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