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Message-Id: <20080226150845.2196bc1a.akpm@linux-foundation.org>
Date: Tue, 26 Feb 2008 15:08:45 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Mike Galbraith <efault@....de>
Cc: Jens Axboe <jens.axboe@...cle.com>,
LKML <linux-kernel@...r.kernel.org>,
Tejun Heo <htejun@...il.com>, linux-ide@...r.kernel.org,
linux-scsi@...r.kernel.org
Subject: Re: regression: CD burning (k3b) went broke
On Tue, 26 Feb 2008 14:36:43 +0100 Mike Galbraith <efault@....de> wrote:
>
> On Tue, 2008-02-26 at 10:48 +0100, Mike Galbraith wrote:
> > Greetings,
> >
> > I straced both a good and a bad kernel (good being .git with attached
> > revert patch applied) and filtered/diffed/merged the output. Scroll
> > down to "HERE" to see the problem (resid).
> >
> > I'm poking around, but not having much luck.
cc's added.
I'm told this is part of "Tejun's DMA drain handling".
> Seems the problem is data_len changes, but raw_data_len doesn't. I've
> not the foggiest IO-land clue, but k3b works again, so the below may
> have some diagnostic value.
So this change fixes a bug? Can we have a recap of how it does this?
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index ba21d97..7a6f784 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -871,7 +871,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
> scsi_end_bidi_request(cmd);
> return;
> }
> - req->data_len = scsi_get_resid(cmd);
> + req->data_len = req->raw_data_len = scsi_get_resid(cmd);
> }
>
> BUG_ON(blk_bidi_rq(req)); /* bidi not support for !blk_pc_request yet */
>
Thanks.
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