3.16.51-rc1 review patch. If anyone has any objections, please let me know.
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From: Benjamin Block bblock@linux.vnet.ibm.com
commit a099b7b1fc1f0418ab8d79ecf98153e1e134656e upstream.
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: 553448f6c483 ("[SCSI] zfcp: Message cleanup") Fixes: ea127f975424 ("[PATCH] s390 (7/7): zfcp host adapter.") (tglx/history.git) Signed-off-by: Benjamin Block bblock@linux.vnet.ibm.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/s390/scsi/zfcp_fc.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/s390/scsi/zfcp_fc.h +++ b/drivers/s390/scsi/zfcp_fc.h @@ -4,7 +4,7 @@ * Fibre Channel related definitions and inline functions for the zfcp * device driver * - * Copyright IBM Corp. 2009 + * Copyright IBM Corp. 2009, 2017 */
#ifndef ZFCP_FC_H @@ -291,6 +291,10 @@ void zfcp_fc_eval_fcp_rsp(struct fcp_res !(rsp_flags & FCP_SNS_LEN_VAL) && fcp_rsp->resp.fr_status == SAM_STAT_GOOD) set_host_byte(scsi, DID_ERROR); + } else if (unlikely(rsp_flags & FCP_RESID_OVER)) { + /* FCP_DL was not sufficient for SCSI data length */ + if (fcp_rsp->resp.fr_status == SAM_STAT_GOOD) + set_host_byte(scsi, DID_ERROR); } }