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 #include <linux/blk-mq.h>
  27
  28 #define DM_MSG_PREFIX "multipath"
  29 #define DM_PG_INIT_DELAY_MSECS 2000
  30 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  31
  32 /* Path properties */
  33 struct pgpath {
  34         struct list_head list;
  35
  36         struct priority_group *pg;      /* Owning PG */
  37         unsigned is_active;             /* Path status */
  38         unsigned fail_count;            /* Cumulative failure count */
  39
  40         struct dm_path path;
  41         struct delayed_work activate_path;
  42 };
  43
  44 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  45
  46 /*
  47  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  48  * Each has a path selector which controls which path gets used.
  49  */
  50 struct priority_group {
  51         struct list_head list;
  52
  53         struct multipath *m;            /* Owning multipath instance */
  54         struct path_selector ps;
  55
  56         unsigned pg_num;                /* Reference number */
  57         unsigned bypassed;              /* Temporarily bypass this PG? */
  58
  59         unsigned nr_pgpaths;            /* Number of paths in PG */
  60         struct list_head pgpaths;
  61 };
  62
  63 /* Multipath context */
  64 struct multipath {
  65         struct list_head list;
  66         struct dm_target *ti;
  67
  68         const char *hw_handler_name;
  69         char *hw_handler_params;
  70
  71         spinlock_t lock;
  72
  73         unsigned nr_priority_groups;
  74         struct list_head priority_groups;
  75
  76         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  77
  78         unsigned pg_init_required;      /* pg_init needs calling? */
  79         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  80         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  81
  82         unsigned nr_valid_paths;        /* Total number of usable paths */
  83         struct pgpath *current_pgpath;
  84         struct priority_group *current_pg;
  85         struct priority_group *next_pg; /* Switch to this PG if set */
  86         unsigned repeat_count;          /* I/Os left before calling PS again */
  87
  88         unsigned queue_io:1;            /* Must we queue all I/O? */
  89         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  90         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  91         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  92         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  93
  94         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  95         unsigned pg_init_count;         /* Number of times pg_init called */
  96         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  97
  98         struct work_struct trigger_event;
  99
 100         /*
 101          * We must use a mempool of dm_mpath_io structs so that we
 102          * can resubmit bios on error.
 103          */
 104         mempool_t *mpio_pool;
 105
 106         struct mutex work_mutex;
 107 };
 108
 109 /*
 110  * Context information attached to each bio we process.
 111  */
 112 struct dm_mpath_io {
 113         struct pgpath *pgpath;
 114         size_t nr_bytes;
 115 };
 116
 117 typedef int (*action_fn) (struct pgpath *pgpath);
 118
 119 static struct kmem_cache *_mpio_cache;
 120
 121 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 122 static void trigger_event(struct work_struct *work);
 123 static void activate_path(struct work_struct *work);
 124 static int __pgpath_busy(struct pgpath *pgpath);
 125
 126
 127 /*-----------------------------------------------
 128  * Allocation routines
 129  *-----------------------------------------------*/
 130
 131 static struct pgpath *alloc_pgpath(void)
 132 {
 133         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 134
 135         if (pgpath) {
 136                 pgpath->is_active = 1;
 137                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 138         }
 139
 140         return pgpath;
 141 }
 142
 143 static void free_pgpath(struct pgpath *pgpath)
 144 {
 145         kfree(pgpath);
 146 }
 147
 148 static struct priority_group *alloc_priority_group(void)
 149 {
 150         struct priority_group *pg;
 151
 152         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 153
 154         if (pg)
 155                 INIT_LIST_HEAD(&pg->pgpaths);
 156
 157         return pg;
 158 }
 159
 160 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 161 {
 162         struct pgpath *pgpath, *tmp;
 163
 164         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 165                 list_del(&pgpath->list);
 166                 dm_put_device(ti, pgpath->path.dev);
 167                 free_pgpath(pgpath);
 168         }
 169 }
 170
 171 static void free_priority_group(struct priority_group *pg,
 172                                 struct dm_target *ti)
 173 {
 174         struct path_selector *ps = &pg->ps;
 175
 176         if (ps->type) {
 177                 ps->type->destroy(ps);
 178                 dm_put_path_selector(ps->type);
 179         }
 180
 181         free_pgpaths(&pg->pgpaths, ti);
 182         kfree(pg);
 183 }
 184
 185 static struct multipath *alloc_multipath(struct dm_target *ti, bool use_blk_mq)
 186 {
 187         struct multipath *m;
 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
 199                 m->mpio_pool = NULL;
 200                 if (!use_blk_mq) {
 201                         unsigned min_ios = dm_get_reserved_rq_based_ios();
 202
 203                         m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 204                         if (!m->mpio_pool) {
 205                                 kfree(m);
 206                                 return NULL;
 207                         }
 208                 }
 209
 210                 m->ti = ti;
 211                 ti->private = m;
 212         }
 213
 214         return m;
 215 }
 216
 217 static void free_multipath(struct multipath *m)
 218 {
 219         struct priority_group *pg, *tmp;
 220
 221         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 222                 list_del(&pg->list);
 223                 free_priority_group(pg, m->ti);
 224         }
 225
 226         kfree(m->hw_handler_name);
 227         kfree(m->hw_handler_params);
 228         mempool_destroy(m->mpio_pool);
 229         kfree(m);
 230 }
 231
 232 static struct dm_mpath_io *get_mpio(union map_info *info)
 233 {
 234         return info->ptr;
 235 }
 236
 237 static struct dm_mpath_io *set_mpio(struct multipath *m, union map_info *info)
 238 {
 239         struct dm_mpath_io *mpio;
 240
 241         if (!m->mpio_pool) {
 242                 /* Use blk-mq pdu memory requested via per_io_data_size */
 243                 mpio = get_mpio(info);
 244                 memset(mpio, 0, sizeof(*mpio));
 245                 return mpio;
 246         }
 247
 248         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 249         if (!mpio)
 250                 return NULL;
 251
 252         memset(mpio, 0, sizeof(*mpio));
 253         info->ptr = mpio;
 254
 255         return mpio;
 256 }
 257
 258 static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
 259 {
 260         /* Only needed for non blk-mq (.request_fn) multipath */
 261         if (m->mpio_pool) {
 262                 struct dm_mpath_io *mpio = info->ptr;
 263
 264                 info->ptr = NULL;
 265                 mempool_free(mpio, m->mpio_pool);
 266         }
 267 }
 268
 269 /*-----------------------------------------------
 270  * Path selection
 271  *-----------------------------------------------*/
 272
 273 static int __pg_init_all_paths(struct multipath *m)
 274 {
 275         struct pgpath *pgpath;
 276         unsigned long pg_init_delay = 0;
 277
 278         if (m->pg_init_in_progress || m->pg_init_disabled)
 279                 return 0;
 280
 281         m->pg_init_count++;
 282         m->pg_init_required = 0;
 283
 284         /* Check here to reset pg_init_required */
 285         if (!m->current_pg)
 286                 return 0;
 287
 288         if (m->pg_init_delay_retry)
 289                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 290                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 291         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 292                 /* Skip failed paths */
 293                 if (!pgpath->is_active)
 294                         continue;
 295                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 296                                        pg_init_delay))
 297                         m->pg_init_in_progress++;
 298         }
 299         return m->pg_init_in_progress;
 300 }
 301
 302 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 303 {
 304         m->current_pg = pgpath->pg;
 305
 306         /* Must we initialise the PG first, and queue I/O till it's ready? */
 307         if (m->hw_handler_name) {
 308                 m->pg_init_required = 1;
 309                 m->queue_io = 1;
 310         } else {
 311                 m->pg_init_required = 0;
 312                 m->queue_io = 0;
 313         }
 314
 315         m->pg_init_count = 0;
 316 }
 317
 318 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 319                                size_t nr_bytes)
 320 {
 321         struct dm_path *path;
 322
 323         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 324         if (!path)
 325                 return -ENXIO;
 326
 327         m->current_pgpath = path_to_pgpath(path);
 328
 329         if (m->current_pg != pg)
 330                 __switch_pg(m, m->current_pgpath);
 331
 332         return 0;
 333 }
 334
 335 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 336 {
 337         struct priority_group *pg;
 338         unsigned bypassed = 1;
 339
 340         if (!m->nr_valid_paths) {
 341                 m->queue_io = 0;
 342                 goto failed;
 343         }
 344
 345         /* Were we instructed to switch PG? */
 346         if (m->next_pg) {
 347                 pg = m->next_pg;
 348                 m->next_pg = NULL;
 349                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 350                         return;
 351         }
 352
 353         /* Don't change PG until it has no remaining paths */
 354         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 355                 return;
 356
 357         /*
 358          * Loop through priority groups until we find a valid path.
 359          * First time we skip PGs marked 'bypassed'.
 360          * Second time we only try the ones we skipped, but set
 361          * pg_init_delay_retry so we do not hammer controllers.
 362          */
 363         do {
 364                 list_for_each_entry(pg, &m->priority_groups, list) {
 365                         if (pg->bypassed == bypassed)
 366                                 continue;
 367                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 368                                 if (!bypassed)
 369                                         m->pg_init_delay_retry = 1;
 370                                 return;
 371                         }
 372                 }
 373         } while (bypassed--);
 374
 375 failed:
 376         m->current_pgpath = NULL;
 377         m->current_pg = NULL;
 378 }
 379
 380 /*
 381  * Check whether bios must be queued in the device-mapper core rather
 382  * than here in the target.
 383  *
 384  * m->lock must be held on entry.
 385  *
 386  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 387  * same value then we are not between multipath_presuspend()
 388  * and multipath_resume() calls and we have no need to check
 389  * for the DMF_NOFLUSH_SUSPENDING flag.
 390  */
 391 static int __must_push_back(struct multipath *m)
 392 {
 393         return (m->queue_if_no_path ||
 394                 (m->queue_if_no_path != m->saved_queue_if_no_path &&
 395                  dm_noflush_suspending(m->ti)));
 396 }
 397
 398 /*
 399  * Map cloned requests
 400  */
 401 static int __multipath_map(struct dm_target *ti, struct request *clone,
 402                            union map_info *map_context,
 403                            struct request *rq, struct request **__clone)
 404 {
 405         struct multipath *m = ti->private;
 406         int r = DM_MAPIO_REQUEUE;
 407         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 408         struct pgpath *pgpath;
 409         struct block_device *bdev;
 410         struct dm_mpath_io *mpio;
 411
 412         spin_lock_irq(&m->lock);
 413
 414         /* Do we need to select a new pgpath? */
 415         if (!m->current_pgpath ||
 416             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 417                 __choose_pgpath(m, nr_bytes);
 418
 419         pgpath = m->current_pgpath;
 420
 421         if (!pgpath) {
 422                 if (!__must_push_back(m))
 423                         r = -EIO;       /* Failed */
 424                 goto out_unlock;
 425         } else if (m->queue_io || m->pg_init_required) {
 426                 __pg_init_all_paths(m);
 427                 goto out_unlock;
 428         }
 429
 430         mpio = set_mpio(m, map_context);
 431         if (!mpio)
 432                 /* ENOMEM, requeue */
 433                 goto out_unlock;
 434
 435         mpio->pgpath = pgpath;
 436         mpio->nr_bytes = nr_bytes;
 437
 438         bdev = pgpath->path.dev->bdev;
 439
 440         spin_unlock_irq(&m->lock);
 441
 442         if (clone) {
 443                 /*
 444                  * Old request-based interface: allocated clone is passed in.
 445                  * Used by: .request_fn stacked on .request_fn path(s).
 446                  */
 447                 clone->q = bdev_get_queue(bdev);
 448                 clone->rq_disk = bdev->bd_disk;
 449                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 450         } else {
 451                 /*
 452                  * blk-mq request-based interface; used by both:
 453                  * .request_fn stacked on blk-mq path(s) and
 454                  * blk-mq stacked on blk-mq path(s).
 455                  */
 456                 *__clone = blk_mq_alloc_request(bdev_get_queue(bdev),
 457                                                 rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
 458                 if (IS_ERR(*__clone)) {
 459                         /* ENOMEM, requeue */
 460                         clear_request_fn_mpio(m, map_context);
 461                         return r;
 462                 }
 463                 (*__clone)->bio = (*__clone)->biotail = NULL;
 464                 (*__clone)->rq_disk = bdev->bd_disk;
 465                 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 466         }
 467
 468         if (pgpath->pg->ps.type->start_io)
 469                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 470                                               &pgpath->path,
 471                                               nr_bytes);
 472         return DM_MAPIO_REMAPPED;
 473
 474 out_unlock:
 475         spin_unlock_irq(&m->lock);
 476
 477         return r;
 478 }
 479
 480 static int multipath_map(struct dm_target *ti, struct request *clone,
 481                          union map_info *map_context)
 482 {
 483         return __multipath_map(ti, clone, map_context, NULL, NULL);
 484 }
 485
 486 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 487                                    union map_info *map_context,
 488                                    struct request **clone)
 489 {
 490         return __multipath_map(ti, NULL, map_context, rq, clone);
 491 }
 492
 493 static void multipath_release_clone(struct request *clone)
 494 {
 495         blk_mq_free_request(clone);
 496 }
 497
 498 /*
 499  * If we run out of usable paths, should we queue I/O or error it?
 500  */
 501 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 502                             unsigned save_old_value)
 503 {
 504         unsigned long flags;
 505
 506         spin_lock_irqsave(&m->lock, flags);
 507
 508         if (save_old_value)
 509                 m->saved_queue_if_no_path = m->queue_if_no_path;
 510         else
 511                 m->saved_queue_if_no_path = queue_if_no_path;
 512         m->queue_if_no_path = queue_if_no_path;
 513         spin_unlock_irqrestore(&m->lock, flags);
 514
 515         if (!queue_if_no_path)
 516                 dm_table_run_md_queue_async(m->ti->table);
 517
 518         return 0;
 519 }
 520
 521 /*
 522  * An event is triggered whenever a path is taken out of use.
 523  * Includes path failure and PG bypass.
 524  */
 525 static void trigger_event(struct work_struct *work)
 526 {
 527         struct multipath *m =
 528                 container_of(work, struct multipath, trigger_event);
 529
 530         dm_table_event(m->ti->table);
 531 }
 532
 533 /*-----------------------------------------------------------------
 534  * Constructor/argument parsing:
 535  * <#multipath feature args> [<arg>]*
 536  * <#hw_handler args> [hw_handler [<arg>]*]
 537  * <#priority groups>
 538  * <initial priority group>
 539  *     [<selector> <#selector args> [<arg>]*
 540  *      <#paths> <#per-path selector args>
 541  *         [<path> [<arg>]* ]+ ]+
 542  *---------------------------------------------------------------*/
 543 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 544                                struct dm_target *ti)
 545 {
 546         int r;
 547         struct path_selector_type *pst;
 548         unsigned ps_argc;
 549
 550         static struct dm_arg _args[] = {
 551                 {0, 1024, "invalid number of path selector args"},
 552         };
 553
 554         pst = dm_get_path_selector(dm_shift_arg(as));
 555         if (!pst) {
 556                 ti->error = "unknown path selector type";
 557                 return -EINVAL;
 558         }
 559
 560         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 561         if (r) {
 562                 dm_put_path_selector(pst);
 563                 return -EINVAL;
 564         }
 565
 566         r = pst->create(&pg->ps, ps_argc, as->argv);
 567         if (r) {
 568                 dm_put_path_selector(pst);
 569                 ti->error = "path selector constructor failed";
 570                 return r;
 571         }
 572
 573         pg->ps.type = pst;
 574         dm_consume_args(as, ps_argc);
 575
 576         return 0;
 577 }
 578
 579 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 580                                struct dm_target *ti)
 581 {
 582         int r;
 583         struct pgpath *p;
 584         struct multipath *m = ti->private;
 585         struct request_queue *q = NULL;
 586         const char *attached_handler_name;
 587
 588         /* we need at least a path arg */
 589         if (as->argc < 1) {
 590                 ti->error = "no device given";
 591                 return ERR_PTR(-EINVAL);
 592         }
 593
 594         p = alloc_pgpath();
 595         if (!p)
 596                 return ERR_PTR(-ENOMEM);
 597
 598         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 599                           &p->path.dev);
 600         if (r) {
 601                 ti->error = "error getting device";
 602                 goto bad;
 603         }
 604
 605         if (m->retain_attached_hw_handler || m->hw_handler_name)
 606                 q = bdev_get_queue(p->path.dev->bdev);
 607
 608         if (m->retain_attached_hw_handler) {
 609 retain:
 610                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 611                 if (attached_handler_name) {
 612                         /*
 613                          * Reset hw_handler_name to match the attached handler
 614                          * and clear any hw_handler_params associated with the
 615                          * ignored handler.
 616                          *
 617                          * NB. This modifies the table line to show the actual
 618                          * handler instead of the original table passed in.
 619                          */
 620                         kfree(m->hw_handler_name);
 621                         m->hw_handler_name = attached_handler_name;
 622
 623                         kfree(m->hw_handler_params);
 624                         m->hw_handler_params = NULL;
 625                 }
 626         }
 627
 628         if (m->hw_handler_name) {
 629                 r = scsi_dh_attach(q, m->hw_handler_name);
 630                 if (r == -EBUSY) {
 631                         char b[BDEVNAME_SIZE];
 632
 633                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 634                                 bdevname(p->path.dev->bdev, b));
 635                         goto retain;
 636                 }
 637                 if (r < 0) {
 638                         ti->error = "error attaching hardware handler";
 639                         dm_put_device(ti, p->path.dev);
 640                         goto bad;
 641                 }
 642
 643                 if (m->hw_handler_params) {
 644                         r = scsi_dh_set_params(q, m->hw_handler_params);
 645                         if (r < 0) {
 646                                 ti->error = "unable to set hardware "
 647                                                         "handler parameters";
 648                                 dm_put_device(ti, p->path.dev);
 649                                 goto bad;
 650                         }
 651                 }
 652         }
 653
 654         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 655         if (r) {
 656                 dm_put_device(ti, p->path.dev);
 657                 goto bad;
 658         }
 659
 660         return p;
 661
 662  bad:
 663         free_pgpath(p);
 664         return ERR_PTR(r);
 665 }
 666
 667 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 668                                                    struct multipath *m)
 669 {
 670         static struct dm_arg _args[] = {
 671                 {1, 1024, "invalid number of paths"},
 672                 {0, 1024, "invalid number of selector args"}
 673         };
 674
 675         int r;
 676         unsigned i, nr_selector_args, nr_args;
 677         struct priority_group *pg;
 678         struct dm_target *ti = m->ti;
 679
 680         if (as->argc < 2) {
 681                 as->argc = 0;
 682                 ti->error = "not enough priority group arguments";
 683                 return ERR_PTR(-EINVAL);
 684         }
 685
 686         pg = alloc_priority_group();
 687         if (!pg) {
 688                 ti->error = "couldn't allocate priority group";
 689                 return ERR_PTR(-ENOMEM);
 690         }
 691         pg->m = m;
 692
 693         r = parse_path_selector(as, pg, ti);
 694         if (r)
 695                 goto bad;
 696
 697         /*
 698          * read the paths
 699          */
 700         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 701         if (r)
 702                 goto bad;
 703
 704         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 705         if (r)
 706                 goto bad;
 707
 708         nr_args = 1 + nr_selector_args;
 709         for (i = 0; i < pg->nr_pgpaths; i++) {
 710                 struct pgpath *pgpath;
 711                 struct dm_arg_set path_args;
 712
 713                 if (as->argc < nr_args) {
 714                         ti->error = "not enough path parameters";
 715                         r = -EINVAL;
 716                         goto bad;
 717                 }
 718
 719                 path_args.argc = nr_args;
 720                 path_args.argv = as->argv;
 721
 722                 pgpath = parse_path(&path_args, &pg->ps, ti);
 723                 if (IS_ERR(pgpath)) {
 724                         r = PTR_ERR(pgpath);
 725                         goto bad;
 726                 }
 727
 728                 pgpath->pg = pg;
 729                 list_add_tail(&pgpath->list, &pg->pgpaths);
 730                 dm_consume_args(as, nr_args);
 731         }
 732
 733         return pg;
 734
 735  bad:
 736         free_priority_group(pg, ti);
 737         return ERR_PTR(r);
 738 }
 739
 740 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 741 {
 742         unsigned hw_argc;
 743         int ret;
 744         struct dm_target *ti = m->ti;
 745
 746         static struct dm_arg _args[] = {
 747                 {0, 1024, "invalid number of hardware handler args"},
 748         };
 749
 750         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 751                 return -EINVAL;
 752
 753         if (!hw_argc)
 754                 return 0;
 755
 756         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 757
 758         if (hw_argc > 1) {
 759                 char *p;
 760                 int i, j, len = 4;
 761
 762                 for (i = 0; i <= hw_argc - 2; i++)
 763                         len += strlen(as->argv[i]) + 1;
 764                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 765                 if (!p) {
 766                         ti->error = "memory allocation failed";
 767                         ret = -ENOMEM;
 768                         goto fail;
 769                 }
 770                 j = sprintf(p, "%d", hw_argc - 1);
 771                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 772                         j = sprintf(p, "%s", as->argv[i]);
 773         }
 774         dm_consume_args(as, hw_argc - 1);
 775
 776         return 0;
 777 fail:
 778         kfree(m->hw_handler_name);
 779         m->hw_handler_name = NULL;
 780         return ret;
 781 }
 782
 783 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 784 {
 785         int r;
 786         unsigned argc;
 787         struct dm_target *ti = m->ti;
 788         const char *arg_name;
 789
 790         static struct dm_arg _args[] = {
 791                 {0, 6, "invalid number of feature args"},
 792                 {1, 50, "pg_init_retries must be between 1 and 50"},
 793                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 794         };
 795
 796         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 797         if (r)
 798                 return -EINVAL;
 799
 800         if (!argc)
 801                 return 0;
 802
 803         do {
 804                 arg_name = dm_shift_arg(as);
 805                 argc--;
 806
 807                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 808                         r = queue_if_no_path(m, 1, 0);
 809                         continue;
 810                 }
 811
 812                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 813                         m->retain_attached_hw_handler = 1;
 814                         continue;
 815                 }
 816
 817                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 818                     (argc >= 1)) {
 819                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 820                         argc--;
 821                         continue;
 822                 }
 823
 824                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 825                     (argc >= 1)) {
 826                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 827                         argc--;
 828                         continue;
 829                 }
 830
 831                 ti->error = "Unrecognised multipath feature request";
 832                 r = -EINVAL;
 833         } while (argc && !r);
 834
 835         return r;
 836 }
 837
 838 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 839                          char **argv)
 840 {
 841         /* target arguments */
 842         static struct dm_arg _args[] = {
 843                 {0, 1024, "invalid number of priority groups"},
 844                 {0, 1024, "invalid initial priority group number"},
 845         };
 846
 847         int r;
 848         struct multipath *m;
 849         struct dm_arg_set as;
 850         unsigned pg_count = 0;
 851         unsigned next_pg_num;
 852         bool use_blk_mq = dm_use_blk_mq(dm_table_get_md(ti->table));
 853
 854         as.argc = argc;
 855         as.argv = argv;
 856
 857         m = alloc_multipath(ti, use_blk_mq);
 858         if (!m) {
 859                 ti->error = "can't allocate multipath";
 860                 return -EINVAL;
 861         }
 862
 863         r = parse_features(&as, m);
 864         if (r)
 865                 goto bad;
 866
 867         r = parse_hw_handler(&as, m);
 868         if (r)
 869                 goto bad;
 870
 871         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 872         if (r)
 873                 goto bad;
 874
 875         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 876         if (r)
 877                 goto bad;
 878
 879         if ((!m->nr_priority_groups && next_pg_num) ||
 880             (m->nr_priority_groups && !next_pg_num)) {
 881                 ti->error = "invalid initial priority group";
 882                 r = -EINVAL;
 883                 goto bad;
 884         }
 885
 886         /* parse the priority groups */
 887         while (as.argc) {
 888                 struct priority_group *pg;
 889
 890                 pg = parse_priority_group(&as, m);
 891                 if (IS_ERR(pg)) {
 892                         r = PTR_ERR(pg);
 893                         goto bad;
 894                 }
 895
 896                 m->nr_valid_paths += pg->nr_pgpaths;
 897                 list_add_tail(&pg->list, &m->priority_groups);
 898                 pg_count++;
 899                 pg->pg_num = pg_count;
 900                 if (!--next_pg_num)
 901                         m->next_pg = pg;
 902         }
 903
 904         if (pg_count != m->nr_priority_groups) {
 905                 ti->error = "priority group count mismatch";
 906                 r = -EINVAL;
 907                 goto bad;
 908         }
 909
 910         ti->num_flush_bios = 1;
 911         ti->num_discard_bios = 1;
 912         ti->num_write_same_bios = 1;
 913         if (use_blk_mq)
 914                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
 915
 916         return 0;
 917
 918  bad:
 919         free_multipath(m);
 920         return r;
 921 }
 922
 923 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 924 {
 925         DECLARE_WAITQUEUE(wait, current);
 926         unsigned long flags;
 927
 928         add_wait_queue(&m->pg_init_wait, &wait);
 929
 930         while (1) {
 931                 set_current_state(TASK_UNINTERRUPTIBLE);
 932
 933                 spin_lock_irqsave(&m->lock, flags);
 934                 if (!m->pg_init_in_progress) {
 935                         spin_unlock_irqrestore(&m->lock, flags);
 936                         break;
 937                 }
 938                 spin_unlock_irqrestore(&m->lock, flags);
 939
 940                 io_schedule();
 941         }
 942         set_current_state(TASK_RUNNING);
 943
 944         remove_wait_queue(&m->pg_init_wait, &wait);
 945 }
 946
 947 static void flush_multipath_work(struct multipath *m)
 948 {
 949         unsigned long flags;
 950
 951         spin_lock_irqsave(&m->lock, flags);
 952         m->pg_init_disabled = 1;
 953         spin_unlock_irqrestore(&m->lock, flags);
 954
 955         flush_workqueue(kmpath_handlerd);
 956         multipath_wait_for_pg_init_completion(m);
 957         flush_workqueue(kmultipathd);
 958         flush_work(&m->trigger_event);
 959
 960         spin_lock_irqsave(&m->lock, flags);
 961         m->pg_init_disabled = 0;
 962         spin_unlock_irqrestore(&m->lock, flags);
 963 }
 964
 965 static void multipath_dtr(struct dm_target *ti)
 966 {
 967         struct multipath *m = ti->private;
 968
 969         flush_multipath_work(m);
 970         free_multipath(m);
 971 }
 972
 973 /*
 974  * Take a path out of use.
 975  */
 976 static int fail_path(struct pgpath *pgpath)
 977 {
 978         unsigned long flags;
 979         struct multipath *m = pgpath->pg->m;
 980
 981         spin_lock_irqsave(&m->lock, flags);
 982
 983         if (!pgpath->is_active)
 984                 goto out;
 985
 986         DMWARN("Failing path %s.", pgpath->path.dev->name);
 987
 988         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 989         pgpath->is_active = 0;
 990         pgpath->fail_count++;
 991
 992         m->nr_valid_paths--;
 993
 994         if (pgpath == m->current_pgpath)
 995                 m->current_pgpath = NULL;
 996
 997         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 998                       pgpath->path.dev->name, m->nr_valid_paths);
 999
1000         schedule_work(&m->trigger_event);
1001
1002 out:
1003         spin_unlock_irqrestore(&m->lock, flags);
1004
1005         return 0;
1006 }
1007
1008 /*
1009  * Reinstate a previously-failed path
1010  */
1011 static int reinstate_path(struct pgpath *pgpath)
1012 {
1013         int r = 0, run_queue = 0;
1014         unsigned long flags;
1015         struct multipath *m = pgpath->pg->m;
1016
1017         spin_lock_irqsave(&m->lock, flags);
1018
1019         if (pgpath->is_active)
1020                 goto out;
1021
1022         if (!pgpath->pg->ps.type->reinstate_path) {
1023                 DMWARN("Reinstate path not supported by path selector %s",
1024                        pgpath->pg->ps.type->name);
1025                 r = -EINVAL;
1026                 goto out;
1027         }
1028
1029         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1030         if (r)
1031                 goto out;
1032
1033         pgpath->is_active = 1;
1034
1035         if (!m->nr_valid_paths++) {
1036                 m->current_pgpath = NULL;
1037                 run_queue = 1;
1038         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1039                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1040                         m->pg_init_in_progress++;
1041         }
1042
1043         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1044                       pgpath->path.dev->name, m->nr_valid_paths);
1045
1046         schedule_work(&m->trigger_event);
1047
1048 out:
1049         spin_unlock_irqrestore(&m->lock, flags);
1050         if (run_queue)
1051                 dm_table_run_md_queue_async(m->ti->table);
1052
1053         return r;
1054 }
1055
1056 /*
1057  * Fail or reinstate all paths that match the provided struct dm_dev.
1058  */
1059 static int action_dev(struct multipath *m, struct dm_dev *dev,
1060                       action_fn action)
1061 {
1062         int r = -EINVAL;
1063         struct pgpath *pgpath;
1064         struct priority_group *pg;
1065
1066         list_for_each_entry(pg, &m->priority_groups, list) {
1067                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1068                         if (pgpath->path.dev == dev)
1069                                 r = action(pgpath);
1070                 }
1071         }
1072
1073         return r;
1074 }
1075
1076 /*
1077  * Temporarily try to avoid having to use the specified PG
1078  */
1079 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1080                       int bypassed)
1081 {
1082         unsigned long flags;
1083
1084         spin_lock_irqsave(&m->lock, flags);
1085
1086         pg->bypassed = bypassed;
1087         m->current_pgpath = NULL;
1088         m->current_pg = NULL;
1089
1090         spin_unlock_irqrestore(&m->lock, flags);
1091
1092         schedule_work(&m->trigger_event);
1093 }
1094
1095 /*
1096  * Switch to using the specified PG from the next I/O that gets mapped
1097  */
1098 static int switch_pg_num(struct multipath *m, const char *pgstr)
1099 {
1100         struct priority_group *pg;
1101         unsigned pgnum;
1102         unsigned long flags;
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 switch_pg_num");
1108                 return -EINVAL;
1109         }
1110
1111         spin_lock_irqsave(&m->lock, flags);
1112         list_for_each_entry(pg, &m->priority_groups, list) {
1113                 pg->bypassed = 0;
1114                 if (--pgnum)
1115                         continue;
1116
1117                 m->current_pgpath = NULL;
1118                 m->current_pg = NULL;
1119                 m->next_pg = pg;
1120         }
1121         spin_unlock_irqrestore(&m->lock, flags);
1122
1123         schedule_work(&m->trigger_event);
1124         return 0;
1125 }
1126
1127 /*
1128  * Set/clear bypassed status of a PG.
1129  * PGs are numbered upwards from 1 in the order they were declared.
1130  */
1131 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1132 {
1133         struct priority_group *pg;
1134         unsigned pgnum;
1135         char dummy;
1136
1137         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1138             (pgnum > m->nr_priority_groups)) {
1139                 DMWARN("invalid PG number supplied to bypass_pg");
1140                 return -EINVAL;
1141         }
1142
1143         list_for_each_entry(pg, &m->priority_groups, list) {
1144                 if (!--pgnum)
1145                         break;
1146         }
1147
1148         bypass_pg(m, pg, bypassed);
1149         return 0;
1150 }
1151
1152 /*
1153  * Should we retry pg_init immediately?
1154  */
1155 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1156 {
1157         unsigned long flags;
1158         int limit_reached = 0;
1159
1160         spin_lock_irqsave(&m->lock, flags);
1161
1162         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1163                 m->pg_init_required = 1;
1164         else
1165                 limit_reached = 1;
1166
1167         spin_unlock_irqrestore(&m->lock, flags);
1168
1169         return limit_reached;
1170 }
1171
1172 static void pg_init_done(void *data, int errors)
1173 {
1174         struct pgpath *pgpath = data;
1175         struct priority_group *pg = pgpath->pg;
1176         struct multipath *m = pg->m;
1177         unsigned long flags;
1178         unsigned delay_retry = 0;
1179
1180         /* device or driver problems */
1181         switch (errors) {
1182         case SCSI_DH_OK:
1183                 break;
1184         case SCSI_DH_NOSYS:
1185                 if (!m->hw_handler_name) {
1186                         errors = 0;
1187                         break;
1188                 }
1189                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1190                       "Error %d.", m->hw_handler_name, errors);
1191                 /*
1192                  * Fail path for now, so we do not ping pong
1193                  */
1194                 fail_path(pgpath);
1195                 break;
1196         case SCSI_DH_DEV_TEMP_BUSY:
1197                 /*
1198                  * Probably doing something like FW upgrade on the
1199                  * controller so try the other pg.
1200                  */
1201                 bypass_pg(m, pg, 1);
1202                 break;
1203         case SCSI_DH_RETRY:
1204                 /* Wait before retrying. */
1205                 delay_retry = 1;
1206         case SCSI_DH_IMM_RETRY:
1207         case SCSI_DH_RES_TEMP_UNAVAIL:
1208                 if (pg_init_limit_reached(m, pgpath))
1209                         fail_path(pgpath);
1210                 errors = 0;
1211                 break;
1212         default:
1213                 /*
1214                  * We probably do not want to fail the path for a device
1215                  * error, but this is what the old dm did. In future
1216                  * patches we can do more advanced handling.
1217                  */
1218                 fail_path(pgpath);
1219         }
1220
1221         spin_lock_irqsave(&m->lock, flags);
1222         if (errors) {
1223                 if (pgpath == m->current_pgpath) {
1224                         DMERR("Could not failover device. Error %d.", errors);
1225                         m->current_pgpath = NULL;
1226                         m->current_pg = NULL;
1227                 }
1228         } else if (!m->pg_init_required)
1229                 pg->bypassed = 0;
1230
1231         if (--m->pg_init_in_progress)
1232                 /* Activations of other paths are still on going */
1233                 goto out;
1234
1235         if (m->pg_init_required) {
1236                 m->pg_init_delay_retry = delay_retry;
1237                 if (__pg_init_all_paths(m))
1238                         goto out;
1239         }
1240         m->queue_io = 0;
1241
1242         /*
1243          * Wake up any thread waiting to suspend.
1244          */
1245         wake_up(&m->pg_init_wait);
1246
1247 out:
1248         spin_unlock_irqrestore(&m->lock, flags);
1249 }
1250
1251 static void activate_path(struct work_struct *work)
1252 {
1253         struct pgpath *pgpath =
1254                 container_of(work, struct pgpath, activate_path.work);
1255
1256         if (pgpath->is_active)
1257                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1258                                  pg_init_done, pgpath);
1259         else
1260                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1261 }
1262
1263 static int noretry_error(int error)
1264 {
1265         switch (error) {
1266         case -EOPNOTSUPP:
1267         case -EREMOTEIO:
1268         case -EILSEQ:
1269         case -ENODATA:
1270         case -ENOSPC:
1271                 return 1;
1272         }
1273
1274         /* Anything else could be a path failure, so should be retried */
1275         return 0;
1276 }
1277
1278 /*
1279  * end_io handling
1280  */
1281 static int do_end_io(struct multipath *m, struct request *clone,
1282                      int error, struct dm_mpath_io *mpio)
1283 {
1284         /*
1285          * We don't queue any clone request inside the multipath target
1286          * during end I/O handling, since those clone requests don't have
1287          * bio clones.  If we queue them inside the multipath target,
1288          * we need to make bio clones, that requires memory allocation.
1289          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1290          *  don't have bio clones.)
1291          * Instead of queueing the clone request here, we queue the original
1292          * request into dm core, which will remake a clone request and
1293          * clone bios for it and resubmit it later.
1294          */
1295         int r = DM_ENDIO_REQUEUE;
1296         unsigned long flags;
1297
1298         if (!error && !clone->errors)
1299                 return 0;       /* I/O complete */
1300
1301         if (noretry_error(error))
1302                 return error;
1303
1304         if (mpio->pgpath)
1305                 fail_path(mpio->pgpath);
1306
1307         spin_lock_irqsave(&m->lock, flags);
1308         if (!m->nr_valid_paths) {
1309                 if (!m->queue_if_no_path) {
1310                         if (!__must_push_back(m))
1311                                 r = -EIO;
1312                 } else {
1313                         if (error == -EBADE)
1314                                 r = error;
1315                 }
1316         }
1317         spin_unlock_irqrestore(&m->lock, flags);
1318
1319         return r;
1320 }
1321
1322 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1323                             int error, union map_info *map_context)
1324 {
1325         struct multipath *m = ti->private;
1326         struct dm_mpath_io *mpio = get_mpio(map_context);
1327         struct pgpath *pgpath;
1328         struct path_selector *ps;
1329         int r;
1330
1331         BUG_ON(!mpio);
1332
1333         r = do_end_io(m, clone, error, mpio);
1334         pgpath = mpio->pgpath;
1335         if (pgpath) {
1336                 ps = &pgpath->pg->ps;
1337                 if (ps->type->end_io)
1338                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1339         }
1340         clear_request_fn_mpio(m, map_context);
1341
1342         return r;
1343 }
1344
1345 /*
1346  * Suspend can't complete until all the I/O is processed so if
1347  * the last path fails we must error any remaining I/O.
1348  * Note that if the freeze_bdev fails while suspending, the
1349  * queue_if_no_path state is lost - userspace should reset it.
1350  */
1351 static void multipath_presuspend(struct dm_target *ti)
1352 {
1353         struct multipath *m = ti->private;
1354
1355         queue_if_no_path(m, 0, 1);
1356 }
1357
1358 static void multipath_postsuspend(struct dm_target *ti)
1359 {
1360         struct multipath *m = ti->private;
1361
1362         mutex_lock(&m->work_mutex);
1363         flush_multipath_work(m);
1364         mutex_unlock(&m->work_mutex);
1365 }
1366
1367 /*
1368  * Restore the queue_if_no_path setting.
1369  */
1370 static void multipath_resume(struct dm_target *ti)
1371 {
1372         struct multipath *m = ti->private;
1373         unsigned long flags;
1374
1375         spin_lock_irqsave(&m->lock, flags);
1376         m->queue_if_no_path = m->saved_queue_if_no_path;
1377         spin_unlock_irqrestore(&m->lock, flags);
1378 }
1379
1380 /*
1381  * Info output has the following format:
1382  * num_multipath_feature_args [multipath_feature_args]*
1383  * num_handler_status_args [handler_status_args]*
1384  * num_groups init_group_number
1385  *            [A|D|E num_ps_status_args [ps_status_args]*
1386  *             num_paths num_selector_args
1387  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1388  *
1389  * Table output has the following format (identical to the constructor string):
1390  * num_feature_args [features_args]*
1391  * num_handler_args hw_handler [hw_handler_args]*
1392  * num_groups init_group_number
1393  *     [priority selector-name num_ps_args [ps_args]*
1394  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1395  */
1396 static void multipath_status(struct dm_target *ti, status_type_t type,
1397                              unsigned status_flags, char *result, unsigned maxlen)
1398 {
1399         int sz = 0;
1400         unsigned long flags;
1401         struct multipath *m = ti->private;
1402         struct priority_group *pg;
1403         struct pgpath *p;
1404         unsigned pg_num;
1405         char state;
1406
1407         spin_lock_irqsave(&m->lock, flags);
1408
1409         /* Features */
1410         if (type == STATUSTYPE_INFO)
1411                 DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);
1412         else {
1413                 DMEMIT("%u ", m->queue_if_no_path +
1414                               (m->pg_init_retries > 0) * 2 +
1415                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1416                               m->retain_attached_hw_handler);
1417                 if (m->queue_if_no_path)
1418                         DMEMIT("queue_if_no_path ");
1419                 if (m->pg_init_retries)
1420                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1421                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1422                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1423                 if (m->retain_attached_hw_handler)
1424                         DMEMIT("retain_attached_hw_handler ");
1425         }
1426
1427         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1428                 DMEMIT("0 ");
1429         else
1430                 DMEMIT("1 %s ", m->hw_handler_name);
1431
1432         DMEMIT("%u ", m->nr_priority_groups);
1433
1434         if (m->next_pg)
1435                 pg_num = m->next_pg->pg_num;
1436         else if (m->current_pg)
1437                 pg_num = m->current_pg->pg_num;
1438         else
1439                 pg_num = (m->nr_priority_groups ? 1 : 0);
1440
1441         DMEMIT("%u ", pg_num);
1442
1443         switch (type) {
1444         case STATUSTYPE_INFO:
1445                 list_for_each_entry(pg, &m->priority_groups, list) {
1446                         if (pg->bypassed)
1447                                 state = 'D';    /* Disabled */
1448                         else if (pg == m->current_pg)
1449                                 state = 'A';    /* Currently Active */
1450                         else
1451                                 state = 'E';    /* Enabled */
1452
1453                         DMEMIT("%c ", state);
1454
1455                         if (pg->ps.type->status)
1456                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1457                                                           result + sz,
1458                                                           maxlen - sz);
1459                         else
1460                                 DMEMIT("0 ");
1461
1462                         DMEMIT("%u %u ", pg->nr_pgpaths,
1463                                pg->ps.type->info_args);
1464
1465                         list_for_each_entry(p, &pg->pgpaths, list) {
1466                                 DMEMIT("%s %s %u ", p->path.dev->name,
1467                                        p->is_active ? "A" : "F",
1468                                        p->fail_count);
1469                                 if (pg->ps.type->status)
1470                                         sz += pg->ps.type->status(&pg->ps,
1471                                               &p->path, type, result + sz,
1472                                               maxlen - sz);
1473                         }
1474                 }
1475                 break;
1476
1477         case STATUSTYPE_TABLE:
1478                 list_for_each_entry(pg, &m->priority_groups, list) {
1479                         DMEMIT("%s ", pg->ps.type->name);
1480
1481                         if (pg->ps.type->status)
1482                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1483                                                           result + sz,
1484                                                           maxlen - sz);
1485                         else
1486                                 DMEMIT("0 ");
1487
1488                         DMEMIT("%u %u ", pg->nr_pgpaths,
1489                                pg->ps.type->table_args);
1490
1491                         list_for_each_entry(p, &pg->pgpaths, list) {
1492                                 DMEMIT("%s ", p->path.dev->name);
1493                                 if (pg->ps.type->status)
1494                                         sz += pg->ps.type->status(&pg->ps,
1495                                               &p->path, type, result + sz,
1496                                               maxlen - sz);
1497                         }
1498                 }
1499                 break;
1500         }
1501
1502         spin_unlock_irqrestore(&m->lock, flags);
1503 }
1504
1505 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1506 {
1507         int r = -EINVAL;
1508         struct dm_dev *dev;
1509         struct multipath *m = ti->private;
1510         action_fn action;
1511
1512         mutex_lock(&m->work_mutex);
1513
1514         if (dm_suspended(ti)) {
1515                 r = -EBUSY;
1516                 goto out;
1517         }
1518
1519         if (argc == 1) {
1520                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1521                         r = queue_if_no_path(m, 1, 0);
1522                         goto out;
1523                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1524                         r = queue_if_no_path(m, 0, 0);
1525                         goto out;
1526                 }
1527         }
1528
1529         if (argc != 2) {
1530                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1531                 goto out;
1532         }
1533
1534         if (!strcasecmp(argv[0], "disable_group")) {
1535                 r = bypass_pg_num(m, argv[1], 1);
1536                 goto out;
1537         } else if (!strcasecmp(argv[0], "enable_group")) {
1538                 r = bypass_pg_num(m, argv[1], 0);
1539                 goto out;
1540         } else if (!strcasecmp(argv[0], "switch_group")) {
1541                 r = switch_pg_num(m, argv[1]);
1542                 goto out;
1543         } else if (!strcasecmp(argv[0], "reinstate_path"))
1544                 action = reinstate_path;
1545         else if (!strcasecmp(argv[0], "fail_path"))
1546                 action = fail_path;
1547         else {
1548                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1549                 goto out;
1550         }
1551
1552         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1553         if (r) {
1554                 DMWARN("message: error getting device %s",
1555                        argv[1]);
1556                 goto out;
1557         }
1558
1559         r = action_dev(m, dev, action);
1560
1561         dm_put_device(ti, dev);
1562
1563 out:
1564         mutex_unlock(&m->work_mutex);
1565         return r;
1566 }
1567
1568 static int multipath_prepare_ioctl(struct dm_target *ti,
1569                 struct block_device **bdev, fmode_t *mode)
1570 {
1571         struct multipath *m = ti->private;
1572         unsigned long flags;
1573         int r;
1574
1575         spin_lock_irqsave(&m->lock, flags);
1576
1577         if (!m->current_pgpath)
1578                 __choose_pgpath(m, 0);
1579
1580         if (m->current_pgpath) {
1581                 if (!m->queue_io) {
1582                         *bdev = m->current_pgpath->path.dev->bdev;
1583                         *mode = m->current_pgpath->path.dev->mode;
1584                         r = 0;
1585                 } else {
1586                         /* pg_init has not started or completed */
1587                         r = -ENOTCONN;
1588                 }
1589         } else {
1590                 /* No path is available */
1591                 if (m->queue_if_no_path)
1592                         r = -ENOTCONN;
1593                 else
1594                         r = -EIO;
1595         }
1596
1597         spin_unlock_irqrestore(&m->lock, flags);
1598
1599         if (r == -ENOTCONN) {
1600                 spin_lock_irqsave(&m->lock, flags);
1601                 if (!m->current_pg) {
1602                         /* Path status changed, redo selection */
1603                         __choose_pgpath(m, 0);
1604                 }
1605                 if (m->pg_init_required)
1606                         __pg_init_all_paths(m);
1607                 spin_unlock_irqrestore(&m->lock, flags);
1608                 dm_table_run_md_queue_async(m->ti->table);
1609         }
1610
1611         /*
1612          * Only pass ioctls through if the device sizes match exactly.
1613          */
1614         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1615                 return 1;
1616         return r;
1617 }
1618
1619 static int multipath_iterate_devices(struct dm_target *ti,
1620                                      iterate_devices_callout_fn fn, void *data)
1621 {
1622         struct multipath *m = ti->private;
1623         struct priority_group *pg;
1624         struct pgpath *p;
1625         int ret = 0;
1626
1627         list_for_each_entry(pg, &m->priority_groups, list) {
1628                 list_for_each_entry(p, &pg->pgpaths, list) {
1629                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1630                         if (ret)
1631                                 goto out;
1632                 }
1633         }
1634
1635 out:
1636         return ret;
1637 }
1638
1639 static int __pgpath_busy(struct pgpath *pgpath)
1640 {
1641         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1642
1643         return blk_lld_busy(q);
1644 }
1645
1646 /*
1647  * We return "busy", only when we can map I/Os but underlying devices
1648  * are busy (so even if we map I/Os now, the I/Os will wait on
1649  * the underlying queue).
1650  * In other words, if we want to kill I/Os or queue them inside us
1651  * due to map unavailability, we don't return "busy".  Otherwise,
1652  * dm core won't give us the I/Os and we can't do what we want.
1653  */
1654 static int multipath_busy(struct dm_target *ti)
1655 {
1656         int busy = 0, has_active = 0;
1657         struct multipath *m = ti->private;
1658         struct priority_group *pg;
1659         struct pgpath *pgpath;
1660         unsigned long flags;
1661
1662         spin_lock_irqsave(&m->lock, flags);
1663
1664         /* pg_init in progress or no paths available */
1665         if (m->pg_init_in_progress ||
1666             (!m->nr_valid_paths && m->queue_if_no_path)) {
1667                 busy = 1;
1668                 goto out;
1669         }
1670         /* Guess which priority_group will be used at next mapping time */
1671         if (unlikely(!m->current_pgpath && m->next_pg))
1672                 pg = m->next_pg;
1673         else if (likely(m->current_pg))
1674                 pg = m->current_pg;
1675         else
1676                 /*
1677                  * We don't know which pg will be used at next mapping time.
1678                  * We don't call __choose_pgpath() here to avoid to trigger
1679                  * pg_init just by busy checking.
1680                  * So we don't know whether underlying devices we will be using
1681                  * at next mapping time are busy or not. Just try mapping.
1682                  */
1683                 goto out;
1684
1685         /*
1686          * If there is one non-busy active path at least, the path selector
1687          * will be able to select it. So we consider such a pg as not busy.
1688          */
1689         busy = 1;
1690         list_for_each_entry(pgpath, &pg->pgpaths, list)
1691                 if (pgpath->is_active) {
1692                         has_active = 1;
1693
1694                         if (!__pgpath_busy(pgpath)) {
1695                                 busy = 0;
1696                                 break;
1697                         }
1698                 }
1699
1700         if (!has_active)
1701                 /*
1702                  * No active path in this pg, so this pg won't be used and
1703                  * the current_pg will be changed at next mapping time.
1704                  * We need to try mapping to determine it.
1705                  */
1706                 busy = 0;
1707
1708 out:
1709         spin_unlock_irqrestore(&m->lock, flags);
1710
1711         return busy;
1712 }
1713
1714 /*-----------------------------------------------------------------
1715  * Module setup
1716  *---------------------------------------------------------------*/
1717 static struct target_type multipath_target = {
1718         .name = "multipath",
1719         .version = {1, 11, 0},
1720         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1721         .module = THIS_MODULE,
1722         .ctr = multipath_ctr,
1723         .dtr = multipath_dtr,
1724         .map_rq = multipath_map,
1725         .clone_and_map_rq = multipath_clone_and_map,
1726         .release_clone_rq = multipath_release_clone,
1727         .rq_end_io = multipath_end_io,
1728         .presuspend = multipath_presuspend,
1729         .postsuspend = multipath_postsuspend,
1730         .resume = multipath_resume,
1731         .status = multipath_status,
1732         .message = multipath_message,
1733         .prepare_ioctl = multipath_prepare_ioctl,
1734         .iterate_devices = multipath_iterate_devices,
1735         .busy = multipath_busy,
1736 };
1737
1738 static int __init dm_multipath_init(void)
1739 {
1740         int r;
1741
1742         /* allocate a slab for the dm_ios */
1743         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1744         if (!_mpio_cache)
1745                 return -ENOMEM;
1746
1747         r = dm_register_target(&multipath_target);
1748         if (r < 0) {
1749                 DMERR("register failed %d", r);
1750                 r = -EINVAL;
1751                 goto bad_register_target;
1752         }
1753
1754         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1755         if (!kmultipathd) {
1756                 DMERR("failed to create workqueue kmpathd");
1757                 r = -ENOMEM;
1758                 goto bad_alloc_kmultipathd;
1759         }
1760
1761         /*
1762          * A separate workqueue is used to handle the device handlers
1763          * to avoid overloading existing workqueue. Overloading the
1764          * old workqueue would also create a bottleneck in the
1765          * path of the storage hardware device activation.
1766          */
1767         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1768                                                   WQ_MEM_RECLAIM);
1769         if (!kmpath_handlerd) {
1770                 DMERR("failed to create workqueue kmpath_handlerd");
1771                 r = -ENOMEM;
1772                 goto bad_alloc_kmpath_handlerd;
1773         }
1774
1775         DMINFO("version %u.%u.%u loaded",
1776                multipath_target.version[0], multipath_target.version[1],
1777                multipath_target.version[2]);
1778
1779         return 0;
1780
1781 bad_alloc_kmpath_handlerd:
1782         destroy_workqueue(kmultipathd);
1783 bad_alloc_kmultipathd:
1784         dm_unregister_target(&multipath_target);
1785 bad_register_target:
1786         kmem_cache_destroy(_mpio_cache);
1787
1788         return r;
1789 }
1790
1791 static void __exit dm_multipath_exit(void)
1792 {
1793         destroy_workqueue(kmpath_handlerd);
1794         destroy_workqueue(kmultipathd);
1795
1796         dm_unregister_target(&multipath_target);
1797         kmem_cache_destroy(_mpio_cache);
1798 }
1799
1800 module_init(dm_multipath_init);
1801 module_exit(dm_multipath_exit);
1802
1803 MODULE_DESCRIPTION(DM_NAME " multipath target");
1804 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1805 MODULE_LICENSE("GPL");