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