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Date: Tue, 23 Oct 2018 19:05:32 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [RFC PATCH 0/2] improve vmalloc allocation
Message-ID: <20181023170532.GW18839@dhcp22.suse.cz>
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To: Matthew Wilcox <willy@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>, Uladzislau Rezki <urezki@gmail.com>, Kees Cook <keescook@chromium.org>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>, Thomas Garnier <thgarnie@google.com>, Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>, Steven Rostedt <rostedt@goodmis.org>, Joel Fernandes <joelaf@google.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Tejun Heo <tj@kernel.org>

On Tue 23-10-18 08:26:40, Matthew Wilcox wrote:
> On Tue, Oct 23, 2018 at 09:02:56AM -0600, Shuah Khan wrote:
[...]
> > The way it can be handled is by adding a test module under lib. test_kmod,
> > test_sysctl, test_user_copy etc.
> 
> The problem is that said module can only invoke functions which are
> exported using EXPORT_SYMBOL.  And there's a cost to exporting them,
> which I don't think we're willing to pay, purely to get test coverage.

Yes, I think we do not want to export internal functionality which might
be still interesting for the testing coverage. Maybe we want something
like EXPORT_SYMBOL_KSELFTEST which would allow to link within the
kselftest machinery but it wouldn't allow the same for general modules
and will not give any API promisses.

I wouldn't be surprised if we found some cases of EXPORT_SYMBOL* just to
make a symbol available for testing which would be unfortunate.
-- 
Michal Hocko
SUSE Labs