Date: Thu, 7 Apr 2005 22:13:14 -0700 (PDT) From: Doug White <dwhite@gumbysoft.com> To: Kevin Oberman <oberman@es.net> Cc: current@freebsd.org Subject: Re: Panic on mount with write-locked USB media (umass) Message-ID: <20050407221215.U57391@carver.gumbysoft.com> In-Reply-To: <20050406163303.3AD345D08@ptavv.es.net> References: <20050406163303.3AD345D08@ptavv.es.net>
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On Wed, 6 Apr 2005, Kevin Oberman wrote: > > Date: Tue, 5 Apr 2005 23:55:27 +0100 (BST) > > From: Robert Watson <rwatson@FreeBSD.org> > > > > On Tue, 5 Apr 2005, Poul-Henning Kamp wrote: > > > > > In message <20050405201820.042685D07@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? > > I hate to see such inconsistency. I don't like seeing very similar > devices behaving differently for no good reason. > > I think a better idea is a new option to allow/reject demotion to > read-only when hardware does not allow writes. POLA is slight and it > lets people do what they want to do with the issue. This would also fix mounting read-only floppies (which right now causes an undead buf when the write fails). -- Doug White | FreeBSD: The Power to Serve dwhite@gumbysoft.com | www.FreeBSD.org
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