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, 6 insertions, 8 deletions

diff --git a/drivers/s390/scsi/zfcp_fsf.c b/drivers/s390/scsi/zfcp_fsf.c
index 62311bd2df03..07b86375b461 100644
--- a/drivers/s390/scsi/zfcp_fsf.c
+++ b/drivers/s390/scsi/zfcp_fsf.c
@@ -84,13 +84,13 @@ static void zfcp_fsf_class_not_supp(struct zfcp_fsf_req *req)
 void zfcp_fsf_req_free(struct zfcp_fsf_req *req)
 {
 	if (likely(req->pool)) {
-		if (likely(req->qtcb))
+		if (likely(!zfcp_fsf_req_is_status_read_buffer(req)))
 			mempool_free(req->qtcb, req->adapter->pool.qtcb_pool);
 		mempool_free(req, req->pool);
 		return;
 	}
 
-	if (likely(req->qtcb))
+	if (likely(!zfcp_fsf_req_is_status_read_buffer(req)))
 		kmem_cache_free(zfcp_fsf_qtcb_cache, req->qtcb);
 	kfree(req);
 }
@@ -393,7 +393,7 @@ static void zfcp_fsf_protstatus_eval(struct zfcp_fsf_req *req)
  */
 static void zfcp_fsf_req_complete(struct zfcp_fsf_req *req)
 {
-	if (unlikely(req->fsf_command == FSF_QTCB_UNSOLICITED_STATUS)) {
+	if (unlikely(zfcp_fsf_req_is_status_read_buffer(req))) {
 		zfcp_fsf_status_read_handler(req);
 		return;
 	}
@@ -710,7 +710,6 @@ static struct zfcp_fsf_req *zfcp_fsf_req_create(struct zfcp_qdio *qdio,
 	init_completion(&req->completion);
 
 	req->adapter = adapter;
-	req->fsf_command = fsf_cmd;
 	req->req_id = adapter->req_no;
 
 	if (likely(fsf_cmd != FSF_QTCB_UNSOLICITED_STATUS)) {
@@ -729,10 +728,10 @@ static struct zfcp_fsf_req *zfcp_fsf_req_create(struct zfcp_qdio *qdio,
 		req->qtcb->prefix.req_seq_no = adapter->fsf_req_seq_no;
 		req->qtcb->prefix.req_id = req->req_id;
 		req->qtcb->prefix.ulp_info = 26;
-		req->qtcb->prefix.qtcb_type = fsf_qtcb_type[req->fsf_command];
+		req->qtcb->prefix.qtcb_type = fsf_qtcb_type[fsf_cmd];
 		req->qtcb->prefix.qtcb_version = FSF_QTCB_CURRENT_VERSION;
 		req->qtcb->header.req_handle = req->req_id;
-		req->qtcb->header.fsf_command = req->fsf_command;
+		req->qtcb->header.fsf_command = fsf_cmd;
 	}
 
 	zfcp_qdio_req_init(adapter->qdio, &req->qdio_req, req->req_id, sbtype,
@@ -745,7 +744,6 @@ static int zfcp_fsf_req_send(struct zfcp_fsf_req *req)
 {
 	struct zfcp_adapter *adapter = req->adapter;
 	struct zfcp_qdio *qdio = adapter->qdio;
-	int with_qtcb = (req->qtcb != NULL);
 	int req_id = req->req_id;
 
 	zfcp_reqlist_add(adapter->req_list, req);
@@ -761,7 +759,7 @@ static int zfcp_fsf_req_send(struct zfcp_fsf_req *req)
 	}
 
 	/* Don't increase for unsolicited status */
-	if (with_qtcb)
+	if (!zfcp_fsf_req_is_status_read_buffer(req))
 		adapter->fsf_req_seq_no++;
 	adapter->req_no++;