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/module.h>
  24 #include <linux/raid/md_u.h>
  25 #include <linux/seq_file.h>
  26 #include <linux/slab.h>
  27 #include "md.h"
  28 #include "multipath.h"
  29
  30 #define MAX_WORK_PER_DISK 128
  31
  32 #define NR_RESERVED_BUFS        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                     !test_bit(Faulty, &rdev->flags)) {
  48                         atomic_inc(&rdev->nr_pending);
  49                         rcu_read_unlock();
  50                         return i;
  51                 }
  52         }
  53         rcu_read_unlock();
  54
  55         pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
  56         return (-1);
  57 }
  58
  59 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  60 {
  61         unsigned long flags;
  62         struct mddev *mddev = mp_bh->mddev;
  63         struct mpconf *conf = mddev->private;
  64
  65         spin_lock_irqsave(&conf->device_lock, flags);
  66         list_add(&mp_bh->retry_list, &conf->retry_list);
  67         spin_unlock_irqrestore(&conf->device_lock, flags);
  68         md_wakeup_thread(mddev->thread);
  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->bi_error = err;
  82         bio_endio(bio);
  83         mempool_free(mp_bh, conf->pool);
  84 }
  85
  86 static void multipath_end_request(struct bio *bio)
  87 {
  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 (!bio->bi_error)
  93                 multipath_end_bh_io(mp_bh, 0);
  94         else if (!(bio->bi_opf & REQ_RAHEAD)) {
  95                 /*
  96                  * oops, IO error:
  97                  */
  98                 char b[BDEVNAME_SIZE];
  99                 md_error (mp_bh->mddev, rdev);
 100                 pr_info("multipath: %s: rescheduling sector %llu\n",
 101                         bdevname(rdev->bdev,b),
 102                         (unsigned long long)bio->bi_iter.bi_sector);
 103                 multipath_reschedule_retry(mp_bh);
 104         } else
 105                 multipath_end_bh_io(mp_bh, bio->bi_error);
 106         rdev_dec_pending(rdev, conf->mddev);
 107 }
 108
 109 static void 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_opf & REQ_PREFLUSH)) {
 116                 md_flush_request(mddev, bio);
 117                 return;
 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_io_error(bio);
 128                 mempool_free(mp_bh, conf->pool);
 129                 return;
 130         }
 131         multipath = conf->multipaths + mp_bh->path;
 132
 133         bio_init(&mp_bh->bio, NULL, 0);
 134         __bio_clone_fast(&mp_bh->bio, bio);
 135
 136         mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
 137         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
 138         mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
 139         mp_bh->bio.bi_end_io = multipath_end_request;
 140         mp_bh->bio.bi_private = mp_bh;
 141         generic_make_request(&mp_bh->bio);
 142         return;
 143 }
 144
 145 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
 146 {
 147         struct mpconf *conf = mddev->private;
 148         int i;
 149
 150         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 151                     conf->raid_disks - mddev->degraded);
 152         rcu_read_lock();
 153         for (i = 0; i < conf->raid_disks; i++) {
 154                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
 155                 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
 156         }
 157         rcu_read_unlock();
 158         seq_printf (seq, "]");
 159 }
 160
 161 static int multipath_congested(struct mddev *mddev, int bits)
 162 {
 163         struct mpconf *conf = mddev->private;
 164         int i, ret = 0;
 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                 pr_warn("multipath: only one IO path left and IO error.\n");
 198                 /* leave it active... it's all we have */
 199                 return;
 200         }
 201         /*
 202          * Mark disk as unusable
 203          */
 204         if (test_and_clear_bit(In_sync, &rdev->flags)) {
 205                 unsigned long flags;
 206                 spin_lock_irqsave(&conf->device_lock, flags);
 207                 mddev->degraded++;
 208                 spin_unlock_irqrestore(&conf->device_lock, flags);
 209         }
 210         set_bit(Faulty, &rdev->flags);
 211         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
 212         pr_err("multipath: IO failure on %s, disabling IO path.\n"
 213                "multipath: Operation continuing on %d IO paths.\n",
 214                bdevname(rdev->bdev, b),
 215                conf->raid_disks - mddev->degraded);
 216 }
 217
 218 static void print_multipath_conf (struct mpconf *conf)
 219 {
 220         int i;
 221         struct multipath_info *tmp;
 222
 223         pr_debug("MULTIPATH conf printout:\n");
 224         if (!conf) {
 225                 pr_debug("(conf==NULL)\n");
 226                 return;
 227         }
 228         pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
 229                  conf->raid_disks);
 230
 231         for (i = 0; i < conf->raid_disks; i++) {
 232                 char b[BDEVNAME_SIZE];
 233                 tmp = conf->multipaths + i;
 234                 if (tmp->rdev)
 235                         pr_debug(" disk%d, o:%d, dev:%s\n",
 236                                  i,!test_bit(Faulty, &tmp->rdev->flags),
 237                                  bdevname(tmp->rdev->bdev,b));
 238         }
 239 }
 240
 241 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 242 {
 243         struct mpconf *conf = mddev->private;
 244         struct request_queue *q;
 245         int err = -EEXIST;
 246         int path;
 247         struct multipath_info *p;
 248         int first = 0;
 249         int last = mddev->raid_disks - 1;
 250
 251         if (rdev->raid_disk >= 0)
 252                 first = last = rdev->raid_disk;
 253
 254         print_multipath_conf(conf);
 255
 256         for (path = first; path <= last; path++)
 257                 if ((p=conf->multipaths+path)->rdev == NULL) {
 258                         q = rdev->bdev->bd_disk->queue;
 259                         disk_stack_limits(mddev->gendisk, rdev->bdev,
 260                                           rdev->data_offset << 9);
 261
 262                         err = md_integrity_add_rdev(rdev, mddev);
 263                         if (err)
 264                                 break;
 265                         spin_lock_irq(&conf->device_lock);
 266                         mddev->degraded--;
 267                         rdev->raid_disk = path;
 268                         set_bit(In_sync, &rdev->flags);
 269                         spin_unlock_irq(&conf->device_lock);
 270                         rcu_assign_pointer(p->rdev, rdev);
 271                         err = 0;
 272                         break;
 273                 }
 274
 275         print_multipath_conf(conf);
 276
 277         return err;
 278 }
 279
 280 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 281 {
 282         struct mpconf *conf = mddev->private;
 283         int err = 0;
 284         int number = rdev->raid_disk;
 285         struct multipath_info *p = conf->multipaths + number;
 286
 287         print_multipath_conf(conf);
 288
 289         if (rdev == p->rdev) {
 290                 if (test_bit(In_sync, &rdev->flags) ||
 291                     atomic_read(&rdev->nr_pending)) {
 292                         pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
 293                         err = -EBUSY;
 294                         goto abort;
 295                 }
 296                 p->rdev = NULL;
 297                 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
 298                         synchronize_rcu();
 299                         if (atomic_read(&rdev->nr_pending)) {
 300                                 /* lost the race, try later */
 301                                 err = -EBUSY;
 302                                 p->rdev = rdev;
 303                                 goto abort;
 304                         }
 305                 }
 306                 err = md_integrity_register(mddev);
 307         }
 308 abort:
 309
 310         print_multipath_conf(conf);
 311         return err;
 312 }
 313
 314 /*
 315  * This is a kernel thread which:
 316  *
 317  *      1.      Retries failed read operations on working multipaths.
 318  *      2.      Updates the raid superblock when problems encounter.
 319  *      3.      Performs writes following reads for array syncronising.
 320  */
 321
 322 static void multipathd(struct md_thread *thread)
 323 {
 324         struct mddev *mddev = thread->mddev;
 325         struct multipath_bh *mp_bh;
 326         struct bio *bio;
 327         unsigned long flags;
 328         struct mpconf *conf = mddev->private;
 329         struct list_head *head = &conf->retry_list;
 330
 331         md_check_recovery(mddev);
 332         for (;;) {
 333                 char b[BDEVNAME_SIZE];
 334                 spin_lock_irqsave(&conf->device_lock, flags);
 335                 if (list_empty(head))
 336                         break;
 337                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 338                 list_del(head->prev);
 339                 spin_unlock_irqrestore(&conf->device_lock, flags);
 340
 341                 bio = &mp_bh->bio;
 342                 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
 343
 344                 if ((mp_bh->path = multipath_map (conf))<0) {
 345                         pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
 346                                bdevname(bio->bi_bdev,b),
 347                                (unsigned long long)bio->bi_iter.bi_sector);
 348                         multipath_end_bh_io(mp_bh, -EIO);
 349                 } else {
 350                         pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
 351                                bdevname(bio->bi_bdev,b),
 352                                (unsigned long long)bio->bi_iter.bi_sector);
 353                         *bio = *(mp_bh->master_bio);
 354                         bio->bi_iter.bi_sector +=
 355                                 conf->multipaths[mp_bh->path].rdev->data_offset;
 356                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
 357                         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 358                         bio->bi_end_io = multipath_end_request;
 359                         bio->bi_private = mp_bh;
 360                         generic_make_request(bio);
 361                 }
 362         }
 363         spin_unlock_irqrestore(&conf->device_lock, flags);
 364 }
 365
 366 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 367 {
 368         WARN_ONCE(sectors || raid_disks,
 369                   "%s does not support generic reshape\n", __func__);
 370
 371         return mddev->dev_sectors;
 372 }
 373
 374 static int multipath_run (struct mddev *mddev)
 375 {
 376         struct mpconf *conf;
 377         int disk_idx;
 378         struct multipath_info *disk;
 379         struct md_rdev *rdev;
 380         int working_disks;
 381
 382         if (md_check_no_bitmap(mddev))
 383                 return -EINVAL;
 384
 385         if (mddev->level != LEVEL_MULTIPATH) {
 386                 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
 387                         mdname(mddev), mddev->level);
 388                 goto out;
 389         }
 390         /*
 391          * copy the already verified devices into our private MULTIPATH
 392          * bookkeeping area. [whatever we allocate in multipath_run(),
 393          * should be freed in multipath_free()]
 394          */
 395
 396         conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
 397         mddev->private = conf;
 398         if (!conf)
 399                 goto out;
 400
 401         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
 402                                    GFP_KERNEL);
 403         if (!conf->multipaths)
 404                 goto out_free_conf;
 405
 406         working_disks = 0;
 407         rdev_for_each(rdev, mddev) {
 408                 disk_idx = rdev->raid_disk;
 409                 if (disk_idx < 0 ||
 410                     disk_idx >= mddev->raid_disks)
 411                         continue;
 412
 413                 disk = conf->multipaths + disk_idx;
 414                 disk->rdev = rdev;
 415                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 416                                   rdev->data_offset << 9);
 417
 418                 if (!test_bit(Faulty, &rdev->flags))
 419                         working_disks++;
 420         }
 421
 422         conf->raid_disks = mddev->raid_disks;
 423         conf->mddev = mddev;
 424         spin_lock_init(&conf->device_lock);
 425         INIT_LIST_HEAD(&conf->retry_list);
 426
 427         if (!working_disks) {
 428                 pr_warn("multipath: no operational IO paths for %s\n",
 429                         mdname(mddev));
 430                 goto out_free_conf;
 431         }
 432         mddev->degraded = conf->raid_disks - working_disks;
 433
 434         conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
 435                                                  sizeof(struct multipath_bh));
 436         if (conf->pool == NULL)
 437                 goto out_free_conf;
 438
 439         mddev->thread = md_register_thread(multipathd, mddev,
 440                                            "multipath");
 441         if (!mddev->thread)
 442                 goto out_free_conf;
 443
 444         pr_info("multipath: array %s active with %d out of %d IO paths\n",
 445                 mdname(mddev), conf->raid_disks - mddev->degraded,
 446                 mddev->raid_disks);
 447         /*
 448          * Ok, everything is just fine now
 449          */
 450         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 451
 452         if (md_integrity_register(mddev))
 453                 goto out_free_conf;
 454
 455         return 0;
 456
 457 out_free_conf:
 458         mempool_destroy(conf->pool);
 459         kfree(conf->multipaths);
 460         kfree(conf);
 461         mddev->private = NULL;
 462 out:
 463         return -EIO;
 464 }
 465
 466 static void multipath_free(struct mddev *mddev, void *priv)
 467 {
 468         struct mpconf *conf = priv;
 469
 470         mempool_destroy(conf->pool);
 471         kfree(conf->multipaths);
 472         kfree(conf);
 473 }
 474
 475 static struct md_personality multipath_personality =
 476 {
 477         .name           = "multipath",
 478         .level          = LEVEL_MULTIPATH,
 479         .owner          = THIS_MODULE,
 480         .make_request   = multipath_make_request,
 481         .run            = multipath_run,
 482         .free           = multipath_free,
 483         .status         = multipath_status,
 484         .error_handler  = multipath_error,
 485         .hot_add_disk   = multipath_add_disk,
 486         .hot_remove_disk= multipath_remove_disk,
 487         .size           = multipath_size,
 488         .congested      = multipath_congested,
 489 };
 490
 491 static int __init multipath_init (void)
 492 {
 493         return register_md_personality (&multipath_personality);
 494 }
 495
 496 static void __exit multipath_exit (void)
 497 {
 498         unregister_md_personality (&multipath_personality);
 499 }
 500
 501 module_init(multipath_init);
 502 module_exit(multipath_exit);
 503 MODULE_LICENSE("GPL");
 504 MODULE_DESCRIPTION("simple multi-path personality for MD");
 505 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 506 MODULE_ALIAS("md-multipath");
 507 MODULE_ALIAS("md-level--4");