?  search:
summary | log | graphiclog1 | graphiclog2 | commit | commitdiff | tree | refs | edit | fork
blame | history | raw | HEAD
pcmcia: CompactFlash driver for PA Semi Electra boards
[pv_ops_mirror.git] / drivers / md / multipath.c
blobb35731cceac671ee647e108174a44cacfa82c381
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/module.h>
23 #include <linux/slab.h>
24 #include <linux/spinlock.h>
25 #include <linux/raid/multipath.h>
26 #include <linux/buffer_head.h>
27 #include <asm/atomic.h>
28
29 #define MAJOR_NR MD_MAJOR
30 #define MD_DRIVER
31 #define MD_PERSONALITY
32
33 #define MAX_WORK_PER_DISK 128
34
35 #define NR_RESERVED_BUFS 32
36
37
38 static int multipath_map (multipath_conf_t *conf)
39 {
40 int i, disks = conf->raid_disks;
41
42 /*
43 * Later we do read balancing on the read side
44 * now we use the first available disk.
45 */
46
47 rcu_read_lock();
48 for (i = 0; i < disks; i++) {
49 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
50 if (rdev && test_bit(In_sync, &rdev->flags)) {
51 atomic_inc(&rdev->nr_pending);
52 rcu_read_unlock();
53 return i;
54 }
55 }
56 rcu_read_unlock();
57
58 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
59 return (-1);
60 }
61
62 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
63 {
64 unsigned long flags;
65 mddev_t *mddev = mp_bh->mddev;
66 multipath_conf_t *conf = mddev_to_conf(mddev);
67
68 spin_lock_irqsave(&conf->device_lock, flags);
69 list_add(&mp_bh->retry_list, &conf->retry_list);
70 spin_unlock_irqrestore(&conf->device_lock, flags);
71 md_wakeup_thread(mddev->thread);
72 }
73
74
75 /*
76 * multipath_end_bh_io() is called when we have finished servicing a multipathed
77 * operation and are ready to return a success/failure code to the buffer
78 * cache layer.
79 */
80 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
81 {
82 struct bio *bio = mp_bh->master_bio;
83 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
84
85 bio_endio(bio, err);
86 mempool_free(mp_bh, conf->pool);
87 }
88
89 static void multipath_end_request(struct bio *bio, int error)
90 {
91 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
92 struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
93 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
94 mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
95
96 if (uptodate)
97 multipath_end_bh_io(mp_bh, 0);
98 else if (!bio_rw_ahead(bio)) {
99 /*
100 * oops, IO error:
101 */
102 char b[BDEVNAME_SIZE];
103 md_error (mp_bh->mddev, rdev);
104 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
105 bdevname(rdev->bdev,b),
106 (unsigned long long)bio->bi_sector);
107 multipath_reschedule_retry(mp_bh);
108 } else
109 multipath_end_bh_io(mp_bh, error);
110 rdev_dec_pending(rdev, conf->mddev);
111 }
112
113 static void unplug_slaves(mddev_t *mddev)
114 {
115 multipath_conf_t *conf = mddev_to_conf(mddev);
116 int i;
117
118 rcu_read_lock();
119 for (i=0; i<mddev->raid_disks; i++) {
120 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
121 if (rdev && !test_bit(Faulty, &rdev->flags)
122 && atomic_read(&rdev->nr_pending)) {
123 struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
124
125 atomic_inc(&rdev->nr_pending);
126 rcu_read_unlock();
127
128 if (r_queue->unplug_fn)
129 r_queue->unplug_fn(r_queue);
130
131 rdev_dec_pending(rdev, mddev);
132 rcu_read_lock();
133 }
134 }
135 rcu_read_unlock();
136 }
137
138 static void multipath_unplug(struct request_queue *q)
139 {
140 unplug_slaves(q->queuedata);
141 }
142
143
144 static int multipath_make_request (struct request_queue *q, struct bio * bio)
145 {
146 mddev_t *mddev = q->queuedata;
147 multipath_conf_t *conf = mddev_to_conf(mddev);
148 struct multipath_bh * mp_bh;
149 struct multipath_info *multipath;
150 const int rw = bio_data_dir(bio);
151
152 if (unlikely(bio_barrier(bio))) {
153 bio_endio(bio, -EOPNOTSUPP);
154 return 0;
155 }
156
157 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
158
159 mp_bh->master_bio = bio;
160 mp_bh->mddev = mddev;
161
162 disk_stat_inc(mddev->gendisk, ios[rw]);
163 disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
164
165 mp_bh->path = multipath_map(conf);
166 if (mp_bh->path < 0) {
167 bio_endio(bio, -EIO);
168 mempool_free(mp_bh, conf->pool);
169 return 0;
170 }
171 multipath = conf->multipaths + mp_bh->path;
172
173 mp_bh->bio = *bio;
174 mp_bh->bio.bi_sector += multipath->rdev->data_offset;
175 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
176 mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
177 mp_bh->bio.bi_end_io = multipath_end_request;
178 mp_bh->bio.bi_private = mp_bh;
179 generic_make_request(&mp_bh->bio);
180 return 0;
181 }
182
183 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
184 {
185 multipath_conf_t *conf = mddev_to_conf(mddev);
186 int i;
187
188 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
189 conf->working_disks);
190 for (i = 0; i < conf->raid_disks; i++)
191 seq_printf (seq, "%s",
192 conf->multipaths[i].rdev &&
193 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
194 seq_printf (seq, "]");
195 }
196
197 static int multipath_congested(void *data, int bits)
198 {
199 mddev_t *mddev = data;
200 multipath_conf_t *conf = mddev_to_conf(mddev);
201 int i, ret = 0;
202
203 rcu_read_lock();
204 for (i = 0; i < mddev->raid_disks ; i++) {
205 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
206 if (rdev && !test_bit(Faulty, &rdev->flags)) {
207 struct request_queue *q = bdev_get_queue(rdev->bdev);
208
209 ret |= bdi_congested(&q->backing_dev_info, bits);
210 /* Just like multipath_map, we just check the
211 * first available device
212 */
213 break;
214 }
215 }
216 rcu_read_unlock();
217 return ret;
218 }
219
220 /*
221 * Careful, this can execute in IRQ contexts as well!
222 */
223 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
224 {
225 multipath_conf_t *conf = mddev_to_conf(mddev);
226
227 if (conf->working_disks <= 1) {
228 /*
229 * Uh oh, we can do nothing if this is our last path, but
230 * first check if this is a queued request for a device
231 * which has just failed.
232 */
233 printk(KERN_ALERT
234 "multipath: only one IO path left and IO error.\n");
235 /* leave it active... it's all we have */
236 } else {
237 /*
238 * Mark disk as unusable
239 */
240 if (!test_bit(Faulty, &rdev->flags)) {
241 char b[BDEVNAME_SIZE];
242 clear_bit(In_sync, &rdev->flags);
243 set_bit(Faulty, &rdev->flags);
244 set_bit(MD_CHANGE_DEVS, &mddev->flags);
245 conf->working_disks--;
246 mddev->degraded++;
247 printk(KERN_ALERT "multipath: IO failure on %s,"
248 " disabling IO path. \n Operation continuing"
249 " on %d IO paths.\n",
250 bdevname (rdev->bdev,b),
251 conf->working_disks);
252 }
253 }
254 }
255
256 static void print_multipath_conf (multipath_conf_t *conf)
257 {
258 int i;
259 struct multipath_info *tmp;
260
261 printk("MULTIPATH conf printout:\n");
262 if (!conf) {
263 printk("(conf==NULL)\n");
264 return;
265 }
266 printk(" --- wd:%d rd:%d\n", conf->working_disks,
267 conf->raid_disks);
268
269 for (i = 0; i < conf->raid_disks; i++) {
270 char b[BDEVNAME_SIZE];
271 tmp = conf->multipaths + i;
272 if (tmp->rdev)
273 printk(" disk%d, o:%d, dev:%s\n",
274 i,!test_bit(Faulty, &tmp->rdev->flags),
275 bdevname(tmp->rdev->bdev,b));
276 }
277 }
278
279
280 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
281 {
282 multipath_conf_t *conf = mddev->private;
283 struct request_queue *q;
284 int found = 0;
285 int path;
286 struct multipath_info *p;
287
288 print_multipath_conf(conf);
289
290 for (path=0; path<mddev->raid_disks; 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 found = 1;
311 }
312
313 print_multipath_conf(conf);
314 return found;
315 }
316
317 static int multipath_remove_disk(mddev_t *mddev, int number)
318 {
319 multipath_conf_t *conf = mddev->private;
320 int err = 0;
321 mdk_rdev_t *rdev;
322 struct multipath_info *p = conf->multipaths + number;
323
324 print_multipath_conf(conf);
325
326 rdev = p->rdev;
327 if (rdev) {
328 if (test_bit(In_sync, &rdev->flags) ||
329 atomic_read(&rdev->nr_pending)) {
330 printk(KERN_ERR "hot-remove-disk, slot %d is identified" " but is still operational!\n", number);
331 err = -EBUSY;
332 goto abort;
333 }
334 p->rdev = NULL;
335 synchronize_rcu();
336 if (atomic_read(&rdev->nr_pending)) {
337 /* lost the race, try later */
338 err = -EBUSY;
339 p->rdev = rdev;
340 }
341 }
342 abort:
343
344 print_multipath_conf(conf);
345 return err;
346 }
347
348
349
350 /*
351 * This is a kernel thread which:
352 *
353 * 1. Retries failed read operations on working multipaths.
354 * 2. Updates the raid superblock when problems encounter.
355 * 3. Performs writes following reads for array syncronising.
356 */
357
358 static void multipathd (mddev_t *mddev)
359 {
360 struct multipath_bh *mp_bh;
361 struct bio *bio;
362 unsigned long flags;
363 multipath_conf_t *conf = mddev_to_conf(mddev);
364 struct list_head *head = &conf->retry_list;
365
366 md_check_recovery(mddev);
367 for (;;) {
368 char b[BDEVNAME_SIZE];
369 spin_lock_irqsave(&conf->device_lock, flags);
370 if (list_empty(head))
371 break;
372 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
373 list_del(head->prev);
374 spin_unlock_irqrestore(&conf->device_lock, flags);
375
376 bio = &mp_bh->bio;
377 bio->bi_sector = mp_bh->master_bio->bi_sector;
378
379 if ((mp_bh->path = multipath_map (conf))<0) {
380 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
381 " error for block %llu\n",
382 bdevname(bio->bi_bdev,b),
383 (unsigned long long)bio->bi_sector);
384 multipath_end_bh_io(mp_bh, -EIO);
385 } else {
386 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
387 " to another IO path\n",
388 bdevname(bio->bi_bdev,b),
389 (unsigned long long)bio->bi_sector);
390 *bio = *(mp_bh->master_bio);
391 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
392 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
393 bio->bi_rw |= (1 << BIO_RW_FAILFAST);
394 bio->bi_end_io = multipath_end_request;
395 bio->bi_private = mp_bh;
396 generic_make_request(bio);
397 }
398 }
399 spin_unlock_irqrestore(&conf->device_lock, flags);
400 }
401
402 static int multipath_run (mddev_t *mddev)
403 {
404 multipath_conf_t *conf;
405 int disk_idx;
406 struct multipath_info *disk;
407 mdk_rdev_t *rdev;
408 struct list_head *tmp;
409
410 if (mddev->level != LEVEL_MULTIPATH) {
411 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
412 mdname(mddev), mddev->level);
413 goto out;
414 }
415 /*
416 * copy the already verified devices into our private MULTIPATH
417 * bookkeeping area. [whatever we allocate in multipath_run(),
418 * should be freed in multipath_stop()]
419 */
420
421 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
422 mddev->private = conf;
423 if (!conf) {
424 printk(KERN_ERR
425 "multipath: couldn't allocate memory for %s\n",
426 mdname(mddev));
427 goto out;
428 }
429
430 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
431 GFP_KERNEL);
432 if (!conf->multipaths) {
433 printk(KERN_ERR
434 "multipath: couldn't allocate memory for %s\n",
435 mdname(mddev));
436 goto out_free_conf;
437 }
438
439 conf->working_disks = 0;
440 ITERATE_RDEV(mddev,rdev,tmp) {
441 disk_idx = rdev->raid_disk;
442 if (disk_idx < 0 ||
443 disk_idx >= mddev->raid_disks)
444 continue;
445
446 disk = conf->multipaths + disk_idx;
447 disk->rdev = rdev;
448
449 blk_queue_stack_limits(mddev->queue,
450 rdev->bdev->bd_disk->queue);
451 /* as we don't honour merge_bvec_fn, we must never risk
452 * violating it, not that we ever expect a device with
453 * a merge_bvec_fn to be involved in multipath */
454 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
455 mddev->queue->max_sectors > (PAGE_SIZE>>9))
456 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
457
458 if (!test_bit(Faulty, &rdev->flags))
459 conf->working_disks++;
460 }
461
462 conf->raid_disks = mddev->raid_disks;
463 conf->mddev = mddev;
464 spin_lock_init(&conf->device_lock);
465 INIT_LIST_HEAD(&conf->retry_list);
466
467 if (!conf->working_disks) {
468 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
469 mdname(mddev));
470 goto out_free_conf;
471 }
472 mddev->degraded = conf->raid_disks - conf->working_disks;
473
474 conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
475 sizeof(struct multipath_bh));
476 if (conf->pool == NULL) {
477 printk(KERN_ERR
478 "multipath: couldn't allocate memory for %s\n",
479 mdname(mddev));
480 goto out_free_conf;
481 }
482
483 {
484 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
485 if (!mddev->thread) {
486 printk(KERN_ERR "multipath: couldn't allocate thread"
487 " for %s\n", mdname(mddev));
488 goto out_free_conf;
489 }
490 }
491
492 printk(KERN_INFO
493 "multipath: array %s active with %d out of %d IO paths\n",
494 mdname(mddev), conf->working_disks, mddev->raid_disks);
495 /*
496 * Ok, everything is just fine now
497 */
498 mddev->array_size = mddev->size;
499
500 mddev->queue->unplug_fn = multipath_unplug;
501 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
502 mddev->queue->backing_dev_info.congested_data = mddev;
503
504 return 0;
505
506 out_free_conf:
507 if (conf->pool)
508 mempool_destroy(conf->pool);
509 kfree(conf->multipaths);
510 kfree(conf);
511 mddev->private = NULL;
512 out:
513 return -EIO;
514 }
515
516
517 static int multipath_stop (mddev_t *mddev)
518 {
519 multipath_conf_t *conf = mddev_to_conf(mddev);
520
521 md_unregister_thread(mddev->thread);
522 mddev->thread = NULL;
523 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
524 mempool_destroy(conf->pool);
525 kfree(conf->multipaths);
526 kfree(conf);
527 mddev->private = NULL;
528 return 0;
529 }
530
531 static struct mdk_personality multipath_personality =
532 {
533 .name = "multipath",
534 .level = LEVEL_MULTIPATH,
535 .owner = THIS_MODULE,
536 .make_request = multipath_make_request,
537 .run = multipath_run,
538 .stop = multipath_stop,
539 .status = multipath_status,
540 .error_handler = multipath_error,
541 .hot_add_disk = multipath_add_disk,
542 .hot_remove_disk= multipath_remove_disk,
543 };
544
545 static int __init multipath_init (void)
546 {
547 return register_md_personality (&multipath_personality);
548 }
549
550 static void __exit multipath_exit (void)
551 {
552 unregister_md_personality (&multipath_personality);
553 }
554
555 module_init(multipath_init);
556 module_exit(multipath_exit);
557 MODULE_LICENSE("GPL");
558 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
559 MODULE_ALIAS("md-multipath");
560 MODULE_ALIAS("md-level--4");
Mirror for ia64_pv_ops.git