nouveau: when mapping a persistent buffer, synchronize on former xfers

If the buffer is being used, we should wait for those uses to be
complete before returning the map.

Fixes: GL45-CTS.direct_state_access.buffers_functional
Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Cc: mesa-stable@lists.freedesktop.org
(cherry picked from commit d9cc58d6ec56e676b1285508a4118a83f5325833)
diff --git a/src/gallium/drivers/nouveau/nouveau_buffer.c b/src/gallium/drivers/nouveau/nouveau_buffer.c
index 17052b2..2c60441 100644
--- a/src/gallium/drivers/nouveau/nouveau_buffer.c
+++ b/src/gallium/drivers/nouveau/nouveau_buffer.c
@@ -406,9 +406,6 @@
        !util_ranges_intersect(&buf->valid_buffer_range, box->x, box->x + box->width))
       usage |= PIPE_TRANSFER_DISCARD_RANGE | PIPE_TRANSFER_UNSYNCHRONIZED;
 
-   if (usage & PIPE_TRANSFER_PERSISTENT)
-      usage |= PIPE_TRANSFER_UNSYNCHRONIZED;
-
    if (buf->domain == NOUVEAU_BO_VRAM) {
       if (usage & NOUVEAU_TRANSFER_DISCARD) {
          /* Set up a staging area for the user to write to. It will be copied
@@ -476,7 +473,8 @@
     * complete its operation, or set up a staging area to perform our work in.
     */
    if (nouveau_buffer_busy(buf, usage & PIPE_TRANSFER_READ_WRITE)) {
-      if (unlikely(usage & PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE)) {
+      if (unlikely(usage & (PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE |
+                            PIPE_TRANSFER_PERSISTENT))) {
          /* Discarding was not possible, must sync because
           * subsequent transfers might use UNSYNCHRONIZED. */
          nouveau_buffer_sync(nv, buf, usage & PIPE_TRANSFER_READ_WRITE);