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/blkdev.h>
  15 #include <linux/ctype.h>
  16 #include <linux/init.h>
  17 #include <linux/mempool.h>
  18 #include <linux/module.h>
  19 #include <linux/pagemap.h>
  20 #include <linux/slab.h>
  21 #include <linux/time.h>
  22 #include <linux/workqueue.h>
  23 #include <linux/delay.h>
  24 #include <scsi/scsi_dh.h>
  25 #include <linux/atomic.h>
  26
  27 #define DM_MSG_PREFIX "multipath"
  28 #define DM_PG_INIT_DELAY_MSECS 2000
  29 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  30
  31 /* Path properties */
  32 struct pgpath {
  33         struct list_head list;
  34
  35         struct priority_group *pg;      /* Owning PG */
  36         unsigned is_active;             /* Path status */
  37         unsigned fail_count;            /* Cumulative failure count */
  38
  39         struct dm_path path;
  40         struct delayed_work activate_path;
  41 };
  42
  43 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  44
  45 /*
  46  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  47  * Each has a path selector which controls which path gets used.
  48  */
  49 struct priority_group {
  50         struct list_head list;
  51
  52         struct multipath *m;            /* Owning multipath instance */
  53         struct path_selector ps;
  54
  55         unsigned pg_num;                /* Reference number */
  56         unsigned bypassed;              /* Temporarily bypass this PG? */
  57
  58         unsigned nr_pgpaths;            /* Number of paths in PG */
  59         struct list_head pgpaths;
  60 };
  61
  62 /* Multipath context */
  63 struct multipath {
  64         struct list_head list;
  65         struct dm_target *ti;
  66
  67         const char *hw_handler_name;
  68         char *hw_handler_params;
  69
  70         spinlock_t lock;
  71
  72         unsigned nr_priority_groups;
  73         struct list_head priority_groups;
  74
  75         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  76
  77         unsigned pg_init_required;      /* pg_init needs calling? */
  78         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  79         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  80
  81         unsigned nr_valid_paths;        /* Total number of usable paths */
  82         struct pgpath *current_pgpath;
  83         struct priority_group *current_pg;
  84         struct priority_group *next_pg; /* Switch to this PG if set */
  85         unsigned repeat_count;          /* I/Os left before calling PS again */
  86
  87         unsigned queue_io:1;            /* Must we queue all I/O? */
  88         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  89         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  90         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  91         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  92
  93         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  94         unsigned pg_init_count;         /* Number of times pg_init called */
  95         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  96
  97         struct work_struct trigger_event;
  98
  99         /*
 100          * We must use a mempool of dm_mpath_io structs so that we
 101          * can resubmit bios on error.
 102          */
 103         mempool_t *mpio_pool;
 104
 105         struct mutex work_mutex;
 106 };
 107
 108 /*
 109  * Context information attached to each bio we process.
 110  */
 111 struct dm_mpath_io {
 112         struct pgpath *pgpath;
 113         size_t nr_bytes;
 114 };
 115
 116 typedef int (*action_fn) (struct pgpath *pgpath);
 117
 118 static struct kmem_cache *_mpio_cache;
 119
 120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 121 static void trigger_event(struct work_struct *work);
 122 static void activate_path(struct work_struct *work);
 123 static int __pgpath_busy(struct pgpath *pgpath);
 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
 163         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 164                 list_del(&pgpath->list);
 165                 dm_put_device(ti, pgpath->path.dev);
 166                 free_pgpath(pgpath);
 167         }
 168 }
 169
 170 static void free_priority_group(struct priority_group *pg,
 171                                 struct dm_target *ti)
 172 {
 173         struct path_selector *ps = &pg->ps;
 174
 175         if (ps->type) {
 176                 ps->type->destroy(ps);
 177                 dm_put_path_selector(ps->type);
 178         }
 179
 180         free_pgpaths(&pg->pgpaths, ti);
 181         kfree(pg);
 182 }
 183
 184 static struct multipath *alloc_multipath(struct dm_target *ti)
 185 {
 186         struct multipath *m;
 187         unsigned min_ios = dm_get_reserved_rq_based_ios();
 188
 189         m = kzalloc(sizeof(*m), GFP_KERNEL);
 190         if (m) {
 191                 INIT_LIST_HEAD(&m->priority_groups);
 192                 spin_lock_init(&m->lock);
 193                 m->queue_io = 1;
 194                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 195                 INIT_WORK(&m->trigger_event, trigger_event);
 196                 init_waitqueue_head(&m->pg_init_wait);
 197                 mutex_init(&m->work_mutex);
 198                 m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 199                 if (!m->mpio_pool) {
 200                         kfree(m);
 201                         return NULL;
 202                 }
 203                 m->ti = ti;
 204                 ti->private = m;
 205         }
 206
 207         return m;
 208 }
 209
 210 static void free_multipath(struct multipath *m)
 211 {
 212         struct priority_group *pg, *tmp;
 213
 214         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 215                 list_del(&pg->list);
 216                 free_priority_group(pg, m->ti);
 217         }
 218
 219         kfree(m->hw_handler_name);
 220         kfree(m->hw_handler_params);
 221         mempool_destroy(m->mpio_pool);
 222         kfree(m);
 223 }
 224
 225 static int set_mapinfo(struct multipath *m, union map_info *info)
 226 {
 227         struct dm_mpath_io *mpio;
 228
 229         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 230         if (!mpio)
 231                 return -ENOMEM;
 232
 233         memset(mpio, 0, sizeof(*mpio));
 234         info->ptr = mpio;
 235
 236         return 0;
 237 }
 238
 239 static void clear_mapinfo(struct multipath *m, union map_info *info)
 240 {
 241         struct dm_mpath_io *mpio = info->ptr;
 242
 243         info->ptr = NULL;
 244         mempool_free(mpio, m->mpio_pool);
 245 }
 246
 247 /*-----------------------------------------------
 248  * Path selection
 249  *-----------------------------------------------*/
 250
 251 static int __pg_init_all_paths(struct multipath *m)
 252 {
 253         struct pgpath *pgpath;
 254         unsigned long pg_init_delay = 0;
 255
 256         if (m->pg_init_in_progress || m->pg_init_disabled)
 257                 return 0;
 258
 259         m->pg_init_count++;
 260         m->pg_init_required = 0;
 261
 262         /* Check here to reset pg_init_required */
 263         if (!m->current_pg)
 264                 return 0;
 265
 266         if (m->pg_init_delay_retry)
 267                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 268                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 269         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 270                 /* Skip failed paths */
 271                 if (!pgpath->is_active)
 272                         continue;
 273                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 274                                        pg_init_delay))
 275                         m->pg_init_in_progress++;
 276         }
 277         return m->pg_init_in_progress;
 278 }
 279
 280 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 281 {
 282         m->current_pg = pgpath->pg;
 283
 284         /* Must we initialise the PG first, and queue I/O till it's ready? */
 285         if (m->hw_handler_name) {
 286                 m->pg_init_required = 1;
 287                 m->queue_io = 1;
 288         } else {
 289                 m->pg_init_required = 0;
 290                 m->queue_io = 0;
 291         }
 292
 293         m->pg_init_count = 0;
 294 }
 295
 296 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 297                                size_t nr_bytes)
 298 {
 299         struct dm_path *path;
 300
 301         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 302         if (!path)
 303                 return -ENXIO;
 304
 305         m->current_pgpath = path_to_pgpath(path);
 306
 307         if (m->current_pg != pg)
 308                 __switch_pg(m, m->current_pgpath);
 309
 310         return 0;
 311 }
 312
 313 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 314 {
 315         struct priority_group *pg;
 316         unsigned bypassed = 1;
 317
 318         if (!m->nr_valid_paths) {
 319                 m->queue_io = 0;
 320                 goto failed;
 321         }
 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                            struct request *rq, struct request **__clone)
 382 {
 383         struct multipath *m = (struct multipath *) ti->private;
 384         int r = DM_MAPIO_REQUEUE;
 385         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 386         struct pgpath *pgpath;
 387         struct block_device *bdev;
 388         struct dm_mpath_io *mpio;
 389
 390         spin_lock_irq(&m->lock);
 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         mpio = map_context->ptr;
 413         mpio->pgpath = pgpath;
 414         mpio->nr_bytes = nr_bytes;
 415
 416         bdev = pgpath->path.dev->bdev;
 417
 418         spin_unlock_irq(&m->lock);
 419
 420         if (clone) {
 421                 /* Old request-based interface: allocated clone is passed in */
 422                 clone->q = bdev_get_queue(bdev);
 423                 clone->rq_disk = bdev->bd_disk;
 424                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 425         } else {
 426                 /* blk-mq request-based interface */
 427                 *__clone = blk_get_request(bdev_get_queue(bdev),
 428                                            rq_data_dir(rq), GFP_ATOMIC);
 429                 if (IS_ERR(*__clone)) {
 430                         /* ENOMEM, requeue */
 431                         clear_mapinfo(m, map_context);
 432                         return r;
 433                 }
 434                 (*__clone)->bio = (*__clone)->biotail = NULL;
 435                 (*__clone)->rq_disk = bdev->bd_disk;
 436                 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 437         }
 438
 439         if (pgpath->pg->ps.type->start_io)
 440                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 441                                               &pgpath->path,
 442                                               nr_bytes);
 443         return DM_MAPIO_REMAPPED;
 444
 445 out_unlock:
 446         spin_unlock_irq(&m->lock);
 447
 448         return r;
 449 }
 450
 451 static int multipath_map(struct dm_target *ti, struct request *clone,
 452                          union map_info *map_context)
 453 {
 454         return __multipath_map(ti, clone, map_context, NULL, NULL);
 455 }
 456
 457 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 458                                    union map_info *map_context,
 459                                    struct request **clone)
 460 {
 461         return __multipath_map(ti, NULL, map_context, rq, clone);
 462 }
 463
 464 static void multipath_release_clone(struct request *clone)
 465 {
 466         blk_put_request(clone);
 467 }
 468
 469 /*
 470  * If we run out of usable paths, should we queue I/O or error it?
 471  */
 472 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 473                             unsigned save_old_value)
 474 {
 475         unsigned long flags;
 476
 477         spin_lock_irqsave(&m->lock, flags);
 478
 479         if (save_old_value)
 480                 m->saved_queue_if_no_path = m->queue_if_no_path;
 481         else
 482                 m->saved_queue_if_no_path = queue_if_no_path;
 483         m->queue_if_no_path = queue_if_no_path;
 484         spin_unlock_irqrestore(&m->lock, flags);
 485
 486         if (!queue_if_no_path)
 487                 dm_table_run_md_queue_async(m->ti->table);
 488
 489         return 0;
 490 }
 491
 492 /*
 493  * An event is triggered whenever a path is taken out of use.
 494  * Includes path failure and PG bypass.
 495  */
 496 static void trigger_event(struct work_struct *work)
 497 {
 498         struct multipath *m =
 499                 container_of(work, struct multipath, trigger_event);
 500
 501         dm_table_event(m->ti->table);
 502 }
 503
 504 /*-----------------------------------------------------------------
 505  * Constructor/argument parsing:
 506  * <#multipath feature args> [<arg>]*
 507  * <#hw_handler args> [hw_handler [<arg>]*]
 508  * <#priority groups>
 509  * <initial priority group>
 510  *     [<selector> <#selector args> [<arg>]*
 511  *      <#paths> <#per-path selector args>
 512  *         [<path> [<arg>]* ]+ ]+
 513  *---------------------------------------------------------------*/
 514 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 515                                struct dm_target *ti)
 516 {
 517         int r;
 518         struct path_selector_type *pst;
 519         unsigned ps_argc;
 520
 521         static struct dm_arg _args[] = {
 522                 {0, 1024, "invalid number of path selector args"},
 523         };
 524
 525         pst = dm_get_path_selector(dm_shift_arg(as));
 526         if (!pst) {
 527                 ti->error = "unknown path selector type";
 528                 return -EINVAL;
 529         }
 530
 531         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 532         if (r) {
 533                 dm_put_path_selector(pst);
 534                 return -EINVAL;
 535         }
 536
 537         r = pst->create(&pg->ps, ps_argc, as->argv);
 538         if (r) {
 539                 dm_put_path_selector(pst);
 540                 ti->error = "path selector constructor failed";
 541                 return r;
 542         }
 543
 544         pg->ps.type = pst;
 545         dm_consume_args(as, ps_argc);
 546
 547         return 0;
 548 }
 549
 550 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 551                                struct dm_target *ti)
 552 {
 553         int r;
 554         struct pgpath *p;
 555         struct multipath *m = ti->private;
 556         struct request_queue *q = NULL;
 557         const char *attached_handler_name;
 558
 559         /* we need at least a path arg */
 560         if (as->argc < 1) {
 561                 ti->error = "no device given";
 562                 return ERR_PTR(-EINVAL);
 563         }
 564
 565         p = alloc_pgpath();
 566         if (!p)
 567                 return ERR_PTR(-ENOMEM);
 568
 569         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 570                           &p->path.dev);
 571         if (r) {
 572                 ti->error = "error getting device";
 573                 goto bad;
 574         }
 575
 576         if (m->retain_attached_hw_handler || m->hw_handler_name)
 577                 q = bdev_get_queue(p->path.dev->bdev);
 578
 579         if (m->retain_attached_hw_handler) {
 580 retain:
 581                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 582                 if (attached_handler_name) {
 583                         /*
 584                          * Reset hw_handler_name to match the attached handler
 585                          * and clear any hw_handler_params associated with the
 586                          * ignored handler.
 587                          *
 588                          * NB. This modifies the table line to show the actual
 589                          * handler instead of the original table passed in.
 590                          */
 591                         kfree(m->hw_handler_name);
 592                         m->hw_handler_name = attached_handler_name;
 593
 594                         kfree(m->hw_handler_params);
 595                         m->hw_handler_params = NULL;
 596                 }
 597         }
 598
 599         if (m->hw_handler_name) {
 600                 r = scsi_dh_attach(q, m->hw_handler_name);
 601                 if (r == -EBUSY) {
 602                         char b[BDEVNAME_SIZE];
 603
 604                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 605                                 bdevname(p->path.dev->bdev, b));
 606                         goto retain;
 607                 }
 608                 if (r < 0) {
 609                         ti->error = "error attaching hardware handler";
 610                         dm_put_device(ti, p->path.dev);
 611                         goto bad;
 612                 }
 613
 614                 if (m->hw_handler_params) {
 615                         r = scsi_dh_set_params(q, m->hw_handler_params);
 616                         if (r < 0) {
 617                                 ti->error = "unable to set hardware "
 618                                                         "handler parameters";
 619                                 dm_put_device(ti, p->path.dev);
 620                                 goto bad;
 621                         }
 622                 }
 623         }
 624
 625         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 626         if (r) {
 627                 dm_put_device(ti, p->path.dev);
 628                 goto bad;
 629         }
 630
 631         return p;
 632
 633  bad:
 634         free_pgpath(p);
 635         return ERR_PTR(r);
 636 }
 637
 638 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 639                                                    struct multipath *m)
 640 {
 641         static struct dm_arg _args[] = {
 642                 {1, 1024, "invalid number of paths"},
 643                 {0, 1024, "invalid number of selector args"}
 644         };
 645
 646         int r;
 647         unsigned i, nr_selector_args, nr_args;
 648         struct priority_group *pg;
 649         struct dm_target *ti = m->ti;
 650
 651         if (as->argc < 2) {
 652                 as->argc = 0;
 653                 ti->error = "not enough priority group arguments";
 654                 return ERR_PTR(-EINVAL);
 655         }
 656
 657         pg = alloc_priority_group();
 658         if (!pg) {
 659                 ti->error = "couldn't allocate priority group";
 660                 return ERR_PTR(-ENOMEM);
 661         }
 662         pg->m = m;
 663
 664         r = parse_path_selector(as, pg, ti);
 665         if (r)
 666                 goto bad;
 667
 668         /*
 669          * read the paths
 670          */
 671         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 672         if (r)
 673                 goto bad;
 674
 675         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 676         if (r)
 677                 goto bad;
 678
 679         nr_args = 1 + nr_selector_args;
 680         for (i = 0; i < pg->nr_pgpaths; i++) {
 681                 struct pgpath *pgpath;
 682                 struct dm_arg_set path_args;
 683
 684                 if (as->argc < nr_args) {
 685                         ti->error = "not enough path parameters";
 686                         r = -EINVAL;
 687                         goto bad;
 688                 }
 689
 690                 path_args.argc = nr_args;
 691                 path_args.argv = as->argv;
 692
 693                 pgpath = parse_path(&path_args, &pg->ps, ti);
 694                 if (IS_ERR(pgpath)) {
 695                         r = PTR_ERR(pgpath);
 696                         goto bad;
 697                 }
 698
 699                 pgpath->pg = pg;
 700                 list_add_tail(&pgpath->list, &pg->pgpaths);
 701                 dm_consume_args(as, nr_args);
 702         }
 703
 704         return pg;
 705
 706  bad:
 707         free_priority_group(pg, ti);
 708         return ERR_PTR(r);
 709 }
 710
 711 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 712 {
 713         unsigned hw_argc;
 714         int ret;
 715         struct dm_target *ti = m->ti;
 716
 717         static struct dm_arg _args[] = {
 718                 {0, 1024, "invalid number of hardware handler args"},
 719         };
 720
 721         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 722                 return -EINVAL;
 723
 724         if (!hw_argc)
 725                 return 0;
 726
 727         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 728
 729         if (hw_argc > 1) {
 730                 char *p;
 731                 int i, j, len = 4;
 732
 733                 for (i = 0; i <= hw_argc - 2; i++)
 734                         len += strlen(as->argv[i]) + 1;
 735                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 736                 if (!p) {
 737                         ti->error = "memory allocation failed";
 738                         ret = -ENOMEM;
 739                         goto fail;
 740                 }
 741                 j = sprintf(p, "%d", hw_argc - 1);
 742                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 743                         j = sprintf(p, "%s", as->argv[i]);
 744         }
 745         dm_consume_args(as, hw_argc - 1);
 746
 747         return 0;
 748 fail:
 749         kfree(m->hw_handler_name);
 750         m->hw_handler_name = NULL;
 751         return ret;
 752 }
 753
 754 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 755 {
 756         int r;
 757         unsigned argc;
 758         struct dm_target *ti = m->ti;
 759         const char *arg_name;
 760
 761         static struct dm_arg _args[] = {
 762                 {0, 6, "invalid number of feature args"},
 763                 {1, 50, "pg_init_retries must be between 1 and 50"},
 764                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 765         };
 766
 767         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 768         if (r)
 769                 return -EINVAL;
 770
 771         if (!argc)
 772                 return 0;
 773
 774         do {
 775                 arg_name = dm_shift_arg(as);
 776                 argc--;
 777
 778                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 779                         r = queue_if_no_path(m, 1, 0);
 780                         continue;
 781                 }
 782
 783                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 784                         m->retain_attached_hw_handler = 1;
 785                         continue;
 786                 }
 787
 788                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 789                     (argc >= 1)) {
 790                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 791                         argc--;
 792                         continue;
 793                 }
 794
 795                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 796                     (argc >= 1)) {
 797                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 798                         argc--;
 799                         continue;
 800                 }
 801
 802                 ti->error = "Unrecognised multipath feature request";
 803                 r = -EINVAL;
 804         } while (argc && !r);
 805
 806         return r;
 807 }
 808
 809 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 810                          char **argv)
 811 {
 812         /* target arguments */
 813         static struct dm_arg _args[] = {
 814                 {0, 1024, "invalid number of priority groups"},
 815                 {0, 1024, "invalid initial priority group number"},
 816         };
 817
 818         int r;
 819         struct multipath *m;
 820         struct dm_arg_set as;
 821         unsigned pg_count = 0;
 822         unsigned next_pg_num;
 823
 824         as.argc = argc;
 825         as.argv = argv;
 826
 827         m = alloc_multipath(ti);
 828         if (!m) {
 829                 ti->error = "can't allocate multipath";
 830                 return -EINVAL;
 831         }
 832
 833         r = parse_features(&as, m);
 834         if (r)
 835                 goto bad;
 836
 837         r = parse_hw_handler(&as, m);
 838         if (r)
 839                 goto bad;
 840
 841         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 842         if (r)
 843                 goto bad;
 844
 845         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 846         if (r)
 847                 goto bad;
 848
 849         if ((!m->nr_priority_groups && next_pg_num) ||
 850             (m->nr_priority_groups && !next_pg_num)) {
 851                 ti->error = "invalid initial priority group";
 852                 r = -EINVAL;
 853                 goto bad;
 854         }
 855
 856         /* parse the priority groups */
 857         while (as.argc) {
 858                 struct priority_group *pg;
 859
 860                 pg = parse_priority_group(&as, m);
 861                 if (IS_ERR(pg)) {
 862                         r = PTR_ERR(pg);
 863                         goto bad;
 864                 }
 865
 866                 m->nr_valid_paths += pg->nr_pgpaths;
 867                 list_add_tail(&pg->list, &m->priority_groups);
 868                 pg_count++;
 869                 pg->pg_num = pg_count;
 870                 if (!--next_pg_num)
 871                         m->next_pg = pg;
 872         }
 873
 874         if (pg_count != m->nr_priority_groups) {
 875                 ti->error = "priority group count mismatch";
 876                 r = -EINVAL;
 877                 goto bad;
 878         }
 879
 880         ti->num_flush_bios = 1;
 881         ti->num_discard_bios = 1;
 882         ti->num_write_same_bios = 1;
 883
 884         return 0;
 885
 886  bad:
 887         free_multipath(m);
 888         return r;
 889 }
 890
 891 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 892 {
 893         DECLARE_WAITQUEUE(wait, current);
 894         unsigned long flags;
 895
 896         add_wait_queue(&m->pg_init_wait, &wait);
 897
 898         while (1) {
 899                 set_current_state(TASK_UNINTERRUPTIBLE);
 900
 901                 spin_lock_irqsave(&m->lock, flags);
 902                 if (!m->pg_init_in_progress) {
 903                         spin_unlock_irqrestore(&m->lock, flags);
 904                         break;
 905                 }
 906                 spin_unlock_irqrestore(&m->lock, flags);
 907
 908                 io_schedule();
 909         }
 910         set_current_state(TASK_RUNNING);
 911
 912         remove_wait_queue(&m->pg_init_wait, &wait);
 913 }
 914
 915 static void flush_multipath_work(struct multipath *m)
 916 {
 917         unsigned long flags;
 918
 919         spin_lock_irqsave(&m->lock, flags);
 920         m->pg_init_disabled = 1;
 921         spin_unlock_irqrestore(&m->lock, flags);
 922
 923         flush_workqueue(kmpath_handlerd);
 924         multipath_wait_for_pg_init_completion(m);
 925         flush_workqueue(kmultipathd);
 926         flush_work(&m->trigger_event);
 927
 928         spin_lock_irqsave(&m->lock, flags);
 929         m->pg_init_disabled = 0;
 930         spin_unlock_irqrestore(&m->lock, flags);
 931 }
 932
 933 static void multipath_dtr(struct dm_target *ti)
 934 {
 935         struct multipath *m = ti->private;
 936
 937         flush_multipath_work(m);
 938         free_multipath(m);
 939 }
 940
 941 /*
 942  * Take a path out of use.
 943  */
 944 static int fail_path(struct pgpath *pgpath)
 945 {
 946         unsigned long flags;
 947         struct multipath *m = pgpath->pg->m;
 948
 949         spin_lock_irqsave(&m->lock, flags);
 950
 951         if (!pgpath->is_active)
 952                 goto out;
 953
 954         DMWARN("Failing path %s.", pgpath->path.dev->name);
 955
 956         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 957         pgpath->is_active = 0;
 958         pgpath->fail_count++;
 959
 960         m->nr_valid_paths--;
 961
 962         if (pgpath == m->current_pgpath)
 963                 m->current_pgpath = NULL;
 964
 965         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 966                       pgpath->path.dev->name, m->nr_valid_paths);
 967
 968         schedule_work(&m->trigger_event);
 969
 970 out:
 971         spin_unlock_irqrestore(&m->lock, flags);
 972
 973         return 0;
 974 }
 975
 976 /*
 977  * Reinstate a previously-failed path
 978  */
 979 static int reinstate_path(struct pgpath *pgpath)
 980 {
 981         int r = 0, run_queue = 0;
 982         unsigned long flags;
 983         struct multipath *m = pgpath->pg->m;
 984
 985         spin_lock_irqsave(&m->lock, flags);
 986
 987         if (pgpath->is_active)
 988                 goto out;
 989
 990         if (!pgpath->pg->ps.type->reinstate_path) {
 991                 DMWARN("Reinstate path not supported by path selector %s",
 992                        pgpath->pg->ps.type->name);
 993                 r = -EINVAL;
 994                 goto out;
 995         }
 996
 997         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
 998         if (r)
 999                 goto out;
1000
1001         pgpath->is_active = 1;
1002
1003         if (!m->nr_valid_paths++) {
1004                 m->current_pgpath = NULL;
1005                 run_queue = 1;
1006         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1007                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1008                         m->pg_init_in_progress++;
1009         }
1010
1011         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1012                       pgpath->path.dev->name, m->nr_valid_paths);
1013
1014         schedule_work(&m->trigger_event);
1015
1016 out:
1017         spin_unlock_irqrestore(&m->lock, flags);
1018         if (run_queue)
1019                 dm_table_run_md_queue_async(m->ti->table);
1020
1021         return r;
1022 }
1023
1024 /*
1025  * Fail or reinstate all paths that match the provided struct dm_dev.
1026  */
1027 static int action_dev(struct multipath *m, struct dm_dev *dev,
1028                       action_fn action)
1029 {
1030         int r = -EINVAL;
1031         struct pgpath *pgpath;
1032         struct priority_group *pg;
1033
1034         list_for_each_entry(pg, &m->priority_groups, list) {
1035                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1036                         if (pgpath->path.dev == dev)
1037                                 r = action(pgpath);
1038                 }
1039         }
1040
1041         return r;
1042 }
1043
1044 /*
1045  * Temporarily try to avoid having to use the specified PG
1046  */
1047 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1048                       int bypassed)
1049 {
1050         unsigned long flags;
1051
1052         spin_lock_irqsave(&m->lock, flags);
1053
1054         pg->bypassed = bypassed;
1055         m->current_pgpath = NULL;
1056         m->current_pg = NULL;
1057
1058         spin_unlock_irqrestore(&m->lock, flags);
1059
1060         schedule_work(&m->trigger_event);
1061 }
1062
1063 /*
1064  * Switch to using the specified PG from the next I/O that gets mapped
1065  */
1066 static int switch_pg_num(struct multipath *m, const char *pgstr)
1067 {
1068         struct priority_group *pg;
1069         unsigned pgnum;
1070         unsigned long flags;
1071         char dummy;
1072
1073         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1074             (pgnum > m->nr_priority_groups)) {
1075                 DMWARN("invalid PG number supplied to switch_pg_num");
1076                 return -EINVAL;
1077         }
1078
1079         spin_lock_irqsave(&m->lock, flags);
1080         list_for_each_entry(pg, &m->priority_groups, list) {
1081                 pg->bypassed = 0;
1082                 if (--pgnum)
1083                         continue;
1084
1085                 m->current_pgpath = NULL;
1086                 m->current_pg = NULL;
1087                 m->next_pg = pg;
1088         }
1089         spin_unlock_irqrestore(&m->lock, flags);
1090
1091         schedule_work(&m->trigger_event);
1092         return 0;
1093 }
1094
1095 /*
1096  * Set/clear bypassed status of a PG.
1097  * PGs are numbered upwards from 1 in the order they were declared.
1098  */
1099 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1100 {
1101         struct priority_group *pg;
1102         unsigned pgnum;
1103         char dummy;
1104
1105         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1106             (pgnum > m->nr_priority_groups)) {
1107                 DMWARN("invalid PG number supplied to bypass_pg");
1108                 return -EINVAL;
1109         }
1110
1111         list_for_each_entry(pg, &m->priority_groups, list) {
1112                 if (!--pgnum)
1113                         break;
1114         }
1115
1116         bypass_pg(m, pg, bypassed);
1117         return 0;
1118 }
1119
1120 /*
1121  * Should we retry pg_init immediately?
1122  */
1123 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1124 {
1125         unsigned long flags;
1126         int limit_reached = 0;
1127
1128         spin_lock_irqsave(&m->lock, flags);
1129
1130         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1131                 m->pg_init_required = 1;
1132         else
1133                 limit_reached = 1;
1134
1135         spin_unlock_irqrestore(&m->lock, flags);
1136
1137         return limit_reached;
1138 }
1139
1140 static void pg_init_done(void *data, int errors)
1141 {
1142         struct pgpath *pgpath = data;
1143         struct priority_group *pg = pgpath->pg;
1144         struct multipath *m = pg->m;
1145         unsigned long flags;
1146         unsigned delay_retry = 0;
1147
1148         /* device or driver problems */
1149         switch (errors) {
1150         case SCSI_DH_OK:
1151                 break;
1152         case SCSI_DH_NOSYS:
1153                 if (!m->hw_handler_name) {
1154                         errors = 0;
1155                         break;
1156                 }
1157                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1158                       "Error %d.", m->hw_handler_name, errors);
1159                 /*
1160                  * Fail path for now, so we do not ping pong
1161                  */
1162                 fail_path(pgpath);
1163                 break;
1164         case SCSI_DH_DEV_TEMP_BUSY:
1165                 /*
1166                  * Probably doing something like FW upgrade on the
1167                  * controller so try the other pg.
1168                  */
1169                 bypass_pg(m, pg, 1);
1170                 break;
1171         case SCSI_DH_RETRY:
1172                 /* Wait before retrying. */
1173                 delay_retry = 1;
1174         case SCSI_DH_IMM_RETRY:
1175         case SCSI_DH_RES_TEMP_UNAVAIL:
1176                 if (pg_init_limit_reached(m, pgpath))
1177                         fail_path(pgpath);
1178                 errors = 0;
1179                 break;
1180         default:
1181                 /*
1182                  * We probably do not want to fail the path for a device
1183                  * error, but this is what the old dm did. In future
1184                  * patches we can do more advanced handling.
1185                  */
1186                 fail_path(pgpath);
1187         }
1188
1189         spin_lock_irqsave(&m->lock, flags);
1190         if (errors) {
1191                 if (pgpath == m->current_pgpath) {
1192                         DMERR("Could not failover device. Error %d.", errors);
1193                         m->current_pgpath = NULL;
1194                         m->current_pg = NULL;
1195                 }
1196         } else if (!m->pg_init_required)
1197                 pg->bypassed = 0;
1198
1199         if (--m->pg_init_in_progress)
1200                 /* Activations of other paths are still on going */
1201                 goto out;
1202
1203         if (m->pg_init_required) {
1204                 m->pg_init_delay_retry = delay_retry;
1205                 if (__pg_init_all_paths(m))
1206                         goto out;
1207         }
1208         m->queue_io = 0;
1209
1210         /*
1211          * Wake up any thread waiting to suspend.
1212          */
1213         wake_up(&m->pg_init_wait);
1214
1215 out:
1216         spin_unlock_irqrestore(&m->lock, flags);
1217 }
1218
1219 static void activate_path(struct work_struct *work)
1220 {
1221         struct pgpath *pgpath =
1222                 container_of(work, struct pgpath, activate_path.work);
1223         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1224
1225         if (pgpath->is_active && !blk_queue_dying(q))
1226                 scsi_dh_activate(q, pg_init_done, pgpath);
1227         else
1228                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1229 }
1230
1231 static int noretry_error(int error)
1232 {
1233         switch (error) {
1234         case -EOPNOTSUPP:
1235         case -EREMOTEIO:
1236         case -EILSEQ:
1237         case -ENODATA:
1238         case -ENOSPC:
1239                 return 1;
1240         }
1241
1242         /* Anything else could be a path failure, so should be retried */
1243         return 0;
1244 }
1245
1246 /*
1247  * end_io handling
1248  */
1249 static int do_end_io(struct multipath *m, struct request *clone,
1250                      int error, struct dm_mpath_io *mpio)
1251 {
1252         /*
1253          * We don't queue any clone request inside the multipath target
1254          * during end I/O handling, since those clone requests don't have
1255          * bio clones.  If we queue them inside the multipath target,
1256          * we need to make bio clones, that requires memory allocation.
1257          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1258          *  don't have bio clones.)
1259          * Instead of queueing the clone request here, we queue the original
1260          * request into dm core, which will remake a clone request and
1261          * clone bios for it and resubmit it later.
1262          */
1263         int r = DM_ENDIO_REQUEUE;
1264         unsigned long flags;
1265
1266         if (!error && !clone->errors)
1267                 return 0;       /* I/O complete */
1268
1269         if (noretry_error(error))
1270                 return error;
1271
1272         if (mpio->pgpath)
1273                 fail_path(mpio->pgpath);
1274
1275         spin_lock_irqsave(&m->lock, flags);
1276         if (!m->nr_valid_paths) {
1277                 if (!m->queue_if_no_path) {
1278                         if (!__must_push_back(m))
1279                                 r = -EIO;
1280                 } else {
1281                         if (error == -EBADE)
1282                                 r = error;
1283                 }
1284         }
1285         spin_unlock_irqrestore(&m->lock, flags);
1286
1287         return r;
1288 }
1289
1290 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1291                             int error, union map_info *map_context)
1292 {
1293         struct multipath *m = ti->private;
1294         struct dm_mpath_io *mpio = map_context->ptr;
1295         struct pgpath *pgpath;
1296         struct path_selector *ps;
1297         int r;
1298
1299         BUG_ON(!mpio);
1300
1301         r  = do_end_io(m, clone, error, mpio);
1302         pgpath = mpio->pgpath;
1303         if (pgpath) {
1304                 ps = &pgpath->pg->ps;
1305                 if (ps->type->end_io)
1306                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1307         }
1308         clear_mapinfo(m, map_context);
1309
1310         return r;
1311 }
1312
1313 /*
1314  * Suspend can't complete until all the I/O is processed so if
1315  * the last path fails we must error any remaining I/O.
1316  * Note that if the freeze_bdev fails while suspending, the
1317  * queue_if_no_path state is lost - userspace should reset it.
1318  */
1319 static void multipath_presuspend(struct dm_target *ti)
1320 {
1321         struct multipath *m = (struct multipath *) ti->private;
1322
1323         queue_if_no_path(m, 0, 1);
1324 }
1325
1326 static void multipath_postsuspend(struct dm_target *ti)
1327 {
1328         struct multipath *m = ti->private;
1329
1330         mutex_lock(&m->work_mutex);
1331         flush_multipath_work(m);
1332         mutex_unlock(&m->work_mutex);
1333 }
1334
1335 /*
1336  * Restore the queue_if_no_path setting.
1337  */
1338 static void multipath_resume(struct dm_target *ti)
1339 {
1340         struct multipath *m = (struct multipath *) ti->private;
1341         unsigned long flags;
1342
1343         spin_lock_irqsave(&m->lock, flags);
1344         m->queue_if_no_path = m->saved_queue_if_no_path;
1345         spin_unlock_irqrestore(&m->lock, flags);
1346 }
1347
1348 /*
1349  * Info output has the following format:
1350  * num_multipath_feature_args [multipath_feature_args]*
1351  * num_handler_status_args [handler_status_args]*
1352  * num_groups init_group_number
1353  *            [A|D|E num_ps_status_args [ps_status_args]*
1354  *             num_paths num_selector_args
1355  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1356  *
1357  * Table output has the following format (identical to the constructor string):
1358  * num_feature_args [features_args]*
1359  * num_handler_args hw_handler [hw_handler_args]*
1360  * num_groups init_group_number
1361  *     [priority selector-name num_ps_args [ps_args]*
1362  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1363  */
1364 static void multipath_status(struct dm_target *ti, status_type_t type,
1365                              unsigned status_flags, char *result, unsigned maxlen)
1366 {
1367         int sz = 0;
1368         unsigned long flags;
1369         struct multipath *m = (struct multipath *) ti->private;
1370         struct priority_group *pg;
1371         struct pgpath *p;
1372         unsigned pg_num;
1373         char state;
1374
1375         spin_lock_irqsave(&m->lock, flags);
1376
1377         /* Features */
1378         if (type == STATUSTYPE_INFO)
1379                 DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);
1380         else {
1381                 DMEMIT("%u ", m->queue_if_no_path +
1382                               (m->pg_init_retries > 0) * 2 +
1383                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1384                               m->retain_attached_hw_handler);
1385                 if (m->queue_if_no_path)
1386                         DMEMIT("queue_if_no_path ");
1387                 if (m->pg_init_retries)
1388                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1389                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1390                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1391                 if (m->retain_attached_hw_handler)
1392                         DMEMIT("retain_attached_hw_handler ");
1393         }
1394
1395         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1396                 DMEMIT("0 ");
1397         else
1398                 DMEMIT("1 %s ", m->hw_handler_name);
1399
1400         DMEMIT("%u ", m->nr_priority_groups);
1401
1402         if (m->next_pg)
1403                 pg_num = m->next_pg->pg_num;
1404         else if (m->current_pg)
1405                 pg_num = m->current_pg->pg_num;
1406         else
1407                 pg_num = (m->nr_priority_groups ? 1 : 0);
1408
1409         DMEMIT("%u ", pg_num);
1410
1411         switch (type) {
1412         case STATUSTYPE_INFO:
1413                 list_for_each_entry(pg, &m->priority_groups, list) {
1414                         if (pg->bypassed)
1415                                 state = 'D';    /* Disabled */
1416                         else if (pg == m->current_pg)
1417                                 state = 'A';    /* Currently Active */
1418                         else
1419                                 state = 'E';    /* Enabled */
1420
1421                         DMEMIT("%c ", state);
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->info_args);
1432
1433                         list_for_each_entry(p, &pg->pgpaths, list) {
1434                                 DMEMIT("%s %s %u ", p->path.dev->name,
1435                                        p->is_active ? "A" : "F",
1436                                        p->fail_count);
1437                                 if (pg->ps.type->status)
1438                                         sz += pg->ps.type->status(&pg->ps,
1439                                               &p->path, type, result + sz,
1440                                               maxlen - sz);
1441                         }
1442                 }
1443                 break;
1444
1445         case STATUSTYPE_TABLE:
1446                 list_for_each_entry(pg, &m->priority_groups, list) {
1447                         DMEMIT("%s ", pg->ps.type->name);
1448
1449                         if (pg->ps.type->status)
1450                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1451                                                           result + sz,
1452                                                           maxlen - sz);
1453                         else
1454                                 DMEMIT("0 ");
1455
1456                         DMEMIT("%u %u ", pg->nr_pgpaths,
1457                                pg->ps.type->table_args);
1458
1459                         list_for_each_entry(p, &pg->pgpaths, list) {
1460                                 DMEMIT("%s ", p->path.dev->name);
1461                                 if (pg->ps.type->status)
1462                                         sz += pg->ps.type->status(&pg->ps,
1463                                               &p->path, type, result + sz,
1464                                               maxlen - sz);
1465                         }
1466                 }
1467                 break;
1468         }
1469
1470         spin_unlock_irqrestore(&m->lock, flags);
1471 }
1472
1473 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1474 {
1475         int r = -EINVAL;
1476         struct dm_dev *dev;
1477         struct multipath *m = (struct multipath *) ti->private;
1478         action_fn action;
1479
1480         mutex_lock(&m->work_mutex);
1481
1482         if (dm_suspended(ti)) {
1483                 r = -EBUSY;
1484                 goto out;
1485         }
1486
1487         if (argc == 1) {
1488                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1489                         r = queue_if_no_path(m, 1, 0);
1490                         goto out;
1491                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1492                         r = queue_if_no_path(m, 0, 0);
1493                         goto out;
1494                 }
1495         }
1496
1497         if (argc != 2) {
1498                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1499                 goto out;
1500         }
1501
1502         if (!strcasecmp(argv[0], "disable_group")) {
1503                 r = bypass_pg_num(m, argv[1], 1);
1504                 goto out;
1505         } else if (!strcasecmp(argv[0], "enable_group")) {
1506                 r = bypass_pg_num(m, argv[1], 0);
1507                 goto out;
1508         } else if (!strcasecmp(argv[0], "switch_group")) {
1509                 r = switch_pg_num(m, argv[1]);
1510                 goto out;
1511         } else if (!strcasecmp(argv[0], "reinstate_path"))
1512                 action = reinstate_path;
1513         else if (!strcasecmp(argv[0], "fail_path"))
1514                 action = fail_path;
1515         else {
1516                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1517                 goto out;
1518         }
1519
1520         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1521         if (r) {
1522                 DMWARN("message: error getting device %s",
1523                        argv[1]);
1524                 goto out;
1525         }
1526
1527         r = action_dev(m, dev, action);
1528
1529         dm_put_device(ti, dev);
1530
1531 out:
1532         mutex_unlock(&m->work_mutex);
1533         return r;
1534 }
1535
1536 static int multipath_prepare_ioctl(struct dm_target *ti,
1537                 struct block_device **bdev, fmode_t *mode)
1538 {
1539         struct multipath *m = ti->private;
1540         unsigned long flags;
1541         int r;
1542
1543         spin_lock_irqsave(&m->lock, flags);
1544
1545         if (!m->current_pgpath)
1546                 __choose_pgpath(m, 0);
1547
1548         if (m->current_pgpath) {
1549                 if (!m->queue_io) {
1550                         *bdev = m->current_pgpath->path.dev->bdev;
1551                         *mode = m->current_pgpath->path.dev->mode;
1552                         r = 0;
1553                 } else {
1554                         /* pg_init has not started or completed */
1555                         r = -ENOTCONN;
1556                 }
1557         } else {
1558                 /* No path is available */
1559                 if (m->queue_if_no_path)
1560                         r = -ENOTCONN;
1561                 else
1562                         r = -EIO;
1563         }
1564
1565         spin_unlock_irqrestore(&m->lock, flags);
1566
1567         if (r == -ENOTCONN) {
1568                 spin_lock_irqsave(&m->lock, flags);
1569                 if (!m->current_pg) {
1570                         /* Path status changed, redo selection */
1571                         __choose_pgpath(m, 0);
1572                 }
1573                 if (m->pg_init_required)
1574                         __pg_init_all_paths(m);
1575                 spin_unlock_irqrestore(&m->lock, flags);
1576                 dm_table_run_md_queue_async(m->ti->table);
1577         }
1578
1579         /*
1580          * Only pass ioctls through if the device sizes match exactly.
1581          */
1582         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1583                 return 1;
1584         return r;
1585 }
1586
1587 static int multipath_iterate_devices(struct dm_target *ti,
1588                                      iterate_devices_callout_fn fn, void *data)
1589 {
1590         struct multipath *m = ti->private;
1591         struct priority_group *pg;
1592         struct pgpath *p;
1593         int ret = 0;
1594
1595         list_for_each_entry(pg, &m->priority_groups, list) {
1596                 list_for_each_entry(p, &pg->pgpaths, list) {
1597                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1598                         if (ret)
1599                                 goto out;
1600                 }
1601         }
1602
1603 out:
1604         return ret;
1605 }
1606
1607 static int __pgpath_busy(struct pgpath *pgpath)
1608 {
1609         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1610
1611         return blk_lld_busy(q);
1612 }
1613
1614 /*
1615  * We return "busy", only when we can map I/Os but underlying devices
1616  * are busy (so even if we map I/Os now, the I/Os will wait on
1617  * the underlying queue).
1618  * In other words, if we want to kill I/Os or queue them inside us
1619  * due to map unavailability, we don't return "busy".  Otherwise,
1620  * dm core won't give us the I/Os and we can't do what we want.
1621  */
1622 static int multipath_busy(struct dm_target *ti)
1623 {
1624         int busy = 0, has_active = 0;
1625         struct multipath *m = ti->private;
1626         struct priority_group *pg;
1627         struct pgpath *pgpath;
1628         unsigned long flags;
1629
1630         spin_lock_irqsave(&m->lock, flags);
1631
1632         /* pg_init in progress or no paths available */
1633         if (m->pg_init_in_progress ||
1634             (!m->nr_valid_paths && m->queue_if_no_path)) {
1635                 busy = 1;
1636                 goto out;
1637         }
1638         /* Guess which priority_group will be used at next mapping time */
1639         if (unlikely(!m->current_pgpath && m->next_pg))
1640                 pg = m->next_pg;
1641         else if (likely(m->current_pg))
1642                 pg = m->current_pg;
1643         else
1644                 /*
1645                  * We don't know which pg will be used at next mapping time.
1646                  * We don't call __choose_pgpath() here to avoid to trigger
1647                  * pg_init just by busy checking.
1648                  * So we don't know whether underlying devices we will be using
1649                  * at next mapping time are busy or not. Just try mapping.
1650                  */
1651                 goto out;
1652
1653         /*
1654          * If there is one non-busy active path at least, the path selector
1655          * will be able to select it. So we consider such a pg as not busy.
1656          */
1657         busy = 1;
1658         list_for_each_entry(pgpath, &pg->pgpaths, list)
1659                 if (pgpath->is_active) {
1660                         has_active = 1;
1661
1662                         if (!__pgpath_busy(pgpath)) {
1663                                 busy = 0;
1664                                 break;
1665                         }
1666                 }
1667
1668         if (!has_active)
1669                 /*
1670                  * No active path in this pg, so this pg won't be used and
1671                  * the current_pg will be changed at next mapping time.
1672                  * We need to try mapping to determine it.
1673                  */
1674                 busy = 0;
1675
1676 out:
1677         spin_unlock_irqrestore(&m->lock, flags);
1678
1679         return busy;
1680 }
1681
1682 /*-----------------------------------------------------------------
1683  * Module setup
1684  *---------------------------------------------------------------*/
1685 static struct target_type multipath_target = {
1686         .name = "multipath",
1687         .version = {1, 10, 0},
1688         .module = THIS_MODULE,
1689         .ctr = multipath_ctr,
1690         .dtr = multipath_dtr,
1691         .map_rq = multipath_map,
1692         .clone_and_map_rq = multipath_clone_and_map,
1693         .release_clone_rq = multipath_release_clone,
1694         .rq_end_io = multipath_end_io,
1695         .presuspend = multipath_presuspend,
1696         .postsuspend = multipath_postsuspend,
1697         .resume = multipath_resume,
1698         .status = multipath_status,
1699         .message = multipath_message,
1700         .prepare_ioctl = multipath_prepare_ioctl,
1701         .iterate_devices = multipath_iterate_devices,
1702         .busy = multipath_busy,
1703 };
1704
1705 static int __init dm_multipath_init(void)
1706 {
1707         int r;
1708
1709         /* allocate a slab for the dm_ios */
1710         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1711         if (!_mpio_cache)
1712                 return -ENOMEM;
1713
1714         r = dm_register_target(&multipath_target);
1715         if (r < 0) {
1716                 DMERR("register failed %d", r);
1717                 r = -EINVAL;
1718                 goto bad_register_target;
1719         }
1720
1721         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1722         if (!kmultipathd) {
1723                 DMERR("failed to create workqueue kmpathd");
1724                 r = -ENOMEM;
1725                 goto bad_alloc_kmultipathd;
1726         }
1727
1728         /*
1729          * A separate workqueue is used to handle the device handlers
1730          * to avoid overloading existing workqueue. Overloading the
1731          * old workqueue would also create a bottleneck in the
1732          * path of the storage hardware device activation.
1733          */
1734         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1735                                                   WQ_MEM_RECLAIM);
1736         if (!kmpath_handlerd) {
1737                 DMERR("failed to create workqueue kmpath_handlerd");
1738                 r = -ENOMEM;
1739                 goto bad_alloc_kmpath_handlerd;
1740         }
1741
1742         DMINFO("version %u.%u.%u loaded",
1743                multipath_target.version[0], multipath_target.version[1],
1744                multipath_target.version[2]);
1745
1746         return 0;
1747
1748 bad_alloc_kmpath_handlerd:
1749         destroy_workqueue(kmultipathd);
1750 bad_alloc_kmultipathd:
1751         dm_unregister_target(&multipath_target);
1752 bad_register_target:
1753         kmem_cache_destroy(_mpio_cache);
1754
1755         return r;
1756 }
1757
1758 static void __exit dm_multipath_exit(void)
1759 {
1760         destroy_workqueue(kmpath_handlerd);
1761         destroy_workqueue(kmultipathd);
1762
1763         dm_unregister_target(&multipath_target);
1764         kmem_cache_destroy(_mpio_cache);
1765 }
1766
1767 module_init(dm_multipath_init);
1768 module_exit(dm_multipath_exit);
1769
1770 MODULE_DESCRIPTION(DM_NAME " multipath target");
1771 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1772 MODULE_LICENSE("GPL");