Date: Mon, 18 Jun 2007 10:06:37 +0400 From: Andrey Chernov <ache@nagual.pp.ru> To: Tim Kientzle <kientzle@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org, Colin Percival <cperciva@FreeBSD.org> Subject: Re: cvs commit: src/lib/libarchive archive_read_open_fd.c archive_read_open_filename.c Message-ID: <20070618060637.GA34022@nagual.pp.ru> In-Reply-To: <46760F7A.8020209@freebsd.org> References: <200706180036.l5I0asac023540@repoman.freebsd.org> <4675DFC8.8060108@freebsd.org> <46760F7A.8020209@freebsd.org>
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On Sun, Jun 17, 2007 at 09:52:10PM -0700, Tim Kientzle wrote:
> Colin Percival wrote:
> > Tim Kientzle wrote:
> >> I fear I'll have to avoid seeks ... tape drives on
> >> FreeBSD seem to return garbage from lseek().
> > Is there any reason why the tape drivers can't be fixed?
>
> Since people are running into this problem today
> on 6.2, I'm planning to fix it where I can. :-/
>
> The basic problem is that an lseek() call to a tape
> drive returns success exactly as if it worked.
> Daniel O'Connor recently sent me the following
> ktrace from bsdtar doing a tar -t of an uncompressed
> tar archive from his Tandberg TS400 connected to an
> Adaptec 29160 controller:
>
> 5378 bsdtar CALL lseek(0x3,0,0,0x1)
> 5378 bsdtar RET lseek 51200/0xc800
> 5378 bsdtar CALL lseek(0x3,0,0x2f800,0x1)
> 5378 bsdtar RET lseek 245760/0x3c000
>
> Note that the second call returns a new file position
> that's exactly 0x2f800 bytes beyond the former file
> position, even though nothing has actually happened.
>
> I think any of the following would be reasonable behaviors:
> * lseek() could return ESPIPE ("illegal seek")
> * lseek() could return an unchanged file offset
> (indicating that the file position was unchanged by
> the attempted seek).
> * lseek() could return ENOTSUP ("unsupported operation")
> As I said though, I just don't know that code well
> enough to propose a fix.
Then it should be fixed in the driver, please do not mask this bug in the
bsdtar workaround. Ask adaptec driver people for help.
--
http://ache.pp.ru/
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