On Tue, Jul 21, 2020 at 08:27:01PM +0200, Christoph Hellwig wrote:

On Tue, Jul 21, 2020 at 05:55:39PM +0100, Al Viro wrote:

quoted

How about fs/for_init.c and putting the damn helpers there?  With
calling conventions as close to syscalls as possible, and a fat
comment regarding their intended use being _ONLY_ the setup
in should-have-been-done-in-userland parts of init?

Where do you want the prototypes to go?  Also do you want devtmpfs
use the same helpers, which then't can't be marked __init (mount,
chdir, chroot), or separate copies?

Hmm...  mount still can be __init (devtmpfs_mount() is), and I suspect
devtmpfs_setup() could also be made such - just turn devtmpfsd()
into
static int __init devtmpfsd(void *p)
{
        int err = devtmpfs_setup(p);

	if (!err)
		devtmpfsd_real();	/* never returns */
	return err;
}
and you are done.  As for the prototypes... include/linux/init_syscalls.h,
perhaps?