Messages in this thread | | | Date | Sat, 2 Jun 2001 20:49:03 -0400 (EDT) | From | Alexander Viro <> | Subject | Re: symlink_prefix |
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On Sun, 3 Jun 2001 Andries.Brouwer@cwi.nl wrote:
> 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.
altroot should be buried, not generalized. It was a mistake and we will be better off forgetting about that nightmare instead of trying to design something around it.
Absolute symlinks... Dunno. _If_ we want that at all, we probably want it on per-mountpoint basis. However, that opens a door to _really_ ugly feature requests. E.g. "if symlink starts with /foo - replace it with /mnt/bar, but if it starts with /foo/baz - replace with /mnt/splat instead".
I can see how to implement per-mountpoint variant. However, I'm less than enthusiastic about the API side of that and about the ugliness it will lead to. It smells like a wrong approach. And no, I don't see a good one right now.
As for the API... How would you pass that option? Yet another mount(2) argument?
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