drivers/md/md-multipath.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * multipath.c : Multiple Devices driver for Linux
   4  *
   5  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
   6  *
   7  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
   8  *
   9  * MULTIPATH management functions.
  10  *
  11  * derived from raid1.c.
  12  */
  13
  14 #include <linux/blkdev.h>
  15 #include <linux/module.h>
  16 #include <linux/raid/md_u.h>
  17 #include <linux/seq_file.h>
  18 #include <linux/slab.h>
  19 #include "md.h"
  20 #include "md-multipath.h"
  21
  22 #define MAX_WORK_PER_DISK 128
  23
  24 #define NR_RESERVED_BUFS        32
  25
  26 static int multipath_map (struct mpconf *conf)
  27 {
  28         int i, disks = conf->raid_disks;
  29
  30         /*
  31          * Later we do read balancing on the read side
  32          * now we use the first available disk.
  33          */
  34
  35         rcu_read_lock();
  36         for (i = 0; i < disks; i++) {
  37                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
  38                 if (rdev && test_bit(In_sync, &rdev->flags) &&
  39                     !test_bit(Faulty, &rdev->flags)) {
  40                         atomic_inc(&rdev->nr_pending);
  41                         rcu_read_unlock();
  42                         return i;
  43                 }
  44         }
  45         rcu_read_unlock();
  46
  47         pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
  48         return (-1);
  49 }
  50
  51 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
  52 {
  53         unsigned long flags;
  54         struct mddev *mddev = mp_bh->mddev;
  55         struct mpconf *conf = mddev->private;
  56
  57         spin_lock_irqsave(&conf->device_lock, flags);
  58         list_add(&mp_bh->retry_list, &conf->retry_list);
  59         spin_unlock_irqrestore(&conf->device_lock, flags);
  60         md_wakeup_thread(mddev->thread);
  61 }
  62
  63 /*
  64  * multipath_end_bh_io() is called when we have finished servicing a multipathed
  65  * operation and are ready to return a success/failure code to the buffer
  66  * cache layer.
  67  */
  68 static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
  69 {
  70         struct bio *bio = mp_bh->master_bio;
  71         struct mpconf *conf = mp_bh->mddev->private;
  72
  73         bio->bi_status = status;
  74         bio_endio(bio);
  75         mempool_free(mp_bh, &conf->pool);
  76 }
  77
  78 static void multipath_end_request(struct bio *bio)
  79 {
  80         struct multipath_bh *mp_bh = bio->bi_private;
  81         struct mpconf *conf = mp_bh->mddev->private;
  82         struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
  83
  84         if (!bio->bi_status)
  85                 multipath_end_bh_io(mp_bh, 0);
  86         else if (!(bio->bi_opf & REQ_RAHEAD)) {
  87                 /*
  88                  * oops, IO error:
  89                  */
  90                 char b[BDEVNAME_SIZE];
  91                 md_error (mp_bh->mddev, rdev);
  92                 pr_info("multipath: %s: rescheduling sector %llu\n",
  93                         bdevname(rdev->bdev,b),
  94                         (unsigned long long)bio->bi_iter.bi_sector);
  95                 multipath_reschedule_retry(mp_bh);
  96         } else
  97                 multipath_end_bh_io(mp_bh, bio->bi_status);
  98         rdev_dec_pending(rdev, conf->mddev);
  99 }
 100
 101 static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
 102 {
 103         struct mpconf *conf = mddev->private;
 104         struct multipath_bh * mp_bh;
 105         struct multipath_info *multipath;
 106
 107         if (unlikely(bio->bi_opf & REQ_PREFLUSH)
 108             && md_flush_request(mddev, bio))
 109                 return true;
 110
 111         mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
 112
 113         mp_bh->master_bio = bio;
 114         mp_bh->mddev = mddev;
 115
 116         mp_bh->path = multipath_map(conf);
 117         if (mp_bh->path < 0) {
 118                 bio_io_error(bio);
 119                 mempool_free(mp_bh, &conf->pool);
 120                 return true;
 121         }
 122         multipath = conf->multipaths + mp_bh->path;
 123
 124         bio_init_clone(multipath->rdev->bdev, &mp_bh->bio, bio, GFP_NOIO);
 125
 126         mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
 127         mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
 128         mp_bh->bio.bi_end_io = multipath_end_request;
 129         mp_bh->bio.bi_private = mp_bh;
 130         mddev_check_write_zeroes(mddev, &mp_bh->bio);
 131         submit_bio_noacct(&mp_bh->bio);
 132         return true;
 133 }
 134
 135 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
 136 {
 137         struct mpconf *conf = mddev->private;
 138         int i;
 139
 140         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
 141                     conf->raid_disks - mddev->degraded);
 142         rcu_read_lock();
 143         for (i = 0; i < conf->raid_disks; i++) {
 144                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
 145                 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
 146         }
 147         rcu_read_unlock();
 148         seq_putc(seq, ']');
 149 }
 150
 151 /*
 152  * Careful, this can execute in IRQ contexts as well!
 153  */
 154 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
 155 {
 156         struct mpconf *conf = mddev->private;
 157         char b[BDEVNAME_SIZE];
 158
 159         if (conf->raid_disks - mddev->degraded <= 1) {
 160                 /*
 161                  * Uh oh, we can do nothing if this is our last path, but
 162                  * first check if this is a queued request for a device
 163                  * which has just failed.
 164                  */
 165                 pr_warn("multipath: only one IO path left and IO error.\n");
 166                 /* leave it active... it's all we have */
 167                 return;
 168         }
 169         /*
 170          * Mark disk as unusable
 171          */
 172         if (test_and_clear_bit(In_sync, &rdev->flags)) {
 173                 unsigned long flags;
 174                 spin_lock_irqsave(&conf->device_lock, flags);
 175                 mddev->degraded++;
 176                 spin_unlock_irqrestore(&conf->device_lock, flags);
 177         }
 178         set_bit(Faulty, &rdev->flags);
 179         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
 180         pr_err("multipath: IO failure on %s, disabling IO path.\n"
 181                "multipath: Operation continuing on %d IO paths.\n",
 182                bdevname(rdev->bdev, b),
 183                conf->raid_disks - mddev->degraded);
 184 }
 185
 186 static void print_multipath_conf (struct mpconf *conf)
 187 {
 188         int i;
 189         struct multipath_info *tmp;
 190
 191         pr_debug("MULTIPATH conf printout:\n");
 192         if (!conf) {
 193                 pr_debug("(conf==NULL)\n");
 194                 return;
 195         }
 196         pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
 197                  conf->raid_disks);
 198
 199         for (i = 0; i < conf->raid_disks; i++) {
 200                 char b[BDEVNAME_SIZE];
 201                 tmp = conf->multipaths + i;
 202                 if (tmp->rdev)
 203                         pr_debug(" disk%d, o:%d, dev:%s\n",
 204                                  i,!test_bit(Faulty, &tmp->rdev->flags),
 205                                  bdevname(tmp->rdev->bdev,b));
 206         }
 207 }
 208
 209 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
 210 {
 211         struct mpconf *conf = mddev->private;
 212         int err = -EEXIST;
 213         int path;
 214         struct multipath_info *p;
 215         int first = 0;
 216         int last = mddev->raid_disks - 1;
 217
 218         if (rdev->raid_disk >= 0)
 219                 first = last = rdev->raid_disk;
 220
 221         print_multipath_conf(conf);
 222
 223         for (path = first; path <= last; path++)
 224                 if ((p=conf->multipaths+path)->rdev == NULL) {
 225                         disk_stack_limits(mddev->gendisk, rdev->bdev,
 226                                           rdev->data_offset << 9);
 227
 228                         err = md_integrity_add_rdev(rdev, mddev);
 229                         if (err)
 230                                 break;
 231                         spin_lock_irq(&conf->device_lock);
 232                         mddev->degraded--;
 233                         rdev->raid_disk = path;
 234                         set_bit(In_sync, &rdev->flags);
 235                         spin_unlock_irq(&conf->device_lock);
 236                         rcu_assign_pointer(p->rdev, rdev);
 237                         err = 0;
 238                         break;
 239                 }
 240
 241         print_multipath_conf(conf);
 242
 243         return err;
 244 }
 245
 246 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 247 {
 248         struct mpconf *conf = mddev->private;
 249         int err = 0;
 250         int number = rdev->raid_disk;
 251         struct multipath_info *p = conf->multipaths + number;
 252
 253         print_multipath_conf(conf);
 254
 255         if (rdev == p->rdev) {
 256                 if (test_bit(In_sync, &rdev->flags) ||
 257                     atomic_read(&rdev->nr_pending)) {
 258                         pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
 259                         err = -EBUSY;
 260                         goto abort;
 261                 }
 262                 p->rdev = NULL;
 263                 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
 264                         synchronize_rcu();
 265                         if (atomic_read(&rdev->nr_pending)) {
 266                                 /* lost the race, try later */
 267                                 err = -EBUSY;
 268                                 p->rdev = rdev;
 269                                 goto abort;
 270                         }
 271                 }
 272                 err = md_integrity_register(mddev);
 273         }
 274 abort:
 275
 276         print_multipath_conf(conf);
 277         return err;
 278 }
 279
 280 /*
 281  * This is a kernel thread which:
 282  *
 283  *      1.      Retries failed read operations on working multipaths.
 284  *      2.      Updates the raid superblock when problems encounter.
 285  *      3.      Performs writes following reads for array syncronising.
 286  */
 287
 288 static void multipathd(struct md_thread *thread)
 289 {
 290         struct mddev *mddev = thread->mddev;
 291         struct multipath_bh *mp_bh;
 292         struct bio *bio;
 293         unsigned long flags;
 294         struct mpconf *conf = mddev->private;
 295         struct list_head *head = &conf->retry_list;
 296
 297         md_check_recovery(mddev);
 298         for (;;) {
 299                 spin_lock_irqsave(&conf->device_lock, flags);
 300                 if (list_empty(head))
 301                         break;
 302                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
 303                 list_del(head->prev);
 304                 spin_unlock_irqrestore(&conf->device_lock, flags);
 305
 306                 bio = &mp_bh->bio;
 307                 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
 308
 309                 if ((mp_bh->path = multipath_map (conf))<0) {
 310                         pr_err("multipath: %pg: unrecoverable IO read error for block %llu\n",
 311                                bio->bi_bdev,
 312                                (unsigned long long)bio->bi_iter.bi_sector);
 313                         multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
 314                 } else {
 315                         pr_err("multipath: %pg: redirecting sector %llu to another IO path\n",
 316                                bio->bi_bdev,
 317                                (unsigned long long)bio->bi_iter.bi_sector);
 318                         *bio = *(mp_bh->master_bio);
 319                         bio->bi_iter.bi_sector +=
 320                                 conf->multipaths[mp_bh->path].rdev->data_offset;
 321                         bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
 322                         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
 323                         bio->bi_end_io = multipath_end_request;
 324                         bio->bi_private = mp_bh;
 325                         submit_bio_noacct(bio);
 326                 }
 327         }
 328         spin_unlock_irqrestore(&conf->device_lock, flags);
 329 }
 330
 331 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
 332 {
 333         WARN_ONCE(sectors || raid_disks,
 334                   "%s does not support generic reshape\n", __func__);
 335
 336         return mddev->dev_sectors;
 337 }
 338
 339 static int multipath_run (struct mddev *mddev)
 340 {
 341         struct mpconf *conf;
 342         int disk_idx;
 343         struct multipath_info *disk;
 344         struct md_rdev *rdev;
 345         int working_disks;
 346         int ret;
 347
 348         if (md_check_no_bitmap(mddev))
 349                 return -EINVAL;
 350
 351         if (mddev->level != LEVEL_MULTIPATH) {
 352                 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
 353                         mdname(mddev), mddev->level);
 354                 goto out;
 355         }
 356         /*
 357          * copy the already verified devices into our private MULTIPATH
 358          * bookkeeping area. [whatever we allocate in multipath_run(),
 359          * should be freed in multipath_free()]
 360          */
 361
 362         conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
 363         mddev->private = conf;
 364         if (!conf)
 365                 goto out;
 366
 367         conf->multipaths = kcalloc(mddev->raid_disks,
 368                                    sizeof(struct multipath_info),
 369                                    GFP_KERNEL);
 370         if (!conf->multipaths)
 371                 goto out_free_conf;
 372
 373         working_disks = 0;
 374         rdev_for_each(rdev, mddev) {
 375                 disk_idx = rdev->raid_disk;
 376                 if (disk_idx < 0 ||
 377                     disk_idx >= mddev->raid_disks)
 378                         continue;
 379
 380                 disk = conf->multipaths + disk_idx;
 381                 disk->rdev = rdev;
 382                 disk_stack_limits(mddev->gendisk, rdev->bdev,
 383                                   rdev->data_offset << 9);
 384
 385                 if (!test_bit(Faulty, &rdev->flags))
 386                         working_disks++;
 387         }
 388
 389         conf->raid_disks = mddev->raid_disks;
 390         conf->mddev = mddev;
 391         spin_lock_init(&conf->device_lock);
 392         INIT_LIST_HEAD(&conf->retry_list);
 393
 394         if (!working_disks) {
 395                 pr_warn("multipath: no operational IO paths for %s\n",
 396                         mdname(mddev));
 397                 goto out_free_conf;
 398         }
 399         mddev->degraded = conf->raid_disks - working_disks;
 400
 401         ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
 402                                         sizeof(struct multipath_bh));
 403         if (ret)
 404                 goto out_free_conf;
 405
 406         mddev->thread = md_register_thread(multipathd, mddev,
 407                                            "multipath");
 408         if (!mddev->thread)
 409                 goto out_free_conf;
 410
 411         pr_info("multipath: array %s active with %d out of %d IO paths\n",
 412                 mdname(mddev), conf->raid_disks - mddev->degraded,
 413                 mddev->raid_disks);
 414         /*
 415          * Ok, everything is just fine now
 416          */
 417         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
 418
 419         if (md_integrity_register(mddev))
 420                 goto out_free_conf;
 421
 422         return 0;
 423
 424 out_free_conf:
 425         mempool_exit(&conf->pool);
 426         kfree(conf->multipaths);
 427         kfree(conf);
 428         mddev->private = NULL;
 429 out:
 430         return -EIO;
 431 }
 432
 433 static void multipath_free(struct mddev *mddev, void *priv)
 434 {
 435         struct mpconf *conf = priv;
 436
 437         mempool_exit(&conf->pool);
 438         kfree(conf->multipaths);
 439         kfree(conf);
 440 }
 441
 442 static struct md_personality multipath_personality =
 443 {
 444         .name           = "multipath",
 445         .level          = LEVEL_MULTIPATH,
 446         .owner          = THIS_MODULE,
 447         .make_request   = multipath_make_request,
 448         .run            = multipath_run,
 449         .free           = multipath_free,
 450         .status         = multipath_status,
 451         .error_handler  = multipath_error,
 452         .hot_add_disk   = multipath_add_disk,
 453         .hot_remove_disk= multipath_remove_disk,
 454         .size           = multipath_size,
 455 };
 456
 457 static int __init multipath_init (void)
 458 {
 459         return register_md_personality (&multipath_personality);
 460 }
 461
 462 static void __exit multipath_exit (void)
 463 {
 464         unregister_md_personality (&multipath_personality);
 465 }
 466
 467 module_init(multipath_init);
 468 module_exit(multipath_exit);
 469 MODULE_LICENSE("GPL");
 470 MODULE_DESCRIPTION("simple multi-path personality for MD (deprecated)");
 471 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
 472 MODULE_ALIAS("md-multipath");
 473 MODULE_ALIAS("md-level--4");