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

[Dan Williams]

On Sun, Jun 3, 2018 at 5:25 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
> On Mon, Jun 04, 2018 at 08:20:38AM +1000, Dave Chinner wrote:
>> On Thu, May 31, 2018 at 09:02:52PM -0700, Dan Williams wrote:
>> > On Thu, May 31, 2018 at 7:24 PM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
>> > > On Thu, May 31, 2018 at 06:57:33PM -0700, Dan Williams wrote:
>> > >> > 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?
>>
>> [....]
>>
>> > >> 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?
>>
>> [....]
>>
>> > > OK, works now I've found the magic config incantantions to turn
>> > > everything I now need on.
>>
>> By enabling these options, my test VM now has a ~30s pause in the
>> boot very soon after the nvdimm subsystem is initialised.
>>
>> [    1.523718] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
>> [    1.550353] 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
>> [    1.552175] Non-volatile memory driver v1.3
>> [    2.332045] tsc: Refined TSC clocksource calibration: 2199.909 MHz
>> [    2.333280] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x1fb5dcd4620, max_idle_ns: 440795264143 ns
>> [   37.217453] brd: module loaded
>> [   37.225423] loop: module loaded
>> [   37.228441] virtio_blk virtio2: [vda] 10485760 512-byte logical blocks (5.37 GB/5.00 GiB)
>> [   37.245418] virtio_blk virtio3: [vdb] 146800640 512-byte logical blocks (75.2 GB/70.0 GiB)
>> [   37.255794] virtio_blk virtio4: [vdc] 1073741824000 512-byte logical blocks (550 TB/500 TiB)
>> [   37.265403] nd_pmem namespace1.0: unable to guarantee persistence of writes
>> [   37.265618] nd_pmem namespace0.0: unable to guarantee persistence of writes
>>
>> The system does not appear to be consuming CPU, but it is blocking
>> NMIs so I can't get a CPU trace. For a VM that I rely on booting in
>> a few seconds because I reboot it tens of times a day, this is a
>> problem....
>
> And when I turn on KASAN, the kernel fails to boot to a login prompt
> because:

What's your qemu and kernel command line? I'll take look at this first
thing tomorrow.