md: move lots of #include lines out of .h files and into .c
[linux-2.6.git] / drivers / md / multipath.c
1 /*
2  * multipath.c : Multiple Devices driver for Linux
3  *
4  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
5  *
6  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
7  *
8  * MULTIPATH management functions.
9  *
10  * derived from raid1.c.
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU General Public License as published by
14  * the Free Software Foundation; either version 2, or (at your option)
15  * any later version.
16  *
17  * You should have received a copy of the GNU General Public License
18  * (for example /usr/src/linux/COPYING); if not, write to the Free
19  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20  */
21
22 #include <linux/blkdev.h>
23 #include <linux/raid/md_u.h>
24 #include <linux/raid/md_k.h>
25 #include <linux/seq_file.h>
26 #include "multipath.h"
27
28 #define MAX_WORK_PER_DISK 128
29
30 #define NR_RESERVED_BUFS        32
31
32
33 static int multipath_map (multipath_conf_t *conf)
34 {
35         int i, disks = conf->raid_disks;
36
37         /*
38          * Later we do read balancing on the read side 
39          * now we use the first available disk.
40          */
41
42         rcu_read_lock();
43         for (i = 0; i < disks; i++) {
44                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
45                 if (rdev && test_bit(In_sync, &rdev->flags)) {
46                         atomic_inc(&rdev->nr_pending);
47                         rcu_read_unlock();
48                         return i;
49                 }
50         }
51         rcu_read_unlock();
52
53         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
54         return (-1);
55 }
56
57 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
58 {
59         unsigned long flags;
60         mddev_t *mddev = mp_bh->mddev;
61         multipath_conf_t *conf = mddev_to_conf(mddev);
62
63         spin_lock_irqsave(&conf->device_lock, flags);
64         list_add(&mp_bh->retry_list, &conf->retry_list);
65         spin_unlock_irqrestore(&conf->device_lock, flags);
66         md_wakeup_thread(mddev->thread);
67 }
68
69
70 /*
71  * multipath_end_bh_io() is called when we have finished servicing a multipathed
72  * operation and are ready to return a success/failure code to the buffer
73  * cache layer.
74  */
75 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
76 {
77         struct bio *bio = mp_bh->master_bio;
78         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
79
80         bio_endio(bio, err);
81         mempool_free(mp_bh, conf->pool);
82 }
83
84 static void multipath_end_request(struct bio *bio, int error)
85 {
86         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
87         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
88         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
89         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
90
91         if (uptodate)
92                 multipath_end_bh_io(mp_bh, 0);
93         else if (!bio_rw_ahead(bio)) {
94                 /*
95                  * oops, IO error:
96                  */
97                 char b[BDEVNAME_SIZE];
98                 md_error (mp_bh->mddev, rdev);
99                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n", 
100                        bdevname(rdev->bdev,b), 
101                        (unsigned long long)bio->bi_sector);
102                 multipath_reschedule_retry(mp_bh);
103         } else
104                 multipath_end_bh_io(mp_bh, error);
105         rdev_dec_pending(rdev, conf->mddev);
106 }
107
108 static void unplug_slaves(mddev_t *mddev)
109 {
110         multipath_conf_t *conf = mddev_to_conf(mddev);
111         int i;
112
113         rcu_read_lock();
114         for (i=0; i<mddev->raid_disks; i++) {
115                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
116                 if (rdev && !test_bit(Faulty, &rdev->flags)
117                     && atomic_read(&rdev->nr_pending)) {
118                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
119
120                         atomic_inc(&rdev->nr_pending);
121                         rcu_read_unlock();
122
123                         blk_unplug(r_queue);
124
125                         rdev_dec_pending(rdev, mddev);
126                         rcu_read_lock();
127                 }
128         }
129         rcu_read_unlock();
130 }
131
132 static void multipath_unplug(struct request_queue *q)
133 {
134         unplug_slaves(q->queuedata);
135 }
136
137
138 static int multipath_make_request (struct request_queue *q, struct bio * bio)
139 {
140         mddev_t *mddev = q->queuedata;
141         multipath_conf_t *conf = mddev_to_conf(mddev);
142         struct multipath_bh * mp_bh;
143         struct multipath_info *multipath;
144         const int rw = bio_data_dir(bio);
145         int cpu;
146
147         if (unlikely(bio_barrier(bio))) {
148                 bio_endio(bio, -EOPNOTSUPP);
149                 return 0;
150         }
151
152         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
153
154         mp_bh->master_bio = bio;
155         mp_bh->mddev = mddev;
156
157         cpu = part_stat_lock();
158         part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
159         part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
160                       bio_sectors(bio));
161         part_stat_unlock();
162
163         mp_bh->path = multipath_map(conf);
164         if (mp_bh->path < 0) {
165                 bio_endio(bio, -EIO);
166                 mempool_free(mp_bh, conf->pool);
167                 return 0;
168         }
169         multipath = conf->multipaths + mp_bh->path;
170
171         mp_bh->bio = *bio;
172         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
173         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
174         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
175         mp_bh->bio.bi_end_io = multipath_end_request;
176         mp_bh->bio.bi_private = mp_bh;
177         generic_make_request(&mp_bh->bio);
178         return 0;
179 }
180
181 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
182 {
183         multipath_conf_t *conf = mddev_to_conf(mddev);
184         int i;
185         
186         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
187                                                  conf->working_disks);
188         for (i = 0; i < conf->raid_disks; i++)
189                 seq_printf (seq, "%s",
190                                conf->multipaths[i].rdev && 
191                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
192         seq_printf (seq, "]");
193 }
194
195 static int multipath_congested(void *data, int bits)
196 {
197         mddev_t *mddev = data;
198         multipath_conf_t *conf = mddev_to_conf(mddev);
199         int i, ret = 0;
200
201         rcu_read_lock();
202         for (i = 0; i < mddev->raid_disks ; i++) {
203                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
204                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
205                         struct request_queue *q = bdev_get_queue(rdev->bdev);
206
207                         ret |= bdi_congested(&q->backing_dev_info, bits);
208                         /* Just like multipath_map, we just check the
209                          * first available device
210                          */
211                         break;
212                 }
213         }
214         rcu_read_unlock();
215         return ret;
216 }
217
218 /*
219  * Careful, this can execute in IRQ contexts as well!
220  */
221 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
222 {
223         multipath_conf_t *conf = mddev_to_conf(mddev);
224
225         if (conf->working_disks <= 1) {
226                 /*
227                  * Uh oh, we can do nothing if this is our last path, but
228                  * first check if this is a queued request for a device
229                  * which has just failed.
230                  */
231                 printk(KERN_ALERT 
232                         "multipath: only one IO path left and IO error.\n");
233                 /* leave it active... it's all we have */
234         } else {
235                 /*
236                  * Mark disk as unusable
237                  */
238                 if (!test_bit(Faulty, &rdev->flags)) {
239                         char b[BDEVNAME_SIZE];
240                         clear_bit(In_sync, &rdev->flags);
241                         set_bit(Faulty, &rdev->flags);
242                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
243                         conf->working_disks--;
244                         mddev->degraded++;
245                         printk(KERN_ALERT "multipath: IO failure on %s,"
246                                 " disabling IO path.\n"
247                                 "multipath: Operation continuing"
248                                 " on %d IO paths.\n",
249                                 bdevname (rdev->bdev,b),
250                                 conf->working_disks);
251                 }
252         }
253 }
254
255 static void print_multipath_conf (multipath_conf_t *conf)
256 {
257         int i;
258         struct multipath_info *tmp;
259
260         printk("MULTIPATH conf printout:\n");
261         if (!conf) {
262                 printk("(conf==NULL)\n");
263                 return;
264         }
265         printk(" --- wd:%d rd:%d\n", conf->working_disks,
266                          conf->raid_disks);
267
268         for (i = 0; i < conf->raid_disks; i++) {
269                 char b[BDEVNAME_SIZE];
270                 tmp = conf->multipaths + i;
271                 if (tmp->rdev)
272                         printk(" disk%d, o:%d, dev:%s\n",
273                                 i,!test_bit(Faulty, &tmp->rdev->flags),
274                                bdevname(tmp->rdev->bdev,b));
275         }
276 }
277
278
279 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
280 {
281         multipath_conf_t *conf = mddev->private;
282         struct request_queue *q;
283         int err = -EEXIST;
284         int path;
285         struct multipath_info *p;
286         int first = 0;
287         int last = mddev->raid_disks - 1;
288
289         if (rdev->raid_disk >= 0)
290                 first = last = rdev->raid_disk;
291
292         print_multipath_conf(conf);
293
294         for (path = first; path <= last; path++)
295                 if ((p=conf->multipaths+path)->rdev == NULL) {
296                         q = rdev->bdev->bd_disk->queue;
297                         blk_queue_stack_limits(mddev->queue, q);
298
299                 /* as we don't honour merge_bvec_fn, we must never risk
300                  * violating it, so limit ->max_sector to one PAGE, as
301                  * a one page request is never in violation.
302                  * (Note: it is very unlikely that a device with
303                  * merge_bvec_fn will be involved in multipath.)
304                  */
305                         if (q->merge_bvec_fn &&
306                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
307                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
308
309                         conf->working_disks++;
310                         mddev->degraded--;
311                         rdev->raid_disk = path;
312                         set_bit(In_sync, &rdev->flags);
313                         rcu_assign_pointer(p->rdev, rdev);
314                         err = 0;
315                         break;
316                 }
317
318         print_multipath_conf(conf);
319
320         return err;
321 }
322
323 static int multipath_remove_disk(mddev_t *mddev, int number)
324 {
325         multipath_conf_t *conf = mddev->private;
326         int err = 0;
327         mdk_rdev_t *rdev;
328         struct multipath_info *p = conf->multipaths + number;
329
330         print_multipath_conf(conf);
331
332         rdev = p->rdev;
333         if (rdev) {
334                 if (test_bit(In_sync, &rdev->flags) ||
335                     atomic_read(&rdev->nr_pending)) {
336                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"
337                                " but is still operational!\n", number);
338                         err = -EBUSY;
339                         goto abort;
340                 }
341                 p->rdev = NULL;
342                 synchronize_rcu();
343                 if (atomic_read(&rdev->nr_pending)) {
344                         /* lost the race, try later */
345                         err = -EBUSY;
346                         p->rdev = rdev;
347                 }
348         }
349 abort:
350
351         print_multipath_conf(conf);
352         return err;
353 }
354
355
356
357 /*
358  * This is a kernel thread which:
359  *
360  *      1.      Retries failed read operations on working multipaths.
361  *      2.      Updates the raid superblock when problems encounter.
362  *      3.      Performs writes following reads for array syncronising.
363  */
364
365 static void multipathd (mddev_t *mddev)
366 {
367         struct multipath_bh *mp_bh;
368         struct bio *bio;
369         unsigned long flags;
370         multipath_conf_t *conf = mddev_to_conf(mddev);
371         struct list_head *head = &conf->retry_list;
372
373         md_check_recovery(mddev);
374         for (;;) {
375                 char b[BDEVNAME_SIZE];
376                 spin_lock_irqsave(&conf->device_lock, flags);
377                 if (list_empty(head))
378                         break;
379                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
380                 list_del(head->prev);
381                 spin_unlock_irqrestore(&conf->device_lock, flags);
382
383                 bio = &mp_bh->bio;
384                 bio->bi_sector = mp_bh->master_bio->bi_sector;
385                 
386                 if ((mp_bh->path = multipath_map (conf))<0) {
387                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
388                                 " error for block %llu\n",
389                                 bdevname(bio->bi_bdev,b),
390                                 (unsigned long long)bio->bi_sector);
391                         multipath_end_bh_io(mp_bh, -EIO);
392                 } else {
393                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
394                                 " to another IO path\n",
395                                 bdevname(bio->bi_bdev,b),
396                                 (unsigned long long)bio->bi_sector);
397                         *bio = *(mp_bh->master_bio);
398                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
399                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
400                         bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
401                         bio->bi_end_io = multipath_end_request;
402                         bio->bi_private = mp_bh;
403                         generic_make_request(bio);
404                 }
405         }
406         spin_unlock_irqrestore(&conf->device_lock, flags);
407 }
408
409 static int multipath_run (mddev_t *mddev)
410 {
411         multipath_conf_t *conf;
412         int disk_idx;
413         struct multipath_info *disk;
414         mdk_rdev_t *rdev;
415
416         if (mddev->level != LEVEL_MULTIPATH) {
417                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
418                        mdname(mddev), mddev->level);
419                 goto out;
420         }
421         /*
422          * copy the already verified devices into our private MULTIPATH
423          * bookkeeping area. [whatever we allocate in multipath_run(),
424          * should be freed in multipath_stop()]
425          */
426         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
427
428         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
429         mddev->private = conf;
430         if (!conf) {
431                 printk(KERN_ERR 
432                         "multipath: couldn't allocate memory for %s\n",
433                         mdname(mddev));
434                 goto out;
435         }
436
437         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
438                                    GFP_KERNEL);
439         if (!conf->multipaths) {
440                 printk(KERN_ERR 
441                         "multipath: couldn't allocate memory for %s\n",
442                         mdname(mddev));
443                 goto out_free_conf;
444         }
445
446         conf->working_disks = 0;
447         list_for_each_entry(rdev, &mddev->disks, same_set) {
448                 disk_idx = rdev->raid_disk;
449                 if (disk_idx < 0 ||
450                     disk_idx >= mddev->raid_disks)
451                         continue;
452
453                 disk = conf->multipaths + disk_idx;
454                 disk->rdev = rdev;
455
456                 blk_queue_stack_limits(mddev->queue,
457                                        rdev->bdev->bd_disk->queue);
458                 /* as we don't honour merge_bvec_fn, we must never risk
459                  * violating it, not that we ever expect a device with
460                  * a merge_bvec_fn to be involved in multipath */
461                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
462                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
463                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
464
465                 if (!test_bit(Faulty, &rdev->flags))
466                         conf->working_disks++;
467         }
468
469         conf->raid_disks = mddev->raid_disks;
470         conf->mddev = mddev;
471         spin_lock_init(&conf->device_lock);
472         INIT_LIST_HEAD(&conf->retry_list);
473
474         if (!conf->working_disks) {
475                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
476                         mdname(mddev));
477                 goto out_free_conf;
478         }
479         mddev->degraded = conf->raid_disks - conf->working_disks;
480
481         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
482                                                  sizeof(struct multipath_bh));
483         if (conf->pool == NULL) {
484                 printk(KERN_ERR 
485                         "multipath: couldn't allocate memory for %s\n",
486                         mdname(mddev));
487                 goto out_free_conf;
488         }
489
490         {
491                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
492                 if (!mddev->thread) {
493                         printk(KERN_ERR "multipath: couldn't allocate thread"
494                                 " for %s\n", mdname(mddev));
495                         goto out_free_conf;
496                 }
497         }
498
499         printk(KERN_INFO 
500                 "multipath: array %s active with %d out of %d IO paths\n",
501                 mdname(mddev), conf->working_disks, mddev->raid_disks);
502         /*
503          * Ok, everything is just fine now
504          */
505         mddev->array_sectors = mddev->size * 2;
506
507         mddev->queue->unplug_fn = multipath_unplug;
508         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
509         mddev->queue->backing_dev_info.congested_data = mddev;
510
511         return 0;
512
513 out_free_conf:
514         if (conf->pool)
515                 mempool_destroy(conf->pool);
516         kfree(conf->multipaths);
517         kfree(conf);
518         mddev->private = NULL;
519 out:
520         return -EIO;
521 }
522
523
524 static int multipath_stop (mddev_t *mddev)
525 {
526         multipath_conf_t *conf = mddev_to_conf(mddev);
527
528         md_unregister_thread(mddev->thread);
529         mddev->thread = NULL;
530         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
531         mempool_destroy(conf->pool);
532         kfree(conf->multipaths);
533         kfree(conf);
534         mddev->private = NULL;
535         return 0;
536 }
537
538 static struct mdk_personality multipath_personality =
539 {
540         .name           = "multipath",
541         .level          = LEVEL_MULTIPATH,
542         .owner          = THIS_MODULE,
543         .make_request   = multipath_make_request,
544         .run            = multipath_run,
545         .stop           = multipath_stop,
546         .status         = multipath_status,
547         .error_handler  = multipath_error,
548         .hot_add_disk   = multipath_add_disk,
549         .hot_remove_disk= multipath_remove_disk,
550 };
551
552 static int __init multipath_init (void)
553 {
554         return register_md_personality (&multipath_personality);
555 }
556
557 static void __exit multipath_exit (void)
558 {
559         unregister_md_personality (&multipath_personality);
560 }
561
562 module_init(multipath_init);
563 module_exit(multipath_exit);
564 MODULE_LICENSE("GPL");
565 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
566 MODULE_ALIAS("md-multipath");
567 MODULE_ALIAS("md-level--4");