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/drivers/md/dm-mpath.c

https://bitbucket.org/ndreys/linux-sunxi
C | 1767 lines | 1248 code | 320 blank | 199 comment | 237 complexity | 5dbe6a692b7dd7709e95fa7e44b180d6 MD5 | raw file
Possible License(s): GPL-2.0, LGPL-2.0, AGPL-1.0
   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-path-selector.h"
  11#include "dm-uevent.h"
  12
  13#include <linux/ctype.h>
  14#include <linux/init.h>
  15#include <linux/mempool.h>
  16#include <linux/module.h>
  17#include <linux/pagemap.h>
  18#include <linux/slab.h>
  19#include <linux/time.h>
  20#include <linux/workqueue.h>
  21#include <scsi/scsi_dh.h>
  22#include <asm/atomic.h>
  23
  24#define DM_MSG_PREFIX "multipath"
  25#define MESG_STR(x) x, sizeof(x)
  26#define DM_PG_INIT_DELAY_MSECS 2000
  27#define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  28
  29/* Path properties */
  30struct pgpath {
  31	struct list_head list;
  32
  33	struct priority_group *pg;	/* Owning PG */
  34	unsigned is_active;		/* Path status */
  35	unsigned fail_count;		/* Cumulative failure count */
  36
  37	struct dm_path path;
  38	struct delayed_work activate_path;
  39};
  40
  41#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  42
  43/*
  44 * Paths are grouped into Priority Groups and numbered from 1 upwards.
  45 * Each has a path selector which controls which path gets used.
  46 */
  47struct priority_group {
  48	struct list_head list;
  49
  50	struct multipath *m;		/* Owning multipath instance */
  51	struct path_selector ps;
  52
  53	unsigned pg_num;		/* Reference number */
  54	unsigned bypassed;		/* Temporarily bypass this PG? */
  55
  56	unsigned nr_pgpaths;		/* Number of paths in PG */
  57	struct list_head pgpaths;
  58};
  59
  60/* Multipath context */
  61struct multipath {
  62	struct list_head list;
  63	struct dm_target *ti;
  64
  65	spinlock_t lock;
  66
  67	const char *hw_handler_name;
  68	char *hw_handler_params;
  69
  70	unsigned nr_priority_groups;
  71	struct list_head priority_groups;
  72
  73	wait_queue_head_t pg_init_wait;	/* Wait for pg_init completion */
  74
  75	unsigned pg_init_required;	/* pg_init needs calling? */
  76	unsigned pg_init_in_progress;	/* Only one pg_init allowed at once */
  77	unsigned pg_init_delay_retry;	/* Delay pg_init retry? */
  78
  79	unsigned nr_valid_paths;	/* Total number of usable paths */
  80	struct pgpath *current_pgpath;
  81	struct priority_group *current_pg;
  82	struct priority_group *next_pg;	/* Switch to this PG if set */
  83	unsigned repeat_count;		/* I/Os left before calling PS again */
  84
  85	unsigned queue_io;		/* Must we queue all I/O? */
  86	unsigned queue_if_no_path;	/* Queue I/O if last path fails? */
  87	unsigned saved_queue_if_no_path;/* Saved state during suspension */
  88	unsigned pg_init_retries;	/* Number of times to retry pg_init */
  89	unsigned pg_init_count;		/* Number of times pg_init called */
  90	unsigned pg_init_delay_msecs;	/* Number of msecs before pg_init retry */
  91
  92	struct work_struct process_queued_ios;
  93	struct list_head queued_ios;
  94	unsigned queue_size;
  95
  96	struct work_struct trigger_event;
  97
  98	/*
  99	 * We must use a mempool of dm_mpath_io structs so that we
 100	 * can resubmit bios on error.
 101	 */
 102	mempool_t *mpio_pool;
 103
 104	struct mutex work_mutex;
 105};
 106
 107/*
 108 * Context information attached to each bio we process.
 109 */
 110struct dm_mpath_io {
 111	struct pgpath *pgpath;
 112	size_t nr_bytes;
 113};
 114
 115typedef int (*action_fn) (struct pgpath *pgpath);
 116
 117#define MIN_IOS 256	/* Mempool size */
 118
 119static struct kmem_cache *_mpio_cache;
 120
 121static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 122static void process_queued_ios(struct work_struct *work);
 123static void trigger_event(struct work_struct *work);
 124static void activate_path(struct work_struct *work);
 125
 126
 127/*-----------------------------------------------
 128 * Allocation routines
 129 *-----------------------------------------------*/
 130
 131static struct pgpath *alloc_pgpath(void)
 132{
 133	struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 134
 135	if (pgpath) {
 136		pgpath->is_active = 1;
 137		INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 138	}
 139
 140	return pgpath;
 141}
 142
 143static void free_pgpath(struct pgpath *pgpath)
 144{
 145	kfree(pgpath);
 146}
 147
 148static struct priority_group *alloc_priority_group(void)
 149{
 150	struct priority_group *pg;
 151
 152	pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 153
 154	if (pg)
 155		INIT_LIST_HEAD(&pg->pgpaths);
 156
 157	return pg;
 158}
 159
 160static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 161{
 162	struct pgpath *pgpath, *tmp;
 163	struct multipath *m = ti->private;
 164
 165	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 166		list_del(&pgpath->list);
 167		if (m->hw_handler_name)
 168			scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 169		dm_put_device(ti, pgpath->path.dev);
 170		free_pgpath(pgpath);
 171	}
 172}
 173
 174static void free_priority_group(struct priority_group *pg,
 175				struct dm_target *ti)
 176{
 177	struct path_selector *ps = &pg->ps;
 178
 179	if (ps->type) {
 180		ps->type->destroy(ps);
 181		dm_put_path_selector(ps->type);
 182	}
 183
 184	free_pgpaths(&pg->pgpaths, ti);
 185	kfree(pg);
 186}
 187
 188static struct multipath *alloc_multipath(struct dm_target *ti)
 189{
 190	struct multipath *m;
 191
 192	m = kzalloc(sizeof(*m), GFP_KERNEL);
 193	if (m) {
 194		INIT_LIST_HEAD(&m->priority_groups);
 195		INIT_LIST_HEAD(&m->queued_ios);
 196		spin_lock_init(&m->lock);
 197		m->queue_io = 1;
 198		m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 199		INIT_WORK(&m->process_queued_ios, process_queued_ios);
 200		INIT_WORK(&m->trigger_event, trigger_event);
 201		init_waitqueue_head(&m->pg_init_wait);
 202		mutex_init(&m->work_mutex);
 203		m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 204		if (!m->mpio_pool) {
 205			kfree(m);
 206			return NULL;
 207		}
 208		m->ti = ti;
 209		ti->private = m;
 210	}
 211
 212	return m;
 213}
 214
 215static void free_multipath(struct multipath *m)
 216{
 217	struct priority_group *pg, *tmp;
 218
 219	list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 220		list_del(&pg->list);
 221		free_priority_group(pg, m->ti);
 222	}
 223
 224	kfree(m->hw_handler_name);
 225	kfree(m->hw_handler_params);
 226	mempool_destroy(m->mpio_pool);
 227	kfree(m);
 228}
 229
 230
 231/*-----------------------------------------------
 232 * Path selection
 233 *-----------------------------------------------*/
 234
 235static void __pg_init_all_paths(struct multipath *m)
 236{
 237	struct pgpath *pgpath;
 238	unsigned long pg_init_delay = 0;
 239
 240	m->pg_init_count++;
 241	m->pg_init_required = 0;
 242	if (m->pg_init_delay_retry)
 243		pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 244						 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 245	list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 246		/* Skip failed paths */
 247		if (!pgpath->is_active)
 248			continue;
 249		if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 250				       pg_init_delay))
 251			m->pg_init_in_progress++;
 252	}
 253}
 254
 255static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 256{
 257	m->current_pg = pgpath->pg;
 258
 259	/* Must we initialise the PG first, and queue I/O till it's ready? */
 260	if (m->hw_handler_name) {
 261		m->pg_init_required = 1;
 262		m->queue_io = 1;
 263	} else {
 264		m->pg_init_required = 0;
 265		m->queue_io = 0;
 266	}
 267
 268	m->pg_init_count = 0;
 269}
 270
 271static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 272			       size_t nr_bytes)
 273{
 274	struct dm_path *path;
 275
 276	path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 277	if (!path)
 278		return -ENXIO;
 279
 280	m->current_pgpath = path_to_pgpath(path);
 281
 282	if (m->current_pg != pg)
 283		__switch_pg(m, m->current_pgpath);
 284
 285	return 0;
 286}
 287
 288static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 289{
 290	struct priority_group *pg;
 291	unsigned bypassed = 1;
 292
 293	if (!m->nr_valid_paths)
 294		goto failed;
 295
 296	/* Were we instructed to switch PG? */
 297	if (m->next_pg) {
 298		pg = m->next_pg;
 299		m->next_pg = NULL;
 300		if (!__choose_path_in_pg(m, pg, nr_bytes))
 301			return;
 302	}
 303
 304	/* Don't change PG until it has no remaining paths */
 305	if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 306		return;
 307
 308	/*
 309	 * Loop through priority groups until we find a valid path.
 310	 * First time we skip PGs marked 'bypassed'.
 311	 * Second time we only try the ones we skipped.
 312	 */
 313	do {
 314		list_for_each_entry(pg, &m->priority_groups, list) {
 315			if (pg->bypassed == bypassed)
 316				continue;
 317			if (!__choose_path_in_pg(m, pg, nr_bytes))
 318				return;
 319		}
 320	} while (bypassed--);
 321
 322failed:
 323	m->current_pgpath = NULL;
 324	m->current_pg = NULL;
 325}
 326
 327/*
 328 * Check whether bios must be queued in the device-mapper core rather
 329 * than here in the target.
 330 *
 331 * m->lock must be held on entry.
 332 *
 333 * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 334 * same value then we are not between multipath_presuspend()
 335 * and multipath_resume() calls and we have no need to check
 336 * for the DMF_NOFLUSH_SUSPENDING flag.
 337 */
 338static int __must_push_back(struct multipath *m)
 339{
 340	return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 341		dm_noflush_suspending(m->ti));
 342}
 343
 344static int map_io(struct multipath *m, struct request *clone,
 345		  struct dm_mpath_io *mpio, unsigned was_queued)
 346{
 347	int r = DM_MAPIO_REMAPPED;
 348	size_t nr_bytes = blk_rq_bytes(clone);
 349	unsigned long flags;
 350	struct pgpath *pgpath;
 351	struct block_device *bdev;
 352
 353	spin_lock_irqsave(&m->lock, flags);
 354
 355	/* Do we need to select a new pgpath? */
 356	if (!m->current_pgpath ||
 357	    (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 358		__choose_pgpath(m, nr_bytes);
 359
 360	pgpath = m->current_pgpath;
 361
 362	if (was_queued)
 363		m->queue_size--;
 364
 365	if ((pgpath && m->queue_io) ||
 366	    (!pgpath && m->queue_if_no_path)) {
 367		/* Queue for the daemon to resubmit */
 368		list_add_tail(&clone->queuelist, &m->queued_ios);
 369		m->queue_size++;
 370		if ((m->pg_init_required && !m->pg_init_in_progress) ||
 371		    !m->queue_io)
 372			queue_work(kmultipathd, &m->process_queued_ios);
 373		pgpath = NULL;
 374		r = DM_MAPIO_SUBMITTED;
 375	} else if (pgpath) {
 376		bdev = pgpath->path.dev->bdev;
 377		clone->q = bdev_get_queue(bdev);
 378		clone->rq_disk = bdev->bd_disk;
 379	} else if (__must_push_back(m))
 380		r = DM_MAPIO_REQUEUE;
 381	else
 382		r = -EIO;	/* Failed */
 383
 384	mpio->pgpath = pgpath;
 385	mpio->nr_bytes = nr_bytes;
 386
 387	if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 388		pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 389					      nr_bytes);
 390
 391	spin_unlock_irqrestore(&m->lock, flags);
 392
 393	return r;
 394}
 395
 396/*
 397 * If we run out of usable paths, should we queue I/O or error it?
 398 */
 399static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 400			    unsigned save_old_value)
 401{
 402	unsigned long flags;
 403
 404	spin_lock_irqsave(&m->lock, flags);
 405
 406	if (save_old_value)
 407		m->saved_queue_if_no_path = m->queue_if_no_path;
 408	else
 409		m->saved_queue_if_no_path = queue_if_no_path;
 410	m->queue_if_no_path = queue_if_no_path;
 411	if (!m->queue_if_no_path && m->queue_size)
 412		queue_work(kmultipathd, &m->process_queued_ios);
 413
 414	spin_unlock_irqrestore(&m->lock, flags);
 415
 416	return 0;
 417}
 418
 419/*-----------------------------------------------------------------
 420 * The multipath daemon is responsible for resubmitting queued ios.
 421 *---------------------------------------------------------------*/
 422
 423static void dispatch_queued_ios(struct multipath *m)
 424{
 425	int r;
 426	unsigned long flags;
 427	struct dm_mpath_io *mpio;
 428	union map_info *info;
 429	struct request *clone, *n;
 430	LIST_HEAD(cl);
 431
 432	spin_lock_irqsave(&m->lock, flags);
 433	list_splice_init(&m->queued_ios, &cl);
 434	spin_unlock_irqrestore(&m->lock, flags);
 435
 436	list_for_each_entry_safe(clone, n, &cl, queuelist) {
 437		list_del_init(&clone->queuelist);
 438
 439		info = dm_get_rq_mapinfo(clone);
 440		mpio = info->ptr;
 441
 442		r = map_io(m, clone, mpio, 1);
 443		if (r < 0) {
 444			mempool_free(mpio, m->mpio_pool);
 445			dm_kill_unmapped_request(clone, r);
 446		} else if (r == DM_MAPIO_REMAPPED)
 447			dm_dispatch_request(clone);
 448		else if (r == DM_MAPIO_REQUEUE) {
 449			mempool_free(mpio, m->mpio_pool);
 450			dm_requeue_unmapped_request(clone);
 451		}
 452	}
 453}
 454
 455static void process_queued_ios(struct work_struct *work)
 456{
 457	struct multipath *m =
 458		container_of(work, struct multipath, process_queued_ios);
 459	struct pgpath *pgpath = NULL;
 460	unsigned must_queue = 1;
 461	unsigned long flags;
 462
 463	spin_lock_irqsave(&m->lock, flags);
 464
 465	if (!m->queue_size)
 466		goto out;
 467
 468	if (!m->current_pgpath)
 469		__choose_pgpath(m, 0);
 470
 471	pgpath = m->current_pgpath;
 472
 473	if ((pgpath && !m->queue_io) ||
 474	    (!pgpath && !m->queue_if_no_path))
 475		must_queue = 0;
 476
 477	if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
 478		__pg_init_all_paths(m);
 479
 480out:
 481	spin_unlock_irqrestore(&m->lock, flags);
 482	if (!must_queue)
 483		dispatch_queued_ios(m);
 484}
 485
 486/*
 487 * An event is triggered whenever a path is taken out of use.
 488 * Includes path failure and PG bypass.
 489 */
 490static void trigger_event(struct work_struct *work)
 491{
 492	struct multipath *m =
 493		container_of(work, struct multipath, trigger_event);
 494
 495	dm_table_event(m->ti->table);
 496}
 497
 498/*-----------------------------------------------------------------
 499 * Constructor/argument parsing:
 500 * <#multipath feature args> [<arg>]*
 501 * <#hw_handler args> [hw_handler [<arg>]*]
 502 * <#priority groups>
 503 * <initial priority group>
 504 *     [<selector> <#selector args> [<arg>]*
 505 *      <#paths> <#per-path selector args>
 506 *         [<path> [<arg>]* ]+ ]+
 507 *---------------------------------------------------------------*/
 508struct param {
 509	unsigned min;
 510	unsigned max;
 511	char *error;
 512};
 513
 514static int read_param(struct param *param, char *str, unsigned *v, char **error)
 515{
 516	if (!str ||
 517	    (sscanf(str, "%u", v) != 1) ||
 518	    (*v < param->min) ||
 519	    (*v > param->max)) {
 520		*error = param->error;
 521		return -EINVAL;
 522	}
 523
 524	return 0;
 525}
 526
 527struct arg_set {
 528	unsigned argc;
 529	char **argv;
 530};
 531
 532static char *shift(struct arg_set *as)
 533{
 534	char *r;
 535
 536	if (as->argc) {
 537		as->argc--;
 538		r = *as->argv;
 539		as->argv++;
 540		return r;
 541	}
 542
 543	return NULL;
 544}
 545
 546static void consume(struct arg_set *as, unsigned n)
 547{
 548	BUG_ON (as->argc < n);
 549	as->argc -= n;
 550	as->argv += n;
 551}
 552
 553static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
 554			       struct dm_target *ti)
 555{
 556	int r;
 557	struct path_selector_type *pst;
 558	unsigned ps_argc;
 559
 560	static struct param _params[] = {
 561		{0, 1024, "invalid number of path selector args"},
 562	};
 563
 564	pst = dm_get_path_selector(shift(as));
 565	if (!pst) {
 566		ti->error = "unknown path selector type";
 567		return -EINVAL;
 568	}
 569
 570	r = read_param(_params, shift(as), &ps_argc, &ti->error);
 571	if (r) {
 572		dm_put_path_selector(pst);
 573		return -EINVAL;
 574	}
 575
 576	if (ps_argc > as->argc) {
 577		dm_put_path_selector(pst);
 578		ti->error = "not enough arguments for path selector";
 579		return -EINVAL;
 580	}
 581
 582	r = pst->create(&pg->ps, ps_argc, as->argv);
 583	if (r) {
 584		dm_put_path_selector(pst);
 585		ti->error = "path selector constructor failed";
 586		return r;
 587	}
 588
 589	pg->ps.type = pst;
 590	consume(as, ps_argc);
 591
 592	return 0;
 593}
 594
 595static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
 596			       struct dm_target *ti)
 597{
 598	int r;
 599	struct pgpath *p;
 600	struct multipath *m = ti->private;
 601
 602	/* we need at least a path arg */
 603	if (as->argc < 1) {
 604		ti->error = "no device given";
 605		return ERR_PTR(-EINVAL);
 606	}
 607
 608	p = alloc_pgpath();
 609	if (!p)
 610		return ERR_PTR(-ENOMEM);
 611
 612	r = dm_get_device(ti, shift(as), dm_table_get_mode(ti->table),
 613			  &p->path.dev);
 614	if (r) {
 615		ti->error = "error getting device";
 616		goto bad;
 617	}
 618
 619	if (m->hw_handler_name) {
 620		struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 621
 622		r = scsi_dh_attach(q, m->hw_handler_name);
 623		if (r == -EBUSY) {
 624			/*
 625			 * Already attached to different hw_handler,
 626			 * try to reattach with correct one.
 627			 */
 628			scsi_dh_detach(q);
 629			r = scsi_dh_attach(q, m->hw_handler_name);
 630		}
 631
 632		if (r < 0) {
 633			ti->error = "error attaching hardware handler";
 634			dm_put_device(ti, p->path.dev);
 635			goto bad;
 636		}
 637
 638		if (m->hw_handler_params) {
 639			r = scsi_dh_set_params(q, m->hw_handler_params);
 640			if (r < 0) {
 641				ti->error = "unable to set hardware "
 642							"handler parameters";
 643				scsi_dh_detach(q);
 644				dm_put_device(ti, p->path.dev);
 645				goto bad;
 646			}
 647		}
 648	}
 649
 650	r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 651	if (r) {
 652		dm_put_device(ti, p->path.dev);
 653		goto bad;
 654	}
 655
 656	return p;
 657
 658 bad:
 659	free_pgpath(p);
 660	return ERR_PTR(r);
 661}
 662
 663static struct priority_group *parse_priority_group(struct arg_set *as,
 664						   struct multipath *m)
 665{
 666	static struct param _params[] = {
 667		{1, 1024, "invalid number of paths"},
 668		{0, 1024, "invalid number of selector args"}
 669	};
 670
 671	int r;
 672	unsigned i, nr_selector_args, nr_params;
 673	struct priority_group *pg;
 674	struct dm_target *ti = m->ti;
 675
 676	if (as->argc < 2) {
 677		as->argc = 0;
 678		ti->error = "not enough priority group arguments";
 679		return ERR_PTR(-EINVAL);
 680	}
 681
 682	pg = alloc_priority_group();
 683	if (!pg) {
 684		ti->error = "couldn't allocate priority group";
 685		return ERR_PTR(-ENOMEM);
 686	}
 687	pg->m = m;
 688
 689	r = parse_path_selector(as, pg, ti);
 690	if (r)
 691		goto bad;
 692
 693	/*
 694	 * read the paths
 695	 */
 696	r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
 697	if (r)
 698		goto bad;
 699
 700	r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
 701	if (r)
 702		goto bad;
 703
 704	nr_params = 1 + nr_selector_args;
 705	for (i = 0; i < pg->nr_pgpaths; i++) {
 706		struct pgpath *pgpath;
 707		struct arg_set path_args;
 708
 709		if (as->argc < nr_params) {
 710			ti->error = "not enough path parameters";
 711			r = -EINVAL;
 712			goto bad;
 713		}
 714
 715		path_args.argc = nr_params;
 716		path_args.argv = as->argv;
 717
 718		pgpath = parse_path(&path_args, &pg->ps, ti);
 719		if (IS_ERR(pgpath)) {
 720			r = PTR_ERR(pgpath);
 721			goto bad;
 722		}
 723
 724		pgpath->pg = pg;
 725		list_add_tail(&pgpath->list, &pg->pgpaths);
 726		consume(as, nr_params);
 727	}
 728
 729	return pg;
 730
 731 bad:
 732	free_priority_group(pg, ti);
 733	return ERR_PTR(r);
 734}
 735
 736static int parse_hw_handler(struct arg_set *as, struct multipath *m)
 737{
 738	unsigned hw_argc;
 739	int ret;
 740	struct dm_target *ti = m->ti;
 741
 742	static struct param _params[] = {
 743		{0, 1024, "invalid number of hardware handler args"},
 744	};
 745
 746	if (read_param(_params, shift(as), &hw_argc, &ti->error))
 747		return -EINVAL;
 748
 749	if (!hw_argc)
 750		return 0;
 751
 752	if (hw_argc > as->argc) {
 753		ti->error = "not enough arguments for hardware handler";
 754		return -EINVAL;
 755	}
 756
 757	m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
 758	request_module("scsi_dh_%s", m->hw_handler_name);
 759	if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
 760		ti->error = "unknown hardware handler type";
 761		ret = -EINVAL;
 762		goto fail;
 763	}
 764
 765	if (hw_argc > 1) {
 766		char *p;
 767		int i, j, len = 4;
 768
 769		for (i = 0; i <= hw_argc - 2; i++)
 770			len += strlen(as->argv[i]) + 1;
 771		p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 772		if (!p) {
 773			ti->error = "memory allocation failed";
 774			ret = -ENOMEM;
 775			goto fail;
 776		}
 777		j = sprintf(p, "%d", hw_argc - 1);
 778		for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 779			j = sprintf(p, "%s", as->argv[i]);
 780	}
 781	consume(as, hw_argc - 1);
 782
 783	return 0;
 784fail:
 785	kfree(m->hw_handler_name);
 786	m->hw_handler_name = NULL;
 787	return ret;
 788}
 789
 790static int parse_features(struct arg_set *as, struct multipath *m)
 791{
 792	int r;
 793	unsigned argc;
 794	struct dm_target *ti = m->ti;
 795	const char *param_name;
 796
 797	static struct param _params[] = {
 798		{0, 5, "invalid number of feature args"},
 799		{1, 50, "pg_init_retries must be between 1 and 50"},
 800		{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 801	};
 802
 803	r = read_param(_params, shift(as), &argc, &ti->error);
 804	if (r)
 805		return -EINVAL;
 806
 807	if (!argc)
 808		return 0;
 809
 810	if (argc > as->argc) {
 811		ti->error = "not enough arguments for features";
 812		return -EINVAL;
 813	}
 814
 815	do {
 816		param_name = shift(as);
 817		argc--;
 818
 819		if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
 820			r = queue_if_no_path(m, 1, 0);
 821			continue;
 822		}
 823
 824		if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
 825		    (argc >= 1)) {
 826			r = read_param(_params + 1, shift(as),
 827				       &m->pg_init_retries, &ti->error);
 828			argc--;
 829			continue;
 830		}
 831
 832		if (!strnicmp(param_name, MESG_STR("pg_init_delay_msecs")) &&
 833		    (argc >= 1)) {
 834			r = read_param(_params + 2, shift(as),
 835				       &m->pg_init_delay_msecs, &ti->error);
 836			argc--;
 837			continue;
 838		}
 839
 840		ti->error = "Unrecognised multipath feature request";
 841		r = -EINVAL;
 842	} while (argc && !r);
 843
 844	return r;
 845}
 846
 847static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 848			 char **argv)
 849{
 850	/* target parameters */
 851	static struct param _params[] = {
 852		{0, 1024, "invalid number of priority groups"},
 853		{0, 1024, "invalid initial priority group number"},
 854	};
 855
 856	int r;
 857	struct multipath *m;
 858	struct arg_set as;
 859	unsigned pg_count = 0;
 860	unsigned next_pg_num;
 861
 862	as.argc = argc;
 863	as.argv = argv;
 864
 865	m = alloc_multipath(ti);
 866	if (!m) {
 867		ti->error = "can't allocate multipath";
 868		return -EINVAL;
 869	}
 870
 871	r = parse_features(&as, m);
 872	if (r)
 873		goto bad;
 874
 875	r = parse_hw_handler(&as, m);
 876	if (r)
 877		goto bad;
 878
 879	r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
 880	if (r)
 881		goto bad;
 882
 883	r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
 884	if (r)
 885		goto bad;
 886
 887	if ((!m->nr_priority_groups && next_pg_num) ||
 888	    (m->nr_priority_groups && !next_pg_num)) {
 889		ti->error = "invalid initial priority group";
 890		r = -EINVAL;
 891		goto bad;
 892	}
 893
 894	/* parse the priority groups */
 895	while (as.argc) {
 896		struct priority_group *pg;
 897
 898		pg = parse_priority_group(&as, m);
 899		if (IS_ERR(pg)) {
 900			r = PTR_ERR(pg);
 901			goto bad;
 902		}
 903
 904		m->nr_valid_paths += pg->nr_pgpaths;
 905		list_add_tail(&pg->list, &m->priority_groups);
 906		pg_count++;
 907		pg->pg_num = pg_count;
 908		if (!--next_pg_num)
 909			m->next_pg = pg;
 910	}
 911
 912	if (pg_count != m->nr_priority_groups) {
 913		ti->error = "priority group count mismatch";
 914		r = -EINVAL;
 915		goto bad;
 916	}
 917
 918	ti->num_flush_requests = 1;
 919	ti->num_discard_requests = 1;
 920
 921	return 0;
 922
 923 bad:
 924	free_multipath(m);
 925	return r;
 926}
 927
 928static void multipath_wait_for_pg_init_completion(struct multipath *m)
 929{
 930	DECLARE_WAITQUEUE(wait, current);
 931	unsigned long flags;
 932
 933	add_wait_queue(&m->pg_init_wait, &wait);
 934
 935	while (1) {
 936		set_current_state(TASK_UNINTERRUPTIBLE);
 937
 938		spin_lock_irqsave(&m->lock, flags);
 939		if (!m->pg_init_in_progress) {
 940			spin_unlock_irqrestore(&m->lock, flags);
 941			break;
 942		}
 943		spin_unlock_irqrestore(&m->lock, flags);
 944
 945		io_schedule();
 946	}
 947	set_current_state(TASK_RUNNING);
 948
 949	remove_wait_queue(&m->pg_init_wait, &wait);
 950}
 951
 952static void flush_multipath_work(struct multipath *m)
 953{
 954	flush_workqueue(kmpath_handlerd);
 955	multipath_wait_for_pg_init_completion(m);
 956	flush_workqueue(kmultipathd);
 957	flush_work_sync(&m->trigger_event);
 958}
 959
 960static void multipath_dtr(struct dm_target *ti)
 961{
 962	struct multipath *m = ti->private;
 963
 964	flush_multipath_work(m);
 965	free_multipath(m);
 966}
 967
 968/*
 969 * Map cloned requests
 970 */
 971static int multipath_map(struct dm_target *ti, struct request *clone,
 972			 union map_info *map_context)
 973{
 974	int r;
 975	struct dm_mpath_io *mpio;
 976	struct multipath *m = (struct multipath *) ti->private;
 977
 978	mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 979	if (!mpio)
 980		/* ENOMEM, requeue */
 981		return DM_MAPIO_REQUEUE;
 982	memset(mpio, 0, sizeof(*mpio));
 983
 984	map_context->ptr = mpio;
 985	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 986	r = map_io(m, clone, mpio, 0);
 987	if (r < 0 || r == DM_MAPIO_REQUEUE)
 988		mempool_free(mpio, m->mpio_pool);
 989
 990	return r;
 991}
 992
 993/*
 994 * Take a path out of use.
 995 */
 996static int fail_path(struct pgpath *pgpath)
 997{
 998	unsigned long flags;
 999	struct multipath *m = pgpath->pg->m;
1000
1001	spin_lock_irqsave(&m->lock, flags);
1002
1003	if (!pgpath->is_active)
1004		goto out;
1005
1006	DMWARN("Failing path %s.", pgpath->path.dev->name);
1007
1008	pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1009	pgpath->is_active = 0;
1010	pgpath->fail_count++;
1011
1012	m->nr_valid_paths--;
1013
1014	if (pgpath == m->current_pgpath)
1015		m->current_pgpath = NULL;
1016
1017	dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1018		      pgpath->path.dev->name, m->nr_valid_paths);
1019
1020	schedule_work(&m->trigger_event);
1021
1022out:
1023	spin_unlock_irqrestore(&m->lock, flags);
1024
1025	return 0;
1026}
1027
1028/*
1029 * Reinstate a previously-failed path
1030 */
1031static int reinstate_path(struct pgpath *pgpath)
1032{
1033	int r = 0;
1034	unsigned long flags;
1035	struct multipath *m = pgpath->pg->m;
1036
1037	spin_lock_irqsave(&m->lock, flags);
1038
1039	if (pgpath->is_active)
1040		goto out;
1041
1042	if (!pgpath->pg->ps.type->reinstate_path) {
1043		DMWARN("Reinstate path not supported by path selector %s",
1044		       pgpath->pg->ps.type->name);
1045		r = -EINVAL;
1046		goto out;
1047	}
1048
1049	r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1050	if (r)
1051		goto out;
1052
1053	pgpath->is_active = 1;
1054
1055	if (!m->nr_valid_paths++ && m->queue_size) {
1056		m->current_pgpath = NULL;
1057		queue_work(kmultipathd, &m->process_queued_ios);
1058	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1059		if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1060			m->pg_init_in_progress++;
1061	}
1062
1063	dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1064		      pgpath->path.dev->name, m->nr_valid_paths);
1065
1066	schedule_work(&m->trigger_event);
1067
1068out:
1069	spin_unlock_irqrestore(&m->lock, flags);
1070
1071	return r;
1072}
1073
1074/*
1075 * Fail or reinstate all paths that match the provided struct dm_dev.
1076 */
1077static int action_dev(struct multipath *m, struct dm_dev *dev,
1078		      action_fn action)
1079{
1080	int r = -EINVAL;
1081	struct pgpath *pgpath;
1082	struct priority_group *pg;
1083
1084	list_for_each_entry(pg, &m->priority_groups, list) {
1085		list_for_each_entry(pgpath, &pg->pgpaths, list) {
1086			if (pgpath->path.dev == dev)
1087				r = action(pgpath);
1088		}
1089	}
1090
1091	return r;
1092}
1093
1094/*
1095 * Temporarily try to avoid having to use the specified PG
1096 */
1097static void bypass_pg(struct multipath *m, struct priority_group *pg,
1098		      int bypassed)
1099{
1100	unsigned long flags;
1101
1102	spin_lock_irqsave(&m->lock, flags);
1103
1104	pg->bypassed = bypassed;
1105	m->current_pgpath = NULL;
1106	m->current_pg = NULL;
1107
1108	spin_unlock_irqrestore(&m->lock, flags);
1109
1110	schedule_work(&m->trigger_event);
1111}
1112
1113/*
1114 * Switch to using the specified PG from the next I/O that gets mapped
1115 */
1116static int switch_pg_num(struct multipath *m, const char *pgstr)
1117{
1118	struct priority_group *pg;
1119	unsigned pgnum;
1120	unsigned long flags;
1121
1122	if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1123	    (pgnum > m->nr_priority_groups)) {
1124		DMWARN("invalid PG number supplied to switch_pg_num");
1125		return -EINVAL;
1126	}
1127
1128	spin_lock_irqsave(&m->lock, flags);
1129	list_for_each_entry(pg, &m->priority_groups, list) {
1130		pg->bypassed = 0;
1131		if (--pgnum)
1132			continue;
1133
1134		m->current_pgpath = NULL;
1135		m->current_pg = NULL;
1136		m->next_pg = pg;
1137	}
1138	spin_unlock_irqrestore(&m->lock, flags);
1139
1140	schedule_work(&m->trigger_event);
1141	return 0;
1142}
1143
1144/*
1145 * Set/clear bypassed status of a PG.
1146 * PGs are numbered upwards from 1 in the order they were declared.
1147 */
1148static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1149{
1150	struct priority_group *pg;
1151	unsigned pgnum;
1152
1153	if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1154	    (pgnum > m->nr_priority_groups)) {
1155		DMWARN("invalid PG number supplied to bypass_pg");
1156		return -EINVAL;
1157	}
1158
1159	list_for_each_entry(pg, &m->priority_groups, list) {
1160		if (!--pgnum)
1161			break;
1162	}
1163
1164	bypass_pg(m, pg, bypassed);
1165	return 0;
1166}
1167
1168/*
1169 * Should we retry pg_init immediately?
1170 */
1171static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1172{
1173	unsigned long flags;
1174	int limit_reached = 0;
1175
1176	spin_lock_irqsave(&m->lock, flags);
1177
1178	if (m->pg_init_count <= m->pg_init_retries)
1179		m->pg_init_required = 1;
1180	else
1181		limit_reached = 1;
1182
1183	spin_unlock_irqrestore(&m->lock, flags);
1184
1185	return limit_reached;
1186}
1187
1188static void pg_init_done(void *data, int errors)
1189{
1190	struct pgpath *pgpath = data;
1191	struct priority_group *pg = pgpath->pg;
1192	struct multipath *m = pg->m;
1193	unsigned long flags;
1194	unsigned delay_retry = 0;
1195
1196	/* device or driver problems */
1197	switch (errors) {
1198	case SCSI_DH_OK:
1199		break;
1200	case SCSI_DH_NOSYS:
1201		if (!m->hw_handler_name) {
1202			errors = 0;
1203			break;
1204		}
1205		DMERR("Could not failover the device: Handler scsi_dh_%s "
1206		      "Error %d.", m->hw_handler_name, errors);
1207		/*
1208		 * Fail path for now, so we do not ping pong
1209		 */
1210		fail_path(pgpath);
1211		break;
1212	case SCSI_DH_DEV_TEMP_BUSY:
1213		/*
1214		 * Probably doing something like FW upgrade on the
1215		 * controller so try the other pg.
1216		 */
1217		bypass_pg(m, pg, 1);
1218		break;
1219	case SCSI_DH_RETRY:
1220		/* Wait before retrying. */
1221		delay_retry = 1;
1222	case SCSI_DH_IMM_RETRY:
1223	case SCSI_DH_RES_TEMP_UNAVAIL:
1224		if (pg_init_limit_reached(m, pgpath))
1225			fail_path(pgpath);
1226		errors = 0;
1227		break;
1228	default:
1229		/*
1230		 * We probably do not want to fail the path for a device
1231		 * error, but this is what the old dm did. In future
1232		 * patches we can do more advanced handling.
1233		 */
1234		fail_path(pgpath);
1235	}
1236
1237	spin_lock_irqsave(&m->lock, flags);
1238	if (errors) {
1239		if (pgpath == m->current_pgpath) {
1240			DMERR("Could not failover device. Error %d.", errors);
1241			m->current_pgpath = NULL;
1242			m->current_pg = NULL;
1243		}
1244	} else if (!m->pg_init_required)
1245		pg->bypassed = 0;
1246
1247	if (--m->pg_init_in_progress)
1248		/* Activations of other paths are still on going */
1249		goto out;
1250
1251	if (!m->pg_init_required)
1252		m->queue_io = 0;
1253
1254	m->pg_init_delay_retry = delay_retry;
1255	queue_work(kmultipathd, &m->process_queued_ios);
1256
1257	/*
1258	 * Wake up any thread waiting to suspend.
1259	 */
1260	wake_up(&m->pg_init_wait);
1261
1262out:
1263	spin_unlock_irqrestore(&m->lock, flags);
1264}
1265
1266static void activate_path(struct work_struct *work)
1267{
1268	struct pgpath *pgpath =
1269		container_of(work, struct pgpath, activate_path.work);
1270
1271	scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1272				pg_init_done, pgpath);
1273}
1274
1275/*
1276 * end_io handling
1277 */
1278static int do_end_io(struct multipath *m, struct request *clone,
1279		     int error, struct dm_mpath_io *mpio)
1280{
1281	/*
1282	 * We don't queue any clone request inside the multipath target
1283	 * during end I/O handling, since those clone requests don't have
1284	 * bio clones.  If we queue them inside the multipath target,
1285	 * we need to make bio clones, that requires memory allocation.
1286	 * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1287	 *  don't have bio clones.)
1288	 * Instead of queueing the clone request here, we queue the original
1289	 * request into dm core, which will remake a clone request and
1290	 * clone bios for it and resubmit it later.
1291	 */
1292	int r = DM_ENDIO_REQUEUE;
1293	unsigned long flags;
1294
1295	if (!error && !clone->errors)
1296		return 0;	/* I/O complete */
1297
1298	if (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ)
1299		return error;
1300
1301	if (mpio->pgpath)
1302		fail_path(mpio->pgpath);
1303
1304	spin_lock_irqsave(&m->lock, flags);
1305	if (!m->nr_valid_paths) {
1306		if (!m->queue_if_no_path) {
1307			if (!__must_push_back(m))
1308				r = -EIO;
1309		} else {
1310			if (error == -EBADE)
1311				r = error;
1312		}
1313	}
1314	spin_unlock_irqrestore(&m->lock, flags);
1315
1316	return r;
1317}
1318
1319static int multipath_end_io(struct dm_target *ti, struct request *clone,
1320			    int error, union map_info *map_context)
1321{
1322	struct multipath *m = ti->private;
1323	struct dm_mpath_io *mpio = map_context->ptr;
1324	struct pgpath *pgpath = mpio->pgpath;
1325	struct path_selector *ps;
1326	int r;
1327
1328	r  = do_end_io(m, clone, error, mpio);
1329	if (pgpath) {
1330		ps = &pgpath->pg->ps;
1331		if (ps->type->end_io)
1332			ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1333	}
1334	mempool_free(mpio, m->mpio_pool);
1335
1336	return r;
1337}
1338
1339/*
1340 * Suspend can't complete until all the I/O is processed so if
1341 * the last path fails we must error any remaining I/O.
1342 * Note that if the freeze_bdev fails while suspending, the
1343 * queue_if_no_path state is lost - userspace should reset it.
1344 */
1345static void multipath_presuspend(struct dm_target *ti)
1346{
1347	struct multipath *m = (struct multipath *) ti->private;
1348
1349	queue_if_no_path(m, 0, 1);
1350}
1351
1352static void multipath_postsuspend(struct dm_target *ti)
1353{
1354	struct multipath *m = ti->private;
1355
1356	mutex_lock(&m->work_mutex);
1357	flush_multipath_work(m);
1358	mutex_unlock(&m->work_mutex);
1359}
1360
1361/*
1362 * Restore the queue_if_no_path setting.
1363 */
1364static void multipath_resume(struct dm_target *ti)
1365{
1366	struct multipath *m = (struct multipath *) ti->private;
1367	unsigned long flags;
1368
1369	spin_lock_irqsave(&m->lock, flags);
1370	m->queue_if_no_path = m->saved_queue_if_no_path;
1371	spin_unlock_irqrestore(&m->lock, flags);
1372}
1373
1374/*
1375 * Info output has the following format:
1376 * num_multipath_feature_args [multipath_feature_args]*
1377 * num_handler_status_args [handler_status_args]*
1378 * num_groups init_group_number
1379 *            [A|D|E num_ps_status_args [ps_status_args]*
1380 *             num_paths num_selector_args
1381 *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1382 *
1383 * Table output has the following format (identical to the constructor string):
1384 * num_feature_args [features_args]*
1385 * num_handler_args hw_handler [hw_handler_args]*
1386 * num_groups init_group_number
1387 *     [priority selector-name num_ps_args [ps_args]*
1388 *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1389 */
1390static int multipath_status(struct dm_target *ti, status_type_t type,
1391			    char *result, unsigned int maxlen)
1392{
1393	int sz = 0;
1394	unsigned long flags;
1395	struct multipath *m = (struct multipath *) ti->private;
1396	struct priority_group *pg;
1397	struct pgpath *p;
1398	unsigned pg_num;
1399	char state;
1400
1401	spin_lock_irqsave(&m->lock, flags);
1402
1403	/* Features */
1404	if (type == STATUSTYPE_INFO)
1405		DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1406	else {
1407		DMEMIT("%u ", m->queue_if_no_path +
1408			      (m->pg_init_retries > 0) * 2 +
1409			      (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1410		if (m->queue_if_no_path)
1411			DMEMIT("queue_if_no_path ");
1412		if (m->pg_init_retries)
1413			DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1414		if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1415			DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1416	}
1417
1418	if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1419		DMEMIT("0 ");
1420	else
1421		DMEMIT("1 %s ", m->hw_handler_name);
1422
1423	DMEMIT("%u ", m->nr_priority_groups);
1424
1425	if (m->next_pg)
1426		pg_num = m->next_pg->pg_num;
1427	else if (m->current_pg)
1428		pg_num = m->current_pg->pg_num;
1429	else
1430		pg_num = (m->nr_priority_groups ? 1 : 0);
1431
1432	DMEMIT("%u ", pg_num);
1433
1434	switch (type) {
1435	case STATUSTYPE_INFO:
1436		list_for_each_entry(pg, &m->priority_groups, list) {
1437			if (pg->bypassed)
1438				state = 'D';	/* Disabled */
1439			else if (pg == m->current_pg)
1440				state = 'A';	/* Currently Active */
1441			else
1442				state = 'E';	/* Enabled */
1443
1444			DMEMIT("%c ", state);
1445
1446			if (pg->ps.type->status)
1447				sz += pg->ps.type->status(&pg->ps, NULL, type,
1448							  result + sz,
1449							  maxlen - sz);
1450			else
1451				DMEMIT("0 ");
1452
1453			DMEMIT("%u %u ", pg->nr_pgpaths,
1454			       pg->ps.type->info_args);
1455
1456			list_for_each_entry(p, &pg->pgpaths, list) {
1457				DMEMIT("%s %s %u ", p->path.dev->name,
1458				       p->is_active ? "A" : "F",
1459				       p->fail_count);
1460				if (pg->ps.type->status)
1461					sz += pg->ps.type->status(&pg->ps,
1462					      &p->path, type, result + sz,
1463					      maxlen - sz);
1464			}
1465		}
1466		break;
1467
1468	case STATUSTYPE_TABLE:
1469		list_for_each_entry(pg, &m->priority_groups, list) {
1470			DMEMIT("%s ", pg->ps.type->name);
1471
1472			if (pg->ps.type->status)
1473				sz += pg->ps.type->status(&pg->ps, NULL, type,
1474							  result + sz,
1475							  maxlen - sz);
1476			else
1477				DMEMIT("0 ");
1478
1479			DMEMIT("%u %u ", pg->nr_pgpaths,
1480			       pg->ps.type->table_args);
1481
1482			list_for_each_entry(p, &pg->pgpaths, list) {
1483				DMEMIT("%s ", p->path.dev->name);
1484				if (pg->ps.type->status)
1485					sz += pg->ps.type->status(&pg->ps,
1486					      &p->path, type, result + sz,
1487					      maxlen - sz);
1488			}
1489		}
1490		break;
1491	}
1492
1493	spin_unlock_irqrestore(&m->lock, flags);
1494
1495	return 0;
1496}
1497
1498static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1499{
1500	int r = -EINVAL;
1501	struct dm_dev *dev;
1502	struct multipath *m = (struct multipath *) ti->private;
1503	action_fn action;
1504
1505	mutex_lock(&m->work_mutex);
1506
1507	if (dm_suspended(ti)) {
1508		r = -EBUSY;
1509		goto out;
1510	}
1511
1512	if (argc == 1) {
1513		if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1514			r = queue_if_no_path(m, 1, 0);
1515			goto out;
1516		} else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1517			r = queue_if_no_path(m, 0, 0);
1518			goto out;
1519		}
1520	}
1521
1522	if (argc != 2) {
1523		DMWARN("Unrecognised multipath message received.");
1524		goto out;
1525	}
1526
1527	if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1528		r = bypass_pg_num(m, argv[1], 1);
1529		goto out;
1530	} else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1531		r = bypass_pg_num(m, argv[1], 0);
1532		goto out;
1533	} else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1534		r = switch_pg_num(m, argv[1]);
1535		goto out;
1536	} else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1537		action = reinstate_path;
1538	else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1539		action = fail_path;
1540	else {
1541		DMWARN("Unrecognised multipath message received.");
1542		goto out;
1543	}
1544
1545	r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1546	if (r) {
1547		DMWARN("message: error getting device %s",
1548		       argv[1]);
1549		goto out;
1550	}
1551
1552	r = action_dev(m, dev, action);
1553
1554	dm_put_device(ti, dev);
1555
1556out:
1557	mutex_unlock(&m->work_mutex);
1558	return r;
1559}
1560
1561static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1562			   unsigned long arg)
1563{
1564	struct multipath *m = (struct multipath *) ti->private;
1565	struct block_device *bdev = NULL;
1566	fmode_t mode = 0;
1567	unsigned long flags;
1568	int r = 0;
1569
1570	spin_lock_irqsave(&m->lock, flags);
1571
1572	if (!m->current_pgpath)
1573		__choose_pgpath(m, 0);
1574
1575	if (m->current_pgpath) {
1576		bdev = m->current_pgpath->path.dev->bdev;
1577		mode = m->current_pgpath->path.dev->mode;
1578	}
1579
1580	if (m->queue_io)
1581		r = -EAGAIN;
1582	else if (!bdev)
1583		r = -EIO;
1584
1585	spin_unlock_irqrestore(&m->lock, flags);
1586
1587	/*
1588	 * Only pass ioctls through if the device sizes match exactly.
1589	 */
1590	if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
1591		r = scsi_verify_blk_ioctl(NULL, cmd);
1592
1593	return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1594}
1595
1596static int multipath_iterate_devices(struct dm_target *ti,
1597				     iterate_devices_callout_fn fn, void *data)
1598{
1599	struct multipath *m = ti->private;
1600	struct priority_group *pg;
1601	struct pgpath *p;
1602	int ret = 0;
1603
1604	list_for_each_entry(pg, &m->priority_groups, list) {
1605		list_for_each_entry(p, &pg->pgpaths, list) {
1606			ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1607			if (ret)
1608				goto out;
1609		}
1610	}
1611
1612out:
1613	return ret;
1614}
1615
1616static int __pgpath_busy(struct pgpath *pgpath)
1617{
1618	struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1619
1620	return dm_underlying_device_busy(q);
1621}
1622
1623/*
1624 * We return "busy", only when we can map I/Os but underlying devices
1625 * are busy (so even if we map I/Os now, the I/Os will wait on
1626 * the underlying queue).
1627 * In other words, if we want to kill I/Os or queue them inside us
1628 * due to map unavailability, we don't return "busy".  Otherwise,
1629 * dm core won't give us the I/Os and we can't do what we want.
1630 */
1631static int multipath_busy(struct dm_target *ti)
1632{
1633	int busy = 0, has_active = 0;
1634	struct multipath *m = ti->private;
1635	struct priority_group *pg;
1636	struct pgpath *pgpath;
1637	unsigned long flags;
1638
1639	spin_lock_irqsave(&m->lock, flags);
1640
1641	/* Guess which priority_group will be used at next mapping time */
1642	if (unlikely(!m->current_pgpath && m->next_pg))
1643		pg = m->next_pg;
1644	else if (likely(m->current_pg))
1645		pg = m->current_pg;
1646	else
1647		/*
1648		 * We don't know which pg will be used at next mapping time.
1649		 * We don't call __choose_pgpath() here to avoid to trigger
1650		 * pg_init just by busy checking.
1651		 * So we don't know whether underlying devices we will be using
1652		 * at next mapping time are busy or not. Just try mapping.
1653		 */
1654		goto out;
1655
1656	/*
1657	 * If there is one non-busy active path at least, the path selector
1658	 * will be able to select it. So we consider such a pg as not busy.
1659	 */
1660	busy = 1;
1661	list_for_each_entry(pgpath, &pg->pgpaths, list)
1662		if (pgpath->is_active) {
1663			has_active = 1;
1664
1665			if (!__pgpath_busy(pgpath)) {
1666				busy = 0;
1667				break;
1668			}
1669		}
1670
1671	if (!has_active)
1672		/*
1673		 * No active path in this pg, so this pg won't be used and
1674		 * the current_pg will be changed at next mapping time.
1675		 * We need to try mapping to determine it.
1676		 */
1677		busy = 0;
1678
1679out:
1680	spin_unlock_irqrestore(&m->lock, flags);
1681
1682	return busy;
1683}
1684
1685/*-----------------------------------------------------------------
1686 * Module setup
1687 *---------------------------------------------------------------*/
1688static struct target_type multipath_target = {
1689	.name = "multipath",
1690	.version = {1, 3, 0},
1691	.module = THIS_MODULE,
1692	.ctr = multipath_ctr,
1693	.dtr = multipath_dtr,
1694	.map_rq = multipath_map,
1695	.rq_end_io = multipath_end_io,
1696	.presuspend = multipath_presuspend,
1697	.postsuspend = multipath_postsuspend,
1698	.resume = multipath_resume,
1699	.status = multipath_status,
1700	.message = multipath_message,
1701	.ioctl  = multipath_ioctl,
1702	.iterate_devices = multipath_iterate_devices,
1703	.busy = multipath_busy,
1704};
1705
1706static int __init dm_multipath_init(void)
1707{
1708	int r;
1709
1710	/* allocate a slab for the dm_ios */
1711	_mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1712	if (!_mpio_cache)
1713		return -ENOMEM;
1714
1715	r = dm_register_target(&multipath_target);
1716	if (r < 0) {
1717		DMERR("register failed %d", r);
1718		kmem_cache_destroy(_mpio_cache);
1719		return -EINVAL;
1720	}
1721
1722	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1723	if (!kmultipathd) {
1724		DMERR("failed to create workqueue kmpathd");
1725		dm_unregister_target(&multipath_target);
1726		kmem_cache_destroy(_mpio_cache);
1727		return -ENOMEM;
1728	}
1729
1730	/*
1731	 * A separate workqueue is used to handle the device handlers
1732	 * to avoid overloading existing workqueue. Overloading the
1733	 * old workqueue would also create a bottleneck in the
1734	 * path of the storage hardware device activation.
1735	 */
1736	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1737						  WQ_MEM_RECLAIM);
1738	if (!kmpath_handlerd) {
1739		DMERR("failed to create workqueue kmpath_handlerd");
1740		destroy_workqueue(kmultipathd);
1741		dm_unregister_target(&multipath_target);
1742		kmem_cache_destroy(_mpio_cache);
1743		return -ENOMEM;
1744	}
1745
1746	DMINFO("version %u.%u.%u loaded",
1747	       multipath_target.version[0], multipath_target.version[1],
1748	       multipath_target.version[2]);
1749
1750	return r;
1751}
1752
1753static void __exit dm_multipath_exit(void)
1754{
1755	destroy_workqueue(kmpath_handlerd);
1756	destroy_workqueue(kmultipathd);
1757
1758	dm_unregister_target(&multipath_target);
1759	kmem_cache_destroy(_mpio_cache);
1760}
1761
1762module_init(dm_multipath_init);
1763module_exit(dm_multipath_exit);
1764
1765MODULE_DESCRIPTION(DM_NAME " multipath target");
1766MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1767MODULE_LICENSE("GPL");