[PARISC] parisc specific kmap API implementation for pa8800
[linux-2.6] / 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/module.h>
23 #include <linux/slab.h>
24 #include <linux/spinlock.h>
25 #include <linux/raid/multipath.h>
26 #include <linux/buffer_head.h>
27 #include <asm/atomic.h>
28
29 #define MAJOR_NR MD_MAJOR
30 #define MD_DRIVER
31 #define MD_PERSONALITY
32
33 #define MAX_WORK_PER_DISK 128
34
35 #define NR_RESERVED_BUFS        32
36
37
38 static int multipath_map (multipath_conf_t *conf)
39 {
40         int i, disks = conf->raid_disks;
41
42         /*
43          * Later we do read balancing on the read side 
44          * now we use the first available disk.
45          */
46
47         rcu_read_lock();
48         for (i = 0; i < disks; i++) {
49                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
50                 if (rdev && test_bit(In_sync, &rdev->flags)) {
51                         atomic_inc(&rdev->nr_pending);
52                         rcu_read_unlock();
53                         return i;
54                 }
55         }
56         rcu_read_unlock();
57
58         printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
59         return (-1);
60 }
61
62 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
63 {
64         unsigned long flags;
65         mddev_t *mddev = mp_bh->mddev;
66         multipath_conf_t *conf = mddev_to_conf(mddev);
67
68         spin_lock_irqsave(&conf->device_lock, flags);
69         list_add(&mp_bh->retry_list, &conf->retry_list);
70         spin_unlock_irqrestore(&conf->device_lock, flags);
71         md_wakeup_thread(mddev->thread);
72 }
73
74
75 /*
76  * multipath_end_bh_io() is called when we have finished servicing a multipathed
77  * operation and are ready to return a success/failure code to the buffer
78  * cache layer.
79  */
80 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
81 {
82         struct bio *bio = mp_bh->master_bio;
83         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
84
85         bio_endio(bio, bio->bi_size, err);
86         mempool_free(mp_bh, conf->pool);
87 }
88
89 static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
90                                  int error)
91 {
92         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
93         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
94         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
95         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
96
97         if (bio->bi_size)
98                 return 1;
99
100         if (uptodate)
101                 multipath_end_bh_io(mp_bh, 0);
102         else if (!bio_rw_ahead(bio)) {
103                 /*
104                  * oops, IO error:
105                  */
106                 char b[BDEVNAME_SIZE];
107                 md_error (mp_bh->mddev, rdev);
108                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n", 
109                        bdevname(rdev->bdev,b), 
110                        (unsigned long long)bio->bi_sector);
111                 multipath_reschedule_retry(mp_bh);
112         } else
113                 multipath_end_bh_io(mp_bh, error);
114         rdev_dec_pending(rdev, conf->mddev);
115         return 0;
116 }
117
118 static void unplug_slaves(mddev_t *mddev)
119 {
120         multipath_conf_t *conf = mddev_to_conf(mddev);
121         int i;
122
123         rcu_read_lock();
124         for (i=0; i<mddev->raid_disks; i++) {
125                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
126                 if (rdev && !test_bit(Faulty, &rdev->flags)
127                     && atomic_read(&rdev->nr_pending)) {
128                         request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
129
130                         atomic_inc(&rdev->nr_pending);
131                         rcu_read_unlock();
132
133                         if (r_queue->unplug_fn)
134                                 r_queue->unplug_fn(r_queue);
135
136                         rdev_dec_pending(rdev, mddev);
137                         rcu_read_lock();
138                 }
139         }
140         rcu_read_unlock();
141 }
142
143 static void multipath_unplug(request_queue_t *q)
144 {
145         unplug_slaves(q->queuedata);
146 }
147
148
149 static int multipath_make_request (request_queue_t *q, struct bio * bio)
150 {
151         mddev_t *mddev = q->queuedata;
152         multipath_conf_t *conf = mddev_to_conf(mddev);
153         struct multipath_bh * mp_bh;
154         struct multipath_info *multipath;
155         const int rw = bio_data_dir(bio);
156
157         if (unlikely(bio_barrier(bio))) {
158                 bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
159                 return 0;
160         }
161
162         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
163
164         mp_bh->master_bio = bio;
165         mp_bh->mddev = mddev;
166
167         disk_stat_inc(mddev->gendisk, ios[rw]);
168         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
169
170         mp_bh->path = multipath_map(conf);
171         if (mp_bh->path < 0) {
172                 bio_endio(bio, bio->bi_size, -EIO);
173                 mempool_free(mp_bh, conf->pool);
174                 return 0;
175         }
176         multipath = conf->multipaths + mp_bh->path;
177
178         mp_bh->bio = *bio;
179         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
180         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
181         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
182         mp_bh->bio.bi_end_io = multipath_end_request;
183         mp_bh->bio.bi_private = mp_bh;
184         generic_make_request(&mp_bh->bio);
185         return 0;
186 }
187
188 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
189 {
190         multipath_conf_t *conf = mddev_to_conf(mddev);
191         int i;
192         
193         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
194                                                  conf->working_disks);
195         for (i = 0; i < conf->raid_disks; i++)
196                 seq_printf (seq, "%s",
197                                conf->multipaths[i].rdev && 
198                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
199         seq_printf (seq, "]");
200 }
201
202 static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
203                                  sector_t *error_sector)
204 {
205         mddev_t *mddev = q->queuedata;
206         multipath_conf_t *conf = mddev_to_conf(mddev);
207         int i, ret = 0;
208
209         rcu_read_lock();
210         for (i=0; i<mddev->raid_disks && ret == 0; i++) {
211                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
212                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
213                         struct block_device *bdev = rdev->bdev;
214                         request_queue_t *r_queue = bdev_get_queue(bdev);
215
216                         if (!r_queue->issue_flush_fn)
217                                 ret = -EOPNOTSUPP;
218                         else {
219                                 atomic_inc(&rdev->nr_pending);
220                                 rcu_read_unlock();
221                                 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
222                                                               error_sector);
223                                 rdev_dec_pending(rdev, mddev);
224                                 rcu_read_lock();
225                         }
226                 }
227         }
228         rcu_read_unlock();
229         return ret;
230 }
231 static int multipath_congested(void *data, int bits)
232 {
233         mddev_t *mddev = data;
234         multipath_conf_t *conf = mddev_to_conf(mddev);
235         int i, ret = 0;
236
237         rcu_read_lock();
238         for (i = 0; i < mddev->raid_disks ; i++) {
239                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
240                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
241                         request_queue_t *q = bdev_get_queue(rdev->bdev);
242
243                         ret |= bdi_congested(&q->backing_dev_info, bits);
244                         /* Just like multipath_map, we just check the
245                          * first available device
246                          */
247                         break;
248                 }
249         }
250         rcu_read_unlock();
251         return ret;
252 }
253
254 /*
255  * Careful, this can execute in IRQ contexts as well!
256  */
257 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
258 {
259         multipath_conf_t *conf = mddev_to_conf(mddev);
260
261         if (conf->working_disks <= 1) {
262                 /*
263                  * Uh oh, we can do nothing if this is our last path, but
264                  * first check if this is a queued request for a device
265                  * which has just failed.
266                  */
267                 printk(KERN_ALERT 
268                         "multipath: only one IO path left and IO error.\n");
269                 /* leave it active... it's all we have */
270         } else {
271                 /*
272                  * Mark disk as unusable
273                  */
274                 if (!test_bit(Faulty, &rdev->flags)) {
275                         char b[BDEVNAME_SIZE];
276                         clear_bit(In_sync, &rdev->flags);
277                         set_bit(Faulty, &rdev->flags);
278                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
279                         conf->working_disks--;
280                         printk(KERN_ALERT "multipath: IO failure on %s,"
281                                 " disabling IO path. \n Operation continuing"
282                                 " on %d IO paths.\n",
283                                 bdevname (rdev->bdev,b),
284                                 conf->working_disks);
285                 }
286         }
287 }
288
289 static void print_multipath_conf (multipath_conf_t *conf)
290 {
291         int i;
292         struct multipath_info *tmp;
293
294         printk("MULTIPATH conf printout:\n");
295         if (!conf) {
296                 printk("(conf==NULL)\n");
297                 return;
298         }
299         printk(" --- wd:%d rd:%d\n", conf->working_disks,
300                          conf->raid_disks);
301
302         for (i = 0; i < conf->raid_disks; i++) {
303                 char b[BDEVNAME_SIZE];
304                 tmp = conf->multipaths + i;
305                 if (tmp->rdev)
306                         printk(" disk%d, o:%d, dev:%s\n",
307                                 i,!test_bit(Faulty, &tmp->rdev->flags),
308                                bdevname(tmp->rdev->bdev,b));
309         }
310 }
311
312
313 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
314 {
315         multipath_conf_t *conf = mddev->private;
316         struct request_queue *q;
317         int found = 0;
318         int path;
319         struct multipath_info *p;
320
321         print_multipath_conf(conf);
322
323         for (path=0; path<mddev->raid_disks; path++) 
324                 if ((p=conf->multipaths+path)->rdev == NULL) {
325                         q = rdev->bdev->bd_disk->queue;
326                         blk_queue_stack_limits(mddev->queue, q);
327
328                 /* as we don't honour merge_bvec_fn, we must never risk
329                  * violating it, so limit ->max_sector to one PAGE, as
330                  * a one page request is never in violation.
331                  * (Note: it is very unlikely that a device with
332                  * merge_bvec_fn will be involved in multipath.)
333                  */
334                         if (q->merge_bvec_fn &&
335                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
336                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
337
338                         conf->working_disks++;
339                         rdev->raid_disk = path;
340                         set_bit(In_sync, &rdev->flags);
341                         rcu_assign_pointer(p->rdev, rdev);
342                         found = 1;
343                 }
344
345         print_multipath_conf(conf);
346         return found;
347 }
348
349 static int multipath_remove_disk(mddev_t *mddev, int number)
350 {
351         multipath_conf_t *conf = mddev->private;
352         int err = 0;
353         mdk_rdev_t *rdev;
354         struct multipath_info *p = conf->multipaths + number;
355
356         print_multipath_conf(conf);
357
358         rdev = p->rdev;
359         if (rdev) {
360                 if (test_bit(In_sync, &rdev->flags) ||
361                     atomic_read(&rdev->nr_pending)) {
362                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"                                " but is still operational!\n", number);
363                         err = -EBUSY;
364                         goto abort;
365                 }
366                 p->rdev = NULL;
367                 synchronize_rcu();
368                 if (atomic_read(&rdev->nr_pending)) {
369                         /* lost the race, try later */
370                         err = -EBUSY;
371                         p->rdev = rdev;
372                 }
373         }
374 abort:
375
376         print_multipath_conf(conf);
377         return err;
378 }
379
380
381
382 /*
383  * This is a kernel thread which:
384  *
385  *      1.      Retries failed read operations on working multipaths.
386  *      2.      Updates the raid superblock when problems encounter.
387  *      3.      Performs writes following reads for array syncronising.
388  */
389
390 static void multipathd (mddev_t *mddev)
391 {
392         struct multipath_bh *mp_bh;
393         struct bio *bio;
394         unsigned long flags;
395         multipath_conf_t *conf = mddev_to_conf(mddev);
396         struct list_head *head = &conf->retry_list;
397
398         md_check_recovery(mddev);
399         for (;;) {
400                 char b[BDEVNAME_SIZE];
401                 spin_lock_irqsave(&conf->device_lock, flags);
402                 if (list_empty(head))
403                         break;
404                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
405                 list_del(head->prev);
406                 spin_unlock_irqrestore(&conf->device_lock, flags);
407
408                 bio = &mp_bh->bio;
409                 bio->bi_sector = mp_bh->master_bio->bi_sector;
410                 
411                 if ((mp_bh->path = multipath_map (conf))<0) {
412                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
413                                 " error for block %llu\n",
414                                 bdevname(bio->bi_bdev,b),
415                                 (unsigned long long)bio->bi_sector);
416                         multipath_end_bh_io(mp_bh, -EIO);
417                 } else {
418                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
419                                 " to another IO path\n",
420                                 bdevname(bio->bi_bdev,b),
421                                 (unsigned long long)bio->bi_sector);
422                         *bio = *(mp_bh->master_bio);
423                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
424                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
425                         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
426                         bio->bi_end_io = multipath_end_request;
427                         bio->bi_private = mp_bh;
428                         generic_make_request(bio);
429                 }
430         }
431         spin_unlock_irqrestore(&conf->device_lock, flags);
432 }
433
434 static int multipath_run (mddev_t *mddev)
435 {
436         multipath_conf_t *conf;
437         int disk_idx;
438         struct multipath_info *disk;
439         mdk_rdev_t *rdev;
440         struct list_head *tmp;
441
442         if (mddev->level != LEVEL_MULTIPATH) {
443                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
444                        mdname(mddev), mddev->level);
445                 goto out;
446         }
447         /*
448          * copy the already verified devices into our private MULTIPATH
449          * bookkeeping area. [whatever we allocate in multipath_run(),
450          * should be freed in multipath_stop()]
451          */
452
453         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
454         mddev->private = conf;
455         if (!conf) {
456                 printk(KERN_ERR 
457                         "multipath: couldn't allocate memory for %s\n",
458                         mdname(mddev));
459                 goto out;
460         }
461
462         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
463                                    GFP_KERNEL);
464         if (!conf->multipaths) {
465                 printk(KERN_ERR 
466                         "multipath: couldn't allocate memory for %s\n",
467                         mdname(mddev));
468                 goto out_free_conf;
469         }
470
471         conf->working_disks = 0;
472         ITERATE_RDEV(mddev,rdev,tmp) {
473                 disk_idx = rdev->raid_disk;
474                 if (disk_idx < 0 ||
475                     disk_idx >= mddev->raid_disks)
476                         continue;
477
478                 disk = conf->multipaths + disk_idx;
479                 disk->rdev = rdev;
480
481                 blk_queue_stack_limits(mddev->queue,
482                                        rdev->bdev->bd_disk->queue);
483                 /* as we don't honour merge_bvec_fn, we must never risk
484                  * violating it, not that we ever expect a device with
485                  * a merge_bvec_fn to be involved in multipath */
486                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
487                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
488                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
489
490                 if (!test_bit(Faulty, &rdev->flags))
491                         conf->working_disks++;
492         }
493
494         conf->raid_disks = mddev->raid_disks;
495         conf->mddev = mddev;
496         spin_lock_init(&conf->device_lock);
497         INIT_LIST_HEAD(&conf->retry_list);
498
499         if (!conf->working_disks) {
500                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
501                         mdname(mddev));
502                 goto out_free_conf;
503         }
504         mddev->degraded = conf->raid_disks = conf->working_disks;
505
506         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
507                                                  sizeof(struct multipath_bh));
508         if (conf->pool == NULL) {
509                 printk(KERN_ERR 
510                         "multipath: couldn't allocate memory for %s\n",
511                         mdname(mddev));
512                 goto out_free_conf;
513         }
514
515         {
516                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
517                 if (!mddev->thread) {
518                         printk(KERN_ERR "multipath: couldn't allocate thread"
519                                 " for %s\n", mdname(mddev));
520                         goto out_free_conf;
521                 }
522         }
523
524         printk(KERN_INFO 
525                 "multipath: array %s active with %d out of %d IO paths\n",
526                 mdname(mddev), conf->working_disks, mddev->raid_disks);
527         /*
528          * Ok, everything is just fine now
529          */
530         mddev->array_size = mddev->size;
531
532         mddev->queue->unplug_fn = multipath_unplug;
533         mddev->queue->issue_flush_fn = multipath_issue_flush;
534         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
535         mddev->queue->backing_dev_info.congested_data = mddev;
536
537         return 0;
538
539 out_free_conf:
540         if (conf->pool)
541                 mempool_destroy(conf->pool);
542         kfree(conf->multipaths);
543         kfree(conf);
544         mddev->private = NULL;
545 out:
546         return -EIO;
547 }
548
549
550 static int multipath_stop (mddev_t *mddev)
551 {
552         multipath_conf_t *conf = mddev_to_conf(mddev);
553
554         md_unregister_thread(mddev->thread);
555         mddev->thread = NULL;
556         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
557         mempool_destroy(conf->pool);
558         kfree(conf->multipaths);
559         kfree(conf);
560         mddev->private = NULL;
561         return 0;
562 }
563
564 static struct mdk_personality multipath_personality =
565 {
566         .name           = "multipath",
567         .level          = LEVEL_MULTIPATH,
568         .owner          = THIS_MODULE,
569         .make_request   = multipath_make_request,
570         .run            = multipath_run,
571         .stop           = multipath_stop,
572         .status         = multipath_status,
573         .error_handler  = multipath_error,
574         .hot_add_disk   = multipath_add_disk,
575         .hot_remove_disk= multipath_remove_disk,
576 };
577
578 static int __init multipath_init (void)
579 {
580         return register_md_personality (&multipath_personality);
581 }
582
583 static void __exit multipath_exit (void)
584 {
585         unregister_md_personality (&multipath_personality);
586 }
587
588 module_init(multipath_init);
589 module_exit(multipath_exit);
590 MODULE_LICENSE("GPL");
591 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
592 MODULE_ALIAS("md-multipath");
593 MODULE_ALIAS("md-level--4");