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Message-ID: <20170719083654.GE4151@linux-x5ow.site>
Date: Wed, 19 Jul 2017 10:36:54 +0200
From: Johannes Thumshirn <jthumshirn@...e.de>
To: Jason L Tibbitts III <tibbs@...h.uh.edu>,
Doug Gilbert <dgilbert@...erlog.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
dvyukov@...gle.com, hare@...e.com, hch@....de,
martin.petersen@...cle.com
Subject: Re: [REGRESSION] 28676d869bbb (scsi: sg: check for valid direction
before starting the request) breaks mtx tape library control
On Wed, Jul 19, 2017 at 03:13:34AM -0500, Jason L Tibbitts III wrote:
> [ 46.304530] sg_is_valid_dxfer: dxfer_direction: -2, dxfer_len: 0
Ahh now I see the -2 (SG_DXFER_TO_DEV) is the crucial point here. It is 0 in
your case.
This would "fix" it but I'm not generally sure it is _the_ solution:
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 1e82d4128a84..b421ec81d775 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -764,7 +764,7 @@ static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
return true;
case SG_DXFER_TO_DEV:
case SG_DXFER_TO_FROM_DEV:
- if (!hp->dxferp || hp->dxfer_len == 0)
+ if (!hp->dxferp)
return false;
return true;
case SG_DXFER_UNKNOWN:
Doug, what are the rules for SG_DXFER_TO_{FROM_}DEV? Apparently we can't
be sure len > 0, can we rely on dxferp being present?
Thanks,
Johannes
--
Johannes Thumshirn Storage
jthumshirn@...e.de +49 911 74053 689
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