Bug-fix in Request_load_recv_iov() when initial value of segment_first is not 0.

Originally Request_load_recv_iov() function assumes that
the initial value of req->dev.segment_first is always zero,
which is not correct if we set it to a non-zero value for
streaming the RMA operations.

The way Request_load_recv_iov() works is that, it is triggered
multiple times for the same receiving request until all data is
received. During this process, req->dev.segment_first is rewritten
to the current offset value. When the initial value of
req->dev.segment_first is non-zero, we need another variable
to store that value until the receiving process for this request
is finished. Here we use a static variable in this function to
reach the purpose.
Signed-off-by: Pavan Balaji <balaji@anl.gov>

src/mpid/ch3/src/ch3u_request.c

@@ -300,6 +300,8 @@ int MPIDI_CH3U_Request_load_send_iov(MPID_Request * const sreq,
     return mpi_errno;
 }
 
+#define MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET (-1)
+
 /*
  * MPIDI_CH3U_Request_load_recv_iov()
  *
@@ -315,10 +317,16 @@ int MPIDI_CH3U_Request_load_send_iov(MPID_Request * const sreq,
 int MPIDI_CH3U_Request_load_recv_iov(MPID_Request * const rreq)
 {
     MPI_Aint last;
+    static MPIDI_msg_sz_t orig_segment_first = MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET;
     int mpi_errno = MPI_SUCCESS;
     MPIDI_STATE_DECL(MPID_STATE_MPIDI_CH3U_REQUEST_LOAD_RECV_IOV);
 
     MPIDI_FUNC_ENTER(MPID_STATE_MPIDI_CH3U_REQUEST_LOAD_RECV_IOV);
+
+    if (orig_segment_first == MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET) {
+        orig_segment_first = rreq->dev.segment_first;
+    }
+
     if (rreq->dev.segment_first < rreq->dev.segment_size)
     {
 	/* still reading data that needs to go into the user buffer */
@@ -351,14 +359,15 @@ int MPIDI_CH3U_Request_load_recv_iov(MPID_Request * const rreq)
 	    rreq->dev.iov[0].MPID_IOV_LEN = data_sz;
             rreq->dev.iov_offset = 0;
 	    rreq->dev.iov_count = 1;
-	    MPIU_Assert(rreq->dev.segment_first + data_sz + 
+	    MPIU_Assert(rreq->dev.segment_first - orig_segment_first + data_sz +
 			rreq->dev.tmpbuf_off <= rreq->dev.recv_data_sz);
-	    if (rreq->dev.segment_first + data_sz + rreq->dev.tmpbuf_off == 
+	    if (rreq->dev.segment_first - orig_segment_first + data_sz + rreq->dev.tmpbuf_off ==
 		rreq->dev.recv_data_sz)
 	    {
 		MPIU_DBG_MSG(CH3_CHANNEL,VERBOSE,
 		  "updating rreq to read the remaining data into the SRBuf");
 		rreq->dev.OnDataAvail = MPIDI_CH3_ReqHandler_UnpackSRBufComplete;
+                orig_segment_first = MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET;
 	    }
 	    else
 	    {
@@ -407,12 +416,13 @@ int MPIDI_CH3U_Request_load_recv_iov(MPID_Request * const rreq)
         }
 	/* --END ERROR HANDLING-- */
 
-	if (last == rreq->dev.recv_data_sz)
+	if (last == rreq->dev.recv_data_sz + orig_segment_first)
 	{
 	    MPIU_DBG_MSG(CH3_CHANNEL,VERBOSE,
      "updating rreq to read the remaining data directly into the user buffer");
 	    /* Eventually, use OnFinal for this instead */
 	    rreq->dev.OnDataAvail = rreq->dev.OnFinal;
+            orig_segment_first = MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET;
 	}
 	else if (MPIDI_Request_get_type(rreq) == MPIDI_REQUEST_TYPE_ACCUM_RECV ||
                  MPIDI_Request_get_type(rreq) == MPIDI_REQUEST_TYPE_GET_ACCUM_RECV ||
@@ -484,6 +494,7 @@ int MPIDI_CH3U_Request_load_recv_iov(MPID_Request * const rreq)
 	    MPIU_Assert(MPIDI_Request_get_type(rreq) == MPIDI_REQUEST_TYPE_RECV);
 	    /* Eventually, use OnFinal for this instead */
 	    rreq->dev.OnDataAvail = rreq->dev.OnFinal;
+            orig_segment_first = MPIDI_LOAD_RECV_IOV_ORIG_SEGMENT_FIRST_UNSET;
 	}
 	else
 	{