Re: UDF label change since commit 2f2730bc77c9

[Jan Kara <jack@suse.cz>]

On Wed 10-08-16 16:23:06, Pali Rohár wrote:
> On Wednesday 10 August 2016 15:39:02 Jan Kara wrote:
> > Hi,
> > 
> > On Wed 10-08-16 14:53:49, Pali Rohár wrote:
> > > On Wednesday 10 August 2016 14:38:59 Jan Kara wrote:
> > > > we have noticed that since commit 2f2730bc77c9 "libblkid: udf: Fix reading
> > > > LABEL, add support for UUID and other udf identifiers" some volumes have
> > > > changed labels which are reported by blkid. See [1] for an example.
> > > 
> > > "You are not authorized to access bug #983165."
> > 
> > Ah, sorry. I forgot the bug is reported against SLES and so is not
> > publically visible. Anyway, the initial comment which is interesting is:
> > 
> > I have a shared paritition with an UDF filesystem. In Win7 64bit its label
> > is 'ssd120_docs'. In SLES12SP1 its label is 'ssd120_dokumente'. In
> > Tumbleweed (and most likely also SP2 Beta) its label is 'ssd120_dosemut'
> > (or similar garbage).
> > 
> > I think there should be some consistency in /dev/disk/by-label/*.
> > ---
> > 
> > As an explanation, SLES12SP1 uses util-linux 2.25 (i.e., before your patch),
> > Tumbleweed is the rolling distro with the latest & greatest version.
> >  
> > > > This is
> > > > because that commit changed what is used for the label - previously we have
> > > > used 'ident' in the Primary Volume Descriptor, and after that commit we use
> > > > Logical Volume ID.
> > > 
> > > Yes, thats true.
> > > 
> > > > I think it would be better to keep consistency with older util-linux
> > > > releases (e.g. valid /etc/fstab that uses labels may be broken by this
> > > > change) but I'm not sure whether there is a point once the new behavior
> > > > has been released in the util-linux release. But still I wanted to raise
> > > > this since I'm not sure how much util-linux cares about these changes and
> > > > also so that people are aware of the change...
> > > > 
> > > > 								Honza
> > > > 
> > > > [1] https://bugzilla.suse.com/show_bug.cgi?id=983165
> > > > 
> > > 
> > > Reason why I proposed that change is because all other software use
> > > Logical Volume Identifier as label. Just linux blkid used something
> > > other.
> > > 
> > > Basically Linux was incompatible with whole world and I think this was a
> > > bug. Also UDF specification say something that LVI is displayed to user.
> > > IIRC also Grub2 uses LVI as label identification.
> > > 
> > > So I do not agree with reverting back old behaviour which is
> > > incompatible with everything except old util-linux versions...
> > 
> > Well, this somewhat does not match the description in the bug. Apparently
> > Win7 uses yet another identifier in the UDF filesystem...
> 
> Not good :-( Anyway, are you able to produce/create UDF disk image/dump
> which show different label under Win7 and new util-linux? With that we
> can inspect which field is Win7 using and could test also other systems
> (like some BSD or Grub2) what see...
> 
> Maybe there could be different behaviour for CD, DVD, HDD or
> multisession CD/DVD...

The reporter has UDF filesystem created on HDD AFAIU. I've asked him to run
udf_test program on the fs image. From its output we should be able to see
various identifiers of the filesystem and thus see whan Win7 uses.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR