Re: DAX can not work on virtual nvdimm device

[Dan Williams]

On Fri, Aug 19, 2016 at 4:19 AM, Xiao Guangrong
<guangrong.xiao@xxxxxxxxxxxxxxx> wrote:
>
> Hi Dan,
>
> Recently, Redhat reported that nvml test suite failed on QEMU/KVM,
> more detailed info please refer to:
>    https://bugzilla.redhat.com/show_bug.cgi?id=1365721
>
> The reason for this bug is that the memory region created by mmap()
> on the dax-based file was gone so that the region can not be found
> in /proc/self/smaps during the runtime.
>
> This is a simple way to trigger this issue:
>    mount -o dax /dev/pmem0 /mnt/pmem/
>    vim /mnt/pmem/xxx
> then 'vim' is crashed due to segment fault.
>
> This bug can be reproduced on your tree, the top commit is
> 10d7902fa0e82b (dax: unmap/truncate on device shutdown), the kernel
> configure file is attached.
>
> Your thought or comment is highly appreciated.

I'm going to be offline until Tuesday, but I will investigate when I'm
back.  In the meantime if Ross or Vishal had an opportunity to take a
look I wouldn't say "no" :).