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, 4 insertions, 4 deletions

diff --git a/drivers/s390/scsi/zfcp_dbf.c b/drivers/s390/scsi/zfcp_dbf.c
index 3b368fcf13f4..d20977bb27a4 100644
--- a/drivers/s390/scsi/zfcp_dbf.c
+++ b/drivers/s390/scsi/zfcp_dbf.c
@@ -81,7 +81,7 @@ void zfcp_dbf_hba_fsf_res(char *tag, int level, struct zfcp_fsf_req *req)
 	rec->id = ZFCP_DBF_HBA_RES;
 	rec->fsf_req_id = req->req_id;
 	rec->fsf_req_status = req->status;
-	rec->fsf_cmd = req->fsf_command;
+	rec->fsf_cmd = q_head->fsf_command;
 	rec->fsf_seq_no = req->seq_no;
 	rec->u.res.req_issued = req->issued;
 	rec->u.res.prot_status = q_pref->prot_status;
@@ -94,7 +94,7 @@ void zfcp_dbf_hba_fsf_res(char *tag, int level, struct zfcp_fsf_req *req)
 	memcpy(rec->u.res.fsf_status_qual, &q_head->fsf_status_qual,
 	       FSF_STATUS_QUALIFIER_SIZE);
 
-	if (req->fsf_command != FSF_QTCB_FCP_CMND) {
+	if (q_head->fsf_command != FSF_QTCB_FCP_CMND) {
 		rec->pl_len = q_head->log_length;
 		zfcp_dbf_pl_write(dbf, (char *)q_pref + q_head->log_start,
 				  rec->pl_len, "fsf_res", req->req_id);
@@ -127,7 +127,7 @@ void zfcp_dbf_hba_fsf_uss(char *tag, struct zfcp_fsf_req *req)
 	rec->id = ZFCP_DBF_HBA_USS;
 	rec->fsf_req_id = req->req_id;
 	rec->fsf_req_status = req->status;
-	rec->fsf_cmd = req->fsf_command;
+	rec->fsf_cmd = FSF_QTCB_UNSOLICITED_STATUS;
 
 	if (!srb)
 		goto log;
@@ -174,7 +174,7 @@ void zfcp_dbf_hba_bit_err(char *tag, struct zfcp_fsf_req *req)
 	rec->id = ZFCP_DBF_HBA_BIT;
 	rec->fsf_req_id = req->req_id;
 	rec->fsf_req_status = req->status;
-	rec->fsf_cmd = req->fsf_command;
+	rec->fsf_cmd = FSF_QTCB_UNSOLICITED_STATUS;
 	memcpy(&rec->u.be, &sr_buf->payload.bit_error,
 	       sizeof(struct fsf_bit_error_payload));