Re: silent semantic changes with reiser4

[Jamie Lokier]

Linus Torvalds wrote:
> > 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.

At which point, userspace comes in.  Who knows what userspace chooses.

> > 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.

I don't mean to imply it's useful behaviour: only that it seems to
happen by default if you don't do anything special to prevent it, if
you see what I mean.

It does seem useful to have _files_ mounted automagically (using
loopback devices): for example, cd into a .iso file and it would be
nice to see the contents.  At this point, deciding on the preferred
-EBUSY or not behaviour becomes relevant, as does deciding whether the
.iso in this example is viewed using the kernel's isofs code, or using
a userspace helper in the same way as we'd use one to browse a .zip file.

-- Jamie
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