On Thu, May 31, 2018 at 06:57:33PM -0700, Dan Williams wrote:
> On Thu, May 31, 2018 at 6:26 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> > 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...?
> >
> > I have similar problems, too, but:
> >
> > $ ndctl list
> > [
> > {
> > "dev":"namespace1.0",
> > "mode":"raw",
> > "size":8589934592,
> > "sector_size":512,
> > "blockdev":"pmem1"
> > },
> > {
> > "dev":"namespace0.0",
> > "mode":"raw",
> > "size":8589934592,
> > "sector_size":512,
> > "blockdev":"pmem0"
> > }
> > ]
> > $ sudo ndctl create-namespace -f -e namespace0.0 --mode=fsdax
> > Error: operation failed, region0 fsdax mode not available
> >
> > failed to reconfigure namespace: Invalid argument
> > $
> >
> > I can't make head or tail of what is going wrong here - how am I
> > supposed to debug this and get it working again?
> >
> > FWIW, XFS+DAX used to just work on this setup (I hadn't even
> > installed ndctl until this morning!) but after changing the kernel
> > it no longer works. That would make it a regression, yes?
>
> This commit caused the behavior change:
>
> 569d0365f571 dax: require 'struct page' by default for filesystem dax
>
> The justification is in that patch, but the short summary is we killed
> off "pageless" dax because it had so many incomplete holes and
> surprise behaviors. It needed to die on the path to making dax not
> experimental, i.e. to close safety holes, and be feature complete for
> all the ways userspace expects to use mappings (direct-io, fork,
> poison handling, etc).
>
> I suspect your kernel does not have CONFIG_ZONE_DEVICE enabled which
> has the following dependencies:
>
> depends on MEMORY_HOTPLUG
> depends on MEMORY_HOTREMOVE
> depends on SPARSEMEM_VMEMMAP
Filesystem DAX now has a dependency on memory hotplug?
Fmeh. No wonder I never enabled CONFIG_ZONE_DEVICE. It's described in
menuconfig as "Device memory (pmem, HMM, etc...) hotplug support".
This isn't for hotplug support - it required for basic DAX
functionality. I've never enabled memory hotplug in any of my test
kernel configs, because the VMs I run the kernels on don't ever get
memory hotplugged....
OK, works now I've found the magic config incantantions to turn
everything I now need on.
Can we get this rationalised to a single top level config
option in the filesystems menu "Enable Filesystem DAX" that turns
on every knob that is required?
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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