linux-kernel - Re: [PATCH 03/13] livepatch: refactor klp_init

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Date:   Wed, 27 Jan 2021 13:58:21 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, Jessica Yu <jeyu@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        dri-devel@...ts.freedesktop.org, live-patching@...r.kernel.org,
        linux-kbuild@...r.kernel.org
Subject: Re: [PATCH 03/13] livepatch: refactor klp_init_object

On Thu 2021-01-21 08:49:49, Christoph Hellwig wrote:
> Merge three calls to klp_is_module (including one hidden inside
> klp_find_object_module) into a single one to simplify the code a bit.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  kernel/livepatch/core.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> index f76fdb9255323d..a7f625dc24add3 100644
> --- a/kernel/livepatch/core.c
> +++ b/kernel/livepatch/core.c
> @@ -54,9 +54,6 @@ static void klp_find_object_module(struct klp_object *obj)
>  {
>  	struct module *mod;
>  
> -	if (!klp_is_module(obj))
> -		return;
> -

We need to either update the function description or keep this check.

I prefer to keep the check. The function does the right thing also
for the object "vmlinux". Also the livepatch code includes many
similar paranoid checks that makes the code less error prone
against any further changes.

Of course, it is a matter of taste.

>  	mutex_lock(&module_mutex);
>  	/*
>  	 * We do not want to block removal of patched modules and therefore

Otherwise, the patch looks fine.

Best Regards,
Petr