/drivers/md/multipath.c
C | 592 lines | 435 code | 85 blank | 72 comment | 50 complexity | 110a61adb6627c307b1df2be4cd9b776 MD5 | raw file
Possible License(s): CC-BY-SA-3.0, GPL-2.0, LGPL-2.0, AGPL-1.0
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 <linux/slab.h>
26#include "md.h"
27#include "multipath.h"
28
29#define MAX_WORK_PER_DISK 128
30
31#define NR_RESERVED_BUFS 32
32
33
34static int multipath_map (multipath_conf_t *conf)
35{
36 int i, disks = conf->raid_disks;
37
38 /*
39 * Later we do read balancing on the read side
40 * now we use the first available disk.
41 */
42
43 rcu_read_lock();
44 for (i = 0; i < disks; i++) {
45 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
46 if (rdev && test_bit(In_sync, &rdev->flags)) {
47 atomic_inc(&rdev->nr_pending);
48 rcu_read_unlock();
49 return i;
50 }
51 }
52 rcu_read_unlock();
53
54 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
55 return (-1);
56}
57
58static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
59{
60 unsigned long flags;
61 mddev_t *mddev = mp_bh->mddev;
62 multipath_conf_t *conf = mddev->private;
63
64 spin_lock_irqsave(&conf->device_lock, flags);
65 list_add(&mp_bh->retry_list, &conf->retry_list);
66 spin_unlock_irqrestore(&conf->device_lock, flags);
67 md_wakeup_thread(mddev->thread);
68}
69
70
71/*
72 * multipath_end_bh_io() is called when we have finished servicing a multipathed
73 * operation and are ready to return a success/failure code to the buffer
74 * cache layer.
75 */
76static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
77{
78 struct bio *bio = mp_bh->master_bio;
79 multipath_conf_t *conf = mp_bh->mddev->private;
80
81 bio_endio(bio, err);
82 mempool_free(mp_bh, conf->pool);
83}
84
85static void multipath_end_request(struct bio *bio, int error)
86{
87 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
88 struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
89 multipath_conf_t *conf = mp_bh->mddev->private;
90 mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
91
92 if (uptodate)
93 multipath_end_bh_io(mp_bh, 0);
94 else if (!bio_rw_flagged(bio, BIO_RW_AHEAD)) {
95 /*
96 * oops, IO error:
97 */
98 char b[BDEVNAME_SIZE];
99 md_error (mp_bh->mddev, rdev);
100 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
101 bdevname(rdev->bdev,b),
102 (unsigned long long)bio->bi_sector);
103 multipath_reschedule_retry(mp_bh);
104 } else
105 multipath_end_bh_io(mp_bh, error);
106 rdev_dec_pending(rdev, conf->mddev);
107}
108
109static void unplug_slaves(mddev_t *mddev)
110{
111 multipath_conf_t *conf = mddev->private;
112 int i;
113
114 rcu_read_lock();
115 for (i=0; i<mddev->raid_disks; i++) {
116 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
117 if (rdev && !test_bit(Faulty, &rdev->flags)
118 && atomic_read(&rdev->nr_pending)) {
119 struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
120
121 atomic_inc(&rdev->nr_pending);
122 rcu_read_unlock();
123
124 blk_unplug(r_queue);
125
126 rdev_dec_pending(rdev, mddev);
127 rcu_read_lock();
128 }
129 }
130 rcu_read_unlock();
131}
132
133static void multipath_unplug(struct request_queue *q)
134{
135 unplug_slaves(q->queuedata);
136}
137
138
139static int multipath_make_request (struct request_queue *q, struct bio * bio)
140{
141 mddev_t *mddev = q->queuedata;
142 multipath_conf_t *conf = mddev->private;
143 struct multipath_bh * mp_bh;
144 struct multipath_info *multipath;
145 const int rw = bio_data_dir(bio);
146 int cpu;
147
148 if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
149 md_barrier_request(mddev, bio);
150 return 0;
151 }
152
153 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
154
155 mp_bh->master_bio = bio;
156 mp_bh->mddev = mddev;
157
158 cpu = part_stat_lock();
159 part_stat_inc(cpu, &mddev->gendisk->part0, ios[rw]);
160 part_stat_add(cpu, &mddev->gendisk->part0, sectors[rw],
161 bio_sectors(bio));
162 part_stat_unlock();
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_TRANSPORT);
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
182static void multipath_status (struct seq_file *seq, mddev_t *mddev)
183{
184 multipath_conf_t *conf = mddev->private;
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
196static int multipath_congested(void *data, int bits)
197{
198 mddev_t *mddev = data;
199 multipath_conf_t *conf = mddev->private;
200 int i, ret = 0;
201
202 if (mddev_congested(mddev, bits))
203 return 1;
204
205 rcu_read_lock();
206 for (i = 0; i < mddev->raid_disks ; i++) {
207 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
208 if (rdev && !test_bit(Faulty, &rdev->flags)) {
209 struct request_queue *q = bdev_get_queue(rdev->bdev);
210
211 ret |= bdi_congested(&q->backing_dev_info, bits);
212 /* Just like multipath_map, we just check the
213 * first available device
214 */
215 break;
216 }
217 }
218 rcu_read_unlock();
219 return ret;
220}
221
222/*
223 * Careful, this can execute in IRQ contexts as well!
224 */
225static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
226{
227 multipath_conf_t *conf = mddev->private;
228
229 if (conf->working_disks <= 1) {
230 /*
231 * Uh oh, we can do nothing if this is our last path, but
232 * first check if this is a queued request for a device
233 * which has just failed.
234 */
235 printk(KERN_ALERT
236 "multipath: only one IO path left and IO error.\n");
237 /* leave it active... it's all we have */
238 } else {
239 /*
240 * Mark disk as unusable
241 */
242 if (!test_bit(Faulty, &rdev->flags)) {
243 char b[BDEVNAME_SIZE];
244 clear_bit(In_sync, &rdev->flags);
245 set_bit(Faulty, &rdev->flags);
246 set_bit(MD_CHANGE_DEVS, &mddev->flags);
247 conf->working_disks--;
248 mddev->degraded++;
249 printk(KERN_ALERT "multipath: IO failure on %s,"
250 " disabling IO path.\n"
251 "multipath: Operation continuing"
252 " on %d IO paths.\n",
253 bdevname (rdev->bdev,b),
254 conf->working_disks);
255 }
256 }
257}
258
259static void print_multipath_conf (multipath_conf_t *conf)
260{
261 int i;
262 struct multipath_info *tmp;
263
264 printk("MULTIPATH conf printout:\n");
265 if (!conf) {
266 printk("(conf==NULL)\n");
267 return;
268 }
269 printk(" --- wd:%d rd:%d\n", conf->working_disks,
270 conf->raid_disks);
271
272 for (i = 0; i < conf->raid_disks; i++) {
273 char b[BDEVNAME_SIZE];
274 tmp = conf->multipaths + i;
275 if (tmp->rdev)
276 printk(" disk%d, o:%d, dev:%s\n",
277 i,!test_bit(Faulty, &tmp->rdev->flags),
278 bdevname(tmp->rdev->bdev,b));
279 }
280}
281
282
283static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
284{
285 multipath_conf_t *conf = mddev->private;
286 struct request_queue *q;
287 int err = -EEXIST;
288 int path;
289 struct multipath_info *p;
290 int first = 0;
291 int last = mddev->raid_disks - 1;
292
293 if (rdev->raid_disk >= 0)
294 first = last = rdev->raid_disk;
295
296 print_multipath_conf(conf);
297
298 for (path = first; path <= last; path++)
299 if ((p=conf->multipaths+path)->rdev == NULL) {
300 q = rdev->bdev->bd_disk->queue;
301 disk_stack_limits(mddev->gendisk, rdev->bdev,
302 rdev->data_offset << 9);
303
304 /* as we don't honour merge_bvec_fn, we must never risk
305 * violating it, so limit ->max_segments to one, lying
306 * within a single page.
307 * (Note: it is very unlikely that a device with
308 * merge_bvec_fn will be involved in multipath.)
309 */
310 if (q->merge_bvec_fn) {
311 blk_queue_max_segments(mddev->queue, 1);
312 blk_queue_segment_boundary(mddev->queue,
313 PAGE_CACHE_SIZE - 1);
314 }
315
316 conf->working_disks++;
317 mddev->degraded--;
318 rdev->raid_disk = path;
319 set_bit(In_sync, &rdev->flags);
320 rcu_assign_pointer(p->rdev, rdev);
321 err = 0;
322 md_integrity_add_rdev(rdev, mddev);
323 break;
324 }
325
326 print_multipath_conf(conf);
327
328 return err;
329}
330
331static int multipath_remove_disk(mddev_t *mddev, int number)
332{
333 multipath_conf_t *conf = mddev->private;
334 int err = 0;
335 mdk_rdev_t *rdev;
336 struct multipath_info *p = conf->multipaths + number;
337
338 print_multipath_conf(conf);
339
340 rdev = p->rdev;
341 if (rdev) {
342 if (test_bit(In_sync, &rdev->flags) ||
343 atomic_read(&rdev->nr_pending)) {
344 printk(KERN_ERR "hot-remove-disk, slot %d is identified"
345 " but is still operational!\n", number);
346 err = -EBUSY;
347 goto abort;
348 }
349 p->rdev = NULL;
350 synchronize_rcu();
351 if (atomic_read(&rdev->nr_pending)) {
352 /* lost the race, try later */
353 err = -EBUSY;
354 p->rdev = rdev;
355 goto abort;
356 }
357 md_integrity_register(mddev);
358 }
359abort:
360
361 print_multipath_conf(conf);
362 return err;
363}
364
365
366
367/*
368 * This is a kernel thread which:
369 *
370 * 1. Retries failed read operations on working multipaths.
371 * 2. Updates the raid superblock when problems encounter.
372 * 3. Performs writes following reads for array syncronising.
373 */
374
375static void multipathd (mddev_t *mddev)
376{
377 struct multipath_bh *mp_bh;
378 struct bio *bio;
379 unsigned long flags;
380 multipath_conf_t *conf = mddev->private;
381 struct list_head *head = &conf->retry_list;
382
383 md_check_recovery(mddev);
384 for (;;) {
385 char b[BDEVNAME_SIZE];
386 spin_lock_irqsave(&conf->device_lock, flags);
387 if (list_empty(head))
388 break;
389 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
390 list_del(head->prev);
391 spin_unlock_irqrestore(&conf->device_lock, flags);
392
393 bio = &mp_bh->bio;
394 bio->bi_sector = mp_bh->master_bio->bi_sector;
395
396 if ((mp_bh->path = multipath_map (conf))<0) {
397 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
398 " error for block %llu\n",
399 bdevname(bio->bi_bdev,b),
400 (unsigned long long)bio->bi_sector);
401 multipath_end_bh_io(mp_bh, -EIO);
402 } else {
403 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
404 " to another IO path\n",
405 bdevname(bio->bi_bdev,b),
406 (unsigned long long)bio->bi_sector);
407 *bio = *(mp_bh->master_bio);
408 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
409 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
410 bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
411 bio->bi_end_io = multipath_end_request;
412 bio->bi_private = mp_bh;
413 generic_make_request(bio);
414 }
415 }
416 spin_unlock_irqrestore(&conf->device_lock, flags);
417}
418
419static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
420{
421 WARN_ONCE(sectors || raid_disks,
422 "%s does not support generic reshape\n", __func__);
423
424 return mddev->dev_sectors;
425}
426
427static int multipath_run (mddev_t *mddev)
428{
429 multipath_conf_t *conf;
430 int disk_idx;
431 struct multipath_info *disk;
432 mdk_rdev_t *rdev;
433
434 if (md_check_no_bitmap(mddev))
435 return -EINVAL;
436
437 if (mddev->level != LEVEL_MULTIPATH) {
438 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
439 mdname(mddev), mddev->level);
440 goto out;
441 }
442 /*
443 * copy the already verified devices into our private MULTIPATH
444 * bookkeeping area. [whatever we allocate in multipath_run(),
445 * should be freed in multipath_stop()]
446 */
447 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
448
449 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
450 mddev->private = conf;
451 if (!conf) {
452 printk(KERN_ERR
453 "multipath: couldn't allocate memory for %s\n",
454 mdname(mddev));
455 goto out;
456 }
457
458 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
459 GFP_KERNEL);
460 if (!conf->multipaths) {
461 printk(KERN_ERR
462 "multipath: couldn't allocate memory for %s\n",
463 mdname(mddev));
464 goto out_free_conf;
465 }
466
467 conf->working_disks = 0;
468 list_for_each_entry(rdev, &mddev->disks, same_set) {
469 disk_idx = rdev->raid_disk;
470 if (disk_idx < 0 ||
471 disk_idx >= mddev->raid_disks)
472 continue;
473
474 disk = conf->multipaths + disk_idx;
475 disk->rdev = rdev;
476 disk_stack_limits(mddev->gendisk, rdev->bdev,
477 rdev->data_offset << 9);
478
479 /* as we don't honour merge_bvec_fn, we must never risk
480 * violating it, not that we ever expect a device with
481 * a merge_bvec_fn to be involved in multipath */
482 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
483 blk_queue_max_segments(mddev->queue, 1);
484 blk_queue_segment_boundary(mddev->queue,
485 PAGE_CACHE_SIZE - 1);
486 }
487
488 if (!test_bit(Faulty, &rdev->flags))
489 conf->working_disks++;
490 }
491
492 conf->raid_disks = mddev->raid_disks;
493 conf->mddev = mddev;
494 spin_lock_init(&conf->device_lock);
495 INIT_LIST_HEAD(&conf->retry_list);
496
497 if (!conf->working_disks) {
498 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
499 mdname(mddev));
500 goto out_free_conf;
501 }
502 mddev->degraded = conf->raid_disks - conf->working_disks;
503
504 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
505 sizeof(struct multipath_bh));
506 if (conf->pool == NULL) {
507 printk(KERN_ERR
508 "multipath: couldn't allocate memory for %s\n",
509 mdname(mddev));
510 goto out_free_conf;
511 }
512
513 {
514 mddev->thread = md_register_thread(multipathd, mddev, NULL);
515 if (!mddev->thread) {
516 printk(KERN_ERR "multipath: couldn't allocate thread"
517 " for %s\n", mdname(mddev));
518 goto out_free_conf;
519 }
520 }
521
522 printk(KERN_INFO
523 "multipath: array %s active with %d out of %d IO paths\n",
524 mdname(mddev), conf->working_disks, mddev->raid_disks);
525 /*
526 * Ok, everything is just fine now
527 */
528 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
529
530 mddev->queue->unplug_fn = multipath_unplug;
531 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
532 mddev->queue->backing_dev_info.congested_data = mddev;
533 md_integrity_register(mddev);
534 return 0;
535
536out_free_conf:
537 if (conf->pool)
538 mempool_destroy(conf->pool);
539 kfree(conf->multipaths);
540 kfree(conf);
541 mddev->private = NULL;
542out:
543 return -EIO;
544}
545
546
547static int multipath_stop (mddev_t *mddev)
548{
549 multipath_conf_t *conf = mddev->private;
550
551 md_unregister_thread(mddev->thread);
552 mddev->thread = NULL;
553 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
554 mempool_destroy(conf->pool);
555 kfree(conf->multipaths);
556 kfree(conf);
557 mddev->private = NULL;
558 return 0;
559}
560
561static struct mdk_personality multipath_personality =
562{
563 .name = "multipath",
564 .level = LEVEL_MULTIPATH,
565 .owner = THIS_MODULE,
566 .make_request = multipath_make_request,
567 .run = multipath_run,
568 .stop = multipath_stop,
569 .status = multipath_status,
570 .error_handler = multipath_error,
571 .hot_add_disk = multipath_add_disk,
572 .hot_remove_disk= multipath_remove_disk,
573 .size = multipath_size,
574};
575
576static int __init multipath_init (void)
577{
578 return register_md_personality (&multipath_personality);
579}
580
581static void __exit multipath_exit (void)
582{
583 unregister_md_personality (&multipath_personality);
584}
585
586module_init(multipath_init);
587module_exit(multipath_exit);
588MODULE_LICENSE("GPL");
589MODULE_DESCRIPTION("simple multi-path personality for MD");
590MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
591MODULE_ALIAS("md-multipath");
592MODULE_ALIAS("md-level--4");