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