Re: Loopback (dir->dir) mounting (NOT -o loop)

From: Aaron Passey (
Date: Fri Jun 02 2000 - 18:52:16 EST

On Fri, 2 Jun 2000 22:31:21 +0200, Jamie Lokier
<> wrote:
>I still don't see _any_ reason for the new vfsmnt/dentry stuff. What do
>you gain? The ability to mount devfs in chroot jails. In a chroot
>jail, you don't want the same devfs tree as you find in /dev anyway.
>What do you lose? The vfs data structure is even more complicated now,
>with yet another layer of indirection. And the user space view of
>filesystems is more complicated too.
>I'm sure it's very clever, but I really don't see the point.

Consider the case where you have several filesystems that you want to
export via NFS to different machines. Say you want each machine to get a
unique view of those filesystems. There is no convienient way to do this
without something similar to the bind functionality -- symlinks are
resolved on the client with NFS.

Here's a simple example:




This exact situation has come up in the past for a product I worked on
(except with a far more complicated set of exported trees). The solution
we came up with was less flexible, less clean, and less elegant than using
bind mounts. (Also note, we had a requirement that the client should only
have to mount one directory from the server to get its entire tree.)


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