On Tue 2021-11-23 12:23:39, Luis Chamberlain wrote:

From: Xiaoming Ni <redacted>

The kernel/sysctl.c is a kitchen sink where everyone leaves
their dirty dishes, this makes it very difficult to maintain.

To help with this maintenance let's start by moving sysctls to
places where they actually belong. The proc sysctl maintainers
do not want to know what sysctl knobs you wish to add for your own
piece of code, we just care about the core logic.

Today though folks heavily rely on tables on kernel/sysctl.c so
they can easily just extend this table with their needed sysctls.
In order to help users move their sysctls out we need to provide a
helper which can be used during code initialization.

We special-case the initialization use of register_sysctl() since
it *is* safe to fail, given all that sysctls do is provide a dynamic
interface to query or modify at runtime an existing variable. So the
use case of register_sysctl() on init should *not* stop if the sysctls
don't end up getting registered. It would be counter productive to
stop boot if a simple sysctl registration failed.

Provide a helper for init then, and document the recommended init
levels to use for callers of this routine. We will later use this
in subsequent patches to start slimming down kernel/sysctl.c tables
and moving sysctl registration to the code which actually needs
these sysctls.

Do we really need a new helper for this?
Is the failure acceptable only during system initialization?

The warning would be useful even for the original register_sysctl().

It should be up-to-the caller to decide if the failure is fatal
or not. It might be enough to document the reasoning why a warning
is enough in most cases.

Best Regards,
Petr