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 mdk_personality_t multipath_personality;
  39
  40
  41 static void *mp_pool_alloc(unsigned int __nocast gfp_flags, void *data)
  42 {
  43         struct multipath_bh *mpb;
  44         mpb = kmalloc(sizeof(*mpb), gfp_flags);
  45         if (mpb)
  46                 memset(mpb, 0, sizeof(*mpb));
  47         return mpb;
  48 }
  49
  50 static void mp_pool_free(void *mpb, void *data)
  51 {
  52         kfree(mpb);
  53 }
  54
  55 static int multipath_map (multipath_conf_t *conf)
  56 {
  57         int i, disks = conf->raid_disks;
  58
  59         /*
  60          * Later we do read balancing on the read side
  61          * now we use the first available disk.
  62          */
  63
  64         rcu_read_lock();
  65         for (i = 0; i < disks; i++) {
  66                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
  67                 if (rdev && rdev->in_sync) {
  68                         atomic_inc(&rdev->nr_pending);
  69                         rcu_read_unlock();
  70                         return i;
  71                 }
  72         }
  73         rcu_read_unlock();
  74
  75         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
  76         return (-1);
  77 }
  78
  79 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  80 {
  81         unsigned long flags;
  82         mddev_t *mddev = mp_bh->mddev;
  83         multipath_conf_t *conf = mddev_to_conf(mddev);
  84
  85         spin_lock_irqsave(&conf->device_lock, flags);
  86         list_add(&mp_bh->retry_list, &conf->retry_list);
  87         spin_unlock_irqrestore(&conf->device_lock, flags);
  88         md_wakeup_thread(mddev->thread);
  89 }
  90
  91
  92 /*
  93  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  94  * operation and are ready to return a success/failure code to the buffer
  95  * cache layer.
  96  */
  97 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
  98 {
  99         struct bio *bio = mp_bh->master_bio;
 100         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
 101
 102         bio_endio(bio, bio->bi_size, err);
 103         mempool_free(mp_bh, conf->pool);
 104 }
 105
 106 static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
 107                                  int error)
 108 {
 109         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 110         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
 111         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
 112         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
 113
 114         if (bio->bi_size)
 115                 return 1;
 116
 117         if (uptodate)
 118                 multipath_end_bh_io(mp_bh, 0);
 119         else if (!bio_rw_ahead(bio)) {
 120                 /*
 121                  * oops, IO error:
 122                  */
 123                 char b[BDEVNAME_SIZE];
 124                 md_error (mp_bh->mddev, rdev);
 125                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
 126                        bdevname(rdev->bdev,b),
 127                        (unsigned long long)bio->bi_sector);
 128                 multipath_reschedule_retry(mp_bh);
 129         } else
 130                 multipath_end_bh_io(mp_bh, error);
 131         rdev_dec_pending(rdev, conf->mddev);
 132         return 0;
 133 }
 134
 135 static void unplug_slaves(mddev_t *mddev)
 136 {
 137         multipath_conf_t *conf = mddev_to_conf(mddev);
 138         int i;
 139
 140         rcu_read_lock();
 141         for (i=0; i<mddev->raid_disks; i++) {
 142                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
 143                 if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
 144                         request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
 145
 146                         atomic_inc(&rdev->nr_pending);
 147                         rcu_read_unlock();
 148
 149                         if (r_queue->unplug_fn)
 150                                 r_queue->unplug_fn(r_queue);
 151
 152                         rdev_dec_pending(rdev, mddev);
 153                         rcu_read_lock();
 154                 }
 155         }
 156         rcu_read_unlock();
 157 }
 158
 159 static void multipath_unplug(request_queue_t *q)
 160 {
 161         unplug_slaves(q->queuedata);
 162 }
 163
 164
 165 static int multipath_make_request (request_queue_t *q, struct bio * bio)
 166 {
 167         mddev_t *mddev = q->queuedata;
 168         multipath_conf_t *conf = mddev_to_conf(mddev);
 169         struct multipath_bh * mp_bh;
 170         struct multipath_info *multipath;
 171
 172         if (unlikely(bio_barrier(bio))) {
 173                 bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
 174                 return 0;
 175         }
 176
 177         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
 178
 179         mp_bh->master_bio = bio;
 180         mp_bh->mddev = mddev;
 181
 182         if (bio_data_dir(bio)==WRITE) {
 183                 disk_stat_inc(mddev->gendisk, writes);
 184                 disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bio));
 185         } else {
 186                 disk_stat_inc(mddev->gendisk, reads);
 187                 disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bio));
 188         }
 189
 190         mp_bh->path = multipath_map(conf);
 191         if (mp_bh->path < 0) {
 192                 bio_endio(bio, bio->bi_size, -EIO);
 193                 mempool_free(mp_bh, conf->pool);
 194                 return 0;
 195         }
 196         multipath = conf->multipaths + mp_bh->path;
 197
 198         mp_bh->bio = *bio;
 199         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
 200         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 201         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
 202         mp_bh->bio.bi_end_io = multipath_end_request;
 203         mp_bh->bio.bi_private = mp_bh;
 204         generic_make_request(&mp_bh->bio);
 205         return 0;
 206 }
 207
 208 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
 209 {
 210         multipath_conf_t *conf = mddev_to_conf(mddev);
 211         int i;
 212
 213         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 214                                                  conf->working_disks);
 215         for (i = 0; i < conf->raid_disks; i++)
 216                 seq_printf (seq, "%s",
 217                                conf->multipaths[i].rdev &&
 218                                conf->multipaths[i].rdev->in_sync ? "U" : "_");
 219         seq_printf (seq, "]");
 220 }
 221
 222 static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
 223                                  sector_t *error_sector)
 224 {
 225         mddev_t *mddev = q->queuedata;
 226         multipath_conf_t *conf = mddev_to_conf(mddev);
 227         int i, ret = 0;
 228
 229         rcu_read_lock();
 230         for (i=0; i<mddev->raid_disks && ret == 0; i++) {
 231                 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
 232                 if (rdev && !rdev->faulty) {
 233                         struct block_device *bdev = rdev->bdev;
 234                         request_queue_t *r_queue = bdev_get_queue(bdev);
 235
 236                         if (!r_queue->issue_flush_fn)
 237                                 ret = -EOPNOTSUPP;
 238                         else {
 239                                 atomic_inc(&rdev->nr_pending);
 240                                 rcu_read_unlock();
 241                                 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
 242                                                               error_sector);
 243                                 rdev_dec_pending(rdev, mddev);
 244                                 rcu_read_lock();
 245                         }
 246                 }
 247         }
 248         rcu_read_unlock();
 249         return ret;
 250 }
 251
 252 /*
 253  * Careful, this can execute in IRQ contexts as well!
 254  */
 255 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
 256 {
 257         multipath_conf_t *conf = mddev_to_conf(mddev);
 258
 259         if (conf->working_disks <= 1) {
 260                 /*
 261                  * Uh oh, we can do nothing if this is our last path, but
 262                  * first check if this is a queued request for a device
 263                  * which has just failed.
 264                  */
 265                 printk(KERN_ALERT
 266                         "multipath: only one IO path left and IO error.\n");
 267                 /* leave it active... it's all we have */
 268         } else {
 269                 /*
 270                  * Mark disk as unusable
 271                  */
 272                 if (!rdev->faulty) {
 273                         char b[BDEVNAME_SIZE];
 274                         rdev->in_sync = 0;
 275                         rdev->faulty = 1;
 276                         mddev->sb_dirty = 1;
 277                         conf->working_disks--;
 278                         printk(KERN_ALERT "multipath: IO failure on %s,"
 279                                 " disabling IO path. \n Operation continuing"
 280                                 " on %d IO paths.\n",
 281                                 bdevname (rdev->bdev,b),
 282                                 conf->working_disks);
 283                 }
 284         }
 285 }
 286
 287 static void print_multipath_conf (multipath_conf_t *conf)
 288 {
 289         int i;
 290         struct multipath_info *tmp;
 291
 292         printk("MULTIPATH conf printout:\n");
 293         if (!conf) {
 294                 printk("(conf==NULL)\n");
 295                 return;
 296         }
 297         printk(" --- wd:%d rd:%d\n", conf->working_disks,
 298                          conf->raid_disks);
 299
 300         for (i = 0; i < conf->raid_disks; i++) {
 301                 char b[BDEVNAME_SIZE];
 302                 tmp = conf->multipaths + i;
 303                 if (tmp->rdev)
 304                         printk(" disk%d, o:%d, dev:%s\n",
 305                                 i,!tmp->rdev->faulty,
 306                                bdevname(tmp->rdev->bdev,b));
 307         }
 308 }
 309
 310
 311 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
 312 {
 313         multipath_conf_t *conf = mddev->private;
 314         int found = 0;
 315         int path;
 316         struct multipath_info *p;
 317
 318         print_multipath_conf(conf);
 319
 320         for (path=0; path<mddev->raid_disks; path++)
 321                 if ((p=conf->multipaths+path)->rdev == NULL) {
 322                         blk_queue_stack_limits(mddev->queue,
 323                                                rdev->bdev->bd_disk->queue);
 324
 325                 /* as we don't honour merge_bvec_fn, we must never risk
 326                  * violating it, so limit ->max_sector to one PAGE, as
 327                  * a one page request is never in violation.
 328                  * (Note: it is very unlikely that a device with
 329                  * merge_bvec_fn will be involved in multipath.)
 330                  */
 331                         if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 332                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
 333                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 334
 335                         conf->working_disks++;
 336                         rdev->raid_disk = path;
 337                         rdev->in_sync = 1;
 338                         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 (rdev->in_sync ||
 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 = kmalloc(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         memset(conf, 0, sizeof(*conf));
 459
 460         conf->multipaths = kmalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 461                                    GFP_KERNEL);
 462         if (!conf->multipaths) {
 463                 printk(KERN_ERR
 464                         "multipath: couldn't allocate memory for %s\n",
 465                         mdname(mddev));
 466                 goto out_free_conf;
 467         }
 468         memset(conf->multipaths, 0, sizeof(struct multipath_info)*mddev->raid_disks);
 469
 470         conf->working_disks = 0;
 471         ITERATE_RDEV(mddev,rdev,tmp) {
 472                 disk_idx = rdev->raid_disk;
 473                 if (disk_idx < 0 ||
 474                     disk_idx >= mddev->raid_disks)
 475                         continue;
 476
 477                 disk = conf->multipaths + disk_idx;
 478                 disk->rdev = rdev;
 479
 480                 blk_queue_stack_limits(mddev->queue,
 481                                        rdev->bdev->bd_disk->queue);
 482                 /* as we don't honour merge_bvec_fn, we must never risk
 483                  * violating it, not that we ever expect a device with
 484                  * a merge_bvec_fn to be involved in multipath */
 485                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
 486                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
 487                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
 488
 489                 if (!rdev->faulty)
 490                         conf->working_disks++;
 491         }
 492
 493         conf->raid_disks = mddev->raid_disks;
 494         mddev->sb_dirty = 1;
 495         conf->mddev = mddev;
 496         spin_lock_init(&conf->device_lock);
 497         INIT_LIST_HEAD(&conf->retry_list);
 498
 499         if (!conf->working_disks) {
 500                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
 501                         mdname(mddev));
 502                 goto out_free_conf;
 503         }
 504         mddev->degraded = conf->raid_disks = conf->working_disks;
 505
 506         conf->pool = mempool_create(NR_RESERVED_BUFS,
 507                                     mp_pool_alloc, mp_pool_free,
 508                                     NULL);
 509         if (conf->pool == NULL) {
 510                 printk(KERN_ERR
 511                         "multipath: couldn't allocate memory for %s\n",
 512                         mdname(mddev));
 513                 goto out_free_conf;
 514         }
 515
 516         {
 517                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
 518                 if (!mddev->thread) {
 519                         printk(KERN_ERR "multipath: couldn't allocate thread"
 520                                 " for %s\n", mdname(mddev));
 521                         goto out_free_conf;
 522                 }
 523         }
 524
 525         printk(KERN_INFO
 526                 "multipath: array %s active with %d out of %d IO paths\n",
 527                 mdname(mddev), conf->working_disks, mddev->raid_disks);
 528         /*
 529          * Ok, everything is just fine now
 530          */
 531         mddev->array_size = mddev->size;
 532
 533         mddev->queue->unplug_fn = multipath_unplug;
 534         mddev->queue->issue_flush_fn = multipath_issue_flush;
 535
 536         return 0;
 537
 538 out_free_conf:
 539         if (conf->pool)
 540                 mempool_destroy(conf->pool);
 541         kfree(conf->multipaths);
 542         kfree(conf);
 543         mddev->private = NULL;
 544 out:
 545         return -EIO;
 546 }
 547
 548
 549 static int multipath_stop (mddev_t *mddev)
 550 {
 551         multipath_conf_t *conf = mddev_to_conf(mddev);
 552
 553         md_unregister_thread(mddev->thread);
 554         mddev->thread = NULL;
 555         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
 556         mempool_destroy(conf->pool);
 557         kfree(conf->multipaths);
 558         kfree(conf);
 559         mddev->private = NULL;
 560         return 0;
 561 }
 562
 563 static mdk_personality_t multipath_personality=
 564 {
 565         .name           = "multipath",
 566         .owner          = THIS_MODULE,
 567         .make_request   = multipath_make_request,
 568         .run            = multipath_run,
 569         .stop           = multipath_stop,
 570         .status         = multipath_status,
 571         .error_handler  = multipath_error,
 572         .hot_add_disk   = multipath_add_disk,
 573         .hot_remove_disk= multipath_remove_disk,
 574 };
 575
 576 static int __init multipath_init (void)
 577 {
 578         return register_md_personality (MULTIPATH, &multipath_personality);
 579 }
 580
 581 static void __exit multipath_exit (void)
 582 {
 583         unregister_md_personality (MULTIPATH);
 584 }
 585
 586 module_init(multipath_init);
 587 module_exit(multipath_exit);
 588 MODULE_LICENSE("GPL");
 589 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */