Re: [PATCH 5/5] dax: "Hotplug" persistent memory for use like normal RAM

[Dan Williams]

On Mon, Jan 28, 2019 at 1:26 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> On Fri 25-01-19 11:15:08, Dan Williams wrote:
> [...]
> > However, we should consider this along with the userspace enabling to
> > control which device-dax instances are set aside for hotplug. It would
> > make sense to have a "clear errors before hotplug" configuration
> > option.
>
> I am not sure I understand. Do you mean to clear HWPoison when the
> memory is hotadded (add_pages) or onlined (resp. move_pfn_range_to_zone)?

Before the memory is hot-added via the kmem driver it shows up as an
independent persistent memory namespace. A namespace can be configured
as a block device and errors cleared by writing to the given "bad
block". Once all media errors are cleared the namespace can be
assigned as volatile memory to the core-kernel mm. The memory range
starts as a namespace each boot and must be hotplugged via startup
scripts, those scripts can be made to handle the bad block pruning.