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

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

struct bd_holder_disk {
	struct list_head	list;
	struct gendisk		*disk;
	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, &bdev->bd_holder_disks, list)
		if (holder->disk == disk)
			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;

	mutex_lock(&bdev->bd_disk->open_mutex);

	WARN_ON_ONCE(!bdev->bd_holder);

	/* FIXME: remove the following once add_disk() handles errors */
	if (WARN_ON(!disk->slave_dir || !bdev->bd_holder_dir))
		goto out_unlock;

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

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

	INIT_LIST_HEAD(&holder->list);
	holder->disk = disk;
	holder->refcnt = 1;

	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
	if (ret)
		goto out_free;

	ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
	if (ret)
		goto out_del;
	/*
	 * bdev could be deleted beneath us which would implicitly destroy
	 * the holder directory.  Hold on to it.
	 */
	kobject_get(bdev->bd_holder_dir);

	list_add(&holder->list, &bdev->bd_holder_disks);
	goto out_unlock;

out_del:
	del_symlink(disk->slave_dir, bdev_kobj(bdev));
out_free:
	kfree(holder);
out_unlock:
	mutex_unlock(&bdev->bd_disk->open_mutex);
	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;

	mutex_lock(&bdev->bd_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(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
		kobject_put(bdev->bd_holder_dir);
		list_del_init(&holder->list);
		kfree(holder);
	}
	mutex_unlock(&bdev->bd_disk->open_mutex);
}
EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
Commit	Line	Data
c66fd019 CH	1	// SPDX-License-Identifier: GPL-2.0-only
	2	#include <linux/genhd.h>
	3
	4	struct bd_holder_disk {
	5	struct list_head list;
	6	struct gendisk *disk;
	7	int refcnt;
	8	};
	9
	10	static struct bd_holder_disk bd_find_holder_disk(struct block_device bdev,
	11	struct gendisk *disk)
	12	{
	13	struct bd_holder_disk *holder;
	14
	15	list_for_each_entry(holder, &bdev->bd_holder_disks, list)
	16	if (holder->disk == disk)
	17	return holder;
	18	return NULL;
	19	}
	20
	21	static int add_symlink(struct kobject from, struct kobject to)
	22	{
	23	return sysfs_create_link(from, to, kobject_name(to));
	24	}
	25
	26	static void del_symlink(struct kobject from, struct kobject to)
	27	{
	28	sysfs_remove_link(from, kobject_name(to));
	29	}
	30
	31	/**
	32	* bd_link_disk_holder - create symlinks between holding disk and slave bdev
	33	* @bdev: the claimed slave bdev
	34	* @disk: the holding disk
	35	*
	36	* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
	37	*
	38	* This functions creates the following sysfs symlinks.
	39	*
	40	* - from "slaves" directory of the holder @disk to the claimed @bdev
	41	* - from "holders" directory of the @bdev to the holder @disk
	42	*
	43	* For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
	44	* passed to bd_link_disk_holder(), then:
	45	*
	46	* /sys/block/dm-0/slaves/sda --> /sys/block/sda
	47	* /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
	48	*
	49	* The caller must have claimed @bdev before calling this function and
	50	* ensure that both @bdev and @disk are valid during the creation and
	51	* lifetime of these symlinks.
	52	*
	53	* CONTEXT:
	54	* Might sleep.
	55	*
	56	* RETURNS:
	57	* 0 on success, -errno on failure.
	58	*/
	59	int bd_link_disk_holder(struct block_device bdev, struct gendisk disk)
	60	{
	61	struct bd_holder_disk *holder;
	62	int ret = 0;
	63
	64	mutex_lock(&bdev->bd_disk->open_mutex);
65
66	WARN_ON_ONCE(!bdev->bd_holder);
67
68	/* FIXME: remove the following once add_disk() handles errors */
69	if (WARN_ON(!disk->slave_dir \|\| !bdev->bd_holder_dir))
70	goto out_unlock;
71
72	holder = bd_find_holder_disk(bdev, disk);
73	if (holder) {
74	holder->refcnt++;
75	goto out_unlock;
76	}
77
78	holder = kzalloc(sizeof(*holder), GFP_KERNEL);
79	if (!holder) {
80	ret = -ENOMEM;
81	goto out_unlock;
82	}
83
84	INIT_LIST_HEAD(&holder->list);
85	holder->disk = disk;
86	holder->refcnt = 1;
87
88	ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
89	if (ret)
90	goto out_free;
91
92	ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
93	if (ret)
94	goto out_del;
95	/*
96	* bdev could be deleted beneath us which would implicitly destroy
97	* the holder directory. Hold on to it.
98	*/
99	kobject_get(bdev->bd_holder_dir);
100
101	list_add(&holder->list, &bdev->bd_holder_disks);
102	goto out_unlock;
103
104	out_del:
105	del_symlink(disk->slave_dir, bdev_kobj(bdev));
106	out_free:
107	kfree(holder);
108	out_unlock:
109	mutex_unlock(&bdev->bd_disk->open_mutex);
110	return ret;
111	}
112	EXPORT_SYMBOL_GPL(bd_link_disk_holder);
113
114	/**
115	* bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
116	* @bdev: the calimed slave bdev
117	* @disk: the holding disk
118	*
119	* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
120	*
121	* CONTEXT:
122	* Might sleep.
123	*/
124	void bd_unlink_disk_holder(struct block_device bdev, struct gendisk disk)
125	{
126	struct bd_holder_disk *holder;
127
128	mutex_lock(&bdev->bd_disk->open_mutex);
129	holder = bd_find_holder_disk(bdev, disk);
130	if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
131	del_symlink(disk->slave_dir, bdev_kobj(bdev));
132	del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
133	kobject_put(bdev->bd_holder_dir);
134	list_del_init(&holder->list);
135	kfree(holder);
136	}
137	mutex_unlock(&bdev->bd_disk->open_mutex);
138	}
139	EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);