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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 = 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->bi_rw & REQ_RAHEAD)) {
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 int multipath_make_request(mddev_t *mddev, struct bio * bio)
110{
111 multipath_conf_t *conf = mddev->private;
112 struct multipath_bh * mp_bh;
113 struct multipath_info *multipath;
114
115 if (unlikely(bio->bi_rw & REQ_FLUSH)) {
116 md_flush_request(mddev, bio);
117 return 0;
118 }
119
120 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
121
122 mp_bh->master_bio = bio;
123 mp_bh->mddev = mddev;
124
125 mp_bh->path = multipath_map(conf);
126 if (mp_bh->path < 0) {
127 bio_endio(bio, -EIO);
128 mempool_free(mp_bh, conf->pool);
129 return 0;
130 }
131 multipath = conf->multipaths + mp_bh->path;
132
133 mp_bh->bio = *bio;
134 mp_bh->bio.bi_sector += multipath->rdev->data_offset;
135 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
136 mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT;
137 mp_bh->bio.bi_end_io = multipath_end_request;
138 mp_bh->bio.bi_private = mp_bh;
139 generic_make_request(&mp_bh->bio);
140 return 0;
141}
142
143static void multipath_status (struct seq_file *seq, mddev_t *mddev)
144{
145 multipath_conf_t *conf = mddev->private;
146 int i;
147
148 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
149 conf->raid_disks - mddev->degraded);
150 for (i = 0; i < conf->raid_disks; i++)
151 seq_printf (seq, "%s",
152 conf->multipaths[i].rdev &&
153 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
154 seq_printf (seq, "]");
155}
156
157static int multipath_congested(void *data, int bits)
158{
159 mddev_t *mddev = data;
160 multipath_conf_t *conf = mddev->private;
161 int i, ret = 0;
162
163 if (mddev_congested(mddev, bits))
164 return 1;
165
166 rcu_read_lock();
167 for (i = 0; i < mddev->raid_disks ; i++) {
168 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
169 if (rdev && !test_bit(Faulty, &rdev->flags)) {
170 struct request_queue *q = bdev_get_queue(rdev->bdev);
171
172 ret |= bdi_congested(&q->backing_dev_info, bits);
173 /* Just like multipath_map, we just check the
174 * first available device
175 */
176 break;
177 }
178 }
179 rcu_read_unlock();
180 return ret;
181}
182
183/*
184 * Careful, this can execute in IRQ contexts as well!
185 */
186static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
187{
188 multipath_conf_t *conf = mddev->private;
189 char b[BDEVNAME_SIZE];
190
191 if (conf->raid_disks - mddev->degraded <= 1) {
192 /*
193 * Uh oh, we can do nothing if this is our last path, but
194 * first check if this is a queued request for a device
195 * which has just failed.
196 */
197 printk(KERN_ALERT
198 "multipath: only one IO path left and IO error.\n");
199 /* leave it active... it's all we have */
200 return;
201 }
202 /*
203 * Mark disk as unusable
204 */
205 if (test_and_clear_bit(In_sync, &rdev->flags)) {
206 unsigned long flags;
207 spin_lock_irqsave(&conf->device_lock, flags);
208 mddev->degraded++;
209 spin_unlock_irqrestore(&conf->device_lock, flags);
210 }
211 set_bit(Faulty, &rdev->flags);
212 set_bit(MD_CHANGE_DEVS, &mddev->flags);
213 printk(KERN_ALERT "multipath: IO failure on %s,"
214 " disabling IO path.\n"
215 "multipath: Operation continuing"
216 " on %d IO paths.\n",
217 bdevname(rdev->bdev, b),
218 conf->raid_disks - mddev->degraded);
219}
220
221static void print_multipath_conf (multipath_conf_t *conf)
222{
223 int i;
224 struct multipath_info *tmp;
225
226 printk("MULTIPATH conf printout:\n");
227 if (!conf) {
228 printk("(conf==NULL)\n");
229 return;
230 }
231 printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
232 conf->raid_disks);
233
234 for (i = 0; i < conf->raid_disks; i++) {
235 char b[BDEVNAME_SIZE];
236 tmp = conf->multipaths + i;
237 if (tmp->rdev)
238 printk(" disk%d, o:%d, dev:%s\n",
239 i,!test_bit(Faulty, &tmp->rdev->flags),
240 bdevname(tmp->rdev->bdev,b));
241 }
242}
243
244
245static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
246{
247 multipath_conf_t *conf = mddev->private;
248 struct request_queue *q;
249 int err = -EEXIST;
250 int path;
251 struct multipath_info *p;
252 int first = 0;
253 int last = mddev->raid_disks - 1;
254
255 if (rdev->raid_disk >= 0)
256 first = last = rdev->raid_disk;
257
258 print_multipath_conf(conf);
259
260 for (path = first; path <= last; path++)
261 if ((p=conf->multipaths+path)->rdev == NULL) {
262 q = rdev->bdev->bd_disk->queue;
263 disk_stack_limits(mddev->gendisk, rdev->bdev,
264 rdev->data_offset << 9);
265
266 /* as we don't honour merge_bvec_fn, we must never risk
267 * violating it, so limit ->max_segments to one, lying
268 * within a single page.
269 * (Note: it is very unlikely that a device with
270 * merge_bvec_fn will be involved in multipath.)
271 */
272 if (q->merge_bvec_fn) {
273 blk_queue_max_segments(mddev->queue, 1);
274 blk_queue_segment_boundary(mddev->queue,
275 PAGE_CACHE_SIZE - 1);
276 }
277
278 spin_lock_irq(&conf->device_lock);
279 mddev->degraded--;
280 rdev->raid_disk = path;
281 set_bit(In_sync, &rdev->flags);
282 spin_unlock_irq(&conf->device_lock);
283 rcu_assign_pointer(p->rdev, rdev);
284 err = 0;
285 md_integrity_add_rdev(rdev, mddev);
286 break;
287 }
288
289 print_multipath_conf(conf);
290
291 return err;
292}
293
294static int multipath_remove_disk(mddev_t *mddev, int number)
295{
296 multipath_conf_t *conf = mddev->private;
297 int err = 0;
298 mdk_rdev_t *rdev;
299 struct multipath_info *p = conf->multipaths + number;
300
301 print_multipath_conf(conf);
302
303 rdev = p->rdev;
304 if (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 }
322abort:
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
338static void multipathd (mddev_t *mddev)
339{
340 struct multipath_bh *mp_bh;
341 struct bio *bio;
342 unsigned long flags;
343 multipath_conf_t *conf = mddev->private;
344 struct list_head *head = &conf->retry_list;
345
346 md_check_recovery(mddev);
347 for (;;) {
348 char b[BDEVNAME_SIZE];
349 spin_lock_irqsave(&conf->device_lock, flags);
350 if (list_empty(head))
351 break;
352 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
353 list_del(head->prev);
354 spin_unlock_irqrestore(&conf->device_lock, flags);
355
356 bio = &mp_bh->bio;
357 bio->bi_sector = mp_bh->master_bio->bi_sector;
358
359 if ((mp_bh->path = multipath_map (conf))<0) {
360 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
361 " error for block %llu\n",
362 bdevname(bio->bi_bdev,b),
363 (unsigned long long)bio->bi_sector);
364 multipath_end_bh_io(mp_bh, -EIO);
365 } else {
366 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
367 " to another IO path\n",
368 bdevname(bio->bi_bdev,b),
369 (unsigned long long)bio->bi_sector);
370 *bio = *(mp_bh->master_bio);
371 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
372 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
373 bio->bi_rw |= REQ_FAILFAST_TRANSPORT;
374 bio->bi_end_io = multipath_end_request;
375 bio->bi_private = mp_bh;
376 generic_make_request(bio);
377 }
378 }
379 spin_unlock_irqrestore(&conf->device_lock, flags);
380}
381
382static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
383{
384 WARN_ONCE(sectors || raid_disks,
385 "%s does not support generic reshape\n", __func__);
386
387 return mddev->dev_sectors;
388}
389
390static int multipath_run (mddev_t *mddev)
391{
392 multipath_conf_t *conf;
393 int disk_idx;
394 struct multipath_info *disk;
395 mdk_rdev_t *rdev;
396 int working_disks;
397
398 if (md_check_no_bitmap(mddev))
399 return -EINVAL;
400
401 if (mddev->level != LEVEL_MULTIPATH) {
402 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
403 mdname(mddev), mddev->level);
404 goto out;
405 }
406 /*
407 * copy the already verified devices into our private MULTIPATH
408 * bookkeeping area. [whatever we allocate in multipath_run(),
409 * should be freed in multipath_stop()]
410 */
411
412 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
413 mddev->private = conf;
414 if (!conf) {
415 printk(KERN_ERR
416 "multipath: couldn't allocate memory for %s\n",
417 mdname(mddev));
418 goto out;
419 }
420
421 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
422 GFP_KERNEL);
423 if (!conf->multipaths) {
424 printk(KERN_ERR
425 "multipath: couldn't allocate memory for %s\n",
426 mdname(mddev));
427 goto out_free_conf;
428 }
429
430 working_disks = 0;
431 list_for_each_entry(rdev, &mddev->disks, same_set) {
432 disk_idx = rdev->raid_disk;
433 if (disk_idx < 0 ||
434 disk_idx >= mddev->raid_disks)
435 continue;
436
437 disk = conf->multipaths + disk_idx;
438 disk->rdev = rdev;
439 disk_stack_limits(mddev->gendisk, rdev->bdev,
440 rdev->data_offset << 9);
441
442 /* as we don't honour merge_bvec_fn, we must never risk
443 * violating it, not that we ever expect a device with
444 * a merge_bvec_fn to be involved in multipath */
445 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
446 blk_queue_max_segments(mddev->queue, 1);
447 blk_queue_segment_boundary(mddev->queue,
448 PAGE_CACHE_SIZE - 1);
449 }
450
451 if (!test_bit(Faulty, &rdev->flags))
452 working_disks++;
453 }
454
455 conf->raid_disks = mddev->raid_disks;
456 conf->mddev = mddev;
457 spin_lock_init(&conf->device_lock);
458 INIT_LIST_HEAD(&conf->retry_list);
459
460 if (!working_disks) {
461 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
462 mdname(mddev));
463 goto out_free_conf;
464 }
465 mddev->degraded = conf->raid_disks - working_disks;
466
467 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
468 sizeof(struct multipath_bh));
469 if (conf->pool == NULL) {
470 printk(KERN_ERR
471 "multipath: couldn't allocate memory for %s\n",
472 mdname(mddev));
473 goto out_free_conf;
474 }
475
476 {
477 mddev->thread = md_register_thread(multipathd, mddev, NULL);
478 if (!mddev->thread) {
479 printk(KERN_ERR "multipath: couldn't allocate thread"
480 " for %s\n", mdname(mddev));
481 goto out_free_conf;
482 }
483 }
484
485 printk(KERN_INFO
486 "multipath: array %s active with %d out of %d IO paths\n",
487 mdname(mddev), conf->raid_disks - mddev->degraded,
488 mddev->raid_disks);
489 /*
490 * Ok, everything is just fine now
491 */
492 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
493
494 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
495 mddev->queue->backing_dev_info.congested_data = mddev;
496
497 if (md_integrity_register(mddev))
498 goto out_free_conf;
499
500 return 0;
501
502out_free_conf:
503 if (conf->pool)
504 mempool_destroy(conf->pool);
505 kfree(conf->multipaths);
506 kfree(conf);
507 mddev->private = NULL;
508out:
509 return -EIO;
510}
511
512
513static int multipath_stop (mddev_t *mddev)
514{
515 multipath_conf_t *conf = mddev->private;
516
517 md_unregister_thread(&mddev->thread);
518 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
519 mempool_destroy(conf->pool);
520 kfree(conf->multipaths);
521 kfree(conf);
522 mddev->private = NULL;
523 return 0;
524}
525
526static struct mdk_personality multipath_personality =
527{
528 .name = "multipath",
529 .level = LEVEL_MULTIPATH,
530 .owner = THIS_MODULE,
531 .make_request = multipath_make_request,
532 .run = multipath_run,
533 .stop = multipath_stop,
534 .status = multipath_status,
535 .error_handler = multipath_error,
536 .hot_add_disk = multipath_add_disk,
537 .hot_remove_disk= multipath_remove_disk,
538 .size = multipath_size,
539};
540
541static int __init multipath_init (void)
542{
543 return register_md_personality (&multipath_personality);
544}
545
546static void __exit multipath_exit (void)
547{
548 unregister_md_personality (&multipath_personality);
549}
550
551module_init(multipath_init);
552module_exit(multipath_exit);
553MODULE_LICENSE("GPL");
554MODULE_DESCRIPTION("simple multi-path personality for MD");
555MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
556MODULE_ALIAS("md-multipath");
557MODULE_ALIAS("md-level--4");