scsi: zfcp: drop duplicate fsf_command from zfcp_fsf_req which is also in QTCB header

Status read buffers (SRBs, unsolicited notifications) never use a QTCB
[zfcp_fsf_req_create()]. zfcp_fsf_req_send() already uses this to
distinguish SRBs from other FSF request types. We can re-use this method in
zfcp_fsf_req_complete(). Introduce a helper function to make the check for
req->qtcb less magic.

SRBs always are FSF_QTCB_UNSOLICITED_STATUS, so we can hard-code this for
the two trace functions dealing with SRBs.

All other FSF request types have a QTCB and we can get the fsf_command from
there.

zfcp_dbf_hba_fsf_response() and thus zfcp_dbf_hba_fsf_res() are only called
for non-SRB requests so it's safe to dereference the QTCB
[zfcp_fsf_req_complete() returns early on SRB, else calls
zfcp_fsf_protstatus_eval() which calls zfcp_dbf_hba_fsf_response()].  In
zfcp_scsi_forget_cmnd() we guard the QTCB dereference with a preceding NULL
check and rely on boolean shortcut evaluation.

As a side effect, this causes an alignment hole which we can close in
a later patch after having cleaned up all fields of struct zfcp_fsf_req.
Before:
$ pahole -C zfcp_fsf_req drivers/s390/scsi/zfcp.ko
...
	u32                        status;               /*   136     4 */
	u32                        fsf_command;          /*   140     4 */
	struct fsf_qtcb *          qtcb;                 /*   144     8 */
...
After:
$ pahole -C zfcp_fsf_req drivers/s390/scsi/zfcp.ko
...
	u32                        status;               /*   136     4 */
	/* XXX 4 bytes hole, try to pack */
	struct fsf_qtcb *          qtcb;                 /*   144     8 */
...

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/drivers/s390/scsi/zfcp_def.h b/drivers/s390/scsi/zfcp_def.h
index 572debf2f528..d65adb0ae9f1 100644
--- a/drivers/s390/scsi/zfcp_def.h
+++ b/drivers/s390/scsi/zfcp_def.h
@@ -277,7 +277,6 @@ static inline u64 zfcp_scsi_dev_lun(struct scsi_device *sdev)
  * @qdio_req: qdio queue related values
  * @completion: used to signal the completion of the request
  * @status: status of the request
- * @fsf_command: FSF command issued
  * @qtcb: associated QTCB
  * @seq_no: sequence number of this request
  * @data: private data
@@ -294,7 +293,6 @@ struct zfcp_fsf_req {
 	struct zfcp_qdio_req	qdio_req;
 	struct completion	completion;
 	u32			status;
-	u32			fsf_command;
 	struct fsf_qtcb		*qtcb;
 	u32			seq_no;
 	void			*data;
@@ -311,4 +309,9 @@ int zfcp_adapter_multi_buffer_active(struct zfcp_adapter *adapter)
 	return atomic_read(&adapter->status) & ZFCP_STATUS_ADAPTER_MB_ACT;
 }
 
+static inline bool zfcp_fsf_req_is_status_read_buffer(struct zfcp_fsf_req *req)
+{
+	return req->qtcb == NULL;
+}
+
 #endif /* ZFCP_DEF_H */