case-folding

The Linux 7.2 kernel has introduced enhancements for reporting case-folding behavior in local file systems, allowing file servers to accurately convey their case sensitivity capabilities. Linus Torvalds merged Virtual File System (VFS) related pull requests that enable local file systems to report case-folding behavior, benefiting services like NFSD and KSMBD, particularly for Microsoft Windows NFS clients. Filesystems can now report case-insensitive and case-nonpreserving behavior through new filekattr flags in their fileattrget implementations. Supported filesystems include FAT, exFAT, NTFS3, HFS, HFS+, XFS, CIFS, NFS, VBoxSF, and ISOFS, with others defaulting to POSIX behavior. NFSd uses this information to report case folding via NFSv3 PATHCONF and implement NFSv4 attributes for case insensitivity and case preservation. The enhancements aim to improve interoperability, allowing Windows NFS clients to function correctly by reporting case-insensitivity, which streamlines operations and avoids unnecessary requests. The Linux NFS client has previously supported case-insensitive shares, requiring adjustments to caching behavior. Accurate case folding reporting is crucial for servers operating in multi-protocol environments to maintain interoperability.