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