[PATCH] device-mapper multipath: Avoid possible suspension deadlock
[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
14 #include <linux/ctype.h>
15 #include <linux/init.h>
16 #include <linux/mempool.h>
17 #include <linux/module.h>
18 #include <linux/pagemap.h>
19 #include <linux/slab.h>
20 #include <linux/time.h>
21 #include <linux/workqueue.h>
22 #include <asm/atomic.h>
23
24 #define MESG_STR(x) x, sizeof(x)
25
26 /* Path properties */
27 struct pgpath {
28         struct list_head list;
29
30         struct priority_group *pg;      /* Owning PG */
31         unsigned fail_count;            /* Cumulative failure count */
32
33         struct path path;
34 };
35
36 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
37
38 /*
39  * Paths are grouped into Priority Groups and numbered from 1 upwards.
40  * Each has a path selector which controls which path gets used.
41  */
42 struct priority_group {
43         struct list_head list;
44
45         struct multipath *m;            /* Owning multipath instance */
46         struct path_selector ps;
47
48         unsigned pg_num;                /* Reference number */
49         unsigned bypassed;              /* Temporarily bypass this PG? */
50
51         unsigned nr_pgpaths;            /* Number of paths in PG */
52         struct list_head pgpaths;
53 };
54
55 /* Multipath context */
56 struct multipath {
57         struct list_head list;
58         struct dm_target *ti;
59
60         spinlock_t lock;
61
62         struct hw_handler hw_handler;
63         unsigned nr_priority_groups;
64         struct list_head priority_groups;
65         unsigned pg_init_required;      /* pg_init needs calling? */
66
67         unsigned nr_valid_paths;        /* Total number of usable paths */
68         struct pgpath *current_pgpath;
69         struct priority_group *current_pg;
70         struct priority_group *next_pg; /* Switch to this PG if set */
71         unsigned repeat_count;          /* I/Os left before calling PS again */
72
73         unsigned queue_io;              /* Must we queue all I/O? */
74         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
75         unsigned saved_queue_if_no_path;/* Saved state during suspension */
76
77         struct work_struct process_queued_ios;
78         struct bio_list queued_ios;
79         unsigned queue_size;
80
81         struct work_struct trigger_event;
82
83         /*
84          * We must use a mempool of mpath_io structs so that we
85          * can resubmit bios on error.
86          */
87         mempool_t *mpio_pool;
88 };
89
90 /*
91  * Context information attached to each bio we process.
92  */
93 struct mpath_io {
94         struct pgpath *pgpath;
95         struct dm_bio_details details;
96 };
97
98 typedef int (*action_fn) (struct pgpath *pgpath);
99
100 #define MIN_IOS 256     /* Mempool size */
101
102 static kmem_cache_t *_mpio_cache;
103
104 struct workqueue_struct *kmultipathd;
105 static void process_queued_ios(void *data);
106 static void trigger_event(void *data);
107
108
109 /*-----------------------------------------------
110  * Allocation routines
111  *-----------------------------------------------*/
112
113 static struct pgpath *alloc_pgpath(void)
114 {
115         struct pgpath *pgpath = kmalloc(sizeof(*pgpath), GFP_KERNEL);
116
117         if (pgpath) {
118                 memset(pgpath, 0, sizeof(*pgpath));
119                 pgpath->path.is_active = 1;
120         }
121
122         return pgpath;
123 }
124
125 static inline void free_pgpath(struct pgpath *pgpath)
126 {
127         kfree(pgpath);
128 }
129
130 static struct priority_group *alloc_priority_group(void)
131 {
132         struct priority_group *pg;
133
134         pg = kmalloc(sizeof(*pg), GFP_KERNEL);
135         if (!pg)
136                 return NULL;
137
138         memset(pg, 0, sizeof(*pg));
139         INIT_LIST_HEAD(&pg->pgpaths);
140
141         return pg;
142 }
143
144 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
145 {
146         struct pgpath *pgpath, *tmp;
147
148         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
149                 list_del(&pgpath->list);
150                 dm_put_device(ti, pgpath->path.dev);
151                 free_pgpath(pgpath);
152         }
153 }
154
155 static void free_priority_group(struct priority_group *pg,
156                                 struct dm_target *ti)
157 {
158         struct path_selector *ps = &pg->ps;
159
160         if (ps->type) {
161                 ps->type->destroy(ps);
162                 dm_put_path_selector(ps->type);
163         }
164
165         free_pgpaths(&pg->pgpaths, ti);
166         kfree(pg);
167 }
168
169 static struct multipath *alloc_multipath(void)
170 {
171         struct multipath *m;
172
173         m = kmalloc(sizeof(*m), GFP_KERNEL);
174         if (m) {
175                 memset(m, 0, sizeof(*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, m);
180                 INIT_WORK(&m->trigger_event, trigger_event, m);
181                 m->mpio_pool = mempool_create(MIN_IOS, mempool_alloc_slab,
182                                               mempool_free_slab, _mpio_cache);
183                 if (!m->mpio_pool) {
184                         kfree(m);
185                         return NULL;
186                 }
187         }
188
189         return m;
190 }
191
192 static void free_multipath(struct multipath *m)
193 {
194         struct priority_group *pg, *tmp;
195         struct hw_handler *hwh = &m->hw_handler;
196
197         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
198                 list_del(&pg->list);
199                 free_priority_group(pg, m->ti);
200         }
201
202         if (hwh->type) {
203                 hwh->type->destroy(hwh);
204                 dm_put_hw_handler(hwh->type);
205         }
206
207         mempool_destroy(m->mpio_pool);
208         kfree(m);
209 }
210
211
212 /*-----------------------------------------------
213  * Path selection
214  *-----------------------------------------------*/
215
216 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
217 {
218         struct hw_handler *hwh = &m->hw_handler;
219
220         m->current_pg = pgpath->pg;
221
222         /* Must we initialise the PG first, and queue I/O till it's ready? */
223         if (hwh->type && hwh->type->pg_init) {
224                 m->pg_init_required = 1;
225                 m->queue_io = 1;
226         } else {
227                 m->pg_init_required = 0;
228                 m->queue_io = 0;
229         }
230 }
231
232 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
233 {
234         struct path *path;
235
236         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
237         if (!path)
238                 return -ENXIO;
239
240         m->current_pgpath = path_to_pgpath(path);
241
242         if (m->current_pg != pg)
243                 __switch_pg(m, m->current_pgpath);
244
245         return 0;
246 }
247
248 static void __choose_pgpath(struct multipath *m)
249 {
250         struct priority_group *pg;
251         unsigned bypassed = 1;
252
253         if (!m->nr_valid_paths)
254                 goto failed;
255
256         /* Were we instructed to switch PG? */
257         if (m->next_pg) {
258                 pg = m->next_pg;
259                 m->next_pg = NULL;
260                 if (!__choose_path_in_pg(m, pg))
261                         return;
262         }
263
264         /* Don't change PG until it has no remaining paths */
265         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
266                 return;
267
268         /*
269          * Loop through priority groups until we find a valid path.
270          * First time we skip PGs marked 'bypassed'.
271          * Second time we only try the ones we skipped.
272          */
273         do {
274                 list_for_each_entry(pg, &m->priority_groups, list) {
275                         if (pg->bypassed == bypassed)
276                                 continue;
277                         if (!__choose_path_in_pg(m, pg))
278                                 return;
279                 }
280         } while (bypassed--);
281
282 failed:
283         m->current_pgpath = NULL;
284         m->current_pg = NULL;
285 }
286
287 static int map_io(struct multipath *m, struct bio *bio, struct mpath_io *mpio,
288                   unsigned was_queued)
289 {
290         int r = 1;
291         unsigned long flags;
292         struct pgpath *pgpath;
293
294         spin_lock_irqsave(&m->lock, flags);
295
296         /* Do we need to select a new pgpath? */
297         if (!m->current_pgpath ||
298             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
299                 __choose_pgpath(m);
300
301         pgpath = m->current_pgpath;
302
303         if (was_queued)
304                 m->queue_size--;
305
306         if ((pgpath && m->queue_io) ||
307             (!pgpath && m->queue_if_no_path)) {
308                 /* Queue for the daemon to resubmit */
309                 bio_list_add(&m->queued_ios, bio);
310                 m->queue_size++;
311                 if (m->pg_init_required || !m->queue_io)
312                         queue_work(kmultipathd, &m->process_queued_ios);
313                 pgpath = NULL;
314                 r = 0;
315         } else if (!pgpath)
316                 r = -EIO;               /* Failed */
317         else
318                 bio->bi_bdev = pgpath->path.dev->bdev;
319
320         mpio->pgpath = pgpath;
321
322         spin_unlock_irqrestore(&m->lock, flags);
323
324         return r;
325 }
326
327 /*
328  * If we run out of usable paths, should we queue I/O or error it?
329  */
330 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path)
331 {
332         unsigned long flags;
333
334         spin_lock_irqsave(&m->lock, flags);
335
336         m->saved_queue_if_no_path = m->queue_if_no_path;
337         m->queue_if_no_path = queue_if_no_path;
338         if (!m->queue_if_no_path)
339                 queue_work(kmultipathd, &m->process_queued_ios);
340
341         spin_unlock_irqrestore(&m->lock, flags);
342
343         return 0;
344 }
345
346 /*-----------------------------------------------------------------
347  * The multipath daemon is responsible for resubmitting queued ios.
348  *---------------------------------------------------------------*/
349
350 static void dispatch_queued_ios(struct multipath *m)
351 {
352         int r;
353         unsigned long flags;
354         struct bio *bio = NULL, *next;
355         struct mpath_io *mpio;
356         union map_info *info;
357
358         spin_lock_irqsave(&m->lock, flags);
359         bio = bio_list_get(&m->queued_ios);
360         spin_unlock_irqrestore(&m->lock, flags);
361
362         while (bio) {
363                 next = bio->bi_next;
364                 bio->bi_next = NULL;
365
366                 info = dm_get_mapinfo(bio);
367                 mpio = info->ptr;
368
369                 r = map_io(m, bio, mpio, 1);
370                 if (r < 0)
371                         bio_endio(bio, bio->bi_size, r);
372                 else if (r == 1)
373                         generic_make_request(bio);
374
375                 bio = next;
376         }
377 }
378
379 static void process_queued_ios(void *data)
380 {
381         struct multipath *m = (struct multipath *) data;
382         struct hw_handler *hwh = &m->hw_handler;
383         struct pgpath *pgpath;
384         unsigned init_required, must_queue = 0;
385         unsigned long flags;
386
387         spin_lock_irqsave(&m->lock, flags);
388
389         if (!m->current_pgpath)
390                 __choose_pgpath(m);
391
392         pgpath = m->current_pgpath;
393
394         if ((pgpath && m->queue_io) ||
395             (!pgpath && m->queue_if_no_path))
396                 must_queue = 1;
397
398         init_required = m->pg_init_required;
399         if (init_required)
400                 m->pg_init_required = 0;
401
402         spin_unlock_irqrestore(&m->lock, flags);
403
404         if (init_required)
405                 hwh->type->pg_init(hwh, pgpath->pg->bypassed, &pgpath->path);
406
407         if (!must_queue)
408                 dispatch_queued_ios(m);
409 }
410
411 /*
412  * An event is triggered whenever a path is taken out of use.
413  * Includes path failure and PG bypass.
414  */
415 static void trigger_event(void *data)
416 {
417         struct multipath *m = (struct multipath *) data;
418
419         dm_table_event(m->ti->table);
420 }
421
422 /*-----------------------------------------------------------------
423  * Constructor/argument parsing:
424  * <#multipath feature args> [<arg>]*
425  * <#hw_handler args> [hw_handler [<arg>]*]
426  * <#priority groups>
427  * <initial priority group>
428  *     [<selector> <#selector args> [<arg>]*
429  *      <#paths> <#per-path selector args>
430  *         [<path> [<arg>]* ]+ ]+
431  *---------------------------------------------------------------*/
432 struct param {
433         unsigned min;
434         unsigned max;
435         char *error;
436 };
437
438 #define ESTR(s) ("dm-multipath: " s)
439
440 static int read_param(struct param *param, char *str, unsigned *v, char **error)
441 {
442         if (!str ||
443             (sscanf(str, "%u", v) != 1) ||
444             (*v < param->min) ||
445             (*v > param->max)) {
446                 *error = param->error;
447                 return -EINVAL;
448         }
449
450         return 0;
451 }
452
453 struct arg_set {
454         unsigned argc;
455         char **argv;
456 };
457
458 static char *shift(struct arg_set *as)
459 {
460         char *r;
461
462         if (as->argc) {
463                 as->argc--;
464                 r = *as->argv;
465                 as->argv++;
466                 return r;
467         }
468
469         return NULL;
470 }
471
472 static void consume(struct arg_set *as, unsigned n)
473 {
474         BUG_ON (as->argc < n);
475         as->argc -= n;
476         as->argv += n;
477 }
478
479 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
480                                struct dm_target *ti)
481 {
482         int r;
483         struct path_selector_type *pst;
484         unsigned ps_argc;
485
486         static struct param _params[] = {
487                 {0, 1024, ESTR("invalid number of path selector args")},
488         };
489
490         pst = dm_get_path_selector(shift(as));
491         if (!pst) {
492                 ti->error = ESTR("unknown path selector type");
493                 return -EINVAL;
494         }
495
496         r = read_param(_params, shift(as), &ps_argc, &ti->error);
497         if (r)
498                 return -EINVAL;
499
500         r = pst->create(&pg->ps, ps_argc, as->argv);
501         if (r) {
502                 dm_put_path_selector(pst);
503                 ti->error = ESTR("path selector constructor failed");
504                 return r;
505         }
506
507         pg->ps.type = pst;
508         consume(as, ps_argc);
509
510         return 0;
511 }
512
513 static struct pgpath *parse_path(struct arg_set *as, struct path_selector *ps,
514                                struct dm_target *ti)
515 {
516         int r;
517         struct pgpath *p;
518
519         /* we need at least a path arg */
520         if (as->argc < 1) {
521                 ti->error = ESTR("no device given");
522                 return NULL;
523         }
524
525         p = alloc_pgpath();
526         if (!p)
527                 return NULL;
528
529         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
530                           dm_table_get_mode(ti->table), &p->path.dev);
531         if (r) {
532                 ti->error = ESTR("error getting device");
533                 goto bad;
534         }
535
536         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
537         if (r) {
538                 dm_put_device(ti, p->path.dev);
539                 goto bad;
540         }
541
542         return p;
543
544  bad:
545         free_pgpath(p);
546         return NULL;
547 }
548
549 static struct priority_group *parse_priority_group(struct arg_set *as,
550                                                    struct multipath *m,
551                                                    struct dm_target *ti)
552 {
553         static struct param _params[] = {
554                 {1, 1024, ESTR("invalid number of paths")},
555                 {0, 1024, ESTR("invalid number of selector args")}
556         };
557
558         int r;
559         unsigned i, nr_selector_args, nr_params;
560         struct priority_group *pg;
561
562         if (as->argc < 2) {
563                 as->argc = 0;
564                 ti->error = ESTR("not enough priority group aruments");
565                 return NULL;
566         }
567
568         pg = alloc_priority_group();
569         if (!pg) {
570                 ti->error = ESTR("couldn't allocate priority group");
571                 return NULL;
572         }
573         pg->m = m;
574
575         r = parse_path_selector(as, pg, ti);
576         if (r)
577                 goto bad;
578
579         /*
580          * read the paths
581          */
582         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
583         if (r)
584                 goto bad;
585
586         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
587         if (r)
588                 goto bad;
589
590         nr_params = 1 + nr_selector_args;
591         for (i = 0; i < pg->nr_pgpaths; i++) {
592                 struct pgpath *pgpath;
593                 struct arg_set path_args;
594
595                 if (as->argc < nr_params)
596                         goto bad;
597
598                 path_args.argc = nr_params;
599                 path_args.argv = as->argv;
600
601                 pgpath = parse_path(&path_args, &pg->ps, ti);
602                 if (!pgpath)
603                         goto bad;
604
605                 pgpath->pg = pg;
606                 list_add_tail(&pgpath->list, &pg->pgpaths);
607                 consume(as, nr_params);
608         }
609
610         return pg;
611
612  bad:
613         free_priority_group(pg, ti);
614         return NULL;
615 }
616
617 static int parse_hw_handler(struct arg_set *as, struct multipath *m,
618                             struct dm_target *ti)
619 {
620         int r;
621         struct hw_handler_type *hwht;
622         unsigned hw_argc;
623
624         static struct param _params[] = {
625                 {0, 1024, ESTR("invalid number of hardware handler args")},
626         };
627
628         r = read_param(_params, shift(as), &hw_argc, &ti->error);
629         if (r)
630                 return -EINVAL;
631
632         if (!hw_argc)
633                 return 0;
634
635         hwht = dm_get_hw_handler(shift(as));
636         if (!hwht) {
637                 ti->error = ESTR("unknown hardware handler type");
638                 return -EINVAL;
639         }
640
641         r = hwht->create(&m->hw_handler, hw_argc - 1, as->argv);
642         if (r) {
643                 dm_put_hw_handler(hwht);
644                 ti->error = ESTR("hardware handler constructor failed");
645                 return r;
646         }
647
648         m->hw_handler.type = hwht;
649         consume(as, hw_argc - 1);
650
651         return 0;
652 }
653
654 static int parse_features(struct arg_set *as, struct multipath *m,
655                           struct dm_target *ti)
656 {
657         int r;
658         unsigned argc;
659
660         static struct param _params[] = {
661                 {0, 1, ESTR("invalid number of feature args")},
662         };
663
664         r = read_param(_params, shift(as), &argc, &ti->error);
665         if (r)
666                 return -EINVAL;
667
668         if (!argc)
669                 return 0;
670
671         if (!strnicmp(shift(as), MESG_STR("queue_if_no_path")))
672                 return queue_if_no_path(m, 1);
673         else {
674                 ti->error = "Unrecognised multipath feature request";
675                 return -EINVAL;
676         }
677 }
678
679 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
680                          char **argv)
681 {
682         /* target parameters */
683         static struct param _params[] = {
684                 {1, 1024, ESTR("invalid number of priority groups")},
685                 {1, 1024, ESTR("invalid initial priority group number")},
686         };
687
688         int r;
689         struct multipath *m;
690         struct arg_set as;
691         unsigned pg_count = 0;
692         unsigned next_pg_num;
693
694         as.argc = argc;
695         as.argv = argv;
696
697         m = alloc_multipath();
698         if (!m) {
699                 ti->error = ESTR("can't allocate multipath");
700                 return -EINVAL;
701         }
702
703         r = parse_features(&as, m, ti);
704         if (r)
705                 goto bad;
706
707         r = parse_hw_handler(&as, m, ti);
708         if (r)
709                 goto bad;
710
711         r = read_param(_params, shift(&as), &m->nr_priority_groups, &ti->error);
712         if (r)
713                 goto bad;
714
715         r = read_param(_params + 1, shift(&as), &next_pg_num, &ti->error);
716         if (r)
717                 goto bad;
718
719         /* parse the priority groups */
720         while (as.argc) {
721                 struct priority_group *pg;
722
723                 pg = parse_priority_group(&as, m, ti);
724                 if (!pg) {
725                         r = -EINVAL;
726                         goto bad;
727                 }
728
729                 m->nr_valid_paths += pg->nr_pgpaths;
730                 list_add_tail(&pg->list, &m->priority_groups);
731                 pg_count++;
732                 pg->pg_num = pg_count;
733                 if (!--next_pg_num)
734                         m->next_pg = pg;
735         }
736
737         if (pg_count != m->nr_priority_groups) {
738                 ti->error = ESTR("priority group count mismatch");
739                 r = -EINVAL;
740                 goto bad;
741         }
742
743         ti->private = m;
744         m->ti = ti;
745
746         return 0;
747
748  bad:
749         free_multipath(m);
750         return r;
751 }
752
753 static void multipath_dtr(struct dm_target *ti)
754 {
755         struct multipath *m = (struct multipath *) ti->private;
756
757         flush_workqueue(kmultipathd);
758         free_multipath(m);
759 }
760
761 /*
762  * Map bios, recording original fields for later in case we have to resubmit
763  */
764 static int multipath_map(struct dm_target *ti, struct bio *bio,
765                          union map_info *map_context)
766 {
767         int r;
768         struct mpath_io *mpio;
769         struct multipath *m = (struct multipath *) ti->private;
770
771         if (bio_barrier(bio))
772                 return -EOPNOTSUPP;
773
774         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
775         dm_bio_record(&mpio->details, bio);
776
777         map_context->ptr = mpio;
778         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
779         r = map_io(m, bio, mpio, 0);
780         if (r < 0)
781                 mempool_free(mpio, m->mpio_pool);
782
783         return r;
784 }
785
786 /*
787  * Take a path out of use.
788  */
789 static int fail_path(struct pgpath *pgpath)
790 {
791         unsigned long flags;
792         struct multipath *m = pgpath->pg->m;
793
794         spin_lock_irqsave(&m->lock, flags);
795
796         if (!pgpath->path.is_active)
797                 goto out;
798
799         DMWARN("dm-multipath: Failing path %s.", pgpath->path.dev->name);
800
801         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
802         pgpath->path.is_active = 0;
803         pgpath->fail_count++;
804
805         m->nr_valid_paths--;
806
807         if (pgpath == m->current_pgpath)
808                 m->current_pgpath = NULL;
809
810         queue_work(kmultipathd, &m->trigger_event);
811
812 out:
813         spin_unlock_irqrestore(&m->lock, flags);
814
815         return 0;
816 }
817
818 /*
819  * Reinstate a previously-failed path
820  */
821 static int reinstate_path(struct pgpath *pgpath)
822 {
823         int r = 0;
824         unsigned long flags;
825         struct multipath *m = pgpath->pg->m;
826
827         spin_lock_irqsave(&m->lock, flags);
828
829         if (pgpath->path.is_active)
830                 goto out;
831
832         if (!pgpath->pg->ps.type) {
833                 DMWARN("Reinstate path not supported by path selector %s",
834                        pgpath->pg->ps.type->name);
835                 r = -EINVAL;
836                 goto out;
837         }
838
839         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
840         if (r)
841                 goto out;
842
843         pgpath->path.is_active = 1;
844
845         m->current_pgpath = NULL;
846         if (!m->nr_valid_paths++)
847                 queue_work(kmultipathd, &m->process_queued_ios);
848
849         queue_work(kmultipathd, &m->trigger_event);
850
851 out:
852         spin_unlock_irqrestore(&m->lock, flags);
853
854         return r;
855 }
856
857 /*
858  * Fail or reinstate all paths that match the provided struct dm_dev.
859  */
860 static int action_dev(struct multipath *m, struct dm_dev *dev,
861                       action_fn action)
862 {
863         int r = 0;
864         struct pgpath *pgpath;
865         struct priority_group *pg;
866
867         list_for_each_entry(pg, &m->priority_groups, list) {
868                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
869                         if (pgpath->path.dev == dev)
870                                 r = action(pgpath);
871                 }
872         }
873
874         return r;
875 }
876
877 /*
878  * Temporarily try to avoid having to use the specified PG
879  */
880 static void bypass_pg(struct multipath *m, struct priority_group *pg,
881                       int bypassed)
882 {
883         unsigned long flags;
884
885         spin_lock_irqsave(&m->lock, flags);
886
887         pg->bypassed = bypassed;
888         m->current_pgpath = NULL;
889         m->current_pg = NULL;
890
891         spin_unlock_irqrestore(&m->lock, flags);
892
893         queue_work(kmultipathd, &m->trigger_event);
894 }
895
896 /*
897  * Switch to using the specified PG from the next I/O that gets mapped
898  */
899 static int switch_pg_num(struct multipath *m, const char *pgstr)
900 {
901         struct priority_group *pg;
902         unsigned pgnum;
903         unsigned long flags;
904
905         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
906             (pgnum > m->nr_priority_groups)) {
907                 DMWARN("invalid PG number supplied to switch_pg_num");
908                 return -EINVAL;
909         }
910
911         spin_lock_irqsave(&m->lock, flags);
912         list_for_each_entry(pg, &m->priority_groups, list) {
913                 pg->bypassed = 0;
914                 if (--pgnum)
915                         continue;
916
917                 m->current_pgpath = NULL;
918                 m->current_pg = NULL;
919                 m->next_pg = pg;
920         }
921         spin_unlock_irqrestore(&m->lock, flags);
922
923         queue_work(kmultipathd, &m->trigger_event);
924         return 0;
925 }
926
927 /*
928  * Set/clear bypassed status of a PG.
929  * PGs are numbered upwards from 1 in the order they were declared.
930  */
931 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
932 {
933         struct priority_group *pg;
934         unsigned pgnum;
935
936         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
937             (pgnum > m->nr_priority_groups)) {
938                 DMWARN("invalid PG number supplied to bypass_pg");
939                 return -EINVAL;
940         }
941
942         list_for_each_entry(pg, &m->priority_groups, list) {
943                 if (!--pgnum)
944                         break;
945         }
946
947         bypass_pg(m, pg, bypassed);
948         return 0;
949 }
950
951 /*
952  * pg_init must call this when it has completed its initialisation
953  */
954 void dm_pg_init_complete(struct path *path, unsigned err_flags)
955 {
956         struct pgpath *pgpath = path_to_pgpath(path);
957         struct priority_group *pg = pgpath->pg;
958         struct multipath *m = pg->m;
959         unsigned long flags;
960
961         /* We insist on failing the path if the PG is already bypassed. */
962         if (err_flags && pg->bypassed)
963                 err_flags |= MP_FAIL_PATH;
964
965         if (err_flags & MP_FAIL_PATH)
966                 fail_path(pgpath);
967
968         if (err_flags & MP_BYPASS_PG)
969                 bypass_pg(m, pg, 1);
970
971         spin_lock_irqsave(&m->lock, flags);
972         if (!err_flags)
973                 m->queue_io = 0;
974         else {
975                 m->current_pgpath = NULL;
976                 m->current_pg = NULL;
977         }
978         queue_work(kmultipathd, &m->process_queued_ios);
979         spin_unlock_irqrestore(&m->lock, flags);
980 }
981
982 /*
983  * end_io handling
984  */
985 static int do_end_io(struct multipath *m, struct bio *bio,
986                      int error, struct mpath_io *mpio)
987 {
988         struct hw_handler *hwh = &m->hw_handler;
989         unsigned err_flags = MP_FAIL_PATH;      /* Default behavior */
990
991         if (!error)
992                 return 0;       /* I/O complete */
993
994         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
995                 return error;
996
997         if (error == -EOPNOTSUPP)
998                 return error;
999
1000         spin_lock(&m->lock);
1001         if (!m->nr_valid_paths) {
1002                 if (!m->queue_if_no_path) {
1003                         spin_unlock(&m->lock);
1004                         return -EIO;
1005                 } else {
1006                         spin_unlock(&m->lock);
1007                         goto requeue;
1008                 }
1009         }
1010         spin_unlock(&m->lock);
1011
1012         if (hwh->type && hwh->type->error)
1013                 err_flags = hwh->type->error(hwh, bio);
1014
1015         if (mpio->pgpath) {
1016                 if (err_flags & MP_FAIL_PATH)
1017                         fail_path(mpio->pgpath);
1018
1019                 if (err_flags & MP_BYPASS_PG)
1020                         bypass_pg(m, mpio->pgpath->pg, 1);
1021         }
1022
1023         if (err_flags & MP_ERROR_IO)
1024                 return -EIO;
1025
1026       requeue:
1027         dm_bio_restore(&mpio->details, bio);
1028
1029         /* queue for the daemon to resubmit or fail */
1030         spin_lock(&m->lock);
1031         bio_list_add(&m->queued_ios, bio);
1032         m->queue_size++;
1033         if (!m->queue_io)
1034                 queue_work(kmultipathd, &m->process_queued_ios);
1035         spin_unlock(&m->lock);
1036
1037         return 1;       /* io not complete */
1038 }
1039
1040 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1041                             int error, union map_info *map_context)
1042 {
1043         struct multipath *m = (struct multipath *) ti->private;
1044         struct mpath_io *mpio = (struct mpath_io *) map_context->ptr;
1045         struct pgpath *pgpath = mpio->pgpath;
1046         struct path_selector *ps;
1047         int r;
1048
1049         r  = do_end_io(m, bio, error, mpio);
1050         if (pgpath) {
1051                 ps = &pgpath->pg->ps;
1052                 if (ps->type->end_io)
1053                         ps->type->end_io(ps, &pgpath->path);
1054         }
1055         if (r <= 0)
1056                 mempool_free(mpio, m->mpio_pool);
1057
1058         return r;
1059 }
1060
1061 /*
1062  * Suspend can't complete until all the I/O is processed so if
1063  * the last path fails we must error any remaining I/O.
1064  * Note that if the freeze_bdev fails while suspending, the
1065  * queue_if_no_path state is lost - userspace should reset it.
1066  */
1067 static void multipath_presuspend(struct dm_target *ti)
1068 {
1069         struct multipath *m = (struct multipath *) ti->private;
1070
1071         queue_if_no_path(m, 0);
1072 }
1073
1074 /*
1075  * Restore the queue_if_no_path setting.
1076  */
1077 static void multipath_resume(struct dm_target *ti)
1078 {
1079         struct multipath *m = (struct multipath *) ti->private;
1080         unsigned long flags;
1081
1082         spin_lock_irqsave(&m->lock, flags);
1083         m->queue_if_no_path = m->saved_queue_if_no_path;
1084         spin_unlock_irqrestore(&m->lock, flags);
1085 }
1086
1087 /*
1088  * Info output has the following format:
1089  * num_multipath_feature_args [multipath_feature_args]*
1090  * num_handler_status_args [handler_status_args]*
1091  * num_groups init_group_number
1092  *            [A|D|E num_ps_status_args [ps_status_args]*
1093  *             num_paths num_selector_args
1094  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1095  *
1096  * Table output has the following format (identical to the constructor string):
1097  * num_feature_args [features_args]*
1098  * num_handler_args hw_handler [hw_handler_args]*
1099  * num_groups init_group_number
1100  *     [priority selector-name num_ps_args [ps_args]*
1101  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1102  */
1103 static int multipath_status(struct dm_target *ti, status_type_t type,
1104                             char *result, unsigned int maxlen)
1105 {
1106         int sz = 0;
1107         unsigned long flags;
1108         struct multipath *m = (struct multipath *) ti->private;
1109         struct hw_handler *hwh = &m->hw_handler;
1110         struct priority_group *pg;
1111         struct pgpath *p;
1112         unsigned pg_num;
1113         char state;
1114
1115         spin_lock_irqsave(&m->lock, flags);
1116
1117         /* Features */
1118         if (type == STATUSTYPE_INFO)
1119                 DMEMIT("1 %u ", m->queue_size);
1120         else if (m->queue_if_no_path)
1121                 DMEMIT("1 queue_if_no_path ");
1122         else
1123                 DMEMIT("0 ");
1124
1125         if (hwh->type && hwh->type->status)
1126                 sz += hwh->type->status(hwh, type, result + sz, maxlen - sz);
1127         else if (!hwh->type || type == STATUSTYPE_INFO)
1128                 DMEMIT("0 ");
1129         else
1130                 DMEMIT("1 %s ", hwh->type->name);
1131
1132         DMEMIT("%u ", m->nr_priority_groups);
1133
1134         if (m->next_pg)
1135                 pg_num = m->next_pg->pg_num;
1136         else if (m->current_pg)
1137                 pg_num = m->current_pg->pg_num;
1138         else
1139                         pg_num = 1;
1140
1141         DMEMIT("%u ", pg_num);
1142
1143         switch (type) {
1144         case STATUSTYPE_INFO:
1145                 list_for_each_entry(pg, &m->priority_groups, list) {
1146                         if (pg->bypassed)
1147                                 state = 'D';    /* Disabled */
1148                         else if (pg == m->current_pg)
1149                                 state = 'A';    /* Currently Active */
1150                         else
1151                                 state = 'E';    /* Enabled */
1152
1153                         DMEMIT("%c ", state);
1154
1155                         if (pg->ps.type->status)
1156                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1157                                                           result + sz,
1158                                                           maxlen - sz);
1159                         else
1160                                 DMEMIT("0 ");
1161
1162                         DMEMIT("%u %u ", pg->nr_pgpaths,
1163                                pg->ps.type->info_args);
1164
1165                         list_for_each_entry(p, &pg->pgpaths, list) {
1166                                 DMEMIT("%s %s %u ", p->path.dev->name,
1167                                        p->path.is_active ? "A" : "F",
1168                                        p->fail_count);
1169                                 if (pg->ps.type->status)
1170                                         sz += pg->ps.type->status(&pg->ps,
1171                                               &p->path, type, result + sz,
1172                                               maxlen - sz);
1173                         }
1174                 }
1175                 break;
1176
1177         case STATUSTYPE_TABLE:
1178                 list_for_each_entry(pg, &m->priority_groups, list) {
1179                         DMEMIT("%s ", pg->ps.type->name);
1180
1181                         if (pg->ps.type->status)
1182                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1183                                                           result + sz,
1184                                                           maxlen - sz);
1185                         else
1186                                 DMEMIT("0 ");
1187
1188                         DMEMIT("%u %u ", pg->nr_pgpaths,
1189                                pg->ps.type->table_args);
1190
1191                         list_for_each_entry(p, &pg->pgpaths, list) {
1192                                 DMEMIT("%s ", p->path.dev->name);
1193                                 if (pg->ps.type->status)
1194                                         sz += pg->ps.type->status(&pg->ps,
1195                                               &p->path, type, result + sz,
1196                                               maxlen - sz);
1197                         }
1198                 }
1199                 break;
1200         }
1201
1202         spin_unlock_irqrestore(&m->lock, flags);
1203
1204         return 0;
1205 }
1206
1207 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1208 {
1209         int r;
1210         struct dm_dev *dev;
1211         struct multipath *m = (struct multipath *) ti->private;
1212         action_fn action;
1213
1214         if (argc == 1) {
1215                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1216                         return queue_if_no_path(m, 1);
1217                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1218                         return queue_if_no_path(m, 0);
1219         }
1220
1221         if (argc != 2)
1222                 goto error;
1223
1224         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1225                 return bypass_pg_num(m, argv[1], 1);
1226         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1227                 return bypass_pg_num(m, argv[1], 0);
1228         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1229                 return switch_pg_num(m, argv[1]);
1230         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1231                 action = reinstate_path;
1232         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1233                 action = fail_path;
1234         else
1235                 goto error;
1236
1237         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1238                           dm_table_get_mode(ti->table), &dev);
1239         if (r) {
1240                 DMWARN("dm-multipath message: error getting device %s",
1241                        argv[1]);
1242                 return -EINVAL;
1243         }
1244
1245         r = action_dev(m, dev, action);
1246
1247         dm_put_device(ti, dev);
1248
1249         return r;
1250
1251 error:
1252         DMWARN("Unrecognised multipath message received.");
1253         return -EINVAL;
1254 }
1255
1256 /*-----------------------------------------------------------------
1257  * Module setup
1258  *---------------------------------------------------------------*/
1259 static struct target_type multipath_target = {
1260         .name = "multipath",
1261         .version = {1, 0, 4},
1262         .module = THIS_MODULE,
1263         .ctr = multipath_ctr,
1264         .dtr = multipath_dtr,
1265         .map = multipath_map,
1266         .end_io = multipath_end_io,
1267         .presuspend = multipath_presuspend,
1268         .resume = multipath_resume,
1269         .status = multipath_status,
1270         .message = multipath_message,
1271 };
1272
1273 static int __init dm_multipath_init(void)
1274 {
1275         int r;
1276
1277         /* allocate a slab for the dm_ios */
1278         _mpio_cache = kmem_cache_create("dm_mpath", sizeof(struct mpath_io),
1279                                         0, 0, NULL, NULL);
1280         if (!_mpio_cache)
1281                 return -ENOMEM;
1282
1283         r = dm_register_target(&multipath_target);
1284         if (r < 0) {
1285                 DMERR("%s: register failed %d", multipath_target.name, r);
1286                 kmem_cache_destroy(_mpio_cache);
1287                 return -EINVAL;
1288         }
1289
1290         kmultipathd = create_workqueue("kmpathd");
1291         if (!kmultipathd) {
1292                 DMERR("%s: failed to create workqueue kmpathd",
1293                                 multipath_target.name);
1294                 dm_unregister_target(&multipath_target);
1295                 kmem_cache_destroy(_mpio_cache);
1296                 return -ENOMEM;
1297         }
1298
1299         DMINFO("dm-multipath version %u.%u.%u loaded",
1300                multipath_target.version[0], multipath_target.version[1],
1301                multipath_target.version[2]);
1302
1303         return r;
1304 }
1305
1306 static void __exit dm_multipath_exit(void)
1307 {
1308         int r;
1309
1310         destroy_workqueue(kmultipathd);
1311
1312         r = dm_unregister_target(&multipath_target);
1313         if (r < 0)
1314                 DMERR("%s: target unregister failed %d",
1315                       multipath_target.name, r);
1316         kmem_cache_destroy(_mpio_cache);
1317 }
1318
1319 EXPORT_SYMBOL_GPL(dm_pg_init_complete);
1320
1321 module_init(dm_multipath_init);
1322 module_exit(dm_multipath_exit);
1323
1324 MODULE_DESCRIPTION(DM_NAME " multipath target");
1325 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1326 MODULE_LICENSE("GPL");