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