Re: [PATCH v2 2/3] init/do_cmounts.c: introduce 'user_root' for initramfs

[Menglong Dong]

On Wed, May 26, 2021 at 12:33 PM Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote:
>
> On Tue, May 25, 2021 at 10:23:09PM -0500, Eric W. Biederman wrote:
> > If we are going to do this something that is so small and clean it can
> > be done unconditionally always.
> [...]
> > The net request as I understand it: Make the filesystem the initramfs
> > lives in be an ordinary filesystem so it can just be used as the systems
> > primary filesystem.
>
> Including the ability to pivot_root it away, which seems like the main
> sticking point.
>
> If this can be done without any overhead, that seems fine, but if this
> involves mounting an extra filesystem, that may add an appreciable
> amount of boot time for systems trying to boot in milliseconds. (Such
> systems would not use an initramfs if they're going to go on and boot a
> separate root filesystem, but they can use an initramfs as their *only*
> filesystem.)

Compared to the time the unpacking spent, a mounting seems nothing. In the
scene above, this change can be disabled by kconfig, if pivot_root
is not needed in initramfs.

Thanks!
Menglong Dong