multifd: Only send pages when packet are not empty

We send packages without pages sometimes for sysnchronizanion.  The
iov functions do the right thing, but we will be changing this code in
future patches.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

diff --git a/migration/ram.c b/migration/ram.c
index 35bd6213e91757f9c3b4ba936d8fae1b01775abc..3034f862c14f2bd5443a9473bc2c9605c7e8c11e 100644 (file)
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -1088,9 +1088,12 @@ static void *multifd_send_thread(void *opaque)
                 break;
             }
 
-            ret = qio_channel_writev_all(p->c, p->pages->iov, used, &local_err);
-            if (ret != 0) {
-                break;
+            if (used) {
+                ret = qio_channel_writev_all(p->c, p->pages->iov,
+                                             used, &local_err);
+                if (ret != 0) {
+                    break;
+                }
             }
 
             qemu_mutex_lock(&p->mutex);
@@ -1317,9 +1320,12 @@ static void *multifd_recv_thread(void *opaque)
         p->num_pages += used;
         qemu_mutex_unlock(&p->mutex);
 
-        ret = qio_channel_readv_all(p->c, p->pages->iov, used, &local_err);
-        if (ret != 0) {
-            break;
+        if (used) {
+            ret = qio_channel_readv_all(p->c, p->pages->iov,
+                                        used, &local_err);
+            if (ret != 0) {
+                break;
+            }
         }
 
         if (flags & MULTIFD_FLAG_SYNC) {