Re: [PATCH 1/2] xfs: always use DAX if mount option is used

[Ross Zwisler]

On Fri, Sep 08, 2017 at 12:20:28AM -0700, Christoph Hellwig wrote:
> On Thu, Sep 07, 2017 at 03:08:31PM -0600, Ross Zwisler wrote:
> > Before support for the per-inode DAX flag was disabled the XFS the code had
> > an issue where the user couldn't reliably tell whether or not DAX was being
> > used to service page faults and I/O when the DAX mount option was used.  In
> > this case each inode within the mounted filesystem started with S_DAX set
> > due to the mount option, but it could be cleared if someone touched the
> > individual inode flag.
> 
> Looks good, but can you please add a testcase to xfstests for this?

Hmm...aside from looking at tracepoints, I'm not sure how to detect whether or
not S_DAX is actually being used for an inode.  I don't see any other xfstests
that try and look at the trace buffer, but I guess that could work.

Do you know of a better way to detect this test failure/success?

> Reviewed-by: Christoph Hellwig <hch@xxxxxx>

Thanks for the review!