Re: [PATCH 02/27] allow hard links to directories, opt-in for any filesystem

Nick Piggin wrote:
Patch seems to work, might want more testing.
It probably should not be applied without a discussion, especially
as no filesystem in kernel tree wants this. I am working on a fs that does.
This is backwards I think. This is not disallowed because there are
no filesystems that want it. Linux doesn't want it so it is disallowed
by the vfs.
> You have to put forward a case for why we want it, rather than show us
> your filesystem that "wants" it. Right?

Agreed. Mostly this is because the design of unix directory semantics preclude it from being possible. You have exactly one ".." entry. More than one ".." would mean confusion (which does ".." refer to?). A different name would confuse more programs.

The VFS is presenting collections of arbitrary filesystems as unix filesystem, it is not a generic abstraction for any kind of storage system that is extended to encompass novel approaches to filesystem structure.

So if you wanted to access such a filesystem via Linux you would need to present this non-unix idea of directory hard links through some kind of ioctl etc.

Besides, we already have bind mounts, which are in many ways like a directory hard link (and, in many other ways, unlike one).

Sam.
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