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

[Dan Williams]

On Thu, Sep 23, 2021 at 1:56 PM Jane Chu <jane.chu@xxxxxxxxxx> wrote:
[..]
> > This (AFAICT) has already been done for dax_zero_page_range, so I sense
> > that Dan is trying to save you a bunch of code plumbing work by nudging
> > you towards doing s/dax_clear_poison/dax_zero_page_range/ to this series
> > and then you only need patches 2-3.
>
> Thanks Darrick for the explanation!
> I don't mind to add DM layer support, it sounds straight forward.
> I also like your latest patch and am wondering if the clear_poison API
> is still of value.

No, the discussion about fallocate(...ZEROINIT...) has lead to a
better solution. Instead of making error clearing a silent /
opportunistic side-effect of writes, or trying to define new fallocate
mode, just add a new RWF_CLEAR_HWERROR flag to pwritev2(). This allows
for dax_direct_access() to map the page regardless of poison and
trigger pmem_copy_from_iter() to precisely handle sub-page poison.