On Mon, Sep 25, 2017 at 11:32 PM, Christoph Hellwig <hch@xxxxxx> wrote: > 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. I wonder if this works better with a reference count mechanism per-file so that we don't need a hold a lock over the whole transition. Similar to request_queue reference counting, when DAX is being turned off we block new references and drain the in-flight ones.
