symlink_prefix

[Andries.Brouwer@cwi.nl]

This evening I needed to work on a filesystem of a non-Linux OS,
full of absolute symlinks. After mounting the fs on /mnt, each
symlink pointing to /foo/bar in that filesystem should be
regarded as pointing to /mnt/foo/bar.

Since doing ls -ld on every component of every pathname was
far too slow, I made a small kernel wart, where a mount option
-o symlink_prefix=/pathname would cause /pathname to be prepended
in front of every absolute symlink in the given filesystem
(when the symlink is followed). That works satisfactorily.

Remain the questions:
(i) is there already a mechanism that would achieve this?
(ii) if not, do we want something like this in the kernel?

There is already a vaguely similar (and much uglier) wart,
namely that of "altroot". It is really ugly - requires a path
set at kernel compile time. And the scope is different.
Instead of all processes and a single filesystem and symlinks only,
altroot affects a single process and all filesystems and all paths.

I do not immediately see a common generalization of these two.

Andries