[net-next-2.6.git] / drivers / md / multipath.c

/*
 * multipath.c : Multiple Devices driver for Linux
 *
 * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
 *
 * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
 *
 * MULTIPATH management functions.
 *
 * derived from raid1.c.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * You should have received a copy of the GNU General Public License
 * (for example /usr/src/linux/COPYING); if not, write to the Free
 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/blkdev.h>
#include <linux/raid/md_u.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include "md.h"
#include "multipath.h"

#define MAX_WORK_PER_DISK 128

#define	NR_RESERVED_BUFS	32


static int multipath_map (multipath_conf_t *conf)
{
	int i, disks = conf->raid_disks;

	/*
	 * Later we do read balancing on the read side 
	 * now we use the first available disk.
	 */

	rcu_read_lock();
	for (i = 0; i < disks; i++) {
		mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
		if (rdev && test_bit(In_sync, &rdev->flags)) {
			atomic_inc(&rdev->nr_pending);
			rcu_read_unlock();
			return i;
		}
	}
	rcu_read_unlock();

	printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
	return (-1);
}

static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
{
	unsigned long flags;
	mddev_t *mddev = mp_bh->mddev;
	multipath_conf_t *conf = mddev->private;

	spin_lock_irqsave(&conf->device_lock, flags);
	list_add(&mp_bh->retry_list, &conf->retry_list);
	spin_unlock_irqrestore(&conf->device_lock, flags);
	md_wakeup_thread(mddev->thread);
}


/*
 * multipath_end_bh_io() is called when we have finished servicing a multipathed
 * operation and are ready to return a success/failure code to the buffer
 * cache layer.
 */
static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
{
	struct bio *bio = mp_bh->master_bio;
	multipath_conf_t *conf = mp_bh->mddev->private;

	bio_endio(bio, err);
	mempool_free(mp_bh, conf->pool);
}

static void multipath_end_request(struct bio *bio, int error)
{
	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
	struct multipath_bh *mp_bh = bio->bi_private;
	multipath_conf_t *conf = mp_bh->mddev->private;
	mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;

	if (uptodate)
		multipath_end_bh_io(mp_bh, 0);
	else if (!(bio->bi_rw & REQ_RAHEAD)) {
		/*
		 * oops, IO error:
		 */
		char b[BDEVNAME_SIZE];
		md_error (mp_bh->mddev, rdev);
		printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n", 
		       bdevname(rdev->bdev,b), 
		       (unsigned long long)bio->bi_sector);
		multipath_reschedule_retry(mp_bh);
	} else
		multipath_end_bh_io(mp_bh, error);
	rdev_dec_pending(rdev, conf->mddev);
}

static void unplug_slaves(mddev_t *mddev)
{
	multipath_conf_t *conf = mddev->private;
	int i;

	rcu_read_lock();
	for (i=0; i<mddev->raid_disks; i++) {
		mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
		if (rdev && !test_bit(Faulty, &rdev->flags)
		    && atomic_read(&rdev->nr_pending)) {
			struct request_queue *r_queue = bdev_get_queue(rdev->bdev);

			atomic_inc(&rdev->nr_pending);
			rcu_read_unlock();

			blk_unplug(r_queue);

			rdev_dec_pending(rdev, mddev);
			rcu_read_lock();
		}
	}
	rcu_read_unlock();
}

static void multipath_unplug(struct request_queue *q)
{
	unplug_slaves(q->queuedata);
}


static int multipath_make_request(mddev_t *mddev, struct bio * bio)
{
	multipath_conf_t *conf = mddev->private;
	struct multipath_bh * mp_bh;
	struct multipath_info *multipath;

	if (unlikely(bio->bi_rw & REQ_HARDBARRIER)) {
		md_barrier_request(mddev, bio);
		return 0;
	}

	mp_bh = mempool_alloc(conf->pool, GFP_NOIO);

	mp_bh->master_bio = bio;
	mp_bh->mddev = mddev;

	mp_bh->path = multipath_map(conf);
	if (mp_bh->path < 0) {
		bio_endio(bio, -EIO);
		mempool_free(mp_bh, conf->pool);
		return 0;
	}
	multipath = conf->multipaths + mp_bh->path;

	mp_bh->bio = *bio;
	mp_bh->bio.bi_sector += multipath->rdev->data_offset;
	mp_bh->bio.bi_bdev = multipath->rdev->bdev;
	mp_bh->bio.bi_rw |= REQ_FAILFAST_TRANSPORT;
	mp_bh->bio.bi_end_io = multipath_end_request;
	mp_bh->bio.bi_private = mp_bh;
	generic_make_request(&mp_bh->bio);
	return 0;
}

static void multipath_status (struct seq_file *seq, mddev_t *mddev)
{
	multipath_conf_t *conf = mddev->private;
	int i;
	
	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
						 conf->working_disks);
	for (i = 0; i < conf->raid_disks; i++)
		seq_printf (seq, "%s",
			       conf->multipaths[i].rdev && 
			       test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
	seq_printf (seq, "]");
}

static int multipath_congested(void *data, int bits)
{
	mddev_t *mddev = data;
	multipath_conf_t *conf = mddev->private;
	int i, ret = 0;

	if (mddev_congested(mddev, bits))
		return 1;

	rcu_read_lock();
	for (i = 0; i < mddev->raid_disks ; i++) {
		mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
		if (rdev && !test_bit(Faulty, &rdev->flags)) {
			struct request_queue *q = bdev_get_queue(rdev->bdev);

			ret |= bdi_congested(&q->backing_dev_info, bits);
			/* Just like multipath_map, we just check the
			 * first available device
			 */
			break;
		}
	}
	rcu_read_unlock();
	return ret;
}

/*
 * Careful, this can execute in IRQ contexts as well!
 */
static void multipath_error (mddev_t *mddev, mdk_rdev_t *rdev)
{
	multipath_conf_t *conf = mddev->private;

	if (conf->working_disks <= 1) {
		/*
		 * Uh oh, we can do nothing if this is our last path, but
		 * first check if this is a queued request for a device
		 * which has just failed.
		 */
		printk(KERN_ALERT 
			"multipath: only one IO path left and IO error.\n");
		/* leave it active... it's all we have */
	} else {
		/*
		 * Mark disk as unusable
		 */
		if (!test_bit(Faulty, &rdev->flags)) {
			char b[BDEVNAME_SIZE];
			clear_bit(In_sync, &rdev->flags);
			set_bit(Faulty, &rdev->flags);
			set_bit(MD_CHANGE_DEVS, &mddev->flags);
			conf->working_disks--;
			mddev->degraded++;
			printk(KERN_ALERT "multipath: IO failure on %s,"
				" disabling IO path.\n"
				"multipath: Operation continuing"
				" on %d IO paths.\n",
				bdevname (rdev->bdev,b),
				conf->working_disks);
		}
	}
}

static void print_multipath_conf (multipath_conf_t *conf)
{
	int i;
	struct multipath_info *tmp;

	printk("MULTIPATH conf printout:\n");
	if (!conf) {
		printk("(conf==NULL)\n");
		return;
	}
	printk(" --- wd:%d rd:%d\n", conf->working_disks,
			 conf->raid_disks);

	for (i = 0; i < conf->raid_disks; i++) {
		char b[BDEVNAME_SIZE];
		tmp = conf->multipaths + i;
		if (tmp->rdev)
			printk(" disk%d, o:%d, dev:%s\n",
				i,!test_bit(Faulty, &tmp->rdev->flags),
			       bdevname(tmp->rdev->bdev,b));
	}
}


static int multipath_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
{
	multipath_conf_t *conf = mddev->private;
	struct request_queue *q;
	int err = -EEXIST;
	int path;
	struct multipath_info *p;
	int first = 0;
	int last = mddev->raid_disks - 1;

	if (rdev->raid_disk >= 0)
		first = last = rdev->raid_disk;

	print_multipath_conf(conf);

	for (path = first; path <= last; path++)
		if ((p=conf->multipaths+path)->rdev == NULL) {
			q = rdev->bdev->bd_disk->queue;
			disk_stack_limits(mddev->gendisk, rdev->bdev,
					  rdev->data_offset << 9);

		/* as we don't honour merge_bvec_fn, we must never risk
		 * violating it, so limit ->max_segments to one, lying
		 * within a single page.
		 * (Note: it is very unlikely that a device with
		 * merge_bvec_fn will be involved in multipath.)
		 */
			if (q->merge_bvec_fn) {
				blk_queue_max_segments(mddev->queue, 1);
				blk_queue_segment_boundary(mddev->queue,
							   PAGE_CACHE_SIZE - 1);
			}

			conf->working_disks++;
			mddev->degraded--;
			rdev->raid_disk = path;
			set_bit(In_sync, &rdev->flags);
			rcu_assign_pointer(p->rdev, rdev);
			err = 0;
			md_integrity_add_rdev(rdev, mddev);
			break;
		}

	print_multipath_conf(conf);

	return err;
}

static int multipath_remove_disk(mddev_t *mddev, int number)
{
	multipath_conf_t *conf = mddev->private;
	int err = 0;
	mdk_rdev_t *rdev;
	struct multipath_info *p = conf->multipaths + number;

	print_multipath_conf(conf);

	rdev = p->rdev;
	if (rdev) {
		if (test_bit(In_sync, &rdev->flags) ||
		    atomic_read(&rdev->nr_pending)) {
			printk(KERN_ERR "hot-remove-disk, slot %d is identified"
			       " but is still operational!\n", number);
			err = -EBUSY;
			goto abort;
		}
		p->rdev = NULL;
		synchronize_rcu();
		if (atomic_read(&rdev->nr_pending)) {
			/* lost the race, try later */
			err = -EBUSY;
			p->rdev = rdev;
			goto abort;
		}
		md_integrity_register(mddev);
	}
abort:

	print_multipath_conf(conf);
	return err;
}


/*
 * This is a kernel thread which:
 *
 *	1.	Retries failed read operations on working multipaths.
 *	2.	Updates the raid superblock when problems encounter.
 *	3.	Performs writes following reads for array syncronising.
 */

static void multipathd (mddev_t *mddev)
{
	struct multipath_bh *mp_bh;
	struct bio *bio;
	unsigned long flags;
	multipath_conf_t *conf = mddev->private;
	struct list_head *head = &conf->retry_list;

	md_check_recovery(mddev);
	for (;;) {
		char b[BDEVNAME_SIZE];
		spin_lock_irqsave(&conf->device_lock, flags);
		if (list_empty(head))
			break;
		mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
		list_del(head->prev);
		spin_unlock_irqrestore(&conf->device_lock, flags);

		bio = &mp_bh->bio;
		bio->bi_sector = mp_bh->master_bio->bi_sector;
		
		if ((mp_bh->path = multipath_map (conf))<0) {
			printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
				" error for block %llu\n",
				bdevname(bio->bi_bdev,b),
				(unsigned long long)bio->bi_sector);
			multipath_end_bh_io(mp_bh, -EIO);
		} else {
			printk(KERN_ERR "multipath: %s: redirecting sector %llu"
				" to another IO path\n",
				bdevname(bio->bi_bdev,b),
				(unsigned long long)bio->bi_sector);
			*bio = *(mp_bh->master_bio);
			bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
			bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
			bio->bi_rw |= REQ_FAILFAST_TRANSPORT;
			bio->bi_end_io = multipath_end_request;
			bio->bi_private = mp_bh;
			generic_make_request(bio);
		}
	}
	spin_unlock_irqrestore(&conf->device_lock, flags);
}

static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
{
	WARN_ONCE(sectors || raid_disks,
		  "%s does not support generic reshape\n", __func__);

	return mddev->dev_sectors;
}

static int multipath_run (mddev_t *mddev)
{
	multipath_conf_t *conf;
	int disk_idx;
	struct multipath_info *disk;
	mdk_rdev_t *rdev;

	if (md_check_no_bitmap(mddev))
		return -EINVAL;

	if (mddev->level != LEVEL_MULTIPATH) {
		printk("multipath: %s: raid level not set to multipath IO (%d)\n",
		       mdname(mddev), mddev->level);
		goto out;
	}
	/*
	 * copy the already verified devices into our private MULTIPATH
	 * bookkeeping area. [whatever we allocate in multipath_run(),
	 * should be freed in multipath_stop()]
	 */
	mddev->queue->queue_lock = &mddev->queue->__queue_lock;

	conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
	mddev->private = conf;
	if (!conf) {
		printk(KERN_ERR 
			"multipath: couldn't allocate memory for %s\n",
			mdname(mddev));
		goto out;
	}

	conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
				   GFP_KERNEL);
	if (!conf->multipaths) {
		printk(KERN_ERR 
			"multipath: couldn't allocate memory for %s\n",
			mdname(mddev));
		goto out_free_conf;
	}

	conf->working_disks = 0;
	list_for_each_entry(rdev, &mddev->disks, same_set) {
		disk_idx = rdev->raid_disk;
		if (disk_idx < 0 ||
		    disk_idx >= mddev->raid_disks)
			continue;

		disk = conf->multipaths + disk_idx;
		disk->rdev = rdev;
		disk_stack_limits(mddev->gendisk, rdev->bdev,
				  rdev->data_offset << 9);

		/* as we don't honour merge_bvec_fn, we must never risk
		 * violating it, not that we ever expect a device with
		 * a merge_bvec_fn to be involved in multipath */
		if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
			blk_queue_max_segments(mddev->queue, 1);
			blk_queue_segment_boundary(mddev->queue,
						   PAGE_CACHE_SIZE - 1);
		}

		if (!test_bit(Faulty, &rdev->flags))
			conf->working_disks++;
	}

	conf->raid_disks = mddev->raid_disks;
	conf->mddev = mddev;
	spin_lock_init(&conf->device_lock);
	INIT_LIST_HEAD(&conf->retry_list);

	if (!conf->working_disks) {
		printk(KERN_ERR "multipath: no operational IO paths for %s\n",
			mdname(mddev));
		goto out_free_conf;
	}
	mddev->degraded = conf->raid_disks - conf->working_disks;

	conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
						 sizeof(struct multipath_bh));
	if (conf->pool == NULL) {
		printk(KERN_ERR 
			"multipath: couldn't allocate memory for %s\n",
			mdname(mddev));
		goto out_free_conf;
	}

	{
		mddev->thread = md_register_thread(multipathd, mddev, NULL);
		if (!mddev->thread) {
			printk(KERN_ERR "multipath: couldn't allocate thread"
				" for %s\n", mdname(mddev));
			goto out_free_conf;
		}
	}

	printk(KERN_INFO 
		"multipath: array %s active with %d out of %d IO paths\n",
		mdname(mddev), conf->working_disks, mddev->raid_disks);
	/*
	 * Ok, everything is just fine now
	 */
	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));

	mddev->queue->unplug_fn = multipath_unplug;
	mddev->queue->backing_dev_info.congested_fn = multipath_congested;
	mddev->queue->backing_dev_info.congested_data = mddev;
	md_integrity_register(mddev);
	return 0;

out_free_conf:
	if (conf->pool)
		mempool_destroy(conf->pool);
	kfree(conf->multipaths);
	kfree(conf);
	mddev->private = NULL;
out:
	return -EIO;
}


static int multipath_stop (mddev_t *mddev)
{
	multipath_conf_t *conf = mddev->private;

	md_unregister_thread(mddev->thread);
	mddev->thread = NULL;
	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
	mempool_destroy(conf->pool);
	kfree(conf->multipaths);
	kfree(conf);
	mddev->private = NULL;
	return 0;
}

static struct mdk_personality multipath_personality =
{
	.name		= "multipath",
	.level		= LEVEL_MULTIPATH,
	.owner		= THIS_MODULE,
	.make_request	= multipath_make_request,
	.run		= multipath_run,
	.stop		= multipath_stop,
	.status		= multipath_status,
	.error_handler	= multipath_error,
	.hot_add_disk	= multipath_add_disk,
	.hot_remove_disk= multipath_remove_disk,
	.size		= multipath_size,
};

static int __init multipath_init (void)
{
	return register_md_personality (&multipath_personality);
}

static void __exit multipath_exit (void)
{
	unregister_md_personality (&multipath_personality);
}

module_init(multipath_init);
module_exit(multipath_exit);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("simple multi-path personality for MD");
MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
MODULE_ALIAS("md-multipath");
MODULE_ALIAS("md-level--4");
Commit	Line	Data
1da177e4 LT	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
bff61975 N	22	#include <linux/blkdev.h>
bff61975 N	23	#include <linux/raid/md_u.h>
bff61975	24	#include <linux/seq_file.h>
5a0e3ad6	25	#include <linux/slab.h>
43b2e5d8	26	#include "md.h"
ef740c37	27	#include "multipath.h"
1da177e4 LT	28
	29	#define MAX_WORK_PER_DISK 128
	30
	31	#define NR_RESERVED_BUFS 32
	32
	33
1da177e4 LT	34	static int multipath_map (multipath_conf_t *conf)
	35	{
	36	int i, disks = conf->raid_disks;
	37
	38	/*
	39	* Later we do read balancing on the read side
	40	* now we use the first available disk.
	41	*/
	42
	43	rcu_read_lock();
	44	for (i = 0; i < disks; i++) {
d6065f7b	45	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
b2d444d7	46	if (rdev && test_bit(In_sync, &rdev->flags)) {
1da177e4 LT	47	atomic_inc(&rdev->nr_pending);
	48	rcu_read_unlock();
	49	return i;
	50	}
	51	}
	52	rcu_read_unlock();
	53
	54	printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
	55	return (-1);
	56	}
	57
	58	static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
	59	{
	60	unsigned long flags;
	61	mddev_t *mddev = mp_bh->mddev;
070ec55d	62	multipath_conf_t *conf = mddev->private;
1da177e4 LT	63
	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);
	68	}
	69
	70
	71	/*
	72	* multipath_end_bh_io() is called when we have finished servicing a multipathed
	73	* operation and are ready to return a success/failure code to the buffer
	74	* cache layer.
	75	*/
	76	static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
	77	{
	78	struct bio *bio = mp_bh->master_bio;
070ec55d	79	multipath_conf_t *conf = mp_bh->mddev->private;
1da177e4	80
6712ecf8	81	bio_endio(bio, err);
1da177e4 LT	82	mempool_free(mp_bh, conf->pool);
	83	}
	84
6712ecf8	85	static void multipath_end_request(struct bio *bio, int error)
1da177e4 LT	86	{
1da177e4 LT	87	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
7b92813c	88	struct multipath_bh *mp_bh = bio->bi_private;
070ec55d	89	multipath_conf_t *conf = mp_bh->mddev->private;
1da177e4 LT	90	mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
1da177e4 LT	91
1da177e4 LT	92	if (uptodate)
1da177e4 LT	93	multipath_end_bh_io(mp_bh, 0);
7b6d91da	94	else if (!(bio->bi_rw & REQ_RAHEAD)) {
1da177e4 LT	95	/*
	96	* oops, IO error:
	97	*/
	98	char b[BDEVNAME_SIZE];
	99	md_error (mp_bh->mddev, rdev);
	100	printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
	101	bdevname(rdev->bdev,b),
	102	(unsigned long long)bio->bi_sector);
	103	multipath_reschedule_retry(mp_bh);
	104	} else
	105	multipath_end_bh_io(mp_bh, error);
	106	rdev_dec_pending(rdev, conf->mddev);
1da177e4 LT	107	}
	108
	109	static void unplug_slaves(mddev_t *mddev)
	110	{
070ec55d	111	multipath_conf_t *conf = mddev->private;
1da177e4 LT	112	int i;
	113
	114	rcu_read_lock();
	115	for (i=0; i<mddev->raid_disks; i++) {
d6065f7b	116	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
b2d444d7 N	117	if (rdev && !test_bit(Faulty, &rdev->flags)
b2d444d7 N	118	&& atomic_read(&rdev->nr_pending)) {
165125e1	119	struct request_queue *r_queue = bdev_get_queue(rdev->bdev);
1da177e4 LT	120
	121	atomic_inc(&rdev->nr_pending);
	122	rcu_read_unlock();
	123
2ad8b1ef	124	blk_unplug(r_queue);
1da177e4 LT	125
	126	rdev_dec_pending(rdev, mddev);
	127	rcu_read_lock();
	128	}
	129	}
	130	rcu_read_unlock();
	131	}
	132
165125e1	133	static void multipath_unplug(struct request_queue *q)
1da177e4 LT	134	{
	135	unplug_slaves(q->queuedata);
	136	}
	137
	138
21a52c6d	139	static int multipath_make_request(mddev_t mddev, struct bio bio)
1da177e4	140	{
070ec55d	141	multipath_conf_t *conf = mddev->private;
1da177e4 LT	142	struct multipath_bh * mp_bh;
	143	struct multipath_info *multipath;
	144
7b6d91da	145	if (unlikely(bio->bi_rw & REQ_HARDBARRIER)) {
a2826aa9	146	md_barrier_request(mddev, bio);
e5dcdd80 N	147	return 0;
	148	}
	149
1da177e4 LT	150	mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
	151
	152	mp_bh->master_bio = bio;
	153	mp_bh->mddev = mddev;
	154
1da177e4 LT	155	mp_bh->path = multipath_map(conf);
1da177e4 LT	156	if (mp_bh->path < 0) {
6712ecf8	157	bio_endio(bio, -EIO);
1da177e4 LT	158	mempool_free(mp_bh, conf->pool);
	159	return 0;
	160	}
	161	multipath = conf->multipaths + mp_bh->path;
	162
	163	mp_bh->bio = *bio;
	164	mp_bh->bio.bi_sector += multipath->rdev->data_offset;
	165	mp_bh->bio.bi_bdev = multipath->rdev->bdev;
7b6d91da	166	mp_bh->bio.bi_rw \|= REQ_FAILFAST_TRANSPORT;
1da177e4 LT	167	mp_bh->bio.bi_end_io = multipath_end_request;
	168	mp_bh->bio.bi_private = mp_bh;
	169	generic_make_request(&mp_bh->bio);
	170	return 0;
	171	}
	172
	173	static void multipath_status (struct seq_file seq, mddev_t mddev)
	174	{
070ec55d	175	multipath_conf_t *conf = mddev->private;
1da177e4 LT	176	int i;
	177
	178	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
	179	conf->working_disks);
	180	for (i = 0; i < conf->raid_disks; i++)
	181	seq_printf (seq, "%s",
	182	conf->multipaths[i].rdev &&
b2d444d7	183	test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
1da177e4 LT	184	seq_printf (seq, "]");
	185	}
	186
0d129228 N	187	static int multipath_congested(void *data, int bits)
	188	{
	189	mddev_t *mddev = data;
070ec55d	190	multipath_conf_t *conf = mddev->private;
0d129228 N	191	int i, ret = 0;
0d129228 N	192
3fa841d7 N	193	if (mddev_congested(mddev, bits))
	194	return 1;
	195
0d129228 N	196	rcu_read_lock();
	197	for (i = 0; i < mddev->raid_disks ; i++) {
	198	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
	199	if (rdev && !test_bit(Faulty, &rdev->flags)) {
165125e1	200	struct request_queue *q = bdev_get_queue(rdev->bdev);
0d129228 N	201
	202	ret \|= bdi_congested(&q->backing_dev_info, bits);
	203	/* Just like multipath_map, we just check the
	204	* first available device
	205	*/
	206	break;
	207	}
	208	}
	209	rcu_read_unlock();
	210	return ret;
	211	}
1da177e4 LT	212
	213	/*
	214	* Careful, this can execute in IRQ contexts as well!
	215	*/
	216	static void multipath_error (mddev_t mddev, mdk_rdev_t rdev)
	217	{
070ec55d	218	multipath_conf_t *conf = mddev->private;
1da177e4 LT	219
	220	if (conf->working_disks <= 1) {
	221	/*
	222	* Uh oh, we can do nothing if this is our last path, but
	223	* first check if this is a queued request for a device
	224	* which has just failed.
	225	*/
	226	printk(KERN_ALERT
	227	"multipath: only one IO path left and IO error.\n");
	228	/* leave it active... it's all we have */
	229	} else {
	230	/*
	231	* Mark disk as unusable
	232	*/
b2d444d7	233	if (!test_bit(Faulty, &rdev->flags)) {
1da177e4	234	char b[BDEVNAME_SIZE];
b2d444d7 N	235	clear_bit(In_sync, &rdev->flags);
b2d444d7 N	236	set_bit(Faulty, &rdev->flags);
850b2b42	237	set_bit(MD_CHANGE_DEVS, &mddev->flags);
1da177e4	238	conf->working_disks--;
750a8f3e	239	mddev->degraded++;
1da177e4	240	printk(KERN_ALERT "multipath: IO failure on %s,"
d7a420c9 NA	241	" disabling IO path.\n"
d7a420c9 NA	242	"multipath: Operation continuing"
1da177e4 LT	243	" on %d IO paths.\n",
	244	bdevname (rdev->bdev,b),
	245	conf->working_disks);
	246	}
	247	}
	248	}
	249
	250	static void print_multipath_conf (multipath_conf_t *conf)
	251	{
	252	int i;
	253	struct multipath_info *tmp;
	254
	255	printk("MULTIPATH conf printout:\n");
	256	if (!conf) {
	257	printk("(conf==NULL)\n");
	258	return;
	259	}
	260	printk(" --- wd:%d rd:%d\n", conf->working_disks,
	261	conf->raid_disks);
	262
	263	for (i = 0; i < conf->raid_disks; i++) {
	264	char b[BDEVNAME_SIZE];
	265	tmp = conf->multipaths + i;
	266	if (tmp->rdev)
	267	printk(" disk%d, o:%d, dev:%s\n",
b2d444d7	268	i,!test_bit(Faulty, &tmp->rdev->flags),
1da177e4 LT	269	bdevname(tmp->rdev->bdev,b));
	270	}
	271	}
	272
	273
	274	static int multipath_add_disk(mddev_t mddev, mdk_rdev_t rdev)
	275	{
	276	multipath_conf_t *conf = mddev->private;
352d768b	277	struct request_queue *q;
199050ea	278	int err = -EEXIST;
1da177e4 LT	279	int path;
1da177e4 LT	280	struct multipath_info *p;
6c2fce2e NB	281	int first = 0;
	282	int last = mddev->raid_disks - 1;
	283
	284	if (rdev->raid_disk >= 0)
	285	first = last = rdev->raid_disk;
1da177e4 LT	286
	287	print_multipath_conf(conf);
	288
6c2fce2e	289	for (path = first; path <= last; path++)
1da177e4	290	if ((p=conf->multipaths+path)->rdev == NULL) {
352d768b	291	q = rdev->bdev->bd_disk->queue;
8f6c2e4b MP	292	disk_stack_limits(mddev->gendisk, rdev->bdev,
8f6c2e4b MP	293	rdev->data_offset << 9);
1da177e4 LT	294
1da177e4 LT	295	/* as we don't honour merge_bvec_fn, we must never risk
627a2d3c N	296	* violating it, so limit ->max_segments to one, lying
627a2d3c N	297	* within a single page.
1da177e4 LT	298	* (Note: it is very unlikely that a device with
	299	* merge_bvec_fn will be involved in multipath.)
	300	*/
627a2d3c N	301	if (q->merge_bvec_fn) {
	302	blk_queue_max_segments(mddev->queue, 1);
	303	blk_queue_segment_boundary(mddev->queue,
	304	PAGE_CACHE_SIZE - 1);
	305	}
1da177e4 LT	306
1da177e4 LT	307	conf->working_disks++;
750a8f3e	308	mddev->degraded--;
1da177e4	309	rdev->raid_disk = path;
b2d444d7	310	set_bit(In_sync, &rdev->flags);
d6065f7b	311	rcu_assign_pointer(p->rdev, rdev);
199050ea	312	err = 0;
ac5e7113	313	md_integrity_add_rdev(rdev, mddev);
199050ea	314	break;
1da177e4 LT	315	}
	316
	317	print_multipath_conf(conf);
199050ea NB	318
199050ea NB	319	return err;
1da177e4 LT	320	}
	321
	322	static int multipath_remove_disk(mddev_t *mddev, int number)
	323	{
	324	multipath_conf_t *conf = mddev->private;
	325	int err = 0;
	326	mdk_rdev_t *rdev;
	327	struct multipath_info *p = conf->multipaths + number;
	328
	329	print_multipath_conf(conf);
	330
	331	rdev = p->rdev;
	332	if (rdev) {
b2d444d7	333	if (test_bit(In_sync, &rdev->flags) \|\|
1da177e4	334	atomic_read(&rdev->nr_pending)) {
dfc70645 N	335	printk(KERN_ERR "hot-remove-disk, slot %d is identified"
dfc70645 N	336	" but is still operational!\n", number);
1da177e4 LT	337	err = -EBUSY;
	338	goto abort;
	339	}
	340	p->rdev = NULL;
fbd568a3	341	synchronize_rcu();
1da177e4 LT	342	if (atomic_read(&rdev->nr_pending)) {
	343	/* lost the race, try later */
	344	err = -EBUSY;
	345	p->rdev = rdev;
ac5e7113	346	goto abort;
1da177e4	347	}
ac5e7113	348	md_integrity_register(mddev);
1da177e4 LT	349	}
	350	abort:
	351
	352	print_multipath_conf(conf);
	353	return err;
	354	}
	355
	356
	357
	358	/*
	359	* This is a kernel thread which:
	360	*
	361	* 1. Retries failed read operations on working multipaths.
	362	* 2. Updates the raid superblock when problems encounter.
	363	* 3. Performs writes following reads for array syncronising.
	364	*/
	365
	366	static void multipathd (mddev_t *mddev)
	367	{
	368	struct multipath_bh *mp_bh;
	369	struct bio *bio;
	370	unsigned long flags;
070ec55d	371	multipath_conf_t *conf = mddev->private;
1da177e4 LT	372	struct list_head *head = &conf->retry_list;
	373
	374	md_check_recovery(mddev);
	375	for (;;) {
	376	char b[BDEVNAME_SIZE];
	377	spin_lock_irqsave(&conf->device_lock, flags);
	378	if (list_empty(head))
	379	break;
	380	mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
	381	list_del(head->prev);
	382	spin_unlock_irqrestore(&conf->device_lock, flags);
	383
	384	bio = &mp_bh->bio;
	385	bio->bi_sector = mp_bh->master_bio->bi_sector;
	386
	387	if ((mp_bh->path = multipath_map (conf))<0) {
	388	printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
	389	" error for block %llu\n",
	390	bdevname(bio->bi_bdev,b),
	391	(unsigned long long)bio->bi_sector);
	392	multipath_end_bh_io(mp_bh, -EIO);
	393	} else {
	394	printk(KERN_ERR "multipath: %s: redirecting sector %llu"
	395	" to another IO path\n",
	396	bdevname(bio->bi_bdev,b),
	397	(unsigned long long)bio->bi_sector);
	398	bio = (mp_bh->master_bio);
	399	bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
	400	bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
7b6d91da	401	bio->bi_rw \|= REQ_FAILFAST_TRANSPORT;
1da177e4 LT	402	bio->bi_end_io = multipath_end_request;
	403	bio->bi_private = mp_bh;
	404	generic_make_request(bio);
	405	}
	406	}
	407	spin_unlock_irqrestore(&conf->device_lock, flags);
	408	}
	409
80c3a6ce DW	410	static sector_t multipath_size(mddev_t *mddev, sector_t sectors, int raid_disks)
	411	{
	412	WARN_ONCE(sectors \|\| raid_disks,
	413	"%s does not support generic reshape\n", __func__);
	414
	415	return mddev->dev_sectors;
	416	}
	417
1da177e4 LT	418	static int multipath_run (mddev_t *mddev)
	419	{
	420	multipath_conf_t *conf;
	421	int disk_idx;
	422	struct multipath_info *disk;
	423	mdk_rdev_t *rdev;
1da177e4	424
0894cc30 AN	425	if (md_check_no_bitmap(mddev))
	426	return -EINVAL;
	427
1da177e4 LT	428	if (mddev->level != LEVEL_MULTIPATH) {
	429	printk("multipath: %s: raid level not set to multipath IO (%d)\n",
	430	mdname(mddev), mddev->level);
	431	goto out;
	432	}
	433	/*
	434	* copy the already verified devices into our private MULTIPATH
	435	* bookkeeping area. [whatever we allocate in multipath_run(),
	436	* should be freed in multipath_stop()]
	437	*/
e7e72bf6	438	mddev->queue->queue_lock = &mddev->queue->__queue_lock;
1da177e4	439
9ffae0cf	440	conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
1da177e4 LT	441	mddev->private = conf;
	442	if (!conf) {
	443	printk(KERN_ERR
	444	"multipath: couldn't allocate memory for %s\n",
	445	mdname(mddev));
	446	goto out;
	447	}
1da177e4	448
9ffae0cf	449	conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
1da177e4 LT	450	GFP_KERNEL);
	451	if (!conf->multipaths) {
	452	printk(KERN_ERR
	453	"multipath: couldn't allocate memory for %s\n",
	454	mdname(mddev));
	455	goto out_free_conf;
	456	}
1da177e4	457
1da177e4	458	conf->working_disks = 0;
159ec1fc	459	list_for_each_entry(rdev, &mddev->disks, same_set) {
1da177e4 LT	460	disk_idx = rdev->raid_disk;
	461	if (disk_idx < 0 \|\|
	462	disk_idx >= mddev->raid_disks)
	463	continue;
	464
	465	disk = conf->multipaths + disk_idx;
	466	disk->rdev = rdev;
8f6c2e4b MP	467	disk_stack_limits(mddev->gendisk, rdev->bdev,
8f6c2e4b MP	468	rdev->data_offset << 9);
1da177e4	469
1da177e4 LT	470	/* as we don't honour merge_bvec_fn, we must never risk
	471	* violating it, not that we ever expect a device with
	472	* a merge_bvec_fn to be involved in multipath */
627a2d3c N	473	if (rdev->bdev->bd_disk->queue->merge_bvec_fn) {
	474	blk_queue_max_segments(mddev->queue, 1);
	475	blk_queue_segment_boundary(mddev->queue,
	476	PAGE_CACHE_SIZE - 1);
	477	}
1da177e4	478
b2d444d7	479	if (!test_bit(Faulty, &rdev->flags))
1da177e4 LT	480	conf->working_disks++;
	481	}
	482
	483	conf->raid_disks = mddev->raid_disks;
1da177e4 LT	484	conf->mddev = mddev;
	485	spin_lock_init(&conf->device_lock);
	486	INIT_LIST_HEAD(&conf->retry_list);
	487
	488	if (!conf->working_disks) {
	489	printk(KERN_ERR "multipath: no operational IO paths for %s\n",
	490	mdname(mddev));
	491	goto out_free_conf;
	492	}
2e333e89	493	mddev->degraded = conf->raid_disks - conf->working_disks;
1da177e4	494
bbba809e	495	conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
26b6e051	496	sizeof(struct multipath_bh));
1da177e4 LT	497	if (conf->pool == NULL) {
	498	printk(KERN_ERR
	499	"multipath: couldn't allocate memory for %s\n",
	500	mdname(mddev));
	501	goto out_free_conf;
	502	}
	503
	504	{
0da3c619	505	mddev->thread = md_register_thread(multipathd, mddev, NULL);
1da177e4 LT	506	if (!mddev->thread) {
	507	printk(KERN_ERR "multipath: couldn't allocate thread"
	508	" for %s\n", mdname(mddev));
	509	goto out_free_conf;
	510	}
	511	}
	512
	513	printk(KERN_INFO
	514	"multipath: array %s active with %d out of %d IO paths\n",
	515	mdname(mddev), conf->working_disks, mddev->raid_disks);
	516	/*
	517	* Ok, everything is just fine now
	518	*/
1f403624	519	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
7a5febe9 N	520
7a5febe9 N	521	mddev->queue->unplug_fn = multipath_unplug;
0d129228 N	522	mddev->queue->backing_dev_info.congested_fn = multipath_congested;
0d129228 N	523	mddev->queue->backing_dev_info.congested_data = mddev;
ac5e7113	524	md_integrity_register(mddev);
1da177e4 LT	525	return 0;
	526
	527	out_free_conf:
	528	if (conf->pool)
	529	mempool_destroy(conf->pool);
990a8baf	530	kfree(conf->multipaths);
1da177e4 LT	531	kfree(conf);
	532	mddev->private = NULL;
	533	out:
	534	return -EIO;
	535	}
	536
	537
	538	static int multipath_stop (mddev_t *mddev)
	539	{
070ec55d	540	multipath_conf_t *conf = mddev->private;
1da177e4 LT	541
	542	md_unregister_thread(mddev->thread);
	543	mddev->thread = NULL;
	544	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
	545	mempool_destroy(conf->pool);
	546	kfree(conf->multipaths);
	547	kfree(conf);
	548	mddev->private = NULL;
	549	return 0;
	550	}
	551
2604b703	552	static struct mdk_personality multipath_personality =
1da177e4 LT	553	{
1da177e4 LT	554	.name = "multipath",
2604b703	555	.level = LEVEL_MULTIPATH,
1da177e4 LT	556	.owner = THIS_MODULE,
	557	.make_request = multipath_make_request,
	558	.run = multipath_run,
	559	.stop = multipath_stop,
	560	.status = multipath_status,
	561	.error_handler = multipath_error,
	562	.hot_add_disk = multipath_add_disk,
	563	.hot_remove_disk= multipath_remove_disk,
80c3a6ce	564	.size = multipath_size,
1da177e4 LT	565	};
	566
	567	static int __init multipath_init (void)
	568	{
2604b703	569	return register_md_personality (&multipath_personality);
1da177e4 LT	570	}
	571
	572	static void __exit multipath_exit (void)
	573	{
2604b703	574	unregister_md_personality (&multipath_personality);
1da177e4 LT	575	}
	576
	577	module_init(multipath_init);
	578	module_exit(multipath_exit);
	579	MODULE_LICENSE("GPL");
0efb9e61	580	MODULE_DESCRIPTION("simple multi-path personality for MD");
1da177e4	581	MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
d9d166c2	582	MODULE_ALIAS("md-multipath");
2604b703	583	MODULE_ALIAS("md-level--4");