From 0e84c2969198419a404adc8df1d254a17b11abd9 Mon Sep 17 00:00:00 2001
From: Jonathan Behrens <fintelia@gmail.com>
Date: Sat, 2 Jan 2021 13:27:42 -0500
Subject: [PATCH] Limit when buffer FAST_DEVICE_ACCESS is requested

---
 wgpu-core/src/device/mod.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/wgpu-core/src/device/mod.rs b/wgpu-core/src/device/mod.rs
index 80d7ea350..39b726429 100644
--- a/wgpu-core/src/device/mod.rs
+++ b/wgpu-core/src/device/mod.rs
@@ -448,7 +448,8 @@ impl<B: GfxBackend> Device<B> {
 
             let mut flags = Uf::empty();
             let map_flags = desc.usage & (Bu::MAP_READ | Bu::MAP_WRITE);
-            if !(desc.usage - map_flags).is_empty() {
+            let map_copy_flags = desc.usage & (Bu::MAP_READ | Bu::MAP_WRITE | Bu::COPY_SRC | Bu::COPY_DST);
+            if map_flags.is_empty() || !(desc.usage - map_copy_flags).is_empty() {
                 flags |= Uf::FAST_DEVICE_ACCESS;
             }
             if transient {