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