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/module.h>
24 #include <linux/raid/md_u.h>
25 #include <linux/seq_file.h>
26 #include <linux/slab.h>
28 #include "multipath.h"
30 #define MAX_WORK_PER_DISK 128
32 #define NR_RESERVED_BUFS 32
34 static int multipath_map (struct mpconf *conf)
36 int i, disks = conf->raid_disks;
39 * Later we do read balancing on the read side
40 * now we use the first available disk.
44 for (i = 0; i < disks; i++) {
45 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
46 if (rdev && test_bit(In_sync, &rdev->flags)) {
47 atomic_inc(&rdev->nr_pending);
54 printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
58 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
61 struct mddev *mddev = mp_bh->mddev;
62 struct mpconf *conf = mddev->private;
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);
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 struct mpconf *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 struct mpconf *conf = mp_bh->mddev->private;
89 struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
92 multipath_end_bh_io(mp_bh, 0);
93 else if (!(bio->bi_rw & REQ_RAHEAD)) {
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_iter.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 multipath_make_request(struct mddev *mddev, struct bio * bio)
110 struct mpconf *conf = mddev->private;
111 struct multipath_bh * mp_bh;
112 struct multipath_info *multipath;
114 if (unlikely(bio->bi_rw & REQ_FLUSH)) {
115 md_flush_request(mddev, bio);
119 mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
121 mp_bh->master_bio = bio;
122 mp_bh->mddev = mddev;
124 mp_bh->path = multipath_map(conf);
125 if (mp_bh->path < 0) {
126 bio_endio(bio, -EIO);
127 mempool_free(mp_bh, conf->pool);
130 multipath = conf->multipaths + mp_bh->path;
133 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
134 mp_bh->bio.bi_bdev = multipath->rdev->bdev;
135 mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT;
136 mp_bh->bio.bi_end_io = multipath_end_request;
137 mp_bh->bio.bi_private = mp_bh;
138 generic_make_request(&mp_bh->bio);
142 static void multipath_status (struct seq_file *seq, struct mddev *mddev)
144 struct mpconf *conf = mddev->private;
147 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
148 conf->raid_disks - mddev->degraded);
149 for (i = 0; i < conf->raid_disks; i++)
150 seq_printf (seq, "%s",
151 conf->multipaths[i].rdev &&
152 test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
153 seq_printf (seq, "]");
156 static int multipath_congested(void *data, int bits)
158 struct mddev *mddev = data;
159 struct mpconf *conf = mddev->private;
162 if (mddev_congested(mddev, bits))
166 for (i = 0; i < mddev->raid_disks ; i++) {
167 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
168 if (rdev && !test_bit(Faulty, &rdev->flags)) {
169 struct request_queue *q = bdev_get_queue(rdev->bdev);
171 ret |= bdi_congested(&q->backing_dev_info, bits);
172 /* Just like multipath_map, we just check the
173 * first available device
183 * Careful, this can execute in IRQ contexts as well!
185 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
187 struct mpconf *conf = mddev->private;
188 char b[BDEVNAME_SIZE];
190 if (conf->raid_disks - mddev->degraded <= 1) {
192 * Uh oh, we can do nothing if this is our last path, but
193 * first check if this is a queued request for a device
194 * which has just failed.
197 "multipath: only one IO path left and IO error.\n");
198 /* leave it active... it's all we have */
202 * Mark disk as unusable
204 if (test_and_clear_bit(In_sync, &rdev->flags)) {
206 spin_lock_irqsave(&conf->device_lock, flags);
208 spin_unlock_irqrestore(&conf->device_lock, flags);
210 set_bit(Faulty, &rdev->flags);
211 set_bit(MD_CHANGE_DEVS, &mddev->flags);
212 printk(KERN_ALERT "multipath: IO failure on %s,"
213 " disabling IO path.\n"
214 "multipath: Operation continuing"
215 " on %d IO paths.\n",
216 bdevname(rdev->bdev, b),
217 conf->raid_disks - mddev->degraded);
220 static void print_multipath_conf (struct mpconf *conf)
223 struct multipath_info *tmp;
225 printk("MULTIPATH conf printout:\n");
227 printk("(conf==NULL)\n");
230 printk(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
233 for (i = 0; i < conf->raid_disks; i++) {
234 char b[BDEVNAME_SIZE];
235 tmp = conf->multipaths + i;
237 printk(" disk%d, o:%d, dev:%s\n",
238 i,!test_bit(Faulty, &tmp->rdev->flags),
239 bdevname(tmp->rdev->bdev,b));
243 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
245 struct mpconf *conf = mddev->private;
246 struct request_queue *q;
249 struct multipath_info *p;
251 int last = mddev->raid_disks - 1;
253 if (rdev->raid_disk >= 0)
254 first = last = rdev->raid_disk;
256 print_multipath_conf(conf);
258 for (path = first; path <= last; path++)
259 if ((p=conf->multipaths+path)->rdev == NULL) {
260 q = rdev->bdev->bd_disk->queue;
261 disk_stack_limits(mddev->gendisk, rdev->bdev,
262 rdev->data_offset << 9);
264 /* as we don't honour merge_bvec_fn, we must never risk
265 * violating it, so limit ->max_segments to one, lying
266 * within a single page.
267 * (Note: it is very unlikely that a device with
268 * merge_bvec_fn will be involved in multipath.)
270 if (q->merge_bvec_fn) {
271 blk_queue_max_segments(mddev->queue, 1);
272 blk_queue_segment_boundary(mddev->queue,
273 PAGE_CACHE_SIZE - 1);
276 spin_lock_irq(&conf->device_lock);
278 rdev->raid_disk = path;
279 set_bit(In_sync, &rdev->flags);
280 spin_unlock_irq(&conf->device_lock);
281 rcu_assign_pointer(p->rdev, rdev);
283 md_integrity_add_rdev(rdev, mddev);
287 print_multipath_conf(conf);
292 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
294 struct mpconf *conf = mddev->private;
296 int number = rdev->raid_disk;
297 struct multipath_info *p = conf->multipaths + number;
299 print_multipath_conf(conf);
301 if (rdev == p->rdev) {
302 if (test_bit(In_sync, &rdev->flags) ||
303 atomic_read(&rdev->nr_pending)) {
304 printk(KERN_ERR "hot-remove-disk, slot %d is identified"
305 " but is still operational!\n", number);
311 if (atomic_read(&rdev->nr_pending)) {
312 /* lost the race, try later */
317 err = md_integrity_register(mddev);
321 print_multipath_conf(conf);
326 * This is a kernel thread which:
328 * 1. Retries failed read operations on working multipaths.
329 * 2. Updates the raid superblock when problems encounter.
330 * 3. Performs writes following reads for array syncronising.
333 static void multipathd(struct md_thread *thread)
335 struct mddev *mddev = thread->mddev;
336 struct multipath_bh *mp_bh;
339 struct mpconf *conf = mddev->private;
340 struct list_head *head = &conf->retry_list;
342 md_check_recovery(mddev);
344 char b[BDEVNAME_SIZE];
345 spin_lock_irqsave(&conf->device_lock, flags);
346 if (list_empty(head))
348 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
349 list_del(head->prev);
350 spin_unlock_irqrestore(&conf->device_lock, flags);
353 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
355 if ((mp_bh->path = multipath_map (conf))<0) {
356 printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
357 " error for block %llu\n",
358 bdevname(bio->bi_bdev,b),
359 (unsigned long long)bio->bi_iter.bi_sector);
360 multipath_end_bh_io(mp_bh, -EIO);
362 printk(KERN_ERR "multipath: %s: redirecting sector %llu"
363 " to another IO path\n",
364 bdevname(bio->bi_bdev,b),
365 (unsigned long long)bio->bi_iter.bi_sector);
366 *bio = *(mp_bh->master_bio);
367 bio->bi_iter.bi_sector +=
368 conf->multipaths[mp_bh->path].rdev->data_offset;
369 bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
370 bio->bi_rw |= REQ_FAILFAST_TRANSPORT;
371 bio->bi_end_io = multipath_end_request;
372 bio->bi_private = mp_bh;
373 generic_make_request(bio);
376 spin_unlock_irqrestore(&conf->device_lock, flags);
379 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
381 WARN_ONCE(sectors || raid_disks,
382 "%s does not support generic reshape\n", __func__);
384 return mddev->dev_sectors;
387 static int multipath_run (struct mddev *mddev)
391 struct multipath_info *disk;
392 struct md_rdev *rdev;
395 if (md_check_no_bitmap(mddev))
398 if (mddev->level != LEVEL_MULTIPATH) {
399 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
400 mdname(mddev), mddev->level);
404 * copy the already verified devices into our private MULTIPATH
405 * bookkeeping area. [whatever we allocate in multipath_run(),
406 * should be freed in multipath_stop()]
409 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
410 mddev->private = conf;
413 "multipath: couldn't allocate memory for %s\n",
418 conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
420 if (!conf->multipaths) {
422 "multipath: couldn't allocate memory for %s\n",
428 rdev_for_each(rdev, mddev) {
429 disk_idx = rdev->raid_disk;
431 disk_idx >= mddev->raid_disks)
434 disk = conf->multipaths + disk_idx;
436 disk_stack_limits(mddev->gendisk, rdev->bdev,
437 rdev->data_offset << 9);
439 /* as we don't honour merge_bvec_fn, we must never risk
440 * violating it, not that we ever expect a device with
441 * a merge_bvec_fn to be involved in multipath */
442 if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
443 blk_queue_max_segments(mddev->queue, 1);
444 blk_queue_segment_boundary(mddev->queue,
445 PAGE_CACHE_SIZE - 1);
448 if (!test_bit(Faulty, &rdev->flags))
452 conf->raid_disks = mddev->raid_disks;
454 spin_lock_init(&conf->device_lock);
455 INIT_LIST_HEAD(&conf->retry_list);
457 if (!working_disks) {
458 printk(KERN_ERR "multipath: no operational IO paths for %s\n",
462 mddev->degraded = conf->raid_disks - working_disks;
464 conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
465 sizeof(struct multipath_bh));
466 if (conf->pool == NULL) {
468 "multipath: couldn't allocate memory for %s\n",
474 mddev->thread = md_register_thread(multipathd, mddev,
476 if (!mddev->thread) {
477 printk(KERN_ERR "multipath: couldn't allocate thread"
478 " for %s\n", mdname(mddev));
484 "multipath: array %s active with %d out of %d IO paths\n",
485 mdname(mddev), conf->raid_disks - mddev->degraded,
488 * Ok, everything is just fine now
490 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
492 mddev->queue->backing_dev_info.congested_fn = multipath_congested;
493 mddev->queue->backing_dev_info.congested_data = mddev;
495 if (md_integrity_register(mddev))
502 mempool_destroy(conf->pool);
503 kfree(conf->multipaths);
505 mddev->private = NULL;
510 static int multipath_stop (struct mddev *mddev)
512 struct mpconf *conf = mddev->private;
514 md_unregister_thread(&mddev->thread);
515 blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
516 mempool_destroy(conf->pool);
517 kfree(conf->multipaths);
519 mddev->private = NULL;
523 static struct md_personality multipath_personality =
526 .level = LEVEL_MULTIPATH,
527 .owner = THIS_MODULE,
528 .make_request = multipath_make_request,
529 .run = multipath_run,
530 .stop = multipath_stop,
531 .status = multipath_status,
532 .error_handler = multipath_error,
533 .hot_add_disk = multipath_add_disk,
534 .hot_remove_disk= multipath_remove_disk,
535 .size = multipath_size,
538 static int __init multipath_init (void)
540 return register_md_personality (&multipath_personality);
543 static void __exit multipath_exit (void)
545 unregister_md_personality (&multipath_personality);
548 module_init(multipath_init);
549 module_exit(multipath_exit);
550 MODULE_LICENSE("GPL");
551 MODULE_DESCRIPTION("simple multi-path personality for MD");
552 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
553 MODULE_ALIAS("md-multipath");
554 MODULE_ALIAS("md-level--4");