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[ARM] pxa: Gumstix Verdex PCMCIA support
[linux-2.6/verdex.git] / drivers / md / multipath.c
blobee7646f974a07165bd368deb3a18f6390e5553dc
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/seq_file.h>
25 #include "md.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->private;
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 = mp_bh->mddev->private;
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 = mp_bh->mddev->private;
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_flagged(bio, BIO_RW_AHEAD)) {
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->private;
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->private;
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_rw_flagged(bio, BIO_RW_BARRIER))) {
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->private;
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->private;
199 int i, ret = 0;
200
201 if (mddev_congested(mddev, bits))
202 return 1;
203
204 rcu_read_lock();
205 for (i = 0; i < mddev->raid_disks ; i++) {
206 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
207 if (rdev && !test_bit(Faulty, &rdev->flags)) {
208 struct request_queue *q = bdev_get_queue(rdev->bdev);
209
210 ret |= bdi_congested(&q->backing_dev_info, bits);
211 /* Just like multipath_map, we just check the
212 * first available device
213 */
214 break;
215 }
216 }
217 rcu_read_unlock();
218 return ret;
219 }
220
221 /*
222 * Careful, this can execute in IRQ contexts as well!
223 */
224 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
225 {
226 multipath_conf_t *conf = mddev->private;
227
228 if (conf->working_disks <= 1) {
229 /*
230 * Uh oh, we can do nothing if this is our last path, but
231 * first check if this is a queued request for a device
232 * which has just failed.
233 */
234 printk(KERN_ALERT
235 "multipath: only one IO path left and IO error.\n");
236 /* leave it active... it's all we have */
237 } else {
238 /*
239 * Mark disk as unusable
240 */
241 if (!test_bit(Faulty, &rdev->flags)) {
242 char b[BDEVNAME_SIZE];
243 clear_bit(In_sync, &rdev->flags);
244 set_bit(Faulty, &rdev->flags);
245 set_bit(MD_CHANGE_DEVS, &mddev->flags);
246 conf->working_disks--;
247 mddev->degraded++;
248 printk(KERN_ALERT "multipath: IO failure on %s,"
249 " disabling IO path.\n"
250 "multipath: Operation continuing"
251 " on %d IO paths.\n",
252 bdevname (rdev->bdev,b),
253 conf->working_disks);
254 }
255 }
256 }
257
258 static void print_multipath_conf (multipath_conf_t *conf)
259 {
260 int i;
261 struct multipath_info *tmp;
262
263 printk("MULTIPATH conf printout:\n");
264 if (!conf) {
265 printk("(conf==NULL)\n");
266 return;
267 }
268 printk(" --- wd:%d rd:%d\n", conf->working_disks,
269 conf->raid_disks);
270
271 for (i = 0; i < conf->raid_disks; i++) {
272 char b[BDEVNAME_SIZE];
273 tmp = conf->multipaths + i;
274 if (tmp->rdev)
275 printk(" disk%d, o:%d, dev:%s\n",
276 i,!test_bit(Faulty, &tmp->rdev->flags),
277 bdevname(tmp->rdev->bdev,b));
278 }
279 }
280
281
282 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
283 {
284 multipath_conf_t *conf = mddev->private;
285 struct request_queue *q;
286 int err = -EEXIST;
287 int path;
288 struct multipath_info *p;
289 int first = 0;
290 int last = mddev->raid_disks - 1;
291
292 if (rdev->raid_disk >= 0)
293 first = last = rdev->raid_disk;
294
295 print_multipath_conf(conf);
296
297 for (path = first; path <= last; path++)
298 if ((p=conf->multipaths+path)->rdev == NULL) {
299 q = rdev->bdev->bd_disk->queue;
300 disk_stack_limits(mddev->gendisk, rdev->bdev,
301 rdev->data_offset << 9);
302
303 /* as we don't honour merge_bvec_fn, we must never risk
304 * violating it, so limit ->max_sector to one PAGE, as
305 * a one page request is never in violation.
306 * (Note: it is very unlikely that a device with
307 * merge_bvec_fn will be involved in multipath.)
308 */
309 if (q->merge_bvec_fn &&
310 queue_max_sectors(q) > (PAGE_SIZE>>9))
311 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
312
313 conf->working_disks++;
314 mddev->degraded--;
315 rdev->raid_disk = path;
316 set_bit(In_sync, &rdev->flags);
317 rcu_assign_pointer(p->rdev, rdev);
318 err = 0;
319 md_integrity_add_rdev(rdev, mddev);
320 break;
321 }
322
323 print_multipath_conf(conf);
324
325 return err;
326 }
327
328 static int multipath_remove_disk(mddev_t *mddev, int number)
329 {
330 multipath_conf_t *conf = mddev->private;
331 int err = 0;
332 mdk_rdev_t *rdev;
333 struct multipath_info *p = conf->multipaths + number;
334
335 print_multipath_conf(conf);
336
337 rdev = p->rdev;
338 if (rdev) {
339 if (test_bit(In_sync, &rdev->flags) ||
340 atomic_read(&rdev->nr_pending)) {
341 printk(KERN_ERR "hot-remove-disk, slot %d is identified"
342 " but is still operational!\n", number);
343 err = -EBUSY;
344 goto abort;
345 }
346 p->rdev = NULL;
347 synchronize_rcu();
348 if (atomic_read(&rdev->nr_pending)) {
349 /* lost the race, try later */
350 err = -EBUSY;
351 p->rdev = rdev;
352 goto abort;
353 }
354 md_integrity_register(mddev);
355 }
356 abort:
357
358 print_multipath_conf(conf);
359 return err;
360 }
361
362
363
364 /*
365 * This is a kernel thread which:
366 *
367 * 1. Retries failed read operations on working multipaths.
368 * 2. Updates the raid superblock when problems encounter.
369 * 3. Performs writes following reads for array syncronising.
370 */
371
372 static void multipathd (mddev_t *mddev)
373 {
374 struct multipath_bh *mp_bh;
375 struct bio *bio;
376 unsigned long flags;
377 multipath_conf_t *conf = mddev->private;
378 struct list_head *head = &conf->retry_list;
379
380 md_check_recovery(mddev);
381 for (;;) {
382 char b[BDEVNAME_SIZE];
383 spin_lock_irqsave(&conf->device_lock, flags);
384 if (list_empty(head))
385 break;
386 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
387 list_del(head->prev);
388 spin_unlock_irqrestore(&conf->device_lock, flags);
389
390 bio = &mp_bh->bio;
391 bio->bi_sector = mp_bh->master_bio->bi_sector;
392
393 if ((mp_bh->path = multipath_map (conf))<0) {
394 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
395 " error for block %llu\n",
396 bdevname(bio->bi_bdev,b),
397 (unsigned long long)bio->bi_sector);
398 multipath_end_bh_io(mp_bh, -EIO);
399 } else {
400 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
401 " to another IO path\n",
402 bdevname(bio->bi_bdev,b),
403 (unsigned long long)bio->bi_sector);
404 *bio = *(mp_bh->master_bio);
405 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
406 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
407 bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
408 bio->bi_end_io = multipath_end_request;
409 bio->bi_private = mp_bh;
410 generic_make_request(bio);
411 }
412 }
413 spin_unlock_irqrestore(&conf->device_lock, flags);
414 }
415
416 static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
417 {
418 WARN_ONCE(sectors || raid_disks,
419 "%s does not support generic reshape\n", __func__);
420
421 return mddev->dev_sectors;
422 }
423
424 static int multipath_run (mddev_t *mddev)
425 {
426 multipath_conf_t *conf;
427 int disk_idx;
428 struct multipath_info *disk;
429 mdk_rdev_t *rdev;
430
431 if (md_check_no_bitmap(mddev))
432 return -EINVAL;
433
434 if (mddev->level != LEVEL_MULTIPATH) {
435 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
436 mdname(mddev), mddev->level);
437 goto out;
438 }
439 /*
440 * copy the already verified devices into our private MULTIPATH
441 * bookkeeping area. [whatever we allocate in multipath_run(),
442 * should be freed in multipath_stop()]
443 */
444 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
445
446 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
447 mddev->private = conf;
448 if (!conf) {
449 printk(KERN_ERR
450 "multipath: couldn't allocate memory for %s\n",
451 mdname(mddev));
452 goto out;
453 }
454
455 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
456 GFP_KERNEL);
457 if (!conf->multipaths) {
458 printk(KERN_ERR
459 "multipath: couldn't allocate memory for %s\n",
460 mdname(mddev));
461 goto out_free_conf;
462 }
463
464 conf->working_disks = 0;
465 list_for_each_entry(rdev, &mddev->disks, same_set) {
466 disk_idx = rdev->raid_disk;
467 if (disk_idx < 0 ||
468 disk_idx >= mddev->raid_disks)
469 continue;
470
471 disk = conf->multipaths + disk_idx;
472 disk->rdev = rdev;
473 disk_stack_limits(mddev->gendisk, rdev->bdev,
474 rdev->data_offset << 9);
475
476 /* as we don't honour merge_bvec_fn, we must never risk
477 * violating it, not that we ever expect a device with
478 * a merge_bvec_fn to be involved in multipath */
479 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
480 queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
481 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
482
483 if (!test_bit(Faulty, &rdev->flags))
484 conf->working_disks++;
485 }
486
487 conf->raid_disks = mddev->raid_disks;
488 conf->mddev = mddev;
489 spin_lock_init(&conf->device_lock);
490 INIT_LIST_HEAD(&conf->retry_list);
491
492 if (!conf->working_disks) {
493 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
494 mdname(mddev));
495 goto out_free_conf;
496 }
497 mddev->degraded = conf->raid_disks - conf->working_disks;
498
499 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
500 sizeof(struct multipath_bh));
501 if (conf->pool == NULL) {
502 printk(KERN_ERR
503 "multipath: couldn't allocate memory for %s\n",
504 mdname(mddev));
505 goto out_free_conf;
506 }
507
508 {
509 mddev->thread = md_register_thread(multipathd, mddev, NULL);
510 if (!mddev->thread) {
511 printk(KERN_ERR "multipath: couldn't allocate thread"
512 " for %s\n", mdname(mddev));
513 goto out_free_conf;
514 }
515 }
516
517 printk(KERN_INFO
518 "multipath: array %s active with %d out of %d IO paths\n",
519 mdname(mddev), conf->working_disks, mddev->raid_disks);
520 /*
521 * Ok, everything is just fine now
522 */
523 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
524
525 mddev->queue->unplug_fn = multipath_unplug;
526 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
527 mddev->queue->backing_dev_info.congested_data = mddev;
528 md_integrity_register(mddev);
529 return 0;
530
531 out_free_conf:
532 if (conf->pool)
533 mempool_destroy(conf->pool);
534 kfree(conf->multipaths);
535 kfree(conf);
536 mddev->private = NULL;
537 out:
538 return -EIO;
539 }
540
541
542 static int multipath_stop (mddev_t *mddev)
543 {
544 multipath_conf_t *conf = mddev->private;
545
546 md_unregister_thread(mddev->thread);
547 mddev->thread = NULL;
548 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
549 mempool_destroy(conf->pool);
550 kfree(conf->multipaths);
551 kfree(conf);
552 mddev->private = NULL;
553 return 0;
554 }
555
556 static struct mdk_personality multipath_personality =
557 {
558 .name = "multipath",
559 .level = LEVEL_MULTIPATH,
560 .owner = THIS_MODULE,
561 .make_request = multipath_make_request,
562 .run = multipath_run,
563 .stop = multipath_stop,
564 .status = multipath_status,
565 .error_handler = multipath_error,
566 .hot_add_disk = multipath_add_disk,
567 .hot_remove_disk= multipath_remove_disk,
568 .size = multipath_size,
569 };
570
571 static int __init multipath_init (void)
572 {
573 return register_md_personality (&multipath_personality);
574 }
575
576 static void __exit multipath_exit (void)
577 {
578 unregister_md_personality (&multipath_personality);
579 }
580
581 module_init(multipath_init);
582 module_exit(multipath_exit);
583 MODULE_LICENSE("GPL");
584 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
585 MODULE_ALIAS("md-multipath");
586 MODULE_ALIAS("md-level--4");
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