[linux-next][XFS][trinity] WARNING: CPU: 32 PID: 31369 at fs/iomap.c:993

[Christoph Hellwig]

On Mon, Sep 18, 2017 at 09:28:55AM -0600, Jens Axboe wrote:
> If it's expected, why don't we kill the WARN_ON_ONCE()? I get it all
> the time running xfstests as well.

Dave insisted on it to decourage users/applications from mixing
mmap and direct I/O.

In many ways a tracepoint might be the better way to diagnose these.