Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array
Date	2017-03-17 21:10 +0100
Message-ID	<tm6md-3nM-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <tlNWh-6eK-17@gated-at.bofh.it> <tlZ1o-6iZ-29@gated-at.bofh.it> <tlZkK-6pR-11@gated-at.bofh.it> <tlZup-6vs-7@gated-at.bofh.it> <tm5Jw-2QT-7@gated-at.bofh.it>
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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?

Thread

[PATCH 6/7] md/raid10, LLVM: get rid of variable length array Michael Davidson <md@google.com> - 2017-03-17 01:30 +0100
  Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-17 13:20 +0100
    Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Alexander Potapenko <glider@google.com> - 2017-03-17 13:40 +0100
      Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-17 13:50 +0100
        Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Michael Davidson <md@google.com> - 2017-03-17 20:30 +0100
          Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-17 21:10 +0100
            Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array hpa@zytor.com - 2017-03-17 21:50 +0100
              Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Dmitry Vyukov <dvyukov@google.com> - 2017-03-24 14:50 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-24 15:20 +0100
      Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Alexander Potapenko <glider@google.com> - 2017-03-17 13:50 +0100
        Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Borislav Petkov <bp@alien8.de> - 2017-03-17 19:10 +0100
          Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Dmitry Vyukov <dvyukov@google.com> - 2017-03-17 19:50 +0100
            Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Borislav Petkov <bp@alien8.de> - 2017-03-17 20:10 +0100
              Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Dmitry Vyukov <dvyukov@google.com> - 2017-03-17 20:10 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-17 20:40 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Dmitry Vyukov <dvyukov@google.com> - 2017-03-24 15:00 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-24 15:20 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Dmitry Vyukov <dvyukov@google.com> - 2017-03-24 15:30 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Peter Zijlstra <peterz@infradead.org> - 2017-03-17 21:40 +0100
                Re: [PATCH 6/7] md/raid10, LLVM: get rid of variable length array Fengguang Wu <fengguang.wu@intel.com> - 2017-03-18 01:50 +0100

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