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[PATCH] Four level pagetables for ppc64
[linux-2.6/sactl.git] / drivers / md / multipath.c
blob2d2ca7fa0265261a71e2493e88b68403cc902c57
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 mdk_personality_t multipath_personality;
39
40
41 static void *mp_pool_alloc(unsigned int __nocast gfp_flags, void *data)
42 {
43 struct multipath_bh *mpb;
44 mpb = kmalloc(sizeof(*mpb), gfp_flags);
45 if (mpb)
46 memset(mpb, 0, sizeof(*mpb));
47 return mpb;
48 }
49
50 static void mp_pool_free(void *mpb, void *data)
51 {
52 kfree(mpb);
53 }
54
55 static int multipath_map (multipath_conf_t *conf)
56 {
57 int i, disks = conf->raid_disks;
58
59 /*
60 * Later we do read balancing on the read side
61 * now we use the first available disk.
62 */
63
64 rcu_read_lock();
65 for (i = 0; i < disks; i++) {
66 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
67 if (rdev && rdev->in_sync) {
68 atomic_inc(&rdev->nr_pending);
69 rcu_read_unlock();
70 return i;
71 }
72 }
73 rcu_read_unlock();
74
75 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
76 return (-1);
77 }
78
79 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
80 {
81 unsigned long flags;
82 mddev_t *mddev = mp_bh->mddev;
83 multipath_conf_t *conf = mddev_to_conf(mddev);
84
85 spin_lock_irqsave(&conf->device_lock, flags);
86 list_add(&mp_bh->retry_list, &conf->retry_list);
87 spin_unlock_irqrestore(&conf->device_lock, flags);
88 md_wakeup_thread(mddev->thread);
89 }
90
91
92 /*
93 * multipath_end_bh_io() is called when we have finished servicing a multipathed
94 * operation and are ready to return a success/failure code to the buffer
95 * cache layer.
96 */
97 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
98 {
99 struct bio *bio = mp_bh->master_bio;
100 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
101
102 bio_endio(bio, bio->bi_size, err);
103 mempool_free(mp_bh, conf->pool);
104 }
105
106 static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
107 int error)
108 {
109 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
110 struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
111 multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
112 mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
113
114 if (bio->bi_size)
115 return 1;
116
117 if (uptodate)
118 multipath_end_bh_io(mp_bh, 0);
119 else if (!bio_rw_ahead(bio)) {
120 /*
121 * oops, IO error:
122 */
123 char b[BDEVNAME_SIZE];
124 md_error (mp_bh->mddev, rdev);
125 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
126 bdevname(rdev->bdev,b),
127 (unsigned long long)bio->bi_sector);
128 multipath_reschedule_retry(mp_bh);
129 } else
130 multipath_end_bh_io(mp_bh, error);
131 rdev_dec_pending(rdev, conf->mddev);
132 return 0;
133 }
134
135 static void unplug_slaves(mddev_t *mddev)
136 {
137 multipath_conf_t *conf = mddev_to_conf(mddev);
138 int i;
139
140 rcu_read_lock();
141 for (i=0; i<mddev->raid_disks; i++) {
142 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
143 if (rdev && !rdev->faulty && atomic_read(&rdev->nr_pending)) {
144 request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
145
146 atomic_inc(&rdev->nr_pending);
147 rcu_read_unlock();
148
149 if (r_queue->unplug_fn)
150 r_queue->unplug_fn(r_queue);
151
152 rdev_dec_pending(rdev, mddev);
153 rcu_read_lock();
154 }
155 }
156 rcu_read_unlock();
157 }
158
159 static void multipath_unplug(request_queue_t *q)
160 {
161 unplug_slaves(q->queuedata);
162 }
163
164
165 static int multipath_make_request (request_queue_t *q, struct bio * bio)
166 {
167 mddev_t *mddev = q->queuedata;
168 multipath_conf_t *conf = mddev_to_conf(mddev);
169 struct multipath_bh * mp_bh;
170 struct multipath_info *multipath;
171
172 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
173
174 mp_bh->master_bio = bio;
175 mp_bh->mddev = mddev;
176
177 if (bio_data_dir(bio)==WRITE) {
178 disk_stat_inc(mddev->gendisk, writes);
179 disk_stat_add(mddev->gendisk, write_sectors, bio_sectors(bio));
180 } else {
181 disk_stat_inc(mddev->gendisk, reads);
182 disk_stat_add(mddev->gendisk, read_sectors, bio_sectors(bio));
183 }
184
185 mp_bh->path = multipath_map(conf);
186 if (mp_bh->path < 0) {
187 bio_endio(bio, bio->bi_size, -EIO);
188 mempool_free(mp_bh, conf->pool);
189 return 0;
190 }
191 multipath = conf->multipaths + mp_bh->path;
192
193 mp_bh->bio = *bio;
194 mp_bh->bio.bi_sector += multipath->rdev->data_offset;
195 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
196 mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST);
197 mp_bh->bio.bi_end_io = multipath_end_request;
198 mp_bh->bio.bi_private = mp_bh;
199 generic_make_request(&mp_bh->bio);
200 return 0;
201 }
202
203 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
204 {
205 multipath_conf_t *conf = mddev_to_conf(mddev);
206 int i;
207
208 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
209 conf->working_disks);
210 for (i = 0; i < conf->raid_disks; i++)
211 seq_printf (seq, "%s",
212 conf->multipaths[i].rdev &&
213 conf->multipaths[i].rdev->in_sync ? "U" : "_");
214 seq_printf (seq, "]");
215 }
216
217 static int multipath_issue_flush(request_queue_t *q, struct gendisk *disk,
218 sector_t *error_sector)
219 {
220 mddev_t *mddev = q->queuedata;
221 multipath_conf_t *conf = mddev_to_conf(mddev);
222 int i, ret = 0;
223
224 rcu_read_lock();
225 for (i=0; i<mddev->raid_disks && ret == 0; i++) {
226 mdk_rdev_t *rdev = conf->multipaths[i].rdev;
227 if (rdev && !rdev->faulty) {
228 struct block_device *bdev = rdev->bdev;
229 request_queue_t *r_queue = bdev_get_queue(bdev);
230
231 if (!r_queue->issue_flush_fn)
232 ret = -EOPNOTSUPP;
233 else {
234 atomic_inc(&rdev->nr_pending);
235 rcu_read_unlock();
236 ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
237 error_sector);
238 rdev_dec_pending(rdev, mddev);
239 rcu_read_lock();
240 }
241 }
242 }
243 rcu_read_unlock();
244 return ret;
245 }
246
247 /*
248 * Careful, this can execute in IRQ contexts as well!
249 */
250 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
251 {
252 multipath_conf_t *conf = mddev_to_conf(mddev);
253
254 if (conf->working_disks <= 1) {
255 /*
256 * Uh oh, we can do nothing if this is our last path, but
257 * first check if this is a queued request for a device
258 * which has just failed.
259 */
260 printk(KERN_ALERT
261 "multipath: only one IO path left and IO error.\n");
262 /* leave it active... it's all we have */
263 } else {
264 /*
265 * Mark disk as unusable
266 */
267 if (!rdev->faulty) {
268 char b[BDEVNAME_SIZE];
269 rdev->in_sync = 0;
270 rdev->faulty = 1;
271 mddev->sb_dirty = 1;
272 conf->working_disks--;
273 printk(KERN_ALERT "multipath: IO failure on %s,"
274 " disabling IO path. \n Operation continuing"
275 " on %d IO paths.\n",
276 bdevname (rdev->bdev,b),
277 conf->working_disks);
278 }
279 }
280 }
281
282 static void print_multipath_conf (multipath_conf_t *conf)
283 {
284 int i;
285 struct multipath_info *tmp;
286
287 printk("MULTIPATH conf printout:\n");
288 if (!conf) {
289 printk("(conf==NULL)\n");
290 return;
291 }
292 printk(" --- wd:%d rd:%d\n", conf->working_disks,
293 conf->raid_disks);
294
295 for (i = 0; i < conf->raid_disks; i++) {
296 char b[BDEVNAME_SIZE];
297 tmp = conf->multipaths + i;
298 if (tmp->rdev)
299 printk(" disk%d, o:%d, dev:%s\n",
300 i,!tmp->rdev->faulty,
301 bdevname(tmp->rdev->bdev,b));
302 }
303 }
304
305
306 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
307 {
308 multipath_conf_t *conf = mddev->private;
309 int found = 0;
310 int path;
311 struct multipath_info *p;
312
313 print_multipath_conf(conf);
314
315 for (path=0; path<mddev->raid_disks; path++)
316 if ((p=conf->multipaths+path)->rdev == NULL) {
317 blk_queue_stack_limits(mddev->queue,
318 rdev->bdev->bd_disk->queue);
319
320 /* as we don't honour merge_bvec_fn, we must never risk
321 * violating it, so limit ->max_sector to one PAGE, as
322 * a one page request is never in violation.
323 * (Note: it is very unlikely that a device with
324 * merge_bvec_fn will be involved in multipath.)
325 */
326 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
327 mddev->queue->max_sectors > (PAGE_SIZE>>9))
328 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
329
330 conf->working_disks++;
331 rdev->raid_disk = path;
332 rdev->in_sync = 1;
333 p->rdev = rdev;
334 found = 1;
335 }
336
337 print_multipath_conf(conf);
338 return found;
339 }
340
341 static int multipath_remove_disk(mddev_t *mddev, int number)
342 {
343 multipath_conf_t *conf = mddev->private;
344 int err = 0;
345 mdk_rdev_t *rdev;
346 struct multipath_info *p = conf->multipaths + number;
347
348 print_multipath_conf(conf);
349
350 rdev = p->rdev;
351 if (rdev) {
352 if (rdev->in_sync ||
353 atomic_read(&rdev->nr_pending)) {
354 printk(KERN_ERR "hot-remove-disk, slot %d is identified" " but is still operational!\n", number);
355 err = -EBUSY;
356 goto abort;
357 }
358 p->rdev = NULL;
359 synchronize_rcu();
360 if (atomic_read(&rdev->nr_pending)) {
361 /* lost the race, try later */
362 err = -EBUSY;
363 p->rdev = rdev;
364 }
365 }
366 abort:
367
368 print_multipath_conf(conf);
369 return err;
370 }
371
372
373
374 /*
375 * This is a kernel thread which:
376 *
377 * 1. Retries failed read operations on working multipaths.
378 * 2. Updates the raid superblock when problems encounter.
379 * 3. Performs writes following reads for array syncronising.
380 */
381
382 static void multipathd (mddev_t *mddev)
383 {
384 struct multipath_bh *mp_bh;
385 struct bio *bio;
386 unsigned long flags;
387 multipath_conf_t *conf = mddev_to_conf(mddev);
388 struct list_head *head = &conf->retry_list;
389
390 md_check_recovery(mddev);
391 for (;;) {
392 char b[BDEVNAME_SIZE];
393 spin_lock_irqsave(&conf->device_lock, flags);
394 if (list_empty(head))
395 break;
396 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
397 list_del(head->prev);
398 spin_unlock_irqrestore(&conf->device_lock, flags);
399
400 bio = &mp_bh->bio;
401 bio->bi_sector = mp_bh->master_bio->bi_sector;
402
403 if ((mp_bh->path = multipath_map (conf))<0) {
404 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
405 " error for block %llu\n",
406 bdevname(bio->bi_bdev,b),
407 (unsigned long long)bio->bi_sector);
408 multipath_end_bh_io(mp_bh, -EIO);
409 } else {
410 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
411 " to another IO path\n",
412 bdevname(bio->bi_bdev,b),
413 (unsigned long long)bio->bi_sector);
414 *bio = *(mp_bh->master_bio);
415 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
416 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
417 bio->bi_rw |= (1 << BIO_RW_FAILFAST);
418 bio->bi_end_io = multipath_end_request;
419 bio->bi_private = mp_bh;
420 generic_make_request(bio);
421 }
422 }
423 spin_unlock_irqrestore(&conf->device_lock, flags);
424 }
425
426 static int multipath_run (mddev_t *mddev)
427 {
428 multipath_conf_t *conf;
429 int disk_idx;
430 struct multipath_info *disk;
431 mdk_rdev_t *rdev;
432 struct list_head *tmp;
433
434 if (mddev->level != LEVEL_MULTIPATH) {
435 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
436 mdname(mddev), mddev->level);
437 goto out;
438 }
439 /*
440 * copy the already verified devices into our private MULTIPATH
441 * bookkeeping area. [whatever we allocate in multipath_run(),
442 * should be freed in multipath_stop()]
443 */
444
445 conf = kmalloc(sizeof(multipath_conf_t), GFP_KERNEL);
446 mddev->private = conf;
447 if (!conf) {
448 printk(KERN_ERR
449 "multipath: couldn't allocate memory for %s\n",
450 mdname(mddev));
451 goto out;
452 }
453 memset(conf, 0, sizeof(*conf));
454
455 conf->multipaths = kmalloc(sizeof(struct multipath_info)*mddev->raid_disks,
456 GFP_KERNEL);
457 if (!conf->multipaths) {
458 printk(KERN_ERR
459 "multipath: couldn't allocate memory for %s\n",
460 mdname(mddev));
461 goto out_free_conf;
462 }
463 memset(conf->multipaths, 0, sizeof(struct multipath_info)*mddev->raid_disks);
464
465 conf->working_disks = 0;
466 ITERATE_RDEV(mddev,rdev,tmp) {
467 disk_idx = rdev->raid_disk;
468 if (disk_idx < 0 ||
469 disk_idx >= mddev->raid_disks)
470 continue;
471
472 disk = conf->multipaths + disk_idx;
473 disk->rdev = rdev;
474
475 blk_queue_stack_limits(mddev->queue,
476 rdev->bdev->bd_disk->queue);
477 /* as we don't honour merge_bvec_fn, we must never risk
478 * violating it, not that we ever expect a device with
479 * a merge_bvec_fn to be involved in multipath */
480 if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
481 mddev->queue->max_sectors > (PAGE_SIZE>>9))
482 blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
483
484 if (!rdev->faulty)
485 conf->working_disks++;
486 }
487
488 conf->raid_disks = mddev->raid_disks;
489 mddev->sb_dirty = 1;
490 conf->mddev = mddev;
491 spin_lock_init(&conf->device_lock);
492 INIT_LIST_HEAD(&conf->retry_list);
493
494 if (!conf->working_disks) {
495 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
496 mdname(mddev));
497 goto out_free_conf;
498 }
499 mddev->degraded = conf->raid_disks = conf->working_disks;
500
501 conf->pool = mempool_create(NR_RESERVED_BUFS,
502 mp_pool_alloc, mp_pool_free,
503 NULL);
504 if (conf->pool == NULL) {
505 printk(KERN_ERR
506 "multipath: couldn't allocate memory for %s\n",
507 mdname(mddev));
508 goto out_free_conf;
509 }
510
511 {
512 mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
513 if (!mddev->thread) {
514 printk(KERN_ERR "multipath: couldn't allocate thread"
515 " for %s\n", mdname(mddev));
516 goto out_free_conf;
517 }
518 }
519
520 printk(KERN_INFO
521 "multipath: array %s active with %d out of %d IO paths\n",
522 mdname(mddev), conf->working_disks, mddev->raid_disks);
523 /*
524 * Ok, everything is just fine now
525 */
526 mddev->array_size = mddev->size;
527
528 mddev->queue->unplug_fn = multipath_unplug;
529 mddev->queue->issue_flush_fn = multipath_issue_flush;
530
531 return 0;
532
533 out_free_conf:
534 if (conf->pool)
535 mempool_destroy(conf->pool);
536 kfree(conf->multipaths);
537 kfree(conf);
538 mddev->private = NULL;
539 out:
540 return -EIO;
541 }
542
543
544 static int multipath_stop (mddev_t *mddev)
545 {
546 multipath_conf_t *conf = mddev_to_conf(mddev);
547
548 md_unregister_thread(mddev->thread);
549 mddev->thread = NULL;
550 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
551 mempool_destroy(conf->pool);
552 kfree(conf->multipaths);
553 kfree(conf);
554 mddev->private = NULL;
555 return 0;
556 }
557
558 static mdk_personality_t multipath_personality=
559 {
560 .name = "multipath",
561 .owner = THIS_MODULE,
562 .make_request = multipath_make_request,
563 .run = multipath_run,
564 .stop = multipath_stop,
565 .status = multipath_status,
566 .error_handler = multipath_error,
567 .hot_add_disk = multipath_add_disk,
568 .hot_remove_disk= multipath_remove_disk,
569 };
570
571 static int __init multipath_init (void)
572 {
573 return register_md_personality (MULTIPATH, &multipath_personality);
574 }
575
576 static void __exit multipath_exit (void)
577 {
578 unregister_md_personality (MULTIPATH);
579 }
580
581 module_init(multipath_init);
582 module_exit(multipath_exit);
583 MODULE_LICENSE("GPL");
584 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
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