linux-kernel - Re: [REGRESSION] 28676d869bbb (scsi: sg: check for valid direction before starting the request) breaks mtx tape library control

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Date:   Wed, 19 Jul 2017 03:13:34 -0500
From:   Jason L Tibbitts III <tibbs@...h.uh.edu>
To:     Johannes Thumshirn <jthumshirn@...e.de>
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

>>>>> "JT" == Johannes Thumshirn <jthumshirn@...e.de> writes:

JT> Can you please apply this debugging patch, so I can see what's going
JT> on.

Sure, no problem.

I generally run "mtx -f /dev/sg7 status" first just to make sure the
library is there; this has always worked as expected.  With the debug
patch applied, this is sent to the console:
[   33.933422] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 56
[   33.940526] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 136
[   33.982429] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240
[   34.569986] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240
[   34.623898] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240

Then running "mtx -f /dev/sg7 next 0" gives this as stdout/err:

Unloading drive 0 into Storage Element 46...mtx: Request Sense: Long
Report=yes
mtx: Request Sense: Valid Residual=no
mtx: Request Sense: Error Code=0 (Unknown?!)
mtx: Request Sense: Sense Key=No Sense
mtx: Request Sense: FileMark=no
mtx: Request Sense: EOM=no
mtx: Request Sense: ILI=no
mtx: Request Sense: Additional Sense Code = 00
mtx: Request Sense: Additional Sense Qualifier = 00
mtx: Request Sense: BPV=no
mtx: Request Sense: Error in CDB=no
mtx: Request Sense: SKSV=no
MOVE MEDIUM from Element Address 1 to 1046 Failed

And this to the console:
[   45.552524] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 56
[   45.559626] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 136
[   45.603544] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240
[   46.204614] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240
[   46.258463] sg_is_valid_dxfer: dxfer_direction: -3, dxfer_len: 4240
[   46.304530] sg_is_valid_dxfer: dxfer_direction: -2, dxfer_len: 0

Would you also want to see the output from that patch applied to a
functioning kernel?

 - J<