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Commit 245f46c2 authored by NeilBrown's avatar NeilBrown
Browse files

md: add ->takeover method to support changing the personality managing an array 



Implement this for RAID6 to be able to 'takeover' a RAID5 array.  The
new RAID6 will use a layout which places Q on the last device, and
that device will be missing.
If there are any available spares, one will immediately have Q
recovered onto it.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
parent 409c57f3

drivers/md/md.c

+92 −9
Original line number Diff line number Diff line
@@ -2649,9 +2649,12 @@ level_show(mddev_t *mddev, char *page) 
static ssize_t

level_store(mddev_t *mddev, const char *buf, size_t len)

{

	char level[16];

	ssize_t rv = len;

	if (mddev->pers)

		return -EBUSY;

	struct mdk_personality *pers;

	void *priv;



	if (mddev->pers == NULL) {

		if (len == 0)

			return 0;

		if (len >= sizeof(mddev->clevel))
@@ -2664,6 +2667,86 @@ level_store(mddev_t *mddev, const char *buf, size_t len) 
		return rv;

	}



	/* request to change the personality.  Need to ensure:

	 *  - array is not engaged in resync/recovery/reshape

	 *  - old personality can be suspended

	 *  - new personality will access other array.

	 */



	if (mddev->sync_thread || mddev->reshape_position != MaxSector)

		return -EBUSY;



	if (!mddev->pers->quiesce) {

		printk(KERN_WARNING "md: %s: %s does not support online personality change\n",

		       mdname(mddev), mddev->pers->name);

		return -EINVAL;

	}



	/* Now find the new personality */

	if (len == 0 || len >= sizeof(level))

		return -EINVAL;

	strncpy(level, buf, len);

	if (level[len-1] == '\n')

		len--;

	level[len] = 0;



	request_module("md-%s", level);

	spin_lock(&pers_lock);

	pers = find_pers(LEVEL_NONE, level);

	if (!pers || !try_module_get(pers->owner)) {

		spin_unlock(&pers_lock);

		printk(KERN_WARNING "md: personality %s not loaded\n", level);

		return -EINVAL;

	}

	spin_unlock(&pers_lock);



	if (pers == mddev->pers) {

		/* Nothing to do! */

		module_put(pers->owner);

		return rv;

	}

	if (!pers->takeover) {

		module_put(pers->owner);

		printk(KERN_WARNING "md: %s: %s does not support personality takeover\n",

		       mdname(mddev), level);

		return -EINVAL;

	}



	/* ->takeover must set new_* and/or delta_disks

	 * if it succeeds, and may set them when it fails.

	 */

	priv = pers->takeover(mddev);

	if (IS_ERR(priv)) {

		mddev->new_level = mddev->level;

		mddev->new_layout = mddev->layout;

		mddev->new_chunk = mddev->chunk_size;

		mddev->raid_disks -= mddev->delta_disks;

		mddev->delta_disks = 0;

		module_put(pers->owner);

		printk(KERN_WARNING "md: %s: %s would not accept array\n",

		       mdname(mddev), level);

		return PTR_ERR(priv);

	}



	/* Looks like we have a winner */

	mddev_suspend(mddev);

	mddev->pers->stop(mddev);

	module_put(mddev->pers->owner);

	mddev->pers = pers;

	mddev->private = priv;

	strlcpy(mddev->clevel, pers->name, sizeof(mddev->clevel));

	mddev->level = mddev->new_level;

	mddev->layout = mddev->new_layout;

	mddev->chunk_size = mddev->new_chunk;

	mddev->delta_disks = 0;

	pers->run(mddev);

	mddev_resume(mddev);

	set_bit(MD_CHANGE_DEVS, &mddev->flags);

	set_bit(MD_RECOVERY_NEEDED, &mddev->recovery);

	md_wakeup_thread(mddev->thread);

	return rv;

}



static struct md_sysfs_entry md_level =

__ATTR(level, S_IRUGO|S_IWUSR, level_show, level_store);

drivers/md/md.h

+10 −0
Original line number Diff line number Diff line
@@ -321,6 +321,16 @@ struct mdk_personality 
	 * others - reserved

	 */

	void (*quiesce) (mddev_t *mddev, int state);

	/* takeover is used to transition an array from one

	 * personality to another.  The new personality must be able

	 * to handle the data in the current layout.

	 * e.g. 2drive raid1 -> 2drive raid5

	 *      ndrive raid5 -> degraded n+1drive raid6 with special layout

	 * If the takeover succeeds, a new 'private' structure is returned.

	 * This needs to be installed and then ->run used to activate the

	 * array.

	 */

	void *(*takeover) (mddev_t *mddev);

};

drivers/md/raid5.c

+59 −5
Original line number Diff line number Diff line
@@ -933,8 +933,10 @@ static int grow_stripes(raid5_conf_t *conf, int num) 
	struct kmem_cache *sc;

	int devs = conf->raid_disks;



	sprintf(conf->cache_name[0], "raid5-%s", mdname(conf->mddev));

	sprintf(conf->cache_name[1], "raid5-%s-alt", mdname(conf->mddev));

	sprintf(conf->cache_name[0],

		"raid%d-%s", conf->level, mdname(conf->mddev));

	sprintf(conf->cache_name[1],

		"raid%d-%s-alt", conf->level, mdname(conf->mddev));

	conf->active_name = 0;

	sc = kmem_cache_create(conf->cache_name[conf->active_name],

			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
@@ -4361,10 +4363,12 @@ static int run(mddev_t *mddev) 
		BUG_ON(mddev->chunk_size != mddev->new_chunk);

		BUG_ON(mddev->delta_disks != 0);

	}



	if (mddev->private == NULL)

		conf = setup_conf(mddev);

	else

		conf = mddev->private;



	if (conf == NULL)

		return -EIO;

	if (IS_ERR(conf))

		return PTR_ERR(conf);
@@ -4880,6 +4884,55 @@ static void raid5_quiesce(mddev_t *mddev, int state) 
	}

}



static struct mdk_personality raid5_personality;



static void *raid6_takeover(mddev_t *mddev)

{

	/* Currently can only take over a raid5.  We map the

	 * personality to an equivalent raid6 personality

	 * with the Q block at the end.

	 */

	int new_layout;



	if (mddev->pers != &raid5_personality)

		return ERR_PTR(-EINVAL);

	if (mddev->degraded > 1)

		return ERR_PTR(-EINVAL);

	if (mddev->raid_disks > 253)

		return ERR_PTR(-EINVAL);

	if (mddev->raid_disks < 3)

		return ERR_PTR(-EINVAL);



	switch (mddev->layout) {

	case ALGORITHM_LEFT_ASYMMETRIC:

		new_layout = ALGORITHM_LEFT_ASYMMETRIC_6;

		break;

	case ALGORITHM_RIGHT_ASYMMETRIC:

		new_layout = ALGORITHM_RIGHT_ASYMMETRIC_6;

		break;

	case ALGORITHM_LEFT_SYMMETRIC:

		new_layout = ALGORITHM_LEFT_SYMMETRIC_6;

		break;

	case ALGORITHM_RIGHT_SYMMETRIC:

		new_layout = ALGORITHM_RIGHT_SYMMETRIC_6;

		break;

	case ALGORITHM_PARITY_0:

		new_layout = ALGORITHM_PARITY_0_6;

		break;

	case ALGORITHM_PARITY_N:

		new_layout = ALGORITHM_PARITY_N;

		break;

	default:

		return ERR_PTR(-EINVAL);

	}

	mddev->new_level = 6;

	mddev->new_layout = new_layout;

	mddev->delta_disks = 1;

	mddev->raid_disks += 1;

	return setup_conf(mddev);

}





static struct mdk_personality raid6_personality =

{

	.name		= "raid6",
@@ -4900,6 +4953,7 @@ static struct mdk_personality raid6_personality = 
	.start_reshape  = raid5_start_reshape,

#endif

	.quiesce	= raid5_quiesce,

	.takeover	= raid6_takeover,

};

static struct mdk_personality raid5_personality =

{