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.h"
  11 #include "dm-path-selector.h"
  12 #include "dm-uevent.h"
  13
  14 #include <linux/ctype.h>
  15 #include <linux/init.h>
  16 #include <linux/mempool.h>
  17 #include <linux/module.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/slab.h>
  20 #include <linux/time.h>
  21 #include <linux/workqueue.h>
  22 #include <linux/delay.h>
  23 #include <scsi/scsi_dh.h>
  24 #include <linux/atomic.h>
  25
  26 #define DM_MSG_PREFIX "multipath"
  27 #define DM_PG_INIT_DELAY_MSECS 2000
  28 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  29
  30 /* Path properties */
  31 struct pgpath {
  32         struct list_head list;
  33
  34         struct priority_group *pg;      /* Owning PG */
  35         unsigned is_active;             /* Path status */
  36         unsigned fail_count;            /* Cumulative failure count */
  37
  38         struct dm_path path;
  39         struct delayed_work activate_path;
  40 };
  41
  42 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  43
  44 /*
  45  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  46  * Each has a path selector which controls which path gets used.
  47  */
  48 struct priority_group {
  49         struct list_head list;
  50
  51         struct multipath *m;            /* Owning multipath instance */
  52         struct path_selector ps;
  53
  54         unsigned pg_num;                /* Reference number */
  55         unsigned bypassed;              /* Temporarily bypass this PG? */
  56
  57         unsigned nr_pgpaths;            /* Number of paths in PG */
  58         struct list_head pgpaths;
  59 };
  60
  61 /* Multipath context */
  62 struct multipath {
  63         struct list_head list;
  64         struct dm_target *ti;
  65
  66         const char *hw_handler_name;
  67         char *hw_handler_params;
  68
  69         spinlock_t lock;
  70
  71         unsigned nr_priority_groups;
  72         struct list_head priority_groups;
  73
  74         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  75
  76         unsigned pg_init_required;      /* pg_init needs calling? */
  77         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  78         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  79
  80         unsigned nr_valid_paths;        /* Total number of usable paths */
  81         struct pgpath *current_pgpath;
  82         struct priority_group *current_pg;
  83         struct priority_group *next_pg; /* Switch to this PG if set */
  84         unsigned repeat_count;          /* I/Os left before calling PS again */
  85
  86         unsigned queue_io:1;            /* Must we queue all I/O? */
  87         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  88         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  89         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  90         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  91
  92         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  93         unsigned pg_init_count;         /* Number of times pg_init called */
  94         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  95
  96         struct work_struct trigger_event;
  97
  98         /*
  99          * We must use a mempool of dm_mpath_io structs so that we
 100          * can resubmit bios on error.
 101          */
 102         mempool_t *mpio_pool;
 103
 104         struct mutex work_mutex;
 105 };
 106
 107 /*
 108  * Context information attached to each bio we process.
 109  */
 110 struct dm_mpath_io {
 111         struct pgpath *pgpath;
 112         size_t nr_bytes;
 113 };
 114
 115 typedef int (*action_fn) (struct pgpath *pgpath);
 116
 117 static struct kmem_cache *_mpio_cache;
 118
 119 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 120 static void trigger_event(struct work_struct *work);
 121 static void activate_path(struct work_struct *work);
 122 static int __pgpath_busy(struct pgpath *pgpath);
 123
 124
 125 /*-----------------------------------------------
 126  * Allocation routines
 127  *-----------------------------------------------*/
 128
 129 static struct pgpath *alloc_pgpath(void)
 130 {
 131         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 132
 133         if (pgpath) {
 134                 pgpath->is_active = 1;
 135                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 136         }
 137
 138         return pgpath;
 139 }
 140
 141 static void free_pgpath(struct pgpath *pgpath)
 142 {
 143         kfree(pgpath);
 144 }
 145
 146 static struct priority_group *alloc_priority_group(void)
 147 {
 148         struct priority_group *pg;
 149
 150         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 151
 152         if (pg)
 153                 INIT_LIST_HEAD(&pg->pgpaths);
 154
 155         return pg;
 156 }
 157
 158 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 159 {
 160         struct pgpath *pgpath, *tmp;
 161         struct multipath *m = ti->private;
 162
 163         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 164                 list_del(&pgpath->list);
 165                 if (m->hw_handler_name)
 166                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 167                 dm_put_device(ti, pgpath->path.dev);
 168                 free_pgpath(pgpath);
 169         }
 170 }
 171
 172 static void free_priority_group(struct priority_group *pg,
 173                                 struct dm_target *ti)
 174 {
 175         struct path_selector *ps = &pg->ps;
 176
 177         if (ps->type) {
 178                 ps->type->destroy(ps);
 179                 dm_put_path_selector(ps->type);
 180         }
 181
 182         free_pgpaths(&pg->pgpaths, ti);
 183         kfree(pg);
 184 }
 185
 186 static struct multipath *alloc_multipath(struct dm_target *ti)
 187 {
 188         struct multipath *m;
 189         unsigned min_ios = dm_get_reserved_rq_based_ios();
 190
 191         m = kzalloc(sizeof(*m), GFP_KERNEL);
 192         if (m) {
 193                 INIT_LIST_HEAD(&m->priority_groups);
 194                 spin_lock_init(&m->lock);
 195                 m->queue_io = 1;
 196                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 197                 INIT_WORK(&m->trigger_event, trigger_event);
 198                 init_waitqueue_head(&m->pg_init_wait);
 199                 mutex_init(&m->work_mutex);
 200                 m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 201                 if (!m->mpio_pool) {
 202                         kfree(m);
 203                         return NULL;
 204                 }
 205                 m->ti = ti;
 206                 ti->private = m;
 207         }
 208
 209         return m;
 210 }
 211
 212 static void free_multipath(struct multipath *m)
 213 {
 214         struct priority_group *pg, *tmp;
 215
 216         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 217                 list_del(&pg->list);
 218                 free_priority_group(pg, m->ti);
 219         }
 220
 221         kfree(m->hw_handler_name);
 222         kfree(m->hw_handler_params);
 223         mempool_destroy(m->mpio_pool);
 224         kfree(m);
 225 }
 226
 227 static int set_mapinfo(struct multipath *m, union map_info *info)
 228 {
 229         struct dm_mpath_io *mpio;
 230
 231         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 232         if (!mpio)
 233                 return -ENOMEM;
 234
 235         memset(mpio, 0, sizeof(*mpio));
 236         info->ptr = mpio;
 237
 238         return 0;
 239 }
 240
 241 static void clear_mapinfo(struct multipath *m, union map_info *info)
 242 {
 243         struct dm_mpath_io *mpio = info->ptr;
 244
 245         info->ptr = NULL;
 246         mempool_free(mpio, m->mpio_pool);
 247 }
 248
 249 /*-----------------------------------------------
 250  * Path selection
 251  *-----------------------------------------------*/
 252
 253 static int __pg_init_all_paths(struct multipath *m)
 254 {
 255         struct pgpath *pgpath;
 256         unsigned long pg_init_delay = 0;
 257
 258         if (m->pg_init_in_progress || m->pg_init_disabled)
 259                 return 0;
 260
 261         m->pg_init_count++;
 262         m->pg_init_required = 0;
 263
 264         /* Check here to reset pg_init_required */
 265         if (!m->current_pg)
 266                 return 0;
 267
 268         if (m->pg_init_delay_retry)
 269                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 270                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 271         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 272                 /* Skip failed paths */
 273                 if (!pgpath->is_active)
 274                         continue;
 275                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 276                                        pg_init_delay))
 277                         m->pg_init_in_progress++;
 278         }
 279         return m->pg_init_in_progress;
 280 }
 281
 282 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 283 {
 284         m->current_pg = pgpath->pg;
 285
 286         /* Must we initialise the PG first, and queue I/O till it's ready? */
 287         if (m->hw_handler_name) {
 288                 m->pg_init_required = 1;
 289                 m->queue_io = 1;
 290         } else {
 291                 m->pg_init_required = 0;
 292                 m->queue_io = 0;
 293         }
 294
 295         m->pg_init_count = 0;
 296 }
 297
 298 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 299                                size_t nr_bytes)
 300 {
 301         struct dm_path *path;
 302
 303         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 304         if (!path)
 305                 return -ENXIO;
 306
 307         m->current_pgpath = path_to_pgpath(path);
 308
 309         if (m->current_pg != pg)
 310                 __switch_pg(m, m->current_pgpath);
 311
 312         return 0;
 313 }
 314
 315 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 316 {
 317         struct priority_group *pg;
 318         unsigned bypassed = 1;
 319
 320         if (!m->nr_valid_paths)
 321                 goto failed;
 322
 323         /* Were we instructed to switch PG? */
 324         if (m->next_pg) {
 325                 pg = m->next_pg;
 326                 m->next_pg = NULL;
 327                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 328                         return;
 329         }
 330
 331         /* Don't change PG until it has no remaining paths */
 332         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 333                 return;
 334
 335         /*
 336          * Loop through priority groups until we find a valid path.
 337          * First time we skip PGs marked 'bypassed'.
 338          * Second time we only try the ones we skipped, but set
 339          * pg_init_delay_retry so we do not hammer controllers.
 340          */
 341         do {
 342                 list_for_each_entry(pg, &m->priority_groups, list) {
 343                         if (pg->bypassed == bypassed)
 344                                 continue;
 345                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 346                                 if (!bypassed)
 347                                         m->pg_init_delay_retry = 1;
 348                                 return;
 349                         }
 350                 }
 351         } while (bypassed--);
 352
 353 failed:
 354         m->current_pgpath = NULL;
 355         m->current_pg = NULL;
 356 }
 357
 358 /*
 359  * Check whether bios must be queued in the device-mapper core rather
 360  * than here in the target.
 361  *
 362  * m->lock must be held on entry.
 363  *
 364  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 365  * same value then we are not between multipath_presuspend()
 366  * and multipath_resume() calls and we have no need to check
 367  * for the DMF_NOFLUSH_SUSPENDING flag.
 368  */
 369 static int __must_push_back(struct multipath *m)
 370 {
 371         return (m->queue_if_no_path ||
 372                 (m->queue_if_no_path != m->saved_queue_if_no_path &&
 373                  dm_noflush_suspending(m->ti)));
 374 }
 375
 376 /*
 377  * Map cloned requests
 378  */
 379 static int multipath_map(struct dm_target *ti, struct request *clone,
 380                          union map_info *map_context)
 381 {
 382         struct multipath *m = (struct multipath *) ti->private;
 383         int r = DM_MAPIO_REQUEUE;
 384         size_t nr_bytes = blk_rq_bytes(clone);
 385         unsigned long flags;
 386         struct pgpath *pgpath;
 387         struct block_device *bdev;
 388         struct dm_mpath_io *mpio;
 389
 390         spin_lock_irqsave(&m->lock, flags);
 391
 392         /* Do we need to select a new pgpath? */
 393         if (!m->current_pgpath ||
 394             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 395                 __choose_pgpath(m, nr_bytes);
 396
 397         pgpath = m->current_pgpath;
 398
 399         if (!pgpath) {
 400                 if (!__must_push_back(m))
 401                         r = -EIO;       /* Failed */
 402                 goto out_unlock;
 403         } else if (m->queue_io || m->pg_init_required) {
 404                 __pg_init_all_paths(m);
 405                 goto out_unlock;
 406         }
 407
 408         if (set_mapinfo(m, map_context) < 0)
 409                 /* ENOMEM, requeue */
 410                 goto out_unlock;
 411
 412         bdev = pgpath->path.dev->bdev;
 413         clone->q = bdev_get_queue(bdev);
 414         clone->rq_disk = bdev->bd_disk;
 415         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 416         mpio = map_context->ptr;
 417         mpio->pgpath = pgpath;
 418         mpio->nr_bytes = nr_bytes;
 419         if (pgpath->pg->ps.type->start_io)
 420                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 421                                               &pgpath->path,
 422                                               nr_bytes);
 423         r = DM_MAPIO_REMAPPED;
 424
 425 out_unlock:
 426         spin_unlock_irqrestore(&m->lock, flags);
 427
 428         return r;
 429 }
 430
 431 /*
 432  * If we run out of usable paths, should we queue I/O or error it?
 433  */
 434 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 435                             unsigned save_old_value)
 436 {
 437         unsigned long flags;
 438
 439         spin_lock_irqsave(&m->lock, flags);
 440
 441         if (save_old_value)
 442                 m->saved_queue_if_no_path = m->queue_if_no_path;
 443         else
 444                 m->saved_queue_if_no_path = queue_if_no_path;
 445         m->queue_if_no_path = queue_if_no_path;
 446         spin_unlock_irqrestore(&m->lock, flags);
 447
 448         if (!queue_if_no_path)
 449                 dm_table_run_md_queue_async(m->ti->table);
 450
 451         return 0;
 452 }
 453
 454 /*
 455  * An event is triggered whenever a path is taken out of use.
 456  * Includes path failure and PG bypass.
 457  */
 458 static void trigger_event(struct work_struct *work)
 459 {
 460         struct multipath *m =
 461                 container_of(work, struct multipath, trigger_event);
 462
 463         dm_table_event(m->ti->table);
 464 }
 465
 466 /*-----------------------------------------------------------------
 467  * Constructor/argument parsing:
 468  * <#multipath feature args> [<arg>]*
 469  * <#hw_handler args> [hw_handler [<arg>]*]
 470  * <#priority groups>
 471  * <initial priority group>
 472  *     [<selector> <#selector args> [<arg>]*
 473  *      <#paths> <#per-path selector args>
 474  *         [<path> [<arg>]* ]+ ]+
 475  *---------------------------------------------------------------*/
 476 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 477                                struct dm_target *ti)
 478 {
 479         int r;
 480         struct path_selector_type *pst;
 481         unsigned ps_argc;
 482
 483         static struct dm_arg _args[] = {
 484                 {0, 1024, "invalid number of path selector args"},
 485         };
 486
 487         pst = dm_get_path_selector(dm_shift_arg(as));
 488         if (!pst) {
 489                 ti->error = "unknown path selector type";
 490                 return -EINVAL;
 491         }
 492
 493         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 494         if (r) {
 495                 dm_put_path_selector(pst);
 496                 return -EINVAL;
 497         }
 498
 499         r = pst->create(&pg->ps, ps_argc, as->argv);
 500         if (r) {
 501                 dm_put_path_selector(pst);
 502                 ti->error = "path selector constructor failed";
 503                 return r;
 504         }
 505
 506         pg->ps.type = pst;
 507         dm_consume_args(as, ps_argc);
 508
 509         return 0;
 510 }
 511
 512 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 513                                struct dm_target *ti)
 514 {
 515         int r;
 516         struct pgpath *p;
 517         struct multipath *m = ti->private;
 518         struct request_queue *q = NULL;
 519         const char *attached_handler_name;
 520
 521         /* we need at least a path arg */
 522         if (as->argc < 1) {
 523                 ti->error = "no device given";
 524                 return ERR_PTR(-EINVAL);
 525         }
 526
 527         p = alloc_pgpath();
 528         if (!p)
 529                 return ERR_PTR(-ENOMEM);
 530
 531         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 532                           &p->path.dev);
 533         if (r) {
 534                 ti->error = "error getting device";
 535                 goto bad;
 536         }
 537
 538         if (m->retain_attached_hw_handler || m->hw_handler_name)
 539                 q = bdev_get_queue(p->path.dev->bdev);
 540
 541         if (m->retain_attached_hw_handler) {
 542                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 543                 if (attached_handler_name) {
 544                         /*
 545                          * Reset hw_handler_name to match the attached handler
 546                          * and clear any hw_handler_params associated with the
 547                          * ignored handler.
 548                          *
 549                          * NB. This modifies the table line to show the actual
 550                          * handler instead of the original table passed in.
 551                          */
 552                         kfree(m->hw_handler_name);
 553                         m->hw_handler_name = attached_handler_name;
 554
 555                         kfree(m->hw_handler_params);
 556                         m->hw_handler_params = NULL;
 557                 }
 558         }
 559
 560         if (m->hw_handler_name) {
 561                 /*
 562                  * Increments scsi_dh reference, even when using an
 563                  * already-attached handler.
 564                  */
 565                 r = scsi_dh_attach(q, m->hw_handler_name);
 566                 if (r == -EBUSY) {
 567                         /*
 568                          * Already attached to different hw_handler:
 569                          * try to reattach with correct one.
 570                          */
 571                         scsi_dh_detach(q);
 572                         r = scsi_dh_attach(q, m->hw_handler_name);
 573                 }
 574
 575                 if (r < 0) {
 576                         ti->error = "error attaching hardware handler";
 577                         dm_put_device(ti, p->path.dev);
 578                         goto bad;
 579                 }
 580
 581                 if (m->hw_handler_params) {
 582                         r = scsi_dh_set_params(q, m->hw_handler_params);
 583                         if (r < 0) {
 584                                 ti->error = "unable to set hardware "
 585                                                         "handler parameters";
 586                                 scsi_dh_detach(q);
 587                                 dm_put_device(ti, p->path.dev);
 588                                 goto bad;
 589                         }
 590                 }
 591         }
 592
 593         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 594         if (r) {
 595                 dm_put_device(ti, p->path.dev);
 596                 goto bad;
 597         }
 598
 599         return p;
 600
 601  bad:
 602         free_pgpath(p);
 603         return ERR_PTR(r);
 604 }
 605
 606 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 607                                                    struct multipath *m)
 608 {
 609         static struct dm_arg _args[] = {
 610                 {1, 1024, "invalid number of paths"},
 611                 {0, 1024, "invalid number of selector args"}
 612         };
 613
 614         int r;
 615         unsigned i, nr_selector_args, nr_args;
 616         struct priority_group *pg;
 617         struct dm_target *ti = m->ti;
 618
 619         if (as->argc < 2) {
 620                 as->argc = 0;
 621                 ti->error = "not enough priority group arguments";
 622                 return ERR_PTR(-EINVAL);
 623         }
 624
 625         pg = alloc_priority_group();
 626         if (!pg) {
 627                 ti->error = "couldn't allocate priority group";
 628                 return ERR_PTR(-ENOMEM);
 629         }
 630         pg->m = m;
 631
 632         r = parse_path_selector(as, pg, ti);
 633         if (r)
 634                 goto bad;
 635
 636         /*
 637          * read the paths
 638          */
 639         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 640         if (r)
 641                 goto bad;
 642
 643         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 644         if (r)
 645                 goto bad;
 646
 647         nr_args = 1 + nr_selector_args;
 648         for (i = 0; i < pg->nr_pgpaths; i++) {
 649                 struct pgpath *pgpath;
 650                 struct dm_arg_set path_args;
 651
 652                 if (as->argc < nr_args) {
 653                         ti->error = "not enough path parameters";
 654                         r = -EINVAL;
 655                         goto bad;
 656                 }
 657
 658                 path_args.argc = nr_args;
 659                 path_args.argv = as->argv;
 660
 661                 pgpath = parse_path(&path_args, &pg->ps, ti);
 662                 if (IS_ERR(pgpath)) {
 663                         r = PTR_ERR(pgpath);
 664                         goto bad;
 665                 }
 666
 667                 pgpath->pg = pg;
 668                 list_add_tail(&pgpath->list, &pg->pgpaths);
 669                 dm_consume_args(as, nr_args);
 670         }
 671
 672         return pg;
 673
 674  bad:
 675         free_priority_group(pg, ti);
 676         return ERR_PTR(r);
 677 }
 678
 679 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 680 {
 681         unsigned hw_argc;
 682         int ret;
 683         struct dm_target *ti = m->ti;
 684
 685         static struct dm_arg _args[] = {
 686                 {0, 1024, "invalid number of hardware handler args"},
 687         };
 688
 689         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 690                 return -EINVAL;
 691
 692         if (!hw_argc)
 693                 return 0;
 694
 695         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 696         if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
 697                                      "scsi_dh_%s", m->hw_handler_name)) {
 698                 ti->error = "unknown hardware handler type";
 699                 ret = -EINVAL;
 700                 goto fail;
 701         }
 702
 703         if (hw_argc > 1) {
 704                 char *p;
 705                 int i, j, len = 4;
 706
 707                 for (i = 0; i <= hw_argc - 2; i++)
 708                         len += strlen(as->argv[i]) + 1;
 709                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 710                 if (!p) {
 711                         ti->error = "memory allocation failed";
 712                         ret = -ENOMEM;
 713                         goto fail;
 714                 }
 715                 j = sprintf(p, "%d", hw_argc - 1);
 716                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 717                         j = sprintf(p, "%s", as->argv[i]);
 718         }
 719         dm_consume_args(as, hw_argc - 1);
 720
 721         return 0;
 722 fail:
 723         kfree(m->hw_handler_name);
 724         m->hw_handler_name = NULL;
 725         return ret;
 726 }
 727
 728 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 729 {
 730         int r;
 731         unsigned argc;
 732         struct dm_target *ti = m->ti;
 733         const char *arg_name;
 734
 735         static struct dm_arg _args[] = {
 736                 {0, 6, "invalid number of feature args"},
 737                 {1, 50, "pg_init_retries must be between 1 and 50"},
 738                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 739         };
 740
 741         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 742         if (r)
 743                 return -EINVAL;
 744
 745         if (!argc)
 746                 return 0;
 747
 748         do {
 749                 arg_name = dm_shift_arg(as);
 750                 argc--;
 751
 752                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 753                         r = queue_if_no_path(m, 1, 0);
 754                         continue;
 755                 }
 756
 757                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 758                         m->retain_attached_hw_handler = 1;
 759                         continue;
 760                 }
 761
 762                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 763                     (argc >= 1)) {
 764                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 765                         argc--;
 766                         continue;
 767                 }
 768
 769                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 770                     (argc >= 1)) {
 771                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 772                         argc--;
 773                         continue;
 774                 }
 775
 776                 ti->error = "Unrecognised multipath feature request";
 777                 r = -EINVAL;
 778         } while (argc && !r);
 779
 780         return r;
 781 }
 782
 783 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 784                          char **argv)
 785 {
 786         /* target arguments */
 787         static struct dm_arg _args[] = {
 788                 {0, 1024, "invalid number of priority groups"},
 789                 {0, 1024, "invalid initial priority group number"},
 790         };
 791
 792         int r;
 793         struct multipath *m;
 794         struct dm_arg_set as;
 795         unsigned pg_count = 0;
 796         unsigned next_pg_num;
 797
 798         as.argc = argc;
 799         as.argv = argv;
 800
 801         m = alloc_multipath(ti);
 802         if (!m) {
 803                 ti->error = "can't allocate multipath";
 804                 return -EINVAL;
 805         }
 806
 807         r = parse_features(&as, m);
 808         if (r)
 809                 goto bad;
 810
 811         r = parse_hw_handler(&as, m);
 812         if (r)
 813                 goto bad;
 814
 815         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 816         if (r)
 817                 goto bad;
 818
 819         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 820         if (r)
 821                 goto bad;
 822
 823         if ((!m->nr_priority_groups && next_pg_num) ||
 824             (m->nr_priority_groups && !next_pg_num)) {
 825                 ti->error = "invalid initial priority group";
 826                 r = -EINVAL;
 827                 goto bad;
 828         }
 829
 830         /* parse the priority groups */
 831         while (as.argc) {
 832                 struct priority_group *pg;
 833
 834                 pg = parse_priority_group(&as, m);
 835                 if (IS_ERR(pg)) {
 836                         r = PTR_ERR(pg);
 837                         goto bad;
 838                 }
 839
 840                 m->nr_valid_paths += pg->nr_pgpaths;
 841                 list_add_tail(&pg->list, &m->priority_groups);
 842                 pg_count++;
 843                 pg->pg_num = pg_count;
 844                 if (!--next_pg_num)
 845                         m->next_pg = pg;
 846         }
 847
 848         if (pg_count != m->nr_priority_groups) {
 849                 ti->error = "priority group count mismatch";
 850                 r = -EINVAL;
 851                 goto bad;
 852         }
 853
 854         ti->num_flush_bios = 1;
 855         ti->num_discard_bios = 1;
 856         ti->num_write_same_bios = 1;
 857
 858         return 0;
 859
 860  bad:
 861         free_multipath(m);
 862         return r;
 863 }
 864
 865 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 866 {
 867         DECLARE_WAITQUEUE(wait, current);
 868         unsigned long flags;
 869
 870         add_wait_queue(&m->pg_init_wait, &wait);
 871
 872         while (1) {
 873                 set_current_state(TASK_UNINTERRUPTIBLE);
 874
 875                 spin_lock_irqsave(&m->lock, flags);
 876                 if (!m->pg_init_in_progress) {
 877                         spin_unlock_irqrestore(&m->lock, flags);
 878                         break;
 879                 }
 880                 spin_unlock_irqrestore(&m->lock, flags);
 881
 882                 io_schedule();
 883         }
 884         set_current_state(TASK_RUNNING);
 885
 886         remove_wait_queue(&m->pg_init_wait, &wait);
 887 }
 888
 889 static void flush_multipath_work(struct multipath *m)
 890 {
 891         unsigned long flags;
 892
 893         spin_lock_irqsave(&m->lock, flags);
 894         m->pg_init_disabled = 1;
 895         spin_unlock_irqrestore(&m->lock, flags);
 896
 897         flush_workqueue(kmpath_handlerd);
 898         multipath_wait_for_pg_init_completion(m);
 899         flush_workqueue(kmultipathd);
 900         flush_work(&m->trigger_event);
 901
 902         spin_lock_irqsave(&m->lock, flags);
 903         m->pg_init_disabled = 0;
 904         spin_unlock_irqrestore(&m->lock, flags);
 905 }
 906
 907 static void multipath_dtr(struct dm_target *ti)
 908 {
 909         struct multipath *m = ti->private;
 910
 911         flush_multipath_work(m);
 912         free_multipath(m);
 913 }
 914
 915 /*
 916  * Take a path out of use.
 917  */
 918 static int fail_path(struct pgpath *pgpath)
 919 {
 920         unsigned long flags;
 921         struct multipath *m = pgpath->pg->m;
 922
 923         spin_lock_irqsave(&m->lock, flags);
 924
 925         if (!pgpath->is_active)
 926                 goto out;
 927
 928         DMWARN("Failing path %s.", pgpath->path.dev->name);
 929
 930         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 931         pgpath->is_active = 0;
 932         pgpath->fail_count++;
 933
 934         m->nr_valid_paths--;
 935
 936         if (pgpath == m->current_pgpath)
 937                 m->current_pgpath = NULL;
 938
 939         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 940                       pgpath->path.dev->name, m->nr_valid_paths);
 941
 942         schedule_work(&m->trigger_event);
 943
 944 out:
 945         spin_unlock_irqrestore(&m->lock, flags);
 946
 947         return 0;
 948 }
 949
 950 /*
 951  * Reinstate a previously-failed path
 952  */
 953 static int reinstate_path(struct pgpath *pgpath)
 954 {
 955         int r = 0, run_queue = 0;
 956         unsigned long flags;
 957         struct multipath *m = pgpath->pg->m;
 958
 959         spin_lock_irqsave(&m->lock, flags);
 960
 961         if (pgpath->is_active)
 962                 goto out;
 963
 964         if (!pgpath->pg->ps.type->reinstate_path) {
 965                 DMWARN("Reinstate path not supported by path selector %s",
 966                        pgpath->pg->ps.type->name);
 967                 r = -EINVAL;
 968                 goto out;
 969         }
 970
 971         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 972         if (r)
 973                 goto out;
 974
 975         pgpath->is_active = 1;
 976
 977         if (!m->nr_valid_paths++) {
 978                 m->current_pgpath = NULL;
 979                 run_queue = 1;
 980         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
 981                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
 982                         m->pg_init_in_progress++;
 983         }
 984
 985         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
 986                       pgpath->path.dev->name, m->nr_valid_paths);
 987
 988         schedule_work(&m->trigger_event);
 989
 990 out:
 991         spin_unlock_irqrestore(&m->lock, flags);
 992         if (run_queue)
 993                 dm_table_run_md_queue_async(m->ti->table);
 994
 995         return r;
 996 }
 997
 998 /*
 999  * Fail or reinstate all paths that match the provided struct dm_dev.
1000  */
1001 static int action_dev(struct multipath *m, struct dm_dev *dev,
1002                       action_fn action)
1003 {
1004         int r = -EINVAL;
1005         struct pgpath *pgpath;
1006         struct priority_group *pg;
1007
1008         list_for_each_entry(pg, &m->priority_groups, list) {
1009                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1010                         if (pgpath->path.dev == dev)
1011                                 r = action(pgpath);
1012                 }
1013         }
1014
1015         return r;
1016 }
1017
1018 /*
1019  * Temporarily try to avoid having to use the specified PG
1020  */
1021 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1022                       int bypassed)
1023 {
1024         unsigned long flags;
1025
1026         spin_lock_irqsave(&m->lock, flags);
1027
1028         pg->bypassed = bypassed;
1029         m->current_pgpath = NULL;
1030         m->current_pg = NULL;
1031
1032         spin_unlock_irqrestore(&m->lock, flags);
1033
1034         schedule_work(&m->trigger_event);
1035 }
1036
1037 /*
1038  * Switch to using the specified PG from the next I/O that gets mapped
1039  */
1040 static int switch_pg_num(struct multipath *m, const char *pgstr)
1041 {
1042         struct priority_group *pg;
1043         unsigned pgnum;
1044         unsigned long flags;
1045         char dummy;
1046
1047         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1048             (pgnum > m->nr_priority_groups)) {
1049                 DMWARN("invalid PG number supplied to switch_pg_num");
1050                 return -EINVAL;
1051         }
1052
1053         spin_lock_irqsave(&m->lock, flags);
1054         list_for_each_entry(pg, &m->priority_groups, list) {
1055                 pg->bypassed = 0;
1056                 if (--pgnum)
1057                         continue;
1058
1059                 m->current_pgpath = NULL;
1060                 m->current_pg = NULL;
1061                 m->next_pg = pg;
1062         }
1063         spin_unlock_irqrestore(&m->lock, flags);
1064
1065         schedule_work(&m->trigger_event);
1066         return 0;
1067 }
1068
1069 /*
1070  * Set/clear bypassed status of a PG.
1071  * PGs are numbered upwards from 1 in the order they were declared.
1072  */
1073 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1074 {
1075         struct priority_group *pg;
1076         unsigned pgnum;
1077         char dummy;
1078
1079         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1080             (pgnum > m->nr_priority_groups)) {
1081                 DMWARN("invalid PG number supplied to bypass_pg");
1082                 return -EINVAL;
1083         }
1084
1085         list_for_each_entry(pg, &m->priority_groups, list) {
1086                 if (!--pgnum)
1087                         break;
1088         }
1089
1090         bypass_pg(m, pg, bypassed);
1091         return 0;
1092 }
1093
1094 /*
1095  * Should we retry pg_init immediately?
1096  */
1097 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1098 {
1099         unsigned long flags;
1100         int limit_reached = 0;
1101
1102         spin_lock_irqsave(&m->lock, flags);
1103
1104         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1105                 m->pg_init_required = 1;
1106         else
1107                 limit_reached = 1;
1108
1109         spin_unlock_irqrestore(&m->lock, flags);
1110
1111         return limit_reached;
1112 }
1113
1114 static void pg_init_done(void *data, int errors)
1115 {
1116         struct pgpath *pgpath = data;
1117         struct priority_group *pg = pgpath->pg;
1118         struct multipath *m = pg->m;
1119         unsigned long flags;
1120         unsigned delay_retry = 0;
1121
1122         /* device or driver problems */
1123         switch (errors) {
1124         case SCSI_DH_OK:
1125                 break;
1126         case SCSI_DH_NOSYS:
1127                 if (!m->hw_handler_name) {
1128                         errors = 0;
1129                         break;
1130                 }
1131                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1132                       "Error %d.", m->hw_handler_name, errors);
1133                 /*
1134                  * Fail path for now, so we do not ping pong
1135                  */
1136                 fail_path(pgpath);
1137                 break;
1138         case SCSI_DH_DEV_TEMP_BUSY:
1139                 /*
1140                  * Probably doing something like FW upgrade on the
1141                  * controller so try the other pg.
1142                  */
1143                 bypass_pg(m, pg, 1);
1144                 break;
1145         case SCSI_DH_RETRY:
1146                 /* Wait before retrying. */
1147                 delay_retry = 1;
1148         case SCSI_DH_IMM_RETRY:
1149         case SCSI_DH_RES_TEMP_UNAVAIL:
1150                 if (pg_init_limit_reached(m, pgpath))
1151                         fail_path(pgpath);
1152                 errors = 0;
1153                 break;
1154         default:
1155                 /*
1156                  * We probably do not want to fail the path for a device
1157                  * error, but this is what the old dm did. In future
1158                  * patches we can do more advanced handling.
1159                  */
1160                 fail_path(pgpath);
1161         }
1162
1163         spin_lock_irqsave(&m->lock, flags);
1164         if (errors) {
1165                 if (pgpath == m->current_pgpath) {
1166                         DMERR("Could not failover device. Error %d.", errors);
1167                         m->current_pgpath = NULL;
1168                         m->current_pg = NULL;
1169                 }
1170         } else if (!m->pg_init_required)
1171                 pg->bypassed = 0;
1172
1173         if (--m->pg_init_in_progress)
1174                 /* Activations of other paths are still on going */
1175                 goto out;
1176
1177         if (m->pg_init_required) {
1178                 m->pg_init_delay_retry = delay_retry;
1179                 if (__pg_init_all_paths(m))
1180                         goto out;
1181         }
1182         m->queue_io = 0;
1183
1184         /*
1185          * Wake up any thread waiting to suspend.
1186          */
1187         wake_up(&m->pg_init_wait);
1188
1189 out:
1190         spin_unlock_irqrestore(&m->lock, flags);
1191 }
1192
1193 static void activate_path(struct work_struct *work)
1194 {
1195         struct pgpath *pgpath =
1196                 container_of(work, struct pgpath, activate_path.work);
1197
1198         if (pgpath->is_active)
1199                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1200                                  pg_init_done, pgpath);
1201         else
1202                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1203 }
1204
1205 static int noretry_error(int error)
1206 {
1207         switch (error) {
1208         case -EOPNOTSUPP:
1209         case -EREMOTEIO:
1210         case -EILSEQ:
1211         case -ENODATA:
1212         case -ENOSPC:
1213                 return 1;
1214         }
1215
1216         /* Anything else could be a path failure, so should be retried */
1217         return 0;
1218 }
1219
1220 /*
1221  * end_io handling
1222  */
1223 static int do_end_io(struct multipath *m, struct request *clone,
1224                      int error, struct dm_mpath_io *mpio)
1225 {
1226         /*
1227          * We don't queue any clone request inside the multipath target
1228          * during end I/O handling, since those clone requests don't have
1229          * bio clones.  If we queue them inside the multipath target,
1230          * we need to make bio clones, that requires memory allocation.
1231          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1232          *  don't have bio clones.)
1233          * Instead of queueing the clone request here, we queue the original
1234          * request into dm core, which will remake a clone request and
1235          * clone bios for it and resubmit it later.
1236          */
1237         int r = DM_ENDIO_REQUEUE;
1238         unsigned long flags;
1239
1240         if (!error && !clone->errors)
1241                 return 0;       /* I/O complete */
1242
1243         if (noretry_error(error))
1244                 return error;
1245
1246         if (mpio->pgpath)
1247                 fail_path(mpio->pgpath);
1248
1249         spin_lock_irqsave(&m->lock, flags);
1250         if (!m->nr_valid_paths) {
1251                 if (!m->queue_if_no_path) {
1252                         if (!__must_push_back(m))
1253                                 r = -EIO;
1254                 } else {
1255                         if (error == -EBADE)
1256                                 r = error;
1257                 }
1258         }
1259         spin_unlock_irqrestore(&m->lock, flags);
1260
1261         return r;
1262 }
1263
1264 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1265                             int error, union map_info *map_context)
1266 {
1267         struct multipath *m = ti->private;
1268         struct dm_mpath_io *mpio = map_context->ptr;
1269         struct pgpath *pgpath;
1270         struct path_selector *ps;
1271         int r;
1272
1273         BUG_ON(!mpio);
1274
1275         r  = do_end_io(m, clone, error, mpio);
1276         pgpath = mpio->pgpath;
1277         if (pgpath) {
1278                 ps = &pgpath->pg->ps;
1279                 if (ps->type->end_io)
1280                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1281         }
1282         clear_mapinfo(m, map_context);
1283
1284         return r;
1285 }
1286
1287 /*
1288  * Suspend can't complete until all the I/O is processed so if
1289  * the last path fails we must error any remaining I/O.
1290  * Note that if the freeze_bdev fails while suspending, the
1291  * queue_if_no_path state is lost - userspace should reset it.
1292  */
1293 static void multipath_presuspend(struct dm_target *ti)
1294 {
1295         struct multipath *m = (struct multipath *) ti->private;
1296
1297         queue_if_no_path(m, 0, 1);
1298 }
1299
1300 static void multipath_postsuspend(struct dm_target *ti)
1301 {
1302         struct multipath *m = ti->private;
1303
1304         mutex_lock(&m->work_mutex);
1305         flush_multipath_work(m);
1306         mutex_unlock(&m->work_mutex);
1307 }
1308
1309 /*
1310  * Restore the queue_if_no_path setting.
1311  */
1312 static void multipath_resume(struct dm_target *ti)
1313 {
1314         struct multipath *m = (struct multipath *) ti->private;
1315         unsigned long flags;
1316
1317         spin_lock_irqsave(&m->lock, flags);
1318         m->queue_if_no_path = m->saved_queue_if_no_path;
1319         spin_unlock_irqrestore(&m->lock, flags);
1320 }
1321
1322 /*
1323  * Info output has the following format:
1324  * num_multipath_feature_args [multipath_feature_args]*
1325  * num_handler_status_args [handler_status_args]*
1326  * num_groups init_group_number
1327  *            [A|D|E num_ps_status_args [ps_status_args]*
1328  *             num_paths num_selector_args
1329  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1330  *
1331  * Table output has the following format (identical to the constructor string):
1332  * num_feature_args [features_args]*
1333  * num_handler_args hw_handler [hw_handler_args]*
1334  * num_groups init_group_number
1335  *     [priority selector-name num_ps_args [ps_args]*
1336  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1337  */
1338 static void multipath_status(struct dm_target *ti, status_type_t type,
1339                              unsigned status_flags, char *result, unsigned maxlen)
1340 {
1341         int sz = 0;
1342         unsigned long flags;
1343         struct multipath *m = (struct multipath *) ti->private;
1344         struct priority_group *pg;
1345         struct pgpath *p;
1346         unsigned pg_num;
1347         char state;
1348
1349         spin_lock_irqsave(&m->lock, flags);
1350
1351         /* Features */
1352         if (type == STATUSTYPE_INFO)
1353                 DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);
1354         else {
1355                 DMEMIT("%u ", m->queue_if_no_path +
1356                               (m->pg_init_retries > 0) * 2 +
1357                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1358                               m->retain_attached_hw_handler);
1359                 if (m->queue_if_no_path)
1360                         DMEMIT("queue_if_no_path ");
1361                 if (m->pg_init_retries)
1362                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1363                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1364                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1365                 if (m->retain_attached_hw_handler)
1366                         DMEMIT("retain_attached_hw_handler ");
1367         }
1368
1369         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1370                 DMEMIT("0 ");
1371         else
1372                 DMEMIT("1 %s ", m->hw_handler_name);
1373
1374         DMEMIT("%u ", m->nr_priority_groups);
1375
1376         if (m->next_pg)
1377                 pg_num = m->next_pg->pg_num;
1378         else if (m->current_pg)
1379                 pg_num = m->current_pg->pg_num;
1380         else
1381                 pg_num = (m->nr_priority_groups ? 1 : 0);
1382
1383         DMEMIT("%u ", pg_num);
1384
1385         switch (type) {
1386         case STATUSTYPE_INFO:
1387                 list_for_each_entry(pg, &m->priority_groups, list) {
1388                         if (pg->bypassed)
1389                                 state = 'D';    /* Disabled */
1390                         else if (pg == m->current_pg)
1391                                 state = 'A';    /* Currently Active */
1392                         else
1393                                 state = 'E';    /* Enabled */
1394
1395                         DMEMIT("%c ", state);
1396
1397                         if (pg->ps.type->status)
1398                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1399                                                           result + sz,
1400                                                           maxlen - sz);
1401                         else
1402                                 DMEMIT("0 ");
1403
1404                         DMEMIT("%u %u ", pg->nr_pgpaths,
1405                                pg->ps.type->info_args);
1406
1407                         list_for_each_entry(p, &pg->pgpaths, list) {
1408                                 DMEMIT("%s %s %u ", p->path.dev->name,
1409                                        p->is_active ? "A" : "F",
1410                                        p->fail_count);
1411                                 if (pg->ps.type->status)
1412                                         sz += pg->ps.type->status(&pg->ps,
1413                                               &p->path, type, result + sz,
1414                                               maxlen - sz);
1415                         }
1416                 }
1417                 break;
1418
1419         case STATUSTYPE_TABLE:
1420                 list_for_each_entry(pg, &m->priority_groups, list) {
1421                         DMEMIT("%s ", pg->ps.type->name);
1422
1423                         if (pg->ps.type->status)
1424                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1425                                                           result + sz,
1426                                                           maxlen - sz);
1427                         else
1428                                 DMEMIT("0 ");
1429
1430                         DMEMIT("%u %u ", pg->nr_pgpaths,
1431                                pg->ps.type->table_args);
1432
1433                         list_for_each_entry(p, &pg->pgpaths, list) {
1434                                 DMEMIT("%s ", p->path.dev->name);
1435                                 if (pg->ps.type->status)
1436                                         sz += pg->ps.type->status(&pg->ps,
1437                                               &p->path, type, result + sz,
1438                                               maxlen - sz);
1439                         }
1440                 }
1441                 break;
1442         }
1443
1444         spin_unlock_irqrestore(&m->lock, flags);
1445 }
1446
1447 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1448 {
1449         int r = -EINVAL;
1450         struct dm_dev *dev;
1451         struct multipath *m = (struct multipath *) ti->private;
1452         action_fn action;
1453
1454         mutex_lock(&m->work_mutex);
1455
1456         if (dm_suspended(ti)) {
1457                 r = -EBUSY;
1458                 goto out;
1459         }
1460
1461         if (argc == 1) {
1462                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1463                         r = queue_if_no_path(m, 1, 0);
1464                         goto out;
1465                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1466                         r = queue_if_no_path(m, 0, 0);
1467                         goto out;
1468                 }
1469         }
1470
1471         if (argc != 2) {
1472                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1473                 goto out;
1474         }
1475
1476         if (!strcasecmp(argv[0], "disable_group")) {
1477                 r = bypass_pg_num(m, argv[1], 1);
1478                 goto out;
1479         } else if (!strcasecmp(argv[0], "enable_group")) {
1480                 r = bypass_pg_num(m, argv[1], 0);
1481                 goto out;
1482         } else if (!strcasecmp(argv[0], "switch_group")) {
1483                 r = switch_pg_num(m, argv[1]);
1484                 goto out;
1485         } else if (!strcasecmp(argv[0], "reinstate_path"))
1486                 action = reinstate_path;
1487         else if (!strcasecmp(argv[0], "fail_path"))
1488                 action = fail_path;
1489         else {
1490                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1491                 goto out;
1492         }
1493
1494         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1495         if (r) {
1496                 DMWARN("message: error getting device %s",
1497                        argv[1]);
1498                 goto out;
1499         }
1500
1501         r = action_dev(m, dev, action);
1502
1503         dm_put_device(ti, dev);
1504
1505 out:
1506         mutex_unlock(&m->work_mutex);
1507         return r;
1508 }
1509
1510 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1511                            unsigned long arg)
1512 {
1513         struct multipath *m = ti->private;
1514         struct pgpath *pgpath;
1515         struct block_device *bdev;
1516         fmode_t mode;
1517         unsigned long flags;
1518         int r;
1519
1520         bdev = NULL;
1521         mode = 0;
1522         r = 0;
1523
1524         spin_lock_irqsave(&m->lock, flags);
1525
1526         if (!m->current_pgpath)
1527                 __choose_pgpath(m, 0);
1528
1529         pgpath = m->current_pgpath;
1530
1531         if (pgpath) {
1532                 bdev = pgpath->path.dev->bdev;
1533                 mode = pgpath->path.dev->mode;
1534         }
1535
1536         if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
1537                 r = -ENOTCONN;
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 (!bdev || ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT) {
1547                 int err = scsi_verify_blk_ioctl(NULL, cmd);
1548                 if (err)
1549                         r = err;
1550         }
1551
1552         if (r == -ENOTCONN && !fatal_signal_pending(current)) {
1553                 spin_lock_irqsave(&m->lock, flags);
1554                 if (!m->current_pg) {
1555                         /* Path status changed, redo selection */
1556                         __choose_pgpath(m, 0);
1557                 }
1558                 if (m->pg_init_required)
1559                         __pg_init_all_paths(m);
1560                 spin_unlock_irqrestore(&m->lock, flags);
1561                 dm_table_run_md_queue_async(m->ti->table);
1562         }
1563
1564         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1565 }
1566
1567 static int multipath_iterate_devices(struct dm_target *ti,
1568                                      iterate_devices_callout_fn fn, void *data)
1569 {
1570         struct multipath *m = ti->private;
1571         struct priority_group *pg;
1572         struct pgpath *p;
1573         int ret = 0;
1574
1575         list_for_each_entry(pg, &m->priority_groups, list) {
1576                 list_for_each_entry(p, &pg->pgpaths, list) {
1577                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1578                         if (ret)
1579                                 goto out;
1580                 }
1581         }
1582
1583 out:
1584         return ret;
1585 }
1586
1587 static int __pgpath_busy(struct pgpath *pgpath)
1588 {
1589         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1590
1591         return dm_underlying_device_busy(q);
1592 }
1593
1594 /*
1595  * We return "busy", only when we can map I/Os but underlying devices
1596  * are busy (so even if we map I/Os now, the I/Os will wait on
1597  * the underlying queue).
1598  * In other words, if we want to kill I/Os or queue them inside us
1599  * due to map unavailability, we don't return "busy".  Otherwise,
1600  * dm core won't give us the I/Os and we can't do what we want.
1601  */
1602 static int multipath_busy(struct dm_target *ti)
1603 {
1604         int busy = 0, has_active = 0;
1605         struct multipath *m = ti->private;
1606         struct priority_group *pg;
1607         struct pgpath *pgpath;
1608         unsigned long flags;
1609
1610         spin_lock_irqsave(&m->lock, flags);
1611
1612         /* pg_init in progress or no paths available */
1613         if (m->pg_init_in_progress ||
1614             (!m->nr_valid_paths && m->queue_if_no_path)) {
1615                 busy = 1;
1616                 goto out;
1617         }
1618         /* Guess which priority_group will be used at next mapping time */
1619         if (unlikely(!m->current_pgpath && m->next_pg))
1620                 pg = m->next_pg;
1621         else if (likely(m->current_pg))
1622                 pg = m->current_pg;
1623         else
1624                 /*
1625                  * We don't know which pg will be used at next mapping time.
1626                  * We don't call __choose_pgpath() here to avoid to trigger
1627                  * pg_init just by busy checking.
1628                  * So we don't know whether underlying devices we will be using
1629                  * at next mapping time are busy or not. Just try mapping.
1630                  */
1631                 goto out;
1632
1633         /*
1634          * If there is one non-busy active path at least, the path selector
1635          * will be able to select it. So we consider such a pg as not busy.
1636          */
1637         busy = 1;
1638         list_for_each_entry(pgpath, &pg->pgpaths, list)
1639                 if (pgpath->is_active) {
1640                         has_active = 1;
1641
1642                         if (!__pgpath_busy(pgpath)) {
1643                                 busy = 0;
1644                                 break;
1645                         }
1646                 }
1647
1648         if (!has_active)
1649                 /*
1650                  * No active path in this pg, so this pg won't be used and
1651                  * the current_pg will be changed at next mapping time.
1652                  * We need to try mapping to determine it.
1653                  */
1654                 busy = 0;
1655
1656 out:
1657         spin_unlock_irqrestore(&m->lock, flags);
1658
1659         return busy;
1660 }
1661
1662 /*-----------------------------------------------------------------
1663  * Module setup
1664  *---------------------------------------------------------------*/
1665 static struct target_type multipath_target = {
1666         .name = "multipath",
1667         .version = {1, 7, 0},
1668         .module = THIS_MODULE,
1669         .ctr = multipath_ctr,
1670         .dtr = multipath_dtr,
1671         .map_rq = multipath_map,
1672         .rq_end_io = multipath_end_io,
1673         .presuspend = multipath_presuspend,
1674         .postsuspend = multipath_postsuspend,
1675         .resume = multipath_resume,
1676         .status = multipath_status,
1677         .message = multipath_message,
1678         .ioctl  = multipath_ioctl,
1679         .iterate_devices = multipath_iterate_devices,
1680         .busy = multipath_busy,
1681 };
1682
1683 static int __init dm_multipath_init(void)
1684 {
1685         int r;
1686
1687         /* allocate a slab for the dm_ios */
1688         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1689         if (!_mpio_cache)
1690                 return -ENOMEM;
1691
1692         r = dm_register_target(&multipath_target);
1693         if (r < 0) {
1694                 DMERR("register failed %d", r);
1695                 kmem_cache_destroy(_mpio_cache);
1696                 return -EINVAL;
1697         }
1698
1699         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1700         if (!kmultipathd) {
1701                 DMERR("failed to create workqueue kmpathd");
1702                 dm_unregister_target(&multipath_target);
1703                 kmem_cache_destroy(_mpio_cache);
1704                 return -ENOMEM;
1705         }
1706
1707         /*
1708          * A separate workqueue is used to handle the device handlers
1709          * to avoid overloading existing workqueue. Overloading the
1710          * old workqueue would also create a bottleneck in the
1711          * path of the storage hardware device activation.
1712          */
1713         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1714                                                   WQ_MEM_RECLAIM);
1715         if (!kmpath_handlerd) {
1716                 DMERR("failed to create workqueue kmpath_handlerd");
1717                 destroy_workqueue(kmultipathd);
1718                 dm_unregister_target(&multipath_target);
1719                 kmem_cache_destroy(_mpio_cache);
1720                 return -ENOMEM;
1721         }
1722
1723         DMINFO("version %u.%u.%u loaded",
1724                multipath_target.version[0], multipath_target.version[1],
1725                multipath_target.version[2]);
1726
1727         return r;
1728 }
1729
1730 static void __exit dm_multipath_exit(void)
1731 {
1732         destroy_workqueue(kmpath_handlerd);
1733         destroy_workqueue(kmultipathd);
1734
1735         dm_unregister_target(&multipath_target);
1736         kmem_cache_destroy(_mpio_cache);
1737 }
1738
1739 module_init(dm_multipath_init);
1740 module_exit(dm_multipath_exit);
1741
1742 MODULE_DESCRIPTION(DM_NAME " multipath target");
1743 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1744 MODULE_LICENSE("GPL");