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 34static 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 atomic_inc(&rdev->nr_pending); 48 rcu_read_unlock(); 49 return i; 50 } 51 } 52 rcu_read_unlock(); 53 54 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n"); 55 return (-1); 56} 57 58static void multipath_reschedule_retry (struct multipath_bh *mp_bh) 59{ 60 unsigned long flags; 61 struct mddev *mddev = mp_bh->mddev; 62 struct mpconf *conf = mddev->private; 63 64 spin_lock_irqsave(&conf->device_lock, flags); 65 list_add(&mp_bh->retry_list, &conf->retry_list); 66 spin_unlock_irqrestore(&conf->device_lock, flags); 67 md_wakeup_thread(mddev->thread); 68} 69 70/* 71 * multipath_end_bh_io() is called when we have finished servicing a multipathed 72 * operation and are ready to return a success/failure code to the buffer 73 * cache layer. 74 */ 75static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err) 76{ 77 struct bio *bio = mp_bh->master_bio; 78 struct mpconf *conf = mp_bh->mddev->private; 79 80 bio_endio(bio, err); 81 mempool_free(mp_bh, conf->pool); 82} 83 84static void multipath_end_request(struct bio *bio, int error) 85{ 86 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 87 struct multipath_bh *mp_bh = bio->bi_private; 88 struct mpconf *conf = mp_bh->mddev->private; 89 struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev; 90 91 if (uptodate) 92 multipath_end_bh_io(mp_bh, 0); 93 else if (!(bio->bi_rw & REQ_RAHEAD)) { 94 /* 95 * oops, IO error: 96 */ 97 char b[BDEVNAME_SIZE]; 98 md_error (mp_bh->mddev, rdev); 99 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n", 100 bdevname(rdev->bdev,b), 101 (unsigned long long)bio->bi_iter.bi_sector); 102 multipath_reschedule_retry(mp_bh); 103 } else 104 multipath_end_bh_io(mp_bh, error); 105 rdev_dec_pending(rdev, conf->mddev); 106} 107 108static void multipath_make_request(struct mddev *mddev, struct bio * bio) 109{ 110 struct mpconf *conf = mddev->private; 111 struct multipath_bh * mp_bh; 112 struct multipath_info *multipath; 113 114 if (unlikely(bio->bi_rw & REQ_FLUSH)) { 115 md_flush_request(mddev, bio); 116 return; 117 } 118 119 mp_bh = mempool_alloc(conf->pool, GFP_NOIO); 120 121 mp_bh->master_bio = bio; 122 mp_bh->mddev = mddev; 123 124 mp_bh->path = multipath_map(conf); 125 if (mp_bh->path < 0) { 126 bio_endio(bio, -EIO); 127 mempool_free(mp_bh, conf->pool); 128 return; 129 } 130 multipath = conf->multipaths + mp_bh->path; 131 132 mp_bh->bio = *bio; 133 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset; 134 mp_bh->bio.bi_bdev = multipath->rdev->bdev; 135 mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT; 136 mp_bh->bio.bi_end_io = multipath_end_request; 137 mp_bh->bio.bi_private = mp_bh; 138 generic_make_request(&mp_bh->bio); 139 return; 140} 141 142static void multipath_status (struct seq_file *seq, struct mddev *mddev) 143{ 144 struct mpconf *conf = mddev->private; 145 int i; 146 147 seq_printf (seq, " [%d/%d] [", conf->raid_disks, 148 conf->raid_disks - mddev->degraded); 149 for (i = 0; i < conf->raid_disks; i++) 150 seq_printf (seq, "%s", 151 conf->multipaths[i].rdev && 152 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_"); 153 seq_printf (seq, "]"); 154} 155 156static int multipath_congested(void *data, int bits) 157{ 158 struct mddev *mddev = data; 159 struct mpconf *conf = mddev->private; 160 int i, ret = 0; 161 162 if (mddev_congested(mddev, bits)) 163 return 1; 164 165 rcu_read_lock(); 166 for (i = 0; i < mddev->raid_disks ; i++) { 167 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev); 168 if (rdev && !test_bit(Faulty, &rdev->flags)) { 169 struct request_queue *q = bdev_get_queue(rdev->bdev); 170 171 ret |= bdi_congested(&q->backing_dev_info, bits); 172 /* Just like multipath_map, we just check the 173 * first available device 174 */ 175 break; 176 } 177 } 178 rcu_read_unlock(); 179 return ret; 180} 181 182/* 183 * Careful, this can execute in IRQ contexts as well! 184 */ 185static void multipath_error (struct mddev *mddev, struct md_rdev *rdev) 186{ 187 struct mpconf *conf = mddev->private; 188 char b[BDEVNAME_SIZE]; 189 190 if (conf->raid_disks - mddev->degraded <= 1) { 191 /* 192 * Uh oh, we can do nothing if this is our last path, but 193 * first check if this is a queued request for a device 194 * which has just failed. 195 */ 196 printk(KERN_ALERT 197 "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_CHANGE_DEVS, &mddev->flags); 212 printk(KERN_ALERT "multipath: IO failure on %s," 213 " disabling IO path.\n" 214 "multipath: Operation continuing" 215 " on %d IO paths.\n", 216 bdevname(rdev->bdev, b), 217 conf->raid_disks - mddev->degraded); 218} 219 220static void print_multipath_conf (struct mpconf *conf) 221{ 222 int i; 223 struct multipath_info *tmp; 224 225 printk("MULTIPATH conf printout:\n"); 226 if (!conf) { 227 printk("(conf==NULL)\n"); 228 return; 229 } 230 printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded, 231 conf->raid_disks); 232 233 for (i = 0; i < conf->raid_disks; i++) { 234 char b[BDEVNAME_SIZE]; 235 tmp = conf->multipaths + i; 236 if (tmp->rdev) 237 printk(" disk%d, o:%d, dev:%s\n", 238 i,!test_bit(Faulty, &tmp->rdev->flags), 239 bdevname(tmp->rdev->bdev,b)); 240 } 241} 242 243static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev) 244{ 245 struct mpconf *conf = mddev->private; 246 struct request_queue *q; 247 int err = -EEXIST; 248 int path; 249 struct multipath_info *p; 250 int first = 0; 251 int last = mddev->raid_disks - 1; 252 253 if (rdev->raid_disk >= 0) 254 first = last = rdev->raid_disk; 255 256 print_multipath_conf(conf); 257 258 for (path = first; path <= last; path++) 259 if ((p=conf->multipaths+path)->rdev == NULL) { 260 q = rdev->bdev->bd_disk->queue; 261 disk_stack_limits(mddev->gendisk, rdev->bdev, 262 rdev->data_offset << 9); 263 264 /* as we don't honour merge_bvec_fn, we must never risk 265 * violating it, so limit ->max_segments to one, lying 266 * within a single page. 267 * (Note: it is very unlikely that a device with 268 * merge_bvec_fn will be involved in multipath.) 269 */ 270 if (q->merge_bvec_fn) { 271 blk_queue_max_segments(mddev->queue, 1); 272 blk_queue_segment_boundary(mddev->queue, 273 PAGE_CACHE_SIZE - 1); 274 } 275 276 spin_lock_irq(&conf->device_lock); 277 mddev->degraded--; 278 rdev->raid_disk = path; 279 set_bit(In_sync, &rdev->flags); 280 spin_unlock_irq(&conf->device_lock); 281 rcu_assign_pointer(p->rdev, rdev); 282 err = 0; 283 md_integrity_add_rdev(rdev, mddev); 284 break; 285 } 286 287 print_multipath_conf(conf); 288 289 return err; 290} 291 292static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev) 293{ 294 struct mpconf *conf = mddev->private; 295 int err = 0; 296 int number = rdev->raid_disk; 297 struct multipath_info *p = conf->multipaths + number; 298 299 print_multipath_conf(conf); 300 301 if (rdev == p->rdev) { 302 if (test_bit(In_sync, &rdev->flags) || 303 atomic_read(&rdev->nr_pending)) { 304 printk(KERN_ERR "hot-remove-disk, slot %d is identified" 305 " but is still operational!\n", number); 306 err = -EBUSY; 307 goto abort; 308 } 309 p->rdev = NULL; 310 synchronize_rcu(); 311 if (atomic_read(&rdev->nr_pending)) { 312 /* lost the race, try later */ 313 err = -EBUSY; 314 p->rdev = rdev; 315 goto abort; 316 } 317 err = md_integrity_register(mddev); 318 } 319abort: 320 321 print_multipath_conf(conf); 322 return err; 323} 324 325/* 326 * This is a kernel thread which: 327 * 328 * 1. Retries failed read operations on working multipaths. 329 * 2. Updates the raid superblock when problems encounter. 330 * 3. Performs writes following reads for array syncronising. 331 */ 332 333static void multipathd(struct md_thread *thread) 334{ 335 struct mddev *mddev = thread->mddev; 336 struct multipath_bh *mp_bh; 337 struct bio *bio; 338 unsigned long flags; 339 struct mpconf *conf = mddev->private; 340 struct list_head *head = &conf->retry_list; 341 342 md_check_recovery(mddev); 343 for (;;) { 344 char b[BDEVNAME_SIZE]; 345 spin_lock_irqsave(&conf->device_lock, flags); 346 if (list_empty(head)) 347 break; 348 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list); 349 list_del(head->prev); 350 spin_unlock_irqrestore(&conf->device_lock, flags); 351 352 bio = &mp_bh->bio; 353 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector; 354 355 if ((mp_bh->path = multipath_map (conf))<0) { 356 printk(KERN_ALERT "multipath: %s: unrecoverable IO read" 357 " error for block %llu\n", 358 bdevname(bio->bi_bdev,b), 359 (unsigned long long)bio->bi_iter.bi_sector); 360 multipath_end_bh_io(mp_bh, -EIO); 361 } else { 362 printk(KERN_ERR "multipath: %s: redirecting sector %llu" 363 " to another IO path\n", 364 bdevname(bio->bi_bdev,b), 365 (unsigned long long)bio->bi_iter.bi_sector); 366 *bio = *(mp_bh->master_bio); 367 bio->bi_iter.bi_sector += 368 conf->multipaths[mp_bh->path].rdev->data_offset; 369 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev; 370 bio->bi_rw |= REQ_FAILFAST_TRANSPORT; 371 bio->bi_end_io = multipath_end_request; 372 bio->bi_private = mp_bh; 373 generic_make_request(bio); 374 } 375 } 376 spin_unlock_irqrestore(&conf->device_lock, flags); 377} 378 379static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks) 380{ 381 WARN_ONCE(sectors || raid_disks, 382 "%s does not support generic reshape\n", __func__); 383 384 return mddev->dev_sectors; 385} 386 387static int multipath_run (struct mddev *mddev) 388{ 389 struct mpconf *conf; 390 int disk_idx; 391 struct multipath_info *disk; 392 struct md_rdev *rdev; 393 int working_disks; 394 395 if (md_check_no_bitmap(mddev)) 396 return -EINVAL; 397 398 if (mddev->level != LEVEL_MULTIPATH) { 399 printk("multipath: %s: raid level not set to multipath IO (%d)\n", 400 mdname(mddev), mddev->level); 401 goto out; 402 } 403 /* 404 * copy the already verified devices into our private MULTIPATH 405 * bookkeeping area. [whatever we allocate in multipath_run(), 406 * should be freed in multipath_stop()] 407 */ 408 409 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL); 410 mddev->private = conf; 411 if (!conf) { 412 printk(KERN_ERR 413 "multipath: couldn't allocate memory for %s\n", 414 mdname(mddev)); 415 goto out; 416 } 417 418 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks, 419 GFP_KERNEL); 420 if (!conf->multipaths) { 421 printk(KERN_ERR 422 "multipath: couldn't allocate memory for %s\n", 423 mdname(mddev)); 424 goto out_free_conf; 425 } 426 427 working_disks = 0; 428 rdev_for_each(rdev, mddev) { 429 disk_idx = rdev->raid_disk; 430 if (disk_idx < 0 || 431 disk_idx >= mddev->raid_disks) 432 continue; 433 434 disk = conf->multipaths + disk_idx; 435 disk->rdev = rdev; 436 disk_stack_limits(mddev->gendisk, rdev->bdev, 437 rdev->data_offset << 9); 438 439 /* as we don't honour merge_bvec_fn, we must never risk 440 * violating it, not that we ever expect a device with 441 * a merge_bvec_fn to be involved in multipath */ 442 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) { 443 blk_queue_max_segments(mddev->queue, 1); 444 blk_queue_segment_boundary(mddev->queue, 445 PAGE_CACHE_SIZE - 1); 446 } 447 448 if (!test_bit(Faulty, &rdev->flags)) 449 working_disks++; 450 } 451 452 conf->raid_disks = mddev->raid_disks; 453 conf->mddev = mddev; 454 spin_lock_init(&conf->device_lock); 455 INIT_LIST_HEAD(&conf->retry_list); 456 457 if (!working_disks) { 458 printk(KERN_ERR "multipath: no operational IO paths for %s\n", 459 mdname(mddev)); 460 goto out_free_conf; 461 } 462 mddev->degraded = conf->raid_disks - working_disks; 463 464 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS, 465 sizeof(struct multipath_bh)); 466 if (conf->pool == NULL) { 467 printk(KERN_ERR 468 "multipath: couldn't allocate memory for %s\n", 469 mdname(mddev)); 470 goto out_free_conf; 471 } 472 473 { 474 mddev->thread = md_register_thread(multipathd, mddev, 475 "multipath"); 476 if (!mddev->thread) { 477 printk(KERN_ERR "multipath: couldn't allocate thread" 478 " for %s\n", mdname(mddev)); 479 goto out_free_conf; 480 } 481 } 482 483 printk(KERN_INFO 484 "multipath: array %s active with %d out of %d IO paths\n", 485 mdname(mddev), conf->raid_disks - mddev->degraded, 486 mddev->raid_disks); 487 /* 488 * Ok, everything is just fine now 489 */ 490 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0)); 491 492 mddev->queue->backing_dev_info.congested_fn = multipath_congested; 493 mddev->queue->backing_dev_info.congested_data = mddev; 494 495 if (md_integrity_register(mddev)) 496 goto out_free_conf; 497 498 return 0; 499 500out_free_conf: 501 if (conf->pool) 502 mempool_destroy(conf->pool); 503 kfree(conf->multipaths); 504 kfree(conf); 505 mddev->private = NULL; 506out: 507 return -EIO; 508} 509 510static int multipath_stop (struct mddev *mddev) 511{ 512 struct mpconf *conf = mddev->private; 513 514 md_unregister_thread(&mddev->thread); 515 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/ 516 mempool_destroy(conf->pool); 517 kfree(conf->multipaths); 518 kfree(conf); 519 mddev->private = NULL; 520 return 0; 521} 522 523static struct md_personality multipath_personality = 524{ 525 .name = "multipath", 526 .level = LEVEL_MULTIPATH, 527 .owner = THIS_MODULE, 528 .make_request = multipath_make_request, 529 .run = multipath_run, 530 .stop = multipath_stop, 531 .status = multipath_status, 532 .error_handler = multipath_error, 533 .hot_add_disk = multipath_add_disk, 534 .hot_remove_disk= multipath_remove_disk, 535 .size = multipath_size, 536}; 537 538static int __init multipath_init (void) 539{ 540 return register_md_personality (&multipath_personality); 541} 542 543static void __exit multipath_exit (void) 544{ 545 unregister_md_personality (&multipath_personality); 546} 547 548module_init(multipath_init); 549module_exit(multipath_exit); 550MODULE_LICENSE("GPL"); 551MODULE_DESCRIPTION("simple multi-path personality for MD"); 552MODULE_ALIAS("md-personality-7"); /* MULTIPATH */ 553MODULE_ALIAS("md-multipath"); 554MODULE_ALIAS("md-level--4"); 555