linux-kernel - Re: [PATCH] kernel: sysctl: make drop

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Message-ID: <20191101110901.GB690103@chrisdown.name>
Date:   Fri, 1 Nov 2019 11:09:01 +0000
From:   Chris Down <chris@...isdown.name>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH] kernel: sysctl: make drop_caches write-only

Hm, not sure why my client didn't show this reply.

Andrew Morton writes:
>Risk: some (odd) userspace code will break.  Fixable by manually chmodding
>it back again.

The only scenario I can construct in my head is that someone has built 
something to watch drop_caches for modification, but we already have the kmsg 
output for that.

>Reward: very little.
>
>Is the reward worth the risk?

There is evidence that this has already caused confusion[0] for many, judging 
by the number of views and votes. I think the reward is higher than stated 
here, since it makes the intent and lack of persistent API in the API clearer, 
and less likely to cause confusion in future.

0: https://unix.stackexchange.com/q/17936/10762