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[PATCH] md: allow array level to be set textually via sysfs
[linux-2.6/sactl.git] / drivers / md / multipath.c
blobe6aa309a66d7b7a4d71525702706f1bae99a8461
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 void *mp_pool_alloc(gfp_t gfp_flags, void *data)
39 {
40 struct multipath_bh *mpb;
41 mpb = kzalloc(sizeof(*mpb), gfp_flags);
42 return mpb;
43 }
44
45 static void mp_pool_free(void *mpb, void *data)
46 {
47 kfree(mpb);
48 }
49
50 static int multipath_map (multipath_conf_t *conf)
51 {
52 int i, disks = conf->raid_disks;
53
54 /*
55 * Later we do read balancing on the read side
56 * now we use the first available disk.
57 */
58
59 rcu_read_lock();
60 for (i = 0; i < disks; i++) {
61 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
62 if (rdev && test_bit(In_sync, &rdev->flags)) {
63 atomic_inc(&rdev->nr_pending);
64 rcu_read_unlock();
65 return i;
66 }
67 }
68 rcu_read_unlock();
69
70 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
71 return (-1);
72 }
73
74 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
75 {
76 unsigned long flags;
77 mddev_t *mddev = mp_bh->mddev;
78 multipath_conf_t *conf = mddev_to_conf(mddev);
79
80 spin_lock_irqsave(&conf->device_lock, flags);
81 list_add(&mp_bh->retry_list, &conf->retry_list);
82 spin_unlock_irqrestore(&conf->device_lock, flags);
83 md_wakeup_thread(mddev->thread);
84 }
85
86
87 /*
88 * multipath_end_bh_io() is called when we have finished servicing a multipathed
89 * operation and are ready to return a success/failure code to the buffer
90 * cache layer.
91 */
92 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
93 {
94 struct bio *bio = mp_bh->master_bio;
95 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
96
97 bio_endio(bio, bio->bi_size, err);
98 mempool_free(mp_bh, conf->pool);
99 }
100
101 static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
102 int error)
103 {
104 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
105 struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
106 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
107 mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
108
109 if (bio->bi_size)
110 return 1;
111
112 if (uptodate)
113 multipath_end_bh_io(mp_bh, 0);
114 else if (!bio_rw_ahead(bio)) {
115 /*
116 * oops, IO error:
117 */
118 char b[BDEVNAME_SIZE];
119 md_error (mp_bh->mddev, rdev);
120 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
121 bdevname(rdev->bdev,b),
122 (unsigned long long)bio->bi_sector);
123 multipath_reschedule_retry(mp_bh);
124 } else
125 multipath_end_bh_io(mp_bh, error);
126 rdev_dec_pending(rdev, conf->mddev);
127 return 0;
128 }
129
130 static void unplug_slaves(mddev_t *mddev)
131 {
132 multipath_conf_t *conf = mddev_to_conf(mddev);
133 int i;
134
135 rcu_read_lock();
136 for (i=0; i<mddev->raid_disks; i++) {
137 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
138 if (rdev && !test_bit(Faulty, &rdev->flags)
139 && atomic_read(&rdev->nr_pending)) {
140 request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
141
142 atomic_inc(&rdev->nr_pending);
143 rcu_read_unlock();
144
145 if (r_queue->unplug_fn)
146 r_queue->unplug_fn(r_queue);
147
148 rdev_dec_pending(rdev, mddev);
149 rcu_read_lock();
150 }
151 }
152 rcu_read_unlock();
153 }
154
155 static void multipath_unplug(request_queue_t *q)
156 {
157 unplug_slaves(q->queuedata);
158 }
159
160
161 static int multipath_make_request (request_queue_t *q, struct bio * bio)
162 {
163 mddev_t *mddev = q->queuedata;
164 multipath_conf_t *conf = mddev_to_conf(mddev);
165 struct multipath_bh * mp_bh;
166 struct multipath_info *multipath;
167 const int rw = bio_data_dir(bio);
168
169 if (unlikely(bio_barrier(bio))) {
170 bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
171 return 0;
172 }
173
174 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
175
176 mp_bh->master_bio = bio;
177 mp_bh->mddev = mddev;
178
179 disk_stat_inc(mddev->gendisk, ios[rw]);
180 disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
181
182 mp_bh->path = multipath_map(conf);
183 if (mp_bh->path < 0) {
184 bio_endio(bio, bio->bi_size, -EIO);
185 mempool_free(mp_bh, conf->pool);
186 return 0;
187 }
188 multipath = conf->multipaths + mp_bh->path;
189
190 mp_bh->bio = *bio;
191 mp_bh->bio.bi_sector += multipath->rdev->data_offset;
192 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
193 mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
194 mp_bh->bio.bi_end_io = multipath_end_request;
195 mp_bh->bio.bi_private = mp_bh;
196 generic_make_request(&mp_bh->bio);
197 return 0;
198 }
199
200 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
201 {
202 multipath_conf_t *conf = mddev_to_conf(mddev);
203 int i;
204
205 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
206 conf->working_disks);
207 for (i = 0; i < conf->raid_disks; i++)
208 seq_printf (seq, "%s",
209 conf->multipaths[i].rdev &&
210 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
211 seq_printf (seq, "]");
212 }
213
214 static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
215 sector_t *error_sector)
216 {
217 mddev_t *mddev = q->queuedata;
218 multipath_conf_t *conf = mddev_to_conf(mddev);
219 int i, ret = 0;
220
221 rcu_read_lock();
222 for (i=0; i<mddev->raid_disks && ret == 0; i++) {
223 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
224 if (rdev && !test_bit(Faulty, &rdev->flags)) {
225 struct block_device *bdev = rdev->bdev;
226 request_queue_t *r_queue = bdev_get_queue(bdev);
227
228 if (!r_queue->issue_flush_fn)
229 ret = -EOPNOTSUPP;
230 else {
231 atomic_inc(&rdev->nr_pending);
232 rcu_read_unlock();
233 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
234 error_sector);
235 rdev_dec_pending(rdev, mddev);
236 rcu_read_lock();
237 }
238 }
239 }
240 rcu_read_unlock();
241 return ret;
242 }
243
244 /*
245 * Careful, this can execute in IRQ contexts as well!
246 */
247 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
248 {
249 multipath_conf_t *conf = mddev_to_conf(mddev);
250
251 if (conf->working_disks <= 1) {
252 /*
253 * Uh oh, we can do nothing if this is our last path, but
254 * first check if this is a queued request for a device
255 * which has just failed.
256 */
257 printk(KERN_ALERT
258 "multipath: only one IO path left and IO error.\n");
259 /* leave it active... it's all we have */
260 } else {
261 /*
262 * Mark disk as unusable
263 */
264 if (!test_bit(Faulty, &rdev->flags)) {
265 char b[BDEVNAME_SIZE];
266 clear_bit(In_sync, &rdev->flags);
267 set_bit(Faulty, &rdev->flags);
268 mddev->sb_dirty = 1;
269 conf->working_disks--;
270 printk(KERN_ALERT "multipath: IO failure on %s,"
271 " disabling IO path. \n Operation continuing"
272 " on %d IO paths.\n",
273 bdevname (rdev->bdev,b),
274 conf->working_disks);
275 }
276 }
277 }
278
279 static void print_multipath_conf (multipath_conf_t *conf)
280 {
281 int i;
282 struct multipath_info *tmp;
283
284 printk("MULTIPATH conf printout:\n");
285 if (!conf) {
286 printk("(conf==NULL)\n");
287 return;
288 }
289 printk(" --- wd:%d rd:%d\n", conf->working_disks,
290 conf->raid_disks);
291
292 for (i = 0; i < conf->raid_disks; i++) {
293 char b[BDEVNAME_SIZE];
294 tmp = conf->multipaths + i;
295 if (tmp->rdev)
296 printk(" disk%d, o:%d, dev:%s\n",
297 i,!test_bit(Faulty, &tmp->rdev->flags),
298 bdevname(tmp->rdev->bdev,b));
299 }
300 }
301
302
303 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
304 {
305 multipath_conf_t *conf = mddev->private;
306 int found = 0;
307 int path;
308 struct multipath_info *p;
309
310 print_multipath_conf(conf);
311
312 for (path=0; path<mddev->raid_disks; path++)
313 if ((p=conf->multipaths+path)->rdev == NULL) {
314 blk_queue_stack_limits(mddev->queue,
315 rdev->bdev->bd_disk->queue);
316
317 /* as we don't honour merge_bvec_fn, we must never risk
318 * violating it, so limit ->max_sector to one PAGE, as
319 * a one page request is never in violation.
320 * (Note: it is very unlikely that a device with
321 * merge_bvec_fn will be involved in multipath.)
322 */
323 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
324 mddev->queue->max_sectors > (PAGE_SIZE>>9))
325 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
326
327 conf->working_disks++;
328 rdev->raid_disk = path;
329 set_bit(In_sync, &rdev->flags);
330 rcu_assign_pointer(p->rdev, rdev);
331 found = 1;
332 }
333
334 print_multipath_conf(conf);
335 return found;
336 }
337
338 static int multipath_remove_disk(mddev_t *mddev, int number)
339 {
340 multipath_conf_t *conf = mddev->private;
341 int err = 0;
342 mdk_rdev_t *rdev;
343 struct multipath_info *p = conf->multipaths + number;
344
345 print_multipath_conf(conf);
346
347 rdev = p->rdev;
348 if (rdev) {
349 if (test_bit(In_sync, &rdev->flags) ||
350 atomic_read(&rdev->nr_pending)) {
351 printk(KERN_ERR "hot-remove-disk, slot %d is identified" " but is still operational!\n", number);
352 err = -EBUSY;
353 goto abort;
354 }
355 p->rdev = NULL;
356 synchronize_rcu();
357 if (atomic_read(&rdev->nr_pending)) {
358 /* lost the race, try later */
359 err = -EBUSY;
360 p->rdev = rdev;
361 }
362 }
363 abort:
364
365 print_multipath_conf(conf);
366 return err;
367 }
368
369
370
371 /*
372 * This is a kernel thread which:
373 *
374 * 1. Retries failed read operations on working multipaths.
375 * 2. Updates the raid superblock when problems encounter.
376 * 3. Performs writes following reads for array syncronising.
377 */
378
379 static void multipathd (mddev_t *mddev)
380 {
381 struct multipath_bh *mp_bh;
382 struct bio *bio;
383 unsigned long flags;
384 multipath_conf_t *conf = mddev_to_conf(mddev);
385 struct list_head *head = &conf->retry_list;
386
387 md_check_recovery(mddev);
388 for (;;) {
389 char b[BDEVNAME_SIZE];
390 spin_lock_irqsave(&conf->device_lock, flags);
391 if (list_empty(head))
392 break;
393 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
394 list_del(head->prev);
395 spin_unlock_irqrestore(&conf->device_lock, flags);
396
397 bio = &mp_bh->bio;
398 bio->bi_sector = mp_bh->master_bio->bi_sector;
399
400 if ((mp_bh->path = multipath_map (conf))<0) {
401 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
402 " error for block %llu\n",
403 bdevname(bio->bi_bdev,b),
404 (unsigned long long)bio->bi_sector);
405 multipath_end_bh_io(mp_bh, -EIO);
406 } else {
407 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
408 " to another IO path\n",
409 bdevname(bio->bi_bdev,b),
410 (unsigned long long)bio->bi_sector);
411 *bio = *(mp_bh->master_bio);
412 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
413 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
414 bio->bi_rw |= (1 << BIO_RW_FAILFAST);
415 bio->bi_end_io = multipath_end_request;
416 bio->bi_private = mp_bh;
417 generic_make_request(bio);
418 }
419 }
420 spin_unlock_irqrestore(&conf->device_lock, flags);
421 }
422
423 static int multipath_run (mddev_t *mddev)
424 {
425 multipath_conf_t *conf;
426 int disk_idx;
427 struct multipath_info *disk;
428 mdk_rdev_t *rdev;
429 struct list_head *tmp;
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
442 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
443 mddev->private = conf;
444 if (!conf) {
445 printk(KERN_ERR
446 "multipath: couldn't allocate memory for %s\n",
447 mdname(mddev));
448 goto out;
449 }
450
451 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
452 GFP_KERNEL);
453 if (!conf->multipaths) {
454 printk(KERN_ERR
455 "multipath: couldn't allocate memory for %s\n",
456 mdname(mddev));
457 goto out_free_conf;
458 }
459
460 conf->working_disks = 0;
461 ITERATE_RDEV(mddev,rdev,tmp) {
462 disk_idx = rdev->raid_disk;
463 if (disk_idx < 0 ||
464 disk_idx >= mddev->raid_disks)
465 continue;
466
467 disk = conf->multipaths + disk_idx;
468 disk->rdev = rdev;
469
470 blk_queue_stack_limits(mddev->queue,
471 rdev->bdev->bd_disk->queue);
472 /* as we don't honour merge_bvec_fn, we must never risk
473 * violating it, not that we ever expect a device with
474 * a merge_bvec_fn to be involved in multipath */
475 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
476 mddev->queue->max_sectors > (PAGE_SIZE>>9))
477 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
478
479 if (!test_bit(Faulty, &rdev->flags))
480 conf->working_disks++;
481 }
482
483 conf->raid_disks = mddev->raid_disks;
484 mddev->sb_dirty = 1;
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(NR_RESERVED_BUFS,
497 mp_pool_alloc, mp_pool_free,
498 NULL);
499 if (conf->pool == NULL) {
500 printk(KERN_ERR
501 "multipath: couldn't allocate memory for %s\n",
502 mdname(mddev));
503 goto out_free_conf;
504 }
505
506 {
507 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
508 if (!mddev->thread) {
509 printk(KERN_ERR "multipath: couldn't allocate thread"
510 " for %s\n", mdname(mddev));
511 goto out_free_conf;
512 }
513 }
514
515 printk(KERN_INFO
516 "multipath: array %s active with %d out of %d IO paths\n",
517 mdname(mddev), conf->working_disks, mddev->raid_disks);
518 /*
519 * Ok, everything is just fine now
520 */
521 mddev->array_size = mddev->size;
522
523 mddev->queue->unplug_fn = multipath_unplug;
524 mddev->queue->issue_flush_fn = multipath_issue_flush;
525
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_to_conf(mddev);
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 };
566
567 static int __init multipath_init (void)
568 {
569 return register_md_personality (&multipath_personality);
570 }
571
572 static void __exit multipath_exit (void)
573 {
574 unregister_md_personality (&multipath_personality);
575 }
576
577 module_init(multipath_init);
578 module_exit(multipath_exit);
579 MODULE_LICENSE("GPL");
580 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
581 MODULE_ALIAS("md-multipath");
582 MODULE_ALIAS("md-level--4");
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