diff options
Diffstat (limited to 'block/holder.c')
| -rw-r--r-- | block/holder.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/block/holder.c b/block/holder.c new file mode 100644 index 0000000000..37d18c13d9 --- /dev/null +++ b/block/holder.c @@ -0,0 +1,154 @@ +// 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 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(&disk->open_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(&disk->open_mutex); + return 0; + +out_del_symlink: + del_symlink(disk->slave_dir, bdev_kobj(bdev)); +out_free_holder: + kfree(holder); +out_unlock: + mutex_unlock(&disk->open_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(&disk->open_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(&disk->open_mutex); +} +EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); |