Re: udf: Prevent write-unsupported filesystem to be remounted read-write

[Jan Kara]

On Tue 15-01-19 09:31:11, Pali Rohár wrote:
> On Monday 14 January 2019 19:07:35 Michael Sabolish wrote:
> > I can try and make a pull-request for udftune, and I can just copy the API for tune2fs.  It would work something like:
> > 
> > udftune -O read-only device            (to set read-only access type)
> > 
> > or:
> > 
> > udftune -O ^read-only device          (to clear read-only access type (aka set rw))
> 
> This API is ambiguous. What does it mean for ^read-only? In UDF you have
> following access types: overwritable, rewritable, writeonce, readonly,
> pseudo-overwritable, unknown.
> 
> So you would need to know to which R/W access type to switch
> (overwritable, rewritable, writeonce or pseudo-overwritable).
> 
> With information of media type, you could be able to guess correct
> access type. But for UDF images stored in VFS there is no media
> information. Also you can have uncommon setup, e.g. usage of CD-R
> writeonce setup on CD-R/W disc. So "autodetection" of media type would
> not work always correctly.
> 
> So I think that it would be better to have following API:
> 
>   udftune --access-type=<new_access_type>
> 
> or
> 
>   udftune --change-access-type=<new_access_type>
> 
> I understand that you would like to have similar API as tune2fs, but UDF
> settings are too different from ext*.

If you wanted to follow tune2fs interface, you can have e.g.:

udftune -E access-type=<foo>

Another question about the feature is - the access type is actually per
partition and there can be multiple partitions on UDF media. So I think we
need to specify the partition number in the command and <foo> has to
actually be something like <partition number>,<access_type>.

								Honza
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR