Re: silent semantic changes with reiser4

[Linus Torvalds]

On Thu, 26 Aug 2004, Jamie Lokier wrote:
>
> > .. but even if it did that, it should use O_DIRECTORY when it did so. If 
> > it doesn't, it's broken.
> 
> Didn't someone just say that O_DIRECTORY will succeed on a device,
> precisely because opendir() is supposed to succeed on the device?

It will succeed on the _name_ of the device, but it won't open the device 
node. It would open the _directory_ node associated with that name.

Think of it this way: a pathname always points to one "container". That 
container is either a directory or a single node - and O_DIRECTORY ends up 
being the thing that chooses between them.

> > I don't think you can do that. The kernel has no idea how to mount the
> > filesystem.
> 
> It is not the kernel which decides.  The filesystem containing
> /dev/hda/part1 opens "the directory branch".

But that filesystem cannot know what the _other_ filesystem configurations 
are. And that's what you'd have to have to mount.

> The obvious implementation has the userspace helper just mounting it,
> end of story.  If the mount command fails, it fails.  Much like autofs.

Yes, that would work, but it's of questionable use. If you want autofs, 
then just _use_ autofs.

		Linus
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