Date: Wed, 06 Apr 2005 09:33:03 -0700 From: "Kevin Oberman" <oberman@es.net> To: Robert Watson <rwatson@FreeBSD.org> Cc: current@freebsd.org Subject: Re: Panic on mount with write-locked USB media (umass) Message-ID: <20050406163303.3AD345D08@ptavv.es.net> In-Reply-To: Your message of "Tue, 05 Apr 2005 23:55:27 BST." <20050405235414.D81173@fledge.watson.org>
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> 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. Because of the existence of "mount -t cd9660 /dev/acd0 /cdrom", I think that default should be to demote. -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634
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