Many systems use UTF-8 locales these days, resulting in file names encoded in UTF-8. On such systems, file names not encoded in UTF-8 can cause problems, making it desirable to detect these problems when the file is created, not when someone attempts to open the file or display the directory contents. In order to support this better on Linux, I implemented an utf8only file system option for ext4. It is an RO_COMPAT option: systems not supporting it will still be able to mount the volume read-only, but cannot create new files. Systems supporting the option will refuse creation of new files with names that are invalid UTF-8 with an EILSEQ errno code. This feature was inspired by the ZFS utf8only property. Unlike the ZFS feature, I propose that the option cannot just be specified when the file system is created, but also later on using tune2fs. The kernel will reject creation of new non-UTF-8 names; existing non-UTF-8 names can still be accessed. This will allow users to run convmv on the volume to convert any remaining non-UTF-8 names. I'm uncertain how fsck should deal with non-UTF-8 files when it sees that the option is turned on. I can imagine these alternatives: - ignore the issue, letting the user use convmv - convert the file names to UTF-8, assuming they are currently Latin-1. This assumption may be incorrect; it may also create conflicts with existing files in the same directory. - convert the file names to UTF-8, assuming an encoding specified on the command line (essentially integrating convmv into fsck). This may still cause conflicts with existing files. - convert non-UTF-8 bytes to private-use characters, encoded in UTF-8. This has a very low but non-zero chance of creating conflicts, and it is possible to locate the converted files afterwards by looking at those PUA characters. - move the files to lost+found, renaming them uniquely (possibly in a way that still allows to recreate the original directory and file name, e.g. <dir-inum>-<inum>-nameWithPUAchars) The patch makes no attempt to provide Unicode normalization. I just noticed that the specific RO feature selected conflicts with the one that was just reserved; I'll update the patches shortly. The patches are in the utf8only branches of https://github.com/loewis/linux https://github.com/loewis/e2fsprogs Please let me know what you think. Regards. Martin -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
