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git.ipfire.org Git - people/ms/linux.git/blob - block/holder.c
1 // SPDX-License-Identifier: GPL-2.0-only
2 #include <linux/blkdev.h>
3 #include <linux/slab.h>
5 struct bd_holder_disk
{
7 struct block_device
*bdev
;
11 static struct bd_holder_disk
*bd_find_holder_disk(struct block_device
*bdev
,
14 struct bd_holder_disk
*holder
;
16 list_for_each_entry(holder
, &disk
->slave_bdevs
, list
)
17 if (holder
->bdev
== bdev
)
22 static int add_symlink(struct kobject
*from
, struct kobject
*to
)
24 return sysfs_create_link(from
, to
, kobject_name(to
));
27 static void del_symlink(struct kobject
*from
, struct kobject
*to
)
29 sysfs_remove_link(from
, kobject_name(to
));
32 static int __link_disk_holder(struct block_device
*bdev
, struct gendisk
*disk
)
36 ret
= add_symlink(disk
->slave_dir
, bdev_kobj(bdev
));
39 ret
= add_symlink(bdev
->bd_holder_dir
, &disk_to_dev(disk
)->kobj
);
41 del_symlink(disk
->slave_dir
, bdev_kobj(bdev
));
46 * bd_link_disk_holder - create symlinks between holding disk and slave bdev
47 * @bdev: the claimed slave bdev
48 * @disk: the holding disk
50 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
52 * This functions creates the following sysfs symlinks.
54 * - from "slaves" directory of the holder @disk to the claimed @bdev
55 * - from "holders" directory of the @bdev to the holder @disk
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:
60 * /sys/block/dm-0/slaves/sda --> /sys/block/sda
61 * /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
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.
71 * 0 on success, -errno on failure.
73 int bd_link_disk_holder(struct block_device
*bdev
, struct gendisk
*disk
)
75 struct bd_holder_disk
*holder
;
78 mutex_lock(&disk
->open_mutex
);
80 WARN_ON_ONCE(!bdev
->bd_holder
);
82 holder
= bd_find_holder_disk(bdev
, disk
);
88 holder
= kzalloc(sizeof(*holder
), GFP_KERNEL
);
94 INIT_LIST_HEAD(&holder
->list
);
97 if (disk
->slave_dir
) {
98 ret
= __link_disk_holder(bdev
, disk
);
105 list_add(&holder
->list
, &disk
->slave_bdevs
);
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.
110 kobject_get(bdev
->bd_holder_dir
);
113 mutex_unlock(&disk
->open_mutex
);
116 EXPORT_SYMBOL_GPL(bd_link_disk_holder
);
118 static void __unlink_disk_holder(struct block_device
*bdev
,
119 struct gendisk
*disk
)
121 del_symlink(disk
->slave_dir
, bdev_kobj(bdev
));
122 del_symlink(bdev
->bd_holder_dir
, &disk_to_dev(disk
)->kobj
);
126 * bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
127 * @bdev: the calimed slave bdev
128 * @disk: the holding disk
130 * DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
135 void bd_unlink_disk_holder(struct block_device
*bdev
, struct gendisk
*disk
)
137 struct bd_holder_disk
*holder
;
139 mutex_lock(&disk
->open_mutex
);
140 holder
= bd_find_holder_disk(bdev
, disk
);
141 if (!WARN_ON_ONCE(holder
== NULL
) && !--holder
->refcnt
) {
143 __unlink_disk_holder(bdev
, disk
);
144 kobject_put(bdev
->bd_holder_dir
);
145 list_del_init(&holder
->list
);
148 mutex_unlock(&disk
->open_mutex
);
150 EXPORT_SYMBOL_GPL(bd_unlink_disk_holder
);
152 int bd_register_pending_holders(struct gendisk
*disk
)
154 struct bd_holder_disk
*holder
;
157 mutex_lock(&disk
->open_mutex
);
158 list_for_each_entry(holder
, &disk
->slave_bdevs
, list
) {
159 ret
= __link_disk_holder(holder
->bdev
, disk
);
163 mutex_unlock(&disk
->open_mutex
);
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
);