OVL_COPY_FS_FLAGS_MASK
if (!(oldfa.flags & OVL_COPY_FS_FLAGS_MASK))
BUILD_BUG_ON(OVL_COPY_FS_FLAGS_MASK & ~FS_COMMON_FL);
newfa.flags &= ~OVL_COPY_FS_FLAGS_MASK;
newfa.flags |= (oldfa.flags & OVL_COPY_FS_FLAGS_MASK);