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