Merge tag 'lsm-pr-20220801' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/lsm
[platform/kernel/linux-starfive.git] / block / holder.c
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 block_device     *bdev;
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->bdev == bdev)
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 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
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
78         mutex_lock(&disk->open_mutex);
79
80         WARN_ON_ONCE(!bdev->bd_holder);
81
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);
95         holder->bdev = bdev;
96         holder->refcnt = 1;
97         if (disk->slave_dir) {
98                 ret = __link_disk_holder(bdev, disk);
99                 if (ret) {
100                         kfree(holder);
101                         goto out_unlock;
102                 }
103         }
104
105         list_add(&holder->list, &disk->slave_bdevs);
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
112 out_unlock:
113         mutex_unlock(&disk->open_mutex);
114         return ret;
115 }
116 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
117
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
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
139         mutex_lock(&disk->open_mutex);
140         holder = bd_find_holder_disk(bdev, disk);
141         if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
142                 if (disk->slave_dir)
143                         __unlink_disk_holder(bdev, disk);
144                 kobject_put(bdev->bd_holder_dir);
145                 list_del_init(&holder->list);
146                 kfree(holder);
147         }
148         mutex_unlock(&disk->open_mutex);
149 }
150 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
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 }