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(&mp_bh->bio, NULL, 0); 125 __bio_clone_fast(&mp_bh->bio, bio); 126 127 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset; 128 bio_set_dev(&mp_bh->bio, multipath->rdev->bdev); 129 mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT; 130 mp_bh->bio.bi_end_io = multipath_end_request; 131 mp_bh->bio.bi_private = mp_bh; 132 mddev_check_writesame(mddev, &mp_bh->bio); 133 mddev_check_write_zeroes(mddev, &mp_bh->bio); 134 submit_bio_noacct(&mp_bh->bio); 135 return true; 136 } 137 138 static void multipath_status(struct seq_file *seq, struct mddev *mddev) 139 { 140 struct mpconf *conf = mddev->private; 141 int i; 142 143 seq_printf (seq, " [%d/%d] [", conf->raid_disks, 144 conf->raid_disks - mddev->degraded); 145 rcu_read_lock(); 146 for (i = 0; i < conf->raid_disks; i++) { 147 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); 148 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_"); 149 } 150 rcu_read_unlock(); 151 seq_putc(seq, ']'); 152 } 153 154 /* 155 * Careful, this can execute in IRQ contexts as well! 156 */ 157 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev) 158 { 159 struct mpconf *conf = mddev->private; 160 char b[BDEVNAME_SIZE]; 161 162 if (conf->raid_disks - mddev->degraded <= 1) { 163 /* 164 * Uh oh, we can do nothing if this is our last path, but 165 * first check if this is a queued request for a device 166 * which has just failed. 167 */ 168 pr_warn("multipath: only one IO path left and IO error.\n"); 169 /* leave it active... it's all we have */ 170 return; 171 } 172 /* 173 * Mark disk as unusable 174 */ 175 if (test_and_clear_bit(In_sync, &rdev->flags)) { 176 unsigned long flags; 177 spin_lock_irqsave(&conf->device_lock, flags); 178 mddev->degraded++; 179 spin_unlock_irqrestore(&conf->device_lock, flags); 180 } 181 set_bit(Faulty, &rdev->flags); 182 set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags); 183 pr_err("multipath: IO failure on %s, disabling IO path.\n" 184 "multipath: Operation continuing on %d IO paths.\n", 185 bdevname(rdev->bdev, b), 186 conf->raid_disks - mddev->degraded); 187 } 188 189 static void print_multipath_conf (struct mpconf *conf) 190 { 191 int i; 192 struct multipath_info *tmp; 193 194 pr_debug("MULTIPATH conf printout:\n"); 195 if (!conf) { 196 pr_debug("(conf==NULL)\n"); 197 return; 198 } 199 pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded, 200 conf->raid_disks); 201 202 for (i = 0; i < conf->raid_disks; i++) { 203 char b[BDEVNAME_SIZE]; 204 tmp = conf->multipaths + i; 205 if (tmp->rdev) 206 pr_debug(" disk%d, o:%d, dev:%s\n", 207 i,!test_bit(Faulty, &tmp->rdev->flags), 208 bdevname(tmp->rdev->bdev,b)); 209 } 210 } 211 212 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev) 213 { 214 struct mpconf *conf = mddev->private; 215 int err = -EEXIST; 216 int path; 217 struct multipath_info *p; 218 int first = 0; 219 int last = mddev->raid_disks - 1; 220 221 if (rdev->raid_disk >= 0) 222 first = last = rdev->raid_disk; 223 224 print_multipath_conf(conf); 225 226 for (path = first; path <= last; path++) 227 if ((p=conf->multipaths+path)->rdev == NULL) { 228 disk_stack_limits(mddev->gendisk, rdev->bdev, 229 rdev->data_offset << 9); 230 231 err = md_integrity_add_rdev(rdev, mddev); 232 if (err) 233 break; 234 spin_lock_irq(&conf->device_lock); 235 mddev->degraded--; 236 rdev->raid_disk = path; 237 set_bit(In_sync, &rdev->flags); 238 spin_unlock_irq(&conf->device_lock); 239 rcu_assign_pointer(p->rdev, rdev); 240 err = 0; 241 break; 242 } 243 244 print_multipath_conf(conf); 245 246 return err; 247 } 248 249 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 250 { 251 struct mpconf *conf = mddev->private; 252 int err = 0; 253 int number = rdev->raid_disk; 254 struct multipath_info *p = conf->multipaths + number; 255 256 print_multipath_conf(conf); 257 258 if (rdev == p->rdev) { 259 if (test_bit(In_sync, &rdev->flags) || 260 atomic_read(&rdev->nr_pending)) { 261 pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number); 262 err = -EBUSY; 263 goto abort; 264 } 265 p->rdev = NULL; 266 if (!test_bit(RemoveSynchronized, &rdev->flags)) { 267 synchronize_rcu(); 268 if (atomic_read(&rdev->nr_pending)) { 269 /* lost the race, try later */ 270 err = -EBUSY; 271 p->rdev = rdev; 272 goto abort; 273 } 274 } 275 err = md_integrity_register(mddev); 276 } 277 abort: 278 279 print_multipath_conf(conf); 280 return err; 281 } 282 283 /* 284 * This is a kernel thread which: 285 * 286 * 1. Retries failed read operations on working multipaths. 287 * 2. Updates the raid superblock when problems encounter. 288 * 3. Performs writes following reads for array syncronising. 289 */ 290 291 static void multipathd(struct md_thread *thread) 292 { 293 struct mddev *mddev = thread->mddev; 294 struct multipath_bh *mp_bh; 295 struct bio *bio; 296 unsigned long flags; 297 struct mpconf *conf = mddev->private; 298 struct list_head *head = &conf->retry_list; 299 300 md_check_recovery(mddev); 301 for (;;) { 302 char b[BDEVNAME_SIZE]; 303 spin_lock_irqsave(&conf->device_lock, flags); 304 if (list_empty(head)) 305 break; 306 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list); 307 list_del(head->prev); 308 spin_unlock_irqrestore(&conf->device_lock, flags); 309 310 bio = &mp_bh->bio; 311 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector; 312 313 if ((mp_bh->path = multipath_map (conf))<0) { 314 pr_err("multipath: %s: unrecoverable IO read error for block %llu\n", 315 bio_devname(bio, b), 316 (unsigned long long)bio->bi_iter.bi_sector); 317 multipath_end_bh_io(mp_bh, BLK_STS_IOERR); 318 } else { 319 pr_err("multipath: %s: redirecting sector %llu to another IO path\n", 320 bio_devname(bio, b), 321 (unsigned long long)bio->bi_iter.bi_sector); 322 *bio = *(mp_bh->master_bio); 323 bio->bi_iter.bi_sector += 324 conf->multipaths[mp_bh->path].rdev->data_offset; 325 bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev); 326 bio->bi_opf |= REQ_FAILFAST_TRANSPORT; 327 bio->bi_end_io = multipath_end_request; 328 bio->bi_private = mp_bh; 329 submit_bio_noacct(bio); 330 } 331 } 332 spin_unlock_irqrestore(&conf->device_lock, flags); 333 } 334 335 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks) 336 { 337 WARN_ONCE(sectors || raid_disks, 338 "%s does not support generic reshape\n", __func__); 339 340 return mddev->dev_sectors; 341 } 342 343 static int multipath_run (struct mddev *mddev) 344 { 345 struct mpconf *conf; 346 int disk_idx; 347 struct multipath_info *disk; 348 struct md_rdev *rdev; 349 int working_disks; 350 int ret; 351 352 if (md_check_no_bitmap(mddev)) 353 return -EINVAL; 354 355 if (mddev->level != LEVEL_MULTIPATH) { 356 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n", 357 mdname(mddev), mddev->level); 358 goto out; 359 } 360 /* 361 * copy the already verified devices into our private MULTIPATH 362 * bookkeeping area. [whatever we allocate in multipath_run(), 363 * should be freed in multipath_free()] 364 */ 365 366 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL); 367 mddev->private = conf; 368 if (!conf) 369 goto out; 370 371 conf->multipaths = kcalloc(mddev->raid_disks, 372 sizeof(struct multipath_info), 373 GFP_KERNEL); 374 if (!conf->multipaths) 375 goto out_free_conf; 376 377 working_disks = 0; 378 rdev_for_each(rdev, mddev) { 379 disk_idx = rdev->raid_disk; 380 if (disk_idx < 0 || 381 disk_idx >= mddev->raid_disks) 382 continue; 383 384 disk = conf->multipaths + disk_idx; 385 disk->rdev = rdev; 386 disk_stack_limits(mddev->gendisk, rdev->bdev, 387 rdev->data_offset << 9); 388 389 if (!test_bit(Faulty, &rdev->flags)) 390 working_disks++; 391 } 392 393 conf->raid_disks = mddev->raid_disks; 394 conf->mddev = mddev; 395 spin_lock_init(&conf->device_lock); 396 INIT_LIST_HEAD(&conf->retry_list); 397 398 if (!working_disks) { 399 pr_warn("multipath: no operational IO paths for %s\n", 400 mdname(mddev)); 401 goto out_free_conf; 402 } 403 mddev->degraded = conf->raid_disks - working_disks; 404 405 ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS, 406 sizeof(struct multipath_bh)); 407 if (ret) 408 goto out_free_conf; 409 410 mddev->thread = md_register_thread(multipathd, mddev, 411 "multipath"); 412 if (!mddev->thread) 413 goto out_free_conf; 414 415 pr_info("multipath: array %s active with %d out of %d IO paths\n", 416 mdname(mddev), conf->raid_disks - mddev->degraded, 417 mddev->raid_disks); 418 /* 419 * Ok, everything is just fine now 420 */ 421 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0)); 422 423 if (md_integrity_register(mddev)) 424 goto out_free_conf; 425 426 return 0; 427 428 out_free_conf: 429 mempool_exit(&conf->pool); 430 kfree(conf->multipaths); 431 kfree(conf); 432 mddev->private = NULL; 433 out: 434 return -EIO; 435 } 436 437 static void multipath_free(struct mddev *mddev, void *priv) 438 { 439 struct mpconf *conf = priv; 440 441 mempool_exit(&conf->pool); 442 kfree(conf->multipaths); 443 kfree(conf); 444 } 445 446 static struct md_personality multipath_personality = 447 { 448 .name = "multipath", 449 .level = LEVEL_MULTIPATH, 450 .owner = THIS_MODULE, 451 .make_request = multipath_make_request, 452 .run = multipath_run, 453 .free = multipath_free, 454 .status = multipath_status, 455 .error_handler = multipath_error, 456 .hot_add_disk = multipath_add_disk, 457 .hot_remove_disk= multipath_remove_disk, 458 .size = multipath_size, 459 }; 460 461 static int __init multipath_init (void) 462 { 463 return register_md_personality (&multipath_personality); 464 } 465 466 static void __exit multipath_exit (void) 467 { 468 unregister_md_personality (&multipath_personality); 469 } 470 471 module_init(multipath_init); 472 module_exit(multipath_exit); 473 MODULE_LICENSE("GPL"); 474 MODULE_DESCRIPTION("simple multi-path personality for MD"); 475 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */ 476 MODULE_ALIAS("md-multipath"); 477 MODULE_ALIAS("md-level--4"); 478