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