[mirror_ubuntu-artful-kernel.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/module.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/raid/multipath.h>
#include <linux/buffer_head.h>
#include <asm/atomic.h>

#define MAJOR_NR MD_MAJOR
#define MD_DRIVER
#define MD_PERSONALITY

#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_to_conf(mddev);

	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 = mddev_to_conf(mp_bh->mddev);

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

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

	if (bio->bi_size)
		return 1;

	if (uptodate)
		multipath_end_bh_io(mp_bh, 0);
	else if (!bio_rw_ahead(bio)) {
		/*
		 * 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);
	return 0;
}

static void unplug_slaves(mddev_t *mddev)
{
	multipath_conf_t *conf = mddev_to_conf(mddev);
	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)) {
			request_queue_t *r_queue = bdev_get_queue(rdev->bdev);

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

			if (r_queue->unplug_fn)
				r_queue->unplug_fn(r_queue);

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

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


static int multipath_make_request (request_queue_t *q, struct bio * bio)
{
	mddev_t *mddev = q->queuedata;
	multipath_conf_t *conf = mddev_to_conf(mddev);
	struct multipath_bh * mp_bh;
	struct multipath_info *multipath;
	const int rw = bio_data_dir(bio);

	if (unlikely(bio_barrier(bio))) {
		bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
		return 0;
	}

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

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

	disk_stat_inc(mddev->gendisk, ios[rw]);
	disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));

	mp_bh->path = multipath_map(conf);
	if (mp_bh->path < 0) {
		bio_endio(bio, bio->bi_size, -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 |= (1 << BIO_RW_FAILFAST);
	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_to_conf(mddev);
	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_issue_flush(request_queue_t *q, struct gendisk *disk,
				 sector_t *error_sector)
{
	mddev_t *mddev = q->queuedata;
	multipath_conf_t *conf = mddev_to_conf(mddev);
	int i, ret = 0;

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

			if (!r_queue->issue_flush_fn)
				ret = -EOPNOTSUPP;
			else {
				atomic_inc(&rdev->nr_pending);
				rcu_read_unlock();
				ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
							      error_sector);
				rdev_dec_pending(rdev, mddev);
				rcu_read_lock();
			}
		}
	}
	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_to_conf(mddev);

	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);
			mddev->sb_dirty = 1;
			conf->working_disks--;
			printk(KERN_ALERT "multipath: IO failure on %s,"
				" disabling IO path. \n	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 found = 0;
	int path;
	struct multipath_info *p;

	print_multipath_conf(conf);

	for (path=0; path<mddev->raid_disks; path++) 
		if ((p=conf->multipaths+path)->rdev == NULL) {
			q = rdev->bdev->bd_disk->queue;
			blk_queue_stack_limits(mddev->queue, q);

		/* as we don't honour merge_bvec_fn, we must never risk
		 * violating it, so limit ->max_sector to one PAGE, as
		 * a one page request is never in violation.
		 * (Note: it is very unlikely that a device with
		 * merge_bvec_fn will be involved in multipath.)
		 */
			if (q->merge_bvec_fn &&
			    mddev->queue->max_sectors > (PAGE_SIZE>>9))
				blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

			conf->working_disks++;
			rdev->raid_disk = path;
			set_bit(In_sync, &rdev->flags);
			rcu_assign_pointer(p->rdev, rdev);
			found = 1;
		}

	print_multipath_conf(conf);
	return found;
}

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;
		}
	}
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_to_conf(mddev);
	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 |= (1 << BIO_RW_FAILFAST);
			bio->bi_end_io = multipath_end_request;
			bio->bi_private = mp_bh;
			generic_make_request(bio);
		}
	}
	spin_unlock_irqrestore(&conf->device_lock, flags);
}

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

	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()]
	 */

	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;
	ITERATE_RDEV(mddev,rdev,tmp) {
		disk_idx = rdev->raid_disk;
		if (disk_idx < 0 ||
		    disk_idx >= mddev->raid_disks)
			continue;

		disk = conf->multipaths + disk_idx;
		disk->rdev = rdev;

		blk_queue_stack_limits(mddev->queue,
				       rdev->bdev->bd_disk->queue);
		/* 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 &&
		    mddev->queue->max_sectors > (PAGE_SIZE>>9))
			blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);

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

	conf->raid_disks = mddev->raid_disks;
	mddev->sb_dirty = 1;
	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_kzalloc_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, "%s_multipath");
		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
	 */
	mddev->array_size = mddev->size;

	mddev->queue->unplug_fn = multipath_unplug;
	mddev->queue->issue_flush_fn = multipath_issue_flush;

	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_to_conf(mddev);

	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,
};

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_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
	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>
	28
	29	#define MAJOR_NR MD_MAJOR
	30	#define MD_DRIVER
	31	#define MD_PERSONALITY
	32
	33	#define MAX_WORK_PER_DISK 128
	34
	35	#define NR_RESERVED_BUFS 32
	36
	37
1da177e4 LT	38	static int multipath_map (multipath_conf_t *conf)
	39	{
	40	int i, disks = conf->raid_disks;
	41
	42	/*
	43	* Later we do read balancing on the read side
	44	* now we use the first available disk.
	45	*/
	46
	47	rcu_read_lock();
	48	for (i = 0; i < disks; i++) {
d6065f7b	49	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
b2d444d7	50	if (rdev && test_bit(In_sync, &rdev->flags)) {
1da177e4 LT	51	atomic_inc(&rdev->nr_pending);
	52	rcu_read_unlock();
	53	return i;
	54	}
	55	}
	56	rcu_read_unlock();
	57
	58	printk(KERN_ERR "multipath_map(): no more operational IO paths?\n");
	59	return (-1);
	60	}
	61
	62	static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
	63	{
	64	unsigned long flags;
	65	mddev_t *mddev = mp_bh->mddev;
	66	multipath_conf_t *conf = mddev_to_conf(mddev);
	67
	68	spin_lock_irqsave(&conf->device_lock, flags);
	69	list_add(&mp_bh->retry_list, &conf->retry_list);
	70	spin_unlock_irqrestore(&conf->device_lock, flags);
	71	md_wakeup_thread(mddev->thread);
	72	}
	73
	74
	75	/*
	76	* multipath_end_bh_io() is called when we have finished servicing a multipathed
	77	* operation and are ready to return a success/failure code to the buffer
	78	* cache layer.
	79	*/
	80	static void multipath_end_bh_io (struct multipath_bh *mp_bh, int err)
	81	{
	82	struct bio *bio = mp_bh->master_bio;
	83	multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
	84
	85	bio_endio(bio, bio->bi_size, err);
	86	mempool_free(mp_bh, conf->pool);
	87	}
	88
75c96f85 AB	89	static int multipath_end_request(struct bio *bio, unsigned int bytes_done,
75c96f85 AB	90	int error)
1da177e4 LT	91	{
	92	int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
	93	struct multipath_bh * mp_bh = (struct multipath_bh *)(bio->bi_private);
	94	multipath_conf_t *conf = mddev_to_conf(mp_bh->mddev);
	95	mdk_rdev_t *rdev = conf->multipaths[mp_bh->path].rdev;
	96
	97	if (bio->bi_size)
	98	return 1;
	99
	100	if (uptodate)
	101	multipath_end_bh_io(mp_bh, 0);
	102	else if (!bio_rw_ahead(bio)) {
	103	/*
	104	* oops, IO error:
	105	*/
	106	char b[BDEVNAME_SIZE];
	107	md_error (mp_bh->mddev, rdev);
	108	printk(KERN_ERR "multipath: %s: rescheduling sector %llu\n",
	109	bdevname(rdev->bdev,b),
	110	(unsigned long long)bio->bi_sector);
	111	multipath_reschedule_retry(mp_bh);
	112	} else
	113	multipath_end_bh_io(mp_bh, error);
	114	rdev_dec_pending(rdev, conf->mddev);
	115	return 0;
	116	}
	117
	118	static void unplug_slaves(mddev_t *mddev)
	119	{
	120	multipath_conf_t *conf = mddev_to_conf(mddev);
	121	int i;
	122
	123	rcu_read_lock();
	124	for (i=0; i<mddev->raid_disks; i++) {
d6065f7b	125	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
b2d444d7 N	126	if (rdev && !test_bit(Faulty, &rdev->flags)
b2d444d7 N	127	&& atomic_read(&rdev->nr_pending)) {
1da177e4 LT	128	request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
	129
	130	atomic_inc(&rdev->nr_pending);
	131	rcu_read_unlock();
	132
	133	if (r_queue->unplug_fn)
	134	r_queue->unplug_fn(r_queue);
	135
	136	rdev_dec_pending(rdev, mddev);
	137	rcu_read_lock();
	138	}
	139	}
	140	rcu_read_unlock();
	141	}
	142
	143	static void multipath_unplug(request_queue_t *q)
	144	{
	145	unplug_slaves(q->queuedata);
	146	}
	147
	148
	149	static int multipath_make_request (request_queue_t q, struct bio bio)
	150	{
	151	mddev_t *mddev = q->queuedata;
	152	multipath_conf_t *conf = mddev_to_conf(mddev);
	153	struct multipath_bh * mp_bh;
	154	struct multipath_info *multipath;
a362357b	155	const int rw = bio_data_dir(bio);
1da177e4	156
e5dcdd80 N	157	if (unlikely(bio_barrier(bio))) {
	158	bio_endio(bio, bio->bi_size, -EOPNOTSUPP);
	159	return 0;
	160	}
	161
1da177e4 LT	162	mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
	163
	164	mp_bh->master_bio = bio;
	165	mp_bh->mddev = mddev;
	166
a362357b JA	167	disk_stat_inc(mddev->gendisk, ios[rw]);
a362357b JA	168	disk_stat_add(mddev->gendisk, sectors[rw], bio_sectors(bio));
1da177e4 LT	169
	170	mp_bh->path = multipath_map(conf);
	171	if (mp_bh->path < 0) {
	172	bio_endio(bio, bio->bi_size, -EIO);
	173	mempool_free(mp_bh, conf->pool);
	174	return 0;
	175	}
	176	multipath = conf->multipaths + mp_bh->path;
	177
	178	mp_bh->bio = *bio;
	179	mp_bh->bio.bi_sector += multipath->rdev->data_offset;
	180	mp_bh->bio.bi_bdev = multipath->rdev->bdev;
	181	mp_bh->bio.bi_rw \|= (1 << BIO_RW_FAILFAST);
	182	mp_bh->bio.bi_end_io = multipath_end_request;
	183	mp_bh->bio.bi_private = mp_bh;
	184	generic_make_request(&mp_bh->bio);
	185	return 0;
	186	}
	187
	188	static void multipath_status (struct seq_file seq, mddev_t mddev)
	189	{
	190	multipath_conf_t *conf = mddev_to_conf(mddev);
	191	int i;
	192
	193	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
	194	conf->working_disks);
	195	for (i = 0; i < conf->raid_disks; i++)
	196	seq_printf (seq, "%s",
	197	conf->multipaths[i].rdev &&
b2d444d7	198	test_bit(In_sync, &conf->multipaths[i].rdev->flags) ? "U" : "_");
1da177e4 LT	199	seq_printf (seq, "]");
	200	}
	201
	202	static int multipath_issue_flush(request_queue_t q, struct gendisk disk,
	203	sector_t *error_sector)
	204	{
	205	mddev_t *mddev = q->queuedata;
	206	multipath_conf_t *conf = mddev_to_conf(mddev);
	207	int i, ret = 0;
	208
	209	rcu_read_lock();
	210	for (i=0; i<mddev->raid_disks && ret == 0; i++) {
d6065f7b	211	mdk_rdev_t *rdev = rcu_dereference(conf->multipaths[i].rdev);
b2d444d7	212	if (rdev && !test_bit(Faulty, &rdev->flags)) {
1da177e4 LT	213	struct block_device *bdev = rdev->bdev;
	214	request_queue_t *r_queue = bdev_get_queue(bdev);
	215
	216	if (!r_queue->issue_flush_fn)
	217	ret = -EOPNOTSUPP;
	218	else {
	219	atomic_inc(&rdev->nr_pending);
	220	rcu_read_unlock();
	221	ret = r_queue->issue_flush_fn(r_queue, bdev->bd_disk,
	222	error_sector);
	223	rdev_dec_pending(rdev, mddev);
	224	rcu_read_lock();
	225	}
	226	}
	227	}
	228	rcu_read_unlock();
	229	return ret;
	230	}
	231
	232	/*
	233	* Careful, this can execute in IRQ contexts as well!
	234	*/
	235	static void multipath_error (mddev_t mddev, mdk_rdev_t rdev)
	236	{
	237	multipath_conf_t *conf = mddev_to_conf(mddev);
	238
	239	if (conf->working_disks <= 1) {
	240	/*
	241	* Uh oh, we can do nothing if this is our last path, but
	242	* first check if this is a queued request for a device
	243	* which has just failed.
	244	*/
	245	printk(KERN_ALERT
	246	"multipath: only one IO path left and IO error.\n");
	247	/* leave it active... it's all we have */
	248	} else {
	249	/*
	250	* Mark disk as unusable
	251	*/
b2d444d7	252	if (!test_bit(Faulty, &rdev->flags)) {
1da177e4	253	char b[BDEVNAME_SIZE];
b2d444d7 N	254	clear_bit(In_sync, &rdev->flags);
b2d444d7 N	255	set_bit(Faulty, &rdev->flags);
1da177e4 LT	256	mddev->sb_dirty = 1;
	257	conf->working_disks--;
	258	printk(KERN_ALERT "multipath: IO failure on %s,"
	259	" disabling IO path. \n Operation continuing"
	260	" on %d IO paths.\n",
	261	bdevname (rdev->bdev,b),
	262	conf->working_disks);
	263	}
	264	}
	265	}
	266
	267	static void print_multipath_conf (multipath_conf_t *conf)
	268	{
	269	int i;
	270	struct multipath_info *tmp;
	271
	272	printk("MULTIPATH conf printout:\n");
	273	if (!conf) {
	274	printk("(conf==NULL)\n");
	275	return;
	276	}
	277	printk(" --- wd:%d rd:%d\n", conf->working_disks,
	278	conf->raid_disks);
	279
	280	for (i = 0; i < conf->raid_disks; i++) {
	281	char b[BDEVNAME_SIZE];
	282	tmp = conf->multipaths + i;
	283	if (tmp->rdev)
	284	printk(" disk%d, o:%d, dev:%s\n",
b2d444d7	285	i,!test_bit(Faulty, &tmp->rdev->flags),
1da177e4 LT	286	bdevname(tmp->rdev->bdev,b));
	287	}
	288	}
	289
	290
	291	static int multipath_add_disk(mddev_t mddev, mdk_rdev_t rdev)
	292	{
	293	multipath_conf_t *conf = mddev->private;
352d768b	294	struct request_queue *q;
1da177e4 LT	295	int found = 0;
	296	int path;
	297	struct multipath_info *p;
	298
	299	print_multipath_conf(conf);
	300
	301	for (path=0; path<mddev->raid_disks; path++)
	302	if ((p=conf->multipaths+path)->rdev == NULL) {
352d768b JJ	303	q = rdev->bdev->bd_disk->queue;
352d768b JJ	304	blk_queue_stack_limits(mddev->queue, q);
1da177e4 LT	305
	306	/* as we don't honour merge_bvec_fn, we must never risk
	307	* violating it, so limit ->max_sector to one PAGE, as
	308	* a one page request is never in violation.
	309	* (Note: it is very unlikely that a device with
	310	* merge_bvec_fn will be involved in multipath.)
	311	*/
352d768b	312	if (q->merge_bvec_fn &&
1da177e4 LT	313	mddev->queue->max_sectors > (PAGE_SIZE>>9))
	314	blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
	315
	316	conf->working_disks++;
	317	rdev->raid_disk = path;
b2d444d7	318	set_bit(In_sync, &rdev->flags);
d6065f7b	319	rcu_assign_pointer(p->rdev, rdev);
1da177e4 LT	320	found = 1;
	321	}
	322
	323	print_multipath_conf(conf);
	324	return found;
	325	}
	326
	327	static int multipath_remove_disk(mddev_t *mddev, int number)
	328	{
	329	multipath_conf_t *conf = mddev->private;
	330	int err = 0;
	331	mdk_rdev_t *rdev;
	332	struct multipath_info *p = conf->multipaths + number;
	333
	334	print_multipath_conf(conf);
	335
	336	rdev = p->rdev;
	337	if (rdev) {
b2d444d7	338	if (test_bit(In_sync, &rdev->flags) \|\|
1da177e4 LT	339	atomic_read(&rdev->nr_pending)) {
	340	printk(KERN_ERR "hot-remove-disk, slot %d is identified" " but is still operational!\n", number);
	341	err = -EBUSY;
	342	goto abort;
	343	}
	344	p->rdev = NULL;
fbd568a3	345	synchronize_rcu();
1da177e4 LT	346	if (atomic_read(&rdev->nr_pending)) {
	347	/* lost the race, try later */
	348	err = -EBUSY;
	349	p->rdev = rdev;
	350	}
	351	}
	352	abort:
	353
	354	print_multipath_conf(conf);
	355	return err;
	356	}
	357
	358
	359
	360	/*
	361	* This is a kernel thread which:
	362	*
	363	* 1. Retries failed read operations on working multipaths.
	364	* 2. Updates the raid superblock when problems encounter.
	365	* 3. Performs writes following reads for array syncronising.
	366	*/
	367
	368	static void multipathd (mddev_t *mddev)
	369	{
	370	struct multipath_bh *mp_bh;
	371	struct bio *bio;
	372	unsigned long flags;
	373	multipath_conf_t *conf = mddev_to_conf(mddev);
	374	struct list_head *head = &conf->retry_list;
	375
	376	md_check_recovery(mddev);
	377	for (;;) {
	378	char b[BDEVNAME_SIZE];
	379	spin_lock_irqsave(&conf->device_lock, flags);
	380	if (list_empty(head))
	381	break;
	382	mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
	383	list_del(head->prev);
	384	spin_unlock_irqrestore(&conf->device_lock, flags);
	385
	386	bio = &mp_bh->bio;
	387	bio->bi_sector = mp_bh->master_bio->bi_sector;
	388
	389	if ((mp_bh->path = multipath_map (conf))<0) {
	390	printk(KERN_ALERT "multipath: %s: unrecoverable IO read"
	391	" error for block %llu\n",
	392	bdevname(bio->bi_bdev,b),
	393	(unsigned long long)bio->bi_sector);
	394	multipath_end_bh_io(mp_bh, -EIO);
	395	} else {
	396	printk(KERN_ERR "multipath: %s: redirecting sector %llu"
	397	" to another IO path\n",
	398	bdevname(bio->bi_bdev,b),
	399	(unsigned long long)bio->bi_sector);
	400	bio = (mp_bh->master_bio);
	401	bio->bi_sector += conf->multipaths[mp_bh->path].rdev->data_offset;
	402	bio->bi_bdev = conf->multipaths[mp_bh->path].rdev->bdev;
	403	bio->bi_rw \|= (1 << BIO_RW_FAILFAST);
	404	bio->bi_end_io = multipath_end_request;
	405	bio->bi_private = mp_bh;
	406	generic_make_request(bio);
	407	}
	408	}
	409	spin_unlock_irqrestore(&conf->device_lock, flags);
410	}
411
412	static int multipath_run (mddev_t *mddev)
413	{
414	multipath_conf_t *conf;
415	int disk_idx;
416	struct multipath_info *disk;
417	mdk_rdev_t *rdev;
418	struct list_head *tmp;
419
420	if (mddev->level != LEVEL_MULTIPATH) {
421	printk("multipath: %s: raid level not set to multipath IO (%d)\n",
422	mdname(mddev), mddev->level);
423	goto out;
424	}
425	/*
426	* copy the already verified devices into our private MULTIPATH
427	* bookkeeping area. [whatever we allocate in multipath_run(),
428	* should be freed in multipath_stop()]
429	*/
430
9ffae0cf	431	conf = kzalloc(sizeof(multipath_conf_t), GFP_KERNEL);
1da177e4 LT	432	mddev->private = conf;
	433	if (!conf) {
	434	printk(KERN_ERR
	435	"multipath: couldn't allocate memory for %s\n",
	436	mdname(mddev));
	437	goto out;
	438	}
1da177e4	439
9ffae0cf	440	conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
1da177e4 LT	441	GFP_KERNEL);
	442	if (!conf->multipaths) {
	443	printk(KERN_ERR
	444	"multipath: couldn't allocate memory for %s\n",
	445	mdname(mddev));
	446	goto out_free_conf;
	447	}
1da177e4	448
1da177e4 LT	449	conf->working_disks = 0;
	450	ITERATE_RDEV(mddev,rdev,tmp) {
	451	disk_idx = rdev->raid_disk;
	452	if (disk_idx < 0 \|\|
	453	disk_idx >= mddev->raid_disks)
	454	continue;
	455
	456	disk = conf->multipaths + disk_idx;
	457	disk->rdev = rdev;
	458
	459	blk_queue_stack_limits(mddev->queue,
	460	rdev->bdev->bd_disk->queue);
	461	/* as we don't honour merge_bvec_fn, we must never risk
	462	* violating it, not that we ever expect a device with
	463	* a merge_bvec_fn to be involved in multipath */
	464	if (rdev->bdev->bd_disk->queue->merge_bvec_fn &&
	465	mddev->queue->max_sectors > (PAGE_SIZE>>9))
	466	blk_queue_max_sectors(mddev->queue, PAGE_SIZE>>9);
	467
b2d444d7	468	if (!test_bit(Faulty, &rdev->flags))
1da177e4 LT	469	conf->working_disks++;
	470	}
	471
	472	conf->raid_disks = mddev->raid_disks;
	473	mddev->sb_dirty = 1;
	474	conf->mddev = mddev;
	475	spin_lock_init(&conf->device_lock);
	476	INIT_LIST_HEAD(&conf->retry_list);
	477
	478	if (!conf->working_disks) {
	479	printk(KERN_ERR "multipath: no operational IO paths for %s\n",
	480	mdname(mddev));
	481	goto out_free_conf;
	482	}
	483	mddev->degraded = conf->raid_disks = conf->working_disks;
	484
26b6e051 MD	485	conf->pool = mempool_create_kzalloc_pool(NR_RESERVED_BUFS,
26b6e051 MD	486	sizeof(struct multipath_bh));
1da177e4 LT	487	if (conf->pool == NULL) {
	488	printk(KERN_ERR
	489	"multipath: couldn't allocate memory for %s\n",
	490	mdname(mddev));
	491	goto out_free_conf;
	492	}
	493
	494	{
	495	mddev->thread = md_register_thread(multipathd, mddev, "%s_multipath");
	496	if (!mddev->thread) {
	497	printk(KERN_ERR "multipath: couldn't allocate thread"
	498	" for %s\n", mdname(mddev));
	499	goto out_free_conf;
	500	}
	501	}
	502
	503	printk(KERN_INFO
	504	"multipath: array %s active with %d out of %d IO paths\n",
	505	mdname(mddev), conf->working_disks, mddev->raid_disks);
	506	/*
	507	* Ok, everything is just fine now
	508	*/
	509	mddev->array_size = mddev->size;
7a5febe9 N	510
	511	mddev->queue->unplug_fn = multipath_unplug;
	512	mddev->queue->issue_flush_fn = multipath_issue_flush;
	513
1da177e4 LT	514	return 0;
	515
	516	out_free_conf:
	517	if (conf->pool)
	518	mempool_destroy(conf->pool);
990a8baf	519	kfree(conf->multipaths);
1da177e4 LT	520	kfree(conf);
	521	mddev->private = NULL;
	522	out:
	523	return -EIO;
	524	}
	525
	526
	527	static int multipath_stop (mddev_t *mddev)
	528	{
	529	multipath_conf_t *conf = mddev_to_conf(mddev);
	530
	531	md_unregister_thread(mddev->thread);
	532	mddev->thread = NULL;
	533	blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
	534	mempool_destroy(conf->pool);
	535	kfree(conf->multipaths);
	536	kfree(conf);
	537	mddev->private = NULL;
	538	return 0;
	539	}
	540
2604b703	541	static struct mdk_personality multipath_personality =
1da177e4 LT	542	{
1da177e4 LT	543	.name = "multipath",
2604b703	544	.level = LEVEL_MULTIPATH,
1da177e4 LT	545	.owner = THIS_MODULE,
	546	.make_request = multipath_make_request,
	547	.run = multipath_run,
	548	.stop = multipath_stop,
	549	.status = multipath_status,
	550	.error_handler = multipath_error,
	551	.hot_add_disk = multipath_add_disk,
	552	.hot_remove_disk= multipath_remove_disk,
	553	};
	554
	555	static int __init multipath_init (void)
	556	{
2604b703	557	return register_md_personality (&multipath_personality);
1da177e4 LT	558	}
	559
	560	static void __exit multipath_exit (void)
	561	{
2604b703	562	unregister_md_personality (&multipath_personality);
1da177e4 LT	563	}
	564
	565	module_init(multipath_init);
	566	module_exit(multipath_exit);
	567	MODULE_LICENSE("GPL");
	568	MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
d9d166c2	569	MODULE_ALIAS("md-multipath");
2604b703	570	MODULE_ALIAS("md-level--4");