Ensure all overlay tests use new tmpfs store paths.

tests/overlay-local-store/common.sh

@@ -12,30 +12,36 @@ setupConfig () {
   echo "build-users-group = " >> "$NIX_CONF_DIR"/nix.conf
 }
 
+
+
 storeDirs () {
-  storesRoot="$TEST_ROOT/stores"
-  mkdir -p "$storesRoot"
-  mount -t tmpfs tmpfs "$storesRoot"
-  storeA="$storesRoot/store-a"
-  storeBTop="$storesRoot/store-b"
-  storeB="local-overlay?root=$storesRoot/merged-store&lower-store=$storeA&upper-layer=$storeBTop"
+  # Attempt to create store dirs on tmpfs volume.
+  # This ensures lowerdir, upperdir and workdir will be on
+  # a consistent filesystem that fully supports OverlayFS.
+  storeVolume="$TEST_ROOT/stores"
+  mkdir -p "$storeVolume"
+  mount -t tmpfs tmpfs "$storeVolume" || true  # But continue anyway if that fails.
+
+  storeA="$storeVolume/store-a"
+  storeBTop="$storeVolume/store-b"
+  storeB="local-overlay?root=$storeVolume/merged-store&lower-store=$storeA&upper-layer=$storeBTop"
   # Creating testing directories
-  mkdir -p "$storesRoot"/{store-a/nix/store,store-b,merged-store/nix/store,workdir}
+  mkdir -p "$storeVolume"/{store-a/nix/store,store-b,merged-store/nix/store,workdir}
 }
 
 # Mounting Overlay Store
 mountOverlayfs () {
-  mergedStorePath="$storesRoot/merged-store/nix/store"
+  mergedStorePath="$storeVolume/merged-store/nix/store"
   mount -t overlay overlay \
     -o lowerdir="$storeA/nix/store" \
     -o upperdir="$storeBTop" \
-    -o workdir="$storesRoot/workdir" \
+    -o workdir="$storeVolume/workdir" \
     "$mergedStorePath" \
     || skipTest "overlayfs is not supported"
 
   cleanupOverlay () {
-    umount "$storesRoot/merged-store/nix/store"
-    rm -r $storesRoot/workdir
+    umount "$storeVolume/merged-store/nix/store"
+    rm -r $storeVolume/workdir
   }
   trap cleanupOverlay EXIT
 }