// SPDX-License-Identifier: GPL-2.0-only #include <linux/blkdev.h> #include <linux/slab.h> struct bd_holder_disk { struct list_head list; struct block_device *bdev; 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->bdev == bdev) 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)); } static int __link_disk_holder(struct block_device *bdev, struct gendisk *disk) { int ret; ret = add_symlink(disk->slave_dir, bdev_kobj(bdev)); if (ret) return ret; ret = add_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); if (ret) del_symlink(disk->slave_dir, bdev_kobj(bdev)); return ret; } /** * 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; mutex_lock(&disk->open_mutex); WARN_ON_ONCE(!bdev->bd_holder); /* FIXME: remove the following once add_disk() handles errors */ if (WARN_ON(!bdev->bd_holder_dir)) goto out_unlock; holder = bd_find_holder_disk(bdev, disk); if (holder) { holder->refcnt++; goto out_unlock; } holder = kzalloc(sizeof(*holder), GFP_KERNEL); if (!holder) { ret = -ENOMEM; goto out_unlock; } INIT_LIST_HEAD(&holder->list); holder->bdev = bdev; holder->refcnt = 1; if (disk->slave_dir) { ret = __link_disk_holder(bdev, disk); if (ret) { kfree(holder); goto out_unlock; } } list_add(&holder->list, &disk->slave_bdevs); /* * 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. */ kobject_get(bdev->bd_holder_dir); out_unlock: mutex_unlock(&disk->open_mutex); return ret; } EXPORT_SYMBOL_GPL(bd_link_disk_holder); static void __unlink_disk_holder(struct block_device *bdev, struct gendisk *disk) { del_symlink(disk->slave_dir, bdev_kobj(bdev)); del_symlink(bdev->bd_holder_dir, &disk_to_dev(disk)->kobj); } /** * 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; mutex_lock(&disk->open_mutex); holder = bd_find_holder_disk(bdev, disk); if (!WARN_ON_ONCE(holder == NULL) && !--holder->refcnt) { if (disk->slave_dir) __unlink_disk_holder(bdev, disk); kobject_put(bdev->bd_holder_dir); list_del_init(&holder->list); kfree(holder); } mutex_unlock(&disk->open_mutex); } EXPORT_SYMBOL_GPL(bd_unlink_disk_holder); int bd_register_pending_holders(struct gendisk *disk) { struct bd_holder_disk *holder; int ret; mutex_lock(&disk->open_mutex); list_for_each_entry(holder, &disk->slave_bdevs, list) { ret = __link_disk_holder(holder->bdev, disk); if (ret) goto out_undo; } mutex_unlock(&disk->open_mutex); return 0; out_undo: list_for_each_entry_continue_reverse(holder, &disk->slave_bdevs, list) __unlink_disk_holder(holder->bdev, disk); mutex_unlock(&disk->open_mutex); return ret; }