Get a unique ID to put in the snaphot context to create a
snapshot. A clone of an object is not created until a write with
the new snapshot context is completed.
@param io the pool in which the snapshot will exist
@param snapid where to store the newly allocated snapshot ID
@returns 0 on success, negative error code on failure
Allocate an ID for a self-managed snapshot
Get a unique ID to put in the snaphot context to create a snapshot. A clone of an object is not created until a write with the new snapshot context is completed.
@param io the pool in which the snapshot will exist @param snapid where to store the newly allocated snapshot ID @returns 0 on success, negative error code on failure