[CC-ing mailing lists, Al and Linus for wider exposure] This issue is this: Ubuntu and SUSE carry an "old" format of overlayfs while mainline has a "new" format. The differences are: - whiteouts are represented differently (symlink + xattr in the old format, chardev in the new) - new one needs a "workdir" mount option, which points to a directory on the same filesystem as upperdir. If upperdir was the root of the filesystem then it needs to be moved into a subdir to make space for the work directory. Migrating from old to new is not a big issue, but Ubuntu people have expressed concerns about systems with mixed kernel versions and want to support the old format alongside the new. This can all be done with out-of-tree code. So from mainline we need two things: - when mounting distinguish between old and new format. - userspace can detect which formats are supported by the kernel. If we'd have a different filesystem type for the old and new formats, then that would solve both (checking /proc/filesystems would indicate which one is supported). Unfortunately that would mean having to change "overlayfs" type to something else in 3.18. Question is, is there some sane name which would fit? "overlayfs2" is perhaps the best, but I'm not overly enthusiastic about it. Any other ideas? Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
