Btrfs Performance Boost: Chunk Allocation with Device Roles

A significant performance improvement is coming to the Btrfs filesystem! A new patch introduces a performance-based chunk allocation method using device roles, addressing the current imbalance caused by allocation based solely on free space. By defining five device roles (metadata_only, metadata, none, data, data_only) and prioritizing roles alongside remaining space, the system can intelligently assign faster devices to metadata and slower devices to data, significantly boosting read/write performance. This improvement avoids complex device speed measurements, leveraging the existing on-disk format for smarter, more efficient storage management.