[linux-block.git] / block / holder.c

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/blkdev.h>
#include <linux/slab.h>

struct bd_holder_disk {
	struct list_head	list;
	struct kobject		*holder_dir;
	int			refcnt;
};

static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
						  struct gendisk *disk)
{
	struct bd_holder_disk *holder;

	list_for_each_entry(holder, &disk->slave_bdevs, list)
		if (holder->holder_dir == bdev->bd_holder_dir)
			return holder;
	return NULL;
}

static int add_symlink(struct kobject *from, struct kobject *to)
{
	return sysfs_create_link(from, to, kobject_name(to));
}

static void del_symlink(struct kobject *from, struct kobject *to)
{
	sysfs_remove_link(from, kobject_name(to));
}

/**
 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
 * @bdev: the claimed slave bdev
 * @disk: the holding disk
 *
 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
 *
 * This functions creates the following sysfs symlinks.
 *
 * - from "slaves" directory of the holder @disk to the claimed @bdev
 * - from "holders" directory of the @bdev to the holder @disk
 *
 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
 * passed to bd_link_disk_holder(), then:
 *
 *   /sys/block/dm-0/slaves/sda --> /sys/block/sda
 *   /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
 *
 * The caller must have claimed @bdev before calling this function and
 * ensure that both @bdev and @disk are valid during the creation and
 * lifetime of these symlinks.
 *
 * CONTEXT:
 * Might sleep.
 *
 * RETURNS:
 * 0 on success, -errno on failure.
 */
int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
	struct bd_holder_disk *holder;
	int ret = 0;

	if (WARN_ON_ONCE(!disk->slave_dir))
		return -EINVAL;

	if (bdev->bd_disk == disk)
		return -EINVAL;

	/*
	 * del_gendisk drops the initial reference to bd_holder_dir, so we
	 * need to keep our own here to allow for cleanup past that point.
	 */
	mutex_lock(&bdev->bd_disk->open_mutex);
	if (!disk_live(bdev->bd_disk)) {
		mutex_unlock(&bdev->bd_disk->open_mutex);
		return -ENODEV;
	}
	kobject_get(bdev->bd_holder_dir);
	mutex_unlock(&bdev->bd_disk->open_mutex);

	mutex_lock(&disk->open_mutex);
	WARN_ON_ONCE(!bdev->bd_holder);

	holder = bd_find_holder_disk(bdev, disk);
	if (holder) {
		kobject_put(bdev->bd_holder_dir);
		holder->refcnt++;
		goto out_unlock;
	}

	holder = kzalloc(sizeof(*holder), GFP_KERNEL);
	if (!holder) {
		ret = -ENOMEM;
		goto out_unlock;
	}

	INIT_LIST_HEAD(&holder->list);
	holder->refcnt = 1;
	holder->holder_dir = bdev->bd_holder_dir;

	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
	if (ret)
		goto out_free_holder;
	ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
	if (ret)
		goto out_del_symlink;
	list_add(&holder->list, &disk->slave_bdevs);

	mutex_unlock(&disk->open_mutex);
	return 0;

out_del_symlink:
	del_symlink(disk->slave_dir, bdev_kobj(bdev));
out_free_holder:
	kfree(holder);
out_unlock:
	mutex_unlock(&disk->open_mutex);
	if (ret)
		kobject_put(bdev->bd_holder_dir);
	return ret;
}
EXPORT_SYMBOL_GPL(bd_link_disk_holder);

/**
 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
 * @bdev: the calimed slave bdev
 * @disk: the holding disk
 *
 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
 *
 * CONTEXT:
 * Might sleep.
 */
void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
	struct bd_holder_disk *holder;

	if (WARN_ON_ONCE(!disk->slave_dir))
		return;

	mutex_lock(&disk->open_mutex);
	holder = bd_find_holder_disk(bdev, disk);
	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
		del_symlink(disk->slave_dir, bdev_kobj(bdev));
		del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
		kobject_put(holder->holder_dir);
		list_del_init(&holder->list);
		kfree(holder);
	}
	mutex_unlock(&disk->open_mutex);
}
EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
Commit	Line	Data
c66fd019	1	// SPDX-License-Identifier: GPL-2.0-only
322cbb50	2	#include <linux/blkdev.h>
b81e0c23	3	#include <linux/slab.h>
c66fd019 CH	4
	5	struct bd_holder_disk {
	6	struct list_head list;
3b3449c1	7	struct kobject *holder_dir;
c66fd019 CH	8	int refcnt;
	9	};
	10
	11	static struct bd_holder_disk bd_find_holder_disk(struct block_device bdev,
	12	struct gendisk *disk)
	13	{
	14	struct bd_holder_disk *holder;
	15
0dbcfe24	16	list_for_each_entry(holder, &disk->slave_bdevs, list)
3b3449c1	17	if (holder->holder_dir == bdev->bd_holder_dir)
c66fd019 CH	18	return holder;
	19	return NULL;
	20	}
	21
	22	static int add_symlink(struct kobject from, struct kobject to)
	23	{
	24	return sysfs_create_link(from, to, kobject_name(to));
	25	}
	26
	27	static void del_symlink(struct kobject from, struct kobject to)
	28	{
	29	sysfs_remove_link(from, kobject_name(to));
	30	}
	31
	32	/**
	33	* bd_link_disk_holder - create symlinks between holding disk and slave bdev
	34	* @bdev: the claimed slave bdev
	35	* @disk: the holding disk
	36	*
	37	* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
	38	*
	39	* This functions creates the following sysfs symlinks.
	40	*
	41	* - from "slaves" directory of the holder @disk to the claimed @bdev
	42	* - from "holders" directory of the @bdev to the holder @disk
	43	*
	44	* For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
	45	* passed to bd_link_disk_holder(), then:
	46	*
	47	* /sys/block/dm-0/slaves/sda --> /sys/block/sda
	48	* /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
	49	*
	50	* The caller must have claimed @bdev before calling this function and
	51	* ensure that both @bdev and @disk are valid during the creation and
	52	* lifetime of these symlinks.
	53	*
	54	* CONTEXT:
	55	* Might sleep.
	56	*
	57	* RETURNS:
	58	* 0 on success, -errno on failure.
	59	*/
	60	int bd_link_disk_holder(struct block_device bdev, struct gendisk disk)
	61	{
	62	struct bd_holder_disk *holder;
	63	int ret = 0;
	64
7abc0777 CH	65	if (WARN_ON_ONCE(!disk->slave_dir))
	66	return -EINVAL;
	67
077a4033 YK	68	if (bdev->bd_disk == disk)
	69	return -EINVAL;
	70
62f535e1 YK	71	/*
	72	* del_gendisk drops the initial reference to bd_holder_dir, so we
	73	* need to keep our own here to allow for cleanup past that point.
	74	*/
	75	mutex_lock(&bdev->bd_disk->open_mutex);
	76	if (!disk_live(bdev->bd_disk)) {
	77	mutex_unlock(&bdev->bd_disk->open_mutex);
	78	return -ENODEV;
	79	}
	80	kobject_get(bdev->bd_holder_dir);
	81	mutex_unlock(&bdev->bd_disk->open_mutex);
c66fd019	82
62f535e1	83	mutex_lock(&disk->open_mutex);
c66fd019 CH	84	WARN_ON_ONCE(!bdev->bd_holder);
c66fd019 CH	85
c66fd019 CH	86	holder = bd_find_holder_disk(bdev, disk);
c66fd019 CH	87	if (holder) {
62f535e1	88	kobject_put(bdev->bd_holder_dir);
c66fd019 CH	89	holder->refcnt++;
	90	goto out_unlock;
	91	}
	92
	93	holder = kzalloc(sizeof(*holder), GFP_KERNEL);
	94	if (!holder) {
	95	ret = -ENOMEM;
	96	goto out_unlock;
	97	}
	98
	99	INIT_LIST_HEAD(&holder->list);
c66fd019	100	holder->refcnt = 1;
3b3449c1 YK	101	holder->holder_dir = bdev->bd_holder_dir;
3b3449c1 YK	102
7abc0777 CH	103	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
	104	if (ret)
	105	goto out_free_holder;
	106	ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
	107	if (ret)
	108	goto out_del_symlink;
0dbcfe24	109	list_add(&holder->list, &disk->slave_bdevs);
7abc0777	110
7abc0777 CH	111	mutex_unlock(&disk->open_mutex);
7abc0777 CH	112	return 0;
759e0fd4	113
7abc0777 CH	114	out_del_symlink:
	115	del_symlink(disk->slave_dir, bdev_kobj(bdev));
	116	out_free_holder:
	117	kfree(holder);
c66fd019	118	out_unlock:
0dbcfe24	119	mutex_unlock(&disk->open_mutex);
62f535e1 YK	120	if (ret)
62f535e1 YK	121	kobject_put(bdev->bd_holder_dir);
c66fd019 CH	122	return ret;
	123	}
	124	EXPORT_SYMBOL_GPL(bd_link_disk_holder);
	125
	126	/**
	127	* bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
	128	* @bdev: the calimed slave bdev
	129	* @disk: the holding disk
	130	*
	131	* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
	132	*
	133	* CONTEXT:
	134	* Might sleep.
	135	*/
	136	void bd_unlink_disk_holder(struct block_device bdev, struct gendisk disk)
	137	{
	138	struct bd_holder_disk *holder;
	139
7abc0777 CH	140	if (WARN_ON_ONCE(!disk->slave_dir))
	141	return;
	142
0dbcfe24	143	mutex_lock(&disk->open_mutex);
c66fd019 CH	144	holder = bd_find_holder_disk(bdev, disk);
c66fd019 CH	145	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
7abc0777	146	del_symlink(disk->slave_dir, bdev_kobj(bdev));
3b3449c1 YK	147	del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
3b3449c1 YK	148	kobject_put(holder->holder_dir);
c66fd019 CH	149	list_del_init(&holder->list);
	150	kfree(holder);
	151	}
0dbcfe24	152	mutex_unlock(&disk->open_mutex);
c66fd019 CH	153	}
c66fd019 CH	154	EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);