dm table: share target argument parsing functions
[linux-2.6.git] / drivers / md / dm-mpath.c
1 /*
2  * Copyright (C) 2003 Sistina Software Limited.
3  * Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
4  *
5  * This file is released under the GPL.
6  */
7
8 #include <linux/device-mapper.h>
9
10 #include "dm-path-selector.h"
11 #include "dm-uevent.h"
12
13 #include <linux/ctype.h>
14 #include <linux/init.h>
15 #include <linux/mempool.h>
16 #include <linux/module.h>
17 #include <linux/pagemap.h>
18 #include <linux/slab.h>
19 #include <linux/time.h>
20 #include <linux/workqueue.h>
21 #include <scsi/scsi_dh.h>
22 #include <linux/atomic.h>
23
24 #define DM_MSG_PREFIX "multipath"
25 #define DM_PG_INIT_DELAY_MSECS 2000
26 #define DM_PG_INIT_DELAY_DEFAULT ((unsigned) -1)
27
28 /* Path properties */
29 struct pgpath {
30         struct list_head list;
31
32         struct priority_group *pg;      /* Owning PG */
33         unsigned is_active;             /* Path status */
34         unsigned fail_count;            /* Cumulative failure count */
35
36         struct dm_path path;
37         struct delayed_work activate_path;
38 };
39
40 #define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
41
42 /*
43  * Paths are grouped into Priority Groups and numbered from 1 upwards.
44  * Each has a path selector which controls which path gets used.
45  */
46 struct priority_group {
47         struct list_head list;
48
49         struct multipath *m;            /* Owning multipath instance */
50         struct path_selector ps;
51
52         unsigned pg_num;                /* Reference number */
53         unsigned bypassed;              /* Temporarily bypass this PG? */
54
55         unsigned nr_pgpaths;            /* Number of paths in PG */
56         struct list_head pgpaths;
57 };
58
59 /* Multipath context */
60 struct multipath {
61         struct list_head list;
62         struct dm_target *ti;
63
64         spinlock_t lock;
65
66         const char *hw_handler_name;
67         char *hw_handler_params;
68
69         unsigned nr_priority_groups;
70         struct list_head priority_groups;
71
72         wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
73
74         unsigned pg_init_required;      /* pg_init needs calling? */
75         unsigned pg_init_in_progress;   /* Only one pg_init allowed at once */
76         unsigned pg_init_delay_retry;   /* Delay pg_init retry? */
77
78         unsigned nr_valid_paths;        /* Total number of usable paths */
79         struct pgpath *current_pgpath;
80         struct priority_group *current_pg;
81         struct priority_group *next_pg; /* Switch to this PG if set */
82         unsigned repeat_count;          /* I/Os left before calling PS again */
83
84         unsigned queue_io;              /* Must we queue all I/O? */
85         unsigned queue_if_no_path;      /* Queue I/O if last path fails? */
86         unsigned saved_queue_if_no_path;/* Saved state during suspension */
87         unsigned pg_init_retries;       /* Number of times to retry pg_init */
88         unsigned pg_init_count;         /* Number of times pg_init called */
89         unsigned pg_init_delay_msecs;   /* Number of msecs before pg_init retry */
90
91         struct work_struct process_queued_ios;
92         struct list_head queued_ios;
93         unsigned queue_size;
94
95         struct work_struct trigger_event;
96
97         /*
98          * We must use a mempool of dm_mpath_io structs so that we
99          * can resubmit bios on error.
100          */
101         mempool_t *mpio_pool;
102
103         struct mutex work_mutex;
104 };
105
106 /*
107  * Context information attached to each bio we process.
108  */
109 struct dm_mpath_io {
110         struct pgpath *pgpath;
111         size_t nr_bytes;
112 };
113
114 typedef int (*action_fn) (struct pgpath *pgpath);
115
116 #define MIN_IOS 256     /* Mempool size */
117
118 static struct kmem_cache *_mpio_cache;
119
120 static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
121 static void process_queued_ios(struct work_struct *work);
122 static void trigger_event(struct work_struct *work);
123 static void activate_path(struct work_struct *work);
124
125
126 /*-----------------------------------------------
127  * Allocation routines
128  *-----------------------------------------------*/
129
130 static struct pgpath *alloc_pgpath(void)
131 {
132         struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
133
134         if (pgpath) {
135                 pgpath->is_active = 1;
136                 INIT_DELAYED_WORK(&pgpath->activate_path, activate_path);
137         }
138
139         return pgpath;
140 }
141
142 static void free_pgpath(struct pgpath *pgpath)
143 {
144         kfree(pgpath);
145 }
146
147 static struct priority_group *alloc_priority_group(void)
148 {
149         struct priority_group *pg;
150
151         pg = kzalloc(sizeof(*pg), GFP_KERNEL);
152
153         if (pg)
154                 INIT_LIST_HEAD(&pg->pgpaths);
155
156         return pg;
157 }
158
159 static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
160 {
161         struct pgpath *pgpath, *tmp;
162         struct multipath *m = ti->private;
163
164         list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
165                 list_del(&pgpath->list);
166                 if (m->hw_handler_name)
167                         scsi_dh_detach(bdev_get_queue(pgpath->path.dev->bdev));
168                 dm_put_device(ti, pgpath->path.dev);
169                 free_pgpath(pgpath);
170         }
171 }
172
173 static void free_priority_group(struct priority_group *pg,
174                                 struct dm_target *ti)
175 {
176         struct path_selector *ps = &pg->ps;
177
178         if (ps->type) {
179                 ps->type->destroy(ps);
180                 dm_put_path_selector(ps->type);
181         }
182
183         free_pgpaths(&pg->pgpaths, ti);
184         kfree(pg);
185 }
186
187 static struct multipath *alloc_multipath(struct dm_target *ti)
188 {
189         struct multipath *m;
190
191         m = kzalloc(sizeof(*m), GFP_KERNEL);
192         if (m) {
193                 INIT_LIST_HEAD(&m->priority_groups);
194                 INIT_LIST_HEAD(&m->queued_ios);
195                 spin_lock_init(&m->lock);
196                 m->queue_io = 1;
197                 m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
198                 INIT_WORK(&m->process_queued_ios, process_queued_ios);
199                 INIT_WORK(&m->trigger_event, trigger_event);
200                 init_waitqueue_head(&m->pg_init_wait);
201                 mutex_init(&m->work_mutex);
202                 m->mpio_pool = mempool_create_slab_pool(MIN_IOS, _mpio_cache);
203                 if (!m->mpio_pool) {
204                         kfree(m);
205                         return NULL;
206                 }
207                 m->ti = ti;
208                 ti->private = m;
209         }
210
211         return m;
212 }
213
214 static void free_multipath(struct multipath *m)
215 {
216         struct priority_group *pg, *tmp;
217
218         list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
219                 list_del(&pg->list);
220                 free_priority_group(pg, m->ti);
221         }
222
223         kfree(m->hw_handler_name);
224         kfree(m->hw_handler_params);
225         mempool_destroy(m->mpio_pool);
226         kfree(m);
227 }
228
229
230 /*-----------------------------------------------
231  * Path selection
232  *-----------------------------------------------*/
233
234 static void __pg_init_all_paths(struct multipath *m)
235 {
236         struct pgpath *pgpath;
237         unsigned long pg_init_delay = 0;
238
239         m->pg_init_count++;
240         m->pg_init_required = 0;
241         if (m->pg_init_delay_retry)
242                 pg_init_delay = msecs_to_jiffies(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
243                                                  m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
244         list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
245                 /* Skip failed paths */
246                 if (!pgpath->is_active)
247                         continue;
248                 if (queue_delayed_work(kmpath_handlerd, &pgpath->activate_path,
249                                        pg_init_delay))
250                         m->pg_init_in_progress++;
251         }
252 }
253
254 static void __switch_pg(struct multipath *m, struct pgpath *pgpath)
255 {
256         m->current_pg = pgpath->pg;
257
258         /* Must we initialise the PG first, and queue I/O till it's ready? */
259         if (m->hw_handler_name) {
260                 m->pg_init_required = 1;
261                 m->queue_io = 1;
262         } else {
263                 m->pg_init_required = 0;
264                 m->queue_io = 0;
265         }
266
267         m->pg_init_count = 0;
268 }
269
270 static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg,
271                                size_t nr_bytes)
272 {
273         struct dm_path *path;
274
275         path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes);
276         if (!path)
277                 return -ENXIO;
278
279         m->current_pgpath = path_to_pgpath(path);
280
281         if (m->current_pg != pg)
282                 __switch_pg(m, m->current_pgpath);
283
284         return 0;
285 }
286
287 static void __choose_pgpath(struct multipath *m, size_t nr_bytes)
288 {
289         struct priority_group *pg;
290         unsigned bypassed = 1;
291
292         if (!m->nr_valid_paths)
293                 goto failed;
294
295         /* Were we instructed to switch PG? */
296         if (m->next_pg) {
297                 pg = m->next_pg;
298                 m->next_pg = NULL;
299                 if (!__choose_path_in_pg(m, pg, nr_bytes))
300                         return;
301         }
302
303         /* Don't change PG until it has no remaining paths */
304         if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes))
305                 return;
306
307         /*
308          * Loop through priority groups until we find a valid path.
309          * First time we skip PGs marked 'bypassed'.
310          * Second time we only try the ones we skipped.
311          */
312         do {
313                 list_for_each_entry(pg, &m->priority_groups, list) {
314                         if (pg->bypassed == bypassed)
315                                 continue;
316                         if (!__choose_path_in_pg(m, pg, nr_bytes))
317                                 return;
318                 }
319         } while (bypassed--);
320
321 failed:
322         m->current_pgpath = NULL;
323         m->current_pg = NULL;
324 }
325
326 /*
327  * Check whether bios must be queued in the device-mapper core rather
328  * than here in the target.
329  *
330  * m->lock must be held on entry.
331  *
332  * If m->queue_if_no_path and m->saved_queue_if_no_path hold the
333  * same value then we are not between multipath_presuspend()
334  * and multipath_resume() calls and we have no need to check
335  * for the DMF_NOFLUSH_SUSPENDING flag.
336  */
337 static int __must_push_back(struct multipath *m)
338 {
339         return (m->queue_if_no_path != m->saved_queue_if_no_path &&
340                 dm_noflush_suspending(m->ti));
341 }
342
343 static int map_io(struct multipath *m, struct request *clone,
344                   struct dm_mpath_io *mpio, unsigned was_queued)
345 {
346         int r = DM_MAPIO_REMAPPED;
347         size_t nr_bytes = blk_rq_bytes(clone);
348         unsigned long flags;
349         struct pgpath *pgpath;
350         struct block_device *bdev;
351
352         spin_lock_irqsave(&m->lock, flags);
353
354         /* Do we need to select a new pgpath? */
355         if (!m->current_pgpath ||
356             (!m->queue_io && (m->repeat_count && --m->repeat_count == 0)))
357                 __choose_pgpath(m, nr_bytes);
358
359         pgpath = m->current_pgpath;
360
361         if (was_queued)
362                 m->queue_size--;
363
364         if ((pgpath && m->queue_io) ||
365             (!pgpath && m->queue_if_no_path)) {
366                 /* Queue for the daemon to resubmit */
367                 list_add_tail(&clone->queuelist, &m->queued_ios);
368                 m->queue_size++;
369                 if ((m->pg_init_required && !m->pg_init_in_progress) ||
370                     !m->queue_io)
371                         queue_work(kmultipathd, &m->process_queued_ios);
372                 pgpath = NULL;
373                 r = DM_MAPIO_SUBMITTED;
374         } else if (pgpath) {
375                 bdev = pgpath->path.dev->bdev;
376                 clone->q = bdev_get_queue(bdev);
377                 clone->rq_disk = bdev->bd_disk;
378         } else if (__must_push_back(m))
379                 r = DM_MAPIO_REQUEUE;
380         else
381                 r = -EIO;       /* Failed */
382
383         mpio->pgpath = pgpath;
384         mpio->nr_bytes = nr_bytes;
385
386         if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
387                 pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path,
388                                               nr_bytes);
389
390         spin_unlock_irqrestore(&m->lock, flags);
391
392         return r;
393 }
394
395 /*
396  * If we run out of usable paths, should we queue I/O or error it?
397  */
398 static int queue_if_no_path(struct multipath *m, unsigned queue_if_no_path,
399                             unsigned save_old_value)
400 {
401         unsigned long flags;
402
403         spin_lock_irqsave(&m->lock, flags);
404
405         if (save_old_value)
406                 m->saved_queue_if_no_path = m->queue_if_no_path;
407         else
408                 m->saved_queue_if_no_path = queue_if_no_path;
409         m->queue_if_no_path = queue_if_no_path;
410         if (!m->queue_if_no_path && m->queue_size)
411                 queue_work(kmultipathd, &m->process_queued_ios);
412
413         spin_unlock_irqrestore(&m->lock, flags);
414
415         return 0;
416 }
417
418 /*-----------------------------------------------------------------
419  * The multipath daemon is responsible for resubmitting queued ios.
420  *---------------------------------------------------------------*/
421
422 static void dispatch_queued_ios(struct multipath *m)
423 {
424         int r;
425         unsigned long flags;
426         struct dm_mpath_io *mpio;
427         union map_info *info;
428         struct request *clone, *n;
429         LIST_HEAD(cl);
430
431         spin_lock_irqsave(&m->lock, flags);
432         list_splice_init(&m->queued_ios, &cl);
433         spin_unlock_irqrestore(&m->lock, flags);
434
435         list_for_each_entry_safe(clone, n, &cl, queuelist) {
436                 list_del_init(&clone->queuelist);
437
438                 info = dm_get_rq_mapinfo(clone);
439                 mpio = info->ptr;
440
441                 r = map_io(m, clone, mpio, 1);
442                 if (r < 0) {
443                         mempool_free(mpio, m->mpio_pool);
444                         dm_kill_unmapped_request(clone, r);
445                 } else if (r == DM_MAPIO_REMAPPED)
446                         dm_dispatch_request(clone);
447                 else if (r == DM_MAPIO_REQUEUE) {
448                         mempool_free(mpio, m->mpio_pool);
449                         dm_requeue_unmapped_request(clone);
450                 }
451         }
452 }
453
454 static void process_queued_ios(struct work_struct *work)
455 {
456         struct multipath *m =
457                 container_of(work, struct multipath, process_queued_ios);
458         struct pgpath *pgpath = NULL;
459         unsigned must_queue = 1;
460         unsigned long flags;
461
462         spin_lock_irqsave(&m->lock, flags);
463
464         if (!m->queue_size)
465                 goto out;
466
467         if (!m->current_pgpath)
468                 __choose_pgpath(m, 0);
469
470         pgpath = m->current_pgpath;
471
472         if ((pgpath && !m->queue_io) ||
473             (!pgpath && !m->queue_if_no_path))
474                 must_queue = 0;
475
476         if (m->pg_init_required && !m->pg_init_in_progress && pgpath)
477                 __pg_init_all_paths(m);
478
479 out:
480         spin_unlock_irqrestore(&m->lock, flags);
481         if (!must_queue)
482                 dispatch_queued_ios(m);
483 }
484
485 /*
486  * An event is triggered whenever a path is taken out of use.
487  * Includes path failure and PG bypass.
488  */
489 static void trigger_event(struct work_struct *work)
490 {
491         struct multipath *m =
492                 container_of(work, struct multipath, trigger_event);
493
494         dm_table_event(m->ti->table);
495 }
496
497 /*-----------------------------------------------------------------
498  * Constructor/argument parsing:
499  * <#multipath feature args> [<arg>]*
500  * <#hw_handler args> [hw_handler [<arg>]*]
501  * <#priority groups>
502  * <initial priority group>
503  *     [<selector> <#selector args> [<arg>]*
504  *      <#paths> <#per-path selector args>
505  *         [<path> [<arg>]* ]+ ]+
506  *---------------------------------------------------------------*/
507 static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
508                                struct dm_target *ti)
509 {
510         int r;
511         struct path_selector_type *pst;
512         unsigned ps_argc;
513
514         static struct dm_arg _args[] = {
515                 {0, 1024, "invalid number of path selector args"},
516         };
517
518         pst = dm_get_path_selector(dm_shift_arg(as));
519         if (!pst) {
520                 ti->error = "unknown path selector type";
521                 return -EINVAL;
522         }
523
524         r = dm_read_arg_group(_args, as, &ps_argc, &ti->error);
525         if (r) {
526                 dm_put_path_selector(pst);
527                 return -EINVAL;
528         }
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         dm_consume_args(as, ps_argc);
539
540         return 0;
541 }
542
543 static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
544                                struct dm_target *ti)
545 {
546         int r;
547         struct pgpath *p;
548         struct multipath *m = ti->private;
549
550         /* we need at least a path arg */
551         if (as->argc < 1) {
552                 ti->error = "no device given";
553                 return ERR_PTR(-EINVAL);
554         }
555
556         p = alloc_pgpath();
557         if (!p)
558                 return ERR_PTR(-ENOMEM);
559
560         r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
561                           &p->path.dev);
562         if (r) {
563                 ti->error = "error getting device";
564                 goto bad;
565         }
566
567         if (m->hw_handler_name) {
568                 struct request_queue *q = bdev_get_queue(p->path.dev->bdev);
569
570                 r = scsi_dh_attach(q, m->hw_handler_name);
571                 if (r == -EBUSY) {
572                         /*
573                          * Already attached to different hw_handler,
574                          * try to reattach with correct one.
575                          */
576                         scsi_dh_detach(q);
577                         r = scsi_dh_attach(q, m->hw_handler_name);
578                 }
579
580                 if (r < 0) {
581                         ti->error = "error attaching hardware handler";
582                         dm_put_device(ti, p->path.dev);
583                         goto bad;
584                 }
585
586                 if (m->hw_handler_params) {
587                         r = scsi_dh_set_params(q, m->hw_handler_params);
588                         if (r < 0) {
589                                 ti->error = "unable to set hardware "
590                                                         "handler parameters";
591                                 scsi_dh_detach(q);
592                                 dm_put_device(ti, p->path.dev);
593                                 goto bad;
594                         }
595                 }
596         }
597
598         r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
599         if (r) {
600                 dm_put_device(ti, p->path.dev);
601                 goto bad;
602         }
603
604         return p;
605
606  bad:
607         free_pgpath(p);
608         return ERR_PTR(r);
609 }
610
611 static struct priority_group *parse_priority_group(struct dm_arg_set *as,
612                                                    struct multipath *m)
613 {
614         static struct dm_arg _args[] = {
615                 {1, 1024, "invalid number of paths"},
616                 {0, 1024, "invalid number of selector args"}
617         };
618
619         int r;
620         unsigned i, nr_selector_args, nr_args;
621         struct priority_group *pg;
622         struct dm_target *ti = m->ti;
623
624         if (as->argc < 2) {
625                 as->argc = 0;
626                 ti->error = "not enough priority group arguments";
627                 return ERR_PTR(-EINVAL);
628         }
629
630         pg = alloc_priority_group();
631         if (!pg) {
632                 ti->error = "couldn't allocate priority group";
633                 return ERR_PTR(-ENOMEM);
634         }
635         pg->m = m;
636
637         r = parse_path_selector(as, pg, ti);
638         if (r)
639                 goto bad;
640
641         /*
642          * read the paths
643          */
644         r = dm_read_arg(_args, as, &pg->nr_pgpaths, &ti->error);
645         if (r)
646                 goto bad;
647
648         r = dm_read_arg(_args + 1, as, &nr_selector_args, &ti->error);
649         if (r)
650                 goto bad;
651
652         nr_args = 1 + nr_selector_args;
653         for (i = 0; i < pg->nr_pgpaths; i++) {
654                 struct pgpath *pgpath;
655                 struct dm_arg_set path_args;
656
657                 if (as->argc < nr_args) {
658                         ti->error = "not enough path parameters";
659                         r = -EINVAL;
660                         goto bad;
661                 }
662
663                 path_args.argc = nr_args;
664                 path_args.argv = as->argv;
665
666                 pgpath = parse_path(&path_args, &pg->ps, ti);
667                 if (IS_ERR(pgpath)) {
668                         r = PTR_ERR(pgpath);
669                         goto bad;
670                 }
671
672                 pgpath->pg = pg;
673                 list_add_tail(&pgpath->list, &pg->pgpaths);
674                 dm_consume_args(as, nr_args);
675         }
676
677         return pg;
678
679  bad:
680         free_priority_group(pg, ti);
681         return ERR_PTR(r);
682 }
683
684 static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
685 {
686         unsigned hw_argc;
687         int ret;
688         struct dm_target *ti = m->ti;
689
690         static struct dm_arg _args[] = {
691                 {0, 1024, "invalid number of hardware handler args"},
692         };
693
694         if (dm_read_arg_group(_args, as, &hw_argc, &ti->error))
695                 return -EINVAL;
696
697         if (!hw_argc)
698                 return 0;
699
700         m->hw_handler_name = kstrdup(dm_shift_arg(as), GFP_KERNEL);
701         request_module("scsi_dh_%s", m->hw_handler_name);
702         if (scsi_dh_handler_exist(m->hw_handler_name) == 0) {
703                 ti->error = "unknown hardware handler type";
704                 ret = -EINVAL;
705                 goto fail;
706         }
707
708         if (hw_argc > 1) {
709                 char *p;
710                 int i, j, len = 4;
711
712                 for (i = 0; i <= hw_argc - 2; i++)
713                         len += strlen(as->argv[i]) + 1;
714                 p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
715                 if (!p) {
716                         ti->error = "memory allocation failed";
717                         ret = -ENOMEM;
718                         goto fail;
719                 }
720                 j = sprintf(p, "%d", hw_argc - 1);
721                 for (i = 0, p+=j+1; i <= hw_argc - 2; i++, p+=j+1)
722                         j = sprintf(p, "%s", as->argv[i]);
723         }
724         dm_consume_args(as, hw_argc - 1);
725
726         return 0;
727 fail:
728         kfree(m->hw_handler_name);
729         m->hw_handler_name = NULL;
730         return ret;
731 }
732
733 static int parse_features(struct dm_arg_set *as, struct multipath *m)
734 {
735         int r;
736         unsigned argc;
737         struct dm_target *ti = m->ti;
738         const char *arg_name;
739
740         static struct dm_arg _args[] = {
741                 {0, 5, "invalid number of feature args"},
742                 {1, 50, "pg_init_retries must be between 1 and 50"},
743                 {0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
744         };
745
746         r = dm_read_arg_group(_args, as, &argc, &ti->error);
747         if (r)
748                 return -EINVAL;
749
750         if (!argc)
751                 return 0;
752
753         do {
754                 arg_name = dm_shift_arg(as);
755                 argc--;
756
757                 if (!strcasecmp(arg_name, "queue_if_no_path")) {
758                         r = queue_if_no_path(m, 1, 0);
759                         continue;
760                 }
761
762                 if (!strcasecmp(arg_name, "pg_init_retries") &&
763                     (argc >= 1)) {
764                         r = dm_read_arg(_args + 1, as, &m->pg_init_retries, &ti->error);
765                         argc--;
766                         continue;
767                 }
768
769                 if (!strcasecmp(arg_name, "pg_init_delay_msecs") &&
770                     (argc >= 1)) {
771                         r = dm_read_arg(_args + 2, as, &m->pg_init_delay_msecs, &ti->error);
772                         argc--;
773                         continue;
774                 }
775
776                 ti->error = "Unrecognised multipath feature request";
777                 r = -EINVAL;
778         } while (argc && !r);
779
780         return r;
781 }
782
783 static int multipath_ctr(struct dm_target *ti, unsigned int argc,
784                          char **argv)
785 {
786         /* target arguments */
787         static struct dm_arg _args[] = {
788                 {0, 1024, "invalid number of priority groups"},
789                 {0, 1024, "invalid initial priority group number"},
790         };
791
792         int r;
793         struct multipath *m;
794         struct dm_arg_set as;
795         unsigned pg_count = 0;
796         unsigned next_pg_num;
797
798         as.argc = argc;
799         as.argv = argv;
800
801         m = alloc_multipath(ti);
802         if (!m) {
803                 ti->error = "can't allocate multipath";
804                 return -EINVAL;
805         }
806
807         r = parse_features(&as, m);
808         if (r)
809                 goto bad;
810
811         r = parse_hw_handler(&as, m);
812         if (r)
813                 goto bad;
814
815         r = dm_read_arg(_args, &as, &m->nr_priority_groups, &ti->error);
816         if (r)
817                 goto bad;
818
819         r = dm_read_arg(_args + 1, &as, &next_pg_num, &ti->error);
820         if (r)
821                 goto bad;
822
823         if ((!m->nr_priority_groups && next_pg_num) ||
824             (m->nr_priority_groups && !next_pg_num)) {
825                 ti->error = "invalid initial priority group";
826                 r = -EINVAL;
827                 goto bad;
828         }
829
830         /* parse the priority groups */
831         while (as.argc) {
832                 struct priority_group *pg;
833
834                 pg = parse_priority_group(&as, m);
835                 if (IS_ERR(pg)) {
836                         r = PTR_ERR(pg);
837                         goto bad;
838                 }
839
840                 m->nr_valid_paths += pg->nr_pgpaths;
841                 list_add_tail(&pg->list, &m->priority_groups);
842                 pg_count++;
843                 pg->pg_num = pg_count;
844                 if (!--next_pg_num)
845                         m->next_pg = pg;
846         }
847
848         if (pg_count != m->nr_priority_groups) {
849                 ti->error = "priority group count mismatch";
850                 r = -EINVAL;
851                 goto bad;
852         }
853
854         ti->num_flush_requests = 1;
855         ti->num_discard_requests = 1;
856
857         return 0;
858
859  bad:
860         free_multipath(m);
861         return r;
862 }
863
864 static void multipath_wait_for_pg_init_completion(struct multipath *m)
865 {
866         DECLARE_WAITQUEUE(wait, current);
867         unsigned long flags;
868
869         add_wait_queue(&m->pg_init_wait, &wait);
870
871         while (1) {
872                 set_current_state(TASK_UNINTERRUPTIBLE);
873
874                 spin_lock_irqsave(&m->lock, flags);
875                 if (!m->pg_init_in_progress) {
876                         spin_unlock_irqrestore(&m->lock, flags);
877                         break;
878                 }
879                 spin_unlock_irqrestore(&m->lock, flags);
880
881                 io_schedule();
882         }
883         set_current_state(TASK_RUNNING);
884
885         remove_wait_queue(&m->pg_init_wait, &wait);
886 }
887
888 static void flush_multipath_work(struct multipath *m)
889 {
890         flush_workqueue(kmpath_handlerd);
891         multipath_wait_for_pg_init_completion(m);
892         flush_workqueue(kmultipathd);
893         flush_work_sync(&m->trigger_event);
894 }
895
896 static void multipath_dtr(struct dm_target *ti)
897 {
898         struct multipath *m = ti->private;
899
900         flush_multipath_work(m);
901         free_multipath(m);
902 }
903
904 /*
905  * Map cloned requests
906  */
907 static int multipath_map(struct dm_target *ti, struct request *clone,
908                          union map_info *map_context)
909 {
910         int r;
911         struct dm_mpath_io *mpio;
912         struct multipath *m = (struct multipath *) ti->private;
913
914         mpio = mempool_alloc(m->mpio_pool, GFP_ATOMIC);
915         if (!mpio)
916                 /* ENOMEM, requeue */
917                 return DM_MAPIO_REQUEUE;
918         memset(mpio, 0, sizeof(*mpio));
919
920         map_context->ptr = mpio;
921         clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
922         r = map_io(m, clone, mpio, 0);
923         if (r < 0 || r == DM_MAPIO_REQUEUE)
924                 mempool_free(mpio, m->mpio_pool);
925
926         return r;
927 }
928
929 /*
930  * Take a path out of use.
931  */
932 static int fail_path(struct pgpath *pgpath)
933 {
934         unsigned long flags;
935         struct multipath *m = pgpath->pg->m;
936
937         spin_lock_irqsave(&m->lock, flags);
938
939         if (!pgpath->is_active)
940                 goto out;
941
942         DMWARN("Failing path %s.", pgpath->path.dev->name);
943
944         pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
945         pgpath->is_active = 0;
946         pgpath->fail_count++;
947
948         m->nr_valid_paths--;
949
950         if (pgpath == m->current_pgpath)
951                 m->current_pgpath = NULL;
952
953         dm_path_uevent(DM_UEVENT_PATH_FAILED, m->ti,
954                       pgpath->path.dev->name, m->nr_valid_paths);
955
956         schedule_work(&m->trigger_event);
957
958 out:
959         spin_unlock_irqrestore(&m->lock, flags);
960
961         return 0;
962 }
963
964 /*
965  * Reinstate a previously-failed path
966  */
967 static int reinstate_path(struct pgpath *pgpath)
968 {
969         int r = 0;
970         unsigned long flags;
971         struct multipath *m = pgpath->pg->m;
972
973         spin_lock_irqsave(&m->lock, flags);
974
975         if (pgpath->is_active)
976                 goto out;
977
978         if (!pgpath->pg->ps.type->reinstate_path) {
979                 DMWARN("Reinstate path not supported by path selector %s",
980                        pgpath->pg->ps.type->name);
981                 r = -EINVAL;
982                 goto out;
983         }
984
985         r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
986         if (r)
987                 goto out;
988
989         pgpath->is_active = 1;
990
991         if (!m->nr_valid_paths++ && m->queue_size) {
992                 m->current_pgpath = NULL;
993                 queue_work(kmultipathd, &m->process_queued_ios);
994         } else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
995                 if (queue_work(kmpath_handlerd, &pgpath->activate_path.work))
996                         m->pg_init_in_progress++;
997         }
998
999         dm_path_uevent(DM_UEVENT_PATH_REINSTATED, m->ti,
1000                       pgpath->path.dev->name, m->nr_valid_paths);
1001
1002         schedule_work(&m->trigger_event);
1003
1004 out:
1005         spin_unlock_irqrestore(&m->lock, flags);
1006
1007         return r;
1008 }
1009
1010 /*
1011  * Fail or reinstate all paths that match the provided struct dm_dev.
1012  */
1013 static int action_dev(struct multipath *m, struct dm_dev *dev,
1014                       action_fn action)
1015 {
1016         int r = -EINVAL;
1017         struct pgpath *pgpath;
1018         struct priority_group *pg;
1019
1020         list_for_each_entry(pg, &m->priority_groups, list) {
1021                 list_for_each_entry(pgpath, &pg->pgpaths, list) {
1022                         if (pgpath->path.dev == dev)
1023                                 r = action(pgpath);
1024                 }
1025         }
1026
1027         return r;
1028 }
1029
1030 /*
1031  * Temporarily try to avoid having to use the specified PG
1032  */
1033 static void bypass_pg(struct multipath *m, struct priority_group *pg,
1034                       int bypassed)
1035 {
1036         unsigned long flags;
1037
1038         spin_lock_irqsave(&m->lock, flags);
1039
1040         pg->bypassed = bypassed;
1041         m->current_pgpath = NULL;
1042         m->current_pg = NULL;
1043
1044         spin_unlock_irqrestore(&m->lock, flags);
1045
1046         schedule_work(&m->trigger_event);
1047 }
1048
1049 /*
1050  * Switch to using the specified PG from the next I/O that gets mapped
1051  */
1052 static int switch_pg_num(struct multipath *m, const char *pgstr)
1053 {
1054         struct priority_group *pg;
1055         unsigned pgnum;
1056         unsigned long flags;
1057
1058         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1059             (pgnum > m->nr_priority_groups)) {
1060                 DMWARN("invalid PG number supplied to switch_pg_num");
1061                 return -EINVAL;
1062         }
1063
1064         spin_lock_irqsave(&m->lock, flags);
1065         list_for_each_entry(pg, &m->priority_groups, list) {
1066                 pg->bypassed = 0;
1067                 if (--pgnum)
1068                         continue;
1069
1070                 m->current_pgpath = NULL;
1071                 m->current_pg = NULL;
1072                 m->next_pg = pg;
1073         }
1074         spin_unlock_irqrestore(&m->lock, flags);
1075
1076         schedule_work(&m->trigger_event);
1077         return 0;
1078 }
1079
1080 /*
1081  * Set/clear bypassed status of a PG.
1082  * PGs are numbered upwards from 1 in the order they were declared.
1083  */
1084 static int bypass_pg_num(struct multipath *m, const char *pgstr, int bypassed)
1085 {
1086         struct priority_group *pg;
1087         unsigned pgnum;
1088
1089         if (!pgstr || (sscanf(pgstr, "%u", &pgnum) != 1) || !pgnum ||
1090             (pgnum > m->nr_priority_groups)) {
1091                 DMWARN("invalid PG number supplied to bypass_pg");
1092                 return -EINVAL;
1093         }
1094
1095         list_for_each_entry(pg, &m->priority_groups, list) {
1096                 if (!--pgnum)
1097                         break;
1098         }
1099
1100         bypass_pg(m, pg, bypassed);
1101         return 0;
1102 }
1103
1104 /*
1105  * Should we retry pg_init immediately?
1106  */
1107 static int pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1108 {
1109         unsigned long flags;
1110         int limit_reached = 0;
1111
1112         spin_lock_irqsave(&m->lock, flags);
1113
1114         if (m->pg_init_count <= m->pg_init_retries)
1115                 m->pg_init_required = 1;
1116         else
1117                 limit_reached = 1;
1118
1119         spin_unlock_irqrestore(&m->lock, flags);
1120
1121         return limit_reached;
1122 }
1123
1124 static void pg_init_done(void *data, int errors)
1125 {
1126         struct pgpath *pgpath = data;
1127         struct priority_group *pg = pgpath->pg;
1128         struct multipath *m = pg->m;
1129         unsigned long flags;
1130         unsigned delay_retry = 0;
1131
1132         /* device or driver problems */
1133         switch (errors) {
1134         case SCSI_DH_OK:
1135                 break;
1136         case SCSI_DH_NOSYS:
1137                 if (!m->hw_handler_name) {
1138                         errors = 0;
1139                         break;
1140                 }
1141                 DMERR("Could not failover the device: Handler scsi_dh_%s "
1142                       "Error %d.", m->hw_handler_name, errors);
1143                 /*
1144                  * Fail path for now, so we do not ping pong
1145                  */
1146                 fail_path(pgpath);
1147                 break;
1148         case SCSI_DH_DEV_TEMP_BUSY:
1149                 /*
1150                  * Probably doing something like FW upgrade on the
1151                  * controller so try the other pg.
1152                  */
1153                 bypass_pg(m, pg, 1);
1154                 break;
1155         case SCSI_DH_RETRY:
1156                 /* Wait before retrying. */
1157                 delay_retry = 1;
1158         case SCSI_DH_IMM_RETRY:
1159         case SCSI_DH_RES_TEMP_UNAVAIL:
1160                 if (pg_init_limit_reached(m, pgpath))
1161                         fail_path(pgpath);
1162                 errors = 0;
1163                 break;
1164         default:
1165                 /*
1166                  * We probably do not want to fail the path for a device
1167                  * error, but this is what the old dm did. In future
1168                  * patches we can do more advanced handling.
1169                  */
1170                 fail_path(pgpath);
1171         }
1172
1173         spin_lock_irqsave(&m->lock, flags);
1174         if (errors) {
1175                 if (pgpath == m->current_pgpath) {
1176                         DMERR("Could not failover device. Error %d.", errors);
1177                         m->current_pgpath = NULL;
1178                         m->current_pg = NULL;
1179                 }
1180         } else if (!m->pg_init_required)
1181                 pg->bypassed = 0;
1182
1183         if (--m->pg_init_in_progress)
1184                 /* Activations of other paths are still on going */
1185                 goto out;
1186
1187         if (!m->pg_init_required)
1188                 m->queue_io = 0;
1189
1190         m->pg_init_delay_retry = delay_retry;
1191         queue_work(kmultipathd, &m->process_queued_ios);
1192
1193         /*
1194          * Wake up any thread waiting to suspend.
1195          */
1196         wake_up(&m->pg_init_wait);
1197
1198 out:
1199         spin_unlock_irqrestore(&m->lock, flags);
1200 }
1201
1202 static void activate_path(struct work_struct *work)
1203 {
1204         struct pgpath *pgpath =
1205                 container_of(work, struct pgpath, activate_path.work);
1206
1207         scsi_dh_activate(bdev_get_queue(pgpath->path.dev->bdev),
1208                                 pg_init_done, pgpath);
1209 }
1210
1211 /*
1212  * end_io handling
1213  */
1214 static int do_end_io(struct multipath *m, struct request *clone,
1215                      int error, struct dm_mpath_io *mpio)
1216 {
1217         /*
1218          * We don't queue any clone request inside the multipath target
1219          * during end I/O handling, since those clone requests don't have
1220          * bio clones.  If we queue them inside the multipath target,
1221          * we need to make bio clones, that requires memory allocation.
1222          * (See drivers/md/dm.c:end_clone_bio() about why the clone requests
1223          *  don't have bio clones.)
1224          * Instead of queueing the clone request here, we queue the original
1225          * request into dm core, which will remake a clone request and
1226          * clone bios for it and resubmit it later.
1227          */
1228         int r = DM_ENDIO_REQUEUE;
1229         unsigned long flags;
1230
1231         if (!error && !clone->errors)
1232                 return 0;       /* I/O complete */
1233
1234         if (error == -EOPNOTSUPP || error == -EREMOTEIO || error == -EILSEQ)
1235                 return error;
1236
1237         if (mpio->pgpath)
1238                 fail_path(mpio->pgpath);
1239
1240         spin_lock_irqsave(&m->lock, flags);
1241         if (!m->nr_valid_paths) {
1242                 if (!m->queue_if_no_path) {
1243                         if (!__must_push_back(m))
1244                                 r = -EIO;
1245                 } else {
1246                         if (error == -EBADE)
1247                                 r = error;
1248                 }
1249         }
1250         spin_unlock_irqrestore(&m->lock, flags);
1251
1252         return r;
1253 }
1254
1255 static int multipath_end_io(struct dm_target *ti, struct request *clone,
1256                             int error, union map_info *map_context)
1257 {
1258         struct multipath *m = ti->private;
1259         struct dm_mpath_io *mpio = map_context->ptr;
1260         struct pgpath *pgpath = mpio->pgpath;
1261         struct path_selector *ps;
1262         int r;
1263
1264         r  = do_end_io(m, clone, error, mpio);
1265         if (pgpath) {
1266                 ps = &pgpath->pg->ps;
1267                 if (ps->type->end_io)
1268                         ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes);
1269         }
1270         mempool_free(mpio, m->mpio_pool);
1271
1272         return r;
1273 }
1274
1275 /*
1276  * Suspend can't complete until all the I/O is processed so if
1277  * the last path fails we must error any remaining I/O.
1278  * Note that if the freeze_bdev fails while suspending, the
1279  * queue_if_no_path state is lost - userspace should reset it.
1280  */
1281 static void multipath_presuspend(struct dm_target *ti)
1282 {
1283         struct multipath *m = (struct multipath *) ti->private;
1284
1285         queue_if_no_path(m, 0, 1);
1286 }
1287
1288 static void multipath_postsuspend(struct dm_target *ti)
1289 {
1290         struct multipath *m = ti->private;
1291
1292         mutex_lock(&m->work_mutex);
1293         flush_multipath_work(m);
1294         mutex_unlock(&m->work_mutex);
1295 }
1296
1297 /*
1298  * Restore the queue_if_no_path setting.
1299  */
1300 static void multipath_resume(struct dm_target *ti)
1301 {
1302         struct multipath *m = (struct multipath *) ti->private;
1303         unsigned long flags;
1304
1305         spin_lock_irqsave(&m->lock, flags);
1306         m->queue_if_no_path = m->saved_queue_if_no_path;
1307         spin_unlock_irqrestore(&m->lock, flags);
1308 }
1309
1310 /*
1311  * Info output has the following format:
1312  * num_multipath_feature_args [multipath_feature_args]*
1313  * num_handler_status_args [handler_status_args]*
1314  * num_groups init_group_number
1315  *            [A|D|E num_ps_status_args [ps_status_args]*
1316  *             num_paths num_selector_args
1317  *             [path_dev A|F fail_count [selector_args]* ]+ ]+
1318  *
1319  * Table output has the following format (identical to the constructor string):
1320  * num_feature_args [features_args]*
1321  * num_handler_args hw_handler [hw_handler_args]*
1322  * num_groups init_group_number
1323  *     [priority selector-name num_ps_args [ps_args]*
1324  *      num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1325  */
1326 static int multipath_status(struct dm_target *ti, status_type_t type,
1327                             char *result, unsigned int maxlen)
1328 {
1329         int sz = 0;
1330         unsigned long flags;
1331         struct multipath *m = (struct multipath *) ti->private;
1332         struct priority_group *pg;
1333         struct pgpath *p;
1334         unsigned pg_num;
1335         char state;
1336
1337         spin_lock_irqsave(&m->lock, flags);
1338
1339         /* Features */
1340         if (type == STATUSTYPE_INFO)
1341                 DMEMIT("2 %u %u ", m->queue_size, m->pg_init_count);
1342         else {
1343                 DMEMIT("%u ", m->queue_if_no_path +
1344                               (m->pg_init_retries > 0) * 2 +
1345                               (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2);
1346                 if (m->queue_if_no_path)
1347                         DMEMIT("queue_if_no_path ");
1348                 if (m->pg_init_retries)
1349                         DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1350                 if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1351                         DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1352         }
1353
1354         if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1355                 DMEMIT("0 ");
1356         else
1357                 DMEMIT("1 %s ", m->hw_handler_name);
1358
1359         DMEMIT("%u ", m->nr_priority_groups);
1360
1361         if (m->next_pg)
1362                 pg_num = m->next_pg->pg_num;
1363         else if (m->current_pg)
1364                 pg_num = m->current_pg->pg_num;
1365         else
1366                 pg_num = (m->nr_priority_groups ? 1 : 0);
1367
1368         DMEMIT("%u ", pg_num);
1369
1370         switch (type) {
1371         case STATUSTYPE_INFO:
1372                 list_for_each_entry(pg, &m->priority_groups, list) {
1373                         if (pg->bypassed)
1374                                 state = 'D';    /* Disabled */
1375                         else if (pg == m->current_pg)
1376                                 state = 'A';    /* Currently Active */
1377                         else
1378                                 state = 'E';    /* Enabled */
1379
1380                         DMEMIT("%c ", state);
1381
1382                         if (pg->ps.type->status)
1383                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1384                                                           result + sz,
1385                                                           maxlen - sz);
1386                         else
1387                                 DMEMIT("0 ");
1388
1389                         DMEMIT("%u %u ", pg->nr_pgpaths,
1390                                pg->ps.type->info_args);
1391
1392                         list_for_each_entry(p, &pg->pgpaths, list) {
1393                                 DMEMIT("%s %s %u ", p->path.dev->name,
1394                                        p->is_active ? "A" : "F",
1395                                        p->fail_count);
1396                                 if (pg->ps.type->status)
1397                                         sz += pg->ps.type->status(&pg->ps,
1398                                               &p->path, type, result + sz,
1399                                               maxlen - sz);
1400                         }
1401                 }
1402                 break;
1403
1404         case STATUSTYPE_TABLE:
1405                 list_for_each_entry(pg, &m->priority_groups, list) {
1406                         DMEMIT("%s ", pg->ps.type->name);
1407
1408                         if (pg->ps.type->status)
1409                                 sz += pg->ps.type->status(&pg->ps, NULL, type,
1410                                                           result + sz,
1411                                                           maxlen - sz);
1412                         else
1413                                 DMEMIT("0 ");
1414
1415                         DMEMIT("%u %u ", pg->nr_pgpaths,
1416                                pg->ps.type->table_args);
1417
1418                         list_for_each_entry(p, &pg->pgpaths, list) {
1419                                 DMEMIT("%s ", p->path.dev->name);
1420                                 if (pg->ps.type->status)
1421                                         sz += pg->ps.type->status(&pg->ps,
1422                                               &p->path, type, result + sz,
1423                                               maxlen - sz);
1424                         }
1425                 }
1426                 break;
1427         }
1428
1429         spin_unlock_irqrestore(&m->lock, flags);
1430
1431         return 0;
1432 }
1433
1434 static int multipath_message(struct dm_target *ti, unsigned argc, char **argv)
1435 {
1436         int r = -EINVAL;
1437         struct dm_dev *dev;
1438         struct multipath *m = (struct multipath *) ti->private;
1439         action_fn action;
1440
1441         mutex_lock(&m->work_mutex);
1442
1443         if (dm_suspended(ti)) {
1444                 r = -EBUSY;
1445                 goto out;
1446         }
1447
1448         if (argc == 1) {
1449                 if (!strcasecmp(argv[0], "queue_if_no_path")) {
1450                         r = queue_if_no_path(m, 1, 0);
1451                         goto out;
1452                 } else if (!strcasecmp(argv[0], "fail_if_no_path")) {
1453                         r = queue_if_no_path(m, 0, 0);
1454                         goto out;
1455                 }
1456         }
1457
1458         if (argc != 2) {
1459                 DMWARN("Unrecognised multipath message received.");
1460                 goto out;
1461         }
1462
1463         if (!strcasecmp(argv[0], "disable_group")) {
1464                 r = bypass_pg_num(m, argv[1], 1);
1465                 goto out;
1466         } else if (!strcasecmp(argv[0], "enable_group")) {
1467                 r = bypass_pg_num(m, argv[1], 0);
1468                 goto out;
1469         } else if (!strcasecmp(argv[0], "switch_group")) {
1470                 r = switch_pg_num(m, argv[1]);
1471                 goto out;
1472         } else if (!strcasecmp(argv[0], "reinstate_path"))
1473                 action = reinstate_path;
1474         else if (!strcasecmp(argv[0], "fail_path"))
1475                 action = fail_path;
1476         else {
1477                 DMWARN("Unrecognised multipath message received.");
1478                 goto out;
1479         }
1480
1481         r = dm_get_device(ti, argv[1], dm_table_get_mode(ti->table), &dev);
1482         if (r) {
1483                 DMWARN("message: error getting device %s",
1484                        argv[1]);
1485                 goto out;
1486         }
1487
1488         r = action_dev(m, dev, action);
1489
1490         dm_put_device(ti, dev);
1491
1492 out:
1493         mutex_unlock(&m->work_mutex);
1494         return r;
1495 }
1496
1497 static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
1498                            unsigned long arg)
1499 {
1500         struct multipath *m = (struct multipath *) ti->private;
1501         struct block_device *bdev = NULL;
1502         fmode_t mode = 0;
1503         unsigned long flags;
1504         int r = 0;
1505
1506         spin_lock_irqsave(&m->lock, flags);
1507
1508         if (!m->current_pgpath)
1509                 __choose_pgpath(m, 0);
1510
1511         if (m->current_pgpath) {
1512                 bdev = m->current_pgpath->path.dev->bdev;
1513                 mode = m->current_pgpath->path.dev->mode;
1514         }
1515
1516         if (m->queue_io)
1517                 r = -EAGAIN;
1518         else if (!bdev)
1519                 r = -EIO;
1520
1521         spin_unlock_irqrestore(&m->lock, flags);
1522
1523         return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
1524 }
1525
1526 static int multipath_iterate_devices(struct dm_target *ti,
1527                                      iterate_devices_callout_fn fn, void *data)
1528 {
1529         struct multipath *m = ti->private;
1530         struct priority_group *pg;
1531         struct pgpath *p;
1532         int ret = 0;
1533
1534         list_for_each_entry(pg, &m->priority_groups, list) {
1535                 list_for_each_entry(p, &pg->pgpaths, list) {
1536                         ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
1537                         if (ret)
1538                                 goto out;
1539                 }
1540         }
1541
1542 out:
1543         return ret;
1544 }
1545
1546 static int __pgpath_busy(struct pgpath *pgpath)
1547 {
1548         struct request_queue *q = bdev_get_queue(pgpath->path.dev->bdev);
1549
1550         return dm_underlying_device_busy(q);
1551 }
1552
1553 /*
1554  * We return "busy", only when we can map I/Os but underlying devices
1555  * are busy (so even if we map I/Os now, the I/Os will wait on
1556  * the underlying queue).
1557  * In other words, if we want to kill I/Os or queue them inside us
1558  * due to map unavailability, we don't return "busy".  Otherwise,
1559  * dm core won't give us the I/Os and we can't do what we want.
1560  */
1561 static int multipath_busy(struct dm_target *ti)
1562 {
1563         int busy = 0, has_active = 0;
1564         struct multipath *m = ti->private;
1565         struct priority_group *pg;
1566         struct pgpath *pgpath;
1567         unsigned long flags;
1568
1569         spin_lock_irqsave(&m->lock, flags);
1570
1571         /* Guess which priority_group will be used at next mapping time */
1572         if (unlikely(!m->current_pgpath && m->next_pg))
1573                 pg = m->next_pg;
1574         else if (likely(m->current_pg))
1575                 pg = m->current_pg;
1576         else
1577                 /*
1578                  * We don't know which pg will be used at next mapping time.
1579                  * We don't call __choose_pgpath() here to avoid to trigger
1580                  * pg_init just by busy checking.
1581                  * So we don't know whether underlying devices we will be using
1582                  * at next mapping time are busy or not. Just try mapping.
1583                  */
1584                 goto out;
1585
1586         /*
1587          * If there is one non-busy active path at least, the path selector
1588          * will be able to select it. So we consider such a pg as not busy.
1589          */
1590         busy = 1;
1591         list_for_each_entry(pgpath, &pg->pgpaths, list)
1592                 if (pgpath->is_active) {
1593                         has_active = 1;
1594
1595                         if (!__pgpath_busy(pgpath)) {
1596                                 busy = 0;
1597                                 break;
1598                         }
1599                 }
1600
1601         if (!has_active)
1602                 /*
1603                  * No active path in this pg, so this pg won't be used and
1604                  * the current_pg will be changed at next mapping time.
1605                  * We need to try mapping to determine it.
1606                  */
1607                 busy = 0;
1608
1609 out:
1610         spin_unlock_irqrestore(&m->lock, flags);
1611
1612         return busy;
1613 }
1614
1615 /*-----------------------------------------------------------------
1616  * Module setup
1617  *---------------------------------------------------------------*/
1618 static struct target_type multipath_target = {
1619         .name = "multipath",
1620         .version = {1, 3, 0},
1621         .module = THIS_MODULE,
1622         .ctr = multipath_ctr,
1623         .dtr = multipath_dtr,
1624         .map_rq = multipath_map,
1625         .rq_end_io = multipath_end_io,
1626         .presuspend = multipath_presuspend,
1627         .postsuspend = multipath_postsuspend,
1628         .resume = multipath_resume,
1629         .status = multipath_status,
1630         .message = multipath_message,
1631         .ioctl  = multipath_ioctl,
1632         .iterate_devices = multipath_iterate_devices,
1633         .busy = multipath_busy,
1634 };
1635
1636 static int __init dm_multipath_init(void)
1637 {
1638         int r;
1639
1640         /* allocate a slab for the dm_ios */
1641         _mpio_cache = KMEM_CACHE(dm_mpath_io, 0);
1642         if (!_mpio_cache)
1643                 return -ENOMEM;
1644
1645         r = dm_register_target(&multipath_target);
1646         if (r < 0) {
1647                 DMERR("register failed %d", r);
1648                 kmem_cache_destroy(_mpio_cache);
1649                 return -EINVAL;
1650         }
1651
1652         kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
1653         if (!kmultipathd) {
1654                 DMERR("failed to create workqueue kmpathd");
1655                 dm_unregister_target(&multipath_target);
1656                 kmem_cache_destroy(_mpio_cache);
1657                 return -ENOMEM;
1658         }
1659
1660         /*
1661          * A separate workqueue is used to handle the device handlers
1662          * to avoid overloading existing workqueue. Overloading the
1663          * old workqueue would also create a bottleneck in the
1664          * path of the storage hardware device activation.
1665          */
1666         kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
1667                                                   WQ_MEM_RECLAIM);
1668         if (!kmpath_handlerd) {
1669                 DMERR("failed to create workqueue kmpath_handlerd");
1670                 destroy_workqueue(kmultipathd);
1671                 dm_unregister_target(&multipath_target);
1672                 kmem_cache_destroy(_mpio_cache);
1673                 return -ENOMEM;
1674         }
1675
1676         DMINFO("version %u.%u.%u loaded",
1677                multipath_target.version[0], multipath_target.version[1],
1678                multipath_target.version[2]);
1679
1680         return r;
1681 }
1682
1683 static void __exit dm_multipath_exit(void)
1684 {
1685         destroy_workqueue(kmpath_handlerd);
1686         destroy_workqueue(kmultipathd);
1687
1688         dm_unregister_target(&multipath_target);
1689         kmem_cache_destroy(_mpio_cache);
1690 }
1691
1692 module_init(dm_multipath_init);
1693 module_exit(dm_multipath_exit);
1694
1695 MODULE_DESCRIPTION(DM_NAME " multipath target");
1696 MODULE_AUTHOR("Sistina Software <dm-devel@redhat.com>");
1697 MODULE_LICENSE("GPL");