[230] in linux-scsi channel archive
Re: st driver open(O_WRONLY) of write-protected tape
daemon@ATHENA.MIT.EDU (Andreas Koppenhoefer)
Tue Jun 6 08:24:22 1995
From: Andreas Koppenhoefer <koppenas@koppenas.informatik.uni-stuttgart.de>
To: Kai.Makisara@metla.fi
Date: Tue, 6 Jun 1995 12:57:25 +0200 (MET DST)
Cc: linux-scsi@vger.rutgers.edu
Reply-To: Andreas.Koppenhoefer@studbox.uni-stuttgart.de (Andreas Koppenhoefer)
In-Reply-To: <Pine.OSF.3.91.950604102133.3060A-100000@abies.metla.fi> from "Kai Makisara" at Jun 4, 95 10:29:56 am
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> Date: Sun, 4 Jun 1995 10:29:56 +0300 (EET DST)
> From: Kai Makisara <makisara@abies.metla.fi>
> To: "Brandon S. Allbery KF8NH" <bsa@kf8nh.wariat.org>
> Cc: linux-scsi@vger.rutgers.edu
> Subject: Re: st driver open(O_WRONLY) of write-protected tape
>
> On Sat, 3 Jun 1995, Brandon S. Allbery KF8NH wrote:
> ...
> > and got a write error "Permission denied" and an aborted backup instead of a
> > re-prompt for the device as GNU tar normally does. This led me to look at
> > st.c, where I found that opening a write-protected tape actuallty opens the
> > tape read-only but causes writes to return -EPERM.
> >
> > README.st makes no mention of this unexpected behavior. Is it in fact
> > deliberate, and if so why? I would much prefer not having to start over in
I agree with Brandon: st.c whould return -EPERM as fast as possible.
> The reason for this behavior is probably to prevent problems with the
> programs that open the device for read/write even if they don't always
> need to write. I did not think about multivolume tars at that moment.
I think we can call it bad programming style if someone opens
files/devices O_RDWR if he/she never wants to write to.
> The quick patch at the end of this message changes the behaviour so that
> the tar problem disappears. Returning EPERM if a write-protected tape is
> opened O_WRONLY is certainly sensible but should we do that also for O_RDWR?
Yes! That's the way other OS are handling this (like Solaris/SunOS).
Please send your quick patch to Linus making it permanent.
Andreas
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