Re: [dm-devel] [PATCH v2 2/7] dax: change bdev_dax_supported() to support boolean returns

[Ross Zwisler]

On Thu, May 31, 2018 at 03:26:45PM -0700, Darrick J. Wong wrote:
> On Thu, May 31, 2018 at 04:52:06PM -0400, Mike Snitzer wrote:
> > On Thu, May 31 2018 at  3:13pm -0400,
> > Darrick J. Wong <darrick.wong@xxxxxxxxxx> wrote:
> > 
> > > On Tue, May 29, 2018 at 04:01:14PM -0600, Ross Zwisler wrote:
> > > > On Tue, May 29, 2018 at 02:25:10PM -0700, Darrick J. Wong wrote:
> > > > > On Tue, May 29, 2018 at 01:51:01PM -0600, Ross Zwisler wrote:
> > > > > > From: Dave Jiang <dave.jiang@xxxxxxxxx>
> > > > > > 
> > > > > > The function return values are confusing with the way the function is
> > > > > > named. We expect a true or false return value but it actually returns
> > > > > > 0/-errno.  This makes the code very confusing. Changing the return values
> > > > > > to return a bool where if DAX is supported then return true and no DAX
> > > > > > support returns false.
> > > > > > 
> > > > > > Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> > > > > > Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> > > > > 
> > > > > Looks ok, do you want me to pull the first two patches through the xfs
> > > > > tree?
> > > > > 
> > > > > Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > > 
> > > > Thanks for the review.
> > > > 
> > > > I'm not sure what's best.  If you do that then Mike will need to have a DM
> > > > branch for the rest of the series based on your stable commits, yea?
> > > > 
> > > > Mike what would you prefer?
> > > 
> > > I /was/ about to say that I would pull in the first two patches, but now
> > > I can't get xfs to mount with pmem at all, and have no way of testing
> > > this...?
> > 
> > Once you get this sorted out, please feel free to pull in the first 2.
> 
> Sorted.  It'll be in Friday's for-next.  Ross helped me bang on the pmem
> devices w/ ndctl to enable fsdax mode and twist qemu until everything
> worked properly. ;)

For anyone else who would like to simulate persistent memory using QEMU, I've
added some hints here:

https://nvdimm.wiki.kernel.org/pmem_in_qemu