[7722] in linux-scsi channel archive
Re: SCSI queueing status.
daemon@ATHENA.MIT.EDU (Juergen Fischer)
Sat Dec 18 11:11:58 1999
From: Juergen_Fischer@t-online.de (Juergen Fischer)
Message-Id: <199912181601.RAA31979@obiwan.jef.norbit.de>
In-Reply-To: <Pine.LNX.4.10.9912171849590.30229-100000@gwyn.tux.org> from Eric
Youngdale at "Dec 18, 1999 00:05:39 am"
To: Eric Youngdale <eric@andante.org>
Date: Sat, 18 Dec 1999 17:01:15 +0100 (MET)
Cc: Linux SCSI Mailing List <linux-scsi@vger.rutgers.edu>
Reply-To: fischer@norbit.de
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> 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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--- orig/linux/drivers/scsi/scsi_merge.c Wed Dec 15 22:38:13 1999
+++ linux/drivers/scsi/scsi_merge.c Sat Dec 18 16:57:51 1999
@@ -552,7 +552,8 @@
/*
* First we need to know how many scatter gather segments are needed.
*/
- if (!sg_count_valid) {
+ if((SCpnt->host->sg_tablesize == SG_ALL && !use_clustering) ||
+ !sg_count_valid) {
count = __count_segments(req, use_clustering, dma_host);
} else {
count = req->nr_segments;
--ELM945532875-22076-0_--
-
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