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