Patch "scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path" has been added to the 3.18-stable tree

This is a note to let you know that I've just added the patch titled

scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path

to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
scsi-zfcp-add-handling-for-fcp_resid_over-to-the-fcp-ingress-path.patch
and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Benjamin Block <[email protected]>
Date: Fri, 28 Jul 2017 12:30:52 +0200
Subject: scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path

From: Benjamin Block <[email protected]>

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.

---
 drivers/s390/scsi/zfcp_fc.h |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -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);
 	}
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-3.18/scsi-zfcp-add-handling-for-fcp_resid_over-to-the-fcp-ingress-path.patch queue-3.18/scsi-zfcp-trace-high-part-of-new-64-bit-scsi-lun.patch queue-3.18/scsi-zfcp-fix-queuecommand-for-scsi_eh-commands-when-dix-enabled.patch queue-3.18/scsi-zfcp-fix-payload-with-full-fcp_rsp-iu-in-scsi-trace-records.patch queue-3.18/scsi-zfcp-trace-hba-fsf-response-by-default-on-dismiss-or-timedout-late-response.patch queue-3.18/scsi-zfcp-fix-missing-trace-records-for-early-returns-in-tmf-eh-handlers.patch