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Linux 4.9.243
[linux/fpc-iii.git] / drivers / md / dm-mpath.c
blob0d437c98ab0872a8dd34e0f97b32729965fa7c63
1 /*
2 * Copyright (C) 2003 Sistina Software Limited.
3 * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
4 *
5 * This file is released under the GPL.
6 */
7
8 #include <linux/device-mapper.h>
9
10 #include "dm-rq.h"
11 #include "dm-bio-record.h"
12 #include "dm-path-selector.h"
13 #include "dm-uevent.h"
14
15 #include <linux/blkdev.h>
16 #include <linux/ctype.h>
17 #include <linux/init.h>
18 #include <linux/mempool.h>
19 #include <linux/module.h>
20 #include <linux/pagemap.h>
21 #include <linux/slab.h>
22 #include <linux/time.h>
23 #include <linux/workqueue.h>
24 #include <linux/delay.h>
25 #include <scsi/scsi_dh.h>
26 #include <linux/atomic.h>
27 #include <linux/blk-mq.h>
28
29 #define DM_MSG_PREFIX "multipath"
30 #define DM_PG_INIT_DELAY_MSECS 2000
31 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
32
33 /* Path properties */
34 struct pgpath {
35 struct list_head list;
36
37 struct priority_group *pg; /* Owning PG */
38 unsigned fail_count; /* Cumulative failure count */
39
40 struct dm_path path;
41 struct delayed_work activate_path;
42
43 bool is_active:1; /* Path status */
44 };
45
46 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
47
48 /*
49 * Paths are grouped into Priority Groups and numbered from 1 upwards.
50 * Each has a path selector which controls which path gets used.
51 */
52 struct priority_group {
53 struct list_head list;
54
55 struct multipath *m; /* Owning multipath instance */
56 struct path_selector ps;
57
58 unsigned pg_num; /* Reference number */
59 unsigned nr_pgpaths; /* Number of paths in PG */
60 struct list_head pgpaths;
61
62 bool bypassed:1; /* Temporarily bypass this PG? */
63 };
64
65 /* Multipath context */
66 struct multipath {
67 struct list_head list;
68 struct dm_target *ti;
69
70 const char *hw_handler_name;
71 char *hw_handler_params;
72
73 spinlock_t lock;
74
75 unsigned nr_priority_groups;
76 struct list_head priority_groups;
77
78 wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
79
80 struct pgpath *current_pgpath;
81 struct priority_group *current_pg;
82 struct priority_group *next_pg; /* Switch to this PG if set */
83
84 unsigned long flags; /* Multipath state flags */
85
86 unsigned pg_init_retries; /* Number of times to retry pg_init */
87 unsigned pg_init_delay_msecs; /* Number of msecs before pg_init retry */
88
89 atomic_t nr_valid_paths; /* Total number of usable paths */
90 atomic_t pg_init_in_progress; /* Only one pg_init allowed at once */
91 atomic_t pg_init_count; /* Number of times pg_init called */
92
93 unsigned queue_mode;
94
95 /*
96 * We must use a mempool of dm_mpath_io structs so that we
97 * can resubmit bios on error.
98 */
99 mempool_t *mpio_pool;
100
101 struct mutex work_mutex;
102 struct work_struct trigger_event;
103
104 struct work_struct process_queued_bios;
105 struct bio_list queued_bios;
106 };
107
108 /*
109 * Context information attached to each io we process.
110 */
111 struct dm_mpath_io {
112 struct pgpath *pgpath;
113 size_t nr_bytes;
114 };
115
116 typedef int (*action_fn) (struct pgpath *pgpath);
117
118 static struct kmem_cache *_mpio_cache;
119
120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
121 static void trigger_event(struct work_struct *work);
122 static void activate_or_offline_path(struct pgpath *pgpath);
123 static void activate_path_work(struct work_struct *work);
124 static void process_queued_bios(struct work_struct *work);
125
126 /*-----------------------------------------------
127 * Multipath state flags.
128 *-----------------------------------------------*/
129
130 #define MPATHF_QUEUE_IO 0 /* Must we queue all I/O? */
131 #define MPATHF_QUEUE_IF_NO_PATH 1 /* Queue I/O if last path fails? */
132 #define MPATHF_SAVED_QUEUE_IF_NO_PATH 2 /* Saved state during suspension */
133 #define MPATHF_RETAIN_ATTACHED_HW_HANDLER 3 /* If there's already a hw_handler present, don't change it. */
134 #define MPATHF_PG_INIT_DISABLED 4 /* pg_init is not currently allowed */
135 #define MPATHF_PG_INIT_REQUIRED 5 /* pg_init needs calling? */
136 #define MPATHF_PG_INIT_DELAY_RETRY 6 /* Delay pg_init retry? */
137
138 /*-----------------------------------------------
139 * Allocation routines
140 *-----------------------------------------------*/
141
142 static struct pgpath *alloc_pgpath(void)
143 {
144 struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
145
146 if (pgpath) {
147 pgpath->is_active = true;
148 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path_work);
149 }
150
151 return pgpath;
152 }
153
154 static void free_pgpath(struct pgpath *pgpath)
155 {
156 kfree(pgpath);
157 }
158
159 static struct priority_group *alloc_priority_group(void)
160 {
161 struct priority_group *pg;
162
163 pg = kzalloc(sizeof(*pg), GFP_KERNEL);
164
165 if (pg)
166 INIT_LIST_HEAD(&pg->pgpaths);
167
168 return pg;
169 }
170
171 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
172 {
173 struct pgpath *pgpath, *tmp;
174
175 list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
176 list_del(&pgpath->list);
177 dm_put_device(ti, pgpath->path.dev);
178 free_pgpath(pgpath);
179 }
180 }
181
182 static void free_priority_group(struct priority_group *pg,
183 struct dm_target *ti)
184 {
185 struct path_selector *ps = &pg->ps;
186
187 if (ps->type) {
188 ps->type->destroy(ps);
189 dm_put_path_selector(ps->type);
190 }
191
192 free_pgpaths(&pg->pgpaths, ti);
193 kfree(pg);
194 }
195
196 static struct multipath *alloc_multipath(struct dm_target *ti)
197 {
198 struct multipath *m;
199
200 m = kzalloc(sizeof(*m), GFP_KERNEL);
201 if (m) {
202 INIT_LIST_HEAD(&m->priority_groups);
203 spin_lock_init(&m->lock);
204 set_bit(MPATHF_QUEUE_IO, &m->flags);
205 atomic_set(&m->nr_valid_paths, 0);
206 atomic_set(&m->pg_init_in_progress, 0);
207 atomic_set(&m->pg_init_count, 0);
208 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
209 INIT_WORK(&m->trigger_event, trigger_event);
210 init_waitqueue_head(&m->pg_init_wait);
211 mutex_init(&m->work_mutex);
212
213 m->mpio_pool = NULL;
214 m->queue_mode = DM_TYPE_NONE;
215
216 m->ti = ti;
217 ti->private = m;
218 }
219
220 return m;
221 }
222
223 static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
224 {
225 if (m->queue_mode == DM_TYPE_NONE) {
226 /*
227 * Default to request-based.
228 */
229 if (dm_use_blk_mq(dm_table_get_md(ti->table)))
230 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
231 else
232 m->queue_mode = DM_TYPE_REQUEST_BASED;
233 }
234
235 if (m->queue_mode == DM_TYPE_REQUEST_BASED) {
236 unsigned min_ios = dm_get_reserved_rq_based_ios();
237
238 m->mpio_pool = mempool_create_slab_pool(min_ios, _mpio_cache);
239 if (!m->mpio_pool)
240 return -ENOMEM;
241 }
242 else if (m->queue_mode == DM_TYPE_BIO_BASED) {
243 INIT_WORK(&m->process_queued_bios, process_queued_bios);
244 /*
245 * bio-based doesn't support any direct scsi_dh management;
246 * it just discovers if a scsi_dh is attached.
247 */
248 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
249 }
250
251 dm_table_set_type(ti->table, m->queue_mode);
252
253 return 0;
254 }
255
256 static void free_multipath(struct multipath *m)
257 {
258 struct priority_group *pg, *tmp;
259
260 list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
261 list_del(&pg->list);
262 free_priority_group(pg, m->ti);
263 }
264
265 kfree(m->hw_handler_name);
266 kfree(m->hw_handler_params);
267 mempool_destroy(m->mpio_pool);
268 kfree(m);
269 }
270
271 static struct dm_mpath_io *get_mpio(union map_info *info)
272 {
273 return info->ptr;
274 }
275
276 static struct dm_mpath_io *set_mpio(struct multipath *m, union map_info *info)
277 {
278 struct dm_mpath_io *mpio;
279
280 if (!m->mpio_pool) {
281 /* Use blk-mq pdu memory requested via per_io_data_size */
282 mpio = get_mpio(info);
283 memset(mpio, 0, sizeof(*mpio));
284 return mpio;
285 }
286
287 mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
288 if (!mpio)
289 return NULL;
290
291 memset(mpio, 0, sizeof(*mpio));
292 info->ptr = mpio;
293
294 return mpio;
295 }
296
297 static void clear_request_fn_mpio(struct multipath *m, union map_info *info)
298 {
299 /* Only needed for non blk-mq (.request_fn) multipath */
300 if (m->mpio_pool) {
301 struct dm_mpath_io *mpio = info->ptr;
302
303 info->ptr = NULL;
304 mempool_free(mpio, m->mpio_pool);
305 }
306 }
307
308 static size_t multipath_per_bio_data_size(void)
309 {
310 return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
311 }
312
313 static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
314 {
315 return dm_per_bio_data(bio, multipath_per_bio_data_size());
316 }
317
318 static struct dm_bio_details *get_bio_details_from_bio(struct bio *bio)
319 {
320 /* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
321 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
322 void *bio_details = mpio + 1;
323
324 return bio_details;
325 }
326
327 static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p,
328 struct dm_bio_details **bio_details_p)
329 {
330 struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
331 struct dm_bio_details *bio_details = get_bio_details_from_bio(bio);
332
333 memset(mpio, 0, sizeof(*mpio));
334 memset(bio_details, 0, sizeof(*bio_details));
335 dm_bio_record(bio_details, bio);
336
337 if (mpio_p)
338 *mpio_p = mpio;
339 if (bio_details_p)
340 *bio_details_p = bio_details;
341 }
342
343 /*-----------------------------------------------
344 * Path selection
345 *-----------------------------------------------*/
346
347 static int __pg_init_all_paths(struct multipath *m)
348 {
349 struct pgpath *pgpath;
350 unsigned long pg_init_delay = 0;
351
352 if (atomic_read(&m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
353 return 0;
354
355 atomic_inc(&m->pg_init_count);
356 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
357
358 /* Check here to reset pg_init_required */
359 if (!m->current_pg)
360 return 0;
361
362 if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
363 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
364 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
365 list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
366 /* Skip failed paths */
367 if (!pgpath->is_active)
368 continue;
369 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
370 pg_init_delay))
371 atomic_inc(&m->pg_init_in_progress);
372 }
373 return atomic_read(&m->pg_init_in_progress);
374 }
375
376 static int pg_init_all_paths(struct multipath *m)
377 {
378 int r;
379 unsigned long flags;
380
381 spin_lock_irqsave(&m->lock, flags);
382 r = __pg_init_all_paths(m);
383 spin_unlock_irqrestore(&m->lock, flags);
384
385 return r;
386 }
387
388 static void __switch_pg(struct multipath *m, struct priority_group *pg)
389 {
390 m->current_pg = pg;
391
392 /* Must we initialise the PG first, and queue I/O till it's ready? */
393 if (m->hw_handler_name) {
394 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
395 set_bit(MPATHF_QUEUE_IO, &m->flags);
396 } else {
397 clear_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
398 clear_bit(MPATHF_QUEUE_IO, &m->flags);
399 }
400
401 atomic_set(&m->pg_init_count, 0);
402 }
403
404 static struct pgpath *choose_path_in_pg(struct multipath *m,
405 struct priority_group *pg,
406 size_t nr_bytes)
407 {
408 unsigned long flags;
409 struct dm_path *path;
410 struct pgpath *pgpath;
411
412 path = pg->ps.type->select_path(&pg->ps, nr_bytes);
413 if (!path)
414 return ERR_PTR(-ENXIO);
415
416 pgpath = path_to_pgpath(path);
417
418 if (unlikely(lockless_dereference(m->current_pg) != pg)) {
419 /* Only update current_pgpath if pg changed */
420 spin_lock_irqsave(&m->lock, flags);
421 m->current_pgpath = pgpath;
422 __switch_pg(m, pg);
423 spin_unlock_irqrestore(&m->lock, flags);
424 }
425
426 return pgpath;
427 }
428
429 static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
430 {
431 unsigned long flags;
432 struct priority_group *pg;
433 struct pgpath *pgpath;
434 unsigned bypassed = 1;
435
436 if (!atomic_read(&m->nr_valid_paths)) {
437 clear_bit(MPATHF_QUEUE_IO, &m->flags);
438 goto failed;
439 }
440
441 /* Were we instructed to switch PG? */
442 if (lockless_dereference(m->next_pg)) {
443 spin_lock_irqsave(&m->lock, flags);
444 pg = m->next_pg;
445 if (!pg) {
446 spin_unlock_irqrestore(&m->lock, flags);
447 goto check_current_pg;
448 }
449 m->next_pg = NULL;
450 spin_unlock_irqrestore(&m->lock, flags);
451 pgpath = choose_path_in_pg(m, pg, nr_bytes);
452 if (!IS_ERR_OR_NULL(pgpath))
453 return pgpath;
454 }
455
456 /* Don't change PG until it has no remaining paths */
457 check_current_pg:
458 pg = lockless_dereference(m->current_pg);
459 if (pg) {
460 pgpath = choose_path_in_pg(m, pg, nr_bytes);
461 if (!IS_ERR_OR_NULL(pgpath))
462 return pgpath;
463 }
464
465 /*
466 * Loop through priority groups until we find a valid path.
467 * First time we skip PGs marked 'bypassed'.
468 * Second time we only try the ones we skipped, but set
469 * pg_init_delay_retry so we do not hammer controllers.
470 */
471 do {
472 list_for_each_entry(pg, &m->priority_groups, list) {
473 if (pg->bypassed == !!bypassed)
474 continue;
475 pgpath = choose_path_in_pg(m, pg, nr_bytes);
476 if (!IS_ERR_OR_NULL(pgpath)) {
477 if (!bypassed)
478 set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
479 return pgpath;
480 }
481 }
482 } while (bypassed--);
483
484 failed:
485 spin_lock_irqsave(&m->lock, flags);
486 m->current_pgpath = NULL;
487 m->current_pg = NULL;
488 spin_unlock_irqrestore(&m->lock, flags);
489
490 return NULL;
491 }
492
493 /*
494 * Check whether bios must be queued in the device-mapper core rather
495 * than here in the target.
496 *
497 * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
498 * same value then we are not between multipath_presuspend()
499 * and multipath_resume() calls and we have no need to check
500 * for the DMF_NOFLUSH_SUSPENDING flag.
501 */
502 static bool __must_push_back(struct multipath *m)
503 {
504 return ((test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) !=
505 test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) &&
506 dm_noflush_suspending(m->ti));
507 }
508
509 static bool must_push_back_rq(struct multipath *m)
510 {
511 bool r;
512 unsigned long flags;
513
514 spin_lock_irqsave(&m->lock, flags);
515 r = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) ||
516 __must_push_back(m));
517 spin_unlock_irqrestore(&m->lock, flags);
518
519 return r;
520 }
521
522 static bool must_push_back_bio(struct multipath *m)
523 {
524 bool r;
525 unsigned long flags;
526
527 spin_lock_irqsave(&m->lock, flags);
528 r = __must_push_back(m);
529 spin_unlock_irqrestore(&m->lock, flags);
530
531 return r;
532 }
533
534 /*
535 * Map cloned requests (request-based multipath)
536 */
537 static int __multipath_map(struct dm_target *ti, struct request *clone,
538 union map_info *map_context,
539 struct request *rq, struct request **__clone)
540 {
541 struct multipath *m = ti->private;
542 int r = DM_MAPIO_REQUEUE;
543 size_t nr_bytes = clone ? blk_rq_bytes(clone) : blk_rq_bytes(rq);
544 struct pgpath *pgpath;
545 struct block_device *bdev;
546 struct dm_mpath_io *mpio;
547
548 /* Do we need to select a new pgpath? */
549 pgpath = lockless_dereference(m->current_pgpath);
550 if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
551 pgpath = choose_pgpath(m, nr_bytes);
552
553 if (!pgpath) {
554 if (must_push_back_rq(m))
555 return DM_MAPIO_DELAY_REQUEUE;
556 return -EIO; /* Failed */
557 } else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
558 test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
559 pg_init_all_paths(m);
560 return r;
561 }
562
563 mpio = set_mpio(m, map_context);
564 if (!mpio)
565 /* ENOMEM, requeue */
566 return r;
567
568 mpio->pgpath = pgpath;
569 mpio->nr_bytes = nr_bytes;
570
571 bdev = pgpath->path.dev->bdev;
572
573 if (clone) {
574 /*
575 * Old request-based interface: allocated clone is passed in.
576 * Used by: .request_fn stacked on .request_fn path(s).
577 */
578 clone->q = bdev_get_queue(bdev);
579 clone->rq_disk = bdev->bd_disk;
580 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
581 } else {
582 /*
583 * blk-mq request-based interface; used by both:
584 * .request_fn stacked on blk-mq path(s) and
585 * blk-mq stacked on blk-mq path(s).
586 */
587 *__clone = blk_mq_alloc_request(bdev_get_queue(bdev),
588 rq_data_dir(rq), BLK_MQ_REQ_NOWAIT);
589 if (IS_ERR(*__clone)) {
590 /* ENOMEM, requeue */
591 clear_request_fn_mpio(m, map_context);
592 return r;
593 }
594 (*__clone)->bio = (*__clone)->biotail = NULL;
595 (*__clone)->rq_disk = bdev->bd_disk;
596 (*__clone)->cmd_flags |= REQ_FAILFAST_TRANSPORT;
597 }
598
599 if (pgpath->pg->ps.type->start_io)
600 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
601 &pgpath->path,
602 nr_bytes);
603 return DM_MAPIO_REMAPPED;
604 }
605
606 static int multipath_map(struct dm_target *ti, struct request *clone,
607 union map_info *map_context)
608 {
609 return __multipath_map(ti, clone, map_context, NULL, NULL);
610 }
611
612 static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
613 union map_info *map_context,
614 struct request **clone)
615 {
616 return __multipath_map(ti, NULL, map_context, rq, clone);
617 }
618
619 static void multipath_release_clone(struct request *clone)
620 {
621 blk_mq_free_request(clone);
622 }
623
624 /*
625 * Map cloned bios (bio-based multipath)
626 */
627 static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_mpath_io *mpio)
628 {
629 size_t nr_bytes = bio->bi_iter.bi_size;
630 struct pgpath *pgpath;
631 unsigned long flags;
632 bool queue_io;
633
634 /* Do we need to select a new pgpath? */
635 pgpath = lockless_dereference(m->current_pgpath);
636 queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
637 if (!pgpath || !queue_io)
638 pgpath = choose_pgpath(m, nr_bytes);
639
640 if ((pgpath && queue_io) ||
641 (!pgpath && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))) {
642 /* Queue for the daemon to resubmit */
643 spin_lock_irqsave(&m->lock, flags);
644 bio_list_add(&m->queued_bios, bio);
645 spin_unlock_irqrestore(&m->lock, flags);
646 /* PG_INIT_REQUIRED cannot be set without QUEUE_IO */
647 if (queue_io || test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
648 pg_init_all_paths(m);
649 else if (!queue_io)
650 queue_work(kmultipathd, &m->process_queued_bios);
651 return DM_MAPIO_SUBMITTED;
652 }
653
654 if (!pgpath) {
655 if (!must_push_back_bio(m))
656 return -EIO;
657 return DM_MAPIO_REQUEUE;
658 }
659
660 mpio->pgpath = pgpath;
661 mpio->nr_bytes = nr_bytes;
662
663 bio->bi_error = 0;
664 bio->bi_bdev = pgpath->path.dev->bdev;
665 bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
666
667 if (pgpath->pg->ps.type->start_io)
668 pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
669 &pgpath->path,
670 nr_bytes);
671 return DM_MAPIO_REMAPPED;
672 }
673
674 static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
675 {
676 struct multipath *m = ti->private;
677 struct dm_mpath_io *mpio = NULL;
678
679 multipath_init_per_bio_data(bio, &mpio, NULL);
680
681 return __multipath_map_bio(m, bio, mpio);
682 }
683
684 static void process_queued_io_list(struct multipath *m)
685 {
686 if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
687 dm_mq_kick_requeue_list(dm_table_get_md(m->ti->table));
688 else if (m->queue_mode == DM_TYPE_BIO_BASED)
689 queue_work(kmultipathd, &m->process_queued_bios);
690 }
691
692 static void process_queued_bios(struct work_struct *work)
693 {
694 int r;
695 unsigned long flags;
696 struct bio *bio;
697 struct bio_list bios;
698 struct blk_plug plug;
699 struct multipath *m =
700 container_of(work, struct multipath, process_queued_bios);
701
702 bio_list_init(&bios);
703
704 spin_lock_irqsave(&m->lock, flags);
705
706 if (bio_list_empty(&m->queued_bios)) {
707 spin_unlock_irqrestore(&m->lock, flags);
708 return;
709 }
710
711 bio_list_merge(&bios, &m->queued_bios);
712 bio_list_init(&m->queued_bios);
713
714 spin_unlock_irqrestore(&m->lock, flags);
715
716 blk_start_plug(&plug);
717 while ((bio = bio_list_pop(&bios))) {
718 r = __multipath_map_bio(m, bio, get_mpio_from_bio(bio));
719 if (r < 0 || r == DM_MAPIO_REQUEUE) {
720 bio->bi_error = r;
721 bio_endio(bio);
722 } else if (r == DM_MAPIO_REMAPPED)
723 generic_make_request(bio);
724 }
725 blk_finish_plug(&plug);
726 }
727
728 /*
729 * If we run out of usable paths, should we queue I/O or error it?
730 */
731 static int queue_if_no_path(struct multipath *m, bool queue_if_no_path,
732 bool save_old_value)
733 {
734 unsigned long flags;
735
736 spin_lock_irqsave(&m->lock, flags);
737
738 if (save_old_value) {
739 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
740 set_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
741 else
742 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
743 } else {
744 if (queue_if_no_path)
745 set_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
746 else
747 clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
748 }
749 if (queue_if_no_path)
750 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
751 else
752 clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
753
754 spin_unlock_irqrestore(&m->lock, flags);
755
756 if (!queue_if_no_path) {
757 dm_table_run_md_queue_async(m->ti->table);
758 process_queued_io_list(m);
759 }
760
761 return 0;
762 }
763
764 /*
765 * An event is triggered whenever a path is taken out of use.
766 * Includes path failure and PG bypass.
767 */
768 static void trigger_event(struct work_struct *work)
769 {
770 struct multipath *m =
771 container_of(work, struct multipath, trigger_event);
772
773 dm_table_event(m->ti->table);
774 }
775
776 /*-----------------------------------------------------------------
777 * Constructor/argument parsing:
778 * <#multipath feature args> [<arg>]*
779 * <#hw_handler args> [hw_handler [<arg>]*]
780 * <#priority groups>
781 * <initial priority group>
782 * [<selector> <#selector args> [<arg>]*
783 * <#paths> <#per-path selector args>
784 * [<path> [<arg>]* ]+ ]+
785 *---------------------------------------------------------------*/
786 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
787 struct dm_target *ti)
788 {
789 int r;
790 struct path_selector_type *pst;
791 unsigned ps_argc;
792
793 static struct dm_arg _args[] = {
794 {0, 1024, "invalid number of path selector args"},
795 };
796
797 pst = dm_get_path_selector(dm_shift_arg(as));
798 if (!pst) {
799 ti->error = "unknown path selector type";
800 return -EINVAL;
801 }
802
803 r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
804 if (r) {
805 dm_put_path_selector(pst);
806 return -EINVAL;
807 }
808
809 r = pst->create(&pg->ps, ps_argc, as->argv);
810 if (r) {
811 dm_put_path_selector(pst);
812 ti->error = "path selector constructor failed";
813 return r;
814 }
815
816 pg->ps.type = pst;
817 dm_consume_args(as, ps_argc);
818
819 return 0;
820 }
821
822 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
823 struct dm_target *ti)
824 {
825 int r;
826 struct pgpath *p;
827 struct multipath *m = ti->private;
828 struct request_queue *q = NULL;
829 const char *attached_handler_name;
830
831 /* we need at least a path arg */
832 if (as->argc < 1) {
833 ti->error = "no device given";
834 return ERR_PTR(-EINVAL);
835 }
836
837 p = alloc_pgpath();
838 if (!p)
839 return ERR_PTR(-ENOMEM);
840
841 r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
842 &p->path.dev);
843 if (r) {
844 ti->error = "error getting device";
845 goto bad;
846 }
847
848 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) || m->hw_handler_name)
849 q = bdev_get_queue(p->path.dev->bdev);
850
851 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
852 retain:
853 attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
854 if (attached_handler_name) {
855 /*
856 * Reset hw_handler_name to match the attached handler
857 * and clear any hw_handler_params associated with the
858 * ignored handler.
859 *
860 * NB. This modifies the table line to show the actual
861 * handler instead of the original table passed in.
862 */
863 kfree(m->hw_handler_name);
864 m->hw_handler_name = attached_handler_name;
865
866 kfree(m->hw_handler_params);
867 m->hw_handler_params = NULL;
868 }
869 }
870
871 if (m->hw_handler_name) {
872 r = scsi_dh_attach(q, m->hw_handler_name);
873 if (r == -EBUSY) {
874 char b[BDEVNAME_SIZE];
875
876 printk(KERN_INFO "dm-mpath: retaining handler on device %s\n",
877 bdevname(p->path.dev->bdev, b));
878 goto retain;
879 }
880 if (r < 0) {
881 ti->error = "error attaching hardware handler";
882 dm_put_device(ti, p->path.dev);
883 goto bad;
884 }
885
886 if (m->hw_handler_params) {
887 r = scsi_dh_set_params(q, m->hw_handler_params);
888 if (r < 0) {
889 ti->error = "unable to set hardware "
890 "handler parameters";
891 dm_put_device(ti, p->path.dev);
892 goto bad;
893 }
894 }
895 }
896
897 r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
898 if (r) {
899 dm_put_device(ti, p->path.dev);
900 goto bad;
901 }
902
903 return p;
904
905 bad:
906 free_pgpath(p);
907 return ERR_PTR(r);
908 }
909
910 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
911 struct multipath *m)
912 {
913 static struct dm_arg _args[] = {
914 {1, 1024, "invalid number of paths"},
915 {0, 1024, "invalid number of selector args"}
916 };
917
918 int r;
919 unsigned i, nr_selector_args, nr_args;
920 struct priority_group *pg;
921 struct dm_target *ti = m->ti;
922
923 if (as->argc < 2) {
924 as->argc = 0;
925 ti->error = "not enough priority group arguments";
926 return ERR_PTR(-EINVAL);
927 }
928
929 pg = alloc_priority_group();
930 if (!pg) {
931 ti->error = "couldn't allocate priority group";
932 return ERR_PTR(-ENOMEM);
933 }
934 pg->m = m;
935
936 r = parse_path_selector(as, pg, ti);
937 if (r)
938 goto bad;
939
940 /*
941 * read the paths
942 */
943 r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
944 if (r)
945 goto bad;
946
947 r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
948 if (r)
949 goto bad;
950
951 nr_args = 1 + nr_selector_args;
952 for (i = 0; i < pg->nr_pgpaths; i++) {
953 struct pgpath *pgpath;
954 struct dm_arg_set path_args;
955
956 if (as->argc < nr_args) {
957 ti->error = "not enough path parameters";
958 r = -EINVAL;
959 goto bad;
960 }
961
962 path_args.argc = nr_args;
963 path_args.argv = as->argv;
964
965 pgpath = parse_path(&path_args, &pg->ps, ti);
966 if (IS_ERR(pgpath)) {
967 r = PTR_ERR(pgpath);
968 goto bad;
969 }
970
971 pgpath->pg = pg;
972 list_add_tail(&pgpath->list, &pg->pgpaths);
973 dm_consume_args(as, nr_args);
974 }
975
976 return pg;
977
978 bad:
979 free_priority_group(pg, ti);
980 return ERR_PTR(r);
981 }
982
983 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
984 {
985 unsigned hw_argc;
986 int ret;
987 struct dm_target *ti = m->ti;
988
989 static struct dm_arg _args[] = {
990 {0, 1024, "invalid number of hardware handler args"},
991 };
992
993 if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
994 return -EINVAL;
995
996 if (!hw_argc)
997 return 0;
998
999 if (m->queue_mode == DM_TYPE_BIO_BASED) {
1000 dm_consume_args(as, hw_argc);
1001 DMERR("bio-based multipath doesn't allow hardware handler args");
1002 return 0;
1003 }
1004
1005 m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
1006
1007 if (hw_argc > 1) {
1008 char *p;
1009 int i, j, len = 4;
1010
1011 for (i = 0; i <= hw_argc - 2; i++)
1012 len += strlen(as->argv[i]) + 1;
1013 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1014 if (!p) {
1015 ti->error = "memory allocation failed";
1016 ret = -ENOMEM;
1017 goto fail;
1018 }
1019 j = sprintf(p, "%d", hw_argc - 1);
1020 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
1021 j = sprintf(p, "%s", as->argv[i]);
1022 }
1023 dm_consume_args(as, hw_argc - 1);
1024
1025 return 0;
1026 fail:
1027 kfree(m->hw_handler_name);
1028 m->hw_handler_name = NULL;
1029 return ret;
1030 }
1031
1032 static int parse_features(struct dm_arg_set *as, struct multipath *m)
1033 {
1034 int r;
1035 unsigned argc;
1036 struct dm_target *ti = m->ti;
1037 const char *arg_name;
1038
1039 static struct dm_arg _args[] = {
1040 {0, 8, "invalid number of feature args"},
1041 {1, 50, "pg_init_retries must be between 1 and 50"},
1042 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1043 };
1044
1045 r = dm_read_arg_group(_args, as, &argc, &ti->error);
1046 if (r)
1047 return -EINVAL;
1048
1049 if (!argc)
1050 return 0;
1051
1052 do {
1053 arg_name = dm_shift_arg(as);
1054 argc--;
1055
1056 if (!strcasecmp(arg_name, "queue_if_no_path")) {
1057 r = queue_if_no_path(m, true, false);
1058 continue;
1059 }
1060
1061 if (!strcasecmp(arg_name, "retain_attached_hw_handler")) {
1062 set_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags);
1063 continue;
1064 }
1065
1066 if (!strcasecmp(arg_name, "pg_init_retries") &&
1067 (argc >= 1)) {
1068 r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
1069 argc--;
1070 continue;
1071 }
1072
1073 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
1074 (argc >= 1)) {
1075 r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
1076 argc--;
1077 continue;
1078 }
1079
1080 if (!strcasecmp(arg_name, "queue_mode") &&
1081 (argc >= 1)) {
1082 const char *queue_mode_name = dm_shift_arg(as);
1083
1084 if (!strcasecmp(queue_mode_name, "bio"))
1085 m->queue_mode = DM_TYPE_BIO_BASED;
1086 else if (!strcasecmp(queue_mode_name, "rq"))
1087 m->queue_mode = DM_TYPE_REQUEST_BASED;
1088 else if (!strcasecmp(queue_mode_name, "mq"))
1089 m->queue_mode = DM_TYPE_MQ_REQUEST_BASED;
1090 else {
1091 ti->error = "Unknown 'queue_mode' requested";
1092 r = -EINVAL;
1093 }
1094 argc--;
1095 continue;
1096 }
1097
1098 ti->error = "Unrecognised multipath feature request";
1099 r = -EINVAL;
1100 } while (argc && !r);
1101
1102 return r;
1103 }
1104
1105 static int multipath_ctr(struct dm_target *ti, unsigned argc, char **argv)
1106 {
1107 /* target arguments */
1108 static struct dm_arg _args[] = {
1109 {0, 1024, "invalid number of priority groups"},
1110 {0, 1024, "invalid initial priority group number"},
1111 };
1112
1113 int r;
1114 struct multipath *m;
1115 struct dm_arg_set as;
1116 unsigned pg_count = 0;
1117 unsigned next_pg_num;
1118
1119 as.argc = argc;
1120 as.argv = argv;
1121
1122 m = alloc_multipath(ti);
1123 if (!m) {
1124 ti->error = "can't allocate multipath";
1125 return -EINVAL;
1126 }
1127
1128 r = parse_features(&as, m);
1129 if (r)
1130 goto bad;
1131
1132 r = alloc_multipath_stage2(ti, m);
1133 if (r)
1134 goto bad;
1135
1136 r = parse_hw_handler(&as, m);
1137 if (r)
1138 goto bad;
1139
1140 r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
1141 if (r)
1142 goto bad;
1143
1144 r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
1145 if (r)
1146 goto bad;
1147
1148 if ((!m->nr_priority_groups && next_pg_num) ||
1149 (m->nr_priority_groups && !next_pg_num)) {
1150 ti->error = "invalid initial priority group";
1151 r = -EINVAL;
1152 goto bad;
1153 }
1154
1155 /* parse the priority groups */
1156 while (as.argc) {
1157 struct priority_group *pg;
1158 unsigned nr_valid_paths = atomic_read(&m->nr_valid_paths);
1159
1160 pg = parse_priority_group(&as, m);
1161 if (IS_ERR(pg)) {
1162 r = PTR_ERR(pg);
1163 goto bad;
1164 }
1165
1166 nr_valid_paths += pg->nr_pgpaths;
1167 atomic_set(&m->nr_valid_paths, nr_valid_paths);
1168
1169 list_add_tail(&pg->list, &m->priority_groups);
1170 pg_count++;
1171 pg->pg_num = pg_count;
1172 if (!--next_pg_num)
1173 m->next_pg = pg;
1174 }
1175
1176 if (pg_count != m->nr_priority_groups) {
1177 ti->error = "priority group count mismatch";
1178 r = -EINVAL;
1179 goto bad;
1180 }
1181
1182 ti->num_flush_bios = 1;
1183 ti->num_discard_bios = 1;
1184 ti->num_write_same_bios = 1;
1185 if (m->queue_mode == DM_TYPE_BIO_BASED)
1186 ti->per_io_data_size = multipath_per_bio_data_size();
1187 else if (m->queue_mode == DM_TYPE_MQ_REQUEST_BASED)
1188 ti->per_io_data_size = sizeof(struct dm_mpath_io);
1189
1190 return 0;
1191
1192 bad:
1193 free_multipath(m);
1194 return r;
1195 }
1196
1197 static void multipath_wait_for_pg_init_completion(struct multipath *m)
1198 {
1199 DEFINE_WAIT(wait);
1200
1201 while (1) {
1202 prepare_to_wait(&m->pg_init_wait, &wait, TASK_UNINTERRUPTIBLE);
1203
1204 if (!atomic_read(&m->pg_init_in_progress))
1205 break;
1206
1207 io_schedule();
1208 }
1209 finish_wait(&m->pg_init_wait, &wait);
1210 }
1211
1212 static void flush_multipath_work(struct multipath *m)
1213 {
1214 set_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1215 smp_mb__after_atomic();
1216
1217 flush_workqueue(kmpath_handlerd);
1218 multipath_wait_for_pg_init_completion(m);
1219 flush_workqueue(kmultipathd);
1220 flush_work(&m->trigger_event);
1221
1222 clear_bit(MPATHF_PG_INIT_DISABLED, &m->flags);
1223 smp_mb__after_atomic();
1224 }
1225
1226 static void multipath_dtr(struct dm_target *ti)
1227 {
1228 struct multipath *m = ti->private;
1229
1230 flush_multipath_work(m);
1231 free_multipath(m);
1232 }
1233
1234 /*
1235 * Take a path out of use.
1236 */
1237 static int fail_path(struct pgpath *pgpath)
1238 {
1239 unsigned long flags;
1240 struct multipath *m = pgpath->pg->m;
1241
1242 spin_lock_irqsave(&m->lock, flags);
1243
1244 if (!pgpath->is_active)
1245 goto out;
1246
1247 DMWARN("Failing path %s.", pgpath->path.dev->name);
1248
1249 pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1250 pgpath->is_active = false;
1251 pgpath->fail_count++;
1252
1253 atomic_dec(&m->nr_valid_paths);
1254
1255 if (pgpath == m->current_pgpath)
1256 m->current_pgpath = NULL;
1257
1258 dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1259 pgpath->path.dev->name, atomic_read(&m->nr_valid_paths));
1260
1261 schedule_work(&m->trigger_event);
1262
1263 out:
1264 spin_unlock_irqrestore(&m->lock, flags);
1265
1266 return 0;
1267 }
1268
1269 /*
1270 * Reinstate a previously-failed path
1271 */
1272 static int reinstate_path(struct pgpath *pgpath)
1273 {
1274 int r = 0, run_queue = 0;
1275 unsigned long flags;
1276 struct multipath *m = pgpath->pg->m;
1277 unsigned nr_valid_paths;
1278
1279 spin_lock_irqsave(&m->lock, flags);
1280
1281 if (pgpath->is_active)
1282 goto out;
1283
1284 DMWARN("Reinstating path %s.", pgpath->path.dev->name);
1285
1286 r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1287 if (r)
1288 goto out;
1289
1290 pgpath->is_active = true;
1291
1292 nr_valid_paths = atomic_inc_return(&m->nr_valid_paths);
1293 if (nr_valid_paths == 1) {
1294 m->current_pgpath = NULL;
1295 run_queue = 1;
1296 } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1297 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1298 atomic_inc(&m->pg_init_in_progress);
1299 }
1300
1301 dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1302 pgpath->path.dev->name, nr_valid_paths);
1303
1304 schedule_work(&m->trigger_event);
1305
1306 out:
1307 spin_unlock_irqrestore(&m->lock, flags);
1308 if (run_queue) {
1309 dm_table_run_md_queue_async(m->ti->table);
1310 process_queued_io_list(m);
1311 }
1312
1313 return r;
1314 }
1315
1316 /*
1317 * Fail or reinstate all paths that match the provided struct dm_dev.
1318 */
1319 static int action_dev(struct multipath *m, struct dm_dev *dev,
1320 action_fn action)
1321 {
1322 int r = -EINVAL;
1323 struct pgpath *pgpath;
1324 struct priority_group *pg;
1325
1326 list_for_each_entry(pg, &m->priority_groups, list) {
1327 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1328 if (pgpath->path.dev == dev)
1329 r = action(pgpath);
1330 }
1331 }
1332
1333 return r;
1334 }
1335
1336 /*
1337 * Temporarily try to avoid having to use the specified PG
1338 */
1339 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1340 bool bypassed)
1341 {
1342 unsigned long flags;
1343
1344 spin_lock_irqsave(&m->lock, flags);
1345
1346 pg->bypassed = bypassed;
1347 m->current_pgpath = NULL;
1348 m->current_pg = NULL;
1349
1350 spin_unlock_irqrestore(&m->lock, flags);
1351
1352 schedule_work(&m->trigger_event);
1353 }
1354
1355 /*
1356 * Switch to using the specified PG from the next I/O that gets mapped
1357 */
1358 static int switch_pg_num(struct multipath *m, const char *pgstr)
1359 {
1360 struct priority_group *pg;
1361 unsigned pgnum;
1362 unsigned long flags;
1363 char dummy;
1364
1365 if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1366 (pgnum > m->nr_priority_groups)) {
1367 DMWARN("invalid PG number supplied to switch_pg_num");
1368 return -EINVAL;
1369 }
1370
1371 spin_lock_irqsave(&m->lock, flags);
1372 list_for_each_entry(pg, &m->priority_groups, list) {
1373 pg->bypassed = false;
1374 if (--pgnum)
1375 continue;
1376
1377 m->current_pgpath = NULL;
1378 m->current_pg = NULL;
1379 m->next_pg = pg;
1380 }
1381 spin_unlock_irqrestore(&m->lock, flags);
1382
1383 schedule_work(&m->trigger_event);
1384 return 0;
1385 }
1386
1387 /*
1388 * Set/clear bypassed status of a PG.
1389 * PGs are numbered upwards from 1 in the order they were declared.
1390 */
1391 static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1392 {
1393 struct priority_group *pg;
1394 unsigned pgnum;
1395 char dummy;
1396
1397 if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1398 (pgnum > m->nr_priority_groups)) {
1399 DMWARN("invalid PG number supplied to bypass_pg");
1400 return -EINVAL;
1401 }
1402
1403 list_for_each_entry(pg, &m->priority_groups, list) {
1404 if (!--pgnum)
1405 break;
1406 }
1407
1408 bypass_pg(m, pg, bypassed);
1409 return 0;
1410 }
1411
1412 /*
1413 * Should we retry pg_init immediately?
1414 */
1415 static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1416 {
1417 unsigned long flags;
1418 bool limit_reached = false;
1419
1420 spin_lock_irqsave(&m->lock, flags);
1421
1422 if (atomic_read(&m->pg_init_count) <= m->pg_init_retries &&
1423 !test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1424 set_bit(MPATHF_PG_INIT_REQUIRED, &m->flags);
1425 else
1426 limit_reached = true;
1427
1428 spin_unlock_irqrestore(&m->lock, flags);
1429
1430 return limit_reached;
1431 }
1432
1433 static void pg_init_done(void *data, int errors)
1434 {
1435 struct pgpath *pgpath = data;
1436 struct priority_group *pg = pgpath->pg;
1437 struct multipath *m = pg->m;
1438 unsigned long flags;
1439 bool delay_retry = false;
1440
1441 /* device or driver problems */
1442 switch (errors) {
1443 case SCSI_DH_OK:
1444 break;
1445 case SCSI_DH_NOSYS:
1446 if (!m->hw_handler_name) {
1447 errors = 0;
1448 break;
1449 }
1450 DMERR("Could not failover the device: Handler scsi_dh_%s "
1451 "Error %d.", m->hw_handler_name, errors);
1452 /*
1453 * Fail path for now, so we do not ping pong
1454 */
1455 fail_path(pgpath);
1456 break;
1457 case SCSI_DH_DEV_TEMP_BUSY:
1458 /*
1459 * Probably doing something like FW upgrade on the
1460 * controller so try the other pg.
1461 */
1462 bypass_pg(m, pg, true);
1463 break;
1464 case SCSI_DH_RETRY:
1465 /* Wait before retrying. */
1466 delay_retry = 1;
1467 case SCSI_DH_IMM_RETRY:
1468 case SCSI_DH_RES_TEMP_UNAVAIL:
1469 if (pg_init_limit_reached(m, pgpath))
1470 fail_path(pgpath);
1471 errors = 0;
1472 break;
1473 case SCSI_DH_DEV_OFFLINED:
1474 default:
1475 /*
1476 * We probably do not want to fail the path for a device
1477 * error, but this is what the old dm did. In future
1478 * patches we can do more advanced handling.
1479 */
1480 fail_path(pgpath);
1481 }
1482
1483 spin_lock_irqsave(&m->lock, flags);
1484 if (errors) {
1485 if (pgpath == m->current_pgpath) {
1486 DMERR("Could not failover device. Error %d.", errors);
1487 m->current_pgpath = NULL;
1488 m->current_pg = NULL;
1489 }
1490 } else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1491 pg->bypassed = false;
1492
1493 if (atomic_dec_return(&m->pg_init_in_progress) > 0)
1494 /* Activations of other paths are still on going */
1495 goto out;
1496
1497 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1498 if (delay_retry)
1499 set_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1500 else
1501 clear_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags);
1502
1503 if (__pg_init_all_paths(m))
1504 goto out;
1505 }
1506 clear_bit(MPATHF_QUEUE_IO, &m->flags);
1507
1508 process_queued_io_list(m);
1509
1510 /*
1511 * Wake up any thread waiting to suspend.
1512 */
1513 wake_up(&m->pg_init_wait);
1514
1515 out:
1516 spin_unlock_irqrestore(&m->lock, flags);
1517 }
1518
1519 static void activate_or_offline_path(struct pgpath *pgpath)
1520 {
1521 struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1522
1523 if (pgpath->is_active && !blk_queue_dying(q))
1524 scsi_dh_activate(q, pg_init_done, pgpath);
1525 else
1526 pg_init_done(pgpath, SCSI_DH_DEV_OFFLINED);
1527 }
1528
1529 static void activate_path_work(struct work_struct *work)
1530 {
1531 struct pgpath *pgpath =
1532 container_of(work, struct pgpath, activate_path.work);
1533
1534 activate_or_offline_path(pgpath);
1535 }
1536
1537 static int noretry_error(int error)
1538 {
1539 switch (error) {
1540 case -EBADE:
1541 /*
1542 * EBADE signals an reservation conflict.
1543 * We shouldn't fail the path here as we can communicate with
1544 * the target. We should failover to the next path, but in
1545 * doing so we might be causing a ping-pong between paths.
1546 * So just return the reservation conflict error.
1547 */
1548 case -EOPNOTSUPP:
1549 case -EREMOTEIO:
1550 case -EILSEQ:
1551 case -ENODATA:
1552 case -ENOSPC:
1553 return 1;
1554 }
1555
1556 /* Anything else could be a path failure, so should be retried */
1557 return 0;
1558 }
1559
1560 /*
1561 * end_io handling
1562 */
1563 static int do_end_io(struct multipath *m, struct request *clone,
1564 int error, struct dm_mpath_io *mpio)
1565 {
1566 /*
1567 * We don't queue any clone request inside the multipath target
1568 * during end I/O handling, since those clone requests don't have
1569 * bio clones. If we queue them inside the multipath target,
1570 * we need to make bio clones, that requires memory allocation.
1571 * (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1572 * don't have bio clones.)
1573 * Instead of queueing the clone request here, we queue the original
1574 * request into dm core, which will remake a clone request and
1575 * clone bios for it and resubmit it later.
1576 */
1577 int r = DM_ENDIO_REQUEUE;
1578
1579 if (!error && !clone->errors)
1580 return 0; /* I/O complete */
1581
1582 if (noretry_error(error))
1583 return error;
1584
1585 if (mpio->pgpath)
1586 fail_path(mpio->pgpath);
1587
1588 if (!atomic_read(&m->nr_valid_paths)) {
1589 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1590 if (!must_push_back_rq(m))
1591 r = -EIO;
1592 }
1593 }
1594
1595 return r;
1596 }
1597
1598 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1599 int error, union map_info *map_context)
1600 {
1601 struct multipath *m = ti->private;
1602 struct dm_mpath_io *mpio = get_mpio(map_context);
1603 struct pgpath *pgpath;
1604 struct path_selector *ps;
1605 int r;
1606
1607 BUG_ON(!mpio);
1608
1609 r = do_end_io(m, clone, error, mpio);
1610 pgpath = mpio->pgpath;
1611 if (pgpath) {
1612 ps = &pgpath->pg->ps;
1613 if (ps->type->end_io)
1614 ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1615 }
1616 clear_request_fn_mpio(m, map_context);
1617
1618 return r;
1619 }
1620
1621 static int do_end_io_bio(struct multipath *m, struct bio *clone,
1622 int error, struct dm_mpath_io *mpio)
1623 {
1624 unsigned long flags;
1625
1626 if (!error)
1627 return 0; /* I/O complete */
1628
1629 if (noretry_error(error))
1630 return error;
1631
1632 if (mpio->pgpath)
1633 fail_path(mpio->pgpath);
1634
1635 if (!atomic_read(&m->nr_valid_paths)) {
1636 if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1637 if (!must_push_back_bio(m))
1638 return -EIO;
1639 return DM_ENDIO_REQUEUE;
1640 }
1641 }
1642
1643 /* Queue for the daemon to resubmit */
1644 dm_bio_restore(get_bio_details_from_bio(clone), clone);
1645
1646 spin_lock_irqsave(&m->lock, flags);
1647 bio_list_add(&m->queued_bios, clone);
1648 spin_unlock_irqrestore(&m->lock, flags);
1649 if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
1650 queue_work(kmultipathd, &m->process_queued_bios);
1651
1652 return DM_ENDIO_INCOMPLETE;
1653 }
1654
1655 static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone, int error)
1656 {
1657 struct multipath *m = ti->private;
1658 struct dm_mpath_io *mpio = get_mpio_from_bio(clone);
1659 struct pgpath *pgpath;
1660 struct path_selector *ps;
1661 int r;
1662
1663 BUG_ON(!mpio);
1664
1665 r = do_end_io_bio(m, clone, error, mpio);
1666 pgpath = mpio->pgpath;
1667 if (pgpath) {
1668 ps = &pgpath->pg->ps;
1669 if (ps->type->end_io)
1670 ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1671 }
1672
1673 return r;
1674 }
1675
1676 /*
1677 * Suspend can't complete until all the I/O is processed so if
1678 * the last path fails we must error any remaining I/O.
1679 * Note that if the freeze_bdev fails while suspending, the
1680 * queue_if_no_path state is lost - userspace should reset it.
1681 */
1682 static void multipath_presuspend(struct dm_target *ti)
1683 {
1684 struct multipath *m = ti->private;
1685
1686 queue_if_no_path(m, false, true);
1687 }
1688
1689 static void multipath_postsuspend(struct dm_target *ti)
1690 {
1691 struct multipath *m = ti->private;
1692
1693 mutex_lock(&m->work_mutex);
1694 flush_multipath_work(m);
1695 mutex_unlock(&m->work_mutex);
1696 }
1697
1698 /*
1699 * Restore the queue_if_no_path setting.
1700 */
1701 static void multipath_resume(struct dm_target *ti)
1702 {
1703 struct multipath *m = ti->private;
1704 unsigned long flags;
1705
1706 spin_lock_irqsave(&m->lock, flags);
1707 if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags))
1708 set_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1709 else
1710 clear_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
1711 spin_unlock_irqrestore(&m->lock, flags);
1712 }
1713
1714 /*
1715 * Info output has the following format:
1716 * num_multipath_feature_args [multipath_feature_args]*
1717 * num_handler_status_args [handler_status_args]*
1718 * num_groups init_group_number
1719 * [A|D|E num_ps_status_args [ps_status_args]*
1720 * num_paths num_selector_args
1721 * [path_dev A|F fail_count [selector_args]* ]+ ]+
1722 *
1723 * Table output has the following format (identical to the constructor string):
1724 * num_feature_args [features_args]*
1725 * num_handler_args hw_handler [hw_handler_args]*
1726 * num_groups init_group_number
1727 * [priority selector-name num_ps_args [ps_args]*
1728 * num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1729 */
1730 static void multipath_status(struct dm_target *ti, status_type_t type,
1731 unsigned status_flags, char *result, unsigned maxlen)
1732 {
1733 int sz = 0;
1734 unsigned long flags;
1735 struct multipath *m = ti->private;
1736 struct priority_group *pg;
1737 struct pgpath *p;
1738 unsigned pg_num;
1739 char state;
1740
1741 spin_lock_irqsave(&m->lock, flags);
1742
1743 /* Features */
1744 if (type == STATUSTYPE_INFO)
1745 DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1746 atomic_read(&m->pg_init_count));
1747 else {
1748 DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1749 (m->pg_init_retries > 0) * 2 +
1750 (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1751 test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags) +
1752 (m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1753
1754 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1755 DMEMIT("queue_if_no_path ");
1756 if (m->pg_init_retries)
1757 DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1758 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1759 DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1760 if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags))
1761 DMEMIT("retain_attached_hw_handler ");
1762 if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1763 switch(m->queue_mode) {
1764 case DM_TYPE_BIO_BASED:
1765 DMEMIT("queue_mode bio ");
1766 break;
1767 case DM_TYPE_MQ_REQUEST_BASED:
1768 DMEMIT("queue_mode mq ");
1769 break;
1770 }
1771 }
1772 }
1773
1774 if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1775 DMEMIT("0 ");
1776 else
1777 DMEMIT("1 %s ", m->hw_handler_name);
1778
1779 DMEMIT("%u ", m->nr_priority_groups);
1780
1781 if (m->next_pg)
1782 pg_num = m->next_pg->pg_num;
1783 else if (m->current_pg)
1784 pg_num = m->current_pg->pg_num;
1785 else
1786 pg_num = (m->nr_priority_groups ? 1 : 0);
1787
1788 DMEMIT("%u ", pg_num);
1789
1790 switch (type) {
1791 case STATUSTYPE_INFO:
1792 list_for_each_entry(pg, &m->priority_groups, list) {
1793 if (pg->bypassed)
1794 state = 'D'; /* Disabled */
1795 else if (pg == m->current_pg)
1796 state = 'A'; /* Currently Active */
1797 else
1798 state = 'E'; /* Enabled */
1799
1800 DMEMIT("%c ", state);
1801
1802 if (pg->ps.type->status)
1803 sz += pg->ps.type->status(&pg->ps, NULL, type,
1804 result + sz,
1805 maxlen - sz);
1806 else
1807 DMEMIT("0 ");
1808
1809 DMEMIT("%u %u ", pg->nr_pgpaths,
1810 pg->ps.type->info_args);
1811
1812 list_for_each_entry(p, &pg->pgpaths, list) {
1813 DMEMIT("%s %s %u ", p->path.dev->name,
1814 p->is_active ? "A" : "F",
1815 p->fail_count);
1816 if (pg->ps.type->status)
1817 sz += pg->ps.type->status(&pg->ps,
1818 &p->path, type, result + sz,
1819 maxlen - sz);
1820 }
1821 }
1822 break;
1823
1824 case STATUSTYPE_TABLE:
1825 list_for_each_entry(pg, &m->priority_groups, list) {
1826 DMEMIT("%s ", pg->ps.type->name);
1827
1828 if (pg->ps.type->status)
1829 sz += pg->ps.type->status(&pg->ps, NULL, type,
1830 result + sz,
1831 maxlen - sz);
1832 else
1833 DMEMIT("0 ");
1834
1835 DMEMIT("%u %u ", pg->nr_pgpaths,
1836 pg->ps.type->table_args);
1837
1838 list_for_each_entry(p, &pg->pgpaths, list) {
1839 DMEMIT("%s ", p->path.dev->name);
1840 if (pg->ps.type->status)
1841 sz += pg->ps.type->status(&pg->ps,
1842 &p->path, type, result + sz,
1843 maxlen - sz);
1844 }
1845 }
1846 break;
1847 }
1848
1849 spin_unlock_irqrestore(&m->lock, flags);
1850 }
1851
1852 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1853 {
1854 int r = -EINVAL;
1855 struct dm_dev *dev;
1856 struct multipath *m = ti->private;
1857 action_fn action;
1858
1859 mutex_lock(&m->work_mutex);
1860
1861 if (dm_suspended(ti)) {
1862 r = -EBUSY;
1863 goto out;
1864 }
1865
1866 if (argc == 1) {
1867 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1868 r = queue_if_no_path(m, true, false);
1869 goto out;
1870 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1871 r = queue_if_no_path(m, false, false);
1872 goto out;
1873 }
1874 }
1875
1876 if (argc != 2) {
1877 DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1878 goto out;
1879 }
1880
1881 if (!strcasecmp(argv[0], "disable_group")) {
1882 r = bypass_pg_num(m, argv[1], true);
1883 goto out;
1884 } else if (!strcasecmp(argv[0], "enable_group")) {
1885 r = bypass_pg_num(m, argv[1], false);
1886 goto out;
1887 } else if (!strcasecmp(argv[0], "switch_group")) {
1888 r = switch_pg_num(m, argv[1]);
1889 goto out;
1890 } else if (!strcasecmp(argv[0], "reinstate_path"))
1891 action = reinstate_path;
1892 else if (!strcasecmp(argv[0], "fail_path"))
1893 action = fail_path;
1894 else {
1895 DMWARN("Unrecognised multipath message received: %s", argv[0]);
1896 goto out;
1897 }
1898
1899 r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1900 if (r) {
1901 DMWARN("message: error getting device %s",
1902 argv[1]);
1903 goto out;
1904 }
1905
1906 r = action_dev(m, dev, action);
1907
1908 dm_put_device(ti, dev);
1909
1910 out:
1911 mutex_unlock(&m->work_mutex);
1912 return r;
1913 }
1914
1915 static int multipath_prepare_ioctl(struct dm_target *ti,
1916 struct block_device **bdev, fmode_t *mode)
1917 {
1918 struct multipath *m = ti->private;
1919 struct pgpath *current_pgpath;
1920 int r;
1921
1922 current_pgpath = lockless_dereference(m->current_pgpath);
1923 if (!current_pgpath)
1924 current_pgpath = choose_pgpath(m, 0);
1925
1926 if (current_pgpath) {
1927 if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1928 *bdev = current_pgpath->path.dev->bdev;
1929 *mode = current_pgpath->path.dev->mode;
1930 r = 0;
1931 } else {
1932 /* pg_init has not started or completed */
1933 r = -ENOTCONN;
1934 }
1935 } else {
1936 /* No path is available */
1937 if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1938 r = -ENOTCONN;
1939 else
1940 r = -EIO;
1941 }
1942
1943 if (r == -ENOTCONN) {
1944 if (!lockless_dereference(m->current_pg)) {
1945 /* Path status changed, redo selection */
1946 (void) choose_pgpath(m, 0);
1947 }
1948 if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1949 pg_init_all_paths(m);
1950 dm_table_run_md_queue_async(m->ti->table);
1951 process_queued_io_list(m);
1952 }
1953
1954 /*
1955 * Only pass ioctls through if the device sizes match exactly.
1956 */
1957 if (!r && ti->len != i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
1958 return 1;
1959 return r;
1960 }
1961
1962 static int multipath_iterate_devices(struct dm_target *ti,
1963 iterate_devices_callout_fn fn, void *data)
1964 {
1965 struct multipath *m = ti->private;
1966 struct priority_group *pg;
1967 struct pgpath *p;
1968 int ret = 0;
1969
1970 list_for_each_entry(pg, &m->priority_groups, list) {
1971 list_for_each_entry(p, &pg->pgpaths, list) {
1972 ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1973 if (ret)
1974 goto out;
1975 }
1976 }
1977
1978 out:
1979 return ret;
1980 }
1981
1982 static int pgpath_busy(struct pgpath *pgpath)
1983 {
1984 struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1985
1986 return blk_lld_busy(q);
1987 }
1988
1989 /*
1990 * We return "busy", only when we can map I/Os but underlying devices
1991 * are busy (so even if we map I/Os now, the I/Os will wait on
1992 * the underlying queue).
1993 * In other words, if we want to kill I/Os or queue them inside us
1994 * due to map unavailability, we don't return "busy". Otherwise,
1995 * dm core won't give us the I/Os and we can't do what we want.
1996 */
1997 static int multipath_busy(struct dm_target *ti)
1998 {
1999 bool busy = false, has_active = false;
2000 struct multipath *m = ti->private;
2001 struct priority_group *pg, *next_pg;
2002 struct pgpath *pgpath;
2003
2004 /* pg_init in progress */
2005 if (atomic_read(&m->pg_init_in_progress))
2006 return true;
2007
2008 /* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2009 if (!atomic_read(&m->nr_valid_paths) && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2010 return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
2011
2012 /* Guess which priority_group will be used at next mapping time */
2013 pg = lockless_dereference(m->current_pg);
2014 next_pg = lockless_dereference(m->next_pg);
2015 if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
2016 pg = next_pg;
2017
2018 if (!pg) {
2019 /*
2020 * We don't know which pg will be used at next mapping time.
2021 * We don't call choose_pgpath() here to avoid to trigger
2022 * pg_init just by busy checking.
2023 * So we don't know whether underlying devices we will be using
2024 * at next mapping time are busy or not. Just try mapping.
2025 */
2026 return busy;
2027 }
2028
2029 /*
2030 * If there is one non-busy active path at least, the path selector
2031 * will be able to select it. So we consider such a pg as not busy.
2032 */
2033 busy = true;
2034 list_for_each_entry(pgpath, &pg->pgpaths, list) {
2035 if (pgpath->is_active) {
2036 has_active = true;
2037 if (!pgpath_busy(pgpath)) {
2038 busy = false;
2039 break;
2040 }
2041 }
2042 }
2043
2044 if (!has_active) {
2045 /*
2046 * No active path in this pg, so this pg won't be used and
2047 * the current_pg will be changed at next mapping time.
2048 * We need to try mapping to determine it.
2049 */
2050 busy = false;
2051 }
2052
2053 return busy;
2054 }
2055
2056 /*-----------------------------------------------------------------
2057 * Module setup
2058 *---------------------------------------------------------------*/
2059 static struct target_type multipath_target = {
2060 .name = "multipath",
2061 .version = {1, 12, 0},
2062 .features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE,
2063 .module = THIS_MODULE,
2064 .ctr = multipath_ctr,
2065 .dtr = multipath_dtr,
2066 .map_rq = multipath_map,
2067 .clone_and_map_rq = multipath_clone_and_map,
2068 .release_clone_rq = multipath_release_clone,
2069 .rq_end_io = multipath_end_io,
2070 .map = multipath_map_bio,
2071 .end_io = multipath_end_io_bio,
2072 .presuspend = multipath_presuspend,
2073 .postsuspend = multipath_postsuspend,
2074 .resume = multipath_resume,
2075 .status = multipath_status,
2076 .message = multipath_message,
2077 .prepare_ioctl = multipath_prepare_ioctl,
2078 .iterate_devices = multipath_iterate_devices,
2079 .busy = multipath_busy,
2080 };
2081
2082 static int __init dm_multipath_init(void)
2083 {
2084 int r;
2085
2086 /* allocate a slab for the dm_mpath_ios */
2087 _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
2088 if (!_mpio_cache)
2089 return -ENOMEM;
2090
2091 r = dm_register_target(&multipath_target);
2092 if (r < 0) {
2093 DMERR("request-based register failed %d", r);
2094 r = -EINVAL;
2095 goto bad_register_target;
2096 }
2097
2098 kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2099 if (!kmultipathd) {
2100 DMERR("failed to create workqueue kmpathd");
2101 r = -ENOMEM;
2102 goto bad_alloc_kmultipathd;
2103 }
2104
2105 /*
2106 * A separate workqueue is used to handle the device handlers
2107 * to avoid overloading existing workqueue. Overloading the
2108 * old workqueue would also create a bottleneck in the
2109 * path of the storage hardware device activation.
2110 */
2111 kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2112 WQ_MEM_RECLAIM);
2113 if (!kmpath_handlerd) {
2114 DMERR("failed to create workqueue kmpath_handlerd");
2115 r = -ENOMEM;
2116 goto bad_alloc_kmpath_handlerd;
2117 }
2118
2119 return 0;
2120
2121 bad_alloc_kmpath_handlerd:
2122 destroy_workqueue(kmultipathd);
2123 bad_alloc_kmultipathd:
2124 dm_unregister_target(&multipath_target);
2125 bad_register_target:
2126 kmem_cache_destroy(_mpio_cache);
2127
2128 return r;
2129 }
2130
2131 static void __exit dm_multipath_exit(void)
2132 {
2133 destroy_workqueue(kmpath_handlerd);
2134 destroy_workqueue(kmultipathd);
2135
2136 dm_unregister_target(&multipath_target);
2137 kmem_cache_destroy(_mpio_cache);
2138 }
2139
2140 module_init(dm_multipath_init);
2141 module_exit(dm_multipath_exit);
2142
2143 MODULE_DESCRIPTION(DM_NAME " multipath target");
2144 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
2145 MODULE_LICENSE("GPL");
Linux with added FPC-III support