Re: [PATCH 3/7] xfs: protect S_DAX transitions in XFS read path

[Christoph Hellwig]

We can't just take locking one level up, as we need differnet locking
for different kinds of I/O.

I think you probably want an IOCB_DAX flag to check IS_DAX once and
then stick to it, similar to what we do for direct I/O.