reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?id=62801d0e24907a20b4724b58ce174bc9a2fc3b4c
        git remote add brauner-vfs https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
        git fetch --no-tags brauner-vfs vfs-6.15.misc
        git checkout 62801d0e24907a20b4724b58ce174bc9a2fc3b4c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash mm/