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

From: Ross Zwisler
Date: Thu May 31 2018 - 16:41:31 EST


On Thu, May 31, 2018 at 12:13:32PM -0700, Darrick J. Wong 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...?
>
> # echo 'file drivers/dax/* +p' > /sys/kernel/debug/dynamic_debug/control
> # mount /dev/pmem3 -o rtdev=/dev/pmem4,dax /mnt
> # dmesg
> <snip>
> SGI XFS with ACLs, security attributes, realtime, scrub, debug enabled
> XFS (pmem3): DAX enabled. Warning: EXPERIMENTAL, use at your own risk
> pmem3: error: dax support not enabled
> pmem4: error: dax support not enabled
> XFS (pmem3): DAX unsupported by block device. Turning off DAX.
> XFS (pmem3): Mounting V5 Filesystem
> XFS (pmem3): Ending clean mount

This same sequence worked fine in my QEMU setup.

My guess is the issue is that your namespaces are in raw mode:

# ndctl list
[
{
"dev":"namespace1.0",
"mode":"raw", << this
"size":18119393280,
"sector_size":512,
"blockdev":"pmem1",
"numa_node":0
},
{
"dev":"namespace0.0",
"mode":"raw", << this
"size":18119393280,
"sector_size":512,
"blockdev":"pmem0",
"numa_node":0
}
]

If so, you can solve this by putting them in fsdax mode with ndctl:

# ndctl create-namespace -f -e namespace0.0 --mode=fsdax
{
"dev":"namespace0.0",
"mode":"fsdax",
"size":"16.61 GiB (17.83 GB)",
"uuid":"4c193c83-c031-41d4-8f96-2ff5c7b59c69",
"raw_uuid":"2f785f09-717a-4a5e-9e9d-88d489ef1030",
"sector_size":512,
"blockdev":"pmem0",
"numa_node":0
}

# ndctl create-namespace -f -e namespace1.0 --mode=fsdax
{
"dev":"namespace1.0",
"mode":"fsdax",
"size":"16.61 GiB (17.83 GB)",
"uuid":"39ec9cc4-a7ef-4f99-8354-60105543bf47",
"raw_uuid":"403fae76-d4f8-4bed-9a3f-ef40924762be",
"sector_size":512,
"blockdev":"pmem1",
"numa_node":0
}

If that doesn't fix it for you, ping me on freenode and we'll figure it out.

Thanks,
- Ross