Merge branch 'r8169-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/romieu...
[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-bio-list.h"
11 #include "dm-bio-record.h"
12 #include "dm-uevent.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 <scsi/scsi_dh.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         const char *hw_handler_name;
65         struct work_struct activate_path;
66         unsigned nr_priority_groups;
67         struct list_head priority_groups;
68         unsigned pg_init_required;      /* pg_init needs calling? */
69         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
70
71         unsigned nr_valid_paths;        /* Total number of usable paths */
72         struct pgpath *current_pgpath;
73         struct priority_group *current_pg;
74         struct priority_group *next_pg; /* Switch to this PG if set */
75         unsigned repeat_count;          /* I/Os left before calling PS again */
76
77         unsigned queue_io;              /* Must we queue all I/O? */
78         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
79         unsigned saved_queue_if_no_path;/* Saved state during suspension */
80         unsigned pg_init_retries;       /* Number of times to retry pg_init */
81         unsigned pg_init_count;         /* Number of times pg_init called */
82
83         struct work_struct process_queued_ios;
84         struct bio_list queued_ios;
85         unsigned queue_size;
86
87         struct work_struct trigger_event;
88
89         /*
90          * We must use a mempool of dm_mpath_io structs so that we
91          * can resubmit bios on error.
92          */
93         mempool_t *mpio_pool;
94 };
95
96 /*
97  * Context information attached to each bio we process.
98  */
99 struct dm_mpath_io {
100         struct pgpath *pgpath;
101         struct dm_bio_details details;
102 };
103
104 typedef int (*action_fn) (struct pgpath *pgpath);
105
106 #define MIN_IOS 256     /* Mempool size */
107
108 static struct kmem_cache *_mpio_cache;
109
110 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
111 static void process_queued_ios(struct work_struct *work);
112 static void trigger_event(struct work_struct *work);
113 static void activate_path(struct work_struct *work);
114
115
116 /*-----------------------------------------------
117  * Allocation routines
118  *-----------------------------------------------*/
119
120 static struct pgpath *alloc_pgpath(void)
121 {
122         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
123
124         if (pgpath)
125                 pgpath->path.is_active = 1;
126
127         return pgpath;
128 }
129
130 static void free_pgpath(struct pgpath *pgpath)
131 {
132         kfree(pgpath);
133 }
134
135 static struct priority_group *alloc_priority_group(void)
136 {
137         struct priority_group *pg;
138
139         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
140
141         if (pg)
142                 INIT_LIST_HEAD(&pg->pgpaths);
143
144         return pg;
145 }
146
147 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
148 {
149         struct pgpath *pgpath, *tmp;
150         struct multipath *m = ti->private;
151
152         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
153                 list_del(&pgpath->list);
154                 if (m->hw_handler_name)
155                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
156                 dm_put_device(ti, pgpath->path.dev);
157                 free_pgpath(pgpath);
158         }
159 }
160
161 static void free_priority_group(struct priority_group *pg,
162                                 struct dm_target *ti)
163 {
164         struct path_selector *ps = &pg->ps;
165
166         if (ps->type) {
167                 ps->type->destroy(ps);
168                 dm_put_path_selector(ps->type);
169         }
170
171         free_pgpaths(&pg->pgpaths, ti);
172         kfree(pg);
173 }
174
175 static struct multipath *alloc_multipath(struct dm_target *ti)
176 {
177         struct multipath *m;
178
179         m = kzalloc(sizeof(*m), GFP_KERNEL);
180         if (m) {
181                 INIT_LIST_HEAD(&m->priority_groups);
182                 spin_lock_init(&m->lock);
183                 m->queue_io = 1;
184                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
185                 INIT_WORK(&m->trigger_event, trigger_event);
186                 INIT_WORK(&m->activate_path, activate_path);
187                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
188                 if (!m->mpio_pool) {
189                         kfree(m);
190                         return NULL;
191                 }
192                 m->ti = ti;
193                 ti->private = m;
194         }
195
196         return m;
197 }
198
199 static void free_multipath(struct multipath *m)
200 {
201         struct priority_group *pg, *tmp;
202
203         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
204                 list_del(&pg->list);
205                 free_priority_group(pg, m->ti);
206         }
207
208         kfree(m->hw_handler_name);
209         mempool_destroy(m->mpio_pool);
210         kfree(m);
211 }
212
213
214 /*-----------------------------------------------
215  * Path selection
216  *-----------------------------------------------*/
217
218 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
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 (m->hw_handler_name) {
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         m->pg_init_count = 0;
232 }
233
234 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg)
235 {
236         struct dm_path *path;
237
238         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count);
239         if (!path)
240                 return -ENXIO;
241
242         m->current_pgpath = path_to_pgpath(path);
243
244         if (m->current_pg != pg)
245                 __switch_pg(m, m->current_pgpath);
246
247         return 0;
248 }
249
250 static void __choose_pgpath(struct multipath *m)
251 {
252         struct priority_group *pg;
253         unsigned bypassed = 1;
254
255         if (!m->nr_valid_paths)
256                 goto failed;
257
258         /* Were we instructed to switch PG? */
259         if (m->next_pg) {
260                 pg = m->next_pg;
261                 m->next_pg = NULL;
262                 if (!__choose_path_in_pg(m, pg))
263                         return;
264         }
265
266         /* Don't change PG until it has no remaining paths */
267         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg))
268                 return;
269
270         /*
271          * Loop through priority groups until we find a valid path.
272          * First time we skip PGs marked 'bypassed'.
273          * Second time we only try the ones we skipped.
274          */
275         do {
276                 list_for_each_entry(pg, &m->priority_groups, list) {
277                         if (pg->bypassed == bypassed)
278                                 continue;
279                         if (!__choose_path_in_pg(m, pg))
280                                 return;
281                 }
282         } while (bypassed--);
283
284 failed:
285         m->current_pgpath = NULL;
286         m->current_pg = NULL;
287 }
288
289 /*
290  * Check whether bios must be queued in the device-mapper core rather
291  * than here in the target.
292  *
293  * m->lock must be held on entry.
294  *
295  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
296  * same value then we are not between multipath_presuspend()
297  * and multipath_resume() calls and we have no need to check
298  * for the DMF_NOFLUSH_SUSPENDING flag.
299  */
300 static int __must_push_back(struct multipath *m)
301 {
302         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
303                 dm_noflush_suspending(m->ti));
304 }
305
306 static int map_io(struct multipath *m, struct bio *bio,
307                   struct dm_mpath_io *mpio, unsigned was_queued)
308 {
309         int r = DM_MAPIO_REMAPPED;
310         unsigned long flags;
311         struct pgpath *pgpath;
312
313         spin_lock_irqsave(&m->lock, flags);
314
315         /* Do we need to select a new pgpath? */
316         if (!m->current_pgpath ||
317             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
318                 __choose_pgpath(m);
319
320         pgpath = m->current_pgpath;
321
322         if (was_queued)
323                 m->queue_size--;
324
325         if ((pgpath && m->queue_io) ||
326             (!pgpath && m->queue_if_no_path)) {
327                 /* Queue for the daemon to resubmit */
328                 bio_list_add(&m->queued_ios, bio);
329                 m->queue_size++;
330                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
331                     !m->queue_io)
332                         queue_work(kmultipathd, &m->process_queued_ios);
333                 pgpath = NULL;
334                 r = DM_MAPIO_SUBMITTED;
335         } else if (pgpath)
336                 bio->bi_bdev = pgpath->path.dev->bdev;
337         else if (__must_push_back(m))
338                 r = DM_MAPIO_REQUEUE;
339         else
340                 r = -EIO;       /* Failed */
341
342         mpio->pgpath = pgpath;
343
344         spin_unlock_irqrestore(&m->lock, flags);
345
346         return r;
347 }
348
349 /*
350  * If we run out of usable paths, should we queue I/O or error it?
351  */
352 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
353                             unsigned save_old_value)
354 {
355         unsigned long flags;
356
357         spin_lock_irqsave(&m->lock, flags);
358
359         if (save_old_value)
360                 m->saved_queue_if_no_path = m->queue_if_no_path;
361         else
362                 m->saved_queue_if_no_path = queue_if_no_path;
363         m->queue_if_no_path = queue_if_no_path;
364         if (!m->queue_if_no_path && m->queue_size)
365                 queue_work(kmultipathd, &m->process_queued_ios);
366
367         spin_unlock_irqrestore(&m->lock, flags);
368
369         return 0;
370 }
371
372 /*-----------------------------------------------------------------
373  * The multipath daemon is responsible for resubmitting queued ios.
374  *---------------------------------------------------------------*/
375
376 static void dispatch_queued_ios(struct multipath *m)
377 {
378         int r;
379         unsigned long flags;
380         struct bio *bio = NULL, *next;
381         struct dm_mpath_io *mpio;
382         union map_info *info;
383
384         spin_lock_irqsave(&m->lock, flags);
385         bio = bio_list_get(&m->queued_ios);
386         spin_unlock_irqrestore(&m->lock, flags);
387
388         while (bio) {
389                 next = bio->bi_next;
390                 bio->bi_next = NULL;
391
392                 info = dm_get_mapinfo(bio);
393                 mpio = info->ptr;
394
395                 r = map_io(m, bio, mpio, 1);
396                 if (r < 0)
397                         bio_endio(bio, r);
398                 else if (r == DM_MAPIO_REMAPPED)
399                         generic_make_request(bio);
400                 else if (r == DM_MAPIO_REQUEUE)
401                         bio_endio(bio, -EIO);
402
403                 bio = next;
404         }
405 }
406
407 static void process_queued_ios(struct work_struct *work)
408 {
409         struct multipath *m =
410                 container_of(work, struct multipath, process_queued_ios);
411         struct pgpath *pgpath = NULL;
412         unsigned init_required = 0, must_queue = 1;
413         unsigned long flags;
414
415         spin_lock_irqsave(&m->lock, flags);
416
417         if (!m->queue_size)
418                 goto out;
419
420         if (!m->current_pgpath)
421                 __choose_pgpath(m);
422
423         pgpath = m->current_pgpath;
424
425         if ((pgpath && !m->queue_io) ||
426             (!pgpath && !m->queue_if_no_path))
427                 must_queue = 0;
428
429         if (m->pg_init_required && !m->pg_init_in_progress) {
430                 m->pg_init_count++;
431                 m->pg_init_required = 0;
432                 m->pg_init_in_progress = 1;
433                 init_required = 1;
434         }
435
436 out:
437         spin_unlock_irqrestore(&m->lock, flags);
438
439         if (init_required)
440                 queue_work(kmpath_handlerd, &m->activate_path);
441
442         if (!must_queue)
443                 dispatch_queued_ios(m);
444 }
445
446 /*
447  * An event is triggered whenever a path is taken out of use.
448  * Includes path failure and PG bypass.
449  */
450 static void trigger_event(struct work_struct *work)
451 {
452         struct multipath *m =
453                 container_of(work, struct multipath, trigger_event);
454
455         dm_table_event(m->ti->table);
456 }
457
458 /*-----------------------------------------------------------------
459  * Constructor/argument parsing:
460  * <#multipath feature args> [<arg>]*
461  * <#hw_handler args> [hw_handler [<arg>]*]
462  * <#priority groups>
463  * <initial priority group>
464  *     [<selector> <#selector args> [<arg>]*
465  *      <#paths> <#per-path selector args>
466  *         [<path> [<arg>]* ]+ ]+
467  *---------------------------------------------------------------*/
468 struct param {
469         unsigned min;
470         unsigned max;
471         char *error;
472 };
473
474 static int read_param(struct param *param, char *str, unsigned *v, char **error)
475 {
476         if (!str ||
477             (sscanf(str, "%u", v) != 1) ||
478             (*v < param->min) ||
479             (*v > param->max)) {
480                 *error = param->error;
481                 return -EINVAL;
482         }
483
484         return 0;
485 }
486
487 struct arg_set {
488         unsigned argc;
489         char **argv;
490 };
491
492 static char *shift(struct arg_set *as)
493 {
494         char *r;
495
496         if (as->argc) {
497                 as->argc--;
498                 r = *as->argv;
499                 as->argv++;
500                 return r;
501         }
502
503         return NULL;
504 }
505
506 static void consume(struct arg_set *as, unsigned n)
507 {
508         BUG_ON (as->argc < n);
509         as->argc -= n;
510         as->argv += n;
511 }
512
513 static int parse_path_selector(struct arg_set *as, struct priority_group *pg,
514                                struct dm_target *ti)
515 {
516         int r;
517         struct path_selector_type *pst;
518         unsigned ps_argc;
519
520         static struct param _params[] = {
521                 {0, 1024, "invalid number of path selector args"},
522         };
523
524         pst = dm_get_path_selector(shift(as));
525         if (!pst) {
526                 ti->error = "unknown path selector type";
527                 return -EINVAL;
528         }
529
530         r = read_param(_params, shift(as), &ps_argc, &ti->error);
531         if (r) {
532                 dm_put_path_selector(pst);
533                 return -EINVAL;
534         }
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         struct multipath *m = ti->private;
555
556         /* we need at least a path arg */
557         if (as->argc < 1) {
558                 ti->error = "no device given";
559                 return NULL;
560         }
561
562         p = alloc_pgpath();
563         if (!p)
564                 return NULL;
565
566         r = dm_get_device(ti, shift(as), ti->begin, ti->len,
567                           dm_table_get_mode(ti->table), &p->path.dev);
568         if (r) {
569                 ti->error = "error getting device";
570                 goto bad;
571         }
572
573         if (m->hw_handler_name) {
574                 r = scsi_dh_attach(bdev_get_queue(p->path.dev->bdev),
575                                    m->hw_handler_name);
576                 if (r < 0) {
577                         dm_put_device(ti, p->path.dev);
578                         goto bad;
579                 }
580         }
581
582         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
583         if (r) {
584                 dm_put_device(ti, p->path.dev);
585                 goto bad;
586         }
587
588         return p;
589
590  bad:
591         free_pgpath(p);
592         return NULL;
593 }
594
595 static struct priority_group *parse_priority_group(struct arg_set *as,
596                                                    struct multipath *m)
597 {
598         static struct param _params[] = {
599                 {1, 1024, "invalid number of paths"},
600                 {0, 1024, "invalid number of selector args"}
601         };
602
603         int r;
604         unsigned i, nr_selector_args, nr_params;
605         struct priority_group *pg;
606         struct dm_target *ti = m->ti;
607
608         if (as->argc < 2) {
609                 as->argc = 0;
610                 ti->error = "not enough priority group aruments";
611                 return NULL;
612         }
613
614         pg = alloc_priority_group();
615         if (!pg) {
616                 ti->error = "couldn't allocate priority group";
617                 return NULL;
618         }
619         pg->m = m;
620
621         r = parse_path_selector(as, pg, ti);
622         if (r)
623                 goto bad;
624
625         /*
626          * read the paths
627          */
628         r = read_param(_params, shift(as), &pg->nr_pgpaths, &ti->error);
629         if (r)
630                 goto bad;
631
632         r = read_param(_params + 1, shift(as), &nr_selector_args, &ti->error);
633         if (r)
634                 goto bad;
635
636         nr_params = 1 + nr_selector_args;
637         for (i = 0; i < pg->nr_pgpaths; i++) {
638                 struct pgpath *pgpath;
639                 struct arg_set path_args;
640
641                 if (as->argc < nr_params) {
642                         ti->error = "not enough path parameters";
643                         goto bad;
644                 }
645
646                 path_args.argc = nr_params;
647                 path_args.argv = as->argv;
648
649                 pgpath = parse_path(&path_args, &pg->ps, ti);
650                 if (!pgpath)
651                         goto bad;
652
653                 pgpath->pg = pg;
654                 list_add_tail(&pgpath->list, &pg->pgpaths);
655                 consume(as, nr_params);
656         }
657
658         return pg;
659
660  bad:
661         free_priority_group(pg, ti);
662         return NULL;
663 }
664
665 static int parse_hw_handler(struct arg_set *as, struct multipath *m)
666 {
667         unsigned hw_argc;
668         struct dm_target *ti = m->ti;
669
670         static struct param _params[] = {
671                 {0, 1024, "invalid number of hardware handler args"},
672         };
673
674         if (read_param(_params, shift(as), &hw_argc, &ti->error))
675                 return -EINVAL;
676
677         if (!hw_argc)
678                 return 0;
679
680         m->hw_handler_name = kstrdup(shift(as), GFP_KERNEL);
681         request_module("scsi_dh_%s", m->hw_handler_name);
682         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
683                 ti->error = "unknown hardware handler type";
684                 kfree(m->hw_handler_name);
685                 m->hw_handler_name = NULL;
686                 return -EINVAL;
687         }
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(kmpath_handlerd);
812         flush_workqueue(kmultipathd);
813         free_multipath(m);
814 }
815
816 /*
817  * Map bios, recording original fields for later in case we have to resubmit
818  */
819 static int multipath_map(struct dm_target *ti, struct bio *bio,
820                          union map_info *map_context)
821 {
822         int r;
823         struct dm_mpath_io *mpio;
824         struct multipath *m = (struct multipath *) ti->private;
825
826         mpio = mempool_alloc(m->mpio_pool, GFP_NOIO);
827         dm_bio_record(&mpio->details, bio);
828
829         map_context->ptr = mpio;
830         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
831         r = map_io(m, bio, mpio, 0);
832         if (r < 0 || r == DM_MAPIO_REQUEUE)
833                 mempool_free(mpio, m->mpio_pool);
834
835         return r;
836 }
837
838 /*
839  * Take a path out of use.
840  */
841 static int fail_path(struct pgpath *pgpath)
842 {
843         unsigned long flags;
844         struct multipath *m = pgpath->pg->m;
845
846         spin_lock_irqsave(&m->lock, flags);
847
848         if (!pgpath->path.is_active)
849                 goto out;
850
851         DMWARN("Failing path %s.", pgpath->path.dev->name);
852
853         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
854         pgpath->path.is_active = 0;
855         pgpath->fail_count++;
856
857         m->nr_valid_paths--;
858
859         if (pgpath == m->current_pgpath)
860                 m->current_pgpath = NULL;
861
862         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
863                       pgpath->path.dev->name, m->nr_valid_paths);
864
865         queue_work(kmultipathd, &m->trigger_event);
866
867 out:
868         spin_unlock_irqrestore(&m->lock, flags);
869
870         return 0;
871 }
872
873 /*
874  * Reinstate a previously-failed path
875  */
876 static int reinstate_path(struct pgpath *pgpath)
877 {
878         int r = 0;
879         unsigned long flags;
880         struct multipath *m = pgpath->pg->m;
881
882         spin_lock_irqsave(&m->lock, flags);
883
884         if (pgpath->path.is_active)
885                 goto out;
886
887         if (!pgpath->pg->ps.type->reinstate_path) {
888                 DMWARN("Reinstate path not supported by path selector %s",
889                        pgpath->pg->ps.type->name);
890                 r = -EINVAL;
891                 goto out;
892         }
893
894         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
895         if (r)
896                 goto out;
897
898         pgpath->path.is_active = 1;
899
900         m->current_pgpath = NULL;
901         if (!m->nr_valid_paths++ && m->queue_size)
902                 queue_work(kmultipathd, &m->process_queued_ios);
903
904         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
905                       pgpath->path.dev->name, m->nr_valid_paths);
906
907         queue_work(kmultipathd, &m->trigger_event);
908
909 out:
910         spin_unlock_irqrestore(&m->lock, flags);
911
912         return r;
913 }
914
915 /*
916  * Fail or reinstate all paths that match the provided struct dm_dev.
917  */
918 static int action_dev(struct multipath *m, struct dm_dev *dev,
919                       action_fn action)
920 {
921         int r = 0;
922         struct pgpath *pgpath;
923         struct priority_group *pg;
924
925         list_for_each_entry(pg, &m->priority_groups, list) {
926                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
927                         if (pgpath->path.dev == dev)
928                                 r = action(pgpath);
929                 }
930         }
931
932         return r;
933 }
934
935 /*
936  * Temporarily try to avoid having to use the specified PG
937  */
938 static void bypass_pg(struct multipath *m, struct priority_group *pg,
939                       int bypassed)
940 {
941         unsigned long flags;
942
943         spin_lock_irqsave(&m->lock, flags);
944
945         pg->bypassed = bypassed;
946         m->current_pgpath = NULL;
947         m->current_pg = NULL;
948
949         spin_unlock_irqrestore(&m->lock, flags);
950
951         queue_work(kmultipathd, &m->trigger_event);
952 }
953
954 /*
955  * Switch to using the specified PG from the next I/O that gets mapped
956  */
957 static int switch_pg_num(struct multipath *m, const char *pgstr)
958 {
959         struct priority_group *pg;
960         unsigned pgnum;
961         unsigned long flags;
962
963         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
964             (pgnum > m->nr_priority_groups)) {
965                 DMWARN("invalid PG number supplied to switch_pg_num");
966                 return -EINVAL;
967         }
968
969         spin_lock_irqsave(&m->lock, flags);
970         list_for_each_entry(pg, &m->priority_groups, list) {
971                 pg->bypassed = 0;
972                 if (--pgnum)
973                         continue;
974
975                 m->current_pgpath = NULL;
976                 m->current_pg = NULL;
977                 m->next_pg = pg;
978         }
979         spin_unlock_irqrestore(&m->lock, flags);
980
981         queue_work(kmultipathd, &m->trigger_event);
982         return 0;
983 }
984
985 /*
986  * Set/clear bypassed status of a PG.
987  * PGs are numbered upwards from 1 in the order they were declared.
988  */
989 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
990 {
991         struct priority_group *pg;
992         unsigned pgnum;
993
994         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
995             (pgnum > m->nr_priority_groups)) {
996                 DMWARN("invalid PG number supplied to bypass_pg");
997                 return -EINVAL;
998         }
999
1000         list_for_each_entry(pg, &m->priority_groups, list) {
1001                 if (!--pgnum)
1002                         break;
1003         }
1004
1005         bypass_pg(m, pg, bypassed);
1006         return 0;
1007 }
1008
1009 /*
1010  * Should we retry pg_init immediately?
1011  */
1012 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1013 {
1014         unsigned long flags;
1015         int limit_reached = 0;
1016
1017         spin_lock_irqsave(&m->lock, flags);
1018
1019         if (m->pg_init_count <= m->pg_init_retries)
1020                 m->pg_init_required = 1;
1021         else
1022                 limit_reached = 1;
1023
1024         spin_unlock_irqrestore(&m->lock, flags);
1025
1026         return limit_reached;
1027 }
1028
1029 static void pg_init_done(struct dm_path *path, int errors)
1030 {
1031         struct pgpath *pgpath = path_to_pgpath(path);
1032         struct priority_group *pg = pgpath->pg;
1033         struct multipath *m = pg->m;
1034         unsigned long flags;
1035
1036         /* device or driver problems */
1037         switch (errors) {
1038         case SCSI_DH_OK:
1039                 break;
1040         case SCSI_DH_NOSYS:
1041                 if (!m->hw_handler_name) {
1042                         errors = 0;
1043                         break;
1044                 }
1045                 DMERR("Cannot failover device because scsi_dh_%s was not "
1046                       "loaded.", m->hw_handler_name);
1047                 /*
1048                  * Fail path for now, so we do not ping pong
1049                  */
1050                 fail_path(pgpath);
1051                 break;
1052         case SCSI_DH_DEV_TEMP_BUSY:
1053                 /*
1054                  * Probably doing something like FW upgrade on the
1055                  * controller so try the other pg.
1056                  */
1057                 bypass_pg(m, pg, 1);
1058                 break;
1059         /* TODO: For SCSI_DH_RETRY we should wait a couple seconds */
1060         case SCSI_DH_RETRY:
1061         case SCSI_DH_IMM_RETRY:
1062         case SCSI_DH_RES_TEMP_UNAVAIL:
1063                 if (pg_init_limit_reached(m, pgpath))
1064                         fail_path(pgpath);
1065                 errors = 0;
1066                 break;
1067         default:
1068                 /*
1069                  * We probably do not want to fail the path for a device
1070                  * error, but this is what the old dm did. In future
1071                  * patches we can do more advanced handling.
1072                  */
1073                 fail_path(pgpath);
1074         }
1075
1076         spin_lock_irqsave(&m->lock, flags);
1077         if (errors) {
1078                 DMERR("Could not failover device. Error %d.", errors);
1079                 m->current_pgpath = NULL;
1080                 m->current_pg = NULL;
1081         } else if (!m->pg_init_required) {
1082                 m->queue_io = 0;
1083                 pg->bypassed = 0;
1084         }
1085
1086         m->pg_init_in_progress = 0;
1087         queue_work(kmultipathd, &m->process_queued_ios);
1088         spin_unlock_irqrestore(&m->lock, flags);
1089 }
1090
1091 static void activate_path(struct work_struct *work)
1092 {
1093         int ret;
1094         struct multipath *m =
1095                 container_of(work, struct multipath, activate_path);
1096         struct dm_path *path = &m->current_pgpath->path;
1097
1098         ret = scsi_dh_activate(bdev_get_queue(path->dev->bdev));
1099         pg_init_done(path, ret);
1100 }
1101
1102 /*
1103  * end_io handling
1104  */
1105 static int do_end_io(struct multipath *m, struct bio *bio,
1106                      int error, struct dm_mpath_io *mpio)
1107 {
1108         unsigned long flags;
1109
1110         if (!error)
1111                 return 0;       /* I/O complete */
1112
1113         if ((error == -EWOULDBLOCK) && bio_rw_ahead(bio))
1114                 return error;
1115
1116         if (error == -EOPNOTSUPP)
1117                 return error;
1118
1119         spin_lock_irqsave(&m->lock, flags);
1120         if (!m->nr_valid_paths) {
1121                 if (__must_push_back(m)) {
1122                         spin_unlock_irqrestore(&m->lock, flags);
1123                         return DM_ENDIO_REQUEUE;
1124                 } else if (!m->queue_if_no_path) {
1125                         spin_unlock_irqrestore(&m->lock, flags);
1126                         return -EIO;
1127                 } else {
1128                         spin_unlock_irqrestore(&m->lock, flags);
1129                         goto requeue;
1130                 }
1131         }
1132         spin_unlock_irqrestore(&m->lock, flags);
1133
1134         if (mpio->pgpath)
1135                 fail_path(mpio->pgpath);
1136
1137       requeue:
1138         dm_bio_restore(&mpio->details, bio);
1139
1140         /* queue for the daemon to resubmit or fail */
1141         spin_lock_irqsave(&m->lock, flags);
1142         bio_list_add(&m->queued_ios, bio);
1143         m->queue_size++;
1144         if (!m->queue_io)
1145                 queue_work(kmultipathd, &m->process_queued_ios);
1146         spin_unlock_irqrestore(&m->lock, flags);
1147
1148         return DM_ENDIO_INCOMPLETE;     /* io not complete */
1149 }
1150
1151 static int multipath_end_io(struct dm_target *ti, struct bio *bio,
1152                             int error, union map_info *map_context)
1153 {
1154         struct multipath *m = ti->private;
1155         struct dm_mpath_io *mpio = map_context->ptr;
1156         struct pgpath *pgpath = mpio->pgpath;
1157         struct path_selector *ps;
1158         int r;
1159
1160         r  = do_end_io(m, bio, error, mpio);
1161         if (pgpath) {
1162                 ps = &pgpath->pg->ps;
1163                 if (ps->type->end_io)
1164                         ps->type->end_io(ps, &pgpath->path);
1165         }
1166         if (r != DM_ENDIO_INCOMPLETE)
1167                 mempool_free(mpio, m->mpio_pool);
1168
1169         return r;
1170 }
1171
1172 /*
1173  * Suspend can't complete until all the I/O is processed so if
1174  * the last path fails we must error any remaining I/O.
1175  * Note that if the freeze_bdev fails while suspending, the
1176  * queue_if_no_path state is lost - userspace should reset it.
1177  */
1178 static void multipath_presuspend(struct dm_target *ti)
1179 {
1180         struct multipath *m = (struct multipath *) ti->private;
1181
1182         queue_if_no_path(m, 0, 1);
1183 }
1184
1185 /*
1186  * Restore the queue_if_no_path setting.
1187  */
1188 static void multipath_resume(struct dm_target *ti)
1189 {
1190         struct multipath *m = (struct multipath *) ti->private;
1191         unsigned long flags;
1192
1193         spin_lock_irqsave(&m->lock, flags);
1194         m->queue_if_no_path = m->saved_queue_if_no_path;
1195         spin_unlock_irqrestore(&m->lock, flags);
1196 }
1197
1198 /*
1199  * Info output has the following format:
1200  * num_multipath_feature_args [multipath_feature_args]*
1201  * num_handler_status_args [handler_status_args]*
1202  * num_groups init_group_number
1203  *            [A|D|E num_ps_status_args [ps_status_args]*
1204  *             num_paths num_selector_args
1205  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1206  *
1207  * Table output has the following format (identical to the constructor string):
1208  * num_feature_args [features_args]*
1209  * num_handler_args hw_handler [hw_handler_args]*
1210  * num_groups init_group_number
1211  *     [priority selector-name num_ps_args [ps_args]*
1212  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1213  */
1214 static int multipath_status(struct dm_target *ti, status_type_t type,
1215                             char *result, unsigned int maxlen)
1216 {
1217         int sz = 0;
1218         unsigned long flags;
1219         struct multipath *m = (struct multipath *) ti->private;
1220         struct priority_group *pg;
1221         struct pgpath *p;
1222         unsigned pg_num;
1223         char state;
1224
1225         spin_lock_irqsave(&m->lock, flags);
1226
1227         /* Features */
1228         if (type == STATUSTYPE_INFO)
1229                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1230         else {
1231                 DMEMIT("%u ", m->queue_if_no_path +
1232                               (m->pg_init_retries > 0) * 2);
1233                 if (m->queue_if_no_path)
1234                         DMEMIT("queue_if_no_path ");
1235                 if (m->pg_init_retries)
1236                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1237         }
1238
1239         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1240                 DMEMIT("0 ");
1241         else
1242                 DMEMIT("1 %s ", m->hw_handler_name);
1243
1244         DMEMIT("%u ", m->nr_priority_groups);
1245
1246         if (m->next_pg)
1247                 pg_num = m->next_pg->pg_num;
1248         else if (m->current_pg)
1249                 pg_num = m->current_pg->pg_num;
1250         else
1251                         pg_num = 1;
1252
1253         DMEMIT("%u ", pg_num);
1254
1255         switch (type) {
1256         case STATUSTYPE_INFO:
1257                 list_for_each_entry(pg, &m->priority_groups, list) {
1258                         if (pg->bypassed)
1259                                 state = 'D';    /* Disabled */
1260                         else if (pg == m->current_pg)
1261                                 state = 'A';    /* Currently Active */
1262                         else
1263                                 state = 'E';    /* Enabled */
1264
1265                         DMEMIT("%c ", state);
1266
1267                         if (pg->ps.type->status)
1268                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1269                                                           result + sz,
1270                                                           maxlen - sz);
1271                         else
1272                                 DMEMIT("0 ");
1273
1274                         DMEMIT("%u %u ", pg->nr_pgpaths,
1275                                pg->ps.type->info_args);
1276
1277                         list_for_each_entry(p, &pg->pgpaths, list) {
1278                                 DMEMIT("%s %s %u ", p->path.dev->name,
1279                                        p->path.is_active ? "A" : "F",
1280                                        p->fail_count);
1281                                 if (pg->ps.type->status)
1282                                         sz += pg->ps.type->status(&pg->ps,
1283                                               &p->path, type, result + sz,
1284                                               maxlen - sz);
1285                         }
1286                 }
1287                 break;
1288
1289         case STATUSTYPE_TABLE:
1290                 list_for_each_entry(pg, &m->priority_groups, list) {
1291                         DMEMIT("%s ", pg->ps.type->name);
1292
1293                         if (pg->ps.type->status)
1294                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1295                                                           result + sz,
1296                                                           maxlen - sz);
1297                         else
1298                                 DMEMIT("0 ");
1299
1300                         DMEMIT("%u %u ", pg->nr_pgpaths,
1301                                pg->ps.type->table_args);
1302
1303                         list_for_each_entry(p, &pg->pgpaths, list) {
1304                                 DMEMIT("%s ", p->path.dev->name);
1305                                 if (pg->ps.type->status)
1306                                         sz += pg->ps.type->status(&pg->ps,
1307                                               &p->path, type, result + sz,
1308                                               maxlen - sz);
1309                         }
1310                 }
1311                 break;
1312         }
1313
1314         spin_unlock_irqrestore(&m->lock, flags);
1315
1316         return 0;
1317 }
1318
1319 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1320 {
1321         int r;
1322         struct dm_dev *dev;
1323         struct multipath *m = (struct multipath *) ti->private;
1324         action_fn action;
1325
1326         if (argc == 1) {
1327                 if (!strnicmp(argv[0], MESG_STR("queue_if_no_path")))
1328                         return queue_if_no_path(m, 1, 0);
1329                 else if (!strnicmp(argv[0], MESG_STR("fail_if_no_path")))
1330                         return queue_if_no_path(m, 0, 0);
1331         }
1332
1333         if (argc != 2)
1334                 goto error;
1335
1336         if (!strnicmp(argv[0], MESG_STR("disable_group")))
1337                 return bypass_pg_num(m, argv[1], 1);
1338         else if (!strnicmp(argv[0], MESG_STR("enable_group")))
1339                 return bypass_pg_num(m, argv[1], 0);
1340         else if (!strnicmp(argv[0], MESG_STR("switch_group")))
1341                 return switch_pg_num(m, argv[1]);
1342         else if (!strnicmp(argv[0], MESG_STR("reinstate_path")))
1343                 action = reinstate_path;
1344         else if (!strnicmp(argv[0], MESG_STR("fail_path")))
1345                 action = fail_path;
1346         else
1347                 goto error;
1348
1349         r = dm_get_device(ti, argv[1], ti->begin, ti->len,
1350                           dm_table_get_mode(ti->table), &dev);
1351         if (r) {
1352                 DMWARN("message: error getting device %s",
1353                        argv[1]);
1354                 return -EINVAL;
1355         }
1356
1357         r = action_dev(m, dev, action);
1358
1359         dm_put_device(ti, dev);
1360
1361         return r;
1362
1363 error:
1364         DMWARN("Unrecognised multipath message received.");
1365         return -EINVAL;
1366 }
1367
1368 static int multipath_ioctl(struct dm_target *ti, struct inode *inode,
1369                            struct file *filp, unsigned int cmd,
1370                            unsigned long arg)
1371 {
1372         struct multipath *m = (struct multipath *) ti->private;
1373         struct block_device *bdev = NULL;
1374         unsigned long flags;
1375         struct file fake_file = {};
1376         struct dentry fake_dentry = {};
1377         int r = 0;
1378
1379         fake_file.f_path.dentry = &fake_dentry;
1380
1381         spin_lock_irqsave(&m->lock, flags);
1382
1383         if (!m->current_pgpath)
1384                 __choose_pgpath(m);
1385
1386         if (m->current_pgpath) {
1387                 bdev = m->current_pgpath->path.dev->bdev;
1388                 fake_dentry.d_inode = bdev->bd_inode;
1389                 fake_file.f_mode = m->current_pgpath->path.dev->mode;
1390         }
1391
1392         if (m->queue_io)
1393                 r = -EAGAIN;
1394         else if (!bdev)
1395                 r = -EIO;
1396
1397         spin_unlock_irqrestore(&m->lock, flags);
1398
1399         return r ? : blkdev_driver_ioctl(bdev->bd_inode, &fake_file,
1400                                          bdev->bd_disk, cmd, arg);
1401 }
1402
1403 /*-----------------------------------------------------------------
1404  * Module setup
1405  *---------------------------------------------------------------*/
1406 static struct target_type multipath_target = {
1407         .name = "multipath",
1408         .version = {1, 0, 5},
1409         .module = THIS_MODULE,
1410         .ctr = multipath_ctr,
1411         .dtr = multipath_dtr,
1412         .map = multipath_map,
1413         .end_io = multipath_end_io,
1414         .presuspend = multipath_presuspend,
1415         .resume = multipath_resume,
1416         .status = multipath_status,
1417         .message = multipath_message,
1418         .ioctl  = multipath_ioctl,
1419 };
1420
1421 static int __init dm_multipath_init(void)
1422 {
1423         int r;
1424
1425         /* allocate a slab for the dm_ios */
1426         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1427         if (!_mpio_cache)
1428                 return -ENOMEM;
1429
1430         r = dm_register_target(&multipath_target);
1431         if (r < 0) {
1432                 DMERR("register failed %d", r);
1433                 kmem_cache_destroy(_mpio_cache);
1434                 return -EINVAL;
1435         }
1436
1437         kmultipathd = create_workqueue("kmpathd");
1438         if (!kmultipathd) {
1439                 DMERR("failed to create workqueue kmpathd");
1440                 dm_unregister_target(&multipath_target);
1441                 kmem_cache_destroy(_mpio_cache);
1442                 return -ENOMEM;
1443         }
1444
1445         /*
1446          * A separate workqueue is used to handle the device handlers
1447          * to avoid overloading existing workqueue. Overloading the
1448          * old workqueue would also create a bottleneck in the
1449          * path of the storage hardware device activation.
1450          */
1451         kmpath_handlerd = create_singlethread_workqueue("kmpath_handlerd");
1452         if (!kmpath_handlerd) {
1453                 DMERR("failed to create workqueue kmpath_handlerd");
1454                 destroy_workqueue(kmultipathd);
1455                 dm_unregister_target(&multipath_target);
1456                 kmem_cache_destroy(_mpio_cache);
1457                 return -ENOMEM;
1458         }
1459
1460         DMINFO("version %u.%u.%u loaded",
1461                multipath_target.version[0], multipath_target.version[1],
1462                multipath_target.version[2]);
1463
1464         return r;
1465 }
1466
1467 static void __exit dm_multipath_exit(void)
1468 {
1469         int r;
1470
1471         destroy_workqueue(kmpath_handlerd);
1472         destroy_workqueue(kmultipathd);
1473
1474         r = dm_unregister_target(&multipath_target);
1475         if (r < 0)
1476                 DMERR("target unregister failed %d", r);
1477         kmem_cache_destroy(_mpio_cache);
1478 }
1479
1480 module_init(dm_multipath_init);
1481 module_exit(dm_multipath_exit);
1482
1483 MODULE_DESCRIPTION(DM_NAME " multipath target");
1484 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1485 MODULE_LICENSE("GPL");