1c66fd019SChristoph Hellwig // SPDX-License-Identifier: GPL-2.0-only
2322cbb50SChristoph Hellwig #include <linux/blkdev.h>
3b81e0c23SChristoph Hellwig #include <linux/slab.h>
4c66fd019SChristoph Hellwig
5c66fd019SChristoph Hellwig struct bd_holder_disk {
6c66fd019SChristoph Hellwig struct list_head list;
73b3449c1SYu Kuai struct kobject *holder_dir;
8c66fd019SChristoph Hellwig int refcnt;
9c66fd019SChristoph Hellwig };
10c66fd019SChristoph Hellwig
11*03f12122SLi Nan static DEFINE_MUTEX(blk_holder_mutex);
12*03f12122SLi Nan
bd_find_holder_disk(struct block_device * bdev,struct gendisk * disk)13c66fd019SChristoph Hellwig static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
14c66fd019SChristoph Hellwig struct gendisk *disk)
15c66fd019SChristoph Hellwig {
16c66fd019SChristoph Hellwig struct bd_holder_disk *holder;
17c66fd019SChristoph Hellwig
180dbcfe24SChristoph Hellwig list_for_each_entry(holder, &disk->slave_bdevs, list)
193b3449c1SYu Kuai if (holder->holder_dir == bdev->bd_holder_dir)
20c66fd019SChristoph Hellwig return holder;
21c66fd019SChristoph Hellwig return NULL;
22c66fd019SChristoph Hellwig }
23c66fd019SChristoph Hellwig
add_symlink(struct kobject * from,struct kobject * to)24c66fd019SChristoph Hellwig static int add_symlink(struct kobject *from, struct kobject *to)
25c66fd019SChristoph Hellwig {
26c66fd019SChristoph Hellwig return sysfs_create_link(from, to, kobject_name(to));
27c66fd019SChristoph Hellwig }
28c66fd019SChristoph Hellwig
del_symlink(struct kobject * from,struct kobject * to)29c66fd019SChristoph Hellwig static void del_symlink(struct kobject *from, struct kobject *to)
30c66fd019SChristoph Hellwig {
31c66fd019SChristoph Hellwig sysfs_remove_link(from, kobject_name(to));
32c66fd019SChristoph Hellwig }
33c66fd019SChristoph Hellwig
34c66fd019SChristoph Hellwig /**
35c66fd019SChristoph Hellwig * bd_link_disk_holder - create symlinks between holding disk and slave bdev
36c66fd019SChristoph Hellwig * @bdev: the claimed slave bdev
37c66fd019SChristoph Hellwig * @disk: the holding disk
38c66fd019SChristoph Hellwig *
39c66fd019SChristoph Hellwig * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
40c66fd019SChristoph Hellwig *
41c66fd019SChristoph Hellwig * This functions creates the following sysfs symlinks.
42c66fd019SChristoph Hellwig *
43c66fd019SChristoph Hellwig * - from "slaves" directory of the holder @disk to the claimed @bdev
44c66fd019SChristoph Hellwig * - from "holders" directory of the @bdev to the holder @disk
45c66fd019SChristoph Hellwig *
46c66fd019SChristoph Hellwig * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
47c66fd019SChristoph Hellwig * passed to bd_link_disk_holder(), then:
48c66fd019SChristoph Hellwig *
49c66fd019SChristoph Hellwig * /sys/block/dm-0/slaves/sda --> /sys/block/sda
50c66fd019SChristoph Hellwig * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
51c66fd019SChristoph Hellwig *
52c66fd019SChristoph Hellwig * The caller must have claimed @bdev before calling this function and
53c66fd019SChristoph Hellwig * ensure that both @bdev and @disk are valid during the creation and
54c66fd019SChristoph Hellwig * lifetime of these symlinks.
55c66fd019SChristoph Hellwig *
56c66fd019SChristoph Hellwig * CONTEXT:
57c66fd019SChristoph Hellwig * Might sleep.
58c66fd019SChristoph Hellwig *
59c66fd019SChristoph Hellwig * RETURNS:
60c66fd019SChristoph Hellwig * 0 on success, -errno on failure.
61c66fd019SChristoph Hellwig */
bd_link_disk_holder(struct block_device * bdev,struct gendisk * disk)62c66fd019SChristoph Hellwig int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
63c66fd019SChristoph Hellwig {
64c66fd019SChristoph Hellwig struct bd_holder_disk *holder;
65c66fd019SChristoph Hellwig int ret = 0;
66c66fd019SChristoph Hellwig
677abc0777SChristoph Hellwig if (WARN_ON_ONCE(!disk->slave_dir))
687abc0777SChristoph Hellwig return -EINVAL;
697abc0777SChristoph Hellwig
70077a4033SYu Kuai if (bdev->bd_disk == disk)
71077a4033SYu Kuai return -EINVAL;
72077a4033SYu Kuai
7362f535e1SYu Kuai /*
7462f535e1SYu Kuai * del_gendisk drops the initial reference to bd_holder_dir, so we
7562f535e1SYu Kuai * need to keep our own here to allow for cleanup past that point.
7662f535e1SYu Kuai */
7762f535e1SYu Kuai mutex_lock(&bdev->bd_disk->open_mutex);
7862f535e1SYu Kuai if (!disk_live(bdev->bd_disk)) {
7962f535e1SYu Kuai mutex_unlock(&bdev->bd_disk->open_mutex);
8062f535e1SYu Kuai return -ENODEV;
8162f535e1SYu Kuai }
8262f535e1SYu Kuai kobject_get(bdev->bd_holder_dir);
8362f535e1SYu Kuai mutex_unlock(&bdev->bd_disk->open_mutex);
84c66fd019SChristoph Hellwig
85*03f12122SLi Nan mutex_lock(&blk_holder_mutex);
86c66fd019SChristoph Hellwig WARN_ON_ONCE(!bdev->bd_holder);
87c66fd019SChristoph Hellwig
88c66fd019SChristoph Hellwig holder = bd_find_holder_disk(bdev, disk);
89c66fd019SChristoph Hellwig if (holder) {
9062f535e1SYu Kuai kobject_put(bdev->bd_holder_dir);
91c66fd019SChristoph Hellwig holder->refcnt++;
92c66fd019SChristoph Hellwig goto out_unlock;
93c66fd019SChristoph Hellwig }
94c66fd019SChristoph Hellwig
95c66fd019SChristoph Hellwig holder = kzalloc(sizeof(*holder), GFP_KERNEL);
96c66fd019SChristoph Hellwig if (!holder) {
97c66fd019SChristoph Hellwig ret = -ENOMEM;
98c66fd019SChristoph Hellwig goto out_unlock;
99c66fd019SChristoph Hellwig }
100c66fd019SChristoph Hellwig
101c66fd019SChristoph Hellwig INIT_LIST_HEAD(&holder->list);
102c66fd019SChristoph Hellwig holder->refcnt = 1;
1033b3449c1SYu Kuai holder->holder_dir = bdev->bd_holder_dir;
1043b3449c1SYu Kuai
1057abc0777SChristoph Hellwig ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
1067abc0777SChristoph Hellwig if (ret)
1077abc0777SChristoph Hellwig goto out_free_holder;
1087abc0777SChristoph Hellwig ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
1097abc0777SChristoph Hellwig if (ret)
1107abc0777SChristoph Hellwig goto out_del_symlink;
1110dbcfe24SChristoph Hellwig list_add(&holder->list, &disk->slave_bdevs);
1127abc0777SChristoph Hellwig
113*03f12122SLi Nan mutex_unlock(&blk_holder_mutex);
1147abc0777SChristoph Hellwig return 0;
115759e0fd4SChristoph Hellwig
1167abc0777SChristoph Hellwig out_del_symlink:
1177abc0777SChristoph Hellwig del_symlink(disk->slave_dir, bdev_kobj(bdev));
1187abc0777SChristoph Hellwig out_free_holder:
1197abc0777SChristoph Hellwig kfree(holder);
120c66fd019SChristoph Hellwig out_unlock:
121*03f12122SLi Nan mutex_unlock(&blk_holder_mutex);
12262f535e1SYu Kuai if (ret)
12362f535e1SYu Kuai kobject_put(bdev->bd_holder_dir);
124c66fd019SChristoph Hellwig return ret;
125c66fd019SChristoph Hellwig }
126c66fd019SChristoph Hellwig EXPORT_SYMBOL_GPL(bd_link_disk_holder);
127c66fd019SChristoph Hellwig
128c66fd019SChristoph Hellwig /**
129c66fd019SChristoph Hellwig * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
130c66fd019SChristoph Hellwig * @bdev: the calimed slave bdev
131c66fd019SChristoph Hellwig * @disk: the holding disk
132c66fd019SChristoph Hellwig *
133c66fd019SChristoph Hellwig * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
134c66fd019SChristoph Hellwig *
135c66fd019SChristoph Hellwig * CONTEXT:
136c66fd019SChristoph Hellwig * Might sleep.
137c66fd019SChristoph Hellwig */
bd_unlink_disk_holder(struct block_device * bdev,struct gendisk * disk)138c66fd019SChristoph Hellwig void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
139c66fd019SChristoph Hellwig {
140c66fd019SChristoph Hellwig struct bd_holder_disk *holder;
141c66fd019SChristoph Hellwig
1427abc0777SChristoph Hellwig if (WARN_ON_ONCE(!disk->slave_dir))
1437abc0777SChristoph Hellwig return;
1447abc0777SChristoph Hellwig
145*03f12122SLi Nan mutex_lock(&blk_holder_mutex);
146c66fd019SChristoph Hellwig holder = bd_find_holder_disk(bdev, disk);
147c66fd019SChristoph Hellwig if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
1487abc0777SChristoph Hellwig del_symlink(disk->slave_dir, bdev_kobj(bdev));
1493b3449c1SYu Kuai del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
1503b3449c1SYu Kuai kobject_put(holder->holder_dir);
151c66fd019SChristoph Hellwig list_del_init(&holder->list);
152c66fd019SChristoph Hellwig kfree(holder);
153c66fd019SChristoph Hellwig }
154*03f12122SLi Nan mutex_unlock(&blk_holder_mutex);
155c66fd019SChristoph Hellwig }
156c66fd019SChristoph Hellwig EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
157