Commit | Line | Data |
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c66fd019 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
322cbb50 | 2 | #include <linux/blkdev.h> |
b81e0c23 | 3 | #include <linux/slab.h> |
c66fd019 CH |
4 | |
5 | struct bd_holder_disk { | |
6 | struct list_head list; | |
0dbcfe24 | 7 | struct block_device *bdev; |
c66fd019 CH |
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 | ||
0dbcfe24 CH |
16 | list_for_each_entry(holder, &disk->slave_bdevs, list) |
17 | if (holder->bdev == bdev) | |
c66fd019 CH |
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(from, to, kobject_name(to)); | |
25 | } | |
26 | ||
27 | static void del_symlink(struct kobject *from, struct kobject *to) | |
28 | { | |
29 | sysfs_remove_link(from, kobject_name(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 | ||
7abc0777 CH |
65 | if (WARN_ON_ONCE(!disk->slave_dir)) |
66 | return -EINVAL; | |
67 | ||
0dbcfe24 | 68 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
69 | |
70 | WARN_ON_ONCE(!bdev->bd_holder); | |
71 | ||
c66fd019 CH |
72 | holder = bd_find_holder_disk(bdev, disk); |
73 | if (holder) { | |
74 | holder->refcnt++; | |
75 | goto out_unlock; | |
76 | } | |
77 | ||
78 | holder = kzalloc(sizeof(*holder), GFP_KERNEL); | |
79 | if (!holder) { | |
80 | ret = -ENOMEM; | |
81 | goto out_unlock; | |
82 | } | |
83 | ||
84 | INIT_LIST_HEAD(&holder->list); | |
0dbcfe24 | 85 | holder->bdev = bdev; |
c66fd019 | 86 | holder->refcnt = 1; |
7abc0777 CH |
87 | ret = add_symlink(disk->slave_dir, bdev_kobj(bdev)); |
88 | if (ret) | |
89 | goto out_free_holder; | |
90 | ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); | |
91 | if (ret) | |
92 | goto out_del_symlink; | |
0dbcfe24 | 93 | list_add(&holder->list, &disk->slave_bdevs); |
7abc0777 | 94 | |
759e0fd4 CH |
95 | /* |
96 | * del_gendisk drops the initial reference to bd_holder_dir, so we need | |
97 | * to keep our own here to allow for cleanup past that point. | |
98 | */ | |
99 | kobject_get(bdev->bd_holder_dir); | |
7abc0777 CH |
100 | mutex_unlock(&disk->open_mutex); |
101 | return 0; | |
759e0fd4 | 102 | |
7abc0777 CH |
103 | out_del_symlink: |
104 | del_symlink(disk->slave_dir, bdev_kobj(bdev)); | |
105 | out_free_holder: | |
106 | kfree(holder); | |
c66fd019 | 107 | out_unlock: |
0dbcfe24 | 108 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
109 | return ret; |
110 | } | |
111 | EXPORT_SYMBOL_GPL(bd_link_disk_holder); | |
112 | ||
113 | /** | |
114 | * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder() | |
115 | * @bdev: the calimed slave bdev | |
116 | * @disk: the holding disk | |
117 | * | |
118 | * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT. | |
119 | * | |
120 | * CONTEXT: | |
121 | * Might sleep. | |
122 | */ | |
123 | void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) | |
124 | { | |
125 | struct bd_holder_disk *holder; | |
126 | ||
7abc0777 CH |
127 | if (WARN_ON_ONCE(!disk->slave_dir)) |
128 | return; | |
129 | ||
0dbcfe24 | 130 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
131 | holder = bd_find_holder_disk(bdev, disk); |
132 | if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { | |
7abc0777 CH |
133 | del_symlink(disk->slave_dir, bdev_kobj(bdev)); |
134 | del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); | |
759e0fd4 | 135 | kobject_put(bdev->bd_holder_dir); |
c66fd019 CH |
136 | list_del_init(&holder->list); |
137 | kfree(holder); | |
138 | } | |
0dbcfe24 | 139 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
140 | } |
141 | EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); |