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Date:   Fri, 1 Nov 2019 12:35:44 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Chris Down <chris@chrisdown.name>,
        Johannes Weiner <hannes@cmpxchg.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, kernel-team@fb.com,
        Alexey Dobriyan <adobriyan@gmail.com>
Subject: Re: [PATCH] kernel: sysctl: make drop_caches write-only
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On Fri, 1 Nov 2019 12:29:20 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:

> > Either change is an upgrade from the current situation, at least. I prefer 
> > towards whatever makes the API the least confusing, which appears to be 
> > Johannes' original change, but I'd support a patch which always set it to 
> > 0 instead if it was deemed safer.
> 
> On the other hand..  As I mentioned earlier, if someone's code is
> failing because of the permissions change, they can chmod
> /proc/sys/vm/drop_caches at boot time and be happy.  They have no such
> workaround if their software misbehaves due to a read always returning
> "0".

I lied.  I can chmod things in /proc but I can't chmod things in
/proc/sys/vm.  Huh, why did we do that?