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