Re: [PATCH] init: Add support for rootwait timeout parameter

[Christian Brauner <brauner@kernel.org>]

On Fri, May 26, 2023 at 03:07:16PM +0200, Loic Poulain wrote:
> Add an optional timeout arg to 'rootwait' as the maximum time in
> seconds to wait for the root device to show up before attempting
> forced mount of the root filesystem.
> 
> This can be helpful to force boot failure and restart in case the
> root device does not show up in time, allowing the bootloader to
> take any appropriate measures (e.g. recovery, A/B switch, retry...).
> 
> In success case, mounting happens as soon as the root device is ready,
> contrary to the existing 'rootdelay' parameter (unconditional delay).
> 
> Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
> ---

Not terribly opposed and not terribly convinced yet.
So, we have rootdelay= with a timeout parameter that allows to specify a
delay before attempting to mount the root device. And we have rootwait
currently as an indefinite wait. Adding a timeout for rootwait doesn't
seem crazy and is backwards compatible. But there's no mention of any
concrete users or use-case for this which is usually preferable. If this
is just "could be useful for someone eventually" it's way less desirable
to merge this than when it's "here's a/multiple user/users"... So I
would love to see a use-case described here.

And this is only useful if there isn't an early userspace init that
parses and manages root=. So we need to hit prepare_namespaces() as a
rootwait timeout isn't meaningful if this is done by and early init in
the initramfs for example.