Return-Path: <linux-kernel-owner+willy=40w.ods.org@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id <S313867AbSHBORW>; Fri, 2 Aug 2002 10:17:22 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org
	id <S314077AbSHBORW>; Fri, 2 Aug 2002 10:17:22 -0400
Received: from ns.virtualhost.dk ([195.184.98.160]:28841 "EHLO virtualhost.dk")
	by vger.kernel.org with ESMTP id <S313867AbSHBORV>;
	Fri, 2 Aug 2002 10:17:21 -0400
Date: Fri, 2 Aug 2002 16:20:37 +0200
From: Jens Axboe <axboe@suse.de>
To: Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>
Cc: martin@dalecki.de, Stephen Lord <lord@sgi.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: A new ide warning message
Message-ID: <20020802142037.GT3010@suse.de>
References: <20020802115940.GF1055@suse.de> <Pine.SOL.4.30.0208021513490.3612-100000@mion.elka.pw.edu.pl>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Pine.SOL.4.30.0208021513490.3612-100000@mion.elka.pw.edu.pl>
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2471
Lines: 65

On Fri, Aug 02 2002, Bartlomiej Zolnierkiewicz wrote:
> 
> On Fri, 2 Aug 2002, Jens Axboe wrote:
> 
> > On Fri, Aug 02 2002, Jens Axboe wrote:
> > > On Fri, Aug 02 2002, Marcin Dalecki wrote:
> > > > U?ytkownik Stephen Lord napisa?:
> > > > >In 2.5.30 I started getting these warning messages out ide during
> > > > >the mount of an XFS filesystem:
> > > > >
> > > > >ide-dma: received 1 phys segments, build 2
> > > > >
> > > > >Can anyone translate that into English please.
> > > >
> > > > It can be found in pcidma.c.
> > > > It is repoting that we have one physical segment needed by
> > > > the request in question but the sctter gather list allocation
> > > > needed to break it up for mapping in two.
> > >
> > > You don't seem to realise that this is a BUG (somewhere, could even be
> > > in the generic mapping functions)! blk_rq_map_sg() must never map a
> > > request to more entries that rq->nr_segments, that's just very wrong.
> > >
> > > That's why I'm suspecting the recent pcidma changes. Just a feeling, I
> > > have not looked at them.
> >
> > I'll take that back. Having looked at Adam's changes there are perfectly
> > fine. I'm now putting my money on IDE breakage somewhere instead. It
> 
> Look again Jens. Adam's changes made IDE queue handling inconsistent.
> hint: 2 * 127 != 255
> 
> But noticed warning deals with design of ll_rw_blk.c. ;-)
> (right now max_segment_size have to be max bv->bv_len aligned)

Yeah that's true, actually was just saying that on linux-scsi
yesterday/today. 

> Jens, please look at segment checking/counting code, it does it on
> bv->bv_len (4kb most likely) not sector granuality...
> 
> So for not 4kb aligned max_segment_size we will get new segment...
> 
> Best fix will be to make block layer count sectors not bv->bv_len...

Well I'm inclined to just make that page size granularity. It's like
that in 2.4 as well (no guarentees that we will honor anything less than
that granularity).

> btw. I like Adam's patch but it was draft not to include in mainline (?).

The concept is sound, so it has a bug... I can say the same for other
stuff in the kernel as well :-)

I probably just wanted more review (my 1 minute review surely wasn't
enough).

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/