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