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 kobject *holder_dir; |
8 | int refcnt; |
9 | }; |
10 | |
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->holder_dir == bdev->bd_holder_dir) |
18 | return holder; |
19 | return NULL; |
20 | } |
21 | |
22 | static int add_symlink(struct kobject *from, struct kobject *to) |
23 | { |
24 | return sysfs_create_link(kobj: from, target: to, name: kobject_name(kobj: to)); |
25 | } |
26 | |
27 | static void del_symlink(struct kobject *from, struct kobject *to) |
28 | { |
29 | sysfs_remove_link(kobj: from, name: kobject_name(kobj: to)); |
30 | } |
31 | |
32 | /** |
33 | * bd_link_disk_holder - create symlinks between holding disk and slave bdev |
34 | * @bdev: the claimed slave bdev |
35 | * @disk: the holding disk |
36 | * |
37 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. |
38 | * |
39 | * This functions creates the following sysfs symlinks. |
40 | * |
41 | * - from "slaves" directory of the holder @disk to the claimed @bdev |
42 | * - from "holders" directory of the @bdev to the holder @disk |
43 | * |
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: |
46 | * |
47 | * /sys/block/dm-0/slaves/sda --> /sys/block/sda |
48 | * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0 |
49 | * |
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. |
53 | * |
54 | * CONTEXT: |
55 | * Might sleep. |
56 | * |
57 | * RETURNS: |
58 | * 0 on success, -errno on failure. |
59 | */ |
60 | int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) |
61 | { |
62 | struct bd_holder_disk *holder; |
63 | int ret = 0; |
64 | |
65 | if (WARN_ON_ONCE(!disk->slave_dir)) |
66 | return -EINVAL; |
67 | |
68 | if (bdev->bd_disk == disk) |
69 | return -EINVAL; |
70 | |
71 | /* |
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. |
74 | */ |
75 | mutex_lock(&bdev->bd_disk->open_mutex); |
76 | if (!disk_live(disk: bdev->bd_disk)) { |
77 | mutex_unlock(lock: &bdev->bd_disk->open_mutex); |
78 | return -ENODEV; |
79 | } |
80 | kobject_get(kobj: bdev->bd_holder_dir); |
81 | mutex_unlock(lock: &bdev->bd_disk->open_mutex); |
82 | |
83 | mutex_lock(&disk->open_mutex); |
84 | WARN_ON_ONCE(!bdev->bd_holder); |
85 | |
86 | holder = bd_find_holder_disk(bdev, disk); |
87 | if (holder) { |
88 | kobject_put(kobj: bdev->bd_holder_dir); |
89 | holder->refcnt++; |
90 | goto out_unlock; |
91 | } |
92 | |
93 | holder = kzalloc(size: sizeof(*holder), GFP_KERNEL); |
94 | if (!holder) { |
95 | ret = -ENOMEM; |
96 | goto out_unlock; |
97 | } |
98 | |
99 | INIT_LIST_HEAD(list: &holder->list); |
100 | holder->refcnt = 1; |
101 | holder->holder_dir = bdev->bd_holder_dir; |
102 | |
103 | ret = add_symlink(from: disk->slave_dir, bdev_kobj(bdev)); |
104 | if (ret) |
105 | goto out_free_holder; |
106 | ret = add_symlink(from: bdev->bd_holder_dir, to: &disk_to_dev(disk)->kobj); |
107 | if (ret) |
108 | goto out_del_symlink; |
109 | list_add(new: &holder->list, head: &disk->slave_bdevs); |
110 | |
111 | mutex_unlock(lock: &disk->open_mutex); |
112 | return 0; |
113 | |
114 | out_del_symlink: |
115 | del_symlink(from: disk->slave_dir, bdev_kobj(bdev)); |
116 | out_free_holder: |
117 | kfree(objp: holder); |
118 | out_unlock: |
119 | mutex_unlock(lock: &disk->open_mutex); |
120 | if (ret) |
121 | kobject_put(kobj: bdev->bd_holder_dir); |
122 | return ret; |
123 | } |
124 | EXPORT_SYMBOL_GPL(bd_link_disk_holder); |
125 | |
126 | /** |
127 | * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder() |
128 | * @bdev: the calimed slave bdev |
129 | * @disk: the holding disk |
130 | * |
131 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. |
132 | * |
133 | * CONTEXT: |
134 | * Might sleep. |
135 | */ |
136 | void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) |
137 | { |
138 | struct bd_holder_disk *holder; |
139 | |
140 | if (WARN_ON_ONCE(!disk->slave_dir)) |
141 | return; |
142 | |
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(from: disk->slave_dir, bdev_kobj(bdev)); |
147 | del_symlink(from: holder->holder_dir, to: &disk_to_dev(disk)->kobj); |
148 | kobject_put(kobj: holder->holder_dir); |
149 | list_del_init(entry: &holder->list); |
150 | kfree(objp: holder); |
151 | } |
152 | mutex_unlock(lock: &disk->open_mutex); |
153 | } |
154 | EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); |
155 | |