drivers/md/dm-mpath.c

   1 /*
   2  * Copyright (C) 2003 Sistina Software Limited.
   3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
   4  *
   5  * This file is released under the GPL.
   6  */
   7
   8 #include <linux/device-mapper.h>
   9
  10 #include "dm-path-selector.h"
  11 #include "dm-uevent.h"
  12
  13 #include <linux/ctype.h>
  14 #include <linux/init.h>
  15 #include <linux/mempool.h>
  16 #include <linux/module.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/slab.h>
  19 #include <linux/time.h>
  20 #include <linux/workqueue.h>
  21 #include <linux/delay.h>
  22 #include <scsi/scsi_dh.h>
  23 #include <linux/atomic.h>
  24
  25 #define DM_MSG_PREFIX "multipath"
  26 #define DM_PG_INIT_DELAY_MSECS 2000
  27 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
  28
  29 /* Path properties */
  30 struct pgpath {
  31         struct list_head list;
  32
  33         struct priority_group *pg;      /* Owning PG */
  34         unsigned is_active;             /* Path status */
  35         unsigned fail_count;            /* Cumulative failure count */
  36
  37         struct dm_path path;
  38         struct delayed_work activate_path;
  39 };
  40
  41 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
  42
  43 /*
  44  * Paths are grouped into Priority Groups and numbered from 1 upwards.
  45  * Each has a path selector which controls which path gets used.
  46  */
  47 struct priority_group {
  48         struct list_head list;
  49
  50         struct multipath *m;            /* Owning multipath instance */
  51         struct path_selector ps;
  52
  53         unsigned pg_num;                /* Reference number */
  54         unsigned bypassed;              /* Temporarily bypass this PG? */
  55
  56         unsigned nr_pgpaths;            /* Number of paths in PG */
  57         struct list_head pgpaths;
  58 };
  59
  60 /* Multipath context */
  61 struct multipath {
  62         struct list_head list;
  63         struct dm_target *ti;
  64
  65         const char *hw_handler_name;
  66         char *hw_handler_params;
  67
  68         spinlock_t lock;
  69
  70         unsigned nr_priority_groups;
  71         struct list_head priority_groups;
  72
  73         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
  74
  75         unsigned pg_init_required;      /* pg_init needs calling? */
  76         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
  77         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
  78
  79         unsigned nr_valid_paths;        /* Total number of usable paths */
  80         struct pgpath *current_pgpath;
  81         struct priority_group *current_pg;
  82         struct priority_group *next_pg; /* Switch to this PG if set */
  83         unsigned repeat_count;          /* I/Os left before calling PS again */
  84
  85         unsigned queue_io:1;            /* Must we queue all I/O? */
  86         unsigned queue_if_no_path:1;    /* Queue I/O if last path fails? */
  87         unsigned saved_queue_if_no_path:1; /* Saved state during suspension */
  88         unsigned retain_attached_hw_handler:1; /* If there's already a hw_handler present, don't change it. */
  89         unsigned pg_init_disabled:1;    /* pg_init is not currently allowed */
  90
  91         unsigned pg_init_retries;       /* Number of times to retry pg_init */
  92         unsigned pg_init_count;         /* Number of times pg_init called */
  93         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
  94
  95         unsigned queue_size;
  96         struct work_struct process_queued_ios;
  97         struct list_head queued_ios;
  98
  99         struct work_struct trigger_event;
 100
 101         /*
 102          * We must use a mempool of dm_mpath_io structs so that we
 103          * can resubmit bios on error.
 104          */
 105         mempool_t *mpio_pool;
 106
 107         struct mutex work_mutex;
 108 };
 109
 110 /*
 111  * Context information attached to each bio we process.
 112  */
 113 struct dm_mpath_io {
 114         struct pgpath *pgpath;
 115         size_t nr_bytes;
 116 };
 117
 118 typedef int (*action_fn) (struct pgpath *pgpath);
 119
 120 #define MIN_IOS 256     /* Mempool size */
 121
 122 static struct kmem_cache *_mpio_cache;
 123
 124 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
 125 static void process_queued_ios(struct work_struct *work);
 126 static void trigger_event(struct work_struct *work);
 127 static void activate_path(struct work_struct *work);
 128
 129
 130 /*-----------------------------------------------
 131  * Allocation routines
 132  *-----------------------------------------------*/
 133
 134 static struct pgpath *alloc_pgpath(void)
 135 {
 136         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
 137
 138         if (pgpath) {
 139                 pgpath->is_active = 1;
 140                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
 141         }
 142
 143         return pgpath;
 144 }
 145
 146 static void free_pgpath(struct pgpath *pgpath)
 147 {
 148         kfree(pgpath);
 149 }
 150
 151 static struct priority_group *alloc_priority_group(void)
 152 {
 153         struct priority_group *pg;
 154
 155         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
 156
 157         if (pg)
 158                 INIT_LIST_HEAD(&pg->pgpaths);
 159
 160         return pg;
 161 }
 162
 163 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
 164 {
 165         struct pgpath *pgpath, *tmp;
 166         struct multipath *m = ti->private;
 167
 168         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
 169                 list_del(&pgpath->list);
 170                 if (m->hw_handler_name)
 171                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
 172                 dm_put_device(ti, pgpath->path.dev);
 173                 free_pgpath(pgpath);
 174         }
 175 }
 176
 177 static void free_priority_group(struct priority_group *pg,
 178                                 struct dm_target *ti)
 179 {
 180         struct path_selector *ps = &pg->ps;
 181
 182         if (ps->type) {
 183                 ps->type->destroy(ps);
 184                 dm_put_path_selector(ps->type);
 185         }
 186
 187         free_pgpaths(&pg->pgpaths, ti);
 188         kfree(pg);
 189 }
 190
 191 static struct multipath *alloc_multipath(struct dm_target *ti)
 192 {
 193         struct multipath *m;
 194
 195         m = kzalloc(sizeof(*m), GFP_KERNEL);
 196         if (m) {
 197                 INIT_LIST_HEAD(&m->priority_groups);
 198                 INIT_LIST_HEAD(&m->queued_ios);
 199                 spin_lock_init(&m->lock);
 200                 m->queue_io = 1;
 201                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
 202                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
 203                 INIT_WORK(&m->trigger_event, trigger_event);
 204                 init_waitqueue_head(&m->pg_init_wait);
 205                 mutex_init(&m->work_mutex);
 206                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
 207                 if (!m->mpio_pool) {
 208                         kfree(m);
 209                         return NULL;
 210                 }
 211                 m->ti = ti;
 212                 ti->private = m;
 213         }
 214
 215         return m;
 216 }
 217
 218 static void free_multipath(struct multipath *m)
 219 {
 220         struct priority_group *pg, *tmp;
 221
 222         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
 223                 list_del(&pg->list);
 224                 free_priority_group(pg, m->ti);
 225         }
 226
 227         kfree(m->hw_handler_name);
 228         kfree(m->hw_handler_params);
 229         mempool_destroy(m->mpio_pool);
 230         kfree(m);
 231 }
 232
 233 static int set_mapinfo(struct multipath *m, union map_info *info)
 234 {
 235         struct dm_mpath_io *mpio;
 236
 237         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
 238         if (!mpio)
 239                 return -ENOMEM;
 240
 241         memset(mpio, 0, sizeof(*mpio));
 242         info->ptr = mpio;
 243
 244         return 0;
 245 }
 246
 247 static void clear_mapinfo(struct multipath *m, union map_info *info)
 248 {
 249         struct dm_mpath_io *mpio = info->ptr;
 250
 251         info->ptr = NULL;
 252         mempool_free(mpio, m->mpio_pool);
 253 }
 254
 255 /*-----------------------------------------------
 256  * Path selection
 257  *-----------------------------------------------*/
 258
 259 static void __pg_init_all_paths(struct multipath *m)
 260 {
 261         struct pgpath *pgpath;
 262         unsigned long pg_init_delay = 0;
 263
 264         m->pg_init_count++;
 265         m->pg_init_required = 0;
 266         if (m->pg_init_delay_retry)
 267                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
 268                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
 269         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
 270                 /* Skip failed paths */
 271                 if (!pgpath->is_active)
 272                         continue;
 273                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
 274                                        pg_init_delay))
 275                         m->pg_init_in_progress++;
 276         }
 277 }
 278
 279 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
 280 {
 281         m->current_pg = pgpath->pg;
 282
 283         /* Must we initialise the PG first, and queue I/O till it's ready? */
 284         if (m->hw_handler_name) {
 285                 m->pg_init_required = 1;
 286                 m->queue_io = 1;
 287         } else {
 288                 m->pg_init_required = 0;
 289                 m->queue_io = 0;
 290         }
 291
 292         m->pg_init_count = 0;
 293 }
 294
 295 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
 296                                size_t nr_bytes)
 297 {
 298         struct dm_path *path;
 299
 300         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
 301         if (!path)
 302                 return -ENXIO;
 303
 304         m->current_pgpath = path_to_pgpath(path);
 305
 306         if (m->current_pg != pg)
 307                 __switch_pg(m, m->current_pgpath);
 308
 309         return 0;
 310 }
 311
 312 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
 313 {
 314         struct priority_group *pg;
 315         unsigned bypassed = 1;
 316
 317         if (!m->nr_valid_paths)
 318                 goto failed;
 319
 320         /* Were we instructed to switch PG? */
 321         if (m->next_pg) {
 322                 pg = m->next_pg;
 323                 m->next_pg = NULL;
 324                 if (!__choose_path_in_pg(m, pg, nr_bytes))
 325                         return;
 326         }
 327
 328         /* Don't change PG until it has no remaining paths */
 329         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
 330                 return;
 331
 332         /*
 333          * Loop through priority groups until we find a valid path.
 334          * First time we skip PGs marked 'bypassed'.
 335          * Second time we only try the ones we skipped, but set
 336          * pg_init_delay_retry so we do not hammer controllers.
 337          */
 338         do {
 339                 list_for_each_entry(pg, &m->priority_groups, list) {
 340                         if (pg->bypassed == bypassed)
 341                                 continue;
 342                         if (!__choose_path_in_pg(m, pg, nr_bytes)) {
 343                                 if (!bypassed)
 344                                         m->pg_init_delay_retry = 1;
 345                                 return;
 346                         }
 347                 }
 348         } while (bypassed--);
 349
 350 failed:
 351         m->current_pgpath = NULL;
 352         m->current_pg = NULL;
 353 }
 354
 355 /*
 356  * Check whether bios must be queued in the device-mapper core rather
 357  * than here in the target.
 358  *
 359  * m->lock must be held on entry.
 360  *
 361  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
 362  * same value then we are not between multipath_presuspend()
 363  * and multipath_resume() calls and we have no need to check
 364  * for the DMF_NOFLUSH_SUSPENDING flag.
 365  */
 366 static int __must_push_back(struct multipath *m)
 367 {
 368         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
 369                 dm_noflush_suspending(m->ti));
 370 }
 371
 372 static int map_io(struct multipath *m, struct request *clone,
 373                   union map_info *map_context, unsigned was_queued)
 374 {
 375         int r = DM_MAPIO_REMAPPED;
 376         size_t nr_bytes = blk_rq_bytes(clone);
 377         unsigned long flags;
 378         struct pgpath *pgpath;
 379         struct block_device *bdev;
 380         struct dm_mpath_io *mpio = map_context->ptr;
 381
 382         spin_lock_irqsave(&m->lock, flags);
 383
 384         /* Do we need to select a new pgpath? */
 385         if (!m->current_pgpath ||
 386             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
 387                 __choose_pgpath(m, nr_bytes);
 388
 389         pgpath = m->current_pgpath;
 390
 391         if (was_queued)
 392                 m->queue_size--;
 393
 394         if ((pgpath && m->queue_io) ||
 395             (!pgpath && m->queue_if_no_path)) {
 396                 /* Queue for the daemon to resubmit */
 397                 list_add_tail(&clone->queuelist, &m->queued_ios);
 398                 m->queue_size++;
 399                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
 400                     !m->queue_io)
 401                         queue_work(kmultipathd, &m->process_queued_ios);
 402                 pgpath = NULL;
 403                 r = DM_MAPIO_SUBMITTED;
 404         } else if (pgpath) {
 405                 bdev = pgpath->path.dev->bdev;
 406                 clone->q = bdev_get_queue(bdev);
 407                 clone->rq_disk = bdev->bd_disk;
 408         } else if (__must_push_back(m))
 409                 r = DM_MAPIO_REQUEUE;
 410         else
 411                 r = -EIO;       /* Failed */
 412
 413         mpio->pgpath = pgpath;
 414         mpio->nr_bytes = nr_bytes;
 415
 416         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
 417                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
 418                                               nr_bytes);
 419
 420         spin_unlock_irqrestore(&m->lock, flags);
 421
 422         return r;
 423 }
 424
 425 /*
 426  * If we run out of usable paths, should we queue I/O or error it?
 427  */
 428 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
 429                             unsigned save_old_value)
 430 {
 431         unsigned long flags;
 432
 433         spin_lock_irqsave(&m->lock, flags);
 434
 435         if (save_old_value)
 436                 m->saved_queue_if_no_path = m->queue_if_no_path;
 437         else
 438                 m->saved_queue_if_no_path = queue_if_no_path;
 439         m->queue_if_no_path = queue_if_no_path;
 440         if (!m->queue_if_no_path && m->queue_size)
 441                 queue_work(kmultipathd, &m->process_queued_ios);
 442
 443         spin_unlock_irqrestore(&m->lock, flags);
 444
 445         return 0;
 446 }
 447
 448 /*-----------------------------------------------------------------
 449  * The multipath daemon is responsible for resubmitting queued ios.
 450  *---------------------------------------------------------------*/
 451
 452 static void dispatch_queued_ios(struct multipath *m)
 453 {
 454         int r;
 455         unsigned long flags;
 456         union map_info *info;
 457         struct request *clone, *n;
 458         LIST_HEAD(cl);
 459
 460         spin_lock_irqsave(&m->lock, flags);
 461         list_splice_init(&m->queued_ios, &cl);
 462         spin_unlock_irqrestore(&m->lock, flags);
 463
 464         list_for_each_entry_safe(clone, n, &cl, queuelist) {
 465                 list_del_init(&clone->queuelist);
 466
 467                 info = dm_get_rq_mapinfo(clone);
 468
 469                 r = map_io(m, clone, info, 1);
 470                 if (r < 0) {
 471                         clear_mapinfo(m, info);
 472                         dm_kill_unmapped_request(clone, r);
 473                 } else if (r == DM_MAPIO_REMAPPED)
 474                         dm_dispatch_request(clone);
 475                 else if (r == DM_MAPIO_REQUEUE) {
 476                         clear_mapinfo(m, info);
 477                         dm_requeue_unmapped_request(clone);
 478                 }
 479         }
 480 }
 481
 482 static void process_queued_ios(struct work_struct *work)
 483 {
 484         struct multipath *m =
 485                 container_of(work, struct multipath, process_queued_ios);
 486         struct pgpath *pgpath = NULL;
 487         unsigned must_queue = 1;
 488         unsigned long flags;
 489
 490         spin_lock_irqsave(&m->lock, flags);
 491
 492         if (!m->current_pgpath)
 493                 __choose_pgpath(m, 0);
 494
 495         pgpath = m->current_pgpath;
 496
 497         if ((pgpath && !m->queue_io) ||
 498             (!pgpath && !m->queue_if_no_path))
 499                 must_queue = 0;
 500
 501         if (m->pg_init_required && !m->pg_init_in_progress && pgpath &&
 502             !m->pg_init_disabled)
 503                 __pg_init_all_paths(m);
 504
 505         spin_unlock_irqrestore(&m->lock, flags);
 506         if (!must_queue)
 507                 dispatch_queued_ios(m);
 508 }
 509
 510 /*
 511  * An event is triggered whenever a path is taken out of use.
 512  * Includes path failure and PG bypass.
 513  */
 514 static void trigger_event(struct work_struct *work)
 515 {
 516         struct multipath *m =
 517                 container_of(work, struct multipath, trigger_event);
 518
 519         dm_table_event(m->ti->table);
 520 }
 521
 522 /*-----------------------------------------------------------------
 523  * Constructor/argument parsing:
 524  * <#multipath feature args> [<arg>]*
 525  * <#hw_handler args> [hw_handler [<arg>]*]
 526  * <#priority groups>
 527  * <initial priority group>
 528  *     [<selector> <#selector args> [<arg>]*
 529  *      <#paths> <#per-path selector args>
 530  *         [<path> [<arg>]* ]+ ]+
 531  *---------------------------------------------------------------*/
 532 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
 533                                struct dm_target *ti)
 534 {
 535         int r;
 536         struct path_selector_type *pst;
 537         unsigned ps_argc;
 538
 539         static struct dm_arg _args[] = {
 540                 {0, 1024, "invalid number of path selector args"},
 541         };
 542
 543         pst = dm_get_path_selector(dm_shift_arg(as));
 544         if (!pst) {
 545                 ti->error = "unknown path selector type";
 546                 return -EINVAL;
 547         }
 548
 549         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
 550         if (r) {
 551                 dm_put_path_selector(pst);
 552                 return -EINVAL;
 553         }
 554
 555         r = pst->create(&pg->ps, ps_argc, as->argv);
 556         if (r) {
 557                 dm_put_path_selector(pst);
 558                 ti->error = "path selector constructor failed";
 559                 return r;
 560         }
 561
 562         pg->ps.type = pst;
 563         dm_consume_args(as, ps_argc);
 564
 565         return 0;
 566 }
 567
 568 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
 569                                struct dm_target *ti)
 570 {
 571         int r;
 572         struct pgpath *p;
 573         struct multipath *m = ti->private;
 574         struct request_queue *q = NULL;
 575         const char *attached_handler_name;
 576
 577         /* we need at least a path arg */
 578         if (as->argc < 1) {
 579                 ti->error = "no device given";
 580                 return ERR_PTR(-EINVAL);
 581         }
 582
 583         p = alloc_pgpath();
 584         if (!p)
 585                 return ERR_PTR(-ENOMEM);
 586
 587         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
 588                           &p->path.dev);
 589         if (r) {
 590                 ti->error = "error getting device";
 591                 goto bad;
 592         }
 593
 594         if (m->retain_attached_hw_handler || m->hw_handler_name)
 595                 q = bdev_get_queue(p->path.dev->bdev);
 596
 597         if (m->retain_attached_hw_handler) {
 598                 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
 599                 if (attached_handler_name) {
 600                         /*
 601                          * Reset hw_handler_name to match the attached handler
 602                          * and clear any hw_handler_params associated with the
 603                          * ignored handler.
 604                          *
 605                          * NB. This modifies the table line to show the actual
 606                          * handler instead of the original table passed in.
 607                          */
 608                         kfree(m->hw_handler_name);
 609                         m->hw_handler_name = attached_handler_name;
 610
 611                         kfree(m->hw_handler_params);
 612                         m->hw_handler_params = NULL;
 613                 }
 614         }
 615
 616         if (m->hw_handler_name) {
 617                 /*
 618                  * Increments scsi_dh reference, even when using an
 619                  * already-attached handler.
 620                  */
 621                 r = scsi_dh_attach(q, m->hw_handler_name);
 622                 if (r == -EBUSY) {
 623                         /*
 624                          * Already attached to different hw_handler:
 625                          * try to reattach with correct one.
 626                          */
 627                         scsi_dh_detach(q);
 628                         r = scsi_dh_attach(q, m->hw_handler_name);
 629                 }
 630
 631                 if (r < 0) {
 632                         ti->error = "error attaching hardware handler";
 633                         dm_put_device(ti, p->path.dev);
 634                         goto bad;
 635                 }
 636
 637                 if (m->hw_handler_params) {
 638                         r = scsi_dh_set_params(q, m->hw_handler_params);
 639                         if (r < 0) {
 640                                 ti->error = "unable to set hardware "
 641                                                         "handler parameters";
 642                                 scsi_dh_detach(q);
 643                                 dm_put_device(ti, p->path.dev);
 644                                 goto bad;
 645                         }
 646                 }
 647         }
 648
 649         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
 650         if (r) {
 651                 dm_put_device(ti, p->path.dev);
 652                 goto bad;
 653         }
 654
 655         return p;
 656
 657  bad:
 658         free_pgpath(p);
 659         return ERR_PTR(r);
 660 }
 661
 662 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
 663                                                    struct multipath *m)
 664 {
 665         static struct dm_arg _args[] = {
 666                 {1, 1024, "invalid number of paths"},
 667                 {0, 1024, "invalid number of selector args"}
 668         };
 669
 670         int r;
 671         unsigned i, nr_selector_args, nr_args;
 672         struct priority_group *pg;
 673         struct dm_target *ti = m->ti;
 674
 675         if (as->argc < 2) {
 676                 as->argc = 0;
 677                 ti->error = "not enough priority group arguments";
 678                 return ERR_PTR(-EINVAL);
 679         }
 680
 681         pg = alloc_priority_group();
 682         if (!pg) {
 683                 ti->error = "couldn't allocate priority group";
 684                 return ERR_PTR(-ENOMEM);
 685         }
 686         pg->m = m;
 687
 688         r = parse_path_selector(as, pg, ti);
 689         if (r)
 690                 goto bad;
 691
 692         /*
 693          * read the paths
 694          */
 695         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
 696         if (r)
 697                 goto bad;
 698
 699         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
 700         if (r)
 701                 goto bad;
 702
 703         nr_args = 1 + nr_selector_args;
 704         for (i = 0; i < pg->nr_pgpaths; i++) {
 705                 struct pgpath *pgpath;
 706                 struct dm_arg_set path_args;
 707
 708                 if (as->argc < nr_args) {
 709                         ti->error = "not enough path parameters";
 710                         r = -EINVAL;
 711                         goto bad;
 712                 }
 713
 714                 path_args.argc = nr_args;
 715                 path_args.argv = as->argv;
 716
 717                 pgpath = parse_path(&path_args, &pg->ps, ti);
 718                 if (IS_ERR(pgpath)) {
 719                         r = PTR_ERR(pgpath);
 720                         goto bad;
 721                 }
 722
 723                 pgpath->pg = pg;
 724                 list_add_tail(&pgpath->list, &pg->pgpaths);
 725                 dm_consume_args(as, nr_args);
 726         }
 727
 728         return pg;
 729
 730  bad:
 731         free_priority_group(pg, ti);
 732         return ERR_PTR(r);
 733 }
 734
 735 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
 736 {
 737         unsigned hw_argc;
 738         int ret;
 739         struct dm_target *ti = m->ti;
 740
 741         static struct dm_arg _args[] = {
 742                 {0, 1024, "invalid number of hardware handler args"},
 743         };
 744
 745         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
 746                 return -EINVAL;
 747
 748         if (!hw_argc)
 749                 return 0;
 750
 751         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
 752         if (!try_then_request_module(scsi_dh_handler_exist(m->hw_handler_name),
 753                                      "scsi_dh_%s", m->hw_handler_name)) {
 754                 ti->error = "unknown hardware handler type";
 755                 ret = -EINVAL;
 756                 goto fail;
 757         }
 758
 759         if (hw_argc > 1) {
 760                 char *p;
 761                 int i, j, len = 4;
 762
 763                 for (i = 0; i <= hw_argc - 2; i++)
 764                         len += strlen(as->argv[i]) + 1;
 765                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
 766                 if (!p) {
 767                         ti->error = "memory allocation failed";
 768                         ret = -ENOMEM;
 769                         goto fail;
 770                 }
 771                 j = sprintf(p, "%d", hw_argc - 1);
 772                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
 773                         j = sprintf(p, "%s", as->argv[i]);
 774         }
 775         dm_consume_args(as, hw_argc - 1);
 776
 777         return 0;
 778 fail:
 779         kfree(m->hw_handler_name);
 780         m->hw_handler_name = NULL;
 781         return ret;
 782 }
 783
 784 static int parse_features(struct dm_arg_set *as, struct multipath *m)
 785 {
 786         int r;
 787         unsigned argc;
 788         struct dm_target *ti = m->ti;
 789         const char *arg_name;
 790
 791         static struct dm_arg _args[] = {
 792                 {0, 6, "invalid number of feature args"},
 793                 {1, 50, "pg_init_retries must be between 1 and 50"},
 794                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
 795         };
 796
 797         r = dm_read_arg_group(_args, as, &argc, &ti->error);
 798         if (r)
 799                 return -EINVAL;
 800
 801         if (!argc)
 802                 return 0;
 803
 804         do {
 805                 arg_name = dm_shift_arg(as);
 806                 argc--;
 807
 808                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
 809                         r = queue_if_no_path(m, 1, 0);
 810                         continue;
 811                 }
 812
 813                 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
 814                         m->retain_attached_hw_handler = 1;
 815                         continue;
 816                 }
 817
 818                 if (!strcasecmp(arg_name, "pg_init_retries") &&
 819                     (argc >= 1)) {
 820                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
 821                         argc--;
 822                         continue;
 823                 }
 824
 825                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
 826                     (argc >= 1)) {
 827                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
 828                         argc--;
 829                         continue;
 830                 }
 831
 832                 ti->error = "Unrecognised multipath feature request";
 833                 r = -EINVAL;
 834         } while (argc && !r);
 835
 836         return r;
 837 }
 838
 839 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
 840                          char **argv)
 841 {
 842         /* target arguments */
 843         static struct dm_arg _args[] = {
 844                 {0, 1024, "invalid number of priority groups"},
 845                 {0, 1024, "invalid initial priority group number"},
 846         };
 847
 848         int r;
 849         struct multipath *m;
 850         struct dm_arg_set as;
 851         unsigned pg_count = 0;
 852         unsigned next_pg_num;
 853
 854         as.argc = argc;
 855         as.argv = argv;
 856
 857         m = alloc_multipath(ti);
 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
 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 = 1;
 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 = 0;
 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  * Map cloned requests
 973  */
 974 static int multipath_map(struct dm_target *ti, struct request *clone,
 975                          union map_info *map_context)
 976 {
 977         int r;
 978         struct multipath *m = (struct multipath *) ti->private;
 979
 980         if (set_mapinfo(m, map_context) < 0)
 981                 /* ENOMEM, requeue */
 982                 return DM_MAPIO_REQUEUE;
 983
 984         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
 985         r = map_io(m, clone, map_context, 0);
 986         if (r < 0 || r == DM_MAPIO_REQUEUE)
 987                 clear_mapinfo(m, map_context);
 988
 989         return r;
 990 }
 991
 992 /*
 993  * Take a path out of use.
 994  */
 995 static int fail_path(struct pgpath *pgpath)
 996 {
 997         unsigned long flags;
 998         struct multipath *m = pgpath->pg->m;
 999
1000         spin_lock_irqsave(&m->lock, flags);
1001
1002         if (!pgpath->is_active)
1003                 goto out;
1004
1005         DMWARN("Failing path %s.", pgpath->path.dev->name);
1006
1007         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1008         pgpath->is_active = 0;
1009         pgpath->fail_count++;
1010
1011         m->nr_valid_paths--;
1012
1013         if (pgpath == m->current_pgpath)
1014                 m->current_pgpath = NULL;
1015
1016         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1017                       pgpath->path.dev->name, m->nr_valid_paths);
1018
1019         schedule_work(&m->trigger_event);
1020
1021 out:
1022         spin_unlock_irqrestore(&m->lock, flags);
1023
1024         return 0;
1025 }
1026
1027 /*
1028  * Reinstate a previously-failed path
1029  */
1030 static int reinstate_path(struct pgpath *pgpath)
1031 {
1032         int r = 0;
1033         unsigned long flags;
1034         struct multipath *m = pgpath->pg->m;
1035
1036         spin_lock_irqsave(&m->lock, flags);
1037
1038         if (pgpath->is_active)
1039                 goto out;
1040
1041         if (!pgpath->pg->ps.type->reinstate_path) {
1042                 DMWARN("Reinstate path not supported by path selector %s",
1043                        pgpath->pg->ps.type->name);
1044                 r = -EINVAL;
1045                 goto out;
1046         }
1047
1048         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1049         if (r)
1050                 goto out;
1051
1052         pgpath->is_active = 1;
1053
1054         if (!m->nr_valid_paths++ && m->queue_size) {
1055                 m->current_pgpath = NULL;
1056                 queue_work(kmultipathd, &m->process_queued_ios);
1057         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1058                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1059                         m->pg_init_in_progress++;
1060         }
1061
1062         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1063                       pgpath->path.dev->name, m->nr_valid_paths);
1064
1065         schedule_work(&m->trigger_event);
1066
1067 out:
1068         spin_unlock_irqrestore(&m->lock, flags);
1069
1070         return r;
1071 }
1072
1073 /*
1074  * Fail or reinstate all paths that match the provided struct dm_dev.
1075  */
1076 static int action_dev(struct multipath *m, struct dm_dev *dev,
1077                       action_fn action)
1078 {
1079         int r = -EINVAL;
1080         struct pgpath *pgpath;
1081         struct priority_group *pg;
1082
1083         list_for_each_entry(pg, &m->priority_groups, list) {
1084                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1085                         if (pgpath->path.dev == dev)
1086                                 r = action(pgpath);
1087                 }
1088         }
1089
1090         return r;
1091 }
1092
1093 /*
1094  * Temporarily try to avoid having to use the specified PG
1095  */
1096 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1097                       int bypassed)
1098 {
1099         unsigned long flags;
1100
1101         spin_lock_irqsave(&m->lock, flags);
1102
1103         pg->bypassed = bypassed;
1104         m->current_pgpath = NULL;
1105         m->current_pg = NULL;
1106
1107         spin_unlock_irqrestore(&m->lock, flags);
1108
1109         schedule_work(&m->trigger_event);
1110 }
1111
1112 /*
1113  * Switch to using the specified PG from the next I/O that gets mapped
1114  */
1115 static int switch_pg_num(struct multipath *m, const char *pgstr)
1116 {
1117         struct priority_group *pg;
1118         unsigned pgnum;
1119         unsigned long flags;
1120         char dummy;
1121
1122         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1123             (pgnum > m->nr_priority_groups)) {
1124                 DMWARN("invalid PG number supplied to switch_pg_num");
1125                 return -EINVAL;
1126         }
1127
1128         spin_lock_irqsave(&m->lock, flags);
1129         list_for_each_entry(pg, &m->priority_groups, list) {
1130                 pg->bypassed = 0;
1131                 if (--pgnum)
1132                         continue;
1133
1134                 m->current_pgpath = NULL;
1135                 m->current_pg = NULL;
1136                 m->next_pg = pg;
1137         }
1138         spin_unlock_irqrestore(&m->lock, flags);
1139
1140         schedule_work(&m->trigger_event);
1141         return 0;
1142 }
1143
1144 /*
1145  * Set/clear bypassed status of a PG.
1146  * PGs are numbered upwards from 1 in the order they were declared.
1147  */
1148 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1149 {
1150         struct priority_group *pg;
1151         unsigned pgnum;
1152         char dummy;
1153
1154         if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1155             (pgnum > m->nr_priority_groups)) {
1156                 DMWARN("invalid PG number supplied to bypass_pg");
1157                 return -EINVAL;
1158         }
1159
1160         list_for_each_entry(pg, &m->priority_groups, list) {
1161                 if (!--pgnum)
1162                         break;
1163         }
1164
1165         bypass_pg(m, pg, bypassed);
1166         return 0;
1167 }
1168
1169 /*
1170  * Should we retry pg_init immediately?
1171  */
1172 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1173 {
1174         unsigned long flags;
1175         int limit_reached = 0;
1176
1177         spin_lock_irqsave(&m->lock, flags);
1178
1179         if (m->pg_init_count <= m->pg_init_retries && !m->pg_init_disabled)
1180                 m->pg_init_required = 1;
1181         else
1182                 limit_reached = 1;
1183
1184         spin_unlock_irqrestore(&m->lock, flags);
1185
1186         return limit_reached;
1187 }
1188
1189 static void pg_init_done(void *data, int errors)
1190 {
1191         struct pgpath *pgpath = data;
1192         struct priority_group *pg = pgpath->pg;
1193         struct multipath *m = pg->m;
1194         unsigned long flags;
1195         unsigned delay_retry = 0;
1196
1197         /* device or driver problems */
1198         switch (errors) {
1199         case SCSI_DH_OK:
1200                 break;
1201         case SCSI_DH_NOSYS:
1202                 if (!m->hw_handler_name) {
1203                         errors = 0;
1204                         break;
1205                 }
1206                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1207                       "Error %d.", m->hw_handler_name, errors);
1208                 /*
1209                  * Fail path for now, so we do not ping pong
1210                  */
1211                 fail_path(pgpath);
1212                 break;
1213         case SCSI_DH_DEV_TEMP_BUSY:
1214                 /*
1215                  * Probably doing something like FW upgrade on the
1216                  * controller so try the other pg.
1217                  */
1218                 bypass_pg(m, pg, 1);
1219                 break;
1220         case SCSI_DH_RETRY:
1221                 /* Wait before retrying. */
1222                 delay_retry = 1;
1223         case SCSI_DH_IMM_RETRY:
1224         case SCSI_DH_RES_TEMP_UNAVAIL:
1225                 if (pg_init_limit_reached(m, pgpath))
1226                         fail_path(pgpath);
1227                 errors = 0;
1228                 break;
1229         default:
1230                 /*
1231                  * We probably do not want to fail the path for a device
1232                  * error, but this is what the old dm did. In future
1233                  * patches we can do more advanced handling.
1234                  */
1235                 fail_path(pgpath);
1236         }
1237
1238         spin_lock_irqsave(&m->lock, flags);
1239         if (errors) {
1240                 if (pgpath == m->current_pgpath) {
1241                         DMERR("Could not failover device. Error %d.", errors);
1242                         m->current_pgpath = NULL;
1243                         m->current_pg = NULL;
1244                 }
1245         } else if (!m->pg_init_required)
1246                 pg->bypassed = 0;
1247
1248         if (--m->pg_init_in_progress)
1249                 /* Activations of other paths are still on going */
1250                 goto out;
1251
1252         if (!m->pg_init_required)
1253                 m->queue_io = 0;
1254
1255         m->pg_init_delay_retry = delay_retry;
1256         queue_work(kmultipathd, &m->process_queued_ios);
1257
1258         /*
1259          * Wake up any thread waiting to suspend.
1260          */
1261         wake_up(&m->pg_init_wait);
1262
1263 out:
1264         spin_unlock_irqrestore(&m->lock, flags);
1265 }
1266
1267 static void activate_path(struct work_struct *work)
1268 {
1269         struct pgpath *pgpath =
1270                 container_of(work, struct pgpath, activate_path.work);
1271
1272         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1273                                 pg_init_done, pgpath);
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 (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ) {
1300                 if ((clone->cmd_flags & REQ_WRITE_SAME) &&
1301                     !clone->q->limits.max_write_same_sectors) {
1302                         struct queue_limits *limits;
1303
1304                         /* device doesn't really support WRITE SAME, disable it */
1305                         limits = dm_get_queue_limits(dm_table_get_md(m->ti->table));
1306                         limits->max_write_same_sectors = 0;
1307                 }
1308                 return error;
1309         }
1310
1311         if (mpio->pgpath)
1312                 fail_path(mpio->pgpath);
1313
1314         spin_lock_irqsave(&m->lock, flags);
1315         if (!m->nr_valid_paths) {
1316                 if (!m->queue_if_no_path) {
1317                         if (!__must_push_back(m))
1318                                 r = -EIO;
1319                 } else {
1320                         if (error == -EBADE)
1321                                 r = error;
1322                 }
1323         }
1324         spin_unlock_irqrestore(&m->lock, flags);
1325
1326         return r;
1327 }
1328
1329 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1330                             int error, union map_info *map_context)
1331 {
1332         struct multipath *m = ti->private;
1333         struct dm_mpath_io *mpio = map_context->ptr;
1334         struct pgpath *pgpath;
1335         struct path_selector *ps;
1336         int r;
1337
1338         BUG_ON(!mpio);
1339
1340         r  = do_end_io(m, clone, error, mpio);
1341         pgpath = mpio->pgpath;
1342         if (pgpath) {
1343                 ps = &pgpath->pg->ps;
1344                 if (ps->type->end_io)
1345                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1346         }
1347         clear_mapinfo(m, map_context);
1348
1349         return r;
1350 }
1351
1352 /*
1353  * Suspend can't complete until all the I/O is processed so if
1354  * the last path fails we must error any remaining I/O.
1355  * Note that if the freeze_bdev fails while suspending, the
1356  * queue_if_no_path state is lost - userspace should reset it.
1357  */
1358 static void multipath_presuspend(struct dm_target *ti)
1359 {
1360         struct multipath *m = (struct multipath *) ti->private;
1361
1362         queue_if_no_path(m, 0, 1);
1363 }
1364
1365 static void multipath_postsuspend(struct dm_target *ti)
1366 {
1367         struct multipath *m = ti->private;
1368
1369         mutex_lock(&m->work_mutex);
1370         flush_multipath_work(m);
1371         mutex_unlock(&m->work_mutex);
1372 }
1373
1374 /*
1375  * Restore the queue_if_no_path setting.
1376  */
1377 static void multipath_resume(struct dm_target *ti)
1378 {
1379         struct multipath *m = (struct multipath *) ti->private;
1380         unsigned long flags;
1381
1382         spin_lock_irqsave(&m->lock, flags);
1383         m->queue_if_no_path = m->saved_queue_if_no_path;
1384         spin_unlock_irqrestore(&m->lock, flags);
1385 }
1386
1387 /*
1388  * Info output has the following format:
1389  * num_multipath_feature_args [multipath_feature_args]*
1390  * num_handler_status_args [handler_status_args]*
1391  * num_groups init_group_number
1392  *            [A|D|E num_ps_status_args [ps_status_args]*
1393  *             num_paths num_selector_args
1394  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1395  *
1396  * Table output has the following format (identical to the constructor string):
1397  * num_feature_args [features_args]*
1398  * num_handler_args hw_handler [hw_handler_args]*
1399  * num_groups init_group_number
1400  *     [priority selector-name num_ps_args [ps_args]*
1401  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1402  */
1403 static void multipath_status(struct dm_target *ti, status_type_t type,
1404                              unsigned status_flags, char *result, unsigned maxlen)
1405 {
1406         int sz = 0;
1407         unsigned long flags;
1408         struct multipath *m = (struct multipath *) ti->private;
1409         struct priority_group *pg;
1410         struct pgpath *p;
1411         unsigned pg_num;
1412         char state;
1413
1414         spin_lock_irqsave(&m->lock, flags);
1415
1416         /* Features */
1417         if (type == STATUSTYPE_INFO)
1418                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1419         else {
1420                 DMEMIT("%u ", m->queue_if_no_path +
1421                               (m->pg_init_retries > 0) * 2 +
1422                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1423                               m->retain_attached_hw_handler);
1424                 if (m->queue_if_no_path)
1425                         DMEMIT("queue_if_no_path ");
1426                 if (m->pg_init_retries)
1427                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1428                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1429                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1430                 if (m->retain_attached_hw_handler)
1431                         DMEMIT("retain_attached_hw_handler ");
1432         }
1433
1434         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1435                 DMEMIT("0 ");
1436         else
1437                 DMEMIT("1 %s ", m->hw_handler_name);
1438
1439         DMEMIT("%u ", m->nr_priority_groups);
1440
1441         if (m->next_pg)
1442                 pg_num = m->next_pg->pg_num;
1443         else if (m->current_pg)
1444                 pg_num = m->current_pg->pg_num;
1445         else
1446                 pg_num = (m->nr_priority_groups ? 1 : 0);
1447
1448         DMEMIT("%u ", pg_num);
1449
1450         switch (type) {
1451         case STATUSTYPE_INFO:
1452                 list_for_each_entry(pg, &m->priority_groups, list) {
1453                         if (pg->bypassed)
1454                                 state = 'D';    /* Disabled */
1455                         else if (pg == m->current_pg)
1456                                 state = 'A';    /* Currently Active */
1457                         else
1458                                 state = 'E';    /* Enabled */
1459
1460                         DMEMIT("%c ", state);
1461
1462                         if (pg->ps.type->status)
1463                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1464                                                           result + sz,
1465                                                           maxlen - sz);
1466                         else
1467                                 DMEMIT("0 ");
1468
1469                         DMEMIT("%u %u ", pg->nr_pgpaths,
1470                                pg->ps.type->info_args);
1471
1472                         list_for_each_entry(p, &pg->pgpaths, list) {
1473                                 DMEMIT("%s %s %u ", p->path.dev->name,
1474                                        p->is_active ? "A" : "F",
1475                                        p->fail_count);
1476                                 if (pg->ps.type->status)
1477                                         sz += pg->ps.type->status(&pg->ps,
1478                                               &p->path, type, result + sz,
1479                                               maxlen - sz);
1480                         }
1481                 }
1482                 break;
1483
1484         case STATUSTYPE_TABLE:
1485                 list_for_each_entry(pg, &m->priority_groups, list) {
1486                         DMEMIT("%s ", pg->ps.type->name);
1487
1488                         if (pg->ps.type->status)
1489                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1490                                                           result + sz,
1491                                                           maxlen - sz);
1492                         else
1493                                 DMEMIT("0 ");
1494
1495                         DMEMIT("%u %u ", pg->nr_pgpaths,
1496                                pg->ps.type->table_args);
1497
1498                         list_for_each_entry(p, &pg->pgpaths, list) {
1499                                 DMEMIT("%s ", p->path.dev->name);
1500                                 if (pg->ps.type->status)
1501                                         sz += pg->ps.type->status(&pg->ps,
1502                                               &p->path, type, result + sz,
1503                                               maxlen - sz);
1504                         }
1505                 }
1506                 break;
1507         }
1508
1509         spin_unlock_irqrestore(&m->lock, flags);
1510 }
1511
1512 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1513 {
1514         int r = -EINVAL;
1515         struct dm_dev *dev;
1516         struct multipath *m = (struct multipath *) ti->private;
1517         action_fn action;
1518
1519         mutex_lock(&m->work_mutex);
1520
1521         if (dm_suspended(ti)) {
1522                 r = -EBUSY;
1523                 goto out;
1524         }
1525
1526         if (argc == 1) {
1527                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1528                         r = queue_if_no_path(m, 1, 0);
1529                         goto out;
1530                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1531                         r = queue_if_no_path(m, 0, 0);
1532                         goto out;
1533                 }
1534         }
1535
1536         if (argc != 2) {
1537                 DMWARN("Unrecognised multipath message received.");
1538                 goto out;
1539         }
1540
1541         if (!strcasecmp(argv[0], "disable_group")) {
1542                 r = bypass_pg_num(m, argv[1], 1);
1543                 goto out;
1544         } else if (!strcasecmp(argv[0], "enable_group")) {
1545                 r = bypass_pg_num(m, argv[1], 0);
1546                 goto out;
1547         } else if (!strcasecmp(argv[0], "switch_group")) {
1548                 r = switch_pg_num(m, argv[1]);
1549                 goto out;
1550         } else if (!strcasecmp(argv[0], "reinstate_path"))
1551                 action = reinstate_path;
1552         else if (!strcasecmp(argv[0], "fail_path"))
1553                 action = fail_path;
1554         else {
1555                 DMWARN("Unrecognised multipath message received.");
1556                 goto out;
1557         }
1558
1559         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1560         if (r) {
1561                 DMWARN("message: error getting device %s",
1562                        argv[1]);
1563                 goto out;
1564         }
1565
1566         r = action_dev(m, dev, action);
1567
1568         dm_put_device(ti, dev);
1569
1570 out:
1571         mutex_unlock(&m->work_mutex);
1572         return r;
1573 }
1574
1575 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1576                            unsigned long arg)
1577 {
1578         struct multipath *m = ti->private;
1579         struct pgpath *pgpath;
1580         struct block_device *bdev;
1581         fmode_t mode;
1582         unsigned long flags;
1583         int r;
1584
1585         bdev = NULL;
1586         mode = 0;
1587         r = 0;
1588
1589         spin_lock_irqsave(&m->lock, flags);
1590
1591         if (!m->current_pgpath)
1592                 __choose_pgpath(m, 0);
1593
1594         pgpath = m->current_pgpath;
1595
1596         if (pgpath) {
1597                 bdev = pgpath->path.dev->bdev;
1598                 mode = pgpath->path.dev->mode;
1599         }
1600
1601         if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path))
1602                 r = -ENOTCONN;
1603         else if (!bdev)
1604                 r = -EIO;
1605
1606         spin_unlock_irqrestore(&m->lock, flags);
1607
1608         /*
1609          * Only pass ioctls through if the device sizes match exactly.
1610          */
1611         if (!bdev || ti->len != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT) {
1612                 int err = scsi_verify_blk_ioctl(NULL, cmd);
1613                 if (err)
1614                         r = err;
1615         }
1616
1617         if (r == -ENOTCONN && !fatal_signal_pending(current))
1618                 queue_work(kmultipathd, &m->process_queued_ios);
1619
1620         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1621 }
1622
1623 static int multipath_iterate_devices(struct dm_target *ti,
1624                                      iterate_devices_callout_fn fn, void *data)
1625 {
1626         struct multipath *m = ti->private;
1627         struct priority_group *pg;
1628         struct pgpath *p;
1629         int ret = 0;
1630
1631         list_for_each_entry(pg, &m->priority_groups, list) {
1632                 list_for_each_entry(p, &pg->pgpaths, list) {
1633                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1634                         if (ret)
1635                                 goto out;
1636                 }
1637         }
1638
1639 out:
1640         return ret;
1641 }
1642
1643 static int __pgpath_busy(struct pgpath *pgpath)
1644 {
1645         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1646
1647         return dm_underlying_device_busy(q);
1648 }
1649
1650 /*
1651  * We return "busy", only when we can map I/Os but underlying devices
1652  * are busy (so even if we map I/Os now, the I/Os will wait on
1653  * the underlying queue).
1654  * In other words, if we want to kill I/Os or queue them inside us
1655  * due to map unavailability, we don't return "busy".  Otherwise,
1656  * dm core won't give us the I/Os and we can't do what we want.
1657  */
1658 static int multipath_busy(struct dm_target *ti)
1659 {
1660         int busy = 0, has_active = 0;
1661         struct multipath *m = ti->private;
1662         struct priority_group *pg;
1663         struct pgpath *pgpath;
1664         unsigned long flags;
1665
1666         spin_lock_irqsave(&m->lock, flags);
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 = 1;
1688         list_for_each_entry(pgpath, &pg->pgpaths, list)
1689                 if (pgpath->is_active) {
1690                         has_active = 1;
1691
1692                         if (!__pgpath_busy(pgpath)) {
1693                                 busy = 0;
1694                                 break;
1695                         }
1696                 }
1697
1698         if (!has_active)
1699                 /*
1700                  * No active path in this pg, so this pg won't be used and
1701                  * the current_pg will be changed at next mapping time.
1702                  * We need to try mapping to determine it.
1703                  */
1704                 busy = 0;
1705
1706 out:
1707         spin_unlock_irqrestore(&m->lock, flags);
1708
1709         return busy;
1710 }
1711
1712 /*-----------------------------------------------------------------
1713  * Module setup
1714  *---------------------------------------------------------------*/
1715 static struct target_type multipath_target = {
1716         .name = "multipath",
1717         .version = {1, 6, 0},
1718         .module = THIS_MODULE,
1719         .ctr = multipath_ctr,
1720         .dtr = multipath_dtr,
1721         .map_rq = multipath_map,
1722         .rq_end_io = multipath_end_io,
1723         .presuspend = multipath_presuspend,
1724         .postsuspend = multipath_postsuspend,
1725         .resume = multipath_resume,
1726         .status = multipath_status,
1727         .message = multipath_message,
1728         .ioctl  = multipath_ioctl,
1729         .iterate_devices = multipath_iterate_devices,
1730         .busy = multipath_busy,
1731 };
1732
1733 static int __init dm_multipath_init(void)
1734 {
1735         int r;
1736
1737         /* allocate a slab for the dm_ios */
1738         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1739         if (!_mpio_cache)
1740                 return -ENOMEM;
1741
1742         r = dm_register_target(&multipath_target);
1743         if (r < 0) {
1744                 DMERR("register failed %d", r);
1745                 kmem_cache_destroy(_mpio_cache);
1746                 return -EINVAL;
1747         }
1748
1749         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1750         if (!kmultipathd) {
1751                 DMERR("failed to create workqueue kmpathd");
1752                 dm_unregister_target(&multipath_target);
1753                 kmem_cache_destroy(_mpio_cache);
1754                 return -ENOMEM;
1755         }
1756
1757         /*
1758          * A separate workqueue is used to handle the device handlers
1759          * to avoid overloading existing workqueue. Overloading the
1760          * old workqueue would also create a bottleneck in the
1761          * path of the storage hardware device activation.
1762          */
1763         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1764                                                   WQ_MEM_RECLAIM);
1765         if (!kmpath_handlerd) {
1766                 DMERR("failed to create workqueue kmpath_handlerd");
1767                 destroy_workqueue(kmultipathd);
1768                 dm_unregister_target(&multipath_target);
1769                 kmem_cache_destroy(_mpio_cache);
1770                 return -ENOMEM;
1771         }
1772
1773         DMINFO("version %u.%u.%u loaded",
1774                multipath_target.version[0], multipath_target.version[1],
1775                multipath_target.version[2]);
1776
1777         return r;
1778 }
1779
1780 static void __exit dm_multipath_exit(void)
1781 {
1782         destroy_workqueue(kmpath_handlerd);
1783         destroy_workqueue(kmultipathd);
1784
1785         dm_unregister_target(&multipath_target);
1786         kmem_cache_destroy(_mpio_cache);
1787 }
1788
1789 module_init(dm_multipath_init);
1790 module_exit(dm_multipath_exit);
1791
1792 MODULE_DESCRIPTION(DM_NAME " multipath target");
1793 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1794 MODULE_LICENSE("GPL");