After updating my tape backup server to 4.12 I found that mtx had issues controlling the tape library. Good behavior: [root@backup2 ~]# mtx -f /dev/sg7 next 0 Unloading drive 0 into Storage Element 4...done Loading media from Storage Element 5 into drive 0...done Bad behavior: [root@backup2 ~]# mtx -f /dev/sg7 next 0 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 This was seen on a machine running Fedora 25 as well as an Ubuntu machine. Relevant tickets: https://bugzilla.redhat.com/show_bug.cgi?id=1471302 http://bugzilla.kernel.org/show_bug.cgi?id=196375 https://bugs.launchpad.net/bugs/1704512 mtx in all cases is 1.3.12; in the Fedora case that's mtx-1.3.12-14.fc24.x86_64. I see this with an Overland Neo T48s library but the Ubuntu user had a Dell ML6000 and we both have completely different HBAs and cabling (LSI3008 SAS and qla2462 FC). I bisected this down to: commit 28676d869bbb5257b5f14c0c95ad3af3a7019dd5 Author: Johannes Thumshirn <jthumshirn@xxxxxxx> Date: Fri Apr 7 09:34:15 2017 +0200 scsi: sg: check for valid direction before starting the request Check for a valid direction before starting the request, otherwise we risk running into an assertion in the scsi midlayer checking for valid requests. [mkp: fixed typo] Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx> Link: http://www.spinics.net/lists/linux-scsi/msg104400.html Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Signed-off-by: Hannes Reinecke <hare@xxxxxxxx> Tested-by: Johannes Thumshirn <jthumshirn@xxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> and confirmed that clean unpatched 4.12 shows the problem, while reverting just that patch fixes the issue. Unfortunately I don't know enough to actually fix this, but I can easily test patches. - J<
