 * num_handler_args hw_handler [hw_handler_args]*
1793 * num_groups init_group_number
1794 *     [priority selector-name num_ps_args [ps_args]*
1795 *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1796 */
1797static void multipath_status(struct dm_target *ti, status_type_t type,
1798			     unsigned int status_flags, char *result, unsigned int maxlen)
1799{
1800	int sz = 0, pg_counter, pgpath_counter;
1801	unsigned long flags;
1802	struct multipath *m = ti->private;
1803	struct priority_group *pg;
1804	struct pgpath *p;
1805	unsigned int pg_num;
1806	char state;
1807
1808	spin_lock_irqsave(&m->lock, flags);
1809
1810	/* Features */
1811	if (type == STATUSTYPE_INFO)
1812		DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1813		       atomic_read(&m->pg_init_count));
1814	else {
1815		DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1816			      (m->pg_init_retries > 0) * 2 +
1817			      (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1818			      test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1819			      (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1820
1821		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1822			DMEMIT("queue_if_no_path ");
1823		if (m->pg_init_retries)
1824			DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1825		if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1826			DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1827		if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1828			DMEMIT("retain_attached_hw_handler ");
1829		if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1830			switch (m->queue_mode) {
1831			case DM_TYPE_BIO_BASED:
1832				DMEMIT("queue_mode bio ");
1833				break;
1834			default:
1835				WARN_ON_ONCE(true);
1836				break;
1837			}
1838		}
1839	}
1840
1841	if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1842		DMEMIT("0 ");
1843	else
1844		DMEMIT("1 %s ", m->hw_handler_name);
1845
1846	DMEMIT("%u ", m->nr_priority_groups);
1847
1848	if (m->next_pg)
1849		pg_num = m->next_pg->pg_num;
1850	else if (m->current_pg)
1851		pg_num = m->current_pg->pg_num;
1852	else
1853		pg_num = (m->nr_priority_groups ? 1 : 0);
1854
1855	DMEMIT("%u ", pg_num);
1856
1857	switch (type) {
1858	case STATUSTYPE_INFO:
1859		list_for_each_entry(pg, &m->priority_groups, list) {
1860			if (pg->bypassed)
1861				state = 'D';	/* Disabled */
1862			else if (pg == m->current_pg)
1863				state = 'A';	/* Currently Active */
1864			else
1865				state = 'E';	/* Enabled */
1866
1867			DMEMIT("%c ", state);
1868
1869			if (pg->ps.type->status)
1870				sz += pg->ps.type->status(&pg->ps, NULL, type,
1871							  result + sz,
1872							  maxlen - sz);
1873			else
1874				DMEMIT("0 ");
1875
1876			DMEMIT("%u %u ", pg->nr_pgpaths,
1877			       pg->ps.type->info_args);
1878
1879			list_for_each_entry(p, &pg->pgpaths, list) {
1880				DMEMIT("%s %s %u ", p->path.dev->name,
1881				       p->is_active ? "A" : "F",
1882				       p->fail_count);
1883				if (pg->ps.type->status)
1884					sz += pg->ps.type->status(&pg->ps,
1885					      &p->path, type, result + sz,
1886					      maxlen - sz);
1887			}
1888		}
1889		break;
1890
1891	case STATUSTYPE_TABLE:
1892		list_for_each_entry(pg, &m->priority_groups, list) {
1893			DMEMIT("%s ", pg->ps.type->name);
1894
1895			if (pg->ps.type->status)
1896				sz += pg->ps.type->status(&pg->ps, NULL, type,
1897							  result + sz,
1898							  maxlen - sz);
1899			else
1900				DMEMIT("0 ");
1901
1902			DMEMIT("%u %u ", pg->nr_pgpaths,
1903			       pg->ps.type->table_args);
1904
1905			list_for_each_entry(p, &pg->pgpaths, list) {
1906				DMEMIT("%s ", p->path.dev->name);
1907				if (pg->ps.type->status)
1908					sz += pg->ps.type->status(&pg->ps,
1909					      &p->path, type, result + sz,
1910					      maxlen - sz);
1911			}
1912		}
1913		break;
1914
1915	case STATUSTYPE_IMA:
1916		sz = 0; /*reset the result pointer*/
1917
1918		DMEMIT_TARGET_NAME_VERSION(ti->type);
1919		DMEMIT(",nr_priority_groups=%u", m->nr_priority_groups);
1920
1921		pg_counter = 0;
1922		list_for_each_entry(pg, &m->priority_groups, list) {
1923			if (pg->bypassed)
1924				state = 'D';	/* Disabled */
1925			else if (pg == m->current_pg)
1926				state = 'A';	/* Currently Active */
1927			else
1928				state = 'E';	/* Enabled */
1929			DMEMIT(",pg_state_%d=%c", pg_counter, state);
1930			DMEMIT(",nr_pgpaths_%d=%u", pg_counter, pg->nr_pgpaths);
1931			DMEMIT(",path_selector_name_%d=%s", pg_counter, pg->ps.type->name);
1932
1933			pgpath_counter = 0;
1934			list_for_each_entry(p, &pg->pgpaths, list) {
1935				DMEMIT(",path_name_%d_%d=%s,is_active_%d_%d=%c,fail_count_%d_%d=%u",
1936				       pg_counter, pgpath_counter, p->path.dev->name,
1937				       pg_counter, pgpath_counter, p->is_active ? 'A' : 'F',
1938				       pg_counter, pgpath_counter, p->fail_count);
1939				if (pg->ps.type->status) {
1940					DMEMIT(",path_selector_status_%d_%d=",
1941					       pg_counter, pgpath_counter);
1942					sz += pg->ps.type->status(&pg->ps, &p->path,
1943								  type, result + sz,
1944								  maxlen - sz);
1945				}
1946				pgpath_counter++;
1947			}
1948			pg_counter++;
1949		}
1950		DMEMIT(";");
1951		break;
1952	}
1953
1954	spin_unlock_irqrestore(&m->lock, flags);
1955}
1956
1957static int multipath_message(struct dm_target *ti, unsigned int argc, char **argv,
1958			     char *result, unsigned int maxlen)
1959{
1960	int r = -EINVAL;
1961	dev_t dev;
1962	struct multipath *m = ti->private;
1963	action_fn action;
1964	unsigned long flags;
1965
1966	mutex_lock(&m->work_mutex);
1967
1968	if (dm_suspended(ti)) {
1969		r = -EBUSY;
1970		goto out;
1971	}
1972
1973	if (argc == 1) {
1974		if (!strcasecmp(argv[0], "queue_if_no_path")) {
1975			r = queue_if_no_path(m, true, false, __func__);
1976			spin_lock_irqsave(&m->lock, flags);
1977			enable_nopath_timeout(m);
1978			spin_unlock_irqrestore(&m->lock, flags);
1979			goto out;
1980		} else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1981			r = queue_if_no_path(m, false, false, __func__);
1982			disable_nopath_timeout(m);
1983			goto out;
1984		}
1985	}
1986
1987	if (argc != 2) {
1988		DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1989		goto out;
1990	}
1991
1992	if (!strcasecmp(argv[0], "disable_group")) {
1993		r = bypass_pg_num(m, argv[1], true);
1994		goto out;
1995	} else if (!strcasecmp(argv[0], "enable_group")) {
1996		r = bypass_pg_num(m, argv[1], false);
1997		goto out;
1998	} else if (!strcasecmp(argv[0], "switch_group")) {
1999		r = switch_pg_num(m, argv[1]);
2000		goto out;
2001	} else if (!strcasecmp(argv[0], "reinstate_path"))
2002		action = reinstate_path;
2003	else if (!strcasecmp(argv[0], "fail_path"))
2004		action = fail_path;
2005	else {
2006		DMWARN("Unrecognised multipath message received: %s", argv[0]);
2007		goto out;
2008	}
2009
2010	r = dm_devt_from_path(argv[1], &dev);
2011	if (r) {
2012		DMWARN("message: error getting device %s",
2013		       argv[1]);
2014		goto out;
2015	}
2016
2017	r = action_dev(m, dev, action);
2018
 
 
2019out:
2020	mutex_unlock(&m->work_mutex);
2021	return r;
2022}
2023
2024static int multipath_prepare_ioctl(struct dm_target *ti,
2025				   struct block_device **bdev)
2026{
2027	struct multipath *m = ti->private;
2028	struct pgpath *pgpath;
2029	unsigned long flags;
2030	int r;
2031
2032	pgpath = READ_ONCE(m->current_pgpath);
2033	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
2034		pgpath = choose_pgpath(m, 0);
2035
2036	if (pgpath) {
2037		if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
2038			*bdev = pgpath->path.dev->bdev;
2039			r = 0;
2040		} else {
2041			/* pg_init has not started or completed */
2042			r = -ENOTCONN;
2043		}
2044	} else {
2045		/* No path is available */
2046		r = -EIO;
2047		spin_lock_irqsave(&m->lock, flags);
2048		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2049			r = -ENOTCONN;
2050		spin_unlock_irqrestore(&m->lock, flags);
2051	}
2052
2053	if (r == -ENOTCONN) {
2054		if (!READ_ONCE(m->current_pg)) {
2055			/* Path status changed, redo selection */
2056			(void) choose_pgpath(m, 0);
2057		}
2058		spin_lock_irqsave(&m->lock, flags);
2059		if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2060			(void) __pg_init_all_paths(m);
2061		spin_unlock_irqrestore(&m->lock, flags);
2062		dm_table_run_md_queue_async(m->ti->table);
2063		process_queued_io_list(m);
2064	}
2065
2066	/*
2067	 * Only pass ioctls through if the device sizes match exactly.
2068	 */
2069	if (!r && ti->len != bdev_nr_sectors((*bdev)))
2070		return 1;
2071	return r;
2072}
2073
2074static int multipath_iterate_devices(struct dm_target *ti,
2075				     iterate_devices_callout_fn fn, void *data)
2076{
2077	struct multipath *m = ti->private;
2078	struct priority_group *pg;
2079	struct pgpath *p;
2080	int ret = 0;
2081
2082	list_for_each_entry(pg, &m->priority_groups, list) {
2083		list_for_each_entry(p, &pg->pgpaths, list) {
2084			ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2085			if (ret)
2086				goto out;
2087		}
2088	}
2089
2090out:
2091	return ret;
2092}
2093
2094static int pgpath_busy(struct pgpath *pgpath)
2095{
2096	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
2097
2098	return blk_lld_busy(q);
2099}
2100
2101/*
2102 * We return "busy", only when we can map I/Os but underlying devices
2103 * are busy (so even if we map I/Os now, the I/Os will wait on
2104 * the underlying queue).
2105 * In other words, if we want to kill I/Os or queue them inside us
2106 * due to map unavailability, we don't return "busy".  Otherwise,
2107 * dm core won't give us the I/Os and we can't do what we want.
2108 */
2109static int multipath_busy(struct dm_target *ti)
2110{
2111	bool busy = false, has_active = false;
2112	struct multipath *m = ti->private;
2113	struct priority_group *pg, *next_pg;
2114	struct pgpath *pgpath;
2115
2116	/* pg_init in progress */
2117	if (atomic_read(&m->pg_init_in_progress))
2118		return true;
2119
2120	/* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2121	if (!atomic_read(&m->nr_valid_paths)) {
2122		unsigned long flags;
2123
2124		spin_lock_irqsave(&m->lock, flags);
2125		if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2126			spin_unlock_irqrestore(&m->lock, flags);
2127			return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2128		}
2129		spin_unlock_irqrestore(&m->lock, flags);
2130	}
2131
2132	/* Guess which priority_group will be used at next mapping time */
2133	pg = READ_ONCE(m->current_pg);
2134	next_pg = READ_ONCE(m->next_pg);
2135	if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2136		pg = next_pg;
2137
2138	if (!pg) {
2139		/*
2140		 * We don't know which pg will be used at next mapping time.
2141		 * We don't call choose_pgpath() here to avoid to trigger
2142		 * pg_init just by busy checking.
2143		 * So we don't know whether underlying devices we will be using
2144		 * at next mapping time are busy or not. Just try mapping.
2145		 */
2146		return busy;
2147	}
2148
2149	/*
2150	 * If there is one non-busy active path at least, the path selector
2151	 * will be able to select it. So we consider such a pg as not busy.
2152	 */
2153	busy = true;
2154	list_for_each_entry(pgpath, &pg->pgpaths, list) {
2155		if (pgpath->is_active) {
2156			has_active = true;
2157			if (!pgpath_busy(pgpath)) {
2158				busy = false;
2159				break;
2160			}
2161		}
2162	}
2163
2164	if (!has_active) {
2165		/*
2166		 * No active path in this pg, so this pg won't be used and
2167		 * the current_pg will be changed at next mapping time.
2168		 * We need to try mapping to determine it.
2169		 */
2170		busy = false;
2171	}
2172
2173	return busy;
2174}
2175
2176/*
2177 *---------------------------------------------------------------
2178 * Module setup
2179 *---------------------------------------------------------------
2180 */
2181static struct target_type multipath_target = {
2182	.name = "multipath",
2183	.version = {1, 14, 0},
2184	.features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2185		    DM_TARGET_PASSES_INTEGRITY,
2186	.module = THIS_MODULE,
2187	.ctr = multipath_ctr,
2188	.dtr = multipath_dtr,
2189	.clone_and_map_rq = multipath_clone_and_map,
2190	.release_clone_rq = multipath_release_clone,
2191	.rq_end_io = multipath_end_io,
2192	.map = multipath_map_bio,
2193	.end_io = multipath_end_io_bio,
2194	.presuspend = multipath_presuspend,
2195	.postsuspend = multipath_postsuspend,
2196	.resume = multipath_resume,
2197	.status = multipath_status,
2198	.message = multipath_message,
2199	.prepare_ioctl = multipath_prepare_ioctl,
2200	.iterate_devices = multipath_iterate_devices,
2201	.busy = multipath_busy,
2202};
2203
2204static int __init dm_multipath_init(void)
2205{
2206	int r = -ENOMEM;
2207
2208	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2209	if (!kmultipathd) {
2210		DMERR("failed to create workqueue kmpathd");
2211		goto bad_alloc_kmultipathd;
2212	}
2213
2214	/*
2215	 * A separate workqueue is used to handle the device handlers
2216	 * to avoid overloading existing workqueue. Overloading the
2217	 * old workqueue would also create a bottleneck in the
2218	 * path of the storage hardware device activation.
2219	 */
2220	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2221						  WQ_MEM_RECLAIM);
2222	if (!kmpath_handlerd) {
2223		DMERR("failed to create workqueue kmpath_handlerd");
2224		goto bad_alloc_kmpath_handlerd;
2225	}
2226
2227	dm_mpath_wq = alloc_workqueue("dm_mpath_wq", 0, 0);
2228	if (!dm_mpath_wq) {
2229		DMERR("failed to create workqueue dm_mpath_wq");
2230		goto bad_alloc_dm_mpath_wq;
2231	}
2232
2233	r = dm_register_target(&multipath_target);
2234	if (r < 0)
2235		goto bad_register_target;
2236
2237	return 0;
2238
2239bad_register_target:
2240	destroy_workqueue(dm_mpath_wq);
2241bad_alloc_dm_mpath_wq:
2242	destroy_workqueue(kmpath_handlerd);
2243bad_alloc_kmpath_handlerd:
2244	destroy_workqueue(kmultipathd);
2245bad_alloc_kmultipathd:
2246	return r;
2247}
2248
2249static void __exit dm_multipath_exit(void)
2250{
2251	destroy_workqueue(dm_mpath_wq);
2252	destroy_workqueue(kmpath_handlerd);
2253	destroy_workqueue(kmultipathd);
2254
2255	dm_unregister_target(&multipath_target);
2256}
2257
2258module_init(dm_multipath_init);
2259module_exit(dm_multipath_exit);
2260
2261module_param_named(queue_if_no_path_timeout_secs, queue_if_no_path_timeout_secs, ulong, 0644);
2262MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2263
2264MODULE_DESCRIPTION(DM_NAME " multipath target");
2265MODULE_AUTHOR("Sistina Software <dm-devel@lists.linux.dev>");
2266MODULE_LICENSE("GPL");