[SCSI] zfcp: Simplify SBAL allocation to fix sparse warnings

When waiting for a request claim the SBAL before waiting. This way,
locking before each check of the free counter is not required and
sparse does not emit warnings for the complicated locking scheme.
Signed-off-by: Christof Schmitt <christof.schmitt@de.ibm.com>
Acked-by: Felix Beck <felix@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/s390/scsi/zfcp_fsf.c

@@ -644,38 +644,38 @@ static void zfcp_fsf_exchange_port_data_handler(struct zfcp_fsf_req *req)
 	}
 }
 
-static int zfcp_fsf_sbal_check(struct zfcp_adapter *adapter)
+static int zfcp_fsf_sbal_available(struct zfcp_adapter *adapter)
 {
-	struct zfcp_qdio_queue *req_q = &adapter->req_q;
-
-	spin_lock_bh(&adapter->req_q_lock);
-	if (atomic_read(&req_q->count))
+	if (atomic_read(&adapter->req_q.count) > 0)
 		return 1;
-	spin_unlock_bh(&adapter->req_q_lock);
+	atomic_inc(&adapter->qdio_outb_full);
 	return 0;
 }
 
-static int zfcp_fsf_sbal_available(struct zfcp_adapter *adapter)
-{
-	unsigned int count = atomic_read(&adapter->req_q.count);
-	if (!count)
-		atomic_inc(&adapter->qdio_outb_full);
-	return count > 0;
-}
-
 static int zfcp_fsf_req_sbal_get(struct zfcp_adapter *adapter)
+	__releases(&adapter->req_q_lock)
+	__acquires(&adapter->req_q_lock)
 {
+	struct zfcp_qdio_queue *req_q = &adapter->req_q;
 	long ret;
 
+	if (atomic_read(&req_q->count) <= -REQUEST_LIST_SIZE)
+		return -EIO;
+	if (atomic_read(&req_q->count) > 0)
+		return 0;
+
+	atomic_dec(&req_q->count);
 	spin_unlock_bh(&adapter->req_q_lock);
 	ret = wait_event_interruptible_timeout(adapter->request_wq,
-					zfcp_fsf_sbal_check(adapter), 5 * HZ);
+					atomic_read(&req_q->count) >= 0,
+					5 * HZ);
+	spin_lock_bh(&adapter->req_q_lock);
+	atomic_inc(&req_q->count);
+
 	if (ret > 0)
 		return 0;
 	if (!ret)
 		atomic_inc(&adapter->qdio_outb_full);
-
-	spin_lock_bh(&adapter->req_q_lock);
 	return -EIO;
 }