From: Jens Axboe <axboe@suse.de>
To: Marcelo Tosatti <marcelo@conectiva.com.br>
Cc: Karsten Weiss <knweiss@gmx.de>,
lkml <linux-kernel@vger.kernel.org>,
Andre Hedrick <andre@linux-ide.org>
Subject: Re: Linux 2.4.19-pre3
Date: Wed, 13 Mar 2002 09:09:46 +0100 [thread overview]
Message-ID: <20020313080946.GC15877@suse.de> (raw)
In-Reply-To: <20020312134631.GE1473@suse.de> <Pine.LNX.4.21.0203121558300.3462-100000@freak.distro.conectiva>
In-Reply-To: <Pine.LNX.4.21.0203121558300.3462-100000@freak.distro.conectiva>
On Tue, Mar 12 2002, Marcelo Tosatti wrote:
> So, Jens, could you please explain the problem in the interrupt handlers
> in detail ?
Ok... It affects all the pio handlers in ide-taskfile.c,
multi-write/read as well. The address for pio transfers is calculated
like so:
va = rq->buffer + (rq->nr_sectors - rq->current_nr_sectors) * SECTOR_SIZE;
which is wrong for two reasons. First of all, rq->buffer cannot be
indexed for the entire nr_sectors range -- it's per definition only the
first segment in the request, and can as such only be indexed within the
first current_nr_sectors number of sectors. The above can be grossly out
of range... Second, nr_sectors and current_nr_sectors are indexing two
different things -- the former indexes the entire request (all segments)
while the latter indexes only the first segments. So
foo = rq->nr_sectors - rq->current_nr_sectors;
makes no sense _at all_ and can only be wrong.
So why does 2.4.19-pre3 work for pio at all? For the same reason that
Andre never found this problem in 2.5 either: the taskfile interrupt
handlers are _never_ used in pio mode. In 2.5 it was by accident, and
when the merge happened they did indeed get used. It ate disks, very
quickly. Take a look at drivers/ide/ide-disk.c, line 64:
#ifdef CONFIG_IDE_TASKFILE_IO
# undef __TASKFILE__IO /* define __TASKFILE__IO */
#else /* CONFIG_IDE_TASKFILE_IO */
# undef __TASKFILE__IO
#endif /* CONFIG_IDE_TASKFILE_IO */
It's a mess... This really should have been fixed prior to 2.4
inclusion. Oh well.
--
Jens Axboe
next prev parent reply other threads:[~2002-03-13 8:10 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-03-11 21:08 Linux 2.4.19-pre3 Marcelo Tosatti
2002-03-11 22:40 ` Eyal Lebedinsky
2002-03-11 23:03 ` Alan Cox
2002-03-11 22:55 ` Stephan von Krawczynski
2002-03-12 1:50 ` Mike Fedyk
2002-03-12 11:06 ` Stephan von Krawczynski
2002-03-11 23:04 ` Eyal Lebedinsky
2002-03-11 23:14 ` Keith Owens
2002-03-12 15:49 ` DevilKin
2002-03-21 12:06 ` [patch] Don't offer CONFIG_INDYDOG on non-ip22 machines Adrian Bunk
2002-03-22 21:13 ` Marcelo Tosatti
2002-03-11 23:21 ` Linux 2.4.19-pre3 Eyal Lebedinsky
2002-03-12 1:40 ` Takeo Saito
2002-03-12 0:04 ` J.A. Magallon
2002-03-12 0:37 ` Ken Brownfield
2002-03-19 2:41 ` I/O APIC fixed in 2.4.19-pre3 & 2.5.6 (was Re: Linux 2.4.19-pre3) Ken Brownfield
2002-03-19 16:22 ` Bill Davidsen
2002-03-20 0:34 ` Ken Brownfield
2002-03-20 4:36 ` Bill Davidsen
2002-03-12 10:35 ` Linux 2.4.19-pre3 Gerd Knorr
2002-03-12 17:24 ` Trond Myklebust
2002-03-12 17:47 ` Gerd Knorr
2002-03-12 13:01 ` Karsten Weiss
2002-03-12 13:17 ` Jens Axboe
2002-03-12 13:37 ` Alan Cox
2002-03-12 13:46 ` Jens Axboe
2002-03-12 19:02 ` Marcelo Tosatti
2002-03-13 8:09 ` Jens Axboe [this message]
2002-03-13 9:00 ` Andre Hedrick
2002-03-13 9:27 ` Jens Axboe
2002-03-13 9:33 ` Andre Hedrick
2002-03-13 17:32 ` Andre Hedrick
2002-03-13 17:40 ` Jens Axboe
2002-03-13 18:52 ` Andre Hedrick
2002-03-14 4:41 ` Marcelo Tosatti
2002-03-14 6:28 ` Andre Hedrick
2002-03-14 3:32 ` Michal Jaegermann
2002-03-12 14:47 ` J.A. Magallon
2002-03-12 13:31 ` Jurgen Philippaerts
2002-03-12 15:43 ` Geert Uytterhoeven
2002-03-12 21:59 ` Paul Mackerras
2002-03-12 0:51 Mikael Pettersson
2002-03-12 5:13 ` skidley
2002-03-12 21:00 ` Dave Jones
[not found] <fa.npg7nmv.si46bq@ifi.uio.no>
2002-03-12 7:26 ` junkio
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