linux-kernel - Re: [RFC PATCH 0/2] improve vmalloc allocation

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Message-ID: <ffec3806-969d-62df-2965-e8800babb8a1@kernel.org>
Date:   Tue, 23 Oct 2018 14:50:53 -0600
From:   Shuah Khan <shuah@...nel.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        Michal Hocko <mhocko@...nel.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>,
        maco@...roid.com, Shuah Khan <shuah@...nel.org>
Subject: Re: [RFC PATCH 0/2] improve vmalloc allocation

On 10/23/2018 02:09 PM, Matthew Wilcox wrote:
> On Tue, Oct 23, 2018 at 01:48:32PM -0600, Shuah Khan wrote:
>> On 10/23/2018 01:30 PM, Joel Fernandes wrote:
>>> On Tue, Oct 23, 2018 at 11:13:36AM -0600, Shuah Khan wrote:
>>>> I like this proposal. I think we will open up lot of test opportunities with
>>>> this approach.
>>>>
>>>> Maybe we can use this stress test as a pilot and see where it takes us.
>>>
>>> I am a bit worried that such an EXPORT_SYMBOL_KSELFTEST mechanism can be abused by
>>> out-of-tree module writers to call internal functionality.
>>
>> That is  valid concern to consider before we go forward with the proposal.
>>
>> We could wrap EXPORT_SYMBOL_KSELFTEST this in an existing debug option. This could
>> be fine grained for each sub-system for its debug option. We do have a few of these
>> now
> 
> This all seems far more complicated than my proposed solution.
> 

Not sure if it that complicated. But it is more involved. It dies have the
advantage of fitting in with the rest of the debug/test type framework we
already have.

The option you proposed sounds simpler, however it sounds a bit adhoc to me.

In any case I went looking for EXPORT_SYMBOL defines and found them in 

tools/include/asm/export.h
tools/include/linux/export.h
tools/virtio/linux/export.h

selftests/powerpc/copyloops/asm/export.h
selftests/powerpc/stringloops/asm/export.h

thanks,
-- Shuah