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_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->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_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->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 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->private;
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 disk_stack_limits(mddev->gendisk, rdev->bdev,
298 rdev->data_offset << 9);
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 queue_max_sectors(q) > (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 md_integrity_add_rdev(rdev, mddev);
317 break;
318 }
319
320 print_multipath_conf(conf);
321
322 return err;
323 }
324
325 static int multipath_remove_disk(mddev_t *mddev, int number)
326 {
327 multipath_conf_t *conf = mddev->private;
328 int err = 0;
329 mdk_rdev_t *rdev;
330 struct multipath_info *p = conf->multipaths + number;
331
332 print_multipath_conf(conf);
333
334 rdev = p->rdev;
335 if (rdev) {
336 if (test_bit(In_sync, &rdev->flags) ||
337 atomic_read(&rdev->nr_pending)) {
338 printk(KERN_ERR "hot-remove-disk, slot %d is identified"
339 " but is still operational!\n", number);
340 err = -EBUSY;
341 goto abort;
342 }
343 p->rdev = NULL;
344 synchronize_rcu();
345 if (atomic_read(&rdev->nr_pending)) {
346 /* lost the race, try later */
347 err = -EBUSY;
348 p->rdev = rdev;
349 goto abort;
350 }
351 md_integrity_register(mddev);
352 }
353 abort:
354
355 print_multipath_conf(conf);
356 return err;
357 }
358
359
360
361 /*
362 * This is a kernel thread which:
363 *
364 * 1. Retries failed read operations on working multipaths.
365 * 2. Updates the raid superblock when problems encounter.
366 * 3. Performs writes following reads for array syncronising.
367 */
368
369 static void multipathd (mddev_t *mddev)
370 {
371 struct multipath_bh *mp_bh;
372 struct bio *bio;
373 unsigned long flags;
374 multipath_conf_t *conf = mddev->private;
375 struct list_head *head = &conf->retry_list;
376
377 md_check_recovery(mddev);
378 for (;;) {
379 char b[BDEVNAME_SIZE];
380 spin_lock_irqsave(&conf->device_lock, flags);
381 if (list_empty(head))
382 break;
383 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
384 list_del(head->prev);
385 spin_unlock_irqrestore(&conf->device_lock, flags);
386
387 bio = &mp_bh->bio;
388 bio->bi_sector = mp_bh->master_bio->bi_sector;
389
390 if ((mp_bh->path = multipath_map (conf))<0) {
391 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
392 " error for block %llu\n",
393 bdevname(bio->bi_bdev,b),
394 (unsigned long long)bio->bi_sector);
395 multipath_end_bh_io(mp_bh, -EIO);
396 } else {
397 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
398 " to another IO path\n",
399 bdevname(bio->bi_bdev,b),
400 (unsigned long long)bio->bi_sector);
401 *bio = *(mp_bh->master_bio);
402 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
403 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
404 bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
405 bio->bi_end_io = multipath_end_request;
406 bio->bi_private = mp_bh;
407 generic_make_request(bio);
408 }
409 }
410 spin_unlock_irqrestore(&conf->device_lock, flags);
411 }
412
413 static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
414 {
415 WARN_ONCE(sectors || raid_disks,
416 "%s does not support generic reshape\n", __func__);
417
418 return mddev->dev_sectors;
419 }
420
421 static int multipath_run (mddev_t *mddev)
422 {
423 multipath_conf_t *conf;
424 int disk_idx;
425 struct multipath_info *disk;
426 mdk_rdev_t *rdev;
427
428 if (md_check_no_bitmap(mddev))
429 return -EINVAL;
430
431 if (mddev->level != LEVEL_MULTIPATH) {
432 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
433 mdname(mddev), mddev->level);
434 goto out;
435 }
436 /*
437 * copy the already verified devices into our private MULTIPATH
438 * bookkeeping area. [whatever we allocate in multipath_run(),
439 * should be freed in multipath_stop()]
440 */
441 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
442
443 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
444 mddev->private = conf;
445 if (!conf) {
446 printk(KERN_ERR
447 "multipath: couldn't allocate memory for %s\n",
448 mdname(mddev));
449 goto out;
450 }
451
452 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
453 GFP_KERNEL);
454 if (!conf->multipaths) {
455 printk(KERN_ERR
456 "multipath: couldn't allocate memory for %s\n",
457 mdname(mddev));
458 goto out_free_conf;
459 }
460
461 conf->working_disks = 0;
462 list_for_each_entry(rdev, &mddev->disks, same_set) {
463 disk_idx = rdev->raid_disk;
464 if (disk_idx < 0 ||
465 disk_idx >= mddev->raid_disks)
466 continue;
467
468 disk = conf->multipaths + disk_idx;
469 disk->rdev = rdev;
470 disk_stack_limits(mddev->gendisk, rdev->bdev,
471 rdev->data_offset << 9);
472
473 /* as we don't honour merge_bvec_fn, we must never risk
474 * violating it, not that we ever expect a device with
475 * a merge_bvec_fn to be involved in multipath */
476 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
477 queue_max_sectors(mddev->queue) > (PAGE_SIZE>>9))
478 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
479
480 if (!test_bit(Faulty, &rdev->flags))
481 conf->working_disks++;
482 }
483
484 conf->raid_disks = mddev->raid_disks;
485 conf->mddev = mddev;
486 spin_lock_init(&conf->device_lock);
487 INIT_LIST_HEAD(&conf->retry_list);
488
489 if (!conf->working_disks) {
490 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
491 mdname(mddev));
492 goto out_free_conf;
493 }
494 mddev->degraded = conf->raid_disks - conf->working_disks;
495
496 conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
497 sizeof(struct multipath_bh));
498 if (conf->pool == NULL) {
499 printk(KERN_ERR
500 "multipath: couldn't allocate memory for %s\n",
501 mdname(mddev));
502 goto out_free_conf;
503 }
504
505 {
506 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
507 if (!mddev->thread) {
508 printk(KERN_ERR "multipath: couldn't allocate thread"
509 " for %s\n", mdname(mddev));
510 goto out_free_conf;
511 }
512 }
513
514 printk(KERN_INFO
515 "multipath: array %s active with %d out of %d IO paths\n",
516 mdname(mddev), conf->working_disks, mddev->raid_disks);
517 /*
518 * Ok, everything is just fine now
519 */
520 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
521
522 mddev->queue->unplug_fn = multipath_unplug;
523 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
524 mddev->queue->backing_dev_info.congested_data = mddev;
525 md_integrity_register(mddev);
526 return 0;
527
528 out_free_conf:
529 if (conf->pool)
530 mempool_destroy(conf->pool);
531 kfree(conf->multipaths);
532 kfree(conf);
533 mddev->private = NULL;
534 out:
535 return -EIO;
536 }
537
538
539 static int multipath_stop (mddev_t *mddev)
540 {
541 multipath_conf_t *conf = mddev->private;
542
543 md_unregister_thread(mddev->thread);
544 mddev->thread = NULL;
545 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
546 mempool_destroy(conf->pool);
547 kfree(conf->multipaths);
548 kfree(conf);
549 mddev->private = NULL;
550 return 0;
551 }
552
553 static struct mdk_personality multipath_personality =
554 {
555 .name = "multipath",
556 .level = LEVEL_MULTIPATH,
557 .owner = THIS_MODULE,
558 .make_request = multipath_make_request,
559 .run = multipath_run,
560 .stop = multipath_stop,
561 .status = multipath_status,
562 .error_handler = multipath_error,
563 .hot_add_disk = multipath_add_disk,
564 .hot_remove_disk= multipath_remove_disk,
565 .size = multipath_size,
566 };
567
568 static int __init multipath_init (void)
569 {
570 return register_md_personality (&multipath_personality);
571 }
572
573 static void __exit multipath_exit (void)
574 {
575 unregister_md_personality (&multipath_personality);
576 }
577
578 module_init(multipath_init);
579 module_exit(multipath_exit);
580 MODULE_LICENSE("GPL");
581 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
582 MODULE_ALIAS("md-multipath");
583 MODULE_ALIAS("md-level--4");
584
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