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 | ||
d6263387 CH |
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 | ||
c66fd019 CH |
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 | */ | |
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 | ||
0dbcfe24 | 78 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
79 | |
80 | WARN_ON_ONCE(!bdev->bd_holder); | |
81 | ||
c66fd019 CH |
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); | |
0dbcfe24 | 95 | holder->bdev = bdev; |
c66fd019 | 96 | holder->refcnt = 1; |
d6263387 CH |
97 | if (disk->slave_dir) { |
98 | ret = __link_disk_holder(bdev, disk); | |
99 | if (ret) { | |
100 | kfree(holder); | |
101 | goto out_unlock; | |
102 | } | |
103 | } | |
c66fd019 | 104 | |
0dbcfe24 | 105 | list_add(&holder->list, &disk->slave_bdevs); |
759e0fd4 CH |
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 | ||
c66fd019 | 112 | out_unlock: |
0dbcfe24 | 113 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
114 | return ret; |
115 | } | |
116 | EXPORT_SYMBOL_GPL(bd_link_disk_holder); | |
117 | ||
d6263387 CH |
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 | ||
c66fd019 CH |
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 | */ | |
135 | void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) | |
136 | { | |
137 | struct bd_holder_disk *holder; | |
138 | ||
0dbcfe24 | 139 | mutex_lock(&disk->open_mutex); |
c66fd019 CH |
140 | holder = bd_find_holder_disk(bdev, disk); |
141 | if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { | |
d6263387 CH |
142 | if (disk->slave_dir) |
143 | __unlink_disk_holder(bdev, disk); | |
759e0fd4 | 144 | kobject_put(bdev->bd_holder_dir); |
c66fd019 CH |
145 | list_del_init(&holder->list); |
146 | kfree(holder); | |
147 | } | |
0dbcfe24 | 148 | mutex_unlock(&disk->open_mutex); |
c66fd019 CH |
149 | } |
150 | EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); | |
d6263387 CH |
151 | |
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 | } |