linux-kernel - Re: [PATCH] tools/testing/selftests/vm/mlock2-tests: fix mlock2 false-negative errors

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Message-ID: <20200323155449.GG23364@optiplex-lnx>
Date:   Mon, 23 Mar 2020 11:54:49 -0400
From:   Rafael Aquini <aquini@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org, shuah@...nel.org
Subject: Re: [PATCH] tools/testing/selftests/vm/mlock2-tests: fix mlock2
 false-negative errors

On Mon, Mar 23, 2020 at 04:51:11PM +0100, Michal Hocko wrote:
> On Mon 23-03-20 11:41:59, Rafael Aquini wrote:
> > On Mon, Mar 23, 2020 at 04:12:56PM +0100, Michal Hocko wrote:
> > > On Mon 23-03-20 11:02:59, Rafael Aquini wrote:
> [...]
> > > > The selftest also checks the kernel visible effect, via
> > > > /proc/kpageflags, and that's where it fails after 9c4e6b1a7027f.
> > > 
> > > I really fail to see your point. Even if you are right that the self
> > > test is somehow evaluating the kernel implementation which I am not sure
> > > is the scope of the selft thest but anyway. The mere fact that the
> > > kernel test fails on a perfectly valid change should just suggest that
> > > the test is leading to false positives and therefore should be fixed.
> > > Your proposed fix is simply suboptimal because it relies on yet another
> > > side effect which might change anytime in the future and still lead to a
> > > correctly behaving kernel. See my point?
> > >
> > 
> > OK, I concede your point on the bogusness of checking the page flags in
> > this particular test and expect certain valuse there, given that no other 
> > selftest seems to be doing that level of inner kenrel detail scrutiny.
> > 
> > I'll repost this fix suggestion getting rif of those related
> > checkpoints.
> 
> Here is what I have after I had to context switch to something else
> before finishing it. Feel free to reuse if you feel like. It is likely
> to not even compile.
>

I'm OK with it, if you want to go ahead and do the kill.

Thanks 
-- Rafael