On 5/10/07, Kay Sievers <kay.sievers@xxxxxxxx> wrote:
On 5/10/07, Karel Zak <kzak@xxxxxxxxxx> wrote:
> On Thu, May 10, 2007 at 12:06:27PM +0200, Matthias Koenig wrote:
> > There *are* of course issues with volume_id, which needs to be discussed:
> > 1. udev creates label symlinks by default in /dev/disk/by-label/
> > However the name of these links are not the label itself, but a safe label,
> > which is derived by the rules:
> > - '/' are skipped
> > - multiple spaces are converted to a underscore '_'
> > This will lead to problems when we have two volumes with label, e.g. say:
> > foobar and
> > foo/bar
> > I think this is a point where blkid is smarter in detecting the ambiguity.
> >
> > 2. Device-by-label lookup is done by following the symlink in
> > /dev/disk/by-label
> > You will have to know the safe label, not the real label.
> > When we want to do a label-by-device lookup, volume_id only provides
> > the label (not the safe label). AFAIK volume_id does not export the
> > way it derives the safe label. But this is important when we want to compare
>
> Well, you can export the replace_untrusted_chars() function, but this
> is not solution, because
>
> replace_untrusted_chars("fooXbar") == replace_untrusted_chars("foo_bar)
>
> if the 'X' is a unsafe character.
>
> The concept is wrong, because you can't convert a "safe label" back
> to the "raw label". The correct solution is escape (hex, oct, ...)
> unsafe chars rather than remove it. So... /dev/disk/by-raw-label.
> Kay?
Right, that sounds much nicer to encode it.
Karel,
how about using url-encoding style strings for the label-links? So the
plain ascii text labels would still look the same, but slashes and
other control chars are safely escaped.
I could export that encoding-function from libvolume_id, and also let
udev create these links in /dev/disk/by-label/. That way, a label:
/home/foo/bar
would create:
/dev/disk/by-label/%2fhome%2ffoo%2fbar
and the device could safely be looked up there with LABEL=.
How does that sound?
Thanks,
Kay
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