// 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 DEFINE_MUTEX(blk_holder_mutex); 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(&blk_holder_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_obj(*holder);	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(&blk_holder_mutex);	return 0; out_del_symlink:	del_symlink(disk->slave_dir, bdev_kobj(bdev));out_free_holder:	kfree(holder);out_unlock:	mutex_unlock(&blk_holder_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(&blk_holder_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(&blk_holder_mutex);}EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);