migration/rdma: Convert qemu_rdma_post_send_control() to Error

Functions that use an Error **errp parameter to return errors should
not also report them to the user, because reporting is the caller's
job.  When the caller does, the error is reported twice.  When it
doesn't (because it recovered from the error), there is no error to
report, i.e. the report is bogus.

qemu_rdma_exchange_send() violates this principle: it calls
error_report() via qemu_rdma_post_send_control().  I elected not to
investigate how callers handle the error, i.e. precise impact is not
known.

Clean this up by converting qemu_rdma_post_send_control() to Error.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Message-ID: <20230928132019.2544702-43-armbru@redhat.com>

migration/rdma.c

@@ -1741,7 +1741,8 @@ static int qemu_rdma_block_for_wrid(RDMAContext *rdma,
  * containing some data and block until the post completes.
  */
 static int qemu_rdma_post_send_control(RDMAContext *rdma, uint8_t *buf,
-                                       RDMAControlHeader *head)
+                                       RDMAControlHeader *head,
+                                       Error **errp)
 {
     int ret;
     RDMAWorkRequestData *wr = &rdma->wr_data[RDMA_WRID_CONTROL];
@@ -1781,13 +1782,13 @@ static int qemu_rdma_post_send_control(RDMAContext *rdma, uint8_t *buf,
     ret = ibv_post_send(rdma->qp, &send_wr, &bad_wr);
 
     if (ret > 0) {
-        error_report("Failed to use post IB SEND for control");
+        error_setg(errp, "Failed to use post IB SEND for control");
         return -1;
     }
 
     ret = qemu_rdma_block_for_wrid(rdma, RDMA_WRID_SEND_CONTROL, NULL);
     if (ret < 0) {
-        error_report("rdma migration: send polling control error");
+        error_setg(errp, "rdma migration: send polling control error");
         return -1;
     }
 
@@ -1945,10 +1946,9 @@ static int qemu_rdma_exchange_send(RDMAContext *rdma, RDMAControlHeader *head,
     /*
      * Deliver the control message that was requested.
      */
-    ret = qemu_rdma_post_send_control(rdma, data, head);
+    ret = qemu_rdma_post_send_control(rdma, data, head, errp);
 
     if (ret < 0) {
-        error_setg(errp, "Failed to send control buffer!");
         return -1;
     }
 
@@ -2002,10 +2002,9 @@ static int qemu_rdma_exchange_recv(RDMAContext *rdma, RDMAControlHeader *head,
     /*
      * Inform the source that we're ready to receive a message.
      */
-    ret = qemu_rdma_post_send_control(rdma, NULL, &ready);
+    ret = qemu_rdma_post_send_control(rdma, NULL, &ready, errp);
 
     if (ret < 0) {
-        error_setg(errp, "Failed to send control buffer!");
         return -1;
     }
 
@@ -2394,6 +2393,7 @@ static int qemu_rdma_write(RDMAContext *rdma,
 
 static void qemu_rdma_cleanup(RDMAContext *rdma)
 {
+    Error *err = NULL;
     int idx;
 
     if (rdma->cm_id && rdma->connected) {
@@ -2405,7 +2405,9 @@ static void qemu_rdma_cleanup(RDMAContext *rdma)
                                        .repeat = 1,
                                      };
             error_report("Early error. Sending error.");
-            qemu_rdma_post_send_control(rdma, NULL, &head);
+            if (qemu_rdma_post_send_control(rdma, NULL, &head, &err) < 0) {
+                error_report_err(err);
+            }
         }
 
         rdma_disconnect(rdma->cm_id);
@@ -3705,10 +3707,11 @@ static int qemu_rdma_registration_handle(QEMUFile *f)
 
 
             ret = qemu_rdma_post_send_control(rdma,
-                                        (uint8_t *) rdma->dest_blocks, &blocks);
+                                    (uint8_t *) rdma->dest_blocks, &blocks,
+                                    &err);
 
             if (ret < 0) {
-                error_report("rdma migration: error sending remote info");
+                error_report_err(err);
                 goto err;
             }
 
@@ -3783,10 +3786,10 @@ static int qemu_rdma_registration_handle(QEMUFile *f)
             }
 
             ret = qemu_rdma_post_send_control(rdma,
-                            (uint8_t *) results, &reg_resp);
+                            (uint8_t *) results, &reg_resp, &err);
 
             if (ret < 0) {
-                error_report("Failed to send control buffer");
+                error_report_err(err);
                 goto err;
             }
             break;
@@ -3818,10 +3821,10 @@ static int qemu_rdma_registration_handle(QEMUFile *f)
                                                        reg->key.chunk);
             }
 
-            ret = qemu_rdma_post_send_control(rdma, NULL, &unreg_resp);
+            ret = qemu_rdma_post_send_control(rdma, NULL, &unreg_resp, &err);
 
             if (ret < 0) {
-                error_report("Failed to send control buffer");
+                error_report_err(err);
                 goto err;
             }
             break;