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