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 fail_count;            /* Cumulative failure count */
  38
  39         struct dm_path path;
  40         struct delayed_work activate_path;
  41
  42         bool is_active:1;               /* Path status */
  43 };
  44
  45 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  46
  47 /*
  48  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  49  * Each has a path selector which controls which path gets used.
  50  */
  51 struct priority_group {
  52         struct list_head list;
  53
  54         struct multipath *m;            /* Owning multipath instance */
  55         struct path_selector ps;
  56
  57         unsigned pg_num;                /* Reference number */
  58         unsigned nr_pgpaths;            /* Number of paths in PG */
  59         struct list_head pgpaths;
  60
  61         bool bypassed:1;                /* Temporarily bypass this PG? */
  62 };
  63
  64 /* Multipath context */
  65 struct multipath {
  66         struct list_head list;
  67         struct dm_target *ti;
  68
  69         const char *hw_handler_name;
  70         char *hw_handler_params;
  71
  72         spinlock_t lock;
  73
  74         unsigned nr_priority_groups;
  75         struct list_head priority_groups;
  76
  77         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  78
  79         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  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
  86         bool queue_io:1;                /* Must we queue all I/O? */
  87         bool queue_if_no_path:1;        /* Queue I/O if last path fails? */
  88         bool saved_queue_if_no_path:1;  /* Saved state during suspension */
  89         bool retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  90         bool pg_init_disabled:1;        /* pg_init is not currently allowed */
  91         bool pg_init_required:1;        /* pg_init needs calling? */
  92         bool pg_init_delay_retry:1;     /* Delay pg_init retry? */
  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
 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 = true;
 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, bool use_blk_mq)
 185 {
 186         struct multipath *m;
 187
 188         m = kzalloc(sizeof(*m), GFP_KERNEL);
 189         if (m) {
 190                 INIT_LIST_HEAD(&m->priority_groups);
 191                 spin_lock_init(&m->lock);
 192                 m->queue_io = true;
 193                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 194                 INIT_WORK(&m->trigger_event, trigger_event);
 195                 init_waitqueue_head(&m->pg_init_wait);
 196                 mutex_init(&m->work_mutex);
 197
 198                 m->mpio_pool = NULL;
 199                 if (!use_blk_mq) {
 200                         unsigned min_ios = dm_get_reserved_rq_based_ios();
 201
 202                         m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
 203                         if (!m->mpio_pool) {
 204                                 kfree(m);
 205                                 return NULL;
 206                         }
 207                 }
 208
 209                 m->ti = ti;
 210                 ti->private = m;
 211         }
 212
 213         return m;
 214 }
 215
 216 static void free_multipath(struct multipath *m)
 217 {
 218         struct priority_group *pg, *tmp;
 219
 220         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 221                 list_del(&pg->list);
 222                 free_priority_group(pg, m->ti);
 223         }
 224
 225         kfree(m->hw_handler_name);
 226         kfree(m->hw_handler_params);
 227         mempool_destroy(m->mpio_pool);
 228         kfree(m);
 229 }
 230
 231 static struct dm_mpath_io *get_mpio(union map_info *info)
 232 {
 233         return info->ptr;
 234 }
 235
 236 static struct dm_mpath_io *set_mpio(struct multipath *m, union map_info *info)
 237 {
 238         struct dm_mpath_io *mpio;
 239
 240         if (!m->mpio_pool) {
 241                 /* Use blk-mq pdu memory requested via per_io_data_size */
 242                 mpio = get_mpio(info);
 243                 memset(mpio, 0, sizeof(*mpio));
 244                 return mpio;
 245         }
 246
 247         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 248         if (!mpio)
 249                 return NULL;
 250
 251         memset(mpio, 0, sizeof(*mpio));
 252         info->ptr = mpio;
 253
 254         return mpio;
 255 }
 256
 257 static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
 258 {
 259         /* Only needed for non blk-mq (.request_fn) multipath */
 260         if (m->mpio_pool) {
 261                 struct dm_mpath_io *mpio = info->ptr;
 262
 263                 info->ptr = NULL;
 264                 mempool_free(mpio, m->mpio_pool);
 265         }
 266 }
 267
 268 /*-----------------------------------------------
 269  * Path selection
 270  *-----------------------------------------------*/
 271
 272 static int __pg_init_all_paths(struct multipath *m)
 273 {
 274         struct pgpath *pgpath;
 275         unsigned long pg_init_delay = 0;
 276
 277         if (m->pg_init_in_progress || m->pg_init_disabled)
 278                 return 0;
 279
 280         m->pg_init_count++;
 281         m->pg_init_required = false;
 282
 283         /* Check here to reset pg_init_required */
 284         if (!m->current_pg)
 285                 return 0;
 286
 287         if (m->pg_init_delay_retry)
 288                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 289                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 290         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 291                 /* Skip failed paths */
 292                 if (!pgpath->is_active)
 293                         continue;
 294                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 295                                        pg_init_delay))
 296                         m->pg_init_in_progress++;
 297         }
 298         return m->pg_init_in_progress;
 299 }
 300
 301 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 302 {
 303         m->current_pg = pgpath->pg;
 304
 305         /* Must we initialise the PG first, and queue I/O till it's ready? */
 306         if (m->hw_handler_name) {
 307                 m->pg_init_required = true;
 308                 m->queue_io = true;
 309         } else {
 310                 m->pg_init_required = false;
 311                 m->queue_io = false;
 312         }
 313
 314         m->pg_init_count = 0;
 315 }
 316
 317 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 318                                size_t nr_bytes)
 319 {
 320         struct dm_path *path;
 321
 322         path = pg->ps.type->select_path(&pg->ps, nr_bytes);
 323         if (!path)
 324                 return -ENXIO;
 325
 326         m->current_pgpath = path_to_pgpath(path);
 327
 328         if (m->current_pg != pg)
 329                 __switch_pg(m, m->current_pgpath);
 330
 331         return 0;
 332 }
 333
 334 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 335 {
 336         struct priority_group *pg;
 337         bool bypassed = true;
 338
 339         if (!m->nr_valid_paths) {
 340                 m->queue_io = false;
 341                 goto failed;
 342         }
 343
 344         /* Were we instructed to switch PG? */
 345         if (m->next_pg) {
 346                 pg = m->next_pg;
 347                 m->next_pg = NULL;
 348                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 349                         return;
 350         }
 351
 352         /* Don't change PG until it has no remaining paths */
 353         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 354                 return;
 355
 356         /*
 357          * Loop through priority groups until we find a valid path.
 358          * First time we skip PGs marked 'bypassed'.
 359          * Second time we only try the ones we skipped, but set
 360          * pg_init_delay_retry so we do not hammer controllers.
 361          */
 362         do {
 363                 list_for_each_entry(pg, &m->priority_groups, list) {
 364                         if (pg->bypassed == bypassed)
 365                                 continue;
 366                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 367                                 if (!bypassed)
 368                                         m->pg_init_delay_retry = true;
 369                                 return;
 370                         }
 371                 }
 372         } while (bypassed--);
 373
 374 failed:
 375         m->current_pgpath = NULL;
 376         m->current_pg = NULL;
 377 }
 378
 379 /*
 380  * Check whether bios must be queued in the device-mapper core rather
 381  * than here in the target.
 382  *
 383  * m->lock must be held on entry.
 384  *
 385  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 386  * same value then we are not between multipath_presuspend()
 387  * and multipath_resume() calls and we have no need to check
 388  * for the DMF_NOFLUSH_SUSPENDING flag.
 389  */
 390 static int __must_push_back(struct multipath *m)
 391 {
 392         return (m->queue_if_no_path ||
 393                 (m->queue_if_no_path != m->saved_queue_if_no_path &&
 394                  dm_noflush_suspending(m->ti)));
 395 }
 396
 397 /*
 398  * Map cloned requests
 399  */
 400 static int __multipath_map(struct dm_target *ti, struct request *clone,
 401                            union map_info *map_context,
 402                            struct request *rq, struct request **__clone)
 403 {
 404         struct multipath *m = ti->private;
 405         int r = DM_MAPIO_REQUEUE;
 406         size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
 407         struct pgpath *pgpath;
 408         struct block_device *bdev;
 409         struct dm_mpath_io *mpio;
 410
 411         spin_lock_irq(&m->lock);
 412
 413         /* Do we need to select a new pgpath? */
 414         if (!m->current_pgpath || !m->queue_io)
 415                 __choose_pgpath(m, nr_bytes);
 416
 417         pgpath = m->current_pgpath;
 418
 419         if (!pgpath) {
 420                 if (!__must_push_back(m))
 421                         r = -EIO;       /* Failed */
 422                 goto out_unlock;
 423         } else if (m->queue_io || m->pg_init_required) {
 424                 __pg_init_all_paths(m);
 425                 goto out_unlock;
 426         }
 427
 428         mpio = set_mpio(m, map_context);
 429         if (!mpio)
 430                 /* ENOMEM, requeue */
 431                 goto out_unlock;
 432
 433         mpio->pgpath = pgpath;
 434         mpio->nr_bytes = nr_bytes;
 435
 436         bdev = pgpath->path.dev->bdev;
 437
 438         spin_unlock_irq(&m->lock);
 439
 440         if (clone) {
 441                 /*
 442                  * Old request-based interface: allocated clone is passed in.
 443                  * Used by: .request_fn stacked on .request_fn path(s).
 444                  */
 445                 clone->q = bdev_get_queue(bdev);
 446                 clone->rq_disk = bdev->bd_disk;
 447                 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 448         } else {
 449                 /*
 450                  * blk-mq request-based interface; used by both:
 451                  * .request_fn stacked on blk-mq path(s) and
 452                  * blk-mq stacked on blk-mq path(s).
 453                  */
 454                 *__clone = blk_mq_alloc_request(bdev_get_queue(bdev),
 455                                                 rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
 456                 if (IS_ERR(*__clone)) {
 457                         /* ENOMEM, requeue */
 458                         clear_request_fn_mpio(m, map_context);
 459                         return r;
 460                 }
 461                 (*__clone)->bio = (*__clone)->biotail = NULL;
 462                 (*__clone)->rq_disk = bdev->bd_disk;
 463                 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 464         }
 465
 466         if (pgpath->pg->ps.type->start_io)
 467                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
 468                                               &pgpath->path,
 469                                               nr_bytes);
 470         return DM_MAPIO_REMAPPED;
 471
 472 out_unlock:
 473         spin_unlock_irq(&m->lock);
 474
 475         return r;
 476 }
 477
 478 static int multipath_map(struct dm_target *ti, struct request *clone,
 479                          union map_info *map_context)
 480 {
 481         return __multipath_map(ti, clone, map_context, NULL, NULL);
 482 }
 483
 484 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
 485                                    union map_info *map_context,
 486                                    struct request **clone)
 487 {
 488         return __multipath_map(ti, NULL, map_context, rq, clone);
 489 }
 490
 491 static void multipath_release_clone(struct request *clone)
 492 {
 493         blk_mq_free_request(clone);
 494 }
 495
 496 /*
 497  * If we run out of usable paths, should we queue I/O or error it?
 498  */
 499 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
 500                             bool save_old_value)
 501 {
 502         unsigned long flags;
 503
 504         spin_lock_irqsave(&m->lock, flags);
 505
 506         if (save_old_value)
 507                 m->saved_queue_if_no_path = m->queue_if_no_path;
 508         else
 509                 m->saved_queue_if_no_path = queue_if_no_path;
 510         m->queue_if_no_path = queue_if_no_path;
 511         spin_unlock_irqrestore(&m->lock, flags);
 512
 513         if (!queue_if_no_path)
 514                 dm_table_run_md_queue_async(m->ti->table);
 515
 516         return 0;
 517 }
 518
 519 /*
 520  * An event is triggered whenever a path is taken out of use.
 521  * Includes path failure and PG bypass.
 522  */
 523 static void trigger_event(struct work_struct *work)
 524 {
 525         struct multipath *m =
 526                 container_of(work, struct multipath, trigger_event);
 527
 528         dm_table_event(m->ti->table);
 529 }
 530
 531 /*-----------------------------------------------------------------
 532  * Constructor/argument parsing:
 533  * <#multipath feature args> [<arg>]*
 534  * <#hw_handler args> [hw_handler [<arg>]*]
 535  * <#priority groups>
 536  * <initial priority group>
 537  *     [<selector> <#selector args> [<arg>]*
 538  *      <#paths> <#per-path selector args>
 539  *         [<path> [<arg>]* ]+ ]+
 540  *---------------------------------------------------------------*/
 541 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 542                                struct dm_target *ti)
 543 {
 544         int r;
 545         struct path_selector_type *pst;
 546         unsigned ps_argc;
 547
 548         static struct dm_arg _args[] = {
 549                 {0, 1024, "invalid number of path selector args"},
 550         };
 551
 552         pst = dm_get_path_selector(dm_shift_arg(as));
 553         if (!pst) {
 554                 ti->error = "unknown path selector type";
 555                 return -EINVAL;
 556         }
 557
 558         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 559         if (r) {
 560                 dm_put_path_selector(pst);
 561                 return -EINVAL;
 562         }
 563
 564         r = pst->create(&pg->ps, ps_argc, as->argv);
 565         if (r) {
 566                 dm_put_path_selector(pst);
 567                 ti->error = "path selector constructor failed";
 568                 return r;
 569         }
 570
 571         pg->ps.type = pst;
 572         dm_consume_args(as, ps_argc);
 573
 574         return 0;
 575 }
 576
 577 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 578                                struct dm_target *ti)
 579 {
 580         int r;
 581         struct pgpath *p;
 582         struct multipath *m = ti->private;
 583         struct request_queue *q = NULL;
 584         const char *attached_handler_name;
 585
 586         /* we need at least a path arg */
 587         if (as->argc < 1) {
 588                 ti->error = "no device given";
 589                 return ERR_PTR(-EINVAL);
 590         }
 591
 592         p = alloc_pgpath();
 593         if (!p)
 594                 return ERR_PTR(-ENOMEM);
 595
 596         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 597                           &p->path.dev);
 598         if (r) {
 599                 ti->error = "error getting device";
 600                 goto bad;
 601         }
 602
 603         if (m->retain_attached_hw_handler || m->hw_handler_name)
 604                 q = bdev_get_queue(p->path.dev->bdev);
 605
 606         if (m->retain_attached_hw_handler) {
 607 retain:
 608                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 609                 if (attached_handler_name) {
 610                         /*
 611                          * Reset hw_handler_name to match the attached handler
 612                          * and clear any hw_handler_params associated with the
 613                          * ignored handler.
 614                          *
 615                          * NB. This modifies the table line to show the actual
 616                          * handler instead of the original table passed in.
 617                          */
 618                         kfree(m->hw_handler_name);
 619                         m->hw_handler_name = attached_handler_name;
 620
 621                         kfree(m->hw_handler_params);
 622                         m->hw_handler_params = NULL;
 623                 }
 624         }
 625
 626         if (m->hw_handler_name) {
 627                 r = scsi_dh_attach(q, m->hw_handler_name);
 628                 if (r == -EBUSY) {
 629                         char b[BDEVNAME_SIZE];
 630
 631                         printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
 632                                 bdevname(p->path.dev->bdev, b));
 633                         goto retain;
 634                 }
 635                 if (r < 0) {
 636                         ti->error = "error attaching hardware handler";
 637                         dm_put_device(ti, p->path.dev);
 638                         goto bad;
 639                 }
 640
 641                 if (m->hw_handler_params) {
 642                         r = scsi_dh_set_params(q, m->hw_handler_params);
 643                         if (r < 0) {
 644                                 ti->error = "unable to set hardware "
 645                                                         "handler parameters";
 646                                 dm_put_device(ti, p->path.dev);
 647                                 goto bad;
 648                         }
 649                 }
 650         }
 651
 652         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 653         if (r) {
 654                 dm_put_device(ti, p->path.dev);
 655                 goto bad;
 656         }
 657
 658         return p;
 659
 660  bad:
 661         free_pgpath(p);
 662         return ERR_PTR(r);
 663 }
 664
 665 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 666                                                    struct multipath *m)
 667 {
 668         static struct dm_arg _args[] = {
 669                 {1, 1024, "invalid number of paths"},
 670                 {0, 1024, "invalid number of selector args"}
 671         };
 672
 673         int r;
 674         unsigned i, nr_selector_args, nr_args;
 675         struct priority_group *pg;
 676         struct dm_target *ti = m->ti;
 677
 678         if (as->argc < 2) {
 679                 as->argc = 0;
 680                 ti->error = "not enough priority group arguments";
 681                 return ERR_PTR(-EINVAL);
 682         }
 683
 684         pg = alloc_priority_group();
 685         if (!pg) {
 686                 ti->error = "couldn't allocate priority group";
 687                 return ERR_PTR(-ENOMEM);
 688         }
 689         pg->m = m;
 690
 691         r = parse_path_selector(as, pg, ti);
 692         if (r)
 693                 goto bad;
 694
 695         /*
 696          * read the paths
 697          */
 698         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 699         if (r)
 700                 goto bad;
 701
 702         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 703         if (r)
 704                 goto bad;
 705
 706         nr_args = 1 + nr_selector_args;
 707         for (i = 0; i < pg->nr_pgpaths; i++) {
 708                 struct pgpath *pgpath;
 709                 struct dm_arg_set path_args;
 710
 711                 if (as->argc < nr_args) {
 712                         ti->error = "not enough path parameters";
 713                         r = -EINVAL;
 714                         goto bad;
 715                 }
 716
 717                 path_args.argc = nr_args;
 718                 path_args.argv = as->argv;
 719
 720                 pgpath = parse_path(&path_args, &pg->ps, ti);
 721                 if (IS_ERR(pgpath)) {
 722                         r = PTR_ERR(pgpath);
 723                         goto bad;
 724                 }
 725
 726                 pgpath->pg = pg;
 727                 list_add_tail(&pgpath->list, &pg->pgpaths);
 728                 dm_consume_args(as, nr_args);
 729         }
 730
 731         return pg;
 732
 733  bad:
 734         free_priority_group(pg, ti);
 735         return ERR_PTR(r);
 736 }
 737
 738 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 739 {
 740         unsigned hw_argc;
 741         int ret;
 742         struct dm_target *ti = m->ti;
 743
 744         static struct dm_arg _args[] = {
 745                 {0, 1024, "invalid number of hardware handler args"},
 746         };
 747
 748         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 749                 return -EINVAL;
 750
 751         if (!hw_argc)
 752                 return 0;
 753
 754         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 755
 756         if (hw_argc > 1) {
 757                 char *p;
 758                 int i, j, len = 4;
 759
 760                 for (i = 0; i <= hw_argc - 2; i++)
 761                         len += strlen(as->argv[i]) + 1;
 762                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 763                 if (!p) {
 764                         ti->error = "memory allocation failed";
 765                         ret = -ENOMEM;
 766                         goto fail;
 767                 }
 768                 j = sprintf(p, "%d", hw_argc - 1);
 769                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 770                         j = sprintf(p, "%s", as->argv[i]);
 771         }
 772         dm_consume_args(as, hw_argc - 1);
 773
 774         return 0;
 775 fail:
 776         kfree(m->hw_handler_name);
 777         m->hw_handler_name = NULL;
 778         return ret;
 779 }
 780
 781 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 782 {
 783         int r;
 784         unsigned argc;
 785         struct dm_target *ti = m->ti;
 786         const char *arg_name;
 787
 788         static struct dm_arg _args[] = {
 789                 {0, 6, "invalid number of feature args"},
 790                 {1, 50, "pg_init_retries must be between 1 and 50"},
 791                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 792         };
 793
 794         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 795         if (r)
 796                 return -EINVAL;
 797
 798         if (!argc)
 799                 return 0;
 800
 801         do {
 802                 arg_name = dm_shift_arg(as);
 803                 argc--;
 804
 805                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 806                         r = queue_if_no_path(m, true, false);
 807                         continue;
 808                 }
 809
 810                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 811                         m->retain_attached_hw_handler = true;
 812                         continue;
 813                 }
 814
 815                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 816                     (argc >= 1)) {
 817                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 818                         argc--;
 819                         continue;
 820                 }
 821
 822                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 823                     (argc >= 1)) {
 824                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 825                         argc--;
 826                         continue;
 827                 }
 828
 829                 ti->error = "Unrecognised multipath feature request";
 830                 r = -EINVAL;
 831         } while (argc && !r);
 832
 833         return r;
 834 }
 835
 836 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 837                          char **argv)
 838 {
 839         /* target arguments */
 840         static struct dm_arg _args[] = {
 841                 {0, 1024, "invalid number of priority groups"},
 842                 {0, 1024, "invalid initial priority group number"},
 843         };
 844
 845         int r;
 846         struct multipath *m;
 847         struct dm_arg_set as;
 848         unsigned pg_count = 0;
 849         unsigned next_pg_num;
 850         bool use_blk_mq = dm_use_blk_mq(dm_table_get_md(ti->table));
 851
 852         as.argc = argc;
 853         as.argv = argv;
 854
 855         m = alloc_multipath(ti, use_blk_mq);
 856         if (!m) {
 857                 ti->error = "can't allocate multipath";
 858                 return -EINVAL;
 859         }
 860
 861         r = parse_features(&as, m);
 862         if (r)
 863                 goto bad;
 864
 865         r = parse_hw_handler(&as, m);
 866         if (r)
 867                 goto bad;
 868
 869         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
 870         if (r)
 871                 goto bad;
 872
 873         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
 874         if (r)
 875                 goto bad;
 876
 877         if ((!m->nr_priority_groups && next_pg_num) ||
 878             (m->nr_priority_groups && !next_pg_num)) {
 879                 ti->error = "invalid initial priority group";
 880                 r = -EINVAL;
 881                 goto bad;
 882         }
 883
 884         /* parse the priority groups */
 885         while (as.argc) {
 886                 struct priority_group *pg;
 887
 888                 pg = parse_priority_group(&as, m);
 889                 if (IS_ERR(pg)) {
 890                         r = PTR_ERR(pg);
 891                         goto bad;
 892                 }
 893
 894                 m->nr_valid_paths += pg->nr_pgpaths;
 895                 list_add_tail(&pg->list, &m->priority_groups);
 896                 pg_count++;
 897                 pg->pg_num = pg_count;
 898                 if (!--next_pg_num)
 899                         m->next_pg = pg;
 900         }
 901
 902         if (pg_count != m->nr_priority_groups) {
 903                 ti->error = "priority group count mismatch";
 904                 r = -EINVAL;
 905                 goto bad;
 906         }
 907
 908         ti->num_flush_bios = 1;
 909         ti->num_discard_bios = 1;
 910         ti->num_write_same_bios = 1;
 911         if (use_blk_mq)
 912                 ti->per_io_data_size = sizeof(struct dm_mpath_io);
 913
 914         return 0;
 915
 916  bad:
 917         free_multipath(m);
 918         return r;
 919 }
 920
 921 static void multipath_wait_for_pg_init_completion(struct multipath *m)
 922 {
 923         DECLARE_WAITQUEUE(wait, current);
 924         unsigned long flags;
 925
 926         add_wait_queue(&m->pg_init_wait, &wait);
 927
 928         while (1) {
 929                 set_current_state(TASK_UNINTERRUPTIBLE);
 930
 931                 spin_lock_irqsave(&m->lock, flags);
 932                 if (!m->pg_init_in_progress) {
 933                         spin_unlock_irqrestore(&m->lock, flags);
 934                         break;
 935                 }
 936                 spin_unlock_irqrestore(&m->lock, flags);
 937
 938                 io_schedule();
 939         }
 940         set_current_state(TASK_RUNNING);
 941
 942         remove_wait_queue(&m->pg_init_wait, &wait);
 943 }
 944
 945 static void flush_multipath_work(struct multipath *m)
 946 {
 947         unsigned long flags;
 948
 949         spin_lock_irqsave(&m->lock, flags);
 950         m->pg_init_disabled = true;
 951         spin_unlock_irqrestore(&m->lock, flags);
 952
 953         flush_workqueue(kmpath_handlerd);
 954         multipath_wait_for_pg_init_completion(m);
 955         flush_workqueue(kmultipathd);
 956         flush_work(&m->trigger_event);
 957
 958         spin_lock_irqsave(&m->lock, flags);
 959         m->pg_init_disabled = false;
 960         spin_unlock_irqrestore(&m->lock, flags);
 961 }
 962
 963 static void multipath_dtr(struct dm_target *ti)
 964 {
 965         struct multipath *m = ti->private;
 966
 967         flush_multipath_work(m);
 968         free_multipath(m);
 969 }
 970
 971 /*
 972  * Take a path out of use.
 973  */
 974 static int fail_path(struct pgpath *pgpath)
 975 {
 976         unsigned long flags;
 977         struct multipath *m = pgpath->pg->m;
 978
 979         spin_lock_irqsave(&m->lock, flags);
 980
 981         if (!pgpath->is_active)
 982                 goto out;
 983
 984         DMWARN("Failing path %s.", pgpath->path.dev->name);
 985
 986         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
 987         pgpath->is_active = false;
 988         pgpath->fail_count++;
 989
 990         m->nr_valid_paths--;
 991
 992         if (pgpath == m->current_pgpath)
 993                 m->current_pgpath = NULL;
 994
 995         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
 996                       pgpath->path.dev->name, m->nr_valid_paths);
 997
 998         schedule_work(&m->trigger_event);
 999
1000 out:
1001         spin_unlock_irqrestore(&m->lock, flags);
1002
1003         return 0;
1004 }
1005
1006 /*
1007  * Reinstate a previously-failed path
1008  */
1009 static int reinstate_path(struct pgpath *pgpath)
1010 {
1011         int r = 0, run_queue = 0;
1012         unsigned long flags;
1013         struct multipath *m = pgpath->pg->m;
1014
1015         spin_lock_irqsave(&m->lock, flags);
1016
1017         if (pgpath->is_active)
1018                 goto out;
1019
1020         if (!pgpath->pg->ps.type->reinstate_path) {
1021                 DMWARN("Reinstate path not supported by path selector %s",
1022                        pgpath->pg->ps.type->name);
1023                 r = -EINVAL;
1024                 goto out;
1025         }
1026
1027         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1028         if (r)
1029                 goto out;
1030
1031         pgpath->is_active = true;
1032
1033         if (!m->nr_valid_paths++) {
1034                 m->current_pgpath = NULL;
1035                 run_queue = 1;
1036         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1037                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1038                         m->pg_init_in_progress++;
1039         }
1040
1041         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1042                       pgpath->path.dev->name, m->nr_valid_paths);
1043
1044         schedule_work(&m->trigger_event);
1045
1046 out:
1047         spin_unlock_irqrestore(&m->lock, flags);
1048         if (run_queue)
1049                 dm_table_run_md_queue_async(m->ti->table);
1050
1051         return r;
1052 }
1053
1054 /*
1055  * Fail or reinstate all paths that match the provided struct dm_dev.
1056  */
1057 static int action_dev(struct multipath *m, struct dm_dev *dev,
1058                       action_fn action)
1059 {
1060         int r = -EINVAL;
1061         struct pgpath *pgpath;
1062         struct priority_group *pg;
1063
1064         list_for_each_entry(pg, &m->priority_groups, list) {
1065                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1066                         if (pgpath->path.dev == dev)
1067                                 r = action(pgpath);
1068                 }
1069         }
1070
1071         return r;
1072 }
1073
1074 /*
1075  * Temporarily try to avoid having to use the specified PG
1076  */
1077 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1078                       bool bypassed)
1079 {
1080         unsigned long flags;
1081
1082         spin_lock_irqsave(&m->lock, flags);
1083
1084         pg->bypassed = bypassed;
1085         m->current_pgpath = NULL;
1086         m->current_pg = NULL;
1087
1088         spin_unlock_irqrestore(&m->lock, flags);
1089
1090         schedule_work(&m->trigger_event);
1091 }
1092
1093 /*
1094  * Switch to using the specified PG from the next I/O that gets mapped
1095  */
1096 static int switch_pg_num(struct multipath *m, const char *pgstr)
1097 {
1098         struct priority_group *pg;
1099         unsigned pgnum;
1100         unsigned long flags;
1101         char dummy;
1102
1103         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1104             (pgnum > m->nr_priority_groups)) {
1105                 DMWARN("invalid PG number supplied to switch_pg_num");
1106                 return -EINVAL;
1107         }
1108
1109         spin_lock_irqsave(&m->lock, flags);
1110         list_for_each_entry(pg, &m->priority_groups, list) {
1111                 pg->bypassed = false;
1112                 if (--pgnum)
1113                         continue;
1114
1115                 m->current_pgpath = NULL;
1116                 m->current_pg = NULL;
1117                 m->next_pg = pg;
1118         }
1119         spin_unlock_irqrestore(&m->lock, flags);
1120
1121         schedule_work(&m->trigger_event);
1122         return 0;
1123 }
1124
1125 /*
1126  * Set/clear bypassed status of a PG.
1127  * PGs are numbered upwards from 1 in the order they were declared.
1128  */
1129 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1130 {
1131         struct priority_group *pg;
1132         unsigned pgnum;
1133         char dummy;
1134
1135         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1136             (pgnum > m->nr_priority_groups)) {
1137                 DMWARN("invalid PG number supplied to bypass_pg");
1138                 return -EINVAL;
1139         }
1140
1141         list_for_each_entry(pg, &m->priority_groups, list) {
1142                 if (!--pgnum)
1143                         break;
1144         }
1145
1146         bypass_pg(m, pg, bypassed);
1147         return 0;
1148 }
1149
1150 /*
1151  * Should we retry pg_init immediately?
1152  */
1153 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1154 {
1155         unsigned long flags;
1156         bool limit_reached = false;
1157
1158         spin_lock_irqsave(&m->lock, flags);
1159
1160         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1161                 m->pg_init_required = true;
1162         else
1163                 limit_reached = true;
1164
1165         spin_unlock_irqrestore(&m->lock, flags);
1166
1167         return limit_reached;
1168 }
1169
1170 static void pg_init_done(void *data, int errors)
1171 {
1172         struct pgpath *pgpath = data;
1173         struct priority_group *pg = pgpath->pg;
1174         struct multipath *m = pg->m;
1175         unsigned long flags;
1176         bool delay_retry = false;
1177
1178         /* device or driver problems */
1179         switch (errors) {
1180         case SCSI_DH_OK:
1181                 break;
1182         case SCSI_DH_NOSYS:
1183                 if (!m->hw_handler_name) {
1184                         errors = 0;
1185                         break;
1186                 }
1187                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1188                       "Error %d.", m->hw_handler_name, errors);
1189                 /*
1190                  * Fail path for now, so we do not ping pong
1191                  */
1192                 fail_path(pgpath);
1193                 break;
1194         case SCSI_DH_DEV_TEMP_BUSY:
1195                 /*
1196                  * Probably doing something like FW upgrade on the
1197                  * controller so try the other pg.
1198                  */
1199                 bypass_pg(m, pg, true);
1200                 break;
1201         case SCSI_DH_RETRY:
1202                 /* Wait before retrying. */
1203                 delay_retry = 1;
1204         case SCSI_DH_IMM_RETRY:
1205         case SCSI_DH_RES_TEMP_UNAVAIL:
1206                 if (pg_init_limit_reached(m, pgpath))
1207                         fail_path(pgpath);
1208                 errors = 0;
1209                 break;
1210         default:
1211                 /*
1212                  * We probably do not want to fail the path for a device
1213                  * error, but this is what the old dm did. In future
1214                  * patches we can do more advanced handling.
1215                  */
1216                 fail_path(pgpath);
1217         }
1218
1219         spin_lock_irqsave(&m->lock, flags);
1220         if (errors) {
1221                 if (pgpath == m->current_pgpath) {
1222                         DMERR("Could not failover device. Error %d.", errors);
1223                         m->current_pgpath = NULL;
1224                         m->current_pg = NULL;
1225                 }
1226         } else if (!m->pg_init_required)
1227                 pg->bypassed = false;
1228
1229         if (--m->pg_init_in_progress)
1230                 /* Activations of other paths are still on going */
1231                 goto out;
1232
1233         if (m->pg_init_required) {
1234                 m->pg_init_delay_retry = delay_retry;
1235                 if (__pg_init_all_paths(m))
1236                         goto out;
1237         }
1238         m->queue_io = false;
1239
1240         /*
1241          * Wake up any thread waiting to suspend.
1242          */
1243         wake_up(&m->pg_init_wait);
1244
1245 out:
1246         spin_unlock_irqrestore(&m->lock, flags);
1247 }
1248
1249 static void activate_path(struct work_struct *work)
1250 {
1251         struct pgpath *pgpath =
1252                 container_of(work, struct pgpath, activate_path.work);
1253
1254         if (pgpath->is_active)
1255                 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1256                                  pg_init_done, pgpath);
1257         else
1258                 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1259 }
1260
1261 static int noretry_error(int error)
1262 {
1263         switch (error) {
1264         case -EOPNOTSUPP:
1265         case -EREMOTEIO:
1266         case -EILSEQ:
1267         case -ENODATA:
1268         case -ENOSPC:
1269                 return 1;
1270         }
1271
1272         /* Anything else could be a path failure, so should be retried */
1273         return 0;
1274 }
1275
1276 /*
1277  * end_io handling
1278  */
1279 static int do_end_io(struct multipath *m, struct request *clone,
1280                      int error, struct dm_mpath_io *mpio)
1281 {
1282         /*
1283          * We don't queue any clone request inside the multipath target
1284          * during end I/O handling, since those clone requests don't have
1285          * bio clones.  If we queue them inside the multipath target,
1286          * we need to make bio clones, that requires memory allocation.
1287          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1288          *  don't have bio clones.)
1289          * Instead of queueing the clone request here, we queue the original
1290          * request into dm core, which will remake a clone request and
1291          * clone bios for it and resubmit it later.
1292          */
1293         int r = DM_ENDIO_REQUEUE;
1294         unsigned long flags;
1295
1296         if (!error && !clone->errors)
1297                 return 0;       /* I/O complete */
1298
1299         if (noretry_error(error))
1300                 return error;
1301
1302         if (mpio->pgpath)
1303                 fail_path(mpio->pgpath);
1304
1305         spin_lock_irqsave(&m->lock, flags);
1306         if (!m->nr_valid_paths) {
1307                 if (!m->queue_if_no_path) {
1308                         if (!__must_push_back(m))
1309                                 r = -EIO;
1310                 } else {
1311                         if (error == -EBADE)
1312                                 r = error;
1313                 }
1314         }
1315         spin_unlock_irqrestore(&m->lock, flags);
1316
1317         return r;
1318 }
1319
1320 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1321                             int error, union map_info *map_context)
1322 {
1323         struct multipath *m = ti->private;
1324         struct dm_mpath_io *mpio = get_mpio(map_context);
1325         struct pgpath *pgpath;
1326         struct path_selector *ps;
1327         int r;
1328
1329         BUG_ON(!mpio);
1330
1331         r = do_end_io(m, clone, error, mpio);
1332         pgpath = mpio->pgpath;
1333         if (pgpath) {
1334                 ps = &pgpath->pg->ps;
1335                 if (ps->type->end_io)
1336                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1337         }
1338         clear_request_fn_mpio(m, map_context);
1339
1340         return r;
1341 }
1342
1343 /*
1344  * Suspend can't complete until all the I/O is processed so if
1345  * the last path fails we must error any remaining I/O.
1346  * Note that if the freeze_bdev fails while suspending, the
1347  * queue_if_no_path state is lost - userspace should reset it.
1348  */
1349 static void multipath_presuspend(struct dm_target *ti)
1350 {
1351         struct multipath *m = ti->private;
1352
1353         queue_if_no_path(m, false, true);
1354 }
1355
1356 static void multipath_postsuspend(struct dm_target *ti)
1357 {
1358         struct multipath *m = ti->private;
1359
1360         mutex_lock(&m->work_mutex);
1361         flush_multipath_work(m);
1362         mutex_unlock(&m->work_mutex);
1363 }
1364
1365 /*
1366  * Restore the queue_if_no_path setting.
1367  */
1368 static void multipath_resume(struct dm_target *ti)
1369 {
1370         struct multipath *m = ti->private;
1371         unsigned long flags;
1372
1373         spin_lock_irqsave(&m->lock, flags);
1374         m->queue_if_no_path = m->saved_queue_if_no_path;
1375         spin_unlock_irqrestore(&m->lock, flags);
1376 }
1377
1378 /*
1379  * Info output has the following format:
1380  * num_multipath_feature_args [multipath_feature_args]*
1381  * num_handler_status_args [handler_status_args]*
1382  * num_groups init_group_number
1383  *            [A|D|E num_ps_status_args [ps_status_args]*
1384  *             num_paths num_selector_args
1385  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1386  *
1387  * Table output has the following format (identical to the constructor string):
1388  * num_feature_args [features_args]*
1389  * num_handler_args hw_handler [hw_handler_args]*
1390  * num_groups init_group_number
1391  *     [priority selector-name num_ps_args [ps_args]*
1392  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1393  */
1394 static void multipath_status(struct dm_target *ti, status_type_t type,
1395                              unsigned status_flags, char *result, unsigned maxlen)
1396 {
1397         int sz = 0;
1398         unsigned long flags;
1399         struct multipath *m = ti->private;
1400         struct priority_group *pg;
1401         struct pgpath *p;
1402         unsigned pg_num;
1403         char state;
1404
1405         spin_lock_irqsave(&m->lock, flags);
1406
1407         /* Features */
1408         if (type == STATUSTYPE_INFO)
1409                 DMEMIT("2 %u %u ", m->queue_io, m->pg_init_count);
1410         else {
1411                 DMEMIT("%u ", m->queue_if_no_path +
1412                               (m->pg_init_retries > 0) * 2 +
1413                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1414                               m->retain_attached_hw_handler);
1415                 if (m->queue_if_no_path)
1416                         DMEMIT("queue_if_no_path ");
1417                 if (m->pg_init_retries)
1418                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1419                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1420                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1421                 if (m->retain_attached_hw_handler)
1422                         DMEMIT("retain_attached_hw_handler ");
1423         }
1424
1425         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1426                 DMEMIT("0 ");
1427         else
1428                 DMEMIT("1 %s ", m->hw_handler_name);
1429
1430         DMEMIT("%u ", m->nr_priority_groups);
1431
1432         if (m->next_pg)
1433                 pg_num = m->next_pg->pg_num;
1434         else if (m->current_pg)
1435                 pg_num = m->current_pg->pg_num;
1436         else
1437                 pg_num = (m->nr_priority_groups ? 1 : 0);
1438
1439         DMEMIT("%u ", pg_num);
1440
1441         switch (type) {
1442         case STATUSTYPE_INFO:
1443                 list_for_each_entry(pg, &m->priority_groups, list) {
1444                         if (pg->bypassed)
1445                                 state = 'D';    /* Disabled */
1446                         else if (pg == m->current_pg)
1447                                 state = 'A';    /* Currently Active */
1448                         else
1449                                 state = 'E';    /* Enabled */
1450
1451                         DMEMIT("%c ", state);
1452
1453                         if (pg->ps.type->status)
1454                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1455                                                           result + sz,
1456                                                           maxlen - sz);
1457                         else
1458                                 DMEMIT("0 ");
1459
1460                         DMEMIT("%u %u ", pg->nr_pgpaths,
1461                                pg->ps.type->info_args);
1462
1463                         list_for_each_entry(p, &pg->pgpaths, list) {
1464                                 DMEMIT("%s %s %u ", p->path.dev->name,
1465                                        p->is_active ? "A" : "F",
1466                                        p->fail_count);
1467                                 if (pg->ps.type->status)
1468                                         sz += pg->ps.type->status(&pg->ps,
1469                                               &p->path, type, result + sz,
1470                                               maxlen - sz);
1471                         }
1472                 }
1473                 break;
1474
1475         case STATUSTYPE_TABLE:
1476                 list_for_each_entry(pg, &m->priority_groups, list) {
1477                         DMEMIT("%s ", pg->ps.type->name);
1478
1479                         if (pg->ps.type->status)
1480                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1481                                                           result + sz,
1482                                                           maxlen - sz);
1483                         else
1484                                 DMEMIT("0 ");
1485
1486                         DMEMIT("%u %u ", pg->nr_pgpaths,
1487                                pg->ps.type->table_args);
1488
1489                         list_for_each_entry(p, &pg->pgpaths, list) {
1490                                 DMEMIT("%s ", p->path.dev->name);
1491                                 if (pg->ps.type->status)
1492                                         sz += pg->ps.type->status(&pg->ps,
1493                                               &p->path, type, result + sz,
1494                                               maxlen - sz);
1495                         }
1496                 }
1497                 break;
1498         }
1499
1500         spin_unlock_irqrestore(&m->lock, flags);
1501 }
1502
1503 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1504 {
1505         int r = -EINVAL;
1506         struct dm_dev *dev;
1507         struct multipath *m = ti->private;
1508         action_fn action;
1509
1510         mutex_lock(&m->work_mutex);
1511
1512         if (dm_suspended(ti)) {
1513                 r = -EBUSY;
1514                 goto out;
1515         }
1516
1517         if (argc == 1) {
1518                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1519                         r = queue_if_no_path(m, true, false);
1520                         goto out;
1521                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1522                         r = queue_if_no_path(m, false, false);
1523                         goto out;
1524                 }
1525         }
1526
1527         if (argc != 2) {
1528                 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1529                 goto out;
1530         }
1531
1532         if (!strcasecmp(argv[0], "disable_group")) {
1533                 r = bypass_pg_num(m, argv[1], true);
1534                 goto out;
1535         } else if (!strcasecmp(argv[0], "enable_group")) {
1536                 r = bypass_pg_num(m, argv[1], false);
1537                 goto out;
1538         } else if (!strcasecmp(argv[0], "switch_group")) {
1539                 r = switch_pg_num(m, argv[1]);
1540                 goto out;
1541         } else if (!strcasecmp(argv[0], "reinstate_path"))
1542                 action = reinstate_path;
1543         else if (!strcasecmp(argv[0], "fail_path"))
1544                 action = fail_path;
1545         else {
1546                 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1547                 goto out;
1548         }
1549
1550         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1551         if (r) {
1552                 DMWARN("message: error getting device %s",
1553                        argv[1]);
1554                 goto out;
1555         }
1556
1557         r = action_dev(m, dev, action);
1558
1559         dm_put_device(ti, dev);
1560
1561 out:
1562         mutex_unlock(&m->work_mutex);
1563         return r;
1564 }
1565
1566 static int multipath_prepare_ioctl(struct dm_target *ti,
1567                 struct block_device **bdev, fmode_t *mode)
1568 {
1569         struct multipath *m = ti->private;
1570         unsigned long flags;
1571         int r;
1572
1573         spin_lock_irqsave(&m->lock, flags);
1574
1575         if (!m->current_pgpath)
1576                 __choose_pgpath(m, 0);
1577
1578         if (m->current_pgpath) {
1579                 if (!m->queue_io) {
1580                         *bdev = m->current_pgpath->path.dev->bdev;
1581                         *mode = m->current_pgpath->path.dev->mode;
1582                         r = 0;
1583                 } else {
1584                         /* pg_init has not started or completed */
1585                         r = -ENOTCONN;
1586                 }
1587         } else {
1588                 /* No path is available */
1589                 if (m->queue_if_no_path)
1590                         r = -ENOTCONN;
1591                 else
1592                         r = -EIO;
1593         }
1594
1595         spin_unlock_irqrestore(&m->lock, flags);
1596
1597         if (r == -ENOTCONN) {
1598                 spin_lock_irqsave(&m->lock, flags);
1599                 if (!m->current_pg) {
1600                         /* Path status changed, redo selection */
1601                         __choose_pgpath(m, 0);
1602                 }
1603                 if (m->pg_init_required)
1604                         __pg_init_all_paths(m);
1605                 spin_unlock_irqrestore(&m->lock, flags);
1606                 dm_table_run_md_queue_async(m->ti->table);
1607         }
1608
1609         /*
1610          * Only pass ioctls through if the device sizes match exactly.
1611          */
1612         if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1613                 return 1;
1614         return r;
1615 }
1616
1617 static int multipath_iterate_devices(struct dm_target *ti,
1618                                      iterate_devices_callout_fn fn, void *data)
1619 {
1620         struct multipath *m = ti->private;
1621         struct priority_group *pg;
1622         struct pgpath *p;
1623         int ret = 0;
1624
1625         list_for_each_entry(pg, &m->priority_groups, list) {
1626                 list_for_each_entry(p, &pg->pgpaths, list) {
1627                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1628                         if (ret)
1629                                 goto out;
1630                 }
1631         }
1632
1633 out:
1634         return ret;
1635 }
1636
1637 static int pgpath_busy(struct pgpath *pgpath)
1638 {
1639         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1640
1641         return blk_lld_busy(q);
1642 }
1643
1644 /*
1645  * We return "busy", only when we can map I/Os but underlying devices
1646  * are busy (so even if we map I/Os now, the I/Os will wait on
1647  * the underlying queue).
1648  * In other words, if we want to kill I/Os or queue them inside us
1649  * due to map unavailability, we don't return "busy".  Otherwise,
1650  * dm core won't give us the I/Os and we can't do what we want.
1651  */
1652 static int multipath_busy(struct dm_target *ti)
1653 {
1654         bool busy = false, has_active = false;
1655         struct multipath *m = ti->private;
1656         struct priority_group *pg;
1657         struct pgpath *pgpath;
1658         unsigned long flags;
1659
1660         spin_lock_irqsave(&m->lock, flags);
1661
1662         /* pg_init in progress or no paths available */
1663         if (m->pg_init_in_progress ||
1664             (!m->nr_valid_paths && m->queue_if_no_path)) {
1665                 busy = true;
1666                 goto out;
1667         }
1668         /* Guess which priority_group will be used at next mapping time */
1669         if (unlikely(!m->current_pgpath && m->next_pg))
1670                 pg = m->next_pg;
1671         else if (likely(m->current_pg))
1672                 pg = m->current_pg;
1673         else
1674                 /*
1675                  * We don't know which pg will be used at next mapping time.
1676                  * We don't call __choose_pgpath() here to avoid to trigger
1677                  * pg_init just by busy checking.
1678                  * So we don't know whether underlying devices we will be using
1679                  * at next mapping time are busy or not. Just try mapping.
1680                  */
1681                 goto out;
1682
1683         /*
1684          * If there is one non-busy active path at least, the path selector
1685          * will be able to select it. So we consider such a pg as not busy.
1686          */
1687         busy = true;
1688         list_for_each_entry(pgpath, &pg->pgpaths, list)
1689                 if (pgpath->is_active) {
1690                         has_active = true;
1691                         if (!pgpath_busy(pgpath)) {
1692                                 busy = false;
1693                                 break;
1694                         }
1695                 }
1696
1697         if (!has_active)
1698                 /*
1699                  * No active path in this pg, so this pg won't be used and
1700                  * the current_pg will be changed at next mapping time.
1701                  * We need to try mapping to determine it.
1702                  */
1703                 busy = false;
1704
1705 out:
1706         spin_unlock_irqrestore(&m->lock, flags);
1707
1708         return busy;
1709 }
1710
1711 /*-----------------------------------------------------------------
1712  * Module setup
1713  *---------------------------------------------------------------*/
1714 static struct target_type multipath_target = {
1715         .name = "multipath",
1716         .version = {1, 11, 0},
1717         .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
1718         .module = THIS_MODULE,
1719         .ctr = multipath_ctr,
1720         .dtr = multipath_dtr,
1721         .map_rq = multipath_map,
1722         .clone_and_map_rq = multipath_clone_and_map,
1723         .release_clone_rq = multipath_release_clone,
1724         .rq_end_io = multipath_end_io,
1725         .presuspend = multipath_presuspend,
1726         .postsuspend = multipath_postsuspend,
1727         .resume = multipath_resume,
1728         .status = multipath_status,
1729         .message = multipath_message,
1730         .prepare_ioctl = multipath_prepare_ioctl,
1731         .iterate_devices = multipath_iterate_devices,
1732         .busy = multipath_busy,
1733 };
1734
1735 static int __init dm_multipath_init(void)
1736 {
1737         int r;
1738
1739         /* allocate a slab for the dm_ios */
1740         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1741         if (!_mpio_cache)
1742                 return -ENOMEM;
1743
1744         r = dm_register_target(&multipath_target);
1745         if (r < 0) {
1746                 DMERR("register failed %d", r);
1747                 r = -EINVAL;
1748                 goto bad_register_target;
1749         }
1750
1751         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1752         if (!kmultipathd) {
1753                 DMERR("failed to create workqueue kmpathd");
1754                 r = -ENOMEM;
1755                 goto bad_alloc_kmultipathd;
1756         }
1757
1758         /*
1759          * A separate workqueue is used to handle the device handlers
1760          * to avoid overloading existing workqueue. Overloading the
1761          * old workqueue would also create a bottleneck in the
1762          * path of the storage hardware device activation.
1763          */
1764         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1765                                                   WQ_MEM_RECLAIM);
1766         if (!kmpath_handlerd) {
1767                 DMERR("failed to create workqueue kmpath_handlerd");
1768                 r = -ENOMEM;
1769                 goto bad_alloc_kmpath_handlerd;
1770         }
1771
1772         DMINFO("version %u.%u.%u loaded",
1773                multipath_target.version[0], multipath_target.version[1],
1774                multipath_target.version[2]);
1775
1776         return 0;
1777
1778 bad_alloc_kmpath_handlerd:
1779         destroy_workqueue(kmultipathd);
1780 bad_alloc_kmultipathd:
1781         dm_unregister_target(&multipath_target);
1782 bad_register_target:
1783         kmem_cache_destroy(_mpio_cache);
1784
1785         return r;
1786 }
1787
1788 static void __exit dm_multipath_exit(void)
1789 {
1790         destroy_workqueue(kmpath_handlerd);
1791         destroy_workqueue(kmultipathd);
1792
1793         dm_unregister_target(&multipath_target);
1794         kmem_cache_destroy(_mpio_cache);
1795 }
1796
1797 module_init(dm_multipath_init);
1798 module_exit(dm_multipath_exit);
1799
1800 MODULE_DESCRIPTION(DM_NAME " multipath target");
1801 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1802 MODULE_LICENSE("GPL");