On Tue, 2017-06-20 at 19:26 +1000, Sergei A. Trusov wrote:

<snip>

Thank you for this point. Now I see all the changes above are
redundant:
we can use a value returned in the *data buffer. It is enough to add 
only two lines of code to achieve the behaviour of this entire patch.

A bit more with a comment explaining the reason behind those 2 lines,
but shorter patches get my vote ;)