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// SPDX-License-Identifier: GPL-2.0-only
#include <linux/blkdev.h>
#include <linux/slab.h>
struct bd_holder_disk {
struct list_head list;
struct kobject *holder_dir;
int refcnt;
};
static DEFINE_MUTEX(blk_holder_mutex);
static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
struct gendisk *disk)
{
struct bd_holder_disk *holder;
list_for_each_entry(holder, &disk->slave_bdevs, list)
if (holder->holder_dir == bdev->bd_holder_dir)
return holder;
return NULL;
}
static int add_symlink(struct kobject *from, struct kobject *to)
{
return sysfs_create_link(from, to, kobject_name(to));
}
static void del_symlink(struct kobject *from, struct kobject *to)
{
sysfs_remove_link(from, kobject_name(to));
}
/**
* bd_link_disk_holder - create symlinks between holding disk and slave bdev
* @bdev: the claimed slave bdev
* @disk: the holding disk
*
* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
*
* This functions creates the following sysfs symlinks.
*
* - from "slaves" directory of the holder @disk to the claimed @bdev
* - from "holders" directory of the @bdev to the holder @disk
*
* For example, if /dev/dm-0 maps to /dev/sda and disk for dm-0 is
* passed to bd_link_disk_holder(), then:
*
* /sys/block/dm-0/slaves/sda --> /sys/block/sda
* /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
*
* The caller must have claimed @bdev before calling this function and
* ensure that both @bdev and @disk are valid during the creation and
* lifetime of these symlinks.
*
* CONTEXT:
* Might sleep.
*
* RETURNS:
* 0 on success, -errno on failure.
*/
int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
struct bd_holder_disk *holder;
int ret = 0;
if (WARN_ON_ONCE(!disk->slave_dir))
return -EINVAL;
if (bdev->bd_disk == disk)
return -EINVAL;
/*
* del_gendisk drops the initial reference to bd_holder_dir, so we
* need to keep our own here to allow for cleanup past that point.
*/
mutex_lock(&bdev->bd_disk->open_mutex);
if (!disk_live(bdev->bd_disk)) {
mutex_unlock(&bdev->bd_disk->open_mutex);
return -ENODEV;
}
kobject_get(bdev->bd_holder_dir);
mutex_unlock(&bdev->bd_disk->open_mutex);
mutex_lock(&blk_holder_mutex);
WARN_ON_ONCE(!bdev->bd_holder);
holder = bd_find_holder_disk(bdev, disk);
if (holder) {
kobject_put(bdev->bd_holder_dir);
holder->refcnt++;
goto out_unlock;
}
holder = kzalloc(sizeof(*holder), GFP_KERNEL);
if (!holder) {
ret = -ENOMEM;
goto out_unlock;
}
INIT_LIST_HEAD(&holder->list);
holder->refcnt = 1;
holder->holder_dir = bdev->bd_holder_dir;
ret = add_symlink(disk->slave_dir, bdev_kobj(bdev));
if (ret)
goto out_free_holder;
ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj);
if (ret)
goto out_del_symlink;
list_add(&holder->list, &disk->slave_bdevs);
mutex_unlock(&blk_holder_mutex);
return 0;
out_del_symlink:
del_symlink(disk->slave_dir, bdev_kobj(bdev));
out_free_holder:
kfree(holder);
out_unlock:
mutex_unlock(&blk_holder_mutex);
if (ret)
kobject_put(bdev->bd_holder_dir);
return ret;
}
EXPORT_SYMBOL_GPL(bd_link_disk_holder);
/**
* bd_unlink_disk_holder - destroy symlinks created by bd_link_disk_holder()
* @bdev: the calimed slave bdev
* @disk: the holding disk
*
* DON'T USE THIS UNLESS YOU'RE ALREADY USING IT.
*
* CONTEXT:
* Might sleep.
*/
void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk)
{
struct bd_holder_disk *holder;
if (WARN_ON_ONCE(!disk->slave_dir))
return;
mutex_lock(&blk_holder_mutex);
holder = bd_find_holder_disk(bdev, disk);
if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) {
del_symlink(disk->slave_dir, bdev_kobj(bdev));
del_symlink(holder->holder_dir, &disk_to_dev(disk)->kobj);
kobject_put(holder->holder_dir);
list_del_init(&holder->list);
kfree(holder);
}
mutex_unlock(&blk_holder_mutex);
}
EXPORT_SYMBOL_GPL(bd_unlink_disk_holder);
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