From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array
Date: Fri, 17 Mar 2017 20:27:46 +0100
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Cc: Alexander Potapenko <glider@google.com>,
        Michal Marek <mmarek@suse.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        "David S. Miller" <davem@davemloft.net>,
        Shaohua Li <shli@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Matthias Kaehlcke <mka@chromium.org>, x86@kernel.org,
        linux-kbuild@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        linux-crypto@vger.kernel.org, linux-raid@vger.kernel.org
To: Michael Davidson <md@google.com>
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On Fri, Mar 17, 2017 at 11:52:01AM -0700, Michael Davidson wrote:
> On Fri, Mar 17, 2017 at 5:44 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> >
> > Be that as it may; what you construct above is disgusting. Surely the
> > code can be refactored to not look like dog vomit?
> >
> > Also; its not immediately obvious conf->copies is 'small' and this
> > doesn't blow up the stack; I feel that deserves a comment somewhere.
> >
> 
> I agree that the code is horrible.
> 
> It is, in fact, exactly the same solution that was used to remove
> variable length arrays in structs from several of the crypto drivers a
> few years ago - see the definition of SHASH_DESC_ON_STACK() in
> "crypto/hash.h" - I did not, however, hide the horrors in a macro
> preferring to leave the implementation visible as a warning to whoever
> might touch the code next.
> 
> I believe that the actual stack usage is exactly the same as it was previously.
> 
> I can certainly wrap this  up in a macro and add comments with
> appropriately dire warnings in it if you feel that is both necessary
> and sufficient.

We got away with ugly in the past, so we should get to do it again?