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

From: Alexander Viro (
Date: Sat Jun 03 2000 - 01:29:05 EST

On Fri, 2 Jun 2000, Jamie Lokier wrote:

> So what use is mount -t bind?
> One use is to hide the fact that anything is linked. This it does very
> well. Disturbingly well :-) I don't know of a legitimate use for this
> though.

Damn. It. Is. Not. A. Link. Could you at least look at the way it works?

> 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.

Show me that "another level of indirection", please. Last time I checked,
file->f_dentry->d_inode still took you to the inode from the struct file.
Where, in your opinion, does this level of indirection live? Excuse me,
but what about, like, looking at the actual data structures? Come on,
there are 5 things in the game - struct file, struct dentry, struct
vfsmount, struct super_block and struct inode. Comparing "before" and
"after" sounds like a good idea if you are making claims about the
changes, no? Or just looking into the l-k archives, for that matter...

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