drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include "dm-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 <linux/delay.h>
  22 #include <scsi/scsi_dh.h>
  23 #include <linux/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define DM_PG_INIT_DELAY_MSECS 2000
  27 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  28
  29 /* Path properties */
  30 struct 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  */
  47 struct 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 */
  61 struct multipath {
  62         struct list_head list;
  63         struct dm_target *ti;
  64
  65         const char *hw_handler_name;
  66         char *hw_handler_params;
  67
  68         spinlock_t lock;
  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:1;            /* Must we queue all I/O? */
  86         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  87         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  88
  89         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  90         unsigned pg_init_count;         /* Number of times pg_init called */
  91         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  92
  93         unsigned queue_size;
  94         struct work_struct process_queued_ios;
  95         struct list_head queued_ios;
  96
  97         struct work_struct trigger_event;
  98
  99         /*
 100          * We must use a mempool of dm_mpath_io structs so that we
 101          * can resubmit bios on error.
 102          */
 103         mempool_t *mpio_pool;
 104
 105         struct mutex work_mutex;
 106 };
 107
 108 /*
 109  * Context information attached to each bio we process.
 110  */
 111 struct dm_mpath_io {
 112         struct pgpath *pgpath;
 113         size_t nr_bytes;
 114 };
 115
 116 typedef int (*action_fn) (struct pgpath *pgpath);
 117
 118 #define MIN_IOS 256     /* Mempool size */
 119
 120 static struct kmem_cache *_mpio_cache;
 121
 122 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 123 static void process_queued_ios(struct work_struct *work);
 124 static void trigger_event(struct work_struct *work);
 125 static void activate_path(struct work_struct *work);
 126
 127
 128 /*-----------------------------------------------
 129  * Allocation routines
 130  *-----------------------------------------------*/
 131
 132 static struct pgpath *alloc_pgpath(void)
 133 {
 134         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 135
 136         if (pgpath) {
 137                 pgpath->is_active = 1;
 138                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 139         }
 140
 141         return pgpath;
 142 }
 143
 144 static void free_pgpath(struct pgpath *pgpath)
 145 {
 146         kfree(pgpath);
 147 }
 148
 149 static struct priority_group *alloc_priority_group(void)
 150 {
 151         struct priority_group *pg;
 152
 153         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 154
 155         if (pg)
 156                 INIT_LIST_HEAD(&pg->pgpaths);
 157
 158         return pg;
 159 }
 160
 161 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 162 {
 163         struct pgpath *pgpath, *tmp;
 164         struct multipath *m = ti->private;
 165
 166         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 167                 list_del(&pgpath->list);
 168                 if (m->hw_handler_name)
 169                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 170                 dm_put_device(ti, pgpath->path.dev);
 171                 free_pgpath(pgpath);
 172         }
 173 }
 174
 175 static void free_priority_group(struct priority_group *pg,
 176                                 struct dm_target *ti)
 177 {
 178         struct path_selector *ps = &pg->ps;
 179
 180         if (ps->type) {
 181                 ps->type->destroy(ps);
 182                 dm_put_path_selector(ps->type);
 183         }
 184
 185         free_pgpaths(&pg->pgpaths, ti);
 186         kfree(pg);
 187 }
 188
 189 static struct multipath *alloc_multipath(struct dm_target *ti)
 190 {
 191         struct multipath *m;
 192
 193         m = kzalloc(sizeof(*m), GFP_KERNEL);
 194         if (m) {
 195                 INIT_LIST_HEAD(&m->priority_groups);
 196                 INIT_LIST_HEAD(&m->queued_ios);
 197                 spin_lock_init(&m->lock);
 198                 m->queue_io = 1;
 199                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 200                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 201                 INIT_WORK(&m->trigger_event, trigger_event);
 202                 init_waitqueue_head(&m->pg_init_wait);
 203                 mutex_init(&m->work_mutex);
 204                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 205                 if (!m->mpio_pool) {
 206                         kfree(m);
 207                         return NULL;
 208                 }
 209                 m->ti = ti;
 210                 ti->private = m;
 211         }
 212
 213         return m;
 214 }
 215
 216 static void free_multipath(struct multipath *m)
 217 {
 218         struct priority_group *pg, *tmp;
 219
 220         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 221                 list_del(&pg->list);
 222                 free_priority_group(pg, m->ti);
 223         }
 224
 225         kfree(m->hw_handler_name);
 226         kfree(m->hw_handler_params);
 227         mempool_destroy(m->mpio_pool);
 228         kfree(m);
 229 }
 230
 231 static int set_mapinfo(struct multipath *m, union map_info *info)
 232 {
 233         struct dm_mpath_io *mpio;
 234
 235         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 236         if (!mpio)
 237                 return -ENOMEM;
 238
 239         memset(mpio, 0, sizeof(*mpio));
 240         info->ptr = mpio;
 241
 242         return 0;
 243 }
 244
 245 static void clear_mapinfo(struct multipath *m, union map_info *info)
 246 {
 247         struct dm_mpath_io *mpio = info->ptr;
 248
 249         info->ptr = NULL;
 250         mempool_free(mpio, m->mpio_pool);
 251 }
 252
 253 /*-----------------------------------------------
 254  * Path selection
 255  *-----------------------------------------------*/
 256
 257 static void __pg_init_all_paths(struct multipath *m)
 258 {
 259         struct pgpath *pgpath;
 260         unsigned long pg_init_delay = 0;
 261
 262         m->pg_init_count++;
 263         m->pg_init_required = 0;
 264         if (m->pg_init_delay_retry)
 265                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 266                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 267         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 268                 /* Skip failed paths */
 269                 if (!pgpath->is_active)
 270                         continue;
 271                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 272                                        pg_init_delay))
 273                         m->pg_init_in_progress++;
 274         }
 275 }
 276
 277 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 278 {
 279         m->current_pg = pgpath->pg;
 280
 281         /* Must we initialise the PG first, and queue I/O till it's ready? */
 282         if (m->hw_handler_name) {
 283                 m->pg_init_required = 1;
 284                 m->queue_io = 1;
 285         } else {
 286                 m->pg_init_required = 0;
 287                 m->queue_io = 0;
 288         }
 289
 290         m->pg_init_count = 0;
 291 }
 292
 293 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 294                                size_t nr_bytes)
 295 {
 296         struct dm_path *path;
 297
 298         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 299         if (!path)
 300                 return -ENXIO;
 301
 302         m->current_pgpath = path_to_pgpath(path);
 303
 304         if (m->current_pg != pg)
 305                 __switch_pg(m, m->current_pgpath);
 306
 307         return 0;
 308 }
 309
 310 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 311 {
 312         struct priority_group *pg;
 313         unsigned bypassed = 1;
 314
 315         if (!m->nr_valid_paths)
 316                 goto failed;
 317
 318         /* Were we instructed to switch PG? */
 319         if (m->next_pg) {
 320                 pg = m->next_pg;
 321                 m->next_pg = NULL;
 322                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 323                         return;
 324         }
 325
 326         /* Don't change PG until it has no remaining paths */
 327         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 328                 return;
 329
 330         /*
 331          * Loop through priority groups until we find a valid path.
 332          * First time we skip PGs marked 'bypassed'.
 333          * Second time we only try the ones we skipped, but set
 334          * pg_init_delay_retry so we do not hammer controllers.
 335          */
 336         do {
 337                 list_for_each_entry(pg, &m->priority_groups, list) {
 338                         if (pg->bypassed == bypassed)
 339                                 continue;
 340                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 341                                 if (!bypassed)
 342                                         m->pg_init_delay_retry = 1;
 343                                 return;
 344                         }
 345                 }
 346         } while (bypassed--);
 347
 348 failed:
 349         m->current_pgpath = NULL;
 350         m->current_pg = NULL;
 351 }
 352
 353 /*
 354  * Check whether bios must be queued in the device-mapper core rather
 355  * than here in the target.
 356  *
 357  * m->lock must be held on entry.
 358  *
 359  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 360  * same value then we are not between multipath_presuspend()
 361  * and multipath_resume() calls and we have no need to check
 362  * for the DMF_NOFLUSH_SUSPENDING flag.
 363  */
 364 static int __must_push_back(struct multipath *m)
 365 {
 366         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 367                 dm_noflush_suspending(m->ti));
 368 }
 369
 370 static int map_io(struct multipath *m, struct request *clone,
 371                   union map_info *map_context, unsigned was_queued)
 372 {
 373         int r = DM_MAPIO_REMAPPED;
 374         size_t nr_bytes = blk_rq_bytes(clone);
 375         unsigned long flags;
 376         struct pgpath *pgpath;
 377         struct block_device *bdev;
 378         struct dm_mpath_io *mpio = map_context->ptr;
 379
 380         spin_lock_irqsave(&m->lock, flags);
 381
 382         /* Do we need to select a new pgpath? */
 383         if (!m->current_pgpath ||
 384             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 385                 __choose_pgpath(m, nr_bytes);
 386
 387         pgpath = m->current_pgpath;
 388
 389         if (was_queued)
 390                 m->queue_size--;
 391
 392         if ((pgpath && m->queue_io) ||
 393             (!pgpath && m->queue_if_no_path)) {
 394                 /* Queue for the daemon to resubmit */
 395                 list_add_tail(&clone->queuelist, &m->queued_ios);
 396                 m->queue_size++;
 397                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 398                     !m->queue_io)
 399                         queue_work(kmultipathd, &m->process_queued_ios);
 400                 pgpath = NULL;
 401                 r = DM_MAPIO_SUBMITTED;
 402         } else if (pgpath) {
 403                 bdev = pgpath->path.dev->bdev;
 404                 clone->q = bdev_get_queue(bdev);
 405                 clone->rq_disk = bdev->bd_disk;
 406         } else if (__must_push_back(m))
 407                 r = DM_MAPIO_REQUEUE;
 408         else
 409                 r = -EIO;       /* Failed */
 410
 411         mpio->pgpath = pgpath;
 412         mpio->nr_bytes = nr_bytes;
 413
 414         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 415                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 416                                               nr_bytes);
 417
 418         spin_unlock_irqrestore(&m->lock, flags);
 419
 420         return r;
 421 }
 422
 423 /*
 424  * If we run out of usable paths, should we queue I/O or error it?
 425  */
 426 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 427                             unsigned save_old_value)
 428 {
 429         unsigned long flags;
 430
 431         spin_lock_irqsave(&m->lock, flags);
 432
 433         if (save_old_value)
 434                 m->saved_queue_if_no_path = m->queue_if_no_path;
 435         else
 436                 m->saved_queue_if_no_path = queue_if_no_path;
 437         m->queue_if_no_path = queue_if_no_path;
 438         if (!m->queue_if_no_path && m->queue_size)
 439                 queue_work(kmultipathd, &m->process_queued_ios);
 440
 441         spin_unlock_irqrestore(&m->lock, flags);
 442
 443         return 0;
 444 }
 445
 446 /*-----------------------------------------------------------------
 447  * The multipath daemon is responsible for resubmitting queued ios.
 448  *---------------------------------------------------------------*/
 449
 450 static void dispatch_queued_ios(struct multipath *m)
 451 {
 452         int r;
 453         unsigned long flags;
 454         union map_info *info;
 455         struct request *clone, *n;
 456         LIST_HEAD(cl);
 457
 458         spin_lock_irqsave(&m->lock, flags);
 459         list_splice_init(&m->queued_ios, &cl);
 460         spin_unlock_irqrestore(&m->lock, flags);
 461
 462         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 463                 list_del_init(&clone->queuelist);
 464
 465                 info = dm_get_rq_mapinfo(clone);
 466
 467                 r = map_io(m, clone, info, 1);
 468                 if (r < 0) {
 469                         clear_mapinfo(m, info);
 470                         dm_kill_unmapped_request(clone, r);
 471                 } else if (r == DM_MAPIO_REMAPPED)
 472                         dm_dispatch_request(clone);
 473                 else if (r == DM_MAPIO_REQUEUE) {
 474                         clear_mapinfo(m, info);
 475                         dm_requeue_unmapped_request(clone);
 476                 }
 477         }
 478 }
 479
 480 static void process_queued_ios(struct work_struct *work)
 481 {
 482         struct multipath *m =
 483                 container_of(work, struct multipath, process_queued_ios);
 484         struct pgpath *pgpath = NULL;
 485         unsigned must_queue = 1;
 486         unsigned long flags;
 487
 488         spin_lock_irqsave(&m->lock, flags);
 489
 490         if (!m->current_pgpath)
 491                 __choose_pgpath(m, 0);
 492
 493         pgpath = m->current_pgpath;
 494
 495         if ((pgpath && !m->queue_io) ||
 496             (!pgpath && !m->queue_if_no_path))
 497                 must_queue = 0;
 498
 499         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
 500                 __pg_init_all_paths(m);
 501
 502         spin_unlock_irqrestore(&m->lock, flags);
 503         if (!must_queue)
 504                 dispatch_queued_ios(m);
 505 }
 506
 507 /*
 508  * An event is triggered whenever a path is taken out of use.
 509  * Includes path failure and PG bypass.
 510  */
 511 static void trigger_event(struct work_struct *work)
 512 {
 513         struct multipath *m =
 514                 container_of(work, struct multipath, trigger_event);
 515
 516         dm_table_event(m->ti->table);
 517 }
 518
 519 /*-----------------------------------------------------------------
 520  * Constructor/argument parsing:
 521  * <#multipath feature args> [<arg>]*
 522  * <#hw_handler args> [hw_handler [<arg>]*]
 523  * <#priority groups>
 524  * <initial priority group>
 525  *     [<selector> <#selector args> [<arg>]*
 526  *      <#paths> <#per-path selector args>
 527  *         [<path> [<arg>]* ]+ ]+
 528  *---------------------------------------------------------------*/
 529 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 530                                struct dm_target *ti)
 531 {
 532         int r;
 533         struct path_selector_type *pst;
 534         unsigned ps_argc;
 535
 536         static struct dm_arg _args[] = {
 537                 {0, 1024, "invalid number of path selector args"},
 538         };
 539
 540         pst = dm_get_path_selector(dm_shift_arg(as));
 541         if (!pst) {
 542                 ti->error = "unknown path selector type";
 543                 return -EINVAL;
 544         }
 545
 546         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 547         if (r) {
 548                 dm_put_path_selector(pst);
 549                 return -EINVAL;
 550         }
 551
 552         r = pst->create(&pg->ps, ps_argc, as->argv);
 553         if (r) {
 554                 dm_put_path_selector(pst);
 555                 ti->error = "path selector constructor failed";
 556                 return r;
 557         }
 558
 559         pg->ps.type = pst;
 560         dm_consume_args(as, ps_argc);
 561
 562         return 0;
 563 }
 564
 565 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 566                                struct dm_target *ti)
 567 {
 568         int r;
 569         struct pgpath *p;
 570         struct multipath *m = ti->private;
 571
 572         /* we need at least a path arg */
 573         if (as->argc < 1) {
 574                 ti->error = "no device given";
 575                 return ERR_PTR(-EINVAL);
 576         }
 577
 578         p = alloc_pgpath();
 579         if (!p)
 580                 return ERR_PTR(-ENOMEM);
 581
 582         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 583                           &p->path.dev);
 584         if (r) {
 585                 ti->error = "error getting device";
 586                 goto bad;
 587         }
 588
 589         if (m->hw_handler_name) {
 590                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
 591
 592                 r = scsi_dh_attach(q, m->hw_handler_name);
 593                 if (r == -EBUSY) {
 594                         /*
 595                          * Already attached to different hw_handler,
 596                          * try to reattach with correct one.
 597                          */
 598                         scsi_dh_detach(q);
 599                         r = scsi_dh_attach(q, m->hw_handler_name);
 600                 }
 601
 602                 if (r < 0) {
 603                         ti->error = "error attaching hardware handler";
 604                         dm_put_device(ti, p->path.dev);
 605                         goto bad;
 606                 }
 607
 608                 if (m->hw_handler_params) {
 609                         r = scsi_dh_set_params(q, m->hw_handler_params);
 610                         if (r < 0) {
 611                                 ti->error = "unable to set hardware "
 612                                                         "handler parameters";
 613                                 scsi_dh_detach(q);
 614                                 dm_put_device(ti, p->path.dev);
 615                                 goto bad;
 616                         }
 617                 }
 618         }
 619
 620         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 621         if (r) {
 622                 dm_put_device(ti, p->path.dev);
 623                 goto bad;
 624         }
 625
 626         return p;
 627
 628  bad:
 629         free_pgpath(p);
 630         return ERR_PTR(r);
 631 }
 632
 633 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 634                                                    struct multipath *m)
 635 {
 636         static struct dm_arg _args[] = {
 637                 {1, 1024, "invalid number of paths"},
 638                 {0, 1024, "invalid number of selector args"}
 639         };
 640
 641         int r;
 642         unsigned i, nr_selector_args, nr_args;
 643         struct priority_group *pg;
 644         struct dm_target *ti = m->ti;
 645
 646         if (as->argc < 2) {
 647                 as->argc = 0;
 648                 ti->error = "not enough priority group arguments";
 649                 return ERR_PTR(-EINVAL);
 650         }
 651
 652         pg = alloc_priority_group();
 653         if (!pg) {
 654                 ti->error = "couldn't allocate priority group";
 655                 return ERR_PTR(-ENOMEM);
 656         }
 657         pg->m = m;
 658
 659         r = parse_path_selector(as, pg, ti);
 660         if (r)
 661                 goto bad;
 662
 663         /*
 664          * read the paths
 665          */
 666         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 667         if (r)
 668                 goto bad;
 669
 670         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 671         if (r)
 672                 goto bad;
 673
 674         nr_args = 1 + nr_selector_args;
 675         for (i = 0; i < pg->nr_pgpaths; i++) {
 676                 struct pgpath *pgpath;
 677                 struct dm_arg_set path_args;
 678
 679                 if (as->argc < nr_args) {
 680                         ti->error = "not enough path parameters";
 681                         r = -EINVAL;
 682                         goto bad;
 683                 }
 684
 685                 path_args.argc = nr_args;
 686                 path_args.argv = as->argv;
 687
 688                 pgpath = parse_path(&path_args, &pg->ps, ti);
 689                 if (IS_ERR(pgpath)) {
 690                         r = PTR_ERR(pgpath);
 691                         goto bad;
 692                 }
 693
 694                 pgpath->pg = pg;
 695                 list_add_tail(&pgpath->list, &pg->pgpaths);
 696                 dm_consume_args(as, nr_args);
 697         }
 698
 699         return pg;
 700
 701  bad:
 702         free_priority_group(pg, ti);
 703         return ERR_PTR(r);
 704 }
 705
 706 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 707 {
 708         unsigned hw_argc;
 709         int ret;
 710         struct dm_target *ti = m->ti;
 711
 712         static struct dm_arg _args[] = {
 713                 {0, 1024, "invalid number of hardware handler args"},
 714         };
 715
 716         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 717                 return -EINVAL;
 718
 719         if (!hw_argc)
 720                 return 0;
 721
 722         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 723         if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
 724                                      "scsi_dh_%s", m->hw_handler_name)) {
 725                 ti->error = "unknown hardware handler type";
 726                 ret = -EINVAL;
 727                 goto fail;
 728         }
 729
 730         if (hw_argc > 1) {
 731                 char *p;
 732                 int i, j, len = 4;
 733
 734                 for (i = 0; i <= hw_argc - 2; i++)
 735                         len += strlen(as->argv[i]) + 1;
 736                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 737                 if (!p) {
 738                         ti->error = "memory allocation failed";
 739                         ret = -ENOMEM;
 740                         goto fail;
 741                 }
 742                 j = sprintf(p, "%d", hw_argc - 1);
 743                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 744                         j = sprintf(p, "%s", as->argv[i]);
 745         }
 746         dm_consume_args(as, hw_argc - 1);
 747
 748         return 0;
 749 fail:
 750         kfree(m->hw_handler_name);
 751         m->hw_handler_name = NULL;
 752         return ret;
 753 }
 754
 755 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 756 {
 757         int r;
 758         unsigned argc;
 759         struct dm_target *ti = m->ti;
 760         const char *arg_name;
 761
 762         static struct dm_arg _args[] = {
 763                 {0, 5, "invalid number of feature args"},
 764                 {1, 50, "pg_init_retries must be between 1 and 50"},
 765                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 766         };
 767
 768         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 769         if (r)
 770                 return -EINVAL;
 771
 772         if (!argc)
 773                 return 0;
 774
 775         do {
 776                 arg_name = dm_shift_arg(as);
 777                 argc--;
 778
 779                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 780                         r = queue_if_no_path(m, 1, 0);
 781                         continue;
 782                 }
 783
 784                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 785                     (argc >= 1)) {
 786                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 787                         argc--;
 788                         continue;
 789                 }
 790
 791                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 792                     (argc >= 1)) {
 793                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 794                         argc--;
 795                         continue;
 796                 }
 797
 798                 ti->error = "Unrecognised multipath feature request";
 799                 r = -EINVAL;
 800         } while (argc && !r);
 801
 802         return r;
 803 }
 804
 805 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 806                          char **argv)
 807 {
 808         /* target arguments */
 809         static struct dm_arg _args[] = {
 810                 {0, 1024, "invalid number of priority groups"},
 811                 {0, 1024, "invalid initial priority group number"},
 812         };
 813
 814         int r;
 815         struct multipath *m;
 816         struct dm_arg_set as;
 817         unsigned pg_count = 0;
 818         unsigned next_pg_num;
 819
 820         as.argc = argc;
 821         as.argv = argv;
 822
 823         m = alloc_multipath(ti);
 824         if (!m) {
 825                 ti->error = "can't allocate multipath";
 826                 return -EINVAL;
 827         }
 828
 829         r = parse_features(&as, m);
 830         if (r)
 831                 goto bad;
 832
 833         r = parse_hw_handler(&as, m);
 834         if (r)
 835                 goto bad;
 836
 837         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 838         if (r)
 839                 goto bad;
 840
 841         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 842         if (r)
 843                 goto bad;
 844
 845         if ((!m->nr_priority_groups && next_pg_num) ||
 846             (m->nr_priority_groups && !next_pg_num)) {
 847                 ti->error = "invalid initial priority group";
 848                 r = -EINVAL;
 849                 goto bad;
 850         }
 851
 852         /* parse the priority groups */
 853         while (as.argc) {
 854                 struct priority_group *pg;
 855
 856                 pg = parse_priority_group(&as, m);
 857                 if (IS_ERR(pg)) {
 858                         r = PTR_ERR(pg);
 859                         goto bad;
 860                 }
 861
 862                 m->nr_valid_paths += pg->nr_pgpaths;
 863                 list_add_tail(&pg->list, &m->priority_groups);
 864                 pg_count++;
 865                 pg->pg_num = pg_count;
 866                 if (!--next_pg_num)
 867                         m->next_pg = pg;
 868         }
 869
 870         if (pg_count != m->nr_priority_groups) {
 871                 ti->error = "priority group count mismatch";
 872                 r = -EINVAL;
 873                 goto bad;
 874         }
 875
 876         ti->num_flush_requests = 1;
 877         ti->num_discard_requests = 1;
 878
 879         return 0;
 880
 881  bad:
 882         free_multipath(m);
 883         return r;
 884 }
 885
 886 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 887 {
 888         DECLARE_WAITQUEUE(wait, current);
 889         unsigned long flags;
 890
 891         add_wait_queue(&m->pg_init_wait, &wait);
 892
 893         while (1) {
 894                 set_current_state(TASK_UNINTERRUPTIBLE);
 895
 896                 spin_lock_irqsave(&m->lock, flags);
 897                 if (!m->pg_init_in_progress) {
 898                         spin_unlock_irqrestore(&m->lock, flags);
 899                         break;
 900                 }
 901                 spin_unlock_irqrestore(&m->lock, flags);
 902
 903                 io_schedule();
 904         }
 905         set_current_state(TASK_RUNNING);
 906
 907         remove_wait_queue(&m->pg_init_wait, &wait);
 908 }
 909
 910 static void flush_multipath_work(struct multipath *m)
 911 {
 912         flush_workqueue(kmpath_handlerd);
 913         multipath_wait_for_pg_init_completion(m);
 914         flush_workqueue(kmultipathd);
 915         flush_work_sync(&m->trigger_event);
 916 }
 917
 918 static void multipath_dtr(struct dm_target *ti)
 919 {
 920         struct multipath *m = ti->private;
 921
 922         flush_multipath_work(m);
 923         free_multipath(m);
 924 }
 925
 926 /*
 927  * Map cloned requests
 928  */
 929 static int multipath_map(struct dm_target *ti, struct request *clone,
 930                          union map_info *map_context)
 931 {
 932         int r;
 933         struct multipath *m = (struct multipath *) ti->private;
 934
 935         if (set_mapinfo(m, map_context) < 0)
 936                 /* ENOMEM, requeue */
 937                 return DM_MAPIO_REQUEUE;
 938
 939         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 940         r = map_io(m, clone, map_context, 0);
 941         if (r < 0 || r == DM_MAPIO_REQUEUE)
 942                 clear_mapinfo(m, map_context);
 943
 944         return r;
 945 }
 946
 947 /*
 948  * Take a path out of use.
 949  */
 950 static int fail_path(struct pgpath *pgpath)
 951 {
 952         unsigned long flags;
 953         struct multipath *m = pgpath->pg->m;
 954
 955         spin_lock_irqsave(&m->lock, flags);
 956
 957         if (!pgpath->is_active)
 958                 goto out;
 959
 960         DMWARN("Failing path %s.", pgpath->path.dev->name);
 961
 962         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 963         pgpath->is_active = 0;
 964         pgpath->fail_count++;
 965
 966         m->nr_valid_paths--;
 967
 968         if (pgpath == m->current_pgpath)
 969                 m->current_pgpath = NULL;
 970
 971         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 972                       pgpath->path.dev->name, m->nr_valid_paths);
 973
 974         schedule_work(&m->trigger_event);
 975
 976 out:
 977         spin_unlock_irqrestore(&m->lock, flags);
 978
 979         return 0;
 980 }
 981
 982 /*
 983  * Reinstate a previously-failed path
 984  */
 985 static int reinstate_path(struct pgpath *pgpath)
 986 {
 987         int r = 0;
 988         unsigned long flags;
 989         struct multipath *m = pgpath->pg->m;
 990
 991         spin_lock_irqsave(&m->lock, flags);
 992
 993         if (pgpath->is_active)
 994                 goto out;
 995
 996         if (!pgpath->pg->ps.type->reinstate_path) {
 997                 DMWARN("Reinstate path not supported by path selector %s",
 998                        pgpath->pg->ps.type->name);
 999                 r = -EINVAL;
1000                 goto out;
1001         }
1002
1003         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1004         if (r)
1005                 goto out;
1006
1007         pgpath->is_active = 1;
1008
1009         if (!m->nr_valid_paths++ && m->queue_size) {
1010                 m->current_pgpath = NULL;
1011                 queue_work(kmultipathd, &m->process_queued_ios);
1012         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1013                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1014                         m->pg_init_in_progress++;
1015         }
1016
1017         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1018                       pgpath->path.dev->name, m->nr_valid_paths);
1019
1020         schedule_work(&m->trigger_event);
1021
1022 out:
1023         spin_unlock_irqrestore(&m->lock, flags);
1024
1025         return r;
1026 }
1027
1028 /*
1029  * Fail or reinstate all paths that match the provided struct dm_dev.
1030  */
1031 static int action_dev(struct multipath *m, struct dm_dev *dev,
1032                       action_fn action)
1033 {
1034         int r = -EINVAL;
1035         struct pgpath *pgpath;
1036         struct priority_group *pg;
1037
1038         list_for_each_entry(pg, &m->priority_groups, list) {
1039                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1040                         if (pgpath->path.dev == dev)
1041                                 r = action(pgpath);
1042                 }
1043         }
1044
1045         return r;
1046 }
1047
1048 /*
1049  * Temporarily try to avoid having to use the specified PG
1050  */
1051 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1052                       int bypassed)
1053 {
1054         unsigned long flags;
1055
1056         spin_lock_irqsave(&m->lock, flags);
1057
1058         pg->bypassed = bypassed;
1059         m->current_pgpath = NULL;
1060         m->current_pg = NULL;
1061
1062         spin_unlock_irqrestore(&m->lock, flags);
1063
1064         schedule_work(&m->trigger_event);
1065 }
1066
1067 /*
1068  * Switch to using the specified PG from the next I/O that gets mapped
1069  */
1070 static int switch_pg_num(struct multipath *m, const char *pgstr)
1071 {
1072         struct priority_group *pg;
1073         unsigned pgnum;
1074         unsigned long flags;
1075         char dummy;
1076
1077         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1078             (pgnum > m->nr_priority_groups)) {
1079                 DMWARN("invalid PG number supplied to switch_pg_num");
1080                 return -EINVAL;
1081         }
1082
1083         spin_lock_irqsave(&m->lock, flags);
1084         list_for_each_entry(pg, &m->priority_groups, list) {
1085                 pg->bypassed = 0;
1086                 if (--pgnum)
1087                         continue;
1088
1089                 m->current_pgpath = NULL;
1090                 m->current_pg = NULL;
1091                 m->next_pg = pg;
1092         }
1093         spin_unlock_irqrestore(&m->lock, flags);
1094
1095         schedule_work(&m->trigger_event);
1096         return 0;
1097 }
1098
1099 /*
1100  * Set/clear bypassed status of a PG.
1101  * PGs are numbered upwards from 1 in the order they were declared.
1102  */
1103 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1104 {
1105         struct priority_group *pg;
1106         unsigned pgnum;
1107         char dummy;
1108
1109         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1110             (pgnum > m->nr_priority_groups)) {
1111                 DMWARN("invalid PG number supplied to bypass_pg");
1112                 return -EINVAL;
1113         }
1114
1115         list_for_each_entry(pg, &m->priority_groups, list) {
1116                 if (!--pgnum)
1117                         break;
1118         }
1119
1120         bypass_pg(m, pg, bypassed);
1121         return 0;
1122 }
1123
1124 /*
1125  * Should we retry pg_init immediately?
1126  */
1127 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1128 {
1129         unsigned long flags;
1130         int limit_reached = 0;
1131
1132         spin_lock_irqsave(&m->lock, flags);
1133
1134         if (m->pg_init_count <= m->pg_init_retries)
1135                 m->pg_init_required = 1;
1136         else
1137                 limit_reached = 1;
1138
1139         spin_unlock_irqrestore(&m->lock, flags);
1140
1141         return limit_reached;
1142 }
1143
1144 static void pg_init_done(void *data, int errors)
1145 {
1146         struct pgpath *pgpath = data;
1147         struct priority_group *pg = pgpath->pg;
1148         struct multipath *m = pg->m;
1149         unsigned long flags;
1150         unsigned delay_retry = 0;
1151
1152         /* device or driver problems */
1153         switch (errors) {
1154         case SCSI_DH_OK:
1155                 break;
1156         case SCSI_DH_NOSYS:
1157                 if (!m->hw_handler_name) {
1158                         errors = 0;
1159                         break;
1160                 }
1161                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1162                       "Error %d.", m->hw_handler_name, errors);
1163                 /*
1164                  * Fail path for now, so we do not ping pong
1165                  */
1166                 fail_path(pgpath);
1167                 break;
1168         case SCSI_DH_DEV_TEMP_BUSY:
1169                 /*
1170                  * Probably doing something like FW upgrade on the
1171                  * controller so try the other pg.
1172                  */
1173                 bypass_pg(m, pg, 1);
1174                 break;
1175         case SCSI_DH_RETRY:
1176                 /* Wait before retrying. */
1177                 delay_retry = 1;
1178         case SCSI_DH_IMM_RETRY:
1179         case SCSI_DH_RES_TEMP_UNAVAIL:
1180                 if (pg_init_limit_reached(m, pgpath))
1181                         fail_path(pgpath);
1182                 errors = 0;
1183                 break;
1184         default:
1185                 /*
1186                  * We probably do not want to fail the path for a device
1187                  * error, but this is what the old dm did. In future
1188                  * patches we can do more advanced handling.
1189                  */
1190                 fail_path(pgpath);
1191         }
1192
1193         spin_lock_irqsave(&m->lock, flags);
1194         if (errors) {
1195                 if (pgpath == m->current_pgpath) {
1196                         DMERR("Could not failover device. Error %d.", errors);
1197                         m->current_pgpath = NULL;
1198                         m->current_pg = NULL;
1199                 }
1200         } else if (!m->pg_init_required)
1201                 pg->bypassed = 0;
1202
1203         if (--m->pg_init_in_progress)
1204                 /* Activations of other paths are still on going */
1205                 goto out;
1206
1207         if (!m->pg_init_required)
1208                 m->queue_io = 0;
1209
1210         m->pg_init_delay_retry = delay_retry;
1211         queue_work(kmultipathd, &m->process_queued_ios);
1212
1213         /*
1214          * Wake up any thread waiting to suspend.
1215          */
1216         wake_up(&m->pg_init_wait);
1217
1218 out:
1219         spin_unlock_irqrestore(&m->lock, flags);
1220 }
1221
1222 static void activate_path(struct work_struct *work)
1223 {
1224         struct pgpath *pgpath =
1225                 container_of(work, struct pgpath, activate_path.work);
1226
1227         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1228                                 pg_init_done, pgpath);
1229 }
1230
1231 /*
1232  * end_io handling
1233  */
1234 static int do_end_io(struct multipath *m, struct request *clone,
1235                      int error, struct dm_mpath_io *mpio)
1236 {
1237         /*
1238          * We don't queue any clone request inside the multipath target
1239          * during end I/O handling, since those clone requests don't have
1240          * bio clones.  If we queue them inside the multipath target,
1241          * we need to make bio clones, that requires memory allocation.
1242          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1243          *  don't have bio clones.)
1244          * Instead of queueing the clone request here, we queue the original
1245          * request into dm core, which will remake a clone request and
1246          * clone bios for it and resubmit it later.
1247          */
1248         int r = DM_ENDIO_REQUEUE;
1249         unsigned long flags;
1250
1251         if (!error && !clone->errors)
1252                 return 0;       /* I/O complete */
1253
1254         if (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ)
1255                 return error;
1256
1257         if (mpio->pgpath)
1258                 fail_path(mpio->pgpath);
1259
1260         spin_lock_irqsave(&m->lock, flags);
1261         if (!m->nr_valid_paths) {
1262                 if (!m->queue_if_no_path) {
1263                         if (!__must_push_back(m))
1264                                 r = -EIO;
1265                 } else {
1266                         if (error == -EBADE)
1267                                 r = error;
1268                 }
1269         }
1270         spin_unlock_irqrestore(&m->lock, flags);
1271
1272         return r;
1273 }
1274
1275 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1276                             int error, union map_info *map_context)
1277 {
1278         struct multipath *m = ti->private;
1279         struct dm_mpath_io *mpio = map_context->ptr;
1280         struct pgpath *pgpath = mpio->pgpath;
1281         struct path_selector *ps;
1282         int r;
1283
1284         BUG_ON(!mpio);
1285
1286         r  = do_end_io(m, clone, error, mpio);
1287         if (pgpath) {
1288                 ps = &pgpath->pg->ps;
1289                 if (ps->type->end_io)
1290                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1291         }
1292         clear_mapinfo(m, map_context);
1293
1294         return r;
1295 }
1296
1297 /*
1298  * Suspend can't complete until all the I/O is processed so if
1299  * the last path fails we must error any remaining I/O.
1300  * Note that if the freeze_bdev fails while suspending, the
1301  * queue_if_no_path state is lost - userspace should reset it.
1302  */
1303 static void multipath_presuspend(struct dm_target *ti)
1304 {
1305         struct multipath *m = (struct multipath *) ti->private;
1306
1307         queue_if_no_path(m, 0, 1);
1308 }
1309
1310 static void multipath_postsuspend(struct dm_target *ti)
1311 {
1312         struct multipath *m = ti->private;
1313
1314         mutex_lock(&m->work_mutex);
1315         flush_multipath_work(m);
1316         mutex_unlock(&m->work_mutex);
1317 }
1318
1319 /*
1320  * Restore the queue_if_no_path setting.
1321  */
1322 static void multipath_resume(struct dm_target *ti)
1323 {
1324         struct multipath *m = (struct multipath *) ti->private;
1325         unsigned long flags;
1326
1327         spin_lock_irqsave(&m->lock, flags);
1328         m->queue_if_no_path = m->saved_queue_if_no_path;
1329         spin_unlock_irqrestore(&m->lock, flags);
1330 }
1331
1332 /*
1333  * Info output has the following format:
1334  * num_multipath_feature_args [multipath_feature_args]*
1335  * num_handler_status_args [handler_status_args]*
1336  * num_groups init_group_number
1337  *            [A|D|E num_ps_status_args [ps_status_args]*
1338  *             num_paths num_selector_args
1339  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1340  *
1341  * Table output has the following format (identical to the constructor string):
1342  * num_feature_args [features_args]*
1343  * num_handler_args hw_handler [hw_handler_args]*
1344  * num_groups init_group_number
1345  *     [priority selector-name num_ps_args [ps_args]*
1346  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1347  */
1348 static int multipath_status(struct dm_target *ti, status_type_t type,
1349                             char *result, unsigned int maxlen)
1350 {
1351         int sz = 0;
1352         unsigned long flags;
1353         struct multipath *m = (struct multipath *) ti->private;
1354         struct priority_group *pg;
1355         struct pgpath *p;
1356         unsigned pg_num;
1357         char state;
1358
1359         spin_lock_irqsave(&m->lock, flags);
1360
1361         /* Features */
1362         if (type == STATUSTYPE_INFO)
1363                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1364         else {
1365                 DMEMIT("%u ", m->queue_if_no_path +
1366                               (m->pg_init_retries > 0) * 2 +
1367                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1368                 if (m->queue_if_no_path)
1369                         DMEMIT("queue_if_no_path ");
1370                 if (m->pg_init_retries)
1371                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1372                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1373                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1374         }
1375
1376         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1377                 DMEMIT("0 ");
1378         else
1379                 DMEMIT("1 %s ", m->hw_handler_name);
1380
1381         DMEMIT("%u ", m->nr_priority_groups);
1382
1383         if (m->next_pg)
1384                 pg_num = m->next_pg->pg_num;
1385         else if (m->current_pg)
1386                 pg_num = m->current_pg->pg_num;
1387         else
1388                 pg_num = (m->nr_priority_groups ? 1 : 0);
1389
1390         DMEMIT("%u ", pg_num);
1391
1392         switch (type) {
1393         case STATUSTYPE_INFO:
1394                 list_for_each_entry(pg, &m->priority_groups, list) {
1395                         if (pg->bypassed)
1396                                 state = 'D';    /* Disabled */
1397                         else if (pg == m->current_pg)
1398                                 state = 'A';    /* Currently Active */
1399                         else
1400                                 state = 'E';    /* Enabled */
1401
1402                         DMEMIT("%c ", state);
1403
1404                         if (pg->ps.type->status)
1405                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1406                                                           result + sz,
1407                                                           maxlen - sz);
1408                         else
1409                                 DMEMIT("0 ");
1410
1411                         DMEMIT("%u %u ", pg->nr_pgpaths,
1412                                pg->ps.type->info_args);
1413
1414                         list_for_each_entry(p, &pg->pgpaths, list) {
1415                                 DMEMIT("%s %s %u ", p->path.dev->name,
1416                                        p->is_active ? "A" : "F",
1417                                        p->fail_count);
1418                                 if (pg->ps.type->status)
1419                                         sz += pg->ps.type->status(&pg->ps,
1420                                               &p->path, type, result + sz,
1421                                               maxlen - sz);
1422                         }
1423                 }
1424                 break;
1425
1426         case STATUSTYPE_TABLE:
1427                 list_for_each_entry(pg, &m->priority_groups, list) {
1428                         DMEMIT("%s ", pg->ps.type->name);
1429
1430                         if (pg->ps.type->status)
1431                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1432                                                           result + sz,
1433                                                           maxlen - sz);
1434                         else
1435                                 DMEMIT("0 ");
1436
1437                         DMEMIT("%u %u ", pg->nr_pgpaths,
1438                                pg->ps.type->table_args);
1439
1440                         list_for_each_entry(p, &pg->pgpaths, list) {
1441                                 DMEMIT("%s ", p->path.dev->name);
1442                                 if (pg->ps.type->status)
1443                                         sz += pg->ps.type->status(&pg->ps,
1444                                               &p->path, type, result + sz,
1445                                               maxlen - sz);
1446                         }
1447                 }
1448                 break;
1449         }
1450
1451         spin_unlock_irqrestore(&m->lock, flags);
1452
1453         return 0;
1454 }
1455
1456 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1457 {
1458         int r = -EINVAL;
1459         struct dm_dev *dev;
1460         struct multipath *m = (struct multipath *) ti->private;
1461         action_fn action;
1462
1463         mutex_lock(&m->work_mutex);
1464
1465         if (dm_suspended(ti)) {
1466                 r = -EBUSY;
1467                 goto out;
1468         }
1469
1470         if (argc == 1) {
1471                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1472                         r = queue_if_no_path(m, 1, 0);
1473                         goto out;
1474                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1475                         r = queue_if_no_path(m, 0, 0);
1476                         goto out;
1477                 }
1478         }
1479
1480         if (argc != 2) {
1481                 DMWARN("Unrecognised multipath message received.");
1482                 goto out;
1483         }
1484
1485         if (!strcasecmp(argv[0], "disable_group")) {
1486                 r = bypass_pg_num(m, argv[1], 1);
1487                 goto out;
1488         } else if (!strcasecmp(argv[0], "enable_group")) {
1489                 r = bypass_pg_num(m, argv[1], 0);
1490                 goto out;
1491         } else if (!strcasecmp(argv[0], "switch_group")) {
1492                 r = switch_pg_num(m, argv[1]);
1493                 goto out;
1494         } else if (!strcasecmp(argv[0], "reinstate_path"))
1495                 action = reinstate_path;
1496         else if (!strcasecmp(argv[0], "fail_path"))
1497                 action = fail_path;
1498         else {
1499                 DMWARN("Unrecognised multipath message received.");
1500                 goto out;
1501         }
1502
1503         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1504         if (r) {
1505                 DMWARN("message: error getting device %s",
1506                        argv[1]);
1507                 goto out;
1508         }
1509
1510         r = action_dev(m, dev, action);
1511
1512         dm_put_device(ti, dev);
1513
1514 out:
1515         mutex_unlock(&m->work_mutex);
1516         return r;
1517 }
1518
1519 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1520                            unsigned long arg)
1521 {
1522         struct multipath *m = ti->private;
1523         struct block_device *bdev;
1524         fmode_t mode;
1525         unsigned long flags;
1526         int r;
1527
1528 again:
1529         bdev = NULL;
1530         mode = 0;
1531         r = 0;
1532
1533         spin_lock_irqsave(&m->lock, flags);
1534
1535         if (!m->current_pgpath)
1536                 __choose_pgpath(m, 0);
1537
1538         if (m->current_pgpath) {
1539                 bdev = m->current_pgpath->path.dev->bdev;
1540                 mode = m->current_pgpath->path.dev->mode;
1541         }
1542
1543         if (m->queue_io)
1544                 r = -EAGAIN;
1545         else if (!bdev)
1546                 r = -EIO;
1547
1548         spin_unlock_irqrestore(&m->lock, flags);
1549
1550         /*
1551          * Only pass ioctls through if the device sizes match exactly.
1552          */
1553         if (!r && ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
1554                 r = scsi_verify_blk_ioctl(NULL, cmd);
1555
1556         if (r == -EAGAIN && !fatal_signal_pending(current)) {
1557                 queue_work(kmultipathd, &m->process_queued_ios);
1558                 msleep(10);
1559                 goto again;
1560         }
1561
1562         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1563 }
1564
1565 static int multipath_iterate_devices(struct dm_target *ti,
1566                                      iterate_devices_callout_fn fn, void *data)
1567 {
1568         struct multipath *m = ti->private;
1569         struct priority_group *pg;
1570         struct pgpath *p;
1571         int ret = 0;
1572
1573         list_for_each_entry(pg, &m->priority_groups, list) {
1574                 list_for_each_entry(p, &pg->pgpaths, list) {
1575                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1576                         if (ret)
1577                                 goto out;
1578                 }
1579         }
1580
1581 out:
1582         return ret;
1583 }
1584
1585 static int __pgpath_busy(struct pgpath *pgpath)
1586 {
1587         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1588
1589         return dm_underlying_device_busy(q);
1590 }
1591
1592 /*
1593  * We return "busy", only when we can map I/Os but underlying devices
1594  * are busy (so even if we map I/Os now, the I/Os will wait on
1595  * the underlying queue).
1596  * In other words, if we want to kill I/Os or queue them inside us
1597  * due to map unavailability, we don't return "busy".  Otherwise,
1598  * dm core won't give us the I/Os and we can't do what we want.
1599  */
1600 static int multipath_busy(struct dm_target *ti)
1601 {
1602         int busy = 0, has_active = 0;
1603         struct multipath *m = ti->private;
1604         struct priority_group *pg;
1605         struct pgpath *pgpath;
1606         unsigned long flags;
1607
1608         spin_lock_irqsave(&m->lock, flags);
1609
1610         /* Guess which priority_group will be used at next mapping time */
1611         if (unlikely(!m->current_pgpath && m->next_pg))
1612                 pg = m->next_pg;
1613         else if (likely(m->current_pg))
1614                 pg = m->current_pg;
1615         else
1616                 /*
1617                  * We don't know which pg will be used at next mapping time.
1618                  * We don't call __choose_pgpath() here to avoid to trigger
1619                  * pg_init just by busy checking.
1620                  * So we don't know whether underlying devices we will be using
1621                  * at next mapping time are busy or not. Just try mapping.
1622                  */
1623                 goto out;
1624
1625         /*
1626          * If there is one non-busy active path at least, the path selector
1627          * will be able to select it. So we consider such a pg as not busy.
1628          */
1629         busy = 1;
1630         list_for_each_entry(pgpath, &pg->pgpaths, list)
1631                 if (pgpath->is_active) {
1632                         has_active = 1;
1633
1634                         if (!__pgpath_busy(pgpath)) {
1635                                 busy = 0;
1636                                 break;
1637                         }
1638                 }
1639
1640         if (!has_active)
1641                 /*
1642                  * No active path in this pg, so this pg won't be used and
1643                  * the current_pg will be changed at next mapping time.
1644                  * We need to try mapping to determine it.
1645                  */
1646                 busy = 0;
1647
1648 out:
1649         spin_unlock_irqrestore(&m->lock, flags);
1650
1651         return busy;
1652 }
1653
1654 /*-----------------------------------------------------------------
1655  * Module setup
1656  *---------------------------------------------------------------*/
1657 static struct target_type multipath_target = {
1658         .name = "multipath",
1659         .version = {1, 4, 0},
1660         .module = THIS_MODULE,
1661         .ctr = multipath_ctr,
1662         .dtr = multipath_dtr,
1663         .map_rq = multipath_map,
1664         .rq_end_io = multipath_end_io,
1665         .presuspend = multipath_presuspend,
1666         .postsuspend = multipath_postsuspend,
1667         .resume = multipath_resume,
1668         .status = multipath_status,
1669         .message = multipath_message,
1670         .ioctl  = multipath_ioctl,
1671         .iterate_devices = multipath_iterate_devices,
1672         .busy = multipath_busy,
1673 };
1674
1675 static int __init dm_multipath_init(void)
1676 {
1677         int r;
1678
1679         /* allocate a slab for the dm_ios */
1680         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1681         if (!_mpio_cache)
1682                 return -ENOMEM;
1683
1684         r = dm_register_target(&multipath_target);
1685         if (r < 0) {
1686                 DMERR("register failed %d", r);
1687                 kmem_cache_destroy(_mpio_cache);
1688                 return -EINVAL;
1689         }
1690
1691         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1692         if (!kmultipathd) {
1693                 DMERR("failed to create workqueue kmpathd");
1694                 dm_unregister_target(&multipath_target);
1695                 kmem_cache_destroy(_mpio_cache);
1696                 return -ENOMEM;
1697         }
1698
1699         /*
1700          * A separate workqueue is used to handle the device handlers
1701          * to avoid overloading existing workqueue. Overloading the
1702          * old workqueue would also create a bottleneck in the
1703          * path of the storage hardware device activation.
1704          */
1705         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1706                                                   WQ_MEM_RECLAIM);
1707         if (!kmpath_handlerd) {
1708                 DMERR("failed to create workqueue kmpath_handlerd");
1709                 destroy_workqueue(kmultipathd);
1710                 dm_unregister_target(&multipath_target);
1711                 kmem_cache_destroy(_mpio_cache);
1712                 return -ENOMEM;
1713         }
1714
1715         DMINFO("version %u.%u.%u loaded",
1716                multipath_target.version[0], multipath_target.version[1],
1717                multipath_target.version[2]);
1718
1719         return r;
1720 }
1721
1722 static void __exit dm_multipath_exit(void)
1723 {
1724         destroy_workqueue(kmpath_handlerd);
1725         destroy_workqueue(kmultipathd);
1726
1727         dm_unregister_target(&multipath_target);
1728         kmem_cache_destroy(_mpio_cache);
1729 }
1730
1731 module_init(dm_multipath_init);
1732 module_exit(dm_multipath_exit);
1733
1734 MODULE_DESCRIPTION(DM_NAME " multipath target");
1735 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1736 MODULE_LICENSE("GPL");