Erez Zadok: > ... Asking = > overlayfs or other stackable file systems to solve this multi-layer = > coherency perfectly is somewhat ridiculous: we don't expect file systems = > like ext3 to detect and correctly handle changes to lower devices =97 = > i.e., if someone hand-edited direct blocks in /dev/sda1, do we? I agree with you if we discuss about union-type-mount, which handles a block device as its member. As long as the layered-fs handles a directory (mounted filesystem) as its member, it is obviously right that users expect the modification on the member fs (by-passing a union) is available. Of course I agree it brings complication to us, and I'd suggest three level options to support this issue. - detect the direct changes and reflect it to union (hardest option) - skip the detection, but verify the parent-child relationship or more at least. (this is something like overlayfs is trying to do) - skip both of the detection and verification (lowest option) this option depends how user sets up the union and its member. if user hides the members totally by over-mounting an empty dir on the member (or something), then he can specify this option. otherwise, this option is dangerous. also some symlinks may not work. # mkdir /hide # mount -o upper=/rw,lower=/ro none /union # mount -o bind /hide /rw # mount -o bind /hide /ro J. R. Okajima -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
