migration: use qemu_file_set_error

Remove the return value of buffered_flush, pass it via the error code
of s->file.  Once this is done, the error can be retrieved simply
via migrate_fd_close's call to qemu_fclose.
Reviewed-by: NOrit Wasserman <owasserm@redhat.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NJuan Quintela <quintela@redhat.com>

migration.c

@@ -518,7 +518,7 @@ int64_t migrate_xbzrle_cache_size(void)
 /* migration thread support */
 
 
-static ssize_t buffered_flush(MigrationState *s)
+static void buffered_flush(MigrationState *s)
 {
     size_t offset = 0;
     ssize_t ret = 0;
@@ -545,9 +545,8 @@ static ssize_t buffered_flush(MigrationState *s)
     s->buffer_size -= offset;
 
     if (ret < 0) {
-        return ret;
+        qemu_file_set_error(s->file, ret);
     }
-    return offset;
 }
 
 static int buffered_put_buffer(void *opaque, const uint8_t *buf,
@@ -586,25 +585,15 @@ static int buffered_put_buffer(void *opaque, const uint8_t *buf,
 static int buffered_close(void *opaque)
 {
     MigrationState *s = opaque;
-    ssize_t ret = 0;
-    int ret2;
 
     DPRINTF("closing\n");
 
     s->xfer_limit = INT_MAX;
     while (!qemu_file_get_error(s->file) && s->buffer_size) {
-        ret = buffered_flush(s);
-        if (ret < 0) {
-            break;
-        }
-    }
-
-    ret2 = migrate_fd_close(s);
-    if (ret >= 0) {
-        ret = ret2;
+        buffered_flush(s);
     }
     s->complete = true;
-    return ret;
+    return migrate_fd_close(s);
 }
 
 static int buffered_get_fd(void *opaque)
@@ -750,7 +739,8 @@ static void *buffered_file_thread(void *opaque)
             g_usleep((initial_time + BUFFER_DELAY - current_time)*1000);
             sleep_time += qemu_get_clock_ms(rt_clock) - current_time;
         }
-        ret = buffered_flush(s);
+        buffered_flush(s);
+        ret = qemu_file_get_error(s->file);
     }
 
     if (ret < 0) {