1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/blkdev.h>
3 #include <linux/slab.h>
4
5 struct bd_holder_disk {
6 struct list_head list;
7 struct block_device *bdev;
8 int refcnt;
9 };
10
bd_find_holder_disk(struct block_device * bdev,struct gendisk * disk)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
16 list_for_each_entry(holder, &disk->slave_bdevs, list)
17 if (holder->bdev == bdev)
18 return holder;
19 return NULL;
20 }
21
add_symlink(struct kobject * from,struct kobject * to)22 static int add_symlink(struct kobject *from, struct kobject *to)
23 {
24 return sysfs_create_link(from, to, kobject_name(to));
25 }
26
del_symlink(struct kobject * from,struct kobject * to)27 static void del_symlink(struct kobject *from, struct kobject *to)
28 {
29 sysfs_remove_link(from, kobject_name(to));
30 }
31
__link_disk_holder(struct block_device * bdev,struct gendisk * disk)32 static int __link_disk_holder(struct block_device *bdev, struct gendisk *disk)
33 {
34 int ret;
35
36 ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
37 if (ret)
38 return ret;
39 ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
40 if (ret)
41 del_symlink(disk->slave_dir, bdev_kobj(bdev));
42 return ret;
43 }
44
45 /**
46 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
47 * @bdev: the claimed slave bdev
48 * @disk: the holding disk
49 *
50 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
51 *
52 * This functions creates the following sysfs symlinks.
53 *
54 * - from "slaves" directory of the holder @disk to the claimed @bdev
55 * - from "holders" directory of the @bdev to the holder @disk
56 *
57 * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
58 * passed to bd_link_disk_holder(), then:
59 *
60 * /sys/block/dm-0/slaves/sda --> /sys/block/sda
61 * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
62 *
63 * The caller must have claimed @bdev before calling this function and
64 * ensure that both @bdev and @disk are valid during the creation and
65 * lifetime of these symlinks.
66 *
67 * CONTEXT:
68 * Might sleep.
69 *
70 * RETURNS:
71 * 0 on success, -errno on failure.
72 */
bd_link_disk_holder(struct block_device * bdev,struct gendisk * disk)73 int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
74 {
75 struct bd_holder_disk *holder;
76 int ret = 0;
77
78 mutex_lock(&disk->open_mutex);
79
80 WARN_ON_ONCE(!bdev->bd_holder);
81
82 holder = bd_find_holder_disk(bdev, disk);
83 if (holder) {
84 holder->refcnt++;
85 goto out_unlock;
86 }
87
88 holder = kzalloc(sizeof(*holder), GFP_KERNEL);
89 if (!holder) {
90 ret = -ENOMEM;
91 goto out_unlock;
92 }
93
94 INIT_LIST_HEAD(&holder->list);
95 holder->bdev = bdev;
96 holder->refcnt = 1;
97 if (disk->slave_dir) {
98 ret = __link_disk_holder(bdev, disk);
99 if (ret) {
100 kfree(holder);
101 goto out_unlock;
102 }
103 }
104
105 list_add(&holder->list, &disk->slave_bdevs);
106 /*
107 * del_gendisk drops the initial reference to bd_holder_dir, so we need
108 * to keep our own here to allow for cleanup past that point.
109 */
110 kobject_get(bdev->bd_holder_dir);
111
112 out_unlock:
113 mutex_unlock(&disk->open_mutex);
114 return ret;
115 }
116 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
117
__unlink_disk_holder(struct block_device * bdev,struct gendisk * disk)118 static void __unlink_disk_holder(struct block_device *bdev,
119 struct gendisk *disk)
120 {
121 del_symlink(disk->slave_dir, bdev_kobj(bdev));
122 del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
123 }
124
125 /**
126 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
127 * @bdev: the calimed slave bdev
128 * @disk: the holding disk
129 *
130 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
131 *
132 * CONTEXT:
133 * Might sleep.
134 */
bd_unlink_disk_holder(struct block_device * bdev,struct gendisk * disk)135 void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
136 {
137 struct bd_holder_disk *holder;
138
139 mutex_lock(&disk->open_mutex);
140 holder = bd_find_holder_disk(bdev, disk);
141 if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
142 if (disk->slave_dir)
143 __unlink_disk_holder(bdev, disk);
144 kobject_put(bdev->bd_holder_dir);
145 list_del_init(&holder->list);
146 kfree(holder);
147 }
148 mutex_unlock(&disk->open_mutex);
149 }
150 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
151
bd_register_pending_holders(struct gendisk * disk)152 int bd_register_pending_holders(struct gendisk *disk)
153 {
154 struct bd_holder_disk *holder;
155 int ret;
156
157 mutex_lock(&disk->open_mutex);
158 list_for_each_entry(holder, &disk->slave_bdevs, list) {
159 ret = __link_disk_holder(holder->bdev, disk);
160 if (ret)
161 goto out_undo;
162 }
163 mutex_unlock(&disk->open_mutex);
164 return 0;
165
166 out_undo:
167 list_for_each_entry_continue_reverse(holder, &disk->slave_bdevs, list)
168 __unlink_disk_holder(holder->bdev, disk);
169 mutex_unlock(&disk->open_mutex);
170 return ret;
171 }
172
