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
= rcu_dereference(conf
->multipaths
[i
].rdev
);
67 if (rdev
&& test_bit(In_sync
, &rdev
->flags
)) {
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
= rcu_dereference(conf
->multipaths
[i
].rdev
);
143 if (rdev
&& !test_bit(Faulty
, &rdev
->flags
)
144 && atomic_read(&rdev
->nr_pending
)) {
145 request_queue_t
*r_queue
= bdev_get_queue(rdev
->bdev
);
147 atomic_inc(&rdev
->nr_pending
);
150 if (r_queue
->unplug_fn
)
151 r_queue
->unplug_fn(r_queue
);
153 rdev_dec_pending(rdev
, mddev
);
160 static void multipath_unplug(request_queue_t
*q
)
162 unplug_slaves(q
->queuedata
);
166 static int multipath_make_request (request_queue_t
*q
, struct bio
* bio
)
168 mddev_t
*mddev
= q
->queuedata
;
169 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
170 struct multipath_bh
* mp_bh
;
171 struct multipath_info
*multipath
;
172 const int rw
= bio_data_dir(bio
);
174 if (unlikely(bio_barrier(bio
))) {
175 bio_endio(bio
, bio
->bi_size
, -EOPNOTSUPP
);
179 mp_bh
= mempool_alloc(conf
->pool
, GFP_NOIO
);
181 mp_bh
->master_bio
= bio
;
182 mp_bh
->mddev
= mddev
;
184 disk_stat_inc(mddev
->gendisk
, ios
[rw
]);
185 disk_stat_add(mddev
->gendisk
, sectors
[rw
], bio_sectors(bio
));
187 mp_bh
->path
= multipath_map(conf
);
188 if (mp_bh
->path
< 0) {
189 bio_endio(bio
, bio
->bi_size
, -EIO
);
190 mempool_free(mp_bh
, conf
->pool
);
193 multipath
= conf
->multipaths
+ mp_bh
->path
;
196 mp_bh
->bio
.bi_sector
+= multipath
->rdev
->data_offset
;
197 mp_bh
->bio
.bi_bdev
= multipath
->rdev
->bdev
;
198 mp_bh
->bio
.bi_rw
|= (1 << BIO_RW_FAILFAST
);
199 mp_bh
->bio
.bi_end_io
= multipath_end_request
;
200 mp_bh
->bio
.bi_private
= mp_bh
;
201 generic_make_request(&mp_bh
->bio
);
205 static void multipath_status (struct seq_file
*seq
, mddev_t
*mddev
)
207 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
210 seq_printf (seq
, " [%d/%d] [", conf
->raid_disks
,
211 conf
->working_disks
);
212 for (i
= 0; i
< conf
->raid_disks
; i
++)
213 seq_printf (seq
, "%s",
214 conf
->multipaths
[i
].rdev
&&
215 test_bit(In_sync
, &conf
->multipaths
[i
].rdev
->flags
) ? "U" : "_");
216 seq_printf (seq
, "]");
219 static int multipath_issue_flush(request_queue_t
*q
, struct gendisk
*disk
,
220 sector_t
*error_sector
)
222 mddev_t
*mddev
= q
->queuedata
;
223 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
227 for (i
=0; i
<mddev
->raid_disks
&& ret
== 0; i
++) {
228 mdk_rdev_t
*rdev
= rcu_dereference(conf
->multipaths
[i
].rdev
);
229 if (rdev
&& !test_bit(Faulty
, &rdev
->flags
)) {
230 struct block_device
*bdev
= rdev
->bdev
;
231 request_queue_t
*r_queue
= bdev_get_queue(bdev
);
233 if (!r_queue
->issue_flush_fn
)
236 atomic_inc(&rdev
->nr_pending
);
238 ret
= r_queue
->issue_flush_fn(r_queue
, bdev
->bd_disk
,
240 rdev_dec_pending(rdev
, mddev
);
250 * Careful, this can execute in IRQ contexts as well!
252 static void multipath_error (mddev_t
*mddev
, mdk_rdev_t
*rdev
)
254 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
256 if (conf
->working_disks
<= 1) {
258 * Uh oh, we can do nothing if this is our last path, but
259 * first check if this is a queued request for a device
260 * which has just failed.
263 "multipath: only one IO path left and IO error.\n");
264 /* leave it active... it's all we have */
267 * Mark disk as unusable
269 if (!test_bit(Faulty
, &rdev
->flags
)) {
270 char b
[BDEVNAME_SIZE
];
271 clear_bit(In_sync
, &rdev
->flags
);
272 set_bit(Faulty
, &rdev
->flags
);
274 conf
->working_disks
--;
275 printk(KERN_ALERT
"multipath: IO failure on %s,"
276 " disabling IO path. \n Operation continuing"
277 " on %d IO paths.\n",
278 bdevname (rdev
->bdev
,b
),
279 conf
->working_disks
);
284 static void print_multipath_conf (multipath_conf_t
*conf
)
287 struct multipath_info
*tmp
;
289 printk("MULTIPATH conf printout:\n");
291 printk("(conf==NULL)\n");
294 printk(" --- wd:%d rd:%d\n", conf
->working_disks
,
297 for (i
= 0; i
< conf
->raid_disks
; i
++) {
298 char b
[BDEVNAME_SIZE
];
299 tmp
= conf
->multipaths
+ i
;
301 printk(" disk%d, o:%d, dev:%s\n",
302 i
,!test_bit(Faulty
, &tmp
->rdev
->flags
),
303 bdevname(tmp
->rdev
->bdev
,b
));
308 static int multipath_add_disk(mddev_t
*mddev
, mdk_rdev_t
*rdev
)
310 multipath_conf_t
*conf
= mddev
->private;
313 struct multipath_info
*p
;
315 print_multipath_conf(conf
);
317 for (path
=0; path
<mddev
->raid_disks
; path
++)
318 if ((p
=conf
->multipaths
+path
)->rdev
== NULL
) {
319 blk_queue_stack_limits(mddev
->queue
,
320 rdev
->bdev
->bd_disk
->queue
);
322 /* as we don't honour merge_bvec_fn, we must never risk
323 * violating it, so limit ->max_sector to one PAGE, as
324 * a one page request is never in violation.
325 * (Note: it is very unlikely that a device with
326 * merge_bvec_fn will be involved in multipath.)
328 if (rdev
->bdev
->bd_disk
->queue
->merge_bvec_fn
&&
329 mddev
->queue
->max_sectors
> (PAGE_SIZE
>>9))
330 blk_queue_max_sectors(mddev
->queue
, PAGE_SIZE
>>9);
332 conf
->working_disks
++;
333 rdev
->raid_disk
= path
;
334 set_bit(In_sync
, &rdev
->flags
);
335 rcu_assign_pointer(p
->rdev
, rdev
);
339 print_multipath_conf(conf
);
343 static int multipath_remove_disk(mddev_t
*mddev
, int number
)
345 multipath_conf_t
*conf
= mddev
->private;
348 struct multipath_info
*p
= conf
->multipaths
+ number
;
350 print_multipath_conf(conf
);
354 if (test_bit(In_sync
, &rdev
->flags
) ||
355 atomic_read(&rdev
->nr_pending
)) {
356 printk(KERN_ERR
"hot-remove-disk, slot %d is identified" " but is still operational!\n", number
);
362 if (atomic_read(&rdev
->nr_pending
)) {
363 /* lost the race, try later */
370 print_multipath_conf(conf
);
377 * This is a kernel thread which:
379 * 1. Retries failed read operations on working multipaths.
380 * 2. Updates the raid superblock when problems encounter.
381 * 3. Performs writes following reads for array syncronising.
384 static void multipathd (mddev_t
*mddev
)
386 struct multipath_bh
*mp_bh
;
389 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
390 struct list_head
*head
= &conf
->retry_list
;
392 md_check_recovery(mddev
);
394 char b
[BDEVNAME_SIZE
];
395 spin_lock_irqsave(&conf
->device_lock
, flags
);
396 if (list_empty(head
))
398 mp_bh
= list_entry(head
->prev
, struct multipath_bh
, retry_list
);
399 list_del(head
->prev
);
400 spin_unlock_irqrestore(&conf
->device_lock
, flags
);
403 bio
->bi_sector
= mp_bh
->master_bio
->bi_sector
;
405 if ((mp_bh
->path
= multipath_map (conf
))<0) {
406 printk(KERN_ALERT
"multipath: %s: unrecoverable IO read"
407 " error for block %llu\n",
408 bdevname(bio
->bi_bdev
,b
),
409 (unsigned long long)bio
->bi_sector
);
410 multipath_end_bh_io(mp_bh
, -EIO
);
412 printk(KERN_ERR
"multipath: %s: redirecting sector %llu"
413 " to another IO path\n",
414 bdevname(bio
->bi_bdev
,b
),
415 (unsigned long long)bio
->bi_sector
);
416 *bio
= *(mp_bh
->master_bio
);
417 bio
->bi_sector
+= conf
->multipaths
[mp_bh
->path
].rdev
->data_offset
;
418 bio
->bi_bdev
= conf
->multipaths
[mp_bh
->path
].rdev
->bdev
;
419 bio
->bi_rw
|= (1 << BIO_RW_FAILFAST
);
420 bio
->bi_end_io
= multipath_end_request
;
421 bio
->bi_private
= mp_bh
;
422 generic_make_request(bio
);
425 spin_unlock_irqrestore(&conf
->device_lock
, flags
);
428 static int multipath_run (mddev_t
*mddev
)
430 multipath_conf_t
*conf
;
432 struct multipath_info
*disk
;
434 struct list_head
*tmp
;
436 if (mddev
->level
!= LEVEL_MULTIPATH
) {
437 printk("multipath: %s: raid level not set to multipath IO (%d)\n",
438 mdname(mddev
), mddev
->level
);
442 * copy the already verified devices into our private MULTIPATH
443 * bookkeeping area. [whatever we allocate in multipath_run(),
444 * should be freed in multipath_stop()]
447 conf
= kmalloc(sizeof(multipath_conf_t
), GFP_KERNEL
);
448 mddev
->private = conf
;
451 "multipath: couldn't allocate memory for %s\n",
455 memset(conf
, 0, sizeof(*conf
));
457 conf
->multipaths
= kmalloc(sizeof(struct multipath_info
)*mddev
->raid_disks
,
459 if (!conf
->multipaths
) {
461 "multipath: couldn't allocate memory for %s\n",
465 memset(conf
->multipaths
, 0, sizeof(struct multipath_info
)*mddev
->raid_disks
);
467 conf
->working_disks
= 0;
468 ITERATE_RDEV(mddev
,rdev
,tmp
) {
469 disk_idx
= rdev
->raid_disk
;
471 disk_idx
>= mddev
->raid_disks
)
474 disk
= conf
->multipaths
+ disk_idx
;
477 blk_queue_stack_limits(mddev
->queue
,
478 rdev
->bdev
->bd_disk
->queue
);
479 /* as we don't honour merge_bvec_fn, we must never risk
480 * violating it, not that we ever expect a device with
481 * a merge_bvec_fn to be involved in multipath */
482 if (rdev
->bdev
->bd_disk
->queue
->merge_bvec_fn
&&
483 mddev
->queue
->max_sectors
> (PAGE_SIZE
>>9))
484 blk_queue_max_sectors(mddev
->queue
, PAGE_SIZE
>>9);
486 if (!test_bit(Faulty
, &rdev
->flags
))
487 conf
->working_disks
++;
490 conf
->raid_disks
= mddev
->raid_disks
;
493 spin_lock_init(&conf
->device_lock
);
494 INIT_LIST_HEAD(&conf
->retry_list
);
496 if (!conf
->working_disks
) {
497 printk(KERN_ERR
"multipath: no operational IO paths for %s\n",
501 mddev
->degraded
= conf
->raid_disks
= conf
->working_disks
;
503 conf
->pool
= mempool_create(NR_RESERVED_BUFS
,
504 mp_pool_alloc
, mp_pool_free
,
506 if (conf
->pool
== NULL
) {
508 "multipath: couldn't allocate memory for %s\n",
514 mddev
->thread
= md_register_thread(multipathd
, mddev
, "%s_multipath");
515 if (!mddev
->thread
) {
516 printk(KERN_ERR
"multipath: couldn't allocate thread"
517 " for %s\n", mdname(mddev
));
523 "multipath: array %s active with %d out of %d IO paths\n",
524 mdname(mddev
), conf
->working_disks
, mddev
->raid_disks
);
526 * Ok, everything is just fine now
528 mddev
->array_size
= mddev
->size
;
530 mddev
->queue
->unplug_fn
= multipath_unplug
;
531 mddev
->queue
->issue_flush_fn
= multipath_issue_flush
;
537 mempool_destroy(conf
->pool
);
538 kfree(conf
->multipaths
);
540 mddev
->private = NULL
;
546 static int multipath_stop (mddev_t
*mddev
)
548 multipath_conf_t
*conf
= mddev_to_conf(mddev
);
550 md_unregister_thread(mddev
->thread
);
551 mddev
->thread
= NULL
;
552 blk_sync_queue(mddev
->queue
); /* the unplug fn references 'conf'*/
553 mempool_destroy(conf
->pool
);
554 kfree(conf
->multipaths
);
556 mddev
->private = NULL
;
560 static mdk_personality_t multipath_personality
=
563 .owner
= THIS_MODULE
,
564 .make_request
= multipath_make_request
,
565 .run
= multipath_run
,
566 .stop
= multipath_stop
,
567 .status
= multipath_status
,
568 .error_handler
= multipath_error
,
569 .hot_add_disk
= multipath_add_disk
,
570 .hot_remove_disk
= multipath_remove_disk
,
573 static int __init
multipath_init (void)
575 return register_md_personality (MULTIPATH
, &multipath_personality
);
578 static void __exit
multipath_exit (void)
580 unregister_md_personality (MULTIPATH
);
583 module_init(multipath_init
);
584 module_exit(multipath_exit
);
585 MODULE_LICENSE("GPL");
586 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */