On Thu, Jul 6, 2017 at 11:46 AM, Piotr Dałek <piotr.da...@corp.ovh.com> wrote:
> How about a hybrid solution? Keep the old rbd_aio_write contract (don't copy
> the buffer with the assumption that it won't change) and instead of
> constructing bufferlist containing bufferptr to copied data, construct a
> bufferlist containing bufferptr made with create_static(user_buffer)?

We must be talking past each other -- there was never such a
pre-Lumunous contract since (1) it did copy the buffer on every IO and
(2) it could have potentially copied before the 'rbd_aio_write' call
returned or after (but at least before the completion was fired). Just
because it works some times doesn't mean it would always work since it
would be a race between two threads.

Unfortunately, until the librados issue is solved, you will still have
to copy the data once when using the C++ API. The only advantage is
that you would be responsible for the copying and it would only need
to be performed once instead of twice.

-- 
Jason
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