dm mpath: add missing static
[linux-2.6.git] / drivers / md / dm-mpath.c
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 "dm.h"
9 #include "dm-path-selector.h"
10 #include "dm-hw-handler.h"
11 #include "dm-bio-list.h"
12 #include "dm-bio-record.h"
13 #include "dm-uevent.h"
14
15 #include <linux/ctype.h>
16 #include <linux/init.h>
17 #include <linux/mempool.h>
18 #include <linux/module.h>
19 #include <linux/pagemap.h>
20 #include <linux/slab.h>
21 #include <linux/time.h>
22 #include <linux/workqueue.h>
23 #include <asm/atomic.h>
24
25 #define DM_MSG_PREFIX "multipath"
26 #define MESG_STR(x) x, sizeof(x)
27
28 /* Path properties */
29 struct pgpath {
30         struct list_head list;
31
32         struct priority_group *pg;      /* Owning PG */
33         unsigned fail_count;            /* Cumulative failure count */
34
35         struct dm_path path;
36 };
37
38 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
39
40 /*
41  * Paths are grouped into Priority Groups and numbered from 1 upwards.
42  * Each has a path selector which controls which path gets used.
43  */
44 struct priority_group {
45         struct list_head list;
46
47         struct multipath *m;            /* Owning multipath instance */
48         struct path_selector ps;
49
50         unsigned pg_num;                /* Reference number */
51         unsigned bypassed;              /* Temporarily bypass this PG? */
52
53         unsigned nr_pgpaths;            /* Number of paths in PG */
54         struct list_head pgpaths;
55 };
56
57 /* Multipath context */
58 struct multipath {
59         struct list_head list;
60         struct dm_target *ti;
61
62         spinlock_t lock;
63
64         struct hw_handler hw_handler;
65         unsigned nr_priority_groups;
66         struct list_head priority_groups;
67         unsigned pg_init_required;      /* pg_init needs calling? */
68         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
69
70         unsigned nr_valid_paths;        /* Total number of usable paths */
71         struct pgpath *current_pgpath;
72         struct priority_group *current_pg;
73         struct priority_group *next_pg; /* Switch to this PG if set */
74         unsigned repeat_count;          /* I/Os left before calling PS again */
75
76         unsigned queue_io;              /* Must we queue all I/O? */
77         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
78         unsigned saved_queue_if_no_path;/* Saved state during suspension */
79         unsigned pg_init_retries;       /* Number of times to retry pg_init */
80         unsigned pg_init_count;         /* Number of times pg_init called */
81
82         struct work_struct process_queued_ios;
83         struct bio_list queued_ios;
84         unsigned queue_size;
85
86         struct work_struct trigger_event;
87
88         /*
89          * We must use a mempool of dm_mpath_io structs so that we
90          * can resubmit bios on error.
91          */
92         mempool_t *mpio_pool;
93 };
94
95 /*
96  * Context information attached to each bio we process.
97  */
98 struct dm_mpath_io {
99         struct pgpath *pgpath;
100         struct dm_bio_details details;
101 };
102
103 typedef int (*action_fn) (struct pgpath *pgpath);
104
105 #define MIN_IOS 256     /* Mempool size */
106
107 static struct kmem_cache *_mpio_cache;
108
109 static struct workqueue_struct *kmultipathd;
110 static void process_queued_ios(struct work_struct *work);
111 static void trigger_event(struct work_struct *work);
112
113
114 /*-----------------------------------------------
115  * Allocation routines
116  *-----------------------------------------------*/
117
118 static struct pgpath *alloc_pgpath(void)
119 {
120         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
121
122         if (pgpath)
123                 pgpath->path.is_active = 1;
124
125         return pgpath;
126 }
127
128 static void free_pgpath(struct pgpath *pgpath)
129 {
130         kfree(pgpath);
131 }
132
133 static struct priority_group *alloc_priority_group(void)
134 {
135         struct priority_group *pg;
136
137         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
138
139         if (pg)
140                 INIT_LIST_HEAD(&pg->pgpaths);
141
142         return pg;
143 }
144
145 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
146 {
147         struct pgpath *pgpath, *tmp;
148
149         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
150                 list_del(&pgpath->list);
151                 dm_put_device(ti, pgpath->path.dev);
152                 free_pgpath(pgpath);
153         }
154 }
155
156 static void free_priority_group(struct priority_group *pg,
157                                 struct dm_target *ti)
158 {
159         struct path_selector *ps = &pg->ps;
160
161         if (ps->type) {
162                 ps->type->destroy(ps);
163                 dm_put_path_selector(ps->type);
164         }
165
166         free_pgpaths(&pg->pgpaths, ti);
167         kfree(pg);
168 }
169
170 static struct multipath *alloc_multipath(struct dm_target *ti)
171 {
172         struct multipath *m;
173
174         m = kzalloc(sizeof(*m), GFP_KERNEL);
175         if (m) {
176                 INIT_LIST_HEAD(&m->priority_groups);
177                 spin_lock_init(&m->lock);
178                 m->queue_io = 1;
179                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
180                 INIT_WORK(&m->trigger_event, trigger_event);
181                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
182                 if (!m->mpio_pool) {
183                         kfree(m);
184                         return NULL;
185                 }
186                 m->ti = ti;
187                 ti->private = m;
188         }
189
190         return m;
191 }
192
193 static void free_multipath(struct multipath *m)
194 {
195         struct priority_group *pg, *tmp;
196         struct hw_handler *hwh = &m->hw_handler;
197
198         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
199                 list_del(&pg->list);
200                 free_priority_group(pg, m->ti);
201         }
202
203         if (hwh->type) {
204                 hwh->type->destroy(hwh);
205                 dm_put_hw_handler(hwh->type);
206         }
207
208         mempool_destroy(m->mpio_pool);
209         kfree(m);
210 }
211
212
213 /*-----------------------------------------------
214  * Path selection
215  *-----------------------------------------------*/
216
217 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
218 {
219         struct hw_handler *hwh = &m->hw_handler;
220
221         m->current_pg = pgpath->pg;
222
223         /* Must we initialise the PG first, and queue I/O till it's ready? */
224         if (hwh->type && hwh->type->pg_init) {
225                 m->pg_init_required = 1;
226                 m->queue_io = 1;
227         } else {
228                 m->pg_init_required = 0;
229                 m->queue_io = 0;
230         }
231
232         m->pg_init_count = 0;
233 }
234
235 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
236 {
237         struct dm_path *path;
238
239         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
240         if (!path)
241                 return -ENXIO;
242
243         m->current_pgpath = path_to_pgpath(path);
244
245         if (m->current_pg != pg)
246                 __switch_pg(m, m->current_pgpath);
247
248         return 0;
249 }
250
251 static void __choose_pgpath(struct multipath *m)
252 {
253         struct priority_group *pg;
254         unsigned bypassed = 1;
255
256         if (!m->nr_valid_paths)
257                 goto failed;
258
259         /* Were we instructed to switch PG? */
260         if (m->next_pg) {
261                 pg = m->next_pg;
262                 m->next_pg = NULL;
263                 if (!__choose_path_in_pg(m, pg))
264                         return;
265         }
266
267         /* Don't change PG until it has no remaining paths */
268         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
269                 return;
270
271         /*
272          * Loop through priority groups until we find a valid path.
273          * First time we skip PGs marked 'bypassed'.
274          * Second time we only try the ones we skipped.
275          */
276         do {
277                 list_for_each_entry(pg, &m->priority_groups, list) {
278                         if (pg->bypassed == bypassed)
279                                 continue;
280                         if (!__choose_path_in_pg(m, pg))
281                                 return;
282                 }
283         } while (bypassed--);
284
285 failed:
286         m->current_pgpath = NULL;
287         m->current_pg = NULL;
288 }
289
290 /*
291  * Check whether bios must be queued in the device-mapper core rather
292  * than here in the target.
293  *
294  * m->lock must be held on entry.
295  *
296  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
297  * same value then we are not between multipath_presuspend()
298  * and multipath_resume() calls and we have no need to check
299  * for the DMF_NOFLUSH_SUSPENDING flag.
300  */
301 static int __must_push_back(struct multipath *m)
302 {
303         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
304                 dm_noflush_suspending(m->ti));
305 }
306
307 static int map_io(struct multipath *m, struct bio *bio,
308                   struct dm_mpath_io *mpio, unsigned was_queued)
309 {
310         int r = DM_MAPIO_REMAPPED;
311         unsigned long flags;
312         struct pgpath *pgpath;
313
314         spin_lock_irqsave(&m->lock, flags);
315
316         /* Do we need to select a new pgpath? */
317         if (!m->current_pgpath ||
318             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
319                 __choose_pgpath(m);
320
321         pgpath = m->current_pgpath;
322
323         if (was_queued)
324                 m->queue_size--;
325
326         if ((pgpath && m->queue_io) ||
327             (!pgpath && m->queue_if_no_path)) {
328                 /* Queue for the daemon to resubmit */
329                 bio_list_add(&m->queued_ios, bio);
330                 m->queue_size++;
331                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
332                     !m->queue_io)
333                         queue_work(kmultipathd, &m->process_queued_ios);
334                 pgpath = NULL;
335                 r = DM_MAPIO_SUBMITTED;
336         } else if (pgpath)
337                 bio->bi_bdev = pgpath->path.dev->bdev;
338         else if (__must_push_back(m))
339                 r = DM_MAPIO_REQUEUE;
340         else
341                 r = -EIO;       /* Failed */
342
343         mpio->pgpath = pgpath;
344
345         spin_unlock_irqrestore(&m->lock, flags);
346
347         return r;
348 }
349
350 /*
351  * If we run out of usable paths, should we queue I/O or error it?
352  */
353 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
354                             unsigned save_old_value)
355 {
356         unsigned long flags;
357
358         spin_lock_irqsave(&m->lock, flags);
359
360         if (save_old_value)
361                 m->saved_queue_if_no_path = m->queue_if_no_path;
362         else
363                 m->saved_queue_if_no_path = queue_if_no_path;
364         m->queue_if_no_path = queue_if_no_path;
365         if (!m->queue_if_no_path && m->queue_size)
366                 queue_work(kmultipathd, &m->process_queued_ios);
367
368         spin_unlock_irqrestore(&m->lock, flags);
369
370         return 0;
371 }
372
373 /*-----------------------------------------------------------------
374  * The multipath daemon is responsible for resubmitting queued ios.
375  *---------------------------------------------------------------*/
376
377 static void dispatch_queued_ios(struct multipath *m)
378 {
379         int r;
380         unsigned long flags;
381         struct bio *bio = NULL, *next;
382         struct dm_mpath_io *mpio;
383         union map_info *info;
384
385         spin_lock_irqsave(&m->lock, flags);
386         bio = bio_list_get(&m->queued_ios);
387         spin_unlock_irqrestore(&m->lock, flags);
388
389         while (bio) {
390                 next = bio->bi_next;
391                 bio->bi_next = NULL;
392
393                 info = dm_get_mapinfo(bio);
394                 mpio = info->ptr;
395
396                 r = map_io(m, bio, mpio, 1);
397                 if (r < 0)
398                         bio_endio(bio, r);
399                 else if (r == DM_MAPIO_REMAPPED)
400                         generic_make_request(bio);
401                 else if (r == DM_MAPIO_REQUEUE)
402                         bio_endio(bio, -EIO);
403
404                 bio = next;
405         }
406 }
407
408 static void process_queued_ios(struct work_struct *work)
409 {
410         struct multipath *m =
411                 container_of(work, struct multipath, process_queued_ios);
412         struct hw_handler *hwh = &m->hw_handler;
413         struct pgpath *pgpath = NULL;
414         unsigned init_required = 0, must_queue = 1;
415         unsigned long flags;
416
417         spin_lock_irqsave(&m->lock, flags);
418
419         if (!m->queue_size)
420                 goto out;
421
422         if (!m->current_pgpath)
423                 __choose_pgpath(m);
424
425         pgpath = m->current_pgpath;
426
427         if ((pgpath && !m->queue_io) ||
428             (!pgpath && !m->queue_if_no_path))
429                 must_queue = 0;
430
431         if (m->pg_init_required && !m->pg_init_in_progress) {
432                 m->pg_init_count++;
433                 m->pg_init_required = 0;
434                 m->pg_init_in_progress = 1;
435                 init_required = 1;
436         }
437
438 out:
439         spin_unlock_irqrestore(&m->lock, flags);
440
441         if (init_required)
442                 hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
443
444         if (!must_queue)
445                 dispatch_queued_ios(m);
446 }
447
448 /*
449  * An event is triggered whenever a path is taken out of use.
450  * Includes path failure and PG bypass.
451  */
452 static void trigger_event(struct work_struct *work)
453 {
454         struct multipath *m =
455                 container_of(work, struct multipath, trigger_event);
456
457         dm_table_event(m->ti->table);
458 }
459
460 /*-----------------------------------------------------------------
461  * Constructor/argument parsing:
462  * <#multipath feature args> [<arg>]*
463  * <#hw_handler args> [hw_handler [<arg>]*]
464  * <#priority groups>
465  * <initial priority group>
466  *     [<selector> <#selector args> [<arg>]*
467  *      <#paths> <#per-path selector args>
468  *         [<path> [<arg>]* ]+ ]+
469  *---------------------------------------------------------------*/
470 struct param {
471         unsigned min;
472         unsigned max;
473         char *error;
474 };
475
476 static int read_param(struct param *param, char *str, unsigned *v, char **error)
477 {
478         if (!str ||
479             (sscanf(str, "%u", v) != 1) ||
480             (*v < param->min) ||
481             (*v > param->max)) {
482                 *error = param->error;
483                 return -EINVAL;
484         }
485
486         return 0;
487 }
488
489 struct arg_set {
490         unsigned argc;
491         char **argv;
492 };
493
494 static char *shift(struct arg_set *as)
495 {
496         char *r;
497
498         if (as->argc) {
499                 as->argc--;
500                 r = *as->argv;
501                 as->argv++;
502                 return r;
503         }
504
505         return NULL;
506 }
507
508 static void consume(struct arg_set *as, unsigned n)
509 {
510         BUG_ON (as->argc < n);
511         as->argc -= n;
512         as->argv += n;
513 }
514
515 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
516                                struct dm_target *ti)
517 {
518         int r;
519         struct path_selector_type *pst;
520         unsigned ps_argc;
521
522         static struct param _params[] = {
523                 {0, 1024, "invalid number of path selector args"},
524         };
525
526         pst = dm_get_path_selector(shift(as));
527         if (!pst) {
528                 ti->error = "unknown path selector type";
529                 return -EINVAL;
530         }
531
532         r = read_param(_params, shift(as), &ps_argc, &ti->error);
533         if (r)
534                 return -EINVAL;
535
536         r = pst->create(&pg->ps, ps_argc, as->argv);
537         if (r) {
538                 dm_put_path_selector(pst);
539                 ti->error = "path selector constructor failed";
540                 return r;
541         }
542
543         pg->ps.type = pst;
544         consume(as, ps_argc);
545
546         return 0;
547 }
548
549 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
550                                struct dm_target *ti)
551 {
552         int r;
553         struct pgpath *p;
554
555         /* we need at least a path arg */
556         if (as->argc < 1) {
557                 ti->error = "no device given";
558                 return NULL;
559         }
560
561         p = alloc_pgpath();
562         if (!p)
563                 return NULL;
564
565         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
566                           dm_table_get_mode(ti->table), &p->path.dev);
567         if (r) {
568                 ti->error = "error getting device";
569                 goto bad;
570         }
571
572         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
573         if (r) {
574                 dm_put_device(ti, p->path.dev);
575                 goto bad;
576         }
577
578         return p;
579
580  bad:
581         free_pgpath(p);
582         return NULL;
583 }
584
585 static struct priority_group *parse_priority_group(struct arg_set *as,
586                                                    struct multipath *m)
587 {
588         static struct param _params[] = {
589                 {1, 1024, "invalid number of paths"},
590                 {0, 1024, "invalid number of selector args"}
591         };
592
593         int r;
594         unsigned i, nr_selector_args, nr_params;
595         struct priority_group *pg;
596         struct dm_target *ti = m->ti;
597
598         if (as->argc < 2) {
599                 as->argc = 0;
600                 ti->error = "not enough priority group aruments";
601                 return NULL;
602         }
603
604         pg = alloc_priority_group();
605         if (!pg) {
606                 ti->error = "couldn't allocate priority group";
607                 return NULL;
608         }
609         pg->m = m;
610
611         r = parse_path_selector(as, pg, ti);
612         if (r)
613                 goto bad;
614
615         /*
616          * read the paths
617          */
618         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
619         if (r)
620                 goto bad;
621
622         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
623         if (r)
624                 goto bad;
625
626         nr_params = 1 + nr_selector_args;
627         for (i = 0; i < pg->nr_pgpaths; i++) {
628                 struct pgpath *pgpath;
629                 struct arg_set path_args;
630
631                 if (as->argc < nr_params)
632                         goto bad;
633
634                 path_args.argc = nr_params;
635                 path_args.argv = as->argv;
636
637                 pgpath = parse_path(&path_args, &pg->ps, ti);
638                 if (!pgpath)
639                         goto bad;
640
641                 pgpath->pg = pg;
642                 list_add_tail(&pgpath->list, &pg->pgpaths);
643                 consume(as, nr_params);
644         }
645
646         return pg;
647
648  bad:
649         free_priority_group(pg, ti);
650         return NULL;
651 }
652
653 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
654 {
655         int r;
656         struct hw_handler_type *hwht;
657         unsigned hw_argc;
658         struct dm_target *ti = m->ti;
659
660         static struct param _params[] = {
661                 {0, 1024, "invalid number of hardware handler args"},
662         };
663
664         r = read_param(_params, shift(as), &hw_argc, &ti->error);
665         if (r)
666                 return -EINVAL;
667
668         if (!hw_argc)
669                 return 0;
670
671         hwht = dm_get_hw_handler(shift(as));
672         if (!hwht) {
673                 ti->error = "unknown hardware handler type";
674                 return -EINVAL;
675         }
676
677         m->hw_handler.md = dm_table_get_md(ti->table);
678         dm_put(m->hw_handler.md);
679
680         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
681         if (r) {
682                 dm_put_hw_handler(hwht);
683                 ti->error = "hardware handler constructor failed";
684                 return r;
685         }
686
687         m->hw_handler.type = hwht;
688         consume(as, hw_argc - 1);
689
690         return 0;
691 }
692
693 static int parse_features(struct arg_set *as, struct multipath *m)
694 {
695         int r;
696         unsigned argc;
697         struct dm_target *ti = m->ti;
698         const char *param_name;
699
700         static struct param _params[] = {
701                 {0, 3, "invalid number of feature args"},
702                 {1, 50, "pg_init_retries must be between 1 and 50"},
703         };
704
705         r = read_param(_params, shift(as), &argc, &ti->error);
706         if (r)
707                 return -EINVAL;
708
709         if (!argc)
710                 return 0;
711
712         do {
713                 param_name = shift(as);
714                 argc--;
715
716                 if (!strnicmp(param_name, MESG_STR("queue_if_no_path"))) {
717                         r = queue_if_no_path(m, 1, 0);
718                         continue;
719                 }
720
721                 if (!strnicmp(param_name, MESG_STR("pg_init_retries")) &&
722                     (argc >= 1)) {
723                         r = read_param(_params + 1, shift(as),
724                                        &m->pg_init_retries, &ti->error);
725                         argc--;
726                         continue;
727                 }
728
729                 ti->error = "Unrecognised multipath feature request";
730                 r = -EINVAL;
731         } while (argc && !r);
732
733         return r;
734 }
735
736 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
737                          char **argv)
738 {
739         /* target parameters */
740         static struct param _params[] = {
741                 {1, 1024, "invalid number of priority groups"},
742                 {1, 1024, "invalid initial priority group number"},
743         };
744
745         int r;
746         struct multipath *m;
747         struct arg_set as;
748         unsigned pg_count = 0;
749         unsigned next_pg_num;
750
751         as.argc = argc;
752         as.argv = argv;
753
754         m = alloc_multipath(ti);
755         if (!m) {
756                 ti->error = "can't allocate multipath";
757                 return -EINVAL;
758         }
759
760         r = parse_features(&as, m);
761         if (r)
762                 goto bad;
763
764         r = parse_hw_handler(&as, m);
765         if (r)
766                 goto bad;
767
768         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
769         if (r)
770                 goto bad;
771
772         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
773         if (r)
774                 goto bad;
775
776         /* parse the priority groups */
777         while (as.argc) {
778                 struct priority_group *pg;
779
780                 pg = parse_priority_group(&as, m);
781                 if (!pg) {
782                         r = -EINVAL;
783                         goto bad;
784                 }
785
786                 m->nr_valid_paths += pg->nr_pgpaths;
787                 list_add_tail(&pg->list, &m->priority_groups);
788                 pg_count++;
789                 pg->pg_num = pg_count;
790                 if (!--next_pg_num)
791                         m->next_pg = pg;
792         }
793
794         if (pg_count != m->nr_priority_groups) {
795                 ti->error = "priority group count mismatch";
796                 r = -EINVAL;
797                 goto bad;
798         }
799
800         return 0;
801
802  bad:
803         free_multipath(m);
804         return r;
805 }
806
807 static void multipath_dtr(struct dm_target *ti)
808 {
809         struct multipath *m = (struct multipath *) ti->private;
810
811         flush_workqueue(kmultipathd);
812         free_multipath(m);
813 }
814
815 /*
816  * Map bios, recording original fields for later in case we have to resubmit
817  */
818 static int multipath_map(struct dm_target *ti, struct bio *bio,
819                          union map_info *map_context)
820 {
821         int r;
822         struct dm_mpath_io *mpio;
823         struct multipath *m = (struct multipath *) ti->private;
824
825         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
826         dm_bio_record(&mpio->details, bio);
827
828         map_context->ptr = mpio;
829         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
830         r = map_io(m, bio, mpio, 0);
831         if (r < 0 || r == DM_MAPIO_REQUEUE)
832                 mempool_free(mpio, m->mpio_pool);
833
834         return r;
835 }
836
837 /*
838  * Take a path out of use.
839  */
840 static int fail_path(struct pgpath *pgpath)
841 {
842         unsigned long flags;
843         struct multipath *m = pgpath->pg->m;
844
845         spin_lock_irqsave(&m->lock, flags);
846
847         if (!pgpath->path.is_active)
848                 goto out;
849
850         DMWARN("Failing path %s.", pgpath->path.dev->name);
851
852         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
853         pgpath->path.is_active = 0;
854         pgpath->fail_count++;
855
856         m->nr_valid_paths--;
857
858         if (pgpath == m->current_pgpath)
859                 m->current_pgpath = NULL;
860
861         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
862                       pgpath->path.dev->name, m->nr_valid_paths);
863
864         queue_work(kmultipathd, &m->trigger_event);
865
866 out:
867         spin_unlock_irqrestore(&m->lock, flags);
868
869         return 0;
870 }
871
872 /*
873  * Reinstate a previously-failed path
874  */
875 static int reinstate_path(struct pgpath *pgpath)
876 {
877         int r = 0;
878         unsigned long flags;
879         struct multipath *m = pgpath->pg->m;
880
881         spin_lock_irqsave(&m->lock, flags);
882
883         if (pgpath->path.is_active)
884                 goto out;
885
886         if (!pgpath->pg->ps.type) {
887                 DMWARN("Reinstate path not supported by path selector %s",
888                        pgpath->pg->ps.type->name);
889                 r = -EINVAL;
890                 goto out;
891         }
892
893         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
894         if (r)
895                 goto out;
896
897         pgpath->path.is_active = 1;
898
899         m->current_pgpath = NULL;
900         if (!m->nr_valid_paths++ && m->queue_size)
901                 queue_work(kmultipathd, &m->process_queued_ios);
902
903         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
904                       pgpath->path.dev->name, m->nr_valid_paths);
905
906         queue_work(kmultipathd, &m->trigger_event);
907
908 out:
909         spin_unlock_irqrestore(&m->lock, flags);
910
911         return r;
912 }
913
914 /*
915  * Fail or reinstate all paths that match the provided struct dm_dev.
916  */
917 static int action_dev(struct multipath *m, struct dm_dev *dev,
918                       action_fn action)
919 {
920         int r = 0;
921         struct pgpath *pgpath;
922         struct priority_group *pg;
923
924         list_for_each_entry(pg, &m->priority_groups, list) {
925                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
926                         if (pgpath->path.dev == dev)
927                                 r = action(pgpath);
928                 }
929         }
930
931         return r;
932 }
933
934 /*
935  * Temporarily try to avoid having to use the specified PG
936  */
937 static void bypass_pg(struct multipath *m, struct priority_group *pg,
938                       int bypassed)
939 {
940         unsigned long flags;
941
942         spin_lock_irqsave(&m->lock, flags);
943
944         pg->bypassed = bypassed;
945         m->current_pgpath = NULL;
946         m->current_pg = NULL;
947
948         spin_unlock_irqrestore(&m->lock, flags);
949
950         queue_work(kmultipathd, &m->trigger_event);
951 }
952
953 /*
954  * Switch to using the specified PG from the next I/O that gets mapped
955  */
956 static int switch_pg_num(struct multipath *m, const char *pgstr)
957 {
958         struct priority_group *pg;
959         unsigned pgnum;
960         unsigned long flags;
961
962         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
963             (pgnum > m->nr_priority_groups)) {
964                 DMWARN("invalid PG number supplied to switch_pg_num");
965                 return -EINVAL;
966         }
967
968         spin_lock_irqsave(&m->lock, flags);
969         list_for_each_entry(pg, &m->priority_groups, list) {
970                 pg->bypassed = 0;
971                 if (--pgnum)
972                         continue;
973
974                 m->current_pgpath = NULL;
975                 m->current_pg = NULL;
976                 m->next_pg = pg;
977         }
978         spin_unlock_irqrestore(&m->lock, flags);
979
980         queue_work(kmultipathd, &m->trigger_event);
981         return 0;
982 }
983
984 /*
985  * Set/clear bypassed status of a PG.
986  * PGs are numbered upwards from 1 in the order they were declared.
987  */
988 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
989 {
990         struct priority_group *pg;
991         unsigned pgnum;
992
993         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
994             (pgnum > m->nr_priority_groups)) {
995                 DMWARN("invalid PG number supplied to bypass_pg");
996                 return -EINVAL;
997         }
998
999         list_for_each_entry(pg, &m->priority_groups, list) {
1000                 if (!--pgnum)
1001                         break;
1002         }
1003
1004         bypass_pg(m, pg, bypassed);
1005         return 0;
1006 }
1007
1008 /*
1009  * Should we retry pg_init immediately?
1010  */
1011 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1012 {
1013         unsigned long flags;
1014         int limit_reached = 0;
1015
1016         spin_lock_irqsave(&m->lock, flags);
1017
1018         if (m->pg_init_count <= m->pg_init_retries)
1019                 m->pg_init_required = 1;
1020         else
1021                 limit_reached = 1;
1022
1023         spin_unlock_irqrestore(&m->lock, flags);
1024
1025         return limit_reached;
1026 }
1027
1028 /*
1029  * pg_init must call this when it has completed its initialisation
1030  */
1031 void dm_pg_init_complete(struct dm_path *path, unsigned err_flags)
1032 {
1033         struct pgpath *pgpath = path_to_pgpath(path);
1034         struct priority_group *pg = pgpath->pg;
1035         struct multipath *m = pg->m;
1036         unsigned long flags;
1037
1038         /*
1039          * If requested, retry pg_init until maximum number of retries exceeded.
1040          * If retry not requested and PG already bypassed, always fail the path.
1041          */
1042         if (err_flags & MP_RETRY) {
1043                 if (pg_init_limit_reached(m, pgpath))
1044                         err_flags |= MP_FAIL_PATH;
1045         } else if (err_flags && pg->bypassed)
1046                 err_flags |= MP_FAIL_PATH;
1047
1048         if (err_flags & MP_FAIL_PATH)
1049                 fail_path(pgpath);
1050
1051         if (err_flags & MP_BYPASS_PG)
1052                 bypass_pg(m, pg, 1);
1053
1054         spin_lock_irqsave(&m->lock, flags);
1055         if (err_flags & ~MP_RETRY) {
1056                 m->current_pgpath = NULL;
1057                 m->current_pg = NULL;
1058         } else if (!m->pg_init_required)
1059                 m->queue_io = 0;
1060
1061         m->pg_init_in_progress = 0;
1062         queue_work(kmultipathd, &m->process_queued_ios);
1063         spin_unlock_irqrestore(&m->lock, flags);
1064 }
1065
1066 /*
1067  * end_io handling
1068  */
1069 static int do_end_io(struct multipath *m, struct bio *bio,
1070                      int error, struct dm_mpath_io *mpio)
1071 {
1072         struct hw_handler *hwh = &m->hw_handler;
1073         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
1074         unsigned long flags;
1075
1076         if (!error)
1077                 return 0;       /* I/O complete */
1078
1079         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1080                 return error;
1081
1082         if (error == -EOPNOTSUPP)
1083                 return error;
1084
1085         spin_lock_irqsave(&m->lock, flags);
1086         if (!m->nr_valid_paths) {
1087                 if (__must_push_back(m)) {
1088                         spin_unlock_irqrestore(&m->lock, flags);
1089                         return DM_ENDIO_REQUEUE;
1090                 } else if (!m->queue_if_no_path) {
1091                         spin_unlock_irqrestore(&m->lock, flags);
1092                         return -EIO;
1093                 } else {
1094                         spin_unlock_irqrestore(&m->lock, flags);
1095                         goto requeue;
1096                 }
1097         }
1098         spin_unlock_irqrestore(&m->lock, flags);
1099
1100         if (hwh->type && hwh->type->error)
1101                 err_flags = hwh->type->error(hwh, bio);
1102
1103         if (mpio->pgpath) {
1104                 if (err_flags & MP_FAIL_PATH)
1105                         fail_path(mpio->pgpath);
1106
1107                 if (err_flags & MP_BYPASS_PG)
1108                         bypass_pg(m, mpio->pgpath->pg, 1);
1109         }
1110
1111         if (err_flags & MP_ERROR_IO)
1112                 return -EIO;
1113
1114       requeue:
1115         dm_bio_restore(&mpio->details, bio);
1116
1117         /* queue for the daemon to resubmit or fail */
1118         spin_lock_irqsave(&m->lock, flags);
1119         bio_list_add(&m->queued_ios, bio);
1120         m->queue_size++;
1121         if (!m->queue_io)
1122                 queue_work(kmultipathd, &m->process_queued_ios);
1123         spin_unlock_irqrestore(&m->lock, flags);
1124
1125         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1126 }
1127
1128 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1129                             int error, union map_info *map_context)
1130 {
1131         struct multipath *m = ti->private;
1132         struct dm_mpath_io *mpio = map_context->ptr;
1133         struct pgpath *pgpath = mpio->pgpath;
1134         struct path_selector *ps;
1135         int r;
1136
1137         r  = do_end_io(m, bio, error, mpio);
1138         if (pgpath) {
1139                 ps = &pgpath->pg->ps;
1140                 if (ps->type->end_io)
1141                         ps->type->end_io(ps, &pgpath->path);
1142         }
1143         if (r != DM_ENDIO_INCOMPLETE)
1144                 mempool_free(mpio, m->mpio_pool);
1145
1146         return r;
1147 }
1148
1149 /*
1150  * Suspend can't complete until all the I/O is processed so if
1151  * the last path fails we must error any remaining I/O.
1152  * Note that if the freeze_bdev fails while suspending, the
1153  * queue_if_no_path state is lost - userspace should reset it.
1154  */
1155 static void multipath_presuspend(struct dm_target *ti)
1156 {
1157         struct multipath *m = (struct multipath *) ti->private;
1158
1159         queue_if_no_path(m, 0, 1);
1160 }
1161
1162 /*
1163  * Restore the queue_if_no_path setting.
1164  */
1165 static void multipath_resume(struct dm_target *ti)
1166 {
1167         struct multipath *m = (struct multipath *) ti->private;
1168         unsigned long flags;
1169
1170         spin_lock_irqsave(&m->lock, flags);
1171         m->queue_if_no_path = m->saved_queue_if_no_path;
1172         spin_unlock_irqrestore(&m->lock, flags);
1173 }
1174
1175 /*
1176  * Info output has the following format:
1177  * num_multipath_feature_args [multipath_feature_args]*
1178  * num_handler_status_args [handler_status_args]*
1179  * num_groups init_group_number
1180  *            [A|D|E num_ps_status_args [ps_status_args]*
1181  *             num_paths num_selector_args
1182  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1183  *
1184  * Table output has the following format (identical to the constructor string):
1185  * num_feature_args [features_args]*
1186  * num_handler_args hw_handler [hw_handler_args]*
1187  * num_groups init_group_number
1188  *     [priority selector-name num_ps_args [ps_args]*
1189  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1190  */
1191 static int multipath_status(struct dm_target *ti, status_type_t type,
1192                             char *result, unsigned int maxlen)
1193 {
1194         int sz = 0;
1195         unsigned long flags;
1196         struct multipath *m = (struct multipath *) ti->private;
1197         struct hw_handler *hwh = &m->hw_handler;
1198         struct priority_group *pg;
1199         struct pgpath *p;
1200         unsigned pg_num;
1201         char state;
1202
1203         spin_lock_irqsave(&m->lock, flags);
1204
1205         /* Features */
1206         if (type == STATUSTYPE_INFO)
1207                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1208         else {
1209                 DMEMIT("%u ", m->queue_if_no_path +
1210                               (m->pg_init_retries > 0) * 2);
1211                 if (m->queue_if_no_path)
1212                         DMEMIT("queue_if_no_path ");
1213                 if (m->pg_init_retries)
1214                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1215         }
1216
1217         if (hwh->type && hwh->type->status)
1218                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1219         else if (!hwh->type || type == STATUSTYPE_INFO)
1220                 DMEMIT("0 ");
1221         else
1222                 DMEMIT("1 %s ", hwh->type->name);
1223
1224         DMEMIT("%u ", m->nr_priority_groups);
1225
1226         if (m->next_pg)
1227                 pg_num = m->next_pg->pg_num;
1228         else if (m->current_pg)
1229                 pg_num = m->current_pg->pg_num;
1230         else
1231                         pg_num = 1;
1232
1233         DMEMIT("%u ", pg_num);
1234
1235         switch (type) {
1236         case STATUSTYPE_INFO:
1237                 list_for_each_entry(pg, &m->priority_groups, list) {
1238                         if (pg->bypassed)
1239                                 state = 'D';    /* Disabled */
1240                         else if (pg == m->current_pg)
1241                                 state = 'A';    /* Currently Active */
1242                         else
1243                                 state = 'E';    /* Enabled */
1244
1245                         DMEMIT("%c ", state);
1246
1247                         if (pg->ps.type->status)
1248                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1249                                                           result + sz,
1250                                                           maxlen - sz);
1251                         else
1252                                 DMEMIT("0 ");
1253
1254                         DMEMIT("%u %u ", pg->nr_pgpaths,
1255                                pg->ps.type->info_args);
1256
1257                         list_for_each_entry(p, &pg->pgpaths, list) {
1258                                 DMEMIT("%s %s %u ", p->path.dev->name,
1259                                        p->path.is_active ? "A" : "F",
1260                                        p->fail_count);
1261                                 if (pg->ps.type->status)
1262                                         sz += pg->ps.type->status(&pg->ps,
1263                                               &p->path, type, result + sz,
1264                                               maxlen - sz);
1265                         }
1266                 }
1267                 break;
1268
1269         case STATUSTYPE_TABLE:
1270                 list_for_each_entry(pg, &m->priority_groups, list) {
1271                         DMEMIT("%s ", pg->ps.type->name);
1272
1273                         if (pg->ps.type->status)
1274                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1275                                                           result + sz,
1276                                                           maxlen - sz);
1277                         else
1278                                 DMEMIT("0 ");
1279
1280                         DMEMIT("%u %u ", pg->nr_pgpaths,
1281                                pg->ps.type->table_args);
1282
1283                         list_for_each_entry(p, &pg->pgpaths, list) {
1284                                 DMEMIT("%s ", p->path.dev->name);
1285                                 if (pg->ps.type->status)
1286                                         sz += pg->ps.type->status(&pg->ps,
1287                                               &p->path, type, result + sz,
1288                                               maxlen - sz);
1289                         }
1290                 }
1291                 break;
1292         }
1293
1294         spin_unlock_irqrestore(&m->lock, flags);
1295
1296         return 0;
1297 }
1298
1299 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1300 {
1301         int r;
1302         struct dm_dev *dev;
1303         struct multipath *m = (struct multipath *) ti->private;
1304         action_fn action;
1305
1306         if (argc == 1) {
1307                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1308                         return queue_if_no_path(m, 1, 0);
1309                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1310                         return queue_if_no_path(m, 0, 0);
1311         }
1312
1313         if (argc != 2)
1314                 goto error;
1315
1316         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1317                 return bypass_pg_num(m, argv[1], 1);
1318         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1319                 return bypass_pg_num(m, argv[1], 0);
1320         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1321                 return switch_pg_num(m, argv[1]);
1322         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1323                 action = reinstate_path;
1324         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1325                 action = fail_path;
1326         else
1327                 goto error;
1328
1329         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1330                           dm_table_get_mode(ti->table), &dev);
1331         if (r) {
1332                 DMWARN("message: error getting device %s",
1333                        argv[1]);
1334                 return -EINVAL;
1335         }
1336
1337         r = action_dev(m, dev, action);
1338
1339         dm_put_device(ti, dev);
1340
1341         return r;
1342
1343 error:
1344         DMWARN("Unrecognised multipath message received.");
1345         return -EINVAL;
1346 }
1347
1348 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1349                            struct file *filp, unsigned int cmd,
1350                            unsigned long arg)
1351 {
1352         struct multipath *m = (struct multipath *) ti->private;
1353         struct block_device *bdev = NULL;
1354         unsigned long flags;
1355         struct file fake_file = {};
1356         struct dentry fake_dentry = {};
1357         int r = 0;
1358
1359         fake_file.f_path.dentry = &fake_dentry;
1360
1361         spin_lock_irqsave(&m->lock, flags);
1362
1363         if (!m->current_pgpath)
1364                 __choose_pgpath(m);
1365
1366         if (m->current_pgpath) {
1367                 bdev = m->current_pgpath->path.dev->bdev;
1368                 fake_dentry.d_inode = bdev->bd_inode;
1369                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1370         }
1371
1372         if (m->queue_io)
1373                 r = -EAGAIN;
1374         else if (!bdev)
1375                 r = -EIO;
1376
1377         spin_unlock_irqrestore(&m->lock, flags);
1378
1379         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1380                                          bdev->bd_disk, cmd, arg);
1381 }
1382
1383 /*-----------------------------------------------------------------
1384  * Module setup
1385  *---------------------------------------------------------------*/
1386 static struct target_type multipath_target = {
1387         .name = "multipath",
1388         .version = {1, 0, 5},
1389         .module = THIS_MODULE,
1390         .ctr = multipath_ctr,
1391         .dtr = multipath_dtr,
1392         .map = multipath_map,
1393         .end_io = multipath_end_io,
1394         .presuspend = multipath_presuspend,
1395         .resume = multipath_resume,
1396         .status = multipath_status,
1397         .message = multipath_message,
1398         .ioctl  = multipath_ioctl,
1399 };
1400
1401 static int __init dm_multipath_init(void)
1402 {
1403         int r;
1404
1405         /* allocate a slab for the dm_ios */
1406         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1407         if (!_mpio_cache)
1408                 return -ENOMEM;
1409
1410         r = dm_register_target(&multipath_target);
1411         if (r < 0) {
1412                 DMERR("register failed %d", r);
1413                 kmem_cache_destroy(_mpio_cache);
1414                 return -EINVAL;
1415         }
1416
1417         kmultipathd = create_workqueue("kmpathd");
1418         if (!kmultipathd) {
1419                 DMERR("failed to create workqueue kmpathd");
1420                 dm_unregister_target(&multipath_target);
1421                 kmem_cache_destroy(_mpio_cache);
1422                 return -ENOMEM;
1423         }
1424
1425         DMINFO("version %u.%u.%u loaded",
1426                multipath_target.version[0], multipath_target.version[1],
1427                multipath_target.version[2]);
1428
1429         return r;
1430 }
1431
1432 static void __exit dm_multipath_exit(void)
1433 {
1434         int r;
1435
1436         destroy_workqueue(kmultipathd);
1437
1438         r = dm_unregister_target(&multipath_target);
1439         if (r < 0)
1440                 DMERR("target unregister failed %d", r);
1441         kmem_cache_destroy(_mpio_cache);
1442 }
1443
1444 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1445
1446 module_init(dm_multipath_init);
1447 module_exit(dm_multipath_exit);
1448
1449 MODULE_DESCRIPTION(DM_NAME " multipath target");
1450 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1451 MODULE_LICENSE("GPL");