[vioscsi] SendSRB minor refactor

The virtqueue_add_buf() routine will return 0 on SUCCESS or otherwise
a negative number, usually -28 (ENOSPC), i.e no space for buffer. An
inline comment is added for edification.

Here we refactor virtqueue_add_buf() handling to only process the SRB
if virtqueue_add_buf() returns SUCCESS. Presently, other positive
return codes would be processed.

Here we define VQ_ADD_BUFFER_SUCCESS in vioscsi\helper.h

To ensure valid data is reported we also move the trace event on
failure to above the call to CompleteRequest() and wrap the line for
improved readability.

Signed-off-by: benyamin-codez <[email protected]>

vioscsi/helper.c

@@ -109,7 +109,7 @@ ENTER_FN_SRB();
         srbExt->out, srbExt->in,
         &srbExt->cmd, va, pa);
 
-    if (res >= 0) {
+    if (res == VQ_ADD_BUFFER_SUCCESS) {
         element = &adaptExt->processing_srbs[index];
         InsertTailList(&element->srb_list, &srbExt->list_entry);
         element->srb_cnt++;
@@ -120,13 +120,16 @@ ENTER_FN_SRB();
             virtqueue_notify(adaptExt->vq[QueueNumber]);
         }
     } else {
+        // virtqueue_add_buf() returned -28 (ENOSPC), i.e. no space for buffer, or some other error
         virtqueue_notify(adaptExt->vq[QueueNumber]);
         ScsiStatus = SCSISTAT_QUEUE_FULL;
         SRB_SET_SRB_STATUS(Srb, SRB_STATUS_BUSY);
         SRB_SET_SCSI_STATUS(Srb, ScsiStatus);
         StorPortBusy(DeviceExtension, 10);
+        RhelDbgPrint(TRACE_LEVEL_WARNING, 
+                " Could not put an SRB into a VQ, so complete it with SRB_STATUS_BUSY. QueueNumber = %lu, SRB = 0x%p, Lun = %d, TimeOut = %d.\n", 
+                QueueNumber, srbExt->Srb, SRB_LUN(Srb), Srb->TimeOutValue);
         CompleteRequest(DeviceExtension, Srb);
-        RhelDbgPrint(TRACE_LEVEL_FATAL, " Could not put an SRB into a VQ, so complete it with SRB_STATUS_BUSY. QueueNumber = %d, SRB = 0x%p, Lun = %d, TimeOut = %d.\n", QueueNumber, srbExt->Srb, SRB_LUN(Srb), Srb->TimeOutValue);
     }
 
 EXIT_FN_SRB();

vioscsi/helper.h

@@ -49,6 +49,8 @@
 #define CACHE_LINE_SIZE 64
 #define ROUND_TO_CACHE_LINES(Size)  (((ULONG_PTR)(Size) + CACHE_LINE_SIZE - 1) & ~(CACHE_LINE_SIZE - 1))
 
+#define VQ_ADD_BUFFER_SUCCESS 0
+
 #include <srbhelper.h>
 
 // Note: SrbGetCdbLength is defined in srbhelper.h