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Add linux-next specific files for 20110421
[linux-2.6/next.git] / drivers / md / dm-mpath.c
bloba550a057d991bc309b68cfa0f97481365bb1de6e
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-path-selector.h"
11 #include "dm-uevent.h"
12
13 #include <linux/ctype.h>
14 #include <linux/init.h>
15 #include <linux/mempool.h>
16 #include <linux/module.h>
17 #include <linux/pagemap.h>
18 #include <linux/slab.h>
19 #include <linux/time.h>
20 #include <linux/workqueue.h>
21 #include <scsi/scsi_dh.h>
22 #include <asm/atomic.h>
23
24 #define DM_MSG_PREFIX "multipath"
25 #define MESG_STR(x) x, sizeof(x)
26 #define DM_PG_INIT_DELAY_MSECS 2000
27 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
28
29 /* Path properties */
30 struct pgpath {
31 struct list_head list;
32
33 struct priority_group *pg; /* Owning PG */
34 unsigned is_active; /* Path status */
35 unsigned fail_count; /* Cumulative failure count */
36
37 struct dm_path path;
38 struct delayed_work activate_path;
39 };
40
41 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
42
43 /*
44 * Paths are grouped into Priority Groups and numbered from 1 upwards.
45 * Each has a path selector which controls which path gets used.
46 */
47 struct priority_group {
48 struct list_head list;
49
50 struct multipath *m; /* Owning multipath instance */
51 struct path_selector ps;
52
53 unsigned pg_num; /* Reference number */
54 unsigned bypassed; /* Temporarily bypass this PG? */
55
56 unsigned nr_pgpaths; /* Number of paths in PG */
57 struct list_head pgpaths;
58 };
59
60 /* Multipath context */
61 struct multipath {
62 struct list_head list;
63 struct dm_target *ti;
64
65 spinlock_t lock;
66
67 const char *hw_handler_name;
68 char *hw_handler_params;
69
70 unsigned nr_priority_groups;
71 struct list_head priority_groups;
72
73 wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
74
75 unsigned pg_init_required; /* pg_init needs calling? */
76 unsigned pg_init_in_progress; /* Only one pg_init allowed at once */
77 unsigned pg_init_delay_retry; /* Delay pg_init retry? */
78
79 unsigned nr_valid_paths; /* Total number of usable paths */
80 struct pgpath *current_pgpath;
81 struct priority_group *current_pg;
82 struct priority_group *next_pg; /* Switch to this PG if set */
83 unsigned repeat_count; /* I/Os left before calling PS again */
84
85 unsigned queue_io; /* Must we queue all I/O? */
86 unsigned queue_if_no_path; /* Queue I/O if last path fails? */
87 unsigned saved_queue_if_no_path;/* Saved state during suspension */
88 unsigned pg_init_retries; /* Number of times to retry pg_init */
89 unsigned pg_init_count; /* Number of times pg_init called */
90 unsigned pg_init_delay_msecs; /* Number of msecs before pg_init retry */
91
92 struct work_struct process_queued_ios;
93 struct list_head queued_ios;
94 unsigned queue_size;
95
96 struct work_struct trigger_event;
97
98 /*
99 * We must use a mempool of dm_mpath_io structs so that we
100 * can resubmit bios on error.
101 */
102 mempool_t *mpio_pool;
103
104 struct mutex work_mutex;
105 };
106
107 /*
108 * Context information attached to each bio we process.
109 */
110 struct dm_mpath_io {
111 struct pgpath *pgpath;
112 size_t nr_bytes;
113 };
114
115 typedef int (*action_fn) (struct pgpath *pgpath);
116
117 #define MIN_IOS 256 /* Mempool size */
118
119 static struct kmem_cache *_mpio_cache;
120
121 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
122 static void process_queued_ios(struct work_struct *work);
123 static void trigger_event(struct work_struct *work);
124 static void activate_path(struct work_struct *work);
125
126
127 /*-----------------------------------------------
128 * Allocation routines
129 *-----------------------------------------------*/
130
131 static struct pgpath *alloc_pgpath(void)
132 {
133 struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
134
135 if (pgpath) {
136 pgpath->is_active = 1;
137 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
138 }
139
140 return pgpath;
141 }
142
143 static void free_pgpath(struct pgpath *pgpath)
144 {
145 kfree(pgpath);
146 }
147
148 static struct priority_group *alloc_priority_group(void)
149 {
150 struct priority_group *pg;
151
152 pg = kzalloc(sizeof(*pg), GFP_KERNEL);
153
154 if (pg)
155 INIT_LIST_HEAD(&pg->pgpaths);
156
157 return pg;
158 }
159
160 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
161 {
162 struct pgpath *pgpath, *tmp;
163 struct multipath *m = ti->private;
164
165 list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
166 list_del(&pgpath->list);
167 if (m->hw_handler_name)
168 scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
169 dm_put_device(ti, pgpath->path.dev);
170 free_pgpath(pgpath);
171 }
172 }
173
174 static void free_priority_group(struct priority_group *pg,
175 struct dm_target *ti)
176 {
177 struct path_selector *ps = &pg->ps;
178
179 if (ps->type) {
180 ps->type->destroy(ps);
181 dm_put_path_selector(ps->type);
182 }
183
184 free_pgpaths(&pg->pgpaths, ti);
185 kfree(pg);
186 }
187
188 static struct multipath *alloc_multipath(struct dm_target *ti)
189 {
190 struct multipath *m;
191
192 m = kzalloc(sizeof(*m), GFP_KERNEL);
193 if (m) {
194 INIT_LIST_HEAD(&m->priority_groups);
195 INIT_LIST_HEAD(&m->queued_ios);
196 spin_lock_init(&m->lock);
197 m->queue_io = 1;
198 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
199 INIT_WORK(&m->process_queued_ios, process_queued_ios);
200 INIT_WORK(&m->trigger_event, trigger_event);
201 init_waitqueue_head(&m->pg_init_wait);
202 mutex_init(&m->work_mutex);
203 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
204 if (!m->mpio_pool) {
205 kfree(m);
206 return NULL;
207 }
208 m->ti = ti;
209 ti->private = m;
210 }
211
212 return m;
213 }
214
215 static void free_multipath(struct multipath *m)
216 {
217 struct priority_group *pg, *tmp;
218
219 list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
220 list_del(&pg->list);
221 free_priority_group(pg, m->ti);
222 }
223
224 kfree(m->hw_handler_name);
225 kfree(m->hw_handler_params);
226 mempool_destroy(m->mpio_pool);
227 kfree(m);
228 }
229
230
231 /*-----------------------------------------------
232 * Path selection
233 *-----------------------------------------------*/
234
235 static void __pg_init_all_paths(struct multipath *m)
236 {
237 struct pgpath *pgpath;
238 unsigned long pg_init_delay = 0;
239
240 m->pg_init_count++;
241 m->pg_init_required = 0;
242 if (m->pg_init_delay_retry)
243 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
244 m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
245 list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
246 /* Skip failed paths */
247 if (!pgpath->is_active)
248 continue;
249 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
250 pg_init_delay))
251 m->pg_init_in_progress++;
252 }
253 }
254
255 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
256 {
257 m->current_pg = pgpath->pg;
258
259 /* Must we initialise the PG first, and queue I/O till it's ready? */
260 if (m->hw_handler_name) {
261 m->pg_init_required = 1;
262 m->queue_io = 1;
263 } else {
264 m->pg_init_required = 0;
265 m->queue_io = 0;
266 }
267
268 m->pg_init_count = 0;
269 }
270
271 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
272 size_t nr_bytes)
273 {
274 struct dm_path *path;
275
276 path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
277 if (!path)
278 return -ENXIO;
279
280 m->current_pgpath = path_to_pgpath(path);
281
282 if (m->current_pg != pg)
283 __switch_pg(m, m->current_pgpath);
284
285 return 0;
286 }
287
288 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
289 {
290 struct priority_group *pg;
291 unsigned bypassed = 1;
292
293 if (!m->nr_valid_paths)
294 goto failed;
295
296 /* Were we instructed to switch PG? */
297 if (m->next_pg) {
298 pg = m->next_pg;
299 m->next_pg = NULL;
300 if (!__choose_path_in_pg(m, pg, nr_bytes))
301 return;
302 }
303
304 /* Don't change PG until it has no remaining paths */
305 if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
306 return;
307
308 /*
309 * Loop through priority groups until we find a valid path.
310 * First time we skip PGs marked 'bypassed'.
311 * Second time we only try the ones we skipped.
312 */
313 do {
314 list_for_each_entry(pg, &m->priority_groups, list) {
315 if (pg->bypassed == bypassed)
316 continue;
317 if (!__choose_path_in_pg(m, pg, nr_bytes))
318 return;
319 }
320 } while (bypassed--);
321
322 failed:
323 m->current_pgpath = NULL;
324 m->current_pg = NULL;
325 }
326
327 /*
328 * Check whether bios must be queued in the device-mapper core rather
329 * than here in the target.
330 *
331 * m->lock must be held on entry.
332 *
333 * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
334 * same value then we are not between multipath_presuspend()
335 * and multipath_resume() calls and we have no need to check
336 * for the DMF_NOFLUSH_SUSPENDING flag.
337 */
338 static int __must_push_back(struct multipath *m)
339 {
340 return (m->queue_if_no_path != m->saved_queue_if_no_path &&
341 dm_noflush_suspending(m->ti));
342 }
343
344 static int map_io(struct multipath *m, struct request *clone,
345 struct dm_mpath_io *mpio, unsigned was_queued)
346 {
347 int r = DM_MAPIO_REMAPPED;
348 size_t nr_bytes = blk_rq_bytes(clone);
349 unsigned long flags;
350 struct pgpath *pgpath;
351 struct block_device *bdev;
352
353 spin_lock_irqsave(&m->lock, flags);
354
355 /* Do we need to select a new pgpath? */
356 if (!m->current_pgpath ||
357 (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
358 __choose_pgpath(m, nr_bytes);
359
360 pgpath = m->current_pgpath;
361
362 if (was_queued)
363 m->queue_size--;
364
365 if ((pgpath && m->queue_io) ||
366 (!pgpath && m->queue_if_no_path)) {
367 /* Queue for the daemon to resubmit */
368 list_add_tail(&clone->queuelist, &m->queued_ios);
369 m->queue_size++;
370 if ((m->pg_init_required && !m->pg_init_in_progress) ||
371 !m->queue_io)
372 queue_work(kmultipathd, &m->process_queued_ios);
373 pgpath = NULL;
374 r = DM_MAPIO_SUBMITTED;
375 } else if (pgpath) {
376 bdev = pgpath->path.dev->bdev;
377 clone->q = bdev_get_queue(bdev);
378 clone->rq_disk = bdev->bd_disk;
379 } else if (__must_push_back(m))
380 r = DM_MAPIO_REQUEUE;
381 else
382 r = -EIO; /* Failed */
383
384 mpio->pgpath = pgpath;
385 mpio->nr_bytes = nr_bytes;
386
387 if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
388 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
389 nr_bytes);
390
391 spin_unlock_irqrestore(&m->lock, flags);
392
393 return r;
394 }
395
396 /*
397 * If we run out of usable paths, should we queue I/O or error it?
398 */
399 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
400 unsigned save_old_value)
401 {
402 unsigned long flags;
403
404 spin_lock_irqsave(&m->lock, flags);
405
406 if (save_old_value)
407 m->saved_queue_if_no_path = m->queue_if_no_path;
408 else
409 m->saved_queue_if_no_path = queue_if_no_path;
410 m->queue_if_no_path = queue_if_no_path;
411 if (!m->queue_if_no_path && m->queue_size)
412 queue_work(kmultipathd, &m->process_queued_ios);
413
414 spin_unlock_irqrestore(&m->lock, flags);
415
416 return 0;
417 }
418
419 /*-----------------------------------------------------------------
420 * The multipath daemon is responsible for resubmitting queued ios.
421 *---------------------------------------------------------------*/
422
423 static void dispatch_queued_ios(struct multipath *m)
424 {
425 int r;
426 unsigned long flags;
427 struct dm_mpath_io *mpio;
428 union map_info *info;
429 struct request *clone, *n;
430 LIST_HEAD(cl);
431
432 spin_lock_irqsave(&m->lock, flags);
433 list_splice_init(&m->queued_ios, &cl);
434 spin_unlock_irqrestore(&m->lock, flags);
435
436 list_for_each_entry_safe(clone, n, &cl, queuelist) {
437 list_del_init(&clone->queuelist);
438
439 info = dm_get_rq_mapinfo(clone);
440 mpio = info->ptr;
441
442 r = map_io(m, clone, mpio, 1);
443 if (r < 0) {
444 mempool_free(mpio, m->mpio_pool);
445 dm_kill_unmapped_request(clone, r);
446 } else if (r == DM_MAPIO_REMAPPED)
447 dm_dispatch_request(clone);
448 else if (r == DM_MAPIO_REQUEUE) {
449 mempool_free(mpio, m->mpio_pool);
450 dm_requeue_unmapped_request(clone);
451 }
452 }
453 }
454
455 static void process_queued_ios(struct work_struct *work)
456 {
457 struct multipath *m =
458 container_of(work, struct multipath, process_queued_ios);
459 struct pgpath *pgpath = NULL;
460 unsigned must_queue = 1;
461 unsigned long flags;
462
463 spin_lock_irqsave(&m->lock, flags);
464
465 if (!m->queue_size)
466 goto out;
467
468 if (!m->current_pgpath)
469 __choose_pgpath(m, 0);
470
471 pgpath = m->current_pgpath;
472
473 if ((pgpath && !m->queue_io) ||
474 (!pgpath && !m->queue_if_no_path))
475 must_queue = 0;
476
477 if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
478 __pg_init_all_paths(m);
479
480 out:
481 spin_unlock_irqrestore(&m->lock, flags);
482 if (!must_queue)
483 dispatch_queued_ios(m);
484 }
485
486 /*
487 * An event is triggered whenever a path is taken out of use.
488 * Includes path failure and PG bypass.
489 */
490 static void trigger_event(struct work_struct *work)
491 {
492 struct multipath *m =
493 container_of(work, struct multipath, trigger_event);
494
495 dm_table_event(m->ti->table);
496 }
497
498 /*-----------------------------------------------------------------
499 * Constructor/argument parsing:
500 * <#multipath feature args> [<arg>]*
501 * <#hw_handler args> [hw_handler [<arg>]*]
502 * <#priority groups>
503 * <initial priority group>
504 * [<selector> <#selector args> [<arg>]*
505 * <#paths> <#per-path selector args>
506 * [<path> [<arg>]* ]+ ]+
507 *---------------------------------------------------------------*/
508 struct param {
509 unsigned min;
510 unsigned max;
511 char *error;
512 };
513
514 static int read_param(struct param *param, char *str, unsigned *v, char **error)
515 {
516 if (!str ||
517 (sscanf(str, "%u", v) != 1) ||
518 (*v < param->min) ||
519 (*v > param->max)) {
520 *error = param->error;
521 return -EINVAL;
522 }
523
524 return 0;
525 }
526
527 struct arg_set {
528 unsigned argc;
529 char **argv;
530 };
531
532 static char *shift(struct arg_set *as)
533 {
534 char *r;
535
536 if (as->argc) {
537 as->argc--;
538 r = *as->argv;
539 as->argv++;
540 return r;
541 }
542
543 return NULL;
544 }
545
546 static void consume(struct arg_set *as, unsigned n)
547 {
548 BUG_ON (as->argc < n);
549 as->argc -= n;
550 as->argv += n;
551 }
552
553 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
554 struct dm_target *ti)
555 {
556 int r;
557 struct path_selector_type *pst;
558 unsigned ps_argc;
559
560 static struct param _params[] = {
561 {0, 1024, "invalid number of path selector args"},
562 };
563
564 pst = dm_get_path_selector(shift(as));
565 if (!pst) {
566 ti->error = "unknown path selector type";
567 return -EINVAL;
568 }
569
570 r = read_param(_params, shift(as), &ps_argc, &ti->error);
571 if (r) {
572 dm_put_path_selector(pst);
573 return -EINVAL;
574 }
575
576 if (ps_argc > as->argc) {
577 dm_put_path_selector(pst);
578 ti->error = "not enough arguments for path selector";
579 return -EINVAL;
580 }
581
582 r = pst->create(&pg->ps, ps_argc, as->argv);
583 if (r) {
584 dm_put_path_selector(pst);
585 ti->error = "path selector constructor failed";
586 return r;
587 }
588
589 pg->ps.type = pst;
590 consume(as, ps_argc);
591
592 return 0;
593 }
594
595 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
596 struct dm_target *ti)
597 {
598 int r;
599 struct pgpath *p;
600 struct multipath *m = ti->private;
601
602 /* we need at least a path arg */
603 if (as->argc < 1) {
604 ti->error = "no device given";
605 return ERR_PTR(-EINVAL);
606 }
607
608 p = alloc_pgpath();
609 if (!p)
610 return ERR_PTR(-ENOMEM);
611
612 r = dm_get_device(ti, shift(as), dm_table_get_mode(ti->table),
613 &p->path.dev);
614 if (r) {
615 ti->error = "error getting device";
616 goto bad;
617 }
618
619 if (m->hw_handler_name) {
620 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
621
622 r = scsi_dh_attach(q, m->hw_handler_name);
623 if (r == -EBUSY) {
624 /*
625 * Already attached to different hw_handler,
626 * try to reattach with correct one.
627 */
628 scsi_dh_detach(q);
629 r = scsi_dh_attach(q, m->hw_handler_name);
630 }
631
632 if (r < 0) {
633 ti->error = "error attaching hardware handler";
634 dm_put_device(ti, p->path.dev);
635 goto bad;
636 }
637
638 if (m->hw_handler_params) {
639 r = scsi_dh_set_params(q, m->hw_handler_params);
640 if (r < 0) {
641 ti->error = "unable to set hardware "
642 "handler parameters";
643 scsi_dh_detach(q);
644 dm_put_device(ti, p->path.dev);
645 goto bad;
646 }
647 }
648 }
649
650 r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
651 if (r) {
652 dm_put_device(ti, p->path.dev);
653 goto bad;
654 }
655
656 return p;
657
658 bad:
659 free_pgpath(p);
660 return ERR_PTR(r);
661 }
662
663 static struct priority_group *parse_priority_group(struct arg_set *as,
664 struct multipath *m)
665 {
666 static struct param _params[] = {
667 {1, 1024, "invalid number of paths"},
668 {0, 1024, "invalid number of selector args"}
669 };
670
671 int r;
672 unsigned i, nr_selector_args, nr_params;
673 struct priority_group *pg;
674 struct dm_target *ti = m->ti;
675
676 if (as->argc < 2) {
677 as->argc = 0;
678 ti->error = "not enough priority group arguments";
679 return ERR_PTR(-EINVAL);
680 }
681
682 pg = alloc_priority_group();
683 if (!pg) {
684 ti->error = "couldn't allocate priority group";
685 return ERR_PTR(-ENOMEM);
686 }
687 pg->m = m;
688
689 r = parse_path_selector(as, pg, ti);
690 if (r)
691 goto bad;
692
693 /*
694 * read the paths
695 */
696 r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
697 if (r)
698 goto bad;
699
700 r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
701 if (r)
702 goto bad;
703
704 nr_params = 1 + nr_selector_args;
705 for (i = 0; i < pg->nr_pgpaths; i++) {
706 struct pgpath *pgpath;
707 struct arg_set path_args;
708
709 if (as->argc < nr_params) {
710 ti->error = "not enough path parameters";
711 r = -EINVAL;
712 goto bad;
713 }
714
715 path_args.argc = nr_params;
716 path_args.argv = as->argv;
717
718 pgpath = parse_path(&path_args, &pg->ps, ti);
719 if (IS_ERR(pgpath)) {
720 r = PTR_ERR(pgpath);
721 goto bad;
722 }
723
724 pgpath->pg = pg;
725 list_add_tail(&pgpath->list, &pg->pgpaths);
726 consume(as, nr_params);
727 }
728
729 return pg;
730
731 bad:
732 free_priority_group(pg, ti);
733 return ERR_PTR(r);
734 }
735
736 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
737 {
738 unsigned hw_argc;
739 int ret;
740 struct dm_target *ti = m->ti;
741
742 static struct param _params[] = {
743 {0, 1024, "invalid number of hardware handler args"},
744 };
745
746 if (read_param(_params, shift(as), &hw_argc, &ti->error))
747 return -EINVAL;
748
749 if (!hw_argc)
750 return 0;
751
752 if (hw_argc > as->argc) {
753 ti->error = "not enough arguments for hardware handler";
754 return -EINVAL;
755 }
756
757 m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
758 request_module("scsi_dh_%s", m->hw_handler_name);
759 if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
760 ti->error = "unknown hardware handler type";
761 ret = -EINVAL;
762 goto fail;
763 }
764
765 if (hw_argc > 1) {
766 char *p;
767 int i, j, len = 4;
768
769 for (i = 0; i <= hw_argc - 2; i++)
770 len += strlen(as->argv[i]) + 1;
771 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
772 if (!p) {
773 ti->error = "memory allocation failed";
774 ret = -ENOMEM;
775 goto fail;
776 }
777 j = sprintf(p, "%d", hw_argc - 1);
778 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
779 j = sprintf(p, "%s", as->argv[i]);
780 }
781 consume(as, hw_argc - 1);
782
783 return 0;
784 fail:
785 kfree(m->hw_handler_name);
786 m->hw_handler_name = NULL;
787 return ret;
788 }
789
790 static int parse_features(struct arg_set *as, struct multipath *m)
791 {
792 int r;
793 unsigned argc;
794 struct dm_target *ti = m->ti;
795 const char *param_name;
796
797 static struct param _params[] = {
798 {0, 5, "invalid number of feature args"},
799 {1, 50, "pg_init_retries must be between 1 and 50"},
800 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
801 };
802
803 r = read_param(_params, shift(as), &argc, &ti->error);
804 if (r)
805 return -EINVAL;
806
807 if (!argc)
808 return 0;
809
810 do {
811 param_name = shift(as);
812 argc--;
813
814 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
815 r = queue_if_no_path(m, 1, 0);
816 continue;
817 }
818
819 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
820 (argc >= 1)) {
821 r = read_param(_params + 1, shift(as),
822 &m->pg_init_retries, &ti->error);
823 argc--;
824 continue;
825 }
826
827 if (!strnicmp(param_name, MESG_STR("pg_init_delay_msecs")) &&
828 (argc >= 1)) {
829 r = read_param(_params + 2, shift(as),
830 &m->pg_init_delay_msecs, &ti->error);
831 argc--;
832 continue;
833 }
834
835 ti->error = "Unrecognised multipath feature request";
836 r = -EINVAL;
837 } while (argc && !r);
838
839 return r;
840 }
841
842 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
843 char **argv)
844 {
845 /* target parameters */
846 static struct param _params[] = {
847 {0, 1024, "invalid number of priority groups"},
848 {0, 1024, "invalid initial priority group number"},
849 };
850
851 int r;
852 struct multipath *m;
853 struct arg_set as;
854 unsigned pg_count = 0;
855 unsigned next_pg_num;
856
857 as.argc = argc;
858 as.argv = argv;
859
860 m = alloc_multipath(ti);
861 if (!m) {
862 ti->error = "can't allocate multipath";
863 return -EINVAL;
864 }
865
866 r = parse_features(&as, m);
867 if (r)
868 goto bad;
869
870 r = parse_hw_handler(&as, m);
871 if (r)
872 goto bad;
873
874 r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
875 if (r)
876 goto bad;
877
878 r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
879 if (r)
880 goto bad;
881
882 if ((!m->nr_priority_groups && next_pg_num) ||
883 (m->nr_priority_groups && !next_pg_num)) {
884 ti->error = "invalid initial priority group";
885 r = -EINVAL;
886 goto bad;
887 }
888
889 /* parse the priority groups */
890 while (as.argc) {
891 struct priority_group *pg;
892
893 pg = parse_priority_group(&as, m);
894 if (IS_ERR(pg)) {
895 r = PTR_ERR(pg);
896 goto bad;
897 }
898
899 m->nr_valid_paths += pg->nr_pgpaths;
900 list_add_tail(&pg->list, &m->priority_groups);
901 pg_count++;
902 pg->pg_num = pg_count;
903 if (!--next_pg_num)
904 m->next_pg = pg;
905 }
906
907 if (pg_count != m->nr_priority_groups) {
908 ti->error = "priority group count mismatch";
909 r = -EINVAL;
910 goto bad;
911 }
912
913 ti->num_flush_requests = 1;
914 ti->num_discard_requests = 1;
915
916 return 0;
917
918 bad:
919 free_multipath(m);
920 return r;
921 }
922
923 static void multipath_wait_for_pg_init_completion(struct multipath *m)
924 {
925 DECLARE_WAITQUEUE(wait, current);
926 unsigned long flags;
927
928 add_wait_queue(&m->pg_init_wait, &wait);
929
930 while (1) {
931 set_current_state(TASK_UNINTERRUPTIBLE);
932
933 spin_lock_irqsave(&m->lock, flags);
934 if (!m->pg_init_in_progress) {
935 spin_unlock_irqrestore(&m->lock, flags);
936 break;
937 }
938 spin_unlock_irqrestore(&m->lock, flags);
939
940 io_schedule();
941 }
942 set_current_state(TASK_RUNNING);
943
944 remove_wait_queue(&m->pg_init_wait, &wait);
945 }
946
947 static void flush_multipath_work(struct multipath *m)
948 {
949 flush_workqueue(kmpath_handlerd);
950 multipath_wait_for_pg_init_completion(m);
951 flush_workqueue(kmultipathd);
952 flush_work_sync(&m->trigger_event);
953 }
954
955 static void multipath_dtr(struct dm_target *ti)
956 {
957 struct multipath *m = ti->private;
958
959 flush_multipath_work(m);
960 free_multipath(m);
961 }
962
963 /*
964 * Map cloned requests
965 */
966 static int multipath_map(struct dm_target *ti, struct request *clone,
967 union map_info *map_context)
968 {
969 int r;
970 struct dm_mpath_io *mpio;
971 struct multipath *m = (struct multipath *) ti->private;
972
973 mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
974 if (!mpio)
975 /* ENOMEM, requeue */
976 return DM_MAPIO_REQUEUE;
977 memset(mpio, 0, sizeof(*mpio));
978
979 map_context->ptr = mpio;
980 clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
981 r = map_io(m, clone, mpio, 0);
982 if (r < 0 || r == DM_MAPIO_REQUEUE)
983 mempool_free(mpio, m->mpio_pool);
984
985 return r;
986 }
987
988 /*
989 * Take a path out of use.
990 */
991 static int fail_path(struct pgpath *pgpath)
992 {
993 unsigned long flags;
994 struct multipath *m = pgpath->pg->m;
995
996 spin_lock_irqsave(&m->lock, flags);
997
998 if (!pgpath->is_active)
999 goto out;
1000
1001 DMWARN("Failing path %s.", pgpath->path.dev->name);
1002
1003 pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1004 pgpath->is_active = 0;
1005 pgpath->fail_count++;
1006
1007 m->nr_valid_paths--;
1008
1009 if (pgpath == m->current_pgpath)
1010 m->current_pgpath = NULL;
1011
1012 dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
1013 pgpath->path.dev->name, m->nr_valid_paths);
1014
1015 schedule_work(&m->trigger_event);
1016
1017 out:
1018 spin_unlock_irqrestore(&m->lock, flags);
1019
1020 return 0;
1021 }
1022
1023 /*
1024 * Reinstate a previously-failed path
1025 */
1026 static int reinstate_path(struct pgpath *pgpath)
1027 {
1028 int r = 0;
1029 unsigned long flags;
1030 struct multipath *m = pgpath->pg->m;
1031
1032 spin_lock_irqsave(&m->lock, flags);
1033
1034 if (pgpath->is_active)
1035 goto out;
1036
1037 if (!pgpath->pg->ps.type->reinstate_path) {
1038 DMWARN("Reinstate path not supported by path selector %s",
1039 pgpath->pg->ps.type->name);
1040 r = -EINVAL;
1041 goto out;
1042 }
1043
1044 r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1045 if (r)
1046 goto out;
1047
1048 pgpath->is_active = 1;
1049
1050 if (!m->nr_valid_paths++ && m->queue_size) {
1051 m->current_pgpath = NULL;
1052 queue_work(kmultipathd, &m->process_queued_ios);
1053 } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1054 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
1055 m->pg_init_in_progress++;
1056 }
1057
1058 dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1059 pgpath->path.dev->name, m->nr_valid_paths);
1060
1061 schedule_work(&m->trigger_event);
1062
1063 out:
1064 spin_unlock_irqrestore(&m->lock, flags);
1065
1066 return r;
1067 }
1068
1069 /*
1070 * Fail or reinstate all paths that match the provided struct dm_dev.
1071 */
1072 static int action_dev(struct multipath *m, struct dm_dev *dev,
1073 action_fn action)
1074 {
1075 int r = -EINVAL;
1076 struct pgpath *pgpath;
1077 struct priority_group *pg;
1078
1079 list_for_each_entry(pg, &m->priority_groups, list) {
1080 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1081 if (pgpath->path.dev == dev)
1082 r = action(pgpath);
1083 }
1084 }
1085
1086 return r;
1087 }
1088
1089 /*
1090 * Temporarily try to avoid having to use the specified PG
1091 */
1092 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1093 int bypassed)
1094 {
1095 unsigned long flags;
1096
1097 spin_lock_irqsave(&m->lock, flags);
1098
1099 pg->bypassed = bypassed;
1100 m->current_pgpath = NULL;
1101 m->current_pg = NULL;
1102
1103 spin_unlock_irqrestore(&m->lock, flags);
1104
1105 schedule_work(&m->trigger_event);
1106 }
1107
1108 /*
1109 * Switch to using the specified PG from the next I/O that gets mapped
1110 */
1111 static int switch_pg_num(struct multipath *m, const char *pgstr)
1112 {
1113 struct priority_group *pg;
1114 unsigned pgnum;
1115 unsigned long flags;
1116
1117 if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1118 (pgnum > m->nr_priority_groups)) {
1119 DMWARN("invalid PG number supplied to switch_pg_num");
1120 return -EINVAL;
1121 }
1122
1123 spin_lock_irqsave(&m->lock, flags);
1124 list_for_each_entry(pg, &m->priority_groups, list) {
1125 pg->bypassed = 0;
1126 if (--pgnum)
1127 continue;
1128
1129 m->current_pgpath = NULL;
1130 m->current_pg = NULL;
1131 m->next_pg = pg;
1132 }
1133 spin_unlock_irqrestore(&m->lock, flags);
1134
1135 schedule_work(&m->trigger_event);
1136 return 0;
1137 }
1138
1139 /*
1140 * Set/clear bypassed status of a PG.
1141 * PGs are numbered upwards from 1 in the order they were declared.
1142 */
1143 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1144 {
1145 struct priority_group *pg;
1146 unsigned pgnum;
1147
1148 if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1149 (pgnum > m->nr_priority_groups)) {
1150 DMWARN("invalid PG number supplied to bypass_pg");
1151 return -EINVAL;
1152 }
1153
1154 list_for_each_entry(pg, &m->priority_groups, list) {
1155 if (!--pgnum)
1156 break;
1157 }
1158
1159 bypass_pg(m, pg, bypassed);
1160 return 0;
1161 }
1162
1163 /*
1164 * Should we retry pg_init immediately?
1165 */
1166 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1167 {
1168 unsigned long flags;
1169 int limit_reached = 0;
1170
1171 spin_lock_irqsave(&m->lock, flags);
1172
1173 if (m->pg_init_count <= m->pg_init_retries)
1174 m->pg_init_required = 1;
1175 else
1176 limit_reached = 1;
1177
1178 spin_unlock_irqrestore(&m->lock, flags);
1179
1180 return limit_reached;
1181 }
1182
1183 static void pg_init_done(void *data, int errors)
1184 {
1185 struct pgpath *pgpath = data;
1186 struct priority_group *pg = pgpath->pg;
1187 struct multipath *m = pg->m;
1188 unsigned long flags;
1189 unsigned delay_retry = 0;
1190
1191 /* device or driver problems */
1192 switch (errors) {
1193 case SCSI_DH_OK:
1194 break;
1195 case SCSI_DH_NOSYS:
1196 if (!m->hw_handler_name) {
1197 errors = 0;
1198 break;
1199 }
1200 DMERR("Could not failover the device: Handler scsi_dh_%s "
1201 "Error %d.", m->hw_handler_name, errors);
1202 /*
1203 * Fail path for now, so we do not ping pong
1204 */
1205 fail_path(pgpath);
1206 break;
1207 case SCSI_DH_DEV_TEMP_BUSY:
1208 /*
1209 * Probably doing something like FW upgrade on the
1210 * controller so try the other pg.
1211 */
1212 bypass_pg(m, pg, 1);
1213 break;
1214 case SCSI_DH_RETRY:
1215 /* Wait before retrying. */
1216 delay_retry = 1;
1217 case SCSI_DH_IMM_RETRY:
1218 case SCSI_DH_RES_TEMP_UNAVAIL:
1219 if (pg_init_limit_reached(m, pgpath))
1220 fail_path(pgpath);
1221 errors = 0;
1222 break;
1223 default:
1224 /*
1225 * We probably do not want to fail the path for a device
1226 * error, but this is what the old dm did. In future
1227 * patches we can do more advanced handling.
1228 */
1229 fail_path(pgpath);
1230 }
1231
1232 spin_lock_irqsave(&m->lock, flags);
1233 if (errors) {
1234 if (pgpath == m->current_pgpath) {
1235 DMERR("Could not failover device. Error %d.", errors);
1236 m->current_pgpath = NULL;
1237 m->current_pg = NULL;
1238 }
1239 } else if (!m->pg_init_required)
1240 pg->bypassed = 0;
1241
1242 if (--m->pg_init_in_progress)
1243 /* Activations of other paths are still on going */
1244 goto out;
1245
1246 if (!m->pg_init_required)
1247 m->queue_io = 0;
1248
1249 m->pg_init_delay_retry = delay_retry;
1250 queue_work(kmultipathd, &m->process_queued_ios);
1251
1252 /*
1253 * Wake up any thread waiting to suspend.
1254 */
1255 wake_up(&m->pg_init_wait);
1256
1257 out:
1258 spin_unlock_irqrestore(&m->lock, flags);
1259 }
1260
1261 static void activate_path(struct work_struct *work)
1262 {
1263 struct pgpath *pgpath =
1264 container_of(work, struct pgpath, activate_path.work);
1265
1266 scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1267 pg_init_done, pgpath);
1268 }
1269
1270 /*
1271 * end_io handling
1272 */
1273 static int do_end_io(struct multipath *m, struct request *clone,
1274 int error, struct dm_mpath_io *mpio)
1275 {
1276 /*
1277 * We don't queue any clone request inside the multipath target
1278 * during end I/O handling, since those clone requests don't have
1279 * bio clones. If we queue them inside the multipath target,
1280 * we need to make bio clones, that requires memory allocation.
1281 * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1282 * don't have bio clones.)
1283 * Instead of queueing the clone request here, we queue the original
1284 * request into dm core, which will remake a clone request and
1285 * clone bios for it and resubmit it later.
1286 */
1287 int r = DM_ENDIO_REQUEUE;
1288 unsigned long flags;
1289
1290 if (!error && !clone->errors)
1291 return 0; /* I/O complete */
1292
1293 if (error == -EOPNOTSUPP || error == -EREMOTEIO)
1294 return error;
1295
1296 if (mpio->pgpath)
1297 fail_path(mpio->pgpath);
1298
1299 spin_lock_irqsave(&m->lock, flags);
1300 if (!m->nr_valid_paths) {
1301 if (!m->queue_if_no_path) {
1302 if (!__must_push_back(m))
1303 r = -EIO;
1304 } else {
1305 if (error == -EBADE)
1306 r = error;
1307 }
1308 }
1309 spin_unlock_irqrestore(&m->lock, flags);
1310
1311 return r;
1312 }
1313
1314 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1315 int error, union map_info *map_context)
1316 {
1317 struct multipath *m = ti->private;
1318 struct dm_mpath_io *mpio = map_context->ptr;
1319 struct pgpath *pgpath = mpio->pgpath;
1320 struct path_selector *ps;
1321 int r;
1322
1323 r = do_end_io(m, clone, error, mpio);
1324 if (pgpath) {
1325 ps = &pgpath->pg->ps;
1326 if (ps->type->end_io)
1327 ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1328 }
1329 mempool_free(mpio, m->mpio_pool);
1330
1331 return r;
1332 }
1333
1334 /*
1335 * Suspend can't complete until all the I/O is processed so if
1336 * the last path fails we must error any remaining I/O.
1337 * Note that if the freeze_bdev fails while suspending, the
1338 * queue_if_no_path state is lost - userspace should reset it.
1339 */
1340 static void multipath_presuspend(struct dm_target *ti)
1341 {
1342 struct multipath *m = (struct multipath *) ti->private;
1343
1344 queue_if_no_path(m, 0, 1);
1345 }
1346
1347 static void multipath_postsuspend(struct dm_target *ti)
1348 {
1349 struct multipath *m = ti->private;
1350
1351 mutex_lock(&m->work_mutex);
1352 flush_multipath_work(m);
1353 mutex_unlock(&m->work_mutex);
1354 }
1355
1356 /*
1357 * Restore the queue_if_no_path setting.
1358 */
1359 static void multipath_resume(struct dm_target *ti)
1360 {
1361 struct multipath *m = (struct multipath *) ti->private;
1362 unsigned long flags;
1363
1364 spin_lock_irqsave(&m->lock, flags);
1365 m->queue_if_no_path = m->saved_queue_if_no_path;
1366 spin_unlock_irqrestore(&m->lock, flags);
1367 }
1368
1369 /*
1370 * Info output has the following format:
1371 * num_multipath_feature_args [multipath_feature_args]*
1372 * num_handler_status_args [handler_status_args]*
1373 * num_groups init_group_number
1374 * [A|D|E num_ps_status_args [ps_status_args]*
1375 * num_paths num_selector_args
1376 * [path_dev A|F fail_count [selector_args]* ]+ ]+
1377 *
1378 * Table output has the following format (identical to the constructor string):
1379 * num_feature_args [features_args]*
1380 * num_handler_args hw_handler [hw_handler_args]*
1381 * num_groups init_group_number
1382 * [priority selector-name num_ps_args [ps_args]*
1383 * num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1384 */
1385 static int multipath_status(struct dm_target *ti, status_type_t type,
1386 char *result, unsigned int maxlen)
1387 {
1388 int sz = 0;
1389 unsigned long flags;
1390 struct multipath *m = (struct multipath *) ti->private;
1391 struct priority_group *pg;
1392 struct pgpath *p;
1393 unsigned pg_num;
1394 char state;
1395
1396 spin_lock_irqsave(&m->lock, flags);
1397
1398 /* Features */
1399 if (type == STATUSTYPE_INFO)
1400 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1401 else {
1402 DMEMIT("%u ", m->queue_if_no_path +
1403 (m->pg_init_retries > 0) * 2 +
1404 (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1405 if (m->queue_if_no_path)
1406 DMEMIT("queue_if_no_path ");
1407 if (m->pg_init_retries)
1408 DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1409 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1410 DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1411 }
1412
1413 if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1414 DMEMIT("0 ");
1415 else
1416 DMEMIT("1 %s ", m->hw_handler_name);
1417
1418 DMEMIT("%u ", m->nr_priority_groups);
1419
1420 if (m->next_pg)
1421 pg_num = m->next_pg->pg_num;
1422 else if (m->current_pg)
1423 pg_num = m->current_pg->pg_num;
1424 else
1425 pg_num = (m->nr_priority_groups ? 1 : 0);
1426
1427 DMEMIT("%u ", pg_num);
1428
1429 switch (type) {
1430 case STATUSTYPE_INFO:
1431 list_for_each_entry(pg, &m->priority_groups, list) {
1432 if (pg->bypassed)
1433 state = 'D'; /* Disabled */
1434 else if (pg == m->current_pg)
1435 state = 'A'; /* Currently Active */
1436 else
1437 state = 'E'; /* Enabled */
1438
1439 DMEMIT("%c ", state);
1440
1441 if (pg->ps.type->status)
1442 sz += pg->ps.type->status(&pg->ps, NULL, type,
1443 result + sz,
1444 maxlen - sz);
1445 else
1446 DMEMIT("0 ");
1447
1448 DMEMIT("%u %u ", pg->nr_pgpaths,
1449 pg->ps.type->info_args);
1450
1451 list_for_each_entry(p, &pg->pgpaths, list) {
1452 DMEMIT("%s %s %u ", p->path.dev->name,
1453 p->is_active ? "A" : "F",
1454 p->fail_count);
1455 if (pg->ps.type->status)
1456 sz += pg->ps.type->status(&pg->ps,
1457 &p->path, type, result + sz,
1458 maxlen - sz);
1459 }
1460 }
1461 break;
1462
1463 case STATUSTYPE_TABLE:
1464 list_for_each_entry(pg, &m->priority_groups, list) {
1465 DMEMIT("%s ", pg->ps.type->name);
1466
1467 if (pg->ps.type->status)
1468 sz += pg->ps.type->status(&pg->ps, NULL, type,
1469 result + sz,
1470 maxlen - sz);
1471 else
1472 DMEMIT("0 ");
1473
1474 DMEMIT("%u %u ", pg->nr_pgpaths,
1475 pg->ps.type->table_args);
1476
1477 list_for_each_entry(p, &pg->pgpaths, list) {
1478 DMEMIT("%s ", p->path.dev->name);
1479 if (pg->ps.type->status)
1480 sz += pg->ps.type->status(&pg->ps,
1481 &p->path, type, result + sz,
1482 maxlen - sz);
1483 }
1484 }
1485 break;
1486 }
1487
1488 spin_unlock_irqrestore(&m->lock, flags);
1489
1490 return 0;
1491 }
1492
1493 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1494 {
1495 int r = -EINVAL;
1496 struct dm_dev *dev;
1497 struct multipath *m = (struct multipath *) ti->private;
1498 action_fn action;
1499
1500 mutex_lock(&m->work_mutex);
1501
1502 if (dm_suspended(ti)) {
1503 r = -EBUSY;
1504 goto out;
1505 }
1506
1507 if (argc == 1) {
1508 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path"))) {
1509 r = queue_if_no_path(m, 1, 0);
1510 goto out;
1511 } else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path"))) {
1512 r = queue_if_no_path(m, 0, 0);
1513 goto out;
1514 }
1515 }
1516
1517 if (argc != 2) {
1518 DMWARN("Unrecognised multipath message received.");
1519 goto out;
1520 }
1521
1522 if (!strnicmp(argv[0], MESG_STR("disable_group"))) {
1523 r = bypass_pg_num(m, argv[1], 1);
1524 goto out;
1525 } else if (!strnicmp(argv[0], MESG_STR("enable_group"))) {
1526 r = bypass_pg_num(m, argv[1], 0);
1527 goto out;
1528 } else if (!strnicmp(argv[0], MESG_STR("switch_group"))) {
1529 r = switch_pg_num(m, argv[1]);
1530 goto out;
1531 } else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1532 action = reinstate_path;
1533 else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1534 action = fail_path;
1535 else {
1536 DMWARN("Unrecognised multipath message received.");
1537 goto out;
1538 }
1539
1540 r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1541 if (r) {
1542 DMWARN("message: error getting device %s",
1543 argv[1]);
1544 goto out;
1545 }
1546
1547 r = action_dev(m, dev, action);
1548
1549 dm_put_device(ti, dev);
1550
1551 out:
1552 mutex_unlock(&m->work_mutex);
1553 return r;
1554 }
1555
1556 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1557 unsigned long arg)
1558 {
1559 struct multipath *m = (struct multipath *) ti->private;
1560 struct block_device *bdev = NULL;
1561 fmode_t mode = 0;
1562 unsigned long flags;
1563 int r = 0;
1564
1565 spin_lock_irqsave(&m->lock, flags);
1566
1567 if (!m->current_pgpath)
1568 __choose_pgpath(m, 0);
1569
1570 if (m->current_pgpath) {
1571 bdev = m->current_pgpath->path.dev->bdev;
1572 mode = m->current_pgpath->path.dev->mode;
1573 }
1574
1575 if (m->queue_io)
1576 r = -EAGAIN;
1577 else if (!bdev)
1578 r = -EIO;
1579
1580 spin_unlock_irqrestore(&m->lock, flags);
1581
1582 return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1583 }
1584
1585 static int multipath_iterate_devices(struct dm_target *ti,
1586 iterate_devices_callout_fn fn, void *data)
1587 {
1588 struct multipath *m = ti->private;
1589 struct priority_group *pg;
1590 struct pgpath *p;
1591 int ret = 0;
1592
1593 list_for_each_entry(pg, &m->priority_groups, list) {
1594 list_for_each_entry(p, &pg->pgpaths, list) {
1595 ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1596 if (ret)
1597 goto out;
1598 }
1599 }
1600
1601 out:
1602 return ret;
1603 }
1604
1605 static int __pgpath_busy(struct pgpath *pgpath)
1606 {
1607 struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1608
1609 return dm_underlying_device_busy(q);
1610 }
1611
1612 /*
1613 * We return "busy", only when we can map I/Os but underlying devices
1614 * are busy (so even if we map I/Os now, the I/Os will wait on
1615 * the underlying queue).
1616 * In other words, if we want to kill I/Os or queue them inside us
1617 * due to map unavailability, we don't return "busy". Otherwise,
1618 * dm core won't give us the I/Os and we can't do what we want.
1619 */
1620 static int multipath_busy(struct dm_target *ti)
1621 {
1622 int busy = 0, has_active = 0;
1623 struct multipath *m = ti->private;
1624 struct priority_group *pg;
1625 struct pgpath *pgpath;
1626 unsigned long flags;
1627
1628 spin_lock_irqsave(&m->lock, flags);
1629
1630 /* Guess which priority_group will be used at next mapping time */
1631 if (unlikely(!m->current_pgpath && m->next_pg))
1632 pg = m->next_pg;
1633 else if (likely(m->current_pg))
1634 pg = m->current_pg;
1635 else
1636 /*
1637 * We don't know which pg will be used at next mapping time.
1638 * We don't call __choose_pgpath() here to avoid to trigger
1639 * pg_init just by busy checking.
1640 * So we don't know whether underlying devices we will be using
1641 * at next mapping time are busy or not. Just try mapping.
1642 */
1643 goto out;
1644
1645 /*
1646 * If there is one non-busy active path at least, the path selector
1647 * will be able to select it. So we consider such a pg as not busy.
1648 */
1649 busy = 1;
1650 list_for_each_entry(pgpath, &pg->pgpaths, list)
1651 if (pgpath->is_active) {
1652 has_active = 1;
1653
1654 if (!__pgpath_busy(pgpath)) {
1655 busy = 0;
1656 break;
1657 }
1658 }
1659
1660 if (!has_active)
1661 /*
1662 * No active path in this pg, so this pg won't be used and
1663 * the current_pg will be changed at next mapping time.
1664 * We need to try mapping to determine it.
1665 */
1666 busy = 0;
1667
1668 out:
1669 spin_unlock_irqrestore(&m->lock, flags);
1670
1671 return busy;
1672 }
1673
1674 /*-----------------------------------------------------------------
1675 * Module setup
1676 *---------------------------------------------------------------*/
1677 static struct target_type multipath_target = {
1678 .name = "multipath",
1679 .version = {1, 3, 0},
1680 .module = THIS_MODULE,
1681 .ctr = multipath_ctr,
1682 .dtr = multipath_dtr,
1683 .map_rq = multipath_map,
1684 .rq_end_io = multipath_end_io,
1685 .presuspend = multipath_presuspend,
1686 .postsuspend = multipath_postsuspend,
1687 .resume = multipath_resume,
1688 .status = multipath_status,
1689 .message = multipath_message,
1690 .ioctl = multipath_ioctl,
1691 .iterate_devices = multipath_iterate_devices,
1692 .busy = multipath_busy,
1693 };
1694
1695 static int __init dm_multipath_init(void)
1696 {
1697 int r;
1698
1699 /* allocate a slab for the dm_ios */
1700 _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1701 if (!_mpio_cache)
1702 return -ENOMEM;
1703
1704 r = dm_register_target(&multipath_target);
1705 if (r < 0) {
1706 DMERR("register failed %d", r);
1707 kmem_cache_destroy(_mpio_cache);
1708 return -EINVAL;
1709 }
1710
1711 kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1712 if (!kmultipathd) {
1713 DMERR("failed to create workqueue kmpathd");
1714 dm_unregister_target(&multipath_target);
1715 kmem_cache_destroy(_mpio_cache);
1716 return -ENOMEM;
1717 }
1718
1719 /*
1720 * A separate workqueue is used to handle the device handlers
1721 * to avoid overloading existing workqueue. Overloading the
1722 * old workqueue would also create a bottleneck in the
1723 * path of the storage hardware device activation.
1724 */
1725 kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1726 WQ_MEM_RECLAIM);
1727 if (!kmpath_handlerd) {
1728 DMERR("failed to create workqueue kmpath_handlerd");
1729 destroy_workqueue(kmultipathd);
1730 dm_unregister_target(&multipath_target);
1731 kmem_cache_destroy(_mpio_cache);
1732 return -ENOMEM;
1733 }
1734
1735 DMINFO("version %u.%u.%u loaded",
1736 multipath_target.version[0], multipath_target.version[1],
1737 multipath_target.version[2]);
1738
1739 return r;
1740 }
1741
1742 static void __exit dm_multipath_exit(void)
1743 {
1744 destroy_workqueue(kmpath_handlerd);
1745 destroy_workqueue(kmultipathd);
1746
1747 dm_unregister_target(&multipath_target);
1748 kmem_cache_destroy(_mpio_cache);
1749 }
1750
1751 module_init(dm_multipath_init);
1752 module_exit(dm_multipath_exit);
1753
1754 MODULE_DESCRIPTION(DM_NAME " multipath target");
1755 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1756 MODULE_LICENSE("GPL");
linux-next