[7727] in linux-scsi channel archive
Re: SCSI queueing status.
daemon@ATHENA.MIT.EDU (Eric Youngdale)
Sun Dec 19 10:43:09 1999
Message-ID: <002e01bf4a3a$1feabfa0$f367420c@zydeco>
From: "Eric Youngdale" <eric@andante.org>
To: <fischer@norbit.de>
Cc: "Linux SCSI Mailing List" <linux-scsi@vger.rutgers.edu>
Date: Sun, 19 Dec 1999 15:56:49 -0000
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Yes, this was the piece of information that I needed.
I will need lo look at the source a bit. In this case I am assuming
that ll_rw_blk.c is correctly counting the segments for us as it builds up
the request. Once I get a chance to look at the source (hard to do when I
am reading mail), I could say more. It sounds like people have a good
workaround now.
-Eric
----- Original Message -----
From: "Juergen Fischer" <Juergen_Fischer@t-online.de>
To: "Eric Youngdale" <eric@andante.org>
Cc: "Linux SCSI Mailing List" <linux-scsi@vger.rutgers.edu>
Sent: Saturday, December 18, 1999 4:01 PM
Subject: Re: SCSI queueing status.
> > 3) There was a report on linux-kernel about a scatter-gather table
> > segment counting problem, which led to a panic. I ask for, but have yet
> > to receive details on this one. As far as I know, there is only one
> > person who has reported this issue.
>
> It seems to apply to scsi drivers that use SG_ALL (ie. don't use the
> merge functions from scsi_merge) without clustering (like the aha152x
> driver).
>
> If the merge functions are not used, ll_rw_blk will count the number
> of non-continuous segments (without actually merging them). __init_io
> also doesn't merge them, but counts all segments.
>
> The attached patch fixes that problem by recounting the segments in
> that case.
>
> A cleaner way might be to change the default behaviour in ll_rw_blk (e.g.
> by default merge functions). As far as I can see the only other thing
> beside scsi_merge that references nr_segments is the DAC960 driver.
>
>
> Jürgen
>
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