EXT4 Case-Insensitive Directories/File-Name Lookups Coming With Linux 5.2

Written by Michael Larabel in Linux Storage on 26 April 2019 at 11:01 AM EDT. 72 Comments
The Linux 5.2 kernel will allow the EXT4 file-system on a per-directory basis to selectively support case-insensitive files/folders.

These patches by Collabora developer Gabriel Krisman Bertazi have long been in development for supporting case-insensitive filenames and UTF-8 encoding support. It seems now the design and implementation are in good enough standing as EXT4 maintainer Ted Ts'o has queued the patches into his tree.

This EXT4 case-insensitive file-name lookup feature works on a per-directory basis when an empty directory is enabled by flipping the +F inode attribute. This includes UTF-8/Unicode case handling and preserving of the actual case on-disk. By making it per-directory, the support can be enabled by system administrators where desired while not interfering with the long-time expectations of Linux/Unix case-sensitive file-systems.

This implementation is just for EXT4 and does not affect other file-systems, though all the Unicode bits are being added as a generic Unicode subsystem within the kernel's file-system area.

One current limitation of this case-insensitive directories/filenames is not supporting both the encoding and per-directory encryption on the same file-system at the same time while eventually they aim to be able to support both features concurrently. The queued work also adds the character set encoding data to the EXT4 superblock with this technically being a backwards incompatible feature.

Over the span of several commits introducing the Unicode handling and then the EXT4 bits, the work is now in place within ext4's dev branch ahead of the Linux 5.2 merge window that will open following the Linux 5.1 stable release in early May. Linux 5.2 should debut as stable with this EXT4 case-insensitive file-name lookup functionality and a lot more features around July.
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