Panic on mount with write-locked USB media (umass)

[Robert Watson]

On Tue, 5 Apr 2005, Poul-Henning Kamp wrote:

> In message <20050405201820.042685D07 at ptavv.es.net>, "Kevin Oberman" writes:
>
>>> It would be useful if mount was smart enough to notice when it is
>>> dealing with a read-only device, and try to mount such things
>>> read-only, rather than trying to mount things read-write by default and
>>> failing.  Of course, the system shouldn't panic, either.  :-)
>>
>> I think that is what I said. I am almost sure that this is how it used
>> to work. I'm not sure whether the change was caused by something in
>> msdosfs or GEOM (or somewhere else), but I sure preferred it when the RO
>> device mounted RO. CDs still do this (thankfully). This makes me suspect
>> msdosfs is the culprit.
>
> There are two ways that a filesystem correctly could handle a R/O media:
>
> 1.	Fail with EROFS unless asked t mouned read-only
>
> 2.	Silently downgrade th emount to read-only.
>
> I personally prefer the first because that way a script does not have to 
> check if it got the mount it wanted or not.

In general, I agree, but this will de-POLA the following command:

     mount -t cd9660 /dev/acd0 /cdrom

I wonder if a useful middle ground is to adopt (1) above except in the 
case of perenially read-only file systems (cd9660), in which case (2) is 
adopted?

Robert N M Watson