Re: [PATCH 0/3] dax: clear poison on the fly along pwrite

[Dan Williams]

On Tue, Sep 14, 2021 at 4:32 PM Jane Chu <jane.chu@xxxxxxxxxx> wrote:
>
> If pwrite(2) encounters poison in a pmem range, it fails with EIO.
> This is unecessary if hardware is capable of clearing the poison.
>
> Though not all dax backend hardware has the capability of clearing
> poison on the fly, but dax backed by Intel DCPMEM has such capability,
> and it's desirable to, first, speed up repairing by means of it;
> second, maintain backend continuity instead of fragmenting it in
> search for clean blocks.
>
> Jane Chu (3):
>   dax: introduce dax_operation dax_clear_poison

The problem with new dax operations is that they need to be plumbed
not only through fsdax and pmem, but also through device-mapper.

In this case I think we're already covered by dax_zero_page_range().
That will ultimately trigger pmem_clear_poison() and it is routed
through device-mapper properly.

Can you clarify why the existing dax_zero_page_range() is not sufficient?

>   dax: introduce dax_clear_poison to dax pwrite operation
>   libnvdimm/pmem: Provide pmem_dax_clear_poison for dax operation
>
>  drivers/dax/super.c   | 13 +++++++++++++
>  drivers/nvdimm/pmem.c | 17 +++++++++++++++++
>  fs/dax.c              |  9 +++++++++
>  include/linux/dax.h   |  6 ++++++
>  4 files changed, 45 insertions(+)
>
> --
> 2.18.4
>