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