linux-kernel - Re: [PATCH v1 1/3] printk: honor the max_reason field in kmsg

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Date:   Mon, 4 May 2020 22:52:20 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     James Morris <jmorris@...ei.org>, Sasha Levin <sashal@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Kees Cook <keescook@...omium.org>, anton@...msg.org,
        ccross@...roid.com, Tony Luck <tony.luck@...el.com>,
        robh+dt@...nel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v1 1/3] printk: honor the max_reason field in kmsg_dumper

> > @@ -3157,12 +3162,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
> >       struct kmsg_dumper *dumper;
> >       unsigned long flags;
> >
> > -     if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
> > -             return;
> > -
> >       rcu_read_lock();
> >       list_for_each_entry_rcu(dumper, &dump_list, list) {
> > -             if (dumper->max_reason && reason > dumper->max_reason)
> > +             if (reason > dumper->max_reason)
> >                       continue;
>
> Why always_kmsg_dump check moved from the dumper loop entry point to the
> dumper registration code? What if the user change always_ksmsg_dump
> dynamically via sysfs?

Hi Sergey,

I changed it to make code cleaner:  for such basic operation there are
too many conditions if we will keep it inside the kmsg_dump().
However, if being able to set always_kmsg_dump dynamically during
runtime is deemed important, I can change it back to be checked in
kmsg_dump.

Thank you,
Pasha

>
>         -ss