2 * multipath.c : Multiple Devices driver for Linux
4 * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
6 * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
8 * MULTIPATH management functions.
10 * derived from raid1.c.
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)
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.
22 #include <linux/blkdev.h>
23 #include <linux/raid/md_u.h>
24 #include <linux/seq_file.h>
26 #include "multipath.h"
28 #define MAX_WORK_PER_DISK 128
30 #define NR_RESERVED_BUFS 32
33 static int multipath_map (multipath_conf_t *conf)
35 int i, disks = conf->raid_disks;
38 * Later we do read balancing on the read side
39 * now we use the first available disk.
43 for (i = 0; i < disks; i++) {
44 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
45 if (rdev && test_bit(In_sync, &rdev->flags)) {
46 atomic_inc(&rdev->nr_pending);
53 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
57 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
60 mddev_t *mddev = mp_bh->mddev;
61 multipath_conf_t *conf = mddev->private;
63 spin_lock_irqsave(&conf->device_lock, flags);
64 list_add(&mp_bh->retry_list, &conf->retry_list);
65 spin_unlock_irqrestore(&conf->device_lock, flags);
66 md_wakeup_thread(mddev->thread);
71 * multipath_end_bh_io() is called when we have finished servicing a multipathed
72 * operation and are ready to return a success/failure code to the buffer
75 static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
77 struct bio *bio = mp_bh->master_bio;
78 multipath_conf_t *conf = mp_bh->mddev->private;
81 mempool_free(mp_bh, conf->pool);
84 static void multipath_end_request(struct bio *bio, int error)
86 int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
87 struct multipath_bh *mp_bh = bio->bi_private;
88 multipath_conf_t *conf = mp_bh->mddev->private;
89 mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
92 multipath_end_bh_io(mp_bh, 0);
93 else if (!bio_rw_flagged(bio, BIO_RW_AHEAD)) {
97 char b[BDEVNAME_SIZE];
98 md_error (mp_bh->mddev, rdev);
99 printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
100 bdevname(rdev->bdev,b),
101 (unsigned long long)bio->bi_sector);
102 multipath_reschedule_retry(mp_bh);
104 multipath_end_bh_io(mp_bh, error);
105 rdev_dec_pending(rdev, conf->mddev);
108 static void unplug_slaves(mddev_t *mddev)
110 multipath_conf_t *conf = mddev->private;
114 for (i=0; i<mddev->raid_disks; i++) {
115 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
116 if (rdev && !test_bit(Faulty, &rdev->flags)
117 && atomic_read(&rdev->nr_pending)) {
118 struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
120 atomic_inc(&rdev->nr_pending);
125 rdev_dec_pending(rdev, mddev);
132 static void multipath_unplug(struct request_queue *q)
134 unplug_slaves(q->queuedata);
138 static int multipath_make_request(mddev_t *mddev, struct bio * bio)
140 multipath_conf_t *conf = mddev->private;
141 struct multipath_bh * mp_bh;
142 struct multipath_info *multipath;
144 if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER))) {
145 md_barrier_request(mddev, bio);
149 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
151 mp_bh->master_bio = bio;
152 mp_bh->mddev = mddev;
154 mp_bh->path = multipath_map(conf);
155 if (mp_bh->path < 0) {
156 bio_endio(bio, -EIO);
157 mempool_free(mp_bh, conf->pool);
160 multipath = conf->multipaths + mp_bh->path;
163 mp_bh->bio.bi_sector += multipath->rdev->data_offset;
164 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
165 mp_bh->bio.bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
166 mp_bh->bio.bi_end_io = multipath_end_request;
167 mp_bh->bio.bi_private = mp_bh;
168 generic_make_request(&mp_bh->bio);
172 static void multipath_status (struct seq_file *seq, mddev_t *mddev)
174 multipath_conf_t *conf = mddev->private;
177 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
178 conf->working_disks);
179 for (i = 0; i < conf->raid_disks; i++)
180 seq_printf (seq, "%s",
181 conf->multipaths[i].rdev &&
182 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
183 seq_printf (seq, "]");
186 static int multipath_congested(void *data, int bits)
188 mddev_t *mddev = data;
189 multipath_conf_t *conf = mddev->private;
192 if (mddev_congested(mddev, bits))
196 for (i = 0; i < mddev->raid_disks ; i++) {
197 mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
198 if (rdev && !test_bit(Faulty, &rdev->flags)) {
199 struct request_queue *q = bdev_get_queue(rdev->bdev);
201 ret |= bdi_congested(&q->backing_dev_info, bits);
202 /* Just like multipath_map, we just check the
203 * first available device
213 * Careful, this can execute in IRQ contexts as well!
215 static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
217 multipath_conf_t *conf = mddev->private;
219 if (conf->working_disks <= 1) {
221 * Uh oh, we can do nothing if this is our last path, but
222 * first check if this is a queued request for a device
223 * which has just failed.
226 "multipath: only one IO path left and IO error.\n");
227 /* leave it active... it's all we have */
230 * Mark disk as unusable
232 if (!test_bit(Faulty, &rdev->flags)) {
233 char b[BDEVNAME_SIZE];
234 clear_bit(In_sync, &rdev->flags);
235 set_bit(Faulty, &rdev->flags);
236 set_bit(MD_CHANGE_DEVS, &mddev->flags);
237 conf->working_disks--;
239 printk(KERN_ALERT "multipath: IO failure on %s,"
240 " disabling IO path.\n"
241 "multipath: Operation continuing"
242 " on %d IO paths.\n",
243 bdevname (rdev->bdev,b),
244 conf->working_disks);
249 static void print_multipath_conf (multipath_conf_t *conf)
252 struct multipath_info *tmp;
254 printk("MULTIPATH conf printout:\n");
256 printk("(conf==NULL)\n");
259 printk(" --- wd:%d rd:%d\n", conf->working_disks,
262 for (i = 0; i < conf->raid_disks; i++) {
263 char b[BDEVNAME_SIZE];
264 tmp = conf->multipaths + i;
266 printk(" disk%d, o:%d, dev:%s\n",
267 i,!test_bit(Faulty, &tmp->rdev->flags),
268 bdevname(tmp->rdev->bdev,b));
273 static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
275 multipath_conf_t *conf = mddev->private;
276 struct request_queue *q;
279 struct multipath_info *p;
281 int last = mddev->raid_disks - 1;
283 if (rdev->raid_disk >= 0)
284 first = last = rdev->raid_disk;
286 print_multipath_conf(conf);
288 for (path = first; path <= last; path++)
289 if ((p=conf->multipaths+path)->rdev == NULL) {
290 q = rdev->bdev->bd_disk->queue;
291 disk_stack_limits(mddev->gendisk, rdev->bdev,
292 rdev->data_offset << 9);
294 /* as we don't honour merge_bvec_fn, we must never risk
295 * violating it, so limit ->max_segments to one, lying
296 * within a single page.
297 * (Note: it is very unlikely that a device with
298 * merge_bvec_fn will be involved in multipath.)
300 if (q->merge_bvec_fn) {
301 blk_queue_max_segments(mddev->queue, 1);
302 blk_queue_segment_boundary(mddev->queue,
303 PAGE_CACHE_SIZE - 1);
306 conf->working_disks++;
308 rdev->raid_disk = path;
309 set_bit(In_sync, &rdev->flags);
310 rcu_assign_pointer(p->rdev, rdev);
312 md_integrity_add_rdev(rdev, mddev);
316 print_multipath_conf(conf);
321 static int multipath_remove_disk(mddev_t *mddev, int number)
323 multipath_conf_t *conf = mddev->private;
326 struct multipath_info *p = conf->multipaths + number;
328 print_multipath_conf(conf);
332 if (test_bit(In_sync, &rdev->flags) ||
333 atomic_read(&rdev->nr_pending)) {
334 printk(KERN_ERR "hot-remove-disk, slot %d is identified"
335 " but is still operational!\n", number);
341 if (atomic_read(&rdev->nr_pending)) {
342 /* lost the race, try later */
347 md_integrity_register(mddev);
351 print_multipath_conf(conf);
358 * This is a kernel thread which:
360 * 1. Retries failed read operations on working multipaths.
361 * 2. Updates the raid superblock when problems encounter.
362 * 3. Performs writes following reads for array syncronising.
365 static void multipathd (mddev_t *mddev)
367 struct multipath_bh *mp_bh;
370 multipath_conf_t *conf = mddev->private;
371 struct list_head *head = &conf->retry_list;
373 md_check_recovery(mddev);
375 char b[BDEVNAME_SIZE];
376 spin_lock_irqsave(&conf->device_lock, flags);
377 if (list_empty(head))
379 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
380 list_del(head->prev);
381 spin_unlock_irqrestore(&conf->device_lock, flags);
384 bio->bi_sector = mp_bh->master_bio->bi_sector;
386 if ((mp_bh->path = multipath_map (conf))<0) {
387 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
388 " error for block %llu\n",
389 bdevname(bio->bi_bdev,b),
390 (unsigned long long)bio->bi_sector);
391 multipath_end_bh_io(mp_bh, -EIO);
393 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
394 " to another IO path\n",
395 bdevname(bio->bi_bdev,b),
396 (unsigned long long)bio->bi_sector);
397 *bio = *(mp_bh->master_bio);
398 bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
399 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
400 bio->bi_rw |= (1 << BIO_RW_FAILFAST_TRANSPORT);
401 bio->bi_end_io = multipath_end_request;
402 bio->bi_private = mp_bh;
403 generic_make_request(bio);
406 spin_unlock_irqrestore(&conf->device_lock, flags);
409 static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
411 WARN_ONCE(sectors || raid_disks,
412 "%s does not support generic reshape\n", __func__);
414 return mddev->dev_sectors;
417 static int multipath_run (mddev_t *mddev)
419 multipath_conf_t *conf;
421 struct multipath_info *disk;
424 if (md_check_no_bitmap(mddev))
427 if (mddev->level != LEVEL_MULTIPATH) {
428 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
429 mdname(mddev), mddev->level);
433 * copy the already verified devices into our private MULTIPATH
434 * bookkeeping area. [whatever we allocate in multipath_run(),
435 * should be freed in multipath_stop()]
437 mddev->queue->queue_lock = &mddev->queue->__queue_lock;
439 conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
440 mddev->private = conf;
443 "multipath: couldn't allocate memory for %s\n",
448 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
450 if (!conf->multipaths) {
452 "multipath: couldn't allocate memory for %s\n",
457 conf->working_disks = 0;
458 list_for_each_entry(rdev, &mddev->disks, same_set) {
459 disk_idx = rdev->raid_disk;
461 disk_idx >= mddev->raid_disks)
464 disk = conf->multipaths + disk_idx;
466 disk_stack_limits(mddev->gendisk, rdev->bdev,
467 rdev->data_offset << 9);
469 /* as we don't honour merge_bvec_fn, we must never risk
470 * violating it, not that we ever expect a device with
471 * a merge_bvec_fn to be involved in multipath */
472 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
473 blk_queue_max_segments(mddev->queue, 1);
474 blk_queue_segment_boundary(mddev->queue,
475 PAGE_CACHE_SIZE - 1);
478 if (!test_bit(Faulty, &rdev->flags))
479 conf->working_disks++;
482 conf->raid_disks = mddev->raid_disks;
484 spin_lock_init(&conf->device_lock);
485 INIT_LIST_HEAD(&conf->retry_list);
487 if (!conf->working_disks) {
488 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
492 mddev->degraded = conf->raid_disks - conf->working_disks;
494 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
495 sizeof(struct multipath_bh));
496 if (conf->pool == NULL) {
498 "multipath: couldn't allocate memory for %s\n",
504 mddev->thread = md_register_thread(multipathd, mddev, NULL);
505 if (!mddev->thread) {
506 printk(KERN_ERR "multipath: couldn't allocate thread"
507 " for %s\n", mdname(mddev));
513 "multipath: array %s active with %d out of %d IO paths\n",
514 mdname(mddev), conf->working_disks, mddev->raid_disks);
516 * Ok, everything is just fine now
518 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
520 mddev->queue->unplug_fn = multipath_unplug;
521 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
522 mddev->queue->backing_dev_info.congested_data = mddev;
523 md_integrity_register(mddev);
528 mempool_destroy(conf->pool);
529 kfree(conf->multipaths);
531 mddev->private = NULL;
537 static int multipath_stop (mddev_t *mddev)
539 multipath_conf_t *conf = mddev->private;
541 md_unregister_thread(mddev->thread);
542 mddev->thread = NULL;
543 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
544 mempool_destroy(conf->pool);
545 kfree(conf->multipaths);
547 mddev->private = NULL;
551 static struct mdk_personality multipath_personality =
554 .level = LEVEL_MULTIPATH,
555 .owner = THIS_MODULE,
556 .make_request = multipath_make_request,
557 .run = multipath_run,
558 .stop = multipath_stop,
559 .status = multipath_status,
560 .error_handler = multipath_error,
561 .hot_add_disk = multipath_add_disk,
562 .hot_remove_disk= multipath_remove_disk,
563 .size = multipath_size,
566 static int __init multipath_init (void)
568 return register_md_personality (&multipath_personality);
571 static void __exit multipath_exit (void)
573 unregister_md_personality (&multipath_personality);
576 module_init(multipath_init);
577 module_exit(multipath_exit);
578 MODULE_LICENSE("GPL");
579 MODULE_DESCRIPTION("simple multi-path personality for MD");
580 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
581 MODULE_ALIAS("md-multipath");
582 MODULE_ALIAS("md-level--4");