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 DEFINE_MUTEX(blk_holder_mutex); |
12 | |
13 | static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev, |
14 | struct gendisk *disk) |
15 | { |
16 | struct bd_holder_disk *holder; |
17 | |
18 | list_for_each_entry(holder, &disk->slave_bdevs, list) |
19 | if (holder->holder_dir == bdev->bd_holder_dir) |
20 | return holder; |
21 | return NULL; |
22 | } |
23 | |
24 | static int add_symlink(struct kobject *from, struct kobject *to) |
25 | { |
26 | return sysfs_create_link(kobj: from, target: to, name: kobject_name(kobj: to)); |
27 | } |
28 | |
29 | static void del_symlink(struct kobject *from, struct kobject *to) |
30 | { |
31 | sysfs_remove_link(kobj: from, name: kobject_name(kobj: to)); |
32 | } |
33 | |
34 | /** |
35 | * bd_link_disk_holder - create symlinks between holding disk and slave bdev |
36 | * @bdev: the claimed slave bdev |
37 | * @disk: the holding disk |
38 | * |
39 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. |
40 | * |
41 | * This functions creates the following sysfs symlinks. |
42 | * |
43 | * - from "slaves" directory of the holder @disk to the claimed @bdev |
44 | * - from "holders" directory of the @bdev to the holder @disk |
45 | * |
46 | * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is |
47 | * passed to bd_link_disk_holder(), then: |
48 | * |
49 | * /sys/block/dm-0/slaves/sda --> /sys/block/sda |
50 | * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0 |
51 | * |
52 | * The caller must have claimed @bdev before calling this function and |
53 | * ensure that both @bdev and @disk are valid during the creation and |
54 | * lifetime of these symlinks. |
55 | * |
56 | * CONTEXT: |
57 | * Might sleep. |
58 | * |
59 | * RETURNS: |
60 | * 0 on success, -errno on failure. |
61 | */ |
62 | int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) |
63 | { |
64 | struct bd_holder_disk *holder; |
65 | int ret = 0; |
66 | |
67 | if (WARN_ON_ONCE(!disk->slave_dir)) |
68 | return -EINVAL; |
69 | |
70 | if (bdev->bd_disk == disk) |
71 | return -EINVAL; |
72 | |
73 | /* |
74 | * del_gendisk drops the initial reference to bd_holder_dir, so we |
75 | * need to keep our own here to allow for cleanup past that point. |
76 | */ |
77 | mutex_lock(&bdev->bd_disk->open_mutex); |
78 | if (!disk_live(disk: bdev->bd_disk)) { |
79 | mutex_unlock(lock: &bdev->bd_disk->open_mutex); |
80 | return -ENODEV; |
81 | } |
82 | kobject_get(kobj: bdev->bd_holder_dir); |
83 | mutex_unlock(lock: &bdev->bd_disk->open_mutex); |
84 | |
85 | mutex_lock(&blk_holder_mutex); |
86 | WARN_ON_ONCE(!bdev->bd_holder); |
87 | |
88 | holder = bd_find_holder_disk(bdev, disk); |
89 | if (holder) { |
90 | kobject_put(kobj: bdev->bd_holder_dir); |
91 | holder->refcnt++; |
92 | goto out_unlock; |
93 | } |
94 | |
95 | holder = kzalloc(size: sizeof(*holder), GFP_KERNEL); |
96 | if (!holder) { |
97 | ret = -ENOMEM; |
98 | goto out_unlock; |
99 | } |
100 | |
101 | INIT_LIST_HEAD(list: &holder->list); |
102 | holder->refcnt = 1; |
103 | holder->holder_dir = bdev->bd_holder_dir; |
104 | |
105 | ret = add_symlink(from: disk->slave_dir, bdev_kobj(bdev)); |
106 | if (ret) |
107 | goto out_free_holder; |
108 | ret = add_symlink(from: bdev->bd_holder_dir, to: &disk_to_dev(disk)->kobj); |
109 | if (ret) |
110 | goto out_del_symlink; |
111 | list_add(new: &holder->list, head: &disk->slave_bdevs); |
112 | |
113 | mutex_unlock(lock: &blk_holder_mutex); |
114 | return 0; |
115 | |
116 | out_del_symlink: |
117 | del_symlink(from: disk->slave_dir, bdev_kobj(bdev)); |
118 | out_free_holder: |
119 | kfree(objp: holder); |
120 | out_unlock: |
121 | mutex_unlock(lock: &blk_holder_mutex); |
122 | if (ret) |
123 | kobject_put(kobj: bdev->bd_holder_dir); |
124 | return ret; |
125 | } |
126 | EXPORT_SYMBOL_GPL(bd_link_disk_holder); |
127 | |
128 | /** |
129 | * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder() |
130 | * @bdev: the calimed slave bdev |
131 | * @disk: the holding disk |
132 | * |
133 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. |
134 | * |
135 | * CONTEXT: |
136 | * Might sleep. |
137 | */ |
138 | void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) |
139 | { |
140 | struct bd_holder_disk *holder; |
141 | |
142 | if (WARN_ON_ONCE(!disk->slave_dir)) |
143 | return; |
144 | |
145 | mutex_lock(&blk_holder_mutex); |
146 | holder = bd_find_holder_disk(bdev, disk); |
147 | if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { |
148 | del_symlink(from: disk->slave_dir, bdev_kobj(bdev)); |
149 | del_symlink(from: holder->holder_dir, to: &disk_to_dev(disk)->kobj); |
150 | kobject_put(kobj: holder->holder_dir); |
151 | list_del_init(entry: &holder->list); |
152 | kfree(objp: holder); |
153 | } |
154 | mutex_unlock(lock: &blk_holder_mutex); |
155 | } |
156 | EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); |
157 | |