c4779ccba1c39bf1ab3f7454706868245f95ea0e
[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/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, err);
86         mempool_free(mp_bh, conf->pool);
87 }
88
89 static void multipath_end_request(struct bio *bio, int error)
90 {
91         int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
92         struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
93         multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
94         mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
95
96         if (uptodate)
97                 multipath_end_bh_io(mp_bh, 0);
98         else if (!bio_rw_ahead(bio)) {
99                 /*
100                  * oops, IO error:
101                  */
102                 char b[BDEVNAME_SIZE];
103                 md_error (mp_bh->mddev, rdev);
104                 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n", 
105                        bdevname(rdev->bdev,b), 
106                        (unsigned long long)bio->bi_sector);
107                 multipath_reschedule_retry(mp_bh);
108         } else
109                 multipath_end_bh_io(mp_bh, error);
110         rdev_dec_pending(rdev, conf->mddev);
111 }
112
113 static void unplug_slaves(mddev_t *mddev)
114 {
115         multipath_conf_t *conf = mddev_to_conf(mddev);
116         int i;
117
118         rcu_read_lock();
119         for (i=0; i<mddev->raid_disks; i++) {
120                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
121                 if (rdev && !test_bit(Faulty, &rdev->flags)
122                     && atomic_read(&rdev->nr_pending)) {
123                         struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
124
125                         atomic_inc(&rdev->nr_pending);
126                         rcu_read_unlock();
127
128                         blk_unplug(r_queue);
129
130                         rdev_dec_pending(rdev, mddev);
131                         rcu_read_lock();
132                 }
133         }
134         rcu_read_unlock();
135 }
136
137 static void multipath_unplug(struct request_queue *q)
138 {
139         unplug_slaves(q->queuedata);
140 }
141
142
143 static int multipath_make_request (struct request_queue *q, struct bio * bio)
144 {
145         mddev_t *mddev = q->queuedata;
146         multipath_conf_t *conf = mddev_to_conf(mddev);
147         struct multipath_bh * mp_bh;
148         struct multipath_info *multipath;
149         const int rw = bio_data_dir(bio);
150
151         if (unlikely(bio_barrier(bio))) {
152                 bio_endio(bio, -EOPNOTSUPP);
153                 return 0;
154         }
155
156         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
157
158         mp_bh->master_bio = bio;
159         mp_bh->mddev = mddev;
160
161         disk_stat_inc(mddev->gendisk, ios[rw]);
162         disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
163
164         mp_bh->path = multipath_map(conf);
165         if (mp_bh->path < 0) {
166                 bio_endio(bio, -EIO);
167                 mempool_free(mp_bh, conf->pool);
168                 return 0;
169         }
170         multipath = conf->multipaths + mp_bh->path;
171
172         mp_bh->bio = *bio;
173         mp_bh->bio.bi_sector += multipath->rdev->data_offset;
174         mp_bh->bio.bi_bdev = multipath->rdev->bdev;
175         mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
176         mp_bh->bio.bi_end_io = multipath_end_request;
177         mp_bh->bio.bi_private = mp_bh;
178         generic_make_request(&mp_bh->bio);
179         return 0;
180 }
181
182 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
183 {
184         multipath_conf_t *conf = mddev_to_conf(mddev);
185         int i;
186         
187         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
188                                                  conf->working_disks);
189         for (i = 0; i < conf->raid_disks; i++)
190                 seq_printf (seq, "%s",
191                                conf->multipaths[i].rdev && 
192                                test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
193         seq_printf (seq, "]");
194 }
195
196 static int multipath_congested(void *data, int bits)
197 {
198         mddev_t *mddev = data;
199         multipath_conf_t *conf = mddev_to_conf(mddev);
200         int i, ret = 0;
201
202         rcu_read_lock();
203         for (i = 0; i < mddev->raid_disks ; i++) {
204                 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
205                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
206                         struct request_queue *q = bdev_get_queue(rdev->bdev);
207
208                         ret |= bdi_congested(&q->backing_dev_info, bits);
209                         /* Just like multipath_map, we just check the
210                          * first available device
211                          */
212                         break;
213                 }
214         }
215         rcu_read_unlock();
216         return ret;
217 }
218
219 /*
220  * Careful, this can execute in IRQ contexts as well!
221  */
222 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
223 {
224         multipath_conf_t *conf = mddev_to_conf(mddev);
225
226         if (conf->working_disks <= 1) {
227                 /*
228                  * Uh oh, we can do nothing if this is our last path, but
229                  * first check if this is a queued request for a device
230                  * which has just failed.
231                  */
232                 printk(KERN_ALERT 
233                         "multipath: only one IO path left and IO error.\n");
234                 /* leave it active... it's all we have */
235         } else {
236                 /*
237                  * Mark disk as unusable
238                  */
239                 if (!test_bit(Faulty, &rdev->flags)) {
240                         char b[BDEVNAME_SIZE];
241                         clear_bit(In_sync, &rdev->flags);
242                         set_bit(Faulty, &rdev->flags);
243                         set_bit(MD_CHANGE_DEVS, &mddev->flags);
244                         conf->working_disks--;
245                         mddev->degraded++;
246                         printk(KERN_ALERT "multipath: IO failure on %s,"
247                                 " disabling IO path.\n"
248                                 "multipath: Operation continuing"
249                                 " on %d IO paths.\n",
250                                 bdevname (rdev->bdev,b),
251                                 conf->working_disks);
252                 }
253         }
254 }
255
256 static void print_multipath_conf (multipath_conf_t *conf)
257 {
258         int i;
259         struct multipath_info *tmp;
260
261         printk("MULTIPATH conf printout:\n");
262         if (!conf) {
263                 printk("(conf==NULL)\n");
264                 return;
265         }
266         printk(" --- wd:%d rd:%d\n", conf->working_disks,
267                          conf->raid_disks);
268
269         for (i = 0; i < conf->raid_disks; i++) {
270                 char b[BDEVNAME_SIZE];
271                 tmp = conf->multipaths + i;
272                 if (tmp->rdev)
273                         printk(" disk%d, o:%d, dev:%s\n",
274                                 i,!test_bit(Faulty, &tmp->rdev->flags),
275                                bdevname(tmp->rdev->bdev,b));
276         }
277 }
278
279
280 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
281 {
282         multipath_conf_t *conf = mddev->private;
283         struct request_queue *q;
284         int err = -EEXIST;
285         int path;
286         struct multipath_info *p;
287         int first = 0;
288         int last = mddev->raid_disks - 1;
289
290         if (rdev->raid_disk >= 0)
291                 first = last = rdev->raid_disk;
292
293         print_multipath_conf(conf);
294
295         for (path = first; path <= last; path++)
296                 if ((p=conf->multipaths+path)->rdev == NULL) {
297                         q = rdev->bdev->bd_disk->queue;
298                         blk_queue_stack_limits(mddev->queue, q);
299
300                 /* as we don't honour merge_bvec_fn, we must never risk
301                  * violating it, so limit ->max_sector to one PAGE, as
302                  * a one page request is never in violation.
303                  * (Note: it is very unlikely that a device with
304                  * merge_bvec_fn will be involved in multipath.)
305                  */
306                         if (q->merge_bvec_fn &&
307                             mddev->queue->max_sectors > (PAGE_SIZE>>9))
308                                 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
309
310                         conf->working_disks++;
311                         mddev->degraded--;
312                         rdev->raid_disk = path;
313                         set_bit(In_sync, &rdev->flags);
314                         rcu_assign_pointer(p->rdev, rdev);
315                         err = 0;
316                         break;
317                 }
318
319         print_multipath_conf(conf);
320
321         return err;
322 }
323
324 static int multipath_remove_disk(mddev_t *mddev, int number)
325 {
326         multipath_conf_t *conf = mddev->private;
327         int err = 0;
328         mdk_rdev_t *rdev;
329         struct multipath_info *p = conf->multipaths + number;
330
331         print_multipath_conf(conf);
332
333         rdev = p->rdev;
334         if (rdev) {
335                 if (test_bit(In_sync, &rdev->flags) ||
336                     atomic_read(&rdev->nr_pending)) {
337                         printk(KERN_ERR "hot-remove-disk, slot %d is identified"
338                                " but is still operational!\n", number);
339                         err = -EBUSY;
340                         goto abort;
341                 }
342                 p->rdev = NULL;
343                 synchronize_rcu();
344                 if (atomic_read(&rdev->nr_pending)) {
345                         /* lost the race, try later */
346                         err = -EBUSY;
347                         p->rdev = rdev;
348                 }
349         }
350 abort:
351
352         print_multipath_conf(conf);
353         return err;
354 }
355
356
357
358 /*
359  * This is a kernel thread which:
360  *
361  *      1.      Retries failed read operations on working multipaths.
362  *      2.      Updates the raid superblock when problems encounter.
363  *      3.      Performs writes following reads for array syncronising.
364  */
365
366 static void multipathd (mddev_t *mddev)
367 {
368         struct multipath_bh *mp_bh;
369         struct bio *bio;
370         unsigned long flags;
371         multipath_conf_t *conf = mddev_to_conf(mddev);
372         struct list_head *head = &conf->retry_list;
373
374         md_check_recovery(mddev);
375         for (;;) {
376                 char b[BDEVNAME_SIZE];
377                 spin_lock_irqsave(&conf->device_lock, flags);
378                 if (list_empty(head))
379                         break;
380                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
381                 list_del(head->prev);
382                 spin_unlock_irqrestore(&conf->device_lock, flags);
383
384                 bio = &mp_bh->bio;
385                 bio->bi_sector = mp_bh->master_bio->bi_sector;
386                 
387                 if ((mp_bh->path = multipath_map (conf))<0) {
388                         printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
389                                 " error for block %llu\n",
390                                 bdevname(bio->bi_bdev,b),
391                                 (unsigned long long)bio->bi_sector);
392                         multipath_end_bh_io(mp_bh, -EIO);
393                 } else {
394                         printk(KERN_ERR "multipath: %s: redirecting sector %llu"
395                                 " to another IO path\n",
396                                 bdevname(bio->bi_bdev,b),
397                                 (unsigned long long)bio->bi_sector);
398                         *bio = *(mp_bh->master_bio);
399                         bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
400                         bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
401                         bio->bi_rw |= (1 << BIO_RW_FAILFAST);
402                         bio->bi_end_io = multipath_end_request;
403                         bio->bi_private = mp_bh;
404                         generic_make_request(bio);
405                 }
406         }
407         spin_unlock_irqrestore(&conf->device_lock, flags);
408 }
409
410 static int multipath_run (mddev_t *mddev)
411 {
412         multipath_conf_t *conf;
413         int disk_idx;
414         struct multipath_info *disk;
415         mdk_rdev_t *rdev;
416         struct list_head *tmp;
417
418         if (mddev->level != LEVEL_MULTIPATH) {
419                 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
420                        mdname(mddev), mddev->level);
421                 goto out;
422         }
423         /*
424          * copy the already verified devices into our private MULTIPATH
425          * bookkeeping area. [whatever we allocate in multipath_run(),
426          * should be freed in multipath_stop()]
427          */
428         mddev->queue->queue_lock = &mddev->queue->__queue_lock;
429
430         conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
431         mddev->private = conf;
432         if (!conf) {
433                 printk(KERN_ERR 
434                         "multipath: couldn't allocate memory for %s\n",
435                         mdname(mddev));
436                 goto out;
437         }
438
439         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
440                                    GFP_KERNEL);
441         if (!conf->multipaths) {
442                 printk(KERN_ERR 
443                         "multipath: couldn't allocate memory for %s\n",
444                         mdname(mddev));
445                 goto out_free_conf;
446         }
447
448         conf->working_disks = 0;
449         rdev_for_each(rdev, tmp, mddev) {
450                 disk_idx = rdev->raid_disk;
451                 if (disk_idx < 0 ||
452                     disk_idx >= mddev->raid_disks)
453                         continue;
454
455                 disk = conf->multipaths + disk_idx;
456                 disk->rdev = rdev;
457
458                 blk_queue_stack_limits(mddev->queue,
459                                        rdev->bdev->bd_disk->queue);
460                 /* as we don't honour merge_bvec_fn, we must never risk
461                  * violating it, not that we ever expect a device with
462                  * a merge_bvec_fn to be involved in multipath */
463                 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
464                     mddev->queue->max_sectors > (PAGE_SIZE>>9))
465                         blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
466
467                 if (!test_bit(Faulty, &rdev->flags))
468                         conf->working_disks++;
469         }
470
471         conf->raid_disks = mddev->raid_disks;
472         conf->mddev = mddev;
473         spin_lock_init(&conf->device_lock);
474         INIT_LIST_HEAD(&conf->retry_list);
475
476         if (!conf->working_disks) {
477                 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
478                         mdname(mddev));
479                 goto out_free_conf;
480         }
481         mddev->degraded = conf->raid_disks - conf->working_disks;
482
483         conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
484                                                  sizeof(struct multipath_bh));
485         if (conf->pool == NULL) {
486                 printk(KERN_ERR 
487                         "multipath: couldn't allocate memory for %s\n",
488                         mdname(mddev));
489                 goto out_free_conf;
490         }
491
492         {
493                 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
494                 if (!mddev->thread) {
495                         printk(KERN_ERR "multipath: couldn't allocate thread"
496                                 " for %s\n", mdname(mddev));
497                         goto out_free_conf;
498                 }
499         }
500
501         printk(KERN_INFO 
502                 "multipath: array %s active with %d out of %d IO paths\n",
503                 mdname(mddev), conf->working_disks, mddev->raid_disks);
504         /*
505          * Ok, everything is just fine now
506          */
507         mddev->array_sectors = mddev->size * 2;
508
509         mddev->queue->unplug_fn = multipath_unplug;
510         mddev->queue->backing_dev_info.congested_fn = multipath_congested;
511         mddev->queue->backing_dev_info.congested_data = mddev;
512
513         return 0;
514
515 out_free_conf:
516         if (conf->pool)
517                 mempool_destroy(conf->pool);
518         kfree(conf->multipaths);
519         kfree(conf);
520         mddev->private = NULL;
521 out:
522         return -EIO;
523 }
524
525
526 static int multipath_stop (mddev_t *mddev)
527 {
528         multipath_conf_t *conf = mddev_to_conf(mddev);
529
530         md_unregister_thread(mddev->thread);
531         mddev->thread = NULL;
532         blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
533         mempool_destroy(conf->pool);
534         kfree(conf->multipaths);
535         kfree(conf);
536         mddev->private = NULL;
537         return 0;
538 }
539
540 static struct mdk_personality multipath_personality =
541 {
542         .name           = "multipath",
543         .level          = LEVEL_MULTIPATH,
544         .owner          = THIS_MODULE,
545         .make_request   = multipath_make_request,
546         .run            = multipath_run,
547         .stop           = multipath_stop,
548         .status         = multipath_status,
549         .error_handler  = multipath_error,
550         .hot_add_disk   = multipath_add_disk,
551         .hot_remove_disk= multipath_remove_disk,
552 };
553
554 static int __init multipath_init (void)
555 {
556         return register_md_personality (&multipath_personality);
557 }
558
559 static void __exit multipath_exit (void)
560 {
561         unregister_md_personality (&multipath_personality);
562 }
563
564 module_init(multipath_init);
565 module_exit(multipath_exit);
566 MODULE_LICENSE("GPL");
567 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
568 MODULE_ALIAS("md-multipath");
569 MODULE_ALIAS("md-level--4");