Implement test for store path deduplication.

tests/overlay-local-store/common.sh

@@ -22,11 +22,12 @@ storeDirs () {
 
 # Mounting Overlay Store
 mountOverlayfs () {
+  mergedStorePath="$TEST_ROOT/merged-store/nix/store"
   mount -t overlay overlay \
     -o lowerdir="$storeA/nix/store" \
     -o upperdir="$storeBTop" \
     -o workdir="$TEST_ROOT/workdir" \
-    "$TEST_ROOT/merged-store/nix/store" \
+    "$mergedStorePath" \
     || skipTest "overlayfs is not supported"
 
   cleanupOverlay () {
@@ -36,6 +37,10 @@ mountOverlayfs () {
   trap cleanupOverlay EXIT
 }
 
+remountOverlayfs () {
+  mount -o remount "$mergedStorePath"
+}
+
 toRealPath () {
   storeDir=$1; shift
   storePath=$1; shift
@@ -54,12 +59,3 @@ initLowerStore () {
 execUnshare () {
   exec unshare --mount --map-root-user "$@"
 }
-
-addTextToStore() {
-  storeDir=$1; shift
-  filename=$1; shift
-  content=$1; shift
-  filePath="$TEST_HOME/$filename"
-  echo "$content" > "$filePath"
-  nix-store --store "$storeDir" --add "$filePath"
-}

tests/overlay-local-store/optimise-inner.sh

@@ -16,4 +16,37 @@ initLowerStore
 
 mountOverlayfs
 
+# Create a file to add to store
+dupFilePath="$TEST_ROOT/dup-file"
+echo Duplicate > "$dupFilePath"
+
+# Add it to the overlay store (it will be written to the upper layer)
+dupFileStorePath=$(nix-store --store "$storeB" --add "$dupFilePath")
+
+# Now add it to the lower store so the store path is duplicated
+nix-store --store "$storeA" --add "$dupFilePath"
+
+# Ensure overlayfs and layers and synchronised
+remountOverlayfs
+
+dupFilename="${dupFileStorePath#/nix/store}"
+lowerPath="$storeA/$dupFileStorePath"
+upperPath="$storeBTop/$dupFilename"
+overlayPath="$mergedStorePath/$dupFilename"
+
+# Check store path exists in both layers and overlay
+lowerInode=$(stat -c %i "$lowerPath")
+upperInode=$(stat -c %i "$upperPath")
+overlayInode=$(stat -c %i "$overlayPath")
+[[ $upperInode == $overlayInode ]]
+[[ $upperInode != $lowerInode ]]
+
+# Run optimise to deduplicate store paths
 nix-store --store "$storeB" --optimise
+remountOverlayfs
+
+stat "$lowerPath"
+stat "$overlayPath"
+expect 1 stat "$upperPath"
+
+#expect 1 stat $(toRealPath "$storeA/nix/store" "$path")