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/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>
29 #define MAJOR_NR MD_MAJOR
31 #define MD_PERSONALITY
33 #define MAX_WORK_PER_DISK 128
35 #define NR_RESERVED_BUFS 32
38 static mdk_personality_t multipath_personality
;
41 static void *mp_pool_alloc(gfp_t gfp_flags
, void *data
)
43 struct multipath_bh
*mpb
;
44 mpb
= kmalloc(sizeof(*mpb
), gfp_flags
);
46 memset(mpb
, 0, sizeof(*mpb
));
50 static void mp_pool_free(void *mpb
, void *data
)
55 static int multipath_map (multipath_conf_t
*conf
)
57 int i
, disks
= conf
->raid_disks
;
60 * Later we do read balancing on the read side
61 * now we use the first available disk.
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
);
75 printk(KERN_ERR
"multipath_map(): no more operational IO paths?\n");
79 static void multipath_reschedule_retry (struct multipath_bh
*mp_bh
)
82 mddev_t
*mddev
= mp_bh
->mddev
;
83 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
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
);
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
97 static void multipath_end_bh_io (struct multipath_bh
*mp_bh
, int err
)
99 struct bio
*bio
= mp_bh
->master_bio
;
100 multipath_conf_t
*conf
= mddev_to_conf(mp_bh
->mddev
);
102 bio_endio(bio
, bio
->bi_size
, err
);
103 mempool_free(mp_bh
, conf
->pool
);
106 static int multipath_end_request(struct bio
*bio
, unsigned int bytes_done
,
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
;
118 multipath_end_bh_io(mp_bh
, 0);
119 else if (!bio_rw_ahead(bio
)) {
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
);
130 multipath_end_bh_io(mp_bh
, error
);
131 rdev_dec_pending(rdev
, conf
->mddev
);
135 static void unplug_slaves(mddev_t
*mddev
)
137 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
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
);
146 atomic_inc(&rdev
->nr_pending
);
149 if (r_queue
->unplug_fn
)
150 r_queue
->unplug_fn(r_queue
);
152 rdev_dec_pending(rdev
, mddev
);
159 static void multipath_unplug(request_queue_t
*q
)
161 unplug_slaves(q
->queuedata
);
165 static int multipath_make_request (request_queue_t
*q
, struct bio
* bio
)
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 const int rw
= bio_data_dir(bio
);
173 if (unlikely(bio_barrier(bio
))) {
174 bio_endio(bio
, bio
->bi_size
, -EOPNOTSUPP
);
178 mp_bh
= mempool_alloc(conf
->pool
, GFP_NOIO
);
180 mp_bh
->master_bio
= bio
;
181 mp_bh
->mddev
= mddev
;
183 disk_stat_inc(mddev
->gendisk
, ios
[rw
]);
184 disk_stat_add(mddev
->gendisk
, sectors
[rw
], bio_sectors(bio
));
186 mp_bh
->path
= multipath_map(conf
);
187 if (mp_bh
->path
< 0) {
188 bio_endio(bio
, bio
->bi_size
, -EIO
);
189 mempool_free(mp_bh
, conf
->pool
);
192 multipath
= conf
->multipaths
+ mp_bh
->path
;
195 mp_bh
->bio
.bi_sector
+= multipath
->rdev
->data_offset
;
196 mp_bh
->bio
.bi_bdev
= multipath
->rdev
->bdev
;
197 mp_bh
->bio
.bi_rw
|= (1 << BIO_RW_FAILFAST
);
198 mp_bh
->bio
.bi_end_io
= multipath_end_request
;
199 mp_bh
->bio
.bi_private
= mp_bh
;
200 generic_make_request(&mp_bh
->bio
);
204 static void multipath_status (struct seq_file
*seq
, mddev_t
*mddev
)
206 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
209 seq_printf (seq
, " [%d/%d] [", conf
->raid_disks
,
210 conf
->working_disks
);
211 for (i
= 0; i
< conf
->raid_disks
; i
++)
212 seq_printf (seq
, "%s",
213 conf
->multipaths
[i
].rdev
&&
214 conf
->multipaths
[i
].rdev
->in_sync
? "U" : "_");
215 seq_printf (seq
, "]");
218 static int multipath_issue_flush(request_queue_t
*q
, struct gendisk
*disk
,
219 sector_t
*error_sector
)
221 mddev_t
*mddev
= q
->queuedata
;
222 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
226 for (i
=0; i
<mddev
->raid_disks
&& ret
== 0; i
++) {
227 mdk_rdev_t
*rdev
= conf
->multipaths
[i
].rdev
;
228 if (rdev
&& !rdev
->faulty
) {
229 struct block_device
*bdev
= rdev
->bdev
;
230 request_queue_t
*r_queue
= bdev_get_queue(bdev
);
232 if (!r_queue
->issue_flush_fn
)
235 atomic_inc(&rdev
->nr_pending
);
237 ret
= r_queue
->issue_flush_fn(r_queue
, bdev
->bd_disk
,
239 rdev_dec_pending(rdev
, mddev
);
249 * Careful, this can execute in IRQ contexts as well!
251 static void multipath_error (mddev_t
*mddev
, mdk_rdev_t
*rdev
)
253 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
255 if (conf
->working_disks
<= 1) {
257 * Uh oh, we can do nothing if this is our last path, but
258 * first check if this is a queued request for a device
259 * which has just failed.
262 "multipath: only one IO path left and IO error.\n");
263 /* leave it active... it's all we have */
266 * Mark disk as unusable
269 char b
[BDEVNAME_SIZE
];
273 conf
->working_disks
--;
274 printk(KERN_ALERT
"multipath: IO failure on %s,"
275 " disabling IO path. \n Operation continuing"
276 " on %d IO paths.\n",
277 bdevname (rdev
->bdev
,b
),
278 conf
->working_disks
);
283 static void print_multipath_conf (multipath_conf_t
*conf
)
286 struct multipath_info
*tmp
;
288 printk("MULTIPATH conf printout:\n");
290 printk("(conf==NULL)\n");
293 printk(" --- wd:%d rd:%d\n", conf
->working_disks
,
296 for (i
= 0; i
< conf
->raid_disks
; i
++) {
297 char b
[BDEVNAME_SIZE
];
298 tmp
= conf
->multipaths
+ i
;
300 printk(" disk%d, o:%d, dev:%s\n",
301 i
,!tmp
->rdev
->faulty
,
302 bdevname(tmp
->rdev
->bdev
,b
));
307 static int multipath_add_disk(mddev_t
*mddev
, mdk_rdev_t
*rdev
)
309 multipath_conf_t
*conf
= mddev
->private;
312 struct multipath_info
*p
;
314 print_multipath_conf(conf
);
316 for (path
=0; path
<mddev
->raid_disks
; path
++)
317 if ((p
=conf
->multipaths
+path
)->rdev
== NULL
) {
318 blk_queue_stack_limits(mddev
->queue
,
319 rdev
->bdev
->bd_disk
->queue
);
321 /* as we don't honour merge_bvec_fn, we must never risk
322 * violating it, so limit ->max_sector to one PAGE, as
323 * a one page request is never in violation.
324 * (Note: it is very unlikely that a device with
325 * merge_bvec_fn will be involved in multipath.)
327 if (rdev
->bdev
->bd_disk
->queue
->merge_bvec_fn
&&
328 mddev
->queue
->max_sectors
> (PAGE_SIZE
>>9))
329 blk_queue_max_sectors(mddev
->queue
, PAGE_SIZE
>>9);
331 conf
->working_disks
++;
332 rdev
->raid_disk
= path
;
338 print_multipath_conf(conf
);
342 static int multipath_remove_disk(mddev_t
*mddev
, int number
)
344 multipath_conf_t
*conf
= mddev
->private;
347 struct multipath_info
*p
= conf
->multipaths
+ number
;
349 print_multipath_conf(conf
);
354 atomic_read(&rdev
->nr_pending
)) {
355 printk(KERN_ERR
"hot-remove-disk, slot %d is identified" " but is still operational!\n", number
);
361 if (atomic_read(&rdev
->nr_pending
)) {
362 /* lost the race, try later */
369 print_multipath_conf(conf
);
376 * This is a kernel thread which:
378 * 1. Retries failed read operations on working multipaths.
379 * 2. Updates the raid superblock when problems encounter.
380 * 3. Performs writes following reads for array syncronising.
383 static void multipathd (mddev_t
*mddev
)
385 struct multipath_bh
*mp_bh
;
388 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
389 struct list_head
*head
= &conf
->retry_list
;
391 md_check_recovery(mddev
);
393 char b
[BDEVNAME_SIZE
];
394 spin_lock_irqsave(&conf
->device_lock
, flags
);
395 if (list_empty(head
))
397 mp_bh
= list_entry(head
->prev
, struct multipath_bh
, retry_list
);
398 list_del(head
->prev
);
399 spin_unlock_irqrestore(&conf
->device_lock
, flags
);
402 bio
->bi_sector
= mp_bh
->master_bio
->bi_sector
;
404 if ((mp_bh
->path
= multipath_map (conf
))<0) {
405 printk(KERN_ALERT
"multipath: %s: unrecoverable IO read"
406 " error for block %llu\n",
407 bdevname(bio
->bi_bdev
,b
),
408 (unsigned long long)bio
->bi_sector
);
409 multipath_end_bh_io(mp_bh
, -EIO
);
411 printk(KERN_ERR
"multipath: %s: redirecting sector %llu"
412 " to another IO path\n",
413 bdevname(bio
->bi_bdev
,b
),
414 (unsigned long long)bio
->bi_sector
);
415 *bio
= *(mp_bh
->master_bio
);
416 bio
->bi_sector
+= conf
->multipaths
[mp_bh
->path
].rdev
->data_offset
;
417 bio
->bi_bdev
= conf
->multipaths
[mp_bh
->path
].rdev
->bdev
;
418 bio
->bi_rw
|= (1 << BIO_RW_FAILFAST
);
419 bio
->bi_end_io
= multipath_end_request
;
420 bio
->bi_private
= mp_bh
;
421 generic_make_request(bio
);
424 spin_unlock_irqrestore(&conf
->device_lock
, flags
);
427 static int multipath_run (mddev_t
*mddev
)
429 multipath_conf_t
*conf
;
431 struct multipath_info
*disk
;
433 struct list_head
*tmp
;
435 if (mddev
->level
!= LEVEL_MULTIPATH
) {
436 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
437 mdname(mddev
), mddev
->level
);
441 * copy the already verified devices into our private MULTIPATH
442 * bookkeeping area. [whatever we allocate in multipath_run(),
443 * should be freed in multipath_stop()]
446 conf
= kmalloc(sizeof(multipath_conf_t
), GFP_KERNEL
);
447 mddev
->private = conf
;
450 "multipath: couldn't allocate memory for %s\n",
454 memset(conf
, 0, sizeof(*conf
));
456 conf
->multipaths
= kmalloc(sizeof(struct multipath_info
)*mddev
->raid_disks
,
458 if (!conf
->multipaths
) {
460 "multipath: couldn't allocate memory for %s\n",
464 memset(conf
->multipaths
, 0, sizeof(struct multipath_info
)*mddev
->raid_disks
);
466 conf
->working_disks
= 0;
467 ITERATE_RDEV(mddev
,rdev
,tmp
) {
468 disk_idx
= rdev
->raid_disk
;
470 disk_idx
>= mddev
->raid_disks
)
473 disk
= conf
->multipaths
+ disk_idx
;
476 blk_queue_stack_limits(mddev
->queue
,
477 rdev
->bdev
->bd_disk
->queue
);
478 /* as we don't honour merge_bvec_fn, we must never risk
479 * violating it, not that we ever expect a device with
480 * a merge_bvec_fn to be involved in multipath */
481 if (rdev
->bdev
->bd_disk
->queue
->merge_bvec_fn
&&
482 mddev
->queue
->max_sectors
> (PAGE_SIZE
>>9))
483 blk_queue_max_sectors(mddev
->queue
, PAGE_SIZE
>>9);
486 conf
->working_disks
++;
489 conf
->raid_disks
= mddev
->raid_disks
;
492 spin_lock_init(&conf
->device_lock
);
493 INIT_LIST_HEAD(&conf
->retry_list
);
495 if (!conf
->working_disks
) {
496 printk(KERN_ERR
"multipath: no operational IO paths for %s\n",
500 mddev
->degraded
= conf
->raid_disks
= conf
->working_disks
;
502 conf
->pool
= mempool_create(NR_RESERVED_BUFS
,
503 mp_pool_alloc
, mp_pool_free
,
505 if (conf
->pool
== NULL
) {
507 "multipath: couldn't allocate memory for %s\n",
513 mddev
->thread
= md_register_thread(multipathd
, mddev
, "%s_multipath");
514 if (!mddev
->thread
) {
515 printk(KERN_ERR
"multipath: couldn't allocate thread"
516 " for %s\n", mdname(mddev
));
522 "multipath: array %s active with %d out of %d IO paths\n",
523 mdname(mddev
), conf
->working_disks
, mddev
->raid_disks
);
525 * Ok, everything is just fine now
527 mddev
->array_size
= mddev
->size
;
529 mddev
->queue
->unplug_fn
= multipath_unplug
;
530 mddev
->queue
->issue_flush_fn
= multipath_issue_flush
;
536 mempool_destroy(conf
->pool
);
537 kfree(conf
->multipaths
);
539 mddev
->private = NULL
;
545 static int multipath_stop (mddev_t
*mddev
)
547 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
549 md_unregister_thread(mddev
->thread
);
550 mddev
->thread
= NULL
;
551 blk_sync_queue(mddev
->queue
); /* the unplug fn references 'conf'*/
552 mempool_destroy(conf
->pool
);
553 kfree(conf
->multipaths
);
555 mddev
->private = NULL
;
559 static mdk_personality_t multipath_personality
=
562 .owner
= THIS_MODULE
,
563 .make_request
= multipath_make_request
,
564 .run
= multipath_run
,
565 .stop
= multipath_stop
,
566 .status
= multipath_status
,
567 .error_handler
= multipath_error
,
568 .hot_add_disk
= multipath_add_disk
,
569 .hot_remove_disk
= multipath_remove_disk
,
572 static int __init
multipath_init (void)
574 return register_md_personality (MULTIPATH
, &multipath_personality
);
577 static void __exit
multipath_exit (void)
579 unregister_md_personality (MULTIPATH
);
582 module_init(multipath_init
);
583 module_exit(multipath_exit
);
584 MODULE_LICENSE("GPL");
585 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */