AIO not working on NFS share - ? Regression

[Jim Ohlstein]

Hello,

For sometime now we've used a backend (non-internet accessible) server 
to generate static content that is shared via NFS to a front-end server 
for internet access. Both machines use ZFS exclusively.

The webserver is nginx and we had AIO set to on, with the AIO module 
built into the kernel.In 10.x it "just worked".

About two weeks ago I upgraded that backend machine to 11-STABLE in 
order to start building packages for 11. I've just updated it again to 
r305417. I don't recall it not working as expected.

More recently I upgraded the front-end machine to 11-STABLE @r305311. 
Since then, AIO is not working and I get a critical error in the nginx 
logs like this:

2016/09/05 15:58:02 [crit] 21145#0: *649 aio_read("/path/to/file") 
failed (45: Operation not supported) while sending response to client ...

In 11 AIO is built into the kernel by default, and I have confirmed that 
it works as expected in files from a local file system. Since the 
webserver isn't aware that the file system in question is shared via 
NFS, it seems this is an operating system issue.

-- 
Jim Ohlstein