drivers/md/multipath.c

   1 /*
   2  * multipath.c : Multiple Devices driver for Linux
   3  *
   4  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
   5  *
   6  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   7  *
   8  * MULTIPATH management functions.
   9  *
  10  * derived from raid1.c.
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2, or (at your option)
  15  * any later version.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * (for example /usr/src/linux/COPYING); if not, write to the Free
  19  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/slab.h>
  24 #include <linux/spinlock.h>
  25 #include <linux/raid/multipath.h>
  26 #include <linux/buffer_head.h>
  27 #include <asm/atomic.h>
  28
  29 #define MAJOR_NR MD_MAJOR
  30 #define MD_DRIVER
  31 #define MD_PERSONALITY
  32
  33 #define MAX_WORK_PER_DISK 128
  34
  35 #define NR_RESERVED_BUFS        32
  36
  37
  38 static int multipath_map (multipath_conf_t *conf)
  39 {
  40         int i, disks = conf->raid_disks;
  41
  42         /*
  43          * Later we do read balancing on the read side
  44          * now we use the first available disk.
  45          */
  46
  47         rcu_read_lock();
  48         for (i = 0; i < disks; i++) {
  49                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
  50                 if (rdev && test_bit(In_sync, &rdev->flags)) {
  51                         atomic_inc(&rdev->nr_pending);
  52                         rcu_read_unlock();
  53                         return i;
  54                 }
  55         }
  56         rcu_read_unlock();
  57
  58         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
  59         return (-1);
  60 }
  61
  62 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  63 {
  64         unsigned long flags;
  65         mddev_t *mddev = mp_bh->mddev;
  66         multipath_conf_t *conf = mddev_to_conf(mddev);
  67
  68         spin_lock_irqsave(&conf->device_lock, flags);
  69         list_add(&mp_bh->retry_list, &conf->retry_list);
  70         spin_unlock_irqrestore(&conf->device_lock, flags);
  71         md_wakeup_thread(mddev->thread);
  72 }
  73
  74
  75 /*
  76  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  77  * operation and are ready to return a success/failure code to the buffer
  78  * cache layer.
  79  */
  80 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
  81 {
  82         struct bio *bio = mp_bh->master_bio;
  83         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
  84
  85         bio_endio(bio, err);
  86         mempool_free(mp_bh, conf->pool);
  87 }
  88
  89 static void multipath_end_request(struct bio *bio, int error)
  90 {
  91         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  92         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
  93         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
  94         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
  95
  96         if (uptodate)
  97                 multipath_end_bh_io(mp_bh, 0);
  98         else if (!bio_rw_ahead(bio)) {
  99                 /*
 100                  * oops, IO error:
 101                  */
 102                 char b[BDEVNAME_SIZE];
 103                 md_error (mp_bh->mddev, rdev);
 104                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
 105                        bdevname(rdev->bdev,b),
 106                        (unsigned long long)bio->bi_sector);
 107                 multipath_reschedule_retry(mp_bh);
 108         } else
 109                 multipath_end_bh_io(mp_bh, error);
 110         rdev_dec_pending(rdev, conf->mddev);
 111 }
 112
 113 static void unplug_slaves(mddev_t *mddev)
 114 {
 115         multipath_conf_t *conf = mddev_to_conf(mddev);
 116         int i;
 117
 118         rcu_read_lock();
 119         for (i=0; i<mddev->raid_disks; i++) {
 120                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 121                 if (rdev && !test_bit(Faulty, &rdev->flags)
 122                     && atomic_read(&rdev->nr_pending)) {
 123                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
 124
 125                         atomic_inc(&rdev->nr_pending);
 126                         rcu_read_unlock();
 127
 128                         if (r_queue->unplug_fn)
 129                                 r_queue->unplug_fn(r_queue);
 130
 131                         rdev_dec_pending(rdev, mddev);
 132                         rcu_read_lock();
 133                 }
 134         }
 135         rcu_read_unlock();
 136 }
 137
 138 static void multipath_unplug(struct request_queue *q)
 139 {
 140         unplug_slaves(q->queuedata);
 141 }
 142
 143
 144 static int multipath_make_request (struct request_queue *q, struct bio * bio)
 145 {
 146         mddev_t *mddev = q->queuedata;
 147         multipath_conf_t *conf = mddev_to_conf(mddev);
 148         struct multipath_bh * mp_bh;
 149         struct multipath_info *multipath;
 150         const int rw = bio_data_dir(bio);
 151
 152         if (unlikely(bio_barrier(bio))) {
 153                 bio_endio(bio, -EOPNOTSUPP);
 154                 return 0;
 155         }
 156
 157         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 158
 159         mp_bh->master_bio = bio;
 160         mp_bh->mddev = mddev;
 161
 162         disk_stat_inc(mddev->gendisk, ios[rw]);
 163         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
 164
 165         mp_bh->path = multipath_map(conf);
 166         if (mp_bh->path < 0) {
 167                 bio_endio(bio, -EIO);
 168                 mempool_free(mp_bh, conf->pool);
 169                 return 0;
 170         }
 171         multipath = conf->multipaths + mp_bh->path;
 172
 173         mp_bh->bio = *bio;
 174         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
 175         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 176         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
 177         mp_bh->bio.bi_end_io = multipath_end_request;
 178         mp_bh->bio.bi_private = mp_bh;
 179         generic_make_request(&mp_bh->bio);
 180         return 0;
 181 }
 182
 183 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
 184 {
 185         multipath_conf_t *conf = mddev_to_conf(mddev);
 186         int i;
 187
 188         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 189                                                  conf->working_disks);
 190         for (i = 0; i < conf->raid_disks; i++)
 191                 seq_printf (seq, "%s",
 192                                conf->multipaths[i].rdev &&
 193                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
 194         seq_printf (seq, "]");
 195 }
 196
 197 static int multipath_issue_flush(struct request_queue *q, struct gendisk *disk,
 198                                  sector_t *error_sector)
 199 {
 200         mddev_t *mddev = q->queuedata;
 201         multipath_conf_t *conf = mddev_to_conf(mddev);
 202         int i, ret = 0;
 203
 204         rcu_read_lock();
 205         for (i=0; i<mddev->raid_disks && ret == 0; i++) {
 206                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 207                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 208                         struct block_device *bdev = rdev->bdev;
 209                         struct request_queue *r_queue = bdev_get_queue(bdev);
 210
 211                         if (!r_queue->issue_flush_fn)
 212                                 ret = -EOPNOTSUPP;
 213                         else {
 214                                 atomic_inc(&rdev->nr_pending);
 215                                 rcu_read_unlock();
 216                                 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
 217                                                               error_sector);
 218                                 rdev_dec_pending(rdev, mddev);
 219                                 rcu_read_lock();
 220                         }
 221                 }
 222         }
 223         rcu_read_unlock();
 224         return ret;
 225 }
 226 static int multipath_congested(void *data, int bits)
 227 {
 228         mddev_t *mddev = data;
 229         multipath_conf_t *conf = mddev_to_conf(mddev);
 230         int i, ret = 0;
 231
 232         rcu_read_lock();
 233         for (i = 0; i < mddev->raid_disks ; i++) {
 234                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
 235                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
 236                         struct request_queue *q = bdev_get_queue(rdev->bdev);
 237
 238                         ret |= bdi_congested(&q->backing_dev_info, bits);
 239                         /* Just like multipath_map, we just check the
 240                          * first available device
 241                          */
 242                         break;
 243                 }
 244         }
 245         rcu_read_unlock();
 246         return ret;
 247 }
 248
 249 /*
 250  * Careful, this can execute in IRQ contexts as well!
 251  */
 252 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
 253 {
 254         multipath_conf_t *conf = mddev_to_conf(mddev);
 255
 256         if (conf->working_disks <= 1) {
 257                 /*
 258                  * Uh oh, we can do nothing if this is our last path, but
 259                  * first check if this is a queued request for a device
 260                  * which has just failed.
 261                  */
 262                 printk(KERN_ALERT
 263                         "multipath: only one IO path left and IO error.\n");
 264                 /* leave it active... it's all we have */
 265         } else {
 266                 /*
 267                  * Mark disk as unusable
 268                  */
 269                 if (!test_bit(Faulty, &rdev->flags)) {
 270                         char b[BDEVNAME_SIZE];
 271                         clear_bit(In_sync, &rdev->flags);
 272                         set_bit(Faulty, &rdev->flags);
 273                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
 274                         conf->working_disks--;
 275                         mddev->degraded++;
 276                         printk(KERN_ALERT "multipath: IO failure on %s,"
 277                                 " disabling IO path. \n Operation continuing"
 278                                 " on %d IO paths.\n",
 279                                 bdevname (rdev->bdev,b),
 280                                 conf->working_disks);
 281                 }
 282         }
 283 }
 284
 285 static void print_multipath_conf (multipath_conf_t *conf)
 286 {
 287         int i;
 288         struct multipath_info *tmp;
 289
 290         printk("MULTIPATH conf printout:\n");
 291         if (!conf) {
 292                 printk("(conf==NULL)\n");
 293                 return;
 294         }
 295         printk(" --- wd:%d rd:%d\n", conf->working_disks,
 296                          conf->raid_disks);
 297
 298         for (i = 0; i < conf->raid_disks; i++) {
 299                 char b[BDEVNAME_SIZE];
 300                 tmp = conf->multipaths + i;
 301                 if (tmp->rdev)
 302                         printk(" disk%d, o:%d, dev:%s\n",
 303                                 i,!test_bit(Faulty, &tmp->rdev->flags),
 304                                bdevname(tmp->rdev->bdev,b));
 305         }
 306 }
 307
 308
 309 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 310 {
 311         multipath_conf_t *conf = mddev->private;
 312         struct request_queue *q;
 313         int found = 0;
 314         int path;
 315         struct multipath_info *p;
 316
 317         print_multipath_conf(conf);
 318
 319         for (path=0; path<mddev->raid_disks; path++)
 320                 if ((p=conf->multipaths+path)->rdev == NULL) {
 321                         q = rdev->bdev->bd_disk->queue;
 322                         blk_queue_stack_limits(mddev->queue, q);
 323
 324                 /* as we don't honour merge_bvec_fn, we must never risk
 325                  * violating it, so limit ->max_sector to one PAGE, as
 326                  * a one page request is never in violation.
 327                  * (Note: it is very unlikely that a device with
 328                  * merge_bvec_fn will be involved in multipath.)
 329                  */
 330                         if (q->merge_bvec_fn &&
 331                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
 332                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 333
 334                         conf->working_disks++;
 335                         mddev->degraded--;
 336                         rdev->raid_disk = path;
 337                         set_bit(In_sync, &rdev->flags);
 338                         rcu_assign_pointer(p->rdev, rdev);
 339                         found = 1;
 340                 }
 341
 342         print_multipath_conf(conf);
 343         return found;
 344 }
 345
 346 static int multipath_remove_disk(mddev_t *mddev, int number)
 347 {
 348         multipath_conf_t *conf = mddev->private;
 349         int err = 0;
 350         mdk_rdev_t *rdev;
 351         struct multipath_info *p = conf->multipaths + number;
 352
 353         print_multipath_conf(conf);
 354
 355         rdev = p->rdev;
 356         if (rdev) {
 357                 if (test_bit(In_sync, &rdev->flags) ||
 358                     atomic_read(&rdev->nr_pending)) {
 359                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"                                " but is still operational!\n", number);
 360                         err = -EBUSY;
 361                         goto abort;
 362                 }
 363                 p->rdev = NULL;
 364                 synchronize_rcu();
 365                 if (atomic_read(&rdev->nr_pending)) {
 366                         /* lost the race, try later */
 367                         err = -EBUSY;
 368                         p->rdev = rdev;
 369                 }
 370         }
 371 abort:
 372
 373         print_multipath_conf(conf);
 374         return err;
 375 }
 376
 377
 378
 379 /*
 380  * This is a kernel thread which:
 381  *
 382  *      1.      Retries failed read operations on working multipaths.
 383  *      2.      Updates the raid superblock when problems encounter.
 384  *      3.      Performs writes following reads for array syncronising.
 385  */
 386
 387 static void multipathd (mddev_t *mddev)
 388 {
 389         struct multipath_bh *mp_bh;
 390         struct bio *bio;
 391         unsigned long flags;
 392         multipath_conf_t *conf = mddev_to_conf(mddev);
 393         struct list_head *head = &conf->retry_list;
 394
 395         md_check_recovery(mddev);
 396         for (;;) {
 397                 char b[BDEVNAME_SIZE];
 398                 spin_lock_irqsave(&conf->device_lock, flags);
 399                 if (list_empty(head))
 400                         break;
 401                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 402                 list_del(head->prev);
 403                 spin_unlock_irqrestore(&conf->device_lock, flags);
 404
 405                 bio = &mp_bh->bio;
 406                 bio->bi_sector = mp_bh->master_bio->bi_sector;
 407
 408                 if ((mp_bh->path = multipath_map (conf))<0) {
 409                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
 410                                 " error for block %llu\n",
 411                                 bdevname(bio->bi_bdev,b),
 412                                 (unsigned long long)bio->bi_sector);
 413                         multipath_end_bh_io(mp_bh, -EIO);
 414                 } else {
 415                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
 416                                 " to another IO path\n",
 417                                 bdevname(bio->bi_bdev,b),
 418                                 (unsigned long long)bio->bi_sector);
 419                         *bio = *(mp_bh->master_bio);
 420                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
 421                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 422                         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
 423                         bio->bi_end_io = multipath_end_request;
 424                         bio->bi_private = mp_bh;
 425                         generic_make_request(bio);
 426                 }
 427         }
 428         spin_unlock_irqrestore(&conf->device_lock, flags);
 429 }
 430
 431 static int multipath_run (mddev_t *mddev)
 432 {
 433         multipath_conf_t *conf;
 434         int disk_idx;
 435         struct multipath_info *disk;
 436         mdk_rdev_t *rdev;
 437         struct list_head *tmp;
 438
 439         if (mddev->level != LEVEL_MULTIPATH) {
 440                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
 441                        mdname(mddev), mddev->level);
 442                 goto out;
 443         }
 444         /*
 445          * copy the already verified devices into our private MULTIPATH
 446          * bookkeeping area. [whatever we allocate in multipath_run(),
 447          * should be freed in multipath_stop()]
 448          */
 449
 450         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
 451         mddev->private = conf;
 452         if (!conf) {
 453                 printk(KERN_ERR
 454                         "multipath: couldn't allocate memory for %s\n",
 455                         mdname(mddev));
 456                 goto out;
 457         }
 458
 459         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 460                                    GFP_KERNEL);
 461         if (!conf->multipaths) {
 462                 printk(KERN_ERR
 463                         "multipath: couldn't allocate memory for %s\n",
 464                         mdname(mddev));
 465                 goto out_free_conf;
 466         }
 467
 468         conf->working_disks = 0;
 469         ITERATE_RDEV(mddev,rdev,tmp) {
 470                 disk_idx = rdev->raid_disk;
 471                 if (disk_idx < 0 ||
 472                     disk_idx >= mddev->raid_disks)
 473                         continue;
 474
 475                 disk = conf->multipaths + disk_idx;
 476                 disk->rdev = rdev;
 477
 478                 blk_queue_stack_limits(mddev->queue,
 479                                        rdev->bdev->bd_disk->queue);
 480                 /* as we don't honour merge_bvec_fn, we must never risk
 481                  * violating it, not that we ever expect a device with
 482                  * a merge_bvec_fn to be involved in multipath */
 483                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 484                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 485                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 486
 487                 if (!test_bit(Faulty, &rdev->flags))
 488                         conf->working_disks++;
 489         }
 490
 491         conf->raid_disks = mddev->raid_disks;
 492         conf->mddev = mddev;
 493         spin_lock_init(&conf->device_lock);
 494         INIT_LIST_HEAD(&conf->retry_list);
 495
 496         if (!conf->working_disks) {
 497                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 498                         mdname(mddev));
 499                 goto out_free_conf;
 500         }
 501         mddev->degraded = conf->raid_disks - conf->working_disks;
 502
 503         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
 504                                                  sizeof(struct multipath_bh));
 505         if (conf->pool == NULL) {
 506                 printk(KERN_ERR
 507                         "multipath: couldn't allocate memory for %s\n",
 508                         mdname(mddev));
 509                 goto out_free_conf;
 510         }
 511
 512         {
 513                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
 514                 if (!mddev->thread) {
 515                         printk(KERN_ERR "multipath: couldn't allocate thread"
 516                                 " for %s\n", mdname(mddev));
 517                         goto out_free_conf;
 518                 }
 519         }
 520
 521         printk(KERN_INFO
 522                 "multipath: array %s active with %d out of %d IO paths\n",
 523                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 524         /*
 525          * Ok, everything is just fine now
 526          */
 527         mddev->array_size = mddev->size;
 528
 529         mddev->queue->unplug_fn = multipath_unplug;
 530         mddev->queue->issue_flush_fn = multipath_issue_flush;
 531         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
 532         mddev->queue->backing_dev_info.congested_data = mddev;
 533
 534         return 0;
 535
 536 out_free_conf:
 537         if (conf->pool)
 538                 mempool_destroy(conf->pool);
 539         kfree(conf->multipaths);
 540         kfree(conf);
 541         mddev->private = NULL;
 542 out:
 543         return -EIO;
 544 }
 545
 546
 547 static int multipath_stop (mddev_t *mddev)
 548 {
 549         multipath_conf_t *conf = mddev_to_conf(mddev);
 550
 551         md_unregister_thread(mddev->thread);
 552         mddev->thread = NULL;
 553         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 554         mempool_destroy(conf->pool);
 555         kfree(conf->multipaths);
 556         kfree(conf);
 557         mddev->private = NULL;
 558         return 0;
 559 }
 560
 561 static struct mdk_personality multipath_personality =
 562 {
 563         .name           = "multipath",
 564         .level          = LEVEL_MULTIPATH,
 565         .owner          = THIS_MODULE,
 566         .make_request   = multipath_make_request,
 567         .run            = multipath_run,
 568         .stop           = multipath_stop,
 569         .status         = multipath_status,
 570         .error_handler  = multipath_error,
 571         .hot_add_disk   = multipath_add_disk,
 572         .hot_remove_disk= multipath_remove_disk,
 573 };
 574
 575 static int __init multipath_init (void)
 576 {
 577         return register_md_personality (&multipath_personality);
 578 }
 579
 580 static void __exit multipath_exit (void)
 581 {
 582         unregister_md_personality (&multipath_personality);
 583 }
 584
 585 module_init(multipath_init);
 586 module_exit(multipath_exit);
 587 MODULE_LICENSE("GPL");
 588 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 589 MODULE_ALIAS("md-multipath");
 590 MODULE_ALIAS("md-level--4");