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Date:   Mon, 18 Jun 2018 14:51:14 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Waiman Long <longman@redhat.com>
Cc:     Takashi Iwai <tiwai@suse.de>, Davidlohr Bueso <dbueso@suse.de>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipc: Limit sysctl value to IPCMNI
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On Mon, 18 Jun 2018 13:27:24 +0800 Waiman Long <longman@redhat.com> wrote:

> >>
> >> Maybe another possible solution would be to add another proc entry to
> >> handle this correctly, and make the old one only for compatibility.
> > Yes, I guess so.  Just leave the old tunable alone.  Possibly we
> > could add a printk_once("please switch to the new interface").
> 
> A problem with that is the fact that those sysctl parameters have been
> there for so long that it may be hard to persuade users to use the new
> sysctl parameters.

That's what a once-off warning could help with.  Tell them they're
using a deprecated interface.  It would take a few years, but when
people see the old interface is scheduled for removal, they'll switch,
over time.