1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/blkdev.h>
3 #include <linux/slab.h>
5 struct bd_holder_disk {
7 struct kobject *holder_dir;
11 static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
14 struct bd_holder_disk *holder;
16 list_for_each_entry(holder, &disk->slave_bdevs, list)
17 if (holder->holder_dir == bdev->bd_holder_dir)
22 static int add_symlink(struct kobject *from, struct kobject *to)
24 return sysfs_create_link(from, to, kobject_name(to));
27 static void del_symlink(struct kobject *from, struct kobject *to)
29 sysfs_remove_link(from, kobject_name(to));
33 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
34 * @bdev: the claimed slave bdev
35 * @disk: the holding disk
37 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
39 * This functions creates the following sysfs symlinks.
41 * - from "slaves" directory of the holder @disk to the claimed @bdev
42 * - from "holders" directory of the @bdev to the holder @disk
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:
47 * /sys/block/dm-0/slaves/sda --> /sys/block/sda
48 * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
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.
58 * 0 on success, -errno on failure.
60 int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
62 struct bd_holder_disk *holder;
65 if (WARN_ON_ONCE(!disk->slave_dir))
68 if (bdev->bd_disk == disk)
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.
75 mutex_lock(&bdev->bd_disk->open_mutex);
76 if (!disk_live(bdev->bd_disk)) {
77 mutex_unlock(&bdev->bd_disk->open_mutex);
80 kobject_get(bdev->bd_holder_dir);
81 mutex_unlock(&bdev->bd_disk->open_mutex);
83 mutex_lock(&disk->open_mutex);
84 WARN_ON_ONCE(!bdev->bd_holder);
86 holder = bd_find_holder_disk(bdev, disk);
88 kobject_put(bdev->bd_holder_dir);
93 holder = kzalloc(sizeof(*holder), GFP_KERNEL);
99 INIT_LIST_HEAD(&holder->list);
101 holder->holder_dir = bdev->bd_holder_dir;
103 ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
105 goto out_free_holder;
106 ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
108 goto out_del_symlink;
109 list_add(&holder->list, &disk->slave_bdevs);
111 mutex_unlock(&disk->open_mutex);
115 del_symlink(disk->slave_dir, bdev_kobj(bdev));
119 mutex_unlock(&disk->open_mutex);
121 kobject_put(bdev->bd_holder_dir);
124 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
127 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
128 * @bdev: the calimed slave bdev
129 * @disk: the holding disk
131 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
136 void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
138 struct bd_holder_disk *holder;
140 if (WARN_ON_ONCE(!disk->slave_dir))
143 mutex_lock(&disk->open_mutex);
144 holder = bd_find_holder_disk(bdev, disk);
145 if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
146 del_symlink(disk->slave_dir, bdev_kobj(bdev));
147 del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
148 kobject_put(holder->holder_dir);
149 list_del_init(&holder->list);
152 mutex_unlock(&disk->open_mutex);
154 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);