On Wednesday 14 February 2007 11:39, Andreas Gruenbacher wrote: > On Wednesday 14 February 2007 07:37, Linus Torvalds wrote: > > We could prepend another '/' (so that you'd have a path that starts with > > "//"). That's still a legal path, but it's also somethign that even POSIX > > says is valid to mean something else (eg "//ftp/.." or "//socket/.." to > > escape into another namespace). > > This sounds good enough to me. My main point is that users that care should > be able to tell the difference. Looking some more into it, appending another slash doesn't look like the best solution after all. Here is a more elaborate description of the cases we have to deal with: * Regular paths that lead up to the root we are interested in. These should obviously be reported as "/dir/file", so I won't mention them any further. * Files on pseudo filesystems such as pipefs. Historically, we are reporting them as "pipe:[439336]" or similar, where "pipe:" is the name of the root dentry, and "[439336]" is the name of the child; no slash between them. * Lazily unmounted directories. Currently, we report them as "dirfile", where "dir" is the name of the directory dentry, and "file" is the name of the child dentry. That's the obvious bug. * Lazily unmounted filesystems. Currently, they and up as "/file", where "/" is the name of the root dentry, and "file" is the name of the child dentry. * Unreachable paths. Currently, we report them as absolute paths, so there is no way to tell the one from the other. What I'm after here is two things: (1) fix the bug with the lazily unmounted dirs, and (2) allow to tell when a path is unreachable. The key problem is that we know when we hit a disconnected path, but it's hard to tell the pseudo filesystem case from the root filesystem case because rootfs also is a pseudo filesystem. Let's look at a few choices we have: [0] Now: -------- pipe: "pipe:[439336]" lazily umounted dir: "dirfile" <== bug lazily unmounted fs: "/file" <== ambiguous path on rootfs: "/file" <== ambiguous rootfs root: "/" <== ambiguous [1] Always make disconnected paths relative: -------------------------------------------- pipe: "pipe:[439336]" (or "pipe/[439336]") lazily umounted dir: "dir/file" lazily unmounted fs: "file" path on rootfs: "file" rootfs root: "." [2] Make disconnected pseudo-fs paths relative and others absolute; special case the rootfs: ------------------------ pipe: "pipe:[439336]" (or "pipe/[439336]") lazily umounted dir: "//dir/file" lazily unmounted fs: "//file" path on rootfs: "//file" rootfs root: "//" [3] Always make disconnected paths double-slashed: -------------------------------------------------- pipe: "//pipe/[439336]" lazily umounted dir: "//dir/file" lazily unmounted fs: "//file" unreachable root: "//"