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c66fd019 CH |
1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | #include <linux/genhd.h> | |
3 | ||
4 | struct bd_holder_disk { | |
5 | struct list_head list; | |
0dbcfe24 | 6 | struct block_device *bdev; |
c66fd019 CH |
7 | int refcnt; |
8 | }; | |
9 | ||
10 | static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev, | |
11 | struct gendisk *disk) | |
12 | { | |
13 | struct bd_holder_disk *holder; | |
14 | ||
0dbcfe24 CH |
15 | list_for_each_entry(holder, &disk->slave_bdevs, list) |
16 | if (holder->bdev == bdev) | |
c66fd019 CH |
17 | return holder; |
18 | return NULL; | |
19 | } | |
20 | ||
21 | static int add_symlink(struct kobject *from, struct kobject *to) | |
22 | { | |
23 | return sysfs_create_link(from, to, kobject_name(to)); | |
24 | } | |
25 | ||
26 | static void del_symlink(struct kobject *from, struct kobject *to) | |
27 | { | |
28 | sysfs_remove_link(from, kobject_name(to)); | |
29 | } | |
30 | ||
d6263387 CH |
31 | static int __link_disk_holder(struct block_device *bdev, struct gendisk *disk) |
32 | { | |
33 | int ret; | |
34 | ||
35 | ret = add_symlink(disk->slave_dir, bdev_kobj(bdev)); | |
36 | if (ret) | |
37 | return ret; | |
38 | ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); | |
39 | if (ret) | |
40 | del_symlink(disk->slave_dir, bdev_kobj(bdev)); | |
41 | return ret; | |
42 | } | |
43 | ||
c66fd019 CH |
44 | /** |
45 | * bd_link_disk_holder - create symlinks between holding disk and slave bdev | |
46 | * @bdev: the claimed slave bdev | |
47 | * @disk: the holding disk | |
48 | * | |
49 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. | |
50 | * | |
51 | * This functions creates the following sysfs symlinks. | |
52 | * | |
53 | * - from "slaves" directory of the holder @disk to the claimed @bdev | |
54 | * - from "holders" directory of the @bdev to the holder @disk | |
55 | * | |
56 | * For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is | |
57 | * passed to bd_link_disk_holder(), then: | |
58 | * | |
59 | * /sys/block/dm-0/slaves/sda --> /sys/block/sda | |
60 | * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0 | |
61 | * | |
62 | * The caller must have claimed @bdev before calling this function and | |
63 | * ensure that both @bdev and @disk are valid during the creation and | |
64 | * lifetime of these symlinks. | |
65 | * | |
66 | * CONTEXT: | |
67 | * Might sleep. | |
68 | * | |
69 | * RETURNS: | |
70 | * 0 on success, -errno on failure. | |
71 | */ | |
72 | int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk) | |
73 | { | |
74 | struct bd_holder_disk *holder; | |
75 | int ret = 0; | |
76 | ||
0dbcfe24 | 77 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
78 | |
79 | WARN_ON_ONCE(!bdev->bd_holder); | |
80 | ||
81 | /* FIXME: remove the following once add_disk() handles errors */ | |
d6263387 | 82 | if (WARN_ON(!bdev->bd_holder_dir)) |
c66fd019 CH |
83 | goto out_unlock; |
84 | ||
85 | holder = bd_find_holder_disk(bdev, disk); | |
86 | if (holder) { | |
87 | holder->refcnt++; | |
88 | goto out_unlock; | |
89 | } | |
90 | ||
91 | holder = kzalloc(sizeof(*holder), GFP_KERNEL); | |
92 | if (!holder) { | |
93 | ret = -ENOMEM; | |
94 | goto out_unlock; | |
95 | } | |
96 | ||
97 | INIT_LIST_HEAD(&holder->list); | |
0dbcfe24 | 98 | holder->bdev = bdev; |
c66fd019 | 99 | holder->refcnt = 1; |
d6263387 CH |
100 | if (disk->slave_dir) { |
101 | ret = __link_disk_holder(bdev, disk); | |
102 | if (ret) { | |
103 | kfree(holder); | |
104 | goto out_unlock; | |
105 | } | |
106 | } | |
c66fd019 | 107 | |
0dbcfe24 | 108 | list_add(&holder->list, &disk->slave_bdevs); |
759e0fd4 CH |
109 | /* |
110 | * del_gendisk drops the initial reference to bd_holder_dir, so we need | |
111 | * to keep our own here to allow for cleanup past that point. | |
112 | */ | |
113 | kobject_get(bdev->bd_holder_dir); | |
114 | ||
c66fd019 | 115 | out_unlock: |
0dbcfe24 | 116 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
117 | return ret; |
118 | } | |
119 | EXPORT_SYMBOL_GPL(bd_link_disk_holder); | |
120 | ||
d6263387 CH |
121 | static void __unlink_disk_holder(struct block_device *bdev, |
122 | struct gendisk *disk) | |
123 | { | |
124 | del_symlink(disk->slave_dir, bdev_kobj(bdev)); | |
125 | del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); | |
126 | } | |
127 | ||
c66fd019 CH |
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 | ||
0dbcfe24 | 142 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
143 | holder = bd_find_holder_disk(bdev, disk); |
144 | if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { | |
d6263387 CH |
145 | if (disk->slave_dir) |
146 | __unlink_disk_holder(bdev, disk); | |
759e0fd4 | 147 | kobject_put(bdev->bd_holder_dir); |
c66fd019 CH |
148 | list_del_init(&holder->list); |
149 | kfree(holder); | |
150 | } | |
0dbcfe24 | 151 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
152 | } |
153 | EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); | |
d6263387 CH |
154 | |
155 | int bd_register_pending_holders(struct gendisk *disk) | |
156 | { | |
157 | struct bd_holder_disk *holder; | |
158 | int ret; | |
159 | ||
160 | mutex_lock(&disk->open_mutex); | |
161 | list_for_each_entry(holder, &disk->slave_bdevs, list) { | |
162 | ret = __link_disk_holder(holder->bdev, disk); | |
163 | if (ret) | |
164 | goto out_undo; | |
165 | } | |
166 | mutex_unlock(&disk->open_mutex); | |
167 | return 0; | |
168 | ||
169 | out_undo: | |
170 | list_for_each_entry_continue_reverse(holder, &disk->slave_bdevs, list) | |
171 | __unlink_disk_holder(holder->bdev, disk); | |
172 | mutex_unlock(&disk->open_mutex); | |
173 | return ret; | |
174 | } |