blk-mq: fix two misuses on RQF_USE_SCHED
[linux-block.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 kobject          *holder_dir;
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->holder_dir == bdev->bd_holder_dir)
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
65         if (WARN_ON_ONCE(!disk->slave_dir))
66                 return -EINVAL;
67
68         if (bdev->bd_disk == disk)
69                 return -EINVAL;
70
71         /*
72          * del_gendisk drops the initial reference to bd_holder_dir, so we
73          * need to keep our own here to allow for cleanup past that point.
74          */
75         mutex_lock(&bdev->bd_disk->open_mutex);
76         if (!disk_live(bdev->bd_disk)) {
77                 mutex_unlock(&bdev->bd_disk->open_mutex);
78                 return -ENODEV;
79         }
80         kobject_get(bdev->bd_holder_dir);
81         mutex_unlock(&bdev->bd_disk->open_mutex);
82
83         mutex_lock(&disk->open_mutex);
84         WARN_ON_ONCE(!bdev->bd_holder);
85
86         holder = bd_find_holder_disk(bdev, disk);
87         if (holder) {
88                 kobject_put(bdev->bd_holder_dir);
89                 holder->refcnt++;
90                 goto out_unlock;
91         }
92
93         holder = kzalloc(sizeof(*holder), GFP_KERNEL);
94         if (!holder) {
95                 ret = -ENOMEM;
96                 goto out_unlock;
97         }
98
99         INIT_LIST_HEAD(&holder->list);
100         holder->refcnt = 1;
101         holder->holder_dir = bdev->bd_holder_dir;
102
103         ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
104         if (ret)
105                 goto out_free_holder;
106         ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
107         if (ret)
108                 goto out_del_symlink;
109         list_add(&holder->list, &disk->slave_bdevs);
110
111         mutex_unlock(&disk->open_mutex);
112         return 0;
113
114 out_del_symlink:
115         del_symlink(disk->slave_dir, bdev_kobj(bdev));
116 out_free_holder:
117         kfree(holder);
118 out_unlock:
119         mutex_unlock(&disk->open_mutex);
120         if (ret)
121                 kobject_put(bdev->bd_holder_dir);
122         return ret;
123 }
124 EXPORT_SYMBOL_GPL(bd_link_disk_holder);
125
126 /**
127  * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
128  * @bdev: the calimed slave bdev
129  * @disk: the holding disk
130  *
131  * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
132  *
133  * CONTEXT:
134  * Might sleep.
135  */
136 void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
137 {
138         struct bd_holder_disk *holder;
139
140         if (WARN_ON_ONCE(!disk->slave_dir))
141                 return;
142
143         mutex_lock(&disk->open_mutex);
144         holder = bd_find_holder_disk(bdev, disk);
145         if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
146                 del_symlink(disk->slave_dir, bdev_kobj(bdev));
147                 del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
148                 kobject_put(holder->holder_dir);
149                 list_del_init(&holder->list);
150                 kfree(holder);
151         }
152         mutex_unlock(&disk->open_mutex);
153 }
154 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);