Up until now zfcp would just ignore the FCP_RESID_OVER flag in the FCP
response IU. When this flag is set, it is possible, in regards to the
FCP standard, that the storage-server processes the command normally, up
to the point where data is missing and simply ignores those.

In this case no CHECK CONDITION would be set, and because we ignored the
FCP_RESID_OVER flag we resulted in at least a data loss or even
-corruption as a follow-up error, depending on how the
applications/layers on top behave. To prevent this, we now set the
host-byte of the corresponding scsi_cmnd to DID_ERROR.

Other storage-behaviors, where the same condition results in a CHECK
CONDITION set in the answer, don't need to be changed as they are
handled in the mid-layer already.

Following is an example trace record decoded with zfcpdbf from the
s390-tools package. We forcefully injected a fc_dl which is one byte too
small:

Timestamp      : ...
Area           : SCSI
Subarea        : 00
Level          : 3
Exception      : -
CPU ID         : ..
Caller         : 0x...
Record ID      : 1
Tag            : rsl_err
Request ID     : 0x...
SCSI ID        : 0x...
SCSI LUN       : 0x...
SCSI result    : 0x00070000
                     ^^DID_ERROR
SCSI retries   : 0x..
SCSI allowed   : 0x..
SCSI scribble  : 0x...
SCSI opcode    : 2a000000 00000000 08000000 00000000
FCP rsp inf cod: 0x00
FCP rsp IU     : 00000000 00000000 00000400 00000001
                                       ^^fr_flags==FCP_RESID_OVER
                                         ^^fr_status==SAM_STAT_GOOD
                                            ^^^^^^^^fr_resid
                 00000000 00000000

As of now, we don't actively handle to possibility that a response IU
has both flags - FCP_RESID_OVER and FCP_RESID_UNDER - set at once.
Reported-by: Luke M. Hopkins <lmhopkin@us.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.vnet.ibm.com>
Fixes: 553448f6 ("[SCSI] zfcp: Message cleanup")
Fixes: ea127f97 ("[PATCH] s390 (7/7): zfcp host adapter.") (tglx/history.git)
Cc: <stable@vger.kernel.org> #2.6.33+
Signed-off-by: Benjamin Block <bblock@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>