diff options
Diffstat (limited to 'block/holder.c')
| -rw-r--r-- | block/holder.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/block/holder.c b/block/holder.c new file mode 100644 index 000000000000..9dc084182337 --- /dev/null +++ b/block/holder.c @@ -0,0 +1,174 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/genhd.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; +} |