F #5058: Context ISO creation w/a for FUSE mounts (#421)

src/tm_mad/common/context

@@ -69,8 +69,11 @@ ISO_DIR="$DS_DIR/.isofiles/$VM_ID"
 ISO_FILE="$VM_ID.iso"
 ISO_PATH="$ISO_DIR/$ISO_FILE"
 
+exec_and_log "rm -rf $ISO_DIR" \
+    "Could not delete temp. to make context dev"
+
 exec_and_set_error "mkdir -p $ISO_DIR" \
-    "Could not create tmp dir to make context dev"
+    "Could not create temp. dir to make context dev"
 [ -n "$ERROR" ] && exit_error
 
 for f in "${SRC[@]}"; do
@@ -95,8 +98,18 @@ for f in "${SRC[@]}"; do
     [ -n "$ERROR" ] && exit_error
 done
 
-exec_and_set_error "$MKISOFS -o $ISO_PATH -V CONTEXT -J -R $ISO_DIR" \
-    "Error creating iso fs"
+# This generates context ISO first into a temporary file and renames to final
+# file, to workaround problem when datastores are on FUSE mounted volume
+# (e.g,. fuse-overlayfs), cached files metadata are not consistent and
+# and tar sparse detection algorithm could identify file as empty.
+MKCONTEXT_CMD=$(cat <<EOF
+    set -e -o pipefail
+    $MKISOFS -o $ISO_PATH.tmp -V CONTEXT -J -R $ISO_DIR
+    mv $ISO_PATH.tmp $ISO_PATH
+EOF
+)
+
+multiline_exec_and_set_error "$MKCONTEXT_CMD" "Error creating iso fs"
 [ -n "$ERROR" ] && exit_error
 
 COPY_CMD=$(cat <<EOF